To see the other types of publications on this topic, follow the link: Light gas gun.
Dissertations / Theses on the topic 'Light gas gun'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Light gas gun.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Kim, Hyundae. "Study of a light-gas gun for launching active transient internal probes /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9997.
Full text
2
Landemoo, Viktor. "Lättgaskanonens innerballistik : Teori, simulering och parameterstudie." Thesis, KTH, Maskinkonstruktion (Avd.), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297861.
Full textAbstract:
En lättgaskanon är en typ av kanon som används vid experiment där mycket snabba förlopp är av intresse, till exempel hypersonisk strömning och höghastighetskollisioner. Kanontypen når betydligt högre hastigheter än en konventionell kanon då projektilen accelereras genom eldröret av en gas med låg molekylmassa som vätgas eller helium istället för krutgaser. Denna lättgas komprimeras först till högt tryck och temperatur i pumptuben av en kolv som accelererats av en krutladdning. Pumptuben är ett rör anslutet till eldröret som initialt är frånskild av ett membran. För kanonen kan en mängd olika parametrar varieras och hur dessa ska väljas för att en viss mynningshastighet ska nås är inte självklart. Vid FOI har val av parametrar historiskt gjorts baserat på erfarenhet och genom experiment vilket kan vara tidsödslande. Syftet med examensarbetet var därför att simulera kanonen och undersöka hur olika parametrar påverkar dess prestanda. Forskningsfrågor som skulle besvaras var hur olika parametrar påverkar projektilens mynningshastighet och vilket utav två eldrörsalternativ som är bäst lämpat för en viss projektilvikt. Det innerballistiska förloppet i kanonen har simulerats för olika parameterkombinationer med ett program utvecklat specifikt för lättgaskanoner vid NASA:s Ames Research Center och modellen har i viss mån kunnat jämföras mot experimentell data. Resultatet av simuleringarna är att mängden lättgas och krut båda har stor inverkan på mynningshastigheten och att högre kolvvikt jämnar ut trycktoppar som uppstår till följd av stötar i gasen. Att ändra membranets öppningstryck ger ingen förbättring av kanonprestandan för den undersökta projektilvikten och utav de två eldrören som undersökts är det med större kaliber mer lämpligt för de aktuella experimenten.A light gas gun is a type of gun which is used for experiments when high velocity phenomena are of interest, such as hypersonic flow and high-velocity impacts. The gun type can reach much higher velocities than a conventional gun as the projectile is accelerated down the barrel by a gas with low molecular mass such as hydrogen or helium instead of combustion gasses. This light gas is first compressed to high pressure and temperature in the pump tube with a piston which is accelerated with a propellant charge. The pump tube is connected to the barrel but initially separated from it with a membrane. A vast array of parameters can be varied on the gun in order to achieve a target muzzle velocity and their selection is not trivial. Historically parameters have been selected at FOI through experience and experiments which can be tedious. The purpose of this thesis was to simulate the gun and investigate how various parameters influence its performance. The research questions to be answered was how the parameters influence the muzzle velocity of the projectile and which of two barrels is the most suitable for a given projectile weight. The internal ballistics of the gun was simulated for various combinations of parameters using a program specifically developed for light gas guns at NASA's Ames Research Center and the model has to some extent been compared to experimental data. The result of the simulations shows that the amount of light gas and the propellant charge have a significant effect of the achieved velocity and that the weight of the piston has a reducing effect on the pressure peaks caused by shockwaves in the gas. Changing the opening pressure of the membrane does not improve gun performance for the investigated projectile weight and of the two barrels investigated the one with larger calibre is better suited for the experiments of interest.
3
Guan, Nan. "Nitride nanowire light-emitting diode." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS372/document.
Full textAbstract:
Les nanofils nitrures présentent des propriétés optoélectroniques extraordinaires et sont considérés comme des matériaux prometteurs pour des diodes électroluminescentes (LEDs), grâce à leur haute qualité cristalline, leurs surfaces non-polaires, leur bonne flexibilité mécanique, leur rapport d’aspect élevé, etc.Cette thèse adresse la croissance, la fabrication, les caractérisations optiques et électriques et la simulation optique des dispositifs à base de nanofils nitrures, avec un accent particulier sur les LEDs à nanofils.Premièrement, cette thèse présente la croissance par épitaxie en phase vapeur aux organométalliques de nanofils nitrures cœur-coquille auto-assemblés contenant des puits quantiques InGaN/GaN sur les facettes plan m avec différentes concentrations d’In. Puis est décrite la fabrication de LEDs utilisant ces nanofils suivant deux différentes stratégies d’intégration (intégrations planaires et verticales).L’intégration planaire est basée sur des nanofils uniques dispersés horizontalement. J’ai proposé une plateforme photonique intégrée composée d’une LED à nanofil, d’un guide d’onde optimisé et d’un photodétecteur à nanofil. J’ai également développé un système d’alignement des nanofils.L’intégration verticale a pour objectif la réalisation de LEDs flexibles reposant sur une assemblée de nanofils verticaux encapsulées dans des polymères. Je montre que ceci permet la fabrication de LEDs flexibles monochromatiques, bi-couleurs ou blanches.Les nanofils épitaxiés sur des matériaux 2D par épitaxie de van de Waals sont faciles à décoller de leur substrat natif. Avec cette motivation, dans la dernière partie de cette thèse, j’ai étudié la croissance organisée des nanofils GaN sur du graphène micro et nano-structuré utilisant l’épitaxie par jets moléculairesNitride nanowires exhibit outstanding opto-electronic and mechanical properties and are considered as promising materials for light-emitting diodes (LEDs), thanks to their high crystalline quality, non-polar facets, good mechanical flexibility, high aspect ratio, etc.This Ph.D. thesis addresses the growth, the device fabrication, the optical and electrical characterizations and the optical simulations of III-nitride NW devices, with a special emphasis on the LED applications.First, this thesis presents the growth of m-plane InGaN/GaN quantum wells with different In concentrations in self-assembled core-shell nanowires by metal-organic chemical vapor deposition. Then, by using these nanowires, LED devices based on two different integration strategies (namely, in-plane and vertical integration) are demonstrated.The in-plane integration is based on the horizontally dispersed single nanowires. I have proposed a basic integrated photonic platform consisting of a nanowire LED, an optimized waveguide and a nanowire photodetector. I have also developed a nanowire alignment system using dielectrophoresis.The vertical integration targets the fabrication of flexible LEDs based on vertical nanowire arrays embedded in polymer membranes. Flexible monochromatic, bi-color, white LEDs have been demonstrated. Their thermal properties have been analyzed.The nanowires grown on 2D materials by van der Waals epitaxy are easy to be lifted-off from their native substrate, which should facilitate the fabrication of flexible nanowire devices. With this motivation, in the last part of this thesis, I have investigated the selective area growth of GaN NWs on micro- and nano- scale graphene by molecular beam epitaxy
4
Sharma, Nikhil. "Characterisation of InGaN/GaN light emitting diodes." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621315.
Full text
5
Feng, Jian. "Power improvement of the InGaN/GaN LED /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202005%20FENG.
Full text
6
Li, Zonglin, and 李宗林. "Reliability study of InGaN/GaN light-emitting diode." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43224155.
Full text
7
Li, Zonglin. "Reliability study of InGaN/GaN light-emitting diode." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43224155.
Full text
8
Girgel, Ionut. "Development of InGaN/GaN core-shell light emitters." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720648.
Full textAbstract:
Gallium nitride (GaN) and its related semiconductor alloys are attracting tremendous interest for their wide range of applications in blue and green LEDs, diode lasers, high-temperature and high-power electronics. Nanomaterials such as InGaN/GaN core-shell three-dimensional nanostructures are seen as a breakthrough technology for future solid-state lighting and nano-electronics devices. In a core-shell LED, the active semiconductor layers grown around a GaN core enable control over a wide range of wavelengths and applications. In this thesis the capability for the heteroepitaxial growth of a proof-of-principle core-shell LED is advanced. A design that can be applied at the wafer scale using metalorganic vapor phase epitaxy (MOVPE) crystal growth on highly uniform GaN nanorod (NR) structures is proposed. This project demonstrates understanding over the growth constraints of active layers and dopant layers. The impact of reactor pressure and temperature on the morphology and on the incorporated InN mole fraction was studied for thick InGaN shells on the different GaN crystal facets. Mg doping and effectiveness of the p-n junction for a core-shell structure was studied by extensive growth experiments and characterization. Sapphire and Si substrates were used, and at all the stages of growth and fabrication. The structures were optimized to achieve geometry homogeneity, high-aspect-ratio, incorporation homogeneity for InN and Mg dopant. The three-dimensional nature of NRs and their light emission provided ample challenges which required adaptation of characterization and fabrication techniques for a core-shell device. Finally, an electrically contacted core-shell LED is demonstrated and characterized. Achieving a proof-of-principle core-shell device could be the starting point in the development of nanostructure-based devices and new physics, or in solving technical problems in planar LEDs, such as the polarization of emitted light, the quantum-confined Stark effect, efficiency droop, or the green gap.
9
Melo, Santos João Miguel. "Hybrid GaN-based optoelectronics for visible light communications." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27924.
