CN111262133A - Method for improving single-layer two-dimensional semiconductor light-emitting brightness - Google Patents

Abstract

The invention relates to a method for improving the luminous brightness of a single-layer two-dimensional semiconductor, belonging to the technical fields of quantum optics and photonic quantum information. The invention integrates a single-layer two-dimensional semiconductor and a three-dimensional semiconductor with a convex structure on the surface to form a composite heterostructure, which produces a greatly enhanced coupling system and greatly improves the luminous brightness of the single-layer two-dimensional semiconductor. The simple and efficient silicon-based composite heterostructure is fully scalable and holds promise as a quantum light source with high brightness, long-term stability, and chip integratability, belonging to the fields of quantum optics and photonic quantum information technology.

Description

A method for improving the luminous brightness of a single-layer two-dimensional semiconductor

technical field

The invention relates to a method for improving the luminous brightness of a single-layer two-dimensional semiconductor. The simple and efficient silicon-based composite heterostructure is expected to be used as a quantum light source with high brightness, long-term stability and chip integration, belonging to quantum optics and photonic quantum light sources. field of information technology.

Background technique

Single quantum emitters (SQEs) are at the heart of quantum optics and photonic quantum information technologies, and SQEs are essential for many applications in quantum information processing. Monolayer transition metal dichalcogenides (TMDCs) have large exciton binding energies and long exciton lifetimes within the layers at room temperature, which make them particularly suitable for single quantum emitter applications. The core requirements of this non-classical light source include long-term stability, high brightness, and on-chip integratability.

However, obtaining high photoluminescence quantum yields remains challenging in monolayer 2D materials. For example, the integration of mechanically exfoliated single-layer WSe ₂ onto a silicon-based photonic structure achieves only an 8-fold enhancement of photoluminescence; the enhancement of the luminescence of a single-layer 2D material through elastic strain engineering is also only a few-fold enhancement. The grown monolayers generally exhibit lower photoluminescence quantum yields than their mechanically exfoliated monolayers. Coupling the grown _WSe monolayers onto a circular Bragg grating structure, enhanced exciton emission is observed. 7 times; the recently reported mechanical relaxation of grown WSe ₂ monolayers by solvent evaporation is decoupled from the substrate, and the emission enhancement of photoluminescence achieved is also only one order of magnitude compared to substrate-coupled grown monolayers. Although many solutions have been proposed to enhance quantum emission in single-layer 2D semiconductors, achieving more efficient photon extraction efficiency, high integration, and scalability still needs to open up new approaches. Using a simple and efficient composite heterostructure of the present application, a greatly enhanced coupling system can be produced, resulting in greatly improved luminous efficiency of single-layer two-dimensional semiconductors, such as chemical vapor deposition (CVD) in our laboratory. The luminescence of the WSe ₂ monolayer material grown by the method was improved by two orders of magnitude.

The composite system formed by a single-layer two-dimensional semiconductor and a three-dimensional semiconductor with a convex structure on the surface improves the luminous intensity, mainly by using the special structure of the three-dimensional semiconductor to have a larger carrier concentration in a specific part, which is different from the single-layer two-dimensional semiconductor. Coupling occurs at the contact site, resulting in interlayer exciton transitions, injecting additional excitons into the monolayer 2D semiconductor, and at the same time, the monolayer 2D semiconductor is subjected to local strain and the band gap continuously changes to produce an exciton funnel effect. These two effects ultimately The luminescence of single-layer two-dimensional semiconductors is greatly improved.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of low photon extraction efficiency and limited integration and expansibility in the prior art, and to provide a method for improving the luminous brightness of a single-layer two-dimensional semiconductor. This method provides a simple and efficient composite heterostructure that enhances the luminescence brightness of single-layer 2D semiconductors, and enables scalability of the fabrication process and on-chip integration.

The purpose of the present invention is achieved through the following technical solutions.

