Ultraviolet light emitting diode and light emitting device

Abstract

The application relates to the technical field of light-emitting diode chips, in particular to an ultraviolet light-emitting diode and a light-emitting device, which comprise: an epitaxial layer, the epitaxial layer having a first semiconductor layer, a light-emitting layer and a second semiconductor layer which are sequentially stacked; a first electrode electrically connected to the first semiconductor layer; a second electrode electrically connected to the second semiconductor layer; a substrate, the substrate having opposite first and second surfaces, the epitaxial layer being arranged on the first surface of the substrate, and a patterned microstructure being arranged on the second surface, wherein the diameter D of a circle circumscribing the bottom of the microstructure is greater than 400 nm and less than 1000 nm. Compared with the prior art, the size of the patterned microstructure arranged on the light-emitting side of the substrate is changed to adapt to the light-emitting wavelength band of the ultraviolet light-emitting diode, so that the ultraviolet light is more easily scattered out, thereby improving the light extraction efficiency of the ultraviolet light-emitting diode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light emitting diode chips, in particular to an ultraviolet light emitting diode and a light emitting device. BACKGROUND

[0002] Light emitting diode (LED) is a semiconductor light emitting element, which is usually made of semiconductors such as GaN, GaAs, GaP, GaAsP, etc. Its core is a PN junction with light emitting characteristics. Under a forward voltage, electrons are injected from the N region to the P region, and holes are injected from the P region to the N region. A part of the minority carriers entering the opposite region recombine with the majority carriers to emit light. LED has the advantages of high light intensity, high efficiency, small size, long service life, etc. and is considered as one of the most potential light sources. In recent years, the great application value of ultraviolet light LED, especially deep ultraviolet light LED, has attracted people's high attention and become a new research hotspot.

[0003] Ultraviolet light emitting diode (UV-LED) is a kind of solid-state semiconductor device that can directly convert electrical energy into ultraviolet light. With the development of technology, ultraviolet light emitting diode has broad market application prospects in the fields of biological medicine, anti-counterfeiting identification, purification (water, air, etc.), computer data storage and military, etc. In recent years, with the increasing demand for drinking water, daily sterilization and disinfection, the application of ultraviolet LED has gradually become a research hotspot.

[0004] In recent years, the great application value of ultraviolet light LED, especially deep ultraviolet light LED, has attracted people's high attention and become a new research hotspot. The light extraction efficiency of deep ultraviolet is the most important. Since deep ultraviolet has strong absorption to various packaging adhesives, even some fluorine-containing silicon adhesives are prone to cracking under long-term UV irradiation. Therefore, UVC packaging is different from blue light, and basically there is no packaging adhesive, which will cause the light of the chip to directly enter the air from the sapphire, increase the total reflection angle, and reduce the light extraction efficiency. In addition, the wavelength of UVC light is shorter, and compared with blue light, red light and other LED chips, it is more prone to total reflection.

[0005] In summary, how to further improve the light extraction efficiency of ultraviolet light LED has become a technical problem to be solved by those skilled in the art. SUMMARY

[0006] To solve the above problems in the prior art, the present application provides an ultraviolet light emitting diode, comprising:

[0007] An epitaxial layer, the epitaxial layer has a first semiconductor layer, a light emitting layer and a second semiconductor layer which are stacked in sequence;

[0008] a first electrode electrically connected to the first semiconductor layer;

[0009] a second electrode electrically connected to the second semiconductor layer;

[0010] a substrate having opposing first and second surfaces, the epitaxial layer disposed on the first surface of the substrate, the second surface having a patterned microstructure formed thereon, the microstructure having a base circumscribed circle with a diameter D greater than 400 nm and less than 1000 nm.

[0011] In some embodiments, the light emitting layer has an emission wavelength range of 200-280 nm or 280-360 nm.

[0012] In some embodiments, the patterned microstructure includes a first microstructure formed on the second surface, the first microstructure comprising the same material as the substrate.

[0013] In some embodiments, the patterned microstructure includes a second microstructure formed on the second surface, the substrate comprising a first material, the second microstructure comprising a second material different from the substrate.

[0014] In some embodiments, further comprising a light extraction layer overlying the second surface and the first microstructure, the microstructure further comprising a third microstructure formed on a surface of the light extraction layer facing away from the substrate, the substrate comprising a first material, the light extraction layer and the third microstructure comprising a second material different from the substrate.

[0015] In some embodiments, further comprising a light extraction layer overlying the second surface, the microstructure comprising a fourth microstructure formed on a surface of the light extraction layer facing away from the substrate, the substrate comprising a first material, the light extraction layer and the fourth microstructure comprising a second material different from the substrate.

[0016] In some embodiments, the light emitting layer has an emission wavelength range of 265-285 nm, the light extraction layer having a thickness between 400-600 Angstroms.

