Method for roughening surface of LED chip and LED chip

Abstract

The application provides a LED chip surface roughening method and a LED chip, wherein the LED chip surface roughening method comprises the following steps: using an etching solution to perform first wet etching on an exposed surface away from a GaAs substrate, the etching solution is a mixture composed of saturated 2-hydroxybutanedioic acid, saturated oxalic acid and 30wt% hydrogen peroxide, and the volume ratio of the components of the etching solution is 1:(0.5-1.5):(1.5-2.5); using a modification solution to perform second wet etching on the exposed surface away from the GaAs substrate, the modification solution is a mixture composed of 37wt% hydrochloric acid, 68wt% nitric acid and 36wt% acetic acid, and the volume ratio of the components of the mixture is (2-3):1:(3-5). The application is used to solve the problem that the ratio of the area with poor roughening state to the area with good roughening state of the epitaxial layer surface of a gallium arsenide LED chip is large in the prior art, so that the light emitting efficiency of the LED is affected.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for roughening the surface of an LED chip and an LED chip. Background Technology

[0002] Light-emitting diodes (LEDs), as a new type of lighting device, have advantages such as low power consumption, long lifespan, and low heat generation. They are gradually replacing traditional lighting devices such as incandescent lamps and fluorescent lamps, and are widely used in indoor and outdoor lighting, screen displays, and backlight modules. LEDs are limited by their luminous efficiency, making it difficult to achieve higher brightness. The main factor affecting LED luminous efficiency is that the light emitted from the active layer cannot be effectively emitted at the surface of the epitaxial layer, i.e., at the interface between the epitaxial layer and the air. Therefore, the roughening structure of the epitaxial layer surface has the most significant impact on the luminous efficiency of LEDs. Figure 1 The diagram shows a poorly structured epitaxial layer in an LED chip. Due to total internal reflection, most light rays cannot effectively exit the epitaxial layer and instead return to it, thus affecting luminous efficiency. (See reference...) Figure 2 As shown, this is a schematic diagram of the well-formed roughened structure of the epitaxial layer of an LED chip. Most of the light can be effectively emitted from the epitaxial layer after being reflected by the surface of the epitaxial layer, thus achieving better LED luminous efficiency.

[0003] To achieve Figure 2 The good light emission state shown indicates that after the epitaxial layer growth is complete, a separate epitaxial layer-air interface roughening process is required. This is achieved by adjusting the surface morphology of the epitaxial layer-air interface using dry or wet etching methods to roughen the epitaxial layer surface. The epitaxial layer surface roughened using the aforementioned dry or wet etching still retains a morphologically satisfactory surface finish. Figure 2 The area of ​​the preferred roughening morphology shown is limited, and the surface morphology of the epitaxial layer is as follows: Figure 1 The large ratio of the area with poor roughening to the area with good roughening, as shown in the diagram, affects the luminous efficiency of the LED.

[0004] In view of this, it is necessary to improve the existing LED chip surface roughening methods to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to disclose a method for roughening the surface of an LED chip and an LED chip, in order to solve the problem in the prior art that the ratio of the area with poor roughening state to the area with good roughening state on the epitaxial layer surface of gallium arsenide LED chips is large, which leads to the impact on the luminous efficiency of the LED.

[0006] To achieve the above objectives, the present invention provides a method for roughening the surface of an LED chip, comprising an epitaxial structure and a first conductive metal layer grown along the surface of a GaAs substrate, wherein the surface roughening method roughens the exposed surface not covered by the first conductive metal layer, characterized in that the surface roughening method includes:

[0007] The exposed surface facing away from the GaAs substrate is subjected to a first wet etching using an etching solution, which is a mixture of saturated 2-hydroxysuccinic acid, saturated oxalic acid and 30 wt% hydrogen peroxide, with the volume ratio of each component of the etching solution being 1:(0.5~1.5):(1.5~2.5).

[0008] A second wet etching was performed on the exposed surface away from the GaAs substrate using a modification solution. The modification solution was a mixture of 37 wt% hydrochloric acid, 68 wt% nitric acid and 36 wt% acetic acid, with the volume ratio of each component in the mixture being (2-3):1:(3-5).

[0009] As a further improvement of the present invention, the temperature of the etching solution is maintained at 50°C to 60°C, and the LED chip is immersed in the etching solution for 30 min to 40 min to perform the first wet etching.

