Multifunctional sensors operating at 300 K based on quasi-ballistic InSb quantum well nanostructures

The high mobility ($\mu )$ of InSb quantum well (QW) heterostructures at 300 K makes them ideally suited for both magnetic and optical sensing. While macroscopic InSb Hall sensors offer the best magnetic sensitivity at 300 K of any material, the operation of sub-micron InSb QW Hall probes have not been reported. Ballistic transport at 300 K in nano-InSb devices was recently described [1]. Here we report the 300 K sensing properties of InSb QW structures fabricated into scanning probe geometries operating in the photoconductive (PC), Hall, and magnetoconductive modes. Sub-micron InSb QW probes exhibit excellent magnetic sensitivity \textless 1$\mu $T/$\surd $Hz and are demonstrated in a scanning Hall probe measurement. InSb QWs exhibit long lived negative photoconductivity in the visible to near-IR for cw excitation, however, significant improvements in dynamic response are found with ac modulated techniques. From spatially resolved PC measurements we determine $\mu \tau $ $\sim$ 3.5 x10$^{-3}$ cm$^{2}$/V. These results provide a benchmark for developing novel InSb QW-metal hybrid nanosensors [2].\\[4pt] [1] A.M. Gilbertson et al., \textit{Appl. Phys.Lett.} \textbf{99}, 242101 (2011)\\[0pt] [2] A.K.M. Newaz et al., \textit{Appl. Phys. Lett.} \textbf{97}, 082105 (2010)