Single-crystal GaN pyramids grown on (1 1 1)Si substrates by selective lateral overgrowth

Single-crystalline GaN/AlN layers have been grown on (1 1 1)Si substrates and subsequently used as the seeding layer for selective lateral overgrowth on a patterned Si3N4 mask. GaN pyramids are formed during the lateral overgrowth. They are epitactically oriented with respect to the Si substrate with the orientation relationships [1 1 2̄ 0]GaN∥[1̄ 1 0]Si and (0 0 0 1)GaN∥(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 very few defects in the upper portion. The threading dislocations that originated from the GaN/AlN seeding layer eventually bend through 90° and emerge at the inclined surface. Many of the threading dislocations are actually half-loops which are self-terminating. The results of this study demonstrate that GaN selective lateral overgrowth can be performed on Si substrates and show that the same GaN crystalline quality can be produced on Si as on sapphire and SiC substrates.