High-saturation photoelectric detector and preparation method thereof

Abstract

The invention provides a high-saturation photoelectric detector and a preparation method thereof. The high-saturation photoelectric detector comprises an N-type silicon substrate (1); the carrier transition region (2), the photoelectron active region (3) and the P-type contact layer (4) are sequentially grown on the N-type silicon substrate (1); the first metal electrode (81) is arranged on the P-type contact layer (4); the second metal electrode (82) is arranged on the N-type silicon substrate (1); the electrical isolation layer (7) grows on the table top of the N-type silicon substrate (1) and grows on the surfaces of the carrier transition region (2), the photoelectron active region (3) and the P-type contact layer (4); the antireflection film grows on the exposed area of the upper surface of the P-type contact layer (4) and the upper surface of the electrical isolation layer (7); wherein the thicknesses of the carrier transition region (2) and the photoelectron active region (3) are designed, so that the transition time of photo-induced electrons and the transition time of holes are the same, and blocking caused by the fact that carriers are not guided out in time under high power can be reduced.

Description

Technical Field

[0001] The present disclosure relates to the fields of silicon-based optoelectronic technology and photoelectric detection technology, and in particular to a high-saturation photoelectric detector and a preparation method thereof. Background Art

[0002] Exponential traffic growth, the need for high-speed wireless data communications, and the continuous deployment of innovative wireless technologies, services, and applications have put tremendous pressure on mobile network operators. In order to meet the broadband requirements of communication systems and reduce energy consumption, wireless communication over fiber technology, which combines microwave radio frequency technology and photonic technology, has attracted widespread attention.

[0003] Wireless communication over optical fiber combines the advantages of high-speed optical communication and mobile wireless communication, and is a very promising development direction for future communication networks. RoF antenna arrays need to receive high-power analog signals and require detectors with high linearity and high dynamic range, which can greatly reduce signal distortion and easily improve system transmission capacity. At the same time, it can eliminate the need for expensive and noisy millimeter-wave amplifiers in traditional RoF links, providing high gain, low noise and high spurious-free dynamic range. Since microwave photonic links and analog signal communication systems require detectors to have higher saturation photocurrents, and long-wavelength light is conducive to propagation in free space. The bandgap width of germanium-tin alloy is adjustable with the change of tin composition, and the wavelength can be extended from 1.55μm to 2μm or even 4μm. The photodetector prepared by germanium-tin alloy has the advantage of being compatible with silicon-based CMOS process and has good economic benefits. Therefore, the development of long-wavelength silicon-based germanium-tin high-saturation detectors has far-reaching significance. Summary of the invention

[0004] In view of the above problems, the present invention provides a high saturation photodetector and a preparation method thereof to solve the above technical problems.

[0005] One aspect of the present disclosure provides a high-saturation photodetector, comprising: an N-type silicon substrate; a carrier transition region grown in the central region of the N-type silicon substrate; a photoelectron active region grown on the upper surface of the carrier transition region; a P-type contact layer grown on the upper surface of the photoelectron active region; a first metal electrode disposed on the P-type contact layer; a second metal electrode disposed on the N-type silicon substrate; an electrical isolation layer grown on the exposed table of the N-type silicon substrate, and grown on the side walls of the carrier transition region, the photoelectron active region and the P-type contact layer and a region extending from the edge of the P-type contact layer to the first metal electrode; an anti-reflection film grown on the exposed region of the upper surface of the P-type contact layer and the upper surface of the electrical isolation layer; wherein the thickness of the carrier transition region and the photoelectron active region are designed so that the transit times of photogenerated electrons and holes are the same.

[0006] Optionally, the shape of the N-type silicon substrate is circular; the carrier transition region, the optoelectronic active region and the P-type contact layer are circles with equal diameters, and the diameters are smaller than the diameter of the N-type silicon substrate, and are coaxial with the N-type silicon substrate; the shape of the first metal electrode is annular, coaxial with the N-type silicon substrate, and its diameter is smaller than the P-type contact layer; the shape of the second metal electrode is annular, coaxial with the N-type silicon substrate, and its diameter is smaller than the N-type silicon substrate and larger than the carrier transition region.

