Gallium antimonide (GaSb) has been widely used for optoelectronic devices in recent years, but the current transport mechanism at the metal-GaSb junction has not yet been clearly identified. In this work, current-voltage (I-V) characteristics of Au/n-GaSb Schottky diodes were analyzed over a wide temperature range (80-340 K) to investigate their current transport mechanisms. Based on the theory that the total current is described as a contribution of several current mechanisms, the measured I-V curves were separated into two components: thermionic emission (TE) current and secondary current. For the TE current, which is the primary current for general Schottky diodes, Schottky diode parameters were extracted and the inhomogeneity of the Schottky barrier was quantified using the temperature dependence of the parameters. For the secondary current, a temperature-dependent predominance between tunneling and Shockley-Read-Hall (SRH) recombination currents was identified by comparing a coefficient of the secondary current with the tunneling coefficient and 2kT. We also revealed that other current transport mechanisms such as Auger and radiative recombination, and leakage currents are negligible for the Au/n-GaSb Schottky diodes in this work. The methodology suggested in this study can be applied for detailed characterization of various Schottky diodes of which the current transport mechanisms are unidentified.