Europium complex and method for preparing gallium nitride-based red light emitting diode using the same as a precursor

Abstract

The application provides an europium complex and a method for preparing a gallium nitride-based red light emitting diode by using the europium complex as a precursor. 28 H 24 Cl3EuN4, and the chemical formula is Eu(Dmphen)2Cl3, wherein Dmphen represents 4,7-dimethyl-1,10-phenanthroline; the complex does not contain oxygen atoms, can be used as an oxygen-free precursor for growing a gallium nitride-based micro red light LED, fundamentally avoids the fluorescence quenching problem caused by the introduction of oxygen impurities in the existing europium doping technology, significantly improves the red light emitting efficiency of the gallium nitride-based red light LED, and improves the light emitting performance and stability of the device.

Description

Technical Field

[0001] This invention relates to gallium nitride-based red light-emitting diodes, belonging to the technical field of full-color semiconductor light-emitting devices, specifically relating to a europium complex and a method for preparing gallium nitride-based red light-emitting diodes using it as a precursor. Background Technology

[0002] Miniature light-emitting diode (LED) chips have important applications in fields such as virtual reality / augmented reality, smart wearables, solid-state lighting, sensing and detection, optical communication, and full-color display due to their advantages such as small size, high integration, high brightness, high contrast, low power consumption, long life, fast response, good thermal stability, and high resolution.

[0003] To achieve full-color display, it is necessary to fabricate red, green, and blue tri-color micro-LED devices, and then combine these devices to achieve full-color display. Currently, the bottleneck restricting tri-color micro-LED display is the fabrication and luminous efficiency of red micro-LED devices. Commercial red light-emitting devices mostly use phosphide semiconductor AlInGaP; however, as chip size shrinks to the micrometer level, the luminous efficiency of AlInGaP-based red light-emitting devices drops sharply, failing to meet practical application requirements.

[0004] To address the aforementioned technical challenges, researchers began using InGaN materials with small band gaps to construct quantum wells in hopes of achieving red light emission. However, the high In content leads to severe lattice mismatch, phase separation, and a strong polarization field. These factors collectively result in low red light emission efficiency of InGaN quantum well-based red micro-LEDs. Furthermore, stress relaxation occurs in the InGaN quantum well after etching the mesa, causing a shift in the emission wavelength and poor controllability. Since europium-doped red light emission (5D0 to 7F2) is insensitive to the structure of the host material gallium nitride, researchers began exploring the use of europium-doped GaN to achieve GaN-based red micro-LED emission. However, to achieve europium doping of GaN, GaN materials usually need to be grown using metal-organic chemical vapor phase epitaxy and a corresponding doping source. The research reported by B. Mitchell et al. in the Journal of Applied Physics in 2014, Volume 115, page 204501, used the europium-coordinated metal-organic compound Eu(DPM)3 as a precursor to achieve europium doping of GaN. However, this precursor has oxygen-containing functional groups, which causes the obtained sample to contain a large amount of oxygen impurities. Oxygen impurities are prone to fluorescence quenching, thereby reducing the luminescence efficiency of the material.

[0005] Therefore, there is an urgent need to develop a novel oxygen-free europium complex that can effectively avoid the introduction of oxygen impurities and fluorescence quenching effects while satisfying the compatibility of growth processes such as molecular beam epitaxy. This would enable efficient and stable europium doping in GaN-based materials, thereby improving the red light emission efficiency and overall performance of the devices. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a europium complex and a method for preparing gallium nitride-based red LEDs using the europium complex as a precursor. By using an oxygen-free europium complex to epitaxially dope gallium nitride, oxygen impurities are reduced and the luminous efficiency of europium-doped gallium nitride-based red LEDs is improved.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a europium complex, the molecular formula of which is C2. 28 H 24 Cl3EuN4, with the chemical formula Eu(Dmphen)2Cl3, where Dmphen represents 4,7-dimethyl-1,10-phenanthroline.

[0008] Furthermore, the europium complex Eu(Dmphen)₂Cl₃ belongs to the triclinic crystal system, with unit cell parameters a = 9.8659 Å, b = 11.1403 Å, c = 12.0241 Å; α = 89.929 Å. o β=84.170 o , γ=85.026 o .

[0009] Secondly, the present invention provides a method for preparing europium complex single crystals, the method comprising the following steps: Step 1: Add an appropriate amount of anhydrous ethanol to the reaction vessel, and then dissolve Dmphen and EuCl3·6H2O in it at a molar ratio of 1.5~2.5:1. Step 2: Place the above reaction vessel in a drying oven and heat it from room temperature to 130-180°C within 250-350 minutes; Step 3: Keep the temperature constant at 130~180℃ for 2800~3000 min, and then lower the temperature from 130~180℃ to 25~35℃ within 550~650 min to obtain a pale yellow single crystal of europium complex Eu(Dmphen)2Cl3.

