Cobalt Anode Quasi-Vertical GaN Schottky Barrier Diodes With Low Turn-On Voltage and Leakage Current Density

Gallium nitride (GaN)-based Schottky barrier diodes (SBDs) are promising candidates for replacing silicon devices in high-frequency and high-temperature applications. The performance of the metal/GaN Schottky contacts is critical to SBDs. In this study, we demonstrate a high-performance quasi-vertical GaN SBD with a cobalt (Co) anode fabricated on state-of-the-art crystal quality GaN films grown on the patterned sapphire substrates. The Co-SBD exhibits near-ideal thermionic emission (TE) transport, with an ideality factor of 1.04 and a Schottky barrier height (SBH) value of 0.74 eV. Key performance metrics of the device include low turn-on voltage (V_on) of 0.48 V, low-specific differential on-resistance R_on,sp of 1.3mΩ · cm², high operating current of 0.96 A at 2.0 V, and high breakdown voltage (V_BR) of 245 V. Temperature-dependent current–voltage (I-V) measurements reveal minimal variation in SBH and ideality factor, indicating excellent thermal stability. The comprehensive analysis of leakage mechanisms confirms that thermionic field emission (TFE) dominates at low biases and variable-range hopping (VRH) conduction at high biases. These results demonstrate Co as a promising anode material for achieving low turn-on voltage and low leakage current density in quasi-vertical GaN SBDs.