Light emitting diode with improved light efficiency and method of manufacturing the same

Abstract

The present disclosure provides a light emitting diode with improved light efficiency and a preparation method thereof, and belongs to the technical field of optoelectronic manufacturing. The light emitting diode comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially stacked; the active layer comprises a plurality of quantum well layers and a plurality of quantum barrier layers which are alternately stacked, the quantum barrier layer comprises a first sublayer and a second sublayer which are sequentially stacked, the first sublayer comprises Mg-doped GaN, and the second sublayer comprises an AlGaN layer. The embodiment of the present disclosure can improve the problem of low carrier injection efficiency and improve the light emitting effect of the light emitting diode.

Description

Technical Field

[0001] This disclosure relates to the field of optoelectronic manufacturing technology, and in particular to a light-emitting diode with improved luminous efficiency and a method for its fabrication. Background Technology

[0002] Light-emitting diodes (LEDs) are highly influential new products in the optoelectronics industry. They are characterized by their small size, long lifespan, rich and colorful colors, and low energy consumption. They are widely used in lighting, displays, signal lights, backlights, toys, and other fields.

[0003] In related technologies, a light-emitting diode (LED) comprises a first semiconductor layer, an active layer, and a second semiconductor layer sequentially stacked on a substrate. To improve luminous efficiency, conventional methods include adjusting the number of cycles in the active layer or optimizing the doping concentration of each functional layer.

[0004] However, in low-current driven LED applications, even with the aforementioned optimization methods, the low injection efficiency of charge carriers under low-current conditions makes them prone to non-radiative recombination at the quantum well interface or epitaxial layer defect sites, resulting in their loss. At the same time, the distribution of charge carriers in the quantum well tends to be uneven in the low-current environment, leading to a significant decrease in the probability of radiative recombination, which ultimately limits the overall luminous efficiency of the LED. Summary of the Invention

[0005] This disclosure provides a light-emitting diode (LED) with improved luminous efficiency and its fabrication method, which can improve the problem of low carrier injection efficiency and enhance the luminous efficacy of the LED. The technical solution is as follows: On one hand, embodiments of this disclosure provide a light-emitting diode, the light-emitting diode comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked sequentially; the active layer comprising a plurality of quantum well layers and a plurality of quantum barrier layers stacked alternately, the quantum barrier layer comprising a first sub-layer and a second sub-layer stacked sequentially, the first sub-layer comprising Mg-doped GaN and the second sub-layer comprising an AlGaN layer.

[0006] Optionally, the Mg doping concentration in the first sublayer is 1×10⁻⁶. 17 cm -3 Up to 1×10 19 cm -3 .

[0007] Optionally, in the first sublayer, the doping concentration of Mg gradually decreases from the side closest to the first semiconductor layer to the side furthest from the first semiconductor layer.

[0008] Optionally, the ratio of the thickness of the first sublayer to the thickness of the quantum barrier layer is 0.2 to 0.5.

[0009] Optionally, the thickness of each quantum barrier layer is 8 nm to 15 nm.

[0010] Optionally, the second sub-layer includes Al x Ga 1-x N layers, 0 < x < 0.3.

[0011] Optionally, the active layer comprises 8 to 15 layers of the quantum well layer and 8 to 15 layers of the quantum barrier layer stacked alternately.

[0012] Optionally, the quantum barrier layer comprises 2 to 10 alternating layers of the first sublayer and 2 to 10 layers of the second sublayer.

[0013] On the other hand, this disclosure also provides a method for fabricating a light-emitting diode, the method comprising: forming a first semiconductor layer on a substrate; forming an active layer on the first semiconductor layer, the active layer comprising alternatingly stacked multiple quantum well layers and multiple quantum barrier layers, the quantum barrier layer comprising sequentially stacked first sublayer and second sublayer, the first sublayer comprising Mg-doped GaN, the second sublayer comprising an AlGaN layer; and forming a second semiconductor layer on the active layer.

[0014] Optionally, growing the first sublayer includes: controlling the flow rate of the Mg source during the growth process, such that the Mg doping concentration of the formed first sublayer gradually decreases in the thickness direction from the side closer to the first semiconductor layer to the side farther away from the first semiconductor layer, and the Mg doping concentration in the first sublayer is 1×10⁻⁶. 17 cm -3 Up to 1×10 19 cm -3 .

