Light emitting diode and light emitting device

Abstract

The invention relates to the technical field of semiconductor electronic devices, in particular to a light-emitting diode and a light-emitting device. The light-emitting diode at least comprises an N-type layer; the active layer is provided with a first surface and a second surface which are oppositely arranged from bottom to top, and the first surface is close to the N-type layer; the P-type layer is positioned above the active layer and is close to the second surface; wherein the active layer is provided with a plurality of potential barrier layers and a plurality of potential well layers which are alternately stacked, the plurality of potential well layers are at least divided into a second well layer group, a third well layer group and a fourth well layer group which have different indium concentrations, and the difference value between the maximum indium concentration and the minimum indium concentration in the three well layer groups is not greater than 4E20atoms / cm < 3 >. A white light spectrum formed by the white light emitting diode manufactured by adopting the epitaxial laminated structure is closer to natural light, so that a more comfortable and natural lighting environment is provided.

Description

Technical Field

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

[0002] Light-emitting diodes (LEDs) are light-emitting devices that convert electrical energy into light energy. They are now widely used in our daily lives. In the field of lighting, people are no longer satisfied with the basic function of illuminating the environment, but are pursuing higher-quality, healthier and more comfortable lighting sources.

[0003] Currently, blue light emitting diodes (LEDs) are usually used to excite phosphors to generate white light as a lighting or display light source. In actual use, the same product will have differences due to different user environments (such as temperature, etc.). At the same time, due to the high proportion of blue light in the spectrum, the generated white light spectrum is somewhat different from the natural light spectrum, which affects the visual effect of this type of lighting source product.

[0004] Therefore, how to make the blue light spectrum produced by blue light emitting diodes closer to natural light sources, and thus make the white light spectrum produced by combining them with phosphors closer to the natural light spectrum, has always been the direction that technicians in this field have been working hard to explore. For example, in future research, we will continue to work hard to optimize the design of blue light emitting diodes and the formula of phosphors, etc., to achieve a white light spectrum closer to natural light, and create a more comfortable and natural lighting environment for humans. Summary of the invention

[0005] The technical problem to be solved by the present invention is to improve the blue light peak in the white light spectrum of the white light emitting diode, improve the problems of different intensities and poor stability of each band in the prior art, and make the white light spectrum closer to the natural light spectrum.

[0006] In order to solve the above technical problems, the present invention provides a light-emitting diode, which can generate a wide spectrum and a low blue light peak band to improve the waveform mutation of the blue light band in the white light spectrum of the light-emitting diode, thereby improving the stability of various indicators of the full-spectrum white light source.

[0007] In order to achieve at least one of the above advantages or other advantages, the present invention provides a light-emitting diode, comprising at least: an N-type layer; an active layer, having a first surface and a second surface arranged opposite to each other from bottom to top, the first surface being close to the N-type layer; a P-type layer, located above the active layer and close to the second surface; wherein the active layer has a plurality of barrier layers and a plurality of potential well layers stacked alternately, the plurality of potential well layers being divided into at least a second well layer group, a third well layer group and a fourth well layer group having different indium concentrations, and the difference between the maximum indium concentration and the minimum indium concentration in the three different well layer groups is not greater than 4E20atoms / cm 3 .

[0008] In some embodiments, in the second well layer group, the third well layer group, and the fourth well layer group, the difference between the maximum indium concentration and the minimum indium concentration is no more than 2E20 atoms / cm 3 .

[0009] In some embodiments, in the second well layer group, the third well layer group, and the fourth well layer group, the difference between the maximum indium concentration and the minimum indium concentration is not less than 1E20 atoms / cm 3 .

[0010] In some embodiments, the indium concentration in the second well layer group is in the range of not less than 5E20 atoms / cm 3 、No more than 1E21atoms / cm 3 .

[0011] In some embodiments, the plurality of potential well layers further include a first well layer group, and the first well layer group has different indium concentrations from the second well layer group to the fourth well layer group. The first well layer group to the fourth well layer group are arranged and distributed along the first surface to the second surface in the active layer. The number of potential well layers in the first well layer group is 1 to 2.

[0012] In some embodiments, the composition content of indium in the second well layer group is B, the composition content of indium in the third well layer group is C, and the composition content of indium in the fourth well layer group is D, wherein B>C>D.

[0013] In some embodiments, the composition content of indium in each potential well layer in the second well layer group is 15% to 22%, and the composition content of indium in each potential well layer in the third well layer group and the fourth well layer group is 12% to 15%.

[0014] In some embodiments, the plurality of potential well layers further include a first well layer group, the composition content of indium in the first well layer group is A, wherein B>C>A>D; the composition content of indium in each potential well layer in the first well layer group is 15% to 22%.

[0015] In some embodiments, the indium concentration in the second well layer group is E2, the indium concentration in the third well layer group is E3, and the indium concentration in the fourth well layer group is E4, wherein E2, E3, and E4 are not less than 3E20 atoms / cm 3 、No more than 1E21atoms / cm 3 .

[0016] In some embodiments, the plurality of potential well layers further include a first well layer group, wherein the indium concentration E1 in the first well layer group is not less than 3E20 atoms / cm 3 、No more than 1E21atoms / cm 3 .

