Chemical Mechanical Polishing of GaN

Chemical mechanical polishing of (0001) GaN has been demonstrated with sodium-hypochlorite-based solutions. Slurries including alumina abrasive provide an efficient means of planarization for both the Ga- and N-face that does not induce significant crystalline damage. Removal rates were found to be ∼ 50 nm/min and were equivalent for both polarities. Additionally, a fine polishing method was developed that includes abrasive-free solutions of either sodium hypochlorite for the N-face or a mixture of sodium hypochlorite and citric acid for the Ga-face. With this fine polishing step, scratch-free surfaces were achieved with a root-mean-square roughness of 0.5-0.6 nm.