Multi-wavelength light emitting diode and light emitting module

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a multi-wavelength light emitting diode and a light emitting module. According to the multi-wavelength light-emitting diode, a multi-quantum well layer comprises n groups of quantum well light-emitting units with different forbidden bandwidths; the n group of quantum well light-emitting units and the (n-1) group of quantum well light-emitting units meet at least one of the following characteristics: (a) the concentration of In in at least one well layer of the n group of quantum well light-emitting units is greater than the concentration of In in at least one well layer of the (n-1) group of quantum well light-emitting units; and (b) the thickness of at least one well layer of the n group of quantum well light-emitting units is greater than that of at least one well layer of the (n-1) group of quantum well light-emitting units. Through the arrangement of the multiple groups of quantum well light-emitting units, under the condition that multiple wavelengths can be generated, stress is fully released, and the photoelectric conversion efficiency is improved.

Description

Technical Field

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

[0002] Light Emitting Diode (LED) is a light-emitting device that can efficiently convert electrical energy into light energy. It releases energy and emits light through the recombination of electrons and holes. It is widely used in the fields of lighting and display. In the prior art, in order to improve the display index of white light LED, dual-wavelength or multi-wavelength blue light-emitting diodes have been developed to excite phosphors to generate white light as a lighting source or display light source.

[0003] The existing disclosed white light emitting module has a wide-band blue light emitting chip and a wavelength conversion layer. The luminescent stack of the wide-band blue light emitting chip emits blue light of multiple wavelengths. At least one of the multiple quantum well layers close to the N-type semiconductor layer can emit the longest wavelength quantum well layer, and the quantum well layer close to the P-type semiconductor layer is the quantum well layer that emits the shortest wavelength. Since multiple groups of light-emitting quantum wells are set up, and the growth conditions of the well layers corresponding to different wavelengths are quite different, this leads to insufficient stress release of the epitaxial structure, resulting in a significant decrease in the luminous efficiency of this multi-wavelength chip compared with the single-wavelength chip. At the same time, the white light spectrum generated by this method has a higher blue light component, and the stronger blue light, especially the short blue light, is easy to cause damage to the human eye. Therefore, it is of great significance to obtain a waveform closer to the standard light source in the blue light band under the premise of ensuring the photoelectric conversion efficiency of the LED chip, so as to cooperate with the wavelength conversion material to produce a spectrum closer to natural light.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One object of the present invention is to provide a multi-wavelength light emitting diode that can generate multiple wavelengths to help obtain a spectrum closer to natural light while fully releasing stress and improving photoelectric conversion efficiency.

[0006] Another object of the present invention is to provide a light emitting module.

[0007] In order to achieve the above-mentioned object of the present invention, the present invention provides a multi-wavelength light emitting diode, comprising: A substrate, and an N-type semiconductor layer, a stress release layer, a multi-quantum well layer and a P-type semiconductor layer sequentially arranged on the substrate; the multi-quantum well layer comprises n groups of quantum well light-emitting units with different bandgap widths to respectively generate n groups of light with different wavelengths, where n≥3; A direction from close to the N-type semiconductor layer to close to the P-type semiconductor layer is defined as a first direction. The n groups of quantum well light-emitting units along the first direction are respectively the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units; each group of quantum well light-emitting units includes at least one well layer and one barrier layer, and the nth group of quantum well light-emitting units and the n-1th group of quantum well light-emitting units meet at least one of the following characteristics: (a) the concentration of In in at least one well layer of the nth group of quantum well light-emitting units is greater than or equal to the concentration of In in at least one well layer of the n-1th group of quantum well light-emitting units; (b) The thickness of at least one well layer of the nth group of quantum well light-emitting units is greater than the thickness of at least one well layer of the n-1th group of quantum well light-emitting units.

[0008] In a specific embodiment of the present invention, the wavelength of light generated by the nth group of quantum well light-emitting units is greater than the wavelength of light generated by the n-1th group of quantum well light-emitting units.

[0009] In a specific embodiment of the present invention, the wavelength of light generated by the first group of quantum well light-emitting units is greater than the wavelength of light generated by the n-1th group of quantum well light-emitting units.

[0010] In a specific embodiment of the present invention, the wavelengths of light generated by the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are λ 1 , 2 , …, λ n-1 , n ; Each wavelength satisfies: λ 1 ≥λ 2 ≥…≥λ n-1 ,λ n-1 ≤λ n ≤λ 1 The quantum well light-emitting unit that is next to the P-type semiconductor layer (the n-1th group of quantum well light-emitting units) has the shortest light-emitting wavelength.

[0011] In a specific embodiment of the present invention, the difference in wavelength of light generated by adjacent groups of quantum well light-emitting units is ≤25nm. Further, the wavelength of light generated by the first group of quantum well light-emitting units is 450-475nm; the wavelength of light generated by the n-1th group of quantum well light-emitting units is 430-450nm; the wavelength of light generated by the nth group of quantum well light-emitting units is 440-470nm.

[0012] In a specific embodiment of the present invention, when the nth group of quantum well light-emitting units and the n-1th group of quantum well light-emitting units meet feature (a), the concentrations of In in the single well layers of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are c1 、c 2 ,…,c n-1 、c n ; Each concentration satisfies c n ≥c n-1 , c 1 ≥c 2 ≥…≥c n-1 At the same time, the thickness of the single well layer of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are defined as h 1 、h 2 ,…,h n-1 、h n ; Among them, h 1 ≥h 2 ≥…≥h n-1 ,h n With h n-1 Satisfy: h n >h n-1 or h n <h n-1 or h n =h n-1 .

[0013] In a specific embodiment of the present invention, when the nth group of quantum well light-emitting units and the n-1th group of quantum well light-emitting units meet the characteristic (b), the thickness of the single well layer of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units is h respectively. 1 、h 2 ,…,h n-1 、h n ; Each thickness satisfies: h n >h n-1 ,h 1 ≥h 2 ≥…≥h n-1 At the same time, the concentrations of In in the well layers of the first group, the second group, ..., the n-1th group, and the nth group of quantum well light-emitting units are defined as c 1 、c 2 ,…,c n-1 、c n ; Among them, c 1 ≥c 2 ≥…≥c n-1 , c n-1 With c n Satisfies: c n >c n-1 or c n =c n-1 or c n <c n-1 .

