Semiconductor laser epitaxial structure with composite electron blocking layer and preparation method thereof

Abstract

This invention relates to the field of semiconductor laser technology, specifically to a semiconductor laser epitaxial structure with a composite electron blocking layer and its fabrication method. The semiconductor laser epitaxial structure, from bottom to top, includes a substrate, a first confinement layer A, a first confinement layer B, a first waveguide layer, an active region, a second waveguide layer, a composite electron blocking layer, a second confinement layer, and a contact layer. The composite electron blocking layer, from bottom to top, includes a first sublayer and a second sublayer. The first sublayer is a single or multilayer high-aluminum AlGaN layer; the second sublayer is a low-aluminum AlGaN layer or GaN layer, with Mg as the dopant element. This invention utilizes the first sublayer to efficiently block electron leakage, and the second sublayer to reduce the magnesium activation energy and increase the hole concentration, thereby effectively improving the electro-optic conversion efficiency, reducing the threshold current and cavity surface temperature rise, and enhancing stability and long-term reliability at high power. It is suitable for high-power gallium nitride-based lasers in the blue-green, violet, and ultraviolet bands.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to a semiconductor laser epitaxial structure with a composite electron blocking layer and its fabrication method. Background Technology

[0002] Gallium nitride (GaN)-based semiconductor lasers achieve broad-spectrum emission coverage from ultraviolet to green light by adjusting the indium composition of the emitting region, and have wide and important applications in industrial processing, laser displays, and lithography machine light sources. With the rapid development of these applications, increasingly higher demands are being placed on the output power and electro-optical conversion efficiency of lasers. However, GaN-based lasers generally suffer from a sharp drop in efficiency at high power operation, with electron leakage being one of the main causes. Under high current density conditions, high-energy electrons in the active region can cross the potential barrier and enter the p-type region, where they recombine with holes non-radiatively, resulting in carrier loss. To suppress electron leakage, the industry commonly adopts a solution of inserting a high-aluminum AlGaN electron blocking layer between the waveguide layer and the p-type optical confinement layer. However, while forming an electron barrier, the AlGaN electron blocking layer also generates a hole barrier at the top of the valence band, which severely hinders the injection of holes into the active region. At the same time, AlGaN material has low p-type doping efficiency, with magnesium activation energy as high as 200 meV or more, and extremely low hole mobility, which leads to increased device series resistance and higher operating voltage, thus restricting further improvement of laser performance.

[0003] To address the contradiction between electron blocking and hole injection, researchers have conducted extensive research from the perspective of optimizing the structure of the electron blocking layer. Patent CN102545058A discloses a structure that replaces the last GaN barrier layer in the active region with an AlGaN layer with a gradually changing aluminum composition to improve the electron accumulation problem at the interface between the barrier layer and the electron blocking layer. Patent CN114583557A discloses a method for preparing an electron blocking layer using a short-period AlGaN / GaN superlattice structure epitaxially grown with magnesium as the electron blocking layer. Magnesium doping is only performed during the growth of the GaN layer, effectively suppressing the diffusion of Mg into the active region, increasing the hole concentration in the p-type region, and reducing the resistivity. Patent CN105870266A discloses a method that uses a low-temperature grown AlGaN monolayer or AlGaN / InGaN superlattice as the electron blocking layer, and grows a p-type GaN layer on it as the hole injection layer, thereby improving the electron overflow in the active region and improving the hole injection efficiency by optimizing the distribution of p-type Mg doping.

[0004] However, the aforementioned existing solutions still have their limitations in practical applications: In the structure of patent CN102545058A, the graded AlGaN layer contains magnesium doping, and the doped layer is extremely close to the quantum well. This results in strong internal absorption when the laser propagates within the cavity, leading to a decrease in laser output power and an increase in threshold current. Simultaneously, to effectively reduce the hole barrier, the compositionally graded electron blocking layer typically requires a thickness of tens to hundreds of nanometers, increasing the difficulty and time cost of epitaxial growth. In patent CN114583557A, the superlattice structure has an average aluminum content of less than 10%, which limits its effectiveness at current densities greater than 10 kA / cm². 2 Under high-power operating conditions, the electron blocking capability decreases significantly, failing to effectively suppress the leakage of high-energy electrons. Patent CN105870266A primarily targets the design of LED devices with low operating current densities, where the aluminum composition of the electron blocking layer is below 30%. Under the much higher operating current densities of gallium nitride (GaN) lasers compared to LEDs, it is difficult to achieve an effective electron blocking effect. Furthermore, the low-temperature growth conditions employed in this patent lead to a deterioration in the crystal quality of AlGaN and p-type GaN materials. Applying this structure to lasers operating at high current densities results in rapid performance degradation, severely impacting the long-term reliability and lifespan of the device. Therefore, developing a simple, thickness-controllable composite electron blocking layer structure that synergistically optimizes electron blocking and hole injection is of significant research value and promising industrial application prospects for overcoming the performance bottlenecks of GaN lasers and achieving high electro-optical conversion efficiency. Summary of the Invention

