Improved Self-Heating in Short-Channel Monolayer WS₂ Transistors with High-Thermal Conductivity BeO Dielectrics

Abstract

Two-dimensional semiconducting transition metal dichalcogenides (TMDs) enable ultimate channel length scaling of transistor technology due to their atomic-thin body nature, which also brings the challenge of a pronounced self-heating effect inside the ultrathin channel. In particular, high current density under high electric field could lead to negative differential resistance behavior due to self-heating, not only limiting the current carrying capability of the TMDs transistors but also leading to severe reliability issues. Here, we report high-performance monolayer WS 2 transistors on a high-thermal-conductivity BeO dielectric with effective suppression of the self-heating effects, eliminating the negative differential resistance behavior at high field, as observed in the case of the HfO 2 dielectric. The monolayer CVD WS 2 device on BeO with a 50 nm channel length exhibits a record-high onstate current of 325 μA/μm, transconductance (g m ) of 150 μS/μm, and a on/off ratio of 1.8 × 10 8 at V ds = 1 V, far exceeding previous results.

Self-Heating Effect in a MoS2 Field-Effect Transistor and Improved Heat Dissipation by the BN Capping Layer

“…However, in practical scenarios, it is often observed that I ds tends to decrease at high voltage after reaching a quasi-saturation point. The definition of NDR is the percentage of the difference between over saturation current and saturation current of the device Δ I ( Δ I = ( I ds – I sat )) and saturation current density I sat , i.e Δ I / I sat × 100%. , …”

“…The definition of NDR is the percentage of the difference between over saturation current and saturation current of the device ΔI (ΔI = (I ds − I sat )) and saturation current density I sat , i.e ΔI/I sat × 100%. 39,40 As shown in Figure 1a, when MoS 2 devices are operated under high voltage, Joule heating is inevitably generated in the channel of the FET. It is obvious that the self-heating effect is ubiquitous in 2D FETs and has a significant influence on the saturation current and the stability of the device.…”