An InP-based Mach-Zehnder interferometric electro-optic modulator and a method for manufacturing the same

Abstract

This invention relates to an InP-based Mach-Zehnder interferometer electro-optic modulator and its fabrication method, belonging to the field of electro-optic modulator fabrication technology. The invention discloses an InP-based Mach-Zehnder interferometer electro-optic modulator, comprising a sequentially connected optical input terminal, an optical modulation region, and an optical output terminal. The traveling wave electrode in the optical modulation region includes a microwave transmission line and several periodically arranged electrodes connected to the transmission line. The electrodes are located on the surface of a P-type contact layer of an active waveguide structure, and the active waveguide structure, from bottom to top, comprises an InP substrate layer and an epitaxial wafer. The epitaxial wafer, from bottom to top, comprises an N-type doped layer, spacer layer I, a quantum well layer, spacer layer II, a lightly doped P-type layer, a P-type doped layer, and a P-type contact layer.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronics technology, and relates to an InP-based Mach-Zehnder interferometer electro-optic modulator and its fabrication method. Background Technology

[0002] With the development of integrated optics technology and the increase in the total amount of information transmitted, optical modulators, as a key link in the optical communication transmission chain, are core devices that urgently need to be developed and broken through. Currently, the electro-optic modulators that are more studied include lithium niobate (LiNbO3) modulators, silicon-based modulators, and group III-V semiconductor modulators. Among them, InP-based modulators have advantages such as flat and high-bandwidth optical modulation characteristics, low driving voltage, small size, and monolithic integration with the light source.

[0003] InP-based Mach-Zehnder (MZ) interferometric modulators primarily employ nip or pin structures. For pin structures, the epitaxial process is simple, but the high carrier absorption of p-type materials leads to significant optical absorption losses. To address this issue, some researchers have adopted NIN device structures; however, while reducing losses, this also increases the driving voltage, hindering cost reduction.

[0004] To better achieve high-performance, low-cost electro-optic modulators, a Mach-Zehnder electro-optic modulator with a novel profile concentration distribution and structure is invented. By adjusting the structure and profile concentration distribution, the light absorption loss and driving voltage of the Mach-Zehnder modulator are reduced. Summary of the Invention

[0005] In view of this, one objective of the present invention is to provide an InP-based Mach-Zehnder interferometric electro-optic modulator; a second objective of the present invention is to provide a method for fabricating an InP-based Mach-Zehnder interferometric electro-optic modulator; and a third objective of the present invention is to provide an application of an InP-based Mach-Zehnder interferometric electro-optic modulator in adjusting light intensity.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] 1. An InP-based Mach-Zehnder interferometer electro-optic modulator, the electro-optic modulator comprising an optical input terminal 1, an optical modulation region, and an optical output terminal 10 connected in sequence;

[0008] The optical modulation region includes a DC bias electrode 2, a traveling wave electrode 4, two modulation arms 6, and two phase electrodes 7 respectively connected to the modulation arms 6. The traveling wave electrode includes a microwave transmission line 3 and a number of periodically arranged periodic electrodes 5 connected to the microwave transmission line 3. The periodic electrodes 5 are located on the surface of the P-type contact layer of the edge waveguide structure. The RF power supply 8 and the resistor 9 are respectively connected to both ends of the microwave transmission line 3.

[0009] The active waveguide structure comprises, from bottom to top, an InP substrate layer and an epitaxial wafer, wherein the epitaxial wafer comprises, from bottom to top, an N-type doped layer, spacer layer I, a quantum well layer, spacer layer II, a lightly doped P-type layer, a P-type doped layer, and a P-type contact layer.

[0010] Preferably, the optical input terminal 1 includes either a Y-type beam splitter or a 1×2 coupler, wherein the other end of either the Y-type beam splitter or the 1×2 coupler is connected to two modulation arms 6 respectively.

[0011] The optical output terminal 10 includes either a Y-type combiner or a 2×2 coupler connected to the other end of the two modulation arms 6.

[0012] Preferably, the thickness of spacer layer I is greater than the thickness of spacer layer II, the thickness of spacer layer I and spacer layer II is not greater than 300 nm, and the material of spacer layer I and spacer layer II is InGaAsP.

