Red light LED epitaxial wafer for display screen and preparation method thereof

Abstract

The application relates to the technical field of LEDs, in particular to a red light LED epitaxial wafer for a display screen and a preparation method thereof. The red light LED epitaxial wafer is sequentially provided with a GaAs substrate, a buffer layer, a DBR reflection layer, an N-type limiting layer, a first N-type double-dilution waveguide layer, an N-type single-dilution waveguide layer, a second N-type double-dilution waveguide layer, a strain-improving light-emitting active layer, a first P-type double-dilution waveguide layer, a P-type single-dilution waveguide layer, a second P-type double-dilution waveguide layer, a P-type limiting layer, a P-type transition layer and a P-type window layer. Through structure optimization, the monochromaticity and consistency of red light and the large-angle light-emitting brightness are effectively improved, and the display performance of the red light LED is improved.

Description

Technical Field

[0001] This invention relates to the field of LED technology, specifically to a red LED epitaxial wafer for display screens and its preparation method. Background Technology

[0002] With the continuous upgrading and iteration of LED technology and the rapid expansion of the application market, the LED display industry is ushering in more development opportunities. Detachable LED displays are mainly used in large-scale concerts, major sporting events, high-end conferences, and large-scale exhibitions. Furthermore, as the size of LED chips continues to shrink and the resolution continues to improve, the LED display market is expanding into more fields.

[0003] With the continuous upgrading of application fields, new challenges are being posed to the performance of LED chips. Quaternary AlGaInP is the preferred material for fabricating red LEDs in displays; however, due to the inherent properties of the material, existing AlGaInP red LEDs are prone to problems such as poor color uniformity and uneven light intensity at multiple angles. The epitaxial structure of a conventional red LED is as follows: Figure 1 As shown, from bottom to top, the structure includes a GaAs substrate 100, a buffer layer 101, a distributed Bragg reflector (DBR reflector) layer 102, an N-type confinement layer 103, an N-side waveguide layer 104, a light-emitting active layer 105, a P-side waveguide layer 106, a P-type confinement layer 107, a P-type transition layer 108, and a P-type window layer 109. Because the quantum well and quantum barrier materials used in the light-emitting active layer have matching compositions and lattices, the stress deformation they experience is compressive strain. When the LED chip is powered on, the internal junction temperature rises. The high temperature causes a significant deviation in the strain of the well / barrier materials compared to room temperature, resulting in a larger full width at half maximum (FWHM) of the red LED's emission spectrum. Consequently, the monochromaticity of the emitted red light is poor, exhibiting a phenomenon of uneven and inconsistent red light color. For a long time, technicians have improved luminous efficiency through epitaxial structure and process improvements. However, measurements of the emission angle of red LED chips show that the main luminous intensity is concentrated directly above the chip, i.e., at the normal angle. Significant brightness improvements have not been achieved across various large angle ranges, resulting in a large difference between the visual brightness at side angles and the normal angle in high-brightness displays. Therefore, to meet market application requirements, the monochromaticity and insufficient brightness at large angles of red LEDs urgently need to be addressed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a red LED epitaxial wafer for display screens and its fabrication method. This red LED epitaxial wafer optimizes the structure based on the conventional red LED epitaxial structure, effectively improving the monochromaticity and consistency of red light, as well as the brightness at large angles, thereby enhancing the display performance of the red LED.

[0005] The purpose of this invention is to provide a red LED epitaxial wafer for a display screen. The red LED epitaxial wafer comprises, from bottom to top, a GaAs substrate, a buffer layer, a DBR reflective layer, an N-type confinement layer, a first N-type double-dilution waveguide layer, an N-type single-dilution waveguide layer, a second N-type double-dilution waveguide layer, a strain-improved light-emitting active layer, a first P-type double-dilution waveguide layer, a P-type single-dilution waveguide layer, a second P-type double-dilution waveguide layer, a P-type confinement layer, a P-type transition layer, and a P-type window layer.

[0006] The strain-enhanced light-emitting active layer is a cyclic structure consisting of alternating spring-type strain quantum barrier layers and compressive strain symmetric quantum well layers.

[0007] This invention is based on the conventional red LED epitaxial structure. By optimizing the structure, a strain-improved light-emitting active layer is set up. The spring-type strain quantum barrier layer adopts a two-sided counter-stress structure of compressive and tensile strain, which provides sufficient stress release space for the barrier layer in the light-emitting region. Similar to a spring, the strain can be adjusted according to the external state, which can improve the crystal quality of the epitaxial material, thereby improving the full width at half maximum (FWHM) of the red LED and effectively improving the monochromaticity and uniformity of red light. The compressive strain symmetric quantum well layer forms a bidirectional complementary lattice mismatch space, ensuring the isolation of the heavy hole band from other bands in the energy band, which can reduce the leakage of charge carriers to other bands and improve the luminous efficiency. The waveguide layers on both sides of the light-emitting active region are set as three-segment diluted doped waveguide layers to enhance side light emission and improve the brightness of large-angle light emission.

[0008] Furthermore, the materials of the first N-type double-dilution waveguide layer, the N-type single-dilution waveguide layer, the second N-type double-dilution waveguide layer, the first P-type double-dilution waveguide layer, the P-type single-dilution waveguide layer, and the second P-type double-dilution waveguide layer are all (Al). x3 Ga 1-x3 ) 0.5 In 0.5 P, where x3 is set to 0.70–0.80. This invention, through the design of multiple diluted doped waveguide layers, can improve the problem of insufficient charge carriers in the light-emitting region far from the central electrode, improve the carrier recombination efficiency in the low current density region, and thus improve the disadvantage of low brightness of red LEDs at large angles.

