A single-chip multi-color light-emitting diode and LED backlight source

Abstract

The present invention relates to the technical field of light emitting diodes, and in particular to a monolithic multicolor light emitting diode and an LED backlight source. The monolithic multicolor light emitting diode comprises a multicolor light emitting layer arranged between an N-type layer and a P-type layer; the multicolor light emitting layer comprises a first light emitting layer emitting light of a first color and a second light emitting layer emitting light of a second color; wherein the peak wavelength λ of the light of the second color is p2 Greater than the peak wavelength λ of the first color of light p1 , and λ p2 ‑λ p1 ≥50nm; the thickness of the second well layer in the second light-emitting layer

Description

Technical Field

[0001] The invention relates to the technical field of light emitting diodes, and in particular to a single-chip multi-color light emitting diode and an LED backlight source. Background Art

[0002] Light-emitting diodes (LEDs) based on gallium nitride (GaN) III-V compound semiconductors typically exhibit excellent light emission characteristics. In theory, LED emissions from GaN-based III-V compound semiconductors such as InGaN, AlGaN, AlInGaN and GaN can cover the entire visible spectrum from short wavelengths (i.e., UV) to longer wavelengths (i.e., red light). It is widely used in signal lights, car lights, landscape and indoor lighting sources, display screens and other fields. Existing LED backlight sources for display screens are divided into RGB-LEDs and white light LEDs. Among them, RGB-LED is a package of three monochromatic LED chips of blue, green and red together. For example, the blue LED chip and the green LED chip are III-nitride compound semiconductor elements, and the red light-emitting element is a GaAs or GaN light-emitting element. The white light LED is formed by combining a monochromatic LED chip with a phosphor. For example, a monochromatic blue light chip is combined with a green phosphor and a red phosphor, or a single blue LED chip is combined with a yellow phosphor. Among them, the RGB three-primary color LED backlight has the best display effect, but the cost is relatively high. White light LEDs require phosphors, such as Figure 1 As shown, in addition to the obvious differences in the NTSC (National Television Standards Committee) color gamut of different phosphor solutions, the uniformity of the phosphor and glue after mixing is also difficult to control, resulting in poor light uniformity, poor color consistency, easy deviation of color temperature and unsatisfactory color rendering.

[0003] It is known that the NTSC color gamut is the ratio of a certain triangle area to the standard triangle area under the NTSC standard. The higher the ratio, the better the color expression. The high color gamut coverage commonly referred to in the industry refers to the NTSC color gamut ratio ≥ 85%. White light with high color gamut coverage is generally achieved by blue light chip + green phosphor + red phosphor. At present, the best solution for achieving high color gamut coverage is β-SiAlON green phosphor, but its half-wave width is still 48nm~55nm, see Figure 2 .

[0004] Therefore, how to reduce the cost of RGB-LED backlight sources and / or reduce the use of phosphors in white LED backlight sources while maintaining a high NTSC level is a technical problem that needs to be solved.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first object of the present invention is to provide a monolithic multi-color light emitting diode, which can emit at least two colors of light on a single LED chip, does not require or reduces the use of fluorescent powder, and reduces the cost of RGB-LED backlight source.

[0007] A second object of the present invention is to provide an LED backlight source.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] The present invention first provides a monolithic multi-color light emitting diode, comprising a multi-color light emitting layer disposed between an N-type layer and a P-type layer;

[0010] The multicolor light-emitting layer includes a first light-emitting layer that emits light of a first color and a second light-emitting layer that emits light of a second color; wherein the peak wavelength λ of the light of the second color is p2 Greater than the peak wavelength λ of the first color of light p1 , and λ p2 -λ p1 ≥50nm;

[0011] The thickness of the second well layer in the second light-emitting layer is less than the thickness of the first well layer in the first light-emitting layer.

[0012] Preferably, a thickness ratio of the second well layer to the first well layer is 0.5-0.95.

[0013] Preferably, the thickness of the second well layer is 27~32Å.

[0014] Preferably, the thickness of the first well layer is 33-38Å.

[0015] Preferably, the first well layer includes In x1 Ga (1-x1) N, the second well layer includes In x2 Ga (1-x2) N, where 1>X2>X1>0.1.

[0016] Preferably, X2=0.22~0.28.

[0017] Preferably, X1=0.13~0.19.

[0018] Preferably, the light of the first color includes blue light, and the light of the second color includes green light.

[0019] Preferably, the peak wavelength λ of the light of the first color is p1 =440~470nm.

[0020] Preferably, the peak wavelength λ of the light of the second color p2 =520~550nm.

[0021] Preferably, when the input current is ≥10 mA, the ratio of the peak wavelength intensity of the light of the first color to the peak wavelength intensity of the light of the second color is ≥5.

[0022] Preferably, the second light-emitting layer includes a second barrier layer, and the first light-emitting layer includes a first barrier layer.

[0023] Preferably, the thickness of the second barrier layer is greater than the thickness of the first barrier layer.

[0024] Preferably, the thickness of the second barrier layer is 100-200Å.

[0025] Preferably, the thickness of the first barrier layer is 90-100Å.

[0026] Preferably, a ratio H2 / H1 of a sum of thicknesses H2 of the second well layer and the second barrier layer to a sum of thicknesses H1 of the first well layer and the first barrier layer is 0.9-1.1.

