Wide-bandgap semiconductors: GaN vs. SiC in practice
Today, industrial power supply solutions need to achieve high power density and efficiency without losing sight of system costs. Wide-bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) provide the necessary flexibility. They reduce switching losses, enable higher switching frequencies than conventional silicon solutions, and improve the thermal behavior of power electronics. Nevertheless, GaN and SiC are not interchangeable alternatives to conventional silicon. Instead, they add specific strengths to the portfolio depending on the application profile. It’s therefore not a matter of which technology is superior to the others, but rather which wide-bandgap technology is the best match for which application.
What are wide-bandgap semiconductors?
Wide-bandgap (WBG) semiconductors push the physical boundaries of conventional silicon power semiconductors. They have high electron mobility and a wide bandgap, which gives them advantages over conventional silicon in many power electronics applications. Transistors made from WBG semiconductors operate at higher breakdown voltages and are more tolerant of high temperatures. In addition, they switch faster and can operate at higher frequencies than silicon semiconductors.
At the system level, that reduces the need for large passive components. Developers can design smaller inductors, transformers, and capacitors, while power density and efficiency increase. At the same time, the high level of efficiency reduces heat loss and hence the effort required to cool the components. To exploit the benefits of WBG semiconductors in industrial power supply, developers must combine design parameters such as topology, gate drive, layout, and thermal design.
GaN: High switching frequency for compact power supply units
GaN power transistors are particularly well-suited for compact power supply units as their low gate charge and low parasitic capacitance enable very fast switching with low switching losses. That allows AC/DC and DC/DC converters, for example, to operate at significantly higher switching frequencies. Developers can make passive components smaller while increasing efficiency and power density.
In industrial power supply applications, GaN is particularly relevant in applications where compact designs, high-speed frequencies, and low dynamic losses are critical, as, for example, in efficient power supply units, DC/DC converters, battery chargers, and inverters.
Due to its high electric strength of up to approximately 1,000 V, its temperature resistance, and its fast switching times, GaN is also suitable for powerful switching power supply units. At the same time, GaN requires a particularly careful system design. Short gate and power loops, low parasitic inductance, a robust EMC design, and precise gate drive determine whether the benefits of the high switching speed can be exploited in the real-world design.
SiC: Robust efficiency at high voltage and temperature
SiC components shine in applications where high voltages, power, and temperatures come together. Typical voltage classes are 650 V, 1,200 V, and 1,700 V, which makes SiC components particularly suitable for:
- Industrial power supply units
- Power factor correction (PFC) circuits
- Inverters
- High-voltage DC/DC converters
- Charging infrastructure
- Motor drives
Low switching and conduction losses, high reverse voltages, and robust thermal properties provide a system advantage here. At the same time, SiC remains challenging in terms of system design. Developers must carry out application-oriented testing of parameters such as gate drive, parasitic effects, short-circuit behavior, and the right cooling concept.
The real trade-off: When is GaN the right choice, and when is SiC?
GaN and SiC differ significantly from conventional silicon: At around 3.4 eV for GaN and 3.2 eV for SiC, their band gaps are about three times as large as that of silicon. As a result, both materials can support higher voltages on smaller chip areas and switch faster.
The differences are particularly evident in the material properties. At around 2,000 cm²/Vs, GaN has a higher electron mobility than silicon (around 1,500 cm²/Vs) and SiC (around 700 cm²/Vs), making it particularly suitable for applications with high switching frequencies, compact designs, and low dynamic losses. GaN and SiC have significantly higher breakdown field strengths than silicon, at 3.3 MV/cm and 3.5 MV/cm, respectively, which means that they can withstand higher voltages per unit of chip thickness.
SiC, on the other hand, scores with regard to heat dissipation: Its thermal conductivity of 5 W/cmK is far higher than that of GaN (1.3 W/cmK) and silicon (1.5 W/cmK), making it the better choice in most cases for high voltages, high power, and thermally demanding applications.
It is therefore not the material alone that matters, but also the system profile. Voltage range, switching frequency, power density, heat dissipation, and EMC performance together determine whether the material advantage translates into a reliable efficiency gain for industrial power supply solutions.
Making a proper comparison between evaluation kits and reference designs
However, the trade-off between switching frequency, thermal behavior, and EMC performance can only be reliably assessed at the system level. Developers should therefore use evaluation kits and reference designs and compare them based on their system integration instead of individual components. Relevant criteria include:
- Topology
- Power range
- Efficiency curves
- EMC performance
- Thermal design
- Protection functions
When it comes to GaN, the focus is often on compact, high-speed switching power supply solutions, such as totem-pole PFC stages, which enable higher power density and efficiency but must also keep voltage spikes and EMC effects under control. SiC reference designs, on the other hand, are geared more toward higher voltage and power classes, such as 3-phase PFC stages for 400V AC inputs, high-voltage DC outputs, and charging or industrial applications.
What should developers and system architects take away from this?
Developers and system architects should not select GaN or SiC based solely on data sheet values. Key factors include the load profile and voltage level, power range, switching frequency, cooling budget, EMC requirements, and the regulatory environment. GaN is suitable primarily for compact designs with high switching frequencies and low dynamic losses. SiC is usually the better choice for high voltages, high power, and thermally demanding applications.
electronica provides an overview of the entire ecosystem, ranging from semiconductor manufacturers, power supply and measurement technology providers, as well as PCB and system integration providers. Design and system integration. Anyone evaluating GaN and SiC for industrial power supply solutions can go there to compare technologies, rank suppliers, and check which wide-bandgap solution suits their specific application.
The Power Electronics Forum explores these interfaces between components, systems, and applications in depth and highlights how power semiconductors, power supply, thermal design, and system integration interact.