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Fowler, Clayton M. "Application of Metamaterials to RF Energy Harvesting and Infrared Photodetection." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7024.
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Techniques for adapting metamaterials for the improvement of RF energy harvesting and infrared photodetection are demonstrated using experimental and computer simulation methods. Two methods for RF energy harvesting are experimentally demonstrated and supported by computer simulation. In the first method, a metamaterial perfect absorber (MPA) is made into a rectenna capable of harvesting RF energy and delivering power to a load by soldering Schottky diodes onto connected split ring resonator (SRR) structures composing the planar metasurface of the perfect absorber. The metamaterial rectenna is accompanied by a ground plane placed parallel to it, which forms a Fabry-Perot cavity between the metasurface and the ground plane. The Fabry-Perot cavity stores energy in the form of standing waves which is transferred to the SRR structures of the metasurface as AC currents that are rectified by the diodes to create DC power. This type of design enables highly efficient energy harvesting for low input power, creates a large antenna capture area, and uses elements with small electrical size, such that 100 uW of power (enough to operate simple devices) can be captured at ambient intensities ~ 1 - 2 uW/cm2. Two designs using this method are presented, one that operates for linear polarizations at 0.9 GHz and a smaller polarization-independent design that operates around 1.5 GHz. In the second method, the energy stored in the standing waves of an MPA Fabry-Perot cavity is instead harvested by placing a separate energy harvesting antenna within the cavity. The cavity shapes and enhances the incident electric field, and then the separate energy harvesting antenna is designed to be inserted into the cavity so that its shape and/or radiation pattern matches the electric field lines within the cavity and maximally extracts the stored energy. This method allows for great customization of antenna design parameters, such as operating frequency, polarization dependence, and directionality, by swapping out different metasurface and antenna designs. Using this method, the amount of power harvested by a simple dipole rectenna placed within a cavity is improved by a factor of 18 as compared to what it would harvest by itself at an ambient intensity of 35 nW/cm2. Lastly, the addition of plasmonic structures to DWELL (quantum dot-in-a-well) infrared photodetectors is investigated by computer simulation. DWELL photodetectors have the potential to one day replace standard mercury cadmium telluride detectors by being cheaper alternatives with a higher operating temperature. The inclusion of gold plasmonic structure arrays into DWELL detectors enables excitation of surface plasmon polariton modes that increase the responsivity of the detector to incident infrared radiation. The peak responsivity of a DWELL detector is demonstrated to improve by a factor of 8 for a 1 um thick layer of plasmonic structures and by a factor of 15 for a 2 um thick layer. These works are steps forward in making RF energy harvesting practically useful and for improving infrared photodetector performance.
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Osedach, Timothy. "Colloidal Quantum Dots and J-Aggregating Cyanine Dyes for Infrared Photodetection." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10088.
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The emergence of nanostructured semiconducting materials enables new approaches toward the realization of photodetectors that operate in the technologically important near- and short-wave infrared (NIR and SWIR) spectral ranges. In particular, organic semiconductors and colloidal quantum dots (QDs) possess numerous advantages over conventional crystalline semiconductors including highly tunable optical and electronic characteristics, the prospect for low-temperature processing, and compatibility with inexpensive and exible substrates. Photodetectors based on such materials may lead to low-cost IR focal plane arrays for night-vision imaging as well as a multitude of novel applications in biological and chemical sensing. This thesis describes the development and detailed characterization of several photodetectors that incorporate colloidal QD and organic semiconductor thin films as active layers. The electronic properties of PbS QDs are thoroughly investigated in a field effect transistor (FET) geometry and several QD-based photoconductive structures exhibiting SWIR photosensitivity are demonstrated. We describe a novel QD-sensitized lateral heterojunction photoconductor in which the functions of optical absorption and charge transport are dissociated into different physical layers that can be independently optimized. This structure is advantageous because it obviates the need for aggressive chemical treatments to the QD film that may compromise the quality of QD surface passivation. Photovoltaic device architectures are addressed, noting their advantages of being operable without an external applied bias and at fast response speeds. We present detailed experimental and theoretical characterization of a photovoltaic structure that is sensitized at NIR wavelengths by a J-aggregating cyanine dye. The high absorption coefficient of the J-aggregate film, combined with the use of a reflective anode and optical spacer layer, enables an external quantum efficiency (EQE) of \(16.1\pm0.1\%(\lambda = 756 nm)\) to be achieved at zero-bias in a device that incorporates an \(8.1\pm0.3 nm\)-thick dye film. The merits and drawbacks of the various device architectures and nanostructured material systems are discussed and the outlook for nanostructured photodetectors that exhibit infrared sensitivity is presented.Engineering and Applied Sciences
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Alvarenga, Deborah Reis. "A study on the physical properties of quantum dot structures for infrared photodetection." Universidade Federal de Minas Gerais, 2011. http://hdl.handle.net/1843/JCBV-8PBLYM.
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This thesis is part of a project where the overall goal is to master the technology of infrared photodetectors based on self-organized semiconductor quantum dots, the Quantum Dot Infrared Photodetectors (QDIPs) for the wavelength range from 2 to 20 ìm. The thesis focuses on the physical properties of quantum dots and QDIPs structures, especially on the intraband transitions and extraction mechanisms involved
in the photocurrent generation. We studied original and innovative structures based on self-organized InAs quantum dots grown on InP substrates. The main results presented in this thesis are based on photocurrent measurements as a function of temperature and
external applied bias voltages, using a Fourier Transform Infrared spectrometer. The experimental techniques of photoluminescence, atomic force microscopy, transmission electron microscopy and current-voltage curves were also performed to achieve a better
understanding of the physical mechanisms involved. To explain the results and assign each photocurrent peak to a particular transition, fully three dimensional theoretical calculations were done. The main results presented in this thesis are: i- It is shown that the intraband Auger effect can be an important process for the photocurrent generation in QDIPs. Intraband photocurrent and absorption measurements, together with a full three-dimensional theoretical modeling revealed that a bound-to-bound optical transition, where the final state is about 200 meV deep below the conduction band continuum, is responsible for the photogenerated current in the particular QDIP structure investigated. Photoluminescence and interband photocurrent spectra further support this conclusion. ii- We studied the influence of different structures in the
neighborhood of the quantum dot on the photocurrent response of quantum dot infrared photodetectors. We measured a photocurrent with positive and a negative sign for the same external electric field in some QDIP structures. The dual sign photocurrent signal is attributed to asymmetries on the structures which can privilege the extraction of the carriers from the dots for one of the two possible senses of the current. This process is seen for small external applied bias voltages or when no bias is applied. For high external fields the photoexcited electrons go in the same sense of the applied field, as expected. iii- We present a very highly selective QDIP, which combines InAs quantum dots and InGaAs wells, operating at 12 ìm. The transition responsible for the exceptionally narrow photocurrent is attributed to photon absorption between quantum dot bound states, followed by a carrier extraction mechanism where the coupling of the final state of the transition to the adjacent quantum well is highlightedEsta tese faz parte de uma proposta mais ampla cujo objetivo global e dominar a tecnologia de fotodetectores de radiacao infravermelha baseados em pontos quanticos semicondutores auto-organizados, os Quantum Dot Infrared Photodetectors (QDIPs), para a faixa de comprimento de onda de 2 a 20 Êm. A tese esta centrada no estudo das propriedades fisicas de pontos quanticos e de estruturas de QDIPs, em especial os mecanismos de transicao intrabanda e de extracao de carga envolvidos no processo de geracao da fotocorrente. Foram estudadas estruturas inovadoras e originais baseadas em pontos quanticos auto organizados de InAs crescidos sobre substratos de InP. Para obter os principais resultados apresentados nesta tese foram feitas medidas de fotocorrente em funcao da temperatura e tensao externa aplicada, utilizando um espectrometro de transformada de Fourier. As tecnicas experimentais de fotoluminescencia, microscopia de forca atomica, microscopia eletronica de transmissao e curvas de corrente versus voltagem tambem foram utilizadas para obter uma melhor compreensao dos mecanismos fisicos envolvidos. Para explicar os resultados e atribuir cada pico de fotocorrente a uma transicao especifica utilizamos um modelo teorico tridimensional. Os resultados que se destacam e sao apresentados nessa tese sao: i. O efeito Auger intrabanda e apontado como um possivel processo importante para gerar a corrente nos QDIPs. Medidas de fotocorrente intrabanda e de absorcao, juntamente com um calculo teorico tridimensional, mostram que a transicao responsavel por gerar a fotocorrente medida em uma estrutura QDIP especifica estudada ocorre entre estados ligados do ponto quantico onde o estado final da transicao esta 200 meV abaixo do continuo. O espalhamento Auger e proposto como o mecanismo responsavel pela extracao de carga do ponto quantico, e portanto pela fotocorrente gerada, nesses dispositivos. Resultados de fotoluminescencia e fotocorrente interbanda fornecem apoio adicional para esta conclusao. ii. Diferentes estruturas nas vizinhancas do ponto quantico influenciam no sentido da corrente, pois os mecanismos de extracao dos eletrons dependem da estrutura como um todo. Os dispositivos aqui estudados apresentam fotocorrente com sentido positivo e negativo para a mesma tensao externa aplicada. Este duplo comportamento e atribuido a assimetria presente nessas estruturas, capaz de favorecer a extracao de eletrons em um dos dois sentidos possiveis para a corrente. Esse processo foi observado apenas para pequenos valores de tensao externa aplicada. Para valores altos de tensao, os eletrons se propagam no mesmo sentido do campo eletrico aplicado, assim como esperado. iii. Apresentamos um QDIP altamente seletivo com resposta espectral em torno de 12 Êm. A estrutura estudada e composta por pocos de InGaAs e pontos quanticos de InAs. A transicao responsavel pela fotocorrente observada ocorre entre estados ligados do ponto quantico, seguida por um mecanismo de extracao de carga onde o acoplamento do estado final da transicao com o poco de potencial vizinho ao ponto quantico tem um papel fundamental.
