A laser epitaxial structure and a preparation method thereof

Abstract

The application relates to a laser epitaxial structure, comprising a substrate and sequentially grown n-GaN transition layer, n-AlGaN lower confinement layer, superlattice structure lower waveguide layer, lower stress release layer, InGaN / GaN quantum well active region, upper stress release layer, superlattice structure upper waveguide layer, p-AlGaN electron blocking layer, p-AlGaN upper confinement layer and p-GaN contact layer on the substrate. The laser epitaxial structure adopts the superlattice structure waveguide layer, the superlattice waveguide can greatly inhibit longitudinal light leakage, suppress high-order mode oscillation, improve output spot quality and mode stability; the stress release layers arranged between the lower waveguide layer and the quantum well and between the quantum well and the upper waveguide layer can reliably release the stress of the active region, and meanwhile, cooperating with the micro-strain compensation effect of the superlattice waveguide layer, can greatly reduce the lattice mismatch stress of the quantum well region, effectively weaken the quantum confinement Stark effect, smooth the quantum well band, improve the carrier radiation recombination efficiency, smooth the overall epitaxial stress state and reduce the wafer warpage.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a laser epitaxial structure and its fabrication method. Background Technology

[0002] InGaN / GaN-based blue, green, and violet semiconductor lasers, with their wavelength advantages, are widely used in laser storage, laser lighting, laser printing, laser display, precision testing, and other fields, and are one of the core products of third-generation semiconductor optoelectronic devices.

[0003] A significant lattice mismatch exists between InGaN and GaN materials. When InGaN single-quantum-well or multi-quantum-well active regions are grown on GaN substrates, high-intensity compressive stress is generated within the active regions. This stress induces a strong quantum confinement Stark effect (QCSE), causing severe bandgap in the quantum wells and hindering effective radiative recombination of charge carriers. This leads to problems such as device operating wavelength drift and spectral broadening. Furthermore, the lattice mismatch also promotes a large number of through-dislocations, V-pit defects, and In composition segregation, resulting in increased nonradiative recombination, reduced product yield, and shortened laser lifespan.

[0004] Currently, the industry commonly uses single-layer InGaN or GaN materials as the upper and lower waveguide layers of lasers. This type of structure has a fixed refractive index, making it impossible to flexibly match the refractive index to the characteristics of the active region, resulting in insufficient optical field confinement. Under high power and high current operating conditions, the optical field easily leaks to the cladding layers on both sides, leading to an increase in the device's threshold current and a decrease in slope efficiency. It also easily excites higher-order modes, causing far-field spot distortion and deteriorating output mode stability. However, this single-layer waveguide structure makes stress matching difficult, and new mismatched dislocations easily form at the interface between the waveguide layer and the active region, further exacerbating device performance degradation.

[0005] Existing technologies also include methods that add a separate stress relief layer, but this method can only improve the stress state of the crystal and cannot meet the needs of light field control. Summary of the Invention

[0006] This invention relates to a laser epitaxial structure and its fabrication method, which can at least solve some of the defects of the prior art.

[0007] This invention relates to a laser epitaxial structure, comprising a substrate, and further comprising, sequentially grown on the substrate, an n-GaN transition layer, an n-AlGaN lower confinement layer, a lower waveguide layer, a lower stress relief layer, an InGaN / GaN quantum well active region, an upper stress relief layer, an upper waveguide layer, a p-AlGaN electron blocking layer, a p-AlGaN upper confinement layer, and a p-GaN contact layer, wherein the lower waveguide layer and the upper waveguide layer are both superlattice structures.

[0008] As one implementation method, the lower waveguide layer and / or the upper waveguide layer is In x Ga 1-x N / Al y Ga 1-y N superlattice structure, where 0 <x<0.15,0≤y<0.10。

[0009] As one implementation method, the lower waveguide layer is an n-type In... x Ga 1-x N / Al y Ga 1-y N superlattice structure, in which In x Ga 1-x N sublayer and Al y Ga 1-y The N sublayers are all doped with Si, and Al y Ga 1-y The Si doping concentration of the N sublayer is higher than that of In. x Ga 1-x The N-sublayer has a high Si doping concentration.

