Effective Electronic Structure of Monoclinic $\beta-(Al_xGa_{1-x})_2O_3$ alloy semiconductor

TL;DR

This study calculates the electronic band structure of the $eta-(Al_xGa_{1-x})_2O_3$ alloy system using band unfolding and supercell models to understand disorder effects on electronic properties.

Contribution

It introduces a method combining band unfolding with special quasirandom structures to analyze disordered alloy semiconductors' electronic properties.

Findings

Disorder causes band broadening and affects electron effective mass.

The technique provides insights into disorder-induced scattering and electron lifetimes.

Bandgap and effective mass vary with aluminium concentration.

Abstract

In this article, the electronic band structure $\beta-(Al_xGa_{1-x})_2O_3$ alloy system is calculated with $\beta-Ga_2O_3$ as the bulk crystal. The technique of band unfolding is implemented to obtain the effective bandstructure \textit{(EBS)} for aluminium fractions varying between 12.5\% and 62.5\% with respect to the gallium atoms. A 160 atom supercell is used to model the disordered system that is generated using the technique of special quasirandom structures which mimics the site correlation of a truly random alloy and reduces the configurational space that arises due to the vast enumeration of alloy occupation sites. The impact of the disorder is then evaluated on the electron effective mass and bandgap which is calculated under the generalized gradient approximation \textit{(GGA)}. The EBS of disordered systems gives an insight into the effect of the loss of translational symmetry on the band topology which manifests as band broadening and can be used to evaluate disorder induced scattering rates and electron lifetimes. This technique of band unfolding can be further extended to alloy phonon dispersion and subsequently phonon lifetimes can also be evaluated from the band broadening.