JP3998414B2 - Semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current confining type semiconductor light emitting device.
[0002]
[Background Art and Problems to be Solved by the Invention]
FIG. 1 shows an example of a conventional constricted LED whose main purpose is to increase the brightness of a light emitting diode. In this constriction type LED, the current confinement layer 1 is disposed on the upper surface of the double hetero luminescent layer inside the device. Therefore, in the manufacturing process, an n-type InGaAlAs cladding layer, an InGaAlAs active layer, a p-type InGaAlAs cladding layer, and an n-type GaAs current confinement layer 1 are epitaxially grown on an n-type GaAs substrate. Thereafter, a part of the current confinement layer 1 is removed by etching, and then a p-type GaP current diffusion layer is epitaxially grown again thereon.
[0003]
As shown in the top view of FIG. 2, the center of the p-electrode formed on the current diffusion layer is removed in a circular shape. This is because the light that has passed through the etched portion of the current confinement layer 1 is extracted to the outside.
[0004]
As described above, in the constricted LED, the number of manufacturing processes is larger than that of a normal LED as the number of epitaxial growth steps is increased, and the time required for manufacturing is also increased.
[0005]
[Means / Actions / Effects to Solve Problems]
The present invention has been devised to effectively solve the above-described problems of the prior art, and provides a semiconductor light emitting device having the following characteristics.
[0006]
In the semiconductor light emitting device of the present invention, the current confinement layer is disposed not on the light emitting device but on the upper surface side of the current diffusion layer. Therefore, it is not necessary to interrupt the growth process of each layer in order to partially etch away the current confinement layer during the manufacturing process as in the prior art. As a result, the manufacturing process can be simplified and the manufacturing time can be reduced. Shortening is also possible.
[0007]
Further, (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is adopted as the current spreading layer, and Al _Z Ga as the current confinement layer located on the upper surface thereof. _{When 1-Z} As (0 ≦ z ≦ 1) is adopted, when the current confinement layer is partially removed by etching, the etching stops in the current diffusion layer, thereby preventing over-etching of the current diffusion layer. Is possible.
[0008]
In the present invention, it is preferable that the surface of the growth substrate is inclined with respect to the (100) plane and each layer thereon is formed by epitaxial growth. In this case, when the current confinement layer is partially etched away due to the influence of the plane orientation of the growth substrate, the corner portion of the constriction layer can be gently inclined, and the electrode formed thereon The possibility of disconnection due to the influence of the corner portion can be reduced. Such effectiveness can be enhanced by using a sulfuric acid-based etchant.
[0009]
Furthermore, in the present invention, it is preferable to dispose a transparent electrode layer on the side of the current confinement layer on the upper surface of the current diffusion layer, and supply current to the current diffusion layer through the transparent electrode layer. As a result, it is possible to uniformly supply current to a desired range of the current diffusion layer and prevent the generation of unnecessary non-light emitting regions. It is preferable to ensure a sufficient interval between the current confinement layer and the transparent electrode layer to prevent the current from flowing around to the lower side of the current confinement layer according to the film thickness of the current diffusion layer.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows a cross-sectional view of the semiconductor light emitting device. In this example, in order to reduce the number of times of epitaxial growth as compared with the conventional example, the current confinement layer 1 is arranged outside the element, not inside the element.
[0011]
The light emitting layer on the n-type GaAs substrate is formed by epitaxial growth of three layers of an n-type InGaAlAs cladding layer 5, an InGaAlAs active layer 6, and a p-type InGaAlAs cladding layer 7 as in the prior art. The process so far is the same as that of the conventional example. In the present invention, subsequently, the p-type GaP current diffusion layer and the n-type GaAs current confinement layer 1 are sequentially epitaxially grown thereon.
[0012]
As described above, in the present invention, in the manufacturing process of the light emitting device, the epitaxial growth process is not divided into two times, and only one time is sufficient. Therefore, it is possible to simplify the manufacturing process and significantly reduce the time.
