PN junction injection type silicon-based electro-optical modulator based on colloid nanocrystal and preparation method of PN junction injection type silicon-based electro-optical modulator

Abstract

The invention belongs to the technical field of integrated photoelectronics, and discloses a PN junction injection type silicon-based electro-optical modulator based on colloid nanocrystals and a preparation method of the PN junction injection type silicon-based electro-optical modulator. The silicon waveguide layer is arranged above the waveguide cladding layer; optical couplers for inputting and outputting optical signals are processed at the two ends of the silicon waveguide layer; the lower electrode layer is communicated with the silicon waveguide layer; the colloid nanocrystalline layer is prepared from oxide semiconductor colloid nanocrystalline and arranged above the silicon waveguide layer, and the colloid nanocrystalline layer and the silicon waveguide layer form a PN junction; and the upper electrode layer is arranged above the colloid nanocrystalline layer. The problems that an existing silicon-based electro-optical modulator is low in modulation efficiency, tedious in processing and difficult in heterogeneous integration are effectively solved, and the silicon-based electro-optical modulator has the advantages of solution preparation and processing substrate compatibility, large-scale integration, high modulation efficiency, high modulation depth, small size and the like, and is expected to promote development of a silicon-based optoelectronic chip towards the direction of high integration.

Description

Technical Field

[0001] The 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 new generation information technology, the total amount of global data has increased rapidly, which has put forward higher requirements on the capacity, bandwidth and power consumption of communication systems. Silicon-based optoelectronic technology combines the ultra-high speed, large bandwidth and low crosstalk advantages of optical communication and the complementary metal oxide semiconductor (CMOS) process compatibility advantages of silicon materials, and is the best platform for realizing high-density, low-cost and low-energy optoelectronic information systems. Silicon-based electro-optical modulators, as components that convert electrical signals into optical signals, are the core active devices of silicon-based optoelectronic chip systems.

[0003] However, since silicon does not have a linear electro-optic effect, it is impossible to achieve high linearity and ultra-high-speed optical modulation like lithium niobate. At the same time, the electro-absorption effect of silicon materials is not significant, and it is impossible to perform ultra-fast electro-absorption modulation like III-V compound semiconductors or germanium materials through the Franz-Keldysh effect or the quantum-confined Stark effect. Existing silicon-based electro-optic modulators are mainly based on the carrier dispersion effect of silicon materials. However, this effect is weak in silicon materials, so the device modulation efficiency is low and the power consumption is high.

[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 disadvantages of the prior art and provide a PN junction injection-type silicon-based electro-optic 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-optic modulator based on colloidal nanocrystals, comprising: a waveguide cladding; a silicon waveguide layer, arranged 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, prepared 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.

[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-optic 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, scraping or solution self-assembly method to prepare a colloidal nanocrystal layer on top of the silicon waveguide layer using oxide semiconductor colloidal nanocrystals; and preparing an upper electrode layer on top of 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 an upper electrode layer above the colloidal nanocrystal layer includes: preparing an 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-optic 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 realizing the modulation of the real part and the imaginary part of the material refractive index through the plasma dispersion effect, and realizing the modulation of the light transmission phase and loss characteristics in the silicon waveguide. The colloidal nanocrystals used have a stronger plasma dispersion effect than silicon materials, and are easy to reach the effect condition of the real part of the dielectric constant tending to zero, which can achieve a large 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 number of carrier injections under a small forward bias, has a high modulation efficiency and low energy consumption, and is compatible with CMOS drive circuits. In the PN junction modulator structure, the colloidal nanocrystal layer of the oxide semiconductor is in direct contact with the silicon waveguide, and the mode overlap between the carrier concentration change region and the silicon waveguide light field is large, which can achieve a large 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 the electrical regulation of free carriers, realizing high modulation efficiency, high integration and large-scale scalable electro-optical modulators, and are 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.

