Patent Grant
RE47417
1. Field of the Invention
The present invention relates to a semiconductor light emitting device, a method of manufacturing the same, and a semiconductor light emitting device package using the same, and more particularly, to a semiconductor light emitting device that ensures a maximum light emitting area to maximize luminous efficiency and perform uniform current spreading by using an electrode having a small area, and enables mass production at low cost with high reliability and high quality, a method of manufacturing the same, and a semiconductor light emitting device package using the same.
2. Description of the Related Art
Semiconductor light emitting devices include materials that emit light. For example, light emitting diodes (LEDs) are devices that use diodes, to which semiconductors are bonded, convert energy generated by combination of electrons and holes into light, and emit light. The semiconductor light emitting devices are being widely used as lighting, display devices, and light sources, and development of semiconductor light emitting devices has been expedited.
In particular, the widespread use of cellular phone keypads, side viewers, and camera flashes, which use GaN-based light emitting diodes that have been actively developed and widely used in recent years, contribute to the active development of general illumination that uses light emitting diodes. Applications of the light emitting diodes, such as backlight units of large TVs, headlights of cars, and general illumination, have advanced from small portable products to large products having high power, high efficiency, and high reliability. Therefore, there has been a need for light sources that have characteristics required for the corresponding products.
In general, a semiconductor junction light emitting device has a structure in which p-type and n-type semiconductors are bonded to each other. In the semiconductor junction structure, light may be emitted by recombination of electrons and holes at a region where the two types of semiconductors are bonded to each other. In order to activate the light emission, an active layer may be formed between the two semiconductors. The semiconductor junction light emitting device includes a horizontal structure and a vertical structure according to the position of electrodes of semiconductor layers. The vertical structure includes an epi-up structure and a flip-chip structure. As described above, structural characteristics of semiconductor light emitting devices that are required according to characteristics of individual products are seriously taken into account.
Referring to
When a voltage is applied to the semiconductor light emitting device 1 through the electrodes 14 and 15, electrons move from the n-type semiconductor layer 12, and holes move from the p-type semiconductor layer 10. Light is emitted by recombination of the electrons and the holes. The semiconductor light emitting device 1 includes the active layer 11, and light is emitted from the active layer 11. In the active layer 11, the light emission of the semiconductor light emitting device 1 is activated, and light is emitted. In order to make an electrical connection, the n-type electrode and the p-type electrode are located on the n-type semiconductor layer 12 and the p-type semiconductor layer 10, respectively, with the lowest contact resistances.
The position of the electrodes may change according to the substrate type. For example, when the substrate 13 is a sapphire substrate that is a non-conductive substrate, the electrode of the n-type semiconductor layer 12 cannot be formed on the non-conductive substrate 13, but on the n-type semiconductor layer 12.
Therefore, referring to
In
However, despite the high luminous efficiency of the flip chip light emitting device 2, the n-type electrode and the p-type electrode in the light emitting device 2 need to be disposed in the same plane and bonded in the semiconductor light emitting device 2. After being bonded, the n-type electrode and the p-type electrode are likely to be separated from the electrode contacts 26 and 27. Therefore, there is a need for expensive precision processing equipment. This causes an increase in manufacturing costs, a decrease in productivity, a decrease in yield, and a decrease in product reliability.
In order to solve a variety of problems including the above-described problems, a vertical light emitting device that uses a conductive substrate, not the non-conductive substrate, appeared. A light emitting device 3, shown in
When the non-conductive substrate is removed, the conductive substrate 33 is formed on the n-type semiconductor layer 32, such that the light emitting device 3 has a vertical structure. When the conductive substrate 33 is used, since a voltage can be applied to the n-type semiconductor layer 32 through the conductive substrate 33, an electrode can be formed on the substrate 33. Therefore, as shown in
However, when a high-power light emitting device having a large area is manufactured, an area ratio of the electrode to the substrate needs to be high for current spreading. Therefore, light extraction is limited, light loss is caused by optical absorption, luminous efficiency decreases, and product reliability is reduced.
