A dual-color infrared detector

Abstract

The application relates to the technical field of semiconductor materials and devices, in particular to a dual-color infrared detector, which comprises an InAs substrate and a buffer layer, a first contact layer, a first absorption layer, a barrier layer, a second absorption layer, a second contact layer and a cap layer which are sequentially grown from bottom to top on the InAs substrate; the first absorption layer and the second absorption layer both comprise a plurality of periods of InAs / GaAs / GaSb / GaAs superlattices. The application adopts the InAs substrate, and designs the first absorption layer and the second absorption layer to adopt the InAs / GaAs / GaSb / GaAs superlattices; the absorption layer is highly matched with the substrate in terms of the crystal lattices, the mismatch dislocations are fundamentally eliminated, the GaAs which has higher thermal stability is used as a superlattice interface layer of the absorption layer, the higher growth temperature is allowed while the high quantum efficiency is maintained, the crystal quality of the epitaxial layer is obviously improved, and the photoelectric performance of the device is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials and devices, and specifically to a dual-color infrared detector. Background Technology

[0002] Dual-color infrared detectors can simultaneously detect information in two different wavelength bands, theoretically possessing better target recognition capabilities and stronger anti-interference advantages, making them an important development direction for high-performance infrared detectors. Currently, back-to-back device structures based on stacked infrared materials have become the main technical route for the development of dual-color infrared detectors. Based on the type of infrared-sensitive material, they can be divided into three main categories: mercury cadmium telluride (HgCd), quantum wells, and superlattices. HgCd dual-color infrared detectors have advantages such as tunable bandgap and high quantum efficiency, but due to the weak Hg-Te bond energy, poor material stability, complex device fabrication processes, and expensive substrates, their development in the field of dual-color devices is greatly limited. Quantum well detectors can be mass-produced based on III-V semiconductor processes, but their low quantum efficiency requires complex grating structures to operate, and they have gradually been replaced by other technical solutions. Superlattice materials have high quantum efficiency and allow for flexible design of device structures using band engineering methods, offering numerous advantages in the design and fabrication of dual-color infrared detectors. Currently, the commonly used material design scheme for superlattice infrared detectors is to design InAs / GaSb superlattices or InAs / InAsSb superlattices based on GaSb substrates to achieve infrared detection. InAs / GaSb superlattices have high quantum efficiency, but their growth process requires InSb as an interface to balance the strain of the superlattice material, which results in a lower growth temperature, hindering the improvement of crystal quality. Although InAs / InAsSb superlattices allow for a slightly higher growth temperature, their quantum efficiency is lower than that of InAs / GaSb superlattices, especially in long-wavelength channels. Summary of the Invention

[0003] The purpose of this invention is to provide a dual-color infrared detector that can at least solve some of the defects in the prior art.

[0004] To achieve the above objectives, the technical solution of the present invention is a dual-color infrared detector, comprising an InAs substrate and a buffer layer, a first contact layer, a first absorption layer, a barrier layer, a second absorption layer, a second contact layer, and a cap layer grown sequentially from bottom to top on the InAs substrate; the first absorption layer and the second absorption layer each comprise a plurality of periods of InAs / GaAs / GaSb / GaAs superlattices.

[0005] As one embodiment, the InAs / GaAs / GaSb / GaAs superlattice includes an InAs layer, a first GaAs layer, a GaSb layer, and a second GaAs layer grown epitaxially in sequence; the thickness of the InAs layer in the first absorption layer is different from the thickness of the InAs layer in the second absorption layer, and the thicknesses of the first GaAs layer, GaSb layer, and second GaAs layer in the first absorption layer are the same as the thicknesses of the first GaAs layer, GaSb layer, and second GaAs layer in the second absorption layer, respectively.

[0006] As one embodiment, the thickness of the InAs layer in the first absorption layer is x ML, and the thickness of the InAs layer in the second absorption layer is y ML; the thicknesses of the first GaAs layer, the GaSb layer, and the second GaAs layer in the first and second absorption layers are 0.043n ML, 0.914n ML, and 0.043n ML, respectively; where x, y, and n are integers, and 7≤x≤11, 14≤y≤18, and 7≤n≤11.

[0007] As one implementation, the barrier layer comprises a plurality of periodic InAs / GaAs / GaSb / GaAs superlattices, wherein the thickness of the InAs layer in the barrier layer is less than the thickness of the InAs layer in the first absorption layer and the second absorption layer.