Full textAbstract:
Development of light-emitting diode technology is driven mainly by the need for efficient solid-state lighting, but it is also creating opportunities for new applications such as visible light communications (VLC). Here, the solid-state visible light sources are used to transmit data with the added requirement of a short excited-state lifetime so that sources can be modulated at high speed. This research focuses on hybrid optical sources for visible light communications with an emphasis on novel formats of colour-converters for multi-wavelength photoluminescence as well as white-light generation. Such converters include red and green colloidal quantum dots, the organic semiconductor BBEHPV andII-VI / III-V epitaxial structures. Solution-processable and environmentally stable polymeric films based on red and green colloidal quantum dots are demonstrated. Modulation bandwidth up to 24 MHz, photoluminescence quantum yields up to 61% and peak emission tunability across the visible spectrum makes these materials interesting as colour-converters for VLC. Free-space data transmission was demonstrated in this case with data rates up to 400 Mbit/s and 500 Mbit/s using 2-PAM modulation scheme for green and red quantum dots, respectively. Hybrid sources consisting of 450nm InGaN LEDs with capillary-bonded micron-thick ZnCdSe/ZnCdMgSe multi-quantum-well colour-converting membranes with peak emission at 540 nm are reported. After processing, the membrane was capillary bonded onto the sapphire side of the μLED resulting in a maximum converted average power of 37 μW. The -3dB optical modulation bandwidth of the bare LED, hybrid device and II-VI were 79 MHz, 51 MHz and 145 MHz, respectively. Visible light communication using both InGaN LEDs and a InGaN laser diode, down-converted by a red-emitting AlInGaP multi-quantum-well nanomembrane are also reported. Similarly to the previous devices, the AlInGaP nanomembrane was bonded onto the μLED array. For the down-converted laser diode approach, the nanomembrane can be sandwiched between a sapphire lens and optionally onto a distributed feedback reflector. The down-converter structure is remotely excited by the laser diode. Data transmission up to 870 Mb/s using M-PAM andOFDM modulation schemes is demonstrated for the μLED integrated nanomembrane. ODFM transmission at 1.2Gb/s is achieved for the laser diode pumped sample.
10
Malinauskas, Tadas. "Investigation of carrier dynamics in wide bandgap semiconductors by light-induced transient grating technique." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20091215_091652-19632.
Full textAbstract:
III-nitrides, diamonds are extremely promising wide band gap semiconductor materials for optoelectronics and high temperature, high power electronics. Therefore, there is huge scientific interest in investigation electrical and optical properties of these materials. The light induced transient grating technique (LITG) is very suitable for exploration of carrier dynamics which governed by fundamental and defect related properties of materials.
The main goals of the thesis were gain a new knowledge on carrier dynamics in wide bandgap semiconductors (namely GaN, InGaN, and diamonds) by using and developing light induced transient grating technique. The experimental studies on numerous samples, grown at different conditions, combined with extensive measurements in a wide range of carrier densities (1016-1020 cm-3) and temperature (9-300K) was targeted to identify the interplay of radiative an nonradiative recombination mechanisms, to determine carrier lifetime dependence on the excess carrier density, to explain the carrier diffusion coefficient dependence on excitation intensity, to find the optimal materials growth conditions.
A novel heterodyne detection scheme for LITG technique was presented. The heterodyning was achieved by coherently mixing the picosecond pulses of diffracted and scattered light. A phase difference between theses fields was controlled by moving holographic beam splitter (HBS) along its grating vector. LITG signal decay kinetics, recorded at two HBS... [to full text]III grupės nitridai bei deimantai tai platų draustinės energijos tarpą turintys puslaidininkiai, pasižymintys unikaliomis medžiagos savybėmis ir turintys didelį potencialą aukštų temperatūrų, didelių galių, opto/elektroniniams taikymams. Todėl šių medžiagų elektrinės bei optinės savybės pastaruoju metu yra intensyviai tiriamos. Šviesa indukuotų dinaminių gardelių (ŠIDG) metodas labai tinka tyrinėti krūvininkų dinamiką, kuri yra nulemta fundamentinių bei defektinių medžiagos savybių. Pagrindiniai darbo tikslai buvo gauti naujų žinių apie krūvininkų dinamiką plačiatarpiuose puslaidininkiuose (GaN, InGaN bei deimantuose) naudojat bei plėtojant šviesa indukuotų gardelių metodiką. Ištirti didelio nepusiausvirųjų krūvininkų tankio rekombinacijos ir difuzijos ypatumus skirtingo defektiškumo GaN, InGaN sluoksniuose bei sintetiniuose deimantuose. Skaitmeniškai modeliuojant krūvininkų dinamiką nustatyti dominuojančius krūvininkų rekombinacijos mechanizmus bei krūvininkų gyvavimo trukmes, difuzijos koeficientus ir nuotolius. Darbe pristatoma nauja ŠIDG eksperimento schema su holografiniu pluoštelio dalikliu, leidžianti supaprastinti eksperimentą. Ši schema taip pat įgalino heterodininį difrakcijos signalo detektavimą. Parodoma, kad fazės skirtumas tarp signalo ir foninės šviesos gali būti kontroliuojamas keičiant holografinio daliklio padėtį išilgai jo gardelės vektoriaus krypties. Ištyrus didelį kiekį GaN sluoksnių, užaugintų skirtingomis technologijomis bei pasižyminčiu skirtingu... [toliau žr. visą tekstą]
11
GARTER, MICHAEL JAMES. "ELECTROLUMINESCENT DEVICES FABRICATED ON ERBIUM DOPED GaN." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin990545888.
Full text
12
Pope, Iestyn A. "Characerisation of Ingan gan quantum well light emitting diodes." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55927/.
Full textAbstract:
By focussing on the properties of InGaN/GaN quantum well (QW) LEDs the key physical processes relevant to all InGaN/GaN light emitters are studied. These include the strength of the piezoelectric field, the important current pathways and the effect doping densities and anneal temperatures have on device performance. Photocurrent absorption spectra, of 35A Ino.1Gao.9N QW LEDs, were measured for a range of reverse bias. A bias of 8.5 V was necessary to counteract the affect of the internal piezoelectric field. Using this value and an appropriate approximation for the depletion width of a p-z'-n junction the calculated piezoelectric field was (1.9 0.15) MVcm"1, in good agreement with 1.8 MVcm"1 calculated using piezoelectric constants interpolated from the binaries. The absorption spectra of 26A wide Ino.i6Gao.84N QW LEDs exhibit a band tail extending to low photon energies whereas emission occurs from the low energy side of this band tail, suggesting emission occurs from localised potential minima. Light-current (LI) characteristics, measured as a function of temperature, are sublinear and exhibit a distinctive temperature dependence. These characteristics are explained in terms of drift leakage which is exacerbated due to the large acceptor activation energy in Mg doped GaN. The data was simulated using a drift diffusion model and good agreement between experimental and simulated results is obtained providing the model includes the band tailing. Emission and absorption spectra and LI characteristics were measured for 25A Ino.1Gao.9N/GaN QW LEDs subject to four different anneal temperatures of 700, 750, 850 and 900°C. Using a drift diffusion model, incorporating different acceptor concentrations to simulate the effect of different anneal temperatures, good agreement was achieved between the trends seen in the experimental results and those produced by the simulations. This confirms the important roles drift leakage and thermal annealing have on these devices.
13
Trieu, Simeon S. "Enhanced Light Extraction Efficiency from GaN Light Emitting Diodes using Photonic Crystal Grating Structures." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/329.
Full textAbstract:
Gallium nitride (GaN) light emitting diodes (LED) embody a large field of research that aims to replace inefficient, conventional light sources with LEDs that have lower power, higher luminosity, and longer lifetime. This thesis presents an international collaboration effort between the State Key Laboratory for Mesoscopic Physics in Peking University (PKU) of Beijing, China and the Electrical Engineering Department of California Polytechnic State University, San Luis Obispo. Over the course of 2 years, Cal Poly’s side has simulated GaN LEDs within the pure blue wavelength spectrum (460nm), focusing specifically on the effects of reflection gratings, transmission gratings, top and bottom gratings, error gratings, 3-fold symmetric photonic crystal, and 2-fold symmetric nano-imprinted gratings. PKU used our simulation results to fabricate GaN high brightness LEDs from the results of our simulation models. We employed the use of the finite difference time domain (FDTD) method, a computational electromagnetic solution to Maxwell’s equations, to measure light extraction efficiency improvements of the various grating structures. Since the FDTD method was based on the differential form of Maxwell’s equations, it arbitrarily simulated complex grating structures of varying shapes and sizes, as well as the reflection, diffraction, and dispersion of propagating light throughout the device.
We presented the optimized case, as well as the optimization trend for each of the single grating structures within a range of simulation parameters on the micron scale and find that single grating structures, on average, doubled the light extraction efficiency of GaN LEDs. Photonic crystal grating research in the micron scale suggested that transmission gratings benefit most when grating cells tightly pack together, while reflection gratings benefit when grating cells space further apart. The total number of grating cells fabricated on a reflection grating layer still affects light extraction efficiency. For the top and bottom grating structures, we performed a partial optimization of the grating sets formed from the optimized single grating cases and found that the direct pairing of optimized single grating structures decreases overall light extraction efficiency. However, through a partial optimization procedure, top and bottom grating designs could improve light extraction efficiency by 118% for that particular case, outperforming either of the single top or bottom grating cases alone. Our research then explored the effects of periodic, positional perturbation in grating designs and found that at a 10-15% randomization factor, light extraction efficiency could improve up to 230% from the original top and bottom grating case. Next, in an experiment with PKU, we mounted a 2-fold symmetric photonic crystal onto a PDMS hemi-cylinder by nano-imprinting to measure the transmission of light at angles from near tangential to normal. Overall transmission of light compared with the non-grating design increases overall light extraction efficiency when integrated over the range of angles. Finally, our research focused on the 3-fold symmetric photonic crystal grating structure and employed the use of 3-D FDTD methods and incoherent light sources to better study the effects of higher-ordered symmetry in grating design. Grating cells were discovered as the source of escaping light from the GaN LED model. The model revealed that light extraction efficiency and the far-field diffraction pattern could be estimated by the position of grating cells in the grating design.
