A micro-nano structure integrated high-performance long-wave infrared quantum well detection device

Abstract

The application discloses a kind of micro-nano structure integrated high-performance long-wave infrared quantum well detection device, belongs to long-wave infrared quantum well detection device technical field.The technical problem to be solved is that existing technical scheme is difficult to achieve balance between high performance, easy preparation, low crosstalk and high yield generally.1) The technical solution points are: upper electrode layer integrates periodic coupling grating structure, and forms composite grating with the first mesa metal reflection layer, excites hybrid mode of guided mode-plasmon, couples normal incidence light to quantum well active layer, generates vertical electric field component, thereby overcoming the problem of low coupling efficiency caused by selection rule under normal incidence condition, and enhancing interband transition absorption;2) Side wall metal reflection layer, enhance light field localization and isolate adjacent pixels, suppress crosstalk;3) Low-absorption dielectric material is used as passivation insulating layer to reduce parasitic absorption;4) The above structure is designed in cooperation with the existing QWIP focal plane technology, and performance and manufacturability are considered.

Description

Technical Field

[0001] This invention relates to the field of long-wave infrared quantum well detector technology, and specifically to a high-performance long-wave infrared quantum well detector with micro-nano structure integration. Background Technology

[0002] The long-wave infrared (LWIR) band represents the peak region of thermal radiation from objects at room temperature on Earth and lies within the atmospheric transmission window, making it a core spectral band for achieving efficient, passive infrared thermal imaging. This technology plays a crucial role in fields such as space remote sensing, meteorological monitoring, industrial inspection, and medical diagnosis.

[0003] In the process of realizing high-performance, miniaturized, and intelligent long-wave infrared detection systems, GaAs / AlGaAs quantum well infrared detectors (QWIPs) have become one of the important international technical routes due to their significant advantages such as good material uniformity, mature fabrication process, fast response speed, precise control of detection wavelength through bandgap engineering, and ease of large-scale focal plane array integration.

[0004] QWIP is a photoconductive detector based on inter-subband transitions, which forms a periodic structure by alternately epitaxially growing GaAs well layers and AlGaAs barrier layers. Thanks to mature III-V semiconductor manufacturing technology, QWIP shows greater potential for industrial application than traditional HgCdTe photovoltaic devices in realizing uniform large-area focal plane arrays.

[0005] However, QWIP itself has some fundamental bottlenecks that limit its further performance improvement: Low normal incidence absorption efficiency: Due to the quantum transition selection rule, QWIP can only effectively absorb the component of the incident electric field vector perpendicular to the quantum well growth plane. For conventional normal incidence light, its electric field is mainly distributed in the direction parallel to the quantum well plane, which cannot be directly and effectively absorbed, resulting in low quantum efficiency; Inconsistent dark current and operating temperature: The dark current of QWIP is quite sensitive to the operating temperature and bias voltage. In order to suppress the dark current caused by thermally excited carriers and obtain higher detection performance, it is usually necessary to operate at a lower temperature.

[0006] To address the aforementioned bottlenecks, micro- and nano-optical structures, as core functional components for achieving efficient optical coupling and field enhancement, are playing an increasingly important role in the field of infrared detection. Currently, various optical coupling enhancement schemes have been proposed both domestically and internationally, ranging from early 45° ground-angle coupling and periodic diffraction grating coupling to more recent advancements such as guided-mode resonant structures, plasmonic microcavities, metallic photonic crystals, hybrid waveguide structures, all-dielectric resonant waveguides, and photonic crystal structures based on quasi-continuous domain bound states. The core principle of these micro- and nano-structures lies in efficiently localizing or coupling incident light energy into the active region of a quantum well through specific electromagnetic resonance modes, thereby forming an enhanced vertical electric field component in the active region of the quantum well. This overcomes the low coupling efficiency problem caused by the interband transition selection rule under conventional normal incidence conditions, achieving effective absorption enhancement in the quantum well.

[0007] However, integrating these high-performance micro / nano structures with QWIP to construct large-scale, highly uniform focal plane arrays still faces a series of severe technical challenges. First, there is the contradiction between structural design and process complexity: many high-performance micro / nano structures are designed to achieve ultimate optical performance, but their fabrication processes are extremely complex, involving multiple steps of high-precision photolithography, deep etching, multi-layer overlay, and fine deposition of different materials. This not only increases manufacturing costs and time but also makes it difficult to be compatible with mature QWIP focal plane array manufacturing processes, hindering their industrial application. Second, there are the challenges of optical crosstalk and pixel isolation: in focal plane arrays, micro / nano structures integrated on adjacent pixels may generate optical crosstalk, meaning that the light field of one pixel may leak and interfere with the signals of adjacent pixels, leading to image blurring and a decrease in signal-to-noise ratio.

[0008] Meanwhile, to reduce dark current, techniques such as deep etching are often used to reduce the effective electrical area of ​​pixels, forming isolated mesa. Ensuring good passivation of the mesa sidewalls and maintaining the optical performance of the micro / nano structure during this process is a key technological challenge. On one hand, there is a trade-off between material loss and performance optimization: when using metallic structures to achieve field enhancement, the inherent ohmic loss of the metal consumes some optical energy, limiting the achievable quantum efficiency. On the other hand, the dielectric materials used for surface passivation and insulation exhibit intrinsic optical absorption in the long-wave infrared band. In coupling structures relying on multiple reflections or strong resonances, this parasitic loss significantly reduces the overall optical efficiency of the device.

[0009] In summary, while micro- and nanostructures offer significant potential for improving QWIP performance, existing technologies often struggle to achieve a balance between high performance, ease of fabrication, low crosstalk, and high yield. Developing a novel micro- and nanostructure integration scheme that is simple in design, highly compatible with various processes, possesses excellent optical performance, and is easily integrated with existing QWIP focal plane array technologies has become an urgent need to drive the practical application and industrialization of high-performance long-wavelength infrared quantum well detectors. Summary of the Invention

[0010] The purpose of this invention is to provide: A high-performance long-wave infrared quantum well detector device with micro / nano structure integration, and related technologies, to solve the technical problems that existing technical solutions often struggle to achieve a balance between high performance, ease of fabrication, low crosstalk, and high yield.

