US20040108511A1 - Light emitting diode and method for manufacturing the same - Google Patents
Light emitting diode and method for manufacturing the same Download PDFInfo
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- US20040108511A1 US20040108511A1 US10/464,514 US46451403A US2004108511A1 US 20040108511 A1 US20040108511 A1 US 20040108511A1 US 46451403 A US46451403 A US 46451403A US 2004108511 A1 US2004108511 A1 US 2004108511A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
- H01L33/46—Reflective coating, e.g. dielectric Bragg reflector
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0093—Wafer bonding; Removal of the growth substrate
Definitions
- the present invention relates to a light emitting diode (LED) and a method for manufacturing the same, and more particularly to a LED comprising a reflective layer including an aluminum layer and an alumina layer so as to improve photoemissive efficiency, which is easily formed using an anode bonding technique, and a method for manufacturing the LED.
- LED light emitting diode
- LEDs are semiconductor devices made of compounds such as GaAs, AlGaAs, GaN, InGaN, AlGaInP, etc., and are widely used as various light sources in the fields of optical communications and electronic devices.
- the LEDs comprise at least one active layer for generating light by recombining electrons with holes.
- a LED comprising active layers, each layer with a thickness of more than 100 ⁇ is referred to as a multiwell (MW) LED
- a LED comprising active layers, each layer with a thickness of less than approximately 100 ⁇ is referred to a multiple quantum well (MQW) LED.
- MQW multiple quantum well
- a LED comprising a single active layer is referred to as a double heterostructure (DH) LED or a single quantum well (SQW) LED. That is, there have been made attempts to improve the luminance of LEDs by adjusting the number and/or the thicknesses of the active layers.
- a reflective layer is formed on the lower surface of a LED, thereby minimizing the amount of light emitted in unnecessary directions, and improving the luminance of light emitted in a desired direction.
- This technique is embodied by forming a back reflective layer made of a metal with high reflectance such as Al, Ag, or etc., on the lower surface of the LED.
- FIGS. 1 a and 1 b illustrate one example of the above conventional technique.
- a LED 10 comprises a substrate 2 , a n-type first conductive clad layer 4 formed on the substrate 2 , an active layer 6 formed on the first conductive clad layer 4 , and a p-type second conductive clad layer 8 formed on the active layer 6 .
- the first conductive clad layer 4 is an n-type layer
- the second conductive clad layer 8 is a p-type layer. Since such configuration is general in LEDs, it is also applied to the present invention.
- the first conductive clad layer 4 may be a p-type layer
- the second conductive clad layer 8 may be an n-type layer. Therefore, selectively, the LED may be grown on a p-type substrate or an n-type substrate.
- the clad layer is formed out of a semiconductor material made of a GaN compound, a sapphire substrate may be used.
- the n-type clad layer 4 is electrically connected to a n-type Ohmic contact layer 11 formed at an area of the upper surface of the n-type clad layer 4 without the active layer 6 and the p-type clad layer 8 grown thereon (more specifically, an area of the upper surface of the n-type clad layer 4 exposed to the outside by growing the active layer 6 and the p-type clad layer 8 thereon and selectively removing the grown active layer 6 and p-type clad layer 8 ), and the p-type clad layer 8 is electrically connected to a p-type Ohmic contact layer 13 .
- a reflective layer 15 made of a metal with high reflectance is formed on the lower surface of the substrate 2 .
- FIG. 1 b schematically illustrates light emission from the active layer 6 .
- the light generated from a point (P) of the active layer 6 is emitted in an upward direction (a) of the LED 10 , i.e., a direction desired by users, and in a downward direction (b) of the LED 10 .
- the quantities of light emitted in the two directions are nearly the same.
- the light (b) emitted in the downward direction of the LED 10 reaches the reflective layer 15 disposed on the lower surface of the substrate 2 , and is reflected by the reflective layer 15 with high reflectance. Then, a certain quantity of the reflected light (b′) is again emitted in the upward direction of the LED 10 due to the high reflectance of the reflective layer 15 and emitted in the upper direction of the LED 10 . Therefore, the reflective layer 15 serves to concentrate the light generated from the active layer 6 so as to emit the light in the upward direction of the LED 10 , thereby minimizing the unnecessary loss light.
- the reflective layer 15 as shown in FIGS. 1 a and 1 b insufficiently improves the photoemissive efficiency of the LED 10 .
- the improvement in photoemissive efficiency of the LED 10 by the reflective layer 15 is not great.
- the reflective layer 15 is formed by an additional deposition step after manufacturing the LED 10 . Therefore, the entire manufacturing process of the LED 10 is complicated and its production cost is increased. Moreover, it is very difficult to form an Al layer or an Ag layer with excellent adhesiveness on the lower surface of the sapphire substrate using a conventional deposition device.
- a LED comprising a reflective layer having an improved configuration and being easily manufactured, and a method for manufacturing the LED, thereby more effectively increasing the luminance of the LED.
- the present invention has been made in view of the above problems, and it is an object of the present invention to provide a LED comprising a reflective layer formed on the lower surface of the LED, including an aluminum layer and an alumina layer with different reflectances, thereby improving reflective characteristics of the reflective layer.
- a light emitting diode comprising: a substrate; a first conductive clad layer formed on the substrate; an active layer formed on the first conductive clad layer; a second conductive clad layer formed on the active layer; an alumina (Al 2 O 3 ) layer formed on the lower surface of the substrate; and an aluminum layer formed on the lower surface of the alumina (A 1 2 O 3 ) layer.
- a light emitting diode comprising: a glass layer; an aluminum layer formed on the glass layer; an alumina (Al 2 O 3 ) layer formed on the aluminum layer; a first conductive clad layer formed on the alumina (Al 2 O 3 ) layer; an active layer formed on the first conductive clad layer; and a second conductive clad layer formed on the active layer.
- a back reflective structure employed by the LED of the present invention includes the aluminum layer and the alumina layer.
- an alumina layer may be additionally formed on the lower surface of the aluminum layer, and the alumina layer serving as a reflective layer may comprise Al atoms at less than 60% of its total weight.
