We have demonstrated an ex situ method of cleaning reactor parts of metal organic chemical vapor deposition (MOCVD) equipment for nitride semiconductors. The etching rate of GaN by Cl-2 gas was sufficiently high compared with that of BCl3 gas and HCl gas. The etching rates of GaN and Al0.1Ga0.9N with 5% Cl-2 at 750 degrees C were higher than 30 and 2 mu m/h, respectively. We confirmed that there was no contamination of Fe, Ni, Cr and Cl in the GaN film by Cl-2 gas dry cleaning. (c) 2006 Elsevier B.V. All rights reserved.