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Lightly doped n-GaN samples were etched with reactive ion etching (RIE) in BCl3/Cl2/Ar and BCl3/Cl2/N2 plasmas. Replacing the argon by nitrogen in the plasma chemistry resulted in better etch rates, and in addition reduced etch damage for relatively low values of the plasma power. By treating the samples in a nitrogen plasma following etching, we dramatically reduced surface damage, as determined from Schottky IV characteristics measurements. Specifically, the reverse breakdown voltages returned to 70% to that measured from control diode samples. Further, x-ray photoelectron spectroscopy analysis showed that the post-etch nitrogen step decreased the Ga/N ratio. These results suggest that much of the damage induced by RIE plasma etching comes from a nitrogen loss mechanism.

GaN films with reactive ion etching (RIE) induced damage were analyzed using photoluminescence (PL). We observed band-edge as well as donor-acceptor peaks with associated phonon replicas, all in agreement with previous studies. While both the control and damaged samples have their band-edge peak location change with temperature following the Varshni formula, its intensity however decreases with damage while the D-A peak increases considerably. Nitrogen post-etch plasma was shown to improve the band edge peak and decrease the D-A peak. This suggests that the N 2 plasma has helped reduce the number of trapped carriers that were participating in the D-A transition and made the D ı X transition more active, which reaffirms the N 2 post-etch plasma treatment as a good technique to heal the GaN surface, most likely by filling the nitrogen vacancies previously created by etch damage.

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