Dimensionality of Excitons in InGaN-Based Light Emitting Devices

Abstract

Temperature dependence of radiative and non-radiative recombination times has been investigated in InxGa1–xN based light emitting devices by employing time-resolved luminescence spectroscopy. The mean In-composition (x value) assessed in this study is 10%, 20% and 30% whose emissions at 300 K correspond to near ultraviolet (390 nm), violet (422 nm) and blue (471 nm), respectively. It was found that the degree of exciton localization was enhanced with increasing In-composition in InxGa1–xN active layers, and that the zero-dimensional feature was revealed best of all in the sample with x = 30%, where radiative recombination time was almost constant (4 to 6 ns) in the temperature range from 20 to 300 K. The internal quantum efficiency of this sample was estimated to exceed 70% at 300 K. It is likely that such high efficiency is a result of zero-dimensionality because capture cross-sections to non-radiative recombination centers are greatly reduced once excitons are trapped at deep localization centers.