JP2949052B2 - Light emitting diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode, and more particularly to a structure for improving the efficiency of extracting light generated inside the light emitting diode to the outside.

[0002]

2. Description of the Related Art FIG. 3 shows an example of the structure of a conventional light emitting diode 90 of this type.
A GaAsP layer 92 is epitaxially grown on 1 to form an n layer. Subsequently, a Si ₃ O ₃ layer was formed on the GaAsP layer 92 with an opening 94 a at a portion where the light emitting section 93 was to be formed.
An N ₄ film 94 is covered, and Zn is diffused from the opening 94 a to form a p-layer 95 in a part of the GaAsP layer 92.

Thereafter, a part of the p layer 95, that is,
An opaque electrode 96 made of aluminum is provided on a part of the light emitting portion 93, and a back electrode 97 is similarly provided on the GaAs substrate 91 side by aluminum or the like, and a current is applied between the opaque electrode 96 and the back electrode 97. GaAsP
The pn junction between the layer 92 and the p-layer 95 emits light.

[0004]

However [0005] In the light emitting diode 90 of the conventional configuration described above, the first, the refractive index n ₁ of the p layer 95 is extremely large and 3.8, pn junction Is generated in the atmosphere (refractive index n ₀ =
1.0), the amount of light that is reflected at the interface between the p-layer 95 and the atmosphere and emitted to the outside is attenuated due to the difference in the refractive index between the two, and the light extraction efficiency is reduced. There is a problem.

The surface of the p-layer 95 may be coated or covered with an epoxy resin or the like for the purpose of preventing moisture. For example, the refractive index of the epoxy resin or the like is about 1.3 to 1.5. However, it does not have the effect of reducing the reflection so much, and the extraction efficiency is still low.

Secondly, the current supplied from the opaque electrode 96 travels straight to the back electrode 97 at the shortest distance as shown in FIG. The portion which becomes the back surface of the opaque electrode 96 without emitting light over the entire surface is mainly the light emitting zone B. Therefore,
Most of the light emitted at the pn junction is shielded by the opaque electrode 96, which also causes a problem that the light extraction efficiency is reduced.

Further, when the current is concentrated as described above, the current density in that portion increases, and for example, heat generation or the like is partially generated, and the light emission amount is saturated. However, there are also problems that are not in a favorable state, and solving these problems is an issue.

[0008]

According to the present invention, as a specific means for solving the above-mentioned conventional problems, Zn is diffused into a n-type GaAsP layer to form a p-layer.
In a light emitting diode in which an n-junction is formed to form a light emitting portion, and an opaque electrode is provided on the light emitting portion and partially covered, the portion of the light emitting portion other than covered by the opaque electrode is an ITO film By providing a light emitting diode characterized by being covered with a transparent auxiliary electrode according to (1), light extraction efficiency is remarkably improved, and the above-mentioned conventional problem is solved.

[0009]

Next, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 shows a light-emitting diode 1 according to the present invention.
A GaAsP layer 3 is epitaxially grown on an aAs substrate 2 to form an n layer, and then a Si ₃ N ₄ film 4 having an opening 4a is formed on the GaAsP layer 3 and Zn is diffused from the opening 4a. This is the same as the conventional example.

Further, the p-layer 5 is formed on the GaAsP layer 3 corresponding to the portion of the opening 4a by the above-described process to form a pn junction. The point that the portion becomes the light emitting section 6 is also the same as the conventional example.

Here, in the present invention, an opaque electrode 7 made of aluminum or the like is provided on a part of the light emitting portion 6, and all portions of the light emitting portion 6 other than those covered with the opaque electrode 7 are made of ITO such as indium oxide. The transparent auxiliary electrode 8 is used for covering. A back electrode 9 is provided on the back side of the GaAs substrate 2 as in the conventional case.

At this time, the procedure for providing the opaque electrode 7 and the transparent auxiliary electrode 8 in the light emitting section 6 is as follows. The opaque electrode 7 is formed in advance, and the transparent auxiliary electrode 7 is deposited on other portions by vapor deposition, sputtering, or the like. 8 may be formed, or a transparent auxiliary electrode 8 may be formed first so as to cover the entire surface of the light emitting unit 6,
The opaque electrode 7 may be provided by removing a part thereof to expose the p-layer.

Next, the operation and effect of the light emitting diode 1 of the present invention having the above-described configuration will be described. First of all, by configuring the transparent auxiliary electrode 8, the p
The layer 6 and the atmosphere come into contact via the transparent auxiliary electrode 8. At this time, the refractive index of the P layer 6 is 3.8
Since the refractive index of the transparent auxiliary electrode 8 is 1.9 to 2.0, the p layer 6 and the atmosphere come into contact with each other via the transparent auxiliary electrode 8 having a refractive index intermediate between the two.

