JP2008166661A - Semiconductor light-emitting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress that a part of light directed to a substrate from a light-emitting layer is absorbed into the substrate having light absorbability, and that luminance of a semiconductor light-emitting apparatus decreases, and to improve luminance of the semiconductor light-emitting apparatus. <P>SOLUTION: A semiconductor light-emitting apparatus has a semiconductor light-emitting element (2) firmly fixed to a supporting surface (1a) of a support (1), and an annular side wall (3) surrounding the semiconductor light-emitting element (2), and a light reflecting coating (4) coating a side surface (2b) of the semiconductor light-emitting element (2) in the side wall (3). The coating (4) annularly coats entire side surface (21b) of a substrate (21) between a light-emitting layer (23) of a compound semiconductor layer (22) and the supporting surface (1a) of the support (1). Since the substrate (21) having light absorbability is used, a problem that light reflected at the side wall (3) and directed to the substrate (21) among light generated by the light-emitting layer (23) is absorbed occurs. In the semiconductor light-emitting apparatus, a part of light emitted from the light-emitting layer (23) is reflected to directions other than a direction to the substrate (21) by the coating (4) to decrease an amount of light absorbed by the substrate (21) and to increase an amount of light directed to upper part of the semiconductor light-emitting element (2). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device such as a light emitting diode, and more particularly to a semiconductor light emitting device capable of suppressing a substrate from absorbing light emitted from a light emitting layer of a compound semiconductor layer.

  A support, a semiconductor light emitting device fixed to the support surface of the support, an annular side wall that surrounds the semiconductor light emitting device and is provided on an outer periphery of the support surface, and covers an upper surface and side surfaces of the semiconductor light emitting device A semiconductor light emitting device including a protective body is known from, for example, Patent Document 1 below. In Patent Document 1, a semiconductor light-emitting element is a compound semiconductor layer such as a gallium nitride-based compound including a light-transmitting insulating substrate such as a sapphire substrate and a light-emitting layer (active layer) formed on the upper surface of the insulating substrate. And have. On the other hand, a semiconductor light emitting device having a silicon substrate as a growth substrate for a gallium nitride-based compound semiconductor is known from Patent Document 2 below. The semiconductor light emitting device of Patent Document 2 has advantages that the material cost is low and the semiconductor light emitting device can be easily manufactured as compared with Patent Document 1 using a sapphire substrate as a growth substrate.

  In recent years, pseudo white light emitting diodes using semiconductor light emitting elements have been realized. In such a light emitting diode, a phosphor is blended in the protective body that covers the semiconductor light emitting element described above, and the light from the semiconductor light emitting element and the light that has been wavelength-converted by the phosphor are mixed to produce a white-based diode. Luminescence can be obtained.

JP 2000-349340 A JP 2005-175462 A

  However, the silicon substrate is opaque and has higher light absorption than the sapphire substrate, and has a problem of absorbing light emitted from the light emitting layer of the gallium nitride compound semiconductor without transmitting it. In the semiconductor light emitting device of Patent Document 2, a reflective film layer is provided below the light emitting layer, and the light directly from the light emitting layer to the silicon substrate is reflected by the reflective film layer to increase the amount of light directed upward of the semiconductor light emitting device. be able to. However, the light emitted from the light emitting layer through the side surface of the semiconductor light emitting element is reflected by the side wall and part of the light is absorbed by the silicon substrate. Therefore, the brightness of the semiconductor light emitting device cannot be sufficiently increased.

  In view of the above, an object of the present invention is to provide a semiconductor light-emitting device that can suppress a reduction in luminance of the semiconductor light-emitting device because a part of the light of the light-emitting layer toward the substrate is absorbed by the light-absorbing substrate. .

