JP4005519B2 - Semiconductor optical device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor optical device and a manufacturing method thereof, and more particularly, to a semiconductor optical device including a tunable twin guide distributed feedback semiconductor laser (TTG-DFB laser) structure and a manufacturing method thereof.
[0002]
[Prior art]
Currently, a wavelength division multiplexing (WDM) system that improves transmission capacity by multiplexing optical signals on a wavelength axis is employed in a backbone transmission system of a large-capacity optical communication network. In order to increase the number of multiplexing in the WDM system, it is necessary to increase the number of semiconductor lasers serving as light sources. At the same time, the same number of backup light sources are required, and the number of varieties to be prepared for backup increases. For this reason, inventory management becomes complicated.
[0003]
From such a background, it is desired to simplify inventory management by using a wavelength tunable light source capable of changing the oscillation wavelength. As a wavelength variable light source used in the WDM system, the wavelength can be continuously changed, and a wide variable width is required.
[0004]
Various wavelength tunable lasers have been proposed as wavelength selective light sources. For example, a distributed feedback (DFB) laser or a distributed Bragg reflection (DBR) laser is used to change the oscillation wavelength by controlling the temperature, and a method to change the oscillation wavelength by controlling the current flowing in the tuning region of the DBR laser. Proposed.
[0005]
A DBR type GCSR-DBR laser having a filter function and an SG / SSG-DBR laser using partial diffraction grating pattern modulation have been proposed. However, these laser light sources cannot obtain a large light output when the wavelength is changed. Further, the range in which the wavelength can be continuously changed is as narrow as several nm, and the wavelength control is complicated. Further, the wavelength may change discontinuously due to mode hopping.
[0006]
The TTG-DFB laser has a feature that the range in which the wavelength can be continuously changed is as wide as about 8 nm, and the wavelength tuning method is simple. The TTG-DFB laser is described in Patent Document 1 and Patent Document 2, for example.
[0007]
[Patent Document 1]
JP 7-131121 A
[Patent Document 2]
JP-A-7-326820
[0008]
[Problems to be solved by the invention]
As described above, the TTG-DFB laser has a feature that it is continuous and has a relatively wide wavelength tunable range, and a control method for wavelength tunability is easy. However, similarly to other semiconductor lasers, when a current is injected into the wavelength tuning layer in order to change the wavelength to the short wave side, the TTG-DFB laser increases the internal loss of the laser and decreases the optical output.
[0009]
It is also possible to inject more current into the active layer to compensate for the reduced light output. However, the increase in the injection current causes an increase in the element temperature, and shifts the oscillation wavelength to the long wave side. As a result, the wavelength variable width is narrowed. In addition, it is necessary to control again the oscillation wavelength shift due to the temperature rise with the current flowing through the wavelength tuning layer, which complicates the wavelength tuning method.
[0010]
Patent Document 2 discloses an optical semiconductor device in which a TTG-DFB laser, an optical phase adjuster, a light intensity adjuster, and a reflecting mirror are integrated. In the method disclosed in Patent Document 2, the absorption loss inside the TTG-DFB laser is compensated by adjusting the return light from the optical phase adjuster and the light intensity adjuster. However, the method described in Patent Document 2 cannot be said to be easy to control. In addition, since optical elements having gain are not integrated, a significant increase in optical output cannot be expected.
[0011]
An object of the present invention is to provide a semiconductor laser having a wide wavelength variable range and capable of obtaining a high optical output even when the wavelength is variable, and a method for manufacturing the same.
[0012]
[Means for Solving the Problems]
According to one aspect of the present invention, a laser oscillator having a striped mesa structure disposed on a first region of a first conductivity type semiconductor substrate, and a stripe oscillator disposed on a second region of the semiconductor substrate. And an optical amplifier that amplifies the laser light incident by the laser light emitted from the laser oscillator, and an embedded layer that embeds both sides of the mesa structure of the laser oscillator and the optical amplifier, The laser oscillator includes a first active layer that generates stimulated emission light by current injection, a tuning layer that changes a refractive index by current injection, and is disposed between the first active layer and the tuning layer. And an intermediate layer of the second conductivity type opposite to the first conductivity type, and a position optically coupled to light generated in the active layer and propagating in the active layer, the intermediate layer, and the tuning layer From the diffraction grating The optical amplifier includes a first laminated structure, and the optical amplifier is disposed on the semiconductor substrate, disposed on the first cladding layer, and radiated from the laser oscillator. A second active layer that amplifies the incident laser light by current injection, and a second cladding layer of the first conductivity type disposed on the second active layer. The buried layer is disposed on the semiconductor substrate and on the lower buried layer on the semiconductor substrate on both sides of the mesa structure of the laser oscillator and the optical amplifier. A first conductivity type or semi-insulating upper buried layer, and on both sides of the mesa structure of the laser oscillator, the lower buried layer has a thickness in contact with an end face of the intermediate layer, On both sides of the mesa structure, the lower buried layer is the first cladding. While in contact with the end surface of the second semiconductor optical device on the end face of the active layer is a thickness which is not in contact is provided.
[0013]
This defines a tuning current path from the lower buried layer to the tuning layer via the intermediate layer. An excitation current path is defined from the lower buried layer to the first active layer via the intermediate layer. An optical amplification current path from the lower buried layer to the second cladding layer via the first cladding layer and the second active layer is defined. Since the lower buried layer does not contact the second active layer, the leakage current flowing from the lower buried layer to the second cladding layer without passing through the active layer can be reduced.
[0014]
According to another aspect of the present invention, (a) a first active layer disposed on a first region of a semiconductor substrate of a first conductivity type and generating stimulated emission light by current injection, a refractive index by current injection. A tuning layer that changes, an intermediate layer of a second conductivity type disposed between the first active layer and the tuning layer, opposite to the first conductivity type, and the active layer generated in the active layer, A laser oscillator including a first laminated structure comprising a diffraction grating disposed at a position optically coupled with an intermediate layer and light propagating in the tuning layer, disposed on a second region of the semiconductor substrate, The first conductivity type first cladding layer disposed on the semiconductor substrate and the laser light emitted from the laser oscillator incident on the first cladding layer are incident by current injection. A second active layer for amplifying laser light; and An optical amplifier for amplifying incident laser light, and a first region between the first region and the second region And (b) forming a laser structure having an optical waveguide disposed on the region 3 and optically coupling the first laminated structure of the laser oscillator and the second active layer of the optical amplifier; A stripe mesa mask extending in a direction in which the first region, the third region, and the second region are arranged on the laser structure, and the stripe mesa mask of the first and third regions A selective growth mask disposed on both sides of the first and second masks, wherein a gap is provided between the stripe mesa mask and the selective growth mask. In the third region, the width of the gap is As approaching the second region from the first region Forming the stripe mesa mask and the selective growth mask; and (c) using the stripe mesa mask and the selective growth mask of the semiconductor substrate as the etching mask, Etching at least until reaching the bottom of the first stacked structure in the region and at least reaching the bottom of the second active layer in the second region, and (d) the stripe mesa mask and the selection On the region not covered with the growth mask, the lower portion of the second conductivity type has a height that reaches the intermediate layer in the first region and does not reach the second active layer in the second region. There is provided a method of manufacturing a semiconductor optical device, comprising: a step of forming a layer; and (e) a step of removing the stripe mesa mask and the selective growth mask. It is.
