Degenerate n-Doping of Few-Layer Transition Metal Dichalcogenides by Potassium

TLDR

The study demonstrates the first degenerate n‑doping of few‑layer MoS₂ and WSe₂ via surface charge transfer with potassium. The authors fabricated top‑gated MoS₂ and WSe₂ n‑FETs with potassium‑doped source/drain contacts that show low contact resistance, and performed ab initio simulations to compare K doping in these chalcogenides with graphene. The doping produced electron sheet densities of ~1.0×10¹³ cm⁻² in MoS₂ and 2.5×10¹² cm⁻² in WSe₂, yielded low contact resistances, and enabled WSe₂ n‑FETs with ~110 cm² V⁻¹ s⁻¹ mobility, highlighting the need for degenerate doping to achieve high‑performance complementary electronics.

Abstract

We report here the first degenerate n-doping of few-layer MoS2 and WSe2 semiconductors by surface charge transfer using potassium. High-electron sheet densities of ~1.0 × 10(13) cm(-2) and 2.5 × 10(12) cm(-2) for MoS2 and WSe2 are obtained, respectively. In addition, top-gated WSe2 and MoS2 n-FETs with selective K doping at the metal source/drain contacts are fabricated and shown to exhibit low contact resistances. Uniquely, WSe2 n-FETs are reported for the first time, exhibiting an electron mobility of ~110 cm(2)/V·s, which is comparable to the hole mobility of previously reported p-FETs using the same material. Ab initio simulations were performed to understand K doping of MoS2 and WSe2 in comparison with graphene. The results here demonstrate the need of degenerate doping of few-layer chalcogenides to improve the contact resistances and further realize high performance and complementary channel electronics.