Polarization and charge carrier density coupling in epitaxial PbZr0.2Ti0.8O3/ZnO heterostructures

Abstract

The integration of ferroelectric materials with semiconductor heterostructures can greatly enhance the functionality of electronic devices, provided the ferroelectric material retains a significant part of its switchable polarization. This work reports polarization switching in epitaxial PbZr0.2Ti0.8O3/ZnO/GaN heterostructures grown on c-cut sapphire single-crystal substrates. The electrical measurements of PbZr0.2Ti0.8O3/ZnO ferroelectric/semiconductor capacitors reveal an unexpected difference between a counterclockwise ferroelectric hysteresis loop and a clockwise C-V loop. A non-linear hysteretic behavior of the capacitance is observed in the voltage range that is at least 3 times narrower than the range of ferroelectric polarization switching voltages. This difference can be explained by charge injection effects at the interface between ferroelectrics and semiconductors. The interaction between electric polarization and the electronic structure of the heterojunction leads to capacitance and charge carrier concentrations that are switchable by polarization of the ferroelectric layer. These findings are important for both fundamental and applied research of switchable and highly tunable ferroelectric/semiconductor heterostructures.