Semiconductor laser epitaxial structure and manufacturing method thereof

Abstract

The application discloses a semiconductor laser epitaxial structure and a manufacturing method thereof. The semiconductor laser epitaxial structure comprises a multi-quantum well layer, the multi-quantum well layer is a periodic structure, each period comprises a well layer, a cap layer and a barrier layer in sequence, and the well layer comprises InGaN material; the cap layer comprises an AlGaN layer, an InGaN layer and a P-type AlGaN layer in sequence, the AlGaN layer is adjacent to the well layer, and the P-type AlGaN layer is adjacent to the barrier layer; the cap layer structure protects the well layer from thermal shock and ensures the crystal quality of the well layer.

Description

Technical Field

[0001] This invention relates to the field of optical chip technology, and in particular to a semiconductor laser epitaxial structure and its fabrication method. Background Technology

[0002] The multi-quantum-well active region is the core structure of a laser. Due to the temperature-dependent nature of In atoms, the InGaN well layer requires a relatively low growth temperature. However, the high growth temperature of the functional layer above the well layer can lead to poor uniformity of the active region and a decrease in luminous efficiency. As the In content increases, the inhomogeneity of the InGaN well layer and interface becomes more prominent. It is necessary to protect the InGaN well layer from thermal shock and ensure crystal quality to meet the high standards required for lasers.

[0003] The low ionization energy of the In-N bond in InGaN leads to the easy enrichment and precipitation of In, affecting its crystal quality and forming non-radiative recombination centers, thus impacting optical output power. Low-temperature growth of InGaN results in numerous defects within the quantum well, affecting device lifetime and reliability. The GaN / InGaN lattice mismatch within the quantum well easily generates stress during overlapping growth, leading to lattice mismatch and dislocations. The polarization effect in multiple quantum wells significantly reduces the spatial overlap of wavefunctions, resulting in reduced spatial overlap of electron-hole pairs and affecting luminous efficiency. Summary of the Invention

[0004] One of the objectives of this invention is to provide a semiconductor laser epitaxial structure that at least solves the technical problems of thermal shock to the well layer and difficulty in ensuring crystal quality in the prior art.

[0005] One of the objectives of this invention is to provide a method for fabricating an epitaxial structure of a semiconductor laser.

[0006] To achieve one of the above-mentioned objectives, one embodiment of the present invention provides a semiconductor laser epitaxial structure, including a multi-quantum well layer. The multi-quantum well layer is a periodic structure, and each period includes a well layer, a cap layer, and a barrier layer in sequence. The well layer includes InGaN material, and the cap layer includes an AlGaN layer, an InGaN layer, and a P-type AlGaN layer in sequence. The AlGaN layer is adjacent to the well layer, and the P-type AlGaN layer is adjacent to the barrier layer.

[0007] As a further improvement of one embodiment of the present invention, the AlGaN layer and the InGaN layer generate a first polarization charge, and the P-type AlGaN layer and the InGaN layer generate a second polarization charge, wherein the first polarization charge and the second polarization charge have opposite polarities.

[0008] As a further improvement of one embodiment of the present invention, the bandgap width of the InGaN layer is smaller than the bandgap width of the AlGaN layer and the bandgap width of the P-type AlGaN layer.

[0009] As a further improvement of one embodiment of the present invention, the proportion of Al component in the P-type AlGaN layer is smaller than the proportion of Al component in the AlGaN layer, and the bandgap of the P-type AlGaN layer is smaller than the bandgap of the AlGaN layer.

[0010] As a further improvement to one embodiment of the present invention, the material composition of the AlGaN layer includes Al a Ga 1-a N, the material composition of the p-type AlGaN layer includes Al c Ga 1-c N, where the value of a ranges from 0.03 to 0.06, the value of c ranges from 0.01 to 0.03, and the value of c is less than the value of a.

[0011] As a further improvement of one embodiment of the present invention, the dopant of the p-type AlGaN layer is Mg, wherein the doping concentration of Mg is 1×10⁻⁶. 15 cm -3 ~1×10 17 cm -3 .

[0012] As a further improvement to one embodiment of the present invention, the material composition of the InGaN layer is In b Ga 1-b N, where b ranges from 0.01 to 0.1.

[0013] As a further improvement of one embodiment of the present invention, the thickness of the AlGaN layer is 0.01nm to 1nm, the thickness of the InGaN layer is 0.01nm to 1nm, the thickness of the P-type AlGaN layer is 0.01nm to 1nm, and the thickness of the cap layer is 0.5nm to 3nm.

[0014] As a further improvement of one embodiment of the present invention, the semiconductor laser epitaxial structure sequentially includes a substrate, a buffer layer, an N-type confinement layer, a lower waveguide layer and a multiple quantum well layer, wherein the well layer in the first period is adjacent to the lower waveguide layer;

[0015] The buffer layer comprises GaN material, the N-type confinement layer comprises N-type doped AlGaN material, and the lower waveguide layer comprises InGaN material.

[0016] As a further improvement of one embodiment of the present invention, the semiconductor laser epitaxial structure sequentially includes a multi-quantum well layer, an upper waveguide layer, an electron blocking layer, a P-type confinement layer, and an ohmic contact layer; the barrier layer in the last cycle is adjacent to the upper waveguide layer; The upper waveguide layer comprises InGaN material, the electron blocking layer comprises AlGaN material, the P-type confinement layer comprises P-type doped AlGaN material, and the ohmic contact layer comprises P-type doped GaN material. The doping concentration of the ohmic contact layer is higher than that of the P-type confinement layer.

[0017] As a further improvement of one embodiment of the present invention, the material composition of the electron blocking layer is Al. d Ga 1-d N, where d ranges from 0.05 to 0.3.

