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 Hf0.5Zr0.5O2 (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 (Vth), the 1T' metallic phase in the MoTe2 PT-FeFET eliminates the OFF state and the corresponding SET Vth, thereby enabling expansion of the memory window across the entire voltage range below the RESET Vth. 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.