Emulation of synaptic behaviors using amorphous indium-gallium-zinc-oxide-based photoelectric synaptic devices

In this paper, we report the emulation of synaptic functions such as paired-pulse facilitation (PPF), spike-frequency dependent plasticity (SFDP), and spike-duration dependent plasticity (SDDP) using a solution-processed amorphous indium-gallium-zinc oxide (IGZO) photoelectric synaptic device. Particularly, instead of using electrical stimuli, we used an optical stimuli (light pulse) to modulate the synaptic weight of the IGZO photoelectric synaptic device which is equivalent to the conductance of the IGZO active layer. The time interval between the paired pulses, frequency and the pulse duration of the optical stimuli were controlled to emulate the PPF, SFDP, and SDDP behaviors, respectively. Also, we emulated the Ebbinghaus forgetting curve which is related to the memory retention behavior, as another possible demonstration of the IGZO-based photoelectric synaptic device.