Planar short wave infrared detector and preparation method and application thereof

Abstract

The invention discloses a planar short-wave infrared detector and a preparation method and application thereof. The preparation method comprises the following steps: S1, sequentially growing the buffer layer, the N-type contact layer, the absorption layer, the undoped P-type layer and the cap layer on the substrate; s2, growing a layer of dielectric film on the surface of the cap layer; corroding the exposed cap layer by adopting a wet etching process; s3, removing the dielectric film after corrosion is finished; p-doped Al < 1-w > InwAs is grown in the corrosion area; s4, removing the cap layer and the P-doped Al < 1-w > InwAs on the upper surface of the undoped P-type layer; s5, growing a layer of passivation film on all the exposed upper surfaces; and forming a pattern of a metal contact layer on the surface of the passive film by photoetching to form a P electrode and an N electrode. According to the invention, the problem of high Zn diffusion process difficulty caused by large lattice mismatch between the epitaxial layer with high In component and the substrate is solved, and the performance of the device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photodetectors, and in particular 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 band of 1.8 μm - 2.5 μm have also attracted more and more research interest. For example, high-resolution multi-spectral imaging in the 1.9 - 2.5 μm band can be used for detecting crop moisture; the near-infrared spectrum of 2.26 - 2.38 μm can be used for detecting gases such as CH4, CO, H2O, and N2O; InGaAs detectors in the 2.5 μm band for observing 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 metalorganic 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 detectors. Planar 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] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present invention provides a method for preparing a planar short-wave infrared detector, which solves the problem of difficulty in Zn diffusion process due to high mismatch structure, achieves efficient controllability of process parameters while retaining the advantages of planar junction devices, and improves the performance of the device.

[0006] The second aspect of the present invention also provides a planar short-wave infrared detector.

[0007] The third aspect of the present invention also provides an application of a planar short-wave infrared detector.

[0008] A method for preparing a planar short-wave infrared detector according to a first aspect of the present invention comprises the following steps:

[0009] S1. Buffer layer Al is grown on n-InP substrate in sequence by MOCVD or MBE deposition. 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; wherein 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; a hole is opened in the dielectric film so that the cap layer Ga 1-z In z As is exposed; the exposed cap layer Ga is etched by wet etching process. 1-z In z As is corroded; the corrosion 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 thickness of As;

[0011] S3, after the etching is completed, the dielectric film is removed; P-doped Al is grown in the etching area using MOCVD or MBE 1- w In w As; wherein w is selected from 0.74 to 0.84;

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

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

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

[0015] The present invention does not use the conventional Zn diffusion process, but rather uses etching and MOCVD or MBE to grow P-doped Al in the etching area. 1-w In w The As method overcomes the difficulty of the Zn diffusion process caused by the large lattice mismatch between the InGaAs epitaxial layer with a high In content and the substrate, and the presence of many dislocations and defects inside the material. It achieves efficient controllability of process parameters while retaining the advantages of planar junction devices and 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 to 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 absorption layer In y Ga 1-y The thickness of As is 1 to 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 to 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 um.

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

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

[0023] According to a preferred embodiment of the present invention, the component of 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 -3 .

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

[0028] i Growth temperature is 450~660℃;

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

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

[0031] A planar short-wave infrared detector provided according to a second aspect of the present invention is prepared by the method for preparing a planar short-wave infrared detector according to the first aspect of the present invention.

[0032] The third aspect of the present invention provides the application of the planar short-wave infrared detector described in the first aspect of the present invention in the fields of space remote sensing, agriculture and industry.

[0033] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] Figure 1 It is a schematic diagram of the process of preparing a planar short-wave infrared detector according to an embodiment of the present invention;

[0036] Figure 2 It is a structural schematic diagram of a planar short-wave infrared detector of comparative example;

[0037] Figure 3 1 is an IV curve diagram of the planar short-wave infrared detector of the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0038] The following are specific embodiments of the present invention, and the technical solutions of the present invention are 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 the present invention are conventional reagents, methods and equipment in the art.

