  In this letter, we demonstrate a lateral AlGaN/GaN Schottky barrier diode
(SBD) on sapphire substrate with low turn-on voltage (Von) and high breakdown
voltage (VBK). By using a double barrier anode (DBA) structure formed by the
mixture of Platinum (Pt) and Tantalum (Ta), the Von of the SBD can be as low as
0.36 V with a leakage current of 2.5E-6 A/mm. Supported by the high-quality
carbon-doped GaN buffer on sapphire, the VBK can reach more than 10 kV with the
anode-to-cathode spacing of 85 {\mu}m. Combining the VBK and the specific
on-resistance (Ron,sp) of 25.1 m{\Omega}.cm^2, the power figure of merit of the
SBD can reach 4.0 GW/cm^2, demonstrating a great potential for the application
in ultra-high-voltage electronics.