[0027] Preferably, a thickness ratio H3 of the second barrier layer to the second well layer is ≥ a thickness ratio H4 of the first barrier layer to the first well layer, and H3 / H4=1-2.

[0028] Preferably, the first barrier layer in the first light emitting layer comprises at least one of GaN, AlGaN or InAlGaN.

[0029] Preferably, the second barrier layer in the second light emitting layer comprises at least one of GaN, AlGaN or InAlGaN.

[0030] Preferably, the number of the first well layers is 10-20, and a first barrier layer is disposed between every two adjacent first well layers.

[0031] Preferably, the number of the second well layers is 1 to 5, and a second barrier layer is disposed on both sides of each of the second well layers.

[0032] Preferably, the first light-emitting layer comprises a first periodic structure in which first well layers and first barrier layers are alternately stacked, and the number of periods of the first periodic structure is 10-20.

[0033] Preferably, the second light emitting layer comprises a second periodic structure in which second well layers and second barrier layers are alternately stacked, and the number of periods of the second periodic structure is 1-5.

[0034] Preferably, the number of the first well layers is 4 to 20 times the number of the second well layers.

[0035] Preferably, the energy band of the second well layer in the second light-emitting layer is lower than the energy band of the first well layer in the first light-emitting layer.

[0036] Preferably, the energy band of the second barrier layer in the second light-emitting layer is lower than the energy band of the first barrier layer in the first light-emitting layer.

[0037] Preferably, the direction from the N-type layer to the P-type layer is defined as the first direction, the energy band of the second barrier layer in the second light-emitting layer is from low to high in the first direction, and the energy band of the first barrier layer in the first light-emitting layer is from high to low in the first direction.

[0038] Preferably, Al is doped between the second well layer and the second barrier layer in the second light emitting layer.

[0039] Preferably, the thickness of the Al layer is less than 1 / 3 of the thickness of the second well layer.

[0040] Preferably, when the injected current is 350 mA, the brightness of the monolithic multi-color light emitting diode is ≥ 770 mW.

[0041] The present invention further provides an LED backlight source, which includes an RGB-LED and a white light LED, wherein the RGB-LED or the white light LED contains the single-chip multi-color light-emitting diode.

[0042] Preferably, the RGB-LED includes the monolithic multi-color light emitting diode and a monochromatic red light emitting diode.

[0043] Preferably, the white light LED includes the monolithic multi-color light-emitting diode, a fluorescent film layer, and a highly reflective white glue arranged around the monolithic multi-color light-emitting diode and the fluorescent film layer; wherein the fluorescent film layer includes a silicone layer and a red fluorescent layer; the red fluorescent powder in the red fluorescent layer includes nitride fluorescent powder and / or fluoride fluorescent powder; when the red fluorescent powder is a fluoride fluorescent powder, the red fluorescent layer is further provided with a silicone protective layer on the side away from the monolithic multi-color light-emitting diode.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The single-chip multi-color light-emitting diode provided by the present invention can emit light of at least two colors, eliminating or reducing the use of fluorescent powder, and reducing the cost of RGB-LED backlight source.

[0046] (2) The monolithic multicolor light-emitting diode provided by the present invention solves the problem that the poor quality of the epitaxially grown buffer layer and the light-emitting layer crystals leads to increased non-radiative recombination, which in turn leads to low internal quantum efficiency of the light-emitting element.

[0047] (3) When the monolithic multi-color LED provided by the present invention is applied to an LED backlight source, the monolithic multi-color LED and a monochrome red light emitting diode are packaged together to form an LED backlight source, or the monolithic multi-color LED and a red phosphor are packaged together to form a white light LED backlight source, or the monolithic multi-color LED forms a single-chip LED that emits red, green and blue light simultaneously, thereby obtaining an LED backlight source with a high color gamut and high brightness.

[0048] (4) The monolithic multi-color light-emitting diode provided by the present invention can improve the crystal quality by thinning the thickness of the blue light quantum barrier layer (the thickness of the first barrier layer).

[0049] (5) In the monolithic multi-color light-emitting diode provided by the present invention, the thick barrier + thin well structure in the second light-emitting layer can reduce the energy band distortion and improve the average energy band.

[0050] (6) The monolithic multi-color light-emitting diode provided by the present invention sets H3 / H4=1~2, which can make the average energy bands of the first light-emitting layer and the second light-emitting layer close to each other, thereby improving the light-emitting efficiency.

[0051] (7) The monolithic multi-color light-emitting diode provided by the present invention has a second well layer thickness less than the first well layer thickness. The chip brightness is better than LED chips with the same blue light well and green light well thickness, and the brightness is increased by at least 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0053] Figure 1 The white light realization scheme with different NTSC values ​​provided by the present invention;

[0054] Figure 2 The peak wavelength and half-wave width parameters of different system LED phosphors provided by the present invention;

[0055] Figure 3 A schematic diagram of the first structure of the multicolor light-emitting layer provided by the present invention;

[0056] Figure 4 A schematic diagram of a second structure of the multicolor light-emitting layer provided by the present invention;

[0057] Figure 5 A schematic diagram of a third structure of the multicolor light-emitting layer provided by the present invention;

