A long-wave infrared detector with complementary barrier CBIRD structure

Abstract

The invention discloses a long-wave infrared detector with a complementary barrier CBIRD structure, belongs to the technical field of infrared detectors, and aims to provide a long-wave infrared detector with a complementary barrier CBIRD structure, introduces a newly designed hole barrier structure, the hole barrier reduces the tunneling related to traps, and the single-stage barrier Np junction between the hole barrier and the absorption layer reduces the SRH related dark current, and the electron barrier is combined to form a complementary barrier CBIRD structure, which solves the problems of high dark current and low responsivity / specific detection rate of InAs / InAsSb T2SL detectors in the prior art. It includes a substrate, and a buffer layer, a bottom contact-hole barrier layer, an absorption layer, an electron barrier layer, and a top contact layer are sequentially arranged on the upper surface of the substrate from bottom to top, and a bottom contact electrode is arranged on the upper surface of the bottom contact-hole barrier layer, and a top contact electrode is arranged on the upper surface of the top contact layer. The invention is applicable to a long-wave infrared detector with a complementary barrier CBIRD structure.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared detectors, and in particular relates to a long-wave infrared detector with a complementary barrier CBIRD structure. Background Art

[0002] In recent years, antimony-based type II superlattice (T2SL) materials have made great progress in epitaxial growth and optoelectronic properties. Among them, antimony-based type II superlattice InAs / InAsSb, as an infrared photosensitive material, has a stable structure, low dark current and high-temperature working characteristics, and excellent photoelectric conversion efficiency. It is an ideal material for the development of high-temperature infrared detectors. Among them, long-wave infrared with a wavelength range of 6-15μm has the advantages of wide range, strong penetration, high accuracy, and identification of camouflage and interference. Therefore, long-wave infrared detectors are widely used in air-to-ground, air-to-air long-range infrared systems, as well as ship-borne, seeker, airborne and other military weapons, and have extremely strong application value in the field of national defense and military.

[0003] The structures of T2SL infrared detectors mainly include PIN photodiodes and barrier structure photodetectors. PIN photodetectors are mainly composed of P-type, unintentionally doped I layers and N-type semiconductor materials. Such devices have high dark currents. Barrier photodetectors are used to reduce / suppress the dark current of devices, and mainly include NBN structure, PBN structure, p-π-Mn structure, CBIRD structure, pMp structure, etc. Among them, the complementary barrier (CBIRD) structure uses a pair of complementary hole barriers (hB) and electron barriers (eB) to sandwich the superlattice absorption layer in the middle, and has zero conduction band and zero valence band offsets relative to the absorption layer, respectively. The hole barrier reduces trap-related tunneling, and the single-stage barrier Np junction between the absorption layer reduces the SRH-related dark current. The electron barrier prevents additional electron injection from the bottom contact. Therefore, the CBIRD structure can significantly reduce band-to-band tunneling, GR and diffusion current, and design devices with zero turn-on bias and high QE. However, the hole barrier structure design of InAs / InAsSb T2SL is still difficult to achieve. The barrier structure of InAs / InAsSb T2SL detectors is mainly concentrated on NBN structure, while InAs / InAsSb T2SL detectors based on CBIRD structure are rarely reported. The main reason is that the existing wide bandgap bulk materials containing aluminum (Al) components and their superlattice structures have a large conduction band offset and a small valence band offset with the InAs / InAsSb T2SL absorption region, and cannot form a large valence band barrier with the InAs / InAsSb absorption region material, so they cannot be used to design the hole barrier of InAs / InAsSb T2SL detectors. This is not conducive to further reducing / suppressing the dark current of InAs / InAsSb T2SL detectors, especially long-wave infrared InAs / InAsSb T2SL detectors. Therefore, designing long-wave infrared InAs / InAsSb T2SL detectors with higher detection performance is a very severe challenge. Summary of the invention

