JPH0897500A - Light emitting device and laser crt employing the same - Google Patents

Abstract

PURPOSE: To provide a light emitting device whose manufacturing process can be simplified and which is highly reliable and a laser CRT employing the light emitting device. CONSTITUTION: A light emitting device 1 has an active layer made of AlGaInN system compound semiconductor and reflective layers 3 and 4 which are provided at least on one of the sides of the active layer 2 and are made of AlGaInN system compound semiconductor. In a laser CRT, an electron beam is applied to the light emitting device 1 as a target and a light having a required wavelength is applied to a screen to obtain a picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device having an AlGaInN-based active layer and a reflective layer, and a laser CRT using the same.

[0002]

2. Description of the Related Art Conventionally, a light emitting element having a structure in which an active layer, which is a light emitting region, and two multilayer reflective layers are sandwiched is known as an optical device capable of highly efficient laser oscillation with a small excitation energy. It is also considered to be used as a target of a laser CRT. For example, GaA
In a light emitting device having a structure in which an active layer made of s is sandwiched between multilayer reflective layers made of AlAs / GaAs, laser light having a wavelength in the infrared region can be oscillated. Also, II-IV
When an active layer made of ZnCdSe, CdSSe or the like belonging to the group is used, laser light having a wavelength in the blue-green region can be oscillated. In the laser CRT, electron beam excitation is performed by using such a light emitting element as a target, and red, green,
A screen is irradiated with the three primary colors of blue to obtain a desired color image.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In a light emitting device using dSe or the like, the active layer Z
A reflective layer material that lattice-matches nCdSe has not been considered, which is a problem in forming an element. Further, in the laser CRT, it is necessary to bond and fix the light emitting element to the support base, which causes a complicated manufacturing process and an increase in cost. Moreover, the epoxy-based adhesive that is usually used as the bonding layer has a low thermal conductivity, and it is difficult to release the heat generated from the light emitting element to the support base side, resulting in deterioration of characteristics due to temperature rise of the light emitting element and shortening of life. It becomes a factor to invite. When the thickness of the light emitting element is shorter than the range of incident electrons, the incident electrons reach the bonding layer and modify the epoxy adhesive, which deteriorates the light transmission and shortens the life of the light emitting element. It becomes a factor to invite.

Therefore, according to the present invention, a light emitting device which can simplify the manufacturing process and has high reliability, and a laser C using the same.
The purpose is to provide RT.

[0005]

The present invention is a light emitting device and a laser CRT using the same which are made to achieve the above object. That is, the present invention relates to AlGaIn
A light-emitting device comprising an N-based active layer and an AlGaInN-based reflective layer provided on at least one side of the active layer, wherein the light-emitting device is irradiated with an electron beam to emit light of a predetermined wavelength. It is a laser CRT that illuminates a screen to obtain an image.

[0006]

In the light emitting device of the present invention, since the AlGaInN system is used as the active layer and the reflection layer, the active layer and the reflection layer can be lattice-matched and a wide range of visible light to ultraviolet light can be obtained. Can be emitted. Further, in the laser CRT of the present invention, since the light emitting element composed of AlGaInN of the same system having the composition ratio corresponding to each color is used as the target for emitting the three primary colors of red, green and blue, the target material can be made common. The manufacturing process can be simplified. Moreover, since a material capable of stacking and molding AlGaInN-based light emitting elements can be used as the support base for supporting the target, the light emitting elements can be provided on the support base without the interposing of the bonding layer.

[0007]

EXAMPLES Examples of a light emitting device of the present invention and a laser CRT using the same will be described below with reference to the drawings. FIG. 1 is a basic configuration diagram illustrating a light emitting device according to the present invention. That is, the light emitting element 1 includes an active layer 2 which is a light emitting region for generating light of a predetermined wavelength, reflective layers 3 and 4 provided, for example, in a state of sandwiching the active layer 2, and a support base for holding these. And the substrate 5 which is the above, and the active layer 2 and the reflective layers 3 and 4 are each made of AlGaInN system.