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Martinez, Bertille. "Étude des propriétés optoélectroniques de nanocristaux colloïdaux à faible bande interdite : application à la détection infrarouge." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS254.
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Les nanocristaux colloïdaux de semiconducteurs sont des nanomatériaux synthétisés en solution. En deçà d’une certaine taille, ils deviennent confinés : leurs propriétés optiques et électroniques sont alors dépendantes de leur taille. Le développement de ces nanocristaux a atteint une grande maturité dans le visible. L’enjeu est maintenant d’étendre la gamme accessible et d’obtenir des nanocristaux ayant des propriétés dans l’infrarouge. Parmi les candidats, on trouve les nanocristaux de tellure de mercure, HgTe, et de séléniure de mercure, HgSe. L’objectif de ce doctorat est d’approfondir la connaissance des propriétés optoélectroniques et de transport de ces matériaux afin de concevoir un système de détection infrarouge. Pour y parvenir, la structure électronique de ces matériaux est mesurée pour différentes tailles et différents ligands. Nous pouvons alors déterminer les énergies des niveaux électroniques et quantifier le niveau de dopage. Nous montrons que ce dopage dépend de la taille des cristaux, qu’il devient de plus en plus n quand la taille du cristal augmente. Dans le cas de HgSe, cette évolution du dopage avec la taille se traduit par une transition semiconducteur-métal. Le contrôle du dopage est ensuite étudié en fonction de la chimie de surface. En utilisant des effets dipolaires ou des transferts d’électrons via des ligands oxydants, nous montrons une modulation du dopage sur plusieurs ordres de grandeur. Ces études nous permettent de proposer un détecteur infrarouge à base de HgTe, fonctionnant à 2.5 µm, dont la structure permet de convertir les photons absorbés en courant. Nous obtenons une réponse de 20 mA/W et une détectivité de 3 × 10 9 JonesColloidal semiconductor nanocrystals are nanomaterials synthesized in solution. Below a certain size, these nanocrystals acquire quantum confinement properties: their optoelectronic properties depend on the nanoparticle size. In the visible range, colloidal nanocrystals are quite mature. The next objective in this field is to get infrared colloidal nanocrystals. Mercury selenide (HgSe) and mercury telluride (HgTe) are potential candidates. The goal of this PhD work is to strengthen our knowledge on optical, optoelectronic and transport properties of these nanocrystals, in order to design an infrared detector.To do so, we studied the electronic structure of HgSe and HgTe for different sizes and surface chemistries. We can then determine the energies of the electronic levels and the Fermi energy, quantify doping level … We show that the nanocrystal size has an influence on doping level, which gets more and more n-type as the nanocrystal size gets larger. We even observe a semiconductor-metal transition in HgSe nanocrystals as the size is increased. The doping control with surface chemistry is then investigated. By using dipolar effects or oxidizing ligands, we show a doping control over several orders of magnitude. Thanks to these studies, we are able to propose a HgTe based device for detection at 2.5 µm, which structure allows to convert effectively the absorbed photons into an electrical current and to get a high signal over noise ratio. We get a photoresponse of 20 mA/W and a detectivity of 3 × 10 9 Jones
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Yeo, Hwee Tiong. "High responsivity tunable step quantum well infrared photodetector." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FYeo.pdf.
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Lantz, Kevin R. "Two color photodetector using an asymmetric quantum well structure." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FLantz.pdf.
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Konukbay, Atakan. "Design of a voltage tunable broadband quantum well infrared photodetector." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FKonukbay.pdf.
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Jiang, Lin. "Investigation of a novel multicolor quantum well infrared photodetector and advanced quantum dot infrared photodetectors." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001249.
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Hanson, Nathan A. "Characterization and analysis of a multicolor quantum well infrared photodetector." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FHanson.pdf.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2006.Thesis Advisor(s): Gamani Karunasiri, James H. Luscombe. "June 2006." Includes bibliographical references (p. 49-50). Also available in print.
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Alves, Fabio Durante Pereira. "Design and analysis of a multicolor quantum well infrared photodetector." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FAlves.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2005.Thesis Advisor(s): Gamani Karunasiri, John Powers, Sherif Michael. Includes bibliographical references (p. 93-97). Also available online.
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Sim, Koon-hung Steven, and 沈觀洪. "Antimonide based quantum-well and its application in infrared photodetector." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31223345.
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Bigioli, Azzurra. "Performance evaluation of a quantum-well infrared photodetector in patch-antenna architecture." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13438/.
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Nel presente lavoro di tesi si dimostra il miglioramento delle perfomances di un detector basato su pozzi quantici (QWIP-Quantum Well Infrared Photo detector)(n-type GaAs/AlGaAs) nel range infrarosso (λ ≈8.6µm), processato in un array di nano-antenne a doppio metallo. I Quantum Well detectors generano fotocorrente attivando transizioni intersottobanda nel supereticolo di pozzi quantici. Le prestazioni di questi detectors sono deteriorate dal rumore associato alla corrente di dark, proporzionale all’area del detector e dipendente esponenzialemente dalla temperatura. In questo lavoro, si dimostra che le antenne
patches agiscono da micro-cavitá che confinano il campo elettrico
incidente in uno strato di semiconduttore con dimensioni minori della lunghezza d’onda, evitano la regola di selezione intersottobanda e raccolgono fotoni da un’area maggiore delle dimensioni fisiche del dispositivo
stesso, riducendo la corrente di dark senza diminuire la fotocorrente. Il miglioramento delle prestazioni del detector é espresso in termini di area di collezione Acoll e di
focusing factor, l’aumento di campo locale. Queste quantitá sono state estratte
da spettri di riflettivitá presi tramite spettroscopia infrarosso a Trasformata di Fourier
(FTIR) a 300K. Caratteristiche tensione-corrente sono state misurate in condizioni dark e di background (300K) da 4K a 300K, e paragonate ad un dispositivo con la stessa regione attiva ma processato con una faccetta a 45 °. Da queste curve la temperatura di BLIP (Background Infrared Limited Performance) è stata ricavata. Misure di fotocorrente in funzione del bias sono state
prese tramite tecnica con amplificatore lock-in. Le figure di merito responsivitá e detectivity sono state estratte dalle misure di fotocorrente, dopo la calibrazione della potenza
radiativa incidente. Queste misure mostrano un miglioramento di
10K nelle performaneces rispetto al dispositivo
mesa, dimostrando un’elevata
sensibilitá fino a temperatura ambiente.
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Arslan, Yetkin. "Large Format Dual-band Quantum Well Infrared Photodetector Focal Plane Arrays." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610936/index.pdf.
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Quantum Well Infrared Photodetectors (QWIPs) are strong competitors to other detector technologies for future third generation thermal imagers. QWIPs have inherent advantages of mature III-V material system and well settled fabrication technology, as well as narrow band photo-response which is an important property facilitating the development of dual-band imagers with low crosstalk. This thesis focuses on the development of long/mid wavelength dual band QWIP focal plane arrays (FPAs) based on the AlGaAs/GaAs material system.
Apart from traditional single band QWIPs, the dual-band operation is achieved by proper design of a bias tunable quantum well structure which has two responsivity peaks at 4.8 and 8.4 um for midwave infrared (MWIR) and longwave infrared (LWIR) atmospheric windows, respectively. The fabricated large format (640x512) FPA has MWIR and LWIR cut-off wavelengths of 5.1 and 8.9 um, and it provides noise equivalent temperature differences (NETDs) of ~ 20 and 32 mK (f/1.5 at 65 K) in these bands, respectively. The employed bias tuning approach for the dual-band operation requires the same fabrication steps established for single band QWIP FPAs, which is an important advantage of the selected method resulting in high-yield, high-uniformity and low-cost. Results are encouraging for fabrication of low cost, large format, and high performance dual band FPAs, making QWIP a stronger candidate in the competition for third generation thermal imagers
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Alves, Fábio Durante Pereira. "Three-band quantum well infrared photodetector using interband and intersubband transitions." Instituto Tecnológico de Aeronáutica, 2008. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=523.
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This thesis presents the modeling, design, fabrication and characterization of a quantum well infrared photodetector (QWIP) capable of detecting near infrared (NIR), mid wavelength infrared (MWIR) and long wavelength infrared (LWIR), simultaneously. The NIR detection was achieved using interband transition while MWIR and LWIR were based on intersubband transition in the conduction band. The quantum-well structure was modeled by solving self-consistently the Schrödinger and Poisson equations with the help of the shooting method. A sample with three different stacks of quantum wells formed by different configurations of GaAs, AlGaAs and InGaAs, separated by n-doped GaAs contact layers was grown on a semi-insulated GaAs substrate using MBE (Molecular Beam Epitaxy). Intersubband absorption in the sample was measured for the MWIR and LWIR using Fourier transform spectroscopy (FTIR) and the measured peak positions were found at 5.3 and 8.7 ?m, respectively which are within 5% of the theoretical values, indicating the good accuracy of the self-consistent model. The test photodetectors were fabricated using a standard photolithography process with exposed middle contacts to allow separate bias and readout of signals from the three wavelength bands. A 45 degree facet was polished to allow light coupling. Performance analyses were conducted in order to obtain the I-V characteristics, responsivity and detectivity of each detection band. The background-limited infrared performance (BLIP) for the LWIR quantum wells shows an upper operating temperature of about 70 K, limiting the overall device. Photocurrent spectroscopy was performed and gave three peaks at 0.84, 5.0 and 8.5 m wavelengths with approximately 0.5, 0.03 and 0.13 A/W peak responsivities for NIR, MWIR and LWIR bands, respectively. Estimated peak detectivities, limited by the number of quantum well repetitions, are 140, 1.6 and 1.2x109 cm.Hz1/2/W for NIR, MWIR and LWIR, respectively. The overall results demonstrate the possibility of detection of widely separated wavelength bands, in a single pixel device, using interband and intersubband transitions in quantum wells.
