Free and bound excitons in p-type GaAs MQW

Photoluminescence attributed to excitons associated with the e1-HH1 transition and bound to neutral impurities have been observed in p-doped (10(17) cm(-3)), 50 angstrom wide GaAs1-xAlxAs, multi-quantum wells grown by MOCVO. A critical analysis of the excitation intensity and temperature dependence of both intrinsic and extrinsic luminescence has been carried out between liquid helium temperatures and room temperature. The energy required to break the neutral impurity-exciton complex E-dis is obtained directly from the PL spectra and found to be E-dis = 10 MeV for 50 angstrom quantum wells. Acceptors are shown to occupy two distinct energy levels in the quantum well, with binding energies in agreement with the theoretical model proposed by Bastard.