Light emitting diode and preparation method thereof

Abstract

The invention provides a light emitting diode and a preparation method thereof, and belongs to the technical field of semiconductors. The light emitting diode comprises a first semiconductor layer, a first multi-quantum well layer, a second multi-quantum well layer and a second semiconductor layer which are stacked in sequence. The first multi-quantum well layer comprises a plurality of first quantum well layers and a plurality of first quantum barrier layers which are alternately stacked, and the second multi-quantum well layer comprises a plurality of second quantum well layers and a plurality of second quantum barrier layers which are alternately stacked; the first quantum barrier layer and the second quantum barrier layer are both AlGaAsP layers, and the content of an Al component in the second quantum barrier layer is smaller than the content of an Al component in the first quantum barrier layer. The brightness of the light emitting diode can be improved.

Description

Technical Field

[0001] This disclosure belongs to the field of semiconductor technology, and specifically relates to a light-emitting diode and its fabrication method. Background Technology

[0002] As an energy-saving device, light-emitting diodes (LEDs) are widely used in full-color displays, lighting, automotive lights, and other fields.

[0003] In related technologies, a light-emitting diode (LED) includes a multiple quantum well layer and a first semiconductor layer and a second semiconductor layer located on both sides of the multiple quantum well layer. The multiple quantum well layer comprises alternating layers of multiple quantum well layers and multiple quantum barrier layers. The quantum barrier layers are AlGaAsP layers with a thickness of 10 nm to 20 nm.

[0004] However, in multi-quantum-well layers, each quantum barrier layer has the same bandgap due to its fixed composition, resulting in consistent energy blocking of charge carriers. Because electrons have high mobility and easily diffuse away, the quantum barrier layers need to have high blocking power to confine them within the quantum well; while holes have low mobility and struggle to cross the barrier, requiring the quantum barrier layers to have lower blocking power to successfully enter the quantum well. Therefore, the structures provided in related technologies cannot simultaneously meet the different transport requirements of electrons and holes, leading to carrier injection imbalance and uneven interlayer distribution, which in turn exacerbates nonradiative recombination losses and ultimately limits the device's luminous efficiency. Summary of the Invention

[0005] This disclosure provides a light-emitting diode (LED) and its fabrication method, which can improve the brightness of the LED. The technical solution is as follows: This disclosure provides a light-emitting diode (LED) comprising a first semiconductor layer, a first multiple quantum well layer, a second multiple quantum well layer, and a second semiconductor layer stacked sequentially. The first multiple quantum well layer comprises alternating layers of multiple first quantum well layers and multiple first quantum barrier layers, and the second multiple quantum well layer comprises alternating layers of multiple second quantum well layers and multiple second quantum barrier layers. Both the first and second quantum barrier layers are AlGaAsP layers, and the Al content in the second quantum barrier layer is less than the Al content in the first quantum barrier layer.

[0006] In another implementation of this disclosure, the Al component content in the first quantum barrier layer is greater than 0.3 and less than 0.4, and the Al component content in the second quantum barrier layer is greater than 0.1 and less than 0.2.

[0007] In another implementation of this disclosure, the number of first quantum well layers is 6 to 8, and the number of first quantum barrier layers is 6 to 8.

[0008] In another implementation of this disclosure, the number of the second quantum well layers is 4 to 6, and the number of the second quantum barrier layers is 4 to 6.

[0009] In another implementation of this disclosure, the thickness of the first quantum well layer and the second quantum well layer is 20 nm to 30 nm.

[0010] In another implementation of this disclosure, the thickness of both the first quantum barrier layer and the second quantum barrier layer is 30 nm to 40 nm.

[0011] In another implementation of this disclosure, the first semiconductor layer includes a first waveguide layer, which is an AlGaAs layer, and the Al content in the first waveguide layer is greater than 0.3 and less than 0.4.

[0012] In another implementation of this disclosure, the second semiconductor layer includes a second waveguide layer, which is an AlGaAs layer, and the Al content in the second waveguide layer is greater than 0.1 and less than 0.2%.

[0013] In another implementation of this disclosure, the second semiconductor layer further includes a second stress transition layer; the second stress transition layer is an AlGaAsP layer, and the Al component content and the As component content in the second stress transition layer both decrease monotonically along the direction from the first semiconductor layer to the second semiconductor layer.

[0014] On the other hand, this disclosure also provides a method for fabricating a light-emitting diode, the method comprising: forming a first semiconductor layer, a first quantum well layer, a second multiple quantum well layer, and a second semiconductor layer stacked sequentially; the first multiple quantum well layer comprising alternatingly stacked first quantum well layers and multiple first quantum barrier layers, and the second multiple quantum well layer comprising alternatingly stacked second quantum well layers and multiple second quantum barrier layers; wherein the first quantum barrier layer and the second quantum barrier layer are both AlGaAsP layers, and the Al content in the second quantum barrier layer is less than the Al content in the first quantum barrier layer.