[0009] Specifically, the thickness of the first N-type double-dilution waveguide layer is 50nm to 80nm; the thickness of the N-type single-dilution waveguide layer is 10nm to 20nm; the thickness of the second N-type double-dilution waveguide layer is 20nm to 50nm; the thickness of the first P-type double-dilution waveguide layer is 20nm to 50nm; the thickness of the P-type single-dilution waveguide layer is 10nm to 20nm; and the thickness of the second P-type double-dilution waveguide layer is 50nm to 80nm.

[0010] Furthermore, in the structure of the spring-type strain quantum barrier layer, the material of the quantum barrier is (Al). x2 Ga 1-x2 ) 0.5 In 0.5 P, with a thickness of 8nm to 12nm, and a x2 value set to 0.60 to 0.70; the quantum well material in the structure of the compressive strain symmetric quantum well layer is (Al). x1 Ga 1-x1 ) 0.5 In 0.5 P, with a thickness of 3nm to 6nm, where x1 is set to 0.03 to 0.09.

[0011] Furthermore, the loop structure has n pairs of loops, where n ranges from 15 to 25 and is an odd number.

[0012] Furthermore, in the spring-type strain quantum barrier layer structure, the strain state from the 1st quantum barrier to the (n+1) / 2nd quantum barrier transitions from compressive strain to tensile strain, and the strain state from the (n+1) / 2nd quantum barrier to the nth quantum barrier transitions from tensile strain to compressive strain, with the strain change value between each quantum barrier ranging from 10 arcseconds to 30 arcseconds; the compressive strain value of the 1st quantum barrier is the same as that of the nth quantum barrier. This invention employs a spring-type strain quantum barrier structure, which can improve the shortcomings of conventional red LEDs where the compressive strain lattice mismatch deviates from the room-temperature mismatch due to high temperature and the rise in junction temperature during illumination. Through the spring-type gradual change structure of compressive and tensile strain, sufficient stress release space is provided in the barrier layer of the light-emitting region, which can improve the crystal quality of the epitaxial material and the monochromaticity and uniformity of red light.

[0013] Furthermore, in the structure of the compressive strain symmetric quantum well layer, the strain state from the first quantum well to the nth quantum well is compressive strain, and the strain change value between each quantum well is 30 arcseconds to 50 arcseconds; the compressive strain value of the first quantum well is the same as that of the nth quantum well. The compressive strain symmetric quantum well structure proposed in this invention can form a bidirectional complementary lattice mismatch space with the spring-type strain quantum barrier structure, which can effectively avoid the lattice mismatch degree of the active region of the red LED deviating from the high light effect change state under high temperature and long-term operation, and has better relaxation, thereby ensuring the isolation of the heavy hole band in the energy band from other energy bands, effectively reducing the leakage of charge carriers to other energy bands, significantly improving the internal quantum efficiency, and making the luminous brightness of the red LED higher.

[0014] This invention also provides a method for fabricating a red LED epitaxial wafer for a display screen. Using MOCVD (metal-organic chemical vapor deposition) equipment, a buffer layer, a DBR reflective layer, an N-type confinement layer, a first N-type double-dilution waveguide layer, an N-type single-dilution waveguide layer, a second N-type double-dilution waveguide layer, a strain-improved active light-emitting layer, a first P-type double-dilution waveguide layer, a P-type single-dilution waveguide layer, a second P-type double-dilution waveguide layer, a P-type confinement layer, a P-type transition layer, and a P-type window layer are sequentially grown on a GaAs substrate.

[0015] Furthermore, the first N-type double-dilution waveguide layer uses SiH4 as the N-type dopant with a doping concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 The doping method involves dual-channel hydrogen dilution, with hydrogen flow rates of 500 sccm to 1000 sccm in both channels. The N-type single-dilution waveguide layer uses SiH4 as the N-type dopant at a concentration of 0.3 × 10⁻⁶. 18 cm -3 ~0.7×10 18 cm -3 The doping method involves single-channel hydrogen dilution with a flow rate of 300 sccm to 500 sccm. The second N-type double-dilution waveguide layer uses SiH4 as the N-type dopant with a doping concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 The doping method employs dual-channel hydrogen dilution, with hydrogen flow rates of 500 sccm to 1000 sccm in each channel. This technical solution uses a combination of dual-channel and single-channel dilution to dope the N-side waveguide layer, avoiding the risk of uneven diffusion associated with conventional direct doping. The multi-dilution doping design also mitigates the drawbacks of excess dopant diffusing into the quantum well region, avoiding brightness attenuation or reliability issues caused by simple doped waveguide layers.

[0016] Furthermore, both the quantum well and quantum barrier of the strain-enhanced light-emitting active layer are undoped; during the cycle, the quantum barrier is grown using a spring-type strain process, and the quantum well is grown using a compressive strain symmetric process.

[0017] Specifically, the spring-type strain growth process is as follows: the strain state from the 1st quantum barrier to the (n+1) / 2nd quantum barrier is a transition from compressive strain to tensile strain, and the strain state from the (n+1) / 2nd quantum barrier to the nth quantum barrier is a transition from tensile strain to compressive strain. The strain change value between each quantum barrier is 10 arcseconds to 30 arcseconds, and the compressive strain value of the 1st quantum barrier is the same as that of the mth quantum barrier.

[0018] The compressive strain symmetric growth process is as follows: the strain state from the first quantum well to the nth quantum well is all compressive strain, and the strain change value between each quantum well is 30 arcseconds to 50 arcseconds; the compressive strain value of the first quantum well is the same as that of the nth quantum well.

