Preparation method of light emitting diode with wet etching P electrode

Abstract

The invention relates to a preparation method of a light emitting diode with a wet etching P electrode. According to the preparation method of the DUV LEDs with the inverted structure, Ni / Au which is in good ohmic contact is treated by adopting a wet etching technology, namely Au is grown after Ni is grown, after Ni / Au is obtained, the Ni / Au is annealed, then Au etching is carried out on thick Au, and a part of Au is removed from particles formed by Au and Ni, so that gaps among the particles are increased, Au is thinned, and thus, the thickness of the particles is reduced. And more photons can be reflected by the metal reflecting mirror through the gaps, so that the transmittance of the photons is increased. According to the invention, the problem that the P electrode in the prior art cannot give consideration to good ohmic contact characteristic and high transmittance at the same time is solved.

Description

Technical Field

[0001] The technical solution of the present invention relates to the field of semiconductor light-emitting devices, and in particular to a method for preparing a light-emitting diode with a P electrode etched by a wet method. Background Art

[0002] Compared with traditional mercury lamps, AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) have the advantages of high efficiency, energy saving, and environmental protection. They have broad application prospects in sterilization, biological detection, sewage purification, and optical storage.

[0003] Although AlGaN-based DUV LEDs have achieved multiple breakthroughs in optoelectronic performance after decades of development. However, compared with InGaN-based blue LEDs, they still have the problem of low external quantum efficiency (EQE). Low light extraction efficiency (LEE) is one of the main reasons limiting high EQE. This is mainly due to the absorption of the P electrode and its P-type contact layer. For the traditional P electrode Ni / Au metal, although it has excellent ohmic contact characteristics, it has only about 30% reflectivity for deep ultraviolet photons and has high absorption. In order to solve this problem, a P electrode with high reflectivity can be used to reduce the absorption of photons, such as Ni / Al [10.1002 / pssa.201700435, Improving the Efficiency of AlGaN Deep-UVLEDs by Using Highly Reflective Ni / Al p-Type Electrodes]. In this technology, the goal of high reflectivity is achieved by directly stacking Ni / Al electrodes on the P-type contact layer and optimizing the thickness of the Ni layer. However, compared with Ni / Au, this method sacrifices the excellent ohmic contact characteristics, resulting in a significant increase in forward voltage, which will affect the reliability of the device.

[0004] Therefore, improving the traditional P-electrode Ni / Au is undoubtedly a more efficient and economical method. This is mainly because it can not only retain the good ohmic contact characteristics between Ni / Au and the P-type contact layer, but also increase its transmittance and improve the optical properties. Summary of the invention

[0005] The purpose of the present invention is to provide a method for manufacturing a light-emitting diode with a wet-etched P electrode in view of the shortcomings of the current technology. In the method for preparing flip-chip DUV LEDs, the method uses a wet etching technique to process the Ni / Au that has formed a good ohmic contact, that is, an Au etching solution is used to etch the Au layer, thereby reducing the absorption of deep ultraviolet photons by the Au layer. The present invention overcomes the problem in the prior art that the P electrode cannot simultaneously take into account good ohmic contact characteristics and high transmittance.

