Hemt terahertz detector based on waveguide coupling

Abstract

The application discloses a HEMT terahertz detector based on waveguide coupling. The HEMT terahertz detector comprises an input waveguide connected with a terahertz signal detection unit and used for collecting a terahertz input signal; an impedance matching structure connected with the input waveguide and used for adjusting electromagnetic waves in the input waveguide to be matched with the impedance of the terahertz signal detection unit and then coupled into the terahertz signal detection unit; and the terahertz signal detection unit used for processing the received terahertz input signal and outputting a terahertz response signal. The HEMT terahertz detector based on waveguide coupling integrates a terahertz mixer, a terahertz signal input part and a terahertz signal output part on the same terahertz detector chip, realizes a high-gain and miniaturized terahertz detector, further improves the sensitivity of the detector and saves the cost.

Description

TECHNICAL FIELD

[0001] The present application relates to a waveguide-coupled HEMT terahertz detector, and belongs to the technical field of terahertz detection. BACKGROUND

[0002] Terahertz wave is a section of electromagnetic spectrum resource which has not been applied on a large scale by human beings, and its wavelength is approximately from 30 μm to 3 mm, and its frequency range is between 0.1 and 10 THz, also known as submillimeter wave and far infrared wave.

[0003] A terahertz detector is a core device of a terahertz human body security check, nondestructive detection, radar imaging and communication system. The sensitivity of the terahertz detector determines key performance parameters such as signal-to-noise ratio, action distance and bandwidth of the above applications.

[0004] When a lens coupling scheme is adopted, the terahertz wave is incident vertically on the lens plane, and is converged at the center of the silicon lens by the silicon lens. The detector chip is integrated at the center position of the lens plane, and at this time, the incident light power received by the detector is the strongest. However, when the incident position or angle of the terahertz wave changes, the light spot converged by the silicon lens may not be converged at the center, and the light power received by the detector is unknown. Meanwhile, because the size of the light spot is comparable to the effective area of the detector, when the light spot deviates from the center, only part of the antenna of the detector may receive irradiation, and the light response may change, that is, the lens coupling effect is limited by the angle of the incident terahertz wave. When a waveguide coupling scheme is adopted, the terahertz light / terahertz wave is incident from the waveguide port of the input waveguide, the transmission mode inside the input waveguide is adjusted, and the transmission is performed according to the mode of the input waveguide inside the base mode, until it is emitted onto the detector chip, and the stability is high. In this way, the position and angle of the incident terahertz wave have no influence on the electric field distribution characteristics of the waveguide port, that is, the coupling degree of the waveguide coupling is higher than that of the lens coupling.

[0005] However, the waveguide-coupled field effect transistor detector has only been preliminarily attempted so far, and the coplanar waveguide is used in the signal transmission process of the field effect transistor, but there is no report on the direct integration of the field effect transistor detector and the spatial waveguide structure. Therefore, whether the waveguide coupling can provide higher sensitivity than the lens-coupled field effect transistor detector is a problem to be studied. If the terahertz detector is directly placed at the waveguide emission port, although a terahertz response signal can be generated, there is a serious impedance mismatch between the waveguide and the detector chip, the terahertz wave coupling efficiency is low, and the sensitivity of the detector is not high. SUMMARY

[0006] The main purpose of the present application is to provide a waveguide-coupled HEMT terahertz detector, so as to overcome the deficiencies in the prior art.

[0007] To achieve the aforementioned purposes of the application, the technical solutions adopted by the application comprise:

[0008] The application provides a HEMT terahertz detector based on waveguide coupling, comprising:

[0009] An input waveguide, connected with the terahertz signal detection unit, and used for collecting a terahertz input signal;

[0010] An impedance matching structure, connected with the input waveguide, and used for adjusting the electromagnetic wave in the input waveguide to be matched with the impedance of the terahertz signal detection unit, and then coupling into the terahertz signal detection unit;

[0011] A terahertz signal detection unit, used for processing the received terahertz input signal and outputting a terahertz response signal.

