To fabricate GaN-based optoelectronic devices successfully, a reproducible etch process with high etch rates, vertical etch profile, and damage-free surface is required. In this study, GaN etching was performed using planar inductively coupled plasmas and the effects of process parameters such as inductive power, bias voltage, pressures and, gas combination on the characteristics of the plasmas were studied using Langmuir probe, optical emission spectroscope (OES), and quadrupole mass spectrometer (QMS). Gas combinations of Cl2/Ar and Cl2/HBr were used to etch GaN. GaN etch rates increased with the increase of chlorine radical and ion energy (bias voltage), and the etch rates close to 4000 Å/min could be obtained without substrate heating over 100 °C. The addition of HBr and Ar (more than 20%) generally reduced GaN etch rates. In our experimental condition, it appears that the chemical reaction between Cl and Ga in GaN affects more significantly to GaN etching compared to physical sputtering, and it was partially confirmed by the data measured by Langmuir probe and OES. Angle resolved XP S data showed the variation of surface Ga/N ratio depending on the process parameters, which influence the formation of low resistance ohmic contact.