JP2004241462A - Light emitting device and epitaxial wafer for light emitting device - Google Patents

Abstract

An object of the present invention is to provide a light emitting device and a light emitting device epitaxial wafer having a structure in which near-infrared light is removed or reduced so as not to be emitted to the outside.
In a light-emitting element manufactured using a semiconductor substrate, near-infrared light (wavelength: 700 to 1100 nm) generated by a distributed Bragg reflector is set in an optical path of light extracted from the distributed Bragg reflector to the outside. It is configured to be removed or reduced by a material having a near-infrared absorption function (such as the distributed Bragg reflector 10).
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting device and an epitaxial wafer for a light emitting device, and more particularly to an AlGaInP-based light emitting diode having a peak wavelength range from 550 nm (yellow green) to 650 nm (red) and an epitaxial wafer for the light emitting diode.
[0002]
[Prior art]
The demand for light emitting diodes having a peak wavelength ranging from 550 nm (yellow-green) to 650 nm (red) with high brightness, which is manufactured using an AlGaInP-based epitaxial wafer, has greatly increased. The main demand is for traffic signals, car tail lamps, outdoor signage and the like.
[0003]
FIG. 2 shows a typical structure (conventional example) of an epitaxial wafer for an AlGaInP-based light emitting diode having an emission wavelength of 630 nm (for example, see Patent Document 1).
[0004]
As shown in FIG. 2, a conventional AlGaInP-based light-emitting diode is formed of a Bragg-type multilayer reflective film on an n-type GaAs substrate 21 by metal organic chemical vapor deposition (hereinafter, referred to as “MOVPE”). A distributed Bragg reflector (DBR) 22, an n-type AlGaInP cladding layer 23, an undoped AlGaInP active layer 24, a p-type AlGaInP cladding layer 25, and a p-type GaP current diffusion layer 26 are sequentially laminated. The electrode (n-side common electrode) 27 has a structure in which a surface electrode (p-side ohmic contact electrode) 28 is provided on a part of the surface of the p-type current dispersion layer. 23 to 25 constitute an AlGaInP quaternary double heterostructure portion (light emitting portion).
[0005]
The distributed Bragg reflector 22 is a multilayer film in which a λ / 4n film of a high refractive index film and a λ / 4n film of a low refractive index film are alternately laminated, where λ is the emission wavelength of the LED and n is the refractive index. It has a function of reflecting light traveling downward (in the direction of the GaAs substrate) out of the light generated from the active layer upward (in the direction of the light extraction surface) to improve the light extraction efficiency. By this effect, it is possible to realize a luminance improvement of 50% or more (in some cases, about 100%) as compared with a case where the device is not provided.
[0006]
In the LED using the AlGaInP mixed crystal as the light emitting layer, the material constituting the distributed Bragg reflector 22 includes a combination of a GaAs layer and an Al _x Ga _1-x As (0 ≦ x ≦ 1) layer, and a GaAs layer and (Al _{x Ga 1-x) 1-} y in y P (0 ≦ x, a combination of y ≦ 1) layer is generally used.
[0007]
[Patent Document 1]
JP-A-2002-237616
[Problems to be solved by the invention]
Incidentally, an AlGaInP-based light-emitting diode ideally emits only light having a wavelength emitted from the active layer to the outside.
[0009]
However, in practice, unintended near-infrared light emission (emission wavelength 860 nm) occurs in the GaAs layer of the DBR (distributed Bragg reflector), and the near-infrared light is combined with the main light (emission wavelength 630 nm) emitted in the active layer. Out. FIG. 3 shows the spectrum.
[0010]
The intensity of near-infrared light (emission wavelength: 860 nm) is about 1/10 that of main light (emission wavelength: 630 nm). This near-infrared ray may cause a malfunction of a sensor using infrared rays which is widely used in the world.
[0011]
Even in the case of a light emitting diode without a DBR (distributed Bragg reflector), the same phenomenon occurs because the GaAs substrate is excited by light from the active layer and unintended excitation light (about 860 nm) is generated. appear.
