Colloid nanocrystal-based MOS (Metal Oxide Semiconductor) type silicon-on-chip electro-optical modulator and preparation method thereof

Abstract

The invention belongs to the technical field of integrated photoelectronics, and discloses an MOS (Metal Oxide Semiconductor) type silicon-on-chip electro-optical modulator based on colloid nanocrystals and a preparation method thereof. The silicon waveguide layer is arranged above the waveguide cladding layer; optical couplers used for inputting and outputting optical signals are arranged at the two ends of the silicon waveguide layer; the dielectric layer is arranged above the silicon waveguide layer in a covering manner; a colloidal nanocrystalline layer disposed over the dielectric layer; the upper electrode layer is arranged above the colloid nanocrystalline layer; the lower electrode layer is communicated with the silicon waveguide layer; and the dielectric layer is used for changing the polarization state according to an external voltage and controlling the inductive charge concentration in the colloid nanocrystalline layer and the silicon waveguide layer through the polarization state. The room-temperature liquid phase processing procedure of the colloidal nanocrystal is simple, and is completely compatible with a silicon-based CMOS (Complementary Metal Oxide Semiconductor) process, so that low-cost and large-scale integration can be carried out; the colloidal nanocrystal has a plasma dispersion effect stronger than that of a silicon material, is easy to realize an ENZ effect, and can realize high modulation efficiency and high modulation depth.

Description

Technical Field

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

[0002] Silicon-based optoelectronic chips, with the advantages of ultra-high speed, large bandwidth, and anti-electromagnetic interference of light, are expected to solve the development bottlenecks of microelectronic chips in terms of speed, capacity, and power consumption. They can also be produced at low cost and on a large scale using the CMOS process (Complementary Metal Oxide Semiconductor), and have therefore been successfully used in data centers, short-distance communications, and other fields.

[0003] However, the development of electro-optic modulators, as the core components for realizing electro-optical signal conversion in silicon-based optoelectronic chips, is still subject to many restrictions. Since silicon does not have a linear electro-optical effect, it is impossible to achieve high-linearity, ultra-high-speed optical modulation like lithium niobate; existing silicon-based electro-optic modulators are mainly based on the carrier dispersion effect of silicon materials, but since this effect is weak in silicon materials, the modulation efficiency is low and the device power consumption is high.

[0004] To solve the above problems, the current technical trend of silicon-based electro-optic modulators in the industry is to heterogeneously integrate silicon-based waveguides with materials with better electro-optical effects, such as III-V compound semiconductors and graphene. However, materials such as III-V compound semiconductors and graphene are incompatible with CMOS processes and are difficult to heterogeneously integrate, which makes it difficult to achieve large-scale and low-cost preparation of silicon-based electro-optic modulators. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a MOS-type silicon-based on-chip 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 MOS-type on-chip electro-optic modulator based on colloidal nanocrystals, comprising: a waveguide cladding; a silicon waveguide layer, arranged above the waveguide cladding; optical couplers for input and output of optical signals are arranged at both ends of the silicon waveguide layer; a dielectric layer, arranged above the silicon waveguide layer in a covering manner; a colloidal nanocrystal layer, arranged above the dielectric layer; an upper electrode layer, arranged above the colloidal nanocrystal layer; and a lower electrode layer connected to the silicon waveguide layer; the dielectric layer is used to change the polarization state according to an applied voltage and control the induced charge concentration in the colloidal nanocrystal layer and the silicon waveguide layer through the polarization state.

[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 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.

[0011] Optionally, the dielectric layer is made of silicon dioxide, aluminum oxide, hafnium dioxide or polymethyl methacrylate.

[0012] Optionally, the silicon waveguide layer is a p-type doped silicon waveguide; the oxide semiconductor colloidal nanocrystals are n-type doped oxide semiconductor colloidal nanocrystals; and the colloidal nanocrystal layer has been subjected to a surface ligand exchange treatment.

