JPH11103126A - Semiconductor optical element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide semiconductor optical element in which the wavelength composition of an active layer is made uniform in every part of the active layer, by a method wherein the width of a stripe-shaped dielectric thin film or the width of a wavelength region is changed in every part of an optical waveguide according to an angle which is formed by the stripe direction of the optical waveguide and a [011] crystal orientation. SOLUTION: An SiO2 mask is formed on an n-InP substrate in such a way that the stripe direction of an input/output waveguide becomes a [011] crystal orientation. Then, an S-shaped active layer part 101 has a stripe shape whose length in its length direction is about 350 μm and that the offset of the optical axis of the input/output waveguide is about 30 μm. In addition, the width of the mask becomes continuously narrow according to an increase in a waveguide angle from about 35 μm at a wavelength angle of 0 deg., the width of the mask in the central part of an element is about 27 μm, and the opening width of the mask is constant at about 0.7 μm in every part of the element. By using a pattern which is formed in this manner, a bulk layer is formed by an MOVPE (metal organic vapor epitaxy) selective growth operation. As a result, an active layer whose wavelength composition is uniform is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor optical device and a method for manufacturing the same, and more particularly, to a semiconductor optical device having a curved optical waveguide and a method for manufacturing the same.

[0002]

2. Description of the Related Art In metalorganic vapor phase epitaxy (MOVPE), selective growth using a stripe-shaped dielectric mask involves the following steps.
Only by changing the width of the dielectric mask can the composition and layer thickness of the semiconductor crystal grown in the growth region sandwiched between the dielectric masks be changed. It is being actively performed. In the conventional selective growth, a 1.5 μm wide semiconductor substrate such as InP is formed.
A pair of stripe-shaped dielectric thin film masks sandwiching a growth region of about
A crystal such as AsP is selectively grown. By appropriately selecting the growth region width so as to maintain the single mode operation of the optical waveguide, the optical waveguide structure can be formed without a semiconductor etching step, so that a high-quality semiconductor optical device can be manufactured with high yield. It is possible. Further, the wavelength composition and the crystal layer thickness of the crystal formed by the selective growth can be controlled only by changing the width of the dielectric mask and the width of the growth region, and are compatible with optical devices such as a semiconductor laser, an optical modulator, and an optical amplifier. Since an optical integrated device in which a passive optical waveguide is integrated can be formed at a time, it is very promising as a method for manufacturing a semiconductor optical device. In particular, in the selective growth at a growth region width of about 3 μm or less, which involves the surface migration and vapor phase diffusion of the group III raw material species on the SiO ₂ mask as a raw material supply mechanism to the growth region, the change in the wavelength composition with respect to the change in the mask width is suppressed. Can be bigger. For the principle that the wavelength composition can be changed by the dielectric mask width described above, Kato et al., ELECTRONICS LETTERS magazine VO
L.28, No.2 (January 16, 1992) Page 153 to 15
It is described on page 4.

As an example of an optical element formed by selective growth, for example, the 1997 Preliminary Conference on Applied Physics,
o. 3 spot size conversion (S
Pot-size converter: SSC, hereafter referred to as semiconductor optical amplifier with SSC) section. In recent years, attention has been paid to application of a semiconductor optical amplifier as a current injection type switching gate. Since a semiconductor optical amplifier can easily obtain a high extinction ratio of generally 50 dB or more, it is promising as a switching gate for realizing a low crosstalk matrix optical switch. In recent years, in order to optically couple a semiconductor laser or a semiconductor optical amplifier to an optical fiber or a silica-based optical waveguide without a lens, researches on integrating SSCs at the input / output ends of these optical elements have been actively conducted. The SSC is a structure in which the cross-sectional area of the semiconductor core layer gradually decreases toward the element end. The optical fiber with a large spot size expands the spot size by weakening the optical confinement of the signal light toward the input and output ends of the element. It is intended to improve optical coupling characteristics when optical coupling is performed without using a lens or a quartz optical waveguide.

A device structure and a method for fabricating the device of the semiconductor optical amplifier will be described with reference to FIGS. FIG. 13 is a sectional view in the element longitudinal direction schematically showing the structure of this semiconductor optical amplifier. FIG. 14 shows a dielectric mask pattern used for forming the active layer of this element by selective growth, and the hatched portions indicate the dielectric mask. In this device, in order to obtain a polarization-independent optical amplification characteristic, the active layer 20 is used.
8 has a width of 420 nm and a height of 300 nm, which is close to a square. The active layer 208 has a shape in which the layer thickness gradually decreases toward the input / output end of the element in the SSC section 102, and the spot size conversion of the signal light is performed by this structure. The entire active layer is 6 μm thick P-In.
It is embedded with a P cladding layer 209. An anti-reflection coating (AR coating) 2 is provided on both ends of the element to reduce reflected return light.
07 and a window 103 are formed. Conventionally, the active layer portion 301 and the active layer 206 of the SSC portion 102 have been formed by two crystal growth steps. However, in this report example, as shown in FIG.
m and the Si in the SSC unit 102
By narrowing the O ₂ mask width Wm toward the device input / output end, the active layer portion 901 and the SSC portion 102 are grown collectively. This makes it possible to form an active layer without a semiconductor etching step. Also, SSC
A semiconductor optical amplifier with an SSC is manufactured only by the same twice crystal growth of a conventional semiconductor optical amplifier that does not wait for a part.

