Infrared detector, method for manufacturing infrared detector, and infrared focal plane array

Abstract

This application provides an infrared detector, a method for fabricating the infrared detector, and an infrared focal plane array. The method includes: providing a substrate, one side of which has a buffer layer and a bottom electrode contact layer, the bottom electrode contact layer being located on the side of the buffer layer facing away from the substrate; forming an absorption layer on the side of the bottom electrode contact layer facing away from the substrate, and while the formation of the absorption layer is in a target stage, starting to form an interface transition layer on the side of the absorption layer facing away from the substrate, the target stage being a preset time period before the absorption layer growth is interrupted, the bottom electrode contact layer and the absorption layer having the same doping type; and sequentially forming a barrier layer and a top electrode contact layer on the side of the interface transition layer facing away from the substrate. This application solves the problem of low sensitivity of infrared detectors in high-temperature environments in the prior art.

Description

Technical Field

[0001] This application relates to the field of infrared photodetector manufacturing technology, and more specifically, to an infrared detector, a method for preparing the infrared detector, and an infrared focal plane array. Background Technology

[0002] Traditional high-performance infrared detectors typically operate at an extremely low temperature of 77K to suppress the high dark current generated by thermal excitation. However, at higher operating temperatures, the dark current caused by thermal noise increases dramatically, severely overwhelming weak signals and causing a significant decrease in detector sensitivity or even failure. To maintain high sensitivity, existing technologies often rely on bulky and extremely power-consuming mechanical cooling devices, which are difficult to meet the stringent size, weight, and power consumption constraints of miniaturized platforms such as power line inspection robots. Therefore, developing an infrared detector that does not require cryogenic cooling and still possesses low dark current and high sensitivity at high operating temperatures has become a pressing technical challenge.

[0003] The information disclosed above in the background section is only intended to enhance the understanding of the background art of the art described herein. Therefore, the background art may contain certain information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0004] The main objective of this application is to provide an infrared detector, a method for fabricating an infrared detector, and an infrared focal plane array to solve the problem of low sensitivity of infrared detectors in high-temperature environments in the prior art.

[0005] To achieve the above objectives, according to one aspect of this application, a method for fabricating an infrared detector is provided, comprising: providing a substrate having a buffer layer and a bottom electrode contact layer on one side of the substrate, the bottom electrode contact layer being located on the side of the buffer layer opposite to the substrate; forming an absorption layer on the side of the bottom electrode contact layer opposite to the substrate, and, when the formation of the absorption layer is in a target stage, starting to form an interface transition layer on the side of the absorption layer opposite to the substrate, the target stage being a preset time period before the growth of the absorption layer is interrupted, the bottom electrode contact layer and the absorption layer having the same doping type; and sequentially forming a barrier layer and a top electrode contact layer on the side of the interface transition layer opposite to the substrate.

[0006] Optionally, the steps of forming the substrate and the buffer layer include: providing a crystalline silicon substrate and performing in-situ deoxidation on the crystalline silicon substrate to obtain the substrate, wherein the temperature range of the in-situ deoxidation treatment is 560°C to 600°C; epitaxially growing the buffer layer on the substrate, wherein the temperature range of the epitaxial growth process is 450°C to 500°C, and the ratio of the gallium source molecular beam to the antimony source molecular beam is 2 to 4.

[0007] Optionally, the step of forming the bottom electrode contact layer includes: forming multiple first single-atom layers and multiple second single-atom layers on the buffer layer, and doping the multiple first single-atom layers and multiple second single-atom layers, wherein the multiple first single-atom layers and multiple second single-atom layers constitute the bottom electrode contact layer, the first single-atom layers and the second single-atom layers are alternately distributed, and the first single-atom layers and the second single-atom layers have the same doping type.

[0008] Optionally, the steps of forming multiple first single-atom layers and multiple second single-atom layers include: in an environment at a first temperature, alternately turning on a first molecular beam and a second molecular beam multiple times to alternately grow multiple first single-atom layers and multiple second single-atom layers on the buffer layer, wherein the first molecular beam includes an indium source molecular beam and an arsenic source molecular beam, the second molecular beam includes an antimony source molecular beam, the first single-atom layer includes InAs, the second single-atom layer includes InAsSb, and the first temperature ranges from 400°C to 460°C.

