基于纳米多孔GaN和ITO光场限制层的硅基GaN微盘激光器研究

硅基GaN微盘激光器模式体积小、功耗低，在单光子发射、化学生物探测等领域具有重要的应用前景。常规GaN微盘激光器采用空气为光场限制层的“蘑菇状”结构，电阻较大、热阻较高，仅实现了光泵浦激射。本项目提出了“三明治状”新结构，可大幅降低电阻与工作电压、热阻与工作结温，显著提升器件性能。初步采用基于AlGaN光场限制层的“三明治状”结构，在国际上首次实现了硅基GaN微盘激光器的室温电注入激射。然而，由于纵向光场限制较弱，器件阈值电流较大、工作结温偏高，只能脉冲工作。本项目拟采用低折射率的纳米多孔GaN和ITO等新型光场限制层代替AlGaN，仿真结果表明光场限制因子可增加60%，串联电阻下降50%，而热阻和内损耗基本不变。将重点围绕硅基GaN微盘激光器的光场调控、光损耗抑制和热传导等关键科学问题，从结构设计、材料生长和器件制备等方面开展研究工作，目标研制出室温连续电注入工作的硅基GaN微盘激光器。

GaN-based microdisk lasers grown on Si featured with small mode volume and low power consumption, have an important application prospect in single photon emission, chemical and biological detection. Conventional GaN-on-Si microdisk lasers utilize a "mushroom-like" structure with air as the cladding layers, causing relatively large series resistance and thermal resistance, and only optically pumped lasing is achieved at present. In this proposal, we proposed a "sandwich-like" structure, which could greatly reduce the series resistance and thermal resistance, resulting in low operation voltage and junction temperature, and hence largely improve the device performance. By using this structure, we reported the first room-temperature electrically injected GaN-on-Si microdisk laser with AlGaN cladding layers in the previous work. However, the longitudinal optical confinement is relatively weak, causing relatively large threshold current and hence high junction temperature, the fabricated microdisk laser could only operate in pulsed mode. This proposal proposed a microdisk laser structure by using nanoporous GaN and indium tin oxide with a small refractive index as the cladding layers instead of AlGaN. Simulation results show that the optical confinement factor can be increased by 60%, the series resistance can be reduced by 50%, the thermal resistance and the absorption loss are constant. This proposal will mainly focus on the optical field regulation, optical loss suppression and thermal conduction of GaN-on-Si microdisk lasers, and study on the structure design, material growth and device fabrication. Finally, the realization of room-temperature continuous-wave operation of GaN-on-Si microdisk lasers is expected.