As an example of an optical integrated device by selective growth,
For example, ELECTRONICS LETTERS Vol. 1 by K. Hamamoto Et. Al. On pages 2265 to 2266
* 4 semiconductor optical amplifier gate type monolithic matrix optical switch. FIG. 15 is a plan view schematically showing the configuration of this element. In this example, four semiconductor optical amplifiers 40 each having an active layer stripe in the [011] direction are used.
1 and a Y-branch passive branch optical waveguide 402 connecting them are collectively formed by changing the dielectric mask width at the time of selective growth, thereby forming a 1-input / 4-output branch / semiconductor optical amplifier gate matrix optical switch. ing. The mask width of each of the semiconductor optical amplifier and the passive optical waveguide is 30 μm.
m and 6 μm. At this time, the semiconductor optical amplifier 40
The bandgap wavelengths of the crystals in the 1 and passive branch optical waveguides 402 are 1.55 μm and 1.40 μm, respectively, and the passive branch optical waveguide 402 has a transparent composition that does not absorb signal light having a wavelength of 1.55 μm. When such an optical integrated device is manufactured by a conventional manufacturing method, it is necessary to separately form a semiconductor optical amplifier and a passive optical waveguide portion by two crystal growth steps. An optical element can be manufactured more easily.

[0006]

The stripe direction of the active layer of the semiconductor laser is generally formed in the [011] direction. This is because the resonator structure required for the operation of the semiconductor laser is formed by using the cleavage surface of the substrate.

However, in order to improve the characteristics of the optical device and reduce the size of the optical integrated device, an optical device having an active layer in an arbitrary stripe direction has been considered. For example, in the example of the monolithic matrix switch described in the previous section, the size of the element can be reduced by using a part of the branch curve waveguide as the active layer of the semiconductor optical amplifier unit. Also, in semiconductor optical amplifiers, the stripe direction of the active layer is set within the substrate plane to suppress reflected light returning to the active layer from the cleavage plane at the element end, the lens for optical coupling, the end face of the optical fiber, etc. [011] There is a report that the end face is arranged at an angle of about 6 to 8 ° with respect to the azimuth, and the end face has an angle. Further, in the semiconductor optical amplifier with the SSC section shown in the previous chapter, an attempt is made to form an active layer stripe in an S-shape in order to improve the ON / OFF extinction ratio during the switching gate operation.

As described above, the fact that the active layer can be formed in an arbitrary shape significantly increases the degree of freedom in device fabrication.

However, passive optical waveguides such as curved optical waveguides have been manufactured using selective growth.
An active optical waveguide including a region to be injected with a current and used as an optical amplification medium has never been manufactured in any stripe direction. Therefore, in the (100) substrate plane, [01
1] As a result of forming an active layer having an arbitrary stripe direction with respect to the direction by selective growth, the stripe direction and the [01]
1] By the angle formed with the azimuth (hereinafter referred to as waveguide angle),
It has been found that the wavelength composition and the cross-sectional shape of the active layer change.

FIG. 9 shows InGaAs formed by selective growth at various waveguide angles on the (100) plane of an InP substrate.
The relationship between the waveguide angle, the peak wavelength of the photoluminescence (PL) spectrum, and the active layer thickness in the P bulk active layer is shown. Here, the growth pressure is 760 Torr, the dielectric mask width and the mask opening width are each 35 μm,
0.7 μm. As the waveguide angle increases, the PL peak wavelength and the active layer thickness increase. Therefore, when an active layer structure having a shape in which the waveguide angle is arbitrarily changed is formed by selective growth, the composition of the active layer becomes non-uniform, and the gain characteristics at the time of current injection may decrease. In addition, since the amount of strain introduced into the active layer becomes non-uniform, the polarization dependence of the gain at the time of current injection may occur. This is because the change in the wavelength composition of the active layer formed by the selective growth is caused by the change in the composition ratio of the group III raw material, and the change in the wavelength composition is accompanied by the change in the in-plane strain of the crystal of the active layer. .

Therefore, the problem to be solved by the present invention is:
The purpose is to make the composition of the active layer formed by selective growth at an arbitrary waveguide angle uniform in each part of the active layer.

[0012]

Means for solving the above problems will be described below.

