Research on quantum efficiency and photoemission characteristics of negative-electron-affinity GaN nanowire arrays photocathode

Abstract

Based on studies about photon absorption, band structure, and electron transport, quantum efficiency formula of negative-electron-affinity (NEA) GaN nanowire arrays (NWAs) photocathode has been derived from one-dimension continuity equation. According to the formula, the quantum efficiency of NEA GaN NWAs photocathode is calculated. It reveals a satisfactory result that the quantum efficiency of NEA GaN NWAs photocathode can reach to 41 % in comparison to 25 % of the conventional reflection-mode GaN photocathode. Meanwhile, the effects of incident angle of entering light and the diameter of nanowire on the spectra response of NEA GaN NWAs photocathode are also investigated. Results suggest that the optimal incident angle is 47° and the optimal diameter is between 100 and 140 nm which is related to the absorption coefficient of different incident light wavelengths. In addition, with the decrease of surface reflectivity or the increase of surface electron escape probability, the photoemission characteristics of NEA GaN NWAs are enhanced. According to all simulated calculation, potential advantages of NEA GaN NWAs photocathode are discovered and NEA GaN NWAs photocathode with more reasonable structure and better performance becomes realizable in the application of electron sources.