Colloidal nanocrystal-based pn junction injection type silicon-based electro-optic modulator and preparation method thereof

Abstract

The application belongs to the technical field of integrated optoelectronics, and discloses a PN junction injection type silicon-based electro-optic modulator based on colloidal nanocrystals and a preparation method thereof, which comprises a waveguide cladding layer, a silicon waveguide layer arranged above the waveguide cladding layer, optical couplers arranged at two ends of the silicon waveguide layer for input and output of optical signals, a lower electrode layer in communication with the silicon waveguide layer, a colloidal nanocrystal layer prepared by using oxide semiconductor colloidal nanocrystals, arranged above the silicon waveguide layer and forming a PN junction with the silicon waveguide layer, and an upper electrode layer arranged above the colloidal nanocrystal layer. The application effectively solves the problems of low modulation efficiency, complicated processing and difficult hetero-integration of the current silicon-based electro-optic modulator, has the characteristics of solution preparation processing substrate compatibility, large-scale integration, high modulation efficiency, high modulation depth and small size, and is expected to promote the development of silicon-based optoelectronic chips in the direction of high integration.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated optoelectronics, and relates to a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals and a preparation method thereof. Background Art

[0002] With the rapid development of next-generation information technology, the global data volume is rapidly increasing, placing higher demands on the capacity, bandwidth, and power consumption of communication systems. Silicon-based optoelectronics technology, combining the ultra-high speed, large bandwidth, and low crosstalk advantages of optical communications with the compatibility of silicon materials with complementary metal oxide semiconductor (CMOS) processes, is the optimal platform for realizing high-density, low-cost, and low-energy optoelectronic information systems. Silicon-based electro-optical modulators, components that convert electrical signals into optical signals, are the core active devices in silicon-based optoelectronic chip systems.

[0003] However, because silicon lacks a linear electro-optic effect, it cannot achieve high-linearity and ultra-fast optical modulation similar to lithium niobate. Furthermore, silicon's electroabsorption effect is not significant, making it incapable of ultrafast electroabsorption modulation similar to the Franz-Keldysh effect or quantum-confined Stark effect seen in III-V compound semiconductors or germanium. Existing silicon-based electro-optic modulators primarily rely on the carrier dispersion effect of silicon, but this effect is weak in silicon, resulting in low modulation efficiency and high power consumption.

[0004] To solve the above problems, the current conventional approach in the industry is to heterogeneously integrate silicon-based waveguides with materials with better electro-optical effects, such as III-V compound semiconductors, germanium materials, and graphene. However, the above materials are incompatible with CMOS processes, making it difficult to achieve large-scale, low-cost, and wafer-level production. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals, comprising: a waveguide cladding; a silicon waveguide layer disposed above the waveguide cladding; optical couplers processed at both ends of the silicon waveguide layer for input and output of optical signals; a lower electrode layer connected to the silicon waveguide layer; a colloidal nanocrystal layer made of oxide semiconductor colloidal nanocrystals, disposed above the silicon waveguide layer, and forming a PN junction with the silicon waveguide layer; and an upper electrode layer disposed above the colloidal nanocrystal layer.

[0008] Optionally, the oxide semiconductor colloidal nanocrystals are: indium oxide colloidal nanocrystals, indium tin oxide colloidal nanocrystals, zinc oxide colloidal nanocrystals, aluminum-doped zinc oxide colloidal nanocrystals or cadmium oxide colloidal nanocrystals.

[0009] Optionally, the structure of the silicon waveguide layer is: a straight waveguide, a Mach-Zehnder interferometer, a directional coupler, a microring resonator or a photonic crystal structure.

[0010] Optionally, the work function of the lower electrode layer material is higher than the work function of the upper electrode layer material.

[0011] Optionally, the waveguide cladding is made of SiO2; the upper electrode layer is made of metal material, graphene or transparent conductive oxide; and the lower electrode layer is made of metal material, graphene or transparent conductive oxide.

[0012] Optionally, the silicon waveguide layer is a p-type doped silicon waveguide; and the oxide semiconductor colloidal nanocrystals are n-type doped oxide semiconductor colloidal nanocrystals.

