Blue-green dual-wavelength epitaxial growth method and structure

Abstract

The invention belongs to the technical field of LED epitaxial structures, and particularly relates to a blue-green dual-wavelength epitaxial growth method and structure, and the growth method comprises the steps: patterning a substrate, carrying out the first filling, then growing green light MQW and NGaN, carrying out the second patterning, forming a multi-layer gradient structure, carrying out the ALN coating, carrying out the second epitaxial filling, then growing blue light MQW, and carrying out the P Side. According to the invention, the smooth transition of the refractive index is realized by carrying out secondary patterning and a multi-layer gradual change structure after green light MQW; through the design of the stress buffer layer, the difference of thermal expansion coefficients of two times of epitaxy is matched, and the blue light MQW is grown, so that the problem of poor material quality after the first time of green light MQW growth can be effectively improved; due to the double-layer graphical design, the light extraction efficiency of the blue light is improved, and the luminance of the green light MQW is excited; the second layer of graphical design is carried out on the NGaN, and due to the fact that the pattern is etched on the GaN material, the designed pattern is ultra-large in height and width and does not affect the growth quality of the subsequent material, and the propagation direction of light can be more effectively changed through a large pyramid structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of LED epitaxial structures, and particularly relates to a method and structure for epitaxial growth of blue-green dual wavelengths. Background Art

[0002] Traditional patterned sapphire substrate (PSS) forms periodic patterns (such as raised structures like cones and pyramids) through one-time etching. Although it can reduce the dislocation density of the epitaxial layer, it has the following defects: Incomplete filling: After the first epitaxial growth, holes or uneven surfaces may remain in the gaps between the patterns, resulting in defects in the subsequent epitaxial layer (such as cracks and dislocation extension).

[0003] Bottleneck in light extraction efficiency: The optimization of a single pattern structure for light scattering and guided mode suppression is limited, and it is difficult to break through the light efficiency ceiling.

[0004] For the blue-green dual-wave structure, the improvement of the brightness of green light has always been a bottleneck. Summary of the Invention

[0005] In view of the problems in the background art, the present invention has developed a method and structure for epitaxial growth of blue-green dual wavelengths, aiming to: through secondary patterning + multi-layer gradient structure after the green MQW of the blue-green dual-wave structure, achieve a smooth transition of the refractive index, reduce interface reflection, and improve the light extraction rate; and then through the design of a stress buffer layer (such as AlN / GaN superlattice), match the difference in thermal expansion coefficients of the two epitaxial growths, grow the blue MQW, and avoid cracking of the epitaxial layer.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for epitaxial growth of blue-green dual wavelengths, comprising the following steps: (1) First patterning and filling: Provide a PSS substrate with a first patterned structure, grow a buffer layer and a filling layer on the PSS substrate, then grow a green MQW and a filling layer, and finally grow an NGaN layer; (2) Second patterning: Perform second patterning on the above NGaN layer to form ultra-large micron-scale patterns; (3) Second epitaxial growth: Deposit a multi-layer gradient structure on the second patterned structure first, then grow a stress buffer layer and a filling layer, and finally grow a blue MQW and an electron blocking layer and a P-layer epitaxial structure.

[0007] Preferably, the substrate is a PSS substrate or a sapphire + SiO2 composite PSS substrate.

[0008] Preferably, the pattern depth and height of the first patterning are 1 - 3 μm.

[0009] Preferably, the depth and height of the super-large micron-scale pattern in the second patterning are 3-7 μm, and it is a cone or hexagonal array.

[0010] Preferably, the multi-layer gradient structure is Al2O3→SiN x →SiO2 or AlN→SiON→SiO2, both of which are refractive index high-medium-low distribution structures.

[0011] Preferably, the stress buffer layer is an AlN or GaN superlattice.

[0012] Preferably, the green light MQW period data ≥ 3.

[0013] Preferably, the blue light MQW period data ≥ 3.

[0014] A blue-green dual-wavelength epitaxial growth structure includes a PSS substrate, and a buffer layer + planarization layer, a green light MQW, a planarization layer, an NGaN layer, a gradient layer, a stress buffer layer, a planarization layer, a blue light MQW, and an electron blocking layer and a P-layer epitaxial structure are sequentially grown on the PSS substrate.

