GaN基激光器有源区退化与应力诱导缺陷的研究

GaN-based laser diodes (GaN-LDs) are widely used in the fields of laser display and laser illumination, the reliability of GaN-LDs has always been the focus in this field. Extensive reports suggested that the degradation of the GaN-LDs happen in the active region, but the essential causes for the degradation of the active region has not been clarified. Previously, we studied the luminescence properties of the active region during aging and obtained the density and activation energy of the defects. Based on our previous studies, this proposal will study from the micro perspective, focusing on the the stress-related defects in the active region, studying the stress and strain in the micro active region using the Nano Beam Diffraction (NBD); characterizing the micro structure and the spatial distribution of the defects and their influence on the luminescence properties by quasi-in-situ study of TEM and CL; exploring the generation, migration and proliferation of the vacancy-like defects. By researching of the project, we will clarify the relation between the defects and the stress, the relation between the defects and the luminescence properties, reveal the essential cause of the degradation and realize the long lifetime and high reliable GaN-LDs.

氮化镓基激光器（GaN-LDs）在激光显示、激光照明等领域具有广阔的应用前景，GaN-LDs的可靠性问题一直是该领域研究的重点。大量研究表明，GaN-LDs的退化主要发生在有源区，但是对有源区退化本质的研究仍不够深入。前期我们对GaN-LDs退化过程中有源区发光特性进行了研究，初步确定了激光器退化过程中有源区产生的缺陷的密度和激活能。在此基础上，本课题将从微观角度出发，研究GaN-LDs有源区退化过程中应力诱导缺陷的产生及演化，采用纳米束衍射技术（NBD）分析有源区退化过程中微区应力应变特性；通过TEM+CL准原位表征方法研究缺陷的微观结构、空间分布特征及其对有源区微区发光特性的影响；探索空位型缺陷的产生、迁移和增殖机制。通过本项目的研究，阐明GaN-LDs退化过程中缺陷的产生、演化与有源区微区应力应变及微区发光特性的关系，揭示有源区退化的本质，实现长寿命、高稳定性的GaN-LDs。

由于氮化镓激光器（GaN-LDs）体积小，效率高等特点，使其成为了激光显示中蓝色和绿色光源的首选。为了实现GaN-LDs在激光显示和激光照明领域的应用，本研究从激光器的可靠性出发，分析了GaN-LDs有源区退化与应力诱导缺陷的产生过程。首先，建立了基于激光器电容频率和电容电压特性的激光器缺陷识别方法，研究了激光器老化前后电容特性和光学损耗的变化。在此基础上，本研究从微观角度出发，分析了激光器有源区微区的应力应变特性，激光器老化过程中产生的缺陷的微观结构、空间分布特征以及其与微区发光特性的关系，阐述了p型限制层的Mg杂质缺陷及其团簇的产生和演化过程，从微观角度揭示了LD退化的本质。激光器波导层缺陷的产生以及p型AlGaN限制层Mg团簇的产生，增加了激光器的光学损耗，从而导致激光器阈值增加，输出功率降低。缺陷的产生同时导致了有源区附近材料的应力弛豫，致使激光器电致发光光谱谱蓝移量减小，最终表现为激光器老化后波长红移。基于以上结果，本研究通过改进激光器的有源区结构设计和波导层限制层的生长条件，实现了寿命长达27300小时的GaN基蓝光激光器。