Superlattice material for infrared detection and infrared detector

Abstract

The invention provides a superlattice material for infrared detection, which is formed by stacking a plurality of InAsN layers and a plurality of GaSb layers, and the InAsN layers and the GaSb layers are alternately stacked. The invention also provides an infrared detector structure with the superlattice material. Compared with an InAs / GaSb superlattice material in the prior art, the InAsN / GaSb superlattice material provided by the invention has the advantages that the conduction band energy level is obviously reduced, the effective bandwidth of the material is reduced, the cut-off wavelength of a detector is expanded, the InAsN / GaSb superlattice material can be used for a barrier layer of the superlattice detector, dark current can be inhibited, and the performance of the device can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical fields of optoelectronics and semiconductors. Specifically, it relates to a superlattice material for infrared detection and an infrared detector. Background Art

[0002] Infrared detection technology is widely used in fields such as satellite remote sensing, gas monitoring, optical communication, and spectral analysis. The antimonide InAs / GaSb type-II superlattice is a periodic structure composed of alternating thin layers of InAs and GaSb. As a third-generation cooled infrared detection material, the absorption wavelength can be flexibly adjusted from 2 μm to 30 μm by changing the thicknesses of InAs and GaSb. It has advantages such as low Auger recombination rate, small tunneling current, high absorption coefficient, and large wavelength tuning range, and has now entered the mass production stage.

[0003] However, for long-wave and very long-wave detection, the period of the InAs / GaSb superlattice is usually very thick, resulting in a weakened overlap of the electron-hole wave functions and a reduction in the absorption coefficient of the material. In addition, for long-wave and very long-wave superlattice detectors, in order to suppress the dark current and achieve high performance, a heterostructure including an electron barrier and a hole barrier is usually adopted. The hole barrier and the electron barrier are usually not the InAs / GaSb superlattice but a difficult-to-grow Al-containing material, which makes the device more complex and the yield of the device not high. Summary of the Invention

[0004] In order to solve the above technical problems existing in the prior art, according to an embodiment of the present invention, a superlattice material for infrared detection and an infrared detector are provided, which can better improve the absorption coefficient of the material and thus enhance the performance of the infrared detector.

[0005] The superlattice material for infrared detection provided by one aspect of the embodiment of the present invention is formed by laminating multiple InAsN layers and multiple GaSb layers, wherein the InAsN layers and the GaSb layers are alternately laminated.

[0006] In an example of the superlattice material provided by the above aspect, the N component in the InAsN layer is less than or equal to 3%, and the thickness is less than or equal to 10 nm.

[0007] In an example of the superlattice material provided by the above aspect, the thickness of the GaSb layer is less than or equal to 10 nm.

[0008] In an example of the superlattice material provided by the above aspect, the superlattice material is used to fabricate the electron barrier layer of the infrared detector; and / or, the superlattice material is used to fabricate the hole barrier layer of the infrared detector.

[0009] On the other hand, according to an embodiment of the present invention, the electron barrier layer and / or hole barrier layer of the infrared detector are formed of the above-mentioned superlattice material.

[0010] In an example of the infrared detector provided on the other hand above, the absorption layer of the infrared detector is formed of the superlattice material.

[0011] In an example of the infrared detector provided on the other hand above, the infrared detector further includes: a P-type substrate, a P-type contact layer, and an N-type contact layer; wherein, the N-type contact layer, the hole barrier layer, the absorption layer, the electron barrier layer, and the P-type contact layer are sequentially stacked on the P-type substrate.

[0012] In an example of the infrared detector provided on the other hand above, the P-type substrate is a P-type InAs substrate or a P-type GaSb substrate.

[0013] In an example of the infrared detector provided on the other hand above, the P-type contact layer is a P-type GaAsSb layer, and / or the N-type contact layer is an N-type InAs layer.

[0014] In an example of the infrared detector provided on the other hand above, the P-type contact layer is a P-type GaSb layer, and / or the N-type contact layer is an N-type InAsN / GaSb superlattice.

[0015] Beneficial effects: Compared with the InAs / GaSb superlattice in the prior art, the superlattice material provided according to the embodiments of the present invention, that is, after doping N element into the existing InAs layer, has at least the following two advantages: First, the doping of N element can reduce the effective bandwidth of the superlattice and improve the absorption coefficient of the material. Because the doping of N element can reduce the bandwidth of InAs, at the same cut-off wavelength, the period thickness of the InAsN / GaSb superlattice can be reduced by more than half compared with the InAs / GaSb superlattice, greatly improving the absorption coefficient of the material and the quantum efficiency of the device.

