Photodetector and method for manufacturing the same

Abstract

Provided are a silicon-based photodetector and a method for manufacturing the same. The photodetector comprises: a silicon substrate (201); a buried oxide layer (202), the buried oxide layer being above the silicon substrate; and a waveguide (203), the waveguide being above the buried oxide layer. The waveguide (203) comprises a silicon-containing Si region and a germanium-tin-containing GeSn region (209), both of which are located between a first doping region (206) and a second doping region (207) of the waveguide (203), thereby forming a PIN diode. The first doping region (206) and the second doping region (207) are respectively connected to a first electrode (210a) and a second electrode (210b), so that the waveguide (203) can be operated as a photodetector.

Description

Field of the Invention

[0001] The invention relates to a silicon-based photodetector and a method for manufacturing the silicon-based photodetector. Background Art

[0002] Photodetectors are ubiquitous in the context of photonic platforms and networks. Conventionally, germanium-based silicon photodetectors have been used as the light absorbing material within the photodetector. However, germanium-based detectors can only operate at a bandgap wavelength of about 1.55 μm at best. However, there are an increasing number of silicon photonic applications at wavelengths beyond 1.55 μm.

[0003] Furthermore, it is convenient to integrate a photodetector or photodiode within a photonic circuit (as opposed to incorporating them into part of the circuit). Incorporated photodiodes induce coupling losses, and incorporation has a certain cost in terms of manufacturing (and also in terms of the yield of the process). In addition, incorporating photodiodes imposes restrictions on the number of devices that can be used in a photonic integrated circuit and the locations where these devices can be placed. In contrast, integrated photodetectors induce substantially no coupling losses and have a high responsivity.

[0004] Figure 1 A conventional silicon photodetector using a PIN junction is shown. P-doped and n-doped regions extend up the sidewalls of the waveguide ridge, and an intrinsic region is located between the p-doped and n-doped regions. Light that passes through the junction is captured by the photodetector and provides a signal. Summary of the invention

[0005] Therefore, in a first aspect, an embodiment of the present invention provides a silicon-based photodetector comprising:

[0006] Silicon substrate;

[0007] a buried oxide layer over the silicon substrate; and

[0008] a waveguide, the waveguide being above the buried oxide layer;

[0009] wherein the waveguide comprises a silicon-containing Si region and a germanium-tin-containing GeSn region, both of which are located between a first doping region and a second doping region of the waveguide, thereby forming a PIN diode;

[0010] And wherein the first doped region and the second doped region are connected to a first electrode and a second electrode, respectively, so that the waveguide can operate as a photodetector.

[0011] Such a photodetector can be integrated in a silicon photonic platform, for example in a photonic integrated circuit (PIC), and has a detectable wavelength of more than 1.55 μm. For example, GeSn as a material has a bandgap wavelength between about 2 μm and about 3 μm.

[0012] The silicon-based photodetector may have any one of the following optional features, or any combination of the following optional features to the extent they are compatible.

[0013] The waveguide may be a rib or ridge waveguide located between the first slab portion and the second slab portion. The first doped region and the second doped region may be located within respective sidewalls of the rib waveguide. The first doped region and the second doped region may extend into the first slab portion and the second slab portion, respectively. The first electrode and the second electrode may contact the first doped region and the second doped region, respectively, in portions of the first doped region and the second doped region within respective slab portions.

[0014] The photodetector may have an operating wavelength of at least 1.3 μm. The photodetector may have an operating wavelength of at least 1.55 μm. The photodetector may have an operating wavelength of no more than 3.5 μm.

[0015] The germanium-tin region may be composed of Ge 93 Sn 7 form.

[0016] The germanium-tin region may be composed of Ge 90 Sn 10 form.

[0017] The width of the germanium-tin containing region measured in a direction perpendicular to the guiding direction of the waveguide and parallel to the surface of the substrate may be at least 40% and no more than 60% of the width of the waveguide region measured in the same direction.

[0018] The germanium-tin containing region may be positioned in the waveguide at a point distal from the buried oxide layer.

[0019] The waveguide may have a height of at least 2.5 μm and no more than 3.5 μm measured from a surface of the buried oxide layer adjacent to the waveguide to a surface of the waveguide farthest from the buried oxide layer.

[0020] The waveguide may have a width of at least 1.5 μm and no more than 2.5 μm measured from a first side and a second side of the waveguide equidistant from the buried oxide layer.

[0021] The first and second plate portions may have a height of at least 0.2 μm and not more than 0.6 μm measured from an uppermost surface of the buried oxide layer to a surface of the respective plate portion farthest from the buried oxide layer.

