High-speed germanium-silicon photoelectric detector with ultrahigh responsivity

Abstract

The invention discloses a high-speed germanium-silicon photoelectric detector with ultrahigh responsivity, which comprises a surface incidence photoelectric detector, and the surface incidence photoelectric detector comprises a substrate, an absorption region, a polycrystalline silicon layer, a top contact region, a top electrode region, a mask layer, a bottom contact region, a bottom electrode region and a metal electrode layer, a light reflection structure is additionally arranged on the surface incidence photoelectric detector, and the light reflection structure is located on the periphery of an absorption area of the surface incidence photoelectric detector. The photoelectric detector has the advantages that the absorption area with the thickness of 400-800nm can be realized, light emitted to the edge of the absorption area is reflected through the light reflection structure, and high responsivity can be kept on the premise of high bandwidth.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology, specifically relating to a high-speed germanium-silicon photodetector with ultra-high responsivity. Background Technology

[0002] High-speed photodiodes are photodetectors that convert photoelectric bandwidth under high-frequency signals. They have the characteristics of fast response speed, high sensitivity, and wide detection wavelength range, and can be widely used in high-speed optical communication, data centers and other fields.

[0003] With the rapid development of 5G communication, computing networks, and artificial intelligence, the requirements for response speed are becoming increasingly stringent. For surface-incident photodiodes (PDs), the carrier transport direction is parallel to the light incident direction. Therefore, the most direct and effective way to improve bandwidth is to reduce the thickness of the light absorption region, reduce the carrier drift bandwidth, or reduce the junction area of ​​the light absorption region to increase the RC bandwidth. However, both reducing the thickness and area of ​​the light absorption region will affect the detector responsivity. Summary of the Invention

[0004] The purpose of this invention is to propose a high-speed germanium-silicon photodetector with ultra-high responsivity. This high-speed germanium-silicon photodetector improves upon the traditional surface-incident photodetector by adding a light-reflecting structure, thereby increasing the optical path length without changing the original light absorption thickness or affecting the device bandwidth, and effectively improving the responsivity.

[0005] The specific technical solutions adopted are as follows: A high-speed germanium-silicon photodetector with ultra-high responsivity includes a surface-incident photodetector. The surface-incident photodetector includes a substrate, an absorption region, a polycrystalline silicon layer, a top contact region, a top electrode region, a mask layer, a bottom contact region, a bottom electrode region, and a metal electrode layer. A light-reflecting structure is added to the surface-incident photodetector, and the light-reflecting structure is located on the outer periphery of the absorption region of the surface-incident photodetector.

[0006] Furthermore, the material of the absorption region is Ge.

[0007] Furthermore, the growth angle of the Ge material between the sidewall of the Ge absorption region and the substrate is greater than 25°. According to the principle of total internal reflection, growing Ge at an angle greater than 25° allows the sidewall of the Ge absorption region to achieve total internal reflection of light, effectively increasing the optical path and improving the responsivity.

[0008] Furthermore, the high-speed germanium-silicon photodetector also includes a substrate lens, which is located on the back side of the substrate to enlarge the equivalent aperture of the device.

[0009] Furthermore, the light reflection structure is a top metal reflective layer made of aluminum, which is located above the top contact area of ​​the surface-incident photodetector.

[0010] Furthermore, several reflective slopes are provided on the surface of the top metal reflective layer, and the reflection angle between the reflective slopes and the surface of the top metal reflective layer is 45°; the light absorption is increased by providing several reflective slopes.

[0011] Furthermore, the light reflection structure consists of a top metal reflective layer, a sidewall metal reflective layer I, and a sidewall metal reflective layer II. The top metal reflective layer is located above the top contact area of ​​the surface-incident photodetector, and the sidewall metal reflective layer I and the sidewall metal reflective layer II are located on the polycrystalline silicon layers on both sides of the absorption area, respectively.

[0012] Furthermore, the absorption region is located on the substrate, and a polycrystalline silicon layer covers the absorption region. The top contact region covers the top of the absorption region, and the bottom contact region covers the bottom of the absorption region. The top and bottom contact regions are formed by ion doping and have opposite polarities.

