Ultraviolet light emitting diode and ultraviolet light emitting device

Abstract

The ultraviolet light-emitting diode at least comprises an epitaxial structure, the epitaxial structure at least comprises a first semiconductor layer structure, an active layer and a second semiconductor layer structure which are stacked in sequence, the active layer is of a multi-quantum well structure, and the second semiconductor layer structure is of a P-type doped layer. Wherein the P-type dopant is diffused from the second semiconductor layer structure to the active layer and forms a doping concentration curve, and the doping concentration curve of the P-type dopant forms at least two sections of descending regions with different slopes in the direction from the second semiconductor layer structure to the first semiconductor layer structure. By controlling the slope of the descending regions and the distance from the turning point of the two sections of descending regions to the quantum well, Mg atoms are effectively prevented from diffusing into the quantum well, the influence of the Mg atoms on the quantum well is reduced, the quality of the quantum well is improved, and the light attenuation resistance of the LED chip is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to an ultraviolet light-emitting diode and an ultraviolet light-emitting device. Background Art

[0002] Light Emitting Diodes (LEDs) have the advantages of high efficiency, long lifespan, small size, low power consumption, etc., and are widely used in fields such as indoor and outdoor white lighting, screen displays, backlights, etc. Among them, ultraviolet light-emitting elements emit UV light and can be used in various fields including curing polymer materials, sterilization of medical devices, device components, light sources for generating white light, etc. Thus, UV light-emitting elements have gradually been applied in various fields.

[0003] Current UVA band products are mainly for high-end exposure machines and industrial curing requirements, and usually require long-term use. Since the change in brightness is extremely likely to affect the curing ability of the glue, a light source with serious light decay is likely to cause a decline in the later curing ability. Therefore, how to improve the light decay resistance of LED chips is the focus of the current industry development. Usually, the P-type semiconductor layer can provide holes to the quantum well under the action of the power supply and be used for light emission, but P-type dopants (such as magnesium (Mg) atoms) are prone to diffuse into the quantum well and become defects at the deep level, thus affecting the relative brightness of the light-emitting element during aging, and further accelerating the long-term light decay of the light-emitting element, especially a more serious light decay effect can occur under high current and high ambient temperature. Therefore, in order to effectively improve the light decay resistance of LED chips, it is necessary to provide a solution that can effectively control and regulate the diffusion of Mg atoms. Summary of the Invention

[0004] In view of the above-mentioned defects and deficiencies in the prior art, the present invention provides an ultraviolet light-emitting diode and an ultraviolet light-emitting device, which can effectively reduce the diffusion of Mg atoms into the quantum well and effectively improve the light decay resistance of LED chips.

[0005] An embodiment of the present invention provides an ultraviolet light-emitting diode, characterized in that the ultraviolet light-emitting diode at least includes an epitaxial structure, and the epitaxial structure at least includes a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked in sequence. The active layer is a multi-quantum well structure, and the second semiconductor layer structure is a P-type doped layer. The P-type dopant therein diffuses from the second semiconductor layer structure to the active layer and forms a doping concentration curve, and the doping concentration curve of the P-type dopant forms at least two descending regions with different slopes in the direction from the second semiconductor layer structure to the first semiconductor layer structure.

[0006] According to another embodiment of the present invention, there is also provided an ultraviolet light-emitting diode, characterized in that the ultraviolet light-emitting diode at least includes an epitaxial structure, and the epitaxial structure at least includes a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked in sequence. The active layer is a multi-quantum well structure, and the second semiconductor layer structure is a P-type doped layer. The P-type dopant therein diffuses from the second semiconductor layer structure to the active layer and forms a doping concentration curve. In the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure is defined as the first quantum well, and the concentration of the P-type dopant in the first quantum well is not greater than 1×10 18 atom / cm.

[0007] According to another embodiment of the present invention, there is provided an ultraviolet light-emitting device, which includes a circuit board and a light-emitting element disposed on the circuit board, and uses the ultraviolet light-emitting diode provided in any of the above embodiments.

[0008] As described above, the ultraviolet light-emitting diode and the ultraviolet light-emitting device of the present application have the following beneficial effects: In the ultraviolet light-emitting diode of the present application, the P-type dopant in the second semiconductor layer structure diffuses from the second semiconductor layer structure to the active layer direction and forms a doping concentration curve. The doping concentration curve of the P-type dopant forms at least two descending regions with different slopes in the direction from the second semiconductor layer structure to the first semiconductor layer structure. By controlling the slope of the descending region and the distance from the turning point at the connection of the two descending regions to the quantum well, the diffusion of Mg atoms into the quantum well is effectively reduced, the influence of Mg atoms on the quantum well is reduced, and thus the light decay resistance of the LED chip is effectively improved. In addition, the concentration of the P-type dopant in the first quantum well of the active layer close to the second semiconductor layer structure can be limited to not greater than 1×10 18 atom / cm 3 , that is, by limiting the diffusion concentration range of Mg atoms in the quantum well, the diffusion of Mg atoms into the quantum well is further effectively reduced, thereby improving the aging performance of the light-emitting diode.

[0009] Other features and beneficial effects of the present invention will be described in the subsequent description, and part of them will become obvious from the description or be understood by implementing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It shows a schematic diagram of the epitaxial structure of the ultraviolet light-emitting diode provided by the embodiment of the present invention; Figure 2 It shows Figure 1 a schematic diagram of the epitaxial structure of part A in the circle; Figure 3It shows the secondary ion mass spectrometry (SIMS) analysis diagram of the ultraviolet light-emitting diode provided by the embodiment of the present invention; Figure 4 It shows the enlarged view at the measurement depth of 0 μm to 0.15 μm in Embodiment 1 of the present invention; Figure 5 It shows the enlarged view at the measurement depth of 0 μm to 0.15 μm in Embodiment 2 of the present invention; Figure 6 It shows the structural schematic diagram of the ultraviolet light-emitting diode provided by the embodiment of the present invention.

[0011] Element number description: 100 Light-emitting element; 110 Substrate; 120 Epitaxial structure; 121 First semiconductor layer structure; 122 Active layer; 1221 First quantum well; 122A Barrier layer; 122B Well layer; 123 Electron blocking layer; 124 Second semiconductor layer structure; First descending region L1; Second descending region L2; Inflection point M; 200 Bonding layer; 210 First electrical connection layer; 221 Transparent conductive layer; 222 Metal reflection layer; 223 Metal connection layer; 220 Second electrical connection layer; 310 Second insulating layer; 320 Third insulating layer; 400 Conductive substrate; 420 Second electrode; Recess G2. Detailed implementation manners

[0012] The following uses specific specific examples to illustrate the implementation manners 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 implementation manners. 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.

[0013] The composition of each layer included in this application can be analyzed in any suitable manner, such as a secondary ion mass spectrometer (SIMS); the thickness of each layer can be analyzed in any suitable manner, such as a transmission electron microscope (TEM) or a scanning electron microscope (SEM), for matching the depth positions of each layer on the SIMS map, for example.

[0014] In view of the above-mentioned defects and deficiencies in the prior art, the present invention provides an ultraviolet light-emitting diode and an ultraviolet light-emitting device, which can effectively reduce the diffusion of Mg atoms into the quantum well and effectively improve the anti-light decay ability of the LED chip.

