Comparison of
GaN and AlN nucleation layers for the oriented growth of GaN on diamond
substrates
G.W.G. van Dreumel, T. Bohnen, J.G. Buijnsters, W.J.P. van Enckevort,
J.J. ter Meulen, P.R. Hageman and E. Vlieg
a Institute for Molecules and Materials, Radboud University Nijmegen,
Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
Abstract:
In this study, {0001} oriented GaN crystals have been grown on
freestanding, polycrystalline diamond substrates using AlN and GaN
nucleation layers (NLs). XRD measurements and SEM analysis showed that
the application of a thin AlN NL gives the best structural results,
because AlN 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.