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Durlin, Quentin. "Nouvelles structures photodétectrices à base d'antimoniures pour la détection du moyen infrarouge." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS042.
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Le monde des détecteurs infrarouge a été révolutionné, depuis le milieu des années 2000, par l'apparition de nouvelles structures photodétectrices dont les performances surclassent celles des photodiodes. Ces photodétecteurs ont permis le développement d'une nouvelle génération de caméras plus compactes, plus fiables et moins gourmandes en énergie. Cette thèse avait pour objectif l'étude de ces nouvelles structures photodétectrices haute performance à base d'antimoniures pour la détection du moyen infrarouge entre 3-5µm.Les performances d'un photodétecteur dépendent directement de la qualité des matériaux utilisés pour la fabrication de celui-ci. Aussi, le matériau retenu pour faire office de couche d'absorption a donc dans un premier temps été finement caractérisé. Les mesures de durée de vie (DDV) des porteurs minoritaires dans le matériau se sont révélées être les plus pertinentes pour juger de la qualité des échantillons, et il est reporté une mesure de (DDV) à l'état de l'art pour une température de 80K. Le second volet de cette thèse portait sur le dimensionnement d'une structure photodétectrice à l'aide du logiciel de simulations numériques SILVACO. Une structure optimisée a été proposée puis a été fabriquée par épitaxie à jets moléculaires. A partir de celle-ci, des composants ont été réalisés en salle blanche par un procédé technologique standard. Le courant d'obscurité mesuré se situait une décade plus bas que le photocourant typique ce qui s'est avéré très encourageant pour le développement futur d'une filière basée sur ce type de structures. La dernière partie de ce manuscrit propose une piste pour faire varier la longueur d'onde de coupure de la nouvelle structure photodétectrive grâce à l'utilisation d'une couche absorbante à base de superréseaux antimoniuresSince the middle of the 2000's, new infrared photodetectors have been proposed that demonstrate better performances than photodiodes. This type of new detectors allowed the development of the compactness, reliability and energy consumption of the next generation of infrared cameras. The aim of this thesis is to study these new high performance photodetectors based on antimony semiconductors dedicated to the 3-5µm mid-infrared domain.Photodetectors performance strongly depends on the quality of its absorption material that has been characterized by diffenrent techniques. Lifetime measurements were identified as the most relevant criterion the evaluation of material quality. A state-of-the-art lifetime value has been reported at a temperature of 80K. Then, an optimized design of the photodetector has been determined using the TCAD SILVACO software. The photodetector structure has been grown by molecular beam epitaxy and devices were made by a standard fabrication process in clean room. The measured dark current was a decade lower than the typical photocurrent : this confirmed the potential of this new structure to be used as a high performance mid-infrared photodetector. Finaly, we demonstrate that the cut-off wavelength of the detector can be tuned using antimony-based superlattices
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Qu, Junling. "Colloidal semiconductor nanocrystals for optoelectronic applications : photodetectors and light emitting diodes." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS021.
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Les nanocristaux dont la dimension est inférieure à leur rayon de Bohr excitonique peuvent fournir des propriétés optoélectroniques accordables avec la taille. Cela permet d’obtenir des propriétés électroniques à façon. En particulier, le développement de la synthèse par voie colloïdale des nanocristaux en fait des briques élémentaires prometteuses pour des applications optoélectroniques à bas coût. Ma thèse cible deux aspects des dispositifs à base de nanocristaux: les photodétecteurs infrarouges et les diodes électroluminescentes (LED). Ma thèse est d'abord centrée sur la photodétection infrarouge sans métaux lourds utilisant soit la transition intrabande d'Ag2Se, soit des nanocristaux plasmoniques ITO. J'ai étudié leurs propriétés optiques et de transport ainsi que leur spectre électronique. J’ai ensuite testé leurs performances pour la photodétection infrarouge. Les performances obtenues sont mises en perspective par rapport à leurs homologues contenant des métaux lourds. Dans une seconde partie de ma thèse, je me focalise sur les LEDs à base de nanocristaux avec des longueurs d’onde visées à la fois dans le visible et le proche infrarouge. La LED visible conçue à l'aide de nanoplaquettes CdSe/CdZnS montre une faible tension de fonctionnement et la durée de vie la plus longue obtenue pour les LED à base de nanoplaquettes. Ensuite, cette LED est couplée à un photodétecteur PbS maison pour réaliser pour la première fois une communication de type LiFi tout nanocristal. Pour les LED proche infrarouge, j’ai utilisé HgTe comme matériau optiquement actif. En formant une hétérojonction à partir de HgTe / ZnO, une LED infrarouge lumineuse capable d'imagerie active est obtenueNanocrystals with a dimension below their excitonic Bohr radius can provide size-tunable optoelectronic properties, enabling on-demand tailoring of properties for specific applications. Especially, the advance of wet chemistry synthesis of colloidal nanocrystals makes them promising building blocks for the next-generation solution-processible low-cost optoelectronics such as light emitting, sensing, and harvesting. My thesis targets two aspects of the nanocrystal-based devices: infrared (IR) photodetector and light emitting diode (LED). My thesis is first focused on the heavy-metal-free IR photodetection using the intraband transition of self-doped Ag2Se or the plasmonic resonance of remotely doped ITO (tin doped indium oxide) nanocrystals. Before integrating them to photoconductive devices, I study their optical and transport properties as well as their energy spectra. I then test their IR photodetection performance and rationalize their weak performance compared with their heavy metal counterparts. In the second part of my thesis, I advance to the all-solution nanocrystal-based LEDs in the visible and SWIR, with an emphasis on their practical applications. The designed visible LED using CdSe/CdZnS nanoplatelets (NPLs) shows the lowest turn-on voltage and the longest lifetime for NPL-based LED. I also provide insights on the origin of efficiency droop. Then, this LED is coupled with a homemade PbS broadband photodetector to achieve, for the first time, an all-nanocrystal based LiFi-like communication setup. For SWIR LEDs, HgTe is used as IR emitter. By forming a HgTe/ZnO bulk heterojunction in the emitting layer, a bright SWIR LED capable of active imaging is obtained
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Ersagun, Ozlem. "Dark Current Mechanisms And Passivation Of Inassb Infrared Photodiodes On Alternative Substrates." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606875/index.pdf.
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This thesis reports a detailed characterization of indium arsenide antimonide (InAs1-
xSbx) photodetectors grown on gallium arsenide (GaAs) substrate by molecular
beam epitaxy. A combination of polyimide and sulphur and a single layer of
polyimide were used as passivation films in this study. Two different epilayer
structures were used for assessing the detector performance and comparing the
above passivation layers. For the first structure, the optical measurements revealed
that Sb mole fraction was 0.13 and the cut-off wavelength was around 4.1 µm at 80 K. The Sb mole fraction of the second structure was 0.2, and the 77 K cut-off wavelength was 4.8 µ
m. Detailed electrical and optical characterizations were performed on 33x33 µ
m2 test diodes. The photodiodes yielded peak detectivities of ~3.65x1010 and ~1.22x1010 cmHz1/2/W at 80 K for the first and second structures, respectively. Considerable 1/f noise current related with trap-assisted tunneling mechanism was observed in both structures at 80 K. Dark current modeling study showed that the dark current was dominated by the shunt and trap-assisted tunneling mechanisms throughout the entire reverse bias voltages for both detectors. The dark current analysis of variable area detectors fabricated with both epilayer structures revealed that the reverse bias current was mainly generated by the surface leakage in small sized (33x33 µ
m2) detectors for both passivation layers. However, the surface current contribution was observed to be lower for the double layer (polyimide and sulphur) passivated detectors suggesting that it is a better passivation technique.
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Elfving, Anders. "Near-infrared photodetectors based on Si/SiGe nanostructures." Doctoral thesis, Linköping : Surface and Semiconductor Physics, Linköping University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5909.
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Sevison, Gary Alan. "Silicon Compatible Short-Wave Infrared Photonic Devices." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1523553057993197.
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Chu, Audrey. "Couplage lumière-matière au sein de détecteurs infrarouges à base de nanocristaux colloïdaux." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS082.
