A light-emitting diode epitaxial wafer and its fabrication method

Abstract

This invention discloses a light-emitting diode (LED) epitaxial wafer and its fabrication method, relating to the field of semiconductor process technology. The LED epitaxial wafer includes an electron blocking layer. The fabrication method includes: sequentially growing n AlGaN layers using ammonia, trimethylaluminum, and trimethylgallium as raw materials, and hydrogen and nitrogen as carrier gases, to prepare the electron blocking layer of the LED epitaxial wafer. The flow rates of the trimethylaluminum and ammonia gradually change with the increase of the number of AlGaN layers, and the flow rate of the trimethylaluminum changes in the opposite direction to that of the ammonia. This invention solves the technical problem in the prior art where the electron blocking layer introduces a large amount of impurities such as C and O, affecting the crystal quality of the electron blocking layer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor process technology, specifically to a light-emitting diode epitaxial wafer and its fabrication method. Background Technology

[0002] LED (Light Emitting Diode) is a semiconductor device that emits light by releasing energy when charge carriers recombine. LED chips have many advantages such as low power consumption, pure color, long life, small size, fast response time, energy saving and environmental protection. They have gradually replaced incandescent lamps and fluorescent lamps, becoming the light source for ordinary household lighting, and are widely used in new scenarios, such as indoor high-resolution displays, outdoor displays, mobile phone and TV backlighting, street lights, vehicle lights, flashlights and other application fields.

[0003] Currently, a common structure for LED epitaxial wafers involves growing an electron blocking layer after the light-emitting layer to reduce electron spillover and improve recombination efficiency. The electron blocking layer typically uses an AlGaN structure with varying Al content, with trimethylaluminum (A) as the Al source. However, A is chemically reactive and can burn rapidly in air. Aluminum reacts violently with acids, alcohols, and even hydrates. Introducing A, when used as the Al source into the electron blocking layer, inevitably introduces impurities such as carbon (C) and oxygen (O), affecting the crystal quality of the electron blocking layer and consequently impacting the optical and electrical properties of the LED epitaxial wafer.

[0004] Therefore, existing light-emitting diode epitaxial wafers generally suffer from the technical problem that the electron blocking layer introduces a large number of impurities such as C and O, which affects the crystal quality of the electron blocking layer. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a light-emitting diode epitaxial wafer and its fabrication method, thereby solving the technical problem that the electron blocking layer introduces a large number of impurities such as C and O, which affects the crystal quality of the electron blocking layer.

[0006] One aspect of this invention is to provide a method for preparing an epitaxial wafer for a light-emitting diode.

[0007] The light-emitting diode epitaxial wafer includes an electron blocking layer, and the method for fabricating the light-emitting diode epitaxial wafer includes:

[0008] Using ammonia, trimethylaluminum, and trimethylgallium as raw materials, and hydrogen and nitrogen as carrier gases, n AlGaN layers are grown sequentially to prepare the electron blocking layer of the light-emitting diode epitaxial wafer.

[0009] The flow rates of the trimethylaluminum and ammonia gradually change with the increase of the number of AlGaN layers, and the flow rate of the trimethylaluminum changes in the opposite direction to that of the ammonia.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for fabricating a light-emitting diode epitaxial wafer provided by the present invention uses ammonia, trimethylaluminum, and trimethylgallium as raw materials, and hydrogen and nitrogen as carrier gases, respectively, to grow n AlGaN layers as electron blocking layers in a reaction chamber. The flow rates of trimethylaluminum and ammonia gradually change with the increase of the number of AlGaN layers. The flow rate of trimethylaluminum changes in the opposite direction to that of ammonia. By controlling the flow rate of trimethylaluminum, electron overflow is reduced and the hole transport rate is increased, thereby improving the quality of the electron blocking layer. Furthermore, by controlling the flow rate of ammonia in relation to the flow rate of trimethylaluminum... Conversely, this method controls the growth process of the electron blocking layer to keep the film growth rate within an optimal range, reducing the unnecessary introduction of C and O, improving the lattice quality of the electron blocking layer, enhancing the luminous efficiency of the light-emitting diode, and avoiding the excessively rapid and intense reaction between trimethylolpropionate and ammonia, which would generate more byproducts and prevent the C and O impurities on the electron blocking layer surface from diffusing and detaching in time. This would lead to an increase in C and O impurities in the electron blocking layer, affecting the crystal quality of the electron blocking layer and consequently impacting the optical and electrical performance of the light-emitting diode epitaxial wafer. This method solves the common technical problem of the electron blocking layer introducing a large amount of C and O impurities, affecting the crystal quality of the electron blocking layer.