[0015]
By using the selective growth mask, it is possible to grow a thick lower layer on the first region and a thin lower layer on the second region by one growth.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1A is a cross-sectional view of the active layer of the semiconductor optical device according to the embodiment cut along a plane parallel to the length direction (light propagation direction) of the optical resonator. A laser emission region L and an optical amplification region G are defined on the surface of the semiconductor substrate 1 made of p-type InP. A buffer layer made of p-type InP may be formed on the surface of the semiconductor substrate 1. The impurity concentration of the semiconductor substrate 1 is 1 × 10¹⁸cm^-3It is.
[0017]
On the surface of the laser emission region L, the lower cladding layer 2, the diffraction grating layer 3, the tuning layer 4, the intermediate layer 5, the active layer 6, and the upper cladding layer 7 are laminated in this order. The laminated structure from the lower clad layer 2 to the upper clad layer 7 constitutes a main part of the TTG-DFB laser oscillator. The lower cladding layer 2 and the upper cladding layer 7 have an impurity concentration of 7 × 10¹⁷cm^-3This is a 150 nm thick layer of p-type InP.
[0018]
The diffraction grating layer 3 has a structure in which a p-type InP layer having a thickness of 200 nm is stacked on a p-type InGaAsP layer having a plurality of recesses periodically formed on the surface. The InGaAsP layer has a composition with a transition wavelength of 1.15 μm, a thickness of 290 nm, and an impurity concentration of 7 × 10.¹⁷cm^-3The depth of the recesses is 50 nm, and the pitch is 240 nm. The impurity concentration of the InP layer is 7 × 10¹⁷cm^-3It is. Note that the phase is shifted by a quarter wavelength (λ / 4) at approximately the center in the length direction of the optical resonator.
[0019]
The tuning layer 4 is made of non-doped InGaAsP having a composition with a transition wavelength of 1.3 μm and has a thickness of 290 nm. The intermediate layer 5 is made of n-type InP, has a thickness of 160 nm, and an n-type impurity concentration of 1 × 10¹⁸cm^-3It is.
[0020]
The active layer 6 has a structure in which a multiple quantum well structure in which quantum well layers and barrier layers are alternately stacked is sandwiched between upper and lower layers by a separate confinement layer (SCH layer). The lower SCH layer is a 40 nm thick layer formed of non-doped InGaAsP having a transition wavelength of 1.25 μm. The quantum well layer is made of non-doped InGaAsP having a compressive strain, and its photoluminescence (PL) wavelength is 1.55 μm, the strain amount is 0.8%, the thickness is 7 nm, and a total of seven layers are arranged. . The barrier layer is made of non-doped InGaAsP having a transition wavelength of 1.25 μm and has a thickness of 9 nm. The upper SCH layer is made of non-doped InGaAsP having a transition wavelength of 1.15 μm and has a thickness of 100 nm.
[0021]
The length of the laser emission region (optical resonator length) is 400 μm. As will be described later, the lower cladding layer 2 to the upper cladding layer 7 have a striped mesa structure with a width of 1.0 μm and a height of 1500 nm.
[0022]
On the surface of the optical amplification region G, an n-type cladding layer 11 made of n-type InP, an active layer 12, and a p-type cladding layer 13 made of p-type InP are laminated in this order. The n-type cladding layer 11, the active layer 12, and the p-type cladding layer 13 constitute the main part of the semiconductor optical amplifier (SOA). These three layers have a striped mesa structure and are continuous with the mesa structure of the laser emission region L. The mesa structure has a width of 1.0 μm, a height of 1500 nm, and a length of 600 nm.
[0023]
The n-type cladding layer 11 has a thickness of 700 nm and an impurity concentration of 1 × 10¹⁸cm^-3It is. The p-type cladding layer 13 has a thickness of 300 nm and an impurity concentration of 7 × 10.¹⁷cm^-3It is.
[0024]
The active layer 12 has a structure in which a multiple quantum well structure in which quantum well layers and barrier layers are alternately stacked is sandwiched between SCH layers from above and below. The multiple quantum well structure including the quantum well layer and the barrier layer is the same as the multiple quantum well structure of the active layer 6 in the laser emission region L. The lower SCH layer is made of non-doped InGaAsP having a composition with a transition wavelength of 1.25 μm, and its thickness is 100 nm. The upper SCH layer is made of non-doped InGaAsP having a composition with a transition wavelength of 1.15 μm and has a thickness of 100 nm.
[0025]
2A and 2B are cross-sectional views taken along one-dot chain lines A2-A2 and B2-B2 in FIG. 1A, respectively. A cross-sectional view taken along one-dot chain line A1-A1 in FIGS. 2A and 2B corresponds to FIG.
[0026]
  As shown in FIG. 2A, in the laser emission region L, on the semiconductor substrate 20, the lower cladding layer 2, the diffraction grating layer 3, the tuning layer 4, the intermediate layer 5, the active layer 6, and the upper cladding layer. A mesa structure consisting of 7 is formed. Both sides of this mesa structure are buried with two layers including a lower buried layer 30 and an upper buried layer 31. The lower buried layer 30 is made of n-type InP and has an impurity concentration of 1 × 10¹⁸cm^-3The thickness is 1300 nm. The upper buried layer 31 is made of p-type InP, and its impurity concentration is 7 × 10.¹⁷cm^-3The thickness is 300 nm.The upper buried layer 31 may be semi-insulating.
[0027]
  As shown in FIG. 2B, in the optical amplification region G, a mesa structure including an n-type cladding layer 11, an active layer 12, and a p-type cladding layer 13 is formed on the semiconductor substrate 1. Both sides of this mesa structure are buried with two layers of a lower buried layer 34 and an upper buried layer 35. The lower buried layer 34 is made of n-type InP, and its impurity concentration is 1 × 10 6.¹⁸cm^-3The thickness is 450 nm. The upper buried layer 35 is made of p-type InP, and its impurity concentration is 7 × 10.¹⁷cm^-3The thickness is 1150 nm.The upper buried layer 35 may be semi-insulating.
