JP4353125B2 - LIGHT EMITTING ELEMENT AND MANUFACTURING METHOD THEREOF - Google Patents

Description

  The present invention relates to a light emitting device and a manufacturing method thereof, and more particularly to a light emitting device using a GaN (gallium nitride) substrate and a manufacturing method thereof.

  2. Description of the Related Art LEDs (Light Emitting Diodes) are actively used for illumination of display devices such as portable information terminals including mobile phones, and for lighting. When an LED is used for a light source such as a display device of a portable information terminal, it is required to improve the light emission characteristics. Further, in the case of an LED that requires a higher output, such as a headlamp or general lighting application, it is more important to further improve the light emission characteristics and to improve the light emission efficiency when a large current is applied.

Japanese Unexamined Patent Publication No. 11-317546 (Patent Document 1) discloses a conventional light emitting device. In the light-emitting element of Patent Document 1, a transparent or light-transmissive n-type semiconductor layer and a p-type semiconductor layer are laminated in this order on the lower surface of a transparent n-type semiconductor substrate. A pn junction region formed by the n-type semiconductor layer and the p-type semiconductor layer is a light emitting layer. A p-electrode is formed on the surface of the p-type semiconductor layer, and an n-electrode is formed on the upper surface of the n-type semiconductor substrate. The n-type semiconductor substrate is mounted on the lead frame with the upper side and the light emitting layer on the lower side. When the light emitting element is energized, the light emitting layer is activated to emit light, and light is emitted from the upper surface of the n type semiconductor substrate through the n type semiconductor layer and the n type semiconductor substrate. Then, the light from the light emitting layer is emitted not only to the main light extraction surface side but also to the side, and the light is emitted from the lower surface of the p-type semiconductor substrate through the p-type semiconductor layer.
JP 11-317546 A

  However, in the semiconductor light emitting device described above, if the amount of current injected into the light emitting layer is increased in order to increase the amount of light emission, the light emission efficiency (internal quantum efficiency) decreases. For this reason, there is a limit to the amount of emitted light, and a sufficient amount of emitted light could not be obtained. This problem is particularly significant for light-emitting elements using a Ga (gallium nitride) substrate.

  Here, it is considered that the above-described problem occurs because dislocations existing in the semiconductor substrate affect the light emission efficiency when the current is increased. Further, for example, it is considered that an overflow of carriers injected from each of the n-type semiconductor layer and the p-type semiconductor layer has an influence. Furthermore, when the light emitting layer is composed of multiple quantum wells, it is considered that the light emission efficiency at low current is increased by fluctuations in the composition of each layer of the multiple quantum well.

  Accordingly, an object of the present invention is to provide a light emitting device capable of improving the light emission amount and a method for manufacturing the same.

  Another object of the present invention is to provide a light emitting element capable of extending the life and reducing power consumption and a method for manufacturing the light emitting element.

The light emitting device of the present invention is formed on a N-plane or N-plane side of a GaN substrate in which one main surface is constituted by an N surface and the other main surface is constituted by a Ga surface, and the surface is formed of Ga. A GaN layer composed of planes can be epitaxially grown on the N-plane of a GaN substrate and is formed adjacent to the surface of the inversion layer having sufficient light transmittance, and the surface is formed by the Ga plane The first luminescent layer that is formed at a position away from the GaN layer when viewed from the GaN substrate on one main surface side of the GaN substrate, and emits light by current injection, and the other GaN substrate. And a second light emitting layer that is formed on the main surface side and emits light by current injection. The inversion layer is selected from the group consisting of an inversion layer formed by roughening one main surface of the GaN substrate, and Al, In, Au, Pt, Cr, and Fe formed on one main surface side of the GaN substrate. Any one of an inversion layer made of at least one kind of metal and an inversion layer made of GaN formed by MOCVD at a temperature of 400 ° C. or more and 800 ° C. or less on one main surface side of the GaN substrate. is there.

The method for manufacturing a light emitting device according to the present invention includes a step of preparing a GaN substrate in which one main surface is constituted by an N surface and the other main surface is constituted by a Ga surface, and a GaN layer whose surface is constituted by a Ga surface. Can be epitaxially grown on the N surface of the GaN substrate, and an inversion layer forming step for forming an inversion layer having sufficient light transmittance on the N surface or the N surface side of the GaN substrate, A GaN layer forming step of epitaxially growing the constituted GaN layer from the surface of the inversion layer; and a first light emitting by injecting current at a position away from the GaN layer when viewed from the GaN substrate on one main surface side of the GaN substrate. A step of forming one light-emitting layer, and a step of forming a second light-emitting layer that emits light by current injection on the other main surface side of the GaN substrate. In the inversion layer forming step, an inversion layer is formed on one main surface of the GaN substrate by roughening one main surface of the GaN substrate, or a group consisting of Al, In, Au, Pt, Cr, and Fe An inversion layer made of at least one metal selected from the above is formed on one main surface side of the GaN substrate, or an inversion layer made of GaN is formed using a MOCVD method at a temperature of 400 ° C. to 800 ° C. Formed on one main surface side.

  Conventionally, since it has been difficult to epitaxially grow a GaN layer with good crystallinity on the N surface of a GaN substrate, a light emitting layer is formed only on the Ga surface side of the GaN substrate, and a light emitting layer is formed on the N surface side. Could not be formed. The inventors of the present application have found a method of epitaxially growing a GaN layer with good crystallinity on the N-plane side of the GaN substrate by forming an inversion layer on the N-plane or N-plane side of the GaN substrate. The surface of the epitaxially grown GaN layer is constituted by a Ga surface. Accordingly, the first light emitting layer can be formed on the GaN layer also on the N surface side of the GaN substrate, and two light emitting layers can be formed. When the light emitting element emits light, the first light emitting layer emits light by injecting current into the first light emitting layer, and the second light emitting layer emits light by injecting current into the second light emitting layer. Therefore, since both the first light emitting layer and the second light emitting layer emit light, the light emission amount can be improved as compared with the conventional light emitting element that emits light only by one light emitting layer.

  In the light emitting device, preferably, one of yellow and blue is emitted from the first light emitting layer, and one of yellow and blue is emitted from the second light emitting layer.

  In a conventional white light emitting element, white light is emitted by colliding electrons with a fluorescent material. On the other hand, in the present invention, yellow and blue light is emitted from each of the two light emitting layers, so that yellow and blue can be superimposed to emit white light. Thereby, the luminance can be improved by the amount of no conversion loss when the light is converted into white by the fluorescent material. Further, since white light can be emitted without using the fluorescent material, the manufacturing cost can be reduced by the amount not using the fluorescent material, and the lifetime can be extended because the fluorescent material is not deteriorated.

  In the above light emitting device, preferably, the distribution of the current injected into the first light emitting layer and the current injected into the second light emitting layer can be adjusted.

  Thereby, since each of yellow light emission intensity | strength and blue light emission intensity | strength can be changed, the color tone of light can be changed and it becomes easy to carry out white light emission.

  Preferably, the light emitting device further includes an electrode electrically connected to the GaN substrate, and a high-concentration GaN layer formed adjacent to the GaN substrate and having an impurity concentration higher than that of the GaN substrate. Yes. The electrode is formed adjacent to the high concentration GaN layer.

  Thereby, the contact resistance of an electrode can be reduced and power consumption can be reduced compared with the case where an electrode is provided adjacent to a GaN substrate.