[0017] In some embodiments, the total number of potential well layers in the second well layer group and the third well layer group does not exceed 10, and the total number of potential well layers in the fourth well layer group is not less than 6.

[0018] In some embodiments, the number of potential well layers in the second well layer group is greater than the number of potential well layers in the third well layer group.

[0019] In some embodiments, the thickness of each barrier layer is greater than the thickness of any potential well layer; the thickness of each barrier layer ranges from 80 angstroms to 120 angstroms, and the thickness of each potential well ranges from 20 angstroms to 50 angstroms.

[0020] In some embodiments, the barrier layer is N-type doped. In some embodiments, the doping concentration of the N-type doping in the barrier layer is no greater than 1E18 atoms / cm 3 .

[0021] In order to achieve at least one of the above advantages or other advantages, the present invention further provides a light emitting device, comprising at least a light emitting diode as described above.

[0022] The light emitting diode and light emitting device provided by the present invention have at least the following advantages compared with the existing conventional or three-band light emitting diodes: 1. When light-emitting diodes are used as white light sources for lighting, the blue light in the white light spectrum can drop smoothly instead of sharply, and at the same time, the cyan light increases to achieve a better full-spectrum effect, making the spectrum of the light-emitting diode close to the white light spectrum of natural light.

[0023] 2. The light emission of the active layer in the light-emitting diode is set to three bands. Compared with existing products, it can slow down the sudden drop of blue light and make the bands of different light colors in the white light spectrum smoother and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of the spectrum of an existing white light emitting diode; Figure 2 It is a structural schematic diagram of an embodiment of a light emitting diode in the present invention; Figure 3A and Figure 3B for Figure 2 Schematic diagrams of enlarged structures of different embodiments of active layers (light-emitting layers) in the light-emitting diodes shown; Figure 4 A schematic diagram of a spectrum of a light emitting diode according to an embodiment of the present invention; Figure 5A and Figure 5B It is a SIMS schematic diagram of the indium (In) concentration in the light-emitting diode of the present invention; Figure 6 Schematic diagram of the spectrum of a light emitting diode according to an embodiment of the present invention at different peaks.

[0026] Figure numerals: 100 - light-emitting diode, 10 - substrate, 12 - buffer layer, 20 - epitaxial stacked structure, 21 - N-type layer, 22 - active layer (light-emitting layer), 22a - first surface, 22b - second surface, 220 - barrier layer, 221 - well layer, 23 - P-type layer, 223 - first well layer group, 224 - second well layer group, 225 - third well layer group, 226 - fourth well layer group, 24 - electron blocking layer, 30 - first electrode, 40 - second electrode, H1 / H2 - thickness. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In addition, the term "including" and any variation thereof all mean "at least including".

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integrally formed connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] The terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "one", "one" and "item" used herein are also intended to include plural numbers. It should also be understood that the terms "include" and / or "comprise" used herein specify the existence of stated features, integers, steps, operations, units and / or components, without excluding the existence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0031] See also Figure 1 , Figure 1 The figure is a schematic diagram of the spectrum of an existing white light emitting diode. In the existing white light emitting diodes used for display light sources or lighting light sources, blue light emitting diodes or blue-green light emitting diodes are usually used in combination with yellow phosphors to generate white light. The white light spectrum of such a light emitting diode generally has two bands (peaks) and at least one blue light band. Figure 1 As shown in the figure, in the white light spectrum of existing white light emitting diodes, the peak of blue light is very different from the peak of other colors of light and the proportion of blue light in the spectrum is relatively high. The blue light peak in the white light spectrum is very sharp, and the relative light intensity of the blue light peak is too strong, causing blue light hazards; the cyan light is partially missing, and the spectrum is quite different from natural light, which is not conducive to eye health as a whole.

[0032] See also Figure 2 , Figure 2Schematic diagram of the structure of an embodiment of a light-emitting diode in the present invention. In order to achieve at least one of the above advantages or other advantages, the present invention provides a light-emitting diode 100, which can be used to generate white light, and at least includes a substrate 10, a buffer layer 12, an epitaxial stacked structure 20, and a first electrode 30 and a second electrode 40 stacked in sequence from bottom to top. The substrate 10 can be made of a conductive or semiconductor material. The material of the substrate 10 can be a material suitable for crystal growth, such as sapphire, silicon carbide, gallium nitride, silicon, a sapphire and silicon dioxide composite substrate. In the illustrated embodiment, the material of the substrate 10 is sapphire. Optionally, the substrate 10 is a patterned sapphire substrate, which can significantly improve the lattice defects during the growth of the epitaxial stacked structure 20, increase the reflection of the substrate 10 to the light-emitting surface, and improve the luminous efficiency. The buffer layer 12 can be formed on the top of the substrate 10 by an epitaxial process, and has a lattice constant that matches the material of the substrate 10 and the material of the epitaxial stacked structure 20. In some embodiments, the material of the buffer layer 12 can be aluminum nitride, gallium nitride, aluminum gallium nitride, etc.