[0010] As a further improvement of the present invention, the temperature of the modification solution is maintained at 40°C to 50°C, and the LED chip is immersed in the modification solution for 1 min to 2 min to perform a second wet etching.

[0011] As a further improvement of the present invention, deionized water is used to clean the residual etching solution on the exposed surface before the second wet etching, and deionized water is used to clean the residual modification solution on the exposed surface after the second wet etching.

[0012] Based on the same inventive concept, this invention also discloses an LED chip, comprising:

[0013] A GaAs substrate, an epitaxial structure and a first conductive metal layer grown along the GaAs substrate, the exposed surface not covered by the first conductive metal layer is roughened by the surface roughening method of GaAs substrate LED chip as described in any of the above inventions, and a second conductive metal layer is epitaxially grown on the back side of the GaAs substrate.

[0014] As a further improvement of the present invention, the epitaxial structure includes a GaAs buffer layer, a DBR layer, an N-type AlGaInP layer, a quantum well active layer, a P-type AlGaInP layer, a first P-type GaP layer and a second P-type GaP layer epitaxially grown on a GaAs substrate.

[0015] As a further improvement of the present invention, the thickness of the GaAs buffer layer is 100 nm, the thickness of the DBR layer is 2400 nm, the thickness of the N-type AlGaInP layer is 400 nm, the thickness of the quantum well active layer is 600 nm, the thickness of the P-type AlGaInP layer is 1000 nm, the thickness of the first P-type GaP layer is 700 nm, and the thickness of the second P-type GaP layer is 1200 nm.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] This invention provides a method for roughening the surface of an LED chip. By using an etching solution composed of 2-hydroxysuccinic acid, oxalic acid, and hydrogen peroxide in any proportion to perform a first wet etching on the exposed surface away from the GaAs substrate, the overall surface of the LED chip is roughened in the first stage. The temperature of the first wet etching is controlled in the range of 50°C to 60°C, and the time of the first wet etching is 30 min to 40 min, so as to ensure that the surface of the LED chip is roughened from a mirror state to form an uneven, mountain-like surface. After the first wet etching, a modification solution composed of hydrochloric acid, nitric acid, and acetic acid in any proportion is used to perform a second wet etching on the exposed surface away from the GaAs substrate. The temperature of the second wet etching is controlled in the range of 40℃ to 50℃, and the etching time is 1 min to 2 min. This further modifies the mountain-like shape formed by the first wet etching, making the mountain shape of the roughened surface steeper and the angles at the peaks and valleys further reduced. This effectively reduces the problem of light not being able to effectively exit the LED chip surface due to total internal reflection, thereby effectively improving the luminous efficiency of the LED chip. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the roughened surface morphology of an epitaxial layer with poor light efficiency.

[0019] Figure 2 This is a schematic diagram illustrating the surface roughening morphology of the epitaxial layer to demonstrate better light efficiency.

[0020] Figure 3 This is a schematic flowchart of the LED chip surface roughening method disclosed in this invention;

[0021] Figure 4 A schematic diagram of the completed epitaxial growth structure on the surface of an LED chip.

[0022] Figure 5 A schematic diagram of the completed growth of the first conductive metal layer and the second surface metal layer on the surface of an LED chip;

[0023] Figure 6is a schematic diagram of the completed structure after roughening the exposed surface of the epitaxial structure of the LED chip. Detailed Description of the Embodiments

[0024] The present invention will be described in detail below with reference to the respective embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not intended to limit the present invention, and all equivalent transformations or substitutions of functions, methods or structures made by those of ordinary skill in the art based on these embodiments shall fall within the protection scope of the present invention.

[0025] Refe Figure 3 is a schematic diagram of a method for roughening the surface of an LED chip (hereinafter sometimes referred to as "roughening method") according to the present invention. Compared with the prior art, in this embodiment, after the first wet etching is performed on the light-emitting surface of the LED chip with an etching solution, the overall roughening effect on the surface of the LED chip is achieved, so as to improve the light-emitting efficiency of the LED chip for the first time. Then, a second wet etching is performed on the light-emitting surface of the LED chip with a modifying solution, so that the mountain-shaped roughened surface formed on the LED chip through the first wet etching undergoes a second morphological modification, to further sharpen the peak shape, so as to further improve the light-emitting efficiency of the light-emitting surface of the LED chip, solve the problem in the prior art that a large amount of light is difficult to exit and thus the light-emitting efficiency of the LED chip is affected due to the poor morphology and large area formed by roughening on the light-emitting surface of the LED chip, and effectively improve the light extraction efficiency of the epitaxial wafer on the premise of simplifying process conditions and reducing production costs.