[0004] The purpose of the present invention is to provide a long-wave infrared detector with a complementary barrier CBIRD structure, introduce a newly designed hole barrier structure, the hole barrier reduces trap-related tunneling, and the single-stage barrier Np junction between the hole barrier and the absorption layer reduces the SRH-related dark current, and is combined with the electron barrier to form a complementary barrier CBIRD structure to solve the problems of high dark current and low responsivity / specific detection rate of InAs / InAsSb T2SL detectors in the prior art.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A long-wave infrared detector with a complementary barrier CBIRD structure comprises a substrate, wherein a buffer layer, a bottom contact-hole barrier layer, an absorption layer, an electron barrier layer, and a top contact layer are sequentially arranged on the upper surface of the substrate from bottom to top, a bottom contact electrode is arranged on the upper surface of the bottom contact-hole barrier layer, and a top contact electrode is arranged on the upper surface of the top contact layer, wherein the bottom contact-hole barrier layer is 4MLs InAs / 1MLs InAs arranged from top to bottom and in a 100-cycle cycle 0.8 Sb 0.2 / 1MLs AlAs 0.2 Sb 0.8 / 1MLs InAs 0.8 Sb 0.2 Superlattice.

[0007] Furthermore, the total thickness of the bottom contact-hole barrier layer is 0.21 μm, and the N-type doping concentration of the bottom contact-hole barrier layer is 10 17 cm -3 .

[0008] Furthermore, the absorption layer is arranged from top to bottom and has 340 cycles of 32MLs InAs / 8MLs InAs 0.5 Sb 0.5 Superlattice.

[0009] Furthermore, the total thickness of the absorption layer is 4.08 μm.

[0010] Furthermore, the top contact layer is 32MLs InAs / 8MLs InAs arranged from top to bottom and in 20 cycles. 0.5 Sb 0.5 Superlattice.

[0011] Furthermore, the total thickness of the top contact layer is 0.24 μm, and the P-type doping concentration of the top contact layer is 10 18 cm -3 .

[0012] Furthermore, the electron barrier layer is 0.15 μm Al 0.8 Ga 0.2 As 0.01 Sb 0.99 .

[0013] Furthermore, the substrate is a GaSb substrate.

[0014] Furthermore, the buffer layer is a 100nm GaSb buffer layer.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0016] 1. In the present invention, the device trap-related tunneling current, SRH current and contact layer minority carrier injection are effectively reduced, and the overall dark current of the device is reduced. The device operating temperature and detection performance indicators such as responsiveness and specific detection rate are improved. At 100K temperature and 100mV working bias, the dark current density is 10 -7 A / cm 2 , cut-off wavelength 12.7μm, maximum responsivity 1.6A / W, maximum specific detection rate 10 13 Jones, maximum external quantum efficiency 25%. Excellent performance.

[0017] 2. In the present invention, the design of the P-type and N-type contact layers can reduce the turn-on voltage / operating voltage of the device, reduce the power consumption of the device as a whole, and be used to prepare low-power devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, among which:

[0019] Figure 1 This is a schematic diagram of the novel hole barrier structure InAs / InAsSb / AlAsSb / InAsSb superlattice structure of the present invention;

[0020] Figure 2 It is a structural schematic diagram of the present invention;

[0021] Figure 3 Schematic diagram of the energy band structure and hole barrier of the present invention;

[0022] Figure 4 It is a schematic diagram of dark current and spectral response of the present invention;

[0023] Markings in the figure: 1-substrate, 2-buffer layer, 3-bottom contact-hole barrier layer, 4-absorption layer, 5-electron barrier layer, 6-top contact layer, 7-bottom contact electrode, 8-top contact electrode. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0027] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use. They are only simplified descriptions for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the descriptions, and cannot be understood as indicating or implying relative importance.

