Improvement and structure optimization of transmission-mode GaAs photocathode performance

In order to improve the performance of transmitted GaAs photoelectric cathode, the quantum efficiencycurve of Chinese transmitted GaAs photoelectric cathode is compared with that of the product of AmericanITT company, showing that the integration sensitivity of Chinese transmitted photoelectric cathode is2130 mu A/lm, and the American ITT company's reaches 2330 mu A/lm. Through the matrix method to solve thethree membranes, the theoretical reflectivity is obtained. Based on the uniform doping transmission GaAsphotocathode quantum efficiency formula, by replacing the fixed value R with variable value , adding theshort wave constraint factor, and modifying the quantum efficiency formula, a modified uniform dopingtransmission GaAs photocathode quantum efficiency formula is obtained. Using the revised quantum efficiency,optical performance and integral sensitivity theory model, through fitting the quantum efficiency curve ofAmerican ITT company product, introducing the ITT cathode component performance parameters, comparingthe performance parameters of Chinese product, the results show that the Chinese photocathode in the windowlayer, the thickness of the emission layer, electron diffusion length and rear interface composite rate has acertain gap with ITT's. In order to shorten the gap between the two and optimize the cathode structureparameters, the transmission GaAs photocathode optical structure software is designed to further analyze theinfluence of the electron diffusion length and the emission layer thickness on the quantum efficiency of thephotocathode. The results show that with an electron diffusion length of 7 mu m and emission layer thickness of1.5 mu m, the transmitted GaAs photocathode sensitivity can be more than 2800 mu A/lm. However, the largeelectron diffusion length has high requirements for cathode materials and preparation level. The reasonsresponsible for the performance gap between Chinese product and other country's are that in China the growthprocess of cathode materials is not jet matureand the cathode preparation equipment is out of date . In thispaper, we study the relationship between GaAs photocathode optical performance and photoemissionperformance, and further optimize the structural design of cathode components, which has certain guidingsignificance for improving the cathode quantum efficiency and the level of image intensifier