[0026] This method for roughening the surface of an LED chip includes the following steps:

[0027] Step S101: Provide an LED chip, where the LED chip includes a GaAs substrate, an epitaxial structure epitaxially grown along the surface of the GaAs substrate, and a first conductivity type metal layer, and perform surface roughening on the exposed surface not covered by the first conductivity type metal layer.

[0028] In this embodiment, a photoresist is spin-coated on the side of the epitaxial structure away from the GaAs substrate, and the typical thickness of the photoresist layer is 1.2 μm. A photomask is used to expose the electrode pattern onto the photoresist layer. Titanium, platinum and gold are sequentially evaporated onto the photoresist layer using an electron beam evaporation apparatus to form the first conductivity type metal layer, and the typical thicknesses of titanium, platinum and gold are 50 nm, 50 nm and 400 nm respectively. An organic solvent (such as acetone) or a photoresist stripping solution is used to strip the unexposed photoresist layer and the first conductivity type metal layer covering the unexposed photoresist layer from the side of the epitaxial structure away from the GaAs substrate, so as to form the exposed surface not covered by the first conductivity type metal layer, and perform the subsequent surface roughening step on it.

[0029] Step S102: Prepare an etching solution. The etching solution is a mixture of saturated 2-hydroxysuccinic acid, saturated oxalic acid and 30wt% hydrogen peroxide. The volume ratio of each component of the etching solution is 1:(0.5~1.5):(1.5~2.5). Specifically, the volume ratio of each component of the etching solution in this embodiment is 1:1.2:2.3.

[0030] Step S103: Heat and maintain the etching solution temperature at 50℃~60℃, immerse the LED chip in the etching solution and let it stand for 30min~40min.

[0031] In this step, the temperature of the etching solution prepared in step S102 is heated to 50℃~60℃. The LED chip prepared in step S101 is immersed in the etching solution for 30min~40min, and the temperature of the etching solution is maintained within the range of 50℃~60℃ throughout the immersion process. In this step, the etching solution composition is adjusted to control the etching rate on the LED chip surface at a relatively slow rate, thereby achieving overall roughening of the LED chip surface. This process transforms the light-emitting surface of the LED chip from a mirror-smooth state to a smooth state, as shown in the image. Figure 1 The uneven, mountainous terrain is shown. The etching solution temperature is maintained within the range of 50℃ to 60℃, and the LED chips are immersed for 30 to 40 minutes. By controlling the etching solution temperature, the reaction effect and efficiency between the LED chip's light-emitting surface and the etching solution are controlled, so that a relatively good etching effect can be achieved on the LED chip surface after the first wet etching. Specifically, in this embodiment, the etching solution temperature is maintained at 55℃, and the etching time is 40 minutes. The etching solution with a volume ratio of 1:1.2:2.3 in step S102 is heated and maintained at 35℃, 45℃, and 55℃ respectively. LED chips numbered 1 and 2 are immersed in the etching solution at 35℃ for 40 minutes, LED chips numbered 3 and 4 are immersed in the etching solution at 45℃ for 40 minutes, and LED chips numbered 5 and 6 are immersed in the etching solution at 55℃ for 40 minutes. The obtained data is shown in Table 1.

[0032]

[0033]

[0034] Table 1

[0035] Table 1 shows the data on the surface roughening effect of LED chips 1 and 2 after immersing them in an etching solution at 35℃ for 40 minutes. Before the first wet etching, the light output efficiencies of chips 1 and 2 were 174.42W and 175.61W, respectively, with an average of 175.02W. After the first wet etching, the light output efficiencies of chips 1 and 2 increased to 322.85W and 319.63W, respectively, with an average of 321.24W. Therefore, the ratio of light output power before and after the first wet etching for chip 1 was 1.85, and for chip 2 it was 1.82. The average ratio of the light output power before and after the first wet etching for both chips was 1.84. A control experiment was conducted using chips 1 and 2. The difference between the experimental data and the average value obtained from chips 1 and 2 was small, in order to avoid excessive numerical deviation caused by experimental errors, which would affect the judgment of the effect at that temperature. Two LED chips were used as controls at 45℃ and 55℃ respectively.

