ENHANCEMENT OF PHOTOLUMINESCENCE FROM DX CENTERS IN ALGAAS HETEROSTRUCTURES

Selectively excited room-temperature photoluminescence spectra of InGa As-GaAs-AlGaAs quantum well heterostructures reveal a broad line at mi dgap energies originating in the Si doped AlGaAs. When carriers are ph otoexcited directly in the wells, this line is dramatically enhanced a t the expense of the quantum well line, indicating carriers escape fro m the wells. The broad emission and its enhancement can be explained i n terms of recombination between electrons trapped at DX centers in Al GaAs 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 co rrelates this line to DX centers.