Terahertz wave detector and terahertz wave detection method

Abstract

The application discloses a terahertz wave detector and a detection method of the terahertz wave. The terahertz wave detector comprises a semiconductor structure, a first electrode, a second electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna and a second antenna. The first antenna and the second antenna are arranged on the semiconductor structure at intervals and form Schottky contact with the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure are arranged between the first antenna and the second antenna and the semiconductor structure respectively. The first ohmic contact structure and the second ohmic contact structure form ohmic contact with the semiconductor structure and are electrically connected with the first antenna and the second antenna respectively. The first electrode and the second electrode are matched with the first antenna and the second antenna respectively. The detection method of the terahertz wave provided by the application adopts a bias working mode to detect the terahertz wave, and the bias working mode increases the stability of the device.

Description

Technical Field

[0001] This invention relates in particular to a terahertz wave detector and a method for detecting terahertz waves, belonging to the field of terahertz wave detection technology. Background Technology

[0002] The terahertz band refers to electromagnetic waves with frequencies ranging from 0.1 to 10 THz (wavelengths from 3 mm to 30 μm), falling between microwaves and infrared in the electromagnetic spectrum. This band represents a transition from microwave electronics to quantum optics; mature microwave and photonic technologies are difficult to apply, and the abundant spectrum and bandwidth resources within this band have not yet been effectively developed and utilized due to limitations in the development level of core components such as radiation sources and detectors. The development of high-speed, high-sensitivity terahertz wave detectors at room temperature will play a significant role in fields such as non-destructive security inspection, terahertz imaging, and 6G communications.

[0003] A terahertz wave detector coupled to an asymmetric dipole antenna, designed and fabricated based on AlGaN / GaN high-mobility field-effect transistors (HEMTs), has achieved significantly improved sensitivity through design modifications such as changing the gate-to-drain distance, using a thin barrier, and employing high-mobility InP material, based on self-mixing theory. Currently, the highest level achieved is 3.7 pW / Hz at room temperature. 1 / 2 The noise equivalent power (NEP) is low. However, this type of detector has a sensitivity as low as 1pW / Hz. 1 / 2 There has been a bottleneck in the development of this type of terahertz wave detector, so it is urgent to optimize the design of this type of terahertz wave detector and to conduct in-depth research on the mechanisms of electromagnetic field coupling and modulation.

[0004] In addition, the rise of two-dimensional materials such as graphene, black scale, and molybdenum disulfide has also injected new vitality into terahertz wave detectors. These detectors generate photocurrent by applying a bias voltage to the electrodes at both ends and using the non-equilibrium excitation of photothermal carriers in two-dimensional materials under terahertz irradiation. However, these detectors are still in the research and development stage and face challenges in terms of detection sensitivity and stability.

[0005] In existing inventions of asymmetric dipole antenna-coupled three-terminal terahertz wave detectors, the antenna design of the "room temperature terahertz wave detector" is composed of Schottky contacts, which is a capacitively coupled three-terminal terahertz wave detector (DET-1), and its structure is as follows: Figure 1a and Figure 1b As shown, in the commonly used asymmetric dipole antenna design of a three-terminal terahertz wave detector, the source-drain antenna is connected to the gate-controlled channel and the source-drain electrode composed of a two-dimensional electron gas through capacitive coupling. That is, the metal source-drain antenna fabricated on the AlGaN / GaN heterojunction surface and the two-dimensional electron gas form a large-area Schottky barrier capacitor. From the equivalent circuit diagram corresponding to the structural schematic in the figure, it can be seen that the channel resistance in the gate-controlled region is r. cThe photocurrent here is represented as i0(V g ), where i is the source-drain output current, which is related to the series resistance. The narrow active region under the dipole antenna will introduce a high source-drain series resistance r. s / r d Furthermore, these three-terminal HEMT detectors generally rely on the high transconductance characteristics of the subthreshold region of HEMT to achieve high responsivity and low current noise detection. In this operating mode, the device channel is almost in a pinch-off state, resulting in a large internal resistance, which is not conducive to the device's response bandwidth and matching with the back-end amplifier circuit. This will limit the device's application in demodulating high-speed pulse and high-speed terahertz modulated signals.

[0006] The three-terminal terahertz wave detector (DET-2) disclosed in Sun Yunfei et al.'s paper "A Terahertz Wave Detector" uses ohmic contacts that simultaneously serve as the source, drain, and antenna structures, as shown in the figure. Figure 2a and Figure 2b As shown, the purpose is to make the device structure compact and easy to integrate, as shown in the corresponding equivalent circuit diagram. Figure 2b It is clear that this design of depositing ohmic contacts on the antenna can reduce the series resistance between the 2DEG source / drain connection and the corresponding antenna region. However, the ohmic contact is flush with or as close as possible to the antenna edge near the gate control region, making it susceptible to the effects of high-temperature rapid annealing. After annealing, the ohmic contact deforms, resulting in poor conformal performance at the antenna tip near the gate, making it difficult to achieve controllable fabrication of the submicron-scale "antenna-gate" gap. As three-terminal terahertz wave detectors develop towards higher sensitivity, core dimensions such as gate length and the gap between the gate and the source / drain antenna tend to be smaller and smaller at the nanoscale, leading to problems such as high fabrication difficulty, poor process consistency, and reduced reliability.

