Waveguide-type germanium photodetector based on photonic crystal and preparation method thereof

Abstract

The present invention provides a waveguide-type germanium photodetector based on a photonic crystal and a preparation method thereof. The germanium photodetector includes: a silicon waveguide structure; a germanium photodetector connected to the silicon waveguide structure. The germanium absorption region of the germanium photodetector and the peripheral silicon material region around the germanium absorption region have periodically arranged dielectric materials to form a photonic crystal structure with a slow light effect. Compared with the traditional waveguide-type germanium photodetector, the present invention can achieve a more efficient light absorption efficiency, and by reducing the device size, a photodetector with low dark current, low capacitance and high responsivity can be prepared.

Description

Technical Field

[0001] The present invention belongs to the fields of semiconductor manufacturing and optical communication, and particularly relates to a waveguide-type germanium photodetector based on a photonic crystal and a preparation method thereof. Background Art

[0002] Photodetectors are widely used in various fields of military and national economy. In the visible or near-infrared band, they are mainly used for optical communication, ray measurement and detection, industrial automatic control, photometric measurement, etc.; in the infrared band, they are mainly used for missile guidance, infrared thermal imaging, infrared remote sensing, etc.

[0003] Germanium (Ge) photodetectors have been widely used in the fields of optical communication, optical interconnection, and optical sensing because they are easy to integrate with silicon (Si). However, there is a large lattice mismatch between germanium (Ge) and silicon (Si) materials, and it is extremely challenging to epitaxially grow high-quality germanium (Ge) materials. Recent research shows that when epitaxially growing germanium (Ge) materials in a narrow channel, linear dislocations will annihilate on the sidewalls of the channel, thus ensuring the epitaxial growth of high-quality germanium (Ge) materials. Limited by the relatively low absorption coefficient of germanium (Ge) materials in the C and L communication bands, in order to achieve high responsivity, the detector must be long enough, which makes it difficult to further optimize the high-speed characteristics and dark current of the detector. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a waveguide-type germanium photodetector based on a photonic crystal and a preparation method thereof, which are used to solve the problem that it is difficult to further optimize the capacitance and dark current of germanium photodetectors in the prior art.

[0005] To achieve the above object and other related objects, the present invention provides a waveguide-type germanium photodetector based on a photonic crystal, and the germanium photodetector includes: a silicon waveguide structure; a germanium photodetector connected to the silicon waveguide structure, and a periodically arranged dielectric material is provided in the germanium absorption region of the germanium photodetector and the peripheral silicon material region outside the germanium absorption region to form a photonic crystal structure with a slow light effect.

[0006] Optionally, the silicon waveguide structure is connected to the peripheral silicon material region of the photonic crystal structure, and the germanium absorption region is directly opposite to the silicon waveguide structure.

[0007] Optionally, the light in the peripheral silicon material region enters the germanium absorption region through direct coupling or evanescent wave coupling.

[0008] Optionally, the germanium photodetector includes: a germanium absorption region, a peripheral silicon material region is disposed around the germanium absorption region, the germanium absorption region has opposite first and second ends, and opposite first and second sides, and the first end of the germanium absorption region is disposed opposite to the silicon waveguide structure; a first contact layer and a second contact layer, which are respectively formed in the peripheral silicon material regions on the first side and the second side of the germanium absorption region; a first electrode and a second electrode, which are respectively formed on the first contact layer and the second contact layer.

[0009] Optionally, the material of the germanium absorption region includes one of SiGe, Ge, GeSn, and GePb.

[0010] Optionally, the dielectric material vertically penetrates the germanium absorption region and the peripheral silicon material region in a cylindrical shape.

[0011] Optionally, the dielectric material and the germanium absorption region and the peripheral silicon material region form a resonant cavity with a periodic structure.

[0012] Optionally, the dielectric material includes silicon dioxide.

