TW201807843A - Light-emitting element having a reflective structure with high efficiency - Google Patents

Abstract

A light-emitting element includes a reflective layer; a first transparent layer on the reflective layer; a light-emitting stacked layer having an active layer on the first transparent layer; and a hole formed in the first transparent layer.

Description

Light-emitting element with high efficiency reflective structure

The present invention relates to a light-emitting element, and more particularly to a light-emitting element having a highly efficient reflective structure.

Photoelectric elements, such as light-emitting diodes (LEDs), have been widely used in optical display devices, traffic signs, data storage devices, communication devices, lighting devices, and medical devices. In addition, the LEDs described above can be combined with other components to form a light emitting device. 1 is a schematic structural view of a conventional illuminating device. As shown in FIG. 1, a illuminating device 1 includes a submount 12 having a circuit 14; a solder 16 is located on the subcarrier 12, The solder 16 thus fixes the LED 11 to the sub-carrier 12 and electrically connects the LED 11 to the circuit 14 on the sub-carrier 12; and an electrical connection structure 18 for electrically connecting the electrode 15 of the LED 11 with the sub-carrier 12. The circuit 14 above; wherein the secondary carrier 12 can be a lead frame or a large mounting substrate.

a light-emitting element comprising: an light-emitting layer comprising an active layer, wherein the light-emitting layer has a first surface and a second surface opposite to the first surface; a first light-transmissive layer is located on the second surface; A plurality of holes are formed in the first light transmissive layer; and a single layer is on the first light transmissive layer; wherein the first light transmissive layer comprises oxide or diamond-like carbon.

The embodiments of the present invention will be described in detail, and in the drawings, the same or the like

Fig. 2 is a cross-sectional view showing a light-emitting element of an embodiment of the present application. As shown in FIG. 2, a light-emitting element 2 has a substrate 20; a bonding layer 22 is disposed on the substrate 20; a reflective structure 24 is disposed on the bonding layer 22; and a light-emitting layer 26 is disposed on the reflective structure 24. A first electrode 21 is disposed under the substrate 20; and a second electrode 23 is disposed above the light emitting laminate 26. The light emitting laminate 26 has a first semiconductor layer 262 over the reflective structure 24, an active layer 264 over the first semiconductor layer 262, and a second semiconductor layer 266 over the active layer 264.

The first electrode 21 and/or the second electrode 23 are for receiving an external voltage and may be composed of a transparent conductive material or a metal material. Transparent conductive materials include, but are not limited to, indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide. (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), gallium phosphide (GaP), indium zinc oxide (IZO), diamond-like carbon film (DLC), indium gallium oxide (IGO), gallium aluminum zinc oxide (GAZO) or a compound of the above materials. Metal materials include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), tin (Sn), gold (Au), nickel (Ni), titanium (Ti), platinum (Pt), lead (Pb) , zinc (Zn), cadmium (Cd), antimony (Sb), cobalt (Co) or an alloy of the above materials.

The light emitting laminate 26 has a roughened upper surface 261 and a roughened lower surface 263, which reduces the probability of total reflection and improves light extraction efficiency. The roughened upper surface has a flat portion 265, and the second electrode 23 can be located above the flat portion 265 to enhance the adhesion between the second electrode 23 and the light emitting laminate 26, and reduce the second electrode 23 due to subsequent processes, such as wire bonding. The probability of peeling off from the light-emitting laminate 26 is also high. The material of the light-emitting layer 26 may be a semiconductor material containing more than one element selected from the group consisting of gallium (Ga), aluminum (Al), indium (In), phosphorus (P), nitrogen (N), and zinc (Zn). ), a group of cadmium (Cd) and selenium (Se). The first semiconductor layer 262 is electrically different from the second semiconductor layer 266 for generating electrons or holes. The active layer 124 may emit one or more colored lights, either visible or invisible, and may be of a single heterostructure, a double heterostructure, a double-sided double heterostructure, a multilayer quantum well or a quantum dot.