[0011] According to one aspect of the above technical solution, before growing the electron blocking layer, the method for fabricating the light-emitting diode epitaxial wafer further includes:

[0012] Provide a substrate for epitaxial growth;

[0013] A buffer layer, an N-type semiconductor layer, and a light-emitting layer are epitaxially grown sequentially on the substrate, and the electron blocking layer is grown on the light-emitting layer.

[0014] After growing the electron blocking layer, the method for fabricating the light-emitting diode epitaxial wafer further includes:

[0015] A P-type semiconductor layer is grown on the electron blocking layer.

[0016] According to one aspect of the above technical solution, the number of AlGaN layers n is 2-50.

[0017] According to one aspect of the above technical solution, the flow function of the trimethylaluminum is: y TMAl =A+B, the flow function of the ammonia gas is: Where A, B, C, and D are all constants, A>0, C>0, and B×D<0.

[0018] According to one aspect of the above technical solution, the flow rate of the trimethylaluminum is in the range of 20-500 sccm, and the flow rate of the ammonia is in the range of 10-300 L / min.

[0019] According to one aspect of the above technical solution, the preparation method further includes:

[0020] As the flow rate of the ammonia gas gradually changes, the flow rate of the nitrogen gas also gradually changes. The trend of the ammonia gas flow rate is opposite to that of the nitrogen gas flow rate. The flow rate function of the nitrogen gas is: Where E is a constant, and E>0.

[0021] According to one aspect of the above technical solution, the flow rate of the nitrogen gas is in the range of 50-500 L / min.

[0022] According to one aspect of the above technical solution, the thickness of the electron barrier is 60-160 nm, the growth temperature is 900-1200 °C, and the growth pressure is 100-300 Torr.

[0023] Another aspect of the present invention is to provide a light-emitting diode epitaxial wafer, which is prepared by any of the above-mentioned technical solutions using the method for preparing a light-emitting diode epitaxial wafer, wherein the light-emitting diode epitaxial wafer includes an electron blocking layer, and the electron blocking layer is an n-layer AlGaN layer;

[0024] The flow rates of trimethylaluminum and ammonia used to grow n AlGaN layers gradually change with the increase of the number of AlGaN layers, and the flow rate of trimethylaluminum changes in the opposite direction to that of ammonia.

[0025] Furthermore, the light-emitting diode epitaxial wafer also includes a substrate, a buffer layer, an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer;

[0026] The buffer layer, the N-type semiconductor layer, the light-emitting layer, the electron blocking layer, and the P-type semiconductor layer are sequentially stacked on the substrate. Attached Figure Description

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0028] Figure 1 This is a flowchart of the method for preparing a light-emitting diode epitaxial wafer in the first embodiment of the present invention;

[0029] Figure 2The graphs show the oxygen concentration of three embodiments and one comparative example of the present invention.

[0030] Figure 3 The graph shows the carbon concentration of three embodiments and one comparative example of the present invention.

[0031] Figure 4 This is a schematic diagram of the structure of the light-emitting diode epitaxial wafer in the fourth embodiment of the present invention;

[0032] Component symbol explanation in the attached diagram:

[0033] Substrate 100, buffer layer 200, N-type semiconductor layer 300, light-emitting layer 400, electron blocking layer 500, AlGaN layer 501, P-type semiconductor layer 600. Detailed Implementation

[0034] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0035] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0036] In this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the related listed items.

[0037] Example 1

[0038] Please see Figure 1The image shows a method for fabricating a light-emitting diode epitaxial wafer according to a first embodiment of the present invention. The light-emitting diode epitaxial wafer includes an electron blocking layer, and the method for fabricating the light-emitting diode epitaxial wafer includes steps S10-S11:

[0039] Step S10: Using ammonia, trimethylaluminum and trimethylgallium as raw materials and hydrogen and nitrogen as carrier gases, n AlGaN layers are grown sequentially to prepare the electron blocking layer of the light-emitting diode epitaxial wafer.

