There have been several attempts to describe the electrical characteristic of metal - SiC Barriers using a range of theoretical approaches. These generally rely on approximations to the Quantum Mechanical (QM) transport model for the barrier and are best suited to a restricted set of bias and temperature conditions. In this work a full QM model is used to derive the current-voltage characteristics for a metal-SiC barrier. The probability for carriers to traverse the potential barrier is calculated numerically using a transfer matrix method. This probability is related to the current density and enables the numerical calculation of the current density through the Schottky Barrier Diode (SBD). The paper utilises a single set of parameters (barrier height and effective Richardson constant) determined from the forward characteristics of the diodes which are subsequently utilised in the modelling of both forward and reverse characteristics. The currents calculated using the QM theory are compared with results obtained utilising other approximate theories (which are using the same set of parameters as QM, in both forward and reverse) to show that only QM provides a good fit for both forward and reverse bias over a wide range of temperatures and voltages using a single set of parameters.