JP2017161830A - Semiconductor optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a heating part easily and stably, efficiently heat a high-mesa waveguide structure to thereby reduce power consumption.SOLUTION: A semiconductor optical element comprises on an InP substrate: an AlInAs oxide layer or a low heat conduction area including a cavity which suppress heat conduction; and, on an area narrower than an arrangement area along a surface direction of the low heat conduction area, on an upper layer of the low heat conduction area, a high-mesa waveguide structure having a waveguide layer and a heating part for heating the high-mesa waveguide structure, the heating part being provided on the edge of the high-mesa waveguide structure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor optical device applied in the field of optical communication.

  With the spread of coherent optical communication, there is an increasing demand for a tunable laser element having a narrow line width. The configuration and operating principle of the wavelength tunable laser element are described in detail in Non-Patent Document 1, for example. In general, in order to narrow the laser beam output from a semiconductor laser element, it is necessary to lengthen the resonator.

  There is a distributed Bragg reflection (DBR) type wavelength tunable laser using a sampled diffraction grating (Sampled Grating) as one of the wavelength tunable laser elements and utilizing the vernier effect (for example, Patent Document 1). In this tunable laser element, two DBR mirrors in which a part of a diffraction grating is sampled in a semiconductor element are used. The reflection spectra of these two DBR mirrors have a shape having comb-like peaks with slightly different periods. Further, the refractive index change can be caused by current injection or heating in the DBR mirror, and the reflection wavelength characteristic can be made variable. By superimposing the reflection peaks of the two DBR mirrors, a resonator can be formed with this superimposed wavelength. At this time, if the resonator length is appropriately designed, the interval between the longitudinal modes, which are the resonator modes, is approximately the same as the band of the reflection peak by the two DBR mirrors, and only one resonator mode is selected. Oscillation is realized.

  As another method for realizing a laser beam having a narrow line width, there is a method of increasing the Q value of the resonator mode by increasing the resonance length using an external resonator structure. Further, for example, in a wavelength tunable laser element (for example, Non-Patent Document 2) in which a resonator is configured by using two ring resonators, a relatively sharp superposition of the filter characteristics (reflection wavelength characteristics) of the ring resonator is used. Thus, the configuration of the resonator can be freely designed.

  In the configuration described above, the wavelength selection method is realized by changing the refractive indexes of two DBR mirrors or ring resonators by current injection or heating. Further, as described in Patent Document 2 and the like, the heating method is provided with a microheater on the waveguide in the region where the refractive index change is desired to be generated, and in order to further increase the efficiency of the heating, it is provided at the lower part of the core layer of the waveguide. By providing the low thermal conductive layer, the outflow of heat to the substrate side is suppressed. As the low thermal conductive layer for suppressing thermal conduction, a mixed crystal semiconductor layer, an oxide layer obtained by oxidizing a semiconductor layer containing aluminum (Al), or the like is used. In particular, the oxide layer is said to have a great effect as a low thermal conductive layer.

US Pat. No. 6,590,924 Japanese Patent Laying-Open No. 2015-12176

Larry A. Coldren et al., “Tunable Semiconductor Lasers: A Tutorial”, JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 22, NO. 1, JANUARY 2004, pp.193-202 Keita Nemoto et al., “Narrow-Spectral-Linewidth Wavelength-Tunable Laser Diode with Si Wire Waveguide Ring Resonators”, Applied Physics Express 5 (2012) 082701

  However, in a general high mesa waveguide structure in a semiconductor optical device, it is difficult to form a microheater electrode on the upper surface of the high mesa waveguide structure because the mesa width is as thin as 1.5 to 2.0 μm. Therefore, the manufacturing yield may be deteriorated. Further, when a heating unit such as a microheater is disposed on the bottom surface portion of the high mesa waveguide structure, the heat generated by the microheater is conducted to the substrate side. For this reason, there is a problem that the core layer in the high mesa waveguide structure cannot be efficiently heated and the power consumption increases.

  The present invention has been made in view of the above, and an object of the present invention is to provide a semiconductor optical device that can easily and stably form a heating unit and efficiently heat a high mesa waveguide structure to reduce power consumption. It is to provide an element.

  In order to solve the above-described problems and achieve the above object, a semiconductor optical device according to the present invention includes a low thermal conduction region that suppresses thermal conduction above a semiconductor substrate, and a low thermal conduction region in an upper layer of the low thermal conduction region. A high mesa waveguide structure having a waveguide layer provided in a region narrower than the arrangement region along the surface direction of the substrate, and a heating unit provided in a skirt portion of the high mesa waveguide structure. To do.

  In the semiconductor optical device according to one embodiment of the present invention, in the above invention, the heating section is provided on a side portion of the high mesa waveguide structure.

  In the semiconductor optical device according to one embodiment of the present invention, in the above invention, the heating portion is provided in a region covering the high mesa waveguide structure.

  The semiconductor optical device according to one embodiment of the present invention is characterized in that, in the above invention, the heating section is provided apart from the high mesa waveguide structure.

  The semiconductor optical device according to one embodiment of the present invention is characterized in that, in the above-described invention, the heating section is provided only at the bottom of the high mesa waveguide structure.