[0013] Furthermore, the absorption region has a thickness of 400-800 nm and a width of 3 μm-15 μm. The top contact region has a width greater than 2 μm, the top electrode region is distributed on the top contact region with a width greater than 1 μm, and the distance between the top electrode region and the absorption region is greater than 1 μm. The bottom contact region has a width greater than 3 μm, the bottom electrode region is distributed on the bottom contact region with a width greater than 1 μm, and the distance between the bottom electrode region and the absorption region is greater than 1 μm.

[0014] Furthermore, the substrate is a Si substrate, the bottom contact area is P-type doped, the polycrystalline silicon layer is made of amorphous silicon or polycrystalline silicon and is N-type doped; the mask layer is made of silicon dioxide; the top electrode area and the bottom electrode area are metal electrodes made of tungsten; and the metal electrode layer is made of aluminum.

[0015] The advantages of this invention compared to the prior art are as follows: The high-speed germanium-silicon photodetector of the present invention has ultra-high responsivity and can achieve an absorption region with a thickness of 400-800nm. Through a light reflection structure, light hitting the edge of the absorption region is reflected, and high responsivity can be maintained under the premise of high bandwidth.

[0016] The present invention relates to a high-speed germanium-silicon photodetector with ultra-high responsivity, suitable for 0.13µm CMOS process.

[0017] The present invention provides a high-speed germanium-silicon photodetector with ultra-high responsivity, by adding a lens on the back side of the substrate to enlarge the equivalent aperture of the device. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of the surface-incident photodetector in Example 1; Figure 2This is a schematic diagram of the cross-sectional structure of the surface-incident photodetector in Example 2; Figure 3 This is a schematic diagram of the cross-sectional structure of the surface-incident photodetector in Example 3; Figure 4 This is a schematic diagram of the cross-sectional structure of a surface-incident photodetector that reflects light from the reaction path. Figure 5 This is a measured image showing the enhanced responsivity of the reflective structure compared to the non-reflective structure in Embodiment 1.

[0019] Wherein, 100-substrate, 110-mask layer, 120-polysilicon layer, 130-absorption region, 140a-bottom electrode region I, 140b-bottom electrode region II, 150a-top electrode region I, 150b-top electrode region II, 160-metal electrode layer, 170-light reflection structure, 170a-top metal reflection layer, 170b-sidewall metal reflection layer I, 170c-sidewall metal reflection layer II, 180-substrate lens, 200-top contact region, 210-bottom contact region. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figure 1 -Appendix Figure 5 The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Example 1

[0022] A high-speed germanium-silicon photodetector with ultra-high responsivity is a surface-incident photodetector; it includes a substrate 100, an absorption region 130, a polycrystalline silicon layer 120, a top contact region 200, a top electrode region, a mask layer 110, a bottom contact region 210, a bottom electrode region, a metal electrode layer 160, a substrate lens 180, and a light-reflecting structure 170.

[0023] In this embodiment, the surface-incident photodetector has an absorption region 130 located on a substrate 100, a polysilicon layer 120 covering the absorption region 130, a top contact region 200 covering the top of the absorption region 130, and a bottom contact region 210 covering the bottom of the absorption region 130. The top contact region 200 and the bottom contact region 210 are formed by ion doping and have opposite polarities. The mask layer 110 is a silicon dioxide passivation layer. The bottom electrode region is distributed on the bottom contact region 210, and bottom electrode region I 140a and bottom electrode region II 140b are distributed on both sides of the absorption region 130, respectively. The top electrode region is distributed on the top contact region 200, and top electrode region I 150a and top electrode region II 150b are distributed on the top contact region 200. A metal electrode layer 160 is also included. In this embodiment, the light reflection structure 170 is a top metal reflection layer 170a, which is located above the top contact area 200; the substrate lens 180 is located on the back side of the substrate 100.

[0024] like Figure 1 As shown, the materials of the lens layer, substrate layer, top electrode region layer and absorption region are all semiconductor materials. The top contact region 200 and the bottom contact region 210 are formed by doping to form P and N electrodes, and the doping polarities of the top contact region 200 and the bottom contact region 210 must be opposite.

