Infrared LED epitaxial wafer for improving spectrum and preparation method thereof

Abstract

The invention relates to the technical field of LEDs, in particular to an infrared LED epitaxial wafer for improving a spectrum and a preparation method of the infrared LED epitaxial wafer. The infrared LED epitaxial wafer sequentially comprises an N-type GaAs substrate, an N-type GaAs buffer layer, an N-type current expansion layer, an N-type limiting layer, a voltage division type single-peak light-emitting layer, a P-type limiting layer, a P-type current expansion layer and a P-surface contact layer from bottom to top. The partial pressure type single-peak light-emitting layer is of a periodic structure formed by sequentially growing a fluctuation layer, a quantum well layer, a strain transition layer and a quantum barrier layer. On the basis of a conventional 940nm infrared LED epitaxial structure, the design of the partial pressure type single-peak light-emitting layer is adopted, the double-peak problem caused by abnormal light-emitting spectrum due to factors such as In component segregation local state, stress mutation energy level splitting and instability of a TMIn source supplied by a precursor can be effectively solved, the infrared LED is stable in spectrum and only has a single light-emitting peak, and the light-emitting efficiency is greatly improved. The performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of LED technology, specifically to an infrared LED epitaxial wafer with improved spectrum and its preparation method. Background Technology

[0002] Infrared LEDs (light-emitting diodes) are semiconductor light sources that emit light in the range of 780nm to 1600nm. Their core technology is based on the electroluminescence effect of III-V group compounds (such as GaAs, AlGaAs, and InGaAs). Unlike visible light LEDs, the light radiation from infrared LEDs cannot be directly observed by the human eye and must be captured by an infrared sensor. Infrared LEDs with an emission wavelength of 940nm are the most widely used infrared products, extensively applied in mobile phone cameras, security monitoring, infrared detection, infrared remote sensing, and high-speed communications.

[0003] As applications deepen, the double-peak problem in the emission spectrum of 940nm infrared LEDs has been a persistent challenge for engineers. Conventional 940nm infrared LED epitaxial structures include... Figure 1 As shown, the epitaxial layers are grown starting from the N-type GaAs substrate 100, and from bottom to top are the N-type GaAs buffer layer 101, the N-type current spreading layer 102, the N-type confinement layer 103, the multi-quantum-well light-emitting layer 104, the P-type confinement layer 105, the P-type current spreading layer 106, and the P-face contact layer 107. During the epitaxial growth process, the thickness of the quantum well structure is uneven due to material stress, or there are regions of different thicknesses in the active region, resulting in differences in the emission wavelength in different regions, thus producing a double peak. In addition, the epitaxial structure is grown using MOCVD (metal-organic chemical vapor deposition). Since the group III source TMI is a solid source material, if there is slight blockage in the TMI pipeline during the growth of the quantum well InGaAs material, it will cause fluctuations in the In composition, resulting in uneven distribution of the In composition within the quantum well and producing a double peak in the emission wavelength. Meanwhile, at a wavelength of 940 nm, quantum well InGaAs materials exhibit significant compressive stress due to the large lattice difference between the material and the substrate, which easily leads to band splitting and the generation of bimodal spectra. This bimodal problem can severely impact the normal operation of applications requiring high monochromaticity, such as optocouplers, biosensors, or communication applications. Therefore, developing an LED that can improve the spectral bimodal problem of 940 nm infrared LEDs is particularly important. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an infrared LED epitaxial wafer with improved spectrum and its preparation method. The infrared LED epitaxial wafer has a stable spectrum with only a single emission peak, effectively solving the problem of double peaks in the emission spectrum of conventional infrared LED quantum wells caused by various factors such as In composition segregation local states, stress-induced energy level splitting, and instability of the TMIn source supplied by the precursor.

[0005] The first objective of this invention is to provide an infrared LED epitaxial wafer with improved spectrum. The infrared LED epitaxial wafer grows an epitaxial layer starting from an N-type GaAs substrate, and sequentially grows an N-type GaAs buffer layer, an N-type current spreading layer, an N-type confinement layer, a voltage divider single-peak emission layer, a P-type confinement layer, a P-type current spreading layer, and a P-face contact layer from bottom to top. The voltage-divided single-peak light-emitting layer is a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially.

