JPH05283736A - Light emitting diode - Google Patents

Abstract

PURPOSE:To provide the title light emitting diode in the composition capable of constantly making a mesa forming trench down to precise position regardless of the dispersion in the layer thickness during the crystal growing step. CONSTITUTION:A buffer layer 2, an etching stop layer 14 are grown on a single crystal substrate 1 while removing the part for an arrow head type trench 13. Next, block layers 3, 4 and a clad layer 5 are grown and after the formation of the arrow head type trench 13, an active layer 6, another clad layer 7 and a cap layer 8 are grown to make mesa forming trenches 12. At this time, the depth of the mesa forming trenches 12 can be decided by an etching stop layer. In the figure, 9 represents the electrodes of insulating films 10, 11.

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 which can be used for light sources such as optical communication and optical sensors.

[0002]

2. Description of the Related Art In a light emitting diode,
In order to realize a high-speed response characteristic with a short fall time, it is considered to reduce the parasitic capacitance of the element (chip) of the light emitting diode. As a method thereof, for example, in a laser diode, a p-InP buffer layer and an n-I are arranged parallel to both sides of a buried portion of an InGaAsP active layer.
A method of forming a mesa structure by digging a mesa forming groove deeper than the interface of the nP block layer is generally used.

FIG. 9 is a sectional view of an example of a conventional laser diode. In the figure, 1 is a p-InP substrate, 2 is a p-I
nP buffer layer, 3 is n-InP block layer, 4 is p-
InP block layer, 5 is a p-InP clad layer, 5a is a p-InP layer, 6 is an InGaAsP active layer, and 6a is I.
nGaAsP layer, 7 is n-InP clad layer, 8 is n
-InGaAsP cap layer, 9 is SiNx insulating film, 1
Reference numeral 0 is a p electrode, 11 is an n electrode, 12 is a mesa forming groove, and 13 is an arrow head type groove.

A method of manufacturing the conventional laser diode shown in FIG. 9 will be described. First, the p-InP buffer layer 2, the n-InP block layer 3, and the p-InP block layer 4 are epitaxially grown on the p-InP single crystal substrate 1 by liquid phase growth. Next, the arrow head type groove 13 is formed by etching in a portion corresponding to the top of the mesa. Furthermore, the p-InP clad layer 5 and InGaAsP
Active layer 6, n-InP clad layer 7, n-InGaAs
The four layers of the P cap layer 8 are embedded and grown by liquid phase growth. Reference numeral 5a is a layer formed simultaneously with the p-InP cladding layer 5, and 6a is a layer formed simultaneously with the InGaAsP active layer 6. Then, on both sides of the arrow head type groove 13 produced previously, the mesa forming groove 12 deeper than the InGaAsP active layer 6 is dug to form a mesa. Then, after forming the SiNx insulating film 9, a stripe type current window is opened on the waveguide to form the p electrode 10 and the n electrode 11 on both sides of p and n. Then, it is cleaved and separated into individual chips to complete a laser diode element.

Since the wafer of embedded growth is relatively small, the mesa forming groove 12 is formed in each of the small wafers and the mesa is formed once. Forming mesas in this process is also useful for reducing manufacturing costs,
This method has been used conventionally.

In the conventional manufacturing method as described above, the mesa forming groove 12 is formed by chemical etching or the like, but the mesa forming groove 12 having the same depth is formed due to the variation in the layer thickness during crystal growth.
Even if the above is manufactured, the bottom of the mesa formation groove 12 may not reach the interface between the p-InP buffer layer 2 and the n-InP block layer 3. In such a case, the target parasitic capacitance cannot be reduced.

When digging the mesa forming groove 12, in order to always keep the bottom of the mesa forming groove 12 at the same position, the crystal layer thickness,
Regarding the relationship between the etching conditions and the depth of the mesa formation groove, etc., create data with sub-micron accuracy,
It is necessary to reproduce it. Also, in some cases,
It is also necessary to observe the progress of etching. Therefore, there is a problem that advanced manufacturing technology is required, process management is expensive, and the cost is high.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and always forms a mesa forming groove up to an accurate position even if the layer thickness varies during crystal growth. An object of the present invention is to provide a light emitting diode having a structure capable of achieving the above.

[0009]

The present invention is characterized in that a light emitting diode having a mesa forming groove on both sides of an active region has an etching stop layer for forming a mesa in a crystal layer.

[0010]

According to the present invention, the depth of selective etching is determined by adopting the structure having the etching stop layer in the crystal layer in the light emitting diode having the mesa forming grooves on both sides of the active region. A desired mesa forming groove can be formed regardless of the crystal layer thickness and etching conditions.

