A method for epitaxial growth of a VCSEL

Abstract

The present application relates to the technical field of VCSEL epitaxial growth, and particularly relates to a VCSEL epitaxial growth method. The VCSEL epitaxial growth method provided by the present application inserts an ALE microcirculation interface flattening at the junction of each DBR period, and combines with HCl pulse cleaning before a low-refractive layer and carrier gas switching, and a low-temperature AsH3 dehydrogenation annealing process, so that an atomic-level flat interface and super-high reflectivity (≥99.5%) are maintained while high-speed growth (growth rate is increased by more than 50%) is realized, and the growth time is significantly shortened and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of VCSEL epitaxial growth technology, and more particularly to a method for VCSEL epitaxial growth. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) are semiconductor lasers that emit light perpendicular to the substrate on which the laser is formed. Compared to edge-emitting semiconductor lasers (FP, DFB, etc.), they offer advantages such as low temperature drift, low threshold voltage, high fiber coupling efficiency, ease of integration and packaging, and high speed, making them widely used in fiber optic communication. With the rise of artificial intelligence, their applications in 3D sensing have also garnered significant attention. However, traditional VCSEL growth suffers from long growth times, high interface roughness, and decreased doping activity, limiting production efficiency and device performance. This is especially true in multi-junction cascaded VCSELs, where the DBR layer accounts for over 75% of the total epitaxial growth time, becoming a key bottleneck restricting production capacity.

[0003] While existing direct high-speed growth methods can shorten the growth time, they result in insufficient atomic migration, severe step aggregation, and reduced doping efficiency. The interface roughness increases from 0.3 nm to over 1.5 nm, the reflectivity decreases by more than 1%, and the resistance and threshold current increase. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a VCSEL epitaxial growth method that achieves high-speed growth and reduces manufacturing costs while ensuring atomically flat interfaces and ultra-high reflectivity of the device.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for epitaxial growth of VCSELs, comprising the following steps: sequentially growing an N-doped DBR layer, an active region layer, an oxide confinement layer, a tunnel junction layer, a P-doped DBR layer, and a surface ohmic contact layer on a substrate surface; wherein the growth of the N-doped DBR layer and the P-doped DBR layer are independent and include:

[0007] After high-speed growth of a high-refractive-index layer, the following steps are performed in sequence: ALE microcirculation interface smoothing, HCl pulse cleaning, first carrier gas switching, low-temperature AsH3 dehydrogenation annealing, high-speed growth of a low-refractive-index layer, and second carrier gas switching.

[0008] The growth rates of the high-speed high-refractive-index layer and the high-speed low-refractive-index layer are independently 4~8 μm / h;

[0009] The ALE microcirculation interface smoothing cycle is repeated 1 to 3 times;

[0010] A single ALE subcycle consists of sequential chlorination and regeneration;

[0011] The chlorination conditions are as follows: the supply of TMGa is cut off, the flow rate of HCl is 5~30 sccm, the pulse duration is 0.1~1s, the flow rate of AsH3 is 100~200 sccm, and the temperature is 680~750℃.

[0012] The regeneration conditions are as follows: the HCl supply is cut off, the flow rate of AsH3 is 180~500 sccm, the flow rate of TMGa is 20~40 sccm, the growth time is 2~5 s, and the growth thickness is 0.3~0.8 nm.

[0013] Preferably, the high-speed growth modes of the high-speed growth of the high-refractive-index layer and the high-speed growth of the low-refractive-index layer independently include: a growth temperature of 680~750℃, a reaction chamber pressure of 80~150mbar, and an initial carrier gas of hydrogen.

[0014] Preferably, the material of the high refractive index layer in the N-doped DBR layer is an N-doped GaAs layer;

[0015] The conditions for high-speed growth of the N-doped GaAs layer are as follows: the source gas is TMGa, AsH3 and SiH4; the flow rate of TMGa is 80~150 sccm, the flow rate of AsH3 is 200~500 sccm, the flow rate of SiH4 is 50~200 sccm, and the V / III ratio is (30~60):1.

[0016] The high-refractive-index layer in the P-doped DBR layer is a P-doped GaAs layer.

