Light emitting diode epitaxial structure, light emitting diode and light emitting device

Abstract

The application relates to a light emitting diode epitaxial structure, at least comprising a first semiconductor layer structure, an active layer and a second semiconductor layer structure which are sequentially stacked, characterized in that the active layer is a multiple quantum well structure, at least two period structures of the active layer comprise a first layer, a second layer, a third layer and a fourth layer, the first layer is a potential well layer, the third layer is a potential barrier layer, and the energy level band gap Eg1 of the first layer, the energy level band gap Eg2 of the second layer, the energy level band gap Eg3 of the third layer and the energy level band gap Eg4 of the fourth layer satisfy the relationship of Eg2, Eg4> Eg3> Eg1. By growing the second layer with a higher energy level band gap between the potential well layer and the potential barrier layer, electron overflow can be effectively inhibited, the growth quality of the quantum well is improved, the radiation recombination efficiency is improved, the internal quantum efficiency is significantly improved, and finally the light emitting efficiency is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a light-emitting diode epitaxial structure, a light-emitting diode, and a light-emitting device. Background Technology

[0002] Light-emitting diodes (LEDs) have advantages such as high efficiency, long lifespan, small size, and low power consumption, and are widely used in indoor and outdoor white light lighting, screen displays, backlights, and other fields. Ultraviolet (UV) LEDs emit UV light and can be used in various fields, including curing polymer materials, sterilizing medical equipment, device components, and light sources for generating white light. Therefore, UV LEDs are increasingly being applied in various fields.

[0003] The active layer of an epitaxial structure for a light-emitting diode (LED) typically employs a multiple quantum well (QB) structure. A conventional QB structure consists of two different semiconductor thin films stacked together to form a potential well / barrier structure that traps electrons and holes. When a voltage is applied across the LED, charge carriers can enter the QB through tunneling, diffusion, or thermal emission, and then undergo radiative recombination within the well layer to produce light. The luminescence brightness primarily depends on the internal quantum efficiency, which can be improved by adjusting the QB structure, such as layer thickness, composition, and structure.

[0004] Existing UVA band light-emitting diodes may experience problems with incomplete ink curing during irradiation. Since curing capability is closely related to luminous efficiency, it is necessary to provide a solution that can improve luminous efficiency and shorten curing time in order to effectively improve the curing capability of light-emitting diodes. Summary of the Invention

[0005] In view of the above-mentioned defects and deficiencies in the prior art, the present invention provides an epitaxial structure for a light-emitting diode and a light-emitting diode, which can effectively suppress electron overflow and improve the growth quality of quantum wells, enhance radiative recombination efficiency, and ultimately achieve an effective improvement in luminous efficiency.

[0006] According to an embodiment of the present invention, a light-emitting diode epitaxial structure is provided, comprising at least a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked sequentially, characterized in that: the active layer is a multiple quantum well structure, and the active layer includes a first layer, a second layer, a third layer, and a fourth layer in at least two periodic structures, the first layer being a potential well layer, the third layer being a potential barrier layer, and the relationship between the energy level band gap Eg1 of the first layer, the energy level band gap Eg2 of the second layer, the energy level band gap Eg3 of the third layer, and the energy level band gap Eg4 of the fourth layer satisfies Eg2, Eg4 > Eg3 > Eg1.

[0007] According to another embodiment of the present invention, a light-emitting diode epitaxial structure is also provided, comprising at least a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked sequentially, characterized in that: the active layer is a multiple quantum well structure, and the active layer includes a first layer, a second layer, a third layer, and a fourth layer in at least two periodic structures, the first layer includes a first sub-layer and a second sub-layer, the second layer is disposed between the first sub-layer and the second sub-layer, and the band gaps Eg5 of the first sub-layer, Eg6 of the second sub-layer, Eg2 of the second layer, Eg3 of the third layer, and Eg4 of the fourth layer satisfy the relationship Eg2, Eg4 > Eg3 > Eg6 > Eg5.

[0008] According to another embodiment of the present invention, a light-emitting diode is also provided, the light-emitting diode including the epitaxial structure as described above, a first electrode electrically connected to a first semiconductor layer structure, and a second electrode electrically connected to a second semiconductor layer structure.

[0009] According to another embodiment of the present invention, a light-emitting device is also provided, including a light-emitting diode as described above.

[0010] This application effectively suppresses electron overflow and improves the growth quality of the quantum well by growing a second layer with a higher energy band gap between the potential well layer and the barrier layer, thereby enhancing the radiative recombination efficiency, significantly improving the internal quantum efficiency, and ultimately achieving an effective improvement in luminescence efficiency.

[0011] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0012] Figure 1 The diagram shown is a structural schematic of the light-emitting diode epitaxial structure provided in an embodiment of the present invention. Figure 2 The diagram shows the structure of the active layer in Embodiment 1 of the present invention. Figure 3 The diagram shows the structure of the active layer in Embodiment 2 of the present invention. Figure 4 The diagram shows the structure of the active layer in Embodiment 3 of the present invention. Figure 5 The diagram shows the structure of the active layer in Embodiment 4 of the present invention. Figure 6 The diagram shown is a schematic diagram of the active layer in Embodiment 5 of the present invention.

