It was recalled that EL2 was the ubiquitous native defect in crystalline GaAs grown by using various techniques. It was thought to be a doubly-charged deep-level centre with 2 states having distinct energy levels in the band-gap. While the singly charged state was widely studied, the doubly-charged state was only rarely treated in the literature. Evidence was provided here for a predominant inadvertent deep level, in p-type GaAs, which was most likely to be the doubly-charged state of the EL2 centre. Deep-level transient spectroscopy was used to characterize epitaxial layers of p-type GaAs grown on p+ GaAs substrates by low-pressure metal organic chemical vapor deposition. A pronounced peak was observed in the majority carrier (hole) emission deep-level spectra. Thermal emission rate of holes from the corresponding deep level was found to exhibit a strong electric field dependence, showing an increase of more than two orders of magnitude with an increase of the electric field by a factor of about 2. The thermal activation energy for this level was found to vary from 0.29 to 0.61eV as the electric field was varied from 2.8 x 105 to 1.4 x 105V/cm. Direct pulse-filling measurements point to a temperature-dependent behavior of the hole capture cross-section of this level. This inadvertent deep-level defect, commonly observed in p-type GaAs grown by a variety of different methods, was identified with the doubly charged state of the well-known AsGa antisite related defect, EL2.

Doubly Charged State of EL2 Defect in MOCVD-Grown GaAs. N.A.Naz, U.S.Qurashi, A.Majid, M.Z.Iqbal: Physica B, 2007, 401-402, 250-3