JP2013191701A - Semiconductor optical element, and optical module having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical function element capable of improving conductivity of an electrode in a separation groove due to a shape of the separation groove, and improving characteristics thereby, and an optical module having the same.SOLUTION: A semiconductor optical element comprises: a semiconductor multilayer having a first separation groove and a second separation groove formed on respective surfaces thereof on both sides of an optical waveguide extending in a first direction; an insulating film; and an electrode to which a wire and the semiconductor multilayer are electrically connected via the first separation groove. The first separation groove includes a bottom face, an inside lateral surface, and an outside lateral surface. The inside lateral surface of the first separation groove includes a first inside lateral part extending in the first direction, and a second inside lateral part formed to be inclined on an opposite side to the bottom face side from a lower edge to an upper edge. The outside lateral surface of the first separation groove includes a first outside lateral part extending in the first direction, and a second outside lateral part formed to be inclined on the opposite side to the bottom face side from a lower edge to an upper edge.

Description

  The present invention relates to a semiconductor optical device and an optical module including the same, and more particularly to improvement in characteristics of a semiconductor optical device having a separation groove on the surface of a semiconductor multilayer.

  2. Description of the Related Art In recent years, semiconductor optical devices having separation grooves formed along an optical waveguide on both sides of a region above the optical waveguide have been used on the surface of a semiconductor multilayer including an active layer. It is known that when the semiconductor optical device has the separation groove, advantageous effects can be obtained from the viewpoint of, for example, current confinement and parasitic capacitance reduction. Electrodes are formed on the surface of the semiconductor multilayer in order to inject current or apply an electric field to the active layer. In order to inject a current (or apply a voltage) to the electrode from an external circuit, a wire is connected to the electrode (wire bonding). Patent Document 1 discloses a semiconductor optical device having a separation groove.

JP 2003-258370 A JP 2010-153826 A

  In a semiconductor optical device having a separation groove, the distance from the region above the optical waveguide to the separation groove is preferably as short as possible from the viewpoint of current confinement and parasitic capacitance reduction. However, when shortening the distance between the region above the optical waveguide and the separation groove, it becomes difficult to bond a wire between the region and the separation groove. Become. For reasons such as manufacturing process conditions, it is common to produce a semiconductor optical device by forming a semiconductor multilayer so that the optical waveguide is along the [0 1 1] direction. The surface of the semiconductor multilayer is covered with an insulating film except for the region above the optical waveguide, and an electrode is formed on the upper side. Due to the structure of the electrode, the region above the optical waveguide on the surface of the semiconductor multilayer contacts the electrode, and current is injected from the wire to the active layer through the electrode (or an electric field is applied). Is done.

  A separation groove is arranged between the region above the optical waveguide of the semiconductor multilayer and the wire, and an electrode is also formed in the separation groove of the semiconductor multilayer via an insulating film. It is desirable that the electrodes are stably formed on the bottom surface and both side surfaces of the separation groove, and the electrical connection between the region above the optical waveguide and the wire is sufficient. However, for example, when the semiconductor multilayer is formed so that the optical waveguide is along the [0 1 1] direction, the separation groove is also formed along the direction. In such a case, when the separation groove is formed by wet etching, both side surfaces of the separation groove have a reverse taper shape or a substantially vertical shape depending on the crystal plane orientation as in the cross-sectional view shown in FIG. Here, the reverse taper shape refers to a shape in which the side surface of the separation groove extends from the lower edge of the bottom surface to the upper edge to the bottom surface side (inward with respect to the bottom surface). That is, the upper edge of the side surface is located on the bottom surface side (inward with respect to the bottom surface) from the lower edge of the side surface.

  A vapor deposition method, a sputtering method, etc. are used for the process of forming an electrode. When the side surface of the separation groove has a reverse taper shape, if an electrode is formed on the separation groove by a vapor deposition process, the electrode material deposited on the side surface of the separation groove becomes insufficient, and the region above the optical waveguide and the wire The electrical conductivity (electrical connection) between the two becomes insufficient. As a result, the characteristics and yield of the semiconductor optical device are reduced. When an electrode is formed in the separation groove by a process using a sputtering method, an electrode is also formed on the side surface of the separation groove, and the conductivity is improved. However, since plasma is used in the sputtering method, there is damage to the semiconductor crystal, and it is difficult to achieve both reliability of the semiconductor element. In addition, since the atoms of the electrode are accelerated by the electric field and driven into the surface of the insulating film, the internal stress of the film increases, which is not desirable for the reliability of the semiconductor optical device. That is, from the viewpoint of damage to the semiconductor crystal and the internal stress of the film, although electrode formation by the vapor deposition method is desirable, sufficient current conduction cannot be obtained in the separation groove by electrode formation by the vapor deposition method.

  Note that when the separation groove is formed by dry etching, the side surface of the separation groove can be made more perpendicular to the bottom surface than when the separation groove is formed by wet etching. Even when the side surface of the separation groove is formed perpendicular to the bottom surface, electrode formation by vapor deposition does not sufficiently deposit the electrode material on the side surface of the separation groove, and sufficient electrical conductivity cannot be obtained. That is, such a problem is difficult to solve by dry etching.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a semiconductor optical functional element in which the electrical conductivity of the electrode in the separation groove is improved by the shape of the separation groove, and the characteristics are improved. An optical module is provided.

