Homogenous Tunnel Diode Based on Two-Dimensional Molybdenum Disulfide with Light Induced n⁺ Doping

Devices based on the quantum transportation mechanism usually achieve higher frequency and more efficient carrier manipulation than traditional devices, which may enable numerous novel functional devices/circuits. The discovery of atomically thin two-dimensional materials provides an additional platform for developing nanoscale quantum devices. In this work, we demonstrated an optically modulated tunnel diode based on a MoS2 n+/p+ homojunction, which presents negative differential resistance (NDR) induced by band to band tunneling of carriers. The n+ doping is applied by sequentially depositing and annealing an Au layer on half of the surface of a MoS2 flake. The annealed Au layer becomes positively charged after ultraviolet light illumination due to an external optoelectric effect and induces n+ doping in the MoS2 channel beneath the Au film. By grounding the positively charged Au film, the n+ doping can be recovered to almost intrinsic doping level, achieving optically tunable n doping. The p+ doping is accomplished by drop coating AuCl3 solution on the other half of the same MoS2 flake. The as-fabricated MoS2 n+/p+ homojunction presents prominent NDR under forward bias with a peak-to-valley ratio of 3.1 at room temperature. This work presents the potential toward the design of atomically thin tunneling field effect transistor and other multifunctional logic devices.