Functional diversification at the single-device level
has become
essential for emerging optical neural network (ONN) development. Stable
ferroelectricity harnessed with strong light sensitivity in α-In2Se3 holds great potential for developing ultrathin
neuromorphic devices. Herein, we demonstrated an all-2D van der Waals
heterostructure-based programmable synaptic field effect transistor
(FET) utilizing a ferroelectric α-In2Se3 nanosheet and monolayer graphene. The devices exhibited reconfigurable,
multilevel nonvolatile memory (NVM) states, which can be successively
modulated by multiple dual-mode (optical and electrical) stimuli and
thereby used to realize energy-efficient, heterosynaptic functionalities
in a biorealistic fashion. Furthermore, under light illumination,
the prototypical device can toggle between volatile (photodetector)
and nonvolatile optical random-access memory (ORAM) logic operation,
depending upon the ferroelectric-dipole induced band adjustment. Finally,
plasticity modulation from short-term to prominent long-term characteristics
over a wide dynamic range was demonstrated. The inherent operation
mechanism owing to the switchable polarization-induced electronic
band alignment and bidirectional barrier height modulation at the
heterointerface was revealed by conjugated electronic transport and
Kelvin-probe force microscopy (KPFM) measurements. Overall, robust
(opto)electronic weight controllability for integrated in-sensor and
in-memory logic processors and multibit ORAM systems was readily accomplished
by the synergistic ferrophotonic heterostructure properties. Our presented
results facilitate the technological implementation of versatile all-2D
heterosynapses for next-generation perception, optoelectronic logic
systems, and Internet-of-Things (IoT) entities.