Near-vertical plasma-free HCl gas etching on (011) β-Ga2O3

Abstract We investigated non-plasma HCl-gas etching properties on (011) β -Ga 2 O 3 , which is an attracting surface orientation allowing pit-free homoepitaxy. The etching occurred selectively in window regions of a patterned SiO 2 mask, and resulting side-etched structures were dependent on the in-plane directions of the window edges. Particularly, the side etching markedly reduced when the windows aligned with the 01 1 ¯ direction due to the formation of (100)-faceted sidewalls. Although the (100) sidewalls were slightly tilted from the surface normal by 6.5°, their surfaces were flat and free of plasma damage. Therefore, the crystallographic etching could be a promising microfabrication process on (011) β -Ga 2 O 3 .