JP2011040555A - Light emitting device - Google Patents

Abstract

In a light emitting device having a structure in which a light emitting layer is laminated on a sapphire layer, light is efficiently emitted from within the sapphire layer.
In a light emitting device in which a light emitting layer 3 is laminated on a sapphire layer 2, a structure changing region 10 such as a crack for changing the propagation direction of a light beam L is provided in the vicinity of the back surface 2b and the side surface 2c of the sapphire layer 2. It is formed by laser light. By entering the structure change region 10, the incident angle of the light beam L to the interface between the sapphire layer 2 and air is set within the critical angle θ and transmitted through the interface.
[Selection] Figure 2

Description

  The present invention relates to a light emitting device such as a light emitting diode used for a backlight of a display, an LED display or the like.

  As a light emitting device such as a light emitting diode (LED), a device in which a light emitting layer is laminated on the surface of a sapphire substrate is provided (Patent Document 1). Such a light-emitting device is manufactured by being divided into a large number of light-emitting devices by laminating a large number of light-emitting layers on the surface of a sapphire substrate, which is a parent substrate, and cutting the streets between the light-emitting layers of the sapphire substrate. The

  Conventionally, as a method of cutting and dividing a substrate such as a sapphire substrate along a street, a laser beam is formed by irradiating a pulse laser beam along the street, and an external force is applied to the laser beam. A method of cleaving a substrate is known (Patent Document 2). In addition, a pulsed laser beam with transparency is irradiated to the inside of the substrate with the focusing point aligned, and an altered layer along the street is continuously formed inside, and an external force is applied to the street where the strength is reduced by this altered layer. There has also been proposed a method of cleaving a substrate by giving (Patent Document 3).

JP-A-10-56203 JP-A-10-305420 Japanese Patent No. 3408805

  In a light emitting device having a structure in which a light emitting layer is laminated on the surface of a sapphire layer such as the sapphire substrate, light emitted from the light emitting layer is emitted to the sapphire layer, and the light passes through the sapphire layer and is emitted into the air. Is done. By the way, the refractive index of sapphire is quite large, which has caused the following problems. That is, the light beam emitted from the light emitting layer to the sapphire layer is reflected without passing through the interface between the sapphire layer and the layer adjacent to the sapphire layer, and the light beam is confined in the sapphire layer, so that the light beam is efficiently sapphire. The problem is that the light is not emitted from the layer.

  This invention is made | formed in view of the said situation, and it aims at providing the light-emitting device from which a light ray is radiate | emitted efficiently from the inside of a sapphire layer.

  The present invention is a light emitting device having a sapphire layer and a light emitting layer laminated on the sapphire layer to emit light to the sapphire layer, and the sapphire layer is emitted from the light emitting layer in the sapphire layer It is characterized in that a structural change region for changing the propagation direction of the light beam is formed by laser light.

  According to the present invention, the incident angle with respect to the interface between the sapphire layer and the layer adjacent to the sapphire layer is displaced to an angle at which the light can pass through the interface by changing the propagation direction of the light beam in the sapphire layer by the structural change region. As a result, the amount of light emitted from the sapphire layer can be increased.

  In the present invention, the sapphire layer has a back surface that is the surface opposite to the light emitting layer and a side surface that extends from the back surface to the light emitting layer, and in the vicinity of the back surface of the sapphire layer and / or the It is preferable that the structure change region is formed in the vicinity of the side surface.

  As the form of the structure change region of the present invention, cracks that scatter light rays and refractive index change regions that refract light rays are effective.

  According to the present invention, there is an effect that it is possible to provide a light emitting device in which light is efficiently emitted from the sapphire layer.

