JP2006093686A - Light emitting element, its manufacturing method, and lighting device using the same light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance light emitting element in which light extraction efficiency is improved, and superior emission intensity can be obtained by small electric power. <P>SOLUTION: The light emitting element comprises a gallium nitride compound semiconductor layer 1 epitaxially grown and containing a light emitting layer 1a, a conductive reflective layer 2 formed on one principal surface 1b1 of the gallium nitride compound semiconductor 1, and a conductive layer 3 electrically connected to a layer 1c on the other principal surface 1c side. The other principal surface 1c1 of the gallium nitride compound semiconductor layer 1 is a surface where a substrate 4 used for epitaxially growing the gallium nitride compound semiconductor layer 1 is removed, or a new surface formed by etching the former surface. Since light can be extracted from the surface side where the substrate 4 is removed without being absorbed by the substrate 4, the light extraction efficiency of the surface side where the substrate 4 is removed is improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light-emitting element (light-emitting diode; LED) that is used in, for example, a lighting device and has energy consumption efficiency twice or more that of a fluorescent lamp, a manufacturing method thereof, and a lighting device using the light-emitting element.

  A light-emitting element using a gallium nitride-based compound semiconductor is widely known as a blue or ultraviolet light-emitting element (see, for example, Patent Documents 1 to 5). In such a light-emitting element, it is important to efficiently extract light generated inside the light-emitting element to the outside, that is, to improve the light extraction efficiency, especially for lighting devices that are being commercialized in recent years. Is indispensable.

  3A to 3C, examples of first to third conventional light-emitting elements devised to improve the light extraction efficiency (hereinafter referred to as first conventional example, second conventional example, A sectional view of a third conventional example is shown. In addition, the same code | symbol is attached | subjected to the same thing and the overlapping description is abbreviate | omitted.

  As shown in FIG. 3A, in the first conventional example, a gallium nitride compound semiconductor layer 11 including a light emitting layer 11a is formed on one surface of a substrate 14, and the light is emitted from the light emitting layer 11a on the other surface. The reflective layer 15 for reflecting the reflected light is formed. The surface of the gallium nitride compound semiconductor layer 11 (the surface not in contact with the substrate 14) is energized to the gallium nitride compound semiconductor layer 11 and emitted from the light emitting layer 11a. A transparent electrode 16 that transmits the transmitted light and an electrode pad 17 for energizing the transparent electrode 16 are formed on a part of the transparent electrode 16 (see, for example, Patent Documents 6 to 8). Here, the gallium nitride-based compound semiconductor layer 11 has a configuration in which the light emitting layer 11a is sandwiched between semiconductor layers 11b and 11c having different conductivity types, and the surface of the semiconductor layer 11c in contact with the substrate 14 is in contact with the substrate 14. An electrode pad 13 for allowing a current to flow between the electrode pad 17 by applying a voltage on the opposite surface is formed.

  As shown in FIG. 3B, in the second conventional example, the light emitted from the light emitting layer 11a at the interface between the gallium nitride compound semiconductor layer 11 including the light emitting layer 11a and the substrate 14 is gallium nitride based. A reflective layer 18 (for example, a Bragg reflector) that reflects toward the compound semiconductor layer 11 is formed, and the gallium nitride compound semiconductor layer 11 is formed on the surface of the gallium nitride compound semiconductor layer 11 (the surface not in contact with the substrate 14). A transparent electrode 16 that transmits current emitted from the light emitting layer 11a and transmits light emitted from the light emitting layer 11a, and an electrode pad 17 for supplying current to the transparent electrode 16 are formed on a part of the transparent electrode 16 (for example, Patent Literature 1). 9 and Patent Document 10).

  Further, as shown in FIG. 3C, in the third conventional example, the gallium nitride compound semiconductor layer 11 is energized on the surface of the gallium nitride compound semiconductor layer 11 including the light emitting layer 11a formed on the substrate 14. In addition, a conductive reflective layer 12 is formed that reflects light emitted from the light emitting layer 11a toward the substrate 14 (see, for example, Patent Documents 11 to 19).

In such a conventional light emitting device, the reflective layer 15, the reflective layer 18 or the conductive reflective layer 12 provided on one side of the light emitting layer 11a functions to reflect the light emitted from the light emitting layer 11a to the other side. Therefore, since the light that is generated radially can be concentrated and extracted in a desired direction without diverging, the light generated inside the light emitting element can be efficiently extracted to the outside. . In the embodiment shown in FIGS. 3A and 3B, the light extraction surface is the surface side of the gallium nitride compound semiconductor layer 11, and in the embodiment shown in FIG. 3C, the gallium nitride compound semiconductor layer. 11 is a surface side in contact with the base 14 of the eleventh.
JP-A-2-42770 JP-A-2-257679 JP-A-5-183189 JP-A-6-196757 JP-A-6-268257 JP-A-8-102549 Japanese Patent Laid-Open No. 2001-7397 Japanese Patent Laid-Open No. 2001-7392 JP-A-3-108778 JP-A-3-163882 JP 2000-31540 A JP 10-144961 A Japanese Patent Laid-Open No. 11-220168 Japanese Patent Laid-Open No. 11-261109 JP 2000-31540 A JP 2000-183400 A JP 2000-294837 A JP 2002-246649 A Registered Utility Model No. 3068814 Special table 2003-532298

  However, in the first conventional example, the light reflected by the reflective layer 15 formed on the substrate 14 is absorbed by the substrate 14 when propagating through the substrate 14 because it travels to the transparent conductive film 16 side which is the light extraction surface. For this reason, there is a problem that even if light is reflected by the reflective layer 15, the light extraction efficiency of the entire light emitting device is not improved so much. In addition, part of the light reflected by the reflective layer 15 is multiple-reflected on the front and back surfaces of the substrate 14 and confined in the substrate 14, and attenuates before being extracted from the transparent conductive film 16 side that is the light extraction surface. There is a problem that the light extraction efficiency of the entire light emitting element is not improved so much. Furthermore, the electrode pad 17 is provided on the light extraction surface, and a conductive wire or the like for electrical conduction is connected to the electrode pad 17, so that the electrode pad 17 or the conductive wire is connected to the gallium nitride compound semiconductor layer 11. As a result, there is a problem that the light extraction efficiency is lowered.