[0025] Generally, in this embodiment, the substrate 100 is a Si substrate, the bottom contact region 210 is p-type doped, the absorption region 130 is made of Ge, the polysilicon layer 120 is made of amorphous silicon or polysilicon, the top of the polysilicon layer 120 is n-type doped, and a top contact region 200 is formed on the top of the polysilicon layer 120. The mask layer 110 is silicon dioxide, the bottom electrode region I 140a and the bottom electrode region II 140b are metal electrodes, generally tungsten; the top electrode region I 150a and the top electrode region II 150b are metal electrodes, generally tungsten; the metal electrode layer 160 is generally aluminum, and the top metal reflective layer 170a is generally aluminum.

[0026] Generally, in this embodiment, the thickness of the absorption region 130 is 400-800 nm, and the width is 3 μm-15 μm. The polysilicon layer 120 must completely cover the absorption region 130, and the top contact region 200 must completely cover the top of the absorption region 130, with a width greater than 2 μm. The bottom contact region 210 must completely cover the bottom of the absorption region 130, with a width greater than 3 μm. The bottom electrode regions I 140a and II 140b are more than 1 μm away from the absorption region, and the width of the distribution area of ​​the bottom electrode regions I 140a and II 140b on the bottom contact region 210 is greater than 1 μm. The top electrode regions I 150a and II 150b are more than 1 μm away from the absorption region, and the width of the distribution area of ​​the top electrode regions I 150a and II 150b on the top contact region 200 is greater than 1 μm.

[0027] The surface-incident photodetector of this embodiment can be fabricated using a 0.13µm CMOS process; the epitaxy of Ge and CMP involved in the process are conventional and mature existing silicon photonics processes.

[0028] Based on a 0.13µm CMOS process, the minimum achievable etching linewidth is 100nm; the manufacturing process flow for the surface-incident photodetector in this embodiment is as follows: Step 1: Prepare substrate 100 (preferably Si substrate), and perform ion implantation on the bottom contact region 210 on substrate 100. The implantation type is P-type impurity. Step 2: Deposit the epitaxial mask layer 110, i.e., the silicon dioxide layer; Step 3: Etch a selective epitaxial window at the location of absorption region 130, and remove all the silicon dioxide within this window; Step 4: Selectively extend Ge within the window to fill the entire window; Step 5: Deposit polycrystalline silicon or amorphous silicon to form a polycrystalline silicon layer 120, and then perform ion implantation on it to form a top contact region 200. The ion implantation type is N-type impurity. Step 6: Etch away the polysilicon or amorphous silicon outside the 120 region of the polysilicon layer; Step 7: Deposit protective layer of medium; Step 8: Make holes for the bottom electrode area and the top electrode area respectively; Step 9: Prepare the metal electrode layer; Step 10: Thin the wafer to make the back lens.

[0029] The surface-incident photodetector of this embodiment can achieve an absorption region with a thickness of 400-800nm. Through a light reflection structure, the light hitting the edge of the absorption region is reflected, maintaining high responsivity while maintaining high bandwidth.

[0030] like Figure 4 As shown, in the surface-incident photodetector of this embodiment, the growth angle of the Ge material between the sidewall of the Ge absorption region and the substrate 100 is greater than 25°. Ge is grown at a specific tilt angle, which can achieve total internal reflection of light, effectively increasing the optical path and improving the responsivity.

[0031] like Figure 5 As shown, the surface-incident photodetector of this embodiment, after testing, showed that the responsivity increased from 0.64 A / W to 0.78 A / W after adding a light reflection structure.

[0032] Example 2

[0033] A high-speed germanium-silicon photodetector with ultra-high responsivity is a surface-incident photodetector; the difference between this embodiment and Embodiment 1 is that the light reflection structure 170 is used.

[0034] The light-reflecting structure 170 of this embodiment is composed of a top metal reflective layer 170a, a sidewall metal reflective layer I 170b, and a sidewall metal reflective layer II 170c. The top metal reflective layer 170a is located above the top contact area 200, and the sidewall metal reflective layers I 170b and II 170c are located above the polycrystalline silicon layers 120 on both sides of the absorption area 130, respectively.

