Ultraviolet photoelectric detector based on ferroelectric and two-dimensional material, array and preparation method

Abstract

The invention discloses an ultraviolet photoelectric detector based on ferroelectricity and a two-dimensional material, an array and a preparation method. The ultraviolet photoelectric detector comprises a silicon substrate, a ferroelectric layer, a silicon dioxide buffer layer, a gold electrode layer and a two-dimensional material layer which are sequentially stacked, the silicon dioxide buffer layer is provided with a connecting hole which exposes the ferroelectric layer; the gold electrode layer comprises a first gold electrode and a second gold electrode which are positioned on two sides of the connecting hole and are not connected with each other; the two-dimensional material layer at least partially covers the connecting hole, and the two-dimensional material layer is connected with the ferroelectric layer, the first gold electrode and the second gold electrode at the same time. Through a synergistic mechanism of photon-generated carriers driven by a ferroelectric polarization field and efficient light absorption of the two-dimensional material, the responsivity and the detection rate of the ultraviolet photoelectric detector are improved, and the dark current density is reduced.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology, specifically relating to an ultraviolet photodetector, array, and fabrication method based on ferroelectric and two-dimensional materials. Background Technology

[0002] Ultraviolet photodetectors have important applications in environmental monitoring (such as ozone layer detection and ultraviolet index monitoring), biomedical imaging (such as early diagnosis of skin cancer), target detection (such as flame detection), industrial process control (such as photolithography process monitoring), and space astronomical observation (such as stellar ultraviolet radiation analysis).

[0003] Common ultraviolet detectors include: (1) Ultraviolet detectors based on wide bandgap semiconductors: These mainly use wide bandgap semiconductor materials (such as GaN, ZnO, SiC, etc.) to construct ultraviolet photodetectors. The typical structure is a PIN (P-type-intrinsic-N-type) or Schottky junction device, which forms a contact between the metal electrode and the semiconductor material and utilizes the light absorption characteristics of the material to realize ultraviolet light detection. For example, GaN-based detectors are prepared by epitaxial growth technology to fabricate multilayer heterostructures and use AlGaN / GaN quantum wells to enhance ultraviolet light absorption efficiency. However, the fabrication process of ultraviolet detectors based on wide bandgap semiconductors is complex and costly. They are also limited by material defects and interface state effects, and generally have slow response speed (microseconds to milliseconds), high dark current, and limited detection sensitivity (responsivity is usually 10). 2 ~10 3 mA / W, detectivity approximately 10 10 ~10 12 Jones) and other issues. (2) Ultraviolet detectors based on two-dimensional materials: Two-dimensional materials (MoS2, WSe2, WS2, etc.) have excellent photoelectric properties such as atomic-level thickness, high carrier mobility and excellent light absorption characteristics, providing a new idea for high-performance ultraviolet detection. Existing schemes mostly adopt pure two-dimensional material thin films or structures combined with other materials (such as graphene, metal nanoparticles). For example, single-layer or multi-layer two-dimensional materials are grown by chemical vapor deposition (CVD) and combined with metal electrodes (such as Au, Ti / Au) to form photoconductive or photovoltaic devices. However, pure two-dimensional material-based detectors still face low responsivity (usually below 10) due to the lack of an effective built-in electric field and low photogenerated carrier separation efficiency, which is caused by fast photogenerated carrier recombination and weak built-in electric field. 3 Due to issues such as slow response times (in mA / W) and slow response speeds (on the order of seconds), the detectivity of this type of ultraviolet detector is approximately 10. 10 ~10 12Jones. (3) Ultraviolet detectors based on composite structures of ferroelectric materials and semiconductors: Ferroelectric materials (such as PMNPT, PZT, BTO) have spontaneous polarization characteristics, which can form a strong built-in electric field through interface charge modulation, effectively promoting the separation and transport of photogenerated carriers. By combining ferroelectric materials (such as PZT, BTO) with traditional semiconductors, the separation efficiency of photogenerated carriers can be enhanced by using the ferroelectric polarization field. For example, a ferroelectric thin film is deposited on a Si substrate, and a heterojunction device is formed by polarizing and modulating the interface barrier. However, the ferroelectric / semiconductor composite structure (such as PZT / Si) is limited by the lattice mismatch and interface defects between the ferroelectric material and the semiconductor, resulting in a high dark current (10). -6 ~10 -7 A) offers limited improvement in response speed (hundreds of microseconds) and poor process compatibility, making it difficult to achieve high-density array integration.

[0004] Furthermore, existing ultraviolet detector arrays are mostly based on discrete devices integrated through back-end packaging processes, such as assembling multiple GaN-based detector chips onto the same substrate using wire bonding or flip-chip bonding. This approach suffers from problems such as large size, high parasitic capacitance, and severe signal crosstalk, limiting the array size (typically less than 100×100 pixels) and system response consistency, and also restricting the application potential of ultraviolet detector arrays in multi-channel imaging and real-time monitoring.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides an ultraviolet photodetector, array, and fabrication method based on ferroelectricity and two-dimensional materials. The technical problem to be solved by this invention is achieved through the following technical solution: In a first aspect, the present invention provides an ultraviolet photodetector based on ferroelectricity and two-dimensional materials, comprising: a silicon substrate; A ferroelectric layer is located on one side of the silicon substrate; A silicon dioxide buffer layer is located on the side of the ferroelectric layer away from the silicon substrate; the silicon dioxide buffer layer has a connection hole that exposes the ferroelectric layer. A gold electrode layer is located on the side of the silicon dioxide buffer layer away from the silicon substrate; the gold electrode layer includes a first gold electrode and a second gold electrode located on both sides of the connection hole and not connected to each other. A two-dimensional material layer that at least partially covers the connection hole and is simultaneously connected to the ferroelectric layer, the first gold electrode, and the second gold electrode.

[0007] In one embodiment of the invention, the two-dimensional material layer covers at least 95% of the bottom area of ​​the connection hole.

[0008] In one embodiment of the present invention, the angle between the sidewall of the connecting hole and the plane where the ferroelectric layer is located is greater than 85°.