[0018] To achieve one of the above-mentioned objectives, one embodiment of the present invention provides a method for fabricating a semiconductor laser epitaxial structure, comprising the following steps: Growing a multi-quantum-well layer on a substrate; The growth of the multiple quantum well layer includes periodically growing a well layer, a cap layer, and a barrier layer, wherein the well layer comprises InGaN material. The growth of the cap layer includes sequentially growing an AlGaN layer, an InGaN layer, and a P-type AlGaN layer on the well layer.

[0019] As a further improvement to one embodiment of the present invention, before growing a multiple quantum well layer on a substrate, the step includes: providing the substrate; The substrate provided specifically includes: controlling the pressure of the reaction environment to be 200-600 Torr, controlling the temperature of the reaction environment to be 1000℃-1200℃, controlling the reaction environment to be a high-purity hydrogen atmosphere, and controlling the reaction time to last 5-8 min; And / or, growing the well layer includes the steps of: The reaction environment is controlled to have a first temperature value and a first pressure value, wherein the first temperature value is 700℃~800℃ and the first pressure value is 100~300Torr, and an N source, a Ga source and an In source are introduced; Growing the cap layer includes the following steps: The reaction environment is controlled to have a second temperature value and a second pressure value, the second temperature value being 700℃~800℃ and the second pressure value being 100~300Torr, and an N source, a Ga source and an Al source are introduced to grow the AlGaN layer; The reaction environment is controlled to have a third temperature value and a third pressure value, wherein the third temperature value is 700℃~800℃ and the third pressure value is 100~300Torr, and an N source, a Ga source and an In source are introduced to grow the InGaN layer. The reaction environment is controlled to have a fourth temperature value and a fourth pressure value, wherein the fourth temperature value is 850℃~900℃ and the fourth pressure value is 100~300Torr, and an N source, a Ga source, an Al source and a P-type dopant are introduced to grow the P-type AlGaN layer. The fourth temperature value is greater than the second temperature value and the third temperature value.

[0020] As a further improvement of one embodiment of the present invention, growing the barrier layer includes the following steps: The temperature of the reaction environment is controlled at 800℃~900℃, the pressure is controlled at 100~300Torr, and N source and Ga source are introduced.

[0021] As a further improvement to one embodiment of the present invention, the step before growing the multiple quantum well layer includes: sequentially growing a buffer layer, an N-type confinement layer, and a lower waveguide layer on the substrate, specifically including: The temperature of the reaction environment is controlled at 1050℃~1150℃, the pressure is controlled at 200~400 Torr, and N source and Ga source are introduced to grow the buffer layer. The temperature of the reaction environment is controlled at 1100℃~1150℃, the pressure is 100~500Torr, and N source, Ga source and Al source are introduced, and N-type dopant is introduced to grow the N-type confinement layer. The reaction environment temperature is controlled at 700–800°C and the pressure at 100–500 Torr. N source, Ga source and In source are introduced to grow the lower waveguide layer. The well layer of the first period is grown on the lower waveguide layer.

[0022] And / or, after growing the multi-quantum-well layer, the process includes the step of sequentially growing an upper waveguide layer, an electron-blocking layer, a P-type confinement layer, and an ohmic contact layer on the barrier layer of the last cycle, specifically including: The temperature of the reaction environment is controlled at 700-800℃ and the pressure is controlled at 100-500 Torr. N source, Ga source and In source are introduced to grow the upper waveguide layer. The reaction environment is controlled at a temperature of 700–800°C and a pressure of 50–200 Torr. N source, Ga source and Al source are introduced to grow the electron blocking layer. The temperature of the reaction environment is controlled at 900–1000 °C and the pressure at 100–400 Torr. N source, Ga source, Al source and P-type dopant are introduced to grow the P-type confinement layer. The reaction environment is controlled at a temperature of 800–950°C and a pressure of 100–400 Torr. An N-source, a Ga-source, and a P-type dopant are introduced to grow the ohmic contact layer.

[0023] Compared with the prior art, the present invention provides a semiconductor laser epitaxial structure, wherein the cap layer comprises an AlGaN layer, an InGaN layer and a P-type AlGaN layer in sequence. The AlGaN layer and the well layer are adjacent and grown at a low temperature to avoid thermal shock to the well layer, while the P-type AlGaN layer is relatively far away from the well layer and grown at a higher temperature, which is beneficial to improving the crystal quality of the multi-quantum-well layer. Al atoms are small and can be used as substitution atoms, and can also block dislocation extension and penetration, thus ensuring the crystal quality of the multi-quantum-well layer. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the epitaxial structure of a semiconductor laser in one embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of a multi-quantum well layer in one embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the cap layer in one embodiment of the present invention.

[0027] Figure 4-5 This is a schematic diagram of a method for fabricating a semiconductor laser epitaxial structure according to an embodiment of the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0029] It should be noted that the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," "third," "fourth," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] The terms “connection,” “connected to,” or any other variations are intended to encompass various relative positions where a connection exists, including both direct and indirect connections. A direct connection can be formed through a pneumatic conduit, while an indirect connection can be formed through devices such as valves or sensors, through pneumatic components such as brake control units, or through any other medium such as air.

[0031] Please see Figure 1 This is a schematic diagram of a semiconductor laser epitaxial structure 100 provided in an embodiment of the present invention.

[0032] The semiconductor laser epitaxial structure 100 includes a multi-quantum well layer 50, which is a periodic structure. Each period includes a well layer 51, a cap layer 52, and a barrier layer 53. The well layer 51 includes InGaN material, and the cap layer 52 includes an AlGaN layer 521, an InGaN layer 522, and a P-type AlGaN layer 523. The AlGaN layer 521 is adjacent to the well layer 51, and the P-type AlGaN layer 523 is adjacent to the barrier layer 53.

