Terahertz detector and method of manufacturing the same

Abstract

The application discloses a terahertz detector and a preparation method thereof. The terahertz detector comprises a substrate, a channel material layer and an electrode. The channel material layer is arranged on the substrate, and an element component of a thermoelectric material in the channel material layer can be regulated to make the thermoelectric material transform from a semiconductor state to a topological nodal semimetal state; and the electrode is in contact with the channel material layer. The terahertz detector and the preparation method thereof can realize the significant enhancement of the terahertz performance through the regulation of the element component of the thermoelectric material in the channel material layer to make the thermoelectric material transform, the optimization of the thermoelectric performance and the topological enhanced detection, and finally realize the significant enhancement of the terahertz performance under the synergistic effect of the two.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a terahertz detector and a method for fabricating the terahertz detector. Background Technology

[0002] Terahertz waves (0.1-10 THz) are a segment of electromagnetic waves between microwaves and infrared radiation that has not yet been fully explored and utilized. They possess unique advantages, such as fingerprint spectral characteristics, high frequency and high bandwidth, high transmittance, and water absorption, making them extremely valuable for scientific research in fields such as biomedicine and future high-speed, high-capacity communications. However, the frequency of terahertz waves is much higher than the cutoff frequency of traditional electronic devices, and their photon energy (1 THz corresponds to 4.14 meV) is much lower than the band gap of traditional semiconductor materials. This makes it difficult to generate and detect terahertz waves using traditional electronic and photonic methods. For a considerable period, the lack of high-speed, highly sensitive, uncooled terahertz detectors has severely restricted the practical application of terahertz waves.

[0003] Currently, room-temperature terahertz detection technology is mainly based on electronic methods and the photothermal effect principle. Electronic detection methods utilize rectification effects to directly detect terahertz waves or achieve heterodyne detection through nonlinear mixing. However, limited by carrier transit time and stray capacitance, the effective detection frequency of this method is typically less than 1 THz, making it difficult to meet the requirements of mid-to-high frequency terahertz detection. Detectors based on the photothermal effect have a response spectrum independent of the bandgap, enabling ultra-wideband terahertz detection, thus becoming the main method for mid-to-high frequency room-temperature terahertz detection. Common photothermal effect terahertz detectors mainly include Golay, pyroelectric, calorimeters, and photothermoelectric detectors. Among them, Golay detectors mainly rely on temperature-induced thin-film deformation and can operate at room temperature with zero bias, but have low integration density, slow response (tens of milliseconds), and are easily affected by external environmental interference. Pyroelectric detectors mainly rely on temperature-induced changes in dielectric polarization intensity, resulting in low sensitivity (>1 nW·Hz). -1 / 2 The response speed is relatively slow (10-50ms); the calorimeter mainly relies on the significant change in material resistance caused by temperature, can operate at room temperature and can be arrayed, but requires an external bias voltage, thus generating additional power consumption and relatively large 1 / f noise. The photothermoelectric effect is a new type of terahertz photothermal detector, which has advantages over the other three detectors, such as zero bias operation, no cooling, and relatively fast response speed.

[0004] Since the first graphene-based photothermoelectric terahertz detector was proposed in 2014, mid-to-high frequency terahertz detection based on the photothermoelectric effect has gradually become a research hotspot. Finding excellent thermoelectric materials with high Seebeck coefficients, low thermal conductivity, and tunable thermoelectric properties is key to achieving high-performance photothermoelectric detection. On the other hand, in recent years, topological quantum materials have attracted widespread attention due to their unique band structure, which leads to high carrier mobility, zero-bandgap topological states, and strong light-matter interactions. However, few materials can possess both excellent thermoelectric properties and a unique topological band structure.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a terahertz detector and a method for preparing the terahertz detector, which can change the state of the thermoelectric material by controlling the elemental composition of the channel material, thereby achieving optimized thermoelectric performance and topology-enhanced detection. Ultimately, the terahertz performance is significantly enhanced through the synergistic effect of the two.