[0009] In one embodiment of the present invention, the material of the ferroelectric layer is PMN-PT, PZT or BTO, and the material of the two-dimensional material layer is MoS2, WSe2 or WS2.

[0010] Secondly, the present invention provides a method for fabricating the above-mentioned ultraviolet photodetector based on ferroelectricity and two-dimensional materials, comprising the following steps: S1. Obtain a silicon substrate and form a ferroelectric layer on one side of the silicon substrate using magnetron sputtering. S2. A silicon dioxide buffer layer is grown on the surface of the ferroelectric layer by chemical vapor deposition. S3. Using electron beam lithography and reactive ion etching, a connection hole is formed on the silicon dioxide buffer layer, and the connection hole exposes the ferroelectric layer; S4. An electron beam evaporation process is used to form a gold electrode layer on a silicon dioxide buffer layer. The gold electrode layer includes a first gold electrode and a second gold electrode located on both sides of the connection hole and not connected to each other. S5. A two-dimensional material film is covered to the connection hole using PDMS-assisted wet transfer technology. The two-dimensional material film is connected to the ferroelectric layer, the first gold electrode, and the second gold electrode at the same time to form a two-dimensional material layer. Then, it is annealed at 200℃~300℃ for 20~40min in an Ar / H2 mixed atmosphere so that the first gold electrode and the second gold electrode form ohmic contact with the two-dimensional material layer.

[0011] In one embodiment of the present invention, step S1 further includes in-situ polarization of the ferroelectric layer after the ferroelectric layer is formed; The in-situ polarization process is as follows: in an argon atmosphere, a directional DC electric field of 2.5 to 3.5 V / μm is applied to the ferroelectric layer, and polarization is continued for 8 to 12 minutes at the polarization temperature, wherein the polarization temperature is less than the Curie temperature of the ferroelectric layer and not greater than 300°C.

[0012] In one embodiment of the present invention, in step S2, the chemical vapor deposition is plasma-enhanced chemical vapor deposition; the silicon source used in the plasma-enhanced chemical vapor deposition is SiH4, the oxygen source is N2O, and the gas flow rate ratio of SiH4 to N2O is 1:3. The thickness of the silicon dioxide buffer layer is 10–50 nm.

[0013] Thirdly, the present invention provides an ultraviolet photodetector array, comprising multiple arrayed detection units, wherein each detection unit is a single ultraviolet photodetector for detecting ultraviolet light; The ultraviolet photodetector array includes a silicon substrate material layer, a ferroelectric material layer, a silicon dioxide buffer material layer, a two-dimensional material array layer, and a gold electrode material layer. The silicon substrate material layer includes the silicon substrate of each detection unit; the ferroelectric material layer includes the ferroelectric layer of each detection unit; the silicon dioxide buffer material layer includes the silicon dioxide buffer layer of each detection unit. The detection unit has a connection hole on its silica buffer layer, which exposes the ferroelectric layer. The two-dimensional material array layer includes two-dimensional material layers for each detection unit; the two-dimensional material layer of each detection unit is connected to the corresponding ferroelectric layer through corresponding connection holes. The gold electrode material layer includes a first gold electrode and a second gold electrode for each detection unit; The first gold electrode of the detection unit is a strip electrode extending along the row direction, and the first gold electrode is connected to the corresponding two-dimensional material layer; the second gold electrode of the detection unit is a strip electrode extending along the column direction, and the second gold electrode is connected to the corresponding two-dimensional material layer; the first orthographic projection of the first gold electrode and the second gold electrode of the detection unit on the corresponding silicon substrate is located within the second orthographic projection of the corresponding two-dimensional material layer on the corresponding silicon substrate, and the first orthographic projection is in the shape of a cross; a silicon oxide isolation layer is provided at the junction of the first gold electrode and the second gold electrode of the detection unit, and the silicon oxide isolation layer is disposed between the corresponding first gold electrode and the second gold electrode to prevent the first gold electrode and the second gold electrode of the detection unit from conducting; The first gold electrodes of each of the detection units in the same row arranged along the row direction are connected to form a row electrode; the second gold electrodes of each of the detection units in the same column arranged along the column direction are connected to form a column electrode.

[0014] Fourthly, the present invention provides a method for fabricating the above-mentioned ultraviolet photodetector array, comprising the following steps: S10. A ferroelectric material layer and a silicon dioxide buffer material layer are sequentially formed on a silicon substrate material layer; S20. Electron beam lithography and reactive ion etching are used to form connection holes for each detector unit arranged in an array on a silicon dioxide buffer material layer, and the connection holes expose the ferroelectric layer. S30. Forming a two-dimensional material array layer, wherein forming the two-dimensional material array layer includes forming a two-dimensional material layer for each detection unit in each connection hole, such that the two-dimensional material layer is connected to the corresponding ferroelectric layer. S40. A row electrode is formed on the two-dimensional material layer using an electron beam evaporation process. The row electrode includes the first gold electrode of each detection unit in the same row. S50. Form a silicon oxide isolation material layer, wherein the silicon oxide isolation material layer includes the silicon oxide isolation layer of each detection unit; S60. An array electrode is formed on the two-dimensional material layer using an electron beam evaporation process, wherein the array electrode includes the second gold electrode of each detection unit in the same array; Wherein, the first orthographic projection of the first gold electrode and the second gold electrode of the detection unit on the corresponding silicon substrate is located within the second orthographic projection of the corresponding two-dimensional material layer on the corresponding silicon substrate, and the first orthographic projection is in the shape of a cross; the silicon oxide isolation layer is located at the intersection of the corresponding first gold electrode and the second gold electrode, and is used to prevent the first gold electrode and the second gold electrode of the detection unit from conducting.

[0015] In one embodiment of the present invention, step S10 further includes in-situ polarization of the ferroelectric material layer after forming the ferroelectric material layer; The in-situ polarization process is as follows: In an argon atmosphere, a directional DC electric field of 2.5 to 3.5 V / μm is applied to the ferroelectric material layer, and polarization is continued for 8 to 12 minutes at the polarization temperature, wherein the polarization temperature is less than the Curie temperature of the ferroelectric material layer and not greater than 300°C.