[0015] According to an embodiment of the present application, an ultraviolet light-emitting diode is provided, characterized in that the ultraviolet light-emitting diode at least includes an epitaxial structure, and the epitaxial structure at least includes a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked in sequence. The active layer is a multiple quantum well structure, and the second semiconductor layer structure is a P-type doped layer. The P-type dopant therein diffuses from the second semiconductor layer structure into the active layer and forms a doping concentration curve. The doping concentration curve of the P-type dopant forms at least two descending regions with different slopes in the direction from the second semiconductor layer structure to the first semiconductor layer structure.

[0016] In some embodiments, the descending region includes a first descending region and a second descending region, and the descending slope k1 of the P-type dopant concentration in the first descending region is less than the descending slope k2 of the P-type dopant concentration in the second descending region.

[0017] In some embodiments, the descending trend of the P-type dopant concentration in the second descending region is steeper than that in the first descending region.

[0018] In some embodiments, in the stacking direction of the epitaxial structure, the second descending region is closer to the active layer than the first descending region.

[0019] By forming at least two descending regions with different slopes through the concentration of the P-type dopant, and further controlling that the descending slope of the second descending region close to the active layer in the stacking direction of the epitaxial structure is greater than that of the first descending region far from the active layer in the stacking direction of the epitaxial structure, thereby accelerating the reduction of the diffusion concentration of the P-type dopant entering the active layer, it can make the concentration of the P-type dopant low enough when entering the active layer. For example, it is a Mg atom, which can effectively reduce the diffusion of Mg atoms into the quantum well and reduce the influence of Mg atoms on the quantum well, thereby effectively improving the anti-light decay ability of the LED chip.

[0020] In some embodiments, the range of the descending slope of the P-type dopant concentration in the first descending region is not greater than 1.

[0021] Furthermore, in some embodiments, the range of the descending slope of the P-type dopant concentration in the first descending region is between 1×10 18 ~8×10 18 (atom / cm 3 ) / 0.01μm.

[0022] In some embodiments, the range of the descending slope of the P-type dopant concentration in the second descending region is not less than 1.

[0023] Furthermore, in some embodiments, the range of the descending slope of the P-type dopant concentration in the second descending region is between 0.5×10 18 ~4×10 18 (atom / cm3 ) / 0.01μm。

[0024] By controlling the decreasing slope ranges of the P-type dopant concentrations in the first and second descending regions, especially the decreasing slope of the P-type dopant concentration in the second descending region closer to the active layer in the stacking direction of the epitaxial structure, the diffusion concentration of the P-type dopant into the active layer can be accelerated to decrease, so that the concentration of the P-type dopant when entering the active layer can be low enough, and the diffusion of Mg atoms into the quantum well can be effectively reduced, thereby improving the aging performance of the light-emitting diode.

[0025] In some embodiments, the concentration range of the P-type dopant in the first descending region is between 2×10 18 atom / cm 3 ~2×10 20 atom / cm 3 。

[0026] In some embodiments, the concentration range of the P-type dopant in the second descending region is between 5×10 16 atom / cm 3 ~2×10 19 atom / cm 3 。

[0027] By controlling the concentration ranges of the P-type dopant in the first and second descending regions, especially the concentration of the P-type dopant in the second descending region closer to the active layer in the stacking direction of the epitaxial structure is not greater than 2×10 19 atom / cm 3 ,the concentration of the P-type dopant when entering the active layer can be low enough, thereby reducing the overall diffusion concentration of the P-type dopant in the quantum well, better controlling the P-type doping level of the active layer, and enabling the light-emitting element to have excellent anti-light decay ability.

[0028] In some embodiments, the decreasing angle of the P-type dopant concentration in the second descending region is α, and α is not less than 45°.

[0029] By controlling the decreasing angle α of the P-type dopant concentration in the second descending region to be as large as possible, at least not less than 45°, the slope of the second descending region can be made as large as possible, the diffusion concentration of the P-type dopant into the active layer can be accelerated to decrease, and then the concentration of the P-type dopant when entering the active layer can be low enough, whereby the diffusion of Mg atoms into the quantum well can be effectively reduced, thereby improving the aging performance of the light-emitting diode.

[0030] In some embodiments, in the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure is defined as the first quantum well, and the concentration of the P-type dopant in the first quantum well is not greater than 1×10 18atoms / cm 3 .

[0031] By restricting the concentration of P-type dopants in the first quantum well structure closest to the second semiconductor layer structure to be no greater than 5×10 17 atoms / cm 3 , the overall diffusion concentration of P-type dopants in the quantum well can be reduced, and the P-type doping level of the active layer can be better controlled, enabling the light-emitting element to have excellent anti-light decay ability.

[0032] In some embodiments, the first descending region is connected to the second descending region, and the connection between the first descending region and the second descending region is a slope turning point M.

[0033] In some embodiments, the distance S from the slope turning point M to the upper surface of the first quantum well is not less than 0.05 μm.

[0034] In some embodiments, the concentration range of P-type dopants in the slope turning point M is between 2×10 18 atoms / cm 3 ~2×10 19 atoms / cm 3 .

[0035] By simultaneously restricting the concentration range of P-type dopants in the turning point M at the connection between the first descending region and the second descending region and the distance from the turning point M to the upper surface of the first quantum well to be as large as possible, the concentration of P-type dopants when entering the active layer can be made low enough, effectively reducing the diffusion of Mg atoms into the quantum well, thereby effectively improving the anti-light decay ability of the LED chip.

[0036] In some embodiments, an electron blocking layer is further formed between the active layer and the second semiconductor layer structure, and the first descending region, the turning point M, and the second descending region are formed in the electron blocking layer.

[0037] In other embodiments, at least part of the first descending region is further formed in the second semiconductor layer structure and / or at least part of the second descending region is further formed in the active layer.

[0038] Controlling the formation of the descending region in the electron blocking layer is beneficial to controlling the concentration of P-type dopants in the electron blocking layer, and further controlling the concentration of P-type dopants when approaching the active layer, so that the concentration of P-type dopants in the active layer is low enough, and the P-type doping level of the active layer can be better controlled, enabling the light-emitting element to have excellent anti-light decay ability.

[0039] In some embodiments, the number of quantum well structures is between 3 and 20, and the number of overlaps between the second descending region and the quantum well structures does not exceed two.

[0040] By controlling the diffusion depth of the P-type dopant in the active layer, it is ensured that quantum wells other than the first quantum well or the second quantum well close to the second semiconductor layer structure do not contain the diffused P-type dopant, thereby controlling the P-type doping level of the active layer and enhancing the light decay resistance of the LED chip.

[0041] According to another embodiment of the present invention, there is also provided an ultraviolet light-emitting diode, characterized in that the ultraviolet light-emitting diode at least includes an epitaxial structure, and the epitaxial structure at least includes a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked in sequence. The active layer is a multi-quantum well structure, and the second semiconductor layer structure is a P-type doped layer. The P-type dopant therein diffuses from the second semiconductor layer structure into the active layer and forms a doping concentration curve; in the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure is defined as the first quantum well, and the concentration of the P-type dopant in the first quantum well is not greater than 1×10 18 atom / cm 3 。

[0042] Through the above-mentioned control of the concentration of the P-type dopant, the concentration of the P-type dopant when entering the active layer is made low enough, such as Mg atoms, effectively reducing the diffusion of Mg atoms into the quantum well, reducing the influence of Mg atoms on the quantum well, and at the same time better controlling the overall level of P-type doping in the active layer, reducing the overall diffusion concentration of the P-type dopant in the quantum well, so that the light-emitting element has excellent light decay resistance.

