Choosing the Best Wide Bandgap Technology for Your Application
Understanding the unique advantages provided by silicon carbide (SiC) and gallium nitride (GaN) can help you select the optimal technology to meet your products’ power, thermal, and size requirements.
Wide bandgap (WBG) technologies have gained traction in automotive applications, including electric vehicle (EV) charging, as shown in Figure 1. Still, their characteristics make them suitable for a broad range of energy management infrastructure scenarios.
Figure 1. Electric vehicle charging can benefit from wide bandgap technology. Image used courtesy of Adobe
No matter the application, power electronics are about delivering the maximum amount of power to the load. Two main challenges are the thermal management of the system and the switching losses.
You can attack those challenges by improving heat conduction and dissipation or reducing switching losses. Both silicon carbide (SiC) and gallium nitride (GaN) are WBG technologies that have become viable alternatives to legacy silicon (Si) semiconductors.
What Is the Bandgap?
Physicists define the bandgap of a material as the difference in energy between the lowest unoccupied state of the conduction band and the highest occupied state of the valence band. When excited by the application of energy, electrons from the valence band can jump to the conduction band. The bandgap determines how much energy electrons need to move from the valence band to the conduction band.
SiC and GaN are Most Likely to Replace Silicon
Legacy silicon materials typically have a bandgap in the range of 1.5 eV. In a WBG semiconductor, the bandgaps are wider—hence the name. GaN has a bandgap of 3.2 eV, while SiC has a bandgap of 3.4 eV.
WBG semiconductor power devices can operate at higher voltages, temperatures, and power. These characteristics make them ideal for automotive applications and other energy storage use cases.
Not only do SiC and GaN differ from legacy silicon, but they also differ from each other. These differences matter when deciding which one to use in power applications.
SiC Scores High on Reliability and Heat Dissipation
A primary benefit of SiC power semiconductors is their superior gate-oxide reliability. SiC employs vertical transistor concepts, whereas GaN transistors have lateral conduction like most silicon devices.
Figure 2. Silicon carbide wafer. Image used courtesy of Infineon Technologies
Other benefits of SiC include efficiency gains through advancements in miniaturization, decreased cooling requirements, and lower overall system costs compared to Si for power applications.
With the thermal properties allowing for high thermal efficiency, SiC shines the most in Onboard Chargers (OBCs) for EVs. SiC employs vertical transistors, and in an OBC, heat gets dissipated through the transistor. When the heat hits the SiC layer, it disperses uniformly—only a diamond could do it better (an expensive proposition).
An OBC is an example of an application in which the maximum power needs to be pumped safely into a limited space without thermally overloading the transistor. SiC is ideal for an OBC because it’s in a sealed, confined space where heat is a factor. The dissipation allows the OBC to charge the vehicle faster while keeping a handle on the heat in a tight space.
The proliferation of fast-charging EV infrastructure requires putting equipment in many different environments as vehicle-to-grid (V2G) and vehicle-to-home (V2H) applications become more widely adopted, two other areas where SiC excels.
Beyond battery charging, SiC’s ability to dissipate in a high-power environment extends to other energy management infrastructures, such as solar power storage systems.
GaN Delivers Density and Fast Switching
GaN distinguishes itself as a lateral transistor that supports fast switching and works well where power density is highly desirable. While SiC offers density at the IC level, GaN allows you to achieve higher power density at the board level.
In a power application, GaN allows for much faster switching for reduced switching losses. As a byproduct of a fast-switching power supply, the higher frequency reduces the size of the magnetics, which also reduces board density and increases system efficiency.
Because of its effective density at the board level and fast switching, GaN is an excellent choice for consumer electronics charging use cases where the goal is quick charging from a low-power state to full power. Examples of applications include battery chargers for laptops and USB-C-type wall plugs. Another ideal application for GaN is switched-mode power supplies in data centers.
Choose the Optimal Wide Bandgap Solution
You might think that selecting your preferred WBG technology and sticking with it is your best bet, but you would want to mix and match SiC and GaN, depending on the application. You may also continue to use legacy silicon, as it still has its place.
As illustrated in Figure 3, SiC is ideal for the highest power applications but is limited in switching frequency. GaN is better suited for high-frequency switching applications.
Figure 3. SiC and GaN applications as a function of power and frequency. Image used courtesy of Infineon Technologies (click to enlarge)
Employing SiC can help you manage the thermal properties, while GaN will reduce your switching losses to almost zero. Sorting through the many application scenarios and selecting the right WBG technologies can be streamlined by reaching out to a vendor who can outline the available options and help you choose the best one for your application.
Given the many use cases for WBG technologies and the continued need for legacy silicon, it’s unlikely that either GaN or SiC will become the sole go-to technology. Infineon’s approach to WBG is to steer customers to the most appropriate choice for their power requirements while maximizing performance. Infineon Technologies has strategically invested in WBG technologies with both front-end and back-end facilities to support fabrication, assembly, and testing.
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