JP2012002929A - Method for manufacturing semiconductor optical element, laser module, and optical transmission apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor optical element which improves the characteristics of a semiconductor optical element with a buried hetero structure by providing a structure capable of reducing parasitic capacitance, and to provide a laser module and an optical transmission apparatus.SOLUTION: The invention relates to a method for manufacturing the semiconductor optical element that has a modulator portion for modulating and emitting light input along an emitting direction. The modulator portion includes: a quantum well layer containing aluminum; a semiconductor multi-layer having a mesa-stripe structure; and a semiconductor buried layer which is disposed on both sides of the semiconductor multi-layer and adjacent to them, and in which impurities are added. The method comprises: the step of forming the mesa-stripe structure by removing a predetermined area from the semiconductor multi-layer; the step of cleaning both surfaces of the semiconductor multi-layer by use of chlorine gas; and the step of forming the semiconductor buried layers on both sides of the semiconductor multi-layer, in this order.

Description

  The present invention relates to a semiconductor optical device, a laser module, and an optical transmission device, and more particularly to improvement of characteristics of a semiconductor optical device including a modulator having a buried hetero structure.

  With the rapid development of broadband networks in recent years, higher communication speeds are increasingly required. On the other hand, a semiconductor optical device, a laser module and an optical transmission device on which the semiconductor optical device is mounted are required to be downsized, reduced in power consumption, and reduced in cost.

  An electroabsorption modulator (hereinafter referred to as an EA (Electro-Absorption) modulator) has a small chirp (wave modulation) during modulation, a large extinction ratio that is the difference between the ON level and the OFF level of an optical signal, and a wide bandwidth. In addition to having such advantageous characteristics as being small, it is widely used because of its small size and low cost.

  The EA modulator is a modulation that modulates light by selectively applying an electric field to the active region of the EA modulator using the quantum confinement Stark effect (hereinafter referred to as QCSE). It is a vessel. Here, the active region is a so-called single-quantum well (hereinafter referred to as SQW) layer or a multiple-quantum well (hereinafter referred to as MQW) layer. Hereinafter, in this specification, MQW includes SQW in addition to normal MQW. Note that QCSE refers to an effect that when an electric field is applied to the MQW layer, the absorption edge of light in the MQW layer shifts to the long wavelength side. In order to obtain a low chirp and a high extinction ratio, an Al-based material such as indium gallium aluminum arsenide (InGaAlAs) is desirable as a material suitable for the MQW layer of the EA modulator.

  Also, the main structure of a semiconductor optical device is a buried heterostructure (hereinafter referred to as a BH structure). The BH structure is a multilayer structure including an MQW layer in which both sides of a mesa stripe structure formed by removing a region outside a waveguide region are embedded with a semiconductor buried layer made of a semi-insulating semiconductor. Refers to the structure.

  After forming the mesa stripe structure by removing both sides of the semiconductor multilayer, there is a concern that the characteristics and reliability of the semiconductor optical device may be lowered when both sides of the MQW layer containing Al of the mesa stripe structure are embedded with a semi-insulating semiconductor. . Moreover, it becomes more remarkable as the content of Al contained in the MQW layer increases.

  In view of the above problems, an object of the present invention is to provide a semiconductor optical device manufacturing method, a laser module, and an optical transmission device, in which characteristics are further improved in a semiconductor optical device including an Al-based material in an MQW layer and having a BH structure. I will provide it.

  (1) A method of manufacturing a semiconductor optical device according to the present invention is a method of manufacturing a semiconductor optical device comprising a modulator unit that modulates and outputs light input along an emission direction, and the modulator unit Comprises a quantum well layer containing aluminum, a semiconductor multilayer having a mesa stripe structure, and a semiconductor buried layer disposed adjacent to both sides of the semiconductor multilayer and doped with impurities, Removing a predetermined region of the semiconductor multilayer to form a mesa stripe structure; cleaning a surface of both sides of the semiconductor multilayer using a chlorine-based gas; and filling the semiconductor buried layer on both sides of the semiconductor multilayer And a step of forming the layers in order.

  (2) The method for manufacturing a semiconductor optical device according to (1), further comprising a step of forming the quantum well layer using indium gallium aluminum arsenide as a material.

  (3) The method for manufacturing a semiconductor optical device according to (2), wherein in the step of forming the quantum well, the quantum well layer is formed by adjusting to a composition used in a 1.3 μm wavelength band. Also good.

  (4) In the method for manufacturing a semiconductor optical device according to (1), the impurity added to the semiconductor buried layer may be ruthenium.

  (5) In the method of manufacturing a semiconductor optical device according to (4), the semiconductor buried layer having a layer thickness of 3.5 μm or more may be formed in the step of forming the semiconductor buried layer.

  (6) The method of manufacturing a semiconductor optical device according to any one of (1) to (5), wherein the semiconductor optical device includes an oscillator unit that outputs the input light, the oscillator unit, and the oscillator unit. And connecting between the modulator sections, and further comprising a waveguide section including a core layer, between the oscillator section and the waveguide section, and between the waveguide section and the oscillator section, A step of connecting the pad joint and forming the core layer may be further included.

  (7) In the method for manufacturing a semiconductor optical device according to (6), in the step of forming the core layer, the core layer is formed using indium gallium arsenide phosphorus or indium gallium aluminum arsenide. Also good.

  (8) In the method of manufacturing a semiconductor optical device according to (6) or (7), the modulator unit is an electroabsorption modulator, and the oscillator unit is a distributed feedback type including a diffraction grating. The semiconductor laser may further include a step of forming a diffraction grating such that the wavelength energy of the oscillation wavelength of the oscillator unit is 23 meV or more and 40 meV or less lower than the wavelength energy at the absorption wavelength end of the modulator unit. .

  (9) In the method of manufacturing a semiconductor optical device according to (8), the modulator unit includes a plurality of light output units, and outputs light from each of the plurality of light output units. A plurality of the semiconductor multilayers having the mesa stripe structure are provided corresponding to a plurality of light output units, and the oscillator unit includes a plurality of diffraction gratings corresponding to the plurality of light output units, respectively. In the step of forming the plurality of diffraction gratings, the plurality of diffraction gratings may be formed so as to have oscillation wavelengths respectively corresponding to the plurality of light output portions.

  (10) The method for manufacturing a semiconductor optical device according to (8) or (9), wherein in the step of forming the mesa stripe structure, the light emitted from the semiconductor optical device is emitted to a predetermined region of the semiconductor multilayer. In the step of forming the semiconductor buried layer, the window structure may be formed by forming the semiconductor buried layer in the step of forming the semiconductor buried layer.

  (11) The laser module according to the present invention may include a semiconductor optical device manufactured by the method for manufacturing a semiconductor optical device according to any one of (1) to (10).