[0017] In some embodiments, the second material has a refractive index relatively smaller than a refractive index of the first material.

[0018] In some embodiments, the first material is selected from Al2O3, GaN, SiC, or glass, and the second material is selected from Al2O3, SiO2, Si3N4, or ZnO2.

[0019] In some embodiments, the microstructure has a base circumscribed circle with a diameter D between 420-710 nm.

[0020] In some embodiments, the diameter D of the circumscribed circle of the bottom of the microstructure is 0.8-1.5 times, or 1.5-1.85 times, or 1.85-2.5 times of the height H of the microstructure.

[0021] In some embodiments, the minimum distance L between the center points of adjacent microstructures is 0.5-1.2 μm.

[0022] In some embodiments, the microstructure is conical, quasi-conical, quasi-circular truncated conical, quasi-polygonal conical, quasi-polygonal truncated conical, cylindrical, or spherical, etc.

[0023] In some embodiments, the microstructures are arranged in a periodic square lattice, a periodic hexagonal close-packed arrangement, a non-periodic quasi-crystal arrangement, or a random arrangement.

[0024] In some embodiments, the light emitting direction of the ultraviolet light emitting diode is from the light emitting layer to the substrate, and the first electrode and the second electrode are located on the side of the substrate away from the second surface.

[0025] In some embodiments, the substrate is subjected to several times of laser stealth dicing process at different depths in the same vertical plane, the diameter D of the circumscribed circle of the bottom of the microstructure is less than the wavelength of the laser, and the wavelength of the laser is 900-1200 nm.

[0026] In some embodiments, the diameter D of the circumscribed circle of the bottom of the microstructure is less than 0.75 times of the wavelength of the laser.

[0027] The present application also provides a light emitting device comprising the ultraviolet light emitting diode as described above.

[0028] Based on the above, compared with the prior art, the ultraviolet light emitting diode provided by the present application changes the size of the patterned microstructure arranged on the light emitting side of the substrate to adapt to the light emitting wavelength band of the ultraviolet light emitting diode, so that the ultraviolet light is more easily scattered out, thereby improving the light extraction efficiency of the ultraviolet light emitting diode.

[0029] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings. In the following description, the positional relationship described in the drawings is the direction of the components shown in the drawings as the reference, unless otherwise specified.

[0031] Figure 1 The first embodiment of the ultraviolet light emitting diode provided by the present application is a cross-sectional schematic view.

[0032] Figure 2 The first embodiment of the ultraviolet light emitting diode provided by the present application is a cross-sectional schematic view. Figure 1 The first embodiment of the ultraviolet light emitting diode provided by the present application is a cross-sectional schematic view.

[0033] Figure 3 The second surface of the substrate in the embodiment of the present application is a schematic view.

[0034] Figure 4 The second embodiment of the present application is a cross-sectional schematic view.

[0035] Figure 5 The process of the embodiment of the present application is a cross-sectional schematic view.

[0036] Figure 6 The third embodiment of the present application is a cross-sectional schematic view.

[0037] Figure 7 The K value result of the ultraviolet light emitting diode sample in the embodiment is a schematic view.

[0038] Figure 8 The fourth embodiment of the present application is a cross-sectional schematic view.

[0039] Figure 9 The cross-sectional schematic view of a pair of ultraviolet light emitting diodes without substrate hidden cutting and splitting.

[0040] Reference signs:

[0041] 100 substrate 200 epitaxial layer 310 first electrode

[0042] 320 second electrode 210 first semiconductor layer 220 light emitting layer

[0043] 230 second semiconductor layer 101 first surface 102 second surface

[0044] 311 first contact electrode 312 first connecting electrode 313 first pad electrode

[0045] 321 second contact electrode 322 second pad electrode 323 current spreading layer

[0046] 400 insulating layer 401 first opening 402 second opening

[0047] 110 microstructure 111 first microstructure 112 second microstructure

[0048] 113 third microstructure 114 fourth microstructure 600 light extraction layer DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application; as long as there is no conflict, the technical features in the different embodiments of the present application can be combined with each other; and all other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without creative effort fall into the protection scope of the present application.

[0050] In the description of the present application, it should be understood that the terms "center", "transverse", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or component referred to must have a particular orientation, or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more. In addition, the term "comprising", and any variation thereof, means "at least including".

[0051] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through an intermediate medium, or internal communication of two components. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0052] As Figure 1 shown, Figure 1is a cross-sectional schematic view of a first embodiment of the ultraviolet light emitting diode provided by the present application, in order to achieve at least one or other advantages, the first embodiment of the present application provides an ultraviolet light emitting diode 1, comprising a substrate 100, an epitaxial layer 200, a first electrode 310 and a second electrode 320.

