JP6231389B2 - Semiconductor optical device and optical module - Google Patents

Description

  The present invention relates to a semiconductor optical device and an optical module.

  2. Description of the Related Art In recent years, semiconductor optical devices such as semiconductor lasers have been increasingly miniaturized in order to meet demands such as miniaturization of optical modules including semiconductor optical devices.

  Patent Document 1 discloses a semiconductor laser device or the like that can suppress an increase in operating voltage of a semiconductor laser element due to heat applied to a current passage portion at the time of fusion even when a junction down method is adopted. Is described.

  Patent Document 2 describes a semiconductor laser that has good heat dissipation and can reduce parasitic capacitance.

  Patent Document 3 describes an optical integrated circuit in which isolation between elements is ensured at the same time without complicating the element manufacturing process and without reducing optical coupling efficiency between elements.

JP2012-151182A JP 2010-199379 A JP-A-7-58310

  However, downsizing of the element causes thermal interference due to the proximity arrangement of the IC driver, and raises the active layer temperature of the element.

  Here, the heat radiation path can be increased by increasing the area of the drive electrode. However, the increase in the area of the drive electrode leads to an increase in parasitic capacitance generated between the drive electrodes, thereby deteriorating the high-frequency characteristics of the semiconductor optical device. Invite.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor optical device and an optical module that further improve heat dissipation performance while suppressing parasitic capacitance of a drive electrode.

  (1) In order to solve the above problems, a semiconductor optical device according to the present invention includes: an optical waveguide portion including an active layer and extending in a light emitting direction including the active layer, and above the optical waveguide portion. A semiconductor multilayer in which a ridge portion located, a first bank portion disposed on a first side of the ridge portion, and a second bank portion disposed on a second side of the ridge portion are formed }, An insulating layer stacked in a predetermined region on the upper surface of the semiconductor multilayer, and {a first contact region that is a top surface of the ridge portion and does not stack the insulating layer; A first drive electrode formed continuously extending to the upper surface of the insulating layer stacked in the two bank portions} and {a part of the top surface of the first bank portion and the insulating layer is not stacked. Including a second contact region and in non-contact with the first drive electrode; Characterized in that it comprises a dummy electrode} to be made.

  (2) In the semiconductor optical device according to (1), the first contact region is a top surface of a contact layer, and the second contact region is a top surface of a cladding layer. And

  (3) In the semiconductor optical device according to (2), the second bank unit includes the contact layer in which the insulating layer is stacked on an upper surface and the contact layer in which the contact layer is stacked on an upper surface. A difference in height between top surfaces of the first drive electrode and the dummy electrode is smaller than a sum of a thickness of the insulating layer and a thickness of the contact layer in the second bank portion, and the dummy layer The electrode has a thickness that is greater than a thickness of a portion of the first drive electrode formed in the second bank portion.

  (4) The semiconductor optical device according to (2), wherein the active layer is not formed below the second bank portion.

  (5) The semiconductor optical device according to (1), wherein the bottom surface of the first gap located between the ridge portion and the first bank portion, and the ridge portion and the second bank portion Isolation grooves extending in parallel with the ridge portion are respectively formed on the bottom surfaces of the second gaps located between the isolation grooves, and the isolation grooves reach under the active layer included in the semiconductor multilayer, It is characterized by that.

  (6) The semiconductor optical device according to (1), wherein the semiconductor multilayer is stacked on an upper surface, and {the top of the semiconductor substrate Including a third contact region of the surface where the semiconductor multilayer is not stacked, and further extending continuously to the upper surface of the insulating layer, and formed in a non-contact manner with the first drive electrode and the dummy electrode, A second drive electrode for supplying a current to the active layer in a pair with the first drive electrode}.

  (7) The semiconductor optical device according to (6), further including an integrated mirror on an extension line of the optical waveguide portion, wherein the third contact region is formed when the ridge portion is viewed from above. An extension line of the optical waveguide portion has a portion positioned so as to penetrate the integrated mirror and the third contact region in this order, and the normal direction of the mirror surface of the integrated mirror is emitted from the optical waveguide portion. It is characterized by crossing with the light emitting direction.

  (8) The semiconductor optical device according to any one of (1) to (7), and {a submount to which the first drive electrode and the dummy electrode are brazed}. This is an optical module.

  (9) The semiconductor optical device according to the present invention includes: an optical waveguide portion including an active layer, a cladding layer, and a contact layer, including the active layer and extending in a light emitting direction, and disposed above the optical waveguide portion. A semiconductor multilayer} that forms a ridge portion, a first bank portion located on a first side of the ridge portion, and a second bank portion disposed on a second side of the ridge portion, An insulating layer stacked in a predetermined region on the upper surface of the semiconductor multilayer; and {the first contact region which is a top surface of the ridge portion and is a top surface of the contact layer on which the insulating layer is not stacked. And a first drive electrode formed continuously extending to the upper surface of the insulating layer stacked on the second bank portion}, and a part of the top surface of the first bank portion. The top of the cladding layer where the insulating layer is not laminated. Include a second contact region is a surface, characterized in that it comprises a dummy electrode} formed by the first drive electrode and the non-contact.

  According to the present invention, there are provided a semiconductor optical device and an optical module having further excellent heat dissipation performance while suppressing parasitic capacitance of the drive electrode.

1 is a perspective view showing a configuration of a semiconductor laser element according to a first embodiment of the present invention. 1 is a cross-sectional view of a semiconductor laser device according to a first embodiment of the present invention. It is a figure which shows the reference value of the thermal resistivity and thermal conductivity of the material used for the semiconductor laser element which concerns on the 1st Embodiment of this invention. It is a figure which shows the thermal radiation path | route in the semiconductor laser element concerning the 1st Embodiment of this invention. It is a figure which shows the thermal radiation path | route of the semiconductor laser element which concerns on a 1st comparative example. It is a figure which shows the thermal radiation path | route of the semiconductor laser element which concerns on a 2nd comparative example. It is a perspective view which shows the semiconductor laser element which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the semiconductor laser element which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the optical module which concerns on the 4th Embodiment of this invention. It is a figure which shows the thermal resistance and the parasitic capacitance of a p-type drive electrode. It is sectional drawing of the optical module which concerns on the 5th Embodiment of this invention. It is sectional drawing of the optical module which concerns on the 6th Embodiment of this invention. It is a top view of the semiconductor laser element concerning the 7th Embodiment of this invention. It is sectional drawing of the optical module which concerns on the 7th Embodiment of this invention. It is a figure which shows the relationship between the area of an n-type drive electrode, and the relative value of thermal resistance.

  Hereinafter, embodiments of the present invention will be described specifically and in detail based on the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. In addition, the figure shown below demonstrates the Example of embodiment to the last, Comprising: The magnitude | size of a figure and the reduced scale as described in a present Example do not necessarily correspond.

[First Embodiment]
FIG. 1 is a perspective view showing the configuration of the semiconductor laser device 1 according to the first embodiment of the present invention. The semiconductor laser device 1 according to the present embodiment is a ridge type semiconductor laser formed including a semiconductor multilayer, and as shown in FIG. 1, a single ridge portion 11 (one waveguide portion) is provided. This is a semiconductor laser element 1. Although the semiconductor laser device 1 according to the present embodiment is a DFB (Distributed Feedback) laser, it is needless to say that the present invention is not limited to this. The semiconductor laser element 1 includes a ridge portion 11 (mesa portion) that is a convex portion of a semiconductor multilayer, and a first bank portion 12 is disposed on the first side (left side in the drawing) of the ridge portion 11. ing. A second bank portion 13 is disposed on the second side of the ridge portion 11 (right side in the figure). The ridge portion 11, the first bank portion 12, and the second bank portion 13 are formed in a semiconductor multilayer. A first gap bottom surface 14 is provided between the ridge portion 11 and the first bank portion 12, and a second gap bottom surface 15 is provided between the ridge portion 11 and the second bank portion 13. Here, an isolation groove 10 extending in parallel with the ridge portion 11 is formed in the first gap bottom surface 14 and the second gap bottom surface 15. The ridge portion 11 includes a top surface of the convex portion and side surfaces on both sides. Similarly, the first bank portion 12 and the second bank portion 13 include a top surface and side surfaces. Here, there may be cases where the boundary between the ridge portion 11 and the first gap bottom surface 14 or the second gap bottom surface 15 is not necessarily clear, such as when the side surfaces on both sides of the ridge portion 11 have gentle hems. Similarly, when the side surface of the first bank portion 12 or the second bank portion 13 has a gentle skirt, the boundary between the first bank portion 12 and the first gap bottom surface 14, or the second bank portion 13 and the second gap bottom surface. The border with 15 may not always be obvious. In such a case, at least a flat portion of the surface sandwiched between the ridge portion 11 and the first bank portion 12 is referred to as a first gap bottom surface. The same applies to the bottom surface of the second gap.