[0015] The beneficial effects of the technical solutions provided in this disclosure are: Because this light-emitting diode includes a first multiple quantum well layer and a second multiple quantum well layer, with the first multiple quantum well layer consisting of alternating layers of first quantum well layers and multiple first quantum barrier layers, and the second multiple quantum well layer consisting of alternating layers of second quantum well layers and multiple second quantum barrier layers. Both the first and second quantum barrier layers are AlGaAsP layers, with the Al content in the second quantum barrier layer being lower than that in the first quantum barrier layer. This design creates a differentiated barrier height configuration. Electrons injected from the n-region, when encountering the higher barrier of the first quantum barrier layer, are effectively reflected and confined within the thicker first quantum well layer, suppressing their escape. Meanwhile, the second quantum barrier layer on the p-region side, due to its lower Al content, forms a low barrier structure, which is more suitable for the characteristics of low hole mobility and high effective mass, thereby promoting hole injection into deeper regions of the thicker second quantum well layer. With this design, the differentiated barrier formed by the first and second quantum well layers can build a carrier concentration gradient throughout the entire first and second quantum well layers, guiding electrons and holes to overlap efficiently in specific regions of space, enhancing the radiative recombination process, and thus obtaining higher luminescence efficiency. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure; Figure 2 This is a schematic diagram of another light-emitting diode structure provided in an embodiment of this disclosure; Figure 3 This is a flowchart of a method for fabricating a light-emitting diode according to an embodiment of this disclosure; Figure 4 This is a flowchart of another method for fabricating a light-emitting diode provided in this embodiment.

[0018] The symbols in the diagram represent the following meanings: 1. First semiconductor layer; 11. First waveguide layer; 12. First ohmic contact layer; 13. First current spreading layer; 14. First confinement layer; 15. Electrode bonding layer; 16. Roughening layer; 2. First multi-quantum well layer; 21. First quantum well layer; 22. First quantum barrier layer; 3. Second multiple quantum well layer; 31. Second quantum well layer; 32. Second quantum barrier layer; 4. Second semiconductor layer; 41. Second waveguide layer; 42. Second confinement layer; 43. Second stress transition layer; 44. Second current spreading layer; 45. Second ohmic contact layer; 5. Growth substrate; 6. Etching stop layer; 7. Buffer layer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0020] This disclosure provides a light-emitting diode, such as... Figure 1 As shown, the light-emitting diode includes a first semiconductor layer 1, a first multiple quantum well layer 2, a second multiple quantum well layer 3, and a second semiconductor layer 4 stacked sequentially.

[0021] The first multiple quantum well layer 2 includes multiple alternating layers of first quantum well layers 21 and multiple alternating layers of first quantum barrier layers 22, and the second multiple quantum well layer 3 includes multiple alternating layers of second quantum well layers 31 and multiple alternating layers of second quantum barrier layers 32.

[0022] In this process, both the first quantum barrier layer 22 and the second quantum barrier layer 32 are AlGaAsP layers, and the Al content in the second quantum barrier layer 32 is less than the Al content in the first quantum barrier layer 22.

[0023] The light-emitting diode includes a first multiple quantum well layer 2 and a second multiple quantum well layer 3. The first multiple quantum well layer 2 consists of alternating layers of first quantum well layers 21 and first quantum barrier layers 22, while the second multiple quantum well layer 3 consists of alternating layers of second quantum well layers 31 and second quantum barrier layers 32. Both the first and second quantum barrier layers are AlGaAsP layers, with the Al content in the second quantum barrier layer being lower than that in the first quantum barrier layer. This design creates a differentiated barrier height configuration. Electrons injected from the n-region, when encountering the higher barrier of the first quantum barrier layer 22, are effectively reflected and confined within the thicker first quantum well layer 21, suppressing their escape. Meanwhile, the second quantum barrier layer 32 on the p-region side, due to its lower Al content, forms a low barrier structure, which is more suitable for the characteristics of low hole mobility and high effective mass, thereby promoting hole injection into the deeper regions of the thicker second quantum well layer 31. With this design, the first quantum well layer 21 and the second quantum well layer 31 form a differentiated barrier, which can build a carrier concentration gradient throughout the entire first quantum well layer 2 and the second quantum well layer 3, guide electrons and holes to overlap efficiently in a specific region of space, enhance the radiative recombination process, and thus obtain higher luminescence efficiency.

[0024] Optionally, the Al content in the first quantum barrier layer 22 is greater than 0.3 and less than 0.4. The Al content in the second quantum barrier layer 32 is greater than 0.1 and less than 0.2.

[0025] In the above implementation, by limiting the Al component content in the first quantum barrier layer 22, a higher potential barrier can be formed, thereby effectively reflecting and confining electrons and preventing their leakage.

[0026] The Al content in the second quantum barrier layer 32 is controlled within a low range of 0.1 to 0.2%, creating a low barrier that is compatible with the low hole mobility, facilitating its injection into the depths of the quantum well. This differentiated configuration of high-aluminum and low-aluminum barriers synergistically creates a favorable carrier concentration gradient within the well, promoting efficient spatial overlap of electrons and holes, thereby significantly improving radiative recombination efficiency and luminescence performance.