- a method for manufacturing a light emitting diode comprising the steps of: preparing a substrate; forming a first conductive clad layer on the substrate; forming an active layer on the first conductive clad layer; forming a second conductive clad layer on the active layer; and bonding the aluminum film to the lower surface of the substrate by heating and compressing the aluminum film and the substrate under an oxygen atmosphere so as to form an aluminum layer provided with an alumina (Al 2 O 3 ) layer at an interface thereof.
- alumina Al 2 O 3
- a method for manufacturing a light emitting diode comprising the steps of: preparing a substrate; forming a first conductive clad layer on the substrate; forming an active layer on the first conductive clad layer; forming a second conductive clad layer on the active layer; removing the substrate so as to expose the lower surface of the first conductive clad layer to the outside; successively disposing an aluminum film and a glass layer on the lower surface of the first conductive clad layer under an oxygen atmosphere; and bonding the aluminum film to the first conductive clad layer and the glass layer to the aluminum film by heating and compressing the three layers.
- the alumina layer is formed on the interface of the aluminum film with the substrate or the first conductive clad layer by heating and compressing the aluminum film and the substrate or the first conductive clad layer under the oxygen atmosphere.
- a heating temperature applied in the bonding step may be in the range of 250° C. to 500° C.
- a pressure applied to the substrate and the aluminum layer in the bonding step may be at least 30 gf/cm 2 .
- a DC voltage in the range of 300V to 600V may be applied to the substrate or the first conductive clad layer in the bonding step.
- FIGS. 1 a and 1 b are a perspective view and a side view of a conventional light emitting diode (LED);
- FIG. 2 is a perspective view of a LED in accordance with one embodiment of the present invention.
- FIG. 3 is a perspective view of a LED in accordance with another embodiment of the present invention.
- FIGS. 4 a and 4 b are schematic views illustrating a bonding step for forming a back reflective structure in a method for manufacturing a LED in accordance with one embodiment of the present invention
- FIG. 5 is a flow chart illustrating a method for manufacturing a LED in accordance with another embodiment of the present invention.
- FIGS. 6 a and 6 b are schematic views illustrating a bonding step for forming a back reflective structure in a method for manufacturing a LED in accordance with another embodiment of the present invention.
- FIG. 2 is a perspective view of a LED in accordance with one embodiment of the present invention.
- a LED 20 of this embodiment of the present invention comprises a substrate 22 , a first n-type clad layer 24 formed on the substrate 22 , an active layer 26 formed on the n-type clad layer 24 , and a second p-type clad layer 28 formed on the active layer 26 .
- the LED 20 further comprises an n-type Ohmic contact layer 31 formed on the n-type clad layer 24 and a p-type Ohmic contact layer 33 formed on the p-type clad layer 28 .
- the first and second conductive clad layers 24 and 28 and the active layer 26 are made of a semiconductor material of group III to V such as GaN, and a sapphire substrate is used as the substrate 22 .
- the LED 20 of the present invention is characterized in that an aluminum (Al) layer 35 with high reflectance is formed on the lower surface of the substrate 22 and an aluminum oxide or alumina (Al 2 O 3 ) layer 37 with lower reflectance than that of aluminum layer 35 is formed on the aluminum layer 35 .
- Al aluminum
- Al 2 O 3 aluminum oxide or alumina
- the reflective layer is made of only a metal with high reflectance such as Ag or Al.
- the reflectance of the conventional metal-made reflective layer is insufficient. Therefore, the present inventor(s) has (have) researched a method for improving the reflectance of the reflective layer, and consequently, considering optical admittance theory for highly reflective coatings, found that higher reflectance is obtained by using two layers with different reflectances rather than using a single layer with high reflectance.
- a back reflective structure obtained by the above method is achieved by the aluminum layer 35 and the alumina layer 37 shown in FIG. 2.
- the reflective structure employed by this embodiment of the present invention is obtained by additionally forming the alumina layer 37 with a comparatively low reflectance on the aluminum layer 35 with comparatively high reflectance.
- such reflective layer structure comprising the aluminum layer 35 and the alumina layer 37 has reflectance higher than that of the pure aluminum layer 35 , thereby being advantageous in terms of reflective effect and improving photoemissive effect of the LED.
- the alumina layer 37 assists the aluminum layer 35 to be firmly bonded to the substrate 22 .
- the alumina layer 37 preferably comprises Al atoms at less than approximately 60% of its total weight.
- the LED 20 of this embodiment of the present invention further comprises another alumina layer 39 formed on the lower surface of the aluminum layer 35 (Hereinafter, the alumina layer 37 serving as the reflective layer is referred to as an upper alumina layer, and the alumina layer 39 is referred to as a lower alumina layer.).
- the lower alumina layer 39 serves to protect the LED 20 from physical or mechanical stresses during subsequent steps or in use.
- a glass layer (not shown) serving as a supporter like the substrate 22 may be additionally formed on the lower surface of the lower alumina layer 39 .
- FIG. 3 is a perspective view of a LED in accordance with another embodiment of the present invention.
- a LED 50 comprises a glass layer 61 , an aluminum layer 55 , an alumina layer 57 , an n-type clad layer 44 , an active layer 46 , and a p-type clad layer 48 .
- the LED 50 further comprises an n-type Ohmic contact layer 51 formed on the n-type clad layer 44 , and a p-type Ohmic contact layer 53 formed on the p-type clad layer 48 .
- the clad layers 44 and 48 and the active layer 46 are made of a semiconductor material of group III to V such as GaN.
- the LED 50 of this embodiment does not comprise a substrate such as a sapphire substrate.
- the sapphire substrate is removed from the LED and a silicon layer serving as a reflective layer and a supporter is formed on the upper surface of the LED.
- the expensive silicon layer having reflectance smaller than that of the aluminum layer must be used, thereby increasing the production cost of the LED.
- another embodiment of the present invention provides an excellent reflective structure constructed by forming the alumina layer 57 and the aluminum layer 55 , serving as a reflective layer, directly on the lower surface of the n-type clad layer 44 . Further, instead of the substrate or the silicon layer serving to support the LED, the glass layer 61 is formed on the lower surface of the aluminum layer 55 , thereby providing a more stable structure of the LED 50 .
- the LED 50 of FIG. 3 is obtained by growing the active layer 46 and the clad layers 44 and 48 on a substrate using a semiconductor material, removing the substrate, and bonding the alumina layer 57 , the aluminum layer 55 , and the glass layer 61 to the lower surface of the n-type clad layer 44 .
