Wafer-scale Epitaxial Graphene Growth on the Si-face of Hexagonal SiC (0001) for High Frequency Transistors

TL;DR

This paper reports the successful growth of high-quality epitaxial graphene on Si-face SiC wafers, achieving record high cutoff frequencies in RF transistors, with detailed characterization and fabrication results.

Contribution

It introduces a novel growth process for wafer-scale epitaxial graphene on SiC and demonstrates high-performance RF transistors with record cutoff frequencies.

Findings

Hall mobilities up to 4000 cm^2/Vs measured

Peak cutoff frequency of 100 GHz achieved in RF-FETs

High-quality graphene characterized by AFM, HRTEM, Raman

Abstract

Up to two layers of epitaxial graphene have been grown on the Si-face of two-inch SiC wafers exhibiting room-temperature Hall mobilities up to 1800 cm^2/Vs, measured from ungated, large, 160 micron x 200 micron Hall bars, and up to 4000 cm^2/Vs, from top-gated, small, 1 micron x 1.5 micron 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 AFM, HRTEM, 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 cm^2/Vs from ungated Hall bars and 1575 cm^2/Vs from top-gated ones. This is by far the highest cut-off frequency measured from any kind of graphene.