[0033] The epitaxial stacked structure 20 is disposed above the side of the buffer layer 12 away from the substrate 10. In some implementations, a UGaN layer (not shown in the figure) may be further disposed between the buffer layer 12 and the epitaxial stacked structure 20. The UGaN layer is an undoped GaN layer, which may be a 3D layer mainly grown in a 3D manner or a 2D layer mainly grown in a 2D manner. The epitaxial stacked structure 20 includes an N-type layer 21, an active layer 22, and a P-type layer 23 stacked in sequence from bottom to top. In some embodiments, an electron blocking layer 24 (EBL) may be further disposed between the active layer 22 and the P-type layer 23. The electron blocking layer 24 cooperates with the active layer 22 to disperse and block the electrons, which can effectively prevent electron overflow and improve the recombination efficiency of electrons and holes. The thickness of the electron blocking layer 24 is relatively thin, which may be 200 angstroms to 2000 angstroms, and can effectively improve the shading effect caused by the excessive thickness of the electron blocking layer 24, thereby improving the brightness of the light-emitting diode 100. In some specific embodiments, the thickness of the electron blocking layer 24 may be 200 angstroms to 1000 angstroms. The first electrode 30 and the second electrode 40 are located above the epitaxial stacked structure 20 and are electrically connected to the N-type layer 21 and the P-type layer 23, respectively. It should be noted that in the light-emitting diode 100, a transparent conductive layer (such as ITO), a current blocking layer, and an insulating layer may be provided between the epitaxial stacked structure 20 and the first electrode 30 and the second electrode 40. These hierarchical structures are not the focus of the invention in this application and will not be described in detail here. Please refer to the structural setting description in the existing light-emitting diode.

[0034] The epitaxial stacked structure 20 can be formed on the substrate 10 by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor deposition (HVPE), physical vapor deposition (PVD) or ion plating. Specifically, along the vertical direction, the substrate 10 has an upper surface and a lower surface relative to each other, the buffer layer 12 is formed on the upper surface of the substrate 10, and the epitaxial stacked structure 20 is formed on the side of the buffer layer 12 away from the upper surface of the substrate 10. Among them, the N-type layer 21 can be grown from the upper surface of the buffer layer 12, and the active layer 22 (or light-emitting layer 22, active layer 22) and the P-type layer 23 are sequentially stacked and grown on the upper surface of the N-type layer 21. In other embodiments, the epitaxial stacked structure 20 can also be formed on the substrate 10 through a bonding layer, and the bonding layer is preferably a light-transmitting material. In some embodiments, a stress release layer, a superlattice layer (not shown in the figure), etc. may be provided between the N-type layer 21 and the active layer 22.

[0035] The epitaxial stacked structure 20 can provide light of a specific central emission wavelength, such as blue light, green light, red light, purple light, or ultraviolet light. In the illustrated embodiment, the epitaxial stacked structure 20 providing blue light is used as an example for explanation, and the light emitting diode 100 formed by combining the epitaxial stacked structure 20 with yellow phosphor can be stimulated to generate white light.

[0036] In the illustrated embodiment, the N-type layer 21 in the epitaxial stacked structure 20 can provide electrons to the active layer 22 under the action of a power source, and is also called an electron supply layer. In some embodiments, the N-type layer 21 includes an N-type doped nitride layer (NGaN layer). The N-type doped nitride layer may include one or more N-type impurities of group IV elements. The N-type impurities may be one of Si, Ge, Sn, or a combination thereof.

[0037] In some embodiments, the active layer 22 (or light-emitting layer 22, active layer 22) may be a multiple quantum well (MQWs) structure in which quantum well layers and quantum barrier layers are alternately stacked. The quantum barrier layer may be a GaN layer or an AlGaN layer. In some embodiments, the active layer 22 may include a multiple quantum well structure of GaN / AlGaN, InAlGaN / InAlGaN or InGaN / AlGaN. In order to improve the luminous efficiency of the active layer 22, it may be achieved by changing the depth of the quantum well, the number of layers of the paired quantum wells and quantum barriers, the thickness and / or other characteristics in the active layer 22.

[0038] In the illustrated embodiment, the P-type layer 23 in the epitaxial stacked structure 20 can provide holes to the light-emitting layer 22 under the action of a power source, and is also called a hole-providing layer. In some embodiments, the P-type layer 23 includes a P-type doped nitride layer (PGaN layer). The P-type doped nitride layer may include one or more P-type impurities of group II elements. The P-type impurity may be one or a combination of Mg, Zn, and Be. The P-type layer 23 may be a single-layer structure or a multi-layer structure having different compositions. The arrangement of the epitaxial stacked structure 20 is not limited thereto, and other types of epitaxial stacked structures 20 may be selected according to actual needs.

[0039] Combination Figure 2 See also Figure 3A and Figure 3B , Figure 3A and Figure 3B for Figure 2 Schematic diagram of the enlarged structure of different embodiments of the active layer (light-emitting layer) in the light-emitting diode shown. In the epitaxial stacked structure 20, the active layer 22 has a first surface 22a and a second surface 22b arranged opposite to each other from bottom to top. The first surface 22a is close to the N-type layer 21, and the second surface 22b is close to the P-type layer 23. In some embodiments, the first surface 22a and the second surface 22b of the active layer 22 may be in non-direct contact with the N-type layer 21 and the P-type layer 23, respectively, and other hierarchical structures may be provided between them according to product requirements. The active layer 22 is a multi-quantum well structure, having a plurality of barrier layers 220 and a plurality of well layers 221 stacked alternately. In the active layer 22, the barrier layers 220 are in contact with the first surface 22a and the second surface 22b, respectively, and the remaining barrier layers 220 and well layers 221 are alternately stacked between the two barrier layers 220. In other words, the N-type layer 21 and the P-type layer 23 are respectively connected to one barrier layer 220, and each potential well layer 221 is connected to two barrier layers 220. The active layer 22 is used to generate a light beam with a wide-band blue light spectrum.

