Programmable optical pulse tuning short-wave infrared photoelectric detector and preparation method thereof
By constructing an asymmetric ferroelectric floating gate structure photodetector on a Si/SiO2 substrate, the responsivity is modulated using optical signals. This solves the problems of high operating voltage and unstable response state of existing photodetectors in low-power systems, realizing low-power, multi-level programmable optical response adjustment, and supporting the integration of visual perception and computing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-13
AI Technical Summary
Existing photodetectors operate at high voltages in low-power systems, suffer from severe crosstalk between devices, and lack reversibility and stability in their response states, making it difficult to meet the integration requirements of high-performance vision systems.
An asymmetric ferroelectric floating gate structure is constructed on a Si/SiO2 substrate. A van der Waals heterojunction is formed by two-dimensional ferroelectric material CuInP2S6 and two-dimensional semiconductor black phosphorus. The responsivity of the device is controlled by optical signals to achieve bidirectional reversible and multi-level programmable adjustment. The stability is improved by combining dry transfer and annealing processes.
It achieves bidirectional reversible adjustment of photoresponsivity under low power consumption, has multi-level programmable stability, supports the integration of visual perception and computing, reduces the complexity of peripheral circuits, and improves the non-volatile storage capability of the device.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of two-dimensional optoelectronic device technology, specifically to a programmable optical pulse tuned short-wave infrared photodetector and its fabrication method, which can be used in fields such as low-power optoelectronic neuromorphic vision. Background Technology
[0002] With the rapid development of artificial intelligence and computer vision technologies, applications such as intelligent monitoring place higher demands on front-end visual perception modules in terms of power consumption and integration. Current intelligent image perception in vision systems primarily relies on artificial neural networks, using large-scale matrix-vector multiplication to complete feature extraction and classification decisions. The computation essentially involves multiplying and adding input features to a weight matrix, and performance depends mainly on the programmable control of the weight parameters. However, in traditional vision processing architectures, image sensors acquire optical information, memory stores weights and intermediate features, and the processing unit handles most of the multiplying and adding operations. A large amount of data must be transferred between the sensing layer and the computation / storage layer, leading to significant energy consumption costs and processing latency. Therefore, there is an urgent need to develop new architectures that can reduce redundant data transmission and achieve close collaboration between perception and computation.
[0003] Against this backdrop, researchers have introduced neuromorphic devices into visual perception architectures. By implementing memory and modulation functions in optoelectronic devices, they use the device's responsivity to incident light as synaptic weights: increased responsivity corresponds to weight enhancement, and decreased responsivity corresponds to weight suppression. This integrates the programmable characteristics of "synaptic weights" at the device level, achieving the integration of optical signal sensing, weight storage, and multiply-accumulate calculations within the same device. Existing solutions typically apply electrical pulses to regulate the internal electric field distribution and carrier states of the device to achieve bidirectional, multi-level adjustment of the responsivity between positive and negative directions. However, these solutions still have the following shortcomings:
[0004] 1. It relies heavily on a high external gate voltage to control the energy band, resulting in a relatively high operating voltage, which is not conducive to low-power system integration;
[0005] 2. Weight adjustment relies heavily on electrical pulses, which can easily cause crosstalk between devices in the array;
[0006] 3. The reversibility and long-term stability of the programmable response state are insufficient, making it difficult to meet the needs of practical applications.
[0007] Therefore, there is an urgent need for a photodetector that can operate under low voltage conditions, whose responsivity can be bidirectionally and reversibly adjusted through optical signals, and which has multi-level programmability and good stability. This would enable it to simultaneously perform optical signal sensing and weight state control at the device level, providing device support for building an integrated vision system that combines high-performance sensing, weight storage, and computing functions. Summary of the Invention
[0008] The purpose of this invention is to overcome the following shortcomings in the prior art and to propose a programmable optical pulse tuned shortwave infrared photodetector and its fabrication method. Without increasing the complexity of the heterojunction structure, the device responsivity is achieved under fully optical control conditions with bidirectional reversibility and multi-level programmable adjustment, while also having low power consumption and good stability.