[0013] Component designation explanation: 110 First semiconductor layer structure; 120 Active layer; 121 First layer; 1211 First sublayer; 1212 Second sublayer; 122 Second layer; 123 Third layer; 124 Fourth layer; 130 Second semiconductor layer structure; 140 Electron blocking layer. Detailed Implementation

[0014] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0015] The composition of each layer contained in this application can be analyzed by any suitable method, such as secondary ion mass spectrometry (SIMS); the thickness of each layer can be analyzed by any suitable method, such as transmission electron microscopy (TEM) or scanning electron microscopy (SEM), in conjunction with, for example, the depth position of each layer on a SIMS spectrum.

[0016] According to one embodiment of this application, a light-emitting diode epitaxial structure is provided, comprising at least a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked sequentially, characterized in that: the active layer is a multiple quantum well structure, and the active layer includes a first layer, a second layer, a third layer, and a fourth layer in at least two periodic structures, the first layer being a potential well layer, the third layer being a potential barrier layer, and the relationship between the energy level band gap Eg1 of the first layer, the energy level band gap Eg2 of the second layer, the energy level band gap Eg3 of the third layer, and the energy level band gap Eg4 of the fourth layer satisfies Eg2, Eg4 > Eg3 > Eg1. Specifically, from the stacking direction of the first semiconductor layer structure to the second semiconductor layer structure, the stacking order of the periodic structure is the first layer, the second layer, the third layer, and the fourth layer. By growing a second layer with a higher energy band gap (Eg2) between the first layer (potential well layer) and the third layer (potential barrier layer), electron overflow can be effectively blocked, preventing electrons from penetrating to the third layer (potential barrier layer) before recombination with holes. On the other hand, the hole mobility can be reduced, thereby more effectively confining charge carriers within the well layer. Under this dual effect, the radiative recombination efficiency is improved. At the same time, the second layer with a high energy band gap can also effectively compress the light field distribution, making the light field more concentrated in the well layer, thereby increasing the overlap factor between the light field and the active region, which is beneficial to the extraction efficiency of stimulated emission and confined spontaneous emission. In addition, growing a fourth layer with a similarly higher energy band gap (Eg4) after the barrier layer can further strengthen the confinement of charge carriers and improve the radiative recombination efficiency, thereby significantly improving the overall quantum efficiency of the light-emitting device and ultimately achieving a comprehensive improvement in luminescence efficiency.

[0017] In some embodiments, all periodic structures of the active layer include a first layer, a second layer, a third layer, and a fourth layer. By inserting a second layer with a high-energy bandgap between the potential well layer and the potential barrier layer in all periodic structures, the radiative recombination efficiency can be further improved, thereby achieving an effective improvement in luminescence efficiency.

[0018] In some embodiments, the second layer is Al x Ga 1-x For N layers, 0.95 ≤ x ≤ 1.

[0019] In some embodiments, the thickness of the second layer is less than 20 angstroms.

[0020] In some embodiments, the second layer is an AlN layer.

[0021] In some embodiments, the thickness of the second layer is no greater than 10 angstroms.

[0022] The second layer of the high-energy-level bandgap can be Al with a high Al composition. x Ga 1-x The N-layer, preferably an AlN layer, is a second layer. By inserting an extremely thin high-energy bandgap layer between the well layer and the barrier layer, the stress distribution at the heterostructure interface can be effectively adjusted to achieve band flattening. This weakens the bandgap caused by polarization, thereby increasing the overlap region of electron-hole wave functions and significantly improving the radiative recombination rate of charge carriers. With the increase in the radiative recombination rate of charge carriers, the overall luminous efficiency of the light-emitting device is also greatly improved. Secondly, the extremely thin AlN layer can also play a good stress buffering role between the well layer and the high-Al content barrier layer, effectively suppressing the formation of dislocation defects caused by lattice mismatch and significantly improving the growth quality of the quantum well. The excellent interface quality can effectively reduce the generation of deep-level defect states, significantly reducing the probability of point defects trapping charge carriers, thereby reducing non-radiative recombination (SRH) losses and further improving the radiative recombination efficiency of charge carriers. In addition, an excessively thick second layer will make it difficult for charge carriers to be injected during normal operation, reducing its injection efficiency, and significantly increasing the resistance of the light-emitting device, which in turn leads to an increase in the operating voltage.

[0023] In some embodiments, the first layer is an InGaN layer or a GaN layer with a thickness of 50-100 angstroms, and the third layer is an AlGaN layer or an AlInGaN layer with a thickness of 100-200 angstroms. By limiting the materials and thicknesses of the potential well layer and the potential barrier layer, it is ensured that the active layer can radiate light of the desired wavelength.

[0024] In some embodiments, the fourth layer is Al y Ga 1-yThe N-layer has a density of 0.95 ≤ y ≤ 1, and the thickness of the fourth layer is less than 30 angstroms. The energy level band gap Eg4 of the fourth layer can be adjusted by adjusting the Al content. Introducing this fourth layer with a high energy level band gap (Eg4) can further enhance the confinement of charge carriers, improve radiative recombination efficiency, and increase luminosity.

[0025] In some embodiments, the fourth layer is an AlN layer with a thickness of 5-15 angstroms. A suitable thickness for the fourth layer is important; if the fourth layer is too thin, its carrier confinement effect is insufficient, and if the fourth layer is too thick, its conductivity deteriorates, leading to a decrease in the performance of the light-emitting region and an increase in the operating voltage.