[0040] The electron blocking layer is used to block electron overflow. Since the migration rate of electrons is greater than that of holes, electrons will migrate to the P-type semiconductor layer and undergo non-radiative recombination in the P-type semiconductor layer, reducing the luminous efficiency of the LED epitaxial wafer. The electron blocking layer can be used to block electrons from the N-type semiconductor layer from migrating to the P-type semiconductor layer, blocking electrons to the light-emitting layer region, enhancing the effective radiative recombination of electrons and holes in the light-emitting layer, and improving the luminous efficiency of the LED epitaxial wafer.

[0041] Specifically, the temperature is set to 900-1200℃, the pressure is adjusted to 100-300 Torr, and ammonia, trimethylaluminum, and trimethylgallium are used as raw materials, while hydrogen and nitrogen are used as carrier gases. These are introduced into the reaction chamber to grow an electron blocking layer with a thickness of 60-160 nm on the light-emitting layer. This electron blocking layer is an n-layer AlGaN layer, where the number of AlGaN layers n is 2-50.

[0042] In step S11, the flow rates of the trimethylaluminum and the ammonia gradually change with the increase of the number of AlGaN layers, and the trend of the flow rate of the trimethylaluminum is opposite to that of the flow rate of the ammonia.

[0043] In order to improve the quality of the electron blocking layer, i.e., reduce electron overflow and increase hole transport rate, the Al composition will be gradually increased or decreased in the n-layer AlGaN layer as the number of layers increases. Therefore, it is necessary to adjust the flow rate of Al source introduced into each layer, i.e. the flow rate of trimethylaluminum introduced will gradually change as the number of AlGaN layers increases.

[0044] However, complex chemical reactions are unavoidable during epitaxial growth. The faster the reaction, the more complex the reaction and the more byproducts are produced. These byproducts contain a large amount of C and O impurities. Due to the high chemical reactivity of trimethylaluminum, the higher the flow rate of ammonia gas, the faster the reaction, and the more byproducts are generated. A large amount of impurities will exist in the electron blocking layer. Simultaneously, the more vigorous and faster the reaction, the less time the C and O impurities on the surface of the electron blocking layer have to diffuse away before being trapped inside. This will increase the amount of C and O impurities in the electron blocking layer, degrade the crystal quality of the electron blocking layer, and consequently affect the optical and electrical performance of the LED epitaxial wafer.

[0045] Therefore, it is necessary to control the reaction rate to reduce C and O impurities in the electron blocking layer. Specifically, as the flow rate of trimethylaluminum is gradually increased, the flow rate of ammonia is controlled to decrease, thus controlling the film growth process to maintain the film growth rate within an optimal range. This reduces the unnecessary introduction of C and O, improves the lattice quality of the electron blocking layer, enhances the luminous efficiency of the LED, and prevents the reaction between trimethylaluminum and ammonia from being too rapid and intense, which would generate more byproducts and prevent the C and O impurities on the electron blocking layer surface from diffusing and detaching, leading to an increase in C and O impurities in the electron blocking layer, affecting the crystal quality of the electron blocking layer, and consequently impacting the optical and electrical performance of the LED epitaxial wafer. Conversely, as the flow rate of trimethylaluminum is decreased, the flow rate of ammonia is increased. The reaction rate of trimethylaluminum slows down, requiring an increase in the ammonia flow rate to increase the growth rate of the electron blocking layer. This controls the film growth process to maintain the film growth rate within an optimal range, ensuring good uniformity and density, thereby improving the crystal quality of the electron blocking layer.

[0046] It should be noted that the flow function of trimethylaluminum is: y TMAl =A+Bn, the flow function of ammonia is: Where A, B, C, and D are constants, A>0, C>0, B×D<0. As the flow rate of trimethylaluminum gradually increases or decreases, the flow rate of ammonia will gradually decrease or increase accordingly. The flow rate of trimethylaluminum ranges from 20-500 sccm, and the flow rate of ammonia ranges from 10-300 L / min. In this embodiment, the flow rate of trimethylaluminum increases from 50 sccm to 400 sccm, and its function is y. TMAl =25+25n, the ammonia flow rate decreases from 200L / min to 60L / min.

