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 the high indium content short-period superlattice (SPSL) underlayer and validated the approach by studying the structural and optical properties. The SPSL underlayers were deposited at temperatures equal to or below the growth temperature 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, albeit at the expense of shorter carrier lifetime, compared to the structures without SPSL underlayer. We attribute the observed changes to the interplay between the transformation of localizing potential and the generation of additional point defects, while the coincidence of modifications results in the formation of regions having high density of both localized states and nonradiative recombination centers.