Capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements of the Au/n-GaAs Schottky barrier diodes (SBDs) in the wide frequency range of 10 kHz-10 MHz at room temperature were carried out in order to evaluate the reason of negative capacitance (NC). Experimental results show that C and G/omega are strong functions of frequency and bias voltage especially in the accumulation region. NC behavior was observed in the C-V plot for each frequency and the magnitude of absolute value of C increases with decreasing frequency in the forward bias region. Contrary to C, G/omega increases with decreasing frequency positively in this region. NC behavior may be explained by considering the loss of interface charges at occupied states below Fermi level due to impact ionization processes. Such behavior of the C and G/omega values can also be attributed to the increase in the polarization especially at low frequencies and the introduction of more carriers in the structure. The values of R-s decrease exponentially with increasing frequency according to literature. In addition, the values of C and G/omega at 1 MHz were corrected to obtain the real diode capacitance by taking the effect of R-s into account. (C) 2013 Elsevier B.V. All rights reserved.