[0007] Three-terminal field-effect terahertz detectors based on asymmetric antenna designs using self-mixing theory, whether capacitively coupled or using ohmic contacts as source, drain, and gate, primarily rely on the gate voltage to modulate the transconductance of the HEMT, outputting a terahertz response through the source and drain electrodes. The transconductance of the effective gate voltage in the gate-controlled region determines the field-effect factor of the detection intensity. At the optimal operating point gate voltage, the three-terminal terahertz detector achieves its best response. However, in this operating mode, the optimal operating point is located at the transconductance maximum, making it extremely sensitive to fluctuations in the device's gate voltage. Even small changes in gate voltage can cause a significant decrease in the device's response output (see...). Figure 3b This is detrimental to the application of the detector. Summary of the Invention

[0008] The main objective of this invention is to provide a terahertz wave detector and a method for detecting terahertz waves, thereby overcoming the shortcomings of the prior art.

[0009] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0010] This invention provides a terahertz wave detector, including a semiconductor structure, a first electrode, a second electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna, and a second antenna.

[0011] The semiconductor structure includes a channel layer and a barrier layer stacked together, and a carrier channel is formed in the semiconductor structure.

[0012] The first antenna and the second antenna are disposed at intervals on the semiconductor structure and both form Schottky contacts with the semiconductor structure;

[0013] The first ohmic contact structure and the second ohmic contact structure are respectively disposed between the first antenna, the second antenna and the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure form ohmic contacts with the semiconductor structure and are electrically connected to the first antenna and the second antenna respectively.

[0014] The first electrode and the second electrode are respectively engaged with the first antenna and the second antenna, and the first electrode and the second electrode are engaged with the semiconductor structure to form a high mobility field-effect transistor. The first electrode and the second electrode are electrically connected to the carrier channel through ohmic contact.

[0015] This invention also provides a terahertz wave detector, including a semiconductor structure, a first electrode, a second electrode, a third electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna, a second antenna, and a third antenna.

[0016] The semiconductor structure includes a channel layer and a barrier layer stacked together, and a carrier channel is formed in the semiconductor structure.

[0017] The first electrode, the second electrode, and the third electrode are disposed at intervals on the semiconductor structure and cooperate with the semiconductor structure to form a high mobility field-effect transistor structure. The first electrode and the second electrode are electrically connected to the carrier channel.

[0018] The first antenna, the second antenna, and the third antenna are spaced apart on the semiconductor structure and all form Schottky contacts with the semiconductor structure.

[0019] The first ohmic contact structure and the second ohmic contact structure are respectively disposed between the first antenna, the second antenna and the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure form ohmic contacts with the semiconductor structure and are electrically connected to the first antenna and the second antenna respectively.

[0020] The first antenna, the second antenna, and the third antenna are respectively engaged with the first electrode, the second electrode, and the third electrode, and the first antenna is also electrically connected to the third antenna.

[0021] This invention also provides a method for detecting terahertz waves, comprising:

[0022] The terahertz wave detector is provided by grounding one of the first and second electrodes and applying a working voltage to the other. The terahertz wave is detected by measuring whether the terahertz wave detector outputs a response current and the magnitude of the response current.

[0023] Compared with the prior art, the advantages of the present invention include:

[0024] 1) The terahertz wave detection method provided in this embodiment of the invention uses a bias voltage working mode to detect terahertz waves, which increases the stability of the terahertz wave detector.

[0025] 2) The terahertz wave detection method provided in this embodiment of the invention proposes a bias working mode for a three-terminal terahertz wave detector coupled with an asymmetric dipole antenna, replacing the working mode that relies on gate voltage to regulate the HEMT device to the optimal operating point in the subthreshold region. By applying a bias voltage in the mixing region, a suitable potential difference is obtained to regulate the terahertz response current output by the 2DEG channel. The stable bias voltage can keep the transconductance of the transistor stable within a certain range, avoiding the disadvantage that the optimal transconductance caused by the gate voltage is easily affected by small changes in the gate voltage, thus affecting the detector responsivity, making the optimal detection state more stable.

[0026] 3) The structure of the two-ended terahertz wave detector provided in this embodiment of the invention is simpler, which significantly reduces the complexity of device design, integrated array, and circuit.

[0027] 4) The two-terminal terahertz wave detector provided in this embodiment of the invention can avoid the difficulties in the asymmetric three-terminal antenna terahertz wave detector, such as the high process precision requirements of the gate and the difficulty in device fabrication, poor device yield and low reliability caused by the fabrication of the ohmic contact at the top of the antenna and the deformation of the antenna. Based on the optimization of core parameters such as antenna distance and field plate structure spacing, a terahertz wave detector with better performance and higher sensitivity can be obtained.

[0028] 5) The two-terminal terahertz wave detector provided in this embodiment of the invention can reduce the series resistance and output impedance of the device, which is beneficial for circuit impedance matching. Attached Figure Description

[0029] Figure 1a This is a schematic diagram and equivalent circuit diagram of a capacitively coupled three-terminal terahertz wave detector (DET-1) in the prior art;

[0030] Figure 1b This is an equivalent circuit diagram of a capacitively coupled three-terminal terahertz wave detector (DET-1) in the prior art.

[0031] Figure 2a This is a schematic diagram of the structure of a three-terminal terahertz wave detector (DET-2) with ohmic contacts deposited on the antenna in the prior art;

[0032] Figure 2b This is the equivalent circuit diagram of a three-terminal terahertz wave detector (DET-2) with ohmic contacts deposited on the antenna in the prior art;

[0033] Figure 3a The localized mixing electric field distribution induced by the AlGaN / GaNHEMT three-terminal terahertz wave detector antenna (simulation results);

[0034] Figure 3b These are the transconductance curves of a three-terminal terahertz wave detector under different source-drain bias and gate voltage.

