A bias reconfigurable wide-spectrum multi-band selective photodetector

Abstract

The present application relates to a kind of photoelectric detection technology, specifically, a kind of bias reconfigurable wide-spectrum multi-waveband selective photodetector.The present application first proposes to control wavelength selectivity through photoelectric current polarity transition state, uses inorganic semiconductor as substrate, prepares semi-metal thin film on substrate surface, and deposits a pair of asymmetric metal electrodes on semi-metal thin film, so that electrode and substrate form asymmetric back-to-back schottky contact, electrode and semi-metal thin film form ohmic contact;Under the condition of light, asymmetric back-to-back schottky junction realizes the transition of bias control photoelectric current polarity from negative to positive, different wavelength light corresponds to different reverse bias, and the selective detection of photodetector is realized.The present application has ultra-low optical crosstalk, monochromatic light recognition, fast in-situ multi-waveband alignment and other functions, with the characteristics of simple structure, high process compatibility and high integration, and has wide application scenarios in the detection field of intelligent system.

Description

Technical Field

[0001] This invention relates to a photoelectric detection technology, specifically a bias-reconfigurable broadband multi-band selective photodetector. Background Technology

[0002] Multi-band photodetectors, as photoelectric devices capable of detecting multiple wavelength ranges (visible light, near-infrared, and mid-infrared), have broadened the range of human perception in modern intelligent sensing systems, enabling the rapid, accurate, and crosstalk-free acquisition of information across multiple wavelengths, which is of extraordinary significance for improving the performance of intelligent systems.

[0003] Traditional optical systems often employ narrowband filter coupling to achieve beam splitting in front of the detector, resulting in a bulky imaging system. Recent work has focused on selective detection at the detector end, primarily achieved through the following two methods:

[0004] One approach involves combining various filters with multiple photosensitive chips to simultaneously receive light signals radiated or reflected from the same target within different narrow spectral bands. Combined with a beam-splitting structure design such as rotating filters, this allows for tuning of multiple detection wavelengths, as illustrated in patent CN116719096A. However, this method often increases the detector's structural size and complexity, and as a mature external detector approach, it has lost its innovativeness.

[0005] Another approach involves designing dual-band or multi-band selective detectors, which can accurately distinguish optical signals of different bands using a single pixel unit. This type of technology currently mainly utilizes metasurfaces and superlattices, such as CN109887943B and CN110911521A, by designing broadband multi-band detection structures with selective absorption enhancement. However, this structure involves complex micro / nano fabrication processes or material processing, and the fixed dual-band absorption peaks make it difficult to achieve flexible modulation capabilities. A similar approach involves stacking two photodiodes with different sensitivity ranges in a series or back-to-back structure, such as CN116960195A. This strategy can achieve intelligent, highly integrated spectral detection through electrical modulation, but these devices operate at fixed wavelengths in two bands, making it difficult to achieve highly flexible wavelength tuning, and significant optical crosstalk exists between the detection bands.

[0006] In summary, existing detector technologies are designed around integrating multiple selective absorption materials, which can only detect specific design bands and cannot flexibly modulate and select the detection band. Furthermore, they suffer from significant optical crosstalk. Existing methods have consistently failed to simultaneously resolve the contradiction between the integration of the detection system and accurate detection. Summary of the Invention

[0007] To address the aforementioned problems and shortcomings, and to resolve the issue that existing multi-band photodetector systems cannot simultaneously achieve both high integration and flexible, precise detection, this invention provides a bias-reconfigurable broadband multi-band selective photodetector. Based on the photocurrent polarity switching transition state generated by an asymmetric back-to-back Schottky junction, it can achieve rapid in-situ arbitrary band alignment with bias modulation, while also possessing ultra-low noise levels for optical crosstalk and monochromatic light recognition capabilities.

[0008] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0009] A bias-reconfigurable broadband multi-band selective photodetector includes an inorganic semiconductor substrate, a half-metal thin film, and electrodes, wherein the half-metal thin film and electrodes are all disposed on the same surface of the substrate.

[0010] The semi-metallic thin film is prepared on an inorganic semiconductor substrate and forms a heterojunction with the semi-metallic thin film to generate an optical gating effect to increase the optical response. It has a narrow band gap or zero band gap and has an absorption effect on infrared light.

[0011] The electrodes consist of two electrodes, a positive and a negative electrode, with different area sizes. The electrodes and the inorganic semiconductor substrate form an asymmetric back-to-back Schottky junction. Under illumination, the back-to-back Schottky junction generates a bias-dependent photocurrent that changes from negative to positive. Furthermore, the semi-metallic thin film is in ohmic contact with the electrodes to form an infrared photoconductive structure, achieving a wide-band photoconductive response. The polarity of its photocurrent does not reverse with the bias voltage and remains positive.

