Formation energy crossings in Ga2O3-Al2O3 quasibinary system: ordered structures and phase transitions in (Al x Ga1−x )2O3

Abstract

Abstract A quasibinary system of Ga2O3-Al2O3 offers a range of applications in wide bandgap semiconductor engineering. Different polymorphs and concentrations of (Al x Ga1−x )2O3 manifest a variety of structural and electronic properties, paving the way for tunability of (Al x Ga1−x )2O3 for specific functions. In this work, we investigate the energetics of alpha (α) and beta (β) polymorphs of Ga2O3 and Al2O3 by considering all possible configurations in a conventional unit cell. Using density functional theory, we show that the formation energies of (Al x Ga1−x )2O3 in α and β configurations start to coincide at 50% concentration (Al0.5Ga0.5)2O3. The corundum configuration then becomes more dominant (lower in energy) than its monoclinic counterpart at around 80% Al concentration. The lowest formation energy configurations for 50% concentration in both α and β polymorphs also manifest a preference towards an ordered phase. These show that the stability of Ga2O3-Al2O3 and its phase transitions are significantly influenced by the relative arrangements of Ga and Al within the quasibinary semiconducting crystal.