Photoelectric detector absorption layer preparation method and photoelectric detector

Abstract

The invention relates to the technical field of optoelectronic devices, in particular to a preparation method of a photoelectric detector absorption layer and a photoelectric detector. The preparation method comprises the following steps: depositing a p-type GeSn thin film on an n-type Si or Ge substrate; executing photoetching and etching steps on the GeSn thin film layer to form a mesa structure; carrying out surface modification on the GeSn film in the table area by using femtosecond laser, and removing precipitated Sn through chemical treatment; depositing a silicon dioxide layer on the GeSn table board; an electrode hole is defined in the silicon dioxide layer, silicon dioxide is removed through etching, and the GeSn layer is exposed; and determining the position of an electrode, and evaporating Ni / Al alloy through an electron beam evaporation technology to prepare the GeSn photoelectric detector with a vertical mesa structure. Through the femtosecond laser processing technology, the nanostructure is induced on the surface of the GeSn material, the GeSn photoelectric detector after femtosecond laser processing has lower dark current, higher light current, higher light responsivity and higher external quantum efficiency, and the light response performance of the photoelectric detector is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and particularly to a method for preparing an absorption layer of a photodetector and a photodetector. Background Art

[0002] With the continuous expansion of short-wave infrared and mid-wave infrared applications, especially in the fields of optical communication, imaging, lidar (LiDAR), and environmental monitoring, the demand for high-performance photodetectors is increasing day by day. The GeSn alloy is a material compatible with the existing silicon-based complementary metal oxide semiconductor (CMOS) process, and can realize the preparation of wafers with a diameter of more than 8 inches. The GeSn alloy is formed by introducing an appropriate amount of tin (Sn) into the germanium (Ge) lattice. As the Sn component increases, the bandgap of the GeSn alloy will continuously decrease, thereby improving light absorption and extending the light response cut-off wavelength of the material. By adjusting the Sn component in the alloy, GeSn alloys with different bandgaps can be obtained, so as to cover the short-wave infrared to mid-infrared bands. Theoretical and experimental studies have shown that the GeSn alloy is a very important short-wave infrared and mid-infrared semiconductor material, and is expected to realize low-cost and high-performance short-wave infrared and mid-infrared photodetectors, with great application potential.

[0003] Although the existing GeSn photodetectors show good detection performance in theory, their actual performance still has a large gap with the theoretical expectation, and is lower than that of commercially available III-V compound material photodetectors. Therefore, many improvement strategies have been proposed successively, including resonant cavity enhancement structures, waveguide structures, surface plasmon resonance structures, photonic crystal structures, avalanche photodiode structures, and photon trapping nanostructures, etc. Although these strategies have improved the performance of GeSn photodetectors to a certain extent, these structures generally use complex, expensive, and non-large-area-fabricable semiconductor processes such as electron beam lithography and etching, which limit the low-cost and large-scale application of these devices.

[0004] Femtosecond laser direct writing, as a high-precision, low-thermal budget, simple, and high-throughput nanomanufacturing technology, has gradually attracted attention in recent years. However, femtosecond laser technology has not been applied to the fabrication of photon trapping nanostructures of GeSn materials. The present invention proposes a GeSn photodetector based on femtosecond laser-induced nanostructures and its manufacturing method to improve the light response and performance of the detector. Summary of the Invention

[0005] Aiming at the above technical problems existing in the prior art, the purpose of the present invention is to provide a method for preparing an absorption layer of a photodetector and a photodetector, which uses femtosecond laser to induce a composite nanostructure of laser-induced periodic surface structures (LIPPS), nanocones, and nanopores in a GeSn thin film, thereby improving the responsivity of the GeSn infrared photodetector.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing an absorption layer of a photodetector, comprising the following steps:

[0008] Step 1: Deposit a p-type GeSn thin film on an n-type Si or Ge substrate, where the GeSn layer is used for infrared light absorption. According to the different Sn components in the GeSn layer, the light absorption wavelength can be extended to the mid-infrared band. Depositing a p-type GeSn is to form a vertical pn-type photodiode; an n-type GeSn thin film can also be deposited on a p-type Si or Ge substrate to form a vertical pn-type photodiode;

