Photoluminescence of localized excitons in InGan quantum dots

Photoluminescence spectra of samples with ultrathin InGaN layers embedded in AlGaN and GaN matrices are studied experimentally in the temperature range of 80 to 300 K. It is shown that the temperature dependences can be understood in the context of Eliseev’s model and that, in the active region of the structures under study, the dispersion σ of the exciton-localization energy depends on the average In content in InGaN-alloy layers. Furthermore, the Urbach energy EU, which characterizes the localization energy of excitons in the tails of the density of states, was determined from an analysis of the shape of the low-energy slope of the spectrum. It is shown that σ and EU, quantities representing the scale of the exciton-localization effects, vary linearly with the photoluminescence-peak wavelength in the range from the ultraviolet to the green region of the spectrum.