JP2011176093A - Substrate for light-emitting element, and light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a light-emitting element that suppresses arising of a problem of peeling of a semiconductor layer from a base substrate and ensures sufficient light extraction efficiency, and the light-emitting element. <P>SOLUTION: The substrate for the light-emitting element includes a semiconductor layer (an n-type semiconductor layer 5, a light-emitting layer 6, a p-type semiconductor layer 7, and a substrate 4) including the light-emitting layer 6, and the base substrate 2 bonded to the semiconductor layer through an intermediate layer 35. A photonic crystal structure layer 3 is formed at a junction portion between the semiconductor layer and base substrate 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light emitting element substrate and a light emitting element, and more particularly to a light emitting element substrate and a light emitting element including a two-dimensional diffraction grating.

  In recent years, III-V compound semiconductors (for example, GaN) have been applied as light emitting device materials. For example, if a group III-V compound semiconductor substrate (for example, a GaN substrate) is used as the substrate constituting the light emitting element, a light emitting layer made of a group III-V compound is formed on the main surface of the substrate, thereby forming a light emitting layer. Generation of stress between the substrate and the substrate can be suppressed. As a result, a light emitting layer with good crystal quality can be formed. However, a III-V compound semiconductor substrate such as a GaN substrate is generally very expensive compared to a silicon substrate or the like. For this reason, although the crystal quality of a light emitting layer falls a little, inexpensive sapphire substrates etc. are used for light emitting elements, such as a light emitting diode (LED).

  In order to provide a low-cost substrate for forming a light-emitting layer with good crystal quality with respect to the above problem, Japanese Patent Laid-Open No. 2006-210660 (Patent Document 1) discloses a GaN film or the like on a silicon (Si) substrate or the like. A method for manufacturing a semiconductor substrate in which a GaN film is bonded to the surface of a Si substrate in order to form the nitride semiconductor film is disclosed. JWChung and two others, “N-Face GaN / AlGaN HEMTs Fabricated Through Layer Transfer Technology”, IEEE Electron Device Letters, 30, 2, 2009 (Non-Patent Document 1) A method for manufacturing a semiconductor substrate in which a GaN film is bonded to the surface of the semiconductor substrate is disclosed.

  GaN, which is one of the III-V group compound semiconductors that are being applied as described above, has a refractive index of about 2.5, which is higher than that of air (refractive index is 1.0). Since it is high, the total reflection angle becomes small. For this reason, there is a problem that light emitted from the light emitting layer is not easily emitted outside the light emitting element, that is, light extraction efficiency is low. This is because light that has been totally reflected once on the surface of the light emitting element propagates inside the light emitting element while repeating total reflection thereafter, but as most of the light propagates, the light emitting element is emitted before it is emitted to the outside. This is because it is absorbed in the electrode and the semiconductor layer.

  In order to improve the light extraction efficiency from the light emitting device and change the directivity of the light emitted from the light emitting device, JJ Wierer and four others, “InGaN / GaN quantum-well heterostructure” light-emitting diodes according photonic crystal structures ”, Applied Physics Letters, 84, 19, May 10, 2004, pp3885-3887 (non-patent document 2), K. McGroddy, and 8 others,“ Directional emission control and increased light extraction in GaN photonic crystal light emitting diodes ", Applied Physics Letters, 93, 103502, 2008 (Non-Patent Document 3) discloses the formation of a photonic crystal structure on the surface of a semiconductor device.

JP 2006-210660 A

J.W.Chung and two others, “N-Face GaN / AlGaN HEMTs Fabricated Through Layer Transfer Technology”, IEEE Electron Device Letters, 30, 2, 2009 J. J. Wierer and 4 others, “InGaN / GaN quantum-well heterostructure light-emitting diodes containing photonic crystal structures”, Applied Physics Letters, May 10, 2004, 84, 19, pp3885-3887 K. McGroddy, 8 others, “Directional emission control and increased light extraction in GaN photonic crystal light emitting diodes”, Applied Physics Letters, 93, 103502, 2008

  However, as disclosed in Patent Document 1, when a nitride semiconductor film is bonded to a basic substrate made of a different material such as a silicon substrate, the bonding strength at the bonding interface between the basic substrate and the nitride semiconductor film is insufficient. In some cases, the nitride semiconductor film may peel off from the base substrate. When such peeling occurs, there arises a problem that the light emitting element does not operate normally.

  In Non-Patent Document 1, a silicon oxide layer using hydrogen silsesquioxane (HSQ) as a precursor is used for the intermediate layer. Thus, when a flat layer of silicon oxide is formed on the nitride semiconductor film, since the refractive index of silicon oxide is as low as 1.5 or less, the light is still at this interface (the nitride semiconductor film and the silicon oxide Total reflection). In Non-Patent Document 1, the application is for a power device, which is not a problem. However, when a nitride semiconductor film is used as an optical element as in the present invention, the total reflection as described above is not effective for light extraction. This causes a decrease, which is a problem.

