InGaN/GaN Schottky Diodes With Enhanced Voltage Handling Capability for Varactor Applications

In this letter, we demonstrate a design of GaN-based Schottky diodes for microwave varactor applications. Using suitable InGaN surface layer structures, the Schottky diodes exhibit an enhanced high-voltage handling capability. The breakdown voltage is increased by ~40 V, and the reverse leakage current is significantly suppressed under high reverse voltages. The breakdown-voltage enhancement and leakage-current suppression are attributed to a reduction in the surface electric field and an increase in the electron tunneling distance due to polarization-induced charges at the InGaN/GaN interface.