Dissertations / Theses on the topic 'GaN Diodes'
To see the other types of publications on this topic, follow the link: GaN Diodes.
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 'GaN Diodes.'
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
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
2
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
3
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
4
Wang, Ke, and 王科. "Some experimental studies of n-type GaN and Au/GaN contacts." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B26663612.
Full text
5
Bavencove, Anne-Laure. "Réalisation de diodes électroluminescentes à base de nanofils GaN." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY037/document.
Full textAbstract:
Ces travaux de thèse portent sur l'évaluation des propriétés de nanofils InGaN/GaN en vue de la réalisation de diodes électroluminescentes (LEDs). Deux types d'architecture, obtenus par des techniques de croissance différentes, ont été étudiés. La technique MBE a conduit à la réalisation de LEDs en structure axiale émettant du domaine spectral bleu au rouge. Les émetteurs uniques présentent dans ce cas des diamètres typiquement inférieurs à 100 nm. La technique MOCVD a conduit quant à elle la fabrication de LEDs émettant des longueurs d'onde plus courtes à partir d'hétérostructures InGaN/GaN en Coeur/Coquille présentant des dimensions micrométriques. Dans les deux cas, la croissance est réalisée de manière spontanée sur un substrat Silicium (111) de conductivité élevée permettant l'injection verticale du courant dans les dispositifs intégrés à l'échelle macroscopique. L'ensemble des briques technologiques nécessaires à la fabrication de LEDs a été évalué par un panel important de techniques expérimentales adaptées aux structures à fort rapport de forme. Ainsi, l'effet de l'incorporation d'espèces dopantes de type n (Silicium) et de type p (Magnésium) a été caractérisé par des expériences de spectroscopie optique couplées à des mesures électriques sur fils uniques. De plus, la cathodoluminescence basse température a été largement utilisée afin d'étudier les propriétés optiques de la zone active à base d'InGaN dans les deux architectures considérées. Après intégration technologique, des caractérisations électro-optiques résolues à l'échelle du fil unique ont montré que les performances des LEDs à nanofils restent principalement limitées par la fluctuation des propriétés électriques et optiques entre émetteurs uniquesThis thesis aims at studying the intrinsic properties of InGaN/GaN nanowires (NWs) in order to fabricate efficient light emitting diodes (LEDs). Two active region designs, obtained through different growth techniques, have been extensively investigated. Axial NW-based LEDs emitting from the blue to the red spectral range have been grown by MBE. In this case, single emitters present diameters typically smaller than 100 nm. MOCVD allowed the fabrication of LEDs emitting shorter wavelengths from Core/Shell heterostructures with typical dimensions in the micrometre range. In both cases, the spontaneous growth has been conducted on Silicon (111) highly conductive substrates in order to inject the current vertically into macroscopically contacted devices. Technological building blocks needed to fabricate LEDs have been investigated using a wide range of characterization techniques adapted for high aspect ratio structures. Thus, n-type (Silicon) and p-type (Magnesium) dopings have been assessed thanks to optical spectroscopy techniques, and these results have been confirmed by electrical measurements carried out on single wires. Furthermore, low temperature cathodoluminescence has been widely used to study the optical properties of InGaN-based active regions. After technological integration, electro-optical characterizations with spatial resolution down to the single wire level have revealed that device performances are mainly limited by the fluctuation of electrical and optical properties between single emitters
6
Xu, Hui Park Minseo. "Fabrication and electrical/optical characterization of bulk GaN-based Schottky diodes." Auburn, Ala, 2009. http://hdl.handle.net/10415/1871.
Full text
7
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
8
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.
9
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
10
Watson, Scott. "High speed systems using GaN visible LEDs and laser diodes." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7205/.
Full textAbstract:
Visible light communication is a developing technology making use of light-emitting diodes (LEDs) and laser diodes in the visible spectrum for communication purposes. This thesis looks at the use of gallium nitride (GaN) devices for high speed measurements in free space, through fibre and underwater. Micro-pixellated LEDs (micro-LEDs) have been used as a source for these measurements and the different ways to drive these devices is explored. LEDs are limited in how fast they can be driven and therefore laser diodes are also considered for these high speed measurements. The frequency responses of such devices are measured and data transmission experiments are conducted. However, these devices can be used for more than just free-space communication. Laser diodes are much more powerful than their LED counterparts and can be modulated much faster making them ideal for fibre communications and underwater communications, where eye-safety is not an issue. By using these devices, a study of step-index plastic optical fibre (SI-POF) and multi-core fibre is carried out, analysing their dispersion properties and transmission characteristics. Further high speed measurements were conducted under the water as the need to communicate with unmanned vehicles under the ocean continues to be an important issue. Many security and defence companies and oil and gas industries are interested in this technology for that purpose, as the current setup is complex, expensive and limited in bandwidth. High modulation bandwidths and high data transmission rates are achieved, with some of the leading results in the field presented here. These results highlight the importance of the topic of visible light communication and show the attractiveness of using these visible GaN devices for this purpose.
11
Lui, Chun Hung. "Optical properties of InGaN/GaN multiple quantum well light emitting diodes /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202006%20LUI.
Full text
12
Kölper, Christopher [Verfasser]. "Optoelectronic Properties of GaN Nanorods and Light Emitting Diodes / Christopher Kölper." München : Verlag Dr. Hut, 2013. http://d-nb.info/1031844554/34.
Full text
13
Jobe, Sean Richard Keali'i. "OPTIMIZATION OF GAN LASER DIODES USING 1D AND 2D OPTICAL SIMULATIONS." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/74.
Full textAbstract:
This paper studies the optical properties of a GaN Laser Diode (LD). Through simulation, the GaN LD is optimized for the best optical confinement factor. It is found that there are optimal thicknesses of each layer in the diode that yield the highest optical confinement factor. There is a strong relationship between the optical confinement factor and lasing threshold—a higher optical confinement factor results in a lower lasing threshold. Increasing optical confinement improves lasing efficiency. Blue LDs are important to the future of lighting sources as they represent the final color in the RGB spectrum that does not have a high efficiency solution. The modeled GaN LD emits blue light at around ~450nm. Each layer of the GaN LD is drawn in a model simulation program called LaserMOD created by RSOFT Design Group, Inc. By properly modifying the properties of each layer, an accurate model of the GaN LD is created and then simulated. This paper describes the steps taken to properly model and optimize the GaN LD in the 1D and 2D models.