[0014] Furthermore, the thickness difference between the single well layer of the nth group of quantum well light-emitting units and the single well layer of the n-1th group of quantum well light-emitting units is 1 to 15Å, preferably 2 to 10Å.

[0015] In a specific embodiment of the present invention, the thicknesses of the barrier layers of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are t 1 ,t 2 ,…,t n-1 ,t n ; Each thickness meets: t n ≥t n-1 , t 1 ≥t 2 ≥…≥t n-1 .

[0016] In a specific embodiment of the present invention, a well layer and a barrier layer in a quantum well light-emitting unit are defined as a period, and the number of periodic structures of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are respectively X 1 , X 2 , …, X n-1 , X n ; The number of periodic structures satisfies: X n-1 >X 1 , X n-1 >X n , X n-1 >X 2 .

[0017] Another aspect of the present invention provides a light-emitting module, comprising any one of the above-mentioned light-emitting diodes and a wavelength conversion unit; the light generated by the light-emitting diode passes through the wavelength conversion unit and then is mixed to generate white light.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The light-emitting diode of the present invention generates multiple wavelengths by setting up multiple groups of quantum well light-emitting units to obtain a light-emitting spectrum close to sunlight; at the same time, by adjusting the In content and / or the thickness of the well layer in the quantum well light-emitting unit closest to the P-type semiconductor layer, the stress between the multi-quantum well layer and the P-type semiconductor layer is fully released, thereby improving the light-emitting efficiency; (2) The light-emitting diode of the present invention has a waveform that is closer to the blue light band of a standard light source and, when combined with a wavelength conversion material, can produce a spectrum that is closer to natural light. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 1 A schematic diagram of the epitaxial structure of a light emitting diode provided in an embodiment of the present invention; Figure 2 A schematic diagram of the structure of a multi-quantum well layer provided by an embodiment of the present invention; Figure 3 A schematic diagram of the structure of a light emitting diode provided in an embodiment of the present invention; Figure 4 A schematic diagram of the bandgap structure of a multi-quantum well layer provided in Example 1 of the present invention; Figure 5 A schematic diagram of the bandgap structure of a multi-quantum well layer provided in Example 2 of the present invention; Figure 6 A schematic diagram of the bandgap structure of a multi-quantum well layer provided in Example 3 of the present invention; Figure 7 A schematic diagram of the bandgap structure of a multi-quantum well layer provided in Example 4 of the present invention; Figure 8 A schematic diagram of the bandgap structure of a multi-quantum well layer provided in Example 5 of the present invention; Fig. 9 A schematic diagram of the bandgap structure of a multi-quantum well layer provided in Example 6 of the present invention; Fig.10 Spectra generated by the light emitting diode of Example 6 of the present invention at different currents; Fig.11 This is a comparison chart of the luminous efficiency of the light emitting diode of Example 6 of the present invention and a traditional light emitting diode at 60 mA.

[0021] Reference numerals: 10-substrate; 20-buffer layer; 30-N-type semiconductor layer; 40-stress release layer; 50-multi-quantum well layer; 60-P-type semiconductor layer; 51-the first group of quantum well light-emitting units; 52-the second group of quantum well light-emitting units; 53-the n-1th group of quantum well light-emitting units; 54-the nth group of quantum well light-emitting units; 510a-well layer of the first group of quantum well light-emitting units; 510b-barrier layer of the first group of quantum well light-emitting units; 520a-well layer of the second group of quantum well light-emitting units; 520b-the second group of quantum well The barrier layer of the light-emitting unit; 530a-the well layer of the n-1th group of quantum well light-emitting units; 530b-the barrier layer of the n-1th group of quantum well light-emitting units; 540a-the well layer of the nth group of quantum well light-emitting units; 540b-the barrier layer of the nth group of quantum well light-emitting units; 511-the first well layer; 512-the first barrier layer; 521-the second well layer; 522-the second barrier layer; 531-the third well layer; 532-the third barrier layer; 541-the fourth well layer; 542-the fourth barrier layer; 551-the fifth well layer; 552-the fifth barrier layer. DETAILED DESCRIPTION

[0022] 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.

[0023] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the 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 element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0024] In multi-wavelength LED technology, for example, dual blue wavelength light-emitting devices, the light-emitting quantum well structure is to first grow 2 to 3 cycles of blue-green quantum wells with an emission peak of 460 to 480nm, and then grow 2 to 3 cycles of blue-violet quantum wells with an emission peak of 430 to 450nm; then excite the yellow light phosphor to form a white light LED. According to the color rendering index, the color rendering index of the white light LED packaged with dual blue light chips is significantly higher than that of the white light LED formed by a single blue light chip. However, in the existing multi-wavelength LED technology, it is impossible to take into account the photoelectric conversion efficiency of the LED chip and make the spectrum close to the natural light spectrum.

[0025] Based on this, the present invention provides a multi-wavelength light emitting diode, Figure 1 A schematic diagram of a light-emitting diode epitaxial structure provided in an embodiment of the present invention, wherein the light-emitting diode epitaxial structure comprises: A substrate 10, and a buffer layer 20, an N-type semiconductor layer 30, a stress release layer 40, a multi-quantum well layer 50 and a P-type semiconductor layer 60 are sequentially arranged on the substrate 10. The multi-quantum well layer includes n groups of quantum well light-emitting units with different bandgap widths to respectively generate n groups of light with different wavelengths, n≥3, such as n can be a natural number such as 3, 4, 5, 6, etc., but is not limited thereto.