[0007] To achieve the above objectives, embodiments of the present invention provide a terahertz detector, comprising: a substrate, a channel material layer, and an electrode. The channel material layer is disposed on the substrate, and the channel material in the channel material layer includes a thermoelectric material. The elemental composition of the thermoelectric material can be tuned to cause the thermoelectric material to transition from a semiconductor state to a topological nodal-line semimetal state. The electrode is in contact with the channel material layer.

[0008] In one or more embodiments of the present invention, the thermoelectric material comprises NbM x Te2, where element M can be Ge or Si, and 1 / 3 ≤ x ≤ 1 / 2.

[0009] In one or more embodiments of the present invention, the thermoelectric material includes Nb3GeTe6 or Nb3SiTe6.

[0010] In one or more embodiments of the present invention, the electrode includes a source electrode, a drain electrode, and a gate electrode, wherein the source electrode and the drain electrode are made of different materials, and the source electrode, the drain electrode, and the gate electrode constitute a three-terminal asymmetric butterfly antenna.

[0011] In one or more embodiments of the present invention, the terahertz detector further includes a gate medium located below the gate electrode, the material of the gate medium including Al2O3, HfO2, SiO2 or h-BN.

[0012] Embodiments of the present invention also provide a method for fabricating a terahertz detector, comprising: providing a substrate; providing a channel material, the channel material comprising a thermoelectric material, wherein the elemental composition of the thermoelectric material can be modulated to cause the thermoelectric material to transition from a semiconductor state to a topological nodal line semimetal state; transferring the channel material to the surface of the substrate to form a channel material layer; and forming an electrode on the substrate, the electrode being in contact with the channel material layer.

[0013] In one or more embodiments of the present invention, the thermoelectric material comprises NbM x Te2, where element M can be Ge or Si, and 1 / 3 ≤ x ≤ 1 / 2.

[0014] In one or more embodiments of the present invention, the thermoelectric material includes Nb3GeTe6 or Nb3SiTe6.

[0015] In one or more embodiments of the present invention, the thermoelectric material is prepared by a chemical vapor transport method, a chemical vapor deposition method, or an epitaxial growth method.

[0016] In one or more embodiments of the present invention, the step of providing a channel material and transferring the channel material to the surface of the substrate to form a channel material layer includes: preparing the channel material: growing elements Nb, M, and Te in a stoichiometric ratio of 1:x:2 at 640°C-740°C for seven days in a vacuum environment, and then lowering the temperature to ambient temperature to obtain NbM. x Te2 crystal, wherein element M can be Ge or Si; NbM x Te2 crystals were mechanically exfoliated to form NbM. x Te2 nanosheets are transferred to the substrate surface.

[0017] In one or more embodiments of the present invention, forming electrodes on the substrate includes: fabricating source and drain electrodes using electron beam lithography, electron beam evaporation, and lift-off techniques, wherein the electrode material is selected from Cr / Au; or, fabricating source and drain electrodes by two lithography and deposition processes, wherein different electrode materials are selected for the two deposition processes, including Cr / Au, Ni / Au, Pd / Au, and Ti / Au; forming a gate dielectric, followed by secondary alignment, and fabricating the gate electrode using a combination of electron beam lithography and electron beam evaporation processes; the source electrode, drain electrode, and gate electrode constitute a three-terminal asymmetric butterfly antenna.

[0018] In one or more embodiments of the present invention, the gate medium is deposited by atomic layer deposition (ALD) or plasma-enhanced CVD, or by dry transfer of h-BN nanosheets as the gate medium.

[0019] Compared with the prior art, the terahertz detector and its fabrication method according to the embodiments of the present invention use a thermoelectric material whose energy of state transitions from semiconductor to topological nodal line half-metal as the channel material, and introduce a topological band structure, thereby bringing high mobility and high conductivity, enhancing detection performance, and optimizing the intrinsic thermoelectric properties of the material. Under the synergistic effect of the two, a significant enhancement of terahertz performance is achieved.

