Chemical etching behavior of non-polar GaN sidewalls

Abstract Wet-chemical etching of non-polar GaN films can be applied to form textured surfaces that enhance light extraction efficiency in light-emitting diodes. The etch-induced shapes (trigonal prisms) on the sidewalls of concave and convex mesa patterns defined on a -plane GaN films exhibited an alignment towards the [ 000 1 ] direction. An etch-rate vector model that includes one fast etching direction and two etching directions normal to the fast direction was developed to explain the creation of the etch-induced trigonal prisms. The large lattice parameter along with [ 000 1 ] and single dangling bond of a -plane surface supply enough space for attack of OH − ions, which is confirmed by XPS analysis that indicates the increased hydroxide spectra on a -plane after KOH etching and these are the reason for different etch rate and formation of trigonal prisms.