Effect of interfacial strain on the formation of AlGaN nanostructures by selective area heteroepitaxy

Abstract

AlGaN hexagonal nano-pyramids were formed on GaN/sapphire, AlN/sapphire and Al 0.5Ga 0.5N/sapphire using selective area heteroepitaxy. It is found that both interfacial strain due to the lattice mismatch and the growth conditions greatly impact growth rate, Al incorporation and facet quality of these AlGaN nanostructures. A correlation between the interfacial strain provided by the underlying template with growth of nanostructures was made, and attributed to the difference in surface diffusion properties as a function of strain. This was directly observed with the difference in the growth rates and Al incorporation of nanostructures when grown on various templates. The growth rates of nanostructures were found to be much higher when grown on an AlN template in comparison to that on a GaN template under the same growth conditions. Detailed characterization of the AlGaN nanostructures shows highly uniform composition. Further, multiple quantum well structures were grown within the nanostructures on different templates. The effect of strain was again visible with differences in emission properties of the quantum wells.