[0013] Preferably, the total thickness of the quantum well layer is 400–800 nm, and the quantum well layer is composed of multiple periodic quantum wells;

[0014] The quantum well comprises a central potential well and two side potential barriers, and the material of the potential well is In. 1-x Ga x As y P 1-y Where y is 0.7~0.9 and x is 0.464~0.466, and the material of the barrier is InP material.

[0015] Preferably, the p-type lightly doped layer is a p-type InP lightly doped layer, wherein the p doping concentration is 3 × 10⁻⁶. 17 ~5×10 17 cm -3 ;

[0016] The p-type doped layer is a p-type InP doped layer, wherein the doping concentration is greater than or equal to 1 × 10⁻⁶. 18 cm -3 .

[0017] Preferably, the N-type doped layer is an N-type InP doped layer, wherein the doping concentration is 1×10⁻⁶.18 ~3×10 18 cm -3 The thickness of the N-type doped layer is 1 ± 0.1 μm;

[0018] The P-type contact layer is a P-type InGaAs layer, wherein the doping concentration is greater than or equal to 1×10⁻⁶. 19 cm -3 The thickness of the P-type contact layer is 0.1 ± 0.01 μm.

[0019] Preferably, the method for fabricating electrodes on an active waveguide structure is as follows:

[0020] (1) Growing an epitaxial wafer on an InP substrate: An N-type doped layer, spacer layer I, quantum well layer, spacer layer II, P-type lightly doped layer, P-type doped layer and P-type contact layer are sequentially prepared on a semi-insulating InP substrate by chemical vapor deposition, thereby forming an epitaxial wafer on the InP substrate and obtaining an active waveguide structure.

[0021] (2) Fabrication of deep ridge waveguide structure: Using SiNx dielectric film as a mask, the waveguide pattern is transferred to the epitaxial wafer of the active waveguide structure by photolithography and etching to form a deep ridge waveguide structure;

[0022] (3) Waveguide passivation: A dielectric film is deposited on the surface of the deep ridge waveguide structure to passivate the waveguide;

[0023] (4) Channel filling: The channel is filled on the passivated waveguide material using a material with a dielectric constant of less than 3.9;

[0024] (5) Electrode fabrication on the surface of active waveguide structure: Electrode fabrication is carried out on the surface of P-type contact layer of active waveguide structure by photolithography or electroplating.

[0025] 2. The method for fabricating the above-mentioned electro-optic modulator, wherein the fabrication method includes the following steps:

[0026] (1) A silicon nitride (SiN) layer with a thickness of 0.2 μm was deposited on the epitaxial wafer using the PECVD method. x The dielectric film is used as a mask;

[0027] (2) Using patterning technology, the waveguide pattern is transferred onto the epitaxial wafer by sequentially performing coating, soft baking, alignment, exposure, development, hard baking and etching.

[0028] (3) Using the silicon nitride (SiN) deposited in step (1) x Using a dielectric film as a mask, the epitaxial wafer is etched using dry or wet methods to fabricate a deep ridge waveguide;

[0029] (4) Continue to deposit silicon nitride (SiN) on the deep ridge waveguide.x The dielectric film is photolithographically patterned with N-steps and coated with silicon nitride (SiN). x The dielectric film is used as a mask for etching;

[0030] (5) Photolithographic traveling wave modulated waveguide, and silicon nitride (SiN) x The dielectric film is used as a mask and etched onto the surface of the top spacer layer to fabricate a passive waveguide;

[0031] (6) Continue to deposit silicon nitride (SiN) on the waveguide. x The dielectric film serves as a passivation film and etching barrier layer for the waveguide;

[0032] (7) Deposit materials with a dielectric constant less than 3.9 to fill channels and planarize devices;

[0033] (8) Deposition of silicon nitride (SiN) x Dielectric film, photolithographic electrode holes, and seed layer evaporated on the surface;

[0034] (9) Microwave transmission lines, periodic electrodes, phase electrodes and DC bias electrodes are fabricated on the seed layer using photolithography and electroplating processes;

[0035] (10) Resistors are prepared by photolithography, evaporation and stripping processes, and ohmic contacts are achieved by alloying process;

[0036] (11) Use a thinning process to reduce the thickness of the epitaxial wafer to the required thickness;

[0037] (12) Metallization process is applied to the back side of the epitaxial wafer to achieve chip integration;

[0038] (13) The entire epitaxial wafer is cleaved into Bar strips, and the Bar strips are further dissected. An anti-reflection film is deposited on the side of the Bar strips to reduce light loss.