[0008] As one implementation, the thicknesses of the InAs layer, the first GaAs layer, the GaSb layer, and the second GaAs layer in the barrier layer are z ML, 0.043(n+t) ML, 0.914(n+t) ML, and 0.043(n+t) ML, respectively; wherein z, n, and t are integers, and 3≤z≤5, 7≤n≤11, and 0≤t≤2.

[0009] As one embodiment, the thickness of both the first absorption layer and the second absorption layer is 2–4 μm, the doping type is n-type, and the doping concentration is 1 × 10⁻⁶. 15 ~3×10 15 cm -3 .

[0010] As one embodiment, the barrier layer has a thickness of 0.15–0.4 μm and is undoped.

[0011] As one embodiment, both the first contact layer and the second contact layer include several periods of InAs / GaAs / GaSb / GaAs superlattices, and the thickness of each layer of the superlattice of the first contact layer is the same as the thickness of each layer of the superlattice of the first absorption layer, and the thickness of each layer of the superlattice of the second contact layer is the same as the thickness of each layer of the superlattice of the second absorption layer.

[0012] As one embodiment, the thickness of both the first contact layer and the second contact layer is 0.2–0.5 μm, the doping type is n-type, and the doping concentration is 1 × 10⁻⁶. 18 ~3×10 18 cm -3 .

[0013] As one implementation method, both the buffer layer and the cap layer are made of InAs material, and both are n-type doped.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses an InAs substrate and designs the first and second absorption layers to use an InAs / GaAs / GaSb / GaAs superlattice. The absorption layer and the substrate are highly matched in terms of lattice, which fundamentally eliminates mismatch dislocations. In addition, the absorption layer uses GaAs with better thermal stability as the superlattice interface layer, which allows for higher growth temperature while maintaining high quantum efficiency, significantly improving the crystal quality of the epitaxial layer and thus improving the optoelectronic performance of the device. (2) By designing the first GaAs layer, GaSb layer and second GaAs layer to have the same thickness in the two absorption layers, and the InAs layer to have different thicknesses in the two absorption layers, the effective bandgap difference between the two absorption layers is completely determined by the thickness of the InAs layer. The cutoff wavelength of the two absorption layers can be flexibly adjusted by changing only the thickness of the InAs layer, thereby realizing dual-color detection of the device. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the dual-color infrared detector provided by the present invention; Figure 2 A flowchart illustrating the fabrication process of one embodiment of the dual-color infrared detector provided by the present invention; In the figure: 1. InAs substrate; 2. Buffer layer; 3. First contact layer; 4. First absorption layer; 5. Barrier layer; 6. Second absorption layer; 7. Second contact layer; 8. Cap layer. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a number" means at least one.

[0020] like Figure 1 As shown, this embodiment provides a dual-color infrared detector, including an InAs substrate 1 and, from bottom to top, a buffer layer 2, a first contact layer 3, a first absorption layer 4, a barrier layer 5, a second absorption layer 6, a second contact layer 7, and a cap layer 8 grown on the InAs substrate 1. Both the first absorption layer 4 and the second absorption layer 6 comprise several periods of InAs / GaAs / GaSb / GaAs superlattices. This embodiment uses an InAs substrate 1 and designs the first absorption layer 4 and the second absorption layer 6 to use an InAs / GaAs / GaSb / GaAs superlattice. The lattice of the absorption layer is highly matched with that of the substrate, fundamentally eliminating mismatch dislocations. Furthermore, the absorption layer uses GaAs, which has better thermal stability, as the superlattice interface layer, allowing for higher growth temperatures while maintaining high quantum efficiency, significantly improving the crystal quality of the epitaxial layer, and thus enhancing the optoelectronic performance of the device.

[0021] In some embodiments, the InAs / GaAs / GaSb / GaAs superlattice comprises sequentially epitaxially grown InAs, a first GaAs, a GaSb, and a second GaAs layer. The thickness of the InAs layer in the first absorption layer 4 is different from the thickness of the InAs layer in the second absorption layer 6. The thicknesses of the first GaAs, GaSb, and second GaAs layers in the first absorption layer 4 are the same as those in the second absorption layer 6. By designing different InAs layer thicknesses in the two absorption layers, and the same thickness for the first GaAs, GaSb, and second GaAs layers, the effective bandgap difference between the two absorption layers is entirely determined by the thickness of the InAs layer. Therefore, the cutoff wavelengths of the two absorption layers can be flexibly controlled simply by changing the thickness of the InAs layer, ultimately achieving dual-color infrared detection in the device.

