Wide-band-gap semiconductors

Electronic devices based on wide-band-gap semiconductors offer a chance to boost the efficiency and power density of power electronics. This makes power-electronics components smaller, faster and more efficient.

Smart energy supplies, electromobility, broadband communication systems and AI applications. The number of interacting and interconnected systems is growing all the time. However, as the number of systems and data traffic volume continues to rise, so too does the primary energy consumption.

Electrical energy always needs to be converted in order for it to be used by the various systems. So the demand for electrical conversion is also increasing. According to estimates, more than three terawatt-hours of energy go to waste in Europe alone every year. Equivalent to the electricity generated by a mid-sized, coal-fired power station.

Power electronics are the key to energy efficiency

Efficient conversion of energy is therefore becoming a major challenge for applications related to Industry 4.0, AI and more. “The most significant key technology for this is power electronics, which are indispensable for the integration of renewable energy sources into electrical supply grids, charging and powertrain technology for electromobility, mains power for data centres or high-frequency telecommunication networks,” says Professor Sibylle Dieckerhoff, Head of the Power Electronics Department at Technische Universität Berlin.

New power-electronics devices, circuits and components are required to generate the appropriate voltage. But also current and frequency profile is needed for each application with a high level of efficiency. Substantial energy savings are made possible by replacing unregulated industrial drives with modern drive systems containing highly efficient power electronics, for example. For energy and vehicle technology alone, previously unused potential can be tapped to make energy savings of up to 35 per cent. This not only brings economic advantages, but also considerably reduces the carbon emissions associated with the applications.

A higher power density with wide-band-gap semiconductors

Electronic devices based on wide-band-gap semiconductors like silicon carbide (SiC) or gallium nitride (GaN) offer the option of elevating power electronics’ efficiency. This makes power-electronics components smaller, faster and more efficient than their counterparts with a silicon (Si) basis.

Even though SiC and GaN might compete with one another in certain areas, it is still possible to roughly differentiate them according to areas of application. GaN-based components can be incorporated into smaller and lighter structures that switch the current more efficiently. Power losses are reduced by up to fifty per cent. GaN can also withstand higher voltages and is particularly of interest for high-frequency circuits. “In the past decade, the market for GaN has mainly consisted of high-performance, premium applications for high-frequency circuits with low resistance and a small form factor on a system level,” claims Ezgi Dogmus from market research institute Yole.

GaN semiconductors can be found in a huge range of applications in electric vehicles. Such as in traction converters, where GaN improves efficiency and enables range to be increased by 20 per cent. In DC-DC converters, GaN reduces the system’s size by 75 per cent. And GaN semiconductors are also used in the on-board charger or LED lighting. However, GaN solutions are also increasingly found in consumer goods nowadays. These might include chargers for notebook computers or smartphones.

SiC is primarily used for high-temperature applications due to its lower thermal expansion and its resilience in the face of harsh ambient conditions. The automotive industry is the main driving force behind the use of SiC. “The 2018–2019 period featured a strong shift towards the adoption of SiC by the automotive industry for its inverter applications,” says Hong Lin from Yole. “With the roll-out of SiC technology by Tesla, the market has reached the point of no return.”

Development continues apace

While SiC and GaN do indeed offer considerable advantages over silicon-based systems, research into the use of new materials for power electronics is far from finished. Aluminium nitride (AlN) is one example. This semiconductor material, to which little research effort has been dedicated so far with regard to electronics applications, has a conduction loss up to 10,000 times lower than silicon devices. What is more, it is characterised by very high dielectric strength and thermal conductivity. So there are ideal characteristics for power semiconductors with high power density and efficiency. This offers potential for quickly and efficiently switching devices that also boast high reliability.

Beta-gallium oxide (β-Ga2O3) is another material. This compound has more than twice the breakdown field strength of SiC and GaN. And it therefore has the potential to further increase the efficiency of power converters equipped with it. High voltages can be applied while using considerably less material. This is the basis for more compact systems. Furthermore, beta-gallium oxide transistors are characterised by low on-state resistance and faster switching operations with the specified voltage resistance. The net result of this is a reduction in power losses.

Whatever the material in question, new technologies will contribute to reducing semiconductors’ power losses, thereby helping to convert energy more efficiently and to conserve resources.

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