[0011] Terminology Explanation: Unless otherwise defined, all technical terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this subject matter pertains. Unless otherwise stated, all patents, patent inventions, and disclosures cited throughout this document are incorporated herein by reference in their entirety. Where multiple definitions exist for terms herein, the definitions provided in this chapter shall prevail.

[0012] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0013] The terms “optional / arbitrary” or “optionally / arbitrarily” mean that the event or situation described below may or may not occur, including both the occurrence and non-occurrence of the event or situation.

[0014] The term “GaAs / AlGaAs quantum well infrared detector (QWIP)” used in this article refers to an infrared photodetector device with a multi-quantum well structure, which is fabricated using gallium arsenide (GaAs) as the potential well material and aluminum gallium arsenide (AlGaAs) as the potential barrier material. It achieves the conversion of infrared light signals into electrical signals by relying on the quantum well subband transition effect.

[0015] The term "GaAs potential well layer" used in this article refers to the thin layer of semiconductor material with a smaller bandgap and bound electrons and holes in the GaAs / AlGaAs quantum well structure, which is the core region for carrier enrichment and transition.

[0016] The term "AlGaAs barrier layer" as used in this article refers to a thin semiconductor layer with a larger bandgap sandwiched between GaAs potential well layers in a GaAs / AlGaAs quantum well structure, used to form an energy barrier to restrict the transport of charge carriers across the layer.

[0017] The term "optical crosstalk" used in this article refers to the optical phenomenon in which light signals from adjacent pixels of an infrared detector are scattered, refracted, and transmitted, causing mutual interference between pixel light signals and a decrease in imaging accuracy.

[0018] The term "pixel isolation" used in this article refers to the process and structural design that uses etching, deposition media, and other processes to physically and optically separate the pixel units of a detector, thereby blocking the mutual interference of optical and electrical signals between pixels.

[0019] The term "pixel unit" used in this article refers to: an independent detection element that constitutes a two-dimensional detection array in an array device; an independent infrared detection element within an array device; it refers to the same physical structure as a unit device and is often used to describe the pixel arrangement of an array.

[0020] The term "unit device" used in this article refers to: a detection element that independently realizes photoelectric conversion in an array device; an independent infrared detection element within an array device; it refers to the same physical structure as a pixel unit and is mostly used to describe semiconductor optoelectronic functional devices.

[0021] The term "micro-nanostructure" as used in this article refers to artificial fine structures with feature sizes on the order of micrometers and nanometers. In this article, it specifically refers to miniature optical structures fabricated on the surface / sidewall of a detector to modulate the light field and enhance optical coupling efficiency.

[0022] The term "dark current" used in this article refers to the current flowing through an infrared detector under operating bias voltage when there is no incident light. It is an important parameter affecting the detector's noise and signal-to-noise ratio.

[0023] The term "deep etching" used in this article refers to a dry / wet etching process with high depth and high aspect ratio used for semiconductor wafers / thin films to achieve structural shaping such as device mesa division and patterned deep trench fabrication.

[0024] The term "mesa" as used in this article refers to the raised semiconductor functional unit structure formed on the surface of a substrate after semiconductor etching, which is the main supporting structure for the detector pixels.

[0025] The term "isolated mesa" as used in this paper refers to a quantum well active region and upper mesa structure of each pixel that are isolated from adjacent pixels by deep etching, while each pixel can maintain the required electrical connection through a common lower electrode layer.

[0026] The term "mesa sidewall" used in this article refers to the side facade of a raised mesa structure, which is a vertical / inclined interface formed by the etching process and is one of the main locations where surface states and light scattering occur in devices.

[0027] The term "passivation" as used in this article refers to the process technology of depositing an insulating dielectric film on the surface and sidewalls of a semiconductor device to reduce surface defect states, suppress leakage current, and improve device stability and reliability.

[0028] The term "parasitic loss" used in this article refers to the energy loss caused by non-target optical channels such as absorption by non-active materials, ohmic loss of metals, scattering, and radiation leakage during optical signal transmission and coupling.

[0029] The term "quantum well active region" used in this article refers to the core functional region of a quantum well formed by alternating stacks of GaAs / AlGaAs layers, which is the main region where light absorption, carrier excitation, and photoelectric conversion occur.

[0030] The term "critical coupling" used in this article refers to the state in which the external radiation coupling loss rate and the internal absorption loss rate of a resonant optical system are matched, which, under ideal conditions, enables the efficient transfer of incident light energy to the internal absorption channel of the device.

[0031] The term "quantum well material" as used in this article refers to a multilayer ultrathin composite semiconductor material system that possesses quantum confinement effects, formed by alternating growth of III-V compound semiconductors such as GaAs and AlGaAs.

[0032] The term "Schottky barrier" used in this article refers to the rectifying barrier formed at the interface between a metal and a semiconductor material. It can regulate the carrier transport characteristics and is often used in the design of device electrodes and junction regions.

[0033] The term "linearly coupled grating array" used in this article refers to a periodic grating array structure arranged in a straight line with equal spacing, which is mainly used to couple incident infrared light into the active region of a quantum well.

[0034] The term "grating coupling mode" used in this article refers to an optical operating mode in which incident light undergoes diffraction and wave vector matching through a periodic grating structure, and then couples into the device for propagation.

[0035] The term "plasmon mode" used in this paper refers to a surface electromagnetic oscillation mode formed by the coupling of the collective oscillation of free electrons and the incident photons at the metal / dielectric interface, which has the characteristic of locally enhancing the optical field.

[0036] The term "optical coupling mode" used in this article refers to the working state of the internal electromagnetic field of a device formed after incident light is subjected to grating diffraction, guided mode coupling, and local field modulation related to the metal interface.

[0037] The term "IBE" used in this article refers to Ion Beam Etching, a micro-nano fabrication process that uses high-energy ion beams to bombard the surface of materials to achieve high-precision pattern etching.

[0038] The term "ICP-RIE" used in this article refers to Inductively Coupled Plasma Reactive Ion Etching, a dry etching process that combines high-density plasma with chemical reactions, and is suitable for processing high aspect ratio and high-precision semiconductor structures.

