Twinning superlattices in indium phosphide nanowires

Abstract

Semiconducting nanowires offer the possibility of nearly unlimited complex bottom-up design, which allows for new device concepts. However, essential parameters that determine the electronic quality of the wires, and which have not been controlled yet for the III-V compound semiconductors, are the wire crystal structure and the stacking fault density. In addition, a significant feature would be to have a constant spacing between rotational twins in the wires such that a twinning superlattice is formed, as this is predicted to induce a direct bandgap in normally indirect bandgap semiconductors, such as silicon and gallium phosphide. Optically active versions of these technologically relevant semiconductors could have a significant impact on the electronics and optics industry. Here we show first that we can control the crystal structure of indium phosphide (InP) nanowires by using impurity dopants. We have found that zinc decreases the activation barrier for two-dimensional nucleation growth of zinc-blende InP and therefore promotes crystallization of the InP nanowires in the zinc-blende, instead of the commonly found wurtzite, crystal structure. More importantly, we then demonstrate that we can, once we have enforced the zinc-blende crystal structure, induce twinning superlattices with long-range order in InP nanowires. We can tune the spacing of the superlattices by changing the wire diameter and the zinc concentration, and we present a model based on the distortion of the catalyst droplet in response to the evolution of the cross-sectional shape of the nanowires to quantitatively explain the formation of the periodic twinning.

Raman spectroscopy of wurtzite and zinc-blende GaAs nanowires: Polarization dependence, selection rules, and strain effects

“…It is found under special conditions such as high pressures and in the nanoscale form such as nanoparticles and nanowires. [37][38][39][40][41][42] To our knowledge, the phonon spectrum of wurtzite GaAs has not been calculated or measured yet. As it has been shown in the case of GaN and SiC, the main characteristics of the phonon dispersion of wurtzite GaAs can be deduced in an approximated way thanks to the straight forward relation between the two structures.…”

In-Situ Analysis of Optoelectronic Properties of Semiconductor Nanostructures and Defects in Transmission Electron Microscopes

“…Such quantum nanostructures have potentials for enhancing the device performance, and also their electron confinement produces quantum electronic states which provide an important system for fundamental physics. Recently, superlattices based on periodic changes of crystal directions, i.e., twinning superlattices (Ikonic et al, 1993), have been proposed in III-V (Xiong & Eklund, 2006, Ohno et al, 2007b, Algra et al, 2008, Bao et al, 2008, II-VI (Ikonic et al, 1996), and VI (Hibino et al, 1998, Fissel et al, 2006 semiconductors and in metals (e.g., Kobayashi & Uchihashi, 2010). It is expected that they can offer as much versatility in tailoring the miniband structure as there exists in heterostructure-based superlattices (e.g., Ikonic et al, 1993, Nakamura & Natori, 2006.…”

Gibbs–Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth

“…vs vs inter inter inter ysz (4) where ΔN denotes the increased number of atoms of the growth species, Δμ 0 the supersaturation with infinite radius of curvature, ΔS vs the surface area increase, α vs the surface energy, ΔS inter the interface area increase, α inter the interface energy, and α ysz the surface energy of substrate (YSZ). Hence, the supersaturation in planar NWs is given by On the basis of the geometries of planar NWs shown in Figure 6, the corresponding G−T equations can be derived as…”