[0027] Optionally, the number of first quantum well layers 21 is 6 to 8; the number of first quantum barrier layers 22 is 6 to 8.

[0028] In the above implementation, the above settings can form a deep electron trapping and confinement region on the side near the n-region, ensuring that electrons are effectively confined in the first multi-quantum well layer 2 and effectively preventing electron leakage.

[0029] The number of first quantum well layers 21 and the number of first quantum barrier layers 22 can be the same or different, as long as they are arranged alternately.

[0030] Optionally, the number of second quantum well layers 31 is 4 to 6, and the number of second quantum barrier layers 32 is 4 to 6.

[0031] In the above implementation, the above settings can construct a broad, efficient hole injection region on one side of the p-region, guiding holes deep into the core of the second multi-quantum well layer 3.

[0032] The number of second quantum well layers 31 and the number of second quantum barrier layers 32 can be the same or different, as long as they are arranged alternately.

[0033] Optionally, the thickness of both the first quantum barrier layer 22 and the second quantum barrier layer 32 is 30nm~40nm.

[0034] In the above implementation, the thickness of both the first quantum barrier layer 22 and the second quantum barrier layer 32 is 30nm~40nm, which allows both the first quantum barrier layer 22 and the second quantum barrier layer 32 to be configured as thin layers. This consistent thin-layer configuration, while ensuring effective carrier isolation and confinement between each quantum well, significantly reduces the total thickness of the multi-quantum-well layers.

[0035] Optionally, the thickness of both the first quantum well layer 21 and the second quantum well layer 31 is 20nm~30nm.

[0036] The above makes the thicknesses of the first quantum well layer 21 and the second quantum well layer 31 much larger than the conventional quantum well thickness. The design of this thickness can expand the accommodation space for carriers. At the same time, by combining with the different barrier heights formed by the first quantum well layer 21 and the second quantum well layer 31, a carrier concentration gradient can be constructed within the entire first multiple quantum well layer 2 and the second multiple quantum well layer 3, guiding electrons and holes to efficiently overlap in a specific spatial region, enhancing the radiative recombination process, and thus obtaining a higher luminous efficiency.

[0037] The light-emitting diode provided in this embodiment is applicable to the chip of a light-emitting diode with an infrared wavelength of 940 nm. By using the first multiple quantum well layer 2 and the second multiple quantum well layer 3 with different barrier heights and combining with the relatively thick first quantum well layer 21 and the second quantum well layer 31, not only can the luminous efficiency be improved, but it is also beneficial to grow a high-quality epitaxial layer, thereby greatly enhancing its luminous intensity.

[0038] Optionally, both the first quantum well layer 21 and the second quantum well layer 31 are In x Ga 1-x As layers, and x satisfies 0.05 < x < 0.15.

[0039] The same In x Ga 1-x As (0.05 < x < 0.15) material is used as the quantum well layer in both the first multiple quantum well layer 2 and the second multiple quantum well layer 3. The In composition range can effectively adjust the emission wavelength to the target range, and at the same time introduce appropriate compressive strain, which helps to improve the carrier recombination efficiency. This combines with the different first quantum barrier layer 22 and the second quantum barrier layer 32 to jointly form an efficient active region system. Among them, the quantum well is responsible for capturing carriers and emitting light, while the functionally partitioned quantum barriers are responsible for restricting electrons and promoting hole injection respectively. This collaborative design of uniform well layers and asymmetric barrier layers ensures that carriers can achieve efficient spatial overlap and radiative recombination in multiple wells, thus significantly improving the overall luminous performance of the device.

[0040] Optionally, the As component content in the first quantum barrier layer 22 and the second quantum barrier layer 32 is greater than 0.7 and less than 0.9.

[0041] The above settings can make both the first quantum barrier layer 22 and the second quantum barrier layer 32 have a high As component setting. The high As component setting ensures excellent lattice matching between the barrier layer material and the well layer, reduces the epitaxial growth stress and dislocation density, and provides a high-quality and low-loss transport channel for carriers.

[0042] Figure 2 is a schematic structural diagram of another light-emitting diode provided in the embodiments of the present disclosure. Combining Figure 2Optionally, the first semiconductor layer 1 includes a first waveguide layer 11, which is connected to the first multiple quantum well layer 2. The first waveguide layer 11 is an AlGaAs layer, and the Al content in the first waveguide layer 11 is greater than 0.3 and less than 0.4. The thickness of the first waveguide layer 11 is 300 nm to 600 nm.

[0043] In the above implementation, the first waveguide layer 11 effectively confines photons generated within the first multiple quantum well layer 2 to a plane perpendicular to the growth direction, suppressing light energy loss and thus improving photon extraction efficiency. Secondly, as an essential pathway for carrier transport, the Al content of the first waveguide layer 11 allows for a smooth conduction band transition with the first quantum barrier layer 22, facilitating smoother electron injection into the first multiple quantum well layer 2 and efficient recombination with holes injected from the p-side. Therefore, the design of the first waveguide layer 11 is crucial for achieving efficient electro-optical conversion. It works synergistically with the differentiated barrier layer design of the first multiple quantum well layer 2 to jointly ensure the high performance of the device.

