Strongly reduced V pit density on InGaNOS substrate by using InGaN/GaN superlattice

Abstract The InGaN pseudo-substrate, namely InGaNOS (InGaN On Sapphire), is used to enhance the In incorporation rate in InyGa1-yN/InxGa1-xN multiple quantum wells (MQWs) to get red emission for micro-display applications. However, the starting material for the InGaNOS fabrication is a non-optimized In0.08Ga0.92N layer grown on GaN on sapphire substrate which exhibits V shaped defects (V pits). Such V pits remain afterwards in the final InGaNOS substrate. We demonstrate here that InxGa1-xN/GaN superlattice has the potential to cover or fill the native V pits while maintaining a pseudomorphic growth. A combination of a thin GaN interlayer and an InGaN layer in a slight tensile strain state for each pair of the superlattice is necessary to achieve this goal. In addition, it is shown that the presence of GaN interlayers improves the material quality and the surface roughness. (0 0 2) X-ray diffraction rocking curve linewidth reduces to 780 arcsec compared to 3000 arcsec for the substrate. Finally, InyGa1-yN/InxGa1-xN multiple quantum wells grown on InxGa1-xN/GaN superlattice buffer layer on InGaNOS 3.205Ȧ substrate shows a central emission wavelength, measured by photoluminescence, of 624 nm at 290 K with an optical internal quantum efficiency value of 6.5%.