JP2002009402A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high luminance, high efficiency and light life in a light emitting device generating light in a visible region or white light. SOLUTION: In a semiconductor laser 25 having a light emitting region over a broad area, an N-Ga1-Z1 AlZ1 N/GaN superlattice clad layer 12, an N or I-GaN optical waveguide layer 13, an In1-Z2 GaZ2N (Si dope)/In1-Z3 GaZ3N multiple quantum well active layer 14, a P-Ga0.8Al0.2N carrier blocking layer 15, an N or I-GaN optical waveguide layer 16. a P-Ga1-Z1 AlZ1 N/GaN superlattice clad layer 17 and a P-GaN contact layer 18 are formed on an N-GaN (0001) substrate 11. The semiconductor laser 25 is used as a stimulation light source, an yttrium/aluminum/garnet based phosphor which is activated by cerium is used as a phosphor 32 which absorbs effectively blue light from the stimulating light source and can generate yellow light. Thereby a light emitting device is constituted.

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, and more particularly, to a phosphor in which visible light or white light composed of light from a light source and light emitted from the phosphor is obtained by exciting a phosphor with light from a light source. And a light-emitting device for obtaining

[0002]

2. Description of the Related Art Conventionally, as a visible light emitting device, an attempt has been made to obtain a multi-color emission or white color in the visible region by exciting a phosphor with an excitation light source. For example, in Japanese Patent Application Laid-Open No. 5-152609, a light emitting element made of a gallium nitride-based compound semiconductor is mounted on a stem, and a fluorescent dye or a fluorescent pigment that emits fluorescence when excited by light from the light emitting element is used. A light emitting diode surrounded by a resin mold to which the phosphor described above is added is disclosed. In addition,
Japanese Patent Application No. 11-199781 discloses a light emitting device having a configuration in which an LED chip that emits blue light is used as an excitation light source to excite a fluorescent substance such as a fluorescent dye or a fluorescent pigment that emits fluorescence having a wavelength longer than that wavelength.

[0003]

A semiconductor laser is an example of an LED that emits blue light. However, as a semiconductor laser of the 410 nm band, Jpn.J.Appl.Phys.Le.
tt., Vol.37.pp.L1020, InGaN / GaN / AlGaN-Based laser
Diodes Grown on GaN Substrates with Fundamental T
Although a ransverse mode is described, since only a transverse fundamental mode oscillation of about 30 mW is obtained, there is a problem that the electro-optical efficiency of the LED is as poor as several percent and the luminance is low.

On the other hand, a fluorescent lamp is a white light source used for lighting or the like. However, the life of the fluorescent lamp is as short as several thousand hours, and there is a problem that the use of mercury or the like is not environmentally friendly. In addition, there is a problem that the life of incandescent and the like is shorter and the energy efficiency is poor.

[0005] As described above, in order to obtain light in the visible region or white light, efficiency, brightness and life are not sufficient.

The present invention has been made in view of the above circumstances, and has as its object to provide a light-emitting device with high efficiency, high luminance, and long life.

[0007]

The light emitting device according to the present invention has a G
an excitation light source including a semiconductor laser having a broad-area emission region having an aN-based semiconductor as an active layer; and a fluorescent light that is excited by the excitation light source and emits fluorescence having a longer wavelength than the wavelength of light emitted from the excitation light source. And a body.

The semiconductor laser may be one in which a plurality of light emitting regions of a broad area are arranged one-dimensionally.

Further, the semiconductor laser may be one in which a plurality of light emitting regions of a broad area are arranged two-dimensionally.

The phosphor is preferably an yttrium-aluminum-garnet-based phosphor activated by a rare earth element.

The rare earth element is desirably at least one selected from the group consisting of Ce, Pr, Dy, Tb and Eu.

[0012] At least a part of the yttrium of the yttrium-aluminum-garnet-based phosphor activated by the rare earth element is substituted with at least one element selected from the group consisting of Lu, Sc, La, Gd and Sm. You may.

[0013] At least a part of the aluminum of the yttrium-aluminum-garnet phosphor activated by the rare earth element may be replaced by at least one element of Ga and In.

The above "broad area" indicates that the oscillation area width is 10 μm or more.

The above-mentioned "GaN-based" indicates that it contains at least Ga element and N element.

[0016]

According to the light emitting device of the present invention, an excitation light source comprising a semiconductor laser having a broad area light emitting region having a GaN-based semiconductor as an active layer, and an excitation light source excited by the excitation light source, Since the light emitting device has a configuration including a phosphor that emits fluorescence having a wavelength longer than the wavelength of the emitted light, light with high luminance, high efficiency, and long life can be obtained.

