Preparation method of semiconductor three-dimensional micro-nano structure with tunable band gap

Abstract

The invention belongs to the technical field of semiconductor device manufacturing, and particularly discloses a preparation method of a semiconductor three-dimensional micro-nano structure with a tunable band gap, which comprises the following steps: heating a semiconductor core optical fiber according to a target heating temperature, and controlling the cooling rate when the optical fiber is cooled, the heating process and the cooling rate have a corresponding relationship with stress applied to a fiber core and a related semiconductor three-dimensional micro-nano structure when the optical fiber is heated, and the stress can be used for tuning a band gap of the semiconductor three-dimensional micro-nano structure; wherein under the condition that the target heating temperature is higher than the melting point of the fiber core, local heating is performed on the optical fiber, so that compression controllable stress is applied to the fiber core to enable the fiber core to form a semiconductor three-dimensional micro-nano structure, and the band gap structure of the fiber core is tuned; and under the condition that the target heating temperature is lower than the melting point of the fiber core, integrally heating the optical fiber to recrystallize the semiconductor three-dimensional micro-nano structure, applying tensile stress to the semiconductor three-dimensional micro-nano structure by utilizing the volume difference between the recrystallized structure and the original structure, and tuning the band gap structure of the semiconductor three-dimensional micro-nano structure.

Description

Technical Field

[0001] The present application belongs to the technical field of semiconductor device manufacturing, and more specifically, relates to a method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap. Background Art

[0002] In recent years, although silicon photonics has been widely used and studied in integrated circuits, existing silicon-based materials are severely limited in terms of technological progress and performance improvement for future devices, which leads to the current lack of suitable semiconductor material devices. Semiconductor materials and their devices are the basis for many key technologies such as electronics, computing, communications, optoelectronics and sensing, and the bandgap structure of semiconductors is the key factor that determines their electrical and optical properties. In the current development of electrical and optical technologies, it is hoped that not only the properties of semiconductors can be adjusted, but also the size of the corresponding devices can be miniaturized.

[0003] In order to break through the limitations of semiconductors in optoelectronic performance, researchers have introduced strain control technology. By precisely controlling the type and size of strain and changing the crystal structure of semiconductor materials, the semiconductor band gap can be tuned. However, the current technical route for adjusting the band gap based on strain engineering not only involves complex operating procedures and high costs, but also has a single function, which can only achieve one of the reduction or increase of the band gap, and cannot meet both requirements at the same time. At the same time, the samples prepared by these technologies are large in volume and difficult to adapt to the high-density integration requirements of electronic devices. In recent years, with the deepening of research on strain control of two-dimensional materials, researchers have reached the limit at almost all levels. However, under the influence of Moore's Law, three-dimensional integration technology will gradually develop, which will open up new paths for the exploration of three-dimensional materials. The strain control technology of three-dimensional materials is expected to overcome the limitations of two-dimensional materials in strain control and achieve more efficient and flexible band gap control. How to conveniently prepare semiconductor three-dimensional micro-nano structures and accurately control the band gap of semiconductor three-dimensional micro-nano structures is a technical problem that needs to be solved in this field. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present application is to realize the convenient preparation of semiconductor three-dimensional micro-nano structures and the precise regulation of the band gap of semiconductor three-dimensional micro-nano structures.

[0005] To achieve the above objectives, in a first aspect, the present application provides a method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap, the method comprising: The optical fiber is heated according to the target heating temperature, and the cooling rate of the optical fiber is controlled. The heating process and the cooling rate have a corresponding relationship with the stress applied to the fiber core and the related semiconductor three-dimensional micro-nano structure when the optical fiber is heated. The stress can be used to tune the semiconductor band gap. Among them, when the target heating temperature is higher than the melting point of the fiber core, the optical fiber is locally heated to apply controllable compressive stress to the fiber core and form a semiconductor three-dimensional micro-nano structure in the fiber core, and tune its band gap structure; when the target heating temperature is lower than the melting point of the fiber core, the optical fiber is heated as a whole to recrystallize the semiconductor three-dimensional micro-nano structure, and the volume difference between the recrystallized structure and the original structure is used to apply tensile stress to the semiconductor three-dimensional micro-nano structure and tune its band gap structure.

[0006] The heating process may be to locally heat the optical fiber when the target heating temperature is higher than the melting point of the fiber core, for example, heating the target area by a first heating source (which will be explained in detail later); the heating process may also be to heat the optical fiber as a whole when the target heating temperature is lower than the melting point of the fiber core, for example, heating the optical fiber as a whole after being treated by the first heating source by a second heating source (which will be explained in detail later).

[0007] The principle of preparing semiconductor three-dimensional micro-nano structures is that due to the difference in the absorption coefficient of the semiconductor material (core) and the cladding to the heating source, the energy of the heating source is mainly absorbed by the semiconductor material, and the absorbed energy causes the core to begin to liquefy. Under the action of capillary instability, the surface tension and viscoelastic force between the core and the cladding work together to split the liquefied cylindrical core into multiple droplets in the cladding. Under certain temperature and stress conditions, these droplets can form micro-nano structures such as spherical, ellipsoidal or rod-shaped, which mainly depends on the thermal expansion characteristics of the optical fiber, the stress distribution during the heating process and the initial shape of the optical fiber. When the optical fiber is uniformly heated, the semiconductor material is subjected to uniform stress in all directions, thus forming stable spherical droplets. However, when the optical fiber is non-uniformly heated or produces an uneven stress distribution (the optical fiber moves at a non-uniform speed, which can produce an uneven stress distribution), the stress inside the semiconductor material is large in a certain direction, causing the core to form an ellipsoidal or rod-shaped shape. Finally, as the heating source moves away from the optical fiber, the cladding and the semiconductor droplets begin to solidify successively, thus forming a semiconductor three-dimensional micro-nano structure inside the optical fiber.

