LED lighting effect improvement simulation method based on high aspect ratio nanometer roughened surface structure

Abstract

The invention discloses an LED lighting effect improvement simulation method based on a high aspect ratio nanometer roughened surface structure. The method comprises the following steps: constructing an LED device model; constructing a nano structure on the surface of the LED device; adding a simulation light source; adding a computational domain and an absorption boundary condition; adding a detector; the ratio of the light emitting power of the simulation target device detected by the detector to the light emitting power of the simulation light source is the light extraction efficiency, the nanometer diameter and the nanometer height are controlled through the equivalent nanometer roughened surface structure, and simulation results of the nanometer structures with different aspect ratios on the LED light extraction efficiency are obtained. The LED device optical simulation means can prove that the LED luminous efficiency is improved by the surface roughening of the high-aspect-ratio nano-structure, so that the method can be conveniently applied to the luminous efficiency improvement design of the LED device, the cost can be reduced, and industrialization is easy.

Description

Technical Field

[0001] The invention relates to the technical field of LED light efficiency improvement, and in particular to a LED light efficiency improvement simulation method based on a high aspect ratio nano-roughened surface structure. Background Art

[0002] An important indicator for judging the quality of LED is the luminous efficiency, which can usually be measured by the external quantum efficiency. The external quantum efficiency is the product of the internal quantum efficiency and the light extraction efficiency. Due to the improvement of material growth quality and device manufacturing process, the internal quantum efficiency of LED can reach a very high value. For example, the internal quantum efficiency of GaN-based blue light can reach more than 90%. Even so, the external quantum efficiency of LED is still low, and the reason lies in the light extraction efficiency. Among the various factors that affect the light extraction efficiency, total internal reflection is the main influencing factor. Total internal reflection will form a light escape cone, and only the light that falls into the light escape cone can contribute to the light extraction efficiency. In order to solve the problem of total internal reflection caused by the light escape cone affecting the light extraction rate, the surface or side of the device is roughened by using surface roughening technology, so that the light propagation path is changed, so that more photons enter the escape cone and are emitted into the air.

[0003] In the prior art, the semiconductor surface roughening technology commonly used in the current industry is wet etching, which involves immersing the sample in a prepared chemical etching solution. The etching solution will gradually corrode and dissolve the contacted material through chemical reactions, leaving a microstructure in the sample corrosion area.

[0004] Currently, the most commonly used surface roughening technology for LEDs is wet etching. However, wet etching has poor selectivity and may not be able to accurately control the degree of corrosion on different materials under certain conditions. It has low anisotropy and is not easy to control, making it difficult to perform fine processing. The feature size is large, usually a micron structure. When wet etching is applied to the surface of LED materials, its technical defects can cause luminescence problems in the device, such as uneven luminous intensity between regions or uncontrollable luminous angles, etc. There will also be electrode contact problems, affecting current injection. Since wet etching usually produces micron structures, it is incompatible with the currently popular Micro LEDs, which are only a few microns in size in some fields. Summary of the invention

[0005] The purpose of the present invention is to provide a simulation method for improving LED light efficiency based on a high aspect ratio nano-roughened surface structure, so as to solve the problem that the LED micron-roughened surface structure formed by wet etching in the prior art has a poor light efficiency improvement effect.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure includes the following steps:

[0008] Step 1: Build an LED device model and determine the simulation target device;

[0009] Step 2: constructing a nanostructure on the surface of an LED device to obtain an equivalent nano-roughened surface structure on the surface of the simulated target device;

[0010] Step 3, adding simulated light sources, and evenly distributing a plurality of simulated light sources in the active light emitting layer of the simulated target device;

[0011] Step 4, adding a calculation domain and absorption boundary conditions, placing the simulation target device in the set calculation domain, and setting all absorption conditions in the calculation domain to a perfectly matched layer;

[0012] Step 5: Add a detector, wherein the detector is used to detect the optical power of the simulated target device;

[0013] Among them, the ratio between the light output power of the simulated target device detected by the detector in step 5 and the luminous power of the simulated light source in step 3 is the light extraction efficiency, and the nano-diameter and nano-height size are controlled by the equivalent nano-roughened surface structure in step 2 to obtain the simulation results of LED light extraction efficiency of nanostructures with different aspect ratios.

