JP2953368B2 - Optical semiconductor integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical semiconductor integrated circuit,
In particular it relates to an optical semiconductor integrated circuit capable of two-way communication.

[0002]

2. Description of the Related Art An optical semiconductor integrated circuit for bidirectional communication in which a light source and a photodetector are integrated on the same substrate has attracted attention as a key device for providing bidirectional communication at a small size and at low cost. As a first conventional example of such an optical semiconductor integrated circuit, 1.3.
1.5m light receiving element (PD: photodiode)
μm band laser (LD: laser diode), LD monitor PD, and directional coupler type WDM (wave length d
A WDM transmitter in which an ivision multiplexing (wavelength multiplexing) coupler is integrated on the same substrate is reported by R. Mats et al. in the post-deadline paper PD1-1 of "Integrated Photonics Research '94". In this WDM transmitter, a signal from the host side to the transmitter side transmits and receives using a light of 1.3 μm band, and a signal (transmission signal) from the transmitter side to the host side uses light of 1.55 μm band. Therefore, this WDM transmitter can perform full-duplex bidirectional communication using the WDM technology. FIG. 13 is a perspective view showing a transmission laser 101, a monitor PD 102, and a reception PD 103. The reception signal is a 1.3 μm band signal, and the transmission signal is a 1.55 band signal.
A directional coupler-type WDM coupler 10 serving as a wavelength discriminating element for transmitting and receiving by wavelength multiplexing using a μm band signal.
4 are integrated. However, since the element size of the directional coupler is as large as about 3 mm, the size of the entire element is as large as 3.7 mm, which makes it difficult to reduce the size and is not suitable for mass production at low cost.

As a conventional example of an optical semiconductor integrated circuit for bidirectional communication capable of simultaneously transmitting a plurality of different media from a host to a transmitter, a WDM transceiver is disclosed in Electronics Letter by PJ Williams et al.
s vol. 30 pp. 1529. FIG. 14 is a perspective view showing a PD 201 for the 1.3 μm band and a 1.55 μm band.
The Mach-Zehnder WDN coupler 2 as a wavelength discriminating element for discriminating and receiving a wavelength multiplexed signal based on a 1.3 μm band signal and a 1.55 μm band signal, a PD 202 for an m band, a LD 203 for a 1.55 μm band, a PD 204 for an LD monitor,
05 are integrated. Furthermore, the input / output part of the Mach-Zehnder type element integrates a directional coupler type 3dB coupler 206, but the length becomes about 3.5 mm only in the WDM coupler area, making it difficult to miniaturize and inexpensively. It is difficult to mass produce.

[0004]

As described above, in a conventional optical semiconductor integrated circuit, a directional coupler type WDM coupler or a Mach-Zehnder type WDM having a large element size is used.
The configuration is such that the coupler is integrated as a wavelength discriminating element. Therefore, the element size becomes large,
There is a problem that it is not suitable for mass production at low cost.
Also, since the core layer wavelength composition of each functional element is different,
Since it is necessary to integrate while repeating the crystal growth step and the etching step, there is a problem that the number of manufacturing steps is increased. Furthermore, at the connection between the functional elements, since the core layer is not formed continuously in the light propagation direction, there is a problem that excessive loss occurs in a region connecting the elements. Further, the transmission signal is limited to a single wavelength, and there is a problem that transmission is limited to single-media transmission even though a plurality of media can be received.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact optical integrated circuit for bidirectional WDM communication without using a wavelength discriminating element such as a WDM coupler and to simplify the manufacturing process thereof. It is to provide a circuit.

[0006]

[0007]

According to the present invention, there is provided at least a branch waveguide on a semiconductor substrate, a semiconductor laser connected to one of the branch waveguides, and a first laser connected to the other of the branch waveguides. An optical semiconductor integrated circuit in which a semiconductor light receiving element and a second semiconductor light receiving element connected to the first semiconductor light receiving element are integrated, wherein a core layer wavelength composition of the second semiconductor light receiving element is the first semiconductor light receiving element. By setting a longer wavelength composition than the core layer wavelength composition of the semiconductor light receiving element, a two-wavelength multiplexed signal can be received, and the core layer of each element is continuously formed in the light propagation direction even in a region connecting the elements, Further, n−2 (n is a positive integer of 3 or more) semiconductor light receiving elements are connected to the subsequent stage of the second semiconductor light receiving element, and the core layer wavelength composition of the semiconductor light receiving element becomes longer as connected to the subsequent stage. N wavelengths Characterized by being capable of receiving a signal.

[0008] Here, in a subsequent stage of the semiconductor laser m-
One (where m is a positive integer of 2 or more) semiconductor lasers is connected, and the m wavelength-multiplexed signal can be transmitted by setting the wavelength composition of the core layer of the semiconductor laser longer as the latter is connected. Good. In this case, a signal light absorber is provided at the subsequent stage of each of the plurality of semiconductor lasers connected, and the wavelength composition of the signal light absorber core layer is the same as or equal to the wavelength composition of the core layer of the preceding semiconductor laser. It is set to be longer and shorter than the core layer wavelength composition of the subsequent semiconductor laser. Further, the signal light absorber may be configured to also serve as a semiconductor light receiving element for monitoring the preceding semiconductor laser.

Alternatively, the present invention provides at least a first semiconductor photodetector on a semiconductor substrate, a branch waveguide connected to the first semiconductor photodetector, and a semiconductor laser connected to one of the branch waveguides. And a second semiconductor light receiving element connected to the other of the branch waveguides, wherein the first semiconductor light receiving element also serves as an input / output port, and the second semiconductor light receiving element The light receiving sensitivity wavelength band of the light receiving element and the transmission signal wavelength band of the semiconductor laser are longer than the light receiving sensitivity wavelength band of the first semiconductor light receiving element, and light is emitted even in a region where the core layer of each element connects the elements. It is characterized by being formed continuously in the propagation direction.

[0010]

[0011] By arranging a plurality of PDs having different wavelength compositions in the order of shorter wavelength composition from the input / output single side, when a wavelength-multiplexed signal is received, a signal having a wavelength longer than the sensitivity wavelength band of a certain PD is received. Pass through the PD and the PD
Can be received only at wavelengths corresponding to the sensitivity wavelength band. Therefore, wavelength discrimination can be performed without using a wavelength discriminating element such as a WDM coupler or the like.
An optical semiconductor integrated circuit for communication can be configured.
By arranging a plurality of LDs on the same principle, WDM communication can be performed for transmission without using a wavelength discriminating element. In the case where a plurality of LDs are arranged, by providing a wavelength absorber between the plurality of LDs, light is prevented from being mixed into the subsequent LD.