  Further, as disclosed in Non-Patent Documents 2 and 3, when forming a two-dimensional diffraction grating (photonic crystal structure) on the surface of the light emitting element, it is necessary to form other structures such as electrodes on the surface of the device. In some cases, a sufficient space for the two-dimensional diffraction grating cannot be secured. In such a case, the effect of improving the light extraction efficiency by the two-dimensional diffraction grating cannot be sufficiently obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to suppress the occurrence of problems such as peeling of the semiconductor layer from the base substrate and to obtain sufficient light extraction efficiency. A light-emitting element substrate and a light-emitting element are provided.

  A substrate for a light emitting device according to the present invention includes a semiconductor layer including a light emitting layer, and a base substrate bonded to the semiconductor layer via an intermediate layer. A two-dimensional diffraction grating is formed at the junction between the semiconductor layer and the base substrate.

  In this way, by forming a layer made of a material having excellent bonding properties between the semiconductor layer and the base substrate as the intermediate layer, peeling between the semiconductor layer and the base substrate can be prevented. Furthermore, since the two-dimensional diffraction grating is formed at the junction between the semiconductor layer and the base substrate, a two-dimensional diffraction grating having a sufficient size can be formed without interfering with other structures such as electrodes. As a result, the effect of improving the light extraction efficiency by the two-dimensional diffraction grating can be enhanced.

  Further, the intermediate layer may be composed of a transparent oxide film having a higher refractive index (than silicon oxide). This relaxes the total reflection condition and allows more light to interact with the two-dimensional diffraction grating. As a result, the light extraction efficiency can be further increased.

  Further, as the intermediate layer, a material having a low refractive index but excellent adhesive strength such as silicon oxide may be used. In this case, the two-dimensional diffraction grating may be provided at a position close to the semiconductor layer of the intermediate layer (for example, a surface layer in contact with the semiconductor layer in the intermediate layer) or in a form penetrating the intermediate layer so as to directly contact the semiconductor layer. preferable. As a result, light coming from the semiconductor layer can receive the contribution of the two-dimensional diffraction grating (interact with the two-dimensional diffraction grating) even if it is totally reflected at the interface between the semiconductor layer and the intermediate layer. As a result, the light extraction efficiency can be further increased while maintaining the adhesion between the substrate and the semiconductor layer.

  A light emitting device according to the present invention uses the above light emitting device substrate. In this way, the possibility of the semiconductor layer peeling off from the base substrate can be reduced, a sufficiently wide two-dimensional diffraction grating is formed, and the semiconductor layer is absorbed and lost while originally confined in the element. Since light can efficiently act on the diffraction grating, a light-emitting element with high reliability and high light extraction efficiency can be realized.

  Thus, according to the present invention, it is possible to suppress the occurrence of a problem such as peeling of the semiconductor layer from the base substrate and to obtain sufficient light extraction efficiency.

It is a cross-sectional schematic diagram which shows Embodiment 1 of the light emitting element according to this invention. 2 is a flowchart for explaining a method of manufacturing the light emitting device shown in FIG. 1. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram which shows Embodiment 2 of the light emitting element by this invention. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the light emitting element shown in FIG. It is a cross-sectional schematic diagram which shows Embodiment 3 of the light emitting element by this invention. FIG. 16 is a schematic cross-sectional view for illustrating the method for manufacturing the light emitting element shown in FIG. 15.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
A first embodiment of a light emitting device according to the present invention will be described with reference to FIG.

  With reference to FIG. 1, the light emitting device 1 is formed on a base substrate 2, an intermediate layer 35 disposed on the base substrate 2, a substrate 4 made of a semiconductor disposed on the intermediate layer 35, and the substrate 4. The n-type semiconductor layer 5, the light emitting layer 6, the p-type semiconductor layer 7, the n-electrode 8, and the p-electrode 9 are provided. The intermediate layer 35 is connected on the main surface of the base substrate 2. The substrate 4 is disposed on the intermediate layer 35. That is, the base substrate 2 and the substrate 4 are bonded via the intermediate layer 35. A photonic crystal structure layer 3 as a two-dimensional diffraction grating is formed at the junction between the substrate 4 and the base substrate 2. Specifically, the photonic crystal structure layer 3 is formed in a surface layer including a surface in contact with the intermediate layer 35 in the basic substrate 2. The photonic crystal structure layer 3 has a structure in which the refractive index periodically changes in a two-dimensional direction, and openings 3b are periodically formed on the upper surface of the base substrate 2 (surface joined to the intermediate layer 35). A plurality are formed (for example, in a matrix). In the photonic crystal structure layer 3, an opening 3 b whose inside is filled with vacuum or air, and a base 3 a that is located between the openings 3 b and is a part of the surface layer of the base substrate 2, In FIG. 4, a photonic crystal structure is formed by different refractive indexes. The shape, size, pitch, arrangement, and the like of the openings 3b of the photonic crystal structure layer 3 can be arbitrarily determined according to required characteristics such as light extraction efficiency.

