GaN基蓝光激光器工作电压的抑制及机理

GaN-based blue laser diodes (LDs) have attracted numerous attention due to the widely applications in small portable projectors, laser-based TVs, optical coherence tomography, atomic clocks and underwater communication. Improving the key performance indicators of GaN-based laser diodes is an important prerequisite for further applications. However, larger numbers of studies have been focused on how to reduce the threshold current density or improve the output optical power of the GaN-based laser diodes. Actually, reducing the operating voltage is one of the technology bottlenecks for fabricating high-performance GaN-based LDs, which is the key to improve the wall-plug efficiency and to prolong the lifetime. In this project, we will reduce the operating voltage and lucubrate related mechanisms. Firstly, we will solve the problem of p-(Al)GaN doping and reduce its resistivity by clarifying the compensation or passivation mechanism of unintentionally-doped impurities, and reduce the series resistance of LDs. Secondly, an excellent p-type ohmic contact with a very small specific contact resistance will be realized by controlling the carbon impurity in the semiconductor-metal interface and expound how carbon impurity has effect on the carrier transport in p-type ohmic contact. Thirdly, a reasonable GaN-based blue LD structure is designed based on analyzing the influence of structure parameters of each layer through theoretical calculation. Finally, the operating voltage of GaN-based blue LD is reduced to lower than 4.8V, which construct a foundation in material growth and device fabrication for high-performance GaN-based blue LDs.

GaN基蓝光激光器在微型投影、激光电视、生物医学、原子钟、水下通讯等领域有重要的应用价值，成为当今研究热点。开展提高GaN基激光器各项性能指标的研究，是进一步推动激光器走向应用的重要前提。然而，早期大量研究都聚焦于如何降低阈值电流密度或提高输出光功率，有关工作电压的研究少有报道。实际上，降低激光器工作电压是制备高性能激光器的技术瓶颈之一，是提高转换效率、延长寿命的关键。本项目拟解决GaN基蓝光激光器工作电压高的难题，抑制工作电压并阐明其机理。研究p-(Al)GaN中杂质并入及补偿机制，掌握低电阻率p-(Al)GaN外延生长技术，降低激光器串联电阻；研究碳杂质对p型欧姆接触特性的影响，调控半导体-金属界面的碳杂质浓度，获得极低的比接触电阻率；借助理论计算，揭示激光器结构设计对工作电压的影响机理。最终，制备工作电压低于4.8V的GaN基蓝光激光器，为研制高性能激光器奠定关键材料及器件基础。

GaN基激光器可以直接发出蓝绿光，在激光存储、激光显示、激光加工、水下通信等领域有重要的应用。本项目一直针对GaN基蓝光激光器的器件性能开展工作，在激光器外延方面，研究了p-GaN杂质补偿、量子阱的发光机理、波导层材料外延等对激光器性能的影响；在激光器器件物理方面研究了量子垒铟组分、复合下波导、下波导插入层等对激光器载流子注入的影响机制，降低激光器阈值；提出非对称量子阱，降低了载流子势垒，提高了注入效率，改善了激光器输出特性。最终制备出高性能的GaN基蓝光激光器，室温连续输出光功率6W，阈值电压4.2V，器件性能处于世界前列。