[0036] Table 1 shows the data on the surface roughening effect of LED chips No. 3 and No. 4 obtained by immersing them in an etching solution at 45℃ for 40 minutes. Before the first wet etching, the light output efficiencies of chips No. 3 and No. 4 were 177.43W and 172.8W, respectively, with an average of 175.12W. After the first wet etching, the light output efficiencies of chips No. 3 and No. 4 increased to 331.65W and 330.44W, respectively, with an average of 331.05W. Therefore, the ratio of light output power before and after the first wet etching of chip No. 3 was 1.87, and the ratio of light output power before and after the first wet etching of chip No. 4 was 1.91. The average value of the ratio of light output power before and after the first wet etching of chips No. 3 and No. 4 was 1.88.

[0037] Table 1 shows the data on the surface roughening effect of LED chips No. 5 and No. 6 after immersing them in an etching solution at 55℃ for 40 minutes. Before the first wet etching, the light output efficiencies of chips No. 5 and No. 6 were 174.08W and 178.77W, respectively, with an average of 176.42W. After the first wet etching, the light output efficiencies of chips No. 5 and No. 6 increased to 339.78W and 340.59W, respectively, with an average of 340.19W. Therefore, the ratio of light output power before and after the first wet etching of chip No. 5 was 1.95, the ratio of light output power before and after the first wet etching of chip No. 6 was 1.91, and the average ratio of light output power before and after the first wet etching of chips No. 3 and No. 4 was 1.93. Since the above three experimental temperatures all used two sets of data for comparison, and the values ​​were stable without significant deviation, the average light output power after the first roughening at the three temperatures is used for comparison below. Specifically: at 35℃, the average light output power of chips 1 and 2 after the first roughening is 321.24W; at 45℃, the average light output power of chips 3 and 4 after the first roughening is 331.05W; and at 55℃, the average light output power of chips 5 and 6 after the first roughening is 340.19W. It can be seen that the average light output power after the first roughening at 45℃ is 2.7% higher than that at 35℃, i.e., the brightness is increased by 2.7%; and at 55℃, the average light output power after the first roughening is 5.9% higher than that at 35℃, i.e., the brightness is increased by 5.9%. Therefore, in step S103, heating and maintaining the etching solution temperature at 55℃ while immersing the LED chip can achieve a better surface roughening effect. That is, while achieving the goal of overall roughening of the light-emitting surface of the LED chip to form a mountain-like shape, it also improves... Figure 1 The apex angle of the mountains shown is the peak angle, which improves the effect of the first wet etching. Meanwhile, according to the light output power ratio of each LED chip before and after the first wet etching in Table 1, it can be seen that whether it is the light output power ratio of chips 1 to 6 before and after the first wet etching, or the average light output power ratio of the two control experiments at the same temperature before and after the first wet etching, the light output power ratio gradually increases with increasing temperature. It should be noted that at 35℃, 45℃, and 55℃, the positive voltage change of chips 1 to 6 before and after wet etching varies within the range of 0.011V to 0.031V, which is relatively small, and therefore is not considered as a factor in selecting the temperature for the first wet etching.

[0038] Step S104: Rinse the exposed surface of the LED chip with 18 MΩ·cm deionized water to remove any remaining etching solution. After the first wet etching is completed, the overall light-emitting surface of the LED chip forms a shape similar to... Figure 1The mountain-like protrusions shown require a second wet etching process to further increase the slope of the mountain peaks, thus achieving the desired effect on the LED chip surface. Figure 2 The LED chip is shown with a greater tilt to allow light to escape. Before the second wet etching, the exposed surface of the LED chip, i.e. the light-emitting surface, is cleaned with 18 megohms of deionized water. This removes the etching solution that remained on the light-emitting surface of the LED chip after the first wet etching to avoid contamination during the second wet etching and affecting the etching effect.

