Integrated Opto-Synaptic IGZO Transistors for Image Recognition Fabricated at Room Temperature
Shu Ming Qi, Jia Cheng Li, Yang Hui Xia, Zi Chun Liu, De Dai, Ting Song, Huixia Yang, Yuan Xiao, Yeliang Wang
Abstract
At room temperature, high-κ HfLaO is adopted as the gate dielectric to fabricate amorphous InGaZnO (a-IGZO) optical synaptic thin-film transistors (TFTs), for which plasma treatments are conducted on the HfLaO dielectric in O 2 and a-IGZO in Ar, respectively, namely, OPT/APT-TFTs. Consequently, high-performance a-IGZO TFTs are obtained with a high carrier mobility of 20.8 cm 2 /V·s, a high I on / I off ratio of 3.2 × 10 6, and a small subthreshold swing (SS) of 0.25 V/dec. As compared to the pristine TFTs, the photocurrent of the OPT/APT-TFTs under a 365 nm ultraviolet (UV) light is significantly raised three times up to 1.4 μA. Meanwhile, the current decay percentage after irradiation removal is reduced from 98% down to 36% within 60 s, indicating an enhanced persistent-photoconductivity (PPC) effect. Accordingly, various optical synaptic plasticities are obtained based on which a simulated neuronal network with a high 93.22% accuracy is achieved to recognize MNIST handwritten digits. Moreover, both neurotransmitter and neuromodulator behaviors are concurrently emulated in a single device through exploiting the native three-terminal structure of the TFT. Importantly, an artificial visual nervous system is successfully constructed by integrating the a-IGZO optoelectronic TFTs for image recognition.