  The semiconductor light emitting device of the present invention surrounds the support (1), the semiconductor light emitting element (2) fixed to the support surface (1a) of the support (1), and the semiconductor light emitting element (2). An annular side wall (3) provided on the outer peripheral portion of the support surface (1a) of (1), and a side surface (2b) of the semiconductor light emitting element (2) disposed within the side wall (3) and reflecting light A covering (4) containing the substance. The semiconductor light emitting device (2) includes a substrate (21) and a compound semiconductor layer (22) including a light emitting layer (23) formed on the upper surface (21a) of the substrate (21). In addition, the compound semiconductor layer (22) has absorptivity to light emitted from the light emitting layer (23). The covering (4) covers the entire side surface (21b) of the substrate (21) in an annular shape between the light emitting layer (23) of the compound semiconductor layer (22) and the supporting surface (1a) of the supporting body (1). To do. In the present invention, since the side surface (21b) of the substrate (21) is covered with the covering (4) between the support surface (1a) and the light emitting layer (23), the light emitting layer (23 of the compound semiconductor layer (22) is provided. The light reflected from the side wall (3) and traveling toward the light-absorbing substrate (21) is not absorbed by the substrate (21) and is reflected in the covering (4). Part of the light emitted from the light emitting layer (23) by the active substance can be reflected in a direction other than the substrate (21). Thereby, the amount of light absorbed by the substrate (21) can be reduced, the amount of light directed upward of the semiconductor light emitting element (2) can be increased, and the luminance of the semiconductor light emitting device can be improved.

  As described above, in the present invention, it is possible to provide a semiconductor light emitting device with high brightness by reducing light absorption by the substrate of the semiconductor light emitting element.

  Next, an embodiment of a semiconductor light emitting device according to the present invention applied to a light emitting diode (LED) made of a gallium nitride compound semiconductor will be described with reference to FIGS.

  As shown in FIG.1 and FIG.2, the light emitting diode (10) of this Embodiment is a light emitting diode chip (2) fixed to the support body (1) and the support surface (1a) of a support body (1). An annular side wall (3) provided on the outer periphery of the support surface (1a) of the support (1) surrounding the light emitting diode chip (2), and a light emitting diode chip ( And a covering (4) covering the side surface (2b) of 2). The support (1) and the side wall (3) are integrally formed by the recess formed in the upper end of the support (1), and the support surface (1a) is formed on the bottom surface in the recess. The side wall (3) serves as a reflector that collects light from the light-emitting diode chip (2) to improve directivity and front luminance, and expands vertically or vertically from the support surface (1a). Formed. A first external lead (6) is formed at the lower end of the support (1) by extending from the support (1), and is adjacent to the first external lead (6). 7) is arranged. The support (1), the side wall (3), the first external lead (6), and the second external lead (7) are made of metal such as copper, iron, aluminum, or an alloy thereof.

  The light emitting diode chip (2) has a silicon substrate (21) and a compound semiconductor layer (22) including a light emitting layer (23) formed on the upper surface (21a) of the silicon substrate (21). In the present embodiment, the compound semiconductor layer (22) is made of a GaN (gallium nitride) compound semiconductor that emits light at a wavelength of about 365 nm to 550 nm. For example, as the light emitting diode chip (2), the peak of the emission wavelength is about. A GaN-based blue light emitting diode chip having a wavelength of 440 nm to 470 nm is used. The compound semiconductor layer (22) includes, for example, an n-type semiconductor region formed of GaN on the upper surface (21a) of an n-type or p-type silicon substrate (21), and a light emitting layer (active layer) formed of InGaN on the n-type semiconductor region. ) (23) is formed, and a p-type semiconductor region is formed of GaN on the light emitting layer (23). An anode electrode (upper surface electrode) (11) made of a metal film such as aluminum is formed on the p-type semiconductor region, and a cathode electrode (lower surface electrode) made of a metal film such as aluminum is formed on the lower surface of the silicon substrate (21). ) (12) is formed. The anode electrode (11) of the light emitting diode chip (2) is electrically connected to the upper end portion of the second external lead (7) by the lead thin wire (8), and the cathode electrode (12) is electrically conductive such as solder. The adhesive (9) is fixed to and electrically connected to the support surface (1a) of the support (1).

  In the present embodiment, a reflective film layer (24) that reflects light from the light emitting layer (23) is formed between the silicon substrate (21) and the compound semiconductor layer (22). The light directly directed from the light emitting layer (23) to the silicon substrate (21) is reflected by the reflective film layer (24), so that the luminance of the light emitting diode can be further improved. The reflective film layer (24) can be formed of a metal such as aluminum, silver, gold and copper or an alloy thereof, for example. The reflective film layer (24) is preferably formed on the entire surface or substantially the entire surface of the silicon substrate (21) and the compound semiconductor layer (22).

