Nitride semiconductor epitaxial structure for improving blue-green dual-wavelength luminous intensity and growth method thereof

Abstract

The invention discloses a nitride semiconductor epitaxial structure for improving blue-green dual-wavelength luminous intensity and a growth method of the nitride semiconductor epitaxial structure. The epitaxial structure sequentially comprises a buffer layer, an undoped GaN layer, an undoped GaN layer, an N-type GaN layer, a stress release layer, a stress release layer, a green light multi-quantum well structure, a V-type defect filling layer, a low-temperature opening Pits layer, a defect blocking layer, a blue light multi-quantum well structure, an electron buffer layer, an electron blocking layer, a P-type GaN layer, an InGaN contact transition layer and a P-type contact layer. Wherein the green light multi-quantum well adopts a wide-well narrow-barrier design to relieve lattice strain and piezoelectric polarization effect; a three-layer defect regulation and control structure is arranged between the green light area and the blue light area, and through stress induction and dislocation conversion, dislocation is prevented from penetrating to extend to the blue light area, and the crystal quality is improved. According to the growth method, the epitaxy of each functional layer is controlled in stages under the conditions of different temperature zones and V / III ratios, and the construction of the high-quality multi-quantum well integrated structure is realized.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic technology, and in particular to a nitride semiconductor epitaxial structure and a growth method thereof for improving the blue-green dual-wavelength luminescence intensity. Background Art

[0002] Gallium nitride (GaN) materials are widely used in light-emitting diode (LED) devices due to their excellent optoelectronic properties. LEDs can efficiently convert electrical energy into light energy at low voltages, offering advantages such as energy saving, high brightness, and long life. They are widely used in various fields, including general lighting, display backlighting, and plant lighting.

[0003] As demand for healthy lighting and high-color rendering displays increases, concerns about blue light damage are gaining traction, driving the development of blue-green dual-wavelength LEDs. These devices, by synergistically emitting specific wavelengths, achieve higher-quality spectral output, meeting the demands of high-color rendering lighting and full-spectrum backlight modules.

[0004] Currently, the epitaxial structure of blue-green dual-wavelength LEDs typically employs an InGaN multiple quantum well (MQW) structure with varying indium (In) compositions grown sequentially along the epitaxial growth direction. The green quantum well with a higher In content is grown first, followed by the blue quantum well with a lower In content. However, due to the significant lattice mismatch between the InGaN with a high In content and the GaN barrier (typically 2% to 3%), a significant piezoelectric polarization effect occurs during the growth of the green quantum well, leading to stress accumulation and increased defect density. Furthermore, structural defects in the green region (such as screw and edge dislocations) tend to extend along the epitaxial direction into the blue region, further degrading the crystal quality of the blue quantum well and reducing its internal quantum efficiency. Ultimately, this results in insufficient blue-green dual-band luminescence intensity across the device, making it difficult to meet the brightness and efficiency requirements for practical applications.

[0005] Therefore, the existing technology urgently needs a nitride semiconductor epitaxial structure and its growth method that can effectively inhibit dislocation propagation, reduce polarization effects, and enhance the blue-green dual-band luminescence intensity, so as to achieve more efficient LED luminescence performance and better spectral output quality. Summary of the Invention

[0006] The present invention provides a nitride semiconductor epitaxial structure and a growth method thereof for improving the blue-green dual-wavelength luminescence intensity, aiming to effectively improve the luminescence intensity and external quantum efficiency of blue-green dual-wavelength LED devices and solve the problem of the piezoelectric polarization effect and structural defects caused by the green light quantum well extending to the blue light region.

[0007] The nitride semiconductor epitaxial structure provided by the present invention includes the following components arranged in order from bottom to top: Buffer layer, undoped GaN layer, N-type GaN layer, stress release layer, green light multiple quantum well structure, V-type defect filling layer, low temperature open Pits layer, defect blocking layer, blue light multiple quantum well structure, electron buffer layer, electron blocking layer, P-type GaN layer, InGaN contact transition layer and P-type contact layer; in, The green light multi-quantum well structure includes 3 to 5 pairs of InGaN quantum wells and GaN barrier layers, the thickness of the InGaN quantum well is 3.5nm to 4nm, the In composition is 0.20 to 0.30, and the thickness of the GaN barrier layer is 4.5nm to 5nm; The V-shaped defect filling layer is a GaN layer with a thickness of 150nm to 200nm; The low-temperature Pits layer is an InGaN layer with a thickness of 150 nm to 300 nm and an In composition of 0.05 to 0.15; The defect blocking layer is an AlGaN layer with a thickness of about 30 nm and an Al composition of 0.10 to 0.20, and a V / III ratio of 2000 to 3000 during its growth process; The energy band barrier difference between the green light multi-quantum well structure and the blue light multi-quantum well structure is 0.2eV to 0.4eV; The V-shaped defect filling layer, low-temperature Pits layer and defect blocking layer are used to alleviate the structural defects caused by the growth of the green light quantum well and inhibit the extension of dislocations to the blue light quantum well region, thereby improving the crystal quality and luminescence efficiency of the blue light quantum well.

