GaN and Al0.25Ga0.75N lateral Schottky rectifiers were fabricated either with (GaN) or without (AlGaN) edge termination. The reverse breakdown voltage VB (3.1 kV for GaN with both p+ guard rings and metal overlap edge terminations; 4.3 kV for Al0.25Ga0.75N without edge termination) displayed a negative temperature coefficient of −6.0 ± 0.4 V·K−1 for both types of rectifiers. The reverse current originated from contact periphery leakage at moderate bias, while the forward turn-on voltage at a current density of 100A·Cm−2 was ∼5 V for GaN and ∼7.5 V for AlGaN. The on-state resistances, RON, were 0.13 Δcm2 for GaN and 2.3 Δcm2 for AlGaN, producing figures-or-merit (VRB)2/RON of 73.9 and 8.2 MW.Cm−2, respectively. The activation energy of the reverse leakage was 0.13 eV at moderate bias.