Infrared detector, preparation method thereof, photoelectric detection device and infrared imaging system

Abstract

This application relates to the field of semiconductor technology, and discloses an infrared detector and its fabrication method, photoelectric detection device, and infrared imaging system. The infrared detector includes a long-wave infrared detection layer and a target microstructure formed on a first side of the long-wave infrared detection layer. The long-wave infrared detection layer is made of mercury cadmium telluride; the target microstructure includes at least two rectangular substructures; the target microstructure is coupled with the target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer, thus enhancing the photoelectric coupling capability of the long-wave infrared detection layer. Its beneficial effect is that by forming a target microstructure containing at least two rectangular substructures on the first side of the long-wave infrared detection layer, absorption competition between the microstructure and the detection layer is effectively suppressed, improving the photoelectric coupling capability of the detection layer. Ultimately, this significantly improves the responsivity, absorptivity, and polarization detection capability of the infrared detector.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to an infrared detector and its fabrication method, a photoelectric detection device, and an infrared imaging system. Background Technology

[0002] Infrared detectors play an important role in meteorological monitoring, remote sensing imaging and astronomical observation. Therefore, it is crucial to develop infrared detectors with high speed, high response and multi-dimensional information sensing capabilities.

[0003] However, although the detection performance can be improved by stimulating plasmon polaritons on the surface of metal microstructures, the strong absorption competition between the metal microstructures and the infrared detection materials still restricts the further improvement of the detector performance. There is an urgent need for an infrared detector with higher detection performance. Summary of the Invention

[0004] This application aims to at least partially solve one of the technical problems in related technologies. To this end, this application proposes an infrared detector and its fabrication method, a photoelectric detection device, and an infrared imaging system. The main technical solutions adopted in this application include: In a first aspect, this application provides an infrared detector, comprising: a long-wave infrared detection layer; wherein the long-wave infrared detection layer is made of mercury cadmium telluride; a target microstructure formed on a first side of the long-wave infrared detection layer; wherein the target microstructure includes at least two rectangular substructures; the target microstructure is coupled with target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer to enhance the photoelectric coupling capability of the long-wave infrared detection layer.

[0005] A long-wave infrared detector layer was fabricated using mercury cadmium telluride (HCdT), leveraging its excellent intrinsic photoelectric conversion properties in the long-wave infrared band to achieve efficient absorption of long-wave infrared light and effective excitation of photogenerated carriers, providing the foundation for signal generation in the infrared detector's photoelectric conversion. By forming a target microstructure containing at least two rectangular substructures on the first side of the long-wave infrared detector layer, the physical mechanism of exciting surface phonon polaritons in silicon carbide was utilized to efficiently localize the incident light energy at the interface, effectively suppressing absorption competition between the microstructure and the detector layer, and enhancing the photoelectric coupling capability of the detector layer. Finally, through heterogeneous integration of the long-wave infrared detector layer and the target microstructure, the responsivity, absorptivity, and polarization detection capability of the infrared detector were significantly improved, achieving high-performance long-wave infrared detection.

[0006] Optionally, the target microstructure is made of silicon carbide.

[0007] Using silicon carbide as the material for the target microstructure can effectively suppress the absorption competition between the microstructure and the detection material, allowing more light energy to be localized and coupled into the long-wave infrared detection layer, thereby improving the photoelectric conversion efficiency.

[0008] Optionally, the infrared detector further includes: an active region located within the long-wave infrared detection layer; wherein the active region includes a PN junction; a passivation layer located on a second side of the long-wave infrared detection layer; wherein the second side and the first side are opposite sides of the long-wave infrared detection layer; and a metal contact structure electrically connected to the PN junction.

[0009] By constructing an active region containing a PN junction within the long-wave infrared detection layer, a physical basis for photoelectric detection is provided. A passivation layer effectively protects the detection material layer from corrosion, thus ensuring the stability of the overall structure. Furthermore, the inclusion of a metal contact structure electrically connected to the PN junction enables efficient collection and output of photocurrent. Ultimately, through the synergistic cooperation of the long-wave infrared detection layer, target microstructure, active region, passivation layer, and metal contact structure, the infrared detector can not only efficiently generate photogenerated carriers but also rapidly and completely convert the enhanced optical signal into a measurable electrical signal, thereby comprehensively improving the response performance and usability of the infrared detector.

[0010] Optionally, the rectangular substructures can be arranged in either a zigzag or matrix pattern.

[0011] The Z-shaped arrangement of the target microstructure enables differentiated responses to incident light of any polarization state (including linear and circular polarization), thus achieving full Stokes polarization detection capability. Furthermore, for the aforementioned photoelectric response characteristic and response speed characteristic tests, the matrix-arranged target microstructure can efficiently excite surface phonon polaritons, achieving strong localization of the light field, thereby significantly improving the detector's absorptivity and responsivity.

[0012] Secondly, this application provides a method for fabricating an infrared detector, which includes: providing a long-wave infrared detection layer; wherein the material of the long-wave infrared detection layer is mercury cadmium telluride; forming a target microstructure on a first side of the long-wave infrared detection layer; wherein the target microstructure includes at least two periodically arranged rectangular substructures; the target microstructure is used to couple with target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer to enhance the photoelectric coupling capability of the long-wave infrared detection layer.

[0013] By providing a long-wave infrared detection layer made of mercury cadmium telluride, the detector's absorption capability in the long-wave infrared band is ensured. Furthermore, by forming a target microstructure containing periodically arranged rectangular substructures on the first side of the long-wave infrared detection layer, and utilizing this microstructure to couple with the target incident light to excite surface phonon polaritons, a high degree of localization of the incident light energy is achieved, effectively enhancing the photoelectric coupling capability of the long-wave infrared detection layer. Through the above fabrication method, high-performance detection materials and artificial microstructures are organically combined, significantly improving the performance of the fabricated infrared detector in terms of responsivity, absorptivity, and polarization detection capability.

