JP3488137B2 - Optical semiconductor device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device and a method of manufacturing the same, and more particularly to an optical semiconductor device in which an active layer is formed by a direct selective MOVPE method using a dielectric film as a selective growth mask. Alternatively, the present invention relates to a method for manufacturing an optical semiconductor device, characterized in that ZnO is used for a part of the selective growth mask.

[0002]

2. Description of the Related Art A technique for increasing the capacity of optical transmission using optical fibers supports the smooth progress of the Internet, which has become widespread in recent years. In the optical fiber amplification technique, a semiconductor laser is used as a pumping light source, and in particular, a high output of the pumping light source is required.

In the optical fiber communication network, the range of application thereof is expanding to the access system and the subscriber system as well as the trunk system. Especially, the FTTH for connecting the optical fiber to each home.
(Fiber-To-The-Home), there is a strong demand for an inexpensive semiconductor laser that can withstand high temperature operation.
In the main line system, in order to respond to the explosive growth of communication demand, several tens of kilometers to several hundreds of kilometers at a high speed of 2.5 Gb / s to 10 Gb / s
There is a demand for a light source capable of transmitting an ultra long distance of m. In order to realize semiconductor lasers for optical subscriber systems and high-power semiconductor lasers for pumping EDFAs that can operate at high temperatures, an active layer with excellent optical gain is required, and even under high-temperature and high-bias conditions. It is essential to realize a current block structure with low leakage current (reactive current). From this perspective, pn
A current block structure composed of a pn thyristor structure is often used.

However, as a means for preventing the phenomenon that the current blocking function does not work due to the turn-on operation under a high bias condition, pnpn is a means.
A DC-PBH structure (double channel planar buried heterostructure) in which a narrow gap InGaAsP recombination layer is inserted into a thyristor has been proposed (conventional example: JP-A-62-102583 / I. Mito et al. , Electron. Lett., Vo
l. 18, p. 953-954,1982 / Y.Sakata et al., IEEE Phot
on. Tech. Lett, vol.9, pp.291-293, 1997).

This DC-PBH structure has a structure in which the same layer structure as the active layer is inserted as a carrier recombination layer between the n-InP substrate and the p-InP block layer, and carrier recombination occurs at high bias. This has the effect of preventing charge-up of the thyristor and suppressing turn-on operation. However, since the recombination layer itself has the same layer structure as the active layer, there is a problem that the reactive current consumed in the recombination layer occurs at the cost of suppressing the turn-on operation. Can not stand output operation. In order to suppress the turn-on operation without introducing a recombination layer, the p-block layer may be thickly doped with high concentration.
The contact area between the block layer and the p-clad layer, which is the injection source of holes, becomes large, and the contact resistance becomes small, which causes an increase in the leakage current, resulting in both leakage current and turn-on operation. It was difficult to control.

A conventional example will be briefly described. JP-A-62-1
No. 02583 discloses a semiconductor laser having a buried structure.
The InP layer is embedded around the nGaAsP active layer. In this, a buffer layer made of a multi-element mixed crystal which is difficult to thermally decompose is provided, and a current block layer is laminated on the buffer layer to improve the breakdown voltage.

JP-A-3-203282 relates to a mesa stripe type semiconductor laser diode for optical communication.
This is one that operates at a low current, can control the oscillation mode singly, has a low oscillation threshold, and has little energization deterioration.

Japanese Unexamined Patent Publication No. 8-64907 relates to a plane-embedded laser diode capable of high-speed modulation.
The purpose is to reduce the leakage current from the junction surface between the semiconductor substrate and the current blocking layer and the leakage current due to the thyristor structure.

SUMMARY OF THE INVENTION An object of the present invention is to provide means for solving the problems of the conventional pnpn current block structure. That is, a semiconductor laser having a thick film / highly-doped p block layer without increasing the contact area between the p block layer and the p clad layer which is the injection source of holes or decreasing the contact resistance, and the manufacturing thereof. To provide a method.

Further, in a semiconductor optical integrated device manufactured by the selective MOVPE method, by providing a means for realizing a structure in which only a part of the semiconductor region is selectively highly doped, a modulator integrated device excellent in high light output characteristics is provided. Type semiconductor laser is provided.

In order to achieve the above object, the present invention adopts the technical constitution described below.