[0026] Figure 2 A schematic diagram of the structure of a multi-quantum well layer provided in an embodiment of the present invention. In the multi-quantum well layer 50, a direction from close to the N-type semiconductor layer 30 to close to the P-type semiconductor layer 60 is defined as a first direction, and n groups of quantum well light-emitting units along the first direction are respectively the first group of quantum well light-emitting units 51, the second group of quantum well light-emitting units 52, ..., the n-1th group of quantum well light-emitting units 53 and the nth group of quantum well light-emitting units 54.

[0027] The nth group of quantum well light emitting units 54 and the n-1th group of quantum well light emitting units 53 satisfy at least one of the following characteristics: (a) the concentration of In in the well layer 540a of the nth group of quantum well light-emitting units is greater than or equal to the concentration of In in the well layer 530a of the n-1th group of quantum well light-emitting units; (b) The thickness of the well layer 540 a of the n-th group of quantum well light-emitting units is greater than the thickness of the well layer 530 a of the n-1-th group of quantum well light-emitting units.

[0028] When the light-emitting diode satisfies one or two of (a) and (b), the nth group of quantum well light-emitting units 54 can fully release the stress between the multi-quantum well layer 50 and the P-type semiconductor layer 60, and achieve the effect of supplementing the relatively weak light-emitting intensity of the first group of quantum well light-emitting units 51. At the same time, fully releasing the stress can significantly improve the light-emitting efficiency of the device.

[0029] The multi-wavelength light-emitting diode of the present invention may satisfy only condition (a), only condition (b), or both condition (a) and condition (b). When condition (a) is satisfied, the thickness of the well layer of each quantum well light-emitting unit can be set in a conventional manner, and the well layer 540a of the nth group of quantum well light-emitting units has an In concentration higher than or equal to that of the well layer 530a of the n-1th group of quantum well light-emitting units, thereby changing the distribution of carriers in the entire multi-quantum well layer 50 and making the carrier distribution closer to the P-type semiconductor layer 60, which helps to improve the brightness. In addition, the wavelength of the light generated by the nth group of quantum well light-emitting units 54 is close to the wavelength of the light generated by the first group of quantum well light-emitting units 51, which can enhance the luminous brightness of the first group of quantum well light-emitting units 51. When (b) is satisfied, the concentration of In in the well layer of the quantum well light-emitting unit can be set conventionally. The well layer 540a of the nth group of quantum well light-emitting units has a thickness greater than that of the well layer 530a of the n-1th group of quantum well light-emitting units. The energy barrier of the well layer 540a of the nth group of quantum well light-emitting units is low, which can pull the energy band of the entire light-emitting area, change the distribution of carriers in the entire multi-quantum well layer 50, and make the carrier distribution closer to the P-type semiconductor layer 60, which helps to improve the brightness.

[0030] In the embodiment of the present invention, as an optional embodiment, the wavelength of the light generated by the nth group of quantum well light emitting units 54 is greater than the wavelength of the light generated by the n-1th group of quantum well light emitting units 53. In actual operation, if the first group of quantum well light emitting units 51 and the nth group of quantum well light emitting units 54 are grown under the same conditions, since the nth group of quantum well light emitting units 54 are closer to the P-type semiconductor layer 60, its electron-hole recombination efficiency is higher under a small current, and the nth group of quantum well light emitting units 54 can enhance the intensity of the light generated by the first group of quantum well light emitting units 51.

[0031] In an embodiment of the present invention, as an optional embodiment, the wavelength of light generated by the first group of quantum well light emitting units 51 close to the N-type semiconductor layer is greater than the wavelength of light generated by the n-1th group of quantum well light emitting units 53 .

[0032] Figure 2A schematic diagram of the structure of a multi-quantum well layer provided in an embodiment of the present invention, wherein the multi-quantum well layer 50 includes, along a first direction, a first group of quantum well light-emitting units 51, a second group of quantum well light-emitting units 52, ..., an n-1th group of quantum well light-emitting units 53 and an nth group of quantum well light-emitting units 54. Each group of quantum well light-emitting units includes at least one periodic structure of well layers and barrier layers alternately stacked, such as the first group of quantum well light-emitting units 51 includes the well layers 510a of the first group of quantum well light-emitting units and the barrier layers 510b of the first group of quantum well light-emitting units alternately stacked, the second group of quantum well light-emitting units 52 includes the well layers 520a of the second group of quantum well light-emitting units and the barrier layers 520b of the second group of quantum well light-emitting units alternately stacked, the n-1th group of quantum well light-emitting units 53 includes the well layers 530a of the n-1th group of quantum well light-emitting units and the barrier layers 530b of the n-1th group of quantum well light-emitting units alternately stacked, and the nth group of quantum well light-emitting units 54 includes the well layers 540a of the nth group of quantum well light-emitting units and the barrier layers 540b of the nth group of quantum well light-emitting units alternately stacked.

[0033] In an embodiment of the present invention, as an optional embodiment, the wavelengths of light generated by the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units along the first direction are λ respectively. 1 , 2 , …, λ n-1 , n ; Each wavelength satisfies: λ 1 ≥λ 2 ≥…≥λ n-1 ,λ n-1 ≤λ n ≤λ 1 The quantum well light emitting unit next to the P-type semiconductor layer 60 has the shortest light emission wavelength.

[0034] In an embodiment of the present invention, as an optional embodiment, the difference in wavelength of light generated by adjacent groups of quantum well light-emitting units is ≤25nm, such as the difference can be 25nm, 22nm, 20nm, 18nm, 15nm, 10nm, 5nm, 2nm or a range consisting of any two of them.

[0035] In an embodiment of the present invention, as an optional embodiment, the wavelength of light generated by the first group of quantum well light-emitting units 51 is 450-475 nm; the wavelength of light generated by the n-1th group of quantum well light-emitting units 53 is 430-450 nm; the wavelength of light generated by the nth group of quantum well light-emitting units 54 is 440-470 nm.