[0012] The inorganic semiconductor substrate and the semi-metallic thin film have a continuous monotonic region in their absorption curves in the visible and near-infrared range.

[0013] Furthermore, the back-to-back Schottky junction is achieved by designing an asymmetric Schottky barrier between the electrode and the substrate, and the symmetry breaking of the back-to-back Schottky junction is achieved by electrode materials with different work functions or different geometric contacts.

[0014] Furthermore, the wavelength selectivity is based on the photocurrent polarity reversal transition state. By breaking the symmetry of the Schottky junction, self-driven photodetection at 0V is achieved, and the photocurrent direction is defined. The Schottky junction operating in reverse dominates the response and generates a negative photocurrent; the Schottky junction operating in the forward direction has a smaller response than the former and generates a positive photocurrent. The total response is the sum of the channel light responses, thus obtaining a negative photocurrent at 0V.

[0015] Furthermore, the electrode material can be any material whose work function matches that of the inorganic semiconductor substrate.

[0016] Furthermore, while the inorganic semiconductor substrate and the semi-metallic thin film form a heterojunction, they also possess a band structure with hole transport and electron blocking, or electron transport and hole blocking, thereby improving the responsivity of the substrate in the response band, generating an optical gating effect to obtain high gain, and improving the responsivity of the detector.

[0017] Furthermore, the photosensitive area on the surface of the photodetector is subjected to aperture shielding treatment to reduce the impact of differences in the photosensitive surface under different irradiations on the reverse bias voltage. The photosensitive area is the planar structure where the electrode channel is located.

[0018] Furthermore, the specific working mechanism of the aforementioned bias-reconfigurable broadband multi-band selective photodetector includes:

[0019] The back-to-back Schottky junctions operate under forward and reverse bias respectively. As the applied voltage increases, the reverse bias junction gradually becomes dominant. When the bias voltage reaches the reverse bias voltage, the photocurrent is zero, thus suppressing the target wavelength. If the bias voltage is further increased, the photocurrent polarity becomes positive.

[0020] By using different reverse bias voltages of the photocurrent polarity transition state, sensitivity to the target wavelength is achieved. The light absorption of the inorganic semiconductor substrate has a monotonic region, and the absorption intensity of each wavelength in the monotonic region is different, resulting in different reverse bias voltages of the photocurrent polarity in each band, thus realizing an optical bandstop detector with adjustable bias voltage.

[0021] Furthermore, the fabrication method of the above-mentioned bias-reconfigurable broadband multi-band selective photodetector includes the following steps:

[0022] Step 1: Clean the surface of the inorganic semiconductor substrate and dry it for later use.

[0023] Step 2: Prepare a semi-metallic thin film on the surface of the inorganic semiconductor substrate obtained in Step 1. The semi-metallic thin film forms a heterojunction with the substrate, and a contact space is reserved for the electrode and the substrate.

[0024] Step 3: Patterned electrodes are prepared on the substrate obtained in Step 2. The patterned electrodes are two positive and negative electrodes with different area sizes. The electrodes form an asymmetric back-to-back Schottky junction with the inorganic semiconductor substrate, and the half-metal thin film is in ohmic contact with the electrodes to form an infrared photoconductive structure. The thickness of the electrodes is sufficient to form a total reflection layer.

[0025] Furthermore, the method for preparing the semi-metallic thin film is any one of thermal evaporation, magnetron sputtering, chemical vapor deposition, physical vapor deposition, and dry / wet transfer.

[0026] This invention is the first to propose a novel approach to wavelength-selective detection using the polarity transition state of photocurrent. In this invention, the magnitude of the reverse bias voltage across different illumination bands is linearly dependent on the light absorption intensity of the photosensitive layer of the Schottky junction, and is also affected by the optical power, operating under conditions where changes in optical power density do not cause crosstalk to the reverse bias voltage due to wavelength changes. This invention achieves wavelength-selective detection without requiring composite materials for multiple sensitive bands, significantly reducing device fabrication complexity and manufacturing costs. Furthermore, it has no size requirements, is compatible with silicon-based processes, and can achieve micro / nano integration, greatly improving the integration density of the detection system.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. It has an ultra-wideband response band from visible light to mid-infrared at 0V and large bias voltage.

[0029] 2. Based on the transition state of photocurrent polarity, the optical signal of a single band can be suppressed to the noise level, completely eliminating optical crosstalk in the corresponding band.

[0030] 3. Compared with existing multi-sensitive material and structural composite devices, such as superlattices, metasurfaces, and multi-diode stacking technologies, this invention breaks through the limitations of fixed wavebands and can flexibly modulate multi-waveband detection.