[0010] As one implementation method, the Al of the lower waveguide layer y Ga 1-y The Si doping concentration of the N-sublayer decreases from the end furthest from the active region to the end closest to the active region.

[0011] As one implementation, the lower stress relief layer and / or the upper stress relief layer are InGaN stress relief layers.

[0012] As one implementation method, when the lower stress relief layer is an InGaN stress relief layer, its In component content increases from the end furthest from the active region to the end closest to the active region; when the upper stress relief layer is an InGaN stress relief layer, its In component content decreases from the end closest to the active region to the end furthest from the active region.

[0013] As one embodiment, a Si-doped GaN layer is further formed between the stress relief layer and the InGaN / GaN quantum well active region, wherein the Si doping concentration of the GaN layer is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .

[0014] The present invention also relates to a method for fabricating the laser epitaxial structure as described above, the method comprising:

[0015] Provide substrate;

[0016] The n-GaN transition layer, the n-AlGaN lower confinement layer, the lower waveguide layer, the lower stress relief layer, the InGaN / GaN quantum well active region, the upper stress relief layer, the upper waveguide layer, the p-AlGaN electron blocking layer, the p-AlGaN upper confinement layer, and the p-GaN contact layer are sequentially grown on the substrate.

[0017] As one implementation method, the lower stress relief layer and / or the upper stress relief layer are InGaN stress relief layers. After the growth of the InGaN stress relief layer is completed, in-situ annealing is performed to achieve at least one of the following in the InGaN stress relief layer: passivation of dislocations, suppression of In segregation, and repair of interface defects.

[0018] As one implementation method, the growth temperature of the InGaN stress relief layer is 780–980°C, the in-situ annealing temperature is 980–1150°C, and the annealing holding time is 1–10 min.

[0019] The present invention has at least the following beneficial effects:

[0020] This invention employs a superlattice waveguide layer. Compared to existing single-layer waveguide structures, the superlattice waveguide can significantly suppress longitudinal optical leakage, suppress high-order mode initiation, and improve output beam quality and mode stability. By setting stress relief layers between the lower waveguide layer and the quantum well, and between the quantum well and the upper waveguide layer, reliable release of compressive stress in the active region can be achieved. Simultaneously, combined with the micro-strain compensation effect of the superlattice waveguide layer itself, the lattice mismatch stress in the quantum well region can be significantly reduced, effectively weakening the quantum confinement Stark effect, smoothing the quantum well bandgap, improving carrier radiative recombination efficiency, easing the overall epitaxial stress state, and reducing epitaxial wafer warpage. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the growth process of a laser epitaxial structure provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] like Figure 1 This invention provides a laser epitaxial structure, including a substrate 101, and further including an n-GaN transition layer 102, an n-AlGaN lower confinement layer 103, a lower waveguide layer 104, a lower stress relief layer 105, an InGaN / GaN quantum well active region 107, an upper stress relief layer 108, an upper waveguide layer 109, a p-AlGaN electron blocking layer 110, a p-AlGaN upper confinement layer 111, and a p-GaN contact layer 112, which are sequentially grown on the substrate 101. The lower waveguide layer 104 and the upper waveguide layer 109 are both superlattice structures.

[0026] The substrate 101 is preferably a GaN substrate 101, but sapphire substrate 101, Si-based substrate 101, SiC substrate 101, etc. can also be used.

[0027] The InGaN / GaN quantum well active region 107 mentioned above can be a single quantum well active region 107 or a multi-quantum well active region 107, and is more preferably an InGaN / GaN quantum well / barrier active region.

[0028] This embodiment employs a superlattice waveguide layer. Compared to existing single-layer waveguide structures, the superlattice waveguide can significantly suppress longitudinal optical leakage, suppress high-order mode initiation, and improve output beam quality and mode stability. By setting stress relief layers between the lower waveguide layer 104 and the quantum well, and between the quantum well and the upper waveguide layer 109, reliable release of compressive stress in the active region can be achieved. Simultaneously, combined with the micro-strain compensation effect of the superlattice waveguide layer itself, the lattice mismatch stress in the quantum well region can be significantly reduced, effectively weakening the quantum confinement Stark effect, smoothing the quantum well band, improving carrier radiative recombination efficiency, easing the overall epitaxial stress state, and reducing epitaxial wafer warpage.

