阅读说明：本技术 一种基于ii类断带能隙量子阱的红外电吸收调制器 (Infrared electric absorption modulator based on II-type broken band energy gap quantum well ) 是由 李俊 陈盟 于 2021-07-13 设计创作，主要内容包括：一种基于II类断带能隙量子阱的红外电吸收调制器,涉及半导体光电子领域。包含(i)至少一个吸收调制区,吸收调制区包含单周期或多周期的II类断带能隙量子阱结构；(ii)对II类断带能隙量子阱结构提供调制偏压的装置；一个周期单元的II类断带能隙量子阱结构由第一势垒、电子势阱、空穴势阱和第二势垒组成,电子势阱和空穴势阱置于第一势垒和第二势垒之间且不依赖相对叠放次序,电子势阱的体材料导带带边的能量低于空穴势阱的体材料价带带边的能量。可采用波导耦合构型或垂直入射构型,以较小偏压摆幅获得较大消光比,调制效率高。可同时对横磁模极化的中红外光和横电模极化的远红外光进行调制。器件覆盖面较小,适于半导体芯片集成。(An infrared electric absorption modulator based on a II-type broken band energy gap quantum well relates to the field of semiconductor photoelectron. Comprises (i) at least one absorption modulation region comprising a single-period or multi-period class II band-break energy gap quantum well structure; (ii) means for providing a modulated bias to the class II bandgap quantum well structure; the type-II band-gap-breaking quantum well structure of one period unit comprises a first potential barrier, an electron potential well, a hole potential well and a second potential barrier, wherein the electron potential well and the hole potential well are arranged between the first potential barrier and the second potential barrier and do not depend on the relative stacking sequence, and the energy of a body material conduction band edge of the electron potential well is lower than the energy of a body material valence band edge of the hole potential well. The waveguide coupling configuration or the vertical incidence configuration can be adopted, a larger extinction ratio is obtained with a smaller bias swing, and the modulation efficiency is high. The medium infrared light polarized in transverse magnetic mode and the far infrared light polarized in transverse electric mode can be modulated simultaneously. The device coverage is small, and the device is suitable for semiconductor chip integration.)

1. An infrared electro-absorption modulator based on class II band-break energy gap quantum wells, comprising: (i) at least one absorption modulation region, wherein the absorption modulation region comprises a single-period or multi-period II-type broken band gap quantum well structure; (ii) a device for providing modulated bias voltage for the II-type broken band gap quantum well structure, which is used for generating an electric field vertical to the plane of the material layer of the II-type broken band gap quantum well structure;

the II-type band-break energy gap quantum well structure of one period unit consists of a first potential barrier, an electron potential well, a hole potential well and a second potential barrier, wherein the electron potential well and the hole potential well are arranged between the first potential barrier and the second potential barrier and do not depend on the relative stacking sequence;

the electron potential well is adjacent to the hole potential well, and the energy of a body material conduction band edge of the electron potential well is lower than that of a body material valence band edge of the hole potential well, so that a II-type broken band gap heterojunction is formed;

the first potential barrier and the second potential barrier form quantum restriction on an electron state wave function and a hole state wave function in an electron potential well and a hole potential well, an electron state wave function body at the bottom of a sub-band with the lowest conduction band is restricted in the electron potential well, and a hole state wave function body at the top of the sub-band with the highest valence band is restricted in the hole potential well;

when on-state bias voltage is applied to two ends of the II-type broken band gap quantum well structure, the quantum well is in a normal band gap phase, and the energy of the band bottom of the lowest conduction band of the electron potential well is higher than the energy of the band top of the highest valence band of the hole potential well;

when off-state bias voltage is applied to two ends of the II-type band-break energy gap quantum well structure, the quantum well is in a reversed band gap phase, and the energy of the band bottom of the lowest conduction band of the electron potential well is lower than the energy of the band top of the highest valence band of the hole potential well.

2. The infrared absorption modulator based on the class-II band-gap quantum well as claimed in claim 1, wherein the electron potential well of the class-II band-gap quantum well structure is made of at least one material selected from InAs, InAsSb, InGaAs and InGaAsSb; the material of the hole potential well is selected from at least one of GaSb, GaInSb, GaAlSb, GaAsSb, GaAlAsSb, GaInAsSb, GaAlInSb and GaAlInAsSb; the material of the first barrier and the second barrier is selected from at least one of AlSb, AlGaSb, AlGaAsSb, AlInSb, AlGaInSb, AlInAsSb and AlGaInAsSb.

3. The infrared electro-absorption modulator based on class II bandgap quantum well as claimed in claim 1 wherein said infrared electro-absorption modulator based on class II bandgap quantum well comprises a waveguide coupling configuration or a normal incidence configuration.

4. The infrared electro-absorption modulator of claim 3 based on class II bandgap quantum well, wherein the waveguide coupling configuration has a waveguide structure comprising at least: a base layer; a first cladding layer, a waveguide core layer and a second cladding layer are sequentially arranged on the upper side of the substrate layer; a first contact electrode is arranged on the lower side of the basal layer or the upper side of the table top exposed by the etching of the first coating layer; a second contact electrode is arranged on the upper side of the second cladding layer; the waveguide core layer comprises at least one absorption modulation region; the first cladding layer and the second cladding layer are respectively doped with the semiconductor single-layer structure or the semiconductor multi-layer structure; the first contact electrode and the second contact electrode respectively apply bias voltage to the absorption modulation region through the first cladding layer and the second cladding layer to form the device for providing modulation bias voltage for the II-type band-break energy gap quantum well structure.

5. The infrared electro-absorption modulator of claim 4 based on class II band-break bandgap quantum wells, wherein the waveguide core layer can adopt a separate confinement structure, further comprising a first separate confinement layer and a second separate confinement layer; the first and second respective confinement layers are doped semiconductor materials or multilayer structures and are respectively adjacent to the lower interface and the upper interface of the absorption modulation region, and the optical refractive indexes of the first and second respective confinement layers are larger than those of the first and second cladding layers.

6. The infrared electric absorption modulator based on the class-II band-break gap quantum well as claimed in claim 4, wherein the base layer further comprises a substrate and a buffer layer, the thickness of the buffer layer is not less than 200nm, and the buffer layer is used for releasing strain, isolating dislocation and impurity, and reducing the influence of the substrate on the device;

a first transition layer and a second transition layer are respectively arranged at the lower interface and the upper interface of the first coating layer, a third transition layer and a fourth transition layer are respectively arranged at the lower interface and the upper interface of the second coating layer, and the transition layers are used for reducing parasitic voltage drop caused by abrupt change of interfaces of adjacent area layers; the transition layers are doped with the doping materials respectively between the two sides.

7. The infrared electro-absorption modulator of claim 3 based on class II band-gap quantum well, wherein the normal incidence configuration is light incident perpendicular to the plane of the material layer of the absorption modulation region, and comprises: the bottom coating layer, the absorption modulation region, the top coating layer, the bottom electrode and the top electrode;

the bottom cladding layer and the top cladding layer are doped with the semiconductor single layer or the multilayer structure; the absorption modulation area is arranged between the bottom coating layer and the top coating layer; the bottom electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the exposed table top of the bottom coating layer after being etched to form electrical contact; the top electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the top coating layer to form electrical contact; and the bottom electrode and the top electrode respectively apply bias voltage to the absorption modulation region through the bottom cladding layer and the top cladding layer to form a device for providing modulation bias voltage for the II-type broken band energy gap quantum well structure.