[0019] Furthermore, the first P-type double-dilution waveguide layer uses Cp2Mg as the P-type dopant with a doping concentration of 0.05 × 10⁻⁶. 18 cm -3 ~0.1×10 18 cm -3 The doping method involves dual-channel hydrogen dilution, with hydrogen flow rates of 500 sccm to 1000 sccm in both channels. The P-type single-dilution waveguide layer uses Cp₂Mg as the P-type dopant at a concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.5×10 18 cm -3 The doping method involves single-channel hydrogen dilution with a flow rate of 300 sccm to 500 sccm. The second P-type double-dilution waveguide layer uses Cp₂Mg as the P-type dopant with a doping concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 The doping method employs dual-channel hydrogen dilution, with hydrogen flow rates of 500 sccm to 1000 sccm in both channels. Similarly, by combining dual-channel and single-channel dilution for material doping of the P-side waveguide layer, not only can the risks of uneven diffusion caused by conventional direct doping be avoided, but also problems such as brightness attenuation or reliability issues caused by simple doped waveguide layers can be avoided, thus improving the brightness of red LEDs at large angles.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention optimizes the structure by replacing the conventional light-emitting active layer with a strain-improved light-emitting active layer. The quantum well / barrier layers are designed as a compressive strain symmetric quantum well layer and a spring-type strain quantum barrier layer, respectively. Utilizing the opposing properties of compressive and tensile strains on both sides of the spring-type strain quantum barrier layer, sufficient stress release space is provided to the barrier layer in the light-emitting region. Similar to a spring, the strain can be adjusted according to external conditions, improving the crystal quality of the epitaxial material and thus improving the full width at half maximum (FWHM) of the red LED, effectively enhancing the monochromaticity and uniformity of the red light. The bidirectional complementary lattice mismatch space formed by the spring-type strain quantum barrier layer provides better lattice relaxation, ensuring the isolation of the heavy hole band from other bands in the energy band structure, reducing carrier leakage to other bands, and improving luminous efficiency. Simultaneously, the waveguide layers on both sides of the light-emitting active region are adjusted to three-segment diluted doped waveguide layers, enhancing side light emission and improving brightness at large angles.

[0022] The present invention proposes a fabrication process design for a strain-improved active light-emitting layer structure and a multi-dilution waveguide layer structure, which can improve the shortcomings of red LEDs where the compressive strain lattice mismatch deviates from the room temperature mismatch due to the high temperature and the rise of the junction temperature during lighting. This effectively improves the monochromaticity and consistency of red light, while also enhancing the brightness and efficiency of large-angle side-emitting light. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a conventional red LED epitaxial wafer;

[0024] Figure 2 This is a schematic diagram of the structure of the red LED epitaxial wafer for the display screen of the present invention;

[0025] Figure 3 This is a schematic diagram of the strain-improved light-emitting active layer of the present invention;

[0026] Figure 4 This is a luminous intensity distribution diagram of a wafer fabricated from a red LED epitaxial wafer for the display screen of this invention;

[0027] Figure 5 The luminous intensity distribution of a wafer fabricated for a conventional red LED epitaxial wafer.

[0028] Explanation of the labels in the diagram:

[0029] 100. GaAs substrate; 101. Buffer layer; 102. DBR reflective layer; 103. N-type confinement layer; 104. N-side waveguide layer; 104-1. First N-type double-dilution waveguide layer; 104-2. N-type single-dilution waveguide layer; 104-3. Second N-type double-dilution waveguide layer; 105. Light-emitting active layer; 105-1. Strain-improved light-emitting active layer; 105-1-1. Spring-type strain quantum barrier layer; 105-1-2. Compressive strain symmetric quantum well layer; 106. P-side waveguide layer; 106-1. First P-type double-dilution waveguide layer; 106-2. P-type single-dilution waveguide layer; 106-3. Second P-type double-dilution waveguide layer; 107. P-type confinement layer; 108. P-type transition layer; 109. P-type window layer. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] In the description of this application, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application.

[0032] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0033] Please see Figures 1 to 5 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0034] An embodiment of the present invention provides a red LED epitaxial wafer for a display screen, the structural schematic of which is shown below. Figure 2 As shown, the red LED epitaxial wafer consists of, from bottom to top, a GaAs substrate 100, a buffer layer 101, a DBR reflective layer 102, an N-type confinement layer 103, a first N-type double-dilution waveguide layer 104-1, an N-type single-dilution waveguide layer 104-2, a second N-type double-dilution waveguide layer 104-3, a strain-improved active light-emitting layer 105-1, a first P-type double-dilution waveguide layer 106-1, a P-type single-dilution waveguide layer 106-2, a second P-type double-dilution waveguide layer 106-3, a P-type confinement layer 107, a P-type transition layer 108, and a P-type window layer 109.

[0035] In some specific embodiments, the first N-type double-dilution waveguide layer, the N-type single-dilution waveguide layer, and the second N-type double-dilution waveguide layer are all made of (Al). x3 Ga 1-x3 ) 0.5 In 0.5 P, where x3 is set to 0.70–0.80. The thickness of the first N-type double-dilution waveguide layer is 50 nm–80 nm; the thickness of the N-type single-dilution waveguide layer is 10 nm–20 nm; and the thickness of the second N-type double-dilution waveguide layer is 20 nm–50 nm.

[0036] In some specific embodiments, the strain-enhanced light-emitting active layer is a cyclic structure of alternating spring-type strain quantum barrier layer 105-1-1 and compressive strain symmetric quantum well layer 105-1-2. In the structure of the spring-type strain quantum barrier layer, the quantum barrier material is (Al). x1 Ga 1-x1 ) 0.5 In 0.5 P, with a thickness of 8nm to 12nm, wherein x1 is set to 0.60 to 0.70; the quantum well material in the structure of the compressive strain symmetric quantum well layer is (Al). x1 Ga 1-x1 ) 0.5 In 0.5 P, with a thickness of 3nm to 6nm, where x1 is set to 0.03 to 0.09.

[0037] In some specific embodiments, the loop structure has n pairs of loops, where n ranges from 15 to 25 and is an odd number.

