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The critical properties of power devices are high reverse breakdown voltage and low forward ON state resistance, Ron,sp, during high forward current density operation. Both of these parameters are very sensitive to temperature. Nowadays silicon carbide (SiC) and GaAs are two most important materials for power device applications. SiC has been widely accepted as being superior to GaAs because it has much higher electric breakdown field, saturated electron drift velocity and thermal conductivity. In this work, the electrical performance and reliability of SiC Schottky diodes (SD) are evaluated and compared to commercially available GaAs SDs. High temperature device characterization has been performed. The specific ON resistance Ron,sp was found to increase with temperature according to T0.72 dependence for GaAs and T1.89 for SiC. The strong temperature dependence of Ron,sp is consistent with phonon scattering theory. Based on Baliga's figure-of-merit (BFOM) model, our result shows that under higher operating temperature (> 210 °C) the GaAs devices have lower Ron,sp than SiC, thus, it may be preferable to use GaAs over SiC for some high temperature power applications.