Patent Application
20190115511
This application claims priority to Chinese Patent Application No. 201710963559.8 filed on Oct. 16, 2017, the disclosure of which is hereby incorporated by reference in its entirety.
Due to long service life, high vibration resistance, low heat emission and low power consumption, light-emitting diodes have been widely applied in domestic appliances, as well as in instruments as indicators or light sources.
Early GaN-based LED chip production processes commonly comprise four procedures, i.e., MESA etching, transparent conductive layer (such as ITO) production, electrode production and protective layer production. A light-emitting diode produced by following such a process is shown in
The present invention provides a light-emitting diode and its fabrication method, wherein forming a transparent conductive layer, then forming a productive layer, and making the electrodes last, so that the protective layer can simultaneously serve as a current blocking layer, thereby reducing the procedures on one hand and effectively enhancing the luminous efficiency of the light-emitting diode on the other hand.
A light-emitting diode as one aspect of the present invention comprises: an epitaxial laminate, including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down, and having a upper surface which providing an electrode area containing a pad area and an extended area; a transparent conductive layer, forming on the first semiconductor layer, having a first opening to exposing a part surface of the first semiconductor layer corresponding to the pad area; a protective layer, forming on the transparent conductive layer, having a second opening and a third opening respectively at a position corresponding to the pad area and the extended area, while exposing a part surface of the first semiconductor layer corresponding to the pad area and a part surface of the transparent conductive layer corresponding to the extended area; a first electrode, forming on the protective layer, and directly contacting the first semiconductor layer corresponding to the pad area via the first and second openings.
The present invention simultaneously provides a light-emitting diode production method, including the following steps: (1) Forming a epitaxial laminate, including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down in sequence, and having a upper surface; (2) Defining a first electrode area on the upper surface of the epitaxial laminate, the first electrode area including a pad area and an extended area; (3) Depositing a transparent conductive layer on the epitaxial laminate, and forming a first opening in the pad area to exposing a part surface of the first semiconductor surface; (4) Depositing a protective layer on the transparent conductive layer, and forming a second opening and a third opening respectively in the pad area and extended area of the first electrode area, while exposing a part surface of the semiconductor layer in the pad area and a part surface of the transparent conductive layer in the extended area; (5) Forming a first electrode on the protective layer which directly contacting the first semiconductor layer in the pad area via the first and second openings.
In some embodiments, the upper surface of epitaxial laminate further providing a second electrode area; and a mesa is formed on the second electrode area to expose a part of the surface of the second semiconductor layer; the protective layer covers the surface of the mesa and has a fourth opening. Further, the light-emitting diode further comprising a second electrode which is formed on the protective layer, and including a pad and an extension branch; a portion of the upper surface of the extension branch is higher than an upper surface of the first electrode corresponding to the pad area.
In other embodiments, t the second opening has a larger size than the first opening, and the first electrode is in contact with the first semiconductor layer and the transparent conductive layer simultaneously in the pad area.
In other embodiments, the second opening is an annular structure which having an inner-ring diameter be smaller than the diameter of the first opening, and an outer-ring diameter be larger than the diameter of the first opening.
Preferably, the protective layer has a thickness d of λ/4n×(2k−1), where λ is the emission wavelength of the light emitting layer, n is the refractive index of the protective layer, and K is a natural number greater than 1. Preferably, k is a natural number greater than 2. In some implementations, the protective layer can be 200-250 nm thick.
In other embodiments, the first electrode has an upper surface that is undulated in the extended area.
In other embodiments, the first electrode having an upper surface which a portion in the extended area is higher than the part of the upper surface in the pad area.
In other embodiments, the first electrode has a stepped pad.
In other embodiments, the protective layer has several fifth openings around the pad area to exposing a part of the transparent conductive layer; the first electrode leads several metal antennas to the fifth openings in the pad area to be contacted the transparent conductive layer.
In other embodiments, the second opening is annular and having at least one antenna extending away from the pad area; the first electrode be in contact with the transparent conductive layer through the said antenna.
