A self-driven broadband photodetector and its fabrication method

Abstract

The present invention aims to provide a self-driven broadband photodetector and its fabrication method, belonging to the field of photodetector technology. In this detector, one side of a narrow-bandgap two-dimensional semiconductor is in contact with a metal, and the other side is in contact with a two-dimensional semi-metal, thereby constructing good asymmetric Schottky and Ohmic contacts on both sides of the narrow-bandgap two-dimensional semiconductor. This structure achieves a wide detection spectral range from visible light to infrared light and high photodetector performance without the need for external power supply, and the device exhibits a low dark current at zero bias, reaching 10-1. ‑13 A, which also has high responsiveness.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology, specifically relating to a self-driven broadband photodetector and its fabrication method. Background Technology

[0002] High-performance photodetectors are key components of optoelectronic integrated systems, including light emitters, waveguides, photodetectors, and electronic circuits, and are the core of modern communication and imaging systems. Among these, photodetectors capable of operating over a wide spectral range are crucial for many applications, such as unmanned vehicles, military reconnaissance, and target tracking. Currently, functional materials with different band gaps, such as Ga2O3, Si, and HgCdTe, have been developed to match various spectral ranges. Commercial broadband photodetectors typically integrate multiple of these materials and usually require an external power supply, leading to difficulties in circuit design and integration. Therefore, designing low-power, self-driven photodetectors covering a wide spectral detectable range from visible light to infrared has become an urgent need to meet the growing demands.

[0003] Two-dimensional materials hold great potential for self-driven photodetectors due to their strong light-matter interactions and ease of integration. Asymmetric contacts are a common method for constructing self-driven photodetectors. By using metal electrodes with large work function differences, a Schottky barrier is established at both ends of the two-dimensional material, creating unidirectional band bending at the interface. This generates a strong built-in electric field in the channel, prompting the separation of photogenerated carriers, resulting in the photovoltaic (PV) effect. However, these self-driven photodetectors with asymmetric contacts are typically based on large-bandgap transition metal chalcogenides (TMDCs), which limits their operation to the visible spectrum.

[0004] With the deepening research on narrow bandgap two-dimensional materials, such as black phosphorus (BP), black arsenic (b-As), and tellurium (Te), the detection range of photodetectors based on these materials has been further extended to the infrared spectrum. However, these types of infrared photodetectors typically require an external power source to drive and generate photocurrent. For example, Chen et al. [1] In designing black phosphorus-based photodetectors, a bias voltage is applied to obtain the corresponding responsivity. Narrow bandgap two-dimensional materials can extend the detection range of photodetectors to the infrared spectrum. However, when the asymmetric contact method described above is implemented on narrow bandgap two-dimensional materials, because these materials have a small Fermi level, the energy bands at both ends of the narrow bandgap two-dimensional material, when in contact with conventional metals, bend upwards to form Schottky contacts. This symmetrical band structure cannot form an effective built-in electric field in the channel, thus preventing self-driven photodetection.

[0005] Therefore, how to construct asymmetric contacts based on narrow bandgap two-dimensional materials to provide a strong built-in electric field, enabling them to operate self-driven in a wide spectral range from visible to infrared light, has become a research focus.

[0006] [1]NATURE COMMUNICATIONS|8:1672|DOI:10.1038 / s41467-017-01978-3 Summary of the Invention

[0007] To address the problems existing in the background technology, the present invention aims to provide a self-driven broadband photodetector and its fabrication method. In this detector, one side of a narrow-bandgap two-dimensional semiconductor is in contact with a metal, and the other side is in contact with a two-dimensional semi-metal, thereby constructing good asymmetric Schottky and Ohmic contacts on both sides of the narrow-bandgap two-dimensional semiconductor, respectively. This structure achieves a wide detection spectral range from visible light to infrared light and high photodetector performance without the need for external power supply, while simultaneously reducing dark current and exhibiting high responsivity.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A self-driven broadband photodetector, characterized in that the broadband photodetector includes an insulating substrate, a narrow bandgap two-dimensional semiconductor layer located on the surface of the substrate, a metal layer disposed on one side of the surface of the narrow bandgap two-dimensional semiconductor layer, and a two-dimensional semi-metal layer disposed on the other side.

[0010] The work function of the two-dimensional semi-metallic layer material is close to the Fermi level of the narrow bandgap two-dimensional semiconductor layer material, so that an ohmic contact is formed at the interface between the two-dimensional semi-metallic layer and the narrow bandgap two-dimensional semiconductor layer.

[0011] Furthermore, the insulating substrate material is preferably silicon dioxide.

[0012] Furthermore, the material of the narrow bandgap two-dimensional semiconductor is preferably black phosphorus; the material of the two-dimensional semi-metal layer is preferably tungsten ditelluride; and the material of the metal layer is preferably a Cr / Au composite electrode.

[0013] Furthermore, the thickness of the two-dimensional semi-metallic layer is 5-15 nm, and the thickness of the narrow bandgap two-dimensional semiconductor layer is 5-15 nm.

