Strain relaxation and ambipolar electrical transport in GaAs/InSb core–shell nanowires

Abstract

The growth, crystal structure, strain relaxation and room temperature transport characteristics of GaAs/InSb core-shell nanowires grown using molecular beam epitaxy are investigated. Due to the large lattice mismatch between GaAs and InSb of 14%, a transition from island-based to layer-like growth occurs during the formation of the shell. High resolution transmission electron microscopy in combination with geometric phase analyses as well as X-ray diffraction with synchrotron radiation are used to investigate the strain relaxation and prove the existence of different dislocations relaxing the strain on zinc blende and wurtzite core-shell nanowire segments. While on the wurtzite phase only Frank partial dislocations are found, the strain on the zinc blende phase is relaxed by dislocations with perfect, Shockley partial and Frank partial dislocations. Even for ultrathin shells of about 2 nm thickness, the strain caused by the high lattice mismatch between GaAs and InSb is relaxed almost completely. Transfer characteristics of the core-shell nanowires show an ambipolar conductance behavior whose strength strongly depends on the dimensions of the nanowires. The interpretation is given based on an electronic band profile which is calculated for completely relaxed core/shell structures. The peculiarities of the band alignment in this situation implies simultaneously occupied electron and hole channels in the InSb shell. The ambipolar behavior is then explained by the change of carrier concentration in both channels by the gate voltage.

Lattice invisibility effect based on transverse Kerker scattering in 1D metalattices

“…As for core@shell structures studied here, it is possible to employ molecular beam epitaxy [48] to achieve the growth of SiO 2 @InSb and Si@InSb MWs, in which the main stages are the growth of SiO 2 (or Si) core and InSb shell in succession. In terms of Si MWs, firstly, since the period's condition and radius of core are strictly required, the electron beam lithography and meta lift-off are suggested to determine the positions and sizes of catalysing metal particles [49] like Au or Cu, which are patterned on an oxide buffered layer thermally grown in Si(1 1 1) wafers.…”

“…In the following, it is feasible to introduce the InSb shell covering the aforementioned Si or SiO 2 core, when the substrate temperature has already been tuned to the growth temperature of InSb. Under proper In rate and Sb flux, the thickness of InSb shell can be designed at will by choosing the growth time reasonably [48,54]. Finally, with all the processes going successfully, it can be expected to obtain 1D SiO 2 @InSb and Si@InSb microwires.…”

Recent Advances in Ambipolar Transistors for Functional Applications

“…In addition, the thickness of the shell can be employed to modulate the electrical behaviors of transistors based on GaAs/InSb core–shell nanowire. Rieger et al demonstrated that the electrical performance of transistors based on GaAs/InSb core–shell nanowire was determined by the energy band of InSb shell rather than GaAs core . They also discovered that Fermi level shift was induced when the thickness of InSb shell gradually changed.…”

Controlling the morphology and wavelength of self-assembled coaxial GaAs/Ga(As)Sb/GaAs single quantum-well nanowires

“…Nevertheless, recent studies have focused on understanding the strain relaxation and morphology transitions in lattice-mismatched core-shell NWs. 20,21 Regulating absorption by regulating the morphology variations in core-shell NWs (e.g. GaP/GaAs 22,23 ) is a promising route for developing novel photovoltaic and optoelectronic devices.…”