- the detailed manufacturing process of the LED 50 will be described later.
- the reflective structure of this embodiment is obtained by additionally forming the alumina layer 57 with comparatively low reflectance on the aluminum layer 55 with comparatively high reflectance.
- the alumina layer 57 comprises Al atoms at less than 60% of its total weight, thereby forming a firmer bonding structure between the n-type clad layer 44 and the aluminum layer 55 .
- the LED 50 of this embodiment may comprise, on the lower surface of the aluminum layer 55 , another alumina layer like the lower alumina layer 37 of FIG. 2.
- the additional alumina layer is interposed between the glass layer 61 and the aluminum layer 55 .
- the present invention provides a method for manufacturing a LED comprising a reflective layer with excellent reflective characteristics.
- the method for manufacturing the LED of the present invention comprises the steps of successively forming a first conductive clad layer, an active layer, and a second conductive clad layer on a substrate, and bonding an aluminum layer to the lower surface of the substrate by applying heat and pressure thereto under an oxygen atmosphere so that an alumina (Al 2 O 3 ) layer is formed at an interface of the aluminum layer and the substrate.
- a reflective layer is formed out of Al foil using an anode bonding process, without a deposition device.
- the reflective layer with excellent adhesiveness is more easily formed on the lower surface of the substrate such as a sapphire substrate.
- FIGS. 4 a and 4 b schematically illustrate a bonding step for forming a back reflective structure in a method for manufacturing a LED in accordance with one embodiment of the present invention.
- FIG. 4 a schematically shows a chamber 100 used in the manufacturing method of this embodiment of the present invention.
- upper and lower jigs 110 b and 110 a are prepared under an oxygen atmosphere so as to compress a laminated structure.
- a substrate 122 is located on the lower jig 110 a within the chamber 100 so that the upper surface of the substrate 122 is turned down.
- the upper surface of the substrate 122 is provided with a LED area 120 comprising a first conductive clad layer, an active layer, and a second conductive clad layer.
- An aluminum film 135 is disposed on the substrate 122 . Then, the substrate 122 and the aluminum film 135 are heated and compressed by means of the upper and lower jigs 110 b and 110 a so that the aluminum film 135 is bonded to the substrate 122 .
- the bonding step since the aluminum film 135 is heated and compressed under the oxygen atmosphere, the upper and lower surfaces of the aluminum film 135 are reacted with oxygen. As a result, as shown in FIG. 4 b, the aluminum film 135 is changed to an aluminum layer 135 ′ having aluminum (Al 2 O 3 ) layers 137 and 139 respectively formed on its lower and upper surfaces.
- the alumina layer 137 formed on the interface of the substrate 122 and the aluminum layer 135 ′ has lower reflectance than that of the aluminum layer 135 ′, and forms a reflective structure together with the aluminum layer 135 ′.
- the alumina layer 139 exposed to the outside serves to protect the aluminum layer 135 ′ from external stresses.
- the alumina layer 137 serving as the reflective layer. Particularly, in order to form a firm bonding structure between the substrate 122 and the aluminum film 135 , the content of Al of the alumina layer 137 is properly limited in a designated range.
- the interior of the chamber 100 is under an oxygen atmosphere, and a pressure applied in the bonding step is preferably in the range of approximately 30 gf/cm 2 to approximately 300 gf/cm 2 .
- a heating temperature applied in the bonding step is more than approximately 250° C. in consideration of a glass transition temperature (Tg) of aluminum of approximately 400° C. and the above pressure condition.
- Tg glass transition temperature
- the heating temperature does not exceed approximately 500° C.
- a designated DC voltage is applied to the substrate 122 by connecting a power to the lower jig 110 a within the chamber 100 .
- Al ions of the aluminum film 135 move to the substrate 122 by applying a designated DC voltage to the substrate 122 . Thereby, a firm bonding structure between the aluminum film 135 and the substrate 122 is obtained.
- a glass layer (not shown) may be formed on the lower surface of the LED.
- the aluminum film is disposed between the substrate 122 and the glass layer, and bonded thereto by an anode bonding process.
- the substrate 122 is partially removed so as to achieve miniaturization of the LED.
- FIG. 5 is a flow chart illustrating a method for manufacturing a LED in accordance with another embodiment of the present invention.
- the method for manufacturing the LED in accordance with another embodiment of the present invention starts from step 210 for preparing a substrate. Then, a first conductive clad layer, an active layer, and a second conductive clad layer are successively formed on the substrate (step 220 ).
- step 230 the substrate is removed so as to expose the lower surface of the first conductive clad layer.
- An aluminum film and a glass layer are successively disposed on the lower surface of the first conductive clad layer under an oxygen atmosphere (step 240 ).
- the laminated structure is heated and compressed so that the aluminum film and the glass layer are bonded to the first conductive clad layer (step 250 ). Thereby, like the LED 50 of FIG. 3, a back reflective structure comprising the aluminum layer and the alumina layer formed on the glass layer is obtained.
- FIGS. 6 a and 6 b are schematic views illustrating a bonding step for forming a back reflective structure in a method for manufacturing the LED shown in FIG. 5.
- FIG. 6 a schematically shows a chamber 300 used in the manufacturing method of this embodiment of the present invention.
- upper and lower jigs 310 b and 310 a are prepared under an oxygen atmosphere so as to compress a laminated structure.
- a LED device 320 obtained by step 230 of FIG. 5, in which the substrate is removed, is located on the lower jig 310 a within the chamber 300 so that the lower surface of a first conductive clad layer is turned up.
- An aluminum film 335 is disposed on the lower upper surface of the first conductive clad layer.
- the laminated structure is heated and compressed by means of the upper and lower jigs 310 b and 310 a so that the aluminum film 335 is bonded to the first conductive clad layer.
- the aluminum film 335 is heated under the oxygen atmosphere, the upper and lower surfaces of the aluminum film 335 are reacted with oxygen.
- the aluminum film 335 is changed to an aluminum layer 335 ′ having aluminum (Al 2 O 3 ) layers 337 and 339 respectively formed on its lower and upper surfaces.
