An enhanced structure of lead salt uncooled medium-wave infrared detector and its preparation method

Abstract

This invention discloses an enhanced lead-salt uncooled mid-wave infrared detector and its fabrication method, relating to the field of photoelectric detection technology. The detector comprises: a substrate, a reflective layer, a dielectric layer, a microstructure array layer, a lead-salt sensitive layer, a metal electrode layer, and a passivation layer. The fabrication method includes: fabricating a metal reflective layer on the substrate surface; fabricating a resonant cavity layer on the reflective layer; fabricating a microstructure array layer on the resonant cavity layer; fabricating a lead-salt sensitive layer on the microstructure array layer; sensitizing the lead-salt sensitive layer; fabricating a metal electrode on the lead-salt sensitive layer; and fabricating a passivation layer on the lead-salt sensitive layer and the metal electrode. The beneficial effect of this invention is that it combines the LSPR effect of the resonant cavity and the artificial plasmon resonance array (i.e., the metal microstructure array), which can effectively enhance the mid-wave infrared radiation absorption of the device. It has the characteristics of high performance, high sensitivity, and high stability, and is expected to be widely used in the field of mid-wave infrared detection.

Description

Technical Field

[0001] This invention relates to the field of mid-wave infrared detector technology, specifically to a lead salt uncooled mid-wave infrared detector based on an artificial plasmon array and its fabrication method. Background Technology

[0002] Mid-infrared (MIR) electromagnetic spectroscopy plays a crucial role in applications such as gas sensing, thermal imaging, biosensing, medical imaging, spectroscopy, and environmental monitoring. The practical application of these technologies hinges on high-response photodetectors. Currently, most mid-infrared detectors on the market are primarily based on III-V compound semiconductors or mercury-cadmium-telluride (HgCdTe) alloys, such as InSb and In... 1-x Ga x As and Hg 1-x Cd x However, devices fabricated using these materials all require cooling, resulting in high costs, large size and weight, and complex manufacturing processes. As an alternative, lead salt compounds (such as PbS, PbSe, etc.) have been used in mid-infrared photoelectric detection since the 1950s. Due to their excellent mid-infrared response characteristics at room temperature and relatively low cost, they have regained attention in recent years and have become the preferred material for uncooled infrared detectors.

[0003] Despite the excellent mid-infrared response of lead salt materials, their relatively low light absorption coefficient leads to lower absorption efficiency in thin-film applications. To compensate for this deficiency, current lead salt detectors typically rely on larger pixel units to increase the absorption area and thus improve the overall signal response intensity. However, this approach limits the resolution improvement of the detector, making it difficult to meet the demands of low-cost, high-resolution detection. To improve the light absorption efficiency of lead salt thin films, researchers have proposed various process improvement methods, such as heterojunction structure design and nanostructuring. Heterojunction structures, by forming a barrier layer or quantum well between lead salt materials and other materials, can effectively improve the carrier separation efficiency, thereby increasing the detector response speed. Nanostructuring utilizes the localized field enhancement effect, achieving enhanced light absorption by etching micro- and nanostructures on the surface of lead salt materials. However, while these methods can improve detection performance to some extent, they also introduce manufacturing complexity and material compatibility issues, making them difficult to apply to large-scale mass production.

[0004] To address the absorption efficiency and integration issues inherent in traditional lead-salt material detectors, researchers have recently proposed design schemes to manipulate the optical field using artificial microphotonic structures (such as photonic crystals, nanogratings, and surface plasmon structures). These artificial microphotonic structures can generate resonance effects in specific wavelength bands, confining incident light to the surface of the lead-salt material, thereby significantly improving light absorption efficiency. This structural design, through coupling with the lead-salt thin film, achieves localized field enhancement for mid-infrared light, providing technical support for the fabrication of small-sized, high-resolution detectors.

[0005] Against this backdrop, a novel lead-salt uncooled mid-wave infrared detector structure was developed. By designing a periodic microphotonic metal array structure, localized enhancement of the optical field was achieved. This design not only improves the detector's performance at room temperature but also avoids the complexity and high cost of traditional gain structures. A search revealed very few similar lead-salt mid-wave infrared detector structures designed and practically applied in publicly available literature, both domestically and internationally. Summary of the Invention

[0006] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a lead salt uncooled mid-wave infrared detector based on an artificial plasma polariton array and its preparation method.

[0007] The technical solution of the present invention is as follows:

[0008] A first aspect of the present invention provides an enhanced lead salt uncooled mid-wave infrared detector, the detector junction comprising: a substrate, a reflective layer, a resonant cavity layer, a microstructure array layer, a lead salt sensitive layer, a metal electrode layer, and a passivation layer;

[0009] The reflective layer is located on the upper surface of the substrate, the resonant cavity layer is located on the upper surface of the reflective layer, the microstructure array layer is located on the upper surface of the resonant cavity layer, the microstructure array layer is a nanoscale metal artificial plasmon array, the lead salt sensitive layer covers the resonant cavity layer and the microstructure array layer, the metal electrode layer is located on the lead salt sensitive layer, and the passivation layer is located on the upper surface of the entire detector.

[0010] The metal electrode layer includes pixel electrodes and common electrodes, and there are two electrode distribution methods:

[0011] One is that the pixel electrode and the common electrode are located on both sides of the lead salt sensitive layer;

[0012] Secondly, the common electrode is ring-shaped, and the pixel electrode is located at the center of this ring structure;

[0013] The substrate is any one of silicon substrate, silicon dioxide substrate, and glass substrate;

[0014] The reflective layer is made of Al metal material and has a thickness of 150nm to 200nm;

[0015] The resonant cavity layer is any one of the dielectric materials CaF2, Si3N4, SiO2, and Al2O3, with a thickness of 500nm to 1.5μm.

[0016] An enhanced lead salt uncooled mid-wave infrared detector, the detector junction comprising: a substrate, a reflective layer, a resonant cavity layer, a microstructure array layer, a lead salt sensitive layer, a metal electrode layer, and a passivation layer;

[0017] The reflective layer is located on the upper surface of the substrate, the resonant cavity layer is located on the upper surface of the reflective layer, the lead salt sensitive layer is located on the upper surface of the resonant cavity layer, the microstructure array layer is located on the upper surface of the lead salt sensitive layer, the microstructure array layer is a nanoscale metal artificial plasmon array, the metal electrode layer is located on the lead salt sensitive layer, the microstructure array layer and the individual elements in the metal electrode layer do not contact each other, and the passivation layer is located on the upper surface of the entire detector.