[0008] The blue light multi-quantum well structure includes multiple InGaN quantum wells and GaN barrier layers. The thickness of the InGaN quantum well is 2.5nm to 3nm, the In composition is 0.10 to 0.18, and the thickness of the GaN barrier layer is 6nm to 8nm.

[0009] The thickness of the electron buffer layer is 5 nm to 15 nm.

[0010] The electron blocking layer is AlGaN, and the aluminum content is 0.15 to 0.25.

[0011] The dopant of the P-type GaN layer is diethyl magnesium (Cp2Mg), and the doping concentration is 1×10 19 to 5×10 19 atoms / cm 3 .

[0012] The thickness of the InGaN contact transition layer is 20 nm to 40 nm.

[0013] The defect blocking layer is used to induce the dislocation line to deviate from the vertical direction and bend by forming a transverse stress field, and promotes the annihilation of different types of dislocations when they meet to reduce the dislocation density.

[0014] The epitaxial structure is suitable for use in blue-green dual-wavelength LED chip application scenarios such as plant lighting, health lighting or liquid crystal display backlight modules.

[0015] The above-mentioned method for growing a nitride semiconductor epitaxial structure comprises the following steps: 1) On a patterned sapphire substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, and a stress release layer are sequentially epitaxially grown; 2) Growing a green light multi-quantum well structure at a first temperature range of 720°C to 760°C, the structure comprising 3 to 5 pairs of InGaN quantum wells and GaN barrier layers, the quantum wells having a thickness of 3.5nm to 4nm, an indium fraction of 0.20 to 0.30, and the barrier layers having a thickness of 4.5nm to 5nm; 3) Raising the temperature to 850°C to 950°C and growing a 150nm to 200nm thick GaN layer as a V-shaped defect filling layer; 4) Lowering the temperature to 750°C to 850°C and growing an InGaN layer with a thickness of 150nm to 300nm and an indium composition of 0.05 to 0.15 in a nitrogen atmosphere to form a low-temperature Pits layer; 5) Growing an aluminum gallium nitride layer with a thickness of about 30 nm and an aluminum content of 0.10 to 0.20 as a defect blocking layer at a V / III ratio of 2000 to 3000; 6) growing a blue light multi-quantum well structure in the second temperature zone, the structure comprising multiple InGaN quantum wells and GaN barrier layers, the quantum wells having a thickness of 2.5 nm to 3 nm, an indium composition of 0.10 to 0.18, and the barrier layers having a thickness of 6 nm to 8 nm; 7) Sequentially grow an electron buffer layer with a thickness of 5nm to 15nm, an aluminum gallium nitride electron blocking layer with an aluminum content of 0.15 to 0.25, and a doping concentration of 1×10 19 to 5×10 19 atoms / cm 3 A P-type GaN layer, an InGaN contact transition layer with a thickness of 20nm to 40nm, and a P-type contact layer.

[0016] The present invention significantly improves the blue-green dual-wavelength luminescence intensity through the following two synergistic technical points: 1. The green light quantum well adopts a "wide well, narrow barrier" structural design: the InGaN quantum well thickness is set to 3.5-4nm, which is wider than the conventional structure. This facilitates the partial release of lattice strain, weakens the piezoelectric field, and increases the electron-hole recombination rate. The GaN barrier layer thickness is set to 4.5-5nm, which can effectively reduce stress accumulation and improve injection efficiency, thereby improving the overall green light emission efficiency.

[0017] 2. The defect-modulating structure significantly improves the quality of the blue light region: A V-shaped defect-filling layer, a low-temperature Pits layer, and a defect-blocking layer are sequentially introduced after the green light quantum well to achieve crystal morphology repair, guided transformation through penetrating dislocations, and dislocation deflection induced by lateral stress, respectively. This effectively prevents dislocations from vertically penetrating into the blue light region, thereby improving the structural integrity and luminescence efficiency of the blue light quantum well.

