Theory of the metastable injection-bleached E3c center in GaAs

The $E3$ transition in irradiated GaAs observed in deep level transient spectroscopy (DLTS) was recently discovered in Laplace-DLTS to encompass three distinct components. The component designated $E3c$ was found to be metastable, reversibly bleached under minority carrier (hole) injection, with an introduction rate dependent upon Si doping density. It is shown through first-principles modeling that the $E3c$ must be the intimate Si-vacancy pair, best described as a Si sitting in a divacancy ${\mathrm{Si}}_{vv}$. The bleached metastable state is enabled by a doubly site-shifting mechanism: Upon recharging, the defect undergoes a second site shift rather returning to its original $E3c$-active configuration via reversing the first site shift. Identification of this defect offers insights into the short-time annealing kinetics in irradiated GaAs.