[0018] The metal electrode layer includes pixel electrodes and common electrodes, and there are two electrode distribution methods:

[0019] One is that the pixel electrode and the common electrode are located on both sides of the lead salt sensitive layer;

[0020] Secondly, the common electrode is ring-shaped, and the pixel electrode is located at the center of this ring structure;

[0021] The substrate is any one of silicon substrate, silicon dioxide substrate, and glass substrate;

[0022] The reflective layer is made of Al metal material and has a thickness of 150nm to 200nm;

[0023] The resonant cavity layer is any one of the dielectric materials CaF2, Si3N4, SiO2, and Al2O3, with a thickness of 500nm to 1.5μm.

[0024] Furthermore, the microstructure array layer is any one of the metal materials Au, Al, and Ti, with a thickness of 20nm to 200nm; the microstructure is any one of periodically arranged cylinders, square pillars, cross-shaped pillars, various polygons, ellipses, and related combinations, with a typical diameter or side length of 200nm to 3μm and a typical center-to-center spacing of 300nm to 3.5μm.

[0025] Furthermore, the lead salt sensitive layer is any one of PbS, PbSe, and PbTe, with a thickness of 400nm to 1.5μm and a pixel size between 3μm×3μm and 5mm×5mm.

[0026] Furthermore, the electrode material is made of any one or at least two alloys of Au, Ti, Al, Ni, Ge, and Cr, with a thickness of 20–150 nm.

[0027] Furthermore, the passivation layer is any one of CaF2, Si3N4, SiO2, ZnS, and TiN, with a thickness of 50–300 nm.

[0028] A method for fabricating an enhanced lead salt uncooled mid-wave infrared detector includes the following steps:

[0029] Step 1: Prepare a metallic reflective layer on the substrate surface;

[0030] A reflective layer was grown on the substrate surface using magnetron sputtering. Al was selected as the target material, a vacuum was drawn, the sputtering power was set, argon was introduced as the sputtering gas, the gas pressure was adjusted to a stable working pressure, the magnetron sputtering source was started, and reflective layers of different thicknesses were formed by controlling the sputtering time.

[0031] Step 2: Fabricate a resonant cavity layer on the reflective layer;

[0032] A resonant cavity layer is grown on the surface of the reflective layer using magnetron sputtering. A target material of one of the following dielectric materials is selected: CaF2, Si3N4, SiO2, or Al2O3. A vacuum is drawn and the sputtering power is set. Argon gas is introduced as the sputtering gas, and the gas pressure is adjusted to a stable working pressure. The magnetron sputtering source is started, and resonant cavity layers of different thicknesses are formed by controlling the sputtering time.

[0033] Step 3: Fabricate a metal layer on the resonant cavity layer and etch it to obtain a microstructure array layer;

[0034] Step 4: Fabricate a lead salt sensitive layer on the microstructure array layer;

[0035] Step 5: Sensitize the lead salt sensitive layer material and etch it into sensitive cells of a set size;

[0036] Step 6: Prepare an electrode layer on the lead salt sensitive layer;

[0037] Step 7: Finally, prepare the passivation layer.

[0038] Furthermore, the step of forming the microstructure array layer in step 3 includes:

[0039] Photolithography combined with etching process is used to uniformly coat photoresist on the resonant cavity layer, and the microstructure array layer pattern is obtained by etching.

[0040] Metal thin films are grown by magnetron sputtering. The target material is selected as Au, Al or Ti. The vacuum is drawn, the sputtering power is set, argon gas is introduced as the sputtering gas, the working pressure is adjusted, the sputtering source is started, and the sputtering time is controlled to obtain metal thin films of different thicknesses. The films are then cleaned with organic solvents such as acetone and alcohol, and dried with N2 to obtain a surface microstructure metal array layer.

[0041] The step of forming the lead salt sensitive layer in step 4 includes:

[0042] A lead salt sensitive layer is grown using one of the following methods: magnetron sputtering, vacuum evaporation, or chemical bath deposition.

[0043] The magnetron sputtering method is as follows: select one of PbS, PbSe or PbTe as the target material, evacuate the vacuum, set the sputtering power, introduce argon gas as the sputtering gas, adjust the working gas pressure, start the sputtering source, and control the sputtering time to obtain lead salt films of different thicknesses.

[0044] The vacuum evaporation method involves heating the lead salt material to its evaporation temperature, causing it to evaporate in a vacuum and deposit on the surface of a metal disk array layer to obtain a lead salt sensitive layer.

[0045] The chemical bath deposition method involves immersing the substrate in a solution containing lead salt precursors and depositing a thin film through a chemical reaction to obtain a lead salt sensitive layer.

[0046] Step 5, which involves sensitizing the lead salt sensitive layer material, includes:

[0047] Lead salt films were sensitized using oxygen sensitization, iodine sensitization, or water bath method.

[0048] Oxygen sensitization is performed by placing the substrate in the center of a tube furnace, oxidizing it in air, using lead salt material as the evaporation source material along the flow direction of the carrier gas from upstream to downstream, setting up the substrate, evacuating the vacuum, heating it up first, then holding it at that temperature, and finally cooling it down to obtain a sensitized lead salt material film.

[0049] Iodine sensitization involves vaporizing iodine and introducing it into a reaction furnace, where it reacts with a lead salt film placed therein under certain temperature and pressure.

[0050] Water bath sensitization involves placing the lead salt sensitive layer in an aqueous solution at a specific temperature. By controlling the temperature and time of the water bath, the sensitive layer undergoes a sensitization reaction under the action of the aqueous solution.

[0051] After sensitization, wet etching or dry etching processes are used to etch sensitive unit structures of different sizes by controlling parameters such as etching time and solution concentration.

