Evidence of exciton recombination at very high temperature in InGaN

Time-resolved electroluminescence measurements are carried out on the blue light emitting diodes with InGaN active layer at temperatures from 30 to 53 0 K. The decay mechanisms of the ultraviolet optical pulses corresponding t o the band-to-band recombinations are investigated. The exciton-related rec ombination is found mainly responsible for this band-edge radiative recombi nation from 250 to 425 K. A thermal equilibrium model, in which the exciton dissociation process is taken into account, is used to fit the experimenta l results. The fitted exciton binding energy is about 48.3 meV. This high e xciton binding energy is attributed to the indium-related localization effe ct in InGaN. Moreover, it is also found that the nonradiative lifetimes in these samples are quite long. This is ascribed to the suppression of the no nradiative recombination centers because of the incorporation of indium in GaN material. (C) 2001 American Institute of Physics.