CN113917713A - Terahertz dual-channel modulator and preparation method thereof - Google Patents
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/0009—Materials therefor
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0102—Constructional details, not otherwise provided for in this subclass
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Abstract
The invention discloses a terahertz dual-channel modulator and a preparation method thereof.A substrate is grown on an epitaxial layer, and a modulation array is arranged on the epitaxial layer; the modulation array is composed of M x N array element structures, a first grid feeder line of each row of array element structures is connected with a first Schottky electrode, a second grid feeder line of each row of array element structures is connected with a second Schottky electrode, M is more than 2, and N is more than 2; the first source-drain feeder line and the second source-drain feeder line of each row of array element structure are both connected with the ohmic electrode; the modulation array is used for passing terahertz waves with different frequencies; the first Schottky electrode and the second Schottky electrode are respectively connected with the ohmic electrode in series through a direct current power supply; the method has the advantages that the resonance mode of the metamaterial structure is changed, and further the terahertz waves of multiple frequency bands are regulated and controlled; the method realizes independent modulation of a plurality of frequency points, has high modulation depth, and has the advantages of small size, easy integration and the like.
Description
Technical Field
The invention relates to the technical field of microwave transmission, in particular to a terahertz dual-channel modulator and a preparation method thereof.
Background
The terahertz wave is an electromagnetic wave between microwave and infrared, the frequency range of the terahertz wave is 0.1-10 THz, and the terahertz wave shows many distinctive electromagnetic characteristics due to the unique frequency band position, so that the terahertz wave can be widely applied to the fields of biomedicine, safety inspection, wireless communication and the like. In recent years, the development of terahertz wireless communication technology is heading towards high speed and long distance, but the development is limited to a certain extent due to the lack of high-performance key devices. The terahertz modulator is one of the key devices, and the improvement of the performance of the terahertz modulator plays a crucial role in the development of the terahertz communication technology, so that the terahertz modulator becomes a research hotspot in recent years.
Since 2004, successive articles related to external terahertz modulators were published in numerous international top-level journal of science, and the contents of the articles include doped semiconductor substrates, phase change materials, graphene and the like, which are combined with metamaterials, and the modulation of terahertz waves propagating in free space is realized by using excitation modes such as external temperature, illumination, electric fields and the like, so that the modulators can be divided into temperature-controlled, light-controlled and electric-controlled modulators. The electronic control modulator has the characteristic of easy integration and has important application in the field of terahertz communication. In 2006, H-T Chen et al propose an electronic control terahertz modulator based on an open resonant ring metamaterial structure, a metal metamaterial structure is in contact with a gallium arsenide substrate to form a Schottky diode structure, and a certain voltage is loaded between ohmic contact and the metal structure of the device, so that modulation of incident terahertz waves can be realized. In 2011, a research team of boston university provides a composite electronic control terahertz modulator based on an open resonator ring metamaterial structure and a HEMT, the concentration of two-dimensional electron gas in a channel of the HEMT is changed through an external voltage, the resonance strength of the metamaterial structure is changed, and then the terahertz wave is regulated and controlled. In 2015, a research team of electronics science and technology university provides a composite metamaterial structure based on an I-shaped metamaterial structure and an HEMT, and the modulation rate of the composite metamaterial structure can reach 1 GHz. In 2017, Zhen Zhou et al propose a terahertz modulator based on a four-opening resonant ring metamaterial structure combined with an HEMT, and under the drive of a 4V grid voltage, the modulation depth can reach 80%, and the modulation rate can reach 2.7 MHz.
Although the modulator has higher modulation depth and modulation rate, only one working channel is provided, that is, only one independent frequency band can implement modulation, but the process of independently modulating signals in each communication frequency band cannot be implemented, and the modulation efficiency and performance of the modulator are affected by the modulation of one independent frequency band.
In view of this, the present application is specifically made.
Disclosure of Invention
The invention aims to solve the technical problem that independent modulation in the communication technology cannot be realized when multiple frequency bands are modulated, and aims to provide a terahertz dual-channel modulator and a preparation method, which can realize independent modulation of multiple frequency points and have high modulation depth.
