JP2009059969A - Semiconductor light-emitting element, light-emitting device, luminaire, display unit, and method for fabricating semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element which can enhance light extraction efficiency more sharply than before without increasing the fabrication cost, and to provide a light-emitting device, a luminaire, a display unit, and a method for fabricating a semiconductor light-emitting element. <P>SOLUTION: On the upper surface of a sapphire substrate 1, an N-type semiconductor layer 2, an active layer 4, and a P-type semiconductor layer 5 are laminated in this order. On the upper surface of the P-type semiconductor layer 5, a current diffusion layer 6 is formed. Near the center of a light-emitting element 50, an N electrode 7 is formed in contact with the N-type semiconductor layer 2. Near the corner of the light-emitting element 50, a bonding electrode, i.e. a P electrode 8, is formed in contact with the P-type semiconductor layer 5. A current diffusion auxiliary interconnect 9 arranged along the vicinity of the outer circumference of the current diffusion layer 6 is extending from the P electrode 8. On the outer circumferential side face of the N-type semiconductor layer 2, an irregular surface 10 consisting of a plurality of protrusions and recesses is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting element used for a light emitting diode or a laser diode, a light emitting device including the semiconductor light emitting element, an illumination device, a display device, and a method for manufacturing the semiconductor light emitting element.

  Gallium nitride (GaN) -based compound semiconductors are known as materials for light-emitting diodes that emit blue light. Conventionally, in a gallium nitride-based compound semiconductor light emitting device, a part of the light emitted from the active layer cannot be extracted outside the device by being totally reflected at the inner and outer boundaries and repeatedly reflected inside the device, Eventually, it has a problem that it is absorbed inside the device and converted into heat.

For this reason, technical development for improving the light extraction efficiency has been performed. Such techniques mainly include a method of roughening the upper surface of the element, a method of inclining a part of the back surface of the substrate, and a method of inclining the outer peripheral portion of the semiconductor layer in a reverse mesa shape. For example, in the semiconductor light emitting device of Patent Document 1, a technique for making the upper surface of the sapphire substrate a fine concavo-convex structure is disclosed. Further, in the nitride-based semiconductor light-emitting element of Patent Document 2, a technique is disclosed in which an inclined side surface is provided on the outer peripheral portion of the semiconductor layer and a reflective film is formed on the inclined surface.
JP 2007-123446 A JP 2006-128659 A

  What is common to these prior arts is that light confined inside the device is guided to the device upper surface (or lower surface) side and extracted. In addition, in order to roughen the upper surface of the element compared to the case where the upper surface of the element is not roughened, it is necessary to grow a considerable film thickness in crystal growth, or a fine concavo-convex structure or a reverse mesa structure. In addition, an extra photolithography process (for example, one or more times) and an additional process such as an etching process and a film forming process are required to form the reflective film, and the manufacturing cost is increased.

  In order to roughen the upper surface of the element, there are methods of roughening by crystal growth or roughening by processing in a process after the crystal growth. The former requires thicker semiconductor layers for roughening. In addition, since the entire upper surface (including electrodes) of the element is roughened, the light reflectance on the upper surface of the element is lowered, and image recognition is performed for confirming the position of the electrode and the like in the wafer process and assembly processes. There is a problem that becomes difficult.

  In the latter case, for example, it is possible to roughen only the necessary part by excluding the electrode part. However, as compared with the case where the roughening process is not performed, the semiconductor layer (or semiconductor) It is necessary to laminate a transparent current diffusion layer or a protective film laminated on the layer thickly. In addition, the roughness depth of the rough surface is usually 1 μm or less, and in order to form a sufficient inclination at this depth, the width of the roughness needs to be the same size as the depth. That is, a photolithography technique having a high resolution of 1 μm or less is required. On the other hand, such a high resolution is usually not required in the manufacturing process of the LED light emitting element, and an exposure apparatus for a semiconductor process is sufficiently practical if it has a resolution of several μm, which can be said to be the lowest level. For this reason, when roughening the upper surface of the element, there is a problem that a new expensive high-resolution exposure apparatus has to be introduced.

  As for the processing of the back surface of the substrate, for example, gallium nitride compound semiconductors often use sapphire substrates or SiC (silicon carbide) substrates, and since both substrates are very hard materials, they are processed by mechanical processing. The jig is consumed quickly and the manufacturing cost is increased. Moreover, since these substrates are chemically stable, processing with chemicals is difficult.

  In addition, as a method for processing the outer peripheral portion of the semiconductor layer into a reverse mesa shape, there is wet etching with high-temperature phosphoric acid. Phosphoric acid is a chemical that is relatively easy to handle at room temperature among acids. For example, when it is 200 ° C. or higher, moisture evaporates in a short time and the concentration becomes unstable. There is difficulty in stability.

  The present invention has been made in view of such circumstances, and by providing a light extraction portion for extracting light on the outer peripheral side surface of the compound semiconductor layer, the light extraction efficiency is significantly higher than that of the related art without increasing the manufacturing cost. Light emitting device including the semiconductor light emitting device, a lighting device and a display device including the semiconductor light emitting device or the light emitting device, and a method for manufacturing the semiconductor light emitting device .

  A semiconductor light-emitting device according to a first aspect of the present invention is a semiconductor light-emitting device in which a compound semiconductor layer is formed on a substrate, and includes a light extraction portion that extracts light on an outer peripheral side surface of the compound semiconductor layer.

  According to a second aspect of the present invention, there is provided the semiconductor light emitting device according to the first aspect, wherein the light extraction portion is an uneven portion formed along the outer peripheral side surface.

  According to a third aspect of the present invention, there is provided the semiconductor light-emitting device according to the first or second aspect, wherein the compound semiconductor layer is laminated on a substrate in the order of an N-type semiconductor layer, an active layer, and a P-type semiconductor layer. The portion is formed on an outer peripheral side surface of the N-type semiconductor layer, and is an uneven portion formed along the outer peripheral side surface.

  In a semiconductor light emitting device according to a fourth invention, in the second invention or the third invention, the concavo-convex portion has a semicircular, semi-elliptical, triangular shape in cross section parallel to the boundary surface between the substrate and the compound semiconductor layer. It is at least one of trapezoidal shape, polygonal shape or parabolic shape, or a combination of two or more.