An aspect of the present invention provides to a semiconductor light emitting device that ensures a maximum light emitting area to maximize luminous efficiency and perform uniform current spreading by using an electrode having a small area, and enables mass production at low cost with high reliability and high quality, a method of manufacturing the same, and a semiconductor light emitting device package using the same.
According to an aspect of the present invention, there is provided a semiconductor light emitting device having a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, a second electrode layer, and insulating layer, a first electrode layer, and a conductive substrate sequentially laminated, wherein the second electrode layer has an exposed area at the interface between the second electrode layer and the second conductivity type semiconductor layer, and the first electrode layer comprises at least one contact hole electrically connected to the first conductivity type semiconductor layer, electrically insulated from the second conductivity type semiconductor layer and the active layer, and extending from one surface of the first electrode layer to at least part of the first conductivity type semiconductor layer.
The semiconductor light emitting device may further include an electrode pad unit formed at the exposed area of the second electrode layer.
The exposed area of the second electrode layer may be a region exposed by a via hole formed through the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer.
The diameter of the via hole may increase in a direction from the second electrode layer toward the first conductivity type semiconductor layer.
An insulating layer may be formed on an inner surface of the via hole.
The exposed area of the second electrode layer may be formed at the edge of the semiconductor light emitting device.
The second electrode layer may reflect light generated from the active layer.
The second electrode layer may include one metal selected from a group consisting of Ag, Al, and Pt.
An irregular pattern may be formed on the surface of the first conductivity type semiconductor layer.
The irregular pattern may have a photonic crystal structure.
The conductive substrate may include one metal selected from a group consisting of Au, Ni, Cu, and W.
The conductive substrate may include one selected from a group consisting of Si, Ge, and GaAs.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor light emitting device, the method including: sequentially laminating a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, a second electrode layer, an insulating layer, a first electrode layer, and a conductive substrate; forming an exposed area at the interface between the second electrode layer and the second conductivity type semiconductor layer; and forming at least one contact hole in the first electrode layer, the contact hole electrically connected to the first conductivity type semiconductor layer, electrically insulated from the second conductivity type semiconductor layer and the active layer, and extending from one surface of the first electrode layer to at least part of the first conductivity type semiconductor layer.
The forming an exposed area of the second electrode layer may include mesa etching the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer.
The conductive substrate may be formed by plating method and laminated. The conductive substrate may be laminated by a substrate bonding method.
According to still another aspect of the present invention, there is provided a semiconductor light emitting device package including: a semiconductor light emitting device package body having a recessed part formed at an upper surface thereof; a first lead frame and a second lead frame mounted to the semiconductor light emitting device package body, exposed at a lower surface of the recessed part, and separated from each other by a predetermined distance; a semiconductor light emitting device mounted to the first lead frame, wherein the semiconductor light emitting device has a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, a second electrode layer, an insulating layer, a first electrode layer, and a conductive substrate sequentially laminated, the second electrode layer comprises an exposed area at the interface between the second electrode layer and the second conductivity type semiconductor layer, and the first electrode layer comprises at least one contact hole electrically connected to the first conductivity type semiconductor layer, electrically insulated from the second conductivity type semiconductor layer and the active layer, and extending from one surface of the first electrode layer to at least part of the first conductivity type semiconductor layer.
The semiconductor light emitting device may further include an electrode pad unit formed at the exposed area of the second electrode layer, and the electrode pad unit is electrically connected to the second lead frame.
The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may however be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
A semiconductor light emitting device 100 according to the exemplary embodiment of the invention includes a first conductivity type semiconductor layer 111, an active layer 112, a second conductivity type semiconductor layer 113, a second electrode layer 120, a first insulating layer 130, a first electrode layer 140, and a conductive substrate 150 that are sequentially laminated. At this time, the second electrode layer 120 has an exposed area at the interface between the second electrode layer 120 and the second conductivity type semiconductor layer 113. The first electrode layer 140 includes at least one contact hole 141. The contact hole 141 is electrically connected to the first conductivity type semiconductor layer 111, electrically insulated from the second conductivity type semiconductor layer 113 and the active layer 112, and extends from one surface of the first electrode layer 140 to at least part of the first conductivity type semiconductor layer 111.
