JPS63233584A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To decrease the coupling loss between the tapered parts of an active layer and a light guide layer, by providing the second light guide layer on the active layer furthermore, and making the distribution center of an electric field of guided light propagating in the active layer to agree with that of guided light propagating in a low NA light guide for light emission. CONSTITUTION:A first light guide layer 2, an active layer 3 and a second light guide layer 2' are sequentially laminated on a semiconductor single crystal substrate, which is to become a first clad layer 1, and a first laminated substrate is obtained. An etching mask plate 8B, which has grooves 9A having the specified width and the specified depth, is prepared. Common etching liquid for the semiconductor single crystal substrate can be used for a material, which constitutes the mask plate 8B. The mask plate 8B is overlapped on the active layer 3 so that the parts of the grooves 9A agree with the positions of the active layer 3, where tapered parts 3T are to be formed. The device is immersed into the etching liquid, and the tapered parts 3T are formed in the active layer 3. Thus a wafer 8A is obtained. Then, the second light guide layer 2' is laminated to a specified thickness. A second clad layer is laminated, and a semiconductor laser is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser used in fields such as optical communication and optical information processing, and a method for manufacturing the same.

[Conventional technology]

InP-InGaAsP system, GaAs-Al1 GaA
Semiconductor lasers, typically s-based, are designed with a high mode confinement rate in their active layer in order to obtain fundamental mode and low threshold oscillation. Therefore, since the radiation angle of the emitted beam is large, a highly accurate lens system is essential for coupling with a guiding waveguide having a low radiation angle such as an optical fiber. This has caused a problem in that it is necessary to incur a great deal of cost for connection with the leading waveguide.

As a structure to solve this problem, a semiconductor laser using a taper coupling as shown in FIG. 12 has been reported ('Integrated GaAs-AJZ xG
a,-,AsDouble-Heterostruct
ure La5er with Independenden
try Controlled 0ptical 0u
tput Divergence”, R, A, Loga
n,F,ni,Re1nha,rt,IEEE J,Q
uantumElectron, ,volQE-11
, pp. 461-464, 1975). In this example, on the n-type All 622Gao, 76AS layer 1, which is the first cladding layer, the n-type Au, +5(iao, as), which is the first optical waveguide layer.
an As layer 2, a non-doped GaAs active layer 3 having a tapered portion, and a p-type AJRo which is a second cladding layer;
22 (iao, 71) has a structure in which SAS layers 4 are stacked in this order.The refractive index of each layer is different from that of the first and second layers.
The refractive index of each of the cladding layers 1 and 4 is nc, the refractive index of the first optical waveguide layer 2 is nw, and the refractive index of the active layer 3 is na.
It is set to satisfy nc<nw<n, and the thickness of the optical waveguide layer 2 is made thicker than the thickness of the active layer 3. Further, a tapered region 3T of the active layer 3 is provided in the central portion.

By adopting such a structure, this report increases the mode confinement rate in the active layer 3 in the left region of the figure,
While effectively utilizing the high gain of the active layer 3, the tapered waveguide is connected to the leading waveguide having a low mode confinement rate in the right region of the figure, that is, a low radiation angle, through the active layer tapered region 3T in the center. The aim is to connect with low loss and obtain oscillation light with high efficiency and a low radiation angle from the right end.

[Problem that the invention seeks to solve]

However, in such a structure, as is clear from the X-direction distribution Ey (x) of the y-direction electric field strength of the TEo mode guided light shown together with the refractive index distribution at the bottom of FIG.
The center of the electric field strength distribution is at two positions A before and after the taper part 3T.
△X=(u a+1 w)/2 in the X-axis direction between and B
Therefore, the active layer taper portion 3T
There was a problem in that the connection loss was large, and therefore it was difficult to oscillate. Here Ila.

ILw is the film thickness of the active layer 3 and the first optical waveguide layer 2, respectively. In fact, in this reported example, pulse oscillation was only obtained at room temperature, and continuous oscillation at room temperature, which is an essential condition for a practical device, was not obtained, and there is no report that it has been improved since then. .