[0012] Compared with the prior art, the application has the following advantages:

[0013] 1) The HEMT terahertz detector based on waveguide coupling provided by the application has high stability, because the terahertz light is incident from the waveguide port and transmitted according to the mode of the internal base mode of the waveguide, and the position and angle of the terahertz wave incidence have no influence on the electric field distribution characteristics of the waveguide port, so the coupling efficiency is higher;

[0014] 2) The HEMT terahertz detector based on waveguide coupling provided by the application solves the problem of impedance mismatch between structures by using a microstrip E-plane probe transition and a microstrip impedance transformer, and further improves the terahertz wave coupling efficiency;

[0015] 3) The HEMT terahertz detector based on waveguide coupling provided by the application integrates the terahertz mixer, the terahertz signal input and output parts on the same terahertz detector chip through a full HEMT process, realizes a high-gain and miniaturized terahertz detector, further improves the sensitivity of the detector, and saves the cost;

[0016] 4) The HEMT terahertz detector based on waveguide coupling provided by the application can also be symmetrically designed and realize terahertz heterodyne detection. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structure schematic diagram of a HEMT terahertz detector based on waveguide coupling provided in a typical embodiment case of the application;

[0018] Figure 2 is a structure schematic diagram of a terahertz mixer provided in a typical embodiment case of the application;

[0019] Figure 3It is an equivalent circuit structure schematic diagram of a terahertz mixer provided in an exemplary embodiment of the present application.

[0020] Figure 4 It is a relationship diagram of noise equivalent power (NEP) of a waveguide coupling based HEMT terahertz detector varying with power supply voltage provided in an exemplary embodiment of the present application.

[0021] Figure 5 It is a relationship diagram of noise equivalent power (NEP) of a waveguide coupling based HEMT terahertz detector varying with terahertz frequency provided in an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0022] In view of the deficiencies in the prior art, the present inventors have long studied and practiced to come up with the technical solution of the present application. The technical solution, its implementation process and principles will be further explained as follows.

[0023] The present application provides a waveguide coupling based HEMT terahertz detector, comprising:

[0024] An input waveguide, connected with the terahertz signal detection unit, and used for collecting a terahertz input signal;

[0025] An impedance matching structure, connected with the input waveguide, and used for adjusting the electromagnetic wave in the input waveguide to be impedance matched with the terahertz signal detection unit, and then coupling into the terahertz signal detection unit;

[0026] A terahertz signal detection unit, used for processing the received terahertz input signal, and outputting a terahertz response signal.

[0027] Further, the impedance matching structure comprises a microstrip probe, a microstrip high inductive line and a microstrip impedance transformer arranged in sequence, the microstrip high inductive line and the microstrip impedance transformer, and the microstrip impedance transformer and the terahertz signal detection unit are connected through a microstrip transmission line; the microstrip probe is connected with the input waveguide, and the electromagnetic wave in the input waveguide can be coupled onto the microstrip transmission line; the microstrip high inductive line is used for eliminating the impedance mismatch due to the change of propagation mode between the input waveguide and the microstrip transmission line; and the microstrip impedance transformer is used for impedance transforming the microstrip transmission line, so as to adjust the electromagnetic wave coupled onto the microstrip transmission line to be impedance matched with the terahertz signal detection unit.

[0028] Further, the microstrip transmission line is used for transmitting the terahertz input signal, the current on the microstrip probe can excite an infinite number of electric field modes, and except for the main mode, the rest of the high-order modes cannot be transmitted in the microstrip transmission line, they will gather around the microstrip probe and produce a reactance effect, and by introducing a microstrip high inductive line, the reactance introduced by the high-order modes can be largely offset, thereby realizing impedance matching between the input waveguide and the microstrip transmission line.

[0029] Further, the microstrip probe first couples the electromagnetic wave in the input waveguide to the microstrip transmission line, and then the microstrip transmission line is matched to the terahertz mixer through a quarter-wavelength impedance transformer and the like to couple the electromagnetic wave to the terahertz mixer, wherein the quarter-wavelength impedance transformation is used for impedance matching between the microstrip transmission lines.