[0036] For example, in an optional embodiment, when the multi-quantum well layer includes 3 groups of quantum well light-emitting units with different bandgap widths, the wavelengths of light generated by the first, second, and third groups of quantum well light-emitting units are 450-475nm, 430-450nm, and 440-470nm, respectively. In another optional embodiment, when the multi-quantum well layer includes 4 groups of quantum well light-emitting units with different bandgap widths, the wavelengths of light generated by the first, second, third, and fourth groups of quantum well light-emitting units are 460-475nm, 445-460nm, 435-445nm, and 455-465nm, respectively. The wavelength of light generated by each specific quantum well light-emitting unit can be adaptively adjusted according to the desired spectral shape.

[0037] In an embodiment of the present invention, as an optional embodiment, the emission wavelength of each group of quantum well light-emitting units is adjusted by regulating at least one of the concentration of In in the well layer, the thickness of the well layer and the thickness of the barrier layer in each group of quantum well light-emitting units, so that the wavelength generated by each group of quantum well light-emitting units meets the above conditions.

[0038] To achieve the wavelength λ of the nth group of quantum well light-emitting units n Greater than the wavelength λ of the n-1th group of quantum well light-emitting units n-1 In an embodiment of the present invention, the thickness of a single well layer of the nth group of quantum well light-emitting units can be set to be greater than the thickness of a single well layer of the n-1th group of quantum well light-emitting units, or the In concentration of a single well layer of the nth group of quantum well light-emitting units can be set to be greater than or equal to the In concentration of a single well layer of the n-1th group of quantum well light-emitting units.

[0039] In an embodiment of the present invention, as an optional embodiment, the thickness of a single barrier layer of each group of quantum well light-emitting units is t 1 ,t 2 ,…,t n-1 ,t n ; Each thickness satisfies: t n ≥t 1 , t 1 ≥t 2 ≥…≥t n-1 .

[0040] In the embodiment of the present invention, as an optional embodiment, one well layer and one barrier layer in the quantum well light-emitting unit is defined as one period, and the number of periodic structures in the n-1 group of quantum well light-emitting units 53 is greater than the number of periodic structures in the first group of quantum well light-emitting units 51. Further, the number of periodic structures in the first group of quantum well light-emitting units 51 is greater than or equal to the number of periodic structures in the nth group of quantum well light-emitting units 54.

[0041] In an embodiment of the present invention, as an optional embodiment, the number of periodic structures in the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units along the first direction of n groups of quantum well light-emitting units is X, respectively. 1 , X 2 , …, X n-1 , X n ; The number of periodic structures satisfies: X n-1 >X 1 , X n-1 >X n , X n-1 >X 2 .

[0042] In an embodiment of the present invention, as an optional embodiment, the well layer / barrier layer periodic structure is InGaN well layer / GaN base barrier layer. Further, in the well layer of each group of quantum well light-emitting units, the concentration of In is greater than 3×10 20 Atoms / cm 3 .

[0043] In an embodiment of the present invention, as an optional embodiment, the nth group of quantum well light-emitting units 54 includes at least two well layers with different In concentrations. Further, the In concentration of at least one well layer in the nth group of quantum well light-emitting units 54 is greater than or equal to the In concentration in the well layer 530a of the n-1th group of quantum well light-emitting units. Further, as an optional embodiment, the In concentration in the well layer of the nth group of quantum well light-emitting units 54 increases or remains unchanged along the direction from the n-1th group of quantum well light-emitting units 53 to the P-type semiconductor layer 60. The increase may be in a regular gradient, may be random, may be monotonically increased, may be fluctuating, and is not limited thereto.

[0044] In an embodiment of the present invention, as an optional embodiment, the thickness of the multi-quantum well layer 50 is 110-170 nm. Further, the thickness of the well layer / barrier layer periodic structure is 10-19 nm; the well layer / barrier layer periodic structure is InGaN / GaN. Further, the thickness of InGaN is 1-4 nm, and the thickness of GaN is 9-15 nm.

[0045] In an embodiment of the present invention, as an optional embodiment, the stress release layer 40 includes an InGaN / GaN superlattice layer. Further, in the stress release layer 40, the concentration of In is less than 3×10 20 Atoms / cm 3 , preferably the concentration of In>4×10 19 Atoms / cm 3 .

[0046] In an embodiment of the present invention, as an optional embodiment, the stress release layer 40 is doped with Si and / or Al.

[0047] In an embodiment of the present invention, as an optional embodiment, the P-type semiconductor layer 60 includes a P-type AlGaN electron blocking layer and a P-type GaN layer doped with Mg. In the P-type GaN layer doped with Mg, the average doping concentration of Mg is 1×10 19 ~1×10 21 Atoms / cm 3 .

[0048] In an embodiment of the present invention, as an optional embodiment, the N-type semiconductor layer 30 includes an undoped GaN layer and an N-type GaN layer doped with Si. The thickness of the undoped GaN layer may be 1.5 to 2.5 μm, and the thickness of the N-type GaN layer doped with Si may be 1.5 to 2.5 μm; in the N-type GaN layer doped with Si, the doping concentration of Si may be 1×10 19 ~1×10 20 Atoms / cm 3 .

[0049] The light-emitting diode formed by the above-mentioned epitaxial structure can be prepared into a front-mounted structure LED chip, a flip-chip LED structure chip, a vertical structure LED chip, a Mini LED and a Micro LED according to actual application needs, and there is no limitation here. For demonstration, Figure 3 A schematic diagram of a normal LED chip structure is shown, including any of the above-mentioned multi-wavelength light-emitting diode epitaxial structures.

[0050] Furthermore, the light emitting diode further comprises a current blocking layer, a current spreading layer, an N electrode, a P electrode and an insulating layer; The current blocking layer is arranged on the P-type semiconductor layer 60; the current spreading layer is stacked on the P-type semiconductor layer 60 and the current blocking layer; the P electrode is arranged on the current spreading layer and is electrically connected to the P-type semiconductor layer 60; the N electrode is arranged in the N step area and is electrically connected to the N-type semiconductor layer 30; the insulating layer covers the P electrode and the N electrode, and exposes part of the P electrode and the N electrode to form an opening.

