Inverse Piezoelectricity and Carrier-Mediated Phase Instability as Intrinsic Limits in Two-Dimensional Transition...

2D transition-metal dichalcogenides (TMDs) are layered semiconducting materials with significant electromechanical coupling, whereby electric fields induce mechanical deformation and mechanical strain alters electronic properties. This electromechanical coupling enables interesting device physics, but its role in electrical degradation remains unexplored. We establish a fundamental framework that decouples and isolates how electric field strength and carrier density independently drive degradation in monolayer MoS2 planar FETs, revealing two competing intrinsic mechanisms that are qualitatively distinct from and largely undetected in conventional bulk semiconductor reliability physics. In carrier-depleted channels (field-dominant regime), strong out-of-plane electric fields in the absence of carriers trigger a dominant inverse piezoelectric effect, inducing compressive strain that dramatically lowers the formation energy for sulfur vacancies. This creates a runaway process where defects accumulate and initiate failure near the drain. Conversely, in carrier-rich channels (carrier-dominant regime), mobile electrons stabilize the semiconducting 2H to metallic 1T phase transition in the presence of dominant tensile strain due to an in-plane electric field, forming highly conductive filaments that burn through via Joule heating. Electrical measurements combined with Raman spectroscopy, photoluminescence, and scanning capacitance microscopy reveal diagnostic signatures distinguishing these pathways. These findings indicate that electrical degradation in 2D materials is strongly governed by material-specific properties, namely, piezoelectricity and phase stability, which are largely absent in bulk semiconductors. This framework enables predictive degradation models for other atomically thin materials with similar electromechanical coupling, establishing piezoelectricity and phase instability as defining intrinsic limits for nanoelectronic and quantum device engineering.