Furthermore, in the case of the semiconductor laser shown in FIG. 12, there were also problems in its manufacturing method. In this example report, the liquid phase growth method (
In this case, as shown in FIG. 13, a lower substrate holding boat 5 and a melt holding board 5' that slide relative to each other are provided, thereby sequentially disposing different patterns on the substrate. A melt of composition 7 is placed inside the melt holding boat 5°,
A sapphire mask 6 is placed above the substrate at a desired position. This restricts diffusion and precipitation of the solute in the melt 7 onto the substrate near the bottom of the sapphire mask 6, thereby forming a tapered portion.

In such a method, the diffusion of the solute near the mask 6 becomes non-uniform, resulting in variations in the composition of the tapered portion compared to a portion where the film thickness is uniform. Therefore, this method can be applied to InGaA
When applied to the manufacture of sP-based semiconductor lasers, mismatching of lattice constants occurs in the tapered portion, significantly impairing film quality.

Therefore, this method is less likely to cause lattice constant mismatch due to compositional fluctuations. This solves the problem that it is applicable only to GaAs-based materials, and the material types are limited.

Furthermore, in this method, it is necessary to install the sapphire substrate 6 at a predetermined distance above the growth substrate between 5 degrees of the melt holding boat, and it requires a high level of skill to form a large number of tapered parts. Requires boat processing. Overall, this manufacturing method is not a general method that can be applied to other materials, and there are problems in that it does not increase productivity.

Therefore, the purpose of the present invention is to solve these drawbacks, and to provide a semiconductor laser that has a low radiation angle, low N (numerical aperture), excellent connection characteristics with a leading waveguide, and that continuously oscillates at room temperature with a low threshold value. It is about providing.

Another object of the present invention is to provide a manufacturing method with excellent productivity in manufacturing such a semiconductor laser.

[Means for solving problems]

In order to achieve such an object, the semiconductor laser of the present invention includes a semiconductor single crystal substrate having a first conductivity type and serving as a first cladding layer, and a first conductive layer on the first cladding layer. a first optical waveguide layer having a conductivity type and having a larger refractive index and a smaller extraction band width than the first cladding layer; an active layer having a larger refractive index and a smaller bandgap than the wave layer; and a second conductivity type having a refractive index and a bandgap intermediate between those of the first cladding layer and the active layer. a second cladding layer which has a second conductivity type and has substantially the same refractive index and forbidden band width as the first cladding layer;
It has a structure in which layers are sequentially stacked in a lattice-matched manner, and at one or both ends perpendicular to the stacking direction of the structure, the active layer tapers toward the end and disappears. Depending on the process, the first cladding layer, the first
An end waveguide is formed by the optical waveguide layer, the second optical waveguide layer, and the second cladding layer.

In the manufacturing method of the present invention, a first optical waveguide layer, an active layer, and a second optical waveguide layer are sequentially laminated on a semiconductor single crystal substrate that becomes a first cladding layer to obtain a first laminated substrate. Step 1 and
An etching mask plate is prepared that is made of a material that can be used with the same etching solution as a semiconductor single crystal substrate and has grooves of a predetermined width and depth, and the surface of the etching mask plate on the side where the grooves are formed; The surface of the second optical waveguide layer of the first laminated substrate is overlapped so that the groove portion matches the position in the active layer where the tapered part is to be formed, and the entire overlapped layer is etched in an etching solution. a second step of obtaining a second laminated substrate with a tapered active layer formed by dipping; and a second step of sequentially laminating a second optical waveguide layer and a second cladding layer on the second laminated substrate. According to the semiconductor laser of the present invention, a second layer is further formed on the active layer.
By providing an optical waveguide layer of The coupling loss between the two in the tapered portion can be significantly reduced, thereby making it possible to obtain continuous oscillation at room temperature.

