Tailoring the Electronic Properties of Monoclinic (InxAl1-x)2O3 Alloys via Substitutional Donors and Acceptors

TL;DR

This study uses density functional theory to explore how substitutional donors and acceptors affect the electronic properties of (InxAl1-x)2O3 alloys, aiming to optimize materials for next-generation power electronic devices.

Contribution

It provides a detailed atomistic analysis of defect energetics in (InxAl1-x)2O3 alloys, identifying promising alternative donors and the role of acceptors in electronic property tuning.

Findings

Hf and Zr are favorable alternative donors under oxygen-poor conditions.

Acceptors like Mg, Zn, and Cu can help achieve semi-insulating layers.

Alloying allows lattice matching and band offset tuning for device integration.

Abstract

Ultra-wide bandgap semiconductors such as \b{eta}-Ga2O3 are ideal materials for next-generation power electronic devices. Electronic and mechanical properties of \b{eta}-Ga2O3 can be tuned by alloying with other sesquioxides, notably Al2O3 and In2O3. Moreover, by tuning the In content of a (InxAl1-x)2O3 alloy, its lattice constants can be matched to those of Ga2O3, while preserving a large conduction-band offset. In view of potential applications to \b{eta}-Ga2O3-based heterostructure, we performed atomistic modelling of (InxAl1-x)2O3 alloys using density functional theory to investigate thermodynamic and electrical properties of conventional group IV dopants (Si, Sn, C, Ge), alternative metal donors (Ta, Zr, Hf), and acceptors (Mg, Zn, Cu). The hybrid Heyd-Scuseria-Ernzerhof functional (HSE06) is used to accurately quantify the defect formation energies, ionization levels, and concentrations over a wide range of experimentally relevant conditions for the oxygen chemical potential and temperature. In our atomistic models, Hf and Zr show favourable properties as alternative donors to Si and other group IV impurities, especially under oxygen-poor conditions. Our findings also suggest that acceptors Mg, Zn, and Cu, while they cannot promote p-doping, can be still beneficial for the compensation of unintentionally n-doped materials, e.g., to generate semi-insulating layers and improve rectification.