[0052] Step 6, the step of forming the metal electrode layer, includes:

[0053] Metal electrode layers can be prepared by vacuum evaporation, which involves covering a substrate with a mask, drawing a vacuum, and heating an alloy of any one or at least two of the metal materials Au, Ti, Al, Ni, Ge, and Cr to evaporate and deposit them on the surface of the sensitive layer in a vacuum, thereby obtaining a metal electrode layer; or by magnetron sputtering to prepare metal electrode layers based on the above-mentioned metal materials.

[0054] The step of forming the passivation layer in step 7 includes:

[0055] A passivation layer is grown by magnetron sputtering. Select any one of the target materials CaF2, Si3N4, SiO2, ZnS, or TiN, evacuate the vacuum, and set the sputtering power. Introduce argon gas as the sputtering gas, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, and form passivation layers of different thicknesses by controlling the sputtering time.

[0056] A method for fabricating an enhanced lead salt uncooled mid-wave infrared detector includes the following steps:

[0057] Step 1: Prepare a metallic reflective layer on the substrate surface;

[0058] A reflective layer was grown on the substrate surface using magnetron sputtering. Al was selected as the target material, a vacuum was drawn, the sputtering power was set, argon was introduced as the sputtering gas, the gas pressure was adjusted to a stable working pressure, the magnetron sputtering source was started, and reflective layers of different thicknesses were formed by controlling the sputtering time.

[0059] Step 2: Fabricate a resonant cavity layer on the reflective layer;

[0060] A resonant cavity layer is grown on the surface of the reflective layer using magnetron sputtering. A target material of one of the following dielectric materials is selected: CaF2, Si3N4, SiO2, or Al2O3. A vacuum is drawn and the sputtering power is set. Argon gas is introduced as the sputtering gas, and the gas pressure is adjusted to a stable working pressure. The magnetron sputtering source is started, and resonant cavity layers of different thicknesses are formed by controlling the sputtering time.

[0061] Step 3: Fabricate a lead salt sensitive layer on the resonant cavity layer;

[0062] Step 4: Sensitize the lead salt sensitive layer;

[0063] Step 5: Fabricate a microstructure array layer on the lead salt sensitive layer.

[0064] Step 6: Prepare an electrode layer on the lead salt sensitive layer;

[0065] Step 7: Finally, prepare the passivation layer.

[0066] Furthermore, the step of forming the lead salt sensitive layer in step 3 includes:

[0067] A lead salt sensitive layer is grown using one of the following methods: magnetron sputtering, vacuum evaporation, or chemical bath deposition.

[0068] The magnetron sputtering method is as follows: select one of PbS, PbSe or PbTe as the target material, evacuate the vacuum, set the sputtering power, introduce argon gas as the sputtering gas, adjust the working gas pressure, start the sputtering source, and control the sputtering time to obtain lead salt films of different thicknesses.

[0069] The vacuum evaporation method involves heating the lead salt material to its evaporation temperature, causing it to evaporate in a vacuum and deposit on the surface of a metal disk array layer to obtain a lead salt sensitive layer.

[0070] The chemical bath deposition method involves immersing the substrate in a solution containing lead salt precursors and depositing a thin film through a chemical reaction to obtain a lead salt sensitive layer.

[0071] Step 4, which involves sensitizing the lead salt sensitive layer material, includes:

[0072] Lead salt films were sensitized using oxygen sensitization, iodine sensitization, or water bath method.

[0073] Oxygen sensitization is performed by placing the substrate in the center of a tube furnace, oxidizing it in air, using lead salt material as the evaporation source material along the flow direction of the carrier gas from upstream to downstream, setting up the substrate, evacuating the vacuum, heating it up first, then holding it at that temperature, and finally cooling it down to obtain a sensitized lead salt material film.

[0074] Iodine sensitization involves vaporizing iodine and introducing it into a reaction furnace, where it reacts with a lead salt film placed therein under certain temperature and pressure.

[0075] Water bath sensitization involves placing the lead salt sensitive layer in an aqueous solution at a specific temperature. By controlling the temperature and time of the water bath, the sensitive layer undergoes a sensitization reaction under the action of the aqueous solution.

[0076] After sensitization, wet etching or dry etching processes are used to etch sensitive unit structures of different sizes by controlling parameters such as etching time and solution concentration.

[0077] Step 5, the step of forming the microstructure array layer, includes:

[0078] Photolithography combined with etching process is used to uniformly coat photoresist on the resonant cavity layer, and the microstructure array layer pattern is obtained by etching.

[0079] Metal thin films are grown by magnetron sputtering. The target material is selected as Au, Al or Ti. The vacuum is drawn, the sputtering power is set, argon gas is introduced as the sputtering gas, the working pressure is adjusted, the sputtering source is started, and the sputtering time is controlled to obtain metal thin films of different thicknesses. The films are then cleaned with organic solvents such as acetone and alcohol, and dried with N2 to obtain a surface microstructure metal array layer.

[0080] Step 6, the step of forming the metal electrode layer, includes:

[0081] Metal electrode layers can be prepared by vacuum evaporation, which involves covering a substrate with a mask, drawing a vacuum, and heating an alloy of any one or at least two of the metal materials Au, Ti, Al, Ni, Ge, and Cr to evaporate and deposit them on the surface of the sensitive layer in a vacuum, thereby obtaining a metal electrode layer; or by magnetron sputtering to prepare metal electrode layers based on the above-mentioned metal materials.

[0082] The step of forming the passivation layer in step 7 includes:

[0083] A passivation layer is grown by magnetron sputtering. Select any one of the target materials CaF2, Si3N4, SiO2, ZnS, or TiN, evacuate the vacuum, and set the sputtering power. Introduce argon gas as the sputtering gas, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, and form passivation layers of different thicknesses by controlling the sputtering time.

[0084] This invention has at least one of the following beneficial effects:

[0085] This invention designs a lead-salt uncooled mid-wave infrared detector based on an artificial plasmon resonance array. By sequentially depositing a resonant structure consisting of a metal reflective layer and a resonant cavity layer, and by using photolithography and etching processes to prepare a microstructure array layer, the incident light energy is concentrated in the lead-salt sensitive layer through the optical coupling of the resonant cavity and the local field enhancement effect of LSPR, which can effectively improve the light absorption rate and enhance the photoelectric response performance of the device.