The reflective structure 24 has a reflective layer 242, a first light transmissive layer 244 and a window layer 248 from the adhesive layer 22 toward the light emitting stack 26. The window layer 248 has a roughened lower surface having a plurality of convex portions 241 and recesses 243. The roughened lower surface further has a flat portion directly under the second electrode 23 for forming an ohmic contact with the first light transmissive layer 244. At least one hole 245 is formed in the first light transmissive layer 244, and the hole 245 may extend downward from the roughened lower surface of the window layer 248 to the reflective layer 242. In another embodiment, the holes 245 may extend downward from the protrusions 241 to the reflective layer 242. The refractive index of the hole 245 is smaller than the refractive index of the window layer 248 and the first light transmissive layer 244. Since the refractive index of the hole 245 is smaller than the refractive index of the window layer 248 and the first light transmissive layer 244, the critical angle of the interface between the window layer 248 and the hole 245 is smaller than the critical angle of the interface between the window layer 248 and the first light transmissive layer 244. Therefore, after the light emitted by the light-emitting layer 26 is directed toward the hole 245, the probability of total reflection at the interface between the window layer 248 and the hole 245 is increased. In addition, the light that is not totally reflected by the window layer 248 and the first light transmissive layer 244 and enters the first light transmissive layer 244, the interface between the first light transmissive layer 244 and the hole 245 also forms total reflection. Thus, the light extraction efficiency of the light-emitting element 2 is improved. The hole 245 may have a funnel shape that is wide and narrow from the cross-sectional view. The reflective structure 24 can further include a second light transmissive layer 246 between the portion of the first light transmissive layer 244 and the window layer 248 to increase the gap between the first light transmissive layer 244 and the window layer 248. Ohmic contact. In another embodiment, the second light transmissive layer 246 can have a hole 245, wherein the hole 245 has a refractive index smaller than that of the window layer 248 and the second light transmissive layer 246. Since the refractive index of the hole 245 is smaller than the refractive index of the window layer 248 and the second light transmissive layer 246, the critical angle between the interface between the second transparent layer 246 and the hole 245 is smaller than the interface between the window layer 248 and the second transparent layer 246. The critical angle is such that after the light emitted by the light-emitting layer 26 is directed toward the hole 245, the probability of total reflection forming at the interface between the second light-transmitting layer 246 and the hole 245 is increased. In yet another embodiment, the reflective structure 24 may have no window layer 248 formed below the light emitting stack 26. At this time, the roughened lower surface 263 of the light-emitting layer 26 has a plurality of convex portions and concave portions to facilitate the formation of the holes 245.

The window layer 248 is transparent to the light emitted by the light-emitting layer 26 for enhancing the light-emitting efficiency, and the material thereof may be a conductive material, including but not limited to indium tin oxide (ITO), indium oxide (InO), and tin oxide (SnO). , cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), gallium phosphide (GaP), oxidation Indium bismuth (ICO), indium tungsten oxide (IWO), indium titanium oxide (ITiO), indium zinc oxide (IZO), indium gallium oxide (IGO), gallium aluminum oxide (GAZO), or a combination thereof. The height difference h between the concave portion 243 and the convex portion 241 of the roughened lower surface is about 1/3 to 2/3 of the thickness t of the window layer, which facilitates the formation of the hole 245.

The material of the first light transmissive layer 244 and/or the second light transmissive layer 246 is transparent to the light emitted by the light emitting layer 26 to increase ohmic contact and current conduction and diffusion between the window layer 248 and the reflective layer 242, and An Omni-Directional Reflector (ODR) is formed with the reflective layer 242. The material may be a transparent conductive material including, but not limited to, indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum oxide zinc (AZO). ), zinc tin oxide (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), gallium phosphide (GaP), indium lanthanum oxide (ICO), indium tungsten oxide (IWO), indium titanium oxide (ITiO), Indium zinc oxide (IZO), indium gallium oxide (IGO), gallium aluminum oxide (GAZO) or a combination of the above. The material of the first light transmissive layer 244 is preferably aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), indium zinc oxide (IZO) or a combination thereof. . The method of forming the first light transmissive layer 244 and/or the second light transmissive layer 246 includes physical vapor deposition, such as electron beam evaporation or sputtering. The reflective layer 242 can reflect light from the light emitting stack 26, and the material thereof can be a metal material including, but not limited to, copper (Cu), aluminum (Al), tin (Sn), gold (Au), silver (Ag), lead. (Pb), titanium (Ti), nickel (Ni), platinum (Pt), tungsten (W) or an alloy of the above materials.

The bonding layer 22 can connect the substrate 20 to the reflective structure 24 and can have a plurality of subordinate layers (not shown). The material of the bonding layer 22 may be a transparent conductive material or a metal material, and the transparent conductive material includes, but is not limited to, indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide. (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), gallium phosphide (GaP), indium oxide oxide (ICO), indium oxide tungsten (IWO) ), indium titanium oxide (ITiO), indium zinc oxide (IZO), indium gallium oxide (IGO), gallium aluminum oxide (GAZO), or a combination thereof. Metal materials include, but are not limited to, copper (Cu), aluminum (Al), tin (Sn), gold (Au), silver (Ag), lead (Pb), titanium (Ti), nickel (Ni), platinum (Pt) , tungsten (W) or an alloy of the above materials.