Further, in the manufacturing method of the present invention, by selectively growing crystals in the gaps of a pair of striped dielectric masks, the fact that the wavelength composition of the grown layer can be controlled by the mask width is utilized. Next, waveguides having different wavelength compositions are collectively formed by one crystal growth. Regarding this technology, the present inventors and others have published ELECTRONIC LETTERS magazine, VO
L.28, NO.2 (January 16, 1992), pages 153 to 154. That is, as shown in FIG. 15A, a width of several μm sandwiched between a pair of stripe-shaped dielectric masks 301.
When the mesa structure 302 including the InGaAsP or InGaAs core layer 303 is selectively crystal-grown in the void portion by using metal organic chemical vapor deposition (MOVPE), the wavelength composition of the growth layer differs depending on the mask width. FIG. 15B shows the relationship between the mask width Wm and the wavelength composition λg of the grown layer when the layer selectively grown by crystal is an InGaAsP bulk layer. As the width Wm of the SiO ₂ mask increases, the composition ratio of In increases, and the wavelength composition of the bulk InGaAsP layer increases.

As can be seen from FIG. 15B, when the width Wm of the SiO ₂ mask is changed from 5 μm to 30 μm,
The wavelength composition can be changed from 1.15 μm to 1.3 μm. This means that even if the regions having different widths Wm of the SiO ₂ mask are formed even in the same wafer, the regions having different wavelength compositions can be formed by one selective growth. Further, when the core layer has a multiple quantum well (MQW) structure, the effect of increasing the composition ratio of In as the mask width Wm is increased and the effect of increasing the growth rate as the mask width Wm is increased are synergistic. Works, Figure 1
As shown in FIG. 6, the dependence of the wavelength composition of the growth layer on the mask width further increases. If the MQW structure is used, the wavelength composition can be changed from 1.15 μm to 1.6 μm within the same wafer.

Thus, in the manufacturing method of the present invention, a waveguide which is transparent to all incident wavelength light and a waveguide which is transparent only to long wavelength light and has a sufficiently large refractive index are formed once. Can be formed at once by the crystal growth of
Compared to a manufacturing method in which etching and crystal growth are repeated, the number of steps can be reduced, and the manufacturing yield can be improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a perspective view of an optical semiconductor integrated circuit according to a first embodiment of the present invention. Y on the semiconductor substrate 1
The branch 2, the 1.3 μm band transmission LD3, the monitoring PD4 of the 1.3 μm band transmission LD3, the 1.3 μm band reception PD5, and the second PD connection passive waveguide 9 are integrated. This optical semiconductor integrated circuit is configured as an optical semiconductor integrated circuit for bidirectional communication that receives a 1.3 μm band signal and transmits a 1.3 μm band signal. It is configured to be able to receive a signal and a wavelength multiplexed signal based on a 1.55 μm band signal.

2 (a), 2 (b), 2 (c), and 2 (d) show AA 'line, BB' line, CC 'line, D
It is a figure which shows the cross-section at the line -D '. As shown in these figures, each device has an n-InGaAsP layer 12, an n-InP spacer layer 13, and a lower SCH (separate confinement hetero-structure) layer 1 formed on an n-InP substrate 11.
4. It comprises an MQW core layer 15, an upper SCH layer 16, and an InP cladding layer 17, and is buried with an InP burying layer 18.

Next, referring to FIGS. 3 and 4, FIGS.
A method of manufacturing the optical semiconductor integrated circuit shown in FIG. First, as shown in FIG. 3A, an SiO ₂ film 21 is deposited on an n-InP substrate 11 to a thickness of about 1000 ° by a thermal CVD method. As shown in FIG. 2B, the grating 20 is provided on the n-InP substrate 11 only in the LD portion. The grating 20 may be manufactured using a normal interference exposure method or an EB (electron beam) exposure method. Si using normal photolithography technology
The O ₂ film 21 is selectively removed, and a pair of stripe-shaped masks as shown in FIG. 3B is formed as a mask 22 for selective crystal growth. The width Wm of the mask 22 is Wm = 6 μm for the Y branch 2 and the second PD connection passive waveguide 9 which are passive waveguides, and Wm for the 1.3 μm band transmission LD 3.
= 13 μm, PD for LD3 monitor for transmission in 1.3 μm band
Wm = 16 μm in the 4 and 1.3 μm band receiving PDs 5. The mask gap Wg is 1.5 in all regions.
μm. The length of each functional element is 1.3 μm band transmission L
It is 300 μm for D3 and 50 μm for the 1.3 μm band transmission LD3 monitor PD4 and 1.3 μm band transmission PD5.

Thereafter, as shown in FIG. 4A, the n-InGaAsP layer 12, the n-InP spacer layer 13, and the lower SCH layer 14 are formed by metal organic chemical vapor deposition (MOVPE) using the mask 22. , An MQW core layer 15 comprising an InGaAsP well layer / InGaAsP barrier layer, an upper SCH layer 16, and an InP cladding layer 17 are sequentially and selectively crystal-grown. Explaining mainly the portion selectively grown in the region where the value of the mask width Wm is Wm = 13 μm, the wavelength composition and the growth layer thickness of each growth layer are such that the n-InGaAsP layer 12 has a wavelength composition of 1.15 μm, Layer thickness 10
The thickness of the n-InP spacer layer 13 is about 400 μm, the thickness of the lower SCH layer 14 is 1.15 μm, and the thickness of the growth layer is 10 μm.
The MQW core layer 15 has seven periods, the InGaAsP well layer has a wavelength composition of 1.4 μm, the grown layer thickness is about 45 °, the InGaAsP barrier layer has a wavelength composition of about 1.15 μm, the grown layer thickness is about 100 mm, and the upper SCH layer 16 has a wavelength composition of 1.15 μm. μm, the thickness of the grown layer is about 1000 mm, and the thickness of the InP clad layer 17 is about 2000 mm.
The wavelength composition of the MQW core layer 15 of each functional element is represented by Y branch 2
The second passive waveguide 9 for PD connection has a composition of 1.15 μm, and the LD 3 for transmission in the 1.3 μm band has a composition of 1.3 μm and 1.3 μm.
The LD4 monitor LD4 for m band transmission and the PD4 for 1.3 μm band reception have a composition of 1.35 μm.

