In this work, a GaN-on-Si quasi-vertical Schottky diode was demonstrated by growing locally the n-GaN drift layer. The diode achieves a high current density of 2.5 kA/cm², a specific on-resistance RON,sp of 1.9 mΩ.cm² despite the crowding effect in quasi-vertical device and on/off current ratio (Ion/Ioff) of 1010. Temperature-dependent cur-rent-voltage characteristics have been measured in the range of 300-433 K to investigate the mechanisms of leakage conduction. At near zero bias, thermionic emission was found to dominate. At voltage range from -1 to -10 V, electrons gain enough energy to excite into trap states, leading to the dominance of Frenkel-Poole emission (FPE). For a relatively higher voltage range (-10V to -40V), the increased electric field promotes electrons hop-ping along the threading dislocations in the “bulk” GaN layers, and thus, Variable Range Hopping becomes the main mechanism for the whole temperature range. This work pro-vides an in-depth insight into the leakage conduction mechanism on vertical GaN-on-Si SBDs grown by localised epitaxy, and also provides a useful design guide for the edge termination of vertical power devices.