Piezo-phototronic effect modulated optoelectronic artificial synapse based on a-Ga2O3/ZnO heterojunction

Amorphous gallium oxide (a-Ga2O3) based optoelectronic devices responds to deep ultraviolet (DUV), which triggers their potential applications for simulating biological vision system. However, there is still lack of research on the influence of multiple stimuli on regulating synaptic plasticity in artificial synapse. Herein, we reported a flexible a-Ga2O3/ZnO film heterostructure with tunable DUV photoresponse, serving as a promising platform for artificial optoelectronic synapse. Based on persistent photoconductivity effect under 265 nm illumination, basic synaptic functions have been mimicked. Notably, the strain-induced piezo-phototronic effect of the heterojunction enables the modulation of synaptic plasticity, playing a role analogous to neuromodulator interaction with biological synapse activity. Strain-evoked an additional degree of freedom controls synapse weight-update rate during learning process and synapse weight-decay during forgetting process. The underlying mechanism is attributed to energy band bending tailored by strain-induced piezo-potential that determines carrier separation/transport and the recombination reaction of ionized oxygen vacancy. The recognition accuracy of MNIST images is as high as 92.31% in the artificial neural network constructed by the heterojunction devices. This work not only exhibits the application prospect of ultra-wide bandgap semiconductor-based heterojunction in artificial optoelectronic synapse, but also opens up a new avenue for multiple stimuli modulating synaptic plasticity.