A light-emitting diode according to the second aspect of the present invention comprises: an epitaxial laminate, including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down, and having a upper surface which providing an electrode area containing a pad area and an extended area; a transparent conductive layer, forming on the first semiconductor layer; a protective layer, forming on the transparent conductive layer, having a first opening and a second opening respectively in the pad area and extended area to exposing a part surface of the transparent conductive layer; wherein, the first opening is annular and having at least one antenna extending away from the pad area; a first electrode, forming on the protective layer, having direct electrical connection to the second semiconductor layer via the first and second openings.
In some embodiments, the upper surface of epitaxial laminate further providing a second electrode area; and a mesa is formed on the second electrode area to expose a part of the surface of the second semiconductor layer; the protective layer covers the surface of the mesa and has a third opening. Further, the light-emitting diode includes a second electrode on the protective layer; the second electrode is contact with the surface of the second semiconductor layer via the third opening structure.
In other embodiments, the antenna is located within the pad area.
In other embodiments, the antenna goes beyond the pad area.
Preferably, the number of antennae is 1-20.
In other embodiments, the transparent conductive layer having a fourth opening in the pad area to exposes a part surface of the first semiconductor layer in the pad area.
Preferably, the first opening has an inner-ring diameter be smaller than the diameter of the fourth opening, and an outer-ring diameter be larger than the diameter of the fourth opening.
In other embodiments, the first opening has an outer ring diameter be smaller than the diameter of the fourth opening; the antenna has an outer diameter be greater than the diameter of the fourth opening; and the diameter of the fourth opening is smaller than the diameter of the pad area.
A light-emitting diode according to the third aspect of the present invention comprising: including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down, and having a upper surface which providing an electrode area containing a pad area and an extended area; a transparent conductive layer forming on the first semiconductor layer; a protective layer forming on the transparent conductive layer, and having a several of first openings around the pad area and a second opening in the extended area to exposing a part surface of the first semiconductor layer; a first electrode forming on the protective layer and including a pad, an extension and an antenna, the antenna having its two ends connect to the pad and the transparent conductive layer via the first opening, the extension branch connecting to the transparent conductive layer via the second opening.
In some embodiments, the protective layer has a third opening which is annular in the pad area.
In other embodiments, the transparent conductive layer has a fourth opening structure in the pad area.
Preferably, the third opening has an inner ring diameter smaller than the diameter of the fourth opening, and an outer ring diameter greater than the diameter of the fourth opening.
Preferably, the diameter of the fourth opening is greater than the outer diameter of the third opening and smaller than the inside tangential circle diameter of the first opening.
In other embodiments, the pad has simultaneous contact with the protective layer and the transparent conductive layer.
In other embodiments, the upper surface of epitaxial laminate further providing a second electrode area; and a mesa is formed on the second electrode area to expose a part of the surface of the second semiconductor layer; the protective layer covers the surface of the mesa and has a fifth opening. Further, the light-emitting diode further comprising a second electrode a second electrode formed on the protective layer; the second electrode is in contact with the second semiconductor surface via the fifth opening structure.
Preferably, the number of the antennae is 1-20.
A light-emitting diode according to the fourth aspect of the present invention comprising: an epitaxial laminate including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down; a transparent conductive layer formed on the first semiconductor layer; a protective layer formed on the transparent conductive layer; a first electrode included a pad and an extension branch, wherein the extension branch being formed on the protective layer and having electrical connection to the first semiconductor layer through a series of through holes, while partial upper surface of the extension branch being higher than the upper surface of the pad.
Preferably, the extension branch forms an omni-directional reflector with the protective layer.
Preferably, the protective layer is a layer of optically thinner medium.
In some embodiments, the transparent conductive layer has a first opening at the location corresponding to the pad.
In other embodiments, the protective layer has a second opening at the location corresponding to the pad.
Preferably, the second opening has a larger size than the first opening.
Preferably, the pad has simultaneous contact with the protective layer, the transparent conductive layer and the first semiconductor layer.
