Single-crystal GaN pyramids grown on (111)Si substrates by selective lateral overgrowth

Single-crystalline GaN/AlN layers have been grown on (1 1 1)Si substrates a nd subsequently used as the seeding layer for selective lateral overgrowth on a patterned Si3N4 mask. GaN pyramids are formed during the lateral overg rowth. They are epitactically oriented with respect to the Si substrate wit h the orientation relationships [1 1 (2) over bar 0](GaN)parallel to[(1) ov er bar 1 0](Si) and (0 0 0 1)(GaN)parallel to(1 1 1)(Si). The pyramids were characterized by transmission electron microscopy and were found to have a reduced defect density compared with continuous layers of GaN on Si and ve ry few defects in the upper portion. The threading dislocations that origin ated from the GaN/AlN seeding layer eventually bend through 90 degrees and emerge at the inclined surface. Many of the threading dislocations are actu ally half-loops which are self-terminating. The results of this study demon strate that GaN selective lateral overgrowth can be performed on Si substra tes and show that the same GaN crystalline quality can be produced on Si as on sapphire and SiC substrates. (C) 1999 Elsevier Science B.V. All rights reserved.