  FIG. 2 is a sectional view of the semiconductor laser device 1 according to the first embodiment of the present invention. FIG. 2 shows a cross section taken along line II-II in FIG. In the semiconductor laser device 1 according to the first embodiment of the present invention, the active layer 4, the cladding layer 5, and the contact layer 6 (cap layer) are sequentially stacked on the upper surface of the InP substrate 2 (n-type semiconductor substrate). A semiconductor multilayer is formed. Here, the InP substrate 2 is formed of, for example, n-type InP, and the active layer 4 is formed of, for example, a multiple quantum well structure using InGaAlAs. The clad layer 5 is made of, for example, p-type InP, and the contact layer 6 is made of, for example, InGaAs. Each semiconductor layer is laminated to a thickness of about several μm by, for example, metal organic vapor phase epitaxy, and has a substantially flat interface. The semiconductor multilayer may include an etching stopper layer in the lower layer portion of the cladding layer 5, and the ridge portion 11 is formed by etching the semiconductor multilayer to the etching stopper layer. In such a case, the first gap bottom surface 14 and the second gap bottom surface 15 are the upper surfaces of the etching stopper layer.

  Here, the “upper surface” of the InP substrate 2 refers to the entire upper surface of the InP substrate 2 in FIG. 2 or a part thereof. The “upper side” in the InP substrate 2 refers to the side on which the active layer 4 and the cladding layer 5 are laminated on the InP substrate 2.

  In the semiconductor laser device 1 according to the first embodiment of the present invention, the insulating layer 7 is stacked in a predetermined region on the upper surface of the semiconductor multilayer. Here, the predetermined region is a region obtained by removing at least a first contact region and a second contact region described later from the entire upper surface of the semiconductor multilayer. Specifically, the predetermined region includes, on the upper surface of the semiconductor multilayer, side surfaces on both sides of the ridge portion 11, the first gap bottom surface 14 and the second gap bottom surface 15, the side surfaces of the first bank portion 12, A part of the top surface of the first bank unit 12 (a portion of the top surface of the first bank unit 12 excluding at least the second contact region), the side surface of the second bank unit 13, and the top surface of the second bank unit 13. It is.

An insulating layer 7 is stacked on the upper surface of the contact layer 6 except for the top surface of the ridge portion 11. The insulating layer 7 is formed of SiO ₂ laminated to a thickness of about several μm, for example. The first contact region is a region on the top surface of the ridge portion 11 where the insulating layer 7 is not stacked. The first contact region is a part of the top surface of the contact layer 6 and is a region where the p-type drive electrode 8 which is the first drive electrode is formed. It can also be said that the first contact region is an interface between the p-type drive electrode 8 and the contact layer 6. The first contact region does not necessarily have to be the entire top surface of the ridge portion 11. The first contact region does not necessarily include the edge along the extending direction of the top surface of the ridge portion 11, or both end portions of the top surface of the ridge portion 11. It may be a part of the top surface such as a region excluding the edge. The p-type drive electrode 8 is a metal layer laminated in the order of Ti, Pt, and Au, for example, and has a thickness of about several μm. Such a configuration is the same for the other electrodes. In addition to the first contact region, the p-type drive electrode 8 is formed so as to continuously spread over the upper surface of the insulating layer 7 stacked on the second bank portion 13.

  There are a case where the n-type drive electrode 3 is fused to the submount and a case where the p-type drive electrode 8 is fused to the submount. The former is called a junction up (j-up) implementation, and the latter is called a junction down (j-down) implementation. Here, if solder or the like is directly fused to the ridge portion 11, the laser characteristics are deteriorated. Therefore, even if either junction-up mounting or junction-down mounting is adopted, the first of the p-type drive electrodes 8 is used. It is desirable that solder or the like is fused to a portion formed in the two bank portion 13 and current is supplied from an external circuit through the fused portion.

  A portion of the p-type drive electrode 8 formed in the first contact region and an n-type electrode 3 which is the second drive electrode formed on the lower surface of the InP substrate 2 are paired to pass current to the active layer 4. Supply. The current is a flow of electrons and holes, and recombination of electrons and holes occurs in the active layer 4 below the ridge portion 11, and light is generated. The generated light is amplified while reciprocating through the optical waveguide portion, and is emitted as laser light from the end face of the optical waveguide portion in a direction perpendicular to the paper surface of FIG. Here, the optical waveguide portion is a portion of the semiconductor multilayer that includes the active layer 4 below the ridge portion 11 and extends in the light emitting direction.

  Note that the “top surface” of the ridge portion 11 refers to a flat surface located at the top of the ridge portion 11, and the same applies to the case of using other portions. Further, the “emission direction” of light at the end face of the optical waveguide section means a direction in which the central axis of the light beam emitted from the end face of the optical waveguide section extends.

  A dummy electrode 9 is formed in the semiconductor laser device 1 according to the first embodiment of the present invention. The second contact region is a part of the top surface of the first bank portion 12 and the region where the insulating layer 7 and the contact layer 6 are not formed. It can be said that the second contact region is an interface between the dummy electrode 9 and the clad layer 5. Since the second contact region is a part of the top surface of the cladding layer 5, the stacked insulating layer 7 and contact layer 6 are removed by etching or the like, or the second contact is formed when the contact layer 6 and insulating layer 7 are stacked. It is necessary to mask the area. The dummy electrode 9 is formed in a non-contact manner with the p-type drive electrode 8 and has a configuration that does not affect the parasitic capacitance of the p-type drive electrode 8. The dummy electrode 9 and the p-type drive electrode 8 are formed so as not to be in physical contact. In the semiconductor laser element 1, the dummy electrode 9 and the p-type drive electrode 8 are semiconductor multi-layers from the viewpoint of electrical connection. Connected through. The portion of the semiconductor multilayer that contributes to the electrical connection between the dummy electrode 9 and the p-type drive electrode 8 has an extremely high resistance compared to the dummy electrode 9 and the p-type drive electrode 8. It can be said that the mold drive electrode 8 is substantially electrically insulated. Therefore, even if the area of the dummy electrode 9 is increased, the parasitic capacitance of the p-type drive electrode 8 is hardly affected. However, since the dummy electrode 9 contributes to heat dissipation, the heat dissipation performance of the semiconductor laser device 1 can be improved while suppressing an increase in the parasitic capacitance of the p-type drive electrode 8. In addition, the state where the p-type drive electrode 8 and the dummy electrode 9 are not in physical contact refers to the state where both electrodes are not in direct contact.

  The isolation groove 10 formed in the first gap bottom surface 14 and the second gap bottom surface 15 is conventionally formed for the purpose of narrowing the current flowing from the ridge portion 11 into the active layer 4 and narrowing the light emitting region. is there. In addition to the above function, the isolation groove 10 in the present embodiment has a function of further increasing the electrical resistance between the p-type drive electrode 8 and the dummy electrode 9 and further suppressing the electrical connection between the electrodes. ing. In order to exert these functions, it is desirable that the deepest part of the isolation groove 10 reaches below the active layer 4. If the deepest part of the isolation groove 10 reaches only above or part of the active layer 4, the charge is transferred through the active layer 4, and the electric resistance between the p-type drive electrode 8 and the dummy electrode 9 is sufficiently high. It is because it cannot be raised.

  When the semiconductor laser element is modulated and driven, the parasitic capacitance generated between the p-type drive electrode 8 and the n-type drive electrode 3 becomes a limiting factor for the high frequency characteristics. This is because the cut-off frequency decreases as the parasitic capacitance increases. Therefore, in order to improve the high frequency characteristics, the area of the p-type drive electrode 8 needs to be as small as possible. On the other hand, in consideration of the heat dissipation characteristics, if the p-type drive electrode 8 having a high thermal conductivity is made as large as possible, the heat dissipation path becomes wider and the heat dissipation characteristics can be improved.

  As described above, the second contact region is a part of the top surface of the cladding layer 5, the dummy electrode 9 is formed in the second contact region, and is stacked above the second contact region in the manufacturing process. The contact layer 6 has been removed. In the present embodiment, in consideration of manufacturing errors when the contact layer 6 is removed or the dummy electrode 9 is formed, the region where the contact layer 6 is removed is the second contact region (the dummy electrode 9 is formed). As shown in FIG. 2, there is a region where the top surface of the cladding layer 5 is exposed around the dummy electrode 9. Similarly, in consideration of manufacturing errors when the contact layer 6 and the insulating layer 7 are removed, the region where the insulating layer 7 is removed is wider than the region where the contact layer 6 is removed. There is a region where the top surface of the contact layer 6 is exposed around the region where the top surface of the layer 5 is exposed.

