The influence of CH4/H2/Ar plasma etching on the conductivity of n-type gallium nitride

The influence of plasma etching on the electrical properties of n-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 H2 results 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 Cl2 or BCl3 plasmas 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.