JP2001148542A - Optical semiconductor device, manufacturing method therefor and optical communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower element resistance by broadening the current path width specified by the width of an active mesa stripe top, including an active layer of an optical semiconductor device having a current restricting structure, thereby improving the operating speed, the operating efficiency, the high-temperature operation characteristics, the high power operation characteristics, the modulation band, etc. SOLUTION: An active mesa stripe, including an active layer, is formed like an inverted mesa shape by the selective growth, and the current path width specified by the width of the active mesa stripe top is broadened to lower the element resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication device and an optical semiconductor device used for the optical communication device, and more particularly, to an optical amplifier, an optical modulator, a light source, or an optical semiconductor device in which these are integrated, suitable for high-speed operation. And its manufacturing method.

[0002]

2. Description of the Related Art With the progress of optical fiber communication technology, the development of long-distance, large-capacity optical communication systems has been promoted.
There is a demand for improved characteristics such as operating speed of optical communication devices, optical communication modules, optical semiconductor devices, and the like used therein. As an example of an optical semiconductor device developed in response to such a demand, there is a semiconductor optical amplifier shown in FIG.

[0003] The semiconductor optical amplifier shown in FIG.
NI formed directly on n-InP substrate 1 by growth
A forward mesa-shaped active mesa stripe 5 composed of an nP cladding layer 2, an InGaAsP multiple quantum well active layer 3, and a p-InP cladding layer 4, and an S on the top of the active mesa stripe
A p-InP block layer 12 and an n-InP block layer 13 formed on both sides of the active mesa stripe 5 by selective growth by forming a dielectric mask such as iO ₂ or SiN or a growth prevention mask by oxidation of an Al-based semiconductor. And n-I
p-InP buried layer 14 formed above nP block layer 13 and active mesa stripe 5 and p-InGaAs
N-InP substrate 1, p-I
nP block layer 12, n-InP block layer 13, p-
Pnpn current confinement structure 6 with InP buried layer 14
Is composed. n-InP substrate back surface and p-InGaAs
Electrodes 17 and 16 are formed on the surface of the s-contact layer 15, respectively, and antireflection coatings (not shown) are formed on both end surfaces.
Is given. The wavelength for amplification is 1.3 μm,
The element length is 600 μm.

[0004]

An optical semiconductor device having an active mesa stripe 5 directly formed by selective MOVPE growth, such as the semiconductor optical amplifier of FIG. The feature is that extremely high precision and uniform reproducibility can be controlled by patterning the mask for use and controlling the growth thickness in MOVPE growth. However, since the active mesa stripe 5 formed by the selective growth has a forward mesa shape, the current path width 7 to the active layer defined by the width on the top of the active mesa stripe 5 is narrow. For this reason, the resistance of the current path to the active layer 3 becomes high, causing the current constriction characteristics to deteriorate, the efficiency to decrease due to heat generation, etc., and adversely affecting the operation speed, operation efficiency, high temperature operation characteristics, high output operation characteristics, etc. There is a problem that exerts.

In general, an optical semiconductor device used for optical communication has an active layer width of 1.8 μm or less in order to suppress the occurrence of higher-order transverse modes. Therefore, the influence of the element characteristics due to the decrease in the current path width as described above is a problem that cannot be ignored. In the conventional semiconductor optical amplifier shown in FIG. 7, the width of the current path is about 0.3 with respect to the active layer width of 1.3 μm.
6 μm, and the element resistance was 10Ω. The current-gain characteristics of this semiconductor optical amplifier are as shown in FIG.
The gain did not increase at an injection current of 200 mA or more, and a gain of 20 dB or more was not obtained due to heat generation and a decrease in current constriction characteristics (increase in leak current).

In an optical semiconductor device such as an optical amplifier or an optical modulator, the active layer width is set to 1 μm or less, and the active layer width and the active layer thickness are set to be substantially equal in order to reduce the polarization dependence. Often. The semiconductor optical amplifier of FIG. 7 shows a conventional example in which this type of design is introduced. However, the width of the top of the active mesa stripe 5 directly formed by selective growth is very narrow, and the current confinement structure is obtained. Is extremely difficult to form.