[0086] This invention employs oxidation, iodination, or water bath methods to treat lead salt thin films. These two methods are simple to operate, low in cost, and can significantly improve the photoelectric properties of lead selenide. By controlling the temperature and immersion time under an appropriate chemical atmosphere, the photoelectric properties of the thin film surface can be enhanced, dark current reduced, and response sensitivity improved. The invention utilizes a multi-layer design structure, which can improve light absorption, enhance detector sensitivity and stability, and increase the light absorption efficiency of lead salt materials in the mid-infrared band, achieving miniaturized, low-cost, and high-sensitivity infrared detection. Attached Figure Description

[0087] Figure 1 This is a schematic diagram of the growth process of the PbSe mid-infrared detector based on an artificial plasmon array in Embodiment 1 of the invention.

[0088] Figure 2 This is a scanning electron microscope (SEM) image of the surface morphology of the Al thin film obtained in Example 1 of the present invention.

[0089] Figure 3 The image shows the reflection spectrum of an Al thin film with a thickness of 200 nm in the mid-wavelength band (3-6 μm) of Embodiment 1 of the present invention.

[0090] Figure 4This is a scanning electron microscope (SEM) image of the surface morphology of the CaF2 thin film obtained in Example 1 of the present invention.

[0091] Figure 5 The transmittance of the CaF2 thin film with a thickness of 1.2 μm in Example 1 of the present invention is shown in the mid-wavelength band (3-6 μm).

[0092] Figure 6 This is a scanning electron microscope (SEM) image of the surface morphology of the PbSe thin film before sensitization in Example 1 of the present invention.

[0093] Figure 7 This is a scanning electron microscope (SEM) image of the surface morphology of the PbSe thin film after sensitization in Example 1 of the present invention.

[0094] Figure 8 This is the structure of the infrared detector in Embodiment 2 of the present invention. Detailed Implementation Plan

[0095] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0096] An embodiment of the present invention provides a lead-salt uncooled mid-wave infrared detector based on an artificial plasmon resonance array. The detector junction includes: a substrate, a reflective layer grown on the upper surface of the substrate, a resonant cavity layer grown on the upper surface of the reflective layer, a microstructure array layer grown on the upper surface of the resonant cavity layer, a lead-salt sensitive layer grown on the upper surface of the microstructure array layer, a metal electrode layer grown on the upper surface of the lead-salt sensitive layer, and a passivation layer grown on the upper surfaces of the lead-salt sensitive layer and the electrode layer.

[0097] In some embodiments, the substrate is a silicon substrate.

[0098] In some embodiments, the reflective layer is an Al thin film with a thickness of 200 nm.

[0099] In some embodiments, the resonant cavity layer is a CaF2 thin film with a thickness of 1.2 μm.

[0100] In some embodiments, the microstructure array layer is a Ti thin film with a thickness of 60 nm.

[0101] The microstructure consists of periodically arranged circular disks with a diameter of 3 μm and a center-to-center distance of 3.5 μm between the two disks.

[0102] In some embodiments, the lead salt sensitive layer is a PbSe thin film with a thickness of 700 nm.

[0103] In some embodiments, the metal electrode layer is an Au thin film with a thickness of 80 nm.

[0104] In some embodiments, the passivation layer is a Si3N4 thin film with a thickness of 200 nm.

[0105] Another embodiment of the present invention provides a method for fabricating an enhanced lead salt uncooled mid-wave infrared detector, comprising the following steps:

[0106] Step 1: Prepare a metallic reflective layer on the substrate surface;

[0107] Step 2: Fabricate a resonant cavity layer on the reflective layer;

[0108] Step 3: Fabricate a metal layer on the resonant cavity layer and etch it to obtain a microstructure array layer;

[0109] Step 4: Fabricate a lead salt sensitive layer on the microstructure array layer;

[0110] Step 5: Sensitize the lead salt sensitive layer material and etch it into sensitive units of a certain size;

[0111] Step 6: Fabricate and etch electrodes on the lead salt sensitive layer;

[0112] Step 7: Finally, prepare the passivation layer.

[0113] In some embodiments, the step of forming the reflective layer in step 1 includes: preparing the reflective layer on the surface of a silicon substrate using magnetron sputtering, selecting an Al target, and evacuating to a vacuum of 7 × 10⁻⁶. -4 Below Pa, set the sputtering power, introduce a small amount of argon gas as the sputtering gas, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, set the sputtering time, and obtain the Al reflective layer.

[0114] In some embodiments, the step of forming the resonant cavity layer in step 2 includes: preparing the resonant cavity layer on the surface of the reflective layer using magnetron sputtering, selecting CaF2 target material, and evacuating to a vacuum of 7×10⁻⁶. -4 Below Pa, set the sputtering power, introduce a small amount of argon gas as the sputtering gas, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, set the sputtering time, and obtain the CaF2 resonant cavity layer.

[0115] In some embodiments, the step of forming the microstructure array layer in step 3 includes: uniformly coating photoresist on the CaF2 resonant cavity layer using photolithography combined with etching process, pre-baking, exposure, post-baking, development, observing the pattern, preparing a metal thin film using magnetron sputtering, selecting a Ti target, evacuating to below 7×10-4 Pa, setting the sputtering power, introducing a small amount of argon gas as the sputtering gas, adjusting the gas pressure to a stable working pressure, starting the sputtering source, setting the sputtering time, cleaning with organic solvents such as acetone and alcohol, and drying with N2 to obtain a metal Ti disk array layer.

[0116] In some embodiments, the step of forming the lead salt sensitive layer in step 4 includes: preparing the lead salt sensitive layer using a vacuum evaporation method, drawing a vacuum, heating the PbSe material to the evaporation temperature, causing it to evaporate in the vacuum and deposit on the surface of the metal disk array layer to obtain the PbSe sensitive layer. Combined with photolithography and etching processes, it is etched into a unit structure of a certain size.