[0019] The invention discloses a method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals. The method adopts spin coating, inkjet printing, drop coating, scraping coating or solution self-assembly method, and uses oxide semiconductor colloidal nanocrystals to prepare a colloidal nanocrystal layer on a silicon waveguide layer. The solution preparation process of the oxide semiconductor colloidal nanocrystal material has low cost and high yield. The room temperature liquid phase processing process of the oxide semiconductor colloidal nanocrystals such as spin coating, inkjet printing, drop coating, scraping coating or solution self-assembly method is not limited by the substrate and is fully compatible with the existing CMOS process. The preparation process is economical and simple, and batch device preparation is easy to realize. Low-cost and large-scale integration can be performed, and it is expected to promote the development of silicon-based electro-optic modulators in the direction of high integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram 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 The flowchart is 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-optic 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 scheme of the present invention, the technical scheme 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 described embodiments 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 creative work should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification 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 data 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 that are 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 further described in detail below in conjunction with 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 comprises 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; the 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 prepared by 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-optic 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 realizing the modulation of the real part and the imaginary part of the material refractive index through the plasma dispersion effect, and realizing the 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 can easily reach the condition where the real part of the dielectric constant tends to zero, so that a larger refractive index modulation can be achieved, thereby improving the modulation efficiency. They are 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 drive 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 mode overlap between the carrier concentration change region and the silicon waveguide light field is large, which can achieve a larger refractive index and light absorption modulation, further improving the modulation efficiency. At the same time, the strong plasma dispersion effect of colloidal nanocrystals and their processing characteristics compatible with CMOS technology are utilized to heterogeneously integrate them with silicon waveguides to form PN junctions to realize electrical regulation 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 a possible implementation, 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 the injection and depletion of carriers in the PN junction region.

[0035] In a possible implementation, the structure of the silicon waveguide layer 3 is: a straight waveguide, a Mach-Zehnder interferometer, a directional coupler, a micro-ring resonator or a photonic crystal structure. Explanatory, the colloidal nanocrystal layer 2 of the oxide semiconductor is located above the silicon waveguide layer 3, and the two form a PN junction, and under the action of an applied voltage, a large amount of carrier injection or depletion is achieved, thereby causing changes in the real and imaginary parts of the refractive index of the two. The phase and loss of light transmission 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 a possible implementation, 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. Explanatory, 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 injection barrier of carriers.

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

[0038] In a possible implementation manner, 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:

[0040] A voltage is applied between the upper electrode layer 1 and the lower electrode layer 4, so that the concentration of free carriers in the PN junction region formed by the colloidal nanocrystal layer 2 and the silicon waveguide layer 3 of the oxide semiconductor changes. The change in the free carrier concentration in the junction region and its degree are controlled by the positive and negative and 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, thereby realizing electrical modulation of the phase and loss of the on-chip silicon waveguide by the electrical signal.

[0041] Among them, when the voltage of the lower electrode layer 4 is higher than that of the upper electrode layer 1, the holes of the silicon waveguide layer 3 and the electrons of the colloidal nanocrystal layer 2 of the oxide semiconductor all move quickly to the junction area, and cause a drastic change in the carrier concentration in the junction area, thereby producing changes in the real part and imaginary part of the refractive index through the plasma dispersion effect. The colloidal nanocrystal layer 2 covers the silicon waveguide layer 3, and the changes in its refractive index and light absorption act on the waveguide optical signal, and cause the modulation of the optical signal transmission phase and loss. Since the change in carrier concentration and the amount of change are related to the positive and negative of the applied voltage signal, the degree of material doping, and the energy level arrangement of each layer of material constituting the device. The present invention utilizes that when the PN junction is under forward bias, the drift motion of the majority carriers in the material intensifies and quickly reaches the junction area, causing an increase in the free carrier concentration in the junction area 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 a 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, scraping 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 invention discloses a method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals. The method adopts spin coating, inkjet printing, drop coating, scraping coating or solution self-assembly method, and uses oxide semiconductor colloidal nanocrystals to prepare a colloidal nanocrystal layer on a silicon waveguide layer. The solution preparation process of the oxide semiconductor colloidal nanocrystal material has low cost and high yield. The room temperature liquid phase processing process of the oxide semiconductor colloidal nanocrystals such as spin coating, inkjet printing, drop coating, scraping coating or solution self-assembly method is not limited by the substrate and is fully compatible with the existing CMOS process. The preparation process is economical and simple, and batch device preparation is easy to realize. Low-cost and large-scale integration can be performed, and it is expected to promote the development of silicon-based electro-optic modulators in the direction of high integration.

