Quantum efficiency of transmission-mode graded bandgap AlxGa1-xAs/GaAs photocathode

Abstract Graded bandgap AlxGa1-xAs/GaAs photocathode with enhanced quantum efficiency is analyzed in this study. We present the relevant quantum efficiency equations by solving onedimensional continuity equations for transmission-mode graded bandgap AlxGa1-xAs/GaAs and standard AlGaAs/GaAs photocathodes. The results show that the built-in electrical field from bandgap gradation efficiently collects photogenerated electrons in the buffer layer such that quantum efficiencies in the short regions are improved in transmission-mode AlxGa1-xAs/GaAs photocathode. The results also show that a thinner buffer layer improves the short-wavelength response of transmission-mode photocathode. Increasing the active layer thickness improves long-wavelength responses but reduces short-wavelength responses. The method presented in this work may provide better estimate of performance and guide the optimum design of graded bandgap AlxGa1-xAs/GaAs photocathode.