Full textAbstract:
Les nanocristaux colloïdaux sont des nanoparticules dont la croissance se fait en solution. Lorsque la taille de ceux-ci est suffisamment faible, des effets de confinement quantique apparaissent et leurs propriétés optiques deviennent ajustables avec leur taille. Ces nanocristaux sont en particulier utilisés pour leur luminescence dans le visible mais peuvent aussi être utilisés pour réaliser de la photodétection dans la gamme infrarouge. Les nanocristaux de HgTe et PbS présentent des propriétés d’absorption dans l’infrarouge. Le mécanisme de transport au sein d’un film de nanocristaux induit leur utilisation sous forme de couches minces, réduisant l’absorption et conduisant à des performances modestes. L’objectif de mon doctorat est d’augmenter le couplage lumière-matière au sein de film de nanocristaux afin d’augmenter l’absorption et donc la réponse. En particulier je démontrerai la possibilité de nanostructurer les électrodes afin d’induire des résonances de modes guidés pour des films de nanocristaux. L’utilisation de ces nanoélectrodes induit une augmentation de la réponse de deux à trois ordres de grandeur grâce à une augmentation de l’absorption et du gain photoconducteur. L’utilisation de telles résonances est une méthode versatile puisqu’elle peut être appliquée à différents matériaux, à différentes longueurs d’onde et pour différentes géométries. Enfin dans une dernière partie je présenterai un dispositif permettant d’exalter les propriétés de transport au sein d’un film de nanocristaux. Ce dispositif atteint une détectivité de 1012 Jones à 2.5 µm, 1 V et à 200 K, ce qui est comparable avec des détecteurs conventionnelsColloidal nanocrystals are nanoparticles grown in solution. When their dimension is reduced below the Bohr radius, quantum confinement appears: optical properties depend on the size of the crystal. These nanocrystals are currently used for their visible emission properties but can also be applied for infrared photodetection. Mercury and lead chalcogenide (and in particular HgTe and PbS) absorb in the infrared. The hopping transport associated with nanocrystal array induced the use of thin film. The absorption of such film remains low and so does their performance. My work consists in induce light-matter coupling within a nanocrystal array in order to boost the absorption and the responsivity. Using nanostructured electrodes, it is possible to induce guided mode resonances within nanocrystal thin films. The responsivity of such devices presents an increase of a factor 102 – 103 compared to a film on conventional electrodes due to an enlargement of the absorption and the photoconductive gain both. This method is versatile and can be used for different materials, at different wavelengths and for different device geometries. In a last part, I will show a device that improve transport properties in a nanocrystal film. This device has a detectivity of 1012 Jones at 2.5 µm, 1 V and 200 K, which is comparable with commercial detectors
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Kocer, Hasan. "Numerical Modeling And Optimization Of Hgcdte Infrared Photodetectors For Thermal Imaging." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613126/index.pdf.
Full textAbstract:
This thesis presents a detailed investigation of the performance limiting factors of long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) p on n HgCdTe detectors through numerical simulations at 77 K incorporating all considerable generation-recombination mechanisms including trap assisted tunneling (TAT), Shockley-Read-Hall (SRH), Auger and radiative processes. Numerical simulations under dark and illuminated conditions were performed with different absorber layer thicknesses, material compositions (cut-off wavelengths), trap density, and trap energy level. The results identify the relative strength of the dark current generation mechanisms by numerically extracting the contribution of each G-R mechanism on the detector characteristics with various cut off wavelengths and practically achievable material parameters.
While the provided information can be used as a guide for optimizing the device processing conditions and detector structure, it also enlights the importance of various intrinsic mechanisms on the detector sensitivity.
The results show that the dominant sensitivity degrading trap level depends on the detector cut-off wavelength being about 0.7Eg for LWIR HgCdTe sensors (cut-off wavelength=10 µm) instead of 0.5Eg which is generally believed to be the most efficient R-G level. TAT related 1/f noise dominates the sensor noise even under small reverse bias voltages at a trap density as low as 1E14 cm-3 for sensors with cut-off wavelength >
11 µ
m. Considering the fact that trap densities below this level are rarely reported for HgCdTe material, exceptionally trap-free material is required to achieve desirable imaging performance with these sensors. Simulation results show that Auger mechanism has twofold effect on the sensitivity of the sensor by increasing the dark current and decreasing the photo current of the detector. As to our knowledge, this work is one of the most comprehensive simulation based investigations of the HgCdTe detector performance providing important results that can be used as a guide for optimization of the detector performance in order to meet the demanding requirements of the third generation thermal imagers.
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Eker, Suleyman Umut. "Single And Dual Band Quantum Well Infrared Photodetector Focal Plane Arrays On Inp Substrates." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611601/index.pdf.
Full textAbstract:
Excellent uniformity and mature material properties of Quantum Well Infrared Photodetectors (QWIPs) have allowed the realization of large format, low cost staring focal plane arrays (FPAs) in various thermal imaging bands. AlGaAs/InGaAs and AlGaAs/GaAs materials systems have been the standard systems for the construction of mid-wavelength infrared (MWIR) and long-wavelength (LWIR) QWIPs. However AlGaAs/GaAs QWIP FPAs suffer from low quantum and conversion efficiencies under high frame rate (low integration time) and/or low background conditions limiting the application area of standard QWIPs. This thesis focuses on the growth and development of InP based single and dual band QWIP FPAs. We experimentally demonstrate that QWIPs on InP substrates provide important advantages that can be utilized to overcome the bottlenecks of the standard GaAs based QWIP technology.
InP/InGaAs material system is an alternative to AlGaAs/GaAs for LWIR QWIPs. We demonstrate a large format (640x512) LWIR QWIP FPA constructed with strained InP/InGaAs material system. The strain introduced to the structure shifts the cut-off wavelength from ~8.5 to 9.7 µm with lambdap=8.9 µ
m. The FPA fabricated with the 40-well epilayer structure yielded a peak quantum efficiency as high as 12% with a broad spectral response (&
#8710
lambda/lambdap=17%). The peak responsivity of the FPA pixels is larger than 1.4 A/W with conversion efficiency as high as 20% in the bias region where the detectivity is reasonably high (2.6x1010 cmHz1/2/W, f/1.5, 65 K). The FPA providing a background limited performance temperature higher than 65 K (f/1.5) satisfies the requirements of most low integration time/low background applications where AlGaAs/GaAs QWIPs cannot be utilized due to low conversion efficiency and read-out circuit noise limited sensitivity. Noise equivalent temperature differences (NETD) of the FPA are as low as 19 and 40 mK with integration times as short as 1.8 ms and 430 µ
s (f/1.5, 65 K), respectively. We also experimentally demonstrate that the cut-off wavelength of MWIR AlInAs/InGaAs QWIPs can be tuned in a sufficiently large range in the MWIR atmospheric window by only changing the quantum well (QW) width at the lattice matched composition. The cut-off wavelength can be shifted up to ~5.0 µ
m with a QW width of 22 Å
in which case very broad spectral response (&
#8710
lambda/lambdap=~30%) and a reasonably high peak detectivity is achievable leading to a NETD as low as 14 mK (f/2) with 25 µ
m pitch in a 640x512 FPA. The advantages of InP based MWIR and LWIR single band QWIPs were combined by growing and fabricating a mid format (320x256) dual band QWIP FPA. The FPA provided NETD (f/1.5, 65 K, 19 ms) values of 27 mK and 29 mK in the MWIR and LWIR modes with an impressively low DC signal nonuniformity of ~ 4%. The results clearly demonstrate that InP based material systems display high potential for MWIR and LWIR single band and MWIR/LWIR dual band QWIP FPAs needed by third generation thermal imagers by overcoming the limitations of the standard GaAs based QWIPs under high frame rate (low integration time) and/or low background conditions.
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Duran, Joshua. "Silicon-Based Infrared Photodetectors for Low-Cost Imaging Applications." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton155653478017603.
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Taalat, Rachid. "Réalisation et caractérisation électro-optique de photodétecteurs infrarouges à superréseaux InAs/GaSb." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20208/document.
Full textAbstract:
Ce manuscrit de thèse porte sur l'étude et la réalisation de photodétecteurs infrarouges à superréseaux (SR), constitués d'hétérostructures de semiconducteurs InAs/GaSb. Ces superréseaux InAs/GaSb sont considérés, depuis le milieu des années 2000, comme des structures pouvant satisfaire les besoins de la prochaine génération de photodétecteurs infrarouges (IR). À l'Institut d'Electronique du Sud (IES) de l'Université Montpellier 2, nous maîtrisons la réalisation des structures périodiques à SR par Epitaxie par Jets Moléculaires sur substrat GaSb et la fabrication technologique des photodiodes pin. Ces composants présentent des performances à l'état de l'art mondial dans le MWIR.L'objectif de mon travail de thèse, financé par la DGA et en collaboration étroite avec l'ONERA, était de contribuer à une meilleure compréhension de la physique du composant et d'améliorer les performances de cette nouvelle filière de détecteur IR. Cette étude s'effectua sur des monoélements (pixels), éléments de base du système imageur IR. En comparant trois structures InAs/GaSb différentes, conçus pour la même gamme spectrale de détection dans le MWIR mais de composition et d'épaisseur différentes (riche en GaSb, symétrique et riche en InAs), nous avons exploité la flexibilité offerte par cette technologie de détecteurs. Cette approche nous a permis de mettre en évidence la dépendance des performances avec la proportion en GaSb. Les résultats obtenus sur les structures asymétriques plus riches en InAs sont à l'état de l'art pour des photodiodes : densité de courant d'obscurité de 5x 10-8 A/cm2 à 77K pour une polarisation inverse de 50 mV. En complément, nous avons réalisé, en collaboration avec le CEA-LETI, la première matrice à SR française. Ces résultats ont contribué à une meilleure compréhension des détecteurs à superréseaux et esquissent des voies d'optimisation prometteusesThis thesis focuses on the study and implementation of infrared photodetectors with InAs/GaSb superlattices (SL). Since the mid-2000s, InAs/GaSb SL are considered as new technology that can meet the criteria of the next generation of infrared (IR) photodetectors. At the Institut d'Electronique du Sud (IES) of the University of Montpellier 2, we control the fabrication of SL periodic structures by Molecular Beam Epitaxy on GaSb substrate and the technological process of pin photodiodes. These devices have performances at the state of the art in the midwave infrared spectral domain.The aim of my thesis work, funded by the DGA and in close collaboration with ONERA, was to contribute to a better understanding of the device physics and improve the performance of this IR detector. This study was carried out on mono-element (pixel), the basic elements of IR imaging system. Comparing three different InAs/GaSb structures, designed for the same detection spectral range (MWIR) but different composition and thickness (GaSb-rich, symmetric and InAs-rich), we used the flexibility offered by this technology detectors. This approach has allowed us to highlight the dependence of performances with the proportion on GaSb in the SL structure. The results obtained on InAs-rich asymmetric photodiodes are at the state of the art: dark current density of 5×10-8 A/cm2 at 77K for a reverse bias of 50 mV. In addition, the first French SL Focal Plane Array has been fabricated and tested. These results contributed to a better understanding of superlattice detectors and outline ways of promising optimization
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Lantz, Kevin Richard. "Organic/Inorganic Hybrid Nanocomposite Infrared Photodetection by Intraband Absorption." Diss., 2011. http://hdl.handle.net/10161/5647.
