LED epitaxial wafer preparation method and micro-led

Abstract

This invention provides a method for fabricating LED epitaxial wafers and a Micro-LED. The method involves fabricating a multi-quantum-well layer with a periodic stacked structure of InGaN / InN / AlGaN / GaN layers. The InGaN layer acts as a potential well layer, allowing electrons and holes to recombine and participate in light emission. The ultra-thin design improves polarization and reduces QCSE (Quantum Conversion Efficiency). Simultaneously, the ultra-thin design also reduces indium segregation caused by high In content. The InN layer enhances effective In incorporation, and sufficient NH3 further reacts with precipitated In atoms to form InN, resulting in effective incorporation. This improves the In content while maintaining crystal quality. Furthermore, the AlGaN layer acts as a high barrier layer, effectively confining electrons, while the GaN layer provides hole-rich channels, thereby improving luminous efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for preparing LED epitaxial wafers and Micro-LEDs. Background Technology

[0002] Traditional red LEDs based on aluminum gallium indium phosphide (AlGaInP) suffer from a sharp drop in external quantum efficiency (EQE) to below 1% when their chip size shrinks to the micrometer scale. Furthermore, the material's weak mechanical strength makes it difficult to meet the demands of high-density Micro-LED full-color displays. Red LEDs based on indium gallium nitride (InGaN), due to their process compatibility with blue and green InGaN-based Micro-LEDs and their better mechanical stability, have become an ideal alternative.

[0003] However, InGaN-based red quantum wells face core challenges such as severe indium segregation under high indium (In) composition, large lattice mismatch stress, significant quantum confinement Stark effect (QCSE), and low hole injection efficiency, resulting in luminous efficiency far lower than that of blue and green light devices, typically less than 2.5%, becoming a key technical bottleneck restricting the full-color development of Micro-LEDs.

[0004] In existing technologies, although there are methods to alleviate stress and improve efficiency by optimizing the multiple quantum well (MQW) structure, introducing V-pits, or using special substrates, these methods are often complex or have limited effects, making it difficult to achieve high crystal quality and efficient carrier recombination while achieving high In composition red light emission. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a method for preparing LED epitaxial wafers and a Micro-LED, which aims to improve the In composition while ensuring crystal quality and simultaneously improve luminous efficiency.

[0006] According to an embodiment of the present invention, a method for preparing an LED epitaxial wafer includes: Fabricating a multi-quantum-well layer, wherein the multi-quantum-well layer is a periodic stacked structure of InGaN layer / InN layer / AlGaN layer / GaN layer, specifically including: During the growth of an InGaN layer in a single cycle, the In composition of the InGaN layer is controlled to be 30%~40% by adjusting the flow ratio of TMI to TMI. During the growth of the InN layer in a single cycle, TMGa is turned off and only TMI is introduced. The growth atmosphere is N2 and NH3. TMI and NH3 react to grow the InN layer, which is used as the In-treated layer. During the growth of AlGaN layers in a single cycle, the Al composition is controlled to be 10%~30% by adjusting the flow ratio of TMIn to TMGa.

[0007] Furthermore, the method also includes: Provide a substrate; A buffer layer, a three-dimensionally grown GaN layer, an undoped GaN layer, an N-type doped GaN layer, a stress relief layer, the multi-quantum well layer, an electron blocking layer, and a P-type doped GaN layer are sequentially deposited on the substrate.

[0008] Furthermore, during the growth of the InGaN layer in a single cycle, the growth temperature is controlled at 650℃~750℃ and the growth pressure is controlled at 100 torr~300 torr.

[0009] Furthermore, during the growth of the InN layer in a single cycle, the growth temperature was controlled at 650℃~750℃, the growth pressure at 100 torr~300 torr, and the growth time at 10s~30s.

[0010] Furthermore, during the growth of AlGaN layers in a single cycle, the growth temperature is controlled at 850℃~950℃ and the growth pressure is controlled at 100 torr~300 torr.

[0011] Furthermore, during the growth of a single GaN layer, the growth temperature is controlled at 850℃~950℃ and the growth pressure is controlled at 100 torr~300 torr.

