Resolution characteristics for reflection-mode exponential-doping GaN photocathode

Abstract

According to the expression for modulation transfer function obtained by solving the established 2D continuity equation, the resolution characteristics for reflection-mode exponential-doping and uniform-doping GaN photocathodes have been calculated and comparatively analyzed. These calculated results show that the exponential-doping structure can upgrade not only the resolution capability but also the quantum efficiency for a GaN photocathode. The improvement mechanism is different from the approach for high resolution applied by reducing Te and L(D) or increasing S(V), which leads to low quantum efficiency. The main contribution factor of this improvement is that the mechanism that transports electrons toward the NEA surface is facilitated by the built-in electric field formed by this exponential-doping structure, and the corresponding lateral diffusion is reduced.

Resolution characteristics of graded doping and graded composition transmission-mode AlGaAs/GaAs photocathodes

“…1. The electric field facilitates photoelectron movement toward the cathode 1559-128X/15/061414-06$15.00/0 © 2015 Optical Society of America surface, and decreases the lateral diffusion of photoelectrons, thereby increasing the resolution [12,13]. However, different electric fields induced by different cathode structures have different effects on the resolution of cathodes.…”