A comparative study was made of wurtzite GaN epilayers prepared by metalorganic chemical vapour deposition on 4H-SiC substrates with orientations vicinal to the (00•1) (misorientation of 0, 3.4 and 8°). Structural analysis using X-ray diffraction, defect-selective etching methods, and (high-resolution-) transmission electron microscopy provided direct evidence for a higher number of defects in GaN epilayers grown on the 8° misoriented substrate compared to the 3.4° and 0° misoriented substrates. Strong differences in morphology were found in the GaN epilayers and in the type and density of the defects formed during growth on both vicinal and nominally exact oriented SiC substrates. The formation of clusters of defects and the non-uniform distribution of strain, resulting in preferential cracking of the GaN films along the [11•0] direction, were both results of growth on misoriented substrates. Based on experimental results, the growth mechanism was analyzed and a model which explained the defect formation was proposed.

Defect Formation in GaN Grown on Vicinal 4H-SiC (0001) Substrates. M.Rudziński, E.Jezierska, J.L.Weyher, L.Macht, P.R.Hageman, J.Borysiuk, T.C.Rödle, H.F.F.Jos, P.K.Larsen: Physica Status Solidi A, 2008, 204[12], 4230-40