The temperature dependence of reverse breakdown voltage (V-RB) and forward turn-on voltage (V-F) of GaN Schottky diode rectifiers is reported. The VRB values display a negative temperature coefficient (-0.92 V K-1 for 25-50 degrees C; -0.17 V K-1 for 50-150 degrees C), indicative of surface- or defect-assisted breakdown. The Vl;values decrease with increasing temperature. The room temperature breakdown voltage is approximately a factor of three lower than the theoretical maximum expected based on avalanche breakdown, and the current performance of GaN rectifiers is comparable to that of Si at the same on-resistance.