[0013] The present invention also provides a method for manufacturing a waveguide-type germanium photodetector based on a photonic crystal. The manufacturing method includes the steps: Step 1), providing an SOI substrate, and etching a silicon waveguide structure on the top silicon layer of the SOI substrate; Step 2), etching a germanium-based material selective epitaxial region on the top silicon layer of the SOI substrate, and retaining a bottom layer of the top silicon layer with a partial thickness at the bottom of the germanium-based material selective epitaxial region; Step 3), selectively epitaxially growing a germanium absorption region in the germanium-based material selective epitaxial region, and forming a first contact layer and a second contact layer in the peripheral silicon material region outside the germanium absorption region by using ion implantation and annealing methods; Step 4), forming periodically arranged grooves in the germanium absorption region and the peripheral silicon material region through photolithography and etching processes, and filling a dielectric material in the grooves to form a photonic crystal structure with a slow light effect; Step 5), defining a first electrode region and a second electrode region in the first contact layer and the second contact layer through photolithography and etching methods, and forming a first electrode and a second electrode.

[0014] Optionally, the height of the germanium absorption region is greater than the depth of the germanium-based material selective epitaxial region.

[0015] As described above, the waveguide-type germanium photodetector based on a photonic crystal and the manufacturing method of the present invention have the following beneficial effects:

[0016] The present invention introduces a photonic crystal structure into a waveguide-type germanium photodetector. Since the resonant cavity formed by the periodic structure has the effect of slow light, the absorption efficiency of the detector can be improved, the size of the detector can be reduced, and it is easier to fabricate a photodetector with low dark current, low capacitance, and high responsivity. At the same time, the periodic germanium / dielectric layer (such as silicon dioxide, etc.) structure can effectively reduce the stress of the germanium material, which is beneficial to improving the quality of the germanium material.

[0017] Compared with the traditional waveguide-type germanium photodetector, the present invention can achieve a more efficient light absorption efficiency, and by reducing the device size, fabricate a photodetector with low dark current, low capacitance, and high responsivity. Brief Description of the Drawings

[0018] As Figures 1 to 3 shown is a schematic structural diagram of a waveguide-type germanium photodetector based on a photonic crystal according to an embodiment of the present invention, wherein, Figure 2 shown as Figure 1 a schematic cross-sectional structural diagram at A - A', Figure 3 shown as Figure 1 a schematic cross-sectional structural diagram at B - B'.

[0019] Figure 4 shown is a schematic structural diagram presented by each step of the preparation method of a waveguide-type germanium photodetector based on a photonic crystal according to an embodiment of the present invention.

[0020] Description of Component Labels

[0021] 10 Silicon waveguide structure

[0022] 20 Germanium photodetector

[0023] 201 Dielectric material

[0024] 202 Germanium absorption region

[0025] 203 Peripheral silicon material region

[0026] 204 First contact layer

[0027] 205 Second contact layer

[0028] 206 First electrode

[0029] 207 Second electrode

[0030] 210 Bottom silicon layer

[0031] 211 Insulating layer

[0032] 212 Top silicon layer

[0033] 30 Reflective structure

[0034] Steps S11 to S15, step 1) to step 5) Detailed implementation manners

[0035] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] When detailing the embodiments of the present invention, for the convenience of description, the cross-sectional views showing the device structure will be enlarged locally in a non-general proportion, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention here. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0037] For the convenience of description, spatial relationship terms such as "beneath", "below", "lower than", "under", "above", "on" may be used herein to describe the relationship between one element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can also be one or more intervening layers.

[0038] In the context of this application, the structure in which the first feature is "above" the second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0039] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in its actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0040] As Figures 1 to 3 shown, among which, Figure 2 is shown as Figure 1 a schematic cross-sectional structure diagram at A - A', Figure 3 is shown as Figure 1 a schematic cross-sectional structure diagram at B - B'. This embodiment provides a waveguide-type germanium photodetector based on a photonic crystal. The waveguide-type germanium photodetector includes a silicon waveguide structure 10 and a germanium photodetector 20.

[0041] The silicon waveguide structure 10 and the germanium photodetector 20 are fabricated based on an SOI substrate. The top silicon layer 212 of the SOI substrate is partially removed to form a selective epitaxial region for germanium-based material. A bottom layer of the top silicon layer with a certain thickness is retained at the bottom of the selective epitaxial region for germanium-based material, and the selective epitaxial region for germanium-based material is used for the epitaxial growth of the germanium absorption region 202.

