Lattice-matched (Al x Sc y Ga1− x − y )2O3/ β -Ga2O3 heterostructures with widely tunable bandgap

Bandgap engineering of β-Ga2O3 is essential for advancing its electronic and optoelectronic applications. However, the growth of high-quality heteroepitaxial structures is often hampered by large lattice mismatches. In this study, we design (AlxScyGa1−x−y)2O3 quaternary alloys in the form of both polycrystalline powders and heteroepitaxial films and demonstrate their lattice matching to β-Ga2O3. Powder x-ray diffraction (XRD) measurements reveal that the lattice parameters of monoclinic (AlxScyGa0.8)2O3 match those of β-Ga2O3 when x/y = 1.5–3.2. (AlxScyGa1−x−y)2O3 thin films are grown on β-Ga2O3 (100) substrates by pulsed-laser deposition by varying the composition ratio x/y and the total substitutional fraction x + y. Nearly perfect lattice-matched epilayers with uniform composition and crystal structure are obtained up to x + y ∼ 0.6, as confirmed by XRD and scanning transmission electron microscopy. Electron energy loss spectroscopy reveals a tunable bandgap from 4.5 to 5.8 eV. These results demonstrate that (AlxScyGa1−x−y)2O3/β-Ga2O3 heterostructures are promising platforms for ultrawide-bandgap semiconductor devices.