A Micro LED Epitaxial Structure and Its Fabrication Method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGXI ZHAO CHI SEMICON CO LTD
- Filing Date
- 2026-05-14
- Publication Date
- 2026-06-19
AI Technical Summary
Existing Micro LED epitaxial structure designs cannot meet the application requirements of small size and low current density, resulting in insufficient efficiency, especially in the current density range of 0.01A/cm2-0.5A/cm2.
A Micro LED epitaxial structure was designed, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, and a P-type semiconductor layer stacked sequentially. The multi-quantum-well light-emitting layer is composed of alternating Inx1GaN layers, a first N-type quantum barrier layer, a second N-type quantum barrier layer, a first P-type quantum barrier layer, and a third P-type quantum barrier layer. By controlling the material type and composition, the electron-hole concentration matching degree is improved, and the electron blocking layer is eliminated to improve the brightness and luminous efficiency at low current densities.
By optimizing the structure of the multi-quantum-well light-emitting layer, the luminous efficacy and brightness of Micro LEDs at low operating current densities were improved, defects were reduced, and the radiative recombination efficiency and yield of the device were enhanced.
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Figure CN122248861A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of light-emitting diodes, and more particularly to a Micro LED epitaxial structure and its fabrication method. Background Technology
[0002] With the rapid development of emerging wearable and portable technologies, micron-sized LED chips (Micro LED) have garnered significant attention and research from scientific institutions and enterprises due to their promising applications in displays, visible light communication, and biomedicine. Furthermore, Micro LED displays possess nanosecond (ns) level high-speed response performance, along with the stable properties of inorganic materials, high luminous efficiency, high reliability, high color purity and contrast, and transparency—a combination of characteristics unattainable by liquid crystal displays (LCDs) and organic LEDs (OLEDs).
[0003] While Micro LEDs possess many superior characteristics, they also face challenges in manufacturing technology and material and device physics. For example, the issue of decreasing peak EQE and correspondingly increasing current density as chip size decreases has not been fully resolved, with the operating current density currently around 0.01 A / cm². 2 -0.5A / cm 2 The efficiency of Micro LEDs in this range remains significantly insufficient. In fact, even standard-sized chips used in general lighting and backlighting applications exhibit relatively low efficiency at this current density. This is because standard-sized chips, in order to balance efficiency and cost, operate at a current density of 20 A / cm². 2 -40A / cm 2 Between these two points, the corresponding epitaxial structure design and material growth aim to improve efficiency under high current density, with its peak EQE typically around 1 A / cm². 2 -4A / cm 2 The current density range was considered, but device efficiency at low current densities was not taken into account.
[0004] Traditional visible light LED epitaxial structure designs are based on conventional applications requiring large chips, high current, and high power. However, Micro LED display applications demand small size, low current, and low power, making traditional epitaxial structure designs inadequate for their requirements. Therefore, redesigning the epitaxial structure for small-size, low-current, and low-power Micro LEDs, and improving their electro-optical conversion efficiency, is a significant challenge. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a Micro LED epitaxial structure suitable for small size and low operating current density and its fabrication method, which can improve the quality of the multi-quantum-well light-emitting layer, improve the matching degree of electron-hole concentration in the light-emitting quantum well region, and improve the luminous efficiency of Micro LED chip at low operating current density.
[0006] To address the aforementioned technical problems, the first aspect of this invention provides a Micro LED epitaxial structure, comprising a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, and a P-type semiconductor layer sequentially stacked, wherein... The multi-quantum-well light-emitting layer comprises a first sublayer, a second sublayer, and a third sublayer stacked sequentially. The first sublayer is a periodically alternating layer of In x1 A superlattice structure formed by a GaN layer and a first N-type quantum barrier layer; the first N-type quantum barrier layer is a periodically alternating layer of GaN and Al. y1 The superlattice structure formed by the GaN layer; The second sublayer is a periodically alternating second N-type quantum barrier layer, In x2 A superlattice structure formed by a GaN layer and a first P-type quantum barrier layer; the second N-type quantum barrier layer is a periodically alternating second GaN layer and Al y2 A superlattice structure formed by GaN layers; the first P-type quantum barrier layer is a periodically alternating third GaN layer and In. a1 The superlattice structure formed by the GaN layer; The third sublayer is composed of periodically alternating In layers. x3 A superlattice structure is formed by a GaN layer and a second P-type quantum barrier layer; the second P-type quantum barrier layer is a periodically alternating fourth GaN layer and In. a2 A superlattice structure formed by GaN layers.
[0007] As an improvement to the above scheme, the emission wavelength of the first sub-layer is λ1, the emission wavelength of the second sub-layer is λ2, and the emission wavelength of the third sub-layer is λ3, where λ2 > λ1 and λ2 > λ3. The number of periods in the first sub-layer is 1-6, wherein the number of periods in the first N-type quantum barrier layer is 2-10; The second sublayer has 2-9 periods, wherein the second N-type quantum barrier layer has 2-5 periods and the first P-type quantum barrier layer has 2-5 periods; The third sublayer has 1-6 periods, and the second P-type quantum barrier layer has 2-10 periods.
[0008] As an improvement to the above scheme, x2 > x1, x2 > x3.
[0009] As an improvement to the above scheme, 0.03≤x1≤0.35; 0.05≤x2≤0.39; 0.03≤x3≤0.35.
[0010] As an improvement to the above solution, the In x1 The GaN layer is an undoped InGaN monolayer or InGaN multilayer structure. x1 The GaN layer thickness ranges from 2.1 nm to 4.8 nm. The In x2 The GaN layer is an undoped InGaN monolayer or InGaN multilayer structure. x2 The GaN layer thickness ranges from 2.1 nm to 4.8 nm. The In x3 The GaN layer is an undoped InGaN monolayer or InGaN multilayer structure. x3 The GaN layer thickness ranges from 2.1 nm to 4.8 nm.
