Photodetector and method of manufacturing the same

Abstract

The application provides a photoelectric detector and a manufacturing method thereof, the photoelectric detector comprising: a waveguide arranged on a substrate and composed of a first material; and a light absorption layer arranged on a surface of the waveguide; the light absorption layer comprises a first material part and a second material part, the first material part is provided with a recess part, the second material part is arranged in the recess part, the first material part is composed of the first material, the second material part is composed of a second material, and the refractive index of the first material is smaller than that of the second material for the light of the predetermined wavelength. According to the application, the light absorption layer of the photoelectric detector is arranged in a structure formed by alternately arranging two materials with different refractive indexes, thereby increasing the absorption rate of the evanescent wave in the absorption layer, and high responsivity and high bandwidth are achieved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a photodetector and a method for manufacturing the same. Background Technology

[0002] A photodetector is a device in an optical transceiver module responsible for photoelectric conversion. It absorbs incident light and then converts it into an electrical signal for output.

[0003] The efficiency of a photodetector is closely related to the light absorption coefficient of the material. Currently, silicon photonic integrated chips mainly use the 1310nm and 1550nm wavelengths, with germanium as the primary active material. With the continuous development of optical communication and the increasing demand for data capacity, various fields such as biology, sensing, and military have also raised new requirements for using different wavelengths for detection. Therefore, extending the detection wavelength to the L-band (1565-1625nm) and U-band (1625-1675nm) is an urgent problem to be solved.

[0004] Since the absorption coefficient of germanium (Ge) drops significantly after 1550 nm, doping germanium with tin (Sn), a group IV direct bandgap material, can extend the wavelength of the detector to the U-band.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] The inventors of this application have discovered that in the field of photodetectors, how to reduce the size of the device is a problem that needs to be considered. Small-sized devices are of great help to high bandwidth. However, the waveguide-type photodetectors reported so far all use a single waveguide for light absorption. In this case, although the size of the detector is reduced, the area for light absorption is also reduced, so the light absorption capacity is reduced and the responsivity is lowered. Therefore, it is difficult to simultaneously achieve high responsivity and high bandwidth.

[0007] This application provides a photodetector and its manufacturing method. The light absorption layer of the photodetector is configured as a structure formed by alternating arrangement of two materials with different refractive indices. This increases the absorption rate of evanescent waves in the absorption layer, thereby achieving both high responsivity and high bandwidth.

[0008] According to one aspect of the embodiments of this application, a photodetector is provided for detecting light of a predetermined wavelength, the photodetector comprising:

[0009] Waveguide, disposed on a substrate, and made of a first material; and

[0010] A light-absorbing layer is disposed on the surface of the waveguide;

[0011] The light-absorbing layer includes a first material portion and a second material portion.

[0012] A recess is formed in the first material portion.

[0013] The second material portion is disposed in the recessed portion.

[0014] The first material section is composed of the first material.

[0015] The second material part is composed of a second material.

[0016] For light of the predetermined wavelength, the refractive index of the first material is less than that of the second material.

[0017] According to another aspect of the embodiments of this application, wherein,

[0018] The first material is silicon.

[0019] The second material is germanium-tin.

[0020] According to another aspect of the embodiments of this application, wherein,

[0021] In the transverse direction parallel to the surface of the substrate, the area ratio of the first material portion to the area of ​​the second material portion is 0.5 to 0.1.

[0022] According to another aspect of the embodiments of this application, wherein,

[0023] The photodetector also includes:

[0024] An upper electrode is disposed on the surface of the light-absorbing layer and is in contact with the surface of the light-absorbing layer.

[0025] The lower electrode is disposed on the outside of the light-absorbing layer and in contact with the contact area disposed on the substrate.

[0026] According to another aspect of the embodiments of this application, wherein,

[0027] The substrate is silicon on insulator (SOI), and the contact area and the waveguide are formed from the top layer of silicon on the silicon on insulator.

[0028] According to another aspect of the embodiments of this application, a method for manufacturing a photodetector is provided, the photodetector being used to detect light of a predetermined wavelength, the manufacturing method comprising:

[0029] A waveguide is formed on a substrate, the waveguide being made of a first material; and

[0030] A light-absorbing layer is formed on the surface of the waveguide;

[0031] The light-absorbing layer includes a first material portion and a second material portion.

[0032] A recess is formed in the first material portion.

