NBn type infrared detector material and preparation method thereof

Abstract

The invention provides an nBn type infrared detector material which comprises a substrate, and a buffer layer, a lower contact layer, an electron barrier layer, an absorption layer, an upper contact layer and a cover layer which are grown on the substrate from bottom to top in sequence, a space charge region modulation layer is arranged between the electron barrier layer and the absorption layer, and the space charge region modulation layer is made of an N-type heavily-doped semiconductor material. According to the nBn-type infrared detector material, the N-type heavily doped superlattice space charge region modulation layer is inserted between the electron barrier layer and the absorption layer, expansion of a depletion region towards a narrow-band gap absorption region under reverse bias is blocked, the suppression effectiveness of an nBn structure on generated-composite dark current under reverse bias is ensured, N-type heavily doping is not carried out on the absorption layer, and the absorption efficiency is improved. The reduction of quantum efficiency is avoided, and the signal-to-noise ratio of the device is further improved; and moreover, the working bias voltage range of the device is increased, and the adaptability with a reading circuit is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor infrared detectors, and particularly relates to an nBn type infrared detector material and a preparation method thereof. BACKGROUND

[0002] Since the spontaneous radiation band of atmospheric background and ground objects in the environment is mainly located in the infrared range, the infrared detector can better perceive the environment. And the longer wavelength of infrared radiation makes it have strong ability to penetrate smoke and water mist, so it performs better in various complex environments. Based on the above characteristics, the infrared detector is widely used in military and civilian fields due to its night vision ability, 24-hour all-weather working ability, strong smoke and water mist penetration ability and other characteristics.

[0003] An infrared detector with high signal-to-noise ratio needs to have low dark current density and high quantum efficiency at the same time. At the working temperature, the dominant dark current component of the traditional homojunction infrared detector is generation-recombination (G-R) dark current. In the nBn structure, by introducing the depletion region into the wide-bandgap barrier (B) layer, the generation-recombination dark current can be better suppressed under small bias. However, the nBn structure is a combination of photovoltaic and photoconductive devices, and compared with the traditional photovoltaic device, a larger opening bias is needed, but the application of reverse bias will cause the depletion region to expand to the narrow-bandgap absorption region, resulting in the weakening or even failure of the nBn structure to suppress the generation-recombination current. In view of this, the existing technology will highly dope the entire absorption region to avoid this problem, but high doping of the absorption region will also reduce the quantum efficiency, ultimately reducing the signal-to-noise ratio of the infrared detector.

[0004] Therefore, how to ensure the better dark current suppression effect of the nBn structure while not reducing the quantum efficiency of the device is a technical problem to be solved. SUMMARY

[0005] The purpose of the present application is to provide an nBn type infrared detector material, which can at least solve some of the defects in the prior art.

[0006] To achieve the above purpose, the present application adopts the following technical scheme:

[0007] An nBn type infrared detector material, comprising a substrate, and a buffer layer, a lower contact layer, an electron barrier layer, an absorption layer, an upper contact layer and a cap layer grown in order from bottom to top on the substrate; a space charge region modulation layer is arranged between the electron barrier layer and the absorption layer, and the space charge region modulation layer is a heavily doped N-type semiconductor material.

[0008] Further, the doping concentration of the space charge region modulation layer is 1×10 17 ~ 5×10 18 cm-3 The thickness is 100-300nm.

[0009] Further, the semiconductor material of the space charge region modulation layer is consistent with the material of the absorption layer.

[0010] Further, the lower contact layer is N-type heavily doped semiconductor material, the material band gap is 0.124-375meV, the doping concentration is 1×10 18 -2×10 18 cm -3 , and the thickness is 100-200nm.

[0011] Further, the electron barrier layer is non-intentionally doped semiconductor material, the material band gap is greater than 0.45meV, and the thickness is 200-400nm.

[0012] Further, the absorption layer is non-intentionally doped semiconductor material, the material band gap is 0.124-375meV, and the thickness is 2000-3000nm.

[0013] Further, the upper contact layer is N-type heavily doped semiconductor material, the material band gap is 0.124-375meV, the doping concentration is 1×10 18 -2×10 18 cm -3 , and the thickness is 100-300nm.

[0014] Further, the cap layer is N-type heavily doped semiconductor material, the doping concentration is 1×10 18 -2×10 18 cm -3 , and the thickness is 10-20nm.

