The etch characteristics of GaN, InN, InAlN, AlN, and InGaN were measured for a new plasma chemistry, IBr/Ar, in an electron cyclotron resonance plasma discharge. The effects of plasma composition (12.5%-100% IBr), microwave (400-1000 W) and rf power (50-250 W) on the etch rates for these materials were examined. The etch rates for GaN depended strongly on plasma composition, while the etch rates were only weakly dependent on microwave power in the range 400-800 W for ail materials. The etch rates for all materials generally increased with increasing rf power, indicating that higher ion energies are much more efficient in enhancing sputter desorption of the etch products. While the etch rates were slower than with either ICl/Ar or Cl-2/Ar, the etched surface of GaN was found to be extremely smooth, with little loss of N from the surface at low rf powers, and no significant residue on the surface.