Abstract
The optical characterization of GaAsSb/GaAs type-II quantum wells (QWs) with top InAs quantum dot (QD) layer composite structures was carried out using the complementary surface photovoltage (SPV) and photoluminescence (PL) spectroscopies. The obtained SPV and PL spectra revealed that the features originated from InAs QDs, modulated potential wells in GaAsSb QWs, the wetting layer (WL) as well as the GaAs cap layer/barrier at room temperature. The optical transition from the modulated potential wells in GaAsSb QWs in the composite structures showed a redshift when the spacer layer was narrowed from 10 to 5 nm. This is attributed to the lower modulated potential minimum in GaAsSb QWs caused by the strain exerted by InAs QDs in the composite structures with the narrower spacer layer. The power-dependent PL measurement showed that the luminescences from the GaAsSb/GaAs heterostructure blue-shifted with increasing excitation power owing to the type-II band alignment. These results demonstrated that SPV and PL are useful techniques for the nondestructive optical characterization of GaAsSb QWs with top InAs QD composite structures.
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