According to a first method of manufacturing a semiconductor optical device of the present invention, a semiconductor substrate having at least partially an optical waveguide serving as an optical amplifying medium, wherein the optical waveguide has a zinc blende type crystal structure. ) Is formed on the substrate surface or on a substrate surface having an inclination of 10 degrees or less from the (100) plane, and the stripe direction of the optical waveguide is at least partially in the plane on the substrate surface with respect to the [011] crystal orientation. In the semiconductor optical device having an angle, the optical waveguide is selectively formed by metal organic chemical vapor deposition on a growth region sandwiched between at least one pair of stripe-shaped dielectric thin films formed on the semiconductor substrate. A method of manufacturing a semiconductor optical device formed by a crystal growing step, wherein the width of the stripe-shaped dielectric thin film or the width of the growth region is set to [01] with the stripe direction of the optical waveguide. ] Wherein the varying in each section of the optical waveguide according to the angle between the crystal orientation.

According to a second method for manufacturing a semiconductor optical device of the present invention, in the first method for manufacturing a semiconductor optical device, the width of the stripe-shaped dielectric thin film is different from the stripe direction of the optical waveguide and the [011] crystal orientation. And narrows according to an increase in the angle formed by the angle.

According to a third method for manufacturing a semiconductor optical device of the present invention, in the first method for manufacturing a semiconductor optical device, the width of the growth region is different from the stripe direction of the optical waveguide by [01].
1] It is characterized in that it becomes narrower as the angle between it and the crystal orientation increases.

According to a fourth method for manufacturing a semiconductor optical device of the present invention, the first to third methods for manufacturing a semiconductor optical device include:
The width of the growth region is 2 μm or less.

According to a fifth aspect of the present invention, there is provided a method for manufacturing a semiconductor optical device, comprising the steps of:
A growth layer selectively formed in a growth region sandwiched between the stripe-shaped dielectric thin films is a bulk.

According to a sixth aspect of the present invention, there is provided a method for manufacturing a semiconductor optical device, comprising the steps of:
The semiconductor substrate having the zinc blende type crystal structure is an InP substrate, and the group III raw material constituting the crystal is In, G
a or any of both, wherein the group V raw material is A
It is a combination of any of s, Al, P, and N.

A semiconductor optical integrated device according to the present invention has a plurality of semiconductor optical amplifiers, and a semiconductor optical integrated circuit having at least a semiconductor branched optical waveguide having a curved and branched shape for guiding signal light within the same substrate surface. The device is characterized in that the stripe direction of the semiconductor optical amplifier has a different curved shape in each part of the active layer in the optical waveguide direction, and is formed as a part of the curved part of the semiconductor branch optical waveguide.

The optical communication module according to the present invention is characterized in that the first
To a semiconductor optical device obtained by the sixth to sixth manufacturing methods, waveguide means for guiding output light from the semiconductor optical device to the outside, and output light from the semiconductor optical device to the waveguide means. It is characterized by having a light condensing means for condensing light and a driving means for driving the semiconductor optical integrated device.

According to a second optical communication module of the present invention, the semiconductor optical device or the semiconductor optical integrated device obtained by the first to sixth manufacturing methods, and input light guided to the semiconductor optical device. Waveguide means for condensing input light from the waveguide means to the semiconductor optical element, and waveguide means for guiding output light from the semiconductor optical element to the outside. And a waveguide for focusing the output light from the semiconductor optical device and a driving device for driving the semiconductor optical integrated device.

An optical communication system according to the present invention includes a communication unit having the semiconductor optical device or the semiconductor optical integrated device obtained by the first to sixth manufacturing methods, and an output light from the communication unit. And receiving means.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 10 is a dielectric mask pattern for selective growth for explaining the operation of the present invention. FIG. 11 shows InG formed using the mask pattern of FIG.
It is a graph which shows the result of having measured PL peak wavelength of aAsP bulk active layer in each position of an active layer. FIG. 12 is a graph for explaining a method for achieving a uniform active layer composition according to the present invention. In order to explain the operation of the present invention, an InGa having an S-shape in which the length of the active layer in the element longitudinal direction is 350 μm and the optical axis shift of the active layer at the input / output end is 30 μm.
Consider the case where the AsP bulk active layer is formed by selective growth. When such a structure is formed by selective growth, FIG.
The pattern of (a) has been used. In the pattern of FIG. 10A, the mask width Wm is 35 μm, and the mask opening width W
o is 0.7 μm. The PL peak wavelength distribution in each part of the active layer formed at this time is as shown in FIG. As the waveguide angle increases, the PL peak wavelength becomes longer. At the center of the active layer where the waveguide angle reaches a maximum of 9.8 °, the wavelength composition is about 7 ° compared to the case where the waveguide angle is 0 °.
It is longer by 0 nm. When a current is injected into an active layer having a non-uniform bandgap composition as described above, a gain with respect to signal light is reduced, and an operating current is increased. In addition, a polarization dependence of the gain occurs.

Therefore, by changing the mask width and the mask opening width according to the change in the waveguide angle of the active layer,
Consider compensating for a longer wavelength composition due to a change in the waveguide angle.

