Red light RCLED epitaxial wafer with improved light efficiency and preparation method thereof

Abstract

The present application relates to the technical field of LED, and particularly relates to a red light RCLED epitaxial wafer for improving light efficiency and a preparation method thereof, wherein the red light RCLED epitaxial wafer is grown from bottom to top on an N-type GaAs substrate and sequentially includes a buffer layer, an N-DBR, an N-type confinement layer, a light-emitting active layer, a P-type confinement layer, a unidirectional transparent conductive mirror layer, a secondary buffer layer, an in-situ oxidation preset P-DBR layer, a P-type transition layer, a P-type window layer and a P-type contact layer. In the present application, the ITO / IZO unidirectional transparent conductive mirror layer is introduced in the conventional red light RCLED process, and the in-situ oxidation preset process is used to grow the P-DBR, so that the problems of the decline of material crystal quality caused by the excessive number of P-DBR and the insufficient light efficiency caused by the insufficient number of P-DBR in the conventional red light RCLED process can be solved.

Description

Technical Field

[0001] This invention relates to the field of LED technology, specifically to a red RCLED epitaxial wafer with improved luminous efficacy and its preparation method. Background Technology

[0002] In the field of red LED technology, traditional devices generally face key bottlenecks such as low luminous efficiency, large beam divergence angle, and poor spectral stability as they move towards miniaturization and integration. Especially in high-end applications such as full-color LED displays and short-range optical communication, the low external quantum efficiency (typically <5%) of red LED devices has become one of the core issues restricting their performance. To address these problems, resonant cavity light-emitting diodes (RCLEDs) are rapidly developing as a high-performance alternative. However, high-resolution displays require more red LED chips, occupying more chip area, leading to continuously rising costs. Furthermore, in applications such as high-end optical communication, high-precision sensing, and biomedical detection, which demand wide spectral lines and small-angle light intensity, the performance of mainstream red RCLEDs currently on the market remains relatively poor. In existing technologies, the epitaxial structure of conventional red RCLEDs is as follows: Figure 1 As shown, from bottom to top, the structure includes an N-type GaAs substrate 100, a buffer layer 101, an N-DBR 102, an N-type confinement layer 103, a light-emitting active layer 104, a P-type confinement layer 105, a P-DBR 106, a P-type transition layer 107, a P-type window layer 108, and a P-type contact layer 109. The microcavity structure formed between the P-DBR and N-DBR can enhance the luminous intensity of the device. However, as the number of P-DBRs increases, problems such as lattice mismatch and material brittleness arise, leading to a decrease in epitaxial crystal quality, reduced luminous efficiency, and a series of reliability issues. Conversely, if the number of P-DBRs is too small, the reflection effect in the resonant cavity will be poor, resulting in insufficient brightness. Furthermore, in the chip manufacturing process of high-efficiency red RCLEDs, lateral oxidation technology is required. However, the AlAs and AlGaAs materials in the P-DBR structure are extremely unstable due to the corrosion rate of wet oxidation in the oxidation furnace. This results in the uncontrolled size of the oxidation pores, which often deviates from the size requirements, thus failing to achieve the effect of oxidation limitation to improve current injection.

[0003] Therefore, developing a red RCLED epitaxial wafer that can improve luminous efficiency is of great significance for applications requiring high spectral linewidth and small-angle light intensity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a red RCLED epitaxial wafer with improved luminous efficiency and its preparation method. This red RCLED epitaxial wafer has high luminous efficiency, good stability and uniformity, and is suitable for applications requiring wide spectral linewidth and high light intensity at small angles.

[0005] The first objective of this invention is to provide a red RCLED epitaxial wafer with improved luminous efficiency, wherein a buffer layer, an N-DBR (N-type Bragg reflector layer), an N-type confinement layer, a light-emitting active layer, a P-type confinement layer, a unidirectional transparent conductive mirror layer, a secondary buffer layer, an in-situ oxidized pre-placed P-DBR layer, a P-type transition layer, a P-type window layer, and a P-type contact layer are grown sequentially from bottom to top starting from an N-type GaAs substrate. The unidirectional transparent conductive reflective mirror layer has a periodic cyclic structure of ITO (indium tin oxide) and IZO (indium zinc oxide); The in-situ oxidized pre-placed P-DBR layer is AlAs and Al. 0.45 Ga 0.55 As a periodic cyclic structure.