[0029] In one embodiment, the lower waveguide layer 104 and / or the upper waveguide layer 109 are In x Ga 1-x N / Al y Ga 1-yN superlattice structure, where 0<x<0.15, 0≤y<0.10. Through precise regulation of the In component and Al component in the superlattice structure, the equivalent refractive index of the waveguide layer can be continuously adjusted, so that the optical field is effectively confined near the active region, further ensuring the suppression effect on the oscillation of high-order modes.

[0030] Under the preferred design, both the waveguide layer 104 and the upper waveguide layer 109 are In x Ga 1-x N / Al y Ga 1-y N superlattice structure. In a further preferred embodiment, the upper waveguide layer 109 and the lower waveguide layer 104 are symmetrical to each other (for example, symmetrical with respect to the active region).

[0031] Preferably, in the above In x Ga 1-x N / Al y Ga 1-y N superlattice structure, the number of superlattice cycles a is 3 to 50, the thickness d1 of the single-layer In x Ga 1-x N is 1 to 100 nm, and the thickness d2 of the single-layer Al y Ga 1-y N is 1 to 100 nm.

[0032] Wherein, the In component of the In x Ga 1-x N sublayer may be constant or varied; the Al component of the Al y Ga 1-y N sublayer may be constant or varied. The growth conditions of the In x Ga 1-x N sublayer and the Al y Ga 1-y N sublayer may be the same or different.

[0033] Based on the above In x Ga 1-x N / Al y Ga 1-y N superlattice structure, by adjusting parameters such as the In component, the period thickness and the number of periods, the equivalent refractive index of the waveguide layer can be continuously and precisely regulated to form a gradient refractive index distribution of confinement layer < waveguide layer < active region, realizing strong field confinement, greatly suppressing longitudinal light leakage, and suppressing high-order mode oscillation, thereby improving the output spot quality and mode stability.

[0034] In one embodiment, the lower waveguide layer 104 is n-type In x Ga 1-x N / Al y Ga 1-yN superlattice structure, in which In x Ga 1-x N sublayer and Al y Ga 1-y The N sublayers are all doped with Si, and Al y Ga 1-y The Si doping concentration of the N sublayer is higher than that of In. x Ga 1-x The N-sublayer has a high Si doping concentration.

[0035] Optionally, Al y Ga 1-y The Si doping concentration of the N-sublayer is 2 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 In x Ga 1-x The Si doping concentration of the N-sublayer is 1×10⁻⁶. 17 cm -3 ~5×10 18 cm -3 .

[0036] Furthermore, the Al of the lower waveguide layer 104 y Ga 1-y The Si doping concentration of the N-sublayer decreases from the end furthest from the active region to the end closest to the active region, preferably in a gradient decreasing manner. Based on this design, a "dam-like" structure can be formed, which can slow down the electron flow rate, reduce the device operating voltage, improve junction temperature characteristics, and enhance the device's thermal stability.

[0037] In one embodiment, the lower stress relief layer 105 and / or the upper stress relief layer 108 are InGaN stress relief layers. Preferably, both are InGaN stress relief layers.

[0038] Furthermore, when the lower stress relief layer 105 is an InGaN stress relief layer, its In content increases from the end furthest from the active region to the end closest to the active region, which can be a linear increase or a gradient increase; when the upper stress relief layer 108 is an InGaN stress relief layer, its In content decreases from the end closest to the active region to the end furthest from the active region, which can be a linear decrease or a gradient decrease. By setting an InGaN stress relief layer with a gradually increasing In content between the lower waveguide layer 104 and the quantum well, and setting an InGaN stress relief layer with a gradually decreasing In content between the quantum well and the upper waveguide layer 109, this stress relief structure with varying composition allows the lattice constant to gradually transition from the small lattice of the waveguide layer to the large lattice of the quantum well, achieving a gradual mismatch release of the compressive stress in the active region without abrupt changes. This avoids the upward extension of high-density dislocations caused by concentrated mismatch at the interface, significantly weakens the quantum-confined Stark effect, and significantly improves spectral stability.

