Comparison of GaN and A1N nucleation layers for the oriented growth of GaN on diamond substrates

摘要

In this study, {0001} oriented GaN crystals have been grown on freestanding, polycrystalline diamond substrates using A1N and GaN nucleation layers (NLs). XRD measurements and SEM analysis showed that the application of a thin A1N NL gives the best structural results, because A1N has a thermal expansion coefficient in between GaN and diamond and thus delocalizes the stress to two interfaces. The optical quality of the layers, investigated with Raman microscopy and photoluminescence spectroscopy, is similar. Although no lateral epitaxy is obtained, new insight is gained on the nucleation of GaN on diamond substrates facilitating the growth of GaN epilayers on polycrystalline diamond substrates.