[0006] This invention is based on conventional red RCLEDs. After epitaxial growth of the P-AlInP confinement layer, an ITO / IZO unidirectional transparent conductive mirror layer is deposited by magnetron sputtering, followed by secondary epitaxial material growth. This not only improves the problems of lattice mismatch and material brittleness caused by the increase in the number of P-DBRs in conventional processes, but also enhances the mode density of the cavity mode at the corresponding wavelength by introducing ITO / IZO as the unidirectional transparent conductive mirror layer, suppresses the light intensity output corresponding to other divergence angles, and improves the power density of the concentrated normal light intensity. Thus, it is possible to significantly improve the luminous efficiency even with a smaller number of P-DBRs.

[0007] Furthermore, in the unidirectional transparent conductive reflective mirror layer, the thickness of the single-layer ITO material is 80nm to 100nm, the sheet resistance is 10Ω / sq to 15Ω / sq, and the transmittance is 97.5% to 99.5%; the thickness of the single-layer IZO material is 15nm to 20nm, the sheet resistance is 6Ω / sq to 8Ω / sq, and the transmittance is 96% to 99%.

[0008] Furthermore, the material of the secondary buffer layer is Al. 0.5 Ga 0.5 As material, with a thickness of 100nm to 300nm and a doping concentration of 1×10⁻⁶. 18 cm -3 ~2×10 18 cm -3 Cp2Mg was used as the P-type dopant.

[0009] Furthermore, in the in-situ oxidized pre-placed P-DBR layer, the thickness of the single AlAs layer is 40nm to 45nm, and the thickness of the single Al layer is... 0.45 Ga 0.55 The thickness of As is 48nm to 53nm, and the AlAs layer and Al 0.45 Ga 0.55 The doping concentration of the As layer is 1×10⁻⁶. 18cm -3 ~3×10 18 cm -3 All of them used Cp2Mg as the P-type dopant.

[0010] The second objective of this invention is to provide a method for fabricating a red RCLED epitaxial wafer with improved luminous efficiency, comprising the following steps: using an MOCVD (metal-organic chemical vapor deposition) apparatus, sequentially growing a buffer layer, an N-DBR, an N-type confinement layer, a light-emitting active layer, a P-type confinement layer, a unidirectional transparent conductive mirror layer, a secondary buffer layer, an in-situ oxidized pre-placed P-DBR layer, a P-type transition layer, a P-type window layer, and a P-type contact layer on an N-type GaAs substrate; wherein... The unidirectional transparent conductive reflective mirror layer is obtained by removing the epitaxial wafer from the MOCVD reaction chamber after the P-type confinement layer is grown epitaxially, and then depositing an ITO / IZO thin film on the P-type confinement layer as a periodic cyclic structure using magnetron sputtering technology. This invention uses an ITO / IZO unidirectional transparent conductive reflective mirror layer and an enhanced resonant cavity structure and process with secondary epitaxial growth, which can effectively solve the problems of decreased material crystal quality due to an excessive number of P-DBRs (P-type Bragg reflective layers) and insufficient luminous efficiency due to an insufficient number of P-DBRs in conventional processes. It can improve the luminous efficiency of the device while taking into account the quality of the epitaxial crystal.

[0011] The in-situ oxidation pre-placed P-DBR layer is obtained using an in-situ oxidation pre-placement process. This invention performs in-situ oxidation of the P-DBR material during epitaxial growth, which facilitates uniform control of the oxidation pore size in the lateral oxidation process of AlAs and AlGaAs materials during subsequent chip fabrication, thereby improving the stability and uniformity of the device fabrication process.

[0012] Furthermore, the fabrication process of the unidirectional transparent conductive reflective mirror layer is as follows: after the P-type confinement layer is grown, the temperature of the MOCVD reaction chamber is reduced to 110℃±5℃, and then the pressure is adjusted to 1000mbar±20mbar. The reaction chamber is opened, the epitaxial wafer is taken out, and the epitaxial wafer is transferred to the sputtering vacuum chamber. Using magnetron sputtering technology, a periodically cyclic ITO / IZO thin film is deposited on the epitaxial P-type confinement layer after one epitaxial growth is completed, with a cycle number of 4 to 6 pairs.

[0013] Furthermore, the thickness of the monolayer ITO film is 80nm–100nm, the sheet resistance is 10Ω / sq–15Ω / sq, the transmittance is 97.5%–99.5%, the sputtering power is 450W–500W, and the oxygen flow rate is 0.2sccm–0.5sccm; the thickness of the monolayer IZO film is 15nm–20nm, the sheet resistance is 6Ω / sq–8Ω / sq, the transmittance is 96%–99%, the sputtering power is 500W–550W, and the oxygen flow rate is 6sccm–10sccm.