[0013]
The configuration of the n-type current confinement layer 1 is set to a layer thickness of 0.1 μm or more and a carrier concentration of 3 × 10 ¹⁸ or more, as in the conventional example. The current confinement layer 1 is first epitaxially grown on the entire upper surface of the current diffusion layer and then partially etched away, so that the current confinement layer 1 exists in about a half region on the current diffusion layer as shown in FIG. It will be. In the present invention, the current spreading layer is not limited to GaP, and a composition widely expressed by (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is adopted. In addition, the current confinement layer is not limited to GaAs, and a composition widely expressed by Al _Z Ga _1-Z As (0 ≦ z ≦ 1) can be employed. By disposing the current confinement layer 1 on the current diffusion layer, when the current confinement layer 1 is partially removed by etching, the etching is stopped in the current diffusion layer, and therefore, overetching can be prevented. Become.
[0014]
Thereafter, a p-electrode 211 is formed in a region extending from the upper surface of the current confinement layer 1 to the upper surface of the current diffusion layer. The electrode portion 211a located on the upper surface of the current confinement layer 1 is used as a wire bonding area, and current is supplied from the outside through the electrode portion 211a. The electrode portion 211c located on the side of the current confinement layer 1 on the current diffusion layer is formed in an E shape as shown in FIG. 4, and a current 27 flows from the electrode portion 211c to the current diffusion layer. . The electrode portions 211a and 211c are connected by an electrode portion 211b.
[0015]
When the current confinement layer 1 is partially removed by etching, for example, when a sulfuric acid-based etchant having a component of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 3: 1: 1 is used, an ammonia-based etchant is used. Compared to the case, the surface orientation of the current confinement layer 1 is likely to appear at the corner 1a after etching removal. As a result, as shown in the partially enlarged view of FIG. 5, the corner portion 1a of the current confinement layer 1 is somewhat gently inclined, but the electrode portion 211b is easily cut off at this portion. This problem can be solved by using an off substrate, as will be described in a second embodiment described later.
[0016]
For example, when the thickness of the current diffusion layer is about 7 μm, the current diffuses in the range of about 20 μm from the electrode. Therefore, in the arrangement of the electrode portion 211c as shown in FIG. As a result, as shown by 28 in FIG. 3, light that cannot be extracted outside the light emitting element is generated. Further, since the current is not sufficiently diffused in the entire desired region in the current diffusion layer, as shown in FIG. 4, a partial non-light-emitting region E is generated between the branch electrode portions 211c. These problems can be solved by using a transparent electrode and securing a predetermined distance between the transparent electrode and the current confinement layer, as will be described in a second embodiment described later.
[0017]
Next, a second embodiment of the present invention will be described with reference to FIGS. The semiconductor light emitting device according to the second embodiment is different from that of the first embodiment in that an off substrate is employed as the epitaxial growth substrate and current is supplied to the current diffusion layer through the transparent electrode. That is. This will be described below in order.
[0018]
(1) Adoption of off substrate As an n-type GaAs substrate, an off substrate whose surface orientation is inclined by 15 degrees in the [011] direction or the [0-1-1] direction from the (100) plane is employed. For this reason, the growth direction of the epitaxial growth is inclined with respect to the growth substrate. As a result, when the wafer is made into an element by scribing, the element shape is inclined as a whole as shown in FIG. Due to the influence of the growth direction, when the current confinement layer 1 is partially etched away using a sulfuric acid-based etchant, the slope of the corner 1a of the current confinement layer is shown in FIG. However, it will be inclined more gently than in the first embodiment. Thereby, the possibility that the electrode portion 312b is cut can be further reduced. Further, since the entire light emitting element is inclined, as shown by 38 in FIG. 6, light can be extracted also from the side surface of the light emitting element, so that the light emission efficiency can be improved. In the illustrated example, the inclination angle is set to 15 degrees. However, if there is an inclination angle of at least 2 degrees or more, an effect that the inclination of the corner portion 1a can be moderated can be obtained.