[0008] The principle of regulating the band gap of semiconductor three-dimensional micro-nano structures is to influence the thermal stress and crystallization degree of the semiconductor material (core) in the optical fiber by precisely controlling the heat treatment cooling rate of the optical fiber. During the heat treatment of the optical fiber, due to different cooling rates, the semiconductor material produces internal stresses of different types and sizes. These internal stresses will affect the crystal structure of the semiconductor material, and then affect its band structure, achieving the purpose of tunable band gap.

[0009] Specifically, thermal stress in semiconductor materials is caused by the difference in thermal expansion coefficients between the core and cladding materials, resulting in a volume mismatch. Some materials (such as silicon and germanium) exhibit abnormal expansion characteristics when they reach a certain temperature during cooling. In addition, the melting point of these semiconductor materials (core) is lower than the softening point of the cladding (such as silicon dioxide).

[0010] In the first case, the heating source heats the fiber core to a molten state. When the fiber begins to cool, the silica cladding solidifies first and forms a fixed cavity whose volume is determined by the cooling rate. The faster the cooling rate, the lower the density of silica and the smaller the fixed cavity formed. Subsequently, the semiconductor material reaches the solidification temperature (melting point) and changes from liquid to solid. During the cooling process, due to the abnormal expansion characteristics of the semiconductor material, its volume begins to increase, which is restricted and compressed by the surrounding cladding. This volume mismatch causes compressive stress to be generated inside the semiconductor material. The cooling rate mainly affects the volume of the cladding when it solidifies, thereby affecting the magnitude of the internal stress of the semiconductor material. A faster cooling rate will cause the cladding to still maintain the material properties at high temperature, and its volume is larger, which further restricts the space of the semiconductor material and generates greater compressive stress inside it.

[0011] In the second case, the heating source only moderately heats the cladding of the optical fiber, but does not reach a molten state, and the heating temperature is lower than the melting point of the core. Under this condition, the semiconductor material mainly undergoes a low-temperature recrystallization process. During the heating and cooling process of the optical fiber, the semiconductor crystal begins to recrystallize due to the distribution of the temperature gradient. During the crystal growth process, new crystal orientations are gradually formed, internal defects are eliminated or reduced, and the internal structure begins to rearrange to form a more compact and orderly crystal structure, resulting in a reduction in the crystal volume. As the volume of the semiconductor material shrinks, the cladding material hardly expands and shrinks, and its volume changes little. Therefore, this volume mismatch causes tensile stress inside the semiconductor material. The cooling rate has a direct effect on the degree of crystallization of the crystal, which in turn affects the volume change and internal stress of the semiconductor material. A faster cooling rate shortens the crystal growth time, forms a smaller crystal, and further reduces the crystal volume, resulting in greater tensile stress. In practical applications, the situation is often more complicated than the theory, and one of the situations cannot be analyzed separately.

[0012] In a possible implementation, heating the optical fiber according to the target heating temperature and controlling the cooling rate of the optical fiber during cooling includes: The target area is heated by a first heating source. During the heating process, various parts of the optical fiber enter and leave the target area at a target moving speed so that the core forms a semiconductor three-dimensional micro-nano structure. The target area and the optical fiber are located on the same horizontal plane. The target heating temperature is specifically the temperature at the center of the target area. The temperature at the center of the target area is higher than the melting point of the core of the optical fiber. The optical fiber has a first cooling rate in the process of leaving the target area.

[0013] The first heating source can be a high-energy light source such as a laser to ensure that the fiber core can reach the melting point. Sufficient heating temperature can be obtained by adjusting the output power of the laser. The size of the laser spot can be changed by adjusting the height of the laser. The heat treatment cooling rate of the optical fiber can be further controlled by adjusting the size of the laser spot. The size of the laser spot determines the size of the area of ​​the optical fiber irradiated by the laser (that is, the above-mentioned target area). When other variables remain unchanged, the larger the spot size, the larger the area irradiated by the laser, the smaller the temperature gradient of the heated part of the optical fiber, and the slower the heat treatment cooling rate. Therefore, the cooling rate of the optical fiber can be adjusted according to different laser spot sizes. When the spot size is large, the cooling rate is slow, and when the spot size is small, the cooling rate is fast.

[0014] In a possible implementation, when the first heating source uniformly heats the target area, the semiconductor three-dimensional micro-nano structure is spherical in shape; When the first heating source performs non-uniform heating on the target area, the shape of the semiconductor three-dimensional micro-nano structure is non-spherical.

[0015] In a possible implementation, the first heating source is a laser, and before the target area is heated by the first heating source, the method further includes: The height of the laser is adjusted to determine the spot size formed by the laser emitted by the laser in the target area. The spot size affects the cooling rate. The smaller the spot size, the faster the cooling rate.