[0015] The beneficial effects of the technical solutions provided in this disclosure include at least the following: The light-emitting diode provided in this disclosure improves luminous efficiency under low current driving by setting a first sublayer (Mg-doped GaN) and a second sublayer (AlGaN layer) stacked sequentially in the quantum barrier layer. In low-current operating environments, conventional LEDs are prone to nonradiative recombination due to low carrier injection efficiency and uneven carrier distribution, resulting in limited luminous efficiency. In this disclosure, the first sublayer of the quantum barrier layer is made of Mg-doped GaN, which effectively improves hole migration capability, promotes efficient migration of holes to the quantum wells on both sides, and enhances the recombination probability of electrons and holes in the quantum wells. Simultaneously, Mg doping raises the conduction band energy level of the quantum barrier layer, forming a built-in electric field pointing towards the well region, blocking excessive migration of electrons to the p-type layer. This optimizes the uniformity of carrier distribution in the quantum wells, reduces nonradiative recombination losses, improves the problem of insufficient luminescence in some quantum wells, enhances internal quantum efficiency, and overcomes the limitation of decreased radiative recombination probability under low-current conditions.

[0016] Furthermore, micro-doping Mg in the quantum barrier layer generates additional Coulomb potential energy in the material, adjusts the valence band energy level arrangement, and makes the heavy hole / light hole energy band replace the original split band as the valence band top, reversing optical anisotropy, enhancing transverse electric wave polarization emission, and better adapting to the special light emission requirements of LEDs.

[0017] The mechanism by which micro-doping Mg in the quantum barrier layer raises the conduction band energy level is the lattice distortion and polarization field modulation induced by Mg doping. Specifically, Mg atoms have a smaller atomic radius than Ga / Al atoms, and when micro-doped into GaN / AlGaN quantum barrier layers, they replace lattice sites, generating compressive stress and causing the lattice constant to shrink. Mg, acting as an acceptor impurity, forms localized positive charge centers after ionization, which superimpose with the inherent spontaneous polarization / piezoelectric polarization field of the quantum barrier layer, increasing the polarization charge density inside the quantum barrier layer. The conduction band energy levels of gallium nitride-based materials are highly sensitive to the polarization field; the built-in electric field formed by the accumulation of polarization charge in the barrier layer raises the conduction band bottom (E0) energy. The acceptor impurity states formed by Mg doping form a weak coupling with the conduction band bottom, which can fine-tune the conduction band energy level distribution, avoiding excessive energy level bending. This ensures the quantum barrier layer's electron blocking effect without affecting hole transport performance. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure; Figure 2This is a flowchart of a method for fabricating a light-emitting diode according to an embodiment of this disclosure.

[0020] The markings in the diagram are explained as follows: 10. Substrate; 21. AlN layer; 22. Nucleation layer; 23. U-shaped GaN layer; 30. First semiconductor layer; 40. Active layer; 41. Quantum well layer; 42. Quantum barrier layer; 421. First sublayer; 422. Second sublayer; 60. Second semiconductor layer; 61. Low-temperature p-type AlGaN layer; 62. p-type electron blocking layer; 63. High-temperature p-type GaN layer; 64. p-type contact layer. Detailed Implementation

[0021] 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.

[0022] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure. For example... Figure 1 As shown, the light-emitting diode includes a first semiconductor layer 30, an active layer 40, and a second semiconductor layer 60 stacked sequentially.

[0023] like Figure 1 As shown, the active layer 40 includes multiple quantum well layers 41 and multiple quantum barrier layers 42 stacked alternately. The quantum barrier layer 42 includes a first sub-layer 421 and a second sub-layer 422 stacked sequentially. The first sub-layer 421 includes Mg-doped GaN, and the second sub-layer 422 includes an AlGaN layer.

[0024] The light-emitting diode provided in this embodiment improves luminous efficiency under low current driving by setting a first sub-layer 421 (Mg-doped GaN) and a second sub-layer 422 (AlGaN layer) stacked sequentially in the quantum barrier layer 42. In low-current operating environments, conventional LEDs are prone to nonradiative recombination due to low carrier injection efficiency and uneven distribution, resulting in limited luminous efficiency. In this embodiment, the first sub-layer 421 of the quantum barrier layer 42 is made of Mg-doped GaN, which effectively improves hole migration capability, promotes efficient migration of holes to the quantum wells on both sides, and enhances the recombination probability of electrons and holes in the quantum wells. Simultaneously, Mg doping raises the conduction band energy level of the quantum barrier layer 42, forming a built-in electric field pointing towards the well region, blocking excessive migration of electrons to the p-type layer, thereby optimizing the uniformity of carrier distribution in the quantum wells, reducing nonradiative recombination losses, improving the problem of insufficient luminescence in some quantum wells, improving internal quantum efficiency, and overcoming the limitation of decreased radiative recombination probability under low current conditions.

[0025] Furthermore, the Mg microdoping in the quantum barrier layer 42 generates additional Coulomb potential energy in the material, adjusts the valence band energy level arrangement, and makes the heavy hole / light hole energy band replace the original split band as the valence band top, reversing optical anisotropy, enhancing transverse electric wave polarization emission, and better adapting to the special light emission requirements of LEDs.

