Electron concentration dependence of exciton localization and freeze-out at local potential fluctuations in InN films
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- Liu, B., Zhang, Z., Zhang, R. et al. Appl. Phys. A (2010) 99: 139. doi:10.1007/s00339-010-5594-3
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InN films with electron concentration ranging from n∼1017 to 1020 cm−3 grown by metal–organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were investigated by variable-temperature photoluminescence and absorption measurements. The energy positions of absorption edge as well as photoluminescence peak of these InN samples with electron concentration above 1018 cm−3 show a distinct S-shape temperature dependence. With a model of potential fluctuations caused by electron-impurity interactions, the behavior can be quantitatively explained in terms of exciton freeze-out in local potential minima at sufficiently low temperatures, followed by thermal redistribution of the localized excitons when the band gap shrinks with increasing temperature. The exciton localization energy σloc is found to follow the n5/12 power relation, which testifies to the observed strong localization effects in InN with high electron concentrations.