The influence of plasma etching on the electrical properties ofn‐type gallium nitride (GaN) thin films has been investigated. Electron‐cyclotron‐resonance microwave plasma reactive ion etching in CH4/H2/Ar, in CH4/H2, and in H2results in an increase in the GaN layer’s sheet carrier concentration and a decrease in the effective Hall mobility. Neither wet chemical etching nor etching in Cl2or BCl3plasmas introduces similar changes. Therefore, the observed damage is considered to be related to the CH4/H2/Ar plasma chemistry. In particular, it suggests hydrogen influence on the defect generation. Subsequent annealing of the affected GaN layers at 800 °C removes the plasma damage.