真空互联下介质膜/(Al)GaN异质结能带偏移的调控及机理研究

Interface optimization of dielectric/(Al)GaN heterostructure is an important approach to improve the performance of GaN-based High Electron Mobility Transistor (HEMT) devices. Thus far, most of the researches have focused on the improved effect on performance of device by interface treatment. However, interface properties, including interface layer and energy band alignment, affected by interface treatments have been seldom investigated so far. Band alignment between semiconductors and dielectrics is one of the most important performance parameters, and is also a significant factor in the energy band engineering to direct device design. This proposal is going to use in-situ surface/interface treatments, growth, and characterizations techniques on the condition of vacuum interconnection without surface contamination and oxidation. In this case, the band alignment of dielectric/(Al)GaN heterostructure will be measured at high accuracy, and can be manipulated as the surface/interface properties are well controllable. Based on the in-situ researches, the effect that surface/interface treatments have on component, chemical states, and band structure at the dielectric/(Al)GaN interface will be determined and the reaction dynamic of dielectric/(Al)GaN interface formation will be explored. In addition, impact mechanism of surface/interface treatments on band alignments will be elucidated, which will provide physical basis for further interface optimization of dielectric/(Al)GaN heterostructures.

介质膜/(Al)GaN异质结的界面优化是提高GaN基HEMT器件性能的重要方法。然而，目前大多数研究工作主要关注界面处理方法对器件性能的影响，而对界面处理后的界面物理化学性质，如界面层成分、能带偏移等研究还很缺乏。能带偏移是介质膜/半导体异质结最重要的性质之一，是能带工程中指导器件设计的重要因素。本项目将在真空互联条件下采用原位的表/界面处理、生长与表征手段，避免空气沾污和氧化层的影响，有效控制表/界面性质，实现介质膜/(Al)GaN异质结能带偏移的精确测量与可控研究。通过原位研究，明确表/界面处理对介质膜/(Al)GaN界面成分、化学价态、能带结构的影响，洞悉介质膜/(Al)GaN界面的形成过程，阐明表/界面处理影响能带偏移的内在机理，为进一步优化介质膜/(Al)GaN异质结界面性质提供物理依据。

半导体表/界面性质与组分是影响异质结材料能带结构与器件性能的重要因素。通常研究过程样品不可避免暴露大气，使材料与器件的表界面受到大气吸附与氧化的影响。本项目基于真空互联系统，实现了p-GaN及欧姆接触的原位生长、制备与表征。相比暴露大气的工艺方法，利用真空互联系统获得了碳氧少、表面平整有序的高质量GaN表面，因此减小了接触势垒与元素扩散而具有更低的欧姆接触电阻。基于三元半导体材料的成分直接影响带隙、能带偏移和表面能带弯曲，本项目研究了一种三元材料的定量分析方法以及不同Al组分(AlxGa1-x)2O3半导体生长方法。进一步地，原位制备了Ga2O3/(AlxGa1-x)2O3异质结，并利用真空互联的XPS表征技术测算能带偏移，明确了Al组分对Ga2O3/(AlxGa1-x)2O3异质结能带偏移的影响。本项目有助于进一步展开介质膜/(Al)GaN异质结能带偏移的可控研究，为器件性能优化进行的界面性质优化提供物理依据。