[0038] Furthermore, in the structure of the spring-type strain quantum barrier layer, the strain state from the 1st quantum barrier to the (n+1) / 2nd quantum barrier transitions from compressive strain to tensile strain, and the strain state from the (n+1) / 2nd quantum barrier to the nth quantum barrier transitions from tensile strain to compressive strain, with the strain change value between each quantum barrier ranging from 10 arcseconds to 30 arcseconds; the compressive strain value of the 1st quantum barrier is the same as that of the nth quantum barrier. For example, when n is 21, the strain state is sequentially increased from -100 arcseconds (compressive strain) at the 1st quantum barrier to +100 arcseconds (tensile strain) at the 11th quantum barrier. Specifically, the strain state of the first quantum barrier is set to -100 arcseconds. Starting from the second quantum barrier layer, the strain grows by increasing by 10 to 30 arcseconds for each quantum barrier until the 11th quantum barrier. When the change value is consistently 20 arcseconds, the second quantum barrier is -80 arcseconds, the third quantum barrier layer is -60 arcseconds, and so on. The strain state is then progressively decreased from +100 arcseconds (tensile strain) at the 11th quantum barrier to -100 arcseconds (compressive strain) at the 21st quantum barrier. Specifically, the strain state of the 11th quantum barrier is set to +100 arcseconds. Starting from the 12th quantum barrier layer, the strain grows by decreasing by 20 arcseconds for each quantum barrier until the 21st quantum barrier, i.e., the 12th quantum barrier is +80 arcseconds, the 13th quantum barrier layer is +60 arcseconds, and so on. Alternatively, each quantum barrier can be set with a different variation value between 10 and 30 arcseconds, but the compressive strain value of the 1st and 21st quantum barriers is the same. For example, the 1st quantum barrier is -100 arcseconds, the 2nd is -90 arcseconds, the 3rd is -70 arcseconds, the 4th is -60 arcseconds, the 5th is -30 arcseconds, the 6th is -10 arcseconds, the 7th is +20 arcseconds, the 8th is +50 arcseconds, and the 9th is +60 arcseconds. The 10th quantum barrier is +80 arcseconds, the 11th quantum barrier is +100 arcseconds, the 12th quantum barrier is +80 arcseconds, the 13th quantum barrier is +60 arcseconds, the 14th quantum barrier is +50 arcseconds, the 15th quantum barrier is +20 arcseconds, the 16th quantum barrier is 0 arcseconds, the 17th quantum barrier is -20 arcseconds, the 18th quantum barrier is -50 arcseconds, the 19th quantum barrier is -60 arcseconds, the 20th quantum barrier is -80 arcseconds, and the 21st quantum barrier is -100 arcseconds.

[0039] Furthermore, in the structure of the compressive strain symmetric quantum well layer, the strain state from the 1st quantum well to the nth quantum well is compressive strain, and the strain change value between each quantum well is 30 arcseconds to 50 arcseconds; the compressive strain value of the 1st quantum well is the same as that of the nth quantum well. For example, when n is 21, the strain state from the 1st quantum well to the 21st quantum well is compressive strain. The strain state can be increased sequentially from -800 arcseconds in the 1st quantum well to -400 arcseconds in the 11th quantum well, growing in increments of 40 arcseconds per quantum well. The strain state can be decreased sequentially from -800 arcseconds in the 11th quantum well to -800 arcseconds in the 21st quantum well, growing in increments of 40 arcseconds per quantum well. Similarly, each quantum well is given a different change value between 30 and 50 arcseconds, but the compressive strain value of the 1st and 21st quantum wells is the same.

[0040] Some embodiments of the present invention provide a method for fabricating a red LED epitaxial wafer for a display screen. Using an MOCVD apparatus, a buffer layer, a DBR reflective layer, an N-type confinement layer, a first N-type double-dilution waveguide layer, an N-type single-dilution waveguide layer, a second N-type double-dilution waveguide layer, a strain-modified active light-emitting layer, a first P-type double-dilution waveguide layer, a P-type single-dilution waveguide layer, a second P-type double-dilution waveguide layer, a P-type confinement layer, a P-type transition layer, and a P-type window layer are sequentially grown on a GaAs substrate. The method specifically includes the following steps:

[0041] (1) MOCVD is pumped to a low pressure of 50 mbar in pure H2 atmosphere, and the reaction chamber is set to 400℃. Then, the GaAs substrate is transferred to the reaction chamber through a robotic hand transfer chamber, and then the temperature is rapidly increased to 760℃~800℃ and kept constant for 4min~8min.

[0042] (2) Growth of buffer layer: The reaction chamber temperature was set to 700℃±20℃, and TMGa and AsH3 were introduced to grow a GaAs buffer layer material with a thickness of 200nm~300nm. SiH4 was used as the N-type dopant with a doping concentration of 3×10 18 cm -3 ~5×10 18 cm -3 .

[0043] (3) Growth of DBR reflective layer: The reaction chamber temperature is set to 700℃±20℃, and TMAl and AsH3 are introduced to grow AlAs material with a thickness of 40nm~50nm and a doping concentration of 1×10 18 cm -3 ~2×10 18 cm -3 Then, TMGa is introduced to grow Al with a thickness of 60nm to 65nm. y1Ga 1-y1 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~2×10 18 cm -3 The value of y1 ranges from 0.4 to 0.5; the above AlAs and Al y1 Ga 1-y1 As growth combination forms the first DBR reflective layer, and then the cycle is repeated for 30 to 35 pairs. SiH4 is used as the N-type dopant for all DBR reflective layers.

[0044] (4) Growth of N-type confinement layer: Set the temperature of the reaction chamber to 730℃±20℃, introduce TMAl, TMIn, and PH3, and grow Al with a thickness of 300nm~400nm. 0.5 In 0.5 P, with a doping concentration of 1×10 18 cm -3 ~2×10 18 cm -3 The N-type dopant is SiH4.