[0012]
Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a light-emitting element and an epitaxial wafer for a light-emitting element having a structure in which the near-infrared light is removed or reduced so as not to be emitted outside.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0014]
The light-emitting element according to the first aspect of the present invention is a light-emitting element manufactured using a semiconductor substrate, wherein near-infrared rays (wavelength: 700 to 1100 nm) generated by the distributed Bragg reflector are extracted from the distributed Bragg reflector to the outside. It is characterized in that it is configured to be removed or reduced by a material having a near-infrared absorption function installed in the optical path.
[0015]
This is a light-emitting portion in which an active layer is sandwiched between a first conductive type lower clad layer and a second conductive type upper clad layer on a first conductive type substrate, similarly to the case of the epitaxial wafer for a light emitting device according to claim 4 below. Is formed, and a first conductivity type distributed Bragg reflector composed of a multilayer film in which a high refractive index film and a low refractive index film are alternately laminated is inserted between the first conductivity type lower cladding layer and the substrate. In the light emitting element, or on the first conductivity type substrate, the active layer is formed by sandwiching the active layer between the first conductivity type lower cladding layer and the second conductivity type upper cladding layer, and the second conductivity type current distribution layer is formed thereon. In a light emitting device having a structure in which a distributed Bragg reflector of the first conductivity type is inserted between the lower clad layer of the first conductivity type and the substrate, in the optical path of light extracted from the distributed Bragg reflector to the outside, A material with near-infrared absorption function is installed and the distribution The near infrared rays emitted by the GaAs layer or a GaAs substrate of lugs reflector is eliminated or reduced, it is intended to include forms that such does not appear to the outside.
[0016]
Light-emitting device according to the invention of claim 2, on the n-type GaAs _{substrate, (Al x Ga 1-x} ) 1-y In y P (0 ≦ x, y ≦ 1) or _Al x _{Ga 1-x} As In a light emitting device having a distributed Bragg reflector comprising a (0 ≦ x ≦ 1) type compound semiconductor layer, an n-type cladding layer, an active layer, a P-type cladding layer, and a current spreading layer, the light is extracted from the distributed Bragg reflector to the outside. A material having a near-infrared absorption function is provided in the optical path of the light to be emitted.
[0017]
According to a third aspect of the present invention, in the light emitting device according to the first or second aspect, a GaAs layer or an Al _x Ga _1-x As (0 ≦ x ≦ 1) layer is formed on the compound semiconductor layer constituting the distributed Bragg reflector. or _{(Al x Ga 1-x)} 1-y In y P (0 ≦ x, y ≦ 1) and characterized in that it comprises a layer.
[0018]
A light emitting device epitaxial wafer according to a fourth aspect of the present invention is a light emitting device epitaxial wafer manufactured using a semiconductor substrate, wherein near infrared rays (wavelength 700 to 1100 nm) generated by the distributed Bragg reflector are transmitted from the distributed Bragg reflector. It is characterized in that it is configured to be removed or reduced by a material having a near-infrared absorption function provided in an optical path of light taken out.
[0019]
Epitaxial wafer for a light emitting device according to the invention of claim 5, on the n-type GaAs _{substrate, (Al x Ga 1-x} ) 1-y In y P (0 ≦ x, y ≦ 1) or _Al x Ga _{1 -XAs} (0 ≦ x ≦ 1) a distributed Bragg reflector comprising a compound semiconductor layer, an n-type clad layer, an active layer, a p-type clad layer, and a current spreading layer, wherein the distributed Bragg is A material having a near-infrared absorption function is provided in an optical path of light extracted from the reflector to the outside.
[0020]
According to a sixth aspect of the present invention, in the light emitting device epitaxial wafer according to the fourth or fifth aspect, the compound semiconductor layer constituting the distributed Bragg reflector has a GaAs layer, Al _x Ga _1-x As (0 ≦ x ≦ 1). ) Layer or (Al _x Ga _1-x ) _1-y In _y P (0 ≦ x, y ≦ 1) layer.
[0021]
<The gist of the invention>
In the present invention, a material having a near-infrared absorption function is provided in the optical path of light extracted from the distributed Bragg reflector to the outside, thereby removing or absorbing near infrared light emitted from the GaAs layer or the GaAs substrate of the distributed Bragg reflector. Reduce it so that it does not go outside.
