In 2014, the United States Department of Energy established a program to develop advanced manufacturing methods for wide-bandgap (WBG) semiconductors, which allow electronic components to be smaller, faster, and more efficient than semiconductors made from silicon (Si). The program, called the PowerAmerica Institute, recently issued a call for projects to help reduce manufacturing costs and increase the availability of these semiconductors in power electronics.
The advantages of WBG semiconductors are significant when compared to their silicon-based counterparts. This technology can be used to design power electronics that control and convert electricity at higher temperatures, higher breakdown voltages, and lower frequencies than Si-based MOSFETs.
Led by North Carolina State University, PowerAmerica was established as a partnership between academic institutions, semiconductor companies, and the Energy Department. It was founded earlier this year and granted a $146-million contract. PowerAmerica has partnered with several companies that maintain semiconductor foundries, including APEI Inc., Cree Inc., Monolith Semiconductor, and Qorvo, among others.
The two main WBG semiconductors that are expected to replace Si-based MOSFETs—the foundation of most power electronics systems—are gallium-nitride (GaN) and silicon-carbide (SiC). The French research firm Yole Developpement estimates that replacing silicon with SiC or GaN components can increase dc-dc conversion efficiency from 85% to 95%; ac-dc conversion efficiency from 85% to 90%; and the efficiency of dc-ac conversion from 96% to 99%.
While the advantages are significant, both SiC and GaN process technologies suffer from critical manufacturing issues. For instance, GaN semiconductors have low thermal conductivity and are highly prone to defects. On the other hand, SiC wafers are very costly and have low electron mobility.
Also known as the Next Generation Power Electronics Manufacturing Innovation Institute, PowerAmerica is promoting projects that can significantly reduce the cost and increase the capacity of GaN and SiC foundries. In addition, PowerAmerica is also looking to develop new device designs and packaging that effectively exploit the properties of wide-bandgap materials, helping to push them into volume manufacturing.
The call for projects is also focused on filtering the technology into commercial markets. According to statistics from the energy department, the share of U.S. electricity flowing through power electronics is expected to be around 80% by 2030. The Energy Department foresees their rapid uptake in industrial motor systems, for instance, which today consume about 70% of the electricity consumed in U.S. manufacturing.
PowerAmerica is also looking for projects that advance the use of WBG semiconductors in large data centers, electric vehicles, and converting renewable energy for the electric grid. The greater conversion efficiency and higher operating temperatures of these WBG materials will reduce the size of the cooling systems used in these applications, Energy Department says.
GaN semiconductors are less mature than SiC technology but still progressing steadily. They have seen increased commercial usage in low-power, high-frequency applications, including microwave and RF amplifiers and transistors. Conversely, SiC is being used in solid-state lighting and high-voltage devices for switching applications.
Si-based power electronics, however, are not going down without a fight. Si-based MOSFETs, which are primarily used in 10- to 500-volt devices, are still a cost-effective option in low-power applications. In the 600- and 1200-volt range, where WBG semiconductors have the potential to make a significant impact, cost remains an issue. High-voltage Si-based devices—super-junction MOSFETs and IGBTs—are ramping up on 300-mm wafers, making them potentially less expensive than GaN and SiC.
PowerAmerica is taking a long-term approach to advancing WBG semiconductors, acknowledging that the amount of work to replace generations of Si-based devices will take a significant amount of time. Thus, its call for projects is also focused on developing educational programs and workforce development in the field of WBG semiconductors. Earlier this year, NC State opened both undergraduate and graduate research programs in WBG semiconductors. For its part, the Energy Department has established a training program through several graduate institutions for power engineering, with its main focus on WBG semiconductors.
“[Power America] is a wonderful opportunity [for students] to get into a new area of technology, but we shouldn’t just say that it’s just WBG semiconductors,” says Jayant Baliga, director of the Power Semiconductor Research Center at NC State. “There is a whole technological ecosystem around WBG technology.”