Visible-short wave infrared InGaAs detector with high quantum efficiency and preparation method thereof

Abstract

The invention provides a visible-short wave infrared InGaAs detector with high quantum efficiency and a preparation method thereof, the visible-short wave infrared InGaAs detector comprises a special readout circuit chip and a photosensitive chip, and the photosensitive chip is composed of a P-type contact electrode region, a passivation layer, an InP cap layer P-type region, an InP cap layer N-type region, an In < 0.53 > Ga < 0.47 > As absorption layer, an N-InGaAsP contact and corrosion stop layer and an antireflection film layer from bottom to top in sequence. A traditional InGaAs detector epitaxial material structure is broken through, the ultra-thin N-InGaAsP layer (smaller than or equal to 20 nm) is adopted as the N-type contact layer and the corrosion stop layer, the material quality is ensured, meanwhile, the epitaxial material structure and the preparation technology of the detector are simplified, and the ultra-thin N-InGaAsP layer can effectively reduce invalid absorption of the N-type layer to visible light; the grid-shaped N-type contact region structure can further reduce invalid absorption of the N-type layer to the visible light wave band, the quantum efficiency of the InGaAs detector in the visible light wave band is improved to the maximum extent, and the detection capability imprisonment of a visible-short wave InGaAs detector is broken through.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of InGaAs short-wave infrared detector, and particularly relates to a high-quantum-efficiency visible-short-wave infrared InGaAs detector and a preparation method thereof. BACKGROUND

[0002] InGaAs detectors have many advantages such as high detection sensitivity, fast response speed, normal-temperature working, and spectral coverage of 0.4-2.6 μm, and are the best choice for developing small, low-power and low-cost short-wave infrared detectors. With the continuous development of InGaAs short-wave infrared detector technology, the InGaAs short-wave infrared detector has been rapidly and widely applied in the fields of night vision / fusion imaging, surveillance, target identification and tracking, civilian intelligent detection, spectral analysis, biomedical science and scientific research.

[0003] Compared with a typical short-wave infrared InGaAs detector (0.9-1.7 μm), a visible-short-wave infrared InGaAs detector (0.4-1.7 μm) has a high quantum efficiency in the visible light band (0.4-0.9 μm) and can better cover the spectral range required for low-light night vision, and can provide more rich scene information under moonlight / starlight and other low-light conditions, so the visible-short-wave infrared InGaAs detector has a good application prospect in the field of low-light night vision.

[0004] A conventional InGaAs detector epitaxial material structure includes an InP substrate, an N-InP contact layer, an InGaAs etching stop layer, an InGaAs absorption layer, and an InP cap layer. The band gap of InP is 1.34 eV, and the corresponding cutoff wavelength is 0.92 μm. For a back-illuminated InGaAs detector, due to the absorption of visible light by the InP substrate and the N-InP contact layer, the quantum efficiency of the InGaAs detector in the visible light band is low, and the detection capability is limited, which limits the use of the InGaAs detector in the field of low-light night vision. If the quantum efficiency of the InGaAs detector in the visible light band can be greatly improved, the visible light and short-wave infrared night vision detection capabilities can be combined, and the InGaAs detector can realize visible and short-wave integrated imaging, which can greatly reduce the complexity, volume, weight and cost of the InGaAs detector system, improve the performance of the InGaAs detector system, and meet the application requirements of the InGaAs detector in the field of low-light night vision. SUMMARY

[0005] In order to improve the quantum efficiency of the InGaAs detector in the visible light band, realize the visible and short wave integration imaging of the InGaAs detector, and meet the application requirements of the InGaAs detector in the low-light night vision field, the application provides a high-quantum-efficiency visible-short-wave infrared InGaAs detector and a preparation method thereof.

[0006] In order to reduce the invalid absorption of the InP layer to the visible light band as much as possible and improve the quantum efficiency of the InGaAs detector in the visible light band, the application mainly adopts the following two technical means to solve the above technical problems: one is to optimize the traditional epitaxial material structure of the InGaAs detector, and an ultrathin N-InGaAsP layer (thickness ≤ 20 nm) is used as an N-type contact layer and an etching stop layer. Compared with the traditional epitaxial structure, the layer can not only meet the N-type contact, but also can be used as an etching stop layer when the InP substrate is removed. The layer can not only ensure the material growth quality, but also simplify the epitaxial material structure and the preparation process of the detector. Moreover, the thickness of the layer is not more than 20 nm, and the invalid absorption of the visible light can be effectively reduced. The other is to prepare a grid-shaped N-type contact area structure in the above ultrathin N-InGaAsP layer (≤ 20 nm). The structure can further reduce the invalid absorption of the N-type contact layer to the visible light band, maximize the quantum efficiency of the InGaAs detector in the visible light band, and meet the application requirements of the InGaAs detector in the low-light night vision field.