[0022] Furthermore, the thickness of the InAs layer in the first absorption layer 4 is x ML (monolayer), and the thickness of the InAs layer in the second absorption layer 6 is y ML. The thicknesses of the first GaAs layer, the GaSb layer, and the second GaAs layer in the first absorption layer 4 and the second absorption layer 6 are 0.043n ML, 0.914n ML, and 0.043n ML, respectively; where x, y, and n are integers, and 7 ≤ x ≤ 11, 14 ≤ y ≤ 18, and 7 ≤ n ≤ 11. By designing the thickness of both the first and second GaAs layers in the two absorption layers to be 0.043n ML, and the thickness of the GaSb layer to be 0.914n ML, the GaAs / GaSb / GaAs structure in the absorption layers can be highly matched to the lattice constant of the InAs substrate 1, thereby reducing the dislocation density of the epitaxial layer and improving device performance.

[0023] In some embodiments, the barrier layer 5 comprises several periods of InAs / GaAs / GaSb / GaAs superlattice, and the thickness of the InAs layer in the barrier layer 5 is less than the thickness of the InAs layer in the first absorption layer 4 and the second absorption layer 6. The barrier layer 5 and the two absorption layers use the same superlattice structure, which not only greatly simplifies the epitaxial growth process but also ensures good interlayer lattice matching, effectively reducing interface dislocation and defect density. Simultaneously, the thickness of the InAs layer in the barrier layer 5 is less than the thickness of the InAs layer in the two absorption layers, resulting in the widest effective bandgap of the superlattice in the barrier layer 5, which effectively blocks electrons and suppresses device dark current.

[0024] Furthermore, the thicknesses of the InAs layer, the first GaAs layer, the GaSb layer, and the second GaAs layer in the barrier layer 5 are z ML, 0.043(n+t) ML, 0.914(n+t) ML, and 0.043(n+t) ML, respectively; where z, n, and t are integers, and 3≤z≤5, 7≤n≤11, and 0≤t≤2. By designing the thickness of the first GaAs layer and the second GaAs layer in the barrier layer 5 to be 0.043(n+t) ML, and the thickness of the GaSb layer to be 0.914(n+t) ML, the GaAs / GaSb / GaAs structure in the barrier layer 5 is highly matched with the lattice constant of the InAs substrate 1, reducing epitaxial interface defects and stress, and effectively reducing the valence band change between the barrier layer 5 and the two absorption layers, thereby achieving low-bias operation of the device.

[0025] In some embodiments, the thickness of both the first absorption layer 4 and the second absorption layer 6 is 2–4 μm, the doping type is n-type, and the doping concentration is 1 × 10⁻⁶. 15 ~3×10 15 cm -3 .

[0026] Furthermore, the barrier layer 5 has a thickness of 0.15–0.4 μm and is undoped.

[0027] In some embodiments, both the first contact layer 3 and the second contact layer 7 comprise a plurality of periods of InAs / GaAs / GaSb / GaAs superlattices, and the thickness of each layer of the superlattice in the first contact layer 3 is the same as the thickness of each layer of the superlattice in the first absorption layer 4, and the thickness of each layer of the superlattice in the second contact layer 7 is the same as the thickness of each layer of the superlattice in the second absorption layer 6. By adopting the same superlattice structure for the first contact layer 3 as for the first absorption layer 4, and the same superlattice structure for the second contact layer 7 as for the second absorption layer 6, lattice matching between each contact layer and its corresponding absorption layer is achieved, eliminating the interface barrier and simplifying the epitaxial growth process. In this embodiment, the value of n in the superlattice structures of the barrier layer 5, the first absorption layer 4, and the second absorption layer 6 is the same.

[0028] Furthermore, the thickness of both the first contact layer 3 and the second contact layer 7 is 0.2–0.5 μm, the doping type is n-type, and the doping concentration is 1 × 10⁻⁶. 18 ~3×10 18 cm -3 .

[0029] The detector in this embodiment adopts an nBn type structure. Both the absorption layer and the contact layer use n-type doped superlattices, while the barrier layer 5 uses an undoped superlattice. The wider effective bandgap of the barrier layer 5 forms a conduction band barrier, which effectively blocks majority carriers without hindering the transport of photogenerated holes, significantly suppressing the dark current of the device. At the same time, there is no obvious barrier in the valence band, ensuring that photogenerated holes can migrate smoothly and be collected efficiently, thus guaranteeing the performance of the dual-color infrared detector.