[0005] To address the technical problems in existing gallium nitride-based semiconductor lasers, such as the inability to balance high Al content and high hole concentration in the AlGaN electron blocking layer, and the severe light absorption and heat loss caused by high Mg doping, this invention provides a semiconductor laser epitaxial structure with a composite electron blocking layer and its fabrication method.

[0006] The technical solution of this invention is as follows: In a first aspect, the present invention provides a semiconductor laser epitaxial structure having a composite electron blocking layer, comprising, from bottom to top, a substrate, a first confinement layer A, a first confinement layer B, a first waveguide layer, an active region, a second waveguide layer, a composite electron blocking layer, a second confinement layer, and a contact layer; wherein the composite electron blocking layer comprises, from bottom to top, a first sublayer and a second sublayer; wherein the first sublayer is Al. x1 Ga 1-x1 Layer N, 0.5≤x1≤1, x gradually changes from high to low values ​​linearly; the second sublayer is Al. x2 Ga 1-x2 The N-layer or GaN-layer has a particle size distribution of 0.05 ≤ x2 ≤ 0.15 and is doped with Mg.

[0007] Furthermore, the substrate is one of gallium nitride, silicon carbide, or zinc oxide, and the substrate conductivity type is n-type.

[0008] Furthermore, in the first sublayer, x1 decreases linearly in a single layer, and the thickness of the first sublayer is 2~15nm, without intentional doping; the high Al composition (x1≥0.5) of the first sublayer provides a high electronic barrier, effectively preventing high-energy electrons from leaking from the active region to the p region; the single-layer gradient Al composition can reduce the abrupt change in the interface electric field and suppress the accumulation of interface electrons; the undoped nature avoids light absorption caused by the introduction of Mg and reduces intracavity loss.

[0009] Furthermore, the thickness of the second sublayer is 5~30 nm, and the Mg doping concentration is 1×10⁻⁶. 18 ~1×10 20 cm -3 The second sublayer with low Al composition (x2≤0.15) significantly reduces the Mg activation energy, achieving high hole concentration and low-resistance hole injection; high Mg doping provides sufficient holes for injection into the active region; low Al composition results in a low valence band barrier and high hole tunneling efficiency.

[0010] Furthermore, the first confinement layer A is an AlGaN layer with an Al composition of 1%~10%, a thickness of 0.8~2μm, and Si as the dopant element with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 The first confinement layer B is a GaN layer with a thickness of 0.2~0.5μm, and the doping element is Si with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 The second confinement layer is an AlGaN layer with an Al composition of 2%~10%, a thickness of 0.2~0.8μm, and Mg as the dopant with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 The contact layer is a GaN layer with a thickness ranging from 5 to 100 nm, and the doping element is Mg with a doping concentration of 2 × 10⁻⁶. 19 ~1×10 20 cm -3 The first confinement layer A (high Al) provides strong n-type light confinement and reduces light field leakage; the first confinement layer B acts as a buffer to reduce lattice stress and improve crystal quality; the second confinement layer provides p-type light confinement and hole propagation; the highly doped contact layer reduces ohmic contact resistance and reduces operating voltage.

[0011] Furthermore, the first waveguide layer is an InGaN layer with a thickness of 0.05~0.5μm, and the doping element is Si with a doping concentration of 1×10⁻⁶. 18 ~1×1019 cm -3 The refractive index of the first waveguide layer is higher than that of the first confinement layer, thus achieving optical field confinement.

