Light-emitting diode and display device

Abstract

A light-emitting diode, at least sequentially comprising an N-type layer (100), a transition layer (200), an active layer (300), and a P-type layer (500), wherein the active layer (300) comprises M periodic well layers (320) and barrier layers (310, 311) which are stacked alternately. The barrier layer (311) on the side of the active layer (300) close to the P-type layer (500) is designed, so as to improve the quantum efficiency in the light-emitting diode.

Description

Light emitting diode and display device thereof Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a light emitting diode and a display device thereof. Background Art

[0002] An LED (Light Emitting Diode) is a semiconductor electronic component that emits light. As a highly efficient, environmentally friendly, and green new solid-state lighting source, LEDs are rapidly gaining widespread application in applications such as traffic lights, automotive interior and exterior lighting, urban landscape lighting, and mobile phone backlights. Improving internal quantum efficiency (IQE) has become a key technical challenge facing the industry. Technical Solutions

[0003] In order to solve the problems of the background technology, in some embodiments of the present invention, a light-emitting diode is provided, which includes at least an N-type layer, a transition layer, an active layer and a P-type layer in sequence, wherein the active layer includes M periods of well layers and barrier layers alternately stacked, and the barrier layer on the side of the active layer close to the P-type layer is Al x1 In y1 Ga 0.5-x1-y1 N 0.5 , where 0≤x1≤1, 0<y1≤0.5, that is, it contains indium components.

[0004] In some embodiments of the present invention, the barrier layer on the side of the active layer close to the P-type layer is Al x1 In y1 Ga 0.5-x1-y1 N 0.5 , where x1 is 0 to 0.2, y1 is 0.005 to 0.02, and M is 2 to 5, or 6 to 15. Here, the coefficients of other components are calculated with N component as the 50% reference point, or with N component as the 100% reference point. In this case, other coefficients need to be adjusted accordingly.

[0005] In some embodiments of the present invention, the energy gap of the barrier layer on the side of the active layer close to the P-type layer is lower than the energy gap of the barrier layers on other active layers. Beneficial effects

[0006] The beneficial effects of the present invention include: further improving the internal quantum efficiency of the light emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0008] FIG1 is a schematic cross-sectional view of an epitaxial structure according to a first embodiment of the present invention;

[0009] FIG2 is an EDX test diagram of the first embodiment of the present invention;

[0010] FIG3 is a schematic top view of a first embodiment of the present invention;

[0011] FIG4 is a schematic cross-sectional view of a chip structure according to a first embodiment of the present invention;

[0012] FIG5 is a schematic diagram of an energy gap according to a second embodiment of the present invention;

[0013] FIG6 is a schematic cross-sectional view of an epitaxial structure according to a third embodiment of the present invention;

[0014] FIG7 is a schematic cross-sectional view of an epitaxial structure according to a fourth embodiment of the present invention;

[0015] FIG8 is a schematic diagram of a display according to a fifth embodiment of the present invention.

[0016] Symbols in the figure: 100, N-type layer; 200, transition layer; 210, first transition layer; 220, second transition layer; 230, third transition layer; 300, active layer; 221 / 231 / 310 / 311, barrier layer; 222 / 232 / 320, well layer; 400, electron blocking layer; 500, P-type layer; 610, first electrode; 620, second electrode; 700, passivation layer; 800, hole injection layer; 900, display unit; S, semiconductor layer sequence. Modes for Carrying Out the Invention

[0017] The following describes the implementation of the present application through specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present application from the disclosure herein. The present application may also be implemented or operated through various other specific implementations, and the details of the present application may be modified or altered based on different viewpoints and applications without departing from the spirit of the present application.

