多晶半导体三碱光电阴极厚度的理论研究

Theoretical Study of Thickness on Polycrystalline Semiconductor Multialkali Photocathode

该文利用辐射强度指数衰减率,多晶半导体三碱光电阴极量子产额公式和光吸收系数公式,首次研究了多晶半导体三碱光电阴极的最佳厚度。结果表明:当I_a/I_0>0.4时,阴极最佳厚度D应在1000A以上,并且D随I_a/I_o上升而增加。高能光子产生的光电子出现在阴极内表面层。该文同时指出:对第一类阴极(S-20,S-20R,S-25),D应为300A左右;对第二类阴极(New S-25,Varo,LEP)则为900A。并预计可通过光电阴极光谱响应峰值位置设计光电阴极厚度。研究结果首次定量给出,随着光电子逸出深度和入射光波长增加,光电阴极厚度增加。如果光电子逸出深度在40～55nm之间,则对1.0μm敏感的阴极最佳厚度D应在1200A左右。

Optimum thickness on polycrystalline semiconductormultialkali photocathode is first studied by radiation intensity expo-nential attenuation rate and formulas of quantum yield spectra andoptical absorption coefficient on multialkali photocathode in this pa-per. It is clear that if I_α/I_o>0.4, the photocathode optimum thick-ness D will exceed 1000A or so; if I_α/I_o increased, D will been largedtoo, and photoelectrons excited by energetic photons appear in the in-ner surface of photocathode. Furthermore, D should be 300 A or sofor the first kind photocathodes (S-20, S-20R and S-25) and 900Afor the second kind photocathodes (New S-25, Waro and LEP). It isestimated that the optimum photocathode thickness D is worked outby spectral response peak of multialkali photocathode. We came to the investigation conclusion that photoelectron escape depth and inci-dent wavelength will raise, and, along with it, the optimum photo-cathode thickness. It is calculated that the optimum thickness onmultialkali photocathodes that possess a good spectral response in thevisible and the infrared spectrum must be 1200 A or so.