4,308V, 20.9 mO·cm 4H-SiC MPS Diodes Based on a 30μm Drift Layer

This paper reports the design, fabrication and characterization of high voltage 4H-SiC merged PiN/Schottky-barrier (MPS) diodes with an active area of 1.4mm. For comparison purposes, Schottky barrier, PiN and MPS diodes of smaller size (8.1x10mm) have also been designed and fabricated on the same wafer with a 30μm, n=2x10cm doped drift layer. The Schottky spacing between the adjacent p+ regions in the MPS diodes has been designed to be 7, 8, 9, and 10μm so that the trade-off between the forward current capability and the reverse leakage current can be investigated. A multi-step junction termination extension (MJTE) structure is utilized to terminate the device edge because it is capable of providing a near theoretical breakdown voltage. MPS diodes have achieved similar breakdown voltages to that of the PiN diodes while providing a forward current close to that of SBDs. MPS diodes have also shown reliable avalanche operations with avalanche breakdown voltage up to 4,308V, limited only by the SiC critical field. One of the best MPS diode achieves a blocking voltage (VB) of 4,308V and conducts a forward current density of 142 A/cm at a forward voltage drop (VF) of 4V with a differential specific onresistance (RSP_ON) of 20.9 mO·cm , yielding a VB/RSP_ON of 888 MW/cm, which is among the highest figure-of-merit (FOM) reported to date.