A method for improving the luminous brightness of a single-layer two-dimensional semiconductor, integrating the single-layer two-dimensional semiconductor into a three-dimensional semiconductor with a convex structure on the surface: the coupling of the single-layer two-dimensional semiconductor and the three-dimensional semiconductor produces an exciton funnel effect and an exciton injection effect, Thereby, the purpose of improving the luminescence of the single-layer two-dimensional semiconductor is achieved.

The specific physical principle is: the three-dimensional semiconductor with the convex structure on the surface causes local strain in the single-layer two-dimensional semiconductor, the energy band structure of the single-layer two-dimensional semiconductor changes, and the exciton funnel effect is formed; There are interlayer exciton transitions in the 3D semiconductor contacts of the raised structure, which can inject additional excitons into the monolayer 2D semiconductor; the exciton injection efficiency depends on the gate voltage, so it can be further adjusted by the gate voltage. Using a composite heterostructure composed of a single-layer two-dimensional semiconductor and a three-dimensional semiconductor with a convex structure on the surface, the exciton funnel effect and interlayer exciton transitions formed together have an influence to achieve the purpose of improving the luminescence brightness of a single-layer two-dimensional semiconductor.

The quantum light source with high brightness, long-term stability and chip integration prepared by the above method includes: a single-layer two-dimensional semiconductor, a three-dimensional semiconductor with a convex structure on the surface, a dielectric layer, a conductive electrode, a wire and a laser light source; The single-layer two-dimensional semiconductor is placed on a three-dimensional semiconductor with a convex structure on the surface to form a composite heterostructure, the single-layer two-dimensional semiconductor is irradiated with a laser light source, a dielectric layer is covered on the single-layer two-dimensional semiconductor, and the dielectric layer is A wire and a conductive electrode are connected to a three-dimensional semiconductor with a convex structure on the surface, so that the composite heterostructure can be easily connected to an electronic system, and the gate voltage can be applied for regulation.

The single-layer two-dimensional semiconductor refers to a material in the nanoscale range in one dimension. For example, but not limited to these, including single-layer WSe ₂ , WS ₂ , GaSe, MoSe ₂ , MoS ₂ , MoTe ₂ , SnSe ₂ , GeSe, and graphene.

The three-dimensional semiconductor with a raised structure on the surface is a substrate for coupling a single-layer two-dimensional semiconductor, which can be any silicon-based three-dimensional semiconductor with deformation or local deformation, such as a wrinkle structure, its wavelength, amplitude, lateral etching depth , the doping concentration is an adjustable parameter. The raised structure of the 3D semiconductor induces local strain in the monolayer 2D semiconductor, resulting in a continuous change in the energy gap to change the motion of the carriers. The structure and size of different parameters are adopted according to the final plan and application scenarios.

The single-layer two-dimensional semiconductor is irradiated by the laser light source, which means that in the process of photoluminescence (PL) characterization, the three-dimensional PL intensity map is obtained by online scanning of the entire structure. The laser wavelength and laser power can be selected according to the single-layer two-dimensional semiconductor.

The dielectric layer refers to an insulating layer used for applying gate voltage. The preparation method of the dielectric layer may be spin coating, evaporation or sputtering.

The gate voltage refers to the electric field applied between the single-layer two-dimensional semiconductor and the three-dimensional semiconductor with a convex structure on the surface, which affects the injection and transition of excitons, thereby affecting the light emission of the single-layer two-dimensional semiconductor.

The conductive electrode refers to forming a conductive electrode on the single-layer two-dimensional semiconductor and the three-dimensional semiconductor having a convex structure on the surface using any method. For example, after the template is formed by photolithography, a layer of metal is coated with a coating machine.

The connecting wire refers to the part having the function of connecting the composite heterostructure to the electronic system, and it is not necessary to have a wire, as long as the composite heterostructure can be connected to the electronic system.