[0047] As the flow rate of ammonia gradually changes, the flow rate of nitrogen also gradually changes, with the flow rate of ammonia changing in the opposite direction to that of nitrogen. The flow rate function of nitrogen is: Where E is a constant, E>0, and the flow rate of nitrogen is in the range of 50-500 L / min to ensure that the total amount of nitrogen, ammonia and hydrogen in the electron blocking layer remains constant. Since nitrogen, ammonia and hydrogen are the three gases with the largest amount of gas in the electron blocking layer reaction, if the flow rate of one of the three gases changes too much, it will affect the growth atmosphere of the entire electron blocking layer, such as pressure and gas concentration, and lead to the generation of more by-products. Therefore, as the flow rate of ammonia gradually increases or decreases, the flow rate of nitrogen also needs to be reduced or increased accordingly.

[0048] In addition, the method for fabricating the light-emitting diode epitaxial wafer before growing the electron blocking layer further includes:

[0049] Provide a substrate for epitaxial growth;

[0050] The substrate is the base material on which the epitaxial layer is grown and supported. Different substrate materials determine different epitaxial growth techniques and chip fabrication techniques. In this embodiment, the substrate can be a sapphire substrate, a silicon substrate, or a silicon carbide substrate, and the substrate can have a patterned structure or a non-patterned structure.

[0051] A buffer layer, an N-type semiconductor layer, and a light-emitting layer are epitaxially grown sequentially on a substrate, with an electron blocking layer grown on top of the light-emitting layer.

[0052] In this process, a buffer layer, which is an AlN thin film, is grown on the substrate. The buffer layer is used to alleviate the lattice mismatch between the epitaxial layer and the substrate, thereby facilitating the growth of subsequent epitaxial layers and improving their crystal quality. Specifically, the temperature is heated to 600-950℃ and the pressure is set to 100-200 Torr to grow an AlN thin film with a thickness of 10-80 nm on the substrate.

[0053] An N-type semiconductor layer is grown on the buffer layer. This N-type semiconductor layer is an N-type doped GaN layer, and the dopant of the N-type doped GaN layer is Si, with a doping concentration of 1×10⁻⁶. 19 cm -3 -5×10 19 cm -3 The N-type semiconductor layer has excess electrons, which are provided to the light-emitting layer, where electrons and holes recombine to emit light.

[0054] Specifically, the temperature is heated to 1050-1200℃, and the pressure is adjusted to 100-600 Torr. An N-type doped GaN layer with a thickness of 3-6 μm is epitaxially grown on the buffer layer. The dopant of the N-type doped GaN layer is Si, and the doping concentration is 1×10⁻⁶. 19 cm -3 -5×10 19 cm -3.

[0055] A light-emitting layer is grown on an N-type semiconductor layer. This light-emitting layer consists of a multi-period stacked well layer and barrier layer with a period of 2-20. The well layer is an InGaN layer with an In content of 12%-40%, and the barrier layer is a GaN layer. The thickness ratio of the well layer to the barrier layer is 1:4. The total thickness of the light-emitting layer is [missing information]. The N-type semiconductor layer provides electrons to the light-emitting layer, and the P-type semiconductor layer provides holes to the light-emitting layer, so that electrons and holes can achieve radiative recombination and light emission on the light-emitting layer.

[0056] After growing the electron blocking layer, the method for fabricating a light-emitting diode epitaxial wafer further includes:

[0057] A P-type semiconductor layer is grown on top of an electron blocking layer.

[0058] The P-type semiconductor layer is a P-type doped GaN layer, and the dopant of the P-type doped GaN layer is magnesium with a doping concentration of 1×10⁻⁶. 19 cm -3 -1×10 21 cm -3 The P-type semiconductor layer has excess holes, which are provided to the light-emitting layer to achieve radiative recombination of electrons and holes in the multiple quantum wells of the light-emitting layer.

[0059] Specifically, the temperature is heated to 900-1050℃ and the pressure is adjusted to 100-500 Torr to epitaxially grow a P-type doped GaN layer with a thickness of 40-200 nm on the electron blocking layer. The dopant in the P-type doped GaN layer is magnesium, and the doping concentration is 1×10⁻⁶. 19 cm -3 -1×10 21 cm -3 .