[0026] The mechanism by which Mg microdoping in the quantum barrier layer 42 raises the conduction band energy level is the lattice distortion and polarization field modulation induced by Mg doping. Specifically, Mg atoms have a smaller atomic radius than Ga / Al atoms, and when microdoped into the GaN / AlGaN quantum barrier layer 42, they replace lattice sites, generating compressive stress and causing the lattice constant to shrink. Mg, acting as an acceptor impurity, forms localized positive charge centers after ionization, which superimpose with the inherent spontaneous polarization / piezoelectric polarization field of the quantum barrier layer 42, increasing the internal polarization charge density. The conduction band energy levels of gallium nitride-based materials are highly sensitive to polarization fields; the built-in electric field formed by the accumulation of polarization charges in the barrier layer raises the conduction band bottom (E0) energy. The acceptor impurity states formed by Mg doping form a weak coupling with the conduction band bottom, which can fine-tune the conduction band energy level distribution, avoiding excessive energy level bending. This ensures the electron blocking effect of the quantum barrier layer 42 without affecting hole transport performance.

[0027] Optionally, the Mg doping concentration in the first sublayer 421 is 1×10⁻⁶. 17 cm -3 Up to 1×10 19 cm -3 .

[0028] By controlling the Mg doping concentration in the first sublayer 421 within the aforementioned range, when Mg atoms replace GaN lattice sites, the size difference induces compressive stress, leading to lattice contraction and the generation of localized polarization charges. Simultaneously, Mg, as an acceptor impurity, forms positive charge centers after ionization, which superimpose with the inherent spontaneous / piezoelectric polarization field of the quantum barrier layer 42. The higher the doping concentration, the greater the polarization charge density, and the stronger the polarization field enhancement effect. Since the conduction band energy level of gallium nitride-based materials is highly sensitive to the polarization field, the built-in electric field within the barrier layer raises the conduction band bottom (E0) energy. When the Mg doping concentration is within the aforementioned range, the polarization field enhancement is positively correlated with the conduction band energy level rise, ensuring that the conduction band is effectively pulled up.

[0029] Optionally, in the first sub-layer 421, the doping concentration of Mg gradually decreases from the side closest to the first semiconductor layer 30 to the side furthest from the first semiconductor layer 30.

[0030] Among them, one of the first semiconductor layer 30 and the second semiconductor layer 60 is an n-type layer, and the other of the first semiconductor layer 30 and the second semiconductor layer 60 is a p-type layer.

[0031] In this embodiment of the present disclosure, the first semiconductor layer 30 is an n-type layer and the second semiconductor layer 60 is a p-type layer.

[0032] In the high-concentration region near the n-type layer, the acceptor impurity states formed by Mg doping are strongly coupled to the bottom of the conduction band, moderately raising the conduction band energy level, enhancing the blocking effect on electrons, and preventing excessive electron migration to the p-type layer. At the same time, the polarization field induced by the high concentration accumulates in this region, strengthening the confinement of the barrier layer on electrons. In the low-concentration region on the far side, the coupling between the impurity states and the bottom of the conduction band weakens, and the energy level distribution is only slightly adjusted through weak interactions to avoid excessive energy level bending, retaining the basic blocking of electrons while significantly reducing the impurity scattering resistance of hole migration to ensure efficient hole transport.

[0033] Exemplarily, in the first sub-layer 421, in the direction from the side close to the first semiconductor layer 30 to the side far from the first semiconductor layer 30, the doping concentration of Mg decreases from 5×10 18 cm -3 to 5×10 17 cm -3 .

[0034] Optionally, the n-type layer can be an n-type GaN layer. The thickness of the n-type layer is 0.5 μm to 3 μm.

[0035] Among them, the dopant of the n-type layer is silane, and the doping concentration of silane can be 5×10 18 cm -3 to 5×10 19 cm -3 .

[0036] Optionally, the p-type layer further includes a low-temperature p-type AlGaN layer 61, a p-type electron blocking layer 62, a high-temperature p-type GaN layer 63, and a p-type contact layer 64. The low-temperature p-type AlGaN layer 61, the p-type electron blocking layer 62, the high-temperature p-type GaN layer 63, and the p-type contact layer 64 are stacked on the active layer 40 in sequence.

[0037] Exemplarily, the p-type electron blocking layer 62 can be a p-type Al y Ga 1-y N layer, where 0.1 < yk < 0.5, and the thickness of the p-type electron blocking layer 62 can be 10 nm to 100 nm.

[0038] If the thickness of the p-type electron blocking layer 62 is too thin, the blocking effect on electrons will be reduced. If the thickness of the p-type electron blocking layer 62 is too thick, the p-type electron blocking layer 62 will increase the absorption of light, resulting in a reduction in the light emission efficiency of the LED.