[0014] Furthermore, the growth step of the secondary buffer layer is as follows: the epitaxial wafer after magnetron sputtering deposition of the unidirectional transparent conductive mirror layer is reintroduced into the MOCVD reaction chamber. The reaction chamber pressure is set to 50 mbar ± 2 mbar, and the reaction chamber temperature is set to 720℃ ± 20℃. TMAl, TMGa, and AsH3 materials are introduced onto the unidirectional transparent conductive mirror layer to grow an Al layer with a thickness of 100 nm to 300 nm. 0.5 Ga 0.5 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~2×10 18 cm -3 Cp2Mg was used as the P-type dopant.

[0015] Furthermore, the in-situ oxidation pre-placed P-DBR layer growth step is as follows: setting the reaction chamber temperature to 710℃±10℃, introducing TMAl and AsH3 onto the secondary buffer layer, and growing AlAs material with a thickness of 40nm~45nm with a doping concentration of 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 After the AlAs material is grown, the flow of the Al source material TMAl is stopped for 2 to 5 seconds. During the pause, high-flow-rate AsH3 and high-flow-rate CCl4 are introduced. After the pause, the growth of Al material with a thickness of 48 nm to 53 nm is resumed. 0.45 Ga 0.55 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~3×10 18 cm -3After completing the growth of the first pair of P-DBR layers, the cycle is repeated for 9 to 17 pairs. This invention employs an in-situ oxidation pre-treatment process at the AlAs and AlGaAs layer interface. After AlAs material growth is complete, growth is paused, and high-flow-rate AsH3 and CCl4 are introduced. The AsH3 pyrolysis and CCl4 decomposition reactions create an in-situ oxidation treatment on the AlAs and AlGaAs surface layers, facilitating subsequent lateral oxidation extension in chip manufacturing. This technology effectively ensures that the wet oxidation pore size is uniform at each location during lateral oxidation processes in subsequent chip fabrication, avoiding uneven pore size and thus limiting the lateral expansion of charge carriers, forcing them to recombine within the active region. Under the action of the oxidation pores, non-radiative recombination on the sidewalls is reduced, leakage current is decreased, and carrier injection and utilization efficiency are improved, thereby further enhancing luminous efficacy.

[0016] Furthermore, during the pause, the flow rate of AsH3 is 500 sccm to 800 sccm, and the flow rate of CCl4 is 20 sccm to 50 sccm; the in-situ oxidized pre-placed P-DBR layers all use Cp2Mg as the P-type dopant.

[0017] Compared with the prior art, the present invention has the following advantages: 1. This invention introduces an ITO / IZO unidirectional transparent conductive reflective mirror layer into the conventional red RCLED process, followed by secondary epitaxial growth to form an enhanced resonant cavity structure and process. This effectively solves the problems of decreased material crystal quality due to an excessive number of P-DBRs and insufficient luminous efficiency due to an insufficient number of P-DBRs in the conventional process, thereby improving the epitaxial crystal quality and the luminous efficiency of the device.

[0018] 2. This invention optimizes the process for preparing P-DBR structures by introducing an in-situ oxidation pre-process. This process allows for the pre-oxidation of P-DBR materials during epitaxial growth, which facilitates uniform control of the oxidation aperture in the lateral oxidation operation of AlAs and AlGaAs materials during subsequent chip fabrication. This not only improves the stability and uniformity of the device process but also reduces non-radiative recombination on the sidewalls, decreases leakage current, and improves carrier injection and utilization efficiency, thereby further enhancing optical efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a conventional red RCLED epitaxial wafer; Figure 2 This is a schematic diagram of the structure of the red RCLED epitaxial wafer of the present invention; Figure 3 This is a graph showing the emission angle and light intensity of the red RCLED of the present invention; Figure 4 This is a graph showing the emission angle and luminous intensity of a conventional red RCLED.

[0020] Explanation of the labels in the diagram: 100. N-type GaAs substrate; 101. Buffer layer; 102. N-DBR; 103. N-type confinement layer; 104. Light-emitting active layer; 105. P-type confinement layer; 106. P-DBR; 107. P-type transition layer; 108. P-type window layer; 109. P-type contact layer; 110. One-way transparent conductive mirror layer; 111. Secondary buffer layer; 112. In-situ oxidized pre-placed P-DBR layer; 113. ITO layer; 114. IZO layer. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] One embodiment of the present invention provides a red RCLED epitaxial wafer with improved luminous efficiency, the structural schematic diagram of which is shown below. Figure 2As shown, starting from the N-type GaAs substrate 100, the following layers are grown sequentially from bottom to top: buffer layer 101, N-DBR 102, N-type confinement layer 103, light-emitting active layer 104, P-type confinement layer 105, unidirectional transparent conductive mirror layer 110, secondary buffer layer 111, in-situ oxidized pre-placed P-DBR layer 112, P-type transition layer 107, P-type window layer 108, and P-type contact layer 109.

