CN102520532B - High-speed terahertz modulator and production method thereof - Google Patents
High-speed terahertz modulator and production method thereof Download PDFInfo
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- CN102520532B CN102520532B CN201110427332.4A CN201110427332A CN102520532B CN 102520532 B CN102520532 B CN 102520532B CN 201110427332 A CN201110427332 A CN 201110427332A CN 102520532 B CN102520532 B CN 102520532B
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Abstract
The invention discloses a high-speed terahertz modulator and a production method thereof. The terahertz high-speed modulator comprises a substrate layer, a buffer layer growing on the substrate layer, a strained quantum well structure growing on the buffer layer and a metal meta-material structure, wherein the metal meta-material structure is prepared on the upper surface of the strained quantum well structure and consists of a periodical array of metal resonant units. Besides, the buffer layer and the substrate layer are made of the same materials, the band gap of a potential well layer is smaller than that of a potential barrier layer, and the difference between the lattice constants of the potential barrier layer and the substrate layer is controlled within 0.5%. A strong piezoelectric field generated from strain is formed in strained quantum well structure, and accordingly recombination lifetime of photon-generated carriers is prolonged and concentration thereof is increased evidently, and requirements for power of a modulated laser are lowered greatly. By changing the In component and quantum well width in the InGaAs/GaAs strained quantum well structure, the strength of the piezoelectric field inside and charge spatial isolation degree can be regulated flexibly, and accordingly the modulation rate of the high-speed terahertz modulator can be regulated conveniently.
Description
Technical field
The invention belongs to the THz wave communications field, relate in particular to a kind of terahertz wave modulator and preparation method thereof.
Background technology
The contradiction of the limited frequency spectrum resource of radio communication and the high speed business demand increasing rapidly forces people to go to develop new spectral band.THz wave refers to that frequency arrives the electromagnetic wave (1THz=10 of 10THz scope at 0.1THz
12hz), wavelength be 0.03mm to 3mm, there is very large bandwidth, therefore develop THz wireless communication technology and there is important actual application value.Wherein terahertz wave modulator is one of requisite device in Terahertz communication system, and the performance of current Terahertz modulator is mainly limited to selection and the preparation of material.The combination of the super material of novel semi-conductor base material and electromagnetism (meta-material) is expected to realize some gordian technique of Terahertz, the especially breakthrough of Terahertz modulation technique.
The THz wave modulator reported in recent years has the method for utilizing semiconductor piece shape material to modulate THz ripple.Silicon (Si) wafer based on ultra-high resistance rate such as the Li Jiusheng of the China Measures Institute, utilizes 808nm Ear Mucosa Treated by He Ne Laser Irradiation to produce photo-generated carrier THz ripple is modulated.Because the recombination lifetime of charge carrier in ultra-high resistance rate Si sheet is longer, so its modulation rate is only 0.2k bps.In gallium arsenide GaAs the life-span of charge carrier shorter, likely become the base material of preparation high speed Terahertz modulator.The people such as the L.Fekete of Czech take at alternately laminated SiO
2with the way that embeds one deck GaAs defect layer in MgO periodic structure to form 1-D photon crystal, utilize the concentration change of the photo-generated carrier that GaAs produces under 810nm Ear Mucosa Treated by He Ne Laser Irradiation to modulate the characteristic that sees through of photonic crystal, thereby realize the object of High Speed Modulation THz ripple.But because the life-span of charge carrier in GaAs is shorter, response time can reach 130ps magnitude, although so can reach GHz magnitude to the modulation rate of THz ripple in theory, but in order to obtain higher photoproduction carrier concentration and larger depth of modulation, the luminous flux of 810nm modulated laser need reach 0.8 μ J/cm
2high magnitude, its corresponding continuous wave Output of laser power needs to reach 10
5more than W, this is extremely restricted it in actual applications.
Summary of the invention
Goal of the invention: for the problem and shortage of above-mentioned existing existence, the invention provides a kind of terahertz wave modulator, the defect that thereby the recombination lifetime that overcomes charge carrier at the existing GaAs based end is too short so that need to super superpower modulated laser, has realized under the shooting conditions of low-power modulated laser and also can carry out High Speed Modulation to THz wave.
