Round-layout anode gradient Schottky diode assembly and frequency doubler

Abstract

The invention, which belongs to the technical field of terahertz communication, discloses a circularly-arranged anode gradient Schottky diode assembly comprising a first branch circuit, a second branch circuit and a third branch circuit which are connected in parallel. Each of the first branch, the second branch and the third branch comprises a metal bonding pad and a plurality of Schottky diodes; and in each branch, the plurality of Schottky diodes are reversely connected in series towards two sides by taking the metal bonding pad as a center. According to the invention, the number of anodes of the Schottky diode is increased by increasing the diode backflow channels in the transverse direction, and when the circularly-arranged anode gradient Schottky diode assembly is applied to a frequency doubler, the tolerable input power and output power of the frequency doubler can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz communication, and in particular relates to a circularly arranged anode gradient Schottky diode component and a frequency doubler. Background Art

[0002] The wide application of electromagnetic spectrum in the economic and military fields, as well as the increasingly prominent resource shortage contradiction brought about by limited spectrum resources, have made electromagnetic spectrum resources one of the important resources that countries around the world compete for. The electromagnetic spectrum currently used covers low-frequency meter waves, millimeter waves, infrared and visible light bands. Among them, electromagnetic waves in the frequency range of 0.1 to 10 THz are called terahertz waves (THz). This frequency band is located exactly in the electromagnetic gap between millimeter waves and infrared rays, so it is called the "THz Gap". At the same time, from the energy point of view, the energy of terahertz waves is between electrons and photons, so this gap is located in the overlapping area of ​​electronics and photonics. The special position of the "THz Gap" allows terahertz waves to integrate the advantages of low-frequency millimeter waves and high-frequency infrared, showing characteristics such as wide bandwidth, high security, strong penetration, and high resolution. This series of characteristics makes terahertz technology widely used in terahertz spectrum, terahertz imaging, terahertz communication, and terahertz military, showing great application value.

[0003] In the development of terahertz application technology, terahertz testing instruments are needed as support, among which terahertz frequency doubling source is a key component. How to obtain high-power, low-cost and highly reliable terahertz source is the primary problem that needs to be solved.

[0004] At present, terahertz sources based on semiconductor devices have gradually become the main way to obtain terahertz waves based on electronics. The nonlinearity of planar Schottky diodes is usually used to realize the function of microwave solid-state frequency sources, and key performance indicators such as the efficiency, output power, and operating bandwidth of the frequency multiplier will determine the overall performance of the solid-state frequency source and the entire terahertz test instrument.

[0005] Figure 1 Schematic diagram of the structure of Schottky diode components in the prior art. Figure 1As shown, the square layout Schottky diode assembly used in the prior art requires excitation in both horizontal and vertical ways because the fundamental wave is coupled to the Schottky diode. Therefore, the output signal will have second harmonics of different phases, resulting in the vector being reduced when the current signal on the microstrip line is superimposed, and the horizontal Schottky diode is not designed with a ground port, so it is impossible to add a bias voltage port through the microstrip design, and the Schottky diode can only be turned on by the radio frequency signal, and the overall frequency doubling efficiency is low. Further, due to the limitations of the lateral size and structure of the cavity, the doubler designed based on the square layout Schottky diode assembly generally uses a 6-junction (Schottky junction) or 8-junction Schottky diode, and the power that each Schottky junction can withstand is about 50mW. Therefore, the input power tolerance of the doubler is not high, and the output power is also limited, which cannot meet the requirements of the contemporary terahertz communication field. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a circular layout of anode gradient Schottky diode components and doublers. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a circular layout anode gradient Schottky diode component, comprising a first branch, a second branch and a third branch connected in parallel; wherein:

[0008] The first branch, the second branch and the third branch all include a metal pad and a plurality of Schottky diodes; in each branch, the plurality of Schottky diodes are reversely connected in series on both sides with the metal pad as the center.

[0009] In one embodiment of the present invention, in each of the branches, a plurality of Schottky diodes are arranged at equal intervals, and the area of ​​the anode of the Schottky diode gradually increases toward both sides with the metal pad as the center.

[0010] In one embodiment of the present invention, the number of Schottky diodes in the first branch is the same as the number of Schottky diodes in the third branch, and the first branch and the third branch are symmetrical with respect to the second branch and are arranged in a circular shape.

[0011] In one embodiment of the present invention, the first branch and the third branch each include 6 Schottky diodes, and the second branch includes 4 Schottky diodes.