[0016] Second, the doping of N element reduces the height of the conduction band of the superlattice, that is, it can effectively control the electron energy level of the superlattice. In this way, ideal electron barriers and hole barriers can be achieved by adjusting the composition of N element, and together with the superlattice absorption region, a detector with a heterostructure is formed, which can suppress dark current and improve device performance. Description of the Drawings

[0017] Through the following description in conjunction with the drawings, the above and other aspects, features, and advantages of the embodiments of the present invention will become clearer. In the drawings: Figure 1Schematic diagram of the energy band alignment of an InAsN / GaSb superlattice according to an embodiment of the present invention; Figure 2 Schematic diagram showing the relationship between the period thickness and the cut-off wavelength of an InAs / GaSb superlattice of the prior art and an InAsN / GaSb superlattice according to an embodiment of the present invention; Figure 3 Schematic diagram of the structure of an infrared detector according to an embodiment of the present invention. Detailed implementation manners

[0018] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and should not be construed as limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and its practical applications, so that other technical personnel in the art can understand various embodiments of the present invention and various modifications suitable for specific intended applications.

[0019] As used herein, the term "comprising" and its variants represent open terms, meaning "including but not limited to". Terms such as "based on", "according to" mean "at least partially based on", "at least partially according to". Terms such as "embodiment", "an example", "an embodiment" and "one embodiment" mean "at least one embodiment". Terms such as "another embodiment", "another embodiment", "another example", "yet another example" mean "at least one other embodiment". Terms such as "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless explicitly specified in the context, the definition of a term is consistent throughout the specification.

[0020] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details of little relevance are omitted.

[0021] As described in the background art, InAs / GaSb superlattice materials are currently important mid- and long-wave infrared detection materials. However, in the long-wave and very long-wave bands, due to the increase in the period thickness of the InAs / GaSb superlattice, the overlap of the electron-hole wave functions is weakened, thereby reducing the absorption coefficient of the material and decreasing the quantum efficiency of long-wave infrared detectors.

[0022] Therefore, in order to solve the above technical problems, an InAsN / GaSb superlattice material for infrared detection is proposed according to an embodiment of the present invention.

[0023] Figure 1Schematic diagram of the energy band alignment of an InAsN / GaSb superlattice according to an embodiment of the present invention.

[0024] Referring to Figure 1 , it can be seen that GaSb and InAsN form a type-II energy band alignment, where the valence band of GaSb is higher than the conduction band of InAsN. When thin layers of the two materials are alternately repeated to form a superlattice and form minibands (as shown by the dashed lines), the electron miniband E c is determined by the conduction band energy level of InAsN, while the hole miniband E v is determined by the valence band energy level of GaSb. Compared with the InAs / GaSb superlattice of the prior art, according to an embodiment of the present invention, N (nitrogen) is doped into the InAs thin layer. After a small number of N atoms replace As atoms, the bandwidth of the InAsN material will be significantly reduced. More importantly, the reduction in bandwidth mainly occurs in the conduction band, and the conduction band of InAsN is lower than that of InAs. This makes the electron energy level E c of the miniband of the InAsN / GaSb superlattice decrease significantly while the hole energy level E v remains basically unchanged. In this way, the effective bandwidth of the superlattice is reduced under the condition of the same superlattice period thickness. At the same time, the characteristic of regulating the conduction band energy level of the superlattice by doping with N element can also be used in energy band engineering. Combining with the change of the superlattice thickness, it can provide an ideal hole barrier and electron barrier for the absorption region of the InAsN / GaSb superlattice, forming a high-performance heterojunction detector.

[0025] To make the above physical picture clearer, the inventors have carried out and provided relevant theoretical calculation evidence.

[0026] Figure 2 is a schematic diagram showing the relationship between the period thickness and the cut-off wavelength of the InAs / GaSb superlattice of the prior art and the InAsN / GaSb superlattice according to an embodiment of the present invention. It should be noted that in Figure 2 , the content of As is not marked. It should be understood that the sum of the content of As and the content of N is 1, that is, the content of N is 0.01 and the content of As is 0.99; the content of N is 0.02 and the content of As is 0.98; the content of N is 0.03 and the content of As is 0.97; and so on.

