Toward barrier free contact to MoSe₂/WSe₂ heterojunctions using two-dimensional metal electrodes

Abstract

In the design of electronic devices based on two-dimensional heterojunctions, the contact between electrodes and different surfaces of two-dimensional heterojunctions may produce different effects. Furthermore, metal–semiconductor contact plays an important role in modern devices. However, due to the Fermi level pinning effect (FLPE), it is difficult to tune the Schottky barrier height between common metals (e.g. Au, Ag, and Cu) and semiconductors. Fortunately, the FLPE becomes weak at the contact between the 2D metal and 2D semiconductor, due to the suppression of metal-induced gap states. Here, we choose monolayer NbS2 as the electrode to be in contact with the MoSe2/WSe2 bilayer. The interfacial properties as well as the stacking dependence are discussed based on the density functional theory, combined with the nonequilibrium Green’s functions. Two configurations are considered, i.e. the WSe2/MoSe2/NbS2 and MoSe2/WSe2/NbS2 stacking sequences. Our results show that barrier free contact can be formed in these 2D metal–semiconductor junctions (MSJs). In addition, the transport properties of the proposed devices are sensitive to the stacking sequence. The drain-source current versus bias voltage (I–V) curve exhibits a linear relationship for the WSe2/MoSe2/NbS2 system and its resistance is much lower than the MoSe2/WSe2/NbS2 MSJ. Detailed analysis reveals that the transport properties are governed by the electronic coupling between specific interlayer states. In WSe2/MoSe2/NbS2 configuration, large overlapping states are observed, which facilitate charge transfer and result in good ohmic contact. Our work may provide a theoretical guidance for the designing of next-generation ultrathin and flexible devices.

Synergistic 2D MoSe2@WSe2 nanohybrid heterostructure toward superior hydrogen evolution and flexible supercapacitor

“…[18][19][20] MoSe 2 and WSe 2 have minimal energy differences between the electronic states and similar lattice structure and constants, and hence are the most favorable choices for the heterostructure. 21 The epitaxial growth of the heterostructure by chemical vapor deposition (CVD) deals with costly sophisticated requirements, high temperature processing, and low yield. Considering this, solution processing of TMDC-based large-area heterostructure is the best alternative.…”

Solution-Processed Uniform MoSe2–WSe2 Heterojunction Thin Film on Silicon Substrate for Superior and Tunable Photodetection

“…The p–n heterojunction between these TMDC materials can (a) modulate the energy band alignment that leads to better charge transfer, (b) significantly improve the absorption in visible-light region, and (c) diminish the effect of surface defects and offer the new dimension for high-performance optoelectronic device. , The MoSe 2 –WSe 2 heterojunction is the most appropriate p–n junction due to their minimal lattice match and energy band alignment . Lee et al studied the rectification characteristic and photovoltaic effect in atomically thin MoSe 2 /WSe 2 heterojunction and concluded that the nanoscale p–n heterojunctions are effective for optoelectronic devices .…”

“…14,15 The MoSe 2 −WSe 2 heterojunction is the most appropriate p−n junction due to their minimal lattice match and energy band alignment. 16 Lee et al studied the rectification characteristic and photovoltaic effect in atomically thin MoSe 2 /WSe 2 heterojunction and concluded that the nanoscale p−n heterojunctions are effective for optoelectronic devices. 17 carriers can be stimulated by the band alignment of type-II heterojunction which is beneficial for the application of photodetector.…”

Schottky-Barrier-Free vdW Contact in a 2D Penta-NiN2/Biphenylene Network Heterostructure

“…Schottky-barrier-free van der Waals (vdW) contacts have attracted tremendous research attention in recent years, and a major focus is on obtaining heterostructures with low contact resistance, − which is crucial for the efficient charge transfer in high-speed ultrathin devices. For conventional metal–semiconductor vdW contacts, an energy barrier, termed the Schottky barrier (Φ SB ), is formed at the vertical interface of the heterojunction due to inevitable differences in electronic energy levels between the metal electrode and semiconducting channel materials, thereby affecting the flow of charge carriers across the heterojunction and overall device functionality.…”