JP2006287026A - Light emitting element and light emitting device employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element capable of improving the external radiative efficiency of light generated in the light emitting element and not generating the incidence of light again whose external radiation is effected once, and a light emitting device employing it. <P>SOLUTION: A recessed side surface 200A consisting of a semicircular curved surface is provided on the side surface of a GaN system semiconductor layer 200 of an LED (Light Emitting Diode) element 2. According to this constitution, light radiated externally out of the GaN system semiconductor layer 200 can be increased. On the other hand, a projected part is formed of the semicircular curved surface so as to form a recessed shape whereby light, radiated externally once, hardly performs incidence again into the neighbored projected part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light-emitting element made of a semiconductor material and a light-emitting device using the same, and in particular, can improve the external radiation efficiency of light generated by the light-emitting element and cause re-incidence of light once emitted externally. TECHNICAL FIELD The present invention relates to a light emitting element having no problem and a light emitting device using the same.

    Conventionally, a method of manufacturing a light emitting device by growing a semiconductor crystal made of a group III nitride compound semiconductor on a base substrate such as sapphire is known. In such a light-emitting element, there is a problem that light generated in the light-emitting layer is confined in a layer having a high light absorption coefficient and becomes laterally propagated light that propagates in the layer. In particular, light confined in a layer having a large light absorption coefficient, such as a group III nitride compound semiconductor, is attenuated as the lateral propagation distance increases, and external radiation becomes impossible.

  In order to efficiently emit the laterally propagated light generated in the light emitting element described above, a light emitting element in which the side surface of the light emitting element is formed in an uneven shape and the critical angle of the side surface is dispersed based on the uneven shape is proposed. (For example, refer to Patent Document 1).

In the light-emitting element of Patent Document 1, the side surface is formed into an irregular shape such as a triangular wave shape or a wavy shape to disperse the normal angle of the side surface to disperse the critical angle, and the light confined in the light emitting region, particularly in the lateral direction. The trapped light is extracted more efficiently.
Japanese Patent Laying-Open No. 2003-110136 ([0011], FIG. 2)

  However, according to the light-emitting element described in Patent Document 1, when unevenness is provided on the side surface, depending on the shape, light once emitted to the outside of the light-emitting element may be re-incident on the adjacent uneven shape, so that the external radiation efficiency There is a problem that cannot be improved.

  Accordingly, an object of the present invention is to improve the external radiation efficiency of light generated by a light emitting element, and to provide a light emitting element that does not cause re-incidence of light once emitted externally and a light emitting device using the same. It is to provide.

  In order to achieve the above-mentioned object, the present invention provides a plurality of concave light extraction portions comprising an inclined surface whose inclination has changed on the side surface of a semiconductor layer including a light emitting layer and a pointed convex portion provided at the tip of the inclined surface. Provided is a light-emitting element including:

  In order to achieve the above object, the present invention provides a plurality of concave light extractions comprising a sloped surface formed of a curved surface on a side surface of a semiconductor layer including a light emitting layer and a pointed convex portion provided at the tip of the sloped surface. Provided is a light-emitting element having a portion.

  In order to achieve the above object, the present invention includes an inclined surface formed by a substantially parabolic straight line on a side surface of a semiconductor layer including a light emitting layer, and a pointed convex portion provided at the tip of the inclined surface. A light emitting device comprising a plurality of concave light extraction portions is provided.

  In order to achieve the above object, the present invention provides a plurality of concave light comprising an inclined surface whose inclination has changed on the side surface of a semiconductor layer including a light emitting layer and a pointed convex portion provided at the tip of the inclined surface. There is provided a light emitting device comprising: a light emitting element having an extraction part; a substrate on which the light emitting element is mounted; and a sealing part for sealing the light emitting element.

  According to the present invention, it is possible to improve the external radiation efficiency of the light generated in the light emitting element by providing a plurality of concave light extraction portions made of inclined surfaces with varying inclinations on the side surfaces of the semiconductor layer including the light emitting layer. . Further, by forming the concave light extraction portion so that the pointed convex portion is formed by the inclined surface whose inclination has changed, the light once radiated to the outside is not re-incident.

(First embodiment)
1A and 1B show a light emitting device according to a first embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view of the light emitting device, and FIG. 1B is an enlarged longitudinal sectional view of an LED element mounted on the light emitting device. is there.

