JPH0697498A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To improve brightness by improving light output efficiency. CONSTITUTION:A semiconductor light emitting element is composed of a light emitting layer 5, which is formed on a semiconductor substrate 2 and is formed of InGaAl P mixed crystal, electrodes 1 and 10 which supply the light emitting layer 5 with current, reflecting layers 3 and 9, which are formed between the semiconductor substrate 2 and the light emitting layer 5 and directly under the electrode 10 on the light output side by alternately laminating different composition III-V compound layers so as to reflect reflecting light from the light emitting layer 5, and a current block layer 7, which is formed between the reflecting layers 3 and 9 and has the conductivity type opposite to the adjacent semiconductor layers 6 and 8 so as to suppress current from flowing into the light emitting layer 5 at the bottom part of the electrode 10 on the light output side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device having improved light extraction efficiency, and more particularly to a high brightness semiconductor light emitting device used for indoor and outdoor information display boards, automobile stop lamps, traffic signals and the like.

[0002]

2. Description of the Related Art Light emitting diodes (LEDs) used in the above-mentioned fields are described in the literature "Nikkei Electronics,
1991.7.1 (Extra issue) P. P. 71-82 ”, LE using an InGaAlP-based semiconductor light-emitting material capable of achieving high brightness from orange color (peak wavelength of about 620 nm) to green color (peak wavelength of about 560 nm).
D is drawing attention and is being put to practical use.

The pellet structure of such InGaAlP mixed crystal LED is as shown in FIG.
On the substrate 101 made of n-GaAs, n-InGaAl is formed.
P-type cladding layer 102, undoped InGaA
Active layer (light emitting layer) 103 made of IP, P-InGaA
A clad layer 104 made of IP and a low-resistance current diffusion layer 105 made of P-GaAlAs are sequentially stacked. A P-side electrode 106 having a predetermined shape is formed on the current diffusion layer 105, and an n-side electrode 107 is formed on the entire surface of the substrate 101 side. Are formed respectively.

In such a structure, both electrodes 106,
By applying a voltage between 107 and supplying a current to the active layer 103, part of the light emitted upward from the active layer 103 is emitted to the outside and taken out.

[0005]

As described above,
A conventional InGaAlP-based LE having a structure as shown in FIG.
In D, since the substrate 101 is made of GaAs, the emitted light emitted downward from the active layer 103 is the substrate 10.
It was absorbed in 1. Further, of the emitted light emitted upward from the active layer 103, the emitted light reaching directly below the P-side electrode 106 was absorbed by the P-side electrode 106.

For this reason, the light extraction efficiency, which indicates the ratio of the light obtained in the active layer 103 that can be extracted to the outside, is remarkably reduced, and the light emission efficiency is reduced.

Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a semiconductor light emitting device which has improved light extraction efficiency and further increased brightness. It is in.

[0008]

To achieve the above object, the invention according to claim 1 provides a light emitting layer formed of a mixed crystal of InGaAlP formed on a semiconductor substrate, and an electrode for supplying a current to the light emitting layer. And is formed between the semiconductor substrate and the light emitting layer and directly below the electrode on the light extraction side, and has a different composition III
-Group V compound layers are alternately laminated to form a reflective layer that reflects the emitted light of the light emitting layer, and the reflective layer is formed between the reflective layers so as to have a conductivity type opposite to that of the adjacent semiconductor layer. And a current blocking layer that suppresses current from flowing through the light emitting layer.

According to a third aspect of the present invention, the current blocking layer is configured to have a band gap larger than that of the light emitting layer so that the current blocking layer is transparent to radiated light.

[0010]

In the above structure, according to the present invention, the absorption of the emitted light by the semiconductor substrate and the electrodes is suppressed by the reflective layer, and the light emitting region of the light emitting layer is set by the current blocking layer except the region below the electrode. ing.

[0011]

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

FIG. 1 is a diagram showing a sectional structure of a semiconductor light emitting device according to a first embodiment of the present invention.

In FIG. 1, an n-type first reflective layer 3 is formed on a semiconductor substrate 2 made of n-type GaAs and having an electrode 1 made of n-type AuGe formed on one surface. The first reflective layer 3 is formed by alternately stacking about 10 to 40 pairs of n-type InGaAlP and n-type InAlP with a stacking cycle of λ / 4 with respect to the emission wavelength (λ). Reflects light emitted from the layer.

