Improving channel mobility in graphene-FETs by minimizing surface phonon scattering - A simulation study

In graphene-based field-effect transistors (graphene FETs), the carrier channel mobility is strongly influenced by substrate and gate dielectric materials. In this paper, we theoretically investigated the carrier channel mobility for the graphene-FET. Surface phonon (SP) scattering, screened Coulomb scattering, acoustic phonon and optical phonon scattering mechanisms are considered in the mobility calculation. Applying Mahan's theory, the SP scattering in a gate stack structure is evaluated. It is found that SP scattering plays an important role especially in high-k dielectrics. The charged impurity and SP scattering can be suppressed effectively by inserting a polymer layer between the gate dielectric and graphene. The thickness of the ploymer layer, however, should be carefully selected to balance the channel carrier mobility enhancement and gate control ability. Our calculation results are consistent with previous calculations and experimental observations.