[0015] Further, the lower contact layer, the space charge region modulation layer, the absorption layer and the upper contact layer adopt the same kind, component and thickness ratio of semiconductor material.

[0016] In addition, the application further provides a preparation method of the nBn type infrared detector material, which comprises sequentially growing a buffer layer, a lower contact layer, an electron barrier layer, a space charge region modulation layer, an absorption layer, an upper contact layer and a cap layer on a substrate by using a molecular beam epitaxy method or a metal organic chemical vapor deposition method.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The nBn type infrared detector material provided by the application blocks the expansion of the depletion region towards the narrow band gap absorption region under reverse bias by inserting the N type heavily doped superlattice space charge region modulation layer between the electron barrier layer and the absorption layer, ensures the effectiveness of the nBn structure in inhibiting the generation-recombination dark current under reverse bias, avoids the N type heavy doping of the absorption layer, avoids the reduction of quantum efficiency, and further improves the signal-to-noise ratio of the device; and increases the working bias range of the device and improves the adaptability to the readout circuit.

[0019] The application will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structure diagram of the nBn type infrared detector material of the application;

[0021] Figure 2 is a band diagram of the nBn type infrared detector material of the application;

[0022] Figure 3 is a comparison diagram of the current density and bias voltage curves of the infrared detector of example 1 and comparative example 1.

[0023] The reference signs are explained as follows: 1, substrate; 2, buffer layer; 3, lower contact layer; 4, electron barrier layer; 5, space charge region modulation layer; 6, absorption layer; 7, upper contact layer; 8, cover layer. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0025] In the description of the application, it should be understood that the terms “center”, “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer” and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0026] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or abutment connection or integral connection; for those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] As Figure 1 shown, the present application provides an nBn type infrared detector material, comprising a substrate, and a buffer layer, a lower contact layer, an electron barrier layer, an absorption layer, an upper contact layer and a cap layer grown on the substrate in turn from bottom to top; a space charge region modulation layer is arranged between the electron barrier layer and the absorption layer, and the space charge region modulation layer is an N-type heavily doped semiconductor material.

[0028] The built-in electric field of the nBn structure under reverse bias is formed by the accumulation region of the contact layer and the depletion region of the electron barrier layer and the absorption layer, and the built-in electric field intensity of the nBn structure under reverse bias is strengthened, and the depletion region boundary will expand to the narrow band gap absorption layer, and based on the electric neutrality condition, the width of the space charge region expanding in the absorption region is inversely proportional to the doping concentration of the absorption region, based on this, in the present application, an N-type heavily doped superlattice space charge region modulation layer is inserted between the electron barrier layer and the absorption layer to reduce the width of the depletion region expansion, thereby blocking the expansion of the depletion region to the narrow band gap absorption layer under reverse bias, ensuring the effectiveness of the nBn structure under reverse bias in inhibiting the generation-recombination dark current, without N-type heavy doping of the absorption layer, avoiding the reduction of quantum efficiency, and further improving the signal-to-noise ratio of the device; and by inserting the N-type heavily doped superlattice space charge region modulation layer between the electron barrier layer and the absorption layer, the working bias range of the device is increased, and the adaptability to the readout circuit is improved.

[0029] Specifically, the doping concentration of the space charge region modulation layer is 1×10 17 ~ 5×10 18 cm -3 , and the thickness is 100~300nm; preferably, the semiconductor material used in the space charge region modulation layer is consistent with the material of the absorption layer. In some embodiments, the space charge region modulation layer is an N-type heavily doped InAs / GaSb superlattice, which is composed of 39~45Å InAs and 20~22Å GaSb per period; in other embodiments, the space charge region modulation layer can also be an InAs / InAsSb superlattice.