[0031] In summary, this invention utilizes a wide-spectrum bias through a photocurrent polarity switching transition state. Based on the operating bias voltage, it offers both wide-spectrum detection and selective detection modes, enabling rapid in-situ alignment in any band. It also features ultra-low noise levels in optical crosstalk and monochromatic light recognition. The proposed spectral selective detection approach provides a potential pathway for multi-band detection applications in autonomous driving, monitoring, and encrypted communication. Attached Figure Description

[0032] Figure 1 This is a cross-sectional structural diagram of the present invention.

[0033] Figure 2 The diagram shows the relationship between the absorption curve and the reverse bias voltage in this embodiment.

[0034] Figure 3 The graph shows the relationship between the multi-band response and bias modulation in the example.

[0035] Figure reference numerals: 1-Inorganic semiconductor substrate, 2a-Positive electrode, 2b-Negative electrode, 3-Half-metal thin film. Detailed Implementation

[0036] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention includes, but is not limited to, the following embodiments.

[0037] like Figure 1 As shown, the bias-reconfigurable broadband multi-band selective photodetector of this embodiment is based on an asymmetric Schottky junction. An inorganic semiconductor is used as the substrate 1, and a half-metal thin film 3 is prepared on the substrate surface. At the same time, space is left for the asymmetric electrode to contact the substrate. Then, a pair of asymmetric electrode pairs 2a and 2b are prepared. The electrode 2 and the substrate form a Schottky contact, the electrode 2 and the half-metal thin film 3 form an ohmic contact, and the substrate 1 and the half-metal thin film 3 form a heterojunction.

[0038] Specifically, in this embodiment, an n-type lightly doped germanium sheet (thickness 500um, size 10×10mm) is used as the substrate, and a PtSe2 half-metal film is grown on a sapphire substrate (thickness 500nm, crystal orientation 0001, size 5×5mm) using a two-step precursor thermal assisted conversion method. A 150nm thick total reflection gold is used as the contact electrode.

[0039] A method for fabricating a bias-reconfigurable broadband multi-band selective photodetector includes the following steps:

[0040] Step 1. Cleaning the substrate: Clean the n-type lightly doped germanium wafer and sapphire substrate in an ultrasonic cleaner for 20 minutes each with acetone, ethanol and pure water in sequence. Dry them with a nitrogen air gun and place them in a dust-free area for later use.

[0041] Step 2. Growth of PtSe2 thin films using a two-step precursor thermally assisted conversion method. One preparation method is described here:

[0042] (1) A 10 nm layer of Pt was deposited on a sapphire substrate by magnetron sputtering, with a sputtering base vacuum of 5 × 10⁻⁶. - 4 Pa, using DC sputtering, power 20W.

[0043] (2) The sputtered substrate was placed downstream of a dual-temperature zone tube furnace, and 100 mg of Se powder was placed upstream. The temperatures of the upper and lower temperature zones were set to 222 °C and 400 °C, respectively. Ar was used as the carrier gas at a flow rate of 50 sccm. The reaction was carried out for 1 hour to obtain a PtSe2 thin film.

[0044] Step 3. Spin-coat a 5µm layer of PMMA onto a sapphire substrate, heat-cur it on a 120°C heating plate for 90 seconds, wet-peel it in a 5% NaOH solution, transfer it to a germanium substrate, place it in a drying oven for 1 hour, remove the adhesive with acetone solution, and wash it in isopropanol and deionized water in sequence.

[0045] Step 4. Prepare a metal electrode on the germanium substrate after PtSe2 transfer. Align a mechanical mask with an electrode area ratio of 4:1 with the substrate and attach it to the sample stage of a thermal evaporator to perform thermal evaporation of the Au electrode with a thickness of 150 nm.

[0046] This invention is based on an asymmetric Schottky junction to realize the photocurrent polarity reversal transition state. The half-metallic thin film has a narrow band gap to realize a wide spectrum response, thereby realizing the mapping between the light absorption curve and the reverse bias voltage. Under illumination, the asymmetric back-to-back Schottky junction realizes the photocurrent polarity change from negative to positive through bias control. Different wavelengths of light correspond to different reverse bias voltages, realizing selective detection of the photodetector. Figure 2 The corresponding relationship between the light absorption curves and the reverse bias voltage of the sample in this embodiment within the range of 405nm-1600nm is shown. Figure 3 The graph shows the relationship between the multi-band response and bias modulation in the example.

[0047] As can be seen from the above embodiments, this invention proposes for the first time the idea of ​​controlling wavelength selectivity through the photocurrent polarity transition state. Under illumination, the narrow bandgap of the half-metal achieves a broad spectral response, and the asymmetric back-to-back Schottky junction enables bias-controlled photocurrent polarity transition from negative to positive. Different wavelengths of illumination correspond to different reverse bias voltages, achieving selective detection by the photodetector. This invention features ultra-low noise level optical crosstalk, monochromatic light recognition, and rapid in-situ multi-band alignment. It is characterized by simple structure, high process compatibility, and high integrability, and has broad application scenarios in the detection field of intelligent systems (such as autonomous driving, monitoring, and encrypted communication).