[0042] The germanium photodetector 20 is connected to the silicon waveguide structure 10. The germanium absorption region 202 of the germanium photodetector 20 and the surrounding silicon material region 203 around the germanium absorption region 202 have periodically arranged dielectric materials 201 to form a photonic crystal structure with a slow light effect. The germanium photodetector 20 includes: a germanium absorption region 202, a first contact layer 204 and a second contact layer 205, and a first electrode 206 and a second electrode 207.

[0043] As Figure 2 and Figure 3 shown, the germanium absorption region 202 is formed in the selective epitaxial region for germanium-based material, and there is a surrounding silicon material region 203 around the germanium absorption region 202. The germanium absorption region 202 has opposite first and second ends, and opposite first and second sides. The first end of the germanium absorption region 202 is disposed opposite to the silicon waveguide structure 10. Specifically, as Figure 1 shown, the silicon waveguide structure 10 is connected to the surrounding silicon material region 203 of the photonic crystal structure, and the germanium absorption region 202 is directly opposite to the silicon waveguide structure 10. The material of the germanium absorption region 202 can be one of SiGe, Ge, GeSn, and GePb. For example, in this embodiment, the material of the germanium absorption region 202 can be selected as SiGe to reduce the lattice mismatch between the germanium absorption region 202 and the top silicon layer 212 and improve the material quality of the germanium absorption region 202.

[0044] The first contact layer 204 and the second contact layer 205 are respectively formed in the surrounding silicon material region 203 on the first side and the second side of the germanium absorption region 202. Specifically, the first contact layer 204 can be formed by performing P-type ion implantation on the surrounding silicon material region 203 on the first side of the germanium absorption region 202 to form heavily doped P-type silicon as the first contact layer 204; the second contact layer 205 can be formed by performing N-type ion implantation on the surrounding silicon material region 203 on the second side of the germanium absorption region 202 to form heavily doped N-type silicon as the second contact layer 205. Both the first contact layer 204 and the second contact layer 205 are in direct contact with the germanium absorption region 202.

[0045] The first electrode 206 and the second electrode 207 are respectively formed on the first contact layer 204 and the second contact layer 205. For example, the first electrode 206 and the second electrode 207 can be formed by metal deposition, photolithography and etching processes; alternatively, the first electrode 206 and the second electrode 207 can be formed by a lift-off process, and the examples listed here are not limiting.

[0046] Light in the peripheral silicon material region 203 enters the germanium absorption region 202 through direct coupling or evanescent wave coupling to reduce optical loss.

[0047] As Figure 1 As shown, the dielectric material 201 vertically penetrates through the germanium absorption region 202 and the peripheral silicon material region 203 in a cylindrical shape. The dielectric material 201 and the germanium absorption region 202 and the peripheral silicon material region 203 form a resonant cavity with a periodic structure. The dielectric material 201 can be silicon dioxide. Of course, the dielectric material 201 can also be selected as other materials with refractive indices such as air, vacuum or silicon oxynitride, and the examples listed here are not limiting. The dielectric material 201 penetrating through the germanium absorption region 202 can effectively reduce the stress in the germanium absorption region 202.

[0048] As Figure 1 And Figure 2 As shown, in this embodiment, the spacing between the dielectric materials 201 in the germanium absorption region 202 is greater than the spacing between the dielectric materials 201 in the peripheral silicon material region 203 to ensure the absorption effect of the germanium absorption region 202.

[0049] As Figure 1 As shown, a reflective structure 30 with a photonic crystal structure is connected to the second end of the germanium photodetector, which can achieve a reflective effect and further increase the absorption efficiency of the germanium photodetector 20.

[0050] In the present invention, a photonic crystal structure is introduced into the waveguide-type germanium photodetector 20. Since the resonant cavity formed by the periodic structure has the effect of slow light, in the photonic crystal, the guided mode is dispersed by the periodic structure of the photonic crystal, and the group velocity will be greatly reduced, thereby realizing the slow light effect of the photonic crystal. The photonic crystal of the present invention has the advantages of flexible structure design, small volume, easy integration with existing optical communication devices, and easy control. It can achieve optical buffering, thereby improving the absorption efficiency of the detector, reducing the size of the detector, and making it easier to fabricate a photodetector with low dark current, low capacitance and high responsivity. At the same time, the periodic germanium / dielectric layer (such as silicon dioxide, etc.) structure can effectively reduce the stress of the germanium material, which is beneficial to improving the quality of the germanium material.

