A GaN-based blue laser and a method for manufacturing the same

Abstract

The present invention relates to the technical field of semiconductor lasers, and particularly relates to a GaN-based blue laser and a preparation method thereof, including a substrate, on which an N-type GaN layer, an N-type lower confinement layer, an N-type lower waveguide layer, an active region, an upper waveguide layer, a P-type electron blocking layer, a P-type upper confinement layer, and a P-type contact layer are sequentially stacked; the P-type upper confinement layer is composed of at least one U-shaped GaN sub-layer and multiple layers of P-type In x Al y Ga 1‑x‑y N sub-layers stacked and compounded, where 0 ≤ x < y < 1, 0 < x < 1, 0 < x + y < 1. The present invention uses at least one U-shaped GaN sub-layer and multiple layers of P-type In x Al y Ga 1‑x‑y N sub-layers stacked and compounded to form the P-type upper confinement layer, which not only improves the crystal quality of the material, enhances the radiative recombination in the active region of the LD device, thereby improving the output optical power and photoelectric conversion efficiency of the LD, but also reduces the voltage and thermal loss of the LD device, and improves the aging life and other performance of the LD device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to a GaN-based blue laser and its fabrication method. Background Technology

[0002] Among optoelectronic devices fabricated using GaN, GaN-based lasers have significant applications in laser storage, laser lighting, laser printing, and laser display due to their advantages such as high luminous efficiency, wide wavelength tuning range, and small size. However, compared to blue LEDs, the development of blue lasers is more challenging during the growth of GaN-based epitaxial wafers: 1) The epitaxial structure of lasers is complex, making it easier to form defects during growth, especially the thick p-type AlGaN confinement layer grown at high temperatures for extended periods, which can easily cause thermal degradation of the quantum well, leading to epitaxial dark spots; 2) The quantum well gain region of lasers requires uniform carrier injection to achieve population inversion and generate optical gain, but blue InGaN quantum wells suffer from severe uneven carrier injection. Quantum wells with low hole injection are difficult to achieve population inversion and thus become optical absorption loss regions; 3) Lasers are sensitive to impurities. Laser light is formed through multiple oscillations and amplifications in the optical cavity, making it more sensitive to impurity absorption. Furthermore, the concentration of p-type impurities in GaN materials is very high, resulting in significant optical absorption loss.

[0003] The degradation of the bulk material in blue GaN-based LDs is one of the most significant factors affecting their reliability. Currently, it is believed that the key factor causing the degradation in blue GaN-based LDs is the diffusion and multiplication of point defects and dislocations in the active region, which leads to an increase in nonradiative recombination in the active region, thereby reducing the internal quantum efficiency. This, in turn, results in a decrease in the output optical power, photoelectric conversion efficiency, threshold current, and slope efficiency of the LD over time, ultimately leading to poor device reliability or dead lamp phenomenon. Summary of the Invention

[0004] The purpose of this invention is to provide a GaN-based blue laser and its fabrication method, which can at least solve some of the defects in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is a GaN-based blue laser, comprising a substrate on which an N-type GaN layer, an N-type lower confinement layer, an N-type lower waveguide layer, an active region, an upper waveguide layer, a P-type electron blocking layer, a P-type upper confinement layer, and a P-type contact layer are sequentially stacked; the P-type upper confinement layer is composed of at least one U-type GaN sublayer and multiple P-type In layers. x Al y Ga 1-x-y It is composed of N sub-layers stacked together, where 0≤x <y<1,0<x<1,0<x+y<1。

[0006] As one of the implementation manners, the P-type upper confinement layer is composed of a U-shaped GaN sub-layer and multiple layers of P-type In x Al y Ga 1-x-y N sub-layers stacked and compounded in sequence; alternatively, the P-type upper confinement layer is composed of a U-shaped GaN sub-layer and single / multiple layers of P-type In x Al y Ga 1-x-y N sub-layers stacked and compounded alternately.

[0007] As one of the implementation manners, in the P-type upper confinement layer, for the multiple layers of P-type In x Al y Ga 1-x-y N sub-layers, the Al component is linearly gradually increased, linearly gradually decreased, gradient increased, gradient decreased, linearly gradually increased and then linearly gradually decreased, or gradient increased and then gradient decreased.

[0008] As one of the implementation manners, in the P-type upper confinement layer, for all the P-type In x Al y Ga 1-x-y N sub-layers, the P-type doping concentration is the same or gradient increased in the direction from the P-type electron blocking layer to the P-type contact layer.

