Epitaxial growth of [beta]-Ga2O3/[epsilon]-Ga2O3 polymorphic heterostructures on c-plane sapphire for deep-ultraviolet optoelectronics

Thin polymorphic gallium oxide films were grown on c-plane sapphire using pulsed laser deposition. The stacked thin films (ε-G_a2O₃ and β-G_a2O₃) were sequentially grown under the same conditions but in a different ambience. Our X-ray diffraction measurements and transmission electron microscopy images confirmed a β-G_a2O₃/ε-G_a2O₃ polymorphic heterostructure with rocking-curve widths of 1.4° (β-G_a2O₃ (¯603)) and 0.6° (ε-G_a2O₃ (006)). The crystallographic orientation relationships between c-plane sapphire and the heterogeneously nucleated ε-G_a2O₃ buffer layer, as well as between the ε-G_a2O₃ and β-G_a2O₃ heterogeneous layers, were determined. Our study will aid in developing novel deep-ultraviolet optoelectronic devices, such as solar-blind and metal-insulator-semiconductor deep-ultraviolet photodiodes.