Preferably, the second opening is of annular structure, having its inner ring diameter smaller than and the outer ring diameter greater than the diameter of the first opening.
Preferably, the light-emitting diode further comprises a second electrode formed on the protective layer and includes a pad and an extension branch. Wherein, a partial upper surface of the extension branch of the second electrode being higher than the upper surface of the pad of the first electrode.
A light-emitting diode according to the fifth aspect of the present invention comprises: an epitaxial laminate including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down; a transparent conductive layer formed on the first semiconductor layer surface; a protective layer formed on the surface of the transparent conductive layer; a first electrode includes a first pad and a first extension branch, being electrically connected to the first semiconductor layer; a second electrode includes a second pad and an second extension branch, wherein the second extension branch being formed on the protective layer, being electrically connected to the second semiconductor via a several of through holes penetrating the protective layer, the transparent conductive layer, the first semiconductor layer and the light-emitting layer, and having a part upper surface higher than the upper surface of the first pad.
Preferably, the second extension branch form an omni-directional reflector with the protective layer.
Preferably, the protective layer is a layer of optically thinner medium.
In some embodiments, the transparent conductive layer has a first opening at a location corresponding to the pad of the first electrode.
In other embodiments, the protective layer has a second opening at the location corresponding to the first and second pads.
Preferably, the second opening has a larger size than the first opening.
In some embodiments, the first pad is stepped.
In other embodiments, the second extension branch is a closed-loop structure.
In other embodiments, the second pad has a partial upper surface higher than the upper surface of the first pad.
In other embodiments, the second electrode is distributed in the central area of the light-emitting diode, wherein the second pad being located at the center and the second extension branch extending from the pad to two opposite directions.
A light-emitting diode according to the sixth aspect of the present invention comprises: an epitaxial laminate including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down; a transparent conductive layer formed on the first semiconductor layer surface; a protective layer formed on the surface of the transparent conductive layer; a first electrode being electrically connected to the first semiconductor layer; a second electrode formed on the protective layer, includes a second pad and an second extension branch, and being electrically connected to the second semiconductor via a series of through holes, while the second pad having the upper surface at the same height with the upper surface of the second extension branch.
Preferably, the second extension branch form an omni-directional reflector with the protective layer.
Preferably, the ratio of the diameter of the though hole below the second pad to the diameter of the second pad is 1:2-1:20.
Preferably, the area of the through hole below the pad of the second electrode accounts for 2%-60% of the pad area of the second electrode.
In some embodiments, the first electrode includes a first pad and a first extension branch. Further, the transparent conductive layer has a first opening at the location corresponding to the first pad.
In other embodiments, the first electrode includes a first pad and a first extension branch. Further, the protective layer has a second opening at the location corresponding to the first pad.
In some embodiments, the first electrode includes a first pad and a first extension branch. Further, the transparent conductive layer has a first opening at the location corresponding to the first pad, the protective layer has a second opening at the location corresponding to the first pad. Preferably, the second opening has a larger size than the first opening. Preferably, the pad of the first electrode has simultaneous contact with the protective layer, the transparent conductive layer and the second semiconductor layer.
In some embodiments, the first electrode has a stepped pad.
In some embodiments, the second pad has partial upper surface higher than the pad upper surface of the first pad.
In some embodiments, the second electrode is distributed in the central area of the light-emitting diode, wherein the second pad being located at the center and the second extension branch extending from the second pad to two opposite directions.
A light-emitting diode according to the seventh aspect of the present invention comprises: an epitaxial laminate including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down; a transparent conductive layer formed on the first semiconductor layer surface; a protective layer formed on the surface of the transparent conductive layer; a first electrode being electrically connected to the first semiconductor layer; a second electrode formed on the protective layer and includes a second pad and a second extension branch, wherein the protective layer provided a first through hole below the second pad and a second through hole below the second extension branch, the first through holes having a diameter smaller than or equal to the diameter of the second through holes.
Preferably, the number of first through holes is above one; when there are more than one first through holes, the holes are distributed symmetrically about the center.