14
Wang, Xianghua, and 王向华. "Design and laser fabrication of GaN/sapphire light-emitting diodes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45143079.
Full text
15
Deforge, David James. "Performance of the UBC two-stage light-gas gun." Thesis, 1993. http://hdl.handle.net/2429/1668.
Full textAbstract:
The performance of UBC two-stage light-gas gun and the associated diagnostics systems were examined under a variety of shot conditions. In the gas gun, the expansion of gas from burning gun powder propels a piston which, in turn, compresses and accelerates the low molecular weight pump gas. The rising pressure of the pump gas eventually opens a petal valve permitting the pump gas to propel a projectile towards the target. At the front of the projectile is a metal disk - the flyer plate. In a typical experiment, the behaviour of the target material under the high pressure conditions that result from the impact between the flyer plate and the target is examined. In this study, the use of gun powder loads of 46 to 150 g, with helium pump gas, resulted in projectile velocities between 2 and 4 km/s for 5 to 9 g projectiles. The ability to measure the projectile velocity with 0.2% uncertainty was demonstrated. Such resolution is comparable to those obtained with systems used by other researchers. The internal ballistics of the gun were modelled with a 1½ dimension Arbitrary Lagrange Eulerian computer code. The calculations had limited success in obtaining the measured projectile velocity. The calculations were also used to estimate the time difference between the arrival of the piston at a preset location along the pump tube and the arrival of the projectile at a given distance from the muzzle of the launch tube. These calculations showed reasonable agreement with the measured values. Experiments were also performed to examine the orientation and curvature of the flyer plate on impact with target. The size and orientation of the tilt of the flyer plate were relatively reproducible for shots with large copper flyer plates in primarily stress-free sabots. The tilt values with these projectiles were less than 10 mrad. It was also demonstrated that the flyer plate curvature was consistently concave for copper flyer plate projectiles with radii of curvature of approximately 1 m.
16
Chung, Cheng-Ban, and 鐘正邦. "GaN-based light-emitting diode with ZnO nanotexture layer prepared using hydrogen gas." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/9tc247.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
95
ZnO films were deposited on an indium tin oxide (ITO), which was the transparent conductive layer (TCL) of GaN-based light-emitting diodes (LED), by ultrasonic spraying pyrolysis to improve the light output power. The ZnO nanotexture was formed by treating the as-deposited ZnO films with hydrogen. The RMS roughness increased from 5.83 nm to 12.53 nm during treatment for 20 min. Typical current-voltage (I-V) characteristics of the GaN-based LED with a ZnO nanotexture layer have a forward-bias voltage of 3.25 V at an injection current of 20 mA. The light output power of GaN-based LED with ZnO nanotexture layer improved as high as about 27.5% at a forward current of 20 mA.
17
Lin, Ching-Liang, and 林京亮. "Light Enhancement of Thin-GaN Light Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/51951559488289706667.
Full textAbstract:
博士國立中央大學
化學工程與材料工程研究所
96
GaN-based materials have leaped to a brand new stage in the past two decades. The single crystalline and direct band-gap GaN film can be grown on the sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The wavelength of the emitting light from GaN ranges from ultra-violate (UV) to blue light region by doping various indium content. Nowadays, the material of the blue light emitting diodes is based on the GaN material. Pumping phosphors or other wavelength converter by blue light, the white light can be generated. Hence, the GaN material is the key material for white solid-state lighting. For the solid-state lighting applications, the GaN-based LED operates under a high electric power. Under such a high operation power, the heat dissipation is a critical issue. The sapphire substrate of the conventional LED has a poor thermal conduction. Also, the degradation of the electric and optical property would be very serious due to the high operation temperature. Therefore, in this study, the thin-GaN LED device is produced by the wafer bonding process and the laser lift-off process, which are used to transfer GaN thin film from the sapphire substrate to a better thermal conductive Si substrate. Owing to the better thermal dissipation, the thin-GaN LED structure is a very promising candidate for developing high-power GaN LED. Two main topics of the studied thin-GaN LED structure in this work: (1) Design a suitable p-GaN contacts and reflector for thin-GaN LED structure. (2) Increase the light extraction efficiency of thin-GaN LED. In thin-GaN LED process, the wafer bonding process is necessary and it is a high temperature and high pressure process. Furthermore, the Si substrate is a non-transparent material for the blue light region. So, the p-type GaN contact should consist of an ohmic contact layer and a reflector as well. It is very important to develop a high thermally stable p-GaN contact. In this study, the Ni/Au/Ni/Al p-GaN contacts and Ni/Ag(Al) p-GaN contacts are investigated. These two thermally stable p-GaN contacts can reduce the degradation of the specific contact resistance and the reflection upon the thermal process. The specific contact resistance of the Ni/Au/Ni/Al p-GaN contact keeps on the order of 10-2 Ω-cm2 after 500 ℃ annealing. The reflectance of the Ni/Au/Ni/Al metal scheme is 60 % after 500 ℃ annealing. This high thermally stable Ni/Au/Ni/Al p-GaN contact is very suitable for the thin-GaN LED structure. Another critical issue is the low light extraction efficiency due to large refraction index difference between GaN and air. The light emitted from the active layer in GaN is significantly trapped in the GaN epi-layer, and a serious total internal reflection occurs. In this study, the aluminum oxide and silicon oxide honeycomb structure are produced on the n-GaN emitting surface by poly-styrene spheres template and sol-gel method. The aluminum oxide and silicon oxide honeycomb structures capping on the n-GaN surface can increase the external quantum efficiency by 35 % and 19 %, respectively. The mechanism of increasing light out-put by the oxide honeycomb structure would be discussed.
18
Hsieh, Yong-long, and 謝永龍. "LIGHT CHARACTERISTIC AND FABRICATION OF GaN LIGHT EMITTING DEVICES." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/31120063840880885085.
Full textAbstract:
碩士國立交通大學
光電工程系所
92
GaN Vertical cavity light emitting diode (RCLED) acknowledged basic difficulty is in in-situ epitaxial growth technology to form high quality resonant cavity. Thanks to have the technology to grow light emitting device with resonant cavity characteristics so that we can study the exam for optical characteristics of the device and fabrication process of VCSEL-like device so as to accumulate the experience in GaN RCLED. Fabrication process and technology of GaN surface light emitting devices and optical pumping were studied in this thesis. In the first section, exam for optical pumping will be done; in the second section, using real structure to make RCLED. A 3λmicro-cavity structure adopted by above device design was considered both in devices characteristics and process needed. In the device structure, chosen the best one to achieve GaN VCSEL : intra- cavity structure with top dielectric DBR and bottom epi growth DBR. Device bottom DBR adopted AlN/GaN materials which can also reach high reflectivity under fewer DBR pairs due to higher index different between AlN and GaN. Device top DBR adopted SiO2/TiO2 dielectric materials which already have good coating technology around 410 nm wavelength to reach high reflectivity more easily. In the first section, by the exam of optical pumping，we observed the dip of DBR could be designed for MOQ’s EL wavelength, the quality factor “Q” is 113, and the status of power increasing was discovered. In the second section for fabrication process of device, due to intra-cavity and micro-cavity, the fabrication process was more difficult than conventional light emitting device. The control of precise etching depth and the confined of current injection were needed. The EL wavelength of the GaN-based surface light emitting device was located at 420 nm with FWHM 4.3 nm. By increasing the injected current density, the EL wavelength has slightly red shift effect due to resonant cavity F-P dip.
19
李奕辰. "Novel Light Emitting AlGaN/GaN HEMT." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/7efx9a.
Full text
20
Chen, Jing-Ru, and 陳靜茹. "Enhancement of Light Extraction of GaN Blue Light Emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/17429763357719245487.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
92
In recent years, even though the light output of GaN-based LED continues to increase, the brightness (~20 lm/W) is still low compared to conventional lighting systems and it is necessary to further improve the light extraction of LEDs. In this study, we utilize flip-chip technique, photoresist microlenses, reflectors and thermoelectric cooler to increase the light extraction of GaN MQW LED. Electroluminescence (EL) and power angular distribution are used to measure the light output intensity of LED. From temperature dependent current-voltage (I-V-T) characteristics, the charge carrier transport mechanisms at different biased regions are also investigated. In the results, back emission of LED with SiO2/Al reflector has maximum light intensity ( 3.28μW ) , which is higher than front emission one ( 2.73μW ) in vertical emitting area ( at 90 angles). LED with P.R. microlenses (refractive index, n=1.62) on backside could improve the light extraction of LED (about 1.2 times) as well. The enhancement of light output is duo to the reduction of light absorption from the metal contact and Fresnel’s transmission losses at GaN (n=2.4)/air (n=1) interface. Finally, we fabricate a high brightness LED with above light enhancement design. EL intensity of LED is increased about 1.25 times than conventional one. Therefore, we can manufacture a LEDs array with above designs to obtain high light output for future solid-state illumination.
21
Jhen-ZihLi and 李溱錙. "Improved Light Extraction Efficiency of GaN-based Light-Emitting Diode by Electrochemical Etched Nanoporus in N-GaN Template." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/00716872301969707860.
