We investigated the effect of Sn doping on the optical, electrical, and magneto transport properties of epitaxial α-Ga2O3 thin films grown by mist-Chemical Vapour Deposition. Sn introduces a shallow donor level at ∼0.1 eV and has a high solubility allowing doping up to 1020 cm−3. The lowest obtained resistivity of the films is 2.0 × 10−1 Ω cm. The Sn doped films with a direct band gap of 5.1 eV remain transparent in the visible and UV range. The electrical conduction mechanism and magneto-transport have been investigated for carrier concentrations below and above the insulator-metal transition. The magnetic properties of the neutral Sn donor and the conduction electrons have been studied by electron spin resonance spectroscopy. A spin S = 1/2 state and C3V point symmetry of the neutral Sn donor is found to be in good agreement with the model of a simple SnGa center.

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