A thousand-state optoelectronic memory for high-precision spatiotemporal encoding

Domain: neuroscience
Published: 2026-04-13
Editorial outcome: major_revision

Abstract
Conventional photodiodes can distinguish subtle illumination variations, but fail to retain information. Conversely, optoelectronic memories can store light information but encounter difficulties in multiple-state storage due to noise from the deexcitation recombination of the photogenerated carriers. Here we develop an optoelectronic memory that can generate a multilevel response to light stimuli and retain the multi-states in a nonvolatile manner. In the designed type-III heterojunction device, electrons flow from high-Fermi-level (E) p-type amorphous carbon to low-E n-type TiO , generating an unusual built-in electric field that enhances majority carrier transport. Photogenerated electrons from the oxygen vacancies in TiO quickly combine with holes from amorphous carbon, effectively reducing deexcitation recombination with charged vacancies and associated noise. The resulting device achieves 1,024 distinguishable optoelectronic memory states without any denoising process, enabling high-precision spatiotemporal information encoding. The thousands of states in optoelectronic memory allows for the emulation raptor vision to perception fast-moving objects.

Introduction
Bioinspired in-sensor vision processing highly demands devices that can store multiple distinct optoelectronic memory states for accurate perception of complex and delicate motions 1-5. Conventional photodiodes, however, are unable to retain light stimuli owing to their transient response. While optoelectronic memories can preserve the information after the removal of light stimuli, they face challenges such as noise from deexcitation recombination and the relaxation of photogenerated electrons and holes 6-8. These factors lead to conductance fluctuations, making optoelectronic memory states indistinguishable and limiting the storage of multiple states.

For an analog resistive switching memory, the intrinsic tunable conductance range allows for an unlimited number of states, because the conductance gap (△G) between adjacent states can be infinitely divided 9. However, the adjacent states of optoelectronic memory can overlap due to spontaneous electron/hole recombination and relaxation 10-12. When △G is small, the neighboring conductance states merge into one state because of noise interference, compromising the storage capacity of the device. In most optoelectronic memory devices, the deexcitation recombination of photogenerated carriers as major noise causes photoconductance relaxation and overlap 13-15, thus limiting the encoding precision. For electrically driven resistive switching memories, random telegraph noise (RTN) associated with defect dynamics causes fluctuations at each conductance state 16. After suppressing RTN from hundreds of nanoamperes to tens of nanoamperes by applying small voltages, Yang et al. demonstrated thousands of conductance states with small △G of 2.0 μS 17. However, the optoelectronic response involves multiple physical processes, including photocarrier generation, transport, and recombination. Defects can be used to alter the decay kinetics of photogenerated carriers 18-20, leading to persistent photoconductivity for information storage. The noise from carrier dynamics of defects can undoubtedly impair precise conductance control in optoelectronic memory devices 21. Meanwhile, the requirements for real-time response in optoelectronic perception also preclude the possibility of employing a post-programming denoising scheme. Consequently, it is essential to explore alternative strategies for multilevel optoelectronic memories that can effectively mitigate noise interference and achieve precise fine-grained conductance control.

In this work, we design an optoelectronic memory device with a vertical structure of fluorine-doped tin oxide (F-doped SnO , FTO)/amorphous carbon (a-Carbon)/TiO /Au. This type-III heterojunction generates an unusual built-in electric field that promotes majority carrier transport. Consequently, the photogenerated electrons from neutral oxygen vacancies (V ) in n-type TiO can rapidly combine with the holes from p-type a-Carbon, largely suppressing the recombination of electrons and conductive oxygen vacancies (V 1+ or V 2+) and resulting in conductance change of TiO . The designed device further enables precise tuning of light-induced conductive vacancies in TiO , achieving thousands of optoelectronic memory states without any denoising technique. By configuring thousands of memory states under high frequency light stimuli, the type-III heterojunction optoelectronic memory can emulate raptor to precisely fuse spatiotemporal vision information for perception complex fast-moving objects.

Results
Mechanisms of type-III heterojunction optoelectronic memory

In a conventional photodiode, electrons and holes quickly recombine after removing light stimuli, thus only supplying a transient photoresponse and failing to store information after light stimuli (left of Fig. 1a, Supplementary Fig. 1). An optoelectronic memory device 22-24 can store information after light stimuli, such as, photogenerated electrons stored in oxygen vacancies. For the designed optoelectronic memory based on the a-Carbon/TiO heterojunction, it relies on the carrier recombination at broadened space charge region (positive bias condition) to finely modulate the concentration of the charged oxygen vacancies, thus building thousands of optoelectronic memory states (right of Fig. 1a). Fig. 1b schematically compares the photoresponse of the optoelectronic memory with a conventional photodiode. The photodiode can respond fast to light stimuli, but fails to build optoelectronic memory states. In contrast, optoelectronic memory devices show multiple memory states through subtly modulating the △G. Within intrinsic conductance range, distinguishable state number n is governed by the △G, which is primarily dominated by the change in the concentration of the storage electrons.

We fabricated an optoelectronic memory features F-doped SnO /a-Carbon/TiO /Au vertical structure (Fig. 1c). The valence-band maximum of p-type a-Carbon exceeds the conduction-band minimum of n-type TiO , creating a type-III heterojunction. For the p-type a-Carbon, the ultraviolet photoelectron spectroscopy (UPS) measurement demonstrated that its Fermi level and valence-band maximum located at -3.55 eV and -4.29 eV, respectively (Supplementary Fig. 2a-2b). The fitting results of the ultraviolet-visible (UV-vis) illustrated that optical band gap of the a-Carbon is 2.23 eV (Supplementary Fig. 2c). According to the valence-band maximum and the optical band gap, the conduction-band minimum is -2.06 eV. The optical band gap of 2.23 eV enables electron-hole pair generation under 405-nm ultraviolet light illumination (3.06 eV photon energy). However, the Raman spectrum illustrated that the p-type a-Carbon involves a large number of π electrons in sp2 orbits, which are highly sensitive to 405-nm light stimuli as well as natural light (Supplementary Fig. 3).

For the n-type TiO , the Fermi level, valence-band maximum, conduction-band minimum, and optical band gap are -5.17 eV, -8.07 eV, -4.91 eV, and 3.16 eV, respectively (Supplementary Fig. 4a-4c). This characteristic suggests that the electron in the valence band of the TiO cannot be directly excited by the 405-nm ultraviolet light. Oxygen vacancies are introduced to form stoichiometric mismatch titanium oxide (TiO ) during the fabrication process 24-26, which is verified by the Ti O component in the titanium oxide through X-ray photoelectron spectroscopy analysis (Supplementary Fig. 5). These vacancies establish defect levels between the valence-band maximum and conduction-band minimum, allowing electrons in these vacancy-induced levels to be excited by 405 nm ultraviolet light.

