Contact Engineering in Two-Dimensional Semiconductor Devices

In two-dimensional semiconductor devices, contact engineering addresses the critical interface between atomically thin channel materials and metallic electrodes, where contact resistance often governs overall device performance. Conventional metal–semiconductor junctions suffer from Fermi-level pinning and chemical disorder, leading to high Schottky barriers and limited charge injection. Strategies to overcome these limitations encompass van der Waals contacts formed by stacking metallic and semiconducting monolayers, phase engineering of transition-metal dichalcogenides to tune work functions, surface treatments and controlled deposition to achieve ultraclean interfaces, and edge contact geometries that enhance carrier injection. Contact gating techniques exploit weak Fermi-level pinning to modulate the pseudo-junction resistance via electric fields at the source. Advances in theoretical modelling and first-principles simulations have deepened understanding of interfacial dipoles, band bending and in-gap state formation, guiding the design of low-resistance Ohmic contacts. Such engineered interfaces underpin high-performance two-dimensional transistors, flexible electronics and optoelectronic applications by minimising energy loss and enabling precise control over charge transport.

Research from Nature Portfolio

Recent studies have demonstrated the emergence of a metastable interfacial Au4S4 phase stabilised by monolayer MoS₂ and WS₂, with enhanced van der Waals interactions that induce a transition from n-type to p-type Schottky contacts and reduce barrier height. Ab initio quantum transport simulations have revealed that traditional energy-band calculations underestimate Schottky barrier heights at monolayer and bilayer MoS₂–metal interfaces, highlighting the importance of many-electron effects and interlayer coupling in lowering contact resistance. Furthermore, a two-path model integrating contact gating has quantitatively explained subthreshold behaviour in back-gated Schottky-barrier transistors based on ultrathin channels, emphasising the role of source contact fields in carrier injection and subthreshold swing control.

Research from all publishers

High-throughput first-principles screening of phase-engineered transition-metal dichalcogenide van der Waals junctions has identified dozens of material pairs with weak Fermi-level pinning and favourable tunnelling probabilities, predicting Ohmic behaviour at the Schottky–Mott limit. Experimentally, semimetallic antimony contacts to MoS₂ in dual-gated field-effect transistors have achieved ultralow contact resistance and pronounced gate-voltage modulation of junction resistance, attributed to suppressed Fermi-level pinning at the interface. Additionally, controlled thermal deposition of indium on MoS₂ has yielded atomically clean van der Waals contacts exhibiting field-emission-dominated Ohmic transport from cryogenic to room temperature, where in-gap state formation mitigates pinning and minimises contact resistance.

Contact Engineering in Two-Dimensional Semiconductor Devices publication trend

The graph below shows the total number of articles in contact engineering in two-dimensional semiconductor devices across all publications each year (not limited to Nature Index journals).

Technical terms

Schottky barrier: Energy barrier at a metal–semiconductor interface that impedes carrier injection and contributes to contact resistance.

Ohmic contact: Low-resistance junction exhibiting linear current–voltage characteristics and efficient carrier injection.

Fermi-level pinning: Phenomenon whereby interface states fix the energy alignment between metal and semiconductor, limiting barrier tuning.

van der Waals contact: Non-covalent interface formed between layered materials and metals, preserving pristine surfaces and minimising disorder.

Contact gating: Modulation of junction resistance or barrier height by electric fields applied near the contact region.

References

1. High‐throughput screening of phase‐engineered atomically thin transition‐metal dichalcogenides for van der Waals contacts at the Schottky–Mott limit. InfoMat (2023).
2. Modulation of Contact Resistance of Dual‐Gated MoS2 FETs Using Fermi‐Level Pinning‐Free Antimony Semi‐Metal Contacts. Advanced Science (2023).
3. Origins of genuine Ohmic van der Waals contact between indium and MoS2. npj 2D Materials and Applications (2021).
4. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations. Scientific Reports (2016).
5. Van der Waals interfacial reconstruction in monolayer transition-metal dichalcogenides and gold heterojunctions. Nature Communications (2020).
6. Understanding contact gating in Schottky barrier transistors from 2D channels. Scientific Reports (2017).