[0026] In some embodiments, the difference between Eg1 and Eg2 is at least 2 eV. This ensures the confinement of charge carriers by the second layer, especially effectively blocking electron overflow and preventing electrons from penetrating to the third layer (barrier layer) before recombination with holes. This confines the charge carriers within the well layer, significantly improving radiative recombination efficiency, optimizing internal quantum efficiency, and ultimately achieving an effective improvement in overall luminescence efficiency.

[0027] In some embodiments, the difference between Eg3 and Eg4 is at least 1.5 eV. This ensures the confinement of charge carriers by the fourth layer, reduces hole mobility, and improves hole injection efficiency, allowing for full recombination of holes and electrons within the trap layer. This is especially important under high-current operating conditions, where the device's need for effective hole injection and confinement is even more pronounced, thereby more effectively improving radiative recombination efficiency.

[0028] In some embodiments, the first layer comprises at least two semiconductor materials stacked together, and the band gaps Eg of the at least two semiconductor materials increase from low to high along the direction gradually approaching the third sublayer. The multi-material stacking creates a smooth energy level transition, weakens abrupt interface barrier changes, makes the carrier transport process more stable, and promotes full recombination of carriers, thereby improving radiative recombination efficiency.

[0029] According to another embodiment of the present invention, a light-emitting diode epitaxial structure is also provided, comprising at least a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked sequentially. The active layer is characterized by being a multiple quantum well structure, wherein at least two periodic structures of the active layer include a first layer, a second layer, a third layer, and a fourth layer. The first layer includes a first sub-layer and a second sub-layer, and the second layer is disposed between the first and second sub-layers. Furthermore, the band gaps Eg5 of the first sub-layer, Eg6 of the second sub-layer, Eg2 of the second layer, Eg3 of the third layer, and Eg4 of the fourth layer satisfy the relationship Eg2, Eg4 > Eg3 > Eg6 > Eg5. Specifically, viewed from the stacking direction from the first semiconductor layer structure to the second semiconductor layer structure, the stacking order of the periodic structures is first sub-layer, second layer, second sub-layer, third layer, and fourth layer. First, by inserting a second layer with a higher energy level bandgap (Eg2) within the first layer (equivalent to inserting a second layer between the first sublayer and the third layer), electron overflow can be effectively blocked, preventing electrons from penetrating to the third layer (barrier layer) before recombination with holes. Simultaneously, hole mobility can be reduced, thus more effectively confining charge carriers within the well layer. This dual effect improves radiative recombination efficiency. Furthermore, this high-energy-level bandgap second layer effectively compresses the light field distribution, concentrating the light field more within the well layer, thereby increasing the overlap factor between the light field and the active region. This is beneficial for the extraction efficiency of stimulated emission and confined spontaneous emission, significantly improving the overall quantum efficiency of the light-emitting device and ultimately achieving a comprehensive improvement in luminescence efficiency. Second, by setting a second sublayer (energy level bandgap Eg6), a smoother energy level transition is formed, weakening the abrupt change in the interface barrier, making the carrier transport process more stable, and simultaneously promoting full recombination of charge carriers, thereby improving radiative recombination efficiency.

[0030] In some embodiments, the first sublayer is an InGaN layer, and the second sublayer is a GaN layer, with the second sublayer being no larger than 10 angstroms. By limiting the material and thickness of the first layer, it is ensured that the active layer can radiate light of the required wavelength, while also facilitating a smooth energy level transition between the first and second, and third layers.

[0031] In some embodiments, all periodic structures of the active layer include a first sublayer, a second layer, a third sublayer, and a fourth layer. This further improves the radiative recombination efficiency, thereby achieving an effective increase in luminescence efficiency.

[0032] In some embodiments, the second layer is Al x Ga 1-x For N layers, 0.95 ≤ x ≤ 1.

[0033] In some embodiments, the thickness of the second layer is less than 20 angstroms.

[0034] By inserting an extremely thin second layer with a high energy band gap and high Al content, the stress distribution on the heterostructure interface can be effectively adjusted to achieve band flattening, thereby weakening the band tilt caused by polarization effect, increasing the overlap region of electron-hole wave functions, significantly improving the radiative recombination rate of charge carriers, and achieving a significant improvement in the overall luminous efficiency of the light-emitting device.

[0035] In some embodiments, the second layer is an AlN layer, and the second layer is no larger than 10 angstroms.

[0036] The extremely thin AlN layer can also act as a good stress buffer between the first layer and the high-Al-content third layer, effectively suppressing the formation of dislocation defects caused by lattice mismatch, significantly improving the growth quality of the quantum well, thereby reducing the generation of deep-level defect states, greatly reducing the probability of point defects trapping charge carriers, and thus reducing non-radiative recombination (SRH) losses, achieving a further improvement in charge carrier radiative recombination efficiency. On the other hand, an excessively thick second layer will make it difficult for charge carriers to be injected during normal operation, reducing its injection efficiency, and at the same time significantly increasing the resistance of the light-emitting device, leading to an increase in operating voltage.

[0037] In some embodiments, the emission wavelength of the active layer is between 340 nm and 430 nm. In light-emitting diodes emitting in this wavelength range, the requirement for curing capability is further increased.

