Epitaxial core–shell and core–multishell nanowire heterostructures

Abstract

Semiconductor heterostructures with modulated composition and/or doping enable passivation of interfaces and the generation of devices with diverse functions. In this regard, the control of interfaces in nanoscale building blocks with high surface area will be increasingly important in the assembly of electronic and photonic devices. Core-shell heterostructures formed by the growth of crystalline overlayers on nanocrystals offer enhanced emission efficiency, important for various applications. Axial heterostructures have also been formed by a one-dimensional modulation of nanowire composition and doping. However, modulation of the radial composition and doping in nanowire structures has received much less attention than planar and nanocrystal systems. Here we synthesize silicon and germanium core-shell and multishell nanowire heterostructures using a chemical vapour deposition method applicable to a variety of nanoscale materials. Our investigations of the growth of boron-doped silicon shells on intrinsic silicon and silicon-silicon oxide core-shell nanowires indicate that homoepitaxy can be achieved at relatively low temperatures on clean silicon. We also demonstrate the possibility of heteroepitaxial growth of crystalline germanium-silicon and silicon-germanium core-shell structures, in which band-offsets drive hole injection into either germanium core or shell regions. Our synthesis of core-multishell structures, including a high-performance coaxially gated field-effect transistor, indicates the general potential of radial heterostructure growth for the development of nanowire-based devices.

An Enhanced UV–Vis–NIR an d Flexible Photodetector Based on Electrospun ZnO Nanowire Array/PbS Quantum Dots Film Heterostructure

“…Some works have been done to broaden the response of ZnO from UV to wider range 13, 14, 15, 16, 17, 18, 19, 20. For example, Kouklin15 doped Cu impurities into ZnO NWs, which results in orders of magnitude enhancement of the spectral sensitivity over both UV and vis spectral ranges.…”

“…ZnO/Si branched NWs heterojunction photodiodes via growing ZnO nanowires on p‐type Si substrate show a 12.8 mA W −1 responsivity at around 900 nm 17. However, the doped structures have flaws in stability and reproducibility especially for p‐type doping,18 and the synthesis process for core–shell usually involves a complex adjustment and also the lattice matching should be considered for this structure 19, 20…”

Ferromagnetic GaAs/GaMnAs Core−Shell Nanowires Grown by Molecular Beam Epitaxy

“…This concept is known in particular in the context of surface passivation to improve the optical and electrical properties in various NW based devices such as NW lasers and NW field effect transistors. 1,[23][24][25][26] In a first growth step we generate GaAs NWs as nonmagnetic templates, followed by LT-MBE growth of a GaMnAs shell on the NW sidewalls. Our approach can be of course expanded to the growth of other III-Mn-V nanowire structures (e.g., InMnSb nanotubes on InSb or CdTe NWs templates) but also to semiconductor/metallic NW heterostructures such as Fe nanotubes grown on lattice matched GaAs NWs or magnetite core-shell NWs as shown by Zhang et al 27 Here we report for the first time the successful integration of a GaMnAs shell in a radial NW heterostructure.…”

Electric and magnetic field effects on the excitonic properties of elliptic core–multishell quantum wires

“…Many research groups have used various growth techniques to synthesize quantum wires composed of two different semiconductor materials, forming several types of wire, for example i) core-shell wires, i.e. a strand of a semiconductor material covered by a layer of another semiconductor material, ii) coremultishell structures, where a wire is covered by a sequence of layers of other materials, and iii) superlattice nanowires, where a longitudinal superlattice is built by stacking cylindrical blocks of different semiconductor materials [4,5,6,7], just to mention a few. Photoluminescence experiments on GaAs/AlGaAs [8,9] and InAs/InP [10,11] core-shell quantum wires have been recently reported, where quantum confinement of the carriers is observed with energies that are in good agreement with theoretical predictions.…”