JP2013069723A - Semiconductor laser element and optical transmitter module and optical transceiver incorporating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ridge waveguide type semiconductor laser element, including an InGaAlAs quantum well layer in its active layer, which improves reliability and restricts the appearance of saturable absorption characteristics at the same time.SOLUTION: The semiconductor laser element comprises: a semiconductor multilayer including an active layer which contains the InGaAlAs quantum well layer, an etching stop layer, and an upper mesa part disposed on the upper side of the etching stop layer; an insulation film formed on the upper surface of the semiconductor multilayer; and an electrode film which is formed so as to cover the semiconductor multilayer and the insulation film, as well as formed in contact with the top face of the upper mesa part. Two side faces of a ridge part each include an exposed region which has no electrode films formed therein and remains exposed. The exposed region on each of the two side faces of the ridge part goes from an end face on one side of the ridge part as far as to reach the inside from the tip at which the electrode film extends over the top face of the ridge part to the end face on the one side.

Description

  The present invention relates to a semiconductor laser device, and more particularly to improvement in device reliability by suppressing strain generated in an active layer at an end surface of the device.

  For example, a semiconductor laser element including an InGaAsP quantum well layer as an active layer as a light source is mounted on a communication optical transmission module. However, in recent years, in place of such a semiconductor laser element, development of a semiconductor laser element including an InGaAlAs quantum well layer as an active layer has been advanced (Non-Patent Document 1). A semiconductor laser element including an InGaAlAs quantum well layer as an active layer is superior in characteristics in a high temperature region as compared with a conventional semiconductor laser element, and thus does not require an electronic cooling element for keeping the temperature of the semiconductor laser element constant. This is because the module can be reduced in size, price, and power consumption.

  It has already been reported in Patent Document 1 and the like that a semiconductor laser element including an InGaAlAs quantum well layer as an active layer has excellent laser characteristics and high reliability exceeding an estimated lifetime of 100,000 hours.

JP 2003-258370 A JP 2007-180522 A JP 2010-1229887 A JP 2010-114430 A

IEEE Journal of Quantum Electronics, Vol. 30, no. 2, p511, (1994) Journal of Applied Physics, Vol. 107, p083109, (2010)

  Internet traffic has increased remarkably with the expansion of the use of high-definition video content. There is a strong demand for downsizing, lowering the price, and reducing power consumption of communication network devices in order to reduce capital investment and operation costs for dealing with this increase in traffic. At the same time, communication network devices are required to be further increased in speed and capacity. In order to satisfy these requirements, it is required to directly modulate the semiconductor laser device at 25 Gbps, which is 2.5 times faster than the conventional 10 Gbps. In the future, it is also expected to perform modulation at a higher speed of 40 Gbps or more. In order to drive the semiconductor laser at higher speed, it is necessary to increase the current density inside the laser resonator, but generally, the higher the operating current density, the faster the degradation rate of the semiconductor laser. Even if the operating current density is increased, it is desirable to ensure high reliability of the element so that the deterioration rate is suppressed. It is desired that a semiconductor laser device having higher reliability can be realized by elucidating a degradation mechanism peculiar to a semiconductor laser device including an InGaAlAs quantum well layer as an active layer and taking measures according to the degradation mechanism. .

  For example, Non-Patent Document 2 describes that in a semiconductor laser element including an InGaAlAs quantum well layer as an active layer, deterioration occurs near the reflection end face, and the deterioration is related to internal stress of the end face protective film. Has been. Patent Document 1 describes that the internal stress of an electrode is related to deterioration.

  Consider a ridge waveguide type semiconductor laser device including an InGaAlAs quantum well layer in an active layer. First, consider a case where the element has a ridge portion on the top thereof, and the upper surface electrode extends over the entire upper surface and both side surfaces of the ridge portion. Here, the upper surface electrode extends to the cleaved end surface opposite to the light emitting side. In this case, due to the internal stress of the upper surface electrode, the active layer in the vicinity of the end surface is distorted, and the reliability of the element is lowered.

  Next, consider a case where a region adjacent to the cleavage end surface is removed from the upper surface electrode. In this case, since no electrode is formed in the vicinity of the end face, internal stress of the upper surface electrode does not occur in the vicinity of the end face, the amount of strain applied to the active layer in the vicinity of the end face can be reduced, and the reliability of the element is improved. Is possible. However, since no electrode is formed in the vicinity of the end face, no current is injected into the active layer near the end face, which may cause a problem that a saturable absorption characteristic appears in the current / light output characteristics of the semiconductor laser element. This becomes a more significant problem when the region where the electrode is not formed becomes long due to the positional shift in the cleavage step. That is, there is a contradiction between improving the reliability of the element and suppressing the saturable absorption characteristic.

  Patent Document 1 discloses a semiconductor in which the upper electrode has a two-layer structure, and the end of the upper layer electrode is provided on the inner side of the end surface, thereby suppressing the strain of the active layer near the end surface due to the internal stress of the electrode near the end surface. A laser element is described. However, even in such an element, the sheet resistance in the vicinity of the end face of the upper surface electrode becomes very high, and the displacement in the cleavage process hinders uniform current injection as in the case where the electrode is not formed in the vicinity of the end face. The problem that the saturable absorption characteristic is developed may arise. Further, along with an increase in sheet resistance near the end face of the upper surface electrode, there may be problems such as a large amount of heat generation near the end face, an increase in laser driving voltage, and a deterioration in frequency response characteristics.

  The inventors investigated the amount of strain of the active layer near the end face caused by the internal stress of the upper surface electrode, and the electrode portion formed on the ridge side surface is more than the electrode portion formed on the ridge upper surface. It was found to affect the strain generated in the active layer.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a ridge that includes an InGaAlAs quantum well layer in an active layer, which achieves both improved reliability and suppression of saturable absorption characteristics. An object of the present invention is to provide a waveguide type semiconductor laser device, an optical transmission module including the same, and an optical transceiver.

  Patent Documents 2, 3 and 4 disclose a semiconductor laser element including an electrode composed of a first electrode layer and a second electrode layer. Here, the first electrode layer is formed to extend to the end surface on the upper surface of the striped ridge portion, and the second electrode layer is formed on the first electrode layer, on the side surface of the ridge portion, with a predetermined distance from the end surface. And on the flat portion around the ridge portion. However, all of the semiconductor laser elements described in these patent documents are limited to those in which the active layer contains a nitride-based semiconductor, and this configuration also prevents electrode breakage or electrode peeling during cleavage. It is for preventing. That is, these patent documents do not describe the internal stress of the electrode.

  (1) In order to solve the above problems, a semiconductor laser device according to the present invention extends along an active layer including a quantum well layer made of an InGaAlAs-based material, an etching stop layer, and an optical waveguide region of the active layer. And an upper mesa portion disposed above the etching stop layer, an insulating film formed on an upper surface of the semiconductor multilayer, and covering the semiconductor multilayer and the insulating film and the upper mesa And an electrode film formed in contact with the upper surface of the portion, and the upper mesa portion and a portion of the insulating film formed in contact with the upper mesa portion that forms a ridge portion Each side surface of the ridge portion has an exposed region that is exposed without forming the electrode film, and the exposed region on each side surface of the ridge portion is the From one end face of the Tsu di portion, the electrode film to the inside from the tip of stretching the top face of the ridge to the one end surface of which extends, it is characterized.

