Channel and Body-Diode Conduction Characteristics in 4H-SiC MOSFETs Under Third-Quadrant Switching Conditions.

Area of Science:

• Materials Science and Engineering
• Semiconductor Physics
• Power Electronics

Background:

• Silicon carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) are crucial for high-power applications.
• Understanding third-quadrant operation (when voltage and current are negative) is essential for device reliability and performance.
• The interaction between the PiN body diode and the MOS channel during this operation is complex and requires detailed investigation.

Purpose of the Study:

• To investigate the carrier transport mechanisms during third-quadrant operation of SiC MOSFETs.
• To analyze the interplay between the PiN body diode and the MOS channel under varying gate-source bias.
• To develop a method for identifying conduction modes and evaluate the impact of negative gate bias on device performance.

Main Methods:

• Experimental characterization of SiC MOSFETs under different gate-source bias conditions.
• Technology Computer-Aided Design (TCAD) simulations to model carrier transport and device behavior.
• Development of a transfer-characteristic-based method to determine gate-voltage boundaries for conduction modes.

Main Results:

• Body-effect-induced threshold voltage (Vth) reduction allows MOS channel conduction even with negative gate bias.
• A novel method effectively identifies gate-voltage boundaries between different conduction modes.
• Quantitative evaluation of reverse recovery parameters (Irr, Qrr, trr) shows the impact of negative gate bias.

Conclusions:

• The study clarifies the physical mechanisms of current sharing between the body diode and MOS channel in SiC MOSFETs during third-quadrant operation.
• The findings enable better control and optimization of SiC MOSFETs by understanding the role of negative gate bias.
• The developed method provides a valuable tool for device design and performance analysis in power electronics.