Electric injection quantum dot vertical cavity surface emitting laser and preparation method thereof

Abstract

The invention relates to an electric injection quantum dot vertical cavity surface emitting laser and a preparation method thereof. The laser structure comprises a substrate, a bottom reflector, a first current expansion layer, a waveguide layer, an electron injection layer, an active layer, a hole injection layer, a second current expansion layer and a top reflector. A corresponding top reflector is arranged in an opening area in the waveguide layer and serves as a resonant cavity of the laser, and a light field is guided by the waveguide layer to be efficiently oscillated and amplified in the resonant cavity. In the preparation process, good lattice matching between the bottom reflector and the substrate is ensured through epitaxial growth, interface defects and stress are reduced, low-cost methods such as spraying, spin coating and ink-jet printing are used, operation is easy and convenient, and large-area preparation can be achieved. The laser realizes bottom light emission, optimizes current injection, improves light emission and heat dissipation performance, controls a resonant cavity light field to improve device performance, and has the advantages of low power consumption, high light beam collimation and the like.

Description

Technical Field

[0001] This application relates to the technical field of vertical cavity surface emitting lasers, and particularly to an electrically injected quantum dot vertical cavity surface emitting laser and a preparation method thereof. Background Art

[0002] As a cutting-edge technology in the field of semiconductor lasers, quantum dot vertical cavity surface emitting lasers (VCSELs) show great application potential in industries such as displays, augmented reality (AR), and virtual reality (VR). In recent years, significant progress has been made in this field. Traditional VCSEL devices have made breakthroughs in structural design, fabrication processes, and performance improvement. Some products have been commercially applied and show certain advantages in terms of beam quality, power consumption, etc.

[0003] However, the existing quantum dot VCSEL technology still faces many problems that need to be solved urgently. In terms of the light output mode, most VCSEL devices adopt a top-emitting structure, which has certain limitations in practical applications. For example, when integrating with some optical systems, it may face difficulties in spatial layout and optical path design. In terms of current injection, traditional current injection methods often require additional electrode preparation processes, which not only increase the fabrication cost and complexity of the device but may also cause the current congestion effect, resulting in a decline in device performance.

[0004] In the selection of substrate materials, some of the currently used substrate materials have deficiencies in conductivity, light output performance, and heat dissipation ability. For example, some substrate materials have poor conductivity, which affects the current injection efficiency; the light output performance is limited, resulting in low beam collimation and severe speckle phenomena; the heat dissipation ability is poor, making the device prone to overheating during operation, which in turn limits the thermal tolerance and threshold current density of the device and is not conducive to the realization of quantum dot VCSEL lasing.

[0005] In addition, the control of the optical field in the resonant cavity is also a key issue. Existing VCSEL devices have large lateral leakage of the optical field and large diffraction losses in the resonant cavity, which will lead to an increase in the Q value of the resonant cavity and affect the laser performance and efficiency of the device. At the same time, the current injection range is large, making it difficult to effectively increase the current injection density of the device, further restricting the optimization of device performance. In summary, it is of great significance to develop a quantum dot vertical cavity surface emitting laser that can achieve bottom emission, optimize the current injection method, have excellent light output performance and heat dissipation ability, and can effectively control the optical field in the resonant cavity. Summary of the Invention

[0006] The object of the present application is to provide an electrically injected quantum dot vertical cavity surface emitting laser and a manufacturing method thereof. Through specific structural design and material selection, bottom emission, optimized current injection, improved light emission and heat dissipation performance, and control of the resonant cavity optical field are achieved to improve the device performance. This laser has advantages such as low power consumption and high beam collimation. The object of the present application is achieved through the following technical solutions. The electrically injected quantum dot vertical cavity surface emitting laser of the present application includes a substrate, a bottom mirror, a first current spreading layer, a waveguide layer, an electron injection layer, an active layer, a hole injection layer, a second current spreading layer, a top mirror, and a top electrode; The bottom mirror is formed on the substrate, the first current spreading layer is formed on the bottom mirror, and the waveguide layer is located between the first current spreading layer and the electron injection layer; The waveguide layer includes a plurality of opening regions, and each opening region has a corresponding top mirror; Wherein, the bottom mirror under the opening region and the corresponding top mirror serve as the resonant cavity of a laser.

[0007] In one embodiment, the area of the top mirror is larger than the area of the opening region in the waveguide layer corresponding to the top mirror, and the top mirror completely covers the opening region.

[0008] In one embodiment, each resonant cavity includes a corresponding second current spreading layer, and the area of the second current spreading layer is larger than the area of the top mirror corresponding to the second current spreading layer.

[0009] In one embodiment, the waveguide layer is formed of a current confinement material.