14
Efthymiou, Loizos. "GaN-on-silicon HEMTs and Schottky diodes for high voltage applications." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/274912.
Full textAbstract:
Gallium Nitride (GaN) is considered a very promising material for use in the field of power devices as its application in power systems would result in a significant increase in the power density, reduced power losses, and the potential to operate at high frequencies. The wide bandgap of the material allows a high critical electric field to be sustained which can lead to the design of devices with a shorter drift region, and therefore with lower on-state resistance, if compared to a silicon-based device with the same breakdown voltage. The use of an AlGaN/GaN heterostructure allows the formation of a two-dimensional electron gas (2DEG) at the heterointerface where carriers can reach very high mobility values. These properties can lead to the production of High Electron Mobility Transistors (HEMTs) and Schottky barrier diodes with superior performance, even when compared to devices based on state-of-the-art technologies such as Silicon Carbide or superjunctions. Furthermore, epitaxial growth of GaN layers on silicon wafers allows a significant reduction in the production cost and makes these devices competitive from a price perspective. This thesis will deal with a variety of topics concerning the characterization, design and optimization of AlGaN/GaN HEMTs and Schottky diodes with a 600 to 650V rating. Discussion will span several topics from device cross-section physics to circuit implementation and will be based on both experimental results and advanced modelling. More specifically, the thesis is concerned with the characterization of AlGaN/GaN Schottky diodes and extraction of their main parameters such as ideality factor, barrier height and series resistance. A thorough investigation of their reverse recovery performance and a comparison to competing technologies is also given. Several topics which concern the operation of AlGaN/GaN HEMTs are then discussed. The underlying physics of p-gate enhancement mode transistors are analysed followed by a discussion of the challenges associated with the implementation of these devices at a circuit level. Finally, a comparison of the performance of a specific area-saving layout (Bonding pad over active area) and a conventional design is given. The thesis aims to significantly enhance the understanding of the behaviour of these devices to enable better or new commercial designs to emerge.
15
Liang, Hu. "Fabrication and characteristics of the InGaN/GaN multiple quantum well blue LEDs /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20LIANG.
Full textAbstract:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 62-66). Also available in electronic version. Access restricted to campus users.
16
Berthelot, Laurent. "Réalisation et caractérisation de composants luminescents à base de semiconducteurs organiques : Diodes à héterojonction PVK/Alq3 : Diodes hybrides GaN/Organique." Ecully, Ecole centrale de Lyon, 1999. http://www.theses.fr/1999ECDL0052.
Full textAbstract:
Ce travail de thèse porte sur l'étude de diodes électroluminescentes organiques (OLED). L'accent a été mis sur la compréhension des caractéristiques de transport ainsi que le contrôle de la couleur. Deux types de composants luminescents très différents ont été réalisés et étudiés : des OLED à hétérojonctions PVK/Alq3 et des diodes hybrides GaN/Organiques. Dans un premier temps, les différentes familles de matériaux ainsi que leurs principales caractéristiques sont présentées. Nous décrivons ensuite l'état de l'art et les limitations de ces structures organiques. La partie expérimentale décrit en détail la technologie des composants, les matériaux utilisés, leurs méthodes de mise en oeuvre ainsi que les caractéristiques physiques et électro-optiques effectuées. Les propriétés électriques et électro-optiques des OLED ont été étudiées en fonction des divers paramètres de réalisation : traitement des substrats, choix de conducteur de trous, épaisseur des couches, nature de l'hétérostructure. Les résultats ont été analysés sur la base des modèles de conduction compatibles avec les semi-conducteurs organiques (charge d'espace ou mobilité dépendante du champ électrique) afin d'identifier les modes de conduction dominants. Dans le but de contrôler la couleur d'émission, deux méthodes ont été évaluées : le dopage d'une des couches de transport par un colorant laser et l'utilisation de couche de recombinaison (oligomère de PPV) insérée entre les deux couches de transport. Les couleurs ont pu être ajustées du vert vers l'orange. Des structures hybrides intégrant des diodes GaN et de matériaux luminescents organiques et inorganiques ont été réalisées. Des composants émettant soit une lumière blanche soit une lumière contrôlable du bleu à l'orange ont été obtenus.
17
Weig, Thomas [Verfasser], and Ulrich T. [Akademischer Betreuer] Schwarz. "Generation of optical ultra–short pulses in (Al,In)GaN laser diodes." Freiburg : Universität, 2015. http://d-nb.info/111499636X/34.
Full text
18
Hsu, Chou-Wei, and 許洲維. "P-type GaN Schottky Diodes Study." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/22036479481422562872.
Full textAbstract:
碩士逢甲大學
電機工程所
92
In this study, the current density-voltage (J-V) characteristic of Schottky diodes of indium-tin-oxide (ITO) contacts to p-type GaN (p-GaN) has been investigated. The calculated barrier-height value of ITO/p-GaN samples using the thermionic field emission (TFE) model is 3.2 eV, which implies that the work function of ITO is equal to 4.3 eV. The result is supported by J-V measurements of ITO/n-type GaN Schottky diodes. On the other hand, the barrier height of ITO/p-GaN was also determined from the x-ray photoelectron spectroscopy (XPS) data. The analysis of the XPS spectral shifts indicated that this observed barrier-height value of ITO/p-GaN by XPS is in good agreement with the value of 3.2 eV obtained from J-V measurements.
19
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 .
20
Chu, Chung Ming, and 曲崇銘. "Electrical Measurements of Schottky Diodes on GaN." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/10899311797402766747.
Full textAbstract:
碩士國立交通大學
電子物理學系
84
In this study, several measurement techniques were used to analyze the electric characteristics and traps in unintentionally doped n-type GaN grown by metal organic chemical vapor deposition.I-V measurements on Schottky diodes indicates the forward current appears due to thermionic field emission of electrons through the Schottky barrier, because there are high trap concentrations near the surface region. On the other hand, the electrons tunnel through the Schottky barrier at large reverse voltage, and through a smaller barrier by the assistance of a trap E2 at small reverse voltage. C-V measurements indicate the smaller V/III ratios, the larger carrier concentrations because of the increase of nitrogen vacancies. Therefore,the series resistance becomes smaller and capacitance larger. Schottky barrier height is much larger than the theoretical value of 0.84eV at low temperature, and is smaller at high temperature. Studies by transient capacitance measurements revealed the presence of a new majority-carrier trap with the activation energy of 1.34eV.