  An n-type semiconductor layer 5 is formed on the upper surface of the substrate 4 (the surface located on the side opposite to the surface bonded to the intermediate layer 35). A light emitting layer 6 is formed on the n-type semiconductor layer. A p-type semiconductor layer 7 is formed on the light emitting layer 6. At the end of the light emitting element 1, a stepped portion 10 is formed by removing a part of the p-type semiconductor layer 7, the light emitting layer 6 and the n-type semiconductor layer 5. An n-electrode 8 is formed on the n-type semiconductor layer 5 exposed in the step portion 10. A p-electrode 9 made of a transparent conductor is formed on the upper surface of the p-type semiconductor layer 7.

  The light emitting element 1 is an LED using, for example, gallium nitride (GaN). In this case, for example, a sapphire substrate can be used as the basic substrate 2. As the basic substrate 2, for example, a substrate made of a transparent material may be used, but another material, for example, a substrate made of metal may be used. For example, the base substrate 2 can be a spinel substrate, a GaN substrate, a silicon carbide (SiC) substrate, or a quartz substrate. The base substrate 2 is preferably finished with a smooth surface.

  As the intermediate layer 35, for example, indium zinc oxide (IZO) can be used. The thickness of the intermediate layer 35 can be set to, for example, 300 nm.

  As the substrate 4, a GaN substrate can be used. Moreover, as the n-type semiconductor layer 5, an n-type GaN epitaxial layer can be used. As the light emitting layer 6, for example, a light emitting layer having a multiple quantum well (MQW) structure can be used. Specifically, for example, a stacked structure in which six combinations of GaN layers and InGaN layers are stacked can be used as the light emitting layer 6.

  As the p-type semiconductor layer 7, for example, a p-type GaN epitaxial layer can be used. The thickness d of the p-type semiconductor layer 7 can be set to 90 nm, for example. In such a light emitting device 1, by forming a layer such as IZO made of an oxide material excellent in bondability between the substrate 4 as the semiconductor layer and the base substrate 2 as the intermediate layer 35, Separation from the base substrate 2 can be prevented. Furthermore, since the photonic crystal structure layer 3 is formed at the junction between the substrate 4 and the base substrate 2 (more specifically, the surface layer in contact with the intermediate layer 35 in the base substrate 2), other structures such as electrodes The photonic crystal structure layer 3 having a sufficient size can be formed without interfering with. As a result, the effect of improving the light extraction efficiency by the photonic crystal structure layer 3 can be enhanced.

  By forming a layer made of a material having excellent bonding properties between the semiconductor layer and the base substrate as the intermediate layer, peeling between the semiconductor layer and the base substrate can be prevented. Furthermore, since the two-dimensional diffraction grating is formed at the junction between the semiconductor layer and the base substrate, a two-dimensional diffraction grating having a sufficient size can be formed without interfering with other structures such as electrodes. In addition, a material having a high refractive index is selected as the intermediate layer 35, and a diffraction grating made of vacuum or air is formed so as to increase the refractive index ratio, thereby increasing the diffraction efficiency. As a result, the effect of improving the light extraction efficiency by the two-dimensional diffraction grating can be enhanced. Further, since a material having a refractive index higher than that of silicon oxide is used for the intermediate layer 35, the total reflection angle at the interface between the substrate 4 and the intermediate layer 35 can be increased. Therefore, the amount of light that can reach the photonic crystal structure layer 3 can be increased, and as a result, the light extraction efficiency can be further increased.

Next, a method for manufacturing the light emitting device shown in FIG. 1 will be described with reference to FIGS.
Referring to FIG. 2, in the method for manufacturing the light emitting device shown in FIG. 1, first, a film forming step (S21) is performed. Specifically, the n-type semiconductor layer 5, the light emitting layer 6, and the p-type semiconductor layer 7 are sequentially formed on the upper surface of the substrate 4 by using, for example, an epitaxial growth method. For example, when forming a blue LED using GaN as a light emitting element, a GaN substrate (or sapphire substrate) may be used as the substrate 4.

