Ultimate thin vertical p–n junction composed of two-dimensional layered molybdenum disulfide

Semiconducting 2D crystals are currently receiving significant attention due to their great potential to be an ultra-thin body for efficient electrostatic modulation which enables to overcome the limitations of silicon technology. Here we report that, as a key building block for 2D semiconductor devices, vertical p-n junctions are fabricated in ultrathin MoS2 by introducing AuCl3 and benzyl viologen dopants. Unlike usual unipolar MoS2, the MoS2 p-n junctions show (i) ambipolar carrier transport, (ii) current rectification via modulation of potential barrier in films thicker than 8 nm, and (iii) reversed current rectification via tunneling in films thinner than 8 nm. The ultimate thinness of the vertical p-n homogeneous junctions in MoS2 is experimentally found to be 3 nm, and the chemical doping depth is found to be 1.5 nm. The ultrathin MoS2 p-n junctions present a significant potential of the 2D crystals for flexible, transparent, high-efficiency electronic and optoelectronic applications.