[0060] Compared to existing technologies, the method for fabricating a light-emitting diode epitaxial wafer provided in this embodiment, which grows an electron blocking layer on the light-emitting layer, has the following advantages: The method uses ammonia, trimethylaluminum, and trimethylgallium as raw materials, and hydrogen and nitrogen as carrier gases, respectively, to grow n AlGaN layers as electron blocking layers in a reaction chamber. The flow rates of trimethylaluminum and ammonia gradually change with the number of AlGaN layers. The flow rate of trimethylaluminum changes in the opposite direction to that of ammonia. By controlling the flow rate of trimethylaluminum, electron overflow is reduced and the hole transport rate is increased, thereby improving the quality of the electron blocking layer. Furthermore, by controlling the flow rate of ammonia... The flow rate variation trend is opposite to that of trimethylaluminum to control the growth process of the electron blocking layer, so as to keep the thin film growth rate within an optimal range, reduce the unnecessary introduction of C and O, improve the lattice quality of the electron blocking layer, improve the luminous efficiency of the light-emitting diode, and avoid the reaction of trimethylaluminum with ammonia being too fast and violent, which would produce more by-products and prevent the C and O impurities on the surface of the electron blocking layer from diffusing and detaching in time, resulting in an increase in C and O impurities in the electron blocking layer, affecting the crystal quality of the electron blocking layer, and thus affecting the optical and electrical performance of the light-emitting diode epitaxial wafer. This solves the technical problem that the electron blocking layer introduces a large amount of C and O impurities, affecting the crystal quality of the electron blocking layer.

[0061] Example 2

[0062] The second embodiment of the present invention provides a method for fabricating a light-emitting diode epitaxial wafer. The difference between the method for fabricating a light-emitting diode epitaxial wafer in this embodiment and the method for fabricating a light-emitting diode epitaxial wafer in the first embodiment is as follows:

[0063] The flow rate of trimethylaluminum increases from 50 sccm to 400 sccm as a function of y. TMAl =25+25n, the ammonia flow rate decreases from 200L / min to 130L / min.

[0064] Example 3

[0065] The third embodiment of the present invention provides a method for fabricating a light-emitting diode epitaxial wafer. The difference between the method for fabricating a light-emitting diode epitaxial wafer in this embodiment and the method for fabricating a light-emitting diode epitaxial wafer in the first embodiment is that:

[0066] The flow rate of trimethylaluminum increases from 50 sccm to 400 sccm as a function of y. TMAl =25+25n, the ammonia flow rate decreases from 200L / min to 32L / min.

[0067] Comparative Example 1

[0068] The first comparative example of this invention provides a method for fabricating a light-emitting diode epitaxial wafer. The difference between the method for fabricating a light-emitting diode epitaxial wafer in this comparative example and the method for fabricating a light-emitting diode epitaxial wafer in the first embodiment is as follows:

[0069] The flow rate of trimethylaluminum ranges from 20 to 500 sccm, and the flow rate of ammonia ranges from 10 to 300 L / min. In this embodiment, the flow rate of trimethylaluminum increases from 50 sccm to 400 sccm as a function of y. TMAl =25+25n, the flow rate of ammonia is 200L / min.

[0070] The following will combine Figures 2-3 The experimental test results are compared and explained with the above Examples 1 to 3 and Comparative Example 1 to fully illustrate the effectiveness of the method for preparing a light-emitting diode epitaxial wafer of the present invention.

[0071] Based on the data from Examples 1 to 3 and Comparative Example 1, it can be seen that the carbon and oxygen concentrations in Examples 1 to 3 are lower than those in Comparative Example 1. In Examples 1 to 3, the flow rate of trimethylaluminum gradually increases with the increase of the number of AlGaN layers, while the flow rate of ammonia gradually decreases with the increase of the number of AlGaN layers. In the comparative example, the flow rate of trimethylaluminum gradually increases with the increase of the number of AlGaN layers, while the flow rate of ammonia remains unchanged. Therefore, controlling the flow rate of ammonia to change in the opposite direction to the flow rate of trimethylaluminum can effectively reduce the unnecessary introduction of C and O, improve the lattice quality of the electron blocking layer, and enhance the luminous efficiency of the light-emitting diode.

[0072] Based on the data from Examples 1, 2, and 3, it can be seen that when the ammonia flow rate is reduced too much (i.e., the reduction coefficient is too large), the carbon and oxygen concentrations decrease significantly in the first few AlGaN layers of the electron blocking layer due to the reduced reaction rate between trimethylaluminum and ammonia. However, in the last few AlGaN layers of the electron blocking layer, the insufficient N source due to the excessive reduction in ammonia flow rate will introduce a large number of impurities, and the carbon and oxygen concentrations will increase rapidly. When the ammonia flow rate is reduced too little (i.e., the reduction coefficient is too small), the growth process of the electron blocking layer is too fast, the growth rate is not controlled within the optimal range, the reaction is intense, and more by-products will be generated. Furthermore, the C and O impurities on the surface of the electron blocking layer will not have time to diffuse and detach, resulting in an increase in C and O impurities in the electron blocking layer. This affects the crystal quality of the electron blocking layer and, consequently, the optical and electrical performance of the light-emitting diode epitaxial wafer.