The invention is realized by the following technical scheme:
the invention provides a terahertz dual-channel modulator which comprises a substrate, an epitaxial layer and a modulation array, wherein the epitaxial layer grows on the substrate, and the modulation array is arranged on the epitaxial layer;
the modulation array is composed of M x N array element structures, a first grid feeder line of each row of array element structures is connected with a first Schottky electrode, a second grid feeder line of each row of array element structures is connected with a second Schottky electrode, M is more than 2, and N is more than 2;
the first source-drain feeder line and the second source-drain feeder line of each row of array element structure are both connected with the ohmic electrode; the modulation array is used for passing terahertz waves with different frequencies;
the first Schottky electrode and the second Schottky electrode are respectively connected with the ohmic electrode in series through a direct current power supply.
The terahertz dual-channel modulator provided by the invention can realize independent modulation of multiple frequency points by arranging a double-doped heterojunction structure, and is high in modulation depth, small in size and easy to integrate.
Preferably, the array element structure comprises a first doped heterojunction structure and a second doped heterojunction structure, the first doped heterojunction structure is connected with the ohmic electrode through the first source-drain feeder line, and the first doped heterojunction structure is connected with the first schottky electrode through the first gate feeder line; the first doped heterojunction structure is respectively connected with the second doped heterojunction structure and the ohmic electrode through the second source-drain feeder line; the second doped heterojunction structure is connected with the second Schottky electrode through the second grid feeder line; and the array element structure is used for passing terahertz waves with different frequencies.
Preferably, the ohmic electrode grows on one side of the epitaxial layer, one end of the ohmic electrode is respectively connected with the first source-drain feeder line and the second source-drain feeder line, and the other end of the ohmic electrode is connected with a positive voltage of a direct-current power supply;
the first Schottky electrode and the second Schottky electrode are grown on the other side of the epitaxial layer and are arranged in parallel;
and an insulating layer is arranged between the first Schottky electrode and the first grid feeder line and is used for isolating the first Schottky electrode from the second grid feeder line.
Preferably, the second source-drain feeder line comprises a first sub-source drain feeder line, a second sub-source drain feeder line and a third sub-source drain feeder line, and the first sub-source drain feeder line is arranged in parallel to the edge of the substrate and is connected with the first doped heterojunction structure; the second sub-source leakage feeder line and the third sub-source leakage feeder line are both perpendicular to the first sub-source leakage feeder line, one end of the second sub-source leakage feeder line is connected with the first sub-source leakage feeder line, the other end of the second sub-source leakage feeder line is connected with the second doped heterojunction structure, one end of the third sub-source leakage feeder line is connected with the first sub-source leakage feeder line, the other end of the third sub-source leakage feeder line is connected with the second doped heterojunction structure, and the second sub-source leakage feeder line and the third sub-source leakage feeder line are arranged in a square mode.
Preferably, the first doped heterojunction structure and the second doped heterojunction structure are both HETM, and the doped material is AlGaN/GaN or AlGaAs/GaAs or InGaAs/GaAs or InGaN/GaN.
Preferably, the ohmic electrode, the first gate feeder, the second gate feeder, the first source-drain feeder, and the second source-drain feeder are made of Ti, Ni, Au, Al, Ag, or Cu.
Preferably, the line width of the first gate feeder line and the line width of the second gate feeder line are both 2 μm, the line width of the first source drain feeder line and the line width of the second source drain feeder line are both 10 μm, and the thicknesses of the first gate feeder line, the second gate feeder line, the first source drain feeder line, and the second source drain feeder line are all 0.2 μm.
Preferably, the insulating layer is a benzocyclobutene insulating layer.
Preferably, the epitaxial layer is a gallium nitride epitaxial layer.
