High-Integrated-Photosensitivity Negative-Electron-Affinity GaAs Photocathodes with Multilayer Be-Doping Structures

The effect of changing Be doping concentration in GaAs layer on the integrated photosensitivity for negative-electron-affinity GaAs photocathodes is investigated.Two GaAs samples with the monolayer structure and the multilayer structure are grown by molecular beam epitaxy.The former has a constant Be concentration of 1e19cm-3,while the latter includes four layers with Be doping concentrations of 1e19,7e18,4e18,and 1e18cm-3 from the bottom to the surface.Negative-electron-affinity GaAs photocathodes are fabricated by exciting the sample surfaces with alternating input of Cs and O in the high vacuum system.The spectral response results measured by the on-line spectral response measurement system show that the integrated photosensitivity of the photocathode with the multilayer structure enhanced by at least 50% as compared to that of the monolayer structure.This attributes to the improvement in the crystal quality and the increase in the surface escape probability.Different stress situations are observed on GaAs samples with monolayer structure and multilayer structure,respectively.