Next, as shown in FIG. 4B, the selective crystal growth mask 22 is removed with buffered hydrofluoric acid, and the InP buried layer 18 is grown on the entire surface. The thickness of the grown layer is about 2 μm. After that, 1.3 μm
Zn is diffused just above the band transmission LD3, LD3 monitor PD4, and 1.3 μm band reception PD5, and metal for electrodes is deposited. Next, the back surface is polished and a metal for an electrode is deposited to complete the device fabrication.

The above is the method of manufacturing the optical semiconductor integrated circuit according to the first embodiment of the present invention. The optical semiconductor integrated circuit according to the present invention can be realized in a small size, is suitable for bidirectional communication, and has a different signal wavelength. The principle by which a plurality of media can be received will be described below. That is, in the present invention, the Y branch 2
And a 1.3 μm band transmission LD3 and a 1.3 μm band transmission LD3 monitor PD connected to one of the Y branches 2
4. A second PD connection passive waveguide 9 connected to the other end of the Y branch 2 is integrated. In this embodiment, the optical terminal for bidirectional communication which transmits and receives a 1.3 μm band signal is provided.
D, for example, by connecting a PD capable of receiving a 1.55 μm band signal, a wavelength multiplexed signal, here, a 1.3 μm band signal and
A wavelength multiplexed signal of 1.55 μm signal can be received. At this time, the wavelength multiplexed signal of the 1.3 μm band signal and the 1.55 μm band signal is first received by the 1.3 μm band receiving PD 5 via the Y branch 2. At this time, since the 1.55 μm band reception signal passes through the 1.3 μm band reception PD 5, it is guided to the second PD connection passive waveguide 9 and introduced into the second PD. At this time,
Since the 1.3 μm band reception signal has already been absorbed by the 1.3 μm band reception PD 5, it does not reach the second PD. on the other hand,
The 1.3 μm band transmission signal transmitted from the 1.3 μm band transmission LD 3 is guided to the input / output port via the Y branch 2.

As described above, this optical semiconductor integrated circuit has:
It is configured to be able to receive a plurality of different wavelength band signal lights without integrating a wavelength discriminating element and to transmit a transmission signal. Since a wavelength discriminating element is not required, an optical semiconductor integrated circuit can be realized in a small size, and is suitable for two-way communication.
In addition, it is possible to receive a plurality of media having different signal wavelength bands.

In this embodiment, a manufacturing method for easily realizing regions having partially different wavelength compositions is used. Specifically, by selectively growing crystals in the gaps of a pair of stripe-shaped dielectric masks, it is possible to control the wavelength composition of the grown layer by the mask width. The structure is formed collectively by one crystal growth. That is, even in the same wafer, regions having different wavelength compositions can be collectively formed by one selective growth by forming regions having different widths Wm of the SiO ₂ mask. When the core layer has a multiple quantum well (MQW) structure, the effect of increasing the composition ratio of In as the mask width Wm is increased and the effect of increasing the growth rate as the mask width Wm is increased are synergistic. As shown in FIG. 16, the wavelength composition is 1.
It can be changed from 15 μm to 1.6 μm. Since the change in the wavelength composition according to the manufacturing method of the present invention is based on the principle of changing the In composition ratio in the solid phase, if a very large change in the wavelength composition is required, a large strain is introduced into the crystal. Become. In this embodiment, 1.
Since the light receiving element in the 55 μm band is externally connected as the second PD, a relatively narrow wavelength composition range from 1.15 μm to 1.35 μm may be integrated as the core layer growth composition. Therefore, for the integrated full-wavelength composition, the crystal distortion hardly matters.

As described above, in the present embodiment, since the core layers of all the integrated elements can be formed collectively by one crystal growth, the number of steps is smaller than that in the manufacturing method in which etching and crystal growth are repeated. It can be manufactured easily and the manufacturing yield is improved. Further, in this manufacturing method, since the core layer is continuous, the optical coupling efficiency between waveguides having different wavelength compositions can be almost 100%. Therefore, the loss of the entire device is small, and the waveguide between waveguides having different wavelength compositions is different. The influence of the generated reflected return light on the element characteristics can be reduced.

In the present embodiment, the wavelength composition of the Y branch 2 is 1.15 μm, but the light confinement strength that is transparent to the 1.3 μm band signal light and sufficient for the 1.55 μm band signal light is sufficient. If there is, it is not limited to this, for example
The present invention can be applied even with a 1.2 μm composition. 1.3 μm band receiving PD5 and 1.3 μm band transmitting L
The wavelength composition of the D3 monitor PD 4 is 1.35 μm, but is not limited to this, and may be any wavelength composition that can sufficiently absorb 1.3 μm band signal light.

In this embodiment, SiO ₂ is used as a mask material for selective crystal growth. However, the present invention is not limited to this. For example, SiN may be used, and thermal CVD may be used as a deposition method. The present invention is not limited to the method, and may be a plasma CVD method. Furthermore, in this embodiment,
Although the InGaAsP layer is used as the well layer and the barrier layer, InGaAs, InGaAsAs, or InGaAsAsP can be used as the well layer or the barrier layer instead. At this time, the well layer and the barrier layer do not necessarily need to be made of a material containing the same element. In this embodiment, the p-type is formed by using the selective diffusion step. However, the present invention is not limited to this. For example, DMZn (dimethyl zinc) as a dopant is used during the crystal growth step. Doping can also be performed. In the present invention, the SiO ₂ mask is entirely removed during the burying growth step, and the entire surface is grown to form the buried layer 18. However, the present invention is not limited to the burying growth step by this method. The present invention is also applicable to a method in which the gap Wg of the originally formed selective growth mask 22 is expanded in advance, and then the embedded layer 18 is formed by selectively performing the embedded growth step.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
It is a perspective view of an optical semiconductor integrated circuit of an embodiment. On the semiconductor substrate 1, a Y-branch 2, a 1.3 μm band transmission LD3, as described in 1.
The PD 3 for monitoring the LD 3 for transmitting 3 μm band, the PD 5 for receiving 1.3 μm band, and the PD 6 for receiving 1.55 μm band are integrated. The optical semiconductor integrated circuit according to the present embodiment has 1.
It is configured as an optical semiconductor integrated circuit for bidirectional communication that receives a wavelength multiplexed signal based on a 3 μm band signal and a 1.55 μm band signal and transmits a 1.3 μm band signal.

FIGS. 6 (a), (b), (c), (d),
(E) is an AA 'line, a BB7 line, and a C- line of FIG.
It is a figure which shows the cross-sectional structure in C7 line, DD 'line, and EE' line cross section. As shown in FIG. 6, each element is n-InP
N-InGaAsP layer 12, n-InP spacer layer 13, lower SCH layer 14, MQW core layer 1 formed on substrate 11
5, an upper SCH layer 16 and an InP cladding layer 17 buried with an InP burying layer 18.

