Ge nanocolumn photodetector modified with metal nanoparticles and preparation method thereof
By introducing metal nanoparticle modification and Ge nanopillar structure into Ge nanocolumn photodetectors, the problems of large dark current and low detection performance of Ge-based photodetectors are solved, and the photodetection effect with high sensitivity and high responsiveness is achieved. It is suitable for low-cost detectors compatible with Si-based CMOS processes.
Patent Information
- Application Number
- CN202111294721.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-11-03
- Publication Date
- 2025-08-19
- Estimated Expiration
- 2041-11-03
AI Technical Summary
The existing Ge-based photodetectors have problems with large dark currents and low detection performance in the 1.55 micron band, and are incompatible with Si-based CMOS processes, which are costly and have safety hazards in material toxicity.
The Ge nanopillars structure modified with metal nanoparticles includes the bottom electrode, the Ge substrate layer, the Ge nanopillars, the metal nanoparticles and graphene electrodes. By adjusting the size and arrangement of the Ge nanopillars, the Michner scattering and light local effects are achieved, and a type II energy band is formed to separate photogenerated carriers.
Effectively reduce dark current, improve photocurrent and responsiveness, enhance detection performance, is suitable for Si-based CMOS processes, is low-cost and safe.
Smart Images
Figure CN114388649B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of photoelectric detectors, and in particular relates to a Ge (germanium) nanocolumn photoelectric detector modified with metal nanoparticles and a preparation method thereof. Background Art
[0002] Photodetectors have a wide range of applications, especially infrared photodetectors, which are widely used in communications, night vision, guidance, astronomical observation, biomedicine, and other fields. For example, in the visible and short-wave infrared bands, photodetectors can be used for radiation measurement and detection, industrial automation, and photometry.
[0003] Common infrared detectors primarily include those based on Group III-V materials (such as InGaAs and InSb) or Group II-VI materials (such as HgCdTe and PbS). However, these photodetectors suffer from complex manufacturing processes, high costs, and incompatibility with standard silicon (Si)-based CMOS (Complementary Metal Oxide Semiconductor) process platforms. These devices also suffer from high device costs and low reliability. Furthermore, materials like HgCdTe and PbS are toxic, posing safety risks.
[0004] Compared with infrared photodetectors based on III-V materials and II-VI materials, Ge-based infrared photodetectors are compatible with Si-based CMOS processes in terms of preparation process. They also have the advantages of high safety, small size, easy integration, low cost, and high performance. Therefore, they are expected to become the mainstream choice for infrared detectors.
[0005] In the prior art, Ge photodetectors based on Si substrates or SOI (Silicon On Insulator) substrates have been widely used in the fields of communication and sensing.
[0006] However, during the development of this invention, the inventors discovered that existing Ge-based photodetectors, due to limitations in their materials, exhibit significant dark current. Dark current refers to the current flowing in a photodetector's light-receiving element in the absence of light. A higher dark current significantly affects the detector's ability to detect low-intensity light waves. Furthermore, due to the limited bandgap of Ge, the absorption coefficient of Ge decreases sharply as wavelengths approach 1.55 microns, resulting in generally poor detection performance for Ge-based photodetectors in the 1.55 micron band. Summary of the Invention
[0007] In order to solve the above problems existing in the prior art, the present invention provides a Ge nanocolumn photodetector modified with metal nanoparticles and a preparation method thereof.
[0008] The technical problem to be solved by the present invention is achieved through the following technical solutions:
[0009] A Ge nanorod photodetector modified with metal nanoparticles, comprising:
[0010] bottom electrode;
[0011] An intrinsic Ge substrate layer covering the bottom electrode;
[0012] A plurality of Ge nanopillars are periodically arranged on the intrinsic Ge substrate layer; metal nanoparticles are adsorbed on the surface of the Ge nanopillars; the work function of the metal is greater than 4.46 eV;
[0013] The graphene electrode covers the plurality of Ge nanorods and is separated from the intrinsic Ge substrate layer by a non-conductive dielectric material.
[0014] Optionally, the diameter of the metal nanoparticles is 10 nanometers to 100 nanometers.
[0015] Optionally, the diameter and height of the Ge nanocolumns and the spacing between adjacent Ge nanocolumns are determined by simulation based on the wavelength of the detection light wave of the Ge nanocolumn photodetector.
[0016] Optionally, when the Ge nanocolumn photodetector is an infrared photodetector with a working band covering 1.55 microns, the diameter of the Ge nanocolumn is 700 nanometers and the height is 450 nanometers; and the spacing distance is 55 nanometers.
[0017] Optionally, the dielectric material includes silicon oxide or aluminum oxide.