[0013] In a second aspect, the present invention provides a method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals, comprising: preparing a lower electrode layer; processing a silicon waveguide layer connected to the lower electrode layer on a waveguide cladding layer, and processing optical couplers for input and output of optical signals at both ends of the silicon waveguide layer; using spin coating, inkjet printing, drop coating, blade coating or solution self-assembly to prepare a colloidal nanocrystal layer above the silicon waveguide layer using oxide semiconductor colloidal nanocrystals; and preparing an upper electrode layer above the colloidal nanocrystal layer.

[0014] Optionally, the preparation of the lower electrode layer includes: on the SOI chip, using an electron beam exposure process to define the shape of the lower electrode layer, and using electron beam evaporation technology to evaporate the lower electrode layer; the processing of a silicon waveguide layer connected to the lower electrode layer on the waveguide cladding, and processing optical couplers for input and output of optical signals at both ends of the silicon waveguide layer includes: on the SOI chip, using an electron beam exposure overlay process and a plasma etching process to prepare the silicon waveguide layer and the optical coupler by grooves on both sides; wherein, a section of silicon material is retained on the silicon waveguide layer without being etched, so that the silicon waveguide layer is connected to the lower electrode layer.

[0015] Optionally, preparing the upper electrode layer above the colloidal nanocrystal layer includes: preparing the upper electrode layer above the colloidal nanocrystal layer using electron beam exposure overlay and electron beam evaporation processes, and removing excess colloidal nanocrystal layer using electron beam exposure and hydrochloric acid wet etching processes.

[0016] Optionally, the upper electrode layer is located on the other side of the silicon waveguide layer relative to the lower electrode layer.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention is a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals. The colloidal nanocrystal layer and the silicon waveguide layer are in contact with each other to form a PN junction. Voltages are applied to the colloidal nanocrystal layer and the silicon waveguide layer of the PN junction respectively through the upper electrode layer and the lower electrode layer to change the carrier concentration near the PN junction and its concentration change, thereby achieving modulation of the real and imaginary parts of the material's refractive index through the plasma dispersion effect, and achieving modulation of the light transmission phase and loss characteristics in the silicon waveguide. The colloidal nanocrystals used exhibit a stronger plasmon dispersion effect than silicon and easily achieve the zero-dielectric-permittivity condition, enabling large refractive index modulation and thus improving modulation efficiency. They are ideal materials for fabricating high-modulation-efficiency electro-optical modulators. The proposed PN junction structure enables extensive carrier injection at a low forward bias, resulting in high modulation efficiency and low energy consumption. Furthermore, the structure is compatible with CMOS drive circuits. Furthermore, the oxide semiconductor colloidal nanocrystal layer in the PN junction modulator is in direct contact with the silicon waveguide, resulting in significant mode overlap between the carrier concentration variation region and the silicon waveguide optical field. This allows for large refractive index and light absorption modulation, further improving modulation efficiency. Furthermore, leveraging the strong plasmon dispersion effect of the colloidal nanocrystals and their CMOS-compatible processing characteristics, they are heterogeneously integrated with the silicon waveguide to form a PN junction for electrical free-carrier control. This results in a highly efficient, highly integrated, and scalable electro-optical modulator. This approach is expected to provide a new solution for large-scale, wafer-scale fabrication of compact, low-power, and low-drive-voltage silicon-based electro-optical modulators.

[0019] The present invention discloses a method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals. The method adopts spin coating, inkjet printing, drop coating, blade coating or solution self-assembly to prepare a colloidal nanocrystal layer on a silicon waveguide layer using oxide semiconductor colloidal nanocrystals. The solution preparation process of the oxide semiconductor colloidal nanocrystal material is low-cost and high-yield. In addition, the room-temperature liquid-phase processing technology of the oxide semiconductor colloidal nanocrystals, such as spin coating, inkjet printing, drop coating, blade coating or solution self-assembly, is not restricted by the substrate and is fully compatible with existing CMOS processes. The preparation process is economical and simple, and batch device preparation is easy to achieve. Low-cost, large-scale integration is possible, and it is expected to promote the development of silicon-based electro-optical modulators towards high integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0021] Figure 2 This is a flow chart of a method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0022] Figure 3 This is a current-voltage curve diagram of a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0023] Figure 4 This is a top view of an optical microscope image of a silicon-based micro-ring electro-optical modulator based on In2O3 colloidal nanocrystals according to an embodiment of the present invention.

[0024] Figure 5 Schematic diagram of the test performance of a silicon-based micro-ring electro-optic modulator based on In2O3 colloidal nanocrystals according to an embodiment of the present invention.