Preferably, the total area of first through holes accounts for 2%-50% of the second pad area.
Preferably, any single one of the first through holes accounts for 1%-5% of the second pad area.
In some embodiments, the upper surface of the second pad is flush with the upper surface of the second extension branch.
In some embodiments, the first electrode included a first pad and a first extension branch, and a series of third through holes are provided on the protective layer below the first extension branch, and a part surface of the transparent conductive layer is exposed.
In some embodiments, the first electrode included a first pad and a first extension branch, and the first is formed on the protective layer, and is in contact with the transparent conductive layer through the extension branch.
In some embodiments, the first electrode included a first pad and a first extension branch, and the transparent conductive layer has an opening structure below the first pad.
In some embodiments, the first electrode included a first pad and a first extension branch, and the protective layer has an opening structure below the first pad.
In some embodiments, the first electrode included a first pad and a first extension branch, and the first pad is a stepped pad.
A light-emitting diode according to the eighth aspect of the present invention comprises: an epitaxial laminate including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down; a transparent conductive layer formed on the first semiconductor layer surface; a protective layer formed on the surface of the transparent conductive layer; a first electrode included a first pad and a first extension branch, wherein the extension branch being formed on the protective layer, and being electrically connected to the transparent conductive layer via a series of first through holes penetrating the protective layer, and; a second electrode included a second pad and a second extension branch, wherein the extension branch being formed on the protective layer, and being connected to the second semiconductor layer via a series of second through holes penetrating the protective layer, the transparent conductive layer, the first semiconductor layer and the light-emitting layer, and; the first through holes have three or more holes arranged in order, which in at least one among the three adjacent first through holes having a distance to its nearest second through hole is not exceeding the distance between the first extension branch and the second extension branch.
In some embodiments, the first extension branch is parallel to the second extension branch.
In some embodiments, at least one among three adjacent first through holes has a connecting line with its nearest second through hole is perpendicular to the first extension branch.
In some embodiments, y, the distance d1 between two adjacent first through holes and the distance d2 between two adjacent through holes meets the following condition: d2≥2d1.
In some embodiments, the transparent conductive layer has a first opening structure under the first pad to expose a part surface of the second semiconductor layer. Further, the protective layer has a second opening structure below the first pad. Preferably, the second opening has a larger size than the first opening.
In some embodiments, the first pad is a stepped pad.
Preferably, the first extension branch has an undulated upper surface.
Preferably, the second extension branch has an undulated upper surface.
A light-emitting diode according to the ninth aspect of the present invention, comprises: an epitaxial laminate including a first semiconductor layer, a light-emitting layer and a second semiconductor layer from up to down; a transparent conductive layer formed on the first semiconductor layer surface; a protective layer formed on the surface of the transparent conductive layer; a first electrode, being electrically connected to the first semiconductor layer; a second electrode formed on the protective layer and included a second pad and a second extension branch, wherein the protective layer having a first opening structure provided below the second pad to expose a part surface of the second semiconductor layer, and the pad being simultaneously in contact with the second semiconductor layer and the protective layer.
In some embodiments, the first opening is of an annularity form.
In some embodiments, the first electrode includes a first pad and a first extension branch, wherein the transparent conductive layer having a second opening structure below the first pad to exposed part of the first semiconductor layer. Further, the protective layer having a third opening structure below the first pad. Preferably, the third opening has a larger size than the second opening.
In other embodiments, the first electrode has a stepped pad.
In other embodiments, the first electrode include a first pad and a first extension branch, and the first extension branch has an undulated upper surface.
In some embodiments, the first electrode includes a first pad and a first extension branch, and the first pad has its upper surface lower than partial upper surface of the first extension branch.
In some embodiments, the first electrode includes a first pad and a first extension branch, and the first pad has its upper surface lower than partial upper surface of the second extension branch.
In some embodiments, the second extension branch has an undulated upper surface.