  (1) In order to solve the above-mentioned problem, a semiconductor optical functional device according to the present invention is laminated including an active layer, and on both sides of a contact region located above an optical waveguide extending in a first direction. A semiconductor multilayer having a first separation groove and a second separation groove formed on each surface; an insulating film formed to cover the surface of the semiconductor multilayer except for the contact region; and the semiconductor multilayer and the insulating film. A wire that is covered and formed in a predetermined shape, and that is bonded to the outside of the first separation groove, and an electrode that electrically connects the semiconductor multilayer via the first separation groove; The first separation groove includes a bottom surface, an inner surface formed on the contact region side, and an outer surface formed on the side opposite to the contact region side, and the inner surface of the first separation groove Said A first inner portion extending along the direction of 1 and a second inner portion formed to be inclined from the lower edge to the upper edge on the opposite side to the bottom surface side, and the first separation groove The outer side surface includes a first outer portion extending along the first direction, and a second outer portion formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. It is characterized by.

  (2) In the semiconductor optical device according to (1), the second inner portion extends from the first inner portion toward the contact region along a second direction different from the first direction. In addition, the first inner portion may be connected via a bent portion for bending from the first direction to the second direction.

  (3) In the semiconductor optical device according to (2), an end portion of the second inner portion on the contact region side is extended from an extended straight line of an upper edge of the first inner portion to the contact region side. The distance may be 1.7 times or more the depth of the first separation groove.

  (4) In the semiconductor optical device according to (1), the second outer portion is closer to the contact region side than the first outer portion along a second direction different from the first direction. The first outer portion may be connected via a bent portion that extends in the opposite direction and bends from the first direction to the second direction.

  (5) In the semiconductor optical device according to (4), an end portion of the second outer portion opposite to the contact region side is extended from the extended straight line of the first outer portion to the contact region side. May be located on the opposite side at a distance of 1.7 times or more the depth of the first separation groove.

  (6) The semiconductor optical device according to (1), wherein the first separation groove includes the first inner portion and the first outer portion facing each other and extends in the first direction. And a second zigzag shape including the second inner portion and the second outer portion facing each other, and a portion extending in a second direction different from the first direction.

  (7) In the semiconductor optical device according to any one of (2) to (6), an angle formed by the first direction and the second direction may be 45 ° or more.

  (8) In the semiconductor optical device according to any one of (2) to (6), an angle formed by the first direction and the second direction may be a right angle.

  (9) In the semiconductor optical device according to (1), the inner side surface includes a curved surface portion, the second inner portion is included in the curved surface portion, and the outer surface is curved. A portion that becomes a surface may be included, and the second outer portion may be included in a portion that becomes the curved surface.

  (10) The semiconductor optical device according to any one of (1) to (9), wherein the second separation groove includes a bottom surface, an inner surface formed on the contact region side, and the contact region side. An outer surface formed on the opposite side of the second separation groove, the inner surface of the second separation groove extending along the first direction, and the bottom surface from the lower edge to the upper edge. A second inner portion formed to be inclined to the opposite side of the side, wherein the outer surface of the second separation groove has a first outer portion extending along the first direction, and a lower edge And a second outer portion formed so as to be inclined to the opposite side to the bottom surface side from the upper edge to the upper edge.

  (11) An optical module according to the present invention may include the semiconductor optical device according to any one of (1) to (10).

  According to the present invention, a semiconductor optical functional element in which the electrical conductivity of the electrode in the separation groove is improved by the shape of the separation groove and the characteristics are improved, and an optical module including the same are provided.

1 is a top view of a semiconductor optical device according to a first embodiment of the present invention. 1 is a cross-sectional view of a semiconductor optical device according to a first embodiment of the present invention. 1 is a cross-sectional view of a semiconductor optical device according to a first embodiment of the present invention. 1 is a cross-sectional view of a semiconductor optical device according to a first embodiment of the present invention. It is a top view of the LGLC wavelength tunable laser device concerning a 2nd embodiment of the present invention. It is a partial top view explaining the structure of the semiconductor optical element concerning the 3rd Embodiment of this invention. It is a partial top view explaining the structure of the semiconductor optical element concerning the 3rd Embodiment of this invention. It is a top view of the semiconductor optical element based on an example of the 4th Embodiment of this invention. It is a top view of the semiconductor optical element which concerns on another example of the 4th Embodiment of this invention. It is a top view of the semiconductor optical element which concerns on another example of the 4th Embodiment of this invention. It is a schematic diagram which shows the structure of TOSA which concerns on the 5th Embodiment of this invention.