[0012] In one embodiment of the present invention, a first beam lead and a second beam lead are further included, which are respectively located at the first end and the second end of each branch circuit connected in parallel.

[0013] In one embodiment of the present invention, the Schottky diode is a GaAS Schottky diode.

[0014] In a second aspect, the present invention further provides a frequency doubler, characterized in that it comprises an input waveguide, a microstrip line, an output microstrip waveguide transition portion, an output waveguide, and a circularly arranged anode gradient Schottky diode assembly as claimed in any one of claims 1 to 6; wherein,

[0015] The input waveguide, the microstrip line, the output microstrip waveguide transition portion and the output waveguide are connected in sequence, and the circular layout anode gradient Schottky diode component is fixed on the cavity of the input waveguide through a beam lead.

[0016] In one embodiment of the present invention, the input waveguide is used to receive an input electromagnetic wave signal and transmit the electromagnetic wave signal in TE10 mode;

[0017] The microstrip line is used to convert the electromagnetic wave signal in the TE10 mode into a fundamental wave in the form of a quasi-TEM wave for transmission, and to provide an output matching microstrip circuit for the circularly arranged anode gradient Schottky diode component;

[0018] The circular layout anode gradient Schottky diode component is used to generate quasi-TEM second harmonic through the matching microstrip circuit under the excitation of the fundamental wave in the form of the quasi-TEM wave;

[0019] The output microstrip waveguide transition section is used to convert the quasi-TEM second harmonic into a TE10 mode;

[0020] The output waveguide is used to output the electromagnetic wave signal in TE10 mode.

[0021] In one embodiment of the present invention, an I-shaped filter is further included to provide a DC bias voltage for the circularly arranged anode gradient Schottky diode component.

[0022] In one embodiment of the present invention, the input waveguide is a two-section structure, the first section is a WR10 waveguide, and the second section is an input height-reduced waveguide; the output waveguide is a WR5 waveguide.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The circular anode gradient Schottky diode assembly provided by the present invention includes a plurality of Schottky diodes, which form a first branch, a second branch and a third branch connected in parallel. The plurality of Schottky diodes in each branch are connected in series in reverse direction to both sides with the metal pad as the center. The number of anodes of the Schottky diodes is increased by increasing the diode return path in the lateral direction. When the circular anode gradient Schottky diode assembly is applied to a doubler, the input power and output power of the doubler can be improved.

[0025] (2) In each branch of the circularly arranged anode gradient Schottky diode assembly, the area of ​​the Schottky diode anode gradually increases toward both sides with the metal pad as the center. The present invention alleviates the problem of low efficiency introduced by the phase difference of the excitation signal by using Schottky diodes with a lateral anode area gradient while keeping the Schottky diodes at equal spacing.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a Schottky diode component in the prior art;

[0028] Figure 2 1 is a schematic structural diagram of a circular anode gradient Schottky diode assembly provided by an embodiment of the present invention;

[0029] Figure 3 Schematic diagram of the structure of the Schottky diode provided by the embodiment of the present invention

[0030] Figure 4 is a schematic diagram of a preparation process of a Schottky diode provided by an embodiment of the present invention;

[0031] Figure 5 is a schematic structural diagram of a frequency doubler provided in an embodiment of the present invention;

[0032] Figure 6 It is a topological structure diagram of a balanced frequency doubler provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0034] Figure 2 Schematic diagram of the structure of the circular anode gradient Schottky diode assembly provided by the embodiment of the present invention. Figure 2 As shown, an embodiment of the present invention provides a circular layout anode gradient Schottky diode component 100, comprising a first branch 1, a second branch 2 and a third branch 3 connected in parallel; wherein,

[0035] The first branch 1 , the second branch 2 and the third branch 3 all include a metal pad 4 and a plurality of Schottky diodes 5 ; in each branch, the plurality of Schottky diodes 5 are connected in series in opposite directions with the metal pad 4 as the center.

[0036] Specifically, the above-mentioned anode gradient Schottky diode component 100 based on circular layout includes multiple Schottky diodes 5, which form three parallel branches, namely a first branch 1, a second branch 2 and a third branch 3, wherein the number of Schottky diodes 5 in the first branch 1 is the same as the number of Schottky diodes 5 in the third branch 3, the Schottky diodes 5 in the second branch 2 are arranged in a straight line, and the first branch 1 and the third branch 3 are symmetrical about the second branch 2 and have a circular layout, and in each branch, multiple Schottky diodes 5 are connected in series in reverse on both sides with the metal pad 4 as the center. This design method can increase the signal path to three, increase the number of anodes of the diode, and also increase the input power and output power tolerance of the Schottky diode 5.