The thin films were deposited under optimized sputtering parameter, showing a low roughness (R ~ 0.9 nm) and providing a high-quality contact interface between TiO film and a-Carbon film (Supplementary Fig. 6). The FTO/a-Carbon forms Schottky contact (Φ > Φ ) that can facilitate the photogenerated electrons to quickly transport out from the a-Carbon. The TiO /Au builds Ohmic contact (Φ > Φ , ΔΦ ~ 0.07eV) that can facilitate the possible residual photogenerated electrons to transport from the TiO after light stimuli, increasing the stability of the optoelectronic memory states (Supplementary Fig. 7). The high-resolution transmission electron microscopy (HR-TEM) characterization shows dense contact interfaces, ensuring the photogenerated carriers with highly efficient transport (Supplementary Fig. 8). The two-terminal device structure provides downward scaling potential and integrate with waveguides that can transmit light beam with smaller spot for advanced in-sensor computing system (Supplementary Fig. 9-11). Notably, small size of the device produces high spatial resolution and the matched nanoscale light source is desirable for optical addressing. For conventional optical system within visible light range, the minimum size of light spot is in micrometer level (1.0~5.0 μm) due to light diffraction limit, causing the optical system such as the spatial light modulator (SLM) with ~12.5 μm pixel pitch. To break through the limitation, extreme manufacturing technologies including superstructure surface based on subwavelength nanocolumn arrays 27, 28 and nanoscale organic light-emitting diodes (OLEDs) 29 are developed for high precision optical addressing. The size of a single light spot for superstructure surface nanocolumn and OLED is as low as several hundred nanometers. These technologies provide a promising chance of optical addressing for the type-III heterojunction optoelectronic memory.

Fig. 1d illustrates the working principle of the designed type-III heterojunction. The Fermi level of p-type a-Carbon is higher than both the Fermi level and the conduction-band minimum of n-type TiO (Supplementary Fig. 12), allowing electrons from a-Carbon to fill the oxygen vacancies in TiO film. It produces neutral oxygen vacancies in TiO . As a result, the built-in electric field (E ) in the type-III heterojunction is directed from p-region (a-Carbon) to n-region (TiO ), fundamentally differing from conventional pn junction. When a positive voltage is applied on the side of p-type a-Carbon (positive bias), the E is enhanced and the space charge region is extended. Under the 405-nm light illumination, the V in TiO converts to conductive charged oxygen vacancies (V 1+and V 2+) and photoelectrons (𝑉 +ℎ𝑣 → 𝑉1+ +1𝑒 or 𝑉 +ℎ𝑣 → 𝑉2+ + 2𝑒) 24, 25, 30, 31. The concentration of V 1+and V 2+ can be controlled by the dosage of the light stimuli, empowering the type-III heterojunction optoelectronic devices to achieve multiple memory states.

The photogenerated electrons from V in TiO are accelerated by the enhanced E . In p-type a-Carbon, electron-hole pairs are generated under light stimuli and then separated by the external electric field (E ). These holes are accelerated by the enhanced E . Consequently, the electrons from TiO quickly recombine with the holes from a-Carbon at the broadened space charge region. The rapid electron-hole recombination plays an essential role in constructing multiple optoelectronic memory states 32-34. For the n-type TiO , this process not only accelerates electron-vacancy separation but also decreases their recombination. For the p-type a-Carbon, this process helps the photogenerated holes rapidly transport out of the a-Carbon, avoiding the electron-hole recombination. The carrier dynamics enable stable modulation of charged oxygen vacancy concentration in the type-III heterojunction device, directly establishing multiple optoelectronic memory states. Notably, noise arising from deexcitation recombination (electron-hole in p-type a-Carbon and electron-vacancy in n-type TiO ) is effectively suppressed by this carrier recombination. This design maximizes the number of encodable optoelectronic memory states within this optoelectronic device, eliminating the need for additional denoising processes.

To elucidate the deexcitation recombination suppression mechanism, we conducted first-principles calculation, external quantum efficiency (EQE) analysis, and electron paramagnetic resonance (EPR) measurement. First-principles calculations reveal unidirectional electron transfer from p-type a-Carbon to n-type TiO (Fig. 1e, Supplementary Fig. 13), demonstrating an inverted E orientation. This unusual behavior originates from the higher Fermi level of p-type a-Carbon relative to n-type TiO . Appropriate reduction the a-Carbon thickness not only avoids overshoot photocurrent but also maintains controllable holes for the recombination with electrons from the TiO layer, while a relative thick TiO layer can accommodate more oxygen vacancy as well as reduces the leakage current.

At the wavelength of 405 nm, the EQE of the a-Carbon is more than eightfold higher than that of the TiO (2.57% for a-Carbon and 0.3% for TiO ) (Fig. 1f). It suggests that p-type a-Carbon can supply much more photogenerated holes than electrons photogenerated from TiO . In this scenario, the quenching of photogenerated electrons is facilitated at the broadened space charge region. In consequence, the photogenerated electrons are swiftly extracted from TiO and eliminated in the junction region, in turn suppressing deexcitation recombination of the V 1+(or V 2+) with photogenerated electrons in TiO . This process in-situ reduces noise from de-excitation recombination during the programming of optoelectronic devices. The optical band gap of 3.16 eV in TiO ensures that nearly all photogenerated electrons originate from oxygen vacancy sites rather than its valence band, although it exhibits a low EQE value.

The existence of V is characterized by the EPR. The V is featured by a specific spectral splitting factor (g value) of 2.003, and its concentration is 3.10×10^12 spins g^-1 (Fig. 1g, Supplementary Fig. 14). Additionally, we extracted the threshold voltage (V , 1.15V) from the space charge limited current mechanism fitted by double logarithm I-V curves of the Au/TiO /Au device, showing a V concentration of 6.6×10^22 m^-3 (Supplementary Fig. 15). These oxygen vacancies are the source of the optoelectronic memory states. Under light illumination, electrons are detrapped from the neutral oxygen vacancy sites, converting the oxygen vacancy from neutral state to charged state. The optoelectronic memory states are reconfigured by controlling the concentration ratio of the charged oxygen vacancies.

High-precision programming for thousands of states

The current-voltage (I-V) curves measured under both dark and illumination reveal that the optoelectronic memory exhibits a positive photoresponse across the entire range of its analog switching behaviour (Fig. 2a). For electric switching mechanism, electrons are progressively injected into the a-Carbon layer when positive voltage scan is applied on Au, subsequently traversing the narrowed space charge region to generates a continuous increase current. When negative voltage is operated, the electron injection is significantly suppressed in TiO due to scattering effect and Coulomb blockade effect. The continuous electrical switching is dominated by the electron trapping/detrapping dynamics instead of the filamentary conduction mechanisms 8,17, 32.

The photoresponse depends on the light dosage and can be efficiently modulated by pulse count, frequency, width, and light intensity (Supplementary Fig. 16a-e). The optoelectronic memory under two consecutive light pulses with different intervals exhibits typical paired-pulse facilitation (PPF), suggesting the good potential to emulate retina synapses for vision information processing (Supplementary Fig. 16f).