  In the present embodiment, the region where the dummy electrode 9 is formed on the upper surface of the semiconductor multilayer is the top surface of the cladding layer 5, but is not limited to this. The region where the dummy electrode is formed on the upper surface of the semiconductor multilayer may further extend from the top surface of the cladding layer 5 and extend to part of the side surface of the contact layer 6 and part of the top surface. Furthermore, if the dummy electrode 9 is formed in a non-contact manner with the p-type drive electrode 8, the dummy electrode 9 may extend to the top surface of the insulating layer 7.

FIG. 3 is a diagram showing reference values of the thermal resistivity and thermal conductivity of the material used for the semiconductor laser device 1 according to the first embodiment of the present invention. The materials are, in order from the top, InP constituting the InP substrate 2 and the cladding layer 5, InGaAs constituting the contact layer 6, SiO ₂ constituting the insulating layer 7, and Au constituting the p-type drive electrode 8. The thermal conductivity of Au constituting the p-type drive electrode 8 is the highest, on the order of 10 ² W / (K · m), whereas InP constituting the InP substrate 2 and the cladding layer 5 is 10 ¹ W / In the order of (K · m), InGaAs constituting the contact layer 6 and SiO ₂ constituting the insulating layer 7 are on the order of 10 ⁰ W / (K · m). In particular, the thermal conductivity of SiO ₂ is small, and it is predicted that the insulating layer 7 will be a layer for confining heat. The thermal resistivity is the reciprocal of the thermal conductivity, and the smaller the thermal resistivity, the better the thermal conductivity.

  FIG. 4 is a diagram showing a heat dissipation path in the semiconductor laser device 1 according to the first embodiment of the present invention. Since heat is generated with light emission in the semiconductor laser element, a device for efficiently releasing heat from the heat generating portion 20 is required. In the present embodiment, in addition to the InP substrate side heat dissipation path 21 and the p-type drive electrode side heat dissipation path 22, a dummy electrode side heat dissipation path 23 is secured. Here, since the lower surface of the dummy electrode 9 is in contact with the cladding layer 5 and does not sandwich the insulating layer 7 and the contact layer 6, heat is radiated without passing through a layer whose thermal conductivity is about one digit smaller than that of InP. This contributes to the improvement of heat dissipation characteristics. Further, in this embodiment, the InP substrate side heat dissipation path 21 is a path of about 100 μm, whereas the dummy electrode side heat dissipation path 23 is a path of about 20 μm, which is shorter and contributes to the improvement of heat dissipation characteristics. The ratio is large.

  The InP substrate side heat dissipation path 21 and the p-type drive electrode side heat dissipation path 22 are paths for releasing heat to the fused wire or submount. On the other hand, when the dummy electrode 9 is not wired, the dummy electrode side heat dissipation path 23 becomes a path for diffusing heat from the electrode surface into the air (or in the atmosphere where the semiconductor laser element 1 is placed). When bonding a wire different from the laser driving wire to the dummy electrode 9, the dummy electrode 9 has a portion in contact with a metal having a much higher thermal conductivity than air. As a result, the heat dissipation performance of the semiconductor laser device 1 is improved as compared with the case where the dummy electrode 9 is not wired.

Although various heat dissipation paths from the heat generating unit 20 are conceivable in addition to those illustrated, only representative paths are shown in FIG. For example, the p-type drive electrode side heat dissipation path 22 is along the p-type drive electrode 8, and this is dominant because the thermal conductivity of Au is about two orders of magnitude higher than that of SiO _2. It is because it is considered.

  FIG. 5 is a diagram illustrating a heat dissipation path of the semiconductor laser device according to the first comparative example. The semiconductor laser device according to the first comparative example is different from the semiconductor laser device 1 according to the first embodiment of the present invention in that the dummy electrode 9 is not formed. Common to the semiconductor laser device 1 according to the first embodiment. In the semiconductor laser device according to the first comparative example, the shape of the p-type drive electrode 8 is the same as that of the semiconductor laser device 1 according to the first embodiment, and thus the p-type drive electrode 8 in the first comparative example. Is considered to be the same as the parasitic capacitance of the p-type drive electrode 8 in the first embodiment. That is, in the semiconductor laser device according to the first comparative example, the increase in parasitic capacitance is suppressed to the same extent as in the semiconductor laser device 1 according to the first embodiment. However, it is considered that the heat dissipation characteristics of the semiconductor laser device according to the first comparative example are inferior to those of the semiconductor laser device 1 according to the first embodiment. This is because, as shown in FIG. 5, in the semiconductor laser device according to the first comparative example, the main heat dissipation paths are the InP substrate side heat dissipation path 21 and the p-type drive electrode side heat dissipation path 22, and the dummy electrode side heat dissipation path 23 is Because it does not exist. Since the p-type drive electrode 8 spreads widely in the second bank part 13, it is considered that the path reaching the second bank part 13 among the p-type drive electrode side heat dissipation path 22 contributes most to the improvement of the heat dissipation performance. On the other hand, since the p-type drive electrode 8 is only slightly formed on the top surface of the first bank part 12, the heat dissipation performance of the path reaching the first bank part 12 in the p-type drive electrode side heat dissipation path 22 is improved. The contribution to is considered small.

  FIG. 6 is a diagram illustrating a heat dissipation path of the semiconductor laser device according to the second comparative example. The structure of the semiconductor laser device according to the second comparative example is different from the semiconductor laser device according to the first comparative example in the following two points. First, the contact layer 6 is formed on the cladding layer 5 over the entire area of the first bank portion 12. Furthermore, the insulating layer 7 is formed over the entire upper surface of the first bank portion 12 (contact layer 6). The p-type drive electrode 8 is formed symmetrically with respect to the ridge portion 11 so as to extend both above the second bank portion 13 and above the first bank portion 12. Except for these two points, the semiconductor laser device according to the second comparative example has the same structure as the semiconductor laser device according to the first comparative example. Compared with the semiconductor laser device according to the first comparative example, the p-type drive electrode 8 is formed so as to extend above the first bank 12 in addition to above the second bank 13. The heat dissipation path to the first bank portion 12 is expanded, and the heat dissipation performance is as high as that of the heat dissipation path to the second bank portion 13, so that the heat dissipation is higher than that of the semiconductor laser device according to the first comparative example. The performance is expected to improve further. However, the area of the p-type drive electrode 8 is increased as compared with the semiconductor laser element according to the first comparative example (and the semiconductor laser element 1 according to the first embodiment), and the p-type drive electrode 8 and the n-type drive electrode 8 are increased. There is an adverse effect that parasitic capacitance generated between the drive electrode 3 and the like increases, and high-speed modulation operation of the semiconductor laser element 1 becomes difficult.

  Thus, there is a trade-off relationship between improving the heat dissipation performance and suppressing the increase in parasitic capacitance, and a device for achieving both is required. In this embodiment, by forming the dummy electrode 9 on a part of the upper surface of the cladding layer 5, it is possible to dissipate heat without passing through the contact layer 6 or the insulating layer 7 having a low thermal conductivity. A heat dissipation mechanism that suppresses temperature rise is provided. Further, by forming the dummy electrode 9 in non-contact with the p-type drive electrode 8, an increase in parasitic capacitance of the p-type drive electrode 8 is suppressed.

[Second Embodiment]
The demand for semiconductor laser devices is increasing with the recent increase in Internet access by mobile terminals and the rapid spread of cloud-based storage and computing. Bandwidths of various networks, such as mobile phone base stations and core networks, data centers, or networks within data centers, are beginning to become tight, and in recent years there has been a demand for higher capacity and higher speed of networks. The range of application of optical technology is expanding from networks to communication systems such as HPC (High Performance Computer), data centers, and storage. For example, in server racks used in data centers, communication between racks and within racks was performed using copper wires. However, in communication based on copper wires, the communication distance becomes shorter as the speed increases, so optical technology is adopted. Optical interconnection technology is expected.

  In long- and medium-distance communication networks, which are the main markets where optical communication systems have been utilized, aiming for large-capacity and high-speed optical communication, wavelength division multiplexing (WDM), time division multiplexing (TDM) From time division multiplexing, the development of technology for spatial multiplexing using multi-core fibers and the like, and the development of technology for multilevel conversion from amplitude modulation of optical signals to phases and polarizations are becoming popular. With the development of these technologies, it is expected that a large-capacity and high-speed communication network can be built. However, the device configuration changes due to the system configuration change are large, and the cost reduction required for the access network is within several years. It seems difficult to realize. In addition, it seems that the miniaturization required for the elements of the access network cannot be dealt with immediately.