8. The infrared electro-absorption modulator based on the class-II broken bandgap quantum well as the claim 7, wherein the bottom high reflection film is provided on the bottom of the bottom cladding layer, or the top high reflection film is provided in the transparent window area of the top electrode on the top of the top cladding layer, or both the bottom high reflection film and the top high reflection film are provided; the bottom high-reflection film and the top high-reflection film are respectively formed by distributed Bragg reflectors or metal films formed by alternately stacking a plurality of dielectric layers to form a symmetrical or asymmetrical Fabry-Perot cavity structure.

9. The infrared electro-absorption modulator of claim 7 based on class II band-gap broken quantum well, wherein at least one of the bottom highly reflective film, the top highly reflective film, the bottom cladding layer or the top cladding layer has a metal strip grating disposed on its upper or lower side for increasing the coupling of the vertical electric field component of the incident light to the absorption modulation region, and the grating period is less than or equal to the selected operating wavelength of the infrared electro-absorption modulator.

10. A method of electro-optic modulation of selected light comprising the steps of:

1) placing an electro-absorption modulator or electro-optic modulator in the path of a selected light, wherein the modulation region of the electro-absorption modulator or electro-optic modulator comprises a semiconductor single-layer or multi-layer structure having the following characteristics:

a. the energy band structure of the semiconductor single-layer or multi-layer structure is provided with a conduction band and a valence band, the electronic state at the bottom of the conduction band and the electronic state at the top of the valence band belong to intrinsic states with different Hamilton quantity properties of the system respectively, and the conduction band and the valence band can be distinguished through the properties of the electronic state at the bottom of the conduction band and the electronic state at the top of the valence band;

b. the semiconductor single-layer or multi-layer structure has a normal band gap phase, and the energy of the conduction band bottom is higher than that of the valence band top;

c. the semiconductor single-layer or multi-layer structure has an inverted band gap phase, and the energy of the conduction band bottom is lower than that of the valence band top;

d. changing the normal band gap phase into the reverse band gap phase by changing the bias voltage applied to the semiconductor single-layer or multi-layer structure;

e. the semiconductor single or multilayer structure has significantly different absorption or refractive indices for selected light in the normal bandgap phase and the inverted bandgap phase;

2) bringing the semiconductor material or multilayer structure in step 1) into said normal bandgap phase by applying a bias voltage to the modulation region of the electro-absorption modulator or electro-optic modulator;

3) changing the bias voltage in step 2) so that the semiconductor single-layer or multilayer structure in step 1) is in an inverted bandgap phase;

4) repeating the steps 2) and 3), reducing the difference value meeting the bias voltage required in the steps 2) and 3), and finding out the critical bias voltage for converting the normal band gap phase into the reversed band gap phase;

5) setting the on-state bias voltage near the critical bias voltage found in the step 4), slightly deviating from the critical bias voltage and enabling the semiconductor single-layer or multi-layer structure to be just in a normal band gap phase;

6) after the open-state bias voltage in the step 5) is set, the bias voltage applied to the semiconductor single-layer or multi-layer structure is changed, so that the semiconductor single-layer or multi-layer structure can be converted from a normal band gap phase to the reversed band gap phase to reach an off state; the transition from the normal bandgap phase to the inverted bandgap phase results in a significant change in the absorption or refractive index of the semiconductor single or multilayer structure; a more pronounced modulation of the intensity or phase of the selected light is achieved with a relatively small bias swing.

Technical Field

The invention relates to the technical field of semiconductor photoelectron, in particular to an infrared electric absorption modulator working in a middle infrared band or a far infrared band, having energy band reverse bias regulation and high performance and based on a II-type band-broken energy gap quantum well.

Background

An electro-absorption modulator is an optoelectronic device that is independent of the light source and that is capable of modulating the intensity of the transmitted light. Compared with the direct modulation of light intensity by using the driving current of the light source, the external modulation based on the electro-absorption modulator has the advantages of high speed, large extinction ratio, low chirp and the like, so the electro-absorption modulator has become one of the core components of the modern high-speed optical communication system. The electro-absorption modulator widely used at present is mainly based on the quantum confinement stark effect of a class I semiconductor quantum well structure (see patent US7142342B2), and has the advantages of small driving voltage, high modulation rate, easiness in monolithic integration with a semiconductor laser and the like. Due to the need for low loss fiber transmission, conventional fiber optic telecommunications electro-absorption modulators are often designed to operate in the near infrared optical bands of 0.85 μm, 1.31 μm, and 1.55 μm.

The mid-infrared band (2.5-25 μm) is an important band of electromagnetic spectrum, can be used for detecting specific molecules, and has wide application in the fields of sensing, environmental monitoring, biomedicine, thermal imaging and the like. In addition, the mid-infrared material has very important value in modern military defense, photoelectric countermeasure, free space optical communication and other technologies. In recent years, with the continuous progress and maturity of mid-infrared quantum cascade lasers and interband cascade lasers, a large number of mid-infrared optoelectronic technologies are rapidly developed. Among them, the great potential of mid-infrared Free-space optical communications (Free-space optical communications) [ see Alexandre Delga, Luc Leviandier, "Free-space optical communications with quaternary capsules," proc. spie 10926, Quantum Sensing and Nano Electronics and Photonics XVI,1092617(2019) ] is also gradually recognized and valued: the mid-infrared free space optical communication takes air as a transmission medium, and the signal wavelength is selected in the range of 3-5 μm and 8-14 μm of a low absorption atmospheric window, so that optical fibers are not needed to be used as the medium, and the mid-infrared free space optical communication has the advantages of being fast in installation, low in cost and safe to human eyes; compared with the method using near infrared light as a carrier, the intermediate infrared free space optical communication is less influenced by smoke, raindrops, dust, air turbulence and the like, so that the transmission distance in the air is longer, and the tolerance to complex weather conditions is higher; compared with wireless radio frequency communication, the bandwidth of the intermediate infrared free space optical communication is wider, the ideal target communication bandwidth can reach 40-50 GHz, and the wireless radio frequency communication has the characteristic of point-to-point signal transmission, so that data is difficult to intercept, and the wireless radio frequency communication has the advantages of electromagnetic interference resistance, high safety degree, low energy consumption, small size and the like. Therefore, the mid-infrared free space optical communication has the comprehensive best advantages in four dimensions of bandwidth capacity, transmission distance, equipment cost and availability, and is expected to become a new-generation communication technology with wide application prospect.