[0018] In the description of this application, it should be noted that the terms "upper," "lower," "inner," and "outer" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships of the product of this application when used in the embodiments. These terms are intended solely to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0019] In some embodiments of the present invention, a light-emitting diode is disclosed, which includes at least an N-type layer, a transition layer, an active layer, and a P-type layer in sequence, wherein the active layer includes M periods of well layers and barrier layers alternately stacked, and the barrier layer on the side of the active layer close to the P-type layer is Al x1 In y1 Ga 0.5-x1-y1 N 0.5 , where x1 is 0 to 0.2, y1 is 0.005 to 0.02, and M is 2 to 5, or 6 to 15. An electron blocking layer is provided between the active layer and the P-type layer. Indium is a material with a relatively low energy gap. Therefore, by using indium as a bridge layer in one or more barrier layers at the end of the active layer, the interface energy gap between the bridge layer and the electron blocking layer can be altered, thereby reducing the high potential barrier between the bridge layer and the electron blocking layer and thereby increasing hole injection. Analysis shows that an indium coefficient higher than 0.02 will, on the contrary, cause a decrease in internal quantum efficiency.

[0020] In some embodiments of the present invention, the N-type layer generates electrons and the P-type layer generates holes, and the electrons and holes move toward the active layer respectively. The transition layer includes a barrier layer of the transition layer and a well layer of the transition layer. The barrier layer of the transition layer includes aluminum gallium nitride or aluminum indium gallium nitride. The transition layer serves to reduce lattice defects. In some embodiments, it also serves to decelerate the electrons generated in the N-type layer.

[0021] In some embodiments of the present invention, the transition layer is composed of a first transition layer, a second transition layer and a third transition layer in sequence from the N-type layer to the P-type layer. The energy gap of the well layer of the transition layer gradually decreases. The second transition layer is a periodic stacking structure of the second barrier layer and the second well layer. The third transition layer is a periodic stacking structure of the third barrier layer and the third well layer, which improves the lattice quality of the active layer on the N side and the electron deceleration effect.

[0022] In some embodiments of the present invention, the second barrier layer is Al e1 In f1 Ga 0.5-e1-f1 N 0.5 , the second well layer Al e2 In f2 Ga 1-e2-f2 N0.5 , 0≤e2≤e1≤0.5, 0≤f1≤f2≤0.5, the number of periods of the second barrier layer and the second well layer is 2 to 10 pairs, and the thickness of the second transition layer in each period is 150 angstroms to 200 angstroms.

[0023] In some embodiments of the present invention, the third barrier layer is Al m1 In n1 Ga 0.5-m1-n1 N 0.5 , the third well layer is Al m2 In n2 Ga 0.5-m2-n2 N 0.5 layer, 0≤m2≤m1≤0.5, 0≤n1≤n2≤0.5, the sum of the number of periods of the third transition layer is 5 to 15 pairs, and the thickness of the third transition layer in each period is 100 angstroms to 150 angstroms.

[0024] In some embodiments of the present invention, the aluminum composition of the third barrier layer is higher than that of the second barrier layer, the aluminum composition of the third barrier layer is more than ten times that of the second barrier layer, and the aluminum composition of the second barrier layer is equal to or higher than that of the first transition layer. The aluminum composition is gradually increased to improve the lattice quality and perform electron deceleration.

[0025] In some embodiments of the present invention, the thickness of the transition layer is 2000 angstroms to 7000 angstroms, with the first transition layer having a thickness of 2000 angstroms ±50%, the second transition layer having a thickness of 2000 angstroms ±50%, and the third transition layer having a thickness of 2000 angstroms ±50%. The design of the second and third transition layers is combined to achieve electron deceleration and lattice matching.

[0026] In some embodiments of the present invention, a hole injection layer is further provided between the active layer and the P-type layer. The hole injection layer includes Al p1 In q1 Ga 0.5-p1-q1 N 0.5 , where p1 is 0 to 0.05, or 0.05 to 0.2. In the hole injection layer, the aluminum component on the side close to the P-type layer is lower than the aluminum component on the active layer side. The hole injection layer is connected to the barrier layer. The thickness of the hole injection layer is 200 angstroms to 2000 angstroms, which reduces the barrier to the injection of holes from the P-type layer side into the active layer.