[0018] Compared with the prior art, the present invention has the following beneficial effects: By optimizing the green region's structural design and incorporating defect-modulating structures, the quantum efficiency of both green and blue light bands was effectively increased. The optimized structure significantly improved the luminous efficiency of both the blue and green bands, achieving higher luminous intensity and external quantum efficiency compared to samples without defect-modulating structures.

[0019] The present invention effectively improves the crystal quality of the blue light multi-quantum well by suppressing the extension of structural defects into the blue light region, reduces non-radiative recombination paths, and further enhances the long-term operation stability of the device.

[0020] The structure of the present invention can be implemented on a conventional GaN LED epitaxial growth platform without adding a complex process flow. The key parameters are clearly controlled and suitable for industrial epitaxial growth using mature equipment such as MOCVD.

[0021] Because it simultaneously outputs high-efficiency green and blue light, the structure of the present invention can be widely used in various scenarios requiring blue-green dual wavelengths, such as plant lighting, health lighting, high-color rendering LED light sources, and liquid crystal display backlight modules, and has good commercial potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic cross-sectional view of a nitride semiconductor epitaxial structure of the present invention.

[0023] Figure 2 This is the EL emission spectrum of a blue-green dual-wavelength LED chip prepared using the existing epitaxial structure.

[0024] Figure 3 This is an EL emission spectrum diagram of a blue-green dual-wavelength LED chip prepared using the epitaxial structure of the present invention.

[0025] Figure 1The typical positions of the P electrode and the N electrode after device processing are also schematically marked to assist in understanding the connection relationship between the epitaxial structure layers. The electrode portion is not part of the epitaxial structure of the present invention.

[0026] The structures shown by the reference numbers in the figure include: 0 — substrate; 1 — buffer layer; 2 — Undoped GaN layer, 3 — N-type GaN layer 4 — stress relief layer; 5 — Green light multi-quantum well structure; 6 — V-shaped defect filling layer; 7 — Open the Pits layer at low temperature; 8 — Defect blocking layer; 9 — Blue light multi-quantum well structure; 10 — electronic buffer layer; 11 — electron blocking layer; 12 — P-type GaN layer; 13 — InGaN contact transition layer; 14 — P-type contact layer. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0028] like Figure 1 As shown, this embodiment provides a nitride semiconductor epitaxial structure, including a buffer layer 1, an undoped GaN layer 2, an N-type GaN layer 3, a stress release layer 4, a green light multi-quantum well structure 5, a V-type defect filling layer 6, a low-temperature Pits layer 7, a defect blocking layer 8, a blue light multi-quantum well structure 9, an electron buffer layer 10, an electron blocking layer 11, a P-type GaN layer 12, an InGaN contact transition layer 13 and a P-type contact layer 14, which are sequentially arranged on a substrate 0 from bottom to top.

[0029] The specific growth method of the epitaxial structure is as follows: Step 1: Substrate pretreatment and initial growth A patterned sapphire substrate (PSS) was selected, with a pattern period of 2 to 3 microns and a pattern depth of 0.8 to 1.2 microns. Using metal-organic chemical vapor deposition (MOCVD), a low-temperature GaN buffer layer 1, an undoped GaN layer 2, an N-type GaN layer 3, and a stress relief layer 4 were sequentially grown on this substrate 0. The undoped GaN layer 2 had a thickness of 1 to 2 µm and served as a high-quality template layer to improve crystal quality. The N-type GaN layer 3 had a thickness of 1 to 2 µm. The stress relief layer 4, constructed from an InGaN / GaN alloy layer, effectively mitigated lattice strain transfer between the lower and upper layers. The thicknesses were 2 to 3 nm and 40 to 60 nm, respectively, with a period of 3 to 6 layers.

[0030] Step 2: Growth of green light multi-quantum well structure In the first temperature zone (720°C to 760°C), a green light multi-quantum well structure 5 is grown. The structure includes a 3-5 period InGaN / GaN double-layer structure, an InGaN quantum well thickness of 3.5nm to 4nm, an In composition of 0.20 to 0.30, and a GaN barrier layer thickness of 4.5nm to 5nm.

