Photoluminescence in degenerate p-type GaAs layers grown by molecular beam epitaxy

The emission spectra of the heavily Be-doped GaAs layers grown by molecular beam epitaxy as a function of dopant concentration have been studied at different temperatures using photoluminescence (PL) spectroscopy. E(0) and the PL peak energy E(M) both change with the increase in temperature and the change can well be described by the Varshni equation. The PL full width al half-maximum was found to increase monotonically while the PL intensity decreases with temperature. The luminescence spectra of the degenerate layers are asymmetric with the maxima shifted towards lower energies as the hole concentration is increased. The spreads of the short-wavelength edges towards higher energy, however, are not as significant as that observed in Zn-doped GaAs grown by liquid phase epitaxy. The room temperature E(M) decreases slowly with hole concentration up to 2.25 x 10(20) cm(-3) while E(M) at 4 K does not change significantly up to 3 x 10(18) cm(-3) and drops drastically thereafter. We suggest that the main emission spectra of the heavily Be-doped layers obtained at 4 K is most likely a result of band-acceptor transitions.