Impact of localized states on the recombination dynamics in InGaN/GaN quantum well structures

Multiple-component decays of photoluminescence (PL) in InGaN/GaN quantum wells have been widely reported. However, their physical interpretations have not been well discussed yet. Based on wavelength-dependent and temperature-varying time-resolved PL measurements, the mechanism of carrier transport among different levels of localized states (spatially distributed) in such an indium aggregated structure was proposed for interpreting the early-stage fast decay, delayed slow rise, and extended slow decay of PL intensity. Three samples of the same quantum well geometry but different nominal indium contents, and hence different degrees of indium aggregation and carrier localization, were compared. The process of carrier transport was enhanced with a certain amount of thermal energy for overcoming potential barriers between spatially distributed potential minimums. In samples of higher indium contents, more complicated carrier localization potential structures led to enhanced carrier transport activities. Free exciton behaviors of the three samples at high temperatures are consistent with previously reported transmission electron microscopy results.