[0009] As one of the implementation manners, the growth temperature of the U-shaped GaN sub-layer is T1, and the growth temperature of the P-type In x Al y Ga 1-x-y N sub-layer is T2, and 0 < T1 - T2 < 50.

[0010] As one of the implementation manners, the total thickness of the P-type upper confinement layer is D, 10 nm < D < 700 nm; the thickness of the U-shaped GaN sub-layer is d1, 0 < d1 < 300 nm; the thickness of the P-type In x Al y Ga 1-x-y N sub-layer is d2, 0 < d2 < 300 nm.

[0011] As one of the implementation manners, the P-type contact layer is a P-type In a Al b Ga 1-a-b N layer, where 0 ≤ a < 1, 0 ≤ b < 1, and 0 ≤ a + b < 1.

[0012] As one of the implementation manners, a U-shaped cover layer is provided between the upper waveguide layer and the P-type electron blocking layer.

[0013] As one embodiment, the N-type lower confinement layer includes a first N-type lower confinement layer, an N-type stress relief layer, and a second N-type lower confinement layer sequentially disposed on the N-type GaN layer.

[0014] The present invention also provides a method for fabricating a GaN-based blue laser according to any one of the above claims, comprising the following steps:

[0015] S1. An N-type GaN layer, an N-type lower confinement layer, an N-type lower waveguide layer, an active region, an upper waveguide layer, and a P-type electron blocking layer are epitaxially grown sequentially on the substrate.

[0016] S2. At least one U-type GaN sublayer and multiple P-type In layers are stacked on the P-type electron blocking layer. x Al y Ga 1-x-y N sublayers form P-type upper confinement layers;

[0017] S3. Epitaxially grow a P-type contact layer on the P-type confinement layer.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention uses a P-type In confinement layer on a P-type to restrict the layer. x Al y Ga 1-x-y Doping the N-sublayer with an appropriate amount of larger-radius In atoms can improve the effective P-type doping of the P-type top confinement layer, increase hole injection, and thus enhance the effective radiative recombination of electrons and holes in the luminescent region, thereby improving luminous efficiency. Furthermore, adding an undoped U-type GaN sublayer to the P-type top confinement layer can improve the current spreading capability of the P-type top confinement layer, reduce the operating voltage of the LD device, thereby reducing heat loss and extending device lifespan. It can also reduce the degree of P-type doping, thereby reducing light absorption loss by the P-type dopant and improving light output efficiency. Additionally, the U-type GaN sublayer can absorb Al / Mg atoms from parasitic reactions in the cavity, reducing defects caused by parasitic reaction atoms, improving the crystal quality of the epitaxial wafer, reducing the damage to the luminescent region caused by the high-temperature region of the traditional P-type top confinement layer, and reducing the increase in non-radiative recombination in the luminescent region due to epitaxial dark spots, which affects the effective radiative recombination of the luminescent region. This method employs at least one U-type GaN sublayer and multiple P-type In sublayers. x Al y Ga 1-x-y The N-sublayer is stacked and combined to form a P-type upper confinement layer, which not only improves the crystal quality of the material and the radiative recombination in the active region of the LD device, but also improves the output optical power, aging lifetime, threshold current and skew efficiency of the LD device.

[0020] (2) The present invention uses a higher temperature to grow the undoped U-type GaN sublayer in the P-type upper confinement layer, which can increase the migration rate of Mg and Al atoms that are stuck at the atomic steps due to parasitic reactions, promote these atoms to be better incorporated into the crystal structure, reduce crystal defects caused by the presence of parasitic atoms, and thus grow an epitaxial layer with higher crystal quality, improve the crystal quality of the device, thereby achieving the purpose of improving the aging life of the device.

[0021] (3) The P-type contact layer of the present invention uses P-type In a Al b Ga 1-a-b The N-layer can form a better ohmic contact with the P-electrode, further reducing the ohmic contact resistance, increasing the current spread of the P-type layer, and reducing the resistance of the device, thereby reducing the heat loss and lifespan of the LD device. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a schematic diagram of the epitaxial structure of a GaN-based blue laser provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of a first embodiment of the P-type upper confinement layer provided in this invention;

[0025] Figure 3 A schematic diagram illustrating a second embodiment of the P-type upper confinement layer provided in this invention;

[0026] Figure 4 A schematic diagram illustrating a third embodiment of the P-type upper confinement layer provided in this invention;

