Top-Down Etch Processes for III-Nitride Nanophotonics

Three-dimensional chemical etch processes for III-nitride (AlGaInN) materials and devices remain significantly underdeveloped due to its apparent inertness to common wet etchants. Further knowledge and development of anisotropic and three-dimensional top-down etch techniques are needed to fully realize the potential of the III-nitrides in new electronic and photonic nano and micro device concepts. Here, we explore the etch characteristics of GaN, AlGaN, and AlN using a two-step dry plus wet etch approach, which allows for the exposure of crystal facets with non-zero and differing etch rates. We apply general geometric principles of crystallographic dissolution processes to enable the prediction of facet-determined etch structures, including high aspect ratio nanowires and nanowalls.