Effect of InGaN well layer growth rate upon photoluminescence of InGaN/GaN multiple-quantum-well structures

The photoluminescence (PL) spectra of a range of InGaN/GaN multiple-quantum-well (MQW) structures dependent on temperature that have different well layer growth rates (WLGRs) were analyzed. The results show that the InGaN well layers of all structures are composed of two separate phases: In-rich clusters and an InGaN matrix. Also, with increasing WLGR, the In-rich clusters-related PL intensity increases significantly relative to its InGaN matrix-related counterpart at low temperatures, meanwhile the behavior of temperature-dependent relaxation followed by expansion of the carriers in both phases becomes less significant. These behaviors are interpreted thus: an increasing WLGR can shorten exposure of the upper layer face to the atmosphere during the growth of InGaN well layers, and this suppresses the migration of In atoms on the surface from the In-rich clusters to the surrounding InGaN matrix, thus resulting in an increasing of the density of states ratio of the In-rich clusters to the InGaN matrix and a weakening of the composition fluctuation in both phases.