InGaZnO-based photoelectric synaptic devices for neuromorphic computing

Photoelectric synaptic devices could emulate synaptic behaviors utilizing photoelectric effects and offer promising prospects with their high-speed operation and low crosstalk. In this study, we introduced a novel InGaZnO-based photoelectric memristor. Under both electrical and optical stimulation, the device successfully emulated synaptic characteristics including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), long-term potentiation (LTP), and long-term depression (LTD). Furthermore, we demonstrated the practical application of our synaptic devices through the recognition of handwritten digits. The devices have successfully shown their ability to modulate synaptic weights effectively through light pulse stimulation, resulting in a recognition accuracy of up to 93.4%. The results illustrated the potential of IGZO-based memristors in neuromorphic computing, particularly their ability to simulate synaptic functionalities and contribute to image recognition tasks.

High-performance amorphous In–Ga–Zn–O thin-film transistor nonvolatile memory with a novel p-SnO/n-SnO_(2) heterojunction charge trapping stack

Amorphous In–Ga–Zn–O(a-IGZO)thin-film transistor(TFT)memories with novel p-SnO/n-SnO_(2) heterojunction charge trapping stacks(CTSs)are investigated comparatively under a maximum fabrication temperature of 280℃.Compared to a single p-SnO or n-SnO_(2) charge trapping layer(CTL),the heterojunction CTSs can achieve electrically programmable and erasable characteristics as well as good data retention.Of the two CTSs,the tunneling layer/p-SnO/nSnO_(2)/blocking layer architecture demonstrates much higher program efficiency,more robust data retention,and comparably superior erase characteristics.The resulting memory window is as large as 6.66 V after programming at 13 V/1 ms and erasing at-8 V/1 ms,and the ten-year memory window is extrapolated to be 4.41 V.This is attributed to shallow traps in p-SnO and deep traps in n-SnO_(2),and the formation of a built-in electric field in the heterojunction.

A field-effect WSe_(2)/Si heterojunction diode

It is significant to develop a heterogeneous integration technology to promote the application of two-dimensional(2D)materials in silicon roadmap. In this paper, we reported a field-effect WSe_(2)/Si heterojunction diode based on ambipolar 2D WSe_(2) and silicon on insulator(SOI). Our results indicate that the device exhibits a p–n diode behavior with a rectifying ratio of ~300 and an ideality factor of 1.37. As a photodetector, it has optoelectronic properties with a response time of 0.13 ms, responsivity of 0.045 A/W, detectivity of 4.5×10~(10) Jones and external quantum efficiency(EQE) of 8.9 %.Due to the ambipolar behavior of the WSe_(2), the rectifying and optoelectronic properties of the heterojunction diode can be modulated by the gate electrical field, enabling various potential applications such as logic optoelectronic devices and neuromorphic optoelectronic devices for in-sensor computing circuits. Thanks to the process based on the mature SOI technique, our field-effect heterojunction diode should have obvious advantages in device isolation and integration.

Recent progress on ambipolar 2D semiconductors in emergent reconfigurable electronics and optoelectronics

In these days,the increasing massive data are being produced and demanded to be processed with the rapid growth of information technology.It is difficult to rely solely on the shrinking of semiconductor devices and scale-up of the integrated circuits(ICs)again in the foreseeable future.Exploring new materials,new-principle semiconductor devices and new computing architectures is becoming an urgent topic in this field.Ambipolar two-dimensional(2D)semiconductors,possessing excellent electrostatic field controllability and flexibly modulated major charge carriers,offer a possibility to construct reconfigurable devices and enable the ICs with new functions,showing great potential in computing capacity,energy efficiency,time delay and cost.This review focuses on the recent significant advancements in reconfigurable electronic and optoelectronic devices of ambipolar 2D semiconductors,and demonstrates their potential approach towards ICs,like reconfigurable circuits and neuromorphic chips.It is expected to help readers understand the device design principle of ambipolar 2D semiconductors,and push forward exploring more new-principle devices and new-architecture computing circuits,and even their product applications.

Two-dimensional complementary gate-programmable PN junctions for reconfigurable rectifier circuit

The unique features of ambipolar two-dimensional materials open up a great opportunity to build gate-programmable devices for reconfigurable circuit applications,e.g.,PN junctions for rectifier circuits.However,current-reported rectifier circuits usually consist of one gate-programmable PN junction as the rectifier and one resistor as the load,which are not conductive to voltage output and large-scale integration.Here we propose an approach of complementary gate-programmable PN junctions to assemble reconfigurable rectifier circuit,which include two symmetric back-to-back black phosphorus(BP)/hexagonal boron nitride(h-BN)/graphene heterostructured semi-gate field-effect transistors(FETs)and perform complementary NP and PN junction like complementary metal-oxide-semiconductor(CMOS)circuit.The investigation exhibits that the circuit can effectively reconfigure the circuit with/without rectifying ability,and can process alternating current(AC)signals with the frequency prior 1 KHz and reconfiguration speed up to 25μs.We also achieve the reconfigurable rectifier circuit memory via complementary semi-floating gate FETs configuration.The complementary configuration here should be of low output impedance and low static power consumption,being beneficial for effective voltage output and large-scale integration.