  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. Also, in the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

[First Embodiment]
FIG. 1 is a top view of a semiconductor optical device 1 according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the semiconductor optical device 1 according to this embodiment, showing a cross section taken along the line II-II shown in FIG. The semiconductor optical device 1 according to this embodiment has a buried hetero (hereinafter referred to as BH) structure. As shown in FIG. 2, a multilayer including the active layer 18 is formed on the n-type InP substrate 10, and the BH structure is a mesa formed by removing portions on both sides of the multilayer optical waveguide. A semiconductor multilayer structure including a stripe 11 and a buried layer 15 filling both sides of the mesa stripe 11. For the buried layer 15, for example, a semi-insulating semiconductor such as InP to which iron (Fe) or ruthenium (Ru) is added as an impurity is used. In the semiconductor multilayer according to the embodiment, the p-type InP layer 16 is stacked on the upper side of the BH structure. Further, as will be described later, a contact layer (not shown) is laminated in a predetermined region above the mesa stripe 11 in order to be electrically connected to the electrode 13.

  The contact region, which is a region located above the optical waveguide, is a region above the mesa stripe 11 in the surface of the semiconductor multilayer, and as shown in FIG. 1, the mesa stripe 11 is vertically aligned in the first direction. Stretched in the direction. As shown in FIGS. 1 and 2, isolation grooves 12 are formed on both sides of the contact region in the surface of the semiconductor multilayer. Of the separation grooves 12, the first separation grooves 12A are arranged on the right side of the contact region in FIG. 1, and the second separation grooves 12B are arranged on the left side of FIG. The separation groove 12 has a zigzag shape in which a portion extending in the up-down direction as the first direction and a portion extending in the left-right direction as the second direction are alternately repeated.

  As shown in FIG. 2, an insulating film 17 is formed so as to cover the surface of the semiconductor multilayer, but the insulating film 17 is not formed in the contact region of the surface of the semiconductor multilayer, and is a contact hole. . The contact hole is preferably formed in all the regions located above the optical waveguide in the region where the electrode 13 described later is formed, but is formed in at least a part of the region located above the optical waveguide. Just do it. That is, the shape of the insulating film is a predetermined shape excluding a region that becomes a contact hole.

  The electrode 13 is formed in a predetermined shape so as to cover the semiconductor multilayer and the insulating film 17. The predetermined shape of the electrode 13 shown in FIG. 1 covers the entire region above the optical waveguide from the end surface on the emission side of the semiconductor optical device 1 to the opposite end surface, and spreads on both the left and right sides of the region. Although it has a shape, the upper edge and the lower edge of FIG. 1 of the portion extending on both the left and right sides are located on the inner side from both end faces. A wire 14 connected to an external circuit is bonded to a region further outside the first separation groove 12A with respect to the contact region (optical waveguide). In other words, the first separation groove 12 </ b> A is disposed between the contact region (optical waveguide) and the wire 14. A contact layer is formed in a region (predetermined region) including a region above the mesa stripe 11 in the surface (uppermost surface) of the semiconductor multilayer, and the electrode 13 is in contact with the contact layer through the contact hole. ing. Therefore, the semiconductor multilayer is electrically connected to the wire 14 via the first separation groove 12A. The electrode 13 shown in FIG. 1 is a p-side electrode. As shown in FIG. 2, an electrode 19 is also formed on the lower surface of the n-type InP substrate 10, and the electrode 19 is an n-side electrode.

  3 and 4 are cross-sectional views of the semiconductor optical device 1 according to this embodiment. 3 shows a cross section taken along line III-III shown in FIG. 1, and FIG. 4 shows a cross section taken along line IV-IV shown in FIG. The mesa stripe 11 of the semiconductor optical device 1 is formed along the [0 1 1] direction. The separation groove 12 is formed by wet etching. Due to the anisotropy of etching, the separation groove 12 is formed in a portion extending in the [0 1 1] direction (first direction) of the separation groove 12 as shown in FIG. Both side surfaces of the taper have a reverse taper shape 20. On the other hand, as shown in FIG. 4, both side surfaces of the separation groove 12 have a forward tapered shape 21 in a portion extending in the [0 −1 1] direction (second direction) of the separation groove 12. Here, as described above, the reverse taper shape refers to a shape in which the side surface of the separation groove 12 extends from the lower edge to the upper edge toward the bottom surface side. On the other hand, the forward tapered shape refers to a shape in which the side surface of the separation groove 12 extends from the lower edge to the upper edge toward the side opposite to the bottom surface side (the outside with respect to the bottom surface).

  As shown in FIG. 3, in the portion where the separation groove 12 extends in the vertical direction (first direction) in FIG. 1, the separation groove 12 having a cross-section having a reverse taper shape 20 is formed on the surface of the semiconductor multilayer. . An insulating film 17 is formed to cover the surface of the semiconductor multilayer, and an electrode 13 is formed on the upper side of the insulating film 17 by vapor deposition. Separation groove 12 includes a bottom surface and inner and outer surfaces formed on both sides of the bottom surface, respectively. 3 is a cross-sectional view of the first separation groove 12A taken along the line III-III in FIG. 1 as viewed from the lower side to the upper side in FIG. 1, and therefore, the left side surface of the separation groove 12 in FIG. 3 is an inner side surface formed on the inner side with respect to the optical waveguide, and the right side surface in FIG. 3 of the separation groove 12 is an outer side surface formed on the side opposite to the contact region side (outer side with respect to the optical waveguide). is there. As described above, since the cross section of the separation groove 12 shown in FIG. 3 has an inversely tapered shape 20, both side surfaces are inclined toward the bottom surface side (inner side with respect to the bottom surface) from the lower edge to the upper edge. Therefore, when the electrode 13 is formed so as to cover the semiconductor multilayer and the insulating film 17 by vapor deposition, the semiconductor multilayer surface spreading from the upper edge of the both side surfaces to the both sides is formed on both side surfaces of the separation groove 12 and both side edge portions of the bottom surface. The electrode material is hardly deposited, and the electrical conductivity from one side to the other side through the separation groove 12 is not sufficiently ensured. Here, the portion extending along the vertical direction (first direction) in FIG. 1 among the inner surface of the separation groove 12 is the first inner portion and the first surface of the outer surface of the separation groove 12 is the first. A portion extending along the direction is referred to as a first outer portion. The portion extending in the up-down direction, which is the first direction of the separation groove 12, includes a first inner portion and a first outer portion that face each other.

