The effects of nitrogen plasma on reactive-ion etching induced damage in GaN

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.