[0006] The technical solution of the present invention is: A method for preparing a light emitting diode device having a wet-etched P electrode, the method comprising the following steps: The first step is the growth of epitaxial wafers: First, in an MOCVD reactor, the substrate is baked at 950°C to 1350°C to remove foreign matter on the substrate surface, and then a buffer layer, an N-type semiconductor transport layer, a multi-quantum well layer, a P-type electron blocking layer, and a P-type semiconductor transport layer are grown respectively; The second step is dry etching steps: On the epitaxial wafer obtained in the first step, photoresist is made into a mesa shape by using photolithography technology and used as a mask, and the part not covered by the photoresist is etched by dry etching technology, thereby revealing the N-type semiconductor transmission layer; The third step is to make an N-type ohmic electrode: On the N-type semiconductor transport layer obtained in the second step, an N-type ohmic electrode pattern is revealed by photolithography, an N-type ohmic electrode is manufactured by evaporation and lift-off process, and a rapid thermal annealing process is performed under a suitable gas atmosphere and temperature; Step 4: Make a P-type ohmic electrode: On the P-type semiconductor transport layer of the DUV LEDs epitaxial wafer, a P-type ohmic electrode pattern is revealed by photolithography, a P-type ohmic electrode is made by evaporation and lift-off process, and a rapid thermal annealing process is performed under a suitable gas atmosphere and temperature; Step 5: wet etching of P-type ohmic electrode: On the P-type ohmic electrode obtained in the fourth step, the metal surface is cleaned with deionized water, and then a layer of photoresist is spin-coated, and the pattern of the P-type ohmic electrode on the mask is transferred to the epitaxial wafer using a photolithography machine, and the part except the P-type ohmic electrode is protected, and then the epitaxial wafer is immersed in Au etching solution for wet etching treatment; after etching, the epitaxial wafer is taken out for cleaning and drying; wherein the etching time is 1 to 20 minutes; The Au etching solution comprises a nitrating acid mixture consisting of 2 to 6 wt% KI, 2 to 6 wt% I2, 1 to 6 ppm chloride, 1 to 6 ppm sulfate and 1 to 5 ppm phosphate; The chloride is specifically cupric chloride; The sulfates are specifically calcium sulfate and aluminum sulfate; The phosphates are specifically potassium phosphate and nickel phosphate; Step 6: Make a highly reflective electrode: On the wet-etched P-type ohmic electrode obtained in the fifth step, a reflector pattern is obtained by photolithography, and a metal with high reflectivity is deposited as a metal reflector by evaporation and lift-off process; Thus, a light emitting diode device having a wet-etched P electrode is manufactured.

[0007] The substrate is a sapphire substrate, a silicon carbide (SiC) substrate, a gallium nitride (GaN) substrate or an aluminum nitride (AlN) substrate; The buffer layer is AlN with a thickness of 1 to 5 μm; The N-type semiconductor transport layer is Al x1 Ga 1-x1 N, where the coefficients of each component should be 0≤x1≤1, 0≤1-x1≤1, and the thickness should be 1-5 μm; The multi-quantum well layer is made of Al x2 Ga 1-x2 N / A x3 Ga 1-x3 N, where 0≤x2≤1, 0≤1-x2≤1, 0≤x3≤1, 0≤1-x3≤1, the bandgap of the quantum barrier should be higher than the bandgap of the quantum well, the number of quantum wells is greater than or equal to 1, and the quantum well Al x2 Ga 1-x2 N thickness is 1 to 20 nm, quantum barrier Al x3 Ga 1-x3 N thickness is 5 to 50 nm; The material of the P-type electron blocking layer is Al x4 Ga 1-x4 N, where 0≤x4≤1, 0≤1-x4≤1, and the thickness is 10 to 300 nm; The material of the P-type semiconductor transport layer is Al x5 Ga 1-x5 N, where 0≤x5≤1, 0≤1-x5≤1, and the thickness is 0.1~1 μm.

[0008] The N-type ohmic electrode is Ti / Al / Ti / Au, Al / Au or Cr / Au, wherein the projected area of ​​the N-type ohmic electrode is 5% to 100% of the area of ​​the exposed N-type semiconductor transport layer; The P-type ohmic electrode is composed of Ni metal and Au metal stacked up and down, wherein the projected area of ​​the P-type ohmic electrode is 5% to 100% of the area of ​​the exposed P-type semiconductor transmission layer; The high reflectivity metal is Al, and the thickness is 100-900 nm.