[0028] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Combined with Figure 1 -Attached Figure 4 ;

[0031] A method comprising a substrate, wherein a buffer layer, a bottom contact-hole barrier layer, an absorption layer, an electron barrier layer, and a top contact layer are sequentially arranged on the upper surface of the substrate from bottom to top, a bottom contact electrode is arranged on the upper surface of the bottom contact-hole barrier layer, a top contact electrode is arranged on the upper surface of the top contact layer, and the bottom contact-hole barrier layer is 4MLs InAs / 1MLs InAs arranged from top to bottom and in a 100-cycle cycle. 0.8 Sb 0.2 / 1MLs AlAs 0.2 Sb 0.8 / 1MLsInAs 0.8 Sb 0.2 Superlattice.

[0032] Furthermore, the total thickness of the bottom contact-hole barrier layer is 0.21 μm, and the N-type doping concentration of the bottom contact-hole barrier layer is 10 17 cm -3 .

[0033] Furthermore, the absorption layer is arranged from top to bottom and has 340 cycles of 32MLs InAs / 8MLs InAs 0.5 Sb 0.5 Superlattice.

[0034] Furthermore, the total thickness of the absorption layer is 4.08 μm.

[0035] Furthermore, the top contact layer is 32MLs InAs / 8MLs InAs arranged from top to bottom and in 20 cycles. 0.5 Sb 0.5 Superlattice.

[0036] Furthermore, the total thickness of the top contact layer is 0.24 μm, and the P-type doping concentration of the top contact layer is 10 18 cm -3 .

[0037] Furthermore, the electron barrier layer is 0.15 μm Al 0.8 Ga 0.2 As 0.01 Sb 0.99 .

[0038] Furthermore, the substrate is a GaSb substrate.

[0039] Furthermore, the buffer layer is a 100nm GaSb buffer layer.

[0040] Traditional AlAs 0.08 Sb 0.92In infrared detectors with barrier layers, in order to meet lattice matching, the barrier material fails to form a sufficiently high potential barrier with the absorption layer and cannot effectively limit the transport of majority carriers in the absorption layer; or it hinders the transport of minority carriers in the absorption layer. Its nearly 200meV high hole barrier limits the transport of photogenerated holes, forcing the operating voltage of such detectors to be maintained at -0.3V or even higher to ensure detection performance.

[0041] During implementation of the present invention:

[0042] 1. New hole barrier structure InAs / InAs 0.8 Sb 0.2 / AlAs 0.2 Sb 0.8 / InAs 0.8 Sb 0.2 Superlattice

[0043] T2SL is a III-V It is an artificial crystal composed of Sb-based materials, such as InAs, GaSb, and AlSb, and their compounds with similar lattice constants, which are stacked alternately according to certain layer thickness, composition and sequential period. For the type II InAs / InAsSb "broken band gap" staggered energy band structure, InAs and InAsSb form electron and hole quantum wells in the layer respectively. Electrons and holes are bound in InAs and InAsSb quantum wells respectively. Tunneling between adjacent wells forms conduction band or valence band microbands. Microbands or energy states basically depend on well width and potential barriers. Band gap E g The electron microstrip E1 (E c ) and the first heavy hole state HH1(E V ) energy difference and can be adjusted within a certain range. In the present invention, 0.5Sb component InAs / InAs 0.5 Sb 0.5 T2SL is used as the absorption region material, and the period is set to 32 / 8MLs (monolayers). At 100K, the energy difference between its E1 and HH1 is about 0.1eV, and the corresponding cutoff absorption wavelength is about 12.4μm. Since the positions of E1 and HH1 of the superlattice material are closely related to the layer thickness, composition, period number and other factors of its periodic structure material, the energy band positions of E1 and HH1 can be precisely controlled by adjusting these variables, thereby designing the required barrier structure. After studying relevant literature, it was found that for InAs / InAs 0.5 Sb 0.5T2SL, at 100K, as the period number and layer thickness decrease, the position of E1 changes little; however, the position of HH1 changes greatly, from -0.27eV (Period = 40ML) to -0.48eV (Period = 10ML). The position of HH1 changes by 0.21eV, but the barrier height of 0.21eV is far from enough to build a hole barrier. Therefore, other methods need to be added to increase the hole barrier height. Since the hole well is located in the InAsSb material in the InAs / InAsSb T2SL, the HH1 position is closely related to the InAsSb material. By reducing the Sb component content in the InAsSb material, the energy band position of the InAsSb with low Sb component, especially the valence band position, is further moved down compared to the high Sb component, and by inserting 1ML of AlAsSb wide bandgap material into the InAsSb material, the HH1 position can be further reduced by about 0.3eV to further increase the hole barrier height. It should be noted that the inserted AlAsSb wide bandgap material should be very thin to reduce stress. By reducing the number of periods, reducing the Sb component content in the InAsSb material, and inserting 1ML of AlAsSb wide bandgap material into the InAsSb material, a hole barrier with a height of about 0.5eV can be finally obtained. In the present invention, the final hole barrier structure is determined to be 4 / 1 / 1 / 1MLs InAs / InAs 0.8 Sb 0.2 / AlAs 0.2 Sb 0.8 / InAs 0.8 Sb 0.2 Superlattice.