[0027] Figure 5 A schematic diagram illustrating a sixth embodiment of the P-type upper confinement layer provided in this invention;

[0028] In the figure: 1. Substrate; 2. N-type GaN layer; 3. N-type lower confinement layer; 4. N-type lower waveguide layer; 5. Active region; 6. Upper waveguide layer; 7. U-type capping layer; 8. P-type electron blocking layer; 9. P-type upper confinement layer; 10. P-type contact layer. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0031] The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0032] As Figures 1-5 shown, this embodiment provides a GaN-based blue laser, including a substrate 1, on which an N-type GaN layer 2, an N-type lower confinement layer 3, an N-type lower waveguide layer 4, an active region 5, an upper waveguide layer 6, a P-type electron blocking layer 8, a P-type upper confinement layer 9, and a P-type contact layer 10 are sequentially stacked; the P-type upper confinement layer 9 is composed of at least one U-shaped GaN sublayer and multiple layers of P-type In x Al y Ga 1-x-y N sublayers stacked and compounded, where 0 ≤ x < y < 1, 0 < x < 1, 0 < x + y < 1. In this embodiment, by using P-type In x Al y Ga 1-x-yDoping the N-sublayer with an appropriate amount of larger-radius In atoms can improve the effective P-type doping of the P-type top confinement layer 9, increase hole injection, and thus improve the effective radiative recombination of electrons and holes in the luminescent region, thereby improving luminous efficiency. Furthermore, adding a U-type GaN sublayer (undoped GaN sublayer) to the P-type top confinement layer 9 can improve the current spreading capability of the P-type top confinement layer 9, reduce the operating voltage of the LD device, thereby reducing heat loss and extending device lifespan. It also reduces the degree of P-type doping, thus reducing light absorption loss by the P-type dopant and improving light output efficiency. Additionally, the U-type GaN sublayer can absorb Al / Mg atoms from parasitic reactions in the cavity, reducing defects caused by parasitic reaction atoms, improving the crystal quality of the epitaxial wafer, reducing the damage to the luminescent region caused by the high-temperature region of the traditional P-type top confinement layer 9, and reducing the increase in non-radiative recombination in the luminescent region due to epitaxial dark spots, which affects the effective radiative recombination of the luminescent region. This method employs at least one U-type GaN sublayer and multiple P-type In sublayers. x Al y Ga 1-x-y The N-sublayer is stacked and composited to form a P-type upper confinement layer 9, which not only improves the crystal quality of the material and enhances the radiative recombination in the active region 5 of the LD device, but also improves the output optical power, aging lifetime, threshold current and skew efficiency of the LD device.

[0033] Furthermore, the P-type upper confinement layer 9 is composed of a U-type GaN sublayer and multiple P-type In layers. x Al y Ga 1-x-y The N-type sublayers are stacked sequentially; or, the P-type upper confinement layer 9 is composed of a U-type GaN sublayer and a single / multi-layer P-type In layer. x Al y Ga 1-x-y It is composed of alternating layers of N sublayers.

[0034] In some embodiments, the P-type upper confinement layer 9 is composed of a U-type GaN sublayer and multiple layers of P-type In with varying Al composition. x Al y Ga 1-x-y N sublayers are formed by sequentially stacking and combining, where 0 ≤ x < 0.01, 0 <y<0.2,0<x+y<1。

[0035] In other embodiments, the P-type upper confinement layer 9 is a U-type GaN sublayer and one or more P-type In layers with varying Al composition. x Al y Ga 1-x-y It is composed of alternating layers of N sublayers.

[0036] In some embodiments, the P-type upper confinement layer 9 is composed of a U-type GaN sublayer and a P-type In layer with constant Al composition.x Al y Ga 1-x-y It is composed in an alternating stack of N sub-layers, where 0 ≤ x < 0.01, 0 < y < 0.2, 0 < x + y < 1, and the U-shaped GaN sub-layer and the P-type In with a constant Al component x Al y Ga 1-x-y The N sub-layers are taken as one period, and the alternating growth period is n, where 0 < n < 50.

[0037] Furthermore, in the P-type upper confinement layer 9, multiple layers of P-type In x Al y Ga 1-x-y The Al component of the N sub-layers increases linearly and gradually, decreases linearly and gradually, increases in gradient, decreases in gradient, increases linearly and gradually and then decreases linearly and gradually, or increases in gradient and then decreases in gradient.

