Monodisperse GaN nanowires prepared by metal-assisted chemical etching with in situ catalyst deposition

Metal-assisted chemical etching (MacEtch) is a top-down liquid semiconductor processing technology applied here to realize highly monodisperse collections of GaN nanowires. Subjecting n-type GaN wafers to AgNO3/HF simultaneously deposits Ag nanoparticle catalysts and initiates the MacEtch process. By varying the solution composition, concentration and etch time under UV illumination, different GaN nanostructures are produced. GaN nanowires form initially on a supporting framework of porous GaN, which can be removed upon prolonged etching, leaving cones of monodisperse nanowires. These results suggest a mechanism in which areas surrounding Ag particles etch faster than areas directly underneath the catalyst and the formation of a localized galvanic cell and associated exothermic production of soluble GaF2(OH).

► Metal-assisted chemical etching is a top-down approach to nanowire production.
► AgNO3/HF simultaneously deposits Ag catalysts and initiates the MacEtch.
► Monodisperse nanowires form initially on a supporting framework of porous GaN.
► Etching is fast directly under the metallic catalyst particles and slow to the side.