  Therefore, as one approach for realizing an increase in capacity of the access network, parallel densification has been attempted. The so-called Si photonics technology, which has recently attracted attention, is considered to be applicable to parallel densification technology. For example, a compact optical device in which an InP semiconductor laser and a Si modulator fabricated on a CMOS platform are hybrid-integrated. A transmitter has been developed. With this technology, a QSFP (Quad Small Form-factor Pluggable) transceiver has been commercialized, which allows 10 Gbps operation signals to be transmitted at 40 Gbps by 4ch parallel transmission. Fabricating the above realizes a small and low cost transceiver.

  In the transceiver as described above, the light from one semiconductor laser is branched into four on the Si platform. In order to further increase the number of branches, it is necessary to increase the number of semiconductor lasers. In such a structure, it is indispensable to develop optical coupling and heat dissipation techniques in semiconductor laser array technology. Therefore, the semiconductor laser device 1 according to the second embodiment of the present invention is an application of the present invention to an arrayed semiconductor laser device, which will be described below.

  FIG. 7 is a perspective view showing a semiconductor laser device 1 according to the second embodiment of the present invention. Whereas the semiconductor laser device 1 according to the first embodiment of the present invention is a single semiconductor laser device, the semiconductor laser device 1 according to the second embodiment of the present invention includes a plurality of ridge portions 11. This is a semiconductor laser device having (a plurality of waveguide portions). That is, it is an arrayed semiconductor laser element, and is composed of a plurality of unit elements. As shown in FIG. 7, a plurality of ridge portions 11 extending along the light emission direction are arranged side by side in a direction perpendicular to the emission direction (lateral direction in the figure) on the upper part of the semiconductor multilayer. A plurality of ridge portions 11 are part of the upper surface of the semiconductor multilayer. A plurality of optical waveguide portions are formed including portions of the active layer 4 located below the plurality of ridge portions 11. The plurality of optical waveguide portions are formed side by side in a direction (lateral direction in the drawing) perpendicular to the light emitting direction (stretching direction of the ridge portion 11). Although two unit elements are shown in FIG. 7, it goes without saying that the number of unit elements can be appropriately selected. The structure of one unit element of the semiconductor laser element 1 according to the second embodiment is the same as the structure of the semiconductor laser element 1 according to the first embodiment. The n-type drive electrode 3 is a common electrode for all unit elements. In the semiconductor laser device 1 according to the second embodiment, as described above, each of the plurality of unit elements includes the ridge portion 11 and the first bank portion 12 and the second bank portion 13 on both sides thereof. In the two adjacent unit elements, the second bank portion 13 of the unit element on the first lateral side (left side in the figure) and the first bank of the unit element on the second side side (right side in the figure) The part 12 forms one bank part. The p-type drive electrode 8 of the first side unit element and the dummy electrode 9 of the second side unit element are formed together above the bank portion. 8 and the dummy electrode 9 are formed in a non-contact manner. That is, there is a portion where the p-type drive electrode 8 and the dummy electrode 9 are not formed above the bank portion. Thus, by arranging the semiconductor laser elements 1 in an array, a semiconductor laser element suitable for large-capacity optical communication can be obtained. In addition, since the n-type drive electrode 3 can be integrally formed with all unit elements, there is an advantage that the manufacturing process is simplified and an increase in manufacturing cost is suppressed.

  The semiconductor laser device 1 according to the second embodiment shown in FIG. 7 achieves a high-density parallel arrangement of laser devices by arraying, and increases the number of channels that can be used as compared with the case of a single laser device. A semiconductor laser device 1 suitable for communication is provided. Further, in the case of the semiconductor laser elements 1 arrayed as shown in FIG. 7, if the junction-up mounting is performed, the number of wire bonding increases, the process becomes complicated, and the production cost increases. On the other hand, in the case of junction down mounting, the p-type drive electrode 8 may be mounted on the wiring patterned on the submount, and the n-type drive electrode 3 is a common electrode throughout the array, so the number of wire bonding increases. As a result, the process becomes simple and an increase in manufacturing cost can be suppressed.

  In order to realize a small multi-channel optical transceiver, it is necessary to have an IC and an optical element in close proximity and an optical element array mounting technology. Furthermore, in order to save power in the optical transceiver, it is necessary to reduce the driving power of the semiconductor optical device and to perform an uncooled operation. As the operating environment temperature of the optical transceiver, for example, operation in a low temperature to high temperature range of 0 to 85 ° C. is required. Since a semiconductor laser generates heat during oscillation, the active layer temperature at a high temperature becomes higher than the outside air temperature, and there is a risk of thermal damage. In the case of a multi-channel transceiver, the active layer temperature of the semiconductor laser element further rises due to thermal interference caused by adjacent semiconductor laser elements and thermal interference caused by the close placement of the IC driver. Therefore, it is necessary to lower the active layer temperature of the semiconductor laser element. It is necessary to provide a mechanism for efficiently radiating the heat generated from the laser.

  In the second embodiment, as in the case of the first embodiment, the dummy electrode 9 is formed on a part of the upper surface of the clad layer 5 so that the contact layer 6 and the insulating layer 7 having low thermal conductivity are formed. A heat dissipating mechanism is provided that can dissipate heat without intervening and suppress the temperature rise of the active layer 4. Further, by forming the dummy electrode 9 in non-contact with the p-type drive electrode 8, an increase in parasitic capacitance of the p-type drive electrode 8 is suppressed.

[Third Embodiment]
FIG. 8 is a cross-sectional view of a semiconductor laser device 1 according to the third embodiment of the present invention. The difference from the first or second embodiment of the present invention is that the dummy electrode 9 is formed not on the cladding layer 5 but on the top surface of the contact layer 6. That is, the second contact region in the present embodiment is a part of the top surface of the first bank portion 12 in the semiconductor multilayer, like the second contact region in the first or second embodiment. However, a part of the top surface of the first bank portion 12 is a part of the top surface of the contact layer 6, unlike the first embodiment, which is a part of the top surface of the cladding layer 5. It can be said that the second contact region in the present embodiment is an interface between the dummy electrode 9 and the contact layer 6. In addition to the above differences, the semiconductor laser device 1 according to the third embodiment has a common structure with the semiconductor laser device 1 according to the first or second embodiment. The mounting method on the submount in this embodiment is the same in that either junction up or junction down may be used. The unit element functions as a single unit, but the same applies to the case where the unit element can be used for optical communication with a larger capacity.

  As shown in FIG. 3, InGaAs, which is the material of the contact layer 6, has a thermal conductivity that is about an order of magnitude smaller than that of InP. Therefore, the heat dissipation performance of the third embodiment is slightly inferior to that of the first embodiment. However, the process for removing the contact layer 6 located in the second contact region is not required in the manufacturing process, and the semiconductor laser device according to the third embodiment can be manufactured through a simpler manufacturing process. Is reduced. Even in the present embodiment, since the heat dissipation performance is improved as compared with the case where the dummy electrode 9 is not formed, the first or second embodiment and the present embodiment are considered in consideration of the balance between the manufacturing cost and the heat dissipation performance. Can be used properly.

  As described above, the second contact region is a part of the top surface of the contact layer 6, the dummy electrode 9 is formed in the second contact region, and is stacked above the second contact region in the manufacturing process. The insulating layer 7 has been removed. In the present embodiment, in consideration of manufacturing errors when the insulating layer 7 is removed or the dummy electrode 9 is formed, the region from which the insulating layer 7 is removed is the second contact region (the dummy electrode 9 is formed). As shown in FIG. 7, there is a region where the top surface of the contact layer 6 is exposed around the dummy electrode 9.

  In the present embodiment, the region where the dummy electrode 9 is formed on the upper surface of the semiconductor multilayer is all the top surface of the contact layer 6, but is not limited thereto. As long as the dummy electrode 9 is formed in a non-contact manner with the p-type drive electrode 8, the dummy electrode 9 may extend to the top surface of the insulating layer 7. Further, in order to suppress the electrical connection between the dummy electrode 9 and the p-type drive electrode 8, the p-type drive electrode 8 is formed on the upper surface of the insulating layer 7 above the first bank portion 12, and the contact layer It is desirable not to be in physical contact with the upper surface of 6. The same applies to the p-type drive electrode 8 of the adjacent first side unit element and the dummy electrode 9 of the second side unit element in the arrayed semiconductor laser elements. In order to suppress electrical connection between the dummy electrode 9 and the p-type drive electrode 8, the p-type drive electrode 8 is formed on the upper surface of the insulating layer 7 above the second bank portion 13, and contact layer It is desirable not to be in physical contact with the upper surface of 6.