[0009] Optionally, the step of forming the absorption layer includes: in an environment at a first temperature, alternately turning on a third molecular beam and a fourth molecular beam to grow multiple layers of a third single-atom layer and multiple layers of a fourth single-atom layer on the side of the bottom electrode contact layer opposite to the substrate, wherein the multiple layers of the third single-atom layer and the multiple layers of the fourth single-atom layer constitute the absorption layer, the third single-atom layer and the fourth single-atom layer are alternately distributed, the third single-atom layer includes InAs, and the fourth single-atom layer includes InAs. 1-x Sb x The value of x ranges from 0.25 to 0.50. The third molecular bundle includes an indium source molecular bundle and an arsenic source molecular bundle. The fourth molecular bundle includes the indium source molecular bundle, the arsenic source molecular bundle, and the antimony source molecular bundle.

[0010] Optionally, the preparation method further includes: when the absorber layer is in the target stage, stopping the activation of the antimony source and indium source molecular beams required for growing the absorber layer, and continuing to activate the arsenic source molecular beam required for growing the absorber layer to grow a first interface transition layer on the absorber layer, wherein the preset time period is 1-5 seconds; activating the aluminum source molecular beam, the arsenic source molecular beam, and the antimony source molecular beam to grow the barrier layer on the first interface transition layer, wherein the barrier layer comprises AlAs y Sb 1-y The range of y is 0.07 to 0.09.

[0011] Optionally, the preparation method further includes: when the absorption layer is in the target stage, stopping the activation of the arsenic and indium source molecular beams required for growing the absorption layer, continuing to activate the antimony source molecular beam required for the absorption layer, and newly activating the aluminum source molecular beam to grow a second interface transition layer on the absorption layer, the preset time period being 1~5s; keeping the aluminum source molecular beam and the antimony source molecular beam activated, growing multiple layers of first barrier layers on the second interface transition layer, the first barrier layer including AlSb; stopping the activation of the aluminum source molecular beam and the antimony source molecular beam, activating the indium source molecular beam and the arsenic source molecular beam, growing multiple layers of second barrier layers on the first barrier layer, the multiple layers of the first barrier layer and the multiple layers of the second barrier layer constituting the barrier layer, the second barrier layer including InAs.

[0012] According to another aspect of this application, an infrared detector is provided, which is prepared by the method described above. The infrared detector includes: a substrate; a buffer layer, a bottom electrode contact layer, an absorption layer, an interface transition layer, a barrier layer, and a top electrode contact layer sequentially located on one side of the substrate, wherein the bottom electrode contact layer and the absorption layer have the same doping type.

[0013] Optionally, the absorber layer comprises InAs and InAs 1-x Sb x The value of x ranges from 0.25 to 0.50, and the barrier layer includes AlAs. y Sb 1-y Alternatively, the barrier layer comprises InAs and AlSb, with y ranging from 0.07 to 0.09.

[0014] According to another aspect of this application, an infrared focal plane array is provided, comprising a plurality of pixel units, each pixel unit containing the infrared detector described above.

[0015] Using the technical solution of this application, a substrate is provided, one side of which has a buffer layer and a bottom electrode contact layer, the bottom electrode contact layer being located on the side of the buffer layer away from the substrate; an absorption layer is formed on the side of the bottom electrode contact layer away from the substrate, and when the formation of the absorption layer is in a target stage, an interface transition layer is formed on the side of the absorption layer away from the substrate, the target stage being the last preset time period before the growth of the absorption layer is interrupted, the bottom electrode contact layer and the absorption layer having the same doping type; a barrier layer and a top electrode contact layer are sequentially formed on the side of the interface transition layer away from the substrate. In this process, when the absorption layer is in the target stage of formation, an interface transition layer is formed on the side of the absorption layer away from the substrate. This step can force the formation of the interface transition layer at the heterogeneous interface between the absorption layer and the barrier layer. The interface transition layer can compensate for the interface strain of the barrier layer and eliminate mismatch dislocations, ensuring that the detector has an extremely low dark current density at high temperatures. This low dark current characteristic at high temperatures can significantly reduce the background noise of the detector system, improve the signal-to-noise ratio and detection sensitivity, and enable it to accurately capture weak early hot spot signals in cable inspection, thereby solving the problem of low sensitivity of infrared detectors in high-temperature environments in the prior art. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0017] Figure 1 A schematic flowchart of a method for fabricating an infrared detector according to an embodiment of this application is shown;

[0018] Figure 2 This diagram illustrates a shutter timing sequence during barrier layer fabrication according to an embodiment of this application.

[0019] Figure 3 This illustrates a shutter timing diagram for another barrier layer fabrication method according to an embodiment of this application.

[0020] Figure 4 A schematic diagram of the structure of an infrared detector according to an embodiment of this application is shown.

[0021] The above figures include the following reference numerals:

[0022] 10. Substrate; 20. Buffer layer; 30. Bottom electrode contact layer; 40. Absorber layer; 50. Barrier layer; 60. Top electrode contact layer. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be an intermediate element present. Furthermore, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element via a third element.