[0012] Furthermore, when the semiconductor laser is in the blue-green light band, the average In composition in the first waveguide layer is 3%~8%. The In composition can be a constant value or it can gradually increase, with the increasing direction from the first confinement layer B to the active region, and the thickness is 0.2~0.3μm. When the semiconductor laser is in the violet or ultraviolet light band, the average In composition in the first waveguide layer is 2%~5%. The In composition can be a constant value or it can gradually increase, with the increasing direction from the first confinement layer B to the active region, and the thickness is 0.05~0.12μm.

[0013] Furthermore, the active region is an InGaN / GaN structure, where InGaN is the quantum well layer and GaN is the barrier layer. The active region is composed of alternating quantum well layers and barrier layers, with an alternation period of 2 to 3. When the semiconductor laser is in the blue-green light band, the thickness of the active region is 20 to 40 Å, and the In composition is 15% to 35%. When the semiconductor laser is in the violet or ultraviolet light band, the thickness of the active region is 60 to 90 Å, and the In composition is 3% to 15%. High In composition realizes the blue-green light band, and low In composition realizes the ultraviolet / violet light band.

[0014] Furthermore, the second waveguide layer is made of InGaN material and has a thickness of 0.05~0.5μm; Furthermore, when the semiconductor laser is in the blue-green light band, the average In composition in the second waveguide layer is 4%~8%. The In composition can be a constant value or it can gradually decrease, with the decreasing direction from the active region to the recombination electron blocking layer. The In composition gradually decreases from 8%~10% to 4%~5%, and the thickness is 0.2~0.3μm. When the semiconductor laser is in the violet or ultraviolet light band, the average In composition in the second waveguide layer is 2%~5%. The In composition can be a constant value or it can decrease linearly, with the decreasing direction from the active region to the recombination electron blocking layer. The In composition gradually decreases from 5%~8% to 2%~3%, and the thickness is 0.05~0.12μm.

[0015] In a second aspect, the present invention provides a method for fabricating a semiconductor laser epitaxial structure having a composite electron blocking layer, comprising the following steps: (1) Growth of the first confinement layer: The substrate is placed in the growth chamber, and nitrogen and hydrogen are introduced as carrier gases, and ammonia is introduced as a reaction gas to provide nitrogen source. The temperature is raised to 1000~1100℃, and trimethylgallium and trimethylaluminum are introduced first to grow the first confinement layer A; then the trimethylaluminum is turned off to grow the first confinement layer B; silane is used as the n-type doping source for the first confinement layer A and the first confinement layer B. (2) Growth of the first waveguide layer: Cool down to 750~850℃, introduce trimethylindium and triethylgallium, and grow the first waveguide layer. Control the indium composition and distribution of the waveguide layer by adjusting the flow rate of trimethylindium or the growth temperature. When the flow rate of trimethylindium decreases, the indium composition in the waveguide layer decreases. When the growth temperature decreases, the indium composition in the waveguide layer increases. (3) Growth of active region: Cool down to 700~800℃, introduce trimethylindium and triethylgallium, and grow the quantum well layer in the active region. Control the indium composition by adjusting the flow rate of trimethylindium or the growth temperature; when the temperature is raised to 800~900℃, only triethylgallium is introduced to grow the barrier layer in the active region. (4) Growth of the second waveguide layer: The temperature is controlled at 750~850℃, and trimethylindium and triethylgallium are introduced to grow the second waveguide layer. The indium composition and its distribution of the second waveguide layer are controlled by adjusting the flow rate of trimethylindium or the growth temperature. (5) Growth of the first sublayer: The temperature is raised to 900~950℃, and trimethylaluminum, trimethylgallium and ammonia are introduced to grow the first sublayer. The aluminum composition and distribution of the first sublayer are controlled by adjusting the flow rate of trimethylaluminum or the growth temperature. (6) Growth of the second sublayer: The temperature is maintained at 900~950℃, the flow rate of trimethylaluminum is reduced or turned off, trimethylgallium and ammonia are introduced, and magnesia is introduced at the same time to grow the second sublayer; (7) Growth of the second confinement layer: The temperature is raised to 850~950℃, and trimethylaluminum and triethylgallium are introduced, while magnesia-dicenocene is introduced at the same time to grow the second confinement layer; (8) Growth of contact layer: The temperature is raised to 850~950℃, and trimethylgallium or triethylgallium is introduced, while magnesia-dicenocene is introduced at the same time to grow the contact layer.