[0010]

[0011]

A first aspect of a method for manufacturing an optical semiconductor device according to the present invention is a method for manufacturing an optical semiconductor device, which comprises a step of depositing a ZnO film on an n-InP substrate,
Patterning the ZnO film to form a ZnO stripe mask, and selectively growing an optical waveguide structure including an n-InP layer, an active layer and a p-InP layer in the opening using the ZnO stripe mask as a growth blocking mask. In addition, Zn from the ZnO film to the n-InP substrate
Solid-phase diffusion of ZnO
Forming a p-type inversion region on the n-InP substrate in a region having a lip mask; forming a dielectric mask only on the mesa top of the p-InP layer; and forming a p-InP layer on the p-type inversion region. and a step of sequentially forming an n-InP layer.

A second aspect of the method for manufacturing an optical semiconductor device according to the present invention is an optical semiconductor device in which at least an electroabsorption optical modulator and a distributed feedback semiconductor laser are integrated on an n-type semiconductor substrate. And a ZnO mask is formed in the semiconductor laser forming region on the low-concentration n-InP buffer layer and the step of forming a low-concentration n-InP buffer layer on the entire surface of the n-type semiconductor substrate. At the same time, in the modulator formation region, a step of forming a Zn-free dielectric mask is performed, an optical waveguide structure is selectively grown in the opening using the mask formed in the step as a growth inhibition mask, and the ZnO mask is used. To the low concentration n-I
Zn solid phase diffusion into the nP buffer layer, growth inhibition mask
The low concentration n-I in a region of the ZnO mask
forming a p-type inversion region in the nP buffer layer, removing part of the ZnO mask formed in the semiconductor laser formation region and part of the Zn-free dielectric mask formed in the modulator formation region, P-In is formed on the p-type inversion region.
And a step of forming a P clad layer.

A third aspect of the method for manufacturing an optical semiconductor device according to the present invention is an optical semiconductor device in which at least an electroabsorption optical modulator and a distributed feedback semiconductor laser are integrated on an n-type semiconductor substrate. And a ZnO mask and a ZnO mask in the semiconductor laser forming region on the low concentration n-InP buffer layer. A Zn-free dielectric mask is formed on the outside of the mask, and a Zn-free dielectric mask is formed in the modulator formation region, and the mask formed in the above step is used as a growth inhibition mask to form an opening. An optical waveguide structure is selectively grown on the portion, and the low concentration n-I is removed from the ZnO mask.
Zn solid phase diffusion into the nP buffer layer, growth inhibition mask
The low concentration n-I in a region of the ZnO mask
forming a p-type inversion region in the nP buffer layer, removing a part of the ZnO mask formed in the semiconductor laser formation region and the Zn-free dielectric mask formed in the modulator formation region, And a step of forming a p-InP clad layer on the inversion region.

[0015]

Further, in a semiconductor optical integrated device manufactured by the selective MOVPE method, by providing a means for realizing a structure in which only a part of the semiconductor device is selectively highly doped, a modulator integrated device having a high optical output characteristic is provided. Type semiconductor laser is provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of a method for manufacturing an optical semiconductor device according to the present invention will be described in detail below with reference to the drawings.

1 and 2 show a first embodiment of the present invention. A zinc oxide (ZnO) film 103 is deposited to a thickness of 150 nm on the n-InP (100) substrate 101 by a sputtering method. After that, a pair of ZnO stripe masks 103 are formed in the [011] direction by a photoresist process. At this time, the stripe opening width was 1.5 μm and the mask width was 10 μm (FIG. 1A).

Using this ZnO film 103 as a growth inhibition mask, metal organic vapor phase epitaxy (MO) is applied to the opening shown in FIG.
VPE: Metal-organic vapor phase epitaxy)
-InP layer (layer thickness 0.15 micron, carrier concentration 1 x
1018cm-3) 106, strained InGaAsP / InGaAs
P multiple quantum well (MQW: Multi-Quantum)
Well) Active layer (6 nm with 0.7% compressive strain introduced)
Thick In.818 Ga.182 As.606 P.394 well layer / bandgap wavelength 1.13 μm, 8 nm thick InGaAsP barrier, 6
Period, photoluminescence wavelength 1.295 μm) 10
7. An optical waveguide structure consisting of a p-InP layer (layer thickness 0.20 μm, carrier concentration 7 × 1017 cm −3) 108 is selectively grown. At this time, in order to raise the substrate temperature for crystal growth, the ZnO film is removed from the n-InP substrate 1.
Zn is solid-phase diffused to 01 to form the p-type inversion region 105. Next, only SiO 2 is formed on the mesa top of the p-InP layer 108.
2 after forming the mask 109 (FIG. 5c), p-InP layer (0.3 μm thickness, p = 3 × 1017 cm−3) 110,
n-InP layer (0.6 μm thickness, n = 1 × 1018 cm−3)
Embedding selective growth of a current blocking layer made of 111 is performed (FIG. 1d). Finally, the SiO2 mask 109 is removed, and p-InP
Cladding layer (1.6 μm thick, p = 1 × 1018 cm−
3) 112, p-InGaAs cap layer (0.3 μm thick, p =
8 × 10 18 cm −3) 113 is grown by MOVPE. SiO2 interlayer film 114, p electrode 115, n electrode 11
6 is formed to obtain a semiconductor laser as shown in FIG.

[0019] First, described in the present embodiment the low threshold, the high-temperature and high-efficiency operation characteristics for reasons which can realize a method of manufacturing a semiconductor laser is excellent. In order to realize a high-performance semiconductor laser, it is necessary to have an active layer with a high gain. In addition to this, it is important to realize a current confinement structure with a small reactive current. As a current confinement structure capable of suppressing a reactive current (leakage current), a pnpn thyristor structure or a buried (BH: buried hetero) structure in which the active layer side is buried with a high resistance layer doped with Fe or the like
The structure is a typical example. In principle, the high resistance BH is said to have the highest current confinement function, but in reality, holes leak easily at high temperature and high bias, and the pnpn thyristor BH achieves better characteristics.

The pnpn thyristor structure also has a problem that the leakage current flowing into the p-InP block layer 110 becomes a gate current in the thyristor, and when the leakage current exceeds a certain level, it turns on. In order to suppress the turn-on operation, the leakage current (gate current) to the p-InP block layer 110 is reduced as much as possible, and even if the leakage current occurs, the p-InP block is increased to increase the turn-on level. The layer 110 may have a thick film and a high concentration. However, the p-InP blocking layer 110
P-InP block layer 1 to suppress leakage current to the
It is necessary to reduce the concentration of the thin film 10 in the thin film, which results in a structure that is contrary to the improvement of the turn-on level.

The present embodiment provides means for solving this problem. As a means for suppressing the leakage current to the p-InP block layer 110 while increasing the thickness and increasing the concentration of the p-InP block layer 110, the high-concentration p-InP layer is placed below the active layer (substrate side). This is a structure in which the high-concentration layer that is formed does not contact the p-InP clad layer 112 that is the hole supply source.

Specifically, narrow-width selective MO is used to form the active layer.
ZnO is used as a selective growth mask at this time by using the VPE method.
By using the film, a high-concentration p-type layer is automatically formed below the active layer (n-type substrate side) simultaneously with selective growth of the active layer. This makes it possible to simultaneously increase the thickness of the p-InP block layer 110 without increasing the contact distance (leakage path width) between the p-InP clad layer 112 and the p-InP block layer 110. This means that a structure that suppresses the leakage current to the p-InP block layer 110 and a structure that can improve the turn-on level of the pnpn thyristor can be realized at the same time.

The produced semiconductor laser was cleaved to both end faces and the cavity length was changed to evaluate the injection current-optical output characteristics. As a result, the internal differential quantum efficiency at room temperature of 25 ° C. was 99.9% or more, the internal loss was 8 cm −1, and the high temperature was 85.
Internal differential quantum efficiency and internal loss are 97% at ℃
And 10 cm −1, and it was confirmed that the leakage current was extremely well suppressed. Next, the resonator length was cut out to 300 μm, 30% reflective film was applied to the front end face and 90% high reflective film coating was applied to the rear end face, and after fusion bonding to an AlN heat sink, laser characteristics were measured.

The threshold currents at 25 ° C. and 85 ° C. are 3.2 mA and 10.5 mA, respectively, and the slope efficiencies at the same temperature are respectively.
Low threshold and high efficiency operation were confirmed even at a high temperature of 0.55 W / A and 0.45 W / A at 85 ° C. The maximum light output at 85 ° C. was 115 mW, and the turn-on operation of the block layer was not observed under the current injection conditions up to 1.5 A measured.

As described above, according to the embodiment of the present invention, the effect of suppressing the leakage current and the BH structure capable of suppressing the turn-on operation can be realized at the same time, so that a low threshold value and a high threshold value can be obtained in a wide temperature range. Efficient operation is possible.

Next, another embodiment of the present invention will be described.

3 to 10 show another embodiment. Figure 3
Is used as a mask for selective growth in the first embodiment.
SiO to cover the existing ZnO mask_TwoThe mask 104 is
This is a turned example. The advantage of this second embodiment is M
The film that affects the selective growth of OVPE is SiO_TwoBecomes the film 104
Therefore, the growth conditions that have been commonly used in the past can be used as they are.
It can be used. n-InP layer 106, M
After the selective growth of the QW active layer 107 and the p-InP layer 108
Through the same steps as in the first embodiment, the semiconductor shown in FIG.
A body laser structure is realized. It also covers the ZnO mask
The mask is SiO _TwoNot limited to SiNx, Si
Any dielectric such as ON that does not contain Zn may be used.

Next, an electroabsorption type (EA: Electro-absorpti)
on) An example applied to a modulator integrated DFB laser is shown. First, a low-concentration n-InP buffer layer (0.3 μm thick, n = 1 × 1017 cm−3) 20 for reducing the device capacity 20
2 is formed on the entire surface of the (100) n-InP substrate, and although not shown, a diffraction grating having a period of 240 nm is formed only in the laser region by a two-beam interference exposure method using a He-Cd laser and wet etching. Thereafter, as shown in FIG. 4, a pair of ZnO masks 203 are patterned in the laser region and a pair of SiO ₂ masks 204 are patterned in the modulator region in the [011] direction. The ZnO mask 203 has a mask width of 1
The SiO ₂ mask 204 was formed with a mask width of 5 μm and an opening width of 1.5 μm. The laser region length was 400 μm and the modulator region length was 175 μm. With a mask pattern like this,
An optical waveguide structure is selectively grown in the opening by the MOVPE method. Since the mask width differs between the laser region and the modulator region, the bandgap wavelength of the selectively grown optical waveguide structure can be changed.

As shown in FIG. 5, the actually formed optical waveguide structure in the laser region is n-InGaAs in the order of growth.
P guide layer (layer thickness 0.1 micron, carrier concentration 1 × 1
018 cm-3) 206, strained MQW active layer (0.65%
8.5nm thick In.693Ga.307 with compressive strain introduced
As.856 P.144 well layer / 8.5 nm thick In. 760 Ga.
240 As. 511P. 489 barrier, 8 periods, photoluminescence wavelength 1.545 μm) 207, p-InP clad layer (layer thickness 0.15 μm, carrier concentration 7 × 1)
017 cm−3) 208, and the optical waveguide structure in the modulator region has an n-InGaAsP guide layer (layer thickness 0.07 μm, carrier concentration 1 × 10 18 cm −) in the order of growth.
3) 206b, strained MQW active layer (6 nm thick In.664Ga.336As.856P.14 with 0.45% compressive strain introduced)
4 well layers / 6 nm thick In. 738 Ga. 262 As. 511P.
489 barrier, 8 periods, photoluminescence wavelength 1.4
75 μm) 207b, p-InP clad layer (layer thickness: 0.
11 microns, carrier concentration 7 x 1017 cm-3) 2
It is 08b.

With respect to this optical waveguide structure, as shown in FIG. 6, after removing a part of the ZnO mask 203 and the SiO 2 mask 204, a p-InP clad layer (1.6 μm thick, p =
1 × 10 18 cm −3) 212, p-InGaAs cap layer (0.3 μm thick, p = 6 × 10 18 cm −3) 2
13 selective growth is performed. Finally, the p-InGaAs cap in the area of 25 μm on the modulator side between the modulator section and the laser section was removed to achieve element isolation, and an electrode formation process was performed to obtain an EA modulator integrated DFB laser as shown in FIG. 7. .

A 90% highly reflective film is applied to the laser side end surface, and a 0.1% non-reflective film coating is applied to the modulator end surface.
When assembled on a heat sink and evaluated, the laser oscillation threshold is 3.5 mA, the slope efficiency is 0.31 W / A, and the optical output when the injection current is 60 mA is 17 mW (± 3 mW), 1
It was confirmed that the light output at the time of injection of 00 mA was 27 mW (± 5 mW), which was a low threshold value, high efficiency, and high output operation . The extinction ratio when a reverse bias of 2 V is applied to the EA modulator is 21 d.
B, the element band was 13.5 GHz. When 800 km transmission of a 1.3-micron zero-dispersion fiber was performed using this device by 2.5 Gb / s modulation, transmission was possible with a low power penalty of 0.8 dB. Also, when 60 km transmission was performed by 10 Gb / s modulation, transmission was possible with a power penalty of 0.9 dB.

The advantages of using the ZnO mask in this third embodiment are as follows. Since the EA modulator integrated DFB laser modulates the modulator at a high speed, it is necessary to reduce the element capacitance and increase the element band above the modulation rate. Therefore, a low-concentration pn junction has been conventionally used to reduce the pn junction capacitance. However, when the pn junction surface is formed at a low concentration, the built-in potential barrier becomes small, so that the current constriction function is significantly reduced in the laser region in which the laser is biased in the forward direction to operate at high output. I can't. Therefore, by adopting the ZnO film only in the laser region as the selective growth mask, the low concentration n-InP buffer layer 202 can be p-type inverted only in the laser region, and a high concentration pn junction can be realized. As a result, since the built-in potential barrier can be increased, the leakage current can be suppressed even in the high bias region.

In the third embodiment, the entire laser region is ZnO.
The film 203 was used to form a selective growth mask. In this case, as can be seen from the AA ′ cross-sectional view of FIG. 6, the ZnO mask 203 was used to selectively grow the p-InP cladding 212 and p-InGaAs cap 213 next time. Zn diffusion proceeds, which causes a variation. Therefore, as a fourth example, an EA modulator integrated DFB laser using a mask pattern as shown in FIG. 8 was manufactured.
First, a low-concentration n-InP buffer layer (0.3 μm thick, n = 1 × 1017 cm−3) for reducing the device capacity 2
02 is formed on the entire surface of the (100) n-InP substrate, and although not shown, a diffraction grating having a period of 240 nm is formed only in the laser region by a two-beam interference exposure method using a He-Cd laser and wet etching. After that, as shown in FIG. 8, a pair of ZnO mask 203 and SiO are formed in the laser region.
_A pair of SiO ₂ masks 204 are patterned in the [011] direction in the mask region consisting of the ₂ masks 204 and the modulator region.

ZnO mask 203 on the laser side and SiO ₂
The SiO ₂ mask 204 on the modulator side is formed by forming a mask width of 15 μm including the mask 204 and an opening width of 1.5 μm.
Was formed with a mask width of 5 μm and an opening width of 1.5 μm. The laser region length is 400 μm and the modulator region length is 175
μm. The width of the ZnO mask 203 on the laser side was the same as the width of the p-InP clad and the p-InGaAs cap layer shown in FIG. By using such a selective growth mask, the waveguide structures 206 and 20 having the same structure as that shown in the third embodiment.
7 and 208 were selectively grown (FIG. 9), and ZnO was added.
Mask 203 and SiO ₂ mask 20 in the modulator region
4 is removed to grow the p-InP clad layer 212 and the p-InGaAs cap layer 213 shown in FIG.

Finally, the p-InGaAs cap in the region of 25 μm on the modulator side between the modulator part and the laser part is removed to achieve element isolation, and an electrode formation process is performed to form an EA modulator integrated DFB as shown in FIG. It was a laser. 90% highly reflective film was applied to the laser side end face and 0.1% non-reflective film coating to the modulator end face, and it was assembled on an AlN heat sink and evaluated. Laser oscillation threshold value 3.5 mA, slope efficiency 0.31 W / A, light output at injection current 60mA is 17mW (± 0.8mW), light output at 100mA injection is 27mW (± 1.3mW), low threshold, high efficiency, and high output operation are highly uniform. It was confirmed that it was done. The extinction ratio when a reverse bias of 2 V was applied to the EA modulator was 21 dB, and the element band was 13.5 GHz. 800k of 1.3 micron zero dispersion fiber using this device
When m transmission was performed by 2.5 Gb / s modulation, transmission was possible with a low power penalty of 0.8 dB. Also, when 60 km transmission was performed by 10 Gb / s modulation, transmission was possible with a power penalty of 0.9 dB.

In the above embodiments, only selective growth by the MOVPE method was explained as a method for forming an optical waveguide, but the invention is not limited to this, and liquid phase growth method (LPE: li).
It goes without saying that other growth methods such as a quid phase epitaxy) and a molecular beam epitaxy (MBE) may be used.

The method of manufacturing an optical semiconductor device according to the present invention is configured as described above, and the active layer is formed by the direct selective MOVPE method using the dielectric film as the selective growth mask. Zn as part of the mask
O is used. Further, as described in the embodiments, the BH structure that has the effect of suppressing the leakage current and suppresses the turn-on operation can be realized at the same time, so that the low threshold value and the high efficiency operation can be performed in a wide temperature range.

