Investigation of Graphene Field Effect Transistors with Al₂O₃ Gate Dielectrics Formed by Metal Oxidation

We propose the epitaxial graphene field-effect transistors (EG-FETs) with Al₂O₃ gate dielectric formed by metal oxidation on semi-insulating 6H-SiC substrate. The Al₂O₃ gate dielectric layer was formed by thermally oxidizing a thin Al film at 500 °C in an O₂ ambient. The electrical characteristics of EG-FETs with Al₂O₃ gate dielectric have been investigated, which exhibits p-type behavior with the field effect mobility of 120 cm² V^-1 s^-1. After the Al₂O₃ formation, the FWHM of G' and D peaks in the Raman-scattering spectra increased, indicating degradation of graphene and thereby accounting for the low field effect mobility of the EG-FETs. This finding suggests that the optimization of post growth heat treatments, such as oxidation and metallization, should play a decisive role in tuning the quality of graphene and the performance of the device made thereof.