[0013] In a second aspect, the present invention provides a method for preparing a MOS-type electro-optic modulator on a silicon substrate 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; preparing a covering dielectric layer above the silicon waveguide layer; using spin coating, inkjet printing, drop coating, scraping or solution self-assembly method to prepare a colloidal nanocrystal layer above the dielectric 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 remains connected to the lower electrode layer.

[0015] Optionally, the step of preparing a covering dielectric layer on the silicon waveguide layer includes: preparing a covering dielectric layer on the silicon waveguide layer using an atomic layer deposition technique; the step of preparing an upper electrode layer on the colloidal nanocrystal layer includes: preparing an upper electrode layer on the colloidal nanocrystal layer using an electron beam exposure overlay and an electron beam evaporation process, and removing excess dielectric layer and colloidal nanocrystal layer using an electron beam exposure and a hydrochloric acid wet etching process.

[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 MOS-type silicon-based electro-optic modulator based on colloidal nanocrystals. The strong plasma dispersion effect of oxide semiconductor colloidal nanocrystals is used to heterogeneously integrate them with silicon waveguides to achieve a high-efficiency, large-scale scalable electro-optic modulator. The colloidal nanocrystal layer, the dielectric layer and the silicon waveguide layer together constitute a MOS-type flat-plate capacitor structure. By applying a voltage signal to the flat-plate capacitor through the upper electrode layer and the lower electrode layer, the polarization state and polarization degree of the dielectric layer can be changed, and the free carrier concentration of the colloidal nanocrystal layer and the silicon waveguide layer can be changed. The change in the free carrier concentration in the colloidal nanocrystal layer and the silicon waveguide layer can cause a significant change in the real and imaginary parts of the material refractive index through the plasma dispersion effect, thereby changing the effective refractive index and absorption loss of the light passing through the modulator structure, and finally changing the phase and intensity of the transmitted light, and achieving efficient electro-optic modulation. The oxide semiconductor colloidal nanocrystals have a plasma dispersion effect stronger than that of silicon materials, and are easy to achieve ENZ effect, which can achieve high modulation efficiency and high modulation depth. The MOS-type silicon-based on-chip electro-optic modulator of the present invention has a larger capacitance, which can cause a more significant change in carrier concentration, thereby producing a stronger plasma dispersion effect and a stronger modulation, and has realized a compact, high-modulation-efficiency and high-modulation-depth silicon-based on-chip electro-optic modulator in the 1550nm communication band.

[0019] The present invention discloses a method for preparing a MOS-type electro-optic modulator on a silicon substrate based on colloidal nanocrystals. The colloidal nanocrystal layer can be prepared by spin coating, inkjet printing, drip coating, scraping coating or solution self-assembly method, and the preparation process cost is low. At the same time, the room temperature liquid phase processing procedure is simple, is not limited by the substrate, and is fully compatible with the existing COMS process, and is easy to realize batch device preparation. The problems of low modulation efficiency, complicated processing and difficult heterogeneous integration faced by the current electro-optic modulator on a silicon substrate are effectively solved, and a new solution is provided for the large-scale preparation of electro-optic modulators on silicon-based optoelectronic chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic structural diagram of a MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0021] Figure 2 The figure is a schematic diagram of a top view of a MOS-type on-silicon electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0022] Figure 3 For the embodiment of the present invention Figure 3 AA section view in.

[0023] Figure 4 For the embodiment of the present invention Figure 3 BB section view in.

[0024] Figure 5 The present invention is a flow chart of a method for preparing a MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0025] Figure 6 It is a schematic diagram of the electro-optic modulation function test results of the MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0026] Figure 7 It is a schematic diagram of the light output power response test results of the MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to an embodiment of the present invention.