Technical scheme: for achieving the above object, the present invention is by the following technical solutions: a kind of THz wave high-speed modulator, comprise substrate layer, on this substrate layer, growth has a cushion, on this cushion, growth has strained quantum well structure, the metal metamaterial structure being made up of metal resonant element periodic array of preparing at the upper surface of this strained quantum well structure; Described strained quantum well structure comprises plural barrier layer and at least one potential well layer, and described potential well layer is in the middle of two barrier layers, and the described strained quantum well structure the superiors and orlop are all barrier layers; Described substrate layer is < 111 > planar orientations, described cushion is identical with substrate layer material, the band gap of described potential well layer is less than barrier layer, and the grating constant of described barrier layer and substrate layer is identical or differ and be no more than 0.5%;
Described substrate layer, cushion and barrier layer material are gallium arsenide, and described potential well layer material is indium gallium arsenic;
In described strained quantum well structure, barrier layer and potential well layer are all < 111 > planar orientations, and described barrier layer thickness is 10～300nm, and described potential well layer thickness is 1～30nm.
As preferably, described buffer layer thickness is 20～300nm.
As preferably, in described metal metamaterial structure, the thickness of metal resonant element is 0.2～5 micron, and the cycle is 20～80 microns.
Another object of the present invention has been to provide a kind of method for making of above-mentioned THz wave high-speed modulator, it is characterized in that comprising the following steps:
A, by metal organic-matter chemical vapor phase epitaxy technique (MOCVD) or molecular beam epitaxy technique (MBE) one deck cushion of growing on substrate layer;
B, then continue to grow successively barrier layer, potential well layer and the barrier layer of < 111 > planar orientations on this cushion, thereby form the Strained Single Quantum Well layer of < 111 > planar orientations, the band gap of the material that wherein potential well layer is selected is less than barrier layer, and the grating constant of described barrier layer and substrate layer is identical or differ and be no more than 0.5%;
C, method by evaporation and etching are prepared the metal metamaterial structure of the metal resonant element composition of one deck periodic arrangement at described Strained Single Quantum Well layer upper surface.
Beneficial effect: compared with prior art, the present invention has the following advantages: by the strained quantum well structure of the Grown <111> orientation in <111> orientation, at the extremely strong piezoelectric field of the inner acquisition of quantum well; This piezoelectric field can separate electronics and the hole in photo-generated carrier effectively, extends significantly the recombination lifetime of photo-generated carrier and increases carrier concentration, thereby can greatly reduce the requirement to externally modulated laser power; Meanwhile, by component and the quantum well width of In in the InGaAs/GaAs strained quantum well of change <111> orientation, the degree that can regulate neatly the size of inner piezoelectric field to separate with charge space, and then can be as required, modulation rate regulates easily the modulation rate of terahertz wave modulator, more than can reach 10Mbps.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is the band structure variation diagram of strained quantum well structure of the present invention under the effect of built-in piezoelectric field;
Fig. 3 is the relation curve of indium (In) component concentration in the intensity of piezoelectric field and potential well layer in strained quantum well structure in embodiment of the present invention;
Fig. 4 is the change curve of the transmitance of THz wave under modulators modulate of the present invention with external excitation light intensity.
Wherein, substrate layer 1, cushion 2, metal metamaterial structure 3, barrier layer 4, potential well layer 5.
Embodiment
Below in conjunction with the drawings and specific embodiments, further illustrate the present invention.Should understand these embodiment and only be not used in and limit the scope of the invention for the present invention is described, after having read the present invention, those skilled in the art all fall within the application's claims limited range to the modification of the various equivalent form of values of the present invention.
As shown in Figure 1, a kind of THz wave high-speed modulator comprises semi-insulating GaAs (GaAs) substrate layer 1 of <111> orientation, first on substrate, pass through MOCVD metal organic-matter chemical vapor phase epitaxy technique growth one deck GaAs cushion 2, these GaAs buffer layer 2 THICKNESS CONTROL are in 20 to 300 nanometers, thereby the larger difference existing in grating constant between the indium gallium arsenic potential well layer 5 in follow-up strained quantum well structure and gallium arsenide substrate layer 1 can be overcome, the final strained quantum well structure structure that obtains high-quality < 111 > planar orientations.