[0033] Specifically, combined Figure 2-3 As shown, the multiple quantum well layer 50 is the active region of the laser. Electron and hole radiation recombine to generate the optical gain required for stimulated emission. The emission wavelength is tuned through the quantum confinement effect, and high crystal quality is key to low threshold current. In one specific embodiment, the number of periods in the multiple quantum well layer 50 is 2-10.

[0034] In the cap layer 52 structure of this application, the growth temperature of the well layer 51 is low. The cap layer 52 is set with an AlGaN layer 521 adjacent to the well layer 51. The growth temperature of the AlGaN layer 521 is also relatively low to avoid thermal shock damage to the well layer 51. The P-type AlGaN layer 523 is relatively far away from the well layer 51. The growth temperature of the P-type AlGaN layer 523 is high. High temperature is beneficial to obtaining high-quality crystals and does not affect the well layer 51, thereby improving the crystal quality of the multi-quantum well layer 50.

[0035] In AlGaN materials, Al atoms are small and can exist as substitution atoms to repair nitrogen vacancies or other point defects, fill defect sites, and reduce the density of nonradiative recombination centers. Al atoms can also block dislocation extension and penetration, thereby improving the crystal quality of the multi-quantum well layer 50.

[0036] AlGaN material has a wide bandgap. AlGaN layer 521 can effectively block electrons and confine them in the well layer 51 region, while P-type AlGaN layer 523 can help block holes from escaping towards barrier layer 53. Together, they can efficiently confine charge carriers within the multi-quantum well layer.

[0037] AlGaN layer 521 and InGaN layer 522 generate a first polarization charge, while p-type AlGaN layer 523 and InGaN layer 522 generate a second polarization charge. The first and second polarization charges have opposite polarities and can compensate for or cancel each other, thus reducing the polarization effect. More specifically, polarization charges are generated at the heterojunctions between AlGaN layer 521 and well layer 51, AlGaN layer 521 and InGaN layer 522, and InGaN layer 522 and p-type AlGaN layer 523. The polarization charges generated at different heterojunctions have opposite polarities and can compensate for or partially cancel each other, thereby reducing the net polarization electric field in the multi-quantum-well layer 50, alleviating the quantum confinement Stark effect, increasing the spatial overlap of electron and hole wave functions, and improving radiative recombination efficiency and luminescence efficiency.

[0038] The bandgap of the InGaN layer 522 is smaller than that of the AlGaN layer 521 and the P-type AlGaN layer 523. The stacked structure formed by the AlGaN layer 521, InGaN layer 522, and P-type AlGaN layer 523 can create a "green channel" for hole injection, improving hole injection efficiency. The InGaN layer 522 in the middle acts as a step in the valence band, increasing the tunneling probability of holes. Furthermore, under the influence of the weakened polarization electric field at the heterojunction, the local hole barrier formed at the valence band top at the interface is reduced or even flattened, making it easier for holes to tunnel or thermally emit across the barrier into the well layer 51, thereby improving hole injection efficiency and luminescence efficiency.

[0039] The p-type AlGaN layer 523 introduces p-type dopants, thereby introducing ionized acceptors, generating shielding charges to counteract polarization charges, alleviating band tilt caused by the polarization electric field, and flattening the band to improve electron-hole wavefunction overlap, thus enhancing radiative recombination efficiency and luminescence efficiency. The p-type AlGaN layer 523 is located on top to prevent p-type dopant atoms from diffusing into the well layer 51, which would lead to a decrease in the lattice quality of the multi-quantum-well layer.

[0040] In one specific embodiment, the Al composition ratio in the P-type AlGaN layer 523 is lower than that in the AlGaN layer 521, and the bandgap width of the P-type AlGaN layer is smaller than that of the AlGaN layer. While ensuring good carrier confinement capability, an excessively high Al composition ratio in the P-type AlGaN layer 523 can easily lead to a high potential barrier, resulting in an undesirable increase in operating voltage.

[0041] In one specific embodiment, the material composition of the AlGaN layer includes Al a Ga 1-a The material composition of the N,P type AlGaN layer includes Al c Ga 1-cN, where the value of a ranges from 0.03 to 0.06, the value of c ranges from 0.01 to 0.03, and the value of c is less than the value of a.

[0042] The bandgap of AlGaN materials increases with increasing Al content. A higher Al content results in a higher conduction band barrier in AlGaN layer 521, blocking electron leakage and enhancing electron confinement, thereby increasing the radiative recombination probability. A lower Al content reduces the valence band barrier height of p-type AlGaN layer 523 and decreases layer resistance. During hole injection, the barrier to overcome is lower, improving injection efficiency; and due to the reduced resistance, the operating voltage does not increase significantly.

[0043] The dopant of the p-type AlGaN layer is Mg, with a Mg doping concentration of 1 × 10⁻⁶. 15 cm -3 ~1×10 17 cm -3 Mg dopants readily diffuse at high temperatures. The p-type AlGaN layer 523 is positioned close to the barrier layer 53 to prevent Mg atoms from diffusing downwards into the well layer 51, which would degrade the crystal quality of the multi-quantum-well layer. If the upper p-type AlGaN layer has a high Al content, a higher growth temperature is required, which would exacerbate the diffusion of Mg atoms into the well layer 51. In this application, the Mg dopant is present in the low-Al content AlGaN layer 521, resulting in a relatively low growth temperature and suppressing the diffusion of Mg atoms.

[0044] Excessive Mg doping concentration can easily damage the lattice quality of the multi-quantum-well layer 50, while insufficient doping concentration will not increase carrier recombination efficiency.

[0045] In one specific embodiment, the material composition of the InGaN layer 522 is In b Ga 1-b N, where b ranges from 0.01 to 0.1, reduces stress buffering at the interface. Specifically, the lattice constant of InGaN material increases with increasing In content. If the In content is too high, it will lead to lattice mismatch with AlGaN layer 521 and P-type AlGaN layer 523, which is detrimental to interface flatness and lattice quality.