It is a perspective view which shows typically the light-emitting device of one Embodiment of this invention. It is sectional drawing which shows typically the state which the light ray has permeate | transmitted the inside of the sapphire layer of the light-emitting device of one Embodiment. It is sectional drawing which shows typically the state which the light ray has permeate | transmitted the inside of the sapphire layer of the conventional light emitting device. It is a side view which shows an example of the method of forming a structure change area | region in a sapphire layer by laser beam irradiation. It is a side view which shows typically a mode that the structure change area | region is formed in the back surface vicinity of a sapphire layer by laser beam irradiation. (A) The side view which shows typically a mode that the structure change area | region is formed in the side surface vicinity of a sapphire layer by laser beam irradiation, (b) is bb arrow sectional drawing of (a).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows a light-emitting device according to an embodiment. The light emitting device 1 has a configuration in which a light emitting layer 3 is laminated on a surface 2a of a sapphire layer 2 as a substrate. In the light emitting device 1, a large number of light emitting layers 3 are stacked on the surface of a sapphire substrate (not shown) which is a parent substrate divided into sapphire layers 2, and the sapphire substrate is cut and divided along the streets between the light emitting layers 3. Can be obtained. The sapphire substrate is cut by, for example, a method of cleaving by applying an external force after the above-described laser processing groove formation or after formation of a deteriorated layer by laser light.

  The light emitting layer 3 is generally known as this kind of material, and is composed of, for example, a band gap layer or a quantum well, but is not limited thereto. Or a compound composed of an II-VI group element, for example, indium gallium nitride (InGaN), gallium nitride (GaN), gallium arsenide (GaAs), gallium indium nitride (GaInN), aluminum gallium nitride (AlGaN), selenide The light-emitting element includes any one of zinc (ZnSe), zinc-doped indium gallium nitride (InGaN: Zn), aluminum indium gallium phosphide (AlInGaP), or gallium phosphide (GaP). Examples of the light emitting element containing any of these materials include the light emitting diodes and EL (Electro Luminescence) elements.

  According to the light emitting device 1, when the light emitting layer 3 emits light, the light emitted from the light emitting layer 3 passes through the sapphire layer 2 and is emitted outside the sapphire layer 2 (for example, in the air). The sapphire layer 2 has a rectangular parallelepiped shape, and a back surface 2b parallel to the surface 2a is formed on the side opposite to the surface 2a on which the light emitting layer 3 is laminated. Further, four side surfaces 2c extending from the back surface 2b to the light emitting layer 3 are formed between the back surface 2b and the front surface 2a. Light rays emitted from the light emitting layer 3 to the sapphire layer 2 are emitted from the back surface 2b and the side surfaces 2c.

  In the present embodiment, the structure change region 10 according to the present invention is formed in the vicinity of the back surface 2b and the side surface 2c of the sapphire layer 2 (see FIG. 2). The structure change region 10 has a function of changing the propagation direction of the light beam L emitted from the light emitting layer 3 to the sapphire layer 2. For example, a crack that scatters the light beam L is suitable. As another form of the structural change region 10, there is a refractive index change region that refracts the light beam L transmitted through the sapphire layer 2.

  FIG. 2 shows an example in which the structure change region 10 is formed in the vicinity of one side surface 2 c ′ of the sapphire layer 2. Since the crack structure change region 10 is formed, the amount of light L emitted from the sapphire layer 2 increases. The reason for this will be described. As shown in FIG. 3, when the light beam L is incident on the side surface 2c in the sapphire layer 2, the light beam L passes through the side surface 2c, that is, the interface between the sapphire layer 2 and air, for example. The critical angle θ that can be emitted into the inside is relatively small, about 34.5 °, based on the refractive indexes of the two. If the light beam L is incident on the side surface 2c at an angle within the critical angle θ, the light beam L is transmitted through the side surface 2c, but the light beam L incident on the side surface 2c at an angle equal to or greater than the critical angle θ is reflected. And depending on the case, a reflection angle is preserve | saved and reflection will be repeated and eventually it will be quenched in the sapphire layer 2.

