Control of GaN inverted pyramids growth on c-plane patterned sapphire substrates

Growth of gallium nitride (GaN) inverted pyramids on c-plane sapphire substrates is benefit for fabricating novel devices as it forms the semipolar facets. In this work, GaN inverted pyramids are directly grown on c-plane patterned sapphire substrates (PSS) by metal organic vapor phase epitaxy (MOVPE). The influences of growth conditions on the surface morphology are experimentally studied and explained by Wulff constructions. The competition of growth rate among {0001}, { }, and { } facets results in the various surface morphologies of GaN. A higher growth temperature of 985 °C and a lower Ⅴ/Ⅲ ratio of 25 can expand the area of { } facets in GaN inverted pyramids. On the other hand, GaN inverted pyramids with almost pure { } facets are obtained by using a lower growth temperature of 930 °C, a higher Ⅴ/Ⅲ ratio of 100, and PSS with pattern arrangement perpendicular to the substrate primary flat.