Identification of paramagnetic AsGa and optical EL2 centers in semi-insulating gallium arsenide

After a brief recall of our main results obtained during a recent theoretical cluster calculation on anion antisite-related defects in GaAs, we discuss the consequences of their resonance parameters. Experimentally, we perform a detailed analysis of the electron paramagnetic resonance data in plastically deformed undoped and Cr-doped semi-insulating materials in conjunction with simultaneous EL2° optical absorption measurements. Combining theoretical calculations and experimental results, we are able to identify the ‘‘As+Ga’’ spectrum as a superposition of spectra ascribed to the isolated As+Ga and to its binary and ternary vacancy complexes, whereas the ternary complex AsGaVGaVAs only is believed to be the probable configuration for EL2.