The semiconductor optical device according to one aspect of the present invention is characterized in that, in the above invention, the low thermal conductivity region is formed of an oxidized layer in which at least one semiconductor layer substantially lattice-matched to the semiconductor substrate is oxidized. . In this configuration, the semiconductor optical device according to one embodiment of the present invention has an Al _{1 -xy} Ga _x In _y As _{1 -z} P _z layer (0 <x + y <1, 0 ≦ x <1, 0 <y <1, 0 ≦ z <1).

  The semiconductor optical device according to one embodiment of the present invention is characterized in that, in the above invention, the low thermal conductivity region is formed of a cavity.

  According to the semiconductor optical device of the present invention, the heating section can be formed easily and stably, and the high mesa waveguide structure can be efficiently heated to reduce power consumption.

FIG. 1 is a schematic perspective view of a wavelength tunable laser device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of the ring-shaped waveguide in FIG. FIG. 3 is a cross-sectional view of a high mesa waveguide structure in a semiconductor optical device according to the second embodiment of the present invention. FIG. 4 is a cross-sectional view of a high mesa waveguide structure in a semiconductor optical device according to the third embodiment of the present invention. FIG. 5 is a sectional view of a high mesa waveguide structure in a semiconductor optical device according to the fourth embodiment of the present invention. FIG. 6 is a cross-sectional view of a high mesa waveguide structure in a semiconductor optical device according to a fifth embodiment of the present invention. FIG. 7 is a cross-sectional view of a high mesa waveguide structure in a semiconductor optical device according to a sixth embodiment of the present invention. FIG. 8 is a cross-sectional view of a high mesa waveguide structure in a semiconductor optical device according to a seventh embodiment of the present invention. FIG. 9 is a cross-sectional view of a high mesa waveguide structure in a semiconductor optical device according to the eighth embodiment of the present invention. FIG. 10 is a sectional view showing the overall configuration of an integrated semiconductor laser device according to the ninth embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by the following embodiment. In the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and repeated descriptions are omitted as appropriate. Furthermore, it should be noted that the drawings are schematic, and dimensional relationships between elements may differ from actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included. Further, “upper” or “upper” and “lower” or “lower” used in the description of the following embodiments indicate a direction away from the main surface of the substrate and a direction approaching the main surface of the substrate, respectively. It should also be noted that the semiconductor device is not mounted in the vertical direction when mounted. In addition, xyz coordinate axes are appropriately shown in the drawing, and directions will be described.

(First embodiment)
First, a wavelength tunable laser element as a semiconductor optical element according to the first embodiment of the present invention will be described. FIG. 1 is a schematic perspective view of a wavelength tunable laser device according to the first embodiment.

  As shown in FIG. 1, the wavelength tunable laser element 1 is configured to oscillate in the 1.55 μm band and output a laser beam L1. The wavelength tunable laser element 1 includes a first waveguide section 10 and a second waveguide section 20 formed on a common base B. The base B is made of, for example, an n-type InP substrate. An n-side electrode 30 is formed on the back surface of the base B. The n-side electrode 30 is configured to contain AuGeNi, for example, and is in ohmic contact with the base B.

  The first waveguide section 10 includes a waveguide section 11, a semiconductor laminated section 12, a p-side electrode 13, and micro heaters 14 and 15 made of Ti. The first waveguide portion 10 is a so-called active element and constitutes an active region. The waveguide portion 11 is formed in the semiconductor stacked portion 12 so as to extend in the z direction. In the first waveguide section 10, a diffraction grating loaded gain section 11a and a phase adjustment section 11b are arranged. The semiconductor laminated portion 12 is configured by laminating semiconductor layers, and has a function of a clad portion with respect to the waveguide portion 11.

The p-side electrode 13 is disposed along the diffraction grating loaded gain section 11 a on the semiconductor multilayer section 12. Note that a SiN _x protective film is formed on the semiconductor multilayer portion 12, and the p-side electrode 13 is in contact with the semiconductor multilayer portion 12 through an opening formed in the SiN _x protective film. The microheater 14 serving as a heating unit is disposed on the SiN _x protective film of the semiconductor stacked unit 12 along the phase adjusting unit 11b. The microheater 15 as a heating unit is arranged along the p-side electrode 13 on the SiN _x protective film of the semiconductor stacked unit 12.

  The second waveguide portion 20 includes a bifurcated portion 21, two arm portions 22 and 23, a ring-shaped waveguide 24, and a micro heater 25 made of Ti. The second waveguide portion 20 is a so-called passive element and constitutes a passive region. The two-branch portion 21 is formed of a 1 × 2 type branching waveguide including a 1 × 2 type multimode interference (MMI) waveguide 21a, and the two-port side is connected to each of the two arm portions 22 and 23. In addition, one port side is connected to the first waveguide section 10 side. One end of each of the two arm portions 22 and 23 is integrated by the bifurcated portion 21 and is optically coupled to the waveguide portion 11.

