A planar infrared detector and a method for manufacturing the same

Abstract

The application discloses a planar infrared detector and a preparation method thereof. The infrared detector comprises a substrate and a buffer layer, an N-type doped contact layer, an superlattice absorption layer and an intrinsic contact layer which are sequentially grown on the substrate, thereby forming a laminated structure; further comprising a first electrode and a second electrode, the first electrode is located in a diffusion area formed on the intrinsic contact layer, and the second electrode is located in a recessed area formed on the N-type doped contact layer. The application forms a photoelectric response channel by P-type diffusion in the intrinsic contact layer, thereby forming a planar PN junction, which can eliminate the sidewall leakage current of the detector and improve the photon injection efficiency. In addition, compared with the traditional mesa-type detector, the application reduces the passivation process, effectively reduces the production cost and improves the product yield.

Description

TECHNICAL FIELD

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

[0002] The infrared detector has important and wide applications in the fields of space communication, medical diagnosis and treatment, industrial detection and aerospace. The antimonide superlattice material based on the III-V semiconductor has the advantages of wide band, high quantum efficiency, good large-area uniformity, high working temperature and low preparation cost, and can meet the requirements of the third generation infrared detector for high detection rate, large array, multi-band, low power consumption and low cost.

[0003] At present, the mesa structure is used in the research and production process of the antimonide superlattice detector, that is, the semiconductor material outside the working area is removed by etching process to realize electrical isolation between devices. However, after etching, the semiconductor crystal continuity is broken, resulting in surface states and inversion layers on the sidewall of the device, so that the conductive channel appears on the sidewall surface and surface leakage current is generated. Although various means such as deposition of SiO2, polyimide and photoresist medium materials are used for passivation treatment of the surface of the detector, the effect is still limited, so the preparation process of the antimonide superlattice infrared detector still needs to be improved. SUMMARY

[0004] The application aims at solving the problems in the prior art, and provides a planar infrared detector and a preparation method thereof, which can eliminate the sidewall leakage current of the infrared detector, improve the photon injection efficiency of the detector, and greatly reduce the complexity and cost of the preparation process of the detector.

[0005] To achieve the above-mentioned purpose, the application provides a preparation method of a planar infrared detector, which comprises the following steps:

[0006] S1, sequentially growing a buffer layer, an N-type doped contact layer, a superlattice absorption layer and an intrinsic contact layer on a substrate to form a laminated structure, and obtaining a first device;

[0007] S2, preparing a diffusion selection layer on the surface of the first device away from the substrate, and then etching a diffusion window on the diffusion selection layer to obtain a second device;

[0008] S3, growing a diffusion layer at the diffusion window on the second device, and growing a diffusion protection layer on the diffusion layer to obtain a third device;

[0009] S4, performing rapid annealing treatment on the third device, and then removing the diffusion protection layer, the diffusion layer and the diffusion selection layer to form a P-type diffusion region on the intrinsic contact layer, and obtaining a fourth device;

[0010] S5, etching the fourth device away from the surface of the substrate to form a recessed region on the N-type doped contact layer, so as to obtain a fifth device exposing the N-type doped contact layer;

[0011] S6, preparing a first electrode and a second electrode on the fifth device away from the surface of the substrate, so as to obtain an infrared detector, wherein the first electrode is located in the recessed region on the N-type doped contact layer, and the second electrode is located in the diffusion region on the intrinsic contact layer.

[0012] Specifically, the rapid annealing process comprises: placing the third device into a rapid annealing furnace and introducing nitrogen, so as to anneal at a temperature of 300-500℃ for 10-30 minutes.

[0013] Specifically, the laminated structure can be prepared by a molecular beam epitaxy method; the diffusion selection layer, the diffusion layer and the diffusion protection layer can be prepared by a plasma enhanced chemical vapor deposition method, a vacuum evaporation method or a magnetron sputtering method.

[0014] Specifically, in the step S5, the fourth device is etched by an inductively coupled plasma, and the recessed region reaches a half of the thickness of the N-type doped contact layer.