[0027] Referring to Figure 2 , the N composition of InAsN includes three types: 1%, 2%, and 3%. It can be seen that for long-wave detection with a cut-off wavelength of 9 μm, the period thickness of the InAs / GaSb superlattice is the largest, reaching 28 atomic monolayers (about 8.4 nm). And the period thickness of the InAsN / GaSb superlattice proposed according to an embodiment of the present invention is significantly reduced. Taking InAs 0.98 N 0.02For example, the period thickness of the InAsN / GaSb superlattice is only 13 atomic monolayers (about 3.9 nm), which is much smaller than that of the InAs / GaSb superlattice. Therefore, the absorption coefficient of the InAsN / GaSb superlattice material is significantly increased, and the quantum efficiency of the corresponding infrared detector is significantly improved.

[0028] The following will detail an infrared detector using the InAsN / GaSb superlattice according to the embodiments of the present invention.

[0029] Figure 3 It is a schematic structural diagram of an infrared detector according to an embodiment of the present invention.

[0030] Refer to Figure 3 According to an embodiment of the present invention, the infrared detector includes: a P-type substrate 10, a P-type contact layer 11, an electron barrier layer 12, an absorption layer 13, a hole barrier layer 14, and an N-type contact layer 15; the N-type contact layer 15, the hole barrier layer 14, the absorption layer 13, the electron barrier layer 12, and the P-type contact layer 11 are sequentially stacked on the P-type substrate 10.

[0031] Specifically, in an example of the infrared detector according to an embodiment of the present invention: The P-type substrate 10 is a P-type InAs material with a thickness of 500 μm and a doping concentration of 1×10 16 cm -3 .

[0032] The P-type contact layer 11 is a P-type GaAsSb material with a thickness of 200 nm and a doping concentration of 1×10 18 cm -3 .

[0033] The electron barrier layer 12 is a P-type InAsN / GaSb superlattice, where the N element is 1%, the thickness of the InAsN layer is 1 nm, and the thickness of the GaSb layer is 3 nm; the doping concentration of the electron barrier layer 12 is 1×10 18 cm -3 ; the number of periods of the electron barrier layer 12 is 60 periods, where one period includes one layer of InAsN layer and one layer of GaSb layer.

[0034] The absorption layer 13 is a P-type InAsN / GaSb superlattice, where the N element is 1%, the thickness of the InAsN layer is 3 nm, and the thickness of the GaSb layer is 3 nm; the doping concentration of the absorption layer 13 is 2×10 15 cm -3 ; the number of periods of the absorption layer 13 is 400 periods.

[0035] The hole barrier layer 14 is an undoped InAsN / GaSb superlattice, where the N element is 2%, the thickness of the InAsN layer is 3 nm, and the thickness of the GaSb layer is 2 nm; the number of periods of the hole barrier layer 14 is 100 periods.

[0036] The N-type contact layer 15 is an N-type InAs material with a thickness of 200 μm and a doping concentration of 1×10 18 cm -3 。

[0037] Therefore, the infrared detector according to the above example has a double heterojunction structure, where the electron barrier is formed by reducing the thickness of the InAsN layer, and the hole barrier is formed by increasing the N component (both relative to the InAsN / GaSb absorption layer). The cut-off wavelength of the absorption region is 10 μm, belonging to a long-wave detector. It can be prepared by metal organic chemical vapor deposition (MOCVD) process, and the product has high cost performance.

[0038] In addition, in another example of the infrared detector according to the embodiment of the present invention: The P-type substrate 10 is a P-type GaSb material with a thickness of 500 μm and a doping concentration of 2×10 16 cm -3 。

[0039] The P-type contact layer 11 is a P-type GaSb material with a thickness of 200 nm and a doping concentration of 5×10 18 cm -3 。

[0040] The electron barrier layer 12 is a P-type InAsN / GaSb superlattice, where the N element is 2%, the thickness of the InAsN layer is 2 nm, and the thickness of the GaSb layer is 2 nm; the doping concentration of the electron barrier layer 12 is 2×10 18 cm -3 ; the number of periods of the electron barrier layer 12 is 100 periods, where one period includes one layer of InAsN layer and one layer of GaSb layer.

[0041] The absorption layer 13 is a P-type InAsN / GaSb superlattice, where the N element is 2%, the thickness of the InAsN layer is 4 nm, and the thickness of the GaSb layer is 2 nm; the doping concentration of the absorption layer 13 is 2×10 16 cm -3 ; the number of periods of the absorption layer 13 is 600 periods.

