Graphene field-effect transistors with self-aligned spin-on-doping of source/drain access regions

The exceptional electronic properties of graphene field-effect transistors (GFETs) make them a promising replacement for conventional Si CMOS transistors for high frequency analog applications. Radio frequency GFETs with intrinsic cut-off frequencies as high as 300GHz have been reported [1], with theoretically predicted THz frequencies only being limited by fabrication challenges. A major factor responsible for degradation of GFET performance is high series resistance of the access regions between the source/drain contacts and the top-gated graphene channel, which reduces maximum possible drive currents. A back-gate bias can be used to modulate this resistance, but this approach does not provide for independent control of multiple GFETs on the same substrate and for GFETs on insulating substrates. GFETs with self-aligned gates overcome this problem by reducing the access region resistance, but their fabrication is not straightforward [1, 2]. Here, we propose a simple scheme of improving GFET performance by reducing the source/drain access resistance using self-aligned charge-transfer doping. A novel and controllable way of “spin-on-doping” of the access regions with chemical dopants is demonstrated.