阅读说明：本技术 基于石墨烯的天线增强太赫兹探测器及其制备方法 (Graphene-based antenna-enhanced terahertz detector and preparation method thereof ) 是由 徐友龙 侯文强 薛旭 姚向华 于 2021-08-27 设计创作，主要内容包括：本发明公开的一种基于石墨烯的天线增强太赫兹探测器及其制备方法,包括对数周期天线和贴片天线；所述对数周期天线包括两个旋转对称且相互连接的天线本体,两个天线本体分别与场效应晶体管的源极和漏极连接,对数周期天线的馈电点与栅极连接,贴片天线与对数周期天线的中心馈电点相连接,贴片天线通过侧馈的方式对周期天线施加激励。利用对数周期天线充当晶体管探测器的源漏天线,在栅极处再加一个对应探测频率的矩形贴片天线。两个天线协同作用,将目标频段的太赫兹信号引入沟道内,增强探测性能。并且对数周期天线可以多频段工作,可以拓宽探测器的探测频谱。(The invention discloses an antenna enhanced terahertz detector based on graphene and a preparation method thereof, wherein the antenna enhanced terahertz detector comprises a log-periodic antenna and a patch antenna; the log periodic antenna comprises two rotationally symmetrical antenna bodies which are connected with each other, the two antenna bodies are respectively connected with a source electrode and a drain electrode of a field effect transistor, a feed point of the log periodic antenna is connected with a grid electrode, a patch antenna is connected with a central feed point of the log periodic antenna, and the patch antenna applies excitation to the periodic antenna in a side feed mode. The log periodic antenna is used as a source-drain antenna of the transistor detector, and a rectangular patch antenna corresponding to the detection frequency is added at the grid. The two antennas act synergistically to introduce terahertz signals of a target frequency band into the channel, so that detection performance is enhanced. And the log periodic antenna can work in multiple frequency bands, so that the detection frequency spectrum of the detector can be widened.)

1. An antenna enhanced terahertz detector based on graphene is characterized by comprising a log-periodic antenna and a patch antenna;

the log periodic antenna comprises two rotationally symmetrical antenna bodies which are connected with each other, the two antenna bodies are respectively connected with a source electrode and a drain electrode of a field effect transistor, a feed point of the log periodic antenna is connected with a grid electrode, a patch antenna is connected with a central feed point of the log periodic antenna, and the patch antenna applies excitation to the periodic antenna in a side feed mode.

2. The graphene-based antenna-enhanced terahertz detector according to claim 1, wherein the antenna body comprises a fan-shaped center feed body, a plurality of antenna arrays are respectively arranged on two sides of the center feed body, the antenna arrays are arranged at intervals in a fan shape along the edge of the center feed body, the antenna arrays on the two sides are arranged in a staggered mode in the radial direction, and the arc length of the inner edge of the antenna array on one side is equal to the arc length of the outer edge of the radially adjacent antenna array on the other side.

3. The graphene-based antenna enhanced terahertz detector according to claim 2, wherein the opening angle β of the central feed body is 30-60 °; the field angle alpha of the antenna element is 30-60 degrees.

4. The graphene-based antenna enhanced terahertz detector according to claim 2, wherein the number of antenna elements on each side of the central feed body is 3-6.

5. The graphene-based antenna enhanced terahertz detector according to claim 2, wherein the scaling factor τ in the log-periodic antenna is determined by the following method:

wherein R is_nThe radius of the excircle of the nth antenna element is shown; r is_nIs the radius of the inner circle of the nth antenna element.

6. The graphene-based antenna enhanced terahertz detector according to claim 1, wherein the grid is connected with the central feed point through a test electrode.

7. The graphene-based antenna-enhanced terahertz detector according to claim 1, wherein a two-dimensional material channel is arranged on the dielectric substrate, the source and the drain are respectively arranged at two ends of the channel, the source and the drain are in ohmic contact with the channel, a gate dielectric layer is deposited on the dielectric substrate, and the gate is arranged on the gate dielectric layer.

8. The graphene-based antenna enhanced terahertz detector according to claim 7, wherein the two-dimensional material is graphene, black phosphorus, molybdenum disulfide or molybdenum diselenide.

9. The graphene-based antenna enhanced terahertz detector according to claim 1, wherein the field effect transistor is of a top gate structure.