[0030] Further, the microstrip probe is in the form of a microstrip E-plane probe inserted into the input waveguide.

[0031] Further, the microstrip impedance transformer includes a quarter-wavelength impedance transformer or a tapered line impedance transformer.

[0032] Further, the HEMT terahertz detector based on waveguide coupling further includes a filter structure and / or a lead electrode structure, the filter structure and the lead electrode structure are respectively connected to the terahertz mixer, the filter structure is used for isolating the terahertz input signal, and the lead electrode structure is used for providing a power supply voltage and outputting a terahertz response signal.

[0033] Further, the terahertz signal detection unit includes a terahertz mixer based on a HEMT structure.

[0034] Further, the source electrode of the terahertz mixer is connected to the filter and grounded, the gate electrode is connected to the filter structure and connected to the power supply voltage, and the drain electrode is connected to the filter structure and outputs the terahertz response signal.

[0035] Further, the terahertz mixer includes a semiconductor structure, a first ohmic contact structure, a second ohmic contact structure, a first electrode, a second electrode, a third electrode, a fourth electrode, and a fifth electrode.

[0036] The semiconductor structure has a carrier channel formed therein, the first ohmic contact structure and the second ohmic contact structure are arranged in a selected direction and are electrically connected to the carrier channel.

[0037] The first electrode is arranged on and electrically connected with a first ohmic contact structure, the fifth electrode is arranged on and electrically connected with a second ohmic contact structure, and the second electrode, the third electrode and the fourth electrode are sequentially and spacedly arranged between the first ohmic contact structure and the second ohmic contact structure along the selected direction and cover part of the carrier channel.

[0038] One of the first electrode and the fifth electrode is used as a source electrode, the other is used as a drain electrode, and the third electrode is used as a gate electrode.

[0039] Further, the first electrode is also electrically connected with the second electrode.

[0040] Further, the first electrode and the second electrode are arranged as a whole.

[0041] Further, the fourth electrode is also electrically connected with the fifth electrode.

[0042] Further, the fourth electrode and the fifth electrode are arranged as a whole.

[0043] Further, the terahertz mixer is of an asymmetric structure.

[0044] Further, the electric field strength between the third electrode and the first electrode in the terahertz mixer is greater than the electric field strength between the third electrode and the fifth electrode.

[0045] Further, at least the impedance matching structure, the terahertz mixer and the filter are monolithically integrated.

[0046] Further, the effective detection frequency of the HEMT terahertz detector based on waveguide coupling on the terahertz signal is 90-112GHz.

[0047] The technical solutions, implementation processes and principles will be further explained in combination with the drawings and specific implementation cases. Unless specifically stated, the quarter wavelength impedance transformer, the tapered line impedance transformer, the filter and the like used in the present application are known to those skilled in the art.

[0048] Embodiment 1

[0049] Please refer to Figure 1 , Figure 1 The area 001 in the figure is an input area of the terahertz wave / terahertz light / terahertz signal. The HEMT terahertz detector based on waveguide coupling includes an input waveguide 100, an impedance matching structure 200, a terahertz mixer based on a HEMT structure 300, a filter structure and a lead electrode structure. The impedance matching structure 200 is connected with the microstrip probe 100 and the terahertz mixer 300 respectively. The filter structure and the lead electrode structure are electrically connected with the terahertz mixer 300 respectively.

[0050] In the embodiment, the input waveguide 100 is used to collect the terahertz input signal (which can be an electromagnetic wave, etc.), the impedance matching structure 200 is used to adjust the terahertz input signal in the input waveguide to match the impedance of the terahertz mixer 300 and then couple and transmit to the terahertz mixer 300, the terahertz mixer 300 can process the terahertz input signal to form a terahertz response signal through self-mixing, the filter structure is used to isolate the terahertz input signal, and the lead electrode structure is used to provide a power supply voltage and output the terahertz response signal.

