“A switching frequency of up to 3MHz allows us to achieve a much greater power density,” said Fraunhofer research associate Richard Reiner.

On the die is two 600V 120mΩ GaN HETS (high electron mobility transistors) and two freewheeling diodes. The diodes are merged with the transistors by integrating Schottky contacts with the GaN HEMT (high electron mobility transistor) structure.

Compact design minimises line impedances, and 240V/ns turn-on and turn-off have been achieved.

“A folded chip layout enables the DC link capacitance to be tightly connected between the supply voltage and ground,” said Fraunhofer. “This design creates an optimised power path and allows for clean, stable switching at high frequencies. The operation of this circuit was demonstrated in a down-converter from 400 to 200V at a switching frequency of 3MHz.”

On-board charging in electric vehicles is the intended market.

“Covering long distances without generating any emissions requires not only powerful batteries but also the development of lightweight electric cars which generate as little energy as possible,” said Fraunhofer. “This can only be accomplished using electronic components based on semiconductor materials such as gallium nitride which, in contrast to silicon carbide, can be grown as epitaxial layer on cost-effective, large area silicon substrates. When used to produce electronic components for electric vehicles, GaN enables higher power densities to be achieved more energy efficiently.

Fraunhofer IAF will be showing its monolithically GaN half-bridge circuit at PCIM in Nuremberg (hall 7 booth 237) next week.

There is a little more information here.