It was recalled that GaN-on-silicon was an alternative to growth on sapphire or SiC. Epitaxial growth was usually performed on Si(111), which had a threefold symmetry. The growth of single crystalline GaN on Si(001) was more difficult, due to the fourfold symmetry of that Si surface; leading to 2 differently aligned domains. It was shown that breaking the symmetry to achieve monocrystalline growth could be done using off-oriented substrates to obtain monocrystalline GaN layers. Another, exotic, Si orientation for GaN growth was Si(110). This was shown to be even better suited than Si(111) for the growth of high-quality GaN-on-silicon, with a nearly threefold reduction in the full-width at half-maximum of the (1¯1•0)ω-scan. It was found that a twofold surface symmetry was, in principle, suitable for the growth of monocrystalline GaN on Si.

Epitaxy of GaN on Silicon - Impact of Symmetry and Surface Reconstruction. A.Dadgar, F.Schulze, M.Wienecke, A.Gadanecz, J.Bläsing, P.Veit, T.Hempel, A.Diez, J.Christen, A.Krost: New Journal of Physics, 2007, 9, 389