[0027] Among them: 1-upper electrode layer; 2-colloidal nanocrystal layer; 3-dielectric layer; 4-silicon waveguide layer; 5-lower electrode layer; 6-waveguide cladding; 7-optical coupler. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0031] See also Figure 1In one embodiment of the present invention, a MOS-type electro-optic modulator on a silicon substrate based on colloidal nanocrystals is provided, comprising a waveguide cladding 6, a silicon waveguide layer 4, a dielectric layer 3, a colloidal nanocrystal layer 2, an upper electrode layer 1 and a lower electrode layer 5. The silicon waveguide layer 4 is arranged above the waveguide cladding 6; optical couplers 7 for input and output of optical signals are arranged at both ends of the silicon waveguide layer 4; the dielectric layer 3 is arranged above the silicon waveguide layer 4; the colloidal nanocrystal layer 2 is arranged above the dielectric layer 3; the upper electrode layer 1 is arranged above the colloidal nanocrystal layer 2; the lower electrode layer 5 is connected to the silicon waveguide layer 4; the dielectric layer 3 is used to change the polarization state according to the applied voltage and control the induced charge concentration in the colloidal nanocrystal layer 2 and the silicon waveguide layer 4 through the polarization state.

[0032] Specifically, the oxide semiconductor colloidal nanocrystals prepared by solution are coated on the upper surface of the on-chip silicon waveguide deposited with the dielectric layer 3, and a MOS type flat-plate capacitor of the structure of "colloidal nanocrystal layer-dielectric layer-silicon waveguide layer" is obtained, wherein the colloidal nanocrystal layer 2 is equivalent to the upper plate of the flat-plate capacitor, and the silicon waveguide layer 4 is equivalent to the lower plate of the flat-plate capacitor. An upper electrode layer 1 is prepared above the colloidal nanocrystal film, and a lower electrode layer 5 is prepared on the lower plate of the flat-plate capacitor structure, i.e., on the side of the silicon waveguide layer 4, for input of electrical signals. Optical couplers 7 are introduced at both ends of the silicon waveguide layer 4 to realize the input and output of optical signals.

[0033] The present invention is a MOS-type silicon-based electro-optic modulator based on colloidal nanocrystals. The strong plasma dispersion effect of oxide semiconductor colloidal nanocrystals is utilized and heterogeneously integrated with silicon waveguides to realize a high-efficiency, large-scale scalable electro-optic modulator. The colloidal nanocrystal layer 2, the dielectric layer 3 and the silicon waveguide layer 4 together constitute a MOS-type flat-plate capacitor structure. The voltage signal is applied to the flat-plate capacitor through the upper electrode layer 1 and the lower electrode layer 5, which can change the polarization state and polarization degree of the dielectric layer 3, and cause the change of the free carrier concentration of the colloidal nanocrystal layer 2 and the silicon waveguide layer 4. The change of the free carrier concentration in the colloidal nanocrystal layer 2 and the silicon waveguide layer 4 can cause a significant change in the real part and the imaginary part of the refractive index of the material through the plasma dispersion effect, thereby changing the effective refractive index and absorption loss of the light passing through the modulator structure, and finally changing the phase and intensity of the transmitted light, and realizing efficient electro-optic modulation. The oxide semiconductor colloidal nanocrystal has a plasma dispersion effect stronger than that of silicon materials, and is easy to realize the ENZ effect, which can achieve high modulation efficiency and high modulation depth. The MOS-type silicon-based on-chip electro-optic modulator of the present invention has a larger capacitance, which can cause a more significant change in carrier concentration, thereby producing a stronger plasma dispersion effect and a stronger modulation, and has realized a compact, high-modulation-efficiency and high-modulation-depth silicon-based on-chip electro-optic modulator in the 1550nm communication band.

[0034] 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. The colloidal nanocrystal layer 2 is located above the dielectric layer 3, and under the action of the polarization of the dielectric layer 3, it gathers / depletes free charges at the interface, causing a change in the free charge concentration distribution in the material, thereby causing a change in the real part and imaginary part of the refractive index of the material.

