High efficiency red plant lighting led epitaxial wafer and method of manufacturing the same

Abstract

The application provides a high-efficiency red light plant lighting LED epitaxial wafer and a manufacturing method, and the structure comprises a GaAs substrate, a GaAs buffer layer, an N-type GaInP cutoff layer, an N-type GaAs ohmic contact layer, an N-type AlGaInP roughening layer, an N-type AlGaInP current spreading layer, an N-type AlInP confinement layer, an N-type AlGaInP waveguide layer, a multi-quantum well layer, a P-type AlGaInP waveguide layer, a P-type AlInP composite doped confinement layer with a three-sublayer structure, a P-type AlGaInP transition layer, a P-type GaP window layer and a P-type GaP ohmic contact layer. The Mg diffusion is effectively inhibited through the composite doped structure, the hole injection efficiency is improved, the device voltage is reduced, the photon efficiency (PPE) and the reliability are significantly improved, and the application is suitable for large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of semiconductor lighting devices, and more particularly to a high-efficiency red light-emitting diode epitaxial wafer for plant lighting and its manufacturing method. Background Technology

[0002] With the rapid development of precision planting scenarios such as facility agriculture and plant factories, higher demands are being placed on the efficiency, stability, and spectral adaptability of artificial light sources. Light-emitting diodes (LEDs), due to their advantages such as low energy consumption, tunable spectrum, and long lifespan, have gradually become the mainstream light source for modern plant lighting. Among them, the red light band (approximately 620nm-660nm) is a key band for promoting plant photosynthesis, flowering, and fruiting, making the photosynthetic photon efficiency (PPE) of red LED chips an important indicator of the performance of plant lighting systems.

[0003] Traditional red LEDs typically employ an AlGaInP multi-quantum-well epitaxial structure with Mg as an acceptor dopant in the P-type confinement layer to provide sufficient holes. However, during high-temperature MOCVD epitaxy, Mg doping suffers from severe diffusion, easily penetrating into the active region and forming non-radiative recombination centers, thus reducing internal quantum efficiency. Simultaneously, while a single heavily doped structure increases the hole concentration, it also increases the lattice defect density, limiting device lifetime and reliability.

[0004] Therefore, effectively suppressing Mg diffusion and improving hole injection efficiency while maintaining low voltage and high hole concentration has become an important research direction for the optimized design of epitaxial structures for red LEDs. Some studies have proposed improving the performance of P-type layers through multi-period superlattices, barrier layers, or gradient doping methods, but these methods suffer from drawbacks such as structural complexity, high growth difficulty, and high cost. Therefore, proposing a more rational, controllable, and mass-producible epitaxial structure for red LEDs is of great significance. Summary of the Invention

[0005] This invention relates to a high-efficiency red light-emitting diode epitaxial wafer suitable for plant lighting and its manufacturing method. It aims to solve the problems of severe Mg diffusion in the P-type doped layer, low hole injection efficiency, and high forward voltage in the existing red LED epitaxial structure, thereby improving the photon efficiency (PPE) and lifespan of the device, reducing energy consumption, and improving the performance and reliability of red LEDs in plant lighting applications.

[0006] The technical solution of the present invention is as follows:

[0007] A high-efficiency red light-emitting diode epitaxial wafer for plant illumination comprises, from bottom to top, the following:

[0008] GaAs substrate;

[0009] GaAs buffer layer;

[0010] N-type GaInP cutoff layer;

[0011] N-type GaAs ohmic contact layer;

[0012] N-type AlGaInP roughening layer;

[0013] N-type AlGaInP current-spreading layer;

[0014] N-type AlInP confinement layer;

[0015] N-type AlGaInP waveguide layer;

[0016] Multiple quantum well layers;

[0017] P-type AlGaInP waveguide layer;

[0018] The P-type AlInP composite doping confinement layer is composed of a first sublayer, a second sublayer, and a third sublayer sequentially disposed near the side of the multi-quantum-well layer.

[0019] P-type AlGaInP transition layer;

[0020] P-type GaP window layer;

[0021] P-type GaP ohmic contact layer;

[0022] in:

[0023] The first sublayer is a low-to-medium concentration Mg-doped AlInP layer with a thickness of 300-500 angstroms and a Mg doping concentration of 3 × 10⁻⁶. 17 -5×10 17 carriers / cm³;

[0024] The second sublayer is a Si and Mg co-doped AlInP periodic superlattice structure, consisting of 8-12 periods, each with a thickness of 50-80 angstroms, and the Mg doping concentration is 6 × 10⁻⁶. 17 -9×10 17 carriers / cm³, Si doping concentration increases linearly along the growth direction;

[0025] The third sublayer is a highly Mg-doped AlInP layer with a thickness of 500-1000 angstroms and a Mg doping concentration of 1×10⁻⁶. 18 -1.5×10 18 carriers / cm³.

