Au/n-GaAs contacts were fabricated using n-GaAs wafer with high doping concentration and their electrical characteristics were investigated via admittance measurements at low temperatures (T <= 300 K) at 1MHz. The main electronic parameters such as barrier height, depletion region width, doping concentration, series resistance and Fermi energy were obtained from experimental data. All these parameters showed dependence on temperature since different conduction mechanisms may play role at a certain voltage and temperature range. The forward bias capacitance-voltage curve exhibited an anomalous peak and then capacitance took negative values for each temperature. Such negative capacitance behaviour can be explained by the loss of interface charges located at junction, the existence of surface states, series resistance and a native interlayer. The decrease in series resistance and increase in surface states with increasing temperature were attributed to the decrease in band gap of GaAs and restructuring and reordering of surface charges.