[0045] (5) Growth of the first N-type double-dilution waveguide layer: The reaction chamber temperature was set to 700℃±10℃. TMAl, TMGa, TMIn, and PH3 were introduced into the N-type confinement layer to grow a (Al) waveguide layer with a thickness of 50nm~80nm. x3 Ga 1-x3 ) 0.5 In 0.5 For P material, x3 is set to 0.70–0.80, and the doping concentration is 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 SiH4 was used as the N-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with the hydrogen gas flow rate of the dual pipelines being 500 sccm to 1000 sccm.

[0046] (6) Growth of N-type single-dilution waveguide layer: Set the reaction chamber temperature to 700℃±10℃, and introduce TMAl, TMGa, TMIn, and PH3 onto the first N-type double-dilution waveguide layer to grow a (Al) layer with a thickness of 10nm~20nm. x3 Ga 1-x3 ) 0.5 In 0.5 For P material, x3 is set to 0.70–0.80, and the doping concentration is 0.3 × 10⁻⁶. 18 cm -3 ~0.7×10 18 cm -3SiH4 was used as the N-type dopant, and the doping method was to use a single-pipeline hydrogen dilution with a single-pipeline hydrogen flow rate of 300 sccm to 500 sccm.

[0047] (7) Growth of the second N-type double-dilution waveguide layer: The reaction chamber temperature is set to 700℃±10℃. TMAl, TMGa, TMIn, and PH3 are introduced onto the N-type single-dilution waveguide layer to grow a (Al) layer with a thickness of 20nm~50nm. x3 Ga 1-x3 ) 0.5 In 0.5 For P material, x3 is set to 0.70–0.80, and the doping concentration is 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 SiH4 was used as the N-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with the hydrogen gas flow rate of the dual pipelines being 500 sccm to 1000 sccm.

[0048] (8) Growth of strain-improved light-emitting active layer: The reaction chamber temperature was set to 690℃±10℃. TMAl, TMGa, TMIn, and PH3 were introduced into the second N-type double-dilution waveguide layer to grow quantum wells / barriers of (Al) x1 Ga 1-x1 ) 0.5 In 0.5 P / (Al x2 Ga 1-x2 ) 0.5 In 0.5 The luminescent material of P. The quantum well is a compressive strain symmetric quantum well layer structure, and the material of the quantum well is (Al). x1 Ga 1-x1 ) 0.5 In 0.5 P, and the x1 values ​​of all components are set to 0.03–0.09, the thickness is 3 nm–6 nm, and the quantum well is undoped. The quantum barrier is a spring-strained quantum barrier layer structure, and the material of the quantum barrier is (Al). x2 Ga 1-x2 ) 0.5 In 0.5 P, and the x2 value of each component is set to 0.60-0.70, the thickness is 8nm-12nm, the quantum barrier is undoped, and the number of cycles of the compressive strain symmetric quantum well layer / spring strain quantum barrier layer is n pairs, where the value of n is in the range of 15-25 and is an odd number. Its structural schematic diagram is shown in the figure. Figure 3 As shown.

[0049] Specifically, the strain state of the spring-like quantum barrier is as follows: from the first quantum barrier to the (n+1) / 2nd quantum barrier, the strain state transitions from compressive strain to tensile strain; from the (n+1) / 2nd quantum barrier to the nth quantum barrier, the strain state transitions from tensile strain to compressive strain; and the strain change value between each quantum barrier is 10 arcseconds to 30 arcseconds; the compressive strain value of the first quantum barrier is the same as that of the nth quantum barrier.

[0050] Specifically, the growth of compressive strain symmetric quantum wells: the strain state from the first quantum well to the (n+1) / 2nd quantum well is compressive strain, and the strain change value between each quantum well is 30 arcseconds to 50 arcseconds; the compressive strain value of the first quantum well is the same as that of the nth quantum well.

[0051] (9) Growth of the first P-type double-dilution waveguide layer: The reaction chamber temperature was set to 700℃±10℃. TMAl, TMGa, TMIn, and PH3 were introduced onto the strain-improved light-emitting active layer to grow a (Al) waveguide layer with a thickness of 20nm~50nm. x3 Ga 1-x3 ) 0.5 In 0.5 For P material, x3 is set to 0.70–0.80, and the doping concentration is 0.05 × 10⁻⁶. 18 cm -3 ~0.1×10 18 cm -3 Cp2Mg was used as the P-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with the hydrogen gas flow rate of the dual pipelines being 500 sccm to 1000 sccm.

[0052] (10) Growth of P-type single-dilution waveguide layer: Set the reaction chamber temperature to 700℃±10℃, and introduce TMAl, TMGa, TMIn, and PH3 onto the first P-type double-dilution waveguide layer to grow a (Al) layer with a thickness of 10nm~20nm. x3 Ga 1-x3 ) 0.5 In 0.5 For P material, x3 is set to 0.70–0.80, and the doping concentration is 0.1 × 10⁻⁶. 18 cm -3 ~0.5×10 18 cm -3 Cp2Mg was used as the P-type dopant, and the doping method was to use single-pipe hydrogen dilution with a single-pipe hydrogen flow rate of 300 sccm to 500 sccm.

[0053] (11) Growth of a second P-type double-dilution waveguide layer: The reaction chamber temperature was set to 700℃±10℃. TMAl, TMGa, TMIn, and PH3 were introduced onto the P-type single-dilution waveguide layer to grow a (Al) layer with a thickness of 50nm~80nm. x3 Ga 1-x3 ) 0.5 In 0.5 For P material, x3 is set to 0.70–0.80, and the doping concentration is 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 Cp2Mg was used as the P-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with the hydrogen gas flow rate of the dual pipelines being 500 sccm to 1000 sccm.

[0054] (12) Growth of P-type confinement layer: Set the temperature of the reaction chamber to 730℃±20℃, introduce TMAl, TMIn, and PH3, and grow Al with a thickness of 500nm~800nm. 0.5 In 0.5 P, with a doping concentration of 0.5 × 10⁻⁶ 18 cm -3 ~1×10 18 cm -3 The p-type dopant used is Cp2Mg.

