Calculated energy distributions of electrons emitted from negative electron affinity GaAs: Cs–O surfaces

Abstract

The energy distribution of electrons emitted from negative electron affinity (NEA) GaAs: Cs–O has been calculated for various doping concentrations (1 × 10¹⁸−2 × 10¹⁹ cm⁻³) and work functions (0.95–1.15 eV). It has been assumed that electrons to be emitted have thermalized at the bottom of the conduction band when they reach the surface bent‐band region. The energy distribution of the electrons reaching the surface is determined by their interactions in the bent‐band region and is calculated from a solution of the Boltzmann transport equation. Multiplication of this distribution with an energy‐dependent transmission probability for the surface barrier yields the energy distribution of the emitted electrons. The width of the bent‐band region, and thus the doping concentration of the emitter material, has a significant influence on the shape and width of the distribution and on its location on the energy scale, while the work function mainly affects the magnitude of the distribution. Measured half‐widths of the energy distributions from NEA GaAs photocathodes and cold cathodes are in good agreement with the calculations.