[0014] Optionally, a target microstructure is formed on the first side of the long-wave infrared detection layer, including: depositing a silicon carbide thin film on the first side of the long-wave infrared detection layer; and patterning the silicon carbide thin film to form the target microstructure. By depositing a silicon carbide thin film on the first side of the long-wave infrared detection layer using plasma-enhanced chemical vapor deposition (PECVD), a uniform and tightly bonded microstructure base material is formed, providing reliable material support for the fabrication of the target microstructure. Subsequently, by patterning the silicon carbide thin film, a rectangular substructure with a specific arrangement and geometry is constructed, completing the precise fabrication of the target microstructure and laying the structural foundation for enhancing the photoelectric coupling capability of the long-wave infrared detection layer.

[0015] Optionally, the silicon carbide thin film is patterned to form the target microstructure, including: forming a photoresist pattern on the silicon carbide thin film; wherein the photoresist pattern is a Z-shaped pattern or a rectangular pattern; and transferring the photoresist pattern onto the silicon carbide thin film by an etching process to form the target microstructure.

[0016] By fabricating Z-shaped or rectangular photoresist patterns on silicon carbide thin films, precise pattern templates are provided for two arrangement modes of the target microstructure. Subsequently, the photoresist patterns are transferred to the silicon carbide thin film using a reactive ion etching process, thereby accurately obtaining the target microstructure with excellent optical properties.

[0017] Optionally, a long-wave infrared detection layer is provided, comprising: providing a substrate; growing a mercury cadmium telluride (HCDT) material layer on a second side of the substrate; forming an active region within the HCDT material layer; wherein the active region includes a PN junction; forming a metal contact structure on the second side of the long-wave infrared detection layer; wherein the metal contact structure is electrically connected to the PN junction; and removing the substrate to form the long-wave infrared detection layer.

[0018] Providing a substrate laid the structural foundation for subsequent epitaxial growth, and growing a mercury cadmium telluride (HCDT) material layer on the second side of the substrate laid the material foundation for photoelectric conversion. Then, ion implantation and annealing processes were used to form the active region, and a metal contact structure was formed on the second side, establishing a low-impedance signal extraction channel and achieving effective collection of photocurrent. Finally, by removing the substrate, the absorption and blocking of long-wavelength infrared light by the substrate was eliminated, providing conditions for the subsequent fabrication of target microstructures and light incidence.

[0019] Thirdly, this application also provides a photoelectric detection device comprising the aforementioned infrared detector.

[0020] Fourthly, this application also provides an infrared imaging system comprising the aforementioned infrared detector. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1a This is a schematic diagram of the structure of an infrared detector according to an embodiment of this application; Figure 1b This is a graph showing the test results of the detection performance according to an embodiment of this application; Figure 1c This is a graph showing the test results of the detection performance provided according to yet another embodiment of this application; Figure 1d This is a graph showing the test results of the detection performance according to another embodiment of this application; Figure 1e This is a graph showing the test results of the detection performance provided according to another embodiment of this application; Figure 1f This is a schematic diagram of a Z-shaped arrangement provided according to an embodiment of this application; Figure 1g This is a graph showing the performance test results generated by a zigzag arrangement according to an embodiment of this application; Figure 1h This is a schematic diagram of a matrix arrangement provided according to an embodiment of this application; Figure 2a This is a flowchart of a method for fabricating an infrared detector according to an embodiment of this application; Figure 2b This is a schematic diagram of the structure of a substrate after it has been formed according to an embodiment of this application; Figure 2c This is a schematic diagram of the structure after growing a layer of mercury cadmium telluride material according to an embodiment of this application; Figure 2d This is a schematic diagram of the structure after forming the active region according to an embodiment of this application; Figure 2e This is a schematic diagram of the structure after forming a metal contact structure according to an embodiment of this application; Figure 3a This is a flowchart of a method for forming a target microstructure according to an embodiment of this application; Figure 3b This is a schematic diagram of the structure after depositing a silicon carbide thin film according to an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0025] Taking long-wave infrared detectors as an example, in order to maintain high absorption performance and high responsivity in the long-wave infrared band, the thickness of the infrared detection material must be increased. This will not only significantly increase the dark current related to the detector volume, but also increase the transit time of photogenerated carriers, thereby reducing the detection response speed.

[0026] It should be noted that, especially for narrow bandgap infrared detectors, the intrinsic carrier concentration increases significantly at room temperature, further exacerbating the dark current problem. This means that such narrow bandgap long-wave infrared detectors must operate in low-temperature environments and have poor response speeds. As a result, the overall performance of long-wave infrared detectors is severely limited. Therefore, there is a need for an infrared detector that can comprehensively improve detection performance.

[0027] Based on this, this application provides an infrared detector, please refer to... Figure 1a ,like Figure 1a As shown, the infrared detector includes a long-wave infrared detection layer 110 and a target microstructure 120.

[0028] The long-wave infrared detection layer 110 can refer to a semiconductor layer used to receive and convert long-wave infrared optical signals into electrical signals. Specifically, the material of the long-wave infrared detection layer can be a material with a high long-wave infrared light absorption coefficient, narrow bandgap characteristics, and excellent photoelectric conversion efficiency. Such materials can achieve efficient photogenerated carrier excitation. For example, materials such as mercury cadmium telluride, indium antimonide, and lead tin telluride can be selected. Preferably, mercury cadmium telluride is selected as the material because it has high response sensitivity in the long-wave infrared band and its process compatibility is relatively mature.