[0055] (15) Growth of P-type transition layer: Set the reaction chamber temperature to 730℃±20℃, introduce TMGa, TMAl, TMIn, and PH3, and grow a (Al) transition layer with a thickness of 10nm~20nm. x4 Ga 1-x4 ) 0.5 In 0.5 P material, doped with Cp₂Mg, with a doping concentration of 2 × 10⁻⁶. 18 cm -3 ~3×10 18 cm -3 The value of x4 ranges from 0.3 to 0.4.

[0056] (16) Growth of P-type window layer: The reaction chamber temperature was set to 690℃±20℃, and TMGa and PH3 were introduced to grow GaP material with a thickness of 4000nm~5000nm. CP2Mg was used as the P-type dopant with a doping concentration of 2×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 .

[0057] (17) Take out the wafer: After the growth is completed, reduce the temperature of the MOCVD reaction chamber to 110°C, then adjust the pressure to 1000 mbar, open the reaction chamber and take out the epitaxial wafer.

[0058] To further illustrate the present invention, a method for preparing a red LED epitaxial wafer for a display screen provided by the present invention will be described in detail below with reference to specific embodiments.

[0059] Example 1

[0060] A method for fabricating a red LED epitaxial wafer for a display screen specifically includes the following steps:

[0061] (1) MOCVD was pumped to a low pressure of 50 mbar in a pure H2 atmosphere, and the reaction chamber was set to a temperature of 400 °C. Then, the GaAs substrate was transferred to the reaction chamber by a robotic hand transfer chamber, and then the temperature was rapidly increased to 770 °C and held constant for 5 min.

[0062] (2) Growth of buffer layer: The reaction chamber was set to 700℃, and TMGa and AsH3 were introduced to grow a GaAs buffer layer material with a thickness of 200nm. SiH4 was used as the N-type dopant with a doping concentration of 3×10⁻⁶. 18 cm -3 .

[0063] (3) Growth of DBR reflective layer: The reaction chamber temperature was set to 700℃, and TMAl and AsH3 were introduced to grow AlAs material with a thickness of 40nm and a doping concentration of 2×10⁻⁶. 18 cm -3 Then, TMGa was introduced to grow Al with a thickness of 60 nm. 0.45 Ga 0.55 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 The above AlAs and Al 0.45 Ga 0.55 As growth combination forms the first DBR reflective layer, and then the cycle is repeated 30 times. The DBR reflective layer uses SiH4 as the N-type dopant.

[0064] (4) Growth of N-type confinement layer: The reaction chamber temperature was set to 730℃, and TMAl, TMIn, and PH3 were introduced to grow an Al layer with a thickness of 400 nm. 0.5 In 0.5 P, with a doping concentration of 1×10 18 cm -3 The N-type dopant is SiH4.

[0065] (5) Growth of the first N-type double-dilution waveguide layer: The reaction chamber temperature was set to 700℃. TMAl, TMGa, TMIn, and PH3 were introduced into the N-type confinement layer to grow a 50nm thick (Al) waveguide layer. 0.7 Ga 0.3 ) 0.5 In 0.5 P material, with a doping concentration of 0.1 × 10⁻⁶ 18 cm -3 SiH4 was used as the N-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with a hydrogen gas flow rate of 1000 sccm in both pipelines.

[0066] (6) Growth of N-type single-dilution waveguide layer: Set the reaction chamber temperature to 700℃, and introduce TMAl, TMGa, TMIn, and PH3 onto the first N-type double-dilution waveguide layer to grow a 10nm thick (Al) waveguide layer. 0.7 Ga 0.3 ) 0.5 In 0.5 P material, with a doping concentration of 0.3 × 10⁻⁶ 18 cm -3 SiH4 was used as the N-type dopant, and the doping method was to use a single-pipeline hydrogen dilution with a single-pipeline hydrogen flow rate of 500 sccm.

[0067] (7) Growth of the second N-type double-dilution waveguide layer: The reaction chamber temperature is set to 700℃. TMAl, TMGa, TMIn, and PH3 are introduced onto the N-type single-dilution waveguide layer to grow a 20nm thick (Al) waveguide. 0.7 Ga 0.3 ) 0.5 In 0.5 P material, with a doping concentration of 0.1 × 10⁻⁶ 18 cm -3 SiH4 was used as the N-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with the hydrogen gas flow rate of the two pipelines being 1000 sccm.

[0068] (8) Growth of strain-improved light-emitting active layer: The reaction chamber temperature is set to 690℃. TMAl, TMGa, TMIn, and PH3 are introduced into the second N-type double-dilution waveguide layer to grow quantum wells / barriers of (Al) 0.05 Ga 0.95 ) 0.5 In 0.5 P / (Al 0.7 Ga 0.3 ) 0.5 In 0.5 The luminescent material of P. The quantum well is a compressive strain symmetric quantum well layer structure, and the material of the quantum well is (Al). 0.05 Ga0.95 ) 0.5 In 0.5 P, all with a thickness of 5 nm, and the quantum well is undoped. The quantum barrier is a spring-strained quantum barrier layer structure, and the material of the quantum barrier is (Al). 0.7 Ga 0.3 ) 0.5 In 0.5 P, with a thickness of 8 nm, has an undoped quantum barrier and a cycle number of 21 pairs for the compressive strain symmetric quantum well layer / spring strain quantum barrier layer.