[0039] In one embodiment, the thicknesses of both the upper stress relief layer 108 and the lower stress relief layer 105 are in the range of 50~200nm; in the lower stress relief layer 105, the In content near the lower waveguide layer 104 is in the range of 0~0.03 (preferably 0.01), and the In content near the quantum well active region 107 is in the range of 0.08~0.15 (preferably 0.12); in the upper stress relief layer 108, the In content near the quantum well is in the range of 0.08~0.15 (preferably 0.12), and the In content near the upper waveguide layer 109 is in the range of 0~0.03.

[0040] Preferably, the InGaN stress-relieving layer with the above-mentioned compositional changes is prepared by a low-temperature growth combined with a high-temperature in-situ annealing process. The growth temperature of the InGaN stress-relieving layer is 780~980 ℃, the in-situ annealing temperature is 980~1150 ℃, and the annealing holding time is 1~10 min, so as to achieve at least one of the effects of passivating dislocations, suppressing In segregation, and repairing interface defects. This can improve the crystal quality of subsequent epitaxial layer growth such as quantum well layers.

[0041] In one embodiment, a Si-doped GaN layer 106 is further formed between the stress relief layer 105 and the InGaN / GaN quantum well active region 107, wherein the Si doping concentration of the GaN layer 106 is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 The highly Si-doped GaN layer 106 can form a high barrier, suppressing V in the InGaN sublayer. Ga Vacancies diffuse into the quantum well, preventing hole formation and improving the thermal stability of the quantum well.

[0042] In summary, this embodiment achieves a synergistic effect of stress relief, defect suppression, optical field modulation, and electrical optimization by organically combining multiple technologies such as superlattice waveguides, compositionally graded stress relief layers, gradient Si doping, and highly Si-doped blocking layers. The overall performance of the laser device is significantly improved, providing a practical technical solution for the commercial mass production of high-power, long-life GaN-based green lasers.

[0043] Example 2

[0044] like Figure 1 This invention provides a method for fabricating the above-mentioned laser epitaxial structure, the method comprising:

[0045] Substrate 101 is provided;

[0046] The following layers are sequentially grown on the substrate 101: n-GaN transition layer 102, n-AlGaN lower confinement layer 103, lower waveguide layer 104, lower stress relief layer 105, InGaN / GaN quantum well active region 107, upper stress relief layer 108, upper waveguide layer 109, p-AlGaN electron blocking layer 110, p-AlGaN upper confinement layer 111, and p-GaN contact layer 112.

[0047] Furthermore, when the lower stress relief layer 105 and / or the upper stress relief layer 108 are InGaN stress relief layers, after the growth of the InGaN stress relief layer is completed, in-situ annealing is performed to achieve at least one of dislocation passivation, In segregation suppression, and interface defect repair in the InGaN stress relief layer. In-situ annealing can passivate dislocations, suppress In segregation, repair interface micro-defects, block the extension of dislocations into the quantum well direction, and reduce the density of non-radiative recombination centers, thereby improving the crystal quality of subsequent epitaxial layer growth such as quantum wells. In addition, in-situ annealing can also effectively reduce the operating voltage of the device, which is attributed to its activation effect on dopants and improvement of the quantum well / barrier interface quality, thereby further optimizing the electrical performance and long-term reliability of the device. Preferably, the growth temperature of the InGaN stress relief layer is 780–980℃, the in-situ annealing temperature is 980–1150℃, and the annealing holding time is 1–10 min.

[0048] Example 3

[0049] This embodiment provides a method for fabricating an epitaxial structure of a green laser, and provides a detailed description of the above-described Embodiment 1 / Embodiment 2.