Claims

1. A bias-reconfigurable broadband multi-band selective photodetector, characterized in that: It includes an inorganic semiconductor substrate, a half-metal thin film, and electrodes, with the half-metal thin film and electrodes all disposed on the same surface of the substrate. The half-metal thin film is prepared on an inorganic semiconductor substrate and forms a heterojunction with the half-metal thin film to generate an optical gating effect to increase the optical response. It has a narrow band gap or zero band gap and has an absorption effect on infrared light. The electrodes consist of two electrodes, a positive and a negative electrode, with different area sizes. The electrodes and the inorganic semiconductor substrate form an asymmetric back-to-back Schottky junction. Under illumination, the back-to-back Schottky junction generates a bias-dependent photocurrent that changes from negative to positive. Furthermore, the semi-metallic thin film is in ohmic contact with the electrodes to form an infrared photoconductive structure, achieving a wide-band photoconductive response. The polarity of its photocurrent does not reverse with the bias voltage and remains positive. The inorganic semiconductor substrate and the semi-metallic thin film have a continuous monotonic region in their absorption curves in the visible and near-infrared range. The back-to-back Schottky junctions operate under forward and reverse bias respectively. As the applied voltage increases, the reverse bias junction gradually becomes dominant. When the bias voltage reaches the reverse bias voltage, the photocurrent is zero, thus suppressing the target wavelength. If the bias voltage is further increased, the photocurrent polarity becomes positive. By using different reverse bias voltages of the photocurrent polarity transition state, sensitivity to the target wavelength is achieved. The light absorption of the inorganic semiconductor substrate has a monotonic region, and the absorption intensity of each wavelength in the monotonic region is different, resulting in different reverse bias voltages of the photocurrent polarity in each band, thus realizing an optical bandstop detector with adjustable bias voltage.

2. The bias-reconfigurable broadband multi-band selective photodetector as described in claim 1, characterized in that: The back-to-back Schottky junction is achieved by designing an asymmetric Schottky barrier between the electrode and the substrate. The symmetry breaking of the back-to-back Schottky junction is achieved by electrode materials with different work functions or different geometric contacts.

3. The bias-reconfigurable broadband multi-band selective photodetector as described in claim 1, characterized in that: The wavelength selectivity is based on the photocurrent polarity reversal transition state. By breaking the symmetry of the Schottky junction, self-driven photodetection at 0 volts is achieved. The direction of the photocurrent is defined. The Schottky junction operating in reverse dominates the response and generates a negative photocurrent. The Schottky junction operating in the forward direction has a smaller response than the former and generates a positive photocurrent. The total response is the sum of the channel light responses, so a negative photocurrent at 0 volts is obtained.

4. The bias-reconfigurable broadband multi-band selective photodetector as described in claim 1, characterized in that: The electrode material can be any material whose work function matches that of the inorganic semiconductor substrate.

5. The bias-reconfigurable broadband multi-band selective photodetector as described in claim 1, characterized in that: While the inorganic semiconductor substrate and the semi-metallic thin film form a heterojunction, they also have a band structure with hole transport and electron blocking, or electron transport and hole blocking, thereby improving the responsivity of the substrate in the response band, generating an optical gating effect to obtain high gain, and improving the responsivity of the detector.

6. The bias-reconfigurable broadband multi-band selective photodetector as described in claim 1, characterized in that: The photosensitive area on the surface of the photodetector is shielded by an aperture to reduce the impact of differences in the photosensitive surface under different irradiations on the reverse bias voltage. The photosensitive area is the planar structure where the electrode channel is located.

7. The fabrication method of the bias-reconfigurable broadband multi-band selective photodetector as described in claim 1, characterized in that, Includes the following steps: Step 1: Clean the surface of the inorganic semiconductor substrate and dry it for later use; Step 2: Prepare a semi-metallic thin film on the surface of the inorganic semiconductor substrate obtained in Step 1. The semi-metallic thin film forms a heterojunction with the substrate, and reserve contact space for the electrode and the substrate. Step 3: Patterned electrodes are prepared on the substrate obtained in Step 2. The patterned electrodes are two positive and negative electrodes with different area sizes. The electrodes form an asymmetric back-to-back Schottky junction with the inorganic semiconductor substrate, and the half-metal thin film is in ohmic contact with the electrodes to form an infrared photoconductive structure. The thickness of the electrodes is sufficient to form a total reflection layer.

8. The method for fabricating a bias-reconfigurable broadband multi-band selective photodetector as described in claim 7, characterized in that: The method for preparing the semi-metallic thin film is any one of thermal evaporation, magnetron sputtering, chemical vapor deposition, or dry / wet transfer.

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