[0053] The substrate 100 has opposite first and second surfaces 101 and 102, in the present embodiment, the ultraviolet light emitting diode 1 is placed in such a manner that the first surface 101 of the substrate 100 faces upward and the second surface 102 faces downward, and the present application does not make special limitations on this. The substrate 100 can be an insulating substrate, and preferably, the substrate 100 can also be made of a transparent or translucent material, such as sapphire Al2O3, GaN, SiC or glass, etc. In the present embodiment, the substrate 100 is taken as an example of a sapphire substrate to illustrate the scheme. The transparency or translucency of the substrate 100 can allow the light emitted by the light emitting layer 220 to pass through the substrate 100 to the side of the substrate 100 away from the epitaxial layer 200. In the present embodiment, the light emitting direction of the ultraviolet light emitting diode 1 is toward the direction from the light emitting layer 220 to the substrate 100, that is, the light emitting side is the side of the substrate 100 away from the epitaxial layer 200 and the first and second electrodes 310 and 320.

[0054] Preferably, in some embodiments, in order to enhance the light extraction efficiency of the substrate 100, especially the effect of extracting light from the bottom surface of the substrate 100, the thickness of the substrate 100 can be appropriately increased, which can be increased to 200-900 μm, preferably 250-400 μm, or 400-550 μm, or 550-750 μm.

[0055] As Figure 1As shown, the epitaxial layer 200 includes a first semiconductor layer 210, a light emitting layer 220, and a second semiconductor layer 230, which are sequentially stacked on the first surface 101 of the substrate 100, and each of the first semiconductor layer 210, the light emitting layer 220, and the second semiconductor layer 230 is transparent. The first semiconductor layer 210 is formed on the first surface 101 of the substrate 100. The first semiconductor layer 210 can be an N-type semiconductor layer, and can provide electrons to the light emitting layer 220 under the action of a power source. In some embodiments, the first semiconductor layer 210 includes an N-type doped nitride layer. The N-type doped nitride layer can include N-type impurities of one or more group IV elements. The N-type impurities can include one or a combination of Si, Ge, and Sn. In some embodiments, a buffer layer can also be provided between the first semiconductor layer 210 and the substrate 100 to alleviate the lattice mismatch between the substrate 100 and the first semiconductor layer 210. The buffer layer can include an undroped GaN (u-GaN) layer or an undroped AlGaN (u-AlGaN) layer. The first semiconductor layer 210 can also be connected to the substrate 100 through an adhesive layer.

[0056] The light emitting layer 220 is formed on the first semiconductor layer 210, and the light emitting layer 220 can be a quantum well (QW) structure. In some embodiments, the light emitting layer 220 can also be a multiple quantum well (MQW) structure, which includes a plurality of quantum well layers (Wells) and a plurality of quantum barrier layers (Barriers) arranged in a repeating pattern, such as a GaN / AlGaN, InAlGaN / InAlGaN, or InGaN / AlGaN MQW structure. In addition, the composition and thickness of the well layers in the light emitting layer 220 determine the wavelength of the generated light. To improve the light emitting efficiency of the light emitting layer 220, the depth of the quantum well, the number of pairs of quantum well and quantum barrier, the thickness, and / or other characteristics of the light emitting layer 220 can be changed. In the present embodiment, the light emitting wavelength range of the ultraviolet light emitting diode 1 is preferably 200-280 nm or 280-360 nm. That is, the light emitting wavelength range of the light emitting layer 220 is 200-280 nm or 280-360 nm.

[0057] In the illustrated embodiment, the second semiconductor layer 230 in the epitaxial layer 200 is a P-type semiconductor layer, which can provide holes to the light-emitting layer 220 under power. In some embodiments, the second semiconductor layer 230 includes a P-type doped nitride layer. The P-type doped nitride layer may include one or more P-type impurities of group II elements. The P-type impurities may include one or a combination of Mg, Zn, and Be. The second semiconductor layer 230 may be a single-layer structure or a multilayer structure with different compositions. Furthermore, the arrangement of the epitaxial layer 200 is not limited to this, and other types of epitaxial layer 200 structures may be selected according to actual needs.

[0058] like Figure 1 As shown, in some embodiments, the epitaxial layer 200 has a plurality of connection channels extending from the surface of the second semiconductor layer 230 to the first semiconductor layer 210. The first electrode 310 includes a first contact electrode 311, a first connection electrode 312, and a first pad electrode 313. The first contact electrode 311 is located at the bottom of the connection channel and is electrically connected to the first semiconductor layer 210 to form an ohmic contact. The first connection electrode 312 is disposed on the first contact electrode 311 and electrically connects each of the first contact electrodes 311 in the plurality of connection channels. Finally, the first contact electrode 311 is electrically connected to the first pad electrode 313 located on one side of the top of the ultraviolet light-emitting diode 1 through the first two electrodes 312. The second electrode 320 includes a second contact electrode 321 and a second pad electrode 322. The second contact electrode 321 is disposed on the epitaxial layer 200, that is, on the upper surface of the second semiconductor layer 230. Its coverage area avoids the area of ​​the connection channel where the first electrode 310 is located. On the one hand, it forms an ohmic contact with the second semiconductor layer 230, and on the other hand, it forms an electrical connection with the second pad electrode 322 located on the other side of the top of the ultraviolet light-emitting diode 1. The materials contained in the first contact electrode 311 and the second contact electrode 321 are selected from one or more of the group consisting of Cr, Pt, Au, Ni, Ti, and Al. The materials contained in the first connection electrode 312 are selected from one or more of the group consisting of Cr, Al, Ti, Ni, Rh, Pt, or Au, but the present invention does not impose any special limitations on this.