[0026] The Al component z of the N-type AlGaInP roughened layer satisfies 0.30 < z < 0.60, and the thickness is 8000 - 12000 Å.

[0027] The Al component w of the N-type AlGaInP current spreading layer satisfies 0.10 < w < 0.50, and the thickness is 15000 - 22000 Å.

[0028] The multiple quantum well layer is composed of 8 - 12 pairs of alternately arranged AlGaInP barrier layers and well layers. The well thickness is 60 - 80 Å, the barrier thickness is 60 - 120 Å, and it is undoped.

[0029] The thickness of the P-type GaP window layer is 1500 - 6000 Å, and the doping concentration is 3×10 18 -5×10 18 carriers / cm³.

[0030] The thickness of the P-type GaP ohmic contact layer is 300 - 600 Å, and the doping concentration is greater than 5×10 19 carriers / cm³.

[0031] The Al component m of the N-type AlGaInP waveguide layer satisfies 0.30 < m < 0.60, and the thickness is 500 - 800 Å.

[0032] The Al component n of the P-type AlGaInP waveguide layer satisfies 0.30 < n < 0.60, and the thickness is 500 - 800 Å.

[0033] The composition of the P-type AlGaInP transition layer is (Al x Ga 1-x ) y In[[ID=3​​​​​​​​​​​​​(2) A P-type AlInP composite doped confinement layer is grown on the P-type AlGaInP waveguide layer, comprising, in sequence:

[0037] First sublayer: 300-500 angstroms thick, Mg doping concentration of 3 × 10⁻⁶ 17 -5×10 17 carriers / cm³;

[0038] The second sublayer: An 8-12 period Si and Mg co-doped AlInP superlattice structure is formed using an alternating pulsed gas supply method, with a thickness of 50-80 Å per period and a Mg doping concentration of 6 × 10⁻⁶. 17 -9×10 17 carriers / cm³, Si doping concentration increases linearly;

[0039] Third sublayer: 500-1000 angstroms thick, Mg doping concentration 1×10⁻⁶ 18 -1.5×10 18 carriers / cm³;

[0040] (3) A P-type AlGaInP transition layer, a P-type GaP window layer and a P-type GaP ohmic contact layer are sequentially grown on the P-type AlInP composite doping confinement layer.

[0041] (4) The above growth steps are completed by layered growth in the temperature range of 700-750℃ using metal-organic chemical vapor deposition (MOCVD).

[0042] The raw material gas used in step (4) includes:

[0043] Metal sources: TMGa (trimethylgallium), TMAl (trimethylaluminum), TMIn (trimethylindium);

[0044] Gas sources: PH3 (phosphine), AsH3 (arsenic);

[0045] N-type doping source: Si2H6 or SiH4; P-type doping source: Cp2Mg (magnesium dicerone) or CBr4 or CCl4.

[0046] The second sublayer employs an alternating pulse gas supply method to precisely control the spatial distribution of Si and Mg, forming a periodic superlattice structure, which is used to regulate Mg diffusion and improve hole injection efficiency.

[0047] The core of this invention lies in replacing the traditional single-doped AlInP structure with a three-sublayer composite doping structure in the P-type confinement layer. This allows for precise control of the spatial distribution of Mg impurities, effectively suppressing Mg diffusion while simultaneously improving hole injection efficiency. The three-sublayer structure includes: a first sublayer: a Mg-doped AlInP layer with a moderate doping concentration, located adjacent to the active region, effectively suppressing Mg diffusion into the quantum well during high-temperature growth, and serving as a hole supply layer to improve recombination efficiency; a second sublayer: a Si and Mg co-doped AlInP superlattice structure, forming a periodic potential barrier to suppress Mg diffusion while enhancing hole storage and injection; and a third sublayer: a heavily Mg-doped AlInP layer, used to reduce the device's forward resistance and operating voltage, ensuring good ohmic contact performance. This composite doping structure not only creates an "injection gradient" for hole transport structurally, avoiding the recombination center problem associated with traditional highly doped layers, but also achieves bandgap control and carrier balance, improving the overall efficiency and reliability of the LED device.

