Optimization of graphene-MoS2 barristor by 3-aminopropyltriethoxysilane (APTES)

• A graphene's Fermi level shift with an applied gate voltage was calculated.
• APTES-treatment process was applied on graphene to block the charge puddle effect.
• An optimized graphene/MoS2 barristor was achieved by using APTES-treated graphene.

We theoretically and experimentally investigated the influence of the Fermi level position of graphene relative to the Dirac point on the performance of a graphene/MoS2 heterojunction barristor. A large Fermi level modulation (ΔEF = 0.28 eV) of graphene, when the VGS is changed between −20 V and +20 V, was theoretically predicted when the Fermi level is located at the Dirac point. For reference, ΔEF = 0.11 eV when the Fermi level is far from the Dirac point. This prediction was experimentally proven using two kinds of barristors with pristine (strongly p-type) and 2.4% APTES-treated (intrinsic) graphene. The on/off-current ratio was improved by a factor of 32 (a 2.1-fold increase in the on-current density and a 15-fold increase in the off-current density) in the APTES-treated device, as compared to the control. Using a temperature-dependent current-voltage measurement, we quantitatively confirmed the larger modulation of the barrier height in the APTES-treated barristor (ΔEF = 0.27 eV) compared to that of the control device (ΔEF = 0.14 eV). This study can be used to guide the design and optimization of graphene-based heterojunction devices.

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