Full textAbstract:
碩士國立成功大學
光電科學與工程學系
100
In this study, we discussed the formation of nanoporous randomly distributed in the n-type gallium nitride (n-GaN) template by electrochemical etching process, and then investigated the photoelectric characteristics of regrown complete LEDs. We expected to see enhanced light output power efficiency due to increase in light scattering by porous-like air void. In this experiment, we changed the bias (20, 30, 40 and 60 V) of the electrochemical etching process to form different types of nanoporous, and conjectured original arborization nanoporous to form oval shape of the porous by recrystallization of n-GaN after regrowth. Finally, we analyzed the optoelectronic characteristics of conventional LED and the LED n-GaN template after E.C. 20, 30, 40, 60 V. Under 20-mA current injection, the forward voltages (Vf）were 2.84 V, 2.85 V, 2.86 V, 2.87 V and 2.87 V, respectively. Compared with the conventional LED, it was found that the bias was slightly higher by 0.01 ~ 0.03 V； light output power @20mA were 8.7 mW, 12.15 mW, 12.34 mW, 12.97 mW and 9.92 mW, respectively. Compared with conventional structure, we achieved an enhancement of approximately 14.02 ~ 49.1 %.
22
Wu, Jou-Hsuan, and 吳柔萱. "An Improved InGaN/GaN Light Emitting Diode." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55854314231693323998.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
101
In these studies, the state-of-the-art two-dimensional device simulation tool, ATLAS, from SILVACO is being evaluated for the purpose of studying light-emitting diodes (LEDs). It predicts the electron behavior of specified semiconductor structures, and provides insight into the internal physical mechanisms associated with device operation. We designed the active layer area is 300 μm 300 μm for blue InGaN/GaN multiple-quantum well (MQW) light-emitting diodes, using the SILVACO ATLAS tool, the two-dimensional device simulation package ATLAS was used to theoretically analyze physical device characteristic. Other important physical mechanisms and optical properties, such as luminescent power, electroluminescence intensity, energy band, electric field, carrier concentration, and recombination rate were also investigated in this study. First, doping of the electron-blocking, barrier and active region layers plays a crucial role in the efficiency of blue InGaN/GaN light-emitting diodes. The carrier concentration characteristics of InGaN/GaN LEDs are systematically studied. Next we investigate the original structure of InGaN/GaN LED. By inserting using Si δ-doped (n+) GaN/InGaN structure into the original structure, we can analyse whether it can improve the carrier confinement effect of quantum well in active region or not. And find out the best region to use Si δ-doped (n+) GaN/InGaN structure. Finally, the proposed structures with Si delta-doped GaN/InGaN are numerically simulated. In the meantime, a systematic analysis on the critical physical mechanisms relevant to the improvement of the optical performance. The carrier confinement effect has enhanced effectively with Si delta-doped GaN/InGaN structure. Key words: light-emitting diodes, InGaN, multiple-quantum well, δ-doped Author* Jou-Hsuan Wu Advisor** Shiou-Ying Cheng Ph. D.
23
Chen, Ming-Sheng, and 陳銘勝. "Process of GaN-based Light-emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/49245573361857716249.
Full text
24
Lee, Chia-Ming, and 李家銘. "Investigation of InGaN/GaN Light Emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/18152097049547423378.
Full textAbstract:
博士國立中央大學
電機工程研究所
92
This dissertation includes the growth, fabrication, and characterization of Mg-doped GaN and InGaN/GaN multiple-quantum-well (MQW) light-emitting diode (LED) by metalorganic chemical vapor deposition (MOCVD). First, we utilized Hall measurement, photoluminescence (PL), and second ion mass spectrum (SIMS) to characterize p-type GaN and Mg distribution in GaN films. Although the Mg flow is constant during growth, the measurement data shows that the Mg concentration increases with growth time since the Mg concentration is higher when closer to the surface. Even when the thickness of p-type GaN reaches 2.5 μm, the increasing hasn’t slow down yet. The effect of different growth condition, such as growth temperature, III/V ratio and carrier gas, upon Mg incorporation in GaN is studied also. We found Mg diffusion not only in bulk p-type GaN but also in InGaN/GaN MQW LEDs. To improve the characteristics of InGaN/GaN MQW LED, we must understand its behavior first. So we tried to identify its emission mechanism by changing the operation temperature and current, and found the major cause of blue shift, which means peak emission wavelength shifts to shorter wavelength with higher injection current, is band-filling effect but not free carrier screen effect. In addition, we can identify whether the emission comes from well states or localized states from the way it shifts. When analyzing the emission mechanism of InGaN/GaN MQW LED, we also found the emission generated by Mg-doped GaN. Therefore, we designed another experiment to study the effect of Mg doping upon InGaN/GaN MQW LED. By the electroluminescence (EL) spectra measured under different operation temperatures, the peak emission wavelength of quantum wells and Mg-doped GaN is 3.1 eV and 2.7 eV respectively. When analyzing this emission behavior with rate equation and the relative intensity variation of these two peaks under different temperature, we can calculate and obtain the activation energy of Mg doping in GaN being 126 meV, which agrees with the results from other academic organization utilizing different otherwise method. We utilized selective activation technique in InGaN/GaN MQW LED process to improve its external quantum efficiency. Using this technique to activate Mg-doped GaN except the area underneath P-type bonding pad made us able to maintain its semi-insulating property, and further, it became a semi-insulating current blocking layer during device operation. This layer is utilized to prevent the injection current flowing through the area below P-pad since P-pad blocks the emission light from below and thus reduces the emission efficiency. From the luminescence intensity versus injection current chart, we did succeed in our effort to improve the external quantum efficiency when comparing to normal InGaN/GaN MQW LED. Since p-type GaN shows poor conductivity, normal InGaN/GaN MQW LED process utilizes a transparent conductive layer for current spreading. However, despite its name, this layer isn’t 100 % transparent, and thus would absorb/reflect certain portion of emission light. To prevent this loss, we changed the normal InGaN/GaN MQW LED structure, which is p-type above and n-type under MQW, by switching the p-type and n-type layers’ positions and adding a n+/p+ tunnel junction. By this change, there’s no need of this transparent conductive layer for current spreading, and the device external quantum efficiency become almost twice as high as before.
25
Liu, Yu-Chuan, and 劉育全. "Investigation of InGaN/GaN Light Emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/79969050495085222285.
Full textAbstract:
碩士國立中央大學
電機工程研究所
92
A light-emitting device comprises a multi-layer structure including one or more active layer configured to irradiate light in response to the application of an electric signal, a transparent passivation layer laid over an outmost surface of the multi-layer stack, a reflector layer laid over the passivation layer, and a plurality of electrode pads coupled with the multi-layer structure. In a manufacture process of the light-emitting device, the reflector layer and the passivation layer are patterned to form at least one opening exposing an area of the multi-layer structure. One electrode pad is formed through the opening of the reflector layer and the passivation layer to connect with the multi-layer structure.
26
Chung, Chao-Chi, and 鍾超己. "Anelasticity study in GaN Light-emitting Diode." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/66796759266305880518.
Full textAbstract:
博士國立中央大學
化學工程與材料工程學系
105
Defects decline the light output efficient and life time of GaN-based LED. In our study, as the defect density of device is 2.17×10-9 cm-2, 3.636×10-9 cm-2, 4.654×10-9 cm-2, respectively, the external quantum efficient is 20.546 %, 19.563%, 16.785%, respectively. To establish a high accuracy and convenient defect measuring system is necessary. However, the defect measuring methods that commonly used have many limits. For example, XRD spectrum is only suitable for wafer size sample. TEM and EPD evaluating method are destructive measurement that waste many sample and cost much time. We established a defect measuring method in this study by analyzing anelasticity behavior of GaN-based LED after applying stress or external electric field. Defects develop Anelasticity behavior in solid. It causes the strain delay-responding after applying stress on material. Although there has complete study about anelasticity behavior of bulk material, the research of thin-film materials and the influence of semiconductors is lack. In this study, the anelasticity of the GaN layer in the GaN light-emitting-diode device was discussed. And, establish defect measurement system can be established. The studied chip was applied by thermal stress, piezoelectric stress, and external stress. The present results show that the decrease of forward-voltage of GaN LED is due to the degree of energy-level change as forward external electric field applied. After removing external electric field, the forward voltage increase with time. We found that the increment of the forward-voltage with time attributes to the delay-response of the piezoelectric fields (internal electrical fields in GaN LED device). We applied -0.5 V reverse bias and heat the chip to 100 oC, respectively. Thus, the forward voltage increases gradually due to the energy-level in GaN LED is flattened with time by thermal stress and external electric field. Furthermore, reverse bias (-1 V) flatten the energy level much more, so, the forward voltage enhancement is higher. As -5 V reverse bias is applying on the GaN LED, the voltage dropped due to the higher reverse bias tilted the energy-level in GaN LED again. Using the correlation of strain-piezoelectric-forward voltage, a plot of strain of the GaN layer against time can be obtained by measuring the forward-voltage of the studied GaN LED against time. The key anelasticity parameter, characteristic relaxation time τ, and anelastic strain Uan of the GaN would be analyzed by the curves of the thermal strain in GaN epi-layers versus time. For estimating the dislocation density, the studied GaN LED chips were etched by H3PO4 in 260 oC. The etching pits on GaN LED after H3PO4 reacted were calculated. GaN LED chip with higher dislocation density has higher τ and Umax, furthermore, the dislocation density and anelastic strain is linear relation. The results show the anelasticity behavior is attributed by defect. In other side, it is possible for establishing a defect measurement system by analyzing anelasticity behavior of GaN LED. The relation of defect density and anelastic strain can be expressed as Vf,max=0.00168×Ddis+0.00329. Vf,max is the forward-voltage difference induced by anelastic strain of GaN-based LED. Ddis is the density of dislocation in GaN-based LED.
27
Huang, Chuan Lee, and 李煌川. "The Improvement of GaN LED light extraction." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/76208383088616843049.