[0014] As a further solution of the present invention: the method for constructing the LED device model in step 1 is: according to the epitaxial structure of the LED device, the epitaxial material is added in the simulation software to construct the LED device model, and the determined simulation target device includes an n-GaN layer, an MQWS layer, a p-GaN layer and an Ag layer arranged in layers from top to bottom.

[0015] As a further solution of the present invention: during the layered setting of the simulation target device, the thickness of the n-GaN layer is 3.5um, and the refractive index is 2.45+0.0016i; the thickness of the MQWS layer is 200nm, and the refractive index is 2.48+0.0000732i; the thickness of the p-GaN layer is 200nm, and the refractive index is 2.45+0.0016i; the thickness of the Ag layer is 60nm, and the refractive index is 0.132.

[0016] As a further solution of the present invention: the method for constructing the surface nanostructure of the LED device in step 2 is: using the WM function of the mathematical software to generate a random equivalent nano-roughened surface structure, and then importing the equivalent nano-roughened surface structure after Gaussian filtering into the finite element simulation software to form a simulation target device.

[0017] As a further solution of the present invention: the nanometer height of the equivalent nano-roughened surface structure in step 2 is 0-1000nm, and the bottom nanometer diameter is 0-300nm.

[0018] As a further solution of the present invention: the method of adding a simulated light source in step 3 is: a plurality of simulated light sources are evenly arranged in the MQWS layer, and the emission wavelength of the simulated light source is 465 nm.

[0019] As a further solution of the present invention: in step 4, the distance between the position of the perfectly matched layer and the simulation target device is not less than 1 / 3 of the simulated light source. Emission wavelength.

[0020] As a further solution of the present invention: the method for adding the detector in step 5 is: setting the detector flush with the light-emitting surface of the n-GaN layer, and the detector can be a point, line or surface detector.

[0021] Beneficial effects of the present invention:

[0022] (1) Through the optical simulation of LED devices, it can be proved that the surface roughening of high aspect ratio nanostructures can improve the light output efficiency of LEDs. The dense high aspect ratio nanostructures indicate a higher degree of surface roughening, making it easier for light to enter the roughened structure, increasing the probability of being emitted into the air. At the same time, the high aspect ratio of the structure has the effect of a gradual refractive index, avoiding total reflection caused by a sudden change in the refractive index.

[0023] (2) The surface roughening of the high aspect ratio nanostructure in the present application can be achieved by non-periodic random dry etching, which has good selectivity and anisotropy and is suitable for preparing microstructures with specific needs. Compared with nanoimprinting, photolithography, wet etching and other technologies, it has low cost and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 is a flow chart of the steps of the present invention;

[0026] Figure 2 This is a schematic diagram of generating an equivalent nano-roughened surface structure in step 2 of the present invention;

[0027] Figure 3 It is a schematic diagram of constructing the surface nanostructure of the LED device in step 2 of the present invention;

[0028] Figure 4 It is a schematic diagram of adding a simulated light source state to the simulated target device in step 3 of the present invention;

[0029] Figure 5It is a schematic diagram of adding a calculation domain and absorbing boundary conditions to the simulation target device in step 4 of the present invention;

[0030] Figure 6 It is a schematic diagram of adding a detector state to the simulation target device in step 5 of the present invention;

[0031] Figure 7 It is a schematic diagram of a high aspect ratio nano-roughened surface structure on the surface of an LED device of the present invention;

[0032] Figure 8 yes Figure 7 Schematic diagram of the light refraction principle of the high aspect ratio nano-roughened surface structure;

[0033] Fig. 9 is a schematic diagram of the light transmittance improvement ratio and the nanostructure size curve of the present invention;

[0034] Fig.10 It is a schematic diagram of the light transmittance improvement ratio and nanometer height size curve of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be understood that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; in the description of the present invention, the meaning of "multiple" and "several" is at least two, for example two, three, etc., unless otherwise clearly and specifically defined.