[0042] The hole barrier layer 14 is an undoped InAsN / GaSb superlattice, where the N element is 3%, the thickness of the InAsN layer is 3 nm, and the thickness of the GaSb layer is 2 nm; the number of periods of the hole barrier layer 14 is 80 periods.

[0043] The N-type contact layer 15 is an N-type InAsN / GaSb superlattice, where the N element is 3%, the thickness of the InAsN layer is 3 nm, and the thickness of the GaSb layer is 2 nm; the doping concentration of the N-type contact layer 15 is 2×10 18 cm -3 ; the number of periods of the N-type contact layer 15 is 80 periods.

[0044] Therefore, the infrared detector according to another example above is also a double heterojunction structure, with a cut-off wavelength of 15 μm, belonging to a very long wavelength detector, and can be prepared by molecular beam epitaxy (MBE) process, with high product performance.

[0045] In summary, in the InAsN / GaSb superlattice according to the embodiment of the present invention, the incorporation of the N element can reduce the effective bandwidth of the superlattice and improve the absorption coefficient of the material. Because the incorporation of the N element can reduce the InAs bandwidth, at the same cut-off wavelength, the period thickness of the InAsN / GaSb superlattice can be reduced by more than half compared with the InAs / GaSb superlattice, greatly improving the absorption coefficient of the material and the quantum efficiency of the device.

[0046] Furthermore, the incorporation of the N element reduces the height of the conduction band of the superlattice, that is, it can effectively control the electron energy level of the superlattice. In this way, the ideal electron barrier and hole barrier can be achieved by adjusting the N element composition, and together with the superlattice absorption region, it forms a detector with a heterostructure, which can suppress dark current and improve device performance.

[0047] The terms "exemplary", "example", etc. used throughout this specification mean "serving as an example, instance, or illustration", and do not mean "preferred" or "having an advantage" over other embodiments. For the purpose of providing an understanding of the described technology, the specific embodiments include specific details. However, these technologies can be implemented without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described embodiments.

[0048] The optional embodiments of the embodiments of the present invention have been described in detail above with reference to the drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

[0049] The foregoing description of the content of this specification is provided to enable any person of ordinary skill in the art to make or use the content of this specification. Various modifications to the content of this specification will be apparent to persons of ordinary skill in the art, and the general principles defined herein can be applied to other variations without departing from the scope of protection of the content of this specification. Therefore, the content of this specification is not limited to the examples and designs described herein, but is consistent with the broadest scope that conforms to the principles and novel features disclosed herein.

Claims

1. A superlattice material for infrared detection, characterized in that: The superlattice material is formed by stacking multiple InAsN layers and multiple GaSb layers, wherein the InAsN layers and the GaSb layers are stacked alternately.

2. The superlattice material according to claim 1, characterized in that: The N component in the InAsN layer is less than or equal to 3%, and the thickness is less than or equal to 10 nm.

3. The superlattice material according to claim 1 or 2, characterized in that: The thickness of the GaSb layer is less than or equal to 10 nm.

4. The superlattice material according to claim 1, characterized in that: The superlattice material is used to make an electron barrier layer that forms an infrared detector; and / or, the superlattice material is used to make a hole barrier layer that forms the infrared detector.

5. An infrared detector, characterized in that: The electron barrier layer and / or hole barrier layer of the infrared detector is formed by the superlattice material according to any one of claims 1 to 3.

6. The infrared detector according to claim 5, characterized in that: The absorption layer of the infrared detector is formed by the superlattice material.

7. The infrared detector according to claim 6, characterized in that: The infrared detector further includes: a P-type substrate, a P-type contact layer and an N-type contact layer; wherein the N-type contact layer, the hole barrier layer, the absorption layer, the electron barrier layer and the P-type contact layer are sequentially stacked on the P-type substrate.

8. The infrared detector according to claim 7, characterized in that: The P-type substrate is a P-type InAs substrate or a P-type GaSb substrate.

9. The infrared detector according to claim 8, characterized in that: The P-type contact layer is a P-type GaAsSb layer, and / or the N-type contact layer is an N-type InAs layer.

10. The infrared detector according to claim 8, characterized in that: The P-type contact layer is a P-type GaSb layer, and / or the N-type contact layer is an N-type InAsN / GaSb superlattice.

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