[0051] In the embodiment, the input waveguide 100 can be a standard WR10 rectangular waveguide, wherein the working frequency range of the WR10 rectangular waveguide is 75-112GHz.

[0052] In the embodiment, the impedance matching structure 200 includes a microstrip probe 210, a microstrip high inductive line 220, a first microstrip transmission line 230, a microstrip impedance transformer 240 and a second microstrip transmission line 250 connected in sequence. The microstrip probe 210 is connected with the input waveguide 100 and forms a waveguide-microstrip transition structure with the input waveguide 100. The second microstrip transmission line 250 is electrically connected with the terahertz mixer 300. Specifically, the microstrip impedance transformer 240 includes a quarter wavelength impedance transformer or a tapered line impedance transformer.

[0053] In the embodiment, the terahertz mixer 300 is a high electron mobility transistor (HEMT), the filter structure includes a first filter 410, a second filter 420 and a third filter 430, the lead electrode structure includes a first lead electrode 510, a second lead electrode 520 and a third lead electrode 530, the terahertz mixer 300 has a first electrode 351, a third electrode 353 and a fifth electrode 355, the first electrode 351 is electrically connected with the first lead electrode 510 through the first filter 410, the third electrode 353 is electrically connected with the second lead electrode 520 through the second filter 420, and the fifth electrode 351 is electrically connected with the third lead electrode 530 through the third filter 430, specifically, the first electrode 351 is a source electrode, the fifth electrode 355 is a drain electrode, and the third electrode 353 is a gate electrode.

[0054] In the embodiment, the microstrip probe 210 is in the form of a microstrip E-plane probe, which is inserted into the input waveguide 100, and then the electromagnetic wave in the input waveguide 100 is coupled to the first microstrip transmission line 230 through the microstrip high inductive line 220 for impedance matching, and then the electromagnetic wave is coupled to the terahertz mixer 300 through the second microstrip transmission line 250 after the first microstrip transmission line 230 is transformed to reach impedance matching through the microstrip impedance transformer 240, the source electrode of the terahertz mixer 300 is connected with a filter and then grounded, the gate electrode is connected with a filter and then connected with a power supply voltage, and the drain electrode is connected with a filter and then outputs a terahertz response signal.

[0055] Specifically, referring to Figure 2 , the terahertz mixer 300 includes a semiconductor structure, a first ohmic contact structure 341, a second ohmic contact structure 342, a first electrode 351, a second electrode 352, a third electrode 353, a fourth electrode 354 and a fifth electrode 355; the semiconductor structure has a carrier channel 301 formed therein, the first ohmic contact structure 341 and the second ohmic contact structure 342 are arranged along a selected direction and are electrically connected with the carrier channel 301; the first electrode 351 is arranged on the first ohmic contact structure 341 and is electrically connected with the first ohmic contact structure 341, the fifth electrode 355 is arranged on the second ohmic contact structure 342 and is electrically connected with the second ohmic contact structure 342, the second electrode 352, the third electrode 353 and the fourth electrode 354 are arranged along the selected direction and are arranged between the first ohmic contact structure 341 and the second ohmic contact structure 342 and cover part of the carrier channel.

[0056] In the embodiment, the semiconductor structure comprises a substrate 310, a channel layer 320 and a barrier layer 330 which are sequentially stacked, and a carrier channel 301 is formed between the channel layer 320 and the barrier layer 330. For example, the channel layer 320 can be made of GaN, and the barrier layer 330 can be made of AlGaN. The carrier channel can be two-dimensional electron gas.