[0027] As described in the background section, it is difficult to obtain infrared detectors with low dark current and high sensitivity at high operating temperatures in the prior art. In order to solve the problem of low sensitivity of infrared detectors in high-temperature environments, the embodiments of this application provide an infrared detector, a method for preparing the infrared detector, and an infrared focal plane array.

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0029] Figure 1 This is a flowchart of a method for fabricating an infrared detector according to an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0030] Step S1, a substrate is provided, one side of which has a buffer layer and a bottom electrode contact layer, the bottom electrode contact layer being located on the side of the buffer layer opposite to the substrate;

[0031] Specifically, the substrate can be a single-crystal GaSb substrate, and a buffer layer and a bottom electrode contact layer can be grown on the substrate by molecular beam epitaxy. The bottom electrode contact layer can be N-type or P-type.

[0032] Step S2: An absorption layer is formed on the side of the bottom electrode contact layer away from the substrate. When the formation of the absorption layer is in the target stage, an interface transition layer is formed on the side of the absorption layer away from the substrate. The target stage is the last preset time period before the growth of the absorption layer is interrupted. The bottom electrode contact layer and the absorption layer have the same doping type.

[0033] Specifically, the absorption layer can be formed by epitaxial growth, and the absorption layer is a gallium-free infrared absorption layer. The absorption layer can be InAs or InAs2. 1-x Sb x Alternatingly stacked type-II superlattice materials. The aforementioned interface transition layer is not a structural layer deposited independently after the absorption layer growth is complete. Instead, it is an atomically bonded layer formed in situ at the heterojunction during the final stage of absorption layer epitaxial growth by controlling the molecular beam epitaxy shutter timing. This results in seamless lattice continuity and chemical bonding between the interface transition layer and the absorption layer, effectively compensating for interfacial strain and eliminating mismatch dislocations, thereby significantly reducing the interfacial density of states. This is fundamentally different from traditional structures that result in numerous interfacial defects and performance degradation due to directly growing subsequent layers on the surface of a pre-prepared absorption layer.

[0034] Step S3: A barrier layer and a top electrode contact layer are sequentially formed on the side of the interface transition layer away from the substrate.

[0035] Specifically, the barrier layer can be an epitaxially grown wide-gap barrier layer, which can be made of gallium-free materials. The valence band level of the wide-gap barrier layer is aligned with the valence band level of the gallium-free absorber layer, and its conduction band level is significantly higher than that of the gallium-free absorber layer. This can be used to block majority carriers and suppress recombination dark current.

[0036] In this embodiment, when the absorption layer is in the target stage of formation, an interface transition layer is formed on the side of the absorption layer away from the substrate. The interface transition layer is formed during the formation of the absorption layer. This can force the formation of the interface transition layer at the heterogeneous interface between the absorption layer and the barrier layer. The interface transition layer can compensate for the interface strain of the barrier layer and eliminate mismatch dislocations, ensuring that the detector has an extremely low dark current density at high temperatures. This low dark current characteristic at high temperatures can significantly reduce the background noise of the detector system, improve the signal-to-noise ratio and detection sensitivity, and enable it to accurately capture weak early hot spot signals in cable inspection. This solves the problem of low sensitivity of infrared detectors in high-temperature environments in the prior art.

[0037] Secondly, the low dark current characteristic means that the detector no longer relies on bulky and high-power liquid nitrogen cooling or large-scale refrigerators, but can be perfectly adapted to miniature thermoelectric coolers or lightweight miniature refrigerators, thereby greatly reducing the size, weight and power consumption of infrared detectors.

[0038] In the specific implementation process, the step of forming the substrate and the buffer layer in step S1 above can be achieved through the following steps:

[0039] A crystalline silicon substrate is provided, and in-situ deoxidation is performed on the substrate to obtain the final substrate. The in-situ deoxidation temperature range is 560℃~600℃. The crystalline silicon substrate can be an N-type GaSb single crystal substrate. It can be placed in the growth chamber of a molecular beam epitaxy system, and the substrate heating program is started. Under the protection of a constant Sb (antimony) molecular beam current, the substrate temperature is controlled to rise to 560℃~600℃ for in-situ deoxidation. Real-time monitoring is performed using reflection high-energy electron diffraction (RHEED) until the reconstructed fringes on the surface of the crystalline silicon substrate are clear. The above temperatures can be 570℃, 580℃, 585℃, 590℃, or 595℃.

