Reconfigurable terahertz detector, modulation method thereof, and array unit

Abstract

The present application relates to a reconfigurable terahertz detector, a modulation method thereof, and an array unit. The reconfigurable terahertz detector includes a ferroelectric transistor comprising a substrate, a ferroelectric layer, a gate, a source electrode, and a drain electrode. The ferroelectric layer is located between the substrate and the gate electrode, and the polarization degree of the ferroelectric layer is adjusted based on a pulse voltage signal input to the gate electrode, so that the operating gate voltage of the reconfigurable terahertz detector is adjustable. An antenna is conductively connected to the source electrode and the gate electrode. Thus, the operating gate voltage of the reconfigurable terahertz detector is adjusted using the ferroelectric transistor, thereby improving application flexibility.

Description

Technical Field

[0001] The present application relates to the field of terahertz detection technology, and in particular to a reconfigurable terahertz detector, a modulation method thereof, and an array unit. Background Art

[0002] Terahertz detectors have broad application prospects in areas such as terahertz wireless communications, imaging, and security inspection. Currently, transistor-based terahertz detectors have become a research hotspot in the field due to their high compatibility with existing semiconductor processes. Terahertz detectors primarily operate in two modes: resonant and non-resonant. The resonant mode exploits the shallow water wave resonance theory of the plasma wave within the transistor channel. The resonant frequency of the plasma wave can be varied with the gate voltage, allowing the gate voltage corresponding to the terahertz detector's peak photoresponse (the value at which detection is optimal) to vary with the terahertz wave frequency. This provides a certain degree of spectral resolution, but it typically requires low-temperature operation to maintain sufficiently long carrier energy relaxation times. The non-resonant mode relies on the self-mixing effect or second-order nonlinear response of carrier transport within the transistor channel to detect terahertz signals. Its advantages include broadband response, high responsivity, and room-temperature operation, making it highly practical.

[0003] In non-resonant detection mode, the peak photoresponse of a terahertz detector typically occurs near a specific gate voltage. This specific gate voltage is primarily determined by the differential characteristics of the transistor's channel conductance with respect to gate voltage, and ultimately by the device's material properties and manufacturing process. Therefore, for a given terahertz detector, the operating gate voltage required to reach its photoresponse peak is typically a fixed and unadjustable value, making terahertz detectors inflexible in practical applications. Summary of the Invention

[0004] In view of this, embodiments of the present application provide a reconfigurable terahertz detector, a modulation method thereof, and an array unit to solve at least one problem existing in the background technology.

[0005] In a first aspect, an embodiment of the present application provides a reconfigurable terahertz detector, comprising:

[0006] A ferroelectric transistor comprising a substrate, a ferroelectric layer, a gate, a source, and a drain, wherein the ferroelectric layer is located between the substrate and the gate, and the polarization degree of the ferroelectric layer is adjusted based on a pulse voltage signal input to the gate, so that the operating gate voltage of the reconfigurable terahertz detector is adjustable;

[0007] An antenna is conductively connected to the source and the gate.

[0008] In conjunction with the first aspect of the present application, in an optional embodiment, the material of the ferroelectric layer includes Al 1-x Sc x N; where 0.1≤x≤0.4.

[0009] In combination with the first aspect of the present application, in an optional implementation, the antenna includes a butterfly antenna, a dipole antenna, or a log-periodic spherical tooth antenna.

[0010] In combination with the first aspect of the present application, in an optional implementation manner, it further includes: a pre-voltage amplifier conductively connected to the drain.

[0011] In a second aspect, an embodiment of the present application provides a modulation method for a reconfigurable terahertz detector, using a reconfigurable terahertz detector as described in any one of the first aspects, the method comprising: grounding the source and the drain, regulating the pulse voltage signal input to the gate to adjust the polarization degree of the ferroelectric layer, and thereby adjusting the operating gate voltage of the reconfigurable terahertz detector; wherein the pulse voltage signal is used to apply an external electric field to the ferroelectric layer, and the external electric field is greater than the coercive electric field of the ferroelectric layer.

[0012] In conjunction with the second aspect of the present application, in an optional implementation, the pulse voltage signal includes a square wave pulse voltage signal.

[0013] In conjunction with the second aspect of the present application, in an optional embodiment, the pulse voltage signal includes at least one short pulse voltage signal, and the pulse width of the short pulse voltage signal is greater than the time required for the ferroelectric domain in the ferroelectric layer to flip;

[0014] The regulating the pulse voltage signal input to the gate to adjust the polarization degree of the ferroelectric layer includes: regulating the number of the short pulse voltage signal input to the gate to adjust the polarization degree of the ferroelectric layer.

[0015] In combination with the second aspect of the present application, in an optional implementation manner, the number of the short pulse voltage signals ranges from 1 to 10.

[0016] In combination with the second aspect of the present application, in an optional embodiment, the thickness of the ferroelectric layer is 20 nm; the voltage amplitude range of the pulse voltage signal includes 10 V to 15 V, and the pulse width range of the pulse voltage signal includes 0.5 ms to 10 ms.

[0017] In a third aspect, an embodiment of the present application provides a reconfigurable terahertz detector array unit, comprising a plurality of reconfigurable terahertz detectors arranged in an array as described in any one of the first aspects; wherein, in each row of the reconfigurable terahertz detectors, the polarization degree of the ferroelectric layer of at least one row of the reconfigurable terahertz detectors is different, so that the operating gate voltage of the reconfigurable terahertz detectors is different; or, in each column of the reconfigurable terahertz detectors, the polarization degree of the ferroelectric layer of at least one column of the reconfigurable terahertz detectors is different, so that the operating gate voltage of the reconfigurable terahertz detectors is different.