In the semiconductor light emitting device 100, the first conductivity type semiconductor layer 111, the active layer 112, and the second conductivity type semiconductor layer 113 perform light emission. Hereinafter, they are referred to as a light emitting lamination 110. That is, the semiconductor light emitting device 100 includes the light emitting lamination 110, the first electrode layer 140, and the first insulating layer 130. The first electrode layer 140 is electrically connected to the first conductivity type semiconductor layer 111. The second electrode layer 120 is electrically connected to the second conductivity type semiconductor layer 113. The first insulating layer 130 electrically insulates the electrode layers 120 and 140 from each other. Further, the conductive substrate 150 is included as a substrate to grow or support the semiconductor light emitting device 100.
Each of the semiconductor layers 111 and 113 may be formed of a semiconductor, such as a GaN-based semiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, a GaP-based semiconductor, and a GaAsP-based semiconductor. The semiconductor layer may be formed by using, for example, molecular beam epitaxy (MBE). In addition, each of the semiconductor layers may be formed of any one of semiconductors, such as a III-V semiconductor, a II-VI semiconductor, and Si. Each of the semiconductor layers 111 and 113 is formed by doping the above-described semiconductor with appropriate impurities in consideration of the conductivity type.
The active layer 112 is a layer where light emission is activated. The active layer 112 is formed of a material that has a smaller energy bandgap than each of the first conductivity type semiconductor layer 111 and the second conductivity type semiconductor layer 113. For example, when each of the first conductivity type semiconductor layer 111 and the second conductivity type semiconductor layer 113 is formed of a GaN-based compound, the active layer 112 may be formed by using an InAlGaN-based compound semiconductor that has a smaller energy bandgap than GaN. That is, the active layer 112 may include InxAlyGa(1-x-y)N (0≤x≤1, 0≤y≤1, 0≤x+y≤1).
In consideration of characteristics of the active layer 112, the active layer 120 is preferably not doped with impurities. A wavelength of light emitted can be controlled by adjusting a mole ratio of constituents. Therefore, the semiconductor light emitting device 100 can emit any one of infrared light, visible light, and UV light according to the characteristics of the active layer 112.
Each of the electrode layers 120 and 140 is formed in order to apply a voltage to the same conductivity type semiconductor layer. Therefore, in consideration of electroconductivity, the electrode layers 120 and 140 may be formed of metal. That is, the electrode layers 120 and 140 include electrodes that electrically connect the semiconductor layers 111 and 113 to an external current source (not shown). The electrode layers 120 and 140 may include, for example, Ti as an n-type electrode, and Pd or Au as a p-type electrode.
The first electrode layer 140 is connected to the first conductivity type semiconductor layer 111, and the second electrode layer 120 is connected to the second conductivity type semiconductor layer 113. That is, since the first and second layers 140 and 120 are connected to the different conductivity type semiconductor layers from each other, the first and second layers 140 and 120 are electrically separated from each other by the first insulating layer 130. Preferably, the first insulating layer 130 is formed of a material having low electroconductivity. The first insulating layer 130 may include, for example, an oxide such as SiO2.
Preferably, the second electrode layer 120 reflects light generated from the active layer 112. Since the second electrode layer 120 is located below the active layer 112, the second electrode layer 120 is located at the other side of a direction in which the semiconductor light emitting device 100 emits light on the basis of the active layer 112. Light moving from the active layer 112 toward the second electrode layer 120 is in an opposition direction to the direction in which the semiconductor light emitting device 100 emits light. Therefore, the light proceeding toward the second electrode layer 120 needs to be reflected to increase luminous efficiency. Therefore, when the second electrode layer 120 has light reflectivity, the reflected light moves toward a light emitting surface to thereby increase the luminous efficiency of the semiconductor light emitting device 100.
In order to reflect the light generated from the active layer 112, preferably, the second electrode layer 120 is formed of metal that appears white in the visible ray region. For example, the white metal may be any one of Ag, Al, and Pt.