First, the uniformization of the active layer composition by the mask width will be described. The graph of FIG. 12A shows InGaAsP when the waveguide angle is 0 °, 5 °, and 10 °.
The relationship between the mask width Wm of the bulk active layer and the PL peak wavelength is shown. The curve at a waveguide angle of 0 ° shows the characteristics of a conventional selective growth active layer having a stripe in the [011] direction. As described with reference to FIG. 9 in the previous section, when compared with the same mask width, the larger the waveguide angle, the larger the P
It can be seen that the L peak wavelength increases. Mask width W
m is 35 μm, and the PL peak wavelength at a waveguide angle of 0 ° is about 1470 nm. It can be seen that in order to obtain the same PL peak wavelength as 0 ° with a stripe having a waveguide angle of 5 °, the mask width Wm may be set to 27 μm. Similarly, when the waveguide angle is 10 °, the same PL is obtained when the mask width Wm is 27 μm.
A peak wavelength is obtained. The maximum waveguide angle in the active layer having the shape used in this description is about 9.8 °. Therefore, by changing the mask width stepwise or continuously from 35 μm to 27 μm according to an increase in the waveguide angle, it is possible to suppress the nonuniformity of the active layer composition. FIG. 9 (b) shows a mask pattern used when the active layer composition is made uniform by continuously changing the mask width Wm. FIG. 11B shows the distribution of the PL peak wavelength in each part of the active layer formed using the mask pattern of FIG. 10B. By continuously changing the mask width according to the change in the waveguide angle, an active layer having a uniform wavelength composition can be realized.

Similarly, the uniformization of the active layer composition by controlling the mask opening width will be described. FIG. 12B shows a relationship between the mask opening width of the InGaAsP bulk active layer and the PL peak wavelength when the waveguide angle is 0 °, 5 °, and 10 °.
The PL peak wavelength at a mask opening width Wo of 0.7 μm and a waveguide angle of 0 ° is about 1470 nm. It can be seen that in order to obtain the same PL peak wavelength as 0 ° with the stripe having the waveguide angle of 5 °, the mask width opening width Wo should be about 1.1 μm. Similarly, when the waveguide angle is 10 °, the same PL peak wavelength is obtained when the mask opening width Wo is 1.23 μm. Therefore, by changing the mask opening width stepwise or continuously from 0.7 μm to 1.23 μm in accordance with the increase in the waveguide angle, the wavelength of the active layer having the structure used in the description of the present operation is obtained. The composition can be made uniform. FIG. 10C shows the shape of the selective growth mask when the mask opening width Wo is continuously changed.
FIG. 11C shows the distribution of the PL peak wavelength in each part of the active layer formed using the mask pattern of FIG. 10C. As with changing the mask width,
By changing the mask opening width, the wavelength composition in each part of the active layer can be made uniform.

By the method described above, the conventional [011]
An active layer having the same quality as the active layer having the azimuth can be realized in an active layer having an arbitrary stripe direction.

[0028]

【Example】

(First Embodiment) A semiconductor optical amplifier with a spot size conversion waveguide, which is a first embodiment, will be described. FIG.
FIG. 4 is a plan view of a dielectric mask pattern used when an active layer of the present device is formed by selective growth. FIG. 2 is a top view and a longitudinal sectional view of the element showing the structure of the present element. FIG. 3 is a plan view of an active layer shape schematically showing another structural example of the present element. As described in the conventional example, attempts have been made to provide a spot size conversion structure in a semiconductor optical amplifier in order to directly optically couple a semiconductor optical amplifier and an optical fiber without using a lens system. However, it was found that when the semiconductor optical amplifier with the spot size conversion unit having the structure described in the conventional example was directly optically coupled to a fiber to form a module, the extinction ratio was about 30 dB. High extinction ratios are required for semiconductor optical amplifiers for gate applications. This is because, in the optical switch, an extinction ratio of 40 dB or more is required to reduce the reception sensitivity degradation due to crosstalk to 1 dB or less, and if it is less than this, the reception sensitivity degradation increases sharply. In the gate operation of the semiconductor optical amplifier, light is amplified when ON (during current injection), while switching is performed based on the operation principle of high light absorption when OFF (during no current injection). It has an extinction ratio.
However, in direct optical coupling between a semiconductor optical amplifier with a spot size converter and a flat end optical fiber, non-guided light (stray light) that does not couple to the waveguide optical mode of the semiconductor optical amplifier in the spot size converter on the input side increases. . When the signal of the semiconductor optical amplifier is OFF, the guided light is absorbed by the active layer, but the stray light propagates through the cladding layer or the semiconductor substrate and reaches the output side fiber. As a result, the extinction ratio during the switching operation decreases.