Then grow successively on this cushion 2 barrier layer 4 of gallium arsenide barrier layer 4, indium gallium arsenic potential well layer 5 and gallium arsenide of < 111 > planar orientations, thereby form the InGaAs/GaAs strained quantum well structure of < 111 > planar orientations, the thickness of wherein said gallium arsenide barrier layer 4 is 10 to 300 nanometers, and the thickness of described indium gallium arsenic potential well layer 5 is 1 to 30 nanometer; Finally prepare by technologies such as photoetching, evaporation and etchings the metal metamaterial structure 3 that one deck is made up of metal resonant element periodic array on the GaAs surface of the superiors, the super material thickness of this metal is 0.2～5 micron, cycle is 20～80 microns, and the geometric configuration of resonant element can be the shape of any vibrotron unit.
The electric field energy of suppressing producing due to lattice mismatch in the InGaAs/GaAs quantum well of above-mentioned <111> orientation separates electronics and the hole in photo-generated carrier effectively, thereby can increase significantly concentration and the recombination lifetime of photo-generated carrier, greatly reduce the power of required externally modulated laser;
The barrier layer of the InGaAs/GaAs quantum well of above-mentioned <111> orientation can be by with gallium arsenide substrate layer Lattice Matching or differ gallium aluminium arsenic (AlGaAs) material in 0.5%, and potential well can be replaced lower than barrier material and with the compound semiconductor materials of backing material lattice mismatch by gallium arsenic phosphide (GaAsP) or other band gap (band gap).
The THz wave of being modulated, successively by metal metamaterial structure 3, strained quantum well structure, cushion 2, finally penetrates from the lower surface of GaAs (111) substrate layer 1, is received and is detected by terahertz time-domain spectroscopy instrument (TDS).Simultaneously, separately having a branch of wavelength is that the modulated laser of 810 nanometers is irradiated on the InGaAs/GaAs strained quantum well structure of <111> orientation, excite photo-generated carrier, its concentration and recombination lifetime can be regulated and controled by strained quantum well structure parameter.Photoproduction carrier concentration changes and is directly proportional to the recombination lifetime of charge carrier with the change of modulation light intensity, can affect resonance frequency and the resonance intensity of metamaterial structure so change modulated laser intensity.What the transmitted spectrum of the THz wave detecting by TDS reflected is exactly through THz wave ovennodulation, that Strength Changes speed is identical with light modulated.
The introducing of the strained quantum well structure of <111> orientation is core innovative point of the present invention, is also to realize the gordian technique of with the laser instrument of common power, THz wave being carried out High Speed Modulation.Due to the grating constant difference of two kinds of semiconductor materials of the strained quantum well of composition <111> orientation, can in quantum well, produce a piezoelectric field perpendicular to quantum well direction by piezoelectric effect.As shown in Figure 2, generation suppress electric field (～10
5v/cm) make the band structure run-off the straight of quantum well, thereby cause electronics and hole effective separation spatially in photo-generated carrier, therefore can significantly increase concentration and the recombination lifetime of photo-generated carrier.It is estimated, the photo-generated carrier life-span can be by tens psecs in common GaAs bulk material, extend to tens nanoseconds in the InGaAs/GaAs quantum well structure of <111> of the present invention orientation.The charge carrier recombination lifetime of this order of magnitude can either meet the even more requirement of high modulation speed of 10Mbps, can greatly reduce again the power of required modulated laser simultaneously, even can realize with the commercial semiconductor laser of common 100mW.
Fig. 3 is indium arsenic gallium/gallium arsenide (In of the <111> orientation that calculates
xga
1-xas/GaAs) change curve of the piezoelectric field intensity In component x in quantum well.Can clearly find out, by changing the In component in strained quantum well, can quantum well in the intensity of piezoelectric field, thereby control the recombination lifetime of photo-generated carrier.
The transmitance that Fig. 4 is THz wave by modulator of the present invention is with the change curve of external excitation light intensity.The maximum percentage modulation that in figure, visible frequency is 0.66THz place can reach 59%, and modulation rate is 10Mbps.