[0026] In some embodiments, the unidirectional transparent conductive reflective mirror layer is an ITO / IZO periodic cyclic structure, including an ITO layer 113 and an IZO layer 114, with 4 to 6 cyclic pairs. The thickness of a single ITO layer is 80 nm to 100 nm, the sheet resistance is 10 Ω / sq to 15 Ω / sq, and the transmittance is 97.5% to 99.5%. The thickness of a single IZO layer is 15 nm to 20 nm, the sheet resistance is 6 Ω / sq to 8 Ω / sq, and the transmittance is 96% to 99%.

[0027] In some embodiments, the material of the secondary buffer layer is Al. 0.5 Ga 0.5 As material, with a thickness of 100nm to 300nm and a doping concentration of 1×10⁻⁶. 18 cm -3 ~2×10 18 cm -3 Cp2Mg was used as the P-type dopant.

[0028] In some embodiments, the in-situ oxidized pre-placed P-DBR layer is AlAs and Al 0.45 Ga 0.55 The As exhibits a periodic cyclic structure with 10 to 18 cycle pairs. The thickness of a single AlAs layer is 40 nm to 45 nm. 0.45 Ga 0.55 The thickness of As is 48nm to 53nm, and the AlAs layer and Al 0.45 Ga 0.55 The doping concentration of the As layer is 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 All of them use Cp2Mg as the P-type dopant.

[0029] Another embodiment of the present invention provides a method for fabricating a red RCLED epitaxial wafer with improved luminous efficiency. The method involves using an MOCVD apparatus to sequentially grow a buffer layer, an N-DBR, an N-type confinement layer, a light-emitting active layer, a P-type confinement layer, a unidirectional transparent conductive mirror layer, a secondary buffer layer, an in-situ oxidized pre-placed P-DBR layer, a P-type transition layer, a P-type window layer, and a P-type contact layer on an N-type GaAs substrate; including the following steps: (1) MOCVD is pumped to a low pressure of 50mbar±2mbar in pure H2 atmosphere, and the reaction chamber temperature is set to 400℃±10℃. Then, the N-type GaAs substrate is transferred to the reaction chamber through a mechanical hand transfer chamber, and then the temperature is rapidly raised to 730℃±20℃ and held constant for 4min~6min.

[0030] (2) Growth of buffer layer: The reaction chamber temperature was set to 700℃±20℃. TMGa and AsH3 were introduced into the N-type GaAs substrate to grow a GaAs buffer layer material with a thickness of 100nm~300nm. SiH4 was used as the N-type dopant with a doping concentration of 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 .

[0031] (3) Growth of N-DBR: The reaction chamber temperature is set to 700℃±20℃, and TMAl and AsH3 are introduced into the buffer layer to grow AlAs material with a thickness of 40nm~45nm and a doping concentration of 1×10 18 cm -3 ~3×10 18 cm -3 Then TMGa was introduced to grow Al with a thickness of 48nm to 53nm. 0.45 Ga 0.55 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~2×10 18 cm -3 The above AlAs and Al 0.45 Ga 0.55 As growth combines to form the first pair of N-DBRs, and then the cycle is repeated 15 to 20 times to form the combined structure. All N-DBRs use SiH4 as the N-type dopant.

[0032] (4) Growth of N-type confinement layer: Set the temperature of the reaction chamber to 730℃±20℃, introduce TMAl, TMIn and PH3 into the N-DBR, and grow Al with a thickness of 200nm~300nm. 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.

[0033] (5) Growth of the luminescent active layer: The reaction chamber temperature is set to 700℃±20℃. TMAl, TMGa, TMIn, and PH3 are introduced into the N-type confinement layer. The growth trap and barrier are respectively (Al x1 Ga1-x1 ) 0.5 In 0.5 P / (Al y1 Ga 1-y1 ) 0.5 In 0.5 The P-type quantum well material has a single-layer well thickness of 2.5 nm to 4.5 nm, where x1 ranges from 0.03 to 0.09, a single-layer barrier thickness of 5 nm to 8 nm, where y1 ranges from 0.6 to 0.7, a period number of 15 to 25 pairs, and an undoped luminescent region.