Full textAbstract:
The ability to detect infrared radiation is vital for a host of applications that include optical communication, medical diagnosis, thermal imaging, atmospheric monitoring, and space science. The need to actively cool infrared photon detectors increases their operation cost and weight, and the focus of much recent research has been to limit the dark current and create room-temperature infrared photodetectors appropriate for mid-to-long-wave infrared detection. Quantum dot infrared photodetectors (QDIPs) provide electron quantum confinement in three dimensions and have been shown to demonstrate high temperature operation (T>150 K) due to lower dark currents. However, these inorganic devices have not achieved sensitivity comparable to state-of-the-art photon detectors, due in large part to the inability to control the uniformity (size and shape) of QDs during strained-layer epitaxy.
The purpose of this dissertation research was to investigate the feasibility of room-temperature infrared photodetection that could overcome the shortfalls of QDIPs by using chemically synthesized inorganic colloidal quantum dots (CQDs). CQDs are coated with organic molecules known as surface ligands that prevent the agglomeration of dots while in solution. When CQDs are suspended in a semiconducting organic polymer, these materials are known as organic/inorganic hybrid nanocomposites. The novel approach investigated in this work was to use intraband transitions in the conduction band of the polymer-embedded CQD for room-temperature photodetection in the mid-wave, and possibly long-wave, infrared ranges. Hybrid nanocomposite materials promise room-temperature operation due to: (i) large bandgaps of the inorganic CQDs and the semiconducting polymer that reduce thermionic emission; and (ii) low dark current due to the three-dimensional electron confinement in the CQD and low carrier mobility in the semiconducting polymer. The primary material system investigated in this research was CdSe CQDs embedded in the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-(1-cyanovinylene)phenylene] (MEH-CN-PPV).
Photoluminescence (PL) spectroscopy of MEH-CN-PPV thin films was conducted to determine the dependence of polymer morphology on deposition method in order to identify a reliable device fabrication technique. Three different deposition methods were investigated: drop-casting and spin-casting, which are solution-based; and matrix-assisted pulsed laser evaporation (MAPLE), which is a vacuum-based method that gently evaporates polymers (or hybrid nanocomposites) and limits substrate exposure to solvents. It was found that MAPLE deposition provides repeatable control of the thin film morphology and thickness, which is important for nanocomposite device optimization.
Ultra-fast PL spectroscopy of MEH-CN-PPV/CdSe thin films was investigated to determine the charge generation and relaxation dynamics in the hybrid nanocomposite thin films. The mathematical fitting of time-integrated and time-resolved PL provided a rigorous and unique model of the charge dynamics, which enabled calculation of the radiative and non-radiative decay lifetimes in the polymer and CQD. These results imply that long-lived electrons exist in the conduction band of the CQD, which demonstrate that it should be possible to generate a mid- to long-wave infrared photocurrent based on intraband transitions. In fact, room-temperature, intraband, mid-infrared absorption was measured in thin films of MEH-CN-PPV/CdSe hybrid nanocomposites by Fourier transform infrared (FTIR) absorbance spectroscopy. In addition, the hybrid nanocomposite confined energy levels and corresponding oscillator strengths were calculated in order to model the absorption spectrum. The calculated absorption peaks agree well with the measured peaks, demonstrating that the developed computer model provides a useful design tool for determining the impact of important materials system properties, such as CQD size, organic surface ligand material choice, and conduction band offset due to differences in CQD and polymer electron affinities.
Finally, a room-temperature, two terminal, hybrid nanocomposite mid-infrared photoconductor based on intraband transitions was demonstrated by FTIR spectral response measurements, measuring a spectral responsivity peak of 4.32 µA/W at 5.5µm (5 volts), and calibrated blackbody spectral photocurrent measurements, measuring a spectral responsivity peak of 4.79 µA/W at 5.7 µm (22 volts). This device characterization demonstrated that while the novel approach of intraband infrared photodetection in hybrid nanocomposites is feasible, significant challenges exist related to device fabrication and operation. Future work is proposed that could address some of these important issues.
Dissertation
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Liu, Kuan-ming, and 劉冠明. "Design and Fabrication of Germanium Quantum Dots Configurations for Near Infrared Photodetection." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/41485894122114831678.
Full textAbstract:
碩士國立中央大學
電機工程學系
102
This thesis produced high-quality and single-crystal Ge quantum dots (QDs) using selectively oxidation of SiGe pillars, and demonstrated Ge-QD P-I-N near-infrared photodetectors with various sizes of Ge QD. The P-I-N photodetectors exhibit various near-infrared photoresponsivities by tuning different sizes of Ge-QD arrays integrated in the photodetectors. Under 2.5 mW illumination at 850, 980, 1310, and 1570 nm, the photodetectors exhibit the photo-current-to-dark-current ratio as high as 28, 15, 2.3, and 1.6, respectively. Under near-infrared illumination, the positive holes confined in the valance band offset between Ge QD and the Si substrate, establishing a built-in electric field (E-field), leading the transient response of the photodetectors as high as 440 MHz. The other topic of this thesis focused the formation of near-infrared photodetectors with a 1-μm-thick Ge QD/Si heterojunction contained various number of Ge QD/Si stacks by using Ultra-High Vacuum Chemical Vapor Deposition (UHV-CVD), and investigated the photoresponsivity of the photodetectors affected by the number of Ge QD/Si stacks. The photo-current-to-dark-current ratio of the photodetectors is 4000 (0.45 mW), 2200 (0.45 mW), 52 (9.4 mW), and 4.2 (5.4 mW) under illumination at 850, 980, 1310, and 1570 nm, respectively. The open-circuit voltage increases with the number of heterojunction of Ge QD/Si, which indicates the increasing built-in E-field improves the photoresponsivity.
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Shen, Yen-yu, and 沈彥宇. "Characterization of Germanium Quantum Dots Phototransistor for Near Infrared Photodetection and Amplification." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/59315495528892879772.
Full textAbstract:
碩士國立中央大學
電機工程學系
102
This thesis focuses on the application of Germanium quantum dots (QDs) phototransistor for the near infrared photodetection and amplification. The main characteristics of the Ge QD phototransistor is based on the framed structure of typical metal-oxide-semiconductor field-effect transistor (MOSFET), incorporating 50 nm Ge QDs embedded in gate dielectrics. The heterostructures of 50 nm Ge QDs/SiO2/Si were formed using the selective oxidation of poly-SiGe pillar, incorporating Ge QDs array into the gate dielectrics of MOSFET, which is a compatible approach with prevailing CMOS technologies. In the darkness, the Ge QDs phototransistors exhibit low off-state leakage (IOFF ~0.27 pA/μm2), high on-off current ratio (ION/IOFF ~106), and good switching behavior (subthreshold slope = 195 mV/dec), indicating a good hetero-interfacial quality of Ge-on-Si due to a 4-5 nm-thick interfacial SiO2 layer between Ge and Si. Additionally, under 0.9 mW illumination at 850 nm, the Ge QDs phototransistors exhibit significant photo-current-to-dark-current ratio and high photoresponsivity as high as 6×106/0.67 A/W at off-state (VG = -5 V), and 64/2.7 A/W at on-state (VG = 4 V), respectively, indicating the strong absorption of Ge QDs. These results offer a great promise for future Si-based optical interconnection applications. Moreover, the temperature-dependent measurement was conducted from 300 to 77 K at the dark and under illumination in order to identify the mechanisms of photocurrent of Ge QDs phototransistors. As temperature decreasing, the photocurrent is invariant indicating the origin of the photoresponse is related to Ge QDs not the traps. The 3-dB bandwidth of Ge QDs phototransistors is ~410 MHz.
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HUNG, WEI-TING, and 洪偉庭. "GeSn floating-base heterojunction phototransistors on silicon for short-wave infrared photodetection." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9p37y6.