[0016] In a possible implementation, the method further includes: Acquire an image of the optical fiber in the target area; Displaying an image and receiving a target input, the image is used to calculate and quantify the value of the cooling rate using the black body radiation principle, and the target input is used to indicate the adjustment amount of the moving speed and the adjustment amount of the output power of the laser; In response to the target input, the target moving speed of the optical fiber and the output power of the laser are controlled based on the adjustment amount of the moving speed and the adjustment amount of the output power.

[0017] In a possible implementation, the method further includes: The optical fiber is carried by a translation stage (the optical fiber is placed horizontally or vertically), and the translation stage is used to carry the optical fiber and move it at a target moving speed during the process of heating the target area by the first heating source.

[0018] In a possible implementation, heating the optical fiber according to the target heating temperature and controlling the cooling rate of the optical fiber during cooling includes: The optical fiber treated by the first heating source is heated as a whole by a second heating source to recrystallize the semiconductor three-dimensional micro-nano structure in the optical fiber. The target heating temperature provided by the second heating source for the optical fiber is lower than the melting point of the fiber core. The overall heating process includes a heating stage from a preset temperature to a target heating temperature, a heat preservation stage, and a cooling stage from the target heating temperature to a preset temperature. The cooling stage has a second cooling rate.

[0019] The second heating source can be a tube furnace, which can adjust the cooling rate of the optical fiber by setting the cooling rate in the furnace. However, the heating method of the tube furnace is different from that of the laser. The laser can locally heat the optical fiber, but the tube furnace is difficult to achieve this. Therefore, the laser is suitable for the preparation of semiconductor three-dimensional micro-nano structures and band gap tuning, and the tube furnace is suitable for tuning the band gap, but not for the preparation of semiconductor three-dimensional micro-nano structures.

[0020] The tubular furnace can simultaneously meet the needs of placing and heating semiconductor three-dimensional micro-nano structures, and can adjust the furnace temperature according to the target furnace temperature, heating and cooling rates, and insulation time under a vacuum environment.

[0021] Specifically, the temperature in the furnace is the recrystallization temperature of the fiber core, which needs to be set below the melting point of the semiconductor material to ensure that the material does not melt and is suitable for crystal growth. The holding time needs to be set sufficiently so that the fiber core can be fully affected by the thermal stress and allow the crystal to have enough time to grow and rearrange. The cooling rate is the cooling rate of the optical fiber, which affects the degree of crystallization of the semiconductor crystal. Therefore, it is necessary to select an appropriate rate to ensure that the internal stress is still retained after cooling.

[0022] In a possible implementation, the second heating source is a tube furnace; The tubular furnace is used to carry the optical fiber containing semiconductor three-dimensional micro-nano structure after being treated by the first heating source, and adjust the temperature in the furnace according to the target furnace temperature, heating rate, cooling rate and insulation time under a vacuum environment. The target furnace temperature is the target heating temperature, and the cooling rate is the second cooling rate.

[0023] In a second aspect, the present application also provides a device for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap, comprising: a carrier platform and a heating module; The carrier is used to place the optical fiber; The heating module is used to heat the optical fiber according to the target heating temperature and control the cooling rate of the optical fiber when it is cooled. The heating process and the cooling rate have a corresponding relationship with the stress applied to the fiber core and the related semiconductor three-dimensional micro-nano structure when the optical fiber is heated. The stress can be used to tune the semiconductor band gap. Among them, when the target heating temperature is higher than the melting point of the fiber core, the optical fiber is locally heated to apply controllable compressive stress to the fiber core so that the fiber core forms a semiconductor three-dimensional micro-nano structure and tunes its band gap structure; when the target heating temperature is lower than the melting point of the fiber core, the optical fiber is heated as a whole to recrystallize the semiconductor three-dimensional micro-nano structure, and the volume difference between the recrystallized structure and the original structure is used to apply tensile stress to the semiconductor three-dimensional micro-nano structure and tune its band gap structure.

[0024] In a possible implementation, the carrier platform may specifically be a displacement platform, the heating module includes a heating source and a controller (such as a control computer), and the heating source and the displacement platform are respectively connected to the controller; The heating source is used to provide the necessary heat and corresponding cooling rate to the optical fiber; The translation stage is used to place the optical fiber and carry the optical fiber for movement; The controller is used to control the moving speed of the optical fiber and is responsible for setting and adjusting the equipment parameters of the heating source.

[0025] It should be noted that if the heating source is movable, the translation stage can also be any platform capable of placing the optical fiber.

[0026] Specifically, the controller controls the translation stage according to the required heating length and moving speed of the optical fiber, and adjusts the output power of the laser according to the melting points of the core and cladding to ensure that the core has sufficient heating time and heating temperature to form a molten state.

[0027] It is understandable that by introducing the optical fiber into the laser irradiation area and performing local heating, and by adjusting the moving speed of the optical fiber and the output power of the laser, the fiber core can reach the melting point to form different semiconductor three-dimensional micro-nano structures. By adjusting the size of the laser spot, the compressive stress applied to the semiconductor three-dimensional micro-nano structure can be further regulated. In addition, by placing the optical fiber containing the semiconductor three-dimensional micro-nano structure in a tubular furnace and performing a low-temperature recrystallization process on it, corresponding tensile stress can be applied. This compressive stress and tensile stress can change the band structure of the semiconductor, thereby realizing the band gap tuning of the semiconductor three-dimensional micro-nano structure.

[0028] Therefore, by using a preparation device composed of a heating source, a displacement stage and a controller, semiconductor three-dimensional micro-nano structures can be conveniently prepared, and by adjusting the heat treatment cooling rate of the optical fiber, the band gap of the semiconductor three-dimensional micro-nano structure can be controlled.