[0035] Compared to Embodiment 1, the surface-incident photodetector of this embodiment has the following further effect: it increases light absorption through reflection from the top metal and sidewall metal, thereby improving the device responsivity.

[0036] Example 3

[0037] like Figure 3 As shown, a high-speed germanium-silicon photodetector with ultra-high responsivity is a surface-incident photodetector; the difference between this embodiment and Embodiment 1 is that the light reflection structure 170 is used.

[0038] In this embodiment, the light reflection structure 170 is a top metal reflective layer 170a, which is located above the top contact area 200. Several reflective slopes are provided on the surface of the top metal reflective layer 170a, and the reflection angle between the reflective slopes and the surface of the top metal reflective layer 170a is 45°. Compared to Embodiment 1, the surface-incident photodetector of this embodiment further enhances light absorption by providing several reflective slopes. A specific angle is used to achieve total internal reflection of the incident light. Figure 3 As shown.

[0039] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-speed germanium-silicon photodetector with ultra-high responsivity, comprising a surface-incident photodetector, said surface-incident photodetector comprising a substrate (100), an absorption region (130), a polycrystalline silicon layer (120), a top contact region (200), a top electrode region, a mask layer (110), a bottom contact region (210), a bottom electrode region, and a metal electrode layer (160), characterized in that, A light reflection structure (170) is added to the surface incident photodetector, and the light reflection structure (170) is located on the outer periphery of the absorption region (130) of the surface incident photodetector.

2. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 1, characterized in that: The material of the absorption region (130) is Ge.

3. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 2, characterized in that: The growth angle α of the Ge material between the sidewall of the Ge absorption region and the substrate (100) is greater than 25°.

4. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 1 or 3, characterized in that: The high-speed germanium-silicon photodetector also includes a substrate lens (180) located on the back side of the substrate (100).

5. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 1 or 3, characterized in that: The light reflection structure is a top metal reflective layer (170a), the material of which is aluminum, and the top metal reflective layer (170a) is located above the top contact area (200) of the surface incident photodetector.

6. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 5, characterized in that: Several reflective slopes are provided on the surface of the top metal reflective layer (170a), and the reflection angle between the reflective slopes and the surface of the top metal reflective layer (170a) is 45°.

7. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 1 or 3, characterized in that: The light reflection structure (170) consists of a top metal reflective layer (170a), a sidewall metal reflective layer I (170b) and a sidewall metal reflective layer II (170c). The top metal reflective layer (170a) is located above the top contact area (200) of the surface incident photodetector, and the sidewall metal reflective layer I (170b) and the sidewall metal reflective layer II (170c) are located above the polycrystalline silicon layers (120) on both sides of the absorption area (130).

8. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 1 or 3, characterized in that: The absorption region (130) is located on the substrate (100), the polycrystalline silicon layer (120) covers the absorption region (130), the top contact region (200) covers the top of the absorption region (130), and the bottom contact region (210) covers the bottom of the absorption region (130). The top contact region (200) and the bottom contact region (210) are formed by ion doping and have opposite polarities.

9. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 8, characterized in that: The absorption region (130) has a thickness of 400-800 nm and a width of 3 μm-15 μm. The top contact region (200) has a width greater than 2 μm. The top electrode region is distributed on the top contact region (200) with a width greater than 1 μm. The distance between the top electrode region and the absorption region (130) is greater than 1 μm. The bottom contact region (210) has a width greater than 3 μm. The bottom electrode region is distributed on the bottom contact region (210) with a width greater than 1 μm. The distance between the bottom electrode region and the absorption region (130) is greater than 1 μm.

10. The high-speed germanium-silicon photodetector with ultra-high responsivity according to claim 1 or 3, characterized in that: The substrate is a Si substrate, the bottom contact area (210) is P-type doped, the polycrystalline silicon layer (120) is made of amorphous silicon or polycrystalline silicon and is doped with N-type; the mask layer (110) is made of silicon dioxide; the top electrode area and the bottom electrode area are metal electrodes made of tungsten; the metal electrode layer (160) is made of aluminum.

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