[0007] Optionally, the material of the carrier transition region is a fully relaxed germanium material; the material of the optoelectronic active region is a germanium-tin material, wherein the tin content is 13% to 15%, and the absorption wavelength range is 2050nm to 3200nm.

[0008] Optionally, the composition in the optoelectronic active region is graded, and the lattice of the contact surface between the optoelectronic active region and the P-type contact layer is equal.

[0009] Optionally, the material of the P-type contact layer is germanium-tin material, which is doped with boron and has a tin content of less than 6%.

[0010] Optionally, the antireflection film includes a silicon nitride antireflection film grown on the upper surface of the P-type contact layer and the upper surface of the electrical isolation layer and in contact with the first metal electrode and the second metal electrode; and a silicon oxide antireflection film covering the silicon nitride antireflection film.

[0011] Optionally, the material of the electrical isolation layer is silicon oxide.

[0012] Optionally, the thickness of the electrical isolation layer is greater than half of the sum of the thicknesses of the carrier transition region, the optoelectronic active region and the P-type contact layer.

[0013] Optionally, the bottom layer of the first metal electrode and the second metal electrode is a nickel layer, and the upper layer is an aluminum layer.

[0014] Another aspect of the present disclosure provides a preparation method, which is applied to the high saturation photodetector as described in any one of the first aspects, comprising: growing a fully relaxed germanium layer as a carrier transition layer on a cleaned N-type silicon substrate by a two-step method; optimizing and reconstructing the surface of the carrier transition layer by cyclic annealing, using the lattice seed crystals on the surface to epitaxially grow germanium tin material to form an optoelectronic active region; epitaxially growing a P-type contact layer in the optoelectronic active region, wherein the P-type contact layer forms a PIN structure with the N-type silicon substrate; etching the carrier transition layer, the optoelectronic active region and the P-type contact layer; and etching the carrier transition layer, the optoelectronic active region and the P-type contact layer. The method comprises the following steps: forming a first metal electrode and a second metal electrode by forming a first layer of a P-type contact layer and a second layer of a N-type silicon substrate; forming a carrier transit layer, a photoelectron active region and a table of a P-type contact layer in the central region of the N-type silicon substrate; growing an electrical isolation layer on the exposed region of the N-type silicon substrate and the surface of the table, etching an opening on the electrical isolation layer to expose the surface of the N-type substrate and the P-type contact layer, and depositing a nickel layer and an aluminum layer in sequence after photolithography to form a first metal electrode and a second metal electrode; growing an antireflection film on the exposed region of the upper surface of the P-type contact layer and the upper surface of the electrical isolation layer to complete the preparation of a high-saturation photodetector.

[0015] At least one of the above technical solutions adopted in the embodiments of the present disclosure can achieve the following beneficial effects:

[0016] According to the high-saturation photodetector provided by the present invention, by calculating the drift speed of electrons and holes in the carrier transition zone and the photoelectron active zone, the thickness of the transition zone and the photoelectron active zone is designed so that the transition time of photogenerated electrons and holes is the same, so as to reduce the blockage caused by the untimely extraction of carriers under high power. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a high saturation photodetector provided by an embodiment of the present disclosure is schematically shown;

[0019] Figure 2 The light response curve and dark current curve of a high saturation photodetector provided by an embodiment of the present disclosure under high-power illumination are schematically shown;

[0020] Figure 3 A schematic diagram of the electric field in a PIN structure of a high saturation photodetector provided by an embodiment of the present disclosure is schematically shown.

[0021] Description of reference numerals:

[0022] 1-N-type silicon substrate; 2-carrier transition region; 3-photoelectron active region; 4-P-type contact layer; 5-silicon oxide anti-reflection film; 6-silicon nitride anti-reflection film; 7-electrical isolation layer; 81-first metal electrode; 82-second metal electrode. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0024] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0025] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0026] like Figure 1 As shown, a high saturation photodetector provided by an embodiment of the present disclosure includes an N-type silicon substrate 1, a carrier transition region 2, an optoelectronic active region 3, a P-type contact layer 4, a first metal electrode 81, a second metal electrode 82, an electrical isolation layer 7 and an anti-reflection film.

