半极性GaN基黄橙光材料研究

It is one of the most challenging objectives in semiconducting materials research to realize the full color visible display by using one single material family. Up to now, the market-available yellow-amber-emitting display devices are primarily made of AlInGaP martial family, which efficacy is very hard to be further enhanced to the satisfactory level. This project will focus on the incorporation effiecnecy of indium compositions to extend the emission wavelength and the enhancement of the quantum efficiency of InGaN materials by taking advantage of the reduced polarization electric field and with tailoring the complained stress in semipolar GaN-based materials. The formation and evolution of defects, and the mechanism of stress relaxation and compensation in eiplayers will be uncovered. The coherent management for the stress, defects and process parameters (we call it as “complained stress engineering) would be helpful to enhance the incorporation of indium compositions in InGaN multi-quantum wells (MQWs) and realize a longer wavelength emission. The quantum efficeieny of InGaN MQWs could therefore be improved by the optimally structural design, controllablly abrupt heterointerface and good morphology of the InGaN MQWs. The compositions, layer stuctures and growth parameters of the materials will be quantitively anlaysed. The emission mechanism of GaN-based materials in correlation with the material crystal quality will be discussed. The controllable growth process of the GaN-based materials with good crystal quality and yellow-amber emission can be achieved by optimzing the growth process. The research results will benefit to developemnt of the semicondutor materials with emission covering the entire visible spectral region for the smart lighting and full-color visible displays.

通过单一材料体系实现全彩色显示是半导体材料领域亟待突破的目标之一，现今市场上黄橙光显示器件主要来自AlInGaP材料体系，其发光效率一直难于提升到满意水平。本项目旨在利用半极性GaN基材料所具有的掺铟率高和极化电场对量子跃迁的影响减弱的优点，研究外延生长中的应力弛豫和补偿机制，揭示微结构缺陷形成与演化规律。通过对应力、缺陷和工艺参数的协同管理（即可协变应力工程）来提高铟组份掺入，达至延伸发光波长。通过改变量子阱结构设计、调控量子阱异质界面形貌和陡峭度来提升量子效率。定量分析材料组分、结构、生长工艺参数对半极性GaN基黄橙光材料可控生长行为、晶体质量和发光性质的影响机制，以及各生长工艺参数之间的相互关系，实现对半极性GaN基黄橙光材料的生长优化与控制，为全可见光谱智慧照明和全彩色显示技术的发展奠定基础。

现今市场上黄橙光显示器件主要来自AlInGaP材料体系，其发光效率一直难于提升到满意水平。本项目旨在研究外延生长中的应力弛豫和补偿机制，揭示微结构缺陷形成与演化规律。通过改变量子阱结构设计、调控量子阱异质界面形貌和陡峭度来提升量子效率, 实现对半极性GaN基黄橙光材料的生长优化与控制。 . 实验发现衬底表面高温氮化处理、缓冲层生长对半极性GaN表面形貌和晶体质量有重要影响，利用AlN或GaN作为缓冲层可制备出了结晶质量优良、表面呈镜面的GaN材料。高分辨x射线衍射测量显示,半极性GaN基材料的晶体质量呈现各向异性，(11-22)衍射峰摇摆曲线的半高宽(FWHM)随不同方位角的变化规律呈现M形，即沿投影方向[-1-123]时最小，沿[10-10]方向时最大。还发现了半极性GaN材料在碱基溶液中的易腐蚀性和呈现小面特征的腐蚀形貌。. 实验发现，半极性InGaN薄膜厚度从0.3um增加到0.6um到1um时，其应力随厚度从0.625GPa减少到0.430GPa到0.195GPa,显示薄膜中的应力得到较好的弛豫，但它们光发射的偏振度却从0.234增加到0.308到0.326。此外，在In0.35Ga0.65N多量子阱结构中观察到多级卫星峰，显示量子阱具有陡峭的异质界面，其偏振度为0.22。. 在m面蓝宝石上设计和成功生长出了半极性黄光、黄橙光和橙光LED，外延片显示出良好的发光特性，在不做出芯片的情况下，加电可以直接发光，这是国内首次实现的半极性黄光和橙光LED材料，经LED光电测试仪测试，黄光LED在注入电流从20mA增到200mA时发光峰的波长从572nm逐渐移到561nm,蓝移11nm，黄橙光LED当注入电流从20mA增加到200mA时，其峰值发光波长分别为581nm和567nm,其蓝移量为14nm。而橙光LED当注入电流从50mA增加到200mA再到350mA时，其峰值发光波长分别为621nm、605nm和602nm,其蓝移量为16nm和19nm。. 半极性黄、橙光LED的实现表明，半极性氮化物材料有潜力解决长波段c面LED材料难以解决挑战，实现全可见光谱氮化物光电器件（LEDs和LDs），满足不同场合的照明、显示、指示或微型背投等应用，提升色彩饱和度和显示指数。