Phase separation and nonradiative carrier recombination in active regions of light-emitting devices based on InGaN quantum dots in a GaN or AlGaN matrix

Abstract

Structures with InGaN nanolayers within GaN and AlGaN matrices, which constitute active regions of light-emitting devices, have been studied. Spectra and relative intensities of photoluminescence (PL) in the temperature range 20–300 K and the dependence of the position of the PL peak on the energy of the excitation photons have been measured. It is shown that, to account for the temperature dependence of the PL intensity, it is necessary to take into consideration, in addition to the nonradiative recombination via defects in the matrix and in the residual quantum well (RQW), an additional recombination channel with low activation energy, which is presumably associated with defects located close to quantum dots. It is demonstrated that structures with the AlGaN matrix show a larger decrease in the PL intensity upon an increase in temperature from 50 to ∼200 K, compared with structures with the GaN matrix. Analysis of the temperature dependence of the PL intensity in terms of the model that considers these three channels of nonradiative recombination shows that this dependence is associated with a decrease in the carrier’s localization energy relative to the ground state in the RQW. Such a decrease is due to suppression of the phase separation in InGaN layers grown within the AlGaN matrix. This behavior is confirmed by PL measurements at different excitation photon’s energies and leads, in addition to the lower localization energy, a decrease in the concentration of recombination centers is observed for these samples.