Near-infrared near-field photoluminescence imaging spectroscopy of exciton localized states in GaInNAs/GaAs quantum wells due to nonuniform distribution of nitrogen

The nonuniform distribution of nitrogen in dilute GaInNAs alloys was investigated by low-temperature near-field photoluminescence (PL) imaging spectroscopy of localized states driven by giant band-gap reduction due to nitrogen incorporation. The depths and spatial profiles of exciton confinement potential were visualized through the measurement of power-dependent PL spectra and high-resolution PL images. For two GaInNAs quantum wells with different nitrogen contents, we observed strongly localized excitons confined in nitrogen clusters and rather delocalized excitons, which indicate the onset of alloy formation.