通过FDTD仿真模拟计算，文中系统地研究了电流阻挡作用对GaN基蓝光激光器增益分布和光学性能的影响，发现回音壁激光模式主要在靠近微盘边缘1.5个波长范围谐振，因此，如果电流阻挡层面积太小，无法最大化减小激光器电流阈值；如果面积太大，回音壁激光模式与无增益区存在耦合效应，从而减少激光功率。另外，随着无增益区域向微盘边缘发生偏移，各个激光模式输出的峰值功率均下降，其中二阶模式峰值功率比一阶模式下降得更加显著，这主要是由于二阶模式分布范围更接近微盘中心区域。同时，进一步发现如果在微盘激光器的仿真模型中引入侧壁缺陷，则将导致边缘无法形成增益区，相比于二阶模式而言，一阶模式的发光功率随侧壁缺陷区域增加而下降的幅度更为显著，这主要是由于一阶模式分布范围更接近微盘边缘。

随着AlGaN基深紫外发光二极管(DUV LED)的发展，其不仅在杀菌消毒领域得到广泛应用，在日盲紫外光通信领域的应用也受到越来越多的关注。这主要是由于相比其他的紫外光源（如汞灯、激光），其具有功耗低、设计灵活且调制带宽高的优势。而DUV LED的带宽严重依赖于器件尺寸，器件尺寸越小，其带宽越高。但是，随着深紫外微型发光二极管(μLED)的尺寸减少，尽管其带宽得到提高，但是其光功率却急剧下降，这严重限制了深紫外μLED在光通信中的应用。文中主要总结了深紫外μLED作为日盲紫外光通信光源的研究现状和综合分析尺寸效应引起器件性能的变化及其机理；并分析出低的光提取效率和严重的自热效应是影响深紫外μLED光功率的两个主要因素。进而综述了各种提高深紫外μLED光提取效率和改善热学特性的方法。文中将为从事深紫外μLED研究的工作者提供一定的研究方向指导。

The hole injection capability is essentially important for GaN-based vertical cavity surface emitting lasers (VCSELs) to enhance the laser power. In this work, we propose GaN-based VCSELs with the p-AlGaN/p-GaN structure as the p-type hole supplier to facilitate the hole injection. The p-AlGaN/p-GaN heterojunction is able to store the electric field and thus can moderately adjust the drift velocity and the kinetic energy for holes, which can improve the thermionic emission process for holes to travel across the p-type electron blocking layer (p-EBL). Besides, the valence band barrier height in the p-EBL can be reduced as a result of usage of the p-AlGaN layer. Therefore, the better stimulated radiative recombination rate and the increased laser power are obtained, thus enhancing the 3 dB frequency bandwidth. Moreover, we also investigate the impact of the p-AlGaN/p-GaN structure with various AlN compositions in the p-AlGaN layer on the hole injection capability, the laser power, and the 3 dB frequency bandwidth.

In this work, a self-powered GaN-based metal-semiconductor-metal photodetector (MSM PD) with high responsivity has been proposed and fabricated. The proposed MSM PD forms an asymmetric feature by using the polarization effect under one electrode, such that we adopt an AlGaN/GaN heterojunction to produce the electric field, and by doing so, an asymmetric energy band between the two electrodes can be obtained even when the device is unbiased. The asymmetric feature is proven by generating the asymmetric current-voltage characteristics both in the dark and the illumination conditions. Our results show that the asymmetric energy band enables the self-powered PD, and the peak responsivity wavelength is 240 nm with the responsivity of 0.005 A/W. Moreover, a high responsivity of 13.56 A/W at the applied bias of 3 V is also achieved. Thanks to the very strong electric field in the charge transport region, when compared to the symmetric MSM PD, the proposed MSM PD can reach an increased photocurrent of 100 times larger than that for the conventional PD, even if the illumination intensity for the light source becomes increased.

The tilted energy band in the multiple quantum wells (MQWs) arising from the polarization effect causes the quantum confined Stark effect (QCSE) for [0001] oriented III-nitride-based near ultraviolet light-emitting diodes (NUV LEDs). Here, we prove that the polarization effect in the MQWs for NUV LEDs can be self-screened once the polarization-induced bulk charges are employed by using the alloy-gradient In_xGa_1-xN quantum barriers. The numerical calculations demonstrate that the electric field in the quantum wells becomes weak and thereby flattens the energy band in the quantum wells, which accordingly increases the spatial overlap for the electron-hole wave functions. The polarization self-screening effect is further proven by observing the blueshift for the peak emission wavelength in the calculated and the measured emission spectra. Our results also indicate that for NUV LEDs with a small conduction band offset between the quantum well and the quantum barrier, the electron injection efficiency for the proposed structure becomes low. Therefore, we suggest doping the proposed quantum barrier structures with Mg dopants.