  In the second conventional example, in order to grow the gallium nitride compound semiconductor layer 11 on the reflective layer 18, it is difficult to increase the reflection efficiency of the reflective layer 18, or the wavelength of the reflected light. Therefore, there is a problem that the light extraction efficiency of the entire light emitting element by the reflective layer 18 is not improved so much. In addition, since the electrode pad 17 is provided on the light extraction surface, and a conductive wire or the like for electrical conduction is connected to the electrode pad 17, the electrode pad 17 or the conductive wire is connected from the gallium nitride compound semiconductor layer 11. As a result, there is a problem that the light extraction efficiency is lowered.

  In the third conventional example, the light reflected by the reflective layer 12 formed on the gallium nitride compound semiconductor layer 11 propagates through the substrate 14 in order to go to the transparent conductive film 16 side which is the light extraction surface. In this case, since the light is absorbed by the substrate 14, the light extraction efficiency of the entire light emitting element is not improved so much even if light is reflected by the reflective layer 12. In addition, part of the light reflected by the reflective layer 12 is multiply reflected by the front and back surfaces of the substrate 14 and confined in the substrate 14 and attenuates before being extracted from the transparent conductive film 16 side that is the light extraction surface. There is a problem that the light extraction efficiency of the entire light emitting element is not improved so much.

  The present invention has been completed in view of the above circumstances, and an object thereof is to improve the light extraction efficiency more greatly, and as a result, a high-performance light-emitting element capable of obtaining a good light emission intensity with a small electric power and its It is an object of the present invention to provide a method for manufacturing a light-emitting element that can reliably manufacture a high-performance light-emitting element and an illumination device using the high-performance light-emitting element.

  The light emitting device of the present invention includes an epitaxially grown gallium nitride compound semiconductor layer including a light emitting layer, a conductive reflective layer formed on one main surface of the gallium nitride compound semiconductor layer, and the gallium nitride compound semiconductor layer. A conductive layer electrically connected to a layer on the other main surface side of the gallium nitride compound semiconductor layer, and the other main surface of the gallium nitride compound semiconductor layer is a substrate used for epitaxial growth of the gallium nitride compound semiconductor layer. The surface is a removed surface or a new surface formed by etching.

  The light-emitting element of the present invention is characterized in that, in the above structure, an antireflection layer is formed on the other main surface of the gallium nitride-based compound semiconductor layer.

  In the light-emitting element of the present invention, in the above structure, the antireflection layer has a large number of protrusions whose top portion is smaller than the base portion and a large number of depressions whose bottom portion is smaller than the opening portion on the main surface. It is characterized by being.

  The light emitting device of the present invention is characterized in that, in the above configuration, a bump electrode is connected to a main surface of the conductive reflective layer.

  The method for manufacturing a light emitting device of the present invention includes a step of epitaxially growing a gallium nitride compound semiconductor layer including a light emitting layer on a substrate, a step of forming a conductive reflective layer on the gallium nitride compound semiconductor layer, And a step of removing the substrate from the gallium nitride compound semiconductor layer while protecting the conductive reflective layer.

  The method for manufacturing a light-emitting element according to the present invention is characterized in that, in the above-described manufacturing method, a step of forming an antireflection layer on the surface of the gallium nitride compound semiconductor layer from which the substrate has been removed is provided. .

  Moreover, the manufacturing method of the light emitting element of this invention comprises the process of connecting a bump electrode on the said electroconductive reflection layer in the said manufacturing method.

  The method for manufacturing a light emitting device of the present invention is characterized in that, in the above manufacturing method, a boride single crystal is used for the substrate.

  An illumination device of the present invention comprises the light emitting element of the present invention having the above-described configuration and at least one of a phosphor and a phosphor that emits light upon receiving light emitted from the light emitting element. It is.

  According to the light emitting device of the present invention, an epitaxially grown gallium nitride compound semiconductor layer including a light emitting layer, a conductive reflective layer formed on one main surface of the gallium nitride compound semiconductor layer, and a gallium nitride compound semiconductor A conductive layer electrically connected to the layer on the other main surface side of the layer, and the substrate used for epitaxial growth of the gallium nitride compound semiconductor layer on the other main surface of the gallium nitride compound semiconductor layer is removed. Or a new surface formed by etching this surface, the conductive reflective layer and the surface from which the substrate has been removed or a new surface formed by etching this surface are linked. The light emitted from the light emitting layer is reflected to the other main surface side of the gallium nitride compound semiconductor layer, and the reflected light is reflected from the other main surface side of the gallium nitride compound semiconductor layer. Since it functions to emit light without being absorbed by the plate, the light generated inside the light-emitting layer can be efficiently extracted by being concentrated in a desired direction without being diverged. The light extraction efficiency from the surface side is greatly improved, and a high performance capable of obtaining a good emission intensity with a small electric power is obtained. In addition, when flip-chip mounting is performed by heating a light-emitting element to a base or the like via a bump electrode or the like, conventionally, a gallium nitride compound semiconductor layer is formed due to a difference in thermal expansion coefficient between the gallium nitride compound semiconductor layer and the substrate. There is a problem that the reliability of the light-emitting element is reduced due to peeling between the substrate and the gallium nitride compound semiconductor layer due to the stress, or distortion in the gallium nitride compound semiconductor layer. However, according to the light-emitting element of the present invention, since the substrate is removed, when the light-emitting element is flip-chip mounted, no stress is applied to the gallium nitride-based compound semiconductor layer, distortion of the gallium nitride-based compound semiconductor layer, etc. It is more reliable than being able to reduce