[0057] In the embodiment, referring to Figure 2 and Figure 3 , the first electrode 351 is electrically connected with the second electrode 352. Preferably, the first electrode 351 and the second electrode 352 are integrated and jointly serve as a source electrode. The fourth electrode 354 is electrically connected with the fifth electrode 355. Preferably, the fourth electrode 354 and the fifth electrode 355 are integrated and jointly serve as a drain electrode. The second electrode 352 and the fourth electrode 354 are arranged above the carrier channel 301. Under the action of source voltage and drain voltage, the direct current in the carrier channel 301 causes the covered carrier channel 301 to be subjected to a certain gate voltage, that is, the second electrode 352 and the fourth electrode 354 play the role of a gate electrode, which can be equivalent to a gate electrode. Specifically, the first electrode 351, the third electrode 353 and the fifth electrode 355 cooperate with the semiconductor structure to form a first high-mobility field effect transistor-gHEMT. The first electrode 351, the second electrode 352 and the fifth electrode 355 cooperate with the semiconductor structure to form a second high-mobility field effect transistor-sHEMT. The first electrode 351, the fourth electrode 354 and the fifth electrode 355 cooperate with the semiconductor structure to form a third high-mobility field effect transistor-dHEMT. The first high-mobility field effect transistor, the second high-mobility field effect transistor and the third high-mobility field effect transistor are connected in series. Each transistor produces a terahertz response signal after the three transistors are connected in series, that is, there are three terahertz response signals. The sum of the three signals is the total response signal. Through relevant design, the detection sensitivity can be improved.

[0058] In the embodiment, the terahertz mixer 300 is an asymmetric structure (the asymmetric structure refers to the distance between the source electrode and the gate electrode being different from the distance between the gate electrode and the drain electrode). The electric field intensity between the gate electrode and the source electrode is not equal to the electric field intensity between the gate electrode and the drain electrode. Specifically, the asymmetric structure is a key feature to realize that the electric field intensity between the gate electrode and the source electrode is greater than the electric field intensity between the gate electrode and the drain electrode. This makes most of the electromagnetic field energy propagate near the gate electrode, that is, there is a net terahertz response voltage, that is, a terahertz response signal.

[0059] In the embodiment, the impedance matching structure 200, the terahertz mixer 300, the filter structure and the lead electrode structure are integrated on the same substrate, which can be a terahertz detector chip, and the waveguide-coupled HEMT terahertz detector further comprises a shell, wherein the input waveguide 100 is arranged in the package shell of the detector, the terahertz detector chip is packaged in the shell, and the terahertz detector can be connected to an external circuit through a three-terminal SMA interface and the lead electrode structure to realize control and readout of the detector.

[0060] In the embodiment, the power supply voltage applied to the terahertz mixer 300 is configured to make the terahertz detector be at an optimal working point; wherein the power supply voltage is a negative voltage (the HEMT of the terahertz mixer in the embodiment is a depletion-mode device, so a negative voltage is needed, and because the HEMT has a threshold voltage, the threshold voltage is about -3.6V, so the voltage range is generally -5V-0V), the negative voltage can make the terahertz mixer be at an optimal working state, that is, the carrier channel of the terahertz mixer has the maximum transconductance, and the noise equivalent power of the terahertz mixer is the minimum. Specifically, the waveguide-coupled HEMT terahertz detector in the embodiment has the maximum transconductance at the threshold voltage of the negative voltage, and the terahertz response signal is proportional to the transconductance, so the response of the detector is the maximum at the threshold voltage, and the noise of the detector changes little with the gate voltage, so the noise equivalent power of the detector is also the minimum at the threshold voltage.

[0061] Specifically, the working mechanism of the waveguide-coupled HEMT terahertz detector in the embodiment is that when the incident terahertz wave is transmitted to the gate of the mixer, the gate receives the terahertz wave and generates an induced electric field in the carrier channel below the gate, the induced electric field is localized in the gate control area, and at the same time, a working gate voltage is applied to the gate to make it be at an optimal signal-to-noise ratio. At this time, the induced electric field can well regulate the two-dimensional electron gas at the interface between the barrier layer and the channel layer, change the concentration and migration speed of the electron gas, and thus generate a photoresponse current along the source-drain direction. The self-mixing submillimeter wave photoresponse obtained in the early stage is:

[0062]

[0063] wherein P THz is the terahertz incident power, μ is the electron mobility, n is the two-dimensional electron gas concentration, W and L are the gate width and length, respectively, is the effective distance between the gate and the two-dimensional electron gas, dn / dVg is the field effect factor, which represents the gate voltage regulation ability of the transistor, and respectively represent the electric field enhancement factors of the terahertz antenna in the horizontal direction and the vertical direction, Z Vand φ represent the free space impedance (377 Ω) and the phase difference of horizontal and vertical electric fields, respectively.