[0044] Optionally, the first semiconductor layer 1 further includes a first ohmic contact layer 12, a first current spreading layer 13, and a first confinement layer 14 stacked sequentially, with the first confinement layer 14 located on the side of the first waveguide layer 11 away from the second semiconductor layer 4. The first confinement layer 14 is connected to the first waveguide layer 11.

[0045] In the above implementation, the first ohmic contact layer 12 is used to achieve ohmic contact. The first current spreading layer 13 is used to rapidly and uniformly spread the injected point or line current in the lateral direction (parallel to the surface of the substrate), so that it can be uniformly injected into the entire light-emitting layer, thereby avoiding current congestion, achieving uniform light emission, and improving device performance and reliability. Without the first current spreading layer 13, the current will take the shortest path with the least resistance, resulting in a highly non-uniform current density distribution. The first confinement layer 14 is used to effectively confine charge carriers, thereby improving recombination efficiency.

[0046] Optionally, the first ohmic contact layer 12 is an n-type GaAs layer with a thickness of 30nm~60nm.

[0047] In the above implementation, the thickness of the first ohmic contact layer 12 is 30nm~60nm. This thickness ensures that the resistance of the first ohmic contact layer 12 is low, providing a sufficient and low-resistance path for charge carriers and ensuring the formation of excellent ohmic contacts. If the thickness is too thin, it may lead to excessively high series resistance, affecting current injection efficiency. On the other hand, if the thickness is too large, it may lead to defects in the crystal (such as dislocations), and the processing time is longer, which is not conducive to improving efficiency.

[0048] For example, the thickness of the first ohmic contact layer 12 is 40nm, 50nm, 55nm, etc. This ensures low resistance and stable and reliable ohmic contact of the first ohmic contact layer 12, while avoiding affecting the process due to excessive thickness.

[0049] Optionally, the first ohmic contact layer 12 is silicon-doped, with Si2H6 as the dopant and a carrier concentration of 4 × 10⁻⁶. 18 ~6×10 18 / cm 3 .

[0050] In the above implementation, the n-doped source used when forming the first ohmic contact layer 12 is a silicon source.

[0051] Since silicon is a group IV element with four valence electrons, while group III elements only have three, there is one extra free electron. This free electron becomes the charge carrier in the electrical conductivity, thus achieving n-type doping. Furthermore, the doping concentration in the first ohmic contact layer 12 is set to 4 × 10⁻⁶. 18 ~6×10 18 / cm 3 This indicates that within the first ohmic contact layer 12, there are 4 × 10⁻⁶ cells per cubic centimeter of volume. 18 ~6×10 18 One free electron. This is represented by heavy doping. Through heavy doping, an extremely thin depletion region is formed on the surface of the first semiconductor layer, allowing electrons to easily pass through via quantum tunneling, thus forming a linear, low-resistance ohmic contact.

[0052] Optionally, the first current spreading layer 13 is an n-type Al with a thickness of 3μm~4μm. x Ga 1-x As (0.1 < x < 0.3) layer.

[0053] The reason for choosing n-type Al in the above implementation method is... x Ga 1-x The As layer serves as the first current spreading layer 13 because of its low resistivity, acting as a conductive platform that allows the current to diffuse laterally before reaching the first multiple quantum well layer 2. The 3μm~4μm thick first current spreading layer 13 provides sufficient lateral transport paths, allowing the current to diffuse uniformly from the electrode contact point to the entire active region, preventing current concentration below the electrode.

[0054] Optionally, the first confinement layer 14 is an n-type Al with a thickness of 300 nm to 600 nm. x Ga 1-x As (0.3 < x < 0.6) layer.

[0055] In the above implementation, the main function of this layer is to form a barrier for the optical waveguide. Because its Al composition is higher than that of the first waveguide layer 11, it has a lower refractive index. By creating a strong refractive index difference with the first waveguide layer 11, it more tightly confines the photons generated within the first multiple quantum well layer 2 to the region formed by the first waveguide layer 11 and the first multiple quantum well layer 2, greatly suppressing photon leakage loss. Simultaneously, its sufficient thickness ensures the sufficiency of the optical confinement effect, ultimately significantly improving the photon extraction efficiency and output power of the device.

[0056] For example, the first confinement layer 14 is silicon-doped, wherein the dopant is Si2H6 and the doping concentration is 0.5 × 10⁻⁶. 18 ~1×10 18 / cm 3 .

[0057] Si₂H₆ (silyl ether) is a commonly used n-type doping source for III-V semiconductors. After decomposition, it can stably provide Si atoms (replacing Ga / Al atoms and providing free electrons), exhibiting high doping efficiency and good uniformity. Setting the above doping concentration ensures that the conductivity of the first confinement layer 14 is sufficiently high (reducing current transmission loss) without increasing crystal defects due to excessive doping (defects reduce carrier mobility).