[0016] In step S30, after forming the two-dimensional material array layer, a hydrogen plasma passivation treatment is further performed; wherein the radio frequency (RF) power used in the hydrogen plasma passivation treatment is 40-55W and the processing time is 25-30s.

[0017] This invention, by constructing a heterojunction of ferroelectric and two-dimensional materials, can synergistically leverage the directional driving effect of the ferroelectric polarization field on charge carriers and the high light absorption efficiency of the two-dimensional material, thereby achieving a significant improvement in the performance and high-density integration of ultraviolet photodetectors. Specifically, it includes the following beneficial effects: 1. Based on the synergistic mechanism of photogenerated carriers driven by ferroelectric polarization field and efficient light absorption of two-dimensional materials, the responsivity of the ultraviolet photodetector reaches 1.231 × 10⁻⁶. 6 mA / W, with detectivity increased to 1.810 × 10 13 Jones achieves a breakthrough in low-light detection sensitivity, improving upon traditional GaN-based devices by 2-3 orders of magnitude. It employs in-situ polarization and hydrogen plasma passivation techniques to suppress dark current density to less than 10-1. -10A. Compared with traditional ferroelectric heterojunction devices, it reduces the density by 3 orders of magnitude. Combined with a monolithic integrated shared electrode design, it constructs a 1000×1000 high-density detector array (5μm spacing), which makes the parasitic capacitance less than 1fF / detector unit and the crosstalk rate less than 1%, breaking through the integration limitations of traditional array design (<100×100 detector units).

[0018] 2. The fabrication method provided by this invention achieves wafer-level manufacturing through low-temperature processes (≤300℃), and electron beam lithography and reactive ion etching processes ensure the stability of the ferroelectric layer. Mass production yield is greater than 90%, and the cost is reduced by 50% compared to the InGaAs solution. SiN is used. x After aging in a harsh environment of 85℃ / 85%RH for 1000 hours, the encapsulated detector exhibits a responsivity decay of less than 5% and a dark current fluctuation of less than 10%, meeting the long-term stability requirements of industrial applications and providing a reliable solution for high-resolution real-time imaging and precision photoelectric monitoring.

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a top view of the ultraviolet photodetector based on ferroelectric and two-dimensional materials provided in an embodiment of the present invention; Figure 2 yes Figure 1 Sectional view of AA in the middle; Figure 3 yes Figure 1 Cross-sectional view of the middle section (BB); Figure 4 This is a top view of the ultraviolet photodetector array provided in an embodiment of the present invention; Figure 5 yes Figure 4 Enlarged schematic diagram of region G in the middle; Figure 6 yes Figure 4 CC section view; Figure 7 yes Figure 4 Cross-sectional view of DD.

[0021] Explanation of reference numerals in the attached figures: 1-Silicon substrate; 2-Ferroelectric layer; 3-Silicon dioxide buffer layer; 31-Connection hole; 4-Gold electrode layer; 41-First gold electrode; 42-Second gold electrode; 5-Two-dimensional material layer; 6-Silicon oxide isolation layer; DH-Row direction; DV-Column direction; RE-Row electrode; CE-Column electrode; 100-Detection unit. Detailed Implementation

[0022] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a detailed explanation of an ultraviolet photodetector, array, and preparation method based on ferroelectric and two-dimensional materials proposed in accordance with the present invention.

[0023] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0024] The terms “comprising,” “including,” or any other variation thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed.

[0025] The terms “thickness,” “upper,” “lower,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0026] This invention provides an ultraviolet photodetector based on ferroelectricity and two-dimensional materials, such as... Figures 1-3 As shown, the array includes a silicon substrate 1, a ferroelectric layer 2, and a silicon dioxide buffer layer 3, which are stacked sequentially. The silicon dioxide buffer layer 3 has a connection hole 31 that exposes the ferroelectric layer 2. A gold electrode layer 4 is disposed on the side of the silicon dioxide buffer layer 3 away from the silicon substrate 1. The gold electrode layer 4 includes a first gold electrode 41 and a second gold electrode 42 located on both sides of the connection hole 31 and not connected to each other. The ultraviolet photodetector also includes a two-dimensional material layer 5, which at least partially covers the connection hole 31 and is simultaneously connected to the ferroelectric layer 2, the first gold electrode 41, and the second gold electrode 42.

[0027] In this embodiment, a two-dimensional material layer 5 is formed in the connection hole 31, simultaneously connected to the ferroelectric layer 2, the first gold electrode 41, and the second gold electrode 42. By introducing the spontaneous polarization characteristics of the ferroelectric material, a strong built-in electric field is formed at the heterojunction between the ferroelectric layer 2 and the two-dimensional material layer 5, directionally driving carrier separation and transport. Combined with the efficient ultraviolet light absorption characteristics of the two-dimensional material, this overcomes the performance bottleneck of two-dimensional material devices and compensates for the shortcomings of pure two-dimensional material-based devices, which suffer from low photogenerated carrier separation efficiency due to the lack of an effective built-in electric field, resulting in low responsivity and slow response speed. Thus, the ultraviolet photodetector provided by this invention can significantly improve the device responsivity and detectivity by adjusting the interface electric field of the heterojunction formed by the ferroelectric layer 2 and the two-dimensional material layer 5, while shortening the response time to the microsecond level. For example, according to the detection results in the embodiment, the responsivity of the ultraviolet photodetector reaches 10. 6 The detector rate reaches the mA / W level, with a detection rate of 10. 13 The response time is on the Jones scale, with a rise time / fall time ratio of ≤10μs.

[0028] In one embodiment of the present invention, such as Figure 1 and Figure 3 As shown, the two-dimensional material layer 5 covers at least 95% of the bottom area of ​​the connection hole 31. Further, the two-dimensional material layer 5 completely covers the connection hole 31.

[0029] In one embodiment of the present invention, the angle between the sidewall of the connecting hole 31 and the plane containing the ferroelectric layer 2 is greater than 85°. Considering the actual process, forming the connecting hole 31 on the silicon dioxide buffer layer 3 generally employs an etching process. In practice, the sidewall of the connecting hole formed is not perpendicular to the plane as it would be mechanically cut. An angle greater than 85° between the sidewall of the connecting hole 31 and the horizontal plane allows for a more complete bond between the subsequently formed two-dimensional material layer 5 and the connecting hole 31, ensuring sufficient and effective contact between the two-dimensional material layer 5 and the ferroelectric layer 2.