[0027] In some embodiments of the present invention, the light-emitting diode is rectangular, the chip has at least one side dimension of 0 to 20 microns, or 20 to 50 microns, the area of ​​the light-emitting diode is no more than 5000 square microns, and the PN junction is micron-level.

[0028] In some embodiments of the present invention, the indium composition of the barrier layer on the side of the active layer close to the P-type layer is higher than the indium composition of other barrier layers of the active layer. The indium composition of the barrier layer on the side of the active layer close to the P-type layer is 1.2 times to 2 times, or 2 times to 10 times, or more than 10 times the indium composition of other barrier layers of the active layer, so as to reduce the high potential barrier between the connecting layer and the electron blocking layer, thereby increasing the injection of holes.

[0029] In some embodiments of the present invention, it is more preferred that y1 be set to 0.007 to 0.015 to optimize the hindrance and crystal growth quality.

[0030] In some embodiments of the present invention, the active layer has 6 to 15 periods, and the barrier layer on the side of the active layer close to the P-type layer is one layer, two layers, or three layers.

[0031] In some embodiments of the present invention, it is suitable for no more than 1 ampere / cm 2 At low current density, electrons cannot easily pass through the active layer, so an aluminum-free or low-aluminum component design can be used in the hole blocking layer.

[0032] In some embodiments of the present invention, the well layer of the active layer is Al x2 In y2 Ga 1-x2-y2 N, where 0≤x2≤x1, y1<y2, the wavelength is shorter than 600nm, where 0.15≤y2≤0.3.

[0033] In some embodiments of the present invention, the growth temperature of the first transition layer is lower than that of the N-type layer, and the carbon content of the first transition layer is higher than that of the N-type layer. This improves the quality of the crystal growth and increases the carbon content, which is beneficial for electron deceleration.

[0034] In some embodiments of the present invention, the In composition of the first transition layer is less than that of the second well layer and less than that of the third well layer, wherein the In composition of the first transition layer is one-tenth to one-fifth of that of the second well layer, or the In composition of the first transition layer is less than one-tenth of that of the second well layer. Providing a gradient in the In composition helps balance lattice quality and electron deceleration.

[0035] In some embodiments of the present invention, the active layer includes carbon, with a carbon content lower than 1E16 / cm 3 , reducing non-radiative recombination in the active layer.

[0036] In some embodiments of the present invention, the hole injection layer is a doped gallium nitride layer or an undoped gallium nitride layer. For example, the hole injection layer does not contain aluminum. Here, due to signal interference or process errors, the actual Sims / EDX measurement value may show that the aluminum component is within 1% of the overall component.

[0037] In some embodiments of the present invention, the first transition layer is a single layer or a periodic multilayer structure, and the first transition layer includes aluminum gallium nitride and / or gallium nitride.

[0038] In some embodiments of the present invention, the first transition layer is aluminum gallium nitride, and the aluminum content is no more than 1%. The aluminum content is used to decelerate electrons, but the aluminum content needs to be controlled to avoid excessive voltage.

[0039] In some embodiments of the present invention, the ratio of the indium content of the third well layer to the indium content of the first transition layer is K1, the ratio of the indium content of the third well layer to the second well layer is K2, K1:K2 is not less than 30, and a gradient change is set for the In component, which is beneficial to taking into account both lattice quality and electron deceleration.

[0040] In some embodiments of the present invention, the energy gap of the barrier layer on the side of the active layer close to the P-type layer is lower than the energy gap of the barrier layers of other active layers to reduce the high barrier between the connecting layer and the electron blocking layer, thereby increasing hole injection.

[0041] A display device proposed in the present invention includes a circuit substrate, a display unit electrically connected to the circuit substrate, and the light-emitting diode in the above solution.

[0042] The product structure is described and illustrated below with reference to various embodiments and accompanying drawings. The composition and dopant content of each layer in the semiconductor device of the present invention can be analyzed by any suitable method, such as secondary ion mass spectrometry (SIMS). The thickness of each layer in the light-emitting diode of the present invention can be analyzed by any suitable method, such as transmission electron microscopy (TEM) or scanning electron microscopy (SEM), to correlate the depth of each layer with the SIMS pattern.