The V builds E that can affect the E amplitude. Under positive bias condition, a large V accelerates carriers fast-transport and rapidly recombines, thus strengthening the suppression of the deexcitation recombination. Under specified V and light stimuli with fixed duty ratio and fixed intensity, the high-frequency stimuli (and correspondingly lower light dosage per pulse) generate smaller △G values, which allows the optoelectronic memory to build more states within its intrinsic conductance range.

Different △G (1.2 nS; 16.12 nS; 181.3 nS; and 1420 nS) can be respectively triggered by the stimuli (0.02V, width of 1.0 ms, interval of 1.0 ms; 0.2 V, width of 10 ms, interval of 10 ms; 0.2 V, width of 10^2 ms, interval of 10^2 ms; and 1.25 V, width of 10^6 ms, interval of 10^6 ms) with constant intensity of 0.75 μW μm^-2 (Fig. 2b). After light stimuli, the optoelectronic memory states can be well maintained for 1,000 s, suggesting that these optoelectronic memory states that across different time scale are nonvolatile (Supplementary Fig. 17). These optoelectronic memory states can be well modulated and retained in different time scales, allowing for various perception tasks across various time scales.

Ultraviolet light with wavelength of 405 nm, intensity of 0.65 μW μm^-2 and width (interval) of 1, 10, and 200 ms is applied to the type-III heterojunction optoelectronic memory device, yielding the △G values of 0.01, 0.58, and 19.80 nS (Fig. 2c, 0.1s sampling step). The finer photocurrent response is feasible for higher light stimuli frequency (2.5 μW μm^-2, width of 50 μs, interval of 50 μs) (Supplementary Fig. 18). Therefore, the △G of the type-III heterojunction optoelectronic memory simultaneously relies on the light stimuli condition (width, interval, and intensity) and the bias, showing as increase as light dosage and bias voltage (Supplementary Fig. 19).

For the type-III heterojunction optoelectronic memory, the non-volatile memory states are stably maintained through optical programming at “1” positions, while active electrical modulation at “0” positions enable fine-tuned control via light pulse sequence-dependent adjustments. Fig. 2d demonstrates the encoding results of “1000000000”, “1000000001”, and “1111111111”. The “1” represents the photoresponse under one pulse light stimulus (intensity of 1.25 μW μm^-2, width of 500 μs, interval of 500 μs, and 0.1 ms sampling step) while the “0” position is matched a reading voltage pulse (0.2 V, 500 μs) denotes the photoresponse under darkness (Supplementary Fig. 20).

Under 1,000 Hz light stimuli (width of 500 μs, interval of 500 μs), the photoresponse is progressively adjusted by various intensities from 0.69 to 2.07 μW μm^-2, demonstrating a high linearity of 99.7% (Fig. 2e, 0.1s sampling step). This high linearity enables the optoelectronic memory to establish uniform △G across multiple memory states, ensuring precise and reliable optical information encoding.

With the multi-bit encoding strategy, different pulse chains yield distinct optoelectronic memory states (Supplementary Fig. 21). Fig. 2f is the sorted photocurrent for the 10-bit encode, in which each current value is achieved after the light stimuli with an intensity of 1.25 μW μm^-2 and width (interval) of 500 μs. Therefore, the type-III heterojunction optoelectronic memory can provide thousands of distinct states for fast vision encoding under specific light dosage by appropriate light stimuli.

Thousands of states in the optoelectronic memory

Fig. 3 shows the thousands of states achieved from the type-III heterojunction optoelectronic memory. Left inset of Fig. 3a schematically shows the optoelectronic memory states triggered by the light pulse chain according to the 10-bit binary code. According to the 10-bit binary code chains, 1,024 optoelectronic memory states are achieved after operating the corresponding light pulse chains with intensity of 1.25 μW μm^-2, width of 500 μs, and interval of 500 μs (right inset of Fig. 3a). After light stimuli for each memory state, the type-III heterojunction optoelectronic memory is reset by a negative voltage pulse (-4.0 V, 500 μs). The 1,024 optoelectronic memory states only possess a volatility rate of ~3% within 1,000 s (Supplementary Fig. 22a). The enlarged region of the Fig. 3a illustrates that these optoelectronic memory states, which are one-by-one triggered by the 10-bit light pulse chain, can be completely distinguished (Supplementary Fig. 22b). To verify the reliability of these states, we carried out the current fluctuation analysis. Fig. 3b depicts the temporal evolution of the programmed current for 420th and 421st states under 0.2 V. The statistical analyses of the 420th and 421st states exhibit a fluctuation of ~ 0.19 nA, which is smaller than the average current gap (△I=0.245 nA) between adjacent levels among the 1,024 states. The programmed conductance states can be well distinguished (Fig. 3c). The mean value gap of 0.25 nA demonstrates a clear separation between the 420th and 421st state. The statistics for the 420th and 421st states, based on consecutive sampling points (sample n and sample n+1), reveal tight intra-state distributions and clear inter-state separation (Fig. 3d). The 1,024 states are tested repeatedly on the same cell 50 times (Fig. 3e). Each set of the 1,024 states is highly consistent and fully reproducible. Therefore, the type-III heterojunction optoelectronic memory shows good cycle-to-cycle stability for the 1,024 states. After each programming cycle, the optoelectronic memory can be reset by a negative voltage (-4.0 V, 500 μs). The 1,024 states are available for each cell within the 24 cells, suggesting excellent device-to-device stability (Supplementary Fig. 23).

Fig. 3f exhibits the average gap between adjacent states (△G) and the current range (i.e., the difference between the 1st state and the 1,024th state), highlighting both cycle-to-cycle and device-to-device stability. These stability metrics illustrate that the 1,024 states are distinguishable with a △G of 1.27 ± 0.02 nS and a current range of 0.28±0.015 μA across 50 cycles and 24 cells. In comparison, the type-II heterojunction optoelectronic memory (FTO/a-Carbon/MoS /Au) and the control optoelectronic memory (Au/TiO /Au) show more than two-order fluctuation (~200 nS) (Supplementary Fig. 24-26).

This photoelectronic synergy encoding mechanism fundamentally relies on the nonequilibrium dynamics of photogenerated carriers. In the a-Carbon layer, intense light absorption generates a substantial population of photogenerated electrons and holes, resulting in an overshoot photocurrent due to carrier accumulation. Conversely, in the TiO layer, photogenerated electrons originate from neutral oxygen vacancies (V ), which subsequently transform into charged oxygen vacancies (V x+), a process that underpins nonvolatile photoconductance memory states.

The recombination of majority carriers (holes, h+, from a-Carbon) with minority carriers (electrons, e-, from V ) in the space charge region leads to a surplus of h+ within this region. Driven by the built-in electric field (E ), these surplus h+ migrate toward the TiO side, effectively shortening the space charge region. This carrier redistribution, however, diminishes the width of the space charge region, thereby weakening its efficiency.