[0040] Subsequently, a buffer layer is epitaxially grown on the substrate. The epitaxial growth temperature range is 450℃~500℃, and the ratio of the Ga (gallium) source molecular beam to the antimony source molecular beam is 2~4. These temperatures can be 460℃, 470℃, 480℃, or 490℃. By opening the shutters of the Ga (gallium) and Sb (antimony) source molecular beams in the molecular beam epitaxy system and adjusting the Ga to Sb molecular beam current ratio between 2.0 and 4.0, a buffer layer (GaSb) homogeneous with the GaSb substrate can be epitaxially grown. Since molecular beam epitaxy is typically performed at high temperatures, a buffer layer homogeneous with the GaSb substrate can provide a high-quality crystalline surface that perfectly matches the substrate's lattice constant, effectively mitigating lattice mismatch stress caused by differences in thermal expansion coefficients or unsatisfactory initial deposition conditions.

[0041] The step of forming the bottom electrode contact layer in step S1 of this application can be achieved through the following steps:

[0042] Multiple first and second single-atom layers are formed on the buffer layer, and these layers are doped. The multiple first and second single-atom layers form the bottom electrode contact layer. The first and second single-atom layers are alternately distributed, and the doping types of the first and second single-atom layers are the same. During the growth of the first and second single-atom layers, a doping source (such as silicon or beryllium) can be introduced simultaneously to perform the same type of doping treatment on both layers. The carrier concentration can be increased to 1 × 10⁻⁶ by adjusting the doping source concentration or the furnace temperature. 18 ~5×10 18 cm -3 This forms an N-type (or P-type) superlattice contact layer with low resistivity and high conductivity, ensuring ohmic contact characteristics and carrier injection efficiency between it and the subsequent absorption layer. The doping type of the first and second single-atom layers can be either N-type or P-type.

[0043] The bottom electrode contact layer formed above has a periodic superlattice structure, wherein the first and second single-atom layers can be composed of different III-V group compounds. The alternating formation of multiple first single-atom layers and multiple layers of second single-atom layers is not limited to one layer of first single-atom layer superimposed with one layer of second single-atom layer; it can be multiple layers of first single-atom layers and multiple layers of second single-atom layers. For example, the number of first single-atom layers can be 15-35, and the number of second single-atom layers can be 5-12. For instance, the first layer of the bottom electrode contact layer may be 15 first single-atom layers, the second layer may be 5 second single-atom layers, the third layer may be 15 first single-atom layers, the fourth layer may be 5 second single-atom layers, and so on. The number of first single-atom layers and the number of second single-atom layers in different layers of the bottom electrode contact layer can be the same or different. The specific stacking method is not specifically limited in this application.

[0044] In some alternative embodiments, the steps of forming multiple first monolayers and multiple second monolayers include:

[0045] Under a first temperature environment, the first and second molecular beams are alternately activated multiple times to alternately grow multiple first and second single-atom layers on the buffer layer. The first molecular beam includes an indium source molecular beam and an arsenic source molecular beam, and the second molecular beam includes an antimony source molecular beam. The first single-atom layer includes InAs, and the second single-atom layer includes InAsSb. The first temperature ranges from 400°C to 460°C. The first and second molecular beams can be alternately activated by a programmable shutter to alternately grow InAs and InAsSb superlattice structure layers. The first temperature can be 410°C, 420°C, 430°C, 440°C, or 450°C. For example, the first layer of the bottom electrode contact layer is 15 layers of InAs, the second layer is 5 layers of InAsSb, the third layer is 15 layers of InAs, the fourth layer is 5 layers of InAsSb, and so on. This application can also ensure lattice matching between the contact layer and the substrate by setting the opening duration ratio of the shutter for each component.

[0046] In some embodiments, step S2 of forming the absorption layer includes:

[0047] Under a first temperature environment, the third and fourth molecular beams are alternately activated to grow multiple third and fourth single-atom layers on the side of the bottom electrode contact layer away from the substrate. These multiple third and fourth single-atom layers constitute the absorption layer, with the third and fourth single-atom layers alternating in distribution. The third and fourth single-atom layers include InAs, and the fourth single-atom layers also include InAs. 1-x Sbx, where x ranges from 0.25 to 0.50, the third molecular beam includes an indium source molecular beam and an arsenic source molecular beam, and the fourth molecular beam includes an indium source molecular beam, an arsenic source molecular beam, and an antimony source molecular beam. This range of x allows the cutoff wavelength of the absorption layer to be tuned to the mid-to-long-wave infrared band of 4.0 μm to 10.0 μm, covering the characteristic band of thermal radiation from the cable surface and matching its overall strain with the substrate lattice. Furthermore, the absorption layer material does not contain Ga, thus eliminating deep-level recombination centers caused by Ga-related intrinsic defects.