- the alumina layer 337 having an interface with the first conductive clad layer has lower reflectance than that of the aluminum layer 335 ′, and forms a reflective structure together with the aluminum layer 335 ′.
- the interior of the chamber 300 is under the oxygen atmosphere, and a pressure applied in the bonding step is preferably in the range of approximately 30 gf/cm 2 to approximately 300 gf/cm 2 .
- a heating temperature applied in the bonding step is more than approximately 250° C. in consideration of the above pressure condition.
- the heating temperature does not exceed approximately 500° C.
- one embodiment of the present invention provides a LED comprising a reflective layer formed on the lower surface of the LED, including an aluminum layer and an alumina layer with different reflectances, thereby improving reflective characteristics of the reflective layer. Further, another embodiment of the present invention provides a LED comprising a reflective layer formed on an exposed surface of the LED after removing a substrate therefrom, including an aluminum layer and an alumina layer with different reflectances, thereby improving luminance the LED as well as reflective characteristics the LED.
- the present invention provides a method for manufacturing a LED, in which an aluminum layer is compressed to an area for a reflective layer on the surface of the LED at a high temperature under an oxygen atmosphere, thereby easily forming the aluminum layer, and simultaneously obtaining a reflective structure including the aluminum layer and an alumina layer with different reflectances. Therefore, a LED with excellent luminance is manufactured by a simple process.
Abstract
Disclosed are a light emitting diode (LED) with high luminance and a method for manufacturing the same. The LED comprises a substrate, a first conductive clad layer formed on the substrate, an active layer formed on the first conductive clad layer, a second conductive clad layer formed on the active layer, an alumina (Al2O3) layer formed on the lower surface of the substrate, and an aluminum layer formed on the lower surface of the alumina (Al2O3) layer. Otherwise, the substrate is removed, the aluminum layer and the alumina layer are formed directly on the lower surface of the first conductive clad layer. Compared to a single reflective layer made of a metal, a reflective layer including the aluminum layer and the alumina layer improves reflective characteristics of the LED.
Description
- 1. Field of the Invention
- The present invention relates to a light emitting diode (LED) and a method for manufacturing the same, and more particularly to a LED comprising a reflective layer including an aluminum layer and an alumina layer so as to improve photoemissive efficiency, which is easily formed using an anode bonding technique, and a method for manufacturing the LED.
- 2. Description of the Related Art
- Generally, light emitting diodes (LEDs) are semiconductor devices made of compounds such as GaAs, AlGaAs, GaN, InGaN, AlGaInP, etc., and are widely used as various light sources in the fields of optical communications and electronic devices.
- One of essential factors for determining characteristics of the LED devices is luminance. There have been made many attempts to improve the luminance of LED devices by variously changing their designs.
- For example, in order to improve the luminance of LEDs, the LEDs comprise at least one active layer for generating light by recombining electrons with holes. Among these LEDs, a LED comprising active layers, each layer with a thickness of more than 100Å, is referred to as a multiwell (MW) LED, and a LED comprising active layers, each layer with a thickness of less than approximately 100Å, is referred to a multiple quantum well (MQW) LED. On the other hand, a LED comprising a single active layer is referred to as a double heterostructure (DH) LED or a single quantum well (SQW) LED. That is, there have been made attempts to improve the luminance of LEDs by adjusting the number and/or the thicknesses of the active layers.
- Such conventional techniques have trended toward maximizing light generated by the active layers. However, the aforementioned techniques for improving the luminance of generated light by changing the structure of the active layers create a complicated design of the LED due to increased number of materials, and it is difficult to apply such techniques to a practical process for manufacturing the LED.
- In addition to the aforementioned conventional techniques, there has been made an attempt to improve the structure of the LED so as to effectively use light in a uniform quantity, emitted from the active layers.
- For example, a reflective layer is formed on the lower surface of a LED, thereby minimizing the amount of light emitted in unnecessary directions, and improving the luminance of light emitted in a desired direction. This technique is embodied by forming a back reflective layer made of a metal with high reflectance such as Al, Ag, or etc., on the lower surface of the LED. FIGS. 1a and 1 b illustrate one example of the above conventional technique.
- With reference to FIG. 1a, a
LED 10 comprises asubstrate 2, a n-type firstconductive clad layer 4 formed on thesubstrate 2, anactive layer 6 formed on the firstconductive clad layer 4, and a p-type secondconductive clad layer 8 formed on theactive layer 6. Conventionally, the firstconductive clad layer 4 is an n-type layer, and the secondconductive clad layer 8 is a p-type layer. Since such configuration is general in LEDs, it is also applied to the present invention. However, the firstconductive clad layer 4 may be a p-type layer, and the secondconductive clad layer 8 may be an n-type layer. Therefore, selectively, the LED may be grown on a p-type substrate or an n-type substrate. Further, in case the clad layer is formed out of a semiconductor material made of a GaN compound, a sapphire substrate may be used. - As shown in FIG. 1a, the n-
type clad layer 4 is electrically connected to a n-typeOhmic contact layer 11 formed at an area of the upper surface of the n-type clad layer 4 without theactive layer 6 and the p-type clad layer 8 grown thereon (more specifically, an area of the upper surface of the n-type clad layer 4 exposed to the outside by growing theactive layer 6 and the p-type clad layer 8 thereon and selectively removing the grownactive layer 6 and p-type clad layer 8), and the p-type clad layer 8 is electrically connected to a p-typeOhmic contact layer 13. Areflective layer 15 made of a metal with high reflectance is formed on the lower surface of thesubstrate 2. - When voltage is applied to the Ohmic
contact layers LED 10, electrons from the n-type clad layer 4 and holes from the p-type clad layer 8 are injected into theactive layer 6. Then, the electrons and the holes injected into theactive layer 6 are recombined with each other, thereby generating light. - FIG. 1b schematically illustrates light emission from the
active layer 6. With reference to FIG. 1b, for example, the light generated from a point (P) of theactive layer 6 is emitted in an upward direction (a) of theLED 10, i.e., a direction desired by users, and in a downward direction (b) of theLED 10. Herein, the quantities of light emitted in the two directions are nearly the same. - In the
LED 10 of FIG. 1b, the light (b) emitted in the downward direction of theLED 10 reaches thereflective layer 15 disposed on the lower surface of thesubstrate 2, and is reflected by thereflective layer 15 with high reflectance. Then, a certain quantity of the reflected light (b′) is again emitted in the upward direction of theLED 10 due to the high reflectance of thereflective layer 15 and emitted in the upper direction of theLED 10. Therefore, thereflective layer 15 serves to concentrate the light generated from theactive layer 6 so as to emit the light in the upward direction of theLED 10, thereby minimizing the unnecessary loss light. - However, the
reflective layer 15 as shown in FIGS. 1a and 1 b insufficiently improves the photoemissive efficiency of theLED 10. Particularly, since much of the light emitted toward thereflective layer 15 or reflected from thereflective layer 15 is absorbed by thesapphire substrate 2 with a large thickness, the improvement in photoemissive efficiency of theLED 10 by thereflective layer 15 is not great. - Further, the
reflective layer 15 is formed by an additional deposition step after manufacturing theLED 10. Therefore, the entire manufacturing process of theLED 10 is complicated and its production cost is increased. Moreover, it is very difficult to form an Al layer or an Ag layer with excellent adhesiveness on the lower surface of the sapphire substrate using a conventional deposition device. - Therefore, there are required a LED comprising a reflective layer having an improved configuration and being easily manufactured, and a method for manufacturing the LED, thereby more effectively increasing the luminance of the LED.
- Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a LED comprising a reflective layer formed on the lower surface of the LED, including an aluminum layer and an alumina layer with different reflectances, thereby improving reflective characteristics of the reflective layer.
- It is another object of the present invention to provide a LED comprising a reflective layer formed on an exposed surface of the LED after removing a substrate, including an aluminum layer and an alumina layer with different reflectances, thereby improving luminance of the LED as well as reflective characteristics the LED.
- It is yet another object of the present invention to provide a method for easily manufacturing a LED with excellent luminance, in which a reflective layer including an aluminum layer and an alumina layer with different reflectances is formed on a surface of the LED by compressing the aluminum -layer on the surface of the LED at a high temperature under an oxygen atmosphere.
- In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a light emitting diode (LED) comprising: a substrate; a first conductive clad layer formed on the substrate; an active layer formed on the first conductive clad layer; a second conductive clad layer formed on the active layer; an alumina (Al2O3) layer formed on the lower surface of the substrate; and an aluminum layer formed on the lower surface of the alumina (A1 2O3) layer.
- In accordance with a further aspect of the present invention, there is provided a light emitting diode (LED) comprising: a glass layer; an aluminum layer formed on the glass layer; an alumina (Al2O3) layer formed on the aluminum layer; a first conductive clad layer formed on the alumina (Al2O3) layer; an active layer formed on the first conductive clad layer; and a second conductive clad layer formed on the active layer.
- A back reflective structure employed by the LED of the present invention includes the aluminum layer and the alumina layer. Preferably, an alumina layer may be additionally formed on the lower surface of the aluminum layer, and the alumina layer serving as a reflective layer may comprise Al atoms at less than 60% of its total weight.
- In accordance with another aspect of the present invention, there is provided a method for manufacturing a light emitting diode (LED), comprising the steps of: preparing a substrate; forming a first conductive clad layer on the substrate; forming an active layer on the first conductive clad layer; forming a second conductive clad layer on the active layer; and bonding the aluminum film to the lower surface of the substrate by heating and compressing the aluminum film and the substrate under an oxygen atmosphere so as to form an aluminum layer provided with an alumina (Al2O3) layer at an interface thereof.
- In accordance with yet another aspect of the present invention, there is provided a method for manufacturing a light emitting diode (LED), comprising the steps of: preparing a substrate; forming a first conductive clad layer on the substrate; forming an active layer on the first conductive clad layer; forming a second conductive clad layer on the active layer; removing the substrate so as to expose the lower surface of the first conductive clad layer to the outside; successively disposing an aluminum film and a glass layer on the lower surface of the first conductive clad layer under an oxygen atmosphere; and bonding the aluminum film to the first conductive clad layer and the glass layer to the aluminum film by heating and compressing the three layers.
- In the bonding step of the method for manufacturing the LED, the alumina layer is formed on the interface of the aluminum film with the substrate or the first conductive clad layer by heating and compressing the aluminum film and the substrate or the first conductive clad layer under the oxygen atmosphere. In order to form the alumina layer, preferably, a heating temperature applied in the bonding step may be in the range of 250° C. to 500° C., and a pressure applied to the substrate and the aluminum layer in the bonding step may be at least 30 gf/cm2. In order to form a firmer bonding structure of the aluminum layer to the substrate or the first conductive clad layer, preferably, a DC voltage in the range of 300V to 600V may be applied to the substrate or the first conductive clad layer in the bonding step.
- The above and other objects, 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:
- FIGS. 1a and 1 b are a perspective view and a side view of a conventional light emitting diode (LED);
- FIG. 2 is a perspective view of a LED in accordance with one embodiment of the present invention;
- FIG. 3 is a perspective view of a LED in accordance with another embodiment of the present invention;
- FIGS. 4a and 4 b are schematic views illustrating a bonding step for forming a back reflective structure in a method for manufacturing a LED in accordance with one embodiment of the present invention;
- FIG. 5 is a flow chart illustrating a method for manufacturing a LED in accordance with another embodiment of the present invention; and
- FIGS. 6a and 6 b are schematic views illustrating a bonding step for forming a back reflective structure in a method for manufacturing a LED in accordance with another embodiment of the present invention.
- Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings.
- FIG. 2 is a perspective view of a LED in accordance with one embodiment of the present invention.