As one method for solving this problem, an active layer is bent as shown in FIG.
03 and the output signal light 204 to separate the output fiber 20
In 5, it is conceivable to remove only the stray light 203. In this case, the guided light bends and travels along the optical waveguide, but the stray light basically goes straight and is separated. FIG.
FIG. 3 shows an example in which the active layer has an S-shape and the optical axis of the input / output waveguide is moved in parallel. The point of removing stray light is that the active layer has such an active layer shape that the optical axis of the input / output waveguide does not overlap. The active layer shapes schematically shown in a) to (c) are also effective. With these structures, a high extinction ratio of the semiconductor optical amplifier to which the SSC unit is added is achieved.

It is considered that this structure is formed by selective growth in a narrow growth region as shown in the conventional example. By setting the mask opening width to about 0.7 μm, a polarization-independent type active layer capable of operating in a single mode can be directly formed. In the selective growth in such a narrow and narrow growth region, not only the gas phase diffusion of the group III source species on the SiO ₂ mask but also the migration length of about 3 μm is required.
Raw materials are supplied to the growth region by both effects of surface migration of group raw materials. In this case, a large wavelength composition change can be obtained with respect to a change in mask width. It is possible to form an SSC portion having a small light absorption with respect to the light wavelength.

However, when an S-shaped active layer structure is grown by the conventional selective growth of a uniform mask width and mask opening width, as described in the section of operation, the wavelength composition depends on the angle of the stripe direction of the active layer. And the wavelength composition of the active layer is 70
It has a distribution of nm. For this reason, [011] shown in the conventional example
The operating current is larger than that of a semiconductor optical amplifier with SSC having an active layer in the direction. In this embodiment, the active layer is formed using the selective growth mask pattern of the present invention, and the operating current of the semiconductor optical amplifier is reduced.

Hereinafter, a specific method for fabricating the device will be described. First, the SiO ₂ mask of FIG. 1 was formed on the n-InP substrate 208 such that the stripe direction of the input / output waveguide was in the [011] direction. The pattern in FIG.
-Shaped active layer 101, SSC 102, and window 1
It consists of 03. The S-shaped active layer portion 101 has a length of 350 μm in the longitudinal direction and an offset 30 of the optical axis of the input / output waveguide.
It has a stripe shape of μm. The mask width of the S-shaped active layer 101 was set to 35 μm at a position where the waveguide angle was 0 °, and the width was continuously narrowed as the waveguide angle increased. The mask width at the central portion of the device where the waveguide angle becomes the maximum of about 9.8 ° was 27 μm. The stripe direction of the SSC portion was the [011] direction, and the shape of the mask gradually narrowed from 35 μm to 4 μm toward the input / output end of the device. The mask opening width Wo was constant at 0.7 μm over each part of the device. 1.5 μm wavelength composition using this pattern
Was formed by MOVPE selective growth. An active layer having a polarization-independent amplification gain was formed in a cross section close to a square having a thickness of 300 nm and a width of 450 nm. In the SSC portion, the active layer has a structure in which the layer thickness gradually decreases from 300 nm to 50 nm toward the input / output end of the device. Due to the active layer structure having the tapered layer thickness change, the light spot size at the end of the optical waveguide can be increased. By expanding the light spot size, good optical coupling with the flat end fiber was obtained by the direct optical coupling method without using a lens system. As a result of measuring the PL peak wavelength of each part of the formed active layer, the variation of the PL peak wavelength in the entire active layer was ± 5 nm. Therefore, according to the present invention, an active layer having a uniform wavelength composition was formed.

After collectively forming the active layer 206 by selective MOVPE, the InGaAsP growth layer other than the active layer portion was removed by etching. After that, an SiO ₂ film (film thickness: 80 nm) for buried selective growth is re-formed on the entire surface,
A pattern for buried selective growth is formed, and a p-InP cladding layer 20 having a doping concentration of 7.0 × 10 ¹⁷ / cm ³ is formed.
9 (layer thickness 6 μm) and doping concentration 10 × 10 ¹⁹ /
p-InGaAs contact layer 210 c ³ (thickness 4
0 nm) was formed by selective MOVPE. After the buried growth, a SiO ₂ film is formed again on the entire surface, and Ti—Au
The SiO2 mask 211 for forming a contact window of the electrode was patterned. After that, the Ti-Au electrode 212 was patterned after the Ti-Au sputtered film was sputtered over the entire surface. Next, the back surface of the InP substrate was polished, the back electrode was formed, and the end face of the element was formed by cleavage. Finally nonreflective coated with SiO _N film on the element end face after cleavage (AR
Coat) 207 was formed. The end face reflectivity was suppressed to about 0.1% by the AR coat 207 and the window 103 for effectively lowering the reflectivity. Thus, the fabrication of the device was completed.

First, the optical coupling loss between the fabricated device and the flat end fiber was measured. After approaching the flat end fiber, light was inserted from outside through the fiber, and the photocurrent flowing through the semiconductor optical amplifier was measured. Thus, the optical coupling loss between the fiber and the present semiconductor optical amplifier is 3d on one side.
B was estimated. Next, the gain characteristics of this device were measured.
A current of 20 mA was injected into the semiconductor optical amplifier, and λ = 1.55
When a signal light of μm and an intensity of 0 dBm was input through the fiber, the signal light was output from the output side fiber without insertion loss (gain between fibers: 0 dB). When no current was injected (OFF), the output from the output side fiber was -50 dBm or less.