[0039] Preferably, the material with a dielectric constant of less than 3.9 is benzocyclobutene (BCB).

[0040] 3. Application of the above-mentioned electro-optic modulator in adjusting the intensity of light.

[0041] The beneficial effects of the present invention are as follows: The present invention discloses an InP-based Mach-Zehnder interferometer electro-optic modulator, comprising an optical input terminal, an optical modulation region, and an optical output terminal connected in sequence. The traveling wave electrode in the optical modulation region includes a microwave transmission line and a plurality of periodically arranged electrodes connected to the wave transmission line. The electrodes are located on the surface of the P-type contact layer of an active waveguide structure, and the active waveguide structure comprises, from bottom to top, an InP substrate layer and an epitaxial wafer. The epitaxial wafer comprises, from bottom to top, an N-type doped layer, spacer layer I, a quantum well layer, spacer layer II, a lightly doped P-type layer, a P-type doped layer, and a P-type contact layer. The InP-based Mach-Zehnder interferometric electro-optic modulator of this invention has the following advantages: (1) It is fabricated on an InP substrate, which has a higher integration density and can be integrated with lasers, amplifiers and other devices to realize an integrated optical module; (2) It uses multiple quantum wells as waveguide cores for optical transmission. The refractive index change caused by the QCSE effect is large, which is easy to phase modulate and can reduce the driving voltage and the total length of the device; (3) It uses a strip-shaped traveling wave electrode for modulation. Compared with lumped electrodes, the 3-dB electro-optic modulation bandwidth of the modulator is improved, and the flexibility of waveguide design is also higher; (4) It adopts a PIN structure, which is simple to grow epitaxially and has a small reverse leakage current, which is conducive to reducing costs; (5) Compared with the P-type in conventional PIN optical modulators, The large carrier absorption of the layer leads to the limitation of the intrinsic region thickness. After adjusting the profile concentration distribution and introducing a light doped layer, the carrier absorption loss caused by the P-type doped layer is reduced, the intrinsic region thickness can be made thinner, the voltage applied to the quantum well is enhanced, and the required driving voltage is also lower; (6) After comprehensively balancing the electro-optic modulation efficiency and insertion loss, an asymmetric spacer layer thickness is adopted; (7) The quaternary material InGaAsP, which matches the InP lattice of the substrate, is adopted. Through simple composition engineering, the bandgap of the material can be adjusted, and a material more suitable for the working wavelength can be selected to achieve a high-efficiency modulator; (8) The channel is filled with a low dielectric constant to replace the air bridge process required for channeled devices, reducing the process difficulty and realizing device planarization.

[0042] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0044] Figure 1This is a structural diagram of an InP-based Mach-Zehnder interferometer electro-optic modulator;

[0045] Figure 2 for Figure 1 Cross-sectional view of the XX' axis;

[0046] Figure 3 for Figure 1 Cross-sectional view of the YY' axis;

[0047] Figure 4 Diagram of an active waveguide structure;

[0048] Figure 5 This is a diagram of a quantum well layer structure.

[0049] Figure 6 Flowchart of fabrication process for InP-based Mach-Zehnder interferometer electro-optic modulator;

[0050] Figure 7 This is a fabrication process diagram of an InP-based Mach-Zehnder interferometer electro-optic modulator.

[0051] Figure 8 This is a diagram of a passive waveguide structure.

[0052] Where 1 is the input terminal, 2 is the DC bias electrode, 3 is the microwave transmission line, 4 is the traveling wave electrode, 5 is the periodic electrode, 6 is the modulation arm, 7 is the bit electrode, 8 is the RF power supply, 9 is the resistor, and 10 is the optical output terminal. Detailed Implementation

[0053] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0054] Example 1

[0055] An InP-based Mach-Zehnder interferometer electro-optic modulator, the structure of which is as follows: Figure 1 As shown in the cross-sectional view of axis XX' Figure 2 As shown, the cross-sectional view of the YY' axis is as follows. Figure 3 As shown, the electro-optic modulator includes an optical input terminal 1 (including any one of a Y-type beam splitter or a 1×2 coupler), an optical modulation area, and an optical output terminal 10 (including any one of a Y-type beam combiner or a 2×2 coupler) connected in sequence.