[0051] As Figures 1 to 4As shown in the figure, this embodiment also provides a preparation method of a waveguide-type germanium photodetector based on a photonic crystal. The preparation method includes the following steps:

[0052] As Figure 4 shown in the figure, first, perform step 1) S11: Provide an SOI substrate, and etch a silicon waveguide structure 10 on the top silicon layer 212 of the SOI substrate.

[0053] Specifically, the SOI substrate specifically includes a bottom silicon layer 210, an insulating layer 211, and a top silicon layer 212. The silicon waveguide structure 10 is formed in the top silicon layer 212 through photolithography and etching processes.

[0054] As Figure 4 shown in the figure, then perform step 2) S12: Etch a germanium-based material selective epitaxial region in the top silicon layer 212 of the SOI substrate, and retain a part of the bottom layer of the top silicon layer with a certain thickness at the bottom of the germanium-based material selective epitaxial region.

[0055] For example, a dielectric layer can be deposited on the top silicon layer 212 of the SOI substrate as a hard mask first, then a transfer window is formed in the dielectric layer through photolithography and etching processes, and then the top silicon layer 212 is further etched to etch out a germanium-based material selective epitaxial region in the top silicon layer 212. A part of the bottom layer of the top silicon layer with a certain thickness is retained at the bottom of the germanium-based material selective epitaxial region to facilitate the subsequent epitaxial growth of the germanium absorption region 202.

[0056] As Figure 4 shown in the figure, then perform step 3) S13: Selectively epitaxially grow a germanium absorption region 202 in the germanium-based material selective epitaxial region, and form a first contact layer 204 and a second contact layer 205 in the peripheral silicon material region 203 outside the germanium absorption region 202 by using ion implantation and annealing methods.

[0057] The material of the germanium absorption region 202 can be one of SiGe, Ge, GeSn, and GePb. For example, in this embodiment, the material of the germanium absorption region 202 can be selected as SiGe to reduce the lattice mismatch between the germanium absorption region 202 and the top silicon layer 212 and improve the material quality of the germanium absorption region 202.

[0058] The height of the germanium absorption region 202 is greater than the depth of the germanium-based material selective epitaxial region to further improve the absorption efficiency of the germanium absorption region 202 without increasing the length of the germanium absorption region.

[0059] Specifically, the first contact layer 204 can be formed by performing P-type ion implantation on the peripheral silicon material region 203 on the first side of the germanium absorption region 202 to form heavily doped P-type silicon as the first contact layer 204; the second contact layer 205 can be formed by performing N-type ion implantation on the peripheral silicon material region 203 on the second side of the germanium absorption region 202 to form heavily doped N-type silicon as the second contact layer 205. Both the first contact layer 204 and the second contact layer 205 are in direct contact with the germanium absorption region 202.

[0060] As Figure 4 shown, then step 4) S14 is performed. Periodically arranged grooves are formed in the germanium absorption region 202 and the peripheral silicon material region 203 through photolithography and etching processes, and a dielectric material 201 is filled in the grooves to form a photonic crystal structure with a slow light effect.

[0061] As Figure 1 shown, the grooves and the dielectric material 201 penetrate vertically through the germanium absorption region 202 and the peripheral silicon material region 203 in a cylindrical shape. The dielectric material 201 and the germanium absorption region 202 and the peripheral silicon material region 203 form a resonant cavity with a periodic structure. The dielectric material 201 can be silicon dioxide. Of course, the dielectric material 201 can also be selected as other materials with refractive indices such as silicon oxynitride, and is not limited to the examples listed here. The dielectric material 201 penetrates the germanium absorption region 202. During the process of forming the periodically arranged grooves, the stress of the germanium absorption region can be released, thereby effectively reducing the stress of the germanium absorption region 202.

[0062] As Figure 4 shown, finally step 5) S15 is performed. The first electrode 206 region and the second electrode 207 region are defined in the first contact layer 204 and the second contact layer 205 through photolithography and etching methods, and the first electrode 206 and the second electrode 207 are formed.

[0063] For example, the first electrode 206 and the second electrode 207 can be formed through metal deposition, photolithography and etching processes; or, the first electrode 206 and the second electrode 207 can be formed through a lift-off process, and is not limited to the examples listed here.