  (12) The optical transmission device according to the present invention may include a semiconductor optical device manufactured by the method for manufacturing a semiconductor optical device according to any one of (1) to (10).

  According to the present invention, there are provided a semiconductor optical device manufacturing method, a laser module, and an optical transmission device in which characteristics are further improved in a semiconductor optical device including an Al-based material in an MQW layer and having a BH structure.

1 is a top view of an EA modulator integrated DFB laser device according to a first embodiment of the present invention. FIG. 1 is a cross-sectional view of an EA modulator integrated DFB laser device according to a first embodiment of the present invention. 1 is a cross-sectional view of an EA modulator integrated DFB laser device according to a first embodiment of the present invention. It is a figure which shows the calculation result of the f3 dB zone | band with respect to the layer thickness d of the buried layer which consists of InP which Ru adds as an impurity. It is a figure showing the optical output P _mod at the time of modulation | alteration with respect to detuning amount (DELTA) H. It is a figure showing extinction ratio ACER at the time of modulation with respect to detuning amount (DELTA) H. It is a figure showing the f3 dB zone | band with respect to detuning amount (DELTA) H. It is a figure showing the optical amplitude OMA at the time of modulation | alteration with respect to detuning amount (DELTA) H. It is a top view of the EA modulator integrated DFB laser device according to the second embodiment of the present invention. It is sectional drawing of the EA modulator integrated type DFB laser element concerning the 2nd Embodiment of this invention. It is sectional drawing of the EA modulator integrated type DFB laser element concerning the 2nd Embodiment of this invention. It is a figure showing the structure of the laser module which concerns on the said embodiment which concerns on the 3rd Embodiment of this invention. It is a top view of the EA modulator integrated type DFB laser array device according to the fourth embodiment of the present invention.

  Embodiments according to the present invention will be described in detail below. However, the drawings shown below are merely examples of each embodiment, and the size of the drawings and the scales described in the present examples do not necessarily match.

[First Embodiment]
The semiconductor optical device according to the first embodiment of the present invention is a modulator integrated semiconductor optical device in which a modulator section and an oscillator section are monolithically integrated on the same semiconductor substrate. Here, the modulator section is an EA modulator, the oscillator section is a distributed feedback semiconductor laser (hereinafter referred to as DFB laser), and is an EA modulator integrated DFB laser element 50. The EA modulator integrated DFB laser element 50 has a BH structure with a semiconductor buried layer doped with ruthenium (Ru) as an impurity, and is used for optical transmission at a transmission speed of 25 Gbit / s in the 1.3 μm wavelength band. , And can be driven at a temperature of 40 ° C. to 60 ° C. Here, the 1.3 μm wavelength band refers to a wavelength band of 1280 nm to 1360 nm.

  FIG. 1A is a top view of the EA modulator integrated DFB laser device 50 according to this embodiment. As described above, in the EA modulator integrated DFB laser element 50, the modulator unit 6 made of the EA modulator and the oscillator unit 11 made of the DFB laser are integrated on the same n-type InP substrate 1. Between the modulator unit 6 and the oscillator unit 11, a waveguide unit 12 serving as a bulk waveguide is provided. In the multilayer structure of the EA modulator integrated DFB laser element 50, there is a waveguide region extending in the lateral direction in the figure near the center. Continuous light that is output from the waveguide region of the oscillator unit 11 in the left direction in the figure passes through the waveguide region of the waveguide unit 12 and is input to the modulator unit 6. In the waveguide region of the modulator section 6, the input light is modulated and emitted to the left side in the figure. The mesa stripe structure of the modulator section 6 is not formed on the right side from the left end face in the figure, but has a window structure 18. The end face on the left side in the figure from which light is emitted is covered with an antireflection film 24 having a reflectance of 1% or less, and the right end face in the figure on the opposite side is covered with a high reflection film 23 having a reflectance of 90% or more. Yes.

  1B and 1C are cross-sectional views of the EA modulator integrated DFB laser device 50 according to this embodiment. 1B shows a cross section through the IB-IB broken line of the EA modulator integrated DFB laser element 50 shown in FIG. 1A, and FIG. 1C shows a cross section through the IC-IC wavy line of the modulator section 6.

  As shown in FIG. 1B, the modulator section 6, the waveguide section 12, and the oscillator section 11 of the EA modulator integrated DFB laser element 50 are each formed of a semiconductor multilayer. An n-type InP buffer layer 2 is formed on the n-type InP substrate 1. In the modulator section 6, an InGaAlAs lower guide layer 3, an MQW layer 4, and a p-type InGaAlAs upper guide layer 5 are formed in this order on the n-type InP buffer layer 2 to form an optical confinement layer. Here, in the MQW layer 4, well layers and barrier layers made of InGaAlAs are alternately stacked. An Al-based material is used for the optical confinement layer of the modulator unit 6.

  In the oscillator unit 11, an n-type InGaAsP lower guide layer 7, an MQW layer 8, a p-type InGaAsP upper guide layer 9, and a diffraction grating layer 10 are formed on the n-type InP buffer layer 2 and serve as an optical confinement layer. ing. Here, in the MQW layer 8, well layers and barrier layers made of InGaAsP are alternately stacked. The diffraction grating layer 10 is made of p-type InGaAsP.

  In the waveguide section 12, a core layer composed of three layers is formed on the n-type InP buffer layer 2, and serves as an optical confinement layer. The core layer has a structure in which InGaAsP layers 13 and 14 having a composition wavelength of 1.1 μm sandwich an InGaAsP layer 15 having a composition wavelength of 1.15 μm. The core layer forms a bulk waveguide made of a bulk crystal. A pad joint connection is made between the MQW layer 4 of the modulator section 6 and the InGaAsP layer 15 of the waveguide section 12, and between the InGaAsP layer 15 of the waveguide section 12 and the MQW layer 8 of the oscillator section 11. .

  Further, a p-type InP cladding layer 16 is provided above the optical confinement layer of the modulator unit 6, the waveguide unit 12, and the oscillator unit 11, and a p-type contact layer 17 is further provided on the modulator unit 6 and the oscillator unit 11. However, the semiconductor multilayer structure is formed.

The diffraction pitch of the diffraction grating is designed so that the oscillation wavelength λ _DFB of the oscillator unit 11 is 1295.5 nm at 50 ° C., and the diffraction grating layer 10 is formed. Further, the composition of the MQW layer 4 of the modulator unit 6 is adjusted so that the absorption edge wavelength λ _EA of the modulator unit 6 is 1250.0 nm at 50 ° C. That is, the detuning amount ΔH defined by the difference between the oscillation wavelength λ _DFB and the absorption edge wavelength λ _EA is adjusted to be 45.5 nm (34.8 meV in terms of energy). Here, the oscillation wavelength λ _DFB is longer than the absorption edge wavelength λ _EA , and in terms of energy, the wavelength energy of the oscillation wavelength λ _DFB is lower than the wavelength energy of the absorption edge wavelength λ _EA .