As shown in FIG. 1A, the light emitting device 1 includes a flip chip type LED element 2, an Al ₂ O ₃ substrate 3 as an inorganic substrate on which the LED element 2 is mounted, and a glass seal as an inorganic sealing material. The stop portion 4 and the Au stud bump 5 for electrically connecting the electrode of the LED element 2 and the circuit pattern 30 formed of tungsten (W) to the mounting surface of the Al ₂ O ₃ substrate 3 are provided.

The Al ₂ O ₃ substrate 3 has a via hole 3A in the cross section, and the circuit pattern 30 on the mounting surface and the circuit pattern 31 on the back surface are electrically connected by a via pattern 32 made of W provided in the via hole 3A. Yes.

The glass sealing portion 4 is formed of a low melting point glass of SiO ₂ —Nb ₂ O ₅ system (refractive index n = 1.8), and has a flat side surface 41 and a flat upper surface 40.

  The LED element 2 is formed by sequentially growing a GaN buffer layer 21, an n-GaN layer 22, a light emitting layer 23, and a p-GaN layer 24 on a sapphire substrate 20, as shown in FIG. The n-GaN layer 22, the light emitting layer 23, and the p-GaN layer 24 form a GaN-based semiconductor layer 200. The side surface of the GaN-based semiconductor layer 200 is provided with a concave side surface 200A in which a plurality of concave portions each having a curved surface are continuously provided, and the n-GaN layer 22 is removed from the p-GaN layer 24 by etching. The n-electrode 25 provided on the exposed n-GaN layer 22 and the p-contact electrode 26 made of rhodium (Rh) as a current diffusion layer and a light reflecting layer on the surface of the p-GaN layer 22 are provided.

  Although it does not specifically limit about the manufacturing method of a LED element, Well-known organometallic vapor phase epitaxy method (MOCVD method), molecular beam crystal growth method (MBE method), halide type | system | group vapor phase epitaxy method (HVPE method), sputtering method, It can be formed by an ion plating method, an electron shower method, or the like. In addition, as a structure of a LED element, the thing of a homo structure, a hetero structure, or a double hetero structure can be used. Furthermore, a quantum well structure (single quantum well structure or multiple quantum well structure) can also be adopted.

(Configuration of LED element 2)
2A and 2B show the configuration of the LED element according to the first embodiment, in which FIG. 2A is a plan view of an electrode forming surface, and FIG. 2B is a partially enlarged view of a concave side surface provided in a GaN-based semiconductor layer.

  The LED element 2 has a concave side surface 200A formed by etching as a light extraction portion on the side surface of the GaN-based semiconductor layer 200 excluding the region where the n-electrode 25 is formed. As shown in FIG. 2B, the concave side surface 200A is formed by a semicircular curved surface, and the cusp-shaped convex portion formed of a curved surface has a predetermined interval from the adjacent cusp-shaped convex portion. It is formed. In the first embodiment, the concave side surface 200A with respect to the width W is formed so that the height H of the convex portion is large.

As shown in FIG. 2B, the light L incident on the concave side surface 200A does not cause interface reflection in the normal direction like the lights L ₁ and L ₃ incident on the curved surface portion 202, as shown in FIG. 200 radiates externally. Further, the light L ₃ incident on the curved surface portion 202 that is within the critical angle of the concave side surface 200A is refracted at the interface and emitted externally. Thus, the light once radiated to the outside for any of the lights L ₁ , L ₃ , and L ₃ does not re-enter the adjacent convex portion.

  FIG. 3 is a characteristic diagram showing the side emissivity of the LED element based on the shape constituting the concave side surface. In FIG. 3, a jaggy shape shown in (a), a round shape consisting of a convex shape of a curved surface shown in (b), an inverted round shape consisting of a concave shape of a curved surface shown in (c), and a rounded jaggy shown in (d). The height H and width W of the unevenness are changed for the four types of side shapes. According to the inventors, as the H / W ratio increases, the side emissivity of the LED element 2 provided with the concave side surface having the jaggy shape of (a) and the reverse round shape of (c) increases. In particular, in the LED element 2 provided with the inverted round-shaped concave side surface, it has been confirmed that the side emissivity is higher than that of the jaggy shape.

  For the concave side surface 200A, if the H / W ratio is 0.125, there is a 5% light extraction effect. If the H / W ratio is larger than that, the light extraction effect is improved. Since the amount of emitted light is reduced, the range of 0.125 to 2 is suitable.

