Deep ultraviolet LED composite periodic electrode and preparation method thereof, and deep ultraviolet LED

Abstract

The invention relates to the technical field of deep ultraviolet LEDs, in particular to a deep ultraviolet LED composite periodic electrode, a preparation method of the deep ultraviolet LED composite periodic electrode and a deep ultraviolet LED. The preparation method comprises the following steps: preparing an epitaxial wafer of a chip; the surface of the P-type semiconductor hole injection layer of the epitaxial wafer is subjected to spin-coating mucilage increasing treatment and spin-coating photoresist treatment in sequence, and then baking treatment is carried out; performing photoetching treatment on the epitaxial wafer by using an MLA photoetching system to obtain a required photoetching pattern, the photoetching pattern being distributed at equal intervals in a longitude and latitude manner, so that the photoetching pattern is formed by arranging a plurality of rectangular grids in an array manner, each rectangular grid comprises four rectangular edges, and the intersection parts of the end parts of the rectangular edges are connected by adopting dots; and performing I CP etching on the epitaxial wafer, and then plating a conductive electrode material. The deep ultraviolet LED composite periodic electrode prepared by the invention adopts a dot-line combination and composite ordered longitude and latitude arrangement design, so that the light transmission effect of front deep ultraviolet light can be remarkably improved, and the deep ultraviolet LED with high light extraction efficiency can be obtained.

Description

Technical Field

[0001] The present application relates to the technical field of deep ultraviolet LEDs, and in particular to a deep ultraviolet LED composite periodic electrode and a preparation method thereof, and a deep ultraviolet LED. Background Art

[0002] In recent years, AlGaN-based deep ultraviolet LEDs have attracted extensive attention and research internationally due to their unique wavelength advantages and broad application prospects. However, the current practical application of deep ultraviolet LEDs and their large-scale promotion still face many technical challenges:

[0003] One of the important limiting factors is the low light extraction efficiency, which is mainly due to the total reflection of the deep ultraviolet LED material and the air interface, the strong light absorption of the metal electrode, etc., which makes the number of photons transmitted from the front of the deep ultraviolet LED very limited, thereby reducing the external quantum efficiency of the device. Traditional metal electrodes will hinder light transmission.

[0004] In addition, the use of visible light transparent conductive materials, such as ITO (indium tin oxide), as electrode materials has significant absorption of deep ultraviolet photons, resulting in poor transmittance of deep ultraviolet light, which is not conducive to the preparation of electrodes for deep ultraviolet LEDs.

[0005] In summary, at present, the preparation of deep ultraviolet LED electrodes mainly faces the following problems: First, traditional metal electrodes have strong light absorption in the deep ultraviolet band, which makes the number of photons passing through the front of the deep ultraviolet LED very limited, affecting the light extraction efficiency; secondly, existing visible light transparent conductive materials such as ITO (indium tin oxide) have significant absorption of deep ultraviolet photons, resulting in poor transmittance of deep ultraviolet light, making the performance of existing electrode conductive materials in the deep ultraviolet band not ideal and unable to meet the preparation requirements of electrodes well. Summary of the invention

[0006] In order to solve the deficiencies of the prior art mentioned in the background technology, the present application provides a highly efficient interconnected integrated deep ultraviolet LED composite periodic electrode and a preparation method thereof, and the technical solution thereof is as follows:

[0007] The preparation method of the deep ultraviolet LED composite periodic electrode provided in the present application comprises the following steps:

[0008] Preparing an epitaxial wafer of a chip; the epitaxial wafer includes, from bottom to top, a substrate, a buffer layer, an N-type semiconductor electron injection layer, a multi-quantum well active layer, and a P-type semiconductor hole injection layer;

[0009] The surface of the P-type semiconductor hole injection layer of the epitaxial wafer is sequentially subjected to spin coating thickening liquid treatment and spin coating photoresist treatment, and then the epitaxial wafer is baked;

[0010] The P-type semiconductor hole injection layer of the baked epitaxial wafer is subjected to photolithography processing by using an MLA photolithography system to obtain a desired photolithography pattern; wherein the photolithography pattern is distributed in equal intervals in longitude and latitude, so that it is arranged in an array of rectangular grids; the rectangular grids include four rectangular edges with a line width of 3 to 5 μm, and the intersections of the ends of the rectangular edges are connected by dots with a diameter of 10 to 20 μm;

[0011] The epitaxial wafer with the photolithography pattern is subjected to ICP etching and then plated with a conductive electrode material to obtain the composite periodic electrode.