[0051] Another aspect of the present invention provides a light-emitting module, comprising any one of the above-mentioned light-emitting diodes and a wavelength conversion unit; light generated by the light-emitting diode passes through the wavelength conversion unit and then mixed to generate white light.

[0052] Based on this, embodiments of the present invention provide a multi-wavelength light emitting diode and a light emitting module, which are described below through embodiments.

[0053] Example 1 Figure 4Schematic diagram of the bandgap structure of the multi-quantum well layer provided in Example 1 of the present invention. The multi-quantum well layer 50 of this embodiment includes three groups of quantum well light-emitting units with different bandgap widths, the first group of quantum well light-emitting units, the second group of quantum well light-emitting units and the third group of quantum well light-emitting units, to respectively generate three groups of light of different wavelengths, and the bandgap widths of the well layers of the three groups of quantum well light-emitting units are Eg1, Eg2 and Eg3, respectively.

[0054] The first group of quantum well light-emitting units is closest to the N-type semiconductor layer, and includes a periodic structure of a first well layer 511 and a first barrier layer 512 alternately stacked; the third group of quantum well light-emitting units is closest to the P-type semiconductor layer, and includes a third well layer 531 and a third barrier layer 532; the second group of quantum well light-emitting units is arranged between the first group of quantum well light-emitting units and the second group of quantum well light-emitting units, and includes a periodic structure of a second well layer 521 and a second barrier layer 522 alternately stacked. The well layer is an InGaN material layer with different In concentrations, and the barrier layer is a GaN-based material layer. The concentration of In in the third well layer 531 is greater than the concentration of In in the second well layer 521. The concentration of In in the first well layer 511 is greater than the concentration of In in the third well layer 531. The emission wavelength λ of the first group of quantum well light-emitting units 1 The longest wavelength of the second group of quantum well light-emitting units is λ 2 Further, in order to adjust the emission wavelength λ of the first group of quantum well light-emitting units 1 In addition to setting a larger In concentration, the thickness of the first well layer 511 can also be set to be greater than the second well layer 521. The light-emitting wavelength of the light-emitting unit can be adjusted by adjusting one or more of the In concentration, well layer thickness, barrier layer thickness, number of cycles, etc.

[0055] In a possible embodiment, the period number X of the first group of quantum well light-emitting units is 1 Less than the period number X of the second group of quantum well light-emitting units 2 , but greater than the period number X of the third group of quantum well light-emitting units 3 . Such as X 1 is 3, X 2 is 6, X 3 is 1.

[0056] The first well layer 511, the second well layer 521, and the third well layer 531 have substantially the same thickness, ranging from 30 to 40 Å. The first barrier layer 512, the second barrier layer 522, and the third barrier layer 532 also have substantially the same thickness, ranging from 90 to 150 Å. The In concentration in the InGaN first well layer 511 is greater than 3×10 20 Atoms / cm 3 , such as 7×10 20 ~8×10 20 Atoms / cm3 ; The In concentration range of the second well layer 521 is 4.5×10 20 ~5×10 20 Atoms / cm 3 ; The In concentration range of the third well layer 531 is 5×10 20 ~6×10 20 Atoms / cm 3 ; The formed multi-wavelength blue light emitting diode has at least three peak wavelengths between 430 and 475 nm.

[0057] Example 2 Figure 5 Schematic diagram of the bandgap structure of the multi-quantum well layer provided in Example 2 of the present invention. The multi-quantum well layer 50 of this embodiment includes 4 groups of quantum well light-emitting units with different bandgap widths, the first group of quantum well light-emitting units, the second group of quantum well light-emitting units, the third group of quantum well light-emitting units and the fourth group of quantum well light-emitting units, to respectively generate 4 groups of light beams with different wavelengths, and the bandgap widths of the well layers of the 4 groups of quantum well light-emitting units are Eg1, Eg2, Eg3 and Eg4 respectively.

[0058] Specifically, the first group of quantum well light-emitting units is closest to the N-type semiconductor layer, and includes a periodic structure of a first well layer 511 and a first barrier layer 512 stacked, with a period number of X. 1 The fourth group of quantum well light-emitting units is closest to the P-type semiconductor layer, including a stacked fourth well layer 541 and a fourth barrier layer 542 with a periodic structure, and the number of periods is X 4 The second group of quantum well light-emitting units is arranged between the first group of quantum well light-emitting units and the fourth group of quantum well light-emitting units, and includes a periodic structure formed by alternately stacked second well layers 521 and second barrier layers 522, the number of which is X. 2 The third group of quantum well light-emitting units is arranged between the second group of quantum well light-emitting units and the fourth group of quantum well light-emitting units and is closest to the fourth group of quantum well light-emitting units, including a periodic structure formed by alternately stacked third well layers 531 and third barrier layers 532, and the number of periods is X 3 Among them, X 3 ≥X 2 >X 1 ≥X 4 In one possible embodiment, X 1 =X 4 =1,X 3 =6,X 2 =2.

[0059] The first well layer 511, the second well layer 521, the third well layer 531, and the fourth well layer 541 are all InGaN material layers, and their In concentration distribution is C 1 , C2 , C 3 , C 4 , whose thicknesses are h 1 、h 2 、h 3 、h 4 Among them, C 1 >C 2 >C 3 , C 4 >C 3 , C 1 >C 4 . C 4 With C 2 The relationship can be C 2 ≥C 4 , or C 2 ≤C 4 The fourth well layer 541 is mainly used to supplement the light-emitting spectrum of the first well layer 511, the second well layer 521, and the third well layer 531 to realize a full-spectrum light-emitting diode.

[0060] Well layer thickness h 2 、h 3 、h 4 Basically the same, in a specific embodiment, h 1 Can be greater than h 2 , can also be equal to h 2 The wavelength of the light beam emitted by the first well layer 511 is the largest, and the wavelength of the light beam emitted by the third well layer 531 is the shortest. A multi-wavelength blue light emitting diode having at least three peak wavelengths in the range of 430 to 475 nm is formed.

