JP2004289182A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device which can improve light emission intensity by a light emitting element including a transparent substrate such as GaP-based, GaAsP-based, GaAlAs-based, or GaN-based substrate. <P>SOLUTION: In the semiconductor light emitting device, an n-type semiconductor layer 3, a p-type semiconductor layer 4, and a light emitting layer 5 are formed on an n-type semiconductor substrate 2, at the same time an n-type electrode 2a and a p-type electrode 4a are formed on the n-type semiconductor substrate 2 and the p-type semiconductor layer 4, respectively. A semiconductor light emitting element 1 is mounted on the mounting surface of the mounting part 21b of a lead frame 21 with a posture in which the n-type semiconductor substrate 2 is at the light emitting side and the light emitting layer 5 is at the mounting surface side of the mounting part 21b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting device including a semiconductor light emitting element in which compound semiconductors such as GaP-based, GaAsP-based, GaAlAs-based, and GaN-based, which can emit red, orange, amber, yellow-green, and green light, are obtained. In particular, the present invention relates to a semiconductor light emitting device capable of improving light emission luminance of a semiconductor light emitting element itself and efficiently reflecting and collecting light leaked from a surface other than the main light extraction surface in a light emitting direction.

  Among the semiconductor light emitting devices in which a semiconductor thin film layer is grown on a crystal substrate, GaP-based, GaAsP-based, GaAlAs-based, and the like, which emit light of red, orange, amber, yellow-green, green, or the like, or Conventionally, III-V group compound semiconductors such as GaN have been used to emit green or blue light.

  In a semiconductor light emitting device using a compound semiconductor such as GaP, GaAsP, and GaAlAs, a conductive semiconductor material is used as a crystal substrate. For this reason, the semiconductor light emitting element may be formed, for example, by epitaxial growth on the upper surface (first main surface) of the n-type semiconductor substrate when an n-conductivity type semiconductor substrate (hereinafter referred to as “n-type semiconductor substrate”) is used. To form a p-type semiconductor layer on the upper surface by epitaxial growth. The electrodes have a configuration in which an n-electrode is formed on the lower surface (second main surface) of the n-type semiconductor substrate and a p-electrode is formed on the upper surface of the p-type semiconductor layer.

  Further, since the light emitting device using this semiconductor light emitting element is mounted on a mounting surface such as a lead frame or a substrate with the semiconductor substrate facing down, the semiconductor substrate is thick and the epitaxial layer formed thereon is thin. The light emitting element is mounted in such an arrangement that the light emitting layer, that is, the pn junction region is on the upper side.

  Further, the semiconductor light-emitting element using a light-transmitting substrate (hereinafter referred to as a transparent substrate) with respect to the emission wavelength of the semiconductor light-emitting element is provided on the main light extraction surface side from the light-emitting layer in the pn junction region Since the light in the opposite direction, that is, the light traveling toward the semiconductor substrate can be allowed to escape to the lead frame or the substrate, the mounting surface of the lead frame or the substrate is configured to be suitable for light reflection.

  On the other hand, in semiconductor light emitting devices using a GaN-based compound semiconductor, the use of insulating sapphire as a crystal substrate has recently become the mainstream. In the case of using such an insulating crystal substrate, unlike the case of using the above-described conductive semiconductor substrate, the n-electrode and the p-electrode are formed on the semiconductor layer forming surface side of the substrate and at the same time as the main light extraction surface side. A configuration is used.

  However, recently, a substrate made of a GaN-based compound semiconductor represented by GaN has been obtained, and a semiconductor light-emitting device made of a GaN-based compound semiconductor using this as a crystal substrate has been manufactured. . For this reason, even in the case of a semiconductor light emitting device using a semiconductor material such as GaN as a crystal substrate, the GaN-based compound semiconductor is transparent to the emission wavelength of the semiconductor light emitting device, so that the above-described GaP-based, GaAsP-based, and GaAlAs-based semiconductors are used. At present, it is possible to have an element configuration similar to that of a semiconductor light emitting element using a compound semiconductor such as a system.

  FIG. 7 is a schematic sectional view showing a typical structure of a conventional LED lamp including a semiconductor light emitting device using a GaP-based, GaAsP-based, and GaAlAs-based compound semiconductor, and FIG. 8 is an enlarged view of a portion on which the semiconductor light-emitting device is mounted.

  As shown in FIG. 7, the conventional LED lamp has a mortar-shaped mounting portion 21b formed at the upper end of one lead 21a of a lead frame 21, and a semiconductor light emitting element 22 is mounted on the mounting portion 21b. is there. A wire 23 is bonded to the semiconductor light emitting element 22 between the lead 21c and the semiconductor light emitting element 22 and the wire 23 are sealed with an epoxy resin 24 to form an LED lamp.