As shown in FIG. 9, an active mesa stripe 5 formed by selective growth on an n-InP substrate 1 is formed on a p-In
Buried with a P buried layer 14, p-InP buried layer 1
The width of the current path is increased by adopting a homo-buried element structure in which the p-InGaAs contact layer 15 is provided on the substrate 4. However, in the structure of FIG.
5 is large, and the junction capacity of the pn homo junction 25 is large, so that high-speed operation is difficult.

An optical communication device or an optical communication module using an optical semiconductor device having inferior characteristics as described above has a poor transmission speed and is not suitable for a long-distance, large-capacity, high-speed transmission optical communication system.

[0009] The present invention has been made to solve the above-mentioned problems, and the first object of the present invention is to provide:
An active mesa stripe directly formed by selective growth;
In an optical semiconductor device having a current confinement structure for injecting a current into an active layer in an active mesa stripe, the current path width to the active layer in the active mesa stripe is increased, and the operation speed, operation efficiency, and high-temperature operation characteristics are increased. Optical semiconductor device with high output operation characteristics, good modulation bandwidth, etc., and using this optical semiconductor device, optical communication capable of high-speed transmission suitable for long-distance, large-capacity, high-speed transmission optical communication systems. It is to provide an apparatus and an optical communication module. The second object is to make it possible to form a current confinement structure even for a selectively grown active mesa stripe in which the active layer width and the active layer thickness are designed to be substantially equal, and to increase the operation speed, operation efficiency, It provides optical semiconductor devices with good high-temperature operation characteristics, high-output operation characteristics, modulation bandwidth, etc., and uses this optical semiconductor device to achieve high-speed transmission suitable for long-distance, large-capacity, high-speed transmission optical communication systems. It is to provide a possible optical communication device and an optical communication module.

[0010]

An optical semiconductor device according to the present invention is an optical semiconductor device having an active mesa stripe including an active layer and a current constriction structure formed on both sides of the active mesa stripe. The stripes are characterized by having an inverted mesa shape formed by selective growth.

Here, the current confinement structure is a pnpn-pn having a p-semiconductor block layer and an n-semiconductor block layer.
A current constriction structure, a structure having a semi-insulating semiconductor block layer, or a structure composed of a spin-coat flattening film such as benzocyclobutene, polyimide, or organic glass and a dielectric insulating film can be used.

Further, as an optical semiconductor device, an optical amplifier,
Semiconductor laser, optical modulator, monolithically integrated optical modulator and semiconductor laser, integrated spot size converter and semiconductor laser, integrated spot size converter and optical amplifier spot size converter Various devices such as a device in which a light modulator and a light modulator are integrated can be used.

According to the manufacturing method of the present invention, an inverted mesa-shaped active mesa stripe including an active layer is directly formed on a semiconductor substrate by selective growth, and a crystal growth inhibition mask is formed on the top of the active mesa stripe. Forming a current confinement structure on both sides of the active mesa stripe by selective growth.
Here, a (100) plane substrate is used as a semiconductor crystal substrate, and a direction in which a mask opening stripe for selective growth of active mesa stripes extends is a desired angle (offset angle) with respect to a [011] direction of the semiconductor substrate. It is effective to displace them.

In the step of forming a current confinement structure, a first conductivity type semiconductor block layer and a second conductivity type semiconductor block layer are sequentially grown on both sides of the active mesa stripe by selective growth, and a pnpn current is formed. A step of forming a constriction structure, or a step of growing a high-resistance semiconductor layer or a semi-insulating semiconductor layer on both sides of an active mesa stripe by selective growth to form a current constriction structure comprising a high-resistance or semi-insulating semiconductor layer Alternatively, a step of forming a current constriction structure formed of a spin-coated flattening film by spin-coating benzocyclobutene, polyimide, organic glass, or the like on both sides of the active mesa stripe can be used. .

According to the manufacturing method of the present invention, when a step of forming a diffraction grating on a part of a semiconductor crystal substrate (a part to be a laser part) is added to the above-described manufacturing steps, the optical modulator and the semiconductor laser can be monolithically formed. An optical semiconductor device integrated in a semiconductor device can be manufactured.