[0038] According to another embodiment of the present invention, a light-emitting diode is also provided, which includes the epitaxial structure as described above, a first electrode electrically connected to a first semiconductor layer structure, and a second electrode electrically connected to a second semiconductor layer structure, so as to achieve an effective improvement in luminous efficiency.

[0039] According to another embodiment of the present invention, a light-emitting device is also provided, including a light-emitting diode as described above, so as to achieve an effective improvement in luminous efficiency.

[0040] Example 1 A preferred embodiment of the present invention is a vertically oriented gallium nitride-based light-emitting diode epitaxial structure, but it is not limited thereto. Alternatively, the light-emitting diode may also have a right-side-mounted or flip-chip structure. Figure 1The diagram shown illustrates the structure of a light-emitting diode (LED) epitaxial structure according to an embodiment of the present invention. From bottom to top, the LED epitaxial structure includes a first semiconductor layer structure 110, an active layer 120, and a second semiconductor layer structure 130. In some embodiments, an electron blocking layer 140 is further disposed between the active layer 120 and the second semiconductor layer structure 130. This LED epitaxial structure is obtained by epitaxial growth on a growth substrate using an MOCVD process. Subsequently, a chip is obtained by transferring the second semiconductor layer structure 130 side onto a permanent substrate. In this embodiment, an AlGaInN-based epitaxial structure capable of providing ultraviolet light is used as an example for illustration.

[0041] The first semiconductor layer structure 110 and the second semiconductor layer structure 130 are made of nitride-based semiconductor layers, which have a wider bandgap than the active layer 120. The first semiconductor layer structure 110 can be an N-type layer, and correspondingly, the second semiconductor layer structure 130 can be a P-type layer, or vice versa. This embodiment uses an N-type first semiconductor layer structure 110 and a P-type second semiconductor layer structure 130 as an example.

[0042] In this embodiment, the first semiconductor layer structure 110 is an N-type AlGaN layer, which can provide electrons to the active layer 120 under the action of a power source. The material of the first semiconductor layer structure 110 can be selected from those having the chemical formula In. a1 Al b1 Ga 1-a1-b1 Semiconductor materials of type N (0≤a1≤1, 0≤b1≤1, 0≤a1+b1≤1), such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, etc. In some embodiments, the first semiconductor layer structure 110 includes an N-type doped nitride layer. The N-type impurity may include one or a combination of Si, Ge, Sn, Se, or Te. Currently, in order to improve the emission efficiency of light radiated from the active layer 120, the surface of the first semiconductor layer structure 110 is roughened, that is, the surface of the first semiconductor layer structure 110 has a roughened structure.

[0043] In this embodiment, the second semiconductor layer structure 130 can be a P-type semiconductor layer, which can provide holes to the active layer 120 under power supply. The material of the second semiconductor layer structure 130 can be selected from those having the chemical formula In. a2 Al b2 Ga 1-a2-b2The second semiconductor layer structure 130 is formed from a semiconductor material of N (0≤a²≤1, 0≤b²≤1, 0≤a²+b²≤1), such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, etc. In a UV light-emitting device, the second semiconductor layer structure 130 may include an AlGaN layer. In some embodiments, the second semiconductor layer structure 130 includes a P-type doped nitride layer, which provides holes by doping with P-type impurities. The P-type impurities may be one or a combination of Mg, Zn, Be, Ca, Sr, and Ba.

[0044] In this embodiment, the electron blocking layer 140 is located between the active layer 120 and the second semiconductor layer structure 130. Its band gap is larger than that of the second semiconductor layer structure 130, and it has a larger lattice constant than the second semiconductor layer structure 130. In an optional embodiment, the electron blocking layer 140 is made of a nitride-based semiconductor layer with a high Al content. This is beneficial for blocking the diffusion of Mg atoms from the P-type semiconductor layer into the active layer 120, thereby improving the recombination efficiency of electrons and holes in the active layer 120. It can be a single-layer or multi-layer structure, such as a superlattice structure. In UV light-emitting devices, the electron blocking layer 140 includes an AlGaN layer. In an optional embodiment, the thickness of the electron blocking layer 140 is between 5 nm and 200 nm. In a further embodiment, the thickness of the electron blocking layer 140 is between 5 nm and 100 nm.

[0045] Optionally, in some embodiments, the light-emitting diode may further include a superlattice layer (not shown) located between the first semiconductor layer structure 110 and the active layer 120, which has the function of adjusting stress and current spread. The superlattice layer contains periodic structures, each periodic structure generally containing at least two thin-layer structures of different materials, the material being a nitride-based semiconductor layer. In one embodiment, the superlattice layer includes an AlGaN / GaN periodic structure. In a preferred embodiment, at least one periodic structure contains three sub-layers, such as InGaN / AlGaN / AlN, GaN / AlGaN / AlN, or InGaN / GaN / AlN. This periodic structure with a high bandgap can adjust the radiative recombination region, thereby improving the recombination efficiency of the active layer and thus increasing brightness. It can also prevent leakage caused by hot holes or electrons gaining additional energy, thereby improving the brightness stability of hot operation, with a hot / cold factor (H / C) value reaching over 70%.