[0029] Furthermore, a target microstructure 120 is formed on the first side of the long-wave infrared detection layer 110.

[0030] The first side can refer to the surface of the long-wave infrared detection layer that receives incident light.

[0031] It should be noted that the light incident surface of an infrared detector may vary depending on the application scenario and the target being detected. For example, for a PIN-type mercury cadmium telluride detector, the main detection requirement is to achieve a high-sensitivity response to weak infrared signals. Therefore, to reduce the obstruction of light by the front metal electrode and optimize the optical path, a back-illuminated structure can be adopted to allow light to enter from the back of the device. During operation, the target incident light enters from this back side to pass through the thin detector layer and is absorbed in the active region (PN junction region). In this example, the first side can refer to the back side of the long-wave infrared detector layer 110, i.e., the light-receiving surface.

[0032] In order to enhance the aforementioned photoelectric properties, a target microstructure 120 is also constructed on the surface of the long-wave infrared detection layer 110.

[0033] The target microstructure 120 can refer to an artificial micro / nano structure layer deposited on the first side surface of the long-wave infrared detection layer 110, which is composed of multiple basic substructures arranged in a specific manner. It can couple with infrared light of a specific wavelength band and change the distribution of light on its surface.

[0034] Specifically, the target microstructure can be coupled with the target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer, so as to enhance the optoelectronic coupling capability of the long-wave infrared detection layer.

[0035] The target incident light can refer to the optical signal in the long-wave infrared band to be detected. Taking a long-wave infrared detector as an example, the target incident light can be infrared radiation with a wavelength range of 10μm to 12μm.

[0036] Understandably, when incident light irradiates the surface of the target microstructure, its photon energy interacts with the lattice vibration modes of the silicon carbide microstructure, exciting the formation of surface phonon polaritons. Once excited, the energy of these surface phonon polaritons no longer exists as freely propagating light waves, but is highly confined and concentrated in the nanoscale interface region between the target microstructure 120 and the long-wave infrared detector layer 110, i.e., the energy is localized at the boundary. Finally, because the energy is highly localized on the surface of the detector layer, it is equivalent to forming a locally enhanced photoelectric field in the region where photogenerated carriers are generated inside the detector material. This allows the detector material to absorb photon energy more fully and generate more photogenerated carriers, thereby achieving the technical effect of enhanced photoelectric coupling capability.

[0037] Furthermore, since the optical function of the target microstructure needs to match the multi-dimensional performance verification requirements of the infrared detector, the infrared detector needs to undergo multi-dimensional verification such as spectral response test, polarization characteristic test and time domain response test before it is officially used, in order to evaluate the various indicators of the detector.

[0038] Among them, the photoelectric response characteristic test refers to the test method for testing the current response capability of the detector to long-wave infrared light, which can verify the photoelectric conversion efficiency and responsivity of the detector. The test procedure is to use infrared light generated by a quantum cascade laser to be incident on detectors with and without target microstructures, collect the current signals formed by photogenerated carriers, and compare the current characteristics of the two structures.

[0039] Spectral polarization characteristic testing refers to a test method for evaluating a detector's response to infrared light with different spectra and polarization states. This method can verify the detector's spectral resolution and polarization extinction ratio. The test procedure involves using infrared light generated by a quantum cascade laser, which is incident on the detector through a polarization optical system. The photogenerated carrier current signal carrying spectral and polarization information is collected, and the detector's spectral and polarization current characteristics are calculated.

[0040] Response speed characteristic testing refers to a test method for evaluating the time-domain current response capability of a detector to infrared light pulses, which can verify the photoelectric conversion response speed of the detector. The test procedure involves using a femtosecond laser to emit a laser pulse, which is then passed through a nonlinear crystal to generate a long-wavelength infrared laser pulse. This pulse is incident on the detector, and the current signal of the photogenerated carriers is collected. The time-domain characteristics of the current are then analyzed using an oscilloscope.

[0041] Based on the above, silicon carbide is preferably the material of the target microstructure. As a polar crystal, silicon carbide has a unique characteristic in the long-wave infrared band: the real part of its dielectric constant is negative. This allows it to naturally support the propagation of surface phonon polaritons, and it also has lower optical loss and higher thermal stability compared to metallic materials.

[0042] For example, Figure 1b The figure shows the absorptivity of long-wave infrared (WIR) detectors in the 10–12 μm range for three structures: a pentagonal WIR detector without microstructures, a square WIR detector based on a gold microstructure, and a circular WIR detector based on a silicon carbide microstructure. The horizontal axis represents the center wavelength of the incident light, and the vertical axis represents the absorptivity of the WIR detector. As can be seen from the figure, at a center wavelength of 11 μm, the absorptivity of the silicon carbide microstructure-based WIR detector is 0.7, significantly higher than the absorptivity of the other two structures.

[0043] Furthermore, Figure 1c The figure also shows the responsivity of the three materials in the long-wave infrared range of 10–12 μm. The horizontal axis represents the center wavelength of the incident light, and the vertical axis represents the photoelectric responsivity of the long-wave infrared detection material. As can be seen from the figure, when the center wavelength of the incident light is 11 μm, the responsivity of the long-wave infrared detection material based on the silicon carbide microstructure is 1.9 A / W, which is much greater than the responsivity of the other two structures.

