功率发光二极管的寿命预测

针对功率发光二极管(LED)的使用寿命问题,提出了利用阿仑尼斯模型预测功率发光二极管器件寿命的方法,以器件输出光功率P下降到初始值P0的50%为失效判据,通过对功率蓝光GaN LED芯片两个结温点的高温恒定应力加速寿命实验结果进行分析计算,求出了功率蓝光GaN LED器件在正常应力条件下的期望寿命,确定阿仑尼斯模型在功率发光二极管寿命实验过程中的适用性,为预测功率发光二极管寿命提供理论依据.     

基于选择性湿法粗化方法制作n型欧姆接触的垂直结构发光二极管的电学性能研究

低阻和高稳定性的氮极性面N型欧姆接触对于GaN基垂直结构发光二极管尤为重要。研究发现,相对于未湿法粗化N型GaN面,湿法粗化N型GaN面的欧姆接触电阻较大,且最终制成的发光二极管具有较高的开启电压和较低的反向漏电。本文提出了一种选择性湿法粗化方法制作氮极性面N型GaN欧姆接触,基于此方法最终制成的垂直结构发光二极管具有更低的开启电压和反向漏电,并且输出光功率略有提升。进一步的老化实验表明该法制作的欧姆接触具有良好的稳定性。     

GaN基发光二极管寿命测试及失效分析

将来自相同外延片和相同制作工艺的30只GaN基绿色发光二极管管芯分成3组,分别加30、40和60 mA电流进行不同时间的老化试验.在老化之前和老化期间测量了器件的光输出功率和I-V特性.将测得的光输出功率数据对时间进行指数函数拟合,得到了每一组器件的退化率及寿命,并推出器件在正常使用条件下的寿命.实验数据分析表明在电流应力作用下,GaN基绿色发光二极管的正向电压随着老化时间的增加单调上升,同时光功率下降.在60 mA下老化的管芯的串联电阻退化严重.对失效器件进行了失效机理分析.     

大功率半导体激光器步进加速老化研究

介绍了半导体激光器寿命测试的理论依据,给出了由电流应力决定的寿命测试的数学模型,据此对AlGaInAs/AlGaAs/GaAs 808nm大功率半导体激光器进行常温电流步进加速老化实验。由步进加速老化的理论依据及数学模型推算出了步进加速寿命实验时间折算公式,利用步进加速寿命实验时间折算公式推算出了器件在额定应力条件下工作的寿命结果;根据实验后器件的失效模式分析,与恒定应力加速老化方式下的实验结果相对比分析,确认该步进加速实验方法可以适用于半导体激光器的加速老化。     

有机电致发光现状和发展趋势

有机电致发光是近年来发展起来的一种具有极大竞争力的固体化平板显示技术,目前已经报道的有机发光二极管最大流明效率已达311m/W,最高半寿命已超过100,000小时,本文对有机发光管理的工作原理,材料特点和老化机理进行了探讨,并分析了该技术在商业显示方面的应用前景。     

在侧壁形成导热膜的GaN基发光二极管

研制了一种在侧壁形成导热膜的GaN基发光二极管(LED),其中导热层由氮氧化铝形成,导热层外再覆盖一保护层,保护层选自氧化物、氮化物或氟化物.对LED进行电流加速老化实验,分析输出功率随老化时间的变化关系,可以看到侧壁形成导热膜的GaN基LED的输出功率衰减缓慢.实验表明由于氮氧化铝膜具有良好的导热性,其可以有效地耗散发光部分产生的热量,因此在器件侧壁形成AlON导热膜可以改善GaN基LED的输出特性并提高器件的可靠性.     

选择性生长技术制备GaN薄膜的研究进展

Ⅲ族氮化物化合物半导体GaN是目前半导体领域的研究热点之一,具有宽禁带、高温下物理、化学性质稳定等特点,在光电子、微电子等领域有广泛的应用.降低缺陷密度制备高质量的GaN外延层是生产高性能和高寿命GaN器件的关键,也是人们始终致力于研究的内容,本讨论对近年来发展的一种采用选择性生长技术生长GaN的方法、原理、进展情况进行了介绍.     