[0018] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0019] On the one hand, the reconfigurable terahertz detector provided in the embodiment of the present application includes a ferroelectric transistor having a ferroelectric layer, and the polarization degree of the ferroelectric layer can be adjusted by a pulse voltage signal input to the gate, thereby regulating the electron concentration in the channel of the ferroelectric transistor and changing the threshold voltage of the ferroelectric transistor, thereby making the working gate voltage of the reconfigurable terahertz detector adjustable; thereby, multi-modal and low-power operation of the same device under different gate voltages can be achieved without changing the device structure, greatly improving the application flexibility of the reconfigurable terahertz detector and further improving the flexibility and simplicity of circuit design; and, the polarization degree of the ferroelectric layer can continue to be maintained after the external pulse voltage signal is cancelled, so that the working gate voltage of the reconfigurable terahertz detector can remain stable after each adjustment, thereby ensuring the stability of the reconfigurable terahertz detector.

[0020] In the second aspect, the modulation method of the reconfigurable terahertz detector provided in the embodiment of the present application uses the reconfigurable detector as described in the first aspect, by grounding the source and drain, inputting a pulse voltage signal to the gate, the pulse voltage signal is used to apply an external electric field to the ferroelectric layer, controlling the external electric field to be greater than the coercive electric field of the ferroelectric layer, so that the polarization direction of the ferroelectric layer can be flipped, and regulating the pulse voltage signal can regulate the external electric field to adjust the polarization degree of the ferroelectric layer, thereby regulating the electron concentration in the channel of the ferroelectric transistor, changing the threshold voltage of the ferroelectric transistor, and finally adjusting the working gate voltage of the reconfigurable terahertz detector; thereby, multi-modal and low-power operation of the same device at different gate voltages can be achieved without changing the device structure, greatly improving the application flexibility of the reconfigurable terahertz detector, and further improving the flexibility and simplicity of circuit design; and, the polarization degree of the ferroelectric layer can continue to be maintained after the external pulse voltage signal is cancelled, so that the working gate voltage of the reconfigurable terahertz detector can remain stable after each reconstruction, thereby ensuring the stability of the reconfigurable terahertz detector.

[0021] In a third aspect, the reconfigurable terahertz detector array unit provided in the embodiment of the present application is provided with a plurality of reconfigurable terahertz detectors arranged in an array as described in the first aspect. The reconfigurable terahertz detector includes a ferroelectric transistor having a ferroelectric layer. The polarization degree of the ferroelectric layer can be adjusted by a pulse voltage signal input to the gate, thereby regulating the electron concentration in the channel of the ferroelectric transistor, changing the threshold voltage of the ferroelectric transistor, and ultimately making the working gate voltage of the reconfigurable terahertz detector adjustable; thereby, multi-modal and low-power operation of the same device under different gate voltages can be achieved without changing the device structure, greatly improving the reconfigurable terahertz detector. The application flexibility is improved, and the flexibility and simplicity of circuit design are further improved; moreover, the polarization degree of the ferroelectric layer can continue to be maintained after the applied pulse voltage signal is cancelled, so that the working gate voltage of the reconfigurable terahertz detector can remain stable after each adjustment, thereby ensuring the stability of the reconfigurable terahertz detector; by setting the polarization degree of the ferroelectric layer of the reconfigurable terahertz detectors in each row (column) of the reconfigurable terahertz detectors to be different, so that the working gate voltage of the reconfigurable terahertz detectors in the row (column) is different, thereby enabling rapid addressing through selective working gate voltage when the reconfigurable terahertz detector array unit reads the signal.

[0022] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0024] Figure 1 A schematic diagram of the structure of a reconfigurable terahertz detector provided in an embodiment of the present application;

[0025] Figure 2 A schematic cross-sectional structure diagram of a ferroelectric high electron mobility transistor provided as a specific example;

[0026] Figure 3 A schematic cross-sectional view of an epitaxial structure of a ferroelectric high electron mobility transistor is provided as a specific example;

[0027] Figure 4 Schematic diagram of the energy band of the positive prepolarized ferroelectric layer;

[0028] Figure 5 Schematic diagram of the energy band of the negatively prepolarized ferroelectric layer;

[0029] Figure 6is the characteristic curve of the conductance variation with gate voltage of the ferroelectric high electron mobility transistor;

[0030] Figure 7 For Figure 6 The corresponding conductivity versus gate voltage differential characteristic curve.

[0031] Description of reference numerals:

[0032] 10. Ferroelectric transistor; 100. Substrate; 200. Nucleation layer; 300. Channel layer; 400. Insertion layer; 500. Ferroelectric layer; 600. Capping layer; 710. Source contact structure; 720. Drain contact structure; 810. Gate; 820. Source; 830. Drain; 811. Gate lead electrode; 821. Source lead electrode; 831. Drain lead electrode; 20. Antenna; 30. Preamplifier. DETAILED DESCRIPTION

[0033] The exemplary embodiments disclosed herein will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the specific embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0034] In the following description, numerous specific details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present application; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures described in detail.

[0035] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0036] When an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. Although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be represented as the second element, component, region, layer, or part. However, when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present application.