[0046] It is understandable that, based on the material composition of InGaN layer 522, AlGaN layer 521 and P-type AlGaN layer 523, it can be reasonably concluded that the bandgap of InGaN layer 522 is smaller than the bandgap of AlGaN layer 521 and the bandgap of P-type AlGaN layer 523, and that the bandgap of P-type AlGaN layer 523 is smaller than the bandgap of AlGaN layer 521.

[0047] In one specific embodiment, the AlGaN layer 521 has a thickness of 0.01 nm to 1 nm, the InGaN layer 522 has a thickness of 0.01 nm to 1 nm, the P-type AlGaN layer 523 has a thickness of 0.01 nm to 1 nm, and the total thickness of the cap layer 52 is 0.5 nm to 3 nm, achieving an extremely thin insertion layer while meeting the requirement of protecting the well layer 51 from thermal shock. Preferably, the AlGaN layer 521 has a thickness of 0.5 nm, the InGaN layer 522 has a thickness of 0.5 nm, the P-type AlGaN layer 523 has a thickness of 0.5 nm, and the total thickness of the cap layer 52 is 1.5 nm.

[0048] In one specific embodiment, the well layer 51 is made of InGaN material, and the In content in the well layer 51 is typically higher than 10% to reduce the band gap and obtain visible light emission. The thickness of the well layer 51 is preferably 3 nm. The barrier layer 53 is made of GaN material, providing a barrier to confine charge carriers within the active region. The thickness of the barrier layer 53 is preferably 5 nm.

[0049] In one specific embodiment, the semiconductor laser epitaxial structure 100 sequentially includes a substrate 10, a buffer layer 20, an N-type confinement layer 30, a lower waveguide layer 40, and a multiple quantum well layer 50, with the well layer 51 of the first period adjacent to the lower waveguide layer 40. The buffer layer 20 comprises GaN material, the N-type confinement layer 30 comprises N-type doped AlGaN material, and the lower waveguide layer 40 comprises InGaN material.

[0050] The multi-quantum well layer 50 is a periodic structure. The first period is characterized by the first period grown above the lower waveguide layer 40 when growing from bottom to top, and the last period is characterized by the last period when growing from bottom to top. It can be understood that the first period is located at the bottom of the multi-quantum well layer 50, and the last period is located at the top of the multi-quantum well layer 50.

[0051] Combination Figure 1 As shown, when applied to the epitaxial structure 100 of a semiconductor laser, the substrate 10 is preferably a GaN homogeneous substrate, which provides mechanical support and a crystal growth substrate, enabling lattice matching with the epitaxial layer, reducing dislocation density, and laying the foundation for subsequent high-quality epitaxy.

[0052] The buffer layer 20 is made of GaN material with a thickness of 20nm to 2000nm, preferably 1000nm. It is grown first on the substrate 10 to alleviate lattice mismatch and thermal mismatch between the substrate 10 and the epitaxial layer above, filter defects on the surface of the substrate 10, prevent dislocations from extending upward and penetrating, and provide a flat surface for the subsequent growth of the epitaxial layer.

[0053] The N-type confinement layer 30 is made of N-type doped AlGaN material with a thickness of 100 nm to 1000 nm, preferably 200 nm. Specifically, the N-type dopant is silane. The N-type confinement layer 30 provides electron injection into the active region. Simultaneously, the AlGaN material has a wide bandgap, which confines electrons within the multi-quantum-well layer 50, preventing electron overflow to the P-type confinement layer side. Utilizing the refractive index difference, the laser beam field is confined near the active region, improving the optical confinement factor.

[0054] The lower waveguide layer 40 is made of InGaN material with a thickness of 100 nm to 500 nm, preferably 300 nm. The lower waveguide layer 40 has a higher refractive index than the N-type confinement layer 30, allowing the optical field to extend moderately downwards from the active region, reducing the overlap between the optical field and the highly doped N-type confinement layer 30 or the substrate 10, and decreasing free carrier absorption losses. The optical absorption coefficient of InGaN material is lower than that of GaN; by optimizing the In composition, the parasitic absorption of laser light by the lower waveguide layer 40 is reduced.

[0055] In one specific embodiment, the semiconductor laser epitaxial structure 100 sequentially includes a multi-quantum well layer 50, an upper waveguide layer 60, an electron blocking layer 70, a P-type confinement layer 80, and an ohmic contact layer 90; the barrier layer 53 of the last cycle is adjacent to the upper waveguide layer 60. The upper waveguide layer 60 comprises InGaN material, the electron blocking layer 70 comprises AlGaN material, the P-type confinement layer 80 comprises P-type doped AlGaN material, and the ohmic contact layer 90 comprises P-type doped GaN material. The doping concentration of the ohmic contact layer 90 is higher than that of the P-type confinement layer 80.

[0056] The semiconductor laser epitaxial structure 100, from bottom to top, consists of a substrate 10, a buffer layer 20, an N-type confinement layer 30, a lower waveguide layer 40, a multiple quantum well layer 50, an upper waveguide layer 60, an electron blocking layer 70, a P-type confinement layer 80, and an ohmic contact layer 90.

[0057] The upper waveguide layer 60 is made of InGaN material with a thickness of 100nm to 500nm, preferably 300nm. Together with the lower waveguide layer 40, it forms a symmetrical optical waveguide structure centered on the multi-quantum-well layer 50, which effectively confines the laser light field near the active region and improves the optical confinement factor.

[0058] The material composition of electron blocking layer 70 is Al d Ga 1-d N, where d ranges from 0.05 to 0.3, and the thickness of the electron blocking layer 70 is from 5 nm to 100 nm, preferably 20 nm. The AlGaN material has a wide bandgap, forming a high conduction band barrier between the multi-quantum well layer 50 and the P-type confinement layer 80, preventing electrons from leaking from the active region to the P-type confinement layer 80 side, and reducing nonradiative recombination.