  On the other hand, in the portion where the separation groove 12 extends in the left-right direction (second direction) in FIG. 1, the separation groove 12 whose cross section has a forward tapered shape 21 is formed on the surface of the semiconductor multilayer as shown in FIG. 4. Is formed. 4 is a cross-sectional view of the first separation groove 12A taken along line IV-IV in FIG. 1 as viewed from the left side to the right side in FIG. 1, and therefore, the left side surface of the separation groove 12 in FIG. 4 is an inner side surface formed on the inner side with respect to the waveguide, and the right side surface in FIG. 4 of the separation groove 12 is an outer side surface formed on the side opposite to the contact region side (outer side with respect to the optical waveguide). . Since the cross section of the separation groove 12 shown in FIG. 4 has a forward tapered shape 21, both side surfaces are inclined from the lower edge to the upper edge on the opposite side (outside the bottom surface) from the bottom surface side. Therefore, when the electrode 13 is formed so as to cover the semiconductor multilayer and the insulating film 17 by vapor deposition, more electrode material is deposited on both side surfaces of the separation groove 12 and both side edges of the bottom surface. Thus, the electrical conductivity from one side to the other side is further ensured. Here, the portion extending along the left-right direction (second direction) in FIG. 1 in the inner surface of the separation groove 12 is the second inner portion, and the second surface of the outer surface of the separation groove 12 is the second. A portion extending along the direction will be referred to as a second outer portion. The portion of the separation groove 12 that extends in the left-right direction, which is the second direction, includes a second inner portion and a second outer portion that face each other.

  A feature of the semiconductor optical device according to this embodiment is that the side surfaces of the separation groove disposed between the wire to be bonded and the contact region have forward tapered portions (second inner portion and second outer portion). Is included in each. As a result, the electrical conductivity from the one side of the separation groove to the other side is improved by compensating the electrical conductivity that cannot be sufficiently ensured in the first inner portion and the first outer portion by the portion having the forward tapered shape. ing.

  In addition, since the second direction is different from the first direction, the side shapes of the second inner portion and the second outer portion may be different from the side shapes of the first inner portion and the first outer portion, respectively. I can do it. The angle formed by the first direction and the second direction is preferably 45 ° or more so that the cross-sectional shapes formed by wet etching are different. Here, the angle formed by the first direction and the second direction is the smaller of the angles formed at the point where the straight line extending in the first direction and the straight line extending in the second direction intersect. This is an angle, and the angle formed by the first direction and the second direction is 90 ° at the maximum. Further, as in this embodiment, the first direction is the [0 1 1] direction of the semiconductor material, the second direction is the [0 −1 1] direction, and the first direction and the second direction. Are orthogonal, that is, when the angle formed by both directions is 90 °, the difference in cross-sectional shape becomes more remarkable, and the effect of the present invention becomes remarkable.

  Furthermore, in the semiconductor optical device according to the embodiment, the first separation groove has a zigzag shape in which a portion extending in the first direction and a portion extending in the second direction are alternately repeated. In addition, the second inner portion and the second outer portion that improve the electrical conductivity can be provided more, and the effect of the present invention is further enhanced.

  The shape of the first separation groove according to the embodiment improves the electrical conductivity between the wire to be bonded and the contact region for injecting current (or applying voltage). Therefore, it is sufficient that at least the first separation groove has the second inner portion and the second outer portion that improve conductivity. However, the separation groove is provided for the purpose of isolation such as current confinement and parasitic capacitance reduction. From the viewpoint of the characteristic stability of the semiconductor optical device, the second separation groove which is the other separation groove in which no wire is bonded to the electrode. The shape of the separation groove may also be the same as the shape of the first separation groove, and the semiconductor optical device according to the embodiment has the shape of the first separation groove and the second separation groove as viewed from above. The shape is symmetrical with respect to the optical waveguide (mesa stripe 11). Therefore, here, also in the second separation groove, the inner surface includes the first inner portion and the second inner portion, and the outer surface includes the first outer portion and the second outer portion. In the embodiment, the second separation groove also has a zigzag shape in which a portion extending in the first direction and a portion extending in the second direction are alternately repeated. Therefore, the first separation groove and the second separation groove have such shapes, thereby improving the reliability of the element characteristics while improving the conductivity of the electrodes. Furthermore, the current-light output characteristics and high frequency response of the semiconductor optical device are improved.

