Absorption-enhanced detector structure and preparation method thereof
By adopting an absorption-enhanced detector structure in the photodetector and regulating the light field using the grating array structure of the optical capture layer, the problem that existing photodetectors are difficult to achieve high bandwidth and high quantum efficiency at the same time is solved, and the high speed and high responsiveness characteristics of the detector are achieved.
Patent Information
- Application Number
- CN202311243395.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-25
- Publication Date
- 2025-03-28
AI Technical Summary
The existing photodetector structures are difficult to achieve high bandwidth and high quantum efficiency at the same time, resulting in difficult to take into account both high speed and high responsiveness characteristics.
An absorption-enhanced detector structure is adopted, including a substrate, a first semiconductor layer, an absorption layer, a second semiconductor layer and an optical capture layer, wherein the optical capture layer is a grating array structure, by adjusting parameters of the grating array (such as diameter, height, and spacing) to maximize the diffraction capability of a specific wavelength light.
The grating array structure of the optical capture layer realizes effective light field regulation of vertical incident light, achieving the optimal diffraction absorption effect, improving the quantum efficiency of the detector, and decoupling the bandwidth and quantum efficiency of the detector, so that the detector has both high speed and high responsiveness characteristics.
Smart Images
Figure CN119730411A_ABST
Abstract
Description
Technical Field
[0001] The present invention discloses an absorption enhanced detector structure and a preparation method thereof, which are intended to improve the quantum efficiency of the photoelectric detector structure and belong to the technical field of photoelectric detectors. Background Art
[0002] Photodetectors have the ability to convert optical signals into electrical signals and are widely used in long-distance, high-speed fiber-optic communication systems and data center interconnection. In optical fiber pathways, the performance of photodetectors is the key to measuring the entire optical communication system. With the development of optical fiber communication systems, the performance requirements for photodetectors are constantly increasing. Photodetectors must have both high saturated output power and high response speed. However, the current mainstream photodetector structure faces the contradiction between large bandwidth and high quantum efficiency, and it is difficult to have both high speed and high responsiveness. Summary of the invention
[0003] 1. Technical issues to be resolved
[0004] Based on the above problems, the present disclosure provides an absorption-enhanced detector structure and a preparation method, which at least partially solves the contradiction between the large bandwidth and high quantum efficiency of the detector structure.
[0005] (II) Technical solution
[0006] On the one hand, the present disclosure provides an absorption-enhanced detector structure, which includes, from bottom to top, a substrate, a first semiconductor layer, an absorption layer, a second semiconductor layer, and an optical capture layer; wherein the upper surface of the second semiconductor layer also includes a P-annular electrode, and the optical capture layer is located within the ring of the P-annular electrode; wherein the optical capture layer is a grating array structure, and the photosensitive surface of the detector is the upper surface of the optical capture layer.
[0007] According to an embodiment of the present disclosure, the grating array structure is a rectangular array composed of cylinders; the diameter of the cylinders is 400-600nm, the height is 300-500nm, and the distance between the centers of adjacent cylinders is 500-700nm; wherein the diameter, height and distance between the centers of adjacent cylinders are adjusted according to the specific wavelength of light, so as to maximize the diffraction ability of light of a specific wavelength.
[0008] According to an embodiment of the present disclosure, the first semiconductor layer is an N-type contact layer and an N transition layer grown sequentially from bottom to top; the N-type contact layer is N-heavily doped InP with a thickness of 150 to 300 nm; the N transition layer is N-doped InGaAsP with a thickness of 100 to 200 nm; wherein the upper surface of the N-type contact layer also includes an N annular electrode, and the N transition layer is located within the ring of the N annular electrode.
[0009] According to an embodiment of the present disclosure, a silicon dioxide passivation layer film is provided between the N annular electrode and the P annular electrode.
[0010] According to an embodiment of the present disclosure, the thickness of the N annular electrode and the P annular electrode is the same as the thickness of the grating array structure.
[0011] According to an embodiment of the present disclosure, the N-annular electrode, the P-annular electrode and the grating array structure include a first metal layer and a second metal layer, and the material of the metal layer includes at least any two of titanium, tantalum, zirconium, tungsten, aluminum, bismuth and gold.
