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 I_on/I_off 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.