[0043] In some embodiments, at the interface between the second semiconductor layer structure and the active layer, the doping concentration curve of the P-type dopant forms a sharp drop region in the direction from the second semiconductor layer structure to the first semiconductor layer structure, and the range of the downward slope of the P-type dopant concentration in the sharp drop region is between 0.5×10 18 ~4×10 18 (atom / cm 3 ) / 0.01μm.

[0044] By controlling the range of the downward slope of the P-type dopant concentration in the sharp drop region near the interface between the second semiconductor layer structure and the active layer, the diffusion concentration of the P-type dopant entering the active layer is accelerated to decrease, so that the concentration of the P-type dopant when entering the active layer can be made low enough, thereby effectively reducing the diffusion of Mg atoms into the quantum well, and thus improving the aging performance of the light-emitting diode.

[0045] In some embodiments, the distance d from the starting point of the drop in the sharp drop region to the upper surface of the first quantum well is not less than 0.05μm.

[0046] In some embodiments, the concentration range of the P-type dopant at the starting point of the drop in the sharp drop region is between 2×10 18atom / cm 3 ~2×10 19 atom / cm 3 。

[0047] By simultaneously restricting the concentration range of the P-type dopant at the starting point of the steep drop region and making the distance from the starting point of the steep drop to the upper surface of the first quantum well as large as possible, the concentration of the P-type dopant when entering the active layer is made low enough, thereby effectively improving the anti-light decay ability of the LED chip.

[0048] In some embodiments, the concentration drop angle of the P-type dopant in the steep drop region is β, and β is not less than 45°.

[0049] By controlling the concentration drop angle β of the P-type dopant in the steep drop region to be as large as possible, at least not less than 45°, the slope of the second drop region is made as large as possible, so that the concentration of the P-type dopant when entering the active layer is low enough, thereby improving the aging performance of the light-emitting diode.

[0050] In some embodiments, an electron blocking layer is further formed between the active layer and the second semiconductor layer structure, and at least a part of the steep drop region is formed in the electron blocking layer.

[0051] Controlling the steep drop region to be formed in the electron blocking layer is beneficial to controlling the concentration of the P-type dopant in the electron blocking layer, and further controlling the concentration of the P-type dopant when approaching the active layer, so that the concentration of the P-type dopant in the active layer is low enough, and the P-type doping level of the active layer can be better controlled.

[0052] In some embodiments, the number of quantum well structures is between 3 and 20, and the number of overlaps between the steep drop region and the quantum well structures does not exceed two.

[0053] By controlling the diffusion depth of the P-type dopant in the active layer, the other quantum wells except the first quantum well or the second quantum well close to the second semiconductor layer structure do not contain the diffused P-type dopant, thereby controlling the P-type doping level of the active layer.

[0054] In some embodiments, the active layer includes In x1 Al y1 Ga 1-x1-y1 N barrier layer and In x2 Al y2 Ga 1-x2-y2 N well layer, where 0 ≤ x1 ≤ 1, 0 ≤ x2 ≤ 1, 0 ≤ y1 ≤ 1, 0 ≤ y2 ≤ 1, 0 ≤ x1 + y1 ≤ 1, 0 ≤ x2 + y2 ≤ 1, In x1 Al y1 Ga 1-x1-y1 N barrier layer and In x2 Al y2 Ga1-x2-y2 The N potential well layers are arranged alternately.

[0055] In some embodiments, the P-type dopant is a magnesium atom.

[0056] In some embodiments, the emission wavelength of the active layer structure is between 340 nm and 425 nm.

[0057] In the ultraviolet light-emitting diode that emits radiation in the above wavelength range, by defining the falling region, the falling turning point, and the diffusion concentration of Mg atoms, the diffusion of Mg atoms into the quantum well can be effectively reduced, and the influence of Mg atoms on the quantum well can be reduced, so that the light-emitting element has excellent anti-light decay ability.

[0058] According to another embodiment of the present invention, there is provided an ultraviolet light-emitting device, which includes a circuit board and a light-emitting element disposed on the circuit board, and uses the ultraviolet light-emitting diode provided in any of the above embodiments. Embodiment 1

[0059] This embodiment provides a semiconductor light-emitting element (also called an LED, a light-emitting diode), as Figure 1 shown, the light-emitting element 100 at least includes an epitaxial structure 120, and the epitaxial structure 120 at least includes a first semiconductor layer structure 121, an active layer 122, and a second semiconductor layer structure 124 stacked in sequence. The epitaxial structure 120 can be any epitaxial structure that can emit light under the action of voltage. For example, it can be an AlGaInN-based epitaxial structure, an AlGaN-based epitaxial structure, or an AlGaInP-based epitaxial structure, etc. In this embodiment, the above epitaxial structure 120 is taken as an AlGaInN-based epitaxial structure capable of providing ultraviolet light for illustration. Optionally, the light-emitting element 100 can be a front-mounted, flip-chip, or vertical structure light-emitting element. This embodiment takes the vertical structure light-emitting element as an example for illustration. Further, the light-emitting diode can include a growth substrate 110 or a support substrate.

[0060] The above first semiconductor layer structure 121 can be an N-type layer. Correspondingly, the second semiconductor layer structure 124 is a P-type layer, and vice versa is also feasible. In this embodiment, the first semiconductor layer structure 121 is taken as an N-type layer, and correspondingly, the second semiconductor layer structure 124 is a P-type layer as an example.

[0061] In this embodiment, the above first semiconductor layer structure 121 is an N-type AlGaN layer, which can provide electrons to the active layer 122 under the action of a power supply. The material of the first semiconductor layer structure 121 can be selected from those having the chemical formula In a1 Al b1 Ga 1-a1-b1A semiconductor material of 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 121 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 extraction efficiency of the light emitted from the active layer 122, the surface of the first semiconductor layer structure 121 is roughened, that is, the surface of the first semiconductor layer structure 121 has a roughened structure.

[0062] Optionally, in some embodiments, the light-emitting diode may further include a superlattice layer (not shown in the figure) located between the first semiconductor layer structure 121 and the active layer 122, which has the function of adjusting stress and current spreading. The superlattice layer contains a periodic structure, and each periodic structure generally includes at least two thin layer structures of different materials, and its material is 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 includes a first sublayer, a second sublayer, and a third sublayer, for example, InGaN / AlGaN / AlN, GaN / AlGaN / AlN, or InGaN / GaN / AlN may be used. The periodic structure with a high energy gap can adjust the radiative recombination region, thereby improving the recombination efficiency of the light-emitting layer and further enhancing the brightness, and can prevent leakage formed by high-temperature hot holes or electrons obtaining additional energy, and improve the brightness stability of the hot-state operation, and its hot / cold factor (H / C) value can reach more than 70%.