[0022] The germanium-tin containing region may be formed of substantially pure germanium-tin.

[0023] The germanium-tin containing region may not contain silicon.

[0024] In a second aspect, an embodiment of the present invention provides a method for manufacturing a silicon-based photodetector, comprising the steps of:

[0025] providing a silicon-based substrate, a buried oxide layer over the silicon substrate, and a waveguide over the buried oxide layer;

[0026] doping the first region with a first type of dopant to form a first doped region;

[0027] doping the second region with a second type of dopant to form a second doped region;

[0028] etching at least a portion of the waveguide between the first doped region and the second doped region to provide a cavity therein; and

[0029] Germanium tin is deposited into the cavity to provide a germanium tin containing region of the waveguide adjacent to a silicon containing region of the waveguide.

[0030] The method may have any one of the following optional features, or any combination of the following optional features to the extent they are compatible.

[0031] Depositing the germanium tin may be performed by selective epitaxial growth.

[0032] The method may further comprise the step of passivating the device by depositing a passivation layer over the uppermost surface of the device.

[0033] The method may include depositing a first electrode and a second electrode in contact with the first doped region and the second doped region, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0035] Figure 1 shows a cross-sectional view of a conventional photodetector;

[0036] FIG. 2A to FIG. 2E Various manufacturing steps of an embodiment of the present invention are shown; and

[0037] Figure 3 A cross-sectional view of a photodetector according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0038] Various aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Other aspects and embodiments will be apparent to those skilled in the art. All documents mentioned herein are incorporated herein by reference.

[0039] FIG. 2A to FIG. 2E Various manufacturing steps of an embodiment of the present invention are shown. Figure 2A In the initial step shown in FIG. 1 , a silicon substrate 201 is provided, a buried oxide layer 202 is provided above the silicon substrate, and a waveguide 203 is provided above the buried oxide layer. The waveguide 203 directs light into or out of the light source in one direction. Figure 2A Then, a first doped region 206 and a second doped region 207 are provided in the respective slab portions 204a and 204b. The slab region and the waveguide region are formed in a silicon-on-insulator layer of an SOI wafer used in the device or in manufacturing the device. The upper surface of the structure is covered by a passivation layer or passivating layer 208, which may be silicon dioxide. The structure may be similar to Figure 1 The structure shown in is substantially the same. This step may be a front end of line (FEOL) processing step.

[0040] Next, etching is performed to remove a portion of the waveguide. The result of this step is Figure 2B 205 can be seen in the upper part of the waveguide 207. In this example, the shape of the cavity is trapezoidal. After etching, a selective epitaxial process is used to grow a germanium tin (GeSn) region 209 within the cavity. This is shown in FIG. Figure 2C After the epitaxial growth process has been performed, a passivation process is performed to provide a continuous passivation treatment or passivation layer 208 over the entire upper surface of the device. Figure 2D Shown in.

[0041] Finally, if Figure 2E As shown, a first electrode 210a and a second electrode 210b are provided to contact the first doped region 206 and the second doped region 207, respectively. This step can be performed in two sub-steps: a first step of etching a through hole through the passivation layer 208, which exposes the uppermost surfaces of the first doped region and the second doped region. Subsequently, a metallization process is used to provide electrical contacts to these exposed surfaces of the doped regions, and electrode pads are provided for connecting to external connectors. FIG. 2C to FIG. 2E The steps shown in may be back-end-of-line (BEOL) processing steps.

[0042] Steps 2A to 2E produce Figure 3 The device 300 according to an embodiment of the present invention is shown. The substrate 201 is formed of silicon, and the buried oxide layer 202 is formed of silicon dioxide (SiO 2 ) is formed. The waveguide 203, the slab portions 204a, 204b, and the doped regions 206 and 207 are all formed of silicon. The germanium-tin-containing region 209 is formed of germanium-tin, having a relatively low content of tin. For example, the germanium-tin-containing region may have a composition of Ge 90 Sn 10 Or Ge 93 Sn 7 .

[0043] The germanium tin containing region 209 has a maximum width of about 1 μm (measured in a direction perpendicular to the guiding direction of the waveguide and perpendicular to the height direction extending from the substrate 201 to the waveguide 203). The germanium tin containing region has a height of about 1.2 μm measured perpendicular to the width. The waveguide 203, which is primarily formed of silicon, itself has a width of about 2 μm and a height of about 3 μm measured from the uppermost surface of the buried oxide layer to the uppermost surface of the waveguide. The slab regions 204a and 204b have a height of about 0.4 μm measured from the uppermost surface of the buried oxide layer to the uppermost surface of one or more slab regions. The electrodes are formed of aluminum.