[0037] Optionally, in each branch, the metal pad 4 is connected to the Schottky diodes 5 adjacent to each other on both sides through the air bridge 6, such as Figure 2 As shown, one end of the air bridge 6 is connected to the metal pad 4, and the other end is connected to the anode 7 of the adjacent Schottky metal tube. A plurality of Schottky diodes 5 are arranged at equal intervals, and each Schottky diode 5 is connected in series with the next Schottky diode 5 through the air bridge 6. Figure 2 The metal component with an arc structure connected to the anode 7 is the cathode 8, and the area of ​​the anode 7 of the Schottky diode 5 in each branch gradually increases toward both sides with the metal pad 4 as the center. It should be understood that the zero-bias capacitance value of each Schottky diode 5 is directly related to the anode radius, and the increase in the anode area will lead to an increase in the zero-bias capacitance value, and the unbalanced excitation of the lateral Schottky diode by the electromagnetic signal will make the capacitive impedance of the Schottky diode far away from the center line (i.e., the straight line perpendicular to the second branch) smaller than that of the Schottky diode close to the center line. Therefore, this embodiment gradually increases the area of ​​the Schottky diode anode in each branch toward both sides of the center line, and uses the zero-bias capacitance brought by the increased anode area to compensate for this imbalance, thereby solving the problem of reduced efficiency caused by the phase difference introduced by the unbalanced signal.

[0038] In this embodiment, the first branch 1 and the third branch 3 each include six Schottky diodes 5 , and the second branch 2 includes four Schottky diodes 5 .

[0039] Specifically, in Figure 2 From the perspective shown, there are two series-connected Schottky diodes 5 on the upper and lower sides of the metal pad 4 in the second branch 2, and three series-connected Schottky diodes 5 on both sides of the metal pad 4 in the first branch 1 and the third branch 3, respectively. The formed Schottky diode assembly 100 includes a total of 16 Schottky diodes 5. Of course, in other embodiments, the number of Schottky diodes 5 in each branch of the Schottky diode assembly 100 can be flexibly designed and adjusted according to actual needs. Figure 2Only 16 Schottky diodes 5 are taken as an example for illustration, and this application does not limit this.

[0040] Optionally, the circular layout anode gradient Schottky diode component 100 further includes a first beam lead 91 and a second beam lead 92, which are respectively located at the first end and the second end of each branch connected in parallel.

[0041] Optionally, the Schottky diode 5 used in the circular layout anode gradient Schottky diode assembly 100 is a GaAS Schottky diode. Figure 3 is a schematic diagram of the structure of a Schottky diode provided by an embodiment of the present invention, Figure 4 is a schematic diagram of the preparation process of the Schottky diode provided in the embodiment of the present invention, see Figures 3-4 , GaAS Schottky diodes can be prepared by the following method:

[0042] Step S1, cleaning the epitaxial wafer:

[0043] like Figure 4 As shown in (a), the epitaxial wafer is cleaned by sequentially placing the homogeneous epitaxial wafer in an acetone solution, an anhydrous ethanol solution and deionized water for ultrasonic cleaning for 5 minutes each, and then blowing it dry with nitrogen.

[0044] Step S2, growing a passivation layer:

[0045] like Figure 4 As shown in (b), the epitaxial wafer is placed in an atomic layer deposition device, and reaction gases trimethylaluminum and water are introduced to deposit Al2O3 with a thickness of 20nm at a temperature of 300℃; then the wafer is placed in a PECVD device, and reaction gases SiH4 and NH3 are introduced to deposit a SiN film with a thickness of 200nm at a temperature of 350℃.

[0046] Step 3: Etching the air capacitor area:

[0047] like Figure 4 As shown in (c), the SiN film covering the air capacitor area is properly overetched using a reactive ion etching device, and then the GaAs epitaxial layer and the buffer layer are slowly etched. After etching, the epitaxial wafer needs to be cleaned and then annealed at 450°C with nitrogen to further repair the interface loss introduced by the slow etching.

[0048] Step 4: Etching the metal contact area:

[0049] like Figure 4 As shown in (d) to (e), an inductively coupled plasma etching device (ICP) is used to etch the metal contact areas and Schottky contact areas on both sides of the device, respectively, wherein the power source power is 300 W, the chamber pressure during etching is 8 mTorr, and the temperature is 150°C.