The AlGaInN-based active layer 2 and the reflective layers 3 and 4 have different composition ratios. The reflective layer 4, the active layer 2 and the reflective layer 3 are formed on the substrate 5 in this order, for example, by MOCVD (organic metal). Chemical vapor deposition) and MBE
They are stacked by (molecular beam growth method). In other words, each layer is of the same type composed of AlGaInN type,
It becomes possible to form a defect-free layer by lattice matching. Moreover, by lattice matching, each layer is not restricted by the critical film thickness, and the film thickness can be set freely.

Further, by using the AlGaInN system,
Substrates 5 on which these can be stacked and formed, for example Al ₂ O ₃ , Z
It becomes possible to use nO, GaAs, and SiC. This eliminates the need to attach the element portion including the active layer 2 and the reflection layers 3 and 4 onto the substrate 5 via the epoxy adhesive. That is, the element portion can be directly grown on the substrate 5, and the heat generated from the element portion can be easily released to the substrate 5 side. In addition, AlGa
By using the active layer 2 and the reflective layers 3 and 4 made of InN, it is possible to configure the light emitting element 1 that can emit a wide range of light from the entire visible light region to the ultraviolet region by selecting the composition ratio thereof.

Next, a specific example of the light emitting device 1 of the present invention
Will be explained. FIG. 2 is a specific example of the light emitting device 1 of the present invention.
It is a schematic diagram explaining. In this light emitting element 1,
Al as the active layer 21_xGa_yIn_1-xyN (0 ≦ x <
1, 0 ≦ y ≦ 1) and Al is used as the reflective layer 31._x1Ga
_y1In_1-x1-y1N, Al_x2Ga_y2In_1-x2-y2Made up of N
Using a multilayer film of_x3Ga_y3In
_1-x3-y3N, Al_x4Ga_y4In_1-x4-y4Multilayer consisting of N
It uses a membrane. It is possible to set x and y of this active layer 21.
And the direct transition type bandgap energy at room temperature
Can be 1.95 eV or more and less than 6.2 eV
It

When the active layer 21 is excited by current, the reflection layer 31 is of p-type or n-type, and the reflection layer 41 is of n-type or p-type. For example, Mg is used as the p-type dopant, and Si is used as the n-type dopant. Further, the multilayer film forming the reflection layers 31 and 41 is in a state in which layers having a larger bandgap and layers having a larger bandgap than the active layer 21 are alternately arranged to enhance the light confinement effect. I am trying.

Each of these layers is manufactured by MOCVD or MBE, for example. The reflective layers 31 and 41 of the same type are lattice-matched with the active layer 21, and it is possible to provide the light emitting device 1 capable of emitting light with high efficiency without defects. For example, electrons and holes are supplied into the active layer 21 by injecting a current into the active layer 21 from the reflective layers 31 and 41 side,
As a result, laser light is emitted in a direction parallel to the stacking direction.

As the active layer 21, hexagonal Al _x Ga _y
When In _1-xy N is used, the band gap energy E _g (eV) at room temperature is given by Equation 1.

[0014]

[Number 1] _{E g = 1.95 (1-y} ) + 3.40y-y (1-y) 1.05

Hexagonal Al _x Ga _y I at room temperature
The a-axis lattice constant (nm) of n _1-xy N is given by Equation 2 according to Vegard's law.

[0016]

## EQU00002 ## 0.3112x + 0.3160y + 0.3544 (1-xy)

Next, an example in which the light emitting element 1 is constructed as a red laser diode will be described. In this case, for example, the active layer _{21 Al x Ga y In 1-} xy N
(X = 0, y = 0.1) is used. The reflective layer 31 has a composition ratio of Al _x1 Ga _y1 In _1-x1-y1
Stacking the N and _{Al x2 Ga y2 In 1-x2} -y2 N alternately. Here, x2>x1> 0, and the thickness of each layer is a value obtained by further dividing a quarter of the emission wavelength by the refractive index of each layer.

[0018]

## EQU00003 ## 0.432x _i + 0.384y _i = 0.0384 (i = 1,2)

The reflective layer 41 is composed of Al _x3 Ga _y3 In _1-x3-y3 N and Al _x4 Ga _y4 In having a composition ratio satisfying the formula (4).
Alternately stack _1-x4-y4 N. Here, x4>
x3> 0, and the thickness of each layer is a value obtained by dividing a quarter of the emission wavelength by the refractive index of each layer.

