Anomalous polarization in the photoluminescence from Si-dopedGaAs−AlxGa1−xAsquantum-well samples

Abstract

The low-temperature photoluminescence observed with the use of circular-polarization excitation and detection techniques shows that GaAs-AlGaAs multiquantum-well structures grown by molecular beam epitaxy with $n$-type, i.e., Si-doped, quantum wells can exhibit highly polarized luminescence. Most striking is the observation that with increasing Si doping, the circular polarization of the luminescence at 5 K with resonant excitation of the $n=2$ heavy-hole exciton decreases markedly and, in fact, becomes opposite to that of the excitation for $n\ensuremath{\approx}{10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. When the temperature is increased to \ensuremath{\cong}20 K, the reduced and negative polarization effects are no longer present.