  As shown in FIG. 1C, the EA modulator integrated DFB laser device 50 according to this embodiment has a mesa stripe structure in which a region outside the waveguide region is removed from the semiconductor multilayer structure. Both sides have a BH structure embedded with a buried layer 19. The buried layer 19 is made of InP to which Ru is added as an impurity, and is a semi-insulating semiconductor. The mesa stripe structure has a width of 1.4 μm and a height of 3.4 μm. The layer thickness of the buried layer 19 is 5.0 μm.

  The buried layer 19 is made of a semi-insulating semiconductor, for example, a semiconductor to which an impurity such as iron (Fe) or Ru is added. Since the impurity that is the p-type dopant of the p-type layer included in the mesa stripe structure and the impurity that is included in the buried layer are mutually diffused, the impurity that is the p-type dopant of the p-type layer is There arises a problem of diffusion from both sides into the buried layer. When the impurity of the p-type layer diffuses into the buried layer, the electric field applied to the MQW layer 4 also spreads to the buried layer 19 when the modulator unit 6 is driven, and the characteristics as the modulator are deteriorated.

  As the p-type dopant of the p-type layer included in the mesa stripe structure, zinc (Zn) is generally used, and when Fe is used as the impurity of the buried layer 19, the mutual diffusion of Zn and Fe is strong. Zn is further diffused into the buried layer 19. From the viewpoint of mutual diffusion with Zn, the impurity added to the buried layer 19 is preferably Ru. Since Ru has weak interdiffusion with Zn as compared with Fe or the like, the diffusion of Zn into the buried layer is suppressed, and the characteristics as a modulator are improved.

  FIG. 2 is a diagram showing a calculation result of the f3 dB band with respect to the layer thickness d of the buried layer made of InP to which Ru is added as an impurity. In this calculation, it is assumed that the modulator length of the EA modulator is 100 μm, the width of the mesa stripe structure is 1.5 μm, and the thickness of the undoped layer including the MQW layer is 260 nm. For example, it can be understood that the thickness d of the buried layer is required to be 3.5 μm or more in order to satisfy the band of 25 GHz enabling 25 Gbit / s operation. Further, by using Ru, which has a small interdiffusion, as the impurity in the buried layer, the leakage current can be reduced in the oscillator unit, so that the threshold current can be reduced and high light output can be realized. Similarly, in the modulator section, electric field leakage during driving can be reduced, so that a voltage is efficiently applied to the MQW layer, and high light output can be realized.

  Further, as described above, a semiconductor multilayer having a mesa stripe structure is not formed on the right side from the left end face in the drawing of FIG. 1B, and the window structure 18 is buried by the buried layer 19. The length of the window structure 18 is desirably 5 μm or more. In the EA modulator integrated DFB laser element 50, the length of the window structure 18 is 15 μm. The window structure 18 refers to a structure embedded in a bulk semiconductor that does not have a light confinement layer at the tip portion with respect to the light emission direction of the waveguide region of the semiconductor optical device. Light that passes through the waveguide region inside the semiconductor optical device passes through the window structure 18 and reaches the antireflection film 24. The reflectance of the antireflection film 24 is very low, and much light passes through the antireflection film 24 and is emitted from the semiconductor optical device to the outside. However, part of the light is reflected by the antireflection film 24 into the semiconductor optical device. Even in this case, since the reflected light is prevented from entering the waveguide region again and reaching the oscillator unit 11 by the window structure 18, the high frequency response characteristic (S21 characteristic) is improved. .

  In the EA modulator integrated DFB laser element 50, the detuning amount ΔH is preferably 23 meV or more and 40 meV or less in terms of energy. These ranges are described as follows.

FIG. 3 is a diagram illustrating the modulation optical output P _mod with respect to the detuning amount ΔH, FIG. 4 is a diagram illustrating the modulation extinction ratio ACER with respect to the detuning amount ΔH, and FIG. 5 is a diagram illustrating the f3 dB band with respect to the detuning amount ΔH. . In the EA modulator integrated DFB laser element used for the measurement, the length of the modulator portion is 100 μm, and the thickness of the undoped layer including the MQW layer of the EA modulator is 260 nm. In addition, the measurement is performed with the laser drive current I _f = 50 mA. The detuning amount ΔH shown in the figure uses the wavelength energy E of the oscillation wavelength λ _DFB of the oscillator unit and the absorption wavelength λ _{EA of the} modulator unit using E = (h / 2π) · (c / λ), respectively. The energy is converted and the difference between them is used. Here, h and c represent the Planck constant and the speed of light in vacuum, respectively.

FIG. 6 is a diagram illustrating the modulation optical amplitude OMA with respect to the detuning amount ΔH. The 100 Gbit / s Ethernet standard, has during modulation optical amplitude OMA (Optical Modulation Amplitude), from the modulated during the extinction ratio ACER modulation at an optical output _{P fmod, OMA = 10log {(} 2 × 10 Pfmod / 10) × (10 ^{ACER / 10} -1) / (10 ^{ACER / 10} +1)}. Here, the modulated optical output P _fmod represents the modulated optical output of the laser module equipped with the EA modulator integrated DFB laser element, and the modulated optical output P _{mod of} the EA modulator integrated DFB laser element Minus the coupling loss. FIG. 6 is illustrated assuming that the coupling loss in the laser module is 3 dB.

As shown in FIG. 3, when the detuning amount ΔH decreases, the absorption in the modulator section increases, so that the modulation light output P _mod decreases, and the modulation extinction ratio ACER increases as shown in FIG. Accordingly, as shown in FIG. 6, the modulation light amplitude OMA also decreases. In order to satisfy −1.3 to +4.5 dBm, which is the specification of the modulated optical amplitude OMA defined in the IEEE 802.3ba standard, the modulated optical output P _mod and the modulated extinction ratio ACER are set to +1.0 to +5.5 dBm (that is, assuming that the coupling loss in the laser module is 3 dB, the modulated light output P _fmod is −2.0 to +2.5 dBm) and a condition of 8.0 dB or more are obtained. The arrows shown in FIGS. 3 and 4 indicate this range, respectively. The range of the detuning amount ΔH obtained from FIGS. 3 and 4 is 23 meV or more and 40 meV or less and 40 meV or less, respectively. At this time, as shown in FIG. 6, the modulated optical amplitude OMA is sufficiently satisfied with respect to the IEEE 802.3ba standard even if the deterioration of characteristics over time is taken into consideration. The arrows shown in FIG. 6 represent IEEE standards.