[0059] Preferably, in some embodiments, such as Figure 1As shown, the ultraviolet light emitting diode 1 further comprises a current spreading layer 323, which is arranged between the second contact electrode 321 and the second semiconductor layer 230. The current spreading layer 323 is used to spread the current, so that the current distribution is more uniform, and the light extraction efficiency of the ultraviolet light emitting diode 1 is improved. The current spreading layer 323 can be made of a transparent conductive material, or a metal material, which can be selected according to the doping of the surface layer (such as the p-type GaN surface layer) of the second semiconductor layer 230. The transparent conductive material can include indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium doped zinc oxide (GZO), tungsten doped indium oxide (IWO), or zinc oxide (ZnO); the metal material can be selected from Ni / Au alloy, Ni / Rh alloy, Ni / Al / Au alloy, etc., but the embodiments of the present disclosure are not limited thereto. Preferably, in order to further improve the light extraction efficiency of the ultraviolet light emitting diode 1, the thickness of the current spreading layer 323 can be set to 500-1500 angstroms in the present embodiment, and a metal plating layer Cr / Ni is plated on the surface of the current spreading layer 323 to form a light reflection structure (not shown in the figure); or the thickness of the current spreading layer 323 can be set to 100-500 angstroms, and a metal plating layer Cr / Al is plated on the surface of the current spreading layer 323 to form a light absorption structure (not shown in the figure).

[0060] In the illustrated embodiment, the ultraviolet light emitting diode 1 further comprises an insulating layer 400 covering the substrate 100, the epitaxial layer 200, the first contact electrode 311, the second contact electrode 321, the first connecting electrode 312, and the like, and serving the effect of insulation and protection. The insulating layer 400 has a first opening 401 and a second opening 402 for exposing the first connecting electrode 312 and the second contact electrode 321, respectively, so as to electrically connect the first connecting electrode 312 with the first pad electrode 313 and electrically connect the second contact electrode 321 with the second pad electrode 322. Meanwhile, part of the insulating layer 400 is located on the sidewall of the connecting channel to block the connection between the first electrode 310 and the second electrode 320, the second semiconductor layer 230, and the light emitting layer 220, thereby avoiding short-circuit abnormality of the ultraviolet light emitting diode 1. In addition, the insulating layer 400 has different effects according to the positions involved, such as covering the sidewall of the epitaxial layer 200 to prevent the first semiconductor layer 210 and the second semiconductor layer 230 from being electrically connected due to leakage of conductive material, thereby reducing short-circuit abnormality of the ultraviolet light emitting diode 1, and the like. The material of the insulating layer 400 comprises a non-conductive material. The non-conductive material is preferably an inorganic material or a dielectric material. The inorganic material can comprise silicone. The dielectric material comprises aluminum oxide (AlO), silicon nitride (SiNx), silicon oxide (SiOx), titanium oxide (TiOx), or magnesium fluoride (MgFx) can be an electrically insulating material. For example, the insulating layer 400 can be silicon dioxide, silicon nitride, titanium oxide, tantalum oxide, niobium oxide, barium titanate, or a combination thereof, which can be a Bragg reflector (DBR) formed by repeatedly stacking two materials, for example.

[0061] Further, in order to improve the light extraction efficiency of the ultraviolet light emitting diode 1, as shown in Figure 1 and Figure 3 , a patterned microstructure is provided on the second surface 102 of the substrate 100 in the present embodiment. The patterned microstructure is a plurality of microstructures 110 arranged periodically or non-periodically on a structure surface by using but not limited to wet etching, dry etching, imprinting technology, electron beam exposure, or nanosphere self-assembly technology. The shape of the microstructure 110 can be a convex shape such as a conical shape, a quasi-conical shape, a quasi-round-taup shape, a quasi-polygonal conical shape, a quasi-polygonal taup shape, a columnar shape, or a spherical shape. The distribution mode can be a periodic square lattice arrangement, a periodic hexagonal close-packed arrangement, a non-periodic quasicrystal arrangement, or a random arrangement. The shape of the microstructure 110 in the present embodiment is taken as a conical shape, and the arrangement mode is taken as a periodic hexagonal close-packed arrangement, but the present embodiment is not limited thereto. The microstructure 110 in the present embodiment is shown in Figure 1As shown, the first microstructure 111 is formed directly on the second surface 102 of the substrate 100, and the first microstructure 111 is in an integral structure with the substrate 100 and thus has the same material as the substrate 100, for example, sapphire. As shown in FIG. 1, the first microstructure 111 is formed on the second surface 102 of the substrate 100, and the first microstructure 111 is in an integral structure with the substrate 100 and thus has the same material as the substrate 100, for example, sapphire. Figure 2 As shown, the diameter D of the bottom circumscribed circle of the first microstructure 111 is greater than 400 nm and less than 1000 nm, and preferably greater than 420 nm and less than 710 nm.

