Phonon regulated memory enabled by opto-ionic-electronic coupling in AgInP2S6/MoS2 van der Waals heterostructure

In conventional field-effect transistors (FETs), the gate dielectric serves solely to electrostatically control the channel and is deliberately engineered to remain inert, insensitive to external stimuli such as temperature or light, and free of mobile ions to ensure stable and reliable operation. Here, we challenge this paradigm by introducing AgInP2S6 (AIPS), a previously unexplored high-κ van der Waals (vdW) thiophosphate, as an active medium that senses and processes multiple physical stimuli through photonic–ionic–electronic-phononic coupling in MoS2 field-effect transistors (FETs) where AIPS serves as the top-gate dielectric. In AIPS, defect-mediated sub-bandgap photoactivity operates independently from phonon-assisted Ag+ ion-migration, yet both converge at the AIPS/MoS2 hetero-interface to modulate channel transport. Optical excitation redistributes charge within the dielectric, driving an ionic reconfiguration that alters MoS2 channel conductance. At low temperatures (~ 0 °C), suppressed phonon activity limits Ag+ mobility, producing persistent photoconductivity. At high temperatures (~80 °C), phonon-assisted ion hopping erases the stored state without external circuitry. This materials-intrinsic retention–forgetting transition redefines the dielectric as an active, multifunctional component, capable of coupling photons, ions, electrons, and phonons to enable context-aware information processing. By reframing the role of the dielectric, our work opens a pathway toward FET architecture where the gate stack becomes a hub for sensing, memory, and computation in autonomous electronics.