[0007] The specific technical scheme of the application is as follows:

[0008] A high-quantum-efficiency visible-short-wave infrared InGaAs detector, the visible-short-wave infrared InGaAs detector comprises a special readout circuit chip and a photosensitive chip, wherein the special readout circuit chip and the photosensitive chip are interconnected through an interconnection indium column flip-chip interconnection. 0.53 Ga 0.47 As absorption layer, N-InGaAsP contact and etching stop layer and antireflection film layer; the InP cap layer is composed of an InP cap layer P-type region and an InP cap layer N-type region; the N-InGaAsP contact and etching stop layer corresponds to the InP cap layer P-type region as a pixel region one by one and is in a grid shape, and the thickness of the N-InGaAsP contact and etching stop layer is 5 nm to 20 nm, so as to reduce the invalid absorption of the visible light.

[0009] Preferably, the doping concentration of the N-InGaAsP contact and etching stop layer is 2 to 5E18 cm -3 ; the In 0.53Ga 0.47 The thickness of the As absorber layer is 2.5 μm to 3 μm, and its carrier concentration is ≤1E¹⁵ cm⁻¹. -3 The InP cap layer has a thickness of 0.5 μm to 1 μm and a doping concentration of 1 to 5E16 cm⁻¹. -3 The thickness of the N-InGaAsP contact and corrosion-stopping layer is 10 nm, and the doping concentration is 5E18 cm⁻¹. -3 .

[0010] A high quantum-efficiency visible-short-wave infrared InGaAs detector and its fabrication method are disclosed, the method comprising the following steps:

[0011] (1) The epitaxial material is grown using MOCVD, ensuring that the thickness of the grown N-InGaAsP contact and etch stop layer is ≤20nm. In this step, the epitaxial material, from bottom to top, consists of: InP substrate, InP buffer layer, N-InGaAsP contact and etch stop layer, In... 0.53 Ga 0.47 An As absorber layer and an InP cap layer; the InP substrate is an intrinsic or doped N-type material with a thickness of approximately 350 μm; the InP buffer layer has a thickness of approximately 500 nm to 1000 nm and a doping concentration of 2 to 5E18 cm⁻¹. -3 The thickness of the N-InGaAsP contact and corrosion stop layer is approximately 5 nm to 20 nm, with a doping concentration of 2 to 5E18 cm⁻¹. -3 In 0.53 Ga 0.47 The thickness of the As absorber layer is 2.5 μm to 3 μm, and the carrier concentration is ≤1E¹⁵ cm⁻¹. -3 The InP cap layer thickness is approximately 0.5 μm to 1 μm, and the doping concentration is 1 to 5E16cm. -3 ;

[0012] (2) The InGaAs detector photosensitive chip was fabricated using the current typical planar junction InGaAs focal plane detector fabrication process. The main processes include surface treatment, dielectric film deposition, Zn diffusion junction formation, photolithography, etching, and electrode fabrication.

[0013] (3) The InGaAs detector dedicated readout circuit chip and InGaAs detector photosensitive chip are connected by indium flip-chip interconnect technology, and the gap between the readout circuit and the photosensitive chip is filled by bottom filling technology.

[0014] (4) Remove the InP substrate and InP buffer layer by mechanical polishing and wet chemical etching;

[0015] (5) A grid-like N-type contact area structure is achieved by using photolithography and etching processes. The array specifications and size of the grid structure are the same as the array specifications and pixel size of the detector. After etching, the photoresist is removed by acetone to finally form a grid-like N-type contact area.

[0016] (6) The final antireflection membrane is prepared by ICPCVD.

[0017] In the fabrication method of this invention, the optimized epitaxial material structure employs an ultrathin N-InGaAsP layer (≤20nm) as both an N-type contact and an etching stop layer. Compared to traditional structures, this layer ensures N-type contact while also serving as an etching stop layer during InP substrate removal. This simplifies the epitaxial material structure and detector fabrication process while maintaining material growth quality. Furthermore, its thickness of no more than 20nm effectively reduces ineffective absorption of visible light. The InGaAs detector photosensitive chip is based on existing InGaAs detector materials and device processes. Through structural optimization of the epitaxial material and N-type contact region, a high-quantum-efficiency visible-shortwave infrared InGaAs detector is fabricated.