[0030] Specifically, the lower contact layer is an N-type heavily doped semiconductor material, the material band gap is 0.124~375meV, and the doping concentration is 1×10 18 ~ 2×10 18 cm-3 The lower contact layer is a heavily doped semiconductor material with a material band gap of 0.124-375 meV and a doping concentration of 1 x 1018-2 x 1020cm-3, and a thickness of 100-300 nm. The electron barrier layer is a non-intentionally doped semiconductor material with a material band gap greater than 0.45 meV and a thickness of 200-400 nm. The absorption layer is a non-intentionally doped semiconductor material with a material band gap of 0.124-375 meV and a thickness of 2000-3000 nm. The upper contact layer is an N-type heavily doped semiconductor material with a material band gap of 0.124-375 meV and a doping concentration of 1 x 1018-2 x 1020cm-3, and a thickness of 100-300 nm. The cap layer is an N-type heavily doped semiconductor material with a doping concentration of 1 x 1018-2 x 1020cm-3 and a thickness of 10-20 nm. In the nBn-type infrared detector material, the semiconductor materials in each layer are selected according to the specific requirements of the infrared device detection wave band; for example, for a mid-wave infrared detector, the lower contact layer, the electron barrier layer, the absorption layer, and the upper contact layer can be selected from, but not limited to, InAs / GaSb, InAs / InAsSb, InSb, InAsSb, and the like; for a long-wave infrared detector, the lower contact layer, the electron barrier layer, the absorption layer, and the upper contact layer can be selected from, but not limited to, InAs / GaSb, InAs / InAsSb, and the like. 18 18 -3 18 18 -3 In the nBn-type infrared detector material, the semiconductor materials in each layer are selected according to the specific requirements of the infrared device detection wave band; for example, for a mid-wave infrared detector, the lower contact layer, the electron barrier layer, the absorption layer, and the upper contact layer can be selected from, but not limited to, InAs / GaSb, InAs / InAsSb, InSb, InAsSb, and the like; for a long-wave infrared detector, the lower contact layer, the electron barrier layer, the absorption layer, and the upper contact layer can be selected from, but not limited to, InAs / GaSb, InAs / InAsSb, and the like.

[0031] Further preferably, the lower contact layer, the space charge region modulation layer, the absorption layer, and the upper contact layer all adopt the same kind, component, and thickness ratio of semiconductor materials, and the growth process parameters are also consistent; through this design, the lattices of each layer can be matched, interface defects, dislocations, and stress caused by lattice mismatch are avoided, the scattering and recombination of carriers at the interface are reduced, the carrier transport efficiency is improved, the dark current is reduced, and the functions of each layer can be flexibly designed by adjusting only the doping concentration and type, thereby simplifying the performance optimization design process of each layer.

[0032] The preparation process and effects of the nBn-type infrared detector material are described below through some specific embodiments.

[0033] Embodiment 1: This embodiment provides a long-wave nBn-type infrared detector material with a space charge region modulation layer. The structure of the infrared detector material from bottom to top is a substrate, a buffer layer, a lower contact layer, an electron barrier layer, a space charge region modulation layer, an absorption layer, an upper contact layer, and a cap layer.

[0034] ​​​​​The substrate is a GaSb substrate, the substrate thickness is 520 μm; the buffer layer is GaSb, the buffer layer thickness is 300 nm; the lower contact layer is N-type heavily doped InAs / GaSb superlattice, each period is composed of 42 Å InAs and 21 Å GaSb, the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; the electron barrier layer is unintentionally doped InAs / GaSb superlattice, each period is composed of 10 Å InAs and 26 Å GaSb, the thickness is 300 nm; the space charge region modulation layer is N-type heavily doped InAs / GaSb superlattice, each period is composed of 42 Å InAs and 21 Å GaSb, the doping concentration is 1×10 17 cm -3 , and the thickness is 200 nm; the absorption layer is unintentionally doped InAs / GaSb superlattice, each period is composed of 42 Å InAs and 21 Å GaSb, the thickness is 2000 nm; the upper contact layer is N-type heavily doped InAs / GaSb superlattice, each period is composed of 42 Å InAs and 21 Å GaSb, the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; the cap layer is N-type heavily doped InAs, the doping concentration is 1×10 18 cm -3 , and the thickness is 10 nm.

[0035] The long-wave nBn type infrared detector material of the embodiment is prepared by a molecular beam epitaxy (MBE) method, and the specific process is as follows:

[0036] (1) growing a buffer layer on a clean substrate after removing the oxide;

[0037] (2) growing a lower contact layer on the buffer layer prepared in step (1);

[0038] (3) growing an electron barrier layer on the lower contact layer prepared in step (2);

[0039] (4) growing a space charge region modulation layer on the electron barrier layer prepared in step (3);

[0040] (5) growing an absorption layer on the space charge region modulation layer prepared in step (4);

[0041] (6) growing an upper contact layer on the absorption layer prepared in step (5);

[0042] (7) growing a cap layer on the upper contact layer prepared in step (6), thereby preparing an nBn type infrared detector material.

[0043] The growth source used in the epitaxial growth process is solid single element source In, Ga, As, Sb, the N-type doping source is Si, and the P-type doping source is Be; the epitaxial growth technology is prior art, and the specific operation process will not be repeated here.