  Next, as shown in FIG. 2, a device processing step (S22) is performed. Specifically, as shown in FIG. 4, a step portion is formed by removing a part of the p-type semiconductor layer 7, the light-emitting layer 6, and the n-type semiconductor layer 5 by etching using a mask formed by a photolithography method. 10 is formed. Then, a p-electrode 9 and an n-electrode 8 are formed on the upper surface of the p-type semiconductor layer 7 and on the surface of the n-type semiconductor layer 5 exposed at the stepped portion 10, respectively. As a method for forming the p electrode 9 and the n electrode 8, any conventionally known method can be used. For example, first, a mask having an opening in a region where an electrode is to be formed is formed by photolithography. A metal film constituting an electrode is formed on the mask and inside the opening by a physical vapor deposition method such as a vacuum heating vapor deposition method. Thereafter, the mask layer is removed (lift-off) to form the p-electrode 9 and the n-electrode 8.

  Next, a support substrate pasting step (S23) shown in FIG. 2 is performed. Specifically, as shown in FIG. 5, a support substrate 25 is attached via an adhesive 26 on the substrate surface on the side where the p-electrode 9 is formed. As the support substrate 25, for example, a silicon substrate can be used.

  Next, a back surface polishing step (S24) is performed as shown in FIG. Specifically, as shown in FIG. 5, the back surface 27 of the substrate 4 is polished. As a result, the thickness of the substrate 4 can be set to a predetermined thickness (for example, about 80 μm). As a polishing method, any method including wet etching and reactive ion etching can be used in addition to so-called mechanical polishing and CMP (chemical mechanical polishing). Further, the back surface 27 of the substrate 4 after polishing is mirror-finished. Then, in order to remove the damaged layer due to the polishing process, the surface layer of the back surface 27 is removed by a predetermined thickness (for example, about 200 nm) by, for example, reactive ion etching using chlorine gas. As a result, it is possible to remove the damaged layer generated by the polishing process described above. Further, the substrate 4 may be removed depending on the film thickness required after polishing. The smaller the combined thickness of the substrate 4 and the substrate 5 after polishing, the closer the photonic crystal structure layer 3 and the light emitting layer 6 to be described later are, so that the light diffraction effect by the photonic crystal structure can be increased. .

  Further, an IZO film to be the intermediate layer 35 is formed on the back surface 27 by sputtering. The thickness of this IZO film can be set to 250 nm, for example. In this way, the intermediate layer 35 shown in FIG. 6 is formed.

  Next, as shown in FIG. 2, a step of forming a two-dimensional diffraction grating (S25) is performed. Specifically, as shown in FIG. 7, a basic substrate 2 made of, for example, a sapphire single crystal is prepared, and a predetermined pattern is formed on the surface of the basic substrate 2 connected to the back surface of the intermediate layer 35 (see FIG. 1). A resist film 28 is formed. Specifically, a resist film 28 having an opening pattern similar to the planar shape of the opening 3b of the photonic crystal structure layer 3 is formed on the surface of the base substrate 2 using an i-line stepper. Note that an electron beam drawing method or a nanoimprint method may be used to form the opening pattern.

  Next, a part of the surface of the base substrate 2 is removed by etching using, for example, reactive ion etching using chlorine gas and the resist film 28 as a mask, so that the opening 3b is formed as shown in FIG. Form. The depth of the opening 3b can be set to, for example, 250 nm. Thereafter, the resist film 28 is removed, and the surface of the basic substrate 2 is washed with acetone. As a result, the photonic crystal structure layer 3 constituted by the opening 3b and the base 3a (see FIG. 1) which is located between the openings 3b and made of the same material as the base substrate 2 is obtained. In this way, the step of forming a two-dimensional diffraction grating (S25) is performed. Note that the planar pattern of the opening 3b of the photonic crystal structure layer 3 can have an arbitrary configuration, for example, a triangular lattice shape. At this time, the lattice pitch of the openings 3b is, for example, 1.60 μm. The planar shape of the opening 3b is circular, and the diameter of the opening 3b is 1.06 μm.

  Next, as shown in FIG. 2, a bonding step (S26) with the base substrate is performed. Specifically, as shown in FIG. 9, the base substrate 2 on which the photonic crystal structure layer 3 is formed is bonded to the substrate 4 via the intermediate layer 35. Any method can be used as a method of joining the substrate 4 and the base substrate 2, for example, the surface of the substrate 4 made of GaN on which the intermediate layer 35 is formed and the base substrate 2 are bonded together in a high vacuum, A method such as pressure bonding can be used. In this way, the base substrate 2 is bonded to the side of the substrate 4 where the intermediate layer 35 is formed, whereby the photonic crystal structure layer 3 including the opening 3b filled with air and the base portion 3a is formed as a basis. It is formed at the boundary between the substrate 2 and the substrate 4 (specifically, the surface layer of the basic substrate 2 in contact with the intermediate layer 35).

  Next, as shown in FIG. 2, a support substrate removing step (S27) is performed. Specifically, the adhesive 26 (see FIG. 9) is softened by heating the bonded substrate to which the basic substrate 2 is bonded with a hot plate or the like. In this state, the support substrate 25 is slid in the direction along the main surface of the substrate 4 to remove the support substrate 25 from the bonded substrate (slide off). Thereafter, the adhesive 26 remaining on the surface of the bonded substrate is dissolved and removed with a chemical solution (remover) or the like. In this manner, a bonded substrate having an LED structure composed of an epitaxial layer having a structure as shown in FIG. 1 can be obtained.

  Then, as shown in FIG. 2, a post-processing process (S28) is implemented. Specifically, the bonded substrate described above is diced using a diamond saw or the like for each region to be a light emitting element, or scribed to form a chip. Then, by fixing the obtained chip (light emitting element) on a stem or the like and forming necessary wiring, a light emitting device can be formed. For example, the basic substrate 2 is attached to the stem with silver paste so that the p-type semiconductor layer 7 faces upward. A light emitting device (LED) can be formed by connecting gold wires to the p electrode 9 and the n electrode 8 of the light emitting element.

(Embodiment 2)
With reference to FIG. 10, Embodiment 2 of the light emitting element by this invention is demonstrated.

  Referring to FIG. 10, light emitting element 1 basically has the same structure as light emitting element 1 shown in FIG. 1, but the structure of photonic crystal structure layer 3 is different. Specifically, the opening 3b constituting the photonic crystal structure layer 3 extends partway in the thickness direction of the intermediate layer 35 without penetrating the intermediate layer 35, and is formed on the surface layer of the basic substrate 2. It also extends. Also with the light emitting element 1 having such a structure, the same effect as that of the light emitting element 1 shown in FIG. 1 can be obtained.

With reference to FIGS. 11-14, the manufacturing method of the light emitting element shown in FIG. 10 is demonstrated.
First, the film forming step (S21) to the back surface polishing step (S24) shown in FIG. Specifically, the same processes as those described with reference to FIGS. As a result, a structure in which an intermediate layer 35 made of IZO is formed on the back surface 27 of the substrate 4 as shown in FIG. 6 is obtained. The thickness of the intermediate layer 35 formed on the substrate 4 side can be set to 150 nm, for example.

  Further, as the step of forming the two-dimensional diffraction grating shown in FIG. 2 (S25), the steps described in FIGS. 11 to 13 are performed. Specifically, first, as shown in FIG. 11, a basic substrate 2 made of, for example, sapphire is prepared, and an intermediate layer 35 is formed on the surface of the basic substrate 2 facing the back side of the substrate 4 (see FIG. 10). Formed. As the intermediate layer 35, an IZO film was formed by sputtering. The thickness of this IZO film can be set to 300 nm, for example.

  Next, as shown in FIG. 12, a resist film 28 having a predetermined pattern is formed on the intermediate layer 35. The opening pattern in resist film 28 is the same as the opening pattern in resist film 28 shown in FIG.

  Next, using the resist film 28 as a mask, a part of the surface of the intermediate layer 35 and the base substrate 2 is removed by etching, thereby forming an opening 3b as shown in FIG. Specifically, first, the pattern of the resist film 28 is transferred to the intermediate layer 35 made of IZO by reactive ion etching using chlorine gas, and the remaining resist film 28 is used to react with chlorine gas. The basic substrate 2 was partially removed by ion etching. As a result, the photonic crystal structure layer 3 constituted by the opening 3b and the base 3a (see FIG. 10) made of the same material as the intermediate layer 35 and the base substrate 2 is located between the openings 3b. can get. In this way, the step of forming a two-dimensional diffraction grating (S25) is performed. Thereafter, the resist film 28 was removed, and the surface of the basic substrate 2 was washed with acetone. Here, the depth of the opening 3 constituting the photonic crystal structure layer 3 can be 300 nm in the intermediate layer 35 portion and 100 nm in the base substrate 2 portion.

  Thereafter, the surface of the intermediate layer 35 (which constitutes the photonic crystal structure layer 3) on the base substrate 2 side made of IZO is polished by 50 nm. Thereby, residues of the resist film 28 remaining on the surface of the intermediate layer 35 can be removed.

  Then, as shown in FIG. 2, a bonding process with a basic substrate (S26) is performed. Specifically, as shown in FIG. 14, the base substrate 2 on which the photonic crystal structure layer 3 is formed is bonded to the back surface 27 side of the substrate 4. As a bonding method between the substrate 4 and the base substrate 2, for example, a method of bonding in a high vacuum and pressure bonding, or any other method can be used.