The substrate 20 can be used to support the light-emitting laminate 26 and other layers or structures thereon, the material of which can be a transparent material or a conductive material. Transparent materials include, but are not limited to, Sapphire, Diamond, Glass, Epoxy, Quartz, Acryl, Al2O3, Zinc Oxide (ZnO) ) or aluminum nitride (AlN) or the like. Conductive materials include, but are not limited to, copper (Cu), aluminum (Al), molybdenum (Mo), tin (Sn), zinc (Zn), cadmium (Cd), nickel (Ni), cobalt (Co), diamond-like carbon film (Diamond Like Carbon; DLC), Graphite, Carbon Fiber, Metal Matrix Composite (MMC), Ceramic Matrix Composite (CMC), Germanium (Si), Phosphating Iodine (IP), zinc selenide (ZnSe), gallium arsenide (GaAs), tantalum carbide (SiC), gallium phosphide (GaP), gallium arsenide (GaAsP), zinc selenide (ZnSe), indium phosphide (InP), lithium gallate (LiGaO2) or lithium aluminate (LiAlO2).

Figure 3 is a cross-sectional view showing a light-emitting element of another embodiment of the present application. A light-emitting element 3 has a similar structure to the above-described light-emitting element 2, but the second light-transmissive layer 246 of the reflective structure 24 has a plurality of holes 30 such that the second light-transmissive layer 246 has a refractive index of less than 1.4, preferably 1.35. As shown in FIG. 4, the hole 30 is formed by fixing the wafer 4 and depositing the second light-transmissive layer 246 by physical vapor deposition in a specific direction, for example, in a direction D perpendicular to the normal angle of the wafer. The material is on the wafer. The hole 30 is formed because the adjustment of the deposition direction D prevents the material from being deposited to a partial region. Among them, the angle θ is about 60 degrees. The refractive index of the second light transmissive layer 246 formed by the hole 30 is lower than that of the light transmissive layer having no holes, which increases the probability of total reflection between the second light transmissive layer 246 and other layer interfaces, and improves the light emitting element. 3 light output efficiency. The first light transmissive layer 244 may be formed under the second light transmissive layer 246 by a physical vapor phase method or a chemical vapor phase method, and the thickness thereof is greater than the thickness of the second light transmissive layer 246, thereby preventing the material of the reflective layer 242 from diffusing to the second layer. Light transmissive layer 246. The first light transmissive layer 244 does not have holes, and the material of the reflective layer 242 is prevented from diffusing into the holes, and the structure of the reflective layer 242 is destroyed, resulting in a decrease in the reflectance of the reflective layer 242. The first light transmissive layer 244 has a first lower surface 247, and the first lower surface 247 can be ground by chemical mechanical polishing (CMP) to have a center line average roughness (Ra) of about 1 nm to 40 nm. When the reflective layer 242 is formed under the first lower surface 247, the reflective layer 242 can form a surface having a lower centerline average roughness, thereby increasing the reflectivity of the reflective layer 242.

The light-emitting element 3 further has at least one conductive portion 32 between the light-emitting layer 26 and the reflective layer 242. In another embodiment, the conductive portion 32 can be located between the window layer 248 and the reflective layer 242. The conductive portion 32 is used to conduct current, and the material thereof may be a transparent conductive material or a metal material, and the transparent conductive material includes, but is not limited to, indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), and cadmium tin oxide (CTO). ), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), gallium phosphide (GaP), indium oxide oxide (ICO), Indium oxide tungsten (IWO), indium titanium oxide (ITiO), indium zinc oxide (IZO), indium gallium oxide (IGO), gallium aluminum oxide (GAZO), or a combination thereof. Metal materials include, but are not limited to, copper (Cu), aluminum (Al), tin (Sn), gold (Au), silver (Ag), lead (Pb), titanium (Ti), nickel (Ni), platinum (Pt) , tungsten (W), germanium (Ge) or an alloy of the above materials.