The present invention at least has the following advantageous effects:
The said light-emitting diode first has a protective layer formed on the transparent conductive layer before electrodes are formed; the protective layer protects the light-emitting diode from damage on one hand, and can directly serve as a current blocking layer to inhibit excessive current injection and enhance current dispersion of the transparent conductive layer;
The said light-emitting diode has its first electrode in direct contact with the semiconductor layer in the pad area to effectively improve the adhesion between the electrode and the epitaxial layer and reduce the risk of the electrode being separated from the adhesion interface upon routing;
Antennae are formed around the pad area of the first electrode to increase the contact area between the pad area of the first electrode and the transparent conductive layer, relieve current congestion on the pad area and the extended area, and reduce the risk of the electrode metal being extracted and burnt;
(4) The protective layer is designed with refraction effect to effectively reduce the light blocking area of metal in the extended area of the electrode and improve the LED extraction efficiency;
The protective layer is designed to be an omni-directional reflector, capable of improving the reflectivity of the electrode extended area and reducing light absorption efficiency;
The said light-emitting diode first has a protective layer formed on the transparent conductive layer before electrode formation, thereby reducing possible oxidation of active metal in the electrode structure during formation of the protective layer.
The said light-emitting diode is produced by combing current blocking layer and protective layer procedures into one procedure, having simplified the process.
In another aspect, a light-emitting system is provided including a plurality of the light-emitting diodes described above. The light-emitting system can be a system of display, lighting, signage, etc.
The other features and advantages of this present disclosure will be described in detail in the following specification, and it is believed that such features and advantages will become more obvious in the specification or through implementations of this invention. The purposes and other advantages of the present disclosure can be realized and obtained in the structures specifically described in the specifications, claims and drawings.
While the invention will be described in conjunction with exemplary embodiments and methods of use, it will be understood by those skilled in the art that such description is not intended to limit the scope of the present disclosure, and various alternations, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, together with the embodiments, are therefore to be considered in all respects as illustrative and not restrictive. In addition, the drawings are merely illustrative, which are not drawn to scale.
The embodiments of the present disclosure will be described in detail with reference to the accompanying drawings and examples, to help understand and practice the disclosed embodiments, regarding how to solve technical problems using technical approaches for achieving the technical effects. It should be noted that the embodiments and their features described in this disclosure may be combined with each other and such technical proposals are deemed to be within the scope of this disclosure without departing from the spirit of this invention.
Specifically, the substrate 201 can be, but without limitation to, any of the following: sapphire, Aluminium nitride, gallium nitride, silicon and silicon carbide, having plain or patterned surface; the N-type layer 211 is formed on the substrate 201; the light emitting layer 212 is formed on the N-type layer 211; the P-type layer 213 is formed on the light emitting layer 212; the transparent conductive layer 220 is formed on the P-type layer 213; the semiconductor protective layer 230 is formed on the transparent conductive layer 220; the first electrode 241 and the second electrode 242 are formed on the semiconductor protective layer 230.
With reference to
The semiconductor protective layer 230 can be made of SiO2, Si3N4, Al2O3 or TiO2, and SiO2 is selected in this implementation. In this embodiment, the semiconductor protective layer 230 functions to protect the light-emitting diode surface on one hand, and to serve as a current blocking layer on the other hand, so as to inhibit excessive injection of current below the electrode and enhance current dispersion of the transparent conductive layer. Therefore, considering requirements of both functions, the semiconductor protective layer has thickness d of λ/4n×(2k−1), where X is the luminous wavelength of the light-emitting layer 212, n is the refractive index of the protective layer, k is a natural number above 1, preferably 2-3, corresponding thickness is better between 150 nm-500 nm; or otherwise excessively small thickness will adversely affect the performance as a current blocking and protective layer, and excessively large thickness will cause additional light loss due to light absorption by the material.