[0058] Optionally, the first semiconductor layer 1 further includes an electrode bonding layer 15 and a roughening layer 16, both of which are located between the first current spreading layer 13 and the first ohmic contact layer 12. The electrode bonding layer 15 is connected to the first ohmic contact layer 12.

[0059] In the above implementation, the electrode bonding layer 15 is used to connect with the first ohmic contact layer 12, and its main function is to provide excellent mechanical adhesion and thermal stability. As a robust adhesive layer, it ensures that the entire metal electrode system can withstand thermal and mechanical stresses during subsequent packaging, bonding, and long-term use, and will not peel off from the semiconductor surface.

[0060] The roughening layer 16 is used to force the current to switch from a lateral expansion mode to a vertical transport mode. Because the roughening layer 16 is a patterned structure, it physically blocks the current through its unetched areas and forces it to flow downwards through the etched window. This design discretizes the large-area injected current into a large number of uniformly distributed injection points, working in conjunction with the lateral transport function of the first current expansion layer 13 to ensure that the current can be uniformly and efficiently injected vertically into the first multi-quantum-well layer 2, thereby significantly improving luminescence uniformity and efficiency.

[0061] Subsequently, the electrode bonding layer 15 is an n-type Ga with a thickness of 70 nm to 150 nm. 0.5 In0.5 The P layer. Among them, the electrode adhesion layer 15 is silicon-doped, the dopant is Si2H6, and the doping concentration is 1×10 18 ~2×10 18 / cm 3 .

[0062] In the above implementation, the GaInP material itself has extremely high chemical stability and mechanical strength, which can effectively prevent the diffusion of the electrode metal. The moderate Si doping concentration (1×10 18 ~2×10 18 / cm 3 ) ensures good conductivity and controls the series resistance at a low level. The thickness of 70nm~150nm balances the relationship between mechanical strength and the total thickness of the device, providing sufficient protection and adhesion while avoiding unnecessary material consumption and stress accumulation.

[0063] Optionally, the roughening layer 16 is an n-type Al<00​​​​​​​​​​​​​​​​​​​​​​​​​​​In the above implementation, the second waveguide layer 41 and the first waveguide layer 11 together constitute an asymmetric optical waveguide structure. The second waveguide layer 41 is located on the p-region side and has a higher refractive index due to its lower Al composition. This helps to more effectively pull the photon recombination region towards the p-region side, thereby compensating for the optical loss that may be caused by the slightly higher absorption of the p-type material. Ultimately, this achieves optimal distribution and confinement of photons within the resonant cavity, improving optical output efficiency. Simultaneously, the low Al composition in this layer also provides a smoother valence band transition for hole injection from the p-region into the second multiple quantum well layer 3. This, combined with the low barrier design of the second quantum barrier layer 32, further promotes hole injection efficiency.

[0067] Optionally, the thickness of the second waveguide layer 41 is 400nm~700nm, and it is undoped.

[0068] In the above implementation, this thickness range ensures that the layer can serve as an effective core layer of the optical waveguide, working together with the first waveguide layer 11 on the n-region side and the first confinement layer 14 to sufficiently expand and confine the optical mode field outside the absorption region far from the metal electrodes. Sufficient thickness is the structural basis for achieving high beam quality and optical output efficiency. Keeping the layer undoped completely eliminates the absorption loss of photons by free carriers, ensuring that photons generated in the first multi-quantum-well layer 2 and entering the waveguide layer can propagate with minimal loss.

[0069] Optionally, the second semiconductor layer 4 further includes a second stress transition layer 43, which is a p-type AlGaAsP layer. The Al and As content in the second stress transition layer 43 both decrease monotonically along the direction from the first semiconductor layer 1 to the second semiconductor layer 4.

[0070] The second stress transition layer 43 is configured as described above, which allows a gradient lattice transition to be formed between the second stress transition layer 43 and the adjacent second confinement layer 42 and second current extension layer 44, gradually releasing interface stress, significantly reducing dislocation density, improving the crystal quality of the epitaxial layer, and simultaneously realizing band gradient between AlGaAs and GaP, improving carrier transport characteristics, reducing carrier recombination loss at the interface, and improving the photoelectric conversion efficiency of the device.

[0071] Optionally, the Al component content in the second stress transition layer 43 gradually decreases from 0.5 to 0, and the As component content gradually decreases from 0.8 to 0.

[0072] The above settings can create a gradually varying lattice constant gradient. This effectively buffers and releases the enormous stress caused by lattice mismatch at the interfaces of different materials, greatly suppressing the generation of defects such as dislocations, and improving material quality and device reliability.

[0073] Optionally, the thickness of the second stress transition layer 43 is 10 nm to 30 nm, the dopant is CCl4, and the carrier concentration is 4 × 10⁻⁶. 18 ~6×10 18 / cm 3 .

