Structural, Optical, and Electronic Properties of Epitaxial β‐(Al_xGa_1‐x)₂O₃ Films for Optoelectronic Devices

Abstract

Bandgap engineering in monoclinic gallium oxide (β‐Ga2O3) is a powerful strategy for designing semiconductor optoelectronic devices with specific functionalities. In this work, aluminum doping is utilized to modulate the bandgap of Ga2O3. By growing epitaxial β‐(AlxGa1‐x)2O3 (0≤ x≤ 0.84) films on c‐plane sapphire substrates using RF magnetron sputtering, it allowed to tune the energy bandgap, achieving values as high as 6.10 eV. The increased luminescence intensity is attributed to the recombination between donor and acceptor transitions induced by Al doping, resulting in more defects. Additionally, the luminescent band experienced blueshifts due to the enhanced bandgaps. Moreover, density of functional theory (DFT) simulations confirmed the sensitivity of the bandgap to Al content, distinguishing between Ga‐dominated (x < 0.5) and Al‐dominated (x > 0.5) β‐(AlxGa1‐x)2O3. Notably, the bandgap increased more rapidly in Ga‐dominated structures compared to Al‐dominated ones. The electronic structure analysis revealed a redistribution of Ga d states from valence to conduction bands, attributed to the introduction of numerous Al p states. These combined experimental and detailed electronic structure investigations proved crucial insights for designing the structure and exploring potential applications of β‐(AlxGa1‐x)2O3 in photonic devices.