[0017] The conditions for high-speed growth of the P-doped GaAs layer are as follows: the source gas is TMGa, AsH3 and CCl4; the flow rate of TMGa is 80~150 sccm, the flow rate of AsH3 is 180 sccm, the flow rate of CCl4 is 50~200 sccm, and the V / III ratio is (30~60):1.

[0018] Preferably, the conditions for the HCl pulse cleaning are: stopping all metal source supply, introducing HCl at a flow rate of 10~40 sccm for a duration of 0.5~2s; and AsH3 at a flow rate of 150~250 sccm.

[0019] Preferably, the first carrier gas switching is: reducing the flow rate of hydrogen and increasing the flow rate of nitrogen so that the volume ratio of hydrogen to nitrogen is 1:(2~10).

[0020] During the first carrier gas switching process, the total flow rate is kept stable. The first carrier gas switching time is 10~30s, and the temperature is 680~750℃.

[0021] Preferably, the temperature of the low-temperature AsH3 dehydrogenation annealing is 500~650℃, the flow rate of AsH3 is 200~400sccm, and the time is 10~120s.

[0022] Preferably, the material of the low-refractive-index layer in the N-doped DBR layer is N-doped AlGaAs;

[0023] The conditions for growing the N-doped AlGaAs are as follows: the source gas is TMGa, TMAl, AsH3 and SiH4; the total group III flow rate is 90~180 sccm; and the carrier gas is hydrogen and nitrogen in a volume ratio of 1:(3~8).

[0024] The material of the low refractive index layer in the P-doped DBR layer is P-doped AlGaAs; the conditions for growing the P-doped AlGaAs are: the source gas is TMGa, TMAl, AsH3 and CCl4; the total Group III flow rate is 90~180 sccm, and the carrier gas is hydrogen and nitrogen in a volume ratio of 1:(3~8).

[0025] Preferably, the second carrier gas is switched to increase the hydrogen flow rate and decrease the nitrogen flow rate so that the volume ratio of hydrogen to nitrogen is greater than 5:1;

[0026] The second carrier gas switching time is 10~20s, and the temperature is 680~750℃.

[0027] Preferably, the number of cycles for growing the N-doped DBR layer is 24 to 49.

[0028] The number of cycles for growing the P-doped DBR layer is 9 to 19.

[0029] This invention provides a VCSEL epitaxial growth method, comprising the following steps: sequentially growing an N-doped DBR layer, an active region layer, an oxide confinement layer, a tunnel junction layer, a P-doped DBR layer, and a surface ohmic contact layer on a substrate surface; the growth of the N-doped DBR layer and the P-doped DBR layer independently includes: after high-speed growth of a high-refractive-index layer, sequentially performing ALE micro-circulation interface planarization, HCl pulse cleaning, switching of the first carrier gas, low-temperature AsH3 dehydrogenation annealing, high-speed growth of a low-refractive-index layer, and switching of the second carrier gas, repeating the above steps; the growth rates of the high-speed growth of the high-refractive-index layer and the high-speed growth of the low-refractive-index layer are independently 4~8 μm. m / h; the number of cycles for smoothing the ALE microcirculation interface is 1 to 3; a single ALE sub-cycle includes sequential chlorination and regeneration; the chlorination conditions are: cutting off the TMGa supply, the flow rate of HCl is 5 to 30 sccm, the pulse duration is 0.1 to 1 s, the flow rate of AsH3 is 100 to 200 sccm, and the temperature is 680 to 750 °C; the regeneration conditions are: cutting off the HCl supply, the flow rate of AsH3 is 180 to 500 sccm, the flow rate of TMGa is 20 to 40 sccm, the growth time is 2 to 5 s, and the growth thickness is 0.3 to 0.8 nm. The epitaxial growth method described in this invention inserts ALE microcirculation interface smoothing at the junction of each DBR cycle, and combines it with HCl pulse cleaning and carrier gas switching before the low refractive index layer, as well as low-temperature AsH3 dehydrogenation annealing process. This achieves high-speed growth (growth rate increased by more than 50%) while maintaining an atomically smooth interface and ultra-high reflectivity (≥99.5%), significantly shortening the growth time and reducing production costs. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the VCSEL obtained by the epitaxial growth method described in Embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the growth process of the N-doped DBR layer and the P-doped DBR layer described in this invention;

[0032] Figure 3 An atomic force microscope image of the VCSEL epitaxial wafer prepared by the epitaxial growth method described in Example 1 of this invention;

