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 {3 417} with a flat top c-plane. When SiO 2 mask were etched away, beside six facets on the bottom, there were 3 extra facets {1 105} exposed on the top.

Currently, the wet etching patterned sapphire substrate (PSS) has attracted much attention for its high production yield. After etching in hot mixed H2SO4 and H3PO4 solution, the several etched facets were exposed on sapphire substrate. In this study, a series of etching process was used to investigate the formation. As shown in Fig. 1, when SiO2 mask still remained, the structure of PSS comprised of six facets {3-417}. When SiO2 mask were etched away, beside six facets, there were three extra facets {1-105} exposed on the top.