低应力低位错密度4英寸GaN单晶的HVPE生长研究

As the 3rd generation semiconductor material, GaN single crystal substrates have been being widely used in the fields of high power devices, RF devices and optoelectronics. With the rapid development of high power devices, 2 inch GaN substrates cannot meet the growing requirement. And the 4 inch GaN single crystal substrates are becoming the intending direction. In order to improve the growth uniformity of the 4 inch single crystals，to effectively reduce the stress and dislocation density of crystals is the key to HVPE growth of 4 inch GaN crystals with high quality. The optimization of the temperature field and gas flow in HVPE growth system, the 4 inch substrates that designed and prepared with uniformly distributed nanosheets as 2D barrier to dislocations and the porous ones prepared by the two steps etching are main research to grow 4 inch GaN crystals with reduced stress and dislocation density. We will systematically study the nucleation mechanisms, interface growth process, stress reduction, dislocation blocking and self-separation mechanisms of GaN crystal growth on several type of novel substrates. In order to obtain the 4 inch self-separation GaN crystals with high quality, we will further optimize the growth process. The implementation of this project is useful to overcome the obstacles to the growth of GaN crystals. It also has important application value on exploring the GaN crystal growth technology with low cost, high reliability and industrialization potential.

氮化镓（GaN）单晶衬底作为第三代半导体材料，广泛应用于大功率电子器件、射频器件和光电子器件等领域。目前随着功率型器件的飞速发展，2英寸GaN衬底已不能满足需求，4英寸GaN单晶衬底的生长成为主要发展方向。如何提高4英寸GaN单晶生长的均匀性，有效降低应力和位错密度是HVPE生长高质量4英寸GaN晶体的关键。本项目拟通过优化HVPE生长系统和温度场、气流场，采用能够在4英寸衬底上均匀分布的新型二维阻断层衬底、两步腐蚀多孔衬底等新型衬底进行GaN单晶生长。系统研究不同衬底上GaN晶体的成核机制、界面生长过程、应力减小和位错阻断机制以及衬底分离机制等问题，优化生长工艺，以期生长出低位错密度、低应力的4英寸自支撑GaN晶体。本项目的实施为攻克大尺寸GaN晶体生长关键技术，探索具有低成本、高可靠性，易产业化的GaN晶体生长技术具有重要应用价值。

GaN作为宽禁带半导体材料是节能产业、尖端军事和空间用电子器件的核心材料，对国民经济和国防建设具有重要意义。但异质外延生长的GaN器件具有较高的位错密度和较大应力，对器件的性能影响很大，成为制约其应用的主要瓶颈，同时随着器件发展衬底尺寸提出更高要求。因此掌握单晶生长技术，并通过降低应力和位错密度生长高质量4英寸GaN晶体是急需解决的关键问题。通过本项目实施，实现了高质量4英寸GaN单晶的稳定生长，研究了不同制备条件对4英寸二维阻断层衬底、水热腐蚀多孔衬底的影响规律，制备出了适合生长高质量4英寸GaN晶体的新型衬底。揭示了单晶生长工艺对二维阻断层衬底、水热腐蚀多孔缓冲衬底上生长GaN晶体的成核及界面生长过程的影响规律，掌握了GaN晶体在不同衬底上的生长习性。揭示了二维阻断层衬底、水热腐蚀多孔衬底等缓冲衬底上生长4英寸GaN晶体的应力减小、位错降低以及晶体与衬底的分离机制，为生长高质量的GaN晶体提供理论依据。相关研究成果发表SCI收录论文18篇，获得授权国家发明专利3项，并与企业合作推进4英寸GaN单晶生长技术产业化。通过指导研究生参与本项目的研究工作，培养了一批在GaN单晶材料领域能够解决科学和技术问题的高水平人才。