  According to the light emitting device of the present invention, in the above configuration, when the antireflection layer is formed on the other main surface of the gallium nitride compound semiconductor layer, the light emitting device is formed on the surface from which the substrate is removed (the other main surface). The antireflection layer transmits the light generated inside the gallium nitride compound semiconductor layer that reaches the other main surface of the gallium nitride compound semiconductor layer without reflecting to the one main surface side of the gallium nitride compound semiconductor layer. Therefore, light that is attenuated by multiple reflection inside the gallium nitride compound semiconductor layer can be reduced and light can be efficiently extracted to the other main surface side of the gallium nitride compound semiconductor layer. A high-performance light-emitting element with improved efficiency is obtained. In addition, since the antireflection layer can be provided without using epitaxial growth, the materials used for the antireflection layer and the manufacturing process can be selected from an optical standpoint, so that the transmission characteristics of light transmitted through the antireflection layer can be selected. As a result, the refractive index, surface shape, etc. of the antireflection layer can be made appropriate so that the light extraction efficiency can be further improved.

  Further, according to the light emitting device of the present invention, in the above configuration, the antireflection layer has a large number of protrusions whose top portion is smaller than the base portion and a large number of depressions whose bottom portion is smaller than the opening portion on the main surface. These protrusions or depressions serve to prevent reflection even for light incident on the antireflection layer from an oblique direction by making the incident angle of light incident on the surface of the protrusions or depressions larger than the critical angle. Therefore, light incident on the antireflection layer from an oblique direction can be transmitted, and the range of the incident angle of the light with respect to the antireflection layer that can transmit the antireflection layer can be widened. Improved performance. In addition, the protrusions or depressions continuously change the refractive index with respect to the light emission direction, and gradually decrease from the high refractive index of the gallium nitride compound semiconductor layer to a low refractive index such as air. Therefore, it also has an effect of lowering the reflectance itself in the light emitting direction, so that a high-performance light-emitting element with further improved light extraction efficiency can be obtained.

  According to the light emitting device of the present invention, in the above configuration, when the bump electrode is connected to the main surface of the conductive reflective layer, the bump electrode fixes the light emitting device to the base or the like on the conductive reflective layer side. In addition, since it works to establish electrical continuity to the light emitting element on the conductive reflective layer side, it is possible to eliminate the need to arrange a conducting wire or the like that blocks light on the light extraction surface side, so that the light extraction efficiency is further improved. It becomes performance.

  According to the method for manufacturing a light emitting device of the present invention, a step of epitaxially growing a gallium nitride compound semiconductor layer including a light emitting layer on a substrate, and a step of forming a conductive reflection layer on the gallium nitride compound semiconductor layer, And removing the substrate from the gallium nitride compound semiconductor layer while protecting the conductive reflective layer. In the step of removing the substrate from the gallium nitride compound semiconductor layer, the gallium nitride compound semiconductor layer As a result, it is possible to suppress the deterioration of the surface and the conductive reflective layer formed thereon due to, for example, contamination / corrosion caused by an etchant or the like, or stress, so that a high-performance light-emitting element can be reliably manufactured. It will be possible.

  According to the method for manufacturing a light emitting element of the present invention, in the above manufacturing method, when the step of forming the antireflection layer is provided on the surface of the gallium nitride compound semiconductor layer from which the substrate has been removed, the antireflection layer is formed. Since the surface to be coated is protected by the substrate before the formation of the antireflection layer, it becomes a clean surface. As a result, a good antireflection layer can be produced, so that a high-performance light-emitting element can be more reliably produced. Will be able to do.

  Further, according to the method for manufacturing a light emitting element of the present invention, in the above manufacturing method, when the step of connecting the bump electrode on the conductive reflective layer is provided, after the bump electrode is formed on the conductive reflective layer, The step of removing the substrate and the step of forming the antireflection layer are performed while the conductive reflection layer and the bump electrode are protected, or the substrate is protected during the step of removing the substrate and the step of forming the antireflection layer. Since the bump electrode is finally formed on the conductive reflective layer, the conductive reflective layer and the bump electrode are not deteriorated by the step of removing the substrate or the step of forming the antireflection layer. As a result, the bump electrode is improved. Since it can be formed, a high-performance light-emitting element can be more reliably manufactured.

  According to the method for manufacturing a light emitting device of the present invention, in the above manufacturing method, when a boride single crystal is used for the substrate, the lattice constants of the boride single crystal substrate and the gallium nitride compound semiconductor layer are matched. Therefore, since a gallium nitride compound semiconductor layer with good crystal quality can be formed, a high-performance light-emitting element can be more reliably manufactured.

  Further, according to the lighting device of the present invention, since the light-emitting element of the present invention having the above-described configuration and at least one of a phosphor and a phosphor that emit light upon receiving light emitted from the light-emitting element are provided, low power consumption is achieved. In this case, the phosphor or phosphor is strongly excited by the light emitted from the light-emitting element having a good emission intensity, so that a good illuminance can be obtained with a small electric power. In addition, such an illuminating device of the present invention can be superior in energy saving and downsizing than conventional fluorescent lamps and discharge lamps, and can be replaced with fluorescent lamps and discharge lamps. .

