Carrier density dependence of localized carrier recombination dynamics in orange-emitting InGaN/GaN nanocolumns

The carrier density dependence of photoluminescence (PL) spectra, PL efficiency, and time-resolved PL (TRPL) in InGaN/GaN nanocolumns with orange emission has been measured over a wide range of carrier densities to investigate the carrier recombination dynamics at low and room temperatures. The TRPL decay curves were analyzed by stretched exponential functions to obtain a distribution of the decay times. The results indicate that the emission origin in InGaN with orange emission under low excitation intensity is the recombination of localized electrons and holes, not from localized excitons. Our analysis shows that the total density of localized states is an important factor to increase PL efficiency, which implies that red-emitting InGaN with a high density of localized states due to large indium fluctuation has the potential to achieve high PL efficiency. In addition, we have shown that the stretched exponential function is an effective approach to analyze several carrier relaxation processes with different decay times.