JPH0595133A - End-face light-emitting diode and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To provide a structure for an end face light emitting device with high emission effect, and its manufacturing method. CONSTITUTION:A region 15 with an activated layer thicker than that of an activated layer 14 is formed on the rear side of the activated layer 14 other than the side facing to a light emitting end face 10. The region 14 with a thin activated layer serves as a light amplifying region and the region 15 with a thicker activated layer serves for confining the emitted light in the activated layer and providing it to the light amplifying region so that the power of the emitted light can be enhanced. After a current blocking layer 2A is removed, a groove formed thereon with varied widths so that a clad layer 3A, which is grown on the groove, is formed in a shape that is evenly at a narrow part, but is bent deeply at a wide part in the groove. Also the activated layer 4A formed thereon is bent deeply and grown thicker at a wide groove part, and thereby the thickness of the activated layer can be changed in regions. Consequently, the activated layers with different thicknesses can be simultaneously formed for different regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge emitting diode used as a light source for optical communication using a fiber and a method for manufacturing the same.

[0002]

2. Description of the Related Art Semiconductor lasers and light emitting diodes are used as optical communication light sources using fibers. In recent years, edge-emitting type light emitting diodes, which are similar to semiconductor lasers in terms of coupling with fibers, but are not affected by return light like semiconductor lasers, have come to be used as light sources. ..

A conventional edge emitting diode will be described below. FIG. 8 and FIG. 9 are a side sectional view of the center of the light emitting surface and a front view of the light emitting surface (excluding the antireflection film) of the conventional edge emitting diode. On the p-type GaAs substrate 1, there is an n-type GaAs current blocking layer 2 for flowing a current only partially, a p-type GaAlAs cladding layer 3 and a p-type Ga.
A double heterostructure is formed by the As active layer 4 and the n-type GaAlAs clad layer 5, and n-type GaAs is further formed thereon.
There is a contact layer 6. There are an n-side electrode 7 and a p-side electrode 8 above and below. An antireflection film 9 is attached to the main light emitting surface 10 and the rear surface 11. The current blocking layer 2 is left on the rear surface 11 side to form a current non-injection area 13, and the light emitting surface side is a current injection area 12.

When a current is applied to the edge emitting diode having the above structure, light is emitted in the active layer of the current injection region 12. Of the light emitted from the current injection region 12, the light traveling toward the light emitting surface 10 is emitted from the light emitting surface 10 while generating stimulated emission light and exponentially amplifying the light. On the other hand, the light traveling toward the rear surface 11 side generates stimulated emission light in the current injection region 12 to be amplified, but is absorbed and attenuated in the current non-injection region 13. Therefore, in the above structure, since there is no reflection of light from the rear, laser oscillation can be suppressed. FIG. 10 shows the states of this amplification and attenuation.

[0005]

In such a conventional end face light emitting diode, the light amplification in the current injection region 12 is isotropic, and the light toward the light emitting surface and the light toward the rear surface have the same amplification degree. Is amplified by. Therefore, the optical power equivalent to the emission power (light emission output) from the light emission surface is absorbed in the current non-injection region 13. Furthermore, if there is even a slight amount of light reflection at the light emitting end face 10, the reflected light at the end face is also amplified and propagates backward, so that the unusable backward optical power becomes large, and as a result, the light is emitted. The luminous efficiency of the light emitted from the surface is greatly reduced.
As described above, the conventional edge emitting diode has a drawback that the light power in the backward direction is larger in principle and the light emission output from the light emitting surface is smaller.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an edge emitting diode having a high light emission output and a method for manufacturing the same.

[0007]

In order to achieve this object, the edge emitting diode of the present invention has a thickness of the active layer on the light emitting surface side behind the active layer on the light emitting surface side in the current injection region. In order to form a thick region and a thin region of the active layer, a groove having a different width is formed in the light guiding region in the waveguiding direction, and the clad on it is formed. The layer was realized by flatly embedding it in a narrow groove portion, curving it in a wide groove portion, and growing it, and then growing an active layer in a thick groove in a wide groove portion.

[0008]

With the above structure, the emitted light is highly confined in the active layer in the thick portion of the active layer. On the other hand, since the injected carrier density is high in the thin portion of the active layer, the gain, that is, the optical amplification degree is large. Utilizing this, light amplification is performed in the thin region of the active layer on the light emission surface side, and light is confined in the active layer in the thick region of the active layer on the rear side to supply light to the light amplification region. As a result, the manner of amplification of the light traveling toward the light emitting surface and the manner of amplification of the light traveling toward the rear surface are changed, and the amplification of the light traveling toward the light emitting surface becomes greater. As described above, by forming the current injection region with the light amplification region having the thin active layer and the light supply region having the thick active layer, the light emission output can be improved.