[0030] Furthermore, both the buffer layer 2 and the cap layer 8 are made of InAs material, and both are n-type doped. Specifically, the thickness of the buffer layer 2 can be approximately 0.5 μm, and the doping concentration can be 1 × 10⁻⁶. 18 ~3×10 18 cm -3 The thickness of the cap layer 8 can be approximately 0.1 μm, and the doping concentration can be 1 × 10⁻⁶. 18 ~3×10 18 cm -3 .

[0031] The growth method of the dual-color infrared detector in this embodiment can be molecular beam epitaxy or metal-organic chemical vapor deposition.

[0032] The structure and fabrication method of the dual-color infrared detector of the present invention will be described in detail below through a specific embodiment.

[0033] A dual-color infrared detector includes an InAs substrate 1 and, from bottom to top, a buffer layer 2, a first contact layer 3, a first absorption layer 4, a barrier layer 5, a second absorption layer 6, a second contact layer 7, and a cap layer 8, grown sequentially on the InAs substrate 1. The buffer layer 2 has a thickness of approximately 0.5 μm, is made of InAs material, is n-type doped, and has a doping concentration of 3 × 10⁻⁶. 18 cm -3 The first contact layer 3 has a total thickness of approximately 0.24 μm and consists of several periods of InAs / GaAs / GaSb / GaAs superlattices. Each period comprises an 8 mL InAs layer, a 0.34 mL first GaAs layer, a 7.32 mL GaSb layer, and a 0.34 mL second GaAs layer. The doping type is n-type doping, and the doping concentration is 1 × 10⁻⁶. 18 cm -3 The first absorption layer 4 has a total thickness of approximately 2.9 μm and consists of several periods of InAs / GaAs / GaSb / GaAs superlattices. Each period comprises an 8 mL InAs layer, a 0.34 mL first GaAs layer, a 7.32 mL GaSb layer, and a 0.34 mL second GaAs layer. The doping type is n-type doping, and the doping concentration is 1 × 10⁻⁶. 15 cm -3The barrier layer 5 has a total thickness of approximately 0.21 μm and consists of several periods of InAs / GaAs / GaSb / GaAs superlattices. Each period consists of a 4 mL InAs layer, a 0.43 mL first GaAs layer, a 9.14 mL GaSb layer, and a 0.43 mL second GaAs layer; it is undoped. The second absorber layer 6 has a total thickness of approximately 2.5 μm and consists of several periods of InAs / GaAs / GaSb / GaAs superlattices. Each period consists of a 16 mL InAs layer, a 0.34 mL first GaAs layer, a 7.32 mL GaSb layer, and a 0.34 mL second GaAs layer; it is n-type doped with a doping concentration of 1 × 10⁻⁶. 15 cm -3 The second contact layer 7 has a total thickness of approximately 0.22 μm and consists of several periods of InAs / GaAs / GaSb / GaAs superlattices. Each period comprises a 16 mL InAs layer, a 0.34 mL first GaAs layer, a 7.32 mL GaSb layer, and a 0.34 mL second GaAs layer. The doping type is n-type doping, and the doping concentration is 1 × 10⁻⁶. 18 cm -3 The cap layer 8 has a thickness of approximately 0.1 μm, is made of InAs material, is n-type doped, and has a doping concentration of 3 × 10⁻⁶. 18 cm -3 .

[0034] like Figure 2 As shown, the fabrication method of the above-mentioned dual-color infrared detector includes the following steps: S1. Epitaxial substrate and pretreatment: InAs substrate 1 with (100) crystal orientation was selected and degassing and deoxidation treatment was performed. S2. Epitaxial growth of buffer layer 2 on the InAs layer: A 0.5 μm InAs layer is grown using Si doping with a doping concentration of 3 × 10⁻⁶. 18 cm -3 ; S3. Epitaxially grow the first contact layer 3 on the InAs buffer layer 2: sequentially grow an 8ML InAs layer, a 0.34ML first GaAs layer, a 7.32ML GaSb layer, and a 0.34ML second GaAs layer, using Si doping with a doping concentration of 3×10⁻⁶. 18 cm -3 Repeat the steps 50 times; the total growth thickness is approximately 0.24 μm. S4. Epitaxially grow the first absorption layer 4 on the first contact layer 3: sequentially grow an 8ML InAs layer, a 0.34ML first GaAs layer, a 7.32ML GaSb layer, and a 0.34ML second GaAs layer, using Si doping with a doping concentration of 1×10⁻⁶. 15 cm -3Repeat the steps 600 times, and the total growth thickness is approximately 2.9 μm. S5. Epitaxially grow barrier layer 5 on first absorber layer 4: grow 4ML InAs layer, 0.43ML first GaAs layer, 9.14ML GaSb layer and 0.43ML second GaAs layer in sequence, without doping; repeat step 50 times, the total growth thickness is about 0.21μm; S6. Epitaxially grow the second absorption layer 6 on the barrier layer 5: sequentially grow a 16ML InAs layer, a 0.34ML first GaAs layer, a 7.32ML GaSb layer, and a 0.34ML second GaAs layer, using Si doping with a doping concentration of 1×10⁻⁶. 15 cm -3 Repeated 350 times, the total thickness is approximately 2.5 μm; S7. Epitaxially grow the second contact layer 7 on the second absorber layer 6; sequentially grow a 16 mL InAs layer, a 0.34 mL first GaAs layer, a 7.32 mL GaSb layer, and a 0.34 mL second GaAs layer, using Si doping with a doping concentration of 1 × 10⁻⁶. 18 cm-3; repeated 30 times, with a total thickness of approximately 0.22 μm; S8: A cap layer 8 is epitaxially grown on the second contact layer 7: a 0.1 μm InAs layer is grown using Si doping with a doping concentration of 3 × 10⁻⁶. 18 cm -3 ; Obtain InAs-based epitaxial wafers that can be used to fabricate dual-color infrared detectors.