[0039] In the embodiments of the present disclosure, both the low-temperature p-type AlGaN layer 61 and the high-temperature p-type GaN layer 63 are Mg-doped.

[0040] The Mg doping concentration of the low-temperature p-type AlGaN layer 61 is 5×1020 cm -3 Up to 1×10 21 cm -3 The Mg doping concentration of the high-temperature p-type GaN layer 63 is 1×10⁻⁶. 18 cm -3 Up to 1×10 20 cm -3 .

[0041] The thickness of the low-temperature p-type AlGaN layer 61 can be from 10 nm to 100 nm. For example, the thickness of the low-temperature p-type AlGaN layer 61 can be 80 nm.

[0042] The thickness of the high-temperature p-type GaN layer 63 can be from 10 nm to 100 nm. For example, the thickness of the high-temperature p-type GaN layer 63 can be 50 nm.

[0043] Optionally, the thickness of the p-type contact layer 64 can be from 1 nm to 30 nm. As an example, in this embodiment of the present disclosure, the thickness of the p-type contact layer 64 is 20 nm.

[0044] Among them, the p-type contact layer 64 is a p-type GaN layer, and the Mg doping concentration of the p-type GaN layer is 1×10⁻⁶. 20 cm -3 Up to 1×10 21 cm -3 .

[0045] If the thickness of the p-type contact layer 64 is too thin, it will affect the current contact between the epitaxial layer and the electrode. If the thickness of the p-type contact layer 64 is too thick, it will increase the absorption of light by the p-type contact layer 64, thereby reducing the luminous efficiency of the LED.

[0046] Optionally, the ratio of the thickness of the first sublayer 421 to the thickness of the quantum barrier layer 42 is 0.2 to 0.5.

[0047] By controlling the ratio of the thickness of the first sublayer 421 to the thickness of the quantum barrier layer 42 within the aforementioned range, the thickness of the first sublayer 421 is ensured to be moderate. This ensures that the key role of Mg doping can be fully utilized to raise the conduction band energy level and optimize the carrier distribution through polarization field accumulation, while avoiding excessive thickness that would lead to increased lattice distortion (compressive stress induced by Mg doping) or increased hole transport resistance. At the same time, the remaining 50% to 80% thickness of the second sublayer 422 (AlGaN) can maintain a high barrier height and work synergistically with the first sublayer 421 to strengthen the blocking of electrons and reduce electron leakage to the P-type layer.

[0048] Furthermore, if the first sublayer 421 is too thin, the polarization effect of Mg doping will be insufficient, while if it is too thick, lattice stress will accumulate, leading to epitaxial defects. A ratio of 0.2-0.5 makes the stress distribution more uniform, and combined with the buffering effect of AlGaN, it improves the structural stability of the quantum barrier layer 42.

[0049] For example, the ratio of the thickness of the first sublayer 421 to the thickness of the quantum barrier layer 42 is 0.3.

[0050] Optionally, the thickness of each quantum barrier layer 42 is 8 nm to 15 nm.

[0051] When the thickness of each quantum barrier layer 42 is controlled between 8nm and 15nm, it can form an effective barrier to prevent electrons from leaking into the p-type layer and maintain the carrier concentration in the quantum well to suppress nonradiative recombination. It can also avoid the accumulation of lattice stress (such as the superposition of compressive stress caused by Mg doping) and epitaxial defects caused by excessive thickness, thus ensuring the structural integrity of the quantum barrier layer 42.

[0052] For example, in the quantum barrier layer 42, the thickness of the first sublayer 421 is 3nm and the thickness of the second sublayer 422 is 7nm, that is, the thickness of the quantum barrier layer 42 is 10nm.

[0053] Optionally, the second sublayer 422 includes Al x Ga 1-x N layers, 0 < x < 0.3. For example, the second sub-layer 422 is Al. 0.15 Ga 0.85 N layers.

[0054] The second sublayer 422 has a low Al content; when x < 0.3, the AlGaN lattice constant is close to that of GaN (the lower the Al content, the better the match). This can significantly reduce the lattice mismatch stress with the first sublayer 421 (GaN-based), avoid the accumulation of epitaxial defects, and improve the structural stability of the quantum barrier layer 42. Secondly, the low Al content can both work synergistically with the first sublayer 421 to block electron leakage to the p-type layer and avoid hindering hole migration due to an excessively high barrier. Combined with the hole-promoting effect of Mg doping in the first sublayer 421, it helps holes to spread uniformly into the quantum well.

[0055] Optionally, the active layer 40 includes 8 to 15 layers of quantum well layers 41 and 8 to 15 layers of quantum barrier layers 42 stacked alternately.

