DX-like properties of theEL6defect family in GaAs

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 $\mathrm{EL}6\mathrm{}$ defect arises from a center that is $\mathrm{DX}$-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 $\mathrm{EL}6\mathrm{}$ sublevels, similar to that recently found for the $\mathrm{DX}$ center in ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ 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 $\mathrm{EL}6\mathrm{}$ 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 $\mathrm{EL}6\mathrm{}$ center is briefly discussed.