Investigations of As-antisite-related defects in GaAs

Optically Detected Magnetic Resonance (ODMR) is a powerful tool to study paramagnetic defects in semiconductors. As an example for the successful application of various methods based on ODMR, investigations of As antisite-related defects in GaAs are presented. Information about defect properties such as their microscopic structure, their metastability and thermal stability can be obtained by ODMR which was measured via the Magnetic Circular Dichroism of the optical Absorption (MCDA).Low temperature irradiation of GaAs (4.2 K) with 2 MeV electrons produces the Ga vacancy and some new As antisite-related defects. Annealing steps were investigated at 77 K and above. At 77 K the isolated As antisite defect is detected if semi-insulating (si) GaAs was irradiated. Between 200 K and 300 K the Ga vacancy decays. Its decay is correlated to the formation of an anti-structure pair. A second annealing step was found at about 520 K. There the anti-structure pair decays. EL2 is formed at that temperature if si material was irradiated, but this EL2 formation is not correlated with the anti-structure pair decay. We performed also magneto-optical measurements to investigate the metastability properties of the three As antisite-related defects. They all show metastability.Paper presented at the 132nd WE-Heraeus-Seminar on Positron Studies of Semiconductor Defects, Halle, Germany, 29 August to 2 September 1994