  For example, in the case of a GaP-based or GaAsP-based semiconductor light emitting element 22, an n-type semiconductor substrate 22a is used, on which an n-type semiconductor layer 22b and a p-type semiconductor layer 22c are sequentially laminated by epitaxial growth. The light emitting layer is a pn junction region 22d. The n-type semiconductor substrate 22a is conductive, a plurality of dot-shaped n-electrodes 22a-1 are formed on the lower surface thereof, and one dot-shaped p-electrode 22b- is formed on the upper surface of the p-type semiconductor layer 22c. 1 is formed, and a wire 23 is bonded to the p-electrode 22b-1. Then, the semiconductor light emitting element 22 is mounted on the mount 21b by a conductive adhesive 25 so as to conduct the n-type semiconductor substrate 22a to the mount 21b side of the lead 21a, and is electrically and mechanically connected and fixed. It is already known that the adhesive 25 is preferably made of, for example, a transparent epoxy resin as a main component and mixed with Ag as a filler, and sufficient conductivity can be obtained by the mixed Ag.

  When the n-type semiconductor substrate 22a is a transparent substrate, if the n-type semiconductor substrate 22a is fixed by the conductive adhesive 25, the adhesive 25 has a high light transmittance and the mounting surface of the mount portion 21b is like a silver mirror surface. If the surface is capable of reflecting light, the light that escapes downward from the light emitting layer, that is, the pn junction region 22d, can be reflected by the mount portion 21b and collected in the light emitting direction.

  Even in the case of a GaN-based compound semiconductor light-emitting device using a transparent substrate such as GaN, the same configuration as in the case of such a GaP-based or GaAsP-based device can be employed.

  FIG. 9 is a longitudinal sectional view showing a main part of an LED lamp using a GaAlAs-based compound semiconductor.

  In the GaAlAs-based light emitting element 31, a p-type semiconductor substrate is used, on which a p-type semiconductor layer 32b, an active layer 32d and an n-type semiconductor layer 32c are sequentially formed by epitaxial growth, and on the upper surface of the n-type semiconductor layer 32c. Form a dot-shaped n-electrode 32b-1. Since the p-type semiconductor substrate is a GaAs substrate and not a transparent substrate, it has a configuration as shown in FIG. 9 in which the p-type semiconductor substrate is removed by etching in order to increase the luminance. In that case, a plurality of dot-shaped p-electrodes 32a-1 are formed on the lower surface of the p-type semiconductor layer 32b.

  In any of the above cases, the pn junction region, which is the light emitting layer, is mounted so as to be above the semiconductor light emitting element.

  FIG. 10 is a schematic diagram for explaining a mode of extracting light from the semiconductor light emitting element 22.

  In the drawing, light isotropically emitted from one point of the light emitting layer A can be considered as being divided into upward light, downward light, and lateral light. In the case of upward light, when the incident angle on the upper surface Su of the semiconductor light emitting element 22 exceeds the critical angle θ, the light is totally reflected on the upper surface Su. The critical angle θ is smallest in the case of the GaP system at θ = 25 °.

  That is, as shown in FIG. 10B, only the light Lu traveling upward in the range of 2θ with the + Y direction as the center can be extracted upward. Similarly, in the case of light traveling downward, when the incident angle on the lower surface Sd exceeds the critical angle θ, the light is totally reflected by the lower surface Sd. Can be taken out. In the case of the lower side, the back electrode, its alloy layer, Ag paste, etc. are present, but if they are neglected (this will be discussed later), the outside light will be applied to the silver plating of the mount portion 21b of the lead frame. The light is reflected by the surface, passes through the semiconductor light emitting element 22 again, and is taken out upward. In the case of light traveling to the side, when the shape of the semiconductor light-emitting element 22 is a cube, if the angle of incidence on the side surface Ss exceeds the critical angle θ, the light is totally reflected by the side surface Ss. Only the light Ls directed toward the range of 2θ around the ± X direction can be taken out. Light L traveling in directions other than the above is confined in the semiconductor light emitting element 22 and cannot be taken out.

  Here, the problems that arise with respect to light extraction are as follows.

  First, when the pn junction region 22d or the active layer 32d, which is the light-emitting layer of the semiconductor light-emitting element 22, is mounted so as to face upward, light directed to the side is particularly affected. That is, most of the light Ls extracted to the outside among the light traveling to the side travels downward as shown in FIG. The light going downward may be reflected by the silver-plated surface of the mount portion 21b of the lead frame and directed upward, may enter the semiconductor light emitting element 22 again, or may be absorbed by the Ag paste. There is a problem that the intensity of light is weaker than that of light traveling toward and the light extraction efficiency is deteriorated.