Next, a method of manufacturing the optical semiconductor integrated circuit shown in FIGS. 5 and 6 will be described with reference to FIG. First, as shown in FIG.
An O ₂ film 21 is deposited to a thickness of about 1000 ° by a thermal CVD method. As shown in FIG. 6B, the grating 20 is provided on the n-InP substrate 11 only in the LD portion in advance. The grating 20 may be manufactured using a normal interference exposure method or EB exposure method. The SiO ₂ film 21 is selectively removed using a normal photolithography technique, and a pair of stripe-shaped masks as shown in FIG. The width Wm of the mask 22 is equal to the width of the Y-branch 2 which is a passive waveguide.
Wm = 6 μm, and Wm = 13 in the 1.3 μm band transmission LD3.
Wm = 16 μm, 1.55 μm for the PD3 for monitoring the LD3 for transmission in the 1.3 μm band and the PD5 for receiving in the 1.3 μm band.
In the m-band receiving PD 6, Wm = 30 μm. The mask gap Wg is 1.5 μm in all the regions. The length of each functional element is 300 μm for 1.3 μm band transmission LD3,
PD4 for monitoring, PD5 and 1.55 for 1.3 μm band reception
The μm band receiving PD 6 is 50 μm.

Thereafter, as shown in FIG. 4A of the first embodiment, the n-InGaAsP layer 12 and the n-
InP spacer layer 13, lower SCH layer 14, MQW core layer 15 composed of InGaAsP well layer / InGaAsP barrier layer,
The upper SCH layer 16 and the InP cladding layer 17 are sequentially and selectively crystal-grown. Explaining mainly the portion selectively grown in the region where the value of the mask width Wm is Wm = 12 μm, the wavelength composition and the growth layer thickness of each growth layer are as follows: the n-InGaAsP layer 12 has a wavelength composition of 1.15 μm; The n-InP spacer layer 13 has a growth layer thickness of about 400 mm, the lower SCH layer 14 has a wavelength composition of 1.15 μm, the growth layer thickness is about 1000 mm, and the MQW core layer 15 has a thickness of about 1000 mm.
In 7 cycles, the InGaAsP well layer has a wavelength composition of 1.4 μm, the growth layer thickness is about 45 °, the InGaAsP barrier layer has a wavelength composition of 1.15 μm,
The growth layer thickness is about 100 mm, and the upper SCH layer 16 has a wavelength composition of 1.15.
μm, the growth layer thickness is about 1000 mm, and the growth layer thickness of the InP cladding layer 17 is about 2000 mm. MQW core layer 15 of each functional element
The wavelength composition of the Y branch 2 is 1.15 μm composition, the 1.3 μm transmission LD 3 is 1.3 μm composition, and the 1.3 μm transmission LD
In PD4 for 3 monitors and PD5 for 1.3 μm band reception
The composition is 1.35 μm and 1.6 μm in the 1.55 μm band receiving PD6.

Next, as shown in FIG. 4B, the selective crystal growth mask 22 is removed with buffered hydrofluoric acid, and the InP buried layer 18 is grown on the entire surface. The thickness of the grown layer is about 2 μm. After that, 1.3 μm
Zn is diffused immediately above the band transmission LD3, LD3 monitor PD4, 1.3 μm band reception PD5, and 1.55 μm band reception PD6 to deposit metal for electrodes. Next, the back surface is polished and a metal for an electrode is deposited to complete the device fabrication.

The above is the manufacturing method of the optical semiconductor integrated circuit according to the second embodiment of the present invention. The optical semiconductor integrated circuit according to the present invention can be realized in a small size, is suitable for bidirectional communication, and has a signal wavelength band. The principle by which a plurality of different media can be received will be described below. That is, in the present invention,
Y branch 2 and 1.3 μm connected to one of the Y branches 2
LD3 for band transmission and the PD4 for monitoring the LD3 for 1.3 μm band transmission, 1.3 μm connected to the other end of the Y branch 2
The band receiving PD5 and the 1.55 μm band receiving PD6 connected to the 1.3 μm band receiving PD5 are integrated. In this embodiment, the 1.3 μm band signal and the 1.55 μm
First, the wavelength multiplexed signal of the band signal is 1.3 μm
It is received by the band receiving PD5. At this time, the 1.55 μm band reception signal passes through the 1.3 μm band reception PD5,
The signal is received by the μm band receiving PD 6. At this time, 1.3 μ
Since the m-band reception signal has already been absorbed by the 1.3 μm band reception PD 5, it does not reach the 1.55 μm band reception PD 6.
On the other hand, the 1.3 μm band transmitted from the LD for transmission 1.3 μm
The band transmission signal is guided to the input / output port via the Y branch 2.

As described above, the optical semiconductor integrated circuit of this embodiment also has a configuration capable of receiving a plurality of different wavelength band signal lights without integrating a wavelength discriminating element and a configuration capable of transmitting a transmission signal. Has become. Since no wavelength discriminating element is required, the optical semiconductor integrated circuit can be miniaturized, and is suitable for two-way communication and can receive a plurality of media having different signal wavelength bands.

In the present embodiment, as in the first embodiment, a manufacturing method for easily realizing regions having partially different wavelength compositions is used. Specifically, by selectively growing crystals in the gaps of a pair of stripe-shaped dielectric masks, it is possible to control the wavelength composition of the grown layer by the mask width. The structure is formed collectively by one crystal growth. As shown in FIG. 16, the wavelength composition of the MQW is changed by changing the mask width.
Since it can be changed from 1.15 μm to 1.6 μm, a light receiving element that fully receives 1.55 μm band signal light from a passive waveguide that is transparent to 1.3 μm band signal light and 1.55 μm band signal light The core layer can be formed collectively by one crystal growth. Therefore, compared to a manufacturing method in which etching and crystal growth are repeated, the number of steps is small, and a simple and good manufacturing yield can be obtained. Further, according to this manufacturing method, since the core layer is continuous, the optical coupling efficiency between the waveguides having different wavelength compositions can be almost 100%, so that the loss of the whole device is small and the waveguides having different wavelength compositions are different. The influence of the reflected return light generated between them on the element characteristics can be reduced.

