Understanding the vapor–liquid–solid growth and composition of ternary III–V nanowires and nanowire heterostructures

Abstract

Based on the recent achievements in vapor–liquid–solid (VLS) synthesis, characterization and modeling of ternary III–V nanowires and axial heterostructures within such nanowires, we try to understand the major trends in their compositional evolution from a general theoretical perspective. Clearly, the VLS growth of ternary materials is much more complex than in standard vapor–solid epitaxy techniques, and even maintaining the necessary control over the composition of steady-state ternary nanowires is far from straightforward. On the other hand, VLS nanowires offer otherwise unattainable material combinations without introducing structural defects and hence are very promising for next-generation optoelectronic devices, in particular those integrated with a silicon electronic platform. In this review, we consider two main problems. First, we show how and by means of which parameters the steady-state composition of Au-catalyzed or self-catalyzed ternary III–V nanowires can be tuned to a desired value and why it is generally different from the vapor composition. Second, we present some experimental data and modeling results for the interfacial abruptness across axial nanowire heterostructures, both in Au-catalyzed and self-catalyzed VLS growth methods. Refined modeling allows us to formulate some general growth recipes for suppressing the unwanted reservoir effect in the droplet and sharpening the nanowire heterojunctions. We consider and refine two approaches developed to date, namely the regular crystallization model for a liquid alloy with a critical size of only one III–V pair at high supersaturations or classical binary nucleation theory with a macroscopic critical nucleus at modest supersaturations.

Full characterization and modeling of graded interfaces in a high lattice-mismatch axial nanowire heterostructure

“…Indeed, interface grading occurs in particle-seeded nanowire systems and is attributed to the solubility of the growth species in the liquid droplet which constitutes a reservoir 40 . This "reservoir effect" can be tuned or suppressed by carefully adjusting the growth parameters and the droplet dimensions to form either sharp or controlled graded interfaces 26,41,42 . In this work, we have grown several nanowire heterostructures with different 𝑅, 𝜀 $ and 𝛼 (growth procedure in Ref 43 and Methods).…”

Tailoring Morphology and Vertical Yield of Self-Catalyzed GaP Nanowires on Template-Free Si Substrates

“…Large surface area to volume ratio enables high sensitivity for sensor applications [ 1 , 3 ]. Small footprint and strain relaxation on sidewalls enable dislocation-free NW epitaxial growth on widely used Si substrates [ 4 ] and open up a route to combine materials with large lattice mismatch in axial or radial NW heterostructures [ 5 ]. In addition that, naturally smooth side facets allow NWs to serve as micro and nano cavities for both Fabry–Perot and whispering gallery modes [ 6 , 7 , 8 ], as well as low-loss optical waveguides [ 9 ].…”

Dynamics of Droplet Consumption in Vapor–Liquid–Solid III–V Nanowire Growth

“…In particular, in order to reduce locally the NW diameter, one can consume partially the droplet during growth. 12,13 Self-catalyzed growth [14][15][16][17][18][19] is a variant of III-V VLS growth, whereby the catalyst droplet contains only the NW elemental constituents, and actually a very large proportion of the group III species. 20 It presents several advantages, such as a reduced risk of contamination of the NW by foreign impurities and the possibility to attain a stationary NW radius.…”