Resolution properties of transmission-mode exponential-doping Ga_(0.37)Al_(0.63)As photocathodes

摘要

Using the modulation transfer function obtained by establishing and solving the two-dimensional continuity equation, we have calculated and comparatively analyzed the resolution characteristics of transmission-mode exponential-doping and uniform-doping Ga_(0.37)Al_(0.63)As photocathodes. The calculations show that compared with a uniform-doping Ga_(0.37)Al_(0.63)As photocathode, the exponential-doping structure can significantly improve not only the resolution, but also the quantum efficiency of the photocathode. This improvement is different from the approach for high resolution by reducing the emission layer thickness T_e and electron diffusion length L_D, or by increasing the recombination velocity of the back-interface, S_V, which results in low quantum efficiency. Furthermore, the improvement in resolution and quantum efficiency for the transmission-mode exponential-doping Ga_(0.37)Al_(0.63)As photocathodes is the result of the effect of the built-in electric field on electron transport and lateral diffusion.