The invention also provides a preparation method of the terahertz dual-channel modulator, which comprises the following steps:
s1: cleaning the substrate by adopting an ultrasonic cleaning mode, and drying the cleaned substrate;
s2: preparing an AlGaN/GaN heterojunction film on a substrate by adopting an organic compound vapor deposition method to obtain a substrate;
s3: spin-coating photoresist with the thickness of 2 microns on the substrate, carrying out photoetching development on the photoresist by using a mask to determine an HEMT active region, etching off the AlGaN/GaN film outside the HEMT active region by adopting an inductive coupling plasma etching method, and removing the residual photoresist on the substrate to obtain the HEMT active region substrate;
s4: respectively depositing a composite metal layer-titanium/aluminum/nickel/gold on two sides of an active region in sequence by utilizing photoetching, electron beam evaporation and stripping processes to serve as a source electrode and a drain electrode of the HEMT;
s5: placing the source and drain at N2Performing rapid thermal annealing treatment on the environment, and forming ohmic contact between a source electrode and a drain electrode and a 2DEG channel;
s6: respectively depositing nickel and gold on the AlGaN/GaN heterojunction film in sequence by utilizing photoetching, electron beam evaporation and stripping processes to form a super-surface structure;
s7: preparing benzocyclobutene on the first Schottky electrode;
s8: and preparing a grid electrode.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. according to the terahertz dual-channel modulator and the preparation method provided by the embodiment of the invention, HEMTs with high-speed dynamic characteristics are designed at two openings of a metamaterial structure, the HEMTs at the two openings are respectively controlled by two electrodes, the two-dimensional electron gas concentration in a HEMT channel is adjusted in a voltage-applied mode, the resonance mode of the metamaterial structure is changed, and the regulation and control of terahertz waves of multiple frequency bands are further realized;
2. the terahertz dual-channel modulator and the preparation method provided by the embodiment of the invention realize independent modulation of multiple frequency points, have high modulation depth, and have the advantages of small size, easiness in integration and the like.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic diagram of a modulator
FIG. 2 is a schematic diagram of an array element structure
FIG. 3 is a cross-sectional view of a first doped heterojunction structure and a second doped heterojunction structure
FIG. 4 is a graph of transmission coefficient of a terahertz modulator
Description of the drawings: 1. an epitaxial layer; 2. an ohmic electrode; 3. a substrate; 4. a second Schottky electrode; 5. a first gate feed line; 6. a second gate feed line; 7. a second doped heterojunction structure; 8. a first doped heterojunction structure; 9. a first Schottky electrode; 10. a first source drain feed line; 11. a second source drain feed line; 12. an insulating layer; 111. a first sub-source drain feed line; 112. a second sub-source drain feed line; 113. a third sub-source drain feed line.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known structures, circuits, materials, or methods have not been described in detail so as not to obscure the present invention.
Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrases "one embodiment," "an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "upper", "lower", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be construed as limiting the scope of the present invention.
Example one
The embodiment discloses a terahertz dual-channel modulator, as shown in fig. 1 and 3, which includes a substrate 3, an epitaxial layer 1 and a modulation array, wherein the epitaxial layer 1 is grown on the substrate 3, and the modulation array is arranged on the epitaxial layer 1;
the modulation array is composed of M x N array element structures, the array element structures are arranged in an array mode, the first grid feeder 5 of each row of array element structures is connected with the first Schottky electrode 9, the second grid feeder 6 of each row of array element structures is connected with the second Schottky electrode 4, M is greater than 2, and N is greater than 2; the first source-drain feeder line 10 and the second source-drain feeder line 11 of each row of array element structure are both connected with the ohmic electrode 2; the modulation array is used for passing terahertz waves with different frequencies; the first schottky electrode 9 and the second schottky electrode 4 are respectively connected in series with the ohmic electrode 2 through a direct current power supply.
The array element structure comprises a first doped heterojunction structure 8 and a second doped heterojunction structure 7, wherein the first doped heterojunction structure 8 is connected with the ohmic electrode 2 through a first source-drain feeder line 10, and the first doped heterojunction structure 8 is connected with a first Schottky electrode 9 through a first grid feeder line 5; the first doped heterojunction structure 8 is respectively connected with the second doped heterojunction structure 7 and the ohmic electrode 2 through a second source-drain feeder 11; the second doped heterojunction structure 7 is connected with the second Schottky electrode 4 through a second grid feeder line 6; and the array element structure is used for passing terahertz waves with different frequencies.