  The semiconductor light emitting device according to a fifth aspect of the present invention is the semiconductor light emitting device according to any one of the second to fourth aspects, wherein the depth and interval of the concave and convex portions are 0.05 μm or more and 20 μm or less, respectively.

  A semiconductor light-emitting device according to a sixth aspect of the present invention is the semiconductor light-emitting device according to any one of the second to fifth aspects, further comprising a coating film that covers the uneven portion, wherein the compound semiconductor layer is a gallium nitride based semiconductor layer, The optical refractive index of the covering film is smaller than the optical refractive index of the gallium nitride based semiconductor layer.

  According to a seventh aspect of the present invention, there is provided the semiconductor light emitting device according to the sixth aspect, wherein the coating film has a thickness of 10 nm to 10 μm.

  A light-emitting device according to an eighth aspect is characterized by including the semiconductor light-emitting element according to any one of the above-described inventions and a reflecting member that reflects light extracted from the light extraction portion of the semiconductor light-emitting element.

  An illuminating device according to a ninth aspect includes the semiconductor light emitting element according to any one of the foregoing inventions or the light emitting device according to the above inventions.

  A display device according to a tenth aspect of the invention includes the semiconductor light-emitting element according to any one of the above-described inventions or the light-emitting device according to the above-described invention.

  According to an eleventh aspect of the present invention, there is provided a method for manufacturing a semiconductor light emitting device, comprising: forming a compound semiconductor layer on a surface of the substrate; and forming an outer peripheral side surface of the compound semiconductor layer. Etching, and forming a concavo-convex portion along the outer peripheral side surface.

  According to a twelfth aspect of the present invention, there is provided a method for manufacturing a semiconductor light emitting device according to the eleventh aspect, wherein the step of forming the concavo-convex portion includes a step of exposing the substrate surface by etching.

  According to a thirteenth aspect of the present invention, there is provided the method for manufacturing a semiconductor light emitting device according to the eleventh aspect, wherein the step of forming the compound semiconductor layer includes at least an undoped layer, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer on the surface of the substrate. The step of forming the concavo-convex portion includes a step of forming in order, and the step of forming the concavo-convex portion on the outer peripheral side surface of the N-type semiconductor layer by etching.

  According to a fourteenth aspect of the present invention, in the thirteenth aspect of the invention, the step of forming the concavo-convex portion includes a step of exposing the undoped layer by etching.

  According to a fifteenth aspect of the present invention, in the thirteenth aspect of the invention, in the thirteenth aspect, the step of forming the concavo-convex portion includes removing the P-type semiconductor layer and the active layer by etching to form an N-type electrode. The method includes a step of exposing the semiconductor layer.

  According to a sixteenth aspect of the present invention, in the eleventh aspect of the invention, the step of forming the concavo-convex portion includes the step of forming a cutting groove for cutting the substrate around the compound semiconductor layer. Features.

  In the first invention, the light extraction portion for extracting light is provided on the outer peripheral side surface of the compound semiconductor layer. By extracting the light that has been reflected multiple times inside the compound semiconductor layer and the substrate from the light extraction part, the light absorbed inside the compound semiconductor layer or the substrate and converted into heat can be extracted outside, and the light extraction efficiency can be improved. In addition to improving the reliability of the element, it is possible to suppress the heat generated inside the element.

  In the second invention and the eleventh invention, the uneven portion is formed along the outer peripheral side surface of the compound semiconductor layer. The shape of the concavo-convex portion can be various shapes such as a semicircular shape, a semielliptical shape, a triangular shape, a trapezoidal shape, a polygonal shape, and a parabolic shape when viewed from the substrate surface. A cutting direction in which the semiconductor light emitting element is cut into a rectangular parallelepiped shape from the wafer is defined as an X axis and a Y axis, and a thickness direction of the substrate is defined as a Z axis. When light generated in the light emitting portion (light emitting layer) of the semiconductor light emitting element is incident on the outer peripheral side surface of the compound semiconductor layer, the incident light is, for example, a boundary surface between the back surface of the substrate and the outside or a boundary surface between the surface of the compound semiconductor layer and the outside. Since the light is totally reflected on the surface (both parallel to the XY plane), the incident angle with respect to the boundary surface is equal to or greater than the critical angle for total reflection. That is, the Z-axis component of incident light has a relatively small value. On the other hand, since the light generated in the light emitting portion of the semiconductor light emitting element is uniformly emitted in almost all directions, the X-axis component or Y-axis component of incident light on the outer peripheral side surface of the compound semiconductor layer has various values. Therefore, it can be seen that in order to extract light from the outer peripheral side surface of the compound semiconductor layer, the X-axis component and the Y-axis component of the incident angle of the light reaching the outer peripheral side surface should be set to the critical angle or less. By forming irregularities along the outer peripheral side surface of the compound semiconductor layer, the outer peripheral side surface of the compound semiconductor layer has various angles with respect to the element cutting surface, and light is incident on the outer peripheral side surface at any angle. Even in such a case, the incident angle at the concavo-convex portion can be led to the outside with a critical angle or less.

  In the third and thirteenth inventions, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer are stacked in this order on a substrate, and an uneven portion is formed along the outer peripheral side surface of the N-type semiconductor layer. For example, the concavo-convex portion is formed in a portion from the vicinity of the boundary with the substrate of the N-type semiconductor layer to the vicinity of the active layer. Thereby, even when the concavo-convex portion is formed, it is possible to suppress an increase in the peripheral length of the PN layer sandwiching the active layer, and an increase in leakage current can be prevented.

  In the fourth invention, the shape of the concavo-convex portion in the cross section parallel to the interface between the substrate and the compound semiconductor layer is at least semicircular, semielliptical, triangular, trapezoidal, polygonal, parabolic. One or a combination of two or more. As a result, the outer peripheral side surface of the compound semiconductor layer has various angles with respect to the element cutting surface, and the incident angle at the concave / convex portion (uneven surface) can be increased no matter what angle light enters the outer peripheral side surface. It can be derived to the outside below the critical angle. In particular, by making the shape of the concavo-convex part a semicircular shape or a polygonal shape, the incident light can be transmitted inside the convex part regardless of the incident angle and at any incident angle in the convex part of the concavo-convex part. Multiple reflections can be derived to the outside.

