Spectroscopic discrimination of non-radiative centers in quantum wells by two wavelength excited photoluminescence

Discrimination of non-radiative recombination centers in Si-doped GaAs/AlGa As quantum well structures has been achieved by means of a two wavelength e xcited photoluminescence technique. In a crystal grown at 700 degrees C, tr aps were found neither in GaAs wells nor in Al0.2Ga0.8As barriers, but insi de external Al0.4Ga0.6As layers which originally were left out of the dopin g region. These traps were classified as a pair: one originating in a latti ce native defect or a residual impurity; and the other by Si atoms (possibl y a DX center) diffused from the doped region. In contrast, traps were foun d even inside the GaAs wells in case of samples grown at 600 degrees C, ref lecting deteriorated crystal quality. (C) 2000 Elsevier Science B.V. All ri ghts reserved.