A slit-enhanced mercury cadmium telluride microcavity infrared detector

Abstract

The application discloses a slit-enhanced tellurium-cadmium-mercury microcavity infrared detector. The detector is a layered structure, and sequentially comprises a surface dielectric layer (1), a tellurium-cadmium-mercury absorption layer (2) and a metal reflection layer (3) with a periodic slit structure from bottom to top. The surface dielectric layer serves as an anti-reflection film and, together with the metal reflection layer with the periodic slit structure, serves as two reflection surfaces, and the tellurium-cadmium-mercury absorption layer serves as a cavity medium between the two reflection surfaces, thus forming a slit-enhanced tellurium-cadmium-mercury microcavity. The structure has the characteristics of high infrared absorption and low noise, solves the problem that a traditional high-performance tellurium-cadmium-mercury infrared detector needs to work under harsh conditions such as liquid nitrogen refrigeration, and has a simple structure, does not need the substrate stripping and the two-side metal structure preparation of the traditional metal-semiconductor-metal structure plasmonic microcavity and other complex preparation processes, greatly simplifies process steps, reduces process difficulty and significantly improves the yield.

Description

Technical Field

[0001] This invention relates to a slit-enhanced mercury cadmium telluride infrared detector, which aims to improve detector performance by reducing the volume of the absorption layer and lowering the intrinsic dark current. It belongs to the field of semiconductor photoelectric detector technology. Background Technology

[0002] Mercury cadmium telluride (MCH) semiconductor materials possess characteristics such as high charge mobility, high quantum efficiency, fast response speed, and tunable bandgap, making them irreplaceable in the field of infrared detection. To improve infrared light absorption efficiency, a conventional method is to increase the thickness of the semiconductor absorption layer. However, with increasing thickness, the dark current of the material also increases significantly. Therefore, traditional MCH detectors, in order to achieve high detectivity and signal-to-noise ratio, need to operate under harsh conditions such as liquid nitrogen cooling to reduce dark current. This results in limitations such as high power consumption, large size, high cost, and lifespan restricted by cooling equipment, hindering the integration of large focal plane arrays and greatly limiting its application scope and development prospects. Developing optical coupling technology to improve the light absorption rate of thin-layer semiconductors is an effective method to reduce intrinsic dark current. Among them, the MSM sandwich structure, composed of a plasmonic metasurface, a semiconductor absorption layer, and a metal reflective layer, combines the characteristics of local field enhancement and effective optical path extension, exhibiting a significant absorption enhancement effect (J. Appl. Phys., 2023, 134, 243106:1-10). However, the fabrication process of this structure is complex, involving peeling the mercury cadmium telluride absorption layer from the epitaxial substrate and then fabricating the metal reflective layer and plasmonic nanostructure on both sides of it. The process involves many steps, a long process, and a low yield. Summary of the Invention

[0003] Technical Problem: Addressing the aforementioned existing technologies, this invention proposes a slit-enhanced mercury cadmium telluride (HCd) microcavity infrared detector. Compared to traditional HCd thin-film structures, it exhibits significantly improved infrared absorption efficiency, thereby allowing for a reduction in the semiconductor absorption layer thickness. This reduces intrinsic dark current, increases operating temperature, and solves the problem of traditional high-performance HCd detectors requiring operation under harsh conditions such as liquid nitrogen cooling. Simultaneously, this invention features a simple structure, greatly simplifying the manufacturing process, reducing costs, and increasing yield.

[0004] Technical solution: The slit-enhanced mercury cadmium telluride (MCH) microcavity infrared detector of the present invention has a layered structure, consisting of a surface dielectric layer, a MCH absorption layer, and a metal reflective layer with a periodic slit structure from bottom to top; wherein, the surface dielectric layer serves as an antireflection film, and together with the metal reflective layer with a periodic slit structure, they form the upper and lower reflective surfaces, and the MCH absorption layer serves as the cavity medium between the two reflective surfaces, the three together constituting a slit-enhanced MCH microcavity.

[0005] The material of the surface dielectric layer is the same material used for the epitaxial growth of mercury cadmium telluride.

[0006] The materials used for the epitaxial growth of mercury cadmium telluride include zinc cadmium telluride and cadmium telluride.

[0007] The material used for epitaxial growth of mercury cadmium telluride has a thickness h1 greater than the skin depth of the material, a refractive index n1, and a thickness h1. The thickness h1, the refractive index n1, and the detection wavelength λ satisfy the following numerical relationship: n1h1≈ m1λ / 4, where m1 is a positive odd integer.

[0008] The thickness of the mercury cadmium telluride absorption layer is h2, and the refractive index is n2. The thickness h2, the refractive index n2 and the detection wavelength λ satisfy the following relationship: n2h2≈ m2λ / 4, where m2 takes positive odd integers.