[0062] In the illustrated embodiment, by controlling the size of the first microstructure 111 to be between 400 nm and 1000 nm, the size of the first microstructure 111 is more matched to the light extraction efficiency of the light-emitting wavelength band of ultraviolet light, so that the ultraviolet light emitted by the ultraviolet light-emitting diode 1 is more easily scattered when passing through the interface between the substrate 100 and the air, i.e., the second surface 102, reducing total reflection of the ultraviolet light at the interface, and increasing the light extraction efficiency of the ultraviolet light-emitting diode 1. Brightness tests were respectively performed on different ultraviolet light-emitting diode samples, including ultraviolet light-emitting diode sample embodiments P11, P12, P13, P14, and P15, and comparative sample embodiments P16, P17, and P18. The sample embodiments P11-P18 are the same in other layer structures, the current spreading layer 323 has the same light reflection structure, and the only difference is that the diameter D of the bottom circumscribed circle of the first microstructure 111 is different. The sample embodiments P11-P18 each have a different diameter D of the bottom circumscribed circle, as shown in Table 1. After the sample embodiments P11-P18 were lit, brightness tests were performed. The test conditions in this embodiment are not limited to a lighting current of 100 mA and a voltage of 5.2 V, and the obtained brightness ranking result is P14>P12>P15>P11>P13>P17>P16. As can be seen, by changing the diameter D of the bottom circumscribed circle of the first microstructure 111, the luminous brightness of the ultraviolet light-emitting diode 1 is significantly improved, and the size selection of the first microstructure 111 on the surface of the substrate 100 is more conducive to the improvement of the light extraction efficiency of the ultraviolet light-emitting diode 1.

[0063] Table 1

[0064] Sample P11 P12 P13 P14 P15 P16 P17 D (nm) 701 422.9 529 573.9 585 254.5 166.7

[0065] As shown in FIG. 1, the first microstructure 111 is formed directly on the second surface 102 of the substrate 100, and the first microstructure 111 is in an integral structure with the substrate 100 and thus has the same material as the substrate 100, for example, sapphire. Figure 2 As shown in some embodiments, the diameter D of the bottom circumscribed circle of the first microstructure 111 is 0.8-2.5 times, and preferably 1.5-1.85 times, the height H of the first microstructure 111; and the minimum distance L between the center points of adjacent two first microstructures 111 is 0.5-1.2 μm.

[0066] Please refer to Figure 4 , Figure 4This is a cross-sectional schematic diagram of the second embodiment of the present invention. To further improve the light extraction efficiency of the ultraviolet light-emitting diode, the second embodiment provides an ultraviolet light-emitting diode 2. Compared with the first embodiment, the epitaxial layer 200, the first electrode 310, and the second electrode 320 of the ultraviolet light-emitting diode 2 have the same structure. The following only describes the differences in detail.

[0067] A patterned microstructure is formed on the second surface 102 of the substrate 100 of the ultraviolet light-emitting diode 2. In this embodiment, the microstructure 110 is grown on a substrate such as... Figure 5 The flat second surface 102 shown has several second microstructures 112. Each second microstructure 112 has a second material different from the first material used in the substrate 100. To reduce the adverse effect on the light extraction efficiency of the ultraviolet light-emitting diode 2 caused by the large total internal reflection angle when ultraviolet light enters the air interface due to its short wavelength, the refractive index of the second material is relatively lower than that of the first material. The first material is selected from, for example, Al2O3, GaN, SiC, or glass. In this embodiment, Al2O3 is used as an example, with a refractive index of 1.8. The second material is selected from, for example, low-refractive-index materials such as Al2O3, SiO2, Si3N4, or ZnO2. In this embodiment, SiO2 is used as an example, with a refractive index of 1.47. The bottom circumscribed circle diameter D of the second microstructure 112 is greater than 400 nm and less than 1000 nm, preferably greater than 420 nm and less than 710 nm.