[0012] Among them, the obtained composite periodic electrode has a pattern of equally spaced longitude and latitude distribution, so that it is arranged in an array of several rectangular grids; the rectangular grid includes four rectangular edges with a line width of 3 to 5 μm, and the intersections of the ends of the rectangular edges are connected by dots with a diameter of 10 to 20 μm.

[0013] In some embodiments, the rectangular grid is a square structure with a side length of 30 to 75 μm.

[0014] In some embodiments, the conductive electrode material is a titanium aluminum titanium electrode material.

[0015] In some embodiments, the rectangular grid is a square structure with a side length of 50 μm; a central dot is provided at the center of the rectangular grid, and the central dot is connected to any one of the four rectangular sides by a connecting line; wherein the connecting lines of each rectangular grid in the photolithography pattern are parallel to each other, the line width of the connecting lines and the rectangular sides is 3 to 5 μm, and the diameter of the central dot is 10 to 20 μm.

[0016] In some embodiments, the rectangular grid is a square structure consisting of four rectangular sides, and the side length is 30 μm.

[0017] In some embodiments, the photolithography process comprises the following steps:

[0018] Zero calibration: After placing the baked epitaxial wafer on the displacement platform of the MLA lithography system, the displacement platform of the MLA lithography system is calibrated to zero;

[0019] After zeroing, focus is performed: the focal plane of the microlens array of the MLA lithography system is adjusted by a computer to be aligned with the desired exposure plane, and then the distance between the focal plane of the microlens array and the desired exposure plane is adjusted to 0.3-0.7 mm;

[0020] After focusing, perform photolithography: The MLA photolithography system is controlled by a computer to perform photolithography on the epitaxial wafer;

[0021] Dissolution: Place the exposed photolithography pattern in a developer for 1 to 3 minutes to dissolve;

[0022] Cleaning and drying: Rinse the dissolved epitaxial wafer with water and blow dry with nitrogen to obtain the desired photolithography pattern.

[0023] In some embodiments, the epitaxial wafer is cleaned and dried before spin coating the viscosity-enhancing liquid; the cleaning and drying process is as follows: firstly, the epitaxial wafer of the chip is placed in an acetone solution for ultrasonication, and then placed in anhydrous ethanol and deionized water for ultrasonication in sequence; wherein, the ultrasonic sound wave power is (100-350) W, the ultrasonic temperature is 25-40° C., and the ultrasonic time of each ultrasonication is (2-15) minutes; finally, the epitaxial wafer after ultrasonic cleaning is dried with nitrogen;

[0024] In some embodiments, the process of spin coating thickening liquid treatment is: placing the blown epitaxial wafer in a coating machine, and spin coating the thickening liquid on the surface of the P-type semiconductor hole injection layer; wherein the spin coating process sequentially performs low-speed spin coating and high-speed spin coating; the rotation speed of the low-speed spin coating is 500-1500 r / min, the duration of the low-speed spin coating is 2-5 s, the rotation speed of the high-speed spin coating is 2000-3500 r / min, and the duration of the high-speed spin coating is 20-40 s;

[0025] In some embodiments, the process of performing spin coating photoresist treatment is: spin coating the surface of the P-type semiconductor hole injection layer with photoresist; wherein the spin coating process sequentially performs low-speed spin coating and high-speed spin coating; the rotation speed of the low-speed spin coating is (500-1500) r / min, the duration of the low-speed spin coating is (1-10) s, the rotation speed of the high-speed spin coating is (2000-4000) r / min, and the duration of the high-speed spin coating is (10-60) s;

[0026] In some embodiments, the baking process is as follows: placing the spin-coated epitaxial wafer on a hot plate for baking at a temperature of 80 to 120° C. for a baking time of 2 to 7 minutes.

[0027] The present application also provides a deep ultraviolet LED composite periodic electrode, which is prepared by the preparation method described above.

[0028] In some embodiments, the pattern of the composite periodic electrode is distributed in longitude and latitude with equal intervals, so that it is arranged in an array of several rectangular grids; the rectangular grid includes four rectangular edges with a line width of 3 to 5 μm, and the ends of the rectangular edges are connected by dots with a diameter of 10 to 20 μm at the intersection; the thickness of the composite periodic electrode is (50 to 150) nm.

