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图形化蓝宝石衬底GaN基LED的研究进展 总被引:3,自引:0,他引:3
蓝宝石衬底作为发光二极管最常用的衬底,经过不断发展,在克服其与GaN间晶格失配和热膨胀失配问题上,研究人员不断提出解决方案。近期发展起来的图形化衬底技术,除了能减少生长在蓝宝石衬底上GaN之间的差排缺陷,提高磊晶质量以解决失配问题,更能提高LED的出光效率。从衬底图形的形状、尺寸、制备工艺出发,回顾了图形化蓝宝石衬底GaN基LED的研究进展,详细介绍了近年来关于图形化衬底技术与其他技术在提高LED性能方面的结合,总结了图形化蓝宝石衬底应用于大尺寸芯片的优势,并对其未来在大功率照明市场的应用进行了展望。 相似文献
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Organic-inorganic hybrid perovskite have recently drawn appreciable attention for applications in light-emitting diodes (LEDs). However, the weak exciton binding energy of the methylammonium lead iodide perovskite introduces large exciton dissociation and low radiative recombination on its application as emission layer in near-infrared LEDs. Herein, we demonstrate the simple method by incorporating of phenethylammonium iodide (PEAI) into the perovskite can concurrently improve the radiative recombination rate for improving perovskite LED performances. Additionally, by introducing PEAI dramatically constrains the growth of perovskite crystals during film forming, producing crystallites with small dimensions, reducing roughness, and pin-hole free. After optimizing the emission layer in the perovskite LED, a high optical output power of 458.03 μW and external quantum efficiency of 5.25% are achieved, which represents a ~50-fold enhancement in the quantum efficiency compared to device without PEAI. Our work suggests a broad application prospect of perovskite materials for high optical output power LEDs and eventually a potential for solution-processed electrically pumped NIR laser diodes. 相似文献
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《Microelectronics Reliability》2015,55(2):389-395
The paper concerns modelling an influence of self-heating and mutual thermal coupling on power LEDs characteristics. The electrothermal model of a power LED for SPICE software taking into account electric, thermal and optical properties of the considered devices, and particularly mutual thermal coupling between the devices situated on the common heat-sink, is presented. The method of estimating model parameters values is proposed and the method of measuring their own and mutual thermal resistance between power LEDs is described. Using the elaborated model the characteristics of selected diodes are calculated at different cooling conditions of the investigated LED. The obtained results of calculations are compared with the measurements results for a single diode, two diodes situated on the common heat-sink and a LED module. 相似文献
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In this study, the heat dissipation efficiencies of high power multi-chip COB (Chip-on-Board) LEDs with five different chip gaps were compared by assessing their junction temperature (Tj) and thermal resistance (Rth). Junction temperatures were measured using an IR camera and were also simulated by computational fluid dynamics (CFD) software. The effects of heat sinks with different surface areas, heat slugs made of different materials and different injection currents (different wattages) on high power LED junction temperatures are discussed. In addition, the optical characteristics of the LED, such as its lumens and luminous efficiency are evaluated. The experimental results show that a chip with a smaller gap has a higher junction temperature and more thermal resistance, and the junction temperature difference between the LEDs with the smallest and largest chip gaps is 3.12 °C. Optical performance analyses show that the LED with a larger chip gap has higher lumens and higher luminous efficiency. Thus, higher junction temperatures reduce the optical performance of high power LEDs. 相似文献
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《Microelectronics Reliability》2015,55(1):52-61
Investigation of changes of operation and noise characteristics during aging process of light-emitting diodes (LEDs) has been carried out. Several groups of different design (different optics) LEDs based on different materials (nitride-based blue and white LEDs, phosphide-based red LEDs) have been investigated. It is found that leakage current components appear due to LED’s defects and their affect is observed as increase of both the low frequency electrical noise intensity and non-ideality factor of current-leakage characteristic in small current region. No considerable changes of light intensity characteristics during LEDs aging have been observed. Noise modeling, spectral and correlation analysis of optical and electrical fluctuations show on partly correlated optical and electrical fluctuations caused by defects in the active region of the LED. Degradation processes of investigated LEDs foremost occur in the diode chip and lead to the leakage current that has important affect to the electrical fluctuation level, but practically has a weak influence to the light emission properties of LED. Phosphorous layer of white LEDs and additional optical elements have no significant influence to the reliability of investigated LEDs under given aging conditions. 相似文献