[0073] It should be noted that the difference between the decreasing flow rate of trimethylaluminum as the number of AlGaN layers increases and the increasing flow rate of trimethylaluminum as the number of AlGaN layers increases are opposites. The flow rate of trimethylaluminum decreases from 400 sccm to 50 sccm as a function of y. TMAl =425-25n, and at the same time, the flow rate difference of ammonia is also an inverse of each other. When the flow rate of ammonia increases from 60L / min to 200L / min, its function is y. TMAl =50 + 10n. The values ​​of its oxygen and carbon concentrations can be found in the data in Example 1.

[0074] In summary, the flow rates of trimethylaluminum and ammonia gradually change with the increase of the number of AlGaN layers. The flow rate of trimethylaluminum changes in the opposite direction to that of ammonia. By controlling the flow rate of ammonia to be opposite to that of trimethylaluminum, the growth process of the electron blocking layer can be effectively controlled, so that the film growth rate is kept within an optimal range, unnecessary introduction of C and O is reduced, the lattice quality of the electron blocking layer is improved, and the luminous efficiency of the light-emitting diode is enhanced.

[0075] Example 4

[0076] Please see Figure 4 The image shows a light-emitting diode epitaxial wafer according to a fourth embodiment of the present invention. The light-emitting diode epitaxial wafer includes a substrate 100, wherein the substrate 100 is a substrate for epitaxial layer growth and support. Different substrate 100 materials determine different epitaxial growth techniques and chip processing techniques. In this embodiment, the substrate 100 material can be sapphire, silicon, or silicon carbide, and the substrate 100 can be a patterned structure or a non-patterned structure.

[0077] A buffer layer 200, an N-type semiconductor layer 300, a light-emitting layer 400, an electron-blocking layer 500, and a P-type semiconductor layer 600 are sequentially stacked on a substrate 100. The buffer layer 200 is an AlN thin film with a thickness of 10-80 nm. The buffer layer 200 is used to alleviate the lattice mismatch between the epitaxial layer and the substrate 100, thereby facilitating the growth of subsequent epitaxial layers and improving the crystal quality of the subsequent epitaxial layers.

[0078] An N-type semiconductor layer 300 is disposed on the buffer layer 200. The N-type semiconductor layer 300 is an N-type doped GaN layer with a thickness of 3-6 μm. The dopant of the N-type doped GaN layer is Si, and the doping concentration is 1×10⁻⁶. 19 cm -3 -5×10 19 cm -3 The N-type semiconductor layer 300 has excess electrons, which are provided to the light-emitting layer 400, where electrons and holes recombine to emit light.

[0079] A light-emitting layer 400 is disposed on the N-type semiconductor layer 300. This light-emitting layer 400 is a multi-period stacked well layer and barrier layer with a period of 2-20. The well layer is an InGaN layer, wherein the In content is 12%-40%, and the barrier layer is a GaN layer. The thickness ratio of the well layer to the barrier layer is 1:4. The total thickness of the light-emitting layer 400 is [missing information]. The N-type semiconductor layer 300 provides electrons to the light-emitting layer 400, and the P-type semiconductor layer 600 provides holes to the light-emitting layer 400, so that electrons and holes can achieve radiative recombination and light emission on the light-emitting layer 400.

[0080] An electron blocking layer 500 is provided on the light-emitting layer 400. The electron blocking layer 500 is an n-layer AlGaN layer 501, where the number of AlGaN layers n is 2-50. The electron blocking layer 500 is used to block electron overflow. To reduce electron overflow and increase the hole transport rate, the Al content in the n-layer AlGaN layer 501 is gradually increased or decreased as the number of layers increases, thereby improving the quality of the electron blocking layer 500. Therefore, it is necessary to adjust the flow rate of the Al source introduced into each layer, that is, the flow rate of trimethylaluminum introduced gradually changes as the number of AlGaN layers 501 increases.