[0030] In one example, the material of the ferroelectric layer 2 is PMN-PT, PZT or BTO, and the material of the two-dimensional material layer 5 is MoS2, WSe2 or WS2.

[0031] The present invention also provides a method for fabricating the above-mentioned ultraviolet photodetector based on ferroelectricity and two-dimensional material layer 5, comprising the following steps: S1. Obtain silicon substrate 1 and form ferroelectric layer 2 on one side of silicon substrate 1 using magnetron sputtering.

[0032] In one example, after forming the ferroelectric layer 2, step S1 further includes in-situ polarization of the ferroelectric layer 2. The in-situ polarization process is as follows: in an argon atmosphere, a directional DC electric field of 2.5–3.5 V / μm is applied to the ferroelectric layer 2, and polarization is continued for 8–12 minutes at a polarization temperature T, wherein the polarization temperature T is less than the Curie temperature of the ferroelectric layer 2 and not greater than 300°C. In this way, through in-situ polarization, the ferroelectric layer 2 can form a stable and consistent spontaneous polarization direction, further enhancing the strong built-in electric field at the heterogeneous interface between the subsequently formed ferroelectric layer 2 and the two-dimensional material layer 5.

[0033] S2. A silicon dioxide buffer layer 3 is grown on the surface of the ferroelectric layer 2 by chemical vapor deposition.

[0034] In one example, in step S2, the chemical vapor deposition is plasma-enhanced chemical vapor deposition. The silicon source used in the plasma-enhanced chemical vapor deposition is SiH4, the oxygen source is N2O, and the gas flow rate ratio of SiH4 to N2O is 1:3; the thickness of the silicon dioxide buffer layer 3 is 10–50 nm.

[0035] S3. Electron beam lithography and reactive ion etching are used to form a connection hole 31 on the silicon dioxide buffer layer 3, and the connection hole 31 exposes the ferroelectric layer 2.

[0036] S4. A gold electrode layer 4 is formed on the silicon dioxide buffer layer 3 using an electron beam evaporation process. The gold electrode layer 4 includes a first gold electrode 41 and a second gold electrode 42 located on both sides of the connection hole 31 and not connected to each other.

[0037] S5. Using PDMS-assisted wet transfer technology, a two-dimensional material film is applied to the connecting hole 31. The two-dimensional material film is simultaneously connected to the ferroelectric layer 2, the first gold electrode 41, and the second gold electrode 42 to form a two-dimensional material layer 5. Then, it is annealed at 200℃~300℃ for 20~40min in an Ar / H2 mixed atmosphere, so that the first gold electrode 41 and the second gold electrode 42 form ohmic contacts with the two-dimensional material layer 5 (contact resistance less than 10 ohms). -5 Ω·cm 2 ).

[0038] The preparation method provided by this invention utilizes low-temperature micro / nano processes to create a heterogeneous interface between the formed ferroelectric layer 2 (such as PMNPT, BTO, etc.) and two-dimensional materials (such as MoS2, WSe2, WS2, etc.) with a strong built-in electric field (greater than 10). 5 V / m), reducing the density of defects at the heterogeneous interface (less than 10). 10 cm -2 Simultaneously, the ferroelectric layer 2 directionally drives the separation of photogenerated carriers, achieving dark current suppression (<10). -9A) Improved process compatibility. In the fabricated ultraviolet photodetector, the spontaneous polarization characteristics of the ferroelectric layer 2 are utilized to form a strong built-in electric field at the heterojunction, which directionally drives the separation and transport of photogenerated carriers. Combined with the efficient ultraviolet light absorption characteristics of two-dimensional materials, the device responsivity is significantly improved (for example, the responsivity of the ultraviolet photodetector fabricated in Example 1 is as high as 1.231 × 10⁻⁶). 6 (mA / W) and detectivity (e.g., the detectivity of the ultraviolet photodetector prepared in Example 1 is as high as 1.810 × 10⁻⁶). 13 Jones).

[0039] In this embodiment, the low-temperature micro / nano process includes the electron beam evaporation process in step S4 and the low-temperature annealing process after forming the two-dimensional material layer 5 in step S5. Although the electron beam evaporation process involves extremely high temperatures when the electron beam bombards the target, the silicon substrate 1 can be kept at a low temperature (typically <150°C) through water cooling or a heat sink, avoiding thermal damage. The low-temperature annealing process uses a low-temperature thermal budget (e.g., 200–300°C) to induce slight interdiffusion at the interface between the gold electrode layer 4 and the two-dimensional material layer 5, reducing the Schottky barrier and thus preventing substrate material degradation due to high temperatures (>400°C) and lattice destruction in the two-dimensional material layer 5.

[0040] The present invention also provides an ultraviolet photodetector array, such as... Figure 4 and Figure 5 As shown, the array includes multiple detector units 100 arranged in an array, each detector unit 100 being a single ultraviolet photodetector used for detecting ultraviolet light. Figure 6 and Figure 7 As shown, the ultraviolet photodetector array includes a silicon substrate material layer, a ferroelectric material layer, a silicon dioxide buffer material layer, a two-dimensional material array layer, and a gold electrode material layer. The silicon substrate material layer includes the silicon substrate 1 of each detection unit 100; the ferroelectric material layer includes the ferroelectric layer 2 of each detection unit 100; the silicon dioxide buffer material layer includes the silicon dioxide buffer layer 3 of each detection unit 100. The silicon dioxide buffer layer 3 of the detection unit 100 has a connection hole 31, which exposes the ferroelectric layer 2. The two-dimensional material array layer includes the two-dimensional material layer 5 of each detection unit 100; the two-dimensional material layer 5 of the detection unit 100 is connected to the corresponding ferroelectric layer 2 through the corresponding connection hole 31. The gold electrode material layer includes a first gold electrode 41 and a second gold electrode 42 of each detection unit 100.