[0043] The relative intensities of Group III elements such as Al / In / Ga can be obtained from SIMS composition profile analysis of general epitaxial structures or EDX elemental analysis in TEM. The intensity of the two elements Al / In can be used to determine the band gap. The higher the Al content, the higher the band gap, and the higher the In content, the lower the band gap.

[0044] In the present invention, unless otherwise specified, the term "peak shape" refers to a line profile consisting of two line segments with slopes of opposite signs, i.e., one segment has a positive slope and the other has a negative slope. "Peak concentration" refers to the highest concentration value between the two line segments of the peak shape with slopes of opposite signs.

[0045] 1 and 2 , in a first embodiment of the present invention, a light-emitting diode includes at least an N-type doped N-type layer 100, a transition layer 200, an active layer 300, an electron blocking layer 400, and a P-type doped P-type layer 500 in sequence, wherein the active layer 300 includes M periods of barrier layers 310 and well layers 320 alternately stacked. To better understand the design of this embodiment, the composition of each layer is detected by EDX (or Sims), wherein the composition ratios of Al, Ga, N, and In are indicated in the figure, with N being 50%, i.e., N=100%. 0.5 The barrier layer 310 on the side of the active layer 300 close to the P-type layer 500 is Al x1 In y1 Ga 0.5-x1-y1 N 0.5 , where x1 is 0 to 0.2, y1 is 0.005 to 0.02, and M is 2 to 5, or 6 to 15. The last barrier layer or layers 311 of the active layer 300 serve as a bridging layer, using indium to modify the interface energy gap between the bridging layer and the electron blocking layer 400. For example, the last one to three barrier layers 311 of the active layer 300 serve as bridging layers. In this embodiment, silicon is used for N-type doping, and magnesium is used for P-type doping. Sims analysis can also be used to test the composition of each layer.

[0046] The indium composition of the barrier layer 311 on the side of the active layer 300 close to the P-type layer 500 is 1.2 times to 2 times, or 2 times to 10 times, or more than 10 times the indium composition of the other barrier layers of the active layer, so as to reduce the high potential barrier between the connecting layer and the electron blocking layer 400, thereby increasing the injection of holes. The number of barrier layers 311 on the side of the active layer 300 close to the P-type layer 500 is, for example, 1 to 3 barrier layers 311 closest to the P-type layer 500.

[0047] In some embodiments, y1 is set to 0.007 to 0.015 to optimize steric barriers and crystal growth quality.

[0048] In some embodiments, except for the connecting layer, the other barrier layers are GaN or AlGaN, that is, the 3 to 9 barrier layers 310 of the active layer 300 close to the N-type layer 100 are GaN or AlGaN. Due to the problem of Sims detection accuracy, the indium component of the other barrier layers is less than 0.005.

[0049] In some embodiments, the indium composition of a barrier layer closest to the N-type layer 100 in the active layer 300 is less than the indium composition of a barrier layer 311 closest to the P-type layer 500 in the active layer 300. A transition layer 200 is disposed between the active layer 300 and the N-type layer 100. The transition layer 200 is a single layer of gallium nitride, or a periodic stack of gallium nitride and indium gallium nitride layers.

[0050] In some embodiments, the well layer 320 of the active layer 300 is Al x2 In y2 Ga 1-x2-y2 N, where 0≤x2≤x1, y1<y2, in some embodiments, for example, when the wavelength is shorter than 600 nm, where 0.15≤y2≤0.3, the energy gap of the well layer 320 in the active layer 300 is lower than that of the barrier layer 310.

[0051] In this embodiment, an electron blocking layer 400 is arranged between the active layer 300 and the P-type layer 500. The electron blocking layer 400 includes an aluminum gallium nitride layer, which increases the density of electrons in the active layer 300 and improves the hole-electron recombination efficiency. The aluminum content in the electron blocking layer 400 is higher than the aluminum content in the barrier layer 310 in the active layer 300.