[0029] In a possible implementation, the optical fiber uses a semiconductor material as its core.

[0030] In a possible implementation, the device further includes: a camera connected to the controller; The camera is used to collect images of the optical fiber at the light-emitting position and send the collected images to the controller; The controller is specifically used to display the image and make corresponding adjustments to the moving speed and the output power of the laser; Specifically, the position and focal length of the camera are adjusted so that it is vertically aligned with the light output position of the laser to observe the temperature distribution of the optical fiber when it is heated; the controller is also used to adjust the image parameters of the camera.

[0031] The images collected show that the heated area of ​​the optical fiber has an alternating solid-liquid interface, which indicates that the optical fiber has reached the preparation conditions. The images can also be used to calculate the cooling rate of the optical fiber using the principle of blackbody radiation.

[0032] In a third aspect, the present application further provides a semiconductor three-dimensional micro-nano structure, which is prepared by applying the preparation method described in the first aspect or any possible implementation of the first aspect.

[0033] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: (1) A preparation principle of bandgap-tunable semiconductor three-dimensional micro-nanostructures is adopted. This principle can not only prepare various types of semiconductor three-dimensional micro-nanostructures, but also regulate the stress and bandgap of semiconductors. By changing the heating method of the heating source (uniform heating or non-uniform heating), micro-nanostructures of different shapes such as spheres, ellipsoids and rods can be prepared. In addition, by controlling the heating process and cooling rate of the heating source, the thermal stress and crystallinity of the semiconductor can be affected, thereby applying compressive stress and tensile stress to the semiconductor, thereby affecting its band structure and achieving bandgap tunability.

[0034] (2) By using a laser to locally heat the optical fiber, only by laser irradiation and by adjusting the optical fiber movement speed, laser spot size and power, the corresponding compressive stress (strain) can be applied to the semiconductor three-dimensional micro-nano structure, thereby affecting the semiconductor's band structure. For direct bandgap materials, compressive strain usually leads to a decrease in the band gap. This is because compressive strain reduces the energy difference between the conduction band and the valence band, thereby reducing the band gap. For indirect bandgap materials, the effect of compressive strain may be more complicated. In some cases, compressive strain can lead to an increase in the band gap because compressive strain can change the position of the energy valley, making it more difficult for electrons to transition from the valence band to the conduction band.

[0035] (3) By placing the optical fiber in a tube furnace for low-temperature recrystallization treatment, adjusting the furnace temperature, holding time, and heating and cooling rates of the tube furnace, the corresponding tensile stress (strain) is applied to the semiconductor three-dimensional micro-nano structure, thereby affecting the semiconductor's band structure. For direct bandgap materials, tensile strain usually leads to an increase in the band gap. This is because tensile strain increases the energy difference between the conduction band and the valence band, thereby increasing the band gap. For indirect bandgap materials, the effect of tensile strain may also be more complicated. In some cases, tensile strain can lead to a decrease in the band gap because tensile strain can change the position of the energy valley, making it easier for electrons to transition from the valence band to the conduction band. The above processes do not require any complex processes such as deposition, sputtering or coating, nor do they rely on large and expensive equipment, which simplifies the manufacturing process and reduces production costs.

[0036] (4) The bandgap-adjustable semiconductor three-dimensional micro-nanostructure produced by the above-mentioned preparation device and method can not only meet the needs of semiconductors with different bandgap, but also facilitate high integration with electronic devices due to the adjustability of the semiconductor three-dimensional micro-nanostructure, especially the optional diameter size of the spherical shape, and can maintain good compatibility with traditional silicon-based devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a method for preparing a semiconductor three-dimensional micro-nano structure using a laser and adjusting the band gap of the semiconductor three-dimensional micro-nano structure provided in an embodiment of the present application; Figure 2 is a Raman spectrum of a semiconductor germanium sphere after laser induced recrystallization provided in an embodiment of the present application; Figure 3 It is a flow chart of a method for heating a semiconductor three-dimensional micro-nano structure using a tube furnace and adjusting the band gap of the semiconductor three-dimensional micro-nano structure provided in an embodiment of the present application; Figure 4 This is a comparison diagram of the Raman spectra of the semiconductor germanium sphere after laser induced recrystallization and low temperature recrystallization provided in the embodiments of the present application; Figure 5 This is a comparison diagram of the photoluminescence spectra of the semiconductor germanium sphere at room temperature after laser induced recrystallization and low temperature recrystallization provided in the examples of the present application; Figure 6 This is an optical microscope image of an independent semiconductor silicon sphere provided in an embodiment of the present application.

[0038] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1: Laser; 2: Camera; 3: Electric translation stage; 4: Control computer; 5: Semiconductor core optical fiber; 6: Semiconductor three-dimensional micro-nano structure. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0040] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0041] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0042] First, the technical terms involved in the embodiments of the present application are introduced.

[0043] (1) Indirect bandgap semiconductors: In indirect bandgap semiconductors, the bottom of the conduction band and the top of the valence band are not in the same Brillouin zone. When electrons jump from the conduction band to the valence band, they need to rely on phonons (lattice vibrations) to satisfy the momentum conservation condition. This makes the light emission and absorption efficiency low. Common indirect bandgap semiconductor materials include silicon, germanium and indium arsenide.

