The effects of added H-2, Ar, and CH4 gases on the etch characteristics of GaN and InGaN were studied using an inductively coupled Cl-2-based plasma. Each added gas had a unique effect on the etch rate, anisotropy, surface roughness, and sidewall morphology. The most anisotropic etch profile was obtained using Cl-2, but the etched surface showed the roughest morphology and was covered with etch residues. the origins of which were the micromasking of the sputtered dielectric. When H-2 gas was added to the Cl-2 plasma, the etch residues were removed and the surface roughness was decreased, even though the etch rate was slightly decreased. The etch rate of GaN by Cl-2/H-2/Ar plasmas was saturated above an Ar flow rate of 16 seem and the surface roughness of the etched GaN was lower; compared with Cl-2/H-2, plasmas at low source power Finally, it was found that the In compound was etched as a result of reaction with CH4.