Angular dependence of the photoelectron energy distribution of InP(100) and GaAs(100) negative electron affinity photocathodes

Energy distribution of the photoelectrons from InP(100) photocathodes are investigated with a photon energy range from 0.62to2.76eV. When the photon energy is less than 1.8eV, only electrons emitted from the Γ valley are observed in the energy distribution curves. At higher photon energies, electrons from the L valley are observed. The angular dependence of the electron energy distributions of InP and GaAs photocathodes are studied and compared. The electrons emitted from the L valley have a larger angular spread than the ones from the Γ valley due to the larger effective mass of the L valley minimum.