All-silicon photodetector based on compensated doping and preparation method thereof

Abstract

The present invention discloses a fully silicon photodetector based on compensated doping and a preparation method thereof, belonging to the field of optoelectronic devices. The fully silicon photodetector includes a compensated doping absorption region and P++ and N++ heavily doped regions for collecting current. On the one hand, through the compensated doping method of mixing P-type and N-type, a defect density exceeding that of traditional single doping is introduced inside the silicon waveguide, and at the same time, an absorption region with the properties of an intrinsic semiconductor is formed, avoiding free carrier absorption that contributes nothing to light detection. On the other hand, the defect density at the interface is increased and the interaction between the defect and light is enhanced through the slit waveguide. Thus, the fully silicon photodetector can utilize the defects introduced in the silicon waveguide and the enhanced interaction between light and defects to achieve light detection in the optical communication band (1.3 - 1.6 μm). In addition, the preparation process of the present invention is fully compatible with the CMOS process, without introducing other materials, and has the advantages of low cost and high integration.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic devices, and more specifically, relates to an all-silicon photodetector based on compensation doping and a preparation method thereof. Background Art

[0002] With the rapid development of optical communication and optical interconnection technologies, integration and miniaturization are the future development trends. Silicon-based photonics technology is compatible with CMOS processes, has the advantages of low cost and high integration, and can meet the requirements of integration and miniaturization. In silicon-based photonics technology, silicon-based photodetectors are the core devices for realizing optoelectronic conversion. However, silicon materials have an absorption cutoff at 1.1 μm and cannot meet the light detection requirements in the optical communication band. In order to achieve light detection of silicon in the optical communication band, two solutions have been proposed. The first solution is to epitaxially grow photosensitive materials (such as germanium) with strong absorption in the optical communication band to achieve light detection in the optical communication band. The second solution uses effects such as sub-bandgap absorption and two-photon absorption of silicon to achieve light detection of silicon in the optical communication band.

[0003] Non-patent Document 1 (Optics Express, 2011, 19(25): 24897-24904.) reported a common method for realizing a photodetector in the optical communication band, that is, to achieve light detection in the optical communication band by epitaxially growing germanium materials. Figure 1 FIG. 13 is a schematic structural diagram of the photodetector in Non-patent Document 1, including a left silicon heavily doped region 101, a silicon lightly doped region 102, a right silicon heavily doped region 103, a germanium heavily doped region 104, a germanium absorption region 105, and a silicon dioxide cladding 106. The bandgap of germanium material is about 0.8 eV and has an absorption cutoff at 1.55 μm. The intrinsic absorption of the epitaxially grown germanium layer can significantly enhance light detection in the optical communication band, but the lattice mismatch between germanium and silicon will significantly increase the dark current, reduce the sensitivity of the detector, and the complex epitaxial growth process will significantly increase the cost.

[0004] To solve the disadvantages of the above solutions, a solution for an all-silicon photodetector has been proposed. Patent Document 2 (CN202111008464.3) discloses a method for improving the infrared response of a silicon-based detector by helium ion implantation. This method uses neutral helium ions to bombard a silicon waveguide, thereby introducing defects into the silicon waveguide, and then using the defect state absorption effect to achieve light detection. The above effect can redshift the absorption cutoff edge of silicon and enhance light detection in the optical communication band, but the defect density generated by this method is small, especially the interaction between the defects and light is weak, which results in low light absorption efficiency.

[0005] To solve the above problems, Non-Patent Document 3 (Journal of Nanophotonics, 2011, 5(1): 9507.) reported an all-silicon photodetector that uses a microring resonator to enhance the interaction between defects and light. The above microring resonator structure introduces defects by ion implantation and enhances the light field intensity in the cavity, thereby enhancing the interaction between the light field in the cavity and the defects. However, because the microring resonator is selective to the operating wavelength and the operating wavelength drifts with temperature changes, the responsivity of this detector is greatly affected by the environment. Summary of the Invention

[0006] In view of the defects and improvement requirements of the prior art, the present invention provides an all-silicon photodetector based on compensated doping and a preparation method thereof, so as to significantly enhance the light detection of the all-silicon photodetector in the optical communication band, and there is no need to epitaxially grow other materials and it is fully compatible with the CMOS process.