[0061] Further, the wavelengths of light generated by the first group of quantum well light-emitting units, the second group of quantum well light-emitting units, the third group of quantum well light-emitting units and the fourth group of quantum well light-emitting units may be 458-475nm, 445-458nm, 435-450nm and 445-460nm, respectively.

[0062] Example 3 Figure 6 Schematic diagram of the bandgap structure of the multi-quantum well layer provided in Example 3 of the present invention. The multi-quantum well layer 50 of this embodiment refers to Example 2, except that the number of periods of each multi-quantum well light-emitting unit is different, wherein the number of periods of the third multi-quantum well light-emitting unit is X 3 Greater than the period number X of the second multi-quantum well light-emitting unit 2 Greater than the period number X of the first multi-quantum well light-emitting unit 1 Greater than the period number X of the fourth multi-quantum well light-emitting unit 1 , that is, X 3 >X 2 >X 1 >X 4In a specific embodiment, X 3 is 4, X 2 is 3, X 1 =2,X 4 is 1. A multi-wavelength blue light emitting diode having at least three peak wavelengths in the range of 430 to 475 nm is formed.

[0063] Example 4 Figure 7 Schematic diagram of the bandgap structure of the multi-quantum well layer provided in Example 4 of the present invention. The multi-quantum well layer 50 of this embodiment includes 4 groups of quantum well light-emitting units with different bandgap widths, the first group of quantum well light-emitting units, the second group of quantum well light-emitting units, the third group of quantum well light-emitting units and the fourth group of quantum well light-emitting units, to respectively generate 4 groups of light of different wavelengths, and the bandgap widths of the well layers of the 4 groups of quantum well light-emitting units are Eg1, Eg2, Eg3 and Eg4' / Eg4'' respectively.

[0064] The first group of quantum well light-emitting units includes a periodic structure of a first well layer 511 and a first barrier layer 512 alternately stacked, the second group of quantum well light-emitting units includes a periodic structure of a second well layer 521 and a second barrier layer 522 alternately stacked, the third group of quantum well light-emitting units includes a periodic structure of a third well layer 531 and a third barrier layer 532 alternately stacked, and the fourth group of quantum well light-emitting units includes at least one group of first periodic structures and second periodic structures alternately stacked. The first periodic structure is a periodic structure of a fourth well layer 541 and a fourth barrier layer 542, and the second periodic structure is a periodic structure of a fifth well layer 551 and a fifth barrier layer 552. The fourth well layer 541 and the fifth well layer 551 have different In concentrations. The In concentrations in the fourth well layer 541 and the fifth well layer 551 are greater than the In concentration in the third well layer 531.

[0065] Furthermore, the wavelengths of light generated by the first group of quantum well light-emitting units, the second group of quantum well light-emitting units, the third group of quantum well light-emitting units, and the fourth group of quantum well light-emitting units may be 458-475 nm, 445-458 nm, 435-450 nm, and 445-460 nm, respectively.

[0066] Example 5 Figure 8 Schematic diagram of the bandgap structure of the multi-quantum well layer provided in Example 5 of the present invention. The difference between this embodiment and Example 1 is that the thickness h of the third well layer 531 is 3 is greater than the thickness h of the second well layer 521 2 The In concentration C of the third well layer 531 is 3 The In concentration C of the second well layer 521 2 The In concentration C of the first well layer 511 is basically the same. 1The thickness of the first well layer 511 is h 1 is greater than the thickness h of the second well layer 521 2 .

[0067] In one possible implementation, the In concentration in the first well layer 511 is greater than 3×10 20 Atoms / cm 3 , such as 6.8×10 20 Atoms / cm 3 ; The thickness of the first well layer 511 is 37Å, and the thickness of the first barrier layer 512 is 120Å.

[0068] Furthermore, the In concentration in the second well layer 521 is greater than 3×10 20 Atoms / cm 3 , such as 5×10 20 Atoms / cm 3 ; The thickness of the second well layer 521 is 33Å, and the thickness of the second barrier layer 522 is 100Å.

[0069] Furthermore, the In concentration in the third well layer 531 is greater than 3×10 20 Atoms / cm 3 , such as 5×10 20 Atoms / cm 3 ; The thickness of the third well layer 531 is 37Å, and the thickness of the third barrier layer 532 is 142Å.

[0070] Further, the wavelengths of light generated by the first group of quantum well light emitting units, the second group of quantum well light emitting units, and the third group of quantum well light emitting units may be 450-470 nm, 435-450 nm, and 445-465 nm, respectively.

[0071] Example 6 Fig. 9 Schematic diagram of the bandgap structure of the multi-quantum well layer provided in Example 6 of the present invention. The multi-quantum well layer 50 of this embodiment includes 4 groups of quantum well light-emitting units with different bandgap widths, the first group of quantum well light-emitting units, the second group of quantum well light-emitting units, the third group of quantum well light-emitting units and the fourth group of quantum well light-emitting units, to respectively generate 4 groups of light of different wavelengths, and the bandgap widths of the well layers of the 4 groups of quantum well light-emitting units are Eg1, Eg2, Eg3 and Eg4 respectively.

[0072] The first group of quantum well light-emitting units includes a periodic structure of a first well layer 511 and a first barrier layer 512 alternately stacked, the second group of quantum well light-emitting units includes a periodic structure of a second well layer 521 and a second barrier layer 522 alternately stacked, the third group of quantum well light-emitting units includes a periodic structure of a third well layer 531 and a third barrier layer 532 alternately stacked, and the fourth group of quantum well light-emitting units includes a periodic structure of a fourth well layer 541 and a fourth barrier layer 542 alternately stacked. The thickness h of the fourth well layer 541 is 4 is greater than the thickness h of the third well layer 531 3 .

[0073] Furthermore, the thickness h of the first well layer 511 is 1 is smaller than the thickness h of the fourth well layer 541 4 , and the thickness of the first well layer 511 is h 1 Less than or equal to the thickness h of the second well layer 521 2 .

[0074] Furthermore, the thickness h of the second well layer 521 is 2 Less than or equal to the thickness h of the third well layer 531 3 .

