纤锌矿结构砷化镓纳米线表面缺陷研究

The existence of surface defects is one of the main reasons causing low photoelectric conversion efficiency of GaAs nanowire based photoelectical devices. As compared with GaAs films made by conventional technologies, GaAs nanowires grown under vapor-liquid-solid (VLS) mechanism have wurtzite crystal structures. Meanwhile, GaAs nanowires prepared under different preparation conditions exhibit various side facets. Therefore, it is necessary to investigate the intrinsic characteristics of surface defects in GaAs nanowires and compare the physical properties with that in conventional GaAs films. This can help us to fully understand the behaviors of surface defects in GaAs semiconductor system. In view of this, in this project, we propose to study the physical properties of surface defects in GaAs nanowires by using photoluminescence spectrum, deep level transient spectrum and X ray photoelectron spectroscopy. Furthermore, the passivation mechanism is to be investigated through systematical passivation experiments. Based on the work aforementioned, the optimization passivation method is expected to be obtained. The successful implementation of this project will lay a solid foundation for the fabrication of GaAs based nano-devices.

表面缺陷的存在是造成砷化镓基纳米器件光电转换性能较低的主要原因之一。与常规方法制备砷化镓薄膜不同，使用金辅助分子束外延技术基于气相-液相-固相技术制备的砷化镓纳米线晶体结构是纤锌矿结构，纳米线侧面（sidefacets）的晶体学方向非常丰富。研究纤锌矿晶体结构下具有不同侧面晶体学方向的砷化镓纳米线中表面缺陷物理性质，比较其同闪锌矿结构砷化镓薄膜材料表面缺陷物理行为的一致与差异，对进一步理解和完善砷化镓材料体系表面缺陷物理性能有着重要的参考意义。鉴于以上原因，本项目提出使用光致发光谱、深能级瞬态谱、X射线光电子能谱对砷化镓纳米线中表面缺陷进行研究以获得表面缺陷的物理性质，同时结合系统的表面硫钝化研究，总结出纤锌矿结构下不同侧面晶体学方向的砷化镓纳米材料表面缺陷钝化机制，并归纳出最优钝化方法。本项目的成功实施可为砷化镓基纳米器件的性能提高打下物理和材料学基础。

由于纳米结构的引入带来的表面/体积比增加，在砷化镓一维纳米结构中，表面缺陷引起的载流子复合是决定光电器件性能的主要因素。在本项目研究中，我们主要研究具有纤锌矿晶体结构的砷化镓纳米线中表面缺陷及其对纳米阵列光伏电池的输出特性影响。通过光致发光谱，x射线光电子能谱获得纤锌矿结构砷化镓纳米线表面缺陷的物理性质和起源，进一步，结合系统的钝化研究，获得纤锌矿结构砷化镓纳米线表面钝化机理和工艺，并在此基础上获得光电转换效率11.4的砷化镓纳米阵列光伏器件。以上工作期望为随后制备纳米光电器件性能提高奠定物理和材料学基础。