[0063] The active layer 122 can be a quantum well structure (Quantum Well, abbreviated as QW). In some embodiments, the active layer 122 can also be a multiple quantum well structure (Multiple Quantum Well, abbreviated as MQW). In the light-emitting diode of this embodiment, the active layer 122 has the chemical formula In x Al y Ga 1-x-y N (0≤x≤1, 0≤y≤1, 0≤x + y≤1). The active layer 122 may include a plurality of In x1 Al y1 Ga 1-x1-y1 N barrier layers 122A and a plurality of In x2 Al y2 Ga 1-x2-y2 N well layers 122B arranged between the barrier layers 122A, where 0≤x1≤1, 0≤x2≤1, 0≤y1≤1, 0≤y2≤1, 0≤x1 + y1≤1, 0≤x2 + y2≤1. According to the embodiment, Inx1 Al y1 Ga 1-x1-y1 The N barrier layer 122A and In x2 Al y2 Ga 1-x2-y2 The N well layer 122B can be arranged alternately, as Figure 2 shown. The number of well layers 122B and barrier layers 122A can be 3 to 20 layers, and the number of well layers 122B and barrier layers 122A can be the same or different. The barrier layer 122A has a larger bandgap than the well layer 122B. The alternating arrangement of the barrier layer 122A and the well layer 122B in the active layer 122 enables the recombination of electrons and holes in the active layer 122. In x1 Al y1 Ga 1-x1-y1 The N barrier layer 122A and In x2 Al y2 Ga 1-x2-y2 The alternating arrangement of the N well layer 122B can ensure that the light emitted after the recombination of electrons and holes is ultraviolet light with a wavelength of about 340 nm to 425 nm. For example, the active layer 122 can be a multi-quantum well structure of GaN / AlGaN, InAlGaN / InAlGaN, or InGaN / AlGaN. In addition, the composition and thickness of the well layer in the active layer 122 determine the wavelength of the generated light. To improve the light emission efficiency of the active layer 122, it can be achieved by changing the depth of the quantum well, the number of pairs of quantum wells and quantum barriers, the thickness, and / or other characteristics in the active layer 122. In one embodiment, in the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure 124 is defined as the first quantum well 1221, and the concentration of P-type dopants in the first quantum well 1221 is not greater than 1×10 18 atom / cm 3 , by restricting the concentration of P-type dopants in the first quantum well structure 1221 closest to the second semiconductor layer structure 124 to not greater than 5×10 17 atom / cm 3 , and thus reducing the overall diffusion concentration of P-type dopants, such as Mg atoms, in the quantum well, the P-type doping level of the active layer can be better controlled, so that the light-emitting element has excellent anti-light decay ability.

[0064] The second semiconductor layer structure 124 can be a P-type semiconductor layer, which can provide holes to the active layer 122 under the action of a power supply. The material of the second semiconductor layer structure 124 can be selected from those with the chemical formula In a2 Al b2 Ga 1-a2-b2formed of a semiconductor material N (0≤a2≤1, 0≤b2≤1, 0≤a2 + b2≤1), for example, selected from GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, etc. In a UV light-emitting device, the second semiconductor layer structure may include AlGaN. In some embodiments, the second semiconductor layer structure 124 includes a P-type doped nitride layer that provides holes by doping with P-type impurities, and the P-type impurities may be one or a combination of Mg, Zn,, Be, Ca, Sr, and Ba. In this embodiment, the P-type impurity is preferably Mg. In an alternative embodiment, as Figure 3 shown, the doping concentration of Mg in the second semiconductor layer structure 124 is greater than or equal to 1×10 18 atom / cm 3 and less than or equal to 1×10 21 atom / cm 3 , in one embodiment, the doping concentration of Mg in the second semiconductor layer structure 124 is greater than or equal to 1×10 19 atom / cm 3 and less than or equal to 1×10 20 Atoms / cm 3 . The second semiconductor layer structure 124 may be a single-layer structure or a multi-layer structure, and the multi-layer structure has different compositions. Further, a contact layer (not shown in the figure) may be formed on the second semiconductor layer structure 124, and the p-type contact layer may be a highly doped p-type GaN layer or a p-type AlGaN layer. For example, a p-type AlGaN layer with a p-type doping concentration greater than 1×10 20 atom / cm 3 is used, which is beneficial for forming a good ohmic contact with the electrode.

[0065] Such as Figure 3As shown, in this embodiment, Mg atoms in the second semiconductor layer structure 124 diffuse toward the active layer 122 from the second semiconductor layer structure 124, and a doping concentration curve is formed. The doping concentration curve of the P-type dopant forms at least two descending regions with different slopes in the direction from the second semiconductor layer structure to the first semiconductor layer structure. In some embodiments, the descending regions include a first descending region L1 and a second descending region L2. In the stacking direction of the epitaxial structure, the second descending region L2 is closer to the active layer 122 than the first descending region L1. Among them, the descending slope k1 of the P-type dopant concentration in the first descending region L1 is less than the descending slope k2 of the P-type dopant concentration in the second descending region L2. That is, the descending trend of the P-type dopant concentration in the second descending region is steeper than that in the first descending region. By forming at least two descending regions with different slopes in the concentration of the P-type dopant, and further controlling that the descending slope of the second descending region L2 close to the active layer 122 in the stacking direction of the epitaxial structure is greater than the descending slope of the first descending region L1 far from the active layer 122 in the stacking direction of the epitaxial structure, the diffusion concentration of the P-type dopant entering the active layer can be accelerated, so that the concentration of the P-type dopant when entering the active layer can be low enough. For example, it is Mg atoms, which can effectively reduce the diffusion of Mg atoms into the quantum well and reduce the influence of Mg atoms on the quantum well, thereby effectively improving the anti-light decay ability of the LED chip.

[0066] Furthermore, in some embodiments, the range of the descending slope k1 of the P-type dopant concentration in the first descending region L1 is not greater than 1, and the range of the descending slope k2 of the P-type dopant concentration in the second descending region L2 is not less than 1. Preferably, the range of the descending slope k1 of the P-type dopant concentration in the first descending region L1 is not greater than 0.6, and the range of the descending slope k2 of the P-type dopant concentration in the second descending region L2 is not less than 1.7. For example, in some preferred embodiments, the range of the descending slope k1 of the P-type dopant concentration in the first descending region L1 is between 0.3 and 0.6, and the range of the descending slope k2 of the P-type dopant concentration in the second descending region L2 is between 1.7 and 6. It should be noted that the descending slope k2 refers to the slope of the line segment connecting the starting point and the ending point between the first descending region L1 and the second descending region L2. The starting point of the first descending region L1 generally refers to the highest doping concentration point of the P-type dopant in the first descending region L1 in the second semiconductor layer structure. The ending point of the first descending region L1 is the connection point between the first descending region L1 and the second descending region L2, that is, the slope turning point M. The starting point of the second descending region L2 is the connection point between the first descending region L1 and the second descending region L2, that is, the slope turning point M. The ending point of the second descending region L2 can be the point where the doping concentration of the P-type dopant in the second descending region L2 in the active layer or the electron blocking layer is lower than 5×10 16 atom / cm 3and the first point in the direction from the second semiconductor layer structure to the first semiconductor layer structure. Further, in some embodiments, the range of the decreasing slope of the P-type dopant concentration in the first decreasing region L1 is between 1×10 18 ~8×10 18 (atom / cm 3 ) / 0.01μm, and the range of the decreasing slope of the P-type dopant concentration in the second decreasing region L2 is between 0.5×10 18 ~4×10 18 (atom / cm 3 ). That is, the change amount of the P-type dopant concentration within every 0.01 μm distance in the first decreasing region L1 is between 1×10 18 atom / cm 3 ~8×10 18 atom / cm 3 , and the change amount of the P-type dopant concentration within every 0.01 μm distance in the second decreasing region L2 is between 0.5×10 18 atom / cm 3 ~4×10 18 atom / cm 3 . It should be noted that the change amount of the P-type dopant concentration within every 0.01 μm distance includes linear doping decrease change or curve-type doping decrease change. By respectively controlling the range of the decreasing slopes of the P-type dopant concentrations in the first and second decreasing regions L2, especially the decreasing slope of the P-type dopant concentration in the second decreasing region L2 closer to the active layer 122 in the stacking direction of the epitaxial structure is large enough, so as to accelerate the reduction of the diffusion concentration of the P-type dopant entering the active layer, it can make the concentration of the P-type dopant low enough when entering the active layer, effectively reduce the diffusion of Mg atoms into the quantum well, and thus improve the aging performance of the light-emitting diode.