  (2) In the semiconductor laser device according to (1), each of the exposed regions on both side surfaces may include a portion extending from the lower end of the side surface to the upper end of the side surface.

  (3) In the semiconductor laser device according to (2), a portion extending from the lower end of the side surface to the upper end of the side surface is a distance of 5 μm or more and 20 μm or less from the one end surface in each exposed region of the both side surfaces. May be extended.

  (4) In the semiconductor laser device according to (1), each of the exposed regions on both side surfaces may include a portion extending from the lower end of the side surface to 2/3 or more of the height of the ridge portion. .

  (5) In the semiconductor laser device according to (4), a portion extending from the lower end of the side surface to 2/3 or more of the height of the ridge portion in the exposed region of each of the both side surfaces is the one end surface. From 5 μm to 20 μm.

  (6) In the semiconductor laser device according to any one of (1) to (5), the electrode film extends from the upper surface of the ridge portion to each of the both side surfaces, and each of the both side surfaces is the one side. It may be extended to the end face and may extend to the exposed area.

  (7) In the semiconductor laser element according to (6), the electrode film may have a tensile stress.

  (8) In the semiconductor laser device according to any one of (1) to (5), both side surfaces of the ridge portion are embedded with an organic insulating layer except at least the exposed region, and the organic insulating layer is It may extend to the exposed area.

  (9) In the semiconductor laser element according to (8), the organic insulating layer may have a tensile stress.

  (10) In the semiconductor laser device according to (6) or (7), both side surfaces of the ridge portion are filled with an organic insulating layer except at least the exposed region, and the electrode film is the organic insulating layer You may spread over.

  (11) The semiconductor laser device according to any one of (1) to (10), wherein the electrode film has an upper surface on the ridge portion on each side of a tip end of the upper surface of the ridge portion extending to the one end surface. Has an upper surface exposed region that is exposed without forming the electrode film, and the upper surface exposed region on both sides of the tip extends to the exposed region on both side surfaces of the ridge portion, respectively. Each of the upper surface exposed regions on both sides of the front end may have a portion that increases in width as it proceeds to the one end surface.

  (12) In the semiconductor laser device according to any one of (1) to (11), a tip of the electrode film that extends the top surface of the ridge portion to the one end surface extends to the one end surface. Also good.

  (13) In the semiconductor laser device according to any one of (1) to (12), the ridge portion may have a portion that extends toward the one end surface and gradually increases in width. Good.

  (14) In the semiconductor laser device according to any one of (1) to (13), each of both side surfaces of the ridge portion may have other exposed regions that are exposed without forming the electrode film. Further, the other exposed regions on both side surfaces of the ridge portion are located on the inner side from the other end surface of the both ends of the ridge portion from the tip where the electrode film extends from the upper surface of the ridge portion to the other end surface. You may extend.

  (15) An optical transmission module according to the present invention may include the semiconductor laser device according to any one of (1) to (14).

  (16) An optical transceiver according to the present invention may include the optical transmission module according to (15).

  The present invention provides a ridge waveguide type semiconductor laser device including an InGaAlAs quantum well layer as an active layer, and an optical transmission module and an optical transceiver including the same, which realize both improvement in reliability and suppression of saturable absorption characteristics. Is done.

1 is a schematic external perspective view of a semiconductor laser device according to a first embodiment of the present invention. It is a top view which shows the other example of the semiconductor laser element concerning the 1st Embodiment of this invention. It is a typical external appearance perspective view which shows the other example of the semiconductor laser element concerning the 1st Embodiment of this invention. It is a typical external appearance perspective view which shows the mounting method of the semiconductor laser element which concerns on the 1st Embodiment of this invention. It is a figure which shows the calculation result of the strain distribution which generate | occur | produces in the active layer of the semiconductor laser element concerning the 1st Embodiment of this invention. It is a typical external appearance perspective view which shows the other example of the semiconductor laser element concerning the 1st Embodiment of this invention. It is a typical external appearance perspective view of the semiconductor laser element concerning the 2nd Embodiment of this invention. It is a typical external appearance perspective view of the semiconductor laser element concerning the 3rd Embodiment of this invention. It is a typical external appearance perspective view of the semiconductor laser element concerning the 4th Embodiment of this invention.

  The semiconductor laser device according to the embodiment of the present invention will be described in detail below. Here, the semiconductor laser device according to the embodiment is a Fabry-Perot laser, but is not limited thereto, and may be a DFB laser (Distributed-Feedback Laser), a DBR laser (Distributed Bragg Reflector Laser), or the like. . In addition, the figure shown below demonstrates the Example of each 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. Moreover, the same code | symbol is attached | subjected to the same component and those description is not repeated.

[First Embodiment]
FIG. 1 is a schematic external perspective view of the semiconductor laser device 17 according to the first embodiment of the present invention. The semiconductor laser device 17 according to this embodiment is a ridge waveguide Fabry-Perot laser including a quantum well layer made of an InGaAlAs-based material in an active layer 3 and emits light in the 1.3 μm band or 1.5 μm band. .

  As shown in FIG. 1, an n-type InGaAlAs light guide layer 2, an active layer 3, a p-type InGaAlAs light guide layer 4, a p-type InAlAs first cladding layer 5, and a p-type InGaAlAs etching stop layer 6 on an n-type InP substrate 1. A semiconductor multilayer composed of the p-type InP second cladding layer 7 and the p-type InGaAs contact layer 8 is formed. The p-type InP second cladding layer 7 and the p-type InGaAs contact layer 8 disposed on the upper side of the p-type InGaAlAs etching stop layer 6 have both sides of the region above the optical waveguide region of the active layer 3 removed. It is the upper mesa part. That is, the upper mesa portion extends along the optical waveguide region of the active layer 3, and as shown in FIG. 1, the extending direction (longitudinal direction) of the upper mesa portion is a direction extending from the front to the back in the drawing. It is.

  An insulating film 10 is formed in a predetermined region on the upper surface of the semiconductor multilayer. Here, the predetermined region is a region on both sides of the upper mesa portion and a region where the upper mesa portion is not formed on the upper surface of the p-type InGaAlAs etching stop layer 6. That is, the insulating film 10 is formed on the entire upper surface of the semiconductor multilayer except for the region on the upper surface of the upper mesa portion. Furthermore, ideally speaking, it is formed on the entire upper surface of the semiconductor multilayer except for the region of the surface (upper surface and side surface) of the p-type InGaAs contact layer 8 located at the uppermost layer of the upper mesa portion. However, the present invention is not limited to this, and the insulating film 10 that spreads on both sides of the upper mesa portion may reach a part of the upper surface of the upper mesa portion (the upper surface of the p-type InGaAs contact layer 8). In addition, the insulating film 10 does not reach the upper ends (boundaries with the upper surface) of both side surfaces of the upper mesa portion, and the insulating film 10 may not be formed in a partial region of both side surfaces including the upper ends of both side surfaces. . Even in this case, it is desirable that the insulating film 10 reaches at least 2/3 of the height of the upper mesa portion on both side surfaces of the upper mesa portion. The semiconductor upper multilayer mesa portion and the portion of the insulating film 10 formed in contact with the upper mesa portion are combined to form the ridge portion 9 of the semiconductor laser element 17.

