Optical properties of AlInGaN quaternary alloys

Carrier recombination dynamics in AlInGaN alloy has been studied by photoluminescence (PL) and time-resolved photoluminescence (TRPL). The fast redshift of PL peak energy is observed and well fitted by a physical model considering the thermal activation and transfer processes. This result provides evidence for the exciton localization in the quantum dot (QD)-like potentials in our AlInGaN alloy. The TRPL signals are found to be described by a stretched exponential function of exp[(-t/τ)^β], indicating the presence of a significant disorder in the material. The disorder is attributed to a randomly distributed quantum dots or clusters caused by indium fluctuations. By studying the dependence of the dispersive exponent β on the temperature and emission energy, we suggest that the exciton hopping dominate the diffusion of carriers localized in the disordered quantum dots. Furthermore, the localized states are found to have 0D density of states up to 250 K, since the radiative lifetime remains almost unchanged with increasing temperature.