Nonvolatile programmable two-terminal diodes using a ferroelectric semiconductor

The conductance of diodes formed by epitaxial (Pb, La)(Zr, Ti)O₃ on SrTiO₃ doped with Nb is programed using the relaxation semiconductor characteristics of a ferroelectric. Namely, a three-terminal device function is given to a two-terminal device by time-domain control. The conductance modulation programed by a short-voltage pulse is perfectly retained for ten days at room temperature and is nondestructively read. The relaxation current at very low bias is also programmable. When the current is regulated by a metal/ferroelectric contact, the pulse modulation is obscure and is not retained. This implies that the surface layer at the metal/ferroelectric contact is negligibly thin or thinner than the tunneling distance.