  A p-type electrode film 11 (upper surface electrode: p-side electrode) is formed on the upper surface of the substrate, and an n-type electrode film 12 (lower surface electrode: n-side electrode) is formed on the lower surface of the substrate. The p-type electrode film 11 covers the semiconductor multilayer and the insulating film 10 and is formed in contact with the upper surface of the upper mesa portion. That is, the p-type electrode film 11 and the upper mesa portion are in contact with each other and electrically connected in a region where the insulating film 10 is not formed in the upper mesa portion (region other than the predetermined region).

  A pair of end faces are provided at both ends of the ridge portion 9 (upper mesa portion) in the longitudinal direction. Here, the pair of end surfaces are the reflection end surfaces 13 and 14, which are cleavage surfaces formed by a cleavage process. The reflective end face 13 is covered with a high reflectance film (not shown), and the reflective end face 14 is covered with a low reflectance film (not shown). That is, the end face on the light emission side of the semiconductor laser element 17 is the reflection end face 14.

  The main feature of this embodiment is the shape of the p-type electrode film 11. Of the p-type electrode film 11 (upper surface electrode), a portion formed on the upper surface of the ridge portion 9 is a ridge upper surface portion, a portion formed on the side surface of the ridge portion 9 is further spread from both sides of the ridge portion 9. Let the part be the other surface part.

  As shown in FIG. 1, the ridge upper surface portion of the p-type electrode film 11 extends to the reflection end surface 13 (one end surface). That is, the ridge upper surface portion of the p-type electrode film 11 is formed on the entire upper surface of the ridge portion 9. On the other hand, on both side surfaces of the ridge portion 9, there are exposed regions where the p-type electrode film 11 is not formed and the insulating film 10 is exposed at a predetermined length from the reflection end surface 13. That is, the ridge side surface portion of the p-type electrode film 11 is formed to extend from the reflection end surface 14 (the other end surface) to a position having a predetermined length inward from the reflection end surface 13 (outer edge of the exposed region). Further, the other surface portion of the p-type electrode film 11 is formed from the reflective end surface 14 to the position having a predetermined length inward from the reflective end surface 13, similarly to the ridge side surface portion. That is, the p-type electrode film 11 extends further outward from the lower ends of both side surfaces of the ridge portion 9.

  Here, it is preferable that the exposed regions on both side surfaces of the ridge portion 9 extend from the lower end of the side surface to the upper surface of the side surface in all of the predetermined length from the reflection end surface 13, but the exposed region is the lower end of the side surface. It may include a portion extending from to the upper end of the side surface. It suffices to include at least a portion extending from the lower end of the side surface to 2/3 or more of the height of the ridge portion 9.

  Increasing the predetermined length of the exposed region reduces the strain generated in the active layer near the end face, but the resistance value of the portion near the end face of the top electrode increases, so the predetermined length is What is necessary is just to determine suitably considering the trade-off of both. Specifically, in the exposed region, it is preferable that a portion extending from the lower end of the side surface to a height of 2/3 or more of the height of the ridge portion 9 extends from the end surface to a length of 5 μm or more and 20 μm or less.

  In the semiconductor laser device 17 according to this embodiment, distortion generated in the active layer 3 near the reflection end surface 13 due to internal stress of the upper surface electrode near the reflection end surface 13 is suppressed, and the reliability of the device is improved. Further, since the upper surface of the ridge of the upper surface electrode (p-type electrode film 11) extends to the reflection end surface 13, current is stably injected into the active layer 3 in the vicinity of the reflection end surface 13, so that the saturable absorption characteristic. Expression is suppressed, and substantially no saturable absorption occurs.

  It is preferable that the tip of the ridge upper surface portion of the upper surface electrode (p-type electrode film 11) extends to the reflective end surface 13, but the tip of the ridge upper surface portion does not reach the reflective end surface 13 due to an error in the manufacturing process. There may be cases. Even in this case, the effect of the present invention can be obtained if the exposed region of the ridge portion 9 extends from the tip of the ridge upper surface portion of the upper surface electrode to the inside.

  The semiconductor laser device according to the embodiment can achieve both improvement of device reliability and suppression of saturable absorption characteristics, and is suitable for a high-speed direct modulation laser for optical communication.

  Next, a method for manufacturing the semiconductor laser device 17 according to this embodiment will be described below. An n-type InGaAlAs light guide layer 2, an active layer 3 including an InGaAlAs quantum well layer, a p-type InGaAlAs light guide layer 4, a p-type InAlAs first film are formed on the n-type InP substrate 1 using metal organic vapor phase epitaxy or the like. The clad layer 5, the p-type InGaAlAs etching stop layer 6, the p-type InP second clad layer 7, and the p-type InGaAs contact layer 8 are laminated in this order to form a semiconductor multilayer (semiconductor multilayer formation step). For example, the thicknesses of these semiconductor layers are about 100 nm, 100 nm, 20 nm, 50 nm, 20 nm, 1500 nm, and 200 nm, respectively. The active layer 3 can emit light having a desired wavelength.

  As described above, the semiconductor laser element may be a DFB laser or the like. In this case, the InGaAsP diffraction grating layer is inserted, for example, between the p-type InGaAlAs etching stop layer 6 and the p-type InP second cladding layer 7. After the p-type InGaAsP diffraction grating layer is laminated on the p-type InGaAlAs etching stop layer 6, a resist is applied on the p-type InGaAsP diffraction grating layer, a diffraction grating pattern is formed by the lithography method, and the diffraction grating pattern is formed by the etching method. The p-type InP second cladding layer 7 and the p-type InGaAs contact layer 8 are transferred onto the surface of the semiconductor multilayer body, and then, using a metal organic vapor phase epitaxy method or the like, on the semiconductor multilayer body on which the diffraction grating is formed. Re-grow up.

  Next, the p-type InP second cladding layer 7 and the p-type InGaAs contact layer 8 are processed by a photolithography method and an etching method so as to form a striped upper mesa portion (upper mesa forming step). The width of the upper mesa portion is about 1.0 μm to 1.5 μm.