  In the fifth invention, the depth and interval (width) of the concavo-convex portions are 0.05 μm or more and 20 μm or less, respectively. When the depth and spacing of the uneven portions exceed 20 μm, the area that can be used as the light emitting portion is reduced as compared with the area of the element, and there arises a problem that the light emission efficiency is lowered and the current density is increased. Further, when the depth and interval of the concavo-convex portions are made smaller than 0.05 μm, it is not practical because it requires a very high resolution capability of the photolithography apparatus. Therefore, by setting the depth and interval of the concavo-convex portions to 0.05 μm or more and 20 μm or less, it is possible to improve the light extraction efficiency while suppressing an increase in current density. Moreover, although the depth and space | interval of an uneven | corrugated | grooved part are dependent also on the magnitude | size of an element and the capability of photolithography, it can be said that about 1 micrometer-20 micrometers are preferable, and also about 2 micrometers-5 micrometers are more preferable.

  In the sixth invention, the concavo-convex portion is covered with a coating film, and the compound semiconductor layer is a gallium nitride based semiconductor layer. The optical refractive index of the coating film is smaller than the optical refractive index of the gallium nitride based semiconductor layer. Thereby, reflection of light at the interface between the gallium nitride semiconductor layer and the coating film can be suppressed, and light extraction efficiency can be improved.

  In the seventh invention, the film thickness of the coating film is 10 nm or more and 10 μm or less. It is difficult to make the thickness of the coating film smaller than 10 nm, and it is not realistic to make it larger than 10 μm. By setting the film thickness of the coating film to 10 nm or more and 10 μm or less, it is possible to easily cover the uneven portion (uneven surface). The film thickness of the coating film is more preferably about 100 nm.

  In the eighth invention, the light emitting device reflects the light extracted from the light extraction portion of the semiconductor light emitting element by the reflecting member. Thereby, the light extracted from the side surface of the semiconductor light emitting device can be added to the light extracted from the upper surface (or lower surface) side of the semiconductor light emitting device, and the light extraction efficiency can be improved. The reflecting surface of the reflecting member can be appropriately set in a required shape according to the light extraction direction.

  According to the ninth aspect of the invention, it is possible to provide an illumination device with good light extraction efficiency.

  In the tenth aspect of the invention, a display device with good light extraction efficiency can be provided.

  In the twelfth invention, the step of forming the concavo-convex portion (concave / convex surface) includes a step of exposing the substrate surface by etching. Thereby, the dimension of the thickness direction of the compound semiconductor layer of the uneven | corrugated | grooved part formed along the outer peripheral side surface of a compound semiconductor layer can be enlarged, and the extraction efficiency of light can be improved. Note that the uneven portion can also be formed on the side surface of the substrate.

  In the fourteenth invention, the step of forming the concavo-convex portion includes a step of exposing the undoped layer by etching. This eliminates the need for etching until the substrate is exposed and facilitates the etching process.

  In the fifteenth invention, when the concavo-convex portion is formed, the P-type semiconductor layer and the active layer are removed by etching to form the N-type electrode, thereby exposing the N-type semiconductor layer. As a result, the concavo-convex portion can be formed in the electrode forming step, and it is possible to prevent the manufacturing cost from increasing without adding a new step, thereby simplifying the process.

  In the sixteenth invention, when forming the concavo-convex portion, a cutting groove for cutting the substrate is formed around the compound semiconductor layer. As a result, the concavo-convex portion can be formed in the process of forming the cut groove, and it is possible to prevent the manufacturing cost from increasing without adding a new process, thereby simplifying the process.

  In the first invention, the light extraction efficiency can be improved, the heat generated in the semiconductor light emitting element can be suppressed, and the reliability of the element can be improved.

  In the second and eleventh inventions, no matter what angle light is incident on the outer peripheral side surface, the incident angle at the concavo-convex portion can be made to be the outside at a critical angle or less.

  In the third invention and the thirteenth invention, even when the concavo-convex portion is formed, it is possible to suppress the peripheral length of the PN junction portion sandwiching the active layer from being increased, and to prevent an increase in leakage current. Can do.

  In the fourth invention, no matter what angle the light is incident on the outer peripheral side surface, the incident angle at the concavo-convex portion can be made to be less than the critical angle and led out of the semiconductor light emitting element. In particular, by making the shape of the concavo-convex part in an arc shape or a polygonal shape, the incident light is multiplexed inside the convex part regardless of the incident angle at any part of the convex part of the concavo-convex part. It can be reflected and led out.

  In the fifth invention, it is possible to improve the light extraction efficiency while suppressing an increase in current density.

  In the sixth invention, the light extraction efficiency can be improved. Further, when the periphery of the PN junction is also covered, the leakage current can be suppressed.

  In the seventh invention, the uneven portion can be covered easily.

  In the eighth invention, the light extracted from the side surface of the semiconductor light emitting element can be added to the light extracted from the upper surface (or lower surface) side of the semiconductor light emitting element to improve the light extraction efficiency. Can do.

  According to the ninth aspect of the invention, it is possible to provide an illumination device with good light extraction efficiency.

  In the tenth aspect of the invention, a display device with good light extraction efficiency can be provided.

  In the twelfth aspect, the thickness in the thickness direction of the compound semiconductor layer of the uneven portion formed along the outer peripheral side surface of the compound semiconductor layer can be increased, and light emission can be improved.

  In the fourteenth invention, it is not necessary to perform etching until the substrate is exposed, and the etching process becomes easy.

  In the fifteenth invention, the uneven portion can be formed in the electrode forming step, and it is possible to prevent the manufacturing cost from increasing without the addition of a new step and to simplify the process. it can.

  According to the sixteenth aspect of the present invention, it is possible to form the concavo-convex portion in the step of forming the cut groove, and it is possible to prevent the manufacturing cost from increasing without the addition of a new step and to simplify the process. Can do.

Embodiment 1
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is an external perspective view showing a schematic configuration of a semiconductor light emitting device according to the present invention. A semiconductor light-emitting element (hereinafter referred to as a light-emitting element) 50 is obtained by cutting a wafer on which a plurality of light-emitting elements are formed into a rectangular parallelepiped shape with a predetermined dimension to separate the light-emitting elements. In FIG. 1, 1 is a sapphire substrate. Instead of the sapphire substrate 1, a SiC (silicon carbide) substrate can be used. The vertical and horizontal dimensions of the sapphire substrate 1 are approximately 0.1 mm to 1 mm.

