Morphologies and plane indices of pyramid patterns on wet-etched patterned sapphire substrate

• This paper analyses the evolution of pyramids on the patterned sapphire substrate (PSS) during wet etching process.
• The morphologies and indices of 18 pyramid facets were investigated.
• When the SiO2 mask remained, pyramid covered with six facets.
• When the SiO2 was etched away, three facets were exposed on the top of pyramid.
• When etching increased, another six facets and three facets appeared.

A wet etching process was employed to investigate the evolution of pyramids on the patterned sapphire substrate (PSS). It has been found that the PSS comprised a hexagonal pyramid covered with six facets {34¯17} when disk-shaped SiO2 mask still remained. Three facets {11¯05} were exposed when mask was etched away. In this study, a continuous etching process was performed. It was found that another six facets {45¯130} and another three facets {11¯010} appeared on the bottom and the top of pyramid. Finally, when the etching time reached around 5 min, most of pyramids on the PSS disappeared.