[0038] In some embodiments, in the P-type upper confinement layer 9, all P-type In x Al y Ga 1-x-y The P-type doping concentrations of the N sub-layers are the same, or all P-type In x Al y Ga 1-x-y The P-type doping concentrations of the N sub-layers increase in gradient from the P-type electron blocking layer 8 to the P-type contact layer 10.

[0039] In some other embodiments, in the P-type upper confinement layer 9, the first few layers of P-type In near the active region 5 x Al y Ga 1-x-y The N sub-layers are not doped or doped with a low doping concentration of P-type dopants, and the P-type In near the P-type contact layer 10 x Al y Ga 1-x-y The N sub-layers are doped with a high doping concentration of P-type dopants.

[0040] In some embodiments, the growth temperature of the U-shaped GaN sub-layer is T1, and the growth temperature of the P-type In x Al y Ga 1-x-y The N sub-layer is T2, where 0 < T1 - T2 < 50. By appropriately increasing the temperature during the growth of the U-shaped GaN sub-layer, the migration rates of Mg and Al atoms staying at the atomic steps due to parasitic reactions can be increased, enabling them to be better incorporated and improving the crystal quality of the epitaxial layer, thereby obtaining an epitaxial wafer with higher crystal quality.

[0041] In this embodiment, the U-shaped GaN sub-layer and the P-type In x Al y Ga 1-x-yThe growth pressures of the N sub-layers can be the same or different; the growth atmospheres of the U-shaped GaN sub-layers and the P-type In x Al y Ga 1-x-y N sub-layers can be the same or different.

[0042] Furthermore, the total thickness of the P-type upper confinement layer 9 is D, where 10 nm < D < 700 nm; the thickness of the U-shaped GaN sub-layer is d1, where 0 < d1 < 300 nm; the thickness of the P-type In x Al y Ga 1-x-y N sub-layer is d2, where 0 < d2 < 300 nm.

[0043] In some embodiments, the P-type contact layer 10 is a P-type In a Al b Ga 1-a-b N layer, where 0 ≤ a < 1, 0 ≤ b < 1, and 0 ≤ a + b < 1. The P-type contact layer 10 can adopt an InGaN ternary compound or an InAlGaN quaternary compound. Both the InGaN ternary compound and the InAlGaN quaternary compound can form a better ohmic contact with the P electrode layer (ITO), further reducing the ohmic contact resistance, improving the current spreading in the P-type layer, reducing the resistance of the device, and thus reducing the thermal loss and extending the service life of the LD device.

[0044] Furthermore, the thickness of the P-type In a Al b Ga 1-a-b N layer is d3, where 0 < d3 < 50 nm; the doping concentration of the P-type In a Al b Ga 1-a-b N layer is 1×10 20 -1×10 21 cm -3 . There are mainly two methods for fabricating the P-type ohmic contact. One is to form an ohmic contact with the P-type contact layer 10 using a high work function metal, and the other is to heavily dope the P-type contact layer 10 to make the potential barrier region where the metal contacts the P-type contact layer 10 thinner, reducing the contact resistance through carrier tunneling. Conventionally, the P-type contact layer 10 uses a P-type GaN layer. Since there is a lack of metals with a work function greater than that of the P-type GaN layer (the work function is about 6.12 eV), in this embodiment, a P-type contact layer 10 doped with a heavy P-type dopant is used to increase the hole concentration and achieve a good ohmic contact. Also, because the work function of P-type InGaN is lower than that of P-type GaN, growing a P-type InGaN contact layer can further reduce the ohmic contact resistance, and a P-type InAlGaN contact layer doped with a small amount of Al component can also achieve the effect of reducing the ohmic contact resistance.

[0045] In some embodiments, a U-shaped capping layer 7 is disposed between the upper waveguide layer 6 and the P-type electron blocking layer 8. By disposing of the U-shaped capping layer 7 (undoped capping layer) between the upper waveguide layer 6 and the P-type electron blocking layer 8, the upper waveguide layer 6 and the active region 5 can be protected.

[0046] In some embodiments, the N-type lower confinement layer 3 includes a first N-type lower confinement layer, an N-type stress relief layer, and a second N-type lower confinement layer sequentially disposed on the N-type GaN layer. In this embodiment, an N-type stress relief layer is inserted in the middle of the N-type lower confinement layer 3 to reduce the stress accumulated during bottom-up growth, thereby reducing the generation of edge cracks and providing a better crystal quality basis for the subsequent growth of epitaxial layers.

