JP4897946B2 - 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 method for manufacturing the same, and more particularly to a semiconductor optical device in which windows are provided at one or both ends of an optical waveguide having a stripe-shaped waveguide and a method for manufacturing the same.
[0002]
[Prior art]
As key devices for high-speed optical communication, semiconductor laser elements that oscillate and output signal light in a predetermined wavelength band, optical modulators that modulate light intensity, and semiconductor laser amplifiers that amplify input optical signals are attracting attention. . Among such semiconductor optical devices, in particular, DFB (Distributed Feedback) laser devices using a diffraction grating as a resonator structure, optical modulators having absorption layers, and traveling wave semiconductor lasers. The amplifier has the property that the wavelength fluctuation is likely to occur due to the return light that is reflected by the output end face and re-enters the optical waveguide. Therefore, in order to achieve stable operation and high performance of the device, Anti-reflective technology is essential.
[0003]
As a technique for making the end face non-reflective in such a semiconductor optical device, an AR (Anti Reflection) coating is applied to the end face of the laser part that oscillates the laser light, or a window part that does not have a light waveguide structure is provided. The method of providing is taken. However, the AR coating requires a multilayer film in which precise film thickness control is performed in order to achieve low reflection, and the process steps become complicated. On the other hand, the window portion has an advantage that its process steps are relatively simple and low reflection can be easily achieved.
[0004]
An example of a conventional embedded DFB laser element having a window portion is shown in a partially cutaway sectional perspective view of FIGS. 24 and 25 and a sectional view taken along the line AXI-AXI.
This DFB laser element has a structure in which a laser part A that oscillates laser light and a window part B that is connected to the emission side are formed on the same semiconductor substrate 10 made of, for example, n-InP. It has become. In this laser part A, for example, a diffraction grating 12 made of InGaAs, a buffer layer 14 made of n-InP, a well layer made of InGaAs and a barrier layer made of InGaAsP are alternately laminated to oscillate light having a wavelength of 1.55 μm. The QW (Quantum Well) structure active layer 16 and the first upper clad layer 18 made of p-InP are sequentially stacked. The laminated structure La is processed into a mesa stripe shape extending in the longitudinal direction, and functions as a waveguide that oscillates light of a predetermined wavelength.
[0005]
Furthermore, a pn carrier block layer 36 in which, for example, a p-InP layer 34a and an n-InP layer 34b are sequentially stacked is embedded on both sides of the mesa stripe-shaped stacked structure La. The upper surfaces of these laminated structures La and the upper surfaces of the pn carrier block layers 36 on both sides thereof are flush with each other. Further, a second upper clad layer 20 made of, for example, p-InP is formed on the laminated structure La and the pn carrier block layer 36 to form a laser part A as a whole.
[0006]
On the other hand, the window portion B includes the pn carrier block layer 36 formed simultaneously with the pn carrier block layer 36 in the laser portion A, and the second upper clad layer 20 formed simultaneously with the second upper clad layer 20 in the laser portion A. Are laminated in order to form a laminated structure Lb of low refractive index semiconductor layers having no waveguide structure.
Furthermore, an upper electrode such as a stripe electrode portion 24a corresponding to the stripe shape of the multilayer structure La is provided on the second upper clad layer 20 in the laser portion A, and a lower electrode 26 is provided on the back surface of the common semiconductor substrate 10. Is provided.
[0007]
In the case of the conventional DFB laser element in which the window portion B formed of the laminated structure Lb is provided on the emission side of the laser portion A in this way, the signal light from the laminated structure La of the laser portion A of the optical waveguide structure is When the light is emitted to the laminated structure Lb in the window portion B, the window portion spreads by an angle θ (usually θ = 24 ° to 30 °), and a part of the spread signal light is reflected by the emission end surface of the window portion B. Since the end face reflected light of B has a very large light spot size, it becomes difficult to couple to the optical waveguide of the original laser part A, and the ratio of the return light re-entering becomes extremely small.
[0008]
That is, if the ratio of the return light that is reflected from the output end face of the signal light from the laser part A and re-enters the optical waveguide is defined as the effective reflectance R, the effective reflectance R is reduced by providing the window part B. The effect of doing is demonstrated.
[0009]
[Problems to be solved by the invention]
By the way, in the above-described conventional DFB laser element having the window portion B, in order to further improve the effect of reducing the effective reflectance R by the window portion B, the length (window portion length) Lw of the window portion B is increased. It is preferable. When the relationship between the effective reflectance R by the window portion B and the window portion length Lw is obtained, it is known that the effective reflectance R decreases rapidly as the window portion length Lw increases as shown in the graph of FIG. ing.
[0010]
On the other hand, when the window length Lw is increased, the mode field of the signal light from the laser section A spreads by an angle θ in the window section B as shown by the broken line with an arrow in FIG. At this time, part of the spread signal light is reflected on the upper surface of the second upper cladding layer 20 in the window portion B.
For this reason, for example, when considering the case where an optical fiber is arranged via a lens on the emission end face side of the DFB laser element, signal light from the DFB laser element is transmitted from the upper surface of the second upper cladding layer 20 of the window portion B. Reflected light is also added, causing a problem that the field of signal light is disturbed and the coupling efficiency with the optical fiber is lowered.
[0011]
As a measure for coping with this problem, when the window length Lw is increased, the thickness of the second upper cladding layer 20 in the window B is increased at the same time, and the mode field of the signal light from the laser part A becomes the window Even if the angle θ spreads in B, it is considered effective to prevent the spread signal light from colliding with the upper surface of the upper cladding layer 20 in the window portion B.
[0012]
The relationship between the thickness of the upper clad layer that prevents the signal light from the optical waveguide from reflecting on the upper surface of the upper clad layer 20 even when the signal light spreads by the angle θ in the window B and the window length Lw is shown in the graph of FIG. It became as to be. That is, if the window length Lw is to be increased without reflecting the signal light on the upper surface of the upper cladding layer 20, the thickness of the upper cladding layer 20 needs to be increased in proportion thereto.
[0013]
However, when the thickness of the second upper clad layer 20 in the window portion B is increased, the thickness of the second upper clad layer 20 in the laser portion A is naturally increased. There arises a problem that the resistance increases, and hence the laser characteristics are deteriorated, and the growth time of the upper clad layer 20 becomes long. For this reason, as a practical matter, increasing the thickness of the second upper cladding layer 20 is limited. As a result, the window length Lw is limited to be increased as in the conventional case, and the effect of sufficiently reducing the effective reflectance R cannot be obtained.