[0056] The optical modulation region includes a DC bias electrode 2, a traveling wave electrode 4, two modulation arms 6, and two phase electrodes 7 respectively connected to the modulation arms 6. The traveling wave electrode includes a microwave transmission line 3 and a number of periodically arranged periodic electrodes 5 connected to the microwave transmission line 3. The periodic electrodes 5 are located on the surface of the P-type contact layer of the edge waveguide structure. The RF power supply 8 and the resistor 9 are respectively connected to both ends of the microwave transmission line 3.

[0057] The above active waveguide structure, from bottom to top, includes an InP substrate layer and an epitaxial wafer (its structure is as follows). Figure 4 As shown), the epitaxial wafer includes, from bottom to top, an N-type doped layer (i.e., an N-type InP doped layer, using N-type InP doped material, with a doping concentration of 1×10⁻⁶). 18 ~3×10 18 cm -3 The N-type doped layer has a thickness of 1 ± 0.1 μm, spacer layer I (material InGaAsP, thickness not greater than 300 nm), and quantum well layer (its structure is as follows). Figure 5 As shown, it consists of 25 quantum wells grown alternately, with a background doping concentration of 5 × 10⁻⁶. 15 cm -3 With a total thickness of 500 nm, this quantum well consists of a central potential well and two side barriers, where the potential well employs a λ-wavelength gradient. PL =1.38 μm, In with a thickness of 14 nm 1-x Ga x As y P 1-y The material consists of: a barrier layer (where y is 0.7~0.9 and x is 0.464~0.466, and the barrier is made of InP material with a thickness of 6 nm), a spacer layer II (made of InGaAsP with a thickness of no more than 300 nm, and the thickness of spacer layer II is less than the thickness of spacer layer I), and a P-type lightly doped layer (a P-type InP lightly doped layer with a doping concentration of 3×10⁻⁶). 17 ~5×10 17 cm -3 (300 nm thick) P-type doped layer (P-type InP doped layer, wherein the doping concentration is greater than or equal to 1 × 10⁻⁶) 18 cm -3 (700 nm thick) and a P-type contact layer (P-type InGaAs layer with a doping concentration greater than or equal to 1 × 10⁻⁶). 19 cm -3 Its thickness is 0.1 ± 0.01 μm.

[0058] The process for fabricating the InP-based Mach-Zehnder interferometer electro-optic modulator described above is as follows: Figure 6 As shown, the specific method includes the following steps (e.g. Figure 7 (as shown)

[0059] (1) The above epitaxial wafer (the preparation method of the epitaxial wafer is: to prepare an N-type doped layer (N) on a semi-insulating InP substrate by chemical vapor deposition) sequentially. + -InP), spacer layer I, quantum well layer (MQW), spacer layer II, lightly doped P-type layer (P-InP), P-type doped layer (P + -InP) and P-type contact layer (P ++ Silicon nitride (SiN) with a thickness of 0.2 μm is deposited on an InP substrate (to form an epitaxial wafer) using PECVD. x The dielectric film is used as a mask.

[0060] (2) Using patterning technology, the waveguide pattern is transferred onto the epitaxial wafer by sequentially performing coating, soft baking, alignment, exposure, development, hard baking and etching.

[0061] (3) Using the silicon nitride (SiN) deposited in step (1) x Using a dielectric film as a mask, the epitaxial wafer is etched using dry or wet methods to fabricate a deep ridge waveguide.

[0062] (4) Continue to deposit silicon nitride (SiN) on the deep ridge waveguide. x The dielectric film is photolithographically patterned with N-steps and coated with silicon nitride (SiN). x The dielectric film is used as a mask for etching in order to subsequently fabricate a DC bias electrode.

[0063] (5) Photolithographic traveling wave modulated waveguide, and silicon nitride (SiN) x The dielectric film is used as a mask and etched onto the surface of the top spacer layer to fabricate a passive waveguide (such as...). Figure 8 (As shown).