Therefore, the transparent auxiliary electrode 8 can be expected to have the same function as an anti-reflection coating film applied to a photographic lens or the like. Therefore, when the wavelength of the light emitted from the light emitting diode 1 is 740 nm, the product of the refractive index and the film thickness of the transparent auxiliary electrode 8 is 1/4.
Wavelength, that is, the thickness of the transparent auxiliary electrode 8 is set to about 9
By setting the thickness to 50 angstroms, the effect of increasing the transmittance is maximized, and the light extraction efficiency can be improved.

Second, the provision of the transparent auxiliary electrode 8 allows the current applied to the opaque electrode 7 to be first conducted to the transparent auxiliary electrode 8 and then to the back electrode 9. Therefore, the pn junction, that is, the light emitting section 6 emits light over the entire surface.

Therefore, in the light emitting diode 1 of the present invention, as shown in FIG. 2, light is emitted not only on the back of the opaque electrode 7 but also on the back of the transparent auxiliary electrode 8.
That is, the light-emitting zone B covers the entire surface of the light-emitting portion 6, and light emitted on the back surface of the transparent auxiliary electrode 8 passes through the transparent auxiliary electrode 8 and is emitted from the light-emitting portion 6 to the outside. In addition, light can be efficiently extracted without being shielded like light emitted on the back surface of the opaque electrode 7.

Since the transparent auxiliary electrode 8 is provided as described above and the entire surface of the light emitting section 6 emits light, a current having a substantially uniform density flows through the entire surface of the pn junction, which is opaque. It is possible to prevent an excessive current from concentrating on a part such as the back surface of the electrode 7 and cause an excessive current, and to expect the effect of extending the life of the light emitting diode 1.

[0018]

As described above, according to the present invention, the light emitting diode in which the portion other than the opaque electrode of the light emitting portion is covered with the transparent auxiliary electrode made of the ITO film is provided. Since the surface of the light emitting section is covered with a transparent auxiliary electrode having a refractive index between 1.9 and 2.0 between the refractive index of the p-layer of 3.8 and the refractive index of the atmosphere of 1.0, the transparent auxiliary electrode Performs the function of an anti-reflection coating film, thereby reducing the reflection loss when light is emitted from the p-layer into the atmosphere and improving the light extraction efficiency. Further, the thickness of the transparent auxiliary electrode is set to nd ≒
By setting it to λ / 4, the above effect is further ensured.

Secondly, since the portion other than the opaque electrode of the light emitting portion is covered with the transparent auxiliary electrode, the current is uniformly applied to the entire surface of the light emitting portion. The part other than the opaque electrode that did not emit light, that is, the back surface of the transparent auxiliary electrode shall also emit light, thereby enabling external emission of the emitted light to pass through the transparent auxiliary electrode, thereby improving the light extraction efficiency. It has the effect of improving. Also, by dispersing the current uniformly over the entire light emitting surface, a considerable effect can be expected for extending the life.

Therefore, in the light emitting diode of the present invention, it is possible to provide a brighter light emitting diode with the same power consumption because of the above synergistic effects. To play.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a light emitting diode according to the present invention.

FIG. 2 is an explanatory diagram showing the operation of the same embodiment.

FIG. 3 is a sectional view showing a conventional example.

FIG. 4 is an explanatory diagram showing the operation of a conventional example.

[Explanation of symbols]

1 ...... emitting diode 2 ...... GaAs substrate 3 ...... GaAsP layer 4 ...... Si ₃ N ₄ film 4a ...... opening 5 ...... p layer 6 ...... emitter 7 ...... opaque electrode 8 ...... transparent auxiliary electrode 9 …… Back electrode B …… Emission zone

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 33/00

Claims (2)

(57) [Claims] 1. An n-type GaAsP layer in which Zn is diffused to form a p-layer, thereby forming a pn junction to form a light-emitting portion. An opaque electrode is provided on the light-emitting portion to partially cover the light-emitting portion. In the light emitting diode according to the present invention, a portion of the light emitting portion other than the portion covered with the opaque electrode is covered with a transparent auxiliary electrode made of an ITO film. 2. The method according to claim 1, wherein the ITO film is formed by nd ≒ λ / 4 (where n
The light emitting diode according to claim 1, wherein is a refractive index of the ITO film, d is a thickness of the ITO film, and λ is a wavelength of light generated by the light emitting diode.