[0041] The first gold electrode 41 of the detection unit 100 is a strip electrode extending along the row direction DH, and is connected to the corresponding two-dimensional material layer 5. The second gold electrode 42 of the detection unit 100 is a strip electrode extending along the column direction DV, and is also connected to the corresponding two-dimensional material layer 5. The first orthographic projection of the first gold electrode and the second gold electrode 42 of the detection unit 100 on the corresponding silicon substrate 1 is located within the second orthographic projection of the corresponding two-dimensional material layer 5 on the corresponding silicon substrate 1, and the first orthographic projection is in the shape of a cross. A silicon oxide isolation layer 6 is provided at the intersection of the first gold electrode 41 and the second gold electrode 42 of the detection unit 100. The silicon oxide isolation layer 6 is disposed between the corresponding first gold electrode 41 and the second gold electrode 42 to prevent the first gold electrode 41 and the second gold electrode 42 of the detection unit 100 from conducting. The first gold electrodes 41 of each detection unit 100 arranged in the same row along the row direction DH are connected to form a row electrode RE; the second gold electrodes 42 of each detection unit 100 arranged in the same column along the column direction DV are connected to form a column electrode CE.

[0042] In the ultraviolet photodetector array provided in this embodiment, the two-dimensional material layer 5 of each detection unit 100 is connected to the corresponding ferroelectric layer 2 through the connection hole 31, realizing the interfacial electric field modulation of the heterojunction between the ferroelectric layer 2 and the two-dimensional material layer 5, improving the responsivity and detectivity of the ultraviolet photodetector array, and shortening the effect time. Simultaneously, in the ultraviolet photodetector array, the first gold electrodes 41 in the same row are connected to form the row electrode RE, and the second gold electrodes 42 in the same column are connected to form the column electrode CE. An insulating layer (silicon oxide isolation layer) is provided between the first gold electrode 41 and the second gold electrode 42 of each detection unit 100, so that the first gold electrode 41 and the second gold electrode 42 are separated at the junction, that is, the first gold electrode 41 and the second gold electrode 42 are not conductive, but it is ensured that the first gold electrode 41 and the second gold electrode 42 are both disposed on the surface of the two-dimensional material layer 5 and connected to the two-dimensional material layer 5. Thus, by applying a gating voltage to one row electrode RE and a cutoff voltage to the other row electrodes RE, the current change of the corresponding column can be read at the column electrode CE, thereby enabling addressing and gating of a single detection unit 100.

[0043] The ultraviolet photodetector array provided by this invention, through an integrated process, arrays connection holes 31 on a silicon dioxide buffer material layer to accommodate two-dimensional materials, thereby realizing the connection between two-dimensional materials and ferroelectric materials. Combined with the regional polarization control of the ferroelectric layer 2, a high-density (greater than 1000×1000 detection units) and low crosstalk (less than 1%) ultraviolet photodetector array can be realized to meet the requirements of multi-channel imaging and real-time monitoring.

[0044] In one example, the spacing between the detection units 100 is 2–5 μm.

[0045] In one example, the thickness of the silicon oxide isolation layer 6 is 40–60 nm.

[0046] The working principle of an ultraviolet photodetector array is as follows: Exposure stage: all row electrodes RE are biased, and each detection unit 100 is in photodetection state. Under ultraviolet light irradiation, each detection unit 100 stores a charge corresponding to the light intensity.

[0047] Readout stage: (1) Row-by-row gating, including applying gating voltage to each row sequentially starting from the first row to activate the detection unit 100 of that row; (2) Synchronous column reading signal, including synchronously acquiring the optical signal of the corresponding column of each column electrode CE and converting it into an electrical signal; (3) Signal processing, including processing the optical signal through analog-to-digital conversion, noise reduction, etc., to form the detection unit 100 data of that row; repeat steps (1) to (3) to obtain the detection unit data of each row; (4) Frame synthesis, including splicing the detection unit data of each row obtained after traversing all rows to form an ultraviolet light intensity distribution image (i.e., detection result).

[0048] The present invention also provides a method for fabricating the above-mentioned ultraviolet photodetector array, the method comprising the following steps: S10. A ferroelectric material layer and a silicon dioxide buffer material layer are sequentially formed on the silicon substrate material layer.

[0049] In one example, after forming the ferroelectric material layer, step S10 further includes in-situ polarization of the ferroelectric material layer. The in-situ polarization process is as follows: in an argon atmosphere, a directional DC electric field of 2.5–3.5 V / μm is applied to the ferroelectric material layer, and polarization is continued for 8–12 minutes at a polarization temperature T, wherein the polarization temperature T is less than the Curie temperature of the ferroelectric material layer and not greater than 300°C. In this way, through in-situ polarization, the ferroelectric material layer can form a stable and consistent spontaneous polarization direction, further enhancing the strong built-in electric field at the heterogeneous interface between the subsequently formed ferroelectric layer 2 and the two-dimensional material layer 5.

[0050] S20. Electron beam lithography and reactive ion etching are used to form connection holes 31 of each detector unit 100 arranged in an array on the silicon dioxide buffer material layer, and the connection holes 31 expose the ferroelectric layer 2.

[0051] S30. Forming a two-dimensional material array layer, which includes forming a two-dimensional material layer 5 for each detection unit 100 in each connection hole 31, so that the two-dimensional material layer 5 is connected to the corresponding ferroelectric layer 2.

[0052] In one example, after forming the two-dimensional material array layer, step S30 further includes performing a hydrogen plasma passivation treatment. The hydrogen plasma passivation treatment uses a radio frequency (RF) power of 40–55 W and a processing time of 25–30 s.

[0053] S40. A row electrode RE is formed on the two-dimensional material layer 5 using an electron beam evaporation process. The row electrode RE includes the first gold electrode of each detection unit 100 in the same row.

[0054] For example, row electrode REs are formed using an electron beam evaporation process with a row electrode mask.

[0055] S50, Form a silicon oxide isolation material layer, the silicon oxide isolation material layer including the silicon oxide isolation layer 6 of each detection unit 100.

[0056] S60. A column electrode CE is formed on a two-dimensional material layer 5 using an electron beam evaporation process. The column electrode CE includes the second gold electrode 42 of each detection unit 100 in the same column.

