Operation of graphene magnetic field sensors near the charge neutrality point

Abstract

Graphene is a promising material for sensing magnetic fields via the Hall effect due to its atomic-scale thickness, ultra-high carrier mobilities and low cost compared to conventional semiconductor sensors. Because of its Dirac band structure, graphene sensors differ from semiconductor sensors in that both electrons and holes participate in the carrier transport. This two-channel transport complicates the sensor operation and causes performance trade-offs that demand careful examination. Here, we examine the operation of graphene sensors operated near the charge neutrality point (CNP) where two-channel transport prevails. We find that, while the largest magnetoresistance occurs exactly at the CNP, the maximum realizable Hall sensitivities occur away from the CNP and depend on linearity constraints and power limitations. In particular, a more stringent linearity constraint reduces the realizable sensitivities for mobilities above a critical value µc, which scales with magnetic field.