[0044] Although the present invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when this disclosure is given. Therefore, the exemplary embodiments of the present invention set forth above are considered to be illustrative rather than restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the present invention.

[0045] All references cited above are incorporated herein by reference.

Claims

1. A silicon-based photodetector, include: Silicon substrate; a buried oxide layer, the buried oxide layer being above the silicon substrate; as well as a waveguide above the buried oxide layer, wherein the waveguide is a rib waveguide between the first slab portion and the second slab portion; wherein the waveguide comprises a silicon-containing Si region and a germanium-tin-containing GeSn region, both of which are located between a first doping region and a second doping region of the waveguide, thereby forming a PIN diode; Wherein, in the height direction extending from the silicon substrate to the waveguide, the lower surface of the GeSn region containing germanium is higher than the upper surfaces of the first plate portion and the second plate portion; And wherein the first doped region and the second doped region are connected to a first electrode and a second electrode, respectively, so that the waveguide can operate as a photodetector. 2 . The silicon-based photodetector of claim 1 , wherein the first doped region and the second doped region are located in corresponding sidewalls of the rib waveguide. 3 . The silicon-based photodetector of claim 2 , wherein the first doped region and the second doped region extend into the first slab portion and the second slab portion, respectively. 4 . The silicon-based photodetector of claim 3 , wherein the first electrode and the second electrode contact the first doped region and the second doped region, respectively, in portions of the first doped region and the second doped region within corresponding slab portions.

5. The silicon-based photodetector of claim 1, having an operating wavelength of at least 1.3 μm.

6. The silicon-based photodetector of claim 1, having an operating wavelength of at least 1.55 μm.

7. The silicon-based photodetector of claim 1, having an operating wavelength not exceeding 3.5 μm.

8. The silicon-based photodetector according to claim 1, wherein the GeSn region is composed of Ge 93 Sn 7 form.

9. The silicon-based photodetector according to claim 1, wherein the GeSn region is composed of Ge 90 Sn 10 form.

10. The silicon-based photodetector of claim 1, wherein a width of the germanium-tin (GeSn) region measured in a direction perpendicular to the guiding direction of the waveguide and parallel to the surface of the substrate is at least 40% and no more than 60% of a width of the waveguide measured in the same direction.

11. The silicon-based photodetector of claim 1, wherein the germanium-tin-containing GeSn region is positioned in the waveguide at a point away from the buried oxide layer.

12. The silicon-based photodetector of claim 1, wherein the waveguide has a height of at least 2.5 μm and no more than 3.5 μm measured from a surface of the buried oxide layer adjacent to the waveguide to a surface of the waveguide farthest from the buried oxide layer.

13. The silicon-based photodetector of claim 1, wherein the waveguide has a width of at least 1.5 μm and no more than 2.5 μm measured from a first side and a second side of the waveguide equidistant from the buried oxide layer.

14. The silicon-based photodetector of claim 1, wherein the first slab portion and the second slab portion have a height of at least 0.2 μm and not more than 0.6 μm measured from the uppermost surface of the buried oxide layer to the surface of the corresponding slab portion farthest from the buried oxide layer. 15 . The silicon-based photodetector according to claim 1 , wherein the germanium-tin-containing GeSn region is formed of pure germanium-tin.

16. The silicon-based photodetector of claim 1, wherein the germanium-tin-containing GeSn region does not contain any silicon.

17. A method for manufacturing a silicon-based photodetector, The following steps are involved: providing a silicon substrate, a buried oxide layer over the silicon substrate, and a waveguide over the buried oxide layer, wherein the waveguide is a rib waveguide located between a first slab portion and a second slab portion; doping the first region with a first type of dopant to form a first doped region; doping the second region with a second type of dopant to form a second doped region; etching at least a portion of the waveguide between the first doped region and the second doped region to provide a cavity therein; as well as Germanium tin is deposited into the cavity to provide a germanium tin GeSn region of the waveguide adjacent to the silicon containing region of the waveguide, wherein in a height direction extending from the silicon substrate to the waveguide, a lower surface of the germanium tin GeSn region is higher than upper surfaces of the first and second slab portions.

18. The method of claim 17, wherein depositing the germanium tin is performed by selective epitaxial growth.

19. The method of claim 17, further comprising: The following steps are involved: The device is passivated by depositing a passivation treatment layer over the uppermost surface of the device.

20. The method of claim 17, further comprising: The following steps are involved: A first electrode and a second electrode are deposited to contact the first doped region and the second doped region, respectively.

Images