[0009] This invention provides a programmable optical pulse tuned short-wave infrared photodetector, comprising: a Si / SiO2 substrate; a patterned bottom gate electrode disposed on the substrate; a two-dimensional ferroelectric material layer, an insulating dielectric layer, and a two-dimensional semiconductor channel layer sequentially stacked on the bottom gate electrode by a dry transfer method to form a van der Waals heterojunction; source and drain electrodes disposed on the two-dimensional semiconductor channel layer; and an upper insulating protective layer covering the two-dimensional semiconductor channel layer.
[0010] Furthermore, the upper surface of the Si / SiO2 substrate is divided into left and right parts. On the left side of the upper surface, from top to bottom, are arranged a bottom gate electrode G-Au, a first insulating dielectric layer, a two-dimensional ferroelectric material layer, a second insulating dielectric layer, and a first two-dimensional semiconductor channel layer. On the right side of the upper surface, a third insulating dielectric layer is arranged, which is connected to the left bottom gate electrode G-Au. Above the third insulating dielectric layer is the second two-dimensional semiconductor channel layer. The left side of the second two-dimensional semiconductor channel layer is connected to the right side of the first insulating dielectric layer and the right side of the two-dimensional ferroelectric material layer. All surfaces have gaps; the first insulating dielectric layer, the second insulating dielectric layer, and the third insulating dielectric layer are vertically connected together to form an insulating dielectric layer, and the first insulating dielectric layer, the second insulating dielectric layer, and the third insulating dielectric layer have the same thickness; the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel layer are vertically connected together to form a two-dimensional semiconductor channel layer, and the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel layer have the same thickness; source and drain electrodes are correspondingly provided on the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel; a protective layer covers the two-dimensional semiconductor channel layer.
[0011] Wherein: the two-dimensional ferroelectric material layer is preferably CuInP2S6 (CIPS) to provide ferroelectric floating gate function;
[0012] The insulating dielectric layer is preferably hexagonal boron nitride (h-BN), which has both insulating and tunneling properties;
[0013] The two-dimensional semiconductor channel layers are preferably black phosphorus (BP) to achieve photoconductive transport.
[0014] The bottom gate electrode G-Au structure and the two-dimensional ferroelectric material layer together form an asymmetric ferroelectric floating gate structure, making the potential distribution of the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel layer asymmetric.
[0015] The two-dimensional ferroelectric material layer and the two-dimensional semiconductor channel layer form a semi-floating gate coupling system, which can synergistically regulate photogenerated charge and polarization state.
[0016] Through the above structural design, the device can obtain different steady-state optical responsivity under different optical programming conditions, and can reversibly switch between positive and negative responses.
[0017] The preferred thickness of CIPS is ≥ 50 nm (generally 50-150 nm), the thickness of h-BN is 4 ~ 15 nm, and the thickness of BP is about 10 nm.
[0018] The method for fabricating the programmable optical pulse tuned shortwave infrared photodetector of the present invention preferably includes the following steps:
[0019] (1) Substrate cleaning: The Si / SiO2 substrate was ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water for 15 min and 60 W, and then dried for later use.
[0020] (2) Fabrication of patterned bottom grid
[0021] On a cleaned Si / SiO2 substrate, a bottom gate electrode G-Au is fabricated by photolithography, and a metal layer (Au) is deposited by thermal evaporation or electron beam evaporation. Then, the substrate is lifted to obtain a patterned bottom gate electrode G-Au.
[0022] (3) The van der Waals heterojunction is stacked in the bottom gate electrode region obtained in step (2), and the two-dimensional ferroelectric material CIPS, the insulating dielectric h-BN and the two-dimensional semiconductor BP are transferred sequentially by dry transfer to construct a CIPS / h-BN / BP van der Waals heterojunction;
[0023] (4) Source-drain electrode transfer
[0024] Using a dry transfer method, the source and drain electrode patterns pre-prepared on other substrates are transferred as a whole and aligned above the BP channel layer to form the source and drain contact area. The preferred spacing between the source and drain electrodes is 10 to 30 μm.