Currently, researchers have successfully implemented Mid-infrared free-space optical Communication links with data transmission rates between 70Mb/s and 3Gb/s in laboratories, but the Communication links implemented are still based on direct modulation of Mid-infrared lasers, with maximum bandwidths of only 330MHz [ Jony j.liu, et al, "Mid and long-wave free-space optical Communication," proc.spie 11133, Laser Communication and Propagation through the atm and Oceans VIII, 3302(2019) ]. Obviously, a huge promotion space still exists for the ideal target bandwidth of 40-50 GHz away from the mid-infrared free space optical communication. Although direct modulation is the simplest way of optical communication coding, the modulation bandwidth is limited by the relaxation of the laser working current, and only relatively low-speed signal transmission can be realized. Just as a semiconductor electro-absorption modulator based on external modulation is an essential device for high-speed optical fiber communication, an electro-absorption modulator with high performance, capable of being integrated and working in a mid-infrared band is also an indispensable important device for realizing high-speed mid-infrared free space optical communication. However, since conventional electro-absorption modulators are typically fabricated using group III-V class I semiconductor quantum wells (patents US7142342B2 and EP0809129a2), while most group III-V semiconductor materials have energy gaps in the near-infrared or visible light range, they cannot be used for modulation of mid-and far-infrared light. On the other hand, except for the research on a small number of mid-infrared modulators based on quantum well subband transition in the last 90 s, only some mid-infrared modulators based on graphene-metal plasma, lithium niobate waveguide and the like have been reported in recent years, but they have not been put into practical use for reasons such as difficulty in preparation, incompatibility with laser and the like. Therefore, the conventional mid-infrared modulator which can be practically applied to free space optical communication is relatively lacked, and particularly, a high-performance mid-infrared electro-absorption modulator which can be compatible with a quantum cascade laser or an interband cascade laser is urgently needed to be developed.

In recent decades, AlSb/InAs/GaSb/AlSb quantum wells have attracted continuous attention of researchers as a type-II break-gap quantum well (type-II break-gap quantum well) structure. The unique property of the quantum well is that the conduction band of InAs is lower than the valence band of GaSb, and the type-II broken band gap band alignment (type-II broken-gapb and alignment) is formed; under the restriction of the AlSb barrier layer, electrons and holes in the quantum wells are respectively restricted in the InAs and GaSb layers, and a two-dimensional electron gas and a two-dimensional hole gas which are separated in space are formed. When the thickness of the InAs or GaSb layer is more than a certain critical value, the Quantum well has an Inverted band gap phase, and opens a micro energy gap caused by electron-hole hybridization at the finite wave vector, and the system is in a two-dimensional topological insulator phase and shows Quantum Spin Hall Effect [ changing light sources ], Quantum Spin Hall Effect in Inverted Type-II Semiconductors, Phys.Rev.Lett.100,236601 (2008); and Knez, i., Du, R.&Sullivan,G.,"Evidence for Helical Edge Modes in Inverted InAs/GaSb Quantum Wells,"Phys.Rev.Lett.107,136603(2011)]. In addition, researchers have also found that electric fields can be used to manipulate the transition of AlSb/InAs/GaSb/AlSb Quantum wells Between normal and reversed bandgap Phases [ Qu, F.et al.electric and Magnetic Tuning BetWeen the Trivial and polar pharmaceuticals in InAs/GaSb Double Quantum wells. Phys.Rev.Lett.115,036803(2015)]Meanwhile, various interesting quantum phenomena exist in the quantum well, such as spiral Luttinger liquid, exciton insulator phase, abnormal magnetic transport oscillation and the like. On the other hand, the material composing the class II broken band gap quantum well belongs toThe antimonide semiconductor family is an important mid-infrared material, and the material system is successfully used for preparing mid-infrared photoelectric detectors, quantum cascade lasers, interband cascade lasers and other mid-infrared devices. Therefore, if the II-type broken band gap quantum well structure is rich and the adjustable physical properties can be well utilized, the novel high-performance mid-infrared photoelectric device is hopefully realized.

Disclosure of Invention

The invention aims to solve the problems that the existing electric absorption modulator which can be used for intermediate infrared free space optical communication is relatively lack, and the like, and provides an infrared electric absorption modulator based on a II-type broken band energy gap quantum well, which can simultaneously work in intermediate infrared or far infrared bands, and has the advantages of high extinction ratio, low driving voltage, low power consumption, high modulation efficiency, small volume, compatibility with antimonide-based quantum cascade lasers and band-to-band cascade lasers, and the like.

Another object of the present invention is to provide a method for electro-optical modulation of selected light with high efficiency based on the principle of bias modulation band inversion.

The infrared electric absorption modulator based on the II-type broken band energy gap quantum well comprises: (i) at least one absorption modulation region, wherein the absorption modulation region comprises a single-period or multi-period II-type broken band gap quantum well structure; (ii) a device for providing modulated bias voltage for the II-type broken band gap quantum well structure, which is used for generating an electric field vertical to the plane of the material layer of the II-type broken band gap quantum well structure;

the II-type band-break energy gap quantum well structure of one period unit consists of a first potential barrier, an electron potential well, a hole potential well and a second potential barrier, wherein the electron potential well and the hole potential well are arranged between the first potential barrier and the second potential barrier and do not depend on the relative stacking sequence;

the electron potential well is adjacent to the hole potential well, and the body material conduction band edge E of the electron potential well_cIs lower than the valence band edge E of the bulk material of the hole potential well_vForming a class II band-break energy gap heterojunction;

the first potential barrier and the second potential barrier form quantum restriction on an electron state wave function and a hole state wave function in an electron potential well and a hole potential well, an electron state wave function body at the bottom of a sub-band with the lowest conduction band is restricted in the electron potential well, and a hole state wave function body at the top of the sub-band with the highest valence band is restricted in the hole potential well;

when on-state bias voltage is applied to two ends of the II-type broken band gap quantum well structure, the quantum well is in a normal band gap phase, and the band bottom of the lowest sub-band of the conduction band of the electron potential well is higher than the band top of the highest valence band of the hole potential well in energy;

when off-state bias voltage is applied to two ends of the II-type band-break energy gap quantum well structure, the quantum well is in a reversed band gap phase, and the band bottom of the lowest sub-band of the conduction band of the electron potential well is lower than the band top of the highest valence band of the hole potential well in energy.

The material of the electron potential well of the II-type broken band gap quantum well structure can be at least one of InAs, InAsSb, InGaAs, InGaAsSb and the like; the material of the hole potential well may be selected from at least one of GaSb, GaInSb, GaAlSb, GaAsSb, GaInAsSb, GaAlInSb, gaalinssb, and the like; the material of the first and second barriers may be selected from at least one of AlSb, AlGaSb, AlGaAsSb, AlInSb, AlGaInSb, AlInAsSb, AlGaInAsSb, etc.

The infrared electric absorption modulator based on the II-type broken band gap quantum well can adopt a waveguide coupling configuration or a vertical incidence configuration.

The waveguide coupling configuration has a waveguide structure comprising at least: a base layer; a first cladding layer, a waveguide core layer and a second cladding layer are sequentially arranged on the upper side of the substrate layer; a first contact electrode is arranged on the lower side of the basal layer or the upper side of the table top exposed by the etching of the first coating layer; a second contact electrode is arranged on the upper side of the second cladding layer; the waveguide core layer comprises at least one absorption modulation region; the first cladding layer and the second cladding layer are respectively doped with a semiconductor material or a multilayer structure; the first contact electrode and the second contact electrode respectively apply bias voltage to the absorption modulation region through the first cladding layer and the second cladding layer to form the device for providing modulation bias voltage for the II-type band-break energy gap quantum well structure.