[0033] Figure 4 An atomic force microscope image of the VCSEL epitaxial wafer prepared by the epitaxial growth method described in Comparative Example 1. Detailed Implementation

[0034] like Figure 2The present invention provides a VCSEL epitaxial growth method, comprising the following steps: sequentially growing an N-doped DBR layer, an active region layer, an oxide confinement layer, a tunnel junction layer, a P-doped DBR layer, and a surface ohmic contact layer on a substrate surface; wherein the growth of the N-doped DBR layer and the P-doped DBR layer are independent and include:

[0035] After high-speed growth of a high-refractive-index layer, the following steps are performed in sequence: ALE microcirculation interface smoothing, HCl pulse cleaning, first carrier gas switching, low-temperature AsH3 dehydrogenation annealing, high-speed growth of a low-refractive-index layer, and second carrier gas switching.

[0036] The growth rates of the high-speed high-refractive-index layer and the high-speed low-refractive-index layer are independently 4~8 μm / h;

[0037] The ALE microcirculation interface smoothing cycle is repeated 1 to 3 times;

[0038] A single ALE subcycle consists of sequential chlorination and regeneration;

[0039] The chlorination conditions are as follows: the supply of TMGa is cut off, the flow rate of HCl is 5~30 sccm, the pulse duration is 0.1~1s, the flow rate of AsH3 is 100~200 sccm, and the temperature is 680~750℃.

[0040] The regeneration conditions are as follows: the HCl supply is cut off, the flow rate of AsH3 is 180~500 sccm, the flow rate of TMGa is 20~40 sccm, the growth time is 2~5 s, and the growth thickness is 0.3~0.8 nm.

[0041] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0042] In this invention, the N-doping concentration in the N-doped DBR layer is preferably (2~5)×10⁻⁶. 18 cm -3 The preferred P-doping concentration in the P-doped DBR layer is (2~5)×10⁻⁶. 18 cm -3 .

[0043] This invention does not impose any special limitations on the substrate; any substrate well-known to those skilled in the art can be used. In an embodiment of this invention, the substrate is specifically an N-type (100) GaAs substrate.

[0044] Before growing the N-doped DBR layer, the present invention preferably includes pretreatment of the substrate, wherein the pretreatment process preferably involves placing the substrate in an MOCVD reaction chamber and preheating it to the temperature for growing the N-doped DBR layer under an AsH3 atmosphere.

[0045] In this invention, the growth of the N-doped DBR layer includes:

[0046] After high-speed growth of a high-refractive-index layer, the following steps are performed in sequence: ALE microcirculation interface smoothing, HCl pulse cleaning, switching of the first carrier gas, low-temperature AsH3 dehydrogenation annealing, high-speed growth of a low-refractive-index layer, and switching of the second carrier gas.

[0047] In this invention, the high refractive index layer is preferably an N-doped GaAs layer; the source gas for growing the N-doped GaAs layer is preferably TMGa, AsH3, and SiH4; the flow rate of TMGa is preferably 80~150 sccm, more preferably 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, or 150 sccm; the flow rate of AsH3 is preferably 200~500 sccm, more preferably 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, or 500 sccm; the flow rate of SiH4 is preferably 50~200 sccm, more preferably 50 sccm, 100 sccm, 150 sccm, or 200 sccm; the V / III ratio is preferably (30~60):1, more preferably 30:1, 40:1, 50:1, or 60:1. The growth temperature is preferably 680~750℃, more preferably 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, or 750℃; the growth rate is 4~8 μm / h, preferably 5 μm / h or 6 μm / h; the reaction chamber pressure is preferably 80~150 mbar, more preferably 100 mbar; the initial carrier gas is preferably hydrogen. In this invention, the growth time of the N-doped GaAs layer is preferably calculated based on the target thickness (e.g., λ / 4n ≈ 67 nm @ 980 nm) and the growth rate. In this invention, the thickness accuracy of the high refractive index layer is controlled within ±2%.

[0048] In this invention, the number of cycles for ALE micro-circulation interface planarization is preferably 1 to 3. When the growth rate of the N-doped GaAs layer is greater than 6 μm / h, the number of cycles for ALE micro-circulation interface planarization is preferably 3; when the growth rate of the N-doped GaAs layer is 4 to 6 μm / h, the number of cycles for ALE micro-circulation interface planarization is preferably 1 to 2.