[0037] See also Figure 1 As shown, the present invention is a simulation method for improving LED light efficiency based on a high aspect ratio nano-roughened surface structure, comprising the following steps:

[0038] Step 1, construct an LED device model and determine the simulation target device; the specific operation method is as follows: according to the epitaxial structure of the LED device, add epitaxial materials in the simulation software to construct an LED device model, and the determined simulation target device includes an n-GaN layer, an MQWS layer, a p-GaN layer and an Ag layer arranged in layers from top to bottom; so that this application takes a flip-chip GaN-based blue light LED device as an example to further illustrate the simulation verification of the improvement of LED light efficiency; it should be understood that the LED device model constructed in this application is not limited to the various functional layers described above.

[0039] In the process of layering the simulation target device in this step, the thickness of the n-GaN layer is 3.5um, and the refractive index is 2.45+0.0016i; the thickness of the MQWS layer is 200nm, and the refractive index is 2.48+0.0000732i; the thickness of the p-GaN layer is 200nm, and the refractive index is 2.45+0.0016i; the thickness of the Ag layer is 60nm, and the refractive index is 0.132.

[0040] Step 2: construct the surface nanostructure of the LED device to obtain the equivalent nano-roughened surface structure of the simulated target device surface; the specific operation method is as follows: use the WM function of the mathematical software to generate a random equivalent nano-roughened surface structure, and the equivalent nano-roughened surface structure produced is as follows: Figure 2 As shown, the equivalent nano-roughened surface structure after Gaussian filtering is then imported into the finite element simulation software to form a simulation target device, and finally the simulation target device generated by the simulation software is as shown in FIG. Figure 3 As shown; the control range of the equivalent nano-roughened surface structure can be designed to be 0-1000nm nano-height size and 0-300nm bottom nano-diameter size.

[0041] It should be understood that when using the WM function of mathematical software to generate a random equivalent nano-roughened surface structure, the WM function can characterize microscopic features such as the height and distribution of micro-convexities and the texture direction on the surface of the LED device.

[0042] Step 3, add simulated light sources, and evenly set up several simulated light sources in the active light-emitting layer of the simulated target device; the specific operation method is as follows: evenly set up several simulated light sources in the MQWS layer, and the emission wavelength of the simulated light source is 465nm; the simulated light source in this step is an electric dipole, which represents the light source generated by the recombination of electrons and holes, so that a stable light source with high power can be set. This substitution is confirmed to be reasonable through literature verification. In theory, the more electric dipole positions there are, the more accurate the results are. However, considering the problem of simulation efficiency, 12 electric dipoles are evenly distributed in the MQWS layer to describe the actual light emission of the active layer, such as Figure 4 shown.

[0043] Step 4: Add the computational domain and absorption boundary conditions, place the simulation target device in the set computational domain, and set all absorption conditions in the computational domain to fully matched layers. Figure 5 As shown; wherein the position of the perfectly matched layer is not less than the distance of the simulated target device from the simulated light source Light emission wavelength; In this step, the perfectly matched layer formed by the computational domain and the absorption boundary conditions is used to absorb light and avoid reflection to ensure the accuracy of the simulation verification.

[0044] Step 5: Add a detector. The detector is used to detect the light output power of the simulated target device. The specific method of adding the detector is to place the detector flush with the light output surface of the n-GaN layer. Figure 6 As shown, the detector may be a point, line or surface detector, and the ratio between the light output power of the simulated target device detected by the detector and the light output power of the simulated light source in step 3 is the light extraction efficiency.

[0045] When using this LED light efficiency enhancement simulation method, if Figure 7 The LED device surface shown has a high aspect ratio nano-roughened surface structure schematic diagram, the obtained high aspect ratio nano-roughened surface structure light refraction principle is as follows Figure 8 As shown, the light extraction efficiency increases significantly with the increase of the height of the pyramidal nanostructure. This is mainly because most of the light generated in the active layer will produce relatively strong scattering on the inclined side, allowing more light to escape vertically from the semiconductor material. The high aspect ratio nano-roughened surface structure can be equivalent to a multi-layer material with a gradient refractive index. The refractive index gradually decreases from the bottom to the top of the structure and is close to the refractive index of air, avoiding sudden changes in the refractive index and having good anti-reflection properties.