  The cover (4) is formed of, for example, an opaque material such as silicone resin, and is mixed with a light reflecting substance such as powdered titanium oxide. The covering (4) is formed by annularly forming the entire side surface (21b) of the silicon substrate (21) between the light emitting layer (23) of the compound semiconductor layer (22) and the support surface (1a) of the support (1). Cover. The covering (4) can be formed of various resins other than the silicone resin. Further, the cover (4) may be formed of a material other than a resin such as a metal alkoxide. The silicon substrate (21) is light-absorbing with respect to the light emitted from the light-emitting layer (23) of the compound semiconductor layer (22), and in a conventional light-emitting diode having no covering (4), the light-emitting layer ( Of the light emitted by 23), the light reflected by the side wall (3) and directed to the silicon substrate (21) is absorbed.In the light emitting diode (10) of the present embodiment, the support surface (1a) and the light emitting layer ( 23), the side surface (21b) of the silicon substrate (21) is covered with the covering (4), and the light reflecting material contained in the covering (4) is directed toward the silicon substrate (21). The light of the light emitting layer (23) can be reflected in a direction other than the silicon substrate (21). Thereby, the amount of light absorbed by the silicon substrate (21) can be reduced, and the amount of light directed upward of the light emitting diode chip (2) can be increased.

  A protective body (5) is disposed in the side wall (3). The upper surface (4a) of the type semiconductor region and the light emitting layer (23) and the covering (4) are covered. The protector (5) is formed of, for example, a material such as a light transmissive metal alkoxide, and is mixed with a powdered phosphor (25). Since the depth of the concave portion of the support (1) is larger than the height of the light emitting diode chip (2), the protective body (5) can be formed with a sufficient thickness in the concave portion. The wavelength of light emitted from the light emitting layer (23) of the compound semiconductor layer (22) can be converted by the phosphor (25) blended in the protective body (5). When the phosphor (25) is contained in the protector (5), the light from the light emitting layer (23) is scattered by the phosphor (25), and the amount of light toward the silicon substrate (21) increases. These lights are reflected upward of the light emitting diode chip (2) by the covering (4). The protector (5) may be formed of a silicone resin or an epoxy resin.

  In the present embodiment, the inner surface (3a) of the side wall (3) is formed in a stepped shape, below the light emitting layer (23) of the compound semiconductor layer (22), and on the support surface (1a) of the support (1). Is provided with a step surface (13) formed above. The step surface (13) is formed in an annular shape along the inner surface (3a) of the circular side wall (3), and is formed in parallel and flat with respect to the support surface (1a) of the support (1). The While observing light reflection from the stepped surface (13) of the side wall (3), filling the cover (4) between the side wall (3) and the side surface (2b) of the light emitting diode chip (2), The filling of the cover (4) can be stopped by the change in the amount of light reflection that occurs when the cover (4) overflows on the stepped surface (13). This prevents the covering (4) from covering the side surface (23b) of the light emitting layer (23) of the compound semiconductor layer (22). The surface of the step surface (13) is formed with a light reflectance different from that of the cover (4) so that the amount of light reflection changes when the cover (4) covers the step surface (13). . In order to increase the difference from the light reflectance of the covering (4), for example, by forming a plurality of fine irregularities on the surface of the step surface (13) by a known surface processing method such as satin processing, The gloss of the surface (13) may be reduced. The difference between the gloss of the stepped surface (13) and the light reflectance of the covering (4) may be increased. Further, unevenness may be formed on the entire inner surface (3a) of the side wall (3), and the adhesiveness between the side wall (3), the covering (4) and the protective body (5) can be improved by the unevenness.

  Further, the upper surface of the protective body (5) and one end of the first external lead (6) and the second external lead (7) are sealed by a sealing body (15) made of a material such as a light-transmitting epoxy resin. The other ends of the first external lead (6) and the second external lead (7) are led out from the flat lower surface of the sealing body (15) which is covered and formed in a bullet shape.