Full textAbstract:
碩士國立交通大學
工學院半導體材料與製程設備學程
100
In this thesis, we propose a method to increasing of LED light extraction by using high temperature wet etcher of phosphoric acid. In this method, we change geometric figure of LED chip. It decreased the reflection when the light met the sidewall of chip. The reflection occurred will increased possibility of light absorption. This technology was achieved by deposition SiO2 on sapphire using by plasma enhanced chemical vapor deposition (PECVD) and making the laser cut by laser scribe. The SiO2 was adopted the block layer and then etched in the mixture of high temperature phosphoric acid and sulfuric acid. The efficiency of sidewall etched profile on light extraction is shown in this thesis. There are three conditions of this study. The first was the changing concentrations of solution with fixed operation temperature and process time. Second was changing the operation temperature with fixed concentration of solution and process time. Third was changing the process time with fixed concentration of solution and process temperature. The results are verified by SWE width (μm), luminous intensity and SEM observation about laser scribe shape and epi layer sidewall profile. Base on the optical and the electrical characterization data, the method propsed in this thesis may increase the luminous intensity of LED through the light extraction efficiency.
28
Chen, Yu-Qiu, and 陳昱酋. "InGaN / GaN Light Emitting Diode Polarization Analysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/14783776738955605854.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
102
In these studies, the state-of-the-art two-dimensional device simulation tool, ATLAS, from SILVACO is being evaluated for the purpose of studying light-emitting diodes (LEDs). It predicts the electron behavior of specified semiconductor structures, and provides insight into the internal physical mechanisms associated with device operation. We designed the active layer area is 300 μm 300 μm for blue InGaN/GaN multiple-quantum well (MQW) light-emitting diodes, using the SILVACO ATLAS tool, the two-dimensional device simulation package ATLAS was used to theoretically analyze physical device characteristic. Other important physical mechanisms and optical properties, such as luminescent power, electroluminescence intensity, energy band, electric field, carrier concentration, and recombination rate were also investigated in this study. In this thesis, the first chapter, a brief history of the development of light-emitting diodes and motivation. The second chapter introduces the basic principles and characteristics of light-emitting diode materials, and a complete discussion of III-V nitride material properties. The third chapter describes the basic elements of this thesis depth to do a complete discussion of the model equations and theories used when TCAD simulation, the model used to do a complete discussion. Chapter IV simulation to identify InGaN / GaN layers doped concentration parameter optimization. Finally, changes its polarization effect, and analyzed at different polarization effects, the influence of an energy band diagram characteristic change element analysis. Key words：light-emitting diodes, InGaN, Polarization effects Author* Yu-Qiu Chen Advisor** Shiou-Ying Cheng Ph.D.
29
Yeh, Wei-Yu, and 葉偉毓. "Design of GaN-based Light-Emitted Diode." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/80356527266233380222.
Full textAbstract:
碩士國立清華大學
電子工程研究所
93
GaN-based Light - emitting diodes, whose active regions are made of InGaN, have vigorous development in recent years. Nitride devices have great potential for various applications, such as optical data storage and full-color displays. But there are many issues to be solved, like the dislocation, behaviors of multi-quantum wells system, and the effects of temperature. References have shown the characteristics of the nitride devices and the possibilities to improve the performances of GaN-based LED. But only a few phenomena or the effects of single parameter have been discussed. A better understanding of the properties of nitride devices could be gained by simulation. APSYS is two-dimensional (2D) software and it uses finite element analysis and modeling software program for semiconductor devices. Its advanced physical models provide a flexible modeling and a simulated environment for modern semiconductor devices. APSYS examines the effects of each parameter and helps the devices to reach their optimization. The results of APSYS simulation provide the information of device’s characteristics and suggest how to improve its performance. By changing polarization and Shockley-Read-Hall lifetime, we develop a method to simulate the real condition. Finally, the temperature effect to the optimal design is considered. With a series of simulation processes, we get familiar with GaN-based LED and know the key point. We also test and verify that the APSYS simulation is feasible for application. We can predict the possible characteristics and effects. Therefore, a more precise direction of the device design helps to save lots of time. With the help of the APSYS simulation, the rapid development of GaN-based LED could be expected.
30
Yu, Chang-Chin, and 余長治. "Study of GaN-based light emitting devices." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/15541291659263219716.
Full textAbstract:
博士國立交通大學
光電工程所
91
The groups III-nitride semiconductors, especially Gallium nitride (GaN), have been successfully employed to realize blue-green light-emitting diodes, blue laser diodes, UV light sources and detectors. However, the performance of such light-emitting diodes and lasers remains limited by several problems related to the formation of low-resistance ohmic contact to the P-type GaN. Moreover, due to their excellent chemical and thermal stabilities, the etching technology and processing are need developing to fabricate these optoelectronic devices for the fastest etching rate and high quality mirror-like facet. In this thesis, we concentrate on these two topics. To investigate beryllium implanted p-type GaN to enhance hole carrier concentration and resolve the ohmic contact problem. Additionally, we also study the dry etching mechanism and technology to fabricate GaN optoelectronic devices and nanostructures, and develop to become an alternate new method to form nanorods or nanostructures. We investigated the electrical and optical characteristics of beryllium implanted Mg-doped GaN materials. The Mg-doped GaN samples were grown by metalorganic chemical vapor deposition system and implanted with Be ions at two different energies of 50, 150 keV and two different doses of about 1013, 1014 cm-2. The implanted samples were subsequently rapidly thermal annealed at 900oC, 1000oC, 1100oC for various periods. The annealed samples showed an increase of hole concentration by three-order of magnitude from non-implanted value of 5.5x1016 to 8.1x1019cm-3 as obtained by Hall measurement. The high hole concentration samples also showed low specific resistance ohmic contact of about 10-3Ωcm2 and 10-6Ωcm2 using Ni/Au and Ni/Pd/Au metallization respectively without any further annealing process. It is also found from the temperature dependent photoluminescence that the activation energy of Mg dopants of the Be implanted samples has an estimated value of about 170meV, which is nearly 30% lower than the as-grown samples of about 250meV. The crystal quality and surface morphology of the Be implanted samples measured by x-ray diffraction and atomic force microscopy show no obvious degradation in the crystal quality and surface morphology. We studied rapid thermal annealing effect on beryllium implanted into in-situ activated p-type GaN samples, and investigate the ramping and the isothermal annealing effect of RTA process. We compared the multiple steps annealing at 1100oC for 15s of four periods with single step annealing for 60s of one period at the same annealing temperature, and observed that the ramping effect with MSA could repair Be-related complex defect and one time, long period isothermal annealing effect with SSA seems to be induced much more defect. It seems that the multiple step annealing is more effective and induces fewer defects than single step annealing for Be-implanted in-situ activated p-type GaN samples. Dry etching of un-doped, n-, p-GaN and InGaN laser structure has been carried out in Cl2/Ar inductively coupled plasmas using Ni mask. As Cl2/Ar gas flow rates were fixed at 10/25 sccm, the etched surface roughness has the lowest value of 0.2 nm at constant ICP/bias power = 300/ 100 W and 5 mTorr chamber pressure for un-doped GaN. The highest etching rate of 12000 Å/min for n-GaN was achieved at 30mTorr, 300W ICP, 100W bias power using low Cl2 flow rate (Cl2/Ar = 10/25 sccm) gas mixtures. The surface roughness was dependent of bais power and chamber pressure, and shows a low RMS roughness value of about 1nm at 50 W of bias power for n- and p-GaN. For etching of InGaN laser structure using high Cl2 flow rate (Cl2/Ar = 50/20 sccm) and low chamber pressure 5 mTorr, a smooth mirror-like facet of InGaN laser diode structure was obtained by ICP system. We established a novel method of fabricating gallium nitride (GaN) nanorods of controllable dimension and density from GaN epitaxial film using inductively coupled plasma reactive ion etching (ICP-RIE). The GaN epitaxial film was grown on a sapphire substrate by metal-organic chemical vapor deposition. Under the fixed Cl2/Ar flow rate of 10/25 sccm and ICP/bias power of 200/200 W, the p-GaN nanorods and array were fabricated with a density of 108 ~ 1010 cm-2 and dimension of 20~100 nm by varying the chamber pressure from 10 to 30 mTorr. From the micro-PL spectra, it can be seen that there are 5~10nm blue-shift for the p-type peaks at the nanorods area. It is suggested that quantum confined effect and band filling effect induce the blue shift of p-type PL peaks. Moreover, we also fabricated InGaN laser structure nanorods with the etching condition of the chamber pressure = 30mTorr, mixed gas Cl2/Ar flow rate = 10/25sccm, and ICP/bias power = 200/100 W for a 1 min etching time, and obtain the InGaN nanorods of about 0.6 m height. The technique offers one-step, controllable method for the fabrication of GaN nanostructures and should be applicable for the fabrication of GaN-based nano-optoelectronic devices.
31
Je-Wei, Lu, and 盧哲偉. "Study of GaN Surface Light Emitting Devices." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/49666033430014212113.
Full textAbstract:
碩士國立交通大學
光電工程所
91
GaN Vertical cavity surface emitting laser (VCSEL) acknowledged basic difficulty is in in-situ epitaxial growth technology to form high quality resonant cavity. This resulting GaN VCSEL still not successfully fabricate to date. Thanks to have the technology to grow light emitting device with resonant cavity characteristics, so we can study the fabrication process of VCSEL-like device. Fabrication process and technology of GaN surface light emitting devices were studied in this thesis. A 3λmicro-cavity structure was considered both in devices characteristics and process needed. In the device structure, chosen the best one to achieve GaN VCSEL : intra- cavity structure with top dielectric DBR and bottom epi growth DBR. Device bottom DBR adopted AlN/GaN materials which can also reach high reflectivity under fewer DBR pairs due to higher index different between AlN and GaN. Device top DBR adopted SiO2/TiO2 dielectric materials which already have good coating technology around 410 nm wavelength to reach high reflectivity more easily. Due to intra-cavity and mirco-cavity, the fabrication process was more difficult than conventional light emitting device. The control of precise etching depth and the confined of current injection were needed. And in the lift-off process of top dielectric DBR : photo-resister will stick on sample surface in high temperature coating environment, so we suggested LOR solution to displace photo-resister to bear high temperature and successfully accomplish lift-off process. The EL wavelength of the GaN-based surface light emitting device was located at 410.6 nm with FWHM 7.4 nm and the cavity quality factor Q about 55.5. By increasing the injected current density, the EL wavelength has slightly red shift effect due to resonant cavity F-P dip.