[0028]
FIG. 1B is a cross-sectional view taken along one-dot chain line B1-B1 in FIGS. A cross-sectional view taken along one-dot chain line A1-A1 in FIG. 2B corresponds to FIG. 1A, and a cross-sectional view in B1-B1 corresponds to FIG. 2A and 2B, the lower buried layer 30 on the laser emission region L and the lower buried layer 34 on the light amplification region G have different thicknesses. Further, the upper surfaces of the upper buried layers 31 and 35 are set to the same height.
[0029]
As shown in FIG. 2A, in the laser emission region L, the lower buried layer 30 contacts the intermediate layer 5 on the side surface of the mesa structure, and both are electrically connected. As shown in FIG. 2B, in the light amplification region G, the upper buried layer 35 is in contact with the active layer 12 and the lower buried layer 34 is in a thickness not in contact with the active layer 12. .
[0030]
As shown in FIGS. 1A, 1B, 2A, and 2B, on the mesa structure of the laser emission region L and the light amplification region G and on the upper buried layers 31 and 35. A planarization layer 15 made of p-type InP is formed. The impurity concentration of the planarization layer 15 is 7 × 10.¹⁷cm^-3And its thickness is 3000 nm.
[0031]
A contact layer 16 made of p-type InGaAs is formed in a region above the mesa structure in the surface of the planarization layer 15. The impurity concentration of the contact layer 16 is 1 × 10¹⁸cm^-3And its thickness is 300 nm. The portion on the laser emission region L of the contact layer 16 and the portion on the light amplification region G are separated from each other. A region where the contact layer 16 is not formed is covered with a protective film 38 made of silicon oxide.
[0032]
As shown in FIGS. 2A and 2B, an opening is formed from the upper surface of the planarization layer 15 to the upper surfaces of the lower buried layers 30 and 34. An electrode 37 is formed on the lower buried layers 30 and 34 exposed at the bottom of the opening.
[0033]
As shown in FIGS. 1A and 2A, an electrode 17 is formed on the contact layer 16 in the laser emission region L. As shown in FIGS. 1A and 2B, an electrode 18 is formed on the contact layer 16 in the light amplification region G. Further, as shown in FIGS. 1A, 1 B, and 2 A, an electrode 19 is formed in a region corresponding to the laser emission region L on the back surface of the semiconductor substrate 1. These electrodes 17, 18, 19 and 37 are made of gold (Au).
[0034]
As shown in FIGS. 1A and 1B, an antireflection film 20 is formed on the end surface on the optical amplification region G side, and an antireflection film 21 is formed on the end surface on the laser emission region L side.
Next, a method for manufacturing the TTG-DFB laser according to the first embodiment shown in FIGS. 1 and 2 will be described.
[0035]
A lower cladding layer 2 is grown on the semiconductor substrate 1 by metal organic chemical vapor deposition (MOCVD). Each of the other semiconductor layers to be formed is grown by MOCVD unless otherwise specified. An InGaAsP layer is formed on the lower cladding layer 2, and a diffraction grating is formed by lithography using two-beam interference exposure or electron beam exposure. The diffraction grating is embedded with InP to form the diffraction grating layer 3. Each layer from the intermediate layer 5 to the upper cladding layer 7 is grown on the diffraction grating layer 3.
[0036]
A region on the laser emission region L of the surface of the upper clad layer 7 is covered with a silicon oxide film, and the stack from the upper clad layer 7 to the lower clad layer 2 on the optical amplification region G is removed by etching. The silicon oxide film can be formed by, for example, CVD. An n-type cladding layer 11, an active layer 12, and a p-type cladding layer 13 are selectively grown on the semiconductor substrate 1 where the optical amplification region G is exposed. At this time, since the silicon oxide film remains on the surface of the laser emission region L, the semiconductor layer does not grow thereon. After these layers are grown on the light amplification region G, the silicon oxide film remaining on the laser emission region L is removed.
[0037]
A striped silicon oxide film for forming a mesa structure is formed on the upper cladding layer 7 and the p-type cladding layer 13. Using this silicon oxide film as an etching mask, etching is performed until the surface of the semiconductor substrate 1 is exposed. Thereby, a striped mesa structure is formed.
[0038]
The light amplification region G is covered with a silicon oxide film, and the lower buried layer 30 and the upper buried layer 31 are selectively grown on both sides of the mesa structure on the laser emission region L. Since the upper surface of the mesa structure and the surface of the light amplification region G are covered with the silicon oxide film, the semiconductor layer does not grow on this region.
[0039]
The silicon oxide film used as a mask for selective growth is removed, and the surface of the laser emission region L and the upper surface of the mesa structure on the light amplification region G are covered with a silicon oxide film. On both sides of the mesa structure on the light amplification region G, the lower buried layer 34 and the upper buried layer 35 are selectively grown. The silicon oxide film used as the selective growth mask is removed.
[0040]
A planarization layer 15 and a contact layer 16 are grown on the entire surface of the substrate. The contact layer 16 is patterned. The planarization layer 15 and the upper buried layers 31 and 35 are etched to form openings for forming the electrodes 37. A protective film 38 made of silicon oxide is formed on the entire surface. The protective film 38 in the region where the electrode is to be formed is removed, and the electrodes 17, 18, 19 and 37 are formed by the lift-off method. The semiconductor substrate 1 is cleaved, and antireflection films 20 and 21 are formed on the end faces.
[0041]
In the first embodiment, as shown in FIG. 2A, the electrode 17 is passed through the planarization layer 15, the upper cladding layer 7, the active layer 6, the intermediate layer 5, and the lower buried layer 30. An excitation current path to the electrode 37 is defined. Further, a tuning current path from the electrode 19 to the electrode 37 via the semiconductor substrate 1, the lower cladding layer 2, the diffraction grating layer 3, the tuning layer 4, the intermediate layer 5, and the lower buried layer 30 is defined. The excitation current flowing through the excitation current path and the tuning current flowing through the tuning current path can be controlled independently of each other.
[0042]
Further, as shown in FIG. 2B, the electrode 18 is connected to the electrode 37 via the planarization layer 15, the p-type cladding layer 13, the active layer 12, the n-type cladding layer 11, and the lower buried layer 34. To which the optical amplification current path is defined.
[0043]
By causing an excitation current to flow through the active layer 6 on the laser emission region L, laser oscillation can be generated. By controlling the current flowing through the tuning layer 4, the oscillation wavelength can be changed continuously and over a wide range. Laser light generated in the active layer 6 on the laser emission region L is introduced into the active layer 12 on the light amplification region G. By flowing a light amplification current through the active layer 12, the laser light can be amplified. The amplified laser light is emitted to the outside through the antireflection film 20.
