Capacitance-voltage and capacitance-frequency characteristics of the metal/n-GaN/metal Schottky contacts with Au, Al and Ag electrodes were investigated as a function of the temperature and external electric field in the frequency range from 100 to 300 kHz. Forward capacitance-voltage measurements were carried out in the frequency range from 100 Hz to 20 MHz. The temperature capacitance coefficient and the electrical tunability were measured as a function of the external DC held for all contacts. The capacitance and dielectric loss measurements show relaxation peaks from 4 to 11 kHz for some electrodes, indicating that interfacial effects play an important role in the electrical properties of the GaN Schottky barrier contact. Low-frequency relaxation Studies were conveniently used to probe interfacial characteristics of the contacts. (c) 2008 Elsevier B.V. All rights reserved.