[0040] In some embodiments, the bandgap widths of the potential well layers 221 are not necessarily the same, and each potential well layer 221 may have a different bandgap width to generate multiple sub-beams with different wavelengths. Multiple sub-beams are superimposed to form a beam with a wide-band blue light spectrum.

[0041] The thickness H1 of the barrier layer 220 and the thickness H2 of the potential well layer 221 will affect the spectral shape ultimately produced by the active layer 22. The thickness H1 of each (layer) barrier layer 220 is greater than the thickness H2 of any potential well layer 221. The thickness H1 of each barrier layer 220 may be the same or different. The thickness H2 of each potential well layer 221 may be the same or different. The thickness of several barrier layers 220 or several potential well layers 221 may be gradually thickened or thinned, or may be arranged in alternating thickness. Optionally, the thickness H1 of each barrier layer 220 is 80 angstroms to 120 angstroms, and the thickness H2 of each potential well layer 221 is 20 angstroms to 50 angstroms, so as to reduce the adverse effects of changes in operating current on the spectral shape of the active layer 22.

[0042] The thickness of the barrier layer 220 and the potential well layer 221 will affect the quality of the epitaxial stack structure 20, and will also affect the half-width (band width). Generally, a narrower half-width is better in a single band, and a larger half-width is better in a multi-band. The thinner the barrier layer 220 and the potential well layer 221, the narrower the half-width. Conversely, the wider the half-width, the poorer the quality of the epitaxial stack structure 20. The thickness of the potential well layer 221 cannot be too thick. Based on this, in a preferred embodiment, the thickness of several barrier layers 220 or several potential well layers 221 is substantially the same.

[0043] In some embodiments, N-type doping may be performed in the active layer 22 to increase the concentration of free electrons in the epitaxial stack structure 20, thereby improving the conductivity and luminous efficiency. Optionally, the doping element for N-type doping in the active layer 22 is Si, which increases the concentration of free electrons in the active layer 22, improves its conductivity and current injection efficiency, and thereby improves the luminous efficiency and brightness of the light-emitting diode 100. The doping concentration of Si is not higher than 1E18atoms / cm3. Generally, the barrier layer 220 in the active layer 22 is N-type doped (fixed doping), and the potential well layer 221 is usually not doped (unintentional doping), but in the SIMS image, there will inevitably be N-type doping signals in the potential well layer 221. The potential well layer 221 is the actual light-emitting area, and doping will affect the quality of the light-emitting diode 100, thereby reducing the luminous brightness.‌

[0044] As shown in Figure 3A and Figure 3B As shown, in the illustrated embodiment, the active layer 22 has at least 14 potential well layers 221 and 15 potential barrier layers 220 alternately stacked. The thickness H1 of each potential barrier layer 220 is substantially the same, and the thickness H2 of each potential well layer 221 is substantially the same. The thickness H1 of each potential barrier layer 220 is 80 angstroms to 120 angstroms, and the thickness H2 of each potential well layer 221 is 20 angstroms to 50 angstroms.

[0045] In some embodiments, Figure 3AAs shown, along the vertical direction, from the first surface 22a (N-type layer 21) to the second surface 22b (P-type layer 23) in the active layer 22, several potential well layers 221 can be divided into a second well layer group 224, a third well layer group 225 and a fourth well layer group 226, each well layer group having a different indium concentration or indium content to generate three sub-beams of different wavelengths.

[0046] In another embodiment, if Figure 3B As shown, along the vertical direction, from the first surface 22a (N-type layer 21) to the second surface 22b (P-type layer 23) in the active layer 22, a plurality of potential well layers 221 are at least divided into a first well layer group 223, a second well layer group 224, a third well layer group 225 and a fourth well layer group 226, each well layer group having a different indium concentration or indium content to generate four sub-beams of different wavelengths. In other embodiments, along the vertical direction, from the first surface 22a (N-type layer 21) to the second surface 22b (P-type layer 23) in the active layer 22, the first well layer group 223, the second well layer group 224, the third well layer group 225 and the fourth well layer group 226 may be arranged in an alternating manner. It can be understood that the order of the well layer groups in the first well layer group 223, the second well layer group 224, the third well layer group 225 and the fourth well layer group 226 in the active layer 22 can be swapped as needed. After the order of different well layer groups is swapped, the peak of the blue light region in the spectrum generated by the light-emitting diode 100 still shows a gentle trend. In the active layer 22, the indium concentration in the well layer group closest to the P-type layer 23 is the lowest. At the same time, affected by the P-type layer, the indium concentration of the potential well layer 221 closest to the P-type layer 23 in the well layer group closest to the P-type layer 23 is relatively low. See Figure 5B , a region with a lower indium concentration than the fourth well layer group 226 may be defined as a stress release layer or a superlattice layer.