[0117] In some embodiments, step 5, the step of sensitizing the lead salt sensitive layer material, includes: placing a substrate with a PbSe thin film in a tube furnace and oxidizing it in air; then, along the flow direction of the carrier gas from upstream to downstream, placing an evaporation source and a substrate in sequence, evacuating the vacuum, setting the heating temperature of the evaporation source and the substrate, and setting the reaction time; the heating rate of the powder during the heating stage is ≤10℃ / min; after sensitization, a wet etching process is used to etch the lead salt sensitive layer into a sensitive unit structure of a certain size.

[0118] In some embodiments, the step of forming the metal electrode layer in step 6 includes: preparing the Au electrode layer by vacuum evaporation, covering the substrate with a strip mask, drawing a vacuum, heating the evaporation source material, causing it to evaporate in the vacuum and deposit on the surface of the sensitized layer to obtain the Au electrode layer.

[0119] In some embodiments, the step of forming the passivation layer in step 7 includes: preparing the passivation layer using magnetron sputtering, selecting Si3N4 target material, and evacuating to a vacuum of 7×10⁻⁶. -4 Below Pa, set the sputtering power, introduce a small amount of argon and nitrogen as sputtering gases, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, set the sputtering time, and obtain the Si3N4 resonant cavity layer.

[0120] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0121] Example 1

[0122] This embodiment provides a PbSe mid-infrared detector based on an artificial plasmon array and its fabrication method, specifically comprising the following steps:

[0123] A schematic diagram of the growth process for preparing a PbSe mid-infrared detector is shown below. Figure 1 As shown, it includes:

[0124] (1) Using a Si substrate, the substrate surface is ultrasonically cleaned for 15 minutes in sequence with acetone and anhydrous ethanol to remove organic impurities. Ultrapure water is then used for ultrasonic cleaning for 10 minutes to remove the cleaning solvent remaining on the substrate surface. Finally, the substrate is dried with N2.

[0125] (2) Growth of the Al reflective layer. A magnetron sputtering deposition machine was used as the deposition and growth equipment, and high-purity Al bulk crystal material was used as the target. The Si substrate was fixed on the substrate tray and transferred to the sputtering chamber. A mechanical pump and a molecular pump were used to evacuate the vacuum to a vacuum level of 7 × 10⁻⁶. -4 The argon flow rate was controlled at 40 sccm, the working pressure was set to 0.5 Pa, the power was set to 80 W, the tray rotation speed was set to 10 r / min, and DC sputtering was performed for 30 min to obtain an Al film with a thickness of 200 nm.

[0126] (3) Growth of the CaF2 resonant cavity layer. Based on the already grown Al substrate, a magnetron sputtering deposition machine was used as the deposition equipment, and high-purity CaF2 bulk crystal material was used as the target. After the already grown Al reflective layer, a vacuum of 7 × 10⁻⁶ was applied. -4 The substrate was heated to 60°C for sputtering. The cavity pressure was set to 0.5 Pa, the sputtering power was set to 120 W, the argon flow rate was controlled to 30 sccm, and the tray rotation speed was set to 10 r / min. After RF sputtering for 90 min, the heating power was turned off and the substrate was allowed to cool naturally to room temperature to obtain a CaF2 film with a thickness of 1.2 μm.

[0127] (4) Fabrication of the Ti disk array layer. On the already grown CaF2 substrate, spin-coated negative resist NR-3000 was applied, pre-baked for 2.5 min to remove solvent, and then the pattern on the mask was transferred to the photoresist by UV (MV) exposure for 7.5 s. After post-baking for 2.5 min and development for 20 s, periodically arranged circular holes were obtained. A magnetron sputtering deposition machine was used as the deposition equipment, and high-purity Ti bulk crystal material was used as the target material. The vacuum was evacuated to a vacuum degree of 7 × 10⁻⁶. -4 The argon flow rate was set to 20 sccm, the working pressure to 0.5 Pa, the power to 50 W, and the tray rotation speed to 10 r / min. After DC sputtering for 12 min, the sputtering was stopped. Excess photoresist was cleaned with organic solvents such as acetone and alcohol. After drying with N2, a metal Ti disk array with a thickness of 60 nm, a disk diameter of 3 μm, and a center-to-center distance of 3.5 μm between the two disks was obtained.

[0128] (5) To grow the PbSe sensitive layer, 1.0 g of PbSe (99.99%) was used as the evaporation source and the substrate was placed in an evaporation machine, and the vacuum degree was evacuated to 2×10⁻⁶. -3 Pa, heating the evaporation source material to 620℃, controlling the evaporation rate to 0.2A / s, and depositing for 6.5h to obtain a 700nm thick PbSe film.

[0129] (6) The PbSe film is oxidized and iodized. Based on the already grown PbSe thin film, air was used as the sensitization source. The PbSe substrate was placed in the center of a horizontal tube furnace and heated to 460°C at a heating rate of 20°C / min. It was then held at 460°C for 30 min and cooled to room temperature in three stages. Along the flow direction of the carrier gas from upstream to downstream, 0.5 g of 99.9% argon gas was placed in the center of the horizontal tube furnace as the evaporation source. The substrate was placed at the end of the furnace, 5 cm away from the outlet. After sealing the tube furnace, a mechanical pump was used to evacuate to a vacuum of 3 Pa. The argon gas flow rate was controlled at 25 sccm. The heating temperature of the evaporation source material was set to 105°C, and the substrate temperature was set to 325°C. The time for the tube furnace to heat from room temperature to the heating temperature of the evaporation source material (105°C) was 17 min. The vapor generated by the reaction source was transported to the surface of the grown PbSe substrate by the carrier gas and reacted for 6 min. Then, the heating power of the tube furnace was cut off, and the furnace was allowed to cool naturally to room temperature to obtain the sensitized PbSe thin film.

[0130] (7) After sensitization, the photolithography and etching processes are combined. Photoresist is used as a mask. After exposure, development and other steps, a 1mm×1mm unit structure is etched by wet etching. The PbSe film is cleaned with ultrapure water and dried with N2.

[0131] (8) Prepare an Au electrode on a PbSe thin film. Design the shape of a strip mask according to the area of ​​the prepared PbSe thin film. Cover the PbSe thin film with the mask and deposit the gold electrode using an evaporation coating equipment. Control the evaporation rate to 1A / s and deposit for about 20 minutes to obtain an 80nm thick Au thin film.