[0029] The present application also provides a deep ultraviolet LED, which includes an epitaxial wafer, an N-type electrode, and a P-type electrode; the epitaxial wafer includes, from bottom to top, a substrate, a buffer layer, an N-type semiconductor electron injection layer, a multi-quantum well active layer, and a P-type semiconductor hole injection layer; wherein the upper surface of the P-type semiconductor hole injection layer is provided with a groove extending to the N-type semiconductor electron injection layer so that the upper surface of the N-type semiconductor electron injection layer forms an exposed area; the surface of the exposed area is provided with the N-type electrode; the surface of the P-type semiconductor hole injection layer is provided with a P-type electrode, and the P-type electrode is a composite periodic electrode prepared by the preparation method as described above.

[0030] In some embodiments, the N-type semiconductor electron injection layer is an N-type aluminum gallium nitride layer;

[0031] In some embodiments, the P-type semiconductor hole injection layer is a P-type gallium nitride layer.

[0032] In some embodiments, an annular groove extending downward to the N-type semiconductor electron injection layer is provided along the outer circumference of the upper surface of the P-type semiconductor hole injection layer, so that the upper surface of the N-type semiconductor electron injection layer forms an annular exposed area; wherein the surface of the exposed area is provided with an annular N-type electrode.

[0033] The preparation method of a deep ultraviolet LED composite periodic electrode provided in this application has the following technical effects compared with the existing technology:

[0034] The deep ultraviolet LED composite periodic electrode prepared in the present application adopts a point-line combination and a composite orderly longitude-latitude arrangement design, which can significantly improve the light transmittance effect of the front deep ultraviolet light, which is conducive to obtaining a deep ultraviolet LED with high light extraction efficiency.

[0035] Moreover, the present application realizes rapid manufacturing with the aid of a microlens array lithography system, which not only greatly improves production efficiency and reduces production costs, and is conducive to large-scale industrial production, but also the electrode design obtained has a compact structure and stable performance, and is suitable for the preparation of various deep ultraviolet LED devices, and has broad application prospects.

[0036] Other features and beneficial effects of the present application will be described in the subsequent description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other beneficial effects of the present application can be achieved and obtained by the structures and / or components indicated in the description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0038] Figure 1 A schematic diagram of the structure of a deep ultraviolet LED with a composite periodic electrode prepared in this application;

[0039] Figure 2 A schematic diagram of the structure of the composite periodic electrode prepared in Examples 1-3 of the present application;

[0040] Figure 3 A schematic diagram of the structure of the composite periodic electrode prepared in Examples 4-6 of the present application;

[0041] Figure 4 This is a SEM (scanning electron microscope) image of the composite periodic electrode prepared in Example 1 of the present application;

[0042] Figure 5 EL (electroluminescence) spectra of Example 1 of the present application measured at voltages of 14, 16, and 18 V respectively;

[0043] Figure 6 IV (current-voltage) diagram of the composite periodic electrode prepared in Examples 1-6 of the present application and a conventional disk electrode with a diameter of 300 μm;

[0044] Figure 7 EL mapping diagram of the composite periodic electrode prepared in Examples 1-6 of the present application and a traditional disk electrode with a diameter of 300 μm.

[0045] Figure ID:

[0046] 100 - substrate, 200 - buffer layer, 300 - N-type semiconductor electron injection layer, 400 - multi-quantum well active layer, 500 - P-type semiconductor hole injection layer, 600 - N-type electrode, 700 - composite periodic electrode, 800 - groove. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0048] The present application also provides the following examples and comparative examples to verify the beneficial effects of the present application:

[0049] Example 1

[0050] The LED device of the composite periodic electrode structure of this embodiment and the preparation method thereof include the following steps:

[0051] Step 1: First, place the epitaxial wafer of the chip in an acetone solution for ultrasonic treatment for 5 minutes, with an ultrasonic power of 240W and a temperature of 25-40°C;

[0052] The epitaxial wafer includes, from bottom to top, an Al2O3 substrate, an AlN buffer layer (gallium aluminum nitride, 1100 nm), an N-type semiconductor electron injection layer (N-type gallium aluminum nitride layer, specifically nAl 0.5 Ga 0.05 N, ~ 1400nm), multi-quantum well active layer (specifically 5per odsMQWs, including 10nm-Al 0.45 Ga 0.55 N, 3nm-A l 0.35 Ga 0.65 N), P-type semiconductor hole injection layer (P-type gallium nitride layer, 120nm thick);

[0053] Step 2: After taking out the epitaxial wafer, place it in anhydrous ethanol and deionized water for ultrasonic treatment. The ultrasonic time is also 5 minutes, the ultrasonic power is 240W, and the temperature is 25℃:

[0054] Step 3: Blow dry the cleaned epitaxial wafer with nitrogen;

[0055] Step 4: Place the dried epitaxial wafer in MOCVD to grow 100nm SiO2 as a mask;