[0056] The number of alternating active layers 40 is controlled within the above range, which can enhance the quantum confinement effect through multiple quantum wells, efficiently confine carriers in the well, reduce leakage to the barrier layer or electrode, and increase the probability of radiative recombination. It can also avoid insufficient confinement caused by too few layers or excessive layers, resulting in lattice stress accumulation (such as the superposition of Mg doping compressive stress) and an increase in epitaxial defects.

[0057] Meanwhile, the multilayer structure increases the total number of light-emitting units. Combined with the carrier control design of quantum barrier layer 42 (such as Mg gradient doping), it can improve the problem of uneven carrier distribution under small current and enhance the overall luminescence intensity.

[0058] Optionally, the quantum barrier layer 42 includes 2 to 10 alternating layers of first sublayer 421 and 2 to 10 layers of second sublayer 422.

[0059] In this embodiment of the disclosure, the quantum barrier layer 42 adopts 2 to 10 alternating layers of first sublayer 421 (Mg-doped GaN) and second sublayer 422 (AlGaN). The alternating layers disperse the thickness of the single layer, avoid the accumulation of lattice distortion (such as Mg-doped compressive stress and AlGaN lattice mismatch stress) caused by excessive single layer thickness, reduce the risk of epitaxial defects, and improve structural stability.

[0060] Furthermore, the multilayer design makes the polarization field (Mg doping and spontaneous / piezoelectric polarization superposition) more uniform and the conduction band energy level rise more gently. This not only ensures effective blocking of electrons, but also optimizes the hole migration path through the 421 segmented doping of the first sublayer, promoting the uniform expansion of holes into the quantum well.

[0061] Optionally, such as Figure 1 As shown, the light-emitting diode also includes a buffer layer, a nucleation layer 22 and a u-shaped GaN layer 23 stacked in sequence, with the first semiconductor layer 30 located on the u-shaped GaN layer 23.

[0062] Optionally, the buffer layer includes AlN layers 21 stacked sequentially.

[0063] In the above implementation, AlN layer 21 serves as the initial transition layer. Although there is a mismatch between the lattice constant of AlN and the substrate, its high melting point and chemical stability can effectively prevent substrate impurities from diffusing to subsequent layers, providing a clean and low-defect initial nucleation substrate for nucleation layer 22 and reducing the interface energy barrier for subsequent GaN nucleation.

[0064] Among them, AlN layer 21 is an AlN layer 21 grown at a temperature between 400℃ and 800℃.

[0065] For example, the nucleation layer 22 may be a GaN layer or an AlGaN layer.

[0066] The nucleation layer 22 alleviates the lattice mismatch between the AlN layer 21 and the u-shaped GaN layer 23 through the merging growth of small-sized island structures. This reduces initial stress concentration, provides a uniform, low-defect nucleation platform for the u-shaped GaN layer 23, and optimizes subsequent crystal quality.

[0067] The thickness of the nucleation layer 22 can be from 0.3 μm to 0.5 μm.

[0068] Among them, the u-shaped GaN layer 23 is grown laterally at high temperature, that is, it extends along the substrate plane. It forms a flat surface with low dislocation density through a two-dimensional growth mode, providing a buffer substrate with low defects and high flatness for the subsequent dislocation blocking layer and epitaxial layer. At the same time, its wide bandgap characteristics can initially reduce electron leakage and assist in the carrier confinement of the subsequent active layer 40.

[0069] For example, the thickness of the u-shaped GaN layer 23 is 0.5 μm to 3 μm. For example, the thickness of the u-shaped GaN layer 23 is 2 μm.

[0070] Optionally, such as Figure 1 As shown, the light-emitting diode may also include a substrate 10, which is a substrate that carries an epitaxial layer, and a buffer layer is stacked on the substrate.

[0071] For example, the substrate is a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate can be a flat substrate or a patterned substrate.

[0072] As an example, in this embodiment of the disclosure, the substrate is a sapphire substrate. Sapphire substrates are a commonly used substrate, with mature technology and low cost. Specifically, it can be a patterned sapphire substrate or a flat sapphire substrate.

[0073] Figure 2 This is a flowchart illustrating a method for fabricating a light-emitting diode according to an embodiment of this disclosure. Figure 2 As shown, the preparation method includes: Step S11: Form a first semiconductor layer on the substrate.

[0074] Step S12: Form an active layer on the first semiconductor layer.

[0075] The active layer includes multiple quantum well layers and multiple quantum barrier layers stacked alternately. The quantum barrier layer includes a first sub-layer and a second sub-layer stacked sequentially. The first sub-layer includes Mg-doped GaN, and the second sub-layer includes an AlGaN layer.

[0076] Step S13: Form a second semiconductor layer on the active layer.