[0069] Specifically, when growing spring-like strain quantum barrier layers: the strain state from the 1st to the 11th quantum barrier transitions from compressive strain to tensile strain, and the strain state from the 11th to the 21st quantum barrier transitions from tensile strain to compressive strain, with a strain change of 20 arcseconds between each quantum barrier; the compressive strain value of the 1st quantum barrier is the same as that of the 21st quantum barrier, both being -100 arcseconds. The strain state increases sequentially from -100 arcseconds (compressive strain) at the 1st barrier to +100 arcseconds (tensile strain) at the 11th barrier. Setting the strain state of the 1st quantum barrier to -100 arcseconds, the growth proceeds from the 2nd quantum barrier layer onwards, increasing by 20 arcseconds for each quantum barrier up to the 11th quantum barrier; that is, the 2nd quantum barrier is -80 arcseconds, the 3rd quantum barrier is -60 arcseconds, and so on. Subsequently, the strain state decreases sequentially from the 11th barrier (tensile strain, +100 arcseconds) to the 21st barrier (compressive strain, -100 arcseconds). The strain state of the 11th quantum barrier is set to +100 arcseconds. Starting from the 12th quantum barrier, the strain increases by 20 arcseconds per quantum barrier until the 21st quantum barrier, i.e., the 12th quantum barrier is +80 arcseconds, the 13th quantum barrier is +60 arcseconds, and so on.

[0070] Specifically, during the growth of the compressive strain symmetric quantum well layer: the strain state from the 1st to the 11th quantum well is compressive strain, and the strain change between each quantum well is 40 arcseconds; the compressive strain value of the 1st quantum barrier is the same as that of the 21st quantum barrier, both being -800 arcseconds. The strain state increases sequentially from -800 arcseconds in the 1st quantum well to -400 arcseconds in the 11th quantum well, increasing by 40 arcseconds for each quantum well. Subsequently, the strain state decreases sequentially from -800 arcseconds in the 11th quantum well to -800 arcseconds in the 21st quantum well, decreasing by 40 arcseconds for each quantum well.

[0071] (9) Growth of the first P-type double-dilution waveguide layer: The reaction chamber temperature was set to 700℃. TMAl, TMGa, TMIn, and PH3 were introduced onto the strain-improved light-emitting active layer to grow a 20nm thick (Al) waveguide layer. 0.7 Ga0.3 ) 0.5 In 0.5 P material, with a doping concentration of 0.05 × 10⁻⁶. 18 cm -3 Cp2Mg was used as the P-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with a hydrogen gas flow rate of 1000 sccm in both pipelines.

[0072] (10) Growth of P-type single-dilution waveguide layer: Set the reaction chamber temperature to 700℃, and introduce TMAl, TMGa, TMIn, and PH3 onto the first P-type double-dilution waveguide layer to grow a 10nm thick (Al) waveguide layer. 0.7 Ga 0.3 ) 0.5 In 0.5 P material, with a doping concentration of 0.1 × 10⁻⁶ 18 cm -3 Cp2Mg was used as the P-type dopant, and the doping method was to use single-pipe hydrogen dilution with a single-pipe hydrogen flow rate of 500 sccm.

[0073] (11) Growth of a second P-type double-dilution waveguide layer: The reaction chamber temperature was set to 700℃. TMAl, TMGa, TMIn, and PH3 were introduced into the P-type single-dilution waveguide layer to grow a 50nm thick (Al) waveguide. 0.7 Ga 0.3 ) 0.5 In 0.5 P material, with a doping concentration of 0.1 × 10⁻⁶ 18 cm -3 Cp2Mg was used as the P-type dopant, and the doping method was to use a dual-pipeline hydrogen dilution, with the hydrogen gas flow rate in both pipelines being 1000 sccm.

[0074] (12) Growth of P-type confinement layer: The reaction chamber temperature was set to 730℃, and TMAl, TMIn, and PH3 were introduced to grow an Al layer with a thickness of 500 nm. 0.5 In 0.5 P, with a doping concentration of 1×10 18 cm -3 The p-type dopant used is Cp2Mg.

[0075] (15) Growth of P-type transition layer: Set the reaction chamber temperature to 730℃, introduce TMGa, TMAl, TMIn, and PH3, and grow a 20nm thick (Al) transition layer. 0.35 Ga 0.65 ) 0.5 In 0.5 P material, doped with Cp₂Mg, with a doping concentration of 3 × 10⁻⁶. 18 cm -3 .

[0076] (16) Growth of P-type window layer: The reaction chamber temperature was set to 690℃, and TMGa and PH3 were introduced to grow GaP material with a thickness of 5000nm. CP2Mg was used as the P-type dopant with a doping concentration of 3×10⁻⁶. 18 cm -3 .

[0077] (17) Take out the wafer: After the growth is completed, reduce the temperature of the MOCVD reaction chamber to 110°C, then adjust the pressure to 1000 mbar, open the reaction chamber and take out the epitaxial wafer.

[0078] Comparative Example 1

[0079] A conventional red LED epitaxial wafer is prepared using existing conventional methods.

[0080] The red LED epitaxial wafers prepared in Example 1 and Comparative Example 1 were respectively fabricated into half-cut wafer chips. The luminous brightness of the wafer chips was tested using mapping, and the results are as follows. Figure 4 and Figure 5 As shown.

[0081] from Figure 4 and Figure 5 The test results show that the epitaxial wafer prepared by the method of the present invention exhibits excellent uniformity of brightness span within the wafer and good monochromaticity of the light source. In contrast, conventional red LEDs, due to strain deviation caused by heat generation at the junction temperature during illumination, show significant dispersion in their luminous brightness, resulting in uneven brightness and an overall brightness lower than that of the epitaxial wafer in Example 1 of the present invention. Therefore, the present invention, through structural optimization and preparation method optimization, can significantly improve the monochromaticity and large-angle luminous brightness of red LEDs.

