Carbon (graphene) transistors are getting really fast.
IBM Research has demonstrated a 100GHz transistor. Fabricated on new 2-inch graphene wafers and operating at room temperature, the RF graphene transistors are said to beat the speeds of all but the fastest GaAs transistors, paving the way to commercialization of high-speed, carbon-based electronics.Big transistors are are not too hard. You essentially lay down a sheet of graphene, dope it (or dope it while it is part of the SiC substrate), and then put a gate pattern over it. You get a power transistor. At 100 GHZ that probaly is indicative of the ability to work at 50 GHz.
"There are all kinds of extraordinary claims being made every day for graphene semiconductors, but this is the first demonstration of a RF graphene transistor that was made under technologically relevant conditions and scale," said IBM Fellow Phaedon Avouris, who oversees carbon-based materials efforts at IBM Research.
The graphene RF transistors were created for the Defense Advanced Research Project Agency under its Carbon Electronics for RF Applications (CERA) program. Almost four times faster than previous demonstrations, the graphene transistors were fabricated at the wafer scale using epitaxially grown graphene processing techniques that are compatible with those used to fabricate silicon transistors.
But they have set their sights on bigger game.
There are several relatively easy steps to further widen the gap between graphene and silicon. For instance, graphene suspended over an air gap and supercooled has achieve carrier mobilities of up to 200,000cm²/Vs compared to silicon's 1400cm²/Vs.Computers are a little different. Take the top speed and divide it by 4. Then allow for 6 levels of logic (AND, OR, and NOT) plus wiring delays and you can divide that number again by 10. So 1 THz/40 = 25 GHz. About 10X faster than today's computers. If they can cut the heat load by a factor of 5 to 10 they will have one screaming machine. Who will be the early adopters? Gamers, server farms, and of course the guys who funded it. The military through the CERA Program.
IBM's demonstration of room-temperature graphene on an insulating substrate only achieved 1500cm²/Vs.
The gate length of IBM's graphene transistor was 240nm, nearly 10x larger than the smallest gate lengths achievable with current lithographic techniques (under 35nm). By optimizing its process to increase mobility and shortening the gate length, IBM will next aim to increase the speed of its graphene transistor up to 1THz, which is the goal for the CERA program.