[0044] (2) Direct bandgap semiconductors: In direct bandgap semiconductors, the bottom of the conduction band and the top of the valence band are located in the same Brillouin zone. Electron transitions do not require the participation of phonons. The light emission and absorption efficiency is high, making them suitable for use in optoelectronic devices such as lasers and photodetectors. Common direct bandgap semiconductor materials include gallium arsenide, indium phosphide, and gallium nitride.

[0045] (3) Strain control technology: Strain control technology mainly changes the lattice structure and band structure of the material by applying stress, thereby achieving the control of the physical properties of the material. Strain type: mainly includes tensile strain and compressive strain. Common ways of applying stress include: stretching or compressing the material by mechanical means, introducing strain by thermal expansion or contraction of the material during heating or cooling, and introducing stress in the material through chemical reactions (such as chemical vapor deposition). Using different stress methods or applying different types of strain will have different effects on the material's band structure, electron mobility, carrier concentration, etc.

[0046] (4) Band structure: The band structure of solid materials is composed of multiple energy bands, which are divided into conduction band, valence band and forbidden band. The gap between the conduction band and the valence band is called forbidden band (energy gap).

[0047] (5) Semiconductor three-dimensional micro-nanostructures: semiconductor material structures with certain functions and at the micrometer or nanometer scale, which are formed by advanced micro-machining processes or material growth processes. These structures exhibit unique electronic, optical and thermal properties by precisely controlling the size, shape and surface characteristics of the material.

[0048] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0049] Embodiment 1 and embodiment 2 are explained by taking semiconductor core optical fiber with pure germanium as the core and aluminosilicate glass as the cladding as an example. This special optical fiber is selected as an embodiment mainly because its cladding and core have similar melting points, which can effectively avoid the situation where the semiconductor three-dimensional micro-nano structure in the optical fiber is broken due to excessive stress, so that a complete semiconductor three-dimensional micro-nano structure can be obtained later. According to the needs of practical applications, the cladding material is not limited to silica, but can also be silicates, borosilicates, phosphates, etc., and the physical properties of the cladding can be adjusted by doping different substances. In addition to germanium, the core can also be other materials that need to be made into micro-nano structures, such as silicon and other crystalline materials, II-VI materials such as Zns, CdTe, ZnSe, III-V materials such as InSb, InP, InAs, gold, tin, lithium or other alloys. However, no matter what materials the cladding and the core are, their thermal and mechanical properties should meet the requirements of the optical fiber melting hot drawing process and the formation of semiconductor three-dimensional micro-nano structures.

[0050] Embodiment 1: A device and method for producing semiconductor three-dimensional micro-nano structures and adjusting the band gap of semiconductor three-dimensional micro-nano structures by using a laser to control the cooling rate.

[0051] Reference Figure 1 The present application provides a device for producing and adjusting semiconductor three-dimensional micro-nano structures, including a laser 1, a camera 2 and an electric translation stage 3, and these three components are connected to a control computer 4. The electric translation stage 3 is used to place the semiconductor core optical fiber 5 and adjust the heating length and moving speed of the semiconductor core optical fiber 5; the laser 1 is placed vertically above the electric translation stage 3, and the size of the laser spot is changed by adjusting the height, and the emitted laser beam locally heats the semiconductor core optical fiber 5 on the electric translation stage 3; the camera 2 is located directly in front of the laser heating area, and is used to observe the temperature distribution of the semiconductor core optical fiber 5 during heating; the control computer 4 is used to regulate the moving distance and speed of the electric translation stage 3, and adjust the output power of the laser 1 and the image parameters of the camera 2. Figure 1 middle Indicates the moving speed of the optical fiber.

[0052] The working principle of using laser to produce semiconductor three-dimensional micro-nano structures is as follows: the semiconductor core optical fiber 5 used in this embodiment has different absorption coefficients of the germanium core and the cladding, so the energy of the laser is mainly absorbed by the core, and the absorbed laser energy liquefies the core. Under the action of capillary instability, due to the surface tension and viscoelastic force between the core and cladding materials, the liquefied cylindrical core splits into multiple droplets in the cladding. As the optical fiber moves away from the laser heating area, the cladding solidifies first because it has a higher melting point than the core, and then the spherical droplets gradually cool and solidify, such as Figure 1 As shown, a solid-state semiconductor three-dimensional micro-nano structure 6 with internal stress is finally formed.

[0053] The working principle of using laser to control cooling rate and adjust the band gap of semiconductor three-dimensional micro-nano structure is as follows: by adjusting the height of the laser, the size of the laser spot can be changed. By adjusting the size of the laser spot, the heat treatment cooling rate of the optical fiber can be further controlled. The size of the laser spot determines the size of the area where the optical fiber is irradiated by the laser. When other variables remain unchanged, the larger the spot size, the larger the area irradiated by the laser, the smaller the temperature gradient of the heated part of the optical fiber, and the slower the heat treatment cooling rate. Therefore, the cooling rate of the optical fiber can be regulated according to different laser spot sizes. When the spot size is large, the cooling rate is slow, and when the spot size is small, the cooling rate is fast. At the same time, the glass transition temperature, density and thermal expansion coefficient of the silica cladding decrease with a faster cooling rate. This is because the faster cooling rate reduces the time for the kinetic energy of the liquid to be converted into thermal energy, resulting in the structure of the liquid glass (cladding material) being solidified at a higher temperature. At an extremely fast cooling rate, the silica cladding still maintains the material properties at high temperature. At this time, the volume of the silica cladding is large, which further reduces the space for the micro-nano structure in the cladding and increases the compressive stress of the semiconductor three-dimensional micro-nano structure.