[0064] (6) Continue to deposit silicon nitride (SiN) on the passive waveguide. x The dielectric film serves as a passivation film and etching barrier layer for waveguides.

[0065] (7) Deposit low dielectric constant material (benzocyclobutene (BCB)) to fill the channel and planarize the device.

[0066] (8) Deposition of silicon nitride (SiN) x A dielectric film is formed, electrode holes are photolithographically created, and a seed layer is evaporated on the surface to prepare for the electroplating process.

[0067] (9) Microwave transmission lines, periodic electrodes, phase electrodes and DC bias electrodes are fabricated using photolithography and electroplating processes.

[0068] (10) A resistor with a resistance of 50 Ω was prepared by photolithography, evaporation and stripping process. At the same time, an alloying process was carried out in order to achieve ohmic contact.

[0069] (11) Use a thinning process to reduce the thickness of the epitaxial wafer to the required thickness.

[0070] (12) To achieve chip integration in the future, a metallization process is adopted on the back side of the epitaxial wafer.

[0071] (13) The entire epitaxial wafer is cleaved into Bar strips, and the Bar strips are further dissected. An anti-reflection film is deposited on the side of the Bar strips to reduce light loss.

[0072] In summary, this invention discloses an InP-based Mach-Zehnder interferometer electro-optic modulator, comprising an optical input terminal, an optical modulation region, and an optical output terminal connected in sequence. The traveling wave electrode in the optical modulation region includes a microwave transmission line and a plurality of periodically arranged electrodes connected to the wave transmission line. The electrodes are located on the surface of the P-type contact layer of an active waveguide structure, and the active waveguide structure comprises, from bottom to top, an InP substrate layer and an epitaxial wafer. The epitaxial wafer comprises, from bottom to top, an N-type doped layer, spacer layer I, a quantum well layer, spacer layer II, a lightly doped P-type layer, a P-type doped layer, and a P-type contact layer. The InP-based Mach-Zehnder interferometric electro-optic modulator of this invention has the following advantages: (1) It is fabricated on an InP substrate, which has a higher integration density and can be integrated with lasers, amplifiers and other devices to realize an integrated optical module; (2) It uses multiple quantum wells as waveguide cores for optical transmission. The refractive index change caused by the QCSE effect is large, which is easy to phase modulate and can reduce the driving voltage and the total length of the device; (3) It uses a strip-shaped traveling wave electrode for modulation. Compared with lumped electrodes, the 3-dB electro-optic modulation bandwidth of the modulator is improved, and the flexibility of waveguide design is also higher; (4) It adopts a PIN structure, which is simple to grow epitaxially and has a small reverse leakage current, which is conducive to reducing costs; (5) Compared with the P-type in conventional PIN optical modulators, The large carrier absorption of the layer leads to the limitation of the intrinsic region thickness. After adjusting the profile concentration distribution and introducing a light doped layer, the carrier absorption loss caused by the P-type doped layer is reduced, the intrinsic region thickness can be made thinner, the voltage applied to the quantum well is enhanced, and the required driving voltage is also lower; (6) After comprehensively balancing the electro-optic modulation efficiency and insertion loss, an asymmetric spacer layer thickness is adopted; (7) The quaternary material InGaAsP, which matches the InP lattice of the substrate, is adopted. Through simple composition engineering, the bandgap of the material can be adjusted, and a material more suitable for the working wavelength can be selected to achieve a high-efficiency modulator; (8) The channel is filled with a low dielectric constant to replace the air bridge process required for channeled devices, reducing the process difficulty and realizing device planarization.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An InP-based Mach-Zehnder interferometer electro-optic modulator, characterized in that, The electro-optic modulator includes an optical input terminal (1), an optical modulation area, and an optical output terminal (10) connected in sequence. The optical modulation region includes a DC bias electrode (2), a traveling wave electrode (4), two modulation arms (6) and two phase electrodes (7) respectively connected to the modulation arms (6). The traveling wave electrode includes a microwave transmission line (3) and a number of periodically arranged periodic electrodes (5) connected to the microwave transmission line (3). The periodic electrodes (5) are located on the surface of the P-type contact layer of the active waveguide structure. An RF power supply (8) and a resistor (9) are respectively connected to both ends of the microwave transmission line (3). The active waveguide structure comprises, from bottom to top, an InP substrate layer and an epitaxial wafer, wherein the epitaxial wafer comprises, from bottom to top, an N-type doped layer, spacer layer I, a quantum well layer, spacer layer II, a lightly doped P-type layer, a P-type doped layer, and a P-type contact layer; The optical input terminal (1) includes either a Y-type beam splitter or a 1×2 coupler, wherein the other end of either the Y-type beam splitter or the 1×2 coupler (1) is connected to two modulation arms (6) respectively. The optical output terminal (10) includes either a Y-type combiner or a 2×2 coupler connected to the other end of the two modulation arms (6); The thickness of spacer layer I is greater than the thickness of spacer layer II, and the thickness of spacer layer I and spacer layer II is no greater than 300 nm. The material of spacer layer I and spacer layer II is InGaAsP.

