INVESTIGATIONS OF AS-ANTISITE-RELATED DEFECTS IN GAAS

Optically Detected Magnetic Resonance (ODMR) is a powerful tool to stu dy paramagnetic defects in semiconductors. As an example for the succe ssful application of various methods based on ODMR, investigations of As antisite-related defects in GaAs are presented. Information about d efect properties such as their microscopic structure, their metastabil ity and thermal stability can be obtained by ODMR which was measured v ia the Magnetic Circular Dichroism of the optical Absorption (MCDA). L ow temperature irradiation of GaAs (4.2 K) with 2 MeV electrons produc es 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 ant isite 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 w as 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 pe rformed also magneto-optical measurements to investigate the metastabi lity properties of the three As antisite-related defects. They all sho w metastability.