[0045] In a possible implementation, the preparing the lower electrode layer 4 on the waveguide cladding 5 includes: on the SOI chip, using an electron beam exposure process to define the shape of the lower electrode layer 4, and using electron beam evaporation technology to evaporate the lower electrode layer 4; the processing of the silicon waveguide layer 3 connected to the lower electrode layer 4 on the waveguide cladding 5, and processing the optical coupler 6 for input and output of optical signals at both ends of the silicon waveguide layer 3 includes: on the SOI chip, using an electron beam exposure overlay process and a plasma etching process, processing and preparing the silicon waveguide layer 3 and the optical coupler 6 in a groove-carving manner 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 a 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-optic 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 micro-ring 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 process and plasma etching process, the silicon waveguide layer 3 and the optical coupler 6 for input and output of optical signals are processed and prepared by grooves on both sides, wherein a section of silicon material with a length of 2 μm is reserved in a certain area on the silicon waveguide without being etched, so that the electrical connection between the silicon waveguide layer 3 and the silicon substrate connected to the lower electrode layer 4 is realized without affecting the light transmission.

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

[0052] Step 4: Prepare a Cr / Au upper electrode layer 1 with a thickness of 5 nm / 40 nm on the colloidal nanocrystalline layer 2 of the oxide semiconductor by using electron beam exposure overlay and electron beam evaporation process.

[0053] Step 5: Using electron beam exposure and hydrochloric acid wet etching process, remove the redundant 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 a possible implementation, a 200 micron long colloidal nanocrystal-based PN junction injection-type silicon-based electro-optic 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 when the modulator was in forward and reverse bias, the current-voltage curve showed a unidirectional conduction phenomenon, indicating the formation of a PN junction.

[0056] In one possible implementation, see Figure 4 An 800-micron-long PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals is integrated into a microring resonator waveguide with a radius of 120 microns, wherein 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 view of the current status and shortcomings of low modulation efficiency, complicated processing and difficult heterogeneous integration faced by silicon-based electro-optic modulators, the present invention proposes a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals and a preparation method. Specifically, the present invention is a silicon-based electro-optic modulator based on colloidal nanocrystals of oxide semiconductors and silicon waveguides that is fully compatible with CMOS technology. The modulator has the characteristics of solution preparation and processing substrate compatibility, large-scale integration, high modulation efficiency, high modulation depth and small size, and realizes a compact, high-modulation-efficiency silicon-based on-chip electro-optic modulator in the 1550nm communication band, which is expected to promote the development of silicon-based optoelectronic chips towards high integration.

[0059] The above contents are 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-optic modulator based on colloidal nanocrystals, characterized in that: include: waveguide cladding (5); A silicon waveguide layer (3) is arranged 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) connected to the silicon waveguide layer (3); A colloidal nanocrystal layer (2) is made of oxide semiconductor colloidal nanocrystals and is disposed above the silicon waveguide layer (3) to form a PN junction with the silicon waveguide layer (3); The upper electrode layer (1) is arranged above the colloidal nanocrystal layer (2).

2. The PN junction injection type silicon-based electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: 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.

3. The PN junction injection type silicon-based electro-optic 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.

4. The PN junction injection type silicon-based electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: 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).

5. The PN junction injection type silicon-based electro-optic 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.

6. The PN junction injection type silicon-based electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: 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.

7. A method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals, characterized in that: include: preparing a lower electrode layer (4); A silicon waveguide layer (3) connected to a lower electrode layer (4) is processed on the waveguide cladding layer (5), and optical couplers (6) for input and output of optical signals are processed 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, scraping coating or solution self-assembly method; An upper electrode layer (1) is prepared on the colloidal nanocrystal layer (2).

8. The method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals according to claim 7, characterized in that: The preparation of the lower electrode layer (4) comprises: on an SOI chip, using an electron beam exposure process to define the shape of the lower electrode layer (4), and using an electron beam evaporation technology to evaporate the 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 an optical coupler (6) for input and output of optical signals at both ends of the silicon waveguide layer (3) comprises: on the SOI chip, using an electron beam exposure overlay process and a plasma etching process, processing and preparing the silicon waveguide layer (3) and the optical coupler (6) in a grooved manner on both sides; 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).

9. The method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals according to claim 7, characterized in that: The method of preparing an upper electrode layer (1) above the colloidal nanocrystal layer (2) comprises: preparing the upper electrode layer (1) above the colloidal nanocrystal layer (2) by using electron beam exposure overlay and electron beam evaporation processes, and removing excess colloidal nanocrystal layer (2) by using electron beam exposure and hydrochloric acid wet etching processes.

10. The method for preparing a PN junction injection-type silicon-based electro-optic modulator based on colloidal nanocrystals according to claim 7, 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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