Abstract
A thermal conversion mechanism of semi-insulating GaAs with a SiOxNy cap was studied. Both SiO- and SiN-rich cap films exhibit n-type conductivity after thermal annealing, and a newly discovered level Ec−0.91 eV is present in these converted samples found by deep-level transient spectroscopy measurements. This conversion phenomenon may be attributed to Ga out-diffusion through the cap layer during thermal annealing.