10. The preparation method of the graphene-based antenna enhanced terahertz detector as claimed in any one of claims 1 to 8, characterized by comprising the following steps:

step 1, transferring a two-dimensional material onto a medium substrate;

step 2, after the channel is defined, removing the two-dimensional material except the channel to form the channel;

step 3, pressing a source electrode and a drain electrode at two ends of the channel to form ohmic contact;

step 4, depositing a gate dielectric layer on the dielectric substrate, and forming a gate on the gate dielectric layer to obtain a field effect transistor;

step 5, forming a log periodic antenna and a patch antenna on the dielectric substrate;

and 6, segmenting the dielectric substrate obtained in the step 5 to obtain a field effect transistor with the dielectric substrate, a log periodic antenna and a patch antenna, and assembling to obtain the graphene-based antenna enhanced terahertz detector.

Technical Field

The invention relates to the technical field of terahertz detection, in particular to an antenna-enhanced terahertz detector based on graphene and a preparation method thereof.

Background

Terahertz waves are a section of electromagnetic waves between 0.1 and 10Thz, and are located between the microwave band and the infrared band. In recent years, with the continuous and deep research on terahertz waves, the terahertz waves are found to have a plurality of unique properties, and have very wide prospects in the fields of terahertz biology, medical research, explosive detection, 6G communication, security detection, nondestructive detection of parts and the like. In order to develop a terahertz wave technology, a terahertz source and a terahertz detector are two important difficulties.

In the case of terahertz detectors, an antenna is one of the most important parts. Because the frequency of the terahertz wave band is high, and the signal intensity is weak, usually, the electrode of the detector is difficult to be decoupled into the terahertz wave in the space, and therefore, the detection efficiency is generally low. In order to improve the detection efficiency of the detector, a well-designed terahertz coupling antenna is needed to help the detector capture terahertz waves in space and transmit the terahertz waves to a sensitive element of the detector.

In addition, the principle of detecting terahertz waves by devices such as Field Effect Transistors (FETs), High Electron Mobility Transistors (HEMTs) and the like is theoretically explained based on the plasma wave oscillation principle proposed by Dyakonov and Shur. The field effect transistor is much faster to detect than a conventional thermal detector. The materials used by the traditional field effect transistor terahertz detector are mainly III-V group semiconductors. At present, GaN/AlGaN materials and the like are used more frequently, and the uniformity is better because the original piece can be directly customized in the original factory. But the original piece has higher price and complex growth process, which is not beneficial to large-scale production. In recent years, the technology of material preparation is followedMature, some novel materials with excellent photoelectric properties are also applied to terahertz detectors, such as graphene, carbon nanotubes, black phosphorus, transition metal disulfides, and the like. The carrier mobility of graphene is about 15000cm at room temperature²and/V s, which is more than 10 times of silicon material. And under certain specific conditions, the mobility can reach 200000cm²Above Vs, is the highest of known semiconductor materials. Also, intrinsic graphene is a zero band gap material, but after special processing, its energy band can be opened and modulated in the range of zero to several hundred milli-electron volts. The graphene material meets the high requirements of the terahertz detection technology on the material, and becomes a pyrothermal material in the field of detectors at present.

At present, a terahertz detector with high sensitivity and low cost at room temperature is still in shortage. The existing reported terahertz detector has single detection frequency, complex preparation process and expensive price of required materials, and always limits the development of the field of terahertz detectors. Therefore, a detector which has reasonable device structure design and simple preparation process and can realize multi-band terahertz wave detection at room temperature is urgently needed to be found.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides an antenna enhanced terahertz detector based on graphene and a preparation method thereof.

The invention is realized by the following technical scheme:

an antenna enhanced terahertz detector based on graphene comprises a log-periodic antenna and a patch antenna;

the log periodic antenna comprises two rotationally symmetrical antenna bodies which are connected with each other, the two antenna bodies are respectively connected with a source electrode and a drain electrode of a field effect transistor, a feed point of the log periodic antenna is connected with a grid electrode, a patch antenna is connected with a central feed point of the log periodic antenna, and the patch antenna applies excitation to the periodic antenna in a side feed mode.

Preferably, the antenna body includes that the body is presented in sectorial center, and the both sides that the body was presented in the center are provided with a plurality of antenna array respectively, and a plurality of antenna array are fan-shaped interval along the edge that the body was presented in the center and arrange to the antenna element of both sides is along radial dislocation set, and wherein the inward flange arc length of the antenna element of one side equals the outward flange arc length of the radial adjacent antenna element of opposite side.