  Each of the arm portions 22 and 23 extends in the z direction and is disposed so as to sandwich the ring-shaped waveguide 24. The arm portions 22 and 23 are close to the ring-shaped waveguide 24, and both are optically coupled to the ring-shaped waveguide 24 with the same coupling coefficient κ. The value of κ is, for example, 0.2. The arm portions 22 and 23 and the ring-shaped waveguide 24 constitute a ring resonance filter RF1. Further, the ring resonant filter RF1 and the bifurcated portion 21 constitute a reflection mirror M1. The micro heaters 25a and 25b as heating portions for heating the optical waveguide are ring-shaped. A microheater 25a is disposed on the outer peripheral side of the ring-shaped waveguide 24, and a microheater 25b is disposed on the inner peripheral side. The microheaters 25 a and 25 b are provided on a dielectric layer as a protective film formed so as to cover the ring-shaped waveguide 24.

  The first waveguide section 10 and the second waveguide section 20 are optically connected to each other, and the diffraction grating layer 11ab of the diffraction grating loaded gain section 11a and the reflection mirror M1 constitute a laser resonator C1. ing. The active core layer 11aa and the phase adjustment unit 11b as the gain unit of the diffraction grating loaded gain unit 11a are arranged in the laser resonator C1.

  2 is a cross-sectional view taken along the line II-II in which the ring-shaped waveguide 24 of the second waveguide section 20 is cut along a plane parallel to the yz plane of FIG. As shown in FIG. 2, the ring-shaped waveguide 24 has a low heat on an n-type InP substrate 41 as a semiconductor substrate constituting the base B in which an InP buffer layer (not shown) of about 500 nm, for example, is formed in the upper layer. It has a high mesa waveguide structure in which a conductive layer 42a, a lower cladding layer 43, an optical waveguide layer 44 as a waveguide layer, and an upper cladding layer 45 are sequentially stacked. The width of the high mesa waveguide structure is about 2 μm.

The low thermal conductive layer 42a is an Al _1-xy Ga _x In _y As _{1-z Pz} layer (0 <x + y <1, 0 ≦ x <1, 0 <y <1, 0 ≦ z <1) as a semiconductor layer. Is formed of an Al _{1 -xy} Ga _x In _y As _{1 -z Pz} oxide layer formed by oxidation from the side end. Specifically, the low thermal conductive layer 42a is made of, for example, an AlInAs oxide layer in which an n-type AlInAs layer 42 with x = z = 0 is oxidized from the side end. The composition of the n-type AlInAs layer 42 is a composition substantially lattice-matched with the n-type InP substrate 41. In the first embodiment, for example, an Al _0.48 In _0.52 As layer (lattice-matched with the n-type InP substrate 41 ( x = 1, y = 0.52, z = 0). The film thickness of the n-type AlInAs layer 42 is not less than 50 nm and less than 150 nm, preferably not more than 130 nm, and is, for example, 100 nm in the first embodiment.

  The lower cladding layer 43 is made of an n-type InP layer having a thickness of 1500 nm, for example. The lower portion of the lower clad layer 43 has an extended portion extending on the low thermal conductive layer 42a and the non-oxidized n-type AlInAs layer 42. The n-type AlInAs layer 42 and the upper lower cladding layer 43 are connected to each other at the extended portion on the non-oxidized n-type AlInAs layer 42. The optical waveguide layer 44 is made of a GaInAsP layer having a thickness of, for example, 300 nm and a band gap wavelength of, for example, 1300 nm. The upper cladding layer 45 is made of a p-type InP layer having a thickness of 1500 nm, for example. For the upper cladding layer 45, a structure in which the carrier concentration in the vicinity of the waveguide is reduced or a non-doped InP layer can be used in order to reduce the loss of the waveguide.

The low thermal conductive layer 42a, the lower clad layer 43, the optical waveguide layer 44, the upper clad layer 45, and the extended portion below the lower clad layer 43 constituting the high mesa waveguide structure form a dielectric layer 46 as a protective film. Covered. The dielectric layer 46 is, for example, a silicon nitride (SiN _x ) film, but may be composed of a silicon oxide (SiO ₂ ) film or a laminated film of a SiO ₂ film and a SiN _x film.

  The bifurcated portion 21 and the arm portions 22 and 23 which are other components of the second waveguide portion 20 also have a high mesa waveguide structure similar to that described above, and are covered with a dielectric layer. That is, the second waveguide section 20 has a second waveguide structure that is different from the first waveguide structure of the first waveguide section 10.

  A microheater 25 is provided on the dielectric layer 46 in the periphery (hereinafter referred to as the skirt) of the bottom of the high mesa waveguide structure constituting the ring-shaped waveguide 24. The microheater 25a is disposed on one hem portion (outer peripheral side) of the high mesa waveguide structure, and the microheater 25b is disposed on the other hem portion (inner peripheral side). The high mesa waveguide structure and the microheater 25 are provided in the formation region along the surface direction of the lower low heat conduction layer 42a, that is, inside the arrangement region of the low heat conduction layer 42a along the surface direction.

