HVPE方法在6H-SiC衬底上生长GaN晶体的应力与表面生长动力学关系研究

As a representative of the third generation of semiconductor materials, GaN has attractive properties such as wide direct band gap, high saturation electron velocity, high breakdown voltage and good thermal conductivity. GaN has great foreground in saving energy industry, sophisticated military and space electronic devices. However, there is a high dislocation density and a large stress in hetero-epitaxial GaN, which has a great influence on the performance of devices and become the bottleneck of applications. The GaN crystals grown on 6H-SiC substrate are main research object. The relationship between stress and surface growth kinetics for GaN crystal will be investigated. The specific contents are as follows: The stress characteristics of GaN crystal grown on 6H-SiC will be determined by using the theoretical calculations, experimental measurement and in-situ stress optical monitoring. Based on different influence factors of growth kinetics, the relational model between stress, microscopic atomic diffusion and growth mode will be built. The project aims to reveal the relationship between the stress and surface growth kinetics, which lays the theoretical and technical foundation for decreasing the dislocation density and grasping the rules of crystal growth stability.

作为第三代半导体材料的代表，GaN具有带隙宽、饱和电子速率高、击穿电压大、导热性能好等特点，在节能产业、尖端军事、空间用电子器件等领域应用前景巨大。但异质外延生长的GaN晶体具有较高的位错密度和较大应力，对光电器件的性能影响很大，成为制约其应用的主要瓶颈。本项目以6H-SiC衬底上生长的GaN晶体为研究对象，对GaN晶体的应力与表面生长动力学的关系进行基础科学研究。具体内容包括：理论计算、实验测试以及原位应力光学监测确定HVPE方法在6H-SiC衬底上生长的GaN晶体的应力特征；研究应力对6H-SiC衬底上GaN晶体生长表面原子扩散的影响；建立基于不同生长动力学影响因素（生长温度、V/III比、衬底极性等）下应力-微观原子扩散-生长模式的关系模型。本项目旨在揭示GaN应力与表面生长动力学的关系，为有效降低GaN晶体位错密度和掌握晶体生长稳定性规律奠定理论和技术基础。

GaN单晶材料具有大的直接带隙（3.4eV），同时其还具有高击穿电压、高电子迁移率、化学性质稳定、耐高温、耐腐蚀等特点，因此在半导体发光二极管、激光二极管、紫外探测器以及高能高频电子器件等方面有广阔的应用前景。异质外延生长的GaN晶体具有较高的位错密度和较大应力，对光电器件的性能影响很大，成为制约其应用的主要瓶颈。本项目以6H-SiC衬底上生长的GaN晶体为研究对象，对GaN晶体的应力与表面生长动力学的关系进行基础科学研究。具体研究内容如下：采用HVPE方法在6H-SiC衬底上成功的生长出了GaN晶体，结构分析和光学表征结果表明应力对GaN晶体生长有显著影响，不同类型的应力对原子迁移率的影响不同，进而能够改变生长模式。在压应力状态下原子迁移率受到抑制，而在拉应力状态下原子迁移率受到增强。建立了应力-微观原子扩散-生长模式的关系模型。本项目揭示了GaN应力与表面生长动力学的关系，为有效降低GaN晶体位错密度和掌握晶体生长稳定性规律奠定理论和技术基础。