JPH07193279A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To provide an optical semiconductor device which can be manufactured at a low cost by simple constitution and improve the leading-out efficiency of light to the outside. CONSTITUTION:An optical semiconductor device 10 is constituted, by containing an optical semiconductor chip 12 formed on a semiconductor substrate 11, an electrode 13 formed in the vicinity of the surface central part of the optical semiconductor chip 12, and a back side electrode 14 formed on the rear of the semiconductor substrate 11, and forming an electric insulation layer 15 in a part of the lower surface of the electrode 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device such as an LED.

[0002]

2. Description of the Related Art Conventionally, an LED having a structure shown in FIGS. 8 and 9 is known as an optical semiconductor device. This LED
1 is an LED chip 3 formed on a semiconductor substrate 2,
It is composed of an electrode 4 formed on the surface of the LED chip 3. The LED chip 3 has an active layer 3a in the middle in the vertical direction, and when a current passes through the active layer 3a, the active layer 3a emits light. A back electrode 5 is formed on the lower surface of the semiconductor substrate 2.

According to the LED 1 thus constructed,
By applying a voltage between the electrode 4 formed on the surface of the LED chip 3 and the back electrode 5 provided on the lower surface of the semiconductor substrate 2, for example, as shown by an arrow in FIG. An electric current will flow toward the back electrode 5. Then, when this current passes through the active layer 3a of the LED chip 3, the active layer 3a emits light. Thus, the light from the active layer 3a is emitted to the outside from the upper surface of the LED 1, that is, the surface of the LED chip 3.

In this case, the current flowing from the electrode 4 toward the back electrode 5 flows so that the resistance value of the path is minimized, that is, the shortest distance is taken. By the way, the electrode 4 is located near the center of the surface of the LED chip 3. Therefore, the current passing through the active layer 3a is concentrated immediately below the electrode 4 in the active layer 3a. For this reason, the emission center of the active layer 3a becomes as shown by the symbol A in FIG. 9, and its emission intensity is maximum in the region corresponding to the electrode 4 as shown in the graph of FIG. If it goes out of range, it will drop sharply.

On the other hand, the electrode 4 formed on the surface of the LED chip 3 blocks light. Therefore, the emission characteristics of the LED 1 are such that the emission intensity to the outside becomes zero in the region of the electrode 4 where the emission intensity is maximum, so that only the shaded portion in FIG. 10 is extracted to the outside. Become. Therefore, there is a problem that the efficiency of extracting light to the outside becomes extremely low.

For this reason, there is known an LED having a structure as shown in FIG. 11, for example, which has an improved light extraction efficiency. That is, in FIG. 11, the LED 6 has a structure different from that of the LED 1 of FIGS. 8 and 9 in that the current blocking layer 3b is provided above the active layer 3a in the LED chip 3. The current blocking layer 3b is formed by forming an island-shaped high resistance region 3c corresponding to the electrode 4 in the crystal of the LED chip 3.

According to this structure, the current from the electrode 4 is
The high resistance region 3c of the current blocking layer 3b is avoided and it wraps around. Therefore, passing through the central portion of the active layer 3a that does not contribute to the emission of light to the outside can be excluded. Thus, the emission center of the active layer 3a becomes as shown by the symbol B in FIG. 11, and the emission efficiency with respect to the input current can be improved.

[0008]

However, in such a back LED 6, when the current blocking layer 3b is formed, in order to define the high resistance region 3c corresponding to the electrode 4, the current blocking layer 3b is formed. When forming, an etching step is required to selectively remove the portion other than the high resistance region 3c. Therefore, LE on the semiconductor substrate 2
In the crystal growth process of the D chip 3, it is necessary to interrupt the crystal growth midway and form the current blocking layer 3b, and then the crystal growth is performed again. Therefore, there is a problem in that the use efficiency of the crystal growth apparatus in the crystal growth step is reduced, and an additional etching step is required, resulting in an increase in the number of steps and an increase in manufacturing cost.

In view of the above points, it is an object of the present invention to provide an optical semiconductor device which can be manufactured at a low cost with a simple structure and can improve the efficiency of extracting light to the outside. There is.

[0010]

To achieve the above object, according to the present invention, an optical semiconductor chip formed on a semiconductor substrate, an electrode formed near the center of the surface of the optical semiconductor chip, and An optical semiconductor device including a back electrode formed on the lower surface of a semiconductor substrate is characterized in that an electrical insulating layer is provided on a part of the lower surface of the electrode.