Full textAbstract:
碩士國立中正大學
機械工程系研究所
107
In this study, the purpose is to develop silicon based GeSn alloy pnp phototransis-tors, by using molecular beam epitaxy (MBE) with low-temperature growth techniques. For CMOS compatibility, use of Group IV semiconductor materials, GeSn, is made and a heterojunction phototransistor (HPT) is fabricated. Germanium photodetectors cover full spectral range of telecommunication(1260~1675 nm), but still cannot be operated in the 2 μm communication range. In this study, we show that adding Sn into Ge can shrink the direct and indirect bandgap effectively, thereby extending the absorption edge to short-wave infrared region. The use of heterojunction transistor improves the quantum efficiency and addition of the GeSn absorber extends photodetection thereby increasing the photocurrent injec-tion. In terms of phototransistors, we perform the electrical properties measurement. At a bias voltage of 1 V, the leakage dark current of bulk and surface is2.03×10−4 A/cm and 0.599 A/cm2, respectively. Then, we perform the photoelectric properties measure-ment. At the source wavelength of 1800nm, responsivity can reach 0.387 A/W with the a bias voltage of 0.5 V, and the highest responsivity, 0.72 A/W is located at 1450 nm. The results show that the photodetection range is extended to 1950 nm, successfully. The larg-est photocurrent gain is obtained at wavelength of 1660nm. Lastly, we show that the anti-reflection coating cause the reflection to decrease nearly 20% and improve the responsiv-ity about 2 times in this study. In conclusion, we demonstrate the first Si-based floating base structure GeSn p-n-p HPTs for SWIR photodetection which is CMOS compatible. In future, high current gain can be achieved by optimizing the thickness and doping concentration of emitter, base, and collector. Furthermore, replacing passivation to anti-reflection film can not only de-crease the dark current, but also improve the responsivity.
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Yu, Chung-Hua, and 喻忠華. "Study of broadband infrared photodetection and thermal radiation control on silicon based micro-nano hybrid structures." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/82608954397987963817.
Full textAbstract:
碩士國立臺灣大學
材料科學與工程學研究所
105
The infrared absorption spectrum in midinfrared (mid IR, MIR) spectral range contains “fingerprints” of the most common molecular bonds, key to sample composition analysis and is useful for nondestructive and rapid analysis for material characterization and environment monitoring. Furthermore, the MIR light can be applied to thermal image that is corresponding spectral regime for the thermal radiation from room temperature to several hundred degrees Celcius. On the other hand, near infrared (NIR) spectral range is the regime for optical telecommunication. To sum the above, photodetectors, light sources, and thermal dissipation routes in infrared spectral range all perform the importance in various applications. However, the study in this field so far faces several problems, including processes being complicated, slow, expensive, and not compatible with silicon semiconductor process technology (Si-CMOS, Silicon-Complementary Metal-Oxide-Semiconductor). This thesis would like to develop silicon-based photodetectors working from NIR to MIR regimes, Moreover, using the broadband, high absorption of silicon-based structures to develop thermal radiation based heat dissipation structures. In the first part of this thesis, the titanium nitride (TiN) thin film coated on a deep trench silicon structure to generate low reflection and high absorption properties at resonace wavelengths. Also, TiN thin film can form a good Schottky contact with a p-Si substrate. When the resonanct wavelength at 10.6 μm, the optical absorption could be as high as 60.7%. The responsivity could be up to 0.632mV W-1 under CO2 laser (light intensity=4.26W/cm2) illumination and up to 246mV W-1 under low light intensity light source (light intensity=2.64mW/cm2). The excess voltage has great linear relationship with light intensity, and the measurement was highly repeatable. Also, the measurements were all conducted at room temperature which could satisfy the low energy comsumption demand. In the second part of this thesis, we would like to develop photodetectors working in optical telecommunication spectral range. We used back illuminated schemes of TiN thin film along with deep trench silicon structure that can perform broadband, wide angle of low reflection, and high absorption properties. The optical absorption was up to 85.7% at 1550nm wavelength. TiN thin film formed a Schottky contact with p-Si substrates and the locations which carriers generated were close to the contact surfaces. When devices conducted at zero bias, the responsivity was up to 0.412 mA W-1, and detectivity was 5.02 x109 Jones. The responsivity of the devices differed very little when the angle of incident light below 60o. In addition, we also demonstrated the photovoltage detection ability of the devices and its responsivity was 15.4mV W-1. In the the third part of this thesis, the TiN thin film and deep trench silicon structure performed broadband high absorption properties in MIR. The high absorption also represented the high emission property. By the optical measurement of practical devices, the average absorption was up to 61%. Use white light of Xe lamp along with AM1.5 filter in order to simulate solar light heating the devices. Its equilibrium temperature was lower 8.5oC than the flat film sample and the decay time constant of cooling was also 3 seconds shorter. The deeper trench, the closer the hole to period ratio (H/P) to 1/3, the lower the equilibrium temperature of the device, certificating that the high absorption conditions in simulations with lower equilibrium temperature. In the the fourth part of this thesis, we used gold (Au) thin film combined with shallow trench silicon oxide (SiO2) and successfully designed a narrow band and high emission device at specific wavelength (4.3μm), making it a high quality factor (Peak wavelength/ Full width at half maximum, Q= λ/Δλ), low energy comsumption thermal emission light source in MIR. In addition, this structure could also apply to enhance the surface enhanced infrared absorption because of its high electric field on its surface. The structure made CO2 absorption signal enhanced 5.3 times without changing the absorption peak ratio of the two peaks of CO2.
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Anumol, S. "A Study of Synthesis and Optoelectronics of Copper Iron Chalcogenide Nanocrystals." Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4984.
Full textAbstract:
Copper iron chalcogenides constitute a promising class of optoelectronic materials courtesy of their narrow bandgaps and earth abundant constitution. However, they are yet to receive the attention they deserve due to the lack of easy synthetic protocols and poorly understood material properties. Discordant narratives in the literature regarding their optoelectronic properties has also prevented them from being used for device-based applications. This thesis is aimed at rectifying a few of these issues. The objective of this thesis is to synthesize and study the properties of copper iron chalcogenide nanocrystals viz., CuFeS2 and CuFeSe2, and to explore their utility in the context of optoelectronic devices.
Chapter 1 provides a brief introduction to the fundamental concepts related to the work described in this thesis. The chapter further discusses the scope and motivation behind the work carried out in this thesis.
Chapter 2 describes our efforts to assign the nature of a feature in the optical absorption spectrum of CuFeS2 nanocrystals occurring at ~500 nm. Using a combination of steady-state and time-resolved optical spectroscopy as well as transport measurements we assign the feature to be a localized surface plasmon resonance and attribute the peculiar properties exhibited by CuFeS2 nanocrystals to this feature. Further, the transport measurements revealed that films of these nanocrystals can support a photoresponse.
Chapter 3 describes the fabrication and characterization of a broadband photodetector based on CuFeS2 nanocrystals. Briefly, we fabricated heterojunctions of CuFeS2 nanocrystals with bulk n type silicon and demonstrated a broadband photoresponse from 460 nm-2200 nm with response time of the order of microseconds. The photodetector was further found to possess a photothermal response that is bolometric in nature, which allows the device to sense hot objects at room temperature.
Chapter 4 describes our efforts to synthesize and study the optoelectronic properties of CuFeSe2 and CuFeSe2-CdS core-shell nanocrystals. We synthesized CuFeSe2 nanocrystals and studied their properties using structural, optical and electrical characterization techniques. The nanocrystals were found to have a very narrow bandgap of 0.11 eV and were also found to exhibit a plasmon resonance at ~410 nm. We further found that the films of these nanocrystals exhibited a photoresponse in the MIR, thus making them a promising candidate for infrared photodetection. We further synthesized highly luminescent CuFeSe2-CdS core-shell nanocrystals and found that the energetic position of their emission is greatly dependent on the sequence in which the shell growth precursors are added to the reaction mixture. Using optical and structural characterization techniques, we find that there are two different core-shell variants that result from the synthesis and their formation is determined by which one of the shell growth precursors is added to the reaction mixture first. The key difference between the two variants were found to be the presence of an interfacial CdSe layer which occurs whenever the cation precursor is added to the reaction mixture first.
Chapter 5 describes the synthesis of CuFexGa1-xS2 nanocrystals, a hitherto unknown composition of nanocrystals. Using alloying as a strategy, we synthesized CuFexGa1-xS2 nanocrystals corresponding to different Fe:Ga ratios. The properties of the resulting nanocrystals were found to be greatly dependent on their composition.
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Kun-Jheng, Wu. "Superlattice Infrared Photodetector with Double Barriers." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2407200611344000.
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Wu, Kun-Jheng, and 吳坤政. "Superlattice Infrared Photodetector with Double Barriers." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/98695020831974367625.
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碩士國立臺灣大學
電子工程學研究所
94
The superlattice structure has been used extensively in the infrared photodetectors. In this thesis, our purpose is to fabricate a superlattice infrared photodetector (SLIP) with high detectivity. First, we propose a novel structure for the superlattice infrared photodetector. The structure is composed of a 15-period superlattice sandwiched between two asymmetric blocking layers. By the simple fabrication process and the measurement setup, we can measure the electrical and optical properties of our devices. This structure shows asymmetric current-voltage characteristic and different photoresponse when we switch the bias polarity. To obtain more information, we change the etching depth and fabricate two detectors Sample A and Sample B. Sample A is with the original structure and Sample B is the detector with only one barrier. The experiment data reveals that the responsivity and detectivity of Sample B are better than that of Sample A. By the comparison of these two detectors, we propose the operational mechanism and have further understanding of the asymmetric current-voltage characteristic. Furthermore, Sample B shows the promising detectivity in comparison with Sample A. This result is helpful for us to improve the performance of our detectors.