- With reference to FIG. 1, a LED20 of this embodiment of the present invention comprises a
substrate 22, a first n-type cladlayer 24 formed on thesubstrate 22, anactive layer 26 formed on the n-type cladlayer 24, and a second p-type cladlayer 28 formed on theactive layer 26. - The same as the
LED 10 of FIG. 1a, the LED 20 further comprises an n-typeOhmic contact layer 31 formed on the n-type cladlayer 24 and a p-typeOhmic contact layer 33 formed on the p-type cladlayer 28. The first and second conductive cladlayers active layer 26 are made of a semiconductor material of group III to V such as GaN, and a sapphire substrate is used as thesubstrate 22. - The LED20 of the present invention is characterized in that an aluminum (Al)
layer 35 with high reflectance is formed on the lower surface of thesubstrate 22 and an aluminum oxide or alumina (Al2O3)layer 37 with lower reflectance than that ofaluminum layer 35 is formed on thealuminum layer 35. Herein, thealuminum layer 35 and thealumina layer 37 serve as a single reflective layer. - Conventionally, the reflective layer is made of only a metal with high reflectance such as Ag or Al. However, the reflectance of the conventional metal-made reflective layer is insufficient. Therefore, the present inventor(s) has (have) researched a method for improving the reflectance of the reflective layer, and consequently, considering optical admittance theory for highly reflective coatings, found that higher reflectance is obtained by using two layers with different reflectances rather than using a single layer with high reflectance. A back reflective structure obtained by the above method is achieved by the
aluminum layer 35 and thealumina layer 37 shown in FIG. 2. - The reflective structure employed by this embodiment of the present invention is obtained by additionally forming the
alumina layer 37 with a comparatively low reflectance on thealuminum layer 35 with comparatively high reflectance. As described above, such reflective layer structure comprising thealuminum layer 35 and thealumina layer 37 has reflectance higher than that of thepure aluminum layer 35, thereby being advantageous in terms of reflective effect and improving photoemissive effect of the LED. - Further, the
alumina layer 37 assists thealuminum layer 35 to be firmly bonded to thesubstrate 22. In order to form a firmer boding of thealuminum layer 35 to the first conductive cladlayer 24, thealumina layer 37 preferably comprises Al atoms at less than approximately 60% of its total weight. - As shown in FIG. 2, the LED20 of this embodiment of the present invention further comprises another
alumina layer 39 formed on the lower surface of the aluminum layer 35 (Hereinafter, thealumina layer 37 serving as the reflective layer is referred to as an upper alumina layer, and thealumina layer 39 is referred to as a lower alumina layer.). In this embodiment, thelower alumina layer 39 serves to protect the LED 20 from physical or mechanical stresses during subsequent steps or in use. - In FIG. 2, in case the
aluminum layer 35 or thelower alumina layer 39 is formed on the lower surface of the LED 20, a glass layer (not shown) serving as a supporter like thesubstrate 22 may be additionally formed on the lower surface of thelower alumina layer 39. - FIG. 3 is a perspective view of a LED in accordance with another embodiment of the present invention.
- With reference to FIG. 3, a
LED 50 comprises aglass layer 61, analuminum layer 55, analumina layer 57, an n-type cladlayer 44, anactive layer 46, and a p-type cladlayer 48. - The
LED 50 further comprises an n-typeOhmic contact layer 51 formed on the n-type cladlayer 44, and a p-typeOhmic contact layer 53 formed on the p-type cladlayer 48. The clad layers 44 and 48 and theactive layer 46 are made of a semiconductor material of group III to V such as GaN. - Differently from the LED20 of FIG. 2, the
LED 50 of this embodiment does not comprise a substrate such as a sapphire substrate. Conventionally, in order to improve the reflective effect of the reflective layer, the sapphire substrate is removed from the LED and a silicon layer serving as a reflective layer and a supporter is formed on the upper surface of the LED. However, in such conventional manner, the expensive silicon layer having reflectance smaller than that of the aluminum layer must be used, thereby increasing the production cost of the LED. - In order to overcome the above problems, another embodiment of the present invention provides an excellent reflective structure constructed by forming the
alumina layer 57 and thealuminum layer 55, serving as a reflective layer, directly on the lower surface of the n-type cladlayer 44. Further, instead of the substrate or the silicon layer serving to support the LED, theglass layer 61 is formed on the lower surface of thealuminum layer 55, thereby providing a more stable structure of theLED 50. - The
LED 50 of FIG. 3 is obtained by growing theactive layer 46 and theclad layers alumina layer 57, thealuminum layer 55, and theglass layer 61 to the lower surface of the n-type cladlayer 44. The detailed manufacturing process of theLED 50 will be described later. - Similarly to the FIG. 2, the reflective structure of this embodiment is obtained by additionally forming the
alumina layer 57 with comparatively low reflectance on thealuminum layer 55 with comparatively high reflectance. Preferably, thealumina layer 57 comprises Al atoms at less than 60% of its total weight, thereby forming a firmer bonding structure between the n-type cladlayer 44 and thealuminum layer 55. - Although not shown in FIG. 3, the
LED 50 of this embodiment may comprise, on the lower surface of thealuminum layer 55, another alumina layer like thelower alumina layer 37 of FIG. 2. In this case, the additional alumina layer is interposed between theglass layer 61 and thealuminum layer 55. - Further, the present invention provides a method for manufacturing a LED comprising a reflective layer with excellent reflective characteristics.
- The method for manufacturing the LED of the present invention comprises the steps of successively forming a first conductive clad layer, an active layer, and a second conductive clad layer on a substrate, and bonding an aluminum layer to the lower surface of the substrate by applying heat and pressure thereto under an oxygen atmosphere so that an alumina (Al2O3) layer is formed at an interface of the aluminum layer and the substrate.
- In the method for manufacturing the LED in accordance with the present invention, a reflective layer is formed out of Al foil using an anode bonding process, without a deposition device. Thereby, the reflective layer with excellent adhesiveness is more easily formed on the lower surface of the substrate such as a sapphire substrate.
- In a manner for forming a reflective layer using the anode bonding process employed by the present invention, the aluminum layer is heated and compressed under the oxygen atmosphere so that Al of the aluminum layer at the interface of the aluminum layer and the substrate is bonded with oxygen and the alumina (Al2O3) layer is formed. FIGS. 4a and 4 b schematically illustrate a bonding step for forming a back reflective structure in a method for manufacturing a LED in accordance with one embodiment of the present invention.