[0052] Referring to Figures 3 and 4 , in this embodiment, the LED is rectangular, with at least one side of the chip ranging from 0 to 20 microns, or from 20 to 50 microns (i.e., the short side is 0 to 20 microns, or from 20 to 50 microns). The LED has an area of ​​no greater than 5,000 square microns and includes a micron-scale PN junction. The LED comprises a semiconductor layer sequence S, a first electrode 610, a second electrode 620, and a passivation layer 700. The semiconductor layer sequence includes an N-type layer 100, a transition layer 200, an active layer 300, an electron blocking layer 400, and a P-type layer 500. The first electrode 610 is electrically connected to the N-type layer 100 via a mesa 110, and the second electrode 620 is electrically connected to the P-type layer 500. The passivation layer 700 is disposed outside the semiconductor layer sequence to provide insulation protection.

[0053] In this embodiment, the indium composition of the barrier layer 311 on the side of the active layer 300 close to the P-type layer 500 is higher than the indium composition of the other barrier layers of the active layer 300. The indium composition of the barrier layer 311 on the side of the active layer 300 close to the P-type layer 500 is 1.2 times to 2 times, or 2 times to 10 times, or more than 10 times the indium composition of the other barrier layers of the active layer 300.

[0054] Referring to FIG5 , in a second embodiment of the present invention, the energy gap of the barrier layer 311 on the side of the active layer 300 close to the P-type layer 500 is lower than the energy gap of the barrier layers of the other active layers 300, thereby reducing the high barrier between the connecting layer and the electron blocking layer 400, thereby increasing the injection of holes. A light-emitting diode comprises at least an N-type layer 100, a transition layer 200, an active layer 300, and a P-type layer 500 in sequence, wherein the active layer 300 comprises M periods of barrier layers 310 and well layers 320 alternately stacked, and the barrier layer 311 on the side of the active layer 300 close to the P-type layer 500 is In x1 Al y1 Ga 0.5-x1-y1 N 0.5, where 0≤x1<0.5, 0≤y1<0.5, where M is 2 to 5, or 6 to 15, the setting of M is related to the composition and thickness, the other barrier layers of the active layer 300 are GaN or AlGaN, and the well layer 320 of the active layer 300 is InGaN.

[0055] The N-type layer 100 generates electrons and the P-type layer 500 generates holes, which move toward the active layer 300. By reducing the energy gap of the connecting layer and changing the interface energy gap, the internal quantum efficiency is improved.

[0056] The barrier layer on the side of the active layer 300 near the P-type layer 500 serves as a bridge layer. The bridge layer can have one to three layers. For example, when M is 2 to 6 pairs, or 7 to 10 pairs, the bridge layer is set to one. Excessive numbers of bridge layer pairs will reduce the P-side blocking effect of the active layer 300 and lead to electron overflow. When M is 11 to 15 layers, setting the bridge layer to two or three layers improves the internal quantum efficiency of the product.

[0057] In some embodiments, the transition layer 200 includes a barrier layer and a well layer of the transition layer. The barrier layer includes aluminum gallium nitride or aluminum indium gallium nitride. The transition layer 200 plays a role in reducing lattice defects.

[0058] 6, in the third embodiment of the present invention, a light emitting diode is provided. Based on the first embodiment, the light emitting diode is further designed, and the electron blocking layer 400 is replaced by a hole injection layer 800. The light emitting diode comprises: an N-type layer 100, a transition layer 200, an active layer 300, a hole injection layer 800 and a P-type layer 400. The hole injection layer 800 comprises Al p1 In q1 Ga 0.5-p1-q1 N 0.5 , where p1 is 0 to 0.05, or 0.05 to 0.2. In the hole injection layer 800, the aluminum component on the side close to the P-type layer 400 is lower than the aluminum component on the side of the active layer 300. The hole injection layer 800 is connected to the barrier layer 310. The thickness of the hole injection layer 800 is 200 angstroms to 2000 angstroms, which reduces the obstruction of holes from the P-type layer 500 side to be injected into the active layer 300. The hole injection layer 800 is a single layer or multiple layers, and the hole injection layer 800 can be composed of gallium nitride, a P-type doped gallium nitride layer, or a combination of the two.

