Highly Nonlinear Memory Selectors with Ultrathin MoS₂/WSe₂/MoS₂ Heterojunction

Resistive random access memory (RRAM) crossbar arrays require the highly nonlinear selector with high current density to address a specific memory cell and suppress leakage current through the unselected cell. 3D monolithic integration of RRAM array requires selector devices with a small footprint and low-temperature processing for ultrahigh-density data storage. Here, an ultrathin two-terminal n-p-n selector with 2D transition metal dichalcogenides (TMDs) is designed by a low-temperature transfer method. The van der Waals contact between transferred Au electrodes and TMDs reduces the Fermi level pinning and retains the intrinsic transport behavior of TMDs. The selector with a single type of TMD exhibits a trade-off between current density and nonlinearity depending on the barrier height. By tuning the Schottky barrier height and controlling the thickness of p-type WSe₂ in MoS₂/WSe₂/MoS₂ n-p-n selector for a punch-through transport, the selector shows high nonlinearity (≈ 230) and high current density (2 × 10³ A cm⁻²) simultaneously. The n-p-n selectors are further integrated with a bipolar hexagonal boron nitride memory and calculate the maximum crossbar size of the 2D material-based one-selector one-resistor according to a 10% read margin, which offers the possible realization of future 3D monolithic integration.