[0057] For example, column electrode CEs are formed using an electron beam evaporation process with a column electrode mask.

[0058] The first orthographic projection of the first gold electrode 41 and the second gold electrode 42 of the detection unit 100 onto the corresponding silicon substrate 1 is located within the second orthographic projection of the corresponding two-dimensional material layer onto the corresponding silicon substrate 1, and the first orthographic projection is in the shape of a cross. The silicon oxide isolation layer is located at the intersection of the corresponding first gold electrode 41 and the second gold electrode 42, and is used to prevent the first gold electrode 41 and the second gold electrode 42 of the detection unit 100 from conducting.

[0059] The method for fabricating an ultraviolet photodetector array provided by this invention ensures the long-term stability and process compatibility of the array through hydrogen plasma passivation and in-situ polarization treatment, achieving low parasitic capacitance (less than 1 fF / pixel) and high stability (attenuation less than 5% after 1000 hours of aging at 85℃ / 85%RH). The ultraviolet photodetector array fabricated by the method provided by this invention overcomes the technical bottlenecks of slow response speed and low integration of traditional ultraviolet detectors, and is suitable for high-sensitivity, fast-response ultraviolet sensing systems.

[0060] The following detailed description is based on specific embodiments.

[0061] Example 1 In this embodiment, the fabrication method of the ultraviolet photodetector based on ferroelectricity and two-dimensional materials includes the following steps: S1. Obtaining the substrate: A single-crystal silicon (Si) substrate is used, and surface contaminants are removed by RCA cleaning.

[0062] Ferroelectric layer 2 deposition: A 300 nm thick ferroelectric layer 2 was deposited on a Si substrate using magnetron sputtering at a sputtering power of 200 W, a working pressure of 0.5 Pa, and a substrate temperature of 400 °C. After deposition, rapid annealing (750 °C for 10 minutes) was performed in a nitrogen atmosphere to obtain a ferroelectric layer 2 with high crystallinity (XRD full width at half maximum < 0.1 °C) and a surface roughness ≤ 1 nm. Ferroelectric layer 2 was then in-situ polarized. The in-situ polarization process included applying a 3 V / μm directional DC electric field to the ferroelectric layer 2 in an argon atmosphere and continuously polarizing it at 250 °C for 10 minutes.

[0063] S2. Deposition of silica buffer layer 3: A silica buffer layer 3 with a thickness of 30 nm is grown on the surface of ferroelectric layer 2 by plasma enhanced chemical vapor deposition (PECVD). The process parameters are: SiH4 / N2O gas flow ratio 1:3, RF power 100W, deposition rate 5 nm / min, and thickness uniformity error <±1 nm.

[0064] S3. Photolithography and Etching: Electron beam lithography (EBL) was used to define a 1×1 μm layer on the silicon dioxide buffer layer 3. 2 The window pattern is aligned with an accuracy of <30nm. Subsequently, reactive ion etching (RIE, CF4 / O2=20 / 5 sccm, power 100W) is used to etch the silicon dioxide buffer layer 3 to form the connection hole 31. The bottom of the connection hole 31 exposes the surface of the ferroelectric layer 2, and the sidewall verticality of the connection hole 31 is >88°.

[0065] S4. Deposition of Gold Electrode Layer: An 80 nm thick gold electrode layer is deposited on the silicon dioxide buffer layer 3 using electron beam evaporation. The gold electrode layer includes a first gold electrode and a second gold electrode located on both sides of the connecting hole 31 and not connected to each other. The evaporation rate of the electron beam evaporation process is 0.2 nm / s, and the vacuum degree is <5 × 10⁻⁶. -6 Torr.

[0066] S5. Transfer of two-dimensional material MoS2: A single-layer two-dimensional material film is grown on a sapphire substrate by chemical vapor deposition (CVD). The two-dimensional material film is precisely covered on the window area using PDMS (polydimethylsiloxane) assisted wet transfer technology. The two-dimensional material film is calibrated by optical microscope to ensure that the two ends of the bridging connection hole 31 are connected to the first gold electrode and the second gold electrode at both ends of the connection hole 31. The coverage of the connection hole 31 is >98%.

[0067] Low-temperature annealing: Annealing at 250°C for 30 minutes in an Ar / H2 (95% / 5%) mixed atmosphere reduced the contact resistance to 3×10⁻⁶. -5 Ω·cm 2This allows the gold electrode layer to form an ohmic contact with the two-dimensional material layer, resulting in an ultraviolet photodetector based on ferroelectricity and two-dimensional materials.

[0068] The performance of the ultraviolet photodetector based on ferroelectric and two-dimensional materials prepared in Example 1 was tested: (1) Detection of photoelectric response parameters Under ultraviolet light irradiation at a wavelength of 254 nm, the light intensity is 1 mW / cm². 2 Under these conditions, the responsivity of the ultraviolet photodetector was measured. R Detection rate D Dark current I dark , clear current I light The results are shown in Table 1.

[0069] (2) Response speed detection By triggering with a pulsed laser (ultraviolet pulsed laser with a pulse width of 10 ns), a fast optical signal was simulated, and the rise time and fall time of the ultraviolet photodetector were detected. The results are shown in Table 1.

[0070] Table 1. Detection results of photoelectric response parameters and corresponding speeds

[0071] As shown in Table 1, the photoelectric response parameter detection results demonstrate that the ultraviolet photodetector based on ferroelectric and two-dimensional materials provided by this invention exhibits extremely high sensitivity to ultraviolet light, low noise, and extremely low leakage current in the off state. This results in a high signal-to-noise ratio for the ultraviolet photodetector, improving its ability to detect weak light signals. Furthermore, the rise and fall times of this ultraviolet photodetector are at the microsecond level, indicating a fast response speed.

[0072] Example 2 This embodiment fabricates an ultraviolet photodetector array, which includes 1000×1000 detection units, with a pixel unit size of 3×3μm. 2 With a spacing of 5 μm, crosstalk is reduced by placing a silicon oxide isolation layer (50 nm thick) between the row and column electrodes. Specific steps include: S10. Obtain the silicon substrate material layer and clean it.