  A resin layer 48 is provided on the outer side portion of the microheater 25 on the side surface side of the high mesa waveguide structure. On the upper surface of the resin layer 48 and the upper surface of the microheater 25, a lead-out wiring 49 electrically connected on the upper surface of the microheater 25 is provided. The lead wiring 49 is made of, for example, a Ti / Au layer, a Ti / Pt / Au layer, a Cr / Au layer, or a Mo / Au layer. The lead wiring 49 is a wiring for energizing the micro heater 25 from the outside. Note that a so-called air bridge structure in which the lead wiring 49 is provided with the resin layer 48 in a space may be employed.

  By energizing the microheater 25 through the lead wiring 49, heat conduction is performed from the region where the microheater 25 is disposed through the lower dielectric layer 46 and the lower cladding layer 43. The low thermal conductive layer 42 a has a thermal conductivity lower than that of at least the upper cladding layer 45, the optical waveguide layer 44, and the lower cladding layer 43. Thereby, the low thermal conductive layer 42a functions as a heat insulating layer for preventing the heating by the microheater 25 from being further transmitted to the lower layer. That is, since the low thermal conductive layer 42a is provided in the lower layer of the microheater 25, the heat generated by the microheater 25 is not conducted to the n-type InP substrate 41 side, but is shown as an arrow in FIG. The optical waveguide layer 44 can be heated by conduction.

  Next, a manufacturing method of the above-described high mesa waveguide structure will be described. First, an n-type AlInAs layer 42, a lower cladding layer 43, and an n-type InP substrate 41 constituting a base B on which an n-type InP buffer layer (not shown) of about 500 nm, for example, is formed as an upper layer are formed by MOCVD. An n-type InP layer to be formed, a GaInAsP layer to be the optical waveguide layer 44, and a p-type InP layer to be the upper cladding layer 45 are sequentially formed.

Next, for example, a SiN _x film is formed on the upper surface of the p-type InP layer to be the upper clad layer 45, and is patterned into a high mesa waveguide structure such as a ring-shaped or straight arm. Subsequently, anisotropic etching is performed using the SiN _x film as an etching mask, for example, by a dry etching method using a chlorine-based gas. After etching with the lower portion of the lower cladding layer 43 remaining, the etching mask is removed. Subsequently, after forming an etching mask in a region including the laminated portion of the high mesa waveguide structure and the extended portion below the lower cladding layer 43, for example, dry etching using a chlorine-based gas is performed. As a result, the remaining portion of the lower cladding layer 43 in the desired region where the oxide layer is to be formed and the n-type AlInAs layer 42 are etched, and one end of the n-type AlInAs layer 42 is exposed. The remaining portion of the lower clad layer 43 and the n-type AlInAs layer 42 may be etched by a wet etching method.

  After that, annealing is performed at a temperature of 450 ° C. or more and 520 ° C. or less in a water vapor atmosphere on the high mesa waveguide structure laminate including the n-type AlInAs layer 42 whose side surface is exposed. Thereby, in the n-type AlInAs layer 42, oxidation proceeds along the surface direction of the n-type AlInAs layer 42 from the exposed end. This oxidation is performed until the n-type AlInAs layer 42 in the lower portion of the arrangement region of the high mesa waveguide structure and the microheater 25 is oxidized. The oxidation time in the oxidation treatment is determined based on oxidation rate data obtained by conducting an oxidation experiment on the AlInAs layer in advance, the design value of the width of the high mesa waveguide structure, and the like. In the first embodiment, since the design width of the low thermal conductive layer 42a is, for example, about 6.0 μm, the oxidation can be performed up to a desired region by performing the oxidation treatment for about 6 hours. As a result, the n-type AlInAs layer 42 is uniformly oxidized below the arrangement region of the high-mesa waveguide structure and the microheater 25, and the low thermal conductive layer 42a formed of a uniform AlInAs oxide layer along the width direction (plane direction). Is formed.

Next, a dielectric layer 46 is formed by, for example, forming a SiN _x film on the entire surface. Thereafter, a metal layer such as a Ti layer is formed in the shape of the microheaters 25a and 25b on the dielectric layer 46 at the bottom of the high mesa waveguide structure by, for example, a lift-off method using a lift-off mask. Thereby, the micro heaters 25a and 25b are formed. Thereafter, a resin layer 48 is formed on the outer portion of the microheater 25 and patterned. Subsequently, a lead wiring 49 is formed by forming, for example, a Ti / Au layer, a Ti / Pt / Au layer, or a Cr / Au layer on at least a part of the microheater 25 and the resin layer 48. As described above, the high mesa waveguide structure in which the low heat conductive layer 42a is provided in the lower portion and the micro heater 25 is provided in the skirt portion is manufactured.

  According to the first embodiment of the present invention described above, the microheater 25 is disposed at the bottom of the high mesa waveguide structure, and the low thermal conductive layer 42a is provided below the microheater 25. Thereby, since the outflow of heat generated by the microheater 25 to the n-type InP substrate 41 side can be suppressed, the optical waveguide layer 44 can be efficiently heated, and power consumption in a semiconductor optical device such as a wavelength tunable laser device Can be reduced. Furthermore, since it is not necessary to form the microheater 25 in the upper layer of the high mesa waveguide structure having a width of about 2.0 μm, the ease of forming the microheater 25 can be improved.