[0020] The terahertz detector and its fabrication method according to the embodiments of the present invention obtain materials Nb3GeTe6 or Nb3SiTe6 with excellent thermoelectric properties and unique topological band structure through the simple and easy method of component control. The topological band structure can bring high carrier mobility and conductivity, which not only helps to improve thermoelectric performance, but also promotes the rapid movement of carriers. Based on this material system, high-speed and highly sensitive room temperature detection can be achieved.

[0021] The terahertz detector and its fabrication method according to the embodiments of the present invention, through component control, allow the excellent thermoelectric properties of the thermoelectric material to work synergistically with the unique band structure, which can further overcome the problem of slow response speed of room temperature thermal effect terahertz detectors.

[0022] The terahertz detector and its fabrication method according to the present invention use a three-terminal asymmetric butterfly antenna, which can increase the temperature gradient under terahertz radiation, thereby increasing the photothermal potential difference and enhancing the terahertz response.

[0023] The terahertz detector and its fabrication method according to the embodiments of the present invention deposit the gate medium by atomic layer deposition (ALD) or plasma-enhanced voltammetry (PECVD), or by dry transfer of h-BN nanosheets as the gate medium. The above methods can reduce the damage to the channel material caused by micro-nano fabrication processes.

[0024] The terahertz detector and its fabrication method according to the embodiments of the present invention can be made of different metal materials for the source electrode and the drain electrode. This asymmetry of the metal contact can enhance the photothermal and electroelectric response performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a terahertz detector coupled with an asymmetric butterfly antenna according to an embodiment of the present invention.

[0026] Figure 2 This is an X-ray photoelectron spectroscopy (XRD) diagram of Nb2GeTe4 thermoelectric material in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention, wherein the horizontal axis represents the 2θ angle (degrees) and the vertical axis represents the normalized intensity.

[0027] Figure 3 This is an angle-resolved photoelectron spectrum (ARPES) diagram of the Nb2GeTe4 thermoelectric material in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention, wherein the horizontal axis represents the wave vector in the x-direction (one angstrom) and the vertical axis represents the energy (electron volts);

[0028] Figure 4 This is a temperature-varying resistance diagram of the Nb2GeTe4 thermoelectric material in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention, wherein the horizontal axis represents temperature (Kelvin) and the vertical axis represents vertical resistance (kiloohms).

[0029] Figure 5 This is a spectrum of the photoresponse current of Nb2GeTe4 thermoelectric material as a function of frequency in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention, wherein the horizontal axis represents the frequency (terahertz) and the vertical axis represents the photocurrent (microamps).

[0030] Figure 6 This is a response time diagram extracted from the zero bias waveform of the Nb2GeTe4 thermoelectric material in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention, wherein the horizontal axis represents time (milliseconds) and the vertical axis represents normalized photocurrent.

[0031] Figure 7 This is an X-ray photoelectron spectroscopy (XRD) diagram of Nb3GeTe6 thermoelectric material in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention, wherein the horizontal axis represents the 2θ angle (degrees) and the vertical axis represents the normalized intensity;

[0032] Figure 8 This is an angle-resolved photoelectron spectrum (ARPES) diagram of Nb3GeTe6 thermoelectric material in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention, wherein the horizontal axis represents the wave vector in the x-direction (one angstrom) and the vertical axis represents the energy (electron volts);

[0033] Figure 9 This is a temperature-varying resistance diagram of the Nb3GeTe6 thermoelectric material in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention, wherein the horizontal axis represents temperature (Kelvin) and the vertical axis represents vertical resistance (kiloohms).

[0034] Figure 10This is a spectrum of the photoresponse current of Nb3GeTe6 thermoelectric material as a function of frequency in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention, wherein the horizontal axis represents the frequency (terahertz) and the vertical axis represents the photocurrent (microamps).