[0009] The thickness of the mercury cadmium telluride absorber layer is on the order of submicron to 1 micrometer.

[0010] The metal reflective layer with a periodic slit structure is made of a highly conductive metal.

[0011] The metal reflective layer with a periodic slit structure is composed of multiple square periodic unit structures arranged periodically in a two-dimensional direction. Each square periodic unit structure has four slits symmetrical about the center of the periodic unit. The square formed by the four slits and the square of the periodic unit are rotated at a 45-degree angle in the plane; that is, the diagonal of the square periodic unit and the diagonal of the square formed by the four slits intersect at a 45-degree angle.

[0012] The length L and width W of the slits are both on the nanometer scale, and the distance d between the two parallel slits satisfies d= Where λ0 is the incident light wavelength, ε d ε′ is the dielectric constant of mercury cadmium telluride. m denoted as ρ, where m is the relative complex permittivity of the metallic reflective layer and m is a positive integer.

[0013] By setting the slit spacing d to the wavelength of the propagating surface plasmon resonance... Integer multiples of (i.e., d = m· (where m is a positive integer) allows propagating surface plasmons excited by adjacent slits to satisfy constructive interference conditions as they propagate laterally at the metal-semiconductor interface. The peak of their interference enhancement falls precisely at the slit location, thus actively achieving resonant coupling between propagating surface plasmons and local surface plasmons, further enhancing the local electric field. The metal layer with a periodic slit structure also constitutes another reflective surface of the microcavity. In other words, the metal layer with a periodic slit structure combines the functions of plasmon resonance enhancement and a microcavity reflective surface, greatly simplifying the detector structure.

[0014] Beneficial Effects: The slit-enhanced mercury cadmium telluride (MCH) microcavity infrared detector proposed in this invention features a periodically slit-structured metal reflective layer that combines the functions of a microcavity reflective surface and plasmon resonance. This simple structure reduces the complexity of the fabrication process. The size design of the periodic slit structure enables resonant coupling between propagating plasmons and local surface plasmons, significantly enhancing the local electric field and improving the infrared light absorption capability of the MCH absorption layer. The epitaxial growth substrate material of MCH, together with the MCH absorption layer grown on it and the periodically slit-structured metal reflective layer, constitutes the MCH microcavity, effectively extending the incident infrared light path and achieving high infrared absorption rate in the thin absorption layer. Furthermore, the thickness design of the epitaxial growth layer gives it the function of an antireflection coating, further improving optical coupling. The slit-enhanced mercury cadmium telluride (MCH) microcavity infrared detector structure, which combines advantages such as enhanced light transmission at the incident surface, extended optical path length in the microcavity, periodic slit-coupled propagation, and enhanced optical field through localized surface plasmon resonance, exhibits high infrared absorption capability and small absorption volume. This effectively reduces the intrinsic dark current and increases the operating temperature of the MCH infrared detector, solving the problem that traditional high-performance MCH infrared detectors need to operate under harsh conditions such as liquid nitrogen cooling.

[0015] Compared to traditional metal-semiconductor-metal plasmon-enhanced microcavity structures, the slit-enhanced mercury cadmium telluride microcavity structure proposed in this invention has two reflective surfaces: a mercury cadmium telluride growth substrate and a metal reflective layer with a periodic slit structure that combines plasmon enhancement and reflection functions. The structure is simple, eliminating the need for substrate stripping and the fabrication of two-sided metal structures, which greatly simplifies the process steps and reduces the process difficulty. As a result, the yield is high, making it suitable for large-scale production. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of the slit-enhanced mercury cadmium telluride microcavity infrared detector of the present invention.

[0017] Figure 2 This is a three-dimensional structural schematic diagram of the slit-enhanced mercury cadmium telluride microcavity infrared detector of the present invention.

[0018] Figure 3 This is a top view schematic diagram of the periodic slit structure unit on the metal reflective layer with slit structure in this invention.

[0019] Figure 4 The images show the infrared absorption spectra of the slit-enhanced mercury cadmium telluride microcavity infrared detector of Example 1 and the control group mercury cadmium telluride thin film infrared detector of the same thickness in the mid-wave band.

[0020] Figure 5 The infrared absorption spectra of the slit-enhanced mercury cadmium telluride microcavity infrared detector of Example 2 and the control group mercury cadmium telluride thin film infrared detector of the same thickness in the long-wavelength band are shown.