[0031] This structure adopts a "wide well and narrow barrier" design, which can reduce the lattice strain between InGaN and GaN, improve the localization effect of the InGaN layer, reduce the piezoelectric polarization strength, thereby enhancing the spatial coincidence and recombination efficiency of carriers, and effectively improving the green light emission intensity.

[0032] Step 3: Defect-regulated structure growth To prevent dislocations and stress defects generated in the green multi-quantum well structure from propagating to the blue region, the present invention sequentially grows the following three-layer structure after the green region: V-shaped defect filling layer 6: uses Ga source trimethylgallium (TMGa) as a precursor, grows in a N2 / H2 / NH3 atmosphere at a temperature of 850°C to 950°C, and has a thickness of 150nm to 200nm. It is used to fill the V-shaped defects formed in the green light region and provide a flat growth interface.

[0033] Low-temperature Pits layer 7: Using TMGa and TMIn as precursors, grown in an N2 atmosphere with NH3 as the nitrogen source at a temperature of 750°C to 850°C, with a thickness of 150nm to 300nm and an In composition of 0.05 to 0.15. This layer induces dislocations to evolve into V-pits and converts some threading dislocations into V-Pits, weakening non-radiative recombination centers and improving hole injection pathways.

[0034] Defect blocking layer 8: On top of the low temperature Pits layer, grow Al with a thickness of about 30nm y Ga 1-yThe N layer, where y is 0.10 to 0.20, and the V / III ratio is controlled between 2000 and 3000 during growth. Due to the approximately 3% lattice mismatch between the AlGaN lattice constant (approximately 3.15 to 3.18 angstroms) and the InGaN layer (approximately 3.22 angstroms), a localized compressive stress field forms at this interface. This stress field is distributed laterally, creating a significant stress gradient that effectively forces the originally vertically extending dislocation lines to deviate, bending horizontally or even folding back, significantly reducing the possibility of them penetrating vertically into the upper blue region.

[0035] Furthermore, under stress regulation, some different types of dislocation lines (such as screw dislocations and edge dislocations) can meet and annihilate, transforming into point defects such as vacancies and interstitial atoms, further alleviating the accumulation of crystal defects. This structure effectively blocks threading dislocations by regulating the stress state, improving the crystal integrity and luminescence efficiency of the blue light quantum well structure.

[0036] Step 4: Growth of blue light multi-quantum well structure A blue multi-quantum well structure 9 is grown on top of the defect-modulating structure. This structure comprises multiple InGaN / GaN bilayer periods, with InGaN quantum wells ranging in thickness from 2.5nm to 3nm, an In composition of 0.10 to 0.18, and GaN barrier layers ranging in thickness from 6nm to 8nm. The energy barrier difference between the green and blue regions is controlled at 0.2 to 0.4 electron volts, which helps form an electron barrier to suppress carrier crosstalk, optimize the injection layer distribution, and improve the recombination efficiency in the blue region.

[0037] Step 5: P-type region structure growth Growing an electron buffer layer 10 with a thickness of 5 nm to 15 nm to improve the transition matching of electron-hole distribution; Growing an AlGaN electron blocking layer 11 with an aluminum composition of 0.15 to 0.25; The P-type GaN layer 12 is grown with diethyl magnesium (Cp2Mg) as the dopant and the doping concentration is 1×10 19 to 5×10 19 atoms / cm 3 ; An InGaN contact transition layer 13 is formed thereon with a thickness of 20 nm to 40 nm to improve ohmic contact performance and enhance device stability; A P-type contact layer 14 is grown on the top to form the device surface electrode contact interface.

[0038] In order to further verify the luminescence performance of the epitaxial structure of the present invention, Figure 2 and Figure 3The electroluminescence (EL) spectra comparison diagrams of a blue-green dual-wavelength LED chip with a conventional epitaxial structure without a defect control structure and an epitaxial structure of the present invention under the same test conditions are respectively shown. Figure 2 The main emission wavelength is 464.3nm, corresponding to the blue light band. The green light emission component is weak, the overall double peaks are asymmetric, the relative intensity of green light is low, and the purity is 0.829. Figure 3 The main peak of mid-blue light is located at 462.6nm, with a significant enhancement in green light emission. The overall spectrum exhibits a clearer double-peak structure, demonstrating a significant synergistic enhancement effect between the blue and green bands. The purity is 0.562, and the intensity of the green light component is significantly increased. As can be seen from the figure, the structure of the present invention achieves higher relative green light emission intensity and better double-peak symmetry, demonstrating excellent blue-green synergistic luminescence ability, verifying the effectiveness of the structural design and growth process.

