Optoelectronic Synapses Based on Photo-Induced Doping in MoS2/h-BN Field-Effect Transistors

Synaptic device is an important component in artificial neural networks. Electrically-controlled long-term depression (LTD) is demonstrated in three-terminal photonic synaptic devices, which is useful for improving the efficiency of artificial neural networks. The mechanism of the three-terminal photonic synaptic device is similar to that of the photo-induced doping effect. Photo-assisted carrier transport and recombination are expected to accelerate the LTD process. However, the effects of photon illumination on LTD are not investigated. Here, the effects of electrical stimulation and photo-stimulation on the long-term plasticity (LTP) and LTD process of photonic synaptic devices based on MoS2/h-BN field-effect transistors (FETs) are systemically investigated. The influences of gate dielectric layer on the photo-induced doping are explored. The non-volatile and electrically-erasable properties of photo-induced doping in MoS2/h-BN FETs are due to the van der Waals energy barrier at the MoS2/h-BN interface. The synaptic functions of LTP and LTD can be mimicked by the photo-induced doping effect. The LTD process will be accelerated with the applications of positive gate voltage and laser illumination, which improves the speed of information processing. These results presented in this paper are useful for realizing high-performance synaptic devices based on the photo-induced doping effect.