Effective-mass theory for superlattices grown on (11N)-oriented substrates

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

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.

Electronic and optical properties of core-shell nanowires in a magnetic field

The electronic and optical properties of zincblende nanowires are investigated in the presence of a uniform magnetic field directed along the [001] growth direction within the k · p method. We focus our numerical study on core-shell nanowires consisting of the III-V materials GaAs, Al(x)Ga(1-x)As and (Al(y)Ga(1-y))₀.₅₁In₀.₄₉P. Nanowires with electrons confined in the core exhibit a Fock-Darwin-like spectrum, whereas nanowires with electrons confined in the shell show Aharonov-Bohm oscillations. Thus, by properly choosing the core and the shell materials of the nanowire, the optical properties in a magnetic field can be tuned in very different ways.

Electronic properties of site-controlled (111)-oriented zinc-blende InGaAs/GaAs quantum dots calculated using a symmetry-adapted k·p Hamiltonian

In this work, we present and evaluate a (111)-rotated eight-band k ⋅p Hamiltonian for the zinc-blende crystal lattice to investigate the electronic properties of site-controlled InGaAs/GaAs quantum dots grown along the [111] direction. We derive the rotated Hamiltonian including strain and piezoelectric potentials. In combination with our previously formulated (111)-oriented continuum elasticity model, we employ this approach to investigate the electronic properties of a realistic site-controlled (111)-grown InGaAs quantum dot. We combine these studies with an evaluation of single-band effective mass and eight-band k ⋅p models, to investigate the capabilities of these models for the description of electronic properties of (111)-grown zinc-blende quantum dots. Moreover, the influence of second-order piezoelectric contributions on the polarization potential in such systems is studied. The description of the electronic structure of nanostructures grown on (111)-oriented surfaces can now be achieved with significantly reduced computational costs in comparison to calculations performed using the conventional (001)-oriented models.

Anisotropic Confinement, Electronic Coupling and Strain Induced Effects Detected by Valence-Band Anisotropy in Self-Assembled Quantum Dots

A method to determine the effects of the geometry and lateral ordering on the electronic properties of an array of one-dimensional self-assembled quantum dots is discussed. A model that takes into account the valence-band anisotropic effective masses and strain effects must be used to describe the behavior of the photoluminescence emission, proposed as a clean tool for the characterization of dot anisotropy and/or inter-dot coupling. Under special growth conditions, such as substrate temperature and Arsenic background, 1D chains of In0.4Ga0.6 As quantum dots were grown by molecular beam epitaxy. Grazing-incidence X-ray diffraction measurements directly evidence the strong strain anisotropy due to the formation of quantum dot chains, probed by polarization-resolved low-temperature photoluminescence. The results are in fair good agreement with the proposed model.

Anisotropic in-plane spin splitting in an asymmetric (001) GaAs/AlGaAs quantum well

The in-plane spin splitting of conduction-band electron has been investigated in an asymmetric (001) GaAs/AlxGa1-xAs quantum well by time-resolved Kerr rotation technique under a transverse magnetic field. The distinctive anisotropy of the spin splitting was observed while the temperature is below approximately 200 K. This anisotropy emerges from the combined effect of Dresselhaus spin-orbit coupling plus asymmetric potential gradients. We also exploit the temperature dependence of spin-splitting energy. Both the anisotropy of spin splitting and the in-plane effective g-factor decrease with increasing temperature.PACS: 78.47.jm, 71.70.Ej, 75.75.+a, 72.25.Fe.