[0068] Please refer to Figure 6 , Figure 6 This is a cross-sectional schematic diagram of the third embodiment of the present invention. To further improve the light extraction efficiency of the ultraviolet light-emitting diode, the second embodiment provides an ultraviolet light-emitting diode 3. Compared with the first embodiment, the epitaxial layer 200, the first electrode 310, and the second electrode 320 of the ultraviolet light-emitting diode 3 have the same structure. The following only describes the differences in detail.

[0069] Based on the ultraviolet light-emitting diode 1, the ultraviolet light-emitting diode 3 has a light extraction layer 600 coated on the surface of the substrate 100 facing away from the epitaxial layer 200, such as... Figure 6As shown, the microstructure 110 in the embodiment includes the first microstructure 111 and the third microstructure 113 formed on the surface of the light extraction layer 600 away from the substrate 100. The ultraviolet light emitting diode 3 is based on the ultraviolet light emitting diode 1, the light extraction layer 600 is grown on the light emitting side of the substrate 100, and the third microstructure 113 is etched or imprinted on the surface of the light extraction layer 600 away from the substrate 100, so that the third microstructure 113 is an integral structure with the light extraction layer 600. The light extraction layer 600 has a second material different from the first material adopted by the substrate 100, in order to reduce the adverse effects of the large total reflection angle of ultraviolet light due to its short wavelength on the light extraction efficiency of the ultraviolet light emitting diode 3, the refractive index of the second material is relatively smaller than the refractive index of the first material. The first material is selected from, for example, Al2O3, GaN, SiC or glass, and in the embodiment, Al2O3 is taken as an example, and its refractive index is 1.8; the second material is selected from, for example, Al2O3, SiO2, Si3N4 or ZnO2, etc. low refractive index materials, and in the embodiment, SiO2 is taken as an example, and its refractive index is 1.47. The diameter D of the circumscribed circle of the bottom of each of the first microstructure 111 and the third microstructure 113 is greater than 400 nm and less than 1000 nm, and preferably greater than 420 nm and less than 710 nm. The size of the first microstructure 111 and the size of the third microstructure 113 can be the same or different, and in the embodiment, the same size is taken as an example for illustration.

[0070] In the illustrated embodiment, by controlling the size of the first microstructure 111 and the third microstructure 113 to be between 400 nm and 1000 nm, the size of the first microstructure 111 is more matched to the light extraction efficiency of the ultraviolet light emitting band, so that the ultraviolet light emitted by the ultraviolet light emitting diode 1 is more easily scattered into the light extraction layer 600 when passing through the interface between the substrate 100 and the light extraction layer 600, i.e. the second surface 102, and at the same time, by using the structure of the light extraction layer 600 with varying refractive index, the adverse effects of the large total reflection angle of ultraviolet light due to its short wavelength on the light extraction efficiency of the ultraviolet light emitting diode 3 are reduced, and the total reflection of ultraviolet light when entering the air interface is reduced, further increasing the light extraction efficiency of the ultraviolet light emitting diode 3.

[0071] The brightness of different UV LED samples, including UV LED 3 embodiment samples P31, P32, P33, P34 and P35, and comparative example samples P36, P37 and P38, was tested. The samples P31-P38 were different in the size of the diameter D of the circumscribed circle of the bottom of the first microstructure 111 and the third microstructure 113, and the samples P31-P38 had the same layer structure except for the light-emitting wavelength range of 200-280 nm. The current spreading layer 323 had the same light reflection structure. The diameter D of the circumscribed circle of the bottom of the samples P31-P38 is shown in Table 2. After the samples P31-P38 were lit, the brightness was tested, and the brightness ranking result was P34>P32>P35>P31>P33>P37>P36>P38. It can be seen that, by designing the size of the diameter D of the circumscribed circle of the bottom of the first microstructure 111 and the third microstructure 113, the light-emitting brightness of the UV LED 3 is obviously improved, and the size selection of the first microstructure 111 and the third microstructure 113 on the light-emitting side of the substrate 100 is more conducive to the improvement of the light extraction efficiency of the UV LED 3.

[0072] Table 2

[0073]

[0074]

[0075] Then, the samples P31-P38 were tested under the same process conditions. The brightness of the chip after dicing and packaging was tested, and the brightness improvement amplitude K after packaging was calculated, where K=(brightness after packaging / brightness before packaging)-1. The test results of the brightness improvement amplitude K are shown in Table 2. It can be seen that the size design of the microstructure 110 in the embodiment not only has a high light extraction efficiency improvement amplitude for the UV LED 3 chip itself, but also has a positive effect on the brightness improvement of the packaging.

