Ga2O3 Bipolar Heterojunction-Based Optoelectronic Synapse Array with Visual Attention.

The human brain efficiently processes only a fraction of visual information, a phenomenon termed attentional control, resulting in energy savings and heightened adaptability. Translating this mechanism into artificial visual neurons holds promise for constructing energy-efficient, bioinspired visual systems. Here, we propose a self-rectifying artificial visual neuron (SEVN) based on a NiO/Ga2O3 bipolar heterojunction with attentional control on patterns with a target color. The device exhibits short-term potentiation (STP) with quantum point contact (QPC) traits at low bias and transitions to long-term potentiation (LTP) at high bias, particularly facilitated by electron capture in deep defects upon ultraviolet (UV) exposure. With the utilization of two wavelengths of light upon the target and interference part of CAPTCHA to simulate top-down attentional control, the recognition accuracy is enhanced from 74 to 84%. These findings have the potential to augment the visual capability of neuromorphic systems with implications for diverse applications, including cybersecurity, healthcare, and machine vision.

Vertically integrated spiking cone photoreceptor arrays for color perception.

The cone photoreceptors in our eyes selectively transduce the natural light into spiking representations, which endows the brain with high energy-efficiency color vision. However, the cone-like device with color-selectivity and spike-encoding capability remains challenging. Here, we propose a metal oxide-based vertically integrated spiking cone photoreceptor array, which can directly transduce persistent lights into spike trains at a certain rate according to the input wavelengths. Such spiking cone photoreceptors have an ultralow power consumption of less than 400 picowatts per spike in visible light, which is very close to biological cones. In this work, lights with three wavelengths were exploited as pseudo-three-primary colors to form 'colorful' images for recognition tasks, and the device with the ability to discriminate mixed colors shows better accuracy. Our results would enable hardware spiking neural networks with biologically plausible visual perception and provide great potential for the development of dynamic vision sensors.

Solution-Processed, Electrolyte-Gated In2O3 Flexible Synaptic Transistors for Brain-Inspired Neuromorphic Applications.

Emulating the essential synaptic behaviors using single synaptic transistor has attracted extensive attention for building the brain-inspired neuromorphic systems. However, few reports on synaptic transistors fabricated by solution processes have been reported. In this article, the indium oxide synaptic transistors based on polyimide substrates were fabricated by a nontoxic water-inducement method at a low temperature, and lithium perchlorate (LiClO4) was dissolved in polyethylene oxide as the gate electrolyte. For water-inducement process, comparable electrical properties of the synaptic transistors can be achieved by prolonging the annealing time rather than high-temperature annealing with a relatively short time. The effect of the annealing time on the electrical performance of the electrolyte-gated transistors annealed at various temperatures was investigated. It is found that the electrolyte-gated-synaptic transistor on polyimide substrate annealed at 200 °C exhibits high electrical performance and good mechanical stability. Due to the ion migration relaxation dynamics in the polymer electrolyte, various important synaptic behaviors such as the excitatory postsynaptic current, paired-pulse facilitation, high-pass filtering characteristics, and long-term memory performance were successfully mimicked. The electrolyte-gated synaptic transistors based on solution-processed In2O3 exhibit great potential in neuromorphological applications.