[0016] The beneficial effects of this invention are as follows: 1. The semiconductor laser epitaxial structure with a composite electron blocking layer provided by the present invention achieves physical separation of electron blocking function and hole supply function by designing the electron blocking layer as a bilayer composite structure comprising an undoped first sublayer with high Al composition and a Mg-doped second sublayer with low Al composition from bottom to top. While effectively blocking high-energy electron leakage, it efficiently generates holes in the low Al composition region, significantly improving hole injection efficiency and reducing device threshold current.

[0017] 2. The first sublayer of the composite electron blocking layer provided by this invention is made of undoped or very low-doped AlGaN, which avoids the severe light absorption and heat loss caused by Mg doping under high Al composition, reduces the cavity surface temperature rise, and improves the long-term reliability and working life of the laser. The use of a gradient Al composition structure further suppresses electron leakage, and at the same time eliminates the need for a structure with a thickness of tens to hundreds of nanometers, simplifying the epitaxial growth process and reducing the process complexity and time cost.

[0018] 3. The present invention provides a composite electron blocking layer in which the second sublayer adopts low-Al composition AlGaN and is heavily doped with Mg. Taking advantage of the characteristic that the activation energy of Mg is significantly reduced under low Al composition, a high hole concentration is obtained. At the same time, the interface polarization effect is used to further reduce the valence band barrier, promote hole tunneling injection, and improve electro-optic conversion efficiency. Attached Figure Description

[0019] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the epitaxial structure of a semiconductor laser provided by the present invention.

[0021] Figure 2 This is a schematic diagram of an existing semiconductor laser epitaxial structure.

[0022] Figure 3 This is a schematic diagram of the band structure of the composite electron blocking layer in the semiconductor laser epitaxial structure prepared in Example 1.

[0023] Figure 4 This is a distribution diagram of aluminum and magnesium elements in the epitaxial structure of the semiconductor laser obtained in Example 1; wherein, 0~10nm is the contact layer, 10~310nm is the second confinement layer, 310~326nm is the composite electron blocking layer, and 326~576nm is the second waveguide layer.

[0024] In the figure, 1-substrate, 2-first confinement layer A, 3-first confinement layer B, 4-first waveguide layer, 5-active region, 6-second waveguide layer, 7-composite electron blocking layer, 701-first sublayer, 702-second sublayer, 8-second confinement layer, 9-contact layer, 10-electron blocking layer. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0026] Example 1 A semiconductor laser epitaxial structure having a composite electron blocking layer 7, such as Figure 1 As shown, from bottom to top, it includes a substrate 1, a first confinement layer A 2, a first confinement layer B 3, a first waveguide layer 4, an active region 5, a second waveguide layer 6, a composite electron blocking layer 7, a second confinement layer 8, and a contact layer 9; the composite electron blocking layer 7 includes a first sublayer 701 and a second sublayer 702 from bottom to top. Substrate 1 is an n-type GaN substrate; The first confinement layer A2 is an AlGaN layer with an Al composition of 4%, a thickness of 1 μm, and Si as the dopant with a doping concentration of 3 × 10⁻⁶. 18 cm -3 ; The first confinement layer B3 is a GaN layer with a thickness of 0.2 μm, doped with Si at a concentration of 3 × 10⁻⁶. 18 cm -3 ; The first waveguide layer 4 is an InGaN layer, in which the In composition gradually increases from 1% to 9%, the thickness is 0.25 μm, the doping element is Si, and the doping concentration is 2 × 10⁻⁶. 18 cm -3 ; The active region 5 is an InGaN / GaN structure, with InGaN as the quantum well layer and GaN as the barrier layer. The active region 5 is composed of alternating quantum well layers and barrier layers, with two alternation periods, a total thickness of 30 Å, and an In composition of 20%. The second waveguide layer 6 is an InGaN layer with an In composition that gradually decreases from 8% to 5% and a thickness of 0.25 μm. The first sublayer 701 is Al x1 Ga 1-x1 N layers, x1 linearly gradients from 0.7 to 0.5, with a thickness of 6nm, unintentionally doped; The second sublayer 702 is Al. 0.1 Ga 0.9 The N-layer has a thickness of 10 nm and is doped with Mg at a concentration of 1 × 10⁻⁶. 19 cm -3 ; The second confinement layer 8 is an AlGaN layer with an Al composition of 5%, a thickness of 0.3 μm, and Mg as the dopant with a doping concentration of 4 × 10⁻⁶. 18 cm -3 ; Contact layer 9 is a GaN layer with a thickness of 10 nm, doped with Mg at a concentration of 2 × 10⁻⁶. 19 cm -3 .