[0014]
For this reason, in spite of having provided the window part B, in order to further reinforce the effect of reducing the effective reflectance R by the window part B, there is a situation in which complicated AR coating must be additionally performed. It was happening.
The present invention has been made in consideration of the above circumstances, and a semiconductor having a window portion that can fully exhibit the effect of reducing the effective reflectance without causing disturbance of the field of signal light. An object is to provide an optical element and a method for manufacturing the same.
[0015]
[Means for Solving the Problems]
The above-described object is achieved by the following semiconductor optical device and its manufacturing method according to the present invention.
That is, in the semiconductor optical device according to the present invention, an optical waveguide portion having a stripe-shaped waveguide and a window portion made of a semiconductor layer connected to one or both ends of the optical waveguide portion are formed on the same semiconductor substrate. The upper surface of the semiconductor layer is higher than the uppermost surface of the optical waveguide portion (claim 1).
[0016]
In the semiconductor optical device according to claim 1, the upper surface of the semiconductor layer of the window portion has a shape that gradually increases from the boundary between the window portion and the optical waveguide portion toward the emission end surface of the window portion. (Claim 2), or may have a substantially flat shape as a whole (Claim 3). The waveguide of the optical waveguide section preferably includes an active layer that performs laser light oscillation, an absorption layer that performs light modulation, or an active layer that performs optical amplification.
[0017]
The method of manufacturing a semiconductor optical device according to the present invention uses selective growth that locally increases the crystal growth rate when a predetermined semiconductor layer is simultaneously formed in the optical waveguide portion forming region and the window portion forming region. The method further comprises the step of making the upper surface of the predetermined semiconductor layer in the window forming region higher than the upper surface of the predetermined semiconductor layer in the optical waveguide forming region.
[0018]
Specifically, after a plurality of semiconductor layers are stacked on a semiconductor substrate to form a stacked body, a striped mask member and the striped mask member are formed on the stacked body of the optical waveguide portion forming region and the window portion forming region. A pair of mask members sandwiching the extension line of the mask are provided, and the stacked body is selectively etched using the stripe-shaped mask member and the pair of mask members, so that the mesa stripe and the pair of mask bodies for selective growth are obtained. When the first and second carrier block layers are simultaneously buried and formed in both the first step of forming and the regions sandwiched between both sides of the mesa stripe and the pair of mask bodies, the crystal growth rate is locally high. The upper surface of the first carrier block layer is made substantially flush with the upper surface of the stacked body, while the upper surface of the second carrier block layer is made to be in the first carrier. After the second step of making the height higher than the upper surface of the block layer, the striped mask member and the pair of mask members are removed, the laminate of the optical waveguide portion formation region, the first carrier block layer, and the window portion formation region An upper cladding layer is formed on the second carrier block layer to form an optical waveguide portion and a window portion, and an upper surface of the semiconductor layer including the first carrier block layer and the upper cladding layer in the window portion is formed. And a third step of making the height higher than the upper surface of the upper cladding layer in the optical waveguide portion.
[0019]
Alternatively, a laminate formed by laminating a plurality of semiconductor layers on a semiconductor substrate is selectively etched to form a mesa stripe in the optical waveguide portion formation region, and then both sides of the mesa stripe and the window portion formation region A first step of embedding a carrier block layer in the substrate to make the upper surface of the carrier block layer substantially flush with the upper surface of the laminate, and sandwiching an extension line of the mesa stripe on the carrier block layer in the window forming region After providing the pair of mask members for selective growth, the first and second layers are formed on the optical block forming region laminate and the carrier block layer, and the carrier block layer sandwiched between the pair of mask members in the window forming region. When the upper clad layers of the first upper clad layer and the upper upper clad layer are simultaneously formed, the upper surface of the second upper clad layer is A second step of making the surface higher than the surface; removing the pair of mask members to form the optical waveguide portion and the window portion; and an upper surface of the semiconductor layer including the carrier block layer and the second upper cladding layer in the window portion And a third step of making the height higher than the upper surface of the first upper clad layer in the optical waveguide portion (claim 7).
[0020]
In the method for manufacturing a semiconductor optical device according to any one of claims 5 to 7, the width in the direction perpendicular to the extension line of the mesa stripe in the pair of mask members provided in the window portion forming region is equal to the window portion forming region. It may be gradually widened from the boundary with the optical waveguide portion forming region toward the end surface of the window forming region (Claim 8), or may be substantially constant (Claim 9).
[0021]
The method of manufacturing a semiconductor optical device according to the present invention includes: an optical waveguide having a stripe-shaped waveguide; and a window formed of a semiconductor layer connected to one or both ends of the optical waveguide on the same semiconductor substrate. A method of manufacturing a semiconductor optical device formed on a semiconductor substrate, wherein a stacked body formed by stacking a plurality of semiconductor layers on a semiconductor substrate is selectively etched to form a mesa stripe in an optical waveguide portion forming region Thereafter, a first step of embedding and forming a carrier block layer on both sides of the mesa stripe and in the window portion forming region so that the upper surface of the carrier block layer is substantially flush with the upper surface of the laminate, Second step of forming an optical waveguide portion by forming an upper clad layer on a carrier block layer sandwiched between a pair of mask members in a laminate, a carrier block layer and a window portion formation region In addition, a supplementary semiconductor layer having a predetermined thickness is selectively stacked on the upper cladding layer in the window forming region to form a window, and the carrier block layer, the upper cladding layer, and the supplementary semiconductor in the window And a third step of making the upper surface of the semiconductor layer including the layer higher than the upper surface of the upper clad layer in the optical waveguide portion (claim 10).
[0022]
Further, after selectively laminating a laminate formed by laminating a plurality of semiconductor layers on a semiconductor substrate to form a mesa stripe in the optical waveguide portion formation region, both sides of the mesa stripe and the window portion formation region are formed. A first step of embedding and forming a carrier block layer so that the upper surface of the carrier block layer is substantially flush with the upper surface of the stacked body; and the stacked structure of the optical waveguide forming region, the carrier block layer, and the window forming region. A second step of forming an upper clad layer on the carrier block layer sandwiched between the pair of mask members to form a window portion, and the upper clad layer in the optical waveguide portion formation region to a predetermined thickness The optical waveguide portion is formed by selectively etching away, and the upper surface of the semiconductor layer including the carrier block layer and the upper cladding layer in the window portion is formed in the upper cladding in the optical waveguide portion. And having a third step higher than the upper surface (claim 11).