[0050] High-purity hydrogen (H2) or nitrogen (N2) is used as the carrier gas, and trimethylgallium (TMGa), trimethylindium (TMIn), trimethylaluminum (TMAl) and ammonia (NH3) are used as Ga, In, Al and N sources, respectively. Silane (SiH4) and magnesium pyrocene (Cp2Mg) are used as n-type and p-type dopants, respectively.

[0051] The growth process includes the following steps:

[0052] Step 101: Heat treatment of substrate 101 and growth of n-GaN transition layer 102

[0053] The GaN substrate 101 was heated to 1130℃ and heat-treated under pure hydrogen to remove surface impurities. NH3 was then introduced for 15 minutes to stabilize the surface and repair surface damage from grinding and polishing. Subsequently, the temperature was raised to 1230℃ and the pressure to 200 torr. An n-GaN transition layer 102 with a thickness of 1.5 μm was grown under a mixed carrier gas of hydrogen and nitrogen, with a Si doping concentration of 5 × 10⁻⁶. 18 cm -3 .

[0054] Step 102: Growth of n-AlGaN lower confinement layer 103

[0055] A 1.0 μm thick n-AlGaN lower confinement layer 103 was grown at 1230 °C and 100 torr pressure, with a Si doping concentration of 5.0 × 10⁻⁶. 18 cm -3 .

[0056] Step 103: Growth of the n-type superlattice waveguide layer 104

[0057] n-type In with a thickness of 300 nm was grown under a pressure of 300 torr. 0.05 Ga 0.95 N / Al 0.02 Ga 0.98 The waveguide layer under the N superlattice is 104, and the superlattice cycle period is 15 cycles.

[0058] The specific growth process is as follows: First, the temperature is lowered to 1100℃, and a 10nm thick Al layer is grown under pure H2 conditions. 0.02 Ga 0.98 N sublayer; then a 10 nm thick In sublayer is grown at 1050 °C under pure N2 conditions. 0.05 Ga 0.95 N sublayers. Each group consists of three sets of five cycles (15 cycles in total), with Al... 0.02 Ga 0.98 The Si doping concentration in the N-sublayer decreases gradually.

[0059] Periods 1-5: Al0.02 Ga 0.98 The Si doping concentration of the N sublayer is 5 × 10⁻⁶. 18 cm -3 ;

[0060] Periods 6-10: Al 0.02 Ga 0.98 The Si doping concentration of the N sublayer is 3 × 10⁻⁶. 18 cm -3 ;

[0061] Periods 11-15: Al 0.02 Ga 0.98 The Si doping concentration of the N sublayer is 1×10⁻⁶. 18 cm -3 .

[0062] In 0.05 Ga 0.95 The Si doping concentration of the N-sublayer is 5 × 10⁻⁶. 17 cm -3 .

[0063] Step 104: Growth and annealing of the lower stress-relief layer 105

[0064] A stress-relieving InGaN layer 105 with a thickness of 150 nm was grown under pure N2, a pressure of 300 torr, and a temperature of 980 °C. The In composition gradually increased from 0 to 0.12, and the Si doping concentration was 3 × 10⁻⁶. 17 cm -3 .

[0065] After the stress-relieving layer 105 of InGaN is grown, it is annealed in situ at 1110℃ for 3 minutes to repair micro-defects at the interface of InGaN layer 106, block the extension of dislocations into quantum wells, and reduce the density of non-radiative recombination centers.

[0066] Step 105: Growth of a highly Si-doped GaN layer 106

[0067] A 10 nm thick GaN layer 106 was grown under pure H2, a pressure of 300 torr, and a temperature of 1100 °C, with a Si doping concentration of 5 × 10⁻⁶. 18 cm -3 .

[0068] Step 106: Growth of the InGaN / GaN quantum well active region 107

[0069] The InGaN / GaN quantum well active region 107 was grown under a growth pressure of 300 torr: an InGaN quantum well layer (single quantum well) with a thickness of 3.0 nm was grown at 840 °C in a pure N2 atmosphere; then the temperature was increased to 980 °C and a GaN barrier layer with a thickness of 3.5 nm was grown in a pure H2 atmosphere.

