Free standing modulation doped core–shell GaAs/AlGaAs hetero‐nanowires

Spirkoska, D.; Morral, Anna Fontcuberta i; Dufouleur, Joseph; Xie, Qian; Abstreiter, G.

doi:10.1002/pssr.201105338

Cited by 31 publications

(42 citation statements)

References 21 publications

(18 reference statements)

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“…Figure 1 show the schematics of a prototypical GaAs/AlGaAs radial heterojunction. A GaAs nanowire, which typically grows along the [111] direction radially exposing the six {110} facets, is epitaxially overgrown by an AlGaAs shell, 13 including a doping layer, 14 and a GaAs capping layer, which protects the AlGaAs layer from oxidation. 15 Surface states of the outer GaAs layer, which lie about the midgap energy, easily deplete the outer layers of the structure, and an electron gas may form at the inner GaAs/AlGaAs hetero-interface.…”

Section: Introductionmentioning

confidence: 99%

Landau levels, edge states, and magnetoconductance in GaAs/AlGaAs core-shell nanowires

2013

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Magnetic states of the electron gas confined in modulation-doped core-shell nanowires are calculated for a transverse field of arbitrary strength and orientation. Magneto-conductance 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 selfconsistent 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 magneto-resistance. The predicted marked anisotropy of the magneto-conductance with field direction is a direct probe of the inhomogeneous electron gas localization of the conductive channel induced by the prismatic geometry.

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Section: Introductionmentioning

confidence: 99%

Landau levels, edge states, and magnetoconductance in GaAs/AlGaAs core-shell nanowires

2013

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“…[http://dx.doi.org/10.1063/1.4896505] Nanowires (NWs) with core-shell heterostructures are receiving much attention since their unique optical properties have some potential applications, [1][2][3][4][5][6][7] in particular, because these heterostructures take up a large volume fraction of the entire NW. 8,9 Obviously, the precise control of interfaces and chemical compositions at nano-scale level is very important for such three-dimensional (3D) structures.…”

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confidence: 99%

Plan-view transmission electron microscopy investigation of GaAs/(In,Ga)As core-shell nanowires

Grandal

Kong

et al. 2014

Applied Physics Letters

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Plan-view transmission electron microscopy in combination with electron energy-loss spectroscopy have been used to analyze the strain and the chemical composition of GaAs/(In,Ga)As core-shell nanowires. The samples consist of an GaAs core and a radially arranged (In,Ga)As layer as quantum well and GaAs outer-shell. The nominal parameters of the quantum well in the two samples under investigation are: an indium concentration of 25% and a quantum well thickness of 22 nm and 11 nm, respectively, while the core and the external shell dimensions are fixed. Scanning transmission electron microscopy using high-angle annular dark field detector was performed to verify the actual dimensions of the layers. Geometric phase analysis was carried out in order to examine the local strain of the radial (In,Ga)As quantum well, while the local chemical composition was determined by means of spatially resolved electron energy-loss spectroscopy. Finite elements calculations were carried out in order to simulate the multi-shell structure and extract the actual strain distribution. The results indicate that there is a uniform strain distribution at the coherent interfaces. In addition, based on calculations, we show that there is no region in the considered core-shell structure absolutely free of strain.

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“…An elegant solution of this problem is to epitaxially coat the nanowire by a shell semiconductor with a higher energy band gap. [3][4][5][6][7][8][9][10] Here, AlGaAs is the perfectly suitable shell material as it supplies charge carriers to the GaAs core by modulation doping [10][11][12] as well as preserves the carriers from the direct influence of the surface defects without additionally introduced strain due to the lattice matching between GaAs and AlGaAs.…”

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confidence: 99%

Preparation of Ohmic contacts to GaAs/AlGaAs-core/shell-nanowires

Wirths

Mikulics

Heintzmann

et al. 2012

Applied Physics Letters

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Ohmic contacts to GaAs/AlGaAs core/shell nanowires are prepared by using a Ni/AuGe/Ni/Au layer system. In contrast to Ohmic contacts to planar GaAs/AlGaAs layer systems here, relatively low alloying temperatures are used in cylindrical geometry. Lowest resistances are found for annealing temperatures of 320 °C and 340 °C. For annealing temperatures exceeding 360 °C, the nanowires degraded completely. Nanowires annealed under optimized conditions preserved their Ohmic characteristics even down to temperatures of 4 K.

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Free standing modulation doped core–shell GaAs/AlGaAs hetero‐nanowires

Cited by 31 publications

References 21 publications

Landau levels, edge states, and magnetoconductance in GaAs/AlGaAs core-shell nanowires

Landau levels, edge states, and magnetoconductance in GaAs/AlGaAs core-shell nanowires

Plan-view transmission electron microscopy investigation of GaAs/(In,Ga)As core-shell nanowires

Preparation of Ohmic contacts to GaAs/AlGaAs-core/shell-nanowires

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