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

Abstract

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.