The gain characteristics of the conventional device manufactured with the SiO ₂ mask width at the time of forming the active layer constant at each part of the active layer were measured in the same manner.
The injection current for B was 30 mA. Therefore, the operating current of the semiconductor optical amplifier having the curved active layer could be reduced by 10 mA by the device manufacturing method of this example.

(Second Embodiment) 1 ×
A four-semiconductor optical amplifier gate type monolithic matrix optical switch will be described. FIG. 4 is a plan view showing the configuration of the present element. FIG. 5 is a plan view of a dielectric mask pattern used when forming the active layer of the device and the core layer of the passive branch optical waveguide by selective growth. This element is a one-input / four-output branch / semiconductor optical amplifier gate type matrix composed of four semiconductor optical amplifiers 401 and a Y-branch type passive branch optical waveguide 402 connecting them, similarly to the matrix optical switch shown in FIG. An optical switch is formed.
However, in this element, the semiconductor optical amplifier 401 is formed in a part of the curved optical waveguide. The length along the curve of the semiconductor optical amplifier 401 is 500 μm. At this time, the waveguide angle in the semiconductor optical amplifier 401 is 3.5 ° around 6.4 °.
To 9.3 °. Passive branch optical waveguide 40
2 is formed in an arc shape with a radius of curvature of 5 mm. The spacing between adjacent waveguides at the output port is 250 μm.

When this semiconductor optical amplifier is manufactured by conventional selective growth, the active layer formed on the curved waveguide has a wavelength composition distribution of 50 nm. However, in this embodiment, it is possible to obtain characteristics equivalent to those of a semiconductor optical amplifier having an active layer stripe in the [011] direction as shown in the conventional example by the device manufacturing method of the present invention. According to the present invention, the active layer portion can be formed even when the device is manufactured by selective growth.
The device can be manufactured in any shape without sacrificing the element characteristics. Thus, in an optical integrated device in which an active element and a passive waveguide are integrated, a gain region can be formed in a curved portion, and the size of the element can be reduced.

The device structure and manufacturing method of this device are described in Example 1.
Since the steps other than the SSC-equipped semiconductor optical amplifier and the steps other than the burying growth step are the same, only a brief description will be given. First, the SiO ₂ shown in FIG. 5 is placed on the n-InP substrate 208 so that the stripe direction of the input / output waveguide becomes the [011] direction.
A mask was formed. The composition distribution of the SiO ₂ mask 501 in the semiconductor optical amplifier section was made uniform by reducing the mask width from 35 μm to 30 μm as the waveguide angle increased. . Semiconductor optical amplifier mask opening width Wo
Was constant at 0.7 μm over each part of the device. The width of the passive branch optical waveguide section SiO ₂ mask 502 is 6 μm.
m, the mask opening width is constant at 10 μm, and the semiconductor optical amplifier section SiO ₂ mask 401 and the passive branch optical waveguide section S
The structure between the iO ₂ masks 502 is smoothly continued by gradually changing the mask opening width over a length of 50 μm.

Using this pattern, a wavelength composition of 1.5 μm
Is formed by MOVPE selective growth. The cross section of the active layer has a thickness of 300 nm and a width of 4
It has a polarization-independent amplification gain at a cross section close to a square of 50 nm. The band gap wavelengths of the crystals in the semiconductor optical amplifier section and the passive optical waveguide section are 1.55 μm, respectively.
1.40 μm, and the passive waveguide section has a wavelength of 1.55 μm.
It functions as a passive waveguide because it has a transparent composition having no absorption for the signal light. After collectively forming the active layer 206 by selective MOVPE, the passive branch optical waveguide 402 was first buried with an undoped InP layer having a thickness of 2 μm. Then, a doping concentration of 7.0 was applied to the semiconductor optical amplifier.
× 10 ¹⁷ / cm ³ p-InP cladding layer 209 (layer thickness 2 μm) and doping concentration 10 × 10 ¹⁹ / cm ³
P-InGaAs contact layer 210 (layer thickness 40n)
m) was formed by selective MOVPE. After the buried growth, a Ti-Au electrode patterning step, a back electrode forming step, an element end face forming step by cleavage, an anti-reflection coating (AR
Through a (coat) forming step, the fabrication of the element is completed. Although the plane orientation of the n-InP substrate was not described in Example 1 and the present example, a favorable element can be obtained by using a (100) substrate or a substrate having an inclination of 10 degrees or less from the (100) plane. Can be made.

In the present device, the semiconductor optical amplifier can be formed in the curved optical waveguide portion without sacrificing the device characteristics by the device manufacturing method of the present invention. Thus, the element length can be reduced by 700 μm as compared with the matrix optical switch shown in the conventional example.

