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 2/spl times/10/sup 15/ and 2/spl times/10/sup 16/ cm/sup -3/ were exposed at room temperature to 200, 350, and 500 MeV proton irradiation at fluences of 3/spl times/10/sup 11/, 10/sup 12/, 10/sup 13/, 3/spl times/10/sup 13/ 10/sup 14/ and 10/sup 15/ cm/sup -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/sub Ga/) and the other at 1.482 eV to the silicon at the arsenic site acceptor (Si/sub As/). The relative introduction rate of these two defects has been measured in the irradiated samples before and after annealing at 550/spl deg/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.