[0035] Figure 11 This is a response time diagram extracted from the zero bias waveform of the Nb3GeTe6 thermoelectric material in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention, wherein the horizontal axis represents time (milliseconds) and the vertical axis represents normalized photocurrent. Detailed Implementation

[0036] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0037] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0038] As mentioned in the background section, the sensitivity and response speed of existing photothermoelectric detectors are not high enough, and there are few means to control the intrinsic thermoelectric properties. In addition, few materials can combine excellent thermoelectric properties with unique topological band structures, thus combining the advantages of different materials.

[0039] Based on this, in order to obtain a terahertz detector with high sensitivity, high response speed and high detection performance, this invention aims to achieve the transformation of the thermoelectric material in the trench material layer from a P-type semiconductor to a topological nodal line half-metal by controlling the elemental composition of the thermoelectric material, thereby introducing a topological band structure, resulting in high mobility and high conductivity, and optimizing the intrinsic thermoelectric properties of the material. At the same time, high-speed, high-sensitivity, self-driven room temperature terahertz detection is achieved under the drive of massless quasi-fermions.

[0040] like Figure 1 As shown, a terahertz detector according to an embodiment of the present invention includes a substrate 10, a channel material layer 20, and electrodes. The channel material layer 20 is disposed on the substrate 10, and the channel material in the channel material layer 20 includes a thermoelectric material. The physical state of this thermoelectric material can be transformed from a semiconductor state to a topological nodal line semimetal state by controlling its elemental composition, thereby introducing a topological band structure, resulting in high mobility and high conductivity, and optimizing the intrinsic thermoelectric properties of the material. Electrodes are formed on the substrate 10 and are in contact with the channel material layer 20. The electrodes are configured in an antenna shape to increase the temperature gradient under terahertz radiation, thereby increasing the photothermal potential difference and enhancing the terahertz response.

[0041] The substrate 10 can be selected from high-resistivity intrinsic silicon substrates, quartz, sapphire, PET, etc.

[0042] For example, thermoelectric materials include NbM x Te2, wherein element M can be Ge or Si, and 1 / 3 ≤ x ≤ 1 / 2. Preferably, the thermoelectric material can be Nb3GeTe6 or Nb3SiTe6.

[0043] In one embodiment of the present invention, the thermoelectric material-NbM can be synthesized using a chemical vapor transport method, a chemical vapor deposition method, or an epitaxial growth method. x Te2 crystals. Specifically, a mixture of Nb powder (99.99%, Aladdin Chemicals), M powder (which can be Ge powder or Si powder (99.999%, Aladdin Chemicals), and Te powder (99.999%, Alfa Aesar) in a stoichiometric ratio of 1:x:2 is placed in a quartz tube, and an appropriate amount of I2 is added as a transport agent. The quartz tube is then evacuated to a high vacuum of -2 × 10⁻⁶. -5 After sealing, the quartz tube was placed in a dual-temperature tube furnace. The high-temperature end (raw material end) and the low-temperature end (growth end) were set to 640℃ and 740℃ respectively, with a temperature difference maintained at 100℃. After 7 days of growth and natural cooling to room temperature, high-quality NbMn with a metallic luster was obtained at the low-temperature end. x Te2 crystals.

[0044] The electrodes include a source electrode 31, a drain electrode 32, and a gate electrode 33. The source electrode 31 is configured in a fan-shaped structure, with its tip located on the trench material layer 20 and in contact with the thermoelectric material. The drain electrode 32 is configured in a strip-shaped structure, with one end located on the trench material layer 20 and in contact with the thermoelectric material. The gate electrode 33 is configured in a fan-shaped structure, with its tip located on the trench material layer 20 and in contact with the thermoelectric material. The source electrode 31, drain electrode 32, and gate electrode 33 constitute a three-terminal asymmetric butterfly antenna, such as... Figure 1 As shown, the three-terminal asymmetric butterfly antenna can increase the temperature gradient under terahertz radiation, thereby increasing the photothermal potential difference and enhancing the terahertz response. In this embodiment, the source electrode 31 and the drain electrode 32 can be made of different metal materials, and this asymmetry of the metal contact can enhance the photothermal response performance.

