High performance all-oxide thin film tunable capacitors on Si substrates for agile microwave applications

Abstract

Here we present all-oxide thin film tunable capacitors (varactors) grown epitaxially on silicon substrates, using a SrTiO3 buffer layer. In the all-oxide varactors, a highly conducting oxide SrMoO3 bottom electrode is covered with a functional 100nm BaxSr1−xTiO3 tunable dielectric layer. A combined Au/Pt layer is used as a top electrode. The microwave properties show a tunability of 2 at 10V bias voltage and a high quality factor Q(0V) = 45 at 1 GHz. Further improvement of the electric performance of the all-oxide varactors is feasible by the optimization of the growth process of the oxide layers and extending the SrMoO3 thicknesses beyond the skin depth at frequencies relevant for the considered application. The all-oxide varactors on Si are suitable for the high performance agile devices with low tuning voltages and ultra-low power consumption.