An optical communication device according to the present invention comprises the above-described optical semiconductor device according to the present invention, optical waveguide means for guiding output light from the optical semiconductor device to the outside, and an optical semiconductor device provided on the optical waveguide means. Composed of an optical communication module including an optical system for inputting output light from the optical system and an electrical interface for driving the optical semiconductor device, or an optical communication unit having the optical semiconductor device according to the present invention described above. And light receiving means for receiving output light from the communication means. The above-described optical communication module can be used as the optical communication means.

In the above-mentioned optical communication module, a semiconductor optical amplifier is used in the optical semiconductor device according to the present invention, a semiconductor optical amplifier driving circuit is built in, and optical coupling optics are respectively provided on the input side and the output side of the semiconductor optical amplifier. An optical semiconductor device according to the present invention having a system and an optical fiber and acting as a repeater, or an optical semiconductor device according to the present invention in which a DFB laser and an optical modulator are integrated, and an optical coupling optical system and an optical fiber on an optical output side as a light source. There is a working optical transmission module and the like.

[0018]

(Embodiment 1) An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an optical semiconductor device according to a first embodiment of the present invention, which has a wavelength of 1.3.
1 shows a semiconductor optical amplifier in the μm band, which is manufactured by the process shown in FIG.

On the n-InP substrate 1 having a plane orientation of (100), _two first selective growth SiO ₂ masks 8 each having a width of 10 μm are formed in parallel with each other, whereby the first selective growth SiO ₂ mask 8 is formed. A mask opening stripe 9 having a width of 1.5 μm is formed between the _two masks 8 (FIG. 2A). Then select M
The n-InP cladding layer 2 and the InGa
AsP multiple quantum well active layer 3, p-InP cladding layer 4
Are sequentially formed, and an active mesa stripe 5 composed of these three layers is directly formed (FIG. 2B). In addition to the mask opening stripe, a semiconductor layer is crystal-grown in a portion where the substrate is exposed without being covered with the mask. However, the growth layer at that portion is not shown). Here, the direction 9a in which the mask opening stripe 9 extends has a slight offset angle 10 with respect to the [011] direction of the substrate crystal, and the growth pressure and the growth rate in MOVPE growth are controlled. -InP
The cladding layer 4 has an inverted mesa shape, and the n-InP cladding layer 2 and the InGaAsP multiple quantum well active layer 3 are p-In
It can be grown so as to be embedded in the P clad layer 4. In the present embodiment, the offset angle 10 is 7 degrees,
A growth pressure of 760 Torr and a growth rate of 0.15 μm /
h, an inverted mesa-shaped p-InP cladding layer 4 covering the n-InP cladding layer 2 and the InGaAsP multiple quantum well active layer 3 was obtained. Next, a second selective growth SiO ₂ mask 1 is formed on the active mesa stripe 5 formed by selective growth.
Then, selective MOVPE growth of the p-InP block layer 12 and the n-InP block layer 13 is performed to form InP block layers 12 and 13 on both sides of the active mesa stripe 5 (FIG. 2C). At this time, the InP block layer 12,
Crystal growth conditions that prevent the overhang 13 on the active mesa stripe 5 are preferable. In this embodiment, the growth pressure is 75 Torr, the growth rate is 1.2 μm / h,
The nP block layers 12 and 13 were prevented from projecting over the active mesa stripe 5. Thereafter, a second selective growth SiO 2 is formed.
_{2 The} mask 11 is removed, and the p-InP buried layer 1 is formed on the n-InP block layer 13 and the active mesa stripe 5.
4. After the p-InGaAs contact layer 15 is sequentially grown, the p-electrode 1 is formed on the p-InGaAs contact layer 15.
6. Form an n-electrode 17 on the back surface of the InP substrate,
The semiconductor optical amplifier shown in FIG. 1 is obtained by cleaving at 00 μm and applying an anti-reflection coating (not shown) on both end surfaces.

In this embodiment, since the p-InP cladding layer 4 has an inverted mesa shape, the current path width 7 defined by the width of the top of the active mesa stripe is as large as about 3 μm, and the element resistance is 3.8Ω. And low values were obtained. As described above, the current path width is wide and the element resistance is reduced, so that the current confinement characteristic to the active layer 3 is improved.
A high gain of 34 dB was obtained at 0 mA.