21
Huang, Shyh-Jer, and 黃士哲. "Theoretical Studies of InGaN/GaN Laser Diodes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/05698630068849835891.
Full textAbstract:
博士國立交通大學
電子工程系所
96
In this dissertation, the InGaN/GaN laser diode is theoretically studied. We have optimized its active region and the cladding layer composed of a p-type AlGaN/GaN superlattice by studying the spillover effect, the influence of dopants, and the key factor making the vertical resistance of the p-type superlattice large. The effects of electron spillover from quantum wells on the optical property of InGaN/GaN laser diodes are theoretically studied in detail. Six-band model including strain effect is used to calculate valence band states. Continuous subbands are simulated deliberately by dense discretized subbands for the spillover electrons. The calculation results show obvious differences in the radiative current densities and the gain spectra between the cases with and without considering the spillover effect. We further investigate the spillover effect on the radiative current densities and the spontaneous emission spectra, with variations in the depth and the width of quantum wells, the total loss of the cavity, and the temperature. For shallow wells, the spillover effect is particularly important. It broadens both the gain and the spontaneous emission spectra and hence deteriorates the threshold of laser diodes. Such an effect can be alleviated by employing lasers with a long cavity and a multi-quantum-well active region. The concepts of the electron spillover studied in this work are not only applicable to the nitride lasers, but also to other kinds of quantum-well lasers. The influences of the modulation-doping in InGaN/GaN laser diodes are also theoretically studied with the effects of electron spillover from quantum wells considered. The calculation results show that the threshold current can be significantly reduced by p-type modulation-doping around the wells but not by n-type doping, supposed that the layers are of a perfect quality and the impurity-induced defects are ignored. Also, the p-type modulation doping can make the threshold current more insensitive to the cavity loss compared with other cases. An optimized threshold current density can be achieved for single-quantum-well lasers by introducing p-type dopants. However, the dopant concentration is high and may be inaccessible. For double-quantum-well lasers an optimized low threshold current can be achieved with a slighter and practicable p-type doping level. We also study the vertical transport of holes through p-type AlGaN/GaN superlattices with both Ga- and N-face polarities by drift-diffusion, tunneling, and thermionic emission models to find the key factors that dominantly influence the average vertical resistivity at different temperatures. It is shown that although the acceptors in the barriers are easily ionized to give a high spatially averaged density of holes, the barriers themselves are the main obstacle to the transport of holes through the superlattices. In our calculation results, the number of barriers in the superlattices dominantly affects the average vertical resistivity if the barriers are thin enough. So the resistivity can be reduced by decreasing the barrier number for a fixed total length of superlattices. Our results show that about 50% reduction in the resistivity can be excepted when the structure varies from Al0.11Ga0.8N(2 nm)/GaN(2 nm) to Al0.11Ga0.8N(6 nm)/GaN(2 nm).
22
Huang, Wen-Pin, and 黃文賓. "Fabrication of GaN High Voltage Schottky Diodes." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/45505821927574799620.
Full textAbstract:
碩士國立中央大學
電機工程研究所
94
It is the goal that the global various countries have wanted to reach all the time to pursue the electric supply and demand of high quality, a large number of construction power plants do not solve the way of the problem, but should improve the efficiency of the electric equipment products. In this thesis, we studied on GaN Schottky diodes with mesa-type n-GaN and planar-type AlGaN/GaN, operating at high forward current and high breakdown voltage. In Mesa-type n-GaN Schottky diodes, having a drift region of 2.8�慆 thickness and doping concentration of 5×1016/cm3, show a breakdown voltage of about 190V. We report I-V characteristics, both at room temperature and in the temperature range 300 to 423K, of Mesa type GaN Schottky diodes fabricated on expitaxial layers incorporating double GaN/SiN nucleation layers. For a more significant reduction of the on-state resistance, AlGaN/GaN heterostrure devices are attractive due to their high mobility and high carrier density of two-dimensional electron gas at the AlGaN/GaN interface. In planar-type AlGaN/GaN Schottky diodes, we studied simulation and fabrication of AlGaN/GaN rectifiers with field plate termination. The extent of metal electrode overlap and dielectric thickness were varied to ascertain their effects on the BV. The circular devices show on-resistance (Ron) of about 13m��-cm2. The experimental breakdown data shows that there is an optimum Si3N4 thickness for which the breakdown voltage (BV) is highest and on either side of this optimum Si3N4 thickness, the BV voltage decreases. In the present case, the highest BV of about 475V is obtained when silicon nitride thickness is around 800nm and the Schottky diodes exhibit a figure of merit (VB2/Ron) of about 17MW/cm2. The 40 finger-type AlGaN/GaN Schottky diodes with wire bonding obtained a forward current 2.5A at an applied forward voltage of 3.5V, and BV of about 436V. In reverse recovery characteristics of the finger-type AlGaN/GaN Schottky rectifiers, when the diode was switched from forward to reverse bias, the device exhibited an ultrafast switching time (trr) 15ns less than 30ns of Si-based device.
23
Huang, Yen-Chieh, and 黃彥傑. "GaN heterostructure Schottky Diodes on Silicon Substrates." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30211069823184628503.
Full text
24
Tu, Guan-Cheng, and 凃冠誠. "MgZnO/GaN Heterojunction Diodes for Optoelectronic Applications." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/gcruh9.
Full textAbstract:
碩士逢甲大學
電子工程學系
106
In this thesis, the ultrasonic spray pyrolysis deposition which has benefits of low-cost and room-temperature operation is used to deposit n-type MgZnO on the p-type GaN to form pn heterojunction. Ti/Al and Ni/Au are deposited by the thermal evaporator to serve as the cathode and the anode of the diode. The present diode can be used as light-emitting diode and photodiode. In order to understand the properties of MgZnO thin films which is deposited by the ultrasonic spray pyrolysis deposition, the following material characterization techniques are used including: (1) photoluminescence, the emission wavelength of the MgZnO thin film, (2) X-ray photoelectron spectroscopy, the composition of the MgZnO thin film, (3) X-ray Diffractometer, the crystal structure of the MgZnO thin film. The current versus voltage characteristic, light output power versus injection current characteristic, and emission wavelength spectrum characteristic are measured. The turn-on voltage of the light-emitting diode is 3.7V, the light output power is 3.4.mW. The emission wavelength occurs blue shift when the Mg contents increase. For estimate the performance of the photodiode, the diode is applied negative bias and the following characteristics are measured including, spectral photoresponse, detectivity, UV-to-visible rejection ratio, and response time characteristics. The photodiode has the largest photoresponse 16.4A/W at 350nm, and with increase of Mg content, the sensing wavelength also blue shift from 350nm (Mg0.1Zn0.9¬O) to 310nm (Mg0.4Zn0.6O). MgZnO/GaN heterojunction optoelectronic diodes are fabricated successfully. The operation mode of the diode is controlled by the polarity of the applied voltage. When the positive voltage is applied, the diode is used as the light-emitting diode. When the negative voltage is applied, the diode is used as the photodiode.