To counteract this weakening effect, a matched positive bias of +0.2 V (E ) is applied to the '0' position. This external field compensates for the E reduction caused by carrier nonequilibrium, restoring the space charge region width and barrier integrity. Importantly, it introduces timing sequence sensitivity, enabling precise light pulse modulation. Consequently, the programming process achieves enhanced stability and reproducibility, as the bias actively mitigates carrier-induced nonequilibrium effects while leveraging the pulse sequence for dynamic control.

The inter-physical mechanism enables the designed type-III heterojunction optoelectronic device with thousands of optoelectronic memory states, but the number of the distinguishable states may be affected by noise sources such as deexcitation recombination noise, RTN, shot noise, and thermal noise. The shot noise can play a significant role in photodiodes operating under reverse bias 35, 36. However, at room temperature and within the terahertz range, thermal and shot noise are frequency-independent and have minimal impact on devices operating at low frequencies 21. In our device, the programmed optoelectronic memory state is read under a direct current (DC) forward bias. The de-excitation recombination noise and RTN as the possible primary noise sources. RTN can be attributed to either electronic 37 or atomic 38 effects.

By introducing EQE difference across the type-III heterojunction, deexcitation recombination noise is in-situ suppressed during the optical programming of the proposed optoelectronic memory. The proposed device is programmed optically instead of electrically, preventing defect migration in the switching layer. This precludes atomic effect-induced RTN. The optical switching behaviours in the proposed device relies on the electron detrapping from oxygen vacancies and collective hopping. RTNs from electronic effects are intimately associated with carrier trapping/emission at local defects. According to the Poole-Frenkel model 39, an applied electric field reduces the emission barrier for electrons in the defect and increases the local temperature nearby, thereby elevating the rate of electron capture and emission at the defect 40. Furthermore, the conductance modulation in the proposed device primarily relies on defects (V ) near the heterojunction interface. The band bending at the heterojunction may further accelerate carrier capture and emission at these defects. The greatly accelerated carrier dynamics result in smoother level averaging and reduced RTN amplitude. Moreover, carrier hopping in the devices involves many defects. The superposition of RTN effects across these defects makes RTN from a single defect indistinguishable, thereby diminishing its impact 41. The low noise amplitude after programming in the proposed device confirms the minimal impact of RTN. Additionally, the sum of multiple random variables tends to follow a normal distribution, provided each variable’s influence is limited 42. In the proposed device, the individual states after programming follow a normal distribution (Fig. 3c), indicating that RTNs from multiple defects overlap, thereby reducing their impact.

The RTN in oxidic memristors comes from the incomplete conduction filaments (ICM) 17, while electron trapping and detrapping along with collective hopping effect eliminate the filament formation in the type-III heterojunction optoelectronic memory 40, 41. The electric fast-RESET (-2.5 V, 100 μs), continuous electrical switching of the control samples (FTO/a-Carbon/Au, FTO/TiO /Au), and SA-TEM observation confirm that the type-III heterojunction optoelectronic memory is dominated by electron trapping and detrapping mechanism instead of the conduction filaments that generally cause an abrupt SET and RESET processes43-46 (Supplementary Fig. 27-29). In addition, the optoelectronic memory states with small fluctuation (~1.0 nS) at different temperatures (300-350 K), indicating that thermal noise is negligible (Supplementary Fig. 30).

High-precision spatiotemporal fusion for motion perception

The proposed device possesses thousands of optoelectronic memory states and a high signal-noise ratio of 51.0 dB and high information transmission rate of 1.7×10^4 bit s^-1 under light stimuli (intensity of 2.5 μW μm^-2, width (interval) of 0 ~ 500 μs), allowing to faithfully emulate the raptor vison for fast-moving object perception (Fig. 4a, and Supplementary Fig. 31). It integrates three key functions: highly sensitive and rapid conversion the light information, swift integration the information, and graded information processing (Fig. 4b). The a-Carbon emulates the high light sensitivity and swift information transmission of the dual cones with an accessory member and a principal member with an oil droplet that is highly sensitive to light and rapidly execute light-to-electronic conversion47, 48. The type-III heterojunction collects the electron and hole and then fast combine them as the manner of information integration of the horizontal cells. The TiO layer offers optically programmable vacancies for information grading processing as the manner of bipolar cells and others.

Fig. 4c exhibits an architecture of the raptor vision-inspired perception and recognition system. The CMOS-based time-integrated exposure or multi-exposure photography has to rely the complex circuit shutter and then fused the frame one by one 49. In contrast, our device provides high-precision frame-free information fusion strategy (Supplementary Fig. 32). A full hardware system is developed (Fig. 4d). The front terminal subsystem executes 10-bit spatiotemporal information fusion for motion perception. An electrical RESET (-4.0 V, width of 500 μs) is operated after 10-bit encoding. The end-terminal subsystem executes the CNN inference for image recognition (Supplementary Fig. 33-34).

Figs. 4e-f demonstrate the raptor vision-inspired hardware system for real wood block moving perception and recognition. The moving from t to t is perceived by the front terminal subsystem. The moving action is well classified with 100% accuracy. Complex unmanned aerial vehicle (UAV) with a high speed (>180 km h^-1) can be precepted when the front terminal subsystem executes 10-bit encoding (Fig. 4g). And it shows an accuracy of 100% and 98.75% for five UAV actions (five categories: up, down, left, right, and blank) and seven UAV actions (seven categories: up, down, left, right, approaching, leaving, and blank) with complex flight postures, including accelerating, decelerating, rising, falling, reciprocating, and circling (Fig. 4h, Supplementary Fig. 35).Therefore, the thousands of optoelectronic memory states outweighs other optoelectronic device capability to fuse the spatiotemporal information (Supplementary Tab. 1).

Compared with conventional electrical operation systems (e.g., CPUs, FPGAs, GPUs), the spatio-temporal encoding system leveraging type-III heterojunction optoelectronic memory demonstrates a power consumption reduction of at least one order of magnitude (Supplementary Tab. 2). This efficiency gain stems from the system’s ability to perform optical programming and electrical modulation in a synergistic manner, minimizing energy-intensive electrical switching. Furthermore, the system achieves a programming throughput of 24,000-bit s^-1 when executing 10-bit parallel encoding across 24 memory cells within a 10 ms time window. This performance highlights the scalability of the optoelectronic architecture, as the throughput scales linearly with the number of cells, enabling high-speed data processing without compromising energy efficiency.

A type-III heterojunction optoelectronic memory can provide thousands of optoelectronic memory states for highly precise perception. The photogenerated carriers (holes from p-type a-Carbon and electrons from n-type TiO ) quickly combine at the broadened space charge region. This process efficiently dampens the deexcitation recombination (major noise source) of electron-hole in a-Carbon and that of electron-charged oxygen vacancy in TiO . Without using post-programming denoising, 1,024 optoelectronic memory states are constructed. The distinguished thousands of memory states enable the type-III heterojunction optoelectronic memory to hold a high SNR of 51.0 dB at 1,000 Hz and an information transmission rate of 1.7×10^4 bit s^-1 within 0~1,000 Hz bandwidth. This work provides a significant optoelectronic mechanism to manufacture denoising-free optoelectronic memory element for highly precise spatiotemporal information fusion.

