A demonstration of what is considered to be the first-ever gallium nitride (GaN)-on-diamond high electron mobility transistor could significantly reduce thermal resistance and increase RF performance in monolithic microwave integrated circuit (MMIC) power amplifiers, DARPA said in a statement.
While MMIC power amplifiers equipped with gallium nitride transistors hold the potential for enhanced RF performance, poor thermal properties exhibited by the thermal junction—where the substrate material of the circuit connects to the GaN transistor—place limits on the equipment’s operational abilities.
However, DARPA’s new GaN-on-diamond high electron mobility transistor (HEMT), developed as part of the Near Junction Thermal transport (NJTT) effort, may have the potential to remove these limits.
“These GaN-on-diamond HEMTs [high electron mobility transistors] could enable a new generation of PF power amplifiers that are three times smaller than the current state-of-the-art GaN amplifiers,” Avram Bar-Cohen, DARPA program manager, said. “Smaller amplifiers would lead to RF systems with better size, weight and power characteristics.”
He added that the new technology could triple the output power of current amplifiers, strengthening signals for communication systems and long-range radar applications.
Using a new epitaxial transfer method, researchers at TriQuint Semiconductor successfully removed GaN from its growth substrate and placed it “in intimate contact” with a synthetically-grown diamond substrate. Synthetic diamond is considered to have the highest known thermal conductivity of any known solid—more than 10 times higher than silicon.
“Providing a high conductivity substrate in intimate contact with the GaN gets us unsurpassed heat tolerance and dissipation capability,” Bar-Cohen said. “We expect this advance will substantially improve the thermally-limited high power RF systems of today.”