Furthermore, since the manufacturing method of the present invention uses a wet etching process that is simple in principle, it is a simple method with extremely high productivity without requiring any skill or expensive equipment. Furthermore, while the conventional example is a manufacturing method that can only be applied to the LPE method, the manufacturing method of the present invention can be applied to the LPE method, molecular beam epitaxial growth (MBE) method, organometallic (
It can be applied to various uses, such as the MOCV[l] method, regardless of the wafer fabrication process.

Therefore, according to the present invention, it is possible to provide a high-performance low emission angle semiconductor laser that operates continuously at room temperature and is excellent in connection with a low NA optical waveguide at an extremely low cost and in large quantities.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the structure of an embodiment of the semiconductor laser of the present invention.

In FIG. 1, a first optical waveguide layer 2 having a first conductivity type, a first or second optical waveguide layer 2 having a first conductivity type, and a first or second The active layer 3 has a conductivity type and has a tapered part 3T formed at one end. In this order, an optical waveguide layer 2° formed to cover the uncoated portion and a second cladding layer 4 having a second conductivity type and having the same refractive index as the first cladding layer 1 are formed. They are stacked to match the lattice. Between the refractive index of each layer and the forbidden band width, QC< (nWI% nW2)<nasEc> so that the light generated in the active layer 3 is effectively guided.
(Ew+, Ewz)>E.

A relationship is maintained. Here, (n(, Ec), (n
w+%Ew+), (nW2, Ew2), (na %E
a) is the refractive index and forbidden band width of the first and second cladding layers 1 and 4, the first optical waveguide layer 2, the second optical waveguide layer 2°, and the active layer 3, respectively.

In such a configuration, in the semiconductor laser of the present invention,
In order to improve the coupling efficiency at the tapered portion 3T of the active layer 3, a second optical waveguide layer 2' is provided on the top of the active layer 3, and as shown in FIG. Match the center of the electric field distribution of the guided light at A with the center of the electric field distribution of the guided light in region B of the low radiation angle guided waveguide whose core layers are the first and second optical waveguide layers 2 and 2° on the right side. .

The coincidence of the electric field distribution centers of the person in both areas A and B is
This can be achieved by controlling the refractive index and film thickness of the first and second optical waveguide layers 2 and 2°.

FIG. 1 schematically shows an example of the TEo mode electric field distribution when the first and second optical waveguide layers 2 and 2° have the same refractive index. In this case, the film thickness of the second optical waveguide layer 2° may be made thicker than the film thickness of the first optical waveguide layer 2,
The film thickness values are the first cladding layer 1, the first optical waveguide layer 2,
This is obtained from mode analysis of a five-layer waveguide consisting of an active layer 3, a second optical waveguide layer 2°, and a second cladding layer 4. To do so, for example, rTheoryofDie
Electric Optical Waveguides
”, Marcuse, Academic Pre
ss., 1974.

According to such a configuration, there is no displacement of the electric field distribution center in a part of the active layer taper as in the conventional example described above, and a taper coupling with extremely low connection loss can be obtained, resulting in a high efficiency and a low radiation angle. A semiconductor laser can be realized.

By the way, in the case of a single-mode guided waveguide such as a semiconductor laser, in order to obtain low-loss taper coupling, the taper length must be (λ/△N) << l.

It is necessary to satisfy the following relationship. (For example, roptic
al Waveguide Theory” 81
lan W, 5nyder.

John D, Love, pp410-412. Ch
Published by Apman and Flai 1, 1983). Here, λ is the wavelength of the guided light, that is, the oscillation light, and ΔN
is the difference between the guided light equivalent refractive index and the refractive index of the 1° second cladding layer 1.4.

Considering an InP-1nGaAsP laser with a wavelength of 1.3 μm, △N a < Q, l ~ 0.2, and in order to satisfy the conditions of the above relational expression, the taper length should be set to 50
It is necessary that the thickness be at least μm. Since the thickness of the active layer 3 is usually 0.1 to 0.3 μm, in order to satisfy such a relational expression, the tapered portion 3T needs to have an extremely gentle taper.