[Fourth Embodiment]
FIG. 9 is a cross-sectional view of an optical module according to the fourth embodiment of the present invention. The optical module according to the present embodiment includes the semiconductor laser device 1 according to any one of the first to third embodiments, and a submount 30 on which the semiconductor laser device 1 is junction-down mounted. The p-type drive electrode 8 and the dummy electrode 9 of the semiconductor laser element 1 are brazed to the submount 30 with solder. FIG. 9 shows a case where the semiconductor laser device 1 according to the first embodiment shown in FIG. Needless to say, the semiconductor laser device 1 according to the second or third embodiment may be junction-down mounted on the submount 30. That is, the semiconductor laser element according to the present embodiment may be a single semiconductor laser element or an arrayed semiconductor laser element. There is an advantage that the number of wire bondings can be reduced by junction-down mounting the arrayed semiconductor laser elements 1. In any case, the semiconductor laser element generally absorbs heat or dissipates heat from the submount 30 side, so it is necessary to make the heat dissipation path from the drive electrode surface in contact with the submount 30 more effective. There is.

  The p-type drive electrode 8, the dummy electrode 9, and the submount 30 are connected through a p-type drive electrode side solder 31 and a dummy electrode side solder 32, respectively. By performing such mounting, the p-type drive electrode side heat dissipation path 22 and the dummy electrode side heat dissipation path 23 described above become paths for releasing heat to the submount 30, and the heat dissipation performance is remarkably improved. Further, when the solder contacts the ridge portion 11, ohmic characteristics are deteriorated or distortion due to thermal stress occurs at the time of fusion, and the laser characteristics of the semiconductor laser element are deteriorated. Therefore, in the present embodiment, a gap is provided between the ridge portion 11 and the submount 30. Here, since the dummy electrode 9 is formed on the upper surface of the cladding layer 5 by removing the contact layer 6 and the insulating layer 7 which are layers having low thermal conductivity, the height of the top surface is the p-type drive electrode. It is different from the height of 8. When the p-type drive electrode 8 and the dummy electrode 9 are stacked in the same process, the difference in height between the top surfaces of the p-type drive electrode 8 and the dummy electrode 9 is the contact layer 6 and the insulating layer 7 in the second bank portion 13. In this embodiment, the thickness is 500 to 1000 nm. For this reason, in this embodiment, the dummy electrode side solder 32 is made thicker than the p type drive electrode side solder 31 so as to cancel the difference in height between the p type drive electrode 8 and the dummy electrode 9. By adopting such a configuration, the semiconductor laser device 1 is mounted closer to the horizontal with respect to the submount 30, and the inclination of the light emission direction in the case of an optical module is suppressed.

  Here, the “thickness” of the contact layer 6 in the second bank portion 13 refers to the maximum value among the layer thicknesses of the contact layer 6 formed in the second bank portion 13. The same applies to the insulating layer 7. The “height” of the top surface of the p-type drive electrode 8 is the maximum value of the heights of the top surface of the p-type drive electrode 8 measured from the lower surface of the n-type drive electrode 3. The same applies to the height of the top surface of the dummy electrode 9. Although there is a degree of freedom in taking the reference point for measuring the height, the amount of attention here is the difference in height between the top surfaces of the p-type drive electrode 8 and the dummy electrode 9, so It does not depend on the direction.

  FIG. 10 is a diagram showing the thermal resistance and the parasitic capacitance of the p-type drive electrode 8. FIG. 10 shows a case where the semiconductor laser device according to the first comparative example shown in FIG. 5 is junction-down mounted on a submount to form an optical module (hereinafter referred to as the case of the first comparative example). , When the semiconductor laser device according to the second comparative example shown in FIG. 6 is junction-down mounted on the submount to form an optical module (in the following description, referred to as the second comparative example), The case of the optical module according to the embodiment is shown respectively. The vertical axis represents the thermal resistance and the parasitic capacitance of the p-type drive electrode 8 as relative values with respect to the first comparative example shown in FIG. The horizontal axis represents the structure, and in order from the left, in the case of the first comparative example shown in FIG. 5, in the case of the second comparative example shown in FIG. 6, in the fourth embodiment of the present invention shown in FIG. Is the case. In the graph, the relative value of the thermal resistance is shown using a black diamond, and the relative value of the parasitic capacitance of the p-type drive electrode 8 is shown using a white square.

  When attention is paid to the case of the second comparative example, the thermal resistance is reduced by a little less than 20% compared to the case of the first comparative example. However, at the same time, the parasitic capacitance of the p-type drive electrode 8 is increased by about 30%. On the other hand, in the case of the fourth embodiment of the present invention, the parasitic capacitance of the p-type drive electrode 8 is not changed from the case of the basic structure, and the thermal resistance is further reduced by several minutes from the case of the second comparative example. . From these facts, according to the fourth embodiment of the present invention, the parasitic capacitance of the p-type drive electrode 8 is suppressed to the same level as in the first comparative example, and the heat dissipation performance is further improved than in the second comparative example. It can be seen that a good semiconductor laser device 1 is provided.

[Fifth Embodiment]
FIG. 11 is a cross-sectional view of an optical module according to the fifth embodiment of the present invention. In the optical module according to the above-described fourth embodiment, the thickness of the dummy electrode side solder 32 is made larger than the thickness of the p-type drive electrode side solder 31, so that the semiconductor laser device 1 is sub-assembled compared to the case where the thickness is equal. It is realized to be mounted close to the horizontal by the mount 30. The optical module according to the present embodiment includes the semiconductor laser device 1 and the submount 30. Unlike the optical module according to the fourth embodiment, the thickness of the dummy electrode side solder 32 and the p-type drive electrode side solder 31 are different. The thickness is equal. However, in the semiconductor laser device 1 according to the present invention, unlike the semiconductor laser device 1 according to the fourth embodiment, the dummy electrode 9 is formed so that the thickness of the dummy electrode 9 is larger than the thickness of the p-type drive electrode 8. ing. Except for the points described above, the optical module according to the present embodiment has the same structure as the optical module according to the fourth embodiment. That is, the semiconductor laser device 1 according to this embodiment is related to any one of the first to third embodiments except that the thickness of the dummy electrode 9 is larger than the thickness of the p-type drive electrode 8. The semiconductor laser device 1 has a common structure.

  In the semiconductor laser device 1 according to the present embodiment, the dummy electrode 9 is made thicker than the portion of the p-type drive electrode 8 formed in the second bank portion 13 as compared with the case where the thickness is equal. The difference in height between the top surfaces of both electrodes is reduced. That is, the difference between the height of the top surface of the p-type drive electrode 8 and the height of the top surface of the dummy electrode 9 is made smaller than the sum of the thickness of the insulating layer 7 and the thickness of the contact layer 6 in the second bank portion 13. . By adopting such a configuration, it is possible to mount the semiconductor laser element 1 closer to the submount 30 even when solder thickness adjustment is omitted. Here, the thickness of the dummy electrode 9 corresponds to the sum of the thicknesses of the contact layer 6 and the insulating layer 7 in the second bank portion 13, and the portion of the p-type drive electrode 8 formed in the second bank portion 13. It is desirable to be thicker than.

  In general, changing the thickness of the p-type drive electrode side solder 31 and the thickness of the dummy electrode side solder 32 complicates the manufacturing process and increases the manufacturing cost. However, in the optical module according to the present embodiment, in the semiconductor laser element 1, the thickness of the dummy electrode 9 is made larger than the thickness of the p-type drive electrode 8, so that the semiconductor laser element 1 is sub-assembled compared to the case where the thickness is equal. It is realized to be mounted close to the horizontal by the mount 30.

  The process of changing the thickness of the dummy electrode 9 and the thickness of the p-type drive electrode 8 is compared with the process of changing the thickness of the p-type drive electrode side solder 31 and the thickness of the dummy electrode side solder 32. Therefore, it is possible to realize more simply, and it is possible to realize the simplification of the manufacturing process and the reduction of the manufacturing cost. As a specific method, the method of forming the dummy electrode 9 and the p-type drive electrode 8 may be changed. After the dummy electrode 9 and the p-type drive electrode 8 are manufactured in a common process, the dummy electrode 9 is further plated by gold plating. You may form thickly. Further, after the dummy electrode 9 and the p-type drive electrode 8 are manufactured in a common process, the height of the top surface of the p-type drive electrode 8 and the top surface of the dummy electrode 9 are improved by chemical mechanical polishing (CMP). The height may be closer. Needless to say, these methods may be combined. For example, the dummy electrode 9 may be further thickened by gold plating and then subjected to chemical mechanical polishing.

