Si衬底上高质量 GaN连续厚膜
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低位错密度GaN连续膜是Si衬底上准垂直结构GaN功率电子器件的核心，对器件耐压特性有重要的影响。然而在Si衬底GaN的外延生长中，通常情况下GaN中位错弯曲湮灭会同时消耗大量压应力，使得GaN残余压应力难以补偿降温中产生的张应力，最终导致外延膜的开裂。即通常低位错密度与厚度是难以兼得的。针对这个难题，我们创新提出了空位工程，在生长中故意引入高浓度Ga空位，使位错通过吸附Ga空位快速发生弯曲湮灭，并且这个过程几乎不消耗压应力。基于这种空位工程技术，我们可以获得表面无裂纹的，厚度超过9.5 μm Si衬底GaN连续厚膜，这种高质量的Si衬底GaN厚膜为实现高耐压的功率器件提供了良好的基础。同时我们也针对Si衬底上AlN薄膜的晶体质量提升开展了多种创新性研究，为后续高质量GaN生长做好铺垫。
Low-dislocation-density continuous GaN films are the core of quasi-vertical structure GaN power electronic devices on Si substrates, and have a significant impact on the breakdown voltage characteristics of the devices. However, during the epitaxial growth of GaN on Si substrates, the bending and annihilation of dislocations in GaN usually consumes a large amount of compressive stress, making it difficult for the residual compressive stress in GaN to compensate for the tensile stress generated during cooling, which ultimately leads to cracking of the epitaxial film. Thus, it is usually difficult to achieve both low dislocation density and large thickness. To address this challenge, we innovatively proposed a vacancy engineering strategy: intentionally introducing high-concentration Ga vacancies during growth, which enables dislocations to rapidly bend and annihilate by adsorbing Ga vacancies, and this process barely consumes compressive stress. Based on this vacancy engineering technology, we can obtain crack-free continuous thick GaN films on Si substrates with a thickness exceeding 9.5 μm. This high-quality thick GaN film on Si substrates provides an excellent foundation for the realization of high-breakdown-voltage power devices. Meanwhile, we also conducted a variety of innovative studies on improving the crystal quality of AlN thin films on Si substrates, laying a solid foundation for subsequent high-quality GaN growth.