  Preferably, the light emitting device further includes an electrode electrically connected to the GaN substrate. The electrode is formed adjacent to the other main surface of the GaN substrate.

  Accordingly, since the electrode is provided adjacent to the Ga surface, the contact resistance of the electrode can be reduced and the power consumption can be reduced as compared with the case where the electrode is provided adjacent to the N surface.

  Preferably, in the above manufacturing method, the inversion layer is formed on one main surface of the GaN substrate by roughening one main surface of the GaN substrate in the inversion layer forming step.

  By forming an inversion layer with one main surface of the GaN substrate roughened, the GaN layer can be easily epitaxially grown with the inversion layer as a base.

  Note that “roughening one main surface of the GaN substrate” means introducing defects into several layers in the depth direction from the surface of one main surface of the GaN substrate and significantly reducing the crystal symmetry of the main surface. I mean.

  Preferably in the manufacturing method, in the inversion layer forming step, at least selected from the group consisting of Al (aluminum), In (indium), Au (gold), Pt (platinum), Cr (chromium), and Fe (iron). An inversion layer made of one or more metals is formed on one main surface side of the GaN substrate.

  By forming the inversion layer made of the metal, the GaN layer is easily grown epitaxially with the inversion layer as a base.

  Preferably, in the above manufacturing method, in the inversion layer forming step, an inversion layer made of GaN is formed on one main surface side of the GaN substrate using a MOCVD (Metal Organic Chemical Vapor Deposition) method at a temperature of 400 ° C. or more and 800 ° C. or less. To do.

  By forming the inversion layer, the GaN layer is easily epitaxially grown with the inversion layer as a base.

  Preferably, in the manufacturing method, the GaN layer forming step includes a step of forming a mask layer so as to cover a portion where the GaN layer is not formed.

  By forming the mask layer, the GaN layer can be selectively grown only in the portion where the inversion layer is exposed.

  The “light emitting device” in the present invention may mean only a laminated structure or a semiconductor chip mainly composed of a GaN substrate and a semiconductor layer laminated thereon, or the semiconductor chip is mounted. In some cases, it refers only to a device mounted on a component and sealed with resin. Furthermore, it may be used for both meanings.

  According to the light emitting device and the method for manufacturing the same of the present invention, the amount of light emission can be improved.

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

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of an LED according to Embodiment 1 of the present invention. With reference to FIG. 1, in the LED as the light emitting element of the present embodiment, a laminated structure 50 is mounted on a mount portion 21 a of a lead frame. First, the configuration of the laminated structure 50 will be described.

  FIG. 2 is an enlarged plan view showing the semiconductor chip (laminated structure) of FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 and 3, the stacked structure 50 includes a GaN substrate 1, an inversion layer 10, a GaN regrowth layer 11 as a GaN layer, a light emitting layer 14 as a first light emitting layer, and a p-electrode 9b. And a light emitting layer 4 as a second light emitting layer, a p-electrode 9a, and an n-electrode 9c. In the GaN substrate 1, one main surface 1a is constituted by an N surface, and the other main surface 1b is constituted by a Ga surface, and is n-type. An inversion layer 10, a GaN regrowth layer 11, a light emitting layer 14, a p-electrode 9b, and an n-electrode 9c are formed on one main surface 1a side of the GaN substrate 1. On the other main surface 1b side of the GaN substrate 1, a light emitting layer 4 and a p-electrode 9a are formed.

  One main surface 1a of the GaN substrate 1 is roughened, and the roughened region of one main surface 1a is an inversion layer 10. In addition to the case where the roughened region of one main surface 1a is the inversion layer 10, the inversion layer is made of at least one metal selected from the group consisting of Al, In, Au, Pt, Cr, and Fe. 10 may be formed on one main surface 1a. Furthermore, in addition to the case where the inversion layer 10 made of the metal is formed, a GaN layer having poor crystallinity may be formed as the inversion layer 10.

  A GaN regrowth layer 11 is formed on the inversion layer 10. The GaN regrowth layer 11 is formed adjacent to the surface of the inversion layer 10 at a position away from the inversion layer 10 when viewed from the GaN substrate 1. The surface 11a of the GaN regrowth layer 11 is a Ga plane.

On the GaN regrowth layer 11, an n-type GaN epitaxial layer 12 is formed. An n-type cladding layer 13 made of, for example, Al _x Ga ₁ -xN (0 ≦ x ≦ 1) is formed on the GaN epitaxial layer 12, and a light emitting layer 14 is formed on the n-type cladding layer 13. Has been. The light emitting layer 14 is formed on one main surface 1 a side of the GaN substrate 1 and is formed at a position farther from the GaN regrowth layer 11 when viewed from the GaN substrate 1. The light emitting layer 14 is composed of a quantum well (MQW: Multi-Quantum Well) in which, for example, an Al _x Ga _1-x N layer and an Al _x In _y Ga _1-xy N layer (0 ≦ y ≦ 1) are stacked. Yes. The light emitting layer 14 emits yellow light by setting the value of y to 0.2 to 0.3. A p-type cladding layer 15 made of, for example, Al _x Ga _1-x N is formed on the light emitting layer 14. A p-type contact layer 16 made of, for example, GaN is formed on the p-type cladding layer 15, and a p-electrode 9 b is formed on the contact layer 16.

  A groove 12a reaching the inside of the GaN epitaxial layer 12 is formed at the left end portion of the LED in FIG. 3, and the n-electrode 9c is formed adjacent to the GaN epitaxial layer 12 in the groove 12a. Thereby, the n-electrode 9 c is electrically connected to the GaN substrate 1 through each of the GaN epitaxial layer 12, the GaN regrowth layer 11, and the inversion layer 10.

Under the other main surface 1b of the GaN substrate 1, an n-type GaN epitaxial layer 2 is formed. An n-type cladding layer 3 made of, for example, Al _x Ga _1-x N is formed under the GaN epitaxial layer 2, and a light emitting layer 4 is formed under the n-type cladding layer 3. The light emitting layer 4 is formed on the other main surface 1 b side of the GaN substrate 1. The light emitting layer 4 is composed of a quantum well in which, for example, an Al _x Ga _1-x N layer and an Al _x In _y Ga _1-xy N layer are stacked. The light emitting layer 4 emits blue light by setting the value of y to about 0.15. A p-type cladding layer 5 made of, for example, Al _x Ga _1-x N is formed on the light emitting layer 4. A p-type contact layer 6 made of, for example, p-type GaN is formed under the p-type cladding layer 5, and a p-electrode 9 a is formed under the contact layer 6.

  Subsequently, the configuration of the LEDs other than the laminated structure 50 will be described.

  Referring to FIG. 1, lead frame mount portion 21a and p-electrode 9a are bonded to each other by, for example, a conductive adhesive (not shown), thereby being electrically connected to each other. The current injected from the p electrode 9a to the light emitting layer 4 can be adjusted by a control device (not shown) connected to the p electrode 9a. Further, the lead portion 21b of the lead frame and the p-electrode 9b are electrically connected via the wire 23a and the control device 28. The current injected from the p-electrode 9b to the light-emitting layer 14 can be adjusted by the control device 28 connected to the p-electrode 9b. The control device is composed of, for example, a diode. Furthermore, the lead portion 21c of the lead frame and the n-electrode 9c are electrically connected via a wire 23b. Insulators 22 are disposed at the intersections of the lead frame mounting portion 21a, the lead portion 21b, and the lead portion 21c, whereby the lead frame mounting portion 21a, the lead portion 21b, and the lead portion 21c. Each is insulated from each other. Each of the laminated structure 50 and the wires 23 a and 23 b is sealed with an epoxy resin 25.