[0011] As an improvement to the above solution, the Al y1 The GaN layer is an AlGaN layer that is not intentionally doped, wherein the Al y2 The GaN layer is an AlGaN layer without intentional doping, y2 < y1; The In a1 The GaN layer is a Mg-doped InGaN layer, wherein the In a2 The GaN layer is a Mg-doped InGaN layer, where a2 > a1.
[0012] As an improvement to the above scheme, 0.01≤y1≤0.36; 0<y2≤0.28; The Al y1 The GaN layer is grown to a thickness of 0.2 nm-3 nm; the Al y2 The GaN layer is grown to a thickness of 0.2 nm-3 nm; 0 < a1 ≤ 0.07, 0.01 ≤ a2 ≤ 0.09; The In a1 The GaN layer thickness ranges from 0.2 nm to 3 nm, and the Mg doping concentration is 2.36 × 10⁻⁶. 18 / cm 3 -7.28×10 19 / cm 3 ; The In a2 The GaN layer thickness ranges from 0.2 nm to 3 nm, and the Mg doping concentration is 2.36 × 10⁻⁶.18 / cm 3 -7.28×10 19 / cm 3 .
[0013] As an improvement to the above scheme, the first GaN layer is a Si-doped GaN layer with a Si doping concentration of 1.25 × 10⁻⁶. 17 / cm 3 -9.78×10 17 / cm 3 The thickness of the first GaN layer is 0.2nm-3nm; The second GaN layer is a Si-doped GaN layer with a Si doping concentration of 1.25 × 10⁻⁶. 17 / cm 3 -9.78×10 17 / cm 3 The growth thickness of the second GaN layer is 0.2nm-3nm; The third GaN layer is a GaN layer without intentional doping, and the growth thickness of the third GaN layer is 0.2nm-3nm; The fourth GaN layer is a GaN layer that is not intentionally doped, and the growth thickness of the fourth GaN layer is 0.2nm-3nm.
[0014] A second aspect of the present invention provides a method for fabricating the aforementioned Micro LED epitaxial structure, comprising the following steps: Provide a substrate; A buffer layer is sequentially grown on the substrate; An N-type semiconductor layer is grown on the buffer layer; A low-temperature stress relief layer is grown on the N-type semiconductor layer; A multi-quantum-well light-emitting layer is grown on the low-temperature stress-relieving layer; A P-type semiconductor layer is grown on the multi-quantum-well light-emitting layer; The multi-quantum-well light-emitting layer comprises a first sublayer, a second sublayer, and a third sublayer stacked sequentially. The first sublayer is a periodically alternating layer of In x1 A superlattice structure formed by a GaN layer and a first N-type quantum barrier layer; the first N-type quantum barrier layer is a periodically alternating layer of GaN and Al. y1 The superlattice structure formed by the GaN layer; The second sublayer is a periodically alternating second N-type quantum barrier layer, In x2 A superlattice structure formed by a GaN layer and a first P-type quantum barrier layer; the second N-type quantum barrier layer is a periodically alternating second GaN layer and Al y2A superlattice structure formed by GaN layers; the first P-type quantum barrier layer is a periodically alternating third GaN layer and In. a1 The superlattice structure formed by the GaN layer; The third sublayer is composed of periodically alternating In layers. x3 A superlattice structure is formed by a GaN layer and a second P-type quantum barrier layer; the second P-type quantum barrier layer is a periodically alternating fourth GaN layer and In. a2 A superlattice structure formed by GaN layers.
[0015] As an improvement to the above solution, the In x1 The growth temperature of the GaN layer is T1, and the In x2 The growth temperature of the GaN layer is T2, and the In x3 The growth temperature of the GaN layer is T3, T1>T2, T3>T2.
[0016] Implementing this invention has the following beneficial effects: In this invention, no electron blocking layer is provided between the multi-quantum-well light-emitting layer and the P-type semiconductor layer, and the multi-quantum-well light-emitting layer includes a first sub-layer, a second sub-layer, and a third sub-layer stacked sequentially. The second sub-layer is the light-emitting unit of the MicroLED at low operating current density. The structure of the multi-quantum-well light-emitting layer is designed and optimized. Specifically, by controlling the material type and composition of the first N-type quantum barrier layer, the second N-type quantum barrier layer, the first P-type quantum barrier layer, and the second P-type quantum barrier layer in the sub-layer, the distribution and concentration of electrons and holes in the second sub-layer can be controlled, thereby improving the matching degree of electron and hole concentration in the light-emitting quantum well region and improving the brightness and luminous efficacy of the MicroLED at low operating current density. Attached Figure Description
[0017] Figure 1 : A schematic diagram of a Micro LED epitaxial structure according to the present invention; Figure 2 : A schematic diagram of the structure of the multi-quantum-well light-emitting layer in this invention; Figure 3 : A schematic diagram of the structure of the first N-type quantum barrier layer in the multi-quantum-well light-emitting layer of this invention; Figure 4 : A schematic diagram of the structure of the second N-type quantum barrier layer in the multi-quantum-well light-emitting layer of this invention; Figure 5 : A schematic diagram of the structure of the first P-type quantum barrier layer in the multi-quantum-well light-emitting layer of this invention; Figure 6 : A schematic diagram of the structure of the second P-type quantum barrier layer in the multi-quantum well light-emitting layer of this invention.
