In this study, HBr-based(Cl-2/HBr, BCl3/HBr, and HCl/HBr) inductively coupled plasmas were used to etch GaN selectively over photoresist and its etch characteristics were investigated. The inductive power and dc bias voltage to the substrate were fixed at 1600 W and -150 V, respectively. Among the gas combinations used in this experiment, BCl3/ HBr showed the highest etch selectivity over photoresist and the etch selectivity of 1.5 with the etch rate of 6400 Angstrom/min could be obtained with 40%, BCl3/60% HBr. Also, the most anisotropic GaN etch profiles could be observed with this gas mixture. The highest etch rate obtained was about 7700 Angstrom/min for pure Cl-2, however, the etch selectivity was lower than 0.6. Optical emission spectroscopy showed that the GaN etch rate and etch selectivity for BCl3/HBr were related to the Cl-2(+) ions. (C) 2002 Elsevier Science Ltd. All rights reserved.