Fig. 1: Geometric designs and operation of ballistic transport devices.
From: Optimum design for the ballistic diode based on graphene field-effect transistors

a Designs for ballistic devices with different geometries. b Configuration of device A shows dimensional parameters: length (L), channel width (dch), neck width (dneck), and tapered angle (30o). c The forward and backward directional motions of charge carriers in the ballistic regime. The ballistic region (blue region) is assumed to be inside a circle of radius λ, and the diffusive region (grey region) is outside the circle.