  Subsequently, an operation method of the LED will be described with reference to FIG.

  When a predetermined potential controlled by the control device 28 is applied to the p-electrode 9b, a voltage is generated between the p-electrode 9b and the n-electrode 9c, and the light-emitting layer 14 is generated from each of the n-type cladding layer 13 and the p-type cladding layer 15. The carrier is injected. The injected carriers are recombined in the light emitting layer 14 to generate yellow light. This light is emitted from the upper surface of the p-electrode 9 b and the side surface of the multilayer structure 50. On the other hand, when a predetermined potential controlled by a control device (not shown) is applied to the p-electrode 9a, a voltage is generated between the p-electrode 9a and the n-electrode 9c, and from each of the n-type cladding layer 3 and the p-type cladding layer 5 Carriers are injected into the light emitting layer 4. Then, the injected carriers are coupled to each other in the light emitting layer 4, and blue light is generated. This light is emitted from the upper surface of the p-electrode 9 b and the side surface of the multilayer structure 50.

  Here, when the light emitting layer 4 emits yellow light and the light emitting layer 14 emits blue light, the light emitting layer emits yellow light due to the band structure of each of the light emitting layer 4 and the light emitting layer 14. The rising voltage 4 (minimum voltage required for light emission) is lower than the rising voltage of the light emitting layer 14 that emits blue light. For this reason, when an equal voltage is applied between the p-electrode 9b and the n-electrode 9c and between the p-electrode 9a and the n-electrode 9c, most of the current flows toward the light emitting layer 4 and the yellow light emission becomes stronger. Cannot emit white light. In addition, since yellow has higher visibility than blue, in order to emit white light, it is necessary to increase the emission intensity of blue rather than yellow. In the present embodiment, by providing a control device for each of the p-electrodes 9a and 9b, the amount of current flowing through each of the light-emitting layer 4 and the light-emitting layer 14 is controlled to enable white light emission.

  In the present embodiment, the case where yellow light is emitted from the light emitting layer 4 and blue light is emitted from the light emitting layer 14 is shown. However, one of yellow and blue light is emitted from the light emitting layer 4. And any one of yellow and blue should just emit light from the light emitting layer 14. Further, light having the same wavelength may be emitted from the two light emitting layers. The wavelength of the light emitted from each of the two light emitting layers is arbitrary.

  Then, the manufacturing method of LED in this Embodiment is demonstrated using FIGS. 10 is a cross-sectional view taken along line XX in FIG. 9, and FIG. 12 is a cross-sectional view taken along line XII-XII in FIG.

  First, referring to FIG. 4, a GaN substrate 1 is prepared. In the GaN substrate 1, one main surface 1a is configured by an N surface, and the other main surface 1b is configured by a Ga surface. Here, “one main surface is constituted by an N surface” means a state in which the outermost surface of one main surface is terminated by N atoms. However, when some processing is performed on one main surface, most of the outermost surface of the processed portion is terminated by N atoms, but atoms other than N atoms are formed on the surface of the processed portion. May be exposed. In the present specification, even if some processing is performed on one main surface, at least the outermost surface of the unprocessed portion is terminated by N atoms, or the outermost surface of the processed portion If most of them are terminated by N atoms, it is assumed that “one main surface is constituted by N surfaces”.

  Similarly, “the other main surface is constituted by a Ga surface” means a state in which the outermost surface of the other main surface is terminated by Ga atoms. In this specification, even if some processing is performed on the other main surface, at least the outermost surface of the unprocessed portion is terminated by Ga atoms, or the outermost surface of the processed portion If the majority is terminated by Ga atoms, it is assumed that “the other main surface is constituted by a Ga surface”.

  Next, for example, oxygen or Si (silicon) is ion-implanted into the GaN substrate 1 to make the GaN substrate 1 n-type. Next, the inversion layer 10 is formed on one main surface 1a of the GaN substrate 1 or on one main surface 1a. Examples of the method for forming the inversion layer 10 include the following three methods.

  The first forming method is a method of forming the inversion layer 10 on one main surface 1a by polishing and roughening one main surface 1a of the GaN substrate 1 using, for example, abrasive grains. One main surface 1a after the polishing becomes uneven as shown in FIG. 5, and the flatness of the surface becomes worse than that before the polishing. The outermost surface 10c of the inversion layer 10 is an unpolished portion, and this portion is composed of N atoms. When the GaN substrate 1 is polished, there is no clear boundary line between the GaN substrate 1 and the inversion layer 10.

  The second forming method is a method in which a film made of at least one metal selected from the group consisting of Al, In, Au, Pt, Cr, and Fe is formed as an inversion layer 10 on one main surface 1a. is there.

  The third forming method is a method of forming a film made of GaN as an inversion layer 10 on one main surface 1a by using MOCVD at a temperature of 400 ° C. or higher and 800 ° C. or lower. When a film made of GaN is formed on the N plane under the above conditions, a GaN crystal having a low crystallinity (LT (Low Temperature) -GAN) is generated, although a GaN crystal having a good crystallinity cannot be obtained.

As the inversion layer, it surface may be a film capable of epitaxially growing a GaN layer formed by Ga face on the N surface of the GaN substrate, a layer having a sufficient optical transparency preferable.

  Next, referring to FIG. 6, the GaN regrowth layer 11 is turned into the inversion layer 10 by using a vapor phase growth method such as HVPE (Hydride Vapor Phase Epitaxy) method, MOCVD method, MBE (Molecular Beam Epitaxy) method or the like. Epitaxial growth is performed from the surface 10b. The surface 11a of the grown GaN regrowth layer 11 is constituted by a Ga surface. That is, the Ga plane can be exposed by inverting the N plane on the N plane side of the GaN substrate 1.

Further, when the GaN regrowth layer 11 is epitaxially grown, for example, if O ₂ gas or H ₂ O gas is mixed into the source gas, the GaN regrowth layer 11 is doped with oxygen, and the n-type GaN regrowth layer 11 is formed. can get. For example, when SiH ₄ gas is mixed with the source gas, Si is doped into the GaN regrowth layer 11 and the n-type GaN regrowth layer 11 is obtained.

Furthermore, when oxygen is doped into the GaN regrowth layer 11, the oxygen concentration in the GaN regrowth layer 11 is preferably 1 × 10 ¹⁷ / cm ³ or more and 2 × 10 ¹⁹ / cm ³ or less. By setting the oxygen concentration to 1 × 10 ¹⁷ / cm ³ or more, the resistance of the GaN regrowth layer 11 is reduced, and the driving voltage of the LED can be reduced. In addition, by setting the oxygen concentration to 2 × 10 ¹⁹ / cm ³ or less, it is possible to keep the blue light transmittance particularly high in the GaN regrowth layer 11.

  Next, referring to FIG. 7, GaN epitaxial layer 12 is epitaxially grown on surface 11a of GaN regrowth layer 11 using, for example, MOCVD. By forming the GaN epitaxial layer 12, the crystallinity of the layer formed in the upper layer is improved. Subsequently, the n-type cladding layer 13, the light emitting layer 14, the p-type cladding layer 15, and the contact layer 16 are each epitaxially grown in this order on the GaN epitaxial layer 12 using, for example, MOCVD. As a result, the light emitting layer 14 is formed on the one main surface 1a side and at a position away from the GaN regrowth layer 11 when viewed from the GaN substrate 1.