[0054] Based on the principle, a method for producing a semiconductor three-dimensional micro-nano structure using a laser and adjusting the band gap of the semiconductor three-dimensional micro-nano structure includes the following steps: Place the semiconductor core optical fiber 5 horizontally on the electric translation stage 3, and first use the laser 1 to emit low-power red light for calibration to ensure that the laser beam vertically illuminates the center of the optical fiber. Next, adjust the height of the laser to change the laser spot size, which will affect the heat treatment cooling rate of the optical fiber, resulting in changes in the internal stress of the semiconductor three-dimensional micro-nano structure. The control computer 4 adjusts the output power of the laser according to the melting point of the fiber core to ensure that the fiber core can melt. At the same time, the control computer 4 adjusts the electric translation stage 3 according to the required heating length and moving speed of the optical fiber to ensure that the optical fiber has enough heating time and heating temperature to form a semiconductor three-dimensional micro-nano structure 6. After the parameter setting is completed, the laser emits laser light, and the translation stage sends the optical fiber into the laser heating zone at the set speed.

[0055] Preferably, the image captured by the camera before production is used to determine whether an alternating solid-liquid interface appears in the heating area of ​​the optical fiber. If so, it indicates that the laser power and moving speed are appropriate. Otherwise, the laser power and moving speed need to be adjusted. Specifically, when the position and focal length of camera 2 are adjusted, and when the alternating solid-liquid interface appears in the heating area of ​​the optical fiber through camera 2, it indicates that the appropriate laser power has been reached, and a string of droplets begins to slowly form. The image of the alternating solid-liquid interface not only shows the morphological changes of the optical fiber during heat treatment, but also can be used to accurately calculate the cooling rate of the optical fiber. By extracting the radiation intensity distribution in the picture, the blackbody radiation principle can be used to quantify the temperature distribution, thereby drawing the temperature distribution curve of the optical fiber during heat treatment and calculating the cooling rate. The blackbody radiation calculation formula is as follows: ; in, is the first radiation constant, is the second radiation constant. By precisely controlling the cooling rate, the internal stress and band gap size of the semiconductor three-dimensional micro-nanostructure can be effectively adjusted.

[0056] As the optical fiber gradually moves away from the heating zone, the spherical droplets solidify to form a solid semiconductor three-dimensional micro-nanostructure 6.

[0057] Preferably, the compressive stress of the semiconductor is regulated by simply changing the size of the laser spot, thereby affecting the band gap. Set the moving speed of the optical fiber to 10 , while keeping the moving speed unchanged, laser beams with different spot diameters are used in turn, which are 1000 , 800 , 600 , 400 When replacing a laser beam with a different spot diameter, the laser power also needs to be adjusted according to the melting point of the semiconductor core.

[0058] The Raman spectrum of the semiconductor germanium sphere prepared by the parameters is as follows: Figure 2 As shown, compared with the Raman peak of the germanium wafer, the diameter of the laser spot is 1000 , 800 , 600 , 400 The Raman peak shifts of the germanium spheres prepared at , 3.85 , 4.59 and 5.33 .

[0059] For germanium materials, the shift of the first-order Raman peak is related to pressure. The relationship between them is: ; Here is the first-order derivative, that is and The rate of change between .

[0060] When the deformation does not exceed a certain elastic limit of the corresponding material, the relationship between stress and strain is: ; For germanium materials, is Young's modulus, taken as 103GPa, is stress, For strain.

[0061] According to the calculation formula, the compressive stress of the semiconductor germanium ball is 0, 0.99±0.07, 1.18±0.06 and 1.37±0.07 GPa respectively. The compressive strain is 0%, 0.96%±0.07%, 1.15%±0.06% and 1.33%±0.07% respectively.

[0062] Example 2: A method for adjusting the band gap of a semiconductor three-dimensional micro-nano structure by controlling the cooling rate using a tube furnace.

[0063] Based on the method described in Example 1, Figure 3 As shown, the method for adjusting the band gap of a semiconductor three-dimensional micro-nano structure using a tube furnace in this embodiment may include operations 7 to 9.

[0064] In operation 7, the optical fiber is placed in a tubular furnace. Since it is difficult to directly fix the optical fiber in the furnace, it is necessary to use high temperature resistant glue to fix the optical fiber on a glass slide first to ensure its stability during the heating process.

[0065] In operation 8, the tube furnace is evacuated, wherein, since the semiconductor material is easy to react with oxygen at high temperature to generate oxides, in order to avoid this, it is necessary to ensure that the tube furnace is in a vacuum environment to prevent oxidation of the semiconductor material.

[0066] In operation 9, the tube furnace program is set, including the furnace temperature, the holding time, and the heating and cooling rates. These three parameters will affect the low-temperature recrystallization process of the semiconductor.

[0067] Among them, the temperature in the furnace is the recrystallization temperature of the semiconductor, which needs to be set below the melting point of the semiconductor material to ensure that the material does not melt. The holding time needs to be set sufficiently so that the semiconductor can be fully affected by the thermal stress and allow the crystal to have enough time to grow and rearrange. The cooling rate is the cooling rate of the optical fiber, which will affect the crystallization degree of the semiconductor. Therefore, it is necessary to select an appropriate cooling rate to ensure that the internal stress of the semiconductor three-dimensional micro-nano structure can still be retained after cooling.