According to the semiconductor laser, a plurality of light emitting areas of a broad area are arranged in a one-dimensional manner.
Since a light source with high output can be obtained, light emitted from the phosphor can be obtained with higher luminance. Further, it can be used as a light source in a wide range.

Alternatively, since the semiconductor laser has a two-dimensional arrangement of a plurality of light emitting regions in a broad area, a higher output and a wider light source can be obtained, so that the light emitted from the phosphor is higher. Bright light can be obtained.

Since the phosphor is an yttrium-aluminum-garnet phosphor activated by a rare earth element, the phosphor emits visible light or white light by blue light of an excitation light source and yellow light emitted from the phosphor. Obtainable.

The rare earth elements are Ce, Pr, Dy, T
By using at least one selected from the group consisting of b and Eu, visible light or white light can be obtained.

At least a part of the yttrium of the yttrium-aluminum-garnet phosphor activated by the rare earth element is composed of Lu, Sc, La, Gd and Sm.
And may be substituted with one or more elements selected from the group consisting of, and light in the visible region or white light can be obtained.

At least a part of the aluminum of the yttrium-aluminum-garnet phosphor activated by the rare earth element may be replaced by at least one element of Ga and In, and light in the visible region or white light may be used. Can be obtained.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A light emitting device for obtaining white light according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of a semiconductor laser having a broad-area light emitting region used as an excitation light source of the light emitting device, and FIG. 2 is a schematic configuration diagram of the light emitting device.

First, a semiconductor laser having a broad-area light-emitting region, which is an excitation light source of the light-emitting device of the present invention, will be described.

As shown in FIG. 1, the metalorganic vapor phase epitaxy method
On the n-GaN (0001) substrate 11, n-Ga_1-z1
Al_z1N / GaN superlattice cladding layer 12 (0.05 <z1 <
1), n or i-GaN optical waveguide layer 13, In_1-z2Ga
_z2N (Si-doped) / In_1-z3Ga _z3N multiple quantum well active
Layer 14 (0.01 <z2 <0.05, 0.1 <z3 <0.3), p-Ga
_0.8Al_0.2N carrier blocking layer 15, n or i
-GaN optical waveguide layer 16, p-Ga_1-z1Al_z1N / GaN super
Forming a lattice cladding layer 17 and a p-GaN contact layer 18;
You. An insulating film 19 is formed and has a width of 5
A stripe region of about 00 μm is removed, and the p-side electrode 20 is removed.
To form Thereafter, the substrate is polished, and the n-side electrode 21 is
Form. After forming the resonator by cleavage,
And a low-reflection coating to make a chip
Finalize. In this semiconductor laser 25, an oscillating wave
The long band is a 440 nm band. Further, the light emitting region width is 500
μm, the resulting output is about 10 W
The air-light efficiency is between 8% and 50%.

Next, the phosphor constituting the light emitting device according to the present embodiment will be described.

As the phosphor constituting the light emitting device of the present embodiment, an yttrium aluminum garnet phosphor activated with cerium is used as a phosphor capable of efficiently absorbing blue light and emitting yellow light. be able to.

Next, the light emitting device of the present invention will be described with reference to FIG.

A semiconductor laser 25 as an excitation light source attached to a Cu block 31 and a yttrium-aluminum-garnet-based phosphor 32 activated with cerium are arranged as shown in FIG. Thereby, the semiconductor laser 25
Blue light from the phosphor 32 is efficiently absorbed by the phosphor 32,
Emits yellow light. Since the blue excitation light and the yellow light emitted from the phosphor are complementary colors to each other, white light can be obtained by mixing colors.

As the phosphor, a sintered body may be used, or the phosphor may be uniformly dispersed and mixed in a resin. Specifically, the resin is preferably a thermoplastic resin such as polyarylate resin, polycarbonate (PC) resin, or polyethylene terephthalate (PET) resin. 5wt in resin
% To about 50% by weight of the phosphor.

Since the semiconductor laser 25 is a semiconductor laser having a broad-area light emitting region, it has a high output. Further, since the electric-optical efficiency is 8% to 50%, the efficiency is high. Further, since the lifetime is as long as 10,000 hours or more, the light-emitting device according to this embodiment can obtain visible light or white light with high luminance, high efficiency, and long life.