  The shape of the chip depends on the shape of the cutting edge of the diamond cutter in the dicing process, and the cut surface of the chip has a tapered surface opposite to the cutter side. That is, as shown in FIG. 8, it is unavoidable from a manufacturing viewpoint that the four side walls of the semiconductor light emitting element 22 become tapered toward the p-type semiconductor layer 22c side. However, when the pn junction region 22d is above the semiconductor light emitting device, the total angle at which light can be extracted outside is as shown in FIG. 10 because the sidewall of the n-type semiconductor substrate 22a is tapered. Is narrower than the range of 8θ when there is no taper, and there is a problem that the amount of light that can be extracted is reduced.

  In addition, light traveling downward from the pn junction region 22d can be reflected from this portion toward the main light extraction surface side by using the mount portion 21b as a reflection surface. However, there are a plurality of metal n-electrodes 22a-1 on the lower surface of the n-type semiconductor substrate 22a, and an interface between the semiconductor layer and this electrode is formed with an alloy layer. Since this alloy layer absorbs light, The amount of light absorption increases in proportion to the area occupied by these n-electrodes 22a-1.

  Further, in the Ag paste in which Ag is included in the adhesive 25, the Ag itself reflects light with respect to the incident light from the outside, whereas the light in the paste adhesive containing Ag is easily confined, Rather, it acts so as to absorb the incident light. Therefore, when an Ag paste is used as the conductive adhesive 25, even if the mount portion 21b is used as a reflection surface, light emission from the main light extraction surface is reduced by light absorption by the Ag paste. In order to compensate for the emission luminance, it is necessary to increase the applied current, and the power consumption cannot be reduced.

  In addition, since the light emitting element 22 generates heat when energized, the heat generates heat of the Ag paste used as the adhesive 25, thereby discoloring the resin contained in the paste. The discolored resin acts to absorb light, and the resin absorbs light in addition to the light absorption of the Ag paste itself. Therefore, the light emission luminance of the light emitting element 22 is reduced, and it is easy to determine that the function is deteriorated, which greatly affects the reliability.

  As described above, there is a problem in that it is not possible to collect all of the downward light by reflecting the light in the original light emission direction.

  Further, in a light emitting device including a GaN-based semiconductor light emitting element, there are the following problems in addition to the above problems. That is, since GaN-based compound semiconductors are generally grown by a method having a relatively low growth rate such as metal organic chemical vapor deposition or MBE, when these compound semiconductors are used, GaP-based or GaAlAs-based semiconductors are used. Unlike the case of using the liquid phase growth method, which can easily grow a thick film, the thickness of the semiconductor layer for light emission formed on the substrate cannot be sufficiently increased. For this reason, the amount of light extracted from the upper surface side of the element in the light upward from the light emitting layer tends to be further limited. Furthermore, GaN-based compound semiconductors have higher resistivity than GaP-based compound semiconductors, and the current that is injected through an electrode formed on the side formed on the semiconductor layer and contributes to light emission spreads in the semiconductor layer. Hard to concentrate directly under the electrode. For this reason, the light emission in the light emitting layer also concentrates directly below the electrode, and the light going upward from the light emitting layer is blocked by the electrode, which makes it more difficult to extract light from the upper surface of the element. There is.

  As described above, in a conventional light-emitting device having a light-emitting element of GaP, GaAsP, GaAlAs, or GaN, even when a transparent substrate or the like is used, light leakage from a surface other than the main light extraction surface cannot be sufficiently collected. Also, there is a limit to the improvement of the light emission luminance.

  The problem to be solved in the present invention is to provide a semiconductor light emitting device capable of improving the light emission luminance of a light emitting element having a transparent substrate or the like of GaP, GaAsP, GaAlAs, GaN or the like.

  The present invention provides a first conductivity type semiconductor substrate, a first conductivity type semiconductor layer epitaxially grown on a first main surface of the first conductivity type semiconductor substrate, and an epitaxial growth on the first conductivity type semiconductor layer. A second conductive type semiconductor layer, a first electrode formed on the second main surface on the first conductive type semiconductor substrate side, and a second electrode formed on the second conductive type semiconductor layer. A semiconductor light emitting device comprising at least an electrode; and a mounting surface such as a lead frame or a substrate for conductively mounting the semiconductor light emitting device, wherein the first conductive type semiconductor substrate side is in a light emitting direction. The semiconductor light emitting element is mounted on the mounting surface such that a light emitting layer formed by the first conductivity type semiconductor layer and the second conductivity type semiconductor layer and formed by a pn junction is on the mounting surface side. The feature is that That is a semiconductor light-emitting device.

  In such a configuration, the efficiency of extracting light traveling from the light emitting layer to the side can be increased, and the emission luminance can be improved.

  According to the first aspect of the present invention, the first conductive type semiconductor substrate is placed on the light emitting direction side, and the light emitting layer is positioned on the mounting surface side, whereby the light emitting layer is brought closer to the mounting surface. Light extraction efficiency can be increased, and emission luminance can be improved.

  According to the second aspect of the present invention, since the conductive adhesive is capable of transmitting light, light that escapes from the light emitting layer toward the mounting portion can be reflected from the mounting portion in the light emitting direction, thereby contributing to an improvement in light emission luminance.

