Band gaps of long-period polytypes of IV, IV-IV, and III-V semiconductors estimated with an Ising-type additivity model

TL;DR

This study develops an Ising-type model to accurately estimate band gaps of various polytypes in IV, IV-IV, and III-V semiconductors, enabling predictions for complex structures where first-principles calculations are difficult.

Contribution

The paper introduces a novel additivity model that predicts band gaps of long-period polytypes with high accuracy, extending beyond computationally intensive first-principles methods.

Findings

Four models estimate band gaps with less than 0.05 eV error.

Predicted wide band gap (>3.4 eV) for a new SiC polytype 15R(1).

Identified metastable 15R(1)-SiC through stability analysis.

Abstract

We apply an Ising-type model to estimate the band gaps of the polytypes of group IV elements (C, Si, and Ge) and binary compounds of groups: IV-IV (SiC, GeC, and GeSi), and III-V (nitride, phosphide, and arsenide of B, Al, and Ga). The models use reference band gaps of the simplest polytypes comprising 2--6 bilayers calculated with the hybrid density functional approximation, HSE06. We report four models capable of estimating band gaps of nine polytypes containing 7 and 8 bilayers with an average error of $\lesssim0.05$ eV. We apply the best model with an error of $<0.04$ eV to predict the band gaps of 497 polytypes with up to 15 bilayers in the unit cell, providing a comprehensive view of the variation in the electronic structure with the degree of hexagonality of the crystal structure. Within our enumeration, we identify four rhombohedral polytypes of SiC -- 9$R$, 12$R$, 15$R$(1), and 15$R$(2) -- and perform detailed stability and band structure analysis. Of these, 15$R$(1) that has not been experimentally characterized has the widest band gap ($>3.4$ eV); phonon analysis and cohesive energy reveal 15$R$(1)-SiC to be metastable. Additionally, we model the energies of valence and conduction bands of the rhombohedral SiC phases at the high-symmetry points of the Brillouin zone and predict band structure characteristics around the Fermi level. The models presented in this study may aid in identifying polytypic phases suitable for various applications, such as the design of wide-gap materials, that are relevant to high-voltage applications. In particular, the method holds promise for forecasting electronic properties of long-period and ultra-long-period polytypes for which accurate first-principles modeling is computationally challenging.