Nano and micro Hall-effect sensors for room-temperature scanning hall probe microscopy
GaAs/AlGaAs two-dimensional electron gas (GaAs-2DEG) Hall probes are impractical for sub-micron room-temperature scanning Hall microscopy (RT-SHPM), due to surface depletion effects that limit the Hall driving current and magnetic sensitivity (Bmin). Nano and micro Hall-effect sensors were fabricated using Bi and InSb thin films and shown to be practical alternatives to GaAs-2DEG probes for high resolution RT-SHPM. The GaAs-2DEG and InSb probes were fabricated using photolithography and the Bi probes by optical and focused ion beam lithography. Surface depletion effects limited the minimum feature size of GaAs-2DEG probes to ∼1.5 μm2 with a maximum drive current Imax of ∼3 μA and Bmin∼0.2 G/Hz. The B min of 1.5 μm2 InSb Hall probes was 6×10 -3 G/Hz at Imax of 100 μA. Further, 200 nm×200 nm Bi probes yielded good RT-SHPM images of garnet films, with Imax and sensitivity of 40 μA and ∼0.80 G/Hz, respectively.