[0056] Step 5: Place the epitaxial wafer after the growth of SiO2 in a coating machine, and spin-coat the surface of the P-type semiconductor hole injection layer with a thickening liquid. The coating process is performed in sequence by low-speed coating and high-speed coating. The speed of the coating machine is set to a low speed of 1000 r / min, a duration of 3 s, and a high speed of 3000 r / min, a duration of 30 s;

[0057] Step 6: After the viscosity enhancing liquid is spin-coated, the surface of the P-type semiconductor hole injection layer is spin-coated with photoresist. The spin coating process is performed in sequence of low-speed spin coating and high-speed spin coating. The speed of the coating machine is set to a low speed of 1000 r / min, a duration of 3 s, and a high speed of 3000 r / min, a duration of 30 s;

[0058] Step 7: Place the spin-coated epitaxial wafer on a hot plate and bake it at 100°C for 4 minutes.

[0059] Step 8: Next, the epitaxial wafer is photolithographically processed using an MLA photolithography system to obtain the desired mesa pattern;

[0060] Step nine: Place the exposed pattern in a developer to dissolve it for 2 minutes, then rinse it with deionized water and blow it dry with nitrogen to obtain the desired mesa pattern.

[0061] Step 10: Place the epitaxial wafer with the pattern on a hot plate and bake it at 120°C for 15 minutes;

[0062] Step 11: According to the mesa pattern, the epitaxial wafer with the mesa pattern is subjected to I CP etching to the middle of the N-type GaN layer;

[0063] Step 12: After repeating the cleaning process of steps 1 to 3, repeat the photoresist spin coating of steps 5 to 9;

[0064] Step 13: Next, use the MLA lithography system to perform lithography on the P-type semiconductor hole injection layer of the epitaxial wafer to obtain the required lithography pattern of the P-type electrode. The specific process is as follows:

[0065] (1) First, the epitaxial wafer needs to be placed on the displacement platform and the displacement platform of the MLA lithography system needs to be zeroed;

[0066] (2) After zero calibration, the focal plane of the microlens array is adjusted by computer to align with the desired exposure plane;

[0067] (3) Next, the distance between the focal plane of the microlens array and the exposure plane needs to be adjusted to 0.5 mm;

[0068] (4) Then, the epitaxial wafer is lithographically processed by a computer-controlled MLA lithography system to obtain a rectangular grid pattern with a dot-line combination period (i.e., side length) of 50 μm;

[0069] (5) placing the exposed pattern in a developer for dissolution for 2 min;

[0070] (6) Rinse the dissolved epitaxial wafer with pure water and blow dry with nitrogen to obtain the desired photolithography pattern.

[0071] like Figure 2 , Figure 4As shown, through the parameter design and control of the MLA lithography system, the formed lithography pattern is: the lithography pattern is located in the middle of the P-type semiconductor hole injection layer, which is evenly spaced in longitude and latitude, and consists of 36 rectangular grids (6 horizontal rows and 6 vertical rows). The rectangular grid is a square structure composed of four rectangular sides, and its side length L is 50μm, the rectangular side line width D1 is 4μm, and the intersection of the ends of the rectangular sides is connected by dots with a diameter R1 of 15μm, and the dots and lines are combined to form a composite periodic structure.

[0072] Step 14: After the epitaxial wafer with the photolithography pattern is subjected to ICP etching, titanium, aluminum and titanium are plated to obtain a composite periodic electrode. The thickness of the composite periodic electrode is 70nm (Ni / Au is 20 / 50nm respectively);

[0073] Step 15: placing the prepared composite periodic electrode in an annealing furnace, and performing a rapid thermal annealing treatment at 450° C. for 10 minutes in a nitrogen environment;

[0074] Step 16: Repeat step 13 and use the MLA lithography system to perform photolithography on the epitaxial wafer to obtain the desired N-type electrode pattern;

[0075] Step 17: Place the exposed pattern in a developer to dissolve for 2 minutes, rinse with pure water, and blow dry with oxygen to obtain the desired N-type electrode pattern;

[0076] Step 18: The epitaxial wafer with the photolithography pattern is plated with titanium, aluminum and titanium using an electron beam thermal evaporation device to obtain the N-type electrode. The thickness of the N-type electrode is 235nm (Ti / Al / Ti is 30 / 200 / 5nm respectively);

[0077] Step 19: Place the prepared N-type electrode in an annealing furnace and perform thermal annealing treatment at 850° C. for 90 seconds in a nitrogen environment to obtain a complete LED device.

