Formation of GaN mesas with reverse-tapered edge structures on a lattice-matched AlInN layer for a positive beveled edge termination

GaN mesas were fabricated by sequential dry and wet etching of a +c-oriented GaN layer onto a lattice-matched AlInN layer for future applications of positive beveled edge termination, which is desirable for preventing premature breakdown of power devices. The dry etching produced hexagonal AlInN/GaN mesas surrounded by m-plane sidewalls with six protrusions at the vertices. The subsequent hot phosphoric acid etching selectively etched the AlInN layer to expose and etch the chemically unstable −c surface of the GaN layer, which formed reverse-tapered { 101¯2¯ } facets. The protrusions were sacrificed during the wet etching to prevent undesirable positive tapering at the vertices.