[0018] Optionally, the material of the bottom electrode includes: gold, silver, copper or aluminum.
[0019] Optionally, the bottom electrode has a thickness of 50 nanometers to 200 nanometers.
[0020] The present invention also provides a method for preparing the above-mentioned Ge nanorod photodetector modified with metal nanoparticles, comprising:
[0021] A bottom electrode is formed on the lower surface of the Ge substrate;
[0022] Depositing a non-conductive dielectric material on the upper surface of the Ge substrate;
[0023] Etching a target area of the dielectric material to expose the Ge substrate below the target area;
[0024] Etching the upper portion of the exposed portion of the Ge substrate to form a plurality of Ge nanopillars; wherein, except for the plurality of Ge nanopillars, the rest of the Ge substrate constitutes an intrinsic Ge substrate layer; and the plurality of Ge nanopillars are periodically arranged on the intrinsic Ge substrate layer;
[0025] Adhering metal nanoparticles to the surface of the Ge nanorods; the work function of the metal is greater than 4.46 eV;
[0026] A graphene film is placed on the plurality of Ge nanorods, and the graphene film is overlapped with the remaining dielectric material to form a graphene electrode.
[0027] Optionally, adhering metal nanoparticles to the surface of the Ge nanorods comprises:
[0028] Metal nanoparticles are adhered to the surface of the Ge nanorods using a pipette.
[0029] Optionally, adhering metal nanoparticles to the surface of the Ge nanorods comprises:
[0030] Depositing metal material on the surface of the Ge nanorods by a magnetron sputtering process;
[0031] The current sample is subjected to a thermal annealing process so that the metal material on the surface of the Ge nanorods becomes metal nanoparticles.
[0032] The metal nanoparticle-modified Ge nanopillar photodetector provided by the present invention utilizes a Ge material structure consisting of an intrinsic Ge substrate layer and multiple Ge nanopillars. This increases the surface-to-volume ratio of the Ge material in the photodetector, correspondingly increasing the series resistance between the graphene electrode and the bottom electrode. This effectively reduces the dark current of the photodetector and improves its sensitivity. The Ge nanopillars' dimensions approximate the wavelength of the incident light. Under near-field conditions, the light is concentrated and distributed between the multiple Ge nanopillars, resulting in ionization between the Ge nanopillars. This effect is consistent with the characteristics of Mie scattering. In other words, the Ge nanopillar photodetector provided by the present invention can achieve Mie scattering and light localization within the device, thereby increasing the detector's light absorption coefficient and enhancing its responsivity. As a result, the photodetector provided by the present invention exhibits relatively high responsivity even in the wavelength band near 1.55 microns. Furthermore, the metal nanoparticles attached to the Ge nanopillars form a type II band in the band structure, effectively separating photogenerated carriers; that is, effectively separating photogenerated electrons and holes, reducing recombination between the two, and further improving the photocurrent and responsivity of the Ge nanopillar photodetector. In summary, the Ge nanorod photodetector provided by the present invention has low dark current, high photocurrent and high responsivity, and has high detection performance.
[0033] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 Schematic diagram of the three-dimensional structure of a Ge nanocolumn photodetector modified with metal nanoparticles provided in an embodiment of the present invention;
[0035] Figure 2 is the energy band diagram of Au (gold) and Ge;
[0036] Figure 3 : is a type II energy band diagram formed by Ge and Au in an embodiment of the present invention;
[0037] Figure 4 yes Figure 1 Side view of the Ge nanopillar photodetector shown;
[0038] Figure 5 yes Figure 1 Top view of the Ge nanopillar photodetector shown;
[0039] FIG6( a ) is a flowchart of a method for preparing a Ge nanorod photodetector modified with metal nanoparticles according to an embodiment of the present invention;
[0040] FIG6( b ) is a graphical flow chart of a method for preparing a Ge nanocolumn photodetector modified with metal nanoparticles provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0041] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.
[0042] In order to improve the performance of Ge-based photodetectors, the present invention provides a Ge nanorod photodetector modified with metal nanoparticles. Figure 1 As shown, the Ge nanorod photodetector includes: a bottom electrode 1, an intrinsic Ge substrate layer 2, a plurality of Ge nanorods 3, metal nanoparticles 4, a dielectric material 5 and a graphene electrode 6.
[0043] The intrinsic Ge substrate layer 2 covers the bottom electrode 1 . The bottom electrode 1 has a thickness of 50 nm to 200 nm and can be made of common electrode materials such as gold, silver, copper or aluminum.
[0044] The above-mentioned multiple Ge nanopillars 3 are periodically arranged on the intrinsic Ge substrate layer 2; the surfaces of these Ge nanopillars 3 are adsorbed with metal nanoparticles 4, and the diameters of these metal nanoparticles 4 are 10 nanometers to 100 nanometers; the metal used to prepare these metal nanoparticles 4 needs to meet the condition that the work function is greater than 4.46 eV, such as gold, platinum, etc.
[0045] The graphene electrode 6 covers the plurality of Ge nanorods 3 and is separated from the intrinsic Ge substrate layer 2 by a non-conductive dielectric material 5. The dielectric material 5 may include common non-conductive materials such as silicon oxide or aluminum oxide that can be used as a dielectric. Figure 1 In the embodiment, the dielectric material 5 is located on one side of the plurality of Ge nanopillars 3. It should be noted that this positional relationship is merely an example and does not limit the present invention. For example, in another positional relationship, the Ge nanopillars 3 can be located in the middle region of the intrinsic Ge substrate layer 2, and the dielectric material 5 can also surround the Ge nanopillars 3.
[0046] Both the Ge nanopillars 3 and the intrinsic Ge substrate layer 2 are made of Ge material. Ge material is compatible with Si-based CMOS processes, has high safety, and is low-cost. Furthermore, although Ge is an indirect bandgap semiconductor, its unique band structure, where its direct bandgap width is only 140 meV larger than the indirect bandgap, can be transformed into a direct bandgap semiconductor by introducing tensile strain or adding other alloys. This allows Ge material to be used as a luminescent material for optoelectronic integration. Furthermore, by fabricating the Ge material integrated into the photodetector with a structure consisting of an intrinsic Ge substrate layer and multiple Ge nanopillars, the surface-to-volume ratio of the Ge material in the photodetector can be increased, correspondingly increasing the series resistance between the graphene electrode 6 and the bottom electrode 1, thereby effectively reducing the dark current of the photodetector and improving its sensitivity. This allows the photodetector to detect even weak light waves, thereby enhancing its detectivity.
[0047] The detection rate is related to the intensity of the weakest light that the photodetector can detect; the smaller the intensity of the weakest light that the photodetector can detect, the higher the detection rate of the photodetector, and the greater the intensity of the weakest light that the photodetector can detect, the lower the detection rate of the photodetector.
[0048] Furthermore, by adjusting the size of the Ge nanopillars 3 to approximate the wavelength of the incident light wave, interaction occurs between the incident light wave and the Ge nanopillars 3. When multiple Ge nanopillars 3 are periodically arranged, the light wave is concentrated and distributed between the multiple Ge nanopillars 3 under near-field conditions, thereby generating an ionization effect between the Ge nanopillars 3, an effect consistent with the characteristics of Mie scattering. In other words, the Ge nanopillar photodetector provided by the embodiment of the present invention achieves Mie scattering and light localization effects within the device by adjusting the size of the Ge nanopillars 3 to resonate with the incident light wave, thereby increasing the detector's light absorption coefficient and enhancing the photodetector's responsivity. Thus, even in the wavelength band near 1.55 microns, the photodetector provided by the embodiment of the present invention has high detection efficiency.
[0049] Detection efficiency can be understood as the response of the photodetector to incident light of unit intensity. The higher the sensitivity of the photodetector to incident light of unit intensity, the higher its detection efficiency, and the lower the sensitivity of the photodetector to incident light of unit intensity, the lower its detection efficiency.
[0050] Moreover, the metal nanoparticles 4 attached to the Ge nanopillars 3 form a type II energy band in the energy band structure with the Ge nanopillars 3, which effectively realizes the separation of photogenerated carriers; that is, it effectively realizes the separation of photogenerated electrons and holes, reduces the recombination of the two, further improves the photocurrent and response of the Ge nanopillar photodetector, and improves the performance of the Ge nanopillar photodetector.
[0051] Specifically, assuming that the material of the metal nanoparticles 4 is gold (Au), see Figure 2 The energy band diagram of gold and Ge materials shown in FIG. 3 shows that after the gold nanoparticles are adsorbed on the Ge nanopillars 3, Ge will have a certain energy band bending, forming the following Figure 3 The type-II energy band shown in , thus achieving the separation of photogenerated electrons and holes. Figure 2 In, E Vac 、E C 、E F and E V Represent different levels of electric potential, E Built Represents the built-in electric field formed by Ge and Au; the small circle with the letter e represents photogenerated electrons, and the small circle with the letter h represents holes.
[0052] It should be noted that, since Au is a conductor rather than a semiconductor, the interaction between Ge and Au is mainly to form a type II energy band, reduce the recombination of photogenerated carriers, and will not form a PN junction.
[0053] Preferably, to maximize the detection efficiency of the Ge nanopillar photodetector, the diameter and height of the Ge nanopillars 3, as well as the spacing between adjacent Ge nanopillars 3, can be determined by simulation based on the wavelength of the detection light wave of the Ge nanopillar photodetector. This simulation can be performed using FDTD Solutions software. FDTD Solutions is an analytical optics software with extensive applications in imaging, illumination, biophotonics, photovoltaics, and other fields.
[0054] Specifically, the device structure model and the wavelength of light to be detected are first set in the FDTD Solutions software. Then, with the optimization goal of maximizing the light absorption coefficient at the set wavelength, the diameter D and height H of the Ge nanopillar 3 are continuously adjusted (see Figure 5 ), and parameter Px=D+2*I x and parameter Py=D+2*I y (See Figure 6), thus obtaining the optimal set of D, H, I x and I y Among them, I x is the spacing distance between adjacent Ge nanopillars 3 in the x direction in the two-dimensional plane, Iy is the spacing distance between adjacent Ge nanopillars 3 in the x direction in a two-dimensional plane.
[0055] In one embodiment, when the Ge nanorod photodetector is an infrared photodetector with a working band covering 1.55 microns, the diameter of the Ge nanorod 3 is preferably 700 nanometers, and the height is preferably 450 nanometers; the spacing between adjacent Ge nanorods is preferably 55 nanometers.
[0056] It should be noted that the Ge nanopillar photodetector provided by the embodiments of the present invention is not limited to the infrared wavelength band. Based on the device structure given in the embodiments of the present invention, by adjusting the size and arrangement of the Ge nanopillars, the Ge nanopillar photodetector provided by the embodiments of the present invention can be applied to a wider range of wavelengths.
[0057] The present invention also provides a method for preparing the above-mentioned Ge nanorod photodetector modified with metal nanoparticles. Referring to Figures 6(a) and 6(b), the method includes the following steps:
[0058] S1: Fabricate a bottom electrode on the lower surface of the Ge substrate.
[0059] Specifically, a metal evaporation process is used to evaporate metal materials such as gold, silver, copper or aluminum onto the lower surface of the Ge substrate to form a bottom electrode 1 with a thickness of 50 nanometers to 200 nanometers.
[0060] S2: Depositing a non-conductive dielectric material on the upper surface of the Ge substrate.
[0061] Specifically, the dielectric material 5 is deposited on the upper surface of the Ge substrate using a PECVD (Plasma Enhanced Chemical Vapor Deposition) process.
[0062] S3: etching the target area of the dielectric material to expose the Ge substrate below the target area.
[0063] Specifically, a dry etching process is used to etch the target area of the dielectric material 5. The target area can be a side area of the dielectric material 5, or a central area of the dielectric material 5, etc.
[0064] S4: etching the upper portion of the exposed portion of the Ge substrate to form a plurality of Ge nanopillars, wherein, except for the plurality of Ge nanopillars, the rest of the Ge substrate constitutes an intrinsic Ge substrate layer; the plurality of Ge nanopillars are periodically arranged on the intrinsic Ge substrate layer.
[0065] Specifically, the upper portion of the exposed portion of the Ge substrate is etched using a dry etching process, so that the lower portion of the exposed portion of the Ge substrate and the portion covered with the dielectric material together constitute the intrinsic Ge substrate layer 2 .
[0066] S5: Adhere metal nanoparticles to the surface of the Ge nanorod, where the work function of the metal is greater than 4.46 eV.
[0067] In step S5, there are various specific implementations for adhering metal nanoparticles 4 to the surfaces of Ge nanopillars 3. For example, in one implementation, a pipette can be used to adhere metal nanoparticles 4 to the surfaces of Ge nanopillars 3. In another implementation, a magnetron sputtering process can be used to deposit metal material onto the surfaces of Ge nanopillars 3; then, the sample is thermally annealed to convert the metal material on the surfaces of Ge nanopillars 3 into metal nanoparticles 4. The latter implementation is more suitable for industrial applications.
[0068] S6: placing a graphene film on the plurality of Ge nanopillars, and making the graphene film overlap the remaining dielectric material to form a graphene electrode.
[0069] Specifically, a graphene film is placed on the plurality of Ge nanorods 3 through a wet transfer process, and the graphene film is overlapped with the remaining dielectric material 5 , thereby forming a graphene electrode 6 .
[0070] The Ge nanopillar photodetector prepared by the method provided by the embodiment of the present invention has a relatively high surface volume of the Ge material in the photodetector, and the series resistance between the graphene electrode and the bottom electrode is relatively large, thereby having a lower dark current and a higher sensitivity. Among them, the size of the Ge nanopillar is close to the wavelength of the incident light wave. Under near-field conditions, the light wave is concentrated and distributed between multiple Ge nanopillars, thereby generating ionization between the Ge nanopillars, realizing Mie scattering and light localization effects. Therefore, the light absorption coefficient of the Ge nanopillar photodetector is high, and the response is high, and this is still the case in the wavelength band near 1.55 microns. In addition, the metal nanoparticles attached to the Ge nanopillars and the Ge nanopillars form a type II energy band in the energy band structure, effectively realizing the separation of photogenerated carriers, and further improving the photocurrent and response of the Ge nanopillar photodetector. In summary, the Ge nanopillar photodetector prepared by the method provided by the embodiment of the present invention has a small dark current, a high photocurrent and response, and has a high detection performance.
[0071] It should be noted that, for the preparation method embodiment, since it is basically similar to the Ge nanorod photodetector embodiment, the description is relatively simple, and the relevant details can be referred to the partial description of the Ge nanorod photodetector embodiment.
[0072] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and reconcile different embodiments or examples described in this specification.
[0073] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art can understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims.
[0074] The above description further details the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. A person skilled in the art would be able to make several simple deductions or substitutions without departing from the spirit of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.
Claims
1. A Ge nanorod photodetector modified with metal nanoparticles, characterized in that: include: bottom electrode; An intrinsic Ge substrate layer covering the bottom electrode; A plurality of Ge nanorods are periodically arranged on the intrinsic Ge substrate layer; Metal nanoparticles are adsorbed on the surface of the Ge nanorods; the work function of the metal is greater than 4.46 eV; a graphene electrode covering the plurality of Ge nanopillars and separated from the intrinsic Ge substrate layer by a non-conductive dielectric material; The diameter and height of the Ge nanopillars and the spacing between adjacent Ge nanopillars are determined by simulation based on the wavelength of the detection light wave of the Ge nanopillar photodetector; When the Ge nanocolumn photoelectric detector is an infrared photoelectric detector with a working band covering 1.55 microns, the diameter of the Ge nanocolumn is 700 nanometers and the height is 450 nanometers; the spacing distance is 55 nanometers.
2. The Ge nanorod photodetector according to claim 1, wherein: The diameter of the metal nanoparticles is 10 nanometers to 100 nanometers.
3. The Ge nanorod photodetector according to claim 1, wherein: The dielectric material includes silicon oxide or aluminum oxide.
4. The Ge nanorod photodetector according to claim 1, wherein: The material of the bottom electrode includes: gold, silver, copper or aluminum.
5. The Ge nanorod photodetector according to claim 1 or 4, characterized in that: The thickness of the bottom electrode is 50 nanometers to 200 nanometers.
6. A method for preparing a Ge nanorod photodetector modified with metal nanoparticles, characterized in that: include: A bottom electrode is formed on the lower surface of the Ge substrate; Depositing a non-conductive dielectric material on the upper surface of the Ge substrate; Etching a target area of the dielectric material to expose the Ge substrate below the target area; Etching the upper portion of the exposed portion of the Ge substrate to form a plurality of Ge nanopillars; wherein, except for the plurality of Ge nanopillars, the rest of the Ge substrate constitutes an intrinsic Ge substrate layer; and the plurality of Ge nanopillars are periodically arranged on the intrinsic Ge substrate layer; Adhering metal nanoparticles to the surface of the Ge nanorods; the work function of the metal is greater than 4.46 eV; placing a graphene film on the plurality of Ge nanorods, and making the graphene film overlap the remaining dielectric material to form a graphene electrode; The diameter and height of the Ge nanopillars and the spacing between adjacent Ge nanopillars are determined by simulation based on the wavelength of the detection light wave of the Ge nanopillar photodetector; When the Ge nanocolumn photoelectric detector is an infrared photoelectric detector with a working band covering 1.55 microns, the diameter of the Ge nanocolumn is 700 nanometers and the height is 450 nanometers; the spacing distance is 55 nanometers.
7. The preparation method according to claim 6, characterized in that Adhering metal nanoparticles to the surface of the Ge nanorods comprises: Metal nanoparticles are adhered to the surface of the Ge nanorods using a pipette.
8. The preparation method according to claim 6, characterized in that Adhering metal nanoparticles to the surface of the Ge nanorods comprises: Depositing metal material on the surface of the Ge nanorods by a magnetron sputtering process; The current sample is subjected to a thermal annealing process so that the metal material on the surface of the Ge nanorods becomes metal nanoparticles.