[0078] Among them, the structure of the complete deep ultraviolet LED is as follows Figure 1 As shown:

[0079] The epitaxial wafer includes, from bottom to top, a substrate 100, a buffer layer 200, an N-type semiconductor electron injection layer 300, a multi-quantum well active layer 400, and a P-type semiconductor hole injection layer 500; wherein, along the outer circumference of the upper surface of the P-type semiconductor hole injection layer 500, there is an annular groove 800 extending downward to the N-type semiconductor electron injection layer 300, so that the upper surface of the N-type semiconductor electron injection layer 300 forms an annular exposed area (i.e., a table); an annular N-type electrode 600 is provided on the surface of the exposed area; a P-type electrode is provided on the surface of the P-type semiconductor hole injection layer, and the P-type electrode is a composite periodic electrode 700 prepared by the preparation method as described above.

[0080] Example 2

[0081] The method of Example 1 was used for preparation. The difference between this comparative example and Example 1 is that: Figure 2 As shown, the side length L of the rectangular checkered pattern is 75 μm.

[0082] Example 3

[0083] The method of Example 1 was used for preparation. The difference between this comparative example and Example 1 is that: Figure 2 As shown, the side length L of the rectangular checkered pattern is 30 μm.

[0084] Example 4

[0085] The method of Example 1 was used for preparation. The difference between this comparative example and Example 1 was only that:

[0086] like Figure 3 As shown: the photolithography pattern is located in the middle of the P-type semiconductor hole injection layer, which is evenly spaced in longitude and latitude, and consists of 16 rectangular grids (4 horizontally and 4 vertically), the side length L of the rectangular grid is 75μm, the line width D1 of the rectangular side is 4μm, and the intersections of the ends of the rectangular sides are connected by dots with a diameter R1 of 15μm; a central dot is provided in the center of the rectangular grid, and the central dot is connected to any one of the four rectangular sides by a connecting line; wherein the connecting lines of each rectangular grid in the photolithography pattern are parallel to each other, the line width D2 of the connecting line is 4μm, and the diameter R2 of the central dot is 15μm.

[0087] Example 5

[0088] The method of Example 1 was used for preparation. The difference between this comparative example and Example 1 was only that:

[0089] like Figure 3As shown, the photolithography pattern is located in the middle of the P-type semiconductor hole injection layer, which is evenly spaced in longitude and latitude, and consists of 36 rectangular squares (6 horizontally and 6 vertically), the side length L of the rectangular square is 50μm, the line width D1 of the rectangular side is 4μm, and the intersections of the ends of the rectangular sides are connected by dots with a diameter R1 of 15μm; a central dot is provided in the center of the rectangular square, and the central dot is connected to any one of the four rectangular sides by a connecting line; wherein the connecting lines of each rectangular square in the photolithography pattern are parallel to each other, the line width D2 of the connecting line is 4μm, and the diameter R2 of the central dot is 15μm.

[0090] Example 6

[0091] The method of Example 1 was used for preparation. The difference between this comparative example and Example 1 was only that:

[0092] like Figure 3 As shown, the photolithography pattern is located in the middle of the P-type semiconductor hole injection layer, which is evenly spaced in longitude and latitude, and consists of 100 rectangular squares (10 horizontally and 10 vertically), the side length L of the rectangular square is 30μm, the line width D1 of the rectangular side is 4μm, and the intersections of the ends of the rectangular sides are connected by dots with a diameter R1 of 15μm; a central dot is provided in the center of the rectangular square, and the central dot is connected to any one of the four rectangular sides by a connecting line; wherein the connecting lines of each rectangular square in the photolithography pattern are parallel to each other, the line width D2 of the connecting line is 4μm, and the diameter R2 of the central dot is 15μm.

[0093] The performance test was carried out on the products obtained in the above embodiment and the comparative example (existing deep ultraviolet LED with disk electrode structure)

[0094] A deep ultraviolet LED with a traditional disk electrode with a diameter of 300μm is set as a comparative example. The structural difference between it and the deep ultraviolet LED prepared in Example 1 is that its P-type electrode does not use a composite periodic electrode, but a disk electrode with a diameter of 300μm, and the electrode material is nickel gold as in Example 1.

[0095] (1) EL spectrum of composite periodic electrode

[0096] The EL spectrum of the product to be tested was measured under the conditions of an emission wavelength of 273nm, a FWHM (full width at half maximum) of 12.36nm, and voltages of 14, 16, and 18V respectively. Figure 5 EL spectra of Example 1 measured at voltages of 14, 16, and 18 V;

[0097] from Figure 5 It can be seen that the deep ultraviolet LED prepared in Example 1 has good luminous performance;

[0098] (2) IV diagram of the product obtained in the embodiment and the deep ultraviolet LED with the existing disk electrode structure

[0099] The test method and test conditions are as follows: two probes connected to positive voltage and negative voltage are used to pierce the P-type electrode and N-type electrode of the prepared deep ultraviolet LED respectively, and the test voltage is from 0V to 20V.

