ENHANCEMENT OF PHOTOLUMINESCENCE FROM DX CENTERS IN ALGAAS HETEROSTRUCTURES

Selectively excited room-temperature photoluminescence spectra of InGaAs-GaAs-AlGaAs quantum well heterostructures reveal a broad line at midgap energies originating in the Si doped AlGaAs. When carriers are photoexcited directly in the wells, this line is dramatically enhanced at the expense of the quantum well line, indicating carriers escape from the wells. The broad emission and its enhancement can be explained in terms of recombination between electrons trapped at DX centers in AlGaAs and holes transferred into AlGaAs from the neighboring wells. We also observe the broad emission by direct over-the-gap photoexcitation of very highly doped Si:AlGaAs. The doping dependence consistently correlates this line to DX centers.