[0011]

1 is a sectional view of a laser diode according to an embodiment of the present invention. 2 to 8 are process charts for explaining an example of the method for manufacturing the laser diode. In the figure, parts similar to those in FIG. 9 are assigned the same reference numerals and explanations thereof are omitted. Reference numeral 14 is a p-InGaAsP etching stop layer, 15 is an InGaAsP mask layer, and 16 is a photoresist.

In this embodiment, like the conventional example described in FIG. 9, the present invention is applied to a laser diode having an arrow head type groove, and the mesa forming grooves 12 formed on both sides of the active region are used. , Mesas are formed.

A method of manufacturing the laser diode shown in FIG. 1 will be described. On the p-InP single crystal substrate 1, a p-InP buffer layer 2 and a p-InGaAsP etching stop layer 14 are formed.
Are grown (FIG. 2). P-I near the portion where the InGaAsP active layer is embedded
The etching stop layer 14 of nGaAsP is removed (FIG. 3). n-InP block layer 3 and p-InP block layer 4
Are grown epitaxially. On top of that, I
Crystal growth of the nGaAsP mask layer 15 is performed (FIG. 4). The InGaAsP mask layer 15 is patterned and etched to form the arrow head type groove 13 (FIG. 5). HCl can be used as the etchant, but other etchants may be used. The InGaAsP mask layer is removed, and four layers of the p-InP clad layer 5, the InGaAsP active layer 6, the n-InP clad layer 7, and the n-InGaAsP cap layer 8 are grown. When the p-InP cladding layer 5 and the InGaAsP active layer 6 are embedded and grown, the p-InP layer 5a is formed.
And the InGaAsP layer 6a are simultaneously formed (FIG. 6). Photoresist 16 for making a mesa pattern
Is formed, and the portion of the mesa formation groove is patterned by photolithography (FIG. 7). Using the photoresist 16 as a mask, n-InGa
The AsP cap layer 8 is n-I with a sulfuric acid-based etchant.
The nP clad layer 7 is etched with a hydrochloric acid-based etchant. Then, the InGaAsP layer 6a is etched with a sulfuric acid-based etchant, and then the p-InP layers 5a and 5p are formed.
The -InP block layer 4 and the n-InP block layer 3 are etched with a hydrochloric acid-based etchant. At the time of this etching, the etching stop layer 14 of p-InGaAsP is used.
This restricts the progress of etching (FIG. 8). After forming the SiNx insulating film 9 on the n side, a stripe type current window is opened on the waveguide (on the arrow head type groove 13) to form the n electrode 11, the p electrode 10 and the individual chips. Cleave (Fig. 1). The laser diode is completed by the above procedure.

InGa in the above manufacturing process
The AsP mask layer 15 may be made of another substance as long as it serves as a mask for the etchant. Further, the material used for each layer constituting the laser diode such as the block layer, the clad layer, the active layer, and the cap layer is not limited to the above-mentioned materials, and other suitable materials may be used. It goes without saying that the manufacturing method of can be applied.

In the above-mentioned embodiments, the p-InGaAsP layer is used as the etching stop layer, but n-InGa is used.
A layer of AsP can also be used. However, in this case, since the etching stop layer forms a pn junction and the parasitic capacitance is not reduced, the n-InGa under the mesa formation groove is not formed.
It is necessary to remove the portion of the AsP layer by etching.

In the above-mentioned embodiments, the p-type substrate is used as the base, but by changing the p-type of each layer to the n-type and changing the n-type to the p-type, a laser diode based on the n-type substrate is manufactured. be able to.

Further, although the above-described embodiments have been described with respect to the case where the present invention is applied to an arrow head type laser diode, the present invention is also applied to other types of laser diodes such as stripe type and edge emitting diodes. It is clear that can be applied.

[0018]

As is apparent from the above description, according to the present invention, a light emitting diode capable of reliably digging a mesa forming groove up to an etching stop layer by selective etching without depending on the layer thickness of each layer is provided. There is an effect that it can be provided. In the manufacturing process, the etching conditions do not affect the etching depth, so that it does not require submicron-precision data and does not particularly require observation of the etching progress. Is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a laser diode manufactured by a manufacturing method of the present invention.

[Figure 2]

FIG. 8 is a process drawing of an example of the manufacturing method of the present invention.

FIG. 9 is a cross-sectional view of a conventional laser diode.

[Explanation of symbols]

 1 p-InP single crystal substrate 2 p-InP buffer layer 3 n-InP block layer 4 p-InP block layer 5 p-InP clad layer 6 InGaAsP active layer 7 n-InP clad layer 8 n-InGaAsP cap layer 9 SiNx insulation Film 10 p electrode 11 n electrode 12 mesa formation groove 13 arrow head type groove 14 p-InGaAsP etching stop layer 14 15 InGaAsP mask layer 16 photoresist

Claims (1)

[Claims] 1. A light emitting diode having a mesa forming groove on both sides of an active region, wherein the light emitting diode has an etching stop layer for forming a mesa in a crystal layer.