[0046] refer to Figure 2 , Figure 2The diagram shows the structure of the active layer in Embodiment 1 of the present invention. The active layer 120 is a multiple quantum well structure, consisting of at least two periodic structures. Each periodic structure generally contains at least two thin-layer structures made of different materials, preferably nitride-based semiconductor layers, which are unintentionally doped. The at least two periodic structures include a first layer 121, a second layer 122, a third layer 123, and a fourth layer 124. In this embodiment, from the stacking direction from the first semiconductor layer structure 110 to the second semiconductor layer structure 130, the stacking order of the periodic structures is the first layer 121, the second layer 122, the third layer 123, and the fourth layer 124. The band gaps Eg1 of the first layer 121, Eg2 of the second layer 122, Eg3 of the third layer 123, and Eg4 of the fourth layer 124 satisfy the following relationship: Eg2, Eg4 > Eg3 > Eg1, that is, Eg2 > Eg3 > Eg1 and Eg4 > Eg3 > Eg1. The first layer 121 serves as a potential well layer, and the third layer 123 serves as a potential barrier layer. By growing a second layer 122 with a higher energy band gap (Eg2) between the first layer 121 (potential well layer) and the third layer 123 (potential barrier layer), electron overflow can be effectively blocked, preventing electrons from penetrating to the third layer 123 (potential barrier layer) before recombination with holes. On the other hand, the hole mobility can be reduced, thus more effectively confining charge carriers within the well layer. Under this dual effect, the radiative recombination efficiency is improved. At the same time, the second layer 122 with a high energy band gap can also effectively compress the light field distribution, making the light field more concentrated in the well layer, thereby increasing the overlap factor between the light field and the active region, which is beneficial to the extraction efficiency of stimulated emission and confined spontaneous emission. In addition, a fourth layer 124 with a similarly higher energy band gap (Eg4) is grown after the barrier layer, which can further enhance the confinement of charge carriers and improve the radiative recombination efficiency, thereby significantly improving the overall quantum efficiency of the light-emitting device and ultimately achieving a comprehensive improvement in luminescence efficiency. Preferably, in some embodiments, all periodic structures of the active layer 120 include a first layer 121, a second layer 122, a third layer 123, and a fourth layer 124. By inserting a high-energy-level bandgap second layer 122 between the potential well layer and the potential barrier layer in all periodic structures, the radiative recombination efficiency can be further improved, thus achieving an effective improvement in luminescence efficiency. The number of periodic structures in the active layer 120 is 2 to 20.

[0047] This epitaxial structure is more suitable for nitride-based light-emitting diodes with an emission wavelength between 340 nm and 430 nm. The periodic structure can be InGaN / AlN / AlGaN / AlN, GaN / AlN / AlGaN / AlN, InGaN / AlGaN / AlInGaN / AlGaN, InGaN / AlN / AlInGaN / AlN, GaN / AlN / AlInGaN / AlGaN, or GaN / AlGaN / AlInGaN / AlN, but the embodiments of the present invention are not limited to these.

[0048] The first layer 121 can use In a Ga 1-a N, where the value of 'a' adjusts the emission wavelength. A larger 'a' results in a shorter emission wavelength, while a smaller 'a' results in a longer emission wavelength. For example, in some embodiments, the first layer 121 is an InGaN layer or a GaN layer with a thickness ranging from 50 to 100 angstroms. The third layer 123 can be made of In... b Al c Ga 1-b-c N (where 0≤b≤1, 0≤c≤1, b+c≤1), for example, in some embodiments, the third layer 123 is an AlGaN layer or an AlInGaN layer with a thickness ranging from 100 to 200 angstroms. The band gap Eg1 of the first layer 121 can be adjusted by the In content, and the band gap Eg3 of the third layer 123 can be adjusted by the Al and In content. The band gap Eg1 of the first layer 121 is preferably 3.2-3.5 eV, more preferably 3.3-3.4 eV, and the band gap Eg3 of the third layer 123 is preferably 3.4-3.8 eV, more preferably 3.6-3.7 eV.

[0049] The second layer 122 can use Al. x Ga 1-x The N-layer (where 0.95 ≤ x ≤ 1) has a thickness of less than 20 angstroms. The second layer 122 with a high energy band gap can be Al with a high Al composition. x Ga 1-xThe N-layer, by inserting an extremely thin high-energy bandgap layer between the potential well layer and the barrier layer, can effectively adjust the stress distribution on the heterostructure interface, thereby achieving band flattening. This weakens the band tilt caused by polarization, increases the overlap region of electron-hole wave functions, and significantly improves the radiative recombination rate of charge carriers. With the increase in the radiative recombination rate of charge carriers, the overall luminous efficiency of the light-emitting device is also greatly improved. Preferably, in some embodiments, the second layer 122 is an AlN layer with a thickness not exceeding 10 angstroms. Optionally, in some embodiments, the thickness of the fourth layer 124 ranges from 1 to 7 angstroms; for example, the thickness of the fourth layer 124 can be 2 angstroms, 3 angstroms, 4 angstroms, 5 angstroms, or 6 angstroms. The extremely thin AlN layer can also act as a good stress buffer between the potential well layer and the high Al content barrier layer, effectively suppressing the formation of dislocation defects caused by lattice mismatch and significantly improving the growth quality of the quantum well. The excellent interface quality can effectively reduce the generation of deep-level defect states, significantly reducing the probability of point defects trapping carriers, thereby reducing non-radiative recombination (SRH) losses and further improving carrier radiative recombination efficiency. Furthermore, an excessively thick second layer 122 will hinder carrier injection during normal operation, making it difficult and reducing its injection efficiency. It also significantly increases the resistance of the light-emitting device, leading to an increase in operating voltage. The Al content of the second layer 122 can adjust its bandgap Eg2. The bandgap Eg2 of the second layer 122 is greater than 5.5 eV. Preferably, when the second layer 122 is an AlN layer, Eg2 is 6.2 eV, which is a high-level bandgap.

