Realistic multiband k.p approach from ab initio and spin-orbit coupling effects of InAs and InP in wurtzite phase

TL;DR

This paper develops an accurate 8x8 k.p model for InAs and InP wurtzite phase semiconductors, incorporating spin-orbit effects, to facilitate the study of their electronic and spin properties in nanostructures.

Contribution

The study provides the first robust, fitted 8x8 k.p Hamiltonian for wurtzite InAs and InP, including spin-orbit coupling, based on ab initio calculations, enabling easier analysis of their physical properties.

Findings

The k.p model accurately reproduces ab initio band structures.

Spin splitting effects are captured with k-dependent spin-orbit terms.

The 8x8 Hamiltonian is more reliable than the 6x6 for these materials.

Abstract

Semiconductor nanowires based on non-nitride III-V compounds can be synthesized under certain growth conditions to favor the appearance of wurtzite crystal phase. Despite the reports in literature of ab initio band structures for these wurtzite compounds, we still lack effective multiband models and parameter sets that can be simply used to investigate physical properties of such systems, for instance, under quantum confinement effects. In order to address this deficiency, in this study we calculate the ab initio band structure of bulk InAs and InP in wurtzite phase and develop an 8$\times$8 k.p Hamiltonian to describe the energy bands around $\Gamma$ point. We show that our k.p model is robust and can be fitted to describe the important features of the ab initio band structure. The correct description of the spin splitting effects that arise due to the lack of inversion symmetry in wurtzite crystals, is obtained with the $k$-dependent spin-orbit term in the Hamiltonian, often neglected in the literature. All the energy bands display a Rashba-like spin texture for the in-plane spin expectation value. We also provide the density of states and the carrier density as functions of the Fermi energy. Alternatively, we show an analytical description of the conduction band, valid close to $\Gamma$ point. The same fitting procedure is applied to the 6$\times$6 valence band Hamiltonian. However, we find that the most reliable approach is the 8$\times$8 k.p Hamiltonian for both compounds. The k.p Hamiltonians and parameter sets that we develop in this paper provide a reliable theoretical framework that can be easily applied to investigate electronic, transport, optical, and spin properties of InAs- and InP-based nanostructures.