[0034] (6) Growth of P-type confinement layer: Set the temperature of the reaction chamber to 730℃±20℃, introduce TMAl, TMIn, and PH3 into the light-emitting active layer, and grow Al with a thickness of 400nm~900nm. 0.5 In 0.5 P material, with a doping concentration of 0.5 × 10⁻⁶ 18 cm -3 ~0.9×10 18 cm -3 The p-type dopant used is Cp2Mg.

[0035] (7) Take out the wafer at one time: lower the temperature of the MOCVD reaction chamber to 110℃±5℃, then adjust the pressure to 1000mbar±20mbar, open the reaction chamber and take out the epitaxial wafer.

[0036] (8) Magnetron sputtering deposition of a unidirectional transparent conductive reflective mirror layer: The epitaxial wafer is introduced into the sputtering vacuum chamber, and magnetron sputtering is used to deposit an ITO / IZO thin film as a transparent conductive reflective mirror layer with a periodic cyclic structure on the P-type confinement layer after one epitaxial growth. The number of cyclic pairs is 4 to 6. The thickness of the single-layer ITO material is 80 nm to 100 nm, the sheet resistance is 10 Ω / sq to 15 Ω / sq, the transmittance is 97.5% to 99.5%, the sputtering power is 450 W to 500 W, and the oxygen flow rate is 0.2 sccm to 0.5 sccm; the thickness of the single-layer IZO material is 15 nm to 20 nm, the sheet resistance is 6 Ω / sq to 8 Ω / sq, the transmittance is 96% to 99%, the sputtering power is 500 W to 550 W, and the oxygen flow rate is 6 sccm to 10 sccm.

[0037] (9) Preparation for secondary MOCVD epitaxy: After the preparation of the unidirectional transparent conductive reflective mirror layer is completed, the epitaxial wafer is returned to the MOCVD reaction chamber for secondary epitaxial growth. The reaction chamber is evacuated to a low pressure of 50 mbar ± 2 mbar in H2 atmosphere, and the reaction chamber temperature is set to 400℃ ± 10℃. Then, the epitaxial wafer to be grown for the second time is transferred into the reaction chamber through the transfer chamber of the robotic arm, and then the temperature is rapidly raised to 720℃ ± 20℃ and maintained at a constant temperature for 2 min to 5 min.

[0038] (10) Growth of a secondary buffer layer: On the unidirectional transparent conductive reflective mirror layer, TMAl, TMGa, and AsH3 are introduced to grow Al. 0.5 Ga 0.5 As material, with a thickness of 100nm to 300nm and a doping concentration of 1×10⁻⁶. 18 cm -3 ~2×10 18 cm -3 The p-type dopant used is Cp2Mg.

[0039] (11) Growth of in-situ oxidized pre-placed P-DBR layer: The reaction chamber temperature is set to 710℃±10℃. TMAl and AsH3 are introduced into the secondary buffer layer to grow AlAs material with a thickness of 40nm~45nm and a doping concentration of 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 After the AlAs material is grown, the flow of the Al source material TMAl is stopped for 2-5 seconds. During this pause, high flow rates of AsH3 and CCl4 are introduced. The flow rate of AsH3 is 500-800 sccm, and the flow rate of CCl4 is 20-50 sccm. After the in-situ oxidation pre-conditioning process is completed, AlAs with a thickness of 48-53 nm is grown again. 0.45 Ga 0.55 As material, Al 0.45 Ga 0.55 The doping concentration of the As layer is 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 The above AlAs and Al 0.45 Ga 0.55 As is combined with in-situ oxidation pre-planting process to grow and combine to form the first pair of P-DBRs, and then repeat the cycle 9 to 17 times to combine the structure, and Cp2Mg is used as the P-type dopant for all P-DBRs.

[0040] (12) Growth of P-type transition layer: Set the temperature of the reaction chamber to 730℃±20℃, introduce TMGa, TMAl, TMIn, and PH3, and grow a (Al) transition layer with a thickness of 30nm~40nm. t1 Ga1 -t1 ) 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 t1 ranges from 0.15 to 0.35.

[0041] (13) Growth of P-type window layer: The reaction chamber temperature was set to 740℃±20℃, and TMGa and PH3 were introduced to grow GaP material with a thickness of 4000nm~4500nm. CP2Mg was used as the P-type dopant with a doping concentration of 2×10 18 cm -3 ~3×10 18 cm -3 .

[0042] (14) Growth of P-type contact layer: The reaction chamber temperature is set to 640℃±20℃, and TMGa and PH3 are introduced to grow GaP material with a thickness of 50nm~80nm. CBr4 is used as the P-type dopant with a doping concentration of 5×10⁻⁶. 19 cm -3 ~9×10 19 cm -3 ; (15) Take out the wafer: After the growth is completed, reduce the temperature of the MOCVD reaction chamber to 110℃±5℃, then adjust the pressure to 1000mbar±20mbar, open the reaction chamber and take out the epitaxial wafer.