[0044] also, Figure 1d The figure shows the photocurrent time-domain characteristics of the target microstructure using silicon carbide as the long-wave infrared detection material at a center wavelength of 11 μm and an incident light power of 1 μW. The curves in the figure show that after receiving a light pulse, the response time of the infrared detector based on the silicon carbide microstructure is only 0.0125 ns, which has extremely high photoelectric response performance.

[0045] Therefore, using silicon carbide as the material for the target microstructure can effectively suppress the absorption competition between the microstructure and the detection material, allowing more light energy to be localized and coupled into the long-wave infrared detection layer, thereby improving the photoelectric conversion efficiency.

[0046] Furthermore, the target microstructure 120 includes at least two rectangular substructures 121. These rectangular substructures can refer to the basic rectangular units constituting the target microstructure, and their shape can be cuboid, collectively forming a target microstructure layer with a specific function on a macroscopic level.

[0047] Understandably, for spectral polarization characteristic testing, the dimensional parameters of each rectangular substructure (including thickness, length, width, and arrangement period) are key design variables determining its resonant coupling with light of a specific wavelength and polarization state. By optimizing these parameters, the target microstructure can selectively respond to target incident light of different wavelengths and polarization directions, thereby precisely improving the detector's detection quality.

[0048] Specifically, the thickness of the rectangular substructure is one of the core parameters affecting the resonance wavelength of surface phonon polaritons. Figure 1eThe graph shows the functional relationship between the resonance wavelength λ of surface phonon polaritons, the peak absorptivity of mercury cadmium telluride (HCDT), and the thickness of the rectangular substructure. The horizontal axis represents the thickness h of the rectangular substructure; the right vertical axis represents the resonance wavelength λ of the surface phonon polaritons, i.e., the incident light wavelength corresponding to the peak absorptivity; the left vertical axis represents the peak absorptivity of HCDT, representing the maximum light absorption of the long-wave infrared detector layer at the resonance wavelength for the corresponding thickness. The circular curves in the graph illustrate the variation of the resonance wavelength with the thickness of the rectangular substructure, while the square curves illustrate the variation of the peak absorptivity with the thickness of the rectangular substructure.

[0049] As shown in the figure, with the increase of the thickness of the rectangular substructure, the resonance wavelength of the surface phonon polaritons redshifts (moves towards longer wavelengths), and the absorption rate of mercury cadmium telluride at this resonance wavelength also changes accordingly. This means that by precisely controlling the thickness of the rectangular substructure, the peak response wavelength of the infrared detector can be continuously adjusted, enabling it to be optimized for target incident light signals of different wavelengths.

[0050] In addition to thickness, the aspect ratio of the rectangular substructure is also one of the core design parameters for controlling polarization response characteristics.

[0051] It should be noted that the relative position of the polarization direction of the incident target light to the major and minor axes of the rectangular substructure directly affects the excitation efficiency of surface phonon polaritons. Specifically, when the polarization direction of the incident target light is parallel to the minor axis of the rectangular substructure, the excited surface phonon polaritons are strongest, and the photoelectric response of the detector is strongest. Conversely, when the polarization direction is parallel to the major axis of the rectangular substructure, the excited surface phonon polaritons are weakest, and the photoelectric response of the detector is smallest.

[0052] Based on the aforementioned polarization-dependent excitation characteristics, high extinction ratio linear polarization detection can be achieved by precisely controlling the aspect ratio of the rectangular substructure. For example, when the target microstructure is used to achieve linear polarization detection, the design parameters of the rectangular substructure can be: length 11 μm, width 2.5 μm, thickness 1.6 μm, and period 2.8 μm. Here, the period refers to the spacing between the repeated rectangular substructures in the plane, that is, the distance between corresponding positions (e.g., centroids) of two adjacent identical substructures. Under this parameter design, surface phonon polaritons exhibit the strongest resonant response at a wavelength of 11 μm, and the polarization extinction ratio measured at wavelength λ = 11 μm can reach 10. 3 above.

[0053] Furthermore, to achieve full Stokes polarization detection, in addition to the two core parameters of thickness and aspect ratio, the detection quality can also be controlled by adjusting the overlap length of two adjacent rectangular substructures. For example, when the target microstructure is used to achieve full Stokes polarization detection, the basic design parameters of the rectangular substructure can be: length 8 μm, width 2.5 μm, thickness 1.6 μm, and period 5.6 μm. Under these basic parameters, two adjacent rectangular substructures can be brought closer together, so that the overlap area along their long axis reaches 5 μm, thus forming a Z-shaped structure to effectively improve the performance of full Stokes polarization detection.

[0054] Based on the aforementioned principles of rectangular substructure size design and combination, multiple rectangular substructures can be arranged according to specific rules to form the target microstructure. Optionally, the arrangement of the rectangular substructures can be either a zigzag arrangement or a matrix arrangement.

[0055] The Z-shaped arrangement refers to a specific arrangement of two or more rectangular substructures, such as close together, partially overlapping, or turning, forming a composite structural unit resembling the letter Z. For example, taking the first side of the long-wave infrared detection layer facing upwards, please refer to... Figure 1f The two rectangular substructures are not neatly aligned in an array, but rather have overlapping areas along their long axis, intersecting each other to form a Z-shape.

[0056] Specifically, to adapt to different target incident light wavelengths, the overlapping region length and arrangement period of the rectangular substructures can be specifically designed. For example, taking the realization of full Stokes polarization detection near the center wavelength of 11 μm as an example, the length of a single rectangular substructure can be set to 8 μm, the width to 2.5 μm, and the thickness to 1.6 μm. Then, two rectangular substructures are brought close together along their length and partially overlapped, with the overlapping region set to a length of 5 μm, thereby constructing a composite unit exhibiting a staggered arrangement. Finally, this composite basic unit is repeatedly arranged on a two-dimensional plane according to a preset arrangement period (e.g., 5.6 μm) to form a complete target microstructure.

