α-In2 Se3 semiconductor crystals realize artificial synapses by tuning in-plane and out-of-plane ferroelectricity with diverse avenues of electrical and optical pulses. While the electrically induced ferroelectricity of α-In2 Se3 shows synaptic memory operation, the optically assisted synaptic plasticity in α-In2 Se3 has also been preferred for polarization flipping enhancement. Here, the synaptic memory behavior of α-In2 Se3 is demonstrated by applying electrical gate voltages under white light. As a result, the induced internal electric field is identified at a polarization flipped conductance channel in α-In2 Se3 /hexagonal boron nitride (hBN) heterostructure ferroelectric field effect transistors (FeFETs) under white light and discuss the contribution of this built-in electric field on synapse characterization. The biased dipoles in α-In2 Se3 toward potentiation polarization direction by an enhanced internal built-in electric field under illumination of white light lead to improvement of linearity for long-term depression curves with proper electric spikes. Consequently, upon applying appropriate electric spikes to α-In2 Se3 /hBN FeFETs with illuminating white light, the recognition accuracy values significantly through the artificial learning simulation is elevated for discriminating hand-written digit number images.
Keywords: 2D materials; Fermi level shift; artificial synapses; built-in electric field; ferroelectric; polarization switching; α-In2Se3.
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