  On the upper surface (upper surface) of the sapphire substrate 1, an N-type semiconductor layer 2, an active layer 4, and a P-type semiconductor layer 5 are laminated in this order. The N-type semiconductor layer 2 includes, for example, an n-GaN (gallium nitride) layer of about 4 μm, an n-AlGaInN cladding layer, and the like, and the active layer 4 includes a GaN / InGaN-MQW (Multi-quantum Well, multiple quantum well). The P-type semiconductor layer 5 is composed of a p-AlGaInN layer, a p-GaN layer of about 0.3 μm, a p-InGaN layer as a contact layer, and the like. Thereby, a compound semiconductor layer is formed to form an LED structure as a light emitting portion. An AlN buffer layer (not shown) and an undoped GaN layer are formed between the N-type semiconductor layer 2 and the sapphire substrate 1.

  A current diffusion layer 6 is formed on the upper surface of the P-type semiconductor layer 5. The current diffusion layer 6 is, for example, an ITO film (indium tin oxide film) that is a conductive transparent film. Near the center of the light emitting element 50, an N electrode 7 is formed in contact with the N-type semiconductor layer 2. Near the corner of the light emitting element 50, a P electrode 8 that is a bonding electrode is formed in contact with the P-type semiconductor layer 5. Further, from the P electrode 8, a current diffusion auxiliary wiring 9 extending along the vicinity of the outer periphery of the current diffusion layer 6 is extended. As a result, the current from the P electrode 8 flows through the current diffusion auxiliary wiring 9 and flows through the entire current diffusion layer 6 to the N-type semiconductor layer 2, and light can be emitted in a wide range of the light emitting element 50. It becomes.

  On the outer peripheral side surface of the N-type semiconductor layer 2, an uneven surface 10 composed of a plurality of uneven portions is formed along the outer peripheral side surface. The uneven surface 10 is formed from the boundary between the N-type semiconductor layer 2 on the outer peripheral side surface of the N-type semiconductor layer 2 and the sapphire substrate 1 to the middle in the thickness direction. That is, the flat side surface portion 3 where the uneven surface 10 is not formed is left on the outer peripheral side surface of the N-type semiconductor layer 2. The irregular surface 10 may be formed only on the outer peripheral side surface of the undoped layer below the N-type semiconductor layer 2 without being formed on the outer peripheral side surface of the N-type semiconductor layer 2.

  FIG. 2 is an enlarged view of the main part of the uneven surface, and FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 2 shows a main part when the light emitting element 10 is viewed from the surface side of the light emitting element 50. As shown in FIG. 2, the uneven surface 10 has a semicircular shape. The depth and width (interval) of the concavo-convex shape of the concavo-convex surface 10 should be at least as large as the wavelength of light, but if it is made too large, the area that can be used as the light emitting portion is reduced compared to the area of the element. On the other hand, the luminous efficiency is lowered and the current density is increased. Therefore, 20 μm or less is desirable. Further, the depth and width of the unevenness may be small, but if it is too small, it is not practical because it requires a very high resolution capability of the photolithography apparatus, so 0.05 μm or more is desirable. . The depth and width of the unevenness depends on the size of the element and the ability of photolithography, but it can be said that the depth is preferably about 1 μm to 20 μm, and more preferably about 2 μm to 5 μm. As an example, the diameter of the semicircle shown in FIG. 2 is 2.5 μm, the depth of the unevenness is 2.5 μm, and the width is 5 μm.

  In addition, as shown in FIG. 3, the uneven surface 10 is formed in a part in the thickness direction (vertical direction) of the outer peripheral side surface of the N-type semiconductor layer 2, and the N-type semiconductor layer 2 in the vicinity of the active layer 4. The outer peripheral side surface is a flat flat side surface portion 3 having no uneven shape. As a result, it is possible to suppress an increase in the peripheral length of the PN layer and to prevent an increase in leakage current.

  In the present invention, attention is paid to the propagation direction of light confined inside the semiconductor light emitting device and the extraction efficiency on each surface of the semiconductor light emitting device. A semiconductor light emitting element is generally cut out from a wafer in a rectangular parallelepiped shape. As a three-dimensional coordinate of the semiconductor light emitting element, the cutting direction of the semiconductor light emitting element in the wafer plane is set as an X axis and a Y axis, and the thickness direction is set as a Z axis. This will be described below.

FIG. 4 is an explanatory view showing an example of a critical angle totally reflected at a boundary surface of a substance, FIG. 5 is an explanatory view showing a concept of the critical angle, and FIG. 6 is a reflection of light inside a conventional semiconductor light emitting device. It is explanatory drawing which shows. As shown in FIG. 4, the medium on the light incident side is GaN (gallium nitride), and the refractive index of the light is 2.5. That is, the example of FIG. 4 shows a condition (critical angle) in which incident light is totally reflected when light propagating in gallium nitride is incident on the exit-side medium. As a medium on the emission side, for example, air, epoxy resin and silicon resin often filled around the semiconductor light emitting element, ITO used as a current diffusion layer formed on the upper surface of the light emitting part of the light emitting element, protective film, etc. As an example, SiO ₂ used as a substrate and sapphire as a substrate material are illustrated together with the refractive index of light. In the case of air, the critical angle is about 23 degrees, about 35 degrees for epoxy resin, SiO ₂ and silicon resin, about 45 degrees for sapphire, and about 53 degrees for ITO.

As shown in FIG. 5, if the critical angle is θ and the incident angle θ1 at the boundary surface is θ1 <θ, the incident light is transmitted, and if θ1> θ, it is totally reflected. As shown in FIG. 5, when considering a so-called Escape Cone, the medium on the incident side of the unit sphere centered on the apex of the cone on the medium boundary surface, that is, out of the surface area of the unit sphere on the gallium nitride side The ratio of the inside of the escape cone is about 8% when the medium on the emission side is air, about 17 to 20% when the epoxy resin, SiO ₂ and silicon resin are used, and about 30% when sapphire is used. In the case of ITO, it is about 40%. In addition, since the reflective surface of a package is normally provided in the back surface (lower surface) of the sapphire substrate in which the compound semiconductor layer was formed on the surface (upper surface) of the sapphire substrate, it may be considered that the back surface of the substrate is almost totally reflected. .