[0025] Among them: 1-upper electrode layer; 2-colloidal nanocrystal layer; 3-silicon waveguide layer; 4-lower electrode layer; 5-waveguide cladding; 6-optical coupler. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] The present invention is described in further detail below with reference to the accompanying drawings:

[0029] See also Figure 1 In one embodiment of the present invention, a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals is provided, which can effectively solve the problems of low modulation efficiency and difficulty in heterogeneous integration faced by current electro-optic modulators on silicon substrates, and effectively improve the modulation efficiency of silicon-based electro-optic modulators.

[0030] Specifically, the PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals of the present invention includes a waveguide cladding layer 5 , a silicon waveguide layer 3 , a lower electrode layer 4 , a colloidal nanocrystal layer 2 and an upper electrode layer 1 .

[0031] Among them, the silicon waveguide layer 3 is arranged above the waveguide cladding layer 5; optical couplers 6 for input and output of optical signals are processed at both ends of the silicon waveguide layer 3; the lower electrode layer 4 is connected to the silicon waveguide layer 3; the colloidal nanocrystal layer 2 is made of oxide semiconductor colloidal nanocrystals, is arranged above the silicon waveguide layer 3, and forms a PN junction with the silicon waveguide layer 3; the upper electrode layer 1 is arranged above the colloidal nanocrystal layer 2.

[0032] The present invention is a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals. The colloidal nanocrystal layer and the silicon waveguide layer are in contact with each other to form a PN junction. Voltages are applied to the colloidal nanocrystal layer and the silicon waveguide layer of the PN junction respectively through the upper electrode layer and the lower electrode layer to change the carrier concentration near the PN junction and its concentration change, thereby achieving modulation of the real and imaginary parts of the material's refractive index through the plasma dispersion effect, and achieving modulation of the light transmission phase and loss characteristics in the silicon waveguide. The oxide semiconductor colloidal nanocrystals used have a stronger plasma dispersion effect than that of silicon materials, and are easy to achieve the effect condition where the real part of the dielectric constant tends to zero, which can achieve a larger refractive index modulation, thereby improving the modulation efficiency. It is one of the ideal materials for preparing high-modulation-efficiency electro-optical modulators. The proposed PN junction structure can achieve a large amount of carrier injection under a small forward bias, has high modulation efficiency and low energy consumption, and is compatible with CMOS driving circuits. In addition, the colloidal nanocrystal layer of the oxide semiconductor in the PN junction modulator structure is in direct contact with the silicon waveguide, and the carrier concentration change region has a large mode overlap with the silicon waveguide light field, which can achieve a larger refractive index and light absorption modulation, further improving the modulation efficiency. At the same time, by utilizing the strong plasma dispersion effect of colloidal nanocrystals and their processing characteristics compatible with CMOS technology, they are heterogeneously integrated with silicon waveguides to form PN junctions to realize electrical control of free carriers, thereby achieving high modulation efficiency, high integration and large-scale scalable electro-optical modulators. It is expected to provide new solutions for the large-scale and wafer-level preparation of low-driving voltage, low-power, compact silicon-based electro-optical modulators, which can be used in optical interconnection and biochemical sensing.

[0033] In one possible embodiment, the oxide semiconductor colloidal nanocrystals are: indium oxide (In2O3) colloidal nanocrystals, indium tin oxide (ITO) colloidal nanocrystals, zinc oxide (ZnO) colloidal nanocrystals, aluminum-doped zinc oxide (AZO) colloidal nanocrystals or cadmium oxide (CdO) colloidal nanocrystals.

[0034] Explanatory, the colloidal nanocrystal layer 2 and the silicon waveguide layer 3 together form a PN junction, and voltages are applied to the colloidal nanocrystal layer 2 and the silicon waveguide layer 3 through the upper electrode layer 1 and the lower electrode layer 4, respectively, causing injection and depletion of carriers in the PN junction region.

[0035] In one possible embodiment, the silicon waveguide layer 3 has a structure such as a straight waveguide, a Mach-Zehnder interferometer, a directional coupler, a microring resonator, or a photonic crystal structure. For illustration, the colloidal nanocrystal layer 2 of oxide semiconductor is positioned above the silicon waveguide layer 3. The two form a PN junction. Under the action of an applied voltage, a large amount of carriers are injected or depleted, causing changes in the real and imaginary parts of the refractive index of both layers. The phase and loss of light transmitted in the silicon waveguide are modulated by the changes in the real and imaginary parts of the refractive index of the colloidal nanocrystal layer 2 and the silicon waveguide layer 3.