In this embodiment, the material of the first light transmissive layer 244 and/or the second light transmissive layer 246 may be an insulating material, such as polybenzamine (PI), benzocyclobutene (BCB), perfluorocyclohexane. Alkane (PFCB), Magnesium Oxide (MgO), Su8, Epoxy, Acrylic Resin, Cyclic Olefin Polymer (COC), Polymethyl Methacrylate (PMMA), Polyterephthalic Acid Ethylene glycol (PET), polycarbonate (PC), polyetherimide, fluorocarbon polymer, glass, alumina (Al2O3), cerium oxide (SiOx), oxidation Titanium (TiO2), lanthanum oxide (Ta2O5), tantalum nitride (SiNx), magnesium fluoride (MgF2), spin-on glass (SOG) or tetraethoxydecane (TEOS).

Figure 5 is a cross-sectional view showing a light-emitting element of another embodiment of the present application. As shown in FIG. 5, a light-emitting element 5 has a substrate 50; a light-emitting layer 52 on the substrate 50; a reflective structure 54 on the light-emitting layer 52; and an electrode 56 on the reflective structure 54. Above. The light emitting layer 52 has a first semiconductor layer 522 over the substrate 50, an active layer 524 over the first semiconductor layer 522, and a second semiconductor layer 526 over the active layer 524. The second semiconductor layer 526 and the active layer 524 are removed to expose the first semiconductor layer 522.

The reflective structure 54 has a window layer 540 on the light emitting layer 52; a first light transmissive layer 542 on the window layer 540; a reflective layer 544 on the first light transmissive layer 542; An insulating layer 546 is located above the reflective layer 544. The window layer 540 has a roughened upper surface 541 having a plurality of convex portions 543 and recesses 545. At least one hole 547 is formed in the first light transmissive layer 542 and is located above the roughened upper surface 541. The refractive index of the hole 547 is smaller than the refractive index of the window layer 540 and the first light transmissive layer 542. In another embodiment, the aperture 547 can extend upward from the recess 545. Since the refractive index of the hole 547 is smaller than the refractive index of the window layer 540 and the first light transmissive layer 542, the critical angle of the interface between the window layer 540 and the hole 547 is smaller than the interface between the window layer 540 and the first light transmissive layer 542. The angle, so that the light emitted by the light-emitting layer 52 is directed toward the hole 547, the probability of total reflection forming at the interface between the window layer 540 and the hole 547 is increased. In addition, the light that is not totally reflected by the window layer 540 and the first light transmissive layer 542 and enters the first light transmissive layer 542, the interface between the first light transmissive layer 542 and the hole 547 also forms total reflection. Therefore, the light-emitting efficiency of the light-emitting element 5 is improved, and the hole 547 can be an inverted funnel shape having a narrow width and a narrow shape as viewed in cross section. Because the light emitted by the light-emitting layer 52 increases the probability of total reflection at the interface between the window layer 540 and the hole 547 and the interface between the first light-transmissive layer 542 and the hole 547, the light is reduced to the electrode 56 and is replaced by the electrode 56. The probability of absorption increases the luminous efficiency of the light-emitting element 5. The first insulating layer 546 can coat the reflective layer 544 such that the reflective layer 544 does not directly contact the electrode 56, and the material of the reflective layer 544 is prevented from diffusing to the electrode 56, reducing the reflectivity of the reflective layer 544. The reflective structure 54 further includes a plurality of channels 549 formed in the first light transmissive layer 542 and the first insulating layer 546, and the electrodes 56 can be electrically connected to the light emitting stack 52 via the vias 549. The reflective structure 54 further includes a second light transmissive layer 548. The second light transmissive layer 548 is located between the portion of the first light transmissive layer 542 and the reflective layer 544. The second light transmissive layer 548 has no holes, and the reflective layer 544 can be avoided. The material diffuses into the holes, destroying the structure of the reflective layer 544, resulting in a decrease in the reflectivity of the reflective layer 544.

The electrode 56 has a first conductive layer 562 and a second conductive layer 564, wherein the first conductive layer 562 and the second conductive layer 564 are not in direct contact with each other. The first conductive layer 562 is connected to the first semiconductor layer 522 via the via 549, and the second conductive layer 564 is connected to the window layer 540 via the via 549. In another embodiment, the light-emitting element 5 further includes a first contact layer 51 between the first conductive layer 562 and the first semiconductor layer 522 to increase ohmic contact between the first conductive layer 562 and the first semiconductor layer 522; A second contact layer 53 is located between the second conductive layer 564 and the window layer 540, increasing the ohmic contact between the second conductive layer 564 and the window layer 540, reducing the operating voltage of the light-emitting element 5 to improve efficiency. The material of the first contact layer 51 and the second contact layer 53 is the same as the material of the above electrode.