[0047] The present invention also provides a method for fabricating a GaN-based blue laser according to any one of the above claims, comprising the following steps:

[0048] S1. On substrate 1, an N-type GaN layer 2, an N-type lower confinement layer 3, an N-type lower waveguide layer 4, an active region 5, an upper waveguide layer 6, and a P-type electron blocking layer 8 are epitaxially grown sequentially.

[0049] S2. At least one U-type GaN sublayer and multiple P-type In layers are stacked on the P-type electron blocking layer 8. x Al y Ga 1-x-y N sublayer, forming P-type upper confinement layer 9;

[0050] S3. Epitaxially grow a P-type contact layer 10 on the P-type confinement layer 9.

[0051] In some embodiments, the specific growth method of the P-type upper confinement layer 9 is as follows: first, an undoped U-type GaN sublayer is grown on the P-type electron blocking layer 8, and then multiple layers of P-type In with varying Al composition are sequentially grown on the U-type GaN sublayer. x Al y Ga 1-x-y The N sublayer forms the P-type upper confinement layer 9.

[0052] In other embodiments, the specific growth method of the P-type upper confinement layer 9 is as follows: first, an undoped U-type GaN sublayer is grown on the P-type electron blocking layer 8, and then one or more P-type In layers with varying Al composition are grown on the U-type GaN sublayer. x Al y Ga 1-x- y N-sublayer, then one U-type GaN sublayer, one or more P-type In sublayers x Al y Ga 1-x-y The N sublayers grow alternately to form the P-type upper confinement layer 9.

[0053] In some embodiments, the specific growth method of the P-type upper confinement layer 9 is as follows: first, an undoped U-type GaN sublayer is grown on the P-type electron blocking layer 8, and then a P-type In with constant Al composition is grown on the U-type GaN sublayer. x Al y Ga 1-x-y N sublayer, then one U-type GaN sublayer, one P-type In x Al y Ga 1-x-y The N sublayers grow alternately to form the P-type upper confinement layer 9.

[0054] In the above embodiments, the growth temperature T1 of the U-type GaN sublayer is 1000-1020℃, and the growth temperature of the P-type In is... x Al y Ga 1-x-y The growth temperature T2 of the N sublayer is 970-990℃, and 0 <T1-T2<50℃。

[0055] Furthermore, the thickness of the N-type GaN layer 2 is 1.0-3.0 μm, and the N-type doping concentration is 1 × 10⁻⁶. 18 cm -3 -1×10 20 cm -3 .

[0056] Furthermore, the total thickness of the N-type lower confinement layer 3 is 2-4 μm. The first N-type lower confinement layer 3 is an AlGaN layer with a thickness of 1.0-2.5 μm, grown at a temperature of 1100℃ and a pressure of 100 torr, with an N-type doping concentration of 1×10⁻⁶. 18 cm -3 -5×10 19 cm -3 The N-type stress relief layer is an InGaN layer with a thickness of 0.05-1.0 μm, a growth temperature of 980℃, a pressure of 200 torr, and an N-type doping concentration of 1×10⁻⁶. 18 cm -3 -5×10 19 cm -3 The second N-type lower confinement layer 3 is an AlGaN layer with a thickness of 0.2-2.0 μm, grown at a temperature of 1100℃ and a pressure of 100 torr, with an N-type doping concentration of 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 .

[0057] Furthermore, the N-type lower waveguide layer 4 is an AlGaN layer with a growth thickness of 50-1000 nm and an N-type doping concentration of 1×10⁻⁶. 17 cm -3-1×10 18 cm -3 .

[0058] Furthermore, the active region 5 includes alternating epitaxial quantum well layers and quantum barrier layers.

[0059] Furthermore, the U-shaped capping layer 7 is an undoped GaN layer with a thickness of 100-200 nm.

[0060] Furthermore, the p-type electron blocking layer 8 is an AlGaN layer with a growth thickness of 5-20 nm and a p-type doping concentration of 5 × 10⁻⁶. 18 cm -3 -1×10 20 cm -3 .

[0061] In this embodiment, the substrate 1 can be any one of the following materials: sapphire, SiC, GaN, AlN, MgO, MgAl2O4, Si, ZnO, LiAlO2, LiGaO2, and GaAs. P-type doping can be achieved using Mg doping, and N-type doping can be achieved using Si doping.

[0062] The preparation method of the present invention will be described in detail below through a specific embodiment.