Since light emission in the light emitting part (light emitting layer) of the semiconductor light emitting element is due to spontaneous emission, it can be considered that an infinite number of light emitting points are arranged in a plane in the light emitting layer (PN layer). The emitted light is emitted evenly in almost all directions immediately after emission. The emitted light is emitted from each layer of the nitride semiconductor, ITO formed on the semiconductor layer and its upper or lower surface, sapphire as the substrate, SiO ₂ as the protective film, or external silicon resin or epoxy resin. It propagates through each part by refraction or reflection at the interface. The difference in the refractive index of light in each layer in the nitride semiconductor is smaller than the difference in the refractive index of light between the nitride semiconductor and the other medium, and compared with the gallium nitride layer that occupies most of the nitride semiconductor, The active layer having a different refractive index and the cladding layer formed on the upper surface or the lower surface of the active layer may be thin, and the semiconductor layer may be considered to be substantially uniform gallium nitride.

  Considering the condition that the nitride semiconductor layer has a dimension in the XY direction of about 0.1 to 1 mm and a dimension in the Z direction of about 5 μm, the light emitted from each light emitting point reaches the side surface of the semiconductor light emitting element. It can be said that most of the light reaching the side surface after repeated reflection on the upper and lower surfaces of the semiconductor light emitting device. In addition, the light once reflected on the upper surface is likely to be repeatedly totally reflected on the upper and lower surfaces until reaching the side surface. In addition, most of the top surface of the nitride semiconductor layer forms an ITO film as a current diffusion layer, and considering that the critical angle is about 53 degrees larger than the side surface, of the light reaching the side surface, The Z-axis component of the incident angle of light that arrives by repeating total reflection on the upper and lower surfaces of the semiconductor light emitting device is reduced. For example, as shown in FIG. 6A, if the critical angle of the interface between the nitride semiconductor layer and the ITO film is α, the Z-axis component of the incident angle of light reaching the side surface of the semiconductor light emitting element is The maximum is (90 ° −α).

  In addition, the side surface of the nitride semiconductor layer is usually in contact with an epoxy resin or silicon resin, or in contact with these resins through a protective film, and the critical angle at the side surface is about 35 degrees. . Therefore, as shown in FIG. 6B, when the X-axis component, the Y-axis component, and the Z-axis component of the light reaching the side surface are larger than the critical angle, more precisely, the X-axis component, the Y-axis When the composite of the component and the Z-axis component exceeds the critical angle, total reflection occurs.

  FIG. 7 is an explanatory view showing a light extraction method using the uneven surface of the semiconductor light emitting device according to the present invention. As described above, the Z-axis component of the light that reaches the side surface is light that is totally reflected by the upper surface or the lower surface of the light-emitting element 50, and is therefore considered to be generally less than the critical angle. Therefore, it can be seen that in order to extract light from the side surface of the light emitting element 50, the X-axis component and the Y-axis component of the incident angle of the light reaching the side surface should be set to be less than the critical angle.

  As described above, since the light generated inside the light emitting element 50 is emitted uniformly in almost all directions, the X-axis component or the Y-axis component of the incident light on the side surface of the light emitting element 50 has various values. By forming a fine uneven surface 10 that is uneven along the surface of the sapphire substrate 1 on the outer peripheral side surface of the N-type semiconductor layer 2, the outer peripheral side surface of the N-type semiconductor layer 2 has various angles with respect to the element cutting surface. Therefore, no matter what angle the light is incident on the outer peripheral side surface, the incident angle of the light on the concavo-convex surface 10 can be made less than the critical angle and the light can be led out of the light emitting element 50. As shown in FIG. 7, by making the uneven shape of the uneven surface 10 semicircular (arc shape), no matter what incident angle and light incident on the convex portion of the uneven surface 10. The incident light can be multiple reflected inside the convex portion and led out to the outside. Thereby, compared with the case where an uneven surface is not formed, the light extraction efficiency can be improved by about 10 to 20%. The uneven shape is not limited to a semicircular shape.

  FIG. 8 is an explanatory view showing another example of the uneven shape of the uneven surface. The irregular shape may be a semi-elliptical shape as shown in FIG. 8A, a triangular shape as shown in FIG. 8B, a trapezoidal shape as shown in FIG. As shown in d), it may be a saw blade, an irregular triangle as shown in FIG. 8 (e), a polygon as shown in FIG. 8 (f), or in FIG. 8 (g). As shown, they may be separated semicircular. Although not shown, it may be parabolic. Moreover, the shape which combined two or more of these shapes periodically or irregularly may be sufficient. As a result, the outer peripheral side surface of the N-type semiconductor layer 2 has various angles with respect to the element cut surface, and the incident angle at the concave / convex surface 10 is critical no matter what angle light is incident on the outer peripheral side surface. It can be derived to the outside below the angle.

  In the above-described example, the uneven surface 10 is provided around the entire side surface of the N-type semiconductor layer 2. However, the uneven surface 10 may be provided partially along the outer periphery.

  Next, a method for manufacturing a semiconductor light emitting device according to the present invention will be described. 9 and 10 are explanatory views showing the manufacturing process of the semiconductor light emitting device. As shown in FIG. 9A, an AlN buffer layer (not shown) is first grown on the sapphire substrate 1 at about 400 ° C. by metal organic chemical vapor deposition (MO-CVD), and then N-type semiconductor layer 2 composed of an n-GaN layer of about 4 μm, an n-AlGaInN cladding layer, etc., an active layer 4 of GaN / InGaN-MQW type, a p-AlGaInN layer, a p-GaN layer of about 0.3 μm, a contact An LED structure in which a P-type semiconductor layer 5 composed of a p-InGaN layer or the like as a layer is formed in this order is generated. While irradiating the substrate taken out from the MO-CVD apparatus with ultraviolet rays, the substrate is heated to about 400 ° C. to activate the P-type semiconductor layer 5.