[0010] In one embodiment, the active layer is a colloidal quantum dot material, the material of the substrate is GaN, the bottom mirror is a GaN / AlInN mirror or an air-gap GaN DBR, and the top mirror is selected from a dielectric film DBR, a grating, or a photonic crystal.

[0011] In addition, the present application further provides a method for manufacturing an electrically injected quantum dot vertical cavity surface emitting laser, including: Forming a bottom mirror on the substrate by an epitaxial growth method; Forming a first current spreading layer on the bottom mirror; Forming a waveguide layer on the first current spreading layer, and forming opening regions in the waveguide layer; Successively forming an electron injection layer, an active layer, and a hole injection layer; Forming a second current spreading layer on the hole injection layer; A top mirror is formed on the second current spreading layer, and the top mirror covers the opening area in the waveguide layer in the vertical projection direction; Wherein, the bottom mirror and the corresponding top mirror under the opening area in the waveguide layer serve as the resonant cavity of a laser.

[0012] In one embodiment, the step of forming the top mirror includes patterning the material layer for forming the top mirror.

[0013] In one embodiment, the area of the top mirror is larger than the area of the opening area in the waveguide layer.

[0014] In one embodiment, an electron injection layer and a hole injection layer are formed by spraying or spin coating, and a colloidal quantum dot layer is prepared as the active layer by inkjet printing, photolithography or spin coating.

[0015] In one embodiment, it further includes the step of forming a top electrode.

[0016] Compared with the prior art, the present application has the following beneficial effects: Through a unique structural design, the present application realizes a bottom-emitting VCSEL device. Structurally, the bottom mirror is formed on the substrate, the first current spreading layer is formed on the bottom mirror, the waveguide layer is located between the first current spreading layer and the electron injection layer, and there are multiple opening areas in the waveguide layer, each opening area corresponding to a top mirror, and the bottom mirror and the corresponding top mirror under the opening area constitute the resonant cavity of the laser. It effectively solves the problems of spatial layout and optical path design faced by the traditional top-emitting structure in practical applications, and provides greater flexibility for the integration and application of the device.

[0017] Using a conductive nitride DBR as the bottom mirror can not only serve as a current injection channel, eliminating the need for additional electrode preparation, simplifying the manufacturing process and reducing costs, but also enabling a vertical current injection method, avoiding the current congestion effect and improving the current injection efficiency. At the same time, a current confinement layer is provided between the waveguide layer and the first current spreading layer, further reducing the device current injection range and increasing the device current injection density, enabling the device to achieve efficient laser emission at a lower current and reducing energy consumption.

[0018] Selecting GaN can, on the one hand, serve as an electrode for current injection, ensuring stable current injection; on the other hand, due to its transparent property, it becomes an excellent light-emitting surface material, enhancing the beam collimation, reducing the speckle phenomenon, and improving the quality of the laser. In addition, the high heat dissipation of the nitride material improves the heat dissipation capacity of the device, enhances the thermal tolerance and threshold current density of the device, provides an important guarantee for realizing the lasing of the quantum dot VCSEL, enables the device to operate stably in a high-temperature environment, extends the service life of the device, and at the same time avoids the thermal quenching phenomenon of the colloidal quantum dot material caused by high temperature.

[0019] The synergistic effect of the current confinement layer and the waveguide layer realizes effective control of the optical field in the resonator. The current confinement layer and the waveguide layer achieve three-dimensional confinement in the physical dimension, reducing the lateral leakage and diffraction loss of the optical field in the resonator, lowering the Q value of the resonator, not only improving the performance and efficiency of the laser, but also enabling the device to output laser more stably, reducing the fluctuations and interference of the optical field, and providing the possibility for high-precision and high-stability laser applications. The electrically injected quantum dot vertical cavity surface emitting laser prepared by this application has advantages such as low power consumption and high beam collimation, and has broad application prospects in fields such as display, augmented reality (AR), and virtual reality (VR). Brief Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of the electrically injected quantum dot vertical cavity surface emitting laser according to an embodiment of this application; Figure 2 is a schematic flow diagram of the preparation method of the electrically injected quantum dot vertical cavity surface emitting laser according to an embodiment of this application; Figure 3 is a schematic structural diagram of the preparation process of the electrically injected quantum dot vertical cavity surface emitting laser according to an embodiment of this application.