[0132] (9) Growth of Si3N4 passivation layer: A magnetron sputtering deposition machine was used as the deposition equipment, and high-purity Si3N4 bulk crystal material was used as the target. The vacuum was evacuated to 7×10⁻⁶. -4 With the gas flow rate set to Ar:N2 = 30:10 (sccm), working pressure set to 0.5 Pa, power set to 80 W, tray rotation speed set to 10 r / min, and RF sputtering for 100 min, a Si3N4 thin film with a thickness of 200 nm was obtained.

[0133] Example 2

[0134] An enhanced lead salt uncooled mid-wave infrared detector, the detector junction comprising: a substrate, a reflective layer, a resonant cavity layer, a microstructure array layer, a lead salt sensitive layer, a metal electrode layer, and a passivation layer;

[0135] The reflective layer is located on the upper surface of the substrate, the resonant cavity layer is located on the upper surface of the reflective layer, the lead salt sensitive layer is located on the upper surface of the resonant cavity layer, the microstructure array layer is located on the upper surface of the lead salt sensitive layer, the microstructure array layer is a nanoscale metal artificial plasmon array, the metal electrode layer is located on the lead salt sensitive layer, the microstructure array layer and the individual elements in the metal electrode layer do not contact each other, and the passivation layer is located on the upper surface of the entire detector.

[0136] The metal electrode layer includes pixel electrodes and common electrodes, and there are two electrode distribution methods:

[0137] One is that the pixel electrode and the common electrode are located on both sides of the lead salt sensitive layer;

[0138] Secondly, the common electrode is ring-shaped, and the pixel electrode is located at the center of this ring structure;

[0139] The substrate is any one of silicon substrate, silicon dioxide substrate, and glass substrate;

[0140] The reflective layer is made of Al metal material and has a thickness of 150nm to 200nm;

[0141] The resonant cavity layer is any one of the dielectric materials CaF2, Si3N4, SiO2, and Al2O3, with a thickness of 500nm to 1.5μm.

[0142] The microstructure array layer is any one of the metal materials Au, Al, and Ti, with a thickness of 20nm to 200nm; the microstructure is any one of the periodically arranged cylinders, square pillars, cross-shaped pillars, various polygons, ellipses, and related combinations, with a typical diameter or side length of 200nm to 3μm and a typical center-to-center spacing of 300nm to 3.5μm.

[0143] The lead salt sensitive layer is any one of PbS, PbSe, and PbTe, with a thickness of 400nm to 1.5μm and a pixel size between 3μm×3μm and 5mm×5mm.

[0144] The electrode material is made of any one or at least two alloys of Au, Ti, Al, Ni, Ge, and Cr, with a thickness of 20–150 nm.

[0145] The passivation layer is any one of CaF2, Si3N4, SiO2, ZnS, and TiN, with a thickness of 50–300 nm.

[0146] This method can be used to obtain a lead salt uncooled mid-wave infrared detector based on an artificial plasma polariton array.

[0147] Figure 2 The image shows the surface morphology of the Al reflective layer obtained in Example 1, which demonstrates the high continuity of the Al film over a large area.

[0148] Figure 3 The image shows the reflectance spectrum of the 200 nm thick Al thin film in Example 1. The reflectance in the mid-wavelength band (3-6 μm) was obtained by Fourier transform infrared spectroscopy (FT-IR). Since its thickness is much greater than the skin depth of mid-infrared waves inside the aluminum metal layer, infrared waves are almost totally reflected at the bottom layer of the structure.

[0149] Figure 4 This is a scanning electron microscope (SEM) image of the CaF2 thin film obtained in Example 1. It exhibits high crystallinity, which is attributed to the ordered arrangement of atoms on the substrate during sputtering. Thin films with high crystallinity often possess better performance.

[0150] Figure 5 The transmission spectrum of the 1.2 μm thick CaF2 film in Example 1 is shown. The transmittance in the mid-wavelength band (3-6 μm) was obtained by Fourier transform infrared spectroscopy (FT-IR). The sharp drop at 3.6 μm is due to the absorption of the mica substrate, which is negligible. The average transmittance is as high as 80% or more. This broadband high transmittance characteristic is an important advantage as a resonant cavity.

[0151] Figure 6 The image shown is a scanning electron microscope (SEM) image of the surface morphology of the PbSe thin film before sensitization in Example 1. It exhibits good crystal quality, with clear boundaries between particles and no obvious defects or impurities.

[0152] Figure 7 The image shows the surface morphology of the PbSe thin film after oxidation and iodination treatment in Example 1. The sensitization treatment promotes the fusion or aggregation between particles, resulting in an increase in particle size. Larger crystal particles help reduce the number of grain boundaries, reduce the scattering and trapping effect of grain boundaries on charge carriers, and are beneficial to increase the number of photogenerated charge carriers and improve the detector responsivity.

[0153] Figure 8 This is a structural diagram of Example 2.

[0154] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An enhanced lead salt uncooled mid-wave infrared detector, the detector comprising: Substrate, reflective layer, resonant cavity layer, microstructure array layer, lead salt sensitive layer, metal electrode layer, passivation layer; The reflective layer is located on the upper surface of the substrate, the resonant cavity layer is located on the upper surface of the reflective layer, the microstructure array layer is located on the upper surface of the resonant cavity layer, the microstructure array layer is a nanoscale metal artificial plasmon array, the lead salt sensitive layer covers the resonant cavity layer and the microstructure array layer, the metal electrode layer is located on the lead salt sensitive layer, and the passivation layer is located on the upper surface of the entire detector. The metal electrode layer includes pixel electrodes and common electrodes, and there are two electrode distribution methods: One is that the pixel electrode and the common electrode are located on both sides of the lead salt sensitive layer; Secondly, the common electrode is ring-shaped, and the pixel electrode is located at the center of this ring structure; The substrate is any one of silicon substrate, silicon dioxide substrate, and glass substrate; The reflective layer is made of Al metal and has a thickness of 150 nm. 200nm; The resonant cavity layer is any one of the dielectric materials CaF2, Si3N4, SiO2, and Al2O3, with a thickness of 500 nm. 1.5um; The microstructure array layer is made of any one of the metals Au, Al, and Ti, and has a thickness of 20 mm. 200nm; the microstructure is any one of the periodically arranged cylinders, square pillars, cross-shaped pillars, various polygons, ellipses, and related combinations, with a diameter or side length of 200nm. 3µm, center-to-center spacing 300nm 3.5um; The lead salt sensitive layer is any one of PbS, PbSe, and PbTe, and has a thickness of 400 nm. 1.5um, pixel size is 3um × 3um Between 5mm and 5mm.

