绿光激光器InGaN量子阱有源区trench缺陷微观结构与形成机理研究

Semiconductor laser diodes (LDs) have been widely used in the field of laser-based displays, because of its low-cost, small size, and long lifetime. High-performance GaN-based green LDs are desirable for laser-based displays. The epitaxial growth of InGaN quantum well (QW) active region with high efficiency and narrow full-width-half-maximums (FWHMs) is a key point to realize LDs with good performances. However, InGaN QW emitting in the green spectrum range, which needs to be grown at low temperature with large mismatch, usually shows high density of trench defects in the interface, which is one of the limitation to improve the performance of GaN-based green LDs. Few studies on trench defects have been reported. Our previous results showed that the formation of trench defects is closely related with In segregation, but the formation mechanism needs further study. In this proposal, we propose to study in details the microstructure and the formation mechanism of trench defects in green InGaN QW. We will also study the dynamics and thermodynamics of MOCVD growth of green InGaN QW, in order to develop new epitaxial growth method to suppress the formation of trench defects. Based on these studies, green InGaN QW with high efficiency and better uniformity will be obtained, and thus the performance of GaN-based green LDs will be improved.

半导体激光器具有成本低、体积小、寿命长等优点，正在兴起的激光显示技术迫切需要高性能的GaN基绿光激光器。绿光InGaN量子阱有源区是GaN基绿光激光器的核心结构，它的晶体质量和光学性质直接决定了器件性能。绿光InGaN量子阱生长温度低、晶格失配大，InGaN量子阱的界面易形成trench缺陷，是限制GaN基绿光激光器效率提升的瓶颈之一。目前关于trench缺陷的研究还很少。我们此前的研究表明trench缺陷的形成与In组分偏析有密切关联，但其微观形成机制还有待研究。本项目拟深入研究GaN基绿光激光器InGaN量子阱有源区trench缺陷的微观结构与形成机理，研究绿光InGaN量子阱的MOCVD生长动力学和热力学，探索抑制InGaN量子阱中trench缺陷形成的外延生长技术，实现高发光效率、低非均匀展宽的绿光InGaN量子阱，为研制高效率的GaN基绿光激光器奠定基础。

GaN基绿光LD在激光显示、深海通讯等领域有非常广阔的市场应用。但是绿光波段面临严重的效率下降问题。InGaN量子阱结构中易形成trench缺陷，是导致绿光InGaN量子阱有源区发光效率低的原因之一。我们系统研究了绿光激光器InGaN量子阱有源区界面trench缺陷的微观结构及光学性质，澄清了缺陷与In偏析的关联，揭示了trench缺陷的形成机理，进一步提出了缺陷密度抑制方法，实现了高发光效率低非均匀展宽的绿光InGaN量子阱有源区, 为实现高性能的GaN基绿光LD提供了材料基础。主要取得了如下成果：. 1. Tench缺陷存在于GaN垒层，缺陷内部存在I1型层错，缺陷边界是V型沟道，缺陷区域InGaN量子阱发光强度弱且有长波长发光，说明缺陷下方的量子阱区域In偏析严重。. 2. 揭示了trench缺陷的形成机理为：在InN表面生长GaN时层错形成能低，而高In组分绿光InGaN量子阱表面易发生In偏析，因此在In偏析严重区域的绿光InGaN量子阱上生长GaN量子垒时易形成层错，层错与理想纤锌矿结构的边界处原子吸附能弱难并入，形成了V型沟道。层错及其边界的V型沟道形成了trench缺陷。. 3. 通过抑制In偏析抑制了trench缺陷密度。实现了高发光效率低非均匀展宽的绿光InGaN量子阱有源区，自发辐射光谱PL半高宽为113meV@530nm。