[0010] Thirdly, the present invention provides a method for preparing europium complex powder, the method comprising the following steps: Step 1: Measure Dmphen and EuCl3·6H2O in a molar ratio of 1.5~2.5:1. Add the measured Dmphen to anhydrous ethanol and heat in a water bath at 65~75℃ until dissolved to obtain an anhydrous ethanol solution containing Dmphen. Step 2: Dissolve the measured EuCl3·6H2O in water to make a solution, add it dropwise to the anhydrous ethanol solution containing Dmphen, stir magnetically at 65~75℃ for 2.5~3.5 hours, and let stand for more than 5 hours; Step 3: Once a pale yellow precipitate appears in the reaction system, filter under reduced pressure and wash with ethanol and deionized water; Step 4: Dry the precipitate obtained from washing at 65~75℃ for more than 10 hours to obtain the powder of europium complex Eu(Dmphen)2Cl3.

[0011] Fourthly, the present invention provides a method for preparing gallium nitride-based red light-emitting diodes using europium complexes as precursors, the method comprising the following steps: Step 1: Prepare or obtain a substrate with a gallium nitride layer of the first doping type. On the surface of the substrate with the gallium nitride layer of the first doping type, use metal-organic chemical vapor phase epitaxy (MOCVE) to prepare a single crystal of europium complex Eu(Dmphen)2Cl3 prepared by the method for preparing europium complex single crystals described in the second aspect or europium complex powder prepared by the method for preparing europium complex powder described in the third aspect as a precursor. Use hydrogen, nitrogen, or a mixture of both as the carrier gas for the precursor. Adjust the doping concentration by adjusting the carrier gas flow rate to grow and form a europium-doped active region. Step 2: On the surface of the europium-doped active region, a second type of gallium nitride layer is grown using metal-organic chemical vapor deposition (MOCVD) to obtain a complete LED epitaxial structure. Step 3: Perform photolithography, etching or ion implantation, and deposition of metal or transparent electrodes on the LED epitaxial structure grown in Step 2 to obtain a gallium nitride-based red LED device.

[0012] Fifthly, the present invention provides another method for preparing gallium nitride-based red light-emitting diodes using europium complexes as precursors, the method comprising the following steps: Step 1: Prepare or obtain a substrate with a gallium nitride layer of the first doping type. On the surface of the gallium nitride layer of the first doping type, use metal-organic chemical vapor deposition (MOCVD) as a precursor. Use the europium complex Eu(Dmphen)2Cl3 single crystal prepared by the method for preparing europium complex single crystals described in the second aspect or the europium complex powder prepared by the method for preparing europium complex powders described in the third aspect as a precursor. Use hydrogen, nitrogen, or a mixture of both as the carrier gas for the precursor. Adjust the doping concentration by adjusting the carrier gas flow rate to grow and form a europium-doped active region. Step 2: On the surface of the europium-doped active region, an electron blocking layer is grown using metal-organic chemical vapor deposition (MOCVD). Step 3: On the surface of the electron blocking layer, a second type of gallium nitride layer is grown using metal-organic chemical vapor deposition (MOCVD) to obtain a complete LED epitaxial structure. Step 4: Perform photolithography, etching or ion implantation, and deposition of metal or transparent electrodes on the LED epitaxial structure grown in Step 3 to obtain a gallium nitride-based red LED device.

[0013] Furthermore, the first doped gallium nitride layer and the second doped gallium nitride layer are respectively n-type doped and p-type doped or p-type doped and n-type doped.

[0014] Furthermore, the europium-doped active region includes one or more of a europium-doped gallium nitride layer, a europium-doped indium gallium nitride layer, and a europium-doped aluminum gallium nitride layer.

[0015] Furthermore, the europium-doped gallium nitride layer growth step in the europium-doped active region includes heating the substrate to 600~1050°C, using nitrogen, hydrogen, or a mixture of both as the carrier gas for the europium complex Eu(Dmphen)2Cl3, and introducing Eu(Dmphen)2Cl3, TEGa or TMGa, and ammonia until the target thickness is reached. The europium-doped indium gallium nitride layer growth step in the europium-doped active region includes heating the substrate to 600~1050°C, using nitrogen, hydrogen or a mixture of both as the carrier gas for the europium complex Eu(Dmphen)2Cl3, and introducing Eu(Dmphen)2Cl3, TEGa or TMGa, TMIn, and ammonia until the target thickness is reached. The europium-doped aluminum gallium nitride layer growth step in the europium-doped active region includes heating the substrate to 900~1250°C, using nitrogen, hydrogen, or a mixture of both as the carrier gas for the europium complex Eu(Dmphen)2Cl3, and introducing Eu(Dmphen)2Cl3, TEGa or TMGa, TMAl, and ammonia until the growth reaches the target thickness.