[0057] Furthermore, taking a target microstructure arranged in a Z-shape with an overlap of 5 μm along its length as an example, Figure 1gThis figure shows the photocurrent response of the long-wave infrared detector layer based on the Z-shaped target microstructure, under target incident light with a center wavelength of 11 μm, corresponding to different polarization angles. The horizontal axis represents the polarization angle of the target incident light, ranging from 0° to 180°; the vertical axis represents the photocurrent intensity output by the infrared detector. As shown in the figure, the photocurrent exhibits a regular periodic variation trend with the polarization angle. Specifically, when the polarization direction is parallel to the short axis of the rectangular substructure (i.e., the polarization angle is 90°), surface phonon polaritons are strongly excited, and the photocurrent intensity reaches its peak value of approximately 5.5 μA. When the polarization direction is parallel to the long axis of the rectangular substructure (i.e., polarization angles of 0° and 180°), surface phonon polaritons are weakly excited, and the photocurrent drops to a trough, close to 0 μA.

[0058] Subsequently, calculations based on the peak-to-valley ratio revealed that the structure exhibits a polarization extinction ratio as high as 2.7 × 10³ at a center wavelength of 11 μm. This result demonstrates that the Z-shaped target microstructure can produce significantly differentiated photoelectric responses to incident light with different polarization states, effectively resolving the complex polarization information contained in optical signals with different polarization states, and greatly enhancing the full Stokes polarization detection capability of infrared detectors.

[0059] Matrix arrangement can refer to a periodic arrangement of rectangular substructures according to a regular two-dimensional grid, such as a matrix where rows and columns are aligned. For example, taking the first side of the long-wave infrared detection layer facing upwards, please refer to... Figure 1h Multiple rectangular substructures are arranged at equal intervals in the row and column directions to form a regular two-dimensional periodic array structure.

[0060] Similarly, to adapt to different target incident light wavelengths and polarization detection requirements, the size and arrangement period of the rectangular substructures can be specifically designed. For example, to achieve linear polarization detection and hyperspectral response near a center wavelength of 11 μm, the length of a single rectangular substructure can be set to 11 μm, the width to 2.5 μm, and the thickness to 1.6 μm. Multiple rectangular substructures are then arranged equidistantly along the row and column directions at a preset spacing (e.g., 2.8 μm) to form a regularly aligned two-dimensional periodic basic unit. Finally, this basic unit is repeatedly expanded on a two-dimensional plane to form a complete target microstructure capable of efficient coupling with 10–12 μm long-wave infrared light.

[0061] The Z-shaped arrangement of the target microstructure enables differentiated responses to incident light of any polarization state (including linear and circular polarization), thus achieving full Stokes polarization detection capability. Furthermore, for the aforementioned photoelectric response characteristic and response speed characteristic tests, the matrix-arranged target microstructure can efficiently excite surface phonon polaritons, achieving strong localization of the light field, thereby significantly improving the detector's absorptivity and responsivity.

[0062] In the above embodiments, a long-wave infrared detector layer is prepared using mercury cadmium telluride (MCH). This material's excellent intrinsic photoelectric conversion characteristics in the long-wave infrared band enable efficient absorption of long-wave infrared light and effective excitation of photogenerated carriers, providing the basis for signal generation in the infrared detector's photoelectric conversion. By forming a target microstructure containing at least two rectangular substructures on the first side of the long-wave infrared detector layer, the physical mechanism of exciting surface phonon polaritons using silicon carbide is utilized to efficiently localize the incident light energy at the interface, effectively suppressing absorption competition between the microstructure and the detector layer, and enhancing the photoelectric coupling capability of the detector layer. Finally, through heterogeneous integration of the long-wave infrared detector layer and the target microstructure, the responsivity, absorptivity, and polarization detection capability of the infrared detector are significantly improved, achieving high-performance long-wave infrared detection.

[0063] In some implementation methods, please continue to refer to Figure 1a The infrared detector also includes an active region, a passivation layer 210, and a metal contact structure 220.

[0064] The active region can refer to a semiconductor region with photoelectric conversion function, located within the long-wave infrared detection layer, which can separate electrons and holes after absorbing incident light from the target to form a photocurrent.

[0065] Specifically, the active region includes a PN junction, which can be a junction formed by the contact between a P-type semiconductor region and an N-type semiconductor region at the interface. Further, to optimize photoelectric conversion efficiency and reduce dark current, the PN junction can be a planar PIN junction. That is, an undoped intrinsic semiconductor layer (i.e., the I-layer) is inserted between the P-type and N-type semiconductor regions, forming a three-layer PIN structure. The intrinsic semiconductor layer can serve as the primary region for light absorption and photogenerated carrier generation, effectively extending the carrier diffusion distance and reducing recombination losses.

[0066] For example, a planar PIN junction can be formed by sequentially arranging a P-type doped region, an intrinsic region (I layer), and an N-type doped region within the long-wave infrared detection layer, with the intrinsic region sandwiched between the P-type and N-type regions. This structure expands the depletion layer width, not only enhancing the absorption volume for long-wave infrared light but also establishing a stronger built-in electric field, thereby enabling faster separation and directional transport of photogenerated carriers.

[0067] Furthermore, a passivation layer 210 is also provided on the second side of the long-wave infrared detection layer. This passivation layer can refer to a functional layer that provides protection, capable of protecting the material surface and reducing interface states.

