JPH0629570A - Light-emitting element structure - Google Patents

Abstract

PURPOSE:To provide the structure of a light-emitting element such as LED, in which light emitted from a p-n junction can be efficiently taken out to the outside and the generation of light of high luminance is made possible. CONSTITUTION:In a light-emitting element structure in which a p-type/n-type semiconductor layer and n-type/p-type semiconductor layer are p-n joined and upper electrode and lower electrode are formed on a light take-out face and opposite-side rear face respectively, a current block layer 2 is formed between a p-n junction 1 directly below the upper electrode 7 and upper electrode, the current block layer 2 is desirably n-type or p-type semiconductor layer or electrically insulating layer, and the current block layer 2 is more desirably formed into the same shape as or a shape similar to that of the upper electrode and has the cross-sectional area of at least 1/2 of that of the upper electrode and 0.05-10.0mum thickness.

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 structure such as a light emitting diode (LED) capable of obtaining high brightness.

[0002]

2. Description of the Related Art Light emitting elements such as LEDs are widely used for numerical value display of measuring instruments and various display boards. A commonly used light emitting device structure includes, for example, as shown in FIG. 5, an n-type / p-type semiconductor layer 5 and a p-type / n-type semiconductor layer 4 stacked on an n-type / p-type semiconductor substrate 6. The pn junction 1 is formed by bonding, and the p-type / n-type semiconductor layer 4 or the current diffusion layer 3 is further laminated if necessary, and a dot shape is formed on this surface (hereinafter referred to as a light extraction surface). An electrode (hereinafter referred to as an upper electrode) 7 is provided, and a flat plate-shaped electrode (hereinafter referred to as a lower electrode) 8 is formed on the front surface (hereinafter referred to as a back surface) of the substrate 6.

[0003]

According to the above light emitting device structure, since the pn junction immediately below the upper electrode 7 is the region into which the most current is injected, the light emitting device emits light at this portion. It becomes the most and becomes a strong light emission. However, although this strong light emission is emitted toward the light extraction surface, it is absorbed by the upper electrode immediately above the light extraction surface and cannot be efficiently extracted to the outside of the element, and the brightness of the light emitting element decreases. In this way, the conventional light emitting device structure has low brightness,
In the market, there is a strong demand for the development of light emitting devices with higher brightness. In response to this, various improvements have been proposed, but in the present circumstances, a light emitting element that sufficiently satisfies the above demand has not yet been developed.

The object of the present invention is to solve the above problems and
It is an object of the present invention to provide a light emitting element structure such as an LED capable of efficiently extracting the light emitted from the n-junction portion to the outside and capable of emitting light with high brightness.

[0005]

As a result of various studies to solve the above problems, the inventors of the present invention have made a structure in which current is not concentrated and injected into a pn junction immediately below the upper electrode. The present invention has been completed by finding that the above can be achieved. That is, the light emitting device structure of the present invention is a light emitting device structure in which an n-type semiconductor layer and a p-type semiconductor layer are pn-junctioned, and an upper electrode is formed on the light extraction surface and a lower electrode is formed on the opposite back surface. A current blocking layer is formed between a pn junction portion immediately below the upper electrode and the upper electrode, and the current blocking layer is preferably an n-type or p-type semiconductor layer or an electrically insulating layer, and more preferably The current blocking layer is formed in the same or similar shape as the upper electrode, has an area of at least ½ of the upper electrode, and has a thickness of 0.05 to 10.0 μm. It is something.

[0006]

According to the above structure, since the current block layer is formed between the upper electrode and the pn junction portion immediately below it, the current flows around the block layer, and the pn in the direction directly below the block layer. The current concentrates around the junction. Therefore, it is possible to prevent current from concentrating on the pn junction portion just below the upper electrode. In addition, since the current is concentrated and flows around the pn junction immediately below the block layer, this portion emits strong light, and this strong light is less likely to be absorbed by the upper electrode. Therefore, the strong light emission of the light emitting element can be efficiently extracted to the outside, and the brightness of the light emitting element can be improved.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the basic structure of the light emitting device of the present invention. The same parts as those of the conventional light emitting device are denoted by the same reference numerals, and detailed description thereof will be omitted. In the figure, the difference from FIG. 5 is that the boundary portion 9 between the current diffusion layer 3 and the p-type / n-type semiconductor layer 4 immediately below the upper electrode 7 is different.
The point is that the current blocking layer 2 is formed on.

