The electronic and interface state density distribution properties obtained from current voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/p-type GaAs Schottky barrier diode (SBD) at room temperature was investigated. The (I-V)-T characteristics are analysed on the basis of thermionic emission (TE). The forward bias I-V of SBDs have been studied at room temperature. SBD parameters such as ideality factor n, series resistance (Rs) determined by Cheung's functions and Schottky barrier height, Phi(bo), are investigated as functions of temperature. The diode parameters such as ideality factor, series resistance and barrier heights were found as 1.76-2.16 and 2.2-1.8 Omega and 0.53-0.72 eV, respectively. The diode shows non-ideal I-V behaviour with an ideality factor greater than unity. Furthermore, the energy distribution of interface state density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The results show the presence of thin interfacial layer between the metal and semiconductor.