透、反射式GaAs光电阴极量子效率间换算机理研究

Aiming at the problem that the photoelectric properties of transmission-mode GaAs photocathode can't be investigated by the experiment of reflection-mode photocathode, this project will research the photoelectron energy distribution on the transmission-mode and reflection-mode cathode surfaces according to the photoemission rules and characteristics of the two kinds of cathode. The structure parameters of NEA surface barrier will be defined by utilizing the combination of quantum efficiency and surface voltage, and thus an accurate function model of electron surface escape probability will be established. On this basis, proportionate relationships between the quantum efficiencies of transmission-mode and reflection-mode photocathodes at various wavelengths will be theoretically solved by solving the emission electrons energy distribution. The mathematical model which realizes the conversion between quantum efficiencies of transmission-mode and reflection-mode photocathodes within total spectral response waveband will be established. The influence rules of thickness and doping structure of emission layer on the performance of transmission-mode photocathode will be simulated and investigated. The research results which may enrich the photoemission theory of NEA GaAs photocathode and providing an indirect and high-efficiency research approach for photoelectric properties of the transmission-mode NEA GaAs photocathode, have scientific significance and application value.

针对透射式GaAs光电阴极的光电性能尚无法借助反射式阴极实验进行研究的问题，本项目根据透、反射式阴极光电发射规律和特点的不同，研究两种阴极表面光电子的能量分布规律；利用阴极量子效率和表面光电压谱相结合的方法确定NEA表面势垒结构参数，从而建立准确的电子表面逸出几率函数模型；在上述基础上推导两种阴极的发射电子能量分布，进而分波长点理论求解两种阴极量子效率的比例关系；最后建立数学模型，实现两种阴极在整个光谱响应波段内量子效率的数值换算；利用该模型进行数字仿真，揭示发射层厚度、掺杂结构等因素对透射式阴极光电性能的影响规律。该研究能够丰富NEA GaAs光电阴极的光电发射理论，并为透射式GaAs光电阴极的光电性能提供一种间接、高效的研究途径，具有一定的科学意义和应用价值。

对透射式GaAs光电阴极光电性能的研究，目前尚不能借助反射式阴极材料的激活实验来进行。本项目研究了相同发射层结构的透射式和反射式阴极在相同强度入射光的照射下，最终达到阴极发射层表面时光强度的差别，发现若到达反射式阴极发射层表面的入射光强为1个单位时，达到透射式阴极发射层表面的光强只有0.7个单位；研究了光电子在向阴极发射表面运动过程中的电子能量分布规律，并利用基于Airy函数的传递矩阵法求解了阴极表面电子逸出几率的理论表达式，确定了电子逸出几率同电子能量、势垒结构参数之间的数学关系；最后对反射式阴极样品进行了清洗和激活实验，分别测量了激活前样品的表面光电压谱曲线和激活后的量子效率曲线，通过二者的对比拟合，得到了电子表面逸出几率的实验曲线，并利用电子表面逸出几率理论公式对该曲线进行了最小二乘法拟合计算，求出了表面势垒的结构参数。上述研究结果为进一步开展透、反射式阴极间量子效率的换算机理研究奠定了良好的理论和实验基础，对丰富和完善GaAs光电阴极理论，促进国内高性能光电材料的科学研究具有一定的科学意义。