The electronic system refers to an electronic system that can apply a voltage between the single-layer two-dimensional semiconductor and the three-dimensional semiconductor with a convex structure on the surface.

beneficial effect

The invention provides a method for improving the luminous brightness of a single-layer two-dimensional semiconductor, which integrates a single-layer two-dimensional semiconductor and a three-dimensional semiconductor with a convex structure on the surface to form a composite heterostructure, resulting in a greatly enhanced coupling system, which greatly improves the single-layer two-dimensional semiconductor. Luminescence brightness of layer two-dimensional semiconductors. The simple and efficient silicon-based composite heterostructure is fully scalable and holds promise as a quantum light source with high brightness, long-term stability, and chip integratability, belonging to the fields of quantum optics and photonic quantum information technology.

Description of drawings

Figure 1 shows step 1, a three-dimensional semiconductor with a raised structure on the surface;

FIG. 2 shows step 2, transferring a single-layer two-dimensional semiconductor to a three-dimensional semiconductor with a raised structure on the surface;

Figure 3 shows step 3, irradiating a single-layer two-dimensional semiconductor test PL with a laser light source;

FIG. 4 is step 4, the composite heterostructure is connected to the electronic system through the wire, and the single-layer two-dimensional semiconductor test PL is irradiated with a laser light source;

5 is a simplified three-dimensional view of a composite heterostructure formed by a single-layer two-dimensional semiconductor and a three-dimensional semiconductor having a raised structure on the surface;

FIG. 6 is a schematic diagram of the principle of improving the luminescence of a single-layer two-dimensional semiconductor by a composite heterostructure;

Figure 7 is an experimental test case;

Figure 8 is a schematic diagram of the exciton dynamics in the composite heterostructure formed by the WSe ₂ monolayer and the three-dimensional periodic SiGe wrinkled structure.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the solutions in the examples of the present invention will be described in more detail below with reference to the drawings in the examples of the present invention. In the drawings, the same or similar symbols denote the same or similar elements or elements having the same or similar functions. The described examples are examples of some, but not all, of the invention.

The examples described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limitations of the present invention. Based on the embodiments of the present invention, those of ordinary skill in the art can obtain all other embodiments without creative work, which belong to the protection scope of the present invention. The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

In the description of the present invention, it is to be understood that the terms "moderate", "reduced", "low level", "higher level", "lower level", "larger", "substantially" and "overlay" The orientation, position or degree relationship of the knowledge is based on the orientation, position or degree relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific Orientation, construction and operation in a particular orientation, and therefore should not be construed as limiting the scope of protection of the present invention.

Example 1

A method for improving the luminescence brightness of a single-layer two-dimensional semiconductor, as shown in Figure 5, adopts a three-dimensional semiconductor with a convex structure on the surface: the single-layer two-dimensional semiconductor is coupled with a three-dimensional semiconductor with a specific structure, and local strain occurs simultaneously to generate excitation. sub-funnel effect, so as to achieve the purpose of improving the luminescence of single-layer two-dimensional semiconductors.

The composite heterostructure prepared by the above method includes: a single-layer two-dimensional semiconductor, a three-dimensional semiconductor with a convex structure on the surface, a dielectric layer, a conductive electrode, a wire and a laser light source; the single-layer two-dimensional semiconductor is placed on the surface with a A compound heterostructure is formed on the three-dimensional semiconductor with a convex structure, and the single-layer two-dimensional semiconductor is irradiated with a laser to observe the change of its PL. The single-layer two-dimensional semiconductor is covered with a dielectric layer, and the dielectric layer and the surface have a convex structure The three-dimensional semiconductor is connected with wires, which is convenient for the composite heterostructure to be connected to the electronic system, and can be controlled by applying gate voltage.

The working method of the quantum light source with high brightness, long-term stability and chip integration is as follows:

As shown in FIG. 1 , in operation step 1, a three-dimensional semiconductor with a raised structure on the surface is prepared, which is exemplified here by using standard Complementary Metal Oxide Semiconductor (CMOS) compatible processing techniques (including photolithography and reactive ion etching techniques). Three-dimensional periodic SiGe wrinkle structure.