[0044] 2. CBIRD Structure InAs / InAsSb T2SL Long-wave Infrared Detector

[0045] In the present invention, Al is selected to match the GaSb substrate lattice. 0.8 Ga 0.2 As 0.01 Sb 0.99 As the electron barrier layer, the electron barrier may also be selected from materials including but not limited to AlSb, AlAsSb, InAs / AlAsSb T2SL, AlAsSb / InAsSb T2SL and the like. The specific composition of the InAs / InAsSb T2SL long-wave infrared detector with CBIRD structure is (from bottom to top): 1. GaSb substrate;

[0046] 2.100nm GaSb buffer layer;

[0047] 3. Bottom contact layer / hole barrier layer: 100 cycles 4 / 1 / 1 / 1MLs InAs / InAs 0.8Sb 0.2 / AlAs 0.2 Sb 0.8 / InAs 0.8 Sb 0.2

[0048] Superlattice, total thickness 0.21μm, N-type doping concentration 10 17 cm -3 .

[0049] 4. Absorption layer: 340 cycles 32 / 8MLs InAs / InAs 0.5 Sb 0.5 Superlattice, total thickness 4.08 μm, unintentionally doped.

[0050] 5.Electron barrier layer: 0.15μm Al 0.8 Ga 0.2 As 0.01 Sb 0.99 , unintentional adulteration.

[0051] 6. Top contact layer: 20 cycles 32 / 8MLs InAs / InAs 0.5 Sb 0.5 Superlattice, total thickness 0.24μm, P-type doping concentration 10 18 cm -3 .

[0052] 7. Bottom contact electrode.

[0053] 8. Top contact electrode.

[0054] According to the simulation results, at 100K and 100mV working bias, the dark current density of the CBIRD structure InAs / InAsSb T2SL long-wave infrared detector in the present invention is 10 -7 A / cm 2 , cut-off wavelength 12.7μm, maximum responsivity 1.6A / W, maximum specific detection rate 10 13 Jones, maximum external quantum efficiency 25%. Excellent performance.

[0055] Example 1

[0056] A long-wave infrared detector with a complementary barrier CBIRD structure comprises a substrate, wherein a buffer layer, a bottom contact-hole barrier layer, an absorption layer, an electron barrier layer, and a top contact layer are sequentially arranged on the upper surface of the substrate from bottom to top, a bottom contact electrode is arranged on the upper surface of the bottom contact-hole barrier layer, and a top contact electrode is arranged on the upper surface of the top contact layer, wherein the bottom contact-hole barrier layer is 4MLs InAs / 1MLs InAs arranged from top to bottom and in a 100-cycle cycle 0.8Sb 0.2 / 1MLs AlAs 0.2 Sb 0.8 / 1MLs InAs 0.8 Sb 0.2 Superlattice.

