III族氮化物半导体微谐振腔中自发辐射特性研究

The spontaneous emission characteristics in an optical micro-cavity are attracting much attention. It will not only enrich the research content on cavity quantum electrodynamics, but also provide important information to develop advanced micro-cavity optoelectronic devices. III-nitride semiconductors are a new material system, and their micro-cavity is of great importance in view of not only research but also in applications due to their unique advantages, including high exciton binding energy, short radiative recombination lifetime, wide wave band application range, etc. Due to its difficulty in fabrication technology, however, it is still at the starting stage. This proposal will focus on the III-nitride semiconductor resonant cavity, including its design，fabrication, and physical property. The nitride resonant cavity with a high quality factor will be demonstrated by designing optimal device structure and overcoming the fabrication difficulties. The photon mode distribution in resonant cavity, the interaction mechanism between resonant mode and emission form cavity media, and the coupling between spontaneous emission and stimulated emission mode in resonant cavity will be systematically studied by using thickness gradient cavity configuration and the micro- photoluminescence technique. The theory of spontaneous emission in III-nitride semiconductor resonant cavity will be set up, and the control of spontaneous emission will be achieved. This program will provide solid foundation on advanced nitride micro-cavity optoelectronic.

半导体光学微腔中自发辐射效应是当前的研究热点，它不仅可以为腔量子电动力学提供丰富的例证，而且对于研制低阈值激光器、新型发光管、高速光探测器等先进的光电子器件具有重要意义。III族氮化物材料是一种新型的半导体材料，具有激子束缚能大、载流子辐射复合时间短、应用波段宽等诸多优点，在微腔应用方面具备许多独特的优势。氮化物微谐振腔无论在理论还是在应用方面都有重要研究价值。但由于制作困难，目前其研究尚处于起步阶段。本项目将围绕氮化物微谐振腔的设计、制备以及物理研究开展工作。通过设计谐振腔结构以及克服制作工艺难点，研制出高质量的微谐振腔，并利用独特的厚度渐变结构以及微区光荧光测试技术对谐振腔的模式分布理论、有源介质与光子模式耦合机制、腔自发辐射与激射模式耦合机理等关键科学问题进行研究，进而建立氮化物谐振腔自发辐射理论，实现自发辐射的调控。本项目可为研制新型氮化物微腔光电子器件提供理论和技术支撑。

本项目围绕氮化物微谐振腔的设计、制备以及物理研究开展工作。通过设计谐振腔结构以及克服制作工艺难点，研制出高质量的微谐振腔，并利用独特的厚度渐变结构以及微区光荧光测试技术对谐振腔的模式分布理论、有源介质与光子模式耦合机制、腔自发辐射与激射模式耦合机理等关键科学问题进行研究，实现自发辐射的调控。 .本项目取得了以下成果: 1）开发完善了激光剥离以及剥离后的抛光技术，利用耦合量子阱方案，大幅度降低了谐振腔内的光损耗。2）通过将谐振腔长度减小到6个波长，获得了至今为止最低的VCSEL激射阈值，413μJ/cm2. 自发辐射因子达到了0.1。这些结果与短谐振腔引起的自发辐射增强，增益系数增大等因素有直接关系。3）观察到了谐振腔光子模式和InGaN量子阱中激子之间强耦合作用引起的极化激元，拉比分裂可以达到130meV。4）通过使得一个微腔的谐振腔长度连续变化，观察到激子极化激元随着激子-光子能量差（又称失谐量）的变化。进一步观察到了InGaN/GaN量子阱的激子极化激元激射。5）在项目执行期间，发表学术论文19篇，培养博士后1名，研究生7 名。