A planar short-wave infrared detector and its preparation method and application

Abstract

This invention discloses a planar short-wave infrared detector, its fabrication method, and its application. The fabrication method includes the following steps: S1, sequentially growing a buffer layer, an N-type contact layer, an absorption layer, an undoped P-type layer, and a cap layer on a substrate; S2, growing a dielectric film on the surface of the cap layer; etching the exposed cap layer using a wet etching process; S3, removing the dielectric film after etching; and growing P-doped Al in the etched region. 1‑w In w As; S4, removal of the cap layer and P-doped Al on the surface of the undoped P-type layer. 1‑ w In w As; S5, a passivation film is grown on all exposed upper surfaces; a pattern of the metal contact layer is formed on the surface of the passivation film using photolithography to form the P-electrode and N-electrode. This invention overcomes the problem of difficult Zn diffusion process caused by large lattice mismatch between the epitaxial layer with high In composition and the substrate, and improves the performance of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of photodetectors, and particularly relates to a planar short-wave infrared detector, a preparation method thereof, and an application thereof. Background Art

[0002] Conventional short-wave infrared InGaAs detectors with a response wavelength range of 0.9 - 1.7 μm can operate at room temperature and have advantages such as a mature epitaxial growth process, low power consumption, and high responsivity. With their wide application in multiple fields such as aerospace, night vision, and detection, InGaAs detectors in the extended wavelength range of 1.8 μm - 2.5 μm have also attracted more and more research interest. For example, high-resolution multispectral imaging in the 1.9 - 2.5 μm band can be used for crop water detection; the near-infrared spectrum of 2.26 - 2.38 μm can be used for gas detection such as CH4, CO, H2O, and N2O; InGaAs detectors in the 2.5 μm band for the observation of clouds, aerosols, and atmospheric radiation, etc., have further promoted the continuous development of extended wavelength InxGa1-xAs (0.53 < x < 0.83) detectors with a response wavelength range of 1.7 - 2.5 μm.

[0003] Group III-V compound In x Ga 1-x As (0.53 < x < 1) can achieve the extension of the cut-off wavelength from 1.7 μm to 2.6 μm by gradually increasing the In component in the In x Ga 1-x As compound between 0.53 and 0.83. High-indium-content In x Ga 1-x As detectors are usually grown on InP or GaAs substrates using techniques such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). According to different junction formation methods, they can be divided into mesa-type detectors and planar-type detectors. Planar-type detectors form a PN junction by Zn diffusion or ion implantation in a local area. This PN junction is inside the epitaxial layer. Therefore, the planar junction has advantages such as low dark current, high reliability, and a device duty cycle close to 100%. Both have been widely studied. Compared with conventional wavelength InGaAs detectors, the high-In-component In x Ga 1-x As (0.53 < x < 1) epitaxial layer has a large lattice mismatch with the substrate, resulting in more dislocations and defects inside the material, making the Zn diffusion process of detectors with a high mismatch structure difficult and the junction depth difficult to accurately control.

[0004] Therefore, it is necessary to develop a preparation method for a new type of planar short-wave infrared detector. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of this invention proposes a method for fabricating a planar shortwave infrared detector. This method solves the problem of high mismatch structure leading to difficult Zn diffusion processes, achieving efficient and controllable process parameters while retaining the advantages of planar junction devices, thus improving device performance.

[0006] A second aspect of the present invention also provides a planar shortwave infrared detector.

[0007] A third aspect of the present invention also provides an application of a planar shortwave infrared detector.

[0008] A method for fabricating a planar shortwave infrared detector according to a first aspect of the present invention includes the following steps:

[0009] S1. Buffer layers Al are sequentially grown on an n-InP substrate using MOCVD or MBE deposition methods. 1-x In x As, N-type contact layer In u Ga 1-u As, absorption layer In y Ga 1-y As, undoped p-type layer Al 1-t In t As and cap layer Ga 1-z In z As; where x is 0.52 to 0.84; y, t, and z are independently selected from 0.74 to 0.84;

[0010] S2, in the cap layer Ga 1-z In z A dielectric film is grown on the surface of As; pores are created in the dielectric film to allow the cap layer Ga to be formed. 1-z In z As is exposed; a wet etching process is used to expose the Ga cap layer. 1-z In z As is used for etching; the etching depth is less than or equal to the cap layer Ga. 1-z In z As and undoped P-type layer Al 1-t In t The sum of the thicknesses of As;

[0011] S3. After etching, remove the dielectric film; grow P-doped Al in the etched region using MOCVD or MBE. 1- w In w As; where w is selected from 0.74 to 0.84;

[0012] S4. Remove the cap layer Ga1-z In z As and in the undoped P-type layer Al 1-t In t P-doped Al on the surface of As 1-w In w As;

[0013] S5. A passivation film is grown on the exposed upper surface using PECVD or ALD; a metal contact layer pattern is formed on the surface of the passivation film using photolithography; and P and N electrodes are formed by magnetron sputtering or electron beam evaporation.

