A study on Au/n-GaAs Schottky barrier diode (SBD) parameters with and without thin native oxide layer fabricated on n-type GaAs has been made. The native oxide layer with different thicknesses on chemically cleaned GaAs surface was obtained by exposing the GaAs surfaces to clean room air before metal evaporation. The native oxide thicknesses of samples AuD2, AuD3, AuD4, AuD5, and AuD6 are in the form AuD2