Photoluminescence study of gallium vacancy defects in gallium arsenide irradiated by relativistic protons

Epitaxially grown n-type gallium arsenide films, doped with silicon to concentrations of 2x10(15) and 2x10(16) cm(-3) were exposed at room temperature to 200, 350, and 500 MeV proton irradiation at fluences of 3x10(11), 10(12), 10(13), 3x10(13), 10(14) and 10(15) cm(-2). The effects of the irradiation were determined through low temperature continuous photoluminescence spectroscopy. Two radiation-induced donor-to-acceptor transitions were observed. The one at 1.476 eV has been associated to the gallium vacancy acceptor (V-Ga) and the other at 1.482 eV to the silicon at the arsenic site acceptor (Si-As) The relative introduction rate of these two defects has been measured in the irradiated samples before and after annealing at 550 degrees C for 30 minutes. The introduction rates are higher than those predicted by relativistic elastic scattering cross-section theory in the energy range studied here. We conclude that inelastic scattering contributes to the cross-section. The introduction rates are lower than non-ionizing energy loss (NIEL) calculations in the 200 to 500 MeV energy range. We suggest that the proton inelastic scattering parameter used in NIEL needs revision. The relativistic inelastic scattering formula is closer to experiment than present NIEL calculations.