[0021] Description of the reference numerals: 100, substrate; 200, bottom mirror; 300, first current spreading layer; 400, waveguide layer; 510, electron injection layer; 520, active layer; 530, hole injection layer; 600, second current spreading layer; 700, top mirror; 800, top electrode. Detailed Description of the Embodiments

[0022] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings. It can be understood that the specific embodiments described herein are only for explaining the present application and not for limiting the present application. Additionally, it should be noted that for ease of description, only the parts related to the present application rather than all structures are shown in the drawings. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0023] The terms "including" and "having" and any variations thereof in the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0024] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears at various positions in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0025] In the current context of the rapid development of semiconductor laser technology, electrically injected quantum dot vertical cavity surface emitting lasers (VCSELs) exhibit great application potential in numerous fields such as displays, augmented reality (AR), and virtual reality (VR) due to their unique advantages. However, existing VCSEL technologies suffer from problems such as limited light emission mode, low current injection efficiency, poor heat dissipation performance, and difficulty in controlling the optical field of the resonant cavity, severely restricting the further improvement of their performance and the expansion of their application scope. To overcome these technical bottlenecks, the present application proposes a new electrically injected quantum dot vertical cavity surface emitting laser, achieving a bottom light emission structure, optimizing the current injection method, improving the light emission performance and heat dissipation ability, and effectively controlling the optical field of the resonant cavity. Next, the specific structure and fabrication method of the electrically injected quantum dot vertical cavity surface emitting laser in the present application will be introduced in detail. Please refer to Figure 1, the electrically injected quantum dot vertical cavity surface emitting laser of the present application includes a substrate 100, a bottom mirror 200, a first current spreading layer 300, a waveguide layer 400, an electron injection layer 510, an active layer 520, a hole injection layer 530, a second current spreading layer 600, a top mirror 700 and a top electrode 800. The bottom mirror 200 is formed on the substrate 100, the first current spreading layer 300 is formed on the bottom mirror 200, the waveguide layer 400 is located between the first current spreading layer 300 and the electron injection layer 510, and the waveguide layer 400 includes a plurality of opening regions, and each opening region has a corresponding top mirror 700. Among them, the bottom mirror 200 under the opening region and the corresponding top mirror 700 serve as the resonant cavity of a laser.

[0026] In the structure of the laser of the present application, the substrate 100 serves as the support of the device and provides a platform for the growth and formation of other layer structures. In a preferred technical solution, the substrate 100 has electrical conductivity and can serve as a current introduction channel to provide a path for the current injection of the device. The bottom mirror 200 is formed on the substrate 100 to provide a reflection structure layer for the photon oscillation and the formation of laser. The first current spreading layer 300 is formed on the bottom mirror 200 to expand the distribution range of the current, so that the current can be more evenly distributed and injected, avoiding the problems of local overheating and performance degradation caused by current concentration. The electron injection layer 510, the active layer 520 and the hole injection layer 530 are sequentially formed on the waveguide layer 400 to jointly constitute the light emitting region of the laser. The second current spreading layer 600 is formed on the hole injection layer 530, and the top mirror 700 is located on the second current spreading layer 600.

[0027] The waveguide layer 400 is located between the first current spreading layer 300 and the electron injection layer 510, and it guides and confines the optical field. The waveguide layer 400 has a plurality of carefully designed opening regions, and each opening region corresponds to a top mirror 700. The bottom mirror 200 under the opening region and the corresponding top mirror 700 jointly constitute the resonant cavity of a laser. The laser can oscillate and amplify efficiently in the resonant cavity. The top mirror 700 completely covers the opening region in the waveguide layer 400 in the vertical projection direction, can effectively reflect light, and together with the bottom mirror 200 forms a stable resonant cavity.

[0028] The resonant cavity formed by the opening region in the waveguide layer 400 and the corresponding top mirror 700 is the core part of the laser in this application. The waveguide layer 400 can guide the optical field to oscillate and amplify efficiently within the resonant cavity. The design of the opening region realizes the three-dimensional confinement in physical dimensions, reducing the lateral leakage and diffraction loss of the optical field in the resonant cavity, decreasing the Q value of the resonant cavity, not only improving the performance and efficiency of the laser, but also making the output of the laser more stable and the beam quality better. Meanwhile, the design with multiple opening regions corresponding to multiple resonant cavities enables the independent output of multiple laser beams, providing the possibility for multi-beam applications of the laser. Most critically, the device structure of this application can greatly simplify the manufacturing method while ensuring the output effect, which will be elaborated in detail in the subsequent manufacturing method section.

[0029] The first current spreading layer 300 and the second current spreading layer 600 can select transparent conductive thin films, specifically, it can be indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), fluorine-doped tin oxide (FTO) and other thin films, which are deposited by physical vapor deposition during the preparation process. The waveguide layer 400 is formed using AlN material. The materials of the electron injection layer 510 include but are not limited to: ZnMgO, TCTA, ZnO. The materials of the hole injection layer 530 include but are not limited to: PEDOT:PSS / TFB, PEDOT:PSS / PF8Cz, PVK, ZnO / ZnMgO. The above materials are some specific examples, and other applicable materials in each layer can also be used.