[0009] The obtained light-emitting diode with wet-etched P-electrode comprises, from bottom to top, a substrate, a buffer layer, and an N-type semiconductor transport layer; wherein the N-type semiconductor transport layer is divided into an upper and a lower layer, the lower layer completely covers the buffer layer, and the area of ​​the upper layer is 5-90% of the area of ​​the lower layer; the thickness of the lower layer is 5-95% of the thickness of the N-type semiconductor transport layer; The surface of the upper part of the N-type semiconductor transport layer is composed of a multi-quantum well layer, a P-type electron blocking layer, a P-type semiconductor transport layer, a P-type ohmic electrode, and a metal reflector from bottom to top. An N-type ohmic electrode is also distributed on the exposed portion of the lower layer of the N-type semiconductor transport layer; The P-type ohmic electrode is composed of a Ni metal electrode layer and an etched Au electrode layer from bottom to top; the thickness of the Ni layer metal is 3-50 nm; and the thickness of the Au layer after being etched by the Au etching solution is 0-50 nm.

[0010] The raw materials, equipment and processes involved in the above-mentioned method for preparing the light-emitting diode device with wet-etched P-electrode are all well known in the technical field.

[0011] The essential features of the present invention are: During the annealing process of the traditional P-type ohmic electrode Ni and Au metal, Ni reacts with O2 to form NiOx, and Au atoms diffuse evenly to the interface between NiOx and the P-type semiconductor transport layer, thereby forming metal clusters with a specific geometric structure. At the same time, this diffusion process will produce gallium vacancies, increase the surface hole concentration, and facilitate the formation of good ohmic contact. It is precisely because of the annealing characteristics of Ni / Au that the presence of thick Au is more conducive to the generation of gallium vacancies. Compared with thin Au, it produces fewer gallium vacancies and worse ohmic contact, but thick Au will seriously absorb ultraviolet photons, resulting in reduced light extraction efficiency.

[0012] In the present invention, Ni is grown and then Au is grown. After Ni / Au is obtained, it is annealed (that is, rapid thermal annealing at 550°C). During the annealing process, Ni and Au will melt and aggregate to form particles, and the particles will form a good ohmic contact. Therefore, the grown Au layer is thicker, so that there will be more Au and P-type semiconductor transport layer in contact. During the contact process, gallium vacancies will be generated in the P-type semiconductor transport layer, ensuring that the surface hole concentration is increased, and the advantages of good electrical properties in the current technology are brought into play. Then, in order to solve the serious problem of light absorption by thick Au, Au is etched, and a part of Au is removed from the particles originally formed by Au and Ni, so that the gaps between the particles are increased. More importantly, as Au is thinned, the absorption of light will be reduced, and more photons can be reflected by the metal reflector through the gaps, increasing its transmittance, thereby improving the optical properties of Ni / Au.

[0013] The beneficial effects of the present invention are: (1) Compared with the traditional structure, the main feature of the light-emitting diode device with wet-etched P electrode in the present invention is to seek the best balance between excellent electrical properties and optical properties, which not only improves the transmittance of P-type ohmic electrode to photons, but also retains good ohmic contact characteristics. The strong absorption of deep ultraviolet photons greatly increases the probability of them entering the escape cone, significantly improving the optical properties of the device. According to calculations, when the thickness of the Au layer in Ni / Au is reduced from 6 nm to 0 nm, the transmittance of deep ultraviolet photons with a wavelength of 275 nm can be increased by 31%. In addition, under the same injection current, the device after wet etching is improved by 10.24% and 9.89% compared with the untreated LOP and WPE respectively. According to the 1000 h reliability test of the device, the device after wet etching does not affect the reliability.

[0014] (2) The light-emitting diode device with wet-etched P electrode in the present invention has a simple manufacturing process, is easy to operate, has strong repeatability and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the accompanying drawings.

[0016] Figure 1 is a schematic diagram of a standard light emitting diode device obtained in Example 1; Figure 2 Schematic diagram of a light emitting diode device with a wet-etched P electrode obtained in Example 2; Figure 3 Schematic diagram of the epitaxial structure of DUV LEDs in Example 2; Figure 4 A schematic diagram of performing photolithography and dry etching processes on an epitaxial wafer of DUV LEDs to form a step in Example 2; Figure 5 Schematic diagram of fabricating an N-type ohmic electrode by photolithography, evaporation and lift-off processes on an epitaxial wafer with a step in Example 2; Figure 6 Schematic diagram of fabricating a P-type ohmic electrode by photolithography, evaporation and lift-off processes on an epitaxial wafer having an N-type ohmic electrode in Example 2; Figure 7 is a schematic diagram of wet etching treatment performed on an epitaxial wafer having a P-type ohmic electrode in Example 2; Figure 8 The figure is a schematic block diagram of the basic process of the method of the present invention.