[0037] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of an element or feature shown in the figures to other elements or features. In addition to the orientations shown in the figures, spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the drawings is turned over, then, the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the above and below orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0038] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present application. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0039] In order to fully understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below. However, in addition to these detailed descriptions, the present application may also have other implementation methods.

[0040] The present invention provides a reconfigurable terahertz detector. Figure 1 and Figure 2 , the reconfigurable terahertz detector includes:

[0041] The ferroelectric transistor 10 includes a substrate 100, a ferroelectric layer 500, a gate 810, a source 820 and a drain 830. The ferroelectric layer 500 is located between the substrate 100 and the gate 810. The polarization degree of the ferroelectric layer 500 is adjusted based on the pulse voltage signal input to the gate 810 so that the operating gate voltage of the reconfigurable terahertz detector can be adjusted; the antenna 20 is conductively connected to the source 820 and the gate 810.

[0042] The embodiment of the present application utilizes a ferroelectric transistor with a ferroelectric layer to form a reconfigurable terahertz detector. Since the polarization degree of the ferroelectric layer can be adjusted by a pulse voltage signal input to the gate, the electron concentration in the channel of the ferroelectric transistor can be controlled, the threshold voltage of the ferroelectric transistor can be changed, and then the working gate voltage of the terahertz detector based on the ferroelectric transistor can be adjusted, and finally a reconfigurable terahertz detector is obtained; thereby, multi-modal and low-power operation of the same device under different gate voltages can be achieved without changing the device structure, which greatly improves the application flexibility of the reconfigurable terahertz detector and further improves the flexibility and simplicity of circuit design; and, the polarization degree of the ferroelectric layer can continue to be maintained after the applied pulse voltage signal is canceled, so that the working gate voltage of the reconfigurable terahertz detector can remain stable after each adjustment, thereby ensuring the stability of the reconfigurable terahertz detector.

[0043] Understandably, the polarization of the ferroelectric layer manifests itself microscopically as the reversal of ferroelectric domains within the ferroelectric layer. The non-centrosymmetry of the ferroelectric material's unit cell structure causes the centers of positive and negative charges to misalign, spontaneously generating an electric dipole moment, or spontaneous polarization. When an external electric field is applied, the ferroelectric domains undergo reversal under the influence of the applied electric field. The greater the strength of the applied electric field, the greater the number of ferroelectric domain reversals and the higher the polarization of the ferroelectric layer. Therefore, the polarization of the ferroelectric layer can be controlled by regulating the strength of the applied electric field. Furthermore, when the electric field is reduced to zero, the polarization strength of the ferroelectric material does not decrease to zero, but rather remains at a residual value, known as the remanent polarization value Pr. Consequently, the electrical properties of the ferroelectric transistor are maintained long after each adjustment, demonstrating its non-volatile nature.

[0044] Understandably, when a given terahertz detector is used, in order to achieve its function, it is usually necessary to design peripheral circuits based on the operating gate voltage of the terahertz detector to ensure optimal detection results. However, this increases the complexity of the peripheral circuits and the difficulty of circuit design. In an embodiment of the present application, a ferroelectric transistor is used as the transistor constituting the terahertz detector. When the threshold voltage of the ferroelectric transistor is adjustable, the operating gate voltage of the terahertz detector can also be adjusted, resulting in a reconfigurable terahertz detector. When a reconfigurable terahertz detector is used, the operating gate voltage of the reconfigurable terahertz detector can be adjusted accordingly based on the conditions of the peripheral circuits, and the reconfigurable terahertz detector can be adapted to various peripheral circuits.

[0045] Optionally, the ferroelectric transistor includes FeHEMT (Ferroelectric High Electron Mobility Transistor), FeMOSFET (Ferroelectric Metal-Oxide-Semiconductor Field Effect Transistor), and Fe2D-FET (Ferroelectric Two-Dimensional Field Effect Transistor).

[0046] In some embodiments, a FeHEMT includes a substrate, a nucleation layer, a channel layer, a barrier layer, a gate, a source, and a drain. At least a portion of the barrier layer is made of a ferroelectric material. In one specific example, the entire barrier layer is made of a ferroelectric material, forming a ferroelectric layer. Thus, the ferroelectric layer acts as a barrier layer, forming a heterojunction structure with the channel layer.

[0047] In some embodiments, a FeMOSFET includes a substrate, a gate dielectric layer, a ferroelectric layer, a gate, a source electrode, and a drain electrode. The ferroelectric layer may be made of at least one of the following materials: HfZrO2, ZrMgO, MgZnO, and BaTiO3. In actual fabrication, the ferroelectric layer may be grown by atomic layer deposition and annealed at a certain temperature to obtain ferroelectric properties. For example, for HfZrO2, after deposition, the layer may be annealed at approximately 300°C.

[0048] In some embodiments, an Fe2D-FET includes a substrate, a two-dimensional material channel layer, a ferroelectric layer, a gate, a source electrode, and a drain electrode. The material of the two-dimensional material channel layer may include at least one of the following: graphene, MoSe2, MoS2, WS2, and WSe2; the material of the ferroelectric layer may include at least one of the following: HfZrO2, AlBN, and GaScN. In some embodiments, the Fe2D-FET further includes a gate dielectric layer located between the ferroelectric layer and the gate. The gate dielectric layer may include Al2O3 and / or HfO2.

[0049] Next, the reconfigurable terahertz detector will be specifically described by taking the ferroelectric transistor FeHEMT as a specific example.

