Operando Probing Carrier Dynamics in van der Waals Ferroelectric Field-Effect Transistors

van der Waals ferroelectric field-effect transistors (FeFETs) hold great promise as next-generation volatile memory and neuromorphic devices. However, their performance is significantly influenced by defects introduced during the fabrication process and interfacial effects in two-dimensional (2D) materials. Moreover, operando measurement of key parameters such as carrier mobility and diffusion length in these micro- and nanodevices remains challenging. To address these challenges, we have developed an electrically coupled spatiotemporally resolved pump–probe device that enables nondestructive measurement of carrier diffusion and relaxation processes in FeFETs under operating conditions. Spatially resolved measurements on a single WSe₂ flake under both ferroelectric and metal gate configurations demonstrate that the ferroelectric gate exerts a highly efficient modulation on the carrier mobility of WSe₂, attaining a carrier mobility/voltage modulation ratio of up to 749.50 cm²/V²s. This significantly outperforms the modulation achieved with a metal gate, which stands at 575.98 cm²/V²s. This finding provides strong direct evidence for the electrostatic doping theoretical model in thin-film transistors. Additionally, compared to the WSe₂ above the metal gate, the carrier recombination lifetime of WSe₂ above the ferroelectric gate is extended by approximately 10 times, suggesting that the volatile weight modulation mechanism in such neuromorphic devices may originate from changes in carrier lifetime. This operando nondestructive measurement technique is poised to deliver a substantial value in advancing the development and optimizing the performance of next-generation two-dimensional transistors.