[0033] The second material portion is disposed in the recessed portion.

[0034] The first material section is composed of the first material.

[0035] The second material part is composed of a second material.

[0036] For light of the predetermined wavelength, the refractive index of the first material is less than that of the second material.

[0037] According to another aspect of the embodiments of this application, wherein,

[0038] The step of forming the light-absorbing layer on the surface of the waveguide includes:

[0039] A first material layer is deposited on the surface of the waveguide;

[0040] Etching the first material layer to form the recess, the retained portion of the first material layer forming the first material portion; and

[0041] A second material layer is selectively epitaxially extended in the recessed portion to form the second material portion.

[0042] According to another aspect of the embodiments of this application, wherein,

[0043] The method further includes:

[0044] Forming an upper electrode and a lower electrode,

[0045] The upper electrode is disposed on the surface of the light absorption layer and is in contact with the surface of the light absorption layer;

[0046] The lower electrode is disposed on the outside of the light absorption layer and is in contact with the contact area disposed on the substrate.

[0047] The beneficial effect of this application is that by setting the light absorption layer of the photodetector as a structure formed by alternating arrangement of two materials with different refractive indices, the absorption rate of evanescent waves in the absorption layer can be increased, ensuring a high absorption rate while keeping the size of the photodetector small, thereby achieving both high responsivity and high bandwidth.

[0048] Specific embodiments of this application are disclosed in detail with reference to the following description and accompanying drawings, indicating how the principles of this application can be adopted. It should be understood that the embodiments of this application are not limited in scope. Within the spirit and scope of the appended claims, embodiments of this application include many changes, modifications, and equivalents.

[0049] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0050] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components. Attached Figure Description

[0051] The accompanying drawings, which form part of the specification, are used to provide a further understanding of the embodiments of this application and illustrate the implementation methods of this application, together with the textual description, to explain the principles of this application. Obviously, the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any creative effort. In the drawings:

[0052] Figure 1 This is a schematic diagram of the photodetector in Example 1;

[0053] Figure 2 This is a schematic diagram of the manufacturing method;

[0054] Figure 3 This is a schematic diagram of step 202. Detailed Implementation

[0055] Referring to the accompanying drawings, the foregoing and other features of this application will become apparent from the following description. Specific embodiments of this application are specifically disclosed in the description and drawings, illustrating partial implementations in which the principles of this application may be employed. It should be understood that this application is not limited to the described embodiments; rather, it includes all modifications, variations, and equivalents falling within the scope of the appended claims.

[0056] In the description of the various embodiments of this application, for ease of description, the direction parallel to the surface of the substrate is referred to as "lateral", and the direction perpendicular to the surface of the substrate is referred to as "longitudinal". The "thickness" of each component refers to the dimension of the component in the "longitudinal". In the "longitudinal", the direction from the buried oxide layer of SOI, which serves as the substrate, to the top silicon layer is referred to as the "up" direction, and the direction opposite to the "up" direction is referred to as the "down" direction.

[0057] Example 1

[0058] Embodiment 1 of this application provides a photodetector for detecting light of a predetermined wavelength.

[0059] Figure 1 This is a schematic diagram of the photodetector in Example 1.

[0060] like Figure 1 As shown, the photodetector 1 includes a waveguide 10 and a light absorption layer 20.

[0061] Waveguide 10 may be disposed on substrate 100, waveguide 10 may be made of a first material, and waveguide 10 may run along... Figure 1 The waveguide extends in the first direction D1 as shown. The light-absorbing layer 20 is disposed on the surface of the waveguide 10.

[0062] like Figure 1 As shown, the light absorption layer 20 includes a first material portion 21 and a second material portion 22.

[0063] A recess 211 is formed in the first material portion 21, and a second material portion 22 is disposed in the recess 211. For example, in the light absorption layer 20, the first material portion 21 and the second material portion 22 can be alternately disposed in the transverse direction of the substrate 100, so that the first material portion 21 and the second material portion 22 form a comb shape.

[0064] The first material section 21 is made of a first material, and the second material section 22 is made of a second material. For light of a predetermined wavelength, the refractive index of the first material is less than that of the second material.