As shown in FIG. 2 , in operation step 2, a single-layer two-dimensional semiconductor is transferred to a three-dimensional semiconductor with a convex structure on the surface. Here, an example is the use of wet transfer to transfer the CVD-grown WSe ₂ single-layer material to a three-dimensional periodic on the wrinkled structure of SiGe.

As shown in Figure 3, a laser light source with a wavelength of 532 nm was used to irradiate different positions of the WSe ₂ monolayer material, and the entire structure was scanned online to obtain a three-dimensional PL intensity map, and the PL changes at different positions were observed.

As shown in Figure 4, in operation step 4, polymethyl methacrylate (PMMA) is spin-coated on a single-layer two-dimensional semiconductor as a dielectric layer, and wires are connected to the dielectric layer material and the three-dimensional periodic SiGe wrinkle structure , connect the composite heterostructure to a meter that can apply a voltage. Apply different voltages to test the change of photoluminescence at the same position on the WSe ₂ monolayer material, and observe its relationship with voltage.

As shown in FIG. 6, a brief description of the principle of improving the luminance of a single-layer two-dimensional semiconductor, when the single-layer two-dimensional semiconductor is transferred to a three-dimensional semiconductor with a convex structure on the surface, local strain is generated in the single-layer two-dimensional semiconductor, This will lead to the change of the energy band structure of the single-layer two-dimensional semiconductor, which is reflected as the change of the carrier concentration of the single-layer two-dimensional semiconductor. The strength is increased to a medium level; at the same time, the three-dimensional semiconductor with a convex structure on the surface has a large carrier concentration in a specific part, and there is an interlayer exciton transition at the contact part between the single-layer two-dimensional semiconductor and the three-dimensional semiconductor, which can be a single-layer two-dimensional semiconductor. The 2D semiconductor injects additional excitons to increase the luminous intensity of the monolayer 2D semiconductor to a higher level, and the exciton injection efficiency depends on the gate voltage, so it can be regulated by the gate voltage. Because of the special integration of monolayer 2D semiconductors with 3D semiconductors with raised structures on the surface, the two effects contribute together, resulting in a greatly enhanced coupled system that enables greatly improved luminous efficiency of growth-based monolayer 2D semiconductors.

As shown in FIG. 7, this is for the convenience of understanding the experimental test data given. The test material is WSe ₂ single-layer semiconductor. Figure A is the sample on SiO ₂ /Si substrate, and the measured PL intensity is ~300; Figure B is the sample on the three-dimensional periodic SiGe wrinkled structure semiconductor, and the measured PL intensity is ~40000 , the PL strength of the WSe ₂ monolayer material is improved by more than two orders of magnitude. Figure C shows the change of the PL intensity of the sample on the three-dimensional periodic SiGe wrinkled structure semiconductor with the applied gate voltage. The measured PL intensity increases with the increase of the gate voltage, and the luminescence intensity of WSe ₂ can be further regulated by the gate voltage.

As shown in Fig. 8, this is a schematic diagram of exciton dynamics in the composite heterostructure formed by _WSe monolayer and three-dimensional periodic SiGe wrinkled structure, indicating that the two effects of exciton funnel effect and exciton transition work together Greatly improve the luminescence of WSe ₂ monolayer material.