[0047] The number of potential well layers 221 in the second well layer group 224 is greater than the number of potential well layers 221 in the first well layer group 223. The number of potential well layers 221 in the fourth well layer group 226 is greater than the number of potential well layers 221 in the second well layer group 224. The number of potential well layers 221 in the third well layer group 225 is greater than or equal to the number of potential well layers 221 in the first well layer group 223, so that the brightness and phosphor can be better combined, which is more in line with the application of the full spectrum of natural light. The less the indium (In) content, the shorter the wavelength, the more indium (In) content, the longer the wavelength, and the more quantum wells (potential well layers), the stronger the spectrum. The stronger the spectrum, the more obvious the sudden drop in different bands in the luminescence spectrum, that is, the greater the difference between the upper and lower peaks in the spectrum. The more barrier layers 220 and potential well layers 221, the greater the difference in relative spectral intensity, and the more obvious the sudden drop in different bands in the luminescence spectrum. The greater the difference in indium concentration in different potential well layers 221 , the flatter the peak in the spectrum. Meanwhile, when the thickness of the potential well layer 221 is appropriately increased, the spectrum is wider and the peak is flatter.

[0048] In the active layer 22, the total number of potential well layers 221 in the first well layer group 223 and the second well layer group 224 does not exceed 6. The number of potential well layers 221 in the first well layer group 223 is 1-2, at least 1. The first well layer group 223 mainly plays a transition role between the N-type layer 21 and the active layer 22, and the number of potential well layers 221 does not need to be large. Furthermore, a potential well layer 221 with a thickness of 1-2 is provided between the N-type layer 21 and the active layer 22, so that the peak in the spectrum can be slightly widened to smooth the sudden drop of the blue light spectrum. The total number of potential well layers 221 in the second well layer group 224 and the third well layer group 225 does not exceed 10. The number of potential well layers 221 in the second well layer group 224 is greater than the number of potential well layers 221 in the third well layer group 225. The number of potential well layers 221 in the second well layer group 224 is no more than 5, the number of potential well layers 221 in the third well layer group 225 is no more than 5, and the number of potential well layers 221 in the fourth well layer group 226 is greater than or equal to 6. The second well layer group 224, the third well layer group 225 and the fourth well layer group 226 serve as the main light-emitting regions, and the number of potential well layers 221 in each group is greater than the number of potential well layers 221 in the first well layer group 223. Furthermore, the total number of potential well layers 221 in the active layer 22 is 10-20 groups. Figure 4 The arrangement of the several potential well layers 221 in the active layer 22 as four groups (four bands) can avoid the peak intensity of the luminous band of each well layer group being too large, and prevent the difference between each well layer group and the adjacent band being too large, thereby making the blue light spectrum realize a trend of a gentle and sudden drop. When the light emission of the active layer 22 exceeds four bands, it is difficult to control the temperature and indium (In), which will affect the product yield in actual production, thereby increasing the production cost.

[0049] The indium concentration (content) in the four well layer groups and each potential well layer 221 is different. The greater the difference in indium concentration in different potential well layers 221, the flatter the peak of the blue light in the luminescence spectrum. In existing products, the concentration of indium in the active layer 22 is basically the same (no obvious difference), and the difference in indium concentration in different well layer groups is small, which causes a significant drop in the blue light peak in the luminescence spectrum. In the present application, the indium concentration of the potential well layer 221 in the second well layer group 224 is greater than the indium concentration of the potential well layer 221 in other well layer groups, which can improve the sudden drop in the blue light peak in the luminescence spectrum, and there is a difference in the peak with other well layer groups, which can further improve the sudden drop in the blue light peak in the luminescence spectrum. In addition, in the same well layer group, the indium concentration in different potential well layers 221 is set to gradually increase or decrease, which can also improve the sudden drop in the blue light peak in the luminescence spectrum, but the effect is not obvious. In comparison, the setting of the indium concentration in different well layer groups and different potential well layers 221 in the present application makes the indium drop between different potential well layers 221 smoothed out section by section, thereby making the blue light peak in the luminescence spectrum smoother overall.

[0050] Alternatively, if Figure 3B As shown, in some embodiments, the active layer 22 has at least 14 potential well layers 221. The number of potential well layers 221 in the first well layer group 223 is 1 (the first potential well layer 221 in the figure), the number of potential well layers 221 in the second well layer group 224 is 3 (the second to fourth potential well layers 221 in the figure), the number of potential well layers 221 in the third well layer group 225 is 2 (the fifth to sixth potential well layers 221 in the figure), and the number of potential well layers 221 in the fourth well layer group 226 is 8 (the seventh to fourteenth potential well layers 221 in the figure). The settings of different well layer groups cooperate with each other to adjust the light spectrum composition when the active layer 22 emits light. The more quantum wells (well layers) there are, the stronger the spectrum.