[0049] In this invention, a single ALE sub-cycle preferably includes sequential chlorination and regeneration. In this invention, the chlorination conditions are preferably as follows: the supply of TMGa is cut off; the flow rate of HCl is preferably 5-30 sccm, more preferably 5 sccm, 10 sccm, 15 sccm, 20 sccm, 25 sccm, or 30 sccm; the pulse duration is preferably 0.1-1 s, more preferably 0.1 s, 0.3 s, 0.5 s, 0.7 s, or 1 s; the flow rate of AsH3 is preferably 100-200 sccm, more preferably 100 sccm, 120 sccm, 140 sccm, 160 sccm, 180 sccm, or 200 sccm; and the temperature is preferably 680-750°C, more preferably 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, or 750°C.

[0050] In this invention, the role of chlorination is to selectively etch surface protrusions and remove 0.2~0.5nm of high-energy sites such as step edges.

[0051] In this invention, the regeneration conditions are preferably as follows: the HCl supply is cut off; the flow rate of AsH3 is preferably 180~500 sccm, more preferably 180 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm or 500 sccm; the flow rate of TMGa introduced is preferably 20~40 sccm, more preferably 20 sccm, 25 sccm, 30 sccm, 35 sccm or 40 sccm; the growth time is preferably 2~5 s, more preferably 2 s, 3 s, 4 s or 5 s; and the growth thickness is preferably 0.3~0.8 nm, more preferably 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm or 0.8 nm.

[0052] In this invention, the thickness of the regenerated material is preferably ≤1 nm.

[0053] In this invention, the role of regeneration is to grow ultrathin GaAs on a clean and flat surface to fill micropores and form an atomically flat interface.

[0054] In this invention, the preferred conditions for the HCl pulse cleaning are: stopping all metal source supply; the flow rate of the HCl pulse is preferably 10~40 sccm, more preferably 10 sccm, 20 sccm, 30 sccm or 40 sccm; the duration is preferably 0.5~2s, more preferably 0.5s, 1s, 1.5s or 2s; and the flow rate of AsH3 is preferably 150~250 sccm, more preferably 150 sccm, 160 sccm, 180 sccm, 200 sccm, 220 sccm, 240 sccm or 250 sccm.

[0055] In this invention, the HCl pulse cleaning is used to remove any trace oxidation and residual contamination that may have been present on the surface after the ALE microcirculation interface has been smoothed.

[0056] In this invention, the first carrier gas switching is preferably performed by: reducing the flow rate of hydrogen and increasing the flow rate of nitrogen so that the volume ratio of hydrogen to nitrogen is 1:(2~10), more preferably 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10. During the first carrier gas switching process, the total flow rate is kept stable. The switching time is preferably 10~30s, more preferably 10s, 15s, 20s, 25s or 30s; the temperature is preferably 680~750℃, more preferably 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃ or 750℃.

[0057] In this invention, the low refractive index layer is a high Al layer, which is extremely sensitive to trace amounts of water and oxygen in the hydrogen carrier gas. At the same time, Si doping (N doping) is easily passivated by H, while nitrogen gas is more inert, reducing the active hydrogen generated by hydrogen cracking, thereby reducing Al surface oxidation and Si doped hydrogen passivation and maintaining stable growth kinetics.

[0058] In this invention, the temperature of the low-temperature AsH3 dehydrogenation annealing is preferably 500~650℃, more preferably 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃; the flow rate of AsH3 is preferably 200~400 sccm, more preferably 200 sccm, 250 sccm, 300 sccm, 350 sccm or 400 sccm; the time is preferably 10~120s, more preferably 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s or 120s.

[0059] In this invention, the low-temperature AsH3 dehydrogenation annealing can provide As atoms to cover the surface through AsH3 pyrolysis, prevent composition fluctuations, promote the desorption of adsorbed hydrogen on the surface, activate Si doping that may be passivated, and release interfacial stress.