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I. P. Smirnova L. K. Markov D. A. Zakheim E. M. Arakcheeva M. R. Rymalis 《Semiconductors》2006,40(11):1363-1367
Characteristics of AlGaInN LEDs with removed sapphire substrate are studied. To remove the substrate from a finished LED crystal mounted by the flip-chip method onto a silicon wafer, the laser lift-off technique was used. To raise the light output efficiency, a scattering profile was formed on the n-GaN surface by ion etching in a Cl2: Ar gas mixture. This resulted in the 25–30% increase in the external quantum efficiency of LEDs. The LEDs fabricated in this way demonstrate stable operation at drive currents of up to 300 mA with an optical power as high as 110 mW. 相似文献
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Shi J.-W. Sheu J.-K. Wang C.-K. Chen C.-C. Hsieh C.-H. Chyi J.-I. Lai W.-C. 《Photonics Technology Letters, IEEE》2007,19(18):1368-1370
In the following study, we demonstrated linear cascade GaN-based light-emitting-diode (LED) arrays at a wavelength of approximately 520 nm. Experimental LEDs were analyzed with the goal to improve the output power and differential efficiency of a single LED. The study shows that using arrays with up to four LEDs connected in series, we can achieve four times the improvement in output power (differential quantum efficiency) under the same bias current as compared to a single LED apparatus. We have also measured the modulation-speed performance of experimental LEDs, and both devices exhibit similar 3-dB bandwidth (90 MHz) under the same bias currents. Experimental results indicate that the cascade connection offers the advantages of significantly enhanced external differential efficiency and provision of a method to use a constant-voltage power supply. The current crowding problem and resistance-capacitance-limited bandwidth degradation issues in a large active area LED can also be minimized using the connection demonstrated in our experiment. 相似文献
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Hsu S.-C. Lee C.-Y. Hwang J.-M. Su J.-Y. Wuu D.-S. Horng R.-H. 《Photonics Technology Letters, IEEE》2006,18(23):2472-2474
We have demonstrated enhanced output power from roughened GaN-based light-emitting diodes (LEDs) by using electrodeless photoelectrochemical etching with a chopped source (ELPEC-CS etching). It was found that the 20-mA output power of the ELPEC-CS treated LED (with roughened surfaces on the top p-type and bottom n-type GaN surface as well as the mesa sidewall) was 1.41 and 2.57 times as high as those LEDs with a roughened p-type GaN surface and a conventional surface, respectively. The light output pattern of the ELPEC-CS treated LED was five times greater than the conventional LED at 0deg which was caused by the roughened GaN surface that improved the light extraction efficiency of the LED 相似文献
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Lee Y.J. Tseng H.C. Kuo H.C. Wang S.C. Chang C.W. Hsu T.C. Yang Y.L. Hsieh M.H. Jou M.J. Lee B.J. 《Photonics Technology Letters, IEEE》2005,17(12):2532-2534
Quaternary AlGaInP light-emitting diodes (LEDs) operating at a wavelength of 630 nm with a stripe-patterned omni-directional reflector (ODR) were fabricated. It is demonstrated that the geometrical shape of stripe-patterned structure improves the light extraction efficiency by increasing the extraction of guided light. The optical and electrical characteristics of stripe-patterned ODR LEDs are presented and compared to typical ODR and distributed Bragg reflector (DBR) LEDs with the same epitaxial structure and emitting wavelength. It is shown that the output power of the stripe-patterned ODR LED exceeds that of the typical ODR and DBR LEDs by a factor of 1.15 and 2 times, respectively, and with an acceptable forward voltage of about 2.2 V. 相似文献