[0100] The measured IV graph is as follows Figure 6 As shown, the horizontal axis is voltage and the vertical axis is current; C0 corresponds to the proportional relationship, A1-A3 corresponds to embodiments 1-3, and B1-B3 corresponds to embodiments 4-6.

[0101] from Figure 6 It can be seen that:

[0102] Comparing the disc-shaped P-type electrode of the comparative example and the P-type electrode of the embodiment (i.e., the composite periodic electrode), it can be found that the IV curve of the P-type electrode of the embodiment has a more obvious upward trend. Under the same voltage, the current flowing through the LED with a disc-shaped P-type electrode is lower and the luminous performance is weaker. The above results can be summarized as follows: Compared with the deep ultraviolet LED with a traditional disc electrode with a diameter of 300μm in the comparative example, the product prepared in the embodiment of the present application has a small resistance, indicating that it can effectively conduct current, improve the photoelectric conversion efficiency of the device, and have better device performance, indicating that it emits more deep ultraviolet photons. Among them, Example 3 is the best, followed by Example 2 and Example 5, which can also reach a very good level.

[0103] (3) EL mapping diagram of the product obtained in the embodiment and the existing deep ultraviolet LED with disk electrode structure

[0104] The test method and test conditions are as follows: use two probes connected to positive and negative voltages to pierce the P-type electrode and N-type electrode respectively, and connect to +18V voltage;

[0105] The measured EL mapping diagram is shown in Figure 7 As shown, C0 corresponds to the corresponding proportion, A1-A3 correspond to embodiments 1-3, and B1-B3 correspond to embodiments 4-6; Figure 7 The "18V" in the figure represents the voltage value connected to the LED device.

[0106] from Figure 7 It can be seen that:

[0107] Compared with the traditional circular electrode of the comparative example, the light radiation of the embodiments of the present application at 18V is enhanced, and the luminous intensity of the comparative example is weaker; and in these embodiments, A3, B1, and B2 have stronger light radiation at 18V.

[0108] For the conventional circular electrode in the comparative example, when current is injected from the P-type electrode, the circular electrode has a large area and no gaps, which blocks and absorbs the photons generated by radiation recombination. Therefore, the photons can only be emitted from the periphery of the circular electrode, resulting in a weak luminous intensity. When the composite periodic electrode in the embodiment is used, Figure 2 and Figure 3 The two arrangements of P-type electrodes shown have a significant effect on enhancing the light extraction efficiency of deep ultraviolet LEDs, among which A3, B1, and B2 produce the strongest light radiation. This shows that the composite periodic electrode can not only improve light emission, but also improve thermal management, which helps to more effectively extract heat from the LED chip, thereby reducing the operating temperature of the device and improving its stability and life.

[0109] The above results show that compared with the traditional deep ultraviolet LED with a disk electrode of 300 μm in diameter in the comparative example, the product prepared in the embodiment of the present application has a significantly improved front light transmission effect, which can effectively reduce the absorption of light by the electrode metal, reduce light absorption loss, and improve light extraction efficiency. In terms of light transmission performance and light extraction efficiency, compared with other embodiments, embodiment 5 has the best comprehensive performance, followed by embodiment 3. Figure 6 Embodiment 2 is equivalent to Embodiment 5, but it is obvious that its light transmittance is lower than that of Embodiment 5 and Embodiment 3. In terms of comprehensive performance, Embodiment 5 and Embodiment 3 are better choices.

[0110] The technical solution of this application includes at least the following objectives, design concepts, and beneficial effects:

[0111] The present application provides a highly efficient interconnected and integrated deep ultraviolet LED composite periodic electrode and a preparation method thereof. The use of the scheme of the present application can not only reduce the light absorption loss in the deep ultraviolet LED, but also effectively conduct current, while maintaining the high stability of the structure and performance of the deep ultraviolet LED device.

[0112] The design principle of this application is to reduce the absorption of light by metal, improve light extraction efficiency, and alleviate the current crowding problem. The preparation process adopts MLA manufacturing technology to achieve fast and efficient structure acquisition, simplify the process, and improve the overall performance of the device. This design aims to optimize the performance of optoelectronic devices and meet practical application needs.