[0007] To achieve the above object, in the first aspect, the present invention provides an all-silicon photodetector based on compensated doping, including a compensated doping absorption region and P++ and N++ heavily doped regions for collecting current, and the absorption region has the properties of an intrinsic semiconductor.

[0008] Further, the absorption region is composed of a slit waveguide.

[0009] Further, the difference in the ion concentrations of P-type doping and N-type doping in the absorption region does not exceed 10 18 cm -3 .

[0010] In the second aspect, the present invention provides a preparation method of an all-silicon photodetector based on compensated doping, including:

[0011] Growing a layer of intrinsic silicon on a substrate;

[0012] Etching an absorption region and heavily doped regions on both sides of the absorption region on the intrinsic silicon;

[0013] Injecting P-type doping ions and N-type doping ions in sequence, or injecting N-type doping ions and P-type doping ions in sequence into the absorption region to form an absorption region with the properties of an intrinsic semiconductor; injecting P++-type doping ions and N++-type doping ions into the heavily doped regions on both sides respectively to form P++ and N++ heavily doped regions in contact with electrodes.

[0014] Further, the structural type of the etched absorption region is a slit waveguide.

[0015] Further, the difference in the ion concentrations of P-type doping and N-type doping in the absorption region does not exceed 10 18 cm -3; The order of magnitude of the ion concentrations of P++-type doping and N++-type doping is 10 20 cm -3 。

[0016] Thirdly, the present invention provides an optical monitor for a wavelength division multiplexing system, including: a transmission waveguide, a thermally tunable microring, an output waveguide, and a fully silicon photodetector based on compensated doping as described in the first aspect;

[0017] wherein, the signal light is input through the transmission waveguide. When passing through the thermally tunable microring, the light of the wavelength channel matching the resonance wavelength of the thermally tunable microring will be partially coupled into the thermally tunable microring, then downloaded through the output waveguide, and finally absorbed and detected by the fully silicon photodetector.

[0018] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0019] (1) The present invention first proposes to introduce a defect density exceeding that of traditional single doping inside the silicon waveguide by means of compensated doping of P-type and N-type mixing, and at the same time form an absorption region with the properties of an intrinsic semiconductor, avoiding free carrier absorption that contributes nothing to optical detection; thereby effectively increasing the defect density of the absorption region and enhancing optical detection in the optical communication band (1.3 - 1.6 μm).

[0020] (2) The present invention determines the structural parameters of the slit waveguide through simulation, making the distribution of the optical field in the slit waveguide consistent with the distribution of the overall defects, which can increase the defect density at the interface and enhance the interaction between the defects and light, thereby further enhancing optical detection in the optical communication band.

[0021] (3) The fully silicon photodetector proposed by the present invention can enhance optical detection in the optical communication band without epitaxially growing other photosensitive materials, which can reduce the process complexity and production cost.

[0022] (4) The manufacturing process of the fully silicon photodetector proposed by the present invention is completely compatible with the CMOS process, and has the advantages of low cost and high integration. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the detector in Non-Patent Document 1;

[0024] Figure 2 It is a schematic diagram of the fully silicon photodetector provided by the embodiment of the present invention;

[0025] Figure 3 It is a curve graph of the photocurrent and dark current varying with voltage provided by the embodiment of the present invention;

[0026] Figure 4Responsivity comparison diagram of the all-silicon photodetector with a slit waveguide absorption region structure and a ridge waveguide absorption region structure provided by the embodiments of the present invention;

[0027] Figure 5 Process flow chart of the all-silicon photodetector provided by the embodiments of the present invention;

[0028] Figure 6 Schematic diagram of the optical monitor of the all-silicon photodetector provided by the embodiments of the present invention. Detailed implementation manners

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, 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.