[0065] Therefore, light of a predetermined wavelength can be transmitted to the absorption layer 20 using the waveguide 10. Furthermore, in the absorption layer 20, due to evanescent wave coupling, light naturally couples from a material with a lower refractive index to a material with a higher refractive index, that is, from the first material section 21 to the second material section 22. When the first material section 21 and the second material section 22 are alternately arranged, after light enters the second material section 22 from the waveguide 10, some light is absorbed. Unabsorbed light encountering the first material section 21 tends to return to the second material section 22 for further absorption. If light passes through the first material section 21 and enters the next portion of the second material section 22, unabsorbed light encountering the next portion of the first material section 21 also tends to return to the second material section 22, and so on, allowing light to be repeatedly absorbed in the second material section. Compared to the case where the light absorption layer 20 only has the second material section 22, the total light absorption of the photodetector 1 is greatly increased, effectively improving the response speed and reducing the device size of the photodetector 1.

[0066] In this embodiment, the area ratio of the first material portion 21 to the second material portion 22 in the transverse direction parallel to the surface of the substrate 100 is 0.5 to 0.1. This ensures that the second material portion 22 has high light absorption efficiency.

[0067] In this embodiment, the substrate 100 can be a wafer commonly used in the semiconductor manufacturing field, such as a silicon wafer, a silicon-on-insulator (SOI) wafer, a germanium-silicon wafer, a germanium wafer, a gallium nitride wafer, a silicon carbide (SiC) wafer, etc., or it can be an insulating wafer such as quartz, sapphire, or glass. Furthermore, various thin films and structures required for semiconductor devices and microelectromechanical systems (MEMS) devices can be further formed on the surface of the substrate. This embodiment is not limited in this respect.

[0068] In the following description of this application, the substrate 100 is used as an example of an SOI wafer. For example, as Figure 1 As shown, the SOI wafer serving as the substrate may have a substrate silicon 101, a buried oxide layer 102, and a top silicon layer 103. The waveguide 10 may be formed by processing the top silicon layer 103 of the SOI wafer.

[0069] In this embodiment, the first material can be silicon, and the second material can be germanium-tin. Thus, when light couples from the silicon material of waveguide 10 into the germanium-tin second material portion 22, some of the light is absorbed. Unabsorbed light encountering the silicon first material portion 21 tends to return to the germanium-tin second material portion 22 for further absorption. If it passes through the silicon first material portion 21 and enters the next portion of the germanium-tin second material portion 22, the unabsorbed light encountering the next portion of the silicon first material portion 21 also tends to return to the germanium-tin second material portion 22, and so on, allowing light to be repeatedly absorbed in the germanium-tin second material portion 22. Compared to providing the entire silicon waveguide 10 with germanium-tin second material portions 22, the total absorption of the device is greatly increased, effectively reducing the device size and contributing to increased device speed. Furthermore, the germanium-tin second material portion 22 enables the photodetector 1 to extend its detection band to the L-band (1565-1625nm) and the U-band (1625-1675nm).

[0070] Furthermore, this application is not limited to this; the first and second materials can also be other materials, thereby enabling the photodetector to detect other wavebands.

[0071] In this embodiment, as Figure 1As shown, the photodetector 1 may further include an upper electrode 30 and a lower electrode (not shown). The upper electrode 30 may be disposed on the surface of the light-absorbing layer 20 and in contact with the surface of the light-absorbing layer 20. The lower electrode may be disposed on the outer side of the light-absorbing layer 20 and in contact with a contact area disposed on the substrate 100, such as the top silicon 103 of an SOI wafer. For details on the arrangement of the lower electrode, please refer to relevant technologies.

[0072] According to this embodiment, the light absorption layer of the photodetector is configured as a structure formed by alternating arrangements of two materials with different refractive indices. This increases the absorption rate of evanescent waves in the absorption layer, ensuring a high absorption rate while maintaining a small size of the photodetector, thereby achieving both high responsivity and high bandwidth.

[0073] Example 2

[0074] Example 2 provides a method for manufacturing a photodetector. This method is used to manufacture the photodetector 1 described in Example 1.

[0075] Figure 2 This is a schematic diagram of the manufacturing method. For example... Figure 2 As shown, the manufacturing method includes:

[0076] Step 201: Forming a waveguide on a substrate, the waveguide being made of a first material; and

[0077] Step 202: Form a light absorption layer on the surface of the waveguide.

[0078] In step 202, the light-absorbing layer includes a first material portion and a second material portion. A recess is formed in the first material portion, and the second material portion is disposed within the recess. The first material portion is composed of the first material, and the second material portion is composed of the second material. For light of the predetermined wavelength, the refractive index of the first material is less than the refractive index of the second material.

