Ge photodetector and preparation method thereof

Abstract

The present invention provides a Ge photodetector and a preparation method thereof, wherein the Ge photodetector includes a heat source layer and further includes a heat conductive layer; thereby, the heat source layer with a high resistance is used as a heat source to increase the temperature of the Ge absorption layer, so that the band gap width of the Ge absorption layer is reduced, so that photons with energy lower than the band gap width of the original Ge absorption layer are absorbed, so as to increase the absorption coefficient of the Ge absorption layer, and realize the extension of the detection range of the Ge photodetector to expand the application range, and through the heat conductive layer with high thermal conductivity located between the Ge absorption layer and the heat source layer, the heat source generated by the heat source layer is effectively transferred to the Ge absorption layer, so as to effectively adjust the responsivity of the Ge photodetector; therefore, the present invention can provide a method with a simple preparation process, and can effectively improve the absorption coefficient of the Ge photodetector under long wavelength conditions, so as to expand the detection range and application range of the Ge photodetector.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic technology and relates to a Ge photoelectric detector and a preparation method thereof. Background Art

[0002] Photodetectors are widely used in various fields of military and national economy. Silicon-based Ge photodetectors are compatible with CMOS processes and easy to integrate, so they are widely used in optical communications, optical interconnection, optical sensing and other fields. Compared with surface-incident photodetectors, waveguide detectors can avoid the problem of mutual constraints between the rate and quantum efficiency of photodetectors, and can be integrated with waveguide optical paths, making it easier to achieve high speed and high responsiveness. They are one of the core devices for realizing high-speed optical communications and optical interconnection chips. However, the absorption coefficient of Ge material drops sharply when the wavelength is greater than 1.55μm, which makes Ge photodetectors unable to meet the application requirements of L-band (long wavelength band, wavelength range 1.56μm~1.63μm) and even U-band (ultra-long wavelength band, wavelength range 1.63μm~1.68μm).

[0003] In order to solve the problem of low absorption coefficient of Ge material at long wavelength, in the prior art, Sn material is usually introduced into Ge material to extend the detection range of Ge photodetector. However, the introduction of Sn material will increase the difficulty of the process. At the same time, the introduction of Sn material will also reduce the thermal stability of Ge material, thereby limiting the practical application.

[0004] Therefore, it is necessary to provide a novel Ge photodetector and a preparation method thereof. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a Ge photodetector and a method for preparing the same, so as to solve the problem of low absorption coefficient of the Ge photodetector under long wavelength conditions in the prior art.

[0006] To achieve the above objectives and other related objectives, the present invention provides a Ge photodetector, comprising:

[0007] Si waveguide, the Si waveguide comprising a bottom Si layer, a buried oxide layer and a top Si layer stacked in sequence; wherein the top Si layer comprises a P-type doped contact region, an I-type region and an N-type doped contact region arranged in sequence in a horizontal direction;

[0008] A Ge absorption layer, wherein the Ge absorption layer is located on the I-type region;

[0009] A passivation layer, the passivation layer covers the P-type doped contact region, the N-type doped contact region and the Ge absorption layer;

[0010] A heat source layer, the heat source layer is located above the Ge absorption layer;

[0011] A metal electrode penetrates the passivation layer and contacts the P-type doped contact region and the N-type doped contact region.

[0012] Optionally, a thickness D of the passivation layer between the heat source layer and the Ge absorption layer ranges from D≥0.5 μm.

[0013] Optionally, the heat source layer includes one or a combination of a TiN layer and a TaN layer.

[0014] Optionally, a heat-conducting layer is further included between the Ge absorption layer and the heat source layer, and the thermal conductivity of the heat-conducting layer is greater than that of the passivation layer.

[0015] Optionally, two opposite surfaces of the heat-conducting layer are in contact with the Ge absorption layer and the heat source layer respectively, wherein the heat-conducting layer includes an AlN layer.