[0035] Figure 4a and Figure 4b These are, respectively, a schematic diagram and an equivalent circuit diagram of a three-terminal terahertz wave detector operating under source-drain bias provided in Embodiment 1 of the present invention;

[0036] Figure 5a and Figure 5b These are, respectively, a planar schematic diagram and a cross-sectional schematic diagram of a terahertz wave detector at both ends of an AlGaN / GaN HEMT provided in Embodiment 2 of the present invention;

[0037] Figure 5c This is an equivalent circuit diagram of a terahertz wave detector at both ends of an AlGaN / GaN HEMT provided in Embodiment 2 of the present invention;

[0038] Figure 6a and Figure 6b These are, respectively, a planar schematic diagram and a cross-sectional schematic diagram of a terahertz wave detector at both ends of an AlGaN / GaN HEMT provided in Embodiment 3 of the present invention;

[0039] Figure 6c This is an equivalent circuit diagram of a terahertz wave detector at both ends of an AlGaN / GaN HEMT provided in Embodiment 3 of the present invention;

[0040] Figure 7 This is a simulation result of the localized mixing electric field distribution induced by the terahertz wave detector antennas at both ends of an AlGaN / GaN HEMT provided in Embodiments 2 and 3 of the present invention.

[0041] Figure 8aThis is a comparison diagram of the photovoltage of a two-terminal terahertz wave detector in Embodiment 1 of the present invention and a three-terminal terahertz wave detector in Comparative Example 1 as a function of bias voltage.

[0042] Figure 8b This is a comparison diagram of the photovoltage of a two-terminal terahertz wave detector in Embodiment 1 of the present invention and a three-terminal terahertz wave detector in Comparative Example 1 as a function of frequency.

[0043] Figure 9a and Figure 9b These are, respectively, a schematic diagram and an equivalent circuit diagram of a structure comprising two parallel-connected terahertz wave detectors provided in Embodiment 5 of the present invention. Detailed Implementation

[0044] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0045] This invention provides a method for detecting terahertz waves, enabling the terahertz wave detector to detect terahertz waves in a biased operating mode. Specifically, the source / gate is grounded and a bias voltage is applied to the drain to control the 2DEG, thereby generating a terahertz response current in the mixing region of the channel below the terahertz coupled antenna.

[0046] Based on the biased operating mode, this embodiment of the invention also provides a two-ended terahertz wave detector. The detector consists of two antennas connected to each other via a carrier channel and an ohmic contact structure. The antennas are then connected to the output electrodes at both ends. Importantly, a certain distance is maintained between the edge of the ohmic contact structure that engages with the semiconductor structure and the edge of the antenna forming a Schottky contact with the semiconductor structure. This creates a "field plate"-like structure between the antenna and the semiconductor structure. When a suitable bias voltage is applied, the detector generates a mixing current in the carrier channel region below it through the electric field coupled to the "field plate" structure, thereby enabling effective and sensitive detection of terahertz waves.

[0047] This invention provides a terahertz wave detector, including a semiconductor structure, a first electrode, a second electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna, and a second antenna.

[0048] The semiconductor structure includes a channel layer and a barrier layer stacked together, and a carrier channel is formed in the semiconductor structure.

[0049] The first antenna and the second antenna are disposed at intervals on the semiconductor structure and both form Schottky contacts with the semiconductor structure;

[0050] The first ohmic contact structure and the second ohmic contact structure are respectively disposed between the first antenna, the second antenna and the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure form ohmic contacts with the semiconductor structure and are electrically connected to the first antenna and the second antenna respectively.

[0051] The first electrode and the second electrode are combined with the semiconductor structure to form a high mobility field-effect transistor, and the first electrode and the second electrode are electrically connected to the carrier channel through ohmic contacts.

[0052] In one specific implementation, the first antenna and the second antenna completely cover the first ohmic contact structure and the second ohmic contact structure, respectively, and the first antenna and the second antenna cooperate with the semiconductor structure to form a "field plate" structure.

[0053] In one specific implementation, there is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, a second distance between the third end of the second ohmic contact structure and the fourth end of the second antenna, and a third distance between the second end of the first antenna and the fourth end of the second antenna. The first end and the second end are pointing towards the second antenna, and the third end and the fourth end are pointing towards the first antenna.

[0054] It should be noted that the third distance between the second end of the first antenna and the fourth end of the second antenna serves as the antenna gap. At least one of the first and second distances, together with the third distance, determines the effective distance (length) of the carrier channel in the semiconductor structure and affects the effective mixing and detection area inside the carrier channel when the device is operating. Specifically, the third distance mainly determines the antenna factor of the first and second antennas, i.e., the antenna's resonant response capability to electromagnetic waves. The first and second distances affect the field effect factor, i.e., the level of regulation of carrier concentration and drift velocity in the carrier channel by the potential difference. The final detector response is positively correlated with the integral of the product of the antenna factor and the field effect over the effective mixing area. The first distance, second distance, and third distance are key design elements of the device. These three factors have an overall mutually restrictive relationship on the device's detection performance. For example, increasing the third distance is beneficial for expanding the mixing area in the carrier channel, but it may also be accompanied by contradictions that are detrimental to device performance, such as decreased antenna performance and increased internal resistance of the carrier channel. To address this, the detection responsivity can be optimized by combining electromagnetic simulation and self-consistent calculation of carrier modulation in the carrier channel, thereby obtaining the optimal size parameters of the first distance, second distance, and third distance.

[0055] In one specific implementation, there is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, and a second distance between the third end of the second ohmic contact structure and the fourth end of the second antenna, which can be 1.5-4 micrometers. The first distance and the second distance can be equal or unequal. The third distance between the second end of the first antenna and the fourth end of the second antenna can be 200 nanometers-3 micrometers. The width of the carrier channel and the first antenna and the second antenna in the mixing region can be 2-12 micrometers.

[0056] Specifically, the gaps (including the corresponding first and second distances) between the first antenna, the second antenna, the first ohmic contact structure, and the second ohmic contact structure form a "field plate" structure with the semiconductor structure, which can control the state of carriers in the carrier channel through electric field coupling.