  As shown in FIG. 9B, an exposed surface 21 (cutting groove) is formed by photolithography and dry etching using the photoresist as a mask to etch the outer periphery of the element until the surface of the sapphire substrate 1 is exposed. At this time, the concavo-convex surface 10 is formed on the outer peripheral side surfaces of the P-type semiconductor layer 5, the active layer 4, and the N-type semiconductor layer 2. In this case, the photolithography mask pattern need only be a semicircular pattern.

  Next, as shown in FIG. 9C, the N-type electrode 7 is provided by etching the P-type semiconductor layer 5 and the active layer 4 where the N-type electrode 7 is provided until the N-type semiconductor layer 2 is exposed by dry etching. For this purpose, an opening 23 is formed. At this time, the upper portion of the concavo-convex surface 10 is etched toward the inside of the element, and the exposed surface 22 is formed by etching until the N-type semiconductor layer 2 is exposed. As a result, the concavo-convex surface 10 is formed on most of the lower side of the outer peripheral side surface of the N-type semiconductor layer 2, and the flat side surface portion 3 is formed on the upper side of the outer peripheral side surface of the N-type semiconductor layer 2 (near the active layer 4).

  As shown in FIG. 9D, a current spreading layer 6 is formed by forming an ITO film, which is a conductive transparent film, on the surface of the P-type semiconductor layer 5 by vacuum deposition and sputtering to a thickness of about 200 nm. At this time, after patterning by the lift-off method, heating to about 400 ° C. in air is performed to make ITO transparent.

  Next, as shown in FIG. 10E, a V / Al / Ti / Au film is formed by vacuum deposition, patterned by a lift-off method, and about 500 ° C. by RTA (Rapid Thermal Anneal) in an Ar atmosphere. Heat to form an N-type ohmic electrode and bonding pad. Thereby, the N electrode 7 is formed.

  As shown in FIG. 10 (f), an Ag—Pd—Cu alloy film is formed by sputtering, patterned by a lift-off method, and heated to about 300 ° C. by RTA in an Ar atmosphere to form a P electrode (bonding pad) 8 Then, the current diffusion auxiliary wiring 9 is formed.

As shown in FIG. 10 (g), the SiO ₂ film 11 is formed on the entire surface by plasma CVD, and as shown in FIG. 10 (h), by dry etching, the P electrode 8 upper portion 24 and the element isolation portion, that is, The SiO ₂ film 11 on the N electrode 7 upper portion 25 is removed to complete the LED wafer. Thereafter, element separation is performed by a cutting groove (exposed surface 21) formed on the sapphire substrate by laser scribing to complete a light emitting element and to assemble a package.

The SiO ₂ film 11 can be 10 nm or more and 10 μm or less. If the thickness of the SiO ₂ film 11 is smaller than 10 nm, it does not function as a protective film, and it is difficult to make it larger than 10 μm. By setting the thickness of the SiO ₂ film 11 to 10 nm or more and 10 μm or less, the uneven surface can be easily covered. The thickness of the SiO ₂ film 11 is more preferably about 100 nm.

The refractive index of light of the SiO ₂ film 11 is 1.46, and the refractive index of light of the N-type semiconductor layer 2 (gallium nitride semiconductor layer) is 2.5. Thereby, the critical angle of the light incident from the N-type semiconductor layer 2 side is about 35 degrees, and the uneven surface 10 makes the incident angle of the light equal to or less than the critical angle, and the N-type semiconductor layer 2 and the SiO ₂ film 11 It is possible to suppress the reflection of light at the boundary surface and to improve the light extraction efficiency.

  As described above, in the present invention, the required uneven surface 10 can be formed only by changing the mask pattern of photolithography, and there is no need to add a new process to the conventional manufacturing process. An increase in cost can be prevented and the process can be simplified.

Embodiment 2
FIG. 11 is an external perspective view showing a schematic configuration of the semiconductor light emitting device of the second embodiment. The difference from the first embodiment (FIG. 1) is that an uneven surface 10 is formed on the outer peripheral side surfaces of the N-type semiconductor layer 2, the active layer 4 and the P-type semiconductor layer 5. Since portions other than this difference are the same as those in the first embodiment, description thereof is omitted. By forming the uneven surface 10 on the outer peripheral side surfaces of the N-type semiconductor layer 2, the active layer 4 and the P-type semiconductor layer 5, the size of the uneven surface 10 in the thickness direction (longitudinal direction) is increased, and the area of the light extraction surface The light extraction efficiency can be further improved.

  Next, a method for manufacturing the semiconductor light emitting device of the second embodiment will be described. 12 and 13 are explanatory views showing manufacturing steps of the semiconductor light emitting device of the second embodiment. As shown in FIG. 12A, an AlN buffer layer (not shown) is first grown on the sapphire substrate 1 at about 400 ° C. by metal organic chemical vapor deposition (MO-CVD), and then N-type semiconductor layer 2 composed of an n-GaN layer of about 4 μm, an n-AlGaInN cladding layer, etc., an active layer 4 of GaN / InGaN-MQW type, a p-AlGaInN layer, a p-GaN layer of about 0.3 μm, a contact An LED structure in which a P-type semiconductor layer 5 composed of a p-InGaN layer or the like as a layer is formed in this order is generated. While irradiating the substrate taken out from the MO-CVD apparatus with ultraviolet rays, the substrate is heated to about 400 ° C. to activate the P-type semiconductor layer 5.

  As shown in FIG. 12B, the exposed surface 21 (cutting groove) is formed by etching the outer periphery of the element until the surface of the sapphire substrate 1 is exposed, using photolithography and dry etching as a mask. At this time, the concavo-convex surface 10 is formed on the outer peripheral side surfaces of the P-type semiconductor layer 5, the active layer 4, and the N-type semiconductor layer 2.

  Next, as shown in FIG. 12C, the N-type electrode 7 is provided by etching the P-type semiconductor layer 5 and the active layer 4 at the position where the N-electrode 7 is provided until the N-type semiconductor layer 2 is exposed by dry etching. For this purpose, an opening 23 is formed.

  As shown in FIG. 12D, the current spreading layer 6 is formed by forming an ITO film, which is a conductive transparent film, on the surface of the P-type semiconductor layer 5 by vacuum deposition and sputtering to a thickness of about 200 nm. At this time, after patterning by the lift-off method, heating to about 400 ° C. in air is performed to make ITO transparent.

