Silicon and graphene are two materials with extremely good properties with respect to usage in power electronics. "Graphene is the material that enables the highest current density and the highest charge carrier mobility", explained the head of the research team, Heiko Weber. "On top of this, it offers very high temperature stability and extreme mechanical strength".
The scientists spread a single-atom graphene layer on top of a SiC crystal and found that this array has excellent switching properties. The SiC-graphene transistors created using this method can be processed and integrated in much the same way as industrial semiconductors are produced, offering the possibility to combine logic circuitry and power transistors as monolithic integrated circuits. "This enables the design of ultra-small power supplies", Weber said. For example, these power supplies could be integrated into LED modules, enabling new designs for incandescent bulb or halogen lamp retrofits.
While the graphene layer can be created in a very elegant way just by heating up the SiC crystal to about 1700°C, SiC transistors are significantly more expensive than today’s conventional transistors. Nevertheless, the researchers are talking to several leading semiconductor companies about commercializing their invention. Industrialization would be rather simple, Weber said, since the graphene transistors can be arranged to ICs in much the same way today’s CMOS integrated circuits are processed.
The SiC-graphene transistors currently offer an on/off ratio of 10 by the power of 5 which is already one magnitude better than industry requirements. Besides its switching properties, the devices will most likely be able to operate under extreme ambient temperatures of up to 500°C, Weber believes. "We have yet to formally test it, but I am optimistic", he said. And there is one more property that could make SiC-graphene transistors interesting for future industrial applications: They have the potential to switch very fast. "The fastest amplifiers currently existing are based on graphene", said Weber. But his team left this field unexplored – yet.