[0017] Fig. 9 This is a graph showing how the transmittance of different Au layer thicknesses in a P-type ohmic electrode varies with the wavelength of the incident light.

[0018] Fig.10 The figure is a relationship diagram of the LOP of the flip-chip light emitting diode LED chip obtained in Example 1 and Example 2 as the injected current changes.

[0019] Fig.11 The graph is a relationship between the WPE of the flip-chip light-emitting diode LED chip obtained in Example 1 and Example 2 and the injected current.

[0020] Fig.12 The figure is a relationship diagram of the relative optical power of the flip-chip light emitting diode LED chip obtained in Example 1 and Example 2 as a function of aging time.

[0021] Among them, 101. substrate, 102. buffer layer, 103. N-type semiconductor transport layer, 104. multi-quantum well layer, 105. P-type electron blocking layer, 106. P-type semiconductor transport layer, 107. N-type ohmic electrode, P-type ohmic electrode (108. Ni, 109. Au), 110. metal reflector. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with embodiments and drawings, but this is not intended to limit the scope of protection of the claims of this application.

[0023] Figure 1 Schematic diagram of the device structure under the standard process flow of Example 1, which includes along the epitaxial growth direction: a substrate 101, a buffer layer 102, an N-type semiconductor transport layer 103, a multi-quantum well layer 104, a P-type current blocking layer 105, a P-type semiconductor transport layer 106, an N-type ohmic electrode 107, a P-type ohmic electrode (Ni 108, Au 109) and a metal reflector 110.

[0024] Figure 2 Schematic diagram of a light-emitting diode device with a wet-etched P-electrode obtained in Example 2, which includes, along the epitaxial growth direction, a substrate 101, a buffer layer 102, an N-type semiconductor transport layer 103, a multi-quantum well layer 104, a P-type current blocking layer 105, a P-type semiconductor transport layer 106, an N-type ohmic electrode 107, a P-type ohmic electrode (Ni 108, Au 109 after etching) and a metal reflector 110.

[0025] Figure 3 The embodiment 2 shown shows an epitaxial wafer structure grown on a substrate 101, which includes, along the epitaxial growth direction, substrate 101, buffer layer 102, N-type semiconductor transport layer 103, multi-quantum well layer 104, P-type current blocking layer 105, and P-type semiconductor transport layer 106.

[0026] Figure 4 The embodiment 2 shown shows that a layer of photoresist is spin-coated on the epitaxial wafer, and a step is made by photolithography and dry etching technology to expose the N-type semiconductor transport layer 103.

[0027] Figure 5 The embodiment 2 shown shows that the N-type ohmic electrode 107 is manufactured by photolithography, evaporation and stripping processes on the N-type semiconductor transport layer 103; Figure 6 The embodiment 2 shown shows that a P-type ohmic electrode (Ni 108, Au 109) is fabricated by photolithography, evaporation and lift-off processes on the P-type semiconductor transport layer 103; Figure 7 The embodiment 2 shown shows a wet etching process using Au etching solution on an epitaxial wafer deposited with a P-type ohmic electrode; Figure 8 The illustrated embodiment shows that the basic process of the method of the present invention is: growing an epitaxial wafer by MOCVD technology → making a step by photolithography and dry etching technology → making an N-type ohmic electrode and annealing by photolithography, evaporation and stripping process → making a P-type ohmic electrode and annealing by photolithography, evaporation and stripping process → removing the Au layer in the P-type ohmic electrode by wet etching with Au etching solution → depositing a reflector on the P-type ohmic electrode after wet etching by photolithography, evaporation and stripping process.