[0012] According to an embodiment of the present disclosure, the absorption layer includes: the absorption layer is a complete absorption layer and an incomplete absorption layer grown sequentially from bottom to top; the complete absorption layer is undoped InGaAs with a thickness of 150 to 250 nm; the incomplete absorption layer is P-doped InGaAs with a thickness of 30 to 50 nm.
[0013] According to an embodiment of the present disclosure, the second semiconductor layer includes: the second semiconductor layer is a P transition layer and a P-type contact layer grown sequentially from bottom to top; the P transition layer is P-doped InGaAsP with a thickness of 30 to 50 nm; the P-type contact layer is P-heavily doped InGaAs with a thickness of 50 to 80 nm.
[0014] On the other hand, the present disclosure provides a method for preparing an absorption-enhanced detector, comprising: providing a substrate, and sequentially growing a first semiconductor layer, an absorption layer, a second semiconductor layer, and an optical capture layer on the substrate from bottom to top; wherein the first semiconductor layer is an N-type contact layer and an N transition layer sequentially grown from bottom to top; and the second semiconductor layer is a P transition layer and a P-type contact layer sequentially grown from bottom to top; etching the edge portion of the P-type contact layer to the N-type contact layer to form a first table on the P-type contact layer; etching the edge portion of the N-type contact layer to the substrate to form a second table on the N-type contact layer; forming a P ring electrode on the upper surface of the first table; forming an N ring electrode on the upper surface of the second table; the N transition layer is located in the ring of the N ring electrode; growing an optical capture layer on the upper surface of the P-type contact layer; wherein the optical capture layer is located in the ring of the P ring electrode and is a grating array structure; and the photosensitive surface of the detector is the upper surface of the optical capture layer.
[0015] According to an embodiment of the present disclosure, growing an optical capture layer on the upper surface of a P-type contact layer includes: depositing a first metal layer and a second metal layer on the upper surface of the P-type contact layer by a BEB process with adhesive, and preparing the optical capture layer by a metal lift-off process.
[0016] (III) Beneficial effects
[0017] The present invention realizes effective light field control of vertically incident light through the grating array structure of the optical capture layer, achieves optimal diffraction absorption effect, and improves the quantum efficiency of the detector under a thin absorption layer; utilizes the optical capture layer to achieve decoupling of the contradiction between the bandwidth and quantum efficiency of the detector, so that the detector has both high speed and high responsiveness characteristics. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 A schematic cross-sectional structure diagram of an absorption enhanced detector structure according to an embodiment of the present disclosure is shown;
[0019] Figure 2 A top view of an absorption enhanced detector structure according to an embodiment of the present disclosure is shown;
[0020] Figure 3 A process flow chart of an optical capture layer of an absorption-enhanced detector structure according to an embodiment of the present disclosure is shown;
[0021] Figure 4 A schematic diagram of a method for preparing an absorption enhanced detector structure according to an embodiment of the present disclosure is shown;
[0022] Description of reference numerals:
[0023] 1-optical capture layer; 2-P annular electrode; 3-P-type contact layer; 4-P transition layer; 5-incomplete absorption layer; 6-complete absorption layer; 7-N transition layer; 8-N annular electrode; 9-N-type contact layer; 10-substrate. DETAILED DESCRIPTION
[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.
[0025] Figure 1 A schematic cross-sectional structure diagram of an absorption enhanced detector structure according to an embodiment of the present disclosure is shown.
[0026] like Figure 1 As shown, the absorption enhanced detector structure of this embodiment includes, from bottom to top, a substrate 10, a first semiconductor layer, an absorption layer, a second semiconductor layer, and an optical capture layer 1; wherein the upper surface of the second semiconductor layer also includes a P ring electrode 2, and the optical capture layer 1 is located within the ring of the P ring electrode 2; wherein the optical capture layer 1 is a grating array structure, and the photosensitive surface of the detector is the upper surface of the optical capture layer 1.
[0027] In this embodiment, the optical trapping layer 1 of the present disclosure is a sub-micron metal grating array structure distributed in a rectangular array.