  According to the third aspect of the present invention, since the p-side electrode is bonded to the mounting portion by the microbump, light is not confined as in the case where an adhesive is used, and the light emission luminance can be further improved.

  According to the fourth aspect of the invention, by optimizing the size and shape of the electrode, the optical path of light reflected from the light emitting layer toward the mounting portion can be widened, and the light emission luminance can be further improved. .

  According to the fifth aspect of the present invention, since the side surface of the light emitting element is inclined so as to be tapered with respect to the light emitting direction, the light emitting layer is arranged so as to be deviated toward the mounting surface side, so that light emitted from the light emitting layer in all directions can be obtained. The emission angle range of the light that can be extracted outside the light emitting element is widened, so that the light emission luminance can be further improved.

  According to the invention of claim 6, the current is uniformly supplied to the entire light emitting layer to widen the light emitting region in the light emitting layer, and the light directed downward from the light emitting layer is reflected and directed upward or to the side of the light emitting element. As a result, the light extraction efficiency can be increased, so that the emission luminance can be further improved.

  According to the invention of claim 7, it is possible to increase the light extraction efficiency from the side of the light emitting element and to prevent a short circuit due to a rise of the adhesive on the side of the light emitting element when the element is fixed with a conductive adhesive. Therefore, the light emission luminance can be improved and the reliability of the semiconductor light emitting device can be improved.

  According to the eighth aspect of the present invention, when the element is fixed with a conductive and light transmissive adhesive to increase the light extraction efficiency from the side surface of the light emitting element, the rise of the adhesive on the element side surface is reduced. As a result, a short circuit can be prevented, so that the light emission luminance can be improved and the reliability of the semiconductor light emitting device can be improved.

  According to the ninth aspect of the present invention, even in a semiconductor light emitting device manufactured using a growth method in which a thick film is difficult to grow, such as a metal organic chemical vapor deposition method or an MBE method, light recovery from the main surface and side surfaces of the semiconductor substrate can be achieved. And the light emission luminance of the light emitting element can be improved.

  The invention according to claim 1, wherein a first conductivity type semiconductor substrate, a first conductivity type semiconductor layer epitaxially grown on a first main surface of the first conductivity type semiconductor substrate, and the first conductivity type semiconductor layer A second conductive type semiconductor layer epitaxially grown on the first conductive type semiconductor substrate, a first electrode formed on the second main surface on the first conductive type semiconductor substrate side, and a second conductive type semiconductor layer formed on the second conductive type semiconductor layer. And a mounting surface such as a lead frame or a substrate for conductively mounting the semiconductor light emitting element, wherein the first conductive type semiconductor is provided. The semiconductor light emitting device is configured such that the substrate side is the light emitting direction, and the light emitting layer formed by the pn junction formed by the first conductive type semiconductor layer and the second conductive type semiconductor layer is on the mounting surface side. Mounted on the mounting surface It is a semiconductor light emitting device according to claim, an effect that can increase the extraction efficiency of light directed laterally from the particular light-emitting layer.

  The invention according to claim 2 is characterized in that the second electrode and the mounting surface are electrically and mechanically joined by a conductive and light-permeable adhesive. The semiconductor light-emitting device according to any one of the preceding claims, having an effect of collecting light by reflecting light that escapes from the light-emitting layer toward the mounting portion toward the light-emitting direction from the mounting portion.

  The invention according to claim 3 is the semiconductor light emitting device according to claim 1, wherein the second electrode and the mounting surface are electrically and mechanically joined via micro bumps. Since no conductive adhesive is used, light absorption can be suppressed, and the effect of further improving the collection of reflected light from the mounting portion can be obtained.

  According to a fourth aspect of the present invention, the first and second electrodes have a plane shape of a circle having a diameter of 10 μm or more and 150 μm or less, a polygon included in the circle, or the circle or the polygon. 4. The semiconductor light emitting device according to claim 1, wherein the electrode has a shape of a metal and does not transmit light by optimizing the size and shape of the electrode. However, it has an effect of securing an optical path of light that is reflected from the light emitting layer toward the mounting portion.

  According to a fifth aspect of the present invention, in the semiconductor light emitting device in the form of a chip, the surface on which the first electrode is formed has an upper surface, and the second electrode having an area larger than that surface is formed. 5. The semiconductor light emitting device according to claim 1, wherein the light emitting element is a polyhedron having a surface as a lower surface, wherein the light is directed in four directions from the light emitting layer due to the inclination of the side surface of the light emitting element, particularly laterally or downward. The light reflected by the lower surface is effectively extracted to the outside from the inclined surface with respect to the light heading toward, and has the effect of increasing the light extraction efficiency.