[0068] The second side can refer to the other side of the long-wave infrared detection layer, that is, the second side and the first side are the two opposite sides of the long-wave infrared detection layer.

[0069] It should be noted that in order to effectively export the weak photoelectric signal generated at the PN junction to an external circuit for reading and processing, a conductive medium must be introduced to establish an electrical connection with the PN junction. Therefore, a metal contact structure is required, and it needs to be electrically connected to the PN junction to achieve the collection and export of photogenerated carriers.

[0070] Among them, the metal contact structure 220 can refer to a metal layer or metal electrode used to form an electrical connection with an external circuit, and its material can be conductive materials such as gold, aluminum or titanium.

[0071] Furthermore, this metal contact structure can also be located on the second side of the long-wave infrared detection layer, deposited on the surface of the long-wave infrared detection layer and penetrating the passivation layer.

[0072] For example, taking a back-illuminated PIN-type mercury cadmium telluride detector as an example, since the target incident light is incident from the first side (back side) which is the light-receiving surface, in order to avoid the metal electrode blocking the light path and reduce the loss of light before reaching the active area, the metal electrode used to collect the electrical signal is usually placed opposite the light incident direction, that is, the non-light-receiving surface (front side) can be used as the second side.

[0073] In the above embodiments, an active region containing a PN junction is constructed within the long-wave infrared detection layer, providing a physical basis for photoelectric detection. A passivation layer effectively protects the detection material layer from corrosion, ensuring the stability of the overall structure. Furthermore, a metal contact structure electrically connected to the PN junction enables efficient collection and output of photocurrent. Ultimately, through the synergistic cooperation of the long-wave infrared detection layer, target microstructure, active region, passivation layer, and metal contact structure, the infrared detector can not only efficiently generate photogenerated carriers but also rapidly and completely convert the enhanced optical signal into a measurable electrical signal, thereby comprehensively improving the response performance and usability of the infrared detector.

[0074] This application also provides a method for fabricating an infrared detector, used to fabricate the aforementioned infrared detector, such as... Figure 2a As shown, the method includes the following steps: S210 provides a long-wave infrared detection layer.

[0075] Optionally, since mercury cadmium telluride has high response sensitivity in the long-wave infrared band and its process compatibility is relatively mature, the material of the long-wave infrared detection layer can be mercury cadmium telluride.

[0076] Specifically, providing a long-wave infrared detection layer may include: first providing a substrate; then growing a mercury cadmium telluride material layer on a second side of the substrate; next forming an active region within the mercury cadmium telluride material layer; then forming a metal contact structure on the second side of the long-wave infrared detection layer; and finally removing the substrate to form the long-wave infrared detection layer.

[0077] The substrate can refer to the base structure used to support and carry the epitaxial growth material, and its material can be sapphire, silicon or gallium arsenide, etc.

[0078] For example, a pre-treated sapphire substrate can be directly selected as the substrate. After polishing and cleaning, its surface is smooth and free of impurities, enabling it to form a good epitaxial relationship with the subsequently grown mercury cadmium telluride material and ensuring crystal quality. For example, Figure 2b The substrate 301 is used for construction.

[0079] Furthermore, after providing the substrate, a buffer layer can be grown on the second side surface (e.g., the front side) of the sapphire substrate using metal-organic vapor deposition (MOV). This buffer layer effectively mitigates lattice mismatch and differences in thermal expansion coefficients between the substrate and subsequent material layers. For example, if the subsequent material layer is a mercury cadmium telluride (HgCdTe) material layer, the buffer layer can be a cadmium telluride (CdTe) layer.

[0080] Subsequently, mercury cadmium telluride (MCH) can be grown on the buffer layer using molecular beam epitaxy (MBE) to construct the basic absorption layer. This layer can then be doped according to process requirements to form a MCH material layer with a specific conductivity type. For example, to form P-type doping, mercury vacancies can be introduced by adjusting the growth conditions to achieve acceptor doping, thus forming a P-type MCH material layer. It should be noted that N-type doping or other types of doping can also be performed depending on the detector design requirements. For example, using P-type MCH as an example... Figure 2c As shown, a buffer layer 303 and a P-type mercury cadmium telluride material layer 305 are grown on the substrate.

[0081] An active region can then be formed within the mercury cadmium telluride material layer.

[0082] The active region includes the PN junction.

[0083] For example, taking P-type mercury cadmium telluride (MCH) with a planar PIN junction, a positive photoresist is first spin-coated onto the surface of the MCH material layer. Photolithography is then used to define the region window for subsequent N-type doping, i.e., the N-region window. Subsequently, using the photoresist as a mask, light ions (e.g., boron ions) are implanted into the P-type MCH material layer through the N-region window using an ion implantation process. This changes the conductivity type of the local area, forming an N-type doped region. After implantation, residual photoresist is removed, and a high-temperature annealing process is performed. The annealing process activates the implanted impurity ions and repairs the lattice damage caused during implantation, while simultaneously allowing the P-type region, N-type region, and the intrinsic region naturally formed between them to collectively constitute the planar PIN junction region. For example, taking P-type MCH as an example, as... Figure 2dAs shown, the active region after forming the PIN junction region includes P-type mercury cadmium telluride 305, N-type mercury cadmium telluride 307, and I-type mercury cadmium telluride 309 located between the two.

[0084] After the active region is formed, in order to guide the photogenerated carriers generated inside to the external circuit, a metal electrode needs to be fabricated on the device surface. Therefore, a metal contact structure can be formed on the second side of the long-wave infrared detection layer.

[0085] The metal contact structure can be electrically connected to the PN junction, forming ohmic contacts with the P-type and N-type regions respectively, thereby achieving effective collection of photogenerated carriers.

