By Aditi Risbud Bartl
DAVIS, Calif.; Feb 2, 2018 – Researchers from UC Davis and UC Santa Barbara have developed and scaled a high-voltage, more efficient power transistor that has the potential to increase the efficiency of smartphones, high-speed trains and electric cars.
Modern power converters are based on solid-state devices: electronic devices with no moving parts, such as a transistor. These components are used to convert power from one form to another, such as switching from one voltage or current level to another, from one frequency to another, or from AC to DC (and back).
In today’s converters, approximately 40 percent of the energy consumed is first converted into electricity. This proportion may increase to as high as 60 percent due to the growing use of electric and plug-in hybrid cars, as well as high-speed trains.
For more than 50 years, power converters have been built using transistors made of silicon, the semiconductor material upon which modern electronics are based. Although silicon has a stronghold on today’s devices, next-generation devices will have to meet consumer demands for functionality, size, efficiency and speed.
At the International Electron Devices Meeting, Srabanti Chowdhury, an associate professor of electrical and computer engineering at UC Davis, and UC Davis electrical engineering and computer science graduate student Dong Ji presented their results for a more efficient transistor based on gallium nitride, a so-called wide band gap semiconductor that can function at much higher voltages and temperatures than silicon. Ji recently completed his Ph.D. in Chowdhury’s group, and their findings were recently published.
“This is the enormous advantage that we are trying to harness,” said Chowdhury. “We could run devices hotter without having to use sophisticated cooling on a given system. For example, you could reduce the number of coolants used in an electric car, and just use air cooling, which increases the car’s efficiency and saves cost and space.”
The UC Davis team is exploring different semiconductor materials, including gallium nitride and diamond, to optimize power converters and maximize their efficiencies. Chowdhury is an expert in gallium nitride-based devices and technologies and holds nearly two-dozen patents on gallium nitride and diamond-based devices.
Ji’s device, which was presented at the IEDM conference, is called an oxide-gallium nitride field-effect transistor. This transistor has a higher operating frequency, better reliability and low energy loss, which translates to higher efficiency.
“A transistor is the ‘heart’ of a power electronics system, and our oxide-gallium nitride transistor will improve system efficiency and reliability. By improving the efficiencies of power electronics systems, we can enable a greener future,” said Ji.
This work was funded by the Advanced Research Projects Agency-Energy (ARPA-E) Strategies for Wide-Bandgap, Inexpensive Transistors for Controlling High-Efficiency Systems (SWITCHES) program.