[0074] The above thickness setting ensures the effectiveness of the second stress transition layer 43 and avoids excessively increasing the total thickness and series resistance of the device. If it is too thin, the gradient will be too abrupt, losing the stress buffering effect and resembling an abrupt heterojunction, which is prone to defects. Moreover, the above doping concentration can form an extremely thin depletion region at the metal-semiconductor interface, allowing carriers to be transported mainly through tunneling, thereby significantly reducing contact resistance.

[0075] Optionally, the second semiconductor layer 4 further includes a second confinement layer 42 and a second current spreading layer 44, the second confinement layer 42 and the second current spreading layer 44 being located on both sides of the second stress transition layer 43, and the second confinement layer 42 being connected to the second waveguide layer 41.

[0076] The second confinement layer 42 is a p-type AlGaAs layer, and the second current spreading layer 44 is a p-type GaP layer.

[0077] In the above implementation, the second confinement layer 42 is used to form a bandgap difference with the second multiple quantum well layer 3, so as to increase the probability of holes and electrons meeting and recombinating in the second multiple quantum well layer 3. The second current spreading layer 44 is used to spread the point-like or line-like injected current uniformly in the lateral direction, so that the current is uniformly injected into the entire second multiple quantum well layer 3.

[0078] Optionally, the thickness of the second current spreading layer 44 is 50 nm to 100 nm, the dopant is Cp₂Mg, and the carrier concentration is 2 × 10⁻⁶. 18 ~4×10 18 / cm 3 .

[0079] In the above implementation, the above configuration allows the second current spreading layer 44 to effectively spread the current laterally. The moderate thickness ensures a low lateral resistance, while the uniform and sufficient Mg doping concentration provides ample charge carriers for the lateral transport of holes. This allows the current to be uniformly distributed across the entire chip area before reaching the underlying roughened layer window, fundamentally avoiding current congestion and ensuring uniform light emission.

[0080] Optionally, the Al content in the second confinement layer 42 (AlGaAs) is greater than 0.3% and less than 0.0%. The thickness of the second confinement layer 42 is 500 nm to 800 nm, the dopant is CCl4, and the carrier concentration is 1 × 10⁻⁶. 18 ~1.5×1018 / cm 3 .

[0081] The second confinement layer 42 is made of AlGaAs material. Its high Al content and large thickness together form a strong barrier on the p-region side, tightly confining photons to the emitting core region and greatly suppressing photon leakage to absorption regions such as p-type metal electrodes. Simultaneously, CCl4 is used for carbon doping, with the concentration controlled at 1×10⁻⁶. 18 ~1.5×10 18 / cm 3 This ensures sufficient conductivity to support longitudinal current transmission while avoiding free carrier absorption losses caused by excessive doping.

[0082] Optionally, the second semiconductor layer 4 further includes a second ohmic contact layer 45, which is stacked on the side of the second current spreading layer 44 away from the second stress transition layer 43. The second ohmic contact layer 45 is a p-type GaP layer.

[0083] In the above implementation, the above settings enable the second ohmic contact layer 45 to have low resistivity and high conductivity, so that the second current spreading layer 44 can act as an excellent conductive layer and achieve ohmic contact with the electrode.

[0084] Optionally, the thickness of the second ohmic contact layer 45 is 10 nm to 50 nm, the dopant is CCl4, and the carrier concentration is 0.8 × 10⁻⁶. 20 ~1.5×10 20 / cm 3 .

[0085] In the above implementation, the design can form a high-quality ohmic contact between the semiconductor and the metal electrode. The extremely high carrier concentration makes the depletion region on the semiconductor side extremely thin, greatly reducing the contact resistance. The lower contact resistance directly translates into lower operating voltage, lower power consumption, and less heat generation, thereby significantly improving the device's electro-optical conversion efficiency, output power, and long-term reliability.

[0086] Optionally, the light-emitting diode further includes a growth substrate 5, an etch stop layer 6, and a buffer layer 7, wherein the buffer layer 7 and the etch stop layer 6 are sequentially stacked on the growth substrate 5, and the etch stop layer 6 is connected to the first ohmic contact layer 12.

[0087] In the above implementation, the growth substrate 5 serves as the growth platform for the entire epitaxial layer of the light-emitting diode, simultaneously undertaking core functions such as physical support, lattice matching, and thermal or electrical conduction, directly affecting the quality of the epitaxial layer and the reliability of the device. The etching stop layer 6 is used to create a difference in etching rate between the etch stop layer 6 and adjacent layers when subsequent processes (such as peeling off the growth substrate 5) require etching a certain layer, achieving "etching stops at etch stop layer 6". The buffer layer 7 serves to transition and prevent the upward propagation of lattice defects and impurities in the growth substrate 5, providing a high-quality epitaxial starting platform with a complete lattice and a clean surface for subsequent functional layers.

[0088] In this embodiment, the growth substrate 5 is a GaAs substrate. The etching stop layer 6 is an n-type GaAs substrate with a thickness of 150 nm to 400 nm. 0.5 In 0.5 The P-layer has Si₂H₆ as the dopant and a carrier concentration of 1×10⁻⁶. 18 ~2×10 18 / cm 3 .

