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• Electrochemical etching-enhanced CMP is proposed for efficient polishing of GaN. • Identical-site observation was conducted to study the etching behaviors of GaN. • A maximum etching rate of 1.462 μm/min has been achieved. • Sa roughness of a dia-lapped GaN surface has been reduced from 69.8 nm to 0.64 nm. An electrochemical etching-enhanced CMP process was proposed to realize the highly efficient and damage-free finishing of GaN. In this process, electrochemical etching was first used to remove the damaged layer induced by grinding or lapping, and CMP was then conducted to flatten the etched surface. The etching rate could reach 1.46 μm/min using NaOH solution as the electrolyte which was highly efficient. It was found that the etching rate and surface roughness can be balanced by adjusting the applied potential. CMP was carried out on an etched GaN sample and the surface roughness was reduced from 69.8 nm to 0.64 nm, and its surface quality was also confirmed to be desirable through photoluminescence. These results demonstrate that the proposed electrochemical etching-enhanced CMP process is highly effective and efficient to obtain a crack-free, damage-free and smooth GaN surface. [ABSTRACT FROM AUTHOR]