[0027] Among them, the carrier transition region 2 is grown in the central area of ​​the N-type silicon substrate 1; the optoelectronic active region 3 is grown on the upper surface of the carrier transition region 2; the P-type contact layer 4 is grown on the upper surface of the optoelectronic active region 3; the first metal electrode 81 is arranged on the P-type contact layer 4; the second metal electrode 82 is arranged on the N-type silicon substrate 1; the electrical isolation layer 7 is grown on the exposed table of the N-type silicon substrate 1, and is grown on the side walls of the carrier transition region 2, the optoelectronic active region 3 and the P-type contact layer 4 and the area extending from the edge of the P-type contact layer 4 to the first metal electrode 81; the anti-reflection film is grown on the exposed area on the upper surface of the P-type contact layer 4 and the upper surface of the electrical isolation layer 7; wherein the thickness of the carrier transition region 2 and the optoelectronic active region 3 is designed so that the transit time of photogenerated electrons and holes is the same.

[0028] refer to Figure 1, the shape of the N-type silicon substrate 1 is circular; the carrier transit region 2, the photoelectron active region 3 and the P-type contact layer 4 are circular with equal diameters, and the diameters are smaller than the diameter of the N-type silicon substrate 1, and are coaxial with the N-type silicon substrate 1; the shape of the first metal electrode 81 is annular, coaxial with the N-type silicon substrate 1, and its diameter is smaller than the P-type contact layer 4; the shape of the second metal electrode 82 is annular, coaxial with the N-type silicon substrate 1, and its diameter is smaller than the N-type silicon substrate 1 and larger than the carrier transit region 2. It should be noted that, Figure 1 The high-saturation photodetector structure shown is one schematic structural form of the high-saturation photodetector provided by the present disclosure, but is not limited thereto.

[0029] In this embodiment, the photoelectron active region 3 is epitaxially grown by a composition gradient method, and a single-component P-type contact layer 4 doped with B element is epitaxially grown on the photoelectron active region 3. The photoelectron active region uses an alloy material with a composition of 13-15%, and the material of the P-type contact layer 4 is a germanium-tin material doped with boron element, and the tin content is less than 6%. The composition gradient method is used to slow down the relaxation speed of the crystal, and the lattice of the outermost layer of the photoelectron active region 3 is roughly equal to the lattice of the fully relaxed P-type contact layer 4.

[0030] In this embodiment, the anti-reflection film includes a silicon nitride anti-reflection film 6, which is grown on the upper surface of the P-type contact layer 4 and the upper surface of the electrical isolation layer 7 and is in contact with the first metal electrode 81 and the second metal electrode 82; and a silicon oxide anti-reflection film 5, which covers the silicon nitride anti-reflection film 6. Light is incident from free space, and through the double-layer anti-reflection effect of silicon oxide and silicon nitride, it has an anti-reflection effect and enters the high-saturation photodetector. Optionally, the anti-reflection film can also use a single-layer film or other anti-reflection film solutions.

[0031] In this embodiment, the electrical isolation layer 7 uses silicon oxide compatible with silicon technology, which plays the role of fixing the dangling bonds of the sidewall and electrically isolating the sidewall of the device. The thickness of the electrical isolation layer 7 is designed according to the thickness of the carrier transition region 2, the photoelectron active region 3 and the thickness of the P-type contact layer 4, and its thickness is greater than half of the sum of the thickness of the carrier transition region 2, the photoelectron active region 3 and the P-type contact layer 4.

[0032] In this embodiment, the bottom layer of the first metal electrode 81 and the second metal electrode 82 is a nickel layer, and the upper layer is an aluminum layer, which can form good adhesion with the semiconductor surface and form a good ohmic contact.

[0033] According to the high-saturation photodetector provided by the embodiment of the present disclosure, when light is incident from free space, it enters the device through the double-layer anti-reflection effect of silicon oxide and silicon nitride, which has the effect of increasing transmittance; after the light passes through the anti-reflection layer, the light is not absorbed or absorbed very little in the P-type contact layer 4, and then enters the photoelectron active area 3 to generate carriers. When the light intensity is large, there are too many photogenerated carriers and they are not exported in time, causing charge crowding in the intrinsic region (active region of photoelectrons and transition region of carriers). In the same uniform medium, the drift speeds of electrons and holes are different. Therefore, after the photogenerated electron-hole pairs are generated, the time they are collected by the electrodes is different. This is an important reason for limiting the decrease in the saturation photocurrent of the detector under high power.

