Radiative recombination inp-typeδ-doped layers in GaAs

Abstract

Thin Zn-doped GaAs layers embedded in bulk GaAs, grown by metal-organic vapor phase epitaxy, are studied by means of optical spectroscopy. The concentration of Zn acceptors varies between $2\ifmmode\times\else\texttimes\fi{}{10}^{18}/{\mathrm{cm}}^{3}$ and $2\ifmmode\times\else\texttimes\fi{}{10}^{20}/{\mathrm{cm}}^{3}$ in 4 nm doping regions. With increasing doping concentration, an optical radiative transition appears in photoluminescence (PL) spectra below the energy position of the transition between the free electrons and holes bound to acceptors in bulk GaAs. The recombination shows a strong dependence on excitation intensity and temperature. Our results indicate that this emission is related to the transition between spatially separated electrons and holes. The holes are located in a p-type Zn-$\ensuremath{\delta}$-doped region, while the electrons are located in the undoped GaAs region. The magnetic-field dependence of this emission in the PL spectrum indicates that the effective mass of the holes involved in the optical transition is about ${0.2m}_{0}.$ To the best of our knowledge, this is the first time that such recombination in p-type $\ensuremath{\delta}$-doped GaAs is confirmed from optical spectroscopy.