[0016] Furthermore, in the aforementioned metal-organic chemical vapor phase epitaxy technology, the precursor heating temperature is 40~90℃.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention designs and synthesizes a novel europium complex, Eu(Dmphen)₂Cl. 3， This complex contains no oxygen atoms and can be used as an oxygen-free precursor for growing gallium nitride-based miniature red LEDs. Compared with existing oxygen-containing europium precursors, it avoids the introduction of oxygen from the source.

[0018] 2. Based on the oxygen-free europium complex Eu(Dmphen)2Cl provided by this invention 3， During the epitaxial growth of gallium nitride-based red LEDs, the concentration of oxygen impurities in the system can be effectively reduced, fundamentally avoiding the fluorescence quenching problem caused by the introduction of oxygen impurities in existing europium doping technology. This significantly improves the red light luminous efficiency of gallium nitride-based red LEDs and enhances the luminous performance and stability of the device.

[0019] 3. This invention provides an epitaxial process for gallium nitride-based red LEDs using europium complex Eu(Dmphen)2Cl3 for europium doping. The material system used in this process is consistent with that of existing blue and green LEDs, both being gallium nitride-based materials with the same refractive index. This facilitates the design and fabrication of optical structures suitable for full-color applications, and therefore has application value in fields such as micro-nano light-emitting and display devices. Attached Figure Description

[0020] Figure 1 This is a molecular structure diagram of the europium complex Eu(Dmphen)2Cl3 of the present invention.

[0021] Figure 2 This is an X-ray powder diffraction pattern of the europium complex powder of the present invention.

[0022] Figure 3 This is a schematic diagram of the growth steps of the europium-doped gallium nitride-based red LED epitaxial structure and a structural diagram of the red micro-LED.

[0023] Figure 4 This is the red light spectrum emitted by the europium-doped gallium nitride-based miniature red LED of the present invention.

[0024] Figure 5 This is a comparison diagram of the oxygen atom concentration in the epitaxial structure of europium-doped gallium nitride-based LEDs prepared by the present invention and existing technologies.

[0025] Figure 6 This is a comparison chart of the luminous intensity of red LEDs prepared by the present invention and those prepared by existing technologies at the same current density. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are merely a part of the technical content of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a europium complex with the chemical composition trichloro-bis(4,7-dimethyl-1,10-phenanthroline)europium(III) and the molecular formula C.28 H 24 Cl3EuN4, with the chemical formula Eu(Dmphen)2Cl3, wherein Dmphen is 4,7-dimethyl-1,10-phenanthroline, and the structure of Dmphen is shown in Formula 1.

[0028] Equation 1: Dmphen structure diagram

[0029] Example 1 The preparation method of the europium complex Eu(Dmphen)₂Cl₃ single crystal of the present invention is as follows: 10 mL of anhydrous ethanol was added to a 15 mL reaction vessel, followed by the dissolution of 0.1 mmol of Dmphen and 0.05 mmol of EuCl3·6H2O. The reaction vessel was placed in a forced-air drying oven, and the temperature was raised from room temperature to 150 °C over 300 min. The temperature was then maintained at 150 °C for 2880 min, followed by a temperature reduction from 150 °C to 30 °C over 600 min. At this point, a pale yellow single crystal of the europium complex Eu(Dmphen)2Cl3 was obtained in the reaction vessel.

[0030] Example 2 The preparation method of the europium complex Eu(Dmphen)₂Cl₃ single crystal of the present invention is as follows: Add 8 mL of anhydrous ethanol to a 15 mL reaction vessel, then dissolve 0.06 mmol of Dmphen and 0.04 mmol of EuCl3·6H2O in it. Place the reaction vessel in a forced-air drying oven and raise the temperature from room temperature to 130 °C over 250 min. Maintain the temperature at 130 °C for 3000 min, then lower the temperature from 130 °C to 25 °C over 550 min. At this point, a pale yellow single crystal of the europium complex Eu(Dmphen)2Cl3 is obtained in the reaction vessel.

[0031] Example 3 The preparation method of the europium complex Eu(Dmphen)₂Cl₃ single crystal of the present invention is as follows: Add 20 mL of anhydrous ethanol to a 30 mL reaction vessel, then dissolve 0.25 mmol of Dmphen and 0.1 mmol of EuCl3·6H2O in it. Place the reaction vessel in a forced-air drying oven and raise the temperature from room temperature to 180 °C over 350 min. Maintain the temperature at 180 °C for 2800 min, then lower the temperature from 180 °C to 35 °C over 650 min. At this point, a pale yellow single crystal of the europium complex Eu(Dmphen)2Cl3 is obtained in the reaction vessel.