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(First embodiment)
FIGS. 1A and 1B are a schematic plan view showing a DFB laser device as an example of a semiconductor optical device according to the first embodiment of the present invention, a cross-sectional view taken along the line AI-AI, and FIGS. FIG. 9 is a process diagram for explaining a first manufacturing method of the DFB laser device of FIG. 1, and FIGS. 9 to 12 are process diagrams for explaining a second method of manufacturing the semiconductor optical device of FIG. . The same components as those of the DFB laser element shown in FIGS. 24 and 25 are given the same reference numerals, and the description thereof will be omitted as appropriate.
[0024]
The semiconductor optical device according to the present embodiment is a QW-structured embedded DFB laser device that outputs signal light in a long wavelength band for optical communication. As shown in FIGS. A laser part A that oscillates light and a window part B that is connected to the emission side are formed on the same semiconductor substrate 10. A highly reflective end surface portion C is provided on the end surface of the laser portion A opposite to the emission side.
[0025]
This laser part A has a mesa stripe-shaped laminated structure La that functions as a waveguide that oscillates light of a predetermined wavelength, as in the conventional case already described with reference to FIGS. A pn carrier block layer 36 is embedded on both sides, and a second upper cladding layer 20 is formed on the laminated structure La and the pn carrier block layer 36 that are in a flush state.
[0026]
On the other hand, the window B is formed of a low refractive index semiconductor layer having no waveguide structure, as in the conventional case already described with reference to FIGS. 24 and 25. The upper surface of the layer 22a is higher than the upper surface of the second upper cladding layer 20 of the laser part A, and the upper surface of the layer 22a is inclined higher from the boundary with the laser part A toward the emission end face side of the window part B. This is a fundamental difference from the conventional case.
[0027]
On the second upper clad layer 20 in the laser part A, an upper electrode 24 including a stripe electrode part 24a corresponding to the stripe shape of the multilayer structure La and a pad electrode part 24b connected to the stripe electrode part 24a is provided. The lower electrode 26 is provided on the back surface of the semiconductor substrate 10 common to the laser part A and the window part B.
Further, in the high reflection end surface portion C, the high reflection film 28 is coated on the end surface opposite to the emission side of the laser portion A.
[0028]
Although not shown, the second upper cladding layer 20 and the upper electrode 24 of the laser part A and the semiconductor layer 22a of the window part B are covered with a passivation film except for the opening on the pad electrode part 24b. Protected.
Next, a first manufacturing method of the semiconductor optical device shown in FIG. 1 will be described.
First, as shown in FIG. 2, for example, using an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, an InGaAs having a large refractive index difference from InP on a semiconductor substrate 10 made of n-InP. A light absorbing layer made of the above is epitaxially grown to form a film, and then a photoresist (not shown) is applied onto the light absorbing layer, followed by, for example, using an EB (Electron Beam) drawing apparatus or an interference exposure apparatus. A resist diffraction grating pattern having a period of ## EQU2 ## is formed, and the light absorption layer is selectively etched using the resist diffraction grating pattern as a mask to form the diffraction grating 12.
[0029]
Next, as shown in FIG. 3, light having a wavelength of 1.55 μm is generated by alternately laminating a buffer layer 14 made of n-InP in which the diffraction grating 12 is embedded, a well layer made of InGaAs, and a barrier layer made of InGaAsP. The QW structure active layer 16 and the first upper clad layer 18 made of p-InP are sequentially stacked to form a stacked structure La, and the intermediate M1 is manufactured.
[0030]
Next, as shown in FIGS. 4A and 4B, after a SiN film is deposited on the first upper cladding layer 18 of the intermediate M1, using, for example, a plasma CVD (Chemical Vapor Deposition) apparatus, The SiN film is patterned using a photolithography technique and an RIE (Reactive Ion Etching) apparatus to form a stripe-shaped mask member 30 in the laser portion forming region and a right triangle in each window forming region. A pair of mask members 30a and 30b are formed.
[0031]
Here, the pair of right-angled triangular mask members 30a and 30b are arranged symmetrically with respect to the extended line of the stripe-shaped mask member 30 in such a manner that the oblique sides of each other are outside, and the sides facing each other across the extended line Are parallel at regular intervals. That is, the distance between the pair of mask members 30a and 30b is constant from the boundary between the laser portion forming region and the window portion forming region to the end portion of the window portion forming region. The widths of the mask members 30a and 30b in the direction orthogonal to the extension line of the mask member 30 gradually increase from the boundary between the laser portion forming region and the window portion forming region toward the end portion of the window portion forming region.
[0032]
Next, the stacked structure La is selectively removed by etching until reaching the semiconductor substrate 10 using the mask members 30, 30 a and 30 b. As a result, as shown in FIG. 5, the mesa stripe 32 in which the upper surface of the mesa stripe-shaped laminated structure La extending in the longitudinal direction in the laser part forming region on the common semiconductor substrate 10 is covered with the mask member 30 is the laser. A pair of triangular columnar mask bodies 32a and 32b for selective growth, which are formed in the portion forming region and have the same laminated structure, are formed in the window forming region.
[0033]
Next, a p-InP layer and an n-InP layer are selectively grown in order on the exposed semiconductor substrate 10. As a result, as shown in FIGS. 6A and 6B, a p-InP layer and an n-InP layer are stacked on both sides of the mesa stripe 32 and around the pair of triangular prism mask bodies 32a and 32b. Embedded with a pn carrier block layer. At this time, the film thickness is controlled so that the upper surface of the pn carrier block layer 36 on both sides of the mesa stripe 32 is substantially flush with the upper surface of the first upper cladding layer 18 of the mesa stripe 32.
[0034]
On the other hand, considering the buried state of the pn carrier block layer in the window forming region at this time, the source atoms (molecules) transported on the semiconductor substrate 10 sandwiched between the pair of triangular prism mask bodies 32a and 32b. Although crystal growth proceeds, source atoms (molecules) supplied to the upper surfaces of the mask members 30a and 30b are detached from the mask members 30a and 30b without crystal growth, and a pair of triangular prism mask bodies 32a, Move to the area between 32b. In addition, as the width of the right triangular mask members 30a and 30b is relatively wide, the amount of movement of the source atoms (molecules) from the region increases, and the concentration of the source atoms (molecules) at the transfer destination increases. Get higher.
[0035]
For this reason, on the semiconductor substrate 10 sandwiched between the pair of triangular prism-shaped mask bodies 32a and 32b, the source atoms (from the boundary between the laser part formation region and the window part formation region toward the end part of the window part formation region ( The concentration of molecules) increases and the crystal growth rate increases. As a result, the upper surface of the pn carrier block layer 36a in this region is higher than the upper surface of the first upper cladding layer 18 in the laser part formation region, and further, from the boundary between the laser part formation region and the window part formation region, It becomes gradually higher toward the end, and its upper surface becomes an inclined surface.
