Fig. 2: Tunable optoelectronic coupling characteristics and Paired-STDP behavior based on vdW phototransistors. | Nature Communications

Fig. 2: Tunable optoelectronic coupling characteristics and Paired-STDP behavior based on vdW phototransistors.

From: Bioinspired high-order in-sensor spatiotemporal enhancement in van der Waals optoelectronic neuromorphic electronics

Fig. 2

a Schematic structure of the InSe phototransistors under light-electric modulation. b Transfer characteristics of the InSe phototransistors recorded under dark, light illumination, and dark conditions, successively. The evolution of the photocurrent before and after light illumination suggests the PPC behavior of the InSe phototransistors. The drain–source voltage (Vds) is 0.1 V. Drain–source current (Ids) is defined as the drain–source current. c Persistent photoconductance response under a light spike with a duration of 5 s and amplitude of 87.83 mW cm−2. The inset histogram shows the distribution of conductance decay variation (ΔG) for the 20 InSe phototransistors (inset). The device variation is defined as the ratio of the standard deviation (\(\sigma\)) to the mean (\(\mu\)). d Experimental and fitted weight variation of asymmetric STDP as a function of time interval of a couple of light-electric spikes. The insets illustrate the applied pulse sequences: in the positive Δt region, the electric pulse precedes the light pulse, denoted as E-L; in the negative Δt region, the light pulse precedes the electric pulse, denoted as L-E. e The evolution of the conductance under the electric-light stimuli sequence in the first quadrant of asymmetric STDP. The measured electric-light pair is a light pulse of 87.83 mW cm−2 (10 ms) and Vbg of −40 V (10 ms). Note that ∆w is defined as (G2 − G1)/(G1 − G0), where G0 is the initial conductance, G1 and G2 are the conductance values following electrical and light stimuli, respectively. f Experimental and fitted weight variation of abnormal STDP as function of time interval of a couple of light-electric spikes. g The evolution of the conductance under the light-electric stimuli sequence in the third quadrant of asymmetric STDP. h The corresponding energy band diagrams to reveal the trap-assisted light-electric (TALE) cooperation behavior. i The corresponding energy band diagrams for TALE competition behavior. The measured light-electric pair is light pulse of 987.82 mW cm−2 (10 ms) and Vbg of 40 V (10 ms).

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