Photoelectronic synaptic performance of SiOy/a-Si1-xRux bilayer based memristors

Neuromorphic computing refers to one of the most promising choices to solve the von Neumann bottleneck. The key to develop neuromorphic computing is to make the device able of simulating biological synaptic behavior. Optically stimulated synaptic devices have the advantages of fast speed and low energy consumption. Many materials including carbon group materials, oxide materials and 2D materials have been used to make photoelectronic synaptic devices. However, most of the devices can only respond by violet and/or ultraviolet light stimulation, and very few of them can work in the near-infrared range. Here, we report an optoelectronic synaptic device based on SiOy/a-Si1-xRux bilayer memristive materials. By doping with ruthenium (Ru), the optical bandgap of amorphous silicon (a-Si) film could be engineered, making the doped a-Si1-xRux film infrared sensitive. Therefore, a-Si1-xRux film can effectively absorb light illumination in a wideband range from 450 nm to 905 nm. Many photoelectronic synaptic behaviors including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF) and short-term plasticity (STP) to long-term plasticity (LTP) transition, have been simulated successfully by using different light spikes at wavelengths of 450 nm, 635 nm and 905 nm, respectively. We refer the obtained synaptic plasticities to originate from the trapping and de-trapping of photogenerated carriers by light-induced defects inside the silicon oxide (SiOy) which was deposited directly on a-Si1- xRux film, and to the generation of electron-hole pairs from the underlying a-Si1-xRux film. Our newly fabricated optoelectronic synaptic device shows a great application potential in neuromorphic computing.