[0030] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects and do not have to be used to describe a specific order or sequence.

[0031] Embodiment 1

[0032] Refer to Figure 2 , the present invention provides an all-silicon photodetector 200 based on compensated doping, including a P++ heavily doped region 201, an absorption region 202, and an N++ heavily doped region 203.

[0033] Among them, the absorption region 202 is formed by P-type doping and N-type doping through compensated doping. Since both donor impurities and acceptor impurities exist in the absorption region, when the concentrations of the two are close, the absorption region will exhibit the properties of an intrinsic semiconductor, and under the same other conditions, the defect density exceeding the traditional single doping can be introduced inside the silicon waveguide to enhance the light detection in the optical communication band. It should be noted that the ion types and doping concentrations of P-type doping and N-type doping are determined by actual requirements and may not be exactly the same. For example, in this embodiment, B+ and P+ are doped successively at a concentration of 2×10 18 cm -3 .

[0034] Furthermore, the absorption region can adopt a slit waveguide structure. Generally, the distribution of the optical field in the waveguide can be changed by changing the slit width of the slit waveguide. The present invention adopts a slit waveguide structure to make the distribution of the optical field in the waveguide consistent with the distribution of the overall defects, so as to increase the defect density at the interface and enhance the interaction between the defects and light. In fact, the distribution of the optical field in the waveguide and the distribution of the overall defects can be obtained through simulation.

[0035] In addition, the heavily doped regions on both sides of the absorption region are doped with P++ and N++ respectively to form a PIN structure, which forms an ohmic contact with the electrodes to collect the generated photo-generated carriers under the action of an electric field.

[0036] The generation of photo-generated carriers depends on the light absorption process of semiconductor materials. For silicon materials, the cut-off wavelength of its intrinsic absorption is about 1.1 μm, which is transparent to the optical communication band. To achieve an all-silicon photodetector, the all-silicon photodetector 200 provided by the present invention utilizes the absorption of light by defect energy levels to generate photo-generated carriers. Since the energy of the defect energy level is less than the conduction band energy level, the absorption cut-off wavelength of silicon is red-shifted, thereby enhancing the light detection in the optical communication band. This method avoids the cost increase caused by epitaxial growth of other photosensitive materials.

[0037] When light is incident on the absorption region of the detector, due to the action of the slit waveguide, the light field distribution overlaps with the defect density distribution, while increasing the light intensity in a limited area and enhancing the interaction between the defect and the light. Compensated doping and the slit structure introduce a large number of defects to interact with the incident light, thereby enhancing the light detection in the optical communication band. The all-silicon detector based on the PIN structure generally operates in the reverse bias state to achieve high-speed detection, that is, the potential of the N++ doped region is higher than that of the P++ doped region. The reverse bias electric field and the built-in electric field of the PIN are in the same direction, forming a high electric field in the absorption region to ensure the high-speed drift motion of internal carriers, so that the photo-generated carriers can move to the external electrodes at the saturated drift velocity to form a photocurrent.

[0038] Figure 3 It is a graph showing the variation of the photocurrent and dark current of the all-silicon photodetector based on compensated doping with voltage. Figure 4 It is a comparison chart of the responsivity of the all-silicon photodetector with the slit waveguide absorption region structure and the ridge waveguide absorption region structure. Refer to Figure 4 It can be seen that the responsivity of the all-silicon photodetector of the present invention has been increased by 4 times.

[0039] Embodiment 2

[0040] As Figure 5 shown, the present invention provides a preparation method of an all-silicon photodetector based on compensated doping, including:

[0041] Growing a layer of intrinsic silicon on a substrate;

[0042] Etching an absorption region and heavily doped regions on both sides of the absorption region on the intrinsic silicon;

[0043] In the absorption region, ions of P-type doping and N-type doping are sequentially implanted, or ions of N-type doping and P-type doping are sequentially implanted, to form an absorption region with the properties of an intrinsic semiconductor; in the heavily doped regions on both sides, ions of P++-type doping and N++-type doping are respectively implanted to form P++ and N++ heavily doped regions in contact with the electrodes.