  In addition, although the electrode 13 of the semiconductor optical device according to the embodiment has the shape shown in FIG. 1, it is not limited to this. For example, either or both of the upper edge and the lower edge of the portion extending from the region above the optical waveguide to the left and right sides may reach the element end face. Further, for example, the electrode may have the shape shown in FIG. 1 in order to ensure heat dissipation. For example, the side opposite to the side where the wire is bonded to the optical waveguide in order to reduce the parasitic capacitance. The electrode may not be provided beyond the second separation groove. The present invention can be widely applied to a semiconductor optical device having a separation groove, and the shape of the electrode may be selected according to the semiconductor optical device to be applied.

  In the semiconductor optical device according to this embodiment, as shown in FIG. 3, the portion extending in the vertical direction (first direction) in FIG. However, it is not necessary to be limited to this. Even in the case where the cross section has a substantially vertical shape, as described above, sufficient electrical conductivity cannot be obtained by electrode formation by vapor deposition in such a portion, and by applying the present invention, a remarkable effect can be obtained. Play.

  Further, in the semiconductor element according to the embodiment, a semiconductor multilayer is formed on an n-type semiconductor substrate, an upper electrode formed so as to cover the semiconductor multilayer is a p-side electrode, and the back surface (lower surface) of the n-type semiconductor substrate is formed. Although the lower electrode to be formed is an n-side electrode, it is not necessary to be limited to this. A semiconductor multilayer may be formed on a p-type semiconductor substrate, the upper electrode may be an n-side electrode, and the lower electrode may be a p-type electrode. Further, the present invention is applied to a semiconductor optical device in which an n-type semiconductor and a p-type semiconductor are formed on a semi-insulating semiconductor substrate (for example, an Fe-InP substrate), and an n-side electrode and a p-type electrode are provided on the device surface side. You may apply.

[Second Embodiment]
The semiconductor optical device according to the second embodiment of the present invention is a laterally coupled directional optical coupler type (Lateral Grating Assisted Lateral Co-directional Coupler: hereinafter referred to as LGLC) wavelength tunable laser device 2. It is a part. Here, the LGLC wavelength tunable laser element 2 is formed of an InGaAsP-based material in an active layer, and is used as a light source in a 1.55 μm band. Patent Document 2 discloses a technique related to an LGLC wavelength tunable laser.

  FIG. 5 is a top view of the LGLC wavelength tunable laser element 2 according to this embodiment. The LGLC wavelength tunable laser element 2 includes an LGLC wavelength tunable filter unit 3, a phase adjustment unit 4, a gain unit 5, and a diffraction grating type reflection mirror unit in order from the end surface opposite to the light emission side to the emission side end surface. (Hereinafter referred to as the DBR reflection mirror section 6) are arranged, and each of these optical components is a semiconductor optical device according to the embodiment. In the optical waveguide (high refractive index optical waveguide) formed in the mesa stripe 11 extending from the opposite end face to the outgoing end face of the LGLC wavelength tunable laser element 2, and mainly in the LGLC wavelength tunable filter section 3, the optical FIG. 5 shows another optical waveguide (low refractive index optical waveguide) provided on the side of the waveguide. Separation grooves 12 are formed on both sides of two optical waveguides (a high refractive index optical waveguide and a low refractive index optical waveguide) on the surface of the semiconductor multilayer, and the shape of the two separation grooves 12 is as follows. Similar to the semiconductor optical device according to the embodiment, it has a zigzag shape.

A current is injected into each of the LGLC wavelength tunable filter unit 3 and the DBR reflection mirror unit 6 to change the refractive index of the semiconductor in the portion of the active layer that becomes the optical waveguide, thereby changing the light transmission wavelength. By controlling the amount of current injected into each, the wavelength of the light output from the LGLC wavelength tunable laser element can be controlled, and light of a desired wavelength can be oscillated. Each of the separation grooves 12 has a zigzag shape as described above. Of the portion extending in the first direction, the side closer to the mesa stripe 11 is a distance of 10 μm from the mesa stripe 11 and the side farther from the mesa stripe 11 is the mesa stripe. A separation groove 12 is formed at a distance of 25 μm from the stripe 11. Therefore, the length of the portion extending in the second direction in which both side surfaces are forward tapered is 15 μm. Further, the width of the separation groove 12 is 5 μm and the depth is 4 μm. The separation groove 12 is formed by wet etching using an HCl-based etching solution. Further, a SiO ₂ film having a thickness of 500 nm is formed as an insulating film 17 on the entire surface of the semiconductor multilayer by a sputtering method. The insulating film 17 in the contact region of the electrode 13 is removed with buffered hydrofluoric acid, and the surface of the semiconductor multilayer is thinly wet-etched to reduce damage to the insulating film 17 due to the sputtering method. The electrode 13 is formed with a thickness of 1 μm using a vacuum deposition method.