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Hu, Ho-Cheng, and 胡合城. "Studies of Quantum Dot Infrared Photodetector." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/61943101035285331011.
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碩士國立交通大學
電子工程系
89
We have designed and fabricated self-assembled InAs-GaAs quantum dot infrared photodetectors which adjusts the dot’s density and impurity’s doping level and growths AlGaAs between quantum dots to decrease dark current. Compare to traditional InAs/GaAs QDIP, our new structure successfully decrease dark current by several order. The intersubband transition peak is observed at the wavelength of 6.5 and shows encouraging normal incident performance characteristic, with detectivity of at a bias of 0.8V and T = 77K . It also shows large responsivity and photoconductive gain which just corresponds to theoretical prediction . The measurements show that our new structure indeed improves original QDIP .
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Tsai, Cheng-Hsuan, and 蔡承軒. "InAs/GaAs quantum dot infrared photodetector." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/80344603298725210425.
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碩士國立清華大學
光電工程研究所
93
Five InAs/GaAs quantum dot infrared photodetector (QDIP) samples with different device structures are discussed in the thesis. The QDIP samples are grown on semi-insulating (100) GaAs substrate by Riber Epineat solid source molecular beam epitaxy (MBE). High dot density of 1 x 1011 cm-2 and short average distance between neighboring quantum dots of 7.4 nm are observed from the uniform quantum dot distribution atomic force microscopy (AFM) image. Three different energy levels are distinguished from the photoluminescence (PL) spectra. The phenomenon is attributed to the state filling effect. The wetting layer formed and mediated the electronics interaction between the barrier states and the localized quantum dot states. Transitions from the occupied quantum dot states to the wetting layer or to the continuum states will result in infrared detection, such that the response signals of a fabricated QDIP devices exhibit the same energy position as the shifted PL spectra relative to the energy of wetting layer. 10- and 30-period InAs/GaAs QDIPs are investigated in the thesis. Lower dark current for 30-period device is attributed to the increase of quantum dot period such that the total barrier thickness is increased. The dark current of the QDIP increases rapidly with temperature, which is due to its exponential dependence on temperature. Such that the background-limited performance (BLIP) temperature can be observed from the temperature varying current-voltage measurement. Since the dark current at higher temperature can be inhibited effectually by higher activation energy in 30-period device, higher BLIP temperature of 60 K for 30-period device can be observed. As a result, 30-period device can still detect the spectral response at 100K while 10-period device can only detect the spectral response at about 50 K. The depression of dark current and the enhancement of responsivity are observed for sample with higher period numbers. In order to investigate the effect of doping density within quantum dots to the performance of QDIP, wafers with InAs quantum dot doping densities varied from 2 x 1018 cm-3, 1 x 1018 cm-3, 5 x 1017 cm-3 to undoped are also investigated. In all silicon doped samples, the PL spectra emitted from quantum dots show multi-peaks emission base on the state filling effect. However undoped sample exhibits only a unique peak. The activation energy increases with decreasing quantum dot density. Such that the dark current can be inhibited effectually with lower quantum dot doping density. The undoped device has the highest BLIP temperature because of its high energy barrier, such that the best operation temperature of 200 K is observed for undoped device. Since higher energy barrier with lower quantum dot doping density not only inhibit the dark current effectually, but also inhibit the photocurrent. There must be an optimum quantum dot doping density of QDIP to design.
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Lin, Tsung-Hsiao, and 林宗孝. "Near Infrared Crystal Germanium film Photodetector." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/25637550710516418917.
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碩士國立中央大學
光電科學與工程學系
103
The particular metal-germanium-metal photodetector (PD) is investigated in this research. Germanium has good absorption coefficient in near infrared such as 850nm, 1310nm and 1550nm which are commonly used in optics communication. Unfortunately, the prohibitive cost of germanium wafer makes it difficult to popularize. Radio frequency (RF) sputtering system is used to deposit single crystal intrinsic germanium film to fabricate the photodetector. It not only keeps performance of Ge but also reduces the cost more than a factor of five. In this investigation, interdigitated electrodes are used on the devices with the purposes of a relative easy process for high-speed devices and a comparable process for the integrated circuit. Three different substrates are used to fabricate photodetectors including n-Si, p-Ge and i-Ge/n-Si. Responsivities and frequency responses are measured and analyzed. Besides, the effect of the Ge thin film on the device was also discussed. The responsivity of PDs are 0.46A/W, 0.257A/W and 2.71mA/W for n-Si, p-Ge and i-Ge/n-Si respectively. The frequency response can be achieved 43.35MHz for Si-based MSM PD.
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Chang, Chia-Yu, and 張嘉佑. "Polymer Near-Infrared Photodetector and its application." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/17691196302665307830.
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Hsu, Chi-Hsiu, and 許齊修. "P- doped Ge quantum dots infrared photodetector." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/64446670494337617929.
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碩士國立臺灣大學
電機工程學研究所
89
Ge quantum dot infrared photodetectors are predicted to have some advantages, such as exhibiting a lower dark current and increasing carrier capture and relaxation time, over conventional quantum infrared photodetectors. While most quantum well infrared photodetectors only weakly response normal incident light, the photoresponse of a Ge QDIP is expected to be sensitive to the normal incident light. In addition, because Ge dots can be grown on a Silicon substrate, Ge QDIPs also provide us a way of the monolithic integration between the detectors and the readout circuits with the mature silicon based technology. In this thesis, we were performed the Ge quantum dots photodetector on Si. In this thesis, we studied the implementation and the performance of the Ge quantum dots photodetectors grown on silicon substrates by using molecular bean epitaxy. In order to improve the device yield rate, a recipet of the wet etching solution is introduced. The fabrication process, experimental setup will be presented. We found that increasing the thickness of the blocking layer can reduce the dark current. The background-limited performance of the fabricated device is up to 80k. In addition, the band diagrams of the devices are studies by the photoluminscence and photoresponse spectra. In summary, our results provide some preliminary understandings of Ge dot infrared photodetectors.
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Lin, Ruei-Long. "Infrared characteristics of SiGe on SOI and heterojunction internal photoemission infrared photodetector." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1807200623381300.
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Lin, Ruei-Long, and 林瑞龍. "Infrared characteristics of SiGe on SOI and heterojunction internal photoemission infrared photodetector." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/66972286302599566531.
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碩士國立臺灣大學
電子工程學研究所
94
Recently, infrared detectors provide greatest contributions and functions in military, medical and astronomy. In order to integrability with the readout circuitry, we think highly of the devices mainly fabricated by SiGe. And the Si1-xGex/Si heterojunction internal photoemission (HIP) infrared photodetectors have many advantages, such as excellent uniformity, sensitivity to normally incident radiation, higher responsivity and easier integration with readout circuitry. Besides, silicon-on-insulator (SOI) technology has been used in CMOS application in recent years, and it have many advantages, such as low leakage-current, low parasitic capacitances, low power and high speed. In this thesis, SiGe/Si heterojunction internal photoemission infrared photodetector has been fabricated on SOI wafer. The infrared characteristics of the structure are measured by Fourier Transform Infrared (FTIR) spectrometer.
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SHEN, JIAN-YU, and 沈建宇. "Superlattice Infrared Photodetector and 1-D Detector Array." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/82171363791662084833.
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碩士國立臺灣大學
電子工程學研究所
91
The superlattice infrared photodetectors have drawn much attention since the observation of intersubband absorption in the far infrared region. For thermal imaging application, the detectors must have high background limited performance temperature TBLIP and 1-D or 2-D (Focal Plane) detector arrays have been used instead of the single detector. In the thesis, we first investigated the effect of the doping density in the superlattice. By the simple fabrication process of samples into devices, and the measurement setup, we can measure the electrical and optical properties of our devices. With comparison the characteristics of the SLIPs with high doping density (1x1017cm-3) and low doping density (5x1016cm-3), it shows that the SLIPs with low doping density has better background limited performance temperature TBLIP, responsivity, quantum efficiency, and detectivity due to the decrease of the impurity scattering. The new fabrication process of 1-D detector array is illustrated. The experimental results show that the response of the detector array is smaller than single device, but the dark current of detector array is much smaller than single device. It leads to the larger detectivity of detector array. By increasing the contact area of metal ring and tilted angle of V-grooves for larger responsivity, it will be a new method to fabricate 1-D detector array.
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Lin, Ding-Jyun, and 林鼎鈞. "Modeling and Simulation of Quantum Well Infrared Photodetector." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/14009147227176627338.
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碩士國立臺灣大學
電子工程學研究所
103
The quantum-well infrared photodetectors (QWIPs) have become research focus in recent years due to its many inherent properties, such as highly sensitive, stability, higher fabrication uniformity, and better production yield. In addition, QWIPs can be fabricated into an imaging system with a large area, low power, low cost by using a high-sensitivity focal plane array (FPA). In order to study the basic processes of a quantum structure devices, we must know the relations between the external physical properties and the internal parameters. However, the measurement of internal parameters is very difficult. Therefore using computer simulation and device modeling is a better way to analyze quantum structure devices. In this Thesis, the electronics performance and the optical performance of a QWIP fabricated with GaAs/AlGaAs superlattice material are discussed. And the characteristics of this QWIP is theoretically analyzed and studied by numerical simulation with MATLAB. A Graphical User Interface (GUI) and SPICE-compatible model are then built for front-end and back-end designers to use. Besides, QWIPs with different quantum structures are compared and theoretically analyzed by simulation. Therefore, we can accelerate the device development process. In addition, the SPICE-compatible model is used in the system-level simulation of QWIP and readout integrated circuit (ROIC) in HSPICE, which results are very close to the expected results.
