A major obstacle with graphene is the difficulty of building a gate dielectric (insulating layer) on its inherently inert surface. However, graphene layers grown by controlled vapor deposition (CVD) can be transferred to many types of substrates. To take advantage of this property, IBM built silicon wafers containing pre-defined embedded gate structures, and then transferred CVD-fabricated graphene layers onto them. As an example they built a frequency doubler which demonstrated a conversion gain of ~-25 dB at an output frequency of 2 GHz. This performance was nearly constant from 25-200°C, indicating that both n- and p-transconductance are temperature-independent in this range, a new finding for CVD graphene-based devices.
The four images on the right show (a) an 8” graphene FET wafer; (b) single die; (c) SEM image of a typical fully processed device and (d) an enlarged view of the device showing the embedded gate structure with two-finger design. Except for the CVD graphene transfer, all processing was done in a conventional 200 nm fab. Graphene technology is finally making it into production.