In this embodiment, the epitaxial laminate forms a mesa 210 and a series of through holes 256 running through the P-type layer 213 and the light-emitting layer 212 to exposing partial surface of the N-type layer 211; the semiconductor protective layer 230 covers the side wall of through hole 256, the side wall between transparent conductive layer 220 and the mesa 210, and the surface of the mesa 210; a fourth opening 254 of a annular form is reserved at the mesa 210; the second electrode 242 is made on the surface of semiconductor protective layer 230, where the pad 245 has contact with the N-type layer 211 via the fourth opening 254, and the extension branch 246 has contact with N-type layer 211 via the through hole 256.
Further, the semiconductor protective layer 230 in this embodiment is preferably made of transparent medium, and can form an omni-reflector with the electrode extension branch, so as to improve the reflective efficiency of the metal-medium interface and reduce light loss due to absorption by the metal.
In this embodiment, the protective layer 230 light-emitting diode functions to protect the light-emitting diode from damage on one hand, and to serve directly as a current blocking layer on the other hand, so as to inhibit excessive current injection below the electrode and improve current dispersion of the transparent conductive layer. Further, the first electrode has direct contact with the semiconductor layer in the pad area to effectively improve the adhesion between the electrode and the epitaxial layer and reduce the risk of the electrode separating from the contact surface upon routing. The pad of the first electrode is designed with steps at multiple locations to effectively buffer impact of wire bonding and to reduce impact and damage to the pad of the first electrode during wire bonding; the extension of the first electrode is provided on the protective layer, and gets in contact with the transparent conductive layer via through holes, so that the extension branch of the first electrode has an undulated upper surface, thereby increasing the angle of light emission at the extension strip, and improving the light extraction efficiency.
This embodiment discloses a light-emitting diode production method, mainly including four procedures, i.e. MESA etching, transparent conductive layer (such as ITO) production, electrode production and protective layer production.
First, provide a epitaxial laminate structure, generally comprising a substrate 201, a N-type layer 211, a light-emitting layer 212, a P-type layer 213.
Then, define a first electrode area and a second electrode area on the surface of the epitaxial laminate with reference to the pattern shown in
Next, make the transparent conductive layer 220 on the P-type layer 213 with reference to the pattern shown in
Next, make the semiconductor protective layer 230 on the transparent conductive layer 220 with reference to the pattern shown in
Next, make first electrode 241 and second electrode 242 on the semiconductor protective layer 230 with reference to the pattern shown in
It should be specially noted that the shape and/or the size of opening 252 are not limited to the description above, and the opening 252 can be designed to a non-circular structure. For example, in some implementations, the first electrode has no protective layer 231 below the pad center, and the pad center has direct contact with P-type layer 213. In other implementations, opening 252 can also be designed to be a structure which has a series antennae distributing around the pad area to expose the transparent conductive layer but no opening structure formed in the pad area, in such case, all the pad part of the first electrode is formed on the protective layer 230, and can be connected with metal leads to the antennae.
It should be specially noted that in some varied embodiments, it is unnecessary for transparent conductive layer 220 to form an opening structure in the pad area; in other embodiments, neither transparent conductive layer 220 nor semiconductor protective layer 230 forms opening in the pad area of the first electrode, in which case pad part 243 of the first electrode is fully formed on the protective layer without contact with transparent conductive layer 220 or P-type layer 213.
In the structure of the light-emitting diode shown in
Further, the semiconductor protective layer 220 can be made of optically thinner material (relative to P-type semiconductor layer, such as GaN); in this case, the semiconductor protective layer has refractive effect; as shown in
In this embodiment, the epitaxial laminate forms a mesa and a series of through holes 255 running through P-type layer 213 and light-emitting layer 212; partial surface of N-type layer 211 is exposed; semiconductor protective layer 230 covers the side wall of through holes 255, the side wall between transparent conductive layer 220 and the mesa, and surface of the mesa; a fourth opening is reserved at the mesa; second electrode 242 is made on the surface of semiconductor protective layer 230; pad part 245 has contact with the N-type layer through the fourth opening, while extension branch 246 has contact with the N-type layer via through holes 255.