[0063] A method for fabricating a GaN-based blue laser, using high-purity hydrogen (H2) or nitrogen (N2) as the carrier gas, and trimethylgallium (TMGa), trimethylindium (TMIn), trimethylaluminum (TMAl), triethylgallium (TEGa), and ammonia (NH3) as Ga, In, Al, and N sources, respectively, and silane (SiH4) and magnesium diacene (Cp2Mg) as n-type and p-type dopant, respectively. The fabrication method includes the following steps:

[0064] 1) Heat GaN substrate 1 to 1100℃ and heat-treat the surface impurities and other residues for 5 minutes under pure hydrogen conditions, then introduce NH3 to stabilize for 6 minutes to repair the surface damaged by grinding and polishing. The heating and stabilization time can be long or short, and the optimal value is to match the growth of the epitaxial wafer.

[0065] 2) The temperature was raised to 1120℃, and NH3 and TMGa sources were introduced under a pressure of 200 torr. A 2µm thick N-type GaN layer was grown under a carrier gas mixture of hydrogen and nitrogen. The Si doping concentration was 5×10⁻⁶. 18 cm -3 ;

[0066] 3) An N-type lower confinement layer 3 is grown on the N-type GaN layer 2. The specific process is as follows:

[0067] First, an AlGaN layer with a thickness of 1.5 μm was grown at a temperature of 1100℃ and a pressure of 100 torr as the first N-type lower confinement layer. The Si doping concentration was 2.0 × 10⁻⁶. 18 cm -3 ;

[0068] The temperature was then lowered to 980℃, and a 200nm thick InGaN layer was grown as an N-type stress relief layer under a pure nitrogen atmosphere and a pressure of 200 torr. The Si doping concentration was 3.0 × 10⁻⁶. 18 cm -3 ;

[0069] The temperature was then increased to 1100℃, and a 900nm thick AlGaN layer was deposited under a pressure of 100 torr as the second N-type lower confinement layer. The Si doping concentration was 2.0 × 10⁻⁶. 18 cm -3 The growth of the N-type lower confinement layer 3 was completed;

[0070] 4) Cool to 980℃ and grow a 200nm thick InGaN layer as the N-type lower waveguide layer 4 under a pure nitrogen atmosphere and a pressure of 200 torr. The Si doping concentration is 3.5×10⁻⁶. 17 cm -3 ;

[0071] 5) Next, a quantum well layer and a quantum barrier layer are grown. First, the quantum barrier layer is grown at a growth temperature of 940℃, a growth pressure of 200 torr, and an atmosphere of nitrogen and hydrogen mixed gas. The thickness of the GaN barrier layer is 3.0 nm. The thickness of the InGaN quantum well layer is 2.5 nm, the growth temperature is 880℃, the growth pressure is the same as that of the quantum barrier layer, and the atmosphere is pure nitrogen. Then, a barrier layer LQB is grown. The LQB layer is composed of GaN layers with a thickness of 3 nm and a growth temperature of 940℃. The atmosphere of the LQB barrier layer is the same as that of the quantum barrier layer.

[0072] 6) Next, a 150 nm thick InGaN layer is grown at 980 °C, in a pure nitrogen atmosphere, and at a pressure of 200 torr as the upper waveguide layer 6.

[0073] 7) Under the same conditions, a 150 nm thick undoped U-shaped capping layer 7 is grown on the upper waveguide layer 6 to protect the upper waveguide layer 6 and the active region 5.

[0074] 8) A 5 nm thick P-type electron blocking layer 8 was grown on the U-shaped capping layer 7 at a growth temperature of 1020 °C and a pressure of 100 torr, with a Mg doping concentration of 5 × 10⁻⁶. 18 cm -3 .

[0075] 9) A P-type upper confinement layer 9 is grown on the P-type electron blocking layer 8. The specific process can be any one of the following six embodiments:

[0076] The first implementation method involves cooling the temperature to 1000℃ to grow a total thickness of 300nm. First, an undoped U-shaped GaN sublayer with a thickness of 15nm is grown under a mixed hydrogen and nitrogen gas environment. Then, an In layer with a 5% Al composition and a thickness of 15nm is grown at 980℃ by introducing a specific In flow rate. 0.002 Al 0.05 Ga 0.948 N-layer, Mg doped to 5×10⁻⁶ 21 cm -3 U-shaped GaN sublayer and In 0.002 Al 0.05 Ga 0.948 N layers grow alternately, with an alternation cycle of n=10, such as Figure 2 As shown;