[0068] Preferably, the optical fiber described in Example 1 is transferred to a pure The optical fiber is fixed on the glass slide with a high temperature resistant glue. Then, the glass slide with the optical fiber is placed in the tube furnace, and the inside of the tube furnace is first vacuumed. Then, the tube furnace is set to heat at a specific heating rate until the reaction temperature reaches 200 and keep it at that temperature for more than 1 hour. The cooling rate is reduced to room temperature at a rate of 1000 ℃ / min, which causes the semiconductor three-dimensional micro-nano structure to undergo a low-temperature recrystallization process and generate tensile stress inside the semiconductor three-dimensional micro-nano structure, thereby further modifying the semiconductor three-dimensional micro-nano structure with adjusted band gap.

[0069] The Raman spectrum of the semiconductor germanium ball prepared in Example 2 is as follows: Figure 4 As shown, compared with the Raman peaks of the germanium wafer and the semiconductor germanium ball prepared in Example 1, the Raman peak shifts of the germanium balls prepared in Example 1 and Example 2 are 3.73 and 1.33, respectively. , -2.63 (Left shift is negative).

[0070] For germanium materials, the Raman peak shift and tensile strain The calculation formula is: ; is a linear coefficient, for example, it can be -395 .

[0071] According to the above calculation formula, the semiconductor germanium balls prepared in Example 1 and Example 2 can be converted into corresponding stress and strain, and the stress magnitudes are respectively 0.96±0.05GPa for compressive stress and 0.69GPa for tensile stress. The strain magnitudes are respectively 0.93%±0.05% for compressive strain and 0.67% for tensile strain.

[0072] In order to characterize the effect of applied stress on semiconductor bandgap regulation, Figure 5 The comparison of the room temperature photoluminescence spectra of the semiconductor germanium balls with compressive and tensile stress prepared by Example 1 and Example 2 is shown. Germanium is an indirect bandgap semiconductor. Taking the direct bandgap energy of the germanium wafer of 0.82eV as the reference point, the characteristic peaks of the room temperature fluorescence spectra of the semiconductor germanium balls prepared by Example 1 and Example 2 are all shifted to the right, indicating that the direct bandgap energy is reduced under the action of stress. Moreover, under the action of compressive stress, the characteristic peak of the room temperature fluorescence spectrum of the semiconductor germanium ball at 0.94eV shows a bandgap splitting, forming a new characteristic peak of the fluorescence spectrum, which enhances the possibility of direct electron transition in the germanium material, and may even induce the transformation of the germanium material from an indirect bandgap semiconductor to a direct bandgap semiconductor.

[0073] It should be noted that the semiconductor three-dimensional micro-nano structure after Example 1 is used in this embodiment to facilitate the comparison of semiconductor band gap characteristics and the subsequent preparation of semiconductor three-dimensional micro-nano structures. However, this embodiment is not limited to the use of processed semiconductor three-dimensional micro-nano structures, and unprocessed semiconductor optical fibers can also achieve the purpose of adjusting the band gap by using this method.

[0074] Example 3: A method for preparing a semiconductor three-dimensional micro-nano structure with tunable band gap to obtain a semiconductor three-dimensional micro-nano structure with adjustable band gap, selectable shape and controllable size.

[0075] Example 3 is explained by taking a semiconductor core optical fiber with pure silicon as the core and silicon dioxide as the cladding as an example. Since hydrofluoric acid can corrode silicon dioxide, but it is not easy to react chemically with semiconductors. By corroding the optical fiber cladding with hydrofluoric acid, the optical fiber cladding can be effectively removed while maintaining the structural integrity of the semiconductor three-dimensional micro-nano structure. Afterwards, the residual hydrofluoric acid and its reaction products are removed by cleaning, thereby obtaining a group of independent semiconductor three-dimensional micro-nano structures with adjustable band gap.

[0076] like Figure 6 The figure shows an optical microscope image of an independent semiconductor silicon sphere. The diameter of the semiconductor sphere is about 126 .

[0077] The semiconductor ball is a silicon core optical fiber that passes through a laser spot size of 1000 , laser power is 25W, fiber moving speed is 5 Prepared.

[0078] The larger the diameter of the fiber core, the larger the size of the semiconductor three-dimensional micro-nano structure. Fiber cores of different diameters are selected according to the needs, and the size of the semiconductor three-dimensional micro-nano structure prepared by the preparation method of Example 1 will be different accordingly. Since the spherical structure has a high degree of symmetry and the stress generated inside is more stable, it is easier to achieve precise size control of the semiconductor ball. The calculation formula for the diameter of the semiconductor ball is as follows: ; is the diameter of the semiconductor ball, is the diameter of the fiber core, is the moving speed of the optical fiber, is the viscosity of the cladding at the heating temperature, is the interfacial tension between the cladding and the core at the heating temperature.

[0079] Therefore, semiconductor three-dimensional micro-nano structures can achieve adjustable band gap, selectable shape, and controllable size. By precisely controlling the size of semiconductor three-dimensional micro-nano structures, fine regulation of material properties can be achieved. Independent semiconductor three-dimensional micro-nano structures can be integrated into electronic devices while maintaining stress, thereby meeting the diverse needs of semiconductor materials with different band gaps in various application fields.