[0021] The diagram shows: 1. Surface dielectric layer; 2. Mercury cadmium telluride absorption layer; 3. Metal reflective layer with a periodic slit structure. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1: like Figure 1 As shown, a slit-enhanced mercury cadmium telluride (MCH) microcavity infrared detector for the mid-wave infrared band is disclosed. The detector has a layered structure, consisting of, from bottom to top, a surface dielectric layer 1, a MCH absorption layer 2, and a metal reflective layer 3 with a periodic slit structure. The surface dielectric layer 1 serves as an antireflection coating and, together with the metal reflective layer 3 with the periodic slit structure, forms the upper and lower reflective surfaces. The MCH absorption layer 2 serves as the cavity medium between the two reflective surfaces. Together, these three elements constitute the slit-enhanced MCH microcavity. The surface dielectric layer 1 is composed of zinc cadmium telluride (CdTe) with a thickness of 300 nm, and the MCH absorption layer 2 is composed of 1200 nm thick Hg with a composition x of 0.27. 1-x Cd x Te, the metal reflective layer 3 with a periodic slit micro / nano structure is made of gold with a thickness of 100 nm, and its internal slit structure is as follows: Figure 2 As shown, the gold slits are orthogonally arranged, with a length of 750 nm, a width of 200 nm, and a spacing of 1.18 μm between adjacent slits.

[0024] Its production method is as follows: Step 1: Epitaxially grow a 1200 nm thick mercury cadmium telluride film on a cadmium zinc telluride substrate; Step 2: Deposit a 100 nm thick metal reflective layer on the mercury cadmium telluride layer;

[0025] Step 3: The periodic slit structure is directly etched on the surface of the gold reflective layer by focused ion beam etching (FIB), thus obtaining the slit-enhanced mercury cadmium telluride microcavity infrared detector.

[0026] The light passes sequentially through the surface dielectric layer 1, the mercury cadmium telluride absorption layer 2, and then is reflected by the gold reflective layer 3 with a periodic slit micro-nano structure. It then repeatedly passes through the mercury cadmium telluride microcavity, extending the optical path and increasing absorption.

[0027] The system comprises a slit-enhanced mercury cadmium telluride (MdCd) microcavity consisting of a periodically slit-structured metal reflective layer 3, a mercury cadmium telluride (MdCd) absorber layer 2, and a surface dielectric layer 1. The localized surface plasmon resonance effect generated by the periodically symmetrical slit structure of the metal reflective layer 3 couples with the propagating surface plasmon resonance effect, significantly enhancing the local electric field. Through the synergistic effect of extending the optical path length via the microcavity and the plasmon resonance effect, highly efficient infrared absorption is achieved in the approximately 1-micron-sized MdCd absorber layer 2.

[0028] The surface dielectric layer 1 is made of cadmium zinc telluride (CdTe), and its functions are: to serve as a substrate for the epitaxial growth of mercury cadmium telluride (HCTM), to serve as an antireflective coating to increase the incident light ratio, and to serve as part of the dielectric mirror forming the microcavity. Its thickness h1 and refractive index n1 satisfy the following relationship with the detection wavelength λ: n1h1 ≈ m1λ / 4 (m1 is a positive odd integer, here m1=1). This ensures that the reflected light from the incident surface interferes destructively with the reflected light formed at the interface between the surface dielectric layer and the HCTM absorption layer, thereby increasing the incident light ratio. Considering that the cutoff wavelength of the HCTM material used in this embodiment is 4.5 micrometers, and taking the midpoint wavelength of the absorption band from 3 to 4.5 micrometers (3.75 μm) for calculation, the final thickness h1 is 300 nm.

[0029] The material of the mercury cadmium telluride absorber layer 2 is Hg. 1-x Cd x The Cd composition x of Te is determined based on the cutoff wavelength λc of the target detection band. The band gap Eg of mercury cadmium telluride (MCH) satisfies the following empirical formula with respect to the Cd composition x and temperature T (in K): , Where 0 ≤ x ≤ 0.37, 4.2 ≤ T ≤ 300 K. From Eg = 1.24 / λ c (Taking the cutoff wavelength λc≈4.5μm), we get Eg≈0.276 eV; substituting into the empirical formula and solving it at room temperature T=300 K, we get x≈0.27. Therefore, the example uses Hg with component x=0.27. 1-x Cd x Te.

[0030] Considering the half-wave loss of the metal reflective layer, h2 and the detection wavelength λ satisfy the relationship: n2h2≈m2λ / 4 (m2 is a positive odd integer; considering that the thinnest cadmium telluride (HCTM) thin film is about 1000 nm, we take m2=5 here). This causes the incident light entering the HCTM absorption layer 2 to be reflected back and forth by the gold reflective layer 3 and the surface dielectric layer 1, oscillating repeatedly in the HCTM absorption layer 2, which greatly increases the optical path and thus improves the absorption efficiency. λ is taken as 3.75 μm, and its thickness h2 is calculated to be 1200 nm.