[0032] Example 4 The single-crystal structure of the europium complex Eu(Dmphen)₂Cl₃ prepared in Example 1 was determined by X-ray single-crystal diffraction, and the crystal structure data are shown in Table 1. As can be seen from Table 1, the europium complex Eu(Dmphen)₂Cl₃ belongs to the triclinic crystal system, with unit cell parameters a = 9.8659 Å, b = 11.1403 Å, c = 12.0241 Å; α = 89.929 Å. o β=84.170 o , γ=85.026 o Analysis of the structural data yielded the molecular structure of Eu(Dmphen)₂Cl₃ single crystal as follows: Figure 1 As shown.

[0033] Table 1. X-ray diffraction data of single crystal structure of Eu(Dmphen)₂Cl₃

[0034] Example 5 The preparation method of europium complex Eu(Dmphen)2Cl3 powder is as follows: 1 mmol of Dmphen was dissolved in 30 mL of anhydrous ethanol in a flask, heated to 70 °C in a water bath, and 5 mL of an aqueous solution containing 0.5 mmol of EuCl3·6H2O was added dropwise. The mixture was magnetically stirred at 70 °C for 3 h, and allowed to stand for 9 h until a pale yellow precipitate appeared at the bottom of the flask. The precipitate was filtered under reduced pressure and washed three times each with ethanol and deionized water. After drying at 70 °C for 12 h, Eu(Dmphen)2Cl3 powder was obtained. The yield of the product was approximately 73.6%.

[0035] Example 6 The preparation method of europium complex Eu(Dmphen)2Cl3 powder is as follows: In a flask, 0.75 mmol of Dmphen was dissolved in 25 mL of anhydrous ethanol. The mixture was heated to 65 °C in a water bath. 5 mL of an aqueous solution containing 0.5 mmol of EuCl3·6H2O was added dropwise. The mixture was magnetically stirred at 65 °C for 2.5 h and allowed to stand for 7 h. When a pale yellow precipitate appeared at the bottom of the flask, the precipitate was filtered under reduced pressure and washed three times each with ethanol and deionized water. The precipitate was then dried at 65 °C for 10 h to obtain Eu(Dmphen)2Cl3 powder.

[0036] Example 7 The preparation method of europium complex Eu(Dmphen)2Cl3 powder is as follows: In a flask, 1.25 mmol of Dmphen was dissolved in 40 mL of anhydrous ethanol. The mixture was heated to 75 °C in a water bath. 5 mL of an aqueous solution containing 0.5 mmol of EuCl3·6H2O was added dropwise. The mixture was magnetically stirred at 75 °C for 3.5 h and allowed to stand for 15 h. When a pale yellow precipitate appeared at the bottom of the flask, the precipitate was filtered under reduced pressure and washed three times each with ethanol and deionized water. The precipitate was then dried at 75 °C for 18 h to obtain Eu(Dmphen)2Cl3 powder.

[0037] Elemental analysis of the europium complex Eu(Dmphen)₂Cl₃ powder sample obtained in Example 5 yielded the following theoretical elemental values: C 49.78%, N 8.29%, H 3.56%; measured values: C 47.51%, N 7.81%, H 3.67%. X-ray powder diffraction was used to determine the diffraction peaks, as shown below. Figure 2 The XRD diffraction pattern shown is from... Figure 2 As can be seen, its main diffraction peaks are located at 2θ = 7.04°, 8.01°, 10.89°, 12.27°, 13.24°, 14.11°, 14.81°, 15.98°, 17.67°, 20.86°, 23.15°, and 30.34°. This diffraction pattern coincides with the main diffraction peaks of the single crystal generated by Mercury software simulation, confirming that the powder product and the single crystal product have the same crystal structure.

[0038] The present invention also provides a method for preparing gallium nitride-based red LEDs using the above-mentioned europium complex as a precursor, specifically comprising the following steps: Step 1: The europium complex Eu(Dmphen)2Cl3 is used as a europium precursor and loaded into the bubbler of the metal-organic chemical vapor deposition system. The bubbler is placed in a constant temperature heater with a temperature range of 40~90℃ for constant temperature heating. Step 2: Prepare or obtain a substrate with an n-type or p-type doped gallium nitride layer. On the substrate, use a metal-organic chemical vapor phase epitaxy system with europium complex Eu(Dmphen)2Cl3 as a precursor and hydrogen, nitrogen or a mixture of both as a carrier gas. Adjust the doping concentration by adjusting the carrier gas flow rate to grow a europium-doped active region. The active region includes a europium-doped gallium nitride layer, an indium gallium nitride layer or an aluminum gallium nitride layer. Step 3: Grow a p-type or n-type doped gallium nitride layer on the surface of the europium-doped active region using a metal-organic chemical vapor deposition system. The doping type is the opposite of that of the gallium nitride substrate prepared in step 2, to obtain a complete LED epitaxial structure. Step 4: Perform photolithography, etching or ion implantation, and deposition of metal or transparent electrodes on the LED epitaxial structure grown in Step 3 to obtain a gallium nitride-based red LED device.