The second electrode layer 120 includes an exposed area at the interface between the second electrode layer 120 and the second conductivity type semiconductor layer 113. A lower surface of the first electrode layer 140 is in contact with the conductive substrate 150, and the first electrode layer 140 is electrically connected to the external current source (not shown) through the conductive substrate 150. However, the second electrode layer 120 requires a separate connecting region so as to be connected to the external current source (not shown). Therefore, the second electrode layer 120 includes an area that is exposed by partially etching the light emitting lamination 110.
In
The via hole 114 is formed by selective etching. In general, the light emitting lamination 110 including the semiconductors is only etched, and the second electrode layer 120 including the metal is not etched. The diameter of the via hole 114 can be appropriately determined by those skilled in the art in consideration of the light emitting area, electrical connection efficiency, and current spreading in the second electrode layer 120.
The first electrode layer 140 includes at least one contact hole 141. The contact hole 141 is electrically connected to the first conductivity type semiconductor layer 111, electrically insulated from the second conductivity type semiconductor layer 113 and the active layer 112, and extends to at least part of the first conductivity type semiconductor layer 111. The first electrode layer 140 includes at least one contact hole 141 in order to connect the first conductivity type semiconductor layer 111 to the external current source (not shown). The contact hole 141 is formed through the second electrode layer 120 between the first electrode layer 140 and the second conductivity type semiconductor layer 113, the second conductivity type semiconductor layer 113, and the active layer 112, and extends to the first conductivity type semiconductor layer 111. Further, the contact hole 141 is formed of an electrode material.
When the contact hole 141 is only used for the electrical connection, the first electrode layer 140 may include one contact hole 141. However, in order to uniformly spread a current that is transmitted to the first conductivity type semiconductor layer 111, the first electrode layer 140 may include a plurality of contact holes 141 at predetermined positions.
The conductive substrate 150 is formed in contact with and is electrically connected to the first electrode layer 140. The conductive substrate 150 may be a metallic substrate or a semiconductor substrate. When the conductive substrate 150 is formed of metal, the metal may be any one of Au, Ni, Cu, and W. Further, when the conductive substrate 150 is the semiconductor substrate, the semiconductor substrate may be formed of any one of Si, Ge, and GaAs. The conductive substrate 150 may be a growth substrate. Alternatively, the conductive substrate 150 may be a supporting substrate. After a non-conductive substrate, such as a sapphire substrate having small lattice-mismatching, is used as a growth substrate, and the non-conductive substrate is removed, the supporting substrate is bonded.
When the conductive substrate 150 is the supporting substrate, it may be formed by using a plating method or a substrate bonding method. Specifically, examples of a method of forming the conductive substrate 150 in the semiconductor light emitting device 100 may include a plating method of forming a plating seed layer to forma substrate and a substrate bonding method of separately preparing the conductive substrate 150 and bonding the conductive substrate 150 by using a conductive adhesive, such as Au, Au—Sn, and Pb—Sr.
With reference to
Referring to
The contact hole 141 is formed to spread the current in the first conductivity type semiconductor layer 111. Therefore, a predetermined number of contact holes 141 are formed, and each of the contact holes 141 has an area small enough to allow uniform current spreading in the first conductivity type semiconductor layer 111. A small number of contact holes 141 may cause deterioration in electrical characteristics due to difficulties in performing current spreading. A large number of contact holes 141 may cause difficulties in forming the contact holes 141 and a reduction in light emitting area due to a decrease in area of the active layer. Therefore, each of the contact holes 141 is formed to have as small area as possible and allow uniform current spreading.
The contact hole 141 extends from the second electrode layer 120 to the inside of the first conductivity type semiconductor layer 111. Since the contact hole 141 is formed to spread the current in the first conductivity type semiconductor layer, the contact hole 141 needs to be electrically separated from the second conductivity type semiconductor layer 113 and the active layer 112. Therefore, preferably, the contact hole 141 is electrically separated from the second electrode layer 120, the second conductivity type semiconductor layer 113, and the active layer 112. Therefore, the first insulating layer 130 may extend while surrounding the contact hole 141. The electrical separation may be performed by using an insulating material, such as a dielectric.