[0031] like Figure 2As shown, a periodically symmetrical slit structure is provided on the metal reflective layer 3 with a periodic slit structure. The slits have a length of 750 nm and a width of 200 nm, and the slits are orthogonally arranged to satisfy the polarization insensitivity to incident light. When the incident light propagates to the metal-semiconductor interface, localized surface plasmon resonance is generated at the edge of the metal slits, producing a local electric field enhancement effect in the subwavelength range. At the same time, the slit structure also excites propagating surface plasmons (SPPs) that propagate laterally at the interface between gold and mercury cadmium telluride. The slit spacing d is set to an integer multiple of the SPP wavelength, so that the SPPs excited by adjacent slits will undergo constructive interference at the slit position, thereby realizing the resonant coupling of SPPs and localized surface plasmons (LSPRs) to jointly enhance the electric field, i.e., satisfying d=m Where λ0 is the incident light wavelength, ε d The dielectric constant of mercury cadmium telluride is approximately 10, ε′ m The relative complex permittivity of the gold reflective layer is approximately -690, and m is taken as 1. The slit spacing is calculated to be 1.18 μm.

[0032] like Figure 4 As shown, the slit-enhanced mercury cadmium telluride microcavity infrared detector achieves a peak absorption rate of 98% at the incident light wavelength of 3.85 μm, which is 245% stronger than that of a mercury cadmium telluride film of the same thickness.

[0033] Example 2: The difference between this embodiment and Embodiment 1 is that it is applicable to the long-wave infrared band, and the absorption layer uses Hg with a component x of 0.154. 1-x Cd x Te, the thickness and refractive index parameters of each part are re-determined according to the detection wavelength using the formula nh ≈ mλ / 4, and the slit spacing is also adjusted accordingly based on the long-wavelength infrared light wavelength. The rest of the structure is the same as in Example 1. The final result is a surface dielectric layer 1 with a thickness of 0.92 μm, a mercury cadmium telluride absorption layer 2 with a thickness of 1400 nm, a gold reflective layer 3 with a thickness of 100 nm, a gold slit length of 1700 nm, a width of 500 nm, and a spacing of 2.54 μm between adjacent slits.

[0034] like Figure 5 As shown, the slit-enhanced mercury cadmium telluride microcavity infrared detector reaches an absorption peak of 92% at an incident light wavelength of 9.75 μm, which is 460% higher than that of a mercury cadmium telluride thin film of the same thickness.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A slit-enhanced mercury cadmium telluride microcavity infrared detector, characterized in that: The detector has a layered structure, consisting of a surface dielectric layer (1), a mercury cadmium telluride absorption layer (2), and a metal reflective layer (3) with a periodic slit structure from bottom to top. The surface dielectric layer (1) serves as an antireflection film and together with the metal reflective layer (3) with a periodic slit structure, they form two upper and lower reflective surfaces. The mercury cadmium telluride absorption layer (2) serves as the cavity medium between the two reflective surfaces. Together, the three form a slit-enhanced mercury cadmium telluride microcavity.

2. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 1, characterized in that: The material of the surface dielectric layer (1) is the material used for epitaxial growth of mercury cadmium telluride.

3. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 2, characterized in that: The materials used for the epitaxial growth of mercury cadmium telluride include zinc cadmium telluride and cadmium telluride.

4. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 3, characterized in that: The material used for epitaxial growth of mercury cadmium telluride has a thickness of h1, which is greater than the skin depth of the material, and a refractive index of n1. The thickness h1, the refractive index n1 and the detection wavelength λ satisfy the following numerical relationship: n1h1 ≈ m1λ / 4, where m1 takes a positive odd integer.

5. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 4, characterized in that: The thickness of the mercury cadmium telluride absorption layer (2) is h2, and the refractive index is n2. The thickness h2, the refractive index n2 and the detection wavelength λ satisfy the following relationship: n2h2≈ m2λ / 4, where m2 is a positive odd integer.

6. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 5, characterized in that: The thickness of the mercury cadmium telluride absorption layer (2) is on the order of submicron to 1 micrometer.

7. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 1, characterized in that: The metal reflective layer (3) with a periodic slit structure is made of a highly conductive metal.

8. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 7, characterized in that: The metal reflective layer (3) with a periodic slit structure is composed of multiple square periodic unit structures arranged periodically in a two-dimensional direction. The square periodic unit structure has 4 slits symmetrical about the center of the periodic unit. The square formed by the 4 slits and the square of the periodic unit are rotated at a 45-degree angle in the plane; that is, the diagonal of the square periodic unit and the diagonal of the square formed by the 4 slits intersect at a 45-degree angle.

9. The slit-enhanced mercury cadmium telluride microcavity infrared detector according to claim 8, characterized in that: The length L and width W of the slits are both on the nanometer scale, and the distance d between the two parallel slits satisfies d= Where λ0 is the incident light wavelength, ε d ε′ is the dielectric constant of mercury cadmium telluride. m denoted as ρ, where m is the relative complex permittivity of the metallic reflective layer and m is a positive integer.

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