Back in February, I wrote about IBM’s development of a new type of field-effect transistor [FET] using graphene, a solid form of carbon in which the atoms are arranged in a “honeycomb” hexagonal lattice, one atom thick. Now, an article in the IEEE Spectrum reports that IBM scientists have fabricated the first integrated circuit using graphene FETs on a silicon carbide substrate.
IBM researchers have built the first integrated circuit (IC) based on a graphene transistor—another step toward overcoming the limits of silicon and a potential path to flexible electronics.
The circuit contains not only the transistors, but also inductors and other circuit elements. Although it is not yet even at the stage of a production prototype, it represents a significant step toward a practical use of graphene technology. The circuit element built by the IBM team is a commonly-used one.
The circuit the team built is a broadband radio-frequency mixer, a fundamental component of radios that processes signals by finding the difference between two high-frequency wavelengths.
Manufacturing devices like this is tricky. Because the graphene is only one atom thick, it is easily damaged by the etching process used to make integrated circuits; moreover, the metals typically used to fabricate other circuit elements (e.g., palladium, gold) don’t necessarily adhere well to the graphene. The IBM team devised some new techniques to address these problems.
One of the attractions of using graphene, rather than silicon, for transistors is that graphene allows considerably higher switching frequencies than silicon at a given gate size. Another advantage found with the new circuit is lower sensitivity to changes in operating temperature.
One remarkable feature is that the performance of the device didn’t change very much when its temperature went from 300 to 400 kelvins (about 27 °C to 127 °C). That means a graphene circuit won’t have to be overdesigned to compensate for temperature changes, potentially leading to a less-complex and less-expensive circuit.
In addition, graphene has some attractive physical properties that may lead to new applications.
Beyond surpassing the performance of silicon, the material, which is strong, transparent, and bendable, could lead to flexible printed electronics. Applications could include cellphones stitched into clothing or GPS receivers on soldiers’ uniforms.
Silicon-based electronics are going to be with us for quite a while yet; but it is encouraging to see relatively rapid progress in developing new materials.