Preferably, the opening angle β of the central feed body is 30-60 °; the field angle alpha of the antenna element is 30-60 degrees.

Preferably, the number of the antenna elements on each side of the central feed body is 3-6.

Preferably, the method for determining the scaling factor τ in the log periodic antenna is as follows:

wherein R is_nThe radius of the excircle of the nth antenna element is shown; r is_nIs the radius of the inner circle of the nth antenna element.

Preferably, the gate is connected to the central feed point via a test electrode.

Preferably, a two-dimensional material channel is arranged on the dielectric substrate, the source electrode and the drain electrode are respectively arranged at two ends of the channel, the source electrode and the drain electrode are in ohmic contact with the channel, a gate dielectric layer is deposited on the dielectric substrate, and the gate electrode is arranged on the gate dielectric layer.

Preferably, the two-dimensional material is graphene, black phosphorus, molybdenum disulfide or molybdenum diselenide.

Preferably, the field effect transistor is a top gate structure.

A preparation method of an antenna enhanced terahertz detector based on graphene comprises the following steps:

step 1, transferring a two-dimensional material onto a medium substrate;

step 2, after the channel is defined, removing the two-dimensional material except the channel to form the channel;

step 3, pressing a source electrode and a drain electrode at two ends of the channel to form ohmic contact;

step 4, depositing a gate dielectric layer on the dielectric substrate, and forming a gate on the gate dielectric layer to obtain a field effect transistor;

step 5, forming a log periodic antenna and a patch antenna on the dielectric substrate;

and 6, segmenting the dielectric substrate obtained in the step 5 to obtain a field effect transistor with the dielectric substrate, a log periodic antenna and a patch antenna, and assembling to obtain the graphene-based antenna enhanced terahertz detector.

Compared with the prior art, the invention has the following beneficial technical effects:

according to the graphene-based antenna enhanced terahertz detector provided by the invention, a log-periodic antenna is used as a source-drain antenna of a transistor detector, and a rectangular patch antenna corresponding to detection frequency is added at a grid. The two antennas act synergistically to introduce terahertz signals of a target frequency band into the channel, so that detection performance is enhanced. And the log periodic antenna can work in multiple frequency bands, so that the detection frequency spectrum of the detector can be widened.

In addition, the two-dimensional material with higher mobility is used as a channel sensitive material in the field effect transistor, so that the working speed and sensitivity of the device can be improved. A source drain electrode of the transistor is integrated with the log periodic antenna, a grid electrode is integrated with the patch antenna, and the double antennas work cooperatively, so that the coupling efficiency of the terahertz wave is improved. The detection performance is improved.

Drawings

FIG. 1 is a schematic diagram of a log periodic antenna according to the present invention;

fig. 2 is a schematic diagram of a novel log periodic-patch cooperative antenna structure in the present invention;

FIG. 3 is a schematic diagram of the overall structure of the detector of the present invention;

FIG. 4 is a schematic cross-sectional view of a transistor portion of the detector of the present invention.

In the figure: 1 is the sector opening angle beta of the center feed of the log periodic antenna(ii) a 2 is the field angle alpha of the fan-shaped sawtooth oscillator; 3 is the longest antenna element with an outer radius of length R (6)₁The inner radius is the length shown as (7) and is recorded as r₁(ii) a (4) Metal test electrodes on two sides of the log periodic antenna; (5) is the feed point of a log periodic antenna.

(11) Is a source electrode; (12) is a grid; (13) a grid dielectric layer; (14) is a drain electrode; (15) is a silicon dioxide layer; (16) a silicon substrate; (17) is a two-dimensional material.

Detailed Description

The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.

Referring to fig. 1 to 4, a graphene-based antenna enhanced terahertz detector includes a dielectric substrate, and a terahertz coupling antenna and a field effect transistor disposed thereon.

The terahertz coupling antenna comprises a log-periodic antenna and a patch antenna, the log-periodic antenna comprises two antenna bodies which are rotationally symmetric and are self-complementary sawtooth vibrators, the circle centers of two sector antenna bodies are connected to form a feed point, the log-periodic antenna is arranged in the center of a dielectric substrate, the patch antenna is connected with the middle feed point of the log antenna through a lead, a graphene material is filled in a channel of a field effect transistor, a source electrode and a drain electrode are pressed at two ends of the graphene channel, a gate dielectric layer is arranged on the graphene, a gate metal is deposited on the dielectric layer to form a top gate structure, the two antenna bodies are respectively connected with the source electrode and the drain electrode of the field effect transistor, and the patch antenna is connected with the gate electrode of the field effect transistor.