[0077] The light-emitting diode (LED) fabricated by the method disclosed in this embodiment improves luminous efficiency under low current driving by sequentially stacking a first sublayer (Mg-doped GaN) and a second sublayer (AlGaN layer) in the quantum barrier layer. This is achieved through a micro-doped magnesium structure in the quantum barrier layer. In low-current operating environments, conventional LEDs are prone to nonradiative recombination due to low carrier injection efficiency and uneven carrier distribution, resulting in limited luminous efficiency. In this embodiment, the first sublayer of the quantum barrier layer is made of Mg-doped GaN, which effectively improves hole migration capability, promotes efficient migration of holes to the quantum wells on both sides, and enhances the recombination probability of electrons and holes in the quantum wells. Simultaneously, Mg doping raises the conduction band energy level of the quantum barrier layer, forming a built-in electric field pointing towards the well region, preventing excessive migration of electrons to the p-type layer. This optimizes the uniformity of carrier distribution within the quantum wells, reduces nonradiative recombination losses, improves the problem of insufficient luminescence in some quantum wells, enhances internal quantum efficiency, and overcomes the limitation of decreased radiative recombination probability under low-current conditions.

[0078] Furthermore, micro-doping Mg in the quantum barrier layer generates additional Coulomb potential energy in the material, adjusts the valence band energy level arrangement, and makes the heavy hole / light hole energy band replace the original split band as the valence band top, reversing optical anisotropy, enhancing transverse electric wave polarization emission, and better adapting to the special light emission requirements of LEDs.

[0079] The mechanism by which micro-doping Mg in the quantum barrier layer raises the conduction band energy level is the lattice distortion and polarization field modulation induced by Mg doping. Specifically, Mg atoms have a smaller atomic radius than Ga / Al atoms, and when micro-doped into GaN / AlGaN quantum barrier layers, they replace lattice sites, generating compressive stress and causing the lattice constant to shrink. Mg, acting as an acceptor impurity, forms localized positive charge centers after ionization, which superimpose with the inherent spontaneous polarization / piezoelectric polarization field of the quantum barrier layer, increasing the polarization charge density inside the quantum barrier layer. The conduction band energy levels of gallium nitride-based materials are highly sensitive to the polarization field; the built-in electric field formed by the accumulation of polarization charge in the barrier layer raises the conduction band bottom (E0) energy. The acceptor impurity states formed by Mg doping form a weak coupling with the conduction band bottom, which can fine-tune the conduction band energy level distribution, avoiding excessive energy level bending. This ensures the quantum barrier layer's electron blocking effect without affecting hole transport performance.

[0080] The following steps may also be included before step S11: The first step is to provide a substrate as the basic support for epitaxial growth.

[0081] The substrate can be a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate can be a flat substrate or a patterned substrate.

[0082] As an example, in this embodiment of the disclosure, the substrate is a sapphire substrate. Sapphire substrates are a commonly used substrate, with mature technology and low cost. Specifically, it can be a patterned sapphire substrate or a flat sapphire substrate.

[0083] In this embodiment of the present disclosure, the sapphire substrate can be subjected to high-temperature cleaning treatment in a hydrogen atmosphere at 1000°C to 1200°C for 5 min to 20 min, and then subjected to nitriding treatment.

[0084] In this embodiment of the disclosure, the sapphire substrate can be pretreated by placing it in an MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber and baking it for 12 to 18 minutes. As an example, in this embodiment of the disclosure, the sapphire substrate is baked for 15 minutes.

[0085] Specifically, the baking temperature can be from 1000°C to 1200°C, and the pressure in the MOCVD reaction chamber during baking can be from 100 mbar to 200 mbar.

[0086] The second step is to grow an AlN layer on the substrate.

[0087] Specifically, an AlN layer is deposited on a sapphire substrate using magnetron sputtering with a physical vapor deposition (PVD) device to obtain a buffer layer. The buffer layer is used to alleviate the lattice mismatch between the substrate and subsequent epitaxial layers.

[0088] The growth temperature in the PVD equipment is 400℃ to 800℃, the sputtering power is 3000W to 5000W, the pressure is 1mtorr to 20mtorr, and the AlN layer deposition thickness is 10nm to 50nm.

[0089] The third step involves placing the AlN-coated substrate into an MOCVD system to grow a 3D nucleation layer. The MOCVD reaction chamber temperature is maintained at 1030°C to 1100°C, and the reaction chamber pressure is controlled at 150 torr to 500 torr. Under a mixed atmosphere of nitrogen, hydrogen, and ammonia, the growth thickness of the nucleation layer ranges from 0.3 μm to 2 µm. The 3D nucleation layer can further optimize the surface flatness of the epitaxial layer.

[0090] The fourth step is to grow a U-shaped GaN layer on the nucleation layer.

[0091] In this embodiment, a U-shaped GaN layer is grown between the nucleation layer and the dislocation blocking layer. By setting the U-shaped GaN layer as a transition layer, the crystal quality of the subsequent epitaxial layer can be improved.