[0043] The present invention will be further described below through specific embodiments: Example 1 A method for fabricating a red RCLED epitaxial wafer with improved luminous efficiency specifically includes the following steps: (1) MOCVD was pumped to a low pressure of 50 mbar in a pure H2 atmosphere, and the reaction chamber temperature was set to 400 °C. Then, the N-type GaAs substrate was transferred to the reaction chamber through a robotic hand transfer chamber, and then the temperature was rapidly increased to 740 °C and held constant for 5 min.

[0044] (2) Growth of buffer layer: The reaction chamber temperature was set to 705℃, and TMGa and AsH3 were introduced into the N-type GaAs substrate 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 2×10⁻⁶. 18cm -3 .

[0045] (3) Growth of N-DBR: The reaction chamber temperature was set to 710℃, and TMAl and AsH3 were introduced into the buffer layer to grow AlAs material with a thickness of 44nm and a doping concentration of 2×10⁻⁶. 18 cm -3 Then TMGa was introduced to grow Al with a thickness of 49 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 combines to form the first pair of N-DBRs, and then the cycle is repeated 18 times for this combination structure. All N-DBRs use SiH4 as the N-type dopant.

[0046] (4) Growth of N-type confinement layer: Set the temperature of the reaction chamber to 730℃, introduce TMAl, TMIn and PH3 into the N-DBR, and grow an Al layer with a thickness of 280nm. 0.5 In 0.5 P, with a doping concentration of 1×10 18 cm -3 The N-type dopant is SiH4.

[0047] (5) Growth of the luminescent active layer: The reaction chamber temperature is set to 700℃, and TMAl, TMGa, TMIn, and PH3 are introduced into the N-type confinement layer. The growth trap and barrier are respectively (Al 0.06 Ga 0.94 ) 0.5 In 0.5 P / (Al 0.65 Ga 0.35 ) 0.5 In 0.5 The P-type quantum well material has a single-layer well thickness of 3.9 nm, a single-layer barrier thickness of 7 nm, 20 period pairs, and an undoped luminescent region.

[0048] (6) Growth of P-type confinement layer: The reaction chamber temperature is set to 730℃, and TMAl, TMIn, and PH3 are introduced into the light-emitting active layer to grow an Al layer with a thickness of 600nm. 0.5 In 0.5 P material, with a doping concentration of 0.8 × 10⁻⁶ 18 cm -3 The p-type dopant used is Cp2Mg.

[0049] (7) Take out the wafer at one time: lower 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.

[0050] (8) Magnetron sputtering deposition of a unidirectional transparent conductive reflective mirror layer: The epitaxial wafer is introduced into the sputtering vacuum chamber, and magnetron sputtering is used to deposit an ITO / IZO thin film as a periodic cyclic transparent conductive reflective mirror layer on the P-type confinement layer after one epitaxial growth. The number of cyclic pairs is 5. The thickness of the single-layer ITO material is 80 nm, the sheet resistance is 12 Ω / sq, the transmittance is 99.0%, the sputtering power is set to 460 W, and the oxygen flow rate is 0.3 sccm; the thickness of the single-layer IZO material is 19 nm, the sheet resistance is 6.2 Ω / sq, the transmittance is 98.5%, the sputtering power is set to 510 W, and the oxygen flow rate is 7.5 sccm.

[0051] (9) Preparation for secondary MOCVD epitaxy: After the preparation of the unidirectional transparent conductive reflective mirror layer is completed, the epitaxial wafer is returned to the MOCVD reaction chamber for secondary epitaxial growth. The reaction chamber is evacuated to a low pressure of 50 mbar in H2 atmosphere, and the reaction chamber temperature is set to 400℃. Then, the epitaxial wafer to be grown for the second time is transferred to the reaction chamber through the transfer chamber of the robotic arm, and then the temperature is rapidly raised to 720℃ and maintained at a constant temperature for 4 min.

[0052] (10) Growth of a secondary buffer layer: On the unidirectional transparent conductive reflective mirror layer, TMAl, TMGa, and AsH3 are introduced to grow Al. 0.5 Ga 0.5 As material, with a thickness of 120 nm and a doping concentration of 1 × 10⁻⁶. 18 cm -3 The p-type dopant used is Cp2Mg.

