Monte Carlo modeling of thin GaAs photocathodes

A Monte Carlo model was developed to simulate electron transport and emission from thin GaAs photocathodes with different active layer thicknesses and dopant concentrations. The simulation accurately predicts expected behavior, namely, quantum efficiency (QE) is enhanced for thicker GaAs photocathodes and for higher dopant concentrations. More significantly, the simulation predicts that electrons excited to the conduction band of the GaAs can be reflected by the band bending regions of the AlGaAs barrier layer, which contributes to enhance QE. The simulation also predicts that electrons in the conduction band suffer more scattering for thicker GaAs photocathodes and for higher dopant concentration, leading to longer emission response time. This Monte Carlo model will improve our understanding and predicting of the performance of more complicated GaAs-based heterojunction structures composed of multiple thin layers.