EPR investigations of the defect chemistry of semi-insulating GaAs : Cr

The effects of some heat treatments under various atmospheres (vacuum, As, Ga2O3, or H2) on GaAs : Cr samples have been investigated by EPR. The equilibria between the two valence states Cr+ and Cr2+ seem to depend on various parameters such as the total amount of Cr, and other defects such as the iron contaminant. A new paramagnetic defect, occurring at g=2.002±0.001 has been identified, whose intensity is highest after the H2 anneal.