[0081] However, trimethylaluminum is chemically reactive and can burn rapidly in air. It also reacts violently with acids, alcohols, and even hydrates. When trimethylaluminum is used as an Al source, it inevitably introduces impurities such as carbon (C) and oxygen (O). Due to its high chemical reactivity, the more ammonia gas is introduced, the faster the reaction rate and the more byproducts are produced. A large amount of impurities will be present in the electron blocking layer 500. Furthermore, the more vigorous and faster the reaction, the less time the C and O impurities on the surface of the electron blocking layer 500 can diffuse away before being trapped inside. This increases the amount of C and O impurities in the electron blocking layer 500, degrades its crystal quality, and consequently affects the optical and electrical properties of the LED epitaxial wafer.

[0082] As the flow rate of trimethylaluminum gradually changes with the increase of the number of AlGaN layers 501, the flow rate of ammonia also gradually changes with the increase of the number of AlGaN layers 501. The trend of the flow rate of trimethylaluminum is opposite to that of the flow rate of ammonia, in order to control the reaction rate and reduce the C and O impurities in the electron blocking layer 500.

[0083] Specifically, as the flow rate of trimethylaluminum gradually increases, the flow rate of ammonia is controlled to decrease, thus controlling the film growth process to maintain the film growth rate within an optimal range. This reduces the unnecessary introduction of C and O, improves the lattice quality of the electron blocking layer 500, and enhances the luminous efficiency of the light-emitting diode. It also prevents the reaction between trimethylaluminum and ammonia from being too rapid and intense, which would generate more byproducts and prevent C and O impurities on the electron blocking layer 500 from diffusing and detaching in time, leading to an increase in C and O impurities and affecting the crystal quality of the electron blocking layer 500, thereby impacting the optical and electrical performance of the LED epitaxial wafer. Conversely, as the flow rate of trimethylaluminum decreases, the flow rate of ammonia is controlled to increase. The reaction rate of trimethylaluminum slows down, requiring an increase in the ammonia flow rate to increase the growth rate of the electron blocking layer 500. This controls the film growth process to maintain the film growth rate within an optimal range, ensuring good uniformity and density, thereby improving the crystal quality of the electron blocking layer 500.

[0084] It should be noted that the flow function of trimethylaluminum is: y TMAl =A+Bn, the flow function of ammonia is: Where A, B, C, and D are constants, A>0, C>0, B×D<0. As the flow rate of trimethylaluminum gradually increases or decreases, the flow rate of ammonia will gradually decrease or increase accordingly. The flow rate of trimethylaluminum ranges from 20-500 sccm, and the flow rate of ammonia ranges from 10-300 L / min.

[0085] As the flow rate of ammonia gradually changes, the flow rate of nitrogen also gradually changes, with the flow rate of ammonia changing in the opposite direction to that of nitrogen. The flow rate function of nitrogen is: Where E is a constant, E>0, and the flow rate of nitrogen is in the range of 50-500 L / min to ensure that the total amount of nitrogen, ammonia and hydrogen in the electron blocking layer 500 remains constant. Since nitrogen, ammonia and hydrogen are the three gases with the largest amount of gas in the reaction of electron blocking layer 500, if the flow rate of one of the three gases changes too much, it will affect the growth atmosphere of the entire electron blocking layer 500, such as pressure and gas concentration, and lead to the generation of more by-products. Therefore, as the flow rate of ammonia gradually increases or decreases, the flow rate of nitrogen also needs to be reduced or increased accordingly.

[0086] A P-type semiconductor layer is disposed on the electron blocking layer. This P-type semiconductor layer is a P-type doped GaN layer with a thickness of 40-200 nm. The dopant of the P-type doped GaN layer is magnesium, and the doping concentration is 1×10⁻⁶. 19 cm -3 -1×10 21 cm -3The P-type semiconductor layer has excess holes, which are provided to the light-emitting layer to achieve radiative recombination of electrons and holes in the multiple quantum wells of the light-emitting layer.