In the present invention, in forming such a tapered part 3T, the drawbacks of the conventional method as described above are solved, and as described below, the tapered part 3T can be formed extremely easily and with good reproducibility. do.

FIG. 2 is a diagram illustrating the principle of the taper forming step that is involved in the method of manufacturing a semiconductor laser of the present invention. As shown in Figure 2,
The length of the long side and short side of the etching target 8 is a.
Let us consider the case where a hole 9 having a rectangular cross section of 2 and b is made and the hole 9 is filled with an etching solution lO. The etching speed is faster in the center of each side where the etching solution IO is easily exchanged with fresh solution, and the etching solution is also consumed on the sides in the depth direction of the plug hole 9 near each corner.
Become slow. If the etching depth is sufficiently small relative to the side lengths a and b, it is safe to assume that etching will not proceed at the corners, and as a result, the etching shape will be a "semi-cylindrical shape" as shown by the dashed line in the figure. . The depths hl and hb at the center of the long and short sides are the lengths a and b of the sides.
ha/h1)-a/b. However, in FIG. 2, the etched shape (dotted chain line) is exaggerated for convenience of explanation. L corresponds to the taper length shown in FIG.

As an example, consider an InP 44 crystal as the object 8 to be etched. Rectangular hole 9 with side length a-b-250tl m
Assume that the chamber is filled with an etching solution 1O having an etching rate of 0.2 μm/sec. Then, after 5 seconds, the etching depth at the center of the side becomes -hb-1 μm. On the other hand, since etching does not proceed at all at the corners, the wall surface of the hole 9 has a taper length L-a/2-125 μm% and a height of 1 μm.
A gentle taper will be formed. The taper length and height are the side length and etching solution 1.
It can be controlled with a concentration of 0 and time.

In the above explanation, the etching state has been explained for the case where the hole 9 is made in the object to be etched 8. However, instead of doing this, for example, as shown in FIG. The rectangular hole 9 may be formed by joining the plate 8A and the grooved plate 8B made of this material. However, if a groove with an upper opening is used instead of the hole 9, too much fresh etching liquid will flow into the groove from the opening, so that tapered etching will not be performed. The inventor of the present invention confirmed that the above-described tapered etching is performed under conditions where fresh etching solution is replaced only at the openings at both ends of the hollow hole, and based on the knowledge of this fact, A method for manufacturing a semiconductor laser according to the present invention has been completed.

In the present invention, by utilizing the above-mentioned phenomenon, the following figures 3 (8) to (D) and 4 (8)
The structure of the semiconductor laser of the present invention shown in FIG. 1 can be manufactured as shown in FIG. 1 and (B).

First, as a first step, a first optical waveguide layer 2 of a first conductivity type and a first or second conductive layer are placed on a semiconductor single crystal substrate, which is a first cladding layer 1 having a first conductivity type. A wafer 8^ as shown in FIG. 3(B) is manufactured by sequentially laminating a type active layer 3 and a second conductivity type second optical waveguide layer 2° to a predetermined thickness.

On the other hand, as shown in FIG. 3 (^), the first cladding layer 1
A flat plate made of the same material as wafer 8A or a material that uses the same etching solution as wafer 8A and has approximately the same etching speed (each layer of the wafer has approximately the same etching speed).
Prepare an etching mask plate 8B in which a plurality of rectangular grooves 9A having a width longer than twice the desired taper length and a predetermined depth are dug parallel to each other at intervals twice the element length. .

- In the second step, the etching mask plate 8B and the wafer 8A are placed one on top of the other as shown in FIG. 3(B), and the entire structure with holes 9 formed therein is immersed in etching solution lO. As a result, the portion indicated by the broken line is etched away into a cross section that is substantially isotropically convex with respect to the rectangular cross section. Next, by removing the mask plate 8B, as shown in FIG.
D) or as shown in FIG. 4(A), a very gentle taper portion 3T is formed in the active layer 3.