In
As shown in
In
In the semiconductor light emitting device 100 according to the exemplary embodiment of the invention, the first conductivity type semiconductor layer 111 forms the outermost edge in a direction in which emitted light moves. Therefore, an irregular pattern 180 can be easily formed on the surface by using a known method, such as photolithography. In this case, the light emitted from the active layer 112 passes through the irregular pattern 180 formed at the surface of the first conductivity type semiconductor layer 111, and then the light is extracted. The irregular pattern 180 results in an increase in light extraction efficiency.
The irregular pattern 180 may have a photonic crystal structure. Photonic crystals contain different media that have different refractive indexes and are regularly arranged like crystals. The photonic crystals can increase light extraction efficiency by controlling light in unit of length corresponding to a multiple of a wavelength of light.
According to another exemplary embodiment of the present invention, a method of manufacturing a semiconductor light emitting device is provided. The method includes sequentially laminating a first conductivity type semiconductor layer 211, an active layer 212, a second conductivity type semiconductor layer 213, a second electrode layer 220, an insulating layer 230, a first electrode layer 240, and a conductive substrate 250; forming an exposed area at the interface between the second electrode layer 220 and the second conductivity type semiconductor layer 213; and forming at least one contact hole 241 in the second conductivity type semiconductor layer 213, the contact hole 241 electrically connected to the first conductivity type semiconductor layer 211, electrically insulated from the second conductivity type semiconductor layer 213 and the active layer 212, and extending from one surface of the first electrode layer 240 to at least part of the first conductivity type semiconductor layer 211.
At this time, the exposed area of the second electrode layer 220 may be formed by forming the via hole 214 in a light emitting lamination 210 (refer to
Referring to
The semiconductor light emitting device 310 and 320 includes a light emitting unit 310 and a conductive substrate 320. The light emitting unit 310 includes first and second semiconductor layers, an active layer, and electrode layers. A via hole is formed in the light emitting unit 310, and the semiconductor light emitting device 310 and 320 further includes an electrode pad unit 330 at an exposed region. The conductive substrate 320 is electrically connected to the first lead frame 370a, and the electrode pad unit 330 is electrically connected to the second lead frame 370b by a wire 340 or the like.
The semiconductor light emitting device 310 and 320 is electrically connected to the second lead frame 370b, to which the semiconductor light emitting device 310 and 320 is not mounted, by wire bonding 340. Therefore, the semiconductor light emitting device can obtain high luminous efficiency and has a vertical structure. As shown in
The relationship between the current density and the luminous efficiency, and light emitting area are numerically shown in Table 1.
Referring to
However, this problem can be solved by ensuring current spreading by using contact holes according to the embodiments of the invention. Therefore, the deterioration in electrical characteristics that may be caused by the reduction in current density can be prevented by using a method of forming contact holes in the semiconductor light emitting device that do not extend to the light emitting surface for current spreading but are formed therein. Therefore, the semiconductor light emitting device according to the embodiments of the invention performs desired current spreading and ensures a maximum light emitting area to obtain desirable luminous efficiency.
As set forth above, according to exemplary embodiments of the invention, the semiconductor light emitting device can prevent emitted light from being reflected or absorbed by electrodes and ensure the maximum light emitting area by forming the electrodes of semiconductor layers, located in a light emitting direction, below an active layer except for part of the electrodes, thereby maximizing luminous efficiency.
Further, at least one contact hole is formed in the electrode to smoothly perform current spreading, such that uniform current spreading can be performed with the electrode having a small area.
Further, since the via hole is formed at the upper surface of the semiconductor light emitting device, alignment is not required during die bonding, and wire bonding can be easily performed. In addition, since the semiconductor light emitting device has a vertical structure, wire bonding and die bonding that can be easily performed at low cost can be used together when manufacturing a package. Therefore, mass production can be achieved at low cost.
Therefore, according to the embodiments of the invention, mass production of light emitting devices at low cost with high reliability and high quality can be realized.
While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.
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| Child | 14835327 | US |