[0020]

(4) 0.432x _i + 0.384y _i = 0.0384 (i = 3,4)

By setting the total number of the reflection layers 31 and 41, the reflectance for the light of the emission wavelength can be selected. In addition, since the bandgap energy of the reflective layers 31 and 41 is larger than the bandgap energy of the active layer 21, carriers are confined in the active layer 21, and the light emitting efficiency of the light emitting element 1 can be improved. For example, x _i = 0.010, y _i = 0.08
9 (i = 1, 3), x _i = 0.089, y _i = 0
By forming the reflection layers 31 and 41 as (i = 2, 4) and exciting the light emitting element 1 with current, red laser light having a wavelength of about 620 nm can be obtained.

Next, the light emitting element 1 is replaced with a green laser diode.
An example in the case of configuring as will be described. In this case,
As the active layer 21, for example, Al_xGa_yIn_1-xyN
(X = 0, y = 0.46) is used. In addition, with the reflective layer 31
Then, Al with a composition ratio satisfying the formula 5 _x1Ga_y1In_1-x1-y1
N and Al_x2Ga_y2In_1-x2-y2Alternately stack N
It Note that here, x2> x1> 0, and the thickness of each layer is
Divide one quarter of the emission wavelength by the refractive index of each layer.
Value.

[0023]

## EQU5 ## 0.432x _i + 0.384y _i = 0.177 (i = 1, 2)

The reflective layer 41 is composed of Al _x3 Ga _y3 In _1-x3-y3 N and Al _x4 Ga _y4 In having a composition ratio satisfying the formula (6).
Alternately stack _1-x4-y4 N. Here, x4>
x3> 0, and the thickness of each layer is a value obtained by dividing a quarter of the emission wavelength by the refractive index of each layer.

[0025]

(6) 0.432x _i + 0.384y _i = 0.177 (i = 3,4)

By setting the total number of the reflection layers 31 and 41, the reflectance with respect to the light of the emission wavelength can be selected. Further, since the bandgap energy of the reflective layers 31 and 41 is larger than the bandgap energy of the active layer 21, carriers are confined in the active layer 21 as described above, and the luminous efficiency of the light emitting element 1 is improved. Will be able to. For example, x _i = 0.0
10, y _i = 0.450 (i = 1, 3), and x _i =
Reflection layer 3 with 0.409, y _i = 0 (i = 2, 4)
The green laser light having a wavelength of about 525 nm can be obtained by configuring the elements 1 and 41 and exciting the light emitting element 1 with current.

Next, the light emitting element 1 is replaced with a blue laser diode.
An example in the case of configuring as will be described. In this case,
As the active layer 21, for example, Al_xGa_yIn_1-xyN
(X = 0, y = 0.67) is used. In addition, with the reflective layer 31
Then, Al having a composition ratio satisfying Equation 7 _x1Ga_y1In_1-x1-y1
N and Al_x2Ga_y2In_1-x2-y2Alternately stack N
It Note that here, x2> x1> 0, and the thickness of each layer is
Divide one quarter of the emission wavelength by the refractive index of each layer.
Value.

[0028]

(7) 0.432x _i + 0.384y _i = 0.257 (i = 1,2)

The reflective layer 41 is composed of Al _x3 Ga _y3 In _1-x3-y3 N and Al _x4 Ga _y4 In having a composition ratio satisfying the formula (8).
Alternately stack _1-x4-y4 N. Here, x4>
x3> 0, and the thickness of each layer is a value obtained by dividing a quarter of the emission wavelength by the refractive index of each layer.

[0030]

(8) 0.432x _i + 0.384y _i = 0.257 (i = 3,4)

By setting the total number of the reflection layers 31 and 41, the reflectance with respect to the light of the emission wavelength can be selected. Further, since the bandgap energy of the reflective layers 31 and 41 is larger than the bandgap energy of the active layer 21, carriers are confined in the active layer 21 as described above, and the luminous efficiency of the light emitting element 1 can be improved. Like For example, x _i = 0.010, y _i
= 0.658 (i = 1,3), x _i = 0.59
5, y _i = 0 (i = 2, 4), the reflective layers 31 and 41 are formed, and the light emitting element 1 is excited by current to generate a wavelength of 46
A blue laser light of about 0 nm can be obtained.