[0012] Furthermore, the thickness of a single InGaN layer is 1nm~2nm, the thickness of a single AlGaN layer is 4nm~6nm, and the thickness of a single GaN layer is 4nm~6nm.

[0013] Furthermore, the number of periods in the multi-quantum well layer is 3 to 8. According to an embodiment of the present invention, a Micro-LED is prepared according to the above-described LED epitaxial wafer preparation method.

[0014] This invention provides a method for fabricating an LED epitaxial wafer and a Micro-LED. By fabricating a multi-quantum-well layer with a periodic stacked structure of InGaN / InN / AlGaN / GaN layers, the InGaN layer acts as a potential well layer, allowing electrons and holes to recombine and participate in light emission. The ultra-thin design improves polarization and reduces QCSE (Quantum Conversion Equivalent Segregation). Simultaneously, the ultra-thin design also reduces indium segregation caused by high In content. The InN layer, on the one hand, increases the effective incorporation of In; on the other hand, sufficient NH3 can further react with the precipitated In atoms to form InN, thus effectively incorporating In. This increases the In content while ensuring crystal quality. Furthermore, the AlGaN layer, as a high barrier layer, effectively confines electrons, while the GaN layer provides hole-rich channels, thereby improving luminous efficiency. Detailed Implementation

[0015] This 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 this invention will be thorough and complete.

[0016] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] The LED epitaxial wafer in this embodiment of the invention includes a substrate and a buffer layer, a three-dimensionally grown GaN layer, an undoped GaN layer, an N-type doped GaN layer, a stress relief layer, the multi-quantum well layer, an electron blocking layer, and a P-type doped GaN layer, which are sequentially stacked on the substrate.

[0019] The substrate can be a sapphire substrate; the buffer layer is made of GaN with a thickness of 15nm to 35nm, for example, the thickness of the buffer layer is 15nm, 20nm, 25nm, 30nm or 35nm, etc., but not limited to these; the thickness of the three-dimensionally grown GaN layer is 500nm to 2000nm, for example, the thickness of the three-dimensionally grown GaN layer is 500nm, 800nm, 1000nm, 1500nm or 2000nm, etc., but not limited to these; the thickness of the undoped GaN layer can be 800nm ​​to 1200nm, for example, the thickness is 800nm, 900nm, 1000nm, 1100nm or 1200nm, etc., but not limited to these, using TMGa as the MO source; the thickness of the N-type doped GaN layer is 1000nm to 3000nm, for example, the thickness is 1000nm, 1500nm, 2000nm, 2500nm or 3000nm, etc. The thickness of the layer can be 10nm to 100nm, but is not limited to this. TMGa is used as the MO source, and this layer is used to provide electrons. The stress relief layer can be a periodic structure with alternating InGaN and GaN layers. The thickness of the InGaN layer can be 1 to 3nm, with an In composition of 5% to 10%, and the thickness of the GaN layer can be 5nm to 15nm, with 2 to 8 periods. The electron blocking layer can be a periodic structure with alternating AlGaN and GaN layers, with a thickness of 10nm to 100nm. For example, the thickness can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm, but is not limited to this. The thickness of the P-type doped GaN layer is 50nm to 300nm, and this layer is used to provide holes. For example, the thickness can be 50nm, 100nm, 150nm, 200nm, 250nm, or 300nm, but is not limited to this.

[0020] The multi-quantum well layer in this embodiment of the invention adopts a periodic stacked structure of InGaN layer / InN layer / AlGaN layer / GaN layer, wherein the In composition is 30%~40%, the InGaN layer thickness is controlled at 1nm~2nm, the InN layer improves the In segregation problem and improves the effective incorporation of In, the AlGaN layer can effectively alleviate the compressive strain reduction defect caused by lattice mismatch at the InGaN / GaN interface and improve the interface clarity, while Al doping can raise the potential barrier and reduce electron overflow.