[0039] The term "flip-chip bonding" as used in this article refers to a semiconductor device packaging interconnect process in which the functional side of the chip is facing down and directly bonded to the readout circuit board via solder bumps to achieve electrical interconnection.

[0040] The term "plasmonic" used in this article refers to the collective oscillation of free electrons on a metal surface under the influence of an electromagnetic field. It can realize local enhancement of optical field and subwavelength optical transmission, and is widely used in optical coupling and optical absorption enhancement design.

[0041] The term "guided mode resonance" used in this article refers to the optical phenomenon in which incident light excites the guided mode of a waveguide and generates a resonance effect, which can realize narrowband filtering, optical field enhancement and efficient optical coupling.

[0042] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A high-performance long-wavelength infrared quantum well detector device with micro-nano structure integration includes multiple pixel units arranged in an array. Each pixel unit includes, from bottom to top, a corrosion barrier layer, a lower electrode layer, a quantum well active region layer, and an upper electrode layer; a coupling grating structure is disposed in the upper electrode layer. A first metal electrode layer is provided on the upper electrode layer corresponding to one end of the lower electrode layer, and a second metal electrode layer is provided on the lower electrode layer at the other end of the lower electrode layer. A first mezzanine metal reflective layer is disposed on the first metal electrode layer and the upper electrode layer; a second mezzanine metal reflective layer is disposed on the second metal electrode layer; The passivation insulating layer covers the entire surface of the device, contacts the first mesa metal reflective layer and the second mesa metal reflective layer, and provides contact openings in the electrical connection areas corresponding to the first mesa metal reflective layer and the second mesa metal reflective layer. A first indium pillar is disposed in the middle of the first metal reflective layer, and a second indium pillar is disposed at the top of the second metal reflective layer; the first indium pillar is electrically connected to the first metal reflective layer through a corresponding contact opening, and the second indium pillar is electrically connected to the second metal reflective layer through a corresponding contact opening. On the passivation insulating layer, a sidewall metal reflective layer is provided around the first indium pillar to wrap the sidewall of the mesa; The tops of the first and second indium pillars are equipped with external electrode plates, which are composed of sapphire and electrically isolated metal connection areas, and can be used to connect external testing equipment, etc.

[0043] First preferred option: The corrosion barrier layer is made of aluminum gallium arsenide (Al). x Ga 1-x As, thickness 200 nm, Al composition x=0.50.

[0044] Second preferred option: The lower electrode layer is an n-type gallium arsenide electrode with a thickness of 700 nm and a doping concentration of 2 × 10⁻⁶. 17 cm -3 .

[0045] Third preferred option: The active region of the quantum well consists of 20 composite periodic structures of gallium arsenide and aluminum gallium arsenide, and an aluminum gallium arsenide layer on top of the composite periodic structures. Each recombination cycle, from top to bottom, consists of a 1.5 nm undoped GaAs layer, a 3 nm doped GaAs layer, a 1.5 nm undoped GaAs layer, and a 50 nm AlGaAs barrier layer; the 3 nm GaAs layer has a doping concentration of 5 × 10⁻⁶. 17 cm -3 ; A 50 nm thick layer of aluminum gallium arsenide is placed on top of the composite periodic structure; The aluminum gallium arsenide material in the active region of the quantum well is Al x Ga 1-x As, where the Al component x=0.18.

[0046] Fourth preferred option: The upper electrode layer is an n-type gallium arsenide electrode with a thickness of 1300 nm and a doping concentration of 2 × 10⁻⁶. 17 cm -3 .

[0047] Fifth preferred option: The coupling grating structure consists of multiple grooves etched on the upper electrode layer, which are periodically arranged along a straight line to form a linear coupling grating array.

[0048] Furthermore, the groove is a cuboid or a cube, etc.

[0049] Sixth preferred option: The first and second metal electrode layers are made of highly conductive metal materials, including but not limited to gold, silver, aluminum, and alloys.

[0050] Seventh preferred option: The materials of the first tabletop metal reflective layer, the second tabletop metal reflective layer, and the sidewall metal reflective layer are all highly conductive metal materials, including but not limited to gold, silver, aluminum, and alloys.

[0051] Eighth preferred option: The passivation insulating layer uses passivation insulating materials including but not limited to silicon nitride and hafnium oxide; the thickness of the passivation insulating layer should meet the insulation withstand voltage requirements under the operating bias conditions of the device, and a corresponding safety factor should be set according to the dielectric strength of the dielectric material used.

[0052] Ninth preferred option: The welding point formed at the top of the first indium pillar and the second indium pillar by a flip-chip bonding process is connected to the outer electrode plate.

[0053] The present invention has at least the following beneficial effects: 1. Compared with the prior art, the present invention has positive technical effects in terms of positive incident light coupling, device photoelectric response, reduction of parasitic absorption and array process compatibility.

[0054] Based on simulation and experimental testing, this invention, through the synergistic design of the upper electrode layer integrating the coupling grating structure with the first mesa metal reflective layer and the sidewall metal reflective layer, forms an enhanced vertical electric field component in the active region of the quantum well, thereby improving the coupling efficiency and effective absorption of normally incident light with the active region of the quantum well.

[0055] Compared to traditional 45° ground-angle coupling devices, the device of this invention, which employs a hafnium oxide passivated insulating layer and integrates a mesa grating and a sidewall metal reflective layer, exhibits overall improved blackbody and spectral responsivity. Simultaneously, the sidewall metal reflective layer can constrain the reflection of lateral light fields propagating towards adjacent pixels, structurally helping to reduce optical crosstalk between adjacent pixels.

[0056] By using hafnium oxide with low optical absorption in the long-wave infrared band to replace traditional silicon nitride as the passivation insulating layer, under the premise of ensuring insulation withstand voltage, the hafnium oxide thickness scheme exhibits lower calculated parasitic absorption under the optical parameters and design thickness of the materials used, which can further improve optical coupling efficiency.

[0057] 2. Compared with the prior art, the present invention provides a technical solution with a different technical concept.