25
Lin, Wei-sheng, and 林偉聖. "InGaN-Based Alternating Current Light-Emitting Diodes with AlGaN/GaN Schottky Barrier Diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/47581537444137671785.
Full textAbstract:
碩士國立中央大學
電機工程研究所
99
In this study, we investigated the detailed mechanisms on fabricating InGaN-based Alternating Current Light-emitting diodes (AC-LEDs) with AlGaN/GaN Schottky Barrier Diodes (SBDs). We tried two methods for integrating vertical structures combined with SBDs and LEDs: (1) AlGaN/GaN SBD structure re-grown on InGaN/GaN LED structure, (2) InGaN/GaN LED structure re-grown on AlGaN/GaN SBD structure. Both of them had an accuracy problem of dry etching, so we developed a selective re-growth method to fabricate AC-LED incorporated with SBDs. In the SBD structure, we employed AlGaN/AlN multi-layers as the buffer layer to acquire the good device characteristics of an operation voltage of 2.75 V at 20 mA and a low leakage current of 75 μA at -200 V. Then we successfully demonstrated the integration of InGaN-based AC-LED chip with GaN SBDs by utilizing the photolithography process. The AC-LED has an emission area of about 88.4 % of the total chip area, while the integrated SBDs in a Wheatstone bridge (WB) scheme occupy only 3.3 % of the total chip area. Compare to the conventional WB AC-LEDs, the AC-LED integrated with SBD WB has a larger emission area by about 47 % and exhibit a higher integrated luminescence intensity by about 28 % at 130 V DC.
26
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.
27
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.
28
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.
29
Liu, Zhe-Yu, and 劉哲宇. "Study of GaN PIN Diodes on Sapphire Substrate." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/26457823768140537737.
Full textAbstract:
碩士國立清華大學
電子工程研究所
102
Due to the dislocation that resulted from the lattice mismatch between GaN and sapphire substrate, patterned sapphire substrate (PSS) was widely used in MOCVD epitaxy to improve the crystalline quality instead of conventional sapphire substrate (CSS). We compared PIN devices fabricated on FSS with those on PSS to investigate how dislocation affects the devices characteristics, such as forward turn-on voltage, reverse leakage current and breakdown voltage. Following electrical measurement including current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS) were applied in this study. Besides, edge effect that resulted from side-wall damage during ICP process is an issue in vertical PIN diodes. To overcome this, SiO2 deposition layer was utilized as side-wall passivation to reduce edge effect. Therefore, we also investigate the breakdown characteristics of diodes to realize the influence of passivation layer.
30
Jin, Chong. "GaN Schottky diodes for signal generation and control." Phd thesis, 2015. https://tuprints.ulb.tu-darmstadt.de/5212/1/thesischong20150325_flattern.pdf.
Full textAbstract:
The aim of this work is to explore the potential of GaN Schottky diodes for high fre- quency signal generation and control, with emphasis on their power handling capability. GaN Schottky diodes are expected to provide superior power handling capability due to the wide band-gap of GaN. Theoretical analysis has been performed analytically and numerically. Devices have been fabricated and their performance has been evaluated experimentally. Demonstration of monolithic integrated circuits utilizing the realized devices was also made.
The diode figure of merits e.g. Cj0, Rs , Vbr , have been considered with respect to power handling and harmonic generation to permit evaluation of the diode design requirements for satisfying specific circuit needs. Numerical simulation allowed the prediction of device performance for specific geometry and material properties. Simulation results have shown that GaN Schottky diodes have a power handling capability at least 2 times higher than their GaAs counterparts, while maintaining acceptable losses.
Several fabrication technology approaches have been studied and implemented for real- izing GaN-based Schottky diodes. Their key steps include dry etching, metal contacts, as well as interconnects. The surface treatment before metal deposition necessary for good quality Schottky contacts has been thoroughly studied. Three means of intercon- nect methods were demonstrated for on-wafer tests. They allowed rapid evaluation of the electrical characteristics of the diodes and set up the basis for the development of monolithic integrated circuits.
High frequency small-signal measurements have been performed for the GaN Schot- tky diodes. The obtained S-parameters were used to extract equivalent circuit models. A parameter extraction procedure was established to de-embed the pad parasitics, and obtaining information about their intrinsic elements permitting in this way diode opti- mization.
The large-signal characteristics of the fabricated diodes were measured on-wafer using a large-signal network analyzer. This novel characterization method provided immediate information about diode features such as power handling, loss etc. The time-domain waveforms of the diodes were obtained under various operating conditions allowing a better insight into the diode operation.
Large-signal models of the diodes have been obtained by considering the extracted small- signal equivalent circuit characteristics and the large-signal measurement results. GaN- based circuits using diodes have been studied. They include a frequency doubler and an analog phase shifter. Consideration of their large-signal characteristics was possible using the extracted diode large-signal models. Doublers made with this technology are expected to provide an output power of 10 dBm at 94 GHz. MMIC phase shifters were designed, fabricated and characterized. They showed a phase tuning (∆φ) of 45◦ and 6-7
dB insertion loss in the 32-38 GHz range.
31
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.
32
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.
33
Lin, Wen-Yu, and 林文禹. "Fabrication of Metal-Substrate GaN-Based Light-Emitting Diodes." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/43839188095470317678.