[0028] Through the embodiments of the present disclosure, the present disclosure uses an optical capture layer to cause incident light to be diffracted and laterally coupled in a grating array structure and absorbed into an absorption layer of a detector, producing an effect similar to photon capture, thereby stimulating more photogenerated carriers, enhancing the absorption capacity of incident light, and reducing reflection of incident light, thereby improving the quantum efficiency of the detector, achieving decoupling of the contradiction between the detector bandwidth and quantum efficiency, and enabling the detector to have both high speed and high responsiveness characteristics.
[0029] On the basis of the above embodiment, the first semiconductor layer is an N-type contact layer 9 and an N-transition layer 7 grown sequentially from the bottom to the top; the N-type contact layer 9 is N-heavily doped InP with a thickness of 150 to 300 nm; the N-transition layer 7 is N-doped InGaAsP with a thickness of 100 to 200 nm; wherein the upper surface of the N-type contact layer 9 also includes an N-annular electrode 8, and the N-transition layer 7 is located within the ring of the N-annular electrode 8.
[0030] In this embodiment, the doping concentration of the N-type contact layer is 10 -19 cm -3 Si; N transition layer doping concentration is 10 -18 cm -3 Si.
[0031] According to the embodiments of the present disclosure, a good ohmic contact is formed with the N-type contact layer and the N-annular electrode; the energy band is smoothed by the N transition layer, which is beneficial to carrier transport.
[0032] On the basis of the above embodiment, the absorption layer includes: the absorption layer is a complete absorption layer 6 and an incomplete absorption layer 5 grown sequentially from the bottom to the top; the complete absorption layer 6 is undoped InGaAs with a thickness of 150 to 250 nm; the incomplete absorption layer 5 is P-doped InGaAs with a thickness of 30 to 50 nm.
[0033] In this embodiment, the doping concentration of the incomplete absorption layer is 10 -18 cm -3 .
[0034] According to the embodiments of the present disclosure, electron-hole pairs are excited in the incomplete absorption layer and the complete absorption layer, and the electrons and holes move to two levels respectively under a bias voltage to form a photogenerated current, thereby exciting more photogenerated carriers.
[0035] On the basis of the above embodiment, the second semiconductor layer includes: the second semiconductor layer is a P transition layer 4 and a P-type contact layer 3 grown sequentially from bottom to top; the P transition layer 4 is P-doped InGaAsP with a thickness of 30 to 50 nm; the P-type contact layer 3 is P-heavily doped InGaAs with a thickness of 50 to 80 nm.
[0036] In this embodiment, the doping concentration of the P transition layer is 10 -18 cm -3 Be; P-type contact layer is 10 -19 cm -3 Be.
[0037] According to the embodiments of the present disclosure, a good ohmic contact is formed with the P-type contact layer and the P-annular electrode 8 ; the energy band is made smoother by the P transition layer, which is beneficial to carrier transmission.
[0038] Based on the above embodiments, Figure 2 FIG. 4 shows a top view of an absorption enhanced detector structure according to an embodiment of the present disclosure. Figure 2 As shown, the grating array structure is a rectangular array composed of cylinders; the diameter of the cylinders is 400-600nm, the height is 300-500nm, and the distance between the centers of adjacent cylinders is 500-700nm; wherein the diameter, height and distance between the centers of adjacent cylinders are adjusted according to the specific wavelength of light to maximize the diffraction ability of light of a specific wavelength.
[0039] According to the embodiments of the present disclosure, by designing the diameter, height and spacing between the centers of the optical trapping layer cylinders, the diffraction capability of light of a specific wavelength can be maximized.
[0040] On the basis of the above embodiment, a silicon dioxide passivation layer film is provided between the N annular electrode 8 and the P annular electrode 2 .
[0041] According to the embodiments of the present disclosure, the N-annular electrode and the P-annular electrode are electrically isolated by the silicon dioxide passivation layer film.
[0042] Based on the above embodiment, the thickness of the N annular electrode 8 and the P annular electrode 2 is the same as the thickness of the grating array structure.
[0043] In this embodiment, for example, the optical trapping layer, the N-annular electrode and the P-annular electrode are 10 nm Ti and 300 nm Au deposited by the EBE process.