[0021] It should be noted that the fabrication of multiple quantum well layers specifically includes: During the growth of an InGaN layer in a single cycle, the In composition of the InGaN layer is controlled to be 30%~40% by adjusting the flow ratio of TMI to TMI. During the growth of the InN layer in a single cycle, TMGa is turned off and only TMI is introduced. The growth atmosphere is N2 and NH3. TMI and NH3 react to grow the InN layer, which is used as the In-treated layer. During the growth of AlGaN layers in a single cycle, the Al composition is controlled to be 10%~30% by adjusting the flow ratio of TMIn to TMGa.

[0022] The number of cycles in the multi-quantum well layer is 3 to 8. For example, the number of cycles in the multi-quantum well layer is 3, 4, 5, 6, 7 or 8.

[0023] Another embodiment of the present invention provides a method for preparing an LED epitaxial wafer, the method specifically comprising: Provide a substrate; A buffer layer, a three-dimensionally grown GaN layer, an undoped GaN layer, an N-type doped GaN layer, a stress relief layer, a multiple quantum well layer, an electron blocking layer, and a P-type doped GaN layer are sequentially deposited on the substrate. Specifically, the fabrication of a multi-quantum-well layer, wherein the multi-quantum-well layer is a periodic stacked structure of InGaN layer / AlGaN layer / GaN layer, includes: During the growth of a single InGaN layer, the growth temperature is controlled at 650℃~750℃, the growth pressure is 100 torr~300 torr, the In composition is 30%~40% by adjusting the flow ratio of TMI to TMGa, the growth atmosphere is N2 and NH3, and the growth thickness is 1nm~2nm. During the growth of the InN layer in a single cycle, the growth temperature is controlled at 650℃~750℃, the growth pressure is 100 torr~300 torr, TMGa is turned off, only TMIn is introduced, and the growth atmosphere is N2 and NH3. TMIn and NH3 react to grow InN. This layer is used as the In treatment layer, and the treatment time is usually 10s~30s, with almost no thickness increase. During the growth of AlGaN layers in a single cycle, the growth temperature is controlled at 850℃~950℃, the growth pressure is 100 torr~300 torr, and the Al composition is 10%~30% by adjusting the flow ratio of TMAl to TMGa, and the growth thickness is 4nm~6nm. During the growth of a single GaN layer, the growth temperature is controlled at 850℃~950℃, the growth pressure at 100 torr~300 torr, and the growth thickness at 4nm~6nm.

[0024] The present invention will be further described below with reference to specific embodiments: Example 1 Embodiment 1 of the present invention provides a method for preparing an LED epitaxial wafer, specifically including: Provide a substrate; A buffer layer, a three-dimensionally grown GaN layer, an undoped GaN layer, an N-type doped GaN layer, a stress relief layer, a multiple quantum well layer, an electron blocking layer, and a P-type doped GaN layer are sequentially deposited on the substrate. Specifically, a multi-quantum-well layer is fabricated, wherein the multi-quantum-well layer is a periodic stacked structure of InGaN layer / AlGaN layer / GaN layer, specifically including: During the growth of a single InGaN layer, the growth temperature was controlled at 700℃, the growth pressure at 200 torr, the In composition was adjusted to 35% by adjusting the flow ratio of TMI to TMGa, the growth atmosphere was N2 and NH3, and the growth thickness was 1.5 nm. During the growth of the InN layer in a single cycle, the growth temperature is controlled at 700℃, the growth pressure is 200 torr, TMGa is turned off, only TMIn is introduced, and the growth atmosphere is N2 and NH3. TMIn and NH3 react to grow InN. This layer is used as an In-treated layer, and the treatment time is usually 20s, with almost no thickness increase. During the growth of AlGaN layers in a single cycle, the growth temperature was controlled at 900℃ and the growth pressure at 200 torr. By adjusting the flow ratio of TMAl to TMGa, the Al composition was kept at 20% and the growth thickness was 5nm. During the growth of a single GaN layer, the growth temperature was controlled at 900℃, the growth pressure at 200 torr, and the growth thickness at 5nm.

[0025] In addition, the number of cycles in the multi-quantum well layer is 6.

[0026] Example 2 Embodiment 2 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the InGaN layer in a single cycle is 0.5 nm.

[0027] Example 3 Embodiment 3 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the InGaN layer in a single cycle is 1 nm.

[0028] Example 4 Embodiment 4 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the InGaN layer in a single cycle is 2 nm.