[0075] Further, the thickness of the fourth barrier layer 542 is greater than the thickness of the first barrier layer 512 .

[0076] Furthermore, the concentration of In in each well layer satisfies: first well layer 511 > second well layer 521 ≥ third well layer 531 ≥ fourth well layer 541 .

[0077] Furthermore, in the first group of quantum well light-emitting units, the period number of the periodic structure of the first well layer 511 / first barrier layer 512 is ≥1, such as 1; the In concentration in the first well layer 511 is >3×10 20 Atoms / cm 3 , such as 7.8×10 20 Atoms / cm 3 ; The thickness of the first well layer 511 is h 1 The thickness of the first barrier layer 512 is 120 Å.

[0078] Furthermore, in the second group of quantum well light-emitting units, the period number of the periodic structure of the second well layer 521 / the second barrier layer 522 is ≥1, such as 2; the In concentration in the second well layer 521 is >3×10 20 Atoms / cm 3 , such as 6.8×10 20 Atoms / cm 3 ; The thickness of the second well layer 521 is h 2 is 33Å, and the thickness of the second barrier layer 522 is 100Å.

[0079] Furthermore, in the third group of quantum well light-emitting units, the period number of the periodic structure of the third well layer 531 / third barrier layer 532 is ≥3, such as 6; the In concentration in the third well layer 531 is >3×10 20 Atoms / cm 3 , such as 5×10 20 Atoms / cm 3 ; The thickness of the third well layer 531 is h 3 is 33Å, and the thickness of the third barrier layer 532 is 100Å.

[0080] Furthermore, in the fourth group of quantum well light-emitting units, the period number of the periodic structure of the fourth well layer 541 / the fourth barrier layer 542 is ≥1, such as 1; the In concentration in the fourth well layer 541 is >3×10 20 Atoms / cm 3 , such as 5×10 20 Atoms / cm 3 ; The thickness of the fourth well layer 541 is h 4 is 37Å, and the thickness of the fourth barrier layer 542 is 142Å.

[0081] Further, the wavelengths of light generated by the first group of quantum well light emitting units, the second group of quantum well light emitting units, the third group of quantum well light emitting units and the fourth group of quantum well light emitting units are λ 1 , 2 , 3 , 4 , where λ 1 >λ 2 >λ 3 ,λ 4 >λ 3 The peak wavelength emitted by the third group of quantum well light-emitting units is the shortest. 1 Range: 458~475nm, λ 2 Range: 446~458nm, λ 3 Range: 435~446nm, λ 4 The wavelength range is 443 to 463 nm, forming a light-emitting diode with at least 4 relatively obvious peak wavelengths.

[0082] In a variant embodiment, the thickness h of the first well layer 511 is 1 The thickness h of the second well layer 521 is 2 is the same as or slightly larger than. Furthermore, the thickness h of the first well layer 511 1 The thickness h of the fourth well layer 541 is 4 Close to each other.

[0083] In another variant embodiment, except for the thickness h of the fourth well layer 541 4 is greater than the thickness h of the third well layer 531 3 In addition, the In concentration of the fourth well layer 541 is also greater than the In concentration of the third well layer 531 , thereby enhancing the intensity supplementation effect of the fourth multi-quantum well light-emitting unit in a relatively long-wavelength spectrum.

[0084] In yet another variant embodiment, the material of at least one of the first barrier layer 512, the second barrier layer 522, the third barrier layer 532, and the fourth barrier layer 542 comprises AlGaN or AlN, and preferably the fourth barrier layer 542 closest to the P-type semiconductor layer comprises a GaN layer and an AlGaN layer, and even further comprises an InAlGaN layer.

[0085] In the variant implementation, the number and period number of each multi-quantum well light-emitting unit are not limited to the examples in the above implementation, but generally follow that the period number of the multi-quantum well light-emitting unit emitting the shortest wavelength is the largest, while the period number of the multi-quantum well light-emitting unit emitting the long wavelength will be reduced. In order to fit a full-spectrum light-emitting diode that is closer to sunlight, the fifth, sixth, seventh and other groups of multi-quantum well light-emitting units may also be included, but the emission wavelength of a group of multi-quantum well light-emitting units closest to the P-type semiconductor layer is longer than the emission wavelength of the multi-quantum well light-emitting unit next to the P-type semiconductor layer, mainly because the last group of multi-quantum well light-emitting units is to supplement the spectrum of the multi-quantum well light-emitting unit close to the N-type layer side, and to fit the full spectrum within a certain band as much as possible.

[0086] Fig.10 Spectrum diagram of the light beam generated by the light emitting diode of Example 6 of the present invention at different currents. Fig.11 The luminous efficiency of the light emitting diode according to Example 6 of the present invention is compared with that of the conventional light emitting diode under 60 mA. Fig.11 It can be seen that the luminous efficiency of the light emitting diode of the present invention at 60 mA is improved by 1.4% compared with the luminous efficiency of the traditional light emitting diode.

[0087] As can be seen from the above, the multi-wavelength light-emitting diode of the present invention generates multiple wavelengths by setting up multiple groups of quantum well light-emitting units to obtain a light-emitting spectrum close to sunlight; at the same time, by adjusting the In content and / or the well layer thickness in the quantum well light-emitting unit closest to the P-type semiconductor layer, the stress between the multi-quantum well layer and the P-type semiconductor layer is fully released, thereby achieving the effect of improving the light-emitting efficiency.

[0088] An embodiment of the present invention further provides a method for preparing a multi-wavelength light emitting diode, comprising the following steps: The first half of the buffer layer 20 is grown on the substrate 10 for 1 minute, in order to compensate for the lattice mismatch and form nucleation islands, and the temperature of this layer is controlled at 800°C and the pressure is 150 torr. The second half of the buffer layer 20 is then grown for 10 to 25 minutes, and the temperature is controlled at 1120°C and the pressure is 200 torr, in order to grow GaN with high crystal growth quality and low defect density.