[0067] In an alternative embodiment, the concentration range of the P-type dopant in the first decreasing region L1 is between 2×10 18 atom / cm 3 ~2×10 20 atom / cm 3 , and the concentration range of the P-type dopant in the second decreasing region L2 is between 5×10 16 16 atom / cm 3 ~2×10 19 atom / cm 3 . Preferably, the concentration of the P-type dopant in the second decreasing region L2 is not greater than 1×10 19 19 atom / cm 3By separately controlling the concentration ranges of P-type dopants in the first and second descending regions, especially the concentration of P-type dopants in the second descending region L2 closer to the active layer 122 in the stacking direction of the epitaxial structure is low enough, so that the concentration of P-type dopants when entering the active layer is low enough, thereby reducing the overall diffusion concentration of P-type dopants in the quantum well, and better controlling the P-type doping level of the active layer, enabling the light-emitting element to have excellent anti-light-decay ability.

[0068] As Figure 3 shown, in this embodiment, the first descending region L1 is connected to the second descending region L2, and the connection between the first descending region L1 and the second descending region L2 is a slope turning point M. As Figure 4 shown in the enlarged view, in some embodiments, the distance S from the slope turning point M to the upper surface of the first quantum well 1221 is not less than 0.05 μm. Preferably, the distance S from the slope turning point M to the upper surface of the first quantum well 1221 is greater than 0.03 μm. The larger the distance S from the turning point M to the upper surface of the first quantum well 1221, when the descending slope k2 of the concentration of P-type dopants in the second descending region L2 is fixed, the lower the concentration of P-type dopants when entering the active layer will be, effectively improving the anti-light-decay ability of the LED chip. Further, in some embodiments, the concentration range of P-type dopants in the slope turning point M is between 2×10 18 atom / cm 3 ~2×10 19 atom / cm 3 . Preferably, the concentration of P-type dopants in the slope turning point M is not greater than 1×10 19 atom / cm 3 . By simultaneously restricting the concentration range of P-type dopants in the turning point M and making the distance S from the turning point M to the upper surface of the first quantum well 1221 as large as possible, the concentration of P-type dopants when entering the active layer is low enough, effectively reducing the diffusion of Mg atoms into the quantum well.

[0069] As Figure 4As shown in the enlarged view, in this embodiment, the concentration of the P-type dopant in the second descending region L2 has a descending angle of α, where α is not less than 45°, preferably, α is greater than 55°, and more preferably, the descending angle α of the concentration of the P-type dopant in the second descending region L2 is between 60° and 80°, for example, α is 60°, 70° or 80°, etc. The so-called descending angle refers to the angle between the descending curve and the horizontal plane in the vertical plane. By controlling the descending angle α of the concentration of the P-type dopant in the second descending region L2 to be as large as possible, at least not less than 45°, the slope of the second descending region L2 can be made as large as possible, which can accelerate the reduction of the diffusion concentration of the P-type dopant entering the active layer, and further make the concentration of the P-type dopant low enough when entering the active layer, thereby effectively reducing the diffusion of Mg atoms into the quantum well.

[0070] In an alternative embodiment, as shown in the figure, in the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure 124 is defined as the first quantum well 1221, and the concentration of the P-type dopant in the first quantum well 1221 is not greater than 1×10 18 atom / cm 3 , and further, it is lower than 5×10 17 atom / cm 3 . By restricting the concentration of the P-type dopant in the first quantum well structure 1221 closest to the second semiconductor layer structure 124, and then reducing the overall diffusion concentration of the P-type dopant in the quantum well, the P-type doping level of the active layer can be better controlled, so that the light-emitting element has excellent anti-light decay ability. In some embodiments, the number of overlaps between the second descending region L2 and the quantum well structure does not exceed two, that is, the depth of diffusion of Mg atoms into the active layer 122 does not exceed two quantum wells. In another alternative embodiment, the active layer 122 includes n quantum wells, where n is between 3 and 20. Starting from the second quantum well away from the second semiconductor layer structure 124, the concentration of Mg atoms is lower than 1×10 17 atom / cm 3 . In another alternative embodiment, in the active layer 122, the number of pairs of the potential well layer 122B and the potential barrier layer 122A is between 3 and 20, and the concentration of the P-type dopant is greater than 1×10 17 atom / cm 3 , and the number of material layers with a concentration of the P-type dopant greater than 1×10 17 atom / cm 3 is less than or equal to 2. Further, the number of material layers with a concentration of the P-type dopant greater than 1×10 Figure 3It shows that there is a Mg atom signal in the active layer 122, and this Mg atom signal is usually an unintentionally doped Mg atomic impurity signal, that is, the noise signal in the test. By restricting the number of overlaps between the descending region and the quantum well, and then controlling the diffusion depth of the P-type dopant in the active layer, so that the other quantum wells except the first quantum well or the second quantum well close to the second semiconductor layer structure do not contain the diffused P-type dopant, thereby controlling the P-type doping level of the active layer and improving the anti-light decay ability of the LED chip.

