The influence of interfacial tensile strain on the charge transport characteristics of MoS₂-based vertical heterojunction devices

We demonstrate the charge transport characteristics of MoS₂-based vertical heterojunction devices through the formation of interfacial strain. Atomically thin MoS₂ bilayers were directly synthesized on a p-type Si substrate by using chemical vapor deposition to introduce an interfacial tensile strain in the vertical heterojunction diode structure, which was confirmed by Raman, X-ray and ultraviolet photoelectron spectroscopy techniques. The electrical and optoelectronic properties of the heterojunction devices with the as-grown MoS₂ (A-MoS₂) on p-Si were compared with those of transferred MoS₂ (T-MoS₂)/p-Si devices. To clearly understand the charge transport characteristics induced by the interfacial tensile strain, the Fowler-Nordheim (FN) analysis of the electrical properties of the diode devices was conducted with the corresponding energy band diagrams. All of the fabricated MoS₂-based vertical diodes exhibited clearly rectifying behaviors, but the photoresponse properties of the A-MoS₂-based and T-MoS₂-based heterojunctions exhibited distinct differences. Interestingly, we found that the tunneling barrier heights of the A-MoS₂-based heterojunction devices were relatively higher than those of the T-MoS₂-based devices and were almost the same before and after illumination due to the interfacial tensile strain, whereas those of the T-MoS₂-based devices were lowered after illumination. Our study will help further understand the charge transport properties of 2D material-based heterojunction devices in the presence of interfacial strain, ultimately enabling the design of electronic and optoelectronic devices with novel functionalities.