[0050] The substrate 100 may be made of semiconductor materials such as Si, SiC, GaN, and AlN, or may include multilayer structures formed of these semiconductor materials, such as GaN on SiC (gallium nitride on silicon carbide) and AlN on SiC (aluminum nitride on silicon carbide). It may also include sapphire. This embodiment of the present application is not limited to this. Optionally, the thickness of the substrate 100 ranges from 300 μm to 500 μm.

[0051] The material of the channel layer 300 may include GaN. Optionally, the thickness of the channel layer 300 ranges from 300 nm to 1500 nm. The ferroelectric layer 500 and the channel layer 300 form a heterojunction structure, and a two-dimensional electron gas (2DEG) is formed on the side of the channel layer 300 close to the ferroelectric layer 500. Figure 2 structure shown by the dashed line).

[0052] In some embodiments, the material of the ferroelectric layer 500 may include Al 1-x Sc x N; wherein, 0.1≤x≤0.4. It can be understood that the Sc content has a great influence on the ferroelectric properties of the ferroelectric layer 500. If the Sc content is too low, the ferroelectricity of the ferroelectric layer 500 is not obvious. When the Sc content exceeds a certain value, a cubic phase of a non-ferroelectric phase will appear, which weakens the ferroelectricity of the ferroelectric layer 500. Therefore, with the increase of the Sc content, the ferroelectricity of AlScN shows a trend of first strengthening and then weakening. Furthermore, 0.15≤x≤0.25. Controlling the Sc content within this range makes Al 1-x Sc x The lattice matching between N and GaN is improved, and Al 1- x Sc x The large defects in N are reduced, which ensures the crystal quality and is more conducive to ensuring the ferroelectricity of the ferroelectric layer 500.

[0053] In a specific example, x=0.18. It can be understood that Al 0.82 Sc0.18 N and GaN have a high lattice matching degree, and defects are minimal and gate leakage is relatively small. Therefore, the ferroelectricity of the ferroelectric layer 500 can reach a relatively optimal value while improving the crystal quality of the ferroelectric layer 500.

[0054] It can be understood that the material of the barrier layer in conventional HEMT can be AlGaN, GaN and AlGaN to form a heterojunction structure. AlGaN and GaN are both materials with non-centrosymmetric lattice structures (hexagonal wurtzite structure), so they can generate electric dipole moments, that is, there is spontaneous polarization; when these materials are subjected to mechanical stress (such as stress caused by lattice mismatch), piezoelectric polarization will also be generated. The superposition of spontaneous polarization and piezoelectric polarization forms a significant built-in electric field at the AlGaN / GaN heterojunction, forming polarized charges at the heterojunction interface, attracting free electrons and forming a two-dimensional electron gas (2DEG). AlScN is a wurtzite ferroelectric material, and a built-in electric field can also be formed at the AlScN / GaN heterojunction. AlScN has extremely strong intrinsic ferroelectricity compared to AlGaN, and its spontaneous polarization intensity and piezoelectric polarization intensity are higher, so a higher concentration of 2DEG can be obtained, resulting in better device performance. Specifically, the electron mobility range of the room temperature two-dimensional electron gas is 1000cm 2 / (V·s) to 1600cm 2 / (V·s), the electron surface density range is 2×10 13 cm -2 to 4×10 13 cm -2 .

[0055] Furthermore, AlScN has two independent spontaneous polarization states, namely, ferroelectric polarization upward (+P, metal polarity) and downward (-P, nitrogen polarity). These two states are defined by thermodynamics, that is, these two polarization states are at the lowest free energy value under ideal conditions, that is, thermodynamically stable phases. AlScN has a large remanent polarization strength Pr (80μC / cm 2 to 110μC / cm 2 ) and coercive electric field Ec (1.8MV / cm), as well as a low heat treatment temperature (<400℃), and the ferroelectricity remains stable at 400℃, with good CMOS (Complementary Metal Oxide Semiconductor) compatibility and third-generation semiconductor compatibility.

[0056] Optionally, the thickness of the ferroelectric layer 500 is in the range of 5 nm to 20 nm. 13 cm -2 When the AlScN is thicker, the electron concentration is higher.

[0057] Please refer to Figure 2 The FeHEMT may further include a nucleation layer 200 located between the substrate 100 and the channel layer 300. The nucleation layer 200 may be made of AlN.

[0058] Optionally, the thickness of the nucleation layer 200 ranges from 2 nm to 50 nm.

[0059] The FeHEMT may also include an insertion layer 400, located between the channel layer 300 and the ferroelectric layer 500. The insertion layer 400 may be made of AlN. As can be appreciated, the insertion layer 400 has a significant impact on the performance of the FeHEMT. On the one hand, the insertion layer 400 introduces greater band bending and piezoelectric polarization, resulting in a higher concentration of the 2DEG. On the other hand, the insertion layer 400 reduces severe alloy scattering at the heterojunction interface of the ferroelectric layer 500, resulting in higher 2DEG mobility.

[0060] Optionally, the insertion layer 400 has a thickness ranging from 1 nm to 2 nm.

[0061] The FeHEMT may further include a cap layer 600 located on a side of the ferroelectric layer 500 away from the channel layer 300. The material of the cap layer 600 may include GaN.

[0062] Optionally, the capping layer 600 has a thickness ranging from 2 nm to 3 nm.

