Novel fermi-level alignment approach to Schottky barrier height modulation in MoTe2 with metal-graphene-semiconductor source/ drain contact

초록

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have shown great potential as promising materials for replacing silicon in scaled-down semiconductor technologies. However, their widespread use is hindered by strong Fermi-level (FL) pinning at the metal/TMD interface, which makes Schottky barrier height (SBH) tuning and control extremely difficult. This inherent FL pinning restricts the broad adoption of 2D TMDs and poses challenges for future complementary metal-oxide-semiconductor (CMOS) applications. In this study, we propose a novel approach to modulate SBH by incorporating a monolayer graphene (Gr) as an interlayer at the metal/semiconductor interface, forming what we term an M-Gr-S contact structure. This method presents a new technology for aligning the FLs of contact metal and the semiconductor, addressing the challenges of unwanted SBH due to FL pinning in 2D TMD devices. The van der Waals contact introduced by Gr mitigates FL pinning at the MoTe2 surface, reducing the metal-induced gap states (MIGS) at the Gr/semiconductor interface. In addition, Gr with the charge-sharing effect effectively aligns the FL of the contact metal to a value favorable for the semiconductor. The introduction of Gr effectively minimizes dependency on the metal's work function, and its atomic-scale thickness makes it ideally suited for 2D TMD-based devices. With the M-Gr-S contact structure, the hole-SBH is reduced from 0.544 eV to 0.243 eV, achieving the minimum possible SBH, which corresponds to the energy difference between the FL and the valence band maximum of MoTe2. As a result, the operation polarity of MoTe2 FET was switched from n-type to p-type solely by modifying the contact structure. Furthermore, MoTe2 homogeneous CMOS inverter characteristics were evaluated using the n-type FET prior to the application of the M-Gr-S contact and the p-type FET after its application. These results demonstrate the feasibility of using M-Gr-S contacts for effective FL alignment which lead to SBH modulation in 2D TMD devices, offering a pathway for scalable, high-performance contact engineering in future 2D semiconductor technologies.

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