The semiconductor material constituting the light emitting device of the present invention is not particularly limited, and any of the materials usually used as a light emitting device such as an LED can be used. Specific examples thereof include InP-based, GaAs-based, GaP-based, AlGa
Examples include those using various p-type or n-type semiconductors such as As type, GaInP type, and GaInAs type. FIG. 4 shows the conduction type of the light emitting element, and the light emitting element structure of the present invention may have either of the configurations of FIG. 4 (a) or (b).

The current spreading layer 3 is provided as needed, and a high carrier concentration layer having a carrier concentration of 5 × 10 ¹⁷ cm ^-3 or more is usually applied. By providing the layer 3 directly under the upper electrode, the current diffusion property is improved, and the upper electrode and the pn
Even if the distance to the junction is close and a dot-shaped electrode having a small area is used as the upper electrode, a current flows through the entire surface of the pn junction, which improves the brightness of the light emitting element, which is preferable. .

This current diffusion layer will be described, for example, in a GaInp system. A method of forming a p ⁺ GaInp layer having a high carrier concentration on the p-type GaInp layer by epitaxial growth. After the epitaxial growth of the p-type GaInp layer, Zn, Mg, A method of increasing the carrier concentration of the surface layer to form a current diffusion layer by diffusion of impurities such as Be and Cd, and a method of forming a current diffusion layer by ion implantation in which p-type impurities are ionized and implanted into the surface of the p-type GaInp layer. And so on.

The thickness of the current diffusion layer is preferably as thin as possible, as long as the current diffusion effect is exhibited, because the layer itself has a self-absorption property of light.
Hereafter, it is preferably 3 μm or less.

The upper electrode 7 is made of Au when the layer immediately below is a p-layer.
When Be, AuZn, AuSn, or the immediately underlying layer is an n-layer, a material such as AuGe is deposited on the surface of the light extraction surface of the semiconductor element by a method such as vacuum deposition, and then a normal treatment such as patterning or annealing is performed. Then, it is molded into an arbitrary shape at an appropriate position such as a central portion or an end portion of the light extraction surface of the semiconductor. The shape of this electrode is not particularly limited and various shapes can be adopted, but it is preferable to use a dot-shaped electrode from the viewpoint of ease of formation.

The lower electrode 8 is made of Au when the immediately lower layer is an n layer.
Be, AuZn, AuSn, Au when the layer immediately below is a p-layer
A material such as Ge is deposited on the lower surface of the light emitting element in the same manner as in the case of the upper electrode 7, and is shaped into an arbitrary size such as a flat plate by a method such as dicing.

The current blocking layer 2 may be of any type as long as it has a function of blocking current, and in the present invention, it is of p-type or n-type.
The current blocking layer is made of a semiconductor or an electrically insulating material to have a current blocking function. Above p
The current blocking layer made of a n-type or n-type semiconductor has a current blocking function by utilizing the rectifying action of the semiconductor. This rectifying action means that when a pn junction is formed in a semiconductor as shown in FIG. 3, for example, in the case of (A), a current flows through the semiconductor, but in the case of (B), no current flows. It means to be an insulator, and the present invention utilizes the property of becoming an insulator.

As the p-type or n-type semiconductor, any material can be used as long as it is lattice-matched to the substrate.
lGaInP / GaAs sub. In the system, a GaAs layer is generally used, and GaInP / GaAsP sub.
In the system, a GaInP layer and a GaAsP layer can be used. Further, as the electrically insulating material, any material having a function of blocking an electric current may be used, and for example, SiO ₂ , SiN, Al
₂ O ₃ or the like can be used, but in the present invention, it is preferable to use the above-mentioned p-type or n-type semiconductor which can lattice match with the substrate and facilitate the growth of another layer on the block layer.