[0006] Based on the existing conventional 940nm infrared LED epitaxial structure, this invention first grows a fluctuation layer before growing each quantum well material InGaAs. By modifying the growth process, it can suppress the localized states formed by the inhomogeneous In composition caused by In segregation in conventional InGaAs material, which is beneficial for repairing the low In region and ensuring that the In composition in each atomic layer of the well layer is uniform. At the same time, after the growth of each quantum well InGaAs is completed, a strain transition layer is grown before the quantum barrier layer is grown. By controlling the In composition, the disadvantage of the strain between the well and the barrier in conventional 940nm infrared LED changing abruptly from compressive stress to tensile strain is improved, avoiding the spectral double peak problem caused by band splitting due to strain abruptness.

[0007] Furthermore, the number of cycle pairs in the periodic structure is 6 to 12.

[0008] Furthermore, the fluctuation layer is made of InAs and has a thickness of 5nm to 10nm in each cycle; the fluctuation layer is undoped.

[0009] Furthermore, the material of the strain transition layer is In. x1 Ga 1-x1The thickness of the AsP material in each cycle is 20nm to 30nm. The initial In composition x1 is set to 0.15. During the growth of the strain transition layer, x1 gradually decreases from 0.15 to 0 at a rate of 0.01 / s. The strain transition layer design proposed in this technical solution utilizes the tensile strain characteristic between the InGaAsP material and the GaAs substrate lattice. By decreasing the In composition while continuously increasing the pH3 during growth, the compressive strain is reduced by decreasing the lattice size through the reduction of the In composition. On the other hand, the strain mode is slowly transitioned from compressive strain to tensile strain through the compensation of the P element, rather than by abrupt stress. This effectively avoids the spectral double-peak problem caused by band splitting due to abrupt strain.

[0010] The second objective of this invention is to provide a method for fabricating an infrared LED epitaxial wafer with improved spectrum. This method utilizes an MOCVD device to sequentially grow an N-type GaAs buffer layer, an N-type current spreading layer, an N-type confinement layer, a voltage-divided single-peak emission layer, a P-type confinement layer, a P-type current spreading layer, and a P-face contact layer on an N-type GaAs substrate. The voltage-divided single-peak emission layer is a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially. The fluctuation layer, quantum well layer, and strain transition layer are all grown using a voltage-divided dual-path TMIn source tandem process.

[0011] Furthermore, the pressure-dividing dual-path TMIn source series process is as follows: two TMIn source bottles are connected in series, and the TMIn source bottle closer to the reaction chamber is set to a pressure of 200mbar to 300mbar during growth, while the TMIn source bottle farther from the reaction chamber is set to a pressure of 800mbar to 1000mbar during growth.

[0012] This invention improves the conventional single-bottle TMIn source used in epitaxial wafer fabrication by employing a dual-channel tandem TMIn source configuration. By using this dual-channel tandem TMIn source process and maintaining a pressure difference between the inlet and outlet bottles, it ensures that the TMIn source entering the reaction chamber always enters under low pressure, while a high-pressure source at the front end acts as a precursor. This improves the problem of unstable TMIn concentration entering the reaction chamber as a solid-state organometallic source, thereby preventing fluctuations in the In composition within the quantum well and reducing bimodal distribution. Furthermore, this pressure-dividing tandem technology also prevents clogging of the TMIn source pipeline during use and avoids the problem of bimodal distribution caused by increased flow rate settings at the bottom of the flask due to In composition fluctuations.

[0013] Furthermore, the growth step of the fluctuation layer is as follows: the reaction chamber temperature is set to 690℃±10℃, TMI and AsH3 are introduced, and InAs material with a thickness of 5nm~10nm is grown.

[0014] Furthermore, after the fluctuation layer growth is completed, it is annealed at an isothermal temperature of 700℃ to 720℃, while TMGa and AsH3 are introduced during the annealing process. The flow rate of TMGa is set to 40 sccm to 60 sccm, and the flow rate of AsH3 is set to 400 sccm to 600 sccm. In this technical solution, after the fluctuation layer is grown, it is annealed at an isothermal temperature of 700℃ to 720℃ and TMGa and AsH3 are introduced. With the help of the InAs cracking effect at high temperature, the broken In bonds can react with Ga and As atoms on the surface of the epitaxial layer to form an InGaAs nucleation buffer layer. This can prevent the bimodal problem caused by the random aggregation of In atoms to form high-In and low-In regions during the conventional growth of InGaAs quantum well structures.

