Effective band structure and crack formation analysis in pseudomorphic epitaxial growth of (In_xGa_1–x)₂O₃ alloys: a first-principles study

Ga₂O₃ is a promising material for power electronic applications. Alloying with In₂O₃ is used for band gap adjustment and reduction of the lattice mismatch. In this study, we calculate the effective band structure of 160-atom (In_xGa_1–x)₂O₃ supercells generated using special quasi-random structures where indium atoms preferentially substitute octahedral gallium sites in β-Ga₂O₃. We find that the disorder has a minimal effect on the lower conduction bands and does not introduce defect states. Employing the Heyd, Scuseria, and Ernzerhof (HSE06) hybrid functional, we accurately model the band gap, which remains indirect for all considered indium fractions, x, linearly decreasing from 4.8 to 4.24 eV in the range of x ∈ [0, 0.31]. Accordingly, the electron effective mass also decreases slightly and linearly. We determined the critical thickness for epitaxial growth of the (In_𝑥Ga_1−𝑥)₂O₃ alloys over β-Ga₂O₃ surfaces along the [100], [010], and [001] directions. Our findings offer new insights into site preference, effective band structure, and crack formation within (In_𝑥Ga_1−𝑥)₂O₃ alloys.