[0044] According to the embodiments of the present disclosure, by depositing N-annular electrodes, P-annular electrodes and a grating array structure with the same thickness at one time, preparation time is saved and preparation efficiency is improved.
[0045] Based on the above embodiments, the N annular electrode 8, the P annular electrode 2 and the grating array structure include a first metal layer and a second metal layer, and the material of the metal layer includes at least any two of titanium, tantalum, zirconium, tungsten, aluminum, bismuth and gold.
[0046] According to the embodiments of the present disclosure, the conductivity of the N-annular electrode and the P-annular electrode is improved by using the composite electrode material, and the parasitic resistance is reduced.
[0047] Another aspect of the present disclosure provides a method for preparing an absorption enhanced detector. Figure 3 FIG. 2 is a schematic diagram showing a method for preparing an absorption enhanced detector structure according to an embodiment of the present disclosure. Figure 3 As shown, specifically, the method includes: providing a substrate 10, and sequentially growing a first semiconductor layer, an absorption layer, a second semiconductor layer, and an optical capture layer 1 on the substrate 10 from bottom to top; wherein the first semiconductor layer is an N-type contact layer 9 and an N-transition layer 7 sequentially grown from bottom to top; the second semiconductor layer is a P-transition layer 4 and a P-type contact layer 3 sequentially grown from bottom to top; etching the edge portion of the P-type contact layer 3 to the N-type contact layer 9 to form a first table (P table) on the P-type contact layer 3; etching The edge of the N-type contact layer 9 extends to the substrate 10, and a second table (N table) is formed on the N-type contact layer 3; a silicon dioxide passivation layer film is grown; a P ring electrode 2 is formed on the upper surface of the first table; an N ring electrode 8 is formed on the upper surface of the second table; the N transition layer 7 is located in the ring of the N ring electrode 8; an optical capture layer 1 is grown on the upper surface of the P-type contact layer 3; wherein the optical capture layer 1 is located in the ring of the P ring electrode 2 and is a grating array structure; the photosensitive surface of the detector is the upper surface of the optical capture layer 1.
[0048] In this embodiment, for example, an N-type contact layer, an N transition layer, a complete absorption layer, an incomplete absorption layer, a P transition layer, and a P-type contact layer are grown layer by layer on an InP substrate by molecular beam epitaxy technology.
[0049] In this embodiment, an ICP etcher is used to perform etching to obtain the first mesa and the second mesa.
[0050] In this embodiment, PECVD is used to grow the silicon dioxide passivation layer film.
[0051] Through the embodiments of the present disclosure, an optical trapping layer is prepared on the P-type contact layer to enhance the absorption of incident light, thereby achieving decoupling of the contradiction between detector bandwidth and quantum efficiency. The prepared detector structure has both high-speed and high-response characteristics, and can be used in ultra-high-speed, ultra-long-distance fiber-optic communication systems and data center inter-transmission.
[0052] On the basis of the above embodiment, preparing the optical capture layer includes: depositing a first metal layer and a second metal layer on the upper surface of the P-type contact layer 3 by a BEB process, and preparing the optical capture layer 1 by a metal lift-off process.
[0053] In this embodiment, for example, Figure 4 FIG. 4 shows a process flow chart of an optical capture layer of an absorption enhanced detector structure according to an embodiment of the present disclosure. Figure 4As shown, the optical capture layer is on the P-type contact layer, a positive photoresist is spin-coated, and a metal array pattern is obtained after electron beam exposure and development and fixing (see Figure 4 (b)), then the tape is used to deposit 10nmTi and 300nmAu using the EBE process (see Figure 4 (c)), and finally a sub-micron metal grating array with rectangular array distribution is obtained through metal lift-off process (see Figure 4 (d)).
[0054] According to the embodiments of the present disclosure, a sub-micron metal grating array structure of an optical capture layer is obtained by depositing metal using a BEB process with adhesive and a metal lift-off process.
[0055] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. An absorption enhanced detector structure, characterized in that: The absorption-enhanced detector structure comprises, from bottom to top, a substrate (10), a first semiconductor layer, an absorption layer, a second semiconductor layer, and an optical capture layer (1); The upper surface of the second semiconductor layer further comprises a P annular electrode (2), and the optical capture layer (1) is located inside the ring of the P annular electrode (2); Wherein, the optical capture layer (1) is a grating array structure, and the photosensitive surface of the detector is the upper surface of the optical capture layer (1).