Figure 6 is a schematic exploded view of a bulb, a bulb 6 having a lamp cover 61; a lens 62 disposed in the lamp cover 61; a lighting module 64 located below the lens 62; and a lamp holder 65 having a The heat dissipation slot 66 is configured to carry the lighting module 64; a connecting portion 67; and an electrical connector 68. The connecting portion 67 connects the socket 65 and the electrical connector 68. The illumination module 66 has a carrier 63; and a plurality of light-emitting elements 60 of any of the foregoing embodiments are located above the carrier 63.

However, the above embodiments are merely illustrative of the principles and effects of the present application, and are not intended to limit the present application. Modifications and variations of the above-described embodiments can be made without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present application is as set forth in the scope of the patent application described below.

1‧‧‧Lighting device

11‧‧‧LED

12‧‧‧ times carrier

13, 20, 50‧‧‧ substrates

14‧‧‧ Circuitry

15, 56‧‧‧ electrodes

16‧‧‧ solder

18‧‧‧Electrical connection structure

2, 3, 40, 5‧‧‧Lighting elements

21‧‧‧First electrode

22‧‧‧Bonded layer

23‧‧‧second electrode

24, 54‧‧‧reflective structure

241, 543‧‧ ‧ convex

242, 544‧‧‧reflective layer

243, 545‧‧ ‧ recess

244, 542‧‧‧ first light transmission layer

245, 30, 547‧‧ holes

246‧‧‧Second light transmission layer

247‧‧‧First lower surface

248, 540‧‧‧ window layer

26‧‧‧Lighting laminate

261, 541‧‧ ‧ rough upper surface

262, 522‧‧‧ first semiconductor layer

263‧‧‧ roughening the lower surface

264, 524‧‧‧ active layer

265‧‧‧flat

266, 526‧‧‧ second semiconductor layer

32‧‧‧Electrical Department

41‧‧‧shade

42‧‧‧ lens

43‧‧‧ Carrier

44‧‧‧Lighting module

45‧‧‧ lamp holder

46‧‧‧heat sink

47‧‧‧Connecting Department

48‧‧‧Electrical connector

51‧‧‧First contact layer

53‧‧‧Second contact layer

546‧‧‧First insulation

548‧‧‧The third light transmission layer

549‧‧‧ channel

562‧‧‧First conductive layer

564‧‧‧Second conductive layer

H‧‧‧height

T‧‧‧thickness

Figure 1 is a schematic view showing the structure of a conventional light-emitting device.

FIG. 2 is a cross-sectional view showing a light-emitting element according to an embodiment of the present application.

FIG. 3 is a cross-sectional view showing a light-emitting element according to another embodiment of the present application.

4 is a schematic view showing a material deposition direction of the second light transmissive layer of the embodiment of FIG. 3.

FIG. 5 is a cross-sectional view showing a light-emitting element according to another embodiment of the present application.

Figure 6 is a schematic exploded view of a light bulb according to an embodiment of the present application.

Claims (10)

A method for fabricating a light-emitting device, comprising: providing a light-emitting layer, wherein the light-emitting layer comprises an active layer; forming a first light-transmissive layer on the light-emitting layer; forming a hole in the first light-transmitting layer And forming a reflective layer over the first light transmissive layer; wherein the first light transmissive layer comprises a transparent oxide. The method of claim 1, further comprising forming a roughened surface on the light emitting stack, wherein the roughened surface comprises a plurality of protrusions and recesses, the holes being formed on at least one of the protrusions. The method of claim 1, further comprising forming a second light transmissive layer over the first light transmissive layer. The method of claim 3, wherein the second light transmissive layer comprises the hole. The method of claim 1, wherein the shape of the hole is funnel shaped. A method of fabricating a light-emitting device, comprising: forming a light-emitting layer, and the light-emitting layer comprises an active layer; forming a window layer on the light-emitting layer; roughening a surface of the window layer to form a roughening Forming a first light transmissive layer over the window layer; forming a hole in the first light transmissive layer; and forming a reflective layer over the first light transmissive layer. The method of claim 6, wherein the roughened surface comprises a plurality of protrusions and recesses, the holes being formed on at least one of the protrusions. The method of claim 7, wherein a portion of the first light transmissive layer is formed on a top end of the convex portion. The method of claim 7, wherein a height difference between the concave portion and the adjacent one of the convex portions is 1/3 to 2/3 of the thickness of the window layer. The method of claim 6, further comprising forming a second light transmissive layer over the window layer.