(Second Embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to the second embodiment of the present invention will be described. In the description and drawings after the second embodiment, in order to facilitate the understanding of the invention, a description is given of a laminated structure in which the description of the resin layer, the dielectric layer, the lead-out wiring, and the like in the high mesa waveguide structure is omitted. To do.

  FIG. 3 is a cross-sectional view showing a high mesa waveguide structure according to the second embodiment. As shown in FIG. 3, in the high mesa waveguide structure 60 according to the second embodiment, an n-type AlInAs layer 42 and an AlInAs oxide layer are formed on an n-type InP substrate 41 as in the first embodiment. The low thermal conductive layer 42a, the lower clad layer 43, the optical waveguide layer 44, and the upper clad layer 45 are sequentially laminated. Micro heaters 61a and 61b are provided at the skirts on both sides of the high mesa waveguide structure 60, respectively. The micro heaters 61 a and 61 b have a portion extending to the lower region of the side surface of the high mesa waveguide structure 60, and one end portion on the side of the high mesa waveguide structure 60 is positioned lower than the optical waveguide layer 44. It is provided as follows.

  Next, in the manufacturing method of the high mesa waveguide structure according to the second embodiment, first, the high mesa waveguide structure 60 and a metal layer such as a Ti layer are formed as in the first embodiment. At this time, the microheater is formed by forming the metal layer using a lift-off mask having a pattern in which a part of the side surface of the high mesa waveguide structure 60 is exposed, which is different from the lift-off mask of the metal layer in the first embodiment. 61a and 61b are formed. Note that the bottom of the lift-off pattern resist is side-etched (over-developed), and vapor deposition is performed by a self-revolving vapor deposition apparatus, so that a micro film made of a metal film covering a part of the side surface of the high mesa waveguide structure 60 can be obtained. Heaters 61a and 61b can be formed. Other configurations and manufacturing methods are the same as those in the first embodiment.

  In the second embodiment, the microheater 61 extends not only to the bottom of the high mesa waveguide structure 60 but also to the lower part of the side surface, and is provided in the vicinity of the optical waveguide layer 44. As a result, the same effects as those of the first embodiment can be obtained, and the heat generated from the microheater 61 is thermally conducted as indicated by arrows in FIG. 3 to improve the heating efficiency of the optical waveguide layer 44. Can be made.

(Third embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to the third embodiment of the present invention will be described. FIG. 4 is a cross-sectional view showing a high mesa waveguide structure according to the third embodiment. As shown in FIG. 4, in the third embodiment, in the high mesa waveguide structure 70 configured similarly to the first embodiment, the micro heater 71 is provided only at one skirt portion. Different from the first embodiment. In FIG. 4, the micro heater 71 is disposed on the left side of the high mesa waveguide structure 70, but may be disposed on the right side. Further, the heat generated by the microheater 71 conducts heat as indicated by arrows in FIG. 4 to heat the optical waveguide layer 44.

  In the manufacturing method of the high mesa waveguide structure according to the third embodiment, first, the high mesa waveguide structure 70 and the metal layer are formed in the same manner as in the first embodiment. At this time, the microheater is formed by forming the metal layer using a lift-off mask having a pattern in which only one hem portion of the high-mesa waveguide structure 70 is exposed, which is different from the lift-off mask of the metal layer in the first embodiment. 71 is formed. Other configurations and manufacturing methods are the same as those in the first embodiment.

  In the third embodiment, by providing the microheater 71 only on one side of the high mesa waveguide structure, the number of lead-out lines formed in the upper layer can be further reduced.

(Fourth embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to the fourth embodiment of the present invention will be described. FIG. 5 is a sectional view showing a high mesa waveguide structure according to the fourth embodiment. As shown in FIG. 5, in the fourth embodiment, in the high mesa waveguide structure 80 configured in the same manner as in the second embodiment, the micro heater 81 is provided only on one skirt and side surface. This is different from the second embodiment. In FIG. 5, the micro heater 81 is disposed on the left side of the high mesa waveguide structure 80, but may be disposed on the right side. Further, the heat generated by the microheater 81 conducts heat as indicated by arrows in FIG. 5 to heat the optical waveguide layer 44.

  In the manufacturing method of the high mesa waveguide structure according to the fourth embodiment, unlike the second embodiment, a lift-off mask having a pattern in which only one skirt and side surfaces of the high mesa waveguide structure 80 are exposed is used. The microheater 81 is formed by forming a metal layer. Other configurations and manufacturing methods are the same as those in the second embodiment.

  In the fourth embodiment, by providing the microheater 81 only on one side surface and the skirt of the high mesa waveguide structure 80, the same effect as in the second and third embodiments can be obtained. it can.

(Fifth embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to a fifth embodiment of the present invention will be described. FIG. 6 is a cross-sectional view showing a high mesa waveguide structure according to the fifth embodiment. As shown in FIG. 6, in the fifth embodiment, micro heaters 91a and 91b are provided at the skirts on both sides of the high mesa waveguide structure 90 having the same configuration as the first embodiment, respectively. . The micro heaters 91a and 91b are different from the first embodiment in that the micro heaters 91a and 91b are provided at the skirt portion of the high mesa waveguide structure 90 so as to be separated from the side surfaces of the high mesa waveguide structure 90. Further, the heat generated by the microheater 91 is conducted as indicated by an arrow in FIG. 6 to heat the optical waveguide layer 44.