[0028] Example 1 The steps of the standard light emitting diode device preparation method of this embodiment are as follows: The first step is the growth of epitaxial wafers: In the MOCVD reactor, the circular sapphire substrate 101 is baked at a high temperature of 1300°C, foreign matter on the surface of the substrate 101 is removed, and then the AlN buffer layer 102 and the N-type Al 0.60 Ga 0.40 N semiconductor transport layer 103; 5 pairs of Al 0.45 Ga 0.55 N / A 0.56 Ga 0.44 N multi-quantum well layer 104; P-type Al 0.60 Ga 0.40 N electron blocking layer 105; P-type Al 0.43 Ga 0.57 N semiconductor transport layer 106; The second step is dry etching steps: On the DUV LEDs epitaxial wafer obtained in the first step, a layer of photoresist is spin-coated, and the photoresist is made into a mesa shape using photolithography technology and used as a mask. The part not covered by the photoresist is etched away using inductively coupled plasma dry etching to reveal the N-type Al 0.60 Ga 0.40 N semiconductor transmission layer 103, N-type Al 0.60 Ga 0.40 The thickness of the N semiconductor transport layer 103 is 400 nm; The third step is to make an N-type ohmic electrode: On the DUV LEDs epitaxial wafer obtained in the second step, a layer of photoresist is spin-coated, and the pattern of the N-type ohmic electrode on the mask is transferred to the exposed N-type Al using a photolithography machine. 0.60 Ga 0.40 N semiconductor transport layer 103, after thermal evaporation of Ti / Al / Ti / Au multilayer film on the epitaxial wafer, part of the metal is peeled off by removing the photoresist to make Ti / Al / Ti / Au N-type ohmic electrode 107, the thickness of which is 20 / 30 / 60 / 100 nm, and then annealed in a N2 environment at 650°C for 60 seconds using a rapid annealing furnace; wherein the projected area of ​​the N-type ohmic electrode is 80% of the area of ​​the exposed N-type semiconductor transport layer; Step 4: Make a P-type ohmic electrode: On the DUV LEDs epitaxial wafer obtained in the third step, a layer of photoresist is spin-coated, and the pattern of the P-type ohmic electrode on the mask is transferred to the P-type Al0.43Ga0.57N semiconductor transport layer 106 using a photolithography machine. Two layers of Ni metal and Au metal are thermally evaporated on the epitaxial wafer with thicknesses of 5 nm and 6 nm respectively. Part of the metal is stripped off by removing the photoresist to make a P-type ohmic electrode (Ni 108, Au 109), and then annealed in a dry air environment at 550°C for 360 seconds using a rapid annealing furnace; Step 5: Make a highly reflective electrode: A layer of photoresist is spin-coated on the P-type ohmic electrode (Ni 108, Au 109) obtained in the fourth step, and the pattern of the metal reflector on the mask is transferred to the N-type ohmic electrode 107 and the P-type ohmic electrode (Ni 108, Au 109) by using a photolithography machine. After thermally evaporating an Al film on the epitaxial wafer, a portion of the metal is stripped off by removing the photoresist to produce a metal reflector 110 with a thickness of 200 nm. Thus, a standard flip-chip light emitting diode (LED) chip is obtained.