[0058] Existing technologies often struggle to balance the design complexity of high-performance micro / nano structures with the compatibility of focal plane array fabrication processes.

[0059] This invention achieves three major functions—optical coupling enhancement, pixel optical isolation, and low-loss passivation—through the coordinated use of three structures: an integrated grating on the top electrode, a sidewall metal reflective layer, and a hafnium oxide passivation insulating layer. These structures enhance each other functionally and are highly compatible in terms of process, eliminating the need for complex heterogeneous integration steps. This design approach differs from the traditional technical path that sacrifices manufacturability in pursuit of a single extreme optical performance.

[0060] 3. Compared with the prior art, the present invention provides a technical solution representing the development of high-performance infrared focal plane detectors toward practical application and industrialization.

[0061] The micro-nano structure integration architecture proposed in this invention, while maintaining the existing advantages of mature QWIP material system, good large-area uniformity, and easy integration with focal plane arrays, verifies through structural innovation that it is beneficial to improve problems such as normal incident coupling efficiency, transverse optical field leakage and medium parasitic loss, and provides a feasible technical path for further process integration of high-performance long-wave infrared QWIP focal plane arrays.

[0062] 4. Although the number of process steps for a single structure may not be significantly less than that of existing solutions, the present invention has significant positive technical effects in terms of structural functional integration, process tolerance, and array fabrication consistency.

[0063] Specifically, the first mesa metal reflective layer of this invention mainly participates in optical coupling and local field modulation, while the sidewall metal reflective layer simultaneously undertakes the function of lateral optical field confinement; the hafnium oxide passivated insulating layer not only meets the insulation withstand voltage requirements but also has low optical loss characteristics, eliminating the need for an additional optical optimization dielectric layer. This functional composite design reduces the mutual constraints between process steps, improves the process window and array uniformity, thereby facilitating higher yields in the fabrication of large-scale focal plane arrays.

[0064] 5. This invention transforms normally incident infrared light into a localized optical field with a strong vertical electric field component within the active region of the quantum well through the synergistic effect of the coupled grating structure and the metal reflection structure. This effectively excites inter-subband transitions in the active region of the quantum well, enabling electrons to transition from the ground state subband to the excited state subband or the continuous state.

[0065] 6. When the incident light wavelength matches the resonant coupling condition formed by the coupling grating structure, the first mesa metal reflective layer, and the sidewall metal reflective layer, the effective absorption within the active region of the quantum well is enhanced, and the device output response is correspondingly improved.

[0066] 7. The sidewall metal reflective layer is wrapped around the outside of the platform sidewall, which can reflect the light field propagating towards the platform sidewall and adjacent unit devices back into the unit device, thereby enhancing the localization of the light field within the unit device and reducing optical crosstalk between adjacent unit devices.

[0067] 8. The passivation insulating layer covers the mesa surface and mesa sidewalls. On the one hand, it reduces the leakage current caused by defect states on the mesa sidewalls and improves the stability of the device under biased operation. On the other hand, the passivation insulating layer uses a low-absorption dielectric material in the long-wave infrared band, which can reduce the parasitic absorption loss of infrared light in the non-quantum well active region, so that more light energy can be coupled and localized to the quantum well active region layer. Attached Figure Description

[0068] Figure 1 This is a two-dimensional structural diagram of the pixel unit of the device of the present invention; Figure 2 For the present invention Figure 1 enlarge Figure 1 ; Figure 3 For the present invention Figure 1 enlarge Figure 2 ; Figure 4 This is a schematic diagram of the coupling grating structure parameters on the device of the present invention; Figure 5 A graph showing the complex refractive index (n, k) of hafnium oxide during electromagnetic simulation calculations for the pixel unit of the device of the present invention; Figure 6 A graph showing the complex refractive index (n, k) of silicon nitride during electromagnetic simulation calculations of the pixel unit of the device of the present invention. Figure 7 A comparison of the absorption rates of 50 nm hafnium oxide and 300 nm silicon nitride films in the long-wave infrared band. Figure 8 A parameter scan diagram showing the effect of the coupled grating period parameter control unit device on the infrared absorption rate when hafnium oxide is used in the passivation insulating layer of the present invention. Figure 9 A comparison of the blackbody responsivity of a conventional 45° ground-angle device and a unit device of the present invention when hafnium oxide and silicon nitride are used for the passivation insulating layer of the present invention; Figure 10 A comparison of the spectral peak response rates of a conventional 45° ground-angle device and a unit device of the present invention when hafnium oxide and silicon nitride are used for the passivation insulating layer of the present invention; Figure 11 This is a diagram showing the electromagnetic power loss density distribution of the XZ cross section of the unit device of the present invention.

[0069] Figure label: 1. Corrosion barrier layer; 2. Lower electrode layer; 3. Quantum well active region layer; 4. Upper electrode layer; 5. Coupling grating structure; 6-1, First metal electrode layer; 6-2, Second metal electrode layer; 7-1, First mesa metal reflective layer; 7-2, Second mesa metal reflective layer; 8. Passivation insulating layer; 9. Electrode external plate; 10. Sidewall metal reflective layer; 11-1. First indium pillar; 11-2. Second indium pillar; 12-1. First solder joint; 12-2. Second solder joint. Detailed Implementation

[0070] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection of the present invention.

[0071] Example 1 Combination Figures 1-3 As shown, the present invention provides a high-performance long-wave infrared quantum well detector device with micro-nano structure integration, including multiple pixel units arranged in an array. Each pixel unit includes, from bottom to top, a corrosion barrier layer 1, a lower electrode layer 2, a quantum well active region layer 3, and an upper electrode layer 4; a coupling grating structure 5 is disposed in the upper electrode layer 4. A first metal electrode layer 6-1 is disposed on the upper electrode layer 4 corresponding to one end of the lower electrode layer 2; A second metal electrode layer 6-2 is disposed on the lower electrode layer 2 at the other end of the lower electrode layer 2; A first mezzanine metal reflective layer 7-1 is provided on the first metal electrode layer 6-1 and the upper electrode layer 4; a second mezzanine metal reflective layer 7-2 is provided on the second metal electrode layer 6-2.