[0015] Furthermore, the growth step of the strain transition layer is as follows: setting the reaction chamber temperature to 690℃±10℃, introducing TMI, TMGa, AsH3, and PH3, and growing an In layer with a thickness of 20nm~30nm. x1 Ga 1-x1 The AsP material has an initial In component x1 set to 0.15. During the growth of the strain transition layer, x1 gradually decreases from 0.15 to 0, and the rate of change of x1 is 0.01 / s.

[0016] Furthermore, during the growth of the strain transition layer, the initial PH3 flow rate is set to 300 sccm, and then during the growth process of the strain transition layer, the PH3 flow rate is gradually increased from 300 sccm to 600 sccm, with the rate of change being 5 sccm / s.

[0017] Compared with the prior art, the present invention has the following advantages: This invention, based on the conventional 940nm infrared LED epitaxial structure, adopts a voltage-divided single-peak emitting layer design. On one hand, by designing the voltage-divided single-peak emitting layer as a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially, the fluctuation layer is used to suppress the localized states formed by the inhomogeneity of In composition caused by In segregation in conventional InGaAs materials, thus solving the double-peak problem caused by the inconsistency of In composition in each layer of the quantum well. The strain transition layer is used to improve the shortcomings of the strain between the well and the barrier in conventional 940nm infrared LEDs, which changes abruptly from compressive stress to tensile strain, avoiding the spectral double-peak problem caused by band splitting due to strain abrupt changes. On the other hand, by using a voltage-divided dual-path TMIn source tandem process to grow the fluctuation layer, quantum well layer, and strain transition layer in the voltage-divided single-peak emitting layer, the problem of unstable concentration of TMIn as a solid organometallic source entering the reaction chamber can be improved, preventing fluctuations in In composition in the quantum well and improving double-peak. At the same time, it can prevent the double-peak problem caused by In composition fluctuations due to blockage in the pipeline or increased flow rate setting at the bottom of the TMIn source during use.

[0018] The infrared LED prepared by this invention has a stable spectrum with only a single emission peak, exhibiting excellent performance and can be applied in optocouplers, biosensors, or communication applications. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a conventional 940nm infrared LED epitaxial wafer; Figure 2 This is a schematic diagram of the structure of the infrared LED epitaxial wafer of the present invention; Figure 3 This is a schematic diagram of a loop structure of the voltage-divided single-peak light-emitting layer of the present invention; Figure 4 This is the infrared LED test spectrum of the present invention; Figure 5 This is a standard 940nm infrared LED test spectrum.

[0020] Explanation of the labels in the diagram: 100. N-type GaAs substrate; 101. N-type GaAs buffer layer; 102. N-type current spreading layer; 103. N-type confinement layer; 104. Multi-quantum-well light-emitting layer; 105. P-type confinement layer; 106. P-type current spreading layer; 107. P-face contact layer; 204. Voltage-divided single-peak light-emitting layer; 205. Fluctuation layer; 206. Quantum well layer; 207. Strain transition layer; 208. Quantum barrier 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] 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.

[0025] One embodiment of the present invention provides an infrared LED epitaxial wafer with improved spectrum, the schematic diagram of which is shown below. Figure 2 As shown, an epitaxial layer is grown starting from an N-type GaAs substrate 100, and from bottom to top, an N-type GaAs buffer layer 101, an N-type current spreading layer 102, an N-type confinement layer 103, a voltage divider single-peak light-emitting layer 204, a P-type confinement layer 105, a P-type current spreading layer 106, and a P-face contact layer 107 are grown sequentially.

[0026] Specifically, the voltage-divided single-peak emitting layer is a periodic structure consisting of a fluctuation layer 205, a quantum well layer 206, a strain transition layer 207, and a quantum barrier layer 208 grown sequentially, with 6 to 12 cycle pairs. A schematic diagram of a single cycle structure is shown below. Figure 3 As shown.

[0027] In some specific embodiments, the fluctuation layer is made of InAs and has a thickness of 5 nm to 10 nm in each cycle; the fluctuation layer is undoped.