[0018] The beneficial effects of this invention include:

[0019] (1) This invention breaks through the traditional epitaxial material structure of InGaAs detectors and uses an ultrathin N-InGaAsP layer (≤20nm) as the N-type contact layer and corrosion stop layer. Compared with the traditional structure, this layer can not only ensure the N-type contact but also serve as the corrosion stop layer for InP substrate removal. It simplifies the epitaxial material structure and detector fabrication process while ensuring material quality. Moreover, its thickness does not exceed 20nm, which can effectively reduce the ineffective absorption of visible light by the N-type layer.

[0020] (2) Based on the optimized ultrathin N-InGaAsP layer (≤20nm) material structure, this invention innovatively proposes the structure of the grid-like N-type contact region and its preparation method. This structure can further reduce the ineffective absorption of the N-type layer in the visible light band, maximize the quantum efficiency of the InGaAs detector in the visible light band, break the detection capability constraint of the visible-short wave InGaAs detector, and meet its application requirements in the field of low light night vision. Attached Figure Description

[0021] Figure 1 The diagram shows the InGaAs detector structure of Examples 1 and 2.

[0022] Figure 2 This is a schematic diagram of the grid-like N-type contact area structure in Examples 1 and 2.

[0023] Figure 3The image shows the test results of the visible-shortwave infrared InGaAs detector prepared in Example 1.

[0024] In the diagram: 1--InGaAs detector readout circuit chip; 2--Interconnect indium pillars; 3--P-type contact electrode region; 4--Passivation layer; 5--InP cap layer P-type region (pixel region); 6--InP cap layer N-type region; 7--In 0.53 Ga 0.47 As absorption layer; 8--Grid-like N-InGaAsP contact and corrosion stop layer (corresponding one-to-one with each pixel); 9--Antireflection coating layer. Detailed Implementation

[0025] A high quantum-efficiency visible-short-wave infrared InGaAs detector, wherein the epitaxial material of the detector, from bottom to top, comprises an InP substrate, an InP buffer layer, an N-InGaAsP contact and etch stop layer, and an In... 0.53 Ga 0.47 The structure and properties of the epitaxial material, consisting of an As absorption layer and an InP cap layer, are shown in Table 1.

[0026] Table 1

[0027]

[0028] The aforementioned epitaxial material structure optimization employs an ultrathin N-InGaAsP layer (≤20nm) as an N-type contact and etch stop layer. Compared with the traditional structure, this layer ensures that the N-type contact is met while also serving as an etch stop layer during InP substrate removal. This simplifies the epitaxial material structure and detector fabrication process while ensuring the material growth quality. Furthermore, its thickness does not exceed 20nm, effectively reducing ineffective absorption of visible light.

[0029] like Figure 1 As shown, the detector structure includes an InGaAs detector dedicated readout circuit chip 1 and an InGaAs detector photosensitive chip, wherein the InGaAs detector dedicated readout circuit chip 1 and the InGaAs detector photosensitive chip are interconnected via flip-chip interconnection via indium indium pillars 2. The photosensitive chip structure, from bottom to top, consists of a P-type contact electrode region 3, a passivation layer 4, an InP cap layer P-type region 5 (pixel region), an InP cap layer N-type region 6, and an In... 0.53 Ga 0.47 As absorption layer 7, grid-like N-InGaAsP contact and corrosion stop layer 8 (corresponding one-to-one with the pixel) and antireflection film layer 9.

[0030] The InGaAs detector photosensitive chip is based on existing InGaAs detector materials and device processes. Through structural optimization of epitaxial materials and N-type contact regions, a high quantum efficiency visible-shortwave infrared InGaAs detector is fabricated.

[0031] Example 1: A high quantum efficiency visible-shortwave infrared InGaAs detector and its fabrication method

[0032] The method steps are as follows:

[0033] 1. Improved InGaAs epitaxial material was grown using MOCVD to ensure that the N-type contact and etch stop layer were InGaAsP with a thickness of 10 nm and a doping concentration of 5E18 cm⁻¹. -3 The remaining layers are, in order: InP substrate, InP buffer layer, In... 0.53 Ga 0.47 An As absorber layer and an InP cap layer; the InP substrate is an intrinsic or doped N-type material with a thickness of approximately 350 μm; the InP buffer layer has a thickness of approximately 800 nm and a doping concentration of 5E18 cm⁻¹. -3 In 0.53 Ga 0.47 The As absorber layer is 2.5 μm thick and the carrier concentration is 1E¹⁵ cm⁻¹. -3 The InP cap layer thickness is 0.5 μm, and the doping concentration is 1E16cm. -3 ;

[0034] 2. The InGaAs detector photosensitive chip was fabricated using a typical planar junction InGaAs focal plane detector fabrication process. The main processes included surface treatment, dielectric film deposition, Zn diffusion junction formation, photolithography, etching, and electrode fabrication.