Full textAbstract:
碩士國立中興大學
材料工程學研究所
93
A vertical conducting GaN/mirror/Cu LED fabricated using the laser lift-off and electroplating techniques is demonstrated. The selective p-GaN top area was first electroplated by a thick copper film, and then a UV laser was employed to separate the GaN thin film from the sapphire substrate. The forward voltages (@ 20 mA) of the original GaN/sapphire and p-side-down GaN/mirror/Cu LED samples were 2.76 and 2.87 V, respectively. These results indicated that the series resistance of the GaN/mirror/Cu LEDs does not arise greatly with the present vertical conducting structure. The leakage currents (@ -5 V) of the original GaN/sapphire and p-side-down GaN/mirror/Cu LED samples were 77.6 and 33.8 nA, respectively. This suggests that the present device structure will not result in additional leakage current in the GaN/mirror/Cu LED device. The luminance intensity of the vertical conducting p-side-down GaN/mirror/Cu LED presented about 2.7 times in magnitude as compared with that of the original GaN/sapphire LED (@ 20 mA). The light output power for the GaN/mirror/Cu LED was about twofold stronger (@ 500 mA). A more stable peak wavelength shift under high current injection was also observed. These results indicated that large-area copper substrate LEDs have better thermal management and good heat sink.
34
Lin, Shin-Wei, and 林仕尉. "Conductive transparent oxide applied to GaN Schottky barrier diodes." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/04735008512118252762.
Full text
35
Shuo-YuanLiao and 廖碩源. "Application of ZnO in GaN-based light-emitting diodes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/nz79bw.
Full text
36
Lin, Pei-ying, and 林佩瑩. "Analysis of AlGaN/GaN High Breakdown Voltage Schottky Diodes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98253923560566605289.
Full textAbstract:
碩士國立中央大學
電機工程研究所
98
In this study, AlGaN / GaN HEMT structures on the high-resistance AlN buffer layer and the conventional GaN buffer layer were grown, respectively. The planar Schottky diodes were then fabricated on these structures. From the I-V measurement, the results indicate the device with high-resistance AlN buffer layer not only substantially promote the breakdown voltage but also keep the low leakage current density. Therefore, in this study we discussed in detail about the factors of SBDs characteristics on different buffer layers, and further analyzed the mechanism of leakage current. In the analysis of material quality, according to the x-ray diffraction GaN (002) rocking curve shows that AlN buffer layer can effectively reduce the screw-type dislocation density of epitaxial materials, thus reducing the leakage current. Besides, the etching pits density (EPD) is also calculated that the dislocation density of the above epitaxial structure reduced to about 3.2x107 cm-2, which is about an order lower compared to the epitaxial material grown on the GaN buffer layer. In the analysis of leakage current, the leakage current in the buffer layer and the AlGaN barrier layer are discussed, respectively. In the discussion, the resistance of the AlN buffer layer is about six orders greater than that of the GaN buffer layer, indicating that the AlN buffer layer has the characteristic of low-leakage current; in addition, temperature-dependent current-voltage (I-V) measurement and frequency-dependent capacitance-voltage (C-V) measurement are used to analyze the mechanism of leakage current. The results show that the primary source for the leakage current during the voltage of 0 V~ - 6 V is the AlGaN barrier layer while the leakage current is dominated by the quality of buffer layer below -6 V. To further discussion, defect energy levels in AlGaN barrier are quantified by the leakage current model of Frenkel-Poole emission (F-P emission).
37
Chen, Ying-chien, and 陳英杰. "Fabrication and analysis of a novel GaN Schottky Diodes." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/93359234175393166653.
Full textAbstract:
碩士國立中央大學
物理研究所
97
In this thesis a new AlGaN/GaN high electron mobility transistor basedrectifier, i.e. P-field effect Schottky barrier diode (P-FESBD), is proposed andfabricated. It consists of a p-n diode and a Schottky diode connected in parallel.With the additional p-type GaN gate, the rectifier is expected to operate in the normally-off mode with low reverse leakage current and low on-resistance. The turn-on voltage, on-state resistance and breakdown voltage of the one finger rectifier with 500×35 μm2 gate area is 0.5 V, 24 mΩ-cm2 and 22 V, respectively. According to secondary ion mass spectroscopy measurement and electrical characterization, diffusion of the p-type dopant, Mg, and leakage current of the GaN buffer layer are concluded to be the main reasons for poor breakdown voltage. Furthermore, in order to increase the forward current and yield of GaN Schottky diodes with multi-finger or large gate area, tested Schottky diodes are connected in parallel by wire bonding. Forward current of 432 mA at 1.5 V is achieved on a six-diode device with 160 V breakdown voltage.
38
Huang, Chao-Shun, and 黃炤舜. "Plasma-Etching Characteristics of GaN-Based Light Emitting Diodes." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/84163827912537590519.
Full textAbstract:
碩士國立中興大學
精密工程學系所
94
GaN-related alloy semiconductors with wide band gap ranging from 3.4 to 6.2 eV at room temperature are the focus of current research for UV or blue emitters and detectors. During the conventional device processing, the wet chemical etching frequently suffers from undercut issue and is gradually replaced by plasma etching. In this thesis, we investigate the plasma-etching characteristics of GaN-based light emitting diodes using an inductively coupled plasma (ICP) etcher. The etch characteristics were investigated by varying the etching parameters, such as ICP power, bias power, chamber pressure, and gas mixture (BCl3, CH4, Ar). Details of the parameter effects on the etch rate, selectivity, etch profile, and surface roughness of GaN epilayers will be discussed. It was found that the ICP power and chamber pressure have large effect on the etch rate. When the ICP power increased from 100 to 500 W, a maximum etch rate of 22 Å/sec can be obtained at 300 W. When the chamber pressure increased from 3 to 20mTorr, we can get a maximum etch rate value of 30 Å/sec at 5 mTorr. As concerning about the surface roughness, with increasing the chamber pressure (³20 mTorr), CH4 (³20 sccm) and Ar (³ 20 sccm) flows, the maximum root mean square roughness of 12, 12 and 20 nm was obtained, respectively. A maximum etch angle of 78, 72 and 73° (i.e. 90° means vertical etch profile) can be achieved under a bias power of 250 W, CH4 flow of 15 sccm, and Ar flow of 20 sccm, respectively. Under a compromised ICP etching parameters (ICP power: 300 W, bias power: 100 W, chamber pressure: 3 mTorr, Cl2 gas: 25sccm, BCl3 gas: 15sccm), a smoother surface and near vertical side wall for GaN can be obtained for subsequent light-emitting-diode fabrication process.
39
Lu, Yi-An, and 盧怡安. "Study on GaN Light Emitting Diodes with Imbeded Electrodes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/27893743342506275485.