In the array element structure, the transverse period px of the structural unit is 215 μm, and the longitudinal period py is 180 μm. The metal rod width w of the upper first gate feeder line 5 is 10 μm, and the middle metal rod width w1 is 2 μm; the lower period is p1 ═ 40 μm, p2 ═ 95 μm, and the width w ═ 10 μm; in the lowermost second gate feed line 6, the length is px, the width w1 is 2 μm, the opening sizes g and g1 are 10 μm, and the thickness t is 0.2 μm.
The second source-drain feeder line 11 comprises a first sub-source drain feeder line 111, a second sub-source drain feeder line 112 and a third sub-source drain feeder line 113, and the first sub-source drain feeder line 111 is arranged in parallel with the edge of the substrate 3 and is connected with the first doped heterojunction structure 8; the second sub-source drain feeder line 112 and the third sub-source drain feeder line 113 are both perpendicular to the first sub-source drain feeder line 111, one end of the second sub-source drain feeder line 112 is connected to the first sub-source drain feeder line 111, the other end of the second sub-source drain feeder line 112 is connected to the second doped heterojunction structure 7, one end of the third sub-source drain feeder line 113 is connected to the first sub-source drain feeder line 111, the other end of the third sub-source drain feeder line is connected to the second doped heterojunction structure 7, and the second sub-source drain feeder line 112 and the third sub-source drain feeder line 113 are arranged in a square shape surrounding a city.
The first doped heterojunction structure 8 and the second doped heterojunction structure 7 are made of AlGaN/GaN, have a thickness of 0.01 μm, and are located at the opening of the double-opening "zenith" type metamaterial, wherein the size of the upper HEMT is 11 μm by 11 μm, and the size of the lower HEMT is 11 μm by 11 μm. And the doped material is not limited to AlGaN/GaN or AlGaAs/GaAs or InGaAs/GaAs or InGaN/GaN.
HEMTs with high-speed dynamic characteristics are designed at two openings of a metamaterial structure, the HEMTs at the two openings are respectively controlled by two electrodes, the concentration of two-dimensional electron gas in a HEMT channel is adjusted in an external voltage mode, the resonance mode of the metamaterial structure is changed, and then the regulation and control of terahertz waves of multiple frequency bands are realized. The modulation depth of the amplitude modulator in a single-channel mode (open at 0.22THz and 0.34THz, respectively) at the center frequency point of 0.22THz and 0.34THz can reach 91.0% and 96.4%, respectively; the amplitude modulator is in dual channel mode (both open at 0.22THz and 0.34 THz) when the modulation depth at the centre frequency point of 0.22THz and 0.34THz is 89.2% and 93.7%, respectively.
The ohmic electrode 2 grows on one side of the epitaxial layer 1, one end of the ohmic electrode is respectively connected with the first source-drain feeder line 10 and the second source-drain feeder line 11, and the other end of the ohmic electrode is connected with the anode of the direct-current power supply;
the first schottky electrode 9 and the second schottky electrode 4 are grown on the other side of the epitaxial layer 1, and the first schottky electrode 9 and the second schottky electrode 4 are arranged in parallel;
and an insulating layer 12 is arranged between the first schottky electrode 9 and the first gate feeder 5, and the insulating layer 12 is used for isolating the conduction between the first schottky and the second gate feeder 6.
In this embodiment, the ohmic electrode 2, the first gate feeder 5, the second gate feeder 6, the first source-drain feeder 10, and the second source-drain feeder 11 are made of Ti, Ni, Au, Al, Ag, or Cu.
The line width of the first gate feeder line 5 and the line width of the second gate feeder line 6 are both 2 μm, the line width of the first source-drain feeder line 10 and the line width of the second source-drain feeder line 11 are both 10 μm, and the thicknesses of the first gate feeder line 5, the second gate feeder line 6, the first source-drain feeder line 10 and the second source-drain feeder line 11 are all 0.2 μm.
In the present embodiment, the insulating layer 12 provided is the benzocyclobutene insulating layer 12, the epitaxial layer 1 provided is the gallium nitride epitaxial layer 1, the dielectric constant is 9.8, and the thickness h is 280 μm, but the present embodiment is not limited to the layered structure of this material.