(Effects of the first embodiment)
According to the first embodiment described above, the following effects are obtained.
(1) Since the concave side surface 200A composed of a semicircular curved surface is provided on the side surface of the GaN-based semiconductor layer 200 of the LED element 2, the light emitted from the GaN-based semiconductor layer 200 can be increased. Further, by forming the convex portion with a semicircular curved surface so as to form a concave shape, it becomes difficult for light emitted once externally to re-enter the adjacent convex portion.

(2) Since the light emitting device 1 is formed by sealing the LED element 2 having the concave side surface 200A with the glass sealing portion 4, the light extraction from the LED element 2 is excellent and the light to the LED element 2 is re-transmitted. The light emitting device 1 having high luminance, excellent moisture resistance, and stable light emission characteristics over a long period can be provided without incidence.

  In the above-described first embodiment, the glass-sealed light emitting device in which the LED element 2 is glass-sealed has been described. However, the sealing portion that seals the LED element 2 is formed of another material. Also good. For example, a resin material such as an epoxy resin or a silicon resin can be used as the other material.

  In the first embodiment, the light emitting device using the flip-chip type LED element 2 has been described. However, the above-described concave side surface 200A may be provided on the face-up type LED element 2. is there.

(Second Embodiment)
4A and 4B show the configuration of an LED element according to the second embodiment of the present invention, where FIG. 4A is a plan view of an electrode forming surface, and FIG. 4B is a partially enlarged view of a concave side surface provided in a GaN-based semiconductor layer. (C) is the elements on larger scale which show the other structure of a concave side surface.

  This LED element 2 is different from that of the first embodiment in a configuration in which an inverted round concave side surface 200A having a substantially parabolic curved surface is provided on the side surface of the GaN-based semiconductor layer 200 by etching.

As shown in FIG. 4B, the concave side surface 200A is formed such that the height H of the convex portion 202A is larger than the width W of the adjacent convex portion 202A (H / W ratio = 1.5). For example, the light L ₁ incident on the curved surface portion 202 is refracted when exiting from the curved surface portion 202 and reaches the adjacent convex portion 202A, but is reflected by the surface of the convex portion 202A and radiated to the outside of the concave portion. . Further, the light L ₃ is radiated to the outside of the concave portion while being refracted when emitted from the curved surface portion 202. In addition, the light L ₃ is not refracted when emitted from the GaN-based semiconductor layer 200, but is reflected from the surface of the curved surface portion 202 and emitted externally. Thus, the light once radiated to the outside for any of the lights L ₁ , L ₃ , and L ₃ does not re-enter the adjacent convex portion.

  Note that the convex portion 202A shown in FIG. 4B may not be stable due to processing accuracy or restrictions, or may be damaged by impact or internal stress because the height H is large relative to the width W. . In order to prevent these, as shown in FIG. 4C, when the GaN-based semiconductor layer 200 is etched, an unprocessed portion 204 may be provided at the tip of the convex portion 202A to give a thickness.

(Effect of the second embodiment)
According to the second embodiment described above, since the reverse round concave side surface 200A having a substantially parabolic curved surface is provided on the side surface of the GaN-based semiconductor layer 200 of the LED element 2, the preferable effect of the first embodiment is achieved. In addition, the light emitted from the GaN-based semiconductor layer 200 can be further increased. Therefore, even when the etching area of the GaN-based semiconductor layer 200 is larger than that of the LED element 2 described in the first embodiment, it is possible to increase the luminance of the light emitting device 1 by improving the side reflectance. Become.

(Third embodiment)
FIG. 5 shows a configuration of an LED element according to the third embodiment of the present invention, where (a) is a plan view of an electrode forming surface, and (b) is a partially enlarged view of a concave side surface provided in a GaN-based semiconductor layer. It is.

  This LED element 2 is different from the second embodiment in a configuration in which a polygonal portion 203 made of a straight line is partially provided at the bottom of the reverse round concave side surface 200A described in the second embodiment. Yes.

(Effect of the third embodiment)
According to the third embodiment described above, when it is difficult to process a curved portion due to processing accuracy or restrictions, even if a part of the concave side surface 200A is formed as a straight portion, the GaN-based semiconductor layer 200 is externally radiated. More light.