The feed point of the log periodic antenna is also connected with a test electrode, the test electrode and the patch electrode are symmetrically arranged on two sides of the feed point, and the test electrode is connected with the grid electrode through a microstrip line.

The antenna body feeds the body including sectorial center, and the both sides that the body was fed to the center are provided with a plurality of antenna array respectively, and a plurality of antenna array are fan-shaped interval along the edge that the body was fed to the center and arrange to the antenna element of both sides is along radial dislocation set, and wherein the inward flange arc length of the antenna element of one side equals the outward flange arc length of the other side along radial adjacent another antenna element.

The number of the antenna elements on each side of the antenna body is 3-5.

The range of the sector opening angle beta of the antenna element is 30-60 degrees; the field angle alpha of the connected fan-shaped sawtooth vibrators with different lengths ranges from 30 degrees to 60 degrees, tau is a scale factor in the log periodic antenna and ranges from 1.5 to 2.5, and the calculation method is as follows

Wherein R is_nThe radius of the excircle of the nth antenna element is shown; r is_nIs the radius of the inner circle of the nth antenna element.

The length R of the sector sawtooth oscillator of the log periodic antenna is different according to different target detection frequencies, and the preferred length R₁The length is 200-1000 μm.

The patch antenna is connected with a feed point of the log periodic antenna through a microstrip line, the patch antenna applies excitation to the periodic antenna in a side feed mode, and a feed area of the patch antenna is overlapped with a feed area of the log periodic antenna.

The length L of the patch antenna is in the range of 200-1000 μm, the width W thereof is in the range of 200-1000 μm,

the testing electrode is arranged on the arc-shaped edge of the antenna oscillator, the antenna oscillator is connected with the source electrode and the drain electrode of the field effect transistor through the testing electrode, the size range of the testing electrode is 100 x 100 mu m to 200 x 200 mu m, the length range of a lead electrode connected with the log periodic antenna is 0-1000 mu m, and the line width is 20-60 mu m.

The thicknesses of the log periodic antenna, the patch antenna and the microstrip line are all between 100nm and 1000 nm.

A two-dimensional material channel is arranged on the dielectric substrate, a source electrode and a drain electrode are arranged at two ends of the channel and are in ohmic contact with the channel, a gate dielectric layer is deposited on the dielectric substrate, and a gate electrode is arranged on the gate dielectric layer. The length and width of the dielectric substrate need to be larger than the area of the antenna structure.

The dielectric substrate is a silicon wafer, gallium nitride, gallium aluminum nitride or silicon carbide, the dielectric constant of the dielectric substrate regulates the size range of the antenna, preferably a silicon/silicon wafer, the whole thickness is 500-550 mu m, the surface is provided with silicon dioxide with the thickness of about 250-300nm, the dielectric constant of the silicon dioxide is 3.9, and the dielectric constant of the silicon is 11.9. The lower surface of the medium substrate is plated with a layer of gold, and the thickness of the gold is 50nm-50 mu m.

The whole channel of the field effect transistor is formed by graphene, the graphene is arranged on the upper surface of the dielectric substrate, the length of the channel is 20 mu m-500nm, and the width of the channel is 50 mu m-500 nm; the two-dimensional material may be a graphene material, or may be replaced with another two-dimensional material, such as black phosphorus, molybdenum disulfide, or molybdenum diselenide.

The source electrode and the drain electrode of the field effect transistor are made of alloy materials, are formed by layered deposition of metals such as titanium, aluminum, nickel, gold and the like, and form ohmic contact with sensitive materials in the channel.

A gate dielectric layer made of aluminum oxide (Al) is formed on the channel₂O₃) Hafnium oxide (HfO)₂) Etc. with a thickness of 10-30 nm.

The length of the grid electrode is between 10 mu m and 50nm and is positioned at the midpoint of the graphene channel. And the rectangular patch antenna and the test electrode patch which are positioned on the two sides of the test electrode patch are respectively connected through microstrip lines.

