Modeling of 2DEG Formation at Polar ε-(AlGa)2O3/ε-Ga2O3 Heterojunctions

We report on the modeling of two-dimensional electron gas (2DEG) formation at the ε-AlGaO₃/ε-Ga₂O₃ interface. Orthorhombic ε-Ga₂O₃ is the second most stable polymorph of Ga₂O₃, with an ultra-wideband gap. ε-Ga₂O₃ is predicted to be a ferroelectric material (APPLIED PHYSICS LETTERS 112, 162101 (2018)), with much larger polarization than polar Gallium Nitride. A (2DEG) formed between polar materials is expected to exhibit high charge density and higher mobility compared to a modulation-doped heterostructure due to the absence of impurity and remote scattering. Ab-initio density functional theory (DFT) modeling was performed on ordered and disordered alloys of ε-(AlGa)₂O₃ to calculate spontaneous polarization, piezoelectric and stiffness coefficients. Band Diagrams calculations using Schrödinger-Poisson simulations show the formation of 2DEG at ε-AlGa₂O₃/ ε-Ga₂O₃ interface with a large sheet charge in the range of 1e13- 5e13 cm^-2 . This work is the first investigation of polar ε-Ga2O3 based heterostructures for potential high frequency and high-power applications.