The current blocking layer 2 is formed by using the above-mentioned material in MO.
By the multi-step growth using the CVD method, the MBE method, the LPE method, or the like, at the boundary between the current diffusion layer 3 and the p-type / n-type semiconductor layer 4 immediately below the upper electrode 7, or the p-type / n-type semiconductor layer. Form in 4.

Since the current blocking layer 2 can be formed in an arbitrary shape according to the shape of the upper electrode, it has the same shape as or similar to the shape of the upper electrode, and its area is ½ of that of the upper electrode.
Or more, preferably 0.8 to 2, and particularly preferably 1.0 to
It may be formed to have a thickness of 1.5. For example, if the upper electrode has a dot shape, a dot-shaped current blocking layer having a diameter of at least ½ or more of the diameter may be used. Further, for example, it may have a width of 4/5 of the maximum width of the upper electrode, and may be formed in a band shape in one direction. If the area of the current blocking layer is less than ½ of that of the upper electrode, the current blocking layer easily flows directly under the electrode and the current blocking effect is reduced, which is not preferable. On the other hand, if it exceeds 2 times, the area of the pn junction that emits light becomes small, and high brightness of the light emitting element cannot be achieved, which is not preferable.

The thickness of this current blocking layer 2 is 0.05.
The thickness is from 10 to 10 μm, preferably from 0.1 to 5 μm, and particularly preferably from 0.5 to 2 μm. The thickness of the current blocking layer is
If it is less than 0.05 μm, it becomes difficult to control the film thickness,
In addition, the current cannot be blocked, which is not preferable. On the other hand, if the thickness exceeds 10 μm, the current diffusion layer becomes thick and the light extraction efficiency of the light emitting element decreases, and the cost becomes high, which is not preferable.

The current blocking layer 2 and the upper electrode 7
Are formed so that the current block layer 2 is located directly below the upper electrode 7. In FIG. 1, the upper electrode 7 is at the center of the light extraction surface, and the current blocking layer 2 is the current diffusion layer 3 and the p-type / n-type semiconductor layer 4 directly below the upper electrode 7.
2, the upper electrode 7 is formed at the end of the light extraction surface, and the current block layer 2 is formed at a position corresponding to the upper electrode 7, as shown in FIG. can do. In this way, if the current block layer 2 is formed so as to be located directly below the upper electrode 7,
Any position is acceptable.

The light emitting device structure of the present invention, for example, FIG.
In the structure shown in (1), when the upper electrode 7 is a positive electrode and the lower electrode 8 is a negative electrode, a current flows due to the rectification action of the semiconductor.
There is no flow from the n-type semiconductor 2 to the p-type semiconductor 4. Therefore, the current flows so as to bypass the n-type semiconductor layer 2 which is the portion directly below the upper electrode 7. Therefore, the current is
Since the current flows intensively around the portion immediately below, the light emitting element H emits strong light in this portion. In addition, since the pn junction immediately below the upper electrode 7 emits almost no light, even if this luminescence is absorbed by the upper electrode 7, the amount of light emitted from the entire light emitting element is hardly affected. As a result, the luminous efficiency of the light emitting element is improved.

In the above example, the current diffusion layer 3 and the semiconductor layer 4 are formed as p-type semiconductors, and the current block layer 2 is formed as an n-type semiconductor. However, in the present invention, as shown in FIG. By reversing the p-type and n-type, a current is applied to the lower electrode 8b.
From the above-mentioned FIG.
The same action and effect as can be obtained.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples. Needless to say, the present invention is not limited to this. Example 1 On an n-type GaAsP substrate having a thickness of 350 μm, a thickness of 10 μm
m n-type GaInP layer and 3 μm thick p-type GaInP layer
After the P layer is sequentially epitaxially grown, the p-type GaI
On the nP layer, n-type GaI having a thickness of 2 μm is formed by the LPE method.
The nP layer was grown on the entire surface. After that, the dot-shaped GaInP layer was left by photolithography, and the rest was removed by etching to form a current block layer. Further, a p-type GaInP layer having a thickness of 5 μm was epitaxially grown on the current blocking layer and the p-type GaInP layer. Next, after vacuum-depositing AuBe on the surface of the wafer after growth, patterning treatment was performed, and a diameter of 150 μm was formed in the central portion of the chip surface which became the light extraction surface when the chip was formed.
m circular electrodes were formed. On the other hand, AuS on the backside of the wafer
n is vacuum-deposited and then diced into chips, as shown in FIG.
A light emitting device H having the structure shown in was produced.