[0051] Furthermore, the wavelength λ1 of the first sub-beam generated by the first well layer group 223 is 445nm~455nm, and it mainly appears as blue light. The wavelength λ2 of the second sub-beam generated by the second well layer group 224 is 467nm~478nm, and it mainly appears as cyan light. The wavelength λ3 of the third sub-beam generated by the third well layer group 225 is 456nm~465nm, and it mainly appears as a mixture of blue light and cyan light. The wavelength λ4 of the fourth sub-beam generated by the fourth well layer group 226 is 432nm~443nm, and it mainly appears as blue light. The size of the wavelengths in different well layer groups is λ2>λ3>λ1>λ4. Figure 4 As shown, the potential well layers 221 in the active layer 22 are divided into four well layer groups and can simultaneously excite sub-beams of different wavelengths to form four different wavelength bands, which are consistent with the spectrum of existing white light emitting diodes (such as Figure 1As shown in FIG. 1 ), the blue light spectrum can achieve a smooth and sudden drop, and the cyan light portion is increased. The spectrum of the light-emitting diode 100 is closer to natural light, which is also beneficial to eye health.

[0052] Theoretically, the concentration of indium doped in the potential well layer 221 is directly related to the wavelength of light emitted when electrons and holes recombine in the potential well layer 221. Multiple well layer groups include at least four potential well layers 221 with different indium concentrations, which can promote the recombination of electrons and holes in the potential well layers 221 with different indium concentrations, and emit sub-beams of different wavelengths. However, the final light waveform of the light-emitting diode 100 is not simply formed by the superposition of these sub-beams. The indium concentration, quantity, position in the active layer 22, and coordination relationship with the adjacent potential well layer 221 in different well layer groups may affect the waveform of the blue light spectrum finally generated by the light-emitting diode 100. After a large number of experiments, it was found that in order to ensure the position and intensity of the main peak inflection point of the wide-band blue light emitted by the light-emitting diode 100, and to have higher stability relative to the operating temperature, in the present application, along the growth direction of the active layer 22, part of the potential well layers 221 of the third well layer group 225 and the fourth well layer group 226 are located in the middle section of the active layer 22. Figure 3B As shown, the main peaks of 457nm~462nm in the blue light spectrum are located in the middle section of the active layer 22, and the main peaks of 470nm~475nm (the second well layer group 224) and 435nm~440nm (the fourth well layer group 226) are located on both sides of the third well layer group 225, so that electrons and holes can recombine relatively more, ensuring that the number of photons generated by the electron-hole recombination in the hot state will not be reduced much.

[0053] Optionally, each potential well layer 221 contains indium (In), and its material may be indium gallium nitride (InGaN), and the material of each barrier layer 220 may be gallium nitride (GaN) or AlGaN. The concentration of indium in the potential well layer 221 will affect the bandgap width of the potential well layer 221, so the bandgap width of the potential well layer 221 can be adjusted by controlling the indium component content in each potential well layer 221, thereby controlling the light emission wavelength of the potential well layer 221. Specifically, the lower the concentration of indium, the higher the bandgap width of the potential well layer 221.

[0054] The material of the potential well layer 211 is indium gallium nitride (InGaN) as an example, and the component content of indium (In) refers to the mass percentage of indium (In) in indium gallium nitride (InGaN). Optionally, the component content of indium (In) in the first well layer group 223 is A, the component content of indium (In) in the second well layer group 224 is B, the component content of indium (In) in the third well layer group 225 is C, and the component content of indium (In) in the fourth well layer group 226 is D, and the component content of indium (In) in different well layer groups is B>C>A>D. That is, the component content of indium (In) in the second well layer group 224 is the highest, and the component content of indium (In) in the fourth well layer group 226 is the lowest. In this structural setting, along the direction from the N-type layer 21 to the P-type layer 23, the content of indium in the first well layer group to the fourth well layer group in the active layer 22 is not distributed in a gradually increasing or decreasing manner, but in a fluctuating distribution. In the same well layer group, the indium concentration in different potential well layers 221 is set to gradually increase or decrease, which can also improve the sudden drop of the blue light peak in the luminescence spectrum, but the effect is not obvious. In contrast, the setting of the indium concentration in different well layer groups and different potential well layers 221 in the present application makes the indium drop between different potential well layers 221 be smoothed section by section, so that the blue light peak in the luminescence spectrum becomes smooth as a whole.

[0055] There are many methods for detecting indium, the commonly used ones are atomic fluorescence spectroscopy, inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectroscopy, etc. By detecting the mass percentage of indium (In) in indium gallium nitride (InGaN), the different contents of indium (In) in the four well layer groups can be distinguished macroscopically, and then the bandgap width of different well layer groups and the wavelength range of the sub-beams can be determined.

[0056] Optionally, in some embodiments, in the first well layer group 223 and the second well layer group 224, the content of indium (In) in each potential well layer 221 is 15% to 22%. In the third well layer group 225 and the fourth well layer group 226, the content of indium (In) in each potential well layer 221 is 12% to 15%. It is further explained that the presence of indium (In) will affect the energy gap and growth quality in the epitaxial stack structure 20. The higher the content or concentration of indium (In), the worse the growth quality of the potential well layer 221, thereby affecting the brightness of the light-emitting diode 100. In view of this, in the same well layer group (the same wavelength band), along the growth direction ( Figure 3A and Figure 3B (in the figure, the active layer 22 is along the direction from the first surface 22a to the second surface 22b), from bottom to top, the component content or concentration of indium (In) in each potential well layer 221 can be set to gradually decrease.