[0030] In the specific design structure, the area of the top mirror 700 is larger than the area of the opening region in the corresponding waveguide layer 400. The top mirror 700 completely covers the opening region in the waveguide layer 400 in terms of position, and they correspond in the vertical projection direction. The larger area of the top mirror 700 means that it can more effectively limit the escape of photons with large-angle radiation. In the resonant cavity of the laser, photons will reflect back and forth between the bottom mirror 200 and the top mirror 700 to form optical oscillation. The larger area of the top mirror 700 completely reflects the large-angle photons, reducing the scattering and loss of photons, and enabling the photons to participate in the resonant process. If the top mirror 700 cannot completely cover the opening region, some photons may leak out from the opening edge, resulting in a weakening of the optical amplification ability and a reduction in the quality and stability of the laser. The design of complete coverage can avoid this situation, enabling the optical field to oscillate more concentratedly and stably within the resonant cavity, thereby generating a high-quality and high-stability laser output, which helps to better shape and confine the laser beam, making the laser beam have better collimation.

[0031] Specifically, each of the resonant cavities includes a corresponding second current spreading layer 600, and the area of the second current spreading layer 600 is larger than the area of the top mirror 700 corresponding to the second current spreading layer 600. The larger area of the second current spreading layer 600 than that of the top mirror 700 allows for a broader distribution space of the current on the second current spreading layer 600. The uniform current distribution helps to ensure the uniform injection of holes in the active layer 520, thereby improving the light-emitting efficiency of the quantum dot active layer 520. The larger area of the second current spreading layer 600 can increase the contact area with the top mirror 700 and other adjacent layers, thus reducing the contact resistance.

[0032] In a further technical solution of the specific structure, the waveguide layer is formed of a current confinement material, that is, the waveguide layer 400 also serves as a current confinement layer, which can effectively confine the injection range of the current, causing the current to be mainly concentrated in a specific area. The current confinement layer can ensure that electrons can be accurately injected into the designed position of the active layer 520. The current confinement layer and the waveguide layer 400 work together to further enhance the light field confinement ability of the resonant cavity. The waveguide layer 400 itself has the function of guiding the light field, and as a current confinement layer, it can prevent electrons from entering the active layer 520 at undesired positions, keeping the position of the resonant cavity at a specific location, so that the light field needs to be reflected and oscillated multiple times between the specific bottom mirror 200 and the top mirror 700. The waveguide layer 400 also confines the size of the light-emitting area in the active layer 520 by restricting the current injection range, making the light field more concentratedly distributed in the resonant cavity. In another technical solution, the waveguide layer 400 can adopt a double-layer structure, and the layer in contact with the first current spreading layer 300 serves as the current confinement layer.

[0033] In terms of specific material selection, the active layer 520 uses colloidal quantum dot materials, the substrate uses GaN, and the bottom mirror 200 uses a GaN / AlInN mirror or an air-gap GaN DBR, which has good lattice matching with the GaN substrate. The top mirror 700 uses a dielectric mirror, a grating, or a photonic crystal. The dielectric mirror has advantages such as high reflectivity and wide bandwidth. Selecting these material combinations can greatly reduce the differences between material layers, which is crucial for fabricating devices using the epitaxial growth method, can effectively reduce the dislocation density, and improve the quality and performance of the devices. Additionally, in a preferred solution, the reflectivity of the top mirror 700 is greater than that of the bottom mirror 200, which is beneficial for light output from the bottom.

[0034] There is a good lattice match between the GaN substrate and the GaN / AlInN bottom mirror 200. During the semiconductor epitaxial growth process, lattice mismatch is one of the main causes of dislocation generation. When the lattice constants of two materials differ significantly, the growth process is difficult to control, stress will be generated at the interface, leading to the formation of dislocations. However, the high lattice match between GaN and GaN / AlInN can reduce the stress at the interface and the probability of dislocation generation. The GaN / AlInN bottom mirror 200 can achieve uniform and continuous epitaxial growth on the GaN substrate 100. The preparation of the dielectric mirror can also be compatible with the previous epitaxial growth process, ensuring the material layer quality of the entire device, thereby reducing the requirements for production equipment and simplifying the device manufacturing process.