  When a voltage is applied between the first external lead (6) and the second external lead (7) of the light emitting diode (10) and the light emitting diode chip (2) is energized to emit light, the inside of the protective body (5) Part of the light from the light emitting diode chip (2) is converted into another wavelength different from the emission wavelength by the phosphor (25), and then emitted to the outside of the light emitting diode (10) through the sealing body (15). The For example, when a light emitting diode (10) that emits white light by converting the wavelength of light of a light emitting diode chip (2) having a GaN-based compound semiconductor layer by a protector (5) containing a fluorescent substance is formed, the light emitting diode chip ( Protective body (blue) light emitted from 2) and white light mixed with green light and red light emitted from the phosphor (25) when excited by blue light. 5) Can be released to the outside.

  In the conventional light emitting diode not having the covering (4), a part of the light emitted from the side surface (2b) of the light emitting diode chip (2) is supported by the support (1 ) Is reflected off the support surface (1a) and emitted to the outside of the protector (5), so that the light in the optical path D emitted from the side surface (2b) of the light emitting diode chip (2) and the light emitting diode chip (2) There was a large difference in the distance passing through the protector (5) between the light beams A and B emitted from the upper surface (2a) of the light. When the distance passing through the protector (5) is different, the degree of wavelength conversion of light by the phosphor (25) is also different, so that when the LED is viewed from above, light is emitted from the center side and the outer periphery side of the LED. Color unevenness occurred. This type of problem is not limited to white light emitting diodes that are a combination of a light emitting diode chip having a GaN-based compound semiconductor layer and a protective material containing a phosphor, and similarly occurs in other semiconductor light emitting devices.

  However, according to the light emitting diode (10) of the present embodiment, the light emitted from the side surface (2b) of the light emitting diode chip (2) is reflected by the covering (4) as shown in the optical path C of FIG. Thus, the protector (5) can be passed through at a shorter distance than before. Therefore, as shown in FIG. 1, the difference in the length of the optical paths A to C passing through the protector (5) is reduced, and the light wavelength conversion rate is uniform between the central side and the outer peripheral side of the light emitting diode chip (2). The color unevenness caused by the light emission of the light emitting diode (10) can be reduced. Further, the light absorption amount of the silicon substrate (21) is reduced by the covering (4) and the luminance on the outer peripheral side of the light emitting diode chip (2) is improved, so that the central side and the outer peripheral side of the light emitting diode chip (2) The light emission luminance can be made uniform.

  When manufacturing the light emitting diode (10) shown in FIGS. 1 and 2, the light emitting diode chip (2) is formed by, for example, an n-type semiconductor region, a light emitting layer (23) and a p-type on a silicon wafer by a known epitaxial growth method. Semiconductor regions are sequentially provided to form a compound semiconductor layer (22). Next, a metal film such as aluminum is formed on the lower surface of the n-type semiconductor region of the compound semiconductor layer (22) by vapor deposition or sputtering. The conductive silicon substrate (21) is formed by doping a silicon wafer with n-type or p-type impurities, and a metal film such as aluminum is formed on the upper surface (21a) of the silicon substrate (21) by vapor deposition or sputtering. The The metal film on the lower surface of the compound semiconductor layer (22) and the metal film on the upper surface (21a) of the silicon substrate (21) are joined together, and the reflective film layer (24) is formed by the joined metal film. Subsequently, an anode electrode (11) made of a metal film such as aluminum is formed on the p-type semiconductor region by vapor deposition or sputtering, and a cathode electrode (12) made of a metal film such as aluminum on the lower surface of the silicon substrate (21). Is formed to complete the light emitting diode chip (2).

