Comparative Study of uniform-doping and gradient-doping NEA GaN photocathodes

High temperature annealing and Cs, O activation is the formations of NEA GaN photocathode of external incentives, GaN material performance of the cathode of the internal factors are fundamental. In this paper, aiming at the difference of the uniform-doping and gradient-doping NEA GaN photocathode in structure, combined with the cathode active changes of the optical current and activated after the success of the spectral characteristics of the uniform-doping and gradient-doping performance of NEA photocathode similarities and differences. Experiments show that: compared to the uniform-doping cathode, graded-doping cathode activated with radiation in the current slow growth rate, activation time is relatively long, successful activation of higher quantum efficiency. Using field-assisted photocathode emission model can explain the differences existing between the two, built-in electric field gradient doping structure to increase the presence of electronic drift to the cathode surface movement; the electron reaches the cathode surface to improve the escape probability of electronic.