[0072] The coupling grating structure 5 and the first mesa metal reflective layer 7-1 form a composite grating, which synergistically modulates the incident light to induce diffraction coupling, guided mode coupling, and metal interface-related local field enhancement, thereby effectively coupling the normally incident light to the active region layer 3 of the quantum well and generating a vertical electric field component. This overcomes the low coupling efficiency problem caused by the selection rule under conventional normally incident conditions and enhances the absorption of inter-subband transitions.

[0073] The mesa refers to the raised semiconductor body structure formed after etching the active region layer 3 and the upper electrode layer 4 of the quantum well. The first indium pillar 11-1 and the second indium pillar 11-2 are provided with an external electrode plate 9. The external electrode plate 9 is an interconnection structure on the mesa and is not part of the mesa body.

[0074] The passivation insulating layer 8 covers the entire surface of the device, contacts the first mesa metal reflective layer 7-1 and the second mesa metal reflective layer 7-2, and provides contact openings in the electrical connection areas corresponding to the first mesa metal reflective layer 7-1 and the second mesa metal reflective layer 7-2. A first indium pillar 11-1 for flip-chip bonding is provided in the middle of the first platform metal reflective layer 7-1, and a second indium pillar 11-2 for flip-chip bonding is provided at the top of the second platform metal reflective layer 7-2; the first indium pillar 11-1 is electrically connected to the first platform metal reflective layer 7-1 through the corresponding contact opening, and the second indium pillar 11-2 is electrically connected to the second platform metal reflective layer 7-2 through the corresponding contact opening. On the passivation insulating layer 8, a sidewall metal reflective layer 10 is provided around the first indium pillar 11-1 to wrap the sidewall of the platform, and the sidewall metal reflective layer 10 is a whole. The top of the first indium pillar 11-1 is connected to the electrode outer plate 9 via the first solder joint 12-1. The top of the second indium pillar 11-2 is connected to the electrode outer plate 9 via the second solder joint 12-2.

[0075] The active region layer 3 of the quantum well serves as the detector material.

[0076] The corrosion barrier layer 1, lower electrode layer 2, quantum well active region layer 3 and upper electrode layer 4 can also be replaced with other infrared detection materials (equivalent to dielectric layers). The corrosion barrier layer 1 is made of aluminum gallium arsenide (Al). x Ga 1-x As, where the Al component x=0.50 and the thickness is 200nm; The lower electrode layer 2 is an n-type gallium arsenide electrode with a thickness of 700 nm and a doping concentration of 2 × 10⁻⁶. 17 cm -3 ; The active region layer 3 of the quantum well consists of 20 composite periodic structures of gallium arsenide and aluminum gallium arsenide, and an aluminum gallium arsenide layer on top of the composite periodic structures. Each composite period, from top to bottom, includes a 1.5 nm undoped GaAs layer, a 3 nm doped GaAs layer, a 1.5 nm undoped GaAs layer, and a 50 nm AlGaAs barrier layer; wherein the doping concentration of the 3 nm GaAs layer is 5 × 10⁻⁶. 17 cm -3 ; A 50 nm thick layer of aluminum gallium arsenide is placed on top of the composite periodic structure.

[0077] The aluminum gallium arsenide material in the active region layer 3 of the quantum well is Al x Ga 1-x As, where the Al component x=0.18.

[0078] The upper electrode layer 4 is an n-type gallium arsenide electrode with a thickness of 1300 nm and a doping concentration of 2 × 10⁻⁶. 17 cm -3 .

[0079] The coupling grating structure 5 is a plurality of cuboid grooves etched to a depth of 1130 nm in the upper electrode layer 4. The coupling grating structure 5 consists of multiple grooves periodically arranged along the same direction. The coupling grating structure 5 can also be designed as a downwardly etched cube or other structure; the design of the coupling grating structure 5 is highly diverse. This embodiment uses cuboid etched grooves. Multiple grooves are periodically arranged along a straight line to form a linear coupling grating array, which constitutes the coupling grating structure 5.

[0080] The simulation design requires strong optical coupling capability in the long-wave infrared band, thereby enabling high effective absorption in the active region layer 3 of the quantum well and placing the target band in an optimal resonant coupling state. Generally, the optical coupling capability is controlled by adjusting the length, width, height dimensions, and center distance of the groove based on the optical parameters of the quantum well material.

[0081] The first metal electrode layer 6-1 and the second metal electrode layer 6-2 are made of highly conductive metallic materials, including but not limited to gold, silver, aluminum, and alloys. After a rapid annealing process, the first metal electrode layer 6-1 and the upper electrode layer 4, and the second metal electrode layer 6-2 and the lower electrode layer 2, respectively form ohmic contacts, thereby reducing the impact of the metal / semiconductor contact barrier on carrier transport. This invention uses 100 nm germanium-gold, 20 nm nickel, and 300 nm gold.

[0082] The first tabletop metal reflective layer 7-1, the second tabletop metal reflective layer 7-2, and the sidewall metal reflective layer 10 are made of highly conductive metal materials, including but not limited to gold, silver, aluminum, alloys, etc. The thickness is required to be no less than twice the skin depth of the electromagnetic wave in the metal. In this invention, 50 nm titanium (as an adhesive layer) and 300 nm gold are used.

[0083] The passivation insulating layer 8 can be made of insulating dielectric materials such as hafnium oxide and silicon nitride, preferably a dielectric material with low parasitic absorption in the target long-wave infrared band and meeting the insulation withstand voltage requirements. The thickness of the passivation insulating layer 8 should meet the insulation withstand voltage requirements under the device's operating bias conditions, and a corresponding safety factor should be set according to the dielectric strength of the dielectric material used. In this embodiment, the safety factor is 2. This invention uses 50 nm hafnium oxide or 300 nm silicon nitride.

[0084] The device employs optical coupling modes such as grating coupling mode and plasmonic mode to enhance device performance. Specifically, the device excites guided mode resonance through coupling grating structure 5, which works synergistically with the surface plasmonic-related local enhancement modes induced by the first mesa metal reflective layer 7-1 and the sidewall metal reflective layer 10, thereby improving the optical coupling efficiency of the device and the effective absorption of the quantum well active region layer 3.