[0036]
Next, after removing the mask members 30, 30a, 30b, the second upper cladding layer 20 made of p-InP is laminated on the entire surface. As a result, as shown in FIG. 7, in the window forming region, a semiconductor layer 22a having no waveguide structure in which the pn carrier blocking layer 36a and the second upper cladding layer 20 are stacked on the semiconductor substrate 10 is formed. The At this time, the upper surface of the semiconductor layer 22a is higher than the upper surface of the second upper cladding layer 20 in the laser part formation region, reflecting the surface shape of the pn carrier block layer 36a, and the laser part formation region and the window part formation region And increases as it goes from the boundary to the end of the window forming region.
[0037]
Next, as shown in FIG. 8, a stripe electrode portion 24a corresponding to the stripe shape of the multilayer structure La and a pad electrode portion 24b connected thereto are formed on the second upper cladding layer 20 in the laser portion formation region. The upper electrode 24 is provided, and the lower electrode 26 is provided on the back surface of the common semiconductor substrate 10.
Next, although not shown in the figure, after a passivation film is formed on the entire surface, the passivation film on the pad electrode part 24b of the upper electrode 24 is selectively removed by etching to form an opening. Thereafter, the wafer-shaped substrate is cleaved in a predetermined direction to form chips, and a laser part A that oscillates laser light and a continuous window part B on the emission side of the laser part A are formed. Further, the high reflection film 28 is coated on the end surface opposite to the emission side of the laser portion A to form the high reflection end surface portion C. In this manner, the semiconductor optical device shown in FIGS. 1A and 1B is manufactured.
[0038]
Next, a second manufacturing method of the semiconductor optical device shown in FIGS. 1A and 1B will be described.
First, in the same manner as in the steps shown in FIGS. 2 and 3, the intermediate body M1 is manufactured, and then a stripe-shaped mask member 30 is formed on the first upper clad layer 18 in the laser portion forming region. The laminated structure La is selectively removed by etching until reaching the semiconductor substrate 10 using the mask member 30 having a shape. As a result, as shown in FIG. 9, the mesa stripe 32 in which the upper surface of the mesa stripe-shaped laminated structure La extending in the longitudinal direction is covered with the mask member 30 is formed in the laser part forming region on the common semiconductor substrate 10. Is done.
[0039]
Next, a p-InP layer and an n-InP layer are selectively grown in order on the exposed semiconductor substrate 10. As a result, as shown in FIGS. 10A and 10B, the pn carrier in which the p-InP layer and the n-InP layer are stacked is formed on both sides of the mesa stripe 32 and the window forming region in the laser forming region. It is embedded with a block layer 36. At this time, the film thickness of the pn carrier block layer 36 is controlled so that the upper surface of the pn carrier block layer 36 is substantially flush with the upper surface of the first upper cladding layer 18 of the mesa stripe 32. In this way, intermediate M2 is produced.
[0040]
Next, as shown in FIGS. 11A and 11B, a pair of mask members 38a and 38b forming a right triangle are formed on the pn carrier block layer 36b in the window portion forming region of the intermediate M2. The mask members 38a and 38b have the same material, shape, and arrangement position as the pair of mask members 30a and 30b shown in FIGS. 4 (a) and 4 (b).
[0041]
Next, as shown in FIGS. 12A and 12B, a p-InP layer is selectively grown using a pair of mask members 38a and 38b, and the first upper cladding layer 18 in the laser part forming region is grown. The second upper cladding layer 20 is laminated on the pn carrier blocking layer 36, and the second upper cladding layer 20a is also formed on the pn carrier blocking layer 36 sandwiched between the pair of mask members 38a and 38b in the window forming region. Are stacked.
[0042]
At this time, in the same manner as in the process shown in FIG. 6, in the region sandwiched between the pair of right-angled mask members 38a and 38b, the window is formed from the boundary between the laser portion forming region and the window portion forming region. Since the crystal growth rate increases toward the end of the part forming region, the upper surface of the second upper cladding layer 20a in this region is higher than the upper surface of the second upper cladding layer 20 formed in the laser part forming region. The inclination increases as it goes from the boundary between the laser portion forming region and the window portion forming region toward the end portion of the window portion forming region.
[0043]
Thus, the semiconductor layer 22a having no waveguide structure in which the pn carrier blocking layer 36 and the second upper cladding layer 20a are stacked on the semiconductor substrate 10 is formed in the window forming region. At this time, the upper surface of the semiconductor layer 22a inherits the surface shape of the second upper cladding layer 20a and becomes higher than the upper surface of the second upper cladding layer 20 in the laser part formation region, and the laser part formation region and the window part formation. As it goes from the boundary with the region toward the end portion of the window forming region, it is inclined and becomes higher.
[0044]
Next, although not shown in the drawing, the semiconductor optical device shown in FIGS. 1A and 1B is formed through the process of forming the upper electrode 24 and the lower electrode 26 in the same manner as in the first manufacturing method. Is made.
[0045]
(Second Embodiment)
FIG. 13 is a schematic cross-sectional view showing a DFB laser device as an example of a semiconductor optical device according to the second embodiment of the present invention, and FIGS. 14 to 16 illustrate a first method for manufacturing the DFB laser device of FIG. FIG. 17 and FIG. 18 are process diagrams for explaining a second manufacturing method of the DFB laser device of FIG. The schematic plan view showing the DFB laser element of the present embodiment is the same as that shown in FIG. 1A of the first embodiment.
[0046]
The semiconductor optical device according to the present embodiment is the same as the semiconductor optical device according to the first embodiment except for the top surface shape of the low refractive index semiconductor layer that does not have the optical waveguide structure provided in the window portion B. Although it is structured, it differs in the following points. That is, as shown in FIG. 13, the upper surface of the low-refractive-index semiconductor layer 22b without the optical waveguide structure provided in the window portion B is higher than the upper surface of the second upper cladding layer 20 of the laser portion A, and It has a steep inclined surface near the boundary with the laser part A, and is substantially flat in other regions.
[0047]
Next, a first manufacturing method of the semiconductor optical device shown in FIG. 13 will be described.
First, in the same manner as the steps shown in FIGS. 2 and 3 of the first embodiment, the intermediate body M1 is manufactured, and then, as shown in FIGS. A stripe-shaped mask member 40 is formed on the first upper cladding layer 18 and a pair of mask members 40a and 40b each having a rectangular shape are formed in the window forming region.