[0060] In this invention, the material of the low-refractive-index layer in the N-doped DBR layer is preferably N-doped AlGaAs; the preferred conditions for growing the N-doped AlGaAs are: the source gas is preferably TMGa, TMAl, AsH3, and SiH4; the total Group III flow rate is preferably 90~180 sccm, more preferably 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, 150 sccm, 160 sccm, 170 sccm, or 180 sccm; the carrier gas is preferably hydrogen and nitrogen in a volume ratio of 1:(3~8), more preferably 1:3, 1:4, 1:5, 1:6, 1:7, or 1:8. In this invention, the growth time for growing the N-doped AlGaAs is preferably calculated based on the target thickness (λ / 4n≈72.9nm@980nm, x=0.90).

[0061] In this invention, the second carrier gas switching is preferably to increase the hydrogen flow rate and decrease the nitrogen flow rate so that the volume ratio of hydrogen to nitrogen is greater than 5:1, more preferably pure hydrogen; the second carrier gas switching time is preferably 10~20s, more preferably 10s, 12s, 14s, 16s, 18s or 20s; the temperature is preferably 680~750℃, more preferably 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃ or 750℃.

[0062] In this invention, the second carrier gas switching is preferably preparation for the growth of the high refractive index layer in the next cycle.

[0063] In this invention, the number of cycles for growing the N-doped DBR layer is preferably 24 to 49 (i.e., the total number of cycles for the high-refractive-index and low-refractive-index layers in the N-doped DBR layer is 25 to 50).

[0064] This invention does not impose any special limitations on the type and preparation method of the active region layer; any type and preparation method well known to those skilled in the art can be used. In the embodiments of this invention, the active region layer is specifically an InGaAs / GaAs quantum well layer.

[0065] This invention does not impose any special limitations on the type and preparation method of the oxide confinement layer; any type and preparation method well known to those skilled in the art can be used. In the embodiments of this invention, the oxide confinement layer is specifically Al. 0.98 GaAs.

[0066] The present invention does not impose any special limitations on the type and preparation method of the tunneling layer; any type and preparation method known to those skilled in the art can be used.

[0067] In this invention, the material of the high refractive index layer in the P-doped DBR layer is preferably a P-doped GaAs layer; the preferred conditions for high-speed growth of the P-doped GaAs layer are: the source gas is preferably TMGa, AsH3, and CCl4; the flow rate of TMGa is preferably 80~150 sccm, more preferably 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, or 150 sccm; the flow rate of AsH3 is preferably 180 sccm; the flow rate of CCl4 is preferably 50~200 sccm, more preferably 50 sccm, 100 sccm, 150 sccm, or 200 sccm; the V / III ratio is preferably (30~60):1, more preferably 30:1, 40:1, 50:1, or 60:1. In this invention, other conditions for high-speed growth of the P-doped GaAs layer are preferably the same as those for high-speed growth of the N-doped GaAs layer and will not be repeated here.

[0068] In this invention, the preferred conditions for high-speed growth of the P-doped AlGaAs are: the source gas is preferably TMGa, TMAl, AsH3, and CCl4; the total Group III flow rate is preferably 90-180 sccm, more preferably 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, 150 sccm, 160 sccm, 170 sccm, or 180 sccm; the carrier gas is preferably hydrogen and nitrogen in a volume ratio of 1:(3-8), and the volume ratio of hydrogen to nitrogen is preferably 1:3, 1:4, 1:5, 1:6, 1:7, or 1:8. In this invention, other conditions for high-speed growth of the P-doped AlGaAs layer are preferably the same as those for high-speed growth of the N-doped AlGaAs layer and will not be repeated here.

[0069] In this invention, the number of cycles for growing the P-doped DBR layer is preferably 9 to 19 (i.e., the total number of logarithmic cycles of the high-refractive-index and low-refractive-index layers in the P-doped DBR layer is 10 to 20).

[0070] The present invention does not impose any special limitations on the type and preparation method of the surface ohmic contact layer; any type and preparation method known to those skilled in the art can be used.

[0071] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0072] Example 1

[0073] Using an N-type (100) GaAs substrate as the substrate, the N-type (100) GaAs substrate was placed in an AIXTRON MOCVD system (reaction chamber pressure of 100 mbar) and preheated to 720°C;

[0074] Growth of N-doped DBR (N-DBR, design wavelength 980nm, 41 pairs of Al) 0.90 Ga 0.10 As / GaAs N-DBR, the GaAs (high refractive index layer) thickness is 67.0 nm, and the N doping concentration is 3 × 10⁻⁶. 18 cm -3 Al 0.90 Ga 0.10 The thickness of the As (low refractive index layer) is 72.9 nm, and the N doping concentration is 2 × 10⁻⁶. 18 cm -3 The growth parameters of the N-doped DBR are: growth temperature of 720℃ and growth rate of 6μm / h (1.7 times that of the conventional 3.5μm / h).

