Evolution of V-pits in the ammonothermal growth of GaN on HVPE-GaN seeds

Abstract

The Am-GaN growth on HVPE-GaN with pit-type defects is investigated. The back etching, ammonothermal regrowth and annihilation processes of the pit-type defects are elucidated by surface morphology and cross section observation. In the annihilation process, the {11−20} planes grow toward the inside of the filled region. And the {11−22} planes are considered growing obliquely upward of the V-pit until the V-pit gets completely filled. Finally, it grows again along the c-planes to form uniform Am-GaN. To study the variation of TDD in different growth regions, the as-grown Am-GaN was etched in a molten NaOH–KOH etchant. The EPD in the laterally grown material is one order of magnitude lower than that grown in the vertical direction.