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。

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.