It was reported that very low threading dislocation densities (8 x 107/cm2) were achieved in uniform GaN layers grown by metalorganic chemical vapor deposition onto (00▪1) 4H-SiC mesa surfaces, 50µm x 50µm in area, that were completely free from steps. Transmission electron microscopy indicated that all of the observable GaN film threading dislocations were of edge type. Transmission electron microscopic analysis of the defect structure of the nucleation layer (AlN) revealed a lack of c-component dislocations, and the clean annihilation of lateral a-type dislocations within the first 200nm of growth, with no lateral dislocations developing threading arms. These results indicated that the elimination of steps on the initial (00▪1) 4H-SiC growth surface could play an important role in the removal of mixed and c-type dislocations in subsequently grown AlN and GaN hetero-epitaxial layers.

Lowered Dislocation Densities in Uniform GaN Layers Grown on Step-Free (0001) 4H-SiC Mesa Surfaces. N.D.Bassim, M.E.Twigg, C.R.Eddy, J.C.Culbertson, M.A.Mastro, R.L.Henry, R.T.Holm, P.G.Neudeck, A.J.Trunek, J.A.Powell: Applied Physics Letters, 2005, 86[2], 021902 (3pp)