  When a separation groove formed along the optical waveguide is formed in the LGLC wavelength tunable laser element, the current-carrying property from one side to the other side of the separation groove is not ensured, and the LGLC wavelength tunable laser element conventionally having desired characteristics is obtained. Therefore, the LGLC wavelength tunable laser element is manufactured without a separation groove. On the other hand, when the characteristics of the LGLC wavelength tunable laser element 2 manufactured by such a process were measured, the efficiency of light output at a low injection current was improved by about 10% compared to the case where there was no separation groove. A remarkable effect is obtained, and a structure capable of stably flowing current from one side of the separation groove to the other side is realized. From the viewpoint of improving the characteristics of the element, it is desirable to apply the present invention to all four optical parts of the LGLC wavelength tunable laser element 2, but the present invention is not limited to this. You may apply this invention to a part.

[Third Embodiment]
The semiconductor optical device according to the third embodiment of the present invention has the same structure as the semiconductor optical device according to the first embodiment, but provides a condition for the length of the portion extending in the second direction. This is different from the semiconductor optical device according to the first embodiment.

  6 and 7 are partial top views for explaining the structure of the semiconductor optical device 1 according to this embodiment. 6 is an enlarged view of the region VI in FIG. 1, and FIG. 7 is an enlarged view of the region VII in FIG. As described above, from the viewpoint of current confinement and parasitic capacitance reduction, the distance between the contact region and the isolation trench should be as short as possible. That is, in the semiconductor optical device according to the first and second embodiments, it is desirable that the length of the portion extending in the second direction is short. However, from the viewpoint of stably securing the second inner portion and the second outer portion whose side shape is a forward tapered shape, the length condition of the portion extending in the second direction is as follows: Is desirable.

  As a result of manufacturing the semiconductor element 1 according to the first embodiment, the inventors have shown that a portion of the side surface of the separation groove 12 bent in a convex shape with respect to the bottom surface has a shape shown in FIG. Discovered. Between the first inner part extending in the first direction (vertical direction in FIG. 7) and the second inner part extending in the second direction (left-right direction in the figure), the second from the first direction. There is a bent portion (convex bent portion) that bends in the direction of, and the bent portion connects the lower end of the first inner portion and the right end of the second inner portion. Here, the portion bent into a convex shape means that the second inner portion extends from the first inner portion to the contact region side (left side) along the second direction (left-right direction). The second inner portion is a portion that is connected to the first inner portion via a bending portion. In such a bent portion, as shown in FIG. 6, side etching is performed at an angle of 45 ° (direction connecting the upper right and the lower left). The portion continuously changes from the reverse tapered shape to the forward tapered shape from the lower end of the first inner portion to the right end of the second inner portion, and very little electrode material is deposited on the inner surface of the portion. In addition, it is difficult to ensure the electrical conductivity due to the disconnection or the portion. Therefore, it is desirable to design the shape of the separation groove 12 so that the second inner portion is formed even when such a bent portion is formed.

  As a result of examining the shape of the separation groove 12 of the manufactured semiconductor optical device 1, the inventors have determined that the depth of the separation groove 12 is d. It was found that the right isosceles triangular portion having the same length was removed. Further, the side surface at the right end of the second inner portion is also side-etched at an angle of 45 °, and the width Lt of the second inner portion when the second inner portion (forward taper shape) is viewed from above the element is 0. Since it is about 7 × d, the top end of the side etching, that is, the right end of the lower edge of the second inner portion extends the upper edge of the first inner portion in the first direction (vertical direction in FIG. 7). It is located at a distance 1.7 times d from the straight line. Therefore, when the distance from the extended straight line of the upper edge of the first inner portion of the left end (end on the contact region side) of the second inner portion is defined as Lb, Lb is moved from the extended straight line to the contact region side, and the separation groove By positioning the left end of the second inner portion so as to be 1.7 times or more of the depth d, the length Lw of the second inner portion has a value of 0 or more and is formed in the second inner portion. Conductivity is ensured by the electrode material. Note that, as shown in FIG. 7, the portion of the side surface of the separation groove 12 that is bent in a concave shape with respect to the bottom surface is hardly affected by the side etching.

  Here, the inner side surface of the separation groove 12 has been described as an example, but the same applies to the outer side surface. That is, when the second outer portion extends from the first outer portion to the side opposite to the contact region side, the second outer portion is still formed even if the bent portion (convex bent portion) is formed. Thus, it is desirable to design the shape of the separation groove 12. The end of the second outer portion opposite to the contact region side is located at a distance of 1.7 times or more the depth of the separation groove on the opposite side from the extended straight line of the upper edge of the first outer portion. It is desirable. Furthermore, although the first separation groove 12A on the side where the wire to be bonded is disposed has been described here, it goes without saying that the same applies to the second separation groove 12B disposed on the opposite side.

  In the semiconductor optical device 1 according to this embodiment, the semiconductor optical device 1 was manufactured with the depth d of the separation groove 12 being 3 μm and the distance Lb being 10 μm. In the manufactured semiconductor optical device 1, the length Lw of the second inner portion having a forward tapered shape was about 5 μm. When the resistance value of the separation groove 12 portion was measured, it was 0.1Ω or less, which could be reduced to a desired resistance value or less. By providing the conditions, a semiconductor optical device with improved characteristics is realized.