[Sixth Embodiment]
FIG. 12 is a cross-sectional view of an optical module according to the sixth embodiment of the present invention. The optical module according to the present embodiment includes the semiconductor laser element 1 and the submount 30. The difference between the semiconductor laser element 1 according to the present embodiment and the semiconductor laser element 1 according to the fifth embodiment is p-type. The difference between the height of the top surface of the drive electrode 8 and the height of the top surface of the dummy electrode 9 is canceled by not stacking a part of the semiconductor multilayer below the second bank portion 13 without changing the thickness of both electrodes. This is the point. Other than that, the optical module according to the present embodiment has the same structure as the optical module according to the fifth embodiment.

  In the semiconductor laser device 1 according to the present embodiment, the semiconductor multilayer is formed such that the height of the top surface of the second bank portion 13 is lower than the height of the top surface of the ridge portion 11. That is, the configuration of the semiconductor multilayer formed between the top surface of the second bank portion 13 and the top surface of the InP substrate 2 is formed between the top surface of the ridge portion 11 and the top surface of the n-type InP substrate 2. In the former semiconductor multilayer, a part of the latter semiconductor multilayer configuration is not formed. Specifically, the active layer 4 and the contact layer 6 are not stacked below the second bank portion 13. The structure of the semiconductor multilayer formed between the top surface of the ridge 11 and the upper surface of the InP substrate 2 is an active layer 4, a cladding layer 5, and a contact layer 6 from the lower layer to the upper layer. In the first to fifth embodiments, the semiconductor multilayer formed between the top surface of the second bank unit 13 and the upper surface of the InP substrate 2 is the same as this configuration, and each layer constituting the semiconductor multilayer is the same. The thicknesses are also equal, and the height of the top surface of the ridge portion 11 is equal to the height of the top surface of the second bank portion 13. On the other hand, in this embodiment, the active layer 4 and the contact layer 6 are not formed between the top surface of the second bank unit 13 and the upper surface of the InP substrate 2, and the configuration of the semiconductor multilayer is as follows. Only the cladding layer 5 is present. Thereby, the height of the top surface of the second bank portion 13 can be made lower than the height of the top surface of the ridge portion 11. Thereby, the height of the top surface of the second bank portion 13 can be made lower than that of the semiconductor laser device 1 according to the first to fifth embodiments. The thickness of the active layer 4 is 200 to 500 nm, and the thickness of the insulating layer 7 is approximately the same as the thickness of the active layer 4, so that the p-type drive electrode 8 and the dummy electrode 9 are used in a common process. Even if they are formed to have the same thickness, the difference in height between the top surface of the p-type drive electrode 8 and the top surface of the dummy electrode 9 can be offset. It is desirable that the thickness of the active layer 4 is equal to the thickness of the insulating layer 7. By adopting such a configuration, the semiconductor laser device 1 can be mounted closer to the horizontal with respect to the submount 30 even if the solder thickness adjustment is omitted.

  In the present embodiment, both the active layer 4 and the contact layer 6 are not stacked below the second bank portion 13, but either one may be stacked. Even in that case, the difference in height between the top surfaces of the p-type drive electrode 8 and the dummy electrode 9 can be made smaller than when both the active layer 4 and the contact layer 6 are laminated. . Moreover, it is good also as employ | adopting the structure which combined 5th Embodiment and 6th Embodiment. That is, when the thickness of the active layer 4 is smaller than the thickness of the insulating layer 7, the thickness of the dummy electrode 9 is set to the p-type drive while the active layer 4 and the contact layer 6 are not stacked below the second bank portion 13. It is good also as making it thicker than the thickness of the part formed in the 2nd bank part among the electrodes 8. FIG. Similarly, when the thickness of the active layer 4 is larger than the thickness of the insulating layer 7, the thickness of the dummy electrode 9 is set to the p-type while the active layer 4 and the contact layer 6 are not stacked below the second bank portion 13. It is good also as making it thinner than the thickness of the part formed in the 2nd bank part among the drive electrodes 8. FIG. For example, when the thickness of the active layer 4 is different from the thickness of the insulating layer 7, the thickness of the dummy electrode 9 and the thickness of the portion formed in the second bank portion of the p-type drive electrode 8 are made different. Thus, the semiconductor laser device 1 can be mounted on the submount 30 closer to the horizontal. Further, the heights of the top surfaces of the p-type drive electrode 8 and the dummy electrode 9 may be made uniform by using chemical mechanical polishing, or the p-type drive electrode side solder 31 and the dummy electrode side solder in the fourth embodiment. You may combine the structure which changes the thickness of 32.

[Seventh Embodiment]
FIG. 13 is a top view of the semiconductor laser device 1 according to the seventh embodiment of the present invention. The semiconductor laser device 1 according to the seventh embodiment includes a DFB laser unit 17 and an integrated mirror 40. Unlike the semiconductor laser device 1 according to the first embodiment, the n-type drive electrode 3 is an InP. It is formed on the upper surface side of the substrate 2. The integrated mirror 40 is formed between the ridge portion 11 and the n-type drive electrode 3. The DFB laser unit 17 according to the present embodiment is common to the semiconductor laser elements 1 according to the first to sixth embodiments except for the n-type drive electrode 3. In the semiconductor laser device 1 according to the present embodiment, as shown in FIG. 13, the n-type drive electrode 3 is visible from above the device (stacking direction side) together with the p-type drive electrode 8 and the dummy electrode 9. As will be more apparent from the following figure, in the present embodiment, a groove 35 reaching the InP substrate 2 formed by removing the semiconductor multilayer by etching or the like is provided at a place different from the place where the p-type drive electrode 8 is formed. The n-type drive electrode 3 is formed so as to reach the bottom surface of the groove 35. Further, the insulating layer 7 is not formed on the bottom surface of the groove 35. The n-type drive electrode 3 is formed so as to continuously spread on the upper surface of the insulating layer 7 and the upper surface of the InP substrate 2. However, the p-type drive electrode 8 and the dummy electrode 9 are formed in a non-contact manner. The third contact region is a region of the upper surface of the InP substrate 2 where no semiconductor multilayer is stacked, and is located on the bottom surface of the groove 35. It can be said that the third contact region is an interface between the n-type drive electrode 3 and the InP substrate 2. The n-type drive electrode 3 is formed so as to continuously extend to the upper surface of the insulating layer 7 including the third contact region. The insulating layer 7 is formed in a predetermined region on the upper surface of the semiconductor multilayer. Here, the predetermined region is the upper surface of the semiconductor multilayer excluding at least the first contact region, the second contact region, and the region where the integrated mirror 40 is formed from the entire upper surface of the semiconductor multilayer. Further, the insulating layer 7 is not formed at least in the third contact region on the upper surface of the InP substrate 2. In order to improve laser characteristics, it is desirable that the insulating layer 7 is formed on at least a portion of the side surface of the groove 35 where the n-type drive electrode 3 is formed. This is to prevent the n-type drive electrode 3 from coming into direct contact with the active layer 4, the clad layer 5, and the like. In the semiconductor laser device 1 according to this embodiment, the n-type drive electrode 3 does not have to be formed on the lower surface of the InP substrate 2, so that the surface emitting type emits laser light from the lower surface side of the InP substrate 2. The configuration is suitable for a semiconductor laser.

  In the semiconductor laser device 1 according to the present embodiment, the integrated mirror 40 is formed on the extension line of the optical waveguide part formed below the ridge part 11, and the n-type drive electrode 3 is further above the extension line. Is formed. When the semiconductor laser device 1 is viewed in plan view from above as shown in FIG. 13, the extension line is the third contact region which is the upper surface of the InP substrate 2 on which the integrated mirror 40 and the n-type drive electrode 3 are formed. Are in this order. Here, the “extension line” of the optical waveguide portion means a line obtained by extending a line passing through the center of the optical waveguide portion. The “extension line” of the optical waveguide part may be said to be an extension line at the center of the luminous flux of the light emitted from the emission side end face of the active layer 4 by the DFB laser part 17.

  FIG. 14 is a cross-sectional view of an optical module according to the seventh embodiment of the present invention. The optical module according to the present embodiment includes the semiconductor laser device 1 according to the present embodiment and a submount 30, and includes an n-type drive electrode 3, a p-type drive electrode 8, a dummy electrode 9, and the semiconductor laser device 1. However, the submount 30 is brazed with solder and mounted in a junction-down manner. FIG. 14 shows a cross section through the XIV-XIV line in FIG. 13 of the semiconductor laser device 1 mounted on the submount 30. The submount 30 has wiring patterns for the p-type drive electrode 8, the dummy electrode 9, and the n-type drive electrode 3, and is fused to each electrode with solder. That is, the p-type drive electrode side solder 31 (not shown) fused to the p-type drive electrode 8, the dummy electrode side solder 32 (not shown) fused to the dummy electrode 9, and the n-type drive electrode 3 are fused. The semiconductor laser element 1 is mounted on the submount 30 by the n-type drive electrode side solder 33 to be attached. Here, the p-type drive electrode side solder 31 is formed on the back side of the paper surface, and the dummy electrode side solder 32 is formed on the near side of the paper surface.