The concentration of two-dimensional electron gas in the HEMT is controlled by the external grid voltage, the on-off of terahertz waves can be controlled, a resonance peak appears at 0.22THz when the voltage is applied to the HEMT at the opening g, and the depth of the modulator obtained by calculation is 91.0%; applying voltage to HEMTs at the openings g and g1 simultaneously can generate resonance peak at 0.34THz, and the modulation depth is calculated to be 96.4%; the voltage applied to the HEMT at opening g will have simultaneous resonant peaks at 0.22THz and 0.34THz, where the modulator depths at 0.22THz and 0.34THz are calculated to be 89.2% and 93.7%, respectively. (ii) a
The modulation depth of the amplitude modulator in a single-channel mode (open at 0.22THz and 0.34THz, respectively) at the center frequency point of 0.22THz and 0.34THz can reach 91.0% and 96.4%, respectively; the amplitude modulator is in dual channel mode (both open at 0.22THz and 0.34 THz) when the modulation depth at the centre frequency point of 0.22THz and 0.34THz is 89.2% and 93.7%, respectively.
As shown in fig. 4, which is a transmission coefficient spectrum of the modulator in different open states, the curves of the squares represent the transmission curves for HEMTs with the openings g and g1 closed, corresponding to no power on; the curve of the circle symbol represents the transmission curve of the HEMT under the opening g with the opening g open, the g1 closed and the HEMT under the opening g1 without power; the curve with the triangular symbol represents the transmission curve when the opening g is closed, g1 is open, and the HEMT under the opening g is not electrified and the HEMT under the opening g1 is electrified; the inverted triangular curve represents the transmission curve for two HEMTs powered on with the openings g and g1 open. When no gate voltage is applied to the HEMT, the modulator resonates at 0.16THz with a transmission coefficient of 0.027, as shown by the black curve with squares in fig. 4; when a gate voltage is applied to the HEMT at the g-opening, the modulator resonates at 0.22THz with a transmission coefficient of 0.065, as shown by the rounded black curve in fig. 4; when a voltage is applied to the HEMTs at g and g1 simultaneously, the modulator resonates at 0.34THz with a transmission coefficient of 0.029, as shown by the black curve with inverted triangles in fig. 4; when a gate voltage is applied to the HEMT at the opening g1, the modulator resonates at 0.22THz, which corresponds to a transmission coefficient of 0.079 at 0.22THz, and at 0.34THz, which corresponds to a transmission coefficient of 0.050 at 0.34 THz. As shown in fig. 4 by the black curve with a positive triangle; the terahertz waves of three frequency bands can be regulated and controlled by changing the grid voltage of the HEMT at the two openings of the modulator. Using the formula MD ═ Toff-Ton/Toff (Toff is the transmission coefficient when the modulator opening is closed and Ton is the transmission coefficient when the modulator opening is open), it can be calculated that the modulation depth of the amplitude modulator can reach 91.0% and 96.4% respectively at the 0.22THz and 0.34THz center frequency points in the single channel mode (open at 0.22THz and 0.34THz respectively); the amplitude modulator is in dual channel mode (both open at 0.22THz and 0.34 THz) when the modulation depth at the centre frequency point of 0.22THz and 0.34THz is 89.2% and 93.7%, respectively.
Example two
The embodiment discloses a preparation method of a terahertz dual-channel modulator, which comprises the following steps:
s1: cleaning the substrate 3 by adopting an ultrasonic cleaning mode, and drying the cleaned substrate 3;
s2: preparing an AlGaN/GaN heterojunction film on a substrate 3 by adopting an organic compound vapor deposition method to obtain a substrate;
s3: spin-coating photoresist with the thickness of 2 microns on the substrate, carrying out photoetching development on the photoresist by using a mask to determine an HEMT active region, etching off the AlGaN/GaN film outside the HEMT active region by adopting an inductive coupling plasma etching method, and removing the residual photoresist on the substrate to obtain the HEMT active region substrate;
and preparing an HEMT active region. Firstly, photoresist with the thickness of 2 microns is coated on a substrate in a spinning mode, and photoetching development is carried out on the photoresist by using a mask plate, so that an active region of the HEMT is determined. Then, the AlGaN/GaN thin film outside the HEMT active region is etched by an Inductively Coupled Plasma Etching (ICPE) method in dry Etching. Use is made of Cl2-BCl3And (4) mixing the gases. At this time, the 2DEG exists only in the active region. And finally, removing the residual photoresist on the substrate to obtain the HEMT active region with the thickness of 120 nm.
