Ferroelectric-Driven Nonvolatile Phase Transition in MoTe₂ Transistors With an Expanded Memory Window

Polymorphic MoTe₂ offers a unique opportunity for phase-transition memristors due to its reversible structural transitions between semiconducting (2H) and metallic (1T') phases. Although gate-tunable phase transitions have been demonstrated, the presence of mobile ions in electrolyte gating leads to volatile behavior. Here, we demonstrate a phase-transition ferroelectric field-effect transistor (PT-FeFET) employing a polymorphic MoTe₂ channel and a Hf_0.5Zr_0.5O₂ (HZO) ferroelectric gate insulator. The ferroelectric polarization of the HZO layer induces an electrically driven, long-term nonvolatile phase transition in the MoTe₂ channel. Unlike conventional FeFETs, in which the memory window is confined between the SET and RESET threshold voltages (V_th), the 1T' metallic phase in the MoTe₂ PT-FeFET eliminates the OFF state and the corresponding SET V_th, thereby enabling expansion of the memory window across the entire voltage range below the RESET V_th. Consequently, the device exhibits both a wide memory window (82.5%) and a high ON/OFF current ratio (10⁶), outperforming conventional FeFETs. Owing to its wide memory window, the PT-FeFET accesses the full spectrum of synaptic weights (0-1) with near-ideal linearity (β = 0.9). As a result, the PT-FeFET achieves 82% accuracy in CIFAR-10 classification, surpassing the 59%-75% accuracy of conventional FeFETs.