[0016] The present invention also provides a method for preparing a Ge photodetector, comprising the following steps:

[0017] Providing an SOI substrate;

[0018] Performing photolithography to form a Si waveguide, wherein the Si waveguide includes a bottom Si layer, a buried oxide layer, and a top Si layer stacked in sequence;

[0019] Forming a P-type doped contact region and an N-type doped contact region in the top Si layer respectively by ion implantation, so as to form a P-type doped contact region, an I-type region and an N-type doped contact region sequentially arranged in a horizontal direction in the top Si layer;

[0020] forming a Ge absorption layer on the I-type region;

[0021] forming a passivation layer, wherein the passivation layer covers the P-type doped contact region, the N-type doped contact region and the Ge absorption layer;

[0022] forming a heat source layer, wherein the heat source layer is located above the Ge absorption layer;

[0023] A metal electrode is formed, wherein the metal electrode penetrates the passivation layer and contacts the P-type doped contact region and the N-type doped contact region.

[0024] Optionally, after forming the Ge absorption layer and before forming the metal electrode, the following steps are included:

[0025] forming a first passivation layer to cover the P-type doped contact region, the N-type doped contact region and the Ge absorption layer;

[0026] forming a heat source layer above the Ge absorption layer;

[0027] forming a second passivation layer covering the heat source layer;

[0028] A trench is formed through the second passivation layer and the first passivation layer, and the trench is filled to form a metal electrode in contact with the P-type doped contact region and the N-type doped contact region.

[0029] Optionally, the thickness D of the first passivation layer between the heat source layer and the Ge absorption layer ranges from D≥0.5μm, wherein the heat source layer includes one or a combination of a TiN layer and a TaN layer; the first passivation layer includes a SiO2 layer; and the second passivation layer includes a SiO2 layer.

[0030] Optionally, after forming the Ge absorption layer and before forming the metal electrode, the following steps are included:

[0031] forming a first passivation layer to cover the P-type doped contact region, the N-type doped contact region and the Ge absorption layer, and performing planarization to expose the Ge absorption layer;

[0032] forming a heat conducting layer and a heat source layer in sequence above the Ge absorption layer;

[0033] forming a second passivation layer covering the heat source layer and the heat conducting layer;

[0034] A trench is formed through the second passivation layer and the first passivation layer, and the trench is filled to form a metal electrode in contact with the P-type doped contact region and the N-type doped contact region.

[0035] Optionally, the two opposite sides of the thermal conductive layer are in contact with the Ge absorption layer and the heat source layer respectively, and the range of the thickness H of the thermal conductive layer includes H≥0.5μm, wherein the heat source layer includes one or a combination of a TiN layer and a TaN layer; the thermal conductive layer includes an AlN layer; the first passivation layer includes a SiO2 layer; and the second passivation layer includes a SiO2 layer.

[0036] As described above, the Ge photodetector and preparation method thereof of the present invention use a heat source layer with a high resistance as a heat source to increase the temperature of the Ge absorption layer, so that the band gap of the Ge absorption layer is reduced, thereby allowing photons with energy lower than the band gap of the original Ge absorption layer to be absorbed, so as to increase the absorption coefficient of the Ge absorption layer, thereby extending the detection range of the Ge photodetector and expanding the application range; further, through a heat conductive layer with a high thermal conductivity located between the Ge absorption layer and the heat source layer, the heat source generated by the heat source layer can also be effectively transferred to the Ge absorption layer, thereby effectively adjusting the responsiveness of the Ge photodetector; therefore, the present invention can provide a method with a simple preparation process, and can effectively improve the absorption coefficient of the Ge photodetector under long wavelength conditions, so as to expand the detection range and application range of the Ge photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Shown is a schematic diagram of the process flow for preparing a Ge photodetector in the present invention.

[0038] Figure 2 to Figure 5 It shows a schematic diagram of the structure presented in each step of preparing a Ge photodetector in Example 1.

[0039] Figure 6 to Figure 9 It shows a schematic diagram of the structure presented in each step of preparing another Ge photodetector in Example 2.

[0040] Component number description

[0041] 110, 210 Si waveguide

[0042] 111, 211 bottom Si layer

[0043] 112, 212 buried oxide layer

[0044] 113, 213 Top Si layer

[0045] 1131, 2131 P-type doped contact area

[0046] 1132, 2132 Type I region

[0047] 1133, 2133 N-type doped contact area

[0048] 120, 220 Ge absorption layer

[0049] 130, 230 First passivation layer

[0050] 140, 240 Heat Source Layer

[0051] 150, 250 Second passivation layer

[0052] 160, 260 Metal Electrode

[0053] 300 Thermal Conductive Layer

[0054] D, H thickness DETAILED DESCRIPTION

[0055] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] See also Figures 1 to 9 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0057] Embodiment 1

