Light-emitting diode lighting device

A light-emitting diode (LED) lighting device includes a substrate, a first bottom electrode, a second bottom electrode, a first bottom transparent isolation layer, a second bottom transparent isolation layer, a first vertical LED, a second vertical LED, and a top transparent electrode. The substrate has a first recess and a second recess therein. The first bottom electrode and the second bottom electrode are respectively disposed in the first recess and the second recess and are reflective. The first vertical LED is disposed in the first recess and on the first bottom electrode. The second vertical LED is disposed in the second recess and on the second bottom electrode. The first bottom transparent isolation layer and the second bottom transparent isolation layer are respectively disposed in the first recess and the second recess. The top transparent electrode electrically connects the first vertical LED and the second bottom electrode.

BACKGROUND

In recent years, light-emitting diode (LED) technologies have improved a lot, and LEDs with high power and high brightness have been presented to the market. In addition, the LEDs used as light bulbs have the advantage of long lifetime. Therefore, such LED light bulbs have the tendency to replace other conventional light sources. LEDs can be applied to various types of lamps, such as traffic lights, street lights, and flashlights.

Since LEDs gradually become mainstream light sources, improving properties of LEDs becomes an important issue, and this becomes the main goal in the R&D departments of the LED industries.

SUMMARY

This disclosure provides a light-emitting diode (LED) lighting device to achieve high power, high luminous efficiency, and longer lifetime.

In one aspect of the disclosure, a LED lighting device is provided. The LED lighting device includes a substrate, a first bottom electrode, a second bottom electrode, a first bottom transparent isolation layer, a second bottom transparent isolation layer, at least one first vertical LED, at least one second vertical LED, and a top transparent electrode. The substrate has at least one first recess and at least one second recess therein, in which at least one of the first recess and the second recess has a bottom surface and at least one tapered side surface adjacent to the bottom surface. The first bottom electrode is disposed in the first recess. The second bottom electrode is disposed in the second recess, in which at least one of the first bottom electrode and the second bottom electrode is reflective and covers at least a part of the bottom surface and at least a part of the tapered side surface. The first vertical LED is disposed in the first recess and on the first bottom electrode. The second vertical LED is disposed in the second recess and on the second bottom electrode. The first bottom transparent isolation layer is disposed in the first recess, in which the first bottom transparent isolation layer has at least one opening therein to expose at least a part of the first vertical LED. The second bottom transparent isolation layer is disposed in the second recess, in which the second bottom transparent isolation layer has at least one opening therein to expose at least a part of the second vertical LED. The top transparent electrode electrically connects the first vertical LED and the second bottom electrode.

By electrically connecting the first vertical LED and the second vertical LED in series, the LED lighting device can achieve high power and high luminous efficiency by electrically connecting to a power supply with high voltage. In addition, the current passing the first vertical LED and the second vertical LED needs not to be large to achieve high power and high luminous efficiency. Therefore, the lifetime of the first vertical LED and the second vertical LED may be longer, and cooling may not become a problem.

DETAILED DESCRIPTION

FIG. 1is a schematic cross-sectional view of a light-emitting diode (LED) lighting device100according to one embodiment of this disclosure. As shown inFIG. 1, an LED lighting device100is provided. The LED lighting device100includes a substrate110, bottom electrodes121and126, bottom transparent isolation layers130and131, at least one vertical LED200, at least one vertical LED400, and a top transparent electrode144. The substrate110has at least one recess113and at least one recess116therein. The recess113has a bottom surface114and at least one tapered side surface115adjacent to the bottom surface114, and the recess116has a bottom surface117and at least one tapered side surface118adjacent to the bottom surface117. The bottom electrode121is disposed in the recess113, and the bottom electrode121is reflective and covers at least a part of the bottom surface114and at least a part of the tapered side surface115. The bottom electrode126is disposed in the recess116, and the bottom electrode126is reflective and covers at least a part of the bottom surface117and at least a part of the tapered side surface118. The vertical LED200is disposed in the recess113and on the bottom electrode121. The vertical LED400is disposed in the recess116and on the bottom electrode126. The bottom transparent isolation layer130is disposed in the recess113and has at least one opening132therein to expose at least a part of the vertical LED200. The bottom transparent isolation layer131is disposed in the recess116and has at least one opening136therein to expose at least a part of the vertical LED400. The top transparent electrode144electrically connects the vertical LED400and the bottom electrode121, such that the vertical LEDs200and400are electrically connected in series.