Preferably, the waveguide core layer can adopt a separate confinement structure, and further comprises a first separate confinement layer and a second separate confinement layer; the first and second respective confinement layers are doped semiconductor materials or multilayer structures and are respectively adjacent to the lower interface and the upper interface of the absorption modulation region, and the optical refractive indexes of the first and second respective confinement layers are larger than those of the first and second cladding layers.

Preferably, the base layer further comprises a substrate and a buffer layer, wherein the thickness of the buffer layer is not less than 200nm, and the buffer layer is used for releasing strain and isolating dislocation and impurities so as to reduce the influence of the substrate on the device.

Preferably, a first transition layer and a second transition layer are respectively arranged at the lower interface and the upper interface of the first cladding layer, a third transition layer and a fourth transition layer are respectively arranged at the lower interface and the upper interface of the second cladding layer, and the transition layers are used for reducing parasitic voltage drop caused by abrupt change of interfaces of adjacent area layers; the transition layers are doped with the doping materials respectively between the two sides.

The normal incidence configuration is that light is incident perpendicular to the plane of the material layer of the absorption modulation region, and the normal incidence configuration at least comprises: the bottom coating layer, the absorption modulation region, the top coating layer, the bottom electrode and the top electrode;

the bottom cladding layer and the top cladding layer are doped with a semiconductor material or a multilayer structure; the absorption modulation area is arranged between the bottom coating layer and the top coating layer; the bottom electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the exposed table top of the bottom coating layer after being etched to form electrical contact; the top electrode is a transparent electrode or a grating electrode or is provided with a light-transmitting window, and is arranged on the upper side of the top coating layer to form electrical contact; and the bottom electrode and the top electrode respectively apply bias voltage to the absorption modulation region through the bottom cladding layer and the top cladding layer to form a device for providing modulation bias voltage for the II-type broken band energy gap quantum well structure.

Preferably, a bottom high-reflection film is arranged on the lower side of the bottom coating layer, or a top high-reflection film is arranged in a light-transmitting window area of the top electrode on the upper side of the top coating layer, or the bottom high-reflection film and the top high-reflection film are arranged at the same time; the bottom high-reflection film and the top high-reflection film are respectively composed of distributed Bragg reflectors (distributed Bragg reflectors) or metal films formed by alternately stacking a plurality of dielectric layers, and a Fabry-Perot cavity (Fabry-Perot cavity) structure with symmetry or asymmetry is formed.

Preferably, a metal strip grating may be disposed on an upper side or a lower side of at least one of the bottom high reflection film, the top high reflection film, the bottom cladding layer or the top cladding layer for increasing coupling of a vertical electric field component of incident light with the absorption modulation region, and a grating period is less than or equal to a selected operating wavelength of the infrared electro-absorption modulator.

The electro-optical modulation method for the selected light comprises the following steps:

1) placing an electro-absorption modulator or electro-optic modulator in the path of a selected light, wherein the modulation region of the electro-absorption modulator or electro-optic modulator comprises a semiconductor single-layer or multi-layer structure having the following characteristics:

a. the energy band structure of the semiconductor single-layer or multi-layer structure is provided with a conduction band and a valence band, the electronic state at the bottom of the conduction band and the hole state at the top of the valence band belong to intrinsic states with different Hamilton quantity properties of the system respectively, and the conduction band and the valence band can be distinguished through the properties of the electronic state at the bottom of the conduction band and the hole state at the top of the valence band;

b. the semiconductor single-layer or multi-layer structure has a normal band gap phase, and the energy of the conduction band bottom is higher than that of the valence band top;

c. the semiconductor single-layer or multi-layer structure has an inverted band gap phase, and the energy of the conduction band bottom is lower than that of the valence band top;

d. changing the normal band gap phase of the semiconductor single-layer or multi-layer structure into an inverted band gap phase by changing the bias voltage applied to the semiconductor single-layer or multi-layer structure;

e. the semiconductor single or multilayer structure has significantly different absorption or refractive indices for selected light in the normal bandgap phase and the inverted bandgap phase;

2) bringing the semiconductor material or multilayer structure in step 1) into said normal bandgap phase by applying a bias voltage to the modulation region of the electro-absorption modulator or electro-optic modulator;

3) changing the bias voltage in step 2) so that the semiconductor single-layer or multilayer structure in step 1) is in an inverted bandgap phase;

4) repeating the steps 2) and 3), reducing the difference value meeting the bias voltage required in the steps 2) and 3), and finding out the critical bias voltage for converting the normal band gap phase into the reversed band gap phase;

5) setting the on-state bias voltage near the critical bias voltage found in the step 4), slightly deviating from the critical bias voltage and enabling the semiconductor single-layer or multi-layer structure to be just in a normal band gap phase;

6) after the open-state bias voltage in the step 5) is set, the bias voltage applied to the semiconductor single-layer or multi-layer structure is changed, so that the semiconductor single-layer or multi-layer structure can generate the conversion from the normal band gap phase to the reversed band gap phase to reach the off-state; the transition from the normal bandgap phase to the inverted bandgap phase results in a significant change in the absorption or refractive index of the semiconductor single or multilayer structure; thereby achieving a more pronounced modulation of the intensity or phase of the selected light with a relatively small bias swing.

From the technical scheme, the invention has the following beneficial effects:

1. the on-state bias and the off-state bias can be arranged near the critical voltage of the II-type broken band gap quantum well, so that the relative difference between the on-state bias and the off-state bias is small, a large extinction ratio can be obtained with a small bias swing, and the modulation efficiency is high. Theoretical calculation shows that the low-temperature modulation efficiency of the preferred infrared electric absorption modulator based on the II-type broken band gap quantum well can reach several times of the modulation efficiency of the conventional optical fiber communication near-infrared electric absorption modulator, and the preferred infrared electric absorption modulator also has the advantages of high extinction ratio, low driving voltage, low dynamic power consumption, high modulation bandwidth-driving voltage ratio and the like. At normal temperature, the performance indexes of the electro-absorption modulator are equivalent to those of the conventional optical fiber communication electro-absorption modulator.

2. The infrared electro-absorption modulator of the present invention is based on band inversion bias regulation of conduction band intersubband transitions and valence band intersubband transitions, and thus can simultaneously modulate mid-infrared light polarized in the transverse magnetic mode (TM) and far-infrared light polarized in the transverse electric mode (TE).

3. Typical modulation region sizes of the infrared electro-absorption modulator of the present invention are: the length is 20-200 mu m, and the width is 5-15 mu m, so that the device coverage is small, and the semiconductor chip is suitable for semiconductor chip integration.

4. The material of the infrared electric absorption modulator of the invention belongs toThe antimonide semiconductor family is compatible with antimonide-based infrared quantum cascade lasers and interband cascades, and therefore process barrier-free integration with the lasers is easy to achieve.