Next, as a third step, as shown in FIG. 4(B), a second optical waveguide layer 2° having a second conductivity type and a second cladding layers 4 are sequentially laminated. If the wafer thus formed is cleaved at intervals at the positions indicated by dotted lines in FIG. 4(B), a semiconductor laser device having a shape very similar to the structure shown in FIG. 1 can be manufactured.

Here, the reason why the second optical waveguide layer 2° was laminated on the active layer 3 in the first step was to protect the active layer during lamination in the third step.

Next, specific instructions of the present invention will be explained.

Mako, tin (Sn) doped n-type 2 x 10'87c
A (100) InP substrate with a carrier concentration of c is used as the first cladding layer 1, and a first optical waveguide layer 2 is formed on this as a tin-topped n-type with a carrier concentration of 2 x 10''/cc and a film thickness of 0.7 pm. Ino, 97”ao, osAso
, oaPo, 94 film, non-doped Ino with a film thickness of 0.3 μm as the active layer 3, 71ca0.298so,
86P0.34 film, and a zinc (Zn) doped p-type film with a carrier concentration of 5 x 10' as the second optical waveguide layer 2°.
77cc, Ino with a film thickness of 1.0 μm, 97Ga0.
A wafer 8A in which 03AS0.06PC1,94 films were sequentially laminated was fabricated by the LPE method.

Next, an etching mask plate 8B was prepared in which a plurality of rectangular grooves 9A having a width of 300 μm and a depth of 250 μm were formed in parallel at intervals of 500 μm on an InP substrate.

This etching mask plate 8B is stacked on the wafer 88 so that the groove direction matches the <TlO> direction of the wafer 8A, and a 20° C. bromine methanol solution (0.8 cc of bromine (Or) and 20 cc of methanol) is added to the etching mask plate 8B. mixture)
was used as an etching solution 1O, and immersed in this for 90 seconds.

Figure 5 shows the results of measuring the etched cross-sectional shape after dipping using a surface roughness meter. From this result, it can be seen that an extremely gentle taper is formed with a height of 1 μm and a length of 150 μm. Since the thickness of the active layer 3 is 0.3 μm, the taper length of the active layer 3 is 50 μm, which satisfies the above-mentioned taper length condition. Here, as described above, the etching mask plate 8B only needs to use a common etching solution for InP, and the etching mask plate 8B may be made of GaAs.
Almost similar results were obtained using .

Next, a second optical waveguide layer 2' is formed on the wafer 8A using a Zn-doped p-type film with a carrier concentration of 5 x 10''/cc.
, Ino with a film thickness of 1.3 μm, 5yGao, 03
AS0.06P0.94 film and second cladding layer 4
As, Zn-doped p-type with carrier concentration 5 x 10”
/cc, a 2 μm thick InP film, and a cap layer 11 (seventh layer) for forming a low resistance ohmic electrode on the p side.
(see figure) were sequentially laminated using the LPE method.

In this example, due to the composition of the active layer 3, the oscillation wavelength is 1.
34 μm, and the refractive index of each layer at this wavelength is nC for the first and second cladding layers 1 and 4, respectively.
-3,194, nWI' in the first and second optical waveguide layers 2 and 2'-mouth w2-3.214, n in the active layer 3, -
3,510.

FIG. 6 shows the normalized electric field distribution function Ey (x) in the TEo mode determined from these refractive indices and the film thickness. Here, A and B correspond to positions A and B in FIG. 1, respectively, and the origin of the X coordinate is located at the boundary between the first cladding layer 1 and the first optical waveguide layer 2. As is clear from FIG. 6, since the X coordinates of the electric field distribution centers at positions A and B match, low-loss taper coupling can be expected.

