Robust non-volatile optical response for optoelectronic synapses in the dual-parallel α-In₂Se₃ device architecture

Two-dimensional (2D) materials have been widely used in optoelectronic detection due to their excellent physical properties. Nevertheless, there has been comparatively little focus on the differentiation of light-matter interactions across distinct channel paths within the same 2D material, as well as on the photoelectric characteristics exhibited by the surface, vertical, and bottom of device. In this paper, dual-parallel device structures utilizing 2D α-In₂Se₃ semiconductors are fabricated with four conductive channels named by bottom-horizontal channel (BHC), middle-vertical channel (MVC), surface-quasi-horizontal channel (SQHC), and surface-horizontal channel (SHC) devices. The SHC device exhibits superior optical response of 101 A/W and external quantum efficiency of 1.857 × 10⁴% across all conductive channels, which is over 32 times greater than that of BHC device. The SHC device boasts a fast response time of 41 ms, comparable to 32 ms offered by the nanoscale channel of the MVC device, and has a slow decay time of 319 ms similar to the 424 ms that comes with the longest channel of the SQHC device. The SHC device has the highest degree of learning and the lowest forgetting rate compared to the other three channels. Optoelectronic synapses based on dual-parallel α-In₂Se₃ device can also mimic biological color image perception and memory functions, which can be used to visually determine the synaptic function of the device. In this work, on top of the excellent optoelectronic and semiconducting properties of the van der Waals semiconductor α-In₂Se₃, the advantages offered by the device structure are further explored to promote the development of integrated optoelectronics.