[0034] Therefore, in this embodiment, the optoelectronic active region 3 uses a germanium-tin material of a certain composition, and electro-optical conversion occurs. The carrier transition region 2 uses a germanium material, and no electro-optical conversion occurs; the optoelectronic active region 3 and the carrier transition region 2 are intrinsic materials, and no net residual charge is generated. Therefore, the electric displacement vector D is continuous in the intrinsic region:

[0035]

[0036] According to the relationship between the electric displacement vector ε and the electric field strength E:

[0037] ε Ge E Ge =ε GeSn E GeSn

[0038] The relationship between carrier mobility μ and migration velocity v is:

[0039] μ h，e E=v h，e

[0040] The carrier transit time τ is:

[0041] τ h，e = l h，e / v h，e

[0042] By rationally designing the drift distance l of holes and electrons so that the transit time of carriers is roughly equal, the accumulation of photogenerated carriers under high light power can be effectively reduced.

[0043] In this embodiment, since the speed of electrons in germanium is about twice that of holes, the germanium layer does not absorb 2 micrometers of light and does not generate photogenerated carriers, and in this embodiment, it serves as the carrier transition region 2.

[0044] In this embodiment, the material of the carrier transit region 2 is a fully relaxed germanium material; the material of the optoelectronic active region 3 is a germanium-tin material, wherein the tin content is 13% to 15%, and the absorption wavelength range is 2050nm to 3200nm.

[0045] like Figure 2 As shown, the photocurrent of the high saturation photodetector provided by the embodiment of the present disclosure can be as high as 60 mA.

[0046] Figure 3 The PIN structure of the high saturation photodetector provided by the embodiment of the present disclosure is shown.

[0047] Another aspect of the present disclosure provides a preparation method for use in Figure 1 The high saturation photodetector shown includes S1 to S6.

[0048] S1, growing a fully relaxed germanium layer as a carrier transition layer on a cleaned N-type silicon substrate 1 by a two-step method.

[0049] S2, cyclic annealing to optimize and reconstruct the surface of the carrier transit layer, using the lattice seed crystals on the surface to epitaxially grow germanium tin material to form the optoelectronic active region 3.

[0050] S3 , epitaxially growing a P-type contact layer 4 in the optoelectronic active region 3 , the P-type contact layer 4 and the N-type silicon substrate 1 forming a PIN structure.

[0051] S4, etching the carrier transit layer, the optoelectronic active region 3 and the P-type contact layer 4 to the N-type silicon substrate 1, and forming a table of the carrier transit layer, the optoelectronic active region 3 and the P-type contact layer 4 in the central area of ​​the N-type silicon substrate 1.

[0052] S5, after growing an electrical isolation layer 7 on the exposed area and the surface of the table of the N-type silicon substrate 1, a hole is etched in the electrical isolation layer to expose the N-type substrate surface and the P-type contact layer 4, and a nickel layer and an aluminum layer are deposited successively after photolithography to form a first metal electrode 81 and a second metal electrode 82.

[0053] S6, growing an anti-reflection film on the exposed area of ​​the upper surface of the P-type contact layer 4 and the upper surface of the electrical isolation layer 7, thereby completing the preparation of a high-saturation photodetector.

[0054] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0055] Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

Claims

1. A high saturation photodetector, characterized in that: include: N-type silicon substrate (1); A carrier transition region (2) grown in the central region of the N-type silicon substrate (1); A photoelectron active region (3) grown on the upper surface of the carrier transition region (2); A P-type contact layer (4) grown on the upper surface of the photoelectron active region (3); A first metal electrode (81) is disposed on the P-type contact layer (4); A second metal electrode (82) is provided on the N-type silicon substrate (1); An electrical isolation layer (7) grown on the exposed table surface of the N-type silicon substrate (1), and grown on the side walls of the carrier transition region (2), the photoelectron active region (3), and the P-type contact layer (4), and a region extending from the edge of the P-type contact layer (4) to the first metal electrode (81); an anti-reflection film, grown on an exposed area on the upper surface of the P-type contact layer (4) and on the upper surface of the electrical isolation layer (7); The thicknesses of the carrier transit region (2) and the photoelectron active region (3) are designed so that the transit times of photogenerated electrons and holes are the same.

