DX-like properties of the EL6 defect family in GaAs

Abstract

Capacitance-voltage characterization at different temperatures and emission and capture deep-level transient spectroscopy carried out on undoped n-type GaAs lend strong confirmation to the recent suggestion that the EL6 defect arises from a center that is DX-like in nature. The evidence comes from the observation of an anomalous filling pulse duration dependence of the peak intensities of three to four different EL6 sublevels, similar to that recently found for the DX center in Al xGa 1-xAs and attributed to the charge redistribution. In addition, capture transients reveal large capture barriers (0.2-0.3 eV), which are typical of a defect undergoing large lattice relaxation into a deep-lying state. These observations indicate that the EL6 defect center comprises of a center with three to four slightly different ground-state configurations, each one of which forms as a result of some bond-breaking atomic displacement on capture of a second electron at the defect site. The significance of this in understanding the microstructure for the EL6 center is briefly discussed.