[0070] Step 107: Growth and annealing of the upper stress-relief layer 108

[0071] A stress-relieving layer 108 with a thickness of 150 nm was grown on InGaN with a gradually varying In composition under pure N2, a pressure of 300 torr, and a temperature of 980 °C. The In composition was linearly and continuously varied from 0.12 to 0.

[0072] After the stress-relieving layer 108 is grown on InGaN, it is annealed in situ at 1040℃ for 4 minutes to repair micro-defects at the interface, reduce the extension of dislocations into the P-type epitaxial layer, and improve the crystal quality of the epitaxial wafer.

[0073] Step 108: Growth of waveguide layer 109 on superlattice

[0074] Undoped In with a thickness of 200 nm was grown under 300 torr pressure. 0.05 Ga 0.95 N / Al 0.02 Ga 0.98 N-superlattice waveguide layer 109: 10 nm thick Al was grown under pure H2 conditions after cooling to 1020 °C. 0.02 Ga 0.98 N sublayer; then a 10 nm thick In sublayer is grown at 980 °C under pure N2 conditions. 0.05 Ga 0.95 N sublayer, superlattice cycle 15 cycles.

[0075] Step 109: Growth of p-AlGaN electron blocking layer 110

[0076] A p-AlGaN electron blocking layer 110 was grown at 1120℃ under 100 torr conditions, with an Al composition of 0.23, a thickness of 15 nm, and a Mg doping concentration of 1×10⁻⁶. 19 cm -3 .

[0077] Step 110: Growth of confinement layer 111 on p-AlGaN

[0078] A p-AlGaN top confinement layer 111 with a thickness of 150 nm was grown under conditions of 200 torr pressure, 1100℃ temperature, and pure H2. The Al composition was 0.05, and the Mg doping concentration was 1×10⁻⁶. 19 cm -3 .

[0079] Step 111: Growth of p-GaN contact layer 112

[0080] A p-GaN contact layer 112 with a thickness of 20 nm was grown at a temperature of 1050℃ under a pressure of 200 torr and a mixed atmosphere of H2 / N2. The Mg doping concentration was 1×10⁻⁶. 20 cm -3 It is used to form ohmic contacts.

[0081] Performance testing

[0082] The performance of the fabricated laser chip was tested, and the results are as follows:

[0083] (1) Compared with the traditional GaN substrate 101 single-layer waveguide structure, the active region compressive stress is reduced by about 35%, the QCSE effect is significantly suppressed, and the spectral stability is greatly improved.

[0084] (2) The superlattice waveguide significantly improves the optical field confinement factor, greatly reduces the leakage loss, and improves the device slope efficiency by more than 8%.

[0085] (3) The component gradient stress relief layer combined with in-situ high temperature annealing effectively suppresses dislocation upward penetration and significantly reduces non-radiative recombination.

[0086] (4) Relying on the advantages of high thermal conductivity and low dislocation of GaN substrate 101, the device has a power attenuation of less than 2% and a wavelength drift of less than 0.3nm after 1000 hours of long-term aging test.

[0087] (5) The threshold current is reduced by about 10% compared with the traditional structure, and the device yield and reliability are significantly better than the traditional structure.

[0088] Example 4

[0089] The difference between this embodiment and Embodiment 3 is as follows:

[0090] Lower waveguide layer 104 is In 0.06 Ga 0.95 N / Al 0.005 Ga 0.995 N superlattice structure, in which In 0.06 Ga 0.95 The In composition of the N sublayer changes linearly (0.02→0.10), with a thickness of 15 nm; Al 0.005 Ga 0.995 The N-sublayer thickness is 20 nm, and the superlattice cycle period is 10 cycles;

[0091] Upper waveguide layer 109 is In 0.06 Ga 0.95 N / Al 0.005 Ga 0.995N superlattice structure, In 0.06 Ga 0.95 The In composition of the N sublayer changes linearly from 0.10 to 0.02, with a thickness of 15 nm and a superlattice cycle of 10 cycles.

