  Recent advances in bottom-up growth are giving rise to a range of new
two-dimensional nanostructures. Hall effect measurements play an important role
in their electrical characterization. However, size constraints can lead to
device geometries that deviate significantly from the ideal of elongated Hall
bars with currentless contacts. Many devices using these new materials have a
low aspect ratio and feature metal Hall probes that overlap with the
semiconductor channel. This can lead to a significant distortion of the current
flow. We present experimental data from InAs 2D nanofin devices with different
Hall probe geometries to study the influence of Hall probe length and width. We
use finite-element simulations to further understand the implications of these
aspects and expand the scope to contact resistance and sample aspect ratios.
Our key finding is that invasive probes lead to a significant underestimation
in the measured Hall voltage, typically of the order of 40-80%. This in turn
leads to a subsequent proportional overestimation of carrier concentration and
an underestimation of mobility