[0025] (5) Remove the support layer
[0026] The sample obtained in step (4) is immersed in acetone solution to remove the organic support layer such as PMMA on the source and drain electrodes during dry transfer, and then cleaned and dried.
[0027] (6) Transfer of upper protective layer
[0028] By using a dry transfer method, a layer of h-BN is transferred to the device channel region to encapsulate the BP channel layer, preventing it from directly contacting the air and improving device stability.
[0029] (7) Annealing treatment
[0030] The device was placed in an inert gas (argon) atmosphere and annealed at 200 °C for 70 min to improve interface quality and enhance the stability of electrical and optoelectronic properties.
[0031] By following the steps above, a BP semi-floating gate phototransistor device based on an asymmetric ferroelectric floating gate structure can be obtained.
[0032] Optical modulation and bidirectional tunable response mechanism:
[0033] The photodetector of this invention exhibits programmable, bidirectionally tunable photoelectric response behavior under illumination conditions of different wavelengths and powers. Its working process can be summarized as follows:
[0034] (1) Programming light 1: Used to suppress or reduce light response
[0035] By selecting short-wavelength light (380 nm) and applying light pulses of different power and pulse widths to the device, the polarization state and local potential distribution in the ferroelectric floating gate structure are altered, reducing the effective carrier concentration in the channel and decreasing the device's open-circuit voltage (V). OC ) and short-circuit current (I SC The light intensity gradually decreases as the power of the programmed light increases, thereby reducing the photoresponsivity.
[0036] (2) Programming light 2: used to enhance light response
[0037] By selecting medium-wavelength light (685 nm) and applying light pulses of different powers and pulse widths, photogenerated charges in the floating gate structure are captured or released, thereby altering the effective barrier and carrier distribution of the channel, and increasing the Vt of the device. OC with I SC The power of the programmed light gradually increases, thereby enhancing the control of optical responsivity.
[0038] (3) Readout light: used for uninterrupted readout of response state
[0039] To avoid interference with the storage state during the readout process, low-energy near-infrared light (980 nm) is selected as the readout source. Under the action of the readout light, the photocurrent of the device can be quickly established and disappear rapidly after the light is turned off, showing good transient switching characteristics. At the same time, since the energy of the readout light is insufficient to significantly change the charge state of the floating gate and interface, the original responsivity programming state of the device remains stable during the readout process.
[0040] Through the combination of the programming light and the readout light, the device of the present invention can achieve reversible switching between increasing and decreasing responsivity without external gate voltage, and form multiple stable and distinguishable optical response states.
[0041] Compared with the prior art, the present invention has at least the following beneficial effects:
[0042] 1. Achieving low-power bidirectional optical response control: Through the asymmetric gate structure design, the positive and negative reversible switching of the responsivity is completely completed by the optical programming process, and the readout process can be performed at zero gate voltage, which significantly reduces power consumption and peripheral circuit complexity.
[0043] 2. Achieve full optical control and multi-level programmable responsivity: By using programmable optical pulses with different powers and pulse widths, multiple repeatable and distinguishable optical response states can be obtained under fixed readout conditions. The responsivity can be monotonically adjusted within a preset range, and no less than ten stable storage states can be formed, which is suitable for weighted adjustment and neuromorphic computing.
[0044] 3. Possesses excellent non-volatile storage and reliability.
[0045] By employing appropriate material thickness and annealing processes, the device of this invention can maintain stable photoresponse characteristics under prolonged illumination, exhibiting excellent non-volatile storage capability and repeatability.
