Electronic structures of [1 1 1]-oriented free-standing InAs and InP nanowires

Huang

et al. 2016

Sci Rep

Self Cite

The [111]-oriented InAs/GaSb and GaSb/InAs core-shell nanowires have been studied by the 8 × 8 Luttinger-Kohn Hamiltonian to search for non-vanishing fundamental gaps between inverted electron and hole bands. We focus on the variations of the band-inverted fundamental gap, the hybridization gap, and the effective gap with the core radius and shell thickness of the nanowires. The evolutions of all the energy gaps with the structural parameters are shown to be dominantly governed by the effect of quantum confinement. With a fixed core radius, a band-inverted fundamental gap exists only at intermediate shell thicknesses. The maximum band-inverted gap found is ~4.4 meV for GaSb/InAs and ~3.5 meV for InAs/GaSb core-shell nanowires, and for the GaSb/InAs core-shell nanowires the gap persists over a wider range of geometrical parameters. The intrinsic reason for these differences between the two types of nanowires is that in the shell the electron-like states of InAs is more delocalized than the hole-like state of GaSb, while in the core the hole-like state of GaSb is more delocalized than the electron-like state of InAs, and both favor a stronger electron-hole hybridization.

Section: Resultssupporting

confidence: 85%

Section: Resultssupporting

confidence: 63%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Band-inverted gaps in InAs/GaSb and GaSb/InAs core-shell nanowires

Huang

et al. 2016

Sci Rep

Self Cite

“…[24][25][26][27][28][29] Due to their well organized crystal structures, relatively high carrier mobilities, small cross sections, and strong quantum confinement effects, III-V semiconductor nanowires have been employed to construct field-effect transistors, [30][31][32][33] infrared photodetectors, 34,35 light emission diodes, 36,37 thermal electrical devices, 38,39 laser devices, 40,41 solar cells, [42][43][44][45] and quantum devices. [11][12][13][14][15][16][17][46][47][48][49] Several theoretical methods, including densityfunctional theory, [50][51][52][53] tight-binding methods, [54][55][56][57][58][59][60][61][62][63] and k.p theory, …”

Section: Introductionmentioning

confidence: 99%

k.p theory of freestanding narrow band gap semiconductor nanowires

2016

AIP Advances

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We report on a theoretical study of the electronic structures of freestanding nanowires made from narrow band gap semiconductors GaSb, InSb and InAs. The nanowires are described by the eight-band k.p Hamiltonians and the band structures are computed by means of the finite element method in a mixture basis consisting of linear triangular elements inside the nanowires and constrained Hermite triangular elements near the boundaries. The nanowires with two crystallographic orientations, namely the [001] and [111] orientations, and with different cross-sectional shapes are considered. For each orientation, the nanowires of the three narrow band gap semiconductors are found to show qualitatively similar characteristics in the band structures. However, the nanowires oriented along the two different crystallographic directions are found to show different characteristics in the valence bands. In particular, it is found that all the conduction bands show simple, good parabolic dispersions in both the [001]- and [111]-oriented nanowires, while the top valence bands show double-maximum structures in the [001]-oriented nanowires, but single-maximum structures in the [111]-oriented nanowires. The wave functions and spinor distributions of the band states in these nanowires are also calculated. It is found that significant mixtures of electron and hole states appear in the bands of these narrow band gap semiconductor nanowires. The wave functions exhibit very different distribution patterns in the nanowires oriented along the [001] direction and the nanowires oriented along the [111] direction. It is also shown that single-band effective mass theory could not reproduce all the band state wave functions presented in this work.Comment: 17 pages, 19 figure

“…[9][10][11] For further development and optimization of devices containing nanowires, it is important to clearly understand the electronic structures of the nanowires along common crystallographic directions such as the [001] and [111] directions. Previously, theoretical methods, such as first-principles methods, [12][13][14][15] the k•p method, [16][17][18] pseudopotential methods 19 and tight-binding methods [20][21][22][23][24][25][26][27][28][29] , have been used to study semiconductor nanowires. However, first-principles calculations are impractical for unit cells containing tens of thousands of atoms.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structures of Free-Standing Nanowires made from Indirect Bandgap Semiconductor Gallium Phosphide

Chen

et al. 2016

Sci Rep

Self Cite

We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)—a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the bands show anti-crossing structures, while the bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the conduction bands, while the maximum of the valence bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest conduction bands and the highest valence bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula.