JP3450210B2 - Semiconductor optical 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 a semiconductor optical device having a light spot size conversion function and a method of manufacturing the same, and more particularly to a semiconductor optical device that can operate at low power and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the spread of optical communication and the like, cost reduction of optical element modules is required. As an effective method for reducing the cost of the optical element module, there is a method of integrating a spot size converter for increasing the spot size of light on an optical element mounted on the module. This makes it possible to ensure the coupling efficiency with an optical fiber or the like having a larger spot size than the optical element without using a lens or the like. That is, it is possible to reduce the component cost and the assembly cost of the optical element module.

A technique for manufacturing the above-mentioned optical device is described, for example, in "Full-select MOVPE growth type 1.3 μm spot size converter integrated LD" (Electronic Society of Electronics, Information and Communication Engineers, Electronics Society Conference, C-4-26). Is disclosed in. The optical element manufactured by this technology is
A laser unit that oscillates a laser by current injection and a spot size conversion unit that converts the spot size of the laser oscillated from the laser unit are provided.

14 (a) and 14 (b) are schematic views showing a specific structure of the above optical element. Note that FIG.
14B is a cross-sectional view taken along the line aa ′ of FIG.
14B is a cross-sectional view taken along the line bb ′ of FIG. As shown in FIGS. 14 (a) and 14 (b), the optical element has an n-type I
nP (indium phosphide) substrate 30, n-type InP clad layer 31, InGaAsP (indium gallium arsenide phosphide) waveguide layer 32, and first p-type InP clad layer 33.
A p-type InP current blocking layer 34, an n-type InP current blocking layer 35, a second p-type InP clad layer 36,
a p-type InGaAs contact layer 37, an insulating layer 38,
And a metal electrode 39.

On the n-type InP substrate 30, an n-type InP clad layer 31, an InGaAsP waveguide layer 32, and a first p-type InP clad layer 33 are formed in this order. In addition, these three layers are, as shown in FIG.
It is divided into three parts, and the central part corresponds to the laser part and the spot size conversion part. The n-type InP cladding layer 31 has a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 100 nm.

The InGaAsP waveguide layer 32 is a layer through which light propagates, and the spot size conversion portion is formed so that its thickness gradually decreases from the laser portion side toward the end face. Thus, the spot size conversion unit converts the spot size by making the layer thickness of the InGaAsP waveguide layer 32 thinner than that of the laser unit. The first p-type InP clad layer 33 has a carrier concentration of about 7 ×.
It is 10 ¹⁷ cm ⁻³ and the layer thickness is about 200 nm.
Then, a laser is generated by applying a predetermined voltage between the first p-type InP clad layer 33 and the n-type InP clad layer 31.

The p-type InP current blocking layer 34 fills the gaps between the n-type InP clad layer 31, the waveguide layer 32, and the first p-type InP clad layer 33, which are divided into three parts, and the laser portion and the spot size. First excluding converter
It is formed on the p-type InP clad layer 33. p-type I
The layer thickness of the nP current blocking layer 34 is about 600 nm,
The carrier concentration is 6 × 10 ¹⁷ cm ⁻³ . n-type In
The P current blocking layer 35 is the p-type InP current blocking layer 3
4 are formed. In addition, the n-type current blocking layer 35
Has a layer thickness of about 600 nm and a carrier concentration of 3 × 10
^{It is 18} cm ^-3 . Thus, since the p-type current block layer 34 and the n-type current block layer 35 are formed in this order in the region excluding the laser section and the spot size conversion section, in this portion, the n-type current block layer is formed. A current does not flow from 35 to the p-type current blocking layer 34.

The second p-type InP clad layer 36 is formed on the n-type current blocking layer 35 and the first p-type InP clad layer 33 corresponding to the laser section and the spot size conversion section. The layer thickness of the second p-type InP clad layer 36 is about 3500 nm, and the carrier concentration is 1 × 10 ^18.
cm ⁻³ . p-type InGaAs contact layer 37
Are formed on the entire surface of the second p-type cladding layer 36. The layer thickness of the p-type InGaAs contact layer 37 is 300 nm, and the carrier concentration is 1 × 10 ¹⁹ cm.
^-3 .

The insulating layer 38 is made of SiO ₂ (silicon dioxide).
It is formed from p, excluding the area corresponding to the laser section.
It is formed on the InGaAs contact layer 37.
This insulating layer 38 makes the current injection region from the metal electrode 39 correspond to the laser portion. Metal electrode 39
Is formed of Au-Cr (gold-chromium) or the like,
It is formed on the insulating layer 38 and the p-type InGaAs contact layer 37 corresponding to the laser portion.

As described above, InGa forming the optical element
By changing the layer thickness of the AsP waveguide layer 32 between the laser section and the spot size conversion section, the laser spot size is converted, and the component cost and assembly cost of the optical element module are reduced. Further, a technique for manufacturing an optical element having the same configuration as the above is also disclosed in JP-A-10-98231 and JP-A-10-308556.

[0011]

In the above technique, the same layer as the laser section (second p-type InP clad layer 36) is formed immediately above the spot size conversion section of the semiconductor optical device. The carrier concentration of the second p-type InP cladding layer 36 must be increased to some extent in order to reduce the operating voltage of the laser section. Further, in the second p-type InP clad layer 36, the higher the carrier concentration, the easier the light absorption due to the inter-valence band absorption. Therefore, in the spot size conversion part where the spot size of the propagating light is large, there is a problem that the propagation loss becomes large when the carrier concentration of the p-type InP cladding layer 36 is high.

Therefore, an object of the present invention is to provide a semiconductor optical device in which a spot size converter capable of reducing an oscillation threshold current, an operating current and an operating voltage is integrated and a manufacturing method thereof.

[0013]

In order to achieve the above object, a semiconductor optical device according to a first aspect of the present invention comprises a light emitting means which emits light when a predetermined voltage is applied,
First spot size conversion means formed adjacent to the light emitting means along the light propagation direction and converting the spot size of the light generated by the light emitting means; and the first spot size conversion means by applying a voltage to the light emitting means. First light blocking means for preventing current from being injected into the spot size converting means, and the light emitting means and the first spot
The unit size conversion means includes a lower clad layer of the first conductivity type,
It is formed on the lower clad layer, propagates light, and
In the portion corresponding to the light means, the layer thickness is almost constant,
At the portion corresponding to the first spot size conversion means, the layer thickness is
A continuously changing waveguide layer and a shape on the waveguide layer.
A first upper clad layer of the second conductivity type formed
And wherein the first current blocking means is the first upper cladding
A second current type first current block formed in a predetermined region on the layer
And a first layer formed on the first current blocking layer.
And a second conductivity type current blocking layer,
It is characterized by According to the present invention, the region in which the current is injected by applying the voltage can be limited by the first current blocking means, and the current is injected only in the necessary portion. Therefore, the operating current of the semiconductor optical device can be reduced.

[0014]

[0015] In addition, in the first spot size conversion means,
Since the thickness of the waveguide layer is different from that of the light emitting means, the wavelength of the light to be absorbed is different, and the propagation loss of light can be reduced.
The first current blocking unit may be longer than the first spot size converting unit, and one end thereof may be formed to coincide with an end of the first spot size converting unit opposite to the light emitting unit. . The first current block means may be shorter than the first spot size conversion means, and one end thereof may be formed to coincide with an end of the first spot size conversion means opposite to the light emitting means. .

In order to reduce device resistance, a second conductivity type second upper clad layer formed on the first upper clad layer and the second current blocking layer, and a second upper clad layer formed on the second upper clad layer. The first current blocking layer of the first current blocking means may have a carrier concentration lower than that of the second upper cladding layer. With this configuration, the spot size conversion means can reduce the carrier concentration of the first current blocking layer to suppress light absorption, and the light emitting portion can increase the carrier concentration of the second upper cladding layer to reduce the device resistance. it can.

An insulating layer formed between the second upper cladding layer and the electrode to limit a region to which a voltage is applied may be further provided. The insulating layer may be formed on the first current blocking unit so as to correspond to a formation region of the first current blocking unit. The insulating layer may be formed on the first current blocking unit so as to be longer or shorter than the formation region of the first current blocking unit.

A second spot size converting means which is formed on the opposite side of the light emitting means from the first spot size converting means and which is substantially the same as the first spot size converting means, and a voltage to the light emitting means. Blocking an electric current from being injected into the second spot size converting means by application,
Second light blocking means substantially the same as the first current blocking means, wherein the light emitting means amplifies the light emitted from one of the first and second spot size converting means and outputs the amplified light to the other. It may be incident.

A semiconductor optical device according to a second aspect of the present invention includes a light emitting region that emits light when a predetermined voltage is applied, and a spot size conversion region that converts the spot size of light generated in the light emitting region. And a first conductivity type semiconductor substrate, a first conductivity type lower clad layer formed on the semiconductor substrate, and a lower clad layer formed on the lower clad layer for propagating light. Formed on the waveguide layer, and a waveguide layer having a substantially constant layer thickness in the light emitting region and a layer thickness continuously changing in the spot size conversion region along the light propagation direction. A second conductive type first upper clad layer, a second conductive type second upper clad layer formed in a light emitting region on the first upper clad layer, and a second upper clad layer formed on the second upper clad layer. An electrode and a strip on the first upper cladding layer A low-concentration layer of the second conductivity type having a carrier concentration lower than that of the second upper clad layer, and formed on the low-concentration layer to form a reverse junction together with the low-concentration layer, A first blocking current injection into the spot size conversion region of the first upper cladding layer;
And a conductivity type current blocking layer.

The waveguide layer may be formed such that a region having a substantially constant layer thickness exists between regions where the layer thickness continuously changes. The waveguide layer, in the spot size conversion region, away from the light emitting region,
The layer thickness may be gradually reduced.

A method for manufacturing a semiconductor optical device according to a third aspect of the present invention is a light emitting means for emitting light when a predetermined voltage is applied, and a spot for converting the spot size of the light generated by the light emitting means. A method for manufacturing a semiconductor optical device comprising size conversion means and current blocking means for preventing current from being injected into the spot size conversion means by applying a voltage to the light emitting means, the method comprising: The lower cladding layer of the first conductivity type is allowed to propagate in a predetermined region, light is propagated, the layer thickness is substantially constant in a portion corresponding to the light emitting means, and the layer thickness is continuous in a portion corresponding to the spot size converting means. A light emitting / converting means for selectively forming a changing waveguide layer and a second conductive type first upper cladding layer to form the light emitting means and the spot size converting means. A forming step, and a current block forming step of selectively forming a second conductive type first current blocking layer and a first conductive type second current blocking layer in a predetermined region on the first upper cladding layer. A second upper cladding forming step of forming a second conductivity type second upper cladding layer having a carrier concentration higher than that of the first current blocking layer on the first upper cladding layer, and the second upper cladding layer. And an electrode forming step of forming an electrode thereon.

In the step of forming the light emitting / converting means, the MO
The method comprises the step of forming the light emitting means and the spot size conversion means by a VPE (metal organic chemical vapor deposition) method, and the current block forming step comprises the step of forming the first current block by a MOVPE (metal organic chemical vapor deposition) method. A step of forming a layer and the second current blocking layer.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a semiconductor optical device according to a first embodiment of the present invention will be described with reference to the drawings.
The semiconductor optical device according to the first embodiment is used for optical communication or the like, and is connected to, for example, an optical fiber or the like as schematically shown in FIG. As shown by hatching in FIG. 1, this semiconductor optical device includes a laser section that oscillates a laser when a predetermined voltage is applied, and a spot that converts the spot size of the laser oscillated from the laser section. And a size conversion unit.

FIGS. 2A, 2B and 2C are schematic views showing a concrete structure of the semiconductor optical device. Figure 2
(A) shows a cross section on the laser section side cut along a plane perpendicular to the laser emission direction. FIG. 2B shows B- of FIG.
2B is a cross-sectional view taken along the line B ', and FIG. 2C is C- in FIG.
It is a C'sectional view. Note that FIG. 2A is a cross-sectional view taken along the line AA ′ of FIG. As shown in FIGS. 2A, 2B, and 2C, the semiconductor optical device includes an n-type substrate 10, an n-type cladding layer 11, a waveguide layer 12, a first p-type cladding layer 13, and The p-type current blocking layer 14, the n-type current blocking layer 15, the second p-type cladding layer 16, the p-type contact layer 17, the insulating layer 18, the metal electrode 19, and the reflective film 20.
It consists of and.

The n-type substrate 10 is a substrate made of n-type InP (indium phosphide). n-type clad layer 11
Is an n-type In having a carrier concentration of about 1 × 10 ¹⁸ cm ^−3.
It is formed of P and is formed on the substrate 10.
The layer thickness of the n-type cladding layer 11 is about 100 nm. In addition, the n-type cladding layer 11 is, as shown in FIG.
It is formed in three parts, that is, a central region corresponding to the laser unit and the spot size conversion unit, and two regions separated from the central region by a predetermined distance. The central area is
The width is 1.5 μm, and the length of 500 μm is 30
0 μm corresponds to the laser section, and the remaining 200 μm corresponds to the spot size conversion section. The distance between the central region and the other two regions is 50 μm in the laser section.
m, and in the spot size conversion unit from 50 μm to 5 μm
It is gradually narrowing to m.

The waveguide layer 12 is a layer through which light propagates,
It is formed on the n-type clad layer 11 divided into three regions. The waveguide layers 12 are each made of InGaAsP.
A multiple quantum well active layer (quantum well number 6) and a guide layer (layer thickness 6) formed of (indium gallium arsenide phosphide).
0 nm, wavelength composition 1130 nm). The multiple quantum well active layer is a guide layer (layer thickness 60 nm,
Wavelength composition 1130 nm), well layer (layer thickness 6 nm, wavelength composition 1270 nm, strain amount 0.7%), barrier layer (layer thickness 1
0 nm, wavelength composition 1130 nm). The wavelength composition indicates the wavelength of light most easily absorbed by each layer, that is, the size of the band gap.
The above-mentioned values are values in the laser section, and
In the spot size conversion portion, the thickness of 2 is formed so as to gradually decrease from the laser portion side toward the end face. Specifically, on the end face of the spot size conversion portion, the thickness of the waveguide layer 12 is formed to be about ⅓ of the laser portion.

The first p-type clad layer 13 is p-type InP.
And is formed on the waveguide layer 12.
The layer thickness of the first p-type cladding layer 13 is about 200 nm.
Yes, carrier concentration is about 7 × 10¹⁷cm^-3Is.
In the laser section, the n-type cladding layer 11 and the first p-type cladding layer
By applying a predetermined voltage between the laser and
The is generated. The p-type current block layer 14 is p-type In.
It is formed of P and has the n-type substrate 10 and the laser portion removed.
It is formed on the first p-type cladding layer 13. Also,
The layer thickness of the p-type current blocking layer 14 is about 600 nm,
Carrier concentration is 6 × 10¹⁷cm ^-3Is.

The n-type current blocking layer 15 is n-type InP.
And is formed on the p-type current block layer 14.
Has been. The layer thickness of the n-type current blocking layer 15 is about 6
00 nm, carrier concentration is 3 × 10¹⁸cm^-3
Is. In this way, p is displayed on the spot size conversion unit.
Type current blocking layer 14 and n type current blocking layer 15
Since they are formed in the order of
The flow does not flow. The second p-type cladding layer 16 is p-type InP.
And is formed of an n-type current blocking layer 15 and a laser.
It is formed on the first p-type clad layer 13 in the z-section. Well
The layer thickness of the second p-type cladding layer 16 is about 3500 nm.
Yes, carrier concentration is 1 × 10 ¹⁸cm^-3Is.

The p-type contact layer 17 is made of p-type InGaA.
s, and is formed on the entire surface of the second p-type cladding layer 16. The layer thickness of the p-type contact layer 17 is 300 nm, and the carrier concentration is 1 × 10 ¹⁹ c.
m ^-3 . As described above, since the carrier concentration increases in the order of the second p-type cladding layer 16 and the p-type contact layer 17 on the laser portion, the device resistance decreases and the current is easily injected into the laser portion. The insulating layer 18 is made of SiO ₂ (silicon dioxide), and is formed on the p-type contact layer 17 except for the region corresponding to the laser portion.
That is, the insulating layer 18 makes the current injection region from the metal electrode 19 correspond to the laser portion.

The metal electrode 19 is formed of Au-Cr (gold-chromium) or the like, and is formed on the insulating layer 18 and the p-type contact layer 17 corresponding to the laser portion. The reflection film 20 is a film having a reflectance of 95% and is formed on the side surface of each layer on the laser section side. The light generated by the laser unit is reflected by the reflection film 20 and amplified. When a voltage is applied to the semiconductor optical device having the above configuration, no current is injected into the spot size conversion portion due to the reverse junction of the p-type current block layer 14 and the n-type current block layer 15. That is, even if a current is efficiently injected into the laser section and a voltage lower than the conventional one is applied, the laser section can maintain the same operating voltage as the conventional one.

Next, a method of manufacturing the semiconductor optical device having the above structure will be described. First, as shown in FIG. 3, the above n divided into three parts by a CVD (Chemical Vapor Deposition) method, photolithography or the like.
The first growth blocking mask 1 corresponding to the distance between the mold cladding layers 11 is formed on the n-type substrate 10. The first growth blocking mask 1 is made of, for example, SiO ₂ .

Next, as shown in FIG. 4, the n-type clad layer 11, the waveguide layer 12, and the first p-type clad layer 13 are formed in this order by the MOVPE (metal organic chemical vapor deposition) method on the n-type substrate. Form on 10. Since each layer is selectively grown by the MOVPE method as described above, the thickness of the layer formed becomes smaller as the width of the first growth prevention mask 1 becomes narrower in the spot size conversion portion. Then, at the end portion of the spot size conversion portion, as described above, the layer thickness is formed to be reduced to about 1/3 of the laser portion. Therefore, the wavelength composition in the spot size conversion section becomes a shorter wavelength composition than the laser section due to the quantum size effect.
That is, the wavelength of the light absorbed by the spot size converter is
The wavelength is longer than the wavelength of light absorbed by the laser unit, and propagation loss hardly occurs in the spot size conversion unit.

Then, the first growth prevention mask 1 is removed,
As shown in FIG. 5, the second growth blocking mask 2 is formed only on the portion corresponding to the laser portion on the first p-type cladding layer 13 by the CVD method, the photolithography, or the like. In addition,
The second growth blocking mask 2 is made of, for example, SiO ₂ . Then, as shown in FIG. 6, the p-type current blocking layer 14 and the n-type current blocking layer 1 are formed in the region where the second growth blocking mask 2 is not formed by the MOVPE method.
5 is selectively grown in this order.

Next, the second growth prevention mask 2 is removed, and M
As shown in FIG. 7, the second p-type clad layer 16 is formed on the n-type current blocking layer 15 and the first p-type clad layer 13 corresponding to the laser section by the OVPE method or the like. Then, as shown in FIG. 7, by the MOVPE method or the like, the second
The p-type contact layer 17 is formed on the p-type cladding layer 16. After that, as shown in FIG. 8, an insulating layer 18 of SiO ₂ is formed on the p-type contact layer 17 excluding the upper portion of the laser portion by a CVD method, photolithography, or the like.

Then, the insulating layer 18 is formed by the CVD method or the like.
Then, the metal electrode 19 is formed on the p-type contact layer 17 corresponding to the laser section, and the reflection film 20 is formed on the side surface of each layer on the laser section side, thereby completing the semiconductor optical device shown in FIG. As described above, since the waveguide layer 12 is formed with different layer thicknesses in the laser section and the spot size conversion section, the laser generated in the laser section is less likely to be absorbed during propagation in the spot size conversion section, and the propagation is reduced. The loss can be reduced.

In the spot size converter, the light spot size increases as the waveguide layer 12 becomes thinner, and the light field (electric field, magnetic field) broadens.
However, as described above, not on the second p-type cladding layer 16 having a high carrier concentration but on the p-type current blocking layer 14 having a low carrier concentration and the n-type current block in which valence band absorption does not occur immediately above the spot size conversion portion. Since the layer 15 is formed, absorption between valence bands hardly occurs and the propagation loss can be further reduced. Therefore, it is possible to connect to an optical fiber or the like with high coupling efficiency without providing a lens or the like.

Further, since the laser section and the spot size conversion section have different wavelength compositions, a sufficient gain cannot be obtained even if a voltage is applied to the spot size conversion section, and light cannot be amplified. Therefore, as described above, the spot size conversion section is configured so that no current is injected by the p-type current block layer 14 and the n-type current block layer 15, and the current is injected only into the laser section. There is. As a result, the leakage current in the spot size converter can be reduced, and even if a lower voltage than before is applied,
The laser section can maintain the same operating voltage as the conventional one. That is, the propagation loss of light can be reduced, and the threshold current and operating current of laser oscillation can be reduced. Specifically, the threshold current at 75 ° C. is changed from 22 mA to 18 mA.
Could be reduced.

Next, a semiconductor optical device according to the second embodiment will be described with reference to the drawings. When forming the waveguide layer 12 of the semiconductor optical device as shown in the first embodiment, depending on the shape of the growth blocking mask, the crystal growth conditions, etc., it may be several tens of μm from the laser portion side of the spot size conversion portion.
The wavelength composition of the waveguide layer 12 may not change much between the portion (for example, about 50 μm) and the laser portion.
In such a case, the light from the laser portion is well absorbed in the portion of several tens of μm from the laser portion side of the spot size conversion portion, so that the light can be amplified by current injection.
That is, several tens of μm from the laser section side of the spot size conversion section
By applying a voltage also to the portion, the threshold current of laser oscillation and the operating current can be reduced.

For the above reasons, in the semiconductor optical device according to the second embodiment, the p-type current block layer 14, the n-type current block layer 15, and the insulating layer 18 on the spot size conversion portion are formed as shown in FIG. As shown in (a), it is formed only in a portion approximately 50 μm in front of the laser portion from the end face of the spot size conversion portion. That is, the second p-type clad layer 16 is formed immediately above a portion of the spot size conversion portion that is approximately 50 μm from the laser portion side, and current is also injected into this portion. The configuration of the semiconductor optical device other than the above is almost the same as that of the semiconductor optical device shown in the first embodiment.

The method of manufacturing the semiconductor optical device having the above structure is almost the same as that of the first embodiment. However, as shown in FIG. 9B, the second growth prevention mask 2 is also formed on the laser portion and on the spot size conversion portion at a portion of about 50 μm from the laser portion side. In addition, the insulating layer 18 is formed on the laser portion and on the spot size conversion portion except for the portion of about 50 μm from the laser portion side. As described above, from the laser unit side of the spot size conversion unit, about 50
A voltage can be applied to the μm portion, and when the wavelength composition of the waveguide layer 12 formed in this portion is almost the same as that of the laser portion, the threshold current of laser oscillation and the operating current are changed. It can be further reduced.

Next, a semiconductor optical device according to the third embodiment of the present invention will be described with reference to the drawings. The waveguide layer 12 of the semiconductor optical device as shown in the first embodiment
When forming the film, depending on the shape of the growth prevention mask, the crystal growth conditions, etc., it is possible to reduce the conduction between the portion of several tens of μm (for example, about 20 μm) from the spot size conversion portion side of the laser portion and the other portion of the laser portion. The wavelength composition of the waveguide layer 12 may change significantly. In such a case, it is difficult to absorb the light in the portion of several tens of μm from the spot size conversion portion side of the laser portion, and the light cannot be amplified by the current injection. Therefore, if no current is injected into this portion, the leakage current is smaller, and the threshold current of laser oscillation and the operating current can be reduced.

For the above reasons, in the semiconductor optical device according to the third embodiment, as shown in FIG. 10A, the p-type current is also applied to a portion of about 20 μm from the spot size conversion portion side of the laser portion. Block layer 14, n-type current block layer 1
5 and the insulating layer 18 are formed. That is, no current is injected into the portion about 20 μm from the spot size conversion portion side of the laser portion. The configuration of the semiconductor optical device other than the above is almost the same as that of the semiconductor optical device shown in the first embodiment.

The method of manufacturing the semiconductor optical device having the above-described structure is almost the same as that of the first embodiment. However, as shown in FIG. 10B, the second growth prevention mask 2 is formed on the laser portion except the portion of about 20 μm from the spot size conversion portion side. Further, the insulating layer 18 is also formed on the laser portion at a portion of about 20 μm from the spot size conversion portion side. As described above, it is possible to prevent the voltage from being applied to the portion of the laser portion that is approximately 20 μm from the spot size conversion portion side, and the wavelength composition of the waveguide layer 12 formed in this portion is set to the laser portion. Is significantly different from
The threshold current of laser oscillation and the operating current can be further reduced.

Next, a semiconductor optical device according to a fourth embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 11A, the semiconductor optical device according to the fourth embodiment has a structure in which the two semiconductor optical devices shown in the first embodiment are face-to-face coupled by a laser section. Has become. Further, the semiconductor optical device according to the fourth embodiment is used, for example, as shown in FIG. 11B, by connecting an optical fiber or the like to each of the two spot size conversion units. Then, the semiconductor optical element functions as a semiconductor optical amplifier that amplifies the light emitted from one of the optical fibers by the laser unit and makes it enter the other optical fiber.

Next, a method of manufacturing the semiconductor optical device having the above structure will be described. First, the first growth prevention mask 1 having the shape shown in FIG. 12 is formed so that the spot size conversion portions are formed on both sides of the laser portion. The shape of the first growth prevention mask 1 has a length of 300 μm and a width of 50 μm in a portion corresponding to a laser portion, and a length of 200 μm and a width in a portion corresponding to two spot size conversion portions. Is gradually narrowed from 50 μm to 5 μm. Next, in the portion where the first growth blocking mask 1 is not formed, as in the first embodiment, MO
The n-type cladding layer 11, the waveguide layer 12,
Then, the first p-type cladding layer 13 is formed in this order. As a result, the layer thickness is almost constant in the laser section,
The two spot size conversion portions are formed such that the layer thickness gradually decreases from the laser portion side toward the end face.

Then, the first growth prevention mask 1 is removed,
A second growth blocking mask 2 is formed on the first p-type cladding layer 13 of the laser section. Then, the p-type current block layer 14 and the n-type current block layer 15 are formed in this order in the region where the second growth blocking mask 2 is not formed by the MOVPE method similar to that of the first embodiment. Next, the second growth blocking mask 2 is removed, and the second p-type cladding layers 16 and p are formed on the n-type current blocking layer 15 and the first p-type cladding layer 13 of the laser section in the same manner as in the first embodiment. The mold contact layer 17 is formed in this order. After that, the insulating layer 18 is formed on the p-type contact layer 17 excluding the laser portion, and the insulating film 18 and the p-type contact layer 17 corresponding to the laser portion are formed.
A metal electrode 19 is formed on the upper portion of the semiconductor optical device to complete the semiconductor optical device shown in FIG.

As described above, it is possible to form the spot size conversion portions on both sides of the laser portion, the layer thickness of which gradually decreases from the laser portion side toward the end face. As a result, the spot size of the light emitted from one optical fiber is reduced by the spot size conversion unit, and the spot size of the light that is amplified by the laser unit (optical amplification unit) and is incident on the other optical fiber is the other spot size. It is enlarged in the size conversion unit. That is, the coupling loss with the optical fiber or the like can be reduced without providing a lens or the like. In addition, the waveguide layer 1
Since the layer thickness of 2 is different between the spot size conversion part and the laser part, the wavelength composition becomes a shorter wavelength composition than the laser part, and the propagation loss in the spot size conversion part can be reduced.

Further, on the two spot size converters, the p-type current block layer 14 and the n-type current block layer 1 are provided.
5 and the insulating layer 18 are formed so that no current is injected. Therefore, current is injected only into the laser section (optical amplification section), current leakage is reduced, and the threshold current and operating current for amplifying light can be reduced. In the manufacture of the semiconductor optical device as described above, the MOV
The shape of the first growth blocking mask 1 or the second growth blocking mask 2 may be changed according to the crystal growth conditions of the PE method and desired characteristics (threshold current, operating current, laser emission angle, etc.),
You may combine the structure of the semiconductor optical device shown in 1st, 2nd, and 3rd embodiment.

Further, in the semiconductor optical device shown in the above-mentioned embodiment, the injected current diffuses inside, so that it is insulated from the region where the p-type current block layer 13 and the n-type current block layer 14 are formed. It is not necessary to match the area where layer 18 is not formed. That is, as shown in FIG. 13A, the formation region of the p-type current block layer 13 and the n-type current block layer 14 may be narrower than the region where the insulating layer 18 is not formed. On the contrary, the p-type current block layer 13 and the n-type current block layer 1 are provided in the spot size conversion unit.
Since no current is injected by means of 4 in FIG.
As shown in (b), the insulating layer 18 may not be formed.

The semiconductor optical device having the spot size conversion parts on both sides of the laser part shown in the fourth embodiment is the second one.
Alternatively, the semiconductor optical devices shown in the third embodiment may be configured such that the laser portions are faced to each other and coupled. Further, the laser section of the semiconductor optical device may only emit light of a certain specific wavelength without oscillating the laser.

[0051]

As is apparent from the above description, according to the present invention, it is possible to reduce the propagation loss of light in a semiconductor optical device in which a spot size converter is integrated without increasing the operating voltage. As a result, the oscillation threshold current, operating current, and operating voltage of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of use of a semiconductor optical device according to a first embodiment.

FIG. 2A is a schematic diagram showing a configuration of a laser section side obtained by cutting the semiconductor optical device according to the first embodiment along a plane perpendicular to a light propagation direction. (B) is BB 'of (a)
FIG. (C) is a CC 'sectional view of (a).

FIG. 3 is a schematic view showing one manufacturing process of the semiconductor optical device according to the first embodiment.

FIG. 4 is a schematic view showing one manufacturing process of the semiconductor optical device according to the first embodiment.

FIG. 5 is a schematic view showing one manufacturing process of the semiconductor optical device according to the first embodiment.

FIG. 6 is a schematic view showing one manufacturing process of the semiconductor optical device according to the first embodiment.

FIG. 7 is a schematic view showing one manufacturing process of the semiconductor optical device according to the first embodiment.

FIG. 8 is a schematic view showing one manufacturing process of the semiconductor optical device according to the first embodiment.

FIG. 9A is a sectional view showing a configuration of a semiconductor optical device according to a second embodiment. (B) is a schematic diagram which shows one manufacturing process of the semiconductor optical device shown in (a).

FIG. 10A is a sectional view showing a configuration of a semiconductor optical device according to a third embodiment. (B) is a schematic diagram which shows one manufacturing process of the semiconductor optical device shown in (a).

FIG. 11A is a sectional view showing a configuration of a semiconductor optical device according to a fourth exemplary embodiment. (B) is a schematic diagram which shows the usage example of the semiconductor optical element shown in (a).

FIG. 12 is a schematic view showing one manufacturing process of the semiconductor optical device shown in FIG.

FIG. 13 is a schematic diagram showing another configuration of the semiconductor optical device according to the embodiment.

FIG. 14A is a schematic diagram showing a configuration of a laser section side obtained by cutting a conventional optical element along a plane perpendicular to a light propagation direction. (B) is a bb 'sectional view of (a).

[Explanation of symbols]

1 First growth prevention mask 2 Second growth prevention mask 10 n-type substrate 11 n-type clad layer 12 Waveguide layer 13 First p-type cladding layer 14 p-type current blocking layer 15 n-type current blocking layer 16 Second p-type cladding layer 17 p-type contact layer 18 Insulation layer 19 metal electrodes 20 reflective film

Claims (13)

(57) [Claims] 1. A light emitting means which emits light when a predetermined voltage is applied, and a spot size of light generated by the light emitting means which is formed adjacent to the light emitting means along the light propagation direction. to a first spot size converting means is composed of a first current blocking means for blocking a current is injected into the first spot size converting means by applying a voltage to said light emitting means, said light emitting means and said The first spot size conversion means is
A lower clad layer of the first conductivity type and a layer formed on the lower clad layer.
Is formed, propagates light, and corresponds to the light emitting means.
Has a substantially constant layer thickness, and the first spot size conversion
In the part corresponding to the means, the layer thickness changes continuously.
A waveguide layer and a second conductivity type first layer formed on the waveguide layer.
A first upper clad layer, and the first current blocking means is formed on the first upper clad layer.
Conductivity type first current block formed in a predetermined region of the
Layer and a first conductive layer formed on the first current blocking layer
A semiconductor optical device characterized a second current blocking layer of the mold is formed from, that. 2. The first current block means is longer than the first spot size conversion means, and one end of the first current block means is the first spot size conversion means.
2. The semiconductor optical device according to claim 1, wherein the spot size conversion means is formed so as to coincide with an end of the spot size conversion means opposite to the light emitting means. 3. The first current blocking means is shorter than the first spot size converting means, and one end of the first current blocking means has the first spot size converting means.
2. The semiconductor optical device according to claim 1, wherein the spot size conversion means is formed so as to coincide with an end of the spot size conversion means opposite to the light emitting means. 4. A second conductivity type second upper clad layer formed on the first upper clad layer and the second current blocking layer to reduce device resistance, and on the second upper clad layer. 2. The first current blocking layer of the first current blocking means has a carrier concentration lower than the carrier concentration of the second upper cladding layer. 4. The semiconductor optical device according to any one of items 1 to 3 . 5. A formed between the electrode and the second upper cladding layer, further comprising an insulating layer for limiting the areas to which a voltage is applied, any one of claims 1 to 4, characterized in that 1 The semiconductor optical device according to item. 6. The semiconductor according to claim 5 , wherein the insulating layer is formed on the first current blocking means so as to correspond to a formation region of the first current blocking means. Optical element. 7. The insulating layer is formed on the first current blocking means so as to be longer or shorter than a formation region of the first current blocking means. 5. The semiconductor optical device according to item 5 . 8. A second spot size converting means, which is formed on the opposite side of the light emitting means from the first spot size converting means and is substantially the same as the first spot size converting means, and to the light emitting means. Further comprising second current blocking means substantially the same as the first current blocking means for preventing current from being injected into the second spot size conversion means by applying the voltage of 1. the one to amplify the light emitted from the first and second spot size converting means, a semiconductor optical device according to any one of claims 1 to 7 to be incident on the other, characterized in that. 9. A semiconductor optical device comprising: a light emitting region that emits light when a predetermined voltage is applied; and a spot size conversion region that converts a spot size of light generated in the light emitting region. A conductive type semiconductor substrate, a first conductive type lower clad layer formed on the semiconductor substrate, and a light emitting region formed on the lower clad layer for propagating light and propagating light. In the spot size conversion region, the layer thickness is substantially constant, and the layer thickness continuously changes, and a second conductivity type first upper clad layer formed on the waveguide layer. A second conductive type second upper clad layer formed in a light emitting region on the first upper clad layer; an electrode formed on the second upper clad layer; and a spot on the first upper clad layer. Formed in the size conversion area, 2. A second conductivity type low-concentration layer having a carrier concentration lower than that of the upper clad layer; and a spot size of the first upper clad layer, which is formed on the low-concentration layer and forms a reverse junction with the low-concentration layer. A semiconductor optical device comprising: a current blocking layer of a first conductivity type that blocks current injection into a conversion region. 10. The waveguide layer is formed such that a region having a substantially constant layer thickness exists between regions where the layer thickness continuously changes. Item 10. The semiconductor optical device according to item 9 . Wherein said waveguide layer is in the spot size conversion area, the distance from the light-emitting region, claim 9 or 10 the layer thickness is gradually thinned, it is characterized by
The semiconductor optical device according to 1. 12. A light emitting means for emitting light when a predetermined voltage is applied, a spot size converting means for converting a spot size of light generated by the light emitting means, and a spot for applying a voltage to the light emitting means. A method for manufacturing a semiconductor optical device, comprising: a current blocking means for preventing a current from being injected into a size conversion means, wherein a first conductivity type lower cladding layer and a light are applied to a predetermined region on a substrate. A waveguide layer having a substantially constant layer thickness in a portion corresponding to the light emitting means and a layer thickness continuously changing in a portion corresponding to the spot size converting means; A light emitting / converting means forming step of forming the light emitting means and the spot size converting means selectively in a predetermined region on the first upper cladding layer; The second conductivity type first
A current block forming step of selectively forming a current blocking layer and a second current blocking layer of the first conductivity type; and a carrier concentration higher than that of the first current blocking layer on the first upper cladding layer. A second step of forming a second upper clad layer of the second conductivity type having a second upper clad forming step, and an electrode forming step of forming an electrode on the second upper clad layer are provided. Production method. 13. The step of forming the light emitting / converting means comprises the step of:
The method comprises the step of forming the light emitting means and the spot size converting means by an OVPE (metal organic chemical vapor deposition) method, and the current block forming step comprises the step of forming the first current block by a MOVPE (metal organic chemical vapor deposition) method. A method of manufacturing a semiconductor optical device according to claim 12 , further comprising the step of forming a layer and the second current blocking layer.