[0059] In some embodiments, the hole injection layer 800 is a doped gallium nitride layer or an undoped gallium nitride layer. For example, the hole injection layer 800 does not contain aluminum during its manufacture, and the actual product Sims measurement value shows that the aluminum component is within 1% of the total component.

[0060] In some embodiments, the applied circuit uses no more than 1 ampere / cm2 The barrier layer 310 of the active layer 300 is AlGaN or GaN, wherein the Al component is not greater than 10%.

[0061] In some alternative embodiments, the application circuit uses more than 1 ampere / cm 2 The current density is high, the active layer 300 is a periodic stack of multiple pairs of AlGaN and InGaN, and the aluminum component of the barrier layer 310 in the active layer 300 is increased, that is, the aluminum component is greater than 0, for example, 1% to 5%, to avoid a decrease in the electron blocking effect due to the addition of In component in the active layer 300 close to the P-side barrier layer 311.

[0062] Referring to FIG. 7 , a fourth embodiment of the present invention provides a light-emitting diode. Based on the third embodiment, the transition layer 200 is further refined. The transition layer 200, extending from the N-type layer 100 to the P-type layer 500, comprises, in sequence, a first transition layer 210, a second transition layer 220, and a third transition layer 230. The energy gap of the well layer in the transition layer 210 gradually decreases. The second transition layer 220 comprises a periodic stack of a second barrier layer 221 and a second well layer 222, while the third transition layer 230 comprises a periodic stack of a third barrier layer 231 and a third well layer 232. This improves the lattice quality and electron deceleration effect of the active layer 300 on the N-side, thereby enhancing internal quantum efficiency.

[0063] The second barrier layer 221 is Al e1 In f1 Ga 0.5-e1-f1 N 0.5 , the second well layer 222 is Al e2 In f2 Ga 1-e2-f2 N 0.5 , 0≤e2≤e1≤0.5, 0≤f1≤f2≤0.5, the number of periods of the second barrier layer 221 and the second well layer 222 is 2 to 10 pairs, and the thickness of the second transition layer of each period is 150 angstroms to 200 angstroms.

[0064] The third barrier layer 231 is Al m1 In n1 Ga 0.5-m1-n1 N 0.5 , the third well layer 232 is Al m2 In n2 Ga 0.5-m2-n2 N 0.5 layer, 0≤m2≤m1≤0.5, 0≤n1≤n2≤0.5, the sum of the number of periods of the third transition layer 230 is 5 to 15 pairs, and the thickness of the third transition layer 230 in each period is 100 angstroms to 150 angstroms.

[0065] The aluminum composition of the third barrier layer 231 is higher than that of the second barrier layer 221. The aluminum composition of the third barrier layer 231 is more than ten times that of the second barrier layer 221, and the aluminum composition of the second barrier layer 221 is equal to or higher than that of the first transition layer 210. The aluminum composition is gradually increased to improve the lattice quality and perform electron deceleration.

[0066] The thickness of the transition layer 200 ranges from 2000 angstroms to 7000 angstroms, with the first transition layer 210 having a thickness of 2000 angstroms ±50%, the second transition layer having a thickness of 2000 angstroms ±50%, and the third transition layer having a thickness of 2000 angstroms ±50%. The design of the second transition layer 220 and the third transition layer 230 together achieves electron deceleration and lattice matching.

[0067] The growth temperature of the first transition layer 210 is lower than that of the N-type layer 100, and the carbon content of the first transition layer 210 is higher than that of the N-type layer 100. On the one hand, the quality of the crystal growth is improved, and on the other hand, the increased carbon content is conducive to achieving electron deceleration.