[0014] The present invention also provides a method for fabricating the above-mentioned broadband photodetector, comprising the following steps:

[0015] Step 1: Using a two-dimensional transfer platform, a narrow bandgap two-dimensional semiconductor is non-destructively transferred onto the substrate surface using a polypropylene carbonate film;

[0016] Step 2: Transfer the two-dimensional semi-metallic layer to one side of the surface of the narrow bandgap two-dimensional semiconductor layer in Step 1 using a non-destructive transfer method;

[0017] Step 3: Combine photolithography and electron beam lithography (EBL) on the other side of the narrow bandgap two-dimensional semiconductor layer to prepare a metal layer, thus obtaining the desired broadband photodetector.

[0018] The mechanism of this invention is as follows:

[0019] If metal electrodes are placed on both sides of a narrow bandgap two-dimensional semiconductor material, the Fermi level of the narrow bandgap two-dimensional semiconductor material is relatively high and the bandgap is relatively narrow. Using dual metal electrodes usually forms a symmetrical Schottky contact, which makes it difficult to form a strong unilateral built-in electric field to drive the spontaneous separation of photogenerated carriers.

[0020] The photodetector of this invention simultaneously constructs good asymmetric Schottky and ohmic contacts on both sides of a narrow-bandgap two-dimensional semiconductor by selecting specific electrode materials. Specifically, the interface between the metal layer and the narrow-bandgap two-dimensional semiconductor is a Schottky contact, while the interface between the two-dimensional half-metal and the narrow-bandgap two-dimensional semiconductor forms an ohmic contact. The structure generates a potential difference within the channel of the narrow-bandgap two-dimensional semiconductor material and produces a built-in electric field, which promotes the separation of photogenerated electrons and holes. At the same time, the narrow-bandgap two-dimensional semiconductor is a photosensitive material in the visible and infrared bands, thereby ensuring that the device can achieve broadband photodetection from the visible to the infrared bands under zero bias.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. The photodetector of this invention can achieve a wide spectral detection range from visible light to infrared light and has the advantage of self-driving; at the same time, due to the inherent depletion region, the dark current of the device under zero bias is small, reaching 10. -13 A.

[0023] 2. The fabrication process of the photodetector of the present invention is simple and easy to implement. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the self-driven broadband photodetector of the present invention, excluding the substrate.

[0025] Figure 2 This is a schematic diagram of the energy bands of the narrow-bandgap two-dimensional semiconductor, metal electrode, and 2.5-position metal in the self-driven broadband photodetector of the present invention before band alignment.

[0026] Figure 3 This is a schematic diagram of the energy band of the self-driven broadband photodetector of the present invention.

[0027] Figure 4This is a schematic diagram of the energy band structure of a photodetector with symmetrical electrodes in the prior art.

[0028] Figure 5 This refers to the photocurrent of the self-driven broadband photodetector of the present invention under different wavelength laser irradiation conditions at zero bias voltage.

[0029] Figure 6 This is a graph showing the photoresponse rate of the self-driven broadband photodetector of the present invention under zero bias conditions and laser irradiation at different wavelengths. Detailed Implementation

[0030] 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 embodiments and accompanying drawings.

[0031] Example 1

[0032] A self-driven broadband photodetector is disclosed. The substrate of the broadband photodetector is a SiO2 insulating layer, typically a Si substrate in practical applications. The Si substrate surface has a 0.5 mm thick heavily doped SiO2 insulating layer. A schematic diagram of the photodetector structure excluding the substrate is shown below. Figure 1 As shown, it includes a narrow bandgap two-dimensional semiconductor layer BP, a metal layer disposed on one side of the surface of the narrow bandgap two-dimensional semiconductor layer, and a two-dimensional semi-metal layer on the other side; the narrow bandgap two-dimensional semiconductor layer BP is disposed on the surface of a heavily doped SiO2 insulating layer.

[0033] For ease of testing, the metal layer serves as the source electrode in the metal electrode, while a larger metal electrode is drawn out on the two-dimensional semi-metallic tungsten ditelluride side as the drain electrode.

[0034] The specific fabrication method of the self-driven broadband photodetector is as follows:

[0035] Step 1. Substrate selection,

[0036] A heavily doped SiO2 / Si substrate with a thickness of 0.5 mm was selected.

[0037] Step 2. Fabrication of two-dimensional semiconductor transfer.

[0038] The narrow-bandgap two-dimensional semiconductor black phosphorus and two-dimensional semiconductor tungsten ditelluride crystals were mechanically peeled off using adhesive tape. Then, using a two-dimensional transfer platform, the narrow-bandgap two-dimensional semiconductor black phosphorus was first transferred non-destructively to the substrate surface using a polypropylene carbonate film, and then the tungsten ditelluride was transferred non-destructively to one side of the black phosphorus surface.

[0039] Step 3. Electrode preparation,

[0040] Source and drain electrode patterns are prepared using electron beam lithography; metal electrodes (chromium / gold, 5 / 50 nm) are prepared using thermal evaporation; and the metal film is peeled off using a lift-off method to obtain source and drain electrodes with a channel width of 3 micrometers, thus obtaining a broadband photodetector.