[0058] Figure 6 A schematic diagram of a fourth structure of the multicolor light-emitting layer provided by the present invention;

[0059] Figure 7 A fifth structural schematic diagram of the multicolor light-emitting layer provided by the present invention;

[0060] Figure 8 A sixth structural schematic diagram of the multicolor light-emitting layer provided by the present invention;

[0061] Fig. 9 A schematic diagram of the structure of a single-chip multi-color light-emitting diode provided by the present invention;

[0062] Fig.10 A schematic cross-sectional view of the structure of a front-mounted LED chip provided by the present invention;

[0063] Fig.11 A schematic cross-sectional view of the structure of a flip-chip LED chip provided by the present invention;

[0064] Fig.12 A schematic diagram of the structure of a white light LED provided by the present invention;

[0065] Fig.13 Another schematic diagram of the structure of the white light LED provided by the present invention;

[0066] Fig.14 The optical power spectrum distribution under different currents provided by the present invention;

[0067] Fig.15 The green light normalized relative intensity spectrum provided by the present invention.

[0068] Reference numerals:

[0069] 100-substrate; 101-first buffer layer; 102-second buffer layer; 103-third buffer layer; 110-N-type layer; 120-multicolor light-emitting layer; 121-first light-emitting layer; 122-second light-emitting layer; 130-P-type layer; 210-current blocking layer; 220-ohmic contact layer; 230-P-type electrode; 240-N-type electrode; 250-insulating protection layer; 261-first P-electrode; 262-second P-electrode; 271-first N-electrode; 272-second N-electrode. DETAILED DESCRIPTION

[0070] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0071] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0072] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0073] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0074] In a first aspect, the present invention provides a monolithic multi-color light emitting diode, which includes an N-type layer 110 , a P-type layer 130 , and a multi-color light emitting layer 120 disposed between the N-type layer 110 and the P-type layer 130 .

[0075] The multicolor light-emitting layer 120 includes a first light-emitting layer 121 that emits light of a first color, and a second light-emitting layer 122 that emits light of a second color.

[0076] Wherein, the peak wavelength λ of the second color light p2 Greater than the peak wavelength λ of the first color of light p1 , and λ p2 -λ p1 ≥50nm.

[0077] Among them, λ p2 -λ p1The value of includes, but is not limited to, any point value of 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, and 150 nm, or a range value between any two of them.

[0078] Furthermore, the thickness of the second well layer in the second light-emitting layer 122 (referring to the thickness of a single layer) is less than the thickness of the first well layer in the first light-emitting layer 121 (referring to the thickness of a single layer).

[0079] The single chip provided by the present invention can emit light emitting diodes of multiple different colors, can emit light of at least two colors, does not require or reduces the use of fluorescent powder, and reduces the cost of RGB-LED backlight sources.

[0080] LED emission from GaN-based III-V compound semiconductors, such as InGaN, AlGaN, AlInGaN and GaN, can cover the entire visible spectrum from short wavelengths (i.e. UV) to longer wavelengths (i.e. red light). For example, different colors / wavelengths of light can be emitted by adjusting the In concentration in the light-emitting well layer. In theory, the higher the In concentration, the longer the wavelength.

[0081] For example, the core structure of a blue-green dual-color LED chip is a green MQW (quantum well) structure and a blue MQW structure that are superimposed and grown together. Since the In concentration in the green MQW is much higher than that in the blue MQW, the two MQW structures will generate strong internal stress when they are superimposed and grown together, causing their growth quality to deteriorate and affecting product performance. This application solves the problem of poor crystal quality of the epitaxially grown buffer layer and the light-emitting layer, which leads to increased non-radiative recombination and low internal quantum efficiency of the light-emitting element by controlling the thickness of the second well layer to be less than that of the first well layer.

[0082] In some specific embodiments, the monolithic multicolor light-emitting diode provided by the present invention comprises at least a green light-emitting layer and a blue light-emitting layer, and the light-emitting diode has a green light emission peak and a blue light emission peak after being powered on. That is, the light of the first color comprises blue light, and the light of the second color comprises green light.

[0083] When applied to LED backlight sources, the blue-green light emitting diodes of the present application are packaged together with the monochromatic red light emitting diodes to form an LED backlight source. Alternatively, the blue-green light emitting diodes of the present application are packaged together with the red phosphor to form a white light LED backlight source, or the present application can form a single chip light emitting diode that can emit red, green and blue at the same time. Thus, an LED backlight source with a high color gamut and high brightness is obtained.

[0084] In some specific embodiments, the ratio of the thickness of the second well layer to the first well layer is 0.5 to 0.95, including but not limited to any point value of 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or any range value between two thereof; preferably 0.8 to 0.9. By adjusting the thickness ratio of the second well layer to the first well layer, the stress and crystal quality in the MQW can be controlled, thereby adjusting the brightness.

[0085] In some specific embodiments, the thickness of the second well layer is 27-32Å, including but not limited to any point value of 27Å, 28Å, 29Å, 30Å, 31Å, 32Å, or a range value between any two of them.

[0086] In some specific embodiments, the thickness of the first well layer is 33-38 Å, including but not limited to any point value of 33 Å, 34 Å, 35 Å, 36 Å, 37 Å, 38 Å, or a range value between any two of them.