[0046] 4. Supports reconfigurable visual perception and image processing
[0047] By using the device's photoresponsivity as the weight of the convolution kernel, edge detection, orientation-selective enhancement, and image sharpening of the input image can be achieved, demonstrating that the present invention has practical application potential in reconstructible visual perception and device-side image processing. Attached Figure Description
[0048] To more clearly illustrate the technical solution of the present invention, embodiments of the present invention are schematically shown in the accompanying drawings, in which:
[0049] Figure 1 is a schematic diagram of the structure of the CIPS / h-BN / BP asymmetric ferroelectric floating grating photodetector of the present invention;
[0050] Figure 2 shows the atomic force microscopy thickness characterization of the device of the present invention using different materials in Example 1;
[0051] Figure 3 shows the photoelectric response characteristics of the device of the present invention under different programming light conditions in Examples 2 and 3;
[0052] Figure 4 is a schematic diagram of the optical response of the device under different optical programming and readout conditions in Example 2;
[0053] Figure 5 shows the stability test of the device in Example 3 under different readout optical powers;
[0054] Figure 6 is a simulation diagram of image convolution processing based on the device's tunable optical responsivity in Example 4. Detailed Implementation
[0055] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to these embodiments.
[0056] Example 1: Device Fabrication
[0057] This embodiment provides a programmable optical pulse tuned BP semi-floating gate phototransistor device (structure shown in [reference]). Figure 1 The preparation method, with specific steps as follows:
[0058] 1. The Si / SiO2 substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water for 15 min at a power of 60 W, and then dried for later use.
[0059] 2. A bottom gate pattern is prepared on a substrate using photolithography, and a metal layer is deposited by thermal evaporation, followed by lift-off to form a patterned bottom gate electrode;
[0060] 3. CIPS, h-BN, and BP are sequentially stacked above the bottom gate electrode using a dry transfer method to form a CIPS / h-BN / BP van der Waals heterojunction. The CIPS thickness is ≥ 75.4 nm, the h-BN thickness is 11.9 nm, and the BP thickness is approximately 13.1 nm. Figure 2 As shown;
[0061] 4. Pre-fabricate source and drain electrode patterns on other substrates, then align and transfer them to the surface of the BP channel layer using a dry transfer method, making the channel width 15 μm;
[0062] 5. Immerse the sample in acetone solution to remove the PMMA support layer used for transfer, then wash and dry.
[0063] 6. A layer of h-BN is coated onto the device channel region as an upper protective layer using a dry transfer method to isolate BP from the air;
[0064] 7. Place the device in an argon atmosphere and anneal at 200 °C for 70 min to improve interface quality and device stability.
[0065] The device obtained through the above steps is the weighted / responsivity light-controlled reversible photodetector of the present invention.
[0066] Example 2: Fully Optically Controlled Bidirectional Adjustable Responsivity
[0067] In this embodiment, optical programming and readout of the device prepared in Example 1 are performed using light sources of different wavelengths:
[0068] 1. Using short-wavelength light (380 nm), under the same readout conditions, gradually increase its power or pulse width, and measure the open-circuit voltage and short-circuit current of the device. It was found that both decrease with increasing programming light dose, corresponding to the suppression of the device's photoresponsivity.
[0069] 2. Using medium wavelength light (685 nm), under the same readout conditions, gradually increase its power or pulse width, and measure the open-circuit voltage and short-circuit current of the device. It was found that both increased with the increase of the programming light dose, and the corresponding photoresponsivity of the device was enhanced.
[0070] 3. Under fixed programming conditions, near-infrared light with low energy (e.g., light with a wavelength of about 980 nm) was selected as the readout light source. It was observed that the photocurrent of the device was rapidly established when the readout light was turned on, and quickly returned to the dark state when it was turned off. This indicates that the readout process has good transient switching characteristics and does not significantly affect the set responsivity state.
[0071] The above results demonstrate that the device of the present invention can achieve bidirectional reversible control of responsivity through different programming lights without an external gate voltage, and can be read without disturbance by the readout light (e.g., Figure 4 (As shown).
[0072] Example 3: Multi-level Programmability and Stability
[0073] Under fixed readout light conditions, adjusting the power and pulse width combinations of the first and second type programming lights yields a series of different responsivity states. Test results show that:
[0074] 1. For example Figure 3 As shown, under different programming conditions, the optical responsivity of the device exhibits a monotonic variation, and at least ten distinguishable responsivity levels can be obtained;
[0075] 2. Under prolonged (1600 s) continuous illumination conditions (see...) Figure 5 The device output waveform maintains a regular rectangular characteristic, indicating that it has excellent non-volatile characteristics and operational stability.