[0048] The aforementioned first temperature ensures the substrate remains consistently at that temperature, and through heat conduction, the temperature of other layers is raised to the first temperature. Alternating InAs layers and InAs... 1-x Sb x The layer comprises an absorption layer with a type II superlattice structure. The antimony source molecular beam can be controlled by switching the arsenic (As) / antimony (Sb) ratio on and off, allowing the Sb ratio to range from 0.25 to 0.50. The periodic structure of the type II superlattice structure of the absorption layer can consist of alternating layers of 15–35 monoatom layers of InAs (indium arsenide) with thicknesses of 5–12 monoatom layers. 1-x Sb xFor specific examples of stacking, please refer to the distance of the bottom electrode contact layer mentioned above; the total thickness of the gallium-free absorption layer can be 2.0~6.0μm, and the absorption layer can be intrinsic or lightly doped N-type, with a doping concentration of 1×10⁻⁶. 14 ~5×10 15 cm -3 .

[0049] The barrier layer can be a film layer made of two materials, the first of which can be AlAs. y Sb 1-y The bulk material, the second material can include InAs and AlSb, Figure 2 For AlAs y Sb 1-y Shutter timing diagram of the barrier layer of the bulk material during fabrication. In some alternative embodiments, such as Figure 2 As shown, the area before the first dashed line is for the preparation of InAs. 1-x Sb x The shutter timing sequence for the absorption layer of the bulk material is shown below. The sequence following the first dashed line represents the shutter timing for preparing the first interface transition layer, and the sequence following the second dashed line represents the shutter timing for preparing the barrier layer. Continuously operating the As source between the first and second dashed lines ensures that the interface of the absorption layer is in an As-rich state, allowing for better initial bonding with the subsequently activated Al source to form the Al-As first interface bonding layer. This Al-As bonding layer, compared to the Al-Sb bonding layer and the subsequently formed AlAs layer, exhibits superior bonding properties. y Sb 1-y The interfaces between the barrier layers of the bulk material are more well-matched, which can better reduce stress. The preparation method also includes:

[0050] When the absorption layer is in the target stage, the antimony source and indium source molecular beams required for growing the absorption layer are turned off, while the arsenic source molecular beam required for growing the absorption layer is turned on, and the first interface transition layer is grown on the absorption layer for a preset time period of 1 to 5 seconds. In the last 1.0 to 5.0 seconds of the absorption layer growth interruption, the shutters of the Sb source and In source are turned off, and only the As source is turned on, forming 1 to 2 Al-As bonding layers (the interface transition layer mentioned above) at the heterogeneous switching interface.

[0051] Subsequently, aluminum source molecular beams, arsenic source molecular beams, and antimony source molecular beams are activated to grow a barrier layer on the first interface transition layer. The barrier layer includes AlAs. y Sb 1-y The range of y is 0.07~0.09. The above steps involve simultaneously opening the shutters of the Al, As, and Sb sources to begin AlAs. y Sb 1-yThe growth of the material barrier layer was achieved by adjusting the needle valve openings and beam ratio of the As and Sb sources, controlling the As source composition in the layer to be between 0.07 and 0.09. A constant growth rate was maintained until AlAs... y Sb 1-y When the total physical thickness of the layer reaches 0.1μm~0.5μm, the shutter of the Al, As (arsenic) and Sb (antimony) sources is turned off to complete the preparation of the barrier layer.

[0052] Figure 3 This is a shutter timing diagram showing the fabrication of the barrier layer containing InAs and AlSb. (See diagram for reference.) Figure 3 As shown, the area before the first dashed line is for the preparation of InAs. 1-x Sb x The shutter timing sequence for the absorption layer of the bulk material is as follows: the sequence before the first dashed line represents the shutter timing for preparing the second interface transition layer; the sequence between the first and third dashed lines represents the shutter timing for forming the second interface transition layer and the first barrier layer AlSb. Continuously turning on the Sb source keeps the interface of the absorption layer in a Sb-rich state, allowing for better bonding with the subsequently turned-on Al source to form the Al-Sb second interface bonding layer, avoiding the formation of the As-Al bonding layer. This ensures better interface matching with the subsequently formed first barrier layer AlSb, reducing stress. The sequence between the third and fourth dashed lines represents the shutter timing for preparing the second barrier layer including InAs, and so on, alternately preparing the first and second barrier layers. In some optional embodiments, the preparation method further includes:

[0053] When the absorption layer is in the target stage, the arsenic and indium source molecular beams required for growing the absorption layer are stopped, the antimony source molecular beam required for the absorption layer is turned on, and the aluminum source molecular beam is turned on. The second interface transition layer is grown on the absorption layer for a preset time period of 1 to 5 seconds. The above steps are as follows: in the last 1.0 to 5.0 seconds of the absorption layer growth interruption, the As source and In source shutters are turned off, only the Sb source is turned on, and the Al source shutter is turned on. An Al-Sb bonding layer (the second interface transition layer mentioned above) is formed at the heterojunction to compensate for the interface strain, so that the energy bands between the absorption layer and the barrier layer are matched. This can increase the operating temperature of the infrared detector to the range of 180K to 250K, making it suitable for multi-stage thermoelectric coolers or micro-coolers.