(Fourth embodiment)
6A and 6B show a configuration of an LED element according to a fourth embodiment of the present invention, where FIG. 6A is a plan view of an electrode forming surface, and FIG. 6B is a partially enlarged view of a concave side surface provided in a GaN-based semiconductor layer. It is.

  This LED element 2 is different from the second embodiment in the configuration in which the reverse round concave side surface 200 </ b> A described in the second embodiment is provided by the polygonal portion 203 formed of a straight line.

(Effect of the fourth embodiment)
According to the above-described fourth embodiment, when curved portion machining is difficult due to processing accuracy and restrictions, the light radiated from the GaN-based semiconductor layer 200 is emitted even if all the concave side surfaces 200A are formed by straight portions. Can be increased more.

The light-emitting device which concerns on the 1st Embodiment of this invention is shown, (a) is a longitudinal cross-sectional view of a light-emitting device, (b) is the expanded longitudinal cross-sectional view of the LED element mounted in a light-emitting device. The structure of the LED element which concerns on 1st Embodiment is shown, (a) is a top view of an electrode formation surface, (b) is the elements on larger scale of the concave side surface provided in a GaN-type semiconductor layer. It is a characteristic view which shows the side surface emissivity of the LED element based on the shape which comprises a concave side surface. The structure of the LED element which concerns on the 2nd Embodiment of this invention is shown, (a) is a top view of an electrode formation surface, (b) is the elements on larger scale of the concave side surface provided in a GaN-type semiconductor layer, (c) FIG. 5 is a partially enlarged view showing another configuration of the concave side surface. The structure of the LED element which concerns on the 3rd Embodiment of this invention is shown, (a) is a top view of an electrode formation surface, (b) is the elements on larger scale of the concave side surface provided in a GaN-type semiconductor layer. The structure of the LED element which concerns on the 4th Embodiment of this invention is shown, (a) is a top view of an electrode formation surface, (b) is the elements on larger scale of the concave side surface provided in a GaN-type semiconductor layer.

Explanation of symbols

1 ... light emitting device, 2 ... LED element, 3 ... _Al 2 _{O 3} substrate, 3A ... hole, 4 ... glass sealing portion, 5 ... Au stud bump, 20 ... sapphire substrate, 21 ... GaN buffer layer, 22 ... n- GaN layer, 23 ... light emitting layer, 24 ... p-GaN layer, 25 ... n-electrode, 26 ... p contact electrode, 30 ... circuit pattern, 31 ... circuit pattern, 32 ... via pattern, 40 ... top surface, 41 ... side surface, 200A ... concave side surface, 200 ... GaN-based semiconductor layer, 202A ... convex part, 202 ... curved surface part, 203 ... polygonal part, 204 ... unprocessed part

Claims (9)

  A light emitting device comprising: a plurality of concave light extraction portions each including an inclined surface whose inclination is changed on a side surface of a semiconductor layer including a light emitting layer and a pointed convex portion provided at a tip of the inclined surface.   A light-emitting element comprising a plurality of concave light extraction portions each including an inclined surface formed of a curved surface on a side surface of a semiconductor layer including a light emitting layer and a pointed convex portion provided at a tip of the inclined surface.   The light emitting device according to claim 1, wherein the inclined surface is formed by a substantially parabolic curve.   The light emitting device according to claim 1, wherein a part of the inclined surface is a curved surface.   It has a plurality of concave light extraction parts composed of an inclined surface formed by a substantially parabolic straight line on a side surface of a semiconductor layer including a light emitting layer and a pointed convex part provided at the tip of the inclined surface. Light emitting element.   The concave light extraction portion is formed such that a ratio of a height between a tip and a bottom of the pointed convex portion and a width of the adjacent pointed convex portion is in a range of 0.125 to 2. 6. The light emitting device according to any one of 5 above. A light-emitting element having a plurality of concave light extraction portions, each of which includes an inclined surface whose inclination is changed on a side surface of a semiconductor layer including a light-emitting layer, and a pointed convex portion provided at a tip of the inclined surface;
A substrate on which the light emitting element is mounted;
A light emitting device comprising: a sealing portion for sealing the light emitting element.   The light emitting device according to claim 7, wherein the light emitting element is flip-mounted on the substrate. The light emitting device according to claim 7, wherein the sealing portion is made of a sealing material made of glass.

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