Full textAbstract:
碩士國立中興大學
精密工程學系所
98
Textured n-GaN side up LED with interdigitated imbedded electrodes (IIE) eliminating the electrode-shading loss with high reflection mirror on silicon substrate and double-side roughening both p-GaN and undoped-GaN layers have been investigated. The devices are subsequently fabricated with wafer-bond, laser lift-off and chemical dry/wet etching techniques. The roughness on p-GaN surface was fabricated via low temperature growth, and that on n-GaN surface was made by wet-etching. This n-GaN side up structure was useful to avoid light-absorbing and enhance the light efficiency. We compared the performance of 4-types LEDs: Original-LED/Sapphire with single rough surface(SR-LED), p-side up-LED with double rough surface(DR-LED), n-side up-DR-LED, n-side up-DR-VB(vertical electrodes by wafer bonding)LED. The forward voltage(at 350 mA) of 4-types LEDs is 4.06 V, 4.11 V, 4.38 V, 4.97 V respectively. The luminance intensity of the final 3-types LEDs(at 700 mA) is 119.83 %, 158.74 % and 26.64 % higher than that of the original LED, respectively. The performance of p-side up-DR-LED which is 119.83 % higher than that of original structure, yet worse than n-side up-DR-LED. It was worthy to mention that the area of electrode shading is only 13% of the light emitting area. Therefore, the obtained above results suggest that the optimum thin film LED structure is the n-GaN with double surface roughness and the high reflection mirror.
40
Lu, Chih-Feng, and 呂志鋒. "Emission Efficiency Improvement of GaN-based Light-emitting Diodes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/63507784391404310165.
Full textAbstract:
博士臺灣大學
光電工程學研究所
98
In this dissertation, we have demonstrated the dependencies of output spectral overall red shift and spectral blue shift in increasing injection current on the prestrained barrier thickness in an InGaN/GaN QW LED of prestrained growth. It was found that a thinner prestrained barrier led to a larger general spectral red shift and a smaller blue shift in increasing injection current because of the stronger prestrain effect. Also, it was found that in terms of device resistance and saturation current, the LED performances of prestrained samples were better than that of a conventional LED. An LED of a thinner prestrained barrier had a better performance. These observations were attributed to the higher average indium content and stronger indium-rich clustering behavior in a sample of stronger prestrain. These attributions were supported by the SSA results in the TEM measurements. Furthermore, a green LED was fabricated based on the prestrained growth technique to compare with an LED of the same emission wavelength based on the conventional growth method. Then, the prestrained underlying growth technique was used to grow three yellow-emitting QWs of high efficiency. The yellow photons were mixed with blue light from an overgrown blue-emitting QW to produce white light. The improved properties of the phosphor-free monolithic white-light LED have been discussed. The reduction of the EQE droop of an LED through the SP-QW coupling mechanism has been demonstrated. With a current spreading grid pattern on the mesa surface, it was found that a smaller grid period led to more effective carrier transport into the QW regions under Ag deposition for stronger SP-QW coupling such that the droop effect was more significantly reduced, including the increase of injection current density of maximum EQE and the decrease of drooping slope. The observation of the SP-QW coupling effect in the samples of thin p-GaN was also supported by the different droop behaviors of the LED samples fabricated with the epitaxial structure of thick p-GaN, in which the SP-QW coupling effect is weak. Besides, we have demonstrated the dependence of the output spectrum on the junction temperature of a blue/green two-color InGaN/GaN QW LED. By decreasing the metal thickness of the p-type Ohmic contact on the device, the contact resistance was increased and hence the junction temperature was also increased. With the junction temperature increased, the probability for the deeper QWs to capture holes became higher such that blue emission could be enhanced to compete with the dominating green emission from the first QW. The conclusion of a higher junction temperature in a sample of a thinner p-type metal layer was consistent with the measurements of the output power versus the injection current, the current versus the applied voltage, and the direct measurement of contact resistance.
41
王偉儒. "Study of Characteristics of High-Power GaN PIN Diodes." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/24947617318478482805.
Full text
42
Zih-FongWang and 王子峯. "Fabrication of GaN/InGaN Based Light-Emitting Diodes (LEDs)." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/wn4cv3.
Full text
43
HSU, YUEH, and 徐岳. "Modeling the diode equation with quantum wells for vertical-injection GaN-based light emitting diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/49633188571021859770.
Full text
44
Lee, Geng-Yen, and 李庚諺. "Growth, Fabrication and Characterization of AlGaN/GaN Schottky Diodes and AlInN/GaN Field-Effect Transistors." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/43165176168569087482.
Full textAbstract:
博士國立中央大學
電機工程學系
104
In this dissertation, the growth mechanisms and device characteristics of AlGaN/GaN-based Schottky barrier diodes (SBDs) with a high breakdown voltage and the AlInN-based high electron mobility transistors (HEMTs) with a high current density have been studied. For the high-voltage GaN SBDs, devices are fabricated on a composite AlGaN/AlN buffer layer with different threading dislocation (TD) densities. The correlation between TDs and the device characteristics could be well linked. The SBDs with an anode-to-cathode distance (LAC) of 30 μm exhibit a low on-state resistance (Ron) of 7.9 mΩ-cm2, a high breakdown voltage (VB) of 3,489 V, and a low leakage current of less than 0.2 μA at -2,000 V, which lead to a high figure-of-merit of 1.54 GW/cm2. Based on the x-ray diffraction, etch pit density, and transmission electron microscopy (TEM) measurements, high breakdown characteristics of the SBDs are attributed to low screw-type and high edge-type dislocations in the AlGaN/GaN buffer layer. Several measurement are implemented for the in-depth analysis. The surface and buffer leakage current could be recognized successfully by the designed test devices. From capacitance-voltage (C-V) measurement, a large amount of initial occupied fixed charges at zero bias are recognized in the material, demonstrating the trapping effect by the edge-type dislocations. Moreover, the simulation results with the associated trap densities in the structures correlate well with the experimental results, which evidences the VB of the device is associated with their edge-type TDs in the material. From dynamic Ron measurement, no obvious charging effect as well as the dynamic Ron degradation is observed during the reverse voltage bias. At room temperature (RT), the SBD with a high edge-type dislocation density show a low reverse recovery time of 17 ns. Under a high temperature of 150 oC, the switching curve of the device almost remain the same as RT’s performance. These performances are comparable to the reported GaN-based SBDs and outperform their silicon counterpart especially at high temperature, which demonstrate their potential for high-power low-loss switching circuits. For the development of AlInN HEMTs, the theoretical calculation of polarization and the growth conditions have been systematically studied. The alloy scattering rate with arbitrary unit could be estimated in both AlGaN and AlInN alloys in comparison. In order to reduce alloy scattering in GaN-based HEMTs, a binary material as an AlN spacer layer with wide bandgap inserting between AlGaN/GaN or AlInN/GaN interface is essential to prevent the electron profile from extending into the barrier layer. The epitaxy growth conditions of the AlInN HEMTs are well investigated. After improving the crystal quality of AlInN HEMTs, the improved surface root-mean-square (RMS) roughness of 0.738 nm and the increased mobility to 1360 cm2/V-s without sacrificing its two-dimensional electron gas (2DEG) density (2.13×1013 cm-2) are successfully demonstrated, leading to a very low sheet resistance (Rsh) of 215 ohm/sq. The benchmark shows the mobility value is one of the best results among AlInN HEMTs grown on silicon substrate. On the other hand, the electrical characteristics of a series of AlInN HEMTs with GaN cap layer thicknesses ranging from 0 to 26 nm have been investigated. The breakdown voltage, mobility of two-dimensional electron gas, on-state resistance, and dynamic Ron of the HEMTs are improved by increasing the cap layer thickness. The off-state breakdown voltage of AlInN MIS-HEMTs is increased from 530 to 675 V by adding a 13-nm-thick GaN cap layer. Detailed studies on the dynamic Ron of the AlInN HEMTs indicate that the GaN cap layer can greatly reduce the dynamic Ron ratio, and that the devices with a 26-nm-thick GaN cap layer can achieve a dynamic Ron ratio comparable to that of AlGaN MIS-HEMTs. These improved electrical characteristics are attributed to the GaN cap layer, which not only reduces the surface E-field but also raises the conduction band of the barrier layer and effectively prevents electrons from being trapped in the AlInN barrier and above. These results show the talents of AlInN/GaN HEMTs for modern power electronic devices.
