Defect production in electron-irradiated, n-type GaAs

Temperature-dependent Hall-effect measurements have been performed on pure, n-type, vapor-phase epitaxial GaAs, irradiated by 1-MeV electrons at room temperature. The energies and production rates of two dominant defect centers, C₂ and C₃, are as follows: E₂=E_C-0.148, E₃=E_C-0.295 ±0.002 eV, τ₂=2.0, and τ₃=0.5±0.2 cm^-1, in good agreement with deep level transient spectroscopy (DLTS) data. However, the most important result of this study is a very high production rate, τ_AS ≂4±1 cm^-1, for ``shallow'' acceptors (C_AS) lying below E₃. In fact, C_AS is produced at a much higher rate than all of the DLTS traps observed in this energy range, proving that close to half of the primary defects in electron-irradiated GaAs are evidently not seen by DLTS. The high C_AS production rate has important implications for microscopic models of C₁ and C₂, rendering unnecessary the assumption that one of these centers must be an acceptor in order to explain the Hall-effect results. Finally, we show that all available Hall-effect and DLTS data are consistent with C_AS representing Ga-sublattice damage, which has not been observed before.