[0050] In some embodiments, the difference between Eg1 and Eg2 is at least 2 eV. This ensures the confinement of charge carriers by the second layer 122, especially effectively blocking electron overflow and preventing electrons from penetrating to the third layer 123 (barrier layer) before recombination with holes. This confines the charge carriers within the well layer, significantly improving radiative recombination efficiency, optimizing internal quantum efficiency, and ultimately achieving an effective improvement in overall luminescence efficiency.

[0051] The fourth layer 124 can use AI. y Ga 1-yThe N-layer (where 0.95 ≤ y ≤ 1) has a thickness of less than 30 angstroms. The energy level band gap Eg4 of the fourth layer 124 can be adjusted by the Al content. Introducing this fourth layer 124 with a high energy level band gap (Eg4) can further enhance the confinement of charge carriers, improve radiative recombination efficiency, and increase brightness. Preferably, the thickness of the fourth layer 124 is greater than that of the second layer 122, making it more difficult for charge carriers to escape and further enhancing the confinement effect. Preferably, in some embodiments, the fourth layer 124 is an AlN layer with a thickness ranging from 5 to 15 angstroms. If the thickness of the fourth layer 124 is too thin, the carrier confinement effect it provides is insufficient; if the thickness of the fourth layer 124 is too thick, its conductivity deteriorates, leading to a decrease in the performance of the light-emitting region and an increase in the operating voltage. The energy level band gap Eg4 of the fourth layer 124 is greater than 5.5 eV. Preferably, when the fourth layer 124 is an AlN layer, Eg4 is 6.2 eV, which is a high energy level band gap.

[0052] In some embodiments, the difference between Eg3 and Eg4 is at least 1.5 eV. This ensures the confinement of charge carriers by the fourth layer 124, reduces hole mobility, and improves hole injection efficiency, allowing for full recombination of holes and electrons within the trap layer. This is especially important under high-current operating conditions, where the device's need for effective hole injection and confinement is even more pronounced, thereby more effectively improving radiative recombination efficiency.

[0053] To further evaluate the actual contribution of this epitaxial structure to the performance of the light-emitting device, the inventors conducted comparative tests on two sets of samples under consistent test conditions. In the comparative example, the stacking order of the active layer in each cycle was the first, third, and fourth layers, while in the experimental example, the stacking order of the active layer in each cycle was the first, second, third, and fourth layers. The test results are shown in Table 1 below: Table 1 Comparison of Voltage and Brightness Test Data

[0054] As can be seen from Table 1, the epitaxial structure of the light-emitting diode of the present invention effectively reduces the operating voltage of the device and significantly improves the luminous brightness, thereby achieving comprehensive optimization of the performance of the light-emitting device.

[0055] Example 2 refer to Figure 3 , Figure 3 The diagram shows the structure of the active layer in Embodiment 2 of the present invention. This embodiment provides a light-emitting diode epitaxial structure. The difference between the light-emitting diode epitaxial structure of this embodiment and the light-emitting diode epitaxial structure of other embodiments is that: the first layer 121 is composed of at least two semiconductor materials stacked together, and along the direction gradually approaching the third sub-layer, the energy level band gap Eg of the at least two semiconductor materials increases from low to high.

[0056] In this embodiment, the first layer 121 includes a first sublayer 1211 and a second sublayer 1212. The band gap Eg5 of the first sublayer 1211 and the band gap Eg6 of the second sublayer 1212 satisfy Eg6 > Eg5. That is, in this embodiment, Eg2 > Eg3 > Eg6 > Eg5. By stacking multiple materials, a smooth energy level transition is formed, weakening the abrupt interface barrier change (between the first sublayer 1211 and the second layer 122, or between the first sublayer 1211 and the third layer 123), making the carrier transport process smoother, and promoting full recombination of carriers, thereby improving the radiative recombination efficiency.

[0057] Example 3 refer to Figure 4 , Figure 4 This is a schematic diagram of the active layer structure in Embodiment 3 of the present invention. This embodiment provides a light-emitting diode epitaxial structure. The difference between the light-emitting diode epitaxial structure of this embodiment and those of other embodiments is that the active layer 120 can also be a combined structure, for example, composed of a first type of periodic structure and a second type of periodic structure. The first type of periodic structure can be configured with reference to the structure of Embodiment 1, that is, from the stacking direction from the first semiconductor layer structure 110 to the second semiconductor layer structure 130, the stacking order of the first type of periodic structure is the first layer 121, the second layer 122, the third layer 123, and the fourth layer 124, and the energy level band gap Eg1 of the first layer 121, the second layer 122, the third layer 123, and the fourth layer 124. The band gaps Eg2 of the first semiconductor layer 121, Eg3 of the third semiconductor layer 123, and Eg4 of the fourth semiconductor layer 124 satisfy Eg2, Eg4 > Eg3 > Eg1, that is, Eg2 > Eg3 > Eg1 and Eg4 > Eg3 > Eg1. From the stacking direction from the first semiconductor layer structure 110 to the second semiconductor layer structure 130, the stacking order of the second type of periodic structure is the first layer 121, the third layer 123, and the fourth layer 124, and the band gaps Eg1 of the first layer 121, Eg3 of the third layer 123, and Eg4 of the fourth layer 124 satisfy Eg4 > Eg3 > Eg1.