[0029] Example 5 Embodiment 5 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the InGaN layer in a single cycle is 2.5 nm.

[0030] Example 6 Embodiment 6 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the growth time of the InN layer in a single cycle is 5s.

[0031] Example 7 Embodiment 7 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the growth time of the InN layer in a single cycle is 10s.

[0032] Example 8 Embodiment 8 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the growth time of the InN layer in a single cycle is 30s.

[0033] Example 9 Embodiment 9 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the growth time of the InN layer in a single cycle is 40s.

[0034] Example 10 Embodiment 10 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the AlGaN layer in a single cycle is 3 nm.

[0035] Example 11 Embodiment 11 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the AlGaN layer in a single cycle is 4 nm.

[0036] Example 12 Embodiment 12 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the AlGaN layer in a single cycle is 6 nm.

[0037] Example 13 Embodiment 13 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the AlGaN layer in a single cycle is 7 nm.

[0038] Example 14 Embodiment 14 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the GaN layer in a single cycle is 3 nm.

[0039] Example 15 Embodiment 15 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the GaN layer in a single cycle is 4 nm.

[0040] Example 16 Embodiment 16 of the present invention also provides a method for preparing an LED epitaxial wafer. The difference from Embodiment 1 is that the thickness of the GaN layer in a single cycle is 6 nm.

[0041] Example 17 Embodiment 17 of the present invention also provides a method for preparing an LED epitaxial wafer, the difference from Embodiment 1 being that the thickness of the GaN layer in a single cycle is 7 nm.

[0042] Example 18 Embodiment 18 of the present invention also provides a method for preparing an LED epitaxial wafer, the difference from Embodiment 1 being that the number of cycles is 2.

[0043] Example 19 Embodiment 19 of the present invention also provides a method for preparing an LED epitaxial wafer, the difference from Embodiment 1 being that the number of cycles is 3.

[0044] Example 20 Embodiment 20 of the present invention also provides a method for preparing an LED epitaxial wafer, the difference from Embodiment 1 being that the number of cycles is 8.

[0045] Example 21 Embodiment 17 of the present invention also provides a method for preparing an LED epitaxial wafer, the difference from Embodiment 1 being that the number of cycles is 9.

[0046] Comparative Example 1 Comparative Example 1 also provides a method for preparing an LED epitaxial wafer. The difference from Example 1 is that the multi-quantum well layer is a periodic stacked structure of InGaN layer / GaN layer, the thickness of a single InGaN layer is 3nm, the thickness of a single GaN layer is 10nm, and the number of cycles is 6.

[0047] Comparative Example 2 Comparative Example 2 also provides an LED epitaxial wafer fabrication method, which is a conventional red light epitaxial technology based on GaAs substrate. It uses AlGaInP material system as the core and achieves efficient red light emission through MOCVD epitaxial growth. Its core structure includes a DBR reflective layer, a lattice matching buffer layer, a multiple quantum well (MQW) active region, and a current spreading layer.

[0048] The LED epitaxial wafers from Examples 1 to 18, as well as Comparative Examples 1 and 2, were fabricated into Micro-LEDs with dimensions of 50 μm × 50 μm. The test current was 10 μA, and the specific test results are as follows:

[0049] The data in the table show that when the InGaN well layer thickness increases from 0.5 nm to 1.5 nm, the efficiency increases significantly with improved compatibility of the composite region and lattice stress balance. However, when the thickness is further increased to 2.5 nm, the efficiency drops rapidly due to enhanced polarization field, intensified carrier separation, and increased defects. When the InN growth time is extended from 5 s to 20 s, the efficiency steadily increases with precise control of the high In content required for red light. However, when extended to 40 s, the efficiency drops sharply due to lattice stress accumulation and phase separation caused by excessively high In content. The AlGaN confinement layer thickness increases from 3 nm to 5 nm. At nm, efficiency improves significantly with enhanced carrier leakage suppression; however, efficiency drops when the thickness increases to 7nm due to excessively high barrier hindering hole injection and exacerbating stress defects. When the GaN barrier layer thickness increases from 3nm to 5nm, efficiency gradually improves with optimized carrier confinement capability; however, efficiency decreases when the thickness increases to 7nm due to stress accumulation and increased carrier transport losses. When the number of multiple quantum well cycles increases from 2 to 6, efficiency increases significantly with the increase in the number of recombination regions; however, efficiency drops when the number of cycles increases to 9 due to overall stress concentration, deterioration of lattice quality, and increased operating voltage.