  On the other hand, as shown in FIG. 5, it is considered that when the detuning amount ΔH is small, the light absorption in the modulator section is large and the high frequency characteristics tend to be deteriorated. In order to enable driving at a transmission speed of 25 Gbit / s, the f3 dB band needs to be 25 GHz or more, and the detuning amount ΔH that satisfies it is 23 meV or more. As described above, the detuning amount ΔH that satisfies all these characteristics is 23 meV or more and 40 meV or less in terms of energy.

  Next, a method for manufacturing the EA modulator integrated DFB laser device 50 according to this embodiment will be described.

First, a semiconductor multilayer that is part of the multilayer structure of the modulator section 6 is formed (modulator semiconductor lower layer forming step). That is, the n-type InP buffer layer 2, the InGaAlAs lower guide layer 3, the MQW layer 4, the p-type InGaAlAs upper guide layer 5, and the p-type InP cap layer are sequentially formed on the n-type InP substrate 1 with an organic metal layer. It is formed by a phase growth method (Metal-Organic Chemical Vapor Deposition: hereinafter referred to as MO-CVD). The p-type InP cap layer is removed in a later step, and the semiconductor multilayer other than the p-type InP cap layer becomes the optical confinement layer of the modulator section 6. Here, the InGaAlAs lower guide layer 3 and the MQW layer 4 are undoped layers to which no impurity is added. Both of the MQW layers 4 are formed by alternately stacking well layers and barrier layers made of InGaAlAs. At this time, the composition of InGaAlAs in the MQW layer 4 is adjusted so that the absorption edge wavelength λ _EA of the modulator section 6 is 1250 nm at 50 ° C.

Then, a silicon dioxide (SiO ₂ ) film is patterned by thermal CVD (Thermal Chemical Vapor Deposition) only in a region of the wafer surface where the modulator portion 6 is to be formed. Using this SiO ₂ film as a mask, dry etching and The semiconductor multilayer in the region other than the region to be the modulator section 6 is removed by wet etching until reaching the upper surface of the n-type InP buffer layer 2.

  Next, a semiconductor multilayer that becomes a part of the multilayer structure of the oscillator unit 11 is formed (oscillator semiconductor lower layer forming step). On the upper side of the n-type InP buffer layer 2, an n-type InGaAsP lower guide layer 7, an MQW layer 8, a p-type InGaAsP upper guide layer 9, a p-type InGaAsP layer having a thickness of 20 nm to be a diffraction grating layer 10, and a p-type An InP cap layer is formed by MO-CVD. A semiconductor multilayer other than the p-type InP cap layer serves as an optical confinement layer of the oscillator unit 11. Here, the MQW layer 8 is an undoped layer, and is formed by alternately laminating well layers and barrier layers made of InGaAsP.

Then, similar to the oscillator semiconductor lower layer forming step, the SiO ₂ film is formed by thermal CVD only on the region of the wafer surface where the modulator unit 6 and the oscillator unit 11 are formed, and by dry etching and wet etching, The semiconductor multilayer in the region other than the region to be the modulator unit 6 and the oscillator unit 11, that is, the region to be the waveguide unit 12 is removed until reaching the upper surface of the n-type InP buffer layer 2.

  Furthermore, a semiconductor multilayer that becomes a part of the multilayer structure of the waveguide section 12 is formed (waveguide section semiconductor lower layer forming step). Similarly, a core layer and a p-type InP cap layer are formed on the upper side of the n-type InP buffer layer 2 by MO-CVD. The core layer becomes an optical confinement layer of the waveguide section 12. Here, the core layer is composed of three layers, both of which are undoped layers. The core layer is formed such that the InGaAsP layers 13 and 14 having a composition wavelength of 1.1 μm sandwich the InGaAsP layer 15 having a composition wavelength of 1.15 μm. At this time, the film thickness of each of the InGaAsP layers 13, 14, and 15 constituting the core layer is set so that the effective refractive index of the modulator unit 6 and the oscillator unit 11 and the effective refractive index of the waveguide unit 12 substantially coincide with each other. It is adjusting. At this time, the modulator section 6 and the waveguide section 12 and the waveguide section 12 and the oscillator section 11 are optically connected by a known pad joint technique.

  Here, the core layer is formed using an InGaAsP-based material, but may be formed using an InGaAlAs-based material. The composition wavelength of the core layer is desirably 1.2 μm or less.

  The process of forming the semiconductor multilayer serving as the light confinement layer in the order of the modulator unit 6, the oscillator unit 11, and the waveguide unit 12 has been described above, but the order of these processes is not limited thereto.

After these steps, the diffraction grating of the oscillator unit 11 is formed (diffraction grating forming step). Of the wafer surface, only the p-type InP cap layer of the oscillator unit 11 is etched to expose the p-type InGaAsP layer of the oscillator unit 11. Then, the diffraction grating layer 10 is formed by subjecting the p-type InGaAsP layer to an interference exposure method to form a diffraction grating. At this time, by designing the pitch so that the oscillation wavelength λ _DFB of the oscillator unit 11 at 50 ° C. is 1295.5 nm, the detuning amount ΔH is set to 45.5 nm (34.8 meV in terms of energy). In the diffraction grating forming step, the diffraction grating may be formed by an electron beam (hereinafter referred to as EB) drawing method instead of the interference exposure method.

  After the diffraction grating layer 10 is formed, the remaining semiconductor multilayer is formed over the entire element (element semiconductor upper layer forming step). The p-type InP cap layer formed on the wafer surface is removed by etching, and the p-type InP cladding layer 16, the p-type contact layer 17, and the p-type InP protective layer are formed by MO-CVD. Zn is used for the p-type dopant of these p-type layers.

After the element semiconductor upper layer forming step, both sides of the semiconductor multilayer are removed to form a mesa stripe structure (mesa stripe forming step). A SiO ₂ film is patterned in a region on the wafer surface above the waveguide region of the device, and the semiconductor multilayer is removed by dry etching or wet etching using the SiO ₂ film as a mask, A mesa stripe structure having a width of 1.4 μm and a height of 3.4 μm is formed across the waveguide portion 12 and the oscillator portion 11. At this time, the respective optical confinement layers including the MQW layers 4 and 8 of the modulator unit 6 and the oscillator unit 11 and the core layer of the waveguide unit 12 are formed on the bottoms on both sides of the mesa stripe structure (n-type InP buffer layer 2). The mesa stripe structure is formed so as to have a height of about 1 μm from the upper surface of each of the regions on both sides of the mesa stripe structure. Further, when the patterned SiO ₂ film, and a wafer surface, the device end face on the exit side of the light (device end face of the modulator 6 side) to 15μm region does not form a SiO ₂ film. As a result, the semiconductor multilayer in this region is removed by etching. That is, the end face on the light emission side of the mesa stripe structure is located about 15 μm inside from the element end face. As described above, the removed region becomes the element window structure 18.