[0040] Example

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

[0042] S1. Use MOCVD machine to grow buffer layer Al on 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 growth temperature of As is 620℃; the vapor pressure is 45 Torr, and the final controlled growth rate is 2A / s. 0.18 In 0.82 The As growth temperature is 630°C; the vapor pressure is 45 Torr, and the final controlled growth rate is 3A / s;

[0043] S2. A dielectric film is grown on the surface of the cap layer; a hole is opened in the dielectric film to expose the cap layer; the exposed cap layer is corroded by a wet etching process; 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 solution etching ratio is: phosphoric acid: citric acid: hydrogen peroxide: water = 3:25:4:25;

[0044] S3, after the etching is completed, the dielectric film is removed; P-doped Al is grown in the etching area using MOCVD 0.18 In 0.82 As, the surface is treated with acid before growth, then soaked in clean isopropanol for 1-5 minutes, dried in a N2 oven, and placed in 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. Use PECVD (growth gases are SiH4:O2:Ar=120:10:116, power is 380W, and growth temperature is 150°C) to grow a layer of SiO2 passivation film on all exposed upper surfaces; use photolithography to form the pattern of the metal contact layer on the surface of the passivation film, and use magnetron sputtering to form P and N electrodes.

[0047] Comparative Example

[0048] This example provides a planar short-wave infrared detector, and its structural diagram is as follows Figure 2 As shown, the preparation steps are as follows:

[0049] S1. Use MOCVD to grow buffer layer Al on n-InP substrate 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 growth temperature of As is 620℃; the vapor pressure is 45 Torr, and the final controlled growth rate is 2A / s. 0.18 In 0.82 The As growth temperature is 630°C; the vapor pressure is 45 Torr, and the final controlled growth rate is 3A / s;

[0050] S2, growing a dielectric film on the surface of the cap layer; opening holes in the dielectric film to expose the cap layer;

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

[0052] S4. Remove the Zn ion-implanted blocking dielectric layer, and grow a layer of SiO2 passivation film on all exposed upper surfaces using PECVD (growth gases are SiH4:O2:Ar=120:10:116, power is 380 W, and growth temperature is 150°C); 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 the P electrode and N electrode.

[0053] Performance Testing

[0054] The planar short-wave infrared detectors prepared in the embodiments of the present invention and the comparative examples were subjected to IV curve tests, and the results are shown in FIG. Figure 3 As shown, from Figure 3 From the dark current test results at room temperature, it can be seen that the dark current of the short-wave infrared detector (red curve) of the embodiment of the present invention is significantly 2 orders of magnitude lower than that of the short-wave infrared detector (black line) of the comparative example, and with the increase of the reverse bias voltage, the increase in the dark current is significantly reduced, and the flat area is longer, indicating that the tunneling leakage of the device is also significantly reduced, indicating that the device performance in the focal plane of this structure is significantly improved.

[0055] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for preparing a planar short-wave infrared detector, characterized in that: The steps include: S1. Buffer layer Al is grown on n-InP substrate in sequence by MOCVD or MBE deposition. 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; wherein x is 0.52 to 0.84; u, y, t and z are independently selected from 0.74 to 0.84; S2, in the cap layer Ga 1-z In z A dielectric film is grown on the surface of As; a hole is opened in the dielectric film so that the cap layer Ga 1-z In z As is exposed; the exposed cap layer Ga is etched by wet etching process. 1-z In z As is corroded; the corrosion 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 thickness of As; S3, after the etching is completed, the dielectric film is removed; P-doped Al is grown in the etching area using MOCVD or MBE 1-w In w As; wherein w is selected from 0.74 to 0.84; S4, removing the cap layer Ga 1-z In z As and Al in the undoped P-type layer 1-t In t P-doped Al on As surface 1- w In w As; S5. A passivation film is grown on the exposed upper surface by using PECVD or ALD; a metal contact layer is patterned on the surface of the passivation film by using photolithography, and a P electrode and an N electrode are formed by using magnetron sputtering or electron beam evaporation.

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

3. The method for preparing a planar short-wave 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 to 1.5 μm.

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

5. The method for preparing a planar short-wave 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 to 1.5 μm.

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

7. The method for preparing a planar short-wave infrared detector according to claim 1, characterized in that: The dielectric film is selected from SiO2 or SiN dielectric film; Preferably, the thickness of the dielectric film is 100-1000 nm; Preferably, the component of the passivation film is selected from one of SiN, SiO2 or Al2O3.

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

9. A planar short-wave infrared detector, characterized in that: The planar short-wave infrared detector is prepared by the preparation method of any one of claims 1 to 8.

10. Application of the planar short-wave infrared detector according to any one of claims 1 to 8 in the fields of space remote sensing, agriculture and industry.

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