The conduction band non-parabolicity of degenerate AZO semiconductors: k.p method

We present a discussion regarding the conduction band non-parabolicity and the Fermi energy of Al doped ZnO (AZO) degenerate semiconductors using the higher orders of Fermi–Dirac (F-D) integrals. We find an analytical expression for Fermi energy, based on two-band k.p theory and modified Boltzmann's classical equation. We examine the accuracy of resulted expression using absolute error value.

CdTe/PbTe Superlattice Energy Bands Analysis Using k.p Method

A model based on the k.p perturbation theory to compute the energy bands in a CdTe/PbTe superlattice structure is developed. The model uses the dispersion relations for the heavy hole, light hole and the split off bands to compute the effective bandgap in a CdTe/PbTe superlattice structure. Given a certain thickness of the layers composing the superlattice the model computes the effective bandgap. This model will be used towards understanding the relationship between film thickness and optical bandgaps in a CdTe/PbTe superlattice. The end goal is to tailor the optical bandgap of a CdTe/PbTe superlattice to result in maximum efficiency when used in a solar cell.

Dirac-Like Cones at Low-Symmetry Points in Phononic Crystals

Many of graphene’s interesting properties originate from its unique dispersion relations around the K point, a high symmetry point in the Brillouin zone (BZ), where two bands cross over each other linearly. In this paper, we study the Dirac-cone-like dispersion relations around the low symmetry points in the BZ of a classical system, i.e., a2D phononic crystal consisting of a triangular array of square-shaped cylinders embedded in water host. We find that the linear dispersions around the degenerate point form a tilted and anisotropic cone, which means not only that the band slopes can be quite different along different k directions, but also that even for the same k direction, the band slopes above and below the degenerate frequency can be very different. The anisotropic behavior in the reciprocal space can be understood in terms of the effective Hamiltonian, which is constructed from the eigenstates at that degenerate point. In addition, the linear slopes of the Dirac-cone-like dispersions along any direction can be accurately predicted by the k.p method and the results of which agree very well with the rigorous band structure calculations. Based on the peculiar anisotropic band structures, some interesting acoustic wave transmission phenomena are investigated.