- FIG. 4a schematically shows a
chamber 100 used in the manufacturing method of this embodiment of the present invention. Within thechamber 100, upper andlower jigs 110 b and 110 a are prepared under an oxygen atmosphere so as to compress a laminated structure. Asubstrate 122 is located on thelower jig 110 a within thechamber 100 so that the upper surface of thesubstrate 122 is turned down. Herein, as described above, the upper surface of thesubstrate 122 is provided with aLED area 120 comprising a first conductive clad layer, an active layer, and a second conductive clad layer. Analuminum film 135 is disposed on thesubstrate 122. Then, thesubstrate 122 and thealuminum film 135 are heated and compressed by means of the upper andlower jigs 110 b and 110 a so that thealuminum film 135 is bonded to thesubstrate 122. - In the bonding step, since the
aluminum film 135 is heated and compressed under the oxygen atmosphere, the upper and lower surfaces of thealuminum film 135 are reacted with oxygen. As a result, as shown in FIG. 4b, thealuminum film 135 is changed to analuminum layer 135′ having aluminum (Al2O3) layers 137 and 139 respectively formed on its lower and upper surfaces. Herein, thealumina layer 137 formed on the interface of thesubstrate 122 and thealuminum layer 135′ has lower reflectance than that of thealuminum layer 135′, and forms a reflective structure together with thealuminum layer 135′. Further, thealumina layer 139 exposed to the outside serves to protect thealuminum layer 135′ from external stresses. - In the aforementioned aluminum layer bonding step, it is important to properly form the
alumina layer 137 serving as the reflective layer. Particularly, in order to form a firm bonding structure between thesubstrate 122 and thealuminum film 135, the content of Al of thealumina layer 137 is properly limited in a designated range. - For this purpose, the interior of the
chamber 100 is under an oxygen atmosphere, and a pressure applied in the bonding step is preferably in the range of approximately 30 gf/cm2 to approximately 300 gf/cm2. - Preferably, a heating temperature applied in the bonding step is more than approximately 250° C. in consideration of a glass transition temperature (Tg) of aluminum of approximately 400° C. and the above pressure condition. However, since the aluminum layer and other layers are deformed at an excessively high temperature, more preferably, the heating temperature does not exceed approximately 500° C.
- In the bonding step shown in FIG. 4a, a designated DC voltage is applied to the
substrate 122 by connecting a power to thelower jig 110 a within thechamber 100. - Therefore, in the bonding step, Al ions of the
aluminum film 135 move to thesubstrate 122 by applying a designated DC voltage to thesubstrate 122. Thereby, a firm bonding structure between thealuminum film 135 and thesubstrate 122 is obtained. - Further, a glass layer (not shown) may be formed on the lower surface of the LED. In this case, similarly to the manner of FIG. 4a, the aluminum film is disposed between the
substrate 122 and the glass layer, and bonded thereto by an anode bonding process. Herein, since the glass layer sufficiently serves as a supporter, preferably, thesubstrate 122 is partially removed so as to achieve miniaturization of the LED. - Differently from the above-described method for manufacturing the LED, there is provided another method for manufacturing a LED comprising the step of removing a substrate and using a glass layer. FIG. 5 is a flow chart illustrating a method for manufacturing a LED in accordance with another embodiment of the present invention.
- With reference to FIG. 5, the method for manufacturing the LED in accordance with another embodiment of the present invention starts from
step 210 for preparing a substrate. Then, a first conductive clad layer, an active layer, and a second conductive clad layer are successively formed on the substrate (step 220). - In
step 230, the substrate is removed so as to expose the lower surface of the first conductive clad layer. An aluminum film and a glass layer are successively disposed on the lower surface of the first conductive clad layer under an oxygen atmosphere (step 240). Next, the laminated structure is heated and compressed so that the aluminum film and the glass layer are bonded to the first conductive clad layer (step 250). Thereby, like theLED 50 of FIG. 3, a back reflective structure comprising the aluminum layer and the alumina layer formed on the glass layer is obtained. - FIGS. 6a and 6 b are schematic views illustrating a bonding step for forming a back reflective structure in a method for manufacturing the LED shown in FIG. 5.
- Similarly to the
chamber 100 of FIG. 4a, FIG. 6a schematically shows achamber 300 used in the manufacturing method of this embodiment of the present invention. Within thechamber 300, upper andlower jigs LED device 320 obtained bystep 230 of FIG. 5, in which the substrate is removed, is located on thelower jig 310 a within thechamber 300 so that the lower surface of a first conductive clad layer is turned up. Analuminum film 335 is disposed on the lower upper surface of the first conductive clad layer. Then, the laminated structure is heated and compressed by means of the upper andlower jigs aluminum film 335 is bonded to the first conductive clad layer. - In the bonding step using the equipment of FIG. 6a, since the
aluminum film 335 is heated under the oxygen atmosphere, the upper and lower surfaces of thealuminum film 335 are reacted with oxygen. As a result, as shown in FIG. 6b, thealuminum film 335 is changed to analuminum layer 335′ having aluminum (Al2O3) layers 337 and 339 respectively formed on its lower and upper surfaces. Herein, thealumina layer 337 having an interface with the first conductive clad layer has lower reflectance than that of thealuminum layer 335′, and forms a reflective structure together with thealuminum layer 335′. - In order to obtain the
alumina layer 337 with desirable reflective characteristics, as described above, the interior of thechamber 300 is under the oxygen atmosphere, and a pressure applied in the bonding step is preferably in the range of approximately 30 gf/cm2 to approximately 300 gf/cm2. - Preferably, a heating temperature applied in the bonding step is more than approximately 250° C. in consideration of the above pressure condition. However, since the aluminum layer and other layers are deformed at an excessively high temperature, more preferably, the heating temperature does not exceed approximately 500° C.
- As apparent from the above description, one embodiment of the present invention provides a LED comprising a reflective layer formed on the lower surface of the LED, including an aluminum layer and an alumina layer with different reflectances, thereby improving reflective characteristics of the reflective layer. Further, another embodiment of the present invention provides a LED comprising a reflective layer formed on an exposed surface of the LED after removing a substrate therefrom, including an aluminum layer and an alumina layer with different reflectances, thereby improving luminance the LED as well as reflective characteristics the LED.
- Moreover, the present invention provides a method for manufacturing a LED, in which an aluminum layer is compressed to an area for a reflective layer on the surface of the LED at a high temperature under an oxygen atmosphere, thereby easily forming the aluminum layer, and simultaneously obtaining a reflective structure including the aluminum layer and an alumina layer with different reflectances. Therefore, a LED with excellent luminance is manufactured by a simple process.
- Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (19)
1. A light emitting diode comprising:
a substrate;
a first conductive clad layer formed on the substrate;
an active layer formed on the first conductive clad layer;
a second conductive clad layer formed on the active layer;
an alumina (Al2O3) layer formed on the lower surface of the substrate; and
an aluminum layer formed on the lower surface of the alumina (Al2O3) layer.
2. The light emitting diode as set forth in claim 1 , further comprising a glass layer formed on the lower surface of the aluminum layer.
3. The light emitting diode as set forth in claim 1 or 2,
further comprising an alumina (Al2O3) layer formed on the lower surface of the aluminum layer or formed between the aluminum layer and the glass layer.
4. The light emitting diode as set forth in claim 1 ,
wherein the first and second conductive clad layers are made of a semiconductor material of a GaN compound, and the substrate is a sapphire substrate.
5. A light emitting diode comprising:
a glass layer;
an aluminum layer formed on the glass layer;
an alumina (Al2O3) layer formed on the aluminum layer;
a first conductive clad layer formed on the alumina (Al2O3) layer;
an active layer formed on the first conductive clad layer; and
a second conductive clad layer formed on the active layer.
6. The light emitting diode as set forth in claim 5 ,
further comprising an alumina (Al2O3) layer formed between the aluminum layer and the glass layer.
7. The light emitting diode as set forth in claim 5 ,
wherein the first and second conductive clad layers are made of a semiconductor material of a GaN compound, and the substrate is a sapphire substrate.
8. A method for manufacturing a light emitting diode (LED), comprising the steps of:
preparing a substrate;
forming a first conductive clad layer on the substrate;
forming an active layer on the first conductive clad layer;
forming a second conductive clad layer on the active layer; and
bonding the aluminum film to the lower surface of the substrate by heating and compressing the aluminum film and the substrate under an oxygen atmosphere so as to form an aluminum layer provided with an alumina (Al2O3) layer at an interface thereof.
9. The method for manufacturing a LED as set forth in claim 8 ,
wherein a heating temperature applied in the step of bonding the aluminum film to the substrate is in the range of 250° C. to 500° C.
10. The method for manufacturing a LED as set forth in claim 8 ,
wherein a pressure applied to the substrate and the aluminum layer in the step of bonding the aluminum film to the substrate is at least 30 gf/cm2.
11. The method for manufacturing a LED as set forth in claim 8 ,
wherein a DC voltage in the range of 300V to 600V is applied to the substrate in the step of bonding the aluminum film to the substrate.
12. The method for manufacturing a LED as set forth in claim 8 ,
wherein a glass layer is bonded to the lower surface of the aluminum layer in the step of bonding the aluminum film to the substrate.
13. The method for manufacturing a LED as set forth in claim 8 ,
wherein an alumina layer is additionally formed on the lower surface of the aluminum layer in the step of bonding the aluminum film to the substrate.
14. The method for manufacturing a LED as set forth in claim 8 ,
wherein the first and second conductive clad layers are made of a semiconductor material of a GaN compound, and the substrate is a sapphire substrate.
15. A method for manufacturing a light emitting diode (LED), comprising the steps of:
preparing a substrate;
forming a first conductive clad layer on the substrate;
forming an active layer on the first conductive clad layer;
forming a second conductive clad layer on the active layer;
removing the substrate so as to expose the lower surface of the first conductive clad layer to the outside;
successively disposing an aluminum film and a glass layer on the lower surface of the first conductive clad layer under an oxygen atmosphere; and
bonding the aluminum film to the first conductive clad layer and the glass layer to the aluminum film by heating and compressing the three layers.
16. The method for manufacturing a LED as set forth in claim 15 ,
wherein a heating temperature applied in the bonding step is in the range of 250° C. to 500° C.
17. The method for manufacturing a LED as set forth in claim 15 ,
wherein a pressure applied to the substrate and the aluminum layer in the bonding step is at least 30 gf/cm2.
18. The method for manufacturing a LED as set forth in claim 15 ,
wherein an alumina layer is additionally formed on the lower surface of the aluminum film contacting the glass layer in the bonding step.
19. The method for manufacturing a LED as set forth in claim 15 ,
wherein the first and second conductive clad layers are made of a semiconductor material of a GaN compound, and the substrate is a sapphire substrate.
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US11/012,331 US7119375B2 (en) | 2002-12-10 | 2004-12-16 | Light emitting diode and method for manufacturing the same |
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KR2002-78456 | 2002-12-10 | ||
KR10-2002-0078456A KR100506730B1 (en) | 2002-12-10 | 2002-12-10 | Method of fabricating light emitting diode |
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US10/464,514 Abandoned US20040108511A1 (en) | 2002-12-10 | 2003-06-19 | Light emitting diode and method for manufacturing the same |
US11/012,331 Expired - Fee Related US7119375B2 (en) | 2002-12-10 | 2004-12-16 | Light emitting diode and method for manufacturing the same |
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US (2) | US20040108511A1 (en) |
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US20060284195A1 (en) * | 2003-08-28 | 2006-12-21 | Hideo Nagai | Semiconductor light emitting device, light emitting module, lighting apparatus, display element and manufacturing method of semiconductor light emitting device |
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JP2006339384A (en) * | 2005-06-01 | 2006-12-14 | Kyocera Corp | Light emitting element, method of manufacturing same, and illuminating apparatus using same |
TW200826322A (en) * | 2006-12-15 | 2008-06-16 | Kinik Co | LED and manufacture method thereof |
KR100886432B1 (en) * | 2007-06-22 | 2009-03-04 | 서울옵토디바이스주식회사 | Light emitting diode having reflection layer and method for manufacturing the same |
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Also Published As
Publication number | Publication date |
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JP2004193548A (en) | 2004-07-08 |
KR100506730B1 (en) | 2005-08-08 |
TW200410430A (en) | 2004-06-16 |
KR20040050597A (en) | 2004-06-16 |
US20050093011A1 (en) | 2005-05-05 |
US7119375B2 (en) | 2006-10-10 |
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AS | Assignment |
Owner name: SAMSUNG ELECTRO-MECHANICS CO., LTD., KOREA, REPUBL Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BAIK, DOO GO;OH, BANG WON;KIM, HAK KYU;REEL/FRAME:014203/0892 Effective date: 20030609 |
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STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |