Characterization of Al2O3 gate dielectric for graphene electronics on flexible substrates

To ensure the high performance of graphene-based field effect transistors (GFETs) on flexible substrates, an uniform and manufacturable dielectric film with good electrical properties is needed. Thus, electrical characterization of the dielectric film on graphene on flexible substrates is very important for the development of flexible electronics based on GFETs. Here, we have fabricated and characterized parallel-plate capacitor test structures consisting of 35 nm thick Al₂O₃ dielectric film and with graphene as bottom electrode on polyethylene terephthalate (PET). It was found that the leakage current density in the Al₂O₃ film is less than 100 μA/cm² at 5 V, which allows for applying it as a gate dielectric in GFETs on flexible substrates. The extracted dielectric constant of the Al₂O₃ film is approx. 7.6, which is close to the bulk value and confirms the good quality of the Al₂O₃ film. Analysis indicates that the measured loss tangent, which is up to 0.2, is governed mainly by the dielectric loss in the Al₂O₃ and can be associated with defects from the Al₂O₃ film and the Al₂O₃/graphene interface. Our results will be used in further development of GFETs on flexible substrates.