[0044] Embodiment 2: The embodiment provides a medium-wave nBn type infrared detector material with a space charge region modulation layer. The infrared detector material structure is sequentially formed from bottom to top by a substrate, a buffer layer, a lower contact layer, an electron barrier layer, a space charge region modulation layer, an absorption layer, an upper contact layer, and a cap layer.

[0045] The substrate is a GaSb substrate, and the substrate thickness is 520 μm; the buffer layer is GaSb, and the buffer layer thickness is 300 nm; the lower contact layer is N-type heavily doped InAs / InAsSb superlattice, each period of which is composed of 35 Å InAs and 15 Å InAsSb, and the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; the electron barrier layer is unintentionally doped AlAs 0.09 Sb 0.91 ternary alloy, and the thickness is 300 nm; the space charge region modulation layer is N-type heavily doped InAs / InAsSb superlattice, each period of which is composed of 35 Å InAs and 15 Å InAsSb, and the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; the absorption layer is unintentionally doped InAs / InAsSb superlattice, each period of which is composed of 35 Å InAs and 15 Å InAsSb, and the thickness is 2000 nm; the upper contact layer is N-type heavily doped InAs / InAsSb superlattice, each period of which is composed of 35 Å InAs and 15 Å InAsSb, and the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; and the cap layer is N-type heavily doped InAs, the doping concentration is 1×10 18 cm -3 , and the thickness is 10 nm.

[0046] The medium-wave nBn type infrared detector material of the embodiment is prepared by a molecular beam epitaxy (MBE) method, and the specific process is as follows:

[0047] (1) growing a buffer layer on a clean substrate after removing the oxide;

[0048] (2) growing a lower contact layer on the buffer layer prepared in step (1);

[0049] (3) growing an electron barrier layer on the lower contact layer prepared in step (2);

[0050] (4) growing a space-charge region modulation layer on the electron barrier layer prepared in step (3);

[0051] (5) growing an absorption layer on the space-charge region modulation layer prepared in step (4);

[0052] (6) growing an upper contact layer on the absorption layer prepared in step (5);

[0053] (7) growing a cap layer on the upper contact layer prepared in step (6), thereby preparing an nBn type infrared detector material.

[0054] The growth sources used in the above epitaxial growth process are solid elemental sources In, Ga, As, and Sb, the N-type doping source is Si, and the P-type doping source is Be; the epitaxial growth technology is prior art, and its specific operation process will not be described here.

[0055] Embodiment 3: This embodiment provides a long-wave nBn type infrared detector material with a space-charge region modulation layer, which has a structure from bottom to top as follows: a substrate, a buffer layer, a lower contact layer, an electron barrier layer, a space-charge region modulation layer, an absorption layer, an upper contact layer, and a cap layer.

[0056] The substrate is a GaSb substrate, and the substrate thickness is 520 μm; the buffer layer is GaSb, and the buffer layer thickness is 300 nm; the lower contact layer is N-type heavily doped InAs / GaSb superlattice, each period of which is composed of 42 Å InAs and 21 Å GaSb, and the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; the electron barrier layer is unintentionally doped InAs / GaSb superlattice, each period of which is composed of 10 Å InAs and 26 Å GaSb, and the thickness is 300 nm; the space-charge region modulation layer is N-type heavily doped InAs / GaSb superlattice, each period of which is composed of 42 Å InAs and 21 Å GaSb, and the doping concentration is 1×10 17 cm -3 , and the thickness is 200 nm; the absorption layer is unintentionally doped InAs / GaSb superlattice, each period of which is composed of 42 Å InAs and 21 Å GaSb, and the thickness is 2000 nm; the upper contact layer is N-type heavily doped InAs / GaSb superlattice, each period of which is composed of 42 Å InAs and 21 Å GaSb, and the doping concentration is 1×10 18 cm -3 , and the thickness is 200 nm; and the cap layer is N-type heavily doped InAs, and the doping concentration is 1×10 18 cm -3 , and the thickness is 10 nm.

