Properties of arsenic antisite defects in Ga1-xMnxAs

We report the results of optical absorption measurements on Ga1-xMnxAs layers grown by low-temperature molecular beam epitaxy. In the paramagnetic layers grown at very low temperatures (below 250 degreesC) the experiments reveal an absorption band at 1.2 eV arising from the presence of neutral arsenic antisites, As-Ga. From the magnitude of the absorption we determine the concentration of As-Ga to be between 4x10(19) and 8x10(19) cm(-3) in these paramagnetic samples. These values are typical for GaAs specimens grown below 250 degreesC. Extrapolating the As-Ga concentration from low-temperature-grown GaAs to Ga1-xMnxAs, we determine the concentration of this defect in ferromagnetic Ga1-xMnxAs layers grown at temperatures above 250 degreesC as 1x10(19) down to 1x10(18) cm(-3). We conclude that the compensating role of arsenic antisites in Ga1-xMnxAs becomes gradually less important with increasing growth temperature. (C) 2004 American Institute of Physics.