Effect of wetting layers on the strain and electronic structure of InAs self-assembled quantum dots

Abstract

The effect of wetting layers on the strain and electronic structure of InAs self-assembled quantum dots grown on GaAs is investigated with an atomistic valence-force-field model and an empirical tight-binding model. By comparing a dot with and without a wetting layer, we find that the inclusion of the wetting layer weakens the strain inside the dot by only 1% relative change, while it reduces the energy gap between a confined electron and hole level by as much as 10%. The small change in the strain distribution indicates that strain relaxes only little through the thin wetting layer. The large reduction of the energy gap is attributed to the increase of the confining-potential width rather than the change of the potential height. First-order perturbation calculations or, alternatively, the addition of an InAs disk below the quantum dot confirm this conclusion. The effect of the wetting layer on the wave function is qualitatively different for the weakly confined electron state and the strongly confined hole state. The electron wave function shifts from the buffer to the wetting layer, while the hole shifts from the dot to the wetting layer.

Electronic structure of self-assembledInAs∕InPquantum dots: Comparison with self-assembledInGong1, Duan2, Li3 et al. 2008Phys. Rev. B

“…For example, a k·p theory predicted small (∼ 1 meV) hole p-p splitting for both types of dots. 12,46,47 The difference in the hole splitting for the two types of dots might comes from their different strain profiles, the band offset, or the interface effects (common cation vs. common anion). We leave this for future investigations.…”

Tight-binding model for semiconductor nanostructures

“…More sophisticated ways to treat the scaling of the interatomic matrix elements, e.g. by calculating the dependence of energy bands on volume effects and different exponents for different orbitals, can be found in the literature 35,41,56 . Furthermore the results of Bertho et al 57 for the calculations of hydrostatic and uniaxial deformation potentials in case of ZnSe show that the d…”

“…Simple model studies based on the effective mass approximation 15,22 or a multi-band k · pmodel 23,24,25 describe the QD by a confinement potential caused by the band offsets, for instance; they give qualitative insights into the formation of bound (hole and electron) states, but they are too crude for quantitative, material specific results or predictions. More suitable for a microscopic description are empirical pseudopotential methods 26,27,28,29 as well as empirical tight-binding models 30,31,32,33,34,35,36,37,38,39,40,41 . The empirical pseudopotential methods allow for a detailed variation of the wave functions on the atomic scale.…”

Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

“…The simulations were performed using well-known NanoElectronic MOdeling (NEMO 3-D) simulator [21,22], in which the strain is computed from atomistic Valence Force Field (VFF) model [23][24][25] and the electronic structure is computed by solving twenty-band sp 3 d 5 s * tight-binding Hamiltonian [26]. The polarization dependent interband optical transition strengths (TE and TM modes) are calculated using Fermi's Golden Rule [3,27].…”