JPH0472784A - Manufacture of semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To enable a radiation beam to be oscillated in a basic mode and to make a light emitting diode high in emission efficiency and low in threshold current by a method wherein a semiconductor layer which is made to serve as a current blocking layer is made to grow on a board-like region where a protrusion is not provided, the semiconductor layer to serve as a first current blocking layer is subjected to a melt etching process to be thin as prescribed into a first current blocking layer, and a second current blocking layer is provided onto the first current blocking layer. CONSTITUTION:An N-InP layer is formed on the region of a P-InP substrate where a mesa stripe 6 is not provided. The N-InP layer is melt-etched using an SiO2. thin film 5 as a mask to form a first current blocking layer 7a. In succession, a P-InP layer is grown on the first current blocking layer 7a to form a second current blocking layer 8. The second current blocking layer 8 is formed so as to come into contact with a new plane 4b of a second clad layer 4 which is formed by removing a part 4a of a second clad layer 4 in contact with an N-InP layer 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor light emitting device used for laser oscillation, and more specifically to an embedded semiconductor used for long distance optical communication, optical measurement equipment, etc. The present invention relates to a method for manufacturing a light emitting element.

[Prior Art] FIGS. 2(a) to 2(d) are process diagrams showing a conventional method for manufacturing a buried semiconductor light emitting device.

As shown in FIG. 2(a), the embedded semiconductor light emitting device includes, for example, a first cladding layer 22 made of p-InP on a p-InP substrate 21, an active layer 23 made of p-InGaAsP, and A second cladding layer 24 made of n-InP is sequentially grown by liquid phase crystal growth to form a double heterojunction, and then, as shown in FIG. 2(b),
After etching each layer forming the double heterojunction to form a mesa stripe-shaped projection 25, as shown in FIG. 2(e), the projection 25 on the substrate 21 is etched.
The first current blocking layer 26 and the second current blocking layer 27 are sequentially grown in a region where the current blocking layer 26 is not formed by liquid phase crystal growth. The embedded semiconductor light emitting device is further completed by forming metal electrode layers 28a and 28b above and below the above structure, as shown in FIG. 2(d).

In the embedded semiconductor light emitting device having the configuration shown in FIG. 2(d), when a voltage is applied between the metal electrode layers 28a and 28b, mesa stripes 25 are formed (,).
In the area where the current flows from the substrate 21 to the first cladding layer 22, the active layer 23, and the second cladding layer 24, the active layer 23 emits light. The current blocking layer 26 and the second current blocking layer 27 are designed so that they are reverse biased and no current flows.

[Problems to be Solved by the Invention] However, in the semiconductor light emitting device obtained by the above-mentioned conventional manufacturing method, when the first current blocking layer made of n-1nP is grown in liquid phase, the side surface of the second cladding layer is The InP melt adheres to the layer, and in order to directly grow the second current blocking layer, current leaks between the first current blocking layer and the second cladding layer through the interface along the side surface of the mesa stripe. There is a problem. If current leaks to a region other than the mesa stripe, the luminous efficiency will decrease or the threshold current will increase.

I, E, E, E, Journal Onkuantan Electronics, N015.1985, p, 452
~453 (Y, Nakano et al, “1.3
μmBuried-Heterostructure
La5era on p-type InPSubst
IEEE JOURNAL OF QU
ANTUM EL, ECTR0NIC3, VOL, QE
-21, No, 5, MAY, pp, 452-453
, (1985)) describes a semiconductor light emitting device that is said to have a structure that solves the above problem. FIG. 3 shows the structure of the semiconductor light emitting device described in the above publication. Third
In the figure, the same components as in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The semiconductor light emitting device described in the above publication thickens the first cladding layer 22 made of p-1nP to prevent contact between the first current blocking layer 26 made of n-InP and the second cladding layer 24, and , the first cladding layer 22 is in contact with the second current blocking layer 27 made of p-InP. According to the above publication, when a p-type semiconductor is used as a substrate, the p-type semiconductors are in contact with each other rather than the cladding layer and current blocking layer, which are n-type semiconductors, are in contact with each other. It is said that when a certain cladding layer and a current blocking layer are in contact with each other, the resistance becomes higher and the current league can be reduced.