[0057] In one specific implementation, the edge region of the first antenna / second antenna forms a Schottky contact with the semiconductor structure and forms the "field plate" structure with the semiconductor structure, the middle region of the first antenna / second antenna completely covers the first ohmic contact structure / second ohmic contact structure and is electrically connected to the first ohmic contact structure / second ohmic contact structure, wherein the edge region is distributed around the middle region.

[0058] In one specific embodiment, the first electrode and the second electrode are disposed at intervals on the semiconductor structure, and the first electrode and the second electrode are electrically connected to the carrier channel.

[0059] For example, the carrier channel in the embodiments of the present invention can be a two-dimensional electron gas channel with high electron mobility formed in a semiconductor heterojunction structure, etc.

[0060] In one specific implementation, the first antenna, the second antenna, and the underlying semiconductor structure form a metal-semiconductor ohmic contact to achieve electrical connection between the first antenna, the second antenna, and the underlying two-dimensional electron gas channel. The first electrode and the second electrode are respectively electrically connected to the first antenna and the second antenna. Specifically, the first electrode and the second electrode can be electrically connected to the first antenna and the second antenna respectively through the carrier channel.

[0061] In one specific implementation, the first electrode and the second electrode are respectively integrated with the first antenna and the second antenna. For example, the first electrode and the second electrode can be electrically connected to the first antenna and the second antenna through metal leads and integrated with each other.

[0062] In one specific implementation, the first antenna and the second antenna can be symmetrically arranged, or antenna structures with different resonant response characteristics can be used to form a non-uniform arrangement of the first antenna and the second antenna.

[0063] In one specific implementation, one of the first electrode and the second electrode serves as the source and the other as the drain, or one of the first electrode and the second electrode serves as the cathode and the other as the anode; one of the first antenna and the second antenna serves as the source antenna and the other as the drain antenna.

[0064] This invention also provides a terahertz wave detector, including a semiconductor structure, a first electrode, a second electrode, a third electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna, a second antenna, and a third antenna.

[0065] The semiconductor structure includes a channel layer and a barrier layer stacked together, and a carrier channel is formed in the semiconductor structure.

[0066] The first electrode, the second electrode, and the third electrode are disposed at intervals on the semiconductor structure and cooperate with the semiconductor structure to form a high mobility field-effect transistor structure. The first electrode and the second electrode are electrically connected to the carrier channel.

[0067] The first antenna, the second antenna, and the third antenna are spaced apart on the semiconductor structure and all form Schottky contacts with the semiconductor structure.

[0068] The first ohmic contact structure and the second ohmic contact structure are respectively disposed between the first antenna, the second antenna and the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure form ohmic contacts with the semiconductor structure and are electrically connected to the first antenna and the second antenna respectively.

[0069] The first antenna, the second antenna, and the third antenna are respectively engaged with the first electrode, the second electrode, and the third electrode, and the first antenna is also electrically connected to the third antenna.

[0070] In one specific implementation, one of the first electrode and the second electrode serves as the source and the other as the drain, the third electrode serves as the gate, one of the first antenna and the second antenna serves as the source antenna and the other as the drain antenna, and the third antenna serves as the gate antenna.

[0071] In one specific implementation, the first antenna and the second antenna completely cover the first ohmic contact structure and the second ohmic contact structure, respectively, and the first antenna and the second antenna respectively form a "field plate" structure with the semiconductor structure.

[0072] In one specific implementation, there is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, a second distance between the third end of the second ohmic contact structure and the fourth end of the second antenna, and a third distance between the second end of the first antenna and the fourth end of the second antenna. The first end and the second end are pointing towards the second antenna, and the third end and the fourth end are pointing towards the first antenna.

[0073] In one specific implementation, the edge region of the first antenna / second antenna forms a Schottky contact with the semiconductor structure and forms the "field plate" structure with the semiconductor structure, the middle region of the first antenna / second antenna completely covers the first ohmic contact structure / second ohmic contact structure and is electrically connected to the first ohmic contact structure / second ohmic contact structure, wherein the edge region is distributed around the middle region.

[0074] This invention also provides a method for detecting terahertz waves, comprising:

[0075] The terahertz wave detector is provided by grounding one of the first and second electrodes and applying a working voltage to the other. The terahertz wave is detected by measuring whether the terahertz wave detector outputs a response current and the magnitude of the response current.

[0076] The following will provide a further explanation of the technical solution, its implementation process, and its principles, in conjunction with the accompanying drawings and specific implementation examples.

[0077] It should be noted that the semiconductor structure in the embodiments of the present invention can be an epitaxial structure of a field-effect transistor, specifically an AlGaN / GaN HEMT epitaxial structure. The semiconductor structure includes a heterojunction, which can be an AlGaN / GaN heterojunction. Of course, other channel structures with carrier channels can also be selected. For example, those skilled in the art can also replace it with materials with different carrier mobility and concentration, such as graphene, indium phosphide, etc., or use heterojunctions with different barrier layer thicknesses.

[0078] In this embodiment of the invention, the first antenna and the second antenna, or the first antenna, the second antenna and the third antenna, serve as terahertz wave coupling antennas. The terahertz wave coupling antennas include, but are not limited to, bow-tie antennas, slot antennas or transmission lines.