[0014] The preparation method according to embodiments of the present invention has at least the following beneficial effects:

[0015] This invention does not employ the traditional Zn diffusion process. Instead, it uses etching and then grows P-doped Al in the etched region via MOCVD or MBE. 1-w In w The As approach overcomes the challenges of Zn diffusion caused by the large lattice mismatch between the high-In-content InGaAs epitaxial layer and the substrate, as well as the presence of numerous dislocations and defects within the material. It achieves efficient and controllable process parameters while retaining the advantages of planar junction devices, thus improving device performance.

[0016] According to a preferred embodiment of the present invention, the buffer layer Al 1-x In x The thickness of As is 2–6 μm.

[0017] According to a preferred embodiment of the present invention, the N-type contact layer In u Ga 1-u The thickness of As is 0.5-1.5um.

[0018] According to a preferred embodiment of the present invention, the absorbent layer In y Ga 1-y The thickness of As is 1–3 μm.

[0019] According to a preferred embodiment of the present invention, the undoped P-type layer Al 1-t In t The thickness of As is 0.3–1.5 μm.

[0020] According to a preferred embodiment of the present invention, the cap layer Ga 1-z In z The thickness of As is 0.01 to 0.1 μm.

[0021] According to a preferred embodiment of the present invention, the dielectric film is selected from SiO2 or SiN dielectric films.

[0022] According to a preferred embodiment of the present invention, the thickness of the dielectric film is 100 to 1000 nm.

[0023] According to a preferred embodiment of the present invention, the passivation film is selected from one of SiN, SiO2 or Al2O3.

[0024] According to a preferred embodiment of the present invention, in step S2, the components of the etching solution using the wet etching process include phosphoric acid, citric acid, hydrogen peroxide and water.

[0025] According to a preferred embodiment of the present invention, the volume ratio of phosphoric acid, citric acid, hydrogen peroxide and water is (8-15):100:(10-20):(100-180).

[0026] According to a preferred embodiment of the present invention, the P-doped Al 1-w In w The Zn doping concentration in As is 3*E18~8*E18 cm⁻¹ -3 .

[0027] According to a preferred embodiment of the present invention, in step S3, the P-doped Al is grown. 1-w In w The conditions for As must include at least:

[0028] The growth temperature is 450–660℃;

[0029] ii. Vapor pressure is 45–75 Torr;

[0030] iii. The growth rate is 0.5–5 A / s.

[0031] According to a second aspect of the present invention, a planar shortwave infrared detector is prepared by the method for preparing a planar shortwave infrared detector as described in the first aspect of the present invention.

[0032] The third aspect of this invention provides applications of the planar shortwave infrared detector described in the first aspect of this invention in space remote sensing, agriculture, and industry.

[0033] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0035] Figure 1 This is a schematic diagram of the process for fabricating a planar shortwave infrared detector according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of a planar shortwave infrared detector in proportion.

[0037] Figure 3 This is an IV curve diagram of the planar shortwave infrared detector in the embodiments and comparative examples of the present invention. Detailed Implementation

[0038] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0039] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0040] Example

[0041] This example provides a planar short-wave infrared detector, and its fabrication process is illustrated in the following diagram. Figure 1 As shown, the preparation steps are as follows:

[0042] S1. Using an MOCVD machine, a buffer layer Al is sequentially grown on an n-InP substrate. x In 1-x As, N-type contact layer InAl 0.82 As, absorption layer In 0.82 Ga 0.18 As, undoped p-type layer Al 0.18 In 0.82 As and cap layer Ga 0.18 In 0.82 As; Al x In 1- x The As growth temperature was 620℃; the vapor pressure was 45 Torr; and the final growth rate was controlled at 2 A / s. 0.18 In 0.82 The As growth temperature was 630℃; the vapor pressure was 45 Torr; and the final growth rate was controlled at 3 A / s.

[0043] S2. Grow a dielectric film on the surface of the cap layer; make openings in the dielectric film to expose the cap layer; use a wet etching process to etch the exposed cap layer; the etching depth is less than or equal to the sum of the thickness of the cap layer and the undoped P-type layer, and the wet etching solution ratio is: phosphoric acid: citric acid: hydrogen peroxide: water = 3:25:4:25;

[0044] S3. After etching, remove the dielectric film; grow P-doped Al in the etched region using MOCVD. 0.18 In 0.82 As, the surface is acid-treated before growth, then soaked in clean isopropanol for 1-5 minutes, then dried in an N2 oven, and then put into the epitaxial equipment to start epitaxial growth;

[0045] S4. Remove the cap layer and the P-doped Al on the surface of the undoped P-type layer. 0.18 In 0.82 As;

[0046] S5. Using PECVD (growth gases SiH4:O2:Ar = 120:10:116, power 380W, growth temperature 150℃), a SiO2 passivation film is grown on all exposed upper surfaces; a metal contact layer pattern is formed on the surface of the passivation film using photolithography, and P and N electrodes are formed by magnetron sputtering.