[0015] Specifically, the step S5 further comprises: preparing a mesa mask on the surface of the fourth device away from the substrate before etching, and removing the mesa mask on the surface of the fifth device after etching, so as to achieve mesa protection.

[0016] In addition, the present application further provides a planar infrared detector prepared by the above preparation method, which comprises a substrate and a buffer layer, an N-type doped contact layer, a superlattice absorption layer and an intrinsic contact layer sequentially grown on the substrate, so as to form a laminated structure; and further comprises a first electrode and a second electrode, wherein the first electrode is located in the diffusion region formed on the intrinsic contact layer, and the second electrode is located in the recessed region formed on the N-type doped contact layer.

[0017] Specifically, the laminated structure further comprises an M-type barrier layer between the N-type doped contact layer and the superlattice absorption layer, so that the intrinsic contact layer, the superlattice absorption layer, the M-type barrier layer and the N-type doped contact layer jointly form a P-π-M-N structure through P-type diffusion.

[0018] Specifically, the substrate is an N-type GaSb substrate, and the buffer layer adopts N-type doped GaSb material with a thickness of 300-1000nm.

[0019] Specifically, the N-type doped contact layer is an N-type doped superlattice layer with a thickness of 250-600nm; the superlattice absorption layer is a P-type doped superlattice layer with a thickness of 1.5-3.5μm; and the intrinsic contact layer is an undoped superlattice layer with a thickness of 10-100nm.

[0020] Specifically, the material of the diffusion selection layer and the diffusion protection layer comprises one or a combination of SiO2, Si x N y , SiON, Al2O3, and has a thickness of 100nm-3μm; the material of the diffusion layer comprises one or a combination of ZnO x , ZnS, and has a thickness of 100nm-3μm. Advantages

[0021] The present application forms an electrical isolation area by exposing the intrinsic contact layer to diffusion through the diffusion selection layer, so that the unexposed area is protected by the diffusion selection layer and does not diffuse, thus eliminating the need for etching a mesa structure to achieve electrical isolation. Meanwhile, the present application forms a recessed area on the N-type doped contact layer through an etching process, thereby exposing the lower electrode, so that the conductive channel from the upper electrode to the lower electrode does not pass through the sidewall, thus eliminating sidewall leakage current.

[0022] The present application uses a diffusion layer and a diffusion protection layer as a diffusion source, which can adjust the diffusion depth of the diffusion layer by diffusion temperature, is conducive to controlling the diffusion effect and improving the photon injection efficiency; on the other hand, the diffusion protection layer can reduce the volatilization of the diffusion layer during thermal diffusion, thereby playing a protective role and further ensuring the diffusion effect and reducing pollution.

[0023] In summary, the present application forms a photoelectric response channel by P-type diffusion in the intrinsic contact layer, thereby forming a planar PN junction, which can eliminate the sidewall leakage current of the detector and improve the photon injection efficiency. In addition, compared with the traditional mesa-type detector, the present application reduces the passivation process, effectively reduces the production cost, and improves the product yield. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a flowchart of the preparation method of the infrared detector in the embodiment of the present application, wherein (a)-(f) are structure diagrams of the first-fifth devices and the infrared detector, respectively;

[0025] Figure 2 Fig. 1 is a flowchart of the preparation method of the infrared detector in the embodiment of the present application, wherein (a)-(f) are structure diagrams of the first-fifth devices and the infrared detector, respectively;

[0026] Figure 3 Fig. 1 is a flowchart of the preparation method of the infrared detector in the embodiment of the present application, wherein (a)-(f) are structure diagrams of the first-fifth devices and the infrared detector, respectively;

[0027] Figure 4 Fig. 1 is a flowchart of the preparation method of the infrared detector in the embodiment of the present application, wherein (a)-(f) are structure diagrams of the first-fifth devices and the infrared detector, respectively;

[0028] Figure 5 Fig. 1 is a flowchart of the preparation method of the infrared detector in the embodiment of the present application, wherein (a)-(f) are structure diagrams of the first-fifth devices and the infrared detector, respectively;

[0029] Figure 6 Figure for the embodiment of the present application shows the variation of the detection rate of the infrared detector in different waveband infrared light;

[0030] The figure includes: 1-substrate, 2-buffer layer, 3-N-type doped contact layer, 4-M-type barrier layer, 5-superlattice absorption layer, 6-intrinsic contact layer, 7-first electrode, 8-second electrode, 9-diffusion selection layer, 10-diffusion layer, 11-diffusion protection layer, 12-diffusion region. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments.

