Tribochemical polishing of bulk gallium nitride substrate

Abstract

In this study, the tribochemical polishing of a bulk GaN substrate, prepared by hydride vapor phase epitaxy, was investigated. Two different types of silica plates, a quartz glass plate and a soda-lime glass plate, were used as a polishing plate to polish the GaN substrate under atmospheric conditions at room temperature. Before and after polishing, the surface morphology was measured and evaluated by scanning white light interferometry and atomic force microscopy. The wear debris and wear track produced by polishing were analyzed in detail. The obtained results showed that an oxide layer was formed on the GaN surface because of the chemical reaction between the surfaces of the glass plate and the GaN substrate. This generated oxide layer was efficiently removed by polishing with the soda-lime glass plate, resulting in an atomic step and terrace structures on the GaN surface. Moreover, the obtained experimental results indicate that the soda-lime glass plate's alkali material components and the temperature increase induced by the frictional heat play important roles in the removal of the tribochemically generated layer on the GaN surface.