[0015] Preferably, the gradient layer is Al2O3→SiN x →SiO2 or AlN→SiON→SiO2 structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Through the collaborative design of two patterning + planarization epitaxy, the present invention breaks through the physical limit of single patterning PSS and has the following advantages: (1) Improve material quality: Improve the problem of poor material quality after the growth of the first green light MQW; (2) Micro-nano photon structure: Double-layer patterning design to improve the blue light extraction efficiency, and then stimulate the luminescence brightness of the green light MQW; and the second patterning design is carried out on the NGaN. Since the pattern is etched on the GaN material, a super-large pattern height and width are designed this time without affecting the quality of the subsequent material growth (because it is homoepitaxy). The larger pyramid structure can more effectively change the light propagation direction; (3) Dislocation double blocking: The initial pattern and the secondary pattern form a three-dimensional defect improvement. Brief Description of the Drawings

[0017] Figure 1 It is a process flow chart before and after the improvement of the present invention.

[0018] Figure 2 It is an epitaxial structure diagram before and after the improvement of the present invention. Detailed Embodiments

[0019] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, detail the specific implementation manners, structures, features and their effects of the present invention as follows.

[0020] As Figure 1 shown, a blue-green dual-wavelength epitaxial growth method includes the following steps: (1) First patterning and planarization: Grow a buffer layer + 2D / 3D planarization layer, green light MQW, planarization layer, and NGaN layer on a conventional PSS substrate or a sapphire + SiO2 composite PSS substrate (pattern depth and height 1 - 3 μm); (2) Second patterning: Form ultra-large micron-scale patterns with a depth and height of 3 - 7 μm, in a cone or hexagonal array, on the above NGaN surface through photolithography + dry etching (ICP or RIE); (3) Second epitaxial growth: Deposit Al2O3 → SiN x → SiO2 materials on the secondary pattern, and finally deposit ALN, and then continuously grow a 2D / 3D planarization layer, blue light MQW, electron blocking layer, and P-layer epitaxial structure.

[0021] As Figure 2 shown, a blue-green dual-wavelength epitaxial structure includes a PSS substrate, and on the PSS substrate, a buffer layer + 2D / 3D planarization layer, green light MQW, planarization layer, NGaN layer, gradient layer (Al2O3 → SiN x → SiO2), ALN, 2D / 3D planarization layer, blue light MQW, and electron blocking layer and P-layer epitaxial structure are grown in sequence.

[0022] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An epitaxial growth method for blue and green dual wavelengths, characterized in that: It includes the following steps: (1) First patterning and planarization: Provide a PSS substrate with a first patterned structure, grow a buffer layer and a planarization layer on the PSS substrate, then grow a green light MQW and a planarization layer, and finally grow an NGaN layer; (2) Second patterning: Perform second patterning on the above NGaN layer to form ultra-large micron-scale patterns; (3) Second epitaxial growth: Deposit multiple graded structures on the second patterned structure first, then grow a stress buffer layer and a planarization layer, and finally grow a blue light MQW and an electron blocking layer and a P-layer epitaxial structure.

2. The epitaxial growth method with blue and green dual wavelengths as described in claim 1, characterized in that: The substrate is a PSS substrate or a sapphire + SiO2 composite PSS substrate.

3. A method for epitaxial growth of blue-green dual wavelengths according to claim 1, characterized in that: The depth and height of the pattern in the first patterning are 1 - 3 μm.

4. The epitaxial growth method with blue and green dual wavelengths as described in claim 1, wherein: The depth and height of the ultra-large micron-scale pattern in the second patterning are 3 - 7 μm, and it is a cone or hexagonal array.

5. The epitaxial growth method with blue and green dual wavelengths as described in claim 1, characterized in that: The multi-layer gradient structure is Al2O3→SiN x →SiO2 or AlN→SiON→SiO2, both of which are structures with high, medium, and low refractive index distributions.

6. The epitaxial growth method with blue and green dual wavelengths as described in claim 1, characterized in that: The stress buffer layer is an AlN or GaN superlattice.

7. The epitaxial growth method with blue and green dual wavelengths as described in claim 1, wherein: The period data of the green light MQW ≥ 3.

8. The epitaxial growth method with blue and green dual wavelengths as described in claim 1, characterized in that: The period data of the blue light MQW ≥ 3.

9. A blue-green dual-wavelength epitaxial growth structure formed as described in any one of claims 1-8, characterized in that: It includes a PSS substrate, and a buffer layer + planarization layer, a green light MQW, a planarization layer, an NGaN layer, a graded layer, a stress buffer layer, a planarization layer, a blue light MQW, and an electron blocking layer and a P-layer epitaxial structure are sequentially grown on the PSS substrate.

10. A blue-green dual-wavelength epitaxial growth structure according to claim 9, characterized in that: The gradient layer is Al2O3→SiN x →SiO2 or AlN→SiON→SiO2 structure.

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