[0068] The In composition of the first transition layer 210, the second well layer 222, and the third well layer 232 gradually increases. Specifically, the In composition of the first transition layer 210 is less than that of the second well layer 222, which is less than that of the third well layer 232. The In composition of the first transition layer 210 is one-tenth to one-fifth of that of the second well layer 222, or less than one-tenth of that of the second well layer 222. A large gradient in the In composition is beneficial for balancing lattice quality and electron deceleration.

[0069] The active layer 300 includes carbon, with a carbon content lower than 1E16 / cm 3 , reducing non-radiative recombination of the active layer 300.

[0070] The ratio of the indium content of the third well layer 232 to the indium content of the first transition layer 210 is K1, and the ratio of the indium content of the third well layer 232 to the second well layer 222 is K2. K1:K2 is not less than 30. Setting a gradient change in the In component is beneficial to balancing lattice quality and electron deceleration.

[0071] In some embodiments, the first transition layer 210 is a single layer or a periodic multilayer structure, and the first transition layer 210 includes aluminum gallium nitride and / or gallium nitride.

[0072] In some embodiments, the first transition layer 210 is made of aluminum gallium nitride, and the aluminum content is no more than 1%. The aluminum content is used to decelerate electrons, but the aluminum content needs to be controlled to avoid excessive voltage.

[0073] In some embodiments, the well layer 320 of the active layer 300 is Al x2 In y2 Ga 1-x2-y2N, where 0≤x2≤x1, y1<y2, the wavelength is shorter than 600nm, where 0.15≤y2≤0.3.

[0074] 8 , in a fifth embodiment of the present invention, a display device is provided, including a circuit substrate and a display unit 900 electrically connected to the circuit substrate. The display unit 900 uses any one of the light emitting diodes in Embodiments 1 to 4.

[0075] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and replacements can be made without departing from the technical principles of the present application. These improvements and replacements should also be regarded as the scope of protection of the present application.

Claims

1. A light emitting diode, comprising at least an N-type layer, a transition layer, an active layer and a P-type layer in sequence, wherein the active layer comprises M periods of well layers and barrier layers alternately stacked, characterized in that: The barrier layer on the side of the active layer close to the P-type layer is Al x1 In y1 Ga 0.5-x1-y1 N 0.5 , wherein x1 is 0 to 0.2, y1 is 0.005 to 0.02, and M is 2 to 5, or 6 to 15.

2. A light emitting diode according to claim 1, characterized in that: The transition layer includes a barrier layer of the transition layer and a well layer of the transition layer, and the barrier layer of the transition layer includes aluminum gallium nitride or aluminum indium gallium nitride.

3. A light emitting diode according to claim 1, characterized in that: The transition layer includes a first transition layer, a second transition layer and a third transition layer in sequence from the N-type layer to the P-type layer. The energy gap of the well layer of the transition layer decreases gradually. The second transition layer is a periodic stacking structure of a second barrier layer and a second well layer. The third transition layer is a periodic stacking structure of a third barrier layer and a third well layer.

4. A light emitting diode according to claim 3, characterized in that: The second barrier layer is Al e1 In f1 Ga 0.5-e1-f1 N 0.5 , the second well layer Al e2 In f2 Ga 1-e2-f2 N 0.5 , 0≤e2≤e1≤0.5, 0≤f1≤f2≤0.5, the number of periods of the second barrier layer and the second well layer is 2 to 10 pairs, and the thickness of the second transition layer in each period is 150 angstroms to 200 angstroms.

5. A light emitting diode according to claim 3, characterized in that: The third barrier layer is Al m1 In n1 Ga 0.5-m1-n1 N 0.5 , the third well layer is Al m2 In n2 Ga 0.5-m2-n2 N 0.5 layer, 0≤m2≤m1≤0.5, 0≤n1≤n2≤0.5, the sum of the number of periods of the third transition layer is 5 to 15 pairs, and the thickness of the third transition layer in each period is 100 angstroms to 150 angstroms.

6. A light emitting diode according to claim 3, characterized in that: The aluminum composition of the third barrier layer is higher than that of the second barrier layer, the aluminum composition of the third barrier layer is more than ten times that of the second barrier layer, and the aluminum composition of the second barrier layer is equal to or higher than that of the first transition layer.