[0036] In one possible embodiment, the work function of the material of the lower electrode layer 4 is higher than that of the material of the upper electrode layer 1. Explanatoryally, the work function of the material of the lower electrode layer 4 is designed to be higher than that of the material of the upper electrode layer 1 to effectively reduce the carrier injection barrier.

[0037] In one possible embodiment, the waveguide cladding 5 is made of SiO2; the upper electrode layer 1 is made of a metal material, graphene, or a transparent conductive oxide; and the lower electrode layer 4 is made of a metal material, graphene, or a transparent conductive oxide. Optionally, the metal material is one or a composite of gold, silver, aluminum, nickel, platinum, copper, and titanium, such as Cr / Au or Ag / Au.

[0038] In a possible implementation, the silicon waveguide layer 3 is a p-type doped silicon waveguide; and the oxide semiconductor colloidal nanocrystals are n-type doped oxide semiconductor colloidal nanocrystals.

[0039] The working principle of the PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals of the present invention is as follows:

[0040] Applying a voltage between the upper electrode layer 1 and the lower electrode layer 4 causes the free carrier concentration in the PN junction region formed by the colloidal nanocrystal layer 2 of the oxide semiconductor and the silicon waveguide layer 3 to change. The change in the free carrier concentration in the junction region and its degree are controlled by the positive and negative signs and the magnitude of the applied voltage signal. The real and imaginary parts of the refractive index of the colloidal nanocrystal layer 2 and the silicon waveguide layer 3 are determined by the change in the carrier concentration and its degree. In this way, electrical modulation of the phase and loss of the on-chip silicon waveguide by the electrical signal can be achieved.

[0041] When the voltage of the lower electrode layer 4 is higher than that of the upper electrode layer 1, holes in the silicon waveguide layer 3 and electrons in the oxide semiconductor colloidal nanocrystal layer 2 rapidly migrate toward the junction region, causing dramatic changes in the junction region's carrier concentration. This, in turn, produces changes in the real and imaginary parts of the refractive index through the plasma dispersion effect. The colloidal nanocrystal layer 2 overlies the silicon waveguide layer 3, and changes in its refractive index and light absorption act on the waveguide optical signal, modulating the optical signal transmission phase and loss. Because the change in carrier concentration and the amount of change are related to the positive or negative sign of the applied voltage signal, the material doping level, and the energy level arrangement of the various layers of the device, the present invention utilizes the fact that when a PN junction is forward biased, the drift motion of majority carriers in the material intensifies and rapidly reaches the junction region, causing an increase in the free carrier concentration in the junction region and a change in the complex refractive index.

[0042] Since the carrier injection barrier is lowered when the PN junction is forward biased, a drastic change in the carrier concentration in the junction region can be achieved through a small voltage change, thereby achieving higher modulation efficiency.

[0043] In another embodiment of the present invention, a method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals is provided, comprising the following steps: preparing a lower electrode layer 4; processing a silicon waveguide layer 3 connected to the lower electrode layer 4 on a waveguide cladding layer 5, and processing optical couplers 6 for input and output of optical signals at both ends of the silicon waveguide layer 3; using spin coating, inkjet printing, drop coating, blade coating or solution self-assembly method to prepare a colloidal nanocrystal layer 2 on top of the silicon waveguide layer 3 using oxide semiconductor colloidal nanocrystals; and preparing an upper electrode layer 1 on top of the colloidal nanocrystal layer 2.

[0044] The present invention discloses a method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals. The method adopts spin coating, inkjet printing, drop coating, blade coating or solution self-assembly to prepare a colloidal nanocrystal layer on a silicon waveguide layer using oxide semiconductor colloidal nanocrystals. The solution preparation process of the oxide semiconductor colloidal nanocrystal material is low-cost and high-yield. In addition, the room-temperature liquid-phase processing technology of the oxide semiconductor colloidal nanocrystals, such as spin coating, inkjet printing, drop coating, blade coating or solution self-assembly, is not restricted by the substrate and is fully compatible with existing CMOS processes. The preparation process is economical and simple, and batch device preparation is easy to achieve. Low-cost, large-scale integration is possible, and it is expected to promote the development of silicon-based electro-optical modulators towards high integration.

