Abstract: By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrdinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we obtain an equation to calculate the emitted electron energy distribution of transmission-mode NEA GaAs photocathodes.According to the equation,we study the effect of cathode surface potential barrier on the electron energy distribution and find a significant effect of the barrier-I thickness or end height,especially the thickness,on the quantum efficiency of the cathode.Barrier II has an effect on the electron energy spread,and an increase in the vacuum level will lead to a narrower electron energy spread while sacrificing a certain amount of cathode quantum efficiency.The equation is also used to fit the measured electron energy distribution curve of the transmission-mode cathode and the parameters of the surface barrier are obtained from the fitting.The theoretical curve is in good agreement with the experimental curve.

Key words: NEA photocathode, surface potential barrier, transmission coefficient, electron energy distribution, quantum efficiency