Wafer-scale vertical GaN nanorod arrays with nonpolar facets using TMAH wet etching

Abstract

Highly aligned gallium nitride (GaN) nanorod arrays on a 2-inch wafer have been demonstrated through a combination of dry and chemical etching by employing nanoimprint lithography. Vertical hexagonal GaN nanorods, consisting of m- and a-planes with nonpolar surfaces, were obtained, and their diameter was precisely controlled by chemical etching using tetramethylammonium hydroxide (TMAH). Based on the temperature-dependent chemical etching behaviors, the activation energies for the chemical reaction of TMAH with the a- and m-planes were estimated to be 0.841 eV and 1.155 eV, respectively. With an increase in etching time or temperature, the nonpolar facets (1 0 1¯0) of GaN nanorods with smooth surfaces became more dominant, and surface defects resulting from ion bombardment during the reactive ion etching process were effectively eliminated. This facile process of creating nanostructures could be beneficial in controlling the shape of semiconductor nanostructures for advancing electronic and optoelectronic devices.