  Hereinafter, a light-emitting element, a manufacturing method thereof, and an illumination device using the light-emitting element of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a light emitting device of the present invention. 2A to 2J are schematic cross-sectional views showing respective steps of the method for manufacturing a light emitting device of the present invention.

  1 and 2, 1 is a gallium nitride compound semiconductor layer, 1a is a light emitting layer, 1b is a first conductivity type semiconductor layer, 1c is a second conductivity type semiconductor layer, 1b1 is a gallium nitride compound semiconductor layer 1 1c1 is the other main surface of the gallium nitride compound semiconductor layer 1, 2 is a conductive reflective layer, 3 is a conductive layer, 4 is a substrate for epitaxially growing the gallium nitride compound semiconductor layer 1, 5 Is an antireflection layer, 5a is a base portion of the antireflection layer 5, 5b is a top portion, 6a and 6b are bump electrodes, and 7 is a protective film.

  As shown in FIG. 1, the light emitting device of the present invention includes an epitaxially grown gallium nitride compound semiconductor layer 1 including a light emitting layer 1a, and a conductive reflection formed on one main surface 1b1 of the gallium nitride compound semiconductor layer 1. A layer 2 and a conductive layer 3 electrically connected to the layer 1c on the other main surface 1c1 side of the gallium nitride-based compound semiconductor layer 1, and the other main surface 1c1 of the gallium nitride-based compound semiconductor layer 1 is nitrided In this configuration, the substrate 4 used for epitaxial growth of the gallium compound semiconductor layer 1 is removed, or a new surface is formed by etching this surface.

  More specifically, in this configuration, the gallium nitride-based compound semiconductor layer 1 includes a light emitting layer 1a as a first conductive semiconductor layer (p-type semiconductor layer in this example) 1b and a second conductive semiconductor layer (in this example n Type semiconductor layer) 1c. The first conductive type semiconductor layer 1b and the second conductive type semiconductor layer 1c may be formed by laminating a plurality of layers (not shown) containing indium (In) or aluminum (Al) on the light emitting layer 1a side. The composition is controlled so that the forbidden band width is wider than that of the light emitting layer 1a. The light emitting layer 1a may also be a multi-layer quantum well structure (MQW), which is a superlattice in which a quantum well structure composed of a barrier layer having a wide forbidden band and a well layer having a narrow forbidden band is regularly stacked a plurality of times. Good (not shown). The first conductivity type semiconductor layer and the second conductivity type semiconductor layer may be an n type semiconductor layer and a p type semiconductor layer, respectively.

The conductive reflective layer 2 has a smooth surface made of a material that reflects the light generated by the light emitting layer 1a without loss and has a good ohmic connection with the first conductive semiconductor layer 1b (p-type semiconductor layer). A layered one is used. Examples of such materials include aluminum (Al), titanium (Ti), nickel (Ni), chromium (Cr), indium (In), tin (Sn), molybdenum (Mo), silver (Ag), Gold (Au), Niobium (Nb), Tantalum (Ta), Vanadium (V), Platinum (Pt), Lead (Pb), Beryllium (Be), Tin oxide (SnO ₂ ), Indium oxide (In ₂ O ₃ ) , Indium tin oxide (ITO), gold-silicon alloy (Au-Si), gold-germanium alloy (Au-Ge), gold-zinc alloy (Au-Zn), gold-beryllium alloy (Au-Be), etc. May be used. Among these, aluminum (Al) or silver (Ag) is preferable because it has a high reflectance with respect to blue or ultraviolet light generated by the light emitting layer 1 a of the gallium nitride compound semiconductor layer 1. Aluminum (Al) is also particularly suitable for the ohmic junction with the p-type semiconductor layer. A plurality of layers selected from the above materials may be stacked. Note that the surface of the conductive reflective layer 2 does not necessarily have to be perfectly smooth, but care must be taken because the reflectance may decrease if the surface is not smooth.

The conductive layer 3 is a layer having a smooth surface made of a material capable of forming a good ohmic connection with the second conductive semiconductor layer 1c (n-type semiconductor layer). Examples of such materials include aluminum (Al), titanium (Ti), nickel (Ni), chromium (Cr), indium (In), tin (Sn), molybdenum (Mo), silver (Ag), Gold (Au), Niobium (Nb), Tantalum (Ta), Vanadium (V), Platinum (Pt), Lead (Pb), Tungsten (W), Tin oxide (SnO ₂ ), Indium oxide (In ₂ O ₃ ) , Indium tin oxide (ITO), gold-silicon alloy (Au-Si), gold-tin alloy (Au-Sn), gold-germanium alloy (Au-Ge), indium-aluminum alloy (In-Al), etc. May be used.

  In FIG. 1, a region where the light emitting layer 1a and the first conductivity type semiconductor layer 1b are not formed is provided in the second conductivity type semiconductor layer 1c, and the conductive layer 3 is formed in this region. Thus, it is preferable to form the conductive layer 3 on the surface opposite to the surface on the other main surface 1c1 side of the second conductivity type semiconductor layer 1c. As a result, a part of the light extraction surface is not blocked by the conductive layer 3, and the conductive reflective layer 2 and the conductive layer 3 are formed in the same direction when the light emitting element is mounted on a base or the like. This makes it easy to implement.

