AlGaN基深紫外激光器的光场调控及高效电注入器件研究

AlGaN-based deep ultraviolet (DUV) lasers have significant application prospects in the military field and national economy. However, the high dislocation density of AlGaN materials with high Al content, low gain of multi-quantum wells (MQWs) active region, and the separately confinment of photons and carriers impose restrictions on the realization of electrically pumped deep ultraviolet lasers. In this program, both nanopatterned AlN templates and grading supperlattices inserted layer will be introduced to filter dislocation and relax strain and low dislocation density MQWs active region can be obtained. The low Si-doped AlxGa1-xN/AlyGa1-yN superlattices inserted layer will play an indispensable role in manipulating the valence band to realize that more TE mode photon can be radiated in MQWs which will cause low reflection loss of the cleavaged cavity mirror, and that current crowding effect can be weakened. Furthermore, step MQWs with different doping methods will be introduced to reduce the quantum-confined Stark effect (QCSE), to improve the spatial overlap of electron - hole wave functions, and to improve the carrier recombination rate. Finally, AlGaN-based DUV lasers with low divergence angle, low loss and low threshold current can be fabricated by combining the strong refractive index strip waveguide with large optical cavity structure and high reflectivity p-type electrode.

AlGaN基深紫外激光器在军事领域和国民经济领域都有重要的应用前景。然而由于高Al组分AlGaN低维量子材料位错密度高、量子阱有源区增益低、光和载流子的分别限制难以实现等关键问题，导致深紫外激光器无法在电注入条件下工作。本申请项目拟结合纳米图形化AlN类横向外延和渐变超晶格插入技术进行位错过滤和应力调控，降低量子阱有源区材料的位错密度。通过低Si掺杂的AlxGa1-xN/AlyGa1-yN超晶格应力插入层实现对量子阱价带的调控，获得更多解理面腔镜反射损耗小的TE模式光，同时缓解电流阻塞效应。设计优化不同掺杂方式的阶梯量子阱有源区结构，减小量子限制斯塔克效应，增加电子-空穴波函数的空间重叠率，提高辐射复合速率。结合大光腔强折射率条形波导结构和高反射率p型电极，最终制备出低发散角、低损耗、低阈值电流的280 nm AlGaN基深紫外激光器。

半导体深紫外激光器是一种强相干的深紫外光源，具有光束质量高、阈值电流低、使用寿命长等优势，且体量微小易于集成，在工业、医疗、商业、科研、信息和军事等领域都具有强烈的应用需求。本项目系统地研究了AlGaN基半导体深紫外激光器的光场调控和电注入原型器件制备。通过引入纳米图形化AlN模板和AlGaN/AlGaN多组分渐变超晶格插入技术，类横向外延生长了高质量高Al组分的AlGaN材料。在此基础上，提出了强量子限制下的高增益超薄GaN/AlN量子阱结构设计，实现有源区的高效发光和偏振模式的精准控制。采用MOCVD外延生长了厚度精确可调的超薄GaN/AlN量子阱，并进行了载流子动力学的研究，从时间分辨寿命曲线的分析中验证了超薄GaN/AlN量子阱的弱激子局域化和光滑陡峭的界面质量。最后，结合非对称大光腔折射率渐变波导结构设计，保证载流子的有效注入和光场的有效约束，完成了全结构电注入深紫外激光器的原型器件设计。受研究时间和研究条件限制，电注入深紫外激光器未能成功激射。最终，在室温光泵浦下实现了波长在242-252 nm间连续可调，阈值190~1153 kW/cm2，TE偏振主导的深紫外激光器。综上，根据项目计划书，完成了项目的研究内容。