[0022]
As a material having a near-infrared absorption function, there is a Bragg-type multilayer reflective film (distributed Bragg reflector) having a function of reflecting only a near-infrared region (around 860 nm) and not reflecting light of a main wavelength (around 630 nm). .
[0023]
Distributed Bragg _reflector, the _{(Al x Ga 1-x)} 1-y In y P (0 ≦ x, y ≦ 1) or _{Al x Ga 1-x As (} 0 ≦ x ≦ 1) compound semiconductor layer Be composed. Typically, a combination of a GaAs layer and an (Al _x Ga _1-x ) _1-y In _y P (0 ≦ x, y ≦ 1) layer, a GaAs layer and an Al _x Ga _1-x As (0 ≦ x ≦ 1) A combination of layers and the like are used.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
[0025]
In the present embodiment, a near-infrared ray (wavelength: 700 to 1100 nm) emitted from the GaAs layer or the GaAs substrate of the distributed Bragg reflector is not placed on the distributed Bragg reflector (first DBR layer) so as not to go outside. Another Bragg-type multilayer reflective film (distributed Bragg reflector) (second DBR layer) is laminated as a material having a function of reflecting an infrared region. However, it is assumed that this second DBR layer has a function of reflecting only in the near infrared region (around 860 nm) and does not have a function of reflecting the main wavelength.
[0026]
An embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a red LED chip having a light emission wavelength of about 630 nm according to the present invention is a distributed Bragg reflector composed of a Bragg-type multilayer reflective film that reflects light near 630 nm on an n-type GaAs substrate 1 by MOVPE. 2 (DBR1), distributed Bragg reflector 10 (DBR2) composed of a Bragg-type multilayer reflective film reflecting around 860 nm, n-type cladding layer 3 composed of an n-type (Al _0.7 Ga _0.3 ) InP layer, undoped Active layer 4 composed of (Al _0.3 Ga _0.7 ) InP layer, p-type cladding layer 5 composed of p-type (Al _0.7 Ga _0.3 ) InP layer, current diffusion layer 6 composed of p-type GaP layer Are sequentially formed. Further, the structure is such that a back surface electrode (n-side common electrode) 7 is provided on the entire back surface of the n-type GaAs substrate 1 and a surface electrode (p-side ohmic contact electrode) 8 is provided on a part of the surface of the p-type current dispersion layer 6. ing.
[0027]
Reference numerals 3 to 5 form an AlGaInP quaternary double heterostructure portion (light emitting portion).
[0028]
The distributed Bragg reflector 2 (DBR1) is formed by stacking 20 pairs of an n-type AlGaAs layer and an n-type AlGaAs layer. This distributed Bragg reflector 2 (DBR1) is designed to reflect light having a desired wavelength of about 630 nm, but as shown in FIG. 3, GaAs / DB which also reflects light in the range of 550 to 650 nm as a result. It is an AlGaInP-based DBR.
[0029]
Further, the n-type AlGaAs-based distributed Bragg reflector 10 of the second DBR layer, which is a feature of the present invention, is formed by stacking 20 pairs of AlGaAs layers and n-type AlGaAs layers having different mixed crystal ratios. The n-type AlGaAs based distributed Bragg reflector 10 (DBR2) removes light in the near infrared region (around 860 nm), which is the second peak wavelength in FIG. 3, for the purpose of removing light. Although it is designed to have a function of reflecting only light and not reflecting light of the main wavelength (around 630 nm), it is actually configured as a distributed Bragg reflector that reflects light of 700 to 1100 nm.
[0030]
As described above, by dividing the DBR layer into two layers, the lower (GaAs substrate side) DBR 1 can efficiently reflect the main light (wavelength: 630 nm) emitted from the active layer, while the upper (light) The DBR 2 (in the direction of the extraction surface) transmits the main light (wavelength 630 nm) emitted from the DBR 1 but reflects the near infrared light (wavelength 860 nm) emitted from the GaAs layer or the GaAs substrate of the DBR 1 so that the near infrared light is emitted. (A wavelength of 860 nm) can be obtained.