In the present embodiment, the wavelength composition of the semiconductor optical amplifier 401 is made uniform by changing the mask width. However, the composition is made uniform by the mask opening width as described in the section of operation. Is also possible. In this case, an active layer having a uniform composition can be obtained by changing the mask opening width from 0.6 μm to 0.8 μm according to an increase in the waveguide angle.

In the matrix optical switch according to the present embodiment, the size of the matrix can be easily increased since the size of the element can be reduced as compared with the conventional structure, and a monolithic integrated type such as 4 × 4, 1 × 8, 8 × 8, etc. This is effective for realizing a matrix optical switch.

(Third Embodiment) FIG.
The semiconductor optical amplifier with the spot size converter of the first embodiment is fixed as the semiconductor optical element 602 on the optical fiber 3, and the optical fibers 601 are optically coupled at both ends of the element on the optical axis.
An optical communication relay module 605 further including a drive circuit 604. With this module, when switching the optical path of a high-speed optical signal of about 10 gigabits per second,
Optical switching with low power consumption and a high ON / OFF ratio is possible.

(Fourth Embodiment) FIG.
3. A 1 × 4 semiconductor optical amplifier gate type monolithic matrix optical switch according to the second embodiment, an optical fiber 601 is optically coupled on the optical axis of the input / output optical waveguide via a lens 701, and a drive circuit 604 is further incorporated. This is the optical communication relay module 605. When this module is used, small-sized, low power consumption, and high ON / OFF ratio optical switching characteristics can be easily obtained in switching the optical path of a high-speed optical signal of about 10 gigabits per second.

(Fifth Embodiment) FIG. 8 shows a cross-connect optical communication system using the middle module 605 for optical communication according to the fourth embodiment. The transmitting device 801 includes the transmitting module 8
03 and a beating system 8 for driving this module 803
02. The optical signal from the transmission module 803 is transmitted after the optical path is selected by the optical communication relay module 605, and is received by the receiving device 8 having the light receiving unit 806.
07. According to the optical communication system according to the present embodiment, an optical cross-connect system having low power consumption, low crosstalk, and excellent scalability can be easily constructed.

[0046]

As described above, according to the present invention, a semiconductor optical waveguide having an arbitrary stripe shape such as a curve and at least partially an optical amplification medium is selected.
In this case, the crystal composition of the semiconductor optical waveguide can be made constant in each part of the waveguide irrespective of the stripe direction of the waveguide. This device fabrication technique significantly expands the possibilities of semiconductor optical devices using selective growth.

The present invention is not limited to the above embodiment. As an embodiment, only an example of an InP-based semiconductor optical amplifier and a semiconductor monolithic integrated matrix optical switch has been described, but the present invention is not limited to this embodiment. As another example, the oscillation wavelengths of a plurality of semiconductor lasers formed in different stripe directions can be made uniform. Alternatively, a semiconductor laser having a Y-branch type active layer and capable of spatial switching or wavelength tuning can be formed by selective growth without sacrificing device characteristics. Further, the present invention is applicable to any semiconductor optical device formed by selective growth and including a gain region, such as an element in which an optical modulator, a directional coupler, and a waveguide array diffraction grating type multiplexer / demultiplexer are integrated. Applicable. Further, the present invention is not limited to an optical element alone, and can significantly improve the performance of an optical communication module or an optical communication system as shown in FIGS. 14 to 16 having the optical element of the present invention as a component, This is extremely effective for improving the scalability of optical communication modules and optical communication systems.

[Brief description of the drawings]

FIG. 1 is a plan view showing a dielectric mask pattern used for manufacturing a semiconductor optical amplifier according to a first embodiment of the present invention.

FIGS. 2A and 2B are a plan view and a cross-sectional view illustrating a structure of a semiconductor optical amplifier according to a first embodiment of the present invention.

FIG. 3 is a plan view showing another example of the structure of the semiconductor optical amplifier according to the first embodiment of the present invention.

FIG. 4 shows a second embodiment of a semiconductor optical amplifier manufactured according to the present invention, which is a Y-branch / semiconductor optical amplifier gate type 1 ×.
It is the top view and sectional drawing which show the structure of 4 monolithic matrix optical switches.

FIG. 5 is a plan view showing the shape of a selective growth mask used when manufacturing a Y-branch / semiconductor optical amplifier gate type 1 × 4 monolithic matrix optical switch according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an optical repeater module according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a relay module according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of an optical communication system according to a fifth embodiment of the present invention.

FIG. 9 is a diagram for explaining the principle of the method for manufacturing a semiconductor optical device of the present invention.

FIG. 10 is a plan view of a dielectric mask pattern for explaining the principle of the method for manufacturing a semiconductor optical device of the present invention.

FIG. 11 is a diagram for explaining the principle of the method for manufacturing a semiconductor optical device of the present invention.

FIG. 12 is a diagram for explaining the principle of the method for manufacturing a semiconductor optical device of the present invention.