[0054] While keeping the aluminum source molecular beam and antimony source molecular beam on, multiple first barrier layers are grown on the second interface transition layer. The first barrier layer includes AlSb. After the interface transition layer is formed, the shutters of the Al source and Sb source are turned on and the shutter opening time is controlled to epitaxially grow 3 to 8 first barrier layers (AlSb).

[0055] Next, the aluminum and antimony source molecular beams are turned off, while the indium and arsenic source molecular beams are turned on. Multiple layers of second barrier layers are grown on the first barrier layer. These multiple first and second barrier layers constitute the barrier layer, which includes InAs. The Al and Sb source shutters are turned off, and the In and As source shutters are quickly switched on to epitaxially grow 1-4 layers of the second barrier layer (InAs). The steps for growing the first and second barrier layers can be repeated cyclically until the total physical thickness of the short-period superlattice structure reaches 0.1-0.5 μm, at which point the cyclic growth stops. The barrier layer is an undoped intrinsic layer with a thickness of 0.1-0.5 μm.

[0056] In the above optional embodiments, a superlattice structure layer of approximately 0.2 μm thick, consisting of overlapping heavily doped InAs and InAsSb, can also be grown on top of the barrier layer as a top electrode contact layer. The doping type is the same as that of the barrier layer, and the specific preparation steps can refer to the preparation of the bottom electrode contact layer. The doping concentration can be 1 × 10⁻⁶. 18 ~5×10 18 cm -3 This creates a single-level barrier structure in the detector (top electrode contact layer - barrier layer - absorption layer, bottom electrode contact layer and absorption layer are doped with the same material). The interface transition layer can compensate for the interface strain of the barrier layer and eliminate mismatch dislocations, enabling the single-level barrier structure to have extremely low dark current density at high temperatures.

[0057] The infrared detector described in this application utilizes a gallium-free InAs / InAsSb type-two superlattice system to construct the bottom electrode contact layer, top electrode contact layer, and absorption layer, thereby extending minority carrier lifetime and increasing detector operating temperature. The fabrication of these layers employs atomic-level shutter timing control, forcibly forming In-Sb or Al-As bonding layers at the heterojunction of the absorption layer. This compensates for strain at the barrier layer interface and eliminates mismatched dislocations, ensuring that the unipolar barrier structure maintains extremely low dark current density even at high temperatures. This technical solution enables the infrared detector chip to be adapted to miniaturized coolers or lightweight cooling components, saving budget and reducing detector size.

[0058] According to another embodiment of this application, an infrared detector is proposed, such as... Figure 4 As shown, the infrared detector is fabricated using an infrared detector fabrication method. The infrared detector includes: a substrate 10; a buffer layer 20, a bottom electrode contact layer 30, an absorption layer 40, an interface transition layer, a barrier layer 50, and a top electrode contact layer 60, which are sequentially located on one side of the substrate 10. The bottom electrode contact layer and the absorption layer have the same doping type.

[0059] The interface transition layer in this embodiment can compensate for the interface strain of the barrier layer and eliminate mismatch dislocations, ensuring that the detector has an extremely low dark current density at high temperatures. This low dark current characteristic at high temperatures can significantly reduce the background noise of the detector system, improve the signal-to-noise ratio and detection sensitivity, and enable it to accurately capture weak early hot spot signals in cable inspection, thereby solving the problem of low sensitivity of infrared detectors in high-temperature environments in the prior art.

[0060] In some alternative implementations, the absorber layer includes InAs and InAs2. 1-x Sb x The value of x ranges from 0.25 to 0.50, and the barrier layer includes AlAs. y Sb 1-y Alternatively, the barrier layer comprises InAs and AlSb, with y ranging from 0.07 to 0.09. InAs... 1- x Sb x The Sb composition x is controlled within the range of 0.25~0.50, which ensures that the superlattice cutoff wavelength accurately covers the mid-to-long-wave infrared band of the power cable's thermal radiation characteristics, enabling a high response rate to thermal radiation on the cable surface, while effectively balancing lattice strain to suppress defect generation; in the barrier layer design, AlAs is selected. y Sb 1-y The material's As composition (y) was optimized to 0.07–0.09, achieving good matching with the GaSb substrate using the lattice constant at this composition. This also allows for the construction of an efficient conduction band barrier and valence band aligned structure, thus suppressing recombination dark current. The combined optimization of the absorption and barrier layers significantly extends the detector's minority carrier lifetime, raising the operating temperature to the 180K–250K range. This perfectly complements miniature cryogenic systems, solving the bottleneck problem of gallium-free detectors requiring extremely low-temperature cooling and excessively high power specifications.