Instead of applying a non-reflective coating to both end surfaces of the semiconductor optical amplifier, a high reflection film is provided on one end surface and a low reflection film is provided on the other end surface, so that the semiconductor optical amplifier can function as a semiconductor laser instead of an optical amplifier. Good. In the above embodiment, the n-InP substrate 1, the p-InP block layer 12,
n-InP block layer 13 and p-InP buried layer 14
Constitutes a pnpn current confinement structure 6, but instead of forming a p-InP block layer 12 and an n-InP block layer 13 on both sides of an active mesa stripe, a semi-insulating or high Resistive semiconductor layer (eg, Fe-doped InP
), And a current confinement structure may be formed by the semi-insulating or high-resistance semiconductor layer.

In the above embodiment, an example of a semiconductor optical amplifier is shown as an optical semiconductor device.
For example, a spot size converter having a tapered active mesa stripe that is thinner as the thickness of the active mesa stripe is closer to the end face may be provided. In this case, for example, FIG.
As shown in FIG. 10, the opening width is different between the semiconductor optical amplifier section and the spot size converter section (FIG. 10A), or the opening width is constant and the width of the SiO ₂ mask 8 on both sides is different (FIG. By performing selective growth using a selective growth mask such as 10 (b)), an optical semiconductor device in which a semiconductor optical amplifier and a spot size converter are integrated can be manufactured. The growth method and the like may be the same as in the above embodiment. The provision of the spot size converter is not limited to this embodiment, and the optical semiconductor device (for example, optical modulator,
Semiconductor laser). Embodiment 2 As a second embodiment of the present invention, an electro-absorption optical modulator and a distributed feedback laser diode (DF)
FIG. 3 shows an optical semiconductor device in which B laser is integrated on one substrate. Here, FIG. 3A shows an IP where an SiO ₂ mask 8 for selective growth is formed on an InP substrate on which a diffraction grating is formed.
FIG. 3B is a perspective view of the optical semiconductor device.

First, in the region to be the laser section 18 of the n-InP substrate 1 having the (100) plane orientation, the period に is shifted by 7 degrees from the [011] direction (in the direction of arrow A) by interference exposure and wet etching. Is formed. Next, as shown in FIG.
An iO ₂ film is deposited, the opening width is 1.5 μm, the width is 18 μm in the laser unit 18, 5 μm in the optical modulator unit, and the length is 250 μm in the laser unit 18 and 150 μm in the optical modulator unit 19. A SiO ₂ mask 8 for selective growth and a mask opening stripe 9 are formed. Here, the direction 9a in which the mask opening stripe extends is inclined by 7 degrees with respect to the [011] direction.
Thereafter, as in the first embodiment, an n-InP cladding layer 2, an InGaAsP multiple quantum well active layer 3, and a p-InP cladding layer 4 are sequentially grown by selective MOVPE growth, and an active mesa stripe comprising these three layers is formed. 5 is formed directly. The growth conditions were such that the growth pressure was 760 Torr, the growth rate was 0.15 μm / h, and an n-InP cladding layer 2 and an inverted-mesa p-InP cladding layer 4 covering the InGaAsP multiple quantum well active layer 3 were obtained. As a result, the active mesa stripe 5 has an inverted mesa shape.

Next, the first selective growth SiO 2_Twomask
After removing 8, a second selection is made on top of the active mesa stripe.
SiO for growth_TwoForm a mask for selective MOVPE growth
Fe-doped semi-insulating InP block layer 21
Are formed on both sides of the active mesa stripe 5. After this,
SiO for selective growth_TwoThe mask is removed and semi-insulating In
P-I on the P block layer 21 and the active mesa stripe 5
nP buried layer 14, p-InGaAs contact layer 1
5 (thickness 0.3 μm, Zn concentration 2 × 10¹⁹cm ^-3)
Next, the semi-insulating InP block layer 21 and the p-In
Active mesa stripe 5 is buried with P buried layer 14
No.