However, in the semiconductor light emitting device described in the above publication, since the width of the active layer 23 (the length in the lateral direction in FIG. 3) is increased, the oscillated radiation beam pattern tends to be in a higher order mode.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to provide a semiconductor light emitting device in which a radiation beam is oscillated in the fundamental mode and high luminous efficiency and low threshold current can be obtained. An object of the present invention is to provide a method for manufacturing an element.

[Means for Solving the Problems] A method for manufacturing a semiconductor light emitting device according to the present invention is a method for manufacturing a semiconductor light emitting device in which a first cladding layer, an active layer, and a second cladding layer are formed into a double heterojunction on a semiconductor substrate. The manufacturing method includes a step of sequentially growing a first cladding layer, an active layer, and a second cladding layer on the substrate to form a double heterojunction, and etching each layer forming the double heterojunction to form a mesa stripe. a step of forming a protrusion in the form of a shape, a step of growing a semiconductor layer forming a first current blocking layer in a region of the substrate where the protrusion is not formed, and forming the first current blocking layer. forming a first current blocking layer by melt etching the semiconductor layer to a predetermined thickness, and then growing a second current blocking layer on the first current blocking layer. .

[Function] According to the manufacturing method of the present invention, the semiconductor layer forming the first current blocking layer is first grown to the same height as the mesa drive-like protrusion, and then melted to a predetermined thickness by melt etching. Back up. At this time, since the second cladding layer is formed of the same type of semiconductor as the semiconductor layer forming the first current blocking layer, the first current blocking layer of the second cladding layer is The surface in contact with the semiconductor layer forming the layer is etched at the same time.

Therefore, the first current blocking layer is formed by melting back so that the top surface of the first current blocking layer is lower than the bottom surface of the second cladding layer, thereby forming the first current blocking layer on the side surface of the second cladding layer. The portion that was in contact with the semiconductor layer is removed. Next, a second current blocking layer made of a semiconductor of a different type from the first current blocking layer and the second cladding layer is grown on the first current blocking layer, thereby forming the i-th current blocking layer. A semiconductor light-emitting device having a structure in which the second cladding layer and the second cladding layer are more completely separated can be obtained.

Furthermore, according to the above-mentioned melt etching, the surface of the first current blocking layer is not exposed to air, so the second current blocking layer is formed subsequent to the formation of the first current blocking layer. Ru.

[Example] The present invention will be explained below based on illustrated embodiments.

FIGS. 1(a) to 1(f) are process diagrams showing a method of manufacturing a semiconductor light emission blocker according to the present invention.

In this example, first, as shown in FIG. 1(a), p-
p-InP and p-InP are grown on a 1nP substrate 1 by liquid phase crystal growth.
InGaAsP and n-InP are sequentially grown to form a first cladding layer 2, an active layer 3, and a second cladding layer 4, respectively. In the semiconductor light emitting device of this example, a double heterojunction is formed by each of the first cladding layer 2, the active layer 3, and the second cladding layer 4. Next, a dielectric thin film 5 of 5iO8 or the like is formed on the second cladding layer 4 to serve as an etching mask in a predetermined pattern by CVD or sputtering. The Sin thin film 5 has a width of 2 on the second cladding layer 4.
It is patterned into stripes of approximately μm size.

Next, as shown in FIG. 1(b), each layer of the first cladding layer 2, active layer 3, and second cladding layer 4 is etched using a bromine methanol solution and the thin film 5 as an etching mask. is etched to form mesa stripes 6. By forming the mesa stripe 6 in this way, the height of the mesa stripe 6 is approximately 1.5 μm1 active layer 3
The width is approximately 1.5 μm. The width of active layer 3 is 1.5 μm
If so, the radiation beam will be oscillated in the fundamental mode and not in the higher order modes. Note that this step can be carried out in the same manner as in the prior art and has nothing to do with current leakage suppression, so the active layer 3 can be arbitrarily set to have a width suitable for fundamental mode oscillation.