[0018] Figure label: 100 - Substrate; 200 - Buffer layer; 300 - N-type semiconductor layer; 400 - Low-temperature stress relief layer; 500 - Multi-quantum well light-emitting layer; 510 - First sublayer; 511 - In x1 GaN layer; 512-first N-type quantum barrier layer; 5121-first GaN layer; 5122-Al y1 GaN layer; 520 - second sublayer; 521 - second N-type quantum barrier layer; 5211 - second GaN layer; 5212 - Al y2 GaN layer; 522-In x2 GaN layer; 523-first p-type quantum barrier layer; 5231-third GaN layer; 5232-In a1 GaN layer; 530-Third sublayer; 531-In x3 GaN layer; 532-Second p-type quantum barrier layer; 5321-Fourth GaN layer; 5322-In a2 GaN layer; 600-P type semiconductor layer. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described in further detail below.
[0020] In the description of this application, it is necessary to understand that the orientation or positional relationship indicated by terms such as "upper", "lower", "top", "bottom", "inner", and "outer" are based on the orientation or positional relationship shown in the accompanying drawings. They are intended only to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the components referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.
[0021] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.
[0022] The dominant factors in the light-emitting mechanism of LED devices differ under different current densities, and the corresponding epitaxial layer structure should also vary. For example, in the operating range of Micro LEDs at 0.01 A / cm²... 2 -0.5A / cm 2At low current densities, the carrier concentration in the quantum well is relatively low, resulting in a smaller Auger recombination rate and a corresponding reduction in the quantum well recombination volume. This reduces the number of quantum wells and defects, improving the EQE (equivalent quantum efficiency) of the device at low current densities. Simultaneously, at low current densities, electron leakage has not yet occurred or is very low. The electron blocking layer structure not only fails to block electrons but also blocks hole injection, reducing the device's quantum efficiency. Therefore, in-depth mechanistic research, design, and growth of LED epitaxial layer structures under low current density operating conditions are essential key technologies for developing high-efficiency Micro LED devices driven by low operating current densities.
[0023] To address the above problems, the first aspect of this invention provides a Micro LED epitaxial structure, please refer to [link to relevant documentation]. Figure 1 The material includes a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500 and a P-type semiconductor layer 600 stacked sequentially, wherein the multi-quantum well light-emitting layer 500 includes a first sub-layer 510, a second sub-layer 520 and a third sub-layer 530 stacked sequentially. Please see Figures 2-6 The first sublayer 510 is a periodically alternating layer of In. x1 The superlattice structure formed by GaN layer 511 and first N-type quantum barrier layer 512; the first N-type quantum barrier layer 512 is a periodically alternating first GaN layer 5121 and Al y1 The superlattice structure formed by the GaN layer 5122; The second sublayer 520 is a periodically alternating second N-type quantum barrier layer 521, In x2 The superlattice structure formed by GaN layer 522 and first P-type quantum barrier layer 523; the second N-type quantum barrier layer 521 is a periodically alternating second GaN layer 5211 and Al y2 The superlattice structure formed by GaN layer 5212; the first P-type quantum barrier layer 523 is a periodically alternating third GaN layer 5231 and In a1 The superlattice structure formed by the GaN layer 5232; The third sublayer 530 is composed of periodically alternating In layers. x3 The superlattice structure formed by GaN layer 531 and second P-type quantum barrier layer 532; the second P-type quantum barrier layer 532 is a periodically alternating fourth GaN layer 5321 and In a2 The superlattice structure formed by the GaN layer 5322.
[0024] In this invention, no electron blocking layer is provided between the multi-quantum-well light-emitting layer 500 and the P-type semiconductor layer 600, and the multi-quantum-well light-emitting layer 500 includes a first sub-layer 510, a second sub-layer 520 and a third sub-layer 530 stacked sequentially. The second sub-layer 520 is the light-emitting unit of the Micro LED at low operating current density. The structure of the multi-quantum-well light-emitting layer 500 is designed and optimized. Specifically, by controlling the material type and composition of the first N-type quantum barrier layer 512, the second N-type quantum barrier layer 521, the first P-type quantum barrier layer 523 and the second P-type quantum barrier layer 532 in the sub-layer, the distribution and concentration of electrons and holes in the second sub-layer 520 can be controlled, thereby improving the matching degree of electron and hole concentration in the light-emitting quantum well region and improving the brightness and luminous efficacy of the Micro LED at low operating current density.
[0025] Optionally, the first sublayer 510 has 1-6 cycles, wherein the first N-type quantum barrier layer 512 has 2-10 cycles; the second sublayer 520 has 2-9 cycles, wherein the second N-type quantum barrier layer 521 has 2-5 cycles and the first P-type quantum barrier layer 523 has 2-5 cycles; and the third sublayer 530 has 1-6 cycles, wherein the second P-type quantum barrier layer 532 has 2-10 cycles.
[0026] Preferably, the first sub-layer 510 emits light at a wavelength of λ1, the second sub-layer 520 emits light at a wavelength of λ2, and the third sub-layer 530 emits light at a wavelength of λ3, where λ2 > λ1 and λ2 > λ3.
[0027] Furthermore, x2 > x1 and x2 > x3, which makes the multi-quantum well light-emitting layer 500 form an InGaN / barrier superlattice structure with increasing and then decreasing In composition. This structure and process design can effectively reduce the lattice mismatch stress between the InGaN material and the barrier material in the second sublayer 520, improve the quality of the light-emitting quantum well region under low operating current density, and thus improve the radiative recombination efficiency of the multi-quantum well light-emitting region. Furthermore, the higher In content and longer emission wavelength in the second sublayer 520 allow for high-temperature growth of InGaN material, resulting in higher atomic mobility and a greater tendency towards two-dimensional material growth. This significantly reduces defects in the InGaN material, making it easier to obtain high-quality InGaN material. In contrast, the lower In content in the first sublayer 510 and the third sublayer 530 reduces the lattice mismatch stress between InGaN and GaN materials, thereby reducing defects caused by large mismatch stress. This further improves the quality of the multi-quantum-well emitting layer 500 and reduces its defects, which is beneficial for improving the radiative recombination efficiency of the active region. Consequently, it enhances the luminous efficacy and yield of Micro LEDs at low operating current densities.
