Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistors (SiC MOSFETs) are type of power semiconductor devices that utilizes Silicon Carbide (SiC) as the semiconductor material. Silicon Carbide is a compound composed of silicon and carbon, and offers high thermal conductivity, wide bandgap, and high breakdown voltage. These properties make SiC an ideal choice for high-power and high-temperature applications. 

Structure of SiC MOSFETs

SiC MOSFETs share a similar structure with traditional MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), consisting of three main layers - the source, the gate, and the drain.

• Source: This layer is the source of electrons in the device and is typically connected to the negative terminal of the power supply.
• Gate: The gate is the control terminal of the MOSFET, responsible for switching the device on and off. It controls the flow of electrons from the source to the drain.
• Drain: The drain is the output terminal of the MOSFET, connected to the load in most power electronic applications.

Working Principle

Cross section of SiC MOSFET with equivalent circuit

When a positive voltage is applied to the gate terminal relative to the source, it creates an electric field that attracts electrons, forming a conductive channel between the source and drain terminals, allowing current to flow, making it the "on" state. Conversely, applying zero or negative voltage to the gate turns off the electric field, blocking current flow and placing the SiC MOSFET in the "off" state.

Design consideration of SiC MOSFET

Designing with Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistors (SiC MOSFETs) requires careful consideration of several key factors to optimize performance and reliability in various applications. Here are some important design considerations for SiC MOSFETs-

• Gate Drive Circuitry: Ensuring that the gate driver can provide the necessary voltage and current for proper switching is crucial. Gate resistors should be used to manage voltage transitions, and galvanic isolation techniques can help protect against noise and voltage spikes.
• Thermal Management: Effective cooling solutions, such as heat sinks and quality thermal interface materials, are essential to manage the heat generated during SiC MOSFET operation, ensuring reliable performance and longevity.
• Voltage and Current Ratings: Matching the SiC MOSFET's voltage and current ratings to the specific application requirements is fundamental in preventing device failure and ensuring optimal operation.
• Gate Voltage and Threshold Voltage: Understanding the gate-source voltage (VGS) requirements and the SiC MOSFET's threshold voltage (VTH) characteristics is crucial to ensure reliable switching behavior and avoid unintended states.
• Switching Frequency: Choosing SiC MOSFETs with suitable switching characteristics, and optimizing for the desired operating frequency, is vital to maximize efficiency and minimize switching losses.
• Protection Circuitry: Implementing protection features like overcurrent, overvoltage, and thermal shutdown mechanisms safeguards the SiC MOSFET and the entire system from faults, enhancing reliability.
• Layout and PCB Design: Careful layout and PCB design help minimize parasitic components, ensuring efficient performance and reducing the risk of voltage spikes or noise interference in the circuit.

Silicon Carbide (SiC) MOSFETs Vs Silicon (Si) MOSFETs

    SiC MOSFET V/S Si MOSFET

The choice between SiC MOSFETs and Si MOSFETs depends on the specific requirements of the application. SiC MOSFETs excel in high-power, high-temperature, and high-frequency applications where efficiency and thermal performance are crucial. Si MOSFETs, on the other hand, are suitable for lower voltage and more general-purpose applications. The differences are further summarized in the table below:

Click here to learn more about SiC MOSFETs featured on everything PE.

Click here to learn more about Silicon MOSFETs featured on everything PE.