[0044]
In the first embodiment, since the optical amplifier is integrated in the TTG-DFB laser, the intensity of the output laser beam can be significantly increased.
In the first embodiment, the lower buried layer 34 on the light amplification region G is thinner than the lower buried layer 30 on the laser emission region L. When the thickness of the lower buried layer 34 on the optical amplification region G is equal to the thickness of the lower buried layer 30 on the laser emission region L, the region below the side surface of the p-type cladding layer 13 in the optical amplification region G Then, it comes into direct contact with the lower buried layer 34. When both are in direct contact, a current flows directly from the p-type cladding layer 13 to the lower buried layer 34 and the current injected into the active layer 12 decreases.
[0045]
As in the first embodiment, in the optical amplification region G, the lower buried layer 34 has a thickness that does not contact the p-type cladding layer 13 and the active layer 12, thereby improving the current injection efficiency into the active layer 12. Can be increased.
[0046]
3A and 3B are sectional views of a semiconductor optical device according to the second embodiment. 3A is a cross-sectional view of the mesa structure portion, and FIG. 3B is a cross-sectional view of the buried layer portions on both sides of the mesa structure.
[0047]
In the semiconductor optical device according to the second embodiment, a coupling region is provided between the laser emission region L and the optical amplification region G of the semiconductor optical device according to the first embodiment shown in FIGS. C is arranged. The stacked structure in the laser emission region L and the optical amplification region G is the same as the stacked structure of the semiconductor optical device shown in FIGS.
[0048]
As shown in FIG. 3A, the lower cladding layer 41, the core layer 42, and the upper cladding layer 43 are stacked on the coupling region C of the semiconductor substrate 1. These three layers constitute a mesa structure. The length of this mesa structure is 200 μm. The lower cladding layer 41 is made of p-type InP, and its impurity concentration is 2 × 10.¹⁷cm^-3The thickness is 850 nm. The core layer 42 is made of non-doped InGaAsP and has a transition wavelength of 1.3 μm and a thickness of 200 nm. The upper cladding layer 43 is made of p-type InP, and its impurity concentration is 2 × 10.¹⁷cm^-3The thickness is 450 nm.
[0049]
The upper and lower cladding layers 41 and 43 and the core layer 42 constitute a waveguide. This waveguide guides the laser light emitted from the laser emission region L to the active layer 12 in the light amplification region G.
[0050]
  As shown in FIG. 3B, two layers of a lower buried layer 45 and an upper buried layer 46 are formed on both sides of the mesa structure in the coupling region C. The lower buried layer 45 is made of n-type InP and has an impurity concentration of 1 × 10¹⁸cm^-3It is. The upper buried layer 46 is made of p-type InP, and its impurity concentration is 7 × 10.¹⁷cm^-3It is.The upper buried layer 46 may be semi-insulating together with the upper buried layers 31 and 35.
[0051]
The lower buried layer 45 has the same thickness as that of the lower buried layer 30 in the laser emission region L at the boundary between the laser emission region L and the coupling region C, and the light is emitted at the boundary between the light amplification region G and the coupling region C. The thickness is the same as that of the lower buried layer 34 in the amplification region G. In the coupling region C, the thickness of the lower buried layer 45 is gradually reduced from the laser emission region L to the optical amplification region G.
[0052]
The height of the upper surface of the upper buried layer 31 in the laser emission region L, the upper buried layer 46 in the coupling region C, and the upper buried layer 35 in the light amplification region G is substantially the same.
Of the surface of the planarization layer 15, the region above the coupling region C is covered with a protective film 38, and no contact layer and electrode are disposed in this region.
[0053]
A method for manufacturing a TTG-DFB laser according to the second embodiment will be described with reference to FIGS.
A stacked structure on the laser emission region L is formed by the same method as in the first embodiment. Next, a stacked structure on the coupling region C is formed. Thereafter, a stacked structure on the light amplification region G is formed.
[0054]
As shown in FIG. 4A, a stripe mesa mask 50 and a selective growth mask 51 made of silicon oxide are formed on the surfaces of the upper cladding layers 7 and 42 and the p-type cladding layer 13. The stripe mesa mask 50 has a stripe pattern having a width of about 1.0 μm extending from the laser emission region L through the coupling region C to the light amplification region G. The selective growth mask 51 is disposed on both sides of the stripe mesa mask 50 at a certain distance from the stripe mesa mask 50 in the laser emission region L and the coupling region C. In the laser emission region L, the distance W between the pair of selective growth masks 51 arranged on both sides of the stripe mesa mask 50 is about 30 μm. In the coupling region C, the distance between the two gradually increases as the laser light emitting region L approaches the light amplification region G. For this reason, the distance between the stripe mesa mask 50 and the selective growth mask 51 is gradually increased from the laser emission region L to the light amplification region G.
[0055]
Using the stripe mesa mask 50 and the selective growth mask 51 as etching masks, etching is performed up to the upper surface of the semiconductor substrate 1 shown in FIG.
4B and 4C are cross-sectional views taken along one-dot chain line B4-B4 and one-dot chain line C4-C4 in FIG. 4A after etching, respectively. The mesa structure remains at the position where the stripe mesa mask 50 is disposed.
[0056]
4D and 4E, the lower buried layers 30 and 34 and the upper buried layers 31 and 35 are selectively grown. On the surface of the semiconductor substrate 1 in the coupling region C, the lower buried layer 45 and the upper buried layer 46 shown in FIG. Since the selective growth mask 51 is formed in the laser emission region L, the lower buried layer 30 grown on the laser emission region L is thicker than the lower buried layer 34 grown on the light amplification region G.
[0057]
In the coupling region C, the distance between the stripe mesa mask 50 and the selective growth mask 51 gradually increases from the laser emission region L to the optical amplification region G. The buried layer 45 gradually becomes thinner from the laser emission region L toward the light amplification region G.
[0058]
When the upper buried layer 46 is grown, the growth rate is made substantially uniform over the entire surface of the substrate by adding a small amount of chlorine gas to the source gas or by controlling the growth temperature. The upper surface of the upper buried layer 46 is not completely flat due to the influence of the variation in the film thickness of the lower buried layer 45, but this degree of undulation does not pose an operational or manufacturing problem.
[0059]
The steps after the flattening layer 15 forming step are the same as the steps of manufacturing the semiconductor optical device according to the first embodiment.
In the second embodiment, a coupling region C is disposed between the laser emission region L and the light amplification region G as shown in FIG. The distance between the electrode 17 on the laser emission region L and the electrode 18 on the light amplification region G is wider than that in the first embodiment, and a region having a high electric resistance is disposed between the two. For this reason, interference between the current injected into the active layer 6 in the laser emission region L and the current injected into the active layer 12 in the light amplification region G can be reduced.