[0071] Optionally, in some embodiments, as Figure 1 shown, the light-emitting diode further includes an electron barrier layer (EBL) 123 located between the active layer 122 and the second semiconductor layer structure 124. Under the action of this electron barrier layer 123, the Mg atoms in the epitaxial structure 120 only diffuse in the P-type semiconductor layer, will not diffuse to the electron barrier layer 123, and will not diffuse to the active layer 122 through the electron barrier layer 123. Therefore, it is beneficial to improve the electron-hole recombination efficiency of the active layer 122 and improve the internal quantum efficiency. When a large current is applied, the electron barrier layer 123 can prevent the electrons injected from the first semiconductor layer structure 121 into the active layer 122 from recombining again in the active layer 122 and flowing to the second semiconductor layer structure 124, so that the probability of recombination between the electrons and holes in the active layer 122 increases, and thus current leakage is prevented. The electron barrier layer 123 can be selected from semiconductor materials with the chemical formula In z Al w Ga 1-z-w N(0≤z≤1, 0≤w≤1, 0≤z + w≤1), and has a larger lattice constant than the second semiconductor layer structure 124. In the UV light-emitting diode, the electron barrier layer 123 includes AlGaN. The electron barrier layer 123 can have a larger bandgap energy than the active layer 122. In an alternative embodiment, the electron barrier layer 123 contains a higher Al content, which is beneficial to blocking the diffusion of Mg atoms in the P-type semiconductor layer into the active layer 122 and is beneficial to improving the recombination efficiency of electrons and holes in the active layer 122. In an alternative embodiment, the thickness of the electron barrier layer 123 ranges from 5 nm to 200 nm. In a further embodiment, the thickness of the electron barrier layer 123 ranges from 5 nm to 100 nm. This thickness can ensure sufficient blocking effect on the diffusion of Mg atoms. In one embodiment, the p-doping concentration of the electron barrier layer 123 is greater than or equal to 1×10 18 atom / cm 3 and less than or equal to 1×10 20 Atoms / cm 3 , more preferably, less than or equal to 5×10 19 Atoms / cm 3and greater than or equal to 5×10 18 Atoms / cm 3 By controlling the p-type doping concentration of the electron blocking layer 123, the concentration of the p-type dopant when entering the active layer can be made low enough, so that the overall diffusion concentration of the p-type dopant in the quantum well is low enough. The electron blocking layer 123 can be a single-layer or multi-layer structure.

[0072] In some embodiments, the first descending region L1, the turning point M, and the second descending region L2 are formed in the electron blocking layer 123. Controlling the formation of the descending region in the electron blocking layer 123 is beneficial to controlling the concentration of the p-type dopant in the electron blocking layer 123, and further controlling the concentration of the p-type dopant when approaching the active layer, so that the concentration of the p-type dopant in the active layer is low enough, and the p-type doping level of the active layer can be better controlled, making the light-emitting element have excellent anti-light-decay ability. In another alternative embodiment, at least part of the first descending region L1 is also formed in the second semiconductor layer structure 124 and / or at least part of the second descending region L2 is also formed in the active layer 122. That is, the first descending region L1 can be formed only in the second semiconductor layer structure 124 or only in the electron blocking layer 123, or the first descending region L1 can also be partially formed in the second semiconductor layer structure 124 and partially in the electron blocking layer 123; the second descending region L2 can be formed only in the electron blocking layer 123 or only in the active layer 122, or the second descending region L2 can also be partially formed in the electron blocking layer 123 and partially in the active layer 122. In this embodiment, at least part of the second descending region L2 is formed in the active layer 122. Through this setting, the p-type doping level of the active layer can be better controlled, and the anti-light-decay ability of the LED chip can be further improved.

[0073] Figure 6 shows a schematic structural diagram of an ultraviolet light-emitting diode implemented according to the present invention. Refer to Figure 6 , and a vertical structure light-emitting diode is provided. From bottom to top, the light-emitting diode includes a conductive substrate 400, an epitaxial structure 120 disposed above the conductive substrate 400. In some embodiments, a bonding metal and / or an insulating dielectric film can be disposed between the conductive substrate 400 and the epitaxial structure 120 as a bonding layer 200.

[0074] The epitaxial structure 120 has sidewalls and opposite first and second surfaces. The first surface is the positive side, and the second surface is the back side. It includes a first semiconductor layer structure 121, an active layer 122, an electron blocking layer 123, and a second semiconductor layer structure 124 arranged in sequence between the first surface and the second surface. The structure of the active layer 122 can refer to Figure 2The structure shown. The second surface of the epitaxial structure 120 has one or a plurality of recesses G2, and the recesses G2 penetrate at least the second semiconductor layer structure 124, the active layer 122, and a part of the first semiconductor layer structure 121. Further, the light-emitting diode further includes a first electrical connection layer 210, a second electrical connection layer 220, and an insulating layer (not shown in the figure). The insulating layer covers the upper surface of the epitaxial structure 120, and optionally covers the sidewalls of the epitaxial structure 120 at the same time to protect the epitaxial structure 120 from damage by impurities such as water vapor and dust. The insulating layer covers the sidewalls of the electrode structure at the same time, or covers a part of the upper surface of the electrode structure at the same time to protect the electrode structure and expose the upper surface of the electrode structure to realize subsequent welding of the light-emitting element 100. Wherein the second electrical connection layer 220 is electrically connected to the second semiconductor layer structure 124. The second electrical connection layer 220 includes a transparent conductive layer 221 for contacting the second semiconductor layer structure 124, a metal reflective layer 222, and a metal connection layer 223. The first electrical connection layer 210 forms a protrusion in the recess G2 and is electrically connected to the first semiconductor layer structure 121 through the recess G2. The first electrical connection layer 210 and the second electrical connection layer 220 are electrically isolated by using a second insulating layer 310 and a third insulating layer 320. The first electrical connection layer 210 and / or the second electrical connection layer 220 includes metal. The conductive substrate 400 serves as the first electrode and is electrically connected to the first electrical connection layer 210. A second electrode 420 is provided on the upper surface of the second electrical connection layer 220. The first electrode and the second electrode 420 are used to connect to an external circuit. Further, a second insulating layer 310 may be provided between the second electrical connection layer 220 and the epitaxial structure 120, which is beneficial to improving the optoelectronic performance of the light-emitting element. It can be understood that in order to increase the light output of the light-emitting diode of this embodiment, the above insulating layer may also be a reflective insulating material layer, such as a DBR structure, etc. Embodiment 2

[0075] This embodiment provides an ultraviolet light-emitting diode. The difference between the ultraviolet light-emitting diode of this embodiment and the ultraviolet light-emitting diode of Embodiment 1 is as follows: As Figure 5 shown, in this embodiment, the P-type dopant diffuses from the second semiconductor layer structure 124 to the active layer 122 and forms a doping concentration curve; in the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure 124 is defined as the first quantum well 1221, and the concentration of the P-type dopant in the first quantum well 1221 is not greater than 1×10 18 atom / cm 3 . Further, it is lower than 5×10 17 atom / cm 3By controlling the concentration of the above-mentioned P-type dopant, the concentration of the P-type dopant when entering the active layer is made low enough, such as Mg atoms, effectively reducing the diffusion of Mg atoms into the quantum well, reducing the influence of Mg atoms on the quantum well, and at the same time better controlling the overall level of P-type doping in the active layer, reducing the overall diffusion concentration of the P-type dopant in the quantum well, so that the light-emitting element has excellent anti-light decay ability.

