High Mobility One- and Two-Dimensional Electron Systems in Nanowire-Based Quantum Heterostructures

Abstract

Free-standing semiconductor nanowires in combination with advanced gate-architectures hold an exceptional promise as miniaturized building blocks in future integrated circuits. However, semiconductor nanowires are often corrupted by an increased number of close-by surface states, which are detrimental with respect to their optical and electronic properties. This conceptual challenge hampers their potentials in high-speed electronics and therefore new concepts are needed in order to enhance carrier mobilities. We have introduced a novel type of core-shell nanowire heterostructures that incorporate modulation or remote doping and hence may lead to high-mobility electrons. We demonstrate the validity of such concepts using inelastic light scattering to study single modulation-doped GaAs/Al0.16Ga0.84As core-multishell nanowires grown on silicon. We conclude from a detailed experimental study and theoretical analysis of the observed spin and charge density fluctuations that one- and two-dimensional electron channels are formed in a GaAs coaxial quantum well spatially separated from the donor ions. A total carrier density of about 3 × 10(7) cm(-1) and an electron mobility in the order of 50,000 cm(2)/(V s) are estimated. Spatial mappings of individual GaAs/Al0.16Ga0.84As core-multishell nanowires show inhomogeneous properties along the wires probably related to structural defects. The first demonstration of such unambiguous 1D- and 2D-electron channels and the respective charge carrier properties in these advanced nanowire-based quantum heterostructures is the basis for various novel nanoelectronic and photonic devices.

Aharonov-Bohm oscillations and electron gas transitions in hexagonal core-shell nanowires with an axial magnetic field

“…2(b)] shows that charge is exclusively accumulated in the InAs shell and preferentially localized at the corners of the hexagonal section. As reported for several core-(multi)shell hexagonal NWs [21][22][23]34], such distribution is favored by Coulomb interactions, which tend to increase the interelectron distance. In Fig.…”

“…Strong anisotropy-induced effects are predicted in this case, such as negative magnetoresistance in a transverse magnetic field [24] and symmetry-induced cancellation of the AB effect in hexagonal quantum rings [25]. The inhomogeneous electron gas localization was crucially exposed in the recent observation of intra-and interband excitations [23,26].…”

“…Such approximations are particularly severe in radial heterostructures, where coupling between the discrete (hexagonal in InAs or GaAs) symmetry and many-electron interactions leads to strongly inhomogeneously distributed electron gas and, in turn, to the coexistence of one-dimensional (1D) and 2D channels at the corners and facets of the hexagonal heterointerfaces [21][22][23]. Strong anisotropy-induced effects are predicted in this case, such as negative magnetoresistance in a transverse magnetic field [24] and symmetry-induced cancellation of the AB effect in hexagonal quantum rings [25].…”

Magnetophotoluminescence in GaAs/AlAs core-multishell nanowires: A theoretical investigation

“…Long single-crystal defect-free cores [6,7], selective radial doping [8], and lateral overgrowth with high-quality interfaces [9] have been successfully realized. Most importantly, complex radial modulation doped heterostructures are now being engineered in coremultishell NWs [10][11][12][13]. More complex than their planar counterparts, radial heterostructures in these systems may host high-mobility electron/hole gases with an inhomogeneous localization in the section of the NW, which strongly depends on doping density and gate potentials [14][15][16].…”

Electron-electron interactions, topological phase, and optical properties of a charged artificial benzene ring

“…However, the weak localization resulted in features different from what is expected in a benzene ring, for example, the five-electron ground state was not doubly degenerate. Recently, Funk et al [53] demonstrated confinement of electrons in six one-dimensional electron channels localized at the six corners of a hexagonal core shell nanowire. If one was to fabricate a wrap-around gate, shown in Fig.…”