[0050] Step 5: Metal deposition:

[0051] like Figure 4 As shown in (f), metal Ti / Al / Ni / Au is deposited in the etched cathode groove area in sequence by electron beam evaporation process, and the electrode is formed after the metal stripping process. Argon gas is introduced into the rapid annealing furnace as a protective gas, the temperature is set to 950°C, and the device is subjected to a rapid thermal annealing treatment for 45 seconds to form an ohmic contact electrode.

[0052] Furthermore, metal Ni / Au is deposited in the anode contact and Schottky contact groove regions by electron beam evaporation, and an anode metal electrode is formed on the surface by metal stripping.

[0053] Step S6: making an air bridge:

[0054] like Figure 4 As shown in (g), photoresist is used for photolithography and development to etch out the air bridge area, anode and cathode electrode areas. Then, metal Ti / Au is deposited on the sample surface by electron beam evaporation to form a plating layer, as shown in FIG. Figure 4 As shown in (h).

[0055] Then, if Figure 4 As shown in (i) to (j), Au with a thickness of 3 μm is plated on the surface of the plated layer, all photoresists are removed, and the excess metal is stripped off, leaving the electroplated layer to form an air bridge, and at the same time, the contact area of ​​the anode and cathode deposition is formed to prepare Figure 3 GaAs Schottky diode shown.

[0056] Figure 5 Schematic diagram of the structure of the frequency doubler provided by the embodiment of the present invention. Figure 5 As shown, the present invention also provides a frequency doubler 200, comprising an input waveguide 10, a microstrip line 11, an output microstrip waveguide transition portion 12, an output waveguide 13 and the above circular layout anode gradient Schottky diode component 100; wherein,

[0057] The input waveguide 10, the microstrip line 11, the output microstrip waveguide transition portion 12 and the output waveguide 13 are connected in sequence, and the circular anode gradient Schottky diode component 100 is fixed to the cavity of the input waveguide 10 through a beam lead. For example, the circular anode gradient Schottky diode component 100 can be pasted on the cavity of the input waveguide 10 through silver paste to form a ground loop.

[0058] Specifically, the input waveguide 10 is used to receive an input electromagnetic wave signal and transmit the electromagnetic wave signal in TE10 mode;

[0059] The microstrip line 11 is used to convert the electromagnetic wave signal of the TE10 mode into a fundamental wave in the form of a quasi-TEM wave for transmission, and to provide an output matching microstrip circuit for the circularly arranged anode gradient Schottky diode component 100;

[0060] The circular layout anode gradient Schottky diode assembly 100 is used to generate quasi-TEM second harmonics through a matching microstrip circuit under the excitation of a fundamental wave in the form of a quasi-TEM wave;

[0061] An output microstrip waveguide transition section 12, used for converting the quasi-TEM second harmonic into a TE10 mode;

[0062] The output waveguide 13 is used to output the electromagnetic wave signal in TE10 mode.

[0063] In this embodiment, the input waveguide 10 may be a two-section structure, the first section is a WR10 waveguide, and the second section is an input height-reduced waveguide; the output waveguide 13 is a WR5 waveguide.

[0064] Next, the working principle of the frequency multiplier is explained.

[0065] First, the electromagnetic wave signal is input into the WR10 waveguide (2.54×1.27 mm) in TE10 mode, and after passing through the microstrip line 11, the electromagnetic wave signal in TE10 mode is converted into a fundamental wave in the form of a quasi-TEM wave for propagation. At this time, the fundamental wave signal (73.8-112 GHz) excites the circularly arranged anode gradient Schottky diode assembly 100 in the form of a quasi-TEM wave, and due to the nonlinearity of the Schottky junction, the output signal of the Schottky diode 5 will generate various harmonics.

[0066] The electromagnetic wave signal input to the frequency doubler 200 is represented by a single sine wave as v in =V0cos(ωt), the output signal of the single Schottky diode 5 is expressed in Fourier series as:

[0067]

[0068] Among them, a i Expressed as the Fourier coefficient of the i-th harmonic.

[0069] It can be seen from the above formula that the current generated by the Schottky diode 5 includes not only a DC component but also second and third harmonics.

[0070] Figure 6 2 is a topological diagram of a balanced frequency doubler provided in an embodiment of the present invention. It should be noted that the frequency doubler 200 provided in the present invention is a 220 GHz frequency doubler, wherein the Schottky diode component 100 adopts Figure 6 When the balanced structure is shown, the output current can be expressed as:

[0071]

[0072] At this time, the output current only contains even-order components. Since the input signal is in TE10 mode, the coupled output signal of the Schottky diode assembly 100 is a quasi-TEM wave, and the two modes are orthogonal, so the input electromagnetic wave signal and the output signal are well isolated. By properly designing the microstrip circuit, the second harmonic is most efficiently extracted from the even-order harmonics output by the Schottky diode assembly 100, and the output waveguide 13 converts the second harmonic (150-220GHz) in the form of a quasi-TEM wave into a TE10 mode output.

