High-mobility ferroelectrics from first principles

Free carriers can be added to ferroelectric materials through chemical substitution, modulation doping in heterostructures, or through excitation across the band gap, while still maintaining a polar structure. The combination of ferroelectricity and high mobility of added free carriers could extend the application of ferroelectrics in novel electronic devices. However, at room temperature, most perovskite ferroelectrics have low mobility, while the perovskites with high mobility, such as doped BaSnO3, are nonpolar. The challenge is to find ways to stabilize the polar ferroelectric phase in high-mobility systems without degrading the mobility. Here, we formulate design principles for experimentally realizable candidate ferroelectric systems in which the high mobility of the added carriers is promoted by the presence of an isolated low-m* band at the conduction band minimum. We report results for crystal structures, polarizations and band structures of selected systems including perovskite oxide compounds, superlattices and heterostructures, obtained using first-principles methods.