[0041] The energy band diagram of the photodetector prepared in this embodiment is shown below. Figure 3 As shown; the output curves under dark conditions and laser irradiation conditions are as follows. Figure 4 As shown; under zero bias conditions, the photocurrent under laser irradiation is as follows Figure 5 As shown, the photoresponsivity is as follows Figure 6 As shown.

[0042] Figure 2 This is a schematic diagram of the energy band structure of the narrow-bandgap two-dimensional semiconductor, metal electrode, and two-and-a-half metal in the self-driven broadband photodetector of the present invention before band alignment. Before band alignment, a Schottky barrier is formed at the interface of the metal because the work function of the metal is much larger than the Fermi level of the narrow-bandgap two-dimensional semiconductor; on the other side, an ohmic contact is formed because the work function of the two-and-a-half metal is basically consistent with the Fermi level of the narrow-bandgap two-dimensional semiconductor.

[0043] Figure 3 This is a schematic diagram of the energy band structure of the self-driven broadband photodetector of this invention. As can be seen from the diagram, when the narrow-bandgap two-dimensional semiconductor is in contact with a metal, the energy band bends upwards, forming a Schottky barrier, because the work function of the metal is much larger than the Fermi level of the narrow-bandgap two-dimensional semiconductor. When the narrow-bandgap two-dimensional semiconductor is in contact with a two-dimensional semi-metal, an ohmic contact is formed because the work function of the two-dimensional semi-metal is essentially the same as the Fermi level of the narrow-bandgap two-dimensional semiconductor. Under zero bias, the photogenerated carriers generated by black phosphorus under laser irradiation are separated by the built-in electric field; electrons move towards tungsten ditelluride, and holes move towards the metal electrode.

[0044] Figure 4 This is a schematic diagram of the energy band structure of a photodetector with symmetrical electrodes in the prior art. When a narrow-bandgap two-dimensional semiconductor comes into contact with a symmetrical metal, the energy bands at both ends bend upwards simultaneously because the work function of the metal is much larger than the Fermi level of the narrow-bandgap two-dimensional semiconductor, forming a symmetrical Schottky barrier. Under zero bias, due to the presence of the barrier at both ends, the photogenerated carriers generated by black phosphorus under laser irradiation cannot be spontaneously separated, and an effective photocurrent cannot be formed.

[0045] Figure 5 and Figure 6 The graph shows the photocurrent and photoresponse rate of the self-driven broadband photodetector of this invention under different wavelength laser irradiation conditions at zero bias voltage. Figure 5Under light irradiation conditions, the asymmetric contact photodetector prepared in this embodiment exhibits self-powered detection capability across a broad spectral range from visible to infrared light, and displays significant photocurrent at zero bias voltage. As shown in the figure, at zero bias voltage, the photocurrent is largest under 532nm illumination, followed by the photocurrent under 1550nm infrared illumination, while the photocurrent is weakest under 808nm illumination. However, the photodetector can achieve detection across the broad spectral range from visible to infrared.

[0046] Figure 6 Under light irradiation conditions and zero bias voltage, the asymmetric contact photodetector prepared in this embodiment exhibits excellent broadband photodetection capabilities. As shown in the figure, under zero bias voltage, the photoresponse rate is the highest under 532nm illumination, which is better than the photoresponse rate under 1550nm infrared illumination, while the photoresponse rate is the weakest under 808nm illumination.

[0047] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A self-driven broadband photodetector, characterized in that, The broadband photodetector includes an insulating substrate, a narrow bandgap two-dimensional semiconductor layer on the surface of the substrate, a metal layer on one side of the surface of the narrow bandgap two-dimensional semiconductor layer, and a two-dimensional semi-metal layer on the other side. The work function of the two-dimensional half-metal layer material is close to the Fermi level of the narrow bandgap two-dimensional semiconductor layer material, so that an ohmic contact is formed at the interface between the two-dimensional half-metal layer and the narrow bandgap two-dimensional semiconductor layer. The interface between the metal layer and the narrow bandgap two-dimensional semiconductor layer is a Schottky contact.

2. The broadband photodetector as described in claim 1, characterized in that, The insulating substrate material is silicon dioxide.

3. The broadband photodetector as described in claim 1, characterized in that, The narrow bandgap two-dimensional semiconductor layer is made of black phosphorus; the two-dimensional semi-metal layer is made of tungsten ditelluride; and the metal layer is made of a Cr / Au composite electrode.

4. The broadband photodetector as described in claim 1, characterized in that, The thickness of the two-dimensional semi-metallic layer is 5-15 nm, and the thickness of the narrow bandgap two-dimensional semiconductor layer is 5-15 nm.

5. The method for fabricating a broadband photodetector as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Using a two-dimensional transfer platform, a narrow bandgap two-dimensional semiconductor layer is non-destructively transferred onto the substrate surface using a polypropylene carbonate film; Step 2: Transfer the two-dimensional semi-metallic layer to one side of the surface of the narrow bandgap two-dimensional semiconductor layer in Step 1 using a non-destructive transfer method; Step 3: Combine photolithography and electron beam lithography (EBL) on the other side of the narrow bandgap two-dimensional semiconductor layer to prepare a metal layer, thus obtaining the desired broadband photodetector.

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