For this reason, the distance between the pair of rectangular mask members 40a and 40b and the width of each mask member 40a and 40b are constant from the boundary between the laser portion forming region and the window portion forming region to the end of the window portion forming region, respectively. It has become.
[0048]
Next, similarly to the process shown in FIGS. 5 and 6 of the first embodiment, the stacked structure La is selectively removed by etching until reaching the semiconductor substrate 10 using the mask members 40, 40a, and 40b. A mesa stripe in which the upper surface of the mesa stripe-shaped laminated structure La is covered with the mask member 40 and a pair of rectangular columnar mask bodies having the same laminated structure are formed in the laser forming region and the window forming region, and then exposed. A p-InP layer and an n-InP layer were selectively grown on the semiconductor substrate 10 in order, and a p-InP layer and an n-InP layer were stacked on both sides of the mesa stripe and around a pair of square columnar mask bodies. It is embedded with a pn carrier block layer.
[0049]
In this case as well, in the same manner as in the process shown in FIG. 6, the crystal growth rate relatively increases in the region sandwiched between the pair of rectangular mask members 42a and 42b. As shown in (b), the film thickness is controlled so that the upper surface of the pn carrier block layer 36 buried on both sides of the mesa stripe in the laser portion forming region is substantially flush with the upper surface of the first upper cladding layer 18. When this is done, the upper surface of the pn carrier block layer 36b embedded in the region sandwiched between the pair of square columnar mask bodies in the window forming region becomes higher than the upper surface of the first upper cladding layer 18 in the laser forming region. In this case, since the pair of mask members 42a and 42b are rectangular instead of right triangles, steep selective growth proceeds at the boundary between the mesa stripe and the pair of square columnar mask bodies. As a result, the first A steep inclined surface is formed from the vicinity of the boundary with the upper clad layer 18, and the remaining region becomes substantially flat.
[0050]
Next, after removing the mask members 40, 40a, and 40b, the second upper cladding layer 20 made of p-InP is laminated on the entire surface. As a result, as shown in FIG. 16, in the window forming region, a semiconductor layer 22b having no waveguide structure in which the pn carrier blocking layer 36b and the second upper cladding layer 20 are laminated on the semiconductor substrate 10 is formed. The At this time, the upper surface of the semiconductor layer 22b is higher than the upper surface of the second upper cladding layer 20 in the laser part formation region, reflecting the surface shape of the pn carrier block layer 36b, and the vicinity of the boundary with the laser part formation region is locally Except for this, it becomes substantially flat.
[0051]
Next, although not shown, the semiconductor shown in FIG. 13 is formed through the process of forming the upper electrode 24 and the lower electrode 26 in the same manner as in the first or second manufacturing method of the first embodiment. An optical element is produced.
Next, a description will be given using a second manufacturing method of the semiconductor optical device shown in FIG.
First, in the same manner as the steps shown in FIGS. 2, 3, 9, and 10 of the first embodiment, an intermediate body M2 is manufactured, and the striped mask member 30 is removed. As shown in FIGS. 17 (a) and 17 (b), a pair of rectangular mask members 42a and 42b are formed again on the pn carrier block layer 36b in the window forming region.
[0052]
Next, in the same manner as in the process shown in FIG. 12 of the first embodiment, a p-InP layer is selectively grown using a pair of rectangular mask members 42a and 42b. The second upper cladding layer 20 is laminated on the upper cladding layer 18 and the pn carrier blocking layer 36, and on the pn carrier blocking layer 36 sandwiched between the pair of rectangular mask members 42a and 42b in the window forming region. Also, the second upper clad layer 20b is laminated.
[0053]
Also in this case, since the crystal growth rate is relatively increased in the region sandwiched between the pair of rectangular mask members 42a and 42b, the first region in this region is shown in FIGS. 2 The upper surface of the upper clad layer 20b is higher than the upper surface of the second upper clad layer 20 in the laser part forming region, and a steep inclined surface is formed from the vicinity of the boundary with the laser part forming region, and the remaining region is substantially flat. Become.
[0054]
Thus, in the window portion formation region, the semiconductor layer 22b having no waveguide structure in which the pn carrier block layer 36 and the second upper cladding layer 20b are stacked on the semiconductor substrate 10 is formed. At this time, the upper surface of the semiconductor layer 22b inherits the surface shape of the second upper clad layer 20b, becomes higher than the upper surface of the second upper clad layer 20 in the laser part formation region, and in the vicinity of the boundary with the laser part formation region It becomes substantially flat except for.
[0055]
Next, although not shown in the drawing, the semiconductor optical device shown in FIG. 13 is manufactured through the process of forming the upper electrode 24 and the lower electrode 26 and the like in the same manner as in the first manufacturing method of the present embodiment.
[0056]
(Third embodiment)
19 is a schematic cross-sectional view showing a DFB laser device as an example of a semiconductor optical device according to a third embodiment of the present invention, and FIGS. 20 and 21 illustrate a first method for manufacturing the DFB laser device of FIG. FIG. 22 and FIG. 23 are process diagrams for explaining a second manufacturing method of the DFB laser element of FIG. The schematic plan view showing the DFB laser element of the present embodiment is the same as that shown in FIG. 1A of the first embodiment.
[0057]
The semiconductor optical device according to the present embodiment is the same as the semiconductor optical device according to the first embodiment except for the top surface shape of the low refractive index semiconductor layer that does not have the optical waveguide structure provided in the window portion B. Although it is structured, it differs in the following points. That is, as shown in FIG. 19, the upper surface of the low refractive index semiconductor layer 22c provided in the window portion B without the optical waveguide structure is higher than the upper surface of the second upper cladding layer 20 of the laser portion A, and It is flat as a whole.
[0058]
Next, a first manufacturing method of the semiconductor optical device shown in FIG. 19 will be described.
First, in the same manner as the steps shown in FIGS. 2, 3, 9, and 10 of the first embodiment, an intermediate body M2 is manufactured, and the striped mask member 30 is removed. As shown in FIG. 20, a second upper clad layer 20 made of p-InP is laminated on the entire surface.
[0059]
Next, as shown in FIG. 21, after forming a mask member 44 made of, for example, a SiN film covering the entire surface of the laser portion forming region, a supplementary semiconductor layer 46 made of, for example, InP is selected using this mask member 44 To grow. Thus, the semiconductor layer 22c having no waveguide structure in which the pn carrier blocking layer 36, the second upper cladding layer 20, and the supplementary semiconductor layer 46 are stacked on the semiconductor substrate 10 is formed in the window forming region. At this time, the upper surface of the semiconductor layer 22c is higher than the upper surface of the second upper cladding layer 20 in the laser portion forming region by the amount of the supplementary semiconductor layer 46, and is flattened as a whole.