[0032] Reference Figure 1 The embodiment provides a preparation method of a planar infrared detector, which comprises the following steps:

[0033] S1, sequentially growing a buffer layer 2, an N-type doped contact layer 3, an M-type barrier layer 4, a superlattice absorption layer 5 and an intrinsic contact layer 6 on a substrate 1, thereby forming a laminated structure and obtaining a first device;

[0034] S2, preparing a diffusion selection layer 9 on the surface of the first device away from the substrate 1, and then etching the diffusion selection layer 9 to form a diffusion window, thereby obtaining a second device;

[0035] S3, growing a diffusion layer 10 at the diffusion window of the second device, and growing a diffusion protection layer 11 on the diffusion layer 10, thereby obtaining a third device;

[0036] S4, performing rapid annealing treatment on the third device, and then removing the diffusion protection layer 11, the diffusion layer 10 and the diffusion selection layer 9 to form a P-type diffusion region 12 on the intrinsic contact layer 6, thereby obtaining a fourth device;

[0037] S5, etching on the surface of the fourth device away from the substrate 1 to form a recessed region on the N-type doped contact layer 3, thereby obtaining a fifth device exposing the N-type doped contact layer 3;

[0038] S6, preparing a first electrode 7 and a second electrode 8 on the surface of the fifth device away from the substrate 1, thereby obtaining an infrared detector, wherein the first electrode 7 is located in the recessed region on the N-type doped contact layer 3, and the second electrode 8 is located in the diffusion region 12 on the intrinsic contact layer 6.

[0039] Specifically, the rapid annealing process includes: placing the third device into a rapid annealing furnace, introducing nitrogen, annealing at a temperature of 300-500°C for 10-30 minutes.

[0040] Specifically, the stack structure can be prepared by a molecular beam epitaxy method, and the diffusion selection layer 9, the diffusion layer 10 and the diffusion protection layer 11 can be prepared by a plasma enhanced chemical vapor deposition method.

[0041] Specifically, in the step S5, the fourth device is etched by an inductively coupled plasma, and the recessed region is deep into half of the thickness of the N-type doped contact layer 3. It should be noted that, in order to avoid interference with the diffusion region 12, etching is performed on the surface of the fourth device away from the diffusion region 12. Meanwhile, before etching, a mesa mask is prepared on the surface of the fourth device away from the substrate 1, and the mesa mask on the surface of the fifth device is removed after etching, further realizing mesa protection.

[0042] Specifically, in the step S6, an electrode mask is prepared on the surface of the fifth device away from the substrate, and an electrode window is etched on the electrode mask, including a first electrode window located in the recessed region and a second electrode window located on the top of the diffusion region 12, and then a first electrode 7 and a second electrode 8 are prepared on the first electrode window and the second electrode window respectively, to obtain an infrared detector.

[0043] In addition, the embodiment also provides a planar infrared detector prepared by the preparation method. Figure 2 The detector includes a substrate 1 and a stack structure sequentially grown on the substrate 1, which includes a buffer layer 2, an N-type doped contact layer 3, an M-type barrier layer 4, a superlattice absorption layer 5 and an intrinsic contact layer 6, thereby forming a stack structure; and a first electrode 7 and a second electrode 8, wherein the second electrode 8 is located in a diffusion region 12 formed on the intrinsic contact layer 6, and the first electrode 7 is located in a recessed region formed on the N-type doped contact layer 3.

[0044] Specifically, infrared light enters the diffusion region 12 from the top of the detector, is absorbed by the superlattice absorption layer 5 to generate photo-generated carriers, under the action of an external electric field, the electrons in the photo-generated carriers move to the intrinsic contact layer 6 and are output through the second electrode 8, and the holes in the photo-generated carriers move to the N-type doped contact layer 3 and are output through the first electrode 7, thereby forming a conductive channel, and the detection of the output current of the infrared light realizes the detection of the infrared light.

