In-plane spectrum in superlattices

Abstract

We show that the existing theory does not give correct in-plane spectrum of superlattices at small in-plane momentum. Magneto-absorption experiments demonstrate that the energy range of the parabolic region of the spectrum near the electron subband bottom is by the order of magnitude lower than the value predicted by the traditional approach. We developed a modified theory according to which the energy range of the parabolic region and carrier in-plane effective masses are determined by the effective bandgap of the superlattice rather than by the bulk bandgaps of the superlattice layers. The results of the new theory are consistent with the experiment

Double well heterostructures for electric modulation of light

“…For calculation of the absorption coefficient and refractive index we use two-band Hamiltonian of the heterostructure where z axis is along the growth direction, the right and left wells occupy regions 1 0 d z − < < and 2 0 z d < < respectively. [23,24] The Hamiltonian includes just the conduction and heavy hole bands because the effect of light holes at the vicinity of the threshold is negligible.…”

Giant $g$-factors and fully spin-polarized states in metamorphic short-period InAsSb/InSb superlattices

“…Such a strong correlation between v F and g ef f suggests that they share a similar physical origin. From our prior works [19,34], we know that v F is determined by an averaged momentum matrix element weighted by the wavefunction overlap between the CB and HH states over the SL layers. The construction of the effective four-band Hamiltonian H from the k • p model (see the Supplementary Information) also reveals that the M 1 parameter is related to another averaged momentum matrix element but weighted by the CB and LH wavefunction overlap.…”

Engineering Dirac Materials: Metamorphic InAs1–xSbx/InAs1–ySby Superlattices with Ultralow Bandgap

“…Another example of semiconductor structure in which zero bandgap can be realized is type II heterostructure with a “broken gap” band alignment in which the effective bandgap is formed by spatially separated electron and hole states. − Type II InAs/GaSb composite quantum wells with zero and inverted bandgaps demonstrate a rich phase diagram containing band insulator and quantum spin Hall insulator states. − The effective bandgap in type II SLs is determined by the thicknesses of the electron and hole containing layers and can be sufficiently different from the bulk bandgaps of the SL layer materials. If the typical width of the SL subbands E S SL in a gapless SL is much larger than the energy scale associated with the in-plane motion E ∥ , the latter can be considered as a perturbation, and the in-plane energy spectrum is similar to that of the gapless bulk material . This condition can also be expressed as: where k ∥ is the in-plane wave vector and d is the SL period .…”

“…If the typical width of the SL subbands E S SL in a gapless SL is much larger than the energy scale associated with the in-plane motion E ∥ , the latter can be considered as a perturbation, and the in-plane energy spectrum is similar to that of the gapless bulk material . This condition can also be expressed as: where k ∥ is the in-plane wave vector and d is the SL period . A short-period SL with zero bandgap can be realized in an InAsSb system.…”

“…To explain qualitatively the experimental results, we used a simple analytical model of two band envelope wave function. , According to this model, the in-plane SL energy spectrum near k ∥ = 0 is similar to this of a Dirac Fermion with the rest energy of E g /2 and Fermi velocity v F . The latter is determined by the structure parameters . The LL energies of electrons and heavy holes can be approximated as: …”