Kanak Datta holds the chip that can transport excitons on acoustic waves.

Surf’s up: Exciton ‘surfing’ could lead to faster computing with less wasted energy

What occurs inside electronic devices at levels invisible to the naked eye makes a big difference in how a device performs. A University of Michigan study revealed new behavior for a quasiparticle that forms in semiconductors, and it could result in faster electronics that consume and waste much less energy.

Electrons play a substantial role in modern electronic devices’ operations. They move both energy and information. But electrical resistance causes about half of that energy to be wasted as heat. The energy loss is a barrier to further electronics advancements.

“If you think of the past almost two decades, the computers have always been at two to three gigahertz — they never increase the speed. And that’s the reason. It just gets too hot,” Parag Deotare, assistant professor of electrical engineering and computer science, said in a news release. “But transistors can go faster if one can remove the excess heat quickly. If you just cut down your communication energy losses, then your processing speed automatically increases.” 

The researchers determined that excitons could help to cut the energy losses. Excitons are neutrally charged quasiparticles composed of a negatively charged electron and a positively charged “electron hole” that are attracted to each other. But because of their neutral charge, excitons can’t move the same way as electrons.

The U-M researchers came up with a fix for the movement issues. It works at room temperature, whereas previous attempts to control excitons had to occur at hundreds of degrees below zero Fahrenheit. They found that sending acoustic waves through the material causes excitons to “surf” on the waves to travel from one part of a semiconductor to another.

The ability to direct excitons with acoustic waves holds potential for boosting energy efficiency in many applications. Moving excitons within solar cells could help the devices more efficiently convert solar energy to electricity. Moving excitons inside an LED could reduce the amount of lost light. The concept also could benefit communication, sensing, and detection technologies.

“What we’re doing right now will enable us to have a computer that can operate at a much higher speed, consume less energy, and be built at a very small scale,” said Zidong Li, a doctoral student in electrical and computer engineering.