[0059] The electron blocking layer 70 reduces the valence band barrier by optimizing the Al composition, making it easier for holes to be injected into the active region from the P-type confinement layer 80 side.

[0060] The p-type confinement layer 80 is a p-type doped AlGaN material with a thickness of 100 nm to 1000 nm, preferably 300 nm, and a doping concentration of 5 × 10⁻⁶. 17 ~5×10 19 cm -3 The P-type confinement layer 80 provides holes to the active region. By utilizing the wide bandgap of the AlGaN material, the holes are confined within the multi-quantum-well layer, preventing leakage of holes to the N-type confinement layer side.

[0061] The P-type confinement layer 80 and the N-type confinement layer 30 together form a vertical optical waveguide. By utilizing the refractive index difference, the optical field is confined within the active region and the waveguide layer, thereby improving gain efficiency. P-type doped AlGaN materials can be grown at higher temperatures to obtain good crystal quality.

[0062] The ohmic contact layer 90 is made of p-type heavily doped GaN material, with a thickness of 10 nm to 100 nm, preferably 50 nm, and a doping concentration of 1 × 10⁻⁶. 20 ~1×10 21 cm -3 It is used to form a good ohmic contact with the metal electrode. The doping concentration of the ohmic contact layer 90 is higher than that of the p-type confinement layer 80, forming a concentration gradient, which helps the transport of holes from the ohmic contact layer 90 to the p-type confinement layer 80 and the active region.

[0063] This application also discloses a method for fabricating a semiconductor laser epitaxial structure 100, used to fabricate the semiconductor laser epitaxial structure 100 in any of the above technical solutions, combined with Figure 4 As shown, the manufacturing method includes the following steps: S10: A multi-quantum well layer 50 is grown on the substrate 10; S20: The growth of the multiple quantum well layer 50 includes the periodic growth of a well layer 51, a cap layer 52, and a barrier layer 53, wherein the well layer 51 comprises InGaN material. S22: Growing the cap layer 52 includes sequentially growing an AlGaN layer 521, an InGaN layer 522, and a P-type AlGaN layer 523 on the well layer 51.

[0064] The growth temperature of the well layer 51 is low. The AlGaN layer 521 is placed adjacent to the well layer 51, and the growth temperature of the AlGaN layer 521 is also relatively low to avoid thermal shock damage to the well layer 51. The P-type AlGaN layer 523 is relatively far away from the well layer 51. The growth temperature of the P-type AlGaN layer 523 is high. The high temperature is conducive to obtaining a high-quality crystal and does not affect the well layer 51, thereby improving the crystal quality of the multi-quantum well layer 50.

[0065] Before growing the multiple quantum well layer 50 on the substrate 10, the step S1 is included: providing the substrate 10; The substrate 10 is specifically provided by: controlling the pressure of the reaction environment to be 200-600 Torr, controlling the temperature of the reaction environment to be 1000℃-1200℃, controlling the reaction environment to be a high-purity hydrogen atmosphere, and controlling the reaction time to last 5-8 minutes; using hydrogen to carry out a reduction reaction to clean the particles and oxides on the surface of the substrate 10.

[0066] S21: The growth well layer 51 includes the steps of: controlling the reaction environment to have a first temperature value and a first pressure value, wherein the first temperature value is 700℃~800℃ and the first pressure value is 100~300 Torr, and introducing an N source, a Ga source and an In source. Specifically, the first temperature value is 720℃ and the first pressure value is 200 Torr, as high temperature and high pressure are not conducive to the incorporation of In atoms.

[0067] Specifically, high-purity ammonia (NH3) is introduced to provide the N source; triethylgallium (TEGa) is introduced to provide the Ga source, with a carrier gas used for the Ga source; and trimethylindium (TMIn) is introduced to provide the In source, with a carrier gas used for the In source. TEGa and TMIn are organometallic sources and require transport via a carrier gas. NH3, as a nitrogen atom donor, decomposes at high temperatures to provide active N atoms, which react with the metal source to form nitrides. NH3 is typically introduced directly into the reaction environment without the need for a carrier gas.

[0068] The carrier gas can be N2, H2, or a mixture of N2 and H2. When growing the well layer 51, H2 reacts with TMIn to generate volatile In-H compounds, which reduces the incorporation efficiency of In. Therefore, when growing the In-containing well layer 51, H2 is usually turned off, and only N2 is used as the carrier gas.

[0069] S22: Growth cap layer 52 includes the following steps: The reaction environment is controlled with a second temperature value and a second pressure value. The second temperature value is 700℃~800℃ and the second pressure value is 100~300Torr. N source, Ga source and Al source are introduced to grow AlGaN layer 521. The reaction environment is controlled with a third temperature value and a third pressure value. The third temperature value is 700℃~800℃ and the third pressure value is 100~300Torr. N source, Ga source and In source are introduced to grow InGaN layer 522. The reaction environment is controlled with a fourth temperature value and a fourth pressure value. The fourth temperature value is 850℃~900℃ and the fourth pressure value is 100~300Torr. N source, Ga source, Al source and P-type dopant are introduced to grow P-type AlGaN layer 523. The fourth temperature value is greater than the second and third temperature values. The second and third temperature values ​​are adjacent to the first temperature value. Thus, the growth of the cap layer 52 is beneficial to reduce the thermal shock to the well layer 51, while the higher fourth temperature value is beneficial to improve the crystal quality of the multi-quantum well layer 50.

[0070] Specifically, the second and third temperature values ​​are 760°C, which is close to the first temperature value, and the fourth temperature value is 860°C. The second, third, and fourth pressure values ​​are all 200 Torr.