By electrically connecting the vertical LEDs200and400in series, the LED lighting device100can achieve high power and high luminous efficiency. In addition, the current passing through the vertical LEDs200and400can remain small to enhance the lifetime of the vertical LEDs200and400and reduce heat generated by the vertical LEDs200and400.

Specifically, for example, if the voltage difference of each of the vertical LEDs200and400is 3.125 volts, and the current passing through the vertical LEDs200and400is 1 ampere, the power of the combination of the vertical LEDs200and400is 6.25 watts. If a single LED is used to achieve the same power, the current should be 2 amperes. As a result, the single LED may have a shorter lifetime due to the larger passing current, and the cooling of the single LED may also be more difficult.

Because the LED lighting device100employs the top transparent electrode144as its top electrode to interconnect different electronic components, a wire bonding process may not be needed. Therefore, the process yield of the LED lighting device100is improved, and the manufacturing cost of the LED lighting device100is lowered.

The substrate110has a high thermal conductivity. Specifically, the substrate110is made of silicon, such as undoped silicon, p-type silicon, or n-type silicon, or a ceramic material.

When the substrate110is made of silicon, the potential of the substrate110may be operated to be the lowest among all elements of the LED lighting device100, such that the contact surface of the substrate110and the conductive elements above the substrate110(for example, the bottom electrode121or the top transparent electrodes144) totally or partially form a reverse bias of the p-n junction. Therefore, the substrate110is electrically insulated from the conductive elements above the substrate110.

Embodiments of this disclosure are not limited thereto.FIG. 2is a schematic cross-sectional view of the LED lighting device100according to another embodiment of this disclosure. As shown inFIG. 2, the substrate110includes an insulation layer111and a conductive layer112. The insulation layer111may be made of silicon dioxide (SiO2), which may be oxidized from silicon. The conductive layer112may be made of metal such as aluminium, and the conductive layer112may function as a heat-dissipating layer.

The potential of the substrate110may be operated to be the intermediate value of the maximum potential and the minimum potential among all elements of the LED lighting device100, such that the potential differences between the substrate110and the conductive elements above the substrate110(for example, the bottom electrode121or the top transparent electrodes142) are not too large. Therefore, the current does not pass through the insulation layer111, and thus the substrate110is electrically insulated from the conductive elements above the substrate110.

The depth of the recess113is in a range from about 5 μm to about 50 μm. People having ordinary skill in the art can make proper modifications to the depth of the recess113depending on the actual application.

The angle between the bottom surface114and the tapered side surface115is in a range from about 120° to about 160°, and the angle between the bottom surface117and the tapered side surface118is in a range from about 120° to about 160° as well. If the substrate110is made of silicon, and the recess113is formed by a wet etching process, the angle between the bottom surface114and the tapered side surface115is about 125.3°.

The bottom electrodes121and126are made of metal, such as silver. Embodiments of this disclosure are not limited thereto. In other embodiments, the bottom electrodes121and126are multi-layer structures. For example, the bottom electrodes121and126are double-layer structures made of copper and silver or triple-layer structures made of copper, titanium, and silver.

The bottom electrodes121and126functions as a reflective layer to reflect light emitted from the vertical LEDs200and400, such that light emitted from the vertical LEDs200and400forwards upwardly. By the cup-shaped bottom electrodes121and126, light emitted from the vertical LEDs200and400are ensured to forward upwardly and does not forward in an unwanted direction.

The vertical LEDs200and400are in the same electricity polarity. Specifically, the vertical LED400further includes a first semiconductor layer410proximal to the top transparent electrode144and a second semiconductor layer420proximal to the bottom electrode126. The vertical LED200further includes a first semiconductor layer210distal to the bottom electrode121and a second semiconductor layer220proximal to the bottom electrode121. The first semiconductor layers210and410of the vertical LEDs200and400are of the same type, and the second semiconductor layers220and420of the vertical LEDs200and400are of the same type.

More specifically, the first semiconductor layers210and410of the vertical LEDs200and400are n-type semiconductor layers, and the second semiconductor layers220and420of the vertical LEDs200and400are p-type semiconductor layers. Embodiments of this disclosure are not limited thereto. In other embodiments, the first semiconductor layers210and410of the vertical LEDs200and400are p-type semiconductor layers, and the second semiconductor layers220and420of the vertical LEDs200and400are n-type semiconductor layers.