[0061] According to another embodiment of this application, an infrared focal plane array is proposed, comprising multiple pixel units, each pixel unit containing an infrared detector. The infrared focal plane array with the aforementioned infrared detector can operate at high temperatures and also possesses extremely low dark current density. During operation, it does not require bulky and high-power liquid nitrogen cooling or large-scale refrigerators to lower the temperature, thus allowing for a smaller overall size.

[0062] Example 1:

[0063] An n-type GaSb substrate was selected. In the molecular beam epitaxy system, in-situ deoxidation was performed at 580 °C, followed by the growth of a 500 nm GaSb buffer layer at 480 °C. The ratio of the gallium source molecular beam to the antimony source molecular beam was set to 2.5.

[0064] A 0.5 μm thick n-type InAs / InAsSb superlattice bottom electrode contact layer was grown, with Si as the dopant element and the concentration adjusted to 1 × 10⁻⁶. 18 cm -3 .

[0065] InAs / InAs with a growth thickness of 3.0 μm 0.75 Sb 0.25 Superlattice absorption layer. The periodic structure consists of 15 monolayers of InAs and 5 monolayers of InAs. 0.75 Sb 0.25 The composition has a carrier concentration of approximately 4 × 10⁻⁶. 14 cm -3 .

[0066] In the last 2.0 seconds before the absorption layer growth is interrupted, the Sb and In source shutters are turned off, leaving only the As source on. After a period of time, the Al source is turned on, forming an Al-As interface bonding layer with a thickness of 1 atom. After growth is complete, AlAs is then processed. y Sb 1-y Wide bandgap barrier layer growth was performed. Al, As, and Sb sources were then simultaneously activated, and the As component ratio was adjusted to 0.07% using a needle valve. The final barrier layer thickness was set to 0.1 μm.

[0067] A growth thickness of 0.2 μm with a doping concentration of 4 × 10⁻⁶ 18 cm -3 The top electrode contact layer of the n-type superlattice structure is used to complete the nBn structure.

[0068] Example 2:

[0069] An n-type GaSb substrate was selected. In the molecular beam epitaxy system, in-situ deoxidation was performed at 580 °C, followed by the growth of an 800 nm GaSb buffer layer at 450 °C. The ratio of the gallium source molecular beam to the antimony source molecular beam was set to 2.5.

[0070] A bottom electrode contact layer with an n-type InAs / InAsSb superlattice structure and a thickness of 0.8 μm was grown, with Si as the dopant element and the concentration adjusted to 5 × 10⁻⁶. 18 cm -3 .

[0071] InAs / InAs with a growth thickness of 3.0 μm 0.5 Sb 0.5 Superlattice absorption layer. The periodic structure consists of 35 atomic layers of InAs and 12 atomic layers of InAs. 0.5 Sb 0.5 The composition has a carrier concentration of approximately 5 × 10⁻⁶. 15 cm -3 .

[0072] In the last 5.0 seconds of the absorption layer growth interruption, the shutters of the As and In sources are turned off, and only the Sb source is kept on. After a period of time, the Al source is turned on to form an Al-Sb interface bonding layer with a thickness of 2 atomic layers and an AlSb wide bandgap barrier layer. After formation, the Al and Sb sources are turned off, and the As and In sources are turned on to grow the InAs wide bandgap barrier layer. Repeating the above steps multiple times can obtain a wide bandgap barrier layer consisting of alternating layers of 4 atomic layers of InAs and 8 atomic layers of AlSb, with a growth thickness of 0.5 μm.

[0073] A growth thickness of 0.2 μm with a doping concentration of 4 × 10⁻⁶ 18 cm -3 The top electrode contact layer of the n-type superlattice structure is used to complete the nBn structure.

[0074] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit 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 protection scope of this application.

Claims

1. A method for fabricating an infrared detector, characterized in that, include: A substrate is provided, wherein a buffer layer and a bottom electrode contact layer are provided on one side of the substrate, and the bottom electrode contact layer is located on the side of the buffer layer opposite to the substrate; An absorption layer is formed on the side of the bottom electrode contact layer away from the substrate. When the formation of the absorption layer is in the target stage, an interface transition layer is formed on the side of the absorption layer away from the substrate. The target stage is the last preset time period before the growth of the absorption layer is interrupted. The bottom electrode contact layer and the absorption layer have the same doping type. A barrier layer and a top electrode contact layer are sequentially formed on the side of the interface transition layer away from the substrate.