[0079] The inventors in this case discovered that all detectors, whether capacitively coupled, directly deposited with ohmic contacts on the antenna, or antenna-coupled three-terminal field-effect transistor terahertz detectors, are based on the self-mixing theory (principle). The asymmetric dipole antenna generates an enhanced terahertz electric field in the HEMT channel, exhibiting three important characteristics: first, the terahertz wave is significantly enhanced on both sides of the gate, exhibiting a localized characteristic; second, the gate edge on the drain side of the antenna has a stronger terahertz electric field than the other side, exhibiting an asymmetric distribution; and third, when the incident terahertz wave is a linearly polarized plane wave (polarization direction parallel to the antenna), it has an in-plane electric field along the x-direction and a vertical component along the z-direction within the gate-controlled channel, respectively controlling the electron drift velocity and electron gas concentration within the channel. According to the self-mixing theory, the DC response current generated by the terahertz wave can be expressed as:

[0080] i0∝Ξ(V G )×Λ(f0,P0)

[0081] Where f0 and P0 are the frequency and power of the incident terahertz wave, respectively, and Ξ(V G )=dG0 / dV G The field-effect factor is determined by the gate control conductance of the channel under no DC source drain bias: G0 = eμWn(V G ) / L, Λ(f0, P0) represents the antenna factor, characterizing the strength of the mixing current generated by the terahertz wave in the 2DEG channel coupled by the antenna, and can be expressed as:

[0082]

[0083] Where MF(f0, P0) is the mixing factor in the channel, which can be specifically expressed as:

[0084]

[0085] In the formula, E x (x, y, z) ch Terahertz electric fields are in-plane electric fields induced by terahertz waves of specific power and frequency within a grid-controlled channel. The potential of the gate-controlled channel relative to the gate is Δφ, where Δφ is the potential of the channel E. x (x, y, z) ch ) and u(x, y, z ch The phase difference between the three factors is the area fraction of the product of the three factors.

[0086] Figure 3aThe distribution of the mixing factor obtained through simulation calculation on the cross-section of a three-terminal terahertz wave detector coupled with an asymmetric dipole antenna is shown. It can be seen that the mixing effect below the gate edge of the drain end is significantly stronger than that below the gate of the source end. This asymmetric feature realized by the gate antenna is the key to the effective detection of terahertz waves and is the main reason for adopting the asymmetric dipole antenna design. It is worth noting that there is also a locally enhanced mixing factor below the top of the drain antenna. Since the channel in this region is not regulated by the gate voltage, the field effect factor is low, and therefore no significant mixing current is generated.

[0087] Based on the above theory, it can be understood that current three-terminal terahertz wave detectors mainly rely on obtaining a suitable transconductance through the gate voltage. Only by adjusting the 2DEG concentration within the channel to a suitable value can a considerable response current be generated in the local mixing region. For example... Figure 3b As shown, different gate voltages V g When the source-drain bias is very small, the transconductance g of the device... m Maintaining a stable maximum value within a very small gate voltage range, electrons in the channel are accelerated to reach saturation drift velocity or voltage, resulting in a transconductance plateau. This means that the transconductance value under source-drain bias remains stable over a large gate voltage range, which is of great benefit to the working stability of the detector. Even if there are fluctuations in the gate voltage of the detector within a certain range, a stable terahertz response current can still be output.

[0088] Unlike the common gate voltage detection mode, the embodiments of the present invention provide a terahertz wave detector and a terahertz wave detection method for terahertz wave photovoltage detection under source-drain bias voltage. The embodiments of the present invention provide a three-terminal terahertz wave detector coupled with a three-lobe asymmetric dipole antenna and a novel two-terminal terahertz wave detector based on self-mixing theory.

[0089] This invention provides a two-ended terahertz wave detector. Both ends of the detector (i.e., the first wire and the second antenna) are electrically connected to the carrier channel via ohmic contacts. The edges of the ohmic contact structure do not coincide with the edges of the antennas but are spaced a certain distance apart, allowing the reserved portion of the antenna edges to form a Schottky contact with the underlying semiconductor structure. This two-ended terahertz wave detector can achieve highly sensitive terahertz wave detection with only two electrodes. One electrode is used to apply a specific operating voltage and output a photoresponse signal, while the other electrode is grounded. The terahertz wave detector provided in this invention can be used as a bare die or integrated with converging lenses or waveguide components.

[0090] The two-ended terahertz wave detector provided in this embodiment of the invention allows for flexible adjustment of the internal resistance of the detector channel through the design of the active region size of the channel, which is beneficial for impedance matching between the detector and the output circuit, as well as for the sensitivity and response speed of the detector.

[0091] This invention also proposes a three-terminal terahertz wave detector that does not utilize the gate voltage but connects the gate to the source or drain and grounds it. The transconductance of this type of detector is controlled by the potential difference brought about by the source-drain bias voltage, generating a terahertz response current in the local mixing region.

[0092] Example 1

[0093] Please see Figure 4a and Figure 4b A three-terminal terahertz wave detector includes a field-effect transistor and a terahertz wave coupling antenna (which can be simply referred to as an antenna or terahertz antenna). The field-effect transistor includes a semiconductor structure and a first electrode, a second electrode, and a third electrode that cooperate with the semiconductor structure. A carrier channel is formed in the semiconductor structure. The first electrode and the second electrode are disposed at intervals on the semiconductor structure and form an ohmic contact with the semiconductor structure. The first electrode and the second electrode are electrically connected to the carrier channel.

[0094] The terahertz wave coupling antenna includes a first antenna, a second antenna, and a third antenna. The first antenna, the second antenna, and the third antenna are spaced apart on the heterojunction and form a Schottky contact with the semiconductor structure. The first antenna, the second antenna, and the third antenna are electrically connected to the first electrode, the second electrode, and the third electrode, respectively. In addition, the third antenna can also be electrically connected to the first antenna through a carrier channel lead.

