Monocrystalline GaN/AlN layers were grown onto (111)Si substrates and used as seeding layer for selective lateral overgrowth on a patterned Si3N4 mask. Pyramids of GaN formed during the lateral overgrowth. They were epitactically oriented with respect to the Si substrate, with the orientation relationship: [11•0]GaN||[¯110]Si and (00•1)GaN||(l11)Si. The pyramids were characterized by means of transmission electron microscopy, and were found to have a reduced defect density, as compared with continuous layers of GaN on Si. They contained very few defects in the upper region. The threading dislocations that originated from the GaN/AlN seeding layer eventually bent through 90º, and emerged at the inclined surface. Many of the threading dislocations were actually half-loops which were self-terminating.

Single-Crystal GaN Pyramids Grown on (111)Si Substrates by Selective Lateral Overgrowth. W.Yang, S.A.McPherson, Z.Mao, S.McKernan, C.B.Carter: Journal of Crystal Growth, 1999, 204[3], 270-4