[0064] Please refer to Figure 4 and Figure 5 , Figure 4 A noise equivalent power (NEP) of a waveguide coupling based HEMT terahertz detector provided by the present application changes with the power supply voltage, as shown in the following figure: Figure 4 The optimal working point can be determined from the figure, Figure 5 A noise equivalent power (NEP) of a waveguide coupling based HEMT terahertz detector provided by the present application changes with the terahertz frequency, as shown in the following figure: Figure 4 and Figure 5 As can be seen from the figure, at the optimal working point, the waveguide coupling based HEMT terahertz detector provided by the present application realizes effective detection of terahertz signals in the frequency range of 90-112 GHz, and the NEP reaches a minimum value at 110 GHz.

[0065] It should be noted that the waveguide coupling based HEMT terahertz detector provided in the embodiment is mainly applied to direct detection of terahertz waves, and therefore the response signal is a response signal formed after the measured terahertz wave is self-mixed by the terahertz mixer, and then the response signal can be controlled and read out through an external circuit.

[0066] Specifically, when waveguide integration is adopted, terahertz light / terahertz waves are incident from the waveguide port of the input waveguide, the transmission mode inside the input waveguide is adjusted, and the transmission is performed according to the mode of the input waveguide inside the base mode, until it is emitted onto the detector chip, with high stability; at the same time, since the lens coupling effect is limited by the angle of the incident terahertz wave, the position and angle of the incident terahertz wave will not affect the electric field distribution characteristics of the waveguide port, that is, it can be considered that the coupling degree of the waveguide coupling is higher than that of the lens coupling.

[0067] The waveguide coupling based HEMT terahertz detector provided by the present application realizes high stability by waveguide integration, so that terahertz light is incident from the waveguide port of the input waveguide and is transmitted according to the mode of the input waveguide inside the base mode, and the position and angle of the incident terahertz wave will not affect the electric field distribution characteristics of the waveguide port, thereby providing higher coupling efficiency than quasi-optical lens coupling; and the present application solves the problem of impedance mismatch between structures by microstrip E-plane probe transition and microstrip impedance transformation, further improves the terahertz wave coupling efficiency, and improves the sensitivity level of the detector.

[0068] The application provides a HEMT terahertz detector based on waveguide coupling, which integrates a terahertz mixer, a terahertz signal input and an output part on the same terahertz detector chip, realizes a high-gain and miniaturized terahertz detector, further improves the sensitivity of the detector, and saves the cost.

[0069] The HEMT terahertz detector based on waveguide coupling can also be symmetrically designed and realize terahertz heterodyne detection.

[0070] It should be understood that the above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A waveguide-coupled HEMT terahertz detector, characterized in that, The application relates to a terahertz signal detection device, which comprises the following parts: an input waveguide connected with a terahertz signal detection unit and used for collecting a terahertz input signal; an impedance matching structure connected with the input waveguide and used for adjusting electromagnetic waves in the input waveguide to be matched with the impedance of the terahertz signal detection unit and then coupled into the terahertz signal detection unit; the terahertz signal detection unit is used for processing the received terahertz input signal and outputting a terahertz response signal, wherein the terahertz signal detection unit comprises a terahertz mixer based on a HEMT structure, and the terahertz mixer comprises a semiconductor structure, a first ohmic contact structure, a second ohmic contact structure, a first electrode, a second electrode, a third electrode, a fourth electrode and a fifth electrode; a carrier channel is formed in the semiconductor structure, the first ohmic contact structure and the second ohmic contact structure are arranged at intervals along a selected direction, and the first ohmic contact structure and the second ohmic contact structure are electrically connected with the carrier channel; the first electrode is arranged on the first ohmic contact structure and electrically connected with the first ohmic contact structure, the fifth electrode is arranged on the second ohmic contact structure and electrically connected with the second ohmic contact structure, and the second electrode, the third electrode and the fourth electrode are arranged at intervals along the selected direction between the first ohmic contact structure and the second ohmic contact structure and cover part of the carrier channel; wherein one of the first electrode and the fifth electrode is used as a source electrode, the other is used as a drain electrode, the third electrode is used as a gate electrode, the first electrode, the third electrode and the fifth electrode cooperate with the semiconductor structure to form a first high-mobility field effect transistor, the first electrode, the second electrode and the fifth electrode cooperate with the semiconductor structure to form a second high-mobility field effect transistor, the first electrode, the fourth electrode and the fifth electrode cooperate with the semiconductor structure to form a third high-mobility field effect transistor, and the first high-mobility field effect transistor, the second high-mobility field effect transistor and the third high-mobility field effect transistor are connected in series.

