Electrical quality improvement of thin Y$_{2}$O$_{3}$ topgates in graphene FETs by high-pressure O$_{2}$ post-deposition annealing

Although extensive research effort has focused on equivalent oxide thickness scaling by the deposition of ultrathin high-$k$ dielectrics on graphene, these dielectrics still suffer from leakage currents under high electric fields. This leakage is a critical concern for the increase in the on-current. Here, we demonstrate a considerable suppression of the gate leakage current by using Y$_{2}$O$_{3}$ film annealed in high-pressure O$_{2}$ at 100 atm (HP-PDA) in top-gated graphene FETs. Consequently, the quantum capacitance measurement for the monolayer graphene reveals the highest Fermi energy modulation ($E_{\mathrm{F}} =$ $\sim $0.52 eV, i.e., the carrier density of $\sim $2 $\times$ 10$^{13}$ cm$^{-2})$ in the solid-state topgate insulators reported so far. HP-PDA of Y$_{2}$O$_{3}$ enables to realize the robust and reproducible top-gated graphene FETs.