In this embodiment, the wavelength composition of the 1.55 μm band receiving PD 6 is 1.6 μm. However, the wavelength composition is not limited to this as long as the wavelength composition can sufficiently absorb the 1.55 μm band signal light. . Also, in the present embodiment, the same modifications as in the first embodiment can be added.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
It is a perspective view of an optical semiconductor integrated circuit of an embodiment. On the semiconductor substrate 1, a Y-branch 2, a 1.3 μm band transmission LD3, as described in 1.
A PD 4 for monitoring the LD 3 for transmitting 3 μm band, an LD 7 for transmitting 1.55 μm band, a PD 8 for monitoring LD 7 for transmitting 1.55 μm band, a PD 5 for receiving 1.3 μm band, and a PD 6 for receiving 1.55 μm band are integrated. The optical semiconductor integrated circuit according to the present embodiment is an optical semiconductor integrated circuit for bidirectional communication that receives a wavelength multiplexed signal based on a 1.3 μm band signal and a 1.55 μm band signal and transmits a wavelength multiplexed signal based on a 1.3 μm band signal and a 1.55 band signal. Is configured as

FIGS. 9 (a), 9 (b), 9 (c), 9 (d),
(E), (f), and (g) are respectively AA 'lines in FIG.
BB 'line, CC' line, DD 'line, EE' line, F
It is a figure which shows the cross-sectional structure in the -F 'line and the GG' line cross section. As shown in FIG. 9, each element is an n-InP substrate 11.
The n-InGaAsP layer 12, the n-InP spacer layer 13, the lower SCH layer 14, the MQW core layer 15, and the upper S
It is composed of a CH layer 16 and an InP cladding layer 17 and is buried by an InP burying layer 18.

Next, a method of manufacturing the optical semiconductor integrated circuit shown in FIGS. 8 and 9 will be described with reference to FIG. First, as shown in FIG.
An iO ₂ film 21 is deposited to a thickness of about 1000 ° by a thermal CVD method. On the n-InP substrate 11, as shown in FIGS.
Is provided. The grating 20 may be manufactured using a normal interference exposure method or EB exposure method. The SiO ₂ film 21 is selectively removed using a normal photolithography technique, and a pair of stripe-shaped masks as shown in FIG. The width Wm of the mask 22 is Wm = 6 μm in the Y branch 2 which is a passive waveguide, Wm = 13 μm in the 1.3 μm band transmission LD 3, and 1.3 μm band transmission LD 3 monitor PD 4 and 1.3 μm band reception PD 5 in the 1.3 μm band transmission LD 3. Wm = 16 μ
m, Wm = 27 μm for LD5 for 1.55 μm band transmission, LD7
Wm = 30 μm for the monitoring PD8 and the 1.55 μm band receiving PD6. The mask gap Wg is 1.5 μm in all the regions. The length of each functional element is 1.3
LD3 for μm band transmission and LD7 for 1.55 μm band transmission are 30
0 μm, PD4 for monitoring, PD5 for receiving 1.3 μm band,
PD8 for LD7 monitor and PD6 for 1.55μm band reception
Is 50 μm.

Thereafter, as shown in FIG. 4A of the first embodiment, the n-InGaAsP layer 12 and the n-
InP spacer layer 13, lower SCH layer 14, MQW core layer 15 composed of InGaAsP well layer / InGaAsP barrier layer,
The upper SCH layer 16 and the InP cladding layer 17 are sequentially and selectively crystal-grown. Explaining mainly the portions selectively grown in the region where the value of the mask width Wm is Wm = 13 μm, the wavelength composition and the growth layer thickness of each growth layer are as follows: the n-InGaAsP layer 12 has a wavelength composition of 1.15 μm; The growth layer thickness is about 1000 mm, the n-InP spacer layer 13 has a growth layer thickness of about 400 mm, the lower SCH layer 14 has a wavelength composition of 1.15 μm, the growth layer thickness is about 1000 mm, and the MQW core layer 1
5 is 7 periods, the wavelength composition of the InGaAsP well layer is 1.4 μm, the thickness of the grown layer is about 45 °, and the wavelength composition of the InGaAsP barrier layer is 1.15 μm.
m, growth layer thickness about 100 mm, upper SCH layer 16 has wavelength composition
The InP cladding layer 17 has a growth layer thickness of about 2000 mm. The wavelength composition of the MQW core layer 15 of each functional element is 1.15 μm composition in the Y branch 2 and the second PD connecting passive waveguide 9, and the 1.3 μm band transmission LD.
3, a 1.3 μm composition, a 1.3 μm transmission LD3 monitor PD4 and a 1.3 μm reception PD5, a 1.35 μm composition, and a 1.55 μm transmission LD7, a 1.55 μm composition, 1.55 μm.
The LD8 monitor LD8 for m band transmission and the PD8 for 1.55 μm band reception have a composition of 1.6 μm.

Next, as shown in FIG. 4B, the selective crystal growth mask 22 is removed with buffered hydrofluoric acid, and the InP buried layer 18 is grown on the entire surface. The thickness of the grown layer is about 2 μm. After that, 1.3 μm
Zn is diffused immediately above the band transmission LD3, LD3 monitor PD4, 1.55 μm band transmission LD7, LD7 monitor PD8, 1.3 μm band reception PD5, and 1.55 μm band reception PD6, and metal for electrodes is deposited. Next, the back surface is polished and a metal for an electrode is deposited to complete the device fabrication.

The above is the method of manufacturing the optical semiconductor integrated circuit according to the third embodiment of the present invention. The optical semiconductor integrated circuit according to the present invention can be realized in a small size, is suitable for bidirectional communication, and has a signal wavelength band. The principle by which a plurality of different media can be received will be described below. That is, in the present invention,
Y branch 2 and 1.3 μm connected to one of the Y branches 2
LD3 for band transmission, LD3 monitor for 1.3 μm band transmission P
D4, a 1.55 μm band transmission LD 7 and an LD 7 monitoring PD 8, a 1.3 μm band reception PD 5 connected to the other end of the Y branch 2, and a 1.55 μm band reception PD 6 connected to the 1.3 μm band reception PD 5. It has an integrated configuration. In this embodiment, the 1.3 μm band signal and the 1.55 μm
First, the wavelength multiplexed signal of the band signal is 1.3 μm
It is received by the band receiving PD5. At this time, since the 1.55 μm band reception signal passes through the 1.3 μm band reception PD 5,
The signal is received by the μm band receiving PD 6. At this time, 1.3 μ
Since the m-band reception signal has already been absorbed by the 1.3 μm band reception PD 5, it does not reach the 1.55 μm band reception PD 6.
On the other hand, the 1.3 μm band transmitted from the LD for transmission 1.3 μm
The band transmission signal is guided to the input / output port via the Y branch 2.