[0028] In some specific embodiments, the material of the strain transition layer is In x1 Ga 1-x1 AsP has a thickness of 20 nm to 30 nm in each cycle. The initial In composition x1 is set to 0.15. During the growth of the strain transition layer, x1 gradually decreases from 0.15 to 0, and the rate of change of x1 is 0.01 / s.

[0029] In some specific embodiments, the fluctuation layer, quantum well layer, and strain transition layer are all grown using a pressure-divided dual-path TMIn source tandem process. This pressure-divided dual-path TMIn source tandem process involves connecting two TMIn source bottles in series. The TMIn source closer to the reaction chamber is grown at a pressure of 200-300 mbar, while the TMIn source farther from the reaction chamber is grown at a pressure of 800-1000 mbar. By optimizing the luminescent quantum well layer of a conventional 940nm infrared LED into a single-peak luminescent region grown using this pressure-divided dual-path TMIn source tandem process, the fluctuation layer addresses the problem of In segregation in InGaAs quantum well materials leading to inhomogeneity and the formation of localized states, while the strain transition layer mitigates the abrupt transition from compressive stress to tensile strain between the well and barrier layers. Ultimately, this solves the double-peak problem in the emission spectrum of conventional 940nm infrared LEDs.

[0030] In another embodiment, the present invention also provides a method for fabricating an infrared LED epitaxial wafer with improved spectrum. Using an MOCVD device, an N-type GaAs buffer layer, an N-type current spreading layer, an N-type confinement layer, a voltage-divided single-peak emission layer, a P-type confinement layer, a P-type current spreading layer, and a P-face contact layer are sequentially grown on an N-type GaAs substrate. The voltage-divided single-peak emission layer is a periodic structure formed by sequentially growing a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer. Specifically, the method includes the following steps: (1) MOCVD was pumped to a low pressure of 50 mbar in a pure H2 atmosphere, and the reaction chamber 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 700 °C and held at 700 °C for 5 min.

[0031] (2) Growth of N-type GaAs buffer layer: The reaction chamber temperature was set to 690℃±10℃, 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 1×10 18 cm-3 ~2×10 18 cm -3 .

[0032] (3) Growth of N-type current-extended layer: The reaction chamber temperature was set to 690℃±10℃, and TMGa, TMAl, and AsH3 were introduced to grow an Al layer with a thickness of 2000nm~3000nm. y1 Ga 1-y1 As material, y1 ranges from 0.1 to 0.15, and SiH4 is used as the N-type dopant with a doping concentration of 0.7 × 10⁻⁶. 18 cm -3 ~1.5×10 18 cm -3 .

[0033] (4) Growth of N-type confinement layer: Set the temperature of the reaction chamber to 720℃±10℃, introduce TMGa, TMAl, and AsH3, and grow Al with a thickness of 400nm~500nm. y2 Ga 1-y2 The material is As, where the value of y2 ranges from 0.25 to 0.50, and SiH4 is used as the N-type dopant with a doping concentration of 1×10⁻⁶. 18 cm -3 ~2×10 18 cm -3 .