[0076] Further, the samples P11, P31, P12, P32, P17 and P37 in the first and third embodiments were taken, and UV LED samples P11', P31', P12', P32', P17' and P37' corresponding thereto were added. The difference between the added samples and the original samples in the corresponding embodiments was only that the current spreading layer 323 of the added samples adopted a light absorption structure instead of the light reflection structure in the original samples, and the added samples had the same light reflection structure. After the original samples P11, P31, P12, P32, P17 and P37 and the added samples P11', P31', P12', P32', P17' and P37' were packaged, the brightness improvement amplitude K was tested, and the results are shown in Table 3. Figure 7As shown. On the one hand, a pairwise comparison between the third embodiment sample and the first embodiment sample shows that adding the light extraction layer 600 and the third microstructure 113 on it has a more positive effect on the brightness improvement of the encapsulated lamp; on the other hand, a pairwise comparison between the corresponding original sample and the newly added sample shows that the light absorption structure adopted by the current spreading layer 323 has a more positive effect on the brightness improvement of the encapsulated lamp.

[0077] Please refer to Figure 8 , Figure 8 This is a cross-sectional schematic diagram of the fourth embodiment of the present invention. To further improve the light extraction efficiency of the ultraviolet light-emitting diode, the fourth embodiment provides an ultraviolet light-emitting diode 4. Compared with the first embodiment, the epitaxial layer 200, the first electrode 310, and the second electrode 320 of the ultraviolet light-emitting diode 4 have the same structure. The following only describes the differences in detail.

[0078] Ultraviolet light-emitting diode 4 is in such Figure 5 A light extraction layer 600 is grown on the flat second surface 102 of the substrate 100, and a fourth microstructure 114 is formed by etching or imprinting on the surface of the light extraction layer 600 facing away from the substrate 100. Therefore, the fourth microstructure 114 and the light extraction layer 600 are an integral structure. The light extraction layer 600 has a second material that is different from the first material used in the substrate 100. To reduce the adverse effect on the light extraction efficiency of the ultraviolet light diode 4 caused by the large total internal reflection angle when ultraviolet light enters the air interface due to its short wavelength, the refractive index of the second material is relatively lower than that of the first material. The first material is selected, for example, from Al2O3, GaN, SiC, or glass. In this embodiment, Al2O3 is used as an example, with a refractive index of 1.8. The second material is selected, for example, from low-refractive-index materials such as Al2O3, SiO2, Si3N4, or ZnO2. In this embodiment, SiO2 is used as an example, with a refractive index of 1.47. The bottom circumscribed circle diameter D of the fourth microstructure 114 is greater than 400 nm and less than 1000 nm, preferably greater than 420 nm and less than 710 nm.

[0079] In some embodiments, the substrate 100 and the light extraction layer 600 are made of materials with different refractive indices. For example, the substrate 100 of the ultraviolet light-emitting diodes 3 and 4 is sapphire, and the light extraction layer 600 is made of SiO2. The thickness of the light extraction layer 600 also has a certain influence on the light extraction efficiency of some wavelengths emitted by the ultraviolet light-emitting diodes 3 and 4. Preferably, in some embodiments, for ultraviolet light-emitting diodes with an emission wavelength range of 265-285nm for the light-emitting layer 220, the thickness of the light extraction layer 600 is between 400-600 angstroms. For example, in one embodiment, for an ultraviolet light-emitting diode emitting ultraviolet light with a wavelength of 275nm, a thickness of 520 angstroms in the light extraction layer 600 results in better brightness testing performance.

[0080] Please refer to Figure 9 , Figure 9 Figure 1 is a schematic diagram of a cross section of a pair of ultraviolet light emitting diodes without substrate backside facetting, in some embodiments, generally in the chip process of thick substrate, for example, the thickness of the substrate 100 is 400 μm, the facetting is carried out by laser, the material in a small range of different depths in the same vertical plane inside the substrate 100 is removed, that is, the laser facetting process needs to be carried out several times, generally three to four times of laser facetting from top to bottom. In order to avoid the energy consumption of laser by the substrate pattern, resulting in uneven laser cutting marks of the final substrate 100, especially in the position with deep cutting depth, the energy is often consumed too much in the conduction path, therefore, in the process of substrate patterning, a non-patterned area is reserved on the side of the substrate 100 far away from the first semiconductor layer 210, which is to be cut, in order to ensure the cutting yield. This obviously increases the difficulty and cost of the process for the manufacture of ultraviolet light emitting diodes.

[0081] In the present application, the size of the microstructure 110 on the substrate 100 is set so that the diameter D of the circumscribed circle of the bottom is less than the wavelength of the laser, in some embodiments, Figure 9 The diameter D of the circumscribed circle of the bottom of the first microstructure 111 and the third microstructure 113 is between 400-1000 nm, for example, D is 701 nm, and the facetting laser adopts a laser with a wavelength of 900-1200 nm, for example, 1064 nm, since the size of the microstructure 110 is relatively smaller than the wavelength of the facetting laser, the interface into the substrate is approximately planar for the facetting laser, which is easy to refract and has low energy loss, avoiding the complex process of reserving a blank area in the laser incidence area, which is beneficial to the reduction of chip manufacturing cost. Preferably, the diameter D of the circumscribed circle of the bottom of the microstructure is less than 0.75 times the wavelength of the facetting laser, and the cutting effect of the laser is more difficult to be affected by the energy loss caused by the scattering of the patterned microstructure.

