Investigation on chemical mechanical polishing of Ga-faced GaN crystal with weak alkaline slurry

A remarkable improvement in the chemical–mechanical polishing (CMP) of GaN using a weakly alkaline ZrO2–SiO2 based slurry is described in detail, and an almost complete atomic step-platform structure with a surface roughness (Ra) of 0.059 nm is obtained. ZrO2 nanoparticles were added to the CMP slurry to replace part of the SiO2 to obtain a higher removal rate. When the content of ZrO2 reaches 0.5 wt%, the material removal rate of GaN is increased by 47.5 % compared with that of SiO2 with equal content, which significantly improves the material removal rate (MRR) of GaN, and does not destroy the atomic ladder-platform structure. In addition, we also investigate the causes of the formation of atomic ladder-terrace morphology on Ga-face, and describe the removal mechanism of materials in CMP process.