GaN vs SiC: Choosing the Right Semiconductor for Power Electronics

In the world of power electronics, the shift from traditional silicon to wide bandgap (WBG) semiconductors is well underway. Two materials dominate this transition: Gallium Nitride (GaN) and Silicon Carbide (SiC). Both offer significant advantages over silicon, but they excel in different application domains. Understanding their strengths and trade-offs is essential for making the right design choice.

At EVSELab, we work with both technologies across our product lines. This article provides an engineering-focused comparison to help guide semiconductor selection for power electronic systems.

Material Properties at a Glance

Before diving into application-level comparisons, it is useful to understand the fundamental material differences between GaN and SiC.

What the Numbers Tell Us

• GaN has higher electron mobility and a slightly wider bandgap, making it excellent for high-frequency, lower-voltage applications.
• SiC has vastly superior thermal conductivity, making it the better choice for high-power, high-temperature applications where thermal management is critical.

Switching Performance

GaN: The Speed Champion

GaN High Electron Mobility Transistors (HEMTs) can achieve switching frequencies in the MHz range with extremely low switching losses. The lateral device structure of GaN-on-Si HEMTs results in very low gate charge (Qg) and output capacitance (Coss), enabling:

• Switching frequencies of 500 kHz to 5 MHz in soft-switched topologies
• Near-zero reverse recovery losses (GaN devices have no body diode in the traditional sense)
• Extremely fast transition times (sub-10 ns rise/fall)

SiC: The Power Workhorse

SiC MOSFETs operate effectively at switching frequencies of 50–200 kHz in hard-switched converters, which is significantly higher than silicon IGBTs but below GaN capabilities. However, SiC devices are available in much higher voltage and current ratings:

• Commercially available SiC MOSFETs rated up to 3.3 kV
• Current ratings exceeding 100 A per die
• Excellent performance in hard-switched topologies where switching losses are dominated by turn-off energy

Rule of thumb: If your design requires switching above 500 kHz, GaN is likely the better choice. Below 200 kHz at high power, SiC is typically more practical.

Voltage and Power Level Considerations

GaN Sweet Spot: Below 900 V

Currently available GaN power devices are predominantly rated at 650 V or lower, with some recent products reaching 900 V. This makes GaN ideal for:

• Consumer electronics and USB-C PD chargers (up to 240 W)
• Telecom and server power supplies (1–3 kW)
• Solar micro-inverters (up to 5 kW)
• On-board chargers up to 6.6 kW (single-phase)
• Low-voltage DC/DC converters in 48 V systems

SiC Sweet Spot: 650 V to 3.3 kV

SiC MOSFETs and diodes are available in voltage ratings from 650 V to 3.3 kV, making them suitable for:

• DC fast chargers (30 kW to 360 kW)
• Industrial motor drives (10 kW to 500 kW)
• On-board chargers for electric vehicles (3.3 kW to 22 kW)
• Grid-tied energy storage inverters
• Traction inverters in electric vehicles

The Overlap Zone

In the 1–10 kW range at bus voltages of 400–800 V, both GaN and SiC can be viable. The choice often comes down to:

• Topology: Resonant topologies favor GaN’s speed; hard-switched topologies favor SiC’s robustness
• Thermal constraints: Tight thermal budgets favor SiC’s superior heat dissipation
• Cost sensitivity: GaN-on-Si can be cheaper at lower power levels; SiC wins at higher power

Thermal Management Differences

This is one of the most critical distinctions in practical design. SiC’s thermal conductivity of 4.9 W/cm-K is nearly 4x higher than GaN’s 1.3 W/cm-K. In practice, this means:

• SiC dies can dissipate more heat through the substrate without requiring elaborate thermal interface solutions
• GaN devices, despite having lower losses, require careful PCB thermal design (especially for GaN-on-Si in QFN packages)
• At high power densities, SiC’s thermal advantage often outweighs GaN’s lower loss profile

Practical Design Implications

For GaN designs, engineers must pay close attention to:

• Multi-layer PCB copper weight and thermal via arrays
• Placement of thermal pads relative to gate driver components
• Airflow management in the immediate vicinity of the device

For SiC designs, the focus shifts to:

• Heatsink selection and thermal interface material (TIM) optimization
• Baseplate or direct-bonded copper (DBC) substrate design
• Liquid cooling channel geometry for high-power modules

Cost Comparison

Device-Level Cost

As of early 2026, the cost landscape is as follows:

• GaN HEMTs (650 V, 15 A): Approximately $2–5 per device in volume
• SiC MOSFETs (1200 V, 30 A): Approximately $5–15 per device in volume
• Silicon IGBTs (1200 V, 30 A): Approximately $2–4 per device in volume

System-Level Cost

Raw device cost is only part of the picture. System-level cost analysis must include:

• Magnetic components: GaN’s higher switching frequency reduces inductor and transformer size and cost by 30–60%
• Cooling system: SiC’s lower losses and better thermal conductivity can reduce cooling system cost by 20–40%
• PCB complexity: GaN designs often require more PCB layers and tighter layout constraints
• Gate driver requirements: SiC gate drivers must manage Miller plateau effects; GaN drivers must handle dV/dt-induced turn-on

Reliability Considerations

GaN Challenges

• Dynamic Rds(on): GaN HEMTs can exhibit increased on-resistance under certain switching conditions due to charge trapping effects
• Threshold voltage stability: Long-term Vth drift under high-temperature gate bias stress
• Limited field history: GaN power devices have a shorter track record in automotive and industrial applications

SiC Challenges

• Gate oxide reliability: SiC MOSFETs rely on a thin SiO2 gate oxide that operates under higher electric fields than in silicon devices
• Body diode degradation: Bipolar degradation in SiC body diodes during third-quadrant conduction (mitigated in modern devices)
• Cosmic ray susceptibility: Higher voltage SiC devices (1700 V+) require careful derating for terrestrial cosmic ray events

How EVSELab Approaches the Decision

At EVSELab, our semiconductor selection process is driven by the specific requirements of each project. Our general guidelines:

• For on-board chargers below 6.6 kW: We evaluate both GaN and SiC, with GaN favored for single-phase designs where switching frequency and power density are paramount
• For on-board chargers 6.6–22 kW: SiC is our default choice due to its higher voltage ratings and thermal robustness
• For DC fast charger modules (20 kW+): SiC is the clear winner, and our Grasshopper platform is built around SiC MOSFETs
• For auxiliary power supplies and low-power DC/DC stages: GaN offers compelling advantages

Conclusion

GaN and SiC are not competing technologies — they are complementary. Each has a domain where it excels, and the best power electronic systems often use both. As costs decrease and device performance improves, the boundary between their application spaces will continue to evolve.

The key is to match the semiconductor to the application requirements, considering not just device-level metrics but the entire system including magnetics, thermal management, EMC, and cost.

Need help selecting the right WBG semiconductor for your power electronics project? Reach out to EVSELab’s engineering team for a consultation.