Photoemission performance of gradient-doping transmission-mode GaAs photocathodes

With an attempt to improve the photoelectron emission efficiency, a gradient-doping structure proposed based on the Spicer's three-step model has been applied to the preparation of the transmission-mode GaAs photocathode via molecular beam epitaxy technique. The Cs-O activation phenomenon suggests that the gradient-doping structure can bring a potential photoemission capability with the increase of activation time, and the spectral response curves show that the gradient-doping photocathode can obtain a higher response capability in the entire waveband region, especially in the regions of short-wavelength threshold and long-wavelength threshold. By fitting quantum yield curves, the obtained cathode performance parameters such as electron average diffusion length and electron escape probability of the gradient-doping photocathode are greater than those of the uniform-doping one. The electron average diffusion length of the gradient-doping photocathode achieves 3.2 μm. The improvement in cathode performance of the gradient-doping photocathode could be ascribed to the downward gradient band-bending structure.