Quantum Transport and Sub-Band Structure of Modulation-Doped GaAs/AlAs Core-Superlattice Nanowires.

Modulation-doped III-V semiconductor nanowire (NW) heterostructures have recently emerged as promising candidates to host high-mobility electron channels for future high-frequency, low-energy transistor technologies. The one-dimensional geometry of NWs also makes them attractive for studying quantum confinement effects. Here, we report correlated investigations into the discrete electronic sub-band structure of confined electrons in the channel of Si δ-doped GaAs-GaAs/AlAs core-superlattice NW heterostructures and the associated signatures in low-temperature transport. On the basis of accurate structural and dopant analysis using scanning transmission electron microscopy and atom probe tomography, we calculated the sub-band structure of electrons confined in the NW core and employ a labeling system inspired by atomic orbital notation. Electron transport measurements on top-gated NW transistors at cryogenic temperatures revealed signatures consistent with the depopulation of the quasi-one-dimensional sub-bands, as well as confinement in zero-dimensional-like states due to an impurity-defined background disorder potential. These findings are instructive toward reaching the ballistic transport regime in GaAs-AlGaAs based NW systems.