[0035] The active layer 520 can be a light-emitting layer formed by colloidal quantum dots, which can be formed by processes such as inkjet printing, lithography, and spin coating. The core-shell structure quantum dots include but are not limited to cadmium sulfide (CdSe), cadmium telluride (CdTe), cadmium sulfide (CdS), zinc selenide (ZnSe), zinc telluride (ZnTe), zinc sulfide (ZnS), copper indium sulfide (CuInS), copper indium selenium sulfide (CuInSeS), silver indium sulfide (AgInS), silver indium selenium sulfide (AgInSeS), indium phosphide (InP), copper zinc selenide (CuZnSe), zinc manganese selenide (ZnMnSe), lead sulfide (PbS), lead selenide (PbSe), Cd-based alloy materials, In-based alloy materials, Zn-based alloy materials, or perovskite materials, etc.; In addition, the core-shell size adjusts relevant light-emitting parameters according to different materials and emission wavelengths. The top mirror 700 uses a dielectric mirror, and the materials include but are not limited to: titanium dioxide (TiO2) / silicon dioxide (SiO2), hafnium dioxide (HfO2) / silicon dioxide (SiO2).

[0036] The bottom mirror 200 can also be a porous mirror. The porous mirror usually has a high reflectivity and can effectively reflect photons, providing sufficient optical feedback for the oscillation of the laser in the resonant cavity. Its porous structure results in extremely low light absorption loss of the reflective layer. Compared with traditional mirrors, it can reduce the loss of light energy during the reflection process and improve the output efficiency of the laser. The high reflectivity of the porous mirror can ensure multiple reflections and amplifications of the laser in the resonant cavity, thereby generating a stronger and more stable laser output.

[0037] The laser also includes an upper electrode connected to the second current spreading layer 600. The upper electrode is connected to the second current spreading layer 600, providing an efficient and stable injection path for holes, reducing the resistance and loss during current transmission, and improving the current injection efficiency. The connection between the upper electrode and the second current spreading layer 600, due to the separate resonant cavity design corresponding to the second current spreading layer 600 and combined with the waveguide layer 400, can achieve independent control of a single resonant cavity.

[0038] In addition, the present application further provides a method for fabricating an electrically injected quantum dot vertical cavity surface emitting laser. Please refer to Figure 2 and Figure 3 . The fabrication method specifically includes: forming a bottom mirror 200 on a substrate 100 by epitaxial growth, forming a first current spreading layer 300 on the bottom mirror 200, forming a waveguide layer 400 on the first current spreading layer 300, forming an opening region in the waveguide layer 400, sequentially forming an electron injection layer 510, an active layer 520, and a hole injection layer 530, forming a second current spreading layer 600 on the hole injection layer 530, and forming a top mirror 700 on the second current spreading layer 600. The top mirror 700 covers the opening region in the waveguide layer 400 in the vertical projection direction. Among them, the bottom mirror 200 and the corresponding top mirror 700 under the opening region in the waveguide layer 400 serve as a resonant cavity of a laser.

[0039] In the fabrication method, first, a bottom mirror 200 is formed on a substrate 100 by epitaxial growth. Epitaxial growth can ensure a good lattice match between the bottom mirror 200 and the substrate 100, reduce interface defects and stress. The material selection of the bottom mirror 200 is crucial. For example, a GaN / AlInN mirror is used, which has a good lattice match with the common GaN substrate 100 and can effectively reduce the dislocation density. Then, a first current spreading layer 300 is formed on the bottom mirror 200. The function of the first current spreading layer 300 is to expand the current distribution range so that the current can be more evenly distributed to the subsequent structures. Physical vapor deposition and other methods can be used to deposit transparent conductive thin films such as ITO, IZO, AZO, FTO, etc. These thin films have good conductivity and transparency and can effectively achieve current spreading and transmission.

[0040] Then, a waveguide layer 400 is formed on the first current spreading layer 300. The formation of the waveguide layer 400 requires precise control of parameters such as its size and refractive index to ensure that it can effectively guide and confine the optical field. An opening region is formed in the waveguide layer 400 through processes such as photolithography and etching. The design of the opening region is the key to realizing multiple independent resonant cavities, and each opening region corresponds to an independent laser resonant cavity. Subsequently, an electron injection layer 510, an active layer 520, and a hole injection layer 530 are sequentially formed, and a second current spreading layer 600 is formed on the hole injection layer 530. The function of the second current spreading layer 600 is similar to that of the first current spreading layer 300, further expanding the current distribution range to ensure uniform injection of holes in the active layer 520. A top mirror 700 is formed on the second current spreading layer 600. The top mirror 700 completely covers the opening region in the waveguide layer 400 in the vertical projection direction, can effectively reflect photons, and together with the bottom mirror 200 forms a stable resonant cavity. The area of the top mirror 700 is larger than the opening region, which can more effectively limit the escape of photons with large-angle radiation, reduce the scattering and loss of photons, enable photons to fully participate in the resonant process, and thus improve the quality and stability of the laser.

