Improving InGaN-LED performance by optimizing the patterned sapphire substrate shape

The epitaxial growths of GaN films and GaN-based LEDs on various patterned sapphire substrates (PSSes) with different values of fill factor (f) and slanted angle (θ) are investigated in detail. The threading dislocation (TD) density is lower in the film grown on the PSS with a smaller fill factor, resulting in a higher internal quantum efficiency (IQE). Also the ability of the LED to withstand the electrostatic discharge (ESD) increases as the fill factor decreases. The illumination output power of the LED is affected by both θ and f. It is found that the illumination output power of the LED grown on the PSS with a lower production of tanθ and f is higher than that with a higher production of tanθ and f.     

p型氮化镓的低温生长及发光二极管器件的研究

采用金属有机物化学气相淀积技术(MOCVD)在蓝宝石衬底上低温(870—980℃)生长p型氮化镓 (p-GaN).用Hall测试仪测量材料的电学性能，发现当温度低于900℃时，材料的电阻率较高 ；在900—980℃均可获得导电性能良好的p-GaN.另外，电导性能除与掺杂浓度有关，还与p- GaN生长条件有关，氮镓摩尔比过低导电性能就较差，过高则会引起表面粗糙.采用优化后的 p-GaN制作了绿光发光二极管器件，发现生长温度越低器件发光强度越高，反向电压也越高 ，但正向电压只是略有升高. 关键词： Ⅲ-Ⅴ族半导体 氮化镓 发光二极管 金属有机物化学气相淀积     

高空穴浓度Mg掺杂InGaN外延材料性能的研究

采用金属有机物化学气相沉积方法生长得到具有不同Mg掺杂浓度In_xGa_1-xN (0≤x≤0.3)外延材料样品. 对样品的电学特性和光学特性进行了系统的研究. 研究发现：在固定Mg掺杂浓度下，随In组分的提高，样品空穴浓度显著提高,最高达2.4×10¹⁹cm^-3,Mg的活化效率提高了近两个数量级；通过对Mg掺杂InGaN(InGaN：Mg)样品的光致发光(PL)谱的分析，解释了InGaN：Mg样品的载流子跃迁机理，并确定了样品中Mg受主激活能和深施主能级的位置. 关键词： Mg掺杂InGaN 高空穴浓度 光致发光 金属有机物化学气相沉积     

Strain effects on optical polarisation properties in （11^-22） plane GaN films

We present the theoretical results of the electronic band structure of wurtzite GaN films under biaxial strains in the （11^-22）-plane. The calculations are performed by the k.p perturbation theory approach through using the effectivemass Hamiltonian for an arbitrary direction. The results show that the transition energies decrease with the biaxial strains changing from -0.5% to 0.5%. For films of （11^-22）-plane, the strains are expected to be anisotropic in the growth plane. Such anisotropic strains give rise to valence band mixing which results in dramatic change in optical polarisation property. The strain can also result in optical polarisation switching phenomena. Finally, we discuss the applications of these properties to the （1132） plane GaN-based light-emitting diode and lase diode.     

菲咯啉类有机钌络合物的合成及其光谱分析

近年来，为寻找性能更优良的荧光材料人们作了很多努力，在有机过渡金属化合物研究方面，取得了较大进展［１，２］．由过渡元素钌和共轭大π键杂环分子形成的有机钌络合物有着相当高的稳定性和活性，作为有机合成反应中的催化剂已被人们用于烷基化催化方面［３］．有机钌...     

Improving InGaN-LED performance by optimizing the patterned sapphire substrate shape

The epitaxial growths of GaN films and GaN-based LEDs on various patterned sapphire substrates(PSSes) with different values of fill factor(f) and slanted angle(θ) are investigated in detail.The threading dislocation(TD) density is lower in the film grown on the PSS with a smaller fill factor,resulting in a higher internal quantum efficiency(IQE).Also the ability of the LED to withstand the electrostatic discharge(ESD) increases as the fill factor decreases.The illumination output power of the LED is affected by both θ and f.It is found that the illumination output power of the LED grown on the PSS with a lower production of tan θ and f is higher than that with a higher production of tan θ and f.     

Strain effects on optical polarisation properties in (11■2) plane GaN films

We present the theoretical results of the electronic band structure of wurtzite GaN films under biaxial strains in the (11■2)-plane.The calculations are performed by the k · p perturbation theory approach through using the effective-mass Hamiltonian for an arbitrary direction.The results show that the transition energies decrease with the biaxial strains changing from 0.5% to 0.5%.For films of (11■2)-plane,the strains are expected to be anisotropic in the growth plane.Such anisotropic strains give rise to valence band mixing which results in dramatic change in optical polarisation property.The strain can also result in optical polarisation switching phenomena.Finally,we discuss the applications of these properties to the (11■2) plane GaN-based light-emitting diode and lase diode.     

Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes （LDs）. The roomtemperature （RT） cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing （FS） GaN substrate by metal organic chemical vapor deposition （MOCVD）. The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efticiency of multiple quantum well （MQW）, respectively.     

Delta掺杂制备p-GaN薄膜及其电性能研究

采用Delta掺杂技术制备了p型氮化镓薄膜，并利用原子力显微镜、霍尔测试、X射线衍射、荧光光谱等测试手段对样品的形貌和电导性能进行了分析，发现Delta掺杂样品比均匀掺杂样品晶体质量和电导性能都有很大提高，说明Delta掺杂可有效抑制缺陷，并对缺陷抑制机理进行了讨论；最后，对掺杂前的预通氨过程作了深入的研究，结果发现，预通氨对掺杂不益. 关键词： 氮化镓 LEDs MOCVD Delta掺杂     

Thermal analysis of GaN laser diodes in a package structure

Using the finite-element method,the thermal resistances of GaN laser diode devices in a TO 56 package for both epi-up configuration and epi-down configuration are calculated.The effects of various parameters on the thermal characteristics are analysed,and the thicknesses of the AlN submount for both epi-up configuration and epi-down configuration are optimized.The obtained result provides a reference for the parameter selection of the package materials.