[0058] See also Figure 5 This embodiment provides a Ge photodetector, which includes a Si waveguide 110, a Ge absorption layer 120, a first passivation layer 130, a heat source layer 140, a second passivation layer 150 and a metal electrode 160. The Si waveguide 110 includes a bottom Si layer 111, a buried oxide layer 112 and a top Si layer 113 stacked in sequence; wherein the top Si layer 113 includes a P-type doped contact area 1131, an I-type area 1132 and an N-type doped contact area 1133 arranged in sequence in a horizontal direction; the Ge absorption layer 120 is located on the I-type area 1132; the first passivation layer 130 covers the P-type doped contact area 1131, the N-type doped contact area 1133 and the Ge absorption layer 120; the heat source layer 140 is located above the Ge absorption layer 120; the second passivation layer 150 covers the heat source layer 140; the metal electrode 160 passes through the first passivation layer 130 and the second passivation layer 150, and is in contact with the P-type doped contact area 1131 and the N-type doped contact area 1133.

[0059] In this embodiment, the heat source layer 140 with a high resistance is used as a heat source to increase the temperature of the Ge absorption layer 120, so that the band gap of the Ge absorption layer 120 is reduced, so that photons with energy lower than the band gap of the original Ge absorption layer are absorbed, so as to increase the absorption coefficient of the Ge absorption layer 120, thereby extending the detection range of the Ge photodetector and expanding the application range.

[0060] See also Figure 1 This embodiment provides a process flow chart for preparing the Ge photodetector, wherein: Figure 2 to Figure 5 The schematic diagram of the structure presented in each step of preparing the Ge photoelectric detector is illustrated. It should be noted that the preparation method of the above-mentioned Ge photoelectric detector is not limited to this.

[0061] See also Figure 2 , first provide an SOI substrate.

[0062] Specifically, the thickness of the SOI substrate may include 150nm to 250nm, such as 200nm, 220nm, etc. The specific thickness and size of the SOI substrate can be selected according to needs and are not limited here. The SOI substrate can be directly purchased or prepared according to needs and is not overly limited here.

[0063] Next, photolithography is performed to form a Si waveguide 110, which includes a bottom Si layer 111, a buried oxide layer 112, and a top Si layer 113 stacked in sequence. The specific preparation process and morphology of the Si waveguide 110 are not overly limited here and can be selected according to needs.

[0064] Next, by ion implantation, a P-type doped contact region 1131 and an N-type doped contact region 1133 are respectively formed in the top Si layer 113 , so as to form a P-type doped contact region 1131 , an I-type region 1132 and an N-type doped contact region 1133 arranged in sequence in a horizontal direction in the top Si layer 113 .

[0065] Specifically, the steps of forming the P-type doped contact region 1131 and the N-type doped contact region 1133 may include:

[0066] Using a deposition process such as CVD, a first SiO2 layer (not shown) is formed on the surface of the top Si layer 113, so that the first SiO2 layer serves as a protective layer for ion implantation;

[0067] Using a first mask (not shown) and anisotropic etching process, the first SiO2 layer in the area corresponding to the P-type doped contact area 1131 is etched away;

[0068] Perform ion implantation to form the P-type doping region 1131, and etch away the first SiO2 layer;

[0069] Next, the deposition process is repeated to form a second SiO2 layer (not shown), so that the second SiO2 layer can be used as a protective layer for ion implantation;

[0070] Using a second mask (not shown) and anisotropic etching process, the second SiO2 layer in the area corresponding to the N-type doped contact area 1133 is etched away;

[0071] Ion implantation is performed to form the N-type doping region 1133, and the second SiO2 layer is etched away.

[0072] When forming the P-type doped contact region 1131 and the N-type doped region 1133, the type, dosage and energy of the ion implantation can be selected as needed, and no excessive restrictions are imposed here. In this embodiment, through the ion implantation process, the P-type doped contact region 1131, the I-type region 1132 and the N-type doped contact region 1133 arranged in sequence in the horizontal direction can be formed in the top Si layer 113, that is, a PIN structure is formed.

[0073] Next, see Figure 3 , a Ge absorption layer 120 is formed on the I-type region 1132 .

[0074] Specifically, a selective epitaxial growth method may be used to form the Ge absorption layer 120 with a thickness of 300 nm to 500 nm, such as 350 nm, 400 nm, 450 nm, etc., on the I-type region 1132 .