32
Liu, Yi-jung, and 劉亦浚. "Fabrication of GaN-Based Light Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/vz4uuw.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
96
In this thesis, two approaches are presented to improve future solid-state lighting devices: GaN-based LEDs. All these approached are all related to how to promote the luminous intensity of nitride-based LEDs. In respect of research on GaN-based LEDs, we have proposed oblique sidewalls and floating p-GaN with an air-buffer layer by using KOH wet-etching process to improve the light-extraction efficiency from device sidewalls and sample surface, respectively. The oblique sidewalls exist along specific directions, creating more escaped cones for output light than conventional ones, thus photons generating within MQW active region can experience multiple opportunities to escape from device sidewalls. With the benefit of wet-etching process, the luminous intensity was increased to nearly 7~8% at short-wavelength band and 3~4% at long-wavelength band compared with conventional process. The second approach is about the concept of modulation-doped superlattice(SL) structures inserted into p-GaN layer or between p-GaN and MQW. In this study we fabricate three kinds of superlattice structures, device B(with p-GaN/i-InGaN SL), device C(with i-GaN/p-InGaN SL), and device D(with p-AlGaN/i-GaN SL), compared with conventional structure, device A(without SL). Via the modification of SL structures, the external quantum efficiency(EQE) as well as the output power are both increased for p-GaN/i-InGaN SL structure and luminous intensity was increased to 127.6% and 113.5% for p-GaN/i-InGaN SL structure and i-GaN/p-InGaN SL structure , compared with the conventional structure, respectively. Moreover, from measuring the leakage currents, the leakage was significantly reduced by nearly two orders of magnitude for p-GaN/i-InGaN SL structure at room temperature. The enhancement can be attributed to the reduction of surface defects induced by threading dislocations which is cause by lattice mismatch between substrate and GaN epi-layer , due to the smoother surface morphology of the devices with SL structures observing from AFM images and better film quality of active layer speculating from small applied voltages of I-V curves .
33
Su, Yu-Shun, and 蘇裕順. "Investigations on Light Extraction Efficiency of GaN-Based Light-Emitting Diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/77572402740740419283.
Full textAbstract:
碩士逢甲大學
資訊電機工程碩士在職專班
99
This article researches the use of GaN epitaxial layer and the sapphire substrate to form the outer and inner chamfer of the morphology with the following two primary methodologies: First, coat barrier layer (SiO2) on flat substrates, define the type of SiO2 diagram by commencing the map with yellow litho process, and proceed with epitaxial process on the graphical SiO2 substrate. While the epitaxial layer is completed, remove the SiO2 between epitaxial and substrate to form the holes at the bottom of the epitaxial layer. Second, use wet etching process to etch the graphical R-Plane sapphire substrate as V-shaped, and then apply the exclusive epitaxy characteristic of MOCVD on C-Plane epitaxial layer to form the holes at the bottom of the epitaxial layer. The two methodologies mentioned above were proved to be able to form a number of holes between the epitaxial layer and the sapphire. After completion, application of lateral wet etching to etch the inside and outsides of the holes on the epitaxial layer would lead to the formation of chamfer morphology of the LED structure. Meanwhile, the structural change of the bottom and lateral sides of the LED will increase the odds of downward and leftward light emitting from the quantum well (MQW), and thus enhance the efficiency of LED light extraction.
34
LIN, JIAN-HONG, and 林建宏. "Improved Efficiency for InGaN/GaN Light-emitting Diodes Using P-GaN Photonic Crystal Structure." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6tn68d.
Full textAbstract:
碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
106
In this dissertation, Studying p-type gallium nitride is surface treated to form a photonic crystal structure to enhance the extraction efficiency of the blue light-emitting diode. Using Plasma Enhanced Chemical Vapor Deposition (PECVD) deposition of cerium oxide on P-type gallium nitride surface, growning Single-layer polystyrene microspheres by spin coating. Etching the cerium oxide layer using polystyrene microspheres as a mask layer using RIE,then etching p-type gallium nitride using ruthenium dioxide layer as mask by ICP. Among them, the spin coating method has the advantages of low cost, easy production, and high speed; When the blue light emitting diode emits light through the photonic crystal, damage and constructive interference will be generated to reduce the total reflection phenomenon, thereby improving the extraction efficiency of the light emitting diode. Preparation of self-assembled styrene nanospheres without the use of large and extremely expensive equipment, simple assembly and ordering of polystyrene nanosphere photonic crystal structures.However,spinning coating method to assemble polystyrene nanospheres. The concentration of polystyrene nanospheres, the number of rotations and the hydrophilicity of the substrate all affect the alignment of the polystyrene nanospheres. Then we use R-Soft FDTD software to simulate the extraction efficiency of P-type gallium nitride photonic crystals on blue light-emitting diodes. The simulation results show that changing the P-type gallium nitride photonic crystal pitch and diameter can effectively increase the extraction efficiency. In the experimental part, when the p-type gallium nitride etching depth is 130 nm and the nano-pillar diameter is 350 nm and the period is 150 nm, the luminous efficiency can be increased by 37% under the driving current of 20 mA. This part is in accordance with the simulation results.
35
Pan, Ching-Ju, and 潘晴如. "Fabrication and Characterization of GaN Light Emitting Diodes." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/32099555409871547855.
Full textAbstract:
碩士國立交通大學
電子物理系
89
In this study, we fabricated and characterized GaN light emitting diodes (LED) and Schottky diodes (SD). The structures for transmission line model (TLM) and circular transmission line model (CTLM) were prepared simultaneously to measure the sheet resistance of p-GaN epilayers and specific contact resistance of Ni-Au/p-GaN ohmic contacts. The luminescence spectra of LEDs are ranged from 450nm to 575nm, with peak wavelength at 500nm. As 20mA current flows, there exist about 3.3V voltage drop across LEDs. Various patterned LED structures give ideality factor 4.1-4.8, and series resistance 37-48 ohms. For Au-Ni/n-GaN Schottky diodes, the ideality factor is 1.4-1.7, the barrier height is 0.76-0.82eV for I-V measurement and is 1.21-1.42eV for C-V measurement.
36
Tsou, Po-Hung, and 鄒博閎. "GaN Light-Emitting Diodes with direction nanoporous structure." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/z4478n.
Full textAbstract:
碩士國立中興大學
材料科學與工程學系所
106
In this thesis, a gallium nitride light-emitting diode with a nano-porous structure is fabricated by epitaxy of Si-doped GaN which under the LED active layer. First, a scribe line with a depth of about 10 μm was fabricated in the non-luminous area by means of surface cutting in the technique of laser cutting,the epitaxial layer of Si-doped GaN which above sapphire is exposed on the side of the LED die,that is the electrochemical etching of the target area, etching of n+-GaN doping Si epitaxial layer by electrochemical etching process,the principle of this electrochemical etching is mainly that nitric acid is used for etching GaN doping Si in the epitaxial layer,let us successfully in the gallium nitride light-emitting diode region below the active layer to produce highly reflective nanoporous structure, This structure can effectively reduce the optical loss of light absorbed by the material before it escapes the LED. Using the method of this paper to produce nanoporous (stacking by GaN / Air) mirrors in a GaN LED,which structure because of it is large difference in refractive index,the principle is the same as making a Bragg reflector (DBR) under the active layer, so you can get a better reflectivity and then improve the luminous intensity. The application of green gallium nitride light emitting diodes, this study found that LED light characteristics Of the measurement, including Photoluminescence 、 Electroluminescence and Beam profile have an upward trend, In the future, this process technology can improve the development of GaN LED luminous characteristics will have great potential.
37
Lam, Jack Biu. "Optical studies of GaN-based light emitting structures." 2005. http://digital.library.okstate.edu/etd/umi-okstate-1387.pdf.
Full text
38
Lin, Jia-Hua, and 林佳樺. "Study on High-Voltage GaN Light Emitting Diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/06498605992635878887.
Full textAbstract:
碩士國立中興大學
精密工程學系所
99
P-GaN side up high-voltage GaN LEDs with high reflection on silicon substrate and both p-GaN and undoped-GaN roughening layers have been investigated. The devices are subsequently fabricated with wafer-bond, laser lift-off, chemical dry/wet etching and double-side roughening techniques to transfer epilayer to silicon substrate with mirror. The roughness on p-GaN surface was fabricated via low temperature growth, and rough surface of u-GaN was made by wet-etching. Then we connected 64 cells by 8×8 chips to get high-voltage LEDs. The forward voltage of LEDs with single side roughening-bare die(SR-B), SR-B), with double side roughening-bare die(DR-B), with single side roughening-packaged(SR-P) and with double side roughening-packaged(DR-P) was 23.521, 23.332, 23.521 and 23.332 V at 80 mA, it implied no destroy occurred on electric properties during processes. The wall plug efficiency of SR-B, DR-B, SR-P and DR-P at 80 mA current injection was 30.311, 38.500, 37.661 and 47.855 %, and light extraction efficiency of SR-B, DR-B, SR-P and DR-P cell was 47.223, 59.498, 58.673 and 73.956 % respectively. Moreover, SR-B and DR-B at 80 mA injection, the highest surface temperature was 53.1 and 43.7 oC. The optical and thermal characteristics of thin film high-voltage LEDs had been obviously improved via wafer bonding process.