[0047] Comparative Example

[0048] This example provides a planar shortwave infrared detector, the schematic diagram of which is shown below. Figure 2 As shown, the preparation steps are as follows:

[0049] S1. Buffer layers Al are sequentially grown on an n-InP substrate using MOCVD. 0.18 In 0.82 As, N-type contact layer InAlAs, absorption layer In 0.82 Ga 0.18 As, undoped p-type layer Al 0.18 In 0.82 As and cap layer Ga 0.18 In 0.82 As, Al x In 1-x The As growth temperature was 620℃; the vapor pressure was 45 Torr; and the final growth rate was controlled at 2 A / s. 0.18 In 0.82 The As growth temperature was 630℃; the vapor pressure was 45 Torr; and the final growth rate was controlled at 3 A / s.

[0050] S2. A dielectric film is grown on the surface of the cap layer; pores are made in the dielectric film to expose the cap layer;

[0051] S3. Zn doping is performed on the opened dielectric pores using a Zn diffusion process. The Zn diffusion conditions are as follows, taking MOCVD as an example: diffusion temperature is 560℃, vapor pressure is 50 Torr, Zn flow rate is 35cc, and Zn ion concentration is not less than 1*E18 cm⁻¹. -3 ;

[0052] S4. Remove the barrier dielectric layer from the Zn ion implantation, and grow a SiO2 passivation film on all exposed upper surfaces using PECVD (growth gases are SiH4:O2:Ar = 120:10:116, power is 380W, growth temperature is 150℃); use photolithography to form the pattern of the metal contact layer on the surface of the passivation film, and use magnetron sputtering or electron beam evaporation to form P and N electrodes.

[0053] Performance testing

[0054] The planar shortwave infrared detectors prepared in the embodiments and comparative examples of this invention were subjected to IV curve tests, and the results are as follows: Figure 3 As shown, from Figure 3 The dark current test results at room temperature show that the dark current of the short-wave infrared detector (red curve) in this embodiment is significantly lower than that of the short-wave infrared detector (black line) in the comparative example by two orders of magnitude. Furthermore, as the reverse bias voltage increases, the increase in dark current decreases significantly, and the flat region is longer, indicating that the tunneling leakage current of the device is also significantly reduced. This indicates that the device performance of the focal plane under this structure is significantly improved.

[0055] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for fabricating a planar shortwave infrared detector, characterized in that, Includes the following steps: S1. Buffer layers Al are sequentially grown on an n-InP substrate using MOCVD or MBE deposition methods. 1-x In x As, N-type contact layer In u Ga 1-u As, absorption layer In y Ga 1-y As, undoped p-type layer Al 1-t In t As and cap layer Ga 1-z In z As; where x is 0.52~0.84; u, y, t and z are independently selected from 0.74~0.84; S2, in the cap layer Ga 1-z In z A dielectric film is grown on the surface of As; pores are created in the dielectric film to allow the cap layer Ga to be formed. 1-z In z As is exposed; a wet etching process is used to expose the Ga cap layer. 1-z In z As is used for etching; the etching depth is less than or equal to the cap layer Ga. 1-z In z As and undoped P-type layer Al 1-t In t The sum of the thicknesses of As; S3. After etching, remove the dielectric film; grow P-doped Al in the etched region using MOCVD or MBE. 1-w In w As; where w is selected from 0.74 to 0.84; S4. Remove the cap layer Ga 1-z In z As and in the undoped P-type layer Al 1-t In t P-doped Al on the surface of As 1- w In w As; S5. A passivation film is grown on the exposed upper surface using PECVD or ALD; a metal contact layer pattern is formed on the surface of the passivation film using photolithography; and P and N electrodes are formed by magnetron sputtering or electron beam evaporation.

2. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The buffer layer Al 1-x In x The thickness of As is 2~6μm.

3. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The N-type contact layer In u Ga 1-u The thickness of As is 0.5~1.5μm.

4. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The absorption layer In y Ga 1-y The thickness of As is 1~3μm.

5. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The undoped P-type layer Al 1-t In t The thickness of As is 0.3~1.5μm.

6. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The cap layer Ga 1-z In z The thickness of As is 0.01~0.1μm.

7. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The dielectric film is selected from SiO2 or SiN dielectric films.

8. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The thickness of the dielectric film is 100~1000nm.

9. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, The passivation film is composed of one of SiN, SiO2 or Al2O3.

10. The method for fabricating a planar shortwave infrared detector according to claim 1, characterized in that, In step S3, the P-doped Al is grown. 1-w In w The conditions for As must include at least: The growth temperature is 450~660℃; ii. Vapor pressure is 45~75 Torr; iii. The growth rate is 0.5~5A / s.

11. A planar shortwave infrared detector, characterized in that, It is prepared by the method of preparing the planar shortwave infrared detector according to any one of claims 1 to 10.

12. The application of the planar shortwave infrared detector according to claim 11 in the fields of space remote sensing and agriculture.

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