  Next, referring to FIG. 8, the GaN substrate 1 is inverted so that one main surface 1a is a lower surface and the other main surface 1b is an upper surface. Then, the GaN epitaxial layer 2 is epitaxially grown on the other main surface 1b by using, for example, the MOCVD method. Since the other main surface 1b of the GaN substrate 1 is constituted by a Ga surface, a GaN crystal having good crystallinity can be epitaxially grown. Then, each of the n-type cladding layer 3, the light emitting layer 4, the p-type cladding layer 5, and the contact layer 6 is epitaxially grown on the GaN epitaxial layer 2 in this order. Next, the GaN substrate 1 is heat-treated to activate the impurities contained in each of the p-type cladding layers 5 and 15 and the contact layers 6 and 16.

  Next, referring to FIG. 9 and FIG. 10, element isolation grooves 27 are formed on one main surface 1a side so as to surround the outer periphery of the laminated structure as viewed in a plan view. Further, on one main surface 1a side, a groove 12a reaching the GaN epitaxial layer 12 is formed in the upper right region in each of the stacked structures. The element isolation groove 27 and the groove 12a are formed by using, for example, a photolithography technique and RIE (Reactive Ion Etching), the contact layer 16, the p-type cladding layer 15, the light emitting layer 14, the n-type cladding layer 13, and the GaN epitaxial layer. Each of the upper portions of 12 is formed by etching with a Cl (chlorine) -based gas. The element isolation groove 27 and the groove 12a may be formed in the same process or may be formed in different processes. Subsequently, on the other main surface 1b side, an element isolation groove 26 is similarly formed in a region overlapping with the element isolation groove 27 in plan view. The element isolation trench 26 is formed by etching each of the contact layer 6, the p-type cladding layer 5, the light emitting layer 4, the n-type cladding layer 3, and the upper part of the GaN epitaxial layer 2.

  Next, referring to FIGS. 11 and 12, the GaN substrate 1 is inverted so that one main surface 1a is an upper surface and the other main surface 1b is a lower surface. Then, the n-electrode 9c is formed at a predetermined position in the groove 12a using, for example, a photolithography technique, a vapor deposition method, and a lift-off method. Similarly, the p electrode 9 b is formed on the entire upper surface of the contact layer 16, and the p electrode 9 a is formed on the entire lower surface of the contact layer 6. Subsequently, scribing is performed so that the chip boundary A in the element isolation groove 27 and the element isolation groove 26 appears as side surfaces, and the chip is divided into individual stacked structures 50 shown in FIGS.

  Next, referring to FIG. 1, the laminated structure 50 is mounted so that the p-electrode 9a is adjacent to the mount portion 21a of the lead frame. Then, a conductive adhesive is applied to the mount portion to fix the laminated structure 50 and the lead frame, and to obtain conduction between the laminated structure 50 and the lead frame. As the conductive adhesive, for example, an Ag-based adhesive having good thermal conductivity is used. Further, as the lead frame, for example, a CuW type material having good thermal conductivity is used. Subsequently, the p-electrode 9b and the lead portion 21b of the lead frame are electrically connected by the wire 23a and the control device 28. Further, the n-electrode 9c and the lead portion 21c of the lead frame are electrically connected by a wire 23b. Furthermore, each of the laminated structure 50 and the wires 23a and 23b is sealed using an epoxy resin 25. Through the above steps, the LED of the present embodiment is completed.

  According to the LED of the present embodiment and the manufacturing method thereof, the GaN regrowth with good crystallinity is formed on the N-plane side of the GaN substrate 1 by forming the inversion layer 10 on the N-plane or N-plane side of the GaN substrate 1. Layer 11 can be epitaxially grown. Thereby, a light emitting layer can be formed on the GaN regrowth layer 11, and the light emitting layer 14 can also be formed on one main surface 1 a side of the GaN substrate 1. Therefore, since both the light emitting layer 4 and the light emitting layer 14 emit light, the amount of light emission can be improved as compared with a conventional light emitting element that emits light by only one light emitting layer.

  In the LED of the present embodiment, either one of yellow and blue light is emitted from the light emitting layer 4, and one of yellow and blue light is emitted from the light emitting layer 14.

  Thereby, since white light can be emitted without using a fluorescent material, the luminance can be improved to the extent that there is no conversion loss when light is converted into white by the fluorescent material. Further, since white light can be emitted without using the fluorescent material, the manufacturing cost can be reduced by the amount not using the fluorescent material, and the lifetime can be extended because the fluorescent material is not deteriorated.

  In the LED of this embodiment, the distribution between the current injected into the light emitting layer 14 and the current injected into the light emitting layer 4 can be adjusted.

  Thereby, since each of yellow light emission intensity | strength and blue light emission intensity | strength can be changed, the color tone of light can be changed and it becomes easy to carry out white light emission.

  In the LED manufacturing method of the present embodiment, preferably, the inversion layer 10 is formed on one main surface 1 a of the GaN substrate 1 by roughening one main surface 1 a of the GaN substrate 1.

  By forming the inversion layer 10 that roughens one main surface 1a of the GaN substrate 1, the GaN regrowth layer 11 is easily epitaxially grown with the inversion layer 10 as a base.

  In the LED manufacturing method of the present embodiment, the inversion layer 10 made of at least one metal selected from the group consisting of Al, In, Au, Pt, Cr, and Fe is preferably formed on one main surface of the GaN substrate 1. It is formed on the surface 1a side.

  By forming the inversion layer 10 made of the metal, the GaN regrowth layer 11 is easily epitaxially grown with the inversion layer 10 as a base.

  Preferably, in the above manufacturing method, the inversion layer 10 made of GaN is formed on the one main surface 1a side of the GaN substrate 1 by MOCVD at a temperature of 400 ° C. or higher and 800 ° C. or lower.

  By forming the inversion layer 10, the GaN regrowth layer 11 is easily grown epitaxially with the inversion layer 10 as a base.

  In the present embodiment, the case of forming the stacked structure on the other main surface 1b side after forming the stacked structure on the one main surface 1a side of the GaN substrate 1 is shown. However, the other main surface 1b side is shown. After forming the laminated structure, the laminated structure on the one main surface 1a side may be formed.

(Embodiment 2)
In the first embodiment, the control device is provided in each of the p-electrodes 9a and 9b to control the amount of current injected into each of the light-emitting layer 4 and the light-emitting layer 14, but any control device is used. One may be sufficient. Further, for example, the amount of current flowing through each of the light emitting layer 4 and the light emitting layer 14 can also be controlled by making the p electrodes 9a and 9b have different shapes.

  For example, as shown in FIGS. 13A and 13B, instead of forming the p-electrode 9b so as to cover the entire top surface of the contact layer 16, mesh-like p-electrodes 9d are scattered on the contact layer 16. Thus, a part of the contact layer 16 may be exposed. In this case, since the occupied area of the p electrode is reduced as compared with the case where the p electrode is formed on the entire upper surface of the contact layer 16, the current density of the current flowing through the p electrode is increased and the current does not easily flow to the light emitting layer 14. Become. As a result, the light emission amount of the light emitting layer 4 can be made smaller than the light emission amount of the light emitting layer 14.