[0071] Specifically, during the growth of the AlGaN layer 521, NH3 is introduced to introduce the N source; TEGa is introduced to introduce the Ga source, with the Ga source introduced via a carrier gas; TMAl is introduced to introduce the Al source, with the Al source introduced via a carrier gas; the carrier gas is N2, and H2 is shut off. Excessive growth pressure is detrimental to Al incorporation, while insufficient growth pressure leads to poor lattice quality.

[0072] When growing the InGaN layer at 522, NH3 is introduced to introduce the N source; TEGa is introduced to introduce the Ga source, with the Ga source introduced via a carrier gas; TMIn is introduced to introduce the In source, with the In source introduced via a carrier gas; the carrier gas is N2, and H2 is shut off. Excessive growth pressure is detrimental to In incorporation, while insufficient pressure results in poor lattice quality.

[0073] During the growth of the p-type AlGaN layer 523, NH3 is introduced to provide the N source; TEGa is introduced to provide the Ga source, with the Ga source introduced via a carrier gas; TMAl is introduced to provide the Al source, with the Al source introduced via a carrier gas; CP2Mg is introduced as a p-type dopant, with the introduction via a carrier gas; the carrier gas is N2, and H2 is shut off to avoid the Mg doping being affected by H2. Excessive p-type doping can easily damage the lattice quality of the multi-quantum-well layer 50, while insufficient p-type doping does not increase the carrier recombination efficiency in the active region.

[0074] S23: The growth of the barrier layer 53 includes the following steps: controlling the temperature of the reaction environment to be 800℃~900℃ and the pressure to be 100~300 Torr, and introducing an N source and a Ga source. Specifically, the barrier layer 53 is a GaN material, and the temperature during the growth of the barrier layer 53 is 850℃, the pressure is 200 Torr, and the preferred growth thickness of the barrier layer 53 is 5nm.

[0075] When growing barrier layer 53, NH3 is introduced to introduce the N source; TEGa is introduced to introduce the Ga source, and the Ga source is introduced by means of a carrier gas, which is a mixture of N2 and H2.

[0076] The above describes the growth method for the well layer 51, cap layer 52, and barrier layer 53 for each cycle. In practice, the growth of the multi-quantum well layer 50 can be completed by periodically repeating the growth of the well layer 51, cap layer 52, and barrier layer 53.

[0077] In one specific embodiment, growing the multiple quantum well layer 50 includes the following steps: S21: Growth trap layer 51, the temperature of the reaction environment is controlled at 720℃, the pressure is controlled at 200 Torr, NH3 is introduced to provide N source, TEGa is introduced as Ga source, TMIn is introduced as In source, N2 is introduced as carrier gas, and the growth thickness is 3nm.

[0078] S22: Growth cap layer 52 includes: An AlGaN layer 521 was grown, with the reaction environment controlled at a temperature of 760℃ and a pressure of 200 Torr. NH3 was introduced to provide the N source, TEGa was introduced as the Ga source, and TMAl was introduced as the Al source. N2 was used as the carrier gas, and the growth thickness was 0.5 nm. An InGaN layer of 522 was grown. The reaction environment was controlled at a temperature of 760℃ and a pressure of 200 Torr. NH3 was introduced to provide the N source, TEGa was introduced as the Ga source, and TMIn was introduced as the In source. N2 was used as the carrier gas, and the growth thickness was 0.5 nm. A p-type AlGaN layer 523 was grown under controlled conditions: temperature 860℃, pressure 200 Torr, NH3 as the N source, TEGa as the Ga source, TMAl as the Al source, CP2Mg as the p-type dopant, N2 as the carrier gas, and a growth thickness of 0.5 nm.

[0079] S23: Growth barrier layer 53, the temperature of the reaction environment is controlled at 850℃, the pressure is controlled at 200 Torr, NH3 is introduced to provide N source, TEGa is introduced as Ga source, N2 and H2 are used as carrier gas, and the growth thickness is 5nm.

[0080] Combination Figure 5 As shown, before growing the multi-quantum-well layer 50, step S11 is included: sequentially growing a buffer layer 20, an N-type confinement layer 30, and a lower waveguide layer 40 on the substrate 10, specifically including: The temperature of the reaction environment was controlled at 1050℃~1150℃, and the pressure was controlled at 200~400 Torr. N source and Ga source were introduced to grow buffer layer 20. The temperature of the reaction environment was controlled at 1100℃~1150℃, the pressure was 100~500Torr, and N source, Ga source and Al source were introduced, along with N-type dopant, to grow N-type confinement layer 30. The reaction environment temperature is controlled at 700-800℃ and the pressure is controlled at 100-500 Torr. N source, Ga source and In source are introduced to grow the lower waveguide layer 40. The first period well layer 51 is grown on the lower waveguide layer 40.

[0081] Specifically, during the growth of buffer layer 20, NH3 is introduced to introduce the N source; trimethylgallium (TMGa) is introduced to introduce the Ga source, and the Ga source is introduced with the help of a carrier gas, which is a mixture of N2 and H2.

[0082] During the growth of the N-type confinement layer 30, NH3 is introduced to introduce the N source; TMGa is introduced to introduce the Ga source, using a carrier gas; TMAl is introduced to introduce the Al source, using a carrier gas, which is a mixture of N2 and H2. Silane (SiH4) is introduced as the N-type dopant.

[0083] When growing the lower waveguide layer 40, NH3 is introduced to introduce the N source; TEGa is introduced to introduce the Ga source, and the Ga source is introduced with the help of a carrier gas; TMIn is introduced to introduce the In source, and the In source is introduced with the help of a carrier gas, which is N2, and H2 is turned off.