[0028] In some specific and preferred embodiments, 0.03≤x1≤0.35, and exemplary x1 can be 0.03, 0.05, 0.07, 0.10, 0.13, 0.15, 0.17, 0.20, 0.23, 0.25, 0.27, 0.30, 0.33, 0.35, but is not limited thereto.
[0029] In some specific and preferred embodiments, 0.05≤x2≤0.39, and exemplary x2 can be 0.05, 0.07, 0.10, 0.13, 0.15, 0.17, 0.20, 0.23, 0.25, 0.27, 0.30, 0.33, 0.35, 0.37, 0.39, but is not limited thereto.
[0030] In some specific and preferred embodiments, 0.03≤x3≤0.35, and exemplary x3 can be 0.03, 0.05, 0.07, 0.10, 0.13, 0.15, 0.17, 0.20, 0.23, 0.25, 0.27, 0.30, 0.33, 0.35, but is not limited thereto.
[0031] Furthermore, the In x1 GaN layer 511 is an undoped InGaN monolayer or InGaN multilayer structure. x1 The GaN layer 511 has a growth thickness of 2.1nm-4.8nm, and can be 2.1nm, 2.5nm, 2.8nm, 3.0nm, 3.3nm, 3.5nm, 3.8nm, 4.0nm, 4.3nm, 4.5nm, or 4.8nm, but is not limited to these.
[0032] The In x2 GaN layer 522 is an undoped InGaN monolayer or InGaN multilayer structure. x2 The GaN layer 522 has a growth thickness of 2.1nm-4.8nm, and can be 2.1nm, 2.5nm, 2.8nm, 3.0nm, 3.3nm, 3.5nm, 3.8nm, 4.0nm, 4.3nm, 4.5nm, or 4.8nm, but is not limited to these.
[0033] The In x3 GaN layer 531 is an undoped InGaN monolayer or InGaN multilayer structure. x3 The GaN layer 531 has a growth thickness of 2.1nm-4.8nm, and can be 2.1nm, 2.5nm, 2.8nm, 3.0nm, 3.3nm, 3.5nm, 3.8nm, 4.0nm, 4.3nm, 4.5nm, or 4.8nm, but is not limited to these.
[0034] Preferably, the first GaN layer 5121 is a Si-doped GaN layer, and the second GaN layer 5211 is a Si-doped GaN layer. The Si element is doped in the first GaN layer 5121 and the second GaN layer 5211, which can provide some electrons to the second sublayer 520.
[0035] In some specific and preferred embodiments, the Si doping concentration in the first GaN layer 5121 is 1.25 × 10⁻⁶. 17 / cm 3 -9.78×10 17 / cm 3 For example, it can be 1.25 × 10 17 / cm 3 1.5×10 17 / cm 3 2×10 17 / cm 3 3×10 17 / cm 3 4×10 17 / cm 3 5×10 17 / cm 3 6×10 17 / cm 3 7×10 17 / cm 3 8×10 17 / cm 3 9×10 17 / cm 3 9.5×10 17 / cm 3 9.78×10 17 / cm 3 However, it is not limited to this.
[0036] In some specific and preferred embodiments, the Si doping concentration in the second GaN layer 5211 is 1.25 × 10⁻⁶. 17 / cm 3 -9.78×10 17 / cm 3 For example, it can be 1.25 × 10 17 / cm 3 1.5×10 17 / cm 3 2×10 17 / cm 3 3×10 17 / cm 3 4×10 17 / cm3 5×10 17 / cm 3 6×10 17 / cm 3 7×10 17 / cm 3 8×10 17 / cm 3 9×10 17 / cm 3 9.5×10 17 / cm 3 9.78×10 17 / cm 3 However, it is not limited to this.
[0037] Further, the growth thickness of the first GaN layer 5121 is 0.2nm-3nm, and the growth thickness of the second GaN layer 5211 is 0.2nm-3nm. For example, the growth thickness of the first GaN layer 5121 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited thereto; the growth thickness of the second GaN layer 5211 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited thereto.
[0038] Preferably, the Al y1 GaN layer 5122 is an AlGaN layer that is not intentionally doped, wherein the Al y2 The GaN layer 5212 is an undoped AlGaN layer. The Al content in the first N-type quantum barrier layer 512 is higher than that in the second N-type quantum barrier layer 521, i.e., y2 < y1. This makes the first N-type quantum barrier layer 512 a GaN / AlGaN superlattice structure layer with high Al content, and the second N-type quantum barrier layer 521 a GaN / AlGaN superlattice structure layer with low Al content. The barrier layer formed by the high bandgap AlGaN and GaN materials can effectively enhance the blocking effect of the quantum barrier layer material on the electron migration of the N-type semiconductor layer 300, reduce the electron concentration injected into the active region from the N-type semiconductor layer 300, thereby increasing the hole injection depth of the P-type semiconductor layer 600. This improves the matching degree of electron and hole concentration in the region of the multi-quantum-well light-emitting layer 500, thereby improving the brightness and luminous efficacy of the Micro LED at low operating current density.
[0039] In some specific and preferred embodiments, 0.01≤y1≤0.36, and y1 can be 0.01, 0.03, 0.05, 0.07, 0.10, 0.13, 0.15, 0.17, 0.20, 0.23, 0.25, 0.27, 0.30, 0.33, or 0.36, but is not limited thereto.