The upper electrode 7 and the lower electrode 8 of this light emitting device H
A current of 20 mA was applied between them to cause the light emitting device H to emit light.
The brightness at this time is measured by a brightness meter (photometer model 5
50-1 manufactured by EG & G) and the results shown in Table 1 were obtained.

Examples 2 to 3 A light emitting device was manufactured in the same manner as in Example 1 except that the diameter of the current blocking layer was changed. The current blocking layer having a diameter of 120 μm was used in Example 2, 180 μm in diameter.
When m was used as Example 3 and the luminance of these light emitting devices was measured in the same manner as in Example 1, the results shown in Table 1 were obtained.

Comparative Example 1 A light emitting device was prepared in the same manner as in Example 1 except that the current blocking layer was not formed in the p-type GaInP layer. When the luminance of this light emitting device was measured in the same manner as in Example 1, the results shown in Table 1 were obtained.

Comparative Examples 2 to 3 Light emitting devices were prepared in the same manner as in Example 1 except that the area of the current blocking layer was changed as shown in Table 1. When the current blocking layer having a diameter of 20 μm was used as Comparative Example 2 and the current blocking layer having a diameter of 300 μm was used as Comparative Example 3, the brightness of these light emitting devices was measured in the same manner as in Example 1 above.
The results shown in Table 1 were obtained.

[0027]

[Table 1]

As is clear from Table 1, the light emitting device structure of the present invention has a high brightness of 5.2 mcd, which is higher than that of the conventional light emitting device structure in which the current blocking layer is not formed. It was a 57% improvement.

[0029]

As described in detail above, according to the present invention,
Since the current blocking layer is formed between the upper electrode and the pn junction immediately below the upper electrode, current is prevented from concentrating on the pn junction directly below the upper electrode. In addition, since the current concentrates and flows around the pn junction portion just below the block layer, strong light emission of the light emitting element can be efficiently extracted to the outside, and the brightness of the light emitting element can be improved. Therefore, the brightness of the light emitting device can be significantly improved as compared with that of the conventional light emitting device structure, resulting in a high brightness light emitting device.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a light emitting device structure according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a light emitting device structure according to another embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a rectifying function of a semiconductor.

FIG. 4 is a schematic cross-sectional view showing a semiconductor conduction type structure in the light emitting device structure of the present invention.

FIG. 5 is a schematic cross-sectional view showing a conventional light emitting device structure.

[Explanation of symbols]

 1 pn junction 2 current blocking layer 3 p-type / n-type current diffusion layer 4 p-type / n-type semiconductor layer 5 n-type / p-type semiconductor layer 6 n-type / p-type semiconductor substrate 7 upper electrode 8 lower electrode 9 boundary H light emitting element

Claims (3)

[Claims] 1. A light emitting device structure in which an n-type semiconductor layer and a p-type semiconductor layer are pn-junctioned, and an upper electrode is formed on a light extraction surface, and a lower electrode is formed on a back surface on the opposite side, which is directly below the upper electrode. A light emitting device structure in which a current blocking layer is formed between the pn junction and the upper electrode in the direction. 2. The light emitting device structure according to claim 1, wherein the current blocking layer is an n-type or p-type semiconductor layer or an electrically insulating layer. 3. The current blocking layer is formed to be the same as or similar to the upper electrode, has an area of at least ½ of the upper electrode, and has a thickness of 0.05 to 1.
The light emitting device structure according to claim 1, which has a thickness of 0.0 μm.