[0075] Next, a passivation layer is formed, where the passivation layer covers the P-type doped contact region 1131 , the N-type doped contact region 1133 and the Ge absorption layer 120 .

[0076] For details, see Figure 3 In this embodiment, after the Ge absorption layer 120 is formed, a first passivation layer 130 is first formed, and the first passivation layer 130 covers the P-type doped contact area 1131, the N-type doped contact area 1133 and the Ge absorption layer 120, and there is a thickness D between the surface of the first passivation layer 130 and the Ge absorption layer 120, wherein the thickness D preferably ranges from D≥0.5μm, such as 1.0μm, 1.5μm, 2μm, etc., to improve the light absorption performance of the Ge absorption layer 120 and reduce the influence of the subsequently formed heat source layer 140 on the light absorption performance of the Ge absorption layer 120.

[0077] Next, see Figure 4 , forming the heat source layer 140 , wherein the heat source layer is located above the Ge absorption layer 120 .

[0078] Specifically, the method for forming the heat source layer 140 can adopt a CVD method, and then patterning. The heat source layer 140 is a material layer with a high resistance value, so that when the heat source layer 140 is connected to a power source (not shown), the heat source layer 140 can be used as a heat source to transfer heat to the Ge absorption layer 120, increase the temperature of the Ge absorption layer 120, and reduce the band gap of the Ge absorption layer 120, so that photons with energy lower than the band gap of the original Ge absorption layer are absorbed, so as to increase the absorption coefficient of the Ge absorption layer 120, and realize the extension of the detection range of the Ge photodetector, so as to expand the application range.

[0079] As an example, the heat source layer 140 may include one or a combination of a TiN layer and a TaN layer, but is not limited thereto.

[0080] As an example, after forming the heat source layer 140 , a step of forming a second passivation layer 150 covering the heat source layer 140 is further included.

[0081] Specifically, in this embodiment, the second passivation layer 150 is preferably provided to protect the heat source layer 140 through the second passivation layer 150, but the present invention is not limited thereto. To simplify the process, the second passivation layer 150 may not be formed, and no excessive limitation is made here.

[0082] As an example, the first passivation layer 130 and the second passivation layer 150 may be made of the same material, such as SiO 2 layer, but it is not limited thereto. The first passivation layer 130 and the second passivation layer 150 may also be made of different materials.

[0083] Finally, see Figure 5 , forming a metal electrode 160 , wherein the metal electrode 160 penetrates the second passivation layer 150 and the first passivation layer 130 , and contacts the P-type doped contact region 1131 and the N-type doped contact region 1132 .

[0084] Specifically, photolithography can be used to first form a groove (not shown) penetrating the second passivation layer 150 and the first passivation layer 130, and the groove is filled with metal, such as electron beam evaporation to form a Cr / Au layer, etc., to form the metal electrode 160 in contact with the P-type doped contact area 1131 and the N-type doped contact area 1133. Regarding the preparation of the metal electrode 160 and the selection of the material, no excessive restrictions are made here.

[0085] Embodiment 2

[0086] In order to further introduce the concept of the present invention, this embodiment also provides a Ge photodetector with a different structure and preparation method from Example 1, wherein the difference between this embodiment and Example 1 mainly lies in that the Ge photodetector of this embodiment also includes a heat-conducting layer located between the Ge absorption layer and the heat source layer, so as to effectively transfer the heat source generated by the heat source layer to the Ge absorption layer through the heat-conducting layer with higher thermal conductivity, thereby further effectively adjusting the responsiveness of the Ge photodetector, improving the absorption coefficient of the Ge photodetector under long wavelength conditions, and expanding the detection range and application range of the Ge photodetector.

[0087] The present embodiment is described in detail below, wherein the preparation, structure, material, etc. of the Ge photodetector can be referred to in the first embodiment.