[0035] 3. The InGaAs detector dedicated readout circuit chip and InGaAs detector photosensitive chip are connected by indium flip-chip interconnect technology, and the gap between the readout circuit and the photosensitive chip is filled by bottom filling technology;

[0036] 4. The InP substrate was thinned to 30 μm by mechanical polishing, and then the remaining InP substrate and InP buffer layer were removed by a mixture of phosphoric acid and hydrochloric acid at 70 °C, leaving 10 nm of N-InGaAsP contact and etching stop layer.

[0037] 5. Based on a 10nm N-InGaAsP contact and etch stop layer, a grid-like pattern is achieved by photolithography. During the photolithography process, a double-sided alignment process is used to pattern the grid-like N-type contact area corresponding to each pixel.

[0038] 6. After the photolithography process is completed, the grid N-type contact area structure is realized by dry etching. The etching gas is SiCl4, the RF power is 250w, and the etching depth is 10nm. After etching, the photoresist is removed by acetone, and finally a grid-like N-type contact area corresponding to each pixel is formed.

[0039] 7. After completing the fabrication of the grid-like N-type contact area structure, the final antireflection film is prepared by ICPCVD. The antireflection film adopts a two-layer antireflection film system of silicon oxide and silicon nitride.

[0040] Example 2: A high quantum efficiency visible-shortwave infrared InGaAs detector and its fabrication method

[0041] The method steps are as follows:

[0042] 1. Improved InGaAs epitaxial material was grown using MOCVD to ensure that the N-type contact layer was InGaAsP with a thickness of 20 nm and a doping concentration of 5E18 cm⁻¹. -3 The remaining layers are, in order: InP substrate, InP buffer layer, In... 0.53 Ga 0.47 An As absorber layer and an InP cap layer; the InP substrate is an intrinsic or doped N-type material with a thickness of approximately 350 μm; the InP buffer layer has a thickness of approximately 800 nm and a doping concentration of 5E18 cm⁻¹. -3 , ;In 0.53 Ga 0.47 The As absorber layer is 2.5 μm thick and the carrier concentration is 1E¹⁵ cm⁻¹. -3 The InP cap layer thickness is 0.5 μm, and the doping concentration is 1E16cm. -3 ;

[0043] 2. The InGaAs detector photosensitive chip was fabricated using a typical planar junction InGaAs focal plane detector fabrication process. The main processes included surface treatment, dielectric film deposition, Zn diffusion junction formation, photolithography, etching, and electrode fabrication.

[0044] 3. The InGaAs detector dedicated readout circuit chip and InGaAs detector photosensitive chip are connected by indium flip-chip interconnect technology, and the gap between the readout circuit and the photosensitive chip is filled by bottom filling technology;

[0045] 4. The InP substrate was thinned to 30 μm by mechanical polishing, and then the remaining InP substrate and InP buffer layer were removed by a mixture of phosphoric acid and hydrochloric acid at 70 °C, leaving 20 nm of N-InGaAsP contact and etching stop layer.

[0046] 5. Based on a 20nm N-InGaAsP contact and etch stop layer, a grid pattern is achieved by photolithography. During the photolithography process, a double-sided alignment process is used to pattern the grid-type N-type contact area corresponding to each pixel.

[0047] 6. After the photolithography process is completed, the mesh N-type contact layer structure is realized by wet etching process. The etching temperature is 30℃, the etching time is 4s, and the etching solution is a mixed solution of phosphoric acid, hydrogen peroxide and water, with 40mL of phosphoric acid, 60mL of hydrogen peroxide and 600mL of water.

[0048] After etching, the photoresist is removed with acetone, ultimately forming a grid-like N-type contact area that corresponds one-to-one with each pixel;

[0049] 7. After completing the fabrication of the grid-like N-type contact area structure, the final antireflection film is prepared by ICPCVD. The antireflection film adopts a two-layer antireflection film system of silicon oxide and silicon nitride.