Next, as shown in FIG. 1C, an n-InP layer 7 is formed by liquid layer crystal growth in a region on the p-InP substrate 1 where the mesa stripe 6 is not formed. Here, n-
The InP layer 7 is grown to the same height as the upper surface of the second cladding layer 4.

Next, the n-InP layer 7 is melt-etched using the InP unsaturated melt using the 5-ins thin film 5 as an etching mask to form a first current blocking layer 7a as shown in FIG. 1(d). It is preferable that the n-InP layer 7 is melted back to a thickness such that its upper surface is lower than the lower surface of the second cladding layer 4. By melting back the n-InP layer 7 as described above, the second cladding layer 4 is made of n-I
Since it has the same composition as the nP layer 7, it undergoes melt etching at the same time, and the portion 4a that was in contact with the n-InP layer 7 is removed.

Next, as shown in FIG. 1(e), the first current blocking layer 7
A p-InP layer is grown on a to form a second current blocking layer 8.

The second current blocking layer 8 is an n-I layer of the second cladding layer.
Since the portion 4a that was in contact with the nP layer 7 is removed and is formed in contact with the new surface 4b of the second cladding layer 4, the first cladding layer 7a and the second cladding layer 4 are separation is more complete and current leakage is reduced.

In the manufacturing method of the present invention, the first current blocking layer 7
The second current blocking layer 8 can be formed following the formation of the second current blocking layer 8. Generally, it is difficult to grow an InP layer again in a liquid phase on an InP layer that has been exposed to air once, but if melt etching using an unsaturated InP melt is used as described above, the InP layer can be grown again in the liquid phase immediately after melt etching.
It becomes possible to liquid phase crystal grow the layer.

Finally, as shown in FIG. 1(f), the 5-ins thin film 5 is removed and metal electrodes 9a and 9b are formed to obtain a semiconductor light emitting device. The removal of the SiO2 thin film 5 is as follows:
For example, wet etching using hydrofluoric acid can be used. Further, the formation of the metal electrodes 9a and 9b is as follows:
This can be done by a conventionally known method.

[Effects of the Invention] As explained in detail above, according to the manufacturing method of the present invention, the side surface of the second cladding layer is simultaneously etched by the melt etching for forming the first current blocking layer, and then the side surface of the second cladding layer is etched. Since the second current blocking layer is formed, the first current blocking layer and the second cladding layer are more completely separated, and leakage of current to regions other than the mesa stripe can be reduced. Therefore, a semiconductor light emitting device with improved luminous efficiency and reduced threshold current can be obtained.

Furthermore, in the manufacturing method of the present invention, since the first current blocking layer is formed by melt etching the InP layer, the formation of the first current blocking layer and the formation of the second current blocking layer are performed successively. be able to.

Furthermore, in the manufacturing method of the present invention, since the formation of the active layer is unrelated to the process for avoiding current leakage to regions other than the mesa stripe, the width of the active layer can be arbitrarily adjusted to favor fundamental mode oscillation. Can be set.

[Brief explanation of the drawing]

1(a) to 1(f) show the steps of an embodiment of the method for manufacturing a semiconductor light emitting device according to the present invention. FIG. 3 is a partial cross-sectional view showing the steps of an example of a method for manufacturing a semiconductor light-emitting device according to the present invention, and FIG. 3 is a partial cross-sectional view showing the structure of another example of another conventional semiconductor light-emitting device. ...p-InP substrate, ...active layer...second cladding layer, a...portion removed by etching, ...first current blocking layer.

Claims (1)

[Claims] A method for manufacturing a semiconductor light emitting device in which a first cladding layer, an active layer, and a second cladding layer are formed into a double heterojunction on a semiconductor substrate, comprising: a first cladding layer, an active layer, and a second cladding layer on the substrate; a step of sequentially growing layers and a second cladding layer to form a double heterojunction; a step of etching each layer forming the double heterojunction to form a mesa stripe-shaped protrusion; A step of growing a semiconductor layer forming a first current blocking layer in a region where no protrusion is formed, and melt etching the semiconductor layer forming the first current blocking layer to a predetermined thickness to form a first current blocking layer. A method for manufacturing a semiconductor light emitting device, comprising: forming a current blocking layer and then growing a second current blocking layer on the first current blocking layer.