Research on quantum efficient fitting and structure of high performance transmission-mode GaAs photocathode

To explore the structural feature of high performance transmission-mode GaAs photocathode, the optical properties and shortwave limitation for the transmission-mode quantum efficient formula is modified. By using the modified formula, a high quantum efficient (≈43%) curve of ITT is well fitted. A series of structural parameters is obtained with in a relative error less than 5%, which indicates that the thickness of the Ga 1- x Al x As window layer is 0.3—0.5 μm, the Al mole value is 0.7, and the thickness of the GaAs active layer is 1.1—1.4 μm. In addition, an optimized structure for the uniform-doping transmission-mode GaAs photocathode is suggested based on the fitted results. When the thickness of the Ga 1- x Al x As ( x =0.7) layer and the GaAs layer are 0.4 μm and 1.1—1.5 μm respectively, the integral sensitivity can exceed 2350 μA/lm.