Drawings

Fig. 1 is a schematic diagram of band profile and wave function distribution of a class II band-break bandgap quantum well of a periodic unit in real space when different biases are applied. Wherein (a) is applied with a bias voltage V_onWhen the quantum well is in the normal band gap phase, the class II band-gap-broken quantum well is in the normal band gap phase; (b) to apply a bias voltage V_offAnd when the type II band-break energy gap quantum well is in an inverted band gap phase.

FIG. 2 is a diagram of the momentum space band dispersion curve of a preferred class II bandgap quantum well. Wherein (a) is that the quantum well is in a normal bandgap phase and (b) is that the quantum well is in an abnormal bandgap phase.

FIG. 3 is a schematic diagram of an embodiment of an IR electro-absorption modulator of the present invention employing a waveguide coupling configuration;

FIG. 4 is a schematic diagram of an embodiment of an IR electro-absorption modulator of the present invention in a normal incidence configuration and in elevation;

FIG. 5 is a spectrum of transverse magnetic mode (TM) light absorption coefficients of AlSb/InAs/GaSb/AlSbII type band-gap-broken quantum wells under different biases for a periodic unit according to a preferred embodiment of the present invention;

FIG. 6 is a spectrum of transverse electric mode (TE) light absorption coefficients of AlSb/InAs/GaSb/AlSbII type band-gap-broken quantum wells under different biases for a periodic unit according to a preferred embodiment of the present invention;

FIG. 7 is a graph showing the extinction ratio of infrared light in different wavelength transverse magnetic mode (TM) polarization as a function of drive voltage in accordance with a preferred embodiment of the present invention.

FIG. 8 is a graph showing the extinction ratios of different wavelength transverse electric mode (TE) polarized far infrared light as a function of driving voltage in accordance with a preferred embodiment of the present invention.

In the figure, each label is:

100-absorption modulation region, 101-first potential barrier, 102-electron potential well, 103-hole potential well, 104-second potential barrier; e_cBand edge of bulk material conduction band, E_vBulk materialValence band edge, E_F-Fermi level, E1(Γ) -bottom of the lowest sub-band of the conduction band E1, E2(Γ) -bottom of the second sub-band of the conduction band E2, HH1(Γ) -top of the highest sub-band of the valence band HH1, HH2(Γ) -top of the second sub-band of the valence band HH2,the electronic wave function at the bottom of sub-band E1,hole-state wave function, V, of the subband HH1 band top_on-bias voltage in on state, V_off-off state bias;

e1-lowest sub-band of conduction band, E2-second sub-band of conduction band, HH 1-highest sub-band of valence band, HH 2-second sub-band of valence band;

300-a base layer, 310-a first cladding layer, 320-a waveguide core layer, 330-a second cladding layer, 340-a first contact electrode, 350-a second contact electrode, 321-a first confinement layer, 322-a second confinement layer, 301-a substrate, 302-a buffer layer, 311-a first transition layer, 312-a second transition layer, 331-a third transition layer, 332-a fourth transition layer;

410-bottom cladding layer, 420-top cladding layer, 430-bottom electrode, 440-top electrode, 450-bottom high reflection film, 460-top high reflection film, 470-metal strip grating.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the specific embodiments. It should be understood that in the drawings, the thicknesses of layers and regions are exaggerated for clarity of the present disclosure and should not be taken as a schematic representation reflecting the geometric dimensions and proportional relationships between the layers; the described embodiments are only a few embodiments of the present invention, not all embodiments, and all other embodiments obtained by those of ordinary skill in the art without any inventive work are within the scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", "bottom", "top", and the like 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 box or the element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The infrared electric absorption modulator based on the II-type broken band energy gap quantum well comprises: (i) at least one absorption modulation region 100, wherein the absorption modulation region 100 comprises a single-period or multi-period II-type band-gap quantum well structure; (ii) and a device for providing modulation bias voltage for the II-type broken band gap quantum well structure, which is used for generating an electric field perpendicular to the plane of the material layer of the II-type broken band gap quantum well structure.

As shown in fig. 1, the class II band-gap quantum well structure of one cycle unit is composed of a first potential barrier 101, an electron well 102, a hole well 103, and a second potential barrier 104, wherein the electron well 102 and the hole well 103 are disposed between the first potential barrier 101 and the second potential barrier 104 without depending on the relative stacking order;

electron potential well 102 is adjacent to hole potential well 103, and conduction band edge E of bulk material of electron potential well 102_cIs lower than the bulk material valence band edge E of the hole potential well 103_vThereby forming a class II band-break bandgap heterojunction;

the first and second potential barriers 101 and 104 form quantum confinement for the electron and hole state wave functions in the electron and hole potential wells 102 and 103, with the lowest conduction band E1 being the band bottom electron state wave functionConfined mainly to the hole state wave function at the top of HH1 band of the highest sub-band of valence band in the electron potential well 102Confined primarily in hole potential well 103;

when a specific bias voltage V is applied to two ends of the II-type band-break energy gap quantum well structure_onIn this case, the quantum well may be in a normal band gap phase characterized by a band bottom E1(Γ) of the conduction band lowest sub-band E1 of the electron potential well 102 being energetically higher than a band top HH1(Γ) of the hole potential well 103 highest valence band sub-band HH1 [ see FIG. 1 (a) diagram]The momentum space band dispersion curve of the normal bandgap phase is shown in fig. 2 (a);

when a specific bias voltage V is applied to two ends of the II-type band-break energy gap quantum well structure_off(V_off≠V_on) In this case, the quantum well may be in an inverted band gap phase characterized in that the conduction band lowest sub-band E1 of the electron potential well 102 has a band bottom E1(Γ) energetically lower than the band top HH1(Γ) of the hole potential well 103 highest valence band sub-band HH1 [ see FIG. 1 (b) diagram]The momentum space band dispersion curve of the reversed bandgap phase is shown in fig. 2 (b).

Preferably, AlSb/InAs/GaSb/AlSb quantum wells are generally used as a typical example of the type II band-break energy gap quantum well structure. It should be understood that the first barrier 101, the electron well 102, the hole well 103 and the second barrier 104 of the class II bandgap quantum well structure can be replaced by materials with similar characteristics, so that the above characteristics a) to e) need only be satisfied, and the class II bandgap quantum well structure should also be considered as belonging to the class II bandgap quantum well structure.

Further, the material of the electron potential well 102 of the type II band-gap quantum well structure is one or more selected from InAs, InAsSb, InGaAs and InGaAsSb; the material of the hole potential well 103 is one or more selected from GaSb, GaInSb, GaAlSb, GaAsSb, GaInAsSb, GaAlInSb, and gaalinssb; the materials of the first barrier 101 and the second barrier 104 are respectively selected from one or more of AlSb, AlGaSb, AlGaAsSb, AlInSb, AlGaInSb, AlInAsSb and AlGaInAsSb; the selected first barrier 101, electron well 102, hole well 103 and second barrier 104 need to satisfy the above-mentioned features a) -e) of the class II bandgap quantum well structure.