  Next, as shown in FIG. 13E, a V / Al / Ti / Au film is formed by vacuum deposition, patterned by a lift-off method, and heated to about 500 ° C. by RTA (Rapid Thermal Anneal) in an Ar atmosphere. Heat to form an N-type ohmic electrode and bonding pad. Thereby, the N electrode 7 is formed.

  As shown in FIG. 13 (f), an Ag—Pd—Cu alloy film is formed by sputtering, patterned by a lift-off method, and heated to about 300 ° C. by RTA in an Ar atmosphere to form a P electrode (bonding pad) 8 Then, the current diffusion auxiliary wiring 9 is formed.

As shown in FIG. 13 (g), the SiO ₂ film 11 is formed on the entire surface by plasma CVD, and as shown in FIG. 13 (h), by dry etching, the P electrode 8 upper portion 24 and the element isolation portion, that is, The SiO ₂ film 11 on the N electrode 7 upper portion 25 is removed to complete the LED wafer. Thereafter, element separation is performed by a cutting groove (exposed surface 21) formed on the sapphire substrate by laser scribing to complete a light emitting element and to assemble a package.

  As described above, according to the present invention, the required uneven surface can be formed only by changing the mask pattern of photolithography, and it is not necessary to add a new process to the conventional manufacturing process. Can be prevented, and the process can be simplified.

  FIG. 14 is an explanatory diagram illustrating an example of a configuration of a light emitting device including a semiconductor light emitting element. The example of FIG. 14 shows an LED lamp 100 as a light emitting device in which the light emitting element 50 is packaged. A concave portion for accommodating the light emitting element 50 is formed in the cup portion 70 at the end of the lead frame 81, and the light emitting element 50 is attached and fixed to the concave portion. One electrode of the light emitting element 50 is connected to the lead frame 81 by a gold wire, and the other electrode of the light emitting element 50 is connected to the lead frame 82 by a gold wire.

  Reflecting surfaces 71 and 71 for reflecting light emitted from the side surface of the light emitting element 50 upward are formed in the concave portion of the cup portion 70. Further, the upper portions of the lead frames 81 and 82 are sealed with a mold portion 60 made of an epoxy resin whose tip portion forms a convex lens portion.

  The LED lamp 100 reflects light extracted from the side surface of the light emitting element 50 at the reflection surface 71. Thereby, the light extracted from the side surface of the light emitting element 50 can be added to the light extracted to the outside from the upper surface side of the light emitting element 50, and the light extraction efficiency can be improved. The reflecting surface can be appropriately set in a required shape according to the light extraction direction.

  FIG. 15 is an explanatory diagram showing another example of the configuration of a light emitting device including a semiconductor light emitting element. The example of FIG. 15 shows a surface mount LED 200 in which the light emitting element 50 is packaged. In FIG. 15, reference numeral 90 denotes a rectangular substrate made of ceramic or glass epoxy resin. The light emitting element 50 is mounted on the center of the upper surface of the substrate 90. External electrodes 93 and 94 are provided near the four corners of the substrate 90, and the external electrodes 93 and 94 are connected to the N electrode and the P electrode of the light emitting element 50 by gold wires (not shown), respectively. By soldering the external electrodes 93 and 94 on the lower surface of the substrate 90 to a required pattern of a printed wiring board (not shown), it can be surface-mounted on the printed wiring board.

  On the upper surface of the substrate 90, light reflecting portions 91, 91 made of ceramic or synthetic resin are provided so as to surround the light emitting element 50. Further, a sealing part (not shown) for sealing the light emitting element 50 is formed.

  The surface-mounted LED 200 reflects light extracted from the side surface of the light emitting element 50 by the reflecting portions 91 and 91. Thereby, the light extracted from the side surface of the light emitting element 50 can be added to the light extracted to the outside from the upper surface side of the light emitting element 50, and the light extraction efficiency can be improved. The reflecting surface can be appropriately set in a required shape according to the light extraction direction.

  As described above, by using the light emitting element 50 according to the present invention, an LED package, or a lighting device such as a light source unit or a lighting fixture using the package or the light emitting element 50, a display device such as a display unit or a display device, etc. Can improve the light output. In addition, since light that is absorbed inside the light emitting element 50 and converted into heat can be extracted to the outside, the temperature inside the light emitting element 50 can be suppressed and deterioration of the light emitting element 50 can be prevented. Deterioration of the LED package, the lighting device, and the display device can be prevented.

  The present invention can be applied not only to a top emission type semiconductor light emitting device using a transparent current layer (or a transparent electrode or a semitransparent electrode) but also to a flip chip type semiconductor light emitting device using a reflective P electrode. . Moreover, the method of processing the peripheral part of a compound semiconductor layer into a reverse mesa type | mold can also be employ | adopted simultaneously.

In the above-described embodiment, a photoresist is used as a mask for dry etching. However, when the gallium nitride layer is thick, it is necessary to increase the thickness of the resist in the photoresist mask. In such a case, it is disadvantageous if the resist is thick in order to make the concave and convex surface into a fine concave and convex shape. Therefore, a so-called hard mask is made of SiO ₂ film or Ni film using a thin photoresist once. In addition, dry etching of the gallium nitride based semiconductor layer can be performed using this as a mask.

Embodiment 3
FIG. 16 is an external plan view of the semiconductor light emitting device of the third embodiment, and FIG.
FIG. 7 is a sectional view taken along line XVII. As shown in FIGS. 16 and 17, in the third embodiment, the uneven surface 10 is formed on the cross section (side surface) in the opening 40 inside the element. That is, the outer peripheral side surface of the compound semiconductor layer also includes a cross section (side surface) inside the element, and the light extraction efficiency can be improved by forming the uneven surface 10 on the side surface inside the element.

  In Embodiment 3, the light extracted from the outer peripheral side surface of the compound semiconductor layer is formed at a position facing the outer peripheral side surface of the compound semiconductor layer, and the N-type semiconductor layer 2, the active layer 4, and the P-type semiconductor layer 5 are formed. It can also be reflected by the reflecting members 30 and 40 made of the above. Reflecting members 31 and 41 are formed with reflecting films 31 and 41 for reflecting light extracted from the side surfaces of the light emitting element 50, respectively.