The first semiconductor layers210and410and the second semiconductor layers220and420can be made of gallium nitride (GaN). People having ordinary skill in the art can make proper modifications to the material of the first semiconductor layers210and410and the second semiconductor layers220and420depending on the actual application.

The vertical LED200further includes an active layer230disposed between the first semiconductor layer210and the second semiconductor layer220. The vertical LED400further includes an active layer430disposed between the first semiconductor layer410and the second semiconductor layer420. Specifically, the active layer230and430can be multiple-quantum-well structures.

The bottom transparent isolation layers130and131have a high refractive index. Specifically, the refractive index of the bottom transparent isolation layers130and131is greater than 1.5. The bottom transparent isolation layers130and131may reduce total reflection in the vertical LEDs200and400and thus enhance the light extraction of the vertical LEDs200and400.

The top transparent electrode144is made of indium tin oxide (ITO). People having ordinary skill in the art can make proper modifications to the material of the top transparent electrode144depending on the actual application.

The LED lighting device100further includes at least one vertical LED300, at least one vertical LED500, and a top transparent electrode142. The vertical LED300is disposed in the recess113and on the bottom electrode121. The vertical LED500is disposed in the recess116and on the bottom electrode126. The bottom transparent isolation layer130has an opening134therein to expose at least a part of the vertical LED300. The bottom transparent isolation layer131has an opening138therein to expose at least a part of the vertical LED500. The top transparent electrode144is further electrically connected to the vertical LED500through the opening138, and the top transparent electrode142is electrically connected to the vertical LEDs200and300through the openings132and134. The bottom electrodes121and the top transparent electrodes142cooperate to electrically connect the vertical LEDs200and300in parallel. The bottom electrodes126and the top transparent electrodes144cooperate to electrically connect the vertical LEDs400and500in parallel.

The vertical LEDs200,300,400, and500are in the same electricity polarity. Specifically, the vertical LED300includes a first semiconductor layer310proximal to the top transparent electrode142and a second semiconductor layer320proximal to the bottom electrode121, and the vertical LED500includes a first semiconductor layer510proximal to the top transparent electrode144and a second semiconductor layer520proximal to the bottom electrode126. The first semiconductor layers210,310,410, and510of the vertical LEDs200,300,400, and500are of the same type, and the second semiconductor layers220,320,420, and520of the vertical LEDs200,300,400, and500are of the same type.

Similarly, the substrate110may further have additional recesses, and the LED lighting device100may further includes additional bottom electrodes, top transparent electrodes, and vertical LEDs.FIG. 3Ais a schematic top view of the LED lighting device100according to one embodiment of this disclosure. For example, as shown inFIG. 3A, the LED light device100further includes bottom electrodes191and192, top transparent electrodes146and148, and vertical LEDs610,620,630, and640. The vertical LEDs200and300,400and500,610and620, and630and640are electrically connected to each other via the bottom electrodes121,126,191, and192and the top transparent electrodes142,144,146and148. The vertical LEDs610and620are electrically connected in parallel via the bottom electrode191and the top transparent electrode146. The vertical LEDs630and640are electrically connected in parallel via the bottom electrode192and the top transparent electrode148.

The LED lighting device100further includes an input electrode710and an output electrode720respectively electrically connected to the top transparent electrodes142and148for allowing a power supply to be electrically connected thereto. The input electrode710and the output electrode720are single-layer structures or multi-layer structures, and the input electrode710and the output electrode720are made of conductive materials. For example, the input electrode710and the output electrode720are single-layer structures made of silver, double-layer structures made of copper and silver, or triple-layer structures made of copper, titanium, and silver. In addition, the input electrode710, the output electrode720, and the bottom electrodes121,126,191, and192may be formed in the same process.

Specifically, the shape of the substrate110is a cuboid, and the bottom electrodes, top transparent electrodes, and vertical LEDs are disposed in a line. Embodiments of this disclosure are not limited thereto. The shape of the substrate110may be a cylindrical column, a triangular prism, a cube, a cuboid, a hexagonal column, an octagonal column, or a polygon column.FIG. 3Bis a schematic top view of the LED lighting device100according to another embodiment of this disclosure. For example, as shown inFIG. 3B, the shape of the substrate110is a cylindrical column, and the bottom electrodes, top transparent electrodes, and vertical LEDs are disposed in a ring.