Next, the p-InGaAs contact layer 15
A resist having a stripe shape wider than the active mesa stripe 5 is formed in the region corresponding to the surface of the active mesa stripe and above the active mesa stripe 5, and the p-InGaAs contact layers 15 and p are formed using the stripe resist as an etching mask. -InP buried layer 14 and semi-insulating InP block layer 21 are etched until reaching InP substrate 1 to form an electrode separation mesa. At this time, in order to reduce the element capacity of the optical modulator section, the etching mask width of the optical modulator section 19 is made smaller than the etching mask width of the laser section 18 so that the electrode separation mesa width of the optical modulator section 19 is reduced. Is smaller than the electrode separation mesa width of the laser section 18.

Finally, the SiO ₂ insulating film 2 having an opening at a position corresponding to the upper part of the active mesa stripe by CVD.
4 is formed, the p-electrode 16 contacting the p-InGaAs contact layer 15 through the opening is formed on the SiO ₂ insulating film 2.
4 and an n-electrode is formed on the back surface of the n-InP substrate. Thereafter, the laser light is cleaved and the reflectivity 90
% Of a high reflection film (not shown) and a low reflection film (not shown) having a reflectance of 0.1% on the end face of the optical modulator section 19, and the electroabsorption optical modulator and the DFB laser are integrated. , FIG.
The optical semiconductor device shown in (b) is completed. Although a DFB laser is formed in the laser unit 18, a semiconductor laser having no diffraction grating may be formed in the laser unit 18.

The modulation band of the optical modulator has a capacitance C and an element resistance R
Therefore, it is important to reduce the element resistance as well as the element capacitance. In the present embodiment, the semi-insulating InP block layer 21 is introduced to reduce the capacitance of the optical modulator section 19, and the active mesa stripe 5 having the active layer 3 is formed into an inverted mesa shape, thereby reducing the element resistance. Is reduced and the small signal response 3 dB band of the optical modulator is reduced to 18
GHz was obtained. Further, the current confinement characteristics of the DFB laser were also improved by reducing the element resistance, and a high output of 15 mW or more was obtained as the optical output at a drive current of 100 mA. (Embodiment 3) FIG. 4 is a perspective view showing an electroabsorption optical modulator in a 1.58 μm wavelength band as an optical semiconductor device according to a third embodiment of the present invention. As in the first embodiment, a mask having a stripe-shaped opening is formed on an n-InP substrate 1, and an n-InP cladding layer 2, an InAlGaAs active layer 22, and an inverted mesa are formed in the mask opening by selective MOVPE growth. P-InP cladding layer 4, p-In
A GaAs contact layer 15 is sequentially grown, and an active mesa stripe 5 composed of these four layers is directly formed. The crystal growth conditions at this time are the same as in the first embodiment. Subsequently, after removing the mask, a flattening process using a spin coat flattening film 23 made of benzocyclobutene, polyimide, organic glass, or the like is performed to form a spin coat flattening film 23 on both sides of the active stripe 5. Further, an SiO ₂ insulating film 24 is formed on the spin coat flattening film 23 by CVD.
To form a current confinement structure including the spin-coat planarization film 23 and the SiO ₂ insulating film 24. Thereafter, electrodes 16 and 1 are respectively provided on the upper portion of the active mesa stripe and on the back surface of the substrate.
After the formation of 7, the device is cleaved to an element length of 120 μm, and an anti-reflection coating (not shown) is applied to both end faces to obtain an electro-absorption optical modulator shown in FIG.

In an optical modulator in which the element length is shortened to improve the modulation band, such as the electro-absorption type optical modulator of the present embodiment, the element resistance is reduced while the element resistance is reduced by shortening the element length. Since a trade-off of increase occurs, it is very important to reduce the element resistance. In the present embodiment, the p-InP cladding layer 4 is formed in a reverse mesa shape to secure a current path width 7 of 3 μm, thereby suppressing the element resistance to as low as 6Ω and providing a small signal response 3 dB band of the optical modulator of 26 GHz. I got (Embodiment 4) As a fourth embodiment of the present invention, a plan view of an optical communication module in which an optical semiconductor device according to the present invention and an optical component are combined is shown in FIG. The optical communication module shown in FIG.
As shown in the above, an optical semiconductor device in which an optical modulator and a DFB laser are integrated is used, and output light from the optical semiconductor device 26 is input to the optical fiber 29 via the aspheric lens 27 and the optical isolator 28. An optical transmission device in which an optical semiconductor device 26, an aspheric lens 27, an optical isolator 28, and an optical fiber 29 are installed and fixed in a package 31a, and an electric interface 30 for driving the optical semiconductor device 26 is built in the package 31a. Module. This optical transmission module is the optical semiconductor device 2 used.
6 has an inverted mesa-shaped active mesa stripe having a wide current path width and is excellent in operation speed, operation efficiency, high-temperature operation characteristics, high-output operation characteristics, modulation band, etc., so that high-speed optical communication signals can be efficiently used. It was able to produce well.