  After the mesa stripe formation step, surface treatment is performed on the mesa stripe structure (surface treatment step). The entire wafer is exposed to a chlorine-based gas atmosphere to clean the sides of the mesa stripe structure. Thereby, the MQW layer 4 of the modulator section 6 exposed on the side surface of the mesa stripe structure is also cleaned, and even if the MQW layer 4 contains Al, the semiconductor whose characteristics are improved after completion The device can be manufactured. In particular, when the MQW layer 4 of the modulator section 6 is formed of a material having a high Al content, the improvement in characteristics is further increased.

  After the surface treatment process, the side surface of the mesa stripe structure is embedded by the embedded layer 19 (embedding process). That is, the buried layer 19 having a thickness of 5.0 μm is formed on both sides and the tip of the mesa stripe structure by InP doped with Ru as an impurity. The crystal growth temperature at this time is preferably set between 550 ° C. and 600 ° C. so that the resistivity and the embedding shape are optimized.

After the embedding process, the p-type electrode 21 and the n-type electrode 22 are formed (electrode forming process). The region of the waveguide portion 12 is removed from the p-type contact layer 17 which is the uppermost layer of the mesa stripe structure. As a result, the p-type contact layer 17 of the modulator unit 6 and the p-type contact layer 17 of the oscillator unit 11 are electrically insulated. Therefore, the groove formed by being removed is called an isolation groove. Further, a passivation film 20 made of SiO ₂ is formed on the entire wafer surface. Of the passivation film 20 to be formed, a part of each of the upper part of the mesa stripe structure of the modulator unit 6 and the oscillator unit 11 is removed to form a through hole. By sequentially depositing a metal film of Ti, Pt, and Au on the wafer surface so as to cover the through holes of the modulator unit 6 and the oscillator unit 11, and applying an electrode pattern by ion milling, the modulator unit 6 and A p-type electrode 21 of each oscillator unit 11 is formed. Thereafter, the lower surface of the wafer is polished until the wafer becomes about 100 μm to 150 μm, and a metal film of AuGe, Ni, Ti, Pt, and Au is sequentially deposited on the lower surface of the wafer to form an n-type electrode 22. To do.

  After the electrode forming step, the wafer is chipped to complete the EA modulator integrated DFB laser element 50 (chip forming step). That is, the wafer is cleaved in a bar shape, and the antireflection film 24 having a reflectance of 1% or less is coated on the end surface on the modulator unit 6 side, and the high reflection film 23 having a reflectance of 90% or more is coated on the end surface on the oscillator unit 11 side. Further, the device is completed by cleaving into a chip state. The EA modulator integrated DFB laser element 50 according to the embodiment manufactured by the manufacturing method is referred to as an element L0.

  A semiconductor optical element, a laser module, and an optical transmission device that have a high transmission speed of 100 Gbit / s and that can perform long-distance optical transmission of, for example, 10 km or more used for metro network transmission are desired. As one of the methods for realizing a 100 Gbit / s Ethernet optical transmission apparatus, a single mode fiber (hereinafter referred to as SMF) is driven at 25 Gbit / s in a 1.3 μm wavelength band where the chromatic dispersion is small. A system for wavelength multiplexing (Wavelength Division Multiplexing: hereinafter referred to as WDM) of semiconductor optical elements having wavelengths is mainly used. Furthermore, from the viewpoint of reducing power consumption, a semiconductor element capable of operating at a temperature of 40 to 60 ° C. (semi-cooled operation) of the semiconductor optical element in the laser module is desirable.

  In the 1.3 μm wavelength band, conventionally, a direct modulation laser that turns light on and off by high-speed current modulation of a DFB laser is generally used. However, since the direct modulation laser has a large chirping, when the high-speed current modulation is performed, a relaxation oscillation phenomenon in which the refractive index of the active layer fluctuates due to instantaneous carrier fluctuation and the wavelength of light fluctuates easily occurs. Therefore, in order to perform high-speed modulation such as a transmission rate of 25 Gbit / s, it is necessary to increase the relaxation oscillation frequency, and it is difficult to manufacture a stable direct modulation type DFB laser element driven at 25 Gbit / s in the 1.3 μm wavelength band. It is.

Therefore, in order to enable 100 Gbit / s driving by WDM, in addition to the above-described element L0, different three-wavelength EA modulator integrated DFB laser elements 50 that are driven at 25 Gbit / s in the 1.3 μm wavelength band are provided. The same manufacturing method was used. These are element L1, element L2, and element L3. The element L1, the element L2, and the element L3 have the oscillation wavelength λ _EA of the oscillator unit 11 such that the absorption wavelength λ _EA of the modulator unit 6 is 1254.0 nm, 1259.0 nm, and 1264.0 nm, respectively, at 50 ° C. _DFB is manufactured to be 1300.0 nm, 1304.5 nm, and 1309.0 nm, respectively, at 50 ° C. Here, the detuning amount ΔH is about 34 meV in terms of energy.

These elements are mounted on a chip carrier made of aluminum nitride (AlN) with a 50Ω termination resistor using AuSn solder, and conductive wires for energizing the oscillator unit 11 and the modulator unit 6 are bonded to each other, and the element temperature The characteristics were evaluated at T _LD = 50 ° C. The modulation light output P _mod and the modulation extinction ratio ACER are evaluated at the reverse bias voltage V _ea = −0.3 V and the modulation voltage V _mod = 2.0 V of the modulator unit 6.

Table 1 is a table showing the element characteristics of the four elements L0, L1, L2, and L3. As shown in Table 1, the optical output P _o at the oscillation threshold current I _th and the laser drive current I _f = 50 mA also shows good values, and both elements are mounted on the 100 Gbit / s Ethernet optical transmission device. It shows sufficient characteristics as an element. In the surface treatment process, it is confirmed that the Al surface of the MQW layer 4 having the mesa stripe structure exhibits good characteristics and reliability.

[Second Embodiment]
The semiconductor optical device according to the second embodiment of the present invention is an EA modulator integrated DFB laser device 50 having a BH structure, as in the first embodiment. The EA modulator integrated DFB laser device 50 according to the present embodiment has the same basic configuration and manufacturing method as the EA modulator integrated DFB laser device 50 according to the first embodiment. The integrated DFB laser element 50 is used for optical transmission at a transmission speed of 40 Gbit / s in the 1.3 μm wavelength band, and can be driven at a temperature of 40 ° C. to 60 ° C.