[0057] like Figure 3BAs shown, along the growth direction of the epitaxial stack structure 20, the potential well layer 221 in the first well layer group 223 is the first potential well layer 221, and the three potential well layers 221 in the second well layer group 224 are the second to fourth potential well layers 221. In the second well layer group 224 region, the component content or concentration of indium (In) in the second potential well layer 221 close to the first well layer group 223 is the largest in the second well layer group 224, and the component content or concentration of indium (In) in the fourth potential well layer 221 close to the third well layer group 225 is the smallest in the second well layer group 224. It can be understood that, along the growth direction of the epitaxial stack structure 20, in the second well layer group 224 region, the component content or concentration of indium (In) in the second to fourth potential well layers 221 tends to decrease gradually. Accordingly, along the growth direction of the epitaxial stack structure 20 , the component content or concentration of indium (In) in the 5th to 6th potential well layers 221 in the third well layer group 225 shows a gradually decreasing trend, and the component content or concentration of indium (In) in the 7th to 14th potential well layers 221 in the fourth well layer group 226 shows a gradually decreasing trend.

[0058] In some embodiments, the material of each potential well layer 221 is indium gallium nitride (InGaN). The indium (In) concentration in the first well layer group 223 is E1, the indium (In) concentration in the second well layer group 224 is E2, the indium (In) concentration in the third well layer group 225 is E3, and the indium (In) concentration in the fourth well layer group 226 is E4. The range of indium (In) concentration in different well layer groups is that E1, E2, E3 and E4 are not less than 3E20atoms / cm 3 、No more than 1E21atoms / cm 3 It can be understood that the indium concentration in each potential well layer 221 in the active layer 22 is not less than 3E20atoms / cm 3 、No more than 1E21atoms / cm 3 .

[0059] In some embodiments, the second well layer group 224 has the highest indium (In) concentration E2, and the fourth well layer group 226 has the lowest indium (In) concentration E4. The difference in indium concentration between the two well layer groups is not less than 1E20 atoms / cm 3 、No more than 4E20atoms / cm 3 In some specific embodiments, the difference between the indium (In) concentration E2 in the second well layer group 224 and the indium (In) concentration E4 in the fourth well layer group 226 is no more than 2E20 atoms / cm 3 In some embodiments, the indium concentration E2 in the second well layer group 224 is not less than 5E20 atoms / cm 3 、No more than 1E21atoms / cm 3. The greater the difference in indium concentration in different potential well layers 221, the flatter the peak in the spectrum. At the same time, the thickness of the potential well layer 221 is appropriately increased, the wider the spectrum, and the flatter the peak. The four well layer groups and each potential well layer 221 have different indium concentrations (contents). The greater the difference in indium concentration in different potential well layers 221, the flatter the peak of blue light in the luminescence spectrum. In existing products, the concentration of indium in the active layer is basically the same (no obvious difference), and the difference in indium concentration in different well layer groups is small, resulting in a significant drop in the blue light peak in the luminescence spectrum. In the present application, the indium concentration of the potential well layer 221 in the second well layer group 224 is greater than the indium concentration of the potential well layer 221 in other well layer groups, which can improve the sudden drop in the blue light peak in the luminescence spectrum, and there is a difference in the peak between the well layer groups and other well layer groups, which can further improve the sudden drop in the blue light peak in the luminescence spectrum.

[0060] To further understand the positional relationship of each potential well layer 221, please refer to Figure 4 and Figure 5A , Figure 5B , Figure 4 A schematic diagram of a spectrum of a light emitting diode according to an embodiment of the present invention; Figure 5A and Figure 5B This is a graph of the concentration of indium (In) in an embodiment of the light emitting diode of the present invention, which is obtained by analyzing the indium concentration of each potential well layer 221 in the active layer 22 along the direction from the P-type layer 23 to the N-type layer 21 using SIMS (secondary ion mass spectrometry). Figure 5A and Figure 5B , the peaks of the indium (In) concentration curves in each potential well layer 221 are not completely consistent. According to the different indium concentrations in each potential well layer 221, the peaks of the indium (In) concentration curves fluctuate up and down. 5A is a local SIMS image of the light-emitting diode 100 (there are many overall views and they cannot all be presented in one view). The red lines are schematic diagrams of different well layer groups of the active layer 22. Figure 5A The red line on the right side of the active layer 22 is a schematic diagram of a stress release layer in this application. Figure 5B for Figure 5A An enlarged schematic diagram of the active layer 22 region is shown in FIG. Figure 5B From right to left, the first peak is the first well layer group 223 , the 2nd to 4th peaks are the second well layer group 224 , the 4th to 5th peaks are the third well layer group 225 , and the 7th to 14th peaks are the fourth well layer group 226 .