基于超程时间减小速率建模的 电磁继电器可靠性寿命分析方法的研究􀀂

电磁继电器触点的磨损和老化是影响继电器可靠性的重要因素之一。超程时间的减小是电磁继电器触点磨损和老化的主要表现形式。本文提出以超程时间减小速率为随机变量，建立了电磁继电器可靠性寿命分析数学模型，给出了寿命可靠度计算方法。实例计算结果表明，该模型是有效的。     

高功率半导体开关DSRD在UWB雷达中的应用

讨论了一种先进的全固态、高速、高功率半导体开关DSRD的物理特性、工作原理、性能特点。利用DSRD的物理特性，提出了一种先进的超宽带雷达发射信号设计方法。利用该方法设计的超宽带雷达发射机具有高功率、高重频、体积小、重量轻、长寿命、高可靠等优点。     

非线性曲线拟合程序及其在半导体物理中的应用

本文论述了曲线拟合的数学模型及其用途与存在的困难。提出联合套用阻尼最小二乘法和复合形法可具有放宽初值要求、收敛速度快等优点。对拟合结果检验的必要性和方法作了讨论,给出非线性拟合的详细通用程序框图。应用本程序对硅太阳电池光谱响应、磷化镓发光二极管光电流谱,硅N-N~+-P结构光伏谱、磷化镓瞬态光电容谱、掺氮或掺铋磷化镓光致发光谱等半导体物理问题作了曲线拟合,并借助拟合结果分析完善了物理模型。     

Improved Reliability and ESD Characteristics of Flip-Chip GaN-Based LEDs With Internal Inverse-Parallel Protection Diodes

In this letter, a GaN/sapphire light-emitting diode (LED) structure was designed with improved electrostatic discharge (ESD) performance through the use of a shunt GaN ESD diode connected in inverse-parallel to the GaN LED. Thus, electrostatic charge can be discharged from the GaN LED through the shunt diode. We found that the ESD withstanding capability of GaN/sapphire LEDs incorporating this ESD-protection feature could be increased from several hundreds up to 3500 V in the human body model. Furthermore, flip-chip (FC) technology was also used to produce ESD-protected LEDs to further improve light output power and reliability. At a 20-mA current injection, the output power of the FC LEDs showed an improvement of around 60%. After a 1200-h aging test, the luminous intensities of the FC LEDs featuring an internal ESD-protection diode decreased by 4%. This decay percentage was far less than those of non-FC LEDs     

GaN基绿光LED芯片电流加速失效机理研究

采用电流加速的电应力老化方法研究GaN基绿光 LED芯片的失效机理。LED芯片在经过60 mA 电流老化424 h后,其发光效率总体趋势都是随老化时间增加而减小 ,但是小测量电流相比于大测量电 流的发光效率衰减程度更为明显。同时,在正向偏压下电流电压曲线基本没有变化,而反向 偏压下的反向 电流随老化时间的增加而快速增加。笔者认为在电应力老化作用下,随老化时间增加,有源 区的缺陷能级 增多,在正向偏压下,缺陷能级起到一个有效陷阱的作用,增加了载流子的寿命,降低了辐 射复合的几率, 使得发光效率降低,但是并没有减小正向偏压下的电流,而反向偏压时,缺陷能级起到了一 个漏电通道的作用,使得反向电流增大。     

Light Extraction Efficiency Enhancement of GaN Blue LED by Liquid-Phase-Deposited ZnO Rods

We investigate the light extraction efficiency of a GaN light-emitting diode (LED) by using liquid-phase-deposited ZnO rods at near-room temperature. Zinc nitrate and hexamethylenetetramine were used as the deposition precursors. Compared with the conventional GaN LED, the optical power output of the GaN LED with crystalline ZnO rods on its surface has about 1.6 times enhancement.     

Improvement of the efficiency droop of GaN-LEDs using an AlGaN/GaN superlattice insertion layer

With an n-AlGaN(4 nm)/GaN(4 nm) superlattice(SL) inserted between an n-GaN and an InGaN/GaN multiquantum well active layer,the efficiency droop of GaN-based LEDs has been improved.When the injection current is lower than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL is relatively small compared to that without an n-AlGaN/GaN SL.However,as the injection current increases more than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL surpasses that of an LED without an n-AlGaN/GaN SL. The wall plug efficiency of an LED has the same trend as lumen efficiency.The improvement of the efficiency droop of LEDs with n-AlGaN/GaN SLs can be attributed to a decrease in electron leakage due to the enhanced current spreading ability and electron blocking effect at high current densities.The reverse current of LEDs at -5 V reverse voltage decreases from 0.2568029 to 0.0070543μA,and the electro-static discharge(ESD) pass yield of an LED at human body mode(HBM)-ESD impulses of 2000 V increases from 60%to 90%.     