[0082] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A red LED epitaxial wafer for a display screen, characterized in that, The red LED epitaxial wafer consists of, from bottom to top, a GaAs substrate, a buffer layer, a DBR reflective layer, an N-type confinement layer, a first N-type double-dilution waveguide layer, an N-type single-dilution waveguide layer, a second N-type double-dilution waveguide layer, a strain-improved light-emitting active layer, a first P-type double-dilution waveguide layer, a P-type single-dilution waveguide layer, a second P-type double-dilution waveguide layer, a P-type confinement layer, a P-type transition layer, and a P-type window layer. The strain-enhanced light-emitting active layer is a cyclic structure consisting of alternating spring-type strain quantum barrier layers and compressive strain symmetric quantum well layers; the number of cycles in the cyclic structure is n pairs. In the structure of the spring-type strain quantum barrier layer, the strain state from the 1st quantum barrier to the (n+1) / 2nd quantum barrier is from compressive strain to tensile strain, and the strain state from the (n+1) / 2nd quantum barrier to the nth quantum barrier is from tensile strain to compressive strain, and the strain change value between each quantum barrier is 10 arcseconds to 30 arcseconds. The compressive strain value of the first quantum barrier is the same as that of the nth quantum barrier; In the structure of the compressive strain symmetric quantum well layer, the strain state from the first quantum well to the nth quantum well is compressive strain, and the strain change value between each quantum well is 30 arcseconds to 50 arcseconds; the compressive strain value of the first quantum well is the same as that of the nth quantum well. The first N-type double-dilution waveguide layer, the second N-type double-dilution waveguide layer, the first P-type double-dilution waveguide layer, and the second P-type double-dilution waveguide layer were prepared using an MOCVD device, wherein the double-dilution doping method was to use dual-pipeline hydrogen dilution; The N-type and P-type single-dilution waveguide layers were prepared using an MOCVD device, wherein the single-dilution doping method was to use single-pipe hydrogen dilution.

2. The red LED epitaxial wafer for a display screen according to claim 1, characterized in that, The first N-type double-dilution waveguide layer, the N-type single-dilution waveguide layer, the second N-type double-dilution waveguide layer, the first P-type double-dilution waveguide layer, the P-type single-dilution waveguide layer, and the second P-type double-dilution waveguide layer are all made of (Al). x3 Ga 1-x3 ) 0.5 In 0.5 P, where x3 is set to 0.70–0.80; the thickness of the first N-type double-dilution waveguide layer is 50 nm–80 nm; the thickness of the N-type single-dilution waveguide layer is 10 nm–20 nm; the thickness of the second N-type double-dilution waveguide layer is 20 nm–50 nm; the thickness of the first P-type double-dilution waveguide layer is 20 nm–50 nm; the thickness of the P-type single-dilution waveguide layer is 10 nm–20 nm; and the thickness of the second P-type double-dilution waveguide layer is 50 nm–80 nm.

3. The red LED epitaxial wafer for a display screen according to claim 1, characterized in that, In the structure of the spring-loaded strain quantum barrier layer, the material of the quantum barrier is (Al). x2 Ga 1-x2 ) 0.5 In 0.5 P, with a thickness of 8nm to 12nm, wherein x2 is set to 0.60 to 0.70; the material of the quantum well in the structure of the compressive strain symmetric quantum well layer is (Al). x1 Ga 1-x1 ) 0.5 In 0.5 P, with a thickness of 3nm to 6nm, where x1 is set to 0.03 to 0.

09.

4. The red LED epitaxial wafer for a display screen according to claim 1, characterized in that, The loop structure has n pairs of loops, where n ranges from 15 to 25 and is an odd number.

5. A method for preparing a red LED epitaxial wafer for a display screen according to any one of claims 1 to 4, characterized in that, Using an MOCVD device, a buffer layer, a DBR reflective layer, an N-type confinement layer, a first N-type double-dilution waveguide layer, an N-type single-dilution waveguide layer, a second N-type double-dilution waveguide layer, a strain-improved light-emitting active layer, a first P-type double-dilution waveguide layer, a P-type single-dilution waveguide layer, a second P-type double-dilution waveguide layer, a P-type confinement layer, a P-type transition layer, and a P-type window layer are sequentially grown on a GaAs substrate.

6. The method for preparing a red LED epitaxial wafer for a display screen according to claim 5, characterized in that, The first N-type double-dilution waveguide layer uses SiH4 as the N-type dopant with a doping concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 The doping method involves dual-channel hydrogen dilution, with hydrogen flow rates of 500 sccm to 1000 sccm in both channels. The N-type single-dilution waveguide layer uses SiH4 as the N-type dopant at a concentration of 0.3 × 10⁻⁶. 18 cm -3 ~0.7×10 18 cm -3 The doping method involves single-channel hydrogen dilution with a flow rate of 300 sccm to 500 sccm. The second N-type double-dilution waveguide layer uses SiH4 as the N-type dopant with a doping concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 The doping method involves using a dual-pipeline hydrogen dilution system, with each pipeline having a hydrogen flow rate of 500 sccm to 1000 sccm.

7. A method for preparing a red LED epitaxial wafer for a display screen according to claim 5, characterized in that, Both the quantum well and quantum barrier of the strain-enhanced light-emitting active layer are undoped; during the cycle, the quantum barrier is grown using a spring-type strain process, and the quantum well is grown using a compressive strain symmetric process.

8. A method for preparing a red LED epitaxial wafer for a display screen according to claim 5, characterized in that, The first P-type double-dilution waveguide layer uses Cp2Mg as the P-type dopant with a doping concentration of 0.05 × 10⁻⁶. 18 cm -3 ~0.1×10 18 cm -3 The doping method involves dual-channel hydrogen dilution, with hydrogen flow rates of 500 sccm to 1000 sccm in both channels. The P-type single-dilution waveguide layer uses Cp₂Mg as the P-type dopant at a concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.5×10 18 cm -3 The doping method involves single-channel hydrogen dilution with a flow rate of 300 sccm to 500 sccm. The second P-type double-dilution waveguide layer uses Cp₂Mg as the P-type dopant with a doping concentration of 0.1 × 10⁻⁶. 18 cm -3 ~0.2×10 18 cm -3 The doping method involves using a dual-pipeline hydrogen dilution system, with each pipeline having a hydrogen flow rate of 500 sccm to 1000 sccm.

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