[0084] Combination Figure 5 As shown, after growing the multi-quantum-well layer 50, step S12 is included: sequentially growing the upper waveguide layer 60, the electron blocking layer 70, the P-type confinement layer 80, and the ohmic contact layer 90 on the barrier layer 53 of the last cycle, specifically including: The temperature of the reaction environment is controlled at 700-800℃ and the pressure is controlled at 100-500 Torr. N source, Ga source and In source are introduced to grow the upper waveguide layer 60. The temperature of the reaction environment was controlled at 700–800℃ and the pressure at 50–200 Torr. N source, Ga source and Al source were introduced to grow an electron blocking layer 70. The temperature of the reaction environment is controlled at 900–1000℃ and the pressure at 100–400 Torr. N source, Ga source, Al source and P-type dopant are introduced to grow a P-type confinement layer 80. The temperature of the reaction environment is controlled at 800–950℃ and the pressure at 100–400 Torr. N-source, Ga-source and P-type dopant are introduced to grow the ohmic contact layer 90.

[0085] Specifically, when growing the upper waveguide layer 60, NH3 is introduced to introduce the N source; TEGa is introduced to introduce the Ga source, and the Ga source is introduced with the help of a carrier gas; TMIn is introduced to introduce the In source, and the In source is introduced with the help of a carrier gas, the carrier gas being N2, and H2 is turned off.

[0086] When growing the electron blocking layer 70, NH3 is introduced to introduce the N source; TEGa is introduced to introduce the Ga source, and the Ga source is introduced with the help of a carrier gas; TMAl is introduced to introduce the Al source, and the Al source is introduced with the help of a carrier gas. The carrier gas is N2, and H2 is turned off.

[0087] When growing the P-type confinement layer 80, NH3 is introduced to introduce the N source; TMGa is introduced to introduce the Ga source, and the Ga source is introduced with the help of a carrier gas; TMAl is introduced to introduce the Al source, and the Al source is introduced with the help of a carrier gas. The carrier gas is N2, and H2 is turned off; CP2Mg is introduced as a P-type dopant.

[0088] When growing the ohmic contact layer 90, NH3 is introduced to introduce the N source; TMGa is introduced to introduce the Ga source, and the Ga source is introduced with the help of a carrier gas, which is N2 and H2 is turned off; CP2Mg is introduced as a P-type dopant.

[0089] The above, combined with Figure 5 As shown, in one specific embodiment, the fabrication method of the semiconductor laser epitaxial structure 100 includes the steps of: providing a substrate 10, and sequentially growing a buffer layer 20, an N-type confinement layer 30, a lower waveguide layer 40, a multiple quantum well layer 50, an upper waveguide layer 60, an electron blocking layer 70, a P-type confinement layer 80, and an ohmic contact layer 90. The growth of the multiple quantum well layer 50 includes periodically growing a well layer 51, a cap layer 52, and a barrier layer 53. The cap layer 52 includes sequentially growing an AlGaN layer 521, an InGaN layer 522, and a P-type AlGaN layer 523 on the well layer 51.

[0090] The beneficial effects of the present invention are as follows: the growth temperature of the well layer 51 is low, the growth temperature of the AlGaN layer 521 adjacent to the well layer 51 is also relatively low, thus avoiding thermal shock damage to the well layer 51; the growth temperature of the P-type AlGaN layer 523 is high, and high temperature is conducive to obtaining high-quality crystals. In AlGaN materials, Al atoms are small and can exist as substitution atoms. Al atoms can also block dislocation extension and penetration, thereby improving the crystal quality of the multi-quantum well layer 50. At the heterojunctions of AlGaN layer 521 and well layer 51, AlGaN layer 521 and InGaN layer 522, and InGaN layer 522 and P-type AlGaN layer 523, polarization charges are generated. The polarization charges generated at different heterojunctions have opposite polarities and can compensate for or partially cancel each other, increasing the spatial overlap of electron and hole wave functions and improving radiative recombination efficiency and luminescence efficiency. The p-type AlGaN layer 523 introduces p-type dopants, thereby introducing ionized acceptors, generating shielding charges to counteract polarization charges, alleviating band tilt caused by the polarization electric field, and flattening the band to improve electron-hole wavefunction overlap, thus enhancing radiative recombination efficiency and luminescence efficiency. The p-type AlGaN layer 523 is located on top to prevent p-type dopant atoms from diffusing into the well layer 51, which would lead to a decrease in the lattice quality of the multi-quantum-well layer. The stacked structure of the cap layer 52 creates a "green channel" for hole injection, improving hole injection efficiency. Due to the effect of the polarization electric field, the valence band top forms a local hole barrier at the interface, which is reduced or even flattened. Holes can more easily tunnel or thermally emit across the barrier to enter the well layer 51, thereby improving hole injection efficiency and luminescence efficiency.

[0091] This can be formed by referring to any of the technical solutions provided above, and will not be elaborated here.

[0092] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0093] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A semiconductor laser epitaxial structure, comprising a multi-quantum-well layer, wherein the multi-quantum-well layer is a periodic structure, each period comprising a well layer, a cap layer, and a barrier layer in sequence, wherein the well layer comprises InGaN material, characterized in that, The cap layer comprises, in sequence, an AlGaN layer, an InGaN layer, and a P-type AlGaN layer, with the AlGaN layer adjacent to the well layer and the P-type AlGaN layer adjacent to the barrier layer.

2. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The AlGaN layer and the InGaN layer generate a first polarization charge, and the P-type AlGaN layer and the InGaN layer generate a second polarization charge, wherein the first polarization charge and the second polarization charge have opposite polarities.

3. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The bandgap of the InGaN layer is smaller than the bandgap of the AlGaN layer and the bandgap of the P-type AlGaN layer.

4. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The proportion of Al component in the P-type AlGaN layer is less than that in the AlGaN layer, and the bandgap of the P-type AlGaN layer is less than that of the AlGaN layer.

5. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The material composition of the AlGaN layer includes Al a Ga 1-a N, the material composition of the p-type AlGaN layer includes Al c Ga 1-c N, where the value of a ranges from 0.03 to 0.06, the value of c ranges from 0.01 to 0.03, and the value of c is less than the value of a.

6. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The dopant of the p-type AlGaN layer is Mg, wherein the Mg doping concentration is 1×10⁻⁶. 15 cm -3 ~1×10 17 cm -3 ; And / or, the material composition of the InGaN layer is In b Ga 1-b N, where b ranges from 0.01 to 0.

1.

7. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The AlGaN layer has a thickness of 0.01 nm to 1 nm, the InGaN layer has a thickness of 0.01 nm to 1 nm, the P-type AlGaN layer has a thickness of 0.01 nm to 1 nm, and the cap layer has a thickness of 0.5 nm to 3 nm.

8. The semiconductor laser epitaxial structure according to claim 1, characterized in that, The semiconductor laser epitaxial structure sequentially includes a substrate, a buffer layer, an N-type confinement layer, a lower waveguide layer, and a multiple quantum well layer, with the well layer in the first period adjacent to the lower waveguide layer; The buffer layer comprises GaN material, the N-type confinement layer comprises N-type doped AlGaN material, and the lower waveguide layer comprises InGaN material. The semiconductor laser epitaxial structure sequentially includes a multi-quantum well layer, an upper waveguide layer, an electron blocking layer, a P-type confinement layer, and an ohmic contact layer; the barrier layer in the last cycle is adjacent to the upper waveguide layer; The upper waveguide layer comprises InGaN material, the electron blocking layer comprises AlGaN material, the P-type confinement layer comprises P-type doped AlGaN material, and the ohmic contact layer comprises P-type doped GaN material. The doping concentration of the ohmic contact layer is higher than that of the P-type confinement layer.

9. The semiconductor laser epitaxial structure according to claim 8, characterized in that, The electron blocking layer is composed of Al. d Ga 1-d N, where d ranges from 0.05 to 0.

3.

10. A method for fabricating an epitaxial structure of a semiconductor laser, comprising the following steps: Growing a multi-quantum-well layer on a substrate; The growth of the multiple quantum well layer includes periodically growing a well layer, a cap layer, and a barrier layer, wherein the well layer comprises InGaN material, characterized in that... The growth of the cap layer includes sequentially growing an AlGaN layer, an InGaN layer, and a P-type AlGaN layer on the well layer.

11. The method for fabricating a semiconductor laser epitaxial structure according to claim 10, characterized in that, Before growing a multi-quantum-well layer on a substrate, the step includes: providing the substrate; The substrate provided specifically includes: controlling the pressure of the reaction environment to be 200-600 Torr, controlling the temperature of the reaction environment to be 1000℃-1200℃, controlling the reaction environment to be a high-purity hydrogen atmosphere, and controlling the reaction time to last 5-8 min; And / or, growing the well layer includes the steps of: The reaction environment is controlled to have a first temperature value and a first pressure value, wherein the first temperature value is 700℃~800℃ and the first pressure value is 100~300Torr, and an N source, a Ga source and an In source are introduced; Growing the cap layer includes the following steps: The reaction environment is controlled to have a second temperature value and a second pressure value, the second temperature value being 700℃~800℃ and the second pressure value being 100~300Torr, and an N source, a Ga source and an Al source are introduced to grow the AlGaN layer; The reaction environment is controlled to have a third temperature value and a third pressure value, wherein the third temperature value is 700℃~800℃ and the third pressure value is 100~300Torr, and an N source, a Ga source and an In source are introduced to grow the InGaN layer. The reaction environment is controlled to have a fourth temperature value and a fourth pressure value, wherein the fourth temperature value is 850℃~900℃ and the fourth pressure value is 100~300Torr, and an N source, a Ga source, an Al source and a P-type dopant are introduced to grow the P-type AlGaN layer. The fourth temperature value is greater than the second temperature value and the third temperature value.

12. The method for fabricating a semiconductor laser epitaxial structure according to claim 10, characterized in that, Growing the barrier layer includes the following steps: The temperature of the reaction environment is controlled at 800℃~900℃, the pressure is controlled at 100~300Torr, and N source and Ga source are introduced.

13. The method for fabricating a semiconductor laser epitaxial structure according to claim 10, characterized in that, Before growing the multi-quantum-well layer, the steps include: sequentially growing a buffer layer, an N-type confinement layer, and a lower waveguide layer on the substrate, specifically including: The temperature of the reaction environment is controlled at 1050℃~1150℃, the pressure is controlled at 200~400 Torr, and N source and Ga source are introduced to grow the buffer layer. The temperature of the reaction environment is controlled at 1100℃~1150℃, the pressure is 100~500Torr, and N source, Ga source and Al source are introduced, and N-type dopant is introduced to grow the N-type confinement layer. The reaction environment temperature is controlled at 700–800°C and the pressure at 100–500 Torr. N source, Ga source and In source are introduced to grow the lower waveguide layer. The well layer of the first period is grown on the lower waveguide layer. And / or, after growing the multi-quantum-well layer, the process includes the step of sequentially growing an upper waveguide layer, an electron-blocking layer, a P-type confinement layer, and an ohmic contact layer on the barrier layer of the last cycle, specifically including: The temperature of the reaction environment is controlled at 700-800℃ and the pressure is controlled at 100-500 Torr. N source, Ga source and In source are introduced to grow the upper waveguide layer. The reaction environment is controlled at a temperature of 700–800°C and a pressure of 50–200 Torr. N source, Ga source and Al source are introduced to grow the electron blocking layer. The temperature of the reaction environment is controlled at 900–1000 °C and the pressure at 100–400 Torr. N source, Ga source, Al source and P-type dopant are introduced to grow the P-type confinement layer. The reaction environment is controlled at a temperature of 800–950°C and a pressure of 100–400 Torr. An N-source, a Ga-source, and a P-type dopant are introduced to grow the ohmic contact layer.

Images