GaN and SiC benefits in industrial electronics

One of the major trends in manufacturing is improving industrial energy efficiency. With the world increasingly shifting to electrical sources, this often comes down to improving the operation of power electronics, for example to make maximum savings from an investment in energy efficient motors.

Most electronics today rely on metal oxide semiconductor field effect transistors (MOSFETs), invented in 1959 at Bell Labs and widely adopted during the early 1960s. MOSFETs control the electrical conductivity of the device channel by changing voltage applied on the gate terminal, enabling signal amplification or switching and power processing.

The main advantage of a MOSFET over traditional bipolar transistors is that they require almost no input current to control the load current. However, they do have certain disadvantages, notably a short life and high susceptibility to overload voltage.

Newer materials are now becoming available that offer significant improvements over silicon-based devices, providing lower losses and higher speeds combined with lower costs.

These new materials include Silicon Carbide (SiC) and Gallium Nitride (GaN).

One of the features of these newer materials is a wider bandgap. This is an energy range in a solid where no electrons can exist and is one of the factors in how well a solid material can conduct electricity – the wider the bandgap, the higher the voltage and temperature it can sustain.

What is Gallium Nitride?

Gallium Nitride (GaN) is a very hard and mechanically stable semiconductor. With a wide bandgap of around 3.2 eV, it offers a much higher breakdown strength, faster switching speed, higher thermal conductivity and lower resistance than silicon based equivalents with bandgaps of around 1.12eV.

This wide bandgap allows GaN to be used for optoelectronic high-power and high-frequency devices.For example, GaN MOSFETs are the ideal basis for power amplifiers for microwave and terahertz (ThZ) devices in applications such as imaging and sensing, as well as Radio Frequency (RF) components and light-emitting diodes (LEDs). These advantages mean that GaN has demonstrated its ability to displace silicon semiconductors in power conversion, RF, and analog applications.

Because GaN crystals can be grown on a variety of substrates, including silicon, existing silicon manufacturing infrastructure can be used, including existing stocks of large diameter silicon wafers.

GaN has several beneficial attributes compared to silicon. These include a lower on-resistance, giving lower conductance losses and therefore reduced energy costs. As GaN semiconductors are inherently more efficient than silicon, less energy is expended as heat, giving smaller system sizes and hence lower material costs.

The material also allows faster devices with a higher switching frequency, which in turn allows smaller inductors and capacitors to be used in power circuits. With a 10 fold increase in frequency comes a 10 fold decrease in the capacitance and inductance, producing a very large decrease in weight and volume, as well as cost. Higher frequencies can also produce lower acoustic noise in motor drive applications. They can also enable wireless power transfer at higher powers, and bigger transmit to receive airgaps between the charging element and the charged device.

With higher switching frequencies and operational temperatures than silicon, GaN devices have lower cooling requirements, and can use smaller heat sinks as well as moving from liquid-cooling to air cooling, eliminating the need for fans.p

GaN semiconductors also result in a lower total system cost. Although GaN semiconductors are generally higher cost than silicon, the reduction in the size and costs of components such as passive inductive and capacitive elements, filters and cooling can produce savings in the order of 10-20%.

What is Silicon Carbide?

Silicon Carbide (SiC) is a compound semiconductor composed of silicon and carbide. With a band gap that is three times greater than silicon at 3.4 eV, it provides several advantages, including ten times the breakdown electric field strength – this makes it possible to configure much higher power device voltages, ranging from 600V to thousands of volts.

SiC makes it possible to achieve simultaneous high withstand voltage, low ON resistance, high-speed operation and much higher temperatures, considerably expanding the range of applications. Essentially, SiC makes possible performance that is not achievable with silicon alone, making it the most viable successor to silicon for next-generation power devices.

Most of the resistance component of high-voltage devices is located in the drift layer, so SiC makes it possible to achieve greater withstand voltages with extremely low ON-resistance per unit area - theoretically, the drift layer resistance per area can be reduced by 300 times compared with silicon at the same withstand voltage.

The advantages of SiC and GaN compared to traditional silicon

The history of energy use has been one of discovering the most efficient ways to convert energy from its source form to its final application.

Today, we think more about how to convert generator output most efficiently to an end-voltage for an almost limitless number of applications, from industrial motor drives to EV battery chargers.

At some point, the energy conversion process will almost certainly use power semiconductor switches, of which silicon-based types have been the norm for decades in the form of Si-MOSFETs and insulated-gate bipolar transistor (IGBTs).

However, the power loss inherent in the use of silicon switches has long been a contributing factor to system inefficiency. Until recently, there have been few alternatives.

Yet, as already shown, SiC and GaN-based semiconductors have characteristics that demonstrably improve power conversion efficiency.

In saying this, it should be noted that these semi-conductors are not hot swappable with Si based chips. Application circuits must be designed to match, particularly if the full performance benefits are to be gained.

Applications of SiC and GaN devices

SiC devices have proven their value as rugged, state-of-the-art drivers in a growing number of applications. Existing applications using Si-MOSFETs or even IGBTs can be safely retrofitted with SiC devices. To achieve the maximum benefits of SiC, new, ground-up designs can also be implemented that take advantage of the higher switching frequencies and miniaturised magnetic components.

GaN devices are finding favour in lower voltage applications because the material’s compound provides the best balance of efficiency and performance. Likely applications include solar inverters, telecoms DC-DC converters, class D audio amplifiers and single-phase AC power supplies.

Energy saving capabilities of SiC and GaN for industry

SiC and GaN technologies in transistors are having significant impacts on strong growth markets.

For example:

• Electric vehicles (EV) and transportation: Efficiency improvements result in lower battery costs and more miles per charge.
• EV charging infrastructure: Greater power delivery and the reduction of charging time by more than half is a major improvement on that achievable by silicon-only solutions.
• Renewable energy: SiC transistors reduce power loss by 50%, which in turn directly lowers the cost of energy generation.
• Industrial power supplies: Up to 10% efficiency improvements in kW power supplies provide compelling OPEX improvements such as lower runtime and maintenance costs.
• 5G and communications: GaN has higher bandwidth and power density compared to alternatives and is critical for global 5G (and beyond) development and deployment.

Conclusion

Both GaN and SiC chips offer benefits for particular applications and are thus not directly competitive. However, their characteristics mean that each now dominate certain markets. For example, by 2026, consumer electronics chargers are expected to make up 66% of the GaN chip market, while automotive applications, mainly BEVs, could account for as much as 60% of the SiC chip market.

The benefits they deliver in energy efficiency combined with compact size are revolutionising the power supply options now available to consumers and industry and are both attractive platforms that, in turn, contribute greatly to more sustainable energy supplies and usage.