Automotive applications are driving the development of more energy-efficient semiconductor technologies — with wide bandgap (WBG) out in front for many car use cases and for supporting infrastructure, such as electronic vehicle (EV) charging.
Their larger bandgap is what differentiates WBG technologies significantly from conventional semiconductors or “legacy silicon.” This bandgap is the energy difference between the top of the valence band and the bottom of the conduction band — this difference enables WBG semiconductor power devices to operate at higher voltages, temperatures, and frequencies, and is possible due to the use of new and emerging non-silicon materials.
WBG power electronics (PE) are a small but growing segment of PE. WBG PE devices are used for the conversion, control, and processing of electricity. Because WBG semiconductor power devices allow for more efficient energy generation, transmission, and consumption, they are ideally suited for many automotive applications.
Mind the Gap … and the Materials
The bandgap for typical semiconductor materials such as silicon ranges from 1 - 1.5 electronvolt (eV), while WBG semiconductors have larger bandgaps in the range of 2 - 4 eV. Essentially, a wider bandgap is better because a WBG semiconductor can operate at higher maximum temperatures than legacy silicon, which is a valued characteristic in automotive applications.
The bandgap of a material as defined by physicists is the difference in energy between the lowest unoccupied state of the conduction band — the band to which those electronics can jump — and the highest occupied state of the valence band, which is the band of electron orbits from which electrons jump when excited by the application of energy. The energy required for electrons to move from the valence band to the conduction band is determined by this bandgap.
Besides the gap itself, the materials used in WBG semiconductors are what set them apart from traditional semiconductors. The most common are gallium nitride (GaN) and silicon carbide (SiC) — the market for these technologies is forecast to surpass $6.9 million by 2032.
GaN has a bandgap of 3.2 eV, while SiC has a bandgap of 3.4 eV, making them around three times greater than silicon. Because of their greater bandgaps, both GaN and SiC can support higher voltages and higher frequencies than can legacy silicon, but they also differ from each other; these factors affect how they work and their use cases — including for automotive applications.
The most notable difference between GaN and SiC is their speed as defined by how quickly electronics can move through the semiconductor material. GaN’s “electronic mobility” is 30 percent faster than that of silicon at 2,000 cm2/Vs, while SiC electron mobility is 650 cm2/Vs. GaN’s higher electronic mobility makes it better for high-performance, high-frequency applications, while SiC’s higher thermal conductivity and lower-frequency operation is more suited for higher-power applications.
These differences are why GaN semiconductors are well-suited for RF devices that switch in the gigahertz range, and why SiC is used in EVs and data centers, some solar-power designs, rail traction, wind turbines, grid distribution, and industrial and medical imaging — they tend to require higher-end voltages and better heat dissipation.
As dominant silicon technologies have started to reach performance limits in a growing number of existing and emerging applications, both GaN and SiC offer several benefits when used in automotive applications.
WBG Can Take the Automotive Heat
The overall benefit of WBG semiconductors is that they can withstand higher electric fields, sustain higher voltages, and operate at higher switching frequencies, which improves performance. They also handle higher maximum temperatures than can legacy silicon.
WBG technologies can also be smaller because the switch is faster — energy is delivered in smaller packets, which means less energy must be stored in the circuit’s passive and inductive devices. Smaller is always good for automotive, especially when it enables higher power and improved energy efficiency; the weight of the car is reduced, which is good for fuel efficiency while reducing carbon emissions. This is especially true for EVs, as GaN and SiC have many applications for not only inside the car but also for EV charging infrastructure.
Because GaN enables smaller, more efficient, and lower-cost power systems, it supports several key aspects of vehicle electrification: smaller, lighter batteries; improved charging performance; and greater EV range. GaN also supports wireless power applications and autonomous vehicle capabilities.
A critical piece of the EV charging infrastructure is an on-board charger (OBC) — every EV needs one, and it must be able to convert AC power from the wall receptacle into the DC power that charges the battery. GaN-based transistors allow for these OBCs to be smaller and lighter, which of course reduces the overall weight of the vehicle and extends driving range. GaN transistors are also used as traction inverters that convert DC into AC in the battery and increase driving range through greater energy efficiency.
Meanwhile, the needed charging infrastructure to support EV adoption is getting help from SiC technology through SiC-based power products, which include bare die, discrete Schottky diodes and MOSFETs, and power modules. The higher power-conversion capabilities, faster switching speeds, and improved thermal performance make SiC ideal for EV fast-charging infrastructure. Like GaN, SiC allows for smaller and lighter devices than does conventional silicon options.
SiC technology plays a critical role in building the fast-charging infrastructure needed to quell any remaining anxieties about EV range, reliability, and ruggedness necessary at the system device level that’s required for EV faster-charging infrastructure. As EVs increase their range through adoption of lighter, high-power density batteries, OBCs are becoming bi-directional through SiC-based solutions that can also support smart grid applications and e-commerce capabilities within a fast-charging EV infrastructure.
Flexibility is also key for automotive designs, something both GaN and SiC technologies support because they are smaller, lighter, and more energy efficient. If EVs are to truly take off, the supporting charging infrastructure will need to accommodate many different types of vehicles and stakeholders — not just EV drivers but also municipalities and business owners who will all have requirements for charging stations that must be met by system designers.
WBG semiconductors have a lot of potential for solving power problems in automotive applications, as well as other applications in alternative energy and uninterruptable power supplies -- check out this eBook to learn more. Increasing power needs coupled with environmental awareness make WBG technologies a great choice for power devices because they reduce size, increase energy efficiency, and reduce overall consumption — all of which are critical in the automotive realm.