2. An enhanced lead salt uncooled mid-wave infrared detector, the detector comprising: Substrate, reflective layer, resonant cavity layer, microstructure array layer, lead salt sensitive layer, metal electrode layer, passivation layer; The reflective layer is located on the upper surface of the substrate, the resonant cavity layer is located on the upper surface of the reflective layer, the lead salt sensitive layer is located on the upper surface of the resonant cavity layer, the microstructure array layer is located on the upper surface of the lead salt sensitive layer, the microstructure array layer is a nanoscale metal artificial plasmon array, the metal electrode layer is located on the lead salt sensitive layer, the microstructure array layer and the individual elements in the metal electrode layer do not contact each other, and the passivation layer is located on the upper surface of the entire detector. The metal electrode layer includes pixel electrodes and common electrodes, and there are two electrode distribution methods: One is that the pixel electrode and the common electrode are located on both sides of the lead salt sensitive layer; Secondly, the common electrode is ring-shaped, and the pixel electrode is located at the center of this ring structure; The substrate is any one of silicon substrate, silicon dioxide substrate, and glass substrate; The reflective layer is made of Al metal and has a thickness of 150 nm. 200nm; The resonant cavity layer is any one of the dielectric materials CaF2, Si3N4, SiO2, and Al2O3, with a thickness of 500 nm. 1.5um; The microstructure array layer is made of any one of the metals Au, Al, and Ti, and has a thickness of 20 nm. 200nm; the microstructure is any one of the periodically arranged cylinders, square pillars, cross-shaped pillars, various polygons, ellipses, and related combinations, with a diameter or side length of 200nm. 3µm, center-to-center spacing 300nm 3.5um; The lead salt sensitive layer is any one of PbS, PbSe, and PbTe, and has a thickness of 400 nm. 1.5um, pixel size is 3um × 3um Between 5mm and 5mm.

3. A lead salt uncooled mid-wave infrared detector with an enhanced structure as described in claim 1 or 2, characterized in that, The electrode material is made of any one or an alloy of at least two of Au, Ti, Al, Ni, Ge, and Cr, with a thickness of 20 mm. 150nm.

4. A lead salt uncooled mid-wave infrared detector with an enhanced structure as described in claim 1 or 2, characterized in that, The passivation layer is any one of CaF2, Si3N4, SiO2, ZnS, and TiN, with a thickness of 50 mm. 300nm.

5. The method for fabricating an enhanced lead salt uncooled mid-wave infrared detector as described in claim 1, comprising the following steps: Step 1: Prepare a metallic reflective layer on the substrate surface; A reflective layer was grown on the substrate surface using magnetron sputtering. Al was selected as the target material, a vacuum was drawn, the sputtering power was set, argon was introduced as the sputtering gas, the gas pressure was adjusted to a stable working pressure, the magnetron sputtering source was started, and reflective layers of different thicknesses were formed by controlling the sputtering time. Step 2: Fabricate a resonant cavity layer on the reflective layer; A resonant cavity layer is grown on the surface of the reflective layer using magnetron sputtering. A target material of one of the following dielectric materials is selected: CaF2, Si3N4, SiO2, or Al2O3. A vacuum is drawn and the sputtering power is set. Argon gas is introduced as the sputtering gas, and the gas pressure is adjusted to a stable working pressure. The magnetron sputtering source is started, and resonant cavity layers of different thicknesses are formed by controlling the sputtering time. Step 3: Fabricate a metal layer on the resonant cavity layer and etch it to obtain a microstructure array layer; Step 4: Fabricate a lead salt sensitive layer on the microstructure array layer; Step 5: Sensitize the lead salt sensitive layer material and etch it into sensitive cells of a set size; Step 6: Prepare an electrode layer on the lead salt sensitive layer; Step 7: Finally, prepare the passivation layer.

6. The method for fabricating an enhanced lead salt uncooled mid-wave infrared detector as described in claim 5, characterized in that, Step 3, which involves forming the microstructure array layer, includes: Photolithography combined with etching process is used to uniformly coat photoresist on the resonant cavity layer, and the microstructure array layer pattern is obtained by etching. Metal thin films are grown by magnetron sputtering. The target material is selected as Au, Al or Ti. The vacuum is drawn, the sputtering power is set, argon gas is introduced as the sputtering gas, the working pressure is adjusted, the sputtering source is started, and the sputtering time is controlled to obtain metal thin films of different thicknesses. The films are then cleaned with organic solvents such as acetone and alcohol, and dried with N2 to obtain a surface microstructure metal array layer. Step 4, which involves forming the lead salt sensitive layer, includes: A lead salt sensitive layer is grown using one of the following methods: magnetron sputtering, vacuum evaporation, or chemical bath deposition. The magnetron sputtering method is as follows: select one of PbS, PbSe or PbTe as the target material, evacuate the vacuum, set the sputtering power, introduce argon gas as the sputtering gas, adjust the working gas pressure, start the sputtering source, and control the sputtering time to obtain lead salt films of different thicknesses. The vacuum evaporation method involves heating the lead salt material to its evaporation temperature, causing it to evaporate in a vacuum and deposit on the surface of a metal disk array layer to obtain a lead salt sensitive layer. The chemical bath deposition method involves immersing the substrate in a solution containing lead salt precursors and depositing a thin film through a chemical reaction to obtain a lead salt sensitive layer. Step 5, which involves sensitizing the lead salt sensitive layer material, includes: Lead salt films were sensitized using oxygen sensitization, iodine sensitization, or water bath method. Oxygen sensitization is performed by placing the substrate in the center of a tube furnace, oxidizing it in air, using lead salt material as the evaporation source material along the flow direction of the carrier gas from upstream to downstream, setting up the substrate, evacuating the vacuum, heating it up first, then holding it at that temperature, and finally cooling it down to obtain a sensitized lead salt material film. Iodine sensitization involves vaporizing iodine and introducing it into a reaction furnace, where it reacts with a lead salt film placed therein under certain temperature and pressure. Water bath sensitization involves placing the lead salt sensitive layer in an aqueous solution at a specific temperature. By controlling the temperature and time of the water bath, the sensitive layer undergoes a sensitization reaction under the action of the aqueous solution. After sensitization, wet etching or dry etching processes are used to etch sensitive unit structures of different sizes by controlling parameters such as etching time and solution concentration. Step 6, forming the metal electrode layer, includes: Metal electrode layers can be prepared by vacuum evaporation, which involves covering a substrate with a mask, drawing a vacuum, and heating an alloy of any one or at least two of the metal materials Au, Ti, Al, Ni, Ge, and Cr to evaporate and deposit them on the surface of the sensitive layer in a vacuum, thereby obtaining a metal electrode layer; or by magnetron sputtering to prepare metal electrode layers based on the above-mentioned metal materials. Step 7, which involves forming the passivation layer, includes: A passivation layer is grown by magnetron sputtering. Select any one of the target materials CaF2, Si3N4, SiO2, ZnS, or TiN, evacuate the vacuum, and set the sputtering power. Introduce argon gas as the sputtering gas, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, and form passivation layers of different thicknesses by controlling the sputtering time.