[0057] The nBn type infrared detector material of the embodiment is prepared by metal organic chemical vapor deposition (MOCVD), and the specific process is as follows:

[0058] (1) growing a buffer layer on a clean substrate after removing oxides;

[0059] (2) growing a lower contact layer on the buffer layer prepared in step (1);

[0060] (3) growing an electron barrier layer on the lower contact layer prepared in step (2);

[0061] (4) growing a space charge region modulation layer on the electron barrier layer prepared in step (3);

[0062] (5) growing an absorption layer on the space charge region modulation layer prepared in step (4);

[0063] (6) growing an upper contact layer on the absorption layer prepared in step (5);

[0064] (7) growing a cap layer on the upper contact layer prepared in step (6) to prepare an nBn type infrared detector material.

[0065] The growth sources used in the above MOCVD growth process are TMIn, TMGa, TMSb, AsH3 and PH3, the N-type doping source is SiH4, and the P-type doping source is DEZn. The MOCVD technology is prior art, and its specific operation process will not be repeated here.

[0066] Comparative Example 1

[0067] The nBn type infrared detector material of the comparative example has substantially the same structure and preparation process as the nBn type infrared detector material of the above embodiment 1, except that no space charge region modulation layer is grown between the electron barrier layer and the absorption layer of the comparative example.

[0068] The nBn type infrared detector material of the comparative example and the nBn type infrared detector material of embodiment 1 are used to prepare infrared detector devices, and the performance of the infrared detector devices is tested, and the test results are shown in Table 1. Figure 3

[0069] As shown in Table 1. Figure 3 ​It can be seen that the infrared detecting device without the space charge region modulation layer (i.e. the comparative example 1) has a clear upward trend of the current with the increase of the reverse bias, indicating that the infrared detecting device without the space charge region modulation layer cannot effectively suppress the generation-recombination dark current and the trap-assisted tunneling dark current. The infrared detecting device with the space charge region modulation layer of the present application has a lower dark current level after the reverse bias of -0.1 V, and the dark current has a clear platform characteristic in the whole bias range, indicating that the infrared detecting device with the space charge region modulation layer effectively suppresses the generation-recombination dark current and the trap-assisted tunneling dark current.

[0070] The above examples are only illustrative of the present application, and do not constitute a limitation on the protection scope of the present application, and any design identical or similar to the present application falls within the protection scope of the present application.

Claims

1. An nBn infrared detector material, characterized by: The substrate and the buffer layer, the lower contact layer, the electron barrier layer, the absorbing layer, the upper contact layer and the cover layer are sequentially grown from bottom to top on the substrate; the space charge region modulation layer is arranged between the electron barrier layer and the absorbing layer, and the space charge region modulation layer is N-type heavily doped semiconductor material.

2. The nBn infrared detector material of claim 1, wherein: The doping concentration of the space charge region modulation layer is 1×10 17 ~5×10 18 cm -3 , and the thickness is 100~300nm.

3. The nBn infrared detector material of claim 1, wherein: The semiconductor material used by the space charge region modulation layer is consistent with the material of the absorbing layer.

4. The nBn infrared detector material of claim 1, wherein: The lower contact layer is N-type heavily doped semiconductor material, material band gap is 0.124-375meV, doping concentration is 1x10 18 ~2x10 18 cm -3 , thickness is 100-200nm.

5. The nBn infrared detector material of claim 1, wherein: The electron barrier layer is unintentionally doped semiconductor material, the material band gap is greater than 0.45meV, and the thickness is 200-400nm.

6. The nBn infrared detector material of claim 1, wherein: The absorbing layer is unintentionally doped semiconductor material, the material band gap is 0.124-375meV, and the thickness is 2000-3000nm.

7. The nBn type infrared detector material as described in claim 1, characterized in that: The upper contact layer is N-type heavily doped semiconductor material, material band gap is 0.124-375meV, doping concentration is 1x10 18 ~2x10 18 cm -3 , thickness is 100-300nm.

8. The nBn infrared detector material of claim 1, wherein: The cap layer is N-type heavily doped semiconductor material, the doping concentration is 1×10 18 ~ 2×10 18 cm -3 , the thickness is 10~20nm.

9. An nBn infrared detector material as claimed in any one of claims 1 to 8, characterized in that: The lower contact layer, the space charge region modulation layer, the absorbing layer and the upper contact layer use the same kind, component and thickness ratio of semiconductor material.

10. A method of producing an nBn-type infrared detector material as claimed in any one of claims 1 to 9, characterized in that: The buffer layer, the lower contact layer, the electron barrier layer, the space charge region modulation layer, the absorbing layer, the upper contact layer and the cover layer are sequentially grown on the substrate by using molecular beam epitaxy method or metal organic chemical vapor deposition method.

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