[0031]
Such an effect can also be achieved by providing another material having a near-infrared absorbing function instead of the DBR2.
[0032]
In the above embodiment, the p-side-up LED array has been described as an example, but the present invention is also applicable to an n-side-up structure LED array formed on a p-type GaAs substrate.
[0033]
It should be noted that what is used as the dopant of the epitaxial layer is not directly related to the present invention, but Zn, Mg, C, and a combination of a plurality thereof can be used as the p-type dopant. As the n-type dopant, other than Se, such as Te or a combination thereof can be used.
[0034]
【The invention's effect】
As described above, the light-emitting device and the epitaxial wafer for the light-emitting device of the present invention are provided with a material having a near-infrared absorption function in the optical path of light extracted from the cloth Bragg reflector to the outside. Near infrared rays emitted from the GaAs layer or the GaAs substrate are removed or reduced so as not to go outside. Therefore, according to the present invention, it is possible to eliminate a problem caused by the near-infrared ray going out, for example, the possibility of causing a sensor using infrared rays, which is widely used in the world, to malfunction.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a structure of an epitaxial wafer for a light emitting device of the present invention.
FIG. 2 is a cross-sectional view showing a structure of a conventional light emitting device epitaxial wafer.
FIG. 3 is a diagram showing an emission spectrum of an AlGaInP-based light emitting device having an emission wavelength of 630 nm.
[Explanation of symbols]
1 n-type GaAs substrate 2 distributed Bragg reflector (first DBR layer)
3 n-type cladding layer 4 active layer 5 p-type cladding layer 6 p-type current spreading layer 7 lower electrode 8 upper electrode 10 distributed Bragg reflector (second DBR layer)

Claims (6)

In a light-emitting element manufactured using a semiconductor substrate,
A configuration in which near infrared rays (wavelength 700 to 1100 nm) generated by the distributed Bragg reflector are removed or reduced by a material having a near infrared absorption function installed in an optical path of light extracted from the distributed Bragg reflector to the outside. Characteristic light emitting element. on the n-type GaAs _{substrate, (Al x Ga 1-x} ) 1-y In y P (0 ≦ x, y ≦ 1) or _{Al x Ga 1-x As (} 0 ≦ x ≦ 1) compound of based semiconductor In a light emitting device having a distributed Bragg reflector comprising a layer, an n-type cladding layer, an active layer, a p-type cladding layer, and a current spreading layer,
A light-emitting device, wherein a material having a near-infrared absorption function is provided in an optical path of light extracted from the distributed Bragg reflector to the outside. The light emitting device according to claim 1, wherein
The compound semiconductor layer constituting the DBR, GaAs _{layer, Al x Ga 1-x As} (0 ≦ x ≦ 1) layer, or _{(Al x Ga 1-x)} 1-y In y P (0 ≦ x, y ≦ 1) A light-emitting element comprising a layer. In an epitaxial wafer for a light emitting element manufactured using a semiconductor substrate,
A configuration in which near infrared rays (wavelength 700 to 1100 nm) generated by the distributed Bragg reflector are removed or reduced by a material having a near infrared absorption function installed in an optical path of light extracted from the distributed Bragg reflector to the outside. Characteristic epitaxial wafer for light emitting device. on the n-type GaAs _{substrate, (Al x Ga 1-x} ) 1-y In y P (0 ≦ x, y ≦ 1) or _{Al x Ga 1-x As (} 0 ≦ x ≦ 1) compound of based semiconductor In a light emitting device epitaxial wafer having a distributed Bragg reflector comprising layers, an n-type cladding layer, an active layer, a p-type cladding layer, and a current spreading layer,
An epitaxial wafer for a light-emitting device, wherein a material having a near-infrared absorption function is provided in an optical path of light extracted from the distributed Bragg reflector to the outside. The epitaxial wafer for a light emitting device according to claim 4 or 5,
The compound semiconductor layer constituting the DBR, GaAs _{layer, Al x Ga 1-x As} (0 ≦ x ≦ 1) layer, or _{(Al x Ga 1-x)} 1-y In y P (0 ≦ 1. An epitaxial wafer for a light emitting device, comprising: x, y ≦ 1) layers.

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