[0053] (11) Growth of in-situ oxidized pre-placed P-DBR layer: The reaction chamber temperature was set to 710℃. TMAl and AsH3 were introduced into the secondary buffer layer to grow AlAs material with a thickness of 43nm and a doping concentration of 1×10⁻⁶. 18 cm -3 After the AlAs material growth was complete, the flow of the Al source material TMAl was stopped for 4 seconds. During this pause, high-flow-rate AsH3 and high-flow-rate CCl4 were introduced. The flow rate of AsH3 was 650 sccm, and the flow rate of CCl4 was 22 sccm. After the in-situ oxidation pre-conditioning process was completed, the growth of AlAs with a thickness of 49 nm was resumed. 0.45 Ga 0.55 As material, Al 0.45 Ga 0.55 The doping concentration of the As layer is 1×10⁻⁶. 18 cm -3 The above AlAs and Al 0.45 Ga 0.55As is combined with an in-situ oxidation pre-planting process to grow and combine the first pair of P-DBRs, and then the combination structure is repeated for 16 cycles, with Cp2Mg as the P-type dopant for all P-DBRs.

[0054] (12) Growth of P-type transition layer: Set the temperature of the reaction chamber to 730℃, introduce TMGa, TMAl, TMIn, and PH3, and grow a 36nm thick (Al) transition layer. 0.3 Ga 0.7 ) 0.5 In 0.5 P material, doped with Cp₂Mg, with a doping concentration of 2 × 10⁻⁶. 18 cm -3 .

[0055] (13) Growth of P-type window layer: The reaction chamber temperature was set to 750℃, and TMGa and PH3 were introduced to grow GaP material with a thickness of 4300nm. CP2Mg was used as the P-type dopant with a doping concentration of 2.3×10⁻⁶. 18 cm -3 .

[0056] (14) Growth of P-type contact layer: The reaction chamber temperature was set to 640℃, and TMGa and PH3 were introduced to grow GaP material with a thickness of 70nm. CBr4 was used as the P-type dopant with a doping concentration of 8×10⁻⁶. 19 cm -3 ; (15) 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.

[0057] Comparative Example 1 A conventional red RCLED epitaxial wafer has the following structure: Figure 1 As shown, it was prepared using conventional methods.

[0058] The emission angle and light intensity curves of the red RCLED prepared in Example 1 of this invention and the conventional red RCLED in Comparative Example 1 were measured, and the results are as follows: Figure 3 and Figure 4 As shown.

[0059] from Figure 3 and Figure 4The results show that the average light intensity of a conventional red RCLED is 3615 mcd, and the average angle θav is 32.9°. The average light intensity of the red RCLED in Example 1 of this invention is 4571 mcd, and the average angle θav is 29.5°. The average light intensity of Example 1 of this invention is 26.45% higher than that of a conventional RCLED, and the emission angle can be reduced by 10.33%. This indicates that the red RCLED prepared using the process of this invention can effectively suppress the light intensity output corresponding to other divergence angles, thereby increasing the power density of the concentrated normal light intensity and significantly improving the luminous efficacy.

[0060] 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 RCLED epitaxial wafer with improved luminous efficacy, characterized in that, Starting from the N-type GaAs substrate, the following layers are grown sequentially from bottom to top: buffer layer, N-DBR, N-type confinement layer, light-emitting active layer, P-type confinement layer, unidirectional transparent conductive mirror layer, secondary buffer layer, in-situ oxidized pre-placed P-DBR layer, P-type transition layer, P-type window layer, and P-type contact layer. The unidirectional transparent conductive reflective mirror layer has a periodic cyclic structure of ITO and IZO. The in-situ oxidized pre-placed P-DBR layer is AlAs and Al. 0.45 Ga 0.55 As a periodic cyclic structure.

2. The red RCLED epitaxial wafer with improved luminous efficiency according to claim 1, characterized in that, In the unidirectional transparent conductive reflective mirror layer, the thickness of the single-layer ITO material is 80nm to 100nm, the sheet resistance is 10Ω / sq to 15Ω / sq, and the transmittance is 97.5% to 99.5%; the thickness of the single-layer IZO material is 15nm to 20nm, the sheet resistance is 6Ω / sq to 8Ω / sq, and the transmittance is 96% to 99%.

3. The red RCLED epitaxial wafer with improved luminous efficiency according to claim 1, characterized in that, The material of the secondary buffer layer is Al. 0.5 Ga 0.5 As material, with a thickness of 100nm to 300nm and a doping concentration of 1×10⁻⁶. 18 cm -3 ~2×10 18 cm -3 Cp2Mg was used as the P-type dopant.

