Ambipolar Gate Modulation Technique for the Reduction of Offset and Flicker Noise in Graphene Hall-effect Sensors

There is a constant need for Hall-effect magnetic sensors with lower noise and lower offset for the high accuracy analog applications driven primarily by industrial and automotive markets, for example, high dynamic range current sensing for battery management in electric vehicles. Graphene-based Hall sensors (GHSs) demonstrate low thermal noise due to their high carrier mobility but suffer from large low-frequency flicker noise and offset limiting the prevalent low-frequency applications. In this paper, we present the results of a recently proposed gate modulation scheme for GHSs that uses dynamic ambipolar operation to up-convert the input magnetic signal to higher modulating frequencies while the offset and flicker noise remain spectrally unchanged and thus enabling thermal noise limited performance. We implement a prototype GHS using a scalable fabrication process with CVD graphene transferred on to silicon-oxide and followed by standard thin film and subsequent photolithographic processes. The measurement results confirm the effectiveness of dynamic ambipolar gate modulation technique in producing low offset of -524 μT in conjunction with three orders of magnitude estimated improvement in the low frequency noise performance.