[0085] The inter-band optical absorption of the active region layer 3 of the quantum well exhibits significant direction selectivity, primarily responding to the component of the incident photoelectric field vector perpendicular to the quantum well growth plane. The etched diffraction grating (coupled grating structure 5) of the upper electrode layer 4, the deposited first mesa metal reflective layer 7-1, and the sidewall metal reflective layer 10 can all effectively enhance the absorption of the active region layer 3 (detector material portion) of the quantum well.

[0086] After forming the mesa sidewalls through deep etching, a sidewall metal reflective layer 10 is deposited on the mesa sidewalls. This can effectively reduce the leakage of the light field to adjacent unit devices, suppress optical crosstalk, and improve the localization of the light field in the active region layer 3 of the quantum well. The deep etching of the mesa sidewalls (the mesa sidewalls are the sidewalls of the pixel unit mesa prepared after etching the quantum well material) can limit the effective electrical area of ​​the pixel and achieve structural isolation between adjacent pixels. Combined with the passivation insulating layer 8 and the sidewall metal reflective layer 10, the electrical characteristics of the mesa sidewalls can be improved respectively, and a reflection constraint can be formed on the laterally propagating light field.

[0087] The passivation insulating layer 8 is designed using hafnium oxide material, which can reduce parasitic absorption under the designed thickness and optical parameters. Contact windows are formed in the predetermined electrical connection area of ​​the passivation insulating layer 8 using IBE or ICP-RIE, exposing the electrical connection areas of the first mesa metal reflective layer 7-1 and the second mesa metal reflective layer 7-2. This allows the first mesa metal reflective layer 7-1 to be flip-chip bonded to the electrode outer plate 9 via the first indium pillar 11-1, and the second mesa metal reflective layer 7-2 to be flip-chip bonded to the electrode outer plate 9 via the second indium pillar 11-2.

[0088] like Figure 4 As shown, the mesa structure parameters of the device have a modulating effect on its optical coupling capability and wavelength selectivity. The grating diffraction and the metal reflection structure (the first mesa metal reflection layer 7-1 and the sidewall metal reflection layer 10) work together to change the coupling conditions of the in-plane wave vector provided by the grating and the related resonance modes of the guided mode and metal interface inside the device when the geometric parameters of the coupled grating structure 5 change, thereby causing changes in the position and absorption intensity of the resonance absorption peak.

[0089] Figure 4 The tabletop structural parameters are as follows: A=27 μm, B=24 μm, C=5 μm, L=22 μm, W=1.13 μm, P=3.4 μm.

[0090] A is the dimension of the square platform of the unit device; B represents the dimension of the first metal reflective layer 7-1 on the square platform; C represents the dimension of the first metal electrode layer 6-1 on the square mesa; P is the periodic dimension of the coupled grating structure 5; L is the length of the coupled grating structure 5 etched on the square platform; W represents the width of the coupled grating structure 5 etched on the square platform.

[0091] Figure 5 The complex refractive indices (n, k) of hafnium oxide used in electromagnetic simulation calculations are given. Figure 6 The complex refractive indices (n, k) of silicon nitride used in electromagnetic simulations are given. Based on this, Figure 7 A comparison of the absorption rates in the long-wave infrared band using 50 nm hafnium oxide and 300 nm silicon nitride thin films was plotted. Based on... Figure 7 As can be seen, the upper curve represents the absorptivity of the 300 nm silicon nitride film in the long-wave infrared band, and the lower curve represents the absorptivity of the 50 nm hafnium oxide film in the long-wave infrared band. The results show that in the target long-wave infrared band (8-12 μm), the parasitic absorption of the 50 nm hafnium oxide film is significantly lower than that of the 300 nm silicon nitride film, verifying the advantage of hafnium oxide as a passivation insulating layer in reducing optical loss.

[0092] like Figure 8 As shown, during the simulation, 50 nm hafnium oxide was used as the mesa to wrap the passivation insulating layer 8, and then titanium and gold were magnetron sputtered to form the sidewall metal reflective layer 10. The parameters of the coupling grating structure 5 were fixed at L=22 μm and W=1.13 μm.

[0093] Figure 8 The scanning results of the parameter scan diagram shown are as follows: As the periodic dimension P of the coupled grating structure 5 varies within the target range, the absorption peak position exhibits a systematic shift. This phenomenon indicates that the grating period alters the diffraction coupling and resonance conditions within the device, thereby causing the absorption peak position to undergo systematic tuning with changes in the period.

[0094] When the period size P of the coupled grating structure 5 deviates from the design value, the absorption peak deviates from the target detection band, and the peak absorptivity decreases accordingly. When the period size P = 3.4 μm, the absorption peak matches the target band, and the absorption in the active region reaches the maximum value within this scanning range, indicating that the coupled grating structure 5 has a superior resonant coupling state under these parameters. These scanning results provide a basis for the process tolerance analysis of the grating period and the design of array uniformity. The optimized parameters for the coupled grating structure 5 are L = 22 μm, W = 1.13 μm, and P = 3.4 μm.

[0095] like Figure 9 As shown in the figure, through batch fabrication of devices, the blackbody response rate of the conventional 45° ground angle device and the various structural parameter unit devices of the present invention are compared when the passivation insulating layer 8 uses hafnium oxide and silicon nitride.

[0096] like Figure 10 As shown in the figure, the peak spectral response of the traditional 45° grinding angle device and various structural parameter unit devices were compared when the passivation insulating layer 8 was obtained by batch fabrication of the device and testing using hafnium oxide and silicon nitride.

[0097] according to Figure 9 Blackbody response rate comparison chart and Figure 10 The comparison chart of spectral response rates shows that: (1) The device responses of different structures and passivation materials are significantly different. Among them, the device with hafnium oxide passivation insulating layer 8 and integrated mesa grating and sidewall metal reflective layer 10 generally exhibits the highest blackbody responsivity and spectral responsivity; the response of some silicon nitride passivation structures is still lower than that of the 45° reference device, indicating that the optical gain of the micro-nano structure is affected by the loss of the passivation insulating layer 8 and the structural parameters.