  In the semiconductor optical device according to the embodiment, the case where the second direction is orthogonal to the first direction is shown, but the present invention is not limited to this. When the angle formed by the first direction and the second direction is 45 ° or more, by applying the above condition, the second inner portion and the second outer portion are formed, and the conductivity is ensured.

[Fourth Embodiment]
The semiconductor optical device according to the fourth embodiment of the present invention is different from the semiconductor optical device according to the first to third embodiments in the shape of the separation groove 12, but has the same structure except for the above. . In order to achieve the effect of the present invention, at least one second inner portion is provided on the inner surface of the first separation groove 12A, and similarly, at least one second outer portion is provided on the outer surface. In other words, the present invention can be widely applied to the separation groove of a semiconductor optical device.

  FIG. 8 is a top view of the semiconductor optical device 7 according to an example of the embodiment. In the semiconductor optical device 7 shown in FIG. 8, in addition to the portion extending along the first direction (vertical direction in FIG. 8), the separation groove 12 has a second direction (in FIG. 8) different from the first direction. The part extended | stretched along the left-right direction) is formed in two places. Thereby, in addition to the first inner portion and the first outer portion formed in the portion extending along the first direction of the separation groove 12, the separation groove 12 extends along the second direction of the separation groove 12. It has the 2nd inner side part and 2nd outer side part formed in the part to extend | stretch, and electricity supply is ensured.

  FIG. 9 is a top view of a semiconductor optical device 8 according to another example of the embodiment. In the semiconductor optical device 8 shown in FIG. 9, the separation groove 12 includes a portion extending along the first direction (vertical direction in FIG. 9) and a portion curved in a semi-ring shape. The inner surface of the separation groove 12 includes a first inner portion extending along the first direction, and a second inner portion formed so as to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. It is out. In the portion where the separation groove 12 is curved in the half ring shape, the inner side surface is a curved surface, and the inner side surface of the separation groove 12 includes a portion that becomes a curved surface. The second inner portion is included in the curved surface.

  The same applies to the outer surface of the separation groove 12, and a first outer portion extending along the first direction, and a second outer portion formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. , Including. In the part where the separation groove 12 is curved in the semi-ring shape, the outer surface is a curved surface, and the outer surface of the separation groove 12 includes a curved part. The second outer portion is included in the curved surface. The separation groove 12 has a second inner portion and a second outer portion, and ensures electrical conductivity.

  FIG. 10 is a top view of a semiconductor optical device 9 according to another example of the embodiment. In the semiconductor optical device 1 shown in FIG. 1, the separation groove 12 has a zigzag shape in which a portion extending in the up-down direction as the first direction and a portion extending in the left-right direction as the second direction are repeated alternately. However, the zigzag shape is not limited to this. In the semiconductor optical device 9 shown in FIG. 8, the separation groove 12 is different from the first direction (vertical direction in the drawing) in the third direction as well as the second direction (direction connecting the upper right and the lower left). (The direction connecting the lower right and the upper left). That is, the separation groove 12 includes a portion extending in the first direction, a portion extending in the second direction, and a portion extending in the third direction. Here, the portion extending in the first direction includes a first inner portion and a first outer portion facing each other, and the portion extending in the second direction is the second inner portion facing each other A second outer portion is included. Here, both the second inner portion and the second outer portion are formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. The separation groove 12 has a second inner portion and a second outer portion, and ensures electrical conductivity. Similarly, both side surfaces of the portion extending in the third direction are also inclined from the lower edge to the upper edge on the side opposite to the bottom surface side, further ensuring conductivity.

  The semiconductor optical device according to the embodiment of the present invention has been described above. In the semiconductor optical device according to the above embodiment, an InGaAsP system is used as a semiconductor material, but the present invention is not limited to this, and even when the material system is a GaAs system, an InAlGaAs system, or other material system, The present invention can be applied. In the semiconductor optical device according to the above embodiment, InP is used for the material such as the substrate and the buried layer. However, the present invention is not limited to this, and a group III-V material such as GaAs may be used. In addition, the present invention can be widely applied if the side surface of the separation groove has the above shape by wet etching. Furthermore, in the semiconductor optical device according to the embodiment, the semiconductor optical device having the BH structure in which the isolation groove is formed is described mainly for the purpose of current confinement (current block). For this purpose, it goes without saying that the present invention can also be applied to direct modulation laser elements and modulator integrated laser elements that require high-frequency characteristics.

[Fifth Embodiment]
The optical module according to the fifth embodiment of the present invention is a TOSA 30 (Transmitter Optical Sub Assembly) including the semiconductor optical device according to the first to fourth embodiments. FIG. 11 is a schematic diagram showing the configuration of the TOSA 30 according to this embodiment, and the LGLC wavelength tunable laser element 2 according to the second embodiment is mounted on the TOSA 30. The light emitted from the LGLC wavelength tunable laser element 2 is converted into parallel light by the lens 31 and enters the isolator 32. The light passing through the isolator 32 passes through the beam splitter 33 and the lens 31 and is output to the optical fiber 36. Further, wavelength control is performed by a wavelength locker configured by the beam splitter 33, the etalon 34, and the monitor PD 35 using light that passes through the isolator 32 and is branched by the beam splitter 33. As a result of manufacturing and measuring the TOSA 30, it has been confirmed that light is oscillated by changing the wavelength in the C band. In the TOSA 30 according to this embodiment, only a laser element is mounted as a wavelength tunable light source. However, a modulation device such as a semiconductor MZ element or an EA modulator may be mounted in the same TOSA and used as a modifiable TOSA. Further, the present invention is not limited to the LGLC wavelength tunable laser element 2 according to the second embodiment, and the semiconductor optical element according to another embodiment may be mounted on the TOSA.