2. The preparation method according to claim 1, characterized in that, The steps of forming the substrate and the buffer layer include: A crystalline silicon substrate is provided, and the crystalline silicon substrate is subjected to in-situ deoxidation treatment to obtain the substrate, wherein the temperature range of the in-situ deoxidation treatment is 560℃~600℃; The buffer layer is epitaxially grown on the substrate, and the temperature range during the epitaxial growth process is 450℃~500℃, with the ratio of gallium source molecular beam to antimony source molecular beam being 2~4.

3. The preparation method according to claim 2, characterized in that, The steps for forming the bottom electrode contact layer include: Multiple first single-atom layers and multiple second single-atom layers are formed on the buffer layer, and the multiple first single-atom layers and multiple second single-atom layers are doped. The multiple first single-atom layers and multiple second single-atom layers constitute the bottom electrode contact layer. The first single-atom layers and the second single-atom layers are alternately distributed, and the doping type of the first single-atom layers and the second single-atom layers is the same.

4. The preparation method according to claim 3, characterized in that, The steps for forming multiple first monolayers and multiple second monolayers include: Under the condition of a first temperature, the first molecular beam and the second molecular beam are alternately turned on multiple times to grow multiple layers of the first single atomic layer and multiple layers of the second single atomic layer on the buffer layer. The first molecular beam includes an indium source molecular beam and an arsenic source molecular beam, the second molecular beam includes an antimony source molecular beam, the first single atomic layer includes InAs, the second single atomic layer includes InAsSb, and the first temperature ranges from 400℃ to 460℃.

5. The preparation method according to claim 1, characterized in that, The steps for forming the absorption layer include: Under a first temperature environment, the third and fourth molecular beams are alternately activated to grow multiple third and fourth single-atom layers on the side of the bottom electrode contact layer opposite to the substrate. These multiple third and fourth single-atom layers constitute the absorption layer. The third and fourth single-atom layers are alternately distributed. The third and fourth single-atom layers comprise InAs, and the fourth single-atom layers also comprise InAs. 1-x Sb x The value of x ranges from 0.25 to 0.

50. The third molecular bundle includes an indium source molecular bundle and an arsenic source molecular bundle. The fourth molecular bundle includes the indium source molecular bundle, the arsenic source molecular bundle, and the antimony source molecular bundle.

6. The preparation method according to claim 1, characterized in that, The preparation method further includes: When the absorption layer is in the target stage, the antimony source and indium source molecular beams required for growing the absorption layer are stopped, and the arsenic source molecular beam required for growing the absorption layer is continued to be turned on, and a first interface transition layer is grown on the absorption layer. The preset time period is 1~5s. The aluminum source molecular beam, the arsenic source molecular beam, and the antimony source molecular beam are activated, and the barrier layer is grown on the first interface transition layer. The barrier layer comprises AlAs. y Sb 1-y The range of y is 0.07 to 0.

09.

7. The preparation method according to claim 1, characterized in that, The preparation method further includes: When the absorption layer is in the target stage, the arsenic source and indium source molecular beams required for growing the absorption layer are stopped, the antimony source molecular beam required for growing the absorption layer is turned on, and the aluminum source molecular beam is turned on to grow a second interface transition layer on the absorption layer. The preset time period is 1~5s. While keeping the aluminum source molecular beam and the antimony source molecular beam on, grow multiple first barrier layers on the second interface transition layer, wherein the first barrier layers include AlSb. Stop turning on the aluminum source molecular beam and the antimony source molecular beam, turn on the indium source molecular beam and the arsenic source molecular beam, and grow multiple layers of the second barrier layer on the first barrier layer. The multiple layers of the first barrier layer and the multiple layers of the second barrier layer constitute the barrier layer, and the second barrier layer includes InAs.

8. An infrared detector, characterized in that, The infrared detector is prepared by the method of any one of claims 1 to 7, and the infrared detector comprises: Substrate; A buffer layer, a bottom electrode contact layer, an absorption layer, an interface transition layer, a barrier layer, and a top electrode contact layer are sequentially located on one side of the substrate, wherein the bottom electrode contact layer and the absorption layer have the same doping type.

9. The infrared detector according to claim 8, characterized in that, The absorption layer includes InAs and InAs 1-x Sb x The value of x ranges from 0.25 to 0.50, and the barrier layer includes AlAs. y Sb 1-y Alternatively, the barrier layer comprises InAs and AlSb, with y ranging from 0.07 to 0.

09.

10. An infrared focal plane array, characterized in that, It includes multiple pixel units, each pixel unit containing the infrared detector as described in claim 8 or 9.

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