Charge transfer in rectifying oxide heterostructures and oxide access elements in ReRAM

The main aspects of the synthesis and experimental research of oxide diode heterostructures are discussed with respect to their use as selector diodes, i.e., access elements in oxide resistive memory. It is shown that charge transfer in these materials differs significantly from the conduction mechanism in $p$–$n$ junctions based on conventional semiconductors (Si, Ge, A$^{\mathrm{III}}-$B$^{\mathrm{V}}$), and the model should take into account the electronic properties of oxides, primarily the low carrier drift mobility. It is found that an increase in the forward current requires an oxide with a small band gap ($<$ 1.3 eV) in the heterostructure composition. Heterostructures with Zn, In–Zn (IZO), Ti, Ni, and Cu oxides are studied; it is found that the CuO–IZO heterojunction has the highest forward current density (10$^4$ A/cm$^2$).