Tin gallium oxide solar-blind photodetectors on sapphire grown by molecular beam epitaxy

We report on tin gallium oxide ((Sn_xGa_1-x)₂O₃) solar-blind metal-semiconductor-metal (MSM) photodetectors grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates with varying tin content up to X_Sn=10%. Incorporation of Sn into Ga₂O₃ was found to shift the optical bandgap of the epilayers from 5.0 eV (248 nm) for 0% Sn to 4.6 eV (270 nm) for 10% Sn content. Varying of the Sn concentration was also found to enable controlled tuning of the peak responsivity and cutoff wavelengths of MSM devices fabricated from the epilayers, with peak responsivity ranging from 0.75 A/W to nearly 16 A/W as the Sn concentration was increased from 0% to 10%. The high responsivity is attributed to photoconductive gain that increases for higher Sn concentrations and is accompanied by a slowing of the temporal response of the MSM detectors.