Wafer-scale epitaxial graphene growth on the Si-face of hexagonal SiC (0001) for high frequency transistors

Up to two layers of epitaxial graphene have been grown on the Si-face of 2 in. SiC wafers exhibiting room-temperature Hall mobilities up to 2750 cm2 V−1 s−1, measured from ungated, large, 160×200 μm2 Hall bars, and up to 4000 cm2 V−1 s−1, from top-gated, small, 1×1.5 μm2 Hall bars. The growth process involved a combination of a cleaning step of the SiC in a Si-containing gas, followed by an annealing step in argon for epitaxial graphene formation. The structure and morphology of this graphene has been characterized using atomic force microscopy, high resolution transmission electron microscopy, and Raman spectroscopy. Furthermore, top-gated radio frequency field-effect transistors (rf-FETs) with a peak cutoff frequency fT of 100 GHz for a gate length of 240 nm were fabricated using epitaxial graphene grown on the Si-face of SiC that exhibited Hall mobilities up to 1450 cm2 V−1 s−1 from ungated Hall bars and 1575 cm2 V−1 s−1 from top-gated ones. This is by far the highest cutoff frequency measured from any kind of graphene.