[0087] In some specific embodiments, the first well layer includes In x1 Ga (1-x1) N, the second well layer includes In x2 Ga (1-x2) N, wherein 1>X2>X1>0.1, that is, the In concentration in the second well layer is greater than the In concentration in the first well layer. The value of X2 or X1 includes but is not limited to any point value of 0.11, 0.13, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9 or any range value between the two.

[0088] Light of different colors / wavelengths can be emitted by adjusting the In concentration in the light-emitting well layer. In theory, the higher the In concentration, the longer the wavelength.

[0089] In some specific embodiments, X2=0.22~0.28, including but not limited to any point value of 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28 or a range of values ​​between any two of them.

[0090] In some specific embodiments, X1=0.13~0.19, including but not limited to any point value of 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or a range of values ​​between any two of them.

[0091] In some specific embodiments, the first color of light includes blue light, and the second color of light includes green light.

[0092] In some specific embodiments, the peak wavelength λ of the first color of light is p1 =440~470nm; including but not limited to any point value of 440nm, 450nm, 460nm, 470nm or the range value between any two of them.

[0093] In some specific embodiments, the peak wavelength λ of the second color light is p2 =520~550nm; including but not limited to any point value of 520nm, 530nm, 540nm, 550nm or the range value between any two of them.

[0094] In some specific embodiments, in order to meet the high color gamut of white light LEDs, when the input current is ≥10mA, the ratio of the peak wavelength intensity of light of the first color to the peak wavelength intensity of light of the second color is ≥5, including but not limited to any point value of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range value between any two of them; preferably 5~10.

[0095] In some specific embodiments, the thickness of the second barrier layer in the second light-emitting layer 122 (single layer thickness) is greater than the thickness of the first barrier layer in the first light-emitting layer 121 (single layer thickness). The present invention can improve crystal quality and brightness by reducing the thickness of the blue light quantum barrier layer (the thickness of the first barrier layer).

[0096] In some specific embodiments, the thickness of the second barrier layer is 100-200Å, including but not limited to any point value of 100Å, 110Å, 120Å, 130Å, 140Å, 150Å, 160Å, 170Å, 180Å, 190Å, 200Å, or a range value between any two of them.

[0097] In some specific embodiments, the thickness of the first barrier layer is 90-100Å, including but not limited to 90Å, 91Å, 92Å, 93Å, 94Å, 95Å, 96Å, 97Å, 98Å, 99Å, 100Å, any one of which or a range between any two of them.

[0098] In some specific embodiments, the ratio of the sum of the thicknesses H2 of the second well layer and the second barrier layer to the sum of the thicknesses H1 of the first well layer and the first barrier layer is H2 / H1=0.9~1.1, including but not limited to any point value of 0.9, 0.95, 1, 1.01, 1.03, 1.05, 1.06, 1.08, 1.1 or a range value between any two of them; preferably, H2 / H1=1~1.1.

[0099] It can be understood that when H2 / H1 = 1, the sum of the thicknesses of the second well layer and the second barrier layer is equal to the sum of the thicknesses of the first well layer and the first barrier layer.

[0100] Preferably, the sum of the thicknesses of the second well layer and the second barrier layer H2>the sum of the thicknesses of the first well layer and the first barrier layer H1, that is, H2 / H1 is preferably greater than 1. The thick barrier + thin well structure in the green light emitting layer (i.e., the second light emitting layer 122) can reduce energy band distortion and improve the average energy band.

[0101] In some specific embodiments, the thickness ratio H3 of the second barrier layer and the second well layer is ≥ the thickness ratio H4 of the first barrier layer and the first well layer (i.e., H3 ≥ H4), preferably the ratio H3 / H4=1-2, including but not limited to any point value of 1, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or any range value between two of them. In this way, the average energy bands of the first light-emitting layer 121 and the second light-emitting layer 122 can be close to each other, thereby improving the light-emitting efficiency.

[0102] In some specific embodiments, the first barrier layer in the first light emitting layer 121 includes at least one of GaN, AlGaN or InAlGaN.

[0103] In some specific embodiments, the second barrier layer in the second light emitting layer 122 includes at least one of GaN, AlGaN or InAlGaN.

[0104] The first barrier layer and the second barrier layer may have the same composition or different compositions, which is not limited in the present invention.

[0105] In some specific implementations, the number of the first well layers is 10 to 20, preferably 10 to 15, and a first barrier layer is disposed between every two adjacent first well layers.

[0106] In some specific implementations, the number of the second well layers is 1 to 5, preferably 1 to 3, and the upper and lower sides adjacent to any second well layer are both second barrier layers.

[0107] In some specific embodiments, the first light-emitting layer 121 includes a first periodic structure in which a first well layer and a first barrier layer are alternately stacked. Preferably, the number of periods of the first periodic structure is 10 to 20, including but not limited to any point value of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20, or a range value between any two of them.

[0108] In some specific embodiments, the second light-emitting layer 122 includes a second periodic structure in which second well layers and second barrier layers are alternately stacked. More preferably, the number of periods of the second periodic structure is 1 to 5, including but not limited to any point value of 1, 2, 3, 4, 5 or a range value between any two of them.

