Abstract
Magnetic states of the electron gas confined in modulation-doped core-shell nanowires are calculated for a transverse field of arbitrary strength and orientation. Magnetoconductance is predicted within the Landauer approach. The modeling takes fully into account the radial material modulation, the prismatic symmetry, and the doping profile of realistic GaAs/AlGaAs devices within an envelope-function approach, and electron-electron interaction is included in a mean-field self-consistent approach. Calculations show that in the low free-carrier density regime, magnetic states can be described in terms of Landau levels and edge states, similar to planar two-dimensional electron gases in a Hall bar. However, at higher carrier density, the dominating electron-electron interaction leads to a strongly inhomogeneous localization at the prismatic heterointerface. This gives rise to a complex band dispersion, with local minima at finite values of the longitudinal wave vector, and a region of negative magnetoresistance. The predicted marked anisotropy of the magnetoconductance with field direction is a direct probe of the inhomogeneous electron gas localization of the conductive channel induced by the prismatic geometry.
Highlights
Modulated semiconductor heterostructures, realized from core-(multi)shell nanowires (CSNWs),1–5 offer new perspectives in quantum electronics.6 Several crucial steps have been taken toward the realization of high-mobility devices based on this new class of nanomaterials and their integration.7 Single-crystal, defect-free cores using several III-V’s,8,9 selective radial doping,10 high-quality interfaces,11 and integration with Si substrates12 have been realized.Figure 1 shows the schematics of a prototypical GaAs/AlGaAs radial heterojunction
We report self-consistent field calculations of realistic CSNWs subjected to a transverse magnetic field in the quantum Hall regime
Electron-electron interaction leads to strongly inhomogeneous localization and is responsible for the stability of the 2DEG in presence of strong magnetic fields
Summary
Modulated semiconductor heterostructures, realized from core-(multi)shell nanowires (CSNWs), offer new perspectives in quantum electronics. Several crucial steps have been taken toward the realization of high-mobility devices based on this new class of nanomaterials and their integration. Single-crystal, defect-free cores using several III-V’s,8,9 selective radial doping, high-quality interfaces, and integration with Si substrates have been realized. Surface states of the outer GaAs layer, which lie about the midgap energy, deplete the outer layers of the structure, and an electron gas may form at the inner GaAs/AlGaAs heterointerface.4 Such radial modulation-doped heterojunctions can host a high-mobility electron gas, to high-mobility twodimensional electron gases (2DEGs), but wrapped around the core. Electronic states showing localization patterns in a similar fashion to this last regime have been recently demonstrated in two separate works on radially heterostructured hexagonal NWs, both combining optical measurements with theoretical simulations. In these studies, the strong localization effects arise from the spatial confinement occurring in narrow coaxial quantum wells. The ensuing negative magnetoresistance and the marked anisotropy of the magnetoconductance with respect to field direction are a direct probe of the inhomogeneous electron gas localization of the conductive channel
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