[0039] The following is an illustration using specific examples.

[0040] Example 8 The method for growing europium-doped gallium nitride-based red LEDs using MOCVD is shown in the figure below, along with the growth pattern and structure of the red LED. Figure 3 As shown.

[0041] Step 1: Europium complex Eu(Dmphen)2Cl3 powder is loaded into the bubbler of the metal-organic chemical vapor deposition system as a europium precursor. The bubbler is placed in a constant temperature water bath heater at 70°C for heat preservation. Step 2: Obtain the substrate and perform pretreatment.

[0042] (1) Using c-plane sapphire as the substrate, after cleaning the substrate, it was placed in a metal-organic chemical vapor deposition (MOCVD) reaction chamber, and the pressure of the reaction chamber was reduced to 2 × 10⁻⁶. 2 Then, hydrogen gas is introduced into the reaction chamber, and the MOCVD reaction chamber pressure is adjusted to 20 Torr. The substrate is heated to 900°C and held for 10 minutes to complete the heat treatment of the substrate.

[0043] (2) Raise the temperature of the reaction chamber to 1000℃, keep the pressure constant, and introduce ammonia gas with a flow rate of 3500sccm for 5 minutes to nitrid the heat-treated substrate.

[0044] Step 3: Growing a high-temperature AlN layer using MOCVD process, such as... Figure 3 (a)

[0045] The reaction chamber temperature was adjusted to 950℃, and under the condition of maintaining a pressure of 20 Torr, hydrogen was used as the carrier gas, while ammonia gas with a flow rate of 3000 sccm and TMAl aluminum source with a flow rate of 40 sccm were introduced to grow a high-temperature AlN nucleation layer with a thickness of 20 nm on the nitrided substrate.

[0046] Step four: An n-type doped gallium nitride layer is grown using MOCVD technology, such as... Figure 3 (b)

[0047] The reaction chamber temperature was adjusted to 1050℃ and the reaction chamber pressure was adjusted to 200 Torr. Hydrogen was used as the gallium source carrier gas, and ammonia, TMGa gallium source with a flow rate of 150 sccm, and SiH4 silicon source with a flow rate of 10 sccm were introduced simultaneously. An n-type doped gallium nitride layer with a thickness of 1000 nm was grown on the AlN nucleation layer, thus completing the fabrication of the n-type doped gallium nitride substrate.

[0048] Step 5: Grow europium-doped gallium nitride layers using MOCVD technology, such as... Figure 3 (c)

[0049] The reaction chamber temperature was adjusted to 950℃, and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the gallium source and europium source carrier gas, while ammonia gas with a flow rate of 2500 sccm, a TMGa gallium source with a flow rate of 150 sccm, and an Eu(Dmphen)2Cl3 europium source with a flow rate of 80 sccm were introduced. A europium-doped gallium nitride layer with a thickness of 500 nm was grown on the n-type doped gallium nitride layer using the MOCVD method.

[0050] Step 6: Grow Al using MOCVD process 0.15 Ga 0.85 N electron blocking layer, such as Figure 3 (d)

[0051] The reaction chamber temperature was adjusted to 1000℃, and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the gallium and aluminum source carrier gas, while ammonia gas at a flow rate of 1000 sccm, a TMGa gallium source at a flow rate of 70 sccm, and a TMAl aluminum source at a flow rate of 20 sccm were simultaneously introduced. A 25 nm thick Al layer was grown on a europium-doped gallium nitride layer using the MOCVD method. 0.15 Ga 0.85 N electron blocking layer.

[0052] Step 7: Grow a p-type doped gallium nitride layer using MOCVD technology, such as... Figure 3 Middle (e).

[0053] The reaction chamber temperature was adjusted to 950℃, and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the gallium source and magnesium source carrier gas, while ammonia gas with a flow rate of 2500 sccm, a TMGa gallium source with a flow rate of 150 sccm, and a MgCd magnesium source with a flow rate of 100 sccm were introduced simultaneously. A p-type doped gallium nitride layer with a thickness of 150 nm was grown on the electron blocking layer using the MOCVD method. Then, the reaction chamber temperature was reduced to 800℃, and the p-type doped gallium nitride was annealed for 10 min under a hydrogen atmosphere at a flow rate of 1000 sccm to activate the p-type doped gallium nitride.

[0054] Step 8: Etch the epitaxial layer outside the device region and expose the n-type doped gallium nitride layer, such as... Figure 3 (f)

[0055] Photolithography and dry etching are used to etch the p-type doped gallium nitride layer, electron blocking layer and europium doped gallium nitride layer outside the light-emitting device area, exposing the underlying n-type doped gallium nitride layer, while retaining the p-type doped gallium nitride layer, electron blocking layer and europium doped gallium nitride layer within the light-emitting device area, and then the photoresist is cleaned.