  In the manufacturing method of the high mesa waveguide structure according to the fifth embodiment, first, the high mesa waveguide structure 90 and a metal layer such as a Ti layer are formed as in the first embodiment. At this time, the microheaters 91a and 91b are formed by forming the metal layer using a lift-off mask having a pattern separated from the side surface of the high mesa waveguide structure 90, which is different from the lift-off mask of the metal layer in the first embodiment. Is formed. Other configurations and manufacturing methods are the same as those in the first embodiment.

  In the fifth embodiment, the microheater 91 is not in contact with the side surface of the high mesa waveguide structure 90. This structure suppresses the influence on the light leaked from the optical waveguide layer 44 by the degree of optical confinement in the optical waveguide layer 44 and the design of the thickness (height) of the lower cladding layer 43. Is a structure that prevents the light from being exposed to the light field. As a result, the possibility that the light propagating through the optical waveguide layer 44 is absorbed or scattered by the microheater 91 can be reduced, so that the optical waveguide layer 44 can be heated while maintaining a low loss of the waveguide. It becomes possible.

(Sixth embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to a sixth embodiment of the present invention will be described. FIG. 7 is a sectional view showing a high mesa waveguide structure according to the sixth embodiment. As shown in FIG. 7, in the sixth embodiment, a micro heater 101 is provided so as to cover the high mesa waveguide structure 100 having the same configuration as that of the first embodiment. That is, the microheater 101 is provided on the top surface, the side surface, and the bottom skirt of the high mesa waveguide structure 100 in the arrangement region along the surface direction of the low thermal conductive layer 42a.

  In the high mesa waveguide structure manufacturing method according to the sixth embodiment, first, the high mesa waveguide structure 100 and a metal layer such as a Ti layer are formed in the same manner as in the first embodiment. At this time, the microheater 101 is formed by forming a metal layer using a lift-off mask having a pattern in which the high mesa waveguide structure 100 is exposed in the arrangement region along the surface direction of the low thermal conductive layer 42a. Note that, on the side surface of the high mesa waveguide structure 100, the deposited film may be formed thinner than the top surface and the bottom skirt, so the uniformity of the deposited film is improved by a self-revolving deposition apparatus. It is effective. Other configurations and manufacturing methods are the same as those in the first embodiment.

  In the sixth embodiment, since the microheater 101 is provided so as to cover the high mesa waveguide structure 100 including the optical waveguide layer 44, heat conduction occurs as shown by arrows in FIG. The heating efficiency of the optical waveguide layer 44 can be greatly improved. In consideration of the possibility that the light loss increases due to the light oozed from the optical waveguide layer 44 being absorbed or scattered by the microheater 101, the light oozes out from the optical waveguide layer 44. It is necessary to consider the design.

(Seventh embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to a seventh embodiment of the present invention will be described. FIG. 8 is a cross-sectional view showing a high mesa waveguide structure according to the seventh embodiment. As shown in FIG. 8, in the seventh embodiment, in the high mesa waveguide structure 110 having the same configuration as that of the first embodiment, the microheaters 111a and 111b are arranged along the surface direction of the low thermal conductive layer 42a. In the arrangement region, the high mesa waveguide structure 110 is provided on the side surface and the bottom of the bottom.

  In the manufacturing method of the high mesa waveguide structure according to the seventh embodiment, first, the high mesa waveguide structure 110 and a metal layer such as a Ti layer are formed as in the first embodiment. At this time, the microheater 111 is formed by forming a metal layer using a lift-off mask having a pattern in which the side surface and the bottom of the high mesa waveguide structure 110 are exposed in the arrangement region along the surface direction of the low thermal conductive layer 42a. It is formed. Other configurations and manufacturing methods are the same as those in the first embodiment.

  In the seventh embodiment, the microheater 111 is provided so as to cover the side surface and the bottom portion of the high mesa waveguide structure 110 including the optical waveguide layer 44. As a result, the same effects as those of the sixth embodiment can be obtained, and heat conduction occurs as indicated by arrows in FIG. 8, so that the heating efficiency of the optical waveguide layer 44 can be greatly improved.

(Eighth embodiment)
Next, a high mesa waveguide structure in a semiconductor optical device according to an eighth embodiment of the present invention will be described. FIG. 9 is a cross-sectional view showing a high mesa waveguide structure according to the eighth embodiment. As shown in FIG. 9, in the high mesa waveguide structure 120 according to the eighth embodiment, unlike the first embodiment, the low heat conduction layer 42a as the low heat conduction region is not provided, and the structure is a hollow structure. A low heat conduction cavity 121 filled with air constitutes a low heat conduction region. In this case, the high mesa waveguide structure 120 is supported on the n-type InP substrate 41 by the n-type AlInAs layer 42. Other configurations are the same as those of the first embodiment.