45
Chen, Tron-min, and 陳聰敏. "The Investigations of High Efficiency Vertical Structured GaN-based Schottky Barrier Diodes and Light Emitting Diodes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42847536340999956033.
Full textAbstract:
博士國立成功大學
微電子工程研究所碩博士班
95
In this dissertation, vertical structure GaN-based Schottky barrier diodes (SBDs) and light emitting diodes (LEDs) were investigated. Vertical-conducting GaN-based SBDs and LEDs were designed, fabricated and characterized, by means of Ni-electroplating substrate transformation in conjunction with laser lift-off technique. A real-time data acquisition (DAQ) technique was also developed for precisely characterizing the junction temperature, light output power, and thermal resistance of light emitting diodes (LEDs). To further promote both contact and current spreading properties of GaN-based SBDs and LEDs, properly surface etching treatment to the top n-GaN layer and high quality metallic contact system were both proposed. Finally, thermal behavior and thermal model of the fabricated devices were analyzed and developed for further investigating their efficiency and reliability. To equalize the resistance of all possible current paths in the fabricated Vertical-conducting Metal-substrate GaN-based Light-Emitting Diodes (VM-LEDs), an anisotropic laser etching to the surface layer (n-GaN) of 40-mil VM-LEDs for improving light emission uniformity and light output power is proposed and demonstrated. Typical improvement in light output power by 38-26% has been obtained. A cost effective ICP mesa etching associated with the IZO TCL was also proposed to serve both as current spreading and current blocking. In experiments, VM-LEDs with the proposed structure have been successfully fabricated and an average improvement in light output power by about 25% has also been obtained. A real-time data acquisition (DAQ) technique was developed for precisely characterizing the junction temperature, light output power, and thermal resistance of light emitting diodes (LEDs). Furthermore, by using the transient state of Tj, thermal resistance and thermal capacitance of LEDs were extracted.
46
Lin, Chuang-sheng, and 林壯聲. "Array of GaN Based Transverse-Junction Blue Light Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/n5rewb.
Full textAbstract:
碩士國立中央大學
電機工程研究所
96
We demonstrate the array of GaN-based blue-light light-emitting diode (LED), which is composed of GaN-based blue wavelength multiple-quantum-wells (MQWs) and a transverse p-n junction. The device was realized by the re-growth of n-type GaN layers on the sidewall of p-type GaN and MQWS. The non-uniform carrier distribution problem that occurs in the multiple quantum wells (MQWs) of traditional vertical p-n junction LEDs can be totally eliminated by incorporating a transverse p-n junction with MQWs. In output power measurements, the transverse junction light-emitting diodes show higher output power as compare with the conventional vertical junction light-emitting diodes. Moreover, the transverse junction light-emitting diodes with more elements small light-emitting diodes have better current spreading and reduce current crowding effect.
47
Yi-JungLiu and 劉亦浚. "Investigation of GaN-Based Light-Emitting Diodes with Improved Performance." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/72c4c9.
Full text
48
Wang, Cheng-Yin, and 王振印. "Fabrication and Analysis of GaN-based Nanorod Light Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/40773024305916468594.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
96
Since p-type GaN is well developed in 1990''s, GaN has been widely useded in short wavelength light emitting diodes. Light emitting diodes have advantages such as low power consumption, long life time, good reliability, short response time. Nevertheless, there are still some spaces to improve it like quantum efficiency, peak wavelength shift. A practical approach to fabricate textured GaN-based light emitting diodes (LEDs) by nanosphere lithography is presented. Due to the refraction index difference between GaN and air, there will be a total reflection at this interface and low external quantum efficiency. The current resolution is growing a rough p-type layer on conventional light emitting diodes to reduce the total reflection, but it needs extra time and more cost to do it. By spin-coating a monolayer of SiO2 nanoparticles as the mask, textured LEDs can be fabricated. Both textured p-GaN and textured ITO LEDs show significant improvement over the conventional LEDs without damaging the electric characteristics. The results show that the method is promising for low-cost manufacturing high efficient GaN-based LEDs. The solution for peak wavelength shift is usually treated by growth some nanostructure to release the strain in material. We further use this practical process to fabricate InGaN/GaN multiple quantum well (MQW) LEDs with a self-organized nanorod structure is demonstrated. Contrary to epitaxy, we provide a novel way in fabrication process to solve the peak wavelength shift. Also, because of the hardness of parallel metal evaporation on tips of nanorods without short circuit, there are only a few related results. The nanorod array is realized by using nature lithography of surface patterned silica spheres followed by dry etching. A layer of spin-on-glass (SOG), which intervening the rod spacing, serves the purpose of electric isolation to each of the parallel nanorod LED units. The electroluminescence (EL) peak wavelengths of the nanorod LEDs nearly remain as constant for an injection current level between 25mA and 100mA, which indicates that the quantum confined stark effect (QCSE) suppressed in the nanorod devices. Furthermore, from the Raman light scattering and x ray diffraction analysis we identify a strain relaxation mechanism for lattice mismatch layers in the nanostructure.
