Damage characteristics of n-GaN thin film surfaces etched by N2 plasmas



Damage characteristics of n-GaN surfaces etched by capacitively-coupled radio frequency N2 plasma, generated with a high applied voltage of 400 V, was studied in terms of synergistic effect between ion bombardment and ultraviolet (UV) light irradiation. The result was compared with that obtained with a low applied voltage of 200 V. Morphology of the surface etched at a low gas pressure of 10 mTorr is similar to that of the as-grown surface even with increasing etching time, whereas N/Ga ratio at the surface decreases. The result can be explained in terms of the physical etching, though the surface is irradiated with the UV light emitted from the plasma. The result obtained at the low gas pressure is independent of the applied voltage. In contrast, the characteristic at the surface etched at a high gas pressure of 50-100 mTorr depends on the applied voltage. A morphological change in the surface etched with the high applied voltage occurs, whereas the N/Ga ratio increases The increase in the N/Ga ratio is not reproduced by the simulation, which implies the contribution of the UV light irradiation. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)