  The invention according to claim 6, wherein the second electrode is formed on substantially the entire surface of the second conductivity type semiconductor layer. A light-emitting device, in which a current injected from a second electrode into a second conductivity type layer is uniformly supplied to the entire light-emitting layer to expand a light-emitting region in the light-emitting layer and reflect light traveling downward from the light-emitting layer. By moving the light emitting element upward or to the side, the light extraction efficiency can be increased.

  The invention according to claim 7, wherein in the side surface of the semiconductor light-emitting element, the first conductive layer extends from at least a part of a surface of the first conductive type semiconductor layer to a part of a surface of the second conductive type layer. The light-transmitting insulating film is formed so as to cover the surface of the junction between the mold semiconductor layer and the second conductivity type layer. 6. The semiconductor light emitting device according to 6, wherein the efficiency of extracting light from the side of the light emitting element is increased, and when the element is fixed by a conductive adhesive, a short circuit due to a rise of the conductive adhesive on a side surface of the element is prevented. It has the effect of preventing.

  The invention according to claim 8 is characterized in that a groove for allowing a part of the adhesive to flow in is formed around the lower surface of the semiconductor light emitting element on the mounting surface. The semiconductor light emitting device according to the above, wherein when the element is fixed with a conductive and light transmissive adhesive to increase the light extraction efficiency from the side surface of the light emitting element, the adhesive on the side surface of the element rises. It has the effect of reducing and preventing short circuits.

  According to a ninth aspect of the present invention, a first conductivity type semiconductor substrate is formed on a first main surface of the first conductivity type semiconductor substrate, and the first conductivity type semiconductor substrate is formed using a metal organic chemical vapor deposition method or an MBE method. A semiconductor laminated structure having a first conductivity type semiconductor layer, a light emitting layer and a second conductivity type semiconductor layer; a first electrode formed on a second main surface on the first conductivity type semiconductor substrate side; A semiconductor light emitting device including at least a second electrode formed on a two-conductivity type semiconductor layer, and a mounting surface such as a lead frame or a substrate for conductively mounting the semiconductor light emitting element. The semiconductor light emitting device is mounted on the mounting surface such that the first conductive type semiconductor substrate side is the main light extraction surface side and the semiconductor laminated structure side is the mounting surface side. Semiconductor light emitting device In a semiconductor light emitting device manufactured using a growth method in which a thick film is difficult to grow, such as a metal vapor deposition method or an MBE method, light can be extracted from the semiconductor substrate side to enable the main surface and the side surface of the semiconductor substrate. Has the effect of improving the light recovery rate from light.

  Hereinafter, specific examples of the embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an enlarged view showing a main part of the semiconductor light emitting device of the present invention. In the illustrated example, the light emitting element is mounted on the mount portion 21b of the lead 21a of the lead frame of the LED lamp shown in FIGS.

  In FIG. 1, a light emitting element 1 uses a GaP-based, GaAsP-based, or GaN-based compound semiconductor, and a transparent or light-transmitting n-type semiconductor layer 3 and a p-type semiconductor layer are formed on a transparent n-type semiconductor substrate 2. 4 are laminated, and a pn junction region formed by these layers is formed as the light emitting layer 5. In other words, the n-type semiconductor substrate 2 has a lamination surface of the n-type semiconductor layer 3 as a first main surface, and has an upper surface as a second main surface in the posture shown in FIG. One n-electrode 2a is formed, and a plurality of p-electrodes 4a are formed on the surface of the p-type semiconductor layer 4 in the same manner as a dot type. Then, the conventional structure shown in FIG. 8 is turned upside down so that the n-type semiconductor substrate 2 is on the upper side and the light emitting layer 5 is on the lower side, and is mounted on the mount portion 21b. Thereby, the light emitting layer 5 can be arranged to be biased downward.

  The light emitting element 1 is fixed to the mount portion 21b by the conductive adhesive 6 applied to the mount portion 21b and is electrically connected to the lead 21a. As described above, the adhesive 6 is made of a transparent epoxy resin as a main component and Ag mixed therein as a filler, and the mixed Ag can make the p-electrode 4a conductive to the lead 21a. The n-electrode 2a is bonded to the lead 21c by a wire 23, and the light emitting element 1 is electrically connected to the leads 21a and 21c.

  In the above configuration, when the light-emitting element 1 is energized, the light-emitting layer 5 is activated and emits light. The transparent or light-transmissive n-type semiconductor layer 3 passes through the transparent n-type semiconductor substrate 2 to extract the main light from the upper surface. Emit light as a surface. Then, the light from the light emitting layer 5 is emitted not only to the main light extraction surface side but also to the side and downward through the transparent or light transmitting p-type semiconductor layer 4.

  Here, the light emitting layer 5 is located below the n-type semiconductor substrate 2 whose upper surface is the main light extraction surface, and the light emitting layer 5 is located on the surface of the mounting portion 21b as compared with the conventional structure shown in FIG. It is unevenly distributed near the side. On the other hand, as shown in FIG. 10A, if the light-emitting layer is disposed on the upper side, most of the extracted light Ls among the light directed to the side goes to the lower side. As mentioned above, the extraction efficiency is reduced.