[0060]
Next, although illustration is omitted, after the mask member 44 is removed, a process of forming the upper electrode 24 and the lower electrode 26 in the same manner as in the first or second manufacturing method of the first embodiment. Then, the semiconductor optical device shown in FIG. 19 is manufactured.
Next, a second manufacturing method of the semiconductor optical device shown in FIG. 19 will be described.
First, in the same manner as the steps shown in FIGS. 2, 3, 9, and 10 of the first embodiment, an intermediate M 2 is manufactured and the striped mask member 30 is removed. As shown in FIG. 5, the second upper cladding layer 20c made of p-InP is laminated on the entire surface, and the thickness of the second upper cladding layer 20c is the original second upper cladding layer in the laser part forming region. To be thicker than required.
[0061]
Next, as shown in FIG. 23, after forming a mask member 48 made of, for example, a SiN film covering the entire surface of the window portion formation region, the second upper cladding layer in the laser portion formation region is formed using this mask member 48. The second upper cladding layer 20 having a predetermined thickness is formed by selectively etching 20c. In this way, the semiconductor layer 22c having no waveguide structure in which the pn carrier block layer 36 and the second upper cladding layer 20c are stacked on the semiconductor substrate 10 is formed in the window forming region. At this time, the upper surface of the semiconductor layer 22c becomes higher than the upper surface of the second upper cladding layer 20 in the laser portion forming region by the amount by which the second upper cladding layer 20c is selectively etched away, and becomes flat as a whole.
[0062]
Next, although illustration is omitted, after the mask member 48 is removed, the process of forming the upper electrode 24 and the lower electrode 26 and the like are performed in the same manner as in the first manufacturing method of the present embodiment. The semiconductor optical device shown is produced.
As described above, according to the first to third embodiments, in the window portion B provided to be connected to the emission side of the laser portion A that oscillates the laser light, the optical light composed of the active layer 16 and the like in the laser portion A. Low-refractive-index semiconductor layers 22a, 22b, and 22c having no optical waveguide structure are formed on the extended line of the waveguide. Therefore, even if the mode field of the signal light oscillated in the optical waveguide of the laser part A spreads by the angle θ in the window part B, the spread signal light is reflected on the upper surface of the window part B. Therefore, the window length Lw can be increased.
[0063]
For this reason, the original effect of suppressing the return light to the optical waveguide due to end face reflection can be fully exhibited, and the field of the signal light can be prevented from being disturbed, for example, optically coupled with an external optical fiber. In this case, the coupling efficiency can be improved.
In addition, in this case, the thickness of the second upper cladding layer 20 in the laser part A does not need to be thicker than usual, so that the resistance to the injection current does not increase and the laser characteristics are not deteriorated.
[0064]
According to the prototypes of the present inventors, in any of the first to third embodiments, a DFB laser element having a window length Lw = 50 μm, which has been difficult in the past, can be manufactured. It was confirmed that the field pattern showed good unimodality in both the horizontal direction and the vertical direction. Also, from the light output spectrum, a good result that the variation (ripple) of light output indicating reflection from the end face is 0.1 dBm or less is obtained, and the influence of return light due to end face reflection is effectively suppressed. I was able to confirm that.
[0065]
In each of the first manufacturing methods of the semiconductor optical device according to the first and second embodiments, the pn carrier block layer 36 in the laser part formation region and the pn carrier block layers 36a and 36b in the window part formation region are formed. At the same time, since selective crystal growth that locally increases the crystal growth rate is employed to form the buried layer, the upper surfaces of the pn carrier block layers 36a and 36b are made higher than the upper surface of the pn carrier block layer 36. Reduction in cost by suppressing an increase in the process when the upper surfaces of the semiconductor layers 22a and 22b including the pn carrier blocking layers 36a and 36b in the window B are made higher than the upper surface of the second upper cladding layer 20 of the uppermost layer of the laser part A Can contribute.
[0066]
In each of the second manufacturing methods of the semiconductor optical device according to the first and second embodiments, the second upper cladding layer 20 in the laser part formation region and the second upper cladding layer 20a in the window part formation region, When forming 20b simultaneously, selective crystal growth that locally increases the crystal growth rate is adopted so that the upper surfaces of the second upper cladding layers 20a and 20b are higher than the upper surface of the second upper cladding layer 20. Therefore, it is possible to suppress an increase in the process when the upper surfaces of the semiconductor layers 22a and 22b including the second upper cladding layers 20a and 20b in the window portion B are made higher than the upper surface of the second upper cladding layer 20 that is the uppermost layer of the laser portion A. And it can contribute to cost reduction.
[0067]
In the first to third embodiments, the case where the semiconductor layers 22a, 22b, and 22c in the window portion B have three kinds of surface shapes has been described. It is not limited. In short, the upper surface of the semiconductor layer is higher than the upper surface of the uppermost layer of the laser part A, and even if the mode field of the signal light oscillated in the optical waveguide of the laser part A spreads by the angle θ in the window part B, it spreads. It is only necessary that the signal light is not reflected on the upper surface of the semiconductor layer.
[0068]
Accordingly, the pattern shape of the pair of mask members used in the selective crystal growth in the first and second manufacturing methods of the semiconductor optical device according to the first and second embodiments is also a mask member 30a having a right triangle. 30b; 38a, 38b and rectangular mask members 40a, 40b; 42a, 42b, and various other pattern shapes may be used. Further, the distance between the pair of mask members can be adjusted as necessary.
[0069]
Moreover, the DFB laser element for high output is illustrated as a semiconductor optical element according to the first to third embodiments, the window part B is provided only on the emission side of the laser part A, and the other end face is a highly reflective end face part. Although the case of C is described, the installation of the window part B is not limited to only one side of the laser part A. For example, in the case of a phase shift type DFB laser element, the window part B in which the semiconductor layers 22a, 22b, and 22c are formed on both sides of the laser part A as in the first to third embodiments is provided. Is preferred.
[0070]
In the first to third embodiments, the diffraction grating 12 is formed as a whole as the waveguide structure of the laser part A to which the window part B is connected, and directly contributes to the oscillation of light of a predetermined wavelength. Although the case of an active waveguide has been described, the present invention is not limited to such a waveguide structure. For example, a waveguide structure in which a passive waveguide that does not directly contribute to the light oscillation is provided in a part of the entire waveguide, more specifically, a region adjacent to the window portion B is guided. The present invention can be applied even when the waveguide has a waveguide structure that is a passive waveguide in which no diffraction grating is formed.