  The semiconductor laser device 1 according to this embodiment is a surface emitting semiconductor laser in which an integrated mirror 40 is formed on an extension line of an optical waveguide portion including an active layer 4. Such a laser is called a LISEL (Lens Integrated Surface Emitting Laser) and has a DFB laser unit 17 as a basic structure. Here, the DFB laser unit 17 is a laser unit characterized by canceling light other than a specific wavelength corresponding to the grating interval due to interference by the diffraction grating layer 16 to amplify and emit light of a specific wavelength. Since the wavelength of the emitted light can be precisely controlled, it is widely used in the field of optical communication or the like that simultaneously uses laser beams of close wavelengths to prevent crosstalk due to misreading of wavelengths. As in the semiconductor laser device 1 according to the present embodiment, the n-type drive electrode 3 is formed on the same side as the p-type drive electrode 8 and the dummy electrode 9, so that all electrodes are junction-down mounted on the submount 30. This makes it possible to eliminate the wire bonding, which has the advantage of further suppressing an increase in manufacturing cost.

  The white arrow in FIG. 14 represents the optical path of the emitted light from the DFB laser unit 17. The normal direction of the mirror surface of the integrated mirror 40 is obliquely crossed with the emission direction of the light emitted from the optical waveguide portion, and the emitted light from the DFB laser portion 17 is reflected by the integrated mirror 40, and the reflected light is The light propagates inside the InP substrate 2 and exits from the lower surface (back surface) of the InP substrate 2 to the outside. The angle formed by the emission direction of the light emitted from the optical waveguide portion of the DFB laser portion 17 and the normal direction of the mirror surface of the integrated mirror 40 is preferably in the range of 45 ° ± 10 °, and more preferably 45 °. The normal direction of the mirror surface of the integrated mirror 40 obliquely intersects with the emission direction of the light emitted from the optical waveguide portion, so that the light emitted from the optical waveguide portion is emitted from the lower surface side of the InP substrate 2 to the outside. The optical path is changed. The integrated mirror 40 is not limited to this, and the integrated mirror 40 is formed so that light reflected by the integrated mirror 40 is emitted from the semiconductor laser element 1 to the outside from the side on which each electrode is formed. May be.

  As shown in FIG. 14, the light emitted from the DFB laser unit 17 is optically path-converted vertically upward in the drawing by the integrated mirror 40, and is emitted to the outside through the integrated lens 42 on which the non-reflective film 41 is formed. By adopting such a configuration, highly efficient direct fiber coupling is possible without using external optical components. When the laser light is emitted from the lower surface side of the InP substrate 2 as described above, junction down mounting is desirable. In the semiconductor laser device 1 according to the present embodiment, as shown in FIG. 14, the cladding layer 5 is formed in front of the emission side end face (the emission side end face of the active layer 4) of the optical waveguide part of the DFB laser part 17. The integrated mirror 40 is formed by removing a part of the cladding layer 5 to form a slope. Since the integrated mirror 40 has such a structure, light emitted from the optical waveguide portion is reflected by the integrated mirror 40, and the reflected light is emitted from the lower surface side of the InP substrate 2 to the outside. On the other hand, when the light reflected by the integrated mirror 40 is emitted to the outside from the side (upper surface side) where each electrode is formed, the integrated mirror 40 may be formed as follows, for example. The semiconductor multilayer such as the cladding layer 5 is removed outside the emission side end face of the optical waveguide part of the DFB laser part 17 (the emission side end face of the active layer 4). Then, the integrated mirror 40 is formed in the semiconductor multilayer disposed further forward of the emission side end face of the DFB laser unit 17. The integrated mirror 40 may have a mirror surface so that the light emitted from the DFB laser unit 17 is reflected to the upper surface side. The normal direction of the mirror surface only needs to be inclined to the upper surface side from the light emitted from the DFB laser unit 17, and the angle formed between the emitted light and the normal direction is preferably 45 °. Further, the integrated mirror 40 may be embedded in a semiconductor multilayer, or may convert the optical path in a direction other than the upper vertical direction in the drawing. However, the integrated mirror 40 is not a reflection film (or reflection suppression film) formed on the end face of a general semiconductor laser element, and is not a mirror that reflects light emitted from the end face of the optical waveguide section again to the optical waveguide section. The integrated mirror 40 is arranged to reflect the light emitted from the DFB laser unit 17 and to emit the light from the lower surface side or the upper surface side of the InP substrate 2 to the outside.

  In the semiconductor laser device 1 according to this embodiment, the n-type drive electrode 3 is formed over the upper surface of the InP substrate 2 and the upper surface of the insulating layer 7, and the top surface of the n-type drive electrode 3 is the n-type drive electrode side solder 33. And is fused to the wiring pattern of the submount 30. Although the n-type drive electrode side heat dissipation path 24 is different from that of the first embodiment, the chip length of the semiconductor laser element 1 (the length in the left-right direction in FIG. 14) is about 400 μm. The distance to the mold drive electrode 3 is longer than that of the dummy electrode side heat dissipation path 23 and the like. Further, since the heat from the heat generating portion 20 is diffused more in the direction orthogonal to the extending direction of the optical waveguide portion, that is, in the direction in which the p-type drive electrode 8 and the dummy electrode 9 are formed, the n-type It is predicted that the heat dissipation effect of the drive electrode side heat dissipation path 24 is smaller than the heat dissipation effect of the dummy electrode side heat dissipation path 23. The influence on the parasitic capacitance of the n-type drive electrode 3 is so small that it can be ignored. The n-type drive electrode 3 may be formed in an L shape or a U shape so as to go around the integrated mirror 40. Also in that case, the n-type drive electrode 3 is required not to physically contact the p-type drive electrode 8 and the dummy electrode 9.

  In the semiconductor laser device 1 shown in FIG. 14, the height of the top surface of the insulating layer 7 where the n-type drive electrode 3 is formed is equal to the height of the top surface of the insulating layer 7 formed in the second bank portion 13. Almost equal. For this reason, when the n-type drive electrode 3 and the p-type drive electrode 8 are formed by a common process and the thicknesses of both are formed approximately equal, the height of the top surface of the n-type drive electrode 3 is the same as the p-type drive electrode 8 Is higher than the height of the top surface of the dummy electrode 9. The thickness of the dummy electrode side solder 32 fused to the dummy electrode 9 is the same as the thickness of the p type drive electrode side solder 31 fused to the p type drive electrode 8 or the n type drive electrode side solder fused to the n type drive electrode 3. By making the thickness greater than 33, the semiconductor laser device 1 can be mounted on the submount 30 so as to be closer to the horizontal. Further, as will be described later, the configuration of the semiconductor laser element 1 shown in the fifth or sixth embodiment may be applied.

FIG. 15 is a diagram illustrating the relationship between the area of the n-type drive electrode and the relative value of the thermal resistance. The semiconductor laser element used in FIG. 15 is a semiconductor laser element in which the dummy electrode 9 is not formed unlike the semiconductor laser element 1 shown in FIG. 13, and the n-type drive electrode 3 is similar to the semiconductor laser element 1 shown in FIG. The LISEL is formed on the same side with respect to the p-type drive electrode 8 and the InP substrate 2. In the optical module used in FIG. 15, the semiconductor laser element is junction-down mounted on the submount 30. In such an optical module, the relative value of the thermal resistance when the area of the n-type drive electrode of the semiconductor laser element is changed is shown in FIG. The thermal resistance serving as a reference for the thermal resistance is an optical module in which the semiconductor laser device according to the first comparative example shown in FIG. For example, when the area of the n-type drive electrode is 27500 μm ² , the chip length (corresponding to the vertical length of the unit element in FIG. 13) is 400 μm, and the chip width (the length of the unit element in the horizontal direction in FIG. 13). Corresponds to the case of a LISEL having a cavity length of 250 μm and the DFB laser part having a resonator length of 150 μm. 15 is compared with FIG. 10, in the case of the optical module according to the fourth embodiment, the relative value of the thermal resistance is about 0.82, whereas the semiconductor laser element (LISEL) used in FIG. However, even if the area of the n-type drive electrode is increased, the relative value of the thermal resistance is only reduced to about 0.87. In the fourth embodiment, the area of the dummy electrode 9 is about 3850 μm ² , and the thermal resistance is lower despite the fact that it is about 1/7 of the area of the n-type drive electrode. It turns out that the effect is higher.