[0076] In this embodiment, the P-type dopant diffuses from the second semiconductor layer structure 124 to the active layer 122. Near the interface between the second semiconductor layer structure 124 and the active layer 122, the doping concentration curve of the P-type dopant forms a steep drop region L in the direction from the second semiconductor layer structure to the first semiconductor layer structure, and at least one steep drop region L is formed. Further, in some embodiments, the range of the descending slope of the P-type dopant concentration in the steep drop region is between 0.5×10 18 ~4×10 18 (atom / cm 3 ) / 0.01μm, that is, the change amount of the P-type dopant concentration within every 0.01μm distance in the steep drop region is between 0.5×10 18 atom / cm 3 ~4×10 18 atom / cm 3 . It should be noted that the change amount of the P-type dopant concentration within every 0.01μm distance includes linear doping decline change or curve-type doping decline change. In some embodiments, the range of the descending slope k of the P-type dopant concentration in the steep drop region L is not less than 1. Preferably, the range of the descending slope k of the P-type dopant concentration in the steep drop region L is not less than 1.7. For example, the range of the descending slope k of the P-type dopant concentration in the steep drop region L is between 1.7 and 6. It should be noted that the descending slope k refers to the slope of the line segment connecting the starting point and the ending point of the steep drop region. The starting point of the steep drop region L generally refers to the highest doping concentration point of the P-type dopant in the steep drop region L in the direction from the second semiconductor layer structure to the first semiconductor layer structure. The ending point of the steep drop region L can be that the doping concentration of the P-type dopant in the active layer or the electron blocking layer is lower than 5×10 16 atom / cm 3and the first point in the direction from the second semiconductor layer structure to the first semiconductor layer structure. By controlling the decreasing slope of the concentration of the P-type dopant in the abrupt drop region L near the interface between the second semiconductor layer structure 124 and the active layer 122, the diffusion concentration of the P-type dopant entering the active layer can be accelerated to decrease, so that the concentration of the P-type dopant when entering the active layer can be low enough, thereby effectively reducing the diffusion of Mg atoms into the quantum well, and thus improving the aging performance of the light-emitting diode. It can be understood that in some embodiments, the P-type dopant diffuses from the second semiconductor layer structure 124 to the active layer 122, and the doping concentration curve of the P-type dopant can also form two consecutive abrupt drop regions, and at least one abrupt drop region is formed near the interface between the second semiconductor layer structure 124 and the active layer 122. In other embodiments, it can also be that the P-type dopant diffuses from the second semiconductor layer structure 124 to the active layer 122, and the doping concentration curve of the P-type dopant can form a gentle drop region and an abrupt drop region, and the abrupt drop region is formed near the interface between the second semiconductor layer structure 124 and the active layer 122. In other embodiments, it can also be that the P-type dopant diffuses from the second semiconductor layer structure 124 to the active layer 122, and the doping concentration curve of the P-type dopant forms a first abrupt drop region, a buffer region and a second abrupt drop region, and the second abrupt drop region is formed near the interface between the second semiconductor layer structure 124 and the active layer 122; in some alternative embodiments, the concentration of the P-type dopant in the buffer region can show an upward trend. In other embodiments, it can also be that the P-type dopant diffuses from the second semiconductor layer structure 124 to the active layer 122, and the doping concentration curve of the P-type dopant forms n descending regions, and at least one abrupt drop region is formed near the interface between the second semiconductor layer structure 124 and the active layer 122. However, the embodiments of the present invention are not limited thereto.

[0077] In an alternative embodiment, the concentration range of the P-type dopant in the abrupt drop region L is between 5×10 16 atom / cm 3 ~2×10 19 atom / cm 3 . Preferably, the concentration of the P-type dopant in the abrupt drop region L is not greater than 1×10 19 atom / cm 3 . By controlling the concentration of the P-type dopant in the abrupt drop region L to be low enough, the concentration of the P-type dopant when entering the active layer can be low enough, thereby reducing the overall diffusion concentration of the P-type dopant in the quantum well, and better controlling the P-type doping level of the active layer, so that the light-emitting element has excellent anti-light decay ability.

[0078] In this embodiment, the steep drop region L has a drop starting point P, which is the peak concentration of the steep drop region. The distance d from the drop starting point P to the upper surface of the first quantum well 1221 is not less than 0.05 μm. Preferably, the distance d from the drop starting point P to the upper surface of the first quantum well 1221 is greater than 0.03 μm. Further, in some embodiments, the concentration range of the P-type dopant in the drop starting point P of the steep drop region L is between 2×10 18 atom / cm 3 ~2×10 19 atom / cm 3 。Preferably, the concentration of the P-type dopant in the drop starting point P is not greater than 1×10 19 atom / cm 3 。Through the above limitations, the concentration of the P-type dopant when entering the active layer is made low enough, thereby effectively reducing the diffusion of Mg atoms into the quantum well. At the same time, when the concentration of the P-type dopant in the drop starting point P is fixed and the drop slope k of the P-type dopant concentration in the steep drop region L is fixed, the greater the distance d from the drop starting point P to the upper surface of the first quantum well 1221, the further the concentration of the P-type dopant will drop when entering the active layer, and the P-type doping level of the active layer can be better controlled.

[0079] In some embodiments, the angle of the drop in the concentration of the P-type dopant in the steep drop region L is β, and β is not less than 45°. Preferably, β is greater than 55°. More preferably, the angle of the drop in the concentration of the P-type dopant in the second drop region L2 is between 60° and 80°, such as β being 60°, 70°, or 80°, etc. The said drop angle refers to the angle between the steep drop curve and the horizontal plane in the vertical plane. By controlling the angle of the drop in the concentration of the P-type dopant in the steep drop region L to be as large as possible, the slope of the steep drop region L can be made as large as possible, which can accelerate the reduction of the diffusion concentration of the P-type dopant entering the active layer, and further make the concentration of the P-type dopant low enough when entering the active layer, thereby improving the aging performance of the light-emitting diode.

[0080] In some embodiments, an electron blocking layer 123 is further formed between the active layer 122 and the second semiconductor layer structure 124, and at least part of the steep drop region is formed in the electron blocking layer 123. By controlling the steep drop region L to be formed in the electron blocking layer 123, it is beneficial to control the concentration of the P-type dopant in the electron blocking layer 123, and further control the concentration of the P-type dopant when approaching the active layer, so that the concentration of the P-type dopant in the active layer is low enough. In another alternative embodiment, at least part of the drop region L is also formed in the active layer 122. Through this setting, the P-type doping level of the active layer can be better controlled, the concentration of the P-type dopant in the active layer can be further reduced, and the anti-light decay ability of the LED chip can be improved.

[0081] In some embodiments, the active layer 122 includes n quantum wells, where n ranges from 3 to 20, the number of pairs of well layers 122B and barrier layers 122A ranges from 3 to 20, and the number of overlaps between the step-down region L and the quantum well structure is no more than two, that is, the depth of Mg atom diffusion into the active layer 122 is no more than two quantum wells. Further, in an alternative embodiment, starting from the second quantum well away from the second semiconductor layer structure 124, the concentration of Mg atoms is lower than 1×10 17 atom / cm 3 . In another alternative embodiment, the number of material layers with a P-type dopant concentration greater than 1×10 17 atom / cm 3 is less than or equal to 2. Further, the number of material layers with a P-type dopant concentration greater than 1×10 17 atom / cm 3 is equal to 1. By restricting the number of overlaps between the descent region L and the quantum wells, the diffusion depth of the P-type dopant in the active layer is controlled, so that the other quantum wells except the first or second quantum well close to the second semiconductor layer structure do not contain the diffused P-type dopant, thereby controlling the P-type doping level of the active layer and improving the anti-light decay ability of the LED chip. Embodiment 3

[0082] This embodiment provides an ultraviolet light-emitting device, which includes a substrate and a light-emitting element disposed on the substrate, where the light-emitting element may be the ultraviolet light-emitting diode provided in the embodiments of the present application. The ultraviolet light-emitting device has excellent aging characteristics.