[0060]
Even if the temperature of each layer of the optical amplification region G rises due to the current flowing in the optical amplification region G, the coupling region C is interposed between the laser emission region L and the optical amplification region G. The temperature rise of each layer of L can be reduced. Since the temperature rise of each layer in the laser emission region L is suppressed, the shift of the oscillation wavelength (lengthening) due to the temperature rise can be suppressed.
[0061]
Furthermore, in the second embodiment, by using the selective growth mask 51 shown in FIG. 4A, the lower buried layers 30 and 34 having different thicknesses can be formed by one growth. . Since the thickness of the lower buried layer 45 changes smoothly in the coupling region C, loss due to light scattering can be reduced. Moreover, it becomes easy to obtain stable guided light in a single mode.
[0062]
Next, a semiconductor optical device according to a third embodiment will be described with reference to FIG.
FIG. 5A shows a cross-sectional view of the laser emission region L of the semiconductor optical device according to the third embodiment, and FIG. 5B shows a cross-sectional view of the optical amplification region G. In the third embodiment, as shown in FIG. 5A, an etching stop layer 53 is disposed between the lower buried layer 30 and the upper buried layer 31. Further, as shown in FIG. 5B, an etching stop layer 55 is disposed between the lower buried layer 34 and the upper buried layer 35.
[0063]
The etching stop layers 53 and 55 are made of n-type InGaAsP and have an impurity concentration of 5 × 10 5.¹⁸cm^-3The transition wavelength is 1.15 μm and the thickness is 30 nm. When the upper buried layers 31 and 35 are etched using a bromine (Br) -based etchant, the etching rate of the etching stop layers 53 and 55 becomes slow. Therefore, even when the depth to be etched is different between the laser emission region L and the optical amplification region G, the etching can be stopped with good reproducibility when the etching stop layers 53 and 55 are exposed.
[0064]
Further, in the third embodiment, the current block layer 54 is disposed on the upper buried layer 31 and the current block layer 56 is disposed on the upper buried layer 35. The current blocking layers 54 and 56 are made of n-type InP and have an impurity concentration of 1 × 10 6.¹⁸cm^-3The thickness is 300 nm. The current blocking layer 54 shields current that flows directly from the planarization layer 15 into the upper buried layer 31. The current blocking layer 56 shields current that flows directly from the planarization layer 15 into the upper buried layer 35.
[0065]
For this reason, in the laser emission region L, the current injection efficiency into the active layer 6 can be increased. In the light amplification region G, the efficiency of current injection into the active layer 12 can be increased.
[0066]
A semiconductor optical device according to the fourth embodiment will be described with reference to FIGS.
FIG. 6A shows a cross-sectional view of the active layer of the semiconductor optical device according to the fourth embodiment cut along a plane parallel to the length direction (light propagation direction) of the optical resonator. FIG. 6B shows a cross-sectional view taken along a plane parallel to the length direction of the optical resonator on the side of the mesa structure including the active layer. FIG. 7 is a cross-sectional view taken along one-dot chain line A7-A7 in FIGS. 6A and 6B.
[0067]
The laminated structure on the laser emission region L is the same as the laminated structure of the semiconductor optical device according to the first embodiment shown in FIGS. 1 (A) and 1 (B). In the first embodiment, as shown in FIG. 1A, an n-type cladding layer 11, an active layer 12, and a p-type cladding layer 13 are stacked on the optical amplification region G in order from the substrate side. However, in the fourth embodiment, as shown in FIG. 6A, the p-type cladding layer 11A, the active layer 12A, and the n-type cladding layer 13A are stacked in this order from the substrate side.
[0068]
In the first embodiment, one electrode 18 is formed on the planarizing layer 15. In the fourth embodiment, one electrode 18 A is formed on the back surface of the semiconductor substrate 1.
[0069]
  In the first embodiment, as shown in FIGS. 1B and 2B, the lower buried layer 34 disposed on both sides of the mesa structure is n-type, and the upper buried layer 35 is p-type. It was a mold. On the other hand, in the fourth embodiment, the lower buried layer 34A shown in FIG. 6B and FIG.Or semi-insulatingThe upper buried layer 35A is n-type. The side surface of the upper buried layer 35A is in contact with the n-type cladding layer 13A. The thickness of the lower buried layer 34A is set so that its upper surface is higher than the active layer 12A. For this reason, the upper buried layer 35A does not contact the p-type cladding layer 11A.
[0070]
An opening is formed in a part of the planarizing layer 15, and the upper surface of the upper buried layer 35A is exposed on the bottom surface. An electrode 18B is formed on the exposed upper buried layer 35A.
A light amplification current path from the electrode 18B to the electrode 18A via the upper buried layer 35A, the n-type cladding layer 13A, the active layer 12A, the p-type cladding layer 11A, and the semiconductor substrate 1 is defined. Since the upper buried layer 35A is not in direct contact with the p-type cladding layer 11A, it is possible to suppress leakage current from flowing from the upper buried layer 35A to the p-type cladding layer 11A without passing through the active layer 12A. For this reason, the efficiency of current injection into the active layer 12A can be increased.
[0071]
Next, a semiconductor optical device according to a fifth embodiment will be described with reference to FIGS.
FIG. 8A shows a plan view of a semiconductor optical device according to the fifth embodiment. A plurality of TTG-DFB lasers 70, an optical waveguide 72, a multimode interference waveguide type (MMI) optical multiplexer 74, and an optical amplifier 76 are formed on the surface of the semiconductor substrate 60. Each of these optical elements has a mesa structure formed on the semiconductor substrate 60. Portions other than the mesa structure are buried with the buried layer.
[0072]
Each TTG-DFB laser 70, optical waveguide 72, and optical amplifier 76 are respectively a TTG-DFB laser and a coupling region C on the laser emission region L of the semiconductor optical device according to the second embodiment shown in FIG. It has the same stacked structure as the upper optical waveguide and the optical amplifier on the optical amplification region G. However, each of the TTG-DFB lasers 70 has a different center oscillation wavelength. The buried layers on both sides of the TTG-DFB laser 70, the buried layers on both sides of the optical waveguide 72, and the buried layers on both sides of the optical amplifier 76 are each a semiconductor according to the second embodiment shown in FIG. The buried layers 30 and 31 on the laser emission region L of the optical device, the buried layers 45 and 46 on the coupling region C, and the buried layers 34 and 35 on the light amplification region G have the same configuration.