[0071]
Also, the semiconductor optical device according to the present invention is not limited to the DFB laser device according to the first to third embodiments, but an optical modulator having an absorption layer, a traveling wave type semiconductor laser amplifier, or the like. As a matter of course, the present invention can be applied to the window portion.
[0072]
【Effect of the invention】
As apparent from the above description, the semiconductor optical device and the method for manufacturing the same according to the present invention can provide the following effects.
In other words, according to the semiconductor optical device of the first aspect, the upper surface of the semiconductor layer of the window portion formed by being connected to one or both ends of the optical waveguide portion is higher than the upper surface of the uppermost layer of the optical waveguide portion. Therefore, even if the mode field of light incident on the window portion from the optical waveguide portion spreads by an angle θ at the window portion, the spread signal light can be increased without being reflected by the upper surface of the window portion B. become. Therefore, it is possible to fully exert the original effect of suppressing the return light to the optical waveguide due to end surface reflection, and to prevent disturbance of the signal light field, for example, coupling with an optical fiber disposed outside This can greatly contribute to the improvement of optical characteristics such as improvement of efficiency.
[0073]
According to the method for manufacturing a semiconductor optical device according to claim 5, the selective growth in which the crystal growth rate is locally increased when a predetermined semiconductor layer is simultaneously formed in the optical waveguide portion forming region and the window portion forming region. To make the upper surface of the predetermined semiconductor layer in the window forming region higher than the upper surface of the predetermined semiconductor layer in the optical waveguide portion forming region. It is possible to suppress the increase in the number of steps when the height is higher than the uppermost surface in the portion, and to contribute to cost reduction.
[0074]
According to the method for manufacturing a semiconductor optical device according to claim 6, after forming the mesa stripe and the pair of selective growth mask bodies in the optical waveguide portion forming region and the window portion forming region, respectively, When the first and second carrier block layers are simultaneously buried and formed in the region sandwiched between the pair of mask bodies, the selective growth that locally increases the crystal growth rate is used. In order to make the upper surface higher than the upper surface of the first carrier block layer, the upper surface of the semiconductor layer including the second carrier block layer in the window portion is made higher than the upper surface of the upper cladding layer forming the uppermost layer in the optical waveguide portion The increase in the number of steps can be suppressed, and the cost can be reduced.
[0075]
According to the method for manufacturing a semiconductor optical device according to claim 7, after providing the pair of mask members for selective growth sandwiching the extension line of the mesa stripe on the carrier block layer in the window forming region, the optical waveguide is formed. When the first and second upper cladding layers are simultaneously formed on the carrier block layer sandwiched between the stacked body of the region, the carrier block layer, and the pair of mask members in the window portion formation region, a local crystal In order to make the upper surface of the second upper cladding layer higher than the upper surface of the first upper cladding layer by using selective growth that increases the growth rate, the upper surface of the semiconductor layer including the second upper cladding layer in the window portion is formed. An increase in the number of steps in the case of making the height higher than the upper surface of the first upper clad layer that forms the uppermost layer in the optical waveguide portion can be suppressed, thereby contributing to cost reduction.
[0076]
According to the method for manufacturing a semiconductor optical device according to claim 10, after the upper clad layer in the optical waveguide portion and the window portion is formed so that the upper surfaces are substantially equal in height, on the upper clad layer in the window portion. In order to selectively form a supplementary semiconductor layer having a predetermined thickness, it is easy to make the upper surface of the semiconductor layer including the supplementary semiconductor layer in the window portion higher than the upper surface of the upper cladding layer forming the uppermost layer in the optical waveguide portion. Can be realized.
[0077]
According to the method for manufacturing a semiconductor optical device according to claim 11, after forming the upper cladding layer in the optical waveguide portion and the window portion so that the upper surfaces thereof are substantially equal in height, the upper cladding layer in the optical waveguide portion is formed. In order to selectively etch away by a predetermined thickness, it is easy to realize that the upper surface of the semiconductor layer including the upper cladding layer in the window portion is higher than the upper surface of the upper cladding layer forming the uppermost layer of the optical waveguide portion. Can do.
[Brief description of the drawings]
FIGS. 1A and 1B are a schematic plan view showing a DFB laser device as an example of a semiconductor optical device according to a first embodiment of the present invention and a cross-sectional view taken along the line AI-AI.
FIG. 2 is a process diagram (part 1) for explaining a first manufacturing method of the DFB laser element of FIG. 1, and is a schematic cross-sectional view showing the DFB laser element in the process;
3 is a process diagram (No. 2) for explaining the first manufacturing method of the DFB laser element of FIG. 1, and is a schematic cross-sectional view showing the DFB laser element in the process; FIG.
FIGS. 4A and 4B are process diagrams (part 3) for explaining the first manufacturing method of the DFB laser element of FIG. 1, wherein FIGS. 4A and 4B are schematic plan views showing the DFB laser element in the process; It is a figure and its AII-AII sectional view taken on the line.
FIG. 5 is a process diagram (part 4) for explaining the first manufacturing method of the DFB laser element of FIG. 1, and is a schematic perspective view showing the DFB laser element in the process;
6 is a process diagram (No. 5) for explaining the first manufacturing method of the DFB laser device of FIG. 1, wherein (a) and (b) are schematic plan views showing the DFB laser device in the middle of the process, respectively. It is a figure and its AIII-AIII sectional view taken on the line.
7 is a process diagram (No. 6) for explaining the first manufacturing method of the DFB laser element shown in FIG. 1, and is a schematic cross-sectional view showing the DFB laser element in the process; FIG.
8 is a process diagram (No. 7) for explaining the first manufacturing method of the DFB laser element shown in FIG. 1, and is a schematic cross-sectional view showing the DFB laser element in the process. FIG.
9 is a process diagram (No. 8) for explaining the first manufacturing method of the DFB laser element of FIG. 1, and is a schematic perspective view showing the DFB laser element in the middle of the process. FIG.
10 is a process diagram (part 1) for explaining a second manufacturing method of the DFB laser device of FIG. 1, wherein (a) and (b) are schematic plan views showing the DFB laser device in the middle of the process, respectively. It is a figure and its AIV-AIV sectional view taken on the line.
FIGS. 11A and 11B are process diagrams (part 2) for explaining a second manufacturing method of the DFB laser device of FIG. 1, wherein FIGS. 11A and 11B are schematic plan views showing the DFB laser device in the process; It is a figure and its AV-AV sectional view taken on the line.
12 is a process diagram (part 3) for explaining the second manufacturing method of the DFB laser element of FIG. 1, wherein (a) and (b) are schematic plan views showing the DFB laser element in the middle of the process, respectively. It is a figure and its AVI-AVI line sectional view.