Organic heterojunction synaptic device with ultra high recognition rate for neuromorphic computing

Traditional computing structures are blocked by the von Neumann bottleneck,and neuromorphic computing devices inspired by the human brain which integrate storage and computation have received more and more attention.Here,a flexible organic device with 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene(C8-BTBT)and 2,9-didecyldinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene(C10-DNTT)heterostructural channel having excellent synaptic behaviors was fabricated on muscovite(MICA)substrate,which has a memory window greater than 20 V.This device shows better electrical characteristics than organic field effect transistors with single organic semiconductor channel.Furthermore,the device simulates organism synaptic behaviors successfully,such as paired-pulse facilitation(PPF),long-term potentiation/depression(LTP/LTD)process,and transition from short-term memory(STM)to long-term memory(LTM)by optical and electrical modulations.Importantly,the neuromorphic computing function was verified using the Modified National Institute of Standards and Technology(MNIST)pattern recognition,with a recognition rate nearly 100%without noise.This research proposes a flexible organic heterojunction with the ultra-high recognition rate in MNIST pattern recognition and provides the possibility for future flexible wearable neuromorphic computing devices.

A high-speed 2D optoelectronic in-memory computing device with 6-bit storage and pattern recognition capabilities

The explosively developed era of big-data compels the increasing demand of nonvolatile memory with high efficiency and excellent storage properties.Herein,we fabricated a high-speed photoelectric multilevel memory device for neuromorphic computing.The novel two-dimensional(2D)MoSSe with a unique Janus structure was employed as the channel,and the stack of Al_(2)O_(3)/black phosphorus quantum dots(BPQDs)/Al_(2)O_(3)was adopted as the dielectric.The storage performance of the resulting memory could be verified by the endurance and retention tests,in which the device could remain stable states of programming and erasing even after 1,000 cycles and 1,000 s.The multibit storage could be realized through both different voltage amplitudes and pulse numbers,which could achieve 6 bits(64 distinguishable levels)under pulse width of 50 ns.Furthermore,our memory device also could realize the simulations of synapses in human brain with optical and electric modulations synergistically,such as excitatory post-synaptic current(EPSC),long-term potentiation/depression(LTP/LTD),and spike-timing-dependent plasticity(STDP).Neuromorphic computing was successfully achieved through a high recognition of handwritten digits up to 92.5%after 103 epochs.This research is a promising avenue for the future development of efficient memory and artificial neural network systems.

Van der Waals contacted WSe_(2) ambipolar transistor for in-sensor computing

Image sensors with an in-sensor computing architecture have shown great potential in meeting the energy-efficient requirements of emergent data-intensive applications,where images are processed within the photodiode arrays.It demands the composed photodiodes are reconfigurable,which are usually achieved by ambipolar two-dimensional(2D)semiconductors.To improve the ambipolar charges injection,here we report a top-gated field-effect transistor(FET)design that is of bottom van der Waals contact via transferring ambipolar 2D WSe_(2) onto Pd/Cr source/drain electrodes.The devices exhibit nearly negligible effective barrier heights for both holes and electrons based on thermionic emission mode,and show an almost balanced on/off ratio in the p-branch and n-branch.By replacing the top gate with two aligned semi-gates,the devices can effectively function as reconfigurable photodiodes.They can be switched between PIN and NIP configurations via controlling the two semi-gates,exhibiting good linearity in terms of short-circuit current(ISC)and incident light power density.The photodiode arrays are also demonstrated for in-sensor optoelectronic convolutional image processing,showing significant potential for in-sensor computing image processors.

Ferroelectric artificial synapse for neuromorphic computing and flexible applications

Research of artificial synapses is increasing in popularity with the development of bioelectronics and the appearance of wearable devices.Because the high-temperature treatment process of inorganic materials is not compatible with flexible substrates,organic ferroelectric materials that are easier to process have emerged as alternatives.An organic synaptic device based on P(VDF-TrFE)was prepared in this study.The device showed reliable P/E endurance over 104 cycles and a data storage retention capability at 80℃ over 104 s.Simultaneously,it possessed excellent synaptic functions,including short-term/long-term synaptic plasticity and spike-timing-dependent plasticity.In addition,the ferroelectric performance of the device remained stable even under bending(7 mm bending radius)or after 500 bending cycles.This work shows that low-temperature processed organic ferroelectric materials can provide new ideas for the future development of wearable electronics and flexible artificial synapses.