  In the manufacturing method of the high mesa waveguide structure according to the eighth embodiment, first, similarly to the first embodiment, an n-type AlInAs layer 42, a lower cladding layer 43, an optical waveguide are formed on an n-type InP substrate 41. The wave layer 44 and the upper cladding layer 45 are sequentially laminated. Thereafter, anisotropic etching is performed partway through the lower cladding layer 43 by dry etching, and one end of the n-type AlInAs layer 42 is exposed by dry etching. Subsequently, the n-type AlInAs layer 42 is selectively etched by a wet etching method using a hydrofluoric acid-based etchant, thereby forming the low thermal conduction cavity 121. Note that one end of the n-type AlInAs layer 42 is exposed and an AlInAs oxide layer is formed by performing an oxidation process in the same manner as in the first embodiment, and then an AlInAs oxide layer using a hydrofluoric acid-based etchant. It is also possible to selectively etch away. In addition, since the low thermal conduction cavity 121 is formed by selectively etching the upper and lower InP layers, the InP layers such as the GaInAs layer, the GaInAsP layer, and the AlGaInAs layer are etched instead of the n-type AlInAs layer 42. A material having a high selectivity and which can be formed on the InP substrate 41 can be used.

  According to the eighth embodiment, by providing the microheater 25 and the low thermal conduction cavity 121, the same effect as that of the first embodiment can be obtained.

(Ninth embodiment)
Next, an integrated semiconductor optical device according to a ninth embodiment to which the present invention is applicable will be described. FIG. 10 is a cross-sectional view showing a wavelength tunable laser element that is an integrated semiconductor optical element according to the ninth embodiment.

  As shown in FIG. 10, in the integrated semiconductor laser device 200 that is a wavelength tunable laser device according to the ninth embodiment, a first sampled grating waveguide portion 201 that is a DBR (Distributed Bragg Reflector) mirror as a back mirror. , A phase adjustment waveguide section 202, a gain waveguide section 203, a second sampled grating waveguide section 204 which is a DBR mirror as a front mirror, and a semiconductor optical amplifier (SOA) 205.

  In the integrated semiconductor laser device 200, the passive region is constituted by the first sampled grating waveguide portion 201, the phase adjustment waveguide portion 202, and the second sampled grating waveguide portion 204 as passive elements. The first sampled grating waveguide unit 201, the phase adjusting waveguide unit 202, and the second sampled grating waveguide unit 204 have a high mesa structure. An active region is constituted by the gain waveguide section 203 and the SOA 205 as active elements. The gain waveguide section 203 and the SOA 205 have a buried structure.

  In the integrated semiconductor laser device 200, an n-type AlInAs layer 220, a lower cladding layer 230, a core layer 240, and an upper cladding layer 250 are sequentially stacked on the main surface of an n-type InP substrate 210. A p-side electrode 261 is provided on the upper surface of the upper cladding layer 250 selectively in the active region via an InGaAs contact layer (not shown). In the passive region, a micro heater 262 is selectively provided in the lower clad layer 230. The microheater 262 is disposed in the upper layer of the low thermal conductive layer 221 in the formation region along the in-plane direction of the lower thermal conductive layer 221. An n-side electrode 270 is provided on the back surface of the n-type InP substrate 210. A non-reflective film 280 is provided on the emission end face of the laser beam in the laminated body of the n-type InP substrate 210, the n-type AlInAs layer 220, the lower cladding layer 230, the core layer 240, and the upper cladding layer 250. Here, the film thickness of the n-type AlInAs layer 220 is determined in the same manner as in the first embodiment, and is, for example, 100 nm.

  The phase adjusting waveguide section 202 in the passive region is configured by sequentially laminating a low thermal conductive layer 221, a lower cladding layer 230, a waveguide core layer 243, and an upper cladding layer 250 on the main surface of the n-type InP substrate 210. ing. The microheater 262 is selectively provided in the lower cladding layer 230 of the upper layer of the low thermal conductive layer 221 in the formation region along the in-plane direction of the lower thermal conductive layer 221. The n-type InP substrate 210 is provided with an n-side electrode 270 on the back surface. The low thermal conductive layer 221 is made of an oxidized n-type AlInAs layer. The lower cladding layer 230 is composed of an n-type InP layer as an n-type semiconductor layer, and the upper cladding layer 250 is composed of a p-type InP layer as a p-type semiconductor layer. The non-oxidized n-type AlInAs layer 220 and the upper lower cladding layer 230 are connected. The waveguide core layer 243 is made of a GaInAsP layer whose band gap wavelength is adjusted to 1.3 μm, for example.

  The first sampled grating waveguide portion 201 and the second sampled grating waveguide portion 204 in the passive region are formed on the main surface of the n-type InP substrate 210 with a low thermal conductive layer 221, a lower cladding layer 230, a grating layer 242, and The upper cladding layer 250 is configured by sequentially stacking. The microheater 262 is selectively provided in the lower cladding layer 230 of the upper layer of the low thermal conductive layer 221 in the formation region along the in-plane direction of the lower thermal conductive layer 221. The n-type InP substrate 210 provided with the n-side electrode 270 on the back surface is shared with the phase adjustment waveguide section 202. The lower cladding layer 230 and the upper cladding layer 250 are made of InP layers. The grating layer 242 is made of a GaInAsP layer in which grating regions in which short-period gratings are formed are arranged at a predetermined period.