[0095] In this embodiment, a first ohmic contact structure and a second ohmic contact structure are further provided between the first antenna, the second antenna, and the heterojunction. The middle regions of the first antenna and the second antenna respectively cover the first ohmic contact structure and the second ohmic contact structure. There is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, a second distance between the third end of the second ohmic contact structure and the fourth end of the second antenna, and a third distance between the second end of the first antenna and the fourth end of the second antenna. The first end and the second end are pointing towards the second antenna, and the third end and the fourth end are pointing towards the first antenna.

[0096] In this embodiment, the field-effect transistor can be an AlGaN / GaN high electron mobility transistor, or a silicon-based CMOS, other heterojunction transistors, graphene transistors, etc., and the carrier channel can be a two-dimensional electron gas (2DEG) channel.

[0097] The method for terahertz wave detection under bias voltage using the three-terminal terahertz wave detector in this embodiment includes:

[0098] The third antenna is grounded in the same way as the first antenna and the first electrode. A voltage is applied to the second antenna. The terahertz wave is detected by measuring whether the terahertz wave detector outputs a response current and the magnitude of the response current.

[0099] It should be noted that, based on the self-mixing theory, since the first and third electrodes are grounded, the potential between the first and third electrodes is zero. According to the gradually changing potential distribution, under a specified bias voltage, a steady-state concentration distribution will be formed in the carrier channel between the third and second electrodes under the potential gradient. When the terahertz antenna receives terahertz radiation, a strong local non-steady-state terahertz mixing electric field will be formed in the carrier channel. This terahertz mixing electric field acts on the carrier channel and drives the carrier concentration to fluctuate and drift, ultimately generating a terahertz response short-circuit current or open-circuit voltage between the electrodes on both sides of the carrier channel of the device.

[0100] It should be noted that the interaction between the antenna and the charge carriers in the carrier channel is a field effect. The antenna should not form an ohmic contact with the carrier channel in the mixing region, so that the antenna can be fully connected to the carrier channel below it. This would cause the field effect of the terahertz wave to fail, and thus it would be impossible to effectively control the charge carriers in the carrier channel.

[0101] Example 2

[0102] When a three-terminal terahertz wave detector is used to detect terahertz waves in biased operating mode, the uncertainty of the process is increased to a certain extent, which increases the complexity of the device structure and integration. Therefore, this embodiment of the invention also provides a two-terminal terahertz wave detector.

[0103] Please see Figure 5a and Figure 5b A two-terminal terahertz wave detector based on AlGaN / GaN HEMT mainly includes a high mobility field-effect transistor, a first ohmic contact structure, a second ohmic contact structure, a first antenna, a second antenna, a first electrode, and a second electrode. The high mobility field-effect transistor includes a substrate and a GaN channel layer and an AlGaN barrier layer stacked sequentially on the substrate. The AlGaN barrier layer is disposed on the GaN channel layer and forms a heterojunction.

[0104] The first ohmic contact structure and the second ohmic contact structure are spaced apart on the heterojunction and form ohmic contacts with the heterojunction. The first antenna and the second antenna are spaced apart on the heterojunction and respectively cover the first ohmic contact structure and the second ohmic contact structure. The first antenna and the second antenna form Schottky contacts with the heterojunction.

[0105] In this embodiment, there is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, a second distance g between the third end of the second ohmic contact structure and the fourth end of the second antenna, and a third distance d between the second end of the first antenna and the fourth end of the second antenna. The first and second ends are pointing towards the second antenna, and the third and fourth ends are pointing towards the first antenna. The first ohmic contact structure and the first antenna, and the second ohmic contact structure and the second antenna form a structure similar to a "field plate".

[0106] In this embodiment, the first electrode and the second electrode are electrically connected to the first antenna and the second antenna, respectively, instead of directly contacting the carrier channel within the heterojunction.

[0107] The method for detecting terahertz waves using the two-terminal terahertz wave detectors in this embodiment under bias voltage includes:

[0108] The first antenna is kept in the same grounded state as the first electrode, and a voltage is applied to the second antenna. The detection of terahertz waves is achieved by measuring whether the terahertz wave detector outputs a response current and the magnitude of the response current.

[0109] pass Figure 5c As can be seen from the equivalent circuit diagram, this two-terminal terahertz wave detector can reduce the series resistance, where rc represents the channel resistance generated by 2DEG between the first antenna and the second antenna.

[0110] Example 3

[0111] In this embodiment, a structure of a two-terminal terahertz wave detector based on AlGaN / GaN HEMT is as follows: Figure 6a , Figure 6b , Figure 6c As shown, the structure of the two-end terahertz wave detector in this embodiment is basically the same as that of the two-end terahertz wave detector in Embodiment 2, except that:

[0112] In this embodiment, the first electrode and the second electrode are disposed on the heterojunction and are in contact with and electrically connected to the carrier channel within the heterojunction. For example, the first antenna and the second antenna can be electrically connected to the first electrode and the second electrode respectively through the carrier channel and the ohmic contact structure.

[0113] pass Figure 6c As can be seen from the equivalent circuit diagram, this two-terminal terahertz wave detector can reduce the series resistance, where r c This represents the channel resistance generated by the carrier channel between the first antenna and the second antenna.

[0114] It should be noted that the two-terminal terahertz field-effect detectors provided in Embodiments 2 and 3 can be fabricated using the process disclosed in CN102445711 A. Of course, other processes known to those skilled in the art can also be used, and no specific limitations are made here.

[0115] Figure 7 The diagram shows the mixing factor distribution corresponding to the two-end terahertz wave detector structures in Examples 2 and 3 obtained from simulation. When the device is working, one end electrode is grounded to zero potential, and a voltage is applied from the other end electrode. According to the gradual distribution of potential in the antenna field plate region (i.e., the region corresponding to the field plate structure), a certain range of transconductance is obtained under a suitable bias voltage, thereby regulating the 2DEG in the channel and generating an effective terahertz response current output in the local mixing region. By adjusting the core dimensions d and g, there is room for further optimization of the sensitivity of the two-end terahertz wave detectors.

