The etch characteristics of GaN were investigated using chemically assisted ion beam etching (CAIBE) for Cl-2 as a function of tilt angle. With increasing tilt angle the measured GaN etch rate showed a maximum at 30 degrees similar to the effect of tilt angle on the sputter yield. The etch profiles of GaN etched by tilting the substrate less than 20 degrees showed sidewall trenching. When the tilt angle was more than 30 degrees, an etch tail was observed at the bottom of the etched structure. With the Cl-2 CAIBE, the anisotropy of the GaN etch profile was enhanced as the tilt angle was increased, and a vertical etch profile could be obtained at a 50 degrees tilt angle. The sidewall roughness of the etched GaN laser device varied with the Cl-2 flow rate and ion beam voltage. A highly anisotropic etch profile with a smooth sidewall could be obtained by optimization of the ion beam voltage/current and Cl-2 flow rate. The surface of GaN etched by the Cl-2 CAIBE system showed a Ga-deficient surface due to the removal of Ga by the formation of GaClx.