透射式GaAs光电阴极性能提高以及结构优化

Improvement and structure optimization of transmissionmode GaAs photocathode performance

为了提高透射式GaAs光电阴极性能,将国内与美国ITT公司的透射式GaAs光电阴极量子效率曲线进行对比,可知我国透射式光电阴极积分灵敏度已经达到2130μA/lm,美国ITT达到了2330μA/lm.利用修正后的量子效率、光学性能以及积分灵敏度的理论模型,分别对两者进行光学结构拟合.结果表明,国内光电阴极在窗口层和发射层的厚度、电子扩散长度以及后界面复合速率等方面均与ITT有一定差距.为了缩短两者的差距,优化阴极结构参数,具体研究了电子扩散长度和发射层厚度对量子效率的影响,结果表明如果均匀掺杂透射式GaAs光电阴极发射层厚度为1.3μm、电子扩散长度为7μm,则积分灵敏度可以达到2800μA/lm以上.

In order to improve the performance of transmitted GaAs photoelectric cathode,the quantum efficiency curve of Chinese transmitted GaAs photoelectric cathode is compared with that of the product of American ITT company,showing that the integration sensitivity of Chinese transmitted photoelectric cathode is 2130μA/lm,and the American ITT company’s reaches 2330μA/lm.Through the matrix method to solve the three membranes,the theoretical reflectivity is obtained.Based on the uniform doping transmission GaAs photocathode quantum efficiency formula,by replacing the fixed value R with variable value Rthe,adding the short wave constraint factor,and modifying the quantum efficiency formula,a modified uniform doping transmission 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 of American ITT company product,introducing the ITT cathode component performance parameters,comparing the performance parameters of Chinese product,the results show that the Chinese photocathode in the window layer,the thickness of the emission layer,electron diffusion length and rear interface composite rate has a certain gap with ITT’s.In order to shorten the gap between the two and optimize the cathode structure parameters,the transmission GaAs photocathode optical structure software is designed to further analyze the influence of the electron diffusion length and the emission layer thickness on the quantum efficiency of the photocathode.The results show that with an electron diffusion length of 7μm and emission layer thickness of 1.5μm,the transmitted GaAs photocathode sensitivity can be more than 2800μA/lm.However,the large electron diffusion length has high requirements for cathode materials and preparation level.The reasons responsible for the performance gap between Chinese product and other country’s are that in China the growth process of cathode materials is not jet matureand the cathode preparation equipment is out of date.In this paper,we study the relationship between GaAs photocathode optical performance and photoemission performance,and further optimize the structural design of cathode components,which has certain guiding significance for improving the cathode quantum efficiency and the level of image intensifier.