Next, an example of a specific structure of such a light emitting device 1 will be described with reference to FIG. 3A and 3B are diagrams showing an example of a specific structure, FIG. 3A is a sectional view, and FIG. 3B is a plan view. As shown in FIG. 3A, this light emitting element 1 has
For example, the reflection layer 41 is laminated on the substrate 5 made of Al ₂ O ₃ , ZnO, GaAs, and SiC, and the active layer 21 and the reflection layer 31 are laminated on the upper surface of the reflection layer 41 in a convex shape in cross section. ing. The active layer 21 and the reflective layer 31 are circular in plan view as shown in FIG. 3B, for example. That is, it has a cylindrical shape as a whole. Note that this shape is not limited to the cylindrical shape.

Further, the p-electrode 6 made of, for example, Au is provided on the upper surface of the cylindrical reflection layer 31, and the n-electrode 7 made of, for example, Al is provided on the upper surface of the reflection layer 41 around the columnar portion. It is provided. By injecting a current into the active layer 2 by the p-electrode 6 and the n-electrode 7, it becomes possible to surface-emit predetermined light toward the p-electrode 6 side or the substrate 5 side.

Here, the substrate 5 is made of Al ₂ O ₃ , ZnO, S.
In the case of a material such as iC that has a sufficient transparency to visible light, light can be extracted from the substrate 5 side, so p
There is no limitation on the thickness of the electrode 6, but when the material is made of a material such as GaAs that has insufficient transparency to visible light, the p-electrode 6 should be sufficiently thin (to allow visible light to pass). deep. In the latter case, when the p-electrode 6 is made of Au, the thickness is set to, for example, several tens of nm, and light is extracted from there. Even when the substrate 5 having a light-transmitting property is used, the p-electrode 6 may be provided thinly and light may be extracted therefrom. With such a configuration, both the reflection type and the transmission type light emitting elements 1 can be dealt with.

In each of the examples shown in FIGS. 1 to 3, the active layers 2 and 21 are the reflection layers 3 and 31 and the reflection layers 4 and 41.
Although the case where the reflective layer is provided on at least one of the active layers 2 and 21 has been described, the same applies to the present invention. For example, in the case of a light emitting diode which is not required to have a very high reflectance, it may have a structure in which a reflecting layer is provided on only one side. In addition, a buffer layer (not shown) made of GaN or AlN may be provided between the substrate 5 and the reflective layers 4 and 41 so as to prevent the generation of lattice defects.

Next, an example of the laser CRT according to the present invention will be described with reference to FIG. FIG. 4 is a schematic sectional view illustrating a laser CRT according to the present invention. The laser CRT 10 in this example is a target 12 which emits laser light of three primary colors of red, green and blue by electron beam excitation.
3 and 14, the light-emitting element 1 (FIG. 1, FIG. 2,
(See FIG. 3).

That is, the target 12 for emitting red laser light, the target 13 for emitting green laser light, and the target 14 for emitting blue laser light are made of Al having a composition ratio corresponding to each color.
The light emitting device 1 (see FIGS. 1, 2 and 3) made of a GaInN system is used to excite each target 12, 13, 14 with an electron beam.

In the laser CRT 10 shown in FIG. 4, since the targets 12, 13 and 14 are transmissive, the substrate 5 of the light emitting element 1 (see FIGS. 1, 2 and 3) is sufficient for visible light. A transparent material such as Al ₂ O ₃ or Zn
O, SiC or the like is used. However, the light emitting device 1 used as the targets 12, 13, and 14 of the laser CRT 10
Then, since the light is emitted by the electron beam excitation, the reflection layers 3 and 31
The reflection layers 4 and 41 (see FIGS. 1, 2, and 3) need not be p-type or n-type.

In order to obtain a desired image with the laser CRT 10, the electrons emitted from the cathode 11a are deflected by the deflection yoke 1.
It is deflected by 1b and applied to the target 11, and the green laser beam is irradiated onto the screen 14 from here. Further, the electrons emitted from the cathode 12a are deflected by the deflection yoke 12b and applied to the target 12, and the red laser light is irradiated onto the screen 14 from there. Furthermore, the cathode 13
Electrons emitted from a are deflected by the deflection yoke 13b and applied to the target 13, from which the blue laser light is applied to the screen 14.