[0058] In this embodiment, reference Figure 4The first type of periodic structure can be disposed adjacent to the second semiconductor layer structure 130, while the second type of periodic structure is disposed adjacent to the first semiconductor layer structure 110. The number of the first type of periodic structures is greater than or equal to the number of the second type of periodic structures, ranging from 2 to 20, and the number of the third type of periodic structures ranging from 1 to 10. Under high-current operating conditions, the device's need for effective hole injection and confinement is more prominent, thereby more effectively improving radiative recombination efficiency. Of course, in other embodiments, the first type of periodic structure can also be disposed adjacent to the first semiconductor layer structure 110, while the second type of periodic structure is disposed adjacent to the second semiconductor layer structure 130; the embodiments of the present invention are not limited thereto.

[0059] Example 4 refer to Figure 5 , Figure 5 This is a schematic diagram of the active layer structure in Embodiment 4 of the present invention. This embodiment provides a light-emitting diode epitaxial structure. The difference between the light-emitting diode epitaxial structure of this embodiment and those of other embodiments is that the active layer 120 can also be a combined structure, for example, composed of a first type of periodic structure, a second type of periodic structure, and a third type of periodic structure. The first type of periodic structure can be configured with reference to the structure of Embodiment 1. That is, looking from the stacking direction from the first semiconductor layer structure 110 to the second semiconductor layer structure 130, the stacking order of the first type of periodic structure is the first layer 121, the second layer 122, the third layer 123, and the fourth layer 124. Furthermore, the band gaps Eg1 of the first layer 121, Eg2 of the second layer 122, and Eg3 of the third layer 123 are... The relationship between the energy level band gaps Eg4 of the third and fourth layers 124 satisfies Eg2, Eg4 > Eg3 > Eg1, that is, Eg2 > Eg3 > Eg1 and Eg4 > Eg3 > Eg1; from the stacking direction from the first semiconductor layer structure 110 to the second semiconductor layer structure 130, the stacking order of the second type of periodic structure is the first layer 121, the third layer 123 and the fourth layer 124, and the relationship between the energy level band gaps Eg1 of the first layer 121, Eg3 of the third layer 123 and Eg4 of the fourth layer 124 satisfies Eg4 > Eg3 > Eg1; the third type of periodic structure only includes the first layer 121 and the third layer 123, and the energy level band gap Eg1 of the first layer 121 is smaller than the energy level band gap Eg3 of the third layer 123.

[0060] In this embodiment, reference Figure 5The first type of periodic structure can be disposed adjacent to the second semiconductor layer structure 130, while the third type of periodic structure is disposed adjacent to the first semiconductor layer structure 110, and the second type of periodic structure is disposed between the first and third type of periodic structures. For example, the number of the first type of periodic structures is 2 to 20, the number of the second type of periodic structures is 1 to 10, and the number of the third type of periodic structures is 1 to 5. Based on this, the radiative recombination efficiency is further improved for high-current operating conditions. Of course, in other embodiments, the first type of periodic structure can also be disposed adjacent to the first semiconductor layer structure 110, while the third type of periodic structure is disposed adjacent to the second semiconductor layer structure 130; the embodiments of the present invention are not limited thereto.

[0061] Example 5 refer to Figure 6 , Figure 6 This diagram illustrates the structure of the active layer in Embodiment 5 of the present invention. This embodiment provides another LED epitaxial structure. The difference between the LED epitaxial structure of this embodiment and those of other embodiments lies in: The first layer 121 includes a first sublayer 1211 and a second sublayer 1212. The band gap Eg5 of the first sublayer 1211 and the band gap Eg6 of the second sublayer 1212 satisfy Eg6 > Eg5. The second layer 122 is disposed between the first sublayer 1211 and the second sublayer 1212. The band gap Eg5 of the first sublayer 1211, the band gap Eg6 of the second sublayer 1212, the band gap Eg2 of the second sublayer 122, the band gap Eg3 of the third layer 123, and the band gap Eg4 of the fourth layer 124 satisfy Eg2, Eg4 > Eg3 > Eg6 > Eg5. First, by inserting a second layer 122 with a higher energy level bandgap (Eg2) into the first layer 121 (which is also equivalent to inserting a second layer 122 between the first sub-layer 1211 and the third layer 123), electron overflow can be effectively blocked, preventing electrons from penetrating to the third layer 123 (barrier layer) before recombination with holes. Simultaneously, the hole mobility can be reduced, thus more effectively confining charge carriers within the well layer. This dual effect improves radiative recombination efficiency. Furthermore, the high energy level bandgap of the second layer 122 effectively compresses the light field distribution, concentrating the light field more in the well layer, thereby increasing the overlap factor between the light field and the active region. This is beneficial for the extraction efficiency of stimulated emission and confined spontaneous emission, significantly improving the overall quantum efficiency of the light-emitting device and ultimately achieving a comprehensive improvement in luminescence efficiency. Second, by setting a second sub-layer 1212 with an energy level bandgap (Eg6), a smoother energy level transition is formed, weakening the interface barrier abrupt change, making the carrier transport process more stable, and simultaneously promoting full recombination of charge carriers, thereby improving radiative recombination efficiency. Preferably, in some embodiments, all periodic structures of the active layer 120 include a first sublayer 1211, a second layer 122, a second sublayer 1212, a third layer 123, and a fourth layer 124. This further improves the radiative recombination efficiency, achieving an effective increase in luminous efficiency. The number of periodic structures in the active layer 120 is 2 to 20.