[0034] (5) Growth of a pressure-partial single-peak luminescent layer: This luminescent layer is a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially, with 6 to 12 pairs of cycles. When growing the fluctuation layer, quantum well layer, and strain transition layer, two TMIn source bottles are connected in series. The TMIn source bottle closer to the reaction chamber is set to a pressure of 200 mbar to 300 mbar during growth, and the TMIn source bottle farther from the reaction chamber is set to a pressure of 800 mbar to 1000 mbar during growth. The growth of a single cycle structure specifically includes the following steps: (a) Growth of the fluctuation layer: The reaction chamber temperature is set to 690℃±10℃, and TMI and AsH3 are introduced to grow InAs material with a thickness of 5nm~10nm. After the fluctuation layer growth is completed, TMI is turned off, and the material is annealed at a constant temperature of 700℃~720℃. During the annealing process, TMI and AsH3 are introduced. The flow rate of TMI is set to 40sccm~60sccm, and the flow rate of AsH3 is set to 400sccm~600sccm. The annealing time is 4min. By taking advantage of the InAs cracking effect at high temperature, the broken In bonds can react with Ga and As atoms on the surface of the epitaxial layer to form an InGaAs nucleation buffer layer. This can prevent the random aggregation of In atoms to form high In and low In regions and the occurrence of non-uniform local states during the conventional growth of InGaAs quantum well structures. The InAs fluctuation layer is undoped. (b) Growth of quantum well layer: The reaction chamber temperature is set to 690℃±10℃, and TMGa, TMIn, and AsH3 are introduced. The growth material is In. x2 Ga 1-x2 As quantum well layer, single-layer quantum well In x2 Ga 1-x2 The thickness of As is 5nm to 8nm, where x2 ranges from 0.13 to 0.20; the quantum well is undoped. (c) Growth of strain transition layer: The reaction chamber temperature is set to 690℃±10℃, and TMI, TMI, AsH3, and PH3 are introduced to grow an In layer with a thickness of 20nm~30nm. x1 Ga 1-x1 The AsP material has an initial In composition x1 set to 0.15. During the growth of the strain transition layer, x1 gradually decreases from 0.15 to 0, with a rate of change of x1 of 0.01 / s. Correspondingly, the initial PH3 flow rate during the growth of the strain transition layer is set to 300 sccm, and then gradually increases from 300 sccm to 600 sccm during the growth process, with a rate of change of 5 sccm / s. The strain transition layer is undoped. On the one hand, the In composition is used to reduce the lattice size and reduce the compressive strain. On the other hand, the strain mode is slowly transitioned from compressive strain to tensile strain through the compensation of P element. This solves the problem of the strain between the well and the barrier in conventional 940nm infrared LEDs changing abruptly from compressive stress to tensile strain, and avoids the problem of double peaks in the spectrum caused by band splitting due to strain abruptness. (d) Growth of quantum barrier layer: The reaction chamber temperature was set to 690℃±10℃, and TMAl, TMGa, AsH3, and PH3 were introduced. The growth material was (Al y3 Ga 1-y3 ) 0.5 As 0.5The quantum barrier layer of P, a single-layer quantum barrier (Al) y3 Ga 1-y3 ) 0.5 As 0.5 The thickness of P is 20nm to 25nm, and the value of y3 ranges from 0.3 to 0.5; the quantum barrier is undoped.

[0035] (6) Growth of P-type confinement layer: Set the temperature of the reaction chamber to 690℃±10℃, introduce TMGa, TMAl, and AsH3, and grow Al with a thickness of 400nm~500nm. y4 Ga 1-y4 The material is As, where the value of y4 ranges from 0.25 to 0.50, and CCl4 is used as the p-type dopant with a doping concentration of 1×10⁻⁶. 18 cm -3 ~2×10 18 cm -3 .

[0036] (7) Growth of P-type current-extended layer: The reaction chamber temperature is set to 690℃±10℃, and TMGa, TMAl, and AsH3 are introduced to grow Al with a thickness of 6000nm~7000nm. y5 Ga 1-y5 As material, y5 ranges from 0.1 to 0.15, and CCl4 is used as the p-type dopant with a doping concentration of 0.7 × 10⁻⁶. 18 cm -3 ~1.5×10 18 cm -3 .

[0037] (8) Growth of P-face contact layer: The reaction chamber temperature is set to 600℃±10℃, and TMGa and AsH3 are introduced to grow GaAs contact layer material with a thickness of 50nm~100nm. CCl4 is used as the P-type dopant with a doping concentration of 0.5×10 20 cm -3 ~2×10 20 cm -3 .

[0038] (9) Taking out the wafer: After the growth is completed, the temperature of the MOCVD reaction chamber is reduced to 110°C, and then the pressure is adjusted to 1000 mbar. The reaction chamber is opened and the epitaxial wafer is taken out.

[0039] To further illustrate the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0040] Example 1 A method for preparing an infrared LED epitaxial wafer with improved spectrum, specifically including the following steps: (1) MOCVD was pumped to a low pressure of 50 mbar in a pure H2 atmosphere, and the reaction chamber 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 700 °C and held at 700 °C for 5 min.

[0041] (2) Growth of N-type GaAs buffer layer: The reaction chamber temperature was set to 690℃, 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 1×10⁻⁶. 18 cm -3 .

[0042] (3) Growth of N-type current-extended layer: The reaction chamber temperature was set to 690℃, and TMGa, TMAl, and AsH3 were introduced to grow an Al layer with a thickness of 3000 nm. 0.1 Ga 0.9 As material, using SiH4 as the N-type dopant, with a doping concentration of 1×10⁻⁶. 18 cm -3 .