[0050] It can be observed that the parameter combination of Example 1 (InGaN 1.5nm, InN growth 20s, AlGaN 5nm, GaN 5nm, number of cycles 6) achieved a peak efficiency of 230.86%, whose brightness and efficiency far exceeded the benchmark and AlGaInP schemes, and whose operating voltage was close to that of conventional GaN-based red LEDs.

[0051] In summary, the LED epitaxial wafer fabrication method and Micro-LED in the embodiments of the present invention utilize a multi-quantum well layer with a periodic stacked structure of InGaN / InN / AlGaN / GaN layers. The InGaN layer acts as a potential well layer, allowing electrons and holes to recombine and participate in light emission. The ultra-thin design improves polarization and reduces QCSE. Simultaneously, the ultra-thin design also reduces indium segregation caused by high In content. The InN layer can improve the effective incorporation of In, and the sufficient NH3 can further react with the precipitated In atoms to form InN, thus effectively incorporating In. This improves the In content while ensuring crystal quality. In addition, the AlGaN layer acts as a high barrier layer to effectively confine electrons, while the GaN layer provides a hole enrichment channel, thereby improving the luminous efficiency.

[0052] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are 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 modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method of preparing an LED epitaxial wafer, characterized by, The method includes: Fabricating a multi-quantum-well layer, wherein the multi-quantum-well layer is a periodic stacked structure of InGaN layer / InN layer / AlGaN layer / GaN layer, specifically including: During the growth of an InGaN layer in a single cycle, the In composition of the InGaN layer is controlled to be 30%~40% by adjusting the flow ratio of TMI to TMI. During the growth of the InN layer in a single cycle, TMGa is turned off and only TMI is introduced. The growth atmosphere is N2 and NH3. TMI and NH3 react to grow the InN layer, which is used as the In-treated layer. During the growth of AlGaN layers in a single cycle, the Al composition is controlled to be 10%~30% by adjusting the flow ratio of TMIn to TMGa.

2. The LED epi-sheet preparation method of claim 1, wherein, The method further includes: Provide a substrate; A buffer layer, a three-dimensionally grown GaN layer, an undoped GaN layer, an N-type doped GaN layer, a stress relief layer, the multi-quantum well layer, an electron blocking layer, and a P-type doped GaN layer are sequentially deposited on the substrate.

3. The method for preparing an LED epitaxial wafer according to claim 2, characterized in that, During the growth of the InGaN layer in a single cycle, the growth temperature is controlled at 650℃~750℃ and the growth pressure is controlled at 100 torr~300 torr.

4. The method for preparing an LED epitaxial wafer according to claim 3, characterized in that, During a single InN layer growth cycle, the growth temperature was controlled at 650℃~750℃, the growth pressure at 100 torr~300 torr, and the growth time at 10s~30s.

5. The method for preparing an LED epitaxial wafer according to claim 4, characterized in that, During the growth of AlGaN layers in a single cycle, the growth temperature was controlled at 850℃~950℃ and the growth pressure was controlled at 100 torr~300 torr.

6. The method for preparing an LED epitaxial wafer according to claim 5, characterized in that, During the growth of a single GaN layer, the growth temperature is controlled at 850℃~950℃ and the growth pressure is controlled at 100 torr~300 torr.

7. The method for preparing an LED epitaxial wafer according to claim 6, characterized in that, The thickness of a single InGaN layer is 1nm~2nm, the thickness of a single AlGaN layer is 4nm~6nm, and the thickness of a single GaN layer is 4nm~6nm.

8. The method for preparing an LED epitaxial wafer according to claim 7, characterized in that, The number of periods in the multi-quantum well layer is 3 to 8.

9. A Micro-LED, characterized in that, The LED epitaxial wafer is prepared according to any one of claims 1-8.

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