[0073] Optionally, the frequency doubler 200 further includes an I-shaped filter 14, which is used for subsequent DC power-on to provide a DC bias voltage for the circular anode gradient Schottky diode assembly 100.

[0074] It can be seen from the above embodiments that the beneficial effects of the present invention are:

[0075] (1) The circular anode gradient Schottky diode assembly provided by the present invention includes a plurality of Schottky diodes, which form a first branch, a second branch and a third branch connected in parallel. The plurality of Schottky diodes in each branch are connected in series in reverse direction to both sides with the metal pad as the center. The number of anodes of the Schottky diodes is increased by increasing the diode return path in the lateral direction. When the circular anode gradient Schottky diode assembly is applied to a doubler, the input power and output power of the doubler can be improved.

[0076] (2) In each branch of the circularly arranged anode gradient Schottky diode assembly, the area of ​​the Schottky diode anode gradually increases toward both sides with the metal pad as the center. The present invention alleviates the problem of low efficiency introduced by the phase difference of the excitation signal by using Schottky diodes with a lateral anode area gradient while keeping the Schottky diodes at equal spacing.

[0077] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0078] The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0079] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A circular anode gradient Schottky diode assembly, characterized in that: It includes a first branch, a second branch and a third branch connected in parallel; wherein, The first branch, the second branch and the third branch all include a metal pad and a plurality of Schottky diodes; in each branch, the plurality of Schottky diodes are reversely connected in series on both sides with the metal pad as the center.

2. The circular anode gradient Schottky diode assembly according to claim 1, characterized in that: In each of the branches, a plurality of Schottky diodes are arranged at equal intervals, and the area of ​​the anode of the Schottky diode gradually increases toward both sides with the metal pad as the center.

3. The circular anode gradient Schottky diode assembly according to claim 2, characterized in that: The number of Schottky diodes in the first branch is the same as the number of Schottky diodes in the third branch, and the first branch and the third branch are symmetrical with respect to the second branch and are arranged in a circular shape.

4. The circular anode gradient Schottky diode assembly according to claim 3, characterized in that: The first branch and the third branch each include 6 Schottky diodes, and the second branch includes 4 Schottky diodes.

5. The circular anode gradient Schottky diode assembly according to claim 2, characterized in that: The invention also comprises a first beam lead and a second beam lead, which are respectively located at the first end and the second end of each branch connected in parallel.

6. The circular anode gradient Schottky diode assembly according to claim 1, characterized in that: The Schottky diode is a GaAS Schottky diode.

7. A frequency doubler, characterized in that: An anode gradient Schottky diode component comprising an input waveguide, a microstrip line, an output microstrip waveguide transition portion, an output waveguide, and a circular layout as claimed in any one of claims 1 to 6; wherein, The input waveguide, the microstrip line, the output microstrip waveguide transition portion and the output waveguide are connected in sequence, and the circular layout anode gradient Schottky diode component is fixed on the cavity of the input waveguide through a beam lead.

8. The frequency doubler according to claim 7, characterized in that: The input waveguide is used to receive an input electromagnetic wave signal and transmit the electromagnetic wave signal in TE10 mode; The microstrip line is used to convert the electromagnetic wave signal in the TE10 mode into a fundamental wave in the form of a quasi-TEM wave for transmission, and to provide an output matching microstrip circuit for the circularly arranged anode gradient Schottky diode component; The circular layout anode gradient Schottky diode component is used to generate quasi-TEM second harmonic through the matching microstrip circuit under the excitation of the fundamental wave in the form of the quasi-TEM wave; The output microstrip waveguide transition section is used to convert the quasi-TEM second harmonic into a TE10 mode; The output waveguide is used to output the electromagnetic wave signal in TE10 mode.

9. The frequency doubler according to claim 8, characterized in that: An I-shaped filter is also included, which is used to provide a DC bias voltage for the anode-gradient Schottky diode component in the circular layout.

10. The frequency doubler according to claim 7, characterized in that: The input waveguide is a two-section structure, the first section is a WR10 waveguide, and the second section is an input height-reduced waveguide; the output waveguide is a WR5 waveguide.

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