Power/Performance Bits: Dec. 23

High mobility transistor
Engineers at the University of Delaware created a high-electron mobility transistor, a device that amplifies and controls electrical current, using gallium nitride (GaN) with indium aluminum-nitride as the barrier on a silicon substrate.

Among devices of its type, the team says their transistor has record-setting properties, including record low gate leakage current, a record high on/off current ratio and a record high current gain cutoff frequency (an indication of how much data can be transmitted with a wide range of frequencies).

The researchers think the transistor could be useful for higher bandwidth wireless communication systems, as for a given current, it can handle more voltage and would require less battery life than other devices of its type.

“We are making this high-speed transistor because we want to expand the bandwidth of wireless communications, and this will give us more information for a certain limited time,” said Yuping Zeng, assistant professor of electrical and computer engineering at the University of Delaware. “It can also be used for space applications because the gallium nitride transistor we used is radiation robust, and it is also wide bandgap material, so it can tolerate a lot of power.”

The transistors are made on a low-cost silicon substrate and are compatible with CMOS.

The researchers are also working on improving the design and working on other technologies, like titanium oxide transistors which are transparent and could be used for backplane displays, competing with the technology for currently commercially used indium-gallium-zinc oxide (InGaZnO) transistors.

“We are trying to continue to break our own record, both for the low power application as well as for the high-speed application,” said Zeng. The team also plans to use their transistors to make power amplifiers that could be particularly useful for wireless communications as well as other internet-of-things.

Structural electrodes
Researchers at Texas A&M University are working to develop batteries that could be built into the structural body panels of electric vehicles or airplanes. This would require development of batteries and supercapacitors with the same sort of mechanical properties as the structural body panels, rather than the brittle materials commonly used for batteries and supercapacitors.

The team focused on creating supercapacitor electrodes with drastically improved mechanical properties based on reduced graphene oxide, which was strengthened and stiffened using dopamine. Most commonly known as a neurotransmitter, dopamine is a highly adhesive molecule that mimics the proteins that allow mussels to stick to virtually any surface. The use of dopamine and calcium ions led to a significant improvement in mechanical performance, inspired by the structure of nacre, often called mother-of-pearl.

Paraskevi Flouda holds sample of new electrode. (Image: Texas A&M Engineering)

The researchers’ supercapacitor electrodes provided the highest, to date, multifunctional efficiency (a metric that evaluates a multifunctional material based on both mechanical and electrochemical performance) for graphene-based electrodes.

In the future, the team hopes this development could lead to an entirely new family of structural electrodes, which would open the door to the development of lighter electric vehicles and aircraft. They also hope to translate the work on supercapacitors into batteries.