A study on gold/n-type Gallium arsenide (Au/n-GaAs) Schottky barrier diode (SBD) parameters with and without thin native oxide layer fabricated on n-type GaAs was made. The native oxide layer for metal/oxide/semiconductor (MIS) SBD was obtained by exposing the chemically cleaned GaAs surface to clean room air for 30 days, before metal evaporation. The values of 1.089 and 0.730 eV for the ideality factor and barrier height of the reference Au/n-GaAs SBD were obtained, respectively, and the values of 1.427 and 0.671 eV for the MIS and SBD, respectively We calculated the density distribution and time constant of the interface states from the capacitance-frequency measurements using the Schottky capacitance spectroscopy method. The interface state density N-ss of the diodes has an exponential rise with bias from the rnidgap towards the top of the conduction band; for example, from 1.20 X 10(10) cm(-2) eV(-1) in (E-c-0.730) eV to 3.41 X 10(12) cm(-2) eV(-1) in (E-c-0.470) eV for reference diode, and from 1.47 X 10(10) cm(-2) eV(-1) in (E-c-0.671) eV to 1.68 X 10(13) cm(-2) eV(-1) in (E-c-0.411) eV for the MIS diode. (C) 2002 Elsevier Science B.V. All rights reserved.