What the future holds for WBG devices

Silicon carbide (SiC) and gallium nitride (GaN) have seen increasing success in the semiconductor device market in recent years. GaN is now used in mobile device chargers and charging systems. Companies such as Apple, Samsung, and Xiaomi have opted for GaN-based chargers that offer high energy density while keeping or even reducing the weight of these components. These chargers use High Electron Mobility Transistor (HEMT) chips provided by companies such as GaN Systems and Navitas Semiconductor.

On the other hand, SiC devices have been mainly used in the field of electrical mobility. In 2017, electric vehicle manufacturers such as Tesla opted to use SiC-based motor controllers, boosting the efficiency of their systems. This has started a race towards developing large quantities of SiC devices to meet the increasing amount of electric vehicles being introduced into the market.

Their popularity begs the question: What distinguishes these new semiconductor materials, and why are they viewed as alternatives to silicon?

SiC and GaN vs. Silicon

as explained Victor Philiadis On July 28, 2022 PSMA webinar, “The State of SiC Energy Technology and Overcoming Barriers,” “SiC and GaN materials have a critical electric field about 10 times higher than that of silicon, with a bandgap 3 times higher… in a semiconductor system , the drift layer is what holds its rated voltage, making the thickness and doping levels of this layer determine the voltage capability of the device.

For a given rated voltage, the thickness of the drift layer is inversely proportional to the critical electric field. This means that GaN and SiC devices with a given voltage capability have drift layers 10 times thinner than those of silicon devices. These factors lead to design changes and have significant implications for semiconductor design.

Due to the thinner drift layers, SiC devices are smaller in size, which reduces their capacity. Thus these devices can switch efficiently at much higher frequencies than is possible with silicon. As a result of higher switching frequency, the size of passive components and magnetic devices such as inductors also decreases. This leads to a significant decrease in the overall size of the system, which increases its energy density. Furthermore, the large SiC bandgap and high thermal conductivity allow for high-temperature operation with simplified cooling management, reducing system weight and size.

None of this means that SiC or GaN is superior or that silicon is obsolete. The choice of semiconductor material to be used depends on the specification of the application in which it is deployed. Silicon remains a strong competitor in devices rated from 15V to 650V while also being much cheaper and more reliable, while GaN is gaining popularity in low-power applications such as portable chargers and similar charging systems. As mentioned earlier, GaN is the only viable broadband-gap alternative to silicon in low-power applications, as SiC is impractical at voltages below 650 V.

power factor correction

GaN enables a power factor correction (PFC) technique known as a “totemic pole non-bridged PFC topology.” On the other hand, a conventional silicon boosting solution would have a diode bridge where two of the diodes would operate continuously. This would contribute to significant losses but is mitigated by GaN due to its essentially zero reverse recovery. 100-V GaN devices are also being deployed in data centers, where server racks are increasingly moving towards 48 V. Moreover, 650-V GaN devices can also be deployed and powered for a PFC circuit. SiC is suitable for higher power applications than is possible with GaN and is available in voltages ranging from 650 V to 3.3 kV, with higher voltage devices being developed.

“Gallium nitride has truly found its killer application in replacing silicon and USB-C chargers for mobile devices,” said Stephen Russell, an expert in power devices at Tech Insights, during a company webinar. 2021 [was] A watershed year in market acceptance, and we only expect this momentum to continue. However, the real advantage of gallium nitride is switching; It is the only viable silicon wideband gap alternative with voltages below 600V”.

All of these devices compete strongly in 650-V capacity, which is important, as these devices are used in the 400-volt bus for electric vehicles.

electric vehicles

Electric vehicles are an important application of these newly adopted high bandgap devices, as the market is expected to expand. This shift is occurring due to rapid electrification across sectors and increased awareness of emissions. They can be seen in motor drivers, DC/DC converters, onboard chargers, etc.

SiC is expected to have an advantage in the electric vehicle sector, as more and more manufacturers are turning towards 800-V EV systems, due to their high-voltage effective operating capability. The transition to higher voltage systems allows for higher power delivery while maintaining the same current levels. This allows copper conductors and other components to be smaller, lighter, and less expensive.

Manufacturers such as Porsche, Audi, BYD and Hyundai are already working on 800-V battery systems, while Lucid has a 900-V system in development. As Veliadis said, “Going to 800 volts while maintaining the same current doubles the power, with fewer losses. This reduces heavy copper cable, providing lighter weight and space-saving advantages.”

Once they are successfully adopted into the EV space, the demand for SiC devices will increase manufacturing. This will eventually lead to lower prices similar to silicon-based devices after mass production. Lowering the cost is an important step, as these devices are more expensive than silicon, with SiC costing roughly 2x to 3x as much as silicon.

price and production

Apart from the high cost, SiC fabrication has its own set of challenges, such as the presence of defects and slower fabrication times compared to silicon, and SiC devices are less rigid. This discourages people from adopting SiC-based systems and is a challenge that must be overcome. Due to their high voltage potential, SiC devices are excellent candidates for deployment in energy applications such as HVDC transmission and renewable energy systems. For example, in the case of photovoltaic applications, although the cost of a SiC device is three times higher than that of silicon, the total cost of the system is lower due to the reduction in the size of the passive elements.

Market outlook for the semiconductor industry

Despite the challenges they face, broadband gap devices are expected to be widely adopted in many industries and markets. Today, SiC and GaN are the only two broadband gap semiconductor materials with commercially available power devices for a wide range of applications. Depending on the strength ratings of their devices, these materials can find applications in a variety of industries.

There are also forecasts that the SiC market is expected to be worth $6.5 billion by 2027. GaN devices will dominate the low-power mobile application industry, with more devices expected to reach the market with power density above 20W/inch.³. These devices are expected to achieve significant improvements in efficiency and user convenience.

Unfortunately, SiC and epitaxy GaN substrate in silicon substrate production is more complex and more labor-intensive than that of silicon wafers, and this leads to increased cost. Moreover, the market for SiC and GaN is much smaller, which is far from a large-scale unified division of labor, as the main process technologies are in the hands of a select few companies. To overcome such issues, SiC and GaN have to be mass-produced, which will bring costs down on a large scale.

This article was originally published E Times.

Maurizio Di Paolo Emilio He holds a Ph.D. in Physics and Communications Engineer. He worked on several international projects in the field of gravitational wave research to design a heat compensation system, micro-X-rays, and space technologies for communications and engine control. Since 2007, he has collaborated with several Italian and English blogs and magazines as a technical writer specializing in electronics and technology. From 2015 to 2018, he was Editor-in-Chief of Firmware and Elettronica Open Source. Maurizio enjoys writing and telling stories about power electronics, broadband gap semiconductors, automobiles, the Internet of Things, digital, energy and quantum. Maurizio is currently the Editor-in-Chief of Power Electronics News and EEWeb, and European Correspondent for the EE Times. He is the presenter of PowerUP, a podcast about power electronics. He has contributed to a number of technical and scientific articles as well as to a number of Springer books on energy harvesting, data acquisition and control systems.