  Thereafter, by performing the support substrate removing step (S27) and the post-processing step (S28) shown in FIG. 2, the light-emitting element shown in FIG. 10 can be obtained.

(Embodiment 3)
With reference to FIG. 15, Embodiment 3 of the light-emitting device according to the present invention will be described.

  The light emitting device 1 shown in FIG. 15 basically has the same structure as the light emitting device shown in FIG. 1, but the arrangement of the photonic crystal structure layer 3 is different. That is, in the light emitting device 1 shown in FIG. 15, the photonic crystal structure layer 3 is formed on the surface layer of the basic substrate 2 including the upper surface of the basic substrate 2 (bonding surface with the intermediate layer 35) and the intermediate layer 35. The formed opening 3b (see FIG. 15) and the base substrate 2 and the intermediate layer 35 located around the opening 3b. From a different point of view, the photonic crystal structure layer 3 in the light emitting device shown in FIG. 15 is the same as the base substrate 2 and the intermediate layer 35 between the opening 3b filled with air and the opening 3b. It consists of a base portion 3a (see FIG. 15) made of a material. The arrangement of the opening 3b is the same as that of the photonic crystal structure layer 3 of the light emitting element 1 shown in FIG. Even with the light-emitting element having such a structure, the same effect as that of the light-emitting element shown in FIG. 1 can be obtained. Moreover, since the intermediate layer 35 itself is the photonic crystal structure layer 35, the light extraction efficiency can be further increased.

With reference to FIG. 16, the manufacturing method of the light emitting element shown in FIG. 15 is demonstrated.
First, the film forming step (S21) to the back surface polishing step (S24) shown in FIG. Then, the process similar to the process demonstrated in FIGS. 11-13 is implemented as a process (S25) of forming the two-dimensional diffraction grating shown in FIG. Thereafter, the resist film 28 was removed, and the surface of the basic substrate 2 was washed with acetone.

  Next, as shown in FIG. 2, a bonding step (S26) with the base substrate is performed. Specifically, as shown in FIG. 16, the base substrate 2 on which the photonic crystal structure layer 3 composed of the intermediate layer 35 and the surface layer of the base substrate 2 is formed is bonded to the back surface 27 of the substrate 4. As a method for joining the substrate 4 and the base substrate 2, a method similar to the bonding step (S26) in the first embodiment can be used, but any other method may be used.

  Thereafter, by performing the support substrate removing step (S27) and the post-processing step (S28) shown in FIG. 2, the light emitting device shown in FIG. 15 can be obtained.

  Hereinafter, although there is a part which overlaps with embodiment mentioned above, the characteristic structure of this invention is enumerated.

  A substrate for a light emitting device according to the present invention includes a semiconductor layer (n-type semiconductor layer 5, light-emitting layer 6, p-type semiconductor layer 7, substrate 4) including a light-emitting layer 6, and a semiconductor layer (n-type semiconductor layer 5, light-emitting element). A layer 6, a p-type semiconductor layer 7, a substrate 4) and a basic substrate 2 joined via an intermediate layer 35. A two-dimensional diffraction grating (photonic crystal structure layer 3) is formed at the junction between the semiconductor layer (n-type semiconductor layer 5, light-emitting layer 6, p-type semiconductor layer 7, substrate 4) and the base substrate 2.

  In this way, by forming a layer made of a material having excellent bonding properties between the substrate 4 and the base substrate 2 as the intermediate layer 35, it is possible to prevent the substrate 4 and the base substrate 2 from peeling off. Furthermore, since the photonic crystal structure layer 3 is formed at the junction between the substrate 4 and the base substrate 2, the photonic crystal structure layer 3 having a sufficient size can be formed without interfering with other structures such as electrodes. can do. As a result, the effect of improving the light extraction efficiency by the photonic crystal structure layer 3 can be enhanced.

  Further, the intermediate layer 35 may be made of a transparent oxide film having a high refractive index (than silicon oxide). Thereby, the total reflection condition is relaxed, and more light can interact with the photonic crystal structure layer 3 as a two-dimensional diffraction grating. As a result, the light extraction efficiency can be further increased.

  The intermediate layer 35 may be made of a material having a low refractive index but excellent adhesive strength, such as silicon oxide. In this case, the two-dimensional diffraction grating is in direct contact with the semiconductor layer (n-type semiconductor layer 5, light-emitting layer 6, p-type semiconductor layer 7, layer on the base substrate 2 side of the substrate 4, for example, the substrate 4). The intermediate layer 35 is preferably provided at a position close to the semiconductor layer (for example, a surface layer in contact with the semiconductor layer in the intermediate layer 35) or in a form penetrating the intermediate layer 35. Thereby, even if the light coming from the semiconductor layer is totally reflected at the interface between the semiconductor layer and the intermediate layer 35, it can receive the contribution of the two-dimensional diffraction grating (interact with the two-dimensional diffraction grating). As a result, the light extraction efficiency can be further enhanced while maintaining the adhesion between the base substrate 2 and the semiconductor layer. In addition, as the material of the base substrate 2, the same material as the semiconductor layer may be used, or a material different from the semiconductor layer may be used.