[0063] The FeHEMT may further include a source ohmic contact structure 710 and a drain ohmic contact structure 720 that extend through the ferroelectric layer 500 and into the channel layer 300. The source ohmic contact structure 710 and the drain ohmic contact structure 720 are electrically connected to the 2DEG. The source ohmic contact structure 710 is electrically connected to the source electrode 820, and the drain ohmic contact structure 720 is electrically connected to the drain electrode 830.

[0064] The gate 810 , the source 820 , and the drain 830 are all made of metal.

[0065] When preparing FeHEMT, please refer to Figure 3 , a nucleation layer 200, a channel layer 300, an insertion layer 400, a ferroelectric layer 500, and a cap layer 600 can be sequentially epitaxially grown on a substrate 100 to obtain a FeHEMT epitaxial structure. Next, a first photoresist layer is formed on the FeHEMT epitaxial structure, and the first photoresist layer is exposed and developed to form a patterned first photoresist layer; using the patterned first photoresist layer as a mask, the FeHEMT epitaxial structure is etched to form a mesa structure, which includes the nucleation layer 200, the channel layer 300, the insertion layer 400, the ferroelectric layer 500, and the cap layer 600; and the first photoresist layer is removed. Then, please refer to Figure 2A source ohmic contact structure 710 and a drain ohmic contact structure 720 are formed at the edge of the mesa structure. The source ohmic contact structure 710 and the drain ohmic contact structure 720 sequentially penetrate the cap layer 600, the ferroelectric layer 500, and the insertion layer 400 and extend into the channel layer 300, thereby conducting with the 2DEG. Finally, a second photoresist layer is formed and exposed or subjected to electron beam lithography, followed by development and fixing to form a patterned second photoresist layer. A metal layer is deposited, and a metal lift-off process is performed to form the gate 810, source 820, and drain 830.

[0066] Optionally, the antenna 20 includes a butterfly antenna, a dipole antenna, or a log-periodic scalloped antenna, thereby facilitating coupling of electromagnetic waves in free space to the ferroelectric transistor to achieve terahertz detection function. Figure 1 Detailed description is given of the case where the antenna 20 is a butterfly antenna.

[0067] In some embodiments, the gate 810 , the source 820 , the drain 830 , and the antenna 20 are all made of metal. The gate 810 , the source 820 , the drain 830 , and the antenna 20 can be formed in the same process based on the same material layer.

[0068] The reconfigurable terahertz detector may also include lead electrodes, including a gate lead electrode 811, a source lead electrode 821, and a drain lead electrode 831, which are electrically connected to the gate 810, source 820, and drain 830, respectively. During the packaging stage, wire bonding can be performed using the lead electrodes to electrically connect the reconfigurable terahertz detector to the packaging frame. Antenna 20 is electrically connected to gate lead electrode 811 and source lead electrode 821.

[0069] Optionally, the reconfigurable terahertz detector further includes: a pre-voltage amplifier 30, which is conductively connected to the drain 830. Figure 1 As shown, when the reconfigurable terahertz detector is working, the source 820 is grounded and the gate 810 is set at the working gate voltage V G The drain 830 is externally connected to a pre-voltage amplifier. The pre-voltage amplifier 30 can amplify the photovoltage signal, thereby improving the signal-to-noise ratio of the weak photovoltage signal and thus improving the measurement accuracy of the reconfigurable terahertz detector.

[0070] The present application also provides a modulation method for a reconfigurable terahertz detector, using the reconfigurable terahertz detector described above. The method includes:

[0071] The source and drain are grounded, and the pulse voltage signal of the input gate is regulated to adjust the polarization degree of the ferroelectric layer, and then adjust the operating gate voltage of the reconfigurable terahertz detector; wherein the pulse voltage signal is used to apply an external electric field to the ferroelectric layer, and the external electric field is greater than the coercive electric field of the ferroelectric layer.

[0072] The embodiment of the present application grounds the source and drain to regulate the pulse voltage signal of the input gate. The pulse voltage signal is used to apply an external electric field to the ferroelectric layer, and controls the external electric field to be greater than the coercive electric field of the ferroelectric layer, so that the polarization direction of the ferroelectric layer can be flipped to adjust the polarization degree of the ferroelectric layer, thereby regulating the electron concentration in the channel of the ferroelectric transistor, changing the threshold voltage of the ferroelectric transistor, and ultimately regulating the working gate voltage of the reconfigurable terahertz detector; thereby, multi-modal and low-power operation of the same device at different gate voltages can be achieved without changing the device structure, greatly improving the application flexibility of the reconfigurable terahertz detector, and further improving the flexibility and simplicity of circuit design; and, the polarization degree of the ferroelectric layer can continue to be maintained after the external pulse voltage signal is canceled, so that the working gate voltage of the reconfigurable terahertz detector can remain stable after each adjustment, thereby ensuring the stability of the reconfigurable terahertz detector.