[0040] In some specific and preferred embodiments, 0 < y2 ≤ 0.28, and exemplary values of y2 can be 0.01, 0.03, 0.05, 0.07, 0.10, 0.13, 0.15, 0.17, 0.20, 0.23, 0.25, 0.28, but are not limited thereto.
[0041] Furthermore, the Al y1 The GaN layer 5122 has a growth thickness of 0.2nm-3nm; the Al y2 The GaN layer 5212 has a growth thickness of 0.2nm-3nm. For example, the Al... y1 The growth thickness of the GaN layer 5122 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited to these; the Al y2 The growth thickness of the GaN layer 5212 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited to these.
[0042] Preferably, the third GaN layer 5231 and the fourth GaN layer 5321 are both undoped GaN layers. The growth thickness of the third GaN layer 5231 is 0.2nm-3nm; the growth thickness of the fourth GaN layer 5321 is 0.2nm-3nm. Exemplarily, the growth thickness of the third GaN layer 5231 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited thereto; the growth thickness of the fourth GaN layer 5321 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited thereto.
[0043] Preferably, the In a1 GaN layer 5232 is a Mg-doped InGaN layer, wherein In a2GaN layer 5322 is a Mg-doped InGaN layer, which can provide some holes to the second sublayer 520. Combining the Si-doped first GaN layer 5121 and the Si-doped second GaN layer 5211, the distribution and concentration of electrons and holes in the second sublayer 520 can be further controlled by adjusting the doping type and concentration in the materials of the first N-type quantum barrier layer 512, the second N-type quantum barrier layer 521, the first P-type quantum barrier layer 523, and the second P-type quantum barrier layer 532. This better improves the matching degree of electron and hole concentration in the second sublayer 520, and further improves the brightness and luminous efficacy of Micro LED at low operating current densities.
[0044] In some specific and preferred embodiments, the In a1 The Mg doping concentration in the GaN layer 5232 is 2.36 × 10⁻⁶. 18 / cm 3 -7.28×10 19 / cm 3 An exemplary doping concentration could be 2.36 × 10⁻⁶. 18 / cm 3 4.36×10 18 / cm 3 6.36×10 18 / cm 3 8.36×10 18 / cm 3 1.0×10 19 / cm 3 1.36×10 19 / cm 3 3.36×10 19 / cm 3 5.36×10 19 / cm 3 7.28×10 19 / cm 3 However, it is not limited to this.
[0045] In some specific and preferred embodiments, the In a2 The Mg doping concentration in the GaN layer 5322 is 2.36 × 10⁻⁶. 18 / cm 3 -7.28×10 19 / cm 3 An exemplary doping concentration could be 2.36 × 10⁻⁶. 18 / cm 3 4.36×10 18 / cm 3 6.36×10 18 / cm 3 8.36×10 18 / cm 3 1.0×10 19 / cm 3 1.36×10 19 / cm 3 3.36×10 19 / cm 3 5.36×10 19 / cm 3 7.28×10 19 / cm 3 However, it is not limited to this.
[0046] Furthermore, the proportion of In component in the first P-type quantum barrier layer 523 is lower than that in the second P-type quantum barrier layer 532, i.e., a2 > a1. This makes the first P-type quantum barrier layer 523 a GaN / InGaN superlattice structure layer with low In component, and the second N-type quantum barrier layer 521 a GaN / InGaN superlattice structure layer with high In component. The barrier layer formed by the low bandgap InGaN and GaN materials can effectively reduce the blocking effect of the quantum barrier layer material on hole injection in the P-type semiconductor layer 600, and increase the hole concentration injected from the P-type semiconductor layer 600 into the multi-quantum well light-emitting layer 500. In addition, the InGaN material is doped with Mg, which can provide some holes, thereby significantly improving the matching degree of electron-hole concentration in the region of the multi-quantum well light-emitting layer 500, allowing the quantum wells near the N-type semiconductor layer 300 to also participate in light emission, thereby further improving the brightness and luminous efficacy of Micro LED at low operating current density.
[0047] In some specific and preferred embodiments, 0 < a1 ≤ 0.07, and exemplary a1 can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, or 0.07, but is not limited thereto.
[0048] In some specific and preferred embodiments, 0.01≤a2≤0.09, and exemplary a2 can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, or 0.09, but is not limited thereto.
[0049] Furthermore, the In a1 The GaN layer 5232 has a growth thickness of 0.2nm-3nm, and the In... a2 The GaN layer 5322 has a growth thickness of 0.2nm-3nm. For example, the In... a1 The growth thickness of the GaN layer 5232 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited to these; the In a2The growth thickness of the GaN layer 5322 can be 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, or 3nm, but is not limited to these.