[0039] Step S201: Prepare a modification solution, which is a mixture of 37 wt% hydrochloric acid, 68 wt% nitric acid, and 36 wt% acetic acid, with a volume ratio of (2-3):1:(3-5). Specifically, in this embodiment, the volume ratio of the modification solution is 2.7:1:4.3.

[0040] Step S202: Heat and maintain the temperature of the modification solution at 40℃~50℃, and immerse the LED chip in the modification solution for 1min~2min to perform a second wet etching.

[0041] In this step, the temperature of the modification solution prepared in step S105 is heated to 40℃~50℃. The LED chip, which has been cleaned in step S104, is immersed in the modification solution for 1min~2min, and the temperature of the modification solution is maintained within the range of 40℃~50℃ during the immersion process. In this step, the proportion of the modification solution components is adjusted to further modify the mountain-like shape formed on the surface of the LED chip in step S103, so as to make the peak angles of the mountains steeper and ultimately achieve... Figure 2 The image shows a state with high light extraction efficiency. By controlling the temperature of the modification solution, the reaction effect and efficiency on the light-emitting surface of the LED chip are controlled, so that the roughened surface formed by the first wet etching can be further modified after the second wet etching, thereby giving the LED chip good light extraction efficiency. Specifically, in this embodiment, the temperature of the modification solution is maintained at 43°C and the etching time is 2 minutes. The modification solution with the volume ratio of each component in step S105 of 2.7:1:4.3 is heated and maintained at 23°C, 33°C, and 43°C, respectively. LED chips numbered 7 and 8 are immersed in the modification solution at 23°C for 2 minutes, LED chips numbered 9 and 10 are immersed in the modification solution at 33°C for 2 minutes, and LED chips numbered 5 and 6 are immersed in the modification solution at 43°C for 2 minutes. It should be noted that chips 5 and 6 are chips 5 and 6 in Table 1, and chips 7 to 10 are chips whose surfaces have undergone the same first wet etching conditions as chips 5 and 6. The obtained data is shown in Table 2:

[0042]

[0043]

[0044] Table 2

[0045] Table 2 shows the data on the surface roughening effect of LED chips 5 and 6 obtained by immersing them in a modification solution at 23℃ for 2 minutes. The light output efficiencies of chips 7 and 8 after the first wet etching were 340.23W and 339.89W, respectively, with an average of 340.06W. After the second wet etching, the light output efficiencies increased to 353.2W and 351.53W, respectively, with an average of 352.37W. Therefore, the ratio of light output power before and after the second wet etching for chip 7 was 1.04, and for chip 8 it was 1.03. The average ratio of the light output power before and after the second wet etching for chips 7 and 8 was 1.04.

[0046] Table 2 shows the data on the surface roughening effect of LED chips 9 and 10 after immersing them in a modification solution at 33℃ for 2 minutes. The light output efficiencies of chips 9 and 10 after the first wet etching were 340.11 W and 340.2 W, respectively, with an average of 340.15 W. After the second wet etching, the light output efficiencies increased to 363.63 W and 359.25 W, respectively, with an average of 361.44 W. Therefore, the ratio of light output power before and after the second wet etching for chip 9 was 1.07, and for chip 10 it was 1.06. The average ratio of the light output power before and after the second wet etching for both chips 9 and 10 was 1.06.

[0047] Table 2 shows the data on the surface roughening effect of LED chips 5 and 6 after immersing them in a modification solution at 43℃ for 2 minutes. The light output efficiencies of chips 5 and 6 after the first wet etching were 339.78W and 340.59W, respectively, with an average of 340.19W. After the second wet etching, the light output efficiencies increased to 378.02W and 377.86W, respectively, with an average of 377.94W. Therefore, the ratio of light output power before and after the second wet etching for both chips 5 and 6 was 1.11. Since the above three experimental temperatures all used two sets of data for comparison, and the values ​​were stable without significant deviation, the following comparison is made using the ratio of light output power before and after the second wet etching at the three temperatures. Specifically, at 23℃, the average ratio of light output power before and after the second wet etching for chips 7 and 8 is 1.04; at 33℃, the average ratio of light output power before and after the second wet etching for chips 9 and 10 is 1.06; and at 43℃, the average ratio of light output power before and after the second wet etching for chips 5 and 6 is 1.11. According to the above data, as the temperature gradually increases, the light output power after the second roughening and the ratio of light output power before and after the second roughening both gradually increase. The second wet etching at 43℃ has the highest light output power and light output power ratio, thus giving the LED chip the best light output effect.

