【作者】 牛军；

【导师】 常本康；

【作者基本信息】 南京理工大学 ， 电子科学与技术， 2011， 博士

【摘要】 为了更深入地研究和发展变掺杂GaAs光电阴极的相关理论与技术,探索我国高性能三代微光像增强器的发展途径,本文在变掺杂GaAs光电阴极的光电特性、制备实验和性能评估等方面进行了相关的研究。针对变掺杂GaAs光电阴极光电发射特性中的基础理论问题,采用理论推导、数字仿真和模拟计算的方法,研究了指数掺杂GaAs光电阴极电子扩散漂移长度的理论表达式,建立了电子扩散漂移长度LDE同指数掺杂系数A和均匀掺杂情况下材料的电子扩散长度LD之间的数值计算关系。研究了指数掺杂GaAs光电阴极量子效率的等效求解方法,简化了求解过程。研究了变掺杂结构对阴极电子发射性能的影响机理,发现变掺杂阴极内建电场的存在,不仅能够提高光电子到达阴极表面的数量,同时还使表面电子的能量分布向高能端偏移,从而使电子的逸出几率得到提高。根据变掺杂GaAs光电阴极的理论研究结果,针对变掺杂技术实用性的问题,采用实验验证的方法,研究了变掺杂GaAs光电阴极电子扩散漂移长度理论表达式的正确性,发现计算结果同实验结果具有很好的一致性。研究了变掺杂技术应用于透射式GaAs光电阴极的可行性,发现阴极组件制备过程不会破坏阴极的变掺杂结构,而且变掺杂的透射式GaAs光电阴极具有较高的光谱积分灵敏度。研究了激活时系统真空度对MBE变掺杂GaAs光电阴极低温激活效果的影响,发现当系统真空度达到1×10-8Pa以上时,能够使低温激活灵敏度比高温提高30%以上在实验基础上,针对变掺杂GaAs光电阴极评估技术不完备的问题,采用理论分析和数学建模的方法,研究了激活过程中Cs在阴极表面的吸附效率,实现了对不同表面掺杂浓度的GaAs阴极材料在不同系统真空度条件下激活时,Cs在阴极表面吸附效率的理论评估。研究了Cs-O激活后NEA GaAs光电阴极表面势垒的评估技术,提出了利用激活中不同阶段阴极光电流的峰值比求解NEA表面势垒参数的方法。对阴极高、低温激活后的NEA表面势垒参数进行了评估,揭示了“高—低温两步激活”过程中阴极表面势垒的变化特点。研究了变掺杂GaAs光电阴极结构性能的评价方法,建立了变掺杂GaAs光电阴极量子效率理论模型,并实现了对阴极结构性能的客观评价。对两种不同变掺杂GaAs光电阴极的结构性能进行了评估,发现了阴极发射层结构设计中存在的缺陷,为指导阴极结构的优化设计提供了有效的分析手段。更多还原

【Abstract】 In order to study and develope the theory and technology of varied doping GaAs photocathodes in depth, and explore a development route of national high porformance third generation LLL image intensifier, the photoelectric characteristic, preparation experiment, and performance evaluation of varied doping GaAs photocathodes were investigated in this paper.Aiming at the foundational theoretical questions about the photoemissive property of varied doping GaAs photocathode, and introducing theoretical derivation, digital simulation, and simulating calculation, the mathematical expression of the electron diffusion and drift length of exponential doping photocathode was deduced, which ascertains the calculation relationship between the electron diffusion and drift length LDE, the exponential doping coefficient A, and the electron diffusion length Lo of uniform doping material. An equivalent methode of solving quantum efficiency of exponential doping GaAs photocathode was presented, which simplify the solving process. The influence mechanism of varied doping structure on the electron emission capability of cathode was discovered, which indicates that the built-in electric field in varied doping cathode can not only increase the number of photoelectrons reaching the surface, but also cause an offset of the electrons energy distribution to high energy, accordingly increase the electron escape probability.According to the theoretical results of varied doping GaAs photocathode, and Aiming at the practicality of varied doping technology, through experiment validation, the accuracy of the theoretical expression of the electron diffusion and drift length of exponential doping photocathode was investigated, and the calculation result is in agreement with the experimental result. The feasibility of varied doping technology applied to transmission-mode GaAs photocathode was researched, and it was found that the preparation of transmission-mode cathode component will not destroy the varied doping structure, and the varied dopped transmission-mode GaAs photocathodes have high integral sensitivity. The influence of system vacuum pressure on the activation results of MBE varied doping GaAs photocathodes was investigated, the result indicates that the low-temperature activation sensitivity can be over 30%than high-temperature when the system vacuum level is above 1×10-8 Pa.Based on experiments, aiming at the question of lacking evaluation technology for varied doping GaAs photocathode, and introducing theoretical analysis and mathematics modeling, the adsorption efficiency of cesium on the cathode surface during activation process was investigated, and realizing the theoretical evaluation of adsorption efficiency of cesium on GaAs cathode materials with varied surface doping concentration and under different system vacuum level. The evaluation technique for the surface potential barrier parameters of activated NEA GaAs photocathodes was investigated, and by ultlizing the ratio of maximum values of the cathode photocurrents arising during two activation phase, a method for evaluating the parameters of NEA surface potential barrier was presented. The parameters of NEA surface potential barrier after high-low temperature two-step activation were evaluated, respectively, and the change regularity of the surface potential barriers was discovered. The valuation technique for the structure performance of varied doping GaAs photocathodes was studied, and the theory model of quantum efficiency of the varied doping GaAs photocathode was proposed, which realizes the objective evaluation of the structure performance of the varied doping cathode materials. The structure performances of two different varied doping GaAs photocathodes were evaluated, and the design defect of varied doping structure was found, which provides an effective analysis tool for guiding the optimization design of cathode structure.更多还原