We report the damageless surface morphology of gallium nitride (GaN) films during argon and nitrogen plasma etching at elevated temperatures up to 600 °C. For Ar plasma bombardment at high substrate temperatures of around 600 °C, Ar+ ion bombardment dissociates Ga–N bonds by the preferential removal of nitrogen, which promotes roughness of the GaN surface by the aggregation of gallium atoms. For the N2 plasma one, the N/Ga remains stoichiometric with higher values above 0.69, and the surface is not significantly roughened, even at 600 °C. Therefore, the aggregation of metallic Ga induces surface roughening during ion-enhanced etching of GaN at elevated substrate temperatures.

The effect of in-situ exposure of n-GaN damaged by Cl2 plasma to atomic hydrogen (H radicals) at room temperature was investigated. We found that the PL intensities of the band-edge emission, which had been drastically reduced by plasma-beam irradiation at a Cl ion dose of 5 × 1016 cm−2, recovered to values close to those of as-grown samples after H radical exposure at a dose of 3.8 × 1017 cm−2. XPS revealed the appearance of a peak at a binding energy of 18.3 eV, which is tentatively assigned to Ga-H, and confirmed the removal of Cl after H radical exposure

In the recovery of photoluminescence intensities for band-edge emissions at around 3.47 eV in the case of gallium nitride (GaN), we have studied the individual roles of hydrogen atoms (H) and hydrogen ions (H n +). Surface defects such as nitrogen vacancies created by plasma etching were passivated by H termination. By utilizing hydrogen plasmas, we clarified the recovery efficiency by optical and stoichiometrical improvements with respect to the balance between the fluxes of H and H n +. By deflecting H n + by applying an electric field, the efficiency was improved using an identical H dosage, since the simultaneous irradiation of the energetic H n + promoted the desorption of the formed passivated Ga–H bonds.

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