[0045] Specifically, the substrate 1 is an N-type GaSb substrate, and the doping concentration is generally not less than 10 17 cm -3 ; the buffer layer 2 adopts N-type doped GaSb material, which can be doped with Te element, and the doping concentration is generally not less than 1018 cm -3 The thickness of the buffer layer 2 is 300-1000 nm, which is used to smooth the surface of the substrate 1 and reduce the growth defects of the subsequent structure.

[0046] Specifically, the intrinsic contact layer 6, the absorption layer 5, the M-type barrier layer 4 and the N-type doped contact layer 3 jointly form a P-π-M-N structure through P-type material diffusion. The N-type doped contact layer 3 can be doped with Si elements, and the doping concentration is generally not less than 10 18 cm -3 The thickness of the N-type doped contact layer 3 is 250-600 nm, which is used to form an ohmic contact with the first electrode 7 (metal lower electrode). The M-type barrier layer 4 is designed to block the reverse movement of holes and reduce the bulk dark current. The superlattice absorption layer 5 is a slightly P-type doped layer, and the undoped carrier concentration is 10 14 ~10 16 cm -3 The thickness of the superlattice absorption layer 5 is 1.5-3.5 μm, which is used to absorb incident infrared light and generate photo-generated carriers. The intrinsic contact layer 6 is an undoped layer, and the thickness is 10-100 nm, which is used to diffuse to form a conductive channel and form an ohmic contact with the second electrode 8 (metal upper electrode).

[0047] Specifically, the material of the superlattice absorption layer 5 includes one of short-wave infrared material, medium-wave infrared material, long-wave infrared material or very long-wave infrared material, so as to realize the detection of infrared light of different wavebands.

[0048] Specifically, the material of the diffusion selection layer 9 and the diffusion protection layer 11 can be one or a combination of SiO2, SixNy, SiON and Al2O3, and the thickness can be 100 nm-3 μm. The material of the diffusion layer 10 can be one or a combination of ZnS and ZnOx, and the thickness can be 100 nm-3 μm.

[0049] Specifically, the structure of the first electrode 7 and the second electrode 8 each includes a Ti layer, a Pt layer formed on the Ti layer, and an Au layer formed on the Pt layer, wherein the thickness of the Ti layer and the Pt layer is 50 nm, and the thickness of the Au layer is 300 nm. The Ti layer can form a good ohmic contact, the Pt can prevent the Au from diffusing into the Ti layer and the infrared detection material, and the Au layer can maintain good stability and bonding in packaging. Preferably, the first electrode 7 and the second electrode 8 are both annular.

[0050] Exemplarily, with reference to Figure 3The substrate 1 is an N-type GaSb substrate with a thickness of about 600 μm; the buffer layer 2 is an N-type doped GaSb material with a thickness of 988 nm; the N-type doped contact layer 3 is an N-type doped 10InAs / 1GaSb / 5AlSb / 1GaSb superlattice layer with a thickness of 524 nm; the M-type barrier layer 4 is an M-type doped 10InAs / 1GaSb / 5AlSb / 1GaSb superlattice layer with a thickness of 524 nm; the superlattice absorption layer 5 is a P-type doped 9.25InAs / 7GaSb superlattice layer with a thickness of 2379 nm; and the intrinsic contact layer 6 is an undoped 9.25InAs / 7GaSb superlattice layer with a thickness of 71 nm.

[0051] Referring to Figure 4 , a ring-shaped upper electrode is prepared in the diffusion region 12 on the top of the intrinsic contact layer 6, and the N-type doped contact layer 3 is exposed by a recessed region to grow a metal as a lower electrode.

[0052] Referring to Figure 5 , the SIMS (secondary ion mass spectrometry) test method can be used to obtain the variation of the diffusion depth of Zn ions at different diffusion temperatures, wherein the horizontal coordinate represents the depth (unit: nm), and the vertical coordinate represents the Zn ion concentration (unit: atoms / cm 2 ). It can be seen that, in general, the higher the temperature, the deeper the diffusion depth of Zn ions, and thus the diffusion depth of the diffusion layer can be adjusted by the diffusion temperature, which is conducive to controlling the diffusion effect and improving the photon injection efficiency.