[0057] Example 2

[0058] On the basis of Example 1, the total thickness of the bottom contact-hole barrier layer is 0.21 μm, and the N-type doping concentration of the bottom contact-hole barrier layer is 10 17 cm -3 .

[0059] Example 3

[0060] Based on the above embodiment, the absorption layer is 32MLsInAs / 8MLs InAs arranged from top to bottom and in 340 cycles. 0.5 Sb 0.5 Superlattice.

[0061] Example 4

[0062] Based on the above embodiment, the total thickness of the absorption layer is 4.08 μm.

[0063] Example 5

[0064] Based on the above embodiment, the top contact layer is 32MLs InAs / 8MLs InAs arranged from top to bottom and in 20 cycles. 0.5 Sb 0.5 Superlattice.

[0065] Example 6

[0066] Based on the above embodiment, the total thickness of the top contact layer is 0.24 μm, and the P-type doping concentration of the top contact layer is 10 18 cm -3 .

[0067] Example 7

[0068] Based on the above embodiment, the electron barrier layer is 0.15 μm Al 0.8 Ga 0.2 As 0.01 Sb 0.99 .

[0069] Example 8

[0070] On the basis of the above embodiment, the substrate is a GaSb substrate.

[0071] Example 9

[0072] On the basis of the above embodiment, the buffer layer is a 100nm GaSb buffer layer.

[0073] As described above, it is the embodiment of the present invention. The above is the preferred embodiment of the present invention. If the preferred implementation methods in each preferred embodiment are not obviously self-contradictory or based on a preferred implementation method, each preferred implementation method can be arbitrarily superimposed and used in combination. The embodiments and specific parameters in the embodiments are only for the purpose of clearly describing the verification process of the invention, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention is still subject to its claims. Any equivalent changes made using the description of the present invention should be included in the protection scope of the present invention.

Claims

1. A long-wave infrared detector with a complementary barrier CBIRD structure, characterized in that: The invention comprises a substrate (1), wherein the upper surface of the substrate (1) is provided with a buffer layer (2), a bottom contact-hole barrier layer (3), an absorption layer (4), an electron barrier layer (5), and a top contact layer (6) in order from bottom to top, wherein a bottom contact electrode (7) is provided on the upper surface of the bottom contact-hole barrier layer (3), and a top contact electrode (8) is provided on the upper surface of the top contact layer (6), wherein the bottom contact-hole barrier layer (3) is a 4MLs InAs / 1MLs InAs layer arranged from top to bottom and in a 100-cycle cycle. 0.8 Sb 0.2 / 1MLs AlAs 0.2 Sb 0.8 / 1MLsInAs 0.8 Sb 0.2 Superlattice.

2. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 1, characterized in that: The total thickness of the bottom contact-hole barrier layer (3) is 0.21 μm, and the N-type doping concentration of the bottom contact-hole barrier layer (3) is 10 17 cm -3 .

3. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 1, characterized in that: The absorption layer (4) is 32MLs InAs / 8MLs InAs arranged from top to bottom and in a cycle of 340 cycles. 0.5 Sb 0.5 Superlattice.

4. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 3, characterized in that: The total thickness of the absorption layer (4) is 4.08 μm.

5. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 1, characterized in that: The top contact layer (6) is 32MLs InAs / 8MLs InAs arranged from top to bottom and in 20 cycles. 0.5 Sb 0.5 Superlattice.

6. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 5, characterized in that: The total thickness of the top contact layer (6) is 0.24 μm, and the P-type doping concentration of the top contact layer (6) is 10 18 cm -3 .

7. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 1, characterized in that: The electron barrier layer (5) is 0.15 μm Al 0.8 Ga 0.2 As 0.01 Sb 0.99 .

8. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 1, characterized in that: The substrate (1) is a GaSb substrate.

9. A long-wave infrared detector with a complementary barrier CBIRD structure according to claim 1, characterized in that: The buffer layer (2) is a 100nm GaSb buffer layer.

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