After forming the upper mesa portion, the insulating film 10 having a thickness of about 500 nm is formed on the entire upper surface of the semiconductor multilayer by a thermal CVD (Chemical Vapor Deposition) method or the like. Next, by removing the insulating film formed on the surface of the p-type InGaAs contact layer 8 by photolithography and etching, an insulating film 10 is formed in a predetermined region on the upper surface of the semiconductor multilayer (insulating). Film formation step). As shown in FIG. 1, it is preferable to remove all of the insulating film formed on the surface of the p-type InGaAs contact layer 8, but at least a part of the insulating film formed on the surface of the p-type InGaAs contact layer 8. Can be removed. Even in that case, in order to ensure uniform current injection into the optical waveguide region of the active layer 3, a region (contact region) where no insulating film is formed on the surface of the p-type InGaAs contact layer 8 is reflected. It is desirable to extend from the end face 13 to the reflective end face 14. Further, it is preferable that the surface (side surface) of the p-type InP second clad layer 7 among both side surfaces of the upper mesa portion is covered with an insulating film, but at least from the lower end of the side surface of the upper mesa portion to the upper mesa portion height It is only necessary that the region reaching the height of 2/3 is covered with the insulating film. The insulating film 10 may be formed of a SiO ₂ (silicon oxide) film, a SiN (silicon nitride) film, an Al ₂ O ₃ (aluminum oxide) film, or the like.

  After the insulating film forming step, a resist is applied to the entire surface of the substrate, and further, a part of the applied resist is removed using a lithography method to leave the resist film in a predetermined region on the substrate surface (resist forming step). ). Here, the predetermined region is a region where the surface of the insulating film 10 is exposed in the semiconductor laser device 17 shown in FIG. 1. Specifically, both the side surfaces of the ridge portion 9 and the outer sides of the side surfaces are exposed. These are regions extending from the reflection end surface 13 to a predetermined length on a flat surface extending respectively. That is, the region where the resist is removed using the lithography method is a region extending from the position having a predetermined length to the inside of the reflection end surface 13 on the entire element surface to the reflection end surface 14, and the upper surface of the ridge portion 9 from the reflection end surface 13. It is a region obtained by combining a region extending over a predetermined length. Here, the predetermined length is preferably 5 μm or more and 20 μm or less. Then, the p-type electrode film 11 is formed on the substrate surface patterned with the resist film by a vapor deposition method or the like (metal film vapor deposition step). The p-type electrode film 11 includes a laminated film in which Ti (titanium), Pt (platinum), and Au (gold) are sequentially laminated, and Ti (titanium), Mo (molybdenum), Ti (titanium), and Au (gold). What is necessary is just a laminated film etc. laminated | stacked in order. The thicknesses of the laminated films are preferably about 25 nm, 25 nm, and 500 nm, respectively, in the former case, and about 25 nm, 80 nm, 40 nm, and 300 nm, respectively, in the latter case. After the deposition of the p-type electrode film 11, the resist film and the electrode film formed on the resist film are removed using an organic solvent such as acetone (upper surface electrode forming step).

  Next, after the lower surface of the n-type InP substrate 1 is polished and thinned to about 100 μm to 150 μm, the n-type electrode film 12 is formed by vapor deposition or heat treatment (lower surface electrode forming step). This completes the wafer process. The n-type electrode film 12 may be a laminated film in which Au (gold) -Ge (germanium), Ni (nickel), Ti (titanium), Pt (platinum), and Au (gold) are sequentially laminated. The thickness of each film of the laminated film is preferably about 60 nm, 10 nm, 100 nm, 100 nm, and 300 nm, for example.

A pair of end surfaces (reflection end surfaces 13 and 14) are formed by cleaving the semiconductor substrate (wafer). The distance between the reflection end faces 13 and 14 is preferably about 100 μm to 200 μm. The reflective end faces 13, 14 formed by cleavage are coated for end face protection and reflectance adjustment. A high reflectance film having a reflectance of 80% or more is formed on the reflection end face 13, and a low reflectance film having a reflectance of 1% or less is formed on the reflection end face 14. These films are Al ₂ O ₃ (aluminum oxide) film, SiO ₂ (silicon oxide) film, a-Si (amorphous silicon) film, and the like. These films may be multilayer films. Further, the semiconductor laser device 17 is produced by cleaving each device. The method for manufacturing the semiconductor laser element has been described above.

  In the manufacturing method according to the embodiment, the p-type electrode film 11 can be formed by a simple process of one resist forming step and one metal film deposition step. Furthermore, since the p-type electrode film 11 is formed in one metal film deposition step, an increase in electrical resistance of the ridge upper surface portion of the p-type electrode film 11 can be suppressed.

  FIG. 2 is a plan view showing another example of the semiconductor laser device according to the embodiment. In the semiconductor laser device 17 shown in FIG. 1, the ridge upper surface portion of the p-type electrode film 11 (upper surface electrode) is formed over the entire upper surface of the ridge portion 9, and is shorter than the ridge upper surface portion of the p-type electrode film 11. The width in the hand direction is constant with respect to the longitudinal direction. On the other hand, in the semiconductor laser device shown in FIG. 2, the ridge upper surface portion of the p-type electrode film 11 extends from the center of both end surfaces of the ridge portion 9 to the reflection end surface 13 with the same width in the longitudinal direction. The width in the short direction of the upper surface of the ridge becomes narrower as it extends, and reaches the tip. In other words, not only the both side surfaces of the ridge portion 9 but also the upper surface of the ridge portion 9 is exposed on the both sides of the ridge upper surface portion of the p-type electrode film 11 without the p-type electrode film 11 being formed. The upper surface exposed region on the upper surface of the ridge portion 9 extends to the exposed region on the side surface of the ridge portion 9. The upper surface exposed region becomes wider as the width of the upper surface of the ridge of the p-type electrode film 11 is reduced in the short direction, and the width from the inner side to the reflecting end surface 13 is increased. It is only necessary to have at least a portion with a wide width on one end face side of the upper surface of the ridge portion 9. In addition, since the electrode film is not formed in the upper surface exposed region, it is desirable that the upper surface exposed region is covered with the insulating film 10.

  Since the upper surface electrode has such a shape, distortion generated in the active layer 3 near the reflective end surface 13 due to internal stress of the upper surface electrode near the reflective end surface 13 is further suppressed, and the reliability of the element is further improved. ing. Furthermore, since the upper surface electrode extends the ridge upper surface to the vicinity of the reflection end surface 13, the expression of the saturable absorption characteristic is suppressed. The width of the top surface of the ridge of the p-type electrode film 11 on the reflective end surface 13 takes into account the trade-off between a reduction in the amount of strain in the active layer near the end surface and an increase in the resistance value near the end surface of the top electrode. What is necessary is just to determine suitably. Specifically, the width of the tip of the ridge upper surface portion of the p-type electrode film 11 is preferably 1 μm or more.