[0088] See also Fig. 9 This embodiment provides a Ge photodetector, which includes a Si waveguide 210, a Ge absorption layer 220, a first passivation layer 230, a heat source layer 240, a heat conductive layer 300, a second passivation layer 250 and a metal electrode 260. The Si waveguide 210 includes a bottom Si layer 211, a buried oxide layer 212 and a top Si layer 213 stacked in sequence; wherein the top Si layer 213 includes a P-type doped contact area 2131, an I-type area 2132 and an N-type doped contact area 2133 arranged in sequence in the horizontal direction; the Ge absorption layer 220 is located on the I-type area 2132; the first passivation layer 230 covers the P-type doped contact area 2131 and the N-type doped contact area 2133, and encapsulates the Ge absorption layer 220; the thermal conductive layer 300 and the heat source layer 240 are sequentially located above the Ge absorption layer 220; the second passivation layer 250 encapsulates the heat source layer 240 and the thermal conductive layer 300; the metal electrode 260 penetrates the first passivation layer 230 and the second passivation layer 250, and contacts the P-type doped contact area 2131 and the N-type doped contact area 2133.

[0089] For details, see Figure 7 to Figure 9 In this embodiment, after forming the Ge absorption layer 220 and before forming the metal electrode 260, the following steps are included:

[0090] First, the first passivation layer 230 is formed, wherein the first passivation layer 230 covers the P-type doped contact region 2131, the N-type doped contact region 2133 and the Ge absorption layer 220, and then planarization is performed, such as a CMP process, to expose the Ge absorption layer 220;

[0091] Next, the heat conducting layer 300 and the heat source layer 240 are sequentially formed on the Ge absorption layer 220 ;

[0092] Next, a second passivation layer 250 is formed to cover the heat source layer 240 and the heat conducting layer 300 ;

[0093] Finally, a trench (not shown) is formed penetrating the second passivation layer 250 and the first passivation layer 230 , and the trench is filled to form the metal electrode 260 in contact with the P-type doped contact region 2131 and the N-type doped contact region 2133 .

[0094] Specifically, the thermal conductive layer 300 is a material layer with high thermal conductivity, and the thermal conductivity of the thermal conductive layer 300 is greater than that of the passivation layer, that is, the thermal conductivity of the thermal conductive layer 300 is greater than the thermal conductivity of the first passivation layer 230 (1.38W / mK). Therefore, through the thermal conductive layer 300 with high thermal conductivity, the heat source generated by the heat source layer 240 can be effectively transferred to the Ge absorption layer 220, thereby further effectively adjusting the responsiveness of the Ge photodetector and improving the absorption coefficient of the Ge photodetector under long wavelength conditions, so as to expand the detection range and application range of the Ge photodetector.

[0095] As an example, it is preferred that the two opposite surfaces of the thermal conductive layer 300 are in contact with the Ge absorption layer 220 and the heat source layer 240 respectively, so as to further improve the heat transfer performance and reduce heat loss, but it is not limited to this. The thermal conductive layer 300 may also only be in contact with the heat source layer 240 or the Ge absorption layer 220 or be located between the heat source layer 240 and the Ge absorption layer 220, and not in contact with the heat source layer 240 and the Ge absorption layer 220.

[0096] As an example, the thickness H of the heat conductive layer 300 preferably ranges from H≥0.5 μm, such as 1.0 μm, 1.5 μm, 2 μm, etc., to improve the light absorption performance of the Ge absorption layer 220 and reduce the influence of the heat source layer 240 on the light absorption performance of the Ge absorption layer 220.

[0097] As an example, the heat conducting layer 300 includes an AlN layer, but is not limited thereto.

[0098] As an example, the heat source layer 240 preferably includes one or a combination of a TiN layer and a TaN layer, but is not limited thereto.

[0099] As an example, the first passivation layer 230 includes a SiO2 layer; the second passivation layer 250 includes a SiO2 layer, but is not limited to this. In this embodiment, the second passivation layer 250 is preferably included to cover the heat source layer 300 and the heat source layer 240 for protection, but is not limited to this. In another embodiment, the second passivation layer 250 may not be included to reduce the complexity of the process, and the materials of the first passivation layer 230 and the second passivation layer 250 are not limited to this, and the two may also use different materials.

[0100] In summary, the Ge photodetector and the preparation method thereof of the present invention use a heat source layer with a high resistance as a heat source to increase the temperature of the Ge absorption layer, so that the band gap of the Ge absorption layer is reduced, so that photons with energy lower than the band gap of the original Ge absorption layer are absorbed, so as to increase the absorption coefficient of the Ge absorption layer, and achieve the extension of the detection range of the Ge photodetector to expand the application range; further, through a heat conductive layer with a high thermal conductivity located between the Ge absorption layer and the heat source layer, the heat source generated by the heat source layer can also be effectively transferred to the Ge absorption layer, so as to effectively adjust the responsiveness of the Ge photodetector; therefore, the present invention can provide a method with a simple preparation process, and can effectively improve the absorption coefficient of the Ge photodetector under long wavelength conditions, so as to expand the detection range and application range of the Ge photodetector.

