• Joined ECE August 2018 as Assistant Professor
  • Postdoctoral Associate, Massachusetts Institute of Technology (MIT), 2017–2018
  • Ph.D., electrical engineering, MIT, 2017
  • M.S., electrical engineering and computer science, MIT, 2013
  • B.S., physics, Peking University, China, 2011

The clamor for smaller, more efficient electronic devices is so constant that many consider it background noise. 

Yuhao Zhang, an assistant professor at the Center for Power Electronics Systems (CPES) and his colleagues, hear the cries, and are examining the most fundamental building blocks of power electronics devices in order to meet the demand.

Zhang works at the intersection of three research areas: semiconductor devices, materials, and power electronics. His work bridges the gap between new materials and applications, and spurs momentum in both directions. 

“We’re creating devices that can’t be purchased on the market or obtained from other companies, and advancing their practical applications in real-world power systems in data centers, electric vehicles and consumer electronics,” he said.

Emerging materials for emerging devices 

The majority of today’s commercial power devices are made of silicon (Si). Many emerging power devices in research and development are based on a group of materials called wide bandgap semiconductors or ultra-wide bandgap semiconductors. These devices use materials such as silicon carbide (SiC), gallium nitride (GaN), diamond, and the less-studied gallium oxide (Ga2O3). With a much larger bandgap, these materials can sustain at least 10 times the voltage of silicon with less power loss, explained Zhang.

“Overall, these materials can achieve 1,000 times higher performance compared to silicon devices—and they allow for switching 

at a higher frequency,” said Zhang. If the system’s switching frequency is higher, then the capacitors and inductors—which take up the majority of the volume of these devices—can also be smaller, significantly reducing the system’s volume. 

“For example, power electronics devices based on wide bandgap semiconductors can shrink the size of a laptop charger to one cubic centimeter,” said Zhang. “These devices can significantly increase the efficiency and decrease the size of the overall system.”

Zhang is trying to expand the application space of these materials in power electronics. He has already begun fabricating novel GaN and Ga2O3 devices in the clean room.

Emerging devices for emerging applications

Zhang’s work isn’t just on the small side. When data centers step down electricity from the grid (480 V ac to 1 V dc), approximately one third of the total energy is lost in the conversion. By incorporating new devices like those CPES researchers are developing, Zhang expects the overall efficiency of power delivery to increase by at least 10 percent, which would pack a punch.

“Recent estimates claim that if we can increase overall power conversion efficiency by just 1 percent, the amount of energy we would save every year is equivalent to five nuclear power plants,” said Zhang.

Whatever the physical size of the devices that will use Zhang’s technology, the energy and space savings will be huge. 

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