2. The absorption enhanced detector structure according to claim 1, wherein: The grating array structure is a rectangular array composed of cylinders; the diameter of the cylinders is 400-600nm, the height is 300-500nm, and the distance between the centers of adjacent cylinders is 500-700nm; The diameter and height of the cylinders and the distance between the centers of adjacent cylinders are adjusted according to a specific wavelength of light to maximize the diffraction capability of light of a specific wavelength.
3. The absorption enhanced detector structure according to claim 1, wherein: The first semiconductor layer is an N-type contact layer (9) and an N transition layer (7) grown in sequence from the bottom to the top; the N-type contact layer (9) is N-heavily doped InP with a thickness of 150 to 300 nm; the N transition layer (7) is N-doped InGaAsP with a thickness of 100 to 200 nm; The upper surface of the N-type contact layer (9) further includes an N-annular electrode (8), and the N transition layer (7) is located inside the ring of the N-annular electrode (8).
4. The absorption enhanced detector structure according to claim 3, characterized in that: A silicon dioxide passivation layer film is provided between the N annular electrode (8) and the P annular electrode (2).
5. The absorption enhanced detector structure according to claim 3, characterized in that: The thickness of the N annular electrode (8) and the P annular electrode (2) is the same as the thickness of the grating array structure.
6. The absorption enhanced detector structure according to claim 3, characterized in that: The N annular electrode (8), the P annular electrode (2) and the grating array structure comprise a first metal layer and a second metal layer, and the material of the metal layer comprises at least any two of titanium, tantalum, zirconium, tungsten, aluminum, bismuth and gold.
7. The absorption enhanced detector structure according to claim 1, wherein: The absorption layer comprises: The absorption layer comprises a complete absorption layer (6) and an incomplete absorption layer (5) which are grown in sequence from the bottom to the top; the complete absorption layer (6) is undoped InGaAs with a thickness of 150 to 250 nm; and the incomplete absorption layer (5) is P-doped InGaAs with a thickness of 30 to 50 nm.
8. The absorption enhanced detector structure according to claim 1, wherein: The second semiconductor layer comprises: The second semiconductor layer is a P transition layer (4) and a P-type contact layer (3) grown in sequence from the bottom to the top; the P transition layer (4) is P-doped InGaAsP with a thickness of 30 to 50 nm; the P-type contact layer (3) is P-heavily doped InGaAs with a thickness of 50 to 80 nm.
9. A method for preparing an absorption enhanced detector, characterized in that: include: A substrate (10) is provided, on which a first semiconductor layer, an absorption layer, a second semiconductor layer, and an optical capture layer (1) are grown in sequence from bottom to top; wherein the first semiconductor layer is an N-type contact layer (9) and an N-transition layer (7) grown in sequence from bottom to top; and the second semiconductor layer is a P-transition layer (4) and a P-type contact layer (3) grown in sequence from bottom to top; Etching the edge portion of the P-type contact layer (3) to the N-type contact layer (9), forming a first mesa on the P-type contact layer (3); Etching the edge portion of the N-type contact layer (9) to the substrate (10) to form a second mesa on the N-type contact layer (3); A P annular electrode (2) is formed on the upper surface of the first table; an N annular electrode (8) is formed on the upper surface of the second table; the N transition layer (7) is located inside the ring of the N annular electrode (8); An optical capture layer (1) is grown on the upper surface of the P-type contact layer (3); wherein the optical capture layer (1) is located inside the ring of the P-type annular electrode (2) and is a grating array structure; and the photosensitive surface of the detector is the upper surface of the optical capture layer (1).
10. The method for preparing an absorption enhanced detector according to claim 9, characterized in that: The method of growing an optical capture layer (1) on the upper surface of the P-type contact layer comprises: A first metal layer and a second metal layer are deposited on the upper surface of a P-type contact layer (3) by a BEB process with adhesive, and an optical capture layer (1) is prepared by a metal lift-off process.