49
Yu-ChihChang and 張宇志. "Fabrication of GaN-Based Light Emitting Diodes with Nanosphere Structures." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/49030196378861344271.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
101
In order to improve light extraction efficiency (LEE) and internal quantum efficiency (IQE) of GaN-based light-emitting diodes (LEDs), the self-assembled SiO2 nanosphere monolayer structure is introduced and studied. Three new nanosphere monolayer-related approaches are proposed in this thesis. The optical and electrical properties as well as related material analyses were also studied and discussed. An interesting approach to improve light extraction efficiency of high power GaN-based LEDs by the use of a three dimensional-photonic crystal (3D-PhC) backside reflector is studied. A 3D-PhC backside reflector is formed by coating a self-assembled SiO2 nanosphere monolayer between the hybrid reflector and backside of sapphire substrate. Firstly, a self-assembled pseudo-hexagonal close packing SiO2 nanosphere monolayer was coated on the backside of sapphire substrate. Then, a distributed Bragg reflector (DBR) and an aluminum (Al) metal mirror were deposited subsequently. By inserting SiO2 nanospheres, hemispherical patterns could be transferred to the deposited reflector. Hence, photons could be redirected into arbitrary angles for light extraction by the transferred concave surface. Total internal reflection (TIR) could be limited. In addition, due to the presence of gap between SiO2 nanospheres, the PhC-like air void arrangement is formed after the deposition of backside reflector. Hence, light scattering effect could be effectively improved. This certainly gives photons more opportunities to find the escape cones. As compared with a conventional LED (without backside reflector), at 350 mA, the studied device exhibits 136% enhancement in light output power without the degradation of electrical properties. Notably, the studied device exhibits 23.6% enhancement in light output power as compared with the LED with a planar hybrid (a DBR + an Al metal mirror) backside reflector. In chapter 3, since SiO2 nanospheres are pulled and adhered on the backside of sapphire substrate by Van der Waals forces, the adhesion between SiO2 nanospheres and sapphire substrate is poor. Hence, in order to alleviate this problem, a new approach to form a 3D backside reflector by using SiO2 nanspheres as a hard mask and inductively coupled plasma (ICP) dry etching process to transfer pseudo-hexagonal close packing hemispherical arrangement patterns on the backside of sapphire substrate. Then, a DBR and an Al metal mirror were deposited subsequently, as mentioned above. Due to the hemispherical arrangement patterns on the backside of sapphire substrate, hemispherical patterns could be transferred to the deposited reflector. Hence, photons could be redirected into arbitrary angles for light extraction by the transferred concave surface. However, since hemispherical patterns structure was formed by ICP process, the PhC-like air void arrangement was not present. As compared with a conventional LED (without backside reflector), at 350 mA, the studied device still exhibits 116% enhancement in light output power. Notably, the studied device exhibits 14.1% enhancement in light output power as compared with the LED with a planar hybrid (a DBR + an Al metal mirror) backside reflector. Moreover, the product yield could also be improved, due to the enhanced adhesion between backside reflector and sapphire substrate In addition, due to the large difference in lattice mismatch and thermal expansion coefficient between GaN and sapphire, many threading dislocations (TDs) on GaN epitaxial layers would be induced. For this reason, the employment of nanospheres-pattern sapphire substrate (NS-PSS) is studied in this work. This NS-PSS is successfully fabricated by using SiO2 nanspheres as the hard mask and inductively coupled plasma (ICP) dry etching process to transfer hemispherical patterns, which exhibits pseudo-hexagonal close packing arrangement, on the sapphire substrate. The use of NS-PSS could effectively decrease threading dislocation density, which reduces undesirable nonradiative recombinations, and enhance light output power. As compared with a conventional LED, at 20 mA, the studied device exhibits 31.4% enhancement in light output power. And forward voltage and leakage current could also be reduced. These results could be attributed to that the crystalline quality of GaN epitaxial layer is effectively improved by using a NS-PSS.
50
Chang, Chun-Chieh, and 張鈞傑. "Investigation of GaN-based Light-Emitting Diodes with AlN Film." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/27295777091457059486.
Full textAbstract:
碩士國立交通大學
光電系統研究所
100
In this study, we examined the characteristics for the application of AIN thin films on GaN light-emitting diode (LED) devices. The devices structure contained a current blocking layer (CBL) and a passivation layer. We also compared the differences in optical and electrical properties between this devices structure and devices that traditionally employing silicon dioxide thin films. We used the sputtering system to grow thin films. Transmittance measurements indicated that the AIN thin film had a transmittance of above 90% in the visible light region. Additionally, a developer was used to test the etch rate of the AIN thin films. The results of this test indicated that after heat treatment in a nitrogen atmosphere for 1 min, the resistance of the AIN thin film to the developer etching increased because of improvements in lattice quality. The experiments also confirmed the feasibility of employing AIN thin films in follow-up experiments on LED devices. Next, we used the AIN thin film as the CBL in the LED. First, current-voltage (I-V) curve indicated that AIN thin films had higher series resistance values compared to that of the silicon dioxide thin films. These values increased with increases in the thin-film thickness. With an AIN thickness of 1800 Å, the corresponding LED light output power with 20 mA injection increased by 8% compared to the conventional LED. The light output power increased because the CBL effectively reduced the probability of the current flowing through the area under the p-type electrode. This improved the phenomenon of the electrode masking the light. Next, we investigated the use of AIN thin films as the sidewall passivation layer for LED devices. Heat treatment experiments indicated that although the heat treatment process can reduce the leakage current in the components, it also reduces the LED’s light output power by approximately 9% compared to the conventional LED. The decrease in light output power was caused by a decline in the thin-film transmittance in the sidewall passivation layer area. Finally, we used the developer to remove the heat-treated AIN passivation layer. The light output power with 20 mA injection increased by approximately 11% compared to that of the conventional LED. The light output power increased because the resistivity of the ITO thin film located in the area surrounding the LED mesa increased and the sidewall resistance value changed. This caused the current to concentrate in the area not covered by the AIN thin film, generating an effect similar to that of the CBL. This effect improved the current spreading in the LED n-type electrode area.