The yttrium / aluminum / garnet-based phosphor is interpreted in a broad sense, and a part or all of yttrium is replaced with at least one element selected from the group consisting of Lu, Sc, La, Gd and Sm. Is also good. Also, part or all of aluminum is G
It may be substituted with at least one of a and In. More _{preferably, Ce: (Re 1-x} Sm x) 3 (Al y
Ga _1-y ) ₅ O ₁₂ (where 0 ≦ x <1, 0 ≦ y ≦ 1, and Re is at least one of Y and Gd). In order to emit yellow light, specifically, Ce: (Y _0.6 Gd _0.4 ) ₃
Al ₅ O ₁₂ is desirable. If the composition ratio of Gd is increased, the red component increases, and if the composition ratio of Gd is decreased, the green component can be increased. By changing the composition in this way, it is possible to continuously adjust the emission color. Alternatively, even when two or more kinds of phosphors having different substitution amounts of Y and Al are used in combination, light emission of various wavelengths in the visible region can be obtained.

Although the yttrium / aluminum / garnet-based phosphor has been described as being activated with Ce, other rare earth elements (Pr, Dy, Tb, Eu, etc.) may be used, and light emission in the visible region is possible. Become. A mixture of a plurality of phosphors containing a rare earth element may be used.

Further, in the present embodiment, the phosphor is used in the form of a block, but it can be used in the form of a sheet, a column, or a tube.

In this embodiment, the above-described semiconductor laser is used as the excitation light source. However, as shown in FIG. 3, the semiconductor laser having a broad-area light-emitting region 43 has a plurality of broad-area light-emitting regions. May be arranged one-dimensionally, and a bar laser having a width of, for example, 10 mm may be used. Further, as shown in FIG. 4, a stack laser in which the light emitting regions 53 are two-dimensionally arranged and the width is, for example, 10 mm may be used. By using such a laser as the excitation light source, higher luminance can be achieved.

In the present invention, the broad area means that the oscillation area width is 10 μm or more.

Therefore, the light-emitting device of the present invention having high efficiency, high luminance and long life can be used as a backlight of a display or an OA device, or a lighting device, and has high performance and high reliability. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor laser constituting a light emitting device according to the present invention.

FIG. 2 is a schematic configuration diagram showing a light emitting device according to the present invention.

FIG. 3 is a perspective view showing a bar laser as an excitation light source.

FIG. 4 is a perspective view showing a stacked laser as an excitation light source.

[Explanation of symbols]

11 n-GaN substrate 12 n-Ga _{1 -z 1} Al _z1 N / GaN superlattice cladding layer 13 n or i-GaN optical waveguide layer 14 In _{1 -z 2} G _{az 2} N (Si-doped) / In _{1 -z 3} Ga
_z3 N multiple quantum well active layer 15 p-Ga _0.8 Al _0.2 N carrier blocking layer 16 n or i-GaN optical waveguide layer _{17 p-Ga 1-z1 Al} z1 N / GaN superlattice cladding layer 18 p-GaN contact layer 19 Insulating film 20 P-side electrode 21 N-side electrode 25 Semiconductor laser 31 Cu block 32 Phosphor

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4H001 CA04 XA08 XA13 XA21 XA31 XA39 XA49 XA57 XA62 XA64 XA71 YA00 YA21 YA39 YA58 YA59 YA65 YA66 5F041 AA04 CA34 CA40 DA46 EE25 5F072 AB01 JJ04 A07 FE04 FA14

Claims (7)

[Claims] 1. An excitation light source comprising a semiconductor laser having a broad area light emitting region having a GaN-based semiconductor as an active layer, and a wavelength longer than a wavelength of light excited by the excitation light source and emitted from the excitation light source. And a phosphor that emits fluorescent light. 2. The light-emitting device according to claim 1, wherein the semiconductor laser is formed by arranging a plurality of light-emitting regions in a broad area one-dimensionally. 3. The light-emitting device according to claim 1, wherein the semiconductor laser comprises a plurality of light-emitting regions of a broad area arranged two-dimensionally. 4. The light emitting device according to claim 1, wherein said phosphor is an yttrium aluminum garnet phosphor activated by a rare earth element. 5. The method according to claim 1, wherein the rare earth element is Ce, Pr, Dy,
The light emitting device according to claim 4, wherein the light emitting device is at least one selected from the group consisting of Tb and Eu. 6. At least a part of yttrium of the yttrium-aluminum-garnet phosphor activated by the rare earth element is composed of Lu, Sc, La, Gd and S.
The light emitting device according to claim 4, wherein the light emitting device is substituted with at least one element selected from the group consisting of m. 7. The yttrium-aluminum-garnet-based phosphor activated by the rare earth element, wherein at least a part of aluminum is replaced by at least one element of Ga and In. 7. The light-emitting device according to 5 or 6.