[0075] GaAs growth conditions: TMGa flow rate 120 sccm, AsH3 flow rate 400 sccm, SiH4 flow rate 150 sccm, carrier gas pure hydrogen at a flow rate of 30 slm, growth time 35 s, actual thickness 67 nm, N doping concentration 3 × 10⁻⁶. 18 cm -3 ;

[0076] Conditions for the first ALE sub-cycle: Chlorination: Cut off the flow of TMGa, HCl flow rate of 15 sccm, AsH3 flow rate of 150 sccm, time of 0.6 s;

[0077] Regeneration: Cut off the HCl flow, TMGa flow rate is 30 sccm, AsH3 flow rate is 400 sccm, time is 3s, and the growth thickness is about 0.5 nm;

[0078] Conditions for the second ALE sub-cycle: Chlorination: Cut off the flow of TMGa, HCl flow rate of 15 sccm, AsH3 flow rate of 150 sccm, time of 0.5 s;

[0079] Regeneration: Cut off the HCl flow, TMGa flow rate is 30 sccm, AsH3 flow rate is 400 sccm, time is 3s, and the growth thickness is about 0.5 nm;

[0080] Conditions for HCl cleaning pulse: cut off the inlet of all metal sources, HCl flow rate of 25 sccm, inlet time of 1s; AsH3 flow rate of 200 sccm.

[0081] First carrier gas switching: The temperature is 720℃, the flow rate of hydrogen is reduced and the flow rate of nitrogen is increased. The initial hydrogen flow rate is 30 slm, the final hydrogen flow rate is 6 slm, and the nitrogen flow rate is 24 slm. The transition from the initial state to the final state is linear and gradual, and the switching time is 20 s. During this process, the flow rate of AsH3 is maintained at 200 sccm.

[0082] Low-temperature AsH3 dehydrogenation annealing: temperature is 640℃, AsH3 flow rate is 350sccm, time is 45s, and then the temperature is rapidly increased to 720℃ within 80s.

[0083] Al growth 0.90 Ga 0.10 As conditions: TMGa flow rate of 50 sccm, TMAl flow rate of 780 sccm, AsH3 flow rate of 180 sccm, SiH4 flow rate of 12 sccm, support of hydrogen gas with a flow rate of 6 slm and nitrogen gas with a flow rate of 24 slm, growth time of 42 s, and actual thickness of 72.9 nm.

[0084] Second carrier gas switching: The temperature is 720℃. The carrier gas is switched from the initial state with a flow rate of 6 slm of hydrogen and 24 slm of nitrogen to the final state with a flow rate of 30 slm of hydrogen. The transition from the initial state to the final state is linear and gradual, and the switching time is 15s.

[0085] Repeat the above process 40 times;

[0086] The active region layer, oxide confinement layer, and tunnel junction layer were prepared using conventional methods.

[0087] Growth of P-doped DBR (P-DBR, 980nm design wavelength, 20 pairs of Al) 0.95 Ga 0.05 The As / GaAs DBR has a GaAs (high refractive index layer) thickness of 67.0 nm and a P-doping concentration of 6 × 10⁻⁶. 18 cm -3 Al 0.95 Ga 0.05 The thickness of the As (low refractive index layer) is 72.9 nm, and the concentration of P doping is 1 × 10⁻⁶. 18 cm -3 ).

[0088] The growth parameters of the P-doped DBR are: growth temperature of 680℃ and growth rate of 6μm / h (1.7 times that of the conventional 3.5μm / h).