S4: respectively depositing a composite metal layer-titanium/aluminum/nickel/gold on two sides of an active region in sequence by utilizing photoetching, electron beam evaporation and stripping processes to serve as a source electrode and a drain electrode of the HEMT; and preparing HEMT source and drain. And respectively depositing a composite metal layer-titanium/aluminum/nickel/gold (20nm/1350nm/1000nm/500nm) on two sides of the active region in sequence by utilizing the processes of photoetching, electron beam evaporation, stripping and the like to serve as a source electrode and a drain electrode of the HEMT.
S5: placing the source and drain at N2Performing rapid thermal annealing treatment on the environment, and forming ohmic contact between a source electrode and a drain electrode and a 2DEG channel;
placing the source and drain electrodes in N2And carrying out rapid thermal annealing treatment on the substrate, wherein the temperature in an annealing furnace is increased from normal temperature to 890 ℃ within 7s, the temperature is maintained for 20s, then the temperature is rapidly reduced to 25 ℃, and the source electrode and the drain electrode form ohmic contact with the 2DEG channel.
S6: respectively depositing nickel and gold on the AlGaN/GaN heterojunction film in sequence by utilizing photoetching, electron beam evaporation and stripping processes to form a super-surface structure;
s7: preparing benzocyclobutene on the first Schottky electrode 9;
and preparing the metamaterial structure. Respectively utilizing the technologies of photoetching, electron beam evaporation, stripping and the like to sequentially deposit nickel with the thickness of 20nm and gold with the thickness of 150nm on the AlGaN/GaN heterojunction film to form a super-surface structure. The source electrode and the drain electrode of the HEMT are covered on two sides of the metamaterial structure opening.
S8: and preparing a grid electrode. Because the grid metal wire in the array is too long, in order to ensure the processing quality of the grid and avoid the accidental falling of the grid in the preparation process, the grid wire is independently prepared after the metal artificial microstructure array. The preparation process is the same as that of the metal artificial microstructure.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A terahertz dual-channel modulator is characterized by comprising a substrate (3), an epitaxial layer (1) and a modulation array, wherein the epitaxial layer (1) is grown on the substrate (3), and the modulation array is arranged on the epitaxial layer (1);
the modulation array is composed of M x N array element structures, a first grid feeder (5) of each row of array element structures is connected with a first Schottky electrode (9), a second grid feeder (6) of each row of array element structures is connected with a second Schottky electrode (4), M is more than 2, and N is more than 2;
the first source-drain feeder line (10) and the second source-drain feeder line (11) of each row of array element structure are both connected with the ohmic electrode (2); the modulation array is used for passing terahertz waves with different frequencies;
the first Schottky electrode (9) and the second Schottky electrode (4) are respectively connected with the ohmic electrode (2) in series through a direct current power supply.
2. The terahertz dual-channel modulator according to claim 1, wherein the array element structure comprises a first doped heterojunction structure (8) and a second doped heterojunction structure (7), the first doped heterojunction structure (8) is connected with the ohmic electrode (2) through the first source-drain feeder (10), and the first doped heterojunction structure (8) is connected with the first schottky electrode (9) through the first gate feeder (5); the first doped heterojunction structure (8) is respectively connected with the second doped heterojunction structure (7) and the ohmic electrode (2) through the second source-drain feeder line (11); the second doped heterojunction structure (7) is connected with the second Schottky electrode (4) through the second grid feeder line (6); and the array element structure is used for passing terahertz waves with different frequencies.