[0116] Comparative Example 1

[0117] Comparative Example 1 is a room-temperature terahertz wave detector disclosed in CN 102054891A, the structure of which is as follows: Figure 1a , Figure 1b As shown.

[0118] Comparative Example 2

[0119] Comparative Example 2 is a terahertz wave detector disclosed in CN 102445711 A, the structure of which is as follows: Figure 2a , Figure 2b As shown.

[0120] Under bias, a terahertz wave detector in Comparative Example 1 and a two-ended terahertz wave detector in Example 1 (such as...) Figure 4a , Figure 4b The comparison results of photovoltage changes are as follows: Figure 8a As shown, it is worth noting that for a three-terminal terahertz wave detector, the bias voltage (Vd) refers to the source-drain bias voltage applied to the second electrode with the third electrode floating and the source terminal grounded. For a two-terminal terahertz wave detector, the bias voltage refers to the bias voltage applied to one electrode and the other electrode grounded. For a three-terminal terahertz wave detector, since the third electrode is floating, an effective longitudinal potential difference cannot be formed in the channel in capacitive coupling mode, and the electron concentration cannot be effectively controlled. Therefore, no matter how the source-drain voltage changes, the resulting photovoltage response is very weak. However, in a two-terminal terahertz wave detector, as the Vd bias voltage increases, a gradually increasing photovoltage response can be obtained.

[0121] To more clearly demonstrate the detection performance of the two terahertz wave detectors, this embodiment also performed frequency sweep tests on the two devices. The test results are as follows: Figure 8b As shown, Figure 8b Comparatively, the photovoltage curves of a terahertz wave detector in Example 1 and a two-terminal terahertz wave detector in Example 1 show the frequency variation. It can be seen that, compared to the photovoltage response of the capacitively coupled detector at its optimal operating point gate voltage, the two-terminal terahertz wave detector, under a suitable second electrode bias voltage (such as...), exhibits significantly higher photovoltage response. Figure 5a , Figure 5b or Figure 6a , Figure 6b With the setup of first electrode grounded and second electrode with an applied voltage of 4V, a greater photovoltage response can be obtained in the 162–252 GHz range.

[0122] In addition, by swapping the two electrodes of the two terahertz wave detectors, a negative photovoltage response can be obtained, which means that the obtained photoresponse is of opposite polarity and the phase of the terahertz mixing region sensed below the two electrodes is opposite. This is consistent with the simulation results of this type of device.

[0123] Based on the above bias experiment results, it can be seen that the two-ended terahertz wave detector can still achieve or even better terahertz detection levels under different operating modes. This invention, based on an AlGaN / GaN HEMT, proposes a two-ended terahertz wave detector that simplifies the original antenna design. Instead of controlling the 2DEG through a third electrode voltage, it controls the 2DEG through an asymmetric, slowly varying potential formed by the field plate structure created by the ohmic contact electrode and the Schottky antenna.

[0124] Example 4

[0125] The two-terminal terahertz wave detectors in Examples 2 and 3 utilize only the mixing region below one antenna. The structure of the two-terminal terahertz wave detector in this example is as follows: Figure 9a , Figure 9b As shown, the carrier channels below the two antennas are grounded via ohmic contacts. A bias voltage is applied to the channel between the two antennas via electrodes, thereby connecting the detector structures at both ends of the two antennas in parallel, further reducing the overall internal resistance of the device. The device load can be formed by setting two discrete ohmic contacts within the 2DEG channel, or an external load can be connected to the device package. This parallel two-end detector structure utilizes the mixing region below both antennas to form a differential signal output, resulting in highly sensitive and effective detection.

[0126] This invention provides a terahertz wave detection method. The biased operating mode increases the stability of the device. The biased operating mode proposed for a three-terminal terahertz wave detector coupled with an asymmetric dipole antenna replaces the operating mode that relies on the third electrode voltage to regulate the HEMT device to the optimal operating point in the subthreshold region. By applying a bias voltage in the mixing region, a suitable potential difference is obtained to regulate the channel carrier output terahertz response current. The stable bias voltage can keep the transistor transconductance stable within a certain range, avoiding the disadvantage that the optimal transconductance caused by the third electrode voltage is easily affected by small changes in the gate voltage, thus affecting the detector responsivity and making the optimal detection state more stable.

[0127] The two-terminal terahertz wave detector provided in this embodiment of the invention has a simpler structure. For the application of biased working mode, the three-terminal terahertz wave detector can be optimized into a two-terminal terahertz wave detector, which significantly reduces the complexity of device design, integrated array, and circuit. Based on the biased working mode, the two-terminal terahertz wave detector simplifies the design of the three-terminal terahertz wave detector by eliminating the gate and the gate-source / drain connection, making the structure simpler and easier to obtain, while maintaining comparable detection performance.

[0128] This invention provides a two-ended terahertz wave detector. By using electrodes at both ends (one grounded, the other with an applied voltage Vd), the carrier concentration in the channel is controlled. Through the action of the field plate structure formed by the Schottky antenna and the ohmic contact structure, a considerable terahertz response current is generated by mixing in the channel below. This two-ended terahertz wave detector avoids the problems of difficult fabrication, poor device consistency, and low reliability caused by antennas composed of ohmic contacts. By optimizing core parameters such as antenna distance and field plate structure spacing, a terahertz wave detector with superior performance and higher sensitivity can be obtained.