[0027] The above-mentioned method for fabricating the semiconductor laser epitaxial structure with the composite electron blocking layer 7 is carried out using an MOCVD device and includes the following steps: (1) Growth of the first confinement layer: The n-type GaN substrate is placed in the growth chamber, and nitrogen and hydrogen are introduced as carrier gases, and ammonia is introduced as a reaction gas to provide nitrogen source. The temperature is raised to 1040℃, and trimethylgallium, trimethylaluminum and silane are introduced first to grow the first confinement layer A2; then the trimethylaluminum is turned off and the first confinement layer B3 is continued to grow; both the first confinement layer A2 and the first confinement layer B3 use silane as the n-type doping source; (2) Growth of the first waveguide layer 4: Cool down to 800℃, introduce trimethylindium and triethylgallium, and grow the first waveguide layer 4. Control the indium composition and distribution of the waveguide layer by adjusting the flow rate of trimethylindium or the growth temperature; when the flow rate of trimethylindium increases, the indium composition in the waveguide layer increases; when the growth temperature decreases, the indium composition in the waveguide layer increases. (3) Growth of active region 5: Cool down to 700℃, introduce trimethylindium and triethylgallium, and grow the quantum well layer in active region 5. Control the indium composition by adjusting the flow rate of trimethylindium or the growth temperature; when the temperature is raised to 800℃, only triethylgallium is introduced to grow the barrier layer in active region 5. (4) Growth of the second waveguide layer 6: The temperature is controlled at 800℃, and trimethylindium and triethylgallium are introduced to grow the second waveguide layer 6. The indium composition and its distribution of the second waveguide layer 6 are controlled by adjusting the flow rate of trimethylindium or the growth temperature. (5) Growth of the first sublayer 701: The temperature is raised to 900℃, and trimethylaluminum, trimethylgallium and ammonia are introduced to grow the first sublayer 701. The aluminum composition and its distribution of the first sublayer 701 are controlled by adjusting the flow rate of trimethylaluminum or the growth temperature. (6) Growth of the second sublayer 702: The temperature is maintained at 900℃, the flow rate of trimethylaluminum is reduced or turned off, trimethylgallium and ammonia are introduced, and magnesia dicerocene is introduced at the same time to grow the second sublayer 702. (7) Growth of the second confinement layer 8: The temperature is raised to 880°C, and trimethylaluminum and triethylgallium are introduced, while magnesia-dicenocene is introduced at the same time to grow the second confinement layer 8; (8) Growth of contact layer 9: The temperature is raised to 880°C, and trimethylgallium or triethylgallium is introduced, while magnesium pyrocene is introduced at the same time to grow contact layer 9.

[0028] Example 2 A semiconductor laser epitaxial structure having a composite electron blocking layer 7, such as Figure 1 As shown, from bottom to top, it includes a substrate 1, a first confinement layer A 2, a first confinement layer B 3, a first waveguide layer 4, an active region 5, a second waveguide layer 6, a composite electron blocking layer 7, a second confinement layer 8, and a contact layer 9; the composite electron blocking layer 7 includes a first sublayer 701 and a second sublayer 702 from bottom to top. Substrate 1 is an n-type GaN substrate; The first confinement layer A2 is an AlGaN layer with an Al composition of 1%, a thickness of 0.9 μm, and Si as the dopant with a doping concentration of 1 × 10⁻⁶. 18 cm -3 ; The first confinement layer B3 is a GaN layer with a thickness of 0.3 μm, doped with Si at a concentration of 1 × 10⁻⁶. 18 cm -3 ; The first waveguide layer 4 is an InGaN layer, in which the In composition gradually increases from 1% to 5%, the thickness is 0.1 μm, the doping element is Si, and the doping concentration is 2 × 10⁻⁶. 18 cm -3 ; The active region 5 is an InGaN / GaN structure, with InGaN as the quantum well layer and GaN as the barrier layer. The active region 5 is composed of alternating quantum well layers and barrier layers, with three alternation periods, a total thickness of 70 Å, and an In composition of 10%. The second waveguide layer 6 is an InGaN layer with an In composition that gradually changes from 5% to 2% and a thickness of 0.1 μm. The first sublayer 701 is a single layer of Al. x1 Ga 1-x1 N layers, x1 linearly gradients from 1 to 0.7, with a thickness of 3nm, unintentionally doped; The second sublayer 702 is Al. 0.06 Ga 0.94 The N-layer has a thickness of 5 nm and is doped with Mg at a concentration of 1 × 10⁻⁶. 19 cm -3 ; The second confinement layer 8 is an AlGaN layer with an Al composition of 2%, a thickness of 0.2 μm, and Mg as the dopant with a doping concentration of 3 × 10⁻⁶. 18 cm -3 ; Contact layer 9 is a GaN layer with a thickness of 50 nm, and the doping element is Mg with a doping concentration of 5 × 10⁻⁶. 19 cm -3 .

