▎ 摘　　要

The interface condition between the graphene channel and aluminum oxide (Al2O3) gate insulator in a graphene field-effect transistor (FET) has been analyzed. The hard X-ray photoelectron spectroscopy technique was employed to analyze the interface. In the obtained C1s spectra, a small peak was found at 284.2 eV, which was considered to be derived from a covalent bond between the graphene and Al2O3. In the pulsed S-parameters measurements, it was found that the direction of the Dirac voltage shift matched the polarity of the applied voltage stress. The Dirac voltage shift demonstrated that there were electron traps at the interface, degrading the FET performance such as the cutoff frequency. It was concluded that the unexpected bond at the interface formed electron traps whose energy level located near the conduction band minimum and that the Dirac voltage shifted in accordance with carrier capturing or emitting by the traps.