[0009] Step 2: Perform a photolithography and etching step on the GeSn thin film layer to form a mesa structure, and only the GeSn thin film in the mesa region is retained, while the rest exposes the Si or Ge substrate. Forming a mesa structure is to electrically isolate adjacent GeSn photodiodes from each other;

[0010] Step 3: Use femtosecond laser to perform surface modification on the GeSn thin film in the mesa region, and remove the precipitated Sn through chemical treatment to form a composite nanostructure of femtosecond laser-induced GeSn LIPPS, nanocones, and nanopores. The composite nanostructure formed by femtosecond laser modification serves as a light-trapping layer, which can reduce the light reflectivity and improve the light absorption rate, thereby improving the performance of the photodetector;

[0011] Step 4: Use plasma-enhanced chemical vapor deposition to deposit a silica layer on the GeSn substrate as an electrical isolation layer and a passivation layer;

[0012] Step 5: Define electrode holes on the silica layer and remove the silica by etching to expose the GeSn layer;

[0013] Step 6: Determine the electrode positions and deposit a Ni / Al alloy by electron beam evaporation technology to form an ohmic contact with the exposed GeSn layer, thereby preparing a vertical mesa structure GeSn photodetector.

[0014] As a preferred technical solution, the carrier concentration range of the n-type Si or Ge substrate in Step 1 is 10 18 cm -3 to 10 20 cm -3 .

[0015] As a preferred technical solution, the thickness of the GeSn thin film in Step 1 is 50 nm to 500 nm, and the elemental component range of Sn in the GeSn layer is 2%-20%.

[0016] As a preferred technical solution, in step 3, the wavelength of the femtosecond laser is 1030 nm, the spot size is 40 - 100 μm, the repetition frequency is 0.025 - 5 MHz, and the energy flux density is 0.6 - 1.2 kJ / m 2 .

[0017] The formed nanostructures are the result of the combined action of wavelength, spot, repetition frequency, energy flux density, scanning speed, etc. Other femtosecond laser parameters can also induce different nanostructures, which are all within the protection scope of this patent.

[0018] As a preferred technical solution, in step 3, a z-shaped scan is performed by a translation stage, the scan rate is 0.4 - 2 mm / s, and the scan interval between two rows is 20 - 200 μm.

[0019] As a preferred technical solution, in step 3, the precipitated tin is removed by putting the GeSn sample into dilute hydrochloric acid.

[0020] As a preferred technical solution, in step 4, the silicon dioxide layer is 200 nm to 500 nm thick.

[0021] The present invention also discloses a photodetector obtained by using the preparation method of the absorption layer of the above photodetector.

[0022] The present invention has the following advantages compared with the prior art:

[0023] 1) Realization of high-performance photodetectors:

[0024] By using femtosecond laser to induce the formation of a composite nanostructure of laser-induced periodic surface structures (LIPPS), nanocones and nanopores on the GeSn thin film, the light response performance of the GeSn photodetector is significantly improved. Specifically, it shows lower dark current, higher photocurrent, higher responsivity and external quantum efficiency (EQE). For example, at a bias voltage of -1V, the responsivity of the detector after femtosecond laser treatment reaches 0.65 A / W, and the external quantum efficiency reaches 52.7%, which is significantly better than that of the untreated detector.

[0025] 2) Low-cost and high-efficiency manufacturing process:

[0026] The manufacturing of traditional GeSn photodetectors usually relies on complex electron beam lithography and dry etching processes, which are costly and difficult to mass-produce. The present invention adopts femtosecond laser direct writing technology, which has the characteristics of high precision, low thermal budget and high throughput, and can rapidly form nanostructures on a large-area GeSn thin film, significantly reducing the manufacturing cost and improving the production efficiency.