[0062] In some embodiments, the first sublayer 1211 is an InGaN layer, and the second sublayer 1212 is a GaN layer. This ensures that the active layer can radiate light of the desired wavelength while facilitating a smooth energy level transition between the first layer 121, the second layer 122, and the third layer 123. It weakens the abrupt interface barrier change (between the first layer 121 and the third layer 123), making the carrier transport process smoother and promoting sufficient carrier recombination, thereby improving radiative recombination efficiency. The thickness of the first sublayer 1211 is greater than that of the second sublayer 1212, and the second sublayer 1212 is no greater than 10 angstroms.

[0063] Example 6 This embodiment provides a light-emitting diode (LED) including any of the epitaxial structures described in the above embodiments, thereby achieving an effective improvement in luminous efficiency. The LED can be a gallium nitride-based LED with a vertical structure. Of course, the LED can have a forward or flip-chip structure. The LED also includes a first electrode electrically connected to a first semiconductor layer structure 110 and a second electrode electrically connected to a second semiconductor layer structure 130.

[0064] Example 7 This embodiment also provides a light-emitting device, including a light-emitting diode as described in the above embodiment, which has excellent luminous efficiency.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A light-emitting diode epitaxial structure, comprising at least a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked sequentially, characterized in that: The active layer is a multiple quantum well structure. The active layer includes a first layer, a second layer, a third layer, and a fourth layer in at least two periodic structures. The first layer is a potential well layer, the third layer is a potential barrier layer, and the energy level band gap Eg1 of the first layer, the energy level band gap Eg2 of the second layer, the energy level band gap Eg3 of the third layer, and the energy level band gap Eg4 of the fourth layer are related by Eg2, Eg4 > Eg3 > Eg1.

2. The light-emitting diode epitaxial structure according to claim 1, characterized in that, All periodic structures of the active layer include a first layer, a second layer, a third layer, and a fourth layer.

3. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The second layer is Al x Ga 1-x For N layers, 0.95 ≤ x ≤ 1.

4. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The thickness of the second layer is less than 20 angstroms.

5. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The second layer is an AlN layer.

6. The light-emitting diode epitaxial structure according to claim 5, characterized in that: The thickness of the second layer is no more than 10 angstroms.

7. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The first layer is an InGaN layer or a GaN layer, and the thickness of the first layer is 50~100 angstroms. The third layer is an AlGaN layer or an AlInGaN layer, and the thickness of the third sub-layer is 100~200 angstroms.

8. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The fourth layer is Al. y Ga 1-y N layers, 0.95≤y≤1, the thickness of the fourth layer is less than 30 angstroms.

9. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The fourth layer is an AlN layer, and the thickness of the fourth layer is 5-15 angstroms.

10. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The difference between Eg1 and Eg2 is at least 2 eV.

11. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The difference between Eg3 and Eg4 is at least 1.5 eV.

12. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The first layer comprises at least two semiconductor materials stacked together, and the band gap Eg of the at least two semiconductor materials increases from low to high along the direction gradually approaching the third layer.

13. A light-emitting diode epitaxial structure, comprising at least a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked sequentially, characterized in that: The active layer is a multiple quantum well structure. The active layer includes a first layer, a second layer, a third layer, and a fourth layer in at least two periodic structures. The first layer includes a first sub-layer and a second sub-layer. The second layer is disposed between the first sub-layer and the second sub-layer. The band gaps Eg5 of the first sub-layer, Eg6 of the second sub-layer, Eg2 of the second layer, Eg3 of the third layer, and Eg4 of the fourth layer satisfy the relationship Eg2, Eg4 > Eg3 > Eg6 > Eg5.

14. The light-emitting diode epitaxial structure according to claim 13, characterized in that, The first sublayer is an InGaN layer, and the second sublayer is a GaN layer, with the second sublayer being no larger than 10 angstroms.

15. The light-emitting diode epitaxial structure according to claim 13, characterized in that, All periodic structures of the active layer include a first sub-layer, a second layer, a third layer, and a fourth layer.

16. The light-emitting diode epitaxial structure according to claim 13, characterized in that, The second layer is Al x Ga 1-x For N layers, 0.95 ≤ x ≤ 1.

17. The light-emitting diode epitaxial structure according to claim 13, characterized in that, The thickness of the second layer is less than 20 angstroms.

18. The light-emitting diode epitaxial structure according to claim 13, characterized in that, The second layer is an AlN layer, and the second layer is no larger than 10 angstroms.

19. A light-emitting diode, characterized in that, It includes the light-emitting diode epitaxial structure according to any one of claims 1 to 18, and a first electrode electrically connected to the first semiconductor layer structure and a second electrode electrically connected to the second semiconductor layer structure.

20. A light-emitting device, characterized in that, Includes the light-emitting diode as described in claim 19.

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