[0089] GaAs growth conditions: TMGa flow rate 120 sccm, AsH3 flow rate 180 sccm, CCl4 flow rate 75 sccm, pure hydrogen gas at a flow rate of 30 slm, growth time 35 s, actual thickness 67 nm, P doping concentration 6 × 10⁻⁶. 18 cm -3 ;

[0090] Conditions for the first ALE sub-cycle: Chlorination: Cut off the flow of TMGa, HCl flow rate of 15 sccm, AsH3 flow rate of 150 sccm, time of 0.8 s;

[0091] Regeneration: Cut off the HCl flow, TMGa flow rate is 30 sccm, AsH3 flow rate is 180 sccm, time is 3s, and the growth thickness is about 0.5 nm.

[0092] Conditions for the second ALE sub-cycle: Chlorination: Cut off the flow of TMGa, HCl flow rate of 15 sccm, AsH3 flow rate of 150 sccm, time of 0.8 s;

[0093] Regeneration: Cut off the HCl flow, TMGa flow rate is 30 sccm, AsH3 flow rate is 180 sccm, time is 3s, and the growth thickness is about 0.5 nm.

[0094] Conditions for HCl cleaning pulse: cut off the inlet of all metal sources, HCl flow rate of 25 sccm, inlet time of 1s; AsH3 flow rate of 200 sccm.

[0095] First carrier gas switching: The temperature is 680℃, the flow rate of hydrogen is reduced and the flow rate of nitrogen is increased. The initial hydrogen flow rate is 30 slm, the final hydrogen flow rate is 6 slm, and the nitrogen flow rate is 24 slm. The transition from the initial state to the final state is linear and gradual, and the switching time is 20 s. During this process, the flow rate of AsH3 is maintained at 200 sccm.

[0096] Low-temperature AsH3 dehydrogenation annealing: temperature is 640℃, AsH3 flow rate is 350sccm, time is 45s, and then the temperature is rapidly increased to 680℃ within 40s.

[0097] Al growth 0.90 Ga 0.10 As conditions: TMGa flow rate of 50 sccm, TMAl flow rate of 780 sccm, AsH3 flow rate of 180 sccm, CCl4 flow rate of 36 sccm, support of hydrogen at a flow rate of 6 slm and nitrogen at a flow rate of 24 slm, growth time of 42 s, and actual thickness of 72.9 nm.

[0098] Second carrier gas switching: The temperature is 680℃. The carrier gas is switched from the initial state (hydrogen flow rate of 6slm and nitrogen flow rate of 24slm) to the final state (hydrogen flow rate of 30slm). The transition from the initial state to the final state is linear and gradual, and the switching time is 15s.

[0099] Repeat the above process 19 times;

[0100] The surface ohmic contact layer was prepared using conventional methods;

[0101] The structural schematic diagram of the VCSEL epitaxial wafer is shown below. Figure 1 As shown, its surface roughness is 0.479 nm (RMS), as... Figure 3 As shown.

[0102] Comparative Example 1

[0103] Referring to Example 1, the epitaxial layer growth rate is the same as in the example, except that ALE microcirculation interface planarization is not performed when growing N-doped DBR and P-doped DBR, resulting in an epitaxial wafer surface roughness of 1.895 nm. Figure 4 As shown.