The above-mentioned specific descriptions further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned descriptions are only specific embodiments of the present invention, and are not intended to limit the protection of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a method for improving the luminous brightness of monolayer two-dimensional semiconductor is characterized in that: monolayer two-dimensional semiconductor is integrated in the three-dimensional semiconductor with convex structure on the surface: monolayer two-dimensional semiconductor and three-dimensional semiconductor are coupled to produce exciton funnel effect And exciton injection effect, so as to achieve the purpose of improving the luminescence of single-layer two-dimensional semiconductor. The three-dimensional semiconductor with a convex structure on the surface causes local strain in the single-layer two-dimensional semiconductor, and the energy band structure of the single-layer two-dimensional semiconductor changes, forming an exciton funnel effect; there are excitons at the contact position between the single-layer two-dimensional semiconductor and the three-dimensional semiconductor. transition, which can inject additional excitons into the monolayer 2D semiconductor; the exciton injection efficiency is gate voltage-dependent, so it can be further tuned with the gate voltage. Using a composite heterostructure composed of a single-layer two-dimensional semiconductor and a three-dimensional semiconductor with a convex structure on the surface, the exciton funnel effect and interlayer exciton transitions formed together have an influence to achieve the purpose of improving the luminescence brightness of a single-layer two-dimensional semiconductor. 2. The quantum light source with high brightness, long-term stability and chip integratability prepared by the method as claimed in claim 1, characterized in that: comprising: a single-layer two-dimensional semiconductor, a three-dimensional semiconductor with a raised structure on the surface, A dielectric layer, a conductive electrode, a wire and a laser light source; the single-layer two-dimensional semiconductor is placed on a three-dimensional semiconductor with a convex structure on the surface to form a composite heterostructure, and the single-layer two-dimensional semiconductor is irradiated with a laser light source, and the single-layer two-dimensional semiconductor is irradiated with a laser light source. The three-dimensional semiconductor is covered with a dielectric layer, and wires and conductive electrodes are connected on the dielectric layer and the three-dimensional semiconductor with a raised structure on the surface, which facilitates the access of the composite heterostructure to the electronic system, and is regulated by applying gate voltage. 3 . The quantum light source according to claim 2 , wherein the single-layer two-dimensional semiconductor refers to a material in the nanoscale range in one dimension. 4 . For example monolayer WSe ₂ , WS ₂ , GaSe, MoSe ₂ , MoS ₂ , MoTe ₂ , SnSe ₂ , GeSe and graphene. 4 . The method of claim 1 , wherein the three-dimensional semiconductor with a convex structure on the surface is any three-dimensional silicon-based semiconductor with deformation or local deformation. 5 . For example, the wrinkle structure, its wavelength, amplitude, lateral etching depth, and doping concentration are adjustable parameters. The protruding structure of the 3D semiconductor induces local strain in the single-layer 2D semiconductor, resulting in a continuous change in the energy gap to change the motion of the carriers, and the structure and size with different parameters are adopted depending on the final plan and the application scenario. 5. The quantum light source according to claim 2, wherein the laser light source irradiates a single-layer two-dimensional semiconductor, which means that in the characterization process of photoluminescence, three-dimensional photoluminescence (PL) is obtained by scanning the entire structure online. ) intensity map. 6 . The quantum light source of claim 2 , wherein the dielectric layer is an insulating layer used to apply a gate voltage. 7 . The preparation method of the dielectric layer is spin coating, evaporation or sputtering. 7. The quantum light source according to claim 2, wherein: the gate voltage refers to the electric field applied between the single-layer two-dimensional semiconductor and the three-dimensional semiconductor with a convex structure on the surface, which affects the excitation voltage. The injection and transition of electrons can affect the luminescence of single-layer two-dimensional semiconductors. 8 . The quantum light source according to claim 2 , wherein the conductive electrode is prepared by forming a template by photolithography and then coating a layer of metal with a coating machine. 9 . 9 . The quantum light source according to claim 2 , wherein the connecting wire refers to a part having the function of connecting the composite heterostructure to the electronic system, and it is not necessary to have a wire, as long as the composite heterostructure can Access the electronic system. 10 . The quantum light source according to claim 2 , wherein the electronic system refers to an electronic system capable of applying a voltage between the single-layer two-dimensional semiconductor and the three-dimensional semiconductor having a convex structure on the surface. 11 . .

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