On the other hand, the active layer grows thicker in the curved portion than in the flat portion in order to fill the recess. Therefore, active layers having different thicknesses can be partially grown.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

1, FIG. 2 and FIG. 3 are a side sectional view of a light emitting surface center of an end face light emitting diode according to an embodiment of the present invention, a front view of the light emitting surface (excluding an antireflection film) and a light emitting surface. It is a parallel sectional view. On the p-type GaAs substrate 1,
There is an n-type GaAs current blocking layer 2A for flowing a current only partially, and p-type GaAlAs cladding layers 3A, p
-Type GaAs active layer 4A, n-type GaAlAs clad layer 5
To form a double hetero structure, and an n-type GaAs contact layer 6 was further provided thereon. Then, an n-side electrode 7 and a p-side electrode 8 are formed vertically. Main light emitting surface 10
An antireflection film 9 is attached to the rear surface 11. Figure 2
Although the front view of the light emitting surface is similar to the conventional one, the side sectional view of FIG. 1 and the sectional view parallel to the light emitting surface of FIG. 3 are different.

A method of manufacturing this structure will be described step by step. First, as shown in FIG. 4A, the p-type GaAs substrate 1
After growing the n-type GaAs block layer 2A on the upper surface by a liquid phase epitaxial growth method to a thickness of 0.8 μm, this n-type Ga is formed.
The As block layer 2A was removed by using a mixed solution of phosphoric acid and hydrogen peroxide, leaving a shape portion shown by diagonal lines in FIG.
A 2 μm groove was formed. The shape of this groove is the length L of the element.
= 350 μm, the narrow groove width is the groove width W1 = 4 μm
m, the length L1 = 200 μm, the wide groove portion has a groove width W2 = 10 μm, and the length L2 = 50 μm. FIG. 4A is a sectional view of BB 'and CC' at this time. Then, as shown in FIG. 4B, p-type GaAlAs
3A on the n-type block layer 2A d31 = 0.25 μm
Has grown to become. At this time, as shown in the figure, the groove width W
The groove is flatly embedded in the area of 1 = 4 μm, but the groove width W2
= 10 μm, the shape became curved. As described above, the filling speed of the groove depends on the groove width. Further, as shown in FIG. 4C, a p-type GaAs active layer 4A was grown so that d41 = 0.08 μm in a flat place. Then, as shown in the figure, the curved portion grows to fill this recess, so that it grows thicker than the flat portion and becomes a curved active layer in the CC ′ cross section, and d42 = 0 at the thickest portion. It became 0.3 μm. In this way
Regions having different active layer thicknesses were simultaneously formed. afterwards,
The n-type GaAlAs clad layer 5 has a thickness of 2.0 μm, and n-type Ga
An As contact layer 6 was grown to a thickness of 3.5 μm to form an n-side electrode 7 and a p-side electrode 8. The cross-sectional structure of BB 'at this time is the same as the front view of the light emitting surface and is shown in FIG.
3 is a sectional view of FIG. Further, an antireflection film was formed on the light emitting surface and the rear surface.

FIG. 1 is a side sectional view of the edge-emitting LED thus manufactured. In the current injection region 12, a thin region 14 of the active layer is arranged on the light emitting surface 10 side, and a thick region 15 of the active layer is arranged behind it.

The operation of the edge emitting diode having the above structure will be described below.

First, a region of the current injection region 12 where the active layer is thin is a light amplification region. When the active layer is thin, the injected carrier density is increased and the optical amplification is increased. Therefore, the light is amplified as the emitted light travels in the direction of the light exit surface.

On the other hand, the thick region of the active layer is the light supply region to the light amplification region. Assuming that the difference in refractive index between the active layer and the cladding layer is 8.4%, the light confinement ratio in the active layer is 28% at a thickness of 0.08 μm, while the light confinement ratio is 0.8%.
When the thickness is 3 μm, it is 85%, which is about three times, and the thicker the active layer is, the light can be confined in the active layer. By arranging the thick region of the active layer behind the light amplification region, the light emitted in this region is efficiently confined in the active layer and the confined light is supplied to the light amplification region.