[0035] Optionally, the colloidal nanocrystal layer 2 may be subjected to a surface ligand exchange treatment to achieve good electrical conductivity.

[0036] In a possible implementation, the structure of the silicon waveguide layer 4 is: a straight waveguide, a Mach-Zehnder interferometer, a directional coupler, a micro-ring resonator or a photonic crystal structure. 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 4.

[0037] Under the action of the polarization of the dielectric layer 3, the silicon waveguide layer 4 gathers / depletes holes at the interface, causing a change in the hole concentration in the material, thereby causing a change in its optical refractive index and light absorption.

[0038] In a possible implementation, the waveguide cladding 6 is made of SiO2; the upper electrode layer 1 is made of metal material, graphene or transparent conductive oxide; the lower electrode layer 5 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.

[0039] In a possible implementation manner, the dielectric layer 3 is made of silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), hafnium dioxide (HfO 2 ) or polymethyl methacrylate (PMMA).

[0040] In a possible implementation manner, the silicon waveguide layer 4 is a p-type doped silicon waveguide; and the oxide semiconductor colloidal nanocrystals are n-type doped oxide semiconductor colloidal nanocrystals.

[0041] In a possible implementation manner, the colloidal nanocrystal layer 2 is subjected to a surface ligand exchange treatment.

[0042] Specifically, the colloidal nanocrystal layer 2 of the oxide semiconductor is subjected to surface ligand exchange treatment to achieve good conductivity. Exemplarily, a possible treatment method is: dissolving nitrosodifluoroborate (NOBF4) in N,N-dimethylformamide (DMF) to obtain a NOBF4 solution with a concentration of 20 mg / ml; at the same time, stably dispersing In2O3 colloidal nanocrystals in a n-hexane solvent at a concentration of 50 mg / ml; then, mixing 5 ml of NOBF4 solution with 0.5 ml of In2O3 nanocrystal solution and fully shaking, during which the surface long-chain ligands of the nanocrystals are replaced with short-chain ligands, so that they are transferred from the n-hexane solvent to the DMF solvent and stably suspended; finally, removing excess n-hexane, and adding toluene to the colloidal nanocrystal solution suspended in DMF to precipitate it, removing toluene after centrifugation and re-dissolving the nanocrystals in DMF to obtain a 25 mg / ml colloidal nanocrystal solution for subsequent processing.

[0043] The working principle of the MOS-type on-chip electro-optic modulator based on colloidal nanocrystals of the present invention is as follows:

[0044] The colloidal nanocrystal layer 2, the dielectric layer 3 and the silicon waveguide layer 4 together constitute a MOS type flat capacitor structure. The colloidal nanocrystal layer 2 and the silicon waveguide layer 4 respectively apply an external voltage to the dielectric layer 3 through the upper electrode layer 1 and the lower electrode layer 5, thereby causing polarization of the dielectric layer 3 and inducing the aggregation or depletion of carriers between the interface between the colloidal nanocrystal layer 2 and the dielectric layer 3 and between the interface between the conductive silicon waveguide layer 4 and the dielectric layer 3. As the applied voltage increases or decreases, the concentration of free carriers in the colloidal nanocrystal layer 2 and the silicon waveguide layer 4 materials increases or decreases, thereby changing the refractive index and absorption of light according to the plasma dispersion effect; the colloidal nanocrystal layer 2 covers the waveguide layer 4, and the changes in its refractive index and light absorption act on the waveguide optical signal, and cause modulation of the optical signal transmission phase and loss.

[0045] Among them, the change of free carrier concentration in the colloidal nanocrystal layer 2 and the silicon waveguide layer 4 can cause significant changes in the real and imaginary parts of the material refractive index through the plasma dispersion effect, thereby changing the effective refractive index and absorption loss of the light passing through the modulator structure, and finally changing the phase and intensity of the transmitted light to achieve efficient electro-optical modulation. The state of polarization of the dielectric layer 3, including the degree and direction, is controlled by the magnitude and positive and negative of the applied voltage signal. The concentration of electrons / holes in the colloidal nanocrystal layer 2 and the silicon waveguide layer 4 is determined by the polarization degree and direction of the dielectric layer 3, so that electrical modulation of its light refraction and light absorption can be achieved.

