Cryogenic high-pressure measurements were made of a defect-related emission at 1.25eV in Si-doped material. The measurements proved that the 1.25eV photon energy was relative to the conduction band; implying the existence of a deep defect level at 0.30eV above the valence band and an electron capture process from the conduction band and into the defect. The defect level moved up in the band-gap at a rate of 0.023eV/GPa. The results were consistent with a vacancy-related defect level which was suggested to arise from a complex which comprised a Ga vacancy and a Si atom on a (second-nearest neighbor) Ga site.

M.Holtz, T.Sauncy, T.Dallas, S.Massie: Physical Review B, 1994, 50[19], 14706-9