  On the other hand, as shown in FIG. 10A, if the light-emitting layer A ′ is disposed on the lower side so as to be close to the surface of the mount portion 21b, light traveling from the light-emitting layer A ′ to the side will be Light emitted in a direction within an angle range of 2θ in the ± X direction, such as L's shown in (b), can be extracted out of the semiconductor light emitting element 22, and the emitted light is 10A, or in a direction in which the light is refracted from the side surface of the n-type layer above the light-emitting layer A 'in the direction of the main light extraction surface as depicted as the optical path of L's in FIG. Can be taken out. Therefore, compared with the case where the light emitting layer is arranged on the upper side, the efficiency of collecting light traveling laterally from the light emitting layer can be increased.

  The light emitted downward in the range of 2d of Ld and L'd shown in FIG. 10B is reflected from Ag contained in the adhesive 6 and the bottom surface of the mount 21b. This is added to the light emitted from the main light extraction surface.

  FIG. 2 is a schematic view of a main part showing another configuration, and the same members as those shown in FIG. 1 are indicated by common reference numerals, and detailed description thereof will be omitted.

  The outer shapes of the n-type semiconductor substrate 2 having the n-electrode 2a of the light-emitting element 1 formed on the upper surface and the n-type semiconductor layer 3 and the p-type semiconductor layer 4 are exactly the same as those in FIG. Are provided with one p-electrode 4a on the lower surface and no conductive adhesive is used.

  That is, the micro bumps 7 are formed on the p-electrode 4a in order to mount and fix the light emitting element 1 on the mount portion 21b and electrically connect with the lead 21a. The micro-bumps 7 are formed integrally with the p-electrode 4a by bonding a wire to the p-electrode 4a and then tearing off leaving only this bonding portion. The assembly mounted and fixed on the mount 21b is based on a method of integrally joining the microbumps 7 by applying ultrasonic vibration and heating to the upper surface of the mount 21b.

  In the light emitting device using the micro bumps 7 as well, the high recovery efficiency of the light emitted to the side from the light emitting layer 5 is the same as that in the example of FIG.

  In addition, since only one p-electrode 4a is provided on the bottom surface of the p-type semiconductor layer 4 to reduce the light-shielding area, the transmission area of light that passes down from the light-emitting layer 5 can be increased. . Therefore, if the mount portion 21b is formed as a reflection surface by a light reflection film or the like, light that has passed downward can be reflected to the main light extraction surface side, and light leakage can be collected. Since no conductive adhesive such as Ag paste is interposed, light is not trapped in the adhesive.

  As described above, if the mounting structure of the light emitting element 1 using the micro bumps 7 is used, the transmitted light to the mount portion 21b side can be increased, and at the same time, the light is not attenuated by the adhesive. Even when compared, the emission luminance is significantly improved.

  When a semiconductor light emitting device using a GaN-based compound semiconductor is used, the current hardly spreads in the p-type semiconductor layer 4 and tends to emit light only directly above the p-electrode 4a. With the configuration in which the p-electrode 4a is provided on almost the entire surface, the current is uniformly spread over the entire layer, and light emission from almost the entire surface of the light emitting layer 5 can be obtained. When the p-electrode 4a is configured to transmit light, similarly to the above-described example, light traveling downward from the light-emitting layer 5 is transmitted to the main light extraction surface side using the reflection surface provided on the mount portion 21b. Can be reflected. When the p-electrode 4a is capable of reflecting light emitted from the light-emitting layer 5, light directed downward from the light-emitting layer 5 is reflected to the side or upward of the light-emitting element by the p-electrode 4a, so that the light is mainly reflected. It is possible to make it face the light extraction surface side.

  FIG. 3 is a plan view showing a preferred example of the n-electrode 2a in the example of FIG. 1 and the n-electrode 2a and the p-electrode 4a in the example of FIG.

  The n or p electrodes 2a and 4a in the example of FIG. 3 have a circular planar shape and a diameter of 10 μm or more and 150 μm or less. Then, instead of such a circular planar shape, a polygonal shape included in a range of a circle of 10 μm to 150 μm may be used.

  Further, as shown in (b) of the figure, a shape having a circular portion at the center and four branches extending radially from the circular portion may be employed. In this case, the distance to the tip of the branch portion may be within the above-mentioned 150 μm circle area, or may be 150 μm circle when extending toward the corner of the light emitting element 1 as shown in the figure. May be longer than the range.

  With such shapes and sizes of the n-electrode 2a and the p-electrode 4a, a sufficient current can be injected into the pn junction region, which is a light-emitting layer, and the area that prevents light extraction from the light-emitting layer can be minimized. Can be limited.