[0109] In some specific embodiments, the number of the first well layers is 4 to 20 times the number of the second well layers, including but not limited to 4 times, 5 times, 6 times, 7 times, 8 times, 10 times, 12 times, 13 times, 14 times, 15 times, 16 times, 18 times, 20 times, any one of the point values ​​or the range value between any two thereof; preferably 6 to 15 times.

[0110] In some specific implementations, see Figure 3 As shown, the multicolor light-emitting layer 120 includes 9 first well layers (denoted as W1) and 1 second well layer (denoted as W2), that is, a total of 10 light-emitting well layers, and a light-emitting barrier layer is arranged between every two adjacent light-emitting well layers. Among them, 9 first well layers are close to the N-type layer 110 and emit blue light. One second well layer is closest to the P-type layer 130 and emits green light. Among them, the In concentration of the second well layer is greater than the In concentration in the first well layer, and the thickness of the second well layer is less than the thickness of the first well layer. The first well layer W1 and the second well layer W2 are both InGaN materials, the difference is that the In content in the second well layer is greater than the In content in the first well layer, so that the first well layer and the second well layer emit light of different wavelengths.

[0111] A first barrier layer (denoted as B1) is disposed between every two adjacent first well layers and between the last first well layer and the first second well layer, and a second barrier layer (denoted as B2) is disposed between the second well layer and the P-type layer 130. The thickness of the second barrier layer is greater than that of the first barrier layer. Both the first barrier layer and the second barrier layer are GaN layers.

[0112] In some specific implementations, see Figure 4 As shown, the multicolor light-emitting layer 120 includes 12 first well layers (denoted as W1) and 1 second well layer (denoted as W2), that is, a total of 13 light-emitting well layers. Among them, the 12 first well layers close to the N-type layer 110 are blue light well layers. The 1 second well layer close to the P-type layer 130 is a green light well layer. A first barrier layer (denoted as B1) is arranged between every two adjacent first well layers. A second barrier layer (denoted as B2) is arranged on the side of the second well layer close to the P-type layer 130. The thickness of the second well layer is less than the thickness of the first well layer, and the number of the first well layers W1 is 12 times the number of the second well layers W2. The sum H2 of the thickness of a pair of second barrier layers and the second well layer is greater than the sum H1 of the thickness of a pair of first barrier layers and the first well layer, that is, H2 / H1 is greater than 1. The thickness of the second barrier layer is greater than the thickness of the first barrier layer. Both the first barrier layer and the second barrier layer are GaN layers.

[0113] In some specific embodiments, the energy band of the second well layer in the second light emitting layer 122 is lower than the energy band of the first well layer in the first light emitting layer 121 , so that the light emission wavelength of the second light emitting layer 122 is longer than that of the first light emitting layer 121 .

[0114] In some specific embodiments, the second barrier energy band in the second light-emitting layer 122 is lower than the first barrier energy band in the first light-emitting layer 121. This can reduce the QCSE effect (quantum confined Stark effect) in the second light-emitting layer 122.

[0115] In some specific implementations, the first barrier layer is an AlGaN+GaN blue barrier layer, such as growing GaN first, then growing AlGaN, and then growing GaN. The second barrier layer is a GaN green barrier layer, but may also contain AlGaN, with a lower Al content than the first barrier layer.

[0116] In some specific implementations, see Figure 5 As shown, the multicolor light-emitting layer 120 includes 12 first well layers and 1 second well layer, that is, a total of 13 light-emitting well layers. The thickness of the second well layer is less than the thickness of the first well layer, and the number of the first well layers is 12 times the number of the second well layers. The first light-emitting layer 121 is arranged at one end close to the N-type layer 110, and the second light-emitting layer 122 is arranged at one end close to the P-type layer 130. Second barrier layers (denoted as B2) are respectively arranged on both sides of the second well layer. At least one group of the first barrier layers (denoted as B1) between adjacent first well layers has an energy level higher than that of the second barrier layer. For example, at least one first barrier layer is an AlGaN layer or an InAlGaN layer, and the second barrier layer is a GaN layer. The thickness of the second barrier layer is greater than the thickness of the first barrier layer.

[0117] In some specific implementations, the direction from the N-type layer 110 to the P-type layer 130 is defined as the first direction, and the energy band of the second barrier layer is from low to high in the first direction, such as first growing GaN and then growing AlGaN, or first growing InGaN with a low In component and then growing GaN. This can improve the serious quantum confined Stark effect (QCSE effect) in the second light-emitting layer 122.

[0118] In some specific implementations, the energy band of the first barrier layer is from high to low in the first direction, such as growing AlGaN first and then growing GaN, or growing GaN first and then growing InGaN with low In content. This can improve the growth interface quality of the barrier layer and the well layer in the first light-emitting layer 121.

[0119] In some specific embodiments, Al is doped between the second well layer and the second barrier layer in the second light-emitting layer 122. That is, a small amount of Al is doped at the junction of the second well layer and the second barrier layer in the second light-emitting layer 122. This can reduce device leakage current.

[0120] In some specific implementations, the thickness of the Al layer is less than 1 / 3 of the thickness of the second well layer.

[0121] In some specific embodiments, when the injected current is 350 mA, the brightness of the monolithic multi-color light-emitting diode is ≥ 770 mW, including but not limited to any point value of 770 mW, 775 mW, 780 mW, 785 mW, 790 mW, 800 mW or a range value between any two of them; preferably 770~790 mW.