[0089] Buffer layer 7 is an n-type GaAs layer with a thickness of 500nm~700nm, doped with Si2H6, and with a carrier concentration of 1×10⁻⁶. 18 ~2×10 18 / cm 3 .

[0090] In the above implementation, the growth substrate 5 uses a GaAs substrate as the crystallographic basis for epitaxial growth; the n-type Ga0.5In0.5P etching stop layer 6 grown on it utilizes the huge etching selectivity of GaInP and GaAs in a specific etching solution to provide a precise etching termination interface for subsequent laser lift-off or substrate thinning processes, ensuring the controllability and consistency of the process; while the n-type GaAs buffer layer 7 above effectively blocks the upward extension of substrate defects, providing a relatively ideal epitaxial growth template for subsequent functional layers and other structures.

[0091] Optionally, the light-emitting diode further includes an n-electrode (not shown) and a p-electrode (not shown). The p-electrode is disposed on the second semiconductor layer 4 and electrically connected to the second ohmic contact layer 45 in the second semiconductor layer 4. The n-electrode is disposed on the first semiconductor layer and electrically connected to the first ohmic contact layer 12.

[0092] Optionally, the light-emitting diode can be a vertical structure, a conventional structure, or a flip-chip structure.

[0093] This disclosure also provides a method for fabricating a light-emitting diode, such as... Figure 3 As shown, the preparation method includes: S301: Forming a first semiconductor layer, a first quantum well layer, a second multiple quantum well layer and a second semiconductor layer stacked sequentially.

[0094] The first multiple quantum well layer includes multiple alternating layers of first quantum wells and multiple layers of first quantum barriers, and the second multiple quantum well layer includes multiple alternating layers of second quantum wells and multiple layers of second quantum barriers.

[0095] The first and second quantum barrier layers are both AlGaAsP layers, with the Al content in the second quantum barrier layer being less than that in the first quantum barrier layer.

[0096] The above preparation methods have the same beneficial effects as the aforementioned light-emitting diodes, and will not be repeated here.

[0097] This disclosure also provides another method for fabricating a light-emitting diode, such as... Figure 4 As shown, the preparation method includes: S401: A buffer layer and an etching stop layer are formed sequentially on the growth substrate.

[0098] For example, the growth substrate 5 may be a GaAs substrate. The growth substrate 5 serves as the base for epitaxial layer growth, providing physical support.

[0099] In this embodiment, a buffer layer 7 and an etching stop layer 6 are sequentially formed on the growth substrate 5 using a metal-organic chemical vapor deposition process.

[0100] S402: Forming the first semiconductor layer on the etch stop layer.

[0101] Optionally, S402 includes implementation in the following manner: The first ohmic contact layer, the electrode bonding layer, the roughening layer, the first current spreading layer, the first confinement layer, and the first waveguide layer are formed sequentially using a metal-organic chemical vapor deposition process.

[0102] Among them, the first waveguide layer Al x Ga 1-x The growth conditions for the As (0.3 < x < 0.4) layer include: a growth thickness of 300 nm to 600 nm, without doping.

[0103] S403: A first multiple quantum well layer and a second multiple quantum well layer are formed on the first semiconductor layer.

[0104] Optionally, the first and second multiple quantum well layers are also formed using a metal-organic chemical vapor deposition process.

[0105] The first quantum well layer In x Ga 1-xAs (0.05 < x < 0.15) with a thickness of 20 nm to 30 nm, the first quantum barrier Al y Ga 1-y As z P 1-z (0.3 < y < 0.4, 0.7 < z < 0.9) with a thickness of 30 nm to 40 nm, and the number of the first quantum well layer and the first quantum barrier layer is 6 to 8; the second quantum well layer In x Ga 1-x The thickness of As (0.05 < x < 0.15) is 20 nm to 30 nm, and the second quantum barrier layer Al y Ga 1-y As z P 1-z The thickness of the (0.1 < y < 0.2, 0.7 < z < 0.9) layer is 30 nm to 40 nm, and the number of the second quantum well layer and the second quantum barrier layer is 4 to 6.

[0106] S404: A second semiconductor layer is formed on the second multiple quantum well layer.

[0107] Optionally, the second semiconductor layer is formed using a metal-organic chemical vapor deposition process. A second waveguide layer, a second confinement layer, a stress transition layer, a second current spreading layer, and a second ohmic contact layer are sequentially formed.

[0108] Among them, the second waveguide layer Al x Ga 1-x The growth conditions for the As (0.1 < x < 0.2) layer include: a growth thickness of 400 nm to 700 nm, and no doping. The Al content of the second waveguide layer should be lower than that of the first waveguide layer.

[0109] Second confinement layer Al x Ga 1-x The growth conditions for the As (0.3 < x < 0.6) layer include: a growth thickness of 500 nm to 800 nm, a dopant of CCl4, and a carrier concentration of 1 × 10⁻⁶. 18 ~1.5×10 18 / cm 3 .