[0086] Specifically, firstly, a passivation layer can be grown on the surface of the mercury cadmium telluride (CdTe) material layer forming the active region using metal-organic vapor deposition (MOCVD). This passivation layer can also be made of cadmium telluride (CdTe) to protect the device surface. Subsequently, a positive photoresist is spin-coated onto the second side surface of the long-wave infrared detection layer. Photolithography is used to expose and develop the photoresist, defining the positions of the metal contact structures on its surface. Next, the CdTe passivation layer at the corresponding positions is removed using wet or dry etching methods, exposing the underlying P-type and N-type regions. Finally, electron beam evaporation is used to deposit multiple metal films (e.g., chromium / gold or titanium / platinum / gold) within the etched window and on part of the passivation layer surface. Ultimately, a separate metal electrode is formed through a lift-off or etching process, serving as the metal contact structure. For example, as shown... Figure 2e As shown, a metal contact structure 220 is formed on the passivation layer 210, and the metal contact structure 220 penetrates the passivation layer 210 to be electrically connected to the underlying active regions (P-type mercury cadmium telluride and N-type mercury cadmium telluride).

[0087] Finally, the substrate can be removed to form a long-wave infrared detection layer.

[0088] Specifically, the entire device with the completed metal contact structure can be fixed in place, and then the substrate can be thinned using a mechanical polishing process to remove most of the sapphire substrate material. Subsequently, a chemical polishing process is used to further remove the remaining substrate material and buffer layer until the first side (i.e., the back side) of the mercury cadmium telluride (HCDT) material layer is exposed. At this point, the substrate and buffer layer are completely removed, leaving the HCDT material layer and the active region formed within it, the passivation layer on the surface, and the metal contact structure, which together constitute the long-wave infrared detection layer.

[0089] Providing a substrate laid the structural foundation for subsequent epitaxial growth, and growing a mercury cadmium telluride (HCDT) material layer on the second side of the substrate laid the material foundation for photoelectric conversion. Then, ion implantation and annealing processes were used to form the active region, and a metal contact structure was formed on the second side, establishing a low-impedance signal extraction channel and achieving effective collection of photocurrent. Finally, by removing the substrate, the absorption and blocking of long-wavelength infrared light by the substrate was eliminated, providing conditions for the subsequent fabrication of target microstructures and light incidence.

[0090] S220, Forming target microstructures on the first side of the long-wave infrared detection layer.

[0091] The target microstructure comprises at least two periodically arranged rectangular substructures. These rectangular substructures can refer to the basic rectangular units constituting the target microstructure, and their shape can be cuboid, collectively forming a target microstructure layer with a specific function on a macroscopic scale.

[0092] Furthermore, the target microstructure can be used to couple with the target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer, thus enhancing the optoelectronic coupling capability of the long-wave infrared detection layer.

[0093] Specifically, the target microstructure can be formed on the first side of the long-wave infrared detector layer through deposition and patterning processes. First, a silicon carbide thin film is deposited on the exposed surface of the first side of the long-wave infrared detector layer. Then, the silicon carbide thin film is patterned, for example, through photolithography and etching processes, to form a target microstructure with periodically arranged rectangular substructures, thereby ultimately constructing a complete infrared detector.

[0094] In the above embodiments, by providing a long-wave infrared detection layer made of mercury cadmium telluride, the detector's absorption capability in the long-wave infrared band is ensured. Furthermore, by forming a target microstructure containing periodically arranged rectangular substructures on the first side of the long-wave infrared detection layer, and utilizing this microstructure to couple with the target incident light to excite surface phonon polaritons, a high degree of localization of the incident light energy is achieved, effectively enhancing the photoelectric coupling capability of the long-wave infrared detection layer. Through the above fabrication method, high-performance detection materials and artificial microstructures are organically combined, significantly improving the performance of the fabricated infrared detector in terms of responsivity, absorptivity, and polarization detection capability.

[0095] In some implementation methods, please refer to the appendix. Figure 3a A target microstructure is formed on the first side of the long-wave infrared detection layer, including: S310. A silicon carbide thin film is deposited on the first side of the long-wave infrared detection layer.

[0096] Specifically, the long-wave infrared detection layer, after being processed by substrate removal to expose the first side (i.e., the back side), can be placed into a reaction chamber. Using plasma-enhanced chemical vapor deposition (PECVD) technology, silicon-containing gas (such as silane) and carbon-containing gas (such as methane) are introduced into the chamber. Under the excitation of radio frequency power, plasma is generated, causing the reaction gas to undergo a chemical reaction and deposit on the first side surface of the long-wave infrared detection layer, thereby forming a dense and uniformly thick silicon carbide thin film.

[0097] During the deposition process, the thickness of the silicon carbide film can be controlled within a target range (e.g., 1.6 μm) by adjusting parameters such as deposition time, gas flow rate, and radio frequency power to meet the optical requirements for subsequent excitation of surface phonon polaritons. For example, as... Figure 3b As shown, a silicon carbide thin film 311 is uniformly deposited on the first side (back side) of the long-wave infrared detection layer.

[0098] S320: Pattern the silicon carbide thin film to form the target microstructure.

[0099] Specifically, the silicon carbide thin film is patterned to form the target microstructure, including: firstly forming a photoresist pattern on the silicon carbide thin film; then transferring the photoresist pattern onto the silicon carbide thin film through an etching process, thereby forming the target microstructure.

