Detection of a Micron-Sized Magnetic Particle Using InSb Hall Sensor

We present our results on the realization of ultra-sensitive and non-invasive magnetic sensors based on double-cross InSb Hall bars with dimensions down to 1.5 mum. Hall sensors were patterned from an epitaxial InSb film characterized by the carrier concentration of 3.9 times 10
¹⁶
cm
^-3
and high carrier mobility of 1.3 m
²
/Vs. We study noise characteristics and magnetotransport properties of Hall sensors as well as their performance with respect to the lateral dimensions of devices. The adjacent crosses are characterized by very similar transport properties, which make them suitable for single magnetic particle detection. The high Hall coefficient, R
_H
les 1000 V/AT, was measured for all devices. The white noise spectral density is of the order of 80 nV/radic Hz providing room-temperature magnetic field sensitivity better than 0.5 muT/ radic Hz. We demonstrate that micron-sized InSb Hall sensors can be successfully used for detection of a single paramagnetic bead with the diameter of 1 mu m. We also model the response of the Hall sensor to an inhomogeneous magnetic field caused by the presence of a magnetic bead.