[0077] The second implementation method involves growing an undoped U-shaped GaN sublayer with a thickness of 30 nm under a mixed hydrogen and nitrogen gas atmosphere at 1000 °C; subsequently, under a mixed hydrogen and nitrogen gas atmosphere at 980 °C, an In sublayer with a thickness of 50 nm and an Al composition of 5% is grown by introducing a certain In flow rate. 0.003 Al 0.05 Ga 0.947 N-layer, Mg doped to 5×10⁻⁶ 18 -1×10 19 cm -3 Next, a 30 nm thick undoped U-shaped GaN sublayer was grown at 1000 °C, followed by the growth of a 100 nm thick In sublayer with the same Al composition at 980 °C. 0.003 Al 0.05 Ga 0.947 N-layer, Mg doped to 1×10⁻⁶ 19 -5×10 19 cm -3 Immediately following, an In layer with an Al composition of 5% and a thickness of 100 nm is grown. 0.003 Al 0.05 Ga 0.947 N-layer, Mg doped to 5×10⁻⁶ 19 -1×10 20 cm -3 ,like Figure 3 As shown, growing an undoped U-type GaN sublayer reduces the light absorption loss of Mg atoms in the P-type layer, reduces the parasitic reactions of Mg and Al atoms, increases the migration rate of Mg / Al atoms, and finally improves the crystal growth quality of the epitaxial layer.

[0078] The third implementation method involves growing an undoped U-shaped GaN sublayer with a thickness of 100 nm at 1020 °C under a mixed hydrogen and nitrogen gas atmosphere; subsequently, an In sublayer with an Al composition of 8% and a thickness of 50 nm is grown at 980 °C under a mixed hydrogen and nitrogen gas atmosphere. 0.002 Al 0.08 Ga 0.918 N sublayer, Mg doped to 3×10⁻⁶ 19 cm -3 Next, an In layer with an Al composition of 5% and a thickness of 100 nm is grown. 0.002 Al 0.05 Ga 0.948 N sublayer, Mg doped to 3×10⁻⁶ 19 cm -3 Immediately following this, a layer of In with an Al composition of 2% and a thickness of 50 nm is grown. 0.002 Al 0.02 Ga 0.978 N sublayer, Mg doped to 5 × 10⁻⁶ 19 cm -3 ,like Figure 4 As shown;

[0079] The fourth implementation method involves growing an undoped U-shaped GaN sublayer with a thickness of 10 nm at 1000 °C under a mixed hydrogen and nitrogen gas environment; subsequently, at 980 °C under a nitrogen / hydrogen mixed gas environment, a multilayer InAlGaN sublayer with an Al composition gradually decreasing from 10% to 0 and a thickness of 10 nm is grown sequentially, with Mg doping at 5 × 10⁻⁶. 19 cm -3 U-shaped GaN sublayers and multilayer InAlGaN sublayers are grown alternately, with an alternation growth cycle of n=25;

[0080] Fifth implementation method: An undoped U-shaped GaN sublayer with a thickness of 100 nm is grown at 1000 °C under a mixed hydrogen and nitrogen gas environment; subsequently, a multilayer InAlGaN sublayer with a thickness of 250 nm, with an Al composition gradually decreasing from 10% to 0, is grown sequentially at 980 °C under a nitrogen / hydrogen mixed gas environment, with Mg doping of 5 × 10⁻⁶. 19 cm -3 ;

[0081] The sixth implementation method: An undoped U-shaped GaN sublayer with a thickness of 100 nm is grown at 1000°C under a mixed hydrogen and nitrogen gas atmosphere; subsequently, an Al sublayer with an Al composition of 5% and a thickness of 20 nm is grown at 980°C under a nitrogen / hydrogen mixed gas atmosphere. 0.05 Ga 0.95 N sublayer, Mg doping level 7 × 10⁻⁶ 18 cm -3 Subsequently, under pure nitrogen conditions, an In layer with a thickness of 20 nm was formed.0.002 Al 0.05 Ga 0.948 N sublayer, Mg doped to 3×10⁻⁶ 19 cm -3 U-shaped GaN sublayer, Al 0.05 Ga 0.95 N sublayer, In 0.002 Al 0.05 Ga 0.948 The N sublayers grow alternately, with an alternation cycle of n=8, such as Figure 5 As shown;

[0082] By first growing an undoped U-type GaN sublayer, the parasitic reaction of Mg in the cavity can be reduced, the impurity defects introduced by ineffective Mg doping that lead to a decrease in the crystal quality of the epitaxial layer and thus a shortened device aging life can be reduced. It can also improve current spread, reduce voltage, thereby reducing device heat loss. At the same time, it can also reduce Mg doping, reduce the absorption loss of light by Mg in the P-type layer, and improve light output efficiency.