[0056] Step nine, deposit the electrode, such as Figure 3 Middle (g).

[0057] The fabrication of a miniature red LED device was completed by sequentially depositing 20 nm of titanium and 50 nm of gold as n-type electrodes on the surface of an n-type doped gallium nitride layer using sputtering or electron beam evaporation methods, and sequentially depositing 10 nm of nickel and 30 nm of gold as p-type electrodes on a p-type doped gallium nitride layer.

[0058] The red light spectrum emitted by europium-doped gallium nitride-based red LEDs grown by MOCVD is as follows: Figure 4 As shown, the emitted red light has a wavelength of 623.03 nm.

[0059] Example 9 Example 9 is the same as Example 8, except that steps five and six are different. All other steps are the same as in Example 8.

[0060] Step 5: Grow europium-doped indium gallium nitride layer using MOCVD process.

[0061] The reaction chamber temperature was adjusted to 750℃, and the reaction chamber pressure was maintained at 200 Torr. Nitrogen was used as the carrier gas for gallium, indium, and europium sources. Ammonia gas with a flow rate of 2500 sccm, TEGa gallium source with a flow rate of 30 sccm, TMIn indium source with a flow rate of 270 sccm, and Eu(Dmphen)2Cl3 europium source with a flow rate of 80 sccm were introduced simultaneously. A europium-doped indium gallium nitride layer with a thickness of 500 nm was grown on an n-type doped gallium nitride layer using the MOCVD method.

[0062] Step 6: Grow Al using MOCVD process 0.05 Ga 0.95 N electron blocking layer.

[0063] The reaction chamber temperature was adjusted to 1000℃, and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the gallium and aluminum source carrier gas, while ammonia gas at a flow rate of 1000 sccm, a TMGa gallium source at a flow rate of 70 sccm, and a TMAl aluminum source at a flow rate of 7 sccm were simultaneously introduced. A 25 nm thick Al layer was grown on a europium-doped indium gallium nitride layer using the MOCVD method. 0.05 Ga 0.95 N electron blocking layer.

[0064] Example 10 Example 10 is the same as Example 8, except that steps five and six are different. All other steps are the same as in Example 8.

[0065] Step 5: Grow europium-doped aluminum gallium nitride layer using MOCVD process.

[0066] The reaction chamber temperature was maintained at 1050℃ and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the carrier gas for gallium, aluminum and europium sources. Ammonia gas with a flow rate of 2500 sccm, TMGa gallium source with a flow rate of 40 sccm, TMAl aluminum source with a flow rate of 65 sccm and Eu(Dmphen)2Cl3 europium source with a flow rate of 80 sccm were introduced at the same time. A europium-doped aluminum gallium nitride layer with a thickness of 500 nm was grown on the n-type doped gallium nitride layer by MOCVD.

[0067] Step 6: Grow Al using MOCVD process 0.65 Ga 0.35 N electron blocking layer.

[0068] The reaction chamber temperature was adjusted to 1000℃, and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the gallium and aluminum source carrier gas, while ammonia gas at a flow rate of 1000 sccm, a TMGa gallium source at a flow rate of 70 sccm, and a TMAl aluminum source at a flow rate of 130 sccm were simultaneously introduced. A 25 nm thick Al layer was grown on the europium-doped aluminum gallium layer using the MOCVD method. 0.65 Ga 0.35 N electron blocking layer.

[0069] Example 11 Example 11 is the same as Example 8, except that steps four to eight are different, while the rest of the steps are the same as in Example 8.

[0070] Step 4: Grow a p-type doped gallium nitride layer using MOCVD process.

[0071] The reaction chamber temperature was maintained at 950℃, and the reaction chamber pressure was increased to 200 Torr. Hydrogen was used as the gallium source and magnesium source carrier gas, while ammonia gas with a flow rate of 2500 sccm, a TMGa gallium source with a flow rate of 150 sccm, and a magnesium bis(magnesium) ...

[0072] Step 5: Grow Al using MOCVD process. 0.15 Ga 0.85 N electron blocking layer.

[0073] The reaction chamber temperature was adjusted to 1000℃, and the pressure was maintained at 200 Torr. Hydrogen was used as the carrier gas for both gallium and aluminum sources. Simultaneously, ammonia gas at a flow rate of 1000 sccm, a TMGa gallium source at a flow rate of 70 sccm, and a TMAl aluminum source at a flow rate of 20 sccm were introduced. A 25 nm thick Al layer was grown on a p-type doped gallium nitride layer using the MOCVD method.0.15 Ga 0.85 N electron blocking layer.