Specifically, extension branch 246 of the second electrode is located in the middle of the chip, and has contact with the N-type layer via several through holes 255; extension branch 246 in areas not connected by through holes has upper surface higher than the upper surface of pad 243 of the first electrode, with the height difference ranging from 50 nm-500 nm; the said height difference is recommended but not restrictive; extension branch 246 of the first electrode may terminate at the shortest through hole covered, or properly extend, but should never have direct contact with the pad of the first electrode, as shown in
In this embodiment, extension branch 246 of the second electrode forms an omni-directional reflector with the protective layer below, so as to improve the reflective efficiency of the metal-medium interface and reduce light loss due to absorption by the metal. Similarly, the protective layer can be made of optically thinner medium with refractive effect, thereby effectively reducing the light blocking area of the extension branch of the second electrode. For the principle, refer to
Further, at the extension branch bottom of the second electrode are through holes 255 provided on the P-type layer and the light emitting layer, enabling a waved extension branch, an increased effective area of ITO and higher efficiency of light extraction.
Specifically, pad 245 of the second electrode may have one or more through holes provided below, where the proportion of single through hole diameter to pad diameter of the second electrode is preferably 1:2-1:20, and the total area of all through holes accounts for 2%-60% of the pad 245 of the second electrode; as the number of holes increase, the proportion of hole area also increases.
In this embodiment, only holes are made at the pad bottom of the second electrode for contact with N-type layer, which may effectively increase ITO area and facilitate current injection; meanwhile, most of the pad of the second electrode is on the protective layer, which is good for light extraction.
In this embodiment, one through hole 258 is formed at the center right below pad 245 of the second electrode; the through hole has area accounting for 1%-5% of the pad area of the second electrode, and preferably has a size smaller than or equal to the size of through hole 255 below extension branch 246.
In this embodiment, pads of the first electrode and the second electrode are basically and directly formed on the protective layer. When SixOx is used for protective layer 230, it has good adhesion to the pad base layer (generally the reflective layer) to effectively reduce the risk of electrode separating from the adhesion surface; further, the extension branch bottom of the second electrode is designed with holes to increase the efficient lighting area and further to promote the light extraction efficiency of the chip.
Specifically, the first electrode is composed of pad 243 and extension branch 244; the second electrode is composed of pad 245 and extension branch 246; extension 244 of the first electrode has contact with transparent conductive layer 220 via through holes 253; extension branch 246 of the second electrode has contact with N-type layer 211 via through holes 255; among three running through holes 253a-253c, at least one through hole 253a has distance d3 from the nearest through hole 255a not exceeding the distance d4 between extension branch 244 of the first electrode and extension branch 246 of the second electrode. In this embodiment, extension branch 244 of the first electrode and extension branch 246 of the second electrode are distributed in parallel; among three running through holes 253a-253c, at least one through hole 253a has connecting line to the nearest second through hole 255a perpendicular to the extension branch of the first electrode; distance d1 between two adjacent through holes 255 and distance d2 between two adjacent through holes 253 meet the following condition: d2≈2d1.
Though in the light-emitting diode shown in
In this embodiment, through hole 253 below extension branch 244 of the first electrode has a size slightly smaller than through hole 255 below the extension branch of the second electrode; among four running through holes 253a-253d, only the first and the last through holes, 253a and 253d, have corresponding through holes 255; in such case, the distance d1 between two adjacent through holes 255 and the distance d2 between two adjacent through holes 253 meet the following condition: d2≈3d1.
Although specific embodiments have been described above in detail, the description is merely for purposes of illustration. It should be appreciated, therefore, that many aspects described above are not intended as required or essential elements unless explicitly stated otherwise. Various modifications of, and equivalent acts corresponding to, the disclosed aspects of the exemplary embodiments, in addition to those described above, can be made by a person of ordinary skill in the art, having the benefit of the present disclosure, without departing from the spirit and scope of the disclosure defined in the following claims, the scope of which is to be accorded the broadest interpretation so as to encompass such modifications and equivalent structures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201710963559.8 | Oct 2017 | CN | national |