  FIG. 4 is a cross-sectional view of a main part showing a configuration example of still another light emitting element, and the same members as those in the examples of FIGS. 1 and 2 are indicated by common reference numerals.

  In the examples of FIGS. 1 and 2, the side surface of the light emitting element 1 has a slightly tapered lower side due to dicing, whereas in the example of FIG. It has a truncated quadrangular pyramid that tapers upward except for the part. That is, the n-type semiconductor substrate 2 has a planar area of the upper surface on which the n-electrode 2a is formed is smaller than the lower surface on which the n-type semiconductor layer 3 is laminated, and all four side surfaces around the n-type semiconductor layer 3 have a trapezoidal surface as shown. These surfaces all form a taper that converges toward the upper end side, that is, the main light extraction surface side.

  FIG. 5 is a plan view for explaining what kind of light emission form is obtained depending on the position of the light emitting layer 5 in the case of the n-type semiconductor substrate 2 having such a taper.

  In the case where the light emitting layer is on the lower side as shown in FIG. 5A, of the light traveling from one central point of the light emitting layer A to four directions in this plane, the n-type semiconductor substrate 2 has an outline indicated by a dotted line. In this case, only light traveling within the range of 4θ indicated by the dotted line is extracted out of the light emitting element, whereas the solid line in which the outer periphery of the n-type semiconductor substrate 2 is tapered is indicated by the solid line. It becomes larger than 4θ as in the range. Specifically, in the case of GaP, since θ = 25 °, the ratio between the dotted line and the solid line is about 1.5 times, 200 °: 297 °. Therefore, the light emitted from the light emitting layer A is efficiently extracted by forming the outer periphery of the n-type semiconductor substrate 2 into a tapered shape so that the emission luminance is improved.

  FIG. 5B illustrates an example in which the side surface of the light emitting element is similar to that of FIG. 5A and the light emitting layer A is positioned on the upper side. Even if the side surface of the light emitting element is tapered, the light component directed obliquely upward in the lateral direction is totally reflected on the upper surface of the light emitting element because the light emitting layer A is on the upper side. Further, since the incident angle of the light component obliquely downward to the side surface of the light emitting element increases, the ratio of total reflection increases. Therefore, in the case where the side surface is a tapered surface and the light-emitting layer A is positioned on the upper side with respect to this tapered surface, the range of light that can be extracted is smaller than 4θ, and specifically, in the case of GaP-based, The ratio between the dotted line and the solid line is 200 °: 131 °, and the amount of light that can be extracted is reduced.

  As described above, the outer shape of the n-type semiconductor substrate 2 which is tapered with respect to the light emitting direction and the light emitting layer A is positioned below the outer shape allows light traveling in all directions from the light emitting layer A to be effectively extracted. You can see that it can be done.

  FIG. 6 is a cross-sectional view of a main part showing still another example of the configuration of the light emitting element, and the same members as those in the examples of FIGS. 1 and 2 are designated by the same reference numerals.

  The outer shapes of the n-type semiconductor substrate 2 having the n-electrode 2a of the light-emitting element 1 formed on the upper surface thereof and the n-type semiconductor layer 3 and the p-type semiconductor layer 4 are substantially the same as those of FIG. That the p-electrode 4 a is provided over substantially the entire surface of the light-emitting element 1, and a light-transmitting insulating film 8 is provided from a part of the p-type semiconductor layer 4 to a part of the n-type semiconductor layer 3 on the side surface of the light emitting element 1. And a groove 21d through which a part of the conductive adhesive 6 flows is provided around the lower surface of the semiconductor light emitting element 1 in the mount 21b. Such a configuration is particularly effective in the case of a semiconductor light emitting device using a compound semiconductor in which it is difficult to sufficiently increase the thickness of the semiconductor layer, that is, a GaN-based compound semiconductor.

  The p-electrode 4a in FIG. 6 can transmit light traveling downward from the light-emitting layer 5, as described in the case of using the semiconductor light-emitting element using a GaN-based compound semiconductor in the structure of FIG. It may be configured such that the light-emitting element can be reflected and taken out from the side or from above.

  Since the insulating film 8 is capable of transmitting light, it can transmit light from the light-emitting layer 5 to the side, reflect the light on the reflection surface of the mount portion 21b, and extract the light upward. Further, a short circuit due to the rising of the adhesive 6 on the side surface of the light emitting element 1 can be prevented. The insulating film 8 has only to have an insulating property and can transmit light. For example, a material having an insulating property such as silicon oxide or silicon nitride can be preferably used.

  Further, in the case where a conductive adhesive is used instead of the light-transmitting material, a groove 21d into which a part of the adhesive 6 can flow is provided around the light emitting element 1 so that the above-described bonding is achieved. The rise of the agent 6 can be further reduced, the effect of preventing short-circuiting can be enhanced in combination with the function of the insulating film 8, and the reliability of the semiconductor light emitting device can be enhanced.