[0074] Step 6: Grow europium-doped gallium nitride layer using MOCVD process.

[0075] The reaction chamber temperature was adjusted to 950℃ and the pressure was maintained at 200 Torr. Hydrogen was used as the gallium source and europium source carrier gas, while ammonia gas with a flow rate of 2500 sccm, a TMGa gallium source with a flow rate of 150 sccm, and an Eu(Dmphen)2Cl3 europium source with a flow rate of 80 sccm were introduced. A europium-doped gallium nitride layer with a thickness of 500 nm was grown on the electron blocking layer using the MOCVD method.

[0076] Step 7: Growing an n-type doped gallium nitride layer using MOCVD process.

[0077] The reaction chamber temperature was adjusted to 1050℃, and the reaction chamber pressure was maintained at 200 Torr. Hydrogen was used as the gallium source carrier gas, and ammonia gas with a flow rate of 2500 sccm, TMGa gallium source gas with a flow rate of 150 sccm, and SiH4 silicon source gas with a flow rate of 10 sccm were introduced simultaneously. An n-type doped gallium nitride layer with a thickness of 150 nm was grown on europium-doped gallium nitride layer using MOCVD method.

[0078] Step 8: Etch the epitaxial layer outside the device region and expose the p-type doped gallium nitride layer.

[0079] Photolithography and dry etching are used to etch the n-type doped gallium nitride layer, europium doped gallium nitride layer, and electron blocking layer outside the light-emitting device area, exposing the underlying p-type doped gallium nitride layer, while retaining the n-type doped gallium nitride layer, europium doped gallium nitride layer, and electron blocking layer within the light-emitting device area, and then the photoresist is cleaned.

[0080] like Figure 5 As shown, secondary ion mass spectrometry was used to characterize the LED epitaxial samples prepared using the europium complex of this invention as a precursor and the LED epitaxial samples prepared using Eu(DPM)3 as a precursor in the prior art. Within the europium doped layer at a depth of 150 nm to 250 nm, the oxygen impurity atom concentration in the LED epitaxial sample prepared by this invention was 10. 20 cm -3 The concentration of oxygen impurity atoms in LED epitaxial samples prepared by existing technologies is on the order of magnitude, while the concentration of oxygen impurity atoms in such samples is 10. 16 cm -3 The oxygen impurity concentration in the present invention is about four orders of magnitude lower, which can significantly improve the luminescence intensity of red light.

[0081] like Figure 6 As shown, at the same 120A / cm 2Under the current density conditions, the luminous intensity of the LED prepared by the method of the present invention reaches about 21 units, while the luminous intensity of the LED prepared by the prior art using Eu(DPM)3 as a precursor is about 6 units. The luminous intensity of the LED of the present invention is significantly higher than that of the LED of the prior art.

[0082] Therefore, the advantages of using the europium complex of the present invention as the europium source are: (1) the oxygen impurity concentration in the epitaxial layer is low; (2) the red light emission intensity of the device is high; (3) the refractive index of europium-doped gallium nitride-based LEDs mainly depends on gallium nitride material, which is the same as the main material gallium nitride of blue and green LEDs, and has the same refractive index, which facilitates the universal optical design of devices of various colors.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A europium complex, characterized in that, The molecular formula of the europium complex is C2 28 H 24 Cl3EuN4, with the chemical formula Eu(Dmphen)2Cl3, where Dmphen represents 4,7-dimethyl-1,10-phenanthroline.

2. The europium complex according to claim 1, characterized in that, The europium complex Eu(Dmphen)₂Cl₃ belongs to the triclinic crystal system, with unit cell parameters a = 9.8659 Å, b = 11.1403 Å, c = 12.0241 Å; α = 89.929 Å. o β=84.170 o , γ=85.026 o .

3. A method for preparing europium complex single crystals, the method comprising the following steps: Step 1: Add an appropriate amount of anhydrous ethanol to the reaction vessel, and then dissolve Dmphen and EuCl3·6H2O in it at a molar ratio of 1.5~2.5:

1. Step 2: Place the above reaction vessel in a drying oven and heat it from room temperature to 130-180°C within 250-350 minutes; Step 3: Keep the temperature constant at 130~180℃ for 2800~3000 min, and then lower the temperature from 130~180℃ to 25~35℃ within 550~650 min to obtain a pale yellow single crystal of europium complex Eu(Dmphen)2Cl3.