[0046] In the process of using the LED light efficiency enhancement simulation method, the nanometer diameter and nanometer height size are controlled by the equivalent nano-roughened surface structure in step 2 to obtain the simulation results of LED light extraction efficiency with nanostructures of different aspect ratios; combined with Fig. 9 and Fig.10 As shown in the figure, when the height of the equivalent nano-roughened surface structure is constant, the light extraction efficiency improvement ratio increases with the decrease of the bottom diameter; when the bottom diameter of the equivalent nano-roughened surface structure is constant, the light extraction efficiency improvement ratio increases with the increase of the height. It can be seen that compared with the micron-roughened structure, the nanostructure with a high aspect ratio has a significant effect on improving the light extraction efficiency.

[0047] The design scheme of the high aspect ratio nano-roughened surface structure in this application is as follows: according to the size of the LED device, the parameters of each functional layering, the height of the nano-structure, the direct size of the bottom of the nano-structure and other parameters, the high aspect ratio nano-roughened surface structure required for molding and design is determined. Since the academic community currently lacks a theoretical answer to what is the optimal light efficiency improvement of the high aspect ratio nano-roughened surface structure, the above parameters can be preliminarily designed with reference to some experience of related research at home and abroad. For example, the nanostructure can be successfully prepared by self-assembling nanospheres or thermally annealing metal film condensation nanospheres. As for the exploration of the high aspect ratio of the nanostructure, it is still to be explored, and further optimization can be made in combination with experiments and simulations in the later stage.

[0048] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A simulation method for improving LED light efficiency based on a high aspect ratio nano-roughened surface structure, characterized in that: The following steps are involved: Step 1: Build an LED device model and determine the simulation target device; Step 2: constructing a nanostructure on the surface of an LED device to obtain an equivalent nano-roughened surface structure on the surface of the simulated target device; Step 3, adding simulated light sources, and evenly distributing a plurality of simulated light sources in the active light emitting layer of the simulated target device; Step 4, adding a calculation domain and absorption boundary conditions, placing the simulation target device in the set calculation domain, and setting all absorption conditions in the calculation domain to a perfectly matched layer; Step 5: Add a detector, wherein the detector is used to detect the optical power of the simulated target device; Among them, the ratio between the light output power of the simulated target device detected by the detector in step 5 and the luminous power of the simulated light source in step 3 is the light extraction efficiency, and the nano-diameter and nano-height size are controlled by the equivalent nano-roughened surface structure in step 2 to obtain the simulation results of LED light extraction efficiency of nanostructures with different aspect ratios.

2. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 1, characterized in that: The method for constructing the LED device model in step 1 is: according to the epitaxial structure of the LED device, the epitaxial material is added in the simulation software to construct the LED device model, and the simulation target device determined includes an n-GaN layer, an MQWS layer, a p-GaN layer and an Ag layer arranged in layers from top to bottom.

3. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 2, characterized in that: During the layered setting process of the simulation target device, the thickness of the n-GaN layer is 3.5um, and the refractive index is 2.45+0.0016i; the thickness of the MQWS layer is 200nm, and the refractive index is 2.48+0.0000732i; the thickness of the p-GaN layer is 200nm, and the refractive index is 2.45+0.0016i; the thickness of the Ag layer is 60nm, and the refractive index is 0.

132.

4. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 2, characterized in that: The method for constructing the surface nanostructure of the LED device in step 2 is: using the WM function of the mathematical software to generate a random equivalent nano-roughened surface structure, and then importing the equivalent nano-roughened surface structure after Gaussian filtering into the finite element simulation software to form a simulation target device.

5. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 4, characterized in that: The nanometer height of the equivalent nano-roughened surface structure in step 2 is 0-1000 nm, and the bottom nanometer diameter is 0-300 nm.

6. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 4, characterized in that: The method of adding the simulated light source in step 3 is: a plurality of simulated light sources are evenly arranged in the MQWS layer, and the emission wavelength of the simulated light source is 465 nm.

7. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 6, characterized in that: The distance between the position of the fully matched layer in step 4 and the simulation target device is not less than 1 / 3 of the simulated light source. Emission wavelength.

8. The LED light efficiency enhancement simulation method based on high aspect ratio nano-roughened surface structure according to claim 7, characterized in that: The method for adding the detector in step 5 is: setting the detector flush with the light-emitting surface of the n-GaN layer. The detector can be a point, line or surface detector.

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