  Next, a first external lead (6) and a second external lead (7) are prepared, and the light emitting diode chip (2) is provided on the support surface (1a) of the support body (1) surrounded by the side wall (3). The cathode electrode (12) is fixed by a conductive adhesive (9) such as solder. Subsequently, a protective device made of fluid silicone resin or the like in which a light reflecting substance such as titanium oxide is blended in the gap between the light emitting diode chip (2) and the side wall (3) by a filling device such as a dispenser (not shown). The body (5) is filled. In the present embodiment, as shown in FIG. 3, while observing light reflection from the stepped surface (13) of the side wall (3) by an image recognition device (not shown), the side wall (3) and the light emitting diode chip (2) are shown. The covering body (4) is filled between the side surface (2b) of the substrate. The covering (4) is gradually filled upward from the support surface (1a), and as shown in FIG. 4, the covering (4) overflows on the step surface (13), and the light on the step surface (13). When the amount of reflection increases or decreases, filling of the covering (4) is stopped. The step surface (13) is formed on the side wall (3) below the light emitting layer (23) of the compound semiconductor layer (22) and above the support surface (1a) of the support (1). When the amount of light reflection of 13) changes, the side surface (23b) of the light emitting layer (23) exposed to the side surface (2b) of the light emitting diode chip (2) is stopped by stopping the filling of the covering (4). It can prevent being covered with the covering (4). Since the support surface (1a) of the support (1), the stepped surface (13) of the side wall (3) and the light emitting layer (23) of the light emitting diode chip (2) are formed substantially in parallel, the side wall (3) When the covering (4) is filled, the covering (4) covers the four side surfaces (2b) of the light-emitting diode chip (2) at the same height to ensure the side surface of the silicon substrate (21). (21b) can be coated.

  Conventionally, the amount of the covering (4) disposed in the side wall (3) is determined by the filling amount or filling time of the covering (4), but in the present embodiment, the amount of the side wall (3) is determined. By using the stepped surface (13) and the image recognition device, the side surface of the silicon substrate (21) is precisely between the light emitting layer (23) of the compound semiconductor layer (22) and the support surface (1a) of the support (1) ( 21b) can be covered with a covering (4). Since the filling of the cover (4) is stopped at a lower height than the light emitting layer (23), the light emission of the light emitting layer (23) is not inhibited by the cover (4) and the light emitting layer (23) is covered. Since the pressure by the body (4) is not applied, the characteristics of the light-emitting diode chip (2) can be prevented from being deteriorated by the pressure.

  Subsequently, the anode electrode (11) of the light-emitting diode chip (2) and the upper end portion of the second external lead (7) are electrically connected by a fine lead wire (8) by a well-known wire bonding method. The filling device fills the light-transmitting fluid material mixed with the phosphor (25), and heat-treats the material to form a protective body (5) made of metal alkoxide in the side wall (3). Then, by molding, the upper surface of the protective body (5) and one end of the first external lead (6) and the second external lead (7) are sealed with a material such as an epoxy resin having optical transparency, and sealed. A stop (15) is formed, and the light emitting diode (10) shown in FIG. 2 is completed.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, the compound semiconductor layer (22) is not limited to a GaN blue light emitting diode chip, and other compound semiconductors such as GaP, GaAs, InP, GaAsP, InGaAlP, InGaAsP, GaAlAs, or ZnSe may be applied. . The light emitting diode (10) may be formed by covering the periphery of the light emitting diode chip (2) including the sapphire substrate with the covering (4). In the sapphire substrate with low light absorption, the effect of improving the luminance of the light emitting diode (10) is small, but the phosphor (25) is formed between the central side and the outer peripheral side of the light emitting diode chip (2) by the covering (4). By making the wavelength conversion rate of the light uniform, it is possible to reduce color unevenness caused by light emission of the light emitting diode (10).

  The present invention may be applied not only to the bullet-type light emitting diode (10) shown in FIG. 2, but also to a surface-mounted light emitting diode (20) as shown in FIG. In the light emitting diode (20), the support (1) includes a support plate made of an insulating material such as an epoxy resin, a strip-shaped first external lead (6) disposed on the outer peripheral surface of the support plate, and a first And a strip-shaped second external lead (7) disposed on the outer peripheral surface of the support plate at a distance from the external lead (6). The support surface (1a) of the support (1) to which the light emitting diode chip (2) is fixed is formed on the upper surface of one end of the first external lead (6). The anode electrode (11) of the light emitting diode chip (2) and one end of the second external lead (7) arranged on the support plate are connected by the thin lead wire (8) arranged in the side wall (3). The The side wall (3) is formed on the first external lead (6) and the second external lead (7) integrally or separately from the support plate by an insulating material. In the side wall (3), the covering (4) and the protective body (5) are arranged in the same manner as the light emitting diode (10) described above. The light emitting diode (20) does not include the sealing body (15), and the upper surface of the curved protective body (5) has a role of a lens that collects light of the light emitting diode chip (2).