FIG. 3 is a schematic external perspective view showing another example of the semiconductor laser device according to the embodiment. Although the upper surface of the semiconductor multilayer of the semiconductor laser device shown in FIG. 1 has two sides of the upper mesa portion extending in a plane, the configurations on both sides of the ridge portion 9 are omitted for clarity of the description of the present invention. doing. On the other hand, FIG. 3 shows the configuration of both sides of the ridge portion 9, and FIG.
As shown in FIG. 2, the p-type InP second cladding layer 7 and the p-type InGaAs contact layer 8 in a region separated from the side surface of the upper mesa portion of the semiconductor multilayer of the semiconductor laser element by a certain distance or more remain without being removed. Is preferred. The insulating film 10 is formed on the entire upper surface of the semiconductor multilayer except for the upper surface of the upper mesa portion (ideally the surface of the p-type InGaAs contact layer 8), as in the semiconductor laser device shown in FIG. Further, the p-type electrode film 11 is formed so as to further spread from both sides of the ridge portion 9, and the other surface portion of the p-type electrode film 11 extends to the outside of both side surfaces of the ridge portion 9. The two cladding layers 7 and the p-type InGaAs contact layer 8 extend over this remaining region. Further, the p-type electrode film 11 has a bonding pad portion 15 for wiring and an electrode lead-out line portion 16 disposed in this region via the insulating film 10. The bonding pad portion 15 to which the wiring is connected and the ridge upper surface portion of the p-type electrode film 11 are electrically connected via the electrode lead-out line portion 16 and the like.

  FIG. 4 is a schematic external perspective view showing a mounting method of the semiconductor laser device 17 according to the embodiment. FIG. 4 shows a state where the semiconductor laser element 17 shown in FIG. 1 is attached to the submount 18 by the junction-up method. The semiconductor laser element 17 and the submount 18 are connected by a solder material such as Au (gold) -Sn (tin).

  The operation of the semiconductor laser device according to the embodiment of the present invention is the same as the conventional one. That is, when a positive bias is applied to the p-side electrode and a negative bias is applied to the n-side electrode, current flows in a concentrated manner in the optical waveguide. Then, electrons and holes are injected into the optical waveguide region of the active layer, and light emission occurs due to recombination of both. Further, when the current is increased, laser oscillation occurs at a certain current value or more.

  FIG. 5 is a diagram showing a calculation result of a strain distribution generated in the active layer of the semiconductor laser device according to the embodiment. FIG. 5 shows the result of calculating the strain distribution of the active layer located immediately below the lower end of the side surface of the ridge portion (also called the neck portion) by the three-dimensional finite element method. Here, as the semiconductor laser element according to the embodiment, the semiconductor laser element used for the calculation has the ridge upper surface portion of the p-type electrode film (upper surface electrode) extending to the end face in the vicinity of the end face, and the end face. The p-type electrode film is not formed on the both sides of the ridge portion and the flat surface extending outward from the ridge portion to a predetermined length (no side electrode), and corresponds to the semiconductor laser device 17 shown in FIG. Each component of the strain ε of the active layer of the semiconductor laser device according to this embodiment is indicated by a thick line as “no side electrode”. In addition, the calculation result of the semiconductor laser device according to the comparative example is also shown. Here, the semiconductor laser device according to the comparative example is a semiconductor laser device in which the ridge side surface portion of the p-type electrode film (upper surface electrode) is formed, and each component of the strain amount ε of the active layer is expressed as “side electrode” It is shown as a thin line as “Yes”.

Here, the material constants used in the analysis are the n-type InP substrate 1, the n-type InGaAlAs light guide layer 2, the active layer 3 including the InGaAlAs quantum well layer, the p-type InGaAlAs light guide layer 4, and the p-type InAlAs first cladding layer 5. For the p-type InGaAlAs etching stop layer 6, the p-type InP second cladding layer 7, and the p-type InGaAs contact layer 8, the values of InP material constants (Young's modulus, Poisson's ratio, linear thermal expansion coefficient) were used. Even if the material constants are used, the generality of the analysis results is not lost. In addition, the case where the insulating film is an SiO ₂ film, the electrode film of the upper electrode is Au, and the insulating film and the electrode film have an initial stress of a tensile stress was analyzed. The reason for the tensile stress is that when an insulating film and an electrode film are formed by thermal CVD and vapor deposition, these films have tensile stress.

The horizontal axis in FIG. 5 indicates the distance L (μm) from the reflection end surface, and the vertical axis indicates the strain ε (%). Of the three strain components (ε _x , ε _y , ε _z ) of the strain ε, ε _x is a strain component in the longitudinal direction of the ridge portion, ε _y is a strain component in the short direction of the ridge portion, and ε _z is a semiconductor This is a strain component in the film forming direction of the multilayer film. Here, a positive strain indicates a tensile strain.

  As shown in FIG. 5, in the region at a distance of 3 μm or more from the reflection end face, the distortion generated in the active layer of the semiconductor laser device according to the present embodiment in all the x, y, and z directions is a comparative example. It is much smaller than the strain generated in the active layer of the semiconductor laser device. This indicates that the strain generated in the active layer in the vicinity of the reflection end face in the semiconductor laser device according to the comparative example is mainly caused by the internal stress of the electrode film formed on the side surface of the ridge portion. This can be understood from a detailed analysis of the calculation result of the strain distribution in the semiconductor laser device according to the comparative example. In the semiconductor laser device according to the comparative example, compressive strain is applied in the x and z directions and tensile strain is applied in the y direction in a region at a distance of 3 μm or more from the reflection end face. Since the insulating film and the electrode film formed on the upper surface of the ridge portion have tensile stress in the x and y directions, the compressive strain is applied in the x and y directions and z in the active layer due to the action and reaction. Tensile strain is induced in the direction, while the insulating film and electrode film formed on the side surface of the ridge portion have tensile stress in the x and z directions, and therefore compressive strain in the x and z directions into the active layer. Considering that tensile strain is induced in the y direction, in the semiconductor laser device according to the comparative example, the strain in the active layer is mainly caused by the internal stress of the insulating film and electrode film formed on the ridge side. You can see that

  As shown in FIG. 5, the distortion in the y direction on the reflection end face is larger in the active layer than that in the semiconductor laser device according to the comparative example. However, it is a strain in the tensile direction, which has the effect of widening the band gap of the quantum well layer disposed in the active layer, reducing light absorption near the reflective end face, and making optical damage at the end face difficult to occur. Since it is strain, it is rather preferable that the strain generated in the active layer of the semiconductor laser device according to the embodiment is larger.

  FIG. 5 shows the calculation result of the strain distribution for the configuration in which no electrode is formed in all regions on the side surface of the ridge as the strain distribution on the semiconductor laser device according to the embodiment. If no electrode film was formed in the region extending from the lower end of the side surface of the ridge portion to 2/3 of the height of the ridge portion, it was confirmed that the strain was sufficiently smaller than the strain in the semiconductor laser device of the comparative example.

  In the semiconductor laser device 17 according to this embodiment, exposed regions formed on both side surfaces of the ridge portion 9 are provided on one end surface. If the exposed region is provided only on one end face, it is preferably provided on the reflecting end face 13 side as shown in FIG. 1, but the present invention is not limited to this, and the reflecting end face 14 that is the end face on the light exit side is not limited thereto. An exposed region may be provided on the side. Further, an exposed region may be provided on both of the pair of end faces.