[0073]
The laminated structure of the optical multiplexer 74 is the same as the laminated structure of the optical waveguide 72, and the surrounding buried layers have the same laminated structure as the buried layers on both sides of the optical amplifier 76. The planar shape of the optical multiplexer 74 is a rectangular shape having a short side length of 40 μm and a long side length of 300 μm. Four input ports are provided on one short side, and one output port is provided on the other short side.
[0074]
FIG. 8B shows a mask pattern for forming a mesa structure. A mesa mask pattern 77 corresponding to the mesa structure of the TTG-DFB laser 70, the optical waveguide 72, the optical multiplexer 74, and the optical amplifier 76 is formed. A selective growth mask pattern 78 is formed on both sides of a mesa mask pattern 77 in a region corresponding to the TTG-DFB laser 70 and the optical waveguide 72.
[0075]
The distance between the mesa mask pattern 70 in the region corresponding to the TTG-DFB laser 70 and the selective growth mask pattern 78 disposed on both sides thereof is substantially constant. The distance between the mesa mask pattern 77 and the selective growth mask pattern 78 in the region corresponding to the optical waveguide 72 gradually increases from the region where the TTG-DFB laser 70 is disposed toward the region where the optical waveguide 77 is disposed. It has become.
[0076]
By performing selective growth of the buried layer using such a selective growth mask pattern 78, the buried layer 45 on the coupling region C of the semiconductor optical device according to the second embodiment shown in FIG. Similarly to the above, the thickness of the buried layer can be gradually changed.
[0077]
An optical waveguide 72 is coupled to each of the TTG-DFB lasers 70. The other end of the optical waveguide 72 is connected to the input port of the optical multiplexer 74. The output port of the optical multiplexer 74 is connected to the optical amplifier 76.
[0078]
By arranging a plurality of TTG-DFB lasers 70 having different central oscillation wavelengths, the wavelength can be changed in a wider range. Furthermore, since the optical amplifier 76 is formed on the same substrate as the TTG-DFB laser, the optical output can be increased.
[0079]
In the above embodiment, the case where a p-type semiconductor substrate is used has been described, but an n-type semiconductor substrate can also be used. In this case, what is necessary is just to make the conductivity type of each layer opposite to the conductivity type of each layer of the said Example. In the above embodiment, the case where the InP substrate is used has been described. However, it is also possible to use a compound semiconductor other than InP, for example, a substrate made of GaAs or the like.
[0080]
Furthermore, although the active layer of the laser emission region and the optical amplification region has a multi-quantum well structure in the above-described embodiment, it can also be composed of a single layer made of a semiconductor.
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0081]
From the embodiments described above, the invention shown in the following supplementary notes is derived.
(Supplementary Note 1) A laser oscillator disposed on a first region of a first conductivity type semiconductor substrate and having a stripe-like mesa structure;
An optical amplifier disposed on the second region of the semiconductor substrate, having a striped mesa structure, and receiving laser light emitted from the laser oscillator and amplifying the laser light;
A buried layer embedding both sides of the mesa structure of the laser oscillator and the optical amplifier;
Have
The laser oscillator includes a first active layer that generates stimulated emission light by current injection, a tuning layer that changes a refractive index by current injection, and is disposed between the first active layer and the tuning layer. An intermediate layer of the second conductivity type opposite to the one conductivity type, and a diffraction grating disposed at a position optically coupled with light generated in the active layer and propagating in the active layer, the intermediate layer, and the tuning layer Comprising a first laminated structure consisting of
The optical amplifier is disposed on the first clad layer of the second conductivity type disposed on the semiconductor substrate, and the laser light emitted from the laser oscillator is incident on the first clad layer, A second active layer that amplifies the incident laser beam by current injection; and a second cladding layer of the first conductivity type disposed on the second active layer;
The buried layer includes a second conductivity type lower buried layer disposed on the semiconductor substrate on both sides of the mesa structure of the laser oscillator and the optical amplifier, and a second buried layer disposed on the lower buried layer. An upper buried layer of one conductivity type or semi-insulating, and on both sides of the mesa structure of the laser oscillator, the lower buried layer has a thickness in contact with an end face of the intermediate layer, and the mesa structure of the optical amplifier On both sides of the semiconductor optical device, the lower buried layer has a thickness that is in contact with the end face of the first cladding layer but is not in contact with the end face of the second active layer.
[0082]
(Supplementary Note 2) The laser oscillator further includes a third clad layer of a first conductivity type disposed under the first stacked structure, and a first conductivity disposed on the first stacked structure. The semiconductor optical device according to appendix 1, including a fourth cladding layer of a mold.
[0083]
(Supplementary Note 3) A third region is further defined between the first region and the second region defined on the surface of the semiconductor substrate,
Or an optical waveguide disposed on the third region of the semiconductor substrate and optically coupling the first stacked structure of the laser oscillator and the second active layer of the optical amplifier. 2. The semiconductor optical device according to 2.
[0084]
(Supplementary Note 4) The lower buried layer is continuously arranged from the first region to the second region via the third region, and the lower region is formed on the third region. 4. The semiconductor optical device according to appendix 3, wherein the thickness of the buried layer is continuously changed.
[0085]
(Supplementary Note 5) Further, the laser oscillator mesa structure, the optical amplifier mesa structure, and a planarization layer made of a first conductivity type semiconductor, disposed on the buried layer,
The buried layer is disposed between the lower buried layer and the upper buried layer, and includes an etching stop layer having different etching characteristics from the upper buried layer;
Further, a recess that penetrates the planarization layer and the upper buried layer and reaches the etching stop layer or the lower buried layer,
An electrode electrically connected to the lower buried layer at the bottom of the recess;
The semiconductor optical device according to any one of appendices 1 to 4, wherein:
[0086]
(Supplementary note 6) The semiconductor optical device according to any one of supplementary notes 1 to 5, wherein the buried layer further includes a second conductivity type current blocking layer disposed on the upper buried layer.
(Supplementary Note 7) The laser oscillator has a plurality of stripe-shaped mesa structures, each of the mesa structures includes the same stacked structure as the first stacked structure, and the center oscillation wavelengths are different from each other.
Furthermore, the laser light emitted from a plurality of mesa structures of the laser oscillator, which is disposed between the first region and the second region, is combined, and the combined laser light is combined with the first light of the optical amplifier. The semiconductor optical device according to any one of appendices 1 to 6, having an optical multiplexer to be introduced into the two active layers.
