Characteristic And Evaluation Of Varied Doping GaAs Photocathode

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.