  FIG. 7A is a top view of the EA modulator integrated DFB laser device 50 according to this embodiment, and FIGS. 7B and 7C are cross-sectional views thereof. 7B shows a cross section through the broken line VIIB-VIIB of the EA modulator integrated DFB laser device 50 shown in FIG. 7A, and FIG. 7C shows a cross section through the broken line VIIC-VIIC.

  Also in the manufacturing method of the EA modulator integrated DFB laser device 50 according to the embodiment, after the mesa stripe formation step, the mesa stripe structure is subjected to surface treatment with a chlorine-based gas, as in the first embodiment. A surface treatment process is performed, followed by a burying process for forming buried layers 19 on both sides of the mesa stripe structure.

Further, in the diffraction grating forming step, the detuning amount ΔH is set to 50 nm (in terms of energy, 38 meV by designing the diffraction pitch of the diffraction grating so that the oscillation wavelength λ _DFB of the oscillator unit 11 at 50 ° C. becomes 1300.0 nm. ).

  In the modulator section 6 of the EA modulator integrated DFB laser element 50 according to this embodiment, a polyimide resin 30 is formed between the pad section of the p-type electrode 21 and the passivation film 20. The modulator section 6 has a parasitic capacitance, and one of them is a parasitic capacitance generated between the pad section of the p-type electrode 21 and the n-type InP substrate 1. Here, the pad portion of the p-type electrode 21 is a rectangular region of the p-type electrode 21 shown in FIG. 7A. The pad portion of the p-type electrode 21 is a region for connecting a conductive wire in order to supply a voltage to be applied to the p-type electrode 21, and has a sufficient area for ensuring electrical connection with the conductive wire. There is a need to. Therefore, in order to reduce the parasitic capacitance, the parasitic capacitance is reduced by disposing the polyimide resin 30 having a dielectric constant smaller than that of the buried layer 19 between the passivation film 20 and the pad portion of the p-type electrode 21. This is equivalent to a series connection of the polyimide resin 30 having a dielectric constant and the buried layer 19, and the parasitic capacitance is reduced.

  In order to form the polyimide resin 30, after forming the passivation film 20 on the entire wafer surface in the electrode forming step described in the first embodiment, the polyimide resin 30 having a thickness of 3 μm is applied to the entire wafer surface. A mask is formed corresponding to the region to be the pad portion of the p-type electrode 21, and the polyimide resin 30 in the unmasked region is removed by etching back with a mixed gas of oxygen and argon. Thereafter, a through hole is formed in the passivation film 20, and a p-type electrode 21 is further formed.

The EA modulator integrated DFB laser element 50 according to the embodiment was evaluated for characteristics in the same manner as in the first embodiment. As a result, at the element temperature T _LD = 50 ° C., the oscillation threshold current I _th = 15.6 mA, the laser output current I _f = 50 mA, the optical output P _o = 9.3 dBm, and the oscillation wavelength λ _DFB = 1300.23 nm. The f3 dB band was 42.1 GHz, the modulated light output P _mod = + 4.9 dBm, and the modulated extinction ratio ACER = 8.1 dB. These show sufficient characteristics for 40 Gbit / s Ethernet serial transmission. In the surface treatment process, it is confirmed that the Al surface of the MQW layer 4 having the mesa stripe structure exhibits good characteristics and reliability.

[Third Embodiment]
The laser module according to the third embodiment of the present invention is a laser module 51 on which the EA modulator integrated DFB laser element 50 according to the first embodiment is mounted, and is driven at a temperature of 40 ° C. to 60 ° C. Is possible.

  FIG. 8 is a diagram illustrating the configuration of the laser module 51 according to this embodiment. The EA modulator integrated DFB laser device 50 according to the first embodiment is mounted on a chip carrier 102 made of aluminum nitride (AlN) with a 50Ω termination resistor using AuSn solder. The chip carrier 102 is mounted on the upper side of the Peltier substrate 103 which is a temperature adjusting means, and these are mounted on the package 110. A thermistor 104, a monitor photodiode 107, and a condensing lens 108 are further mounted on the package 110. Here, the condensing lens 108 condenses the forward output light 105 output in the light emission direction of the EA modulator integrated DFB laser element 50 onto the optical fiber 109 connected to the light emission destination. It is a lens for. The monitor photodiode 107 receives the backward output light 106 output in the direction opposite to the light emission direction of the EA modulator integrated DFB laser element 50.

  A laser drive current source 111 is provided outside the package 110, and the power fluctuation of the backward output light 106 received by the monitor photodiode 107 is fed back to the laser drive current source 111, and the amount of current supplied to the oscillator unit 11 is increased. By being controlled, APC (Auto Power Control) control is performed to keep the power of the front output light 105 constant. A modulator driving signal is supplied from the modulator high-frequency signal source 112 to the modulator unit 6 of the EA modulator integrated DFB laser element 50.

  The Peltier drive current source 113 performs ATC (Auto Temperature Control) control on the EA modulator integrated DFB laser element 50. That is, the thermistor 104 detects the temperature of the EA modulator integrated DFB laser element 50 and outputs the detected temperature to the Peltier drive current source 113 as the monitor temperature. Corresponding to the monitor temperature, the Peltier drive current is supplied from the Peltier drive current source 113 to the Peltier substrate 103. By the ATC control, the temperature of the EA modulator integrated DFB laser element 50 can be kept constant.

  25.8 Gbit / s modulation evaluation was performed on each laser module 51 mounted with each of the four elements L0, L1, L2, and L3 described in the EA modulator integrated DFB laser element 50 according to the first embodiment. However, each laser module 51 exhibits sufficient characteristics as a laser module mounted on a 100 Gbit / s Ethernet optical transmission device.

  Similarly, the optical transmission / reception module according to the embodiment is an optical transmission / reception module including an optical transmission unit on which the EA modulator integrated DFB laser element 50 according to the first embodiment is mounted and a known optical reception unit. . The configuration of the optical transmitter of the optical transceiver module is the same as that of the laser module 51.

  Furthermore, the optical transmission apparatus according to this embodiment is an optical transmission apparatus in which the laser module 51 or the optical transmission / reception module is mounted. Other configurations of the optical transmission apparatus are the same as those known.

[Fourth Embodiment]
The semiconductor optical device according to the fourth embodiment of the present invention is an EA modulator integrated DFB laser array element 52 that includes four integrated laser units that are monolithically provided on the same semiconductor. is there. Although the four elements L0, L1, L2, and L3 have been described as the EA modulator integrated DFB laser element 50 according to the first embodiment, the EA modulator integrated DFB laser array element 52 includes the four elements. Each of these elements is provided as an integrated laser section. That is, each of the integrated laser portions of the EA modulator integrated DFB laser array element 52 is used for optical transmission at a transmission speed of 25 Gbit / s in the 1.3 μm wavelength band, and can be driven at a temperature of 40 ° C. to 60 ° C. It is. Therefore, the EA modulator integrated DFB laser array element 52 outputs light from each of the four integrated laser units, and thus has four optical output units. The transmission rate is 100 Gbit / s by WDM. It can be used for optical transmission.

