GaN Schottky rectifiers have been fabricated on free-standing substrates and on epi/substrate structures. Forward turn-on voltages were as low as 3 V at 25°C. Reverse recovery was complete in <600 ns, with a characteristic time constant of ∼163 ns. The temperature coefficient for reverse breakdown voltage (VB) was -2.5 ± 0.6 V K-1 which is much lower than for lateral rectifiers reported previously, where values up to -30 V K-1 were achieved. Reverse currents increased with rectifying contact diameter and VB decreased with increasing contact size. The best on-state resistance was 20.5 mΩcm-2 for diodes with VB = 450 V, producing a figure-of-merit (VB)2/RON of ∼10 MW cm-2.