Enhanced carrier confinement in AlInGaN-InGaN quantum wells in near ultraviolet light-emitting diodes

To increase carrier confinement, the GaN barrier layer was substituted with an AlInGaN quaternary barrier layer which was lattice-matched to GaN in the GaN-InGaN multiple quantum wells (MQWs). Photoluminescence (PL) and high-resolution X-ray diffraction measurements showed that the AlInGaN barrier layer has a higher bandgap energy than the originally used GaN barrier layer. The PL intensity of the five periods of AlInGaN-InGaN MQWs was increased by three times compared to that of InGaN-GaN MQWs. The electroluminescence (EL) emission peak of AlInGaN-InGaN MQWs ultraviolet light-emitting diode (UV LED) was blue-shifted, compared to a GaN-InGaN MQWs UV LED and the integrated EL intensity of the AlInGaN-InGaN MQWs UV LED increased linearly up to 100 mA. These results indicated that the AlInGaN-InGaN MQWs UV LED has a stronger carrier confinement than a GaN-InGaN MQWs UV LED due to the larger barrier height of the AlInGaN barrier layer compared to a GaN barrier layer.     

GaN基LED与Si键合技术的研究

采用金属键合技术结合激光剥离技术将GaN基LED从蓝宝石衬底成功转移到Si衬底上。利用X射线光电子谱(XPS)研究不同阻挡层对Au向GaN扩散所起的阻挡作用,确定键合所需的金属过渡层。利用多层金属过渡层,在真空、温度400℃和加压300 N下实现GaN基LED和Si的键合,通过激光剥离技术将蓝宝石衬底从键合结构上剥离下来,形成GaN基LED/金属层/Si结构。用金相显微镜及原子力显微镜(AFM)观察结构的表面形貌,测得表面粗糙度(RMS)为12.1 nm。X射线衍射(XRD)和Raman测试结果表明,衬底转移后,GaN基LED的结构及其晶体质量没有发生明显变化,而且GaN与蓝宝石衬底间的压应力得到了释放,使得Si衬底上GaN基LED的电致发光(EL)波长发生红移现象。     

Nano-Processing Techniques Applied in GaN-Based Light-Emitting Devices With Self-Assembly Ni Nano-Masks

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.     

Nitride Nanocolumns for the Development of Light-Emitting Diode

The progress of light-emitting-diode (LED) development based on nitride nanocolumn (NC) growth, including InGaN/GaN quantum-well (QW) growth on NCs and regularly arranged GaN NC growth, is first reviewed. Then, the coalescence-overgrowth results based on patterned GaN NC growth are introduced. The overgrowth quality dependence on NC cross-sectional size and NC spacing size is discussed. Generally, a smaller NC dimension and spacing size lead to higher overgrowth quality, including lower threading dislocation (TD) density and larger lateral domain size. Next, the emission enhancement results of blue- and green-emitting InGaN/GaN QW and LED structures based on NC growth and coalescence overgrowth are presented. Significant enhancements (up to ~100% output intensity increase in a blue LED) are demonstrated. For LED applications, the TD density reduction in an overgrown GaN template can more effectively enhance the emission efficiency of a blue LED, when compared with a green LED.     

Fabrication of extremely thermal-stable GaN template on Mo substrate using double bonding and step annealing process

A new layer transfer technique which comprised double bonding and a step annealing process was utilized to transfer the GaN epilayer from a sapphire substrate to a Mo substrate. Combined with the application of the thermal-stable bonding medium, the resulting two-inch-diameter GaN template showed extremely good stability under high temperature and low stress state. Moreover, no cracks and winkles were observed. The transferred GaN template was suitable for homogeneous epitaxial, thus could be used for the direct fabrication of vertical LED chips as well as power electron devices. It has been confirmed that the double bonding and step annealing technique together with the thermal-stable bonding layer could significantly improve the bonding strength and stress relief, finally enhancing the thermal stability of the transferred GaN template.     

高出光率GaN基光子晶体LED的研究进展

在LED上制作光子晶体结构将会提高LED的出光效率,这使得LED应用范围更广.主要从不同的光子晶体加工工艺出发,总结近年来GaN基光子晶体LED的研究进展,介绍新的工艺和实验结果.通过比较发现,利用光子晶体的光子禁带效应和光栅衍射原理,都能够提高LED的出光效率,但需要和光子晶体的结构参数以及相应的加工工艺相结合,使出光效率和光场能流密度有大幅度的提高,从而实现LED出光效率的提高,使LED取代白炽灯等光源应用于生活照明成为可能.