Why does the SiC Schottky barrier diode (SBD) have a high withstand voltage?

SiC (Silicon Carbide) is a wide-band-gap semiconductor. Compared with Si (Silicon), as shown in the table below, it is characterized by high band gap, high electric breakdown field, high saturation speed, etc.

When reverse bias is applied to the SBD of a general structure, the depletion layer expands from the metal-semiconductor interface. The image of the electric field at this time is as shown in the figure, and is the maximum at the metal-semiconductor interface. The breakdown electric field is the theoretical maximum value of the electric field and the withstand voltage is equal to the area of the triangle indicated by the width of the depletion layer and the electric field.

Since the breakdown electric field of SiC is about 10 times that of Si, SiC SBD with high withstand voltage can be formed.

Physical characteristics of Si and main wide-band-gap semiconductors

Property Unit Si 4H-SiC 6H-SiC 3C-SiC GaN GaAs Diamond
Band gap eV 1.12 3.26 3.02 2.23 3.39 1.43 5.47
Electron mobility μe cm2/Vs 1400 1000/1200 450/100 1000 900 8500 2200
Hole mobility μh 600 120 100 50 150 400 1600

Electric breakdown

field Ec

V/cm 3.0×105 2.8×106 3.0×106 1.5×106 3.3×106 4.0×105 1.0×107
Thermal conductivity  λ W/cmK 1.5 4.9 4.9 4.9 2.0 0.5 20

Saturated electron

drift velocity Vsat

cm/s 1.0×107 2.2×107 1.9×107 2.7×107 2.7x107 2.0×107 2.7×107

Relative dielectric

constant ε

  11.8 9.7/10.2 9.7/10.2 9.7 9.0 12.8 5.5
Electric breakdown field