[0092] The thickness of the u-shaped GaN layer is from 0.5 μm to 3 μm. For example, the thickness of the u-shaped GaN layer is 2 μm.

[0093] Specifically, an undoped GaN buffer recovery layer is grown by MOCVD. In the MOCVD system, the temperature is adjusted to 1000°C to 1150°C, and in an environment with a growth pressure of 100 torr to 500 torr, a U-shaped GaN layer with a thickness of 0.5 μm to 3 μm is grown. The U-shaped GaN layer is used to repair possible defects in the previous buffer layer and improve the subsequent epitaxial quality.

[0094] Step S11 may include: growing an n-type layer on the U-shaped GaN layer.

[0095] Optionally, the n-type layer may be an n-type GaN layer. The thickness of the n-type layer is 0.5 μm to 3 μm. Among them, the dopant of the n-type layer is silane. The n-type GaN layer is the first semiconductor layer close to the substrate in the LED structure and provides an electron injection channel for the growth of the subsequent active layer.

[0096] Specifically, in the MOCVD system, the temperature is adjusted to 1000°C to 1150°C, and in an environment with a growth pressure of 100 torr to 300 torr, an n-type doped GaN layer with a thickness of 0.5 μm to 3 μm is grown, and the concentration of Si doped in the n-type GaN layer is 1×10 18 cm -3 to 5×10 19 cm -3 .

[0097] Step S12 may include: growing an alternately stacked quantum well layer and quantum barrier layer to form an active layer.

[0098] Exemplarily, the active layer includes 8 to 15 alternately stacked quantum well layers and 8 to 15 quantum barrier layers.

[0099] Among them, the growth conditions of the quantum well layer include: a pure nitrogen atmosphere, controlling the growth temperature to be 700°C to 850°C, controlling the growth pressure to be 200 Tott to 500 Torr, and ensuring that the In component is uniformly incorporated.

[0100] Exemplarily, the quantum well layer includes In g Ga 1-g N (0.2 < g < 0.5), and the thickness of each quantum well layer is 3 nm to 5.

[0101] Among them, the quantum barrier layer includes alternately stacked first sub-layers and second sub-layers. For example, the number of periods of the first sub-layer is 2 to 10, and the number of periods of the second sub-layer is also 2 to 10.

[0102] Exemplarily, the first sub-layer includes a Mg-doped GaN layer, and the second sub-layer includes an Al x Ga 1-x N layer, 0 < x < 0.3.

[0103] Among them, the thickness of each quantum barrier layer is 8 nm to 15 nm. Exemplarily, the first sub-layer is 3 nm and the second sub-layer is 7 nm.

[0104] Exemplarily, the ratio of the thickness of the first sub-layer to the total thickness of the quantum barrier layer is 0.2 to 0.5.

[0105] Exemplarily, in the first sub-layer, the Mg doping concentration is 1×10 17 cm -3 to 1×10 19 cm -3 . And in the first sub-layer, from the side close to the first semiconductor layer to the side far from the first semiconductor layer, the Mg doping concentration gradually decreases. The concentration gradient is achieved by dynamically adjusting the Mg source flow rate during the growth process.

[0106] The growth conditions of the first sub-layer include: a mixed atmosphere of nitrogen and hydrogen, a temperature of 800 °C to 960 °C, and a growth pressure of 100 Torr to 300 Torr.

[0107] Exemplarily, the ratio of the thickness of the second sub-layer to the total thickness of the quantum barrier layer is 0.5 to 0.8.

[0108] The growth conditions of the second sub-layer include: a mixed atmosphere of nitrogen and hydrogen, a temperature of 800 °C to 960 °C, and a growth pressure of 100 Torr to 300 Torr.

[0109] Step S13 may include: growing a p-type layer on the active layer.

[0110] Among them, the p-type layer includes a low-temperature p-type AlGaN layer, a p-type electron blocking layer, a high-temperature p-type GaN layer, and a p-type contact layer that are sequentially stacked on the active layer.

[0111] Exemplarily, the p-type electron blocking layer may be a p-type Al y Ga 1-y N (0.1 < y < 0.5) layer, and the thickness of the p-type electron blocking layer may be 10 nm to 100 nm.

[0112] In the embodiments of the present disclosure, both the low-temperature p-type AlGaN layer and the high-temperature p-type GaN layer are Mg-doped.

[0113] Exemplarily, the low-temperature p-type AlGaN layer includes an Al w Ga 1-w N layer, 0.1 < w < 0.3.

[0114] The Mg doping concentration of the low-temperature p-type AlGaN layer is 5×10 20 cm -3 to 1×10 21 cm -3The Mg doping concentration of the high-temperature p-type GaN layer is 1×10⁻⁶. 18 cm -3 Up to 1×10 20 cm -3 .