On the first reflective layer 3, n-type InGa is formed.
A cladding layer 4 made of AlP, a light emitting layer 5 made of n-type InGaAlP, and a cladding layer 6 made of P-type InGaAlP are sequentially formed.

On the clad layer 6, n-type InGaAl is formed.
A current block layer 7 made of P is laminated. The current blocking layer 7 suppresses a current from flowing in the light emitting layer 5 in a region corresponding to a portion directly below the electrode 10 on the light extraction side, which will be described later, and makes the light emitting region in the light emitting layer 5 a partial region corresponding to a portion directly below the electrode 10. Set to the area excluding. The current blocking layer 7 needs to be formed to have a conductivity type opposite to that of the adjacent layer in order to achieve the above-mentioned function, and to obtain a sufficient current suppressing effect on the light emitting layer 5, the current blocking layer 7 and It needs to be formed in the same or large area. Further, the current blocking layer 7 has a band gap larger than that of the light emitting layer 5 so that the light blocking efficiency is further increased when the current blocking layer 7 is transparent to the light emitted from the light emitting layer 5. Is possible.

A current diffusion layer 8 made of P-type GaAlAs is formed on the current blocking layer 7 and the cladding layer 6 to diffuse the current supplied to the light emitting layer 5. A second reflective layer 9 similar to the first reflective layer is formed on the current diffusion layer 5 in a substantially central portion of the semiconductor substrate 2, and a light extraction side made of P-type AuZn is formed on the second reflective layer 9. The electrode 10 is laminated.

Next, one manufacturing method for obtaining such a structure will be described.

First, metalorganic vapor phase epitaxy (MOCVD
Method, the first reflective layer is laminated and then In
0.5 (Ga1-xAlx) 0.5P has a thickness of about 1 μm, and In0.5 (Ga1-yAly) 0.5P has a thickness of 0.6.
μm, In0.5 (Ga1-zAlz) 0.
5P with a thickness of about 1.0 μm and In0.5 (Ga1-u
Alu) 0.5P is sequentially grown to a thickness of about 0.2 μ, and the cladding layer 4, the light emitting layer 5, the cladding layer 6, and the current blocking layer are laminated and formed.

Next, a resist pattern having a predetermined shape is formed by a lithography process, and the current block layer is selectively removed by wet or dry etching using this register pattern as a mask to form a current block layer 7 having a predetermined shape. .

Next, after removing the register pattern, M
Ga1-wAlwAs is grown to a thickness of about 7.0 μm by the OCVD method to form the current diffusion layer 8, and then the second reflective layer is grown and formed.

Here, the n-clad layer 4, the light emitting layer 5, and the P-
The Al mixed crystal ratio of the clad layer 6 is set to z≈x> y, and the Al mixed crystal ratio of the light emitting layer 5 and the current block layer 7 is set to u> y. 8 Al
The mixed crystal ratio (W) is also set to be transparent to the emission wavelength.

Next, AuGe is applied to the semiconductor substrate 2 side, and the second
After vapor deposition of AuZn on the reflective layer, 1 at 500 ° C
Heat treatment is performed for 0 minutes to form an ohmic electrode layer.

Next, a resist pattern is formed on the ohmic electrode layer of AuZn by a photolithography process so as to have an area equal to or smaller than the area of the current block layer 7. Subsequently, the AuZn ohmic electrode layer and the second reflective layer are selectively removed by wet or dry etching using the resist pattern as a mask to form a second reflective layer 9 and a P-side electrode 10 having a predetermined shape. , A light extraction surface is formed around the P-side electrode 10 for extracting the emitted light from the light emitting layer 5 to the outside.

Finally, the devices are individualized by a dicing process to manufacture a semiconductor light emitting device as shown in FIG.

In the light emitting device having the structure manufactured by such a process, the first and the first electrodes are provided between the semiconductor substrate 2, the light emitting layer 5, and between the light emitting layer 5 and the electrode 10 on the light extraction side.
Since the second reflective layers 3 and 9 are provided, the emitted light from the light emitting layer 5 is reflected by the reflective layers 3 and 9, respectively, and absorption of the emitted light by the semiconductor substrate 2 and the electrode 10 is suppressed.

Further, the current blocking layer 7 is used to form the light emitting layer 5.
Since the light emitting area is set immediately below the extraction surface, a part of the emitted light from the light emitting area to the upper side is directly extracted from the light extraction surface to the outside without any hindrance.