4. The red RCLED epitaxial wafer with improved luminous efficiency according to claim 1, characterized in that, In the in-situ oxidized pre-placed P-DBR layer, the thickness of the single AlAs layer is 40nm to 45nm, and the single Al layer... 0.45 Ga 0.55 The thickness of As is 48nm to 53nm, and the AlAs layer and Al 0.45 Ga 0.55 The doping concentration of the As layer is 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 All of them used Cp2Mg as the P-type dopant.

5. A method for preparing a red RCLED epitaxial wafer with improved luminous efficiency according to any one of claims 1 to 4, characterized in that, Includes the following steps: Using MOCVD equipment, a buffer layer, N-DBR, N-type confinement layer, light-emitting active layer, P-type confinement layer, unidirectional transparent conductive mirror layer, secondary buffer layer, in-situ oxidized pre-placed P-DBR layer, P-type transition layer, P-type window layer, and P-type contact layer were sequentially grown on an N-type GaAs substrate; among which... The unidirectional transparent conductive reflective mirror layer is obtained by removing the epitaxial wafer from the MOCVD reaction chamber after the P-type confinement layer is grown, and depositing an ITO / IZO thin film on the P-type confinement layer as a periodic cyclic structure using magnetron sputtering technology. The in-situ oxidation pre-placed P-DBR layer is obtained using an in-situ oxidation pre-placement process.

6. The method for preparing a red RCLED epitaxial wafer with improved luminous efficiency according to claim 5, characterized in that, The fabrication process of the unidirectional transparent conductive reflective mirror layer is as follows: after the P-type confinement layer is grown, the temperature of the MOCVD reaction chamber is reduced to 110℃±5℃, and then the pressure is adjusted to 1000mbar±20mbar. The reaction chamber is opened, the epitaxial wafer is taken out, and the epitaxial wafer is transferred to the sputtering vacuum chamber. Using magnetron sputtering technology, a periodically cyclic ITO / IZO thin film is deposited on the epitaxial P-type confinement layer after one epitaxial growth is completed. The number of cycles is 4 to 6 pairs.

7. The method for preparing a red RCLED epitaxial wafer with improved luminous efficiency according to claim 6, characterized in that, The thickness of a single-layer ITO film is 80nm–100nm, the sheet resistance is 10Ω / sq–15Ω / sq, the transmittance is 97.5%–99.5%, the sputtering power is 450W–500W, and the oxygen flow rate is 0.2sccm–0.5sccm; the thickness of a single-layer IZO film is 15nm–20nm, the sheet resistance is 6Ω / sq–8Ω / sq, the transmittance is 96%–99%, the sputtering power is 500W–550W, and the oxygen flow rate is 6sccm–10sccm.

8. The method for preparing a red RCLED epitaxial wafer with improved luminous efficiency according to claim 5, characterized in that, The growth steps of the secondary buffer layer are as follows: the epitaxial wafer after magnetron sputtering deposition of the unidirectional transparent conductive mirror layer is reintroduced into the MOCVD reaction chamber. The reaction chamber pressure is set to 50 mbar ± 2 mbar, and the reaction chamber temperature is set to 720℃ ± 20℃. TMAl, TMGa, and AsH3 materials are introduced onto the unidirectional transparent conductive mirror layer to grow an Al layer with a thickness of 100 nm to 300 nm. 0.5 Ga 0.5 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~2×10 18 cm -3 Cp2Mg was used as the P-type dopant.

9. The method for preparing a red RCLED epitaxial wafer with improved luminous efficiency according to claim 5, characterized in that, The growth steps of the in-situ oxidized pre-placed P-DBR layer are as follows: The reaction chamber temperature is set to 710℃±10℃; TMAl and AsH3 are introduced onto the secondary buffer layer to grow AlAs material with a thickness of 40nm~45nm and a doping concentration of 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 After the AlAs material is grown, the flow of the Al source material TMAl is stopped for 2 to 5 seconds. During the pause, high-flow-rate AsH3 and high-flow-rate CCl4 are introduced. After the pause, the growth of Al material with a thickness of 48 nm to 53 nm is resumed. 0.45 Ga 0.55 As material, with a doping concentration of 1×10⁻⁶ 18 cm -3 ~3×10 18 cm -3 After completing the growth of the first pair of P-DBR layers, the cycle is repeated for 9 to 17 pairs.

10. The method for preparing a red RCLED epitaxial wafer with improved luminous efficiency according to claim 9, characterized in that, During the pause, the flow rate of AsH3 was 500 sccm to 800 sccm, and the flow rate of CCl4 was 20 sccm to 50 sccm; the in-situ oxidized pre-placed P-DBR layers all used Cp2Mg as the P-type dopant.

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