[0029] Example 2 The light emitting diode device with wet-etched P electrode of this embodiment is prepared as follows: The first step is the growth of epitaxial wafers: In the MOCVD reactor, the round sapphire substrate 101 is baked at 1300°C for 20 min to remove foreign matter on the surface of the substrate 101. Then, an AlN buffer layer 102 with a thickness of 2 μm is grown. 0.60 Ga 0.40 N semiconductor transmission layer 103, thickness 1 μm; 5 pairs of Al 0.45 Ga 0.55 N / A 0.56 Ga 0.44 N multi-quantum well layer 104 has a thickness of 75 nm, wherein Al 0.45 Ga 0.55 The thickness of N is 3 nm, and the thickness of Al 0.56 Ga 0.44 The thickness of N is 12 nm; P-type Al 0.60 Ga 0.40 N electron blocking layer 105, thickness 20 nm; P-type Al 0.43 Ga 0.57 N semiconductor transport layer 106, with a thickness of 175 nm; The second step is dry etching steps: On the DUV LEDs epitaxial wafer obtained in the first step, a layer of photoresist is spin-coated, and the photoresist is made into a mesa shape using photolithography technology and used as a mask. The part not covered by the photoresist is etched away using inductively coupled plasma dry etching to reveal the N-type Al 0.60 Ga 0.40 N semiconductor transmission layer 103, N-type Al 0.60 Ga 0.40 The thickness of the N semiconductor transport layer 103 is 400 nm; the area etched away is 40% of the total area of ​​103; The third step is to make an N-type ohmic electrode: On the DUV LEDs epitaxial wafer obtained in the second step, a layer of photoresist is spin-coated, and the pattern of the N-type ohmic electrode on the mask is transferred to the exposed N-type Al using a photolithography machine. 0.60 Ga 0.40 N semiconductor transport layer 103, after thermal evaporation of Ti / Al / Ti / Au multilayer film on the epitaxial wafer, part of the metal is peeled off by removing the photoresist to make Ti / Al / Ti / Au N-type ohmic electrode 107, the thickness of which is 20 / 30 / 60 / 100 nm, and then annealed in a N2 environment at 650°C for 60 seconds using a rapid annealing furnace; wherein the projected area of ​​the N-type ohmic electrode is 80% of the area of ​​the exposed N-type semiconductor transport layer; Step 4: Make a P-type ohmic electrode: On the DUV LEDs epitaxial wafer obtained in the third step, a layer of photoresist is spin-coated, and the pattern of the P-type ohmic electrode on the mask is transferred to the P-type Al using a photolithography machine. 0.43 Ga 0.57 N semiconductor transport layer 106, two layers of Ni metal and Au metal are thermally evaporated on the epitaxial wafer, with thicknesses of 5 nm and 6 nm respectively, and part of the metal is stripped off by removing the photoresist to make a P-type ohmic electrode (Ni 108, Au 109), and then annealed in a dry air environment at 550°C for 360 seconds using a rapid annealing furnace; Step 5: wet etching of P-type ohmic electrode: On the P-type ohmic electrode (Ni 108, Au 109) obtained in the fourth step, deionized water is used to clean the metal surface, a layer of photoresist is spin-coated, and the pattern of the P-type ohmic electrode on the mask is transferred to the epitaxial wafer using a photolithography machine, and the part except the P-type ohmic electrode is protected, and then the epitaxial wafer is immersed in Au etching solution for wet etching treatment, wherein the Au etching solution is a nitrating acid mixture composed of 4 wt% KI, 4.5 wt% I2, 3 ppm chloride, 3 ppm sulfate and 2 ppm phosphate components, and the solution pH value is less than 6, wherein the chloride is 3 ppm copper chloride, the sulfate is 3 ppm calcium sulfate and 3 ppm aluminum sulfate, and the phosphate is 2 ppm potassium phosphate and 2 ppm nickel phosphate, and the etching time is 10 min; after etching, the thickness of Au 109 will be thinned to 0 nm; after etching, the epitaxial wafer is taken out and rinsed with deionized water for 3 min and use N2 blowing for drying to ensure that the residual etching solution and impurities are completely removed; Step 6: Make a highly reflective electrode: A layer of photoresist is spin-coated on the P-type ohmic electrode (Ni 108, Au 109) obtained in the fifth step, and the pattern of the metal reflector on the mask is transferred to the N-type ohmic electrode 107 and the P-type ohmic electrode (Ni 108, Au 109) by using a photolithography machine. After thermally evaporating an Al film on the epitaxial wafer, a portion of the metal is stripped off by removing the photoresist to produce a metal reflector 110 with a thickness of 200 nm. Thus, a light emitting diode device having a wet-etched P electrode is manufactured.

[0030] Fig. 9 The curve shown is simulated by FDTD simulation software. The transmittance of the P-type ohmic electrode Ni / Au changes linearly with the thickness of the Au layer before and after being treated with Au etching solution. When the Au layer is set to 6 nm and 0 nm, the transmittance of the P-type ohmic electrode is 35% and 46%, respectively, which is an increase of 31%. This is because the thinning of Au reduces the absorption of photons.