[0048] Taking chips 5 and 6 as examples, the optical output powers of chips 5 and 6 after the second wet etching are 378.02W and 377.86W, respectively. Before the first wet etching, the optical output powers of chips 5 and 6 were 174.08W and 178.77W, respectively. Therefore, the optical output power ratio of chip 5 after the first and second wet etching is 2.17, and the optical output power ratio of chip 6 after the second wet etching is 2.11. Compared with the optical output power ratio of 1.95 and 1.91 of chips 5 and 6 after only the first wet etching, this represents a significant improvement, thus effectively improving the optical output efficiency. It should be noted that at 23℃, 33℃, and 43℃, the positive voltage changes of chips 5 to 10 before and after the second wet etching ranged from -0.001V to 0.002V, which was relatively small. Therefore, it was not considered as a factor in selecting the temperature for the second wet etching.

[0049] Step S203: The exposed surface of the LED chip is rinsed with 18 MΩ·cm deionized water to remove the residual modifying solution. After the LED chip is cleaned, the entire surface roughening process is completed. Through the above LED chip surface roughening method, compared with the problem in the prior art that the surface roughening effect of the LED chip is difficult to control, resulting in poor large-area roughening effect on the LED chip surface and affecting the light extraction efficiency, the first wet etching is performed to roughen the entire surface of the LED chip into an undulating mountain shape. In this state, a mountain morphology is formed on the surface of the LED chip, but there are still a large number of peaks in the mountain morphology with relatively large angles, which leads to the problem that light is difficult to exit. The LED chip is subjected to a second wet etching, which modifies the mountain morphology formed on the surface of the LED chip after the first wet etching, so that the included angle of the peaks is effectively reduced, thereby achieving the numerical change of the light output power after the first wet etching and after the second wet etching as shown in Table 2, making the light output efficiency affected by the surface morphology of the LED chip, which is difficult to control in the prior art, controllable, and thus improving the light-emitting effect of the LED chip.

[0050] Based on the same inventive concept, the present invention further discloses an LED chip, as ref Figures 4 to 6 erence to the illustration, comprising: a GaAs substrate 1, an epitaxial structure epitaxially grown along the GaAs substrate 1, and a first conductive type metal layer 9. The exposed surface not covered by the first conductive type metal layer 9 is subjected to surface roughening by the LED chip surface roughening method in the foregoing embodiment, and a second conductive type metal layer 10 is epitaxially grown on the back surface of the GaAs substrate 1.

[0051] ref Figures 4 to 6 erence to the illustration, the epitaxial structure includes a GaAs buffer layer 2, a DBR layer 3, an N-type AlGaInP layer 4, a quantum well active layer 5, a P-type AlGaInP layer 6, a first P-type GaP layer 7 and a second P-type GaP layer 8 which are epitaxially grown on the GaAs substrate 1; the thickness of the GaAs buffer layer 2 is 100 nm, the thickness of the DBR layer 3 is 2400 nm, the thickness of the N-type AlGaInP layer 4 is 400 nm, the thickness of the quantum well active layer 5 is 600 nm, the thickness of the P-type AlGaInP layer 6 is 1000 nm, the thickness of the first P-type GaP layer 7 is 700 nm, and the thickness of the second P-type GaP layer 8 is 1200 nm.

[0052] The epitaxial structure is grown on the GaAs substrate 1 by using an MOCVD process (Metal-Organic Chemical Vapor Deposition): the GaAs buffer layer 2 and the DBR layer 3 are grown on the GaAs substrate 1, wherein the DBR layer is composed of Al 0.6 Ga 0.4As and AlAs are grown in 13-17 pairs (alternating), followed by the sequential growth of an N-type AlGaInP layer 4, a quantum well active layer 5, a P-type AlGaInP layer 6, a first P-type GaP layer 7, and a second P-type GaP layer 8. It should be noted that the GaAs buffer layer 2 and the DBR layer 3 are mainly used to reflect the red light emitted by the quantum well active layer 5. In this embodiment, the growth pressure of the first P-type GaP layer 7 is 200-300 torr, the growth rate is 500 nm / h-1500 nm / h, and the growth temperature is 800-900 degrees Celsius; the growth pressure of the second P-type GaP layer 8 is 500-600 torr, the growth rate is 1500 nm / h-2700 nm / h, and the growth temperature is 700-750 degrees Celsius. Both the first P-type GaP layer 7 and the second P-type GaP layer 8 are made of Mg. 2+ Doping is performed, with a doping concentration greater than 10. 18 / cm 3 It should be noted that, in the aforementioned embodiment, the surface of the LED chip that is roughened (the exposed surface not covered by the first conductive metal layer 9) is the side of the second P-type GaP layer 8 away from the first P-type GaP layer 7. The specific morphology after roughening is as follows: Figure 6 As shown.

