Dimensionality of excitons in InGaN-based light emitting devices

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 Ii 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.