In this paper, a further leakage reduction of AlGaN/GaN Schottky barrier diodes with gated edge termination (GET-SBDs) has been achieved by optimizing the physical vapor deposited TiN as the anode metal without severe degradation of <sc>on</sc>-state characteristics. The optimized GET-SBD multifinger power diodes with 10 mm anode width deliver $\sim 4$ A at 2 V and show a median leakage of 1.3 $\mu \text{A}$ at 25 °C and 3.8 $\mu \text{A}$ at 150 °C measured at a reverse voltage of −200 V. The temperature-dependent leakage of Si, SiC, and our GaN power diodes has been compared. The breakdown voltage (BV) of GET-SBDs was evaluated by the variation of anode-to-cathode spacing ( $L_{\mathrm{ AC}}$ ) and the length of field plate. We observed a saturated BV of $\sim 600$ V for the GET-SBDs with $L_{\mathrm{ AC}}$ larger than 5 $\mu \text{m}$ . The GET-SBD breakdown mechanism is shown to be determined by the parasitic vertical leakage current through the 2.8 $\mu \text{m}$ -thick buffer layers measured with a grounding substrate. Furthermore, we show that the forward voltage of GET-SBDs can be improved by shrinking the lateral dimension of the edge termination due to reduced series resistance. The leakage current shows no dependence on the layout dimension $L_{G}$ (from 2 to 0.75 $\mu \text{m}$ ) and remains at a value of $\sim 10$ nA/mm. The optimized Au-free GET-SBD with low leakage current and improved forward voltage competes with high-performance lateral AlGaN/GaN SBDs reported in the literature.