Bandgap engineering of α-(Al<inf>x</inf>Ga<inf>1-x</inf>)<inf>2</inf>O<inf>3</inf> by a mist chemical vapor deposition two-chamber system and verification of Vegard's Law
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This work reports growth of α-(AlxGa1-x)2O3 single crystals with high incorporation of Al by a Mist Chemical Vapor Deposition two-chamber system, which was rationally designed to avoid side-reactions between different precursors during solution preparation for multi-component thin film growth. Multiple acceleration voltages were used in Energy Dispersive X-ray measurements to reliably obtain the Al composition x of the films. As a result, Vegard's law for lattice constants was verified and found to be valid in the α-(AlxGa1-x)2O3 system. However, Vegard's law for optical bandgaps, derived from different models, required an additional term to account for the bowing effect. At x = 0.71, the gaps were 7.74, 7.03, 7.26, and 7.34 eV as derived from the Tauc plots for the direct bandgap, indirect bandgap, Tauc-Lorentz model, and O'Leary-Johnson-Lim model, respectively. The two-chamber system provides reliable and effective control of the Al content in α-(AlxGa1-x)2O3 alloys and heterostructures.
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40 - Engineering::4009 - Electronics, sensors and digital hardware::400904 - Electronic device and system performance evaluation, testing and simulation
34 - Chemical sciences::3403 - Macromolecular and materials chemistry::340309 - Theory and design of materials
40 - Engineering::4016 - Materials engineering::401603 - Compound semiconductors
34 - Chemical sciences::3403 - Macromolecular and materials chemistry::340307 - Structure and dynamics of materials