At this time, the transmission signal in the 1.3 μm band is Y-branch 2
The 1.3 μm band transmission signal is absorbed by the 1.3 μm band transmission LD 7 monitor PD 4 at the subsequent stage while the 1.3 μm band transmission signal is absorbed by the 1.3 μm band transmission LD 7.
No band transmission signal is mixed. Therefore, the 1.55 μm band transmission LD can avoid the influence of the 1.3 μm band signal light. In addition,
The 1.55 μm band transmission signal is transmitted to the 1.3 μm band transmission LD3 and 1.
Since the light passes through the 3 μm band transmission LD 3 and the monitoring PD 4, it is guided to the input / output port via the Y branch 2 as it is.

As described above, also in the present embodiment, the configuration is such that a plurality of different wavelength band signal lights can be received without transmitting a wavelength discriminating element, and a transmission signal can be transmitted. Since no wavelength discriminating element is required, the optical semiconductor integrated circuit can be miniaturized, and is suitable for two-way communication and can receive a plurality of media having different signal wavelength bands.

In the present embodiment, as in the first embodiment, a manufacturing method for easily realizing regions having partially different wavelength compositions is used. Specifically, by selectively growing crystals in the gaps of a pair of stripe-shaped dielectric masks, it is possible to control the wavelength composition of the grown layer by the mask width. The structure is formed collectively by one crystal growth. As shown in FIG. 16, the wavelength composition of the MQW is changed by changing the mask width.
Since it can be changed from 1.15 μm to 1.6 μm, a light receiving element that fully receives 1.55 μm band signal light from a passive waveguide that is transparent to 1.3 μm band signal light and 1.55 μm band signal light The core layer can be formed collectively by one crystal growth. Therefore, compared to a manufacturing method in which etching and crystal growth are repeated, the number of steps is small, and a simple and good manufacturing yield can be obtained. Further, according to this manufacturing method, since the core layer is continuous, the optical coupling efficiency between the waveguides having different wavelength compositions can be almost 100%, so that the loss of the whole device is small and the waveguides having different wavelength compositions are different. The influence of the reflected return light generated between them on the element characteristics can be reduced.

In this embodiment, the same modifications as those of the second embodiment can be added.

(Fourth Embodiment) FIG. 11 is a perspective view of an optical semiconductor integrated circuit according to a fourth embodiment of the present invention. Y-branch 2, PD5 for receiving 1.5 μm band, 1.55 on semiconductor substrate 1
The LD 7 for transmitting μm band, the PD 8 for monitoring LD 7 for transmitting 1.55 μm band, and the PD 6 for receiving 1.55 μm band are integrated. The optical semiconductor integrated circuit according to the present embodiment has 1.
It is configured as an optical semiconductor integrated circuit for bidirectional communication that receives a wavelength multiplexed signal based on a 3 μm band signal and a 1.55 μm band signal and transmits a wavelength multiplexed signal based on a 1.55 band signal.

AA 'line, BB' line, C-
The cross-sectional structures taken along lines C ′, DD ′, and EE ′ are shown in FIGS. 6A, 6B, 6C, 6D, and 6D in the first embodiment.
This is the same as shown in FIG. As shown in FIG. 11, each element was formed on an n-InP substrate
AsP layer 12, n-InP spacer layer 13, lower SCH layer 1
4. It comprises an MQW core layer 15, an upper SCH layer 16, and an InP cladding layer 17, and is buried with an InP burying layer 18.

Next, a method of manufacturing the optical semiconductor integrated circuit shown in FIG. 11 will be described with reference to FIG. First,
As shown in FIG. 12A, an n-InP substrate
_{The second} film 21 is deposited to a thickness of about 1000 ° by a thermal CVD method. As shown in FIGS. 6B and 6D, the grating 20 is provided on the n-InP substrate 11 only in the LD portion in advance. The grating 20 may be manufactured using a normal interference exposure method or EB exposure method. The SiO ₂ film 21 is selectively removed using a normal photolithography technique, and a pair of stripe-shaped masks as shown in FIG. The width Wm of the mask 22 is Y, which is a passive waveguide.
Wm = 16 μm for branch 2 and PD5 for 1.3 μm band reception
m, Wm = 27 μm for LD5 for 1.55 μm band transmission, LD7
Wm = 30 μm for the monitoring PD8 and the 1.55 μm band receiving PD6. The mask gap Wg is 1.5 μm in all the regions. The length of each functional element is 1.3
50μm and 1.55μm band PD for μm band PD5
6, 50 μm, 1.55 band transmission LD7, 300 μm, LD
The thickness is 50 μm for 7 monitor PD8.

Thereafter, as shown in FIG. 4A of the first embodiment, the n-InGaAsP layers 12 and n-
InP spacer layer 13, lower SCH layer 14, MQW core layer 15 composed of InGaAsP well layer / InGaAsP barrier layer,
The upper SCH layer 16 and the InP cladding layer 17 are sequentially and selectively crystal-grown. Explaining mainly the portion selectively grown in the region where the value of the mask width Wm is Wm = 16 μm, the wavelength composition and the growth layer thickness of each growth layer are as follows: the n-InGaAsP layer 12 has a wavelength composition of 1.15 μm; The n-InP spacer layer 13 has a growth layer thickness of about 400 mm, the lower SCH layer 14 has a wavelength composition of 1.15 μm, the growth layer thickness is about 1000 mm, and the MQW core layer 15 has a thickness of about 1000 mm.
In 7 cycles, the InGaAsP well layer has a wavelength composition of 1.4 μm, the growth layer thickness is about 45 °, the InGaAsP barrier layer has a wavelength composition of 1.15 μm,
The growth layer thickness is about 100 mm, and the upper SCH layer 16 has a wavelength composition of 1.15.
μm, the growth layer thickness is about 1000 mm, and the growth layer thickness of the InP cladding layer 17 is about 2000 mm. MQW core layer 15 of each functional element
The wavelength composition of the PD5 for Y branch 2 and 1.3 μm band reception
1.35μm composition and 1.55μm in 1.55μm transmission LD7
The m composition, the PD6 for 1.55 μm band reception PD6 and the PD8 for 1.55 μm band transmission LD7 monitor PD8 have a 1.6 μm composition.

Next, as shown in FIG. 4B, the selective crystal growth mask 22 is removed with buffered hydrofluoric acid, and the InP buried layer 18 is grown on the entire surface. The thickness of the grown layer is about 2 μm. After that, 1.3 μm
Zn is diffused immediately above the band receiving LD 5, the 1.55 μm band receiving PD 6, the 1.55 μm band transmitting LD 7, and the LD 7 monitor PD 8, and metal for the electrode is deposited. Next, the back surface is polished and a metal for an electrode is deposited to complete the device fabrication.

