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Patent Issued for Semiconductor Light Emitting Element, Light Emitting Device Using Semiconductor Light Emitting Element, and Electronic Apparatus

February 12, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Hodota, Takashi (Ichihara, JP); Okabe, Takehiko (Ichihara, JP), filed on December 9, 2010, was published online on January 28, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8637888 is assigned to Toyoda Gosei Co., Ltd. (Aichi-ken, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "A semiconductor light emitting element using a group III nitride semiconductor such as GaN is usually configured by forming a group III nitride semiconductor layer including a light emitting layer on a substrate of, for example, sapphire. As such semiconductor light emitting elements, there are those which emit light outputted from the light emitting layer to outside through the substrate by mounting the semiconductor light emitting element on a wiring board by flip-chip bonding.

"As a conventional technique described in a gazette, there is a known technique for reflecting light, which has been outputted from a light emitting layer in an opposite direction of a substrate, toward the substrate by forming a reflection layer of a metal composed of silver or the like on a surface of a group III nitride semiconductor layer, which surface is opposite to a contact surface with the substrate (refer to Patent Literature 1).

"Moreover, as another conventional technique described in a gazette, there is a known technique in which a multilayer reflection film composed of a dielectric material is formed on a surface side of a group III nitride semiconductor layer, which is opposite to a contact surface thereof with a substrate, to reflect light toward the substrate side, the light having been outputted from a light emitting layer toward an opposite side of the substrate (refer to Patent Literature 2)."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "Technical Problem

"However, light is outputted in directions other than the directions toward the substrate side and the side opposite to the substrate from the light emitting layer, and consideration has not been given to extraction of such light.

"An object of the present invention is to improve light extraction efficiency in a semiconductor light emitting element mounted by flip-chip bonding.

"Solution to Problem

"In order to attain the object, in the present invention, there is provided a semiconductor light emitting element including: a first semiconductor layer composed of a group III nitride semiconductor having a first conduction type; a light emitting layer that is laminated on one surface of the first semiconductor layer so as to expose a part of the one surface and emits light by current flow; a second semiconductor layer composed of a group III nitride semiconductor having a second conduction type, which is different from the first conduction type, and laminated on the light emitting layer; a first multilayer reflection film configured by alternately laminating first refractive index layers each having a first refractive index and transparency to light emitted from the light emitting layer and second refractive index layers each having a second refractive index, which is higher than the first refractive index, and transparency to light emitted from the light emitting layer, the first multilayer reflection film being laminated on the part of the one surface of the first semiconductor layer that has been exposed; a first conductor portion that is formed to penetrate the first multilayer reflection film, and one end thereof is connected to the exposed part of the first semiconductor layer; and a first electrode which is laminated on the first multilayer reflection film, and to which the other end of the first conductor portion is connected.

"Moreover, the semiconductor light emitting element further includes: a transparent conductive layer that is composed of a metal oxide having transparency to light emitted from the light emitting layer and conductivity, and is laminated on the second semiconductor layer; a second multilayer reflection film configured by alternately laminating first refractive index layers each having a first refractive index and transparency to light emitted from the light emitting layer and second refractive index layers each having a second refractive index, which is higher than the first refractive index, and transparency to light emitted from the light emitting layer, the second multilayer reflection film being laminated on the transparent conductive layer; a second conductor portion that is formed to penetrate the second multilayer reflection film, and one end thereof is connected to the transparent conductive layer; and a second electrode which is laminated on the second multilayer reflection film, and to which the other end of the second conductor portion is connected.

"Further, the second conductor portion has plural connective conductors, one end of each of which is connected to the transparent conductive layer and the other end of each of which is connected to the second electrode. Moreover, the plural connective conductors constituting the second conductor portion are formed so that a distance between the nearest neighbors out of the plural connective conductors becomes shorter as a distance from a joint portion of the first conductor portion and the first semiconductor layer becomes longer. Moreover, the plural connective conductors constituting the second conductor portion are formed so that a cross-sectional area thereof is increased as a distance from a joint portion of the first conductor portion and the first semiconductor layer becomes longer.

"Further, the first electrode includes a first reflection layer having a reflecting property to light emitted from the light emitting layer and the second electrode includes a second reflection layer having a reflecting property to light emitted from the light emitting layer.

"Still further, the second conductor portion and the second electrode are formed with plural layers continuing in a surface direction. Moreover, the first multilayer reflection film and the second multilayer reflection film are configured as one piece continuing in a surface direction.

"Further, the first electrode and the second electrode have a first opening portion and a second opening portion used for electrical connection with outside, and further have a first bump electrode and a second bump electrode used for electrical connection with outside at the first opening portion and the second opening portion, and each of the first bump electrode and the second bump electrode includes a connective electrode containing Sn for connecting to outside on a tip end portion thereof.

"Further, from another standpoint, in the present invention, there is provided a light emitting device including: a base portion on which a first wiring and a second wiring are formed; and a semiconductor light emitting element mounted on the base portion by flip-chip bonding, wherein the semiconductor light emitting element includes: a first semiconductor layer composed of a group III nitride semiconductor having a first conduction type; a light emitting layer that is laminated on one surface of the first semiconductor layer so as to expose a part of the one surface and emits light by current flow; a second semiconductor layer composed of a group III nitride semiconductor having a second conduction type, which is different from the first conduction type, and laminated on the light emitting layer; a first multilayer reflection film configured by alternately laminating first refractive index layers each having a first refractive index and transparency to light emitted from the light emitting layer and second refractive index layers each having a second refractive index, which is higher than the first refractive index, and transparency to light emitted from the light emitting layer, the first multilayer reflection film being laminated on the part of the one surface of the first semiconductor layer that has been exposed; a first conductor portion that is formed to penetrate the first multilayer reflection film, and one end thereof is connected to the exposed part of the first semiconductor layer; and a first electrode which is laminated on the first multilayer reflection film, and to which the other end of the first conductor portion is connected.

"Further, an electronic apparatus to which the present invention is applied is equipped with the above-described semiconductor light emitting element.

"Advantageous Effects of Invention

"According to the present invention, it is possible to improve the light extraction efficiency in the semiconductor light emitting element mounted by flip-chip bonding."

URL and more information on this patent, see: Hodota, Takashi; Okabe, Takehiko. Semiconductor Light Emitting Element, Light Emitting Device Using Semiconductor Light Emitting Element, and Electronic Apparatus. U.S. Patent Number 8637888, filed December 9, 2010, and published online on January 28, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=56&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2781&f=G&l=50&co1=AND&d=PTXT&s1=20140128.PD.&OS=ISD/20140128&RS=ISD/20140128

Keywords for this news article include: Electronics, Semiconductor, Toyoda Gosei Co. Ltd.

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Source: Electronics Newsweekly


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