[0027] 3) Excellent performance at room temperature:

[0028] The GeSn photodetector after femtosecond laser treatment exhibits excellent performance at room temperature, making this detector more competitive in practical applications, especially in scenarios requiring portable or low-power devices.

[0029] 4) Light trapping effect of nanostructures:

[0030] The composite nanostructures induced by femtosecond laser as a light trapping layer effectively reduce the light reflectivity and improve the light absorption rate. This structure not only enhances the light trapping ability of the photodetector but also further improves the photoelectric conversion efficiency by increasing the interaction path between light and materials.

[0031] 5) Compatibility of materials and processes:

[0032] The GeSn alloy material is compatible with existing silicon-based CMOS processes. In this invention, nanostructures are formed on the GeSn thin film through femtosecond laser technology, further expanding the application potential of GeSn materials in the short-wave infrared to mid-infrared bands while maintaining compatibility with existing semiconductor processes.

[0033] 6) Scalability and potential for mass production:

[0034] The high throughput and low cost characteristics of femtosecond laser technology make the method of this invention suitable for mass production. By optimizing femtosecond laser parameters (such as wavelength, spot size, repetition frequency, energy flux density, etc.), consistent nanostructures can be achieved on GeSn thin films of different sizes, ensuring the stability and repeatability of device performance.

[0035] 7) Versatility and wide range of applications:

[0036] The GeSn photodetector prepared by this invention has broad application prospects in the fields of optical communication, imaging, lidar (LiDAR), and environmental monitoring. Its high performance and low cost characteristics make it a strong competitor to replace traditional III-V compound photodetectors.

[0037] In summary, compared with traditional electron beam lithography and dry etching processes, the method of this invention has high efficiency, low cost, and scalability, and is suitable for mass production. In addition, the fabricated GeSn photodetector exhibits excellent performance at room temperature and has broad application prospects. Description of the Drawings

[0038] Figure 1a is the top view of the scanning electron microscope of the GeSn nanostructure thin film processed by femtosecond laser in this invention;

[0039] Figure 1b is the tilted view of the scanning electron microscope of the GeSn nanostructure thin film processed by femtosecond laser in this invention;

[0040] Figure 2a These are the Raman spectra of the GeSn nanostructured thin film processed by femtosecond laser and the GeSn thin film without femtosecond laser processing in the present invention;

[0041] Figure 2b These are the optical absorption curves of the GeSn nanostructured thin film processed by femtosecond laser and the GeSn thin film without femtosecond laser processing in the present invention;

[0042] Figure 3 This is the schematic structural diagram of the GeSn photodetector constructed in the present invention;

[0043] Figure 4a These are the dark current curves of the GeSn photodetectors with a mesa diameter of 60 μm processed by femtosecond laser and without femtosecond laser processing in the present invention;

[0044] Figure 4b These are the photocurrent curves of the GeSn photodetectors with a mesa diameter of 60 μm processed by femtosecond laser and without femtosecond laser processing in the present invention under illumination with a power of 1 mW and a wavelength of 1550 nm.

[0045] Figure 5a These are the responsivity curves of the GeSn photodetectors processed by femtosecond laser and without femtosecond laser processing in the present invention under illumination with incident light at a wavelength of 1550 nm;

[0046] Figure 5b These are the external quantum efficiency (EQE) curves of the GeSn photodetectors processed by femtosecond laser and without femtosecond laser processing under illumination with incident light at a wavelength of 1550 nm. Detailed implementation manners

[0047] The present invention will be further described in detail below with reference to the accompanying drawings.

[0048] This embodiment discloses a preparation method for the absorption layer of a photodetector, including the following steps:

[0049] Step 1, deposit a 200-nm-thick p-type GeSn thin film on an n-type Si or Ge substrate with a resistivity of 0.01 Ω·cm using magnetron sputtering technology; the mass content of Sn in the GeSn thin film is precisely controlled at 4.4%.

[0050] Step 2, perform a photolithography and etching step on the GeSn thin film layer to form the mesa structure of the GeSn photodetector; use inductively coupled plasma etching (ICP) technology to etch the GeSn thin film into a mesa with a diameter ranging from 20 to 200 μm, and only retain the GeSn thin film in the mesa area, while the rest exposes the Si or Ge substrate;

[0051] Step 3: Use femtosecond laser to perform surface modification on the GeSn thin film in the mesa region; then place the GeSn sample after femtosecond laser modification into dilute hydrochloric acid for 30 seconds to remove the precipitated tin, thereby obtaining the composite nanostructure of femtosecond laser-induced GeSn LIPPS, nanocones, and nanopores as shown in Figure 1.

[0052] Among them, the wavelength of the femtosecond laser is 1030 nm, the spot size is 40 μm, the repetition frequency is 0.025 MHz, and the energy fluence is 1.15 kJ / m 2 ; Through the z-shaped scanning of the translation stage, the scanning rate is 0.4 mm / s, and the scanning interval between two rows is 20 μm;

[0053] Measure the Raman spectra of the GeSn nanostructure samples (laser-treated) and the GeSn samples without femtosecond laser treatment (as-grown). As shown in Figure 2(a), the Ge-Ge Raman peaks are detected in both samples, indicating that the crystal properties of the GeSn thin film in the GeSn samples after femtosecond laser treatment have not changed, and the nanostructure samples still have good crystallization performance.

[0054] Step 4: Use plasma-enhanced chemical vapor deposition (PECVD) technology to deposit a 300-nm-thick silica layer on the GeSn substrate after femtosecond laser treatment as the electrical isolation layer and passivation layer of the photodetector;

[0055] Step 5: Use photolithography and etching technology to define electrode holes on the silica layer, and then remove the silica by reactive ion etching (RIE) to expose the GeSn layer;

[0056] Step 6: Determine the electrode positions of the GeSn photodetector by photolithography technology, and deposit Ni / Al alloy by electron beam evaporation technology to fabricate a femtosecond laser-induced nanostructure GeSn photodetector with a vertical mesa structure.

[0057] Perform photoelectric performance tests on the above GeSn photodetectors with and without femtosecond laser treatment respectively:

[0058] Figure 4(a) shows the dark current curves of the GeSn photodetectors with a mesa diameter of 60 μm with and without femtosecond laser treatment. It can be observed from the figure that the dark current of the GeSn photodetector after femtosecond laser treatment at -1 V is 9.24×10 -6 A, while the dark current of the untreated GeSn photodetector is 4.81×10 -6A. This indicates that the photodetector fabricated from the nanostructured GeSn thin film processed by femtosecond laser has a lower dark current, thus improving the overall performance of the device.

[0059] Figure 4(b) shows the photocurrent curves of the GeSn photodetectors with and without femtosecond laser treatment under the illumination of incident light with a wavelength of 1550 nm and a light power of 1 mW. At a bias voltage of -1 V, the photocurrent of the treated detector is 6.68×10 -4 A, while that of the untreated detector is 8.02×10 -4 A. This indicates that the nanostructured GeSn thin film photodetector after femtosecond laser treatment exhibits a higher photocurrent, thus enhancing the overall performance of the device.

[0060] Figure 5(a) shows the responsivity curves of the femtosecond laser-treated and untreated GeSn photodetectors under the illumination of incident light with a wavelength of 1550 nm. The responsivities at -1 V are 0.65 A / W and 0.80 A / W respectively, indicating that the photodetector fabricated from the nanostructured GeSn thin film after femtosecond laser treatment has a higher responsivity, improving the device performance. Figure 5(b) shows the external quantum efficiency (EQE) curves of the femtosecond laser-treated and untreated GeSn photodetectors under the illumination of incident light with a wavelength of 1550 nm. The external quantum efficiencies at -1 V are 52.7% and 63.9% respectively, indicating that the photodetector fabricated from the nanostructured GeSn thin film after femtosecond laser treatment has a higher external quantum efficiency, improving the device performance.

[0061] In this invention, femtosecond laser was used to induce the formation of nanostructures in GeSn thin film and a photodetector was fabricated based on this nanostructured thin film. The results show that the nanostructured GeSn photodetector after femtosecond laser treatment has a lower dark current, higher responsivity and external quantum efficiency, improving the performance of the device.

[0062] Figure 5(a) shows the responsivity curves of the femtosecond laser-treated and untreated GeSn photodetectors under the illumination of incident light with a wavelength of 1550 nm. At a bias voltage of -1 V, the responsivity of the femtosecond laser-treated GeSn photodetector reaches 0.65 A / W, while that of the untreated GeSn photodetector is 0.80 A / W. This indicates that the photodetector fabricated from the nanostructured GeSn thin film after femtosecond laser treatment exhibits a higher responsivity, thus enhancing the device performance.

[0063] Figure 5(b) presents the external quantum efficiency (EQE) curves of the two detectors under the same conditions. At a bias voltage of -1V, the external quantum efficiency of the detector treated with femtosecond laser is 52.7%, and that of the untreated detector is 63.9%. This further demonstrates that the photodetector fabricated from the femtosecond laser-treated nanostructured GeSn film has a higher external quantum efficiency, which also improves the device performance.

[0064] The present invention utilizes femtosecond laser to induce the formation of nanostructures in GeSn films and fabricates photodetectors based on this structure. The research results show that the nanostructured GeSn photodetector treated with femtosecond laser exhibits lower dark current, higher photo-responsivity, and external quantum efficiency at room temperature, significantly improving the overall performance of the device and having broad application prospects.

[0065] The above embodiments are described with

[0066] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a photodetector absorption layer, characterized in that: The steps include: Step 1: depositing a p-type GeSn thin film on an n-type Si or Ge substrate, wherein the GeSn layer is used for infrared light absorption; Step 2: Perform photolithography and etching steps on the GeSn thin film layer to form a mesa structure, retaining only the GeSn thin film in the mesa area, and exposing the Si or Ge substrate in the rest; Step 3: Use femtosecond laser to modify the surface of GeSn film in the mesa region, and remove the precipitated Sn by chemical treatment to form a composite nanostructure of femtosecond laser-induced GeSn LIPPS, nanocones and nanopores; Step 4: Plasma-enhanced chemical vapor deposition is used to deposit a silicon dioxide layer on the GeSn substrate as an electrical isolation layer and passivation layer; Step 5: Define electrode holes on the silicon dioxide layer, and remove the silicon dioxide by etching to expose the GeSn layer; Step 6: Determine the electrode position and evaporate Ni / Al alloy by electron beam evaporation technology to form an ohmic contact with the exposed GeSn layer, thereby preparing a vertical table-structured GeSn photodetector.

2. The method for preparing a photodetector absorption layer according to claim 1, characterized in that: The carrier concentration range of the n-type Si or Ge substrate in step 1 is 10 18 cm -3 ~10 20 cm -3 .

3. The method for preparing a photodetector absorption layer according to claim 1, characterized in that: The thickness of the GeSn film in step 1 is 50 nm to 500 nm, and the element composition of Sn in the GeSn layer is in the range of 2% to 20%.

4. The method for preparing a photodetector absorption layer according to claim 1, characterized in that: In step 3, the wavelength of the femtosecond laser is 1030nm, the spot size is 40-100μm, the repetition frequency is 0.025-5MHz, and the energy flux density is 0.6-1.2kJ / m 2 .

5. The method for preparing a photodetector absorption layer according to claim 1, characterized in that: In step 3, the translation stage performs zigzag scanning at a scanning rate of 0.4-2 mm / s and a scanning interval of 20-200 μm between two lines.

6. The method for preparing a photodetector absorption layer according to claim 1, characterized in that: In step 3, the precipitated tin is removed by placing the GeSn sample in dilute hydrochloric acid.

7. The method for preparing a photodetector absorption layer according to claim 1, characterized in that: In step 4, the thickness of the silicon dioxide layer is 200 nm to 500 nm.

8. A photodetector obtained by using the method for preparing a photodetector absorption layer according to any one of claims 1 to 7.

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