The above is the manufacturing method of the optical semiconductor integrated circuit according to the fourth embodiment of the present invention. The optical semiconductor integrated circuit according to the present invention can be realized in a small size, is suitable for bidirectional communication, and has a signal wavelength band. The principle by which a plurality of different media can be received will be described below. That is, in the present invention,
1.3 μm band receiving PD5 also serving as input / output port
Y branch 2 connected to 1.3 μm band receiving PD 5, 1.55 μm band transmitting LD 7 and LD 7 monitoring PD 8 connected to one of Y branch 2, and 1.3 μm band connected to the other of Y branch 2 The receiving PD 6 is integrated. In this embodiment, the 1.3 μm band signal and 1.55 μm
The wavelength-multiplexed reception signal of the m-band signal is first received by the 1.3 μm-band receiving PD 5. At this time, since the 1.55 μm band reception signal is transmitted through the 1.3 μm band reception PD 5, the Y branch 2
And received by the receiving PD 6 in the 1.55 μm band. Y branch 2 has a composition of 1.35 μm, but 1.55 μm
It is transparent to the band signal light. 1.3 μm band reception signal
Since it has already been absorbed by the 1.3 μm band receiving PD5, 1.
It does not reach the receiving PD 6 in the 55 μm band. On the other hand, 1.55μm
The 1.55 μm band transmission signal transmitted from the band transmission LD 7 is Y
Heat the input / output port via branch 2 for 1.3 μm band reception P
Sent to D5. At this time, the transmission signal of the 1.55 μm band is 1.3
Since it is hardly absorbed in the PD 5 μm band receiving PD5,
It is emitted as it is.

As described above, the configuration is such that a plurality of different wavelength band signal lights can be received without transmitting a wavelength discriminating element, and a transmission signal can be transmitted. Since no wavelength discriminating element is required, the optical semiconductor integrated circuit can be miniaturized, and is suitable for two-way communication and can receive a plurality of media having different signal wavelength bands.

In the present embodiment, as in the first embodiment, a manufacturing method for easily realizing regions having partially different wavelength compositions is used. Specifically, by selectively growing crystals in the gaps of a pair of stripe-shaped dielectric masks, it is possible to control the wavelength composition of the grown layer by the mask width. The structure is formed collectively by one crystal growth. Since the change in the wavelength composition in this embodiment is based on the principle of changing the In composition ratio in the solid phase, if a very large change in the wavelength composition is required, a large strain will be introduced into the crystal. In this embodiment, the 1.3 μm band signal light and 1.55
First, a wavelength-division multiplexed signal composed of μm band
Since the light is received by D5, the 1.3 μm band signal light is absorbed here, and the wavelength composition of the passive waveguide is the same as that of the 1.3 μm band PD.
The composition is 35 μm, and a relatively narrow wavelength composition range from 1.35 μm to 1.6 μm is integrated as the core layer growth composition of the optical integrated circuit according to this embodiment. Therefore, the crystal distortion of the integrated full-wavelength composition hardly matters.

As described above, in the present embodiment, since the core layers of all the integrated elements are formed collectively by one crystal growth, the number of steps is smaller than that of the manufacturing method in which etching and crystal growth are repeated, and the method is simple. As a result, the production yield can be improved. Further, if this manufacturing method is used, since the core layer is continuous, the optical coupling efficiency between waveguides having different wavelength compositions can be almost 100%, so that the loss of the entire device is small,
In addition, the influence of reflected return light generated between waveguides having different wavelength compositions on device characteristics can be reduced.

In the present embodiment, the wavelength composition of the Y branch 2 is 1.35 μm. However, the Y-branch 2 is transparent to the 1.55 μm band signal light and has sufficient light confinement strength for the 1.55 μm band signal light. If there is, it is not limited to this, for example
The present invention can be applied even with a 1.4 μm composition. In addition, the wavelength composition of the PD 5 for receiving 1.3 μm band is 1.35 μm.
m is used, but is not limited to this, and may be any wavelength composition that can sufficiently absorb 1.3 μm band signal light.

In this embodiment, SiO ₂ is used as a mask material for selective crystal growth. However, the present invention is not limited to this. For example, SiN may be used, and a thermal CVD method may be used as a deposition method. The plasma CVD method may be used. Further, in this embodiment, InGa
Although the AsP layer has been used as the well layer and the barrier layer, InGaAs, InGaAsAs, or InGaAsAsP can be used as the well layer or the barrier layer instead. At this time, the well layer and the barrier layer do not necessarily need to be made of a material containing the same element. In the present embodiment, the p-type is formed by using the selective diffusion step. However, the present invention is not limited to this. For example, DMZn as a dopant during the crystal growth step is used.
Doping can also be performed using (dimethyl zinc). Further, in the present invention, S
The buried layer 18 is formed by removing the entire iO ₂ mask and growing the entire surface to form the buried layer 18. However, the buried layer 18 is not limited to the buried growth step by this method. The present invention is also applicable to a method of forming the buried layer 18 by selectively performing the burying growth step after the gap Wg of the mask for use 22 is expanded in advance.

[0056]

As described above, the present invention provides at least a branch waveguide on a semiconductor substrate, a semiconductor laser connected to one of the branch waveguides, and a semiconductor laser connected to the other of the branch waveguides. 1. An optical semiconductor integrated circuit in which one semiconductor light receiving element and a second semiconductor light receiving element connected to the first semiconductor light receiving element are integrated, wherein the wavelength composition of the core layer of the second semiconductor light receiving element is By setting the wavelength composition longer than the core layer wavelength composition of the first semiconductor light receiving element, a two-wavelength multiplexed signal can be received, and the core layer of each element is formed continuously in the light propagation direction even in a region connecting the elements. And n-2 pieces (n is 3 ) at the subsequent stage of the second semiconductor light receiving element.
Since the semiconductor light receiving element of the above (positive integer) is connected, and the later it is connected, an n-wavelength multiplexed signal can be received by setting the core layer wavelength composition of the semiconductor light receiving element to be longer. It is possible to obtain an optical semiconductor integrated circuit for bidirectional WDM communication capable of performing WDM transmission in each of transmission and reception using a wavelength composition difference without using a wavelength composition difference, and to obtain an optical semiconductor integrated circuit having a simple structure and a small size. it can.