[0098] (2) In summary, the device using hafnium oxide passivation insulating layer and integrating mesa grating and sidewall metal reflective layer 10 achieved the highest set of blackbody responsivity and peak spectral responsivity, verifying the effectiveness of the present invention in co-designing low-loss passivation material and efficient optical coupling structure, and providing an optimized combination of material and structural parameters for the fabrication of high-performance long-wave infrared quantum well focal plane arrays.

[0099] like Figure 11 As shown, the electromagnetic power loss density distribution of the XZ cross section of the micro / nano structure integrated long-wavelength infrared quantum well unit device is presented. Here, the X direction is the periodic arrangement direction of the coupled grating structure 5, the Y direction is the extension direction of the grating groove, and the Z direction is the epitaxial growth direction of the quantum well material, i.e., the direction perpendicular to the active region layer 3 of the quantum well. Figure 11The colors represent the electromagnetic power loss density per unit volume at different locations within the device, characterizing the spatial distribution of absorption and dissipation of incident infrared light within the device. Simulations for pixel units also consider the material stacking structure that may form within the grating trenches during thin-film deposition. Theoretically, the mesa grating and the first mesa metal reflective layer 7-1 work together to induce mode mixing through light diffraction and reflection mechanisms, achieving efficient coupling between waveguide modes and surface plasmon modes, thereby significantly enhancing optical coupling efficiency. Simulation results show that: (1) Under the consideration of grating trench film stacking conditions, obvious electromagnetic energy redistribution and local loss regions are still formed near the coupling grating structure 5 and the first mesa metal reflective layer 7-1, indicating that the actual process structure can still achieve effective incident light coupling.

[0100] (2) Under the design parameters of L=22 μm, W=1.13 μm and P=3.4 μm, the high electromagnetic power loss density is mainly distributed in the region near the grating and the active region layer 3 of the quantum well, indicating that the incident light can be coupled into the vicinity of the active region layer 3 of the quantum well after being controlled by the micro-nano structure and then absorbed and dissipated.

[0101] (3) Combination Figure 8 Absorption rate parameter scanning results and Figure 9 , Figure 10 Based on the device responsivity test results, it can be concluded that this combination of structural parameters can achieve good optical coupling and photoelectric response performance.

[0102] Working principle: The device of this invention requires an external circuit and a signal readout circuit to operate. Specifically, the external circuit forms electrical connections with the upper electrode layer 4 and the lower electrode layer 2 through the external electrode plate 9, the first indium pillar 11-1, the second indium pillar 11-2, the first metal electrode layer 6-1, and the second metal electrode layer 6-2, respectively, thereby applying a bias voltage across the active region layer 3 of the quantum well. This bias voltage is used to establish an electric field along the growth direction of the quantum well within the active region layer 3, enabling the carriers generated by photoexcitation in the active region layer 3 to be transported and collected under the influence of the bias electric field. This forms a measurable photocurrent signal through the external readout circuit, which can then be converted into a voltage signal by an external readout or preamplifier circuit.

[0103] After a bias voltage is applied to the external circuit, incident long-wave infrared light is incident from the light-incident side of the device (etching barrier layer 1) to the side where the upper electrode layer 4 is located. The incident light interacts with the coupling grating structure 5 disposed in the upper electrode layer 4. The periodic structure of the coupling grating structure 5 can provide transverse wave vector compensation for the normally incident infrared light, so that the normally incident light, which is originally difficult to be directly absorbed by the active region layer 3 of the quantum well, undergoes diffraction coupling and is transformed from a free-space propagation mode into an optical coupling mode that can propagate inside the device or be localized.

[0104] Simultaneously, the first mesa metal reflective layer 7-1 and the sidewall metal reflective layer 10 together constitute a metal reflection structure and a localized field modulation structure. This metal reflection structure can reflect, confine, and localize infrared light entering the device, and can induce surface plasmon-related local enhancement effects at the metal / semiconductor or metal / dielectric interface. Consequently, incident infrared light undergoes optical phenomena such as diffraction, reflection, guided mode coupling, and localized field enhancement within the unit device, resulting in an enhanced vertical electric field component within the quantum well active region layer 3.

[0105] The light absorption of GaAs / AlGaAs quantum well infrared detectors is limited by the subband transition selection rule, primarily absorbing the component of the incident electric field vector perpendicular to the quantum well layer. For ordinary normally incident infrared light, the electric field is mainly parallel to the quantum well layer, making it difficult to be effectively absorbed by the active region layer 3 of the quantum well. This invention, through the synergistic effect of the coupling grating structure 5 and the metal reflection structure, transforms normally incident infrared light into a localized light field with a strong perpendicular electric field component within the active region layer 3 of the quantum well. This effectively excites interband transitions in the active region layer 3 of the quantum well, causing electrons to transition from the ground state subband to the excited state subband or the continuous state.

[0106] After the aforementioned light absorption process, the carriers excited by infrared light undergo directional transport under the electric field established by the external bias circuit, and are collected by the external readout circuit via the upper electrode layer 4, lower electrode layer 2, first metal electrode layer 6-1, second metal electrode layer 6-2, and external electrode plate 9. Thus, the incident infrared light signal is converted into a change in device photocurrent, which can be converted into a corresponding voltage signal by the external readout circuit. Within the linear response range of the device, the greater the incident light intensity, the more carriers are effectively excited and collected in the active region layer 3 of the quantum well, and the stronger the corresponding output photoelectric signal. When the incident light wavelength matches the resonant coupling condition formed by the coupling grating structure 5, the first mesa metal reflective layer 7-1, and the sidewall metal reflective layer 10, the effective absorption in the active region layer 3 of the quantum well is enhanced, and the device output response is correspondingly improved.

[0107] In addition, the sidewall metal reflective layer 10 covers the outer side of the mesa sidewall, which can reflect the light field propagating towards the mesa sidewall and adjacent unit devices back into the unit device, thereby enhancing the localization of the light field within the unit device and reducing optical crosstalk between adjacent unit devices.