[0073] Ferroelectric material layer deposition: A 300 nm thick ferroelectric material layer was deposited on a silicon substrate using magnetron sputtering at a power of 200 W, a working pressure of 0.5 Pa, and a substrate temperature of 400 °C. After deposition, rapid annealing (750 °C for 10 minutes) was performed in a nitrogen atmosphere to obtain a ferroelectric material layer with high crystallinity (XRD full width at half maximum < 0.1 °C) and a surface roughness ≤ 1 nm. The ferroelectric material layer was then in-situ polarized. The in-situ polarization process included applying a 3 V / μm directional DC electric field to the ferroelectric material layer in an argon atmosphere and maintaining polarization at 250 °C for 10 minutes.

[0074] Deposition of silica buffer material layer: A silica buffer material layer with a thickness of 30 nm was grown on the surface of the ferroelectric material layer by plasma enhanced chemical vapor deposition (PECVD). The process parameters were: SiH4 / N2O gas flow ratio 1:3, RF power 100 W, deposition rate 5 nm / min, and thickness uniformity error <±1 nm.

[0075] S20. Electron beam lithography and reactive ion etching (RIE, CF4 / O2=20 / 5 sccm, power 100 W) are used to form connection holes for each detector unit arranged in an array on the silicon dioxide buffer material layer. The connection holes expose the ferroelectric layer 2, and the sidewall verticality of the connection holes is >85°.

[0076] S30. Using a pre-fabricated mask, a two-dimensional material layer is formed in each connecting hole through an electron beam evaporation process, so that the two-dimensional material layer is connected to the corresponding ferroelectric layer 2. Then, hydrogen plasma passivation treatment is performed (RF power of 50W, processing time of 30s).

[0077] S40. A row electrode is formed on a two-dimensional material layer using an electron beam evaporation process. The width of the row electrode is 200 nm. The row electrode includes the first gold electrode of each detection unit in the same row.

[0078] S50. Form a silicon oxide isolation material layer, which includes silicon oxide isolation layers for each detection unit, and the thickness of the silicon oxide isolation layer is 50 nm.

[0079] S60. An array electrode is formed on a two-dimensional material layer using an electron beam evaporation process. The width of the array electrode is 150 nm. The array electrode includes the second gold electrode of each detection unit in the same array. The first orthographic projection of the first gold electrode and the second gold electrode of the detection unit onto the corresponding silicon substrate 1 is located within the second orthographic projection of the corresponding two-dimensional material layer onto the corresponding silicon substrate 1, and the first orthographic projection is in the shape of a cross. A silicon oxide isolation layer is located at the intersection of the corresponding first gold electrode and the second gold electrode to prevent the first gold electrode and the second gold electrode of the detection unit from conducting.

[0080] The following tests were performed on the prepared ultraviolet photodetector array: 1. Crosstalk test: Irradiate any two adjacent detector units with ultraviolet light, collect 50 sets of data, and the average crosstalk rate is 0.76%.

[0081] 2. Parasitic capacitance test: By testing the capacitance-voltage characteristic curve (CV test), the average parasitic capacitance of the detection unit is 0.7 fF, which can meet the detection requirements of high frequencies greater than 1 MHz.

[0082] 3. Yield statistics: Using the method provided in Example 2, 10 mass-produced ultraviolet photodetector arrays were prepared. The yield of the detector units in the array was calculated to be 92.8%, indicating that the preparation process has high stability.

[0083] 4. Using SiN x After packaging the ultraviolet photodetector array and aging the obtained detector device in a harsh environment of 85℃ / 85%RH for 1000 hours, the detection responsivity decreased by 4.73% and the dark current fluctuated by 9.52%.

[0084] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An ultraviolet photodetector based on ferroelectricity and two-dimensional materials, characterized in that, include: Silicon substrate (1); A ferroelectric layer (2) is located on one side of the silicon substrate (1); A silicon dioxide buffer layer (3) is located on the side of the ferroelectric layer (2) away from the silicon substrate (1); the silicon dioxide buffer layer (3) has a connection hole (31) that exposes the ferroelectric layer (2); The gold electrode layer (4) is located on the side of the silicon dioxide buffer layer (3) away from the silicon substrate (1); the gold electrode layer (4) includes a first gold electrode (41) and a second gold electrode (42) located on both sides of the connecting hole (31) and not connected to each other; A two-dimensional material layer (5) at least partially covers the connection hole (31), and the two-dimensional material layer (5) is simultaneously connected to the ferroelectric layer (2), the first gold electrode (41), and the second gold electrode (42).

2. The ultraviolet photodetector based on ferroelectricity and two-dimensional materials according to claim 1, characterized in that, The two-dimensional material layer (5) covers at least 95% of the bottom area of ​​the connecting hole (31).

3. The ultraviolet photodetector based on ferroelectricity and two-dimensional materials according to claim 1, characterized in that, The angle between the sidewall of the connecting hole (31) and the plane where the ferroelectric layer (2) is located is greater than 85°.

4. The ultraviolet photodetector based on ferroelectricity and two-dimensional materials according to any one of claims 1-3, characterized in that, The ferroelectric layer (2) is made of PMN-PT, PZT or BTO, and the two-dimensional material layer (5) is made of MoS2, WSe2 or WS2.

5. A method for fabricating an ultraviolet photodetector based on ferroelectric and two-dimensional materials as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Obtain a silicon substrate (1) and form a ferroelectric layer (2) on one side of the silicon substrate (1) by magnetron sputtering. S2. A silicon dioxide buffer layer (3) is grown on the surface of the ferroelectric layer (2) by chemical vapor deposition; S3. Electron beam lithography and reactive ion etching are used to form a connection hole (31) on the silicon dioxide buffer layer (3), and the connection hole (31) exposes the ferroelectric layer (2); S4. A gold electrode layer (4) is formed on the silicon dioxide buffer layer (3) using an electron beam evaporation process. The gold electrode layer (4) includes a first gold electrode (41) and a second gold electrode (42) located on both sides of the connection hole (31) and not connected to each other. S5. A two-dimensional material film is covered to the connection hole (31) using PDMS-assisted wet transfer technology. The two-dimensional material film is connected to the ferroelectric layer (2), the first gold electrode (41), and the second gold electrode (42) at least simultaneously to form a two-dimensional material layer (5). Then, it is annealed at 200℃~300℃ for 20~40min in an Ar / H2 mixed atmosphere so that the first gold electrode (41) and the second gold electrode (42) both form ohmic contact with the two-dimensional material layer (5).