  In the above configuration, the conductive reflective layer 2 applies a forward bias voltage to the conductive reflective layer 2 and the conductive layer 3 to cause a bias current to flow through the gallium nitride-based compound semiconductor layer 1 and to emit light at a wavelength of 350 at the light emitting layer 1a. While generating ultraviolet to near-ultraviolet light of about ˜400 nm, the light generated on the conductive reflective layer 2 side of the ultraviolet to near-ultraviolet light emitted from the light emitting layer 1 a is emitted from the gallium nitride compound semiconductor layer 1. The other main surface 1c1 is reflected. In this manner, the light emitting device of the present invention is from the other main surface 1c1 side of the gallium nitride compound semiconductor layer 1 (that is, the surface from which the substrate 4 has been removed or a new surface formed by etching this surface). It operates so that the ultraviolet to near ultraviolet light is extracted.

  As described above, according to the light emitting device of the present invention, ultraviolet light to near ultraviolet light generated in the light emitting layer 1a is generated by the function of the conductive reflective layer 2 and the other main surface 1c1 of the gallium nitride compound semiconductor layer 1 linked together. Ultraviolet to near-ultraviolet light that can be concentrated in a desired direction without diverging radially and is reflected by the conductive reflective layer 2 is absorbed by the substrate 4 from the other main surface 1c1 side of the gallium nitride compound semiconductor layer 1. Therefore, it is possible to extract ultraviolet to near-ultraviolet light generated in the light emitting layer 1a more efficiently than in the prior art, so that the other main surface 1c1 side of the gallium nitride compound semiconductor layer 1 can be extracted. The light extraction efficiency from the light source is greatly improved, and good light emission intensity can be obtained with a small electric power.

  As shown in FIG. 1, in the light emitting device of the present invention, the antireflection layer 5 may be formed on the other main surface 1c1 of the gallium nitride-based compound semiconductor layer 1, and the antireflection layer 5 is formed on the main surface. It is preferable to have a plurality of protrusions whose top portion 5b is smaller than the base portion 5a or a depression whose bottom portion is smaller than the opening portion.

The antireflection layer 5 is formed by forming a dielectric such as quartz (SiO ₂ ), alumina (Al ₂ O ₃ ), or polycarbonate in a single layer or multiple layers on the surface of the gallium nitride compound semiconductor layer 1 from which the substrate 4 is removed. That's fine. In this case, the refractive index is gradually decreased from the gallium nitride-based compound semiconductor layer 1 side, or the film thickness of the antireflection layer 5 is changed within the antireflection layer 5 of ultraviolet to near ultraviolet light generated in the light emitting layer 1a. What is necessary is just to make it become about 1/4 of a wavelength. As a result, the multiple reflected lights in the antireflection layer 5 weaken each other and easily interfere with each other, and a standing wave is less likely to be generated.

  When the antireflection layer 5 is provided as described above, the antireflection layer 5 causes ultraviolet to near-ultraviolet light generated inside the gallium nitride compound semiconductor layer 1 to be on the one main surface 1b1 side of the gallium nitride compound semiconductor layer 1. Therefore, light that is attenuated by multiple reflection inside the gallium nitride compound semiconductor layer 1 is reduced, and light is efficiently emitted to the one main surface 1b1 side of the gallium nitride compound semiconductor layer 1. Therefore, the light extraction efficiency of the light emitting device of the present invention can be further improved. Further, since the substrate 4 is removed, the antireflection layer 5 can be provided on the surface without depending on the epitaxial growth. Therefore, various materials and manufacturing processes used for the antireflection layer 5 can be selected from an optical standpoint. Light from the surface side from which the substrate 4 has been removed with an appropriate refractive index and surface shape of the antireflection layer 5 so as to improve the transmission characteristics of the light transmitted through the antireflection layer 5. The extraction efficiency can be further improved.

  Moreover, you may form in the main surface the protrusion which the top part 5b is smaller than the base 5a, or the hollow whose bottom part is smaller than an opening part with respect to such an antireflection layer 5. Specifically, the structure of the protrusions or depressions of the antireflection layer 5 may be a polygonal pyramid shape or a conical shape. Note that the polygonal pyramid or conical shape includes a polygonal pyramid or a cone having a curved surface having no inflection point in an arbitrary cross section in addition to the polygonal pyramid and the cone. Further, the top 5b may be planar with respect to any one of a polygonal pyramid shape and a conical shape. Further, the protrusion or depression of the antireflection layer 5 may be hemispherical. The hemispherical shape includes not only a hemisphere but also a slope whose hemisphere has a curved line having no inflection point in an arbitrary cross section. The width of the base 5a or the opening is not more than 1 times the wavelength in the antireflection layer 5 of ultraviolet to near-ultraviolet light generated in the light emitting layer 1a, and is high from the base 5a to the top 5b or from the opening to the bottom. The size may be at least one time.

  Such protrusions or depressions may be formed by etching using a photolithography technique and a dry or wet etching technique. Further, the surface of the gallium nitride compound semiconductor layer 1 from which the substrate 4 has been removed is etched by using a photolithography technique and a dry or wet etching technique to thereby form a part of the gallium nitride compound semiconductor layer 1 (second conductivity type semiconductor). Such protrusions or depressions may be formed in a part of the layer 1c. In this case, when the gallium nitride-based compound semiconductor layer 1 is viewed in the thickness direction, a portion where irregularities due to protrusions or depressions are formed (in FIG. 1, from a dotted line provided in the second conductivity type semiconductor layer 1c). The upper part) is defined as an antireflection layer 5. What is necessary is just to form as many such protrusions or depressions as possible with no gap with respect to the surface of the second conductivity type semiconductor layer.

