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.
Highly crystalline α-phase gallium oxide (Ga2O3) thin films were grown by fine-channel mist chemical vapor deposition on c-sapphire substrates at 400 °C at a deposition rate of more than 20 nm/min. The thin films were doped with Sn(IV) atoms, which were obtained from Sn(II) chloride by the reaction SnCl2+ H2O2+ 2HCl→SnCl4+ 2H2O. Conductive α-phase Ga2O3 thin films were successfully grown from source solutions containing less than 10 at. % Sn(IV). The source solution containing 4 at. % Sn(IV) resulted in obtaining a thin film with an n-type conductivity as high as 0.28 S cm-1, a mobility of 0.23 cm2 V-1 s-1, a carrier concentration of 7×1018 cm-3, and a full width at half maximum (FWHM) of the (0006) reflection X-ray rocking curve as low as 64 arcsec.
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