[Brief description of drawings]

1A to 1E are cross-sectional views of an optical semiconductor device of the present invention.

FIG. 2 is a representative perspective view of FIG.

3A to 3E are cross-sectional views of a second embodiment in which a SiO ₂ mask is patterned so as to cover the ZnO mask as used in the first embodiment.

FIG. 4 is an explanatory diagram of a modulator region and a laser region on a substrate.

5 is an explanatory diagram of an AA cross section and a BB cross section of FIG. 4;

FIG. 6 is an explanatory diagram of selective growth of a clad layer and a cap layer.

FIG. 7 is an illustration of an EA modulator integrated DFB laser.

FIG. 8 is an explanatory diagram of an EA modulator integrated DFB laser using a mask pattern.

9 is an explanatory diagram of an AA cross section and a BB cross section of FIG. 8;

FIG. 10 shows a cladding layer 212 and a cap layer 21.
It is explanatory drawing of the post-growth DFB laser production of FIG.

[Explanation of symbols]

101 n-InP (100) substrate 103 ZnO film 104 SiO ₂ mask 106 n-InP layer 107 MQW active layer 108 p-InP layer 109 SiO ₂ mask 110 p-InP block layer 111 n-InP layer 112 p-InP clad layer 113 p-InGaAs cap layer 114 SiO ₂ interlayer film 115 p electrode 116 n electrode 202 n-InP buffer layer 	 203 ZnO mask 204 SiO ₂ mask 205 Zn diffusion region 206 n-InGaAsP guide layer 207 MQW active layer 208 p -InP clad layer 206b n-InGaAsP guide layer 207b MQW absorption layer 208b p-InP clad layer

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 H01L 33/00

Claims (3)

(57) [Claims] 1. A method of manufacturing an optical semiconductor device , comprising: depositing a ZnO film on an n-InP substrate; patterning the ZnO film;
A step of forming a mask and opening the ZnO stripe mask as a growth prevention mask.
It is composed of an n-InP layer, an active layer and a p-InP layer.
ZnO film with selective growth of an optical waveguide structure
Zn to the n-InP substrate by solid phase diffusion from the
Area with the ZnO stripe mask as a stop mask
Forming a p-type inversion region on the n-InP substrate
And forming a dielectric mask only on the mesa top of the p-InP layer.
Then, a p-InP layer and an n-I layer are formed on the p-type inversion region.
a step of sequentially forming an nP layer, and a method for manufacturing an optical semiconductor device. 2. An n-type semiconductor substrate having at least an electric field absorption
Integrating a converging optical modulator and a distributed feedback semiconductor laser
And a low concentration n-InP buffer layer over the entire surface of the n-type semiconductor substrate.
And a step of forming the semiconductor laser on the low concentration n-InP buffer layer.
In the formation region, a ZnO mask is formed and
A Zn-free dielectric mask is formed in the controller formation region.
And the mask formed in the above step as a growth prevention mask.
An optical waveguide structure is selectively grown at the mouth and
Zn from the O mask to the low concentration n-InP buffer layer
The ZnO mask which is a solid phase diffused and growth inhibition mask
In the low concentration n-InP buffer layer in a certain region
Of the ZnO mask formed in the semiconductor laser forming region.
Of Zn which is formed in the modulator and the modulator formation region
A part of the electric mask is removed, and p- is formed on the p-type inversion region.
A step of forming an InP clad layer, and a method of manufacturing an optical semiconductor device. 3. An n-type semiconductor substrate on which at least an electric field absorption layer is formed.
Integrating a converging optical modulator and a distributed feedback semiconductor laser
And a low concentration n-InP buffer layer over the entire surface of the n-type semiconductor substrate.
And a step of forming the semiconductor laser on the low concentration n-InP buffer layer.
In the formation region, the ZnO mask and the outside of this ZnO mask
In addition to forming a dielectric mask not containing Zn in
A Zn-free dielectric mask is formed in the modulator formation area.
And the mask formed in the previous step is used as a growth prevention mask.
An optical waveguide structure is selectively grown at the mouth and
Solid phase Zn from O mask to low concentration n-InP buffer layer
The ZnO mask, which is a diffusion-preventing mask, is used as a mask.
In the low concentration n-InP buffer layer in the region
A zone, a ZnO mask formed in the semiconductor laser forming region, and
A Zn-free dielectric matrix formed in the modulator formation region.
And removing p-InP on the p-type inversion region.
A method of manufacturing an optical semiconductor device, comprising: forming a clad layer .