[0087]
(Supplementary Note 8) A laser oscillator disposed on the first region of the first conductivity type semiconductor substrate and having a stripe-like mesa structure;
An optical amplifier disposed on the second region of the semiconductor substrate, having a striped mesa structure, and receiving laser light emitted from the laser oscillator and amplifying the laser light;
Embedded layers embedding both sides of the mesa structure of the laser oscillator and the optical amplifier;
Have
The laser oscillator includes a first active layer that generates stimulated emission light by current injection, a tuning layer that changes a refractive index by current injection, and is disposed between the first active layer and the tuning layer. An intermediate layer of the second conductivity type opposite to the one conductivity type, and a diffraction grating disposed at a position optically coupled with light generated in the active layer and propagating in the active layer, the intermediate layer, and the tuning layer Comprising a first laminated structure consisting of
The optical amplifier is disposed on the first clad layer of the first conductivity type disposed on the semiconductor substrate, the laser light emitted from the laser oscillator is incident on the first clad layer, A second active layer that amplifies the incident laser beam by current injection; and a second conductivity type second clad layer disposed on the second active layer, wherein the buried layer comprises: A first conductivity type first lower layer disposed on the semiconductor substrate on both sides of the mesa structure of the laser oscillator on the first region and in contact with an end face of the intermediate layer of the laser oscillator; And a first conductive type or semi-insulating first upper layer disposed on the lower layer of the first semiconductor layer, and the semiconductor substrate on both sides of the mesa structure of the optical amplifier on the second region. An end of the first cladding layer and the second active layer disposed on A first conductive type or semi-insulating second lower layer in contact with the second lower layer, and a second conductive type second upper layer disposed on the second lower layer and in contact with the end surface of the second cladding layer A semiconductor optical device.
[0088]
(Additional remark 9) (a) The 1st active layer which is arrange | positioned on the 1st area | region on the semiconductor substrate of 1st conductivity type, and generate | occur | produces stimulated emission light by electric current injection, The tuning layer from which a refractive index changes with electric current injection A second conductive type intermediate layer disposed between the first active layer and the tuning layer, opposite to the first conductive type, and generated in the active layer, the active layer, the intermediate layer, and A laser oscillator including a first laminated structure including a diffraction grating disposed at a position optically coupled with light propagating in the tuning layer, disposed on a second region of the semiconductor substrate, and disposed on the semiconductor substrate; A first clad layer of the second conductivity type disposed, and a laser beam emitted from the laser oscillator is incident on the first clad layer, and the incident laser beam is amplified by current injection A second active layer, and the second active layer An optical amplifier for amplifying incident laser light, and a third region between the first region and the second region Forming a laser structure having an optical waveguide disposed and optically coupling the first stacked structure of the laser oscillator and the second active layer of the optical amplifier;
(B) a stripe mesa mask extending in a direction in which the first region, the third region, and the second region are arranged on the laser structure, and the first and third regions; A selective growth mask disposed on both sides of the stripe mesa mask, wherein a gap is provided between the stripe mesa mask and the selective growth mask, and the gap is formed in the third region. Forming the stripe mesa mask and the selective growth mask so that the width of the portion increases from the first region toward the second region;
(C) Using the stripe mesa mask and the selective growth mask of the semiconductor substrate as an etching mask, at least the bottom of the first stacked structure is reached in the first region, and in the second region, Etching until at least the bottom of the second active layer is reached;
(D) On the region not covered by the stripe mesa mask and the selective growth mask, the first region reaches the intermediate layer, and the second region reaches the second active layer. Forming a second conductivity type lower layer that does not reach the height;
(E) removing the stripe mesa mask and the selective growth mask;
The manufacturing method of the semiconductor optical device which has this.
[0089]
(Additional remark 10) Furthermore, (f) The manufacturing method of the semiconductor optical device of Additional remark 9 which has the process of forming a semi-insulating upper layer on the said lower layer.
(Additional remark 11) Between the said process (e) and the process (f), the process of forming the etching stop layer which consists of a material in which etching resistance differs from the said upper layer on the said lower layer,
After the step (f),
Forming a planarization layer of a first conductivity type on the mesa structure and the upper layer;
Forming an opening penetrating the planarizing layer and the upper layer under a condition that an etching rate of the upper layer is higher than an etching rate of the etching stop layer, and stopping the etching when the etching stop layer is exposed. When,
Forming an electrode electrically connected to the lower layer on a bottom surface of the opening;
The method of manufacturing a semiconductor optical device according to appendix 10, wherein:
[0090]
【The invention's effect】
As described above, according to the present invention, by integrating an optical amplifier in a TTG-DFB laser, a continuous and wide variable wavelength range can be realized and a high optical output can be obtained. Further, the thickness of the lower buried layer disposed on both sides of the mesa structure of the optical amplifier and the lower buried layer disposed on both sides of the mesa structure of the TTG-DFB laser are made different, thereby enabling the activity of the optical amplifier. The efficiency of current injection into the layer can be increased.
[Brief description of the drawings]
FIG. 1 is a sectional view of a semiconductor laser according to a first embodiment.
FIG. 2 is a sectional view of a semiconductor laser according to a first embodiment.
FIG. 3 is a sectional view of a semiconductor laser according to a second embodiment.
FIG. 4 is a plan view of a mask for explaining a semiconductor laser manufacturing method according to a second embodiment and a cross-sectional view in the middle of manufacturing.
FIG. 5 is a sectional view of a semiconductor laser according to a third embodiment.
FIG. 6 is a sectional view of a semiconductor laser according to a fourth embodiment.
FIG. 7 is a sectional view of a semiconductor laser according to a fourth embodiment.
FIG. 8 is a plan view of a semiconductor laser according to a fifth embodiment and a plan view of a mask pattern used in the manufacturing process.