[0053] The state after the epitaxial structure has grown is as follows Figure 5 As shown, photoresist is spin-coated on the side of the second P-type GaP layer 8 away from the first P-type GaP layer 7. The typical thickness of the photoresist layer is 1.2 μm. Electrode patterns are exposed onto the photoresist layer using a photomask. Titanium, platinum, and gold are sequentially deposited onto the photoresist layer using an electron beam evaporation apparatus to form the first conductive metal layer 9. The typical thicknesses of titanium, platinum, and gold are 50 nm, 50 nm, and 400 nm, respectively. The unexposed photoresist layer and the first conductive metal layer 9 covering the unexposed photoresist layer are peeled off from the surface of the second P-type GaP layer 8 using an organic solvent (such as acetone) or a resist remover to form an exposed surface not covered by the first conductive metal layer 9. The LED chip surface roughening step described in the aforementioned embodiment is then performed to finally form the surface shown in the figure. Figure 6 The roughened surfaces of the first conductive metal layer 9 and the second P-type GaP layer 8 are shown.

[0054] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0056] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for roughening the surface of an LED chip, the LED chip comprising a GaAs substrate, an epitaxial structure epitaxially grown along the surface of the GaAs substrate, and a first conductive metal layer, the surface roughening method roughening the exposed surface not covered by the first conductive metal layer, characterized in that, The surface roughening method includes: The exposed surface facing away from the GaAs substrate was subjected to a first wet etching using an etching solution, which was a mixture of saturated 2-hydroxysuccinic acid, saturated oxalic acid, and 30 wt% hydrogen peroxide, with the volume ratio of each component of the etching solution being 1:(0.5~1.5):(1.5~2.5). A second wet etching process was performed on the exposed surface away from the GaAs substrate using a modification solution. The modification solution was a mixture of 37 wt% hydrochloric acid, 68 wt% nitric acid, and 36 wt% acetic acid, with the volume ratio of each component of the modification solution being (2~3):1:(3~5). Maintain the etching solution temperature at 50°C~60°C, and immerse the LED chip in the etching solution for 30min~40min to perform the first wet etching. Maintain the temperature of the modification solution at 40℃~50℃, and immerse the LED chip in the modification solution for 1min~2min to perform a second wet etching.

2. The LED chip surface roughening method according to claim 1, characterized in that, Before the second wet etching, deionized water was used to clean the exposed surface of any residual etching solution. After the second wet etching, deionized water was used to clean the exposed surface of any residual modification solution.

3. An LED chip, characterized in that, include: A GaAs substrate, an epitaxial structure and a first conductive metal layer grown along the GaAs substrate, the exposed surface not covered by the first conductive metal layer is roughened by the surface roughening method of GaAs substrate LED chip as described in claim 1 or 2, and a second conductive metal layer is epitaxially grown on the back side of the GaAs substrate.

4. The LED chip according to claim 3, characterized in that, The epitaxial structure includes a GaAs buffer layer, a DBR layer, an N-type AlGaInP layer, a quantum well active layer, a P-type AlGaInP layer, a first P-type GaP layer, and a second P-type GaP layer epitaxially grown on a GaAs substrate.

5. The LED chip according to claim 4, characterized in that, The thickness of the GaAs buffer layer is 100 nm, the thickness of the DBR layer is 2400 nm, the thickness of the N-type AlGaInP layer is 400 nm, the thickness of the quantum well active layer is 600 nm, the thickness of the P-type AlGaInP layer is 1000 nm, the thickness of the first P-type GaP layer is 700 nm, and the thickness of the second P-type GaP layer is 1200 nm.

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