FIG. 13 is a schematic cross-sectional view showing a DFB laser device as an example of a semiconductor optical device according to a second embodiment of the present invention.
14A and 14B are process diagrams (part 1) for explaining a first manufacturing method of the DFB laser element shown in FIG. 13, wherein FIGS. 14A and 14B are schematic plan views showing the DFB laser element in the process; It is a figure and its AVII-AVII sectional view taken on the line.
15 is a process diagram (part 2) for explaining the first method of manufacturing the DFB laser device of FIG. 13, wherein (a) and (b) are schematic plan views showing the DFB laser device in the middle of the process, respectively. It is a figure and its AVIII-AVIII sectional view taken on the line.
16 is a process diagram (part 3) for explaining the first manufacturing method of the DFB laser device of FIG. 13, and is a schematic cross-sectional view showing the DFB laser device in the middle of the process;
FIGS. 17A and 17B are process diagrams (part 1) for explaining a second manufacturing method of the DFB laser device shown in FIG. 13; FIGS. 17A and 17B are schematic plan views showing the DFB laser device in the process; It is a figure and its AIX-AIX line sectional view.
18A and 18B are process diagrams (part 2) for explaining the second manufacturing method of the DFB laser device of FIG. 13, wherein FIGS. 18A and 18B are schematic plan views showing the DFB laser device in the process. It is a figure and its AX-AX sectional view taken on the line.
FIG. 19 is a schematic cross-sectional view showing a DFB laser device as an example of a semiconductor optical device according to a third embodiment of the present invention.
FIG. 20 is a process diagram (part 1) for describing the first manufacturing method of the DFB laser device of FIG. 19, and is a schematic cross-sectional view showing the DFB laser device in the middle of the process;
FIG. 21 is a process diagram (part 2) for describing the first manufacturing method of the DFB laser device of FIG. 19, and is a schematic cross-sectional view showing the DFB laser device in the middle of the process;
FIG. 22 is a process diagram (part 1) for describing the second manufacturing method of the DFB laser device of FIG. 19, and is a schematic cross-sectional view showing the DFB laser device in the middle of the process;
FIG. 23 is a process diagram (part 2) for describing the second manufacturing method of the DFB laser device of FIG. 19, and is a schematic cross-sectional view showing the DFB laser device in the middle of the process;
FIG. 24 is a partially cutaway perspective view showing a conventional DFB laser device.
25 is a cross-sectional view taken along the line AXI-AXI of the DFB laser element of FIG. 24. FIG.
FIG. 26 shows the relationship between the effective reflectivity R due to the window in the DFB laser element and the window length Lw, and the thickness of the upper cladding layer that prevents the signal light from the optical waveguide from being reflected from the upper surface of the upper cladding layer. It is a graph which shows the relationship between window and window part length Lw.
[Explanation of symbols]
A Laser unit
B Window
C High reflection end face
10 Semiconductor substrate
12 Diffraction grating
14 Buffer layer
16 Active layer
18 First upper cladding layer
20, 20a, 20b, 20c Second upper cladding layer
22a, 22b, 22c Semiconductor layer
24 Upper electrode
24a Striped electrode part
24b Pad electrode part
26 Lower electrode
28 High reflective film
30, 40 Striped mask member
30a, 30b; 38a, 38b A pair of right triangle mask members
32 Mesa stripe
32a, 32b A pair of triangular prismatic mask bodies
34a p-InP layer
34b n-InP layer
36, 36a, 36b pn carrier block layer
40a, 40b; 42a, 42b A pair of rectangular mask members
44, 48 Mask member
46 Supplementary semiconductor layer
La, Lb laminated structure
M1, M2 intermediate

Claims (5)

A method of manufacturing a semiconductor optical device, wherein an optical waveguide portion having a stripe-shaped waveguide and a window portion made of a semiconductor layer connected to one end or both ends of the optical waveguide portion are formed on the same semiconductor substrate. ,
A stacked body formed by laminating a plurality of semiconductor layers on a semiconductor substrate is selectively etched to form a mesa stripe in the optical waveguide portion forming region, and then a carrier block on both sides of the mesa stripe and in the window portion forming region. A first step of embedding a layer so that the upper surface of the carrier block layer is substantially flush with the upper surface of the laminate;
The laminate and the carrier blocking layer of the optical waveguide part forming area, and, on the front Symbol carrier blocking layer of the window portion forming region, to form an upper cladding layer, a second for forming the optical waveguide section Process,
A third step of forming a mask member serving as a mask on the upper clad layer in the optical waveguide portion forming region;
On the upper cladding layer of said window portion forming region, and selectively stacked recruitment semiconductor layer having a predetermined thickness, thereby forming the window portion, the carrier blocking layer in the window portion, the upper cladding layer And a fourth step of making the upper surface of the semiconductor layer including the supplementary semiconductor layer higher than the upper surface of the upper cladding layer in the optical waveguide portion;
A fifth step of removing the mask member;
A method for producing a semiconductor optical device, comprising: A method of manufacturing a semiconductor optical device, wherein an optical waveguide portion having a stripe-shaped waveguide and a window portion made of a semiconductor layer connected to one end or both ends of the optical waveguide portion are formed on the same semiconductor substrate. ,
A stacked body formed by laminating a plurality of semiconductor layers on a semiconductor substrate is selectively etched to form a mesa stripe in the optical waveguide portion forming region, and then a carrier block on both sides of the mesa stripe and in the window portion forming region. A first step of embedding a layer so that the upper surface of the carrier block layer is substantially flush with the upper surface of the laminate;
The laminate and the carrier blocking layer of the optical waveguide part forming area, and, on the front Symbol carrier blocking layer of the window portion forming region, to form an upper cladding layer, a second step of forming the window portion When,
Selectively etching away said upper cladding layer of the optical waveguide part forming area to a predetermined thickness, thereby forming the optical waveguide section, including the carrier blocking layer and the upper clad layer in the window And a third step of making the upper surface of the semiconductor layer higher than the upper surface of the upper clad layer in the optical waveguide portion. The method of manufacturing a semiconductor optical device according to claim 1, wherein a length of the window portion in the waveguide direction is 50 μm or more. 3. The semiconductor according to claim 2, wherein in the third step, a mask member is formed on the carrier block layer in the window portion formation region, and the upper cladding layer in the optical waveguide portion formation region is selectively etched. Manufacturing method of optical element. The method of manufacturing a semiconductor optical device according to claim 1, wherein the mask member is made of a SiN film.

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