The conduction-band energies at the Γ point of GaAs are determined experimentally in the 10–60-eV range by means of angle-resolved constant-initial-state measurements. The most prominent conduction-band states reached from the top (${\mathrm{\Gamma }}_{15}^{\mathit{v}}$) and the bottom (${\mathrm{\Gamma }}_1^{\mathit{v}}$) of the valence band lie at 10.72, 12.60, 15.20, 22.62, 32.38, 34.13, 35.61, 49.43, 55.67, and 58.61 eV above the valence-band maximum, respectively. These values are compared with available theoretical conduction-band calculations. We observe resonant photoemission at 20.30 eV, which corresponds to the transition from the Ga 3d surface core level to the unoccupied Ga-derived dangling bond. Associated with this transition is a surface exciton with a binding energy of approximately 0.93 eV. We observe also a weak but reproducible resonance at 106.40 eV, which is associated with the transition from the Ga 3p core to the same unoccupied band. A further resonance at 43.86 eV is assigned to the excitation of the As 3d core level into the bulk conduction band. The contribution of intra- as well as inter- atomic Auger processes and of inelastic scattering due to plasmon losses in the measured spectra is also considered.

• Received 14 May 1990

DOI:https://doi.org/10.1103/PhysRevB.42.8966