Methods
Device fabrication.

The optoelectronic memory devices were fabricated by radio frequency (RF) magnetron sputtering technology and physical vapor deposition. An amorphous Carbon (a-Carbon) target with a high purity of 99.999% was sputtered in 1.0 Pa Ar ambient at the power of 30 W for 30 minutes. For the TiO layer, 100 W sputtering power and 150 V bias voltage were applied on a TiO target with a purity of 99.99% for 60 minutes under the 1.0 Pa high-purity Ar ambient (purity >99.99%). The F-doped SnO (FTO) electrodes consisting of 32 lateral bars were prepared by sputtering while the Au top electrodes were deposited by physical vapor deposition under ultra-vacuum conditions (5.0×10^-4 Pa). According to the above methods, a device with a sandwich structure (FTO/a-Carbon/TiO /Au) and a corresponding crossbar array with a scale of 32×32 was developed in this work.

Optoelectronic property measurements.

An integrated electrical test system composed of semiconductor analyzer systems (Keithley 4200-SCS, B1500A) and probe station (Lakeshore, TTPX) was employed to conduct the electrical measurements such as the current-time (i-t) and current-voltage (I-V) tests. An integrated photoelectrical test system, including a 405-nm laser (Cobolt, 0405-06-01-0100-100) with tunable light intensity, a laser (Chang Chun Liang Li optoelectronic Equipment Co., Ltd.) with tunable light wavelength (this work uses the wavelength of 405 nm) and light intensity, and function waveform generator (UTG7062B) for light frequency modulation, is used to perform the optoelectrical measurements of the FTO/a-Carbon/TiO /Au devices. Moving objects are generally described by the fusion of sequential 4~10 frames. Thus, sequential light stimuli with 4~10 pulses could be applied to the heterostructure optoelectronic devices for mapping the spatiotemporal information of the moving objects in the real world. Each of the optoelectronic devices can independently sense and process the spatiotemporal frame information at the pixel level based on the temporal accumulating photocurrents under a series of light pulses. Accordingly, the photocurrent response under different sampling frequencies (the frequency of light pulse application used to capture information about the motion of a moving object) ranging from 10^-4 ~10^4 Hz was used to capture the action information of the moving objects with varying speeds.

Electron state calculations.

The (101) surface of anatase TiO and the a-Carbon from Timothy Clark's study were built to investigate the electron states at the a-Carbon/TiO interface based on the density functional theory, which was implemented in the Cambridge Sequential Total Energy Package (CASTEP). To avoid mirror interactions, we employed a surface model with a 20 Å vacuum thickness on the (101) tetragonal structure. The structure optimization utilized a plane-wave cutoff energy of 750 eV and Monkhorst-Pack k-point sampling of the Brillouin zone with Gamma points. The convergence tolerance for energy during geometric optimization was set to 3×10^-5 eV atom^-1. The residual force was 0.00089 eV Å^-1, and the maximum atomic displacement was 0.00095.

Neuromorphic computing simulations.