[0073] The non-centrosymmetric unit cell structure of ferroelectric materials causes the centers of positive and negative charges to misalign, resulting in a spontaneous electric dipole moment, or spontaneous polarization. Because the polarization orientations of ferroelectric materials are initially irregular, the macroscopic appearance of a zero polarization intensity (the electric dipole moment per unit volume is called the spontaneous polarization intensity) is apparent. Under the action of an external electric field, the spontaneous polarization orientations gradually converge, and the polarization intensity gradually increases. When the external electric field is sufficiently large, the polarization intensity reaches a saturation value, known as the saturation polarization value. Applying an external electric field in the opposite direction of the spontaneous polarization returns the polarization intensity to zero. At this point, the electric field is called the coercive field Ec of the ferroelectric material, which reflects the material's ability to resist polarization reversal. As can be understood, ferroelectric domain reversal occurs only when the applied electric field strength exceeds the coercive field Ec of the ferroelectric material. When the applied electric field reaches a certain negative value, the polarization intensity approaches saturation. Therefore, the degree of polarization in the ferroelectric layer can be controlled by regulating the applied electric field strength. Furthermore, when the electric field is reduced to zero, the polarization strength of the ferroelectric material does not decrease to zero, but has a residual value, known as the remanent polarization. Therefore, the electrical properties of the ferroelectric transistor can be maintained for a long time after each adjustment, making it non-volatile.

[0074] Next, the modulation method of the reconfigurable terahertz detector will be described in detail by taking the ferroelectric transistor FeHEMT as a specific example.

[0075] Figure 4 Schematic diagram of the energy band of the positive prepolarized ferroelectric layer; Figure 5 is the energy band diagram of the negative prepolarized ferroelectric layer. It should be noted that Figure 4 "+V G " refers to the gate voltage being positive relative to the channel of the FeHEMT, Figure 5 "-V G” means that the gate voltage is negative relative to the channel of FeHEMT; Figure 4 and Figure 5 Specifically shown is a multilayer material structure of a gate 810 , a cap layer 600 , a ferroelectric layer 500 , an insertion layer 400 , and a channel layer 300 in a FeHEMT.

[0076] When the source and drain are grounded, a positive pulse voltage signal is applied to the gate, so that the gate is at a positive voltage relative to the channel of the FeHEMT, and positive prepolarization is performed. The polarization field direction in the ferroelectric layer 500 is as follows: Figure 4 As shown by the middle arrow, it points from the gate 810 to the channel layer 300. Correspondingly, when a positive pulse voltage signal is applied, the gate potential is lower than the channel potential; in the case of positive prepolarization, negative polarization charges are distributed on the side of the ferroelectric layer 500 close to the gate 810, and positive polarization charges are distributed on the side of the ferroelectric layer 500 close to the channel layer 300. The positive polarization charges will attract more electrons to the side of the channel layer 300 close to the ferroelectric layer 500, thereby increasing the channel electron concentration. Therefore, when the FeHEMT is working after positive prepolarization, a stronger reverse gate voltage needs to be applied to offset the attraction of the positive polarization charges on electrons compared to the HEMT without prepolarization treatment, so as to deplete the electrons in the channel, that is, the threshold voltage of the FeHEMT after positive prepolarization moves in the negative direction.

[0077] When the source and drain are grounded, a negative pulse voltage signal is applied to the gate 810, so that the gate is at a negative voltage relative to the channel of the FeHEMT, thereby performing negative prepolarization. The polarization field direction in the ferroelectric layer 500 is as follows: Figure 5 As shown by the middle arrow, it points from the channel layer 300 to the gate 810. Correspondingly, when a negative pulse voltage signal is applied, the potential of the gate is higher than the channel potential; in the case of negative prepolarization, the side of the ferroelectric layer 500 close to the gate 810 is distributed with positive polarization charges, and the side of the ferroelectric layer 500 close to the channel layer 300 is distributed with negative polarization charges. The negative polarization charges repel some electrons in the channel, thereby reducing the channel electron concentration. Therefore, when the FeHEMT is working after negative prepolarization, applying a smaller negative gate voltage can deplete the remaining electrons in the channel compared to the HEMT without prepolarization treatment, that is, the threshold voltage of the FeHEMT moves in the positive direction after negative prepolarization. It should be noted that after the epitaxy of the FeHEMT is completed, due to the spontaneous polarization of the ferroelectric layer and the piezoelectric polarization caused by the strain of the heterojunction interface, the intrinsic two-dimensional electron gas with a higher concentration in the channel cannot be completely depleted of electrons in the channel after negative prepolarization. Therefore, Figure 5 The energy bands shown are not the final equilibrium states but the intermediate states shown to illustrate the negative prepolarization. In order to more clearly illustrate the situation where some electrons in the channel are repelled, Figure 5 In the figure, holes are used as an illustration in the channel layer 300 .

[0078] Next, we will take negative prepolarization as an example to explain the changes in the electrical characteristics of FeHEMT. Figure 6 and Figure 7 . Figure 6 is the characteristic curve of the conductance variation with gate voltage of the ferroelectric high electron mobility transistor; Figure 7 For Figure 6 The corresponding conductivity versus gate voltage differential characteristic curve. It should be noted that, Figure 6 and Figure 7 The gate voltage V G It refers to the gate voltage when FeHEMT is operating.

[0079] Please refer to Figure 6 , after the FeHEMT is negatively prepolarized, the threshold voltage moves to a more positive direction (closer to 0V) compared to the case of no polarization. Correspondingly, please refer to Figure 7 , dG / dV of FeHEMT G The peak value also moves in a more positive direction (close to 0V) compared to the case of non-polarization treatment. For the terahertz detector based on FeHEMT, the theoretical value of its photoresponse voltage is Δu∝G -1 × (dG / dV G ), where G is the channel conductance of the ferroelectric transistor, V G is the gate voltage of the ferroelectric transistor. The peak value of the photoresponse voltage corresponds to V G is the working gate voltage of the reconfigurable terahertz detector (in this field, the working gate voltage is usually set to V corresponding to the peak value of the photoresponse voltage). G More positive pressure). Therefore, Figure 7 This reflects the change in the photoresponse voltage, and thus the change in the operating gate voltage of the reconfigurable terahertz detector. Understandably, after negative prepolarization, the operating gate voltage of the reconfigurable terahertz detector shifts toward a more positive direction (closer to 0V) compared to when it was not polarized. This reduces gate leakage current, the noise current of the reconfigurable terahertz detector, and the power consumption of the reconfigurable terahertz detector, enabling low-power operation.