[0087] Compared to existing technologies, the LED epitaxial wafer provided in this embodiment has the following advantages: In the LED epitaxial wafer provided by this invention, the electron blocking layer is an n-layer AlGaN layer. The flow rates of trimethylaluminum and ammonia gradually change with the increase of the number of AlGaN layers. The flow rate of trimethylaluminum changes in the opposite direction to that of ammonia. By controlling the flow rate of trimethylaluminum, electron overflow is reduced and the hole transport rate is increased, thereby improving the quality of the electron blocking layer. Furthermore, by controlling the flow rate of ammonia to be opposite to that of trimethylaluminum, the growth process of the electron blocking layer is controlled. This approach aims to maintain the thin film growth rate within an optimal range, reduce the unnecessary introduction of C and O, improve the lattice quality of the electron blocking layer, enhance the luminous efficiency of the light-emitting diode, and prevent the excessively rapid and intense reaction between trimethylolpropionate and ammonia, which would generate more byproducts and prevent the C and O impurities on the electron blocking layer surface from diffusing and detaching in time. This would increase the C and O impurities in the electron blocking layer, affecting its crystal quality and consequently its optical and electrical performance. Therefore, this method solves the common technical problem of introducing large amounts of C and O impurities into the electron blocking layer, thus affecting its crystal quality.

[0088] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for fabricating a light-emitting diode epitaxial wafer, characterized in that, The light-emitting diode epitaxial wafer includes an electron blocking layer, and the method for fabricating the light-emitting diode epitaxial wafer includes: Using ammonia, trimethylaluminum, and trimethylgallium as raw materials, and hydrogen and nitrogen as carrier gases, n AlGaN layers are grown sequentially to prepare the electron blocking layer of the light-emitting diode epitaxial wafer. The flow rates of trimethylaluminum and ammonia gradually change with the increase of the number of AlGaN layers. The flow rate of trimethylaluminum changes in the opposite direction to that of ammonia, and the flow rate of ammonia changes in the opposite direction to that of nitrogen. The flow rate function of trimethylaluminum is: y TMAl =A+Bn, the flow function of ammonia is: Where A, B, C, and D are all constants, A>0, C>0, B×D<0, and the flow rate function of nitrogen is: Where E is a constant, E>

0. The flow rate of trimethylaluminum decreased from 400 sccm to 50 sccm as a function of y. TMAl =425-25n, the ammonia flow rate increases from 60 L / min to 200 L / min, its function is y TMAl =50+10n, the flow rate of nitrogen is 50-500L / min.

2. The method for fabricating a light-emitting diode epitaxial wafer according to claim 1, characterized in that, Before growing the electron blocking layer, the method for fabricating the light-emitting diode epitaxial wafer further includes: Provide a substrate for epitaxial growth; A buffer layer, an N-type semiconductor layer, and a light-emitting layer are epitaxially grown sequentially on the substrate, and the electron blocking layer is grown on the light-emitting layer. After growing the electron blocking layer, the method for fabricating the light-emitting diode epitaxial wafer further includes: A P-type semiconductor layer is grown on the electron blocking layer.

3. The method for fabricating a light-emitting diode epitaxial wafer according to claim 1, characterized in that, The number of AlGaN layers, n, is 2-50.

4. The method for fabricating a light-emitting diode epitaxial wafer according to claim 1, characterized in that, The electron barrier has a thickness of 60-160 nm, a growth temperature of 900-1200 °C, and a growth pressure of 100-300 Torr.

5. A light-emitting diode epitaxial wafer, prepared using the method for preparing a light-emitting diode epitaxial wafer according to any one of claims 1-4, characterized in that, The light-emitting diode epitaxial wafer includes an electron blocking layer, which is an n-layer AlGaN layer; In this process, the flow rates of trimethylaluminum and ammonia used for growing n AlGaN layers gradually change with the increase of the number of AlGaN layers. The flow rate of trimethylaluminum changes in the opposite direction to that of ammonia, and the flow rate of ammonia changes in the opposite direction to that of nitrogen. The flow rate function of trimethylaluminum is: y TMAl =A+Bn, the flow function of ammonia is: Where A, B, C, and D are all constants, A>0, C>0, B×D<0, and the flow rate function of nitrogen is: Where E is a constant, E>

0. The flow rate of trimethylaluminum decreased from 400 sccm to 50 sccm as a function of y. TMAl =425-25n, the ammonia flow rate increases from 60 L / min to 200 L / min, its function is y TMAl =50+10n, the flow rate of nitrogen is 50-500L / min.

6. The light-emitting diode epitaxial wafer according to claim 5, characterized in that, The light-emitting diode epitaxial wafer also includes a substrate, a buffer layer, an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer; The buffer layer, the N-type semiconductor layer, the light-emitting layer, the electron blocking layer, and the P-type semiconductor layer are sequentially stacked on the substrate.

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