  The semiconductor light emitting device according to the present invention is capable of increasing the luminous efficiency and using a compound semiconductor such as a GaP-based, GaAsP-based, GaAlAs-based, or GaN-based semiconductor capable of obtaining emission colors such as red, orange, amber, yellow-green and green. It is useful as a semiconductor light emitting device including a stacked semiconductor light emitting element.

FIG. 1 is a schematic diagram showing a main part of a light emitting device according to an embodiment of the present invention. Schematic diagram of main parts showing another configuration example of the light emitting device FIG. 2 is a plan view showing shapes of an n-electrode and a p-electrode formed on an n-type semiconductor substrate or a p-type semiconductor layer, respectively. Schematic diagram showing main parts of a light-emitting device in which an n-type semiconductor substrate has a substantially truncated pyramid shape FIG. 4 is an explanatory view showing a light emitting mode according to the position of a light emitting layer in the example of FIG. Schematic diagram of main parts showing still another configuration example of the light emitting device Schematic diagram of a conventional LED lamp Schematic diagram of the main part showing the mounting structure of the light emitting element of the LED lamp of FIG. Schematic diagram of main parts showing the mounting structure of a GaAlAs-based light emitting element (A) is a schematic diagram showing a light emission mode from the light emitting layer of the light emitting element upward, side, and downward, and (b) is a schematic diagram showing a distribution of a critical angle θ in each direction.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 light emitting element 2 n-type semiconductor substrate 2 an n-electrode 3 n-type semiconductor layer 4 p-type semiconductor layer 4 a p-electrode 5 light-emitting layer 6 adhesive 7 microbump 8 insulating film 21 lead frame 21 a lead 21 b mounting part 21 c lead 21 d groove 23 Wire

Claims (9)

A first conductivity type semiconductor substrate; a first conductivity type semiconductor layer epitaxially grown on a first main surface of the first conductivity type semiconductor substrate; and a second conductivity type epitaxially grown on the first conductivity type semiconductor layer. A type semiconductor layer, a first electrode formed on a second main surface on the first conductive type semiconductor substrate side, and a second electrode formed on the second conductive type semiconductor layer. A semiconductor light-emitting device comprising at least a semiconductor light-emitting element and a mounting surface such as a lead frame or a substrate for conductively mounting the semiconductor light-emitting element, wherein the first conductive type semiconductor substrate side is a light-emitting direction, The semiconductor light emitting device is mounted on the mounting surface such that a light emitting layer formed by a pn junction formed by the first conductive type semiconductor layer and the second conductive type semiconductor layer is on the mounting surface side. Semiconductor Light equipment. 2. The semiconductor light emitting device according to claim 1, wherein the second electrode and the mounting surface are electrically and mechanically joined by a conductive and light transmissive adhesive. 2. The semiconductor light emitting device according to claim 1, wherein the second electrode and the mounting surface are electrically and mechanically joined via micro bumps. The first and second electrodes have a planar shape of a circle having a diameter of 10 μm or more and 150 μm or less, a polygon included in the circle, or a shape having branches radially extending from the circle or the polygon. The semiconductor light-emitting device according to claim 1, 2, or 3, wherein: The semiconductor light-emitting element formed into a chip is characterized in that it is a polyhedron having a surface on which a first electrode is formed as an upper surface and a surface having an area larger than the surface on which the second electrode is formed as a lower surface. The semiconductor light emitting device according to claim 1, 2, 3, or 4. 6. The semiconductor light emitting device according to claim 1, wherein the second electrode is formed on substantially the entire surface of the second conductivity type semiconductor layer. On the side surface of the semiconductor light emitting element, at least a part of the surface of the first conductive type semiconductor layer to a part of the surface of the second conductive type layer, the first conductive type semiconductor layer and the second conductive type layer 7. The semiconductor light emitting device according to claim 1, wherein an insulating film capable of transmitting light is formed so as to cover a surface of the joint. 8. The semiconductor light emitting device according to claim 2, wherein a groove for allowing a part of the adhesive to flow in is formed around a lower surface of the semiconductor light emitting element on the mounting surface. A first conductivity type semiconductor substrate; a first conductivity type semiconductor layer provided on the first main surface of the first conductivity type semiconductor substrate and sequentially formed by using a metal organic chemical vapor deposition method or an MBE method; A semiconductor layered structure having a second conductive type semiconductor layer, a first electrode formed on a second main surface on the first conductive type semiconductor substrate side, and a second electrode formed on the second conductive type semiconductor layer And a mounting surface such as a lead frame or a substrate for conductively mounting the semiconductor light emitting element, wherein the first conductive type semiconductor is provided. A semiconductor light emitting device wherein the semiconductor light emitting element is mounted on the mounting surface with the substrate side being the main light extraction surface side and the semiconductor laminated structure side being the mounting surface side.

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