[0041] When forming the waveguide layer 400, insulating materials such as silicon dioxide or aluminum nitride can be used and prepared through precise epitaxial growth processes. Its thickness is usually precisely adjusted according to the design requirements and performance requirements of the laser, generally ranging from dozens to hundreds of nanometers. The waveguide layer 400, as a current confinement layer at the same time, can precisely confine the electron injection range within a specific area, ensure that electrons can be accurately injected into the designated position of the active layer 520, enhance the ability of the resonant cavity to confine the optical field, reduce the generation of unexpected optical fields, and make the optical field more concentratedly distributed in the resonant cavity composed of the bottom mirror 200, the opening region, and the top mirror 700.

[0042] The step of forming the top mirror includes patterning the material layer for forming the top mirror. To simplify the manufacturing method, the material layer for forming the top mirror can be formed on the entire surface, and then through the patterning method, the top mirrors 700 at multiple positions can be formed simultaneously in one step. The area of the top mirror 700 is larger than the area of the opening region in the waveguide layer 400, which can more effectively limit the escape of photons with large-angle radiation. In the resonant cavity of the laser, photons are reflected back and forth between the bottom mirror 200 and the top mirror 700, reducing the scattering and loss of photons.

[0043] In the preparation process of an electrically injected quantum dot vertical cavity surface emitting laser, for the formation of the electron injection layer 510 and the hole injection layer 530, the spraying or spin coating method is adopted. A solution containing an electron injection material or a hole injection material is evenly sprayed on the corresponding substrate 100 or the previous layer structure. In the spin coating method, the substrate 100 is fixed on a spin coater, an appropriate amount of the injection material solution is dropped at the center of the substrate 100, and then the substrate 100 is rotated at a high speed. The solution is evenly spread on the surface of the substrate 100 by centrifugal force to form a uniform thin film layer. Both of these methods have the advantages of simple operation, relatively low equipment cost, and can be prepared in large areas. For the preparation of the active layer 520, an inkjet printing, photolithography or spin coating method is used to prepare a colloidal quantum dot layer. The inkjet printing technology is a non-contact patterning technology. It controls the ejection of ink droplets by means of piezoelectric crystals or thermal bubbles, etc., and precisely prints the ink containing colloidal quantum dots to a specified position to form a quantum dot layer with a specific pattern and thickness. The spin coating method is also applicable to the preparation of the quantum dot layer. The quantum dot solution is dropped on the substrate 100, and the solution is evenly spread by rotating the substrate 100 to form a uniform quantum dot thin film. By using methods such as spraying, spin coating, and inkjet printing, large-area production can be achieved. Combining the device structure design in this application can greatly reduce the manufacturing cost.

[0044] The equipment costs of methods such as spraying, spin coating, and inkjet printing are relatively low. Compared with some complex semiconductor manufacturing process equipment, the structures of spraying and spin coating equipment are simple and the prices are relatively cheap. The cost of inkjet printing equipment is also within an acceptable range, and with the continuous development of technology, its cost is gradually decreasing. This makes the investment in laser preparation using these methods smaller and reduces the production cost. These methods also simplify the laser preparation process. Operations such as spraying, spin coating, and inkjet printing are relatively simple, do not require a complex vacuum environment and high-temperature conditions, reduce the process steps and time. Methods such as spraying, spin coating, and inkjet printing can flexibly adjust the preparation process parameters to meet the preparation requirements of lasers with different specifications and performances. Due to the design of the device structure with the waveguide layer 400 in this application, the use of these methods can improve the product quality and increase the output. These methods are relatively simple, reduce defects and errors introduced by complex process steps. Methods such as spraying, spin coating, and inkjet printing avoid these complex etching processes, reduce the generation probability of process defects, and improve the yield of the device.

[0045] Specifically, it further includes the step of forming the top electrode 800, which can be formed on the second current spreading layer 600 exposed by etching the top mirror 700, so that the top electrode 800 is in direct contact with the second current spreading layer 600. Specific embodiments The following will further introduce some specific implementation manners to further elaborate on the technical solutions of this application.

[0047] First, a bulk gallium nitride (GaN) substrate obtained by hydride vapor phase epitaxy (HVPE), ammonothermal method or low-pressure flux method is selected as the support material. Since the GaN material has etchable properties, it can be pre-etched to form a specific thickness or shape. Subsequently, multiple pairs of high-quality conductive GaN / AlInN distributed Bragg reflectors (DBRs) are epitaxially grown on the patterned substrate. The reflectivity of the bottom DBR mirror can be as high as approximately 99.6%, providing good optical feedback for the resonator of the subsequent laser.

[0048] A transparent conductive film, such as ITO, IZO, AZO, FTO, etc., is deposited on the sample surface as the first current spreading layer to effectively expand the current distribution range and improve the uniformity of current injection. Patterning deposition is carried out on the ITO film to sequentially form a current confinement layer / waveguide layer (AlN). The current confinement layer can precisely control the current injection region, reduce current leakage, and improve the efficiency and stability of the device; the waveguide layer plays a role in guiding and confining the optical field to ensure the effective propagation of light in the resonator.