We demonstrate action detection and recognition of complex moving objects in the real world. A comparison of the ability to detect and recognize complex actions between the raptor retina-inspired optoelectronic memory device and conventional image sensors was made. A dataset composed of 2800 images was customized based on the UAV flight video that includes 7 types of actions (up, down, left, right, approaching, leaving, and blank). The single-frame image with a scale of 32×32 pixels was mapped as “1” and “0” in the gray level, suggesting that the specific space information could be obtained from the single-frame image. Thus, the detection of the complex actions of the moving objects based on multi-frame fusing images with spatiotemporal information can be obtained through mapping the specific pixel information on the raptor retina-inspired optoelectronic memory devices. The recognition system was built using a convolutional neural network (CNN) consisting of an input layer, a 3×3×4 convolutional kernel, a 2×2 subsampling pooling. ARM processor is used to operate the ReLU activation and 2×2 max pooling (stride 2), compressing the data into a 3×3×1 feature vector (9-dimensional). This vector feeds into a 9×7 fully-connected layer to generate a 7-dimensional output, with final classification probabilities delivered via the SoftMax function.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors present a nonvolatile optoelectronic memory capable of generating and retaining thousands of conductance states in response to optical stimuli without additional denoising. The device, based on an F-doped SnO₂/a-carbon/TiOx/Au type-III heterojunction, is demonstrated in a 24-cell array. Light-controlled oxygen vacancy dynamics in TiOx, combined with engineered carrier transport across the heterojunction, enable precise modulation of conductance and low-noise multilevel operation. Under 405 nm illumination, oxygen vacancies are photo-ionized into charged vacancies and electrons, while the heterojunction’s built-in electric field drives electrons toward the junction and separates electron–hole pairs in a-carbon, with holes accelerated in the space-charge region to promote recombination. This suppresses random telegraph noise, resulting in high-density, denoising-free memory with conductance states tunable by illumination frequency—from 128 states at 100 Hz to 1,024 at 1,000 Hz—enabling fine-grained spatiotemporal information fusion.\n\nThe authors further demonstrate a neuromorphic sensing system: visual input is binarized, and a 24-pixel memory array detects fast-moving targets within a 10 ms encoding window using 10-bit optical pulse trains, while static regions remain unmodulated. Output currents are converted to voltages, digitized into 8-bit grayscale images, and processed by a downstream memristor crossbar CNN. In a raptor-vision-inspired fast-motion task, the system integrates up to 10 frames to detect UAVs over 180 km h⁻¹, achieving 92.5% accuracy across seven action classes.\n\nWhile the work is compelling, several points require clarification. Scalability is unclear: a 600 µm optical spot and 750 µm inter-cell spacing are used, yet the manuscript claims a 1.0 µm feature size, raising questions about optical addressing at scale. System-level energy efficiency also needs discussion, as the setup includes DACs, ADCs, and photoelectric conversion stages; a quantitative comparison with conventional electrical systems would strengthen the manuscript. The programming throughput of the optoelectronic memory array warrants further detail. Finally, the device’s spectral response may limit natural-light compatibility: a-carbon responds up to ~559 nm, while TiOx is limited to ~392 nm, suggesting reliance on laser-array illumination for natural images.\n\nIn summary, this work presents a compelling optoelectronic memory platform with impressive multilevel capability, noise suppression, and system-level validation. Addressing the above questions, particularly regarding scalability, energy efficiency, and spectral response, would further strengthen the manuscript and clarify its practical impact.", "reviewer_2": "I appreciate the authors’ thorough and thoughtful response to my previous comments. The revised manuscript has been substantially improved, and I am satisfied with the revisions addressing the switching mechanism clarification, the pulse terminology corrections, the additional retention and endurance data, and the expanded explanation of the biological inspiration. The manuscript is now suitable for publication. I made minor following up comments.\n\nComment 1. Following up comment to the Reviewer#2 Comment 8 response.\nThank you for the detailed explanation and related figures. However, the physical mechanism underlying temporal encoding remains unclear. The authors stated “Notably, each ‘0’ position is associated with a reading voltage pulse (-0.2 V, 500 μs), which enhances temporal vacancy accumulation during light stimulation by increasing the activity of trapped electrons through the applied electric field (Eext).” This suggests that the ‘0’ is not simply a read voltage, but actively affects the memory state of the device.\n\nIf the ‘0’ pulse compensates for residual effects while the light pulse establishes non-volatile memory states via conductive oxygen vacancies, what mechanism allows temporal position to affect the final encoded state? Stable non-volatility would imply no temporal dependence, which creates confusion. Similarly, Figure 1b implies that a single light pulse can provide stable non-volatile memory characteristics after an initial overshoot.\n\nPlease clarify whether the encoding relies on (a) a slow decay process that maintains non-volatility while still permitting position-dependent encoding, or (b) stable non-volatile memory from optical programming at ‘1’ positions, combined with active electrical modulation at ‘0’ positions that provides fine-tuning dependent on pulse sequence. I believe clarifying the relationship between non-volatility and temporal encoding will remove ambiguity and enhance understanding.\n\nComment 2. Figure S20a shows the reading voltage as 0.2 V, and the Methods section also describes 0.2 V, while the main text states Vread = -0.2 V. Please clarify or correct this inconsistency.", "reviewer_3": "The reviewer appreciates the authors’ efforts to address the concerns raised in the previous round. All of my concerns have been satisfactorily addressed through additional experiments and further clarification, and I therefore recommend acceptance of the manuscript for publication in Nature Communications in its present form."}, "author_response": "Point−by−point response\nWe would like to thank all reviewers for carefully evaluating our manuscript. We also\nthank VERY MUCH for the reviewers’ time and efforts to provide us with detailed and valuable\ncomments. The constructive and professional suggestions greatly help us improve the quality\nof this work. We are delighted that the reviewers are satisfied with most of our revisions.\nReviewer #1\nThe authors present a nonvolatile optoelectronic memory capable of generating and retaining\nthousands of conductance states in response to optical stimuli without additional denoising.\nThe device, based on an F-doped SnO₂/a-carbon/TiO /Au type-III heterojunction, is\nx\ndemonstrated in a 24-cell array. Light-controlled oxygen vacancy dynamics in TiO , combined\nx\nwith engineered carrier transport across the heterojunction, enable precise modulation of\nconductance and low-noise multilevel operation. Under 405 nm illumination, oxygen vacancies\nare photo-ionized into charged vacancies and electrons, while the heterojunction’s built-in\nelectric field drives electrons toward the junction and separates electron–hole pairs in a-carbon,\nwith holes accelerated in the space-charge region to promote recombination. This suppresses\nrandom telegraph noise, resulting in high-density, denoising-free memory with conductance\nstates tunable by illumination frequency—from 128 states at 100 Hz to 1,024 at 1,000 Hz—\nenabling fine-grained spatiotemporal information fusion. The authors further demonstrate a\nneuromorphic sensing system: visual input is binarized, and a 24-pixel memory array detects\nfast-moving targets within a 10 ms encoding window using 10-bit optical pulse trains, while\nstatic regions remain unmodulated. Output currents are converted to voltages, digitized into 8-\nbit grayscale images, and processed by a downstream memristor crossbar CNN. In a raptor-\nvision-inspired fast-motion task, the system integrates up to 10 frames to detect UAVs over\n180 km h⁻¹, achieving 92.5% accuracy across seven action classes. In summary, this work\npresents a compelling optoelectronic memory platform with impressive multilevel capability,\nnoise suppression, and system-level validation. Addressing the above questions, particularly\nregarding scalability, energy efficiency, and spectral response, would further strengthen the\nmanuscript and clarify its practical impact.