Study on the resolution of uniformly doped transmission-mode GaAs photocathode

A negative-electron-affinity (NEA) photocathode is a cathode in which the vacuum level at the surface lies below the conduction band minimum in the bulk. Therefore, the photoelectrons can diffiuse to the cathode surface and tunnel through the surface potential barrier with high probability. The NEA GaAs photocathode has already found widespread applications in photomultiplier tubes and high-performance image intensifiers in the past several decades because of their high quantum efficiency and good long-wavelength response. GaAs semiconductor is the key factor in determining the performance of NEA GaAs photocathode. Although there have been many investigation into the quantum efficiency, spin polarization and the emitted energy distribution of NEA GaAs photocathode, there are few works concerning the resolution of photocathode. The formers suppose that there is no dispersion phenomenon after one bright spot irradiation at the GaAs photocathode interface, namely remains a point on the exit-face, so the resolution of GaAs photocathode is infinity, leading to the smaller experimental value of image intensifier resolution than the theoretical value. In this paper, we consummate the theoretical model of GaAs photocathode image intensified technology in resolution mechanism and analyze the related factors influenced the resolution of GaAs photocathode.