2. The high saturation photodetector according to claim 1, characterized in that: The N-type silicon substrate (1) is circular in shape; the carrier transition region (2), the photoelectron active region (3) and the P-type contact layer (4) are circular in shape with equal diameters, and the diameters are smaller than the diameter of the N-type silicon substrate (1), and are coaxial with the N-type silicon substrate (1); the first metal electrode (81) is annular in shape, coaxial with the N-type silicon substrate (1), and has a diameter smaller than the P-type contact layer (4); the second metal electrode (82) is annular in shape, coaxial with the N-type silicon substrate (1), and has a diameter smaller than the N-type silicon substrate (1) and larger than the carrier transition region (2).

3. The high saturation photodetector according to claim 1, characterized in that: The material of the carrier transition region (2) is a fully relaxed germanium material; the material of the photoelectron active region (3) is a germanium-tin material, wherein the tin content is 13% to 15% and the absorption wavelength range is 2050nm to 3200nm.

4. The high saturation photodetector according to claim 3, characterized in that: The composition of tin in the photoelectron active region (3) gradually increases from bottom to top, and the lattice of the contact surface between the tin and the P-type contact layer (4) is equal.

5. The high saturation photodetector according to claim 1, characterized in that: The material of the P-type contact layer (4) is germanium-tin material, which is doped with boron element and has a tin content of less than 6%.

6. The high saturation photodetector according to claim 1, characterized in that: The antireflection film comprises: a silicon nitride anti-reflection film, grown on the upper surface of the P-type contact layer (4) and the upper surface of the electrical isolation layer (7), and in contact with the first metal electrode (81) and the second metal electrode (82); A silicon oxide anti-reflection film (5) covers the silicon nitride anti-reflection film (6).

7. The high saturation photodetector according to claim 1, characterized in that: The material of the electrical isolation layer (7) is silicon oxide.

8. The high saturation photodetector according to claim 7, characterized in that: The thickness of the electrical isolation layer (7) is greater than half of the sum of the thicknesses of the carrier transit region (2), the photoelectron active region (3) and the P-type contact layer (4).

9. The high saturation photodetector according to claim 1, characterized in that: The bottom layer of the first metal electrode (81) and the second metal electrode (82) is a nickel layer, and the upper layer is an aluminum layer.

10. A preparation method, applied to the high saturation photodetector according to any one of claims 1 to 9, characterized in that: include: A fully relaxed germanium layer is grown on a cleaned N-type silicon substrate (1) by a two-step method to serve as a carrier transition layer; Cyclic annealing optimizes and reconstructs the surface of the carrier transit layer, and uses the lattice seed crystals on the surface to epitaxially grow germanium tin material to form an optoelectronic active region (3); Epitaxially growing a P-type contact layer (4) in the photoelectron active region (3), wherein the P-type contact layer (4) and the N-type silicon substrate (1) form a PIN structure; Etching the carrier transit layer, the photoelectron active region (3) and the P-type contact layer (4) to the N-type silicon substrate (1), and forming a table of the carrier transit layer, the photoelectron active region (3) and the P-type contact layer (4) in the central region of the N-type silicon substrate (1); After growing an electrical isolation layer (7) on the exposed area of ​​the N-type silicon substrate (1) and the surface of the table, etching holes in the electrical isolation layer to expose the surface of the N-type substrate and the P-type contact layer (4), and depositing a nickel layer and an aluminum layer in sequence after photolithography to form a first metal electrode (81) and a second metal electrode (82); An anti-reflection film is grown on the exposed area on the upper surface of the P-type contact layer (4) and the upper surface of the electrical isolation layer (7), thereby completing the preparation of a high-saturation photoelectric detector.

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