The electric field distribution function in Fig. 6 is obtained by approximating the Gaussian distribution with a Gaussian distribution, and when the distance in the X-axis direction from the maximum weight strength point to 1/e is W, the radiation angle θ is as follows: θ= tan -' (λ/rt w) --(1). From FIG. 6, W at positions A and B is WA-0,
34 μm and WB-1.28 μm, and from equation (1), the radiation angle θ6 to the left in Fig. 1 is 51.4°.
, the radiation angle θ8 to the right is 18.4°, and a sufficiently small radiation angle can be expected.

After manufacturing a wafer with a tapered active layer as described above, in this embodiment, the process proceeds to a normal BH (buried) type semiconductor laser manufacturing process. That is, <11
The wafer is subjected to reverse mesa etching to form stripes so that the width of the active layer 3 is 1.5 μm in the 0> direction, and a p-type 1nP buried layer 12 and an n-type InP buried layer 12 are formed.
A P buried layer 12' is formed of LPE. Furthermore, an Au-Zn electrode 13 is placed on the p side, and an Al1-5n electrode 'Fi1 is placed on the n side.
After the process of attaching 3°, as shown in Figure 7,
A BH type semiconductor laser with a tapered active layer on one side was fabricated. Here, the element length is 300 μm, of which the tapered portion 3T of the active layer 3 is 50 μm, and the length of the low radiation angle guided waveguide having the first and second optical waveguide layers 2 and 2° as core layers is 20 μm. Met.

Next, the characteristics of the semiconductor laser device thus manufactured will be described. The semiconductor laser in this example is at room temperature (RT).
Continuous oscillation (cw) t. FIG. 8 shows the relationship between the input terminal and the output optical power. The oscillation threshold was 40 μmA, and an output of 2 mW or more was obtained at one end when the input current was 63 mA or more. As is clear from the spectrum shown in FIG. 9, the oscillation wavelength was 1.344 μm.

FIG. 10 shows the angular dependence of the intensity of light emitted from the low radiation angle waveguide side (right side in FIG. 1). The emission angle of a semiconductor laser is usually 1 from the peak of relative luminosity in FIG.
Full Width at FWHM (Full Width at
11alf Maximum). In the case of this example, the values are 13.5° in both the 2θ1 direction perpendicular to the waveguide layer and the 2θ7 direction parallel to the waveguide layer. , has become significantly smaller. In addition, in this example, pW
HM was 13.5°, but if the refractive index and film thickness of the first and second optical waveguide layers 2 and 2' are changed, the FWI
Since IM can be freely changed according to the leading waveguide to be connected, the best value can be selected accordingly.

Here, the field of application of the semiconductor laser of the present invention will be described. FIG. 11 is an example. As shown in Figure 11,
A non-reflection coating film 14 is provided on both end faces of the semiconductor laser of the present invention, which is provided with low radiation angle optical waveguides 2 and 2' coupled to each other via an active layer taper portion 3T on both sides. Thereby, this laser acts as an optical amplification element. Since this laser has a low radiation angle, it can be used by directly inserting it between silica-based optical fibers 15, as shown in the figure, without the need for a high-precision lens system like conventional conventional lasers. It is possible to construct an inexpensive optical amplifier with an extremely simple structure. Furthermore, the semiconductor laser of the present invention is made of Ti-diffused LiN.
Of course, it can be directly connected to the b2O+ optical waveguide, so a high spectral purity light source integrated with the LiNb2O3 waveguide modulator can be easily obtained.

(Effects of the Invention) As explained above, according to the semiconductor laser of the present invention, by further providing the second optical waveguide layer on the active layer, the guided light propagating in the active layer can be It becomes possible to match the electric field distribution center with the guided light propagating in the wave path, and as a result, the coupling loss between the two at the tapered part of the active layer can be significantly reduced, thereby achieving continuous oscillation at room temperature. You can also do it.

Furthermore, since the manufacturing method of the present invention uses a wet etching process that is simple in principle, it is a simple method with extremely high productivity without requiring any skill or expensive equipment. In addition, while the conventional example is a manufacturing method that can only be applied to the LPE method, the manufacturing method of the present invention
It has the advantage that it can be effectively applied to various uses, such as LPE method, MBE method, MOCVD method, etc., regardless of the wafer fabrication process.

