The etching behavior of gallium nitride (GaN), aluminum gallium nitride (AlxGa1−xN), and aluminum nitride (AlN) has been systematically examined in an inductively coupled plasma (ICP) using Cl2 and Ar as the reagents. Etch rates were strongly influenced by ICP power and dc bias, while relatively insensitive to pressure, flow rate, and gas composition. Maximum etch rates of 9800 Å/min for GaN, 9060 Å/min for Al0.28Ga0.72N, and 7490 Å/min for AlN were attained. The etch profiles were highly anisotropic over the range of conditions studied. The dc bias had to exceed certain voltages before significant etch rates were obtained. These values were <−20 V for GaN, −40 V for Al0.28Ga0.72N, and >−50 V for AlN. As such, increasing selectivity for GaN over Al0.28Ga0.72N and AlN was achieved at dc biases below −40 V. At −20 V, the GaN etch rates were 38 times greater than AlN and a factor of 10 greater than Al0.28Ga0.72N. These results demonstrate the importance of ion bombardment in the etching of these materials. © 1997 American Institute of Physics.