Example 1

In this embodiment, a silicon/silicon dioxide sheet is used as the silicon substrate 16 of the antenna, the silicon thickness is 500 μm, the silicon dioxide thickness is 300nm, and the R of the log periodic antenna is₁960 μm, 45 degrees for both beta and alpha, 800 μm for the length L, 980 μm for the width W, and 0.5 μm for the thickness of the rectangular patch antenna, which is specific to the 0.1THz band.

In this example, the channel length and the channel width are both 10 μm; the thickness of the gate dielectric layer is 20nm, and the thickness of the gate metal is 200 nm; the source and drain electrodes are made of titanium/gold alloy, wherein the titanium is 20nm, and the gold is 180 nm; the rectangular patch antenna and the center of the log periodic antenna are connected through microstrip lines with different thicknesses, and the two antennas work in a cooperative mode to jointly introduce signals into a feed area.

The model of the log periodic antenna is constructed in HFSS simulation software, and has good absorption peaks in more than multiple bands in the range of 100-200 GHz. With return loss reaching 26dB at 100 GHz.

The following describes in detail a method for manufacturing the graphene-based antenna enhanced terahertz detector, including the following steps:

step 1, cleaning a medium substrate.

If a silicon/silicon dioxide sheet is taken as an example, a silicon dioxide layer 15 is arranged on a silicon substrate 16, and after being cleaned for 30min at 80 ℃ by using a sulfuric acid solution, the silicon substrate is ultrasonically cleaned for 10 min by using acetone, isopropanol, ethanol and deionized water respectively, and then dried for later use;

step 2, completely transferring the two-dimensional material 17 onto a substrate by adopting a wet transfer method;

step 3, after the photoresist is used for defining the channel, the two-dimensional material outside the channel is removed by a dry etching process means, and only the two-dimensional material 17 in the channel region is reserved;

and 4, pressing a source electrode 11 and a drain electrode 14 on two ends of the channel two-dimensional material and forming ohmic contact.

Pressing source and drain electrodes on two ends of a channel two-dimensional material by utilizing photoetching and electron beam evaporation to form ohmic contact with the two-dimensional material, wherein the two-dimensional material is made of an alloy material and is formed by depositing one or more metals such as titanium, aluminum, nickel, gold and the like in a layered mode;

and 5, defining the position of the gate dielectric layer on the dielectric substrate by utilizing photoetching, and growing an oxide layer dielectric with a certain thickness by utilizing an atomic layer deposition technology to form a gate dielectric layer 13.

Step 6, defining the position of a grid electrode on the grid dielectric layer by utilizing a photoetching technology, and growing grid electrode metal by utilizing electron beam evaporation to form a grid electrode 12;

and 7, forming a log periodic antenna, a patch antenna, a test electrode and a microstrip line on the dielectric substrate.

Making a log periodic antenna connected at the source electrode and the drain electrode, a rectangular patch antenna connected at the grid electrode, a test electrode and a related microstrip line by utilizing a photoetching technology and an electron beam evaporation technology;

and 8, scribing the medium substrate, and subpackaging to complete the preparation of the device.

The invention provides a graphene-based antenna enhanced terahertz detector, which adopts a method of double-antenna cooperative work, and when the traditional single antenna works in terahertz detection and is applied, such as a butterfly wire, a dipole antenna and the like, the traditional single antenna is often directly used as a source drain or source gate electrode of a transistor detector. When the terahertz wave source-drain electrode is used as a source-drain electrode, the antenna can form a corresponding coupling electric field in a channel, but no corresponding terahertz signal is introduced on a grid electrode. If the antenna is used as a source and gate structure, the missing marks are only used as lead wires to lead out signals, and at the moment, the symmetry of the dipole is destroyed. The cooperative combined antenna designed in the invention utilizes a log periodic antenna as a source-drain antenna of a transistor detector, and adds a rectangular patch antenna corresponding to detection frequency at a grid. The two antennas act synergistically to introduce terahertz signals of a target frequency band into the channel, so that detection performance is enhanced. And the log periodic antenna can work in multiple frequency bands, so that the detection frequency spectrum of the detector can be widened.

In addition, the two-dimensional material with higher mobility is used as a channel sensitive material in the field effect transistor, so that the working speed and sensitivity of the device can be improved. A source drain electrode of the transistor is integrated with the log periodic antenna, a grid electrode is integrated with the patch antenna, and the double antennas work cooperatively, so that the coupling efficiency of the terahertz wave is improved. The detection performance is improved.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.