  The gain waveguide section 203 and the SOA 205 in the active region are formed on the main surface of the n-type InP substrate 210 by an n-type AlInAs layer 220, a lower cladding layer 230, an active layer 241, an upper cladding layer 250, and a GaInAs contact layer (not shown). P-side electrode 261 is sequentially stacked. The n-type InP substrate 210, the lower cladding layer 230, and the upper cladding layer 250 are shared with the first sampled grating waveguide unit 201, the phase adjustment waveguide unit 202, and the second sampled grating waveguide unit 204. . The n-type AlInAs layer 220 is an unoxidized region of the low thermal conductive layer 221 that is not oxidized. The active layer 241 is composed of a GaInAsP layer having a multiple quantum well (MQW) structure.

  In the integrated semiconductor laser device 200, the low thermal conductive layer 221 in which the n-type AlInAs layer 220 is oxidized is provided between the microheater 262 and the n-type InP substrate 210 along the stacking direction. The same effect as that of the first embodiment can be obtained.

  According to the ninth embodiment, in the passive region, the microheater 262 is selectively provided in the upper layer portion of the low thermal conductive layer 221 in the formation region along the in-plane direction of the low thermal conductive layer 221. Thus, the same effect as that of the first embodiment can be obtained.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as necessary.

In the above-described embodiment, the n-type AlInAs layers 42 and 220 are made of AlInAs having a single composition. However, they may not necessarily have a single composition. _{Specifically, Al 1-xy Ga x In} y As 1-z P z layer and the _{Al 1-pq Ga p In q} As 1-r P r layer (0 <x + y <1,0 <p + q <1, x A structure of so-called distortion compensation in which ≠ p, y ≠ q, z ≠ r) are alternately stacked may be used.

  In the above-described embodiment, the low thermal conductive layers 42a and 221 are composed of an AlInAs oxide layer obtained by oxidizing one n-type AlInAs layer. However, the present invention is not necessarily limited to one layer. Specifically, a low thermal conductive layer can be configured by providing a plurality of AlInAs layers as layers to be oxidized sandwiched between semiconductor layers having other compositions such as an InP layer. Further, instead of the low thermal conductive layer 221, a low thermal conductive cavity constituted by a cavity can be used. In this case, the same effect as the effect of the low thermal conductive layer 221 can be obtained.

DESCRIPTION OF SYMBOLS 1 Wavelength variable laser element 10 1st waveguide part 11 Waveguide part 11a Diffraction grating loading type gain part 11aa Active core layer 11ab Diffraction grating layer 11b Phase adjustment part 12 Semiconductor laminated part 13,261 p side electrode 14,15,25 , 25a, 25b, 61, 61a, 61b, 71, 81, 91, 91a, 91b, 101, 111, 111a, 111b, 262 Microheater 20 Second waveguide portion 21 Branching portion 21a Multimode interference waveguide 22 , 23 Arm part 24 Ring-shaped waveguide 30, 270 n-side electrode 41, 210 n-type InP substrate 42, 220 n-type AlInAs layer 42a, 221 low thermal conduction layer 43, 230 lower clad layer 44 optical waveguide layer 45, 250 upper clad Layer 46 Dielectric layer 48 Resin layer 49 Lead-out wiring 60, 70, 80, 90, 100 110,120 high-mesa waveguide structure 121 low thermal conductivity cavity 200 integrated semiconductor laser element 240 core layer 241 active layer 242 grating layer 243 waveguide core layer

Claims (8)

Above the semiconductor substrate,
A low heat conduction region that suppresses heat conduction;
A high mesa waveguide structure having a waveguide layer and a skirt portion of the high mesa waveguide structure provided in a region narrower than an arrangement region along the plane direction of the low heat conduction region in the upper layer of the low heat conduction region. And a heating unit provided. A semiconductor optical device comprising:   The semiconductor optical device according to claim 1, wherein the heating unit is provided on a side portion of the high mesa waveguide structure.   The semiconductor optical device according to claim 1, wherein the heating unit is provided in a region that covers the high mesa waveguide structure.   The semiconductor optical device according to claim 1, wherein the heating unit is provided apart from the high mesa waveguide structure.   The semiconductor optical device according to claim 1, wherein the heating unit is provided only at a skirt portion of the high mesa waveguide structure.   6. The semiconductor light according to claim 1, wherein the low thermal conduction region is formed of an oxidized layer in which at least one semiconductor layer substantially lattice-matched to the semiconductor substrate is oxidized. element. The semiconductor substrate is an InP substrate, and the semiconductor layer is an Al _{1 -xy} Ga _x In _y As _{1 -z} P _z layer (0 <x + y <1, 0 ≦ x <1, 0 <y <1, 0 ≦ The semiconductor optical device according to claim 6, wherein z <1).   The semiconductor optical device according to claim 1, wherein the low thermal conductivity region is formed of a cavity.

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