[0082] The present application also provides a light emitting device comprising the ultraviolet light emitting diode as described in any one of the above.

[0083] In summary, compared with the prior art, the ultraviolet light emitting diode provided by the present application changes the size of the patterned microstructure arranged on the light emitting side of the substrate, so that it is adapted to the light emitting wavelength band of the ultraviolet light emitting diode, so that the ultraviolet light is more easily scattered out, thereby improving the light extraction efficiency of the ultraviolet light emitting diode.

[0084] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present application can only be improved in one or several aspects, and it is not necessary to solve all the technical problems listed in the prior art or background art at the same time. Those skilled in the art should understand that what is not mentioned in a claim should not be regarded as a limitation on the claim.

[0085] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and 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 application.

Claims

1. An ultraviolet light emitting diode, characterized by, The application relates to an ultraviolet light emitting diode (UV-LED) comprising: an epitaxial layer having a first semiconductor layer, a light emitting layer and a second semiconductor layer stacked in sequence; a first electrode electrically connected to the first semiconductor layer; a second electrode electrically connected to the second semiconductor layer; a substrate having opposite first and second surfaces, the epitaxial layer being disposed on the first surface of the substrate, the second surface being provided with a patterned microstructure capable of refracting laser light into the substrate for a stealth dicing process, the microstructure having a bottom circumscribed circle with a diameter D smaller than the wavelength of the laser light, the diameter D of the bottom circumscribed circle of the microstructure being greater than 400 nm and smaller than 1000 nm.

2. The UV LED of claim 1, wherein: The light emitting layer has a light emitting wavelength range of 200-280 nm or 280-360 nm.

3. The UV LED of claim 1, wherein: The patterned microstructure comprises first microstructures formed on the second surface, the first microstructures comprising the same material as the substrate.

4. The UV LED of claim 1, wherein: The patterned microstructure comprises second microstructures formed on the second surface, the substrate comprising a first material, the second microstructures comprising a second material different from the substrate.

5. The UV LED of claim 3, wherein: The application further comprises a light extraction layer covering the second surface and the first microstructures, the microstructure further comprising third microstructures formed on the surface of the light extraction layer facing away from the substrate, the substrate comprising a first material, the light extraction layer and the third microstructures comprising a second material different from the substrate.

6. The UV LED of claim 1, wherein: The application further comprises a light extraction layer covering the second surface, the microstructure comprising fourth microstructures formed on the surface of the light extraction layer facing away from the substrate, the substrate comprising a first material, the light extraction layer and the fourth microstructures comprising a second material different from the substrate.

7. The UV LED of claim 5 or 6, wherein: The light emitting layer has a light emitting wavelength range of 265-285 nm, and the light extraction layer has a thickness of 400-600 angstroms.

8. The UV LED of any of claims 4-6, wherein: The second material has a refractive index relatively smaller than that of the first material.

9. The UV LED of claim 8, wherein: The first material is selected from Al2O3, GaN, SiC or glass, and the second material is selected from Al2O3, SiO2, Si3N4 or ZnO2.

10. The UV LED of claim 1, wherein: The diameter D of the bottom circumscribed circle of the microstructure is 420-710 nm.

11. The UV LED of claim 1, wherein: The diameter D of the bottom circumscribed circle of the microstructure is 0.8-1.5 times, 1.5-1.85 times or 1.85-2.5 times of the height H of the microstructure.

12. The UV LED of claim 1, wherein: The minimum distance L between the center points of adjacent microstructures is 0.5-1.2 microns.

13. The UV LED of claim 1, wherein: The microstructure is conical, quasi-conical, quasi-circular truncated conical, quasi-polygonal conical, quasi-polygonal truncated conical, cylindrical or spherical.

14. The UV LED of claim 1, wherein: The plurality of microstructures are arranged in a periodic square lattice, a periodic hexagonal close-packed arrangement, a non-periodic quasi-crystalline arrangement or a random arrangement.

15. The UV LED of claim 1, wherein: The light emitting direction of the ultraviolet light emitting diode is from the light emitting layer to the substrate, and the first electrode and the second electrode are located on the side of the substrate facing away from the second surface.

16. The UV LED of claim 1, wherein: The substrate is subjected to a plurality of laser stealth dicing processes at different depths in the same vertical plane, and the wavelength of the laser is 900-1200 nm.

17. The UV LED of claim 16, wherein: The diameter D of the circumscribed circle of the bottom of the microstructure is 0.75 times or less of the wavelength of the laser.

18. A light-emitting device, characterized in that: An ultraviolet light emitting diode comprising the ultraviolet light emitting diode according to any one of claims 1 to 17.

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