Embodiment 4
18 is an external plan view of the semiconductor light emitting device of the fourth embodiment, and FIG. 19 is a cross-sectional view taken along line XIX-XIX in FIG. As shown in FIG. 18 and FIG. 19, in the fourth embodiment, a combination with a technique for forming the outer peripheral portion of a conventional compound semiconductor layer into an inverted mesa structure is performed. That is, the light emitting element of Embodiment 4 has a structure in which the depth of the unevenness of the uneven surface 10 becomes shallow along the direction of the sapphire substrate 1. Thereby, the light extraction efficiency can be improved.

  In the above-described embodiment, as an example in which the area of the light extraction surface can be secured widely in the vertical direction (thickness direction), an example has been shown in which the uneven surface 10 is provided in the portion of the element isolation cutting groove. The present invention is not limited, and the present invention can form the concavo-convex surface 10 by slightly changing the pattern of the mask used for photolithography of each layer. Even if it is applied to all the layers such as patterning of the protective film and patterning of the protective film, the manufacturing cost does not increase. The uneven surface 10 can also be formed on the sapphire substrate.

It is an external appearance perspective view which shows schematic structure of the semiconductor light-emitting device based on this invention. It is a principal part enlarged view of an uneven surface. It is the III-III sectional view taken on the line of FIG. It is explanatory drawing which shows the example of the critical angle totally reflected in the interface of a substance. It is explanatory drawing which shows the concept of a critical angle. It is explanatory drawing which shows reflection of the light inside the conventional semiconductor light-emitting device. It is explanatory drawing which shows the extraction method of the light by the uneven surface of the semiconductor light-emitting device which concerns on this invention. It is explanatory drawing which shows the other example of the uneven | corrugated shape of an uneven surface. It is explanatory drawing which shows the manufacturing process of a semiconductor light-emitting device. It is explanatory drawing which shows the manufacturing process of a semiconductor light-emitting device. FIG. 5 is an external perspective view showing a schematic configuration of a semiconductor light emitting element of a second embodiment. FIG. 10 is an explanatory diagram showing a manufacturing process of the semiconductor light-emitting element of the second embodiment. FIG. 10 is an explanatory diagram showing a manufacturing process of the semiconductor light-emitting element of the second embodiment. It is explanatory drawing which shows an example of a structure of a light-emitting device provided with a semiconductor light-emitting element. It is explanatory drawing which shows the other example of a structure of a light-emitting device provided with a semiconductor light-emitting device. FIG. 6 is an external plan view of a semiconductor light emitting element according to a third embodiment. It is the XVII-XVII sectional view taken on the line of FIG. FIG. 10 is an external plan view of a semiconductor light emitting element according to a fourth embodiment. It is the XIX-XIX sectional view taken on the line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sapphire substrate 2 N type semiconductor layer 3 Flat side surface part 4 Active layer 5 P type semiconductor layer 6 Current diffusion layer 7 N electrode 8 P electrode 9 Current diffusion auxiliary wiring 10 Uneven surface (light extraction portion, uneven portion)
11 SiO ₂ film 21, 22 Exposed surface 71 Reflecting surface 91 Reflecting portion

Claims (16)

In a semiconductor light emitting device in which a compound semiconductor layer is formed on a substrate,
A semiconductor light emitting device comprising a light extraction portion for extracting light on an outer peripheral side surface of the compound semiconductor layer. The light extraction part is:
The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element is a concavo-convex portion formed along the outer peripheral side surface. The compound semiconductor layer is
An N-type semiconductor layer, an active layer, and a P-type semiconductor layer are stacked in this order on the substrate.
The light extraction part is:
3. The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element is an uneven portion formed on an outer peripheral side surface of the N-type semiconductor layer and formed along the outer peripheral side surface. The uneven portion is
The cross section parallel to the interface between the substrate and the compound semiconductor layer is at least one of semicircular, semielliptical, triangular, trapezoidal, polygonal or parabolic, or a combination of two or more. The semiconductor light-emitting device according to claim 2 or 3. The depth and spacing of the irregularities is
5. The semiconductor light emitting device according to claim 2, wherein each of the semiconductor light emitting devices is 0.05 μm or more and 20 μm or less. Comprising a coating film covering the uneven portion;
The compound semiconductor layer is
A gallium nitride based semiconductor layer,
The refractive index of the coating film is
6. The semiconductor light emitting device according to claim 2, wherein the semiconductor light emitting device has a smaller refractive index than that of the gallium nitride based semiconductor layer.   The semiconductor light emitting element according to claim 6, wherein the coating film has a thickness of 10 nm to 10 μm.   8. A light emitting device comprising: the semiconductor light emitting element according to claim 1; and a reflecting member that reflects light extracted from a light extraction portion of the semiconductor light emitting element.   An illumination device comprising the semiconductor light-emitting element according to claim 1 or the light-emitting device according to claim 8.   A display device comprising the semiconductor light-emitting element according to claim 1 or the light-emitting device according to claim 8. In a method for manufacturing a semiconductor light emitting device in which a compound semiconductor layer is formed on a substrate,
Forming a compound semiconductor layer on the surface of the substrate;
And etching the outer peripheral side surface of the compound semiconductor layer to form a concavo-convex portion along the outer peripheral side surface. The step of forming the uneven portion includes
12. The method of manufacturing a semiconductor light emitting element according to claim 11, further comprising a step of exposing the substrate surface by etching. The step of forming the compound semiconductor layer includes
Including a step of forming an undoped layer, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer at least in this order on the surface of the substrate;
The step of forming the uneven portion includes
The method for manufacturing a semiconductor light emitting element according to claim 11, wherein an uneven portion is formed on an outer peripheral side surface of the N-type semiconductor layer by etching. The step of forming the uneven portion includes
14. The method of manufacturing a semiconductor light emitting device according to claim 13, further comprising a step of exposing the undoped layer by etching. The step of forming the uneven portion includes
14. The method of manufacturing a semiconductor light emitting device according to claim 13, further comprising a step of exposing the N type semiconductor layer by removing the P type semiconductor layer and the active layer by etching to form an N type electrode. The step of forming the uneven portion includes
12. The method of manufacturing a semiconductor light emitting device according to claim 11, further comprising a step of forming a cutting groove for cutting the substrate around the compound semiconductor layer.

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