[0115] The thickness of the low-temperature p-type AlGaN layer can be from 10 nm to 100 nm; for example, the thickness of the low-temperature p-type GaN layer can be 80 nm.

[0116] The thickness of the high-temperature p-type GaN layer can be from 10 nm to 100 nm, for example, the thickness of the low-temperature p-type GaN layer can be 50 nm.

[0117] When growing low-temperature p-type AlGaN layers, the growth temperature is adjusted to 700℃ to 800℃, and the growth pressure is 200 to 500 torr to grow low-temperature p-type AlGaN layers with a thickness of 10 nm to 100 nm.

[0118] When growing the p-type electron blocking layer, the growth temperature is adjusted to 800℃ to 1000℃ and the growth pressure is 50 to 300 torr.

[0119] When growing high-temperature p-type GaN layers, the growth pressure is controlled at 200 to 600 torr, the growth temperature is 800°C to 1000°C, and the p-type GaN layer thickness is 10 nm to 100 nm.

[0120] When growing the p-type contact layer, the growth temperature is controlled at 850℃ to 1000℃, the growth pressure is controlled at 100 torr to 300 torr, and the p-type contact layer thickness is 1nm to 30nm.

[0121] The Mg doping concentration in the p-type contact layer is 1×10⁻⁶. 20 Up to 1×10 21 cm -3 .

[0122] After step S13, the preparation method may further include annealing the light-emitting diode.

[0123] After epitaxial growth is completed, the temperature of the reaction chamber is lowered to 650°C to 850°C and annealed in an N2 atmosphere for 5 to 15 minutes. Then, it is gradually lowered to room temperature. Subsequently, the chip is fabricated through cleaning, deposition, photolithography and etching processes.

[0124] In specific implementation, embodiments of this disclosure may use high-purity H2 and / or N2 as carrier gas, TEGa or TMGa as Ga source, TMIn as In source, SiH4 as n-type dopant, TMAl as aluminum source, ammonia as N source, and Cp2Mg as p-type dopant.

[0125] 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 includes a first semiconductor layer (30), an active layer (40), and a second semiconductor layer (60) stacked sequentially. The active layer (40) includes multiple quantum well layers (41) and multiple quantum barrier layers (42) stacked alternately. The quantum barrier layer (42) includes a first sublayer (421) and a second sublayer (422) stacked sequentially. The first sublayer (421) includes Mg-doped GaN, and the second sublayer (422) includes an AlGaN layer.

2. The light-emitting diode according to claim 1, characterized in that, The Mg doping concentration in the first sublayer (421) is 1×10⁻⁶. 17 cm -3 Up to 1×10 19 cm -3 .

3. The light-emitting diode according to claim 2, characterized in that, In the first sub-layer (421), the doping concentration of Mg gradually decreases from the side closest to the first semiconductor layer (30) to the side furthest from the first semiconductor layer (30).

4. The light-emitting diode according to any one of claims 1 to 3, characterized in that, The ratio of the thickness of the first sublayer (421) to the thickness of the quantum barrier layer (42) is 0.2 to 0.

5.

5. The light-emitting diode according to claim 4, characterized in that, The thickness of each quantum barrier layer (42) is 8 nm to 15 nm.

6. The light-emitting diode according to any one of claims 1 to 3, characterized in that, The second sublayer (422) includes Al x Ga 1-x N layers, 0 < x < 0.

3.

7. The light-emitting diode according to any one of claims 1 to 3, characterized in that, The active layer (40) comprises 8 to 15 layers of the quantum well layer (41) and 8 to 15 layers of the quantum barrier layer (42) stacked alternately.

8. The light-emitting diode according to any one of claims 1 to 3, characterized in that, The quantum barrier layer (42) comprises 2 to 10 alternating layers of the first sublayer (421) and 2 to 10 layers of the second sublayer (422).

9. A method for fabricating a light-emitting diode, characterized in that, The preparation method includes: A first semiconductor layer is formed on the substrate; An active layer is formed on the first semiconductor layer. The active layer includes a plurality of quantum well layers and a plurality of quantum barrier layers stacked alternately. The quantum barrier layer includes a first sub-layer and a second sub-layer stacked sequentially. The first sub-layer includes Mg-doped GaN, and the second sub-layer includes an AlGaN layer. A second semiconductor layer is formed on the active layer.

10. The preparation method according to claim 9, characterized in that, Growing the first sublayer includes: During the growth process, the flow rate of the Mg source is controlled so that the Mg doping concentration of the first sublayer gradually decreases in the thickness direction from the side closest to the first semiconductor layer to the side furthest from the first semiconductor layer. The Mg doping concentration in the first sublayer is 1×10⁻⁶. 17 cm -3 Up to 1×10 19 cm -3 .

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