Strain-induced quantum dots like island formations were demonstrated to effectively suppress pits/dislocation generation in high indium content (26.8%) InGaN active layers. In addition to the strain redistribution in the quantum dot-like islands, strain modulation on the InGaN active layers by using the GaN island capping was employed to form an increased surface potential barrier around the dislocation cores, which inhibits the carrier transport to the surrounding dislocations. Cathodoluminescence showed distinct double-peak emissions at 503nm and 444nm, corresponding to the In-rich quantum dots-like emission and the normal quantum well emission, respectively. The quantum dots-like emission became dominated in photoluminescence due to the carrier localization effect of In-rich InGaN quantum dots at relatively low so-called carrier injection current. Accordingly, green emission might be enhanced by reduction in the pit/dislocation density, carrier localization and strain reduction in quantum dots, strain modulation by GaN island capping and enhanced light extraction with faceted GaN islands on the surface.

Green Emission from a Strain-Modulated InGaN Active Layer. G.B.Wang, X.Huan, Y.X.Lin, Z.L.Fang, J.Y.Kang, D.Yu, W.Z.Shen: Chinese Physics Letters, 2012, 29[6], 068101