[0045] The terahertz detector of the present invention also includes a leaded electrode structure, which comprises a metal lead 341 and a cubic electrode 342. There are three leaded electrode structures, which are respectively connected to the source electrode 31, the drain electrode 32, and the gate electrode 33, facilitating subsequent performance testing.

[0046] Understandably, the terahertz detector also includes a gate dielectric located below the gate electrode 33. The gate dielectric material includes Al2O3, HfO2, SiO2, or h-BN. Exemplarily, the gate dielectric can be deposited by atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD), or h-BN nanosheets can be dry-transferred as the gate dielectric. These methods can reduce damage to the channel material caused by micro / nano fabrication processes.

[0047] The present invention also provides a method for fabricating a terahertz detector, comprising: providing a substrate; providing a channel material, the channel material including a thermoelectric material; transferring the channel material to the surface of the substrate to form a channel material layer, wherein the physical state of the thermoelectric material is transformed from a semiconductor state to a topological nodal line semimetal state by regulating its internal elemental composition, thereby introducing a topological band structure, resulting in high mobility and high electrical conductivity, and optimizing the intrinsic thermoelectric properties of the material; and finally forming an electrode on the substrate, the electrode being in contact with the channel material layer.

[0048] For example, thermoelectric materials include NbM x Te2, wherein element M can be Ge or Si, and 1 / 3 ≤ x ≤ 1 / 2. Preferably, the thermoelectric material can be Nb3GeTe6 or Nb3SiTe6.

[0049] For example, the step of providing a substrate includes:

[0050] The 4-inch silicon wafer was organically cleaned using acetone, isopropanol, and deionized water. Then, patterns were created on the 4-inch silicon wafer using processes such as ultraviolet lithography, electron beam evaporation, and stripping (to facilitate subsequent positioning and alignment). Finally, the 4-inch silicon wafer was cut into 1.5*1.5cm pieces for subsequent device fabrication.

[0051] For example, the step of providing a channel material and transferring the channel material to a substrate surface to form a channel material layer includes:

[0052] Preparation of channel material: The thermoelectric material-NbM is synthesized using chemical vapor transport, chemical vapor deposition, or epitaxial growth methods. x Te2 crystals. Specifically, a mixture of Nb powder (99.99%, Aladdin Chemicals), M powder (which can be Ge powder or Si powder (99.999%, Aladdin Chemicals), and Te powder (99.999%, Alfa Aesar) in a stoichiometric ratio of 1:x:2 is placed in a quartz tube, and an appropriate amount of I2 is added as a transport agent. The quartz tube is then evacuated to a high vacuum of -2 × 10⁻⁶. -5After sealing, the quartz tube was placed in a dual-temperature tube furnace. The high-temperature end (raw material end) and the low-temperature end (growth end) were set to 640℃ and 740℃ respectively, with a temperature difference maintained at 100℃. After 7 days of growth and natural cooling to room temperature, high-quality NbMn with a metallic luster was obtained at the low-temperature end. x Te2 crystals.

[0053] NbM x Te2 crystals were cleaved into NbM crystals via micromechanical exfoliation. x Te2 nanosheets of suitable thickness were selected and transferred onto a 1.5 x 1.5 cm silicon wafer, where their positions were marked. A layout was then created, including source and drain electrodes and a block electrode connected by metal leads. NbM nanosheets were then mechanically peeled off and transferred to the substrate. x The positions of Te2 nanosheets are random, therefore, these positions need to be marked for NbM in the electronic layout. x Te2 nanosheets were positioned and the device structure was drawn at the specified locations.

[0054] For example, the step of forming electrodes on a substrate includes:

[0055] Source and drain electrodes can be fabricated using electron beam lithography, electron beam evaporation, and lift-off techniques, with Cr / Au being a suitable electrode material. Alternatively, source and drain electrodes can be fabricated using two separate photolithography and deposition processes, with different electrode materials used for the two deposition processes, including Cr / Au, Ni / Au, Pd / Au, and Ti / Au.