[0122] In some specific implementations, see Figure 6 As shown, the first light-emitting layer 121 is arranged at one end close to the N-type layer 110, and the second light-emitting layer 122 is arranged at one end close to the P-type layer 130. A first barrier layer is arranged between every two adjacent first well layers, and a second barrier layer is arranged on the side of the second well layer close to the P-type layer 130. The first barrier layer is a GaN / AlGaN / GaN structure ( Figure 6 The raised part in the middle is AlGaN. The inclusion of Al increases the energy level and increases the barrier layer's blocking ability as a barrier layer). The second barrier layer is GaN.

[0123] In some specific embodiments, the second light-emitting layer 122 may be located between the first light-emitting layer 121 and the P-type layer 130, or between the N-type layer 110 and the first light-emitting layer 121. Figure 7 As shown, the second light-emitting layer 122 emitting long wavelengths is closer to the N-type layer 110, and includes a plurality of second well layers W2 and second barrier layers B2 that are alternately stacked; the first light-emitting layer emitting shorter wavelengths is closer to the P-type layer 130, and includes a plurality of first well layers W1 and first barrier layers B1 that are alternately stacked; wherein the thickness of the second well layer W2 is less than the thickness of the first well layer W1, and the thickness of the second barrier layer B2 is greater than the thickness of the first barrier layer B1. At the same time, the sum of the thickness of the first barrier layer and the first well layer in one period is less than the sum of the thickness of the second barrier layer and the second well layer in one period. The number of the first well layer is greater than the second well layer, and the luminous intensity of the first light-emitting layer 121 is greater than the luminous intensity of the second light-emitting layer 122.

[0124] In some specific embodiments, the second light-emitting layer 122 is located in the middle of the first light-emitting layer 121, such as Figure 8 shown.

[0125] The relative positions of the first light-emitting layer 121 and the second light-emitting layer 122 are related to the number of the second well layers. When the number of the second well layers (green light wells) is greater than 3, the second light-emitting layer 122 is disposed at one end close to the N-type layer 110; when the number of the second well layers (green light wells) is less than 3, the second light-emitting layer 122 is disposed at one end close to the P-type layer 130.

[0126] In some specific implementations, see Fig. 9 As shown, the epitaxial structure layer of the monolithic multi-color light-emitting diode comprises at least a substrate 100, and a first buffer layer 101, an N-type layer 110, a second buffer layer 102, a third buffer layer 103, a first light-emitting layer 121, a second light-emitting layer 122 and a P-type layer 130 sequentially grown on the substrate 100. The substrate 100 comprises a sapphire-based substrate 100, a silicon substrate 100, a GaN-based substrate 100, a GaAS-based substrate 100, etc.; the first buffer layer 101 is at least one of an AlN layer, a GaN layer, and an AlGaN layer. When the material of the substrate 100 is inconsistent with the N-type material, such as the substrate 100 is sapphire, it is used to alleviate the lattice mismatch between the sapphire substrate 100 and the N-type layer 110; the N-type layer 110 is usually a nitride semiconductor layer doped with n-type impurities, which is used to provide electrons, such as a Si-doped GaN layer; the second buffer layer 102 and the second buffer layer 130 are respectively formed of a nitride semiconductor layer doped with n-type impurities and a first buffer layer 101 and a second buffer layer 130. 102 is located between the multi-color light-emitting layer 120 and the N-type layer 110, and plays a role of buffer transition. The second buffer layer 102 and the third buffer layer 103 are generally structures of alternating InGaN layers and GaN layers, wherein the In content of the InGaN layer of the second buffer layer 102 is less than the In content of the InGaN layer of the third buffer layer 103, and the In content of the InGaN layer of the third buffer layer 103 is less than the In content in the well layer of the multi-color light-emitting layer 120; the P-type layer 130 is generally a nitride layer doped with P-type impurities, used to provide holes, such as a Mg-doped GaN layer.

[0127] In some specific implementations, the epitaxial structure can be prepared into a positive structure chip, a flip-chip structure chip, a vertical structure chip, and a high-voltage structure chip as needed. Although the chip structure types are different, they all include a P electrode (P-PAD) electrically connected to the P-type layer 130, and an N electrode electrically connected to the N-type GaN layer. The P electrode and the N electrode are connected to an external power source and emit light under the action of an external current. The luminous efficiency of the light-emitting layer will be different for different currents.

[0128] like Fig.10The structure diagram of the front-mounted LED chip is shown, which includes a P-type electrode 230 electrically connected to the P-type layer 130, and an N-type electrode 240 electrically connected to the N-type layer 110; an insulating protective layer 250 is arranged on the LED chip, and is provided with openings exposing the P-type electrode 230 and the N-type electrode 240; a current blocking layer 210 is also arranged between the P-type electrode 230 and the P-type layer 130, and an ohmic contact layer 220 is arranged on the current blocking layer 210, and the current blocking layer 210 is a film layer formed by one or more materials of SiO2, SiN2, Al2O3, and TiO2 materials, and its shape is basically the same as that of the P electrode. The ohmic contact layer 220 is usually one or more of a conductive transparent film layer or a conductive reflective film layer, and is a transparent conductive film layer in the front-mounted product, such as ITO.