[0083] 10) Finally, cool down to 920℃ to grow a P-type InAlGaN layer or a P-type InGaN layer as a P-type contact layer 10, with a growth thickness of 0-15 nm and a Mg doping concentration of 1×10⁻⁶. 20 -1×10 21 cm -3 .

[0084] The epitaxial equipment described above is metal-organic chemical vapor deposition, but it is not limited to this. After epitaxial growth is completed, the grown epitaxial wafer is subjected to semiconductor processing techniques such as cleaning, deposition, photolithography, and etching to produce a single chip.

[0085] 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 GaN-based blue laser, comprising a substrate, characterized in that: An N-type GaN layer, an N-type lower confinement layer, an N-type lower waveguide layer, an active region, an upper waveguide layer, a P-type electron blocking layer, a P-type upper confinement layer, and a P-type contact layer are sequentially stacked on the substrate; the P-type upper confinement layer is composed of at least one U-shaped GaN sub-layer and multiple P-type In x Al y Ga 1-x-y N sub-layers stacked and compounded, where 0 ≤ x < y < 1, 0 < x < 1, 0 < x + y < 1; the growth temperature of the U-shaped GaN sub-layer is T1, and the growth temperature of the P-type In x Al y Ga 1-x- y N sub-layer is T2, and 0 < Tl - T2 < 50.

2. The GaN-based blue laser as described in claim 1, characterized in that: The P-type upper confinement layer consists of a U-type GaN sublayer and multiple P-type In layers. x Al y Ga 1-x-y The N-type sublayers are stacked sequentially; or, the P-type upper confinement layer is composed of U-type GaN sublayers and single / multi-layer P-type In. x Al y Ga 1-x-y It is composed of alternating layers of N sublayers.

3. The GaN-based blue laser as described in claim 2, characterized in that: In the P-type upper confinement layer, multiple P-type In x Al y Ga 1-x-y The Al composition of the N sublayer can be linearly gradually increasing, linearly gradually decreasing, gradient increasing, gradient decreasing, linearly gradually increasing and then linearly gradually decreasing, or gradient increasing and then gradient decreasing.

4. The GaN-based blue laser as described in claim 2, characterized in that: In the P-type upper confinement layer, all P-type In x Al y Ga 1-x-y The N-sublayer has the same P-type doping concentration or the gradient increases from the P-type electron blocking layer to the P-type contact layer.

5. The GaN-based blue laser as described in claim 1, characterized in that: The total thickness of the P-type upper confinement layer is D, where 10 nm < D < 700 nm; the thickness of the U-shaped GaN sub-layer is d1, where 0 < d1 < 300 nm; the thickness of the P-type In x Al y Ga 1-x-y N sub-layer is d2, where 0 < d2 < 300 nm.

6. The GaN-based blue laser as described in claim 1, characterized in that: The P-type contact layer is a P-type In a Al b Ga 1-a-b There are N layers, where 0 ≤ a < 1, 0 ≤ b < 1, and 0 ≤ a + b < 1.

7. The GaN-based blue laser as described in claim 1, characterized in that: A U-shaped covering layer is provided between the upper waveguide layer and the P-type electron blocking layer.

8. The GaN-based blue laser as described in claim 1, characterized in that: The N-type lower confinement layer includes a first N-type lower confinement layer, an N-type stress relief layer, and a second N-type lower confinement layer, which are sequentially disposed on the N-type GaN layer.

9. A method for fabricating a GaN-based blue laser according to any one of claims 1-8, characterized in that, Includes the following steps: S1. An N-type GaN layer, an N-type lower confinement layer, an N-type lower waveguide layer, an active region, an upper waveguide layer, and a P-type electron blocking layer are epitaxially grown sequentially on the substrate. S2. At least one U-type GaN sublayer and multiple P-type In layers are stacked on the P-type electron blocking layer. x Al y Ga 1-x-y N sublayers form P-type upper confinement layers; S3. Epitaxially grow a P-type contact layer on the P-type confinement layer.

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