[0050] Example 3: Testing the visible-shortwave infrared InGaAs detector prepared in Example 1

[0051] (1) Test results are shown in the figure. Figure 3 As shown, the detector's response band is 0.4μm to 1.7μm, achieving a visible-shortwave response;

[0052] (2) The test results show that the detector has high quantum efficiency in the 0.4μm~1.7μm band, realizing the fabrication of a high quantum efficiency visible-shortwave infrared InGaAs detector.

Claims

1. A high quantum efficiency visible-shortwave infrared InGaAs detector, wherein the visible-shortwave infrared InGaAs detector comprises a dedicated readout circuit chip (1) and a photosensitive chip, wherein, The dedicated readout circuit chip (1) and the photosensitive chip are interconnected via flip-chip interconnection through interconnect indium pillars (2); characterized in that the photosensitive chip consists of, from bottom to top, a P-type contact electrode region (3), a passivation layer (4), an InP cap layer, and an In... 0.53 Ga 0.47 The InP capping layer consists of an As absorption layer (7), an N-InGaAsP contact and corrosion stop layer (8), and an antireflection film layer (9). The InP capping layer consists of an InP capping layer P-type region (5) and an InP capping layer N-type region (6). The N-InGaAsP contact and corrosion stop layer (8) corresponds one-to-one with the InP capping layer P-type region (5) which is the pixel region and is in a grid shape. The thickness of the N-InGaAsP contact and corrosion stop layer (8) is 5nm-20nm, which is used to reduce the ineffective absorption of visible light.

2. The visible-shortwave infrared InGaAs detector according to claim 1, characterized in that: The doping concentration of the N-InGaAsP contact and corrosion-stopping layer (8) is 2~5E18 cm⁻¹. -3 .

3. The visible-shortwave infrared InGaAs detector according to claim 1, characterized in that, The In 0.53 Ga 0.47 The thickness of the As absorber layer (7) is 2.5 μm to 3 μm, and its carrier concentration is ≤1E15 cm⁻¹. -3 .

4. The visible-shortwave infrared InGaAs detector according to claim 1, characterized in that, The InP cap layer has a thickness of 0.5 μm to 1 μm and a doping concentration of 1 to 5E16 cm⁻¹. -3 .

5. The visible-shortwave infrared InGaAs detector according to claim 2, characterized in that, The thickness of the N-InGaAsP contact and corrosion-stopping layer (8) is 10 nm, and the doping concentration is 5E18 cm⁻¹. -3 .

6. A method for fabricating a high quantum efficiency visible-shortwave infrared InGaAs detector as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) The epitaxial material is grown by MOCVD, and the epitaxial material, from bottom to top, consists of an InP substrate, an InP buffer layer, an N-InGaAsP contact and etch stop layer, and an InP substrate. 0.53 Ga 0.47 As absorber layer and InP cap layer; (2) The InGaAs detector photosensitive chip was fabricated using a planar junction InGaAs focal plane detector fabrication process; (3) The InGaAs detector dedicated readout circuit chip and InGaAs detector photosensitive chip are connected by indium flip-chip interconnect technology, and the gap between the readout circuit and the photosensitive chip is filled by bottom filling technology. (4) Remove the InP substrate and InP buffer layer by mechanical polishing and wet chemical etching; (5) A grid-like N-type contact area structure is achieved by using photolithography and etching processes. After etching, the photoresist is removed by acetone, and finally a grid-like N-type contact area is formed. (6) The final antireflection membrane is prepared by ICPCVD.

7. The preparation method according to claim 6, characterized in that, In step (1): The InP substrate is an intrinsic or doped N-type material with a thickness of 350 μm; The InP buffer layer has a thickness of 500 nm to 1000 nm and a doping concentration of 2 to 5E18 cm⁻¹. -3 ; The thickness of the N-InGaAsP contact and corrosion stop layer is 5nm~20nm, and the doping concentration is 2~5E18cm. -3 .

8. The preparation method according to claim 6, characterized in that, The process in step (2) includes surface treatment, dielectric film deposition, Zn diffusion junction formation, photolithography, etching and electrode fabrication.

9. The preparation method according to claim 6, characterized in that, In step (5): The array specifications and size of the grid structure of the grid-like N-type contact area are the same as the array specifications and pixel size of the detector.

10. The preparation method according to claim 7, characterized in that, The InP substrate is an intrinsic or doped N-type material with a thickness of 350 μm; the InP buffer layer has a thickness of 800 nm and a doping concentration of 5E18 cm⁻¹. -3 .

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