Significant enhancement of carrier localization in InGaN MQWs by underlying high-In-content superlattice

To improve the emission efficiency of InGaN/GaN multiple quantum wells (MQWs), we used a high-indium-content short-period superlattice (SPSL) underlayer and validated the approach through structural and optical characterization. The SPSL underlayers were deposited at temperatures equal to or lower than those used for the growth of active region MQWs. The impact of such underlayers was studied using XRD, photoluminescence (PL), and light-induced transient grating (LITG) techniques. The large redshift of the PL band and higher PL efficiency at low excitations were achieved in the MQWs grown on SPSLs, although this enhancement came at the cost of reduced carrier lifetime compared to the structures without the SPSL underlayer. We attribute the observed changes to the interplay between the transformation of localizing potential and the generation of additional defects. The coincidence of these modifications results in the formation of regions with a high density of both localized states and nonradiative recombination centers.