[0064] The first electrode 206 and the second electrode 207 can respectively form ohmic contacts with the first contact layer 204 and the second contact layer 205 through thermal annealing or the like to reduce their resistance and at the same time reduce the parasitic capacitance.

[0065] As described above, the waveguide-type germanium photodetector based on a photonic crystal and the manufacturing method thereof according to the present invention have the following beneficial effects:

[0066] The present invention introduces a photonic crystal structure into a waveguide-type germanium photodetector. Since the resonant cavity formed by the periodic structure has the effect of slow light, it can improve the absorption efficiency of the detector, reduce the size of the detector, and make it easier to fabricate a photodetector with low dark current, low capacitance, and high responsivity. At the same time, the periodic germanium / dielectric layer (such as silica, etc.) structure can effectively reduce the stress of the germanium material, which is beneficial to improving the quality of the germanium material.

[0067] Compared with the traditional waveguide-type germanium photodetector, the present invention can achieve a more efficient light absorption efficiency, and can fabricate a photodetector with low dark current, low capacitance, and high responsivity by reducing the device size.

[0068] Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0069] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A waveguide-type germanium photodetector based on a photonic crystal, characterized in that, the germanium photodetector comprises: a silicon waveguide structure; a germanium photodetector connected to the silicon waveguide structure, wherein a periodically arranged dielectric material is provided in a germanium absorption region of the germanium photodetector and a peripheral silicon material region outside the germanium absorption region to form a photonic crystal structure with a slow light effect, the germanium absorption region has opposite first and second ends, and opposite first and second sides, a first end of the germanium absorption region is disposed opposite to the silicon waveguide structure, and a second end of the germanium absorption region is connected to a reflection structure having the photonic crystal structure.

2. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: the silicon waveguide structure is connected to the peripheral silicon material region of the photonic crystal structure, and the germanium absorption region is directly opposite to the silicon waveguide structure.

3. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: light in the peripheral silicon material region enters the germanium absorption region by direct coupling or evanescent wave coupling.

4. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: the germanium photodetector further comprises: a first contact layer and a second contact layer respectively formed in the peripheral silicon material regions on the first and second sides of the germanium absorption region; a first electrode and a second electrode respectively formed on the first contact layer and the second contact layer.

5. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: the material of the germanium absorption region comprises one of SiGe, Ge, GeSn and GePb.

6. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: the dielectric material vertically penetrates through the germanium absorption region and the peripheral silicon material region in a cylindrical shape.

7. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: the dielectric material and the germanium absorption region and the peripheral silicon material region form a resonant cavity with a periodic structure.

8. The waveguide-type germanium photodetector based on a photonic crystal according to claim 1, characterized in that: the dielectric material comprises air or silicon dioxide.

9. A method for manufacturing a waveguide-type germanium photodetector based on a photonic crystal according to any one of claims 1 to 8, characterized in that, the manufacturing method comprises the steps of: Step 1), providing an SOI substrate, and etching a silicon waveguide structure on a top silicon layer of the SOI substrate; Step 2), etching a germanium-based material selective epitaxial region on the top silicon layer of the SOI substrate, and retaining a bottom layer of the top silicon layer with a partial thickness at the bottom of the germanium-based material selective epitaxial region; Step 3), selectively epitaxially growing a germanium absorption region in the germanium-based material selective epitaxial region, and forming a first contact layer and a second contact layer in a peripheral silicon material region outside the germanium absorption region by ion implantation and annealing, the germanium absorption region has opposite first and second ends, and a first end of the germanium absorption region is disposed opposite to the silicon waveguide structure; Step 4), forming periodically arranged grooves in the germanium absorption region and the surrounding silicon material region through photolithography and etching processes, and filling a dielectric material in the grooves to form a photonic crystal structure with a slow light effect; Step 5), defining a first electrode region and a second electrode region in the first contact layer and the second contact layer through photolithography and etching methods, and forming a first electrode and a second electrode.

10. The method for preparing a waveguide-type germanium photodetector based on a photonic crystal according to claim 9, characterized in that: the height of the germanium absorption region is greater than the depth of the germanium-based material selective epitaxial region.

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