  In the light emitting element substrate, the photonic crystal structure layer 3 includes a base substrate side hole group (opening 3b in FIG. 1) formed in the surface layer of the base substrate 2 in contact with the intermediate layer 35, and the base substrate side. And a portion of the surface layer around the hole group. The intermediate layer 35 may be made of a material (for example, IZO) having a refractive index higher than that of silicon oxide. In this case, since the refractive index of the intermediate layer 35 is higher than that of silicon oxide, the total reflection angle at the interface between the substrate 4 and the intermediate layer 35 can be made larger than when silicon oxide is used as the intermediate layer 35. . As a result, a larger proportion of the light emitted from the light emitting layer 6 can reach the base substrate 2 side through the intermediate layer 35. For this reason, the light extraction efficiency can be easily increased by the photonic crystal structure layer 3 formed on the base substrate 2 side.

  In the light emitting element substrate, the photonic crystal structure layer 3 includes a group of holes (openings 3b) periodically formed in the intermediate layer 35 and a portion of the intermediate layer 35 around the openings 3b. May be. In this case, the photonic crystal structure layer 3 can be easily formed by periodically forming the openings 3 b in the intermediate layer 35. Further, since the intermediate layer 35 itself is used as a two-dimensional diffraction grating (photonic crystal structure layer 3), light that does not reach the surface of the base substrate 2 can be extracted outside the device by the photonic crystal structure layer 3. .

  In the light emitting element substrate, the photonic crystal structure layer 3 is formed on the surface of the base substrate 2 so as to be continuous with each hole of the hole group formed in the intermediate layer 35, as shown in FIGS. The base substrate side hole group formed in the layer and a portion of the surface layer around the base substrate side hole group may further be included. In this case, the photonic crystal structure layer 3 can be easily formed by periodically forming the openings 3 b in the intermediate layer 35 and the surface layer of the basic substrate 2. Further, by using a material having a relatively high refractive index (for example, a material having a higher refractive index than that of silicon oxide) as the intermediate layer 35, the refractive index ratio between the opening 3b and the surrounding portion may be increased. Good. In this case, higher diffraction efficiency can be obtained.

  In the light emitting element substrate, the material constituting the intermediate layer 35 in the structure as shown in FIG. 15 may be silicon oxide. Although silicon oxide has a refractive index of 1.5 or less and a relatively low value in oxides, in the case of FIG. 15, the photonic crystal structure layer 3 is in direct contact with the substrate 4, so The effect can be fully expected. In addition, the bonding strength between the basic substrate 2 and the substrate 4 can be reliably increased by utilizing the high adhesiveness of silicon oxide.

  In the light emitting element substrate, the intermediate layer 35 may be made of an oxide. In this case, peeling between the substrate 4 and the base substrate 2 can be reliably prevented by using an oxide (such as silicon oxide) having high adhesion between the substrate 4 and the base substrate 2.

In the light emitting element substrate, the material constituting the intermediate layer 35 is silicon oxynitride (SiON), indium tin oxide (ITO), indium zinc oxide (IZO), titania (TiO ₂ ), zirconia (ZrO), It may include at least one material selected from the group consisting of zinc oxide (ZnO), tin oxide (SnO), spinel (MgAlO ₃ ), and gallium oxide (Ga ₂ O ₃ ). Since these materials all have a higher refractive index than silicon oxide, the total reflection angle at the interface between the substrate 4 and the intermediate layer 35 can be made larger than when silicon oxide is used as the intermediate layer. As a result, the light emitted from the light emitting layer 6 can reach the base substrate 2 side through the intermediate layer 35 more. For this reason, even when the photonic crystal structure layer 3 is formed on the base substrate 2 side, the light extraction efficiency can be easily increased.

  In the light-emitting element substrate, the semiconductor layers (n-type semiconductor layer 5, light-emitting layer 6, p-type semiconductor layer 7, and substrate 4) may contain gallium nitride. As a result, it is possible to provide a light emitting element substrate and a light emitting element capable of obtaining sufficient light extraction efficiency in the ultraviolet to visible (for example, green) wavelength region. The semiconductor layer may contain a III-V group compound semiconductor.

  In the light emitting element substrate, the base substrate 2 may be a transparent substrate. In this case, light can be extracted also from the base substrate 2 side. Here, the transparent substrate means a substrate having a visible light transmittance of 60% or more per unit thickness (for example, 1 mm) of the substrate.