7. The method for fabricating an enhanced lead salt uncooled mid-wave infrared detector as described in claim 2, comprising the following steps: Step 1: Prepare a metallic reflective layer on the substrate surface; A reflective layer was grown on the substrate surface using magnetron sputtering. Al was selected as the target material, a vacuum was drawn, the sputtering power was set, argon was introduced as the sputtering gas, the gas pressure was adjusted to a stable working pressure, the magnetron sputtering source was started, and reflective layers of different thicknesses were formed by controlling the sputtering time. Step 2: Fabricate a resonant cavity layer on the reflective layer; A resonant cavity layer is grown on the surface of the reflective layer using magnetron sputtering. A target material of one of the following dielectric materials is selected: CaF2, Si3N4, SiO2, or Al2O3. A vacuum is drawn and the sputtering power is set. Argon gas is introduced as the sputtering gas, and the gas pressure is adjusted to a stable working pressure. The magnetron sputtering source is started, and resonant cavity layers of different thicknesses are formed by controlling the sputtering time. Step 3: Fabricate a lead salt sensitive layer on the resonant cavity layer; Step 4: Sensitize the lead salt sensitive layer; Step 5: Fabricate a microstructure array layer on the lead salt sensitive layer. Step 6: Prepare an electrode layer on the lead salt sensitive layer; Step 7: Finally, prepare the passivation layer.

8. The method for fabricating an enhanced lead salt uncooled mid-wave infrared detector as described in claim 7, characterized in that, Step 3, which involves forming the lead salt sensitive layer, includes: A lead salt sensitive layer is grown using one of the following methods: magnetron sputtering, vacuum evaporation, or chemical bath deposition. The magnetron sputtering method is as follows: select one of PbS, PbSe or PbTe as the target material, evacuate the vacuum, set the sputtering power, introduce argon gas as the sputtering gas, adjust the working gas pressure, start the sputtering source, and control the sputtering time to obtain lead salt films of different thicknesses. The vacuum evaporation method involves heating the lead salt material to its evaporation temperature, causing it to evaporate in a vacuum and deposit on the surface of a metal disk array layer to obtain a lead salt sensitive layer. The chemical bath deposition method involves immersing the substrate in a solution containing lead salt precursors and depositing a thin film through a chemical reaction to obtain a lead salt sensitive layer. Step 4, which involves sensitizing the lead salt sensitive layer material, includes: Lead salt films were sensitized using oxygen sensitization, iodine sensitization, or water bath method. Oxygen sensitization is performed by placing the substrate in the center of a tube furnace, oxidizing it in air, using lead salt material as the evaporation source material along the flow direction of the carrier gas from upstream to downstream, setting up the substrate, evacuating the vacuum, heating it up first, then holding it at that temperature, and finally cooling it down to obtain a sensitized lead salt material film. Iodine sensitization involves vaporizing iodine and introducing it into a reaction furnace, where it reacts with a lead salt film placed therein under certain temperature and pressure. Water bath sensitization involves placing the lead salt sensitive layer in an aqueous solution at a specific temperature. By controlling the temperature and time of the water bath, the sensitive layer undergoes a sensitization reaction under the action of the aqueous solution. After sensitization, wet etching or dry etching processes are used to etch sensitive unit structures of different sizes by controlling parameters such as etching time and solution concentration. Step 5, which involves forming the microstructure array layer, includes: Photolithography combined with etching process is used to uniformly coat photoresist on lead salt sensitive layer, and microstructure array layer pattern is obtained by etching. Metal thin films are grown by magnetron sputtering. The target material is selected as Au, Al or Ti. The vacuum is drawn, the sputtering power is set, argon gas is introduced as the sputtering gas, the working pressure is adjusted, the sputtering source is started, and the sputtering time is controlled to obtain metal thin films of different thicknesses. The films are then cleaned with organic solvents such as acetone and alcohol, and dried with N2 to obtain a surface microstructure metal array layer. Step 6, forming the metal electrode layer, includes: Metal electrode layers can be prepared by vacuum evaporation, which involves covering a substrate with a mask, drawing a vacuum, and heating an alloy of any one or at least two of the metal materials Au, Ti, Al, Ni, Ge, and Cr to evaporate and deposit them on the surface of the sensitive layer in a vacuum, thereby obtaining a metal electrode layer; or by magnetron sputtering to prepare metal electrode layers based on the above-mentioned metal materials. Step 7, which involves forming the passivation layer, includes: A passivation layer is grown by magnetron sputtering. Select any one of the target materials CaF2, Si3N4, SiO2, ZnS, or TiN, evacuate the vacuum, and set the sputtering power. Introduce argon gas as the sputtering gas, adjust the gas pressure to a stable working pressure, start the magnetron sputtering source, and form passivation layers of different thicknesses by controlling the sputtering time.

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