  Further, when the antireflection layer 5 has such protrusions or depressions, the light that is incident on the surface of the protrusions or depressions even when the protrusions or depressions enter the antireflection layer 5 from an oblique direction. In order to prevent reflection by making the incident angle larger than the critical angle, it is possible to transmit light incident from an oblique direction to the antireflection layer 5 and to transmit the antireflection layer 5. Therefore, the light extraction efficiency can be further improved. Such protrusions or depressions gradually change the refractive index with respect to the light emitting direction to gradually increase the refractive index of the gallium nitride compound semiconductor layer 1 from a low refractive index such as air. Since it also has a function of decreasing, it also has an effect of lowering the reflectance itself in the light emission direction, and a light emitting element with further improved light extraction efficiency can be obtained. Further, a translucent member 8 may be newly joined to the antireflection layer 5. The translucent member 8 preferably has a high transmittance with respect to light emitted from the gallium nitride compound semiconductor layer. For example, a resin layer made of silicone resin, epoxy resin, fluorine resin, benzocyclobutene, polyimide, etc., optical plastic, or oxide layer such as sapphire, quartz, zinc oxide, indium tin oxide (ITO) Use it. Further, a multilayer structure may be employed so that the refractive index of the translucent member 8 changes stepwise from the refractive index of the gallium nitride compound semiconductor to the refractive index of air. Further, on the light extraction surface side of the translucent member 8, as in the antireflection layer 5, as many projections or depressions as possible may be formed without gaps in order to prevent reflection. In this case, light that has been transmitted without reflection from the inside of the gallium nitride-based compound semiconductor layer to the translucent member 8 is almost reflected from the surface (light extraction surface) on which the protrusions or depressions of the translucent member 8 are formed. Can be transmitted without any problems. By joining the translucent member 8 in this manner, the mechanical strength of the light-emitting element can be improved, and damage to the light-emitting element due to handling during mounting or the like can be prevented. It can be produced reliably.

  Further, as shown in FIG. 1, the bump electrode 6 a may be connected to the main surface of the conductive reflective layer 2, and 6 b may be connected to the main surface of the conductive layer 3. The bump electrodes 6a and 6b serve to fix the light emitting element to a base or the like on the conductive reflective layer 2 side and to establish electrical conduction to the light emitting element on the conductive reflective layer 2 side. As a result, it is possible to eliminate the need to arrange a conducting wire or the like that blocks light on the light extraction surface side, so that the light extraction efficiency can be further improved. Further, since the substrate 4 has been removed, the thermal expansion of the gallium nitride compound semiconductor layer 1 and the substrate 4 when the light emitting element is heated to the base or the like via the bump electrodes 6a and 6b and flip chip mounting is performed. Since the stress applied to the gallium nitride compound semiconductor layer 1 due to the difference in the coefficients can be eliminated, the distortion generated in the gallium nitride compound semiconductor layer 1 when the light emitting element is flip-chip mounted is reduced to increase the reliability. be able to.

  As materials used for the bump electrodes 6a and 6b, gold (Au), indium (In), gold-tin alloy solder (Au-Sn), tin-silver alloy solder (Sn-Ag), tin-silver-copper alloy solder (Sn—Ag—Cu), tin-bismuth alloy solder (Sn—Bi), tin-lead alloy solder (Sn—Pb), or the like may be used.

  Next, the manufacturing method of the light emitting device of the present invention will be described taking the light emitting device shown in FIG. 1 as an example. 2 (a) to 2 (j) are cross-sectional views showing the manufacturing process of the light emitting device of the present invention, the process of epitaxially growing the gallium nitride compound semiconductor layer 1 including the light emitting layer 1a on the substrate 4, and the nitridation thereof. It shows a step of forming the conductive reflective layer 2 on the gallium compound semiconductor layer 1 and a step of removing the substrate 4 from the gallium nitride compound semiconductor layer 1 while protecting the conductive reflective layer 2. is there.

Specifically, as shown in FIG. 2A, the gallium nitride compound semiconductor layer 1 is epitaxially grown on the substrate 4 by metal organic chemical vapor deposition (MOCVD). The gallium nitride compound semiconductor layer 1 includes a first n-type cladding layer and a second layer on a substrate 4 via a buffer layer (not shown) made of aluminum nitride (AlN) or aluminum gallium nitride (AlGaN). This is a superlattice in which a second conductivity type semiconductor layer 1c formed by sequentially laminating an n-type cladding layer is formed, and a quantum well layer composed of a well layer sandwiched between barrier layers is repeatedly laminated thereon a plurality of times. A light emitting layer 1a composed of a multilayer quantum well layer (MQW) is formed, and a first p-type cladding layer, a second p-type cladding layer, and a p-type contact layer are sequentially stacked thereon. A first conductivity type semiconductor layer 1b is formed. More specifically, the buffer layer and the gallium nitride-based compound semiconductor layer 1 may be manufactured as follows, for example. The buffer layer may be formed with a substrate temperature of 400 to 950 ° C. and aluminum nitride (AlN) or aluminum gallium nitride (AlGaN) with a thickness of about 20 to 300 nm on the substrate 4. In addition, the first n-type cladding layer may be formed with a substrate temperature of about 950 to 1150 ° C. and a thickness of about several μm (for example, 1 to 5 μm) of gallium nitride (GaN) on the buffer layer. The second n-type cladding layer has a substrate temperature of about 700 ° C. and indium gallium nitride (In _0.02 Ga _0.98 N) with a thickness of about 0.1 to 1 μm on the first n-type cladding layer. What is necessary is just to produce. The multilayer quantum well layer (light emitting layer 1a) has a substrate temperature of about 700 ° C., a barrier layer made of indium / aluminum nitride (In _0.01 Ga _0.99 N) and a thickness of about 10 to 100 nm. A well layer made of indium-aluminum nitride (In _0.11 Ga _0.89 N) having a thickness of about 100 nm and a barrier layer having the same thickness and the same composition as the barrier layer and the well layer; The well layer may be formed, for example, by repeating twice, and finally the barrier layer having the same thickness and the same composition as the barrier layer may be formed. The first p-type cladding layer has a substrate temperature of about 700 ° C., and a thickness of about 50 to 300 nm of aluminum nitride / gallium (Al _0.2 Ga _0.8 N) on the barrier layer of the multilayer quantum well layer. What is necessary is just to produce. The second p-type cladding layer has a substrate temperature of about 820 ° C. and aluminum nitride / gallium (Al _0.2 Ga _0.8 N) on the first p-type cladding layer with a thickness of about 50 to 300 nm. What is necessary is just to produce. Further, the p-type contact layer may be formed with a substrate temperature of about 820 to 1050 ° C. and gallium nitride (GaN) with a thickness of about 0.1 to 1 μm on the second p-type cladding layer. The material of the substrate 4 may be sapphire or silicon carbide (SiC), but if a boride single crystal such as zirconium boride (ZrB ₂ ) or titanium boride (TiB ₂ ) is used, Since the lattice constant matches with the gallium nitride compound semiconductor layer 1, the gallium nitride compound semiconductor layer 1 having good crystal quality can be formed, which is preferable.