  FIG. 6 is a schematic external perspective view showing another example of the semiconductor laser device according to the embodiment. The shapes on both sides of the reflection end faces 13 and 14 of the p-type electrode film 11 of the semiconductor laser element shown in FIG. 6 are the shapes on the reflection end face 13 side of the p-type electrode film 11 of the semiconductor laser element shown in FIG. That is, in addition to the exposed regions formed on both side surfaces of the ridge portion on one end surface, the other exposed surfaces of the other end surface that are exposed without electrode films formed on both side surfaces of the ridge portion. An area is provided. Similarly to the exposed region, the other exposed region may extend inward from the tip on the other end surface side of the ridge upper surface portion of the p-type electrode film 11. Since the exposed regions are formed on both side surfaces of the ridge portion together with the pair of end surfaces, the strain generated in each active layer 3 near the pair of end surfaces can be suppressed, and the effect of the present invention is further enhanced. Note that the tip of the top surface of the ridge of the p-type electrode film 11 shown in FIG. 6 does not reach the reflection end surface 13, and the top surface and side surfaces of the p-type InGaAs contact layer 8 are partially exposed. This indicates a case where the tip of the ridge upper surface portion of the upper surface electrode does not reach the reflection end surface due to an error in the manufacturing process as described above. The same applies to FIGS. 7, 8, and 9 shown below.

[Second Embodiment]
The semiconductor laser device 20 according to the second embodiment of the present invention has the same configuration as the semiconductor laser device 17 according to the first embodiment except that the structure of the upper surface electrode is different. In the explanatory diagram of the second embodiment, the same components in the explanatory diagram of the first embodiment are denoted by the same reference numerals.

  FIG. 7 is a schematic external perspective view of a semiconductor laser device 20 according to the second embodiment of the present invention. The upper surface electrode of the semiconductor laser device 20 according to this embodiment includes a p-type first electrode film 21 and a p-type second electrode film 22. The p-type first electrode film 21 is formed on the entire upper surface of the ridge portion 9 from the reflection end face 14 to the reflection end face 13. The p-type second electrode film 22 is formed so as to extend further to the upper surface of the ridge portion 9, both side surfaces of the ridge portion 9, and further to the outside of both side surfaces of the ridge portion 9, but from the reflection end surface 13 to a predetermined length. The p-type second electrode film 22 is not formed in this region.

  As shown in FIG. 7, the p-type first electrode film 21 extends in the longitudinal direction on the upper surface of the ridge portion 9, and its tip extends to the vicinity of the reflection end face 13. On the other hand, on both side surfaces of the ridge portion 9, there are exposed regions where the upper surface electrode (p-type second electrode film 22) is not formed and the insulating film 10 is exposed at a predetermined length from the reflection end surface 13. The exposed region extends from the reflection end face 13 to the inside of the tip of the p-type first electrode film 21. Thereby, in the semiconductor laser device 20 according to the embodiment, both improvement of device reliability and suppression of saturable absorption characteristics are realized.

  As in the first embodiment, the exposed regions on both sides of the ridge portion 9 preferably extend from the lower end of the side surface to the upper surface of the side surface, but at least 2/2 of the height of the ridge portion 9 from the lower end of the side surface. It suffices to include a portion extending up to 3 or more. Such a portion preferably extends from the end face to a length of 5 μm or more and 20 μm or less.

  Next, a method for manufacturing the semiconductor laser device according to the embodiment will be described. This is the same as the semiconductor laser device manufacturing method according to the first embodiment except for the process of forming the upper electrode. The insulating film 10 is formed in a predetermined region on the upper surface of the semiconductor multilayer by the same process (up to the insulating film forming process) as in the first embodiment.

  A resist is applied to the entire surface of the substrate, and a region in contact with the p-type InGaAs contact layer 8 is removed from the applied resist by using a lithography method to leave a resist film (first resist forming step). Then, a p-type first electrode film 21 is formed on the substrate surface on which the resist film is patterned by a vapor deposition method or the like (first metal film vapor deposition step). The p-type first electrode film 21 is a laminated film in which Ti (titanium), Pt (platinum), and Au (gold) are sequentially laminated, or Ti (titanium), Mo (molybdenum), Ti (titanium), and Au (gold). ) May be a laminated film sequentially laminated. The thicknesses of the laminated films are preferably about 25 nm, 25 nm, and 500 nm, respectively, in the former case, and about 25 nm, 80 nm, 40 nm, and 300 nm, respectively, in the latter case. After the deposition of the p-type first electrode film 21, the resist film and the electrode film formed on the resist film are removed using an organic solvent such as acetone (first electrode forming step).

  Next, a resist is applied again on the entire substrate surface on which the p-type first electrode film 21 is formed, and a part of the applied resist is removed using a lithography method, and a resist film is applied to a predetermined region on the substrate surface. (Second resist forming step). Here, the predetermined region is a region where the p-type second electrode film 22 is not formed on the device surface in the semiconductor laser device shown in FIG. 7, and specifically, the upper surface and both side surfaces of the ridge portion 9. And a region extending from the reflection end surface 13 to a predetermined length on a flat surface extending outward from the side surface. That is, the region where the resist is removed using the lithography method is a region extending from the position having a predetermined length to the inside of the reflection end surface 13 on the entire element surface to the reflection end surface 14. Here, the predetermined length is preferably 5 μm or more and 20 μm or less. Then, a p-type second electrode film 22 is formed on the surface of the substrate on which the resist film is patterned by a vapor deposition method or the like (second metal film vapor deposition step). The p-type second electrode film 22 is a laminated film of Ti (titanium), Pt (platinum), Au (gold) or a laminated film of Ti (titanium), Mo (molybdenum), Ti (titanium), Au (gold), etc. To do. For example, the thickness of each metal film is preferably about 25 nm, 25 nm, and 500 nm in the former case, and about 25 nm, 80 nm, 40 nm, and 300 nm in the latter case. After the deposition of the p-type second electrode film 22, the resist and the electrode film formed on the resist are removed using an organic solvent such as acetone (second electrode forming step).

  Subsequent steps (steps below the lower surface electrode forming step) are the same as those in the first embodiment to manufacture the semiconductor laser device. The method for manufacturing the semiconductor laser element has been described above.

  In the manufacturing method according to the embodiment, by forming the p-type electrode film 11 by two resist forming steps and two metal film vapor deposition steps, the upper surface electrode is formed in a shape that further suppresses manufacturing errors. Is made.

  In the semiconductor laser device 20 according to this embodiment, the ridge upper surface portion of the p-type electrode film 11 extends to the vicinity of the reflection end surface 13, and both side surfaces and outer sides of the ridge portion extend from the end surface to a predetermined length. The p-type electrode film 11 is not formed on the flat surface extending in FIG. 5, and the calculation result of the semiconductor laser element shown in FIG. 5 is applied. That is, like the semiconductor laser device 17 according to the first embodiment, the semiconductor laser device 20 according to this embodiment has a preferable strain distribution shown in FIG.