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Lien, I.-Chun, and 連翊鈞. "Investigation of Graphene Applied on Near Infrared Photodetector." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/33957835316435088911.
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碩士國立中央大學
照明與顯示科技研究所
105
A graphene-germanium-graphene photodetector (GSG PD) is investigated in this research with transparent graphene electrodes. Germanium is a good absorption coefficient material in near infrared wavelength including 850 nm, 1310 nm and 1550 nm for optics communication. Generally, the metal electrode was utilized for the photodetector applications. However, there were a lot of light loss for the non-transparency. In recent years, graphene has been found to be a good transparent conductive film (TCF) with a two-dimensional monolayer composed by sp2-bonded carbon atoms. Due to its exceptional electrical conductivity and high optical transmittance especially including near infrared, graphene is one of the promising candidates for TCFs. Therefore, the higher photo-current and responsivity of the device with graphene can be achieved. In this investigation, interdigitated graphene electrodes were applied to a near infrared photodetector. We used a n-type germanium as the substrates and graphene layers as the interdigitated electrodes of the photodetector. The interdigitated graphene electrodes were prepared by chemical vapor deposition (CVD), and transferred to the substrate first, then patterned by O2 plasma. The responsivity of the n-Ge PD was 0.39 A/W, 0.59 A/W and 0.77 A/W for the wavelength 850 nm, 1310 nm and 1550 nm of the incident light, separately. And the photo to dark current ratio was over three orders.
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Lee, Cheng-De, and 李政德. "Infrared Imaging Analyses for InAs/GaAs Quantum Dot Infrared Photodetector Focal Plane Array." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46739111721356553893.
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碩士國防大學中正理工學院
電子工程研究所
95
Two 256×256 focal plane arrays (FPAs), 30 and 10 stacked InAs/GaAs quantum dot infrared photodetector (QDIP) structure grown by solid-source molecular beam epi-taxy (MBE) and metal organic chemical vapor deposition (MOCVD) technique, were demonstrated have dual-band mid- (2.7~ 5.6μm) and long- (7.5~ 13.5μm) wavelength normal-incident detection ability without extra grating and passivated process on surface. The 256×256 QDIP FPA hybridized with snapshot-mode readout integrated circuit (ROIC) was mounted in a 68 pin leadless ceramic chip (PLCC) carrier which was in the testing dewar with IR optical cold spectral filters of the 2.9~ 5.5μm and 6.5~ 14.5μm for the dual-band IR detections, respectively. The testing scheme for thermal imaging uniformity of the InAs/GaAs QDIP FPA has been proposed and calibrated using a plane-typed blackbody source of a high temperature of 3731K and lower temperature of 300K for the two-point temperature correction. The averaged of spe-cific detectivity (D*) and operability of the QDIP FPA have reached 1.5 1010 cm-Hz1/2/W and 99% at 80K, respectively. The dominant noise equivalent temperature differences(NEDT) of typical figure of merit for QDIP thermal imaging module op-erated under temperature 80K, and integration time 32ms with infrared optics and two-point temperature correction( =300K and =473K), MBE grew QDIP FPA at biases voltage –0.7 V are 1.065K(Mid-wavelength IR) and 131mK(Long-wavelength IR) for TH, MOCVD grew QDIP FPA at biases voltage –0.25 V are 171mK (Mid-wavelength IR) and 44mK (Long-wavelength IR) for TH, respectively. Mean-while, it is worth to note that these are the first confirmation for dual-band detections of FPA from direct InAs quantum dots matrix embedded in heterostructure GaAs. In the future, the dual-band IR QDIP FPA would be one of the important candidates for hy-per-spectral detection and thermal imaging fusion application.
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Hsieh, Kuang-Jou. "Subwavelength Metallic Grating Structure on Quantum Well Infrared Photodetector." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2407200611185100.
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Lai, Ching-Hung, and 賴景鴻. "Characteristics of Metallic Grating on Quantum Well Infrared Photodetector." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/30242267441707466814.
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碩士國立臺灣大學
電子工程學研究所
95
Electromagnetic wave exited around metallic grating and transmitted through grating is complicated and interesting. Recent studies about subwavelength metallic structure were mainly experiments measuring transmission spectrums which photodectors were set vary far from the sample. We wanted to understand the characteristics of grating near the sample. We fabricated grating structure on QWIP and the active region of QWIP is under the surface about 1 μm. By observing spectral response of QWIP with grating, we successively found fundamental characteristics about grating and there was a good correspondence to transmission spectrums. The experiments showed that the grating peak appeared at similar position in response of QWIP and transmission spectrum of sample, dominated by period of grating and refractive index of substrate. The grating peak of QWIP experiment was excited by TM incident light, but TE incident contributed peak in transmission spectrum, due to the distance of the measurement. We tuned the grating peak to structure peak to enhance the responsivity. In the mean time, we discovered that the edge coupling provided a large part of response, which came from TM incident light in Brewster’s angle. Normal incidence of hollow frame also provided response because of finite size effect. We discovered that the grating thickness could raise the ratio of TM over TE mode, because the TE mode decayed faster than TM mode. But it is a trade off that the total responsivity was decreased. At last, we could embed grating in to QWIP, the grating was much closer to the active region of QWIP. More quantity of exited wave absorbed to enhance responsivity. On the other hand, as the thickness increase, the transmitted electromagnetic wave decays, less wave went through grating to decrease responsivity. We could find some balance between these two factors.
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Hsieh, Kuang-Jou, and 謝寬洲. "Subwavelength Metallic Grating Structure on Quantum Well Infrared Photodetector." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/46740722933625407625.
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碩士國立臺灣大學
電子工程學研究所
94
In this work, we have used metallic grating to diffract the normal incident radiation. Both TE-polarized and TM-polarized light can be detected by QWIP due to finite-size grating effect. For the response of 10.5 μm, we find polarization selectivity is more obvious under backside-illumination among the three different incident directions including normal incidence of 45o-facet, top and back side. And then, we fabricate two devices with the same grating period but different slit areas for topside-illumination. Polarization selectivity is proportional to the slit area. In the case of different incident light angle, polarization selectivity is the largest for the incident angle of 30o. In summary, the experimental results confirm the applicability of QWIPs with grating structure for normal incident light coupling and the tunable response shape. Polarization selectivity is also proposed to improve the photodetector performance. Finally, the above phenomenon is observable in our experimental results.
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TSAI, YAO-JEN, and 蔡曜任. "The Investigation of InAs/GaAs Quantum Dot Infrared Photodetector." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/46735982971651626160.
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碩士國立臺灣大學
電機工程學研究所
89
In this thesis, the electrical and optical characteristics of InAs/GaAs quantum dot infrared photodetectors (QDIP) prepared by MBE have been studied in detail. The device fabrication processes and measurement system are described. Several phenomena of QDIP are observed and explained. QDIP without blocking barrier shows high responsivity and performance. Broadband detection spectra of QDIP is observed. There are three distinct region of photocurrent as a function of bias. With increasing biases, the photocurrent reaches its maximum value. This is negative differential conductance (NDC) is attributed to the local high field region at low temperature. QDIP is regarded less polarization-sensitive, which is observed in the experiment. In order to understand the influence of the blocking barrier, the single-side Al0.3Ga0.7As barrier is adopted. The current transport mechanism of QDIP with single-side barrier behaves similar to the Mott barrier. The dark current is successfully suppressed by the blocking barrier and the operation temperature is improved. QDIP and the superlattice infrared photodetector (SLIP) are compared. SLIP exhibits narrow band detection spectra, low absorption of TE mode, and similar performance at high temperature operation.
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Tsai, Chiou-Yun, and 蔡秋雲. "The Characteristics of InAs/GaAs Quantum Dot Infrared Photodetector." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/76669589348610532204.
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碩士國立臺灣大學
電機工程學研究所
90
The self-assembled InAs quantum dots (QDs) growth mechanisms are investigated by using the AFM, SEM and PL. The growth mechanism process can be separated to three stages by the InAs coverage thicknesses: (1) The InAs thickness is too thin to form QDs. The sprayed InAs material forms the thin film, i.e. the wetting layer. (2) The InAs thickness is sufficient to form QDs that are free from dislocations. (3) With further InAs coverage thickness, the near QDs are combined to the 3D islands with dislocations. The single QD’s shape is not the simple pyramid- like but more complicated. There are at least two facet groups to form QDs. The InAs/GaAs quantum dot infrared photodetectors (QDIPs) with two AlGaAs barrier layers are studied. The negative differential conductance (NDC) is observed. Increasing the barrier height will improve the background limiting performance (BLIP) temperature of QDIPs. QDIP adopted 3 ML InAs QDs are less polarization-sensitive than that adopted 2.2 ML InAs QDs. It is because the aspect ratio of height to radius of 3 ML InAs QDs is higher than that of 2.2ML InAs QDs. The photovoltaic effect of QDIPs adopted undoped QDs is resulted from the wetting layers of QDs, which cause the asymmetrical band diagram at zero bias of the QDIP.
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Balakrishnam, Raju J. "Design, Fabrication And Characterization Of Corrugated-Quantum Well Infrared Photodetector." Thesis, 2005. https://etd.iisc.ac.in/handle/2005/1426.
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Balakrishnam, Raju J. "Design, Fabrication And Characterization Of Corrugated-Quantum Well Infrared Photodetector." Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1426.
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