High Tunneling Electro-Resistance Due to Resonant-Type Tunneling in a Ferroelectric Tunnel Junction (FTJ) with a Composite Barrier

Recently, ferroelectric tunnel junctions (FTJs) have emerged as potential devices for memory sector wherein the tunneling current is used to sense the direction of polarization with a nondestructive reading operation. The tunneling electro-resistance ratio (TER) is the figure of merit of this device. A composite ferroelectric-dielectric barrier is expected to achieve a high TER with enhanced performance. A theoretical modeling of a FTJ with a composite barrier (CB) consisting of a dielectric (SrTiO3) and ferroelectric (BaTiO3) layers is proposed. The potential energy profile and the transmission characteristics of a typical (20Å) SrRuO3/(20Å) SrTiO3/(20Å) BaTiO3/(12Å) Pt FTJ system were extensively studied, for both OFF and ON states. The tunneling current density and TER were computed with the variation of bias as well as with varying ferroelectric layer width. Under electric bias, an asymmetric triangular well develops at the dielectric-ferroelectric interface in its ON state whose effect in producing a resonant-type tunneling and a high tunneling current density in its ON state is explained.