[0092] Example 5

[0093] The difference between this embodiment and Embodiment 3 is that the lower stress relief layer 105 adopts a gradient change method (non-linear change). Under pure N2, a pressure of 300 torr, and a temperature of 1000℃, the InGaN stress relief layer is grown in three layers with a total thickness of 150 nm.

[0094] Sublayer 1: 50 nm thick, In composition 0.01;

[0095] Sublayer 2: 50 nm thick, In composition 0.05;

[0096] Sublayer 3: 50 nm thick, In composition 0.08.

[0097] The Si doping concentration of all three sublayers is 3×10⁻⁶. 17 cm -3 .

[0098] After the three-layer sublayer growth is completed, the material is annealed in situ at 1130℃ for 3 minutes.

[0099] The In composition of the upper stress-relieving layer 108 is gradient-changed from 0.08 to 0.01, and the growth method is the same as that of the lower stress-relieving layer 105. This gradient change method can also achieve progressive lattice matching and stress relief.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 laser epitaxial structure, comprising a substrate, characterized in that, It also includes an n-GaN transition layer, an n-AlGaN lower confinement layer, a lower waveguide layer, a lower stress relief layer, an InGaN / GaN quantum well active region, an upper stress relief layer, an upper waveguide layer, a p-AlGaN electron blocking layer, a p-AlGaN upper confinement layer, and a p-GaN contact layer grown sequentially on the substrate, wherein the lower waveguide layer and the upper waveguide layer are both superlattice structures.

2. The laser epitaxial structure as described in claim 1, characterized in that: The lower waveguide layer and / or the upper waveguide layer are In x Ga 1-x N / Al y Ga 1-y N superlattice structure, where 0 <x<0.15,0≤y<0.10。 3. The laser epitaxial structure as described in claim 2, characterized in that: The lower waveguide layer is an n-type In x Ga 1-x N / Al y Ga 1-y N superlattice structure, in which In x Ga 1-x N sublayer and Al y Ga 1-y The N sublayers are all doped with Si, and Al y Ga 1-y The Si doping concentration of the N sublayer is higher than that of In. x Ga 1-x The N-sublayer has a high Si doping concentration.

4. The laser epitaxial structure as described in claim 3, characterized in that: Al of the lower waveguide layer y Ga 1-y The Si doping concentration of the N-sublayer decreases from the end furthest from the active region to the end closest to the active region.

5. The laser epitaxial structure as described in claim 1, characterized in that: The lower stress relief layer and / or the upper stress relief layer are InGaN stress relief layers.

6. The laser epitaxial structure as described in claim 5, characterized in that: When the lower stress relief layer is an InGaN stress relief layer, its In component content increases from the end furthest from the active region to the end closest to the active region; when the upper stress relief layer is an InGaN stress relief layer, its In component content decreases from the end closest to the active region to the end furthest from the active region.

7. The laser epitaxial structure as described in claim 1, characterized in that: A Si-doped GaN layer is also formed between the stress relief layer and the InGaN / GaN quantum well active region, and the Si doping concentration of the GaN layer is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .

8. The method for fabricating a laser epitaxial structure according to any one of claims 1 to 7, characterized in that, The preparation method includes: Provide substrate; The n-GaN transition layer, the n-AlGaN lower confinement layer, the lower waveguide layer, the lower stress relief layer, the InGaN / GaN quantum well active region, the upper stress relief layer, the upper waveguide layer, the p-AlGaN electron blocking layer, the p-AlGaN upper confinement layer, and the p-GaN contact layer are sequentially grown on the substrate.

9. The preparation method according to claim 8, characterized in that, The lower stress relief layer and / or the upper stress relief layer are InGaN stress relief layers. After the growth of the InGaN stress relief layer is completed, in-situ annealing is performed to achieve at least one of the following in the InGaN stress relief layer: passivation of dislocations, suppression of In segregation, and repair of interface defects.

10. The preparation method according to claim 9, characterized in that, The growth temperature of the InGaN stress-relieving layer is 780–980℃, the in-situ annealing temperature is 980–1150℃, and the annealing holding time is 1–10 min.

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