[0049] The electron injection layer is prepared by spin coating, and various material combinations can be selected, such as ZnMgO, TCTA, ZnO. The colloidal quantum dot light-emitting layer is prepared by using process methods such as inkjet printing, photolithography, and spin coating. The quantum dot materials include but are not limited to CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, CuInS, CuInSeS, AgInS, AgInSeS, InP, CuZnSe, ZnMnSe, PbS, PbSe, Cd-based alloy materials, In-based alloy materials, Zn-based alloy materials, or perovskite materials, etc.

[0050] By using process methods such as spin coating and blade coating, a hole injection layer is prepared on the surface of the sample. The materials that can be selected include PEDOT:PSS / TFB, PEDOT:PSS / PF8Cz, PVK, ZnO / ZnMgO. Then, a transparent conductive thin film is deposited on the surface of the sample again as the second current spreading layer, and the thin film materials can also be selected from ITO, IZO, AZO, FTO, etc. By using process methods such as masking and photolithography, a patterned top mirror is deposited on the surface of the sample. The mirror materials can be selected from dielectric film DBR, grating, etc., and the dielectric film materials include but are not limited to titanium dioxide (TiO2) / silicon dioxide (SiO2), hafnium dioxide (HfO2) / silicon dioxide (SiO2), etc. The reflectivity of the top mirror is greater than that of the bottom mirror, which can be as high as approximately 99.99%, and together with the bottom mirror, it forms a stable resonant cavity to enhance the oscillation and output effect of the laser. Finally, by using process methods such as masking and photolithography, a p-type metal electrode is deposited on the surface of the sample to complete the device preparation. The metal electrode materials can be selected from aluminum (Al), silver (Ag), gold (Au), and metal combination schemes, etc., and the p-type metal electrode provides electrical connection for the device.

[0051] This application provides an electrically injected quantum dot vertical cavity surface emitting laser (VCSEL) and its preparation method. The structure of the laser includes a substrate (gallium nitride / GaN), a nitride DBR bottom mirror, a transparent conductive thin film (such as ITO, IZO, AZO, FTO, etc.), a dielectric film current confinement layer, an electron injection layer (ETL), a quantum dot layer (covering various materials such as CdSe, CdTe, etc., with adjustable size), a hole injection layer (HTL), a p-type electrode, and a top mirror. The bottom and top mirrors together form an optical resonant cavity. The nitride DBR bottom mirror is composed of conductive nitrides such as GaN / AlInN, which can not only serve as a current injection channel, avoid the preparation of additional electrodes, achieve vertical current injection, reduce the current congestion effect, but also cooperate with the GaN substrate. Using its transparent property as an excellent light-emitting surface material, at the same time, the high heat dissipation of the nitride material improves the heat dissipation ability of the device, enhances the heat tolerance and threshold current density, and provides guarantee for the lasing of the quantum dot VCSEL.

[0052] In the preparation process, the waveguide layer (such as SiO2 / AlN) reduces the device current injection range and increases the current injection density; on the other hand, it realizes three-dimensional confinement in the physical dimension, reduces the lateral leakage and diffraction loss of the optical field in the resonant cavity, and reduces the Q value of the resonant cavity. In addition, using a GaN-based substrate can synchronously construct a metal-oxide-semiconductor field effect transistor (MOSFET) drive circuit, realize a monolithic integration process, improve the system integration degree, reduce the production cost by more than 30%, and improve the thermal stability of the device.

[0053] As a new type of semiconductor laser device, VCSEL has core advantages such as excellent beam quality, high modulation bandwidth, long lifespan, and outstanding single-mode stability. Its compact structure (typical size in the order of hundreds of micrometers) enables high-density integration with electronic components and optoelectronic devices, and has important application values in fields such as optical communication systems, 3D sensing networks, industrial precision machining, biomedical devices, and national defense security. The innovative preparation scheme of this application has successfully achieved the lasing of quantum dot VCSEL, and solved defects such as low carrier injection efficiency, insufficient thermal management ability of the quantum dot active region, and the optical field confinement mechanism of the resonant cavity.