In the fourth embodiment, an optical semiconductor device in which an optical modulator and a DFB laser are integrated is used as the optical semiconductor device 26. However, other optical semiconductor devices, for example, the optical modulator of the third embodiment, Optical amplifiers, semiconductor lasers, etc.
Having an active mesa stripe including an inverted mesa-shaped cladding layer,
Any optical semiconductor device having a wide current path may be used. For example, when the optical amplifier described in the first embodiment is used for the optical semiconductor device 26, another set of the aspheric lens 27, the optical isolator 28, and the optical fiber 29 are added to the optical semiconductor device in addition to the configuration of FIG. A configuration in which the optical components shown in FIG. 5 are arranged around the object 26 (optical components are also arranged on the light input side), that is, an optical fiber 29, an optical isolator 28, an aspheric lens 27, An optical semiconductor device 26, an aspheric lens 27, an optical isolator 28,
By adopting a configuration in which the optical fibers 29 are arranged, an optical repeater module can be configured. Also in this case, as described in the first embodiment, since the characteristics of the optical semiconductor device 26 are excellent, the optical communication signal can be amplified and reproduced at high speed.

In the fourth embodiment, the optical modulator and the D
When an integrated device that incorporates a spot size converter in addition to an FB laser, an optical amplifier, and the like is used, an aspheric lens can be omitted, and an optical communication module with a small number of components can be realized. (Embodiment 5) FIG. 6 is a block diagram showing an optical communication apparatus using an optical transmission module 31 of Embodiment 4 as a fifth embodiment of the present invention. This optical communication device
The optical transmitting device 32, the optical receiving device 34, these devices 3
And an optical fiber 29 connecting between the two. The optical transmission device 32 has an optical transmission module 31 and an optical transmission module driving device 33 for driving the optical transmission module 31. The optical receiving device 34 has a light receiving module 35. The signal light output from the optical transmission module 31 of the optical transmission device 32 is transmitted through the optical fiber 29 and detected by the light receiving module 35 in the reception device 34.

Since the optical communication device of the present embodiment uses the optical transmission module 31 of the fourth embodiment, high-speed optical transmission can be easily realized. This is because, as described in the fourth embodiment, the optical transmission module according to the fourth embodiment has an optical semiconductor device excellent in operation efficiency, high-temperature operation characteristics, high-output operation characteristics, modulation band, and the like. And good optical transmission signals can be obtained with high efficiency.

In each of the above embodiments, the end face is formed by cleavage and the (011) plane is used as the end face (the direction in which the active mesa stripe extends is not orthogonal to the end face (obliquely intersects)). , Forming an end face by etching,
A plane inclined by several degrees from the (011) plane to the (010) plane or the (001) plane, for example, a plane inclined by the same angle θ as the offset angle of the mesa stripe, in this case, a plane inclined by 7 degrees (FIG. a) The surface B) indicated by a two-dot chain line may be used as an end surface. In this case, the direction 9 in which the active mesa stripe extends
a is perpendicular to the end face.

In the above embodiment, a semiconductor optical amplifier, an electro-absorption modulator integrated distributed feedback laser diode, and an electro-absorption optical modulator have been described as optical semiconductor devices, but other optical semiconductor devices, for example, It can be applied to a semiconductor laser or the like. Also, the wavelength bands are 1.3 μm band, 1.55 μm band, and 1.58 μm band described in the embodiment.
It is not limited to the μm band.

