Observation of Room Temperature Excitons in GaSb–AlGaSb Multi-Quantum Wells

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Abstract
Absorption peaks due to excitons in GaSb (7 nm)–Al0.25Ga0.75Sb (3 nm) multi-quantum-wells (MQW) were first observed at room temperature. The absorption spectrum exhibited a double-peak structure. The shorter wavelength and the longer wavelength peaks were assigned to be n=1 light hole and heavy hole excitons, respectively, based on a study of the polarization dependence of the guided spontaneous emission of an MQW laser diode. Measurement of asymmetric X-ray double crystal diffraction showed that negligible strain was induced in the GaSb quantum wells grown on GaSb substrate. This result implies that the hole band reversal observed by other authors using the MQW grown on a lattice-mismatched GaAs substrate rarely occurs in GaSb quantum wells grown on a GaSb substrate. The electric field effect on the exciton absorption is also presented.