Reconfigurable Homojunction\nPhototransistor for Near-Zero\nPower Consumption Artificial Biomimetic Retina Function

Semiconductor photodetectors integrating\npreliminary\nsignal-processing\nfunctions play a vital role in artificial biomimetic retina systems.\nHerein, we propose a tungsten diselenide (WSe<sub>2</sub>) phototransistor\nwith a dual-layer gate dielectric and an asymmetric graphene insert\nstructure. This phototransistor exhibits a bidirectional self-powered\nphotocurrent by controlling the gate voltage via the formation of\nreconfigurable p<sup>+</sup>–p and n–p homojunctions\nin the channel from the asymmetric graphene insert. At the same time,\nthe nonvolatile electron and hole stored in the dual-layer gate dielectric\nare generated using a temporary gate voltage, which can replace the\ngate voltage to regulate the channel charge. Moreover, the photocurrent\nshows a linear relation with the temporary programming gate voltage.\nThe phototransistor exhibits a rectification ratio of >4 orders\nof\nmagnitude without the gate voltage, indicating its significant capability\nto operate in a fully self-powered mode with near-zero power consumption.\nBased on the device characteristics, we successfully simulate the\nbiological functions of the photoreceptor layer and bipolar cell layer\nin the retinal receptive field. The identification of the object motion\ndirection in the receptive field can be realized by integrating three\nprogrammable devices on the chip. Furthermore, edge enhancement of\nthe image is achieved by independently modulating the light response\nof each pixel in the sensor by varying the programming gate voltage.\nThis study will promote the developing progress of future artificial\nbiomimetic retina systems.