图形衬底侧向外延硅基InAs/GaAs量子点激光器材料及器件研究

Si-based lasers are core devices for realization of new generation optoelectronic integration, which is chip-scale optical communication and interconnection for compatibility with Si integrated circuit. Unfortunately, their performance is still poor for practical application due to the high-density dislocations and thermal stress in GaAs/Si epilayers. In this project, the strategy for epitaxial lateral overgrowth of GaAs layers on nano-scale Si-based patterned substrates using metal-organic chemical vapor deposition has been proposed to fabricate high-quality GaAs/Si epilayers and InAs/GaAs quantum dot laser materials and devices. Optimizing the patterned structure and growth conditions of the epitaxial lateral overgrowth, the dislocation density and thermal stress can be reduced efficiently by using the patterned structure with large aspect ratio. Meanwhile, the growth conditions and separate-confinement structure will be optimized to supply proper optical and carrier confinement, and the low growth-temperatrue GaInP upper cladding layer and the modulation p-doping will be used to avoid the degradation of the optical properties of quantum dots, and increase optical modal gain. The strategy has the advantage of simultaneous reduction both the dislocation density and thermal stress. Through implementation of the project, optimum material structure and growth condition will be explored to reduce the dislocation density and obtain the quantum dot with high optical gain. Therefore, the 1.3 um wavelength Si-based InAs/GaAs quantum dot laser with low threshold current and high reliability at room-temperature will be achieved. This project is significant for both basic research and practical applications of Si-based InAs/GaAs quantum dot lasers.

硅基激光器是实现新一代与硅集成电路兼容的光通信和光互连芯片级光电子集成核心器件。但目前直接外延硅基激光器的光电性能距离实用化还有很大的差距，这主要归因于直接外延GaAs/Si材料的高位错密度和热应力。本项目提出一种采用硅基纳米尺寸图形衬底侧向外延结合金属有机化学气相沉积方案，探索应用硅图形衬底侧向外延高质量GaAs/Si材料生长方法，并制备InAs/GaAs量子点激光器材料和器件。重点优化图形衬底结构和侧向外延生长条件，利用大高宽比图形掩膜结构阻挡穿透位错机制，有效降低硅基激光器有源区的位错密度和材料热应力。同时，采用低温GaInP上限制层和p型调制掺杂方法，优化分别限制结构和量子点有源区及其生长条件，避免量子点光电性能退化，增加光学模式增益。此方案具有同时减小材料位错密度和热应力的优点。拟通过本项目实施，实现波长1.3微米硅基量子点激光器的低阈值高可靠性室温工作，为器件实用化奠定基础。

目前快速增长的海量信息高速传输和处理对半导体芯片提出巨大挑战。硅基激光器是实现新一代与硅集成电路兼容的光通信和光互连芯片级光电子集成核心器件。但目前直接外延硅基激光器的光电性能距离实用化还有很大的差距。本项目优化了GaAs/Si材料的外延工艺，最终得到了位错密度为8E5/cm2，表面粗糙度为1.8nm（10×10μm2）的高质量GaAs/Si异质外延材料。以此为基础，探索GaInP上限制层低温生长条件改善激光器量子点有源区的光增益性能，制备高质量的硅基量子点激光器材料和器件，结合MOCVD和MBE两种外延方法，材料的室温光致荧光谱半高宽为30meV，实现了波长1.3微米波段直接外延硅基量子点激光器的室温连续激射，激光器单管的阈值电流密度降低到203.5A/cm2，斜率效率到达0.5W/A，室温下连续输出光功率达到65mW，单管室温工作寿命超过10万小时。同时，研制了一种用于硅基外延激光器的对称负极芯片结构，相比于传统共面电极芯片结构，该芯片结构可将器件微分电阻降低约75%。当注入电流从1.2倍增加到2.8倍阈值电流时，激射波长红移量减少约4.5倍，特征温度由27.2K提高到43.4K，斜率效率增加了约26.4%，最大电光转换效率增大约4.7倍。本项研究不仅提高了我国硅基半导体激光器外延材料和器件的基础研究水平，达到该研究领域的国际领先地位，而且还促进了硅基单片集成光源研发，具有重要科学研究意义和迫切的应用需求，有望在通信、光计算、人工智能等领域发挥重要作用。