[0050] Accordingly, a second aspect of the present invention provides a method for fabricating the aforementioned Micro LED epitaxial structure, comprising the following steps: (1) Provide a substrate 100; (2) A buffer layer 200 is sequentially grown on the substrate 100; (3) An N-type semiconductor layer 300 is grown on the buffer layer 200; (4) A low-temperature stress relief layer 400 is grown on the N-type semiconductor layer 300; (5) A multi-quantum well light-emitting layer 500 is grown on the low-temperature stress relief layer 400; (6) A P-type semiconductor layer 600 is grown on the multi-quantum-well light-emitting layer 500; The multi-quantum-well light-emitting layer 500 includes a first sub-layer 510, a second sub-layer 520 and a third sub-layer 530 stacked sequentially. The first sublayer 510 is a periodically alternating layer of In. x1 The superlattice structure formed by GaN layer 511 and first N-type quantum barrier layer 512; the first N-type quantum barrier layer 512 is a periodically alternating first GaN layer 5121 and Al y1 The superlattice structure formed by the GaN layer 5122; The second sublayer 520 is a periodically alternating second N-type quantum barrier layer 521, In x2 The superlattice structure formed by GaN layer 522 and first P-type quantum barrier layer 523; the second N-type quantum barrier layer 521 is a periodically alternating second GaN layer 5211 and Al y2 The superlattice structure formed by GaN layer 5212; the first P-type quantum barrier layer 523 is a periodically alternating third GaN layer 5231 and In a1 The superlattice structure formed by the GaN layer 5232; The third sublayer 530 is composed of periodically alternating In layers. x3 The superlattice structure formed by GaN layer 531 and second P-type quantum barrier layer 532; the second P-type quantum barrier layer 532 is a periodically alternating fourth GaN layer 5321 and In a2 The superlattice structure formed by the GaN layer 5322.
[0051] Preferably, the In x1 The growth temperature of the GaN layer 511 is T1, and the In x2The growth temperature of the GaN layer 522 is T2, and the In x3 The growth temperature of GaN layer 531 is T3, where T1 > T2 and T3 > T2. The second sublayer 520 has a higher In composition and a longer emission wavelength. Adjusting the growth temperature T1 > T2 and T3 > T2 can further improve the quality of the multi-quantum-well emitting layer 500, reduce the generation of defects, and help improve the radiative recombination efficiency of the active region, thereby improving the luminous efficacy and yield of Micro LED at low operating current densities.
[0052] Furthermore, the In x1 The growth temperature T1 of the GaN layer 511 is 620℃-923℃, and the growth pressure is 30 torr-360 torr; the In x2 The growth temperature T2 of the GaN layer 522 is 580℃-923℃, and the growth pressure is 30 torr-360 torr; the In x3 The growth temperature T3 of GaN layer 531 is 620℃-923℃, and the growth pressure is 30 torr-360 torr.
[0053] In some embodiments, in the first sub-layer 510, the growth temperature of the first GaN layer 5121 is 800℃-950℃, and the growth pressure is 30 torr-360 torr; the Al y1 The growth temperature of the GaN layer 5122 is 800℃-950℃, and the pressure is 30 torr-360 torr.
[0054] In some embodiments, in the second sublayer 520, the growth temperature of the second GaN layer 5211 is 800℃-950℃, and the growth pressure is 30 torr-360 torr; the Al y2 The growth temperature of the GaN layer 5212 is 800℃-950℃, and the growth pressure is 30 torr-360 torr; the growth temperature of the third GaN layer 5231 is 800℃-950℃, and the growth pressure is 30 torr-360 torr; the In... a1 The growth temperature of the GaN layer 5232 is 800℃-950℃, and the growth pressure is 30 torr-360 torr.
[0055] In some embodiments, in the third sub-layer 530, the growth temperature of the fourth GaN layer 5321 is 800℃-950℃, and the growth pressure is 30 torr-360 torr; the In a2 The growth temperature of the GaN layer 5322 is 800℃-950℃, and the growth pressure is 30 torr-360 torr.
[0056] It is understood that the substrate 100 can be a sapphire substrate, a silicon carbide substrate, or a silicon substrate; the buffer layer 200, the N-type semiconductor layer 300, the low-temperature stress relief layer 400, and the P-type semiconductor layer 600 are all grown using existing processes and materials, and will not be further described in this invention.
[0057] The present invention will be further described below with reference to specific embodiments: Example 1 This embodiment provides a Micro LED epitaxial structure, including a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, and a P-type semiconductor layer stacked sequentially. The multi-quantum-well light-emitting layer includes a first sub-layer, a second sub-layer, and a third sub-layer stacked sequentially. The emission wavelength of the first sub-layer is λ1, the emission wavelength of the second sub-layer is λ2, and the emission wavelength of the third sub-layer is λ3, where λ2 > λ1 and λ2 > λ3.
[0058] The first sublayer consists of periodically alternating In layers. x1 The superlattice structure formed by the GaN layer and the first N-type quantum barrier layer has a period number of 3; the first N-type quantum barrier layer is a periodically alternating layer of the first GaN layer and Al. y1 The superlattice structure formed by the GaN layer has a period number of 6; Among them, In x1 In the GaN layer, x1=0.23, In x1 The GaN layer has a growth thickness of 3.1 nm; the first GaN layer is a Si-doped GaN layer with a Si doping concentration of 4.5 × 10⁻⁶. 17 / cm 3 The growth thickness is 1.6 nm; Al y1 The GaN layer is an AlGaN layer without intentional doping, y1=0.17, and has a growth thickness of 1.6nm; The second sublayer is a periodically alternating second N-type quantum barrier layer, In. x2 The superlattice structure formed by the GaN layer and the first P-type quantum barrier layer has a period number of 5; the second N-type quantum barrier layer is a periodically alternating second GaN layer and Al y2 The superlattice structure formed by the GaN layer has a period number of 3; the first p-type quantum barrier layer is a periodically alternating third GaN layer and In. a1 The superlattice structure formed by the GaN layer has a period number of 3; Among them, In x2 In the GaN layer, x2=0.23, In x2 The GaN layer has a thickness of 3.1 nm; the second GaN layer is a Si-doped GaN layer with a Si doping concentration of 4.5 × 10⁻⁶. 17 / cm 3The growth thickness is 1.6 nm; Al y2 The GaN layer is an undoped AlGaN layer with y² = 0.17 and a growth thickness of 1.6 nm; the third GaN layer is also an undoped GaN layer with a growth thickness of 1.6 nm; In a1 The GaN layer is a Mg-doped InGaN layer with a1=0.05 and a Mg doping concentration of 1.36×10⁻⁵. 19 / cm 3 The growth thickness is 1.6 nm; The third sublayer consists of periodically alternating In layers. x3 The superlattice structure formed by the GaN layer and the second P-type quantum barrier layer has a period number of 3; the second P-type quantum barrier layer is a periodically alternating fourth GaN layer and In. a2 The superlattice structure formed by the GaN layer; Among them, In x3 In the GaN layer, x3 = 0.23, In x3 The GaN layer has a thickness of 3.1 nm; the third GaN layer is an undoped GaN layer with a growth thickness of 1.6 nm; In a2 The GaN layer is a Mg-doped InGaN layer with a² = 0.05 and a Mg doping concentration of 1.36 × 10⁻⁵. 19 / cm 3 The growth thickness is 1.6 nm.