Although an example in which a quantum well active layer is used as an active layer of an optical semiconductor device has been described, an active layer of a strained quantum well structure, a bulk crystal, or a natural superlattice active layer may be used. Further, although an example has been shown in which the conductivity type of the substrate is n-type, the present invention can be applied to a case where a p-type or semi-insulating substrate is used.

Although the examples using InGaAsP / InP and InAlGaAs / InP as the material system have been described above, the present invention is not limited to these material systems.
aAs / GaAs system, AlGaInP / GaInP system,
Any other material may be used.
Also, an example is shown in which the (100) substrate is used and the mask opening stripe for selective growth of the active layer mesa stripe has an offset angle of 7 degrees with respect to the [011] direction. As long as the layer is capable of crystal growth in an inverted mesa shape, the plane orientation and the stripe direction of the substrate to be used are not limited to these, and the growth conditions such as the growth pressure and the growth rate in the selective MOVPE growth are also applied. However, the present invention is not limited to the values described in the embodiment.

In this specification, "selection MOVPE"
The expression "active mesa stripe directly formed by growth" is used. In this case, "direct formation" means that a mesa stripe of a normal mesa shape or an inverted mesa shape is formed by selective growth without etching. Meaning.

[0037]

According to the optical semiconductor device of the present invention, an active mesa stripe sandwiched on both sides by a block layer constituting a current constriction structure is formed in an inverted mesa shape, and is defined by the width of the top of the active mesa stripe. The current path width is wide and the element resistance is reduced. As a result, the operating speed, operating efficiency, high-temperature operating characteristics, high-output operating characteristics, modulation band, and the like have been improved. For example, in the optical amplifier of the embodiment, the current confinement characteristics to the active layer were improved, and a high gain of 34 dB was obtained at an injection current of 300 mA. In an optical semiconductor device in which a DFB laser and an optical modulator are integrated, the small signal response of the optical modulator is 3 dB.
A band of 18 GHz was obtained, and the current confinement characteristics of the distributed feedback laser diode portion were also improved by reducing the element resistance, and a high output of 15 mW or more was obtained as the optical output at a driving current of 100 mA. The optical modulator is 26G as a small signal response 3dB band.
Hz was obtained.

An optical communication device or an optical communication module according to the present invention mounts the above-described optical semiconductor device in which active mesa stripes sandwiched on both sides are formed in an inverted mesa shape in a block layer constituting a current confinement structure. Therefore, a high-speed optical communication signal can be efficiently generated, which is suitable for a long-distance, large-capacity, high-speed optical transmission optical communication system.

[Brief description of the drawings]

FIG. 1 is a perspective view of a semiconductor optical amplifier according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor optical amplifier according to the first embodiment.

FIG. 3 is a plan view of a substrate on which a selective growth mask is formed and a perspective view of an optical semiconductor device in which an optical modulator and a DFB laser are integrated, showing a second embodiment.

FIG. 4 is a perspective view of an optical modulator according to a third embodiment.

FIG. 5 is a plan view of an optical transmission module according to a fourth embodiment.

FIG. 6 is a block diagram of an optical communication device according to a fifth embodiment.

FIG. 7 is a perspective view of a conventional optical semiconductor device (optical amplifier).

FIG. 8 is a diagram showing characteristics of the optical amplifier shown in FIG. 7;

FIG. 9 is a perspective view of a conventional optical semiconductor device (optical amplifier).

FIG. 10 is a plan view of a selective growth mask when a semiconductor optical amplifier, an optical modulator, or a semiconductor laser and a spot size converter are monolithically integrated.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 n-InP substrate 2 n-InP cladding layer 3 InGaAsP multiple quantum well active layer 4 p-InP cladding layer 5 active mesa stripe 6 pnpn current confinement structure 7 current path width 8 first selective growth SiO ₂ mask 9 Mask opening stripe 9a Direction of extending mask opening stripe 10 Offset angle 11 Second selective growth SiO ₂ mask 12 p-InP block layer 13 n-InP block layer 14 p-InP buried layer 15 p- InGaAs contact layer 16 p-electrode 17 n-electrode 18 laser unit 19 optical modulator unit 20 diffraction grating 21 semi-insulating InP block layer 22 InAlGaAs active layer 23 spin coat flattening film 24 SiO ₂ insulating film 25 pn homojunction 26 Optical semiconductor device 27 Aspherical lens 28 Optical isolator 29 Optical fiber 30 Electrical interface for driving an optical semiconductor device 31 Optical transmission module 31a Package 32 Optical transmission device 33 Optical transmission module driving device 34 Receiving device 35 Light receiving module