[0076] Example 4: Reconstructable Convolutional Visual Processing Applications
[0077] Based on the photoelectric characteristic parameters of individual devices, the photodetector of this invention is integrated and simulated in an array configuration (e.g., a 3×3 pixel array) using Matlab. Each pixel device is assigned a different photoresponsivity value under different programming light conditions, which serves as the weight in the convolution kernel. By changing the spatial distribution and parameters of the programming light, different types of convolution kernels can be configured, such as for edge detection in the X direction, edge detection in the Y direction, and image sharpening (see...). Figure 6 ).
[0078] Under near-infrared readout light illumination, each array pixel generates a photocurrent output corresponding to a preset responsivity based on the local incident light intensity, thereby achieving convolution operation on the input image. Processing results show that the image convolved by the array of the device of this invention has clear edges or sharpened features, verifying the feasibility of this invention in the fields of visual perception and image processing.
[0079] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Various equivalent substitutions or modifications made by those skilled in the art without departing from the concept of the invention should fall within the protection scope of the invention.
Claims
1. A programmable optical pulse tuned shortwave infrared photodetector, characterized in that, include: Si / SiO2 substrate; Patterned bottom gate electrode disposed on the substrate; A van der Waals heterojunction is formed by sequentially stacking a two-dimensional ferroelectric material layer, an insulating dielectric layer, and a two-dimensional semiconductor channel layer on the bottom gate electrode using a dry transfer method. Source and drain electrodes disposed on the two-dimensional semiconductor channel layer; An upper insulating protective layer covering the two-dimensional semiconductor channel layer.
2. A programmable optical pulse tuned shortwave infrared photodetector according to claim 1, characterized in that, The upper surface of the Si / SiO2 substrate is divided into left and right parts. On the left side of the upper surface, from top to bottom, are arranged a bottom gate electrode G-Au, a first insulating dielectric layer, a two-dimensional ferroelectric material layer, a second insulating dielectric layer, and a first two-dimensional semiconductor channel layer. On the right side of the upper surface, a third insulating dielectric layer is arranged, which is connected to the bottom gate electrode G-Au on the left. Above the third insulating dielectric layer is the second two-dimensional semiconductor channel layer. The left side of the second two-dimensional semiconductor channel layer, the right side of the first insulating dielectric layer, and the right side of the two-dimensional ferroelectric material layer all have... There are gaps; the first insulating dielectric layer, the second insulating dielectric layer, and the third insulating dielectric layer are vertically connected together to form an insulating dielectric layer, and the first insulating dielectric layer, the second insulating dielectric layer, and the third insulating dielectric layer have the same thickness; the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel layer are vertically connected together to form a two-dimensional semiconductor channel layer, and the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel layer have the same thickness; source and drain electrodes are correspondingly provided on the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel; a protective layer covers the two-dimensional semiconductor channel layer.
3. A programmable optical pulse tuned shortwave infrared photodetector according to claim 1, characterized in that, The two-dimensional ferroelectric material layer is preferably CuInP2S6 (CIPS) to provide ferroelectric floating gate functionality; the insulating dielectric layer is preferably hexagonal boron nitride (h-BN) to provide both insulation and tunneling properties; the two-dimensional semiconductor channel layer is preferably black phosphorus (BP) to achieve photoconductive transport; the bottom gate electrode G-Au structure and the two-dimensional ferroelectric material layer together form an asymmetric ferroelectric floating gate structure, making the potential distribution of the first two-dimensional semiconductor channel layer and the second two-dimensional semiconductor channel layer asymmetric; the two-dimensional ferroelectric material layer and the two-dimensional semiconductor channel layer constitute a semi-floating gate coupling system, which can synergistically regulate photogenerated charge and polarization state.
4. A programmable optical pulse tuned shortwave infrared photodetector according to claim 3, characterized in that, CIPS thickness ≥ 50 nm (typically 50-150 nm).
5. A programmable optical pulse tuned shortwave infrared photodetector according to claim 3, characterized in that, The thickness of h-BN is 4 ~ 15 nm.