[0129] This invention provides a two-terminal terahertz wave detector that reduces the device's series resistance and output impedance. Furthermore, this two-terminal terahertz wave detector connects the carrier channel to the terahertz antenna via an ohmic contact, reducing the series resistance generated by the carrier channel in the source and drain regions of the antenna connection in a three-terminal terahertz wave detector. In addition, the operating mode of this two-terminal terahertz wave detector means that the device's channel resistance can be flexibly designed by adjusting the structural dimensions of the active region, providing significant optimization space for impedance matching with the backend link. The implementation of a low-resistance device helps reduce output impedance, alleviates output bandwidth limitations, and solves problems such as difficulty in impedance matching with the backend low-noise amplifier.

[0130] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A two-terminal terahertz wave detector, characterized in that... Includes a semiconductor structure, a first electrode, a second electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna, and a second antenna. The semiconductor structure includes a channel layer and a barrier layer stacked together, and a carrier channel is formed in the semiconductor structure. The first antenna and the second antenna are disposed at intervals on the semiconductor structure and both form Schottky contacts with the semiconductor structure; The first ohmic contact structure and the second ohmic contact structure are respectively disposed between the first antenna, the second antenna and the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure form ohmic contacts with the semiconductor structure and are electrically connected to the first antenna and the second antenna respectively. The first antenna and the second antenna completely cover the first ohmic contact structure and the second ohmic contact structure respectively. The first antenna and the second antenna respectively form a "field plate" structure with the semiconductor structure. There is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, a second distance between the third end of the second ohmic contact structure and the fourth end of the second antenna, and a third distance between the second end of the first antenna and the fourth end of the second antenna. The first end and the second end are pointing towards the second antenna, and the third end and the fourth end are pointing towards the first antenna. The first electrode and the second electrode are respectively connected to the first antenna and the second antenna, and the first electrode and the second electrode are connected to the semiconductor structure to form a high mobility field-effect transistor. The first electrode and the second electrode are electrically connected to the carrier channel.

2. The two-terminal terahertz wave detector according to claim 1, characterized in that: The edge region of the first antenna / second antenna forms a Schottky contact with the semiconductor structure and forms the "field plate" structure with the semiconductor structure. The middle region of the first antenna / second antenna completely covers the first ohmic contact structure / second ohmic contact structure and is electrically connected to the first ohmic contact structure / second ohmic contact structure. The edge region is distributed around the middle region.

3. The two-terminal terahertz wave detector according to claim 1, characterized in that: The first electrode and the second electrode are disposed at intervals on the semiconductor structure, and the first electrode and the second electrode are electrically connected to the carrier channel.

4. The two-terminal terahertz wave detector according to claim 1, characterized in that: The first electrode and the second electrode are electrically connected to the first antenna and the second antenna, respectively.

5. The two-terminal terahertz wave detector according to claim 1, characterized in that: The first electrode and the second electrode are respectively integrated with the first antenna and the second antenna.

6. The two-terminal terahertz wave detector according to claim 1, characterized in that: The first antenna and the second antenna are arranged symmetrically.

7. The two-terminal terahertz wave detector according to claim 1, characterized in that: One of the first electrode and the second electrode serves as the source electrode, and the other serves as the drain electrode.

8. A three-terminal terahertz wave detector, characterized in that... Includes a semiconductor structure, a first electrode, a second electrode, a third electrode, a first ohmic contact structure, a second ohmic contact structure, a first antenna, a second antenna, and a third antenna: The semiconductor structure includes a channel layer and a barrier layer stacked together, and a carrier channel is formed in the semiconductor structure. The first electrode, the second electrode, and the third electrode are disposed at intervals on the semiconductor structure and cooperate with the semiconductor structure to form a high mobility field-effect transistor structure. The first electrode and the second electrode are electrically connected to the carrier channel. The first antenna, the second antenna, and the third antenna are spaced apart on the semiconductor structure and all form Schottky contacts with the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure are respectively disposed between the first antenna, the second antenna and the semiconductor structure. The first ohmic contact structure and the second ohmic contact structure form ohmic contacts with the semiconductor structure and are electrically connected to the first antenna and the second antenna respectively. The first antenna and the second antenna completely cover the first ohmic contact structure and the second ohmic contact structure respectively. The first antenna and the second antenna respectively form a "field plate" structure with the semiconductor structure. There is a first distance between the first end of the first ohmic contact structure and the second end of the first antenna, a second distance between the third end of the second ohmic contact structure and the fourth end of the second antenna, and a third distance between the second end of the first antenna and the fourth end of the second antenna. The first end and the second end are pointing towards the second antenna, and the third end and the fourth end are pointing towards the first antenna. The first antenna, the second antenna, and the third antenna are respectively engaged with the first electrode, the second electrode, and the third electrode, and the first antenna is also electrically connected to the third antenna.

9. The three-terminal terahertz wave detector according to claim 8, characterized in that: One of the first electrode and the second electrode serves as the source and the other as the drain, and the third electrode serves as the gate.

10. The three-terminal terahertz wave detector according to claim 8, characterized in that: The edge region of the first antenna / second antenna forms a Schottky contact with the semiconductor structure and forms the "field plate" structure with the semiconductor structure. The middle region of the first antenna / second antenna completely covers the first ohmic contact structure / second ohmic contact structure and is electrically connected to the first ohmic contact structure / second ohmic contact structure. The edge region is distributed around the middle region.

11. A method for detecting terahertz waves, characterized in that, include: A two-terminal terahertz wave detector according to any one of claims 1-7 or a three-terminal terahertz wave detector according to any one of claims 8-9 is provided, wherein one of the first electrode and the second electrode is grounded and a working voltage is applied to the other electrode, and the terahertz wave is detected by measuring whether the terahertz wave detector outputs a response current and the magnitude of the response current.

Images