\nare delighted that the reviewer recognizes the value of our works. We have carefully revised\nthe manuscript according to the reviewer’s comments. The revision has been Included in the\nupdated manuscript.\nComment 1\nA 600 µm optical spot and 750 µm inter-cell spacing are used, yet the manuscript claims a\n1.0 µm feature size, raising questions about optical addressing at scale.\nResponse: We ’thank the reviewer very much for raising this point. For the 600 µm optical\nspot, we adopted it to test optoelectronic memory device with a size of 200 µm and inter-cell\nspacing of 750 µm, which can effectively prevent optical crosstalk. Such 750 µm inter-cell\nspacing ensures that adjacent 600 µm spots do not optically interfere, allowing for reliable,\nindependent, and parallel addressing across a large area.\nTo answer the reviewer’s previous concern on the scalability and high-density\napplications, we demonstrated a small optoelectronic memory (1.0 µm and inter-cell spacing\n5.0 µm) by electron beam lithography (EBL) (Fig. R1). For example, in a multi-photon process,\nthe reaction is confined to the center of the focal spot, creating features much smaller than the\nwavelength of light used. Individual device of 1.0 µm size is selected from the 24-cell array\nthrough mask process, showing a good photoresponse performance (Fig. R2).\nThe device size indeed causes the problem of the optical addressing. A small size of\noptoelectronic device creates higher spatial resolution and higher integration, but it introduces\ndifficulty in high precision optical addressing that requires the light spot size to less than the\ndevice size. For conventional optical system within visible light range, the minimum size of\nlight spot is in micrometer level (1.0 ~ 5.0 μm) due to light diffraction limit, causing the optical\nsystem such as the spatial light modulator (SLM) with ~12.5 μm pixel pitch. To break through\nthe limitation, extreme manufacturing technologies including superstructure surface based on\nsubwavelength nanocolumn arrays1,2 and nanoscale OLEDs 3 are developed for high precision\noptical addressing. The size of a single light spot for superstructure surface nanocolumn and\nOLED is as low as several hundred nanometers. These technologies provide a promising\nchance of optical addressing for optoelectronic memory. We sincerely thanks for your this\n2\nwarm reminding. The corresponding expression has been corrected in the revised manuscript.\nFig. R1. Vertical integration scheme. The a-Carbon/TiO optoelectronic memory can be vertically integrated\nx\non the vertically carved waveguide with 220 nm Si waveguide.\nFig. R2. Device scalability and photoresponsivity. a, The type-III heterojunction optoelectronic memory\narray based on the electron beam lithography (EBL) technic, showing a feature size of 1.0 μm2. b, Typical\nI-V curves of the EBL-based type-III heterojunction device. c, Photoresponsivity of the memory state\ntriggered by the light intensity of 1.25 μW/μm2 and width of 500 μs.\nReferences\n1. Holman, A., et al. Trapping of single atoms in metasurface optical tweezer arrays. Nature 649, 859-\n865 (2026).\n2. Fang, C., et al. Interleaved dual-species arrays of single atoms using a passive optical element and\none trapping laser. Sci. Adv. 11, eadw4166 (2025).\n3. Zhang, C., et al. Individually addressable nanoscale OLEDs. Sci. Adv. 11, eadz8579 (2025).\nPage 4-5\nThe two-terminal device structure provides downward scaling potential and integrate with\nwaveguides that can transmit light beam with smaller spot (Supplementary Fig. S9-S11).\nNotably, small size of the device produces high spatial resolution, which requires the matched\nnanoscale light source for optical addressing. For conventional optical system within visible\nlight range, the minimum size of light spot is in micrometer level (1.0~5.0 μm) due to light\n3\ndiffraction limit, causing the optical system such as the spatial light modulator (SLM) with\n~12.5 μm pixel pitch. To break through the limitation, extreme manufacturing technologies\nincluding superstructure surface based on subwavelength nanocolumn arrays 27, 28 and\nnanoscale OLEDs 29 are developed for high precision optical addressing. The size of a single\nlight spot for superstructure surface nanocolumn and OLED is as low as several hundred\nnanometers. These technologies provide a promising chance of optical addressing for the type-\nIII heterojunction optoelectronic memory.\nSI-page 7\nNotably, a 600 µm optical spot and 750 µm inter-cell spacing are used in this work. To\ndemonstrate the scalability and integration, we prepared the type-III heterojunction memory\nwith size 1.0 µm and 5.0 µm inter-cell spacing for integration potential with waveguides.\nIndividual device with a size of 1.0 µm is selected from the 24-cell array. Notably, a small size\nof optoelectronic device creates higher spatial resolution and higher integration, but it\nintroduces difficulty in high precision optical addressing that requires the light spot size to less\nthan the device size.\nComment 2\nSystem-level energy efficiency also needs discussion, as the setup includes DACs, ADCs, and\nphotoelectric conversion stages; a quantitative comparison with conventional electrical\nsystems would strengthen the manuscript.\nResponse: Thank the reviewer very much for the question. The perception system involves 24\noptoelectronic memory cells, peripheral circuit (3-DACs, 2-ADCs), laser system. The power\nconsumption majorly comes from the peripheral circuit (~500 mW), laser system (~100 mW),\nand 24 cells (~7 μW), thus yielding the overall power consumption ~600 mW.\nBy comparing the conventional computing platform such as CPU, GPU, and FPGA, the\npower consumption reduces at least one order. Processing 10-frame information of video based\non 4K pixels, the GPU platform with standard frame ratio of 30 fps and power efficiency of\noptoelectronic memory system only consumes ~2.0 W. Thus, the power consumption of the a-\nCarbon/TiO optoelectronic memory system reduces at least two-order when processing the\nx\nsame intelligent video task. And the revision has been added into the revised manuscript.\nplatforms and the type-III heterojunction optoelectronic memory\nComputing platform Manufacturing Power consumption\nCPU (E5-2699 V3) 22nm 145W\nGPU (Tesla K80) 28nm 300W\nFPGA(Virtex7-690T) 28nm 30W\nType-III heterojunction memory 2 0 0 μ m ~0.6W\nReferences\n4. Horowitz, M. Computing's energy problem (and what we can do about it). IEEE Internat. Solid-\nState Circuits Conference (ISSCC). 10-14 (2014).\n5. Han, S., et al. Efficient inference engine on compressed deep neural network. ACM SIGARCH\nComputer Architecture News. 44, 243-254 (2016).\nPage 16\nCompared with conventional electrical operation systems (e.g., CPUs, FPGAs, GPUs), the\nspatio-temporal encoding system leveraging type-III heterojunction optoelectronic memory\ndemonstrates a power consumption reduction of at least one order of magnitude\n(Supplementary Tab. S2).\nComment 3\nThe programming throughput of the optoelectronic memory array warrants further detail.\nFinally, the device’s spectral response may limit natural-light compatibility: a-carbon responds\nup to ~559 nm, while TiO is limited to ~392 nm, suggesting reliance on laser-array\nx\nillumination for natural images.\nResponse: Many thanks for this valuable comment and concern. The system contains 24 cells\nfeatured by the type-III heterojunction structure and executes 10-bit encoding with 1,000 Hz\n(duty ratio of 50%). The throughput of system (F) can be calculated as following:\n(1)\n𝑇𝑜𝑡𝑎𝑙 𝑑𝑎𝑡𝑎 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛\nTaking parallel encoding of the𝐹 2=4 ce𝑇ll𝑎s𝑡 𝑎i𝑙n 𝑒to𝑛𝑐 𝑜a𝑑c𝑖c𝑛o𝑔u 𝑡n𝑖𝑚t, 𝑒the total data transmission within the\nencoding time (10 ms) is 240 bits, yielding a maximal throughput of 24,000 bps.\nFor the device’s spectral response concern, the large energy gap (E ) for the TiO can\ng x\npartially avoid the recombination between photogenerated electrons from valence band (E )\nV\nand charged vacancies (V x+) that is directly used to build the memory states, while the a-\no\ng\nThe Raman spectrum of the prepared amorphous-Carbon films shows the feature peak of\ndisordered carbon (D-peak) at 1354 cm-1 with an intensity of 199.795 (I ) illustrates that the\nD\ndefects mainly originated from the sp3 orbitals (Fig. R3). Such defects build rich energy levels\nbetween Fermi level and conduction band level, enabling the type-III heterojunction\noptoelectronic device to response the light with a wavelength longer than 559 nm.\nFig. R3. Raman spectrum of the amorphous carbon. Typical feature peaks of the disordered carbon (D-\npeak) and graphitic carbon (G-peak) located at 1354 cm-1 and 1580 cm-1, respectively, suggesting the\nexistence of sp2 and sp3 in the amorphous carbon. The exciting laser wavelength is 532 n\nTherefore, the defects in a-Carbon enables to response the length wavelength light. Under\nnatural light stimuli with intensity of 3.18 μW·μm-2 and width of 20 ms, the a-Carbon/TiO\nx\noptoelectronic device exhibits an obvious photocurrent response, indicating that the type-III\nheterojunction device shows natural-light compatibility (Fig. R4). The statement of technology\nlevel has added into the revised manuscript.