Doping concentration optimization for ultra-low-loss 4H-SiC floating junction Schottky barrier diode (Super-SBD)

Previous simulation works and experiments on the loss of 4H-SiC floating junction Schottky barrier diodes (Super-SBDs) show that the loss is related to the doping concentration in the drift region and the pattern of the floating layer. The effect of the doping concentration for lowering the loss is characterized the breakdown voltage (V_bd) and the on-state resistances (R_onS) of the Super-SBDs based on Baliga's figure of Merit (BFOM). Experimental devices with two doping concentrations in the drift region are fabricated to investigate the static characteristics: V_bd and R_onS. The V_bd of the Super-SBDs is close to the simulation result, near 3000 V. However the tendency of the V_bd by the doping concentration is not similar to the simulation result. And the RonS are about 3.22 mΩcm² which is higher than that of simulation result. The doping concentration optimized in this study does not show significant lowering loss and the design of the floating layer in the termination region affect the low-loss static characteristics of the Super-SBD. In addition, adopting PiN structure with floating layer (Super-PiN) affects the low-loss dynamic characteristics, optimizing the doping concentration in the drift region. We conclude that the fabricated Super-SBDs with the floating layer in the termination region, the drift region with a doping concentration of 1.0×10¹⁶ cm^-3 and mesa-shaped termination structure, have excellent Vbd of 2990 V which is almost same as that of simulation result and RonS of 3.22 mΩcm².