39
Bo, Siao Cheng, and 鄭柏孝. "Study of GaN-based Microcavity Light Emitting Devices." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/78151964739593664769.
Full textAbstract:
博士國立交通大學
光電工程學系
100
For several decades, GaN-based material has attracted much attention of academia and industry and widely used in several optoelectronic devices due to its wide direct bandgap and strong binding energy, such as light emitting diodes, laser diodes, and photon-detectors which can be applied in lighting, optical storage, display, and biotechnology. The thesis is focus on the design and fabrication of the electrically pumped GaN-based microcavity light emitting devices with hybrid distributed Bragg reflectors and an AlN current blocking layer. We have recently demonstrated the continuous wave (cw) current injection of GaN-based VCSEL with hybrid mirrors at 77K with 240 nm ITO and 300 K with 30 nm sputtered ITO. Meanwhile, the room temperature operation of GaN-based VCSEL devices was reported using optical cavities sandwiched by double dielectric DBRs. The major improvements of these devices to achieve room temperature operation are by using a thinner transparent conducting layer of about 50 nm to improve the current spreading and by using the GaN substrate to ensure the good crystal quality of active layers. However, to form VCSELs with double dielectric DBRs required complex fabrication process, such as laser lift-off or elaborated polishing and bonding process. Despite of demonstration of room temperature current injected GaN-based VCSELs, the lateral optical confinement and the transparent conductive ITO film was still a lack in these VCSEL structures, resulting in higher optical loss and difficulty in controlling the quality of output beams. About ITO characteristics improvement, the study consists of the design, fabrication, and characteristics of the ITO films. In order to improve the optical confinement of these devices, we investigated a microcavity light emitting device (MCLED) with a buried AlN current aperture, which can also be used as a lateral optical confinement layer. Since a pre-defined current aperture with a small diameter is introduced in the MCLED structure, the transparent current spreading layer can be omitted from the optical path. The current still can be injected effectively in the current aperture and the optical loss introducing by the transparent current spreading layer could be neglected. The emission from the MCLED with a buried AlN layer shows a very narrow linewidth of 0.52 nm, corresponding to a cavity Q-value of 846, and a dominant emission peak wavelength at 440 nm. The measured cavity mode spacing is approximately 0.7 nm, which is consistent with the estimated value, demonstrating the effect of lateral optical confinement provided by the AlN layer. In addition, the emission peak wavelength as a function of the current is almost invariant with an increasing injection current indicating potential temperature-sensitive applications. Further optimization of bottom DBR growth and crystal quality in this structure would promise to realize low threshold GaN-based VCSELs or GaN-based polariton lasers.
40
Chang, Ming-Nan, and 張敏南. "Improved light illumination efficiency of GaN-based LEDs." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/22660636767613931380.
Full textAbstract:
碩士國立成功大學
光電科學與工程研究所
97
In this thesis, we had mainly investigated the light output power improvements in GaN-based light emitting diode. First, the textured sidewall mesa and GaN micro size pillars (μ-pillars) around the mesa region were fabricated on the GaN-based LEDs. And we had demonstrated experimentally that the textured sidewall mesa and GaN μ-pillars around mesa using in LED structure could enhance light output power effectively by disrupting the waveguide mode in GaN/air interface and also in good agreement with our results of ray-tracing simulation. Moreover, when GaN-based LEDs with textured sidewall mesa, GaN μ-pillars around mesa region, patterned sapphire substrate (PSS), and highly reflective Ag/Cr/Au metal electrode pads could enhance LED output power by more than 90%, as compared to the conventional GaN-based LEDs. But the higher contact resistance determined by n+-GaN/Ag resulted in higher turn-on voltage.Following, Ag-based materials were performed as reflective current blocking layer on GaN-based LEDs owing to its higher reflection and the rectify characteristic of Ag/GaN interface. Comparing with conventional GaN-based LED, the light output power enhancement of these three types reflective current blocking layers of Ag/p-GaN, Ag/O2 plasma treated p-GaN, and Ag/SiO2/p-GaN on GaN-based LEDs were 5.3%,8.5%,and 14.4%, respectively, under the 20mA current injection.And the 20mA-forward voltage (Vf) of all LEDs were approximately at 3.0V indicating these designed reflective blocking layers between interface of indium tin oxide (ITO) film and p-GaN layer did not deteriorate the electrical properties of LEDs. In summary, we efficiently enhanced light extraction efficiency and external quantum efficiency by texturing structure. We believed that these methods played a role on pursuing high power LEDS
41
Chen, Po-Yu, and 陳柏宇. "Linear Cascade GaN Based Microstructure Green Light Emitting." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/4b23ry.
Full textAbstract:
碩士國立中央大學
電機工程研究所
96
In this paper, we demonstrated a linear cascade green light-emitting diode (LED) array for plastic optical fiber (POF) communication in car or in harsh environment. Under the whole range of measured temperature (room temperature (RT) to 120℃), our three-LEDs array driven by the constant voltage bias of in-car battery output (12V) exhibits a very small variation of coupled power vs. temperature (-0.12%℃-1 at RT) and achieves a high-speed (90MHz) and high coupled power (~0.9mW) to POF (NA:0.3). Even under high bias current (100mA) operation, our device can sustain a clear 150MHz eye-opening from RT to 120℃ operation. The static and dynamic measurement results indicate that both the speed and power performance of our device are more insensitive to the variation of ambient temperature as compared to those of red RCLED for POF communication.
42
Chih-ChienLin and 林志堅. "Investigation of light output extraction enhancement in GaN-based light emitting diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/28749446707170459089.
Full text
43
Chou, Hsiu-Mei, and 周秀玫. "Improvement of Current Spreading in GaN-based Light Emitting Diode Grown on Nanorods GaN Template." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/21649078852940937568.
Full textAbstract:
碩士國立中央大學
照明與顯示科技研究所
99
This thesis investigation, we studied the growth of different concentrations of n-type GaN film on the nanorods GaN / sapphire substrate to improve the p-side-up mesa-structure GaN LED of the current crowding, expectations used in high current density to enhance the current spreading uniformity of GaN LED. First, Growth of different concentrations of n-type GaN film on the nanorods GaN / sapphire substrate, the surface morphology and structural characteristics were analyzed. Next, we make use of theory to calculate the current distribution of different concentrations of n-type GaN film grown on the nanorods GaN / sapphire substrate.When the resistance of n-type GaN film and the transparent current layer were match so that the current is distributed will be even. Therefore, we grow high concentrations of n-type GaN film to reduce the resistance of n-type GaN film, but heavily Si-doped of n-type GaN film could made film quality has poor. So, we using nanorods GaN / sapphire substrate could effectively suppress the threading dislocation density by increasing Si-doped of n-type GaN film. The measurement results revealed that GaN LED grown on nanorods GaN / sapphire substrate GaN substrate, at 20mA injection current, the optical output power was enhanced by 12%, respectively, compared to those of a conventional LED.We adjusted the different reisistance of n-type GaN film grown on nanorods GaN / sapphire substrate, the light output power was enhanced by 15%, because of changing n-type GaN film resistance could let the current distributed evenly.
44
Lee, Chien-hsun, and 李建勳. "Efficiency enhancement of GaN-based Light Emitting Diode prepared on SiO2 nanorod patterned GaN template." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/79089551858052695784.
Full textAbstract:
碩士國立中央大學
照明與顯示科技研究所
99
GaN have emerged as important semiconductor materials for light-emitting diodes (LEDs). However, It was well known that light-extraction efficiency (LEE) of LED is limited mainly by the large difference in refractive index between GaN film and the surrounding air. Since the refractive indexes of GaN and the air are 2.5 and 1. Critical angle is crucially important for the light extraction efficiency of LEDs. It has been shown that one can enhance light output by light scattering layer (e.g., patterned substrate.), photons generated in the active layer will have multiple opportunities to find the escape cone. In the study, the LED device with the embedded micro-size SiO2 stripe was fabricated. We labeled the LED as LED M1. In order to clarify the light scattering in different scale, we fabricate the LED device with the embedded nano-size SiO2 nanorods stripe. We labeled the LED as LED N1. For comparison, convention LED was also prepared, we labeled as LED C1. With 20 mA current injection, it was found that output power of LED C1, LED M1 and LED N1 was 3.15mW, 4.37 mW, and 5.07 mW, respectively. To clarify the enhancement in light output power, the finite-difference time-domain (FDTD) analysis is used to study the irradiance behavior of the proposed LED with SiO2 patterned structure. Shows the simulated light emission of proposed LED with SiO2 patterned structure. We can found in this figure, the photon density in nano-size structure was larger than micro-size structure. The result shows that nano sized structure could provide more light scattering center than micro size structure. In conclusion, we can enhance the 20 mA LED output power by 42% from the LED N1 compared with the conventional LED. The increasing of light scattering centers could reduce the probability of photons restricted in GaN epitaxial layers.
45
Chien-Chung, Hsu, and 許建中. "Nano-patterned sapphire substrates enhanced the light efficiency of GaN light emitting diodes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/39834448088092104073.