[0056] The gate dielectric is deposited by atomic layer deposition (ALD) or plasma-enhanced CVD, or by dry transfer of h-BN nanosheets as the gate dielectric, followed by secondary alignment, and then by electron beam lithography, electron beam evaporation and other processes to prepare the gate electrode.

[0057] Finally, a complete terahertz detector was fabricated using mature semiconductor packaging and wire bonding technologies.

[0058] To conduct performance testing of the terahertz detector of this invention, and to compare the thermoelectric materials based on different compositions - NbM x To assess the response performance of Te2 terahertz detectors, this application uses nanosheets of similar thickness after micromechanical exfoliation to fabricate terahertz detectors with the same structure and conducts comparative tests.

[0059] With NbGe x Taking Te2 as an example, the thermoelectric material selected in the first embodiment is Nb2GeTe4 when x = 1 / 2; the thermoelectric material selected in the second embodiment is Nb3GeTe6 when x = 1 / 3.

[0060] Step 1: Preparation of Nb2GeTe4 in the first embodiment and Nb3GeTe6 in the second embodiment:

[0061] Thermoelectric material Nb₂GeTe₄ crystal was synthesized using a chemical vapor transport method. Specifically, a mixture of Nb powder (99.99%, Aladdin Chemicals), Ge powder (99.999%, Aladdin Chemicals), and Te powder (99.999%, Alfa Aesar) in a stoichiometric ratio of 2:1:4 was placed in a quartz tube, and an appropriate amount of I₂ was added as a transport agent. The quartz tube was then evacuated to a high vacuum (2 × 10⁻⁶). -5 The quartz tube was sealed and then placed in a dual-temperature tube furnace. The high-temperature end (raw material end) and the low-temperature end (growth end) were set to 640℃ and 740℃ respectively, with a temperature difference maintained at 100℃. After 7 days of growth and natural cooling to room temperature, high-quality Nb2GeTe4 crystals with metallic luster were obtained at the low-temperature end. The structure and composition of the obtained Nb2GeTe4 crystals were preliminarily confirmed by XRD, XPS, Raman, and STEM, and the results are as follows. Figures 2 to 4 As shown.

[0062] Thermoelectric material Nb3GeTe6 crystal was synthesized using a chemical vapor transport method. Specifically, a mixture of Nb powder (99.99%, Aladdin Chemicals), Ge powder (99.999%, Aladdin Chemicals), and Te powder (99.999%, Alfa Aesar) in a stoichiometric ratio of 3:1:6 was placed in a quartz tube, and an appropriate amount of I2 was added as a transport agent. The quartz tube was then evacuated to a high vacuum (2 × 10⁻⁶). -5 The quartz tube was sealed and then placed in a dual-temperature tube furnace. The high-temperature end (raw material end) and the low-temperature end (growth end) were set to 640℃ and 740℃ respectively, with a temperature difference maintained at 100℃. After 7 days of growth and natural cooling to room temperature, high-quality Nb2GeTe4 crystals with metallic luster were obtained at the low-temperature end. The structure and composition of the obtained Nb3GeTe6 crystals were preliminarily confirmed by XRD, XPS, Raman, and STEM, and the results are as follows. Figures 7 to 9 As shown.

[0063] pass Figure 2 and Figure 7 It can be seen that the obtained crystal materials have different crystal phases when x = 1 / 2 and x = 1 / 3. The band structure of the obtained crystals was characterized using angle-resolved photoelectron spectroscopy, and the results are as follows: Figure 3 and Figure 8 As shown. (Through) Figure 3 and Figure 8It can be seen that the obtained crystal materials have different band structures; when x = 1 / 2, the band structure diagram of Nb2GeTe4 shows typical semiconductor characteristics; while when x = 1 / 3, the band structure diagram of Nb3GeTe6 shows typical topological half-metal characteristics. The trend of resistance with temperature obtained by low-temperature electrical transport testing is as follows: Figure 4 and Figure 9 As shown, through Figure 4 and Figure 9 It can be seen that the resistance changes with temperature obtained from the low-temperature electrical transport test of each crystal are consistent with the band structure, exhibiting P-type semiconductor characteristics and half-metal characteristics respectively.