6. The method for fabricating an ultraviolet photodetector based on ferroelectricity and two-dimensional materials according to claim 5, characterized in that, In step S1, after forming the ferroelectric layer (2), the ferroelectric layer (2) is further polarized in situ. The in-situ polarization process is as follows: In an argon atmosphere, a directional DC electric field of 2.5 to 3.5 V / μm is applied to the ferroelectric layer (2), and polarization is continued for 8 to 12 minutes at the polarization temperature, wherein the polarization temperature is less than the Curie temperature of the ferroelectric layer (2) and not greater than 300℃.

7. The method for fabricating an ultraviolet photodetector based on ferroelectricity and two-dimensional materials according to claim 5, characterized in that, In step S2, the chemical vapor deposition is plasma-enhanced chemical vapor deposition; the silicon source used in the plasma-enhanced chemical vapor deposition is SiH4, the oxygen source is N2O, and the gas flow rate ratio of SiH4 to N2O is 1:

3. The thickness of the silicon dioxide buffer layer (3) is 10-50 nm.

8. An ultraviolet photodetector array, characterized in that, It includes multiple arrayed detection units (100), each of which is a single ultraviolet photodetector for detecting ultraviolet light; The ultraviolet photodetector array includes a silicon substrate material layer, a ferroelectric material layer, a silicon dioxide buffer material layer, a two-dimensional material array layer, and a gold electrode material layer. The silicon substrate material layer includes the silicon substrate (1) of each detection unit (100); the ferroelectric material layer includes the ferroelectric layer (2) of each detection unit (100); the silicon dioxide buffer material layer includes the silicon dioxide buffer layer (3) of each detection unit (100); The detection unit (100) has a connection hole (31) on its silica buffer layer (3), which exposes the ferroelectric layer (2); The two-dimensional material array layer includes a two-dimensional material layer (5) of each detection unit (100); the two-dimensional material layer (5) of the detection unit (100) is connected to the corresponding ferroelectric layer (2) through the corresponding connection hole (31); The gold electrode material layer includes a first gold electrode (41) and a second gold electrode (42) for each detection unit (100); The first gold electrode (41) of the detection unit (100) is a strip electrode extending along the row direction, and the first gold electrode (41) is connected to the corresponding two-dimensional material layer (5); the second gold electrode (42) of the detection unit (100) is a strip electrode extending along the column direction, and the second gold electrode (42) is connected to the corresponding two-dimensional material layer (5); the first orthographic projection of the first gold electrode (41) and the second gold electrode (42) of the detection unit (100) on the corresponding silicon substrate (1) is located within the second orthographic projection of the corresponding two-dimensional material layer (5) on the corresponding silicon substrate (1), and the first orthographic projection is in the shape of a cross; a silicon oxide isolation layer (6) is provided at the intersection of the first gold electrode (41) and the second gold electrode (42) of the detection unit (100), and the silicon oxide isolation layer (6) is disposed between the corresponding first gold electrode (41) and the second gold electrode (42) to prevent the first gold electrode (41) and the second gold electrode (42) of the detection unit (100) from conducting; The first gold electrodes (41) of each of the detection units (100) arranged in the same row along the row direction are connected to form a row electrode (RE); the second gold electrodes (42) of each of the detection units (100) arranged in the same column along the column direction are connected to form a column electrode (CE).

9. A method for fabricating the ultraviolet photodetector array according to claim 8, characterized in that, Includes the following steps: S10. A ferroelectric material layer and a silicon dioxide buffer material layer are sequentially formed on a silicon substrate material layer; S20. Electron beam lithography and reactive ion etching are used to form connection holes (31) of each detector unit (100) arranged in an array on a silicon dioxide buffer material layer, wherein the connection holes (31) expose the ferroelectric layer (2). S30. Forming a two-dimensional material array layer, wherein forming the two-dimensional material array layer includes forming a two-dimensional material layer (5) of each detection unit (100) in each connection hole (31), such that the two-dimensional material layer (5) is connected to the corresponding ferroelectric layer (2); S40. A row electrode (RE) is formed on the two-dimensional material layer (5) using an electron beam evaporation process. The row electrode (RE) includes the first gold electrode (41) of each detection unit (100) in the same row. S50, Form a silicon oxide isolation material layer, the silicon oxide isolation material layer including the silicon oxide isolation layer (6) of each detection unit (100); S60. An array electrode (CE) is formed on the two-dimensional material layer (5) using an electron beam evaporation process. The array electrode (CE) includes the second gold electrode (42) of each detection unit (100) in the same array. Wherein, the first orthographic projection of the first gold electrode (41) and the second gold electrode (42) of the detection unit (100) on the corresponding silicon substrate (1) is located within the second orthographic projection of the corresponding two-dimensional material layer (5) on the corresponding silicon substrate (1), and the first orthographic projection is in the shape of a cross; the silicon oxide isolation layer (6) is located at the intersection of the corresponding first gold electrode (41) and the second gold electrode (42), and is used to make the first gold electrode (41) and the second gold electrode (42) of the detection unit (100) non-conductive.

10. The method for fabricating an ultraviolet photodetector array according to claim 9, characterized in that, In step S10, after forming the ferroelectric material layer, the ferroelectric material layer is further polarized in situ. The in-situ polarization process is as follows: In an argon atmosphere, a directional DC electric field of 2.5 to 3.5 V / μm is applied to the ferroelectric material layer, and polarization is continued for 8 to 12 minutes at the polarization temperature, wherein the polarization temperature is less than the Curie temperature of the ferroelectric material layer and not greater than 300°C. In step S30, after forming the two-dimensional material array layer, a hydrogen plasma passivation treatment is further performed; wherein the radio frequency power used in the hydrogen plasma passivation treatment is 40-55W and the processing time is 25-30s.

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