Growth, structure and phase transitions of epitaxial nanowires of III-V semiconductors

Abstract

Abstract. We review and illustrate the impact of TEM on the study of nanowires of nonnitride III-V semiconductors, with particular emphasis on the understanding of the thermodynamics and kinetics of their formation assisted by nano-sized catalyst particles. Besides providing basic information about the morphology of the nanowires and their growth rate as a function of diameter, TEM offers insights into the peculiar crystalline structure that they adopt. We discuss the formation of the unusual wurtzite hexagonal crystalline phase and that of planar stacking defects in these nanowires and show that they are kinetically controlled. We also demonstrate the transformation of wurtzite into cubic sphalerite upon epitaxial burying of the nanowires. Nanowires are particularly interesting in that they allow the fabrication of precisely positioned quantum dots with well-defined geometries. In this respect, we discuss the formation of strained quantum-size inclusions in nanowires, their critical dimensions and the kinetic and thermodynamic factors governing the changes of the crystalline structure that sometimes occur around a hetero-interface.

Phase Transformation in Radially Merged Wurtzite GaAs Nanowires

“…Phase transformation of grown GaAs NWs has been observed previously, where 2H structure epitaxially buried in planar 3C overgrowth gradually adopted the structure of the burying layer. 18 , 19 Phase transformation has also been observed in InGaAs NWs, using an electron beam to deliver a high energy dose to the structure, enough to transform 2H to a mixed 3C/2H structure. 20 In the case of epitaxial burying, one layer at a time of the metastable 2H is gradually surrounded with a layer of the stable 3C structure.…”

Tunable Polarity in a III–V Nanowire by Droplet Wetting and Surface Energy Engineering

“…Since the pioneering works on semiconductor micro/nanowires spanning from the mid‐1960s to the early 2000s, the field of nanowire research has expanded exponentially to include numerous applications, supported by constant progress in the understanding of their fundamental growth mechanisms . Metal‐seeded III–V nanowires is an important group within the semiconductor nanowire family thanks to the maturity reached in terms of controlled growth, offering excellent properties of these materials, such as high carrier mobility, superior optical properties, and the possibility of band gap engineering …”

Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires

“…In contrast, most studies which find predominantly WZ structure find a contact angle close to 90°(in cases where contact angle was shown or reported) 7,12,34,35 . In addition, a number of studies also found a greater density of ZB defects/regions near the foot of nanowires 12,16,36,37 . This is likely due to the fact that during the initial stages of nanowire growth the contact angle is much less than 90°, since the catalysing droplet is situated on a flat surface and the angle α in equation 2 is therefore equal to zero.…”