Location of energy levels of oxygen-vacancy complex in GaAs

Abstract
Experimental results of photoexcitation and thermal deactivation of localized vibrational mode absorption of the oxygen-vacancy complex in GaAs are reported. Two levels within the energy gap are observed, one located at 0.14 eV and the other between 0.57 eV and 0.75 eV below the conduction-band minimum. It is proposed that this center exhibits a negative U property with the second electron ionization energy higher than that of the first electron.