In the laser CRT 10, each cathode 11
By adjusting the amount of current flowing through a, 12a, and 13a, laser light of a corresponding light amount, that is, a predetermined light amount of green, red, and blue laser light is emitted from the targets 11, 12, and 13 and the ratio is adjusted. Color image on screen 14
Is reflected in. Moreover, each deflection yoke 11a, 11
The deflection of the electron beam by b and 11c is synchronized, and the target 11, 12, and 13 are scanned by the electron beam, so that a desired color image is displayed at a predetermined position on the screen 14.

With such a laser CRT 10, it is possible to obtain a high-luminance color image having a high luminous efficiency. Further, in the laser CRT 10 according to the present invention, all of the targets 11, 12 and 13 are made of AlGaI.
Since the light emitting element 1 of the same system made of nN is used, the materials, the crystal growth apparatus, and the like can be shared, and the manufacturing process can be simplified. In addition, as described above, in the light emitting device 1 shown in FIGS. 1 to 3, the element portion including the active layers 2 and 21, the reflection layers 3 and 31 and the reflection layers 4 and 41 is stacked and formed directly on the substrate 5. Therefore, a bonding layer made of an epoxy-based adhesive or the like is unnecessary. Therefore, by using such a light emitting element 1 as the targets 11, 12 and 13, a laser CR can be obtained.
It becomes possible to improve the heat dissipation of T10.

The numerical values such as the composition ratio, the lattice constant, and the wavelength of each layer shown in this embodiment are examples, and the present invention is not limited to this. In other words, the same applies if the active layers 2 and 21, the reflective layers 3 and 31, and the reflective layers 4 and 41 are made of AlGaInN and the composition ratio is selected according to the desired emission wavelength and reflection efficiency. Further, the light emitting element 1 is not limited to the laser diode, and for example, the active layer 2,
21, each of the reflection layers 3 and 31 and the reflection layers 4 and 41 is A
The same applies to a light emitting diode which is made of a material composed of 1GaInN system, has a composition ratio corresponding to a desired emission color selected, and is manufactured by adding impurities to each layer.

[0043]

As described above, the light emitting device of the present invention and the laser CRT using the same have the following effects. That is, according to the light emitting device of the present invention, by using AlGaInN-based materials for the active layer and the reflective layer, it is possible to set a desired direct transition type band gap while achieving lattice matching between the active layer and the reflective layer. It will be possible. This makes it possible to provide a light emitting element that can emit light with high efficiency.

Further, according to the laser CRT of the present invention in which such a light emitting element is used as a target, it is possible to obtain a high-luminance image, and at the same time, an element composed of an active layer and a reflective layer of the target light emitting element. Since the parts can be directly laminated on the support base (substrate), the manufacturing process can be simplified, and the productivity can be greatly improved and the cost can be reduced. Moreover, since the bonding layer between the element portion and the support base is not necessary, heat from the element portion can be easily released to the support base side, and the life of the laser CRT and the light emitting element can be extended. Is possible. Further, since it is not necessary to consider the influence of the bonding layer, each film thickness of the light emitting element can be freely selected, and it becomes possible to relax design restrictions. With these features, the manufacturing process can be simplified and the light emitting element and laser CR are highly reliable.
It becomes possible to provide T.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram illustrating a light emitting device of the present invention.

FIG. 2 is a schematic diagram illustrating a specific example of a light emitting element.

FIG. 3 is a diagram showing an example of a specific structure of a light emitting element,
(A) is sectional drawing, (b) is a top view.

FIG. 4 is a schematic sectional view illustrating a laser CRT according to the present invention.

[Explanation of symbols]

 1 Light-Emitting Element 2, 21 Active Layer 3, 31, 4, 41 Reflective Layer 5 Substrate 10 Laser CRT 11, 12, 13 Target 14 Screen

Claims (2)

[Claims] 1. An active layer made of AlGaInN system, and AlGaInN provided on at least one side of the active layer.
A light emitting device comprising a reflective layer made of a system. 2. A laser CRT for irradiating a target with an electron beam to emit light of a predetermined wavelength from the target and irradiating the screen with the light to obtain a desired image, wherein the target is the target. A laser CRT using the above light emitting device.