[Explanation of symbols]
1 Semiconductor substrate
2 Lower cladding layer
3 Diffraction grating layer
4 Tuning layer
5 middle class
6 Active layer
7 Upper cladding layer
11 n-type cladding layer
12 Active layer
13 p-type cladding layer
15 Planarization layer
16 Contact layer
17, 18, 18A, 18B, 19 electrodes
20, 21 Antireflection film
30 Lower buried layer
31 Upper buried layer
34, 34A Lower buried layer
35, 35A Upper buried layer
37 electrodes
38 Protective film
41 Lower cladding layer
42 Core layer
43 Upper cladding layer
45 Lower buried layer
46 Upper buried layer
50 Stripe Mesa Mask
51 Mask for selective growth
53, 55 Etching stop layer
54, 56 Current blocking layer

Claims (10)

A laser oscillator disposed on a first region of a first conductivity type semiconductor substrate and having a striped mesa structure;
An optical amplifier disposed on the second region of the semiconductor substrate, having a striped mesa structure, and receiving laser light emitted from the laser oscillator and amplifying the laser light;
Embedded layers embedding both sides of the mesa structure of the laser oscillator and the optical amplifier,
The laser oscillator includes a first active layer that generates stimulated emission light by current injection, a tuning layer that changes a refractive index by current injection, and is disposed between the first active layer and the tuning layer. An intermediate layer of the second conductivity type opposite to the one conductivity type, and a diffraction grating disposed at a position optically coupled with light generated in the active layer and propagating in the active layer, the intermediate layer, and the tuning layer Comprising a first laminated structure consisting of
The optical amplifier is disposed on the first clad layer of the second conductivity type disposed on the semiconductor substrate, and the laser light emitted from the laser oscillator is incident on the first clad layer, A second active layer that amplifies the incident laser beam by current injection; and a second cladding layer of the first conductivity type disposed on the second active layer;
The buried layer includes a second conductivity type lower buried layer disposed on the semiconductor substrate on both sides of the mesa structure of the laser oscillator and the optical amplifier, and a second buried layer disposed on the lower buried layer. An upper buried layer of one conductivity type or semi-insulating, and on both sides of the mesa structure of the laser oscillator, the lower buried layer has a thickness in contact with an end face of the intermediate layer, and the mesa structure of the optical amplifier On both sides of the semiconductor optical device, the lower buried layer has a thickness that is in contact with the end face of the first cladding layer but is not in contact with the end face of the second active layer.   The laser oscillator further includes a third clad layer of a first conductivity type disposed under the first stacked structure, and a fourth of a first conductivity type disposed on the first stacked structure. The semiconductor optical device according to claim 1, further comprising: a cladding layer. A third region is further defined between the first region and the second region defined on the surface of the semiconductor substrate;
The optical waveguide is further disposed on the third region of the semiconductor substrate and optically couples the first stacked structure of the laser oscillator and the second active layer of the optical amplifier. Or a semiconductor optical device according to 2;   The lower buried layer is continuously disposed from the first region to the second region via the third region, and the lower buried layer is formed on the third region. 4. The semiconductor optical device according to claim 3, wherein the thickness changes continuously. Furthermore, the mesa structure of the laser oscillator, the mesa structure of the optical amplifier, and a planarization layer made of a semiconductor of the first conductivity type, disposed on the buried layer,
The buried layer is disposed between the lower buried layer and the upper buried layer, and includes an etching stop layer having different etching characteristics from the upper buried layer;
Further, a recess that penetrates the planarization layer and the upper buried layer and reaches the etching stop layer or the lower buried layer,
The semiconductor optical device according to claim 1, further comprising an electrode electrically connected to the lower buried layer at a bottom surface of the recess.   6. The semiconductor optical device according to claim 1, wherein the buried layer further includes a second conductivity type current blocking layer disposed on the upper buried layer. The laser oscillator has a plurality of striped mesa structures, each of the mesa structures includes the same stacked structure as the first stacked structure, and the center oscillation wavelengths are different from each other,
Furthermore, the laser light emitted from a plurality of mesa structures of the laser oscillator, which is disposed between the first region and the second region, is combined, and the combined laser light is combined with the first light of the optical amplifier. The semiconductor optical device according to claim 1, further comprising an optical multiplexer introduced into the two active layers. A laser oscillator disposed on a first region of a first conductivity type semiconductor substrate and having a striped mesa structure;
An optical amplifier disposed on the second region of the semiconductor substrate, having a striped mesa structure, and receiving laser light emitted from the laser oscillator and amplifying the laser light;
Embedded layers embedding both sides of the mesa structure of the laser oscillator and the optical amplifier,
The laser oscillator includes a first active layer that generates stimulated emission light by current injection, a tuning layer that changes a refractive index by current injection, and is disposed between the first active layer and the tuning layer. An intermediate layer of the second conductivity type opposite to the one conductivity type, and a diffraction grating disposed at a position optically coupled with light generated in the active layer and propagating in the active layer, the intermediate layer, and the tuning layer Comprising a first laminated structure consisting of
The optical amplifier is disposed on the first clad layer of the first conductivity type disposed on the semiconductor substrate, the laser light emitted from the laser oscillator is incident on the first clad layer, A second active layer that amplifies incident laser light by current injection; and a second conductivity type second cladding layer disposed on the second active layer;
The buried layer is disposed on the semiconductor substrate on both sides of the mesa structure of the laser oscillator on the first region, and is in contact with the end surface of the intermediate layer of the laser oscillator. A first conductive type or semi-insulating first upper layer disposed on the first lower layer, and the mesa structure of the optical amplifier is formed on the second region. A first conductivity type or semi-insulating second lower layer disposed on both sides of the semiconductor substrate and in contact with end faces of the first cladding layer and the second active layer; and the second lower layer And a second upper layer of the second conductivity type that is disposed on the second contact layer and is in contact with the end face of the second cladding layer. (A) a first active layer that is disposed on a first region of a first conductivity type semiconductor substrate and generates stimulated emission light by current injection; a tuning layer whose refractive index changes by current injection; An intermediate layer disposed between the active layer and the tuning layer and having a second conductivity type opposite to the first conductivity type, and generated in the active layer and propagating through the active layer, the intermediate layer, and the tuning layer A laser oscillator including a first laminated structure composed of a diffraction grating disposed at a position optically coupled with light to be transmitted, a second oscillator disposed on the second region of the semiconductor substrate, and disposed on the semiconductor substrate A first clad layer of conductivity type, and a second activity which is disposed on the first clad layer and receives the laser beam emitted from the laser oscillator and amplifies the incident laser beam by current injection A layer and a second active layer An optical amplifier that amplifies incident laser light, and a third region between the first region and the second region, and the laser Forming a laser structure having an optical waveguide that optically couples the first stacked structure of the oscillator and the second active layer of the optical amplifier;
(B) a stripe mesa mask extending in a direction in which the first region, the third region, and the second region are arranged on the laser structure, and the first and third regions; A selective growth mask disposed on both sides of the stripe mesa mask, wherein a gap is provided between the stripe mesa mask and the selective growth mask, and the gap is formed in the third region. Forming the stripe mesa mask and the selective growth mask so that the width of the portion increases from the first region toward the second region;
(C) Using the stripe mesa mask and the selective growth mask of the semiconductor substrate as an etching mask, at least the bottom of the first stacked structure is reached in the first region, and in the second region, Etching until at least the bottom of the second active layer is reached;
(D) On the region not covered by the stripe mesa mask and the selective growth mask, the first region reaches the intermediate layer, and the second region reaches the second active layer. Forming a second conductivity type lower layer that does not reach the height;
(E) removing the stripe mesa mask and the selective growth mask ;
(F) forming a semi-insulating upper layer on the lower layer; and a method of manufacturing a semiconductor optical device. The semiconductor optical device according to claim 1, wherein the first conductivity type is p-type and the second conductivity type is n-type.

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