According to the characteristics of the infrared electric absorption modulator based on the II-type broken band gap quantum well structure, the invention also provides a high-efficiency electro-optical modulation method for selected light based on the bias regulation energy band inversion principle, which comprises the following steps:

1) placing an electro-absorption modulator or electro-optic modulator in the propagation path of the selected light, wherein the modulation region of the electro-absorption modulator or electro-optic modulator comprises a semiconductor single-layer or multi-layer structure having the following characteristics:

a. the semiconductor material or the energy band structure of the multilayer structure has a conduction band and a valence band, the electronic state at the bottom of the conduction band and the electronic state at the top of the valence band belong to intrinsic states with different Hamilton quantity properties of the system respectively, and the conduction band and the valence band can be distinguished through the properties of the electronic state at the bottom of the conduction band and the electronic state at the top of the valence band; the class II band-gap quantum well structure shown in FIG. 1 has the electronic state wave function of the conduction band lowest sub-band E1 and the valence band highest sub-band HH1, and the sub-band E1 at the bottom of the bandAnd the sub-band HH1 band top hole state wave functionMainly distributed in an electron potential well (102) and a hole potential well (103), respectively, and the lowest conduction band E1 and the highest valence band HH1 can be distinguished by the distribution characteristics;

b. the semiconductor material or the multilayer structure has a normal band gap phase and is characterized in that the energy of the conduction band bottom is higher than that of the valence band top; for example, with the class II bandgap quantum well structure embodiment shown in figure 1 (a), the conduction band lowest sub-band E1 has a higher energy at the bottom E1(Γ) than the valence band highest sub-band HH1 and the top HH1(Γ), which is in the normal bandgap phase.

c. The semiconductor material or the multilayer structure has an inverted band gap phase, and is characterized in that the energy of the conduction band bottom is lower than that of the valence band top; for example, with the class II bandgap quantum well structure embodiment shown in figure 1 (b), the conduction band lowest sub-band E1 band bottom E1(Γ) has lower energy than the valence band highest sub-band HH1 band top HH1(Γ), which is in an inverted bandgap phase;

d. the normal bandgap phase can be changed into the reversed bandgap phase by changing the bias voltage applied to the semiconductor material or the multilayer structure; for example, the class II band-gap quantum well structure of one period unit shown in FIG. 1 is used as an embodiment, and is biased by V_onBecomes V_offWhen the quantum well is in the normal band gap phase, the quantum well is converted into the reversed band gap phase;

e. the semiconductor material or multilayer structure has significantly different absorption or refractive indices for the selected light when in the normal bandgap phase and the inverted bandgap phase; for example, the class II bandgap-broken quantum well structure shown in fig. 1 is taken as an example: in the normal bandgap phase shown in FIG. 1 (a), the Fermi level E is considered to be the level_FBelow the conduction band lowest sub-band E1 band bottom E1(Γ) and above the valence band highest sub-band HH1 band top HH1(Γ), neither the conduction band lowest sub-band E1 nor the valence band highest sub-band HH1 is filled, inter-sub-band transitions are forbidden, light absorption is weak; in the case of the reversed bandgap phase shown in the diagram (b) of FIG. 1, the Fermi level E is caused_FAbove the conduction band lowest sub-band E1 band bottom E1(Γ) and below the valence band highest sub-band HH1 band top HH1(Γ), the conduction band lowest sub-band E1 and valence band highest sub-band HH1 distributions are filled with electrons and holes, both conduction band inter-band transitions E1-E2 and valence band inter-band transitions HH1-HH2 are allowed, resulting in a significant increase in the absorbance of light complying with the corresponding transition rules;

2) bringing the semiconductor material or multilayer structure in step 1) into the normal bandgap phase by biasing the modulation region of the electro-absorption or electro-optic modulator;

3) changing the bias voltage described in step 2) so that the semiconductor material or multilayer structure in step 1) is in the inverted bandgap phase;

4) repeating the steps 2) and 3), reducing the difference value which meets the requirements of the bias voltages in the steps 2) and 3), and finding out the critical bias voltage for converting the normal band gap phase into the reversed band gap phase;

5) setting an on-state bias voltage near the critical bias voltage found in step 4), slightly deviating from the critical bias voltage and making the semiconductor material or multilayer structure just in the normal bandgap phase;

6) after the on-state bias voltage in the step 5) is set, the bias voltage applied to the semiconductor material or the multilayer structure is slightly changed, so that the normal band gap phase can be converted to the reverse band gap phase to reach an off state; again according to e of step 1), the transition from the normal bandgap phase to the inverted bandgap phase is necessarily accompanied by a significant change in the absorption or refractive index of the semiconductor material or multilayer structure; thus, the above steps may enable a more significant modulation of the intensity or phase of the selected light with a relatively small bias swing.

Obviously, the electro-optical modulation method is suitable for the infrared electro-absorption modulator based on the II-type broken band gap quantum well structure. It should be noted that the electro-optical modulation method is not limited to the infrared electro-absorption modulator of the present invention, and any electro-absorption modulator or electro-optical modulator having the features a) to e) described in step 1) (for example, an electro-absorption modulator or electro-optical modulator including a topological insulator with a property of bias-controlled topological band inversion) can be used to perform high-efficiency electro-optical modulation.

Specific examples are given below, but the present invention is not limited to the configurations of the following examples.

Example 1

With the waveguide coupling configuration as shown in fig. 3, there is a waveguide structure comprising at least: a base layer 300; a first cladding layer 310, a waveguide core layer 320 and a second cladding layer 330 are sequentially arranged on the upper side of the substrate layer 300; a first contact electrode 340 is arranged on the lower side of the substrate layer 300 or the upper side of the mesa exposed by etching of the first cladding layer 310 and forms electrical contact with the first contact electrode; a second contact electrode 350 is provided on the upper side of the second cladding layer 330 and forms an electrical contact; wherein, the waveguide core layer 320 includes at least one absorption modulation region 100 therein; the first cladding layer 310 and the second cladding layer 330 are respectively doped with a semiconductor material or a multilayer structure; the first contact electrode 340 and the second contact electrode 350 bias the absorption modulation region 100 through the first cladding layer 310 and the second cladding layer 330, respectively, to form the device for providing modulation bias to the class II band-break bandgap quantum well structure.

The waveguide core layer 320 adopts a separate confinement structure, and further comprises a first separate confinement layer 321 and a second separate confinement layer 322; the first and second confinement layers 321 and 322 are doped semiconductor materials or multi-layer structures, respectively adjacent to the lower and upper interfaces of the absorption modulation region 100, and are characterized by optical refractive indices greater than those of the first and second cladding layers 310 and 330.

The base layer 300 further comprises a substrate 301 and a buffer layer 302, wherein: the buffer layer 302 is not less than 200nm thick and functions to relieve strain and isolate dislocations and impurities to reduce the influence of the substrate 301 on the device.

In order to reduce the parasitic voltage drop caused by the abrupt interface transition of the adjacent regions, a first transition layer 311 and a second transition layer 312 may be disposed at the lower interface and the upper interface of the first cladding layer 310, and a third transition layer 331 and a fourth transition layer 332 may be disposed at the lower interface and the upper interface of the second cladding layer 330, respectively, and the transition layers may be characterized by having a doping concentration between the doping concentrations of the adjacent materials at the two sides thereof, respectively.