Full textAbstract:
碩士國立聯合大學
光電工程學系碩士班
100
In this study, we discussed light extract, ion efficiency of GaN-based light emitting diodes (LEDs) with nano-patterned sapphire substrates (NPSS) which were prepared by nano-imprint lithography. Compare with various period of NPSS, we found that the NPSS with the period of 800 nm shown higher efficiency that the NPSS with the period of 600 nm. Compare with various sapphire substrates, the LEDs with NPSS exhibited higher efficiency resulted from better light extraction ability of NPSS. Under the injection current of 20 mA, the power of LED with common sapphire substrate (CSS), patterned sapphire substrate (PSS), and NPSS was 17.8 mW, 23.56 mW and 24.3 mW, respectively. Compare with the LED with PSS, the power of the device with NPSS was improved 36.5%. Furthermore, under the injection current of 200 mA, the power improvement of NPSS to period of 800nm was 42.2%. It indicated that the efficiency of LED could be improved with NPSS.
46
Lee, Tsung-Xian, and 李宗憲. "The Light Extraction Analysis and Chip Design for GaN-based Light-Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/49986336503891749685.
Full textAbstract:
博士國立中央大學
光電科學研究所
96
The light extraction efficiency of light-emitting diodes (LEDs) is limited by many effects. For this reason, we present a quantitative analysis model for LED light extraction characteristics based on Monte Carlo ray tracing method, According to this model, the light extraction and loss mechanisms in GaN-based LEDs is studied. We furthermore verify the validity of the Monte Carlo simulation results by packaging experiments at low temperature. In the thesis, there are five topics is discussed in detail. First at all, we analyze the issue of absorption in active layer, the simulation also take into account the effect of photon recycling. According to the simulation results, the light extraction efficiency of LED with light extraction structure is more sensitive to active layer absorption than that of typical LED. Secondly, the realistic geometry of chip scale is analyzed. According to the simulation results, the structure of chip shaping and patterned substrate is suitable for small chip, and the ThinGaN LED with Surface texture is suitable for large chip. Besides, the suggested thickness for sapphire substrate is 50~100um. Then we analyze the issue of contact and current spreading. The results show that the light extraction efficiency decreases due to the shadow effect of the p-contact while the current crowds near the p-contact. In order to overcome this effect, the light extraction efficiency can be greatly improved by integrating high reflectivity contact, current blocking layer and diffused bottom mirror. We also compare the light extraction efficiency of LED packaging with bare chip. From the optical point of view, the patterned substrate should be regarded as the most effective way in enhancing light extraction efficiency in an encapsulated flip-chip LED. Besides, the diameter of encapsulant lens must be larger 2.5 times than chip size, and to increase the encapsulant’s refractive index usually is more effective at improving light extraction efficiency than light extraction structure. Finally, in order to improve light extraction efficiency, the LED with micro-structure is analyzed and optimized. The simulation results show that the light extraction efficiency is improved by multiple reflections and reflected scattering in a LED chip, so that increasing reflectivity of the bottom mirror is an important key factor.
47
Chiang, Yen-Chih, and 江彥志. "Fabrications and Light Extraction Improvements in High Power GaN-Based Light-Emitting Diodes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/62234158062386987580.
Full textAbstract:
博士國立交通大學
照明與能源光電博士學位學程
104
The luminous component developed by GaN materials can be widely used in such as indicators, traffic lights, LCD back-lighting source, and variety styles of lighting equipment, even in the medical domain. Since 1960 years, the relevant GaN materials to be an important research topic in the whole world. The internal or external quantum efficiency is at the same time constantly discussing and demonstrating in the international seminar. In this dissertation, we were focused on light extraction efficiency of GaN-based light emitting diode in high-voltage and high-power (LED) methods with blue or ultraviolet wavelength, and analyze the characteristics of these various high-power light emitting components. The first part, the first step was made high-voltage blue light emitting diodes with (1.15x1.15 mm2, 15 series-connection) on sapphire substrate. The achievement of high-voltage light emitting diode is adopting the side-wall protective layer (passivation layer) to protect the PN junction and using bridged metals to form a series circuit (Inter-connection). We were studied and investigated the differences in upper light output power (compared the differences at the bottom of the sapphire add reflective layer or not), downward light output power (presented by high-voltage light-emitting diode in flip-chip style) and effects on the light extraction efficiency. High-voltage light emitting diode with low operating current to avoid the high current is easy to cause the current crowding effect, achieve more uniform light distribution of good current spreading. We demonstrated the high-voltage flip-chip light emitting diode combine a good feature of the low light shielding effect in flip-chip style and the aforementioned advantages of high-voltage light emitting diode. Experimental results demonstrate that (under the same input current of 20mA. High-voltage light-emitting diode on sapphire without adding a reflective layer: 315mW; high-voltage light-emitting diode on sapphire add reflective layer: 415mW; high-voltage flip-chip light-emitting diode: 432mW), high-voltage flip-chip light-emitting diode enhance the 37.1% luminous intensity, and enhance the power efficiency reached 38.4% in the same 1 watt power consumption. We were also investigated in a high-voltage blue light-emitting diode (1.15x1.15 mm2, 15 series-connection), through geometry design and etching at the bottom of sapphire substrate (8 kinds of geometrical design), then etched the bottom of the sapphire substrate surface depositing on the reflective layer. The main research in discussion with etched sapphire geometry and planar reflective layer in the light extraction efficiency of collocation. The experimental results show that (the efficiency of the equivalent 1 watt power consumption, the plane: 32.6%; etching out of the sapphire geometry (the best design): 37.1%). The best design to enhance the efficiency of 13.8%. The improvement of these two studies can be referred by the TracePro optical simulation. In the second part, a large area (1.15x1.15 mm2) ultraviolet light emitting diode is fabricated on the silicon substrate. Through wafer bonding and laser lift-off (LLO) techniques to easily achieve the sapphire substrate be deleted and replaced by silicon substrates in UV light-emitting diode. The main research is to study the enhancement of light extraction efficiency of P-GaN with and without non-insulated current blocking layer and the degree of roughening in the ultraviolet light emitting surface. Experimental results show that (under the same input current of 350mA, using non-insulated type current blocking layer LOP: 433, without using non-insulated type current blocking layer LOP: 138), the difference is due to the non-insulated type current blocking layer makes the current spreading becomes more uniform, and takes the light has a very significant improvement. According to the result, the luminous intensity was promoted to 214%, and efficiency difference is nearly 3.1 times by adding non-insulated type current blocking layer. Furthermore, comparison results of different degree rough surface show (under the same input current of 350mA, flat-surface LOP: 433, Rms: 17nm; large pyramid & low density LOP: 698, Rms: 163nm; small pyramid & high density LOP: 858, Rms: 377nm), the differences in the extent of roughening directly influence scattering of quality and increase light escape probability, and brings very significant improvement on the light extraction. According to different degree of roughening surface that makes luminous intensity were improved 61% and 98%. The difference of efficiency was also improved nearly 1.8 and 2.1 times. Furthermore, we combine flip-chip light-emitting diode can avoid electrode shading effect and vertical light-emitting diode in high operating current with superior heat dissipation ability, explore and research the difference of optical and electrical properties in new thin-film type vertical light-emitting diode and the traditional vertical light-emitting diodes. In new thin-film type of vertical light emitting diodes, through the diode structure design leads P and N electrodes on the same side before the metal bonding. After that, continue complete the metal bonding and laser lift-off (LLO) process, making a large area (1.15x1.15 mm2) UV light emitting diode on the silicon substrate. Finally, p-electrode be induced outside and lead to a contact electrode. The main research is to discuss the differences of current spreading and the shading effect in both structures (the new thin-film type of vertical light-emitting diode and the traditional vertical light-emitting diode). And then discuss the improvement of the light extraction efficiency. Finally, we present the wafer-level thin-film flip-chip ultraviolet light-emitting diode and fabrication method, in addition to simplifying the chip-level of the complicated process, compared to traditional vertical light-emitting diode and the traditional flip-chip light emitting diode, it has superior performance of photoelectric characteristics. The wafer-level thin-film flip-chip ultraviolet light-emitting diode is fabricated by the traditional flip-chip method, and the difference is that the substrate is hereby replaced by the metal copper and the sapphire is removed by the laser.
48
Chen, Yan-hao, and 陳彥豪. "Study of Light Extraction Efficiency in GaN based Flip-Chip Light-Emitting Diodes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06248069534004885616.
Full textAbstract:
碩士國立交通大學
光電工程學系
100
In this study, we change the process of GaN-based flip chip light-emitting diodes (LEDs), we want to investigate the light extraction efficiency of flip-chip LEDs. The first part of the study is to improve the reflective electrode of the flip-chip light-emitting diodes and produce a ohmic contact with the p-type GaN. Materials architecture of reflective contact metal includes: ohmic layer (high transmittance and ohmic contact), the reflective layer (light extraction), the barrier layer (block the diffusion of metals), different thickness of contact metal can get low resistance of ohmic contact, and provide different reflectance, discuss the relationship between the reflectance and the light extraction efficiency by the different reflectivity of p-contact electrodes. We try to produce high reflectivity electrode after the heat-treated, also achieve a ohmic contact (specific contact resistance) in the 10-2ohm-cm2 level, and corresponding to 93.6% of reflectance in the 450nm wavelength. We can get a better reflectivity electrode in application. The second part, we use patterned sapphire substrate of different shapes and scales to investigate the light extraction efficiency of flip-chipLEDs. Using the same process to produce flip-chip LEDs, and then discuss by I-V curve, light intensity and the simulation by rigorous coupled-wave analysis method, to get the light extraction of different patterned sapphire substrates. Finally we can derive suitable patterned sapphire substrate for flip-chip light emitting diodes.
49
Barletta, Philip. "Study of GaN-based materials for light-emitting applications." 2006. http://www.lib.ncsu.edu/theses/available/etd-08132006-215853/unrestricted/etd.pdf.
Full text
50
Horng-Shyang, Chen. "Light-emitting Devices Based on InGaN/GaN Nano-structures." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2107200615535400.
Full text