Further, according to the present invention, preferably, the semiconductor substrate is provided with a concave portion opened downward in a region immediately below the electrode.

[0012]

According to the first structure, part of the lower surface of the electrode,
For example, since an electric insulating layer is provided near the center except for the periphery, the presence of the electric insulating layer causes the current from the electrode to enter the LED chip from the periphery of the electrode and travel toward the back electrode. Become. Therefore, in the active layer of the LED chip, the light emission height is maximized in the region corresponding to the peripheral edge of the electrode, and the light emission intensity is reduced from there to the outside and the inside.

Further, according to the second structure, since the recessed portion is provided in the region corresponding to the electrode on the lower surface of the semiconductor substrate, the existence of this recessed portion causes the current from the electrode to flow in the LED chip. After entering, it will proceed toward the back electrode so as to avoid the recess. Therefore, LE
In the active layer of the D chip, the emission intensity becomes maximum in the region corresponding to the peripheral edge of the electrode, and the emission intensity decreases from the region toward the outside and inside. Here, since the current from the electrode circulates toward the periphery so as to avoid the concave portion, the emission intensity from the electrode periphery to the outside can be increased.

Thus, in any structure, the light emission intensity is lowered in the region of the active layer corresponding to the electrode.
As a whole, the efficiency of extracting light to the outside can be improved. In addition, the crystal growth process for forming the LED chip can be continuously performed without interruption in the middle, and an etching process or the like is not necessary. Therefore, the number of processes does not increase, and the optical semiconductor device is simple. It is manufactured at low cost.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. 1 and 2 show a first embodiment of an LED to which the present invention is applied, and the LED 10 is
The LED chip 12 is formed on the semiconductor substrate 11, and the electrode 13 is formed on the surface of the LED chip 12. The LED chip 12 has an active layer 12a in the middle in the vertical direction, and when a current passes through the active layer 12a, the active layer 12a emits light. A back electrode 14 is formed on the lower surface of the semiconductor substrate 11.

The above structure is the same as that of the conventional LED 1 shown in FIGS. 8 and 9, but in the LED 10 according to the embodiment of the present invention, a part of the lower surface of the electrode 13, that is, in the case of the drawing, is used. Is slightly smaller than the electrode 13 and has a circular shape,
For example, an electric insulating layer 15 made of SiO ₂ , SiNx or the like is formed.

The LED 10 according to the embodiment of the present invention is configured as described above, and a voltage is applied between the electrode 13 formed on the surface of the LED chip 12 and the back electrode 14 provided on the lower surface of the semiconductor substrate 11. By applying, a current flows from the electrode 13 to the back electrode 14 as indicated by an arrow in FIG. That is, first, in the electrode 13, the current moves toward the periphery of the electrode 13 and then the electrode 1
It enters into the LED chip 12 from the peripheral part of 3. When this current passes through the active layer 12a of the LED chip 12, the active layer 12a emits light, and the light from the active layer 12a is emitted to the outside from the upper surface of the LED 10, that is, the surface of the LED chip 12. Will be done.

Thus, the emission center of the active layer 12a is located at a position corresponding to the peripheral edge of the electrode 13 as indicated by the symbol C in the drawing, and the emission intensity is as shown in FIG.
3 is the largest at the periphery, and decreases from the outer edge to the inner edge. At that time, due to the presence of the electrode 13, the emission intensity of the light extracted to the outside is only in the shaded portion in FIG. In this case, within the drive current range of the LED that is efficiently converted into light,
Since the internal light emission intensity in the active layer is almost proportional to the drive current, as compared with the light emission intensity of the conventional LED 1 shown in FIG. The light extraction efficiency can be improved.

4 to 6 show an LED to which the present invention is applied.
In the second embodiment, the LED 20 is a semiconductor substrate 21.
It is composed of an LED chip 22 formed above and an electrode 23 formed on the surface of the LED chip 22. The LED chip 22 has an active layer 22a in the middle in the vertical direction, and when a current passes through the active layer 22a, the active layer 22a emits light. Further, on the lower surface of the semiconductor substrate 21,
The back electrode 24 is formed.