  In the illustrated light emitting diode (10, 20), the covering (4) covers the entire side surface (21b) of the silicon substrate (21) between the light emitting layer (23) and the support surface (1a). The n-type semiconductor region or the reflective film layer (24) disposed below the light emitting layer (23) may be exposed from the covering (4). When the thickness of the conductive adhesive (9) changes, the height from the support surface (1a) to the light emitting layer (23) also changes, but at least the side surface (21b) of the silicon substrate (21) covers the covering (4). By covering with, it is possible to reduce the amount of light absorbed by the silicon substrate (21) and increase the amount of light directed upward of the light emitting diode chip (2).

  As shown in FIG. 6, the height of the side wall (3) may be smaller than the thickness of the light emitting diode chip (2). If the upper surface (3b) of the side wall (3) is made lower than the light emitting layer (23), the covering (4) is formed between the light emitting layer (23) and the support surface (1a) of the support (1). It is possible to satisfactorily prevent the covering (4) from coming into contact with the light emitting layer (23). In the light emitting diode (30) of FIG. 6, the upper surface (3b) of the side wall (3) serves as the step surface (13) described above. While observing light reflection from the upper surface (3b) of the side wall (3), the covering (4) is filled between the side wall (3) and the side surface (2b) of the light emitting diode chip (2), thereby covering the side wall (3). The filling of the covering (4) can be stopped by the change in the amount of light reflection that occurs when the body (4) overflows on the upper surface (3b) of the side wall (3).

  The present invention can be suitably applied to various semiconductor light emitting devices including a semiconductor light emitting element constituted by a light absorbing substrate.

The expanded sectional view which shows embodiment of the semiconductor light-emitting device by this invention Sectional drawing which shows embodiment of the semiconductor light-emitting device by this invention Plan view showing the filling process of the cover FIG. 3 is a plan view of the step surface covered with a covering. Sectional drawing which shows other embodiment of the semiconductor light-emitting device by this invention FIG. 1 is an enlarged cross-sectional view showing another embodiment of FIG.

Explanation of symbols

  (1) ・ ・ Support, (1a) ・ ・ Support surface, (2) ・ ・ Light-emitting diode chip (semiconductor light-emitting device), (2a) ・ ・ Top surface, (2b) ・ ・ Side, (3) ・ ・ Side wall (3a) ・ ・ Inner surface, (4) ・ ・ Coating, (4a) ・ ・ Top surface, (5) ・ ・ Protective body, (13) ・ ・ Step surface, (21) ・ ・ Board, (21a) ・・ Top surface, (22) ・ ・ Compound semiconductor layer, (23) ・ ・ Light emitting layer, (24) ・ ・ Reflective film layer, (25) ・ ・ Phosphor,

Claims (4)

A support, a semiconductor light emitting device fixed to the support surface of the support, an annular side wall surrounding the semiconductor light emitting device and provided on an outer periphery of the support surface of the support, and disposed in the side wall Covering the side surface of the semiconductor light emitting element and including a light reflective material,
The semiconductor light emitting device has a substrate and a compound semiconductor layer including a light emitting layer formed on the upper surface of the substrate,
The substrate has absorbability with respect to light emitted from the light emitting layer of the compound semiconductor layer,
The said covering body coat | covers the whole side surface of the said board | substrate cyclically between the light emitting layer of the said compound semiconductor layer, and the support surface of the said support body, The semiconductor light-emitting device characterized by the above-mentioned. Providing a protector that covers the upper surface of the semiconductor light emitting element and the upper surface of the covering;
The semiconductor light-emitting device according to claim 1, wherein a phosphor is blended in the protective body. The side wall includes a step surface formed on the inner surface below the light emitting layer of the compound semiconductor layer and above the support surface of the support,
3. The semiconductor light emitting device according to claim 1, wherein light reflectivities of the stepped surface and the covering are different.   The semiconductor light-emitting device according to claim 1, wherein a reflective film layer that reflects light of the light-emitting layer of the compound semiconductor layer is provided between the substrate and the compound semiconductor layer.

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