  Therefore, when the structural change region 10 is formed in the vicinity of the side surface 2c ′ as shown in FIG. 2, the light beam that is reflected in the sapphire layer 2 and is about to enter the side surface 2c ′ is reflected on the side surface 2c ′. It enters the structural change region 10 before this. The light beam L incident on the structure change region 10 is scattered and enters the side surface 2c at a transmission angle that is within the critical angle θ with respect to the side surface 2c ′. For this reason, the reflection angle of the light beam L incident on the structure change region 10 is eliminated, and the light beam L is transmitted through the side surface 2c 'and emitted from the sapphire layer 2 into the air. In this way, if the structural change region 10 does not exist, the light beam L that has been quenched can be emitted from the sapphire layer 2 by entering the structural change region 10 and being scattered. The amount of light L emitted from the sapphire increases, and the light L is efficiently emitted from the sapphire layer 2.

  By the way, in the light-emitting device 1, due to the shape of the sapphire layer 2, the structure of the light-emitting device 1 itself, etc., the amount of light emission (the amount of light L emitted) at each location in the back surface 2b and each side surface 2c. The distribution may not be constant. In that case, after examining the light emission amount on the back surface 2b and each side surface 2c, the structure change region 10 is located in the vicinity of the back surface 2b and each side surface 2c with a small light emission amount (for example, a region from the surface to a depth of about 10 μm). Form. As a result, the structure change region 10 can be formed at a location where a large amount of light reaching the back surface 2b and the side surfaces 2c from outside the critical angle θ can be formed. As a result, the light beam L from the sapphire layer 2 can be efficiently formed. The emission efficiency can be improved.

  The structure change region 10 is formed by laser light irradiation, and can be suitably formed by irradiating a pulse laser (including femtosecond laser) having a pulse width of 100 ps (picosecond) or less. In order to form the structure change region 10 by laser light irradiation, as shown in FIG. 4, a large number of light emitting layers 3 are formed on the surface (lower surface in FIG. 4) of the sapphire substrate 2 </ b> A constituting the sapphire layer 2. It can be performed by condensing the laser beam B irradiated from the back surface side of the sapphire substrate 2A into the sapphire substrate 2A before being divided into the light emitting devices 1.

  FIG. 5 schematically shows a state in which the structure change region 10 is formed by irradiating the laser beam B in the vicinity of the back surface 2c of the sapphire layer 2 (the back surface of the sapphire substrate 2A) with the method shown in FIG. ing. In order to form the structure change region 10 in the vicinity of the back surface 2c, the condensing point of the laser beam B is set in the vicinity of the back surface 2b, and the structure change region 10 is formed by scanning the laser beam B in parallel with the back surface 2b. can do.

  FIGS. 6A and 6B are schematic views showing that the structure change region 10 is formed by irradiating the vicinity of the side surface 2c of the sapphire layer 2 with the laser beam B by the method shown in FIG. It shows. In order to form the structural change region 10 in the vicinity of the side surface 2c, as shown in FIG. 6B, the condensing point of the laser beam B to be scanned is gradually made closer from the side farther from the irradiation side of the laser beam B. That is, when irradiation is performed while moving in a stepwise direction in the direction of the arrow P, the laser beam B is condensed without being affected by the previously formed structural change region 10, and a plurality of structural change regions 10 are provided with a certain quality near the side surface 2c. Can be formed. The formation of the structural change region 10 by irradiating the side surface 2c with the laser beam may be formed simultaneously with the irradiation of the laser beam to cut the sapphire substrate 2A.

DESCRIPTION OF SYMBOLS 1 ... Light emitting device 2 ... Sapphire layer 2a ... Front surface 2b ... Back surface 2c, 2c '... Side surface 3 ... Light emitting layer 10 ... Structure change area L ... Light beam

Claims (4)

A light-emitting device having a sapphire layer and a light-emitting layer laminated on the sapphire layer to emit light to the sapphire layer,
The sapphire layer has a structure change region for changing a propagation direction of the light beam emitted from the light emitting layer formed in the sapphire layer by a laser beam. The sapphire layer has a back surface that is a surface opposite to the light emitting layer, and a side surface that extends from the back surface to the light emitting layer.
The light emitting device according to claim 1, wherein the structural change region is formed in the vicinity of the back surface and / or the side surface of the sapphire layer.   The light emitting device according to claim 1, wherein the structural change region is a crack that scatters the light beam.   The light emitting device according to claim 1, wherein the structural change region is a refractive index change region that refracts the light beam.

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