The Formation and the Plane Indices of Etched Facets of Wet Etching Patterned Sapphire Substrate

A two-step chemical wet etching processes were used to investigated the formation and the plane indexes of exposed etched facets of wet etching patterned sapphire substrate (PSS). It was found when SiO 2 mask still remained on the top c -plane, the structure of PSS comprised of a hexagonal pyramid covered with six facets with a flat top c -plane. When SiO 2 mask were etched away, beside six facets on the bottom, there were 3 extra facets exposed on the top.