[Sixth Embodiment]
The optical module according to the sixth embodiment of the present invention is a transceiver including the TOSA according to the fifth embodiment. It has been confirmed that the transceiver performs NRZ modulation by combining an LN modulator with the TOSA according to the fifth embodiment, thereby achieving desired transmission characteristics in the C band. In the transceiver according to this embodiment, an optical signal is modulated using an LN modulator. However, the present invention is not limited to this, and in the transceiver, the TOSA includes a semiconductor MZ element, an EA modulator, and other modulators. You may combine. The optical modules according to the fifth and sixth embodiments are provided with the semiconductor optical device according to the present invention, thereby realizing improvement in characteristics.

  DESCRIPTION OF SYMBOLS 1 Semiconductor optical element, 2 LGLC wavelength tunable laser element, 3 LGLC wavelength tunable filter part, 4 Phase adjustment part, 5 Gain part, 6 DBR reflection mirror part, 7, 8, 9 Semiconductor optical element, 10 n-type InP substrate, 11 Mesa stripe, 12 separation groove, 12A first separation groove, 12B second separation groove, 13 electrode, 14 wire, 15 buried layer, 16 p-type InP layer, 17 insulating film, 18 active layer, 19 electrode, 20 reverse taper shape , 21 Forward taper shape, 30 TOSA, 31 Lens, 32 Isolator, 33 Beam splitter, 34 Etalon, 35 Monitor PD, 36 Optical fiber.

Claims (11)

A semiconductor multi-layer having a first separation groove and a second separation groove formed on each surface on both sides of a contact region positioned above an optical waveguide extending in a first direction, and including an active layer; ,
An insulating film formed over the semiconductor multilayer surface except for the contact region;
The semiconductor multilayer and the insulating film are formed in a predetermined shape, and a wire bonded to the outer side of the first separation groove is electrically connected to the semiconductor multilayer via the first separation groove. The electrode,
With
The first separation groove includes a bottom surface, an inner surface formed on the contact region side, and an outer surface formed on the side opposite to the contact region side,
The inner surface of the first separation groove has a first inner portion extending along the first direction, and a second inner side formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. Including, and
The outer surface of the first separation groove has a first outer portion extending along the first direction, and a second outer surface formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. Including, and
A semiconductor optical device. The semiconductor optical device according to claim 1,
The second inner portion extends from the first inner portion toward the contact region along a second direction different from the first direction, and bends from the first direction to the second direction. Connected to the first inner portion via a bent portion for
A semiconductor optical device. The semiconductor optical device according to claim 2,
The end of the second inner portion on the contact region side is a distance of 1.7 times or more the depth of the first separation groove from the extended straight line of the upper edge of the first inner portion to the contact region side. To position,
A semiconductor optical device. The semiconductor optical device according to claim 1,
The second outer portion extends from the first outer portion to a side opposite to the contact region side along a second direction different from the first direction, and extends from the first direction to the second direction. Connected to the first outer portion through a bent portion that is bent in a direction;
A semiconductor optical device. The semiconductor optical device according to claim 4,
An end portion of the second outer portion opposite to the contact region side is set to a depth of 1.7 of the first separation groove on the opposite side of the contact region side from the extended straight line of the first outer portion. Located more than double the distance,
A semiconductor optical device. The semiconductor optical device according to claim 1,
The first separation groove includes a portion extending in the first direction including the first inner portion and the first outer portion facing each other, and the second inner portion and the second outer portion facing each other. A zigzag shape including a portion extending in a second direction different from the first direction,
A semiconductor optical device. A semiconductor optical device according to any one of claims 2 to 6,
An angle formed by the first direction and the second direction is 45 ° or more.
A semiconductor optical device. A semiconductor optical device according to any one of claims 2 to 6,
The angle formed by the first direction and the second direction is a right angle.
A semiconductor optical device. The semiconductor optical device according to claim 1,
The inner surface includes a portion that becomes a curved surface, and the second inner portion is included in a portion that becomes the curved surface,
The outer surface includes a portion that becomes a curved surface, and the second outer portion is included in a portion that becomes the curved surface.
A semiconductor optical device. A semiconductor optical device according to any one of claims 1 to 9,
The second separation groove includes a bottom surface, an inner surface formed on the contact region side, and an outer surface formed on the side opposite to the contact region side,
The inner surface of the second separation groove has a first inner portion extending along the first direction, and a second inner side formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. Including, and
The outer surface of the second separation groove has a first outer portion extending along the first direction, and a second outer surface formed to be inclined from the lower edge to the upper edge on the side opposite to the bottom surface side. Including, and
A semiconductor optical device.   An optical module comprising the semiconductor optical device according to claim 1.

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