Similarly, the shape of the substrate110may be a cylindrical column, a triangular prism, a cube, a cuboid, a hexagonal column, an octagonal column, or a polygon column. The shape of the bottom electrode122,124,126,191, and192may be a cylindrical column, a cube, a cuboid, a dumbbell-shaped column, or a polygon column. The shape of the LEDs200,300,400,500,610,620,630, and640may be a cylindrical column, a cube, a cuboid, a hexagonal column, an octagonal column, or a polygon column. The shape of the top transparent electrodes142,144,146, and148may be a cylindrical column, a cube, a cuboid, a hexagonal column, an octagonal column, or a polygon column. The shape of the input electrode710and the output electrode720may be a cylindrical column, a cube, a cuboid, a hexagonal column, an octagonal column, or a polygon column.

As shown inFIG. 1, the first vertical LED200further includes a patterned dielectric layer240. The patterned dielectric layer240is disposed between the first semiconductor layer210and the top transparent electrode142. The patterned dielectric layer240covers an edge portion of the first semiconductor layer210and has an opening242. The top transparent electrode142is electrically connected to the vertical LED200through the opening242. The function of the patterned dielectric layer240is to prevent the surface recombination of the vertical LED200and to prevent the leakage of the current through the side surface of the vertical LED200, thereby enhancing the luminous efficiency of the vertical LED200.

Specifically, the material of the patterned dielectric layer240is silicon nitride or silicon dioxide. The patterning of the patterned dielectric layer240is performed by developing and etching process or screen printing and etching process.

The vertical LED200further includes a guard ring250disposed on the patterned dielectric layer240. The function of the guard ring250is to prevent electrostatic discharge (ESD) and to make the current in the top transparent electrode142spread and evenly enter the vertical LED200.

Specifically, the guard ring250is made of metal, such as silver. The patterning of the guard ring250is performed by developing and etching process or screen printing and etching process. If the shapes of the horizontal cross-sections of the patterned dielectric layer240and the guard ring250are the same, the patterning of the guard ring250may be used as the mask of the patterned dielectric layer240.

FIGS. 4A to 4Care horizontal cross-sectional views of the patterned dielectric layer240according to different embodiments of this disclosure. As shown inFIGS. 4A to 4C, the shape of the horizontal cross-section of the patterned dielectric layer240may be a ring, a ring with a cross, or a plurality of rings with a cross. The shape of the horizontal cross-section of guard ring250may be similar to the shape of the horizontal cross-section of the patterned dielectric layer240. Specifically, the shape of the horizontal cross-section of guard ring250may be a ring, a ring with a cross, or a plurality of rings with a cross.

As shown inFIG. 1, other vertical LEDs such as vertical LED300,400, or500may have patterned dielectric layer and the guard ring similar to the vertical LED200as well.

Specifically, the top transparent electrodes142and144may be patterned from a transparent conductive layer. The patterning of top transparent electrodes142and144is performed by developing and etching process or screen printing and etching process.

The substrate110further has a top surface119between the recess113and the recess116, and a part of the bottom electrode121is disposed on the top surface119. The bottom transparent isolation layer130covers the bottom electrode121and exposes the part of the bottom electrode121disposed on the top surface119. Therefore, the top transparent electrode144and the bottom electrode121make an electrical contact with each other on the top surface119, such that the part of the bottom electrode121disposed on the top surface191functions as an auxiliary electrode of the top transparent electrode144, and the bottom electrode121is electrically isolated from the top transparent electrode142by the bottom transparent isolation layer130. The function of the auxiliary electrode is to enhance the conductivity of the top transparent electrode144.

The LED lighting device100further includes at least one top transparent isolation layer160covering at least one of the recesses113and116and at least one of the vertical LEDs200,300,400, and500. The top transparent isolation layer160has a high refractive index. Specifically, the refractive index of the top transparent isolation layer160is greater than 1.5. The refractive index of the bottom transparent isolation layer130and131is greater than or equal to the refractive index of top transparent isolation layer160. The top transparent isolation layer160may reduce total reflection in the LED light device100and thus enhance the light extraction of the vertical LEDs200,300,400, and500.

Specifically, a part of the top transparent isolation layer160covers the recess113and the vertical LED200and300, and another part of top transparent isolation layer160covers the recess116and the vertical LEDs400and500.