[0113] Compared with the existing deep ultraviolet LEDs with traditional electrode structures, the deep ultraviolet LED composite periodic electrode prepared in this application adopts a point-line combination and a composite orderly longitude-latitude arrangement design:

[0114] The pattern of the composite periodic electrode is distributed in equal intervals in longitude and latitude, so that it is arranged in an array of rectangular grids; the rectangular grid includes four rectangular edges with a line width of 3 to 5 μm, and the intersections of the ends of the rectangular edges are connected by dots with a diameter of 10 to 20 μm; such a design can significantly improve the front light transmittance, which is conducive to obtaining a deep ultraviolet LED with high light extraction efficiency. The specific design concept and beneficial effects are as follows:

[0115] 1. The composite periodic electrode design significantly improves the front light extraction efficiency. This design not only makes the current more evenly spread inside the device, but also avoids the problems of current congestion and local overheating, thereby improving the stability and life of the device;

[0116] 2. Compared with the traditional disordered nanowires, the ordered arrangement characteristics of the electrode prepared in this application further optimize the current transmission performance. The ordered arrangement not only reduces the resistance, but also improves the current transmission efficiency, so that the overall performance of the device is significantly improved;

[0117] 3. The point-line combined grid structure of the composite electrode plays a composite effect in the current expansion. By precisely controlling the shape and arrangement of the electrodes, efficient expansion and distribution of the current is achieved, thereby improving the photoelectric conversion efficiency of the device;

[0118] 4. In addition, the above-mentioned composite periodic electrode is prepared with the aid of MLA (microlens array) equipment. The method of the present application realizes rapid manufacturing with the aid of MLA (microlens array) equipment, which not only greatly improves production efficiency and reduces production costs, and is conducive to large-scale industrial production, but also has a compact design structure and stable performance, and is suitable for the preparation of various deep ultraviolet LED devices, and has broad application prospects.

[0119] It should be noted that:

[0120] In this article, “~” is used to indicate a numerical range, and the range indicated by this expression includes two endpoint values.

[0121] The full name of the MLA lithography system is the microlens array lithography system, which is an existing device. This application adopts the existing MLA lithography system to set the corresponding preparation procedures and processes to obtain the required electrodes;

[0122] ICP etching is the full name of inductively coupled plasma etching, which is an existing process method implemented by using an existing plasma etcher, and its functional principle will not be described here again;

[0123] In addition to the titanium-aluminum-titanium conductive electrode material used for the composite periodic electrode in the above specific embodiments, other conductive electrode materials may also be used, such as nickel-aluminum-nickel-gold, ITO, etc., preferably titanium-aluminum-titanium conductive electrode material.

[0124] In summary, the specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments of the present application, but are not intended to limit the present application. Those skilled in the art may make adaptive adjustments within the scope of the present application.

[0125] In addition, unless otherwise specified, the raw materials used may also be conventional commercial products in the art, or prepared by conventional methods in the art; that is, the reagents and instruments used in this embodiment are not indicated with information such as the manufacturer, and are all conventional products that can be purchased on the market.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a deep ultraviolet LED composite periodic electrode, Features , including the following steps: Preparing an epitaxial wafer of a chip; the epitaxial wafer includes, from bottom to top, a substrate, a buffer layer, an N-type semiconductor electron injection layer, a multi-quantum well active layer, and a P-type semiconductor hole injection layer; Then, the surface of the P-type semiconductor hole injection layer of the epitaxial wafer is subjected to spin coating thickening liquid treatment and spin coating photoresist treatment in sequence, and then the epitaxial wafer is subjected to baking treatment; The P-type semiconductor hole injection layer of the baked epitaxial wafer is subjected to photolithography processing by using an MLA photolithography system to obtain a desired photolithography pattern; wherein the photolithography pattern is distributed in equal intervals in longitude and latitude, so that it is arranged in an array of rectangular grids; the rectangular grids include four rectangular edges with a line width of 3 to 5 μm, and the intersections of the ends of the rectangular edges are connected by dots with a diameter of 10 to 20 μm; The epitaxial wafer with the photolithography pattern is subjected to ICP etching and then plated with a conductive electrode material to obtain the composite periodic electrode.

2. The method for preparing the deep ultraviolet LED composite periodic electrode according to claim 1, Features: The rectangular grid is a square structure with a side length of 30 to 75 μm.

3. A method for preparing a deep ultraviolet LED composite periodic electrode according to any one of claims 1 to 2, Features: The conductive electrode material is titanium-aluminum-titanium electrode material.