[0079] In this embodiment, the first material is silicon and the second material is germanium-tin.

[0080] In this embodiment, the ratio of the area of ​​the first material portion to the area of ​​the second material portion is 0.5 to 0.1 in the transverse direction parallel to the surface of the substrate.

[0081] Figure 3 This is a schematic diagram of step 202, as shown below. Figure 3 As shown, step 202 may include:

[0082] Step 2021: Deposit a first material layer on the surface of the waveguide;

[0083] Step 2022: Etch the first material layer to form the recess, wherein the retained portion of the first material layer forms the first material portion; and

[0084] Step 2023: Selectively extend a second material layer in the recess to form the second material portion.

[0085] like Figure 2 As shown, the manufacturing method may further include:

[0086] Step 203: Form the upper electrode and the lower electrode.

[0087] The upper electrode is disposed on the surface of the light-absorbing layer and is in contact with the surface of the light-absorbing layer; the lower electrode is disposed on the outside of the light-absorbing layer and is in contact with the contact area disposed on the substrate.

[0088] According to this embodiment, the light absorption layer of the photodetector is configured as a structure formed by alternating arrangements of two materials with different refractive indices. This increases the absorption rate of evanescent waves in the absorption layer, ensuring a high absorption rate while maintaining a small size of the photodetector, thereby achieving both high responsivity and high bandwidth.

[0089] The present application has been described above with reference to specific embodiments. However, those skilled in the art should understand that these descriptions are exemplary and not intended to limit the scope of protection of the present application. Those skilled in the art can make various modifications and variations to the present application based on its spirit and principles, and these modifications and variations are also within the scope of the present application.

Claims

1. A photodetector for detecting light of a predetermined wavelength, characterized in that, The photodetector includes: Waveguide, disposed on a substrate, and made of a first material; and A light-absorbing layer is disposed on the surface of the waveguide; The light-absorbing layer includes a first material portion and a second material portion. A recess is formed in the first material portion. The second material portion is disposed in the recessed portion. The first material section is composed of the first material. The second material part is composed of a second material. For light of the predetermined wavelength, the refractive index of the first material is less than that of the second material. The first material is silicon. The second material is germanium-tin.

2. The photodetector as described in claim 1, characterized in that, In the transverse direction parallel to the surface of the substrate, the area ratio of the first material portion to the area of ​​the second material portion is 0.5 to 0.

1.

3. The photodetector as described in claim 1, characterized in that, The photodetector also includes: An upper electrode is disposed on the surface of the light-absorbing layer and is in contact with the surface of the light-absorbing layer. The lower electrode is disposed on the outside of the light-absorbing layer and in contact with the contact area disposed on the substrate.

4. The photodetector as described in claim 3, characterized in that, The substrate is silicon on insulator, and the contact area and the waveguide are formed from the top layer of silicon on insulator.

5. A method for manufacturing a photodetector, the photodetector being used to detect light of a predetermined wavelength, characterized in that, The manufacturing method includes: A waveguide is formed on a substrate, the waveguide being made of a first material; and A light-absorbing layer is formed on the surface of the waveguide; The light-absorbing layer includes a first material portion and a second material portion. A recess is formed in the first material portion. The second material portion is disposed in the recessed portion. The first material section is composed of the first material. The second material part is composed of a second material. For light of the predetermined wavelength, the refractive index of the first material is less than that of the second material. The first material is silicon. The second material is germanium-tin.

6. The manufacturing method as described in claim 5, characterized in that, In the transverse direction parallel to the surface of the substrate, the area ratio of the first material portion to the area of ​​the second material portion is 0.5 to 0.

1.

7. The manufacturing method as described in claim 5, characterized in that, The step of forming the light-absorbing layer on the surface of the waveguide includes: A first material layer is deposited on the surface of the waveguide; Etching the first material layer to form the recess, the retained portion of the first material layer forming the first material portion; and A second material layer is selectively epitaxially extended in the recessed portion to form the second material portion.

8. The manufacturing method as described in claim 5, characterized in that, The method further includes: Forming an upper electrode and a lower electrode, The upper electrode is disposed on the surface of the light absorption layer and is in contact with the surface of the light absorption layer; The lower electrode is disposed on the outside of the light absorption layer and is in contact with the contact area disposed on the substrate.

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