2. The waveguide-coupled HEMT terahertz detector of claim 1, wherein: The impedance matching structure comprises a microstrip probe, a microstrip high inductive line and a microstrip impedance transformer arranged in sequence, and the microstrip high inductive line and the microstrip impedance transformer are connected with the microstrip transmission line, and the microstrip impedance transformer is connected with the terahertz signal detection unit: the microstrip probe is connected with the input waveguide, and the electromagnetic waves in the input waveguide can be coupled to the microstrip transmission line; the microstrip high inductive line is used for eliminating the impedance mismatch caused by the change of the propagation mode between the input waveguide and the microstrip transmission line; and the microstrip impedance transformer is used for performing impedance transformation on the microstrip transmission line, so that the electromagnetic waves coupled to the microstrip transmission line are adjusted to be matched with the impedance of the terahertz signal detection unit.

3. The waveguide-coupled HEMT terahertz detector of claim 2, wherein: The microstrip probe is in the form of a microstrip E-plane probe inserted into the input waveguide.

4. The waveguide-coupled HEMT terahertz detector of claim 3, wherein: The microstrip impedance transformer comprises a quarter-wave impedance transformer or a tapered line impedance transformer.

5. The waveguide-coupled HEMT terahertz detector of claim 1, wherein: The filter structure and / or the lead electrode structure are respectively connected with the terahertz mixer, the filter structure is used for isolating a terahertz input signal, and the lead electrode structure is used for providing a power supply voltage and outputting a terahertz response signal.

6. The waveguide-coupled HEMT terahertz detector of claim 5, wherein: The source of the terahertz mixer is connected with the filter structure and grounded, the gate is connected with the filter structure and connected with the power supply voltage, and the drain is connected with the filter structure and outputs the terahertz response signal.

7. The waveguide-coupled HEMT terahertz detector of claim 6, wherein: The first electrode is electrically connected with the second electrode.

8. The waveguide-coupled HEMT terahertz detector of claim 7, wherein: The first electrode and the second electrode are integrated.

9. The waveguide-coupled HEMT terahertz detector of claim 6, wherein: The fourth electrode is electrically connected with the fifth electrode.

10. The waveguide-coupled HEMT terahertz detector of claim 9, wherein: The fourth electrode and the fifth electrode are integrated.

11. The waveguide-coupled HEMT terahertz detector of claim 6, wherein: The terahertz mixer is of an asymmetric structure.

12. The waveguide-coupled HEMT terahertz detector of claim 11, wherein: The electric field intensity between the third electrode and the first electrode is greater than the electric field intensity between the third electrode and the fifth electrode in the terahertz mixer.

13. The waveguide-coupled HEMT terahertz detector of claim 5, wherein: At least the impedance matching structure, the terahertz mixer and the filter structure are monolithically integrated.

14. The waveguide-coupled HEMT terahertz detector of claim 13, wherein: The effective detection frequency of the waveguide coupling based HEMT terahertz detector for a terahertz signal is 90-112 GHz.

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