[0045] In one possible embodiment, preparing the lower electrode layer 4 on the waveguide cladding 5 includes: defining the shape of the lower electrode layer 4 on the SOI chip using an electron beam exposure process, and vapor-depositing the lower electrode layer 4 using electron beam evaporation technology; processing the silicon waveguide layer 3 connected to the lower electrode layer 4 on the waveguide cladding 5, and processing the optical couplers 6 for input and output of optical signals at both ends of the silicon waveguide layer 3 includes: using an electron beam exposure overlay process and a plasma etching process on the SOI chip to process and prepare the silicon waveguide layer 3 and the optical coupler 6 by grooves on both sides; wherein, a section of silicon material is retained on the silicon waveguide layer 3 without being etched, so that the silicon waveguide layer 3 is connected to the lower electrode layer 4.

[0046] In one possible embodiment, the preparation of the upper electrode layer 1 above the colloidal nanocrystal layer 2 includes: using electron beam exposure overlay and electron beam evaporation process to prepare the upper electrode layer 1 above the colloidal nanocrystal layer 2, and using electron beam exposure and hydrochloric acid wet etching process to remove excess colloidal nanocrystal layer 2.

[0047] Exemplarily, the preparation method of the PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals of the present invention can be prepared on-chip based on an SOI (silicon on insulator) chip. The SOI chip is a three-layer structure material, the upper layer of which is a silicon flat layer, the middle layer is a SiO2 insulating layer, and the bottom layer is a bulk silicon substrate.

[0048] In one possible implementation, see Figure 2 Based on the SOI chip, the thickness of the silicon flat layer is 220nm, the thickness of the SiO2 insulating layer is 2μm, and the structure of the silicon waveguide layer 3 adopts a microring resonator. The preparation method of the PN junction injection type silicon-based electro-optical modulator based on colloidal nanocrystals of the present invention includes the following steps:

[0049] Step 1: On a clean SOI chip, the shape of the lower electrode layer (4) is defined by electron beam exposure process, and after development, Cr / Au electrodes with a thickness of 5nm / 40nm are evaporated by electron beam evaporation technology, and the lower electrode layer 4 with a specific shape is obtained after peeling.

[0050] Step 2: Using electron beam exposure overlay and plasma etching, the silicon waveguide layer 3 and the optical coupler 6 for optical signal input and output are fabricated by grooves on both sides. A 2 μm section of silicon material is left unetched in a certain area of ​​the silicon waveguide to achieve electrical connection between the silicon waveguide layer 3 and the silicon substrate connected to the lower electrode layer 4 without affecting light transmission.

[0051] Step 3: Use a buffered oxide etchant to clean the surface of the silicon waveguide layer 3 to remove any possible SiO2 oxide layer, and deposit the n-type doped oxide semiconductor colloidal nanocrystal layer 2 on the silicon waveguide layer 3 using a spin coating process.

[0052] Step 4: Using electron beam exposure overlay and electron beam evaporation process, a Cr / Au top electrode layer 1 with a thickness of 5 nm / 40 nm is prepared on the colloidal nanocrystal layer 2 of the oxide semiconductor.

[0053] Step 5: Using electron beam exposure and hydrochloric acid wet etching process, remove the excess colloidal nanocrystal layer 2 on the SOI chip to achieve electrical isolation between the upper electrode layer 5 and the lower electrode layer 1 of the device.

[0054] In one possible implementation, a 200-micron-long colloidal nanocrystal-based PN junction injection-type silicon-based electro-optical modulator is integrated into a straight waveguide, and the current-voltage curve is measured through an optical coupler 6 .

[0055] See also Figure 3 It was found that the current-voltage curve of the modulator showed unidirectional conduction when it was forward biased and reverse biased, indicating the formation of PN junction.

[0056] In one possible implementation, see Figure 4 An 800-micron-long PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals is integrated into a microring resonator waveguide with a radius of 120 microns. The oxide semiconductor colloidal nanocrystals are In2O3 colloidal nanocrystals, and the transmitted power is measured by an optical coupler 6.

[0057] See also Figure 5 , showing the position of the resonance peak of the same order near the 1550nm band under different bias voltages. The resonance peak of the same order moves with the change of the applied voltage, verifying the wavelength modulation of more than 100pm and the modulation efficiency of 20pm / V.