6. A programmable optical pulse tuned shortwave infrared photodetector according to claim 3, characterized in that, The thickness of BP is approximately 10 nm.
7. A programmable optical pulse tuned shortwave infrared photodetector according to claim 1, characterized in that, The spacing between the source and drain electrodes is 10 ~ 30 μm.
8. The method for fabricating the programmable optical pulse tuned shortwave infrared photodetector according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Substrate cleaning: The Si / SiO2 substrate was ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water for 15 min and 60 W, and then dried for later use. (2) Fabrication of patterned bottom grid On a cleaned Si / SiO2 substrate, a bottom gate electrode G-Au is fabricated by photolithography, and a metal layer (Au) is deposited by thermal evaporation or electron beam evaporation. Then, the substrate is lifted to obtain a patterned bottom gate electrode G-Au. (3) The van der Waals heterojunction is stacked in the bottom gate electrode region obtained in step (2), and the two-dimensional ferroelectric material CIPS, the insulating dielectric h-BN and the two-dimensional semiconductor BP are transferred sequentially by dry transfer to construct a CIPS / h-BN / BP van der Waals heterojunction; (4) Source-drain electrode transfer Using a dry transfer method, the source and drain electrode patterns pre-prepared on other substrates are transferred as a whole and aligned above the BP channel layer to form a source and drain contact area. The preferred spacing between the source and drain electrodes is 10 to 30 μm. (5) Remove the support layer The sample obtained in step (4) is immersed in acetone solution to remove the organic support layer such as PMMA on the source and drain electrodes during dry transfer, and then cleaned and dried. (6) Transfer of upper protective layer By using a dry transfer method, a layer of h-BN is transferred to the device channel region to encapsulate the BP channel layer, preventing it from directly contacting the air and improving device stability. (7) Annealing treatment The device was placed in an inert gas (argon) atmosphere and annealed at 200 °C for 70 min to improve interface quality and enhance the stability of electrical and optoelectronic properties.
9. The method for optical control and bidirectional adjustable response of the programmable optical pulse tuned shortwave infrared photodetector according to any one of claims 1-7, characterized in that, Under illumination conditions of different wavelengths and powers, the device can obtain different steady-state photoresponsivity and can reversibly switch between positive and negative responses; (1) Programming light 1: Used to suppress or reduce light response By selecting short-wavelength light (380 nm) and applying light pulses of different power and pulse widths to the device, the polarization state and local potential distribution in the ferroelectric floating gate structure are altered, reducing the effective carrier concentration in the channel and decreasing the device's open-circuit voltage (V). OC ) and short-circuit current (I SC The light intensity gradually decreases as the power of the programmed light increases, thereby reducing the photoresponsivity. (2) Programming light 2: used to enhance light response By selecting medium-wavelength light (685 nm) and applying light pulses of different powers and pulse widths, photogenerated charges in the floating gate structure are captured or released, thereby altering the effective barrier and carrier distribution of the channel, and increasing the Vt of the device. OC with I SC The power of the programmed light gradually increases, thereby enhancing the control of optical responsivity. (3) Readout light: used for uninterrupted readout of response state To avoid interference with the storage state during the readout process, low-energy near-infrared light (980 nm) was selected as the readout source. Under the action of the readout light, the photocurrent of the device can be quickly established and disappear rapidly after the light is turned off, showing good transient switching characteristics. At the same time, since the energy of the readout light is insufficient to significantly change the charge state of the floating gate and interface, the original responsivity programming state of the device remains stable during the readout process. Through the combination of the programming light and the readout light, the device can achieve reversible switching between increasing and decreasing responsivity without an external gate voltage, and form multiple stable and distinguishable optical response states.
10. The application of the programmable optical pulse tuned shortwave infrared photodetector according to any one of claims 1-7 is suitable for class weight adjustment and neuromorphic computing; by using the photoresponsivity of the device as the weight of the convolution kernel, it realizes functions such as edge detection, orientation selective enhancement and image sharpening of the input image, and is applied in visual perception and device-side image processing.