Comparison of the Forward Voltage Drop of Si and SiC High Voltage Diodes

Abstract

Obtaining a high coefficient of efficiency for a power converter requires that the components used to build it are well chosen. Power semiconductor switches are responsible for significant power loss. For the same breakdown voltage, a silicon carbide (SiC) bipolar device has a significantly thinner, lightly doped drift region (n- base) compared to silicon (Si) devices and, therefore, low switching losses and low voltage drops in the drift region. The forward voltage drop of a bipolar device is the sum of the drift region voltage drop and the junction voltages. The junction voltages of a Si device are significantly smaller as compared to a SiC device since its band gap is smaller. Therefore, for lower voltage devices (< 6.5 kV), the forward voltage drop will be smaller for Si as compared to SiC devices. For high voltage devices, the opposite is true. In this work, physics-based models of Si and SiC diodes were used to calculate the forward voltage drop for different breakdown voltages; and the simulation results are compared to determine the difference between Si and SiC devices.