We study the two samples of AIInGaN, i.e., 1-μm GaN grown at 1030℃ on the buffer and followed by a 0.6-μm-thick epilayer of AIInGaN under the Iow pressure of 76 Torr and the AIInGaN layer deposited directly on the buffer layer without the high-temperature GaN layer, by temperature-dependent photoluminescence (PL)spectroscopy and picosecond time-resolved photoluminescence (TRPL) spectroscopy. The TRPL signals of both the samples were fitted well as a stretched exponential decay at all temperatures, indicating significant disorder in the material. We attribute the disorder to nanoscale quantum dots or discs of high indium concentration.Temperature dependence of dispersive exponentβ shows that the stretched exponential decay of the two samples comes from different mechanisms. The different depths of the localization potential account for the difference,which is illustrated by the results of temperature dependence of radiative recombination lifetime and PL peak energy.