[0031] Fig.10 The figure shows the relationship curve of the light output power of the flip-chip light-emitting diode LED chips obtained in Example 1 and Example 2 under the current injection of 0-300 mA at room temperature using an integrating sphere, and tested every 20 mA. The curve shows that the flip-chip light-emitting diode LED chips obtained in Example 1 and Example 2 have significantly improved LOP due to the wet etching process. At an injection current of 100 mA, the LOP of the standard device and the etched device are 16.21 mW and 17.89 mW, respectively, an increase of 10.24%.

[0032] Fig.11 The WPE vs. injection current curve is obtained by dividing the light power collected by the flip-chip LED chips obtained in Example 1 and Example 2 at room temperature with the voltage-current curve. The curve shows that the WPE of the flip-chip LED chips obtained in Example 1 and Example 2 is significantly improved due to the wet etching treatment. At an injection current of 100 mA, the WPE of the standard device and the etched device are 2.73% and 3.02%, respectively, an increase of 10.62%.

[0033] Fig.12 The graph shows that the flip-chip light-emitting diode LED chips obtained in Example 1 and Example 2 were continuously lit for 1000 seconds at room temperature using an injection current of 40 mA. The curve shows that the relative optical power of the light-emitting diode device with a wet-etched P electrode is similar to that of a standard light-emitting diode device. This is mainly because the wet-etched P electrode process does not affect the reliability of the light-emitting diode device.

[0034] The above embodiment can achieve that the P-type ohmic electrode treated with Au etching solution can not only retain the ohmic contact characteristics of Ni / Au, but also significantly increase its transmittance, reduce the absorption of photons by the P-type ohmic electrode, so that more photons can be reflected by the top metal reflector and re-enter the DUV LEDs escape cone, thereby greatly improving the LED light output efficiency. In addition, the device reliability will not be reduced after wet etching treatment. The method of the present invention has a simple manufacturing process, strong repeatability, low production cost, and is easy to operate.

[0035] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a light emitting diode device having a wet-etched P electrode, The method is characterized in that it comprises the following steps: The first step is the growth of epitaxial wafers: First, in an MOCVD reactor, the substrate is baked at 950°C to 1350°C to remove foreign matter on the substrate surface, and then a buffer layer, an N-type semiconductor transport layer, a multi-quantum well layer, a P-type electron blocking layer, and a P-type semiconductor transport layer are grown respectively; The second step is dry etching steps: On the epitaxial wafer obtained in the first step, photoresist is made into a mesa shape by using photolithography technology and used as a mask, and the part not covered by the photoresist is etched by dry etching technology, thereby revealing the N-type semiconductor transmission layer; The third step is to make an N-type ohmic electrode: On the N-type semiconductor transport layer obtained in the second step, an N-type ohmic electrode pattern is revealed by photolithography, and an N-type ohmic electrode is manufactured by evaporation and lift-off process, followed by thermal annealing treatment; Step 4: Make a P-type ohmic electrode: On the P-type semiconductor transport layer of the DUV LEDs epitaxial wafer, a P-type ohmic electrode pattern is revealed by photolithography, a P-type ohmic electrode is made by evaporation and lift-off process, and a thermal annealing process is performed under a suitable gas atmosphere and temperature; Step 5: wet etching of P-type ohmic electrode: On the P-type ohmic electrode obtained in the fourth step, the metal surface is cleaned with deionized water, and then a layer of photoresist is spin-coated, and the pattern of the P-type ohmic electrode on the mask is transferred to the epitaxial wafer using a photolithography machine, and the part except the P-type ohmic electrode is protected, and then the epitaxial wafer is immersed in Au etching solution for wet etching treatment; after etching, the epitaxial wafer is taken out for cleaning and drying; wherein the etching time is 1 to 20 minutes; The Au etching solution comprises a nitrating acid mixture consisting of 2 to 6 wt% KI, 2 to 6 wt% I2, 1 to 5 ppm chloride, 1 to 6 ppm sulfate and 1 to 6 ppm phosphate; The chloride is specifically cupric chloride; The sulfates are specifically calcium sulfate and aluminum sulfate; The phosphates are specifically potassium phosphate and nickel phosphate; Step 6: Make a highly reflective electrode: On the wet-etched P-type ohmic electrode obtained in the fifth step, a reflector pattern is obtained by photolithography, and a metal with high reflectivity is deposited as a metal reflector by evaporation and lift-off process; Thus, a light emitting diode device having a wet-etched P electrode is manufactured.