Further, since the light emitting region is set around the electrode 10 on the light extraction side by the current blocking layer 7,
Multiple reflection between the first and second reflective layers 3 and 9 is reduced, and the influence of re-absorption caused by the light reflected by the reflective layers 3 and 9 passing through the light emitting layer 5 can be reduced. Further, by setting the current blocking layer 7 to be transparent to the emitted light, absorption of the emitted light reflected by the reflective layers 3 and 9 can be reduced.

From the above, in the structure as shown in FIG. 2, it is possible to effectively take out the emitted light which was invalid without being taken out to the outside in the structure shown in FIG. The extraction efficiency is significantly improved, and the brightness can be increased to about 10 times that of the conventional structure.

FIG. 2 is a diagram showing a sectional structure of a semiconductor light emitting device according to a second embodiment of the present invention.

The feature of the second embodiment is that
The current blocking layer 11 is arranged and formed so as to be P-type between the first reflection layer 3 and the n-type cladding layer 4, and the other structure is the same as that of FIG. With such a structure,
It is possible to obtain the same effect as that of the first embodiment.

FIG. 3 is a diagram showing a sectional structure of a semiconductor light emitting device according to a third embodiment of the present invention.

The characteristic feature of this third embodiment is that
In comparison with the structure shown in FIG. 1, the light extraction surface is set at the center of the pellet, and the current blocking layer 12, the second reflection layer 13,
The P-side electrode 14 is disposed and formed around the pellet. With such a structure, the light converging property is improved, and it is suitable for the use where directivity is required.

FIG. 4 is a diagram showing a sectional structure of a semiconductor light emitting device according to a fourth embodiment of the present invention.

The feature of this fourth embodiment is that
In the structure shown in FIG. 3, the current blocking layer 15 is arranged and formed so as to be P-type between the first reflection layer 3 and the n-type cladding layer 4, and the other structure is different from that in FIG. It is the same. Even with such a structure, it is possible to obtain the same effect as that of the third embodiment.

The present invention is not limited to the above embodiment, and the semiconductor substrate and each layer may be P type.

[0036]

As described above, according to the present invention, since the reflection layer suppresses the radiation of the light emitted from the light emitting layer to the semiconductor substrate and the electrode on the light extraction side, the effective radiation extracted to the outside can be obtained. You can increase the light. In addition, the light emitting area is set to the area excluding the area under the electrode on the light extraction side by the current blocking layer, and it is set to be transparent to the emitted light, so that the effective emitted light that is extracted to the outside can be increased. You can

As a result, the light extraction efficiency is improved and higher brightness can be achieved.

[Brief description of drawings]

FIG. 1 is a view showing a sectional structure of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2 is a view showing a sectional structure of a semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a sectional structure of a semiconductor light emitting device according to a third embodiment of the invention.

FIG. 4 is a view showing a sectional structure of a semiconductor light emitting device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 n-AuGe electrode 2 n-GaAs substrate 3 1st reflective layer 4 n-clad layer 5 light emitting layer 6 P-clad layer 7, 11, 12, 15 current blocking layer 8 current diffusion layer 9, 13 second reflective layer 10 , 14 P-AuZn electrode

Claims (5)

[Claims] 1. InGaAl formed on a semiconductor substrate
A light emitting layer made of a mixed crystal of P, an electrode for supplying a current to the light emitting layer, and a III-V group compound layer having different compositions are formed between the semiconductor substrate and the light emitting layer and directly below the electrode on the light extraction side. Reflective layers that are alternately laminated to reflect the emitted light of the light emitting layer, and are formed between the reflective layers so as to have a conductivity type opposite to that of the adjacent semiconductor layer, and a current flows in the light emitting layer below the electrode on the light extraction side. And a current blocking layer for suppressing the above. 2. The semiconductor light emitting device according to claim 1, wherein the current blocking layer has an area equal to or wider than that of the electrode on the light extraction side. 3. The semiconductor light emitting device according to claim 1, wherein the band gap of the current blocking layer is larger than the band gap of the light emitting layer. 4. The semiconductor light emitting device according to claim 1, wherein the electrode on the light extraction side is formed in a substantially central part of the semiconductor substrate. 5. The semiconductor light emitting device according to claim 1, wherein the electrode on the light extraction side is formed in a peripheral portion on a semiconductor substrate.