Interface modification of the InGaN/GaN quantum wells: the strain pre-reliefeffect

Abstract

Interface modification by inserting an ultrathin low-temperature GaN layer prior to thegrowth of high-temperature GaN barriers followed by an annealing process was employedto improve the properties of the InGaN/GaN quantum wells. By detailed studies andcomparisons of the surface morphology, photoluminescence and the surface compositions ofthe InGaN/GaN quantum wells at different growth stages with and without the interfacemodification, we find that with the interface modification the surface morphology wassignificantly improved with better smoothness, and smaller and shallower pits oflower density compared with that without interface modification; further, theindium aggregation and phase separation were suppressed. The physical phenomenaare attributed to the ‘strain pre-relief effect’ by the formation of quasi-dots (∼20 nm in diameter) prior to temperature ramping and growth of high-temperature GaNbarriers. Furthermore, the ultrathin low-temperature GaN layers have a good protectionproperty as confirmed by PL and XPS measurements.