In some embodiments, the number of the top transparent isolation layers160is at least two, and the top transparent isolation layers160are stacked. The refractive indices of the top transparent isolation layers160increase toward the vertical LEDs200and300or the vertical LEDs400and500, and the number of the top transparent isolation layers160is up to 5.

The material of the top transparent isolation layer160may be the same as the material of the bottom transparent isolation layer130. People having ordinary skill in the art can make proper modifications to the material of the top transparent isolation layer160depending on the actual application.

The LED lighting device100further includes a phosphor layer170disposed on the top transparent isolation layer160and covering at least one of the recesses113and116and at least one of the vertical LEDs200,300,400, and500.

Specifically, a part of the phosphor layer170covers the recess113and the vertical LEDs200and300, and another part of the phosphor layer170covers the recess116and the vertical LEDs400and500.

The refractive index of the bottom transparent isolation layer130is greater than or equal to the refractive index of the phosphor layer170, and the refractive index of the top transparent isolation layer160is greater than or equal to the refractive index of the phosphor layer170.

The top transparent isolation layer160is shaped to allow optical path lengths from at least one of the vertical LEDs200,300,400, and500through different portions of the phosphor layer170to be substantially the same. Specifically, the top transparent isolation layer160is substantially dome shaped. Therefore, the color of the light passing the phosphor layer170is even. The situation that the color of some of the light passing the phosphor layer170is yellowish and the color of the other of the light passing the phosphor layer170is bluish is avoided.

The LED lighting device100further includes an encapsulation layer180disposed on the phosphor layer170. The encapsulation layer180covers at least one of the recesses113and116and at least one of the vertical LEDs200,300,400, and500. Specifically, a part of the encapsulation layer180covers the recess113and the vertical LEDs200and300, and another part of the encapsulation layer180covers the recess116and the vertical LEDs400and500. Embodiments of this disclosure are not limited thereto.FIG. 5is a schematic cross-sectional view of the LED lighting device100according to another embodiment of this disclosure. As shown inFIG. 5, the encapsulation layer180integrally covers the recesses113and116and the vertical LEDs200,300,400and500.

FIG. 6is a schematic cross-sectional view of the LED lighting device100according to another embodiment of this disclosure. As shown inFIG. 6, the top transparent isolation layer160integrally covers the recesses113and116and the vertical LEDs200,300,400and500. The phosphor layer170integrally covers the recesses113and116and the vertical LEDs200,300,400and500. The encapsulation layer180integrally covers the recesses113and116and the vertical LEDs200,300,400and500.

Specifically, the vertical LEDs200,300,400, and500have top surfaces, and heights of the top surfaces of the vertical LEDs200,300,400, and500are lower than a height of the top surface119of the substrate110. Therefore, lateral light emitted from the vertical LEDs200,300,400, and500is reflected by the bottom electrodes121and126, and there are rooms to dispose additional transparent dielectric layers or phosphor layers in the recesses113and116to adjust optical paths, such that light efficiency of the LED lighting device100is optimized.

As shown inFIG. 1, the number of the vertical LEDs in the recess113and the number of the vertical LEDs in the recess116are the same. Embodiments of this disclosure are not limited thereto. In some embodiment, the number of the vertical LEDs in the recess113and the number of the vertical LEDs in the recess116are different. For example, in some embodiments, the LED lighting device100does not include the vertical LED300. In some embodiments, the LED lighting device100further includes at least one additional vertical LED in the recess113.

FIG. 7is a schematic cross-sectional view of the LED lighting device100according to another embodiment of this disclosure. In the embodiment, the bottom electrode121is not disposed on the top surface119, and a part of the top transparent electrode144is disposed on the tapered side surface115. The top transparent electrode144and the bottom electrode121make an electrical contact with each other on the tapered side surface115.

As shown inFIGS. 1, 2, 5, 6, and 7, the LED lighting device100includes only one substrate, i.e., the substrate110, and all other structures are stacked on the substrate110. Therefore, the manufacturing processes of the LED lighting device100become easy, and problems such as alignment difficulty are avoided, such that the process yield is enhanced and the production cost is lowered.

By electrically connecting the vertical LEDs in series, the LED lighting device100can achieve high power and high luminous efficiency by electrically connecting to a power supply with high voltage. In addition, the current passing the vertical LEDs needs not to be large to achieve high power and high luminous efficiency. Therefore, the lifetime of the vertical LEDs may be longer, and cooling may not become a problem.