[0059] This embodiment provides a method for fabricating a Micro LED epitaxial structure, including the following steps: (1) Provide a substrate; (2) Buffer layers are grown sequentially on the substrate; (3) An N-type semiconductor layer is grown on the buffer layer; (4) A low-temperature stress relief layer is grown on the N-type semiconductor layer; (5) A multi-quantum well light-emitting layer is grown on the low-temperature stress relief layer; (6) A P-type semiconductor layer is grown on the multi-quantum-well light-emitting layer; Among them, In x1 The growth temperature T1 of the GaN layer is 750℃, and the growth pressure is 200 torr; the growth temperature of the first GaN layer is 875℃, and the growth pressure is 200 torr; Al y1 The GaN layer is grown at a temperature of 880℃-950℃ and a pressure of 200 torr.
[0060] In x2 The growth temperature T2 of the GaN layer was 750℃, and the growth pressure was 200 torr; the growth temperature of the second GaN layer was 875℃, and the growth pressure was 200 torr; Aly2 The GaN layer was grown at 880℃ under a growth pressure of 200 torr; the third GaN layer was grown at 875℃ under a growth pressure of 200 torr; In a1 The GaN layer was grown at a temperature of 875℃ and a growth pressure of 200 torr.
[0061] In x3 The growth temperature T3 of the GaN layer was 750℃, and the growth pressure was 200 torr; the growth temperature of the fourth GaN layer was 875℃, and the growth pressure was 200 torr; In a2 The GaN layer was grown at a temperature of 875℃ and a growth pressure of 200 torr.
[0062] Example 2 This embodiment provides a Micro LED epitaxial structure, which is basically the same as that in Embodiment 1, except that: In x1 In the GaN layer, x1=0.18, In x3 x3 = 0.18 in the GaN layer.
[0063] The preparation method described in Example 1 was used, with the following differences: In x1 The growth temperature T1 of the GaN layer is 770℃, and the In... x3 The growth temperature T3 of the GaN layer is 770℃.
[0064] Example 3 This embodiment provides a Micro LED epitaxial structure, which is basically the same as that in Embodiment 2, except that: y2=0.14.
[0065] The preparation method is the same as in Example 2.
[0066] Example 4 This embodiment provides a Micro LED epitaxial structure, which is basically the same as that in Embodiment 3, except that: a1=0.03.
[0067] The preparation method is the same as in Example 2.
[0068] Comparative Example 1 This comparative example provides a Micro LED epitaxial structure, which is basically the same as that in Example 1, except that: The multi-quantum-well light-emitting layer comprises a first sublayer and a second sublayer stacked sequentially.
[0069] Comparative Example 2 This comparative example provides a Micro LED epitaxial structure, which is basically the same as that in Example 1, except that: The multi-quantum-well light-emitting layer consists of a first sublayer and a third sublayer stacked sequentially.
[0070] Comparative Example 3 This comparative example provides a Micro LED epitaxial structure, which is basically the same as that in Example 1, except that: The multi-quantum-well light-emitting layer consists of a second sublayer and a third sublayer stacked sequentially.
[0071] Using the Micro LED epitaxial structures obtained in Examples 1-4 and Comparative Examples 1-3, 20μm × 20μm Micro LED chips were fabricated under the same chip processing conditions. 300 LED chips were then extracted from each chip and processed at 0.1 A / cm². 2 The chip's luminous efficacy was improved under current testing, with the improvement calculated based on Comparative Example 1.
[0072] The specific test results are shown in Table 1.
[0073] Table 1. Test results of the examples and comparative examples
[0074] The results above show that by not setting an electron blocking layer between the multi-quantum-well light-emitting layer and the P-type semiconductor layer, and by optimizing the structure of each layer, the matching degree of electron-hole concentration in the light-emitting quantum well region can be improved, thereby increasing the brightness and luminous efficacy of Micro LED at low operating current density.
[0075] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.
Claims
1. A Micro LED epitaxial structure, characterized in that, It includes a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, and a P-type semiconductor layer, which are stacked sequentially. The multi-quantum-well light-emitting layer comprises a first sublayer, a second sublayer, and a third sublayer stacked sequentially. The first sublayer is a periodically alternating layer of In x1 A superlattice structure formed by a GaN layer and a first N-type quantum barrier layer; the first N-type quantum barrier layer is a periodically alternating layer of GaN and Al. y1 The superlattice structure formed by the GaN layer; The second sublayer is a periodically alternating second N-type quantum barrier layer, In x2 A superlattice structure formed by a GaN layer and a first P-type quantum barrier layer; the second N-type quantum barrier layer is a periodically alternating second GaN layer and Al y2 A superlattice structure formed by GaN layers; the first P-type quantum barrier layer is a periodically alternating third GaN layer and In. a1 The superlattice structure formed by the GaN layer; The third sublayer is composed of periodically alternating In layers. x3 A superlattice structure is formed by a GaN layer and a second P-type quantum barrier layer; the second P-type quantum barrier layer is a periodically alternating fourth GaN layer and In. a2 A superlattice structure formed by GaN layers.