[0046] See also Figures 2 to 4, showing the structure of the MOS-type silicon-based electro-optic modulator based on colloidal nanocrystals in the case where the structure of the silicon waveguide layer 4 adopts a microring resonator.

[0047] In another embodiment of the present invention, a method for preparing a MOS-type on-chip electro-optic modulator based on colloidal nanocrystals is provided, comprising the following steps:

[0048] A lower electrode layer 5 is prepared on the waveguide cladding 6; a silicon waveguide layer 4 in contact with the lower electrode layer 5 is processed on the waveguide cladding 6, and optical couplers 7 for input and output of optical signals are processed at both ends of the silicon waveguide layer 4; a covering dielectric layer 3 is prepared above the silicon waveguide layer 4; a colloidal nanocrystal layer 2 is prepared above the dielectric layer 3 using oxide semiconductor colloidal nanocrystals by spin coating, inkjet printing, drop coating, scraping or solution self-assembly method; and an upper electrode layer 1 is prepared above the colloidal nanocrystal layer 2.

[0049] The present invention discloses a method for preparing a MOS-type electro-optic modulator on a silicon substrate based on colloidal nanocrystals. The colloidal nanocrystal layer can be prepared by spin coating, inkjet printing, drip coating, scraping coating or solution self-assembly method, and the preparation process cost is low. At the same time, the room temperature liquid phase processing procedure is simple, is not limited by the substrate, and is fully compatible with the existing COMS process, and is easy to realize batch device preparation. The problems of low modulation efficiency, complicated processing and difficult heterogeneous integration faced by the current electro-optic modulator on a silicon substrate are effectively solved, and a new solution is provided for the large-scale preparation of electro-optic modulators on silicon-based optoelectronic chips.

[0050] In a possible implementation, the preparing the lower electrode layer 5 on the waveguide cladding 6 includes: defining the shape of the lower electrode layer 5 by an electron beam exposure process, and vapor-depositing the lower electrode layer 5 by an electron beam evaporation technique; processing the silicon waveguide layer 4 in contact with the lower electrode layer 5 on the waveguide cladding 6, and processing the optical coupler 7 for input and output of optical signals at both ends of the silicon waveguide layer 4 includes: using an electron beam exposure overlay process and a plasma etching process to prepare the silicon waveguide layer 4 and the optical coupler 7 by grooves on both sides; wherein a section of silicon material is retained on the silicon waveguide layer 4 without being etched, so that the silicon waveguide layer 4 is connected to the lower electrode layer 5.

[0051] In a possible embodiment, the preparation of the covering dielectric layer 3 above the silicon waveguide layer 4 includes: preparing the covering dielectric layer 3 above the silicon waveguide layer 4 using atomic layer deposition technology; the preparation of the upper electrode layer 1 above the colloidal nanocrystal layer 2 includes: preparing the upper electrode layer 1 above the colloidal nanocrystal layer 2 using electron beam exposure overlay and electron beam evaporation technology, and removing excess dielectric layer 3 and colloidal nanocrystal layer 2 using electron beam exposure and hydrochloric acid wet etching technology.

[0052] Exemplarily, the method for preparing a MOS-type silicon-based on-chip 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, with an upper layer being a silicon flat layer, a middle layer being a SiO2 insulating layer, and a bottom layer being a block silicon substrate.

[0053] In one possible implementation, see Figure 5 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 4 adopts a micro-ring resonator. The preparation method of the MOS-type silicon-based electro-optical modulator based on colloidal nanocrystals of the present invention includes the following steps:

[0054] Step 1: On a clean SOI chip, the shape of the lower electrode layer 5 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 5 with a specific pattern shape is obtained after peeling.

