Micro-photoluminescence (PL) mapping was investigated to elucidate the detailed mechanism of surface plasmon (SP)-enhanced emissions from InGaN/GaN quantum wells (QWs) with Ag or Al coating. The PL wavelengths were obviously red-shifted with Ag films, while the PL peak wavelengths were not changed with Al coating. The relationship between the PL peak intensity and the PL wavelength at each pixel showed a positive or negative correlation for the uncoated part of the InGaN/GaN QWs with blue or green emission, respectively. We found that these correlations disappeared in the Ag-coated regions. These results suggest that the energy transfer from the excitons to the SPs should be much faster than that in the exciton localization and charge screening processes of the piezoelectric field in QWs. These effects were not observed for the Al-coated regions because the mechanism of PL enhancement should be quite different as we have suggested previously.
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