[0053] Figure 6 The detection rate variation of the above-mentioned embodiment for different waveband infrared light is shown in the figure, wherein the horizontal coordinate represents the infrared light wavelength (unit: μm), and the vertical coordinate represents the detectability (unit: cm×Hz 1 / 2 / W). In the field of infrared detectors, the detection rate is usually closely related to the key index of detectability (D), and the detectability is often used as a parameter when the performance of the infrared detector is described. The greater the D value, the more sensitive the detector, that is, under the same bandwidth and area conditions, a smaller optical power signal can be detected. It can be seen that the detector has good mid-wave infrared light detection capability at a temperature of 77K.

[0054] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for fabricating a planar infrared detector, characterized by, The method comprises the following steps: S1, sequentially growing a buffer layer, an N-doped contact layer, a superlattice absorption layer and an intrinsic contact layer on a substrate to form a stack structure, thereby obtaining a first device; S2, preparing a diffusion selection layer on a surface of the first device away from the substrate, and then etching a diffusion window on the diffusion selection layer to obtain a second device; S3, growing a diffusion layer on the diffusion window of the second device, and growing a diffusion protection layer on the diffusion layer to obtain a third device; S4, performing a rapid annealing treatment on the third device, and then removing the diffusion protection layer, the diffusion layer and the diffusion selection layer to form a P-doped diffusion region on the intrinsic contact layer, thereby obtaining a fourth device; S5, etching a recessed region on the N-doped contact layer on a surface of the fourth device away from the substrate to obtain a fifth device exposing the N-doped contact layer; S6, preparing a first electrode and a second electrode on a surface of the fifth device away from the substrate, wherein the first electrode is located in the recessed region on the N-doped contact layer, and the second electrode is located in the diffusion region on the intrinsic contact layer.

2. The production method according to claim 1, characterized by, The rapid annealing treatment comprises: placing the third device in a rapid annealing furnace and introducing nitrogen gas to anneal the third device at a temperature of 300-500 ℃ for 10-30 minutes.

3. The preparation method according to claim 1, characterized in that, The stack structure is prepared by a molecular beam epitaxy method, and the diffusion selection layer, the diffusion layer and the diffusion protection layer are prepared by a plasma-enhanced chemical vapor deposition method, a vacuum evaporation method or a magnetron sputtering method.

4. The method of claim 1, wherein, In the step S5, the fourth device is etched by an inductively coupled plasma, and the recessed region reaches a half thickness of the N-doped contact layer.

5. The preparation method according to claim 1, characterized in that, The step S5 further comprises: preparing a mesa mask on a surface of the fourth device away from the substrate before etching, and removing the mesa mask on the surface of the fifth device after etching.

6. A planar infrared detector prepared by the method of any one of claims 1 to 5, characterized in that The method comprises the following steps:

7. The planar infrared detector according to claim 6, wherein The stack structure further comprises an M-type barrier layer between the N-doped contact layer and the superlattice absorption layer, so that the intrinsic contact layer, the superlattice absorption layer, the M-type barrier layer and the N-doped contact layer jointly form a P-π-M-N structure through P-type diffusion.

8. The planar infrared detector according to claim 6, wherein The substrate is an N-type GaSb substrate, and the buffer layer is made of N-doped GaSb material with a thickness of 300-1000 nm.

9. The planar infrared detector according to claim 6, wherein The N-doped contact layer is an N-doped superlattice layer with a thickness of 250-600 nm, the superlattice absorption layer is a P-doped superlattice layer with a thickness of 1.5-3.5 μm, and the intrinsic contact layer is an undoped superlattice layer with a thickness of 10-100 nm.

10. The planar infrared detector according to claim 6, wherein The material of the diffusion selection layer and diffusion protection layer includes one or a combination of SiO2, Si x N y , SiON, Al2O3, and has a thickness of 100 nm to 3 μm; the material of the diffusion layer includes one or a combination of ZnO x , ZnS, and has a thickness of 100 nm to 3 μm.

Images