FIG. 13 is a cross-sectional perspective view showing the structure of a semiconductor optical amplifier with a spot size converter, which is a conventional example of a semiconductor optical device manufactured using a selective growth technique.

FIG. 14 is a plan view showing a shape of a dielectric mask pattern used for manufacturing a semiconductor optical amplifier with a spot size converter, which is a conventional example of a semiconductor optical device manufactured using a selective growth technique.

FIG. 15 shows a conventional Y-branch / semiconductor optical amplifier gate type 1 × 4 semiconductor optical device manufactured using a selective growth technique.
FIG. 3 is a plan view illustrating a configuration of a monolithic matrix optical switch.

[Explanation of symbols]

Reference Signs List 101 S-shaped active layer portion 102 SSC portion 103 Window portion 104 SiO ₂ mask 105 Growth region 106 Offset 201 Input side fiber 202 Input signal light 203 Stray light 204 Output signal light 205 Output side fiber 206 Active layer 207 AR coat 208 InP substrate 209 p-InP cladding layer 210 p-InGaAs contact layer 211 electrode window forming SiO ₂ mask 212 Ti / Au electrode 301 active layer 401 semiconductor optical amplifier 402 passive branch optical waveguide 501 semiconductor optical amplifier SiO ₂ mask 502 passive branch optical waveguide part SiO ₂ mask 601 optical fiber 602 optical semiconductor element 603 submount 604 driving circuit 605 relay module 701 lens 801 feeding the transmission device 802 transmits module drive system 803 for optical communication optical communication Module 804 relay device 805 relays module drive system 806 receiving unit 807 receiving device

Claims (10)

[Claims] An optical waveguide serving as an optical amplifying medium is provided at least partially on the (100) plane of a semiconductor substrate having a zinc blende type crystal structure or within 10 degrees from the (100) plane. Wherein the stripe direction of the optical waveguide is at least partially at an angle with respect to the [011] crystal orientation in a plane on the substrate surface. An optical waveguide formed by a step of selectively growing a crystal by a metalorganic chemical vapor deposition method in a growth region sandwiched between at least one pair of striped dielectric thin films formed on the semiconductor substrate; The method of manufacturing, wherein the width of the stripe-shaped dielectric thin film or the width of the growth region is set according to an angle between a stripe direction of the optical waveguide and a [011] crystal orientation. The method of manufacturing a semiconductor optical device characterized by changing in the respective sections. 2. The method of manufacturing a semiconductor optical device according to claim 1, wherein the width of said striped dielectric thin film is increased by an increase in an angle between a stripe direction of said optical waveguide and a [011] crystal orientation. A method for manufacturing a semiconductor optical device, characterized in that the width of the semiconductor optical device becomes narrower. 3. The method of manufacturing a semiconductor optical device according to claim 1, wherein the width of the growth region is increased in accordance with an increase in an angle between a stripe direction of the optical waveguide and a [011] crystal orientation. A method for manufacturing a semiconductor optical device. 4. The method of manufacturing a semiconductor optical device according to claim 1, wherein said growth region has a width of 2 μm or less. 5. The method for manufacturing a semiconductor optical device according to claim 1, wherein a growth layer selectively formed in a growth region interposed between said striped dielectric thin films is bulk. A method for manufacturing a semiconductor optical device. 6. The method for manufacturing a semiconductor optical device according to claim 1, wherein the semiconductor substrate having the zinc blende type crystal structure is an InP substrate, and the group III raw material constituting the crystal is In. , Ga, or Al or a combination thereof, and the group V raw material is any of As, P, N, or a combination thereof. 7. A semiconductor optical integrated device having a plurality of semiconductor optical amplifiers and at least a semiconductor branched optical waveguide having a curved shape and a branched shape for guiding signal light on the same substrate surface. Wherein the stripe direction has a different curved shape in each portion of the active layer in the optical waveguide direction, and is formed as a part of the curved portion of the semiconductor branch optical waveguide. 8. A semiconductor optical device manufactured by the device manufacturing method according to claim 1, a waveguide means for guiding output light from the semiconductor optical device to the outside, and the waveguide means. An optical communication module comprising: a light condensing means for converging output light from the semiconductor optical element; and a driving means for driving the semiconductor optical integrated element. 9. A semiconductor optical device manufactured by the device manufacturing method according to claim 1 or a semiconductor optical integrated device according to claim 7, and a light guide for guiding input light to the semiconductor optical device. Wave means, light condensing means for converging input light from the waveguide means to the semiconductor optical device, wave guiding means for guiding output light from the semiconductor optical element to the outside, and An optical communication module comprising: a light condensing means for converging output light from the semiconductor optical element to a wave means; and a driving means for driving the semiconductor optical integrated element. 10. A communication device having a semiconductor optical device manufactured by the device manufacturing method according to claim 1 or a semiconductor optical integrated device according to claim 7, and receiving output light from the communication device. Optical communication system having a receiving means for the communication.