4. The method for preparing a deep ultraviolet LED composite periodic electrode according to claim 1, Features: The rectangular grid is a square structure with a side length of 50 μm; A central dot is provided at the center of the rectangular grid, and the central dot is connected to any one of the four rectangular sides by a connecting line; wherein the connecting lines of each rectangular grid in the photolithography pattern are parallel to each other, the line width of the connecting lines and the rectangular sides is 3 to 5 μm, and the diameter of the central dot is 10 to 20 μm.

5. The method for preparing the deep ultraviolet LED composite periodic electrode according to claim 1, Features: The rectangular grid is a square structure composed of four rectangular sides, and the side length is 30 μm.

6. The method for preparing a deep ultraviolet LED composite periodic electrode according to claim 1, It is characterized in that The process of the photolithography process comprises the following steps: Zero calibration: After placing the baked epitaxial wafer on the displacement platform of the MLA lithography system, the displacement platform of the MLA lithography system is calibrated to zero; After zeroing, focus is performed: the focal plane of the microlens array of the MLA lithography system is adjusted by a computer to be aligned with the desired exposure plane, and then the distance between the focal plane of the microlens array and the desired exposure plane is adjusted to 0.3-0.7 mm; After focusing, perform photolithography: The MLA photolithography system is controlled by a computer to perform photolithography on the epitaxial wafer; Dissolution: Place the exposed photolithography pattern in a developer for 1 to 3 minutes to dissolve; Cleaning and drying: Rinse the dissolved epitaxial wafer with water and blow dry with nitrogen to obtain the desired photolithography pattern.

7. The method for preparing a deep ultraviolet LED composite periodic electrode according to claim 1, Features: The epitaxial wafer is cleaned and dried before spin coating the viscosity-enhancing liquid; the cleaning and drying process is as follows: the epitaxial wafer of the chip is first placed in an acetone solution for ultrasonic treatment, and then placed in anhydrous ethanol and deionized water for ultrasonic treatment in sequence; wherein the ultrasonic sound wave power is (100-350) W, the ultrasonic temperature is 25-40° C., and the ultrasonic time of each ultrasonic treatment is (2-15) minutes; finally, the epitaxial wafer after ultrasonic cleaning is dried with nitrogen; and / or, The process of spin coating thickening liquid treatment is as follows: placing the blown-dried epitaxial wafer in a coating machine, and spin coating the thickening liquid on the surface of the P-type semiconductor hole injection layer; wherein the spin coating process sequentially performs low-speed spin coating and high-speed spin coating; the rotation speed of the low-speed spin coating is 500-1500 r / min, the duration of the low-speed spin coating is 2-5 s, the rotation speed of the high-speed spin coating is 2000-3500 r / min, and the duration of the high-speed spin coating is 20-40 s; and / or, The process of spin coating photoresist treatment is as follows: spin coating the surface of the P-type semiconductor hole injection layer with photoresist; wherein the spin coating process sequentially performs low-speed spin coating and high-speed spin coating; the rotation speed of the low-speed spin coating is (500-1500) r / min, the duration of the low-speed spin coating is (1-10) s, the rotation speed of the high-speed spin coating is (2000-4000) r / min, and the duration of the high-speed spin coating is (10-60) s; and / or, The process of baking treatment is as follows: placing the spin-coated epitaxial wafer on a hot plate for baking, the baking temperature is 80-120° C., and the baking time is 2-7 minutes.

8. A deep ultraviolet LED composite periodic electrode, Features: The method is prepared according to any one of claims 1 to 7.

9. A deep ultraviolet LED, Features: Including epitaxial wafer, N-type electrode, P-type electrode; The epitaxial wafer includes, from bottom to top, a substrate, a buffer layer, an N-type semiconductor electron injection layer, a multi-quantum well active layer, and a P-type semiconductor hole injection layer; The upper surface of the P-type semiconductor hole injection layer is provided with a groove extending to the N-type semiconductor electron injection layer, so that the upper surface of the N-type semiconductor electron injection layer forms an exposed area; the surface of the exposed area is provided with the N-type electrode; A P-type electrode is provided on the surface of the P-type semiconductor hole injection layer, and the P-type electrode is a composite periodic electrode prepared by the preparation method described in any one of claims 1 to 7.

10. The deep ultraviolet LED according to claim 9, Features: An annular groove extending downward to the N-type semiconductor electron injection layer is provided along the outer circumference of the upper surface of the P-type semiconductor hole injection layer, so that the upper surface of the N-type semiconductor electron injection layer forms an annular exposed area; Wherein, a ring-shaped N-type electrode is provided on the surface of the exposed area.

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