GaAs电子源光电发射理论与稳定性机理研究

项目名称： GaAs电子源光电发射理论与稳定性机理研究

项目编号： No.60801036

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 原子能技术

项目作者： 邹继军

作者单位： 东华理工大学

项目金额： 19万元

中文摘要： GaAs 电子源是一种量子效率高、发射电子能量与角度分布集中、发射电流密度大、发射电子脉冲结构好和自旋极化率高的真空电子源，是当今光电发射领域的重要研究热点。本项目通过理论计算与实验测试相结合，研究了电子在体内与表面能带弯曲区的输运特性和隧穿表面势垒的几率，仿真分析了表面势垒形状对发射电子能量分布的影响，并对实验测试的电子能量分布进行了拟合；在综合考虑Γ33021;谷、L能谷与热电子发射的基础上，求解得到了新的反射式电子源量子效率公式，完善了GaAs 电子源光电发射理论；通过实验优化了外延GaAs电子源制备工艺；分析了不同衬底或缓冲层材料、不同发射层厚度或掺杂浓度对电子源发射性能的影响；通过对表面电荷限制现象的仿真分析，提出了减小表面电荷限制效应的具体措施；通过计算电子源表面势垒与表面模型参数，揭示了真空系统中GaAs 电子源的稳定性机理；基于GaAs电子源自旋驰豫机制与自旋输运特性的分析，研究了温度、发射层厚度和掺杂浓度对GaAs电子源自旋极化率的影响。本项目对推动GaAs 电子源基础理论研究，满足高能物理、自旋电子学和电子束平面曝光技术等领域对高性能电子源的迫切需求，具有理论意义和实际价值。

中文关键词： GaAs电子源；光电发射；稳定性；电子能量分布；自旋

英文摘要： GaAs electron source is a high-performance vacuum electron source due to their high quantum efficiency, low energy spread and emittance, large emission current, good emitted electron pulse structure, and high spin polarization. GaAs electron source has become a hot topic in current photoemission research. According to the theoretical calculation and experimental measurement, we studied the transport properties of electrons in bulk GaAs and surface band-bending region, calculated the escape probability tunneling the surface potential barriers, and simulated the effect of potential barrier profile on electron energy distribution and fitted the experimental electron energy distribution. Based on Γalley, L valley and hot electron photoemission, we obtained a new quantum efficiency equation for reflecton-mode cathode and perfected the photoemission theory of GaAs electron source. According to the experiment investigation, we optimized preperation technology for GaAs electron source using epitaxial wafer. We analyzed the effect of different substrates or buffer layers, different active layer thickness or doping concentration on photoemission properties. Based on the simulation of surface charge limit phenomena, some methods used to eliminate the effect of surface charge limit are provided. According to the calculation of parameters for potential barriers and activation-layer model on electron source surface, we revealed the stability mechanism of GaAs electron source in a vacuum system. In addition, we studied the spin relaxation mechanism and spin transport properties, and simulated the effect of temperature, active layer thickness and doping concentration on spin polarization of GaAs electron source. This work will drive forward the fundmental theory investigation of GaAs electron source, satisfy the impending demands for high performance electron source in high energy nuclear physics, spintronics, parallel multi-electron beam lithography technology and other fields, and is of great theoretical significance and practical value.

英文关键词： GaAs electron source; photoemission; stability; electron energy distribution; spin