[0048] Compared with the prior art, the present invention has the following significant technical advantages:

[0049] Effective suppression of Mg diffusion: The doping transition band and diffusion barrier constructed by the first and second sublayers significantly reduce the migration of Mg vector quantum wells and reduce the number of nonradiative recombination centers;

[0050] Improving hole injection efficiency: The band ladder structure formed by the three sublayers is conducive to hole injection and accumulation in the active region, thereby increasing the recombination probability;

[0051] Lowering device voltage: The high-concentration Mg doping design of the third sublayer reduces the resistance of the P-type region, enabling low-voltage drive and effectively improving PPE;

[0052] Simple structure and mass production capability: The three-layer structure is simpler than the multi-period superlattice process, reducing process complexity and making it feasible for industrial applications.

[0053] Significantly improved performance in actual tests: Compared with the traditional single-doped structure, under the same test conditions (700mA), the forward voltage of the device decreased from 2.05V to 1.97V, and the PPE increased from 4.30 to 4.42, achieving a significant increase in PPE and a significant decrease in voltage.

[0054] In summary, this invention systematically solves the technical contradiction between luminous efficiency and energy consumption of red LEDs from the material design level by constructing a P-type composite doped structure with functional division and gradient control. It has substantial innovation and significant technological progress, and has good application prospects and industrialization value. Attached Figure Description

[0055] Figure 1This is a schematic diagram of the epitaxial structure of a common red light-emitting diode in the prior art.

[0056] Figure 2 This is a schematic diagram of the structure of the high-efficiency red light-emitting diode epitaxial wafer for plant illumination described in this invention. Detailed Implementation

[0057] To make the technical solution of the present invention clearer, the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the present invention is not limited to the specific embodiments described below. Without departing from the spirit and scope of the present invention, those skilled in the art can make various modifications and variations, all of which should fall within the protection scope of the present invention.

[0058] This invention provides a high-efficiency red light-emitting diode (LED) epitaxial wafer suitable for plant lighting and its fabrication method. By constructing a P-type AlInP composite doping confinement layer, the carrier behavior is optimized, significantly improving the photonic efficiency (PPE) and reliability of the device, making it particularly suitable for the fabrication of high-power red LED chips.

[0059] like Figure 2 As shown, the present invention provides a high-efficiency red light-emitting diode epitaxial wafer for plant illumination, the epitaxial structure of which comprises, from bottom to top:

[0060] GaAs substrate 600: Provides a lattice-matching basis for the entire epitaxial growth process and is suitable for growing AlGaInP group semiconductor materials;

[0061] GaAs buffer layer 601: A GaAs buffer layer 601 is grown on a GaAs substrate 600 using an N-type doping source, with the doping source being Si₂H₆ or SiH₄, and a doping concentration of 1 × 10⁻⁶. 18 -3×10 18 carriers / cm³;

[0062] N-type GaInP stop layer 200: An N-type GaInP stop layer 200 is grown on the GaAs buffer layer 601, using an N-type doping source, with the doping source being Si2H6 or SiH4, and a doping concentration of 1 × 10⁻⁶. 18 -3×10 18 carriers / cm³;

[0063] N-type GaAs ohmic contact layer 201: 500-800 angstroms thick, using an N-type doping source, doping concentration >5×10⁻⁶. 18 carriers / cm³, using Si2H6 or SiH4 as doping source;

[0064] N-type (Al) z Ga 1-zInP roughening layer 202: Al composition z is 0.30-0.60, thickness is 8000-12000 angstroms, using N-type doping, doping source is Si2H6 or SiH4, doping concentration is 1× 10⁻⁶ 18 -3×10 18 carriers / cm³;

[0065] N-type (Al) w Ga 1-w InP current-extended layer 203: Al composition w is 0.10-0.50, thickness is 15000-22000 angstroms, using an N-type doping source, the doping source is Si2H6 or SiH4, and the doping concentration is 1× 10⁻⁶. 18 -2×10 18 carriers / cm³;

[0066] The N-type AlInP confinement layer 204 has a thickness of 3000-5000 angstroms, using an N-type doping source of Si₂H₆ or SiH₄, with a doping concentration of 1 × 10⁻⁶. 18 -2×10 18 carriers / cm³;

[0067] N-type (Al) n Ga 1-n InP waveguide layer 205: Al composition m is 0.30-0.60, and thickness is 500~800 Å;

[0068] The multi-quantum-well layer 206 consists of 8-12 pairs of alternating AlGaInP barrier layers and well layers. The barrier thickness is 60-120 Å and the well thickness is 60-80 Å. It is undoped and is used to emit red light (λ≈630-660nm), serving as the luminescent core region.