[0061] See also Figure 6 , FIG6 is a schematic diagram of the spectrum of a light emitting diode in an embodiment of the present invention at different peaks. In this application, Figure 6is the PL spectrum, and the other views are EL spectrum. The principles of PL spectrum and EL spectrum are similar, except that the excitation of the two is different. PL is light excitation, and EL is electron excitation. Photoluminescence spectroscopy (abbreviated as PL spectrum) refers to the electrons of a substance jumping from the valence band to the conduction band and leaving holes in the valence band under the excitation of light; the electrons and holes reach their respective unoccupied lowest excited states (the bottom of the conduction band and the top of the valence band in intrinsic semiconductors) through relaxation in their respective conduction bands and valence bands, becoming a quasi-equilibrium state; the electrons and holes in the quasi-equilibrium state then emit light through recombination, forming a spectrum of intensity or energy distribution of light of different wavelengths. The principle of EL spectroscopy is a method of measuring the number and velocity distribution of electrons (charges) in a substance using optical technology. EL spectroscopy is usually used to analyze the composition, deformation, damage, etc. of materials. Its working principle is based on Coulomb scattering, which is a physical phenomenon that indicates how charges scatter light in a substance. Figure 6 In the figure, four peaks can be clearly seen in the light spectrum of the light emitting diode 100, and the sudden drop trend in the spectrum has become significantly gentle. The light spectrum generated by the light emitting diode 100 is consistent with the requirements of the natural spectrum, so that the application range of the light emitting diode 100 is wider.

[0062] To achieve at least one of the above advantages or other advantages, an embodiment of the present invention further provides a light emitting device, comprising at least the light emitting diode 100 as described above.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A light emitting diode, characterized in that: At least: N-type layer; An active layer, having a first surface and a second surface arranged opposite to each other from bottom to top, wherein the first surface is close to the N-type layer; A P-type layer, located above the active layer and close to the second surface; The active layer has a plurality of barrier layers and a plurality of potential well layers stacked alternately, and the plurality of potential well layers are at least divided into a second well layer group, a third well layer group, and a fourth well layer group with different indium concentrations, and the difference between the maximum indium concentration and the minimum indium concentration in the three different well layer groups is not greater than 4E20atoms / cm 3 .

2. The light emitting diode according to claim 1, characterized in that: In the second well layer group, the third well layer group and the fourth well layer group, the difference between the maximum indium concentration and the minimum indium concentration is no more than 2E20atoms / cm 3 .

3. The light emitting diode according to claim 1, characterized in that: In the second well layer group, the third well layer group and the fourth well layer group, the difference between the maximum indium concentration and the minimum indium concentration is not less than 1E20 atoms / cm 3 .

4. The light emitting diode according to claim 1, characterized in that: The indium concentration in the second well layer group is not less than 5E20atoms / cm 3 、No more than 1E21atoms / cm 3 .

5. The light emitting diode according to claim 1, characterized in that: The plurality of potential well layers further include a first well layer group, wherein the first well layer group and the second to fourth well layer groups have different indium concentrations; the first to fourth well layer groups are arranged and distributed along the first surface toward the second surface.

6. The light emitting diode according to claim 5, characterized in that: The number of the potential well layers in the first well layer group is 1 to 2.

7. The light emitting diode according to claim 1, characterized in that: The component content of indium in the second well layer group is B, the component content of indium in the third well layer group is C, and the component content of indium in the fourth well layer group is D, wherein B>C>D.

8. The light emitting diode according to claim 7, characterized in that: The content of indium in each of the potential well layers in the second well layer group is 15% to 22%, and the content of indium in each of the potential well layers in the third well layer group and the fourth well layer group is 12% to 15%.

9. The light emitting diode according to claim 7, characterized in that: The potential well layers further include a first well layer group, the component content of indium in the first well layer group is A, wherein B>C>A>D; the component content of indium in each of the potential well layers in the first well layer group is 15% to 22%.

10. The light emitting diode according to claim 1, characterized in that: The indium concentration in the second well layer group is E2, the indium concentration in the third well layer group is E3, and the indium concentration in the fourth well layer group is E4, wherein E2, E3 and E4 are not less than 3E20 atoms / cm 3 、No more than 1E21atoms / cm 3 .

11. The light emitting diode according to claim 10, characterized in that: The potential well layers further include a first well layer group, wherein the indium concentration E1 in the first well layer group is not less than 3E20 atoms / cm 3 、No more than 1E21atoms / cm 3 .

12. The light emitting diode according to claim 1, characterized in that: The total number of the potential well layers in the second well layer group and the third well layer group is no more than 10, and the total number of the potential well layers in the fourth well layer group is no less than 6.

13. The light emitting diode according to claim 12, characterized in that: The number of the potential well layers in the second well layer group is greater than the number of the potential well layers in the third well layer group.

14. The light emitting diode according to claim 1, characterized in that: The thickness of each of the potential barrier layers is greater than the thickness of any of the potential well layers; the thickness of each of the potential barrier layers ranges from 80 angstroms to 120 angstroms, and the thickness of each of the potential well layers ranges from 20 angstroms to 50 angstroms.

15. The light emitting diode according to claim 1, characterized in that: The barrier layer is N-type doped.

16. The light emitting diode according to claim 15, characterized in that: The doping concentration of the N-type doping is not greater than 1E18atoms / cm 3 .

17. A light emitting device, characterized in that: At least comprising the light emitting diode according to any one of claims 1 to 16.

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