[0044] Preferably, the structural type of the etched absorption region is a slit waveguide.

[0045] Preferably, the difference in the ion concentrations of P-type doping and N-type doping in the absorption region does not exceed 10 18 cm -3 ; the order of magnitude of the ion concentrations of P++-type doping and N++-type doping is 10 20 cm -3 .

[0046] Embodiment 3

[0047] Figure 6 FIG. 600 is a schematic diagram of an optical monitor 600 for a wavelength division multiplexing system provided by the present invention. The optical monitor 600 is used to monitor the optical power in the wavelength division multiplexing system and includes a transmission waveguide 601, a thermally tunable microring 602, an output waveguide 603, and the all-silicon photodetector 604 mentioned in Embodiment 1.

[0048] The signal light is input through the transmission waveguide 601. When passing through the thermally tunable microring 602, the light in the wavelength channel matching the resonance wavelength of the thermally tunable microring will be partially coupled into the thermally tunable microring, then downloaded through the output waveguide 603, and finally absorbed and detected by the all-silicon photodetector 604. This optical monitor can be flexibly switched. When the resonance peak of the thermally tunable microring is adjusted to be in a detuned state, the signal light in the transmission waveguide can pass through the monitor normally. In addition, by designing the coupling coefficient of the thermally tunable microring, only a small part of the optical power can be downloaded without affecting the transmission of the signal light. The optical monitor 600 of this embodiment has a high responsivity and dark current ratio, and the sensitivity is higher than -30 dBm, which can meet the requirements of optical monitoring for low optical power detection.

[0049] It is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fully silicon photodetector based on compensated doping, characterized in that, it includes a compensated doping absorption region, P++ and N++ heavily doped regions for collecting current, and the absorption region is formed by P-type doping and N-type doping through compensated doping; P-type doping and N-type doping ions are sequentially implanted into the absorption region, or N-type doping and P-type doping ions are sequentially implanted, to form an absorption region with the properties of an intrinsic semiconductor; the absorption region is composed of a slit waveguide.

2. The fully silicon photodetector based on compensated doping according to claim 1, characterized in that, The difference in ion concentration between P-type doping and N-type doping in the absorption region does not exceed 10 18 cm -3 .

3. A method for manufacturing a fully silicon photodetector based on compensated doping, characterized in that, it includes: growing a layer of intrinsic silicon on a substrate; etching an absorption region and heavily doped regions on both sides of the absorption region on the intrinsic silicon; sequentially implanting P-type doping and N-type doping ions into the absorption region, or sequentially implanting N-type doping and P-type doping ions, to form an absorption region with the properties of an intrinsic semiconductor; respectively implanting P++-type doping and N++-type doping ions into the heavily doped regions on both sides to form P++ and N++ heavily doped regions in contact with electrodes.

4. The method for manufacturing a fully silicon photodetector based on compensated doping according to claim 3, characterized in that, the structural type of the etched absorption region is a slit waveguide.

5. The method for manufacturing a fully silicon photodetector based on compensated doping according to claim 3, characterized in that, The difference in ion concentration between P-type doping and N-type doping in the absorption region does not exceed 10 18 cm -3 ; the order of magnitude of the ion concentration of P++-type doping and N++-type doping is 10 20 cm -3 .

6. An optical monitor for a wavelength division multiplexing system, characterized in that, it includes: a transmission waveguide, a thermally tunable microring, an output waveguide, and the fully silicon photodetector based on compensated doping according to any one of claims 1 to 2; wherein, the signal light is input by the transmission waveguide. When passing through the thermally tunable microring, the light of the wavelength channel matching the resonant wavelength of the thermally tunable microring will be partially coupled into the thermally tunable microring, then downloaded through the output waveguide, and finally absorbed and detected by the fully silicon photodetector.

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