  Next, as shown in FIG. 2B, a conductive reflective layer 2 is formed on the gallium nitride compound semiconductor layer 1 by vacuum deposition or sputtering.

  Next, as shown in FIG. 2C, the conductive reflective layer 2 and a part of the gallium nitride-based compound semiconductor layer 1 are etched until the surface of the second conductive type semiconductor layer 1c is exposed. It is preferable to provide a step of forming the conductive layer 3. By forming the conductive layer 3 in this manner, when the light emitting element is mounted on a base or the like, the conductive layer 3 is electrically connected to the other main surface 1c1 side of the gallium nitride-based compound semiconductor layer 1 which is a light extraction surface. Since it is not necessary to form a conducting wire for connection, it is possible to mount without blocking the light extraction surface.

  Next, as shown in FIG. 2D, it is preferable to provide a step of connecting the bump electrodes 6a and 6b on the conductive reflective layer 2 and the conductive layer 3 by screen printing or the like.

  Next, in the step of removing the substrate 4 from the gallium nitride compound semiconductor layer 1 while protecting the conductive reflective layer 2, first, as shown in FIG. Then, after covering the bump electrodes 6a and 6b with the protective film 7, the substrate 4 may be removed as shown in FIG. In order to remove the substrate 4, a chemical / physical method can be used according to the material of the substrate 4. For example, when the material of the substrate 4 is zirconium boride, the substrate 4 may be chemically etched using an acid or the like as an etchant. Further, when the material of the substrate 4 is sapphire, the interface between the substrate 4 and the gallium nitride compound semiconductor layer 1 is irradiated with laser light having a wavelength of about 370 nm to melt a part of the gallium nitride compound semiconductor layer 1. The substrate 4 may be detached. Further, the protective film 7 may be formed of a material that can withstand the process of removing the substrate 4, and may be formed by spin coating an inorganic or organic coating material, for example.

Next, as shown in FIG. 2G, it is preferable to include a step of forming an antireflection layer 5 on the surface of the gallium nitride compound semiconductor layer 1 from which the substrate 4 has been removed. In this step, the antireflection layer 5 may be formed by a normal thin film forming method, for example, quartz (SiO ₂ ). Further, the surface of the gallium nitride compound semiconductor layer 1 is etched using photolithography technology and dry etching technology to form a protrusion whose top portion 5b is smaller than the base portion 5a or a recess whose bottom portion is smaller than the opening portion. It is good also considering the made part as the antireflection layer 5. In addition, after forming the anti-reflective layer 5 as shown in FIG.2 (g), when the translucent member 8 is newly joined on the antireflective layer 5 as shown in FIG.2 (h), a translucent member is shown. If 8 is made of a thermosetting resin, it can be formed by applying by a spin coating method, a dip method or the like. If the translucent member 8 is a plate, it can be formed from a gallium nitride compound semiconductor layer. Can be bonded via a liquid adhesive made of a material such as a silicone resin having a high transmittance with respect to the emitted light. Further, when a projection or depression for preventing reflection is formed on the light extraction surface side of the translucent member 8 as in the antireflection layer 5, the projection or the like is chemically formed by a dry or wet etching technique. Alternatively, it may be formed by mechanically roughening.

  Next, as shown in FIGS. 2I and 2J, the protective film 7 is removed to complete the light emitting device of the present invention. In order to remove the protective film 7, for example, it may be removed by a dry etching technique (dry etching).

  According to the method for manufacturing the light emitting device of the present invention shown in FIG. 2, the conductive reflective layer 2 is protected in the step of removing the substrate 4 from the gallium nitride compound semiconductor layer 1, so that the gallium nitride compound is protected. The surface of the semiconductor layer 1 and the conductive reflective layer 2 formed thereon can be protected from contamination / corrosion by, for example, an etching solution, and the gallium nitride compound semiconductor layer 1 can be mechanically reinforced. Therefore, the gallium nitride compound semiconductor layer 1 and the conductive reflective layer 2 can be prevented from being deteriorated by contamination or corrosion due to etching or the like, or stress, so that a high-performance light-emitting element can be reliably manufactured. It will be possible.

  In addition, since the antireflection layer 5 is formed on the surface of the gallium nitride compound semiconductor layer 1 from which the substrate 4 is removed, the surface on which the antireflection layer 5 is formed until the antireflection layer 5 is formed. Since it is protected by the substrate 4, it becomes a clean surface. As a result, a good antireflection layer 5 can be formed, so that a higher-performance light-emitting element can be reliably manufactured.