[0043] (4) Growth of N-type confinement layer: The reaction chamber temperature was set to 720℃, and TMGa, TMAl, and AsH3 were introduced to grow an Al layer with a thickness of 400nm. 0.3 Ga 0.7 As material, using SiH4 as the N-type dopant, with a doping concentration of 2×10⁻⁶. 18 cm -3 .

[0044] (5) Growth of a pressure-partial single-peak luminescent layer: This luminescent layer is a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially, with 11 cycles. When growing the fluctuation layer, quantum well layer, and strain transition layer, two TMIn source bottles are connected in series. The TMIn source bottle closer to the reaction chamber is set to a pressure of 300 mbar during growth, and the TMIn source bottle farther from the reaction chamber is set to a pressure of 1000 mbar during growth. The growth of a single cycle structure specifically includes the following steps: (a) Growth of fluctuation layer: The reaction chamber temperature was set to 690℃, TMI and AsH3 were introduced to grow InAs material with a thickness of 5nm. After the fluctuation layer growth was completed, TMI was turned off and the material was annealed at a constant temperature of 720℃. During the annealing process, TMI and AsH3 were introduced. The flow rate of TMI was set to 60sccm and the flow rate of AsH3 was set to 400sccm. The annealing time was 4min. The InAs fluctuation layer was undoped. (b) Growth of quantum well layer: The reaction chamber temperature is set to 690℃, and TMGa, TMIn, and AsH3 are introduced. The growth material is In.0.13 Ga 0.87 As quantum well layer, single-layer quantum well In 0.13 Ga 0.87 The thickness of As is 6 nm, and the quantum well is undoped; (c) Growth of strain transition layer: The reaction chamber temperature is set to 690℃±10℃, and TMI, TMI, AsH3, and PH3 are introduced to grow an In layer with a thickness of 23 nm. x1 Ga 1-x1 The AsP material has an initial In composition x1 set to 0.15, which is then gradually decreased from 0.15 to 0 during the growth of the strain transition layer, with a rate of change of x1 of 0.01 / s. Simultaneously, the initial PH3 flow rate during the growth of the strain transition layer is set to 300 sccm, which is then gradually increased from 300 sccm to 600 sccm during the growth process, with a rate of change of 5 sccm / s. The strain transition layer is undoped. (d) Growth of quantum barrier layer: The reaction chamber temperature was set to 690℃, and TMAl, TMGa, AsH3, and PH3 were introduced. The growth material was (Al 0.4 Ga 0.6 ) 0.5 As 0.5 The quantum barrier layer of P, a single-layer quantum barrier (Al) 0.4 Ga 0.6 ) 0.5 As 0.5 The thickness of P is 25 nm, and the quantum barrier is undoped.

[0045] (6) Growth of P-type confinement layer: The reaction chamber temperature is set to 700℃, and TMGa, TMAl, and AsH3 are introduced to grow an Al layer with a thickness of 500nm. 0.45 Ga 0.55 As material, using CCl4 as the p-type dopant, with a doping concentration of 2 × 10⁻⁶. 18 cm -3 .

[0046] (7) Growth of P-type current-extended layer: The reaction chamber temperature was set to 690℃, and TMGa, TMAl, and AsH3 were introduced to grow an Al layer with a thickness of 7000 nm. 0.1 Ga 0.9 As material, using CCl4 as the p-type dopant with a doping concentration of 1.0 × 10⁻⁶. 18 cm -3 .

[0047] (8) Growth of P-face contact layer: The reaction chamber temperature was set to 610℃, and TMGa and AsH3 were introduced to grow a GaAs contact layer material with a thickness of 80nm. CCl4 was used as the P-type dopant with a doping concentration of 1×10⁻⁶. 20 cm -3 .

[0048] (9) Taking out the wafer: After the growth is completed, the temperature of the MOCVD reaction chamber is reduced to 110°C, and then the pressure is adjusted to 1000 mbar. The reaction chamber is opened and the epitaxial wafer is taken out.

[0049] Comparative Example 1 A conventional 940nm infrared LED epitaxial wafer, fabricated using conventional methods, is shown in the schematic diagram below. Figure 1 As shown.

[0050] Test case The emission spectra of the infrared LED obtained in Example 1 and the conventional 940nm infrared LED obtained in Comparative Example 1 were tested under a 20mA current. The results are as follows: Figure 4 and Figure 5 As shown.

