Fully-Vertical GaN-on-SiC Schottky Barrier Diode: Role of Conductive Buffer Structure

This article reports a low ON-resistance fully-vertical GaN-on-SiC Schottky barrier diode (SBD) featuring a highly conductive buffer structure between the GaN drift layer and SiC substrate. To optimize the buffer structure, which is critical to the fully-vertical GaN-on-SiC SBD, heavily doped Al0.25Ga0.75N buffer layer on top of SiC substrate and graded Al $_{{0.25}\to {0}}$ Ga $_{{0.75}\to {1}}\text{N}$ layer at the GaN/Al0.25Ga0.75N interface are implemented, yielding a reduced specific ON-resistance of 0.96 $\text{m}\Omega \cdot $ cm2. The fully-vertical GaN-on-SiC SBD exhibits a high forward current density over 3000 A/cm2, a high current swing of ~ $10^{{11}}$ , a nearly ideal Schottky interface with a low ideality factor of ~1.03, and an enhanced reverse blocking voltage of ~520 V with fluorine-implanted termination (FIT). The optimization scheme of the buffer structure and its impact on the electrical performance have been analyzed and revealed. The demonstration of the fully-vertical GaN-on-SiC SBD with highly conductive buffer structure shows a practical approach to realizing fully-vertical GaN-on-SiC power devices and paves the way toward monolithic integration of GaN/SiC power devices.