[0054] As can be seen from the above, the electrically injected quantum dot vertical cavity surface emitting laser of this application is composed of a substrate, a bottom mirror, a first current spreading layer, a waveguide layer, an electron injection layer, an active layer, a hole injection layer, a second current spreading layer, and a top mirror. The waveguide layer is located between the first current spreading layer and the electron injection layer, and has the function of guiding and confining the optical field. Multiple carefully designed opening regions are provided inside it, and each opening region corresponds to a top mirror. The two together with the bottom mirror under the opening region jointly form the resonant cavity of the laser, reducing the lateral leakage and diffraction loss of the optical field, and improving the laser performance and efficiency. Multiple opening regions correspond to multiple resonant cavities, enabling the independent output of multiple laser beams. In terms of material selection, the active layer uses quantum dot materials, the substrate selects GaN, and the bottom mirror uses a GaN / AlInN mirror, which has good lattice matching with the GaN substrate, can reduce the dislocation density, and improve the device quality and performance. The top mirror selects a dielectric mirror, which has advantages such as high reflectivity and wide bandwidth.

[0055] This application also provides a method for preparing an electrically injected quantum dot vertical cavity surface emitting laser, including epitaxially growing a bottom mirror on the substrate, and sequentially forming a first current spreading layer, a waveguide layer (where opening regions are formed), an electron injection layer, an active layer, a hole injection layer, a second current spreading layer, and a top mirror. The electron injection layer and the hole injection layer can be formed by spraying or spin coating methods, and the active layer can be prepared by inkjet printing, photolithography, or spin coating methods. Epitaxial growth ensures good lattice matching between the bottom mirror and the substrate, reducing interface defects and stress; methods such as spraying, spin coating, and inkjet printing have low equipment costs, are easy to operate, and can be prepared on a large scale. In summary, the electrically injected quantum dot vertical cavity surface emitting laser of this application has been optimized in terms of structural design and manufacturing process, can effectively improve the laser performance and efficiency, and reduce the manufacturing cost.

[0056] The above is only a specific embodiment of this application, and any improvements made on the premise of the concept of this application are regarded as the protection scope of this application.

Claims

1. An electrically injected quantum dot vertical cavity surface emitting laser, characterized in that, It includes a substrate, a bottom mirror, a first current spreading layer, a waveguide layer, an electron injection layer, an active layer, a hole injection layer, a second current spreading layer, a top mirror and a top electrode; The bottom mirror is formed on the substrate, the first current spreading layer is formed on the bottom mirror, and the waveguide layer is located between the first current spreading layer and the electron injection layer; The waveguide layer includes a plurality of opening regions, and each opening region has a corresponding top mirror; Wherein, the bottom mirror under the opening region and the corresponding top mirror serve as the resonant cavity of a laser.

2. The electrically injected quantum dot vertical cavity surface emitting laser according to claim 1, wherein The area of the top mirror is larger than the area of the opening region in the waveguide layer corresponding to the top mirror, and the top mirror completely covers the opening region.

3. The electrically injected quantum dot vertical cavity surface emitting laser according to claim 2, characterized in that, Each of the resonant cavities includes a corresponding second current spreading layer, and the area of the second current spreading layer is larger than the area of the top mirror corresponding to the second current spreading layer.

4. The electrically injected quantum dot vertical cavity surface emitting laser according to claim 1, characterized in that The waveguide layer is formed of a current confinement material.

5. The electrically injected quantum dot vertical cavity surface emitting laser according to claim 1, characterized in that, The active layer is a colloidal quantum dot material, the material of the substrate is GaN, the bottom mirror is a GaN / AlInN mirror or an air-gap GaN DBR, and the top mirror is selected from a dielectric film DBR, a grating or a photonic crystal.

6. A method for fabricating an electrically injected quantum dot vertical cavity surface emitting laser, characterized in that, It includes: Forming a bottom mirror on the substrate by epitaxial growth; Forming a first current spreading layer on the bottom mirror; Forming a waveguide layer on the first current spreading layer, and forming opening regions in the waveguide layer; Sequentially forming an electron injection layer, an active layer, and a hole injection layer; Forming a second current spreading layer on the hole injection layer; Forming a top mirror on the second current spreading layer, and the top mirror covers the opening region in the waveguide layer in the vertical projection direction; Wherein, the bottom mirror under the opening region in the waveguide layer and the corresponding top mirror serve as the resonant cavity of a laser.

7. The method for fabricating an electrically injected quantum dot vertical cavity surface emitting laser according to claim 6, wherein The step of forming the top mirror includes patterning the material layer for forming the top mirror.

8. The method for fabricating an electrically injected quantum dot vertical cavity surface emitting laser according to claim 7, wherein The area of the top mirror is larger than the area of the opening region in the waveguide layer.

9. The method for preparing an electrically injected quantum dot vertical cavity surface emitting laser according to claim 6, wherein The electron injection layer and the hole injection layer are formed by spraying or spin coating, and the colloidal quantum dot layer is prepared by inkjet printing, photolithography or spin coating as the active layer.

10. The method for preparing an electrically injected quantum dot vertical cavity surface emitting laser according to claim 6, wherein It further includes the step of forming a top electrode.

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