  In addition, since the bump electrode 6a is connected to the conductive reflective layer 2, after the bump electrode 6a is formed on the conductive reflective layer 2, the conductive reflective layer 2 and the bump electrode 6a are protected. In this state, the step of removing the substrate 4 and the step of forming the antireflection layer 5 are performed, or the conductive reflective layer 2 protected during the step of removing the substrate 4 and the step of forming the antireflection layer 5. Finally, since the bump electrode 6a is formed, the conductive reflective layer 2 and the bump electrode 6a are not deteriorated by the step of removing the substrate 4 or the step of forming the antireflection layer 5, and as a result, the bump electrode 6a is good. Therefore, a higher performance light emitting element can be surely manufactured.

  Next, an illuminating device of the present invention includes the light emitting element of the present invention and at least one of a phosphor and a phosphor that emits light upon receiving light emitted from the light emitting element. For example, in a configuration in which a phosphor is provided on the light extraction surface side of the light emitting element, the light emitting element emits light with, for example, ultraviolet to near ultraviolet light having a wavelength of 350 to 400 nm, and the phosphor receives the light emitted as excitation light, for example It operates as a lighting device by emitting light.

  Since the illuminating device of the present invention has such a configuration, the phosphor is strongly excited by light of a light emitting element having a good light emission intensity with a small power, and thus, for example, white light with a good illuminance is obtained with a small power. be able to. In addition, the lighting device of the present invention can be a white light source that is more energy-saving and downsized than conventional fluorescent lamps and discharge lamps, and can be replaced with such fluorescent lamps and discharge lamps. it can.

  Thus, according to the present invention, the light extraction efficiency is greatly improved, and a high-performance light-emitting element capable of obtaining a good light emission intensity with a small power and a light-emitting capable of reliably producing the high-performance light-emitting element. An element manufacturing method and a lighting device using the high-performance light-emitting element can be provided.

  It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the gist of the present invention. There can be no improvement. For example, after the antireflection layer 5 is formed, the surface of the antireflection layer 5 is covered with a protective layer made of an organic or inorganic coating material, which can transmit light from the light emitting layer 2a, The protective film 7 protecting the conductive reflective layer 2 and the like may be removed. In this case, the protective layer covering the antireflection layer 5 protects the antireflection layer 5 and prevents the gallium nitride compound semiconductor layer 1 that is a thin layer from cracking or the like. The semiconductor layer 1 is structurally reinforced. For this reason, since it is possible to obtain a light-emitting element that does not easily break even when various external forces are applied to the light-emitting element after the manufacturing process or after completion, the yield in the manufacturing process is improved and the completed light-emitting element is not easily broken and is durable. Reliable.

  Further, an insulating reflective layer that reflects light generated in the light emitting layer 1a may be formed on a surface other than the light extraction surface of the gallium nitride-based compound semiconductor layer.

It is typical sectional drawing which shows an example of embodiment of the light emitting element of this invention. (A)-(h) is typical sectional drawing for every process which shows the manufacturing method of the light emitting element of this invention, respectively. It is a schematic diagram which shows the example of the conventional light emitting element, (a), (b), (c) is sectional drawing which shows the 1st, 2nd, 3rd conventional example, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gallium nitride type compound semiconductor layer 1a ... Light emitting layer 1b ... 1st conductivity type semiconductor layer (p-type semiconductor layer)
1b1 .. one main surface 1c ... second conductivity type semiconductor layer (n-type semiconductor layer)
1c1 ··· the other main surface 2 ··· conductive reflection layer 3 ··· conductive layer 4 ··· substrate 5 · · · antireflection layer 6a, 6b · · · bump electrode 7 · · · protective film 8 ... Translucent member

Claims (9)

An epitaxially grown gallium nitride compound semiconductor layer including a light emitting layer, a conductive reflective layer formed on one main surface of the gallium nitride compound semiconductor layer, and a layer on the other main surface side of the gallium nitride compound semiconductor layer The other main surface of the gallium nitride compound semiconductor layer is a surface from which the substrate used for epitaxial growth of the gallium nitride compound semiconductor layer is removed, or A light emitting device characterized in that this surface is a new surface formed by etching. The light-emitting element according to claim 1, wherein an antireflection layer is formed on the other main surface of the gallium nitride compound semiconductor layer. 3. The light emitting device according to claim 2, wherein the antireflection layer has a large number of protrusions whose top portion is smaller than a base portion and a large number of depressions whose bottom portion is smaller than an opening portion on a main surface. . The light emitting device according to any one of claims 1 to 3, wherein a bump electrode is connected to a main surface of the conductive reflective layer. A step of epitaxially growing a gallium nitride-based compound semiconductor layer including a light-emitting layer on a substrate; a step of forming a conductive reflective layer on the gallium nitride-based compound semiconductor layer; and a state of protecting the conductive reflective layer And a step of removing the substrate from the gallium nitride compound semiconductor layer. 6. The method for manufacturing a light-emitting element according to claim 5, further comprising a step of forming an antireflection layer on the surface of the gallium nitride compound semiconductor layer from which the substrate has been removed. The method for manufacturing a light-emitting element according to claim 5, further comprising a step of connecting a bump electrode on the conductive reflective layer. 8. The method for manufacturing a light-emitting element according to claim 5, wherein a boride single crystal is used for the substrate. An illumination device comprising: the light-emitting element according to claim 1; and at least one of a phosphor and a phosphor that emits light upon receiving light emitted from the light-emitting element.

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