The substrate 301 specifically adopts an n-type GaSb substrate;

the buffer layer 302 is doped with an n-type GaSb material at a doping concentration of 1 × 10¹⁷cm^-3～2×10¹⁸cm^-3The interval is 0.2 to 1.5 μm thick;

the first cladding layer 310 is made of a material which is doped with the n-type InAs/AlSb short-period superlattice or AlGaAsSb alloy, and has a refractive index in a range of 3.20-3.40 and a doping concentration of 0.1 × 10¹⁹cm^-3～1.5×10¹⁹cm^-3Interval, thickness is in the interval of 1-5 μm;

the first respective confinement layers 321 are n-type GaSb materials with refractive indexes ranging from 3.70 to 3.90 and doping concentrations of 0.5 × 10¹⁷cm^-3～2×10¹⁷cm^-3Interval, thickness is in the interval of 0.5-2 μm;

the absorption modulation region 100 adopts a 1-15 period II-type band-break energy gap quantum well, wherein: the first potential barrier 101 and the second potential barrier 104 are made of AlSb or AlGaSb materials, and the thickness of the first potential barrier is 5-50 nm; the electron barrier 102 is made of InAs material, and the thickness is in a range of 3-20 nm; the hole barrier 103 is made of GaSb material, and the thickness of the hole barrier is 3-20 nm;

the second respective confinement layers 322 are n-type GaSb materials with refractive indexes ranging from 3.70 to 3.90 and doping concentrations of 0.5 × 10¹⁷cm^-3～2×10¹⁷cm^-3Interval, thickness is in the interval of 0.5-2 μm;

the second cladding layer 330 is made of a material doped with the n-type InAs/AlSb short-period superlattice or AlGaAsSb alloy, has a refractive index in a range of 3.20-3.40, and is doped with the n-type InAs/AlSb short-period superlattice or AlGaAsSb alloy at a concentration of 0.1 × 10¹⁹cm^-3～1.5×10¹⁹cm^-3Interval, thickness is in the interval of 0.5-3 μm;

a first contact electrode 340 formed on the lower side of the substrate 301, and made of a metal material such as Ti, Pt, Au, Ag, Cu, or an alloy thereof;

a second contact electrode 350 formed over the first cladding layer 310 and including a cap layer and a metal electrode disposed thereon, wherein the cap layer is doped with a short-period superlattice of heavily-doped n-type InAs/AlSb or a heavily-doped n-type InAs material, and the doping concentration of the cap layer is greater than 1.0 × 10¹⁹cm^-3The thickness is 0.1-0.5 μm; the metal electrode is made of metal materials such as Ti, Pt, Au, Ag, Cu and the like or alloys thereof;

as a further preference, a first transition layer 311 and a second transition layer 312 may be inserted at the lower interface and the upper interface of the first clad layer 310, respectively, and a third transition layer 331 and a fourth transition layer 332 may be inserted at the lower interface and the upper interface of the second clad layer 330, respectively; first transition layer 311, second transition layer 312, third transition layer 331, and fourth transition layer 332 may each be an n-type doped InAs/AlSb short-period superlattice with a doping concentration between the doping concentrations of the adjacent side materials, and with a typical value of 1 × 10¹⁷cm^-3～5×10¹⁸cm^-3An interval;

through a standard photolithography process, the present embodiment has a ridge waveguide structure as shown in fig. 1, the waveguide width w is within a range of 3 to 15 μm, the modulation length is determined by the coverage length L of the first contact electrode 340, and a typical L value is within a range of 20 to 200 μm.

Through the simultaneous self-consistent calculation of an eight-band k.p effective mass model and a Poisson equation, transverse magnetic mode (TM) and transverse electric mode (TE) light absorption coefficient spectrums of AlSb/InAs/GaSb/AlSbII type band-broken energy gap quantum wells of one period unit of the quantum wells under different bias voltages are respectively given in FIGS. 5 and 6. It can be seen that when the amplitude of the reverse bias voltage (V < 0) increases to the band inversion of the class II band-gap quantum well, the optical absorption coefficient spectrum of the transverse magnetic mode (TM) exhibits a narrow and strong absorption peak in the mid-infrared band, which corresponds to the intersubband transition of E1-E2, see fig. 5; meanwhile, the far infrared band of the light absorption coefficient spectrum shows a broad transverse electric mode (TE) absorption peak corresponding to the transitions of HH1-HH2 and HH1 to other sub-bands, see FIG. 6. It can be seen that if the operating wavelength of the infrared electro-absorption modulator is set in the absorption peak region, light of that wavelength can be effectively modulated by applying a bias voltage.

According to the high-efficiency electro-optic modulation method based on the bias regulation energy band inversion principle, the on-state bias voltage V of the infrared electro-absorption modulator of the preferred embodiments in FIGS. 5 and 6 can be obtained_onSet near the critical bias of class II band-break bandgap quantum well band inversion and just put it in normal bandgap phase, e.g. set V_on-0.30V. At this time, the energy band of the class II band-break bandgap quantum well can be inverted by slightly changing the bias voltage, for example, making the bias voltage V → -0.35V, and at this time, the optical absorption coefficient spectrum will have a sub-band transition absorption peak at a specific wavelength. If the reverse bias is further increased, the absorption peak will be significantly enhanced. The off-state bias voltage V of the infrared electro-absorption modulator_offIs set at the bias voltage required to achieve the desired extinction ratio for the operating wavelength of light.

For an electro-absorption modulator in a waveguide coupling configuration, the extinction ratio, ER, can be calculated by:

wherein, I_onAnd I_offThe emergent light intensity of the electric absorption modulator in an on state and an off state respectively, gamma is the coupling limiting factor of the waveguide, alpha (V) is a function of the variation of the absorption coefficient of the modulated light with the bias voltage, and L is the waveguide modulationAnd (4) manufacturing the length. For an infrared electric absorption modulator with a single-period II-type broken band gap quantum well, the waveguide light limiting factor is gamma^spAbout 0.02 with a driving voltage ofFor an infrared electro-absorption modulator with N periodic class II band-break bandgap quantum wells, the waveguide coupling confinement factor can be approximated as Γ ≈ NΓ^spAnd its driving voltage is approximatelyFig. 7 and 8 show the variation of extinction ratios of transverse magnetic mode (TM) polarized mid-ir light and transverse electric mode (TE) polarized far-ir light with driving voltage for different wavelengths in a preferred embodiment having a waveguide coupling configuration with a waveguide modulation length L of 100 μm and N of 4 periods of AlSb/InAs/GaSb/alsbi class gap quantum wells. As can be seen from FIGS. 7 and 8, for the light with the corresponding wavelength near the sub-band transition absorption peak, such as the middle infrared transverse magnetic mode (TM) polarized light with 4.46 μm and the far infrared transverse electric mode (TE) polarized light with 22.5-62.0 μm, only about 0.3V and 0.65V are needed to realize the high-efficiency electro-absorption modulation with the extinction ratio of 20 dB. In addition, the low driving voltage and the small device footprint will also provide the advantages of low dynamic power consumption, high modulation bandwidth, etc. for this embodiment.