[0100] The photoresist pattern can be either a Z-shaped pattern or a rectangular pattern. A Z-shaped pattern can refer to a periodic composite pattern formed by multiple rectangular units arranged in an alternating Z-shape. A rectangular pattern can refer to a two-dimensional periodic array pattern formed by multiple independent rectangular blocks aligned according to row and column rules. It should be noted that when a certain photoresist pattern is selected as the etching mask, the etched silicon carbide film will replicate the topology of that pattern to form the target microstructure arranged in a Z-shape or matrix.

[0101] Specifically, a negative photoresist is first spin-coated onto the deposited silicon carbide thin film, and then selectively exposed using a mask with a zigzag or rectangular pattern. After exposure, development is performed, and using the remaining photoresist as an etching mask, reactive ion etching (RIE) is employed. High-energy ions bombard the unprotected silicon carbide areas, removing them and precisely transferring the two-dimensional pattern from the photoresist onto the underlying silicon carbide thin film. After etching, the remaining photoresist is removed, resulting in a specifically patterned periodic silicon carbide microstructure, i.e., the target microstructure, on the first side of the long-wave infrared detection layer.

[0102] Understandably, taking a rectangular pattern as an example of a photoresist pattern, Figure 1aThe infrared detector shown contains a target microstructure consisting of multiple rectangular substructures arranged in a matrix on the first side of the long-wave infrared detection layer.

[0103] By fabricating Z-shaped or rectangular photoresist patterns on silicon carbide thin films, precise pattern templates are provided for two arrangement modes of the target microstructure. Subsequently, the photoresist patterns are transferred to the silicon carbide thin film using a reactive ion etching process, thereby accurately obtaining the target microstructure with excellent optical properties.

[0104] In the above embodiments, a silicon carbide thin film was deposited on the first side of the long-wave infrared detection layer using plasma-enhanced chemical vapor deposition (PECVD), forming a uniform and tightly bonded microstructure base material, providing reliable material support for the fabrication of the target microstructure. Subsequently, by patterning the silicon carbide thin film, rectangular substructures with specific arrangements and geometries were constructed, completing the precise fabrication of the target microstructure and laying the structural foundation for enhancing the photoelectric coupling capability of the long-wave infrared detection layer.

[0105] It should be understood that although the steps in the flowchart above are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowchart above may include multiple steps or stages, which are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0106] This application also provides a photoelectric detection device, which includes the infrared detector described above.

[0107] For specific limitations regarding a photoelectric detection device, please refer to the limitations for an infrared detector mentioned above, which will not be repeated here.

[0108] This application also provides an infrared imaging system that includes the infrared detector described above.

[0109] For specific limitations regarding an infrared imaging system, please refer to the limitations regarding an infrared detector mentioned above, which will not be repeated here.

[0110] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0111] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0112] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0113] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0114] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0115] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An infrared detector, characterized in that, include: Long-wave infrared detection layer; wherein, the material of the long-wave infrared detection layer is mercury cadmium telluride; A target microstructure is formed on the first side of the long-wave infrared detection layer; wherein the target microstructure includes at least two rectangular substructures; the target microstructure is coupled with the target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer to enhance the photoelectric coupling capability of the long-wave infrared detection layer; the rectangular substructures are arranged in a Z-shape; the Z-shape arrangement refers to bringing two rectangular substructures close to each other and partially overlapping them to construct a composite unit with a staggered arrangement; the composite unit is repeatedly arranged on a two-dimensional plane according to a preset arrangement period to form a complete target microstructure; the target microstructure is made of silicon carbide.

2. The infrared detector according to claim 1, characterized in that, The infrared detector also includes: An active region located within the long-wave infrared detection layer; wherein, the active region includes a PN junction; A passivation layer located on the second side of the long-wave infrared detection layer; wherein the second side and the first side are opposite sides of the long-wave infrared detection layer; A metal contact structure electrically connected to the PN junction.

3. A method for fabricating an infrared detector, characterized in that, The method for preparing the infrared detector of claim 1 includes: A long-wave infrared detection layer is provided; wherein the material of the long-wave infrared detection layer is mercury cadmium telluride; A target microstructure is formed on a first side of the long-wave infrared detection layer; wherein the target microstructure includes at least two rectangular substructures arranged periodically; the target microstructure is used to couple with the target incident light to excite surface phonon polaritons, thereby localizing the energy of the target incident light at the boundary between the target microstructure and the long-wave infrared detection layer to enhance the photoelectric coupling capability of the long-wave infrared detection layer.

4. The preparation method according to claim 3, characterized in that, The formation of the target microstructure on the first side of the long-wave infrared detection layer includes: A silicon carbide thin film is deposited on the first side of the long-wave infrared detection layer; The silicon carbide thin film is patterned to form the target microstructure.

5. The preparation method according to claim 4, characterized in that, The process of patterning the silicon carbide thin film to form the target microstructure includes: A photoresist pattern is formed on the silicon carbide thin film; wherein the photoresist pattern is a Z-shaped pattern; The photoresist pattern is transferred onto the silicon carbide thin film through an etching process, thereby forming the target microstructure.

6. The preparation method according to claim 3, characterized in that, The long-wave infrared detection layer includes: Provide substrate; A mercury cadmium telluride material layer is grown on the second side of the substrate; An active region is formed within the mercury cadmium telluride material layer; wherein, the active region includes a PN junction; A metal contact structure is formed on the second side of the long-wave infrared detection layer; wherein the metal contact structure is electrically connected to the PN junction; The substrate is removed to form the long-wave infrared detection layer.

7. A photoelectric detection device, characterized in that, It includes the infrared detector as described in claim 1.

8. An infrared imaging system, characterized in that, It includes the infrared detector as described in claim 1.

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