[0019]
(2) Adoption of transparent electrode A transparent electrode 311 made of an ITO film is disposed between the electrode portion 312c and the current diffusion layer. Since the transparent electrode 311 is employed, the current 36 supplied from the electrode portion 312c is sufficiently diffused over the entire desired region in the current diffusion layer. As a result, it is possible to effectively prevent the non-light emitting region E (see FIG. 4) generated between the branch-like electrode portions in the first embodiment.
[0020]
The transparent electrode 311 is formed to a thickness of about 0.5 to 1.0 μm by sputtering or the like. All the light in the wavelength region of 550 to 630 nm is not absorbed by the transparent electrode 311 and can be extracted to the outside of the light emitting element, thereby realizing high light emission efficiency.
[0021]
(3) Distance between transparent electrode and current confinement layer In the second embodiment, the thickness of the current diffusion layer is 7 μm. As already described in the first embodiment, when such a film thickness is adopted, the current diffusion region is in a range of 20 μm from the electrode. In the second embodiment, since current is supplied to the current diffusion layer via the transparent electrode 311, the current diffusion region eventually becomes a region expanded by 20 μm from the outer peripheral edge of the transparent electrode 311. Therefore, as shown in FIG. 6, by securing a gap L between the current confinement layer 1 and the transparent electrode 311 of 30 μm, it is possible to prevent the current from flowing downward to the current confinement layer 1. This prevents light emission that cannot be extracted to the outside as shown in FIG. In this way, the luminous efficiency can be improved. Note that the specific value of the distance L necessary to prevent the current from flowing downward to the current confinement layer 1 varies depending on the thickness of the current diffusion layer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a conventional semiconductor light emitting device.
2 is a top view of the semiconductor light emitting device of FIG. 1. FIG.
FIG. 3 is a cross-sectional view of the semiconductor light emitting device according to the first embodiment of the present invention.
4 is a top view of the semiconductor light emitting device of FIG. 3. FIG.
FIG. 5 is an enlarged view of a region within a circle in FIG. 3;
FIG. 6 is a cross-sectional view of a semiconductor light emitting device according to a second embodiment of the present invention.
7 is a top view of the semiconductor light emitting device of FIG. 6. FIG.
FIG. 8 is an enlarged view of a region in a circle in FIG.
[Explanation of symbols]
1 current confinement layer 5 n-clad layer 6 active layer 7 p-clad layer
27 Current
28 Light that cannot be extracted outside the element
29 Light emitting area
211 p-electrode
36 Current
37 Flash area
38 Light extracted from the element side
311 Transparent electrode layer
312 p-electrode

Claims (2)

On the growth substrate, a light emitting layer, a current diffusion layer, and a current confinement layer are grown and formed in this order.
On the upper surface of the current diffusion layer, a transparent electrode layer is disposed on the side of the current confinement layer, and the peripheral portion of the current confinement layer facing the transparent electrode layer is inclined,
A p − electrode extending from the upper surface of the current confinement layer to the upper surface of the transparent electrode layer through a thin electrode portion, and an n − electrode disposed on the lower surface of the growth substrate ,
A predetermined interval is secured between the current confinement layer and the transparent electrode layer,
The semiconductor light emitting element according to claim 1, wherein the predetermined interval is set as a distance sufficient to prevent a current from flowing around to the lower side of the current confinement layer according to the film thickness of the current diffusion layer. A method for manufacturing a semiconductor light emitting device according to claim 1, comprising:
As the growth substrate, a substrate whose surface is inclined with respect to the (100) plane is used.
On the growth substrate, each layer is formed by epitaxial growth,
After partially removing a part of the current confinement layer formed on the entire top surface of the current diffusion layer using a sulfuric acid-based etchant having components of H ₂ SO ₄ , H ₂ O ₂ , and H ₂ O, Place a transparent electrode at the removed position ,
A production method, comprising providing the p - electrode and the n - electrode .

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