[0129] like Fig.11 The figure shows a schematic diagram of the structure of a flip-chip LED chip. In the flip-chip structure, the ohmic contact layer 220 can be one or more of an ITO transparent conductive layer or an Ag reflective layer or an Al reflective layer, such as an ITO layer and an Ag reflective layer; the insulating protective layer 250 and the current blocking layer 210 can include a distributed Bragg reflective layer in addition to a single protective film layer. The second P electrode 262 and the second N electrode 272 are electrically connected to the first P electrode 261 and the first N electrode 271 respectively through the opening of the non-protective layer.

[0130] In some specific embodiments, the chip size is 25×51mil 2 When the injection current is 350mA, the brightness of a single blue LED chip is 890-900mW, the brightness of a blue-green LED chip with equal thickness of the blue light well (i.e., the first well layer) and the green light well (i.e., the second well layer) is 680-700mW, and the brightness of a blue-green LED chip with the structure of the present invention (thin green light well, i.e., the thickness of the second well layer < the thickness of the first well layer) is 770-790mW. It can be seen that the brightness of the single-chip multi-color light-emitting diode chip provided by the present invention is better than that of a blue-green LED chip with the same thickness of the blue light well and the green light well. The brightness is increased by at least 10%.

[0131] In a second aspect, the present invention provides an LED backlight source, which includes an RGB-LED and a white light LED, wherein the RGB-LED or the white light LED contains the above-mentioned single-chip multi-color light-emitting diode.

[0132] In some specific implementations, the RGB-LED includes the monolithic multi-color light emitting diode and a monochromatic red light emitting diode.

[0133] In some specific implementations, the white light LED is formed by combining the monolithic multi-color light emitting diode with phosphor.

[0134] In some specific implementations, the white light LED includes the single multi-color light emitting diode, a fluorescent film layer, and a highly reflective white glue disposed around (all around) the single multi-color light emitting diode and the fluorescent film layer. The fluorescent film layer includes a silicone layer and a red fluorescent layer.

[0135] White LEDs are formed by packaging a monolithic multi-color light-emitting diode, see Fig.12 As shown, it is a chip-level package, which is formed by setting a fluorescent film layer on the light-emitting surface of the blue-green dual-wavelength LED chip of the flip-chip structure, and setting high-reflective white glue around the fluorescent film layer and the LED chip. The fluorescent film layer is a wavelength conversion film layer formed by mixing silica gel and red fluorescent film.

[0136] In some specific implementations, the red phosphor in the red phosphor layer includes nitride phosphor and / or fluoride phosphor.

[0137] In some specific implementations, when the red phosphor is a fluoride phosphor, a silicone protective layer is further provided on a side of the red phosphor layer away from the monolithic multi-color light emitting diode.

[0138] When the phosphor is a KSF fluorescent film, in order to protect the KSF fluorescent film layer, a transparent silicone protective layer can be firstly provided on the light emitting surface of the fluorescent film layer, and then a highly reflective white glue can be provided. Fig.13 As shown. Among them, KSF phosphor (K2SiF6:Mn 4+ ) belongs to the fluoride system phosphor, which will be severely degraded in high temperature and high humidity and high temperature environment, showing brightness attenuation and color drift. The present invention provides a transparent silica gel protective layer, which can solve the problem of "KSF phosphor being severely degraded in high temperature and high humidity and high temperature environment, resulting in brightness attenuation and color drift".

[0139] In some specific embodiments, when the input current is ≥10mA, the ratio of the peak wavelength intensity of the first color of light (blue light) to the peak wavelength intensity of the second color of light (green light) is ≥5, preferably 5~10. After a red fluorescent film layer is set on the surface of the blue-green dual-wavelength LED chip, it is packaged to form a white light LED. In the process of forming the white light spectrum, a part of the blue light excites the red fluorescence to form red light. Therefore, in the spectrum of the white light LED, the peak intensity of the blue light will be significantly reduced, but the peak intensity of the green light spectrum remains basically unchanged. In order to meet the high color gamut of white light LEDs, the peak intensity of blue light in the white light spectrum also needs to meet certain requirements. Therefore, when setting up the blue-green dual-wavelength LED chip, it is necessary to set the ratio of the peak intensity of the blue light wavelength to the peak intensity of the green light wavelength. Fig.14 Shown is the optical power spectrum distribution at different currents.

[0140] like Fig.15 The figure shows the normalized relative intensity spectrum of green light. Among them, curve 1 is the spectrum curve of single blue LED chip + green powder + red powder; curve 2 is the spectrum curve of blue-green dual-color LED chip; curve 3 is the spectrum curve of blue-green dual-color LED chip + red phosphor. Compared with curve 1 and curve 3, the half width of the green light spectrum of curve 3 is significantly smaller than that of curve 1; compared with curve 2 and curve 3, the peak intensity of blue light is weak, and the peak intensity of green light has basically not changed, so it can be determined that the red phosphor is mainly excited by blue light.