[0029] The above-mentioned method for fabricating the semiconductor laser epitaxial structure with the composite electron blocking layer 7 is carried out using an MOCVD device and includes the following steps: (1) Growth of the first confinement layer: The n-type GaN substrate is placed in the growth chamber, and nitrogen and hydrogen are introduced as carrier gases, and ammonia is introduced as a reaction gas to provide nitrogen source. The temperature is raised to 1040℃, and trimethylgallium, trimethylaluminum and silane are introduced first to grow the first confinement layer A2; then the trimethylaluminum is turned off and the first confinement layer B3 is continued to grow; both the first confinement layer A2 and the first confinement layer B3 use silane as the n-type doping source; (2) Growth of the first waveguide layer 4: Cool down to 800℃, introduce trimethylindium and triethylgallium, and grow the first waveguide layer 4. Control the indium composition and distribution of the waveguide layer by adjusting the flow rate of trimethylindium or the growth temperature; when the flow rate of trimethylindium increases, the indium composition in the waveguide layer increases; when the growth temperature decreases, the indium composition in the waveguide layer increases. (3) Growth of active region 5: Cool down to 700℃, introduce trimethylindium and triethylgallium, and grow the quantum well layer in active region 5. Control the indium composition by adjusting the flow rate of trimethylindium or the growth temperature; when the temperature is raised to 800℃, only triethylgallium is introduced to grow the barrier layer in active region 5. (4) Growth of the second waveguide layer 6: The temperature is controlled at 800℃, and trimethylindium and triethylgallium are introduced to grow the second waveguide layer 6. The indium composition and its distribution of the second waveguide layer 6 are controlled by adjusting the flow rate of trimethylindium or the growth temperature. (5) Growth of the first sublayer 701: The temperature is raised to 900℃, and trimethylaluminum, trimethylgallium and ammonia are introduced to grow the first sublayer 701. The aluminum composition and its distribution of the first sublayer 701 are controlled by adjusting the flow rate of trimethylaluminum or the growth temperature. (6) Growth of the second sublayer 702: The temperature is maintained at 900℃, the flow rate of trimethylaluminum is reduced or turned off, trimethylgallium and ammonia are introduced, and magnesia dicerocene is introduced at the same time to grow the second sublayer 702. (7) Growth of the second confinement layer 8: The temperature is raised to 880°C, and trimethylaluminum and triethylgallium are introduced, while magnesia-dicenocene is introduced at the same time to grow the second confinement layer 8; (8) Growth of contact layer 9: The temperature is raised to 880°C, and trimethylgallium or triethylgallium is introduced, while magnesium pyrocene is introduced at the same time to grow contact layer 9.

