Advantages of Silicon Carbide (SiC) and Gallium Nitride (GaN) in Power Electronics

Silicon carbide (SiC) and gallium nitride (GaN) are making waves in the power electronics market, driving significant changes that promise better efficiency, improved performance, and reduced costs. These innovative materials are at the heart of a shift that is reshaping industries from renewable energy to 5G communications.

SiC and GaN deliver key advantages in all stages of a typical power converter, from totem pole rectifier PFC stage through main inverter to synchronous output rectifiers. They offer significant efficiency gains through miniaturization advancements, decreased cooling requirements, and lower overall system costs by as much as 10-20% over traditional silicon materials.

Si-IGBTs, which have insulated gates but a high total gate charge, require significant drive power. In contrast, Si-MOSFETs, which were invented in 1959 at Bell Labs and widely adopted during the early 1960s, have much lower gate charge and lower drive power requirements. However, SiC gates must be driven to nearly 20V for full enhancement, while GaN HEMTs are current-driven by voltage in the range of 3V.

Gate drives for SiC and GaN devices will typically include extra series resistance to deliberately slow switching edge rates as a compromise between electromagnetic interference and efficiency. Absolute maximum gate voltage for Si-MOSFETs is typically +/-25V, and the gate is often driven to a negative voltage, in the range of -12V, to switch the device OFF.

Both SiC and GaN can experience 'phantom' turn ON due to high current rate-of-change and instantaneous rate of voltage change over time. This can be remedied by the application of a few volts of negative gate drive at the proposed OFF-state.

In the realm of high voltages, IGBTs are still preferred, but MOSFETs can be stacked in some topologies to reduce voltage stress. The maximum voltage for high power Si-MOSFETs is around 950V, for GaN HEMTs it is 600V, and for SiC MOSFETs, it is approximately 1,700V.

SiC transistors halve power loss, directly lowering the cost of energy generation in renewable energy. For instance, Infineon Technologies quotes a 20% reduction in system costs due to thermal design simplifications in renewable energy due to SiC transistors.

The companies Broadcom, Infineon, Microchip, Nexperia, ON Semiconductor, and STMicroelectronics have joined forces to develop Silicon Carbide and Gallium Nitride products. This partnership was announced during the Mobile World Congress in Barcelona, Spain, in March 2023.

A recent study by Gartner reports that SiC and GaN technologies in transistors are having significant impacts on strong growth markets such as electric vehicles (EV), transportation, EV charging infrastructure, renewable energy, industrial power supplies, and 5G and communications.

GaN, in particular, has higher bandwidth and power density compared to alternatives, critical for global 5G development and deployment. With up to 10% efficiency improvements in kW power supplies, these advancements provide compelling operational expenditure (Opex) improvements in industrial power supplies.

Performance limits have been reached for silicon, the building block of MOSFETs since their inception. However, SiC and GaN are poised to overcome these limitations, driving the semiconductor industry towards a more efficient, cost-effective, and high-performance future.

Advantages of Silicon Carbide (SiC) and Gallium Nitride (GaN) in Power Electronics