Growth Mechanism of Truncated Triangular III–V Nanowires

Abstract

What's in a wire? To determine the fundamental reason for obtaining tapered nanowires, GaAs nanowires were grown on {111}B GaAs substrates. Their novel structural characteristics (e.g., a truncated triangular cross section at the base of the nanowires; see image) were carefully investigated using high‐resolution SEM and various TEM techniques. Based on the obtained structural characteristics of these nanowires and the growth environment, an asymmetrical lateral‐growth mechanism has been identified.

Polarity driven formation of InAs/GaAs hierarchical nanowire heterostructures

“…According to crystallography, the zinc-blende structure possesses polarity ͓i.e., ͑h , k , l͒ ͑h , k , l͔͒, leading to the six ͕112͖ possible sidewalls dividing into two sets of equivalent ͕112͖ atomic planes ͓i.e., ͕112͖ A and ͕112͖ B ͔ and they appear alternately in the six ͕112͖ sidewalls. 19 The triangular morphology of InAs on the alternating ͕112͖ sidewalls, as shown in Fig. 2͑d͒, suggests that InAs preferentially grew on either the ͕112͖ A or the ͕112͖ B facets.…”

“…1͑c͒, the nanowires are tapered due to the radial growth. 18,19 However, based on our previous study, 19 the initially grown GaAs nanowires can have equilateral hexagonal cross sections at the top region of the nanowires, i.e., before radial growth took place. 18 It is anticipated that when the InAs growth starts, InAs can contribute to the radial growth on sidewalls of nanowires with hexagonal cross sections.…”

“…Due to the difference in the polarity of III-V nanowires' sidewalls, different faceting behaviors can be observed, depending on the growth conditions. 18,19 For example, GaAs nanowires grown in arsenic rich conditions show rapid radial growth on ͕112͖ A facets than ͕112͖ B facets of the nanowire sidewalls, 19 although this radial growth can be restricted by reducing the growth temperature. 20 However, if this radial growth phenomenon can be intentionally adopted in the growth of radial nanowire heterostructures, it is possible to design nanowire heterostructures with extraordinary structural characteristics.…”

“…Since nanowires grew along the ͓111͔ direction and since stacking faults ͓several were shown in Fig. 2͑a͔͒ cannot change this polarity, 19 we can then uniquely determine the ͑111͒ ‫ء‬ diffraction spot in Fig. 2͑f͒.…”

Evolution of InAs branches in InAs∕GaAs nanowire heterostructures

“…10 The vapor-liquid-solid ͑VLS͒ mechanism, using metal nanoparticles ͑NPs͒ as nucleation sites, is a commonly used process for semiconductor NW growth, in which Au NPs have been generally used in this process. [11][12][13] This mechanism offers the flexibility to produce axial and radial NW heterostructures, 12,13 which can be achieved by varying the vapor chemistry during NWs growth. 13 Attainment of lateral lattice relaxation of misfit strain due to the smaller growth area is an inherent advantage of axial NW heterostructures, which enables the integration of high lattice mismatch materials with few or without misfit dislocations.…”