[0083] The above embodiments merely illustrate the principles and effects of the present invention and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An ultraviolet light-emitting diode, characterized in that The ultraviolet light-emitting diode at least includes an epitaxial structure, the epitaxial structure at least includes a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked in sequence, the active layer is a multiple quantum well structure, the second semiconductor layer structure is a P-type doped layer, and the P-type dopant therein diffuses from the second semiconductor layer structure to the active layer and forms a doping concentration curve, and the doping concentration curve of the P-type dopant forms at least two descending regions with different slopes in the direction from the second semiconductor layer structure to the first semiconductor layer structure.

2. The ultraviolet light-emitting diode according to claim 1, characterized in that The descending region includes a first descending region and a second descending region, and the descending slope k1 of the P-type dopant concentration in the first descending region is less than the descending slope k2 of the P-type dopant concentration in the second descending region.

3. The ultraviolet light-emitting diode according to claim 2, wherein The descending trend of the P-type dopant concentration in the second descending region is steeper than that in the first descending region.

4. The ultraviolet light-emitting diode according to claim 2, wherein In the stacking direction of the epitaxial structure, the second descending region is closer to the active layer than the first descending region.

5. The ultraviolet light emitting diode according to claim 2, characterized in that, The range of the descending slope of the P-type dopant concentration in the first descending region is not greater than 1.

6. The ultraviolet light-emitting diode according to claim 2, characterized in that, The descending slope of the P-type dopant concentration in the first descending region ranges from 1×10 18 to 8×10 18 (atoms / cm 3 ) / 0.01 μm.

7. The ultraviolet light-emitting diode according to claim 2, characterized in that, The range of the descending slope of the P-type dopant concentration in the second descending region is not less than 1.

8. The ultraviolet light-emitting diode according to claim 2, wherein The descending slope of the P-type dopant concentration in the second descending region ranges from 0.5×10 18 to 4×10 18 (atoms / cm 3 ) / 0.01 μm.

9. The ultraviolet light-emitting diode according to claim 2, characterized in that, The concentration range of the P-type dopant in the first descending region is between 2×10 18 atom / cm 3 ~2×10 20 atom / cm 3 .

10. The ultraviolet light-emitting diode according to claim 2, characterized in that, The concentration range of the P-type dopant in the second descending region is between 5×10 16 atom / cm 3 ~2×10 19 atom / cm 3 .

11. The ultraviolet light-emitting diode according to claim 2, wherein, The concentration descending angle α of the P-type dopant in the second descending region is not less than 45°.

12. The ultraviolet light-emitting diode according to claim 1, characterized in that, In the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure is defined as the first quantum well, and the concentration of the P-type dopant in the first quantum well is not greater than 1×10 18 atom / cm 3 .

13. The ultraviolet light-emitting diode according to claim 2, characterized in that, The first descending region is connected to the second descending region, and the connection point between the first descending region and the second descending region is a slope turning point M.

14. The ultraviolet light-emitting diode according to claim 13, wherein, The distance S from the slope turning point M to the upper surface of the first quantum well is not less than 0.05 μm.

15. The ultraviolet light-emitting diode according to claim 13, wherein The concentration range of the P-type dopant in the slope turning point M is between 2×10 18 atom / cm 3 ~2×10 19 atom / cm 3 。 16. The ultraviolet light-emitting diode according to claim 13, characterized in that, An electron blocking layer is further formed between the active layer and the second semiconductor layer structure, and the first descending region, the turning point M, and the second descending region are formed in the electron blocking layer.

17. The ultraviolet light-emitting diode according to claim 16, wherein, At least part of the first descending region is further formed in the second semiconductor layer structure and / or at least part of the second descending region is further formed in the active layer.

18. The ultraviolet light-emitting diode according to claim 2, characterized in that The number of the quantum well structures is between 3 and 20, and the number of overlaps between the second descending region and the quantum well structures does not exceed two.

19. An ultraviolet light-emitting diode, characterized in that, The ultraviolet light-emitting diode at least includes an epitaxial structure, the epitaxial structure at least includes a first semiconductor layer structure, an active layer, and a second semiconductor layer structure stacked in sequence, the active layer is a multiple quantum well structure, the second semiconductor layer structure is a P-type doped layer, and the P-type dopant therein diffuses from the second semiconductor layer structure to the active layer and forms a doping concentration curve; In the stacking direction of the epitaxial structure, the quantum well structure closest to the second semiconductor layer structure is defined as the first quantum well, and the concentration of the P-type dopant in the first quantum well is not greater than 1×10 18 atom / cm 3 .

20. The ultraviolet light-emitting diode according to claim 19, wherein, Near the interface between the second semiconductor layer structure and the active layer, the doping concentration curve of the P-type dopant forms a steep drop region in the direction from the second semiconductor layer structure to the first semiconductor layer structure, and the range of the descending slope of the P-type dopant concentration in the steep drop region is between 0.5×10 18 ~4×10 18 (atom / cm 3 ) / 0.01 μm.

21. The ultraviolet light-emitting diode according to claim 20, characterized in that, The distance d from the descending starting point of the steep descending region to the upper surface of the first quantum well is not less than 0.05 μm.

22. The ultraviolet light-emitting diode according to claim 20, wherein The concentration range of the P-type dopant at the start point of the drop in the drop region is between 2×10 18 atom / cm 3 ~2×10 19 atom / cm 3 .

23. The ultraviolet light-emitting diode according to claim 20, wherein, The concentration descending angle β of the P-type dopant in the steep descending region is not less than 45°.

24. The ultraviolet light-emitting diode according to claim 20, wherein, An electron blocking layer is further formed between the active layer and the second semiconductor layer structure, and at least part of the steep descending region is formed in the electron blocking layer.

25. The ultraviolet light-emitting diode according to claim 20, wherein The number of the quantum well structures is between 3 and 20, and the number of overlaps between the steep descending region and the quantum well structures does not exceed two.

26. The ultraviolet light-emitting diode according to claim 1 or 19, characterized in that, The active layer includes In x1 Al y1 Ga 1-x1-y1 N barrier layers and In x2 Al y2 Ga 1-x2-y2 N well layers, where 0 ≤ x1 ≤ 1, 0 ≤ x2 ≤ 1, 0 ≤ y1 ≤ 1, 0 ≤ y2 ≤ 1, 0 ≤ x1 + y1 ≤ 1, 0 ≤ x2 + y2 ≤ 1, and the In x1 Al y1 Ga 1-x1-y1 N barrier layers and the In x2 Al y2 Ga 1-x2-y2 N well layers are arranged alternately.

27. The ultraviolet light-emitting diode according to any one of claims 1 to 26, wherein The P-type dopant is a magnesium atom.

28. The ultraviolet light-emitting diode according to claim 27, wherein The emission wavelength of the active layer is between 340 nm and 425 nm.

29. An ultraviolet light emitting device, characterized in that, It includes a circuit board and a light-emitting element disposed on the circuit board, and the light-emitting element includes the ultraviolet light-emitting diodes described in claims 1 to 28.

Images