Study on higher-energy emission observed locally around V-pits on InGaN/GaN quantum wells grown on moderate-temperature GaN

Abstract

We investigated the origin of the multi-peak higher-energy (HE) emission observed in the local photoluminescence (PL) spectra of InGaN/GaN quantum wells (QWs) grown on moderate-temperature-grown GaN (MT-GaN) layers and evaluated the relationship among the energy difference between the HE emission and InGaN/GaN single QW (SQW) emission corresponding to the potential barrier height and the V-pit diameter. The distribution of HE emissions and dark spots suggested the formation of so-called potential barriers around dislocations in the InGaN SQWs on the MT-GaN layers. Multiple HE emissions were observed in the local PL spectra acquired from the InGaN SQWs on the MT-GaN layers as well in the case of InGaN multiple QW on MT-GaN previously reported. This observation suggested that the origin of multi-peak HE emissions is an in-plane variation in In composition and/or well thickness. The energy difference between InGaN emission from c-plane QW and HE emission from V-pit facet increased as the MT-GaN layer thickness or V-pit diameter increased. The origin of both the multiple HE emissions and the increase in the energy difference with V-pit diameter in InGaN/GaN SQW on MT-GaN was probably the diffusion of group III atoms between different facets of the InGaN SQWs in sub-micrometer scale V-pits.