[0080] It is understandable that the present application uses a laser to perform local heating treatment on an optical fiber with a semiconductor as the core, and anneals it through a tubular furnace, and finally releases a semiconductor three-dimensional micro-nano structure from the optical fiber. The present application achieves bandgap regulation of the semiconductor bandgap structure by controlling the cooling rate of the heating source and introducing stresses of different types and sizes. The obtained semiconductor three-dimensional micro-nano structure can be used as an independent three-dimensional optical and acoustic element material, suitable for the construction of electronic devices.

[0081] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap, characterized in that: include: The semiconductor core optical fiber is heated according to the target heating temperature, and the cooling rate of the optical fiber is controlled. The heating process and the cooling rate have a corresponding relationship with the stress applied to the core and the semiconductor three-dimensional micro-nano structure in the optical fiber. The stress can tune the band gap of the semiconductor three-dimensional micro-nano structure. Among them, when the target heating temperature is higher than the melting point of the fiber core, the optical fiber is locally heated to apply compressive stress to the fiber core so that the fiber core forms a semiconductor three-dimensional micro-nano structure; when the target heating temperature is lower than the melting point of the fiber core, the optical fiber is heated as a whole to make the semiconductor three-dimensional micro-nano structure recrystallize, and the volume difference between the recrystallized structure and the original structure is used to apply tensile stress to the semiconductor three-dimensional micro-nano structure and tune the band gap structure.

2. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 1, characterized in that: The step of heating the semiconductor core optical fiber according to the target heating temperature and controlling the cooling rate of the optical fiber during cooling includes: The target area is heated by a first heating source. During the heating process, various parts of the optical fiber enter and leave the target area at a target moving speed so that the core forms a semiconductor three-dimensional micro-nano structure. The target area and the optical fiber are located on the same horizontal plane. The target heating temperature is specifically the temperature at the center of the target area. The temperature at the center of the target area is higher than the melting point of the core of the optical fiber. The optical fiber has a first cooling rate in the process of leaving the target area.

3. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 2, characterized in that: When the first heating source uniformly heats the target area, the semiconductor three-dimensional micro-nano structure is spherical in shape; When the first heating source performs non-uniform heating on the target area, the shape of the semiconductor three-dimensional micro-nano structure is non-spherical.

4. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 2, characterized in that: The first heating source is a laser. Before the target area is heated by the first heating source, the method further includes: The height of the laser is adjusted to determine the spot size formed by the laser emitted by the laser in the target area. The spot size affects the cooling rate. The smaller the spot size, the faster the cooling rate.

5. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 4, characterized in that: Also includes: Acquire an image of the optical fiber in the target area; Displaying an image and receiving a target input, the image is used to calculate and quantify the value of the cooling rate using the black body radiation principle, and the target input is used to indicate the adjustment amount of the moving speed and the adjustment amount of the output power of the laser; In response to the target input, the target moving speed of the optical fiber and the output power of the laser are controlled based on the adjustment amount of the moving speed and the adjustment amount of the output power.

6. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 2, characterized in that: Also includes: The optical fiber is carried by a translation stage, and the translation stage is used to carry the optical fiber and move at a target moving speed during the process of heating the target area by the first heating source.

7. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 1, characterized in that: The step of heating the semiconductor core optical fiber according to the target heating temperature and controlling the cooling rate of the optical fiber during cooling includes: The optical fiber treated by the first heating source is heated as a whole by a second heating source to recrystallize the semiconductor three-dimensional micro-nano structure in the optical fiber. The target heating temperature provided by the second heating source for the optical fiber is lower than the melting point of the fiber core. The overall heating process includes a heating stage from a preset temperature to a target heating temperature, a heat preservation stage, and a cooling stage from the target heating temperature to a preset temperature. The cooling stage has a second cooling rate.

8. The method for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap according to claim 7, characterized in that: The second heating source is a tube furnace; The tubular furnace is used to carry the optical fiber containing semiconductor three-dimensional micro-nano structure after being treated by the first heating source, and adjust the temperature in the furnace according to the target furnace temperature, heating rate, cooling rate and insulation time under a vacuum environment. The target furnace temperature is the target heating temperature, and the cooling rate is the second cooling rate.

9. A device for preparing a semiconductor three-dimensional micro-nano structure with tunable bandgap, characterized in that: include: Carrying table and heating module; The carrier is used to place the optical fiber; The heating module is used to heat according to the target heating temperature and control the cooling rate when the optical fiber is cooled. The heating process and the cooling rate have a corresponding relationship with the stress applied to the core and the semiconductor three-dimensional micro-nano structure in the optical fiber. The stress can tune the band gap of the semiconductor three-dimensional micro-nano structure. Among them, when the target heating temperature is higher than the melting point of the fiber core, the optical fiber is locally heated to apply compressive stress to the fiber core so that the fiber core forms a semiconductor three-dimensional micro-nano structure; when the target heating temperature is lower than the melting point of the fiber core, the optical fiber is heated as a whole to make the semiconductor three-dimensional micro-nano structure recrystallize, and the volume difference between the recrystallized structure and the original structure is used to apply tensile stress to the semiconductor three-dimensional micro-nano structure and tune the band gap structure.

10. A semiconductor three-dimensional micro-nano structure, characterized in that: The semiconductor three-dimensional micro-nano structure is prepared by applying the method for preparing a semiconductor three-dimensional micro-nano structure with tunable band gap as described in any one of claims 1-8.

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