2. The method for preparing a light emitting diode device having a wet-etched P electrode according to claim 1, characterized in that The substrate is a sapphire substrate, a silicon carbide (SiC) substrate, a gallium nitride (GaN) substrate or an aluminum nitride (AlN) substrate; The buffer layer is AlN with a thickness of 1 to 5 μm; The N-type semiconductor transport layer is Al x1 Ga 1-x1 N, where the coefficients of each component should be 0≤x1≤1, 0≤1-x1≤1, and the thickness should be 1-5 μm; The multi-quantum well layer is made of Al x2 Ga 1-x2 N / A x3 Ga 1-x3 N, where 0≤x2≤1, 0≤1-x2≤1, 0≤x3≤1, 0≤1-x3≤1, the bandgap of the quantum barrier should be higher than the bandgap of the quantum well, the number of quantum wells is greater than or equal to 1, and the quantum well Al x2 Ga 1-x2 N thickness is 1 to 20 nm, quantum barrier Al x3 Ga 1-x3 N thickness is 5 to 50 nm; The material of the P-type electron blocking layer is Al x4 Ga 1-x4 N, where 0≤x4≤1, 0≤1-x4≤1, and the thickness is 10 to 300 nm; The material of the P-type semiconductor transport layer is Al x5 Ga 1-x5 N, where 0≤x5≤1, 0≤1-x5≤1, and thickness is 0.1~1 μm; The high reflectivity metal is Al, and the thickness is 100-900 nm.

3. The method for preparing a light-emitting diode device with a wet-etched P-electrode according to claim 1, wherein the N-type ohmic electrode is Ti / Al / Ti / Au, Al / Au or Cr / Au, wherein: The projected area of ​​the N-type ohmic electrode is 5% to 100% of the area of ​​the exposed N-type semiconductor transmission layer.

4. The method for preparing a light emitting diode device having a wet-etched P electrode according to claim 1, characterized in that The P-type ohmic electrode is composed of Ni metal and Au metal stacked up and down, wherein the projected area of ​​the P-type ohmic electrode is 5% to 100% of the area of ​​the exposed P-type semiconductor transport layer, the thickness of the Ni metal before etching is 3 to 50 nm, and the thickness of the Au metal before etching is 2 to 60 nm.

5. The method for preparing a light-emitting diode device with a wet-etched P electrode according to claim 1, wherein the obtained light-emitting diode with a wet-etched P electrode comprises, from bottom to top, a substrate, a buffer layer, and an N-type semiconductor transmission layer; wherein, The N-type semiconductor transmission layer is divided into two layers, the lower layer completely covers the buffer layer, and the area of ​​the upper layer is 5-90% of the area of ​​the lower layer; the thickness of the lower layer is 5-95% of the thickness of the N-type semiconductor transmission layer; The surface of the upper part of the N-type semiconductor transport layer is composed of a multi-quantum well layer, a P-type electron blocking layer, a P-type semiconductor transport layer, a P-type ohmic electrode, and a metal reflector from bottom to top. An N-type ohmic electrode is also distributed on the exposed portion of the lower layer of the N-type semiconductor transmission layer.

6. The method for preparing a light-emitting diode device with a wet-etched P-electrode as claimed in claim 1, characterized in that the P-type ohmic electrode is a Ni metal electrode layer and an etched Au electrode layer from bottom to top; the thickness of the Ni layer metal is 3~50nm; the thickness of the Au layer after etching with Au etching solution is 0~50nm.

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