Epitaxial Stabilization of Complete Solid-solution β-(AlxGa1-x)2O3 (100) Films by Pulsed-laser Deposition

We report on the lattice and band structures of complete solid-solution beta-(AlxGa1-x)(2)O-3 (x = 0-1) films that were epitaxially grown on beta-Ga2O3 (100) substrates by using oxygen-radical-assisted pulsed-laser deposition. We found that oxygen-plasma treatment of the substrate surface was the key to achieving a two-dimensional growth mode of not only beta-Ga2O3 but also theta-Al2O3 with the beta-gallia structure. The band gap of beta-(AlxGa1-x)(2)O-3 increased from 4.51 +/- 0.02 eV (x = 0) to 6.91 +/- 0.02 eV (x = 1). The x-dependence of the (100) spacing and band gap showed the anomalous bowing behavior, as the curvatures changed around x similar to 0.5. This tendency was ascribed to the different arrangements of the Al and Ga cations along their tetrahedral and octahedral site preference in the beta-gallia structure. We also fabricated a short-period superlattice composed of theta-Al2O3 and beta-Ga2O3 layers to verify the sharp interface from the X-ray diffraction profile.

Automated summary

This study on the lattice and band structures of complete solid-solution beta-(AlxGa1-x)(2)O-3 (x = 0-1) films grown on beta-Ga2O3 substrates revealed that oxygen-plasma treatment was key to achieving a two-dimensional growth mode. The band gap of beta-(AlxGa1-x)(2)O-3 increased with x, showing anomalous bowing behavior around x ≈ 0.5.