[0064] As can be seen from the above, Nb2GeTe4 is a typical P-type semiconductor with excellent thermoelectric properties and easy gate voltage control, while Nb3GeTe6 is a typical topological nodal-line half-metal with both excellent thermoelectric properties and high conductivity and mobility brought by the topological band structure, which is more conducive to the realization of high-speed, high-sensitivity room temperature terahertz detection.

[0065] Step 2: Fabrication of the Nb2GeTe4-based terahertz detectors of the first embodiment and the Nb3GeTe6-based terahertz detectors of the second embodiment.

[0066] Figure 5 This is a spectrum of the photoresponse current of Nb2GeTe4 thermoelectric material as a function of frequency in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention. Figure 6 This is a response time diagram extracted from the zero bias waveform of the Nb2GeTe4 thermoelectric material in a terahertz detector based on Nb2GeTe4 thermoelectric material according to the first embodiment of the present invention. Figure 10 This is a spectrum of the photoresponse current of Nb3GeTe6 thermoelectric material as a function of frequency in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention. Figure 11 This is a response time diagram extracted from the zero bias waveform of the Nb3GeTe6 thermoelectric material in a terahertz detector based on Nb3GeTe6 thermoelectric material according to the second embodiment of the present invention.

[0067] The photoresponse current and response time extracted from the waveforms of the two devices were compared through terahertz performance testing under the same power terahertz wave incident conditions. The results are as follows: Figure 5 and Figure 10 as well as Figure 6 and Figure 11 It can be seen that the terahertz detector based on Nb3GeTe6 thermoelectric material in the second embodiment achieves higher speed and higher sensitivity detection through the synergistic effect of excellent thermoelectric performance and topological band structure.

[0068] With NbSi x Taking Te2 as an example, the thermoelectric material selected in the third embodiment is Nb2SiTe4 when x = 1 / 2; the thermoelectric material selected in the fourth embodiment is Nb3SiTe6 when x = 1 / 3.

[0069] The Nb₂SiTe₄ of the third embodiment and the Nb₃SiTe₆ of the fourth embodiment were fabricated, respectively; and the terahertz detectors based on Nb₂SiTe₄ of the third embodiment and Nb₃SiTe₆ of the fourth embodiment were fabricated. The structure and composition of the obtained Nb₂SiTe₄ and Nb₃SiTe₆ crystals were preliminarily confirmed using XRD, XPS, Raman spectroscopy, and STEM. Furthermore, the band structure of the crystals was characterized using angle-resolved photoelectron spectroscopy. It was found that when x = 1 / 2, the band structure of Nb₂SiTe₄ exhibits typical semiconductor characteristics; while when x = 1 / 3, the band structure of Nb₃SiTe₆ exhibits typical topological half-metal characteristics. In addition, the resistance change with temperature obtained by low-temperature electrical transport testing also matches the band structure, exhibiting P-type semiconductor and half-metal characteristics, respectively. By comparing the photoresponse current and response time extracted from the waveforms of the two devices under the same power terahertz wave incident, it can be concluded that the latter achieves higher speed and higher sensitivity detection through the synergistic effect of excellent thermoelectric performance and topological band structure.

[0070] The terahertz detector and its fabrication method according to the embodiments of the present invention obtain materials Nb3GeTe6 or Nb3SiTe6 with excellent thermoelectric properties and unique topological band structure through the simple and easy method of component control. The topological band structure can bring high carrier mobility and conductivity, which not only helps to improve thermoelectric performance, but also promotes the rapid movement of carriers. Based on this material system, high-speed and highly sensitive room temperature detection can be achieved.

