The defects induced by inductively coupled plasma reactive ion etching (ICP-RIE) on a Si-doped gallium nitride (GaN:Si) surface have been analyzed. According to the capacitance analysis, the interfacial states density after the ICP-etching process may be higher than 5.4 x 10(12) eV(-1) cm(-2), compared to around 1.5 x 10(11) eV(-1) cm(-2) of non-ICP-treated samples. After the ICP-etching process, three kinds of interfacial states density are observed and characterized at different annealing parameters. After the annealing process, the ICP-induced defects could be reduced more than one order of magnitude in both N-2 and H-2 ambient. The H-2 ambient shows a better behavior in removing ICP-induced defects at a temperature around 500 degrees C, and the interfacial states density around 2.2 x 10(11) eV(-1) cm(-2) can be achieved. At a temperature higher than 600 degrees C, the N-2 ambient provides a much more stable interfacial states behavior than the H-2 ambient. (c) 2006 Elsevier Ltd. All rights reserved.