[Third Embodiment]
The semiconductor laser device 30 according to the third embodiment of the present invention has the same configuration as that of the semiconductor laser device 17 according to the first embodiment except that the shape of the ridge portion 9 and the shape of the upper surface electrode are different. doing. Therefore, in the explanatory diagram of the third embodiment, the same components as those in the explanatory diagrams of the first and second embodiments are denoted by the same reference numerals.

  FIG. 8 is a schematic external perspective view of a semiconductor laser device 30 according to the third embodiment of the present invention. In the semiconductor laser device 17 shown in FIG. 1, the width in the short direction of the upper mesa portion (ridge portion 9) of the semiconductor multilayer is constant with respect to the longitudinal direction. On the other hand, in the semiconductor laser device 30 according to this embodiment, the upper mesa portion (ridge portion 9) of the semiconductor multilayer has the same width (width 32) in the longitudinal direction from the center of both end surfaces of the ridge portion 9 to the reflection end surface 13. The width of the upper mesa portion (ridge portion 9) in the short direction becomes wider as it extends in the longitudinal direction. The end surface 13 is reached. That is, in the ridge portion 9, the width 31 in the short direction of the reflection end surface 13 is wider than the width 32 in the short direction at the center of both end surfaces of the ridge portion 9.

  Here, the width 31 of the ridge portion 9 on the reflection end face 13 is preferably set to 2 μm or less so that the high-order transverse mode is not excited even at high output. Moreover, the ridge part 9 should just have a part which becomes wide gradually as it extends to the reflective end surface 13. From the viewpoint of allowing an error in the cleavage position, it is preferable that a region where the width of the ridge portion 9 is constant is provided in the vicinity of the reflection end face 13. Furthermore, the length in the longitudinal direction of the region where the width of the ridge portion 9 is wider than the width 32 near the center of both end faces is compared with the semiconductor laser device in which the width of the ridge portion 9 is constant between both end faces. However, it is preferable to set the length so short that the laser characteristics hardly change. Specifically, 15 μm or less is desirable. For example, the width 31 in the reflection end face 13 is about 1.7 μm, the width 32 in the center of both end faces is about 1.5 μm, and the length in the longitudinal direction of the region where the width of the ridge 9 is equal to the width 31 near the reflection end face 13. The length in the longitudinal direction of the region that gently changes from the width 31 to the width 32 along the longitudinal direction is about 10 μm.

  For example, when the width 31 of the ridge portion 9 is 1.7 μm and the width 32 is 1.5 μm in the semiconductor laser device according to this embodiment, the photon density in the vicinity of the reflective end surface 13 is determined at both end surfaces when the device is operating. It is as small as about 0.9 times the photon density near the center. Therefore, the photon density near the reflection end face can be reduced, and the reliability of the element is further improved.

  In the method of manufacturing the semiconductor laser device according to this embodiment, the shape of the upper mesa portion to be formed in the upper mesa forming step in which the p-type InP second cladding layer 7 and the p-type InGaAs contact layer 8 are processed to form the upper mesa portion. Is different from the first embodiment, and has the shape described above. Furthermore, the insulating film forming step for forming the insulating film 10 in the semiconductor multilayer, and the resist forming step for forming a resist film in a predetermined region of the substrate surface to form the upper surface electrode, The shape of the resist film is different from that of the first embodiment as the shape of the upper mesa portion is different. Other than that, the semiconductor laser device according to this embodiment is manufactured through the same steps as those of the first embodiment.

  Note that the top electrode of the semiconductor laser device according to this embodiment may be composed of a p-type first electrode film and a p-type second electrode film, as in the second embodiment. In such a method of manufacturing a semiconductor laser device, the shape of the upper mesa portion formed in the upper mesa forming step is different from that of the second embodiment, and in the subsequent step, the shape of the upper mesa portion is different. The shapes of the insulating film 10 and the resist film are different. Other than that, the semiconductor laser device according to this embodiment is manufactured through the same steps as those of the second embodiment.

[Fourth Embodiment]
The semiconductor laser device 40 according to the fourth embodiment of the present invention is formed between the insulating film 10 and the upper surface electrode so that both sides of the ridge portion 9 are embedded with the organic insulating layer. The semiconductor laser device has the same configuration as that of the semiconductor laser device according to the first embodiment except that the shape is changed. Therefore, in the explanatory diagram of the fourth embodiment, the same components in the explanatory diagrams of the first to third embodiments are denoted by the same reference numerals.

  FIG. 9 is a schematic external perspective view of a semiconductor laser device 40 according to the fourth embodiment of the present invention. As shown in FIG. 9, both sides of the ridge portion 9 are embedded with the organic insulating layer 41, but the organic insulating layer 41 is not formed in a region from the reflection end face 13 to a predetermined length. The ridge upper surface portion of the p-type electrode film 11 extends in the longitudinal direction from the upper surface of the ridge portion 9, and its tip extends to the vicinity of the reflection end surface 13. Further, the p-type electrode film 11 extends over the organic insulating layer 41 and is formed on the upper surface of the organic insulating layer 41.

  On both side surfaces of the ridge portion 9, there are regions where the p-type electrode film 11 is not formed and the insulating film 10 is exposed to a predetermined length from the reflection end surface 13, and are embedded on both sides of the ridge portion 9. The organic insulating layer 41 extending over the exposed region. It is sufficient that both side surfaces of the ridge portion 9 are filled with the organic insulating layer 41 except at least the exposed region. In the semiconductor laser device 17 shown in FIG. 1, the p-type electrode film 11 is formed on the side surface of the ridge portion 9, but in the semiconductor laser device 40 shown in FIG. 9, the organic insulating layer 41 is formed on the side surface of the ridge portion 9. Is formed. Since the organic insulating layer 41 has a tensile stress as in the case of the electrode film, if the organic insulating layer 41 is formed so as to extend to the reflective end face 13, the organic insulating layer 41 is formed near the reflective end face 13 in the vicinity of the ridge portion 9. Even if the p-type electrode film 11 is not formed on both side surfaces, the active layer in the vicinity of the reflection end surface 13 is distorted. In the semiconductor laser device 40 according to this embodiment, as described above, the organic insulating layer 41 is not formed in a region from the reflection end surface 13 to a predetermined length, and the exposed regions on both side surfaces of the ridge portion 9 are organic insulating. The layer 41 is also exposed. Thereby, in the semiconductor laser device 40 according to the embodiment, distortion generated in the active layer 3 in the vicinity of the reflection end face 13 is suppressed, the reliability of the device is improved, and the saturable absorption characteristic is suppressed.

