异质衬底上h-BN单晶外延材料的高温CVD制备及生长机理研究

h-BN has great potential in civil and national defense applications. However, the high-quality h-BN single crystals are very difficult to be obtained. The primary cause is that the growth mechanism of h-BN epilayer on foreign substrates is still unclear. In addition, the growth techniques are not perfect and need to be improved furthermore. The proposed project will study the fabrication and the growth mechanism of h-BN single-crystal epilayer on foreign substrates by using micro-nano structured substrates, the in-situ etching technique at high temperature by interrupting the growth and the epitaxial lateral overgrowth techniques on home-made high-temperature chemical vapor deposition apparatus. By the association of experimental result and theoretical simulation, the origin and development of stress during the epitaxial growth will be studied deeply to realize the controllable strain during the high-temperature growth. The origin and development of structural defects will be studied systematically and the effective method to decrease the defects will be developed. The influence mechanism of the strain, the structure defects and their interaction on the deterioration of crystal quality as the thickness increase will be systematically studied. On this base, the optical and electrical properties will be studied and their correlations with structural defects will be disclosed. By this study, the critical epitaxial growth techniques will be obtained and the large-size high-quality h-BN single crystal exptaxy on foreign substrates will be accomplished, which will give great support for the development of deep ultraviolet optoelectronic, thermal neutron detectors and graphene-based electronic devices of our country.

h-BN材料在民用和国防安全等方面具有巨大的应用前景。然而，目前高质量h-BN单晶异质外延材料难以获得，其根本原因在于对h-BN 异质外延生长机制尚不清楚，生长技术也不完善。本项目拟采用自主研发的高温化学气相外延设备，采用微纳图形衬底、高温原位刻蚀和侧向外延生长等技术，开展大尺寸h-BN单晶材料外延制备和生长机理研究。围绕上述目标，理论与实验相结合，研究h-BN异质外延生长过程中的应力起源、演变机理，实现应力可控生长；研究h-BN材料中结构缺陷的产生和演变机理，探索降低缺陷密度的有效途径；系统研究应力、缺陷以及它们的相互作用对h-BN材料质量随厚度增加而恶化的影响机理；探究材料的光电特性，揭示其与结构缺陷的关联关系。掌握高质量单晶材料异质外延生长的关键技术，制备出大尺寸高质量的h-BN单晶外延材料，为我国在深紫外光电子器件、中子探测器件和石墨烯电子器件等领域的高速发展奠定坚实的材料基础。

h-BN材料在深紫外发光和探测器件、固态中子探测器件、基于石墨烯的电子器件等领域具有巨大的应用前景。然而，目前高质量h-BN单晶异质外延材料难以获得，其根本原因在于对h-BN 异质外延生长机制尚不清楚，生长技术也不完善。本项目采用自主研发的超高温HVPE，开展了h-BN高温异质外延生长研究，从理论上研究了其生长动力学过程，实验上深入研究了材料生长过程中的缺陷产生和演变过程及其机理。课题首先开展了适合h-BN生长的高温HVPE设备的设计与改进，顺利获得适合BN生长的温度高达1700oC的HVPE设备。采用第一性原理，研究了h-BN缓冲层厚度对蓝宝石衬底上异质外延生长h-BN过程中吸附原子的迁移过程。并进一步研究了氮作为杂质对h-BN的结构稳定性、电子结构和光学性质的影响。实验上系统开展了蓝宝石衬底上异质外延h-BN材料的生长特性研究，对温度、压力和V/III比对生长动力学过程的影响进行了深入研究。通过TEM测试手段，研究了异质外延过程中的缺陷产生与演变和生长模式的演变，有助于深入理解其外延生长机理。采用Raman测试手段研究了材料中的光谱特性与材料结构和应力的关联关系。探索研究了h-BN自支撑衬底的制备技术，结合其材料结构特点，采用自剥离技术，成果获得了2英寸厚度为470微米的h-BN自支撑衬底，具有较好的可见光通透性。本研究结果，有助于开发具有自主知识产权的h-BN衬底材料，并占领国际研究前沿，有力支撑我国在深紫外光电器件、固态中子探测器件、基于石墨烯的电子器件等领域领的快速发展进程，并在国际竞争中占领制高点。