7. A light emitting diode according to claim 3, characterized in that: The thickness of the transition layer is 2000 angstroms to 7000 angstroms, wherein the thickness of the first transition layer is 2000 angstroms ±50%, the thickness of the second transition layer is 2000 angstroms ±50%, and the thickness of the third transition layer is 2000 angstroms ±50%.

8. The light emitting diode according to claim 1, characterized in that: The invention also includes a hole injection layer disposed between the active layer and the P-type layer, wherein the hole injection layer includes Al p1 In q1 Ga 0.5-p1-q1 N 0.5 , where p1 is 0 to 0.05, or 0.05 to 0.

2. In the hole injection layer, the aluminum component on the side close to the P-type layer is lower than the aluminum component on the side of the active layer. The hole injection layer is connected to the barrier layer, and the thickness of the hole injection layer is 200 angstroms to 2000 angstroms.

9. The light emitting diode according to claim 1, characterized in that: The light emitting diode is rectangular, and at least one side of the chip has a size of 0 micrometers to 20 micrometers, or 20 micrometers to 50 micrometers, and the area of ​​the light emitting diode is not greater than 5000 square micrometers.

10. The light emitting diode according to claim 1, characterized in that: The indium composition of the barrier layer on the side of the active layer close to the P-type layer is higher than the indium composition of other barrier layers of the active layer. The indium composition of the barrier layer on the side of the active layer close to the P-type layer is 1.2 times to 2 times, or 2 times to 10 times, or more than 10 times the indium composition of other barrier layers of the active layer.

11. The light emitting diode according to claim 1, characterized in that: Where y1 is 0.007 to 0.

015.

12. The light emitting diode according to claim 1, characterized in that: The active layer has 6 to 15 periods, and the barrier layer on the side of the active layer close to the P-type layer is one layer, two layers or three layers.

13. The light emitting diode according to claim 1, characterized in that: Applicable to no more than 1 ampere / cm 2 The applied current density.

14. The light emitting diode according to claim 1, characterized in that: The well layer of the active layer is Al x2 In y2 Ga 1-x2-y2 N, where 0≤x2≤x1, y1<y2, wavelength shorter than 600nm, where 0.15≤y2≤0.

3.

15. The light emitting diode according to claim 3, characterized in that: The growth temperature of the first transition layer is lower than that of the N-type layer, and the carbon content of the first transition layer is higher than that of the N-type layer.

16. A light emitting diode according to claim 3, characterized in that: The In composition of the first transition layer is less than that of the second well layer and less than that of the third well layer, wherein the In composition of the first transition layer is one tenth to one fifth of that of the second well layer, or the In composition of the first transition layer is less than one tenth of that of the second well layer.

17. The light emitting diode according to claim 1, characterized in that: The active layer includes carbon with a carbon content lower than 1E16 / cm 3 , reducing the non-radiative recombination in the active layer.

18. The light emitting diode according to claim 1, characterized in that: The hole injection layer is a doped gallium nitride layer or an undoped gallium nitride layer.

19. The light emitting diode according to claim 3, characterized in that: The first transition layer is a single layer or a periodic multilayer structure, and the first transition layer includes aluminum gallium nitride and / or gallium nitride.

20. A light emitting diode according to claim 19, characterized in that: The first transition layer is aluminum gallium nitride, and the aluminum content is no more than 1%.

21. The light emitting diode according to claim 3, characterized in that: The ratio of the indium content of the third well layer to the indium content of the first transition layer is K1, the ratio of the indium content of the third well layer to the second well layer is K2, and K1:K2 is not less than 30.

22. The light emitting diode according to claim 1, characterized in that: The energy gap of the barrier layer on the side of the active layer close to the P-type layer is lower than the energy gap of the barrier layers of other active layers.

23. A display device according to claim 1, comprising a circuit substrate and a display unit electrically connected to the circuit substrate, characterized in that: The display unit includes the light emitting diode according to claim 1 to claim 21.

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