[0080] It can be understood that the two extreme prepolarizations of positive prepolarization and negative prepolarization mentioned above correspond to the situations where the ferroelectric layer is completely polarized or the ferroelectric layer in the ferroelectric layer is completely flipped. In the actual modulation process, the pulse voltage signal of the input gate can be regulated to control the polarization degree of the ferroelectric layer, thereby regulating the electron concentration in the channel of the ferroelectric transistor, so that the FeHEMT threshold voltage can be in the middle of the two extreme cases mentioned above, so that the reconfigurable terahertz detector can operate under different gate voltages, thereby meeting the actual circuit needs.

[0081] Optionally, the pulse voltage signal includes a square wave pulse voltage signal. This makes it easier to control the pulse voltage signal. Of course, the embodiment of the present application does not exclude the case where the pulse voltage signal includes a triangular wave pulse voltage signal.

[0082] Optionally, the pulse voltage signal includes at least one short pulse voltage signal, the pulse width of the short pulse voltage signal being greater than the time required for the ferroelectric domain in the ferroelectric layer to flip; regulating the pulse voltage signal of the input gate to adjust the polarization degree of the ferroelectric layer includes: regulating the number of short pulse voltage signals of the input gate to adjust the polarization degree of the ferroelectric layer. It is understandable that ferroelectric domain flipping is discrete, and a single short pulse voltage signal may not be able to completely flip all ferroelectric domains. The cumulative effect of multiple consecutive short pulse voltage signals can gradually approach the target polarization state to achieve metastable state control; and the polarization degree of the ferroelectric layer can be adjusted by regulating the number of short pulse voltage signals of the input gate. The more short pulses input, the more thorough the polarization. Compared with readjusting the pulse voltage signal for each prepolarization, the modulation method of the embodiment of the present application has more precise control over the polarization degree of the ferroelectric layer and is more convenient to operate; controlling the pulse width of the short pulse voltage signal (single polarization time) to be greater than the flipping time of the ferroelectric domain avoids the short pulse voltage signal pulse width being too short, resulting in the invalidation of the single prepolarization performed by the single short pulse voltage signal. During actual modulation, the voltage amplitude and pulse width of each short pulse voltage signal can be flexibly adjusted, which is more conducive to accurately controlling the polarization degree of the ferroelectric layer.

[0083] Optionally, the number of short pulse voltage signals ranges from 1 to 10. Furthermore, the number of short pulse voltage signals ranges from 3 to 5. It is understandable that if the number of short pulse voltage signals is too small, it may be difficult to achieve complete polarization, and the range of regulating the polarization degree of the ferroelectric layer is insufficient; if the number of short pulse voltage signals is too large, repeated loading of pulse energy may cause material fatigue and degradation, resulting in heat accumulation and material delamination; therefore, controlling the number of short pulse voltage signals within this range is more conducive to achieving the desired effect.

[0084] In some embodiments, the thickness of the ferroelectric layer is 5 nm; the voltage amplitude of the pulse voltage signal ranges from 4 V to 6 V; and the pulse width of the pulse voltage signal ranges from 0.5 ms to 10 ms.

[0085] In some embodiments, the thickness of the ferroelectric layer is 20 nm; the voltage amplitude of the pulse voltage signal ranges from 10 V to 15 V, and the pulse width of the pulse voltage signal ranges from 0.5 ms to 10 ms.

[0086] It can be understood that the external electric field at the ferroelectric layer is related to the thickness of the ferroelectric layer and the voltage amplitude of the pulse voltage signal. The thicker the ferroelectric layer, the larger the voltage amplitude of the required pulse voltage signal. Therefore, during actual modulation, it is necessary to set a suitable pulse voltage signal according to the thickness of the ferroelectric layer. For a 20nm thick ferroelectric layer, controlling the voltage amplitude of the pulse voltage signal within the range of 10V to 15V can ensure that the external electric field is greater than the coercive electric field of the ferroelectric layer, so that the ferroelectric domain can be flipped, and the pulse voltage signal can be prevented from being too high and causing breakdown, thereby increasing leakage current; controlling the pulse width of the pulse voltage signal within the range of 0.5ms to 10ms can ensure that the pulse width of the pulse voltage signal is greater than the time required for the ferroelectric domain to flip, so that the ferroelectric domain can flip, and the pulse energy impact time can be prevented from being too long, thereby causing heat accumulation; ultimately, polarization controllability and device reliability are guaranteed.

[0087] An embodiment of the present application also provides a reconfigurable terahertz detector array unit, comprising a plurality of reconfigurable terahertz detectors as described above arranged in an array; wherein, in each row of reconfigurable terahertz detectors, the polarization degree of the ferroelectric layer of at least one row of reconfigurable terahertz detectors is different, so that the operating gate voltage of the reconfigurable terahertz detectors is different; or, in each column of reconfigurable terahertz detectors, the polarization degree of the ferroelectric layer of at least one column of reconfigurable terahertz detectors is different, so that the operating gate voltage of the reconfigurable terahertz detectors is different.