Claims (17)

[Claims] 1. An optical semiconductor device comprising: an active mesa stripe including an active layer; and a current confinement structure formed on both sides of the active mesa stripe, wherein the active mesa stripe is formed by selective growth. An optical semiconductor device having a mesa shape. 2. The optical semiconductor device according to claim 1, wherein the current confinement structure is a pnpn current confinement structure having a p-semiconductor block layer and an n-semiconductor block layer. 3. The optical semiconductor device according to claim 1, wherein the current confinement structure has a semi-insulating semiconductor block layer. 4. The optical semiconductor device according to claim 1, wherein the current confinement structure comprises a dielectric insulating film and a spin-coat planarizing film. 5. The optical semiconductor device according to claim 4, wherein the spin coat flattening film is made of benzocyclobutene, polyimide, or organic glass. 6. The optical semiconductor device according to claim 1, wherein the optical modulator and the semiconductor laser are monolithically integrated. 7. A step of directly forming an inverted mesa-shaped active mesa stripe including an active layer on a semiconductor substrate by selective growth, a step of forming a crystal growth-inhibiting mask on top of the active mesa stripe, and forming a current by selective growth. Forming a constriction structure on both sides of the active mesa stripe. 8. A step of forming a pnpn current constriction structure by sequentially growing a first conductivity type semiconductor block layer and a second conductivity type semiconductor block layer on both sides of the active mesa stripe by selective growth. The method for manufacturing an optical semiconductor device according to claim 7, comprising: 9. A step of growing a high-resistance semiconductor layer or a semi-insulating semiconductor layer on both sides of the active mesa stripe by selective growth to form a current confinement structure comprising the high-resistance or semi-insulating semiconductor layer. 8. The method according to claim 7, wherein
The manufacturing method of the optical semiconductor device described in the above. 10. A step of directly forming an inverted mesa-shaped active mesa stripe including an active layer on a semiconductor substrate by selective growth, and forming a spin-coated flattening film on both sides of the active mesa stripe. Forming a current constriction structure having a coat flattening film. 11. A direction in which a mask opening stripe for selectively growing an inverted mesa active mesa stripe including an active layer has an offset angle with respect to a crystal orientation of a semiconductor crystal substrate. The method for manufacturing an optical semiconductor device according to claim 7. 12. The semiconductor crystal substrate is a (100) plane substrate, and a direction in which a mask aperture stripe extends has an offset angle with respect to a [011] direction of the semiconductor substrate. Item 12. The method for manufacturing an optical semiconductor device according to any one of Items 7 to 11. 13. The optical semiconductor device according to claim 7, further comprising a step of forming a diffraction grating in a portion to be a laser portion of the semiconductor crystal substrate, wherein the optical modulator and the semiconductor laser are monolithically integrated. Production method. 14. An optical semiconductor device according to claim 1, an optical waveguide means for guiding output light from the optical semiconductor device to the outside, and the optical semiconductor device provided on the optical waveguide means. An optical communication device comprising an optical communication module including an optical system for inputting output light from the device and an electrical interface for driving the optical semiconductor device. 15. The optical semiconductor device according to claim 1, an optical waveguide for guiding a signal light to the optical semiconductor device, and a signal light from the optical waveguide. An optical system for inputting an optical semiconductor device, an optical waveguide unit for guiding output light from the optical semiconductor device to the outside, and an optical system for inputting output light from the optical semiconductor device to the optical waveguide unit; An optical communication device comprising an optical communication module including an electrical interface for driving the optical semiconductor device. 16. An optical communication device comprising: an optical communication device having the optical semiconductor device according to claim 1; and an optical receiving device for receiving output light from the communication device. 17. The optical communication device according to claim 16, wherein the optical communication means is the optical communication module according to claim 14.