By using optically detected electron paramagnetic resonance techniques, a predominant defect with a quartet hyperfine split spectrum was observed in p-type and semi-insulating material which had been electron-irradiated at 4.2K and kept below 60K. The defect was suggested to be of Ga vacancy type. It decayed at about room temperature, while an As antisite-related defect (which had previously been identified as an anti-structure pair: AsGa with GaAs as a second-nearest neighbor) formed. The spectrum of the magnetic circular dichroism of the Ga vacancy-related defect was supposed to originate from photo-ionization transitions to the valence band.

K.Krambrock, J.M.Spaeth: Solid State Communications, 1995, 93[4], 285-9