Tunable electronic properties of κ-(Al, In)2O3/Ga2O3 digital alloys via superlattice design

Abstract

κ-Ga2O3-based digital-alloy superlattices offer a promising alternative to traditional random alloys for high performance heterostructure devices. Using density functional theory, we model (Al2O3/κ-Ga2O3) and (In2O3/κ-Ga2O3) superlattices with varying monolayer (ML) thicknesses (1 ML/3 ML, 2 ML/2 ML, and 3 ML/1 ML). Our calculations reveal precise tuning of lattice parameters and bandgaps dependent on layer thickness. The incorporation of Al2O3 introduces tensile strain and widens bandgap up to 6.65 eV, while In2O3-rich structures exhibit compressive strain with bandgap reduction down to 3.32 eV. Element-projected band structures confirm quantum confinement effects and interfacial contributions to electronic states. Notably, intersubband transition energies are controllable via ML thickness, enabling absorption in the telecom-compatible wavelength range (∼1.55 μm). Band alignment analysis reveals significant conduction band offsets (up to 3.71 eV for Al2O3/Ga2O3), which is vital for polarization-induced 2DEG (two-dimensional electron gas) formation. This work demonstrates the feasibility of κ-Ga2O3 digital-alloy superlattices for tailored high-electron-mobility transistors and quantum-well infrared photodetectors.