[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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-color infrared detector, characterized in that: It includes an InAs substrate and a buffer layer, a first contact layer, a first absorption layer, a barrier layer, a second absorption layer, a second contact layer, and a cap layer grown sequentially from bottom to top on the InAs substrate; the first absorption layer and the second absorption layer each include a number of periods of InAs / GaAs / GaSb / GaAs superlattices.

2. The dual-color infrared detector as described in claim 1, characterized in that: The InAs / GaAs / GaSb / GaAs superlattice comprises an InAs layer, a first GaAs layer, a GaSb layer, and a second GaAs layer grown epitaxially in sequence; the thickness of the InAs layer in the first absorption layer is different from the thickness of the InAs layer in the second absorption layer, and the thicknesses of the first GaAs layer, GaSb layer, and second GaAs layer in the first absorption layer are the same as the thicknesses of the first GaAs layer, GaSb layer, and second GaAs layer in the second absorption layer, respectively.

3. The dual-color infrared detector as described in claim 2, characterized in that: The thickness of the InAs layer in the first absorption layer is x ML, and the thickness of the InAs layer in the second absorption layer is y ML; the thicknesses of the first GaAs layer, the GaSb layer, and the second GaAs layer in the first and second absorption layers are 0.043n ML, 0.914n ML, and 0.043n ML, respectively; where x, y, and n are integers, and 7≤x≤11, 14≤y≤18, and 7≤n≤11.

4. The dual-color infrared detector as described in claim 2 or 3, characterized in that: The barrier layer comprises several periods of InAs / GaAs / GaSb / GaAs superlattices, and the thickness of the InAs layer in the barrier layer is less than the thickness of the InAs layer in the first absorption layer and the second absorption layer.

5. The dual-color infrared detector as described in claim 4, characterized in that: The thicknesses of the InAs layer, the first GaAs layer, the GaSb layer, and the second GaAs layer in the barrier layer are z ML, 0.043(n+t) ML, 0.914(n+t) ML, and 0.043(n+t) ML, respectively; where z, n, and t are integers, and 3≤z≤5, 7≤n≤11, and 0≤t≤2.

6. The dual-color infrared detector as described in claim 1, characterized in that: Both the first and second absorption layers have a thickness of 2–4 μm, are n-type doped, and have a doping concentration of 1 × 10⁻⁶. 15 ~3×10 15 cm -3 .

7. The dual-color infrared detector as described in claim 6, characterized in that: The barrier layer has a thickness of 0.15–0.4 μm and is undoped.

8. The dual-color infrared detector as described in claim 2 or 3, characterized in that: Both the first contact layer and the second contact layer include several periods of InAs / GaAs / GaSb / GaAs superlattices, and the thickness of each layer of the superlattice of the first contact layer is the same as the thickness of each layer of the superlattice of the first absorption layer, and the thickness of each layer of the superlattice of the second contact layer is the same as the thickness of each layer of the superlattice of the second absorption layer.

9. The dual-color infrared detector as described in claim 8, characterized in that: The thickness of both the first and second contact layers is 0.2–0.5 μm, the doping type is n-type, and the doping concentration is 1 × 10⁻⁶. 18 ~3×10 18 cm -3 .

10. The dual-color infrared detector as described in claim 1, characterized in that: Both the buffer layer and the cap layer are made of InAs material, and both are n-type doped.

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