Evidence for Luminescence Involving Arsenic Vacancy-Acceptor Centers inp-Type GaAs

The observed similarity in the temperature behavior of peak shift, half-width, and intensity of the 1.37-eV band in $p$-type GaAs and the self-coactivated luminescence in ZnS substantiate a previously proposed model of recombination at an arsenic vacancy bound to an acceptor (Zn or Cd). The excitation spectra obtained through the use of GaAs laser diodes show a shoulder at 1.46 eV, just on the lower-energy side of the absorption edge. The shoulder is ascribable to absorption at the luminescence center responsible for the 1.37-eV band. Approximate configuration-coordinate curves are constructed for the centers in both Zn- and Cd-doped GaAs crystals from the experimental values of the low-temperature emission and excitation peak energies, the vibration frequency of the center in its excited state, and the activation energy for the temperature dependence of intensity. The non-Gaussian shape of the emission band is explained in terms of a small displacement between the minima of the configuration-coordinate curves. A vibration energy of 0.011 eV is determined for the excited state of the center, and a value between 0.011 and 0.0344 eV for the ground state of the center.