  FIG. 9 is a top view of the EA modulator integrated DFB laser array element 52 according to this embodiment. In the EA modulator integrated DFB laser array element 52 according to this embodiment, the cross section passing through the AA broken line shown in FIG. 9 is the cross section shown in FIG. 1B, and the cross section passing through the BB broken line is shown in FIG. FIG.

The composition of the MQW layer 4 of the modulator section 6 is adjusted so that the absorption edge wavelength λ _EA of each of the four integrated laser sections is 1259 nm at 50 ° C. In addition, the oscillation wavelength λ _DFB of the oscillator unit 11 of each of the four integrated laser units is 1295.5 nm, 1300.0 nm, 1304.5 nm, and 1309.0 nm in order at 50 ° C. Each pitch is designed, and each diffraction grating layer 10 is formed. These four integrated laser units correspond to the four elements according to the first embodiment, L0, L1, L2, and L3, respectively, and are integrated laser units L0, L1, L2, and L3, respectively. . Here, in the four integrated laser units, the detuning amount ΔH is 36.5 nm, 41.0 nm, 45.5 nm, and 50.0 nm in order (27.8 meV, 31.1 meV, and 34, respectively, in terms of energy). .3 meV, 37.6 meV).

  The manufacturing method of the EA modulator integrated DFB laser array element 52 according to this embodiment is basically the same as the manufacturing method of the EA modulator integrated DFB laser element 50 according to the first embodiment. After the stripe formation process, a surface treatment process is performed on the mesa stripe structure by performing a surface treatment with a chlorine-based gas, and thereafter, an embedding process for forming the buried layers 19 on both sides of the mesa stripe structure is performed.

  The manufacturing method of the EA modulator integrated DFB laser array element 52 according to this embodiment is mainly different from the manufacturing method of the EA modulator integrated DFB laser element 50 according to the first embodiment in the following points.

In the modulator semiconductor lower layer formation step, the composition of InGaAlAs in the MQW layer 4 of each modulator section 6 is such that the absorption edge wavelength λ _EA of each of the four integrated laser sections is 1259 nm at 50 ° C. Adjust.

Further, in the diffraction grating formation step, the oscillation wavelength λ _DFB of each of the four integrated laser units is 1295.5 nm, 1300.0 nm, 1304.5 nm, 1309 in order at 50 ° C. by the EB drawing method. Each diffraction pitch of the diffraction grating is designed so as to be 0.0 nm, and the diffraction grating is formed.

  Further, in the chip forming process, four adjacent integrated laser portions are cleaved as one chip.

By manufacturing by the above manufacturing method, the EA modulator integrated DFB laser array element 52 according to the embodiment can emit light having different oscillation wavelengths λ _DFB from each integrated laser section.

The EA modulator integrated DFB laser array element 52 according to this embodiment was evaluated at an element temperature T _LD = 50 ° C. as in the first embodiment. At this time, since the four integrated laser portions to which the high-frequency voltage is applied are disposed adjacent to each other in the waveguide region, it is necessary to devise mounting when mounting on the chip carrier.

Table 2 is a table showing characteristics of the four integrated laser portions L0, L1, L2, and L3 of the EA modulator integrated DFB laser array element 52. The modulation light output P _mod and the modulation extinction ratio ACER are evaluated for the reverse bias voltage V _ea of the modulator unit 6 according to the values shown in Table 2 and at the modulation voltage V _mod = 2.0V.

In the four integrated laser parts of the EA modulator integrated DFB laser array element 52, the detuning amounts ΔH are different from each other, so that the optical output P _o at the laser drive current I _f = 50 mA is the integrated laser part L3. Is the largest. Further, by increasing the absolute value of the reverse bias voltage V _ea as the wavelength becomes longer, a near-modulation extinction ratio ACER is realized in each integrated laser unit. In addition, the other characteristics show sufficient characteristics as elements to be mounted on the 100 Gbit / s Ethernet optical transmission device by changing the driving conditions. In the surface treatment process, it is confirmed that the Al surface of the MQW layer 4 having the mesa stripe structure exhibits good characteristics and reliability.

  The semiconductor optical device and laser module according to the present invention have been described above. A feature of the present invention is that, in a semiconductor optical device including a modulator having a BH structure including a quantum well layer containing Al and a semiconductor buried layer to which an impurity is added, a buried layer is formed after the mesa stripe structure is formed. Between the steps, a step of cleaning the surfaces on both sides of the mesa stripe structure using a chlorine-based gas is performed.

  The quantum well layer containing Al is, for example, an MQW layer made of InGaAlAs, but has a higher Al content in the MQW layer of the EA modulator in the 1.3 μm wavelength band than in the 1.55 μm wavelength band. . Therefore, it is difficult to manufacture an element with high characteristics and reliability in an EA modulator in the 1.3 μm wavelength band. Therefore, the present invention is applied to an EA modulator in the 1.3 μm wavelength band. Thus, the effect of the present invention is further enhanced. The thickness of the buried layer is preferably 3.5 μm or more.

  Further, Ru is desirable as an impurity added to the semiconductor buried layer. Compared to Fe or the like, interdiffusion is suppressed with respect to Zn added as a p-type dopant to a p-type layer having a mesa stripe structure, so that the characteristics of the modulator are improved by making the impurity Ru. .

  When performing optical transmission in the 1.3 μm wavelength band with small chromatic dispersion using SMF, the propagation loss of SMF is as large as about 0.3 to 0.4 dB / km. Therefore, the semiconductor optical device is required to have a larger light output than the optical transmission in the 1.55 μm wavelength band.

  In a modulator integrated semiconductor optical device in which the modulator unit and the oscillator unit are monolithically integrated on the same semiconductor substrate, a waveguide unit is provided between the modulator unit and the oscillator unit, and the composition is determined from the oscillation wavelength of the oscillator unit. It is desirable to provide a core layer having a short wavelength bulk waveguide, and to form the core layer so as to make a butt joint connection with each of the modulator section and the oscillator section. As a result, the light output characteristics of the modulator integrated semiconductor optical device are further improved. The core layer is more preferably formed using either InGaAsP or InGaAlAs. In the 1.3 μm wavelength band modulator integrated semiconductor optical device, it is more desirable to form the core layer so that the composition wavelength of the core layer is 1.2 μm or less.