Example 2

On the basis of embodiment 1, unlike embodiment 1, the substrate 301 employs an n-type GaAs substrate; the buffer layer 302 is doped with n-type AlGaSb material at a concentration of 1 × 10¹⁷cm^-3～2×10¹⁸cm^-3The interval is 0.5 to 3 μm thick.

The embodiment 2 has the advantages that the common GaAs substrate is adopted, the preparation cost is relatively low, the preparation process is mature, and the optical interconnection integration is convenient to realize.

Example 3

On the basis of example 1, in contrast to example 1, wherein:

the substrate 301 adopts an n-type InAs substrate;

the buffer layer 302 is doped with an n-type InAs material at a concentration of 1 × 10¹⁷cm^-3～2×10¹⁸cm^-3The interval is 0.2 to 1.5 μm thick;

the first cladding layer 310 has a refractive index within a range of 2.80-3.10, and is doped with a highly doped n-type InAs material and a highly doped concentration of 0.5 × 10¹⁹cm^-3～2×10¹⁹cm^-3Interval, thickness is in the interval of 1-4 μm;

the first respective confinement layers 321 have refractive indices in a range of 3.20-3.60, and are doped with n-type InAs materials at a doping concentration of 0.1 × 10¹⁷cm^-3～5×10¹⁷cm^-3Interval, thickness is in the interval of 0.5-3 μm;

the refractive index of the second respective confinement layers 322 is within a range of 3.20-3.60, and the second respective confinement layers are doped with n-type InAs materials at a doping concentration of 0.1 × 10¹⁷cm^-3～5×10¹⁷cm^-3Interval, thickness is in the interval of 0.5-3 μm;

the second cladding layer 330 has a refractive index in a range of 2.80-3.10, and is doped with a highly doped n-type InAs material and a doping concentration of 0.5 × 10¹⁹cm^-3～2×10¹⁹cm^-3Interval, thickness is in the interval of 0.5-2 μm;

second contact electrode 350, which is doped with the second cap layer and the second InAs material, and which is doped with the second cap layer and the second InAs material at a concentration greater than 1 × 10¹⁹cm^-3The thickness is 0.1-0.5 μm;

embodiment 3 has the advantages of using an InAs substrate, having high mobility and thermal conductivity, and easily realizing an infrared electro-absorption modulator with ultra-high speed and good heat dissipation.

Example 4

With the normal incidence configuration as shown in fig. 4, light is incident perpendicular to the plane of the material layer of the absorption modulation region 100, and includes at least: a bottom cladding layer 410, an absorption modulation region 100, a top cladding layer 420, a bottom electrode 430, a top electrode 440;

the bottom cladding layer 410 and the top cladding layer 420 are doped with a semiconductor material or a multilayer structure; the absorption modulation region 100 is disposed between the bottom cladding layer 410 and the top cladding layer 420; the bottom electrode 430 is a transparent electrode or a grating electrode or is provided with a light-transmitting window, is arranged on the upper side of the etched exposed table top of the bottom coating layer 410 and forms electrical contact; the top electrode 440 is a transparent electrode or a grating electrode or is provided with a light-transmitting window, is arranged on the upper side of the top cladding layer 420 and forms an electrical contact; the bottom electrode 430 and the top electrode 440 bias the absorption modulation region 100 through the bottom cladding layer 410 and the top cladding layer 420, respectively, constituting a means of providing a modulation bias to the class II bandgap quantum well structure.

With a symmetric or asymmetric Fabry-perot cavity (Fabry-perot cavity) structure: a bottom highly reflective film 450 is provided on the lower side of the bottom cladding layer 410, or a top highly reflective film 460 is provided in the light transmission window area of the top electrode 440 on the upper side of the top cladding layer 420, or both the bottom highly reflective film 450 and the top highly reflective film 460 are provided; the bottom high-reflection film 450 and the top high-reflection film 460 are respectively composed of distributed Bragg reflectors (distributed Bragg reflectors) or metal films formed by alternately stacking a plurality of dielectric layers;

to increase the coupling of the vertical electric field component of the incident light to the absorption modulation region 100, a metal strip grating 470 is disposed on the upper or lower side of one or more of the bottom highly reflective film 450, the top highly reflective film 460, the bottom cladding layer 410, and the top cladding layer 420, with a grating period less than or equal to the selected operating wavelength of the ir electroabsorption modulator of the present invention.

The bottom cladding layer 410 is doped with a short-period superlattice of either a highly doped n-type InAs material or an n-type InAs/AlSb material at a concentration of 0.1 × 10¹⁹cm^-3～2×10¹⁹cm^-3The interval is 0.1-1 μm thick;

the absorption modulation region 100 adopts a 1-40 period II-type band-break energy gap quantum well, wherein: the first potential barrier 101 and the second potential barrier 104 are made of AlSb materials, and the thickness of the first potential barrier is 5-50 nm; the electron barrier 102 is made of InAs material, and the thickness is in a range of 3-20 nm; the hole barrier 103 is made of GaSb material, and the thickness of the hole barrier is 3-20 nm;

the top cladding layer 420 is doped with a highly doped n-type InAs material or a n-type InAs/AlSb short period superlattice at a doping concentration of 0.1 × 10¹⁹cm^-3～2×10¹⁹cm^-3Interval, thickness in 0.1 ℃1 μm interval;

a top electrode 440 formed on the top cladding layer 420, made of metal material such as Ti, Pt, Au, Ag, Cu, etc. or alloy thereof, and having a light-transmitting window;

a bottom highly reflective film 450 is provided under the bottom cladding layer 410; the bottom high-reflection film 450 is a distributed Bragg reflector formed by alternately stacking 4-30 pairs of GaSb and AlAsSb with the thickness of 1/4 wavelengths;

optionally, a top highly reflective film 460 is disposed within the light transmissive window of the top electrode 440 on the top cladding layer 420; the top highly reflective film 460 is formed by 4-6 pairs of Ge and Al with the thickness of 1/4 wavelengths₂O₃Distributed Bragg reflectors formed by alternately stacking; arranging a metal strip grating 470 on the top high reflection film 460, wherein the grating period is in the range of 0.5-3 μm;

optionally, for the design without the top high reflection film 460, a metal strip grating 470 may be disposed in the light-transmitting window of the top electrode 440 and on the top cladding layer 420, and the grating period is in the range of 0.5-3 μm;

the structure above the bottom cladding layer 410 may be formed into a mesa as shown in fig. 4 by standard photolithography processes; disposing a bottom electrode 430 around the formed mesa over the bottom cladding layer 410 to form the light transmissive window; the bottom electrode 430 is made of a metal material such as Ti, Pt, Au, Ag, Cu, or an alloy thereof.

According to the vertical incidence configuration of the present embodiment, light can be vertically incident from the top highly reflective film 460 from top to bottom, and also can be vertically incident from the bottom highly reflective film 450 from bottom to top; the device structure can be prepared on a semiconductor substrate, and can also be directly formed on the emergent surface of a Vertical Cavity Surface Emitting Laser (VCSEL), thereby realizing the integration with the VCSEL.

The above-described embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.