[0071] The terahertz detector and its fabrication method according to the embodiments of the present invention, through component control, allow the excellent thermoelectric properties of the thermoelectric material to work synergistically with the unique band structure, which can further overcome the problem of slow response speed of room temperature thermal effect terahertz detectors.

[0072] The terahertz detector and its fabrication method according to the present invention use a three-terminal asymmetric butterfly antenna, which can increase the temperature gradient under terahertz radiation, thereby increasing the photothermal potential difference and enhancing the terahertz response.

[0073] The terahertz detector and its fabrication method according to the embodiments of the present invention deposit the gate medium by atomic layer deposition (ALD) or plasma-enhanced voltammetry (PECVD), or by dry transfer of h-BN nanosheets as the gate medium. The above methods can reduce the damage to the channel material caused by micro-nano fabrication processes.

[0074] The terahertz detector and its fabrication method according to the embodiments of the present invention can be made of different metal materials for the source electrode and the drain electrode. This asymmetry of the metal contact can enhance the photothermal and electroelectric response performance.

[0075] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A terahertz detector, characterized in that, include: Substrate; A channel material layer is disposed on the substrate, wherein the channel material in the channel material layer includes a thermoelectric material, and the elemental composition of the thermoelectric material can be tuned to cause the thermoelectric material to transform from a semiconductor state to a topological nodal-line half-metal state; The electrode is in contact with the channel material layer; The thermoelectric material includes NbM x Te2, where element M can be Ge or Si, and 1 / 3 ≤ x ≤ 1 / 2.

2. The terahertz detector as described in claim 1, characterized in that, The thermoelectric material includes Nb3GeTe6 or Nb3SiTe6.

3. The terahertz detector as described in claim 1, characterized in that, The electrodes include a source electrode, a drain electrode, and a gate electrode. The source electrode and the drain electrode are made of different materials. The source electrode, the drain electrode, and the gate electrode constitute a three-terminal asymmetric butterfly antenna.

4. A method for fabricating a terahertz detector, characterized in that, include: Provide substrate; A channel material is provided, the channel material including a thermoelectric material, the elemental composition of the thermoelectric material can be tuned to cause the thermoelectric material to transform from a semiconductor state to a topological nodal line semimetal state, and the channel material is transferred to the surface of the substrate to form a channel material layer; An electrode is formed on the substrate, and the electrode is in contact with the channel material layer; The thermoelectric material includes NbM x Te2, where element M can be Ge or Si, and 1 / 3 ≤ x ≤ 1 / 2.

5. The method for fabricating a terahertz detector as described in claim 4, characterized in that, The thermoelectric material includes Nb3GeTe6 or Nb3SiTe6.

6. The method for fabricating a terahertz detector as described in claim 4, characterized in that, The thermoelectric material is prepared by chemical vapor transport, chemical vapor deposition, or epitaxial growth.

7. The method for fabricating a terahertz detector as described in claim 4, characterized in that, The step of providing a channel material and transferring the channel material to the surface of the substrate to form a channel material layer includes: Preparation of channel material: In a vacuum environment, Nb, M, and Te were grown at 640℃-740℃ for seven days in a stoichiometric ratio of 1:x:

2. The temperature was then lowered to ambient temperature to obtain NbM. x Te2 crystal, wherein element M can be Ge or Si; NbM x Te2 crystals were mechanically exfoliated to form NbM. x Te2 nanosheets are transferred to the substrate surface.

8. The method for fabricating a terahertz detector as described in claim 4, characterized in that, Forming electrodes on the substrate includes: Source and drain electrodes are fabricated using electron beam lithography, electron beam evaporation, and lift-off techniques, wherein the electrode material is selected from Cr / Au; or, source and drain electrodes are fabricated by two separate photolithography and coating processes, with different electrode materials selected for the two coating processes, including Cr / Au, Ni / Au, Pd / Au, and Ti / Au. The gate dielectric is formed, followed by secondary alignment, and then the gate electrode is prepared by electron beam lithography and electron beam evaporation. The source electrode, drain electrode, and gate electrode constitute a three-terminal asymmetric butterfly antenna.

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