The present invention also relates to a semiconductor device having at least
Also, a first semiconductor light receiving element and the first semiconductor light receiving element
And a branch waveguide connected to one of the branch waveguides.
Connected to the semiconductor laser connected to the other side of the branch waveguide.
Optical semiconductor integrated with continued second semiconductor light receiving element
An integrated circuit, wherein the first semiconductor light receiving element receives and emits light.
The port also serves as a port, and receives light from the second semiconductor light receiving element.
Sensitivity wavelength band and transmission signal wavelength of the semiconductor laser
The band is shorter than the light receiving sensitivity wavelength band of the first semiconductor light receiving element.
And the area where the core layer of each element connects the elements.
In the light propagation direction even in the
Utilizes wavelength composition difference without using wavelength discriminating element
WDM transmission for both transmission and reception
It is possible to obtain a simple optical semiconductor integrated circuit for bidirectional WDM communication.
It is possible to obtain a small-sized optical semiconductor integrated circuit with a simple structure.
Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an optical semiconductor integrated circuit according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA ′, line BB ′, and line CC ′ of FIG. 1;

FIG. 3 is a first perspective view illustrating a method of manufacturing the optical semiconductor integrated circuit in FIG. 1 in the order of steps;

FIG. 4 is a second perspective view illustrating a method of manufacturing the optical semiconductor integrated circuit in FIG. 1 in the order of steps;

FIG. 5 is a perspective view illustrating a configuration of an optical semiconductor integrated circuit according to a second embodiment of the present invention.

6 is a line AA ′, line BB ′, line CC ′ in FIG.
It is each sectional drawing of the DD 'line and the EE' line.

7 is a perspective view of a part of a step for describing a method for manufacturing the optical semiconductor integrated circuit in FIG.

FIG. 8 is a perspective view illustrating a configuration of an optical semiconductor integrated circuit according to a third embodiment of the present invention.

9 is a line AA ′, line BB ′, line CC ′ in FIG.
It is each sectional drawing of DD 'line, EE' line, FF 'line, and GG' line.

10 is a perspective view of a part of the process for describing the method for manufacturing the optical semiconductor integrated circuit in FIG.

FIG. 11 is a perspective view illustrating a configuration of an optical semiconductor integrated circuit according to a fourth embodiment of the present invention.

FIG. 12 is a first perspective view of part of a step for describing the method for manufacturing the optical semiconductor integrated circuit in FIG.

FIG. 13 is a perspective view showing a first conventional example.

FIG. 14 is a perspective view showing a second conventional example.

FIG. 15 is a diagram showing a relationship between a mask width and a wavelength composition of a bulk core layer.

FIG. 16 is a diagram showing a relationship between a mask width and a wavelength composition of an MQW core layer.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate 2 Y branch 3 1.3 μm band transmission LD 4 1.3 μm band transmission LD 3 monitor PD 5 1.3 μm band reception PD 6 1.55 μm band reception PD 7 1.55 μm band transmission LD 8 1.55 μm band transmission LD7 monitoring PD 9 second PD connection passive waveguide 11 n-InP substrate 12 n-InGaAsP layer 13 n-InP spacer layer 14 lower SCH layer 15 MQW core layer 16 upper SCH layer 17 InP clad layer 18 InP buried layer Reference Signs List 20 grating 21 SiO ₂ film 22 mask for selective crystal growth Wm mask width Wg mask gap

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenshin Taguchi 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Tatsuya Sasaki 5-7-1 Shiba, Minato-ku, Tokyo Japan Inside Electric Corporation (72) Inventor Masako Hayashi 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Ikuo Mito 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-7-231144 (JP, A) 1995 IEICE Electro Society Conference C-210 p. 210 1995 IEICE Electro Society Conference C-211 p. 211 1995 IEICE Electro Society Conference C-181 p. 18 1995 IEICE General Conference C-387 p. 387 (58) Field surveyed (Int.Cl. ⁶ , DB name) H01S 3/18 G02B 6/12

Claims (5)

(57) [Claims] A semiconductor laser connected to at least one of the branch waveguides on a semiconductor substrate; a semiconductor laser connected to one of the branch waveguides; a first semiconductor light receiving element connected to the other of the branch waveguides; Second semiconductor light-receiving element
An optical semiconductor integrated circuit in which the second semiconductor light receiving element is integrated, wherein the core layer wavelength composition of the second semiconductor light receiving element is set longer than the core layer wavelength composition of the first semiconductor light receiving element. A wavelength multiplexed signal can be received, and a core layer of each element is formed continuously in the light propagation direction even in a region connecting the elements, and n-2 (-2) ( (where n is a positive integer of 3 or more) is connected, and an n-wavelength multiplexed signal can be received by setting the core layer wavelength composition of the semiconductor light receiving element to be longer as the latter is connected. Optical semiconductor integrated circuit. 2. The semiconductor laser according to claim 1, wherein m-1 (m is a positive integer of 2 or more) semiconductor lasers are connected at a subsequent stage, and the wavelength composition of the core layer of the semiconductor laser is set to be longer as the semiconductor lasers are connected at a later stage. optical semiconductor integrated circuit according to claim 1 which enables transmitting the m wavelength-multiplexed signals in. 3. A signal light absorber is provided at a stage subsequent to each of the plurality of semiconductor lasers connected to each other, and the wavelength composition of the signal light absorber core layer is the same as the wavelength composition of the core layer of the preceding semiconductor laser. 3. The optical semiconductor integrated circuit according to claim 2, wherein the optical semiconductor integrated circuit is set to be longer or shorter than the core layer wavelength composition of the subsequent semiconductor laser. Wherein said signal light absorber, claim also serves as a semiconductor light-receiving element for monitoring the front of the semiconductor laser 3
3. The optical semiconductor integrated circuit according to claim 1. 5. A semiconductor substrate having at least a first semiconductor light receiving element on a semiconductor substrate, a branch waveguide connected to the first semiconductor light receiving element, a semiconductor laser connected to one of the branch waveguides, and An optical semiconductor integrated circuit in which a second semiconductor light receiving element connected to the other side of the waveguide is integrated, wherein the first semiconductor light receiving element also serves as an input / output port, and the second semiconductor light receiving element The light-receiving sensitivity wavelength band and the transmission signal wavelength band of the semiconductor laser are longer than the light-receiving sensitivity wavelength band of the first semiconductor light-receiving element, and the light propagation direction also in a region where the core layer of each element connects the elements. An optical semiconductor integrated circuit, wherein the optical semiconductor integrated circuit is formed continuously.