  Further, in the EA modulator integrated DFB laser element in which the modulator unit is an EA modulator and the oscillator unit is a DFB laser, it is desirable that the detuning amount ΔH is in a range of 23 meV to 40 meV. That is, it is desirable to form the diffraction grating so that the wavelength energy of the oscillation wavelength of the oscillator unit is 23 meV or more and 40 meV or less lower than the wavelength energy at the absorption wavelength end of the modulator unit. This further enhances the characteristics of the EA modulator integrated DFB laser element.

In addition, the semiconductor optical device according to the present invention may be a laser array device in which a plurality of integrated laser parts serving as lasers such as the EA modulator integrated DFB laser device are integrated on the same substrate. The semiconductor optical device includes a plurality of light output units. The modulator sections of the plurality of integrated laser sections are formed so that the absorption edge wavelength λ _EA of the modulator section has the same wavelength in the process of forming the optical confinement layer of the modulator section (modulator semiconductor lower layer forming process). In the step of forming the diffraction gratings of each of the plurality of integrated laser units (diffraction grating forming step), it is desirable to form the diffraction gratings according to the oscillation wavelength λ _DFB of each integrated laser unit. At that time, it is more desirable that the detuning amount ΔH of each integrated laser unit is 23 meV or more and 40 meV or less. Thereby, the characteristics of the laser array element are further enhanced.

  Moreover, it is desirable to have a window structure in which no mesa stripe structure exists inside the outgoing side end face of the semiconductor optical device. Thereby, the characteristics of the element are further enhanced. A stripe structure is formed by removing a predetermined region of the semiconductor multilayer. In this step, the semiconductor multilayer in this region is removed including the region to be a window structure in the predetermined region. Further, in the step of filling the buried layer, the buried layer is also formed in this region. As a result, the leading end of the stripe structure is positioned on the inner side of the end face on the emission side, and a window structure is formed. It is desirable that the length of the window structure, that is, the distance from the front end of the stripe structure to the emission side end face is 5 μm or more. At this time, the region within 5 μm from the end face on the emission side is included in the region to be removed when the stripe structure is formed.

  1 n-type InP substrate, 2 n-type InP buffer layer, 3 InGaAlAs lower guide layer, 4 MQW layer, 5 p-type InGaAlAs upper guide layer, 6 modulator section, 7 n-type InGaAsP lower guide layer, 8 MQW layer, 9 p-type InGaAsP upper guide layer, 10 diffraction grating layer, 11 oscillator section, 12 waveguide section, 13, 14, 15 InGaAsP layer, 16 p-type InP cladding layer, 18 window structure, 19 buried layer, 20 passivation film, 21 p-type electrode, 22 n-type electrode, 23 highly reflective film, 24 antireflection film, 50 EA modulator integrated DFB laser element, 51 laser module, 52 EA modulator integrated DFB laser array element, 102 chip carrier, 103 Peltier Substrate, 104 thermistor, 105 front output light, 106 rear output light, 107 monitor photodiode, 108 condenser lens, 109 fiber, 110 package, 111 laser drive current source, 112 modulator high frequency signal source, 113 Peltier drive current source.

Claims (12)

A method for manufacturing a semiconductor optical device comprising a modulator unit that modulates and emits light input along an emission direction,
The modulator section is
A semiconductor multilayer having a quantum well layer containing aluminum and having a mesa stripe structure;
A semiconductor buried layer disposed adjacent to both sides of the semiconductor multilayer and doped with impurities,
Removing a predetermined region of the semiconductor multilayer to form a mesa stripe structure;
Cleaning the surfaces of both sides of the semiconductor multilayer using a chlorine-based gas;
Forming the semiconductor buried layer on both sides of the semiconductor multilayer;
The manufacturing method of the semiconductor optical element characterized by including in order. A method for producing a semiconductor optical device according to claim 1,
Further comprising the step of forming the quantum well layer using indium gallium aluminum arsenide as a material,
A method of manufacturing a semiconductor optical device. A method of manufacturing a semiconductor optical device according to claim 2,
In the step of forming the quantum well,
Adjusting the composition used in the 1.3 μm wavelength band to form the quantum well layer;
A method of manufacturing a semiconductor optical device. A method for producing a semiconductor optical device according to claim 1,
The impurity added to the semiconductor buried layer is ruthenium.
A method of manufacturing a semiconductor optical device. It is a manufacturing method of the semiconductor optical element according to claim 4,
In the step of forming the semiconductor buried layer,
Forming the semiconductor buried layer having a layer thickness of 3.5 μm or more;
A method of manufacturing a semiconductor optical device. A method of manufacturing a semiconductor optical device according to any one of claims 1 to 5,
The semiconductor optical element is
An oscillator unit for outputting the input light;
While connecting between the oscillator unit and the modulator unit, a waveguide unit comprising a core layer,
Further comprising
A step of connecting a joint between the oscillator unit and the waveguide unit and between the waveguide unit and the oscillator unit and forming the core layer,
Furthermore, the manufacturing method of the semiconductor optical element characterized by including. A method of manufacturing a semiconductor optical device according to claim 6,
In the step of forming the core layer,
Forming the core layer using indium gallium arsenide phosphorus or indium gallium aluminum arsenide as a material;
A method of manufacturing a semiconductor optical device. A method of manufacturing a semiconductor optical device according to claim 6 or 7,
The modulator unit is an electroabsorption modulator,
The oscillator unit is a distributed feedback semiconductor laser including a diffraction grating,
Further including the step of forming a diffraction grating such that the wavelength energy of the oscillation wavelength of the oscillator unit is 23 meV or more and 40 meV or less lower than the wavelength energy at the absorption wavelength end of the modulator unit.
A method of manufacturing a semiconductor optical device. A method for producing a semiconductor optical device according to claim 8, comprising:
The modulator section includes a plurality of light output sections, outputs light from each of the plurality of light output sections, and the semiconductor multilayer having the mesa stripe structure corresponding to the plurality of light output sections. Multiple
The oscillator unit includes a plurality of diffraction gratings corresponding to the plurality of light output units, respectively.
In the step of forming the diffraction grating,
Forming each of the plurality of diffraction gratings to have oscillation wavelengths respectively corresponding to the plurality of light output units;
A method of manufacturing a semiconductor optical device. A method of manufacturing a semiconductor optical device according to claim 8 or 9, wherein
In the step of forming the mesa stripe structure, the predetermined region of the semiconductor multilayer includes a region that is within 5 μm from the end surface on the light emission side of the semiconductor optical element,
In the step of forming the semiconductor buried layer, the window structure is formed in the region by forming the semiconductor buried layer.
A method for manufacturing a semiconductor device, characterized in that:   A laser module provided with the semiconductor optical element manufactured by the manufacturing method of the semiconductor optical element in any one of Claims 1 thru | or 10.   An optical transmission device comprising a semiconductor optical device manufactured by the method for manufacturing a semiconductor optical device according to claim 1.

Images