2. The Micro LED epitaxial structure as described in claim 1, characterized in that, The emission wavelength of the first sub-layer is λ1, the emission wavelength of the second sub-layer is λ2, and the emission wavelength of the third sub-layer is λ3, where λ2 > λ1 and λ2 > λ3. The number of periods in the first sub-layer is 1-6, wherein the number of periods in the first N-type quantum barrier layer is 2-10; The second sublayer has 2-9 periods, wherein the second N-type quantum barrier layer has 2-5 periods and the first P-type quantum barrier layer has 2-5 periods; The third sublayer has 1-6 periods, and the second P-type quantum barrier layer has 2-10 periods.
3. The Micro LED epitaxial structure as described in claim 1, characterized in that, x2 > x1, x2 > x3.
4. The Micro LED epitaxial structure as described in claim 3, characterized in that, 0.03≤x1≤0.35; 0.05≤x2≤0.39; 0.03≤x3≤0.
35.
5. The Micro LED epitaxial structure as described in claim 1, characterized in that, The In x1 The GaN layer is an undoped InGaN monolayer or InGaN multilayer structure. x1 The GaN layer thickness ranges from 2.1 nm to 4.8 nm. The In x2 The GaN layer is an undoped InGaN monolayer or InGaN multilayer structure. x2 The GaN layer thickness ranges from 2.1 nm to 4.8 nm. The In x3 The GaN layer is an undoped InGaN monolayer or InGaN multilayer structure. x3 The GaN layer thickness ranges from 2.1 nm to 4.8 nm.
6. The Micro LED epitaxial structure as described in claim 1, characterized in that, The Al y1 The GaN layer is an AlGaN layer that is not intentionally doped, wherein the Al y2 The GaN layer is an AlGaN layer without intentional doping, y2 < y1; The In a1 The GaN layer is a Mg-doped InGaN layer, wherein the In a2 The GaN layer is a Mg-doped InGaN layer, where a2 > a1.
7. The Micro LED epitaxial structure as described in claim 6, characterized in that, 0.01≤y1≤0.36; 0<y2≤0.28; The Al y1 The GaN layer is grown to a thickness of 0.2 nm-3 nm; the Al y2 The GaN layer is grown to a thickness of 0.2 nm-3 nm; 0 < a1 ≤ 0.07, 0.01 ≤ a2 ≤ 0.09; The In a1 The GaN layer thickness ranges from 0.2 nm to 3 nm, and the Mg doping concentration is 2.36 × 10⁻⁶. 18 / cm 3 -7.28×10 19 / cm 3 ; The In a2 The GaN layer thickness ranges from 0.2 nm to 3 nm, and the Mg doping concentration is 2.36 × 10⁻⁶. 18 / cm 3 -7.28×10 19 / cm 3 .
8. The Micro LED epitaxial structure as described in claim 1, characterized in that, The first GaN layer is a Si-doped GaN layer with a Si doping concentration of 1.25 × 10⁻⁶. 17 / cm 3 -9.78×10 17 / cm 3 The thickness of the first GaN layer is 0.2nm-3nm; The second GaN layer is a Si-doped GaN layer with a Si doping concentration of 1.25 × 10⁻⁶. 17 / cm 3 -9.78×10 17 / cm 3 The growth thickness of the second GaN layer is 0.2nm-3nm; The third GaN layer is a GaN layer without intentional doping, and the growth thickness of the third GaN layer is 0.2nm-3nm; The fourth GaN layer is a GaN layer that is not intentionally doped, and the growth thickness of the fourth GaN layer is 0.2nm-3nm.
9. A method for fabricating a Micro LED epitaxial structure as described in any one of claims 1-8, characterized in that, Includes the following steps: Provide a substrate; A buffer layer is sequentially grown on the substrate; An N-type semiconductor layer is grown on the buffer layer; A low-temperature stress relief layer is grown on the N-type semiconductor layer; A multi-quantum-well light-emitting layer is grown on the low-temperature stress-relieving layer; A P-type semiconductor layer is grown on the multi-quantum-well light-emitting layer; The multi-quantum-well light-emitting layer comprises a first sublayer, a second sublayer, and a third sublayer stacked sequentially. The first sublayer is a periodically alternating layer of In x1 A superlattice structure formed by a GaN layer and a first N-type quantum barrier layer; the first N-type quantum barrier layer is a periodically alternating layer of GaN and Al. y1 The superlattice structure formed by the GaN layer; The second sublayer is a periodically alternating second N-type quantum barrier layer, In x2 A superlattice structure formed by a GaN layer and a first P-type quantum barrier layer; the second N-type quantum barrier layer is a periodically alternating second GaN layer and Al y2 A superlattice structure formed by GaN layers; the first P-type quantum barrier layer is a periodically alternating third GaN layer and In. a1 The superlattice structure formed by the GaN layer; The third sublayer is composed of periodically alternating In layers. x3 A superlattice structure is formed by a GaN layer and a second P-type quantum barrier layer; the second P-type quantum barrier layer is a periodically alternating fourth GaN layer and In. a2 A superlattice structure formed by GaN layers.
10. The method for fabricating a Micro LED epitaxial structure as described in claim 9, characterized in that, The In x1 The growth temperature of the GaN layer is T1, and the In x2 The growth temperature of the GaN layer is T2, and the In x3 The growth temperature of the GaN layer is T3, T1>T2, T3>T2.