[0101] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A Ge photodetector, characterized in that: include: Si waveguide, the Si waveguide comprising a bottom Si layer, a buried oxide layer and a top Si layer stacked in sequence; wherein the top Si layer comprises a P-type doped contact region, an I-type region and an N-type doped contact region arranged in sequence in a horizontal direction; A Ge absorption layer, wherein the Ge absorption layer is located on the I-type region; A passivation layer, the passivation layer covers the P-type doped contact region, the N-type doped contact region and the Ge absorption layer; A heat source layer, the heat source layer is located above the Ge absorption layer; A metal electrode, the metal electrode penetrates the passivation layer and contacts the P-type doped contact region and the N-type doped contact region; The thickness D of the passivation layer between the heat source layer and the Ge absorption layer is in the range of D≥0.5 μm; and the heat source layer includes one or a combination of a TiN layer and a TaN layer.

2. The Ge photodetector according to claim 1, characterized in that: It also includes a heat-conducting layer located between the Ge absorption layer and the heat source layer, and the thermal conductivity of the heat-conducting layer is greater than that of the passivation layer.

3. The Ge photodetector according to claim 2, characterized in that: Two opposite surfaces of the heat-conducting layer are in contact with the Ge absorption layer and the heat source layer respectively, wherein the heat-conducting layer includes an AlN layer.

4. A method for preparing a Ge photodetector, characterized in that: The following steps are involved: Providing an SOI substrate; Performing photolithography to form a Si waveguide, wherein the Si waveguide includes a bottom Si layer, a buried oxide layer, and a top Si layer stacked in sequence; Forming a P-type doped contact region and an N-type doped contact region in the top Si layer respectively by ion implantation, so as to form a P-type doped contact region, an I-type region and an N-type doped contact region sequentially arranged in a horizontal direction in the top Si layer; forming a Ge absorption layer on the I-type region; forming a passivation layer, wherein the passivation layer covers the P-type doped contact region, the N-type doped contact region and the Ge absorption layer; forming a heat source layer, wherein the heat source layer is located above the Ge absorption layer; A metal electrode is formed, wherein the metal electrode penetrates the passivation layer and contacts the P-type doped contact region and the N-type doped contact region.

5. The method for preparing a Ge photodetector according to claim 4, characterized in that: After forming the Ge absorption layer and before forming the metal electrode, the following steps are included: forming a first passivation layer to cover the P-type doped contact region, the N-type doped contact region and the Ge absorption layer; forming a heat source layer above the Ge absorption layer; forming a second passivation layer covering the heat source layer; A trench is formed through the second passivation layer and the first passivation layer, and the trench is filled to form a metal electrode in contact with the P-type doped contact region and the N-type doped contact region.

6. The method for preparing a Ge photodetector according to claim 5, characterized in that: The range of the thickness D of the first passivation layer between the heat source layer and the Ge absorption layer includes D≥0.5μm, wherein the heat source layer includes one or a combination of a TiN layer and a TaN layer; the first passivation layer includes a SiO2 layer; and the second passivation layer includes a SiO2 layer.

7. The method for preparing a Ge photodetector according to claim 4, characterized in that: After forming the Ge absorption layer and before forming the metal electrode, the following steps are included: forming a first passivation layer to cover the P-type doped contact region, the N-type doped contact region and the Ge absorption layer, and performing planarization to expose the Ge absorption layer; forming a heat conducting layer and a heat source layer in sequence above the Ge absorption layer; forming a second passivation layer covering the heat source layer and the heat conducting layer; A trench is formed through the second passivation layer and the first passivation layer, and the trench is filled to form a metal electrode in contact with the P-type doped contact region and the N-type doped contact region.

8. The method for preparing a Ge photodetector according to claim 7, characterized in that: The two opposite sides of the thermal conductive layer are in contact with the Ge absorption layer and the heat source layer respectively, and the range of the thickness H of the thermal conductive layer includes H≥0.5μm, wherein the heat source layer includes one or a combination of a TiN layer and a TaN layer; the thermal conductive layer includes an AlN layer; the first passivation layer includes a SiO2 layer; and the second passivation layer includes a SiO2 layer.

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