[0030] Example 3 A semiconductor laser epitaxial structure having a composite electron blocking layer 7 includes, from bottom to top, a substrate 1, a first confinement layer A 2, a first confinement layer B 3, a first waveguide layer 4, an active region 5, a second waveguide layer 6, a composite electron blocking layer 7, a second confinement layer 8, and a contact layer 9; the composite electron blocking layer 7 includes, from bottom to top, a first sublayer 701 and a second sublayer 702; Among them, substrate 1 is an n-type silicon carbide substrate 1; The first confinement layer A2 is an AlGaN layer with an Al composition of 10%, a thickness of 2 μm, and Si as the dopant with a doping concentration of 5 × 10⁻⁶. 18 cm -3 ; The first confinement layer B3 is a GaN layer with a thickness of 0.5 μm, doped with Si at a concentration of 1 × 10⁻⁶. 19 cm -3 ; The first waveguide layer 4 is an InGaN layer, in which the In composition gradually increases from 5% to 10%, the thickness is 0.3 μm, the doping element is Si, and the doping concentration is 1×10⁻⁶. 19 cm -3 ; The active region 5 is an InGaN / GaN structure, with InGaN as the quantum well layer and GaN as the barrier layer. The active region 5 is composed of alternating quantum well layers and barrier layers, with three alternation periods, a total thickness of 40 Å, and an In composition of 25%. The second waveguide layer 6 is an InGaN layer with an In composition of 5% and a thickness of 0.3 μm; The first sublayer 701 is a single layer of Al. x1 Ga 1-x1 N layers, x1 gradually changes from 1 to 0.6, with a thickness of 15nm, and unintentionally doped; The second sublayer 702 is Al. 0.15 Ga 0.85 The N-layer has a thickness of 30 nm and is doped with Mg at a concentration of 1 × 10⁻⁶. 20 cm -3 ; The second confinement layer 8 is an AlGaN layer with an Al composition of 10%, a thickness of 0.8 μm, and Mg as the dopant with a doping concentration of 1 × 10⁸ μm. 20 cm -3 ; Contact layer 9 is a GaN layer with a thickness of 100 nm, and the doping element is Mg with a doping concentration of 1×10⁻⁶. 20 cm -3 .

[0031] The above-mentioned method for fabricating the semiconductor laser epitaxial structure with the composite electron blocking layer 7 is carried out using an MOCVD device and includes the following steps: (1) Growth of the first confinement layer: An n-type GaN substrate is placed in a growth chamber, and nitrogen and hydrogen are introduced as carrier gases, while ammonia is introduced as a reaction gas to provide a nitrogen source. The temperature is raised to 1000℃, and trimethylgallium, trimethylaluminum and silane are introduced first to grow the first confinement layer A2; then the trimethylaluminum is turned off and the first confinement layer B3 is continued to grow; both the first confinement layer A2 and the first confinement layer B3 use silane as the n-type doping source; (2) Growth of the first waveguide layer 4: Cool down to 800℃, introduce trimethylindium and triethylgallium, and grow the first waveguide layer 4. Control the indium composition and distribution of the waveguide layer by adjusting the flow rate of trimethylindium or the growth temperature; when the flow rate of trimethylindium increases, the indium composition in the waveguide layer increases; when the growth temperature decreases, the indium composition in the waveguide layer increases. (3) Growth of active region 5: Cool down to 700℃, introduce trimethylindium and triethylgallium, and grow the quantum well layer in active region 5. Control the indium composition by adjusting the flow rate of trimethylindium or the growth temperature; when the temperature is raised to 800℃, only triethylgallium is introduced to grow the barrier layer in active region 5. (4) Growth of the second waveguide layer 6: The temperature is controlled at 800℃, and trimethylindium and triethylgallium are introduced to grow the second waveguide layer 6; (5) Growth of the first sublayer 701: The temperature is raised to 900℃, and trimethylaluminum, trimethylgallium and ammonia are introduced to grow the first sublayer 701. The aluminum composition and its distribution of the first sublayer 701 are controlled by adjusting the flow rate of trimethylaluminum or the growth temperature. (6) Growth of the second sublayer 702: The temperature is maintained at 900℃, the flow rate of trimethylaluminum is reduced or turned off, trimethylgallium and ammonia are introduced, and magnesia dicerocene is introduced at the same time to grow the second sublayer 702. (7) Growth of the second confinement layer 8: The temperature is raised to 880°C, and trimethylaluminum and triethylgallium are introduced, while magnesia-dicenocene is introduced at the same time to grow the second confinement layer 8; (8) Growth of contact layer 9: The temperature is raised to 880°C, and trimethylgallium or triethylgallium is introduced, while magnesium pyrocene is introduced at the same time to grow contact layer 9.

[0032] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A semiconductor laser epitaxial structure with a composite electron blocking layer, characterized in that, The epitaxial growth direction includes a substrate, a first confinement layer A, a first confinement layer B, a first waveguide layer, an active region, a second waveguide layer, a composite electron blocking layer, a second confinement layer, and a contact layer; the composite electron blocking layer includes a first sublayer and a second sublayer along the epitaxial growth direction; wherein, the first sublayer is Al. x1 Ga 1-x1 Nth layer, 0.5≤x1≤1; the second sub-layer is Al. x2 Ga 1-x2 The N-layer or GaN-layer has a particle size distribution of 0.05 ≤ x2 ≤ 0.15 and is doped with Mg.

2. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 1, characterized in that, In the first sublayer, x1 decreases linearly and gradually along the epitaxial growth direction, and the thickness of the first sublayer is 2~15nm, which is not intentionally doped.

3. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 1, characterized in that, The thickness of the second sublayer is 5~30 nm, and the Mg doping concentration is 1×10⁻⁶. 18 ~1×10 20 cm -3 .

4. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 1, characterized in that, The first confinement layer A is an AlGaN layer with an Al composition of 1%~10%, a thickness of 0.8~2μm, and Si as the dopant element with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 The first confinement layer B is a GaN layer with a thickness of 0.2~0.5μm, and the doping element is Si with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 The second confinement layer is an AlGaN layer with an Al composition of 2%~10%, a thickness of 0.2~0.8μm, and Mg as the dopant with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 The contact layer is a GaN layer with a thickness ranging from 5 to 100 nm, and the doping element is Mg with a doping concentration of 2 × 10⁻⁶. 19 ~1×10 20 cm -3 .

5. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 1, characterized in that, The first waveguide layer is an InGaN layer with a thickness of 0.05~0.5μm, and the doping element is Si with a doping concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 .

6. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 5, characterized in that, When the semiconductor laser is in the blue-green light band, the average value of the In component in the first waveguide layer is 3%~8%. The In component can be a constant value or a linearly gradual change. The gradual change is from a low value to a high value, and the thickness is 0.2~0.3μm. When the semiconductor laser is in the violet or ultraviolet band, the average value of the In composition of the first waveguide layer is 2% to 5%. The In composition can be a constant value or a linear gradient, with the gradient changing from a low value to a high value. The thickness is 0.05 to 0.12 μm.

7. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 1, characterized in that, The active region is an InGaN / GaN structure; when the semiconductor laser is in the blue-green light band, the thickness of the active region is 20~40Å and the In composition is 15%~35%; when the semiconductor laser is in the violet or ultraviolet light band, the thickness of the active region is 60~90Å and the In composition is 3%~15%.

8. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 1, characterized in that, The second waveguide layer is an InGaN layer with a thickness of 0.05~0.5μm.

9. The semiconductor laser epitaxial structure with a composite electron blocking layer as described in claim 8, characterized in that, When the semiconductor laser is in the blue-green light band, the average value of the In composition in the second waveguide layer is 4%~8%. The In composition can be a constant value or a linearly gradual change. The gradual change is from a high value to a low value, and the thickness is 0.2~0.3μm. When the semiconductor laser is in the violet or ultraviolet band, the average value of the In composition of the second waveguide layer is 2% to 5%. The In composition can be a constant value or a linearly gradual change. The gradual change is from a high value to a low value, and the thickness is 0.05 to 0.12 μm.

10. A method for fabricating a semiconductor laser epitaxial structure with a composite electron blocking layer as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Growth of the first confinement layer: Place the substrate in the growth chamber and heat it to 1000~1100℃. First, introduce trimethylgallium and trimethylaluminum to grow the first confinement layer A; then turn off the trimethylaluminum and grow the first confinement layer B. (2) Growth of the first waveguide layer: Cool down to 750~850℃, introduce trimethylindium and triethylgallium, and grow the first waveguide layer; (3) Growth of active region: Cool down to 700~900℃, introduce trimethylindium and triethylgallium to grow active region; (4) Growth of the second waveguide layer: The temperature is controlled at 750~850℃, and trimethylindium and triethylgallium are introduced to grow the second waveguide layer; (5) Growth of the first sublayer: The temperature is raised to 900~950℃, and trimethylaluminum and trimethylgallium are introduced to grow the first sublayer; (6) Growth of the second sublayer: The temperature is maintained at 900~950℃, the flow rate of trimethylaluminum is reduced or turned off, and trimethylgallium is introduced to grow the second sublayer; (7) Growth of the second confinement layer: The temperature is raised to 850~950℃, and trimethylaluminum and triethylgallium are introduced to grow the second confinement layer; (8) Growth of contact layer: The temperature is raised to 850~950℃, and trimethylgallium or triethylgallium is introduced to grow the contact layer.

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