Claims

1. A nitride semiconductor epitaxial structure for enhancing the blue-green dual-wavelength luminescence intensity, characterized in that: Including the following settings: Buffer layer, undoped GaN layer, N-type GaN layer, stress release layer, green light multiple quantum well structure, V-type defect filling layer, low temperature open Pits layer, defect blocking layer, blue light multiple quantum well structure, electron buffer layer, electron blocking layer, P-type GaN layer, InGaN contact transition layer and P-type contact layer; in, The green light multi-quantum well structure includes 3 to 5 pairs of InGaN quantum wells and GaN barrier layers, the thickness of the InGaN quantum well is 3.5nm to 4nm, the In composition is 0.20 to 0.30, and the thickness of the GaN barrier layer is 4.5nm to 5nm; The V-shaped defect filling layer is a GaN layer with a thickness of 150nm to 200nm; The low-temperature Pits layer is an InGaN layer with a thickness of 150 nm to 300 nm and an In composition of 0.05 to 0.15; The defect blocking layer is an AlGaN layer with a thickness of about 30 nm and an Al composition of 0.10 to 0.20, and a V / III ratio of 2000 to 3000 during its growth process; The energy band barrier difference between the green light multi-quantum well structure and the blue light multi-quantum well structure is 0.2eV to 0.4eV; The V-shaped defect filling layer, low-temperature Pits layer and defect blocking layer are used to alleviate the structural defects caused by the growth of the green light quantum well and inhibit the extension of dislocations to the blue light quantum well region, thereby improving the crystal quality and luminescence efficiency of the blue light quantum well.

2. The epitaxial structure according to claim 1, wherein: The blue light multi-quantum well structure includes multiple InGaN quantum wells and GaN barrier layers. The thickness of the InGaN quantum well is 2.5nm to 3nm, the In composition is 0.10 to 0.18, and the thickness of the GaN barrier layer is 6nm to 8nm.

3. The epitaxial structure according to claim 1, wherein: The thickness of the electron buffer layer is 5 nm to 15 nm.

4. The epitaxial structure according to claim 1, wherein: The electron blocking layer is AlGaN, and the aluminum content is 0.15 to 0.

25.

5. The epitaxial structure according to claim 1, wherein: The dopant of the P-type GaN layer is diethyl magnesium (Cp2Mg), and the doping concentration is 1×10 19 to 5×10 19 atoms / cm 3 .

6. The epitaxial structure according to claim 1, wherein: The thickness of the InGaN contact transition layer is 20 nm to 40 nm.

7. The method for growing a nitride semiconductor epitaxial structure according to claim 1, wherein: The steps include: 1) Epitaxially growing a buffer layer and an N-type GaN layer on a patterned sapphire substrate; 2) Growing a green light multi-quantum well structure at a first temperature range of 720°C to 760°C, the structure comprising 3 to 5 pairs of InGaN quantum wells and GaN barrier layers, the quantum wells having a thickness of 3.5nm to 4nm, an indium fraction of 0.20 to 0.30, and the barrier layers having a thickness of 4.5nm to 5nm; 3) Raising the temperature to 850°C to 950°C and growing a 150nm to 200nm thick GaN layer as a V-shaped defect filling layer; 4) Lowering the temperature to 750°C to 850°C and growing an InGaN layer with a thickness of 150nm to 300nm and an indium composition of 0.05 to 0.15 in a nitrogen atmosphere to form a low-temperature Pits layer; 5) Growing an aluminum gallium nitride layer with a thickness of about 30 nm and an aluminum content of 0.10 to 0.20 as a defect blocking layer under conditions of a V / III ratio of 2000 to 3000; 6) growing a blue light multi-quantum well structure in the second temperature zone, the structure comprising multiple InGaN quantum wells and GaN barrier layers, the quantum wells having a thickness of 2.5 nm to 3 nm, an indium composition of 0.10 to 0.18, and the barrier layers having a thickness of 6 nm to 8 nm; 7) Sequentially grow an electron buffer layer with a thickness of 5nm to 15nm, an aluminum gallium nitride electron blocking layer with an aluminum content of 0.15 to 0.25, and a doping concentration of 1×10 19 to 5×10 19 atoms / cm 3 A P-type GaN layer, an InGaN contact transition layer with a thickness of 20nm to 40nm, and a P-type contact layer.

Images