High mobility ZnO thin film deposition on SrTiO3 and transparent field effect transistor fabrication

We obtain high electron mobility values in epitaxial ZnO thin films deposited on (110) oriented strontium titanate substrates. Values up to 400 cm2/V s are found below 50 K in samples grown by a two step method: firstly a thin ZnO relaxing layer is deposited on the SrTiO3 (110) substrate at relatively low temperature (550 ∘C) and then the deposition temperature is raised up to 750 ∘C for the growth of a second ZnO layer. The realized epitaxial ZnO/SrTiO3 heterostructures are used to fabricate field effect transistors transparent at visible wavelength. By conventional photolithographic techniques we realize micrometric sized devices in planar side-gate configuration. The transistors have an 80% transmittance, on-off ratios up to 106, and field effect mobilities up to 30 cm2/V s.