In this study, the etching characteristics of AlxGa1-xN/GaN superlattices with x = 0.11 and 0.21 of Al and n-GaN with Cl-2/SiCl4/Ar plasma using reactive ion etching (RIE) system were investigated. By varying gas ratio and rf power, it was found that SiCl4 is an effective getter to remove residual oxygen in the chamber and has a strong physical sputtering effect to remove the oxide layer during the etching, and a nearly nonselective smooth etching of AlxGa1-xN/GaN SLs with the high etch rate of 220 nm/min could be obtained. X-ray photoelectron spectroscopy (XPS) and Hall measurements were employed together to reveal the correlation between stoichiometry and electrical changes of n-GaN induced by plasma etching. Combining with N2O plasma post-etch treatments to restore etched surfaces, those results suggested that oxygen not only influences morphology of the All-containing samples, but also electrical properties of n-GaN by changing the status of oxygen-related defects, which may play crucial roles in determining the nature of the damage. (c) 2006 Elsevier B.V. All rights reserved.