2. The electro-optic modulator according to claim 1, characterized in that, The total thickness of the quantum well layer is 400–800 nm, and the quantum well layer is composed of multiple periodic quantum wells; The quantum well comprises a potential well in the middle and a potential barrier on both sides, the material of the potential well is In 1-x Ga x As y P 1-y , wherein y is 0.7-0.9, x is 0.464-0.466, and the material of the potential barrier is InP.

3. The electro-optic modulator according to claim 1, characterized in that, The p-type lightly doped layer is a p-type InP lightly doped layer, wherein the p doping concentration is 3 × 10⁻⁶. 17 ~5×10 17 cm -3 ; The p-type doped layer is a p-type InP doped layer, wherein the doping concentration is greater than or equal to 1 × 10⁻⁶. 18 cm -3 .

4. The electro-optic modulator according to claim 1, characterized in that, The N-type doped layer is an N-type InP doped layer, with a doping concentration of 1×10⁻⁶. 18 ~3×10 18 cm -3 The thickness of the N-type doped layer is 1 ± 0.1 μm; The P-type contact layer is a P-type InGaAs layer, wherein the doping concentration is greater than or equal to 1×10⁻⁶. 19 cm -3 The thickness of the P-type contact layer is 0.1 ± 0.01 μm.

5. A method for fabricating the electro-optic modulator according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) A silicon nitride dielectric film with a thickness of 0.2 μm was deposited on the epitaxial wafer using the PECVD method as a mask; (2) Using patterning technology, the waveguide pattern is transferred onto the epitaxial wafer by sequentially performing coating, soft baking, alignment, exposure, development, hard baking and etching. (3) Using the silicon nitride dielectric film deposited in step (1) as a mask, the epitaxial wafer is etched by dry or wet methods to fabricate a deep ridge waveguide; (4) Continue to deposit silicon nitride dielectric film on deep ridge waveguide, photolithographically pattern N-step pattern, and use silicon nitride dielectric film as mask for etching; (5) Photolithography is performed on the traveling wave modulated waveguide, and a silicon nitride dielectric film is used as a mask to etch to the surface of the top spacer layer to prepare a passive waveguide; (6) Continue to deposit a silicon nitride dielectric film on the waveguide as a passivation film and an etching barrier layer for the waveguide; (7) Deposit materials with a dielectric constant less than 3.9 to fill channels and planarize devices; (8) Deposit silicon nitride dielectric film, photolithographically etch electrode holes, and evaporate seed layer on the surface; (9) Microwave transmission lines, periodic electrodes, phase electrodes and DC bias electrodes are fabricated on the seed layer using photolithography and electroplating processes; (10) Resistors are prepared by photolithography, evaporation and stripping processes, and ohmic contacts are achieved by alloying process; (11) Use a thinning process to reduce the thickness of the epitaxial wafer to the required thickness; (12) Metallization process is applied to the back side of the epitaxial wafer to achieve chip integration; (13) The entire epitaxial wafer is cleaved into Bar strips, and the Bar strips are further dissected. An anti-reflection film is deposited on the side of the Bar strips to reduce light loss.

6. The preparation method according to claim 5, characterized in that, The material with a dielectric constant less than 3.9 is benzocyclobutene.

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