[0051] Comparison Figure 4 and Figure 5 It can be seen that the infrared LED prepared by this invention has a single, stable spectrum with no two emission peaks; in contrast, the spectrum of a conventional 940nm infrared LED exhibits two emission peaks, i.e., a double-peak phenomenon. This demonstrates that the technical solution of this invention can effectively solve the problem of double-peak emission in conventional 940nm infrared LEDs caused by structural and process instability.

[0052] 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. An infrared LED epitaxial wafer with improved spectrum, characterized in that, The infrared LED epitaxial wafer grows an epitaxial layer starting from an N-type GaAs substrate, and from bottom to top, it grows an N-type GaAs buffer layer, an N-type current spreading layer, an N-type confinement layer, a voltage divider single-peak light-emitting layer, a P-type confinement layer, a P-type current spreading layer, and a P-face contact layer. The voltage-divided single-peak light-emitting layer is a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially.

2. The infrared LED epitaxial wafer with improved spectrum according to claim 1, characterized in that, The number of cycle pairs in the periodic structure is 6 to 12.

3. The infrared LED epitaxial wafer with improved spectrum according to claim 1, characterized in that, The fluctuation layer is made of InAs and has a thickness of 5 nm to 10 nm in each cycle; the fluctuation layer is undoped.

4. The infrared LED epitaxial wafer with improved spectrum according to claim 1, characterized in that, The strain transition layer is made of In. x1 Ga 1-x1 AsP has a thickness of 20 nm to 30 nm in each cycle. The initial In composition x1 is set to 0.

15. During the growth of the strain transition layer, x1 gradually decreases from 0.15 to 0, and the rate of change of x1 is 0.01 / s.

5. A method for preparing an infrared LED epitaxial wafer with improved spectrum according to any one of claims 1 to 4, characterized in that, Using an MOCVD device, an N-type GaAs buffer layer, an N-type current spreading layer, an N-type confinement layer, a voltage-divided single-peak light-emitting layer, a P-type confinement layer, a P-type current spreading layer, and a P-face contact layer are sequentially grown on an N-type GaAs substrate. The voltage-divided single-peak light-emitting layer is a periodic structure consisting of a fluctuation layer, a quantum well layer, a strain transition layer, and a quantum barrier layer grown sequentially. The fluctuation layer, quantum well layer, and strain transition layer are all grown using a voltage divider dual-path TMIn source tandem process.

6. The method for preparing an infrared LED epitaxial wafer with improved spectrum according to claim 5, characterized in that, The pressure-dividing dual-path TMIn source series process is as follows: two TMIn source bottles are connected in series. The TMIn source bottle closer to the reaction chamber is set to a pressure of 200 mbar to 300 mbar during growth, and the TMIn source bottle farther from the reaction chamber is set to a pressure of 800 mbar to 1000 mbar during growth.

7. The method for preparing an infrared LED epitaxial wafer with improved spectrum according to claim 5, characterized in that, The growth steps of the fluctuation layer are as follows: set the reaction chamber temperature to 690℃±10℃, introduce TMI and AsH3, and grow InAs material with a thickness of 5nm~10nm.

8. The method for preparing an infrared LED epitaxial wafer with improved spectrum according to claim 5, characterized in that, After the growth of the fluctuation layer is completed, it is annealed at a constant temperature of 700℃~720℃. At the same time, TMGa and AsH3 are introduced during the annealing process, wherein the flow rate of TMGa is set to 40sccm~60sccm and the flow rate of AsH3 is set to 400sccm~600sccm.

9. The method for preparing an infrared LED epitaxial wafer with improved spectrum according to claim 5, characterized in that, The growth steps of the strain transition layer are as follows: setting the reaction chamber temperature to 690℃±10℃, introducing TMI, TMGa, AsH3, and PH3, and growing an In layer with a thickness of 20nm~30nm. x1 Ga 1-x1 AsP material.

10. The method for preparing an infrared LED epitaxial wafer with improved spectrum according to claim 5, characterized in that, The strain transition layer is grown with an initial PH3 flow rate of 300 sccm. Then, during the growth of the strain transition layer, the PH3 flow rate is gradually increased from 300 sccm to 600 sccm, with a gradual change rate of 5 sccm / s.

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