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热学特性是影响功率型LED光学和电学特性的主要因素之一,设计了一套基于脉冲式U-I特性的功率型LED热学特性测试系统,可以测试在不同结温下LED工作电流与正向电压的关系,从而获得LED的热学特性参数。该系统通过产生窄脉冲电流来驱动LED,对其峰值时的电压电流进行采样,同时控制和采集LED的热沉温度,从而获得不同温度下LED的U-I特性曲线。与其他U-I测试系统相比,文中采用了窄脉冲(1 s)工作电流,LED器件PN结区处于发热与散热的交替过程,不会造成大的热积累,大大提高了测量精度。实验中,对某功率型LED进行了测试,获得了该器件的电压、电流和结温特性曲线,并利用B样条建立该器件的U-I-T模型,进而实现了对其结温的实时在线检测。 相似文献
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Masui H. Nakamura S. DenBaars S.P. Mishra U.K. 《Electron Devices, IEEE Transactions on》2010,57(1):88-100
It has been several years since InGaN/GaN light-emitting diodes (LEDs) on nonpolar and semipolar orientations were first demonstrated. Prominent performance and inherent potential of these crystallographic orientations have been revealed as bulk-GaN substrates of arbitrary orientations became available for epitaxial device growth. At this point in time, we intend to survey the progress made to date and prospect the future requirements for further device improvements. The discussion begins with a historical background: how nonpolar/semipolar orientations were introduced to III-nitride LEDs and why they are beneficial. The discussion then provides information on elementary crystallography and piezoelectricity in addition to the electronic band structure of wurtzite crystals. Later in this paper, LED reports are collected to develop comprehensive knowledge of the past research efforts and trends. Nonpolar and semipolar orientations provide not only high LED performances, e.g., optical output power and wavelength ranges, but also unique functions, e.g., polarized light emission, which will explore new fields of applications. 相似文献
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利用恒流LED驱动器设计高效率LED照明系统 总被引:1,自引:0,他引:1
随着高功率LED的问世,照明产业开始面临新的挑战。LED的使用寿命及电源转换效率成为设计LED照明系统时的主要考虑因素。而为了提供恒流(constantcurrent)以维持LED色彩与亮度的一致性,恒流LED驱动器可作为一个提供恒流输出的开关式转换器。此外,省电或是高效率的电源转换需求更是在LED照明应用上不可缺少的要因,而滞后型脉冲频率调制技术(HystereticPFM)可以大幅提升无论在轻载或重载时的电源转换效率。本文将探讨如何利用恒流LED驱动器设计出高效率、高稳定性的LED照明系统。 相似文献
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Ching-Hua Chiu Ming-Hua Lo Tien-Chang Lu Peichen Yu Huang H.W. Hao-Chung Kuo Shing-Chung Wang 《Lightwave Technology, Journal of》2008,26(11):1445-1454
We have developed a simple method to fabricate nanoscale masks by using self-assembly Ni clusters formed through a rapid thermal annealing (RTA) process. The density and dimensions of the Ni nano-masks could be precisely controlled. The nano-masks were successfully applied to GaN-based light-emitting diodes (LEDs) with nano-roughened surface, GaN nanorods, and GaN-based nanorod LEDs to enhance light output power or change structure properties. The GaN-based LED with nano-roughened surface by Ni nano-masks and excimer laser etching has increased 55% light output at 20 mA when compared to that without the nano-roughened process. The GaN nanorods fabricated by the Ni nano-masks and ICP-RIE dry etching showed 3.5 times over the as-grown sample in photoluminescence (PL) intensity. The GaN-based nanorod LEDs assisted by photo-enhanced chemical (PEC) wet oxidation process were also demonstrated. The electroluminescence (EL) intensity of the GaN-based nanorod LED with PEC was about 1.76 times that of the as-grown LED. The fabrication, structure properties, physical features, and the optical and electrical properties of the fabricated devices will be discussed. 相似文献
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Ming-Te Lin Shang-Ping Ying Ming-Yao Lin Kuang-Yu Tai Jyh-Chen Chen 《Microelectronics Reliability》2012,52(5):878-883
A LED package structure with vertical geometry of W5II is proposed for high power optoelectronic semiconductor devices. To provide an efficient and easy method of assembling high-power LEDs to sockets of the fixtures, a vertical design referenced from the typical Edison screw base found in US-based lamp systems is used in the structure. The thermal simulation of the structure, fabrication processes and thermal characteristic are evaluated. Thermal resistance measurements are performed to characterize the thermal performance of W5II, and the optical and electrical characteristics of W5II are also verified. The good heat dissipation of W5II could be utilized to enhance the reliability and thermal fatigue capability of high-power LED packages. 相似文献
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《Photonics Technology Letters, IEEE》2008,20(23):1923-1925