[0110] Stress transition layer, also known as gradually changing Al x Ga 1-x As y P 1-y The growth conditions for the layer (0 < x < 0.5, 0 < y < 0.8, where x gradually decreases from 0.5 to 0 and y gradually decreases from 0.8 to 0) include: a growth thickness of 10 nm to 30 nm, a dopant of CCl4, and a carrier concentration of 4 × 10⁻⁶. 18 ~6×10 18 / cm3 .

[0111] The growth conditions for the second current extension layer, the p-type GaP layer, include: a growth thickness of 50 nm to 100 nm, a dopant of Cp₂Mg, and a carrier concentration of 2 × 10⁻⁶. 18 ~4×10 18 / cm 3 .

[0112] The growth conditions for the second ohmic contact layer, the p-type GaP layer, include: a growth thickness of 10 nm to 50 nm, CCl4 as the dopant, and a carrier concentration of 0.8 × 10⁻⁶. 20 ~1.5×10 20 / cm 3 .

[0113] The above steps will yield the epitaxial layer of the light-emitting diode.

[0114] Then, the epitaxial layer is bonded to a sapphire substrate and electrodes are formed, which enables the light-emitting diode to be used in different devices.

[0115] The light-emitting diode provided in this embodiment can be used as an infrared 940nm wavelength light-emitting diode. By employing a multi-quantum well layer with varying barrier heights and wide wells, along with a gradient AlGaAsP stress transition layer, not only is the luminous efficiency of the multi-quantum well layer improved, but it also facilitates the growth of a high-quality epitaxial layer, thereby significantly enhancing its luminous intensity. Through multiple mechanisms such as strain modulation, bandgap optimization, carrier confinement, and injection optimization, the light extraction efficiency and output power of the light-emitting diode can be effectively improved.

[0116] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A light-emitting diode, characterized in that, The light-emitting diode comprises a first semiconductor layer (1), a first multi-quantum well layer (2), a second multi-quantum well layer (3), and a second semiconductor layer (4) stacked sequentially. The first multi-quantum well layer (2) includes multiple alternating stacked first quantum well layers (21) and multiple first quantum barrier layers (22), and the second multi-quantum well layer (3) includes multiple alternating stacked second quantum well layers (31) and multiple second quantum barrier layers (32). The first quantum barrier layer (22) and the second quantum barrier layer (32) are both AlGaAsP layers, and the Al content in the second quantum barrier layer (32) is less than the Al content in the first quantum barrier layer (22).

2. The light-emitting diode according to claim 1, characterized in that, The Al content in the first quantum barrier layer (22) is greater than 0.3 and less than 0.4, and the Al content in the second quantum barrier layer (32) is greater than 0.1 and less than 0.

2.

3. The light-emitting diode according to claim 1 or 2, characterized in that, The number of the first quantum well layer (21) is 6 to 8, and the number of the first quantum barrier layer (22) is 6 to 8.

4. The light-emitting diode according to claim 1 or 2, characterized in that, The number of the second quantum well layer (31) is 4 to 6, and the number of the second quantum barrier layer (32) is 4 to 6.

5. The light-emitting diode according to claim 1 or 2, characterized in that, The thickness of the first quantum well layer (21) and the second quantum well layer (31) is 20nm~30nm.

6. The light-emitting diode according to claim 1 or 2, characterized in that, The thickness of the first quantum barrier layer (22) and the second quantum barrier layer (32) is 30nm~40nm.

7. The light-emitting diode according to claim 1 or 2, characterized in that, The first semiconductor layer (1) includes a first waveguide layer (11), which is an AlGaAs layer, and the Al component content in the first waveguide layer (11) is greater than 0.3 and less than 0.

4.

8. The light-emitting diode according to claim 1 or 2, characterized in that, The second semiconductor layer (4) includes a second waveguide layer (41), which is an AlGaAs layer, and the Al component content in the second waveguide layer (41) is greater than 0.1 and less than 0.

2.

9. The light-emitting diode according to claim 8, characterized in that, The second semiconductor layer (4) also includes a second stress transition layer (43); The second stress transition layer (43) is an AlGaAsP layer. The content of Al component and As component in the second stress transition layer (43) both decrease monotonically along the direction from the first semiconductor layer (1) to the second semiconductor layer (4).

10. A method for fabricating a light-emitting diode, characterized in that, The preparation method includes: A first semiconductor layer, a first multi-quantum well layer, a second multi-quantum well layer, and a second semiconductor layer are formed in sequence. The first multiple quantum well layer includes multiple alternating layers of first quantum well layers and multiple layers of first quantum barrier layers, and the second multiple quantum well layer includes multiple alternating layers of second quantum well layers and multiple layers of second quantum barrier layers. Wherein, both the first quantum barrier layer and the second quantum barrier layer are AlGaAsP layers, and the Al component content in the second quantum barrier layer is less than the Al component content in the first quantum barrier layer.

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