  Therefore, the heat radiation effect is improved in the configuration in which the dummy electrode 9 is formed and the area of the n-type drive electrode 3 is maximized as in the semiconductor laser device 1 according to the seventh embodiment. However, as described above, the contribution to the heat dissipation performance by increasing the area of the n-type drive electrode 3 is smaller than the contribution by increasing the area of the dummy electrode 9.

  The semiconductor laser device 1 according to the seventh embodiment shown in FIG. 13 is a single semiconductor laser device 1, but a configuration in which a plurality of semiconductor laser devices 1 are arranged in an array can also be employed. For example, a configuration in which the single elements shown in FIG. By adopting such a configuration and performing junction-down mounting, all the drive electrode wirings can be concentrated on the submount 30 and wire bonding can be eliminated, thereby simplifying the process and increasing the manufacturing cost. Can be further suppressed.

  Further, in the case where a plurality of semiconductor laser devices 1 according to the seventh embodiment are arranged side by side, the n-type drive electrode 3 is formed over all the unit elements by continuously forming the n-type drive electrode 3 over the plurality of unit elements. As a common electrode, a junction mount can be mounted on the submount 30. When such a configuration is adopted, in addition to the advantage that wire bonding can be eliminated, the n-type drive electrode 3 can be integrally formed with all unit elements, so that the manufacturing process is further simplified and the manufacturing cost is reduced. Is further suppressed. Because of the advantages as described above, the configuration in which the semiconductor laser elements 1 according to the seventh embodiment are arrayed is particularly effective in the case of an optical module in which the arrayed surface emitting semiconductor laser is mounted on the submount 30. Become.

  Further, the p-type drive electrode 8 and the dummy electrode 9 of the semiconductor laser device 1 shown in FIG. 13 are similar to the p-type drive electrode 8 and the dummy electrode 9 according to the fifth embodiment in that the thickness of the dummy electrode 9 is p-type. The dummy electrode 9 may be formed so as to be thicker than the portion of the drive electrode 8 formed in the second bank portion 13. At this time, by forming the n-type drive electrode 3 in the same process as the p-type drive electrode 8, the thickness of the n-type drive electrode 3 can be formed substantially equal to the thickness of the p-type drive electrode 8, and the junction down is achieved. When mounted, the semiconductor laser element 1 can be mounted on the submount 30 closer to the horizontal. Such a configuration can also be applied to the case of an arrayed surface emitting semiconductor laser, and an optical module in which variations in the emitting direction of laser light between unit elements are suppressed can be obtained.

  In addition, the semiconductor multilayer structure of the semiconductor laser device 1 shown in FIG. 13 is similar to the semiconductor multilayer structure according to the sixth embodiment in that the height of the top surface of the second bank portion 13 is the top surface of the ridge portion 11. A semiconductor multilayer may be formed so as to be lower than the height. In this case, the semiconductor multi-layer structure in the second bank unit 13 is also adopted for the semiconductor multi-layer formed below the n-type drive electrode 3, and the height of the top surface of the n-type drive electrode 3 and the top surface of the dummy electrode 9 are adopted. The difference in height may be reduced. By adopting such a configuration, it is possible to mount the semiconductor laser element 1 closer to the submount 30 closer to the horizontal when the junction down mounting is performed. As described above, the present invention can also be applied to an arrayed surface emitting semiconductor laser. Moreover, it is good also as applying combining both the structure of the dummy electrode 9 which concerns on 5th Embodiment, and the structure of the semiconductor multilayer based on 6th Embodiment.

  Embodiments of the present invention are not limited to those described above. For example, when the n-type drive electrode 3 is formed on the upper surface of the InP substrate 2, the integrated mirror 40 may not be formed, and the laser light may be emitted from the end face of the optical waveguide portion. In addition, a configuration in which the polarity of the drive electrode is opposite to that of the embodiment described above may be employed. In addition, various modifications can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 Semiconductor laser element, 2 InP board | substrate, 3 n-type drive electrode, 4 active layer, 5 clad layer, 6 contact layer, 7 insulating layer, 8 p-type drive electrode, 9 dummy electrode, 10 isolation groove, 11 ridge part, 12 First bank part, 13 Second bank part, 14 First gap bottom face, 15 Second gap bottom face, 16 Diffraction grating layer, 17 DFB laser part, 20 Heat generating part, 21 InP substrate side heat dissipation path, 22 p-type drive electrode Side heat dissipation path, 23 dummy electrode side heat dissipation path, 24 n-type drive electrode side heat dissipation path, 30 submount, 31 p-type drive electrode side solder, 32 dummy electrode side solder, 33 n-type drive electrode side solder, 35 groove, 40 Integrated mirror, 41 Non-reflective film, 42 Integrated lens.

Claims (8)

An optical waveguide portion including an active layer and extending in the light emitting direction including the active layer; a ridge portion located above the optical waveguide portion; and a first side disposed on a first side of the ridge portion. A semiconductor multilayer in which a bank portion and a second bank portion disposed on a second side of the ridge portion are formed;
An insulating layer stacked in a predetermined region on the upper surface of the semiconductor multilayer;
A first contact region that is a top surface of the ridge portion and on which the insulating layer is not stacked, and further extends continuously to an upper surface of the insulating layer stacked on the second bank portion; One drive electrode;
A dummy electrode formed in a non-contact manner with the first drive electrode, including a second contact region which is a part of the top surface of the first bank portion and is not laminated with the insulating layer;
Equipped with a,
The first contact region includes
The top surface of the contact layer,
The second contact region includes
The top surface of the cladding layer,
A semiconductor optical device. The semiconductor optical device according to claim 1 ,
The second bank part is
The contact layer on which the insulating layer is stacked; and
The cladding layer on the upper surface of the contact layer, and
The difference in height between the top surfaces of the first drive electrode and the dummy electrode is:
Smaller than the sum of the thickness of the insulating layer and the thickness of the contact layer in the second bank portion;
The thickness of the dummy electrode is
It is thicker than the thickness of the portion formed in the second bank portion of the first drive electrode.
A semiconductor optical device. The semiconductor optical device according to claim 1 ,
The active layer is
It is not formed below the second bank part,
A semiconductor optical device. The semiconductor optical device according to claim 1,
The first gap bottom surface located between the ridge portion and the first bank portion and the second gap bottom surface located between the ridge portion and the second bank portion are arranged in parallel with the ridge portion. Each extending isolation groove is formed,
The isolation groove is
The deepest part reaches under the active layer included in the semiconductor multilayer,
A semiconductor optical device. The semiconductor optical device according to claim 1,
A semiconductor substrate on which the semiconductor multilayer is stacked;
Including the third contact region in which the semiconductor multilayer is not stacked on the upper surface of the semiconductor substrate, and further continuously extending to the upper surface of the insulating layer, it is not in contact with the first drive electrode and the dummy electrode A second drive electrode that is paired with the first drive electrode and supplies a current to the active layer;
A semiconductor optical device, further comprising: The semiconductor optical device according to claim 5 ,
Further comprising an integrated mirror on an extension line of the optical waveguide portion,
The third contact region is
When the ridge portion is viewed from above, an extension line of the optical waveguide portion has a portion located so as to penetrate the integrated mirror and the third contact region in this order,
The normal direction of the mirror surface of the integrated mirror is:
Obliquely with the emission direction of the light emitted from the optical waveguide portion,
A semiconductor optical device. A semiconductor optical device according to any one of claims 1 to 6 ;
A submount to which the first drive electrode and the dummy electrode are brazed;
An optical module comprising: An optical waveguide portion including an active layer, a cladding layer, and a contact layer, extending in the light emitting direction including the active layer, a ridge portion disposed above the optical waveguide portion, and a first side of the ridge portion A first bank portion located on the second side, a second bank portion disposed on a second side of the ridge portion,
A semiconductor multilayer to form
An insulating layer stacked in a predetermined region on the upper surface of the semiconductor multilayer;
Including the first contact region, which is the top surface of the ridge portion and is the top surface of the contact layer on which the insulating layer is not stacked, and further up to the top surface of the insulating layer stacked on the second bank portion. A first drive electrode formed continuously and continuously,
A dummy electrode formed in a non-contact manner with the first drive electrode, including a second contact region that is a part of a top surface of the first bank portion and is a top surface of the cladding layer on which the insulating layer is not stacked. When,
A semiconductor optical device comprising:

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