Spontaneous growth of In _x Ga _1-x N nanostructures directly on c-plane sapphire by plasma assisted molecular beam epitaxy

Effect of growth temperature on the morphology, structural and optical properties of In _x Ga _1-x N layers grown under nitrogen-rich conditions, by plasma assisted molecular beam epitaxy, on c-plane Sapphire have been studied. By varying the substrate temperature we are able to obtain tapered as well as flat-top nanorod and interconnected random network morphology. An increase of indium incorporation, determined by HRXRD, from 1% to 23% with decrease in growth temperature has been obtained. Room temperature photoluminescence (PL) and absorption measurements on the grown samples follow Vegard's law. A band bowing parameter of 1.54 eV has been determined for the observed composition range. A good quality - In _x Ga N _x-1 N film having no phase separation with significant PL emission intensity is obtained at a growth temperature much lower than that conventionally used in MBE for - In _x GaN _x-1 N growth on sapphire.