In the substrate for a light emitting element, the material constituting the base substrate 2 is aluminum oxide (Al ₂ O ₃ : sapphire), gallium oxide (Ga ₂ O ₃ ), spinel (MgAlO ₃ ), aluminum nitride (AlN), silicon carbide. One selected from the group consisting of (SiC), gallium nitride (GaN), zinc selenide (ZnSe), zinc oxide (ZnO), carbon, diamond, glass (for example, synthetic quartz, soda glass, low alkali glass, etc.) It may consist of These materials are cheaper than materials constituting the semiconductor layer such as the substrate 4 (for example, III-V group compound semiconductors such as GaN), and are bonded together when the entire bonded substrate for the light emitting element is formed from the semiconductor. The manufacturing cost of the substrate can be reduced.

  As shown in FIGS. 1, 10, and 15, a light emitting device 1 according to the present invention uses the light emitting device substrate. In this way, the possibility that the substrate 4 is peeled off from the base substrate 2 can be reduced, and a sufficiently large photonic crystal structure layer 3 can be formed, so that light emission with high reliability and high light extraction efficiency can be achieved. Element 1 can be realized.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is advantageously applied to a light emitting element substrate having a two-dimensional diffraction grating and a light emitting element.

  DESCRIPTION OF SYMBOLS 1 Light emitting element, 2 Base substrate, 3 Photonic crystal structure layer, 3a base part, 3b opening part, 4 board | substrate, 5 n-type semiconductor layer, 6 Light emitting layer, 7 p-type semiconductor layer, 8 n electrode, 9 p electrode, 10 steps, 25 support substrate, 26 adhesive, 27 back surface, 28 resist film, 35 intermediate layer.

Claims (17)

A semiconductor layer including a light emitting layer;
Comprising a base substrate joined via the semiconductor layer and an intermediate layer,
A light-emitting element substrate, wherein a two-dimensional diffraction grating is formed at a junction between the semiconductor layer and the base substrate. The two-dimensional diffraction grating includes a base substrate side hole group formed in a surface layer of the base substrate in contact with the intermediate layer, and a portion of the surface layer around the base substrate side hole group,
The light emitting element substrate according to claim 1, wherein the intermediate layer is made of a material having a refractive index higher than that of silicon oxide.   The light emitting element substrate according to claim 2, wherein the intermediate layer is made of an oxide.   The material constituting the intermediate layer is at least one material selected from the group consisting of silicon oxynitride, indium tin oxide, indium zinc oxide, titania, zirconia, zinc oxide, tin oxide, spinel, and gallium oxide. The substrate for a light-emitting element according to claim 2, comprising:   The light emitting element substrate according to claim 2, wherein the semiconductor layer includes gallium nitride.   The light emitting element substrate according to claim 2, wherein the base substrate is a transparent substrate.   The material constituting the base substrate is composed of one selected from the group consisting of aluminum oxide, gallium oxide, spinel, aluminum nitride, silicon carbide, gallium nitride, zinc selenide, zinc oxide, carbon, diamond, and glass. The light emitting element use substrate according to any one of claims 2 to 6.   The light emitting element using the board | substrate for light emitting elements of any one of Claims 1-7.   The light-emitting element substrate according to claim 1, wherein the two-dimensional diffraction grating includes a group of holes periodically formed in the intermediate layer and a portion of the intermediate layer around the hole group.   The two-dimensional diffraction grating includes a base substrate side hole group formed in a surface layer of the base substrate so as to be continuous with each hole of the hole group formed in the intermediate layer, and the base substrate side void. The light emitting element substrate according to claim 9, further comprising a portion of the surface layer around the hole group.   The light emitting element substrate according to claim 9, wherein the intermediate layer is made of an oxide.   The material constituting the intermediate layer is at least one material selected from the group consisting of silicon oxynitride, indium tin oxide, indium zinc oxide, titania, zirconia, zinc oxide, tin oxide, spinel, and gallium oxide. The board | substrate for light emitting elements of Claim 9 or 10 containing.   The light emitting element substrate according to claim 9 or 10, wherein a material constituting the intermediate layer is silicon oxide.   The light emitting element substrate according to claim 9, wherein the semiconductor layer contains gallium nitride.   The light emitting element substrate according to claim 9, wherein the base substrate is a transparent substrate.   The material constituting the base substrate is composed of one selected from the group consisting of aluminum oxide, gallium oxide, spinel, aluminum nitride, silicon carbide, gallium nitride, zinc selenide, zinc oxide, carbon, diamond, and glass. The light emitting element use substrate according to any one of claims 9 to 15.   The light emitting element using the board | substrate for light emitting elements of any one of Claims 9-16.

Images