[0089] The N-type semiconductor layer 30 is grown on the buffer layer 20 to provide electrons. The N-type semiconductor layer 30 is doped with Si to provide electrons. The temperature is controlled at 1050°C and the pressure is 200 torr. The concentration of silicon doping is 1e+19 to 2e+20 Atoms / cm 3 .

[0090] A stress release layer 40 is grown on the N-type semiconductor layer 30 to release the compressive stress caused by the lattice mismatch between the subsequently grown InGaN quantum well and the GaN of the N-type semiconductor layer 30. The temperature is controlled at 800-900°C and the pressure is 200 torr. The layer can be a single layer or a multilayer structure, and can be doped with elements such as Si / Al / In. The concentration of silicon doping is 1e+17 Atoms / cm 3 ~5e+18 Atoms / cm 3 , indium doping concentration is 0~1e+20Atoms / cm 3 .

[0091] The multi-quantum well layer 50 is continuously grown on the stress release layer 40. The multi-quantum well layer 50 emits light through the convergence of electrons and holes. The temperature of the layer is controlled at 700-800°C and the pressure is 200tor.

[0092] A P-type semiconductor layer 60 is grown on the multi-quantum well layer 50. The function of this layer is to provide holes for the device. The temperature of this layer is controlled at 700-1000°C and the pressure is 1000tor.

[0093] 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 multi-wavelength light emitting diode, characterized in that: At least: An N-type semiconductor layer, and a stress release layer, a multi-quantum well layer and a P-type semiconductor layer sequentially arranged on the N-type semiconductor layer; the multi-quantum well layer comprises n groups of quantum well light-emitting units with different bandgap widths to respectively generate n groups of light with different wavelengths, where n≥3; A direction from close to the N-type semiconductor layer to close to the P-type semiconductor layer is defined as a first direction. The n groups of quantum well light-emitting units along the first direction are respectively the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units; each group of quantum well light-emitting units includes at least one well layer and one barrier layer, and the nth group of quantum well light-emitting units and the n-1th group of quantum well light-emitting units meet at least one of the following characteristics: (a) the concentration of In in at least one well layer of the nth group of quantum well light-emitting units is greater than or equal to the concentration of In in at least one well layer of the n-1th group of quantum well light-emitting units; (b) The thickness of at least one well layer of the nth group of quantum well light-emitting units is greater than the thickness of at least one well layer of the n-1th group of quantum well light-emitting units.

2. The multi-wavelength light emitting diode according to claim 1, characterized in that: The wavelength of light generated by the nth group of quantum well light-emitting units is greater than the wavelength of light generated by the n-1th group of quantum well light-emitting units; And / or, the wavelength of light generated by the first group of quantum well light-emitting units is greater than the wavelength of light generated by the n-1th group of quantum well light-emitting units.

3. The multi-wavelength light emitting diode according to claim 1, characterized in that: The wavelengths of light generated by the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are λ1, λ2, ..., λ n-1 , n ; Each wavelength satisfies: λ1≥λ2≥…≥λ n-1 ,λ n-1 ≤λ n ≤λ1.

4. The multi-wavelength light emitting diode according to claim 3, characterized in that: The difference in wavelength of light generated by adjacent groups of quantum well light-emitting units is Δλ≤25nm; The wavelength of light generated by the first group of quantum well light-emitting units is 450-475 nm; the wavelength of light generated by the n-1th group of quantum well light-emitting units is 430-450 nm; and the wavelength of light generated by the nth group of quantum well light-emitting units is 440-470 nm.

5. The multi-wavelength light emitting diode according to claim 1, characterized in that: The concentrations of In in the single well layers of the 1st, 2nd, ..., n-1th, and nth quantum well light-emitting units are c1, c2, ..., c n-1 、c n , each concentration satisfies: c n ≥c n-1 , c1≥c2≥…≥c n-1 .

6. The multi-wavelength light emitting diode according to claim 5, characterized in that: The thicknesses of the single well layers of the 1st group, the 2nd group, ..., the n-1th group and the nth group of quantum well light-emitting units are h1, h2, ..., h n-1 、h n ; Among them, h1≥h2≥…≥h n-1 ,h n With h n-1 Satisfy: h n >h n-1 or h n <h n-1 or h n =h n-1 .

7. The multi-wavelength light emitting diode according to claim 1, characterized in that: The thicknesses of the single well layers of the 1st group, the 2nd group, ..., the n-1th group and the nth group of quantum well light-emitting units are h1, h2, ..., h n-1 、h n ; Each thickness satisfies: h n >h n-1 , h1≥h2≥…≥h n-1 .

8. The multi-wavelength light emitting diode according to claim 7, characterized in that: The difference between the thickness of a single well layer of the nth group of quantum well light-emitting units and the thickness of a single well layer of the n-1th group of quantum well light-emitting units is 1 to 15 Å.

9. The multi-wavelength light emitting diode according to claim 7, characterized in that: The concentrations of In in the single well layers of the 1st, 2nd, ..., n-1th, and nth quantum well light-emitting units are c1, c2, ..., c n-1 、c n ; Among them, c1≥c2≥…≥c n-1 , c n-1 With c n Satisfies: c n >c n-1 or c n =c n-1 or c n <c n-1 .

10. The multi-wavelength light emitting diode according to claim 1, characterized in that: The thicknesses of the barrier layers of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are t1, t2, ..., t n-1 ,t n ; Each thickness satisfies: t n ≥t n-1 , t1≥t2≥…≥t n-1 .

11. The multi-wavelength light emitting diode according to claim 1, characterized in that: A well layer and a barrier layer in a quantum well light-emitting unit are defined as a period. The number of periodic structures of the first group, the second group, ..., the n-1th group and the nth group of quantum well light-emitting units are X1, X2, ..., X n-1 , X n ; Among them, X n-1 >X1,X n-1 >X n , X n-1 >X2.

12. A light emitting module, characterized in that: It comprises the multi-wavelength light emitting diode according to any one of claims 1 to 11, wherein the light generated by the light emitting diode passes through a wavelength conversion unit and then is mixed to generate white light.

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