Tunable optoelectronic and ferroelectric properties in Sc-based III-nitrides

TL;DR

This study investigates Sc-based III-nitride alloys using Density Functional Theory, revealing their tunable optoelectronic and ferroelectric properties, with potential for advanced electronic applications.

Contribution

It demonstrates the retention of wide direct band gaps and ferroelectricity in Sc-based III-nitrides, with insights into strain effects and stability up to certain compositions.

Findings

Wide band gaps remain direct up to specific Sc concentrations.

Epitaxial strain stabilizes alloys and prevents spinodal decomposition.

Ferroelectricity emerges at high Sc content in ScGaN.

Abstract

Sc-based III-nitride alloys were studied using Density Functional Theory with special quasi-random structures and were found to retain wide band gaps which stay direct up to x = 0.125 (ScxAl1-xN) and x = 0.375 (ScxGa1-xN). Epitaxial strain stabilization prevents spinodal decomposition up to x = 0.3 (ScxAl1-xN on GaN) and x = 0.24 (ScxGa1-xN on GaN), with critical thicknesses for strain relaxation ranging from 3 nm to near-infinity. The increase in Sc content introduces compressive in-plane stress with respect to AlN and GaN, and leads to composition- and stress-tunable band gaps and polarization, and ultimately introduces ferroelectric functionality in ScxGa1-xN at x = 0.625.