3. The terahertz dual-channel modulator according to claim 2, wherein the ohmic electrode (2) is grown on one side of the epitaxial layer (1), and one end of the ohmic electrode is connected to the first source-drain feeder line (10) and the second source-drain feeder line (11), respectively, and the other end of the ohmic electrode is connected to a positive electrode of a direct current power supply;
the first Schottky electrode (9) and the second Schottky electrode (4) are grown on the other side of the epitaxial layer (1), and the first Schottky electrode (9) and the second Schottky electrode (4) are arranged in parallel;
and an insulating layer (12) is arranged between the first Schottky electrode (9) and the first grid feeder line (5), and the insulating layer (12) is used for isolating the first Schottky and the second grid feeder line (6) from conducting electricity.
4. The terahertz dual-channel modulator according to claim 2, wherein the second source-drain feeder line (11) comprises a first sub-source drain feeder line (111), a second sub-source drain feeder line (112) and a third sub-source drain feeder line (113), the first sub-source drain feeder line (111) is arranged in parallel to the edge of the substrate (3) and is connected with the first doped heterojunction structure (8); the second sub-source leakage feeder line (112) and the third sub-source leakage feeder line (113) are both perpendicular to the first sub-source leakage feeder line (111), one end of the second sub-source leakage feeder line (112) is connected with the first sub-source leakage feeder line (111), the other end of the second sub-source leakage feeder line is connected with the second doped heterojunction structure (7), one end of the third sub-source leakage feeder line (113) is connected with the first sub-source leakage feeder line (111), the other end of the third sub-source leakage feeder line is connected with the second doped heterojunction structure (7), and the second sub-source leakage feeder line (112) and the third leakage feeder line (113) are arranged in a square shape.
5. The terahertz dual-channel modulator according to claim 2, wherein the first doped heterojunction structure (8) and the second doped heterojunction structure (7) are both HETM and the doped material is AlGaN/GaN or AlGaAs/GaAs or InGaAs/GaAs or InGaN/GaN.
6. The terahertz dual-channel modulator according to claim 5, wherein the material of the ohmic electrode (2), the first gate feed line (5), the second gate feed line (6), the first source drain feed line (10) and the second source drain feed line (11) is Ti or Ni or Au or Al or Ag or Cu.
7. The terahertz dual-channel modulator according to claim 6, wherein the line width of the first gate feeder line (5) and the line width of the second gate feeder line (6) are both 2 μm, the line width of the first source drain feeder line (10) and the line width of the second source drain feeder line (11) are both 10 μm, and the thicknesses of the first gate feeder line (5), the second gate feeder line (6), the first source drain feeder line (10), and the second source drain feeder line (11) are all 0.2 μm.
8. The terahertz dual-channel modulator according to claim 3, wherein the insulating layer (12) is a benzocyclobutene insulating layer (12).
9. Terahertz dual-channel modulator according to claim 4, characterized in that the epitaxial layer (1) is a gallium nitride epitaxial layer (1).
10. A preparation method of a terahertz dual-channel modulator is characterized by comprising the following steps:
s1: cleaning the substrate (3) by adopting an ultrasonic cleaning mode, and drying the cleaned substrate (3);
s2: preparing an AlGaN/GaN heterojunction film on a substrate (3) by adopting an organic compound vapor deposition method to obtain a substrate;
s3: spin-coating photoresist with the thickness of 2 microns on the substrate, carrying out photoetching development on the photoresist by using a mask to determine an HEMT active region, etching off the AlGaN/GaN film outside the HEMT active region by adopting an inductive coupling plasma etching method, and removing the residual photoresist on the substrate to obtain the HEMT active region substrate;
s4: respectively depositing a composite metal layer-titanium/aluminum/nickel/gold on two sides of an active region in sequence by utilizing photoetching, electron beam evaporation and stripping processes to serve as a source electrode and a drain electrode of the HEMT;
s5: placing the source and drain at N2Performing rapid thermal annealing treatment on the environment, and forming ohmic contact between a source electrode and a drain electrode and a 2DEG channel;
s6: respectively depositing nickel and gold on the AlGaN/GaN heterojunction film in sequence by utilizing photoetching, electron beam evaporation and stripping processes to form a super-surface structure;
s7: preparing benzocyclobutene on the first Schottky electrode (9);
s8: and preparing a grid electrode.
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