  Referring to FIG. 1, the contact resistance between p electrode 9b and contact layer 16 is made close to a Schottky contact, and the contact resistance between p electrode 9b and contact layer 16 is set to p electrode 9a and contact layer 6. It may be larger than the contact resistance between the two. Also in this case, since the current hardly flows to the light emitting layer 14, the light emission amount of the light emitting layer 4 can be made smaller than the light emission amount of the light emitting layer 14.

(Embodiment 3)
FIG. 14 is a cross-sectional view showing the configuration of the laminated structure according to Embodiment 3 of the present invention. Referring to FIG. 14, in LED stacked structure 50a of the present embodiment, a groove 10a reaching inversion layer 10 is formed, and n electrode 9c is formed adjacent to inversion layer 10 in groove 10a. ing. As a result, the n-electrode 9 c is electrically connected to the GaN substrate 1 through the inversion layer 10.

  In addition, since the structure of LED other than this is as substantially the same as the structure of LED of Embodiment 1, the same code | symbol is attached | subjected to the same member and the description is not repeated.

  Next, the manufacturing method of LED of this Embodiment is demonstrated using FIGS. 15-18. 16 is a cross-sectional view taken along line XVI-XVI in FIG.

First, the inversion layer 10 is formed by the same method as in the first embodiment, and the structure shown in FIG. 4 is obtained. Next, referring to FIG. 15 and FIG. 16, the region for forming the groove 10a on the inversion layer 10 and the element isolation groove 27 are formed by using, for example, a photolithography technique, a sputter deposition method, and a lift-off method. A mask layer 29 made of, for example, SiO ₂ (silicon oxide), SiN (silicon nitride), W (tungsten), Ni (nickel), or Ti (titanium) is formed in the region to be formed.

  Next, referring to FIG. 17, GaN regrowth layer 11 is formed on inversion layer 10 by the same method as in the first embodiment. At this time, GaN does not epitaxially grow on the mask layer 29 but selectively grows epitaxially only on the inversion layer 10 not covered with the mask layer 29. Subsequently, the GaN epitaxial layer 12, the n-type cladding layer 13, the light emitting layer 14, the p-type cladding layer 15, and the contact layer 16 are formed on the GaN regrowth layer 11. As a result, these layers are not formed in the region covered with the mask layer 29, and the trench 10a and the element isolation trench 27 are formed.

  Next, referring to FIG. 18, each of GaN epitaxial layer 2, n-type cladding layer 3, light-emitting layer 4, p-type cladding layer 5, and contact layer 6 is attached to the other by the same method as in the first embodiment. Epitaxial growth is performed in this order on the main surface 1b side. Then, by heat-treating the GaN substrate 1, impurities contained in each of the p-type cladding layers 5 and 15 and the contact layers 6 and 16 are activated. Subsequently, the element isolation groove 26 is similarly formed in a region overlapping the element isolation groove 27 in plan view on the other main surface 1b side by the same method as in the first embodiment.

  Next, the mask layer 29 is removed using, for example, a hydrofluoric acid solvent. Then, each of p electrode 9a, p electrode 9b, and n electrode 9c is formed in a predetermined region by the same method as in the first embodiment. Subsequently, scribing is performed so that the chip boundaries in the element isolation groove 27 and the element isolation groove 26 appear as side surfaces, and the chip structure is divided into a stacked structure 50a shown in FIG. Thereafter, the laminated structure 50a is mounted on the lead frame, and the LED of this embodiment is completed.

  According to the LED of this embodiment and the manufacturing method thereof, the same effect as that of Embodiment 1 can be obtained.

  In the LED manufacturing method of the present embodiment, the mask layer 29 is formed so as to cover a portion where the GaN regrowth layer 11 is not formed. Thereby, the GaN regrowth layer 11 can be selectively epitaxially grown.

(Embodiment 4)
FIG. 19 is a cross-sectional view showing the configuration of the laminated structure according to Embodiment 4 of the present invention. Referring to FIG. 19, in the LED stacked structure 50b of the present embodiment, one main surface 1a of the GaN substrate 1 is a lower surface and the other main surface 1b is an upper surface. A groove 2 a reaching the GaN epitaxial layer 2 is formed, and the n-electrode 9 c is formed adjacent to the GaN epitaxial layer 2 in the groove 2 a. As a result, the n-electrode 9 c is electrically connected to the GaN substrate 1.

  In addition, the structure of LED other than this is as substantially the same as LED of Embodiment 1. FIG. In addition, the LED of the present embodiment can be manufactured by a method substantially similar to the manufacturing method of the first embodiment. Therefore, the description will not be repeated.

  According to the LED of the present embodiment, the same effect as in the first embodiment can be obtained.

(Embodiment 5)
FIG. 20 is a cross-sectional view showing the configuration of the laminated structure in the fifth embodiment of the present invention. Referring to FIG. 20, in LED stack structure 50c of the present embodiment, one main surface 1a of GaN substrate 1 is a lower surface and the other main surface 1b is an upper surface. A groove 1c reaching the other main surface 1b of the GaN substrate 1 is formed. In the groove 1c, an n-electrode 9c as an electrode is formed adjacent to the other main surface 1b. As a result, the n-electrode 9 c is electrically connected to the GaN substrate 1.

  In addition, the structure of LED other than this is as substantially the same as LED of Embodiment 1. FIG. In addition, the LED of the present embodiment can be manufactured by a method substantially similar to the manufacturing method of the first embodiment. Therefore, the description will not be repeated.

  According to the LED of the present embodiment, the same effect as in the first embodiment can be obtained.

  In the LED of the present embodiment, the n-electrode 9 c is formed adjacent to the other main surface 1 b of the GaN substrate 1. Thereby, since the n electrode 9c is provided adjacent to the Ga surface, the contact resistance of the n electrode can be reduced and the power consumption can be reduced as compared with the case where the n electrode is provided adjacent to the N surface. it can.

(Embodiment 6)
FIG. 21 is a cross-sectional view showing the configuration of the LED in the sixth embodiment of the present invention. Referring to FIG. 21, in LED laminated structure 50 d of the present embodiment, one main surface 1 a of GaN substrate 1 is a lower surface and the other main surface 1 b is an upper surface. A high-concentration GaN layer 30 is formed adjacent to the GaN substrate 1 on the other main surface 1 b side of the GaN substrate 1. The high concentration GaN layer 30 has an impurity concentration higher than that of the GaN substrate 1. Further, a groove 30 a reaching the high concentration GaN layer 30 is formed, and the n electrode 9 c is formed adjacent to the high concentration GaN layer 30 in the groove 30 a. As a result, the n-electrode 9 c is electrically connected to the GaN substrate 1.

  In addition, the structure of LED other than this is as substantially the same as LED of Embodiment 1. FIG. The LED of this embodiment is the same as the embodiment except that the high-concentration GaN layer 30 is epitaxially grown on the other main surface 1b of the GaN substrate 1 and the GaN epitaxial layer 2 is epitaxially grown on the high-concentration GaN layer 30. It can be manufactured by a method substantially similar to the manufacturing method 1. Therefore, the description will not be repeated.

  According to the LED of the present embodiment, the same effect as in the first embodiment can be obtained.

  The LED of the present embodiment further includes a high-concentration GaN layer 30 formed adjacent to the GaN substrate 1 and having an impurity concentration higher than that of the GaN substrate 1. The n electrode 9 c is formed adjacent to the high concentration GaN layer 30.