\nFig. R4. Multiple wavelength adaption. Photocurrent response under natural light stimuli (intensity of 1.25\nμW·μm-2, width of 20 ms).\nHowever, the Raman spectrum illustrated that the p-type a-Carbon involves a large number of π\nelectrons in sp2 orbits, which are highly sensitive to 405-nm light stimuli as well as natural light\n(Supplementary Fig. S3).\nPage 16\nFurthermore, the system achieves a programming throughput of 24,000 bits per second (bps)\nwhen executing 10-bit parallel encoding across 24 memory cells within a 10 ms time window\n(Supplementary Note V). This performance highlights the scalability of the optoelectronic\narchitecture, as the throughput scales linearly with the number of cells, enabling high-speed\ndata processing without compromising energy efficiency.\nReviewer #2\nI appreciate the authors’ thorough and thoughtful response to my previous comments. The\nrevised manuscript has been substantially improved, and I am satisfied with the revisions\naddressing the switching mechanism clarification, the pulse terminology corrections, the\nadditional retention and endurance data, and the expanded explanation of the biological\ninspiration. The manuscript is now suitable for publication. I made minor following up comments.\nResponse: Many thanks for your great effort and time on our manuscript. Your insightful\nand constructive comments are valuable for the improvement of this work. Many thanks for\nyou. The corresponding revision has been added into the revised manuscript.\nComment 1\nThe physical mechanism underlying temporal encoding remains unclear. The authors stated\n“Notably, each ‘0’ position is associated with a reading voltage pulse (-0.2 V, 500 μs),\nwhich enhances temporal vacancy accumulation during light stimulation by increasing the\nactivity of trapped electrons through the applied electric field (E ).” This suggests that the\next\n‘0’ is not simply a read voltage, but actively affects the memory state of the device. If the\n‘0’ pulse compensates for residual effects while the light pulse establishes non-volatile\nmemory states via conductive oxygen vacancies, what mechanism allows temporal position to\naffect the final encoded state? Stable non-volatility would imply no temporal dependence,\nwhich creates confusion. Similarly, Figure 1b implies that a single light pulse can provide stable\n7\nnon-volatile memory characteristics after an initial overshoot. Please clarify whether the\nencoding relies on (a) a slow decay process that maintains non-volatility while still permitting\nposition-dependent encoding, or (b) stable non-volatile memory from optical programming at‘1’ positions, combined with active electrical modulation at‘0’ positions that provides\nfine-tuning dependent on pulse sequence. I believe clarifying the relationship between non-\nvolatility and temporal encoding will remove ambiguity and enhance understanding.\nResponse: Many thanks for this warm reminding and concern. For the type-III heterojunction\noptoelectronic memory, the stable non-volatile memory from optical programming at ‘1’\npositions, combined with active electrical modulation at ‘0’ positions that provides fine-tuning\ndependent on pulse sequence.\nThis optoelectronic encoding mechanism fundamentally relies on the nonequilibrium\ndynamics of photogenerated carriers. In the a-Carbon layer, intense light absorption generates\na substantial population of photogenerated electrons and holes, resulting in an overshoot\nphotocurrent due to carrier accumulation. Conversely, in the TiO layer, photogenerated\nx\nelectrons originate from neutral oxygen vacancies (V ), which subsequently transform into\no\ncharged oxygen vacancies (V x+), a process that underpins nonvolatile photoconductance\no\nmemory states.\nThe recombination of majority carriers (holes, h+, from a-Carbon) with minority carriers\n(electrons, e-, from V ) in the space charge region leads to a surplus of h+ within this region.\no\nDriven by the built-in electric field (E ), these surplus h+ migrate toward the TiO side,\nin x\neffectively shortening the space charge region. This carrier redistribution, however, diminishes\nthe width of the space charge region, thereby weakening its efficiency.\nTo counteract this weakening effect, a matched positive bias of +0.2 V (E ) is applied to\next\nthe '0' position. This external field compensates for the E reduction caused by carrier\nin\nnonequilibrium, restoring the space charge region width and barrier integrity. Importantly, it\nintroduces timing sequence sensitivity, enabling precise light pulse modulation. Consequently,\nthe programming process achieves enhanced stability and reproducibility, as the bias actively\nmitigates carrier-induced nonequilibrium effects while leveraging the pulse sequence for\ndynamic control (Fig. R1). The revision has been added into the revised manuscript. Many\n8\nthanks for you.\nFig. R1. Optoelectronic switching mechanism. The photogenerated holes (Majority carrier) from a-Carbon\nrecombines with the photogenerated electrons (Minority carrier) from TiO at the space charge region, in\nx\nturn suppressing the deexcitation recombination noise (DRN) for stable nonvolatile memory states. While\nthe surplus carriers (h+) shorten the width of the space charge region. A refine positive bias is feasible for\ncompensation such weaken E .\nin\nPage 9\nFor the type-III heterojunction optoelectronic memory, the non-volatile memory states are\nstably maintained through optical programming at “1” positions, while active electrical\nmodulation at “0” positions enables fine-tuned control via light pulse sequence-dependent\nadjustments.\nPage 12\nThis optoelectronic encoding mechanism fundamentally relies on the nonequilibrium\ndynamics of photogenerated carriers. In the a-Carbon layer, intense light absorption generates\na substantial population of photogenerated electrons and holes, resulting in an overshoot\nphotocurrent due to carrier accumulation. Conversely, in the TiO layer, photogenerated\nx\nelectrons originate from neutral oxygen vacancies (V ), which subsequently transform into\no\ncharged oxygen vacancies (V x+), a process that underpins nonvolatile photoconductance\no\nmemory states.\nThe recombination of majority carriers (holes, h+, from a-Carbon) with minority carriers\n(electrons, e-, from V ) in the space charge region leads to a surplus of h+ within this region.\no\nDriven by the built-in electric field (E ), these surplus h+ migrate toward the TiO side,\nin x\neffectively shortening the space charge region. This carrier redistribution, diminishes the width\nof the space charge region, thereby weakening its efficiency.\next\nthe '0' position. This external field compensates for the E reduction caused by carrier\nin\nnonequilibrium, restoring the space charge region width and barrier integrity. Importantly, it\nintroduces timing sequence sensitivity, enabling precise light pulse modulation. Consequently,\nthe programming process achieves enhanced stability and reproducibility, as the bias actively\nmitigates carrier-induced nonequilibrium effects while leveraging the pulse sequence for\ndynamic control.\nComment 2\nFigure S20a shows the reading voltage as 0.2 V, and the Methods section also describes 0.2 V,\nwhile the main text states V = -0.2 V. Please clarify or correct this inconsistency.\nread\nResponse: Many thanks for the reviewer’s kind reminder. We have carefully checked whole\nthe manuscript and corrected the typos. The corresponding revision has highlighted as red color.\nPage 12\nThe “1” represents the photoresponse under one pulse light stimulus (intensity of 1.25 μW μm-\n2, width of 500 μs, interval of 500 μs, and 0.1 ms sampling step) while the “0” position is\nmatched a reading voltage pulse (0.2 V, 500 μs) denotes the photoresponse under darkness\n(Supplementary Fig. S20).\nReviewer #3\nThe reviewer appreciates the authors’ efforts to address the concerns raised in the previous\nround. All of my concerns have been satisfactorily addressed through additional experiments\nand further clarification, and I therefore recommend acceptance of the manuscript for\npublication in Nature Communications in its present form.\nResponse: Many thanks for constructive, insightful, and valuable comments. These\ncomments greatly help for the improvement of this work.\n10"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The author’s response has essentially addressed the concerns raised in the previous round of review. I recommend accepting the manuscript.", "reviewer_2": "I appreciate the authors’ thorough and thoughtful efforts to address the concerns raised in the previous rounds. The revised manuscript now has much clearer description. The manuscript is now suitable for publication without further clarification. I recommend acceptance of the manuscript for publication in Nature Communications in its present form."}, "author_response": ""}]

Decision letter