[0069] P-type (Al) n Ga 1-n InP waveguide layer 207: Al composition n is 0.30-0.60, and thickness is 500~800 Å;

[0070] P-type AlInP composite doped layer 208:

[0071] First sublayer: 300-500 angstroms thick, Mg doping concentration of 3 × 10⁻⁶ 17 -5×10 17 carriers / cm³, close to the quantum well;

[0072] The second sublayer is a Si and Mg co-doped AlInP superlattice structure, consisting of 8-12 periods, each with a thickness of 50-80 angstroms. The Mg concentration is 6 × 10⁻⁶. 17 -9×1017 carriers / cm³, ensuring the overall performance shows P-type conductivity; the Si concentration increases linearly, starting from 1×10 17 -2×10 17 carriers / cm³, reaching a maximum of 2×10 17 -3×10 17 carriers / cm³;

[0073] The third sub-layer: with a thickness of 500 - 1000 Å and a Mg concentration of 1×10 18 -1.5×10 18 carriers / cm³, away from the quantum well;

[0074] P-type (Al x Ga 1-x )yIn 1-y P-type transition layer 209: where 0.15 < x < 0.25, 0.65 < y < 0.75, using a P-type doping source, the doping source is Cp2Mg, and the doping concentration is 2× 10 18 ~3×10 18 carriers / cm³, with a thickness of 150 - 250 Å;

[0075] P-type GaP window layer 210, with a thickness of 1500 - 6000 Å, using P-type doping, the doping source is CP2Mg, and the doping concentration is 3×10 18 ~5×10 18 carriers / cm³;

[0076] P-type GaP ohmic contact layer 211: with a thickness of 300 - 600 Å and a doping concentration > 5×10 19 carriers / cm³), using CBr4 or CCl4 as the doping source to improve the conductivity and contact performance of the P electrode.

[0077] This invention uses MOCVD (Metal Organic Chemical Vapor Deposition) technology to grow the above structure layer by layer at 700 - 750°C.

[0078] Gas source selection: Using TMGa (trimethylgallium), TMAl (trimethylaluminum), TMIn (trimethylindium) as metal source gases, and PH3 (phosphine) and AsH3 (arsine) as group V gas sources;

[0079] Doping source: Si2H6 or SiH4 is used for N-type doping, and Cp2Mg (bis(cyclopentadienyl)magnesium) or CBr4 / CCl4 is used for P-type doping;

[0080] Doping control: Especially in the second sublayer, the spatial distribution of Si and Mg is precisely controlled by alternating pulse gas supply to form a periodic superlattice structure, which is used to regulate Mg diffusion and hole behavior.

[0081] III. Technical Effects and Experimental Data Support

[0082] Compared with the traditional single-doped AlInP structure, under the same injection current (700mA), the structure described in this invention achieves the following performance improvements:

[0083] Structure type Forward voltage VF (V) PPE (μmol / J) Conventional structure (monolayer Mg doping) 2.05 4.30 Mg / Si+Mg(4 groups) / Mg (trilayer structure) 2.02 4.33 Mg / Si+Mg(8 groups) / Mg (trilayer structure) 1.98 4.36 Mg / Si+Mg(12 groups) / Mg (trilayer structure) 1.97 4.42

[0084] The above data shows that the three-sublayer composite doping structure effectively reduces the forward voltage (VF drops by a maximum of 0.08V) and increases the PPE by a maximum of about 2.8%, which is significantly better than the existing technology, demonstrating the technological progress of this invention in terms of luminous efficiency and power utilization.

Claims

1. A high-efficiency red light-emitting diode epitaxial wafer for plant illumination, characterized in that, Comprising, successively arranged from bottom to top: GaAs substrate; GaAs buffer layer; N-type GaInP blocking layer; N-type GaAs ohmic contact layer; N-type AlGaInP roughening layer; N-type AlGaInP current spreading layer; N-type AlInP confinement layer; N-type AlGaInP waveguide layer; Multiple quantum well layer; P-type AlGaInP waveguide layer; P-type AlInP complex doped confinement layer, the P-type AlInP complex doped confinement layer consists of a first sub-layer, a second sub-layer and a third sub-layer successively arranged on one side close to the multiple quantum well layer; P-type AlGaInP transition layer; P-type GaP window layer; P-type GaP ohmic contact layer; Where: The first sublayer is a low-to-medium concentration Mg-doped AlInP layer with a thickness of 300-500 angstroms and a Mg doping concentration of 3 × 10⁻⁶. 17 -5×10 17 carriers / cm³; The second sublayer is a Si and Mg co-doped AlInP periodic superlattice structure, consisting of 8-12 periods, each with a thickness of 50-80 angstroms, and the Mg doping concentration is 6 × 10⁻⁶. 17 -9×10 17 carriers / cm³, Si doping concentration increases linearly along the growth direction; The third sublayer is a highly Mg-doped AlInP layer with a thickness of 500-1000 angstroms and a Mg doping concentration of 1×10⁻⁶. 18 -1.5×10 18 carriers / cm³.

2. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The Al component z of the N-type AlGaInP roughening layer satisfies 0.30 < z < 0.60, and the thickness is 8000 - 12000 Å.

3. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The Al component w of the N-type AlGaInP current spreading layer satisfies 0.10 < w < 0.50, and the thickness is 15000 - 22000 Å.

4. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The multiple quantum well layer is composed of 8 - 12 pairs of AlGaInP barrier layers and well layers alternating with each other, the well thickness is 60 - 80 Å, the barrier thickness is 60 - 120 Å, and it is undoped.

5. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The thickness of the p-type GaP window layer is 1500-6000 angstroms, and the doping concentration is 3×10⁻⁶. 18 -5×10 18 carriers / cm³.

6. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The thickness of the p-type GaP ohmic contact layer is 300-600 angstroms, and the doping concentration is greater than 5 × 10⁻⁶. 19 carriers / cm³.

7. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The Al component m of the N-type AlGaInP waveguide layer satisfies 0.30 < m < 0.60, and the thickness is 500 - 800 Å.

8. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The Al component n of the P-type AlGaInP waveguide layer satisfies 0.30 < n < 0.60, and the thickness is 500 - 800 Å.

9. The high-efficiency red light-emitting diode epitaxial wafer according to claim 1, characterized in that, The composition of the P-type AlGaInP transition layer is (Al x Ga 1-x ) y In 1-y P. The Al component x satisfies 0.15 < x < 0.25, the In component ratio 1 - y satisfies 0.65 < y < 0.75, the thickness is 150 - 250 Å, and the doping concentration is 2×10 18 - 3×10 18 carriers / cm³.

10. A method for manufacturing a high-efficiency red light-emitting diode epitaxial wafer as described in any one of claims 1-9, characterized in that, Including: (1) Providing a GaAs substrate, and successively epitaxially growing a GaAs buffer layer, a N-type GaInP blocking layer, a N-type GaAs ohmic contact layer, a N-type AlGaInP roughening layer, a N-type AlGaInP current spreading layer, a N-type AlInP confinement layer, a N-type AlGaInP waveguide layer, a multiple quantum well layer and a P-type AlGaInP waveguide layer; (2) Growing a P-type AlInP complex doped confinement layer on the P-type AlGaInP waveguide layer, successively including: First sublayer: 300-500 angstroms thick, Mg doping concentration of 3 × 10⁻⁶ 17 -5×10 17 carriers / cm³; The second sublayer: An 8-12 period Si and Mg co-doped AlInP superlattice structure is formed using an alternating pulsed gas supply method, with a thickness of 50-80 Å per period and a Mg doping concentration of 6 × 10⁻⁶. 17 -9×10 17 carriers / cm³, Si doping concentration increases linearly; Third sublayer: 500-1000 angstroms thick, Mg doping concentration 1×10⁻⁶ 18 -1.5×10 18 carriers / cm³; (3) Growing a P-type AlGaInP transition layer, a P-type GaP window layer and a P-type GaP ohmic contact layer successively on the P-type AlInP complex doped confinement layer; (4) The above growth steps are completed by metalorganic chemical vapor deposition (MOCVD) method in a temperature range of 700 - 750 °C by layer growth.

11. The manufacturing method according to claim 10, characterized in that, The source gases used in the step (4) include: The metal sources are TMGa, TMAl, TMIn; The gas sources are PH3, AsH3; The N-type doping source is Si2H6 or SiH4; The P-type doping source is Cp2Mg or CBr4 or CCl4.

12. The manufacturing method according to claim 10, characterized in that, The second sub-layer adopts an alternating pulse gas supply mode to precisely control the spatial distribution of Si and Mg, form a periodic superlattice structure, and is used to regulate Mg diffusion and improve hole injection efficiency.

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