Claims (4)
1. a THz wave high-speed modulator, it is characterized in that: comprise substrate layer (1), there is a cushion (2) in the upper growth of this substrate layer (1), there are strained quantum well structure, the metal metamaterial structure (3) being formed by metal resonant element periodic array of preparing at the upper surface of this strained quantum well structure in the upper growth of this cushion (2); Described strained quantum well structure comprises plural barrier layer (4) and at least one potential well layer (5), and described potential well layer (5) is in the middle of two barrier layers (4), and the described strained quantum well structure the superiors and orlop are all barrier layers; Described substrate layer (1) is < 111 > planar orientations, described cushion (2) is identical with substrate layer (1) material, the band gap of described potential well layer (5) is less than barrier layer (4), and the grating constant of described barrier layer (4) and substrate layer (1) is identical or differ and be no more than 0.5%;
Described substrate layer (1), cushion (2) and barrier layer (4) material are gallium arsenide, and described potential well layer (5) material is indium gallium arsenic;
Barrier layer in described strained quantum well structure (4) and potential well layer (5) are all < 111 > planar orientations, and described barrier layer (4) thickness is 10～300nm, and described potential well layer (5) thickness is 1～30nm.
2. THz wave high-speed modulator according to claim 1, is characterized in that: described cushion (2) thickness is 20～300nm.
3. THz wave high-speed modulator according to claim 1, is characterized in that: in described metal metamaterial structure (3), the thickness of metal resonant element is 0.2～5 micron, and the cycle is 20～80 microns.
4. a method for making for THz wave high-speed modulator described in claim 1, is characterized in that comprising the following steps:
A, by metal organic-matter chemical vapor phase epitaxy technique (MOCVD) or molecular beam epitaxy technique (MBE) at substrate layer (1) upper growth one deck cushion (2);
B, then continue to grow successively barrier layer (4), potential well layer (5) and the barrier layer (4) of < 111 > planar orientations on this cushion (2), thereby form the Strained Single Quantum Well layer of < 111 > planar orientations, the band gap of the material that wherein potential well layer (5) is selected is less than barrier layer (4), and the grating constant of described barrier layer (4) and substrate layer (1) is identical or differ and be no more than 0.5%;
C, method by evaporation and etching are prepared the metal metamaterial structure (3) of the metal resonant element composition of one deck periodic arrangement at described Strained Single Quantum Well layer upper surface.
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| CN103364973A (en) * | 2013-06-29 | 2013-10-23 | 天津大学 | Soft terahertz wave modulator |
| CN103457669B (en) * | 2013-09-05 | 2016-03-23 | 南开大学 | Schottky gate array type Terahertz modulator and regulate and control method thereof |
| CN104635358B (en) * | 2013-11-06 | 2017-12-01 | 中国科学院苏州纳米技术与纳米仿生研究所 | Terahertz modulator based on ferroelectric thin film and preparation method thereof |
| CN103984124B (en) * | 2014-05-15 | 2017-01-25 | 东南大学 | Multi-frequency response TeraHertz wave modulator |
| CN104950477B (en) * | 2015-07-03 | 2017-11-28 | 上海理工大学 | A kind of multi-channel terahertz ripple modulator approach and system |
| CN105509882B (en) * | 2015-12-04 | 2017-07-04 | 福州大学 | A kind of implementation method of the terahertz detector based on GaAs single quantum trap |
| CN105372850B (en) * | 2015-12-07 | 2018-02-13 | 电子科技大学 | A kind of THz wave fast modulator based on co-planar waveguide binding crystal pipe |
| CN105896095A (en) * | 2016-04-28 | 2016-08-24 | 东南大学 | Light-operated programmable terahertz 1-bit artificial electromagnetic surface and regulation and control method |
| CN107340612B (en) * | 2017-06-21 | 2019-10-01 | 电子科技大学 | A kind of light-operated Terahertz outside phase-modulator |
| CN108319040A (en) * | 2018-01-23 | 2018-07-24 | 中国计量大学 | A kind of automatically controlled THz wave switch of more metal layers structure |
| CN110018531B (en) * | 2019-04-04 | 2021-04-23 | 湖南理工学院 | Polarization-insensitive terahertz doped semiconductor metamaterial lens |
| CN110828604A (en) * | 2019-11-18 | 2020-02-21 | 中国科学院上海技术物理研究所 | Adjustable room-temperature black arsenic-phosphorus terahertz detector and preparation method thereof |
| CN111061113B (en) * | 2019-12-16 | 2020-12-18 | 北京航空航天大学 | Nonlinear terahertz wave regulation and control device based on nano-opening metamaterial |
| CN112382859A (en) * | 2020-10-31 | 2021-02-19 | 华南理工大学 | Double-capacitor terahertz metamaterial electric regulation and control device structure |
| CN113267913B (en) * | 2021-05-29 | 2022-10-04 | 枣庄学院 | Metamaterial modulator |
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