Impact of invasive metal probes on Hall measurements in semiconductor nanostructures

Abstract: 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