[0104] From the above examples and comparative examples, it is evident that ALE (Atomic Layer Etching) planarization improves surface quality because it introduces a "chlorination-regeneration" microcycle at each DBR interface, achieving a self-limiting etching and regeneration process at the atomic level. In the chlorination stage, HCl selectively reacts with high-energy sites on the surface (such as protrusions and step edges), preferentially etching these protruding areas and removing excess atomic layers. In the subsequent regeneration stage, TMGa and AsH3 are reintroduced, allowing new GaAs atoms to preferentially nucleate and grow on the planarized low-energy surface, filling micro-pits. Since the etching and regeneration thickness of each ALE cycle is only about 0.5 nm, the surface can be repaired layer by layer without damaging the overall structure, achieving "atomic self-repair." This selective etching and precise compensation mechanism effectively suppresses step accumulation and island growth during high-speed growth, fundamentally reducing interface roughness and forming an atomically smooth mirror interface, thereby significantly improving reflectivity and optical performance.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for epitaxial growth of VCSELs, comprising the following steps: An N-doped DBR layer, an active region layer, an oxide confinement layer, a tunnel junction layer, a P-doped DBR layer, and a surface ohmic contact layer are sequentially grown on the substrate surface; characterized in that the growth of the N-doped DBR layer and the P-doped DBR layer is independent and includes: After high-speed growth of a high-refractive-index layer, the following steps are performed in sequence: ALE microcirculation interface smoothing, HCl pulse cleaning, first carrier gas switching, low-temperature AsH3 dehydrogenation annealing, high-speed growth of a low-refractive-index layer, and second carrier gas switching. The growth rates of the high-speed high-refractive-index layer and the high-speed low-refractive-index layer are independently 4~8 μm / h; The ALE microcirculation interface smoothing cycle is repeated 1 to 3 times; A single ALE subcycle consists of sequential chlorination and regeneration; The chlorination conditions are as follows: the supply of TMGa is cut off, the flow rate of HCl is 5~30 sccm, the pulse duration is 0.1~1s, the flow rate of AsH3 is 100~200 sccm, and the temperature is 680~750℃. The regeneration conditions are as follows: the HCl supply is cut off, the flow rate of AsH3 is 180~500 sccm, the flow rate of TMGa is 20~40 sccm, the growth time is 2~5 s, and the growth thickness is 0.3~0.8 nm. The high-speed growth modes for the high-speed growth of high-refractive-index layers and the high-speed growth of low-refractive-index layers independently include: a growth temperature of 680~750℃, a reaction chamber pressure of 80~150mbar, and an initial carrier gas of hydrogen. The high-refractive-index layer in the N-doped DBR layer is made of N-doped GaAs. The conditions for high-speed growth of the N-doped GaAs layer are as follows: the source gas is TMGa, AsH3 and SiH4; the flow rate of TMGa is 80~150 sccm, the flow rate of AsH3 is 200~500 sccm, the flow rate of SiH4 is 50~200 sccm, and the V / III ratio is (30~60):

1. The high refractive index layer in the P-doped DBR layer is a P-doped GaAs layer. The conditions for high-speed growth of the P-doped GaAs layer are as follows: the source gas is TMGa, AsH3 and CCl4; the flow rate of TMGa is 80~150 sccm, the flow rate of AsH3 is 180 sccm, the flow rate of CCl4 is 50~200 sccm, and the V / III ratio is (30~60):

1. The first carrier gas switching is: reducing the flow rate of hydrogen and increasing the flow rate of nitrogen so that the volume ratio of hydrogen to nitrogen is 1:(2~10). The temperature for the low-temperature AsH3 dehydrogenation annealing is 500~650℃; The material of the low-refractive-index layer in the N-doped DBR layer is N-doped AlGaAs; The conditions for growing the N-doped AlGaAs are as follows: the source gas is TMGa, TMAl, AsH3 and SiH4; the total group III flow rate is 90~180 sccm; and the carrier gas is hydrogen and nitrogen in a volume ratio of 1:(3~8). The material of the low refractive index layer in the P-doped DBR layer is P-doped AlGaAs; the conditions for growing the P-doped AlGaAs are: the source gas is TMGa, TMAl, AsH3 and CCl4; the total group III flow rate is 90~180 sccm; and the carrier gas is hydrogen and nitrogen in a volume ratio of 1:(3~8). The second carrier gas is switched to increase the hydrogen flow rate and decrease the nitrogen flow rate so that the volume ratio of hydrogen to nitrogen is greater than 5:

1.

2. The VCSEL epitaxial growth method as described in claim 1, characterized in that, The conditions for the HCl pulse cleaning are as follows: all metal source supplies are stopped, the flow rate of HCl is 10~40 sccm, and the duration is 0.5~2s; the flow rate of AsH3 is 150~250 sccm.

3. The VCSEL epitaxial growth method as described in claim 1, characterized in that, During the first carrier gas switching process, the total flow rate is kept stable. The first carrier gas switching time is 10~30s, and the temperature is 680~750℃.

4. The VCSEL epitaxial growth method as described in claim 1, characterized in that, The flow rate of AsH3 in the low-temperature AsH3 dehydrogenation annealing is 200~400 sccm, and the time is 10~120 s.

5. The VCSEL epitaxial growth method as described in claim 1, characterized in that, The second carrier gas switching time is 10~20s, and the temperature is 680~750℃.

6. The VCSEL epitaxial growth method as described in claim 1, characterized in that, The number of cycles for growing the N-doped DBR layer is 24 to 49. The number of cycles for growing the P-doped DBR layer is 9 to 19.

Images