FIG. 6 shows the state of light amplification in the active layer of the edge emitting diode of the present invention in comparison with the conventional structure. A solid line 16 shows how light is amplified in the active layer of the edge emitting diode of the present invention. The broken line 17 shows the state of optical amplification in the active layer of the conventional structure, which is the same as FIG. In the region 15 where the active layer is thick, the injection carrier density is lower than that in the region 14 where the active layer is thin, so that the amplification degree is small, but more light is trapped and more light becomes a seed for optical amplification. Current non-injection region 1 of current injection region 12
The light traveling from the vicinity of the boundary with the direction 3 toward the light emitting surface has a small amplification degree in the thick region 15 of the active layer, but there is a large amount of light that becomes a seed of light amplification, so the intensity of the guided light is the same as in the conventional structure. Greater than That is, more light can be supplied to the thin region 14 of the active layer than in the conventional structure. Then, in the region 14 where the active layer is thin, the amplification degree is larger than that in the region 15 where the active layer is thick and reaches the light emitting surface. On the other hand, the light traveling from the vicinity of the light emitting surface toward the rear surface is amplified in the region 14 where the active layer is thin as in the conventional structure, but the amplification degree becomes small in the region 15 where the active layer is thick. Then, it is absorbed and attenuated in the current non-injection region 13. In this way, in the current injection region 12, the amplification of the light traveling toward the light emitting surface becomes larger than the amplification of the light traveling toward the rear direction.

FIG. 7 shows current vs. light emission output characteristics of the edge emitting diode according to one embodiment of the present invention and the conventional edge emitting LED. A solid line 18 represents the current-to-light-emission output characteristic of the edge emitting LED according to the embodiment of the present invention, and a broken line 19 represents the current-to-emission output characteristic of the conventional edge-emitting LED. As is apparent from FIG. 7, the end face light emitting diode of one embodiment of the present invention has a larger light emission output.

As described above, with respect to the light emission surface direction,
By arranging a region where the active layer is thicker than the light emitting surface side behind the active layer on the light emitting surface side, the light emission output can be increased. Further, it is possible to simultaneously form active layers having different thicknesses by utilizing that the width of the groove is changed and the filling speed of the groove depends on the width of the groove.

[0020]

As described above, according to the present invention, the region where the active layer is thicker than the light emitting surface side is disposed behind the active layer on the light emitting surface side with respect to the light emitting surface direction. It is possible to provide an edge emitting diode with high output. Further, the width of the groove formed by removing the current block layer is changed, and the clad layer grown on the groove blocks the narrow groove width to be flat.
If it is curved in the wide groove portion, the active layer further growing on it will be curved in the wide groove portion and grow thicker than other portions, so that the thickness of the active layer is locally changed. As a result, it is possible to provide a method for manufacturing an edge-emitting diode in which active layers having different thicknesses are locally formed simultaneously.

[Brief description of drawings]

FIG. 1 is a side sectional view of an end face light emitting diode according to an embodiment of the present invention.

FIG. 2 is a front view of a light emitting surface of the edge emitting diode (excluding an antireflection film) of FIG.

FIG. 3 is a cross-sectional view of a portion where the thickness of the active layer is parallel to the front view of FIG.

FIG. 4 is a process sectional view showing a method for manufacturing an edge-emitting LED according to an embodiment of the present invention.

FIG. 5 is a pattern diagram when a groove is formed in the current blocking layer 2A of FIG.

6 is a diagram showing how light is amplified and attenuated in the active layer of the edge emitting diode of FIG. 1 in comparison with a conventional example.

FIG. 7 is a diagram showing current vs. light emission output characteristics of the edge emitting diode of FIG. 1 in comparison with a conventional example.

FIG. 8 is a side sectional view of a conventional edge emitting diode, and a sectional structural view.

9 is a front view of the light emitting surface of the edge emitting diode (excluding the antireflection film) of FIG.

10 is a diagram showing how light is amplified and attenuated in the active layer of the edge-emitting diode shown in FIG.

[Explanation of symbols]

 1 p-type GaAs substrate 2A n-type GaAs block layer 3A p-type GaAlAs clad layer 4A p-type GaAs active layer (active layer) 5 n-type GaAlAs clad layer 6 n-type GaAs contact layer 7 n-side electrode 8 p-side electrode 9 antireflection Film 10 Light emitting surface 11 Rear surface 12 Current injection region 13 Current non-injection region 14 Thin current injection region of active layer 15 Thick current injection region of active layer

Claims (2)

[Claims] 1. An end face light emitting diode, which has at least an active layer region that is thicker than the thickness of the active layer on the light emitting surface side behind the active layer on the main light emitting surface side. 2. A groove having a different width is formed in a light guiding region in a waveguiding direction, and a clad layer is embedded thereon by flattening a narrow groove portion and curving a wide groove portion. Further, there is provided a method of manufacturing an end face light emitting diode, which further comprises at least a step of growing the active layer in such a manner that the active layer is curved in a wide portion of the groove to be thick and the thickness of the active layer is locally changed in an optical waveguide direction.