  Thereby, the contact resistance of the n electrode can be reduced and the power consumption can be reduced as compared with the case where the n electrode is provided adjacent to the GaN substrate.

  Examples of the present invention will be described below.

  In this example, each of Invention Example A and Comparative Example B were prepared by the following method, and the output (light emission amount) of light emitted from each was compared.

(Invention Sample A)
Using the manufacturing method shown in the following (a1) to (a13), the light-emitting element described in Embodiment 1 that emits blue light from both of the two light-emitting layers was manufactured.

(A1) A GaN off-substrate shifted by 0.5 ° from the c-plane was prepared. This substrate had a specific resistance of 0.01 Ω · cm, a dislocation density of 1 × 10 ⁷ / cm ² , and a thickness of 400 μm.

(A2) Next, the N surface, which is one main surface of the GaN substrate, was polished using abrasive grains having an abrasive grain size of 5 μm, and an inversion layer was formed on one main surface. After polishing, the thickness of the inversion layer (processed alteration layer) of the cross section of the GaN substrate was measured using SEM (Scanning Electron Microscope) and CL (cathode luminescence method). As a result, the thickness of the inversion layer was 5 μm. Subsequently, a GaN regrowth layer having a thickness of 6 μm was epitaxially grown on the inversion layer using the HVPE method. The GaN regrowth layer was grown for 5 minutes in an atmospheric pressure at a temperature of 1000 ° C. As source gases, 100 sccm GaCl, 6000 sccm NH _3, and O ₂ gas as a dopant source gas were used. After the GaN regrowth layer was formed, the oxygen concentration in the GaN regrowth layer was measured by a secondary ion mass spectrometer (SIMS). As a result, the oxygen concentration was about 5 × 10 ¹⁸ / cm ³ in any part of the GaN regrowth layer and was almost uniform. Further, after the formation of the GaN regrowth layer, the outermost surface atomic species of GaN was examined by a CAICISS method (Coaxial Impact Collision Ion Scattering Spectroscopy). As a result, it was confirmed that the surface of the Ga regrowth layer was a Ga surface. Thus, it was found that by providing an inversion layer on the N surface of the GaN substrate, the surface of the GaN layer formed thereon was inverted to become a Ga surface.

(A3) Next, the following laminated structure was formed on the Ga surface, which is the other main surface of the GaN substrate, using MOCVD. (Si-doped n-type GaN layer (GaN epitaxial layer) / Clad layer Si-doped n-type Al _0.2 Ga _0.8 N layer (n-type clad layer) / GaN layer and In _0.15 Ga _0.85 N layer are 3 layers) MQW (light emitting layer) / clad layer Mg-doped p-type Al _0.2 Ga _0.8 N layer (p-type clad layer) / Mg-doped p-type GaN layer (contact layer)). The emission wavelength of this MQW corresponds to 450 nm.

(A4) Next, the following laminated structure was formed on the Ga surface of the GaN regrown layer by MOCVD. (Si-doped n-type GaN layer (GaN epitaxial layer) / Clad layer Si-doped n-type Al _0.2 Ga _0.8 N layer (n-type clad layer) / GaN layer and In _0.15 Ga _0.85 N layer are 3 layers) Stacked MQW (light emitting layer) / clad layer Mg-doped p-type Al _0.2 Ga _0.8 N layer (p-type clad layer) / Mg-doped p-type GaN layer (contact layer)) The emission wavelength of this MQW corresponds to 450 nm. .

(A5) Next, this wafer was activated to reduce the resistance of the Mg-doped p-type layer. The carrier concentration by hole measurement was 5 × 10 ¹⁷ / cm ³ for the Mg-doped p-type Al _0.2 Ga _0.8 N layer and 1 × 10 ¹⁸ / cm ³ for the Mg-doped p-type GaN layer.

(A6) Next, element isolation grooves were formed on one main surface side and the other main surface side of the GaN substrate by photolithography technique and RIE. The element isolation groove was formed at a position where it overlaps on one main surface side and the other main surface side. In addition, a groove for providing an n-electrode was simultaneously formed by RIE to expose the n-type GaN layer on one main surface side. Referring to FIG. 9, the groove for providing the n-electrode has a square planar shape whose one side d ₁ is 500 μm, and the width d ₂ of the element isolation groove is 100 μm. Further, the interval d ₃ between the portions where the n electrodes are provided was set to 2 mm in the vertical and horizontal directions, and the shape of the light emitting portion (MQW) was a square planar shape having a side d ₄ of 1.9 mm.

(A7) Next, an n electrode having a square planar shape with a side d ₅ of 400 μm as shown in FIG. 11 is formed in the groove formed to provide the n electrode by photolithography, vapor deposition, and lift-off. It was formed on the n-type GaN layer. As the n-electrode, a stacked structure of (Ti layer 20 nm / Al layer 100 nm / Ti layer 20 nm / Au layer 200 nm) was formed in order from the bottom in contact with the n-type GaN layer. This was heated in a nitrogen (N ₂ ) atmosphere so that the contact resistance was 1 × 10 ⁻⁵ Ω · cm ² or less.

(A8) Next, a p-electrode was formed in contact with each of the Mg-doped p-type GaN layers formed on both sides of the GaN substrate. As the p-electrode, a 4 nm thick Ni layer was formed, and a 4 nm thick Au layer was formed on the entire surface. And this was heat-processed in inert gas atmosphere, and contact resistance was ^5x10 <^-4> ohm * cm < ² >. The contact resistance was 5 × 10 ⁻⁴ Ω · cm ² or less.

(A9) After that, scribing was performed so that the chip boundary appeared as a side surface, and the resulting chip was used as the light emitting device. The light emitting area (MQW area) of the light emitting device formed into a chip was 7 mm ² .

  (A10) Next, the light emitting device (LED) was formed by mounting so that the p electrode on the other main surface side of the chip was in contact with the mount portion of the lead frame. The light emitting device and the mount are fixed by a conductive adhesive applied to the mount portion, and conduction is obtained.

  (A11) In order to improve the heat dissipation from the light emitting device, the p-type GaN layer of the light emitting device was mounted so as to be in contact with the entire mount portion. Also, an Ag-based adhesive with good thermal conductivity was selected, and a lead frame of CuW-based adhesive with high thermal conductivity was selected. Thereby, the obtained thermal resistance was 8 ° C./W.

  (A12) Further, the n electrode and the lead portion of the lead frame were made conductive by wire bonding, and then resin sealing was performed with an epoxy resin to form a lamp.

  (A13) A control circuit is provided to adjust the current injected into each of the two light emitting layers.

(Comparative Example B)
Using the manufacturing method shown in the following (b1) to (b11), a light emitting device including only one light emitting layer that emits blue light was produced.

(B1) A GaN off-substrate shifted by 0.5 ° from the c-plane was prepared. This substrate had a specific resistance of 0.01 Ω · cm, a dislocation density of 1 × 10 ⁷ / cm ² , and a thickness of 400 μm.

(B2) Next, the following laminated structure was formed on the Ga surface of the GaN substrate by MOCVD. (SiW doped n-type GaN layer / Si doped n type Al _0.2 Ga _0.8 N layer / GaN layer and In _0.15 Ga _0.85 N layer, three layers of MQW / clad layer Mg doped p) (Type Al _0.2 Ga _0.8 N layer / Mg-doped p-type GaN layer) The emission wavelength of this MQW corresponds to 450 nm.