4. A method for preparing europium complex powder, the method comprising the following steps: Step 1: Measure Dmphen and EuCl3·6H2O in a molar ratio of 1.5~2.5:

1. Add the measured Dmphen to anhydrous ethanol and heat in a water bath at 65~75℃ until dissolved to obtain an anhydrous ethanol solution containing Dmphen. Step 2: Dissolve the measured EuCl3·6H2O in water to make a solution, add it dropwise to the anhydrous ethanol solution containing Dmphen, stir magnetically at 65~75℃ for 2.5~3.5 hours, and let stand for more than 5 hours; Step 3: Once a pale yellow precipitate appears in the reaction system, filter under reduced pressure and wash with ethanol and deionized water; Step 4: Dry the precipitate obtained from washing at 65~75℃ for more than 10 hours to obtain the powder of europium complex Eu(Dmphen)2Cl3.

5. A method for preparing a gallium nitride-based red light-emitting diode using a europium complex as a precursor, the method comprising the following steps: Step 1: Prepare or obtain a substrate with a gallium nitride layer of the first doping type. On the surface of the gallium nitride layer of the first doping type, use metal-organic chemical vapor phase epitaxy (MOCVE) to prepare a single crystal of europium complex Eu(Dmphen)2Cl3 prepared by the method for preparing europium complex single crystals as described in claim 3, or europium complex powder prepared by the method for preparing europium complex powder as described in claim 4, as a precursor. Use hydrogen, nitrogen, or a mixture of both as the carrier gas for the precursor. Adjust the doping concentration by adjusting the carrier gas flow rate to grow and form a europium-doped active region. Step 2: On the surface of the europium-doped active region, a second type of gallium nitride layer is grown using metal-organic chemical vapor deposition (MOCVD) to obtain a complete LED epitaxial structure. Step 3: Perform photolithography, etching or ion implantation, and deposition of metal or transparent electrodes on the LED epitaxial structure grown in Step 2 to obtain a gallium nitride-based red LED device.

6. A method for preparing a gallium nitride-based red light-emitting diode using a europium complex as a precursor, the method comprising the following steps: Step 1: Prepare or obtain a substrate with a gallium nitride layer of the first doping type. On the surface of the gallium nitride layer of the first doping type, use metal-organic chemical vapor phase epitaxy (MOCVE) to prepare a single crystal of europium complex Eu(Dmphen)2Cl3 prepared by the method for preparing europium complex single crystals as described in claim 3, or europium complex powder prepared by the method for preparing europium complex powder as described in claim 4, as a precursor. Use hydrogen, nitrogen, or a mixture of both as the carrier gas for the precursor. Adjust the doping concentration by adjusting the carrier gas flow rate to grow and form a europium-doped active region. Step 2: On the surface of the europium-doped active region, an electron blocking layer is grown using metal-organic chemical vapor deposition (MOCVD). Step 3: On the surface of the electron blocking layer, a second type of gallium nitride layer is grown using metal-organic chemical vapor deposition (MOCVD) to obtain a complete LED epitaxial structure. Step 4: Perform photolithography, etching or ion implantation, and deposition of metal or transparent electrodes on the LED epitaxial structure grown in Step 3 to obtain a gallium nitride-based red LED device.

7. The method for preparing gallium nitride-based red light-emitting diodes using europium complexes as precursors according to claim 5 or 6, characterized in that, The first doped gallium nitride layer and the second doped gallium nitride layer are respectively n-type doped and p-type doped or p-type doped and n-type doped.

8. The method for preparing gallium nitride-based red light-emitting diodes using europium complexes as precursors according to claim 5 or 6, characterized in that, The europium-doped active region includes one or more of a europium-doped gallium nitride layer, a europium-doped indium gallium nitride layer, and a europium-doped aluminum gallium nitride layer.

9. The method for preparing gallium nitride-based red light-emitting diodes using europium complexes as precursors according to claim 8, characterized in that, The europium-doped gallium nitride layer growth step in the europium-doped active region includes heating the substrate to 600~1050°C, using nitrogen, hydrogen or a mixture of both as the carrier gas, and introducing Eu(Dmphen)2Cl3, TEGa or TMGa, and ammonia until the target thickness is reached. The europium-doped indium gallium nitride layer growth step in the europium-doped active region includes heating the substrate to 600~1050°C, using nitrogen, hydrogen or a mixture of both as the carrier gas for the europium complex Eu(Dmphen)2Cl3, and introducing Eu(Dmphen)2Cl3, TEGa or TMGa, TMIn, and ammonia until the target thickness is reached. The europium-doped aluminum gallium nitride layer growth step in the europium-doped active region includes heating the substrate to 900~1250°C, using nitrogen, hydrogen, or a mixture of both as the carrier gas for the europium complex Eu(Dmphen)2Cl3, and introducing Eu(Dmphen)2Cl3, TEGa or TMGa, TMAl, and ammonia until the growth reaches the target thickness.

10. The method for preparing gallium nitride-based red light-emitting diodes using europium complexes as precursors according to claim 5 or 6, characterized in that, The precursor heating temperature for the aforementioned metal-organic chemical vapor phase epitaxy technology is 40~90℃.

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