[0108] The passivation insulating layer 8 covers the mesa surface and mesa sidewalls. On the one hand, it reduces the leakage current caused by defect states on the mesa sidewalls and improves the stability of the device under biased operation. On the other hand, the passivation insulating layer 8 uses a low-absorption dielectric material in the long-wave infrared band, which can reduce the parasitic absorption loss of infrared light in the non-quantum well active region layer, so that more light energy can be coupled and localized to the quantum well active region layer 3.

[0109] Therefore, with the cooperation of the external bias circuit and the readout circuit, the present invention, through the synergistic design of the coupling grating structure 5, the metal reflection structure and the low absorption passivation insulating layer 8, enables the incident long-wave infrared light to generate optical phenomena such as diffraction coupling, guided mode resonance, surface plasmon resonance-related local enhancement and sidewall reflection constraint inside the device. This, in turn, forms an enhanced vertical electric field component in the active region layer 3 of the quantum well, improves the effective absorption of the quantum well, and finally converts it into a photoelectric response signal that can be read by the external circuit, thus achieving comprehensive optimization of positive incident light coupling enhancement, effective absorption improvement, pixel crosstalk suppression and process compatibility.

[0110] The device of the present invention can be formed by the following preparation method: S1. Provide a GaAs / AlGaAs quantum well epitaxial wafer, the epitaxial wafer comprising, from bottom to top, a corrosion barrier layer 1, a lower electrode layer 2, a quantum well active region layer 3 and an upper electrode layer 4.

[0111] S2. Electron beam lithography is performed on the surface of the upper electrode layer 4 to define the coupling grating pattern, and a coupling grating structure 5 is formed in the upper electrode layer 4 by dry etching process (ICP-RIE). The coupling grating structure 5 is a periodic groove grating structure.

[0112] S3. Photolithography is performed on the quantum well epitaxial wafer, and the mesa structure of each unit device is formed by mesa etching process (ICP-RIE) to isolate the quantum well active region layer and the upper mesa structure of adjacent unit devices from each other.

[0113] S4. The first metal electrode layer 6-1 and the second metal electrode layer 6-2 are formed by photolithography and metal deposition processes, respectively, and ohmic contact is formed between them and the corresponding semiconductor electrode layers by rapid thermal annealing.

[0114] S5. The first mesa metal reflective layer 7-1 and the second mesa metal reflective layer 7-2 are formed by photolithography and metal deposition processes.

[0115] S6. Deposit passivation insulating material on the device surface to form a passivation insulating layer 8 covering the mesa surface and mesa sidewalls. Then, after photolithography, use IBE or ICP-RIE processes to create openings in predetermined areas of the passivation insulating layer 8, exposing the electrical connection areas of the first mesa metal reflective layer 7-1 and the second mesa metal reflective layer 7-2.

[0116] S7. A sidewall metal reflective layer 10 is formed by photolithography and metal deposition processes. The sidewall metal reflective layer 10 covers the outer sidewall of the mesa and is used to enhance the localization of the light field and suppress optical crosstalk between adjacent unit devices.

[0117] S8. A first indium pillar 11-1 is formed at the corresponding position of the first mesa metal reflective layer 7-1, and a second indium pillar 11-2 is formed at the corresponding position of the second mesa metal reflective layer 7-2. The first solder joint 12-1 of the first indium pillar 11-1 and the second solder joint 12-2 of the second indium pillar 11-2 are prepared by flip-chip bonding process. The first solder joint 12-1 and the second solder joint 12-2 are respectively connected to the electrode external plate 9 to realize the electrical interconnection between the device and the external readout circuit or test circuit.

[0118] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A high-performance long-wavelength infrared quantum well detector device integrated with micro / nano structures, characterized in that, It includes multiple pixel units arranged in an array, each pixel unit comprising, from bottom to top, an etch barrier layer, a lower electrode layer, a quantum well active region layer, and an upper electrode layer; a coupling grating structure is disposed within the upper electrode layer; A first metal electrode layer is provided on the upper electrode layer corresponding to one end of the lower electrode layer, and a second metal electrode layer is provided on the lower electrode layer at the other end of the lower electrode layer. A first mezzanine metal reflective layer is disposed on the first metal electrode layer and the upper electrode layer; a second mezzanine metal reflective layer is disposed on the second metal electrode layer; A passivation insulating layer covering the entire surface of the device is in contact with the first mesa metal reflective layer and the second mesa metal reflective layer, and contact openings are provided in the electrical connection areas corresponding to the first mesa metal reflective layer and the second mesa metal reflective layer. A first indium pillar is disposed in the middle of the first metal reflective layer, and a second indium pillar is disposed at the top of the second metal reflective layer; the first indium pillar is electrically connected to the first metal reflective layer through a corresponding contact opening, and the second indium pillar is electrically connected to the second metal reflective layer through a corresponding contact opening. On the passivation insulating layer, a sidewall metal reflective layer is provided around the first indium pillar to wrap the sidewall of the mesa; Electrode external plates are provided on the top of the first indium pillar and the second indium pillar.

2. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The corrosion barrier layer is made of aluminum gallium arsenide (Al). x Ga 1-x As.

3. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The lower electrode layer is an n-type gallium arsenide electrode.

4. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The active region of the quantum well consists of a multilayered composite periodic structure of gallium arsenide and aluminum gallium arsenide, and an aluminum gallium arsenide layer on top of the composite periodic structure.

5. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The upper electrode layer is an n-type gallium arsenide electrode.

6. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The coupling grating structure consists of multiple grooves etched on the upper electrode layer, which are periodically arranged along a straight line to form a linear coupling grating array.

7. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The first and second metal electrode layers are made of highly conductive metallic materials.

8. The high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The first platform metal reflective layer, the second platform metal reflective layer, and the sidewall metal reflective layer are all made of highly conductive metal materials.

9. A high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The passivation insulating layer uses passivation insulating materials including, but not limited to, silicon nitride and hafnium oxide.

10. A high-performance long-wavelength infrared quantum well detector device with micro / nano structure integration according to claim 1, characterized in that, The tops of the first and second indium pillars are connected to the outer electrode plate via solder joints.

Images