Transconductance as a Probe of Valley Thermodynamics in Multilayer WSe${}_2$

Abstract

Transconductance is a central figure of merit in field-effect transistors, typically governed by charge accumulation and carrier mobility. In multilayer WSe${}_2$ transistors, however, it is shown to carry a nonlinear transport signature of inter-valley carrier redistribution between the $K$ and $\Gamma$ valleys. This valley-crossover contribution suppresses transconductance in bilayer WSe${}_2$ and reverses sign in trilayer, while remaining absent in single-valley systems. Unlike extrinsic mechanisms such as trap-state filling or contact resistance, the anomaly leaves the subthreshold swing unchanged and cannot be reproduced within conventional single-valley transport models. Introducing the valley susceptibility ${\chi }_v\equiv \partial f_{\Gamma }/\partial V_{\mathrm{GS}}$, bounded by an intrinsic thermodynamic limit $(4k_{B}T{)}^{-1}$, we quantify this response and show that it reaches $\sim 0.20{\mathrm{V}}^{-1}$ in bilayer WSe${}_2$ near threshold at room temperature. The sign, magnitude, and temperature dependence of the anomaly provide directly measurable fingerprints of valley thermodynamics, establishing transconductance as an electrical probe of internal electronic degrees of freedom and revealing a previously hidden nonlinear response in standard transistor measurements.

8 pages; 4 figures

References in corpus (12)

• 2D materials and van der Waals heterostructures
• The Valley Hall Effect in MoS2 Transistors
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Electron and Hole Mobilities in Single-Layer WSe2
• The Integration of High-k Dielectric on Two-Dimensional Crystals by Atomic Layer Deposition
• Charge-transfer Contact to a High-Mobility Monolayer Semiconductor
• Biaxial Tensile Strain Enhances Electron Mobility of Monolayer Transition Metal Dichalcogenides
• Odd-integer quantum Hall states and giant spin susceptibility in p-type few-layer WSe2
• Valley-engineering mobilities in two-dimensional materials
• How do Quantum Effects Influence the Capacitance and Carrier Density of Monolayer MoS${}_2$ Transistors?
• Impact of indirect transitions on valley polarization in WS${}_2$ and WSe${}_2$
• Enhancement of Carrier Mobility in Semiconductor Nanostructures by Carrier Distribution Engineering