[0058] In response to the current status and shortcomings of silicon-based electro-optical modulators, such as low modulation efficiency, complicated processing, and difficulty in heterogeneous integration, the present invention proposes a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals and a preparation method. Specifically, the present invention is a silicon-based electro-optical modulator based on colloidal nanocrystals of oxide semiconductors and silicon waveguides that is fully compatible with CMOS processes. It has the characteristics of solution preparation and processing substrate compatibility, large-scale integration, high modulation efficiency, high modulation depth and small size. It realizes a compact, high-modulation-efficiency silicon-based on-chip electro-optical modulator in the 1550nm communication band, and is expected to promote the development of silicon-based optoelectronic chips towards high integration.

[0059] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals, characterized in that: include: waveguide cladding (5); A silicon waveguide layer (3) is provided above a waveguide cladding layer (5); optical couplers (6) for input and output of optical signals are processed at both ends of the silicon waveguide layer (3); a lower electrode layer (4) communicating with the silicon waveguide layer (3); A colloidal nanocrystal layer (2) is prepared using oxide semiconductor colloidal nanocrystals, is disposed above the silicon waveguide layer (3), and forms a PN junction with the silicon waveguide layer (3); An upper electrode layer (1) is disposed above the colloidal nanocrystal layer (2); The oxide semiconductor colloidal nanocrystals are: indium oxide colloidal nanocrystals, indium tin oxide colloidal nanocrystals, zinc oxide colloidal nanocrystals, aluminum-doped zinc oxide colloidal nanocrystals or cadmium oxide colloidal nanocrystals; The work function of the material of the lower electrode layer (4) is higher than the work function of the material of the upper electrode layer (1); The silicon waveguide layer (3) is a p-type doped silicon waveguide; and the oxide semiconductor colloidal nanocrystal is an n-type doped oxide semiconductor colloidal nanocrystal.

2. The PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals according to claim 1, characterized in that: The structure of the silicon waveguide layer (3) is: Straight waveguides, Mach-Zehnder interferometers, directional couplers, microring resonators or photonic crystal structures.

3. The PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals according to claim 1, characterized in that: The waveguide cladding (5) is made of SiO2; the upper electrode layer (1) is made of metal material, graphene or transparent conductive oxide; and the lower electrode layer (4) is made of metal material, graphene or transparent conductive oxide.

4. A method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals according to claim 1, characterized in that: include: preparing a lower electrode layer (4); A silicon waveguide layer (3) communicating with a lower electrode layer (4) is fabricated on a waveguide cladding layer (5), and optical couplers (6) for input and output of optical signals are fabricated at both ends of the silicon waveguide layer (3); A colloidal nanocrystal layer (2) is prepared on top of a silicon waveguide layer (3) using oxide semiconductor colloidal nanocrystals by spin coating, inkjet printing, drop coating, blade coating or solution self-assembly method; An upper electrode layer (1) is prepared above the colloidal nanocrystal layer (2).

5. The method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals according to claim 4, characterized in that: The preparation of the lower electrode layer (4) comprises: defining the shape of the lower electrode layer (4) on the SOI chip by using an electron beam exposure process, and vapor-depositing the lower electrode layer (4) by using an electron beam evaporation technology; processing a silicon waveguide layer (3) connected to the lower electrode layer (4) on the waveguide cladding layer (5), and processing optical couplers (6) for input and output of optical signals at both ends of the silicon waveguide layer (3) comprises: processing and preparing the silicon waveguide layer (3) and the optical coupler (6) by grooves on both sides on the SOI chip by using an electron beam exposure overlay process and a plasma etching process; wherein a section of silicon material is retained on the silicon waveguide layer (3) and is not etched, so that the silicon waveguide layer (3) is connected to the lower electrode layer (4).

6. The method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals according to claim 4, characterized in that: The method of preparing the upper electrode layer (1) above the colloidal nanocrystal layer (2) comprises: using electron beam exposure overlay and electron beam evaporation processes to prepare the upper electrode layer (1) above the colloidal nanocrystal layer (2), and using electron beam exposure and hydrochloric acid wet etching processes to remove excess colloidal nanocrystal layer (2).

7. The method for preparing a PN junction injection-type silicon-based electro-optical modulator based on colloidal nanocrystals according to claim 4, characterized in that: The upper electrode layer (1) is located on the other side of the silicon waveguide layer (3) relative to the lower electrode layer (4).

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