[0088] It can be understood that the reconfigurable terahertz detector includes a ferroelectric transistor having a ferroelectric layer, and the polarization degree of the ferroelectric layer of the ferroelectric transistor can be adjusted by a pulse voltage signal input to the gate, thereby regulating the electron concentration in the channel of the ferroelectric transistor, changing the threshold voltage of the ferroelectric transistor, and ultimately adjusting the working gate voltage of the reconfigurable terahertz detector; thereby, multi-modal and low-power operation of the same device under different gate voltages can be achieved without changing the device structure, greatly improving the application flexibility of the reconfigurable terahertz detector and further improving the flexibility and simplicity of circuit design; and, the polarization degree of the ferroelectric layer can continue to be maintained after the applied pulse voltage signal is removed, so that the working gate voltage of the reconfigurable terahertz detector can remain stable after each adjustment, thereby ensuring the stability of the reconfigurable terahertz detector; by setting the polarization degree of the ferroelectric layer of the reconfigurable terahertz detectors in each row (column) of the reconfigurable terahertz detectors to be different, so that the working gate voltage of the reconfigurable terahertz detectors in the row (column) is different, thereby enabling rapid addressing by selective working gate voltage when reading signals in the reconfigurable terahertz detector array unit.

[0089] In some embodiments, the polarization degree of the ferroelectric layer of each row of reconfigurable terahertz detectors is different, so that the operating gate voltage of the reconfigurable terahertz detectors is different; or the polarization degree of the ferroelectric layer of each column of reconfigurable terahertz detectors is different, so that the operating gate voltage of the reconfigurable terahertz detectors is different. This is more conducive to fast addressing.

[0090] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementation methods. Various modifications and changes may be made to the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present application that may not be explicitly described. Therefore, the above embodiments merely express several implementation methods of the present application and do not limit the scope of protection of the patent application.

Claims

1. A reconfigurable terahertz detector, characterized in that: include: A ferroelectric transistor comprising a substrate, a ferroelectric layer, a gate, a source, and a drain, wherein the ferroelectric layer is located between the substrate and the gate, and the polarization degree of the ferroelectric layer is adjusted based on a pulse voltage signal input to the gate, so that the operating gate voltage of the reconfigurable terahertz detector is adjustable; wherein the pulse voltage signal applies an external electric field to the ferroelectric layer, the external electric field is greater than the coercive electric field of the ferroelectric layer, and the pulse width of the pulse voltage signal is greater than the time required for ferroelectric domain switching in the ferroelectric layer; An antenna is conductively connected to the source and the gate.

2. The reconfigurable terahertz detector according to claim 1, characterized in that: The material of the ferroelectric layer includes Al 1-x Sc x N; where 0.1≤x≤0.

4.

3. The reconfigurable terahertz detector according to claim 1, characterized in that: The antenna includes a butterfly antenna, a dipole antenna or a log-periodic scalloped antenna.

4. The reconfigurable terahertz detector according to claim 1, characterized in that: Also includes: A pre-voltage amplifier is conductively connected to the drain.

5. A modulation method for a reconfigurable terahertz detector, using the reconfigurable terahertz detector according to any one of claims 1 to 4, characterized in that: The method comprises: The source and the drain are grounded, and the pulse voltage signal input to the gate is regulated to adjust the polarization degree of the ferroelectric layer, thereby adjusting the operating gate voltage of the reconfigurable terahertz detector; wherein the pulse voltage signal is used to apply an external electric field to the ferroelectric layer, and the external electric field is greater than the coercive electric field of the ferroelectric layer.

6. The modulation method of the reconfigurable terahertz detector according to claim 5, characterized in that: The pulse voltage signal includes a square wave pulse voltage signal.

7. The modulation method of the reconfigurable terahertz detector according to claim 5, characterized in that: The pulse voltage signal includes at least one short pulse voltage signal, wherein the pulse width of the short pulse voltage signal is greater than the time required for the ferroelectric domain in the ferroelectric layer to flip; The regulating the pulse voltage signal input to the gate to adjust the polarization degree of the ferroelectric layer includes: regulating the number of the short pulse voltage signal input to the gate to adjust the polarization degree of the ferroelectric layer.

8. The modulation method of the reconfigurable terahertz detector according to claim 7, characterized in that: The number of the short pulse voltage signals ranges from 1 to 10.

9. The modulation method of the reconfigurable terahertz detector according to claim 5, characterized in that: The thickness of the ferroelectric layer is 20 nm; the voltage amplitude range of the pulse voltage signal includes 10 V to 15 V, and the pulse width range of the pulse voltage signal includes 0.5 ms to 10 ms.

10. A reconfigurable terahertz detector array unit, characterized in that: The reconfigurable terahertz detectors according to any one of claims 1 to 4 are provided, comprising a plurality of array-arranged reconfigurable terahertz detectors; wherein, in each row of the reconfigurable terahertz detectors, the polarization degree of the ferroelectric layer of at least one row of the reconfigurable terahertz detectors is different, so that the operating gate voltages of the reconfigurable terahertz detectors are different; or, in each column of the reconfigurable terahertz detectors, the polarization degree of the ferroelectric layer of at least one column of the reconfigurable terahertz detectors is different, so that the operating gate voltages of the reconfigurable terahertz detectors are different.

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