Identification of EL2 in GaAs

Abstract

Combining electron paramagnetic resonance under optical excitation, deep level transient spectroscopy, electron irradiation, annealing, and quenching on LEC semi-insulating GaAs and lightly Si-doped material grown in the same way as the semi-insulating material, we have shown that (i) the irradiated material contains two types of defects related to the antisite AsGa, one As∇Ga, present before irradiation, identified to EL2 from its characteristic photoquenching behavior and the other As*Ga, created by the irradiation, stable under photoexcitation; (ii) As∇Ga anneals partially under a 850 °C thermal treatment followed by a quench and the remaining defects are transformed into As*Ga; (iii) further annealing around 120 °C converts As*Ga into As∇Ga, the process being thermally activated (0.5±0.2 eV). From these results and using observations of absorption on vibrational modes of the C-As interstitial pair in electron irradiated material, we are able to conclude that As*Ga is the isolated antisite and As∇Ga, i.e., EL2, is a complex of an As antisite and an As interstitial.