Therefore, according to the present invention, it is possible to provide a high-performance, low-emission-angle semiconductor laser that operates continuously at room temperature and is excellent for connection with a low-NA optical waveguide at an extremely low cost and in large quantities.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an embodiment of the semiconductor laser of the present invention, FIG. 2 is an explanatory diagram of the principle of the manufacturing method of the semiconductor laser of the present invention, and FIGS. 3(A) to (D) are the semiconductor lasers of the present invention. 4A and 4B are explanatory diagrams of the manufacturing process of the tapered part in an embodiment of the method for manufacturing a laser, FIG. 4A and FIG. 6 is a diagram showing the electric field intensity distribution of the semiconductor laser according to the embodiment of the present invention. FIG. 7 is a diagram showing the structure of the semiconductor laser according to the embodiment of the present invention. The figure is a characteristic diagram showing the current versus light intensity of the embodiment of the present invention. Figure 9 is a diagram showing the spectrum of light intensity of the embodiment of the present invention. Figure 1O is the characteristic diagram showing the light intensity versus radiation angle of the embodiment of the present invention. 11 is a sectional view showing an example of an optical amplifier constructed using the semiconductor laser of the present invention, FIG. 12 is a sectional view showing an example of the structure of a conventional semiconductor laser, and FIG. 13 is a sectional view showing an example of the structure of a conventional semiconductor laser. It is an explanatory view showing an example of a manufacturing method. DESCRIPTION OF SYMBOLS 1... First cladding layer, 2... First optical waveguide layer, 2°... Second optical waveguide layer, 3... Active layer, 3T... Taper part, 4...・Second cladding layer, 5... Lower substrate holding slide boat, 5°... Melt holding slide boat, 6... Sapphire mask, 7... Melt, 8... Object to be etched, 8A. ... Wafer, 8B... Etching mask plate, 9... Rectangular hole, 9^... Groove, lO... Etching liquid, 11... Cap layer, 12... P-type InP buried layer, 12°""n-type 1nP buried layer, 13---Au-Zn electrode, 13°...^-5n electrode, 14... Anti-reflection coating film, 15... Quartz-based optical fiber.

Claims (1)

[Scope of Claims] 1) a semiconductor single crystal substrate having a first conductivity type and serving as a first cladding layer; a first optical waveguide layer having a larger refractive index and a smaller forbidden band width than the first cladding layer; and a first optical waveguide layer having a first or second conductivity type and having a larger refraction than the first optical waveguide layer. an active layer having a refractive index and a small bandgap; and a second optical waveguide having a second conductivity type and having a refractive index and a bandgap between those of the first cladding layer and the active layer. and a second cladding layer having a second conductivity type and having substantially the same refractive index and forbidden band width as the first cladding layer, are sequentially laminated so as to be lattice matched. At least one end of the structure in a direction perpendicular to the stacking direction, the active layer decreases in a tapered shape toward the end and disappears, so that the first cladding layer and the A semiconductor laser characterized in that an end waveguide is constituted by a first optical waveguide layer, the second optical waveguide layer, and the second cladding layer. 2) A first step of sequentially laminating a first optical waveguide layer, an active layer, and a second optical waveguide layer on a semiconductor single crystal substrate serving as a first cladding layer to obtain a first laminated substrate. , preparing an etching mask plate made of a material that can use the same etching solution as the semiconductor single crystal substrate and having grooves of a predetermined width and depth; and the surface of the second optical waveguide layer of the first multilayer substrate are superimposed so that the groove portion matches the position of the active layer where the tapered portion is to be formed, and a second step of immersing the entire stacked structure in the etching solution to obtain a second multilayer substrate in which the active layer has a tapered portion; and a second optical waveguide layer on the second multilayer substrate. and a third step of sequentially laminating a second cladding layer.