Electrical transport through (formula presented) p-n and p-p heterostructures modulated by bound charges at a ferroelectric surface: ferroelectric p-n diode

Current through (Formula presented) ferroelectrics on perovskite semiconductors is found to exhibit diode characteristics of which polarity is universally determined by the carrier conduction-type semiconductors. A persisting highly reproducible resistance modulation by a dc voltage, which has a short retention, is observed and is ascribed to a band bending of the ferroelectric by the formation of charged traps. This interpretation is consistent with a large relaxation current observed at a low voltage. On the other hand, a reproducible resistance modulation by a pulse voltage, which has a long retention, is observed in metal/(Formula presented) but not in metal/(Formula presented) and is attributed to a possible band bending due to the spontaneous polarization (Formula presented) switching. The observed current voltage (Formula presented) characteristics, the polarity dependence, the relaxation, and the modulation are explicable, if we assume a (Formula presented) or a (Formula presented) junction at the ferroelectric semiconductor interface (p: hole conduction type, n: electron conduction type). The analysis suggests that an intrinsically inhomogeneous P (Formula presented) near the ferroelectric/metal interface is likely very weak or existing in a very thin layer, when a reaction of the metal with the ferroelectric is eliminated. Additionally, the various aspects of transport through ferroelectrics are explained as a transport in the carrier depleted region.