  (B3) Next, the internal quantum efficiency was conveniently calculated by comparing the PL (Photo Luminescence) intensity at a low temperature of 4.2K and the PL intensity at a room temperature of 298K. As a result, the internal quantum efficiency was 50%.

(B4) Next, this wafer was activated to reduce the resistance of the Mg-doped p-type layer. The carrier concentration by hole measurement was 5 × 10 ¹⁷ / cm ³ for the Mg-doped p-type Al _0.2 Ga _0.8 N layer and 1 × 10 ¹⁸ / cm ³ for the Mg-doped p-type GaN layer.

  (B5) Next, this wafer was further etched with Cl-based gas from the Mg-doped p-type layer side to the Si-doped n-type layer by photolithography and RIE. By this etching, an element isolation groove was formed and element isolation was performed. The width of the element isolation groove was 100 μm.

(B6) Next, an n-electrode having a diameter (D) of 500 μm was formed at the center of the chip every 400 μm on the N surface of the GaN substrate by photolithography, vapor deposition, and lift-off method. As the n-electrode, a stacked structure (Ti layer 20 nm / Al layer 100 nm / Ti layer 20 nm / Au layer 200 nm) was formed in order from the bottom in contact with the GaN substrate. This was heated in a nitrogen (N ₂ ) atmosphere so that the contact resistance was 1 × 10 ⁻⁵ Ω · cm ² or less. As the n-electrode, a circular plane shape having a diameter of 500 μm was formed.

(B7) Next, a p-electrode was formed. As a p-electrode, a 4 nm thick Ni layer was formed in contact with the p-type GaN layer, and a 4 nm thick Au layer was formed on the entire surface. This was heat-treated in an inert gas atmosphere to make the contact resistance 5 × 10 ⁻⁴ Ω · cm ² .

(B8) Thereafter, scribing was performed so that the chip boundary appeared as a side surface, and the chip was made into a light emitting device. In the light emitting device formed into a chip, the light emission surface has a square shape with a side length of 1.9 mm, and the chip has a square shape with a side length of 2 mm. The light emission area (MQW area) was 3.6 mm ² .

  (B9) Next, the chip was mounted so that the p-type GaN layer side of the chip was in contact with the mount portion of the lead frame to form a light emitting device. At this time, the light emitting device and the mount were fixed by a conductive adhesive applied to the mount portion, and conduction was obtained.

  (B10) Next, in order to improve heat dissipation from the light emitting device, the p-type GaN layer of the light emitting device was mounted so as to be in contact with the entire surface mount portion. Also, an Ag-based adhesive with good thermal conductivity was selected, and a lead frame of CuW-based adhesive with high thermal conductivity was selected. Thereby, the obtained thermal resistance was 8 ° C./W.

  (B11) Further, the n electrode and the lead portion of the lead frame were made conductive by wire bonding, and then resin sealing was performed with an epoxy resin to form a lamp.

  Next, each of Invention Example A and Comparative Example B produced by the above method are mounted in an integrating sphere, a predetermined current is injected into the light emitting layer, and the emitted light is condensed, and from the detector The output of the output light was measured. The results are shown in Table 1.

  Referring to Table 1, when a current of 1 A was injected, only 0.39 W of output was obtained in Comparative Example B, whereas 0.4 W of Example of Invention A was obtained. . In addition, when a current of 6 A was injected, only 1.8 W of output was obtained in Comparative Example B, whereas in Example A of the present invention, the output did not increase 6 times. An output of 1 W was obtained. Thus, it was found that Example A of the invention including two light emitting layers emits higher output light than Comparative Example B including only one light emitting layer.

Here, the light emission area of Comparative Example B is 3.6 mm ² , while the light emission area of Invention Example A is 7 mm ^2, which is about twice the light emission area of Comparative Example B. Since the current density of the current injected into the light emitting layer is inversely proportional to the light emitting area, the current density of Comparative Example B is 28 A / cm ² and 167 A / cm ² respectively, while the current density of Invention Example A is each has a ^{14A / cm 2, 86A / cm} 2, which is about one-half the current density of Comparative example B.

FIG. 22 is a diagram showing the relationship between the current density J and the external quantum efficiency η _ex in the GaN-based light emitting device. As shown in FIG. 22, although it depends on the film structure and manufacturing conditions, it is known that the light emitting efficiency (external quantum efficiency η _ex ) of the GaN-based light emitting device decreases with an increase in current density. For this reason, in Invention Example A, it is considered that the decrease in luminous efficiency is suppressed by keeping the current density low.

  In this example, each of Invention Example C and Comparative Example D were prepared by the following method, and the luminance of white light emission was compared.

(Invention Sample C)
Using the manufacturing method shown in the following (c1) to (c13), the light-emitting element shown in Embodiment 1 that emits yellow and blue light from each of the two light-emitting layers was manufactured.

  (C1) to (c3) The same treatment as (a1) to (a3) in Invention Example A was performed.

(C4) Next, the following laminated structure was formed on the Ga surface of the GaN regrowth layer using MOCVD. (Si-doped n-type GaN layer (GaN epitaxial layer) / Clad layer Si-doped n-type Al _0.2 Ga _0.8 N layer (n-type clad layer) / GaN layer and In _0.28 Ga _0.72 N layer have three layers) Stacked MQW (light emitting layer) / Mg-doped p-type Al _0.2 Ga _0.8 N layer (p-type clad layer) / Mg-doped p-type GaN layer (contact layer) of the clad layer) The emission wavelength of this MQW corresponds to 580 nm. .

  (C5) to (c13) The same treatment as (a5) to (a13) in Invention Example A was performed.

(Comparative Example D)
Using the manufacturing method shown in the following (d1) to (d11), a light-emitting element including one light-emitting layer and further including a fluorescent material for converting light from the light-emitting layer into white is manufactured. did.

  (D1) to (d8) The same processing as (b1) to (b8) in Comparative Example B was performed.

  (D9) Next, the chip was mounted so that the p-type GaN layer side of the chip was in contact with the mount portion of the lead frame. At this time, the light emitting device and the mount were fixed by a conductive adhesive applied to the mount portion, and electrical conduction was obtained. Next, a fluorescent material was mounted on the n-electrode side to form a light emitting device. As the fluorescent material, a fluorescent material capable of obtaining 180 lm (lumen) per watt when 450 nm light was output was used.

  (D10) to (d11) The same processing as (b10) to (b11) in Comparative Example B was performed.

  Next, each of Invention Example A and Comparative Example B produced by the above method were mounted in an integrating sphere, and a predetermined current was injected into the light emitting layer. Here, in Example C of the present invention, the amount of current injected into each of the two light emitting layers was appropriately adjusted to emit white light. The light emitted in this way was collected, and the luminance of the light output from the detector was measured.

  As a result, the luminance of white light per chip was 288 ml in Comparative Example D, whereas it was 317 ml in Invention Example C. Thus, it was found that Example C of the invention having two light emitting layers emits white light with higher luminance than Comparative Example D having only one light emitting layer.

  The difference in luminance between Example C of the present invention and Comparative Example D is considered to occur for the following reason. That is, in Comparative Example D, a part of the emitted blue light is converted into yellow light by the fluorescent material to realize white light emission, and thus the light emission efficiency is poor by the loss due to the conversion. On the other hand, in Example C of the present invention, white light emission is realized by mixing the emitted blue light and yellow light, so there is no loss due to color conversion as in Comparative Example D, and the light emission efficiency is good. High brightness can be obtained.

