Hybrid vehicles enter the SiC era

China’s Hybrid Technology Is Leveraging Silicon Carbide to Drive an Efficiency Revolution

 

 

Recently, Wuling Motors officially announced the adoption of silicon carbide (SiC) technology in its hybrid vehicles. Around the same time, Chery Auto also unveiled new developments related to SiC-based hybrid systems. Leading Chinese automakers such as Geely, Changan, BAIC, and Hongqi have also made strategic investments in the silicon carbide hybrid space. The application of SiC technology has become a major highlight.

 

 

In electric drive systems, the integration of SiC power modules—combined with HPDmini packaging technology—has led to a 268% increase in power density, a 70% improvement in current output capability, and a 40% enhancement in heat dissipation efficiency.

 

 

Additionally, motor speeds can now reach up to 24,000 rpm, significantly improving power response and energy efficiency. China’s hybrid market is now experiencing a wave of technological evolution centered around the “SiC + Hybrid” model, with numerous automakers and Tier 1 suppliers accelerating their deployments.

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What Is the Outlook for the Hybrid Market?

 

An increasing number of application cases indicate that technological upgrades and large-scale expansion in China’s hybrid market are forming a synergistic momentum. According to the latest industry data, in 2024, the installed base of DHT (Dedicated Hybrid Transmission) systems in China’s plug-in hybrid vehicle sector reached 3.713 million units—soaring by 94.61% year-on-year. Among these, hybrid systems adopting a dual-motor architecture accounted for as much as 97.7%, confirming that highly efficient, highly integrated dual-motor solutions have become the mainstream choice.

 

This technological trend is closely linked with the installed volume of dual electronic control units, which reached 3.628 million sets—a year-on-year increase of 91.99%. It demonstrates that automakers have made significant progress in core technologies such as power decoupling and multi-mode driving. According to the 2025 White Paper on Silicon Carbide (SiC) Devices and Modules Industry Research, as the cost of SiC devices continues to decline, the hybrid market is expected to enter a second growth phase between 2025 and 2030.

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Commonly Used SiC Products in Electric Vehicles

 

 

1. SiC MOSFET (Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistor)

Applications:

• Main drive inverter (traction inverter): Drives the motor by converting high-voltage DC power into three-phase AC power.

• DC-DC converter: Stabilizes battery voltage to power low-voltage systems.

• On-board charger (OBC): Converts AC grid power into DC power for battery charging.

Advantages:

• High switching frequency → Improves system efficiency

• Reduces overall system size and weight

• Lowers thermal management requirements

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2. SiC SBD (Silicon Carbide Schottky Barrier Diode)

Applications:

• Widely used in on-board chargers (OBC) and DC-DC converters

• Functions as a rectifier to improve efficiency and reduce reverse recovery losses

Advantages:

• Zero reverse recovery time → Suitable for high-frequency switching

• Excellent thermal stability

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3. SiC Power Modules

Applications:

• Integrates multiple SiC components (e.g., MOSFETs + SBDs) into a compact module

• Used in electric drive systems, motor controllers, and high-voltage systems

Advantages:

• Compact design suitable for high power density

• Optimized thermal management and EMI suppression performance

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6inch and 8inch Silicon Carbide Substrates and Epitaxial Wafers: The Backbone of Next-Generation Power Devices

 

Abstract of SiC as a Material

Silicon carbide is a wide bandgap semiconductor with a bandgap of 3.26 eV (for 4H-SiC), compared to 1.12 eV for silicon. It also possesses:

• High critical electric field (~10x higher than silicon)

• High thermal conductivity (~3x higher than silicon)

• High breakdown voltage

• High electron saturation velocity

These properties make SiC especially suitable for high-power, high-frequency, and high-temperature applications. Unlike silicon, SiC can operate at higher voltages and temperatures while reducing energy losses, which is critical for power conversion efficiency.

 

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SiC Substrates: The Foundation

Crystal Structure and Polytypes

SiC exists in many polytypes, but 4H-SiC is the preferred material for power electronics due to its higher electron mobility and wide bandgap. The substrate is typically a monocrystalline wafer sliced from a bulk SiC boule grown by physical vapor transport (PVT) methods.

Production of SiC Substrates

The production process involves:

1. Crystal Growth – Using PVT or modified Lely methods, high-purity SiC powder is sublimated and recrystallized onto a seed crystal under high temperature (~2000°C) and low pressure.

2. Wafer Slicing – The grown boule is precisely sliced into wafers (2", 4", 6", or 8").

3. Lapping & Polishing – Wafers are ground, lapped, and polished to achieve ultra-flat surfaces with minimal defects.

4. Inspection – Substrates are inspected for dislocations, micropipes, basal plane dislocations (BPDs), and other crystalline defects.

Key Parameters

• Diameter: 2", 4", 6", and emerging 8" (200 mm)

• Off-Axis Angle: 4° typical for 4H-SiC to improve epitaxial growth

• Surface Finish: CMP polished (epiready)

• Resistivity: Conductive or semi-insulating, depending on doping (N-type, P-type, or intrinsic)

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SiC Epitaxial Wafers: Enabling Device Design

What Is an Epitaxial Wafer?

An epitaxial wafer consists of a thin, doped SiC layer grown on a polished SiC substrate. The epitaxial layer is designed with specific electrical and thickness profiles to meet the exact requirements of power devices.

Epitaxial Growth Techniques

The most common technique is Chemical Vapor Deposition (CVD). It allows precise control over:

• Layer thickness (usually a few to tens of micrometers)

• Doping concentration (from 10¹⁵ to 10¹⁹ cm⁻³)

• Uniformity across large wafer areas

Gases like silane (SiH₄) and propane (C₃H₈) are used as precursors, along with nitrogen for n-type doping or aluminum for p-type doping.

Application-Oriented Design

• MOSFETs: Require low-doped drift layers (5–15 µm) for high blocking voltage

• SBDs: Require shallower epitaxial layers with controlled doping for low forward voltage drop

• JFETs/IGBTs: Customized layer structures for specific on-resistance and switching behavior

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Advantages of SiC Substrates & Epilayers

These advantages directly contribute to reduced size, weight, and cost of power conversion systems in EVs, chargers, solar inverters, and industrial drives.

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Challenges and Industry Trends

Challenges

• Defect Control: Basal plane dislocations (BPDs), micropipes, and stacking faults affect device yield.

• Wafer Cost: SiC substrates are significantly more expensive than Si, due to growth time, yield, and complexity.

• Scalability: 6-inch wafers are mainstream, but 8-inch wafer production remains in R&D and pilot stages.

Trends

• Migration to 8-inch wafers to reduce cost per chip

• Improved substrate quality through defect reduction techniques

• Vertical integration by manufacturers to control the full value chain from substrate to packaged device

• Rapid growth in demand driven by automotive (EV) and renewable energy markets

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Conclusion

Silicon carbide substrates and epitaxial wafers represent the core of next-generation power electronics. Their superior material properties make them indispensable in high-efficiency, high-reliability applications. As the world transitions toward electrification and carbon neutrality, the demand for SiC wafers will continue to surge, driving innovation and capacity expansion across the industry.

 

Whether you're a semiconductor device manufacturer, EV developer, or power system integrator, understanding and choosing the right SiC substrates and epilayers is a critical step toward achieving performance and commercial success.