The above structure is similar to the conventional LED 1 shown in FIGS. 8 and 9, but in the LED 20 according to the second embodiment, the semiconductor substrate 21 is further added.
However, in the region immediately below the electrode 23, the recessed portion 21a opened downward is provided. Here, the thickness of the semiconductor substrate 21 is, for example, about 100 to 300 μm, but the thickness of the LED chip 22 is, for example, about several μm to several tens of μm, and the active layer 22 a of the LED chip 22.
Are arranged very close to the semiconductor substrate 21.

The LED 20 according to the second embodiment is configured as described above, and a voltage is applied between the electrode 23 formed on the surface of the LED chip 22 and the back electrode 24 provided on the lower surface of the semiconductor substrate 21. By applying, a current flows from the electrode 23 to the back electrode 24, for example, as shown by the arrow in FIG. That is, the current is the LED chip 2
The active layer 22a emits light when entering the inside of the LED 2 and passing through the active layer 22a of the LED chip 22, and the light from the active layer 22a is emitted to the outside from the upper surface of the LED 20, that is, the surface of the LED chip 22. become.

In this case, the semiconductor substrate 21 has the concave portion 21a.
With the provision of, the electric current will sneak in the LED chip 22 so as to avoid the concave portion 21a. Therefore, when the current passes through the active layer 22a,
It will escape to the periphery from the region corresponding to the electrode 23.
Therefore, the emission center of the active layer 22a is at a position corresponding to the peripheral edge of the electrode 23, as indicated by the symbol D in FIG.
As shown in FIG. 7, the emission intensity is maximum at the periphery of the electrode 23 and decreases from the outside toward the outside and inside. At that time, due to the presence of the electrode 23,
The emission intensity of the light extracted to the outside is only the shaded portion in FIG. 7.

Here, since the current sneak in the LED chip 22 so as to avoid the concave portion 21a,
In the region corresponding to the outside of the peripheral edge of the electrode 23, the emission intensity is improved as compared with the conventional LED 1.

In the above embodiment, the present invention is LE
Although the case where the present invention is applied to D has been described, it is obvious that the present invention can be applied to not only this but also other optical semiconductor devices.

[0025]

As described above, according to the present invention, the light emission intensity is lowered in the region of the active layer corresponding to the electrode, so that the efficiency of extracting light to the outside can be improved as a whole. In addition, the crystal growth process for forming the LED chip can be continuously performed without interruption in the middle, and an etching process or the like is not necessary.
The optical semiconductor device can be easily manufactured at low cost without increasing the number of steps. Thus, according to the present invention, there is provided an optical semiconductor device that can be manufactured at a low cost with a simple configuration and that the efficiency of extracting light to the outside can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of an LED to which the present invention has been applied.

2 is a cross-sectional view of the LED of FIG.

FIG. 3 is a graph showing the emission intensity of the LED of FIG.

FIG. 4 is a sectional view of a second embodiment of an LED to which the present invention has been applied.

FIG. 5 is a perspective view of the LED of FIG. 4 viewed from below.

FIG. 6 is a plan view of the LED of FIG.

FIG. 7 is a graph showing the emission intensity of the LED of FIG.

FIG. 8 is a plan view showing an example of a conventional LED.

9 is a cross-sectional view of the LED of FIG.

10 is a graph showing the emission intensity of the LED of FIG.

FIG. 11 is a cross-sectional view showing another example of a conventional LED.

[Explanation of symbols]

 10 LED 11 Semiconductor Substrate 12 LED Chip 13 Electrode 14 Back Electrode 15 Electrical Insulation Layer 20 LED 21 Semiconductor Substrate 21a Recess 22 LED Chip 23 Electrode 24 Back Electrode

Claims (2)

[Claims] 1. An optical semiconductor including an optical semiconductor chip formed on a semiconductor substrate, an electrode formed near the center of the surface of the optical semiconductor chip, and a back electrode formed on the lower surface of the semiconductor substrate. The device is an optical semiconductor device characterized in that an electrical insulating layer is provided on a part of the lower surface of the electrode. 2. An optical semiconductor chip including an optical semiconductor chip formed on a semiconductor substrate, an electrode formed near the center of the surface of the optical semiconductor chip, and a back electrode formed on the lower surface of the semiconductor substrate. A semiconductor device, wherein the semiconductor substrate is provided with a concave portion opened downward in a region immediately below the electrode.