Photoluminescence spectroscopy with sub-wavelength lateral resolution was used to probe individual localization centers in a thin InGaN/GaN quantum well. Spectrally narrow emission lines with a line-width as small as 0.0008eV could be resolved, originating from the recombination of an electron-hole pair occupying a single localized state. Surprisingly, the individual emission lines show a pronounced blue-shift when raising the temperature, while virtually no energy shift occurred for increasing excitation density. These findings were in remarkable contrast to the behavior usually found in macro-photoluminescence measurements and give a fundamental new insight into the recombination process in semiconductor nanostructures in the presence of localization and strong internal electric fields. Clear indications were found of a bi-exciton state with a negative binding energy of about 0.005eV.

Probing Individual Localization Centers in an InGaN/GaN Quantum Well. H.Schömig, S.Halm, A.Forchel, G.Bacher, J.Off, F.Scholz: Physical Review Letters, 2004, 92[10], 106802 (3pp)