  The embodiments and examples disclosed above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

It is sectional drawing which shows the structure of LED in Embodiment 1 of this invention. It is a top view which expands and shows the laminated structure of FIG. It is sectional drawing which follows the III-III line of FIG. It is sectional drawing which shows the 1st process of the manufacturing method of LED in Embodiment 1 of this invention. It is the B section enlarged view of FIG. It is sectional drawing which shows the 2nd process of the manufacturing method of LED in Embodiment 1 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of LED in Embodiment 1 of this invention. It is sectional drawing which shows the 4th process of the manufacturing method of LED in Embodiment 1 of this invention. It is a top view which shows the 5th process of the manufacturing method of LED in Embodiment 1 of this invention. It is sectional drawing which follows the XX line of FIG. It is a top view which shows the 6th process of the manufacturing method of LED in Embodiment 1 of this invention. It is sectional drawing which follows the XII-XII line | wire of FIG. (A) It is a top view which shows the structure of the laminated structure in Embodiment 2 of this invention. (B) It is the C section enlarged view of (a). It is sectional drawing which shows the structure of the laminated structure in Embodiment 3 of this invention. It is a top view which shows the 1st process of the manufacturing method of LED in Embodiment 3 of this invention. It is sectional drawing which follows the XVI-XVI line | wire of FIG. It is sectional drawing which shows the 2nd process of the manufacturing method of LED in Embodiment 3 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of LED in Embodiment 3 of this invention. It is sectional drawing which shows the structure of the laminated structure in Embodiment 4 of this invention. It is sectional drawing which shows the structure of the laminated structure in Embodiment 5 of this invention. It is sectional drawing which shows the structure of the laminated structure in Embodiment 6 of this invention. It is a figure which shows the relationship between the current density J and external quantum efficiency (eta) _ex in a GaN-type light emitting element.

Explanation of symbols

  1 GaN substrate, 1a, 1b GaN substrate main surface, 1c, 2a, 10a, 12a, 30a groove, 2,12 GaN epitaxial layer, 3,13 n-type cladding layer, 4,14 light emitting layer, 5,15 p-type cladding Layer, 6, 16 contact layer, 9a, 9b, 9d p electrode, 9cn electrode, 10 inversion layer, 10b inversion layer surface, 10c outermost surface, 11 GaN regrowth layer, 11a GaN regrowth layer surface, 21a mount part, 21b, 21c Lead part, 22 Insulator, 23a, 23b Wire, 25 Epoxy resin, 26, 27 Element isolation groove, 28 Control device, 29 Mask layer, 30 High-concentration GaN layer, 50, 50a to 50d Multilayer structure, A Chip boundary.

Claims (9)

A GaN substrate in which one principal surface is constituted by an N surface and the other principal surface is constituted by a Ga surface;
A GaN layer formed on the N-face or N-face side of the GaN substrate and having a surface constituted by a Ga face can be epitaxially grown on the N-face of the GaN substrate, and the inversion has sufficient light transmittance. Layers,
A GaN layer formed adjacent to the surface of the inversion layer and having a surface constituted by a Ga surface;
A first light emitting layer that is formed on the one main surface side of the GaN substrate at a position farther from the GaN layer when viewed from the GaN substrate, and emits light by current injection;
A second light emitting layer formed on the other main surface side of the GaN substrate and emitting light by current injection ;
The inversion layer is an inversion layer formed by roughening the one main surface of the GaN substrate, Al, In, Au, Pt, Cr, and Fe formed on the one main surface side of the GaN substrate. An inversion layer made of at least one metal selected from the group consisting of, and an inversion made of GaN formed on the one main surface side of the GaN substrate by MOCVD at a temperature of 400 ° C. to 800 ° C. any der Ru, light emitting elements of the layers.   2. The light emitting device according to claim 1, wherein one of yellow and blue light is emitted from the first light emitting layer, and one of yellow and blue light is emitted from the second light emitting layer.   The light emitting device according to claim 2, wherein the distribution of the current injected into the first light emitting layer and the current injected into the second light emitting layer can be adjusted. An electrode electrically connected to the GaN substrate;
A high-concentration GaN layer formed adjacent to the GaN substrate and having an impurity concentration higher than that of the GaN substrate;
The light emitting device according to claim 1, wherein the electrode is formed adjacent to the high concentration GaN layer. An electrode electrically connected to the GaN substrate;
The light emitting device according to claim 1, wherein the electrode is formed adjacent to the other main surface of the GaN substrate. A step of preparing a GaN substrate in which one principal surface is constituted by an N surface and the other principal surface is constituted by a Ga surface;
A GaN layer whose surface is constituted by a Ga surface can be epitaxially grown on the N surface of the GaN substrate, and an inversion layer having sufficient light transmittance is formed on the N surface or the N surface side of the GaN substrate. An inversion layer forming step,
A GaN layer forming step of epitaxially growing a GaN layer whose surface is constituted by a Ga surface from the surface of the inversion layer;
Forming a first light emitting layer that emits light by current injection at a position away from the GaN layer when viewed from the GaN substrate on the one main surface side of the GaN substrate;
Forming a second light emitting layer that emits light by injecting current on the other main surface side of the GaN substrate,
In the inversion layer forming step, the by roughening the one main surface of the GaN substrate, and forming the inversion layer on the one main surface of the GaN substrate, the manufacturing method of the light emission element. A step of preparing a GaN substrate in which one principal surface is constituted by an N surface and the other principal surface is constituted by a Ga surface;
A GaN layer whose surface is constituted by a Ga surface can be epitaxially grown on the N surface of the GaN substrate, and an inversion layer having sufficient light transmittance is formed on the N surface or the N surface side of the GaN substrate. An inversion layer forming step,
A GaN layer forming step of epitaxially growing a GaN layer whose surface is constituted by a Ga surface from the surface of the inversion layer;
Forming a first light emitting layer that emits light by current injection at a position away from the GaN layer when viewed from the GaN substrate on the one main surface side of the GaN substrate;
Forming a second light emitting layer that emits light by injecting current on the other main surface side of the GaN substrate,
In the inversion layer forming step, the inversion layer made of at least one metal selected from the group consisting of Al, In, Au, Pt, Cr, and Fe is formed on the one main surface side of the GaN substrate. wherein the method of manufacturing a light emission device. A step of preparing a GaN substrate in which one principal surface is constituted by an N surface and the other principal surface is constituted by a Ga surface;
A GaN layer whose surface is constituted by a Ga surface can be epitaxially grown on the N surface of the GaN substrate, and an inversion layer having sufficient light transmittance is formed on the N surface or the N surface side of the GaN substrate. An inversion layer forming step,
A GaN layer forming step of epitaxially growing a GaN layer whose surface is constituted by a Ga surface from the surface of the inversion layer;
Forming a first light emitting layer that emits light by current injection at a position away from the GaN layer when viewed from the GaN substrate on the one main surface side of the GaN substrate;
Forming a second light emitting layer that emits light by injecting current on the other main surface side of the GaN substrate,
In the inversion layer forming step, and forming the inversion layer of GaN by MOCVD at a temperature of 400 ° C. or higher 800 ° C. or less to the one main surface of the GaN substrate, light emission element Manufacturing method. The GaN layer formation step, and a step of forming a mask layer so as to cover the portion not forming the GaN layer, the manufacturing method of the light emitting device according to any one of claims 6-8.

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