[0141] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A monolithic multi-color light emitting diode, characterized in that: including a multicolor light-emitting layer disposed between an N-type layer and a P-type layer; The multicolor light-emitting layer includes a first light-emitting layer that emits light of a first color and a second light-emitting layer that emits light of a second color; wherein the peak wavelength λ of the light of the second color is p2 Greater than the peak wavelength λ of the first color of light p1 , and λ p2 -λ p1 ≥50nm; The thickness of the second well layer in the second light-emitting layer is less than the thickness of the first well layer in the first light-emitting layer; Al is doped between the second well layer and the second barrier layer in the second light-emitting layer; and the thickness of the layer doped with Al is less than 1 / 3 of the thickness of the second well layer.

2. The monolithic multi-color light emitting diode according to claim 1, characterized in that: At least one of the following conditions is met: (1) A ratio of the thickness of the second well layer to the thickness of the first well layer is 0.5 to 0.95; (2) The thickness of the second well layer is 27-32 Å; (3) The thickness of the first well layer is 33~38Å.

3. The monolithic multi-color light emitting diode according to claim 1, characterized in that: The first well layer includes In x1 Ga (1-x1) N, the second well layer includes In x2 Ga (1-x2) N, where 1>X2>X1>0.

1.

4. The monolithic multi-color light emitting diode according to claim 3, characterized in that: The X2=0.22~0.28; and / or, the X1=0.13~0.

19.

5. The monolithic multi-color light emitting diode according to claim 1, characterized in that: At least one of the following conditions is met: (1) The light of the first color includes blue light, and the light of the second color includes green light; (2) The peak wavelength λ of the first color light p1 =440~470nm; (3) The peak wavelength λ of the second color light p2 =520~550nm; (4) When the input current is ≥10 mA, the ratio of the peak wavelength intensity of the light of the first color to the peak wavelength intensity of the light of the second color is ≥5.

6. The monolithic multi-color light emitting diode according to claim 1, characterized in that: The second light-emitting layer includes a second barrier layer, the first light-emitting layer includes a first barrier layer, and the monolithic multi-color light-emitting diode satisfies at least one of the following conditions: (1) The thickness of the second barrier layer is greater than the thickness of the first barrier layer; (2) The thickness of the second barrier layer is 100~200Å; (3) The thickness of the first barrier layer is 90~100Å; (4) a ratio H2 / H1 of the sum of the thicknesses of the second well layer and the second barrier layer to the sum of the thicknesses of the first well layer and the first barrier layer = 0.9 to 1.1; (5) A thickness ratio H3 between the second barrier layer and the second well layer is ≥ a thickness ratio H4 between the first barrier layer and the first well layer, and H3 / H4=1-2.

7. The monolithic multi-color light emitting diode according to claim 1, characterized in that: The first barrier layer in the first light-emitting layer comprises at least one of GaN, AlGaN or InAlGaN; And / or, the second barrier layer in the second light emitting layer includes at least one of GaN, AlGaN or InAlGaN.

8. The monolithic multi-color light emitting diode according to claim 1, characterized in that: The number of the first well layers is 10 to 20, and a first barrier layer is disposed between every two adjacent first well layers; And / or, the number of the second well layers is 1 to 5, and a second barrier layer is disposed on both sides of each of the second well layers.

9. The monolithic multi-color light emitting diode according to claim 1, characterized in that: The first light-emitting layer comprises a first periodic structure in which first well layers and first barrier layers are alternately stacked, and the number of periods of the first periodic structure is 10 to 20; And / or, the second light-emitting layer includes a second periodic structure in which second well layers and second barrier layers are alternately stacked, and the number of periods of the second periodic structure is 1-5.

10. The monolithic multi-color light emitting diode according to claim 8 or 9, characterized in that: The number of the first well layers is 4 to 20 times the number of the second well layers.

11. The monolithic multi-color light emitting diode according to claim 1, characterized in that: At least one of the following conditions is met: (1) The energy band of the second well layer in the second light-emitting layer is lower than the energy band of the first well layer in the first light-emitting layer; (2) The energy band of the second barrier layer in the second light-emitting layer is lower than the energy band of the first barrier layer in the first light-emitting layer; (3) A direction from the N-type layer to the P-type layer is defined as a first direction, an energy band of the second barrier layer in the second light-emitting layer is from low to high in the first direction, and an energy band of the first barrier layer in the first light-emitting layer is from high to low in the first direction.

12. The monolithic multi-color light emitting diode according to claim 1, characterized in that: When the injected current is 350 mA, the brightness of the single-chip multi-color light-emitting diode is ≥770 mW.

13. An LED backlight source, characterized in that: The LED backlight source includes RGB-LED and white light LED, and the RGB-LED or the white light LED contains the single-chip multi-color light-emitting diode as described in any one of claims 1 to 12.

14. The LED backlight source according to claim 13, characterized in that: At least one of the following conditions is met: (1) The RGB-LED includes the monolithic multi-color light-emitting diode and the monochromatic red light-emitting diode; (2) The white light LED comprises the single-chip multi-color light-emitting diode, a fluorescent film layer, and a highly reflective white glue arranged around the single-chip multi-color light-emitting diode and the fluorescent film layer; wherein the fluorescent film layer comprises a silicone layer and a red fluorescent layer; the red fluorescent powder in the red fluorescent layer comprises a nitride fluorescent powder and / or a fluoride fluorescent powder; when the red fluorescent powder is a fluoride fluorescent powder, the red fluorescent layer is further provided with a silicone protective layer on a side away from the single-chip multi-color light-emitting diode.

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