Could graphene mixer breakthrough enable faster electronics?

According to a team from Chalmers University of Technology, the mixer paves the way for new opportunities in future electronics as it enables compact circuit technology, potential to reach high frequencies and integration with silicon technology. A mixer is a device that combines two or more electronic signals into one or two composite output signals. Future applications at THz frequencies such as radar systems for security and safety, radio astronomy, process monitoring and environmental monitoring will require large arrays of mixers for high resolution imaging and high speed data acquisition. Such mixer arrays or multipixel receivers need new type of devices that are not only sensitive but also power efficient and compact. The ability in graphene to switch between hole or electon carrier transport via the field effect requires a unique niche for graphene for rf ic applications. The researchers say this symmetrical electrical characteristic has enabled them to build a G-FET subharmonic resistive mixer using only one transistor. This means no extra feeding circuits are required, which makes the mixer circuit more compact compared with conventional mixers. As a result, it requires less wafer area when constructed and can open up for advanced sensor arrays, for example for imaging at millimetre waves and even sub millimetre waves as G-FET technology progress. Jan Stake, professor of the research team: "The performance of the mixer can be improved by further optimising the circuit, as well as fabricating a G-FET device with a higher on/off current ratio. Using a G-FET in this new topology enables us to extend its operation to higher frequencies, thereby exploiting the exceptional properties of graphene. This paves the way for future technologies operating at extremely high frequencies." In addition to enabling compact circuits, the G-FET provides potential to reach high frequencies thanks to the high velocity in graphene, and the fact that a subharmonic mixer only requires half the local oscillator (lo) frequency compared to a fundamental mixer. This property is attractive especially at high frequencies (THz) where there is a lack of sources providing sufficient lo power. According to the researchers, the G-FET can also be integrated with silicon technology. For example, it is cmos compatible and among other things it can be used in cmos electronics for backend processing on a single chip.