[0055] Step 2: Using electron beam exposure overlay process and plasma etching process, the silicon waveguide layer 4 and the optical signal inlet and outlet of the optical waveguide, namely the optical coupler 7, are processed 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 as to ensure the electrical connection between the silicon waveguide layer 4 and the silicon substrate in contact with the lower electrode layer 5 without disrupting the light transmission.

[0056] Step 3: Prepare a 30 nm thick Al2O3 layer, ie, dielectric layer 3, on the SOI chip using atomic layer deposition technology.

[0057] Step 4: Prepare a colloidal nanocrystal layer 2 on the dielectric layer 3 using oxide semiconductor colloidal nanocrystals by spin coating, inkjet printing, drop coating, scraper coating or solution self-assembly.

[0058] Step 5: Prepare a Cr / Au upper electrode layer 1 with a thickness of 5 nm / 40 nm on the colloidal nanocrystal layer 2 by using electron beam exposure overlay and electron beam evaporation process.

[0059] Step 6: Using electron beam exposure and hydrochloric acid wet etching process, remove the redundant dielectric layer 3 and colloidal nanocrystal layer 2 on the SOI chip to achieve better electrical isolation and facilitate electrical testing.

[0060] In a possible implementation manner, the upper electrode layer 1 is located on the other side of the silicon waveguide layer 4 relative to the lower electrode layer 5 .

[0061] Explanatory, in order to facilitate electrical testing and avoid insertion loss caused by metal absorption, the upper electrode layer 1 is placed on the other side of the silicon waveguide layer 4 relative to the lower electrode layer 5.

[0062] The present invention introduces colloidal nanocrystals prepared by solution into silicon-based optoelectronic integrated chips, realizing a high-modulation-efficiency on-chip electro-optical modulator that is compatible with CMOS technology and can be integrated on a large scale, and can be used in the fields of on-chip optical interconnection and biochemical sensing.

[0063] In one possible implementation, a 700 micron long MOS-type silicon-based electro-optic modulator based on colloidal nanocrystals is integrated into a micro-ring resonator waveguide with a radius of 120 microns, and the transmitted power is measured by an optical coupler 7, and the significant change of the same-level resonance peak with the external voltage is obtained. Figure 6 , showing the response of the resonant wavelength to the applied voltage, i.e., the electro-optical modulation function of the device, with a modulation efficiency of about 20pm / V. When the upper electrode layer 1 is grounded and a voltage of 0V-10V is applied to the lower electrode layer 5, the resonant wavelength of the microring gradually blueshifts, and the quality factor of the resonance peak decreases, proving that the modulator achieves modulation of the real and imaginary parts of the light refractive index through voltage signals.

[0064] In one possible implementation, a 100 micron long MOS-type silicon-based electro-optic modulator based on colloidal nanocrystals is integrated into a micro-ring resonator waveguide with a radius of 80 microns, and the transmitted power is measured by an optical coupler 7 to obtain the response of the transmitted power at a certain wavelength to a 5V square wave signal. Figure 7 , showing the response of the optical output power when a 5V square wave signal is input at a wavelength of 1550nm, showing a response speed of less than 1ms, confirming the sub-ms response speed.

[0065] In view of the current status and shortcomings of electro-optic modulators on silicon substrates, such as low modulation efficiency, complicated processing and difficulty in heterogeneous integration, the present invention proposes an electro-optic modulator based on oxide semiconductor colloidal nanocrystals that is fully compatible with CMOS. The electro-optic modulator has the characteristics of solution preparation and 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 towards a highly integrated direction.

