High-k perovskite gate oxide BaHfO3

We have investigated epitaxial BaHfO3 as a high-k perovskite dielectric. From x-ray diffraction measurement, we confirmed the epitaxial growth of BaHfO3 on BaSnO3 and MgO. We measured optical and dielectric properties of the BaHfO3 gate insulator; the optical bandgap, the dielectric constant, and the breakdown field. Furthermore, we fabricated a perovskite heterostructure field effect transistor using epitaxial BaHfO3 as a gate insulator and La-doped BaSnO3 as a channel layer on SrTiO3 substrate. To reduce the threading dislocations and enhance the electrical properties of the channel, an undoped BaSnO3 buffer layer was grown on SrTiO3 substrates before the channel layer deposition. The device exhibited a field effect mobility value of 52.7 cm2 V−1 s−1, a Ion/Ioff ratio higher than 107, and a subthreshold swing value of 0.80 V dec−1. We compare the device performances with those of other field effect transistors based on BaSnO3 channels and different gate oxides.