[0066] 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 MOS-type silicon-based on-chip electro-optic modulator based on colloidal nanocrystals, characterized in that: include: waveguide cladding (6); A silicon waveguide layer (4) is arranged above the waveguide cladding layer (6); optical couplers (7) for input and output of optical signals are arranged at both ends of the silicon waveguide layer (4); A dielectric layer (3) is disposed overlying the silicon waveguide layer (4); A colloidal nanocrystal layer (2) is disposed above the dielectric layer (3); An upper electrode layer (1) is arranged above the colloidal nanocrystal layer (2); A lower electrode layer (5) connected to the silicon waveguide layer (4); The dielectric layer (3) is used to change the polarization state according to an applied voltage and to control the induced charge concentration in the colloidal nanocrystal layer (2) and the silicon waveguide layer (4) through the polarization state.

2. The MOS-type silicon-based on-chip 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 MOS-type silicon-based on-chip electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: The structure of the silicon waveguide layer (4) is: Straight waveguides, Mach-Zehnder interferometers, directional couplers, microring resonators or photonic crystal structures.

4. The MOS-type silicon-based on-chip electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: The waveguide cladding (6) is made of SiO2; the upper electrode layer (1) is made of metal material, graphene or transparent conductive oxide; and the lower electrode layer (5) is made of metal material, graphene or transparent conductive oxide.

5. The MOS-type silicon-based on-chip electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: The dielectric layer (3) is made of silicon dioxide, aluminum oxide, hafnium dioxide or polymethyl methacrylate.

6. The MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to claim 1, characterized in that: The silicon waveguide layer (4) is a p-type doped silicon waveguide; the oxide semiconductor colloidal nanocrystals are n-type doped oxide semiconductor colloidal nanocrystals; and the colloidal nanocrystal layer (2) has been subjected to a surface ligand exchange treatment.

7. A method for preparing a MOS-type on-chip electro-optic modulator based on colloidal nanocrystals, characterized in that: include: preparing a lower electrode layer (5); A silicon waveguide layer (4) connected to a lower electrode layer (5) is processed on a waveguide cladding layer (6), and optical couplers (7) for input and output of optical signals are processed at both ends of the silicon waveguide layer (4); Preparing a covering dielectric layer (3) above the silicon waveguide layer (4); Using spin coating, inkjet printing, drop coating, scraping or solution self-assembly method, a colloidal nanocrystal layer (2) is prepared on the dielectric layer (3) using oxide semiconductor colloidal nanocrystals; An upper electrode layer (1) is prepared on the colloidal nanocrystal layer (2).

8. The method for preparing a MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to claim 7, characterized in that: The preparation of the lower electrode layer (5) comprises: on an SOI chip, using an electron beam exposure process to define the shape of the lower electrode layer (5), and using an electron beam evaporation technology to evaporate the lower electrode layer (5); processing a silicon waveguide layer (4) connected to the lower electrode layer (5) on a waveguide cladding layer (6), and processing an optical coupler (7) for input and output of optical signals at both ends of the silicon waveguide layer (4) comprises: on the SOI chip, using an electron beam exposure overlay process and a plasma etching process, processing and preparing the silicon waveguide layer (4) and the optical coupler (7) in a grooved manner on both sides; wherein a section of silicon material is retained on the silicon waveguide layer (4) and is not etched, so that the silicon waveguide layer (4) and the lower electrode layer (5) remain connected.

9. The method for preparing a MOS-type on-chip electro-optic modulator based on colloidal nanocrystals according to claim 7, characterized in that: The step of preparing a covering dielectric layer (3) on the silicon waveguide layer (4) comprises: preparing the covering dielectric layer (3) on the silicon waveguide layer (4) by using an atomic layer deposition technique; the step of preparing an upper electrode layer (1) on the colloidal nanocrystal layer (2) comprises: preparing the upper electrode layer (1) on the colloidal nanocrystal layer (2) by using an electron beam exposure overlay and electron beam evaporation process, and removing excess dielectric layer (3) and colloidal nanocrystal layer (2) by using an electron beam exposure and hydrochloric acid wet etching process.

10. The method for preparing a MOS-type on-chip 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 (4) relative to the lower electrode layer (5).

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