  As in the first to third embodiments, it is desirable that the exposed regions on both side surfaces of the ridge portion 9 extend from the lower end of the side surface to the upper surface of the side surface, but at least the height of the ridge portion 9 from the lower end of the side surface. It is only necessary to include a portion extending to 2/3 or more. In consideration of a trade-off between the reduction in the amount of strain of the active layer near the end face and the increase in resistance near the end face of the upper surface electrode, such a portion extends over a length of 5 μm to 20 μm from the end face. Is preferred. Therefore, the side surface on the reflective end face 13 side of the organic insulating layer 41 is preferably at a distance of 5 μm or more from the reflective end face 13.

  In the semiconductor laser element 40 shown in FIG. 9, the p-type electrode film 11 is formed on the upper surface of the organic insulating layer 41 so as to extend to both sides of the upper surface of the ridge portion 9. The p-type electrode film 11 is not formed on the side surface of the organic insulating layer 41 on the reflective end face 13 side, and the organic insulating layer 41 extends to the exposed region of the ridge portion 9. As the predetermined length in which the organic insulating layer 41 is not formed is made longer, the exposed region of the ridge portion 9 becomes longer accordingly, and the resistance value in the vicinity of the end face of the upper surface electrode increases. End up. In this case, the p-type electrode film 11 only needs to be formed on both sides of the ridge portion 9 so as to reach the exposed region in the vicinity of the reflection end face 13. At this time, the ridge portion 9 of the p-type electrode film 11 is also formed on both side surfaces, and the ridge side surface portion of the p-type electrode film 11 extends to the exposed region. In addition, on both sides of the ridge portion 9, the p-type electrode film 11 spreads on the side surface of the organic insulating layer 41 on the reflective end face 13 side and on the flat surface on both sides of the ridge side portion in addition to the upper surface of the organic insulating layer 41. Yes. The shape of the p-type electrode film 11 in the vicinity of the reflection end face 13 may be the same as that of the p-type electrode film 11 shown in FIG. As described above, the shapes of the organic insulating layer 41 and the p-type electrode film 11 are selected so that the resistance value of the portion near the end face of the upper surface electrode is as desired while ensuring the exposed region of the ridge portion 9. That's fine.

  As in the semiconductor laser device according to the embodiment, by embedding both sides of the ridge portion with an organic insulating layer, the shape of the p-type electrode film can be further flattened, and the electrode film can be formed more stably. I can do it. However, if both sides of the ridge portion are embedded with an organic insulating layer up to the end surface, the organic insulating layer has tensile stress, so that the active layer near the end surface is caused by the organic insulating layer. Such distortion is applied. With the semiconductor laser device according to this embodiment, the amount of strain due to the organic insulating layer is reduced, and the reliability of the device is improved, while the saturable absorption characteristics are suppressed.

  Next, a method for manufacturing the semiconductor laser device 40 according to this embodiment will be described. The same except for the manufacturing method of the semiconductor laser device 17 according to the first embodiment and the step of forming the organic insulating layer 41 and that the step of forming the upper electrode is different accordingly. is there. The insulating film 10 is formed in a predetermined region on the upper surface of the semiconductor multilayer by the same process (up to the insulating film forming process) as in the first embodiment.

  The organic insulating layer 41 is formed by spin-coating and baking a low dielectric constant polymer material on the surface of the substrate on which the insulating film 10 is formed. The low dielectric constant polymer material is a cyclic fluororesin, tetrafluoroethylene resin, fluorinated aryl ether resin, aryl ether resin, benzocyclobutene (BCB) resin, polyimide, monomethylhydroxysilane condensate, amorphous carbon, or the like. Next, the organic insulating layer 41 formed on the upper surface of the substrate is gradually etched from the surface by a dry etching method or the like to expose at least a part of the p-type InGaAs contact layer 8. At this time, the height of the organic insulating layer 41 embedded on both sides of the ridge portion 9 is preferably about the height of the upper end of the insulating film 10 on both side surfaces of the ridge portion 9, but is not limited thereto. . Further, the organic insulating layer 41 formed in a region having a predetermined length from the reflection end face 13 is removed by using a photolithography method and a dry etching method (organic insulating layer forming step).

  After the organic insulating layer forming step, a resist is applied to the entire surface of the substrate on which the organic insulating layer 41 is formed, and a part of the applied resist is removed using a lithography method to obtain a predetermined region on the substrate surface. The resist film is left on (resist formation step). Here, in the case of the semiconductor laser element 40 shown in FIG. 9, the predetermined region extends from the reflection end surface 13 to a predetermined length on both side surfaces of the ridge portion 9 and flat surfaces extending outward from the side surfaces. The region and the region serving as the side surface on the reflective end face 13 side of the organic insulating layer 41 are combined. As described above, the predetermined region may be determined according to the shape of the p-type electrode film 11. After the resist formation step, as in the first embodiment, a p-type electrode film 11 is formed on the substrate surface on which the resist film is patterned by vapor deposition or the like, and an organic solvent such as acetone is used to form the resist film. And the electrode film formed on the resist film is removed (upper surface electrode forming step).

  Subsequent steps (steps below the lower surface electrode forming step) are the same as those in the first embodiment to manufacture the semiconductor laser device. The method for manufacturing the semiconductor laser element has been described above.

  Note that the top electrode of the semiconductor laser device according to this embodiment may be composed of a p-type first electrode film and a p-type second electrode film, as in the second embodiment. In addition, the ridge portion of the semiconductor laser according to this embodiment may have a portion that extends to the reflection end face and gradually widens, as in the third embodiment.

  The semiconductor laser elements according to the first to fourth embodiments have been described above. Also in the second to fourth embodiments, similarly to the semiconductor laser device shown in FIG. 2, there may be upper exposed regions on both sides of the ridge upper surface of the p-type electrode film. The upper surface exposed region further reduces the amount of strain in the active layer near the end surface, and the tip of the ridge upper surface portion of the p-type electrode film extends to the vicinity of the end surface, thereby suppressing the saturable absorption characteristics.

  Also in the second to fourth embodiments, similarly to the semiconductor laser element shown in FIG. 3, the p-type InP second cladding layer in a region separated from the side surface of the upper mesa portion of the semiconductor multilayer of the semiconductor laser element by a certain distance or more. 7 and the p-type InGaAs contact layer 8 are preferably left without being removed. In the case of the fourth embodiment, the space of the certain distance from the side surface of the upper mesa portion is buried with the organic insulating layer.

  Also in the second to fourth embodiments, similarly to the mounting method shown in FIG. 4, the semiconductor laser element is attached to the submount by the junction-up method, and the operation of the semiconductor laser element is the same as that of the first embodiment. .

  Also in the second to fourth embodiments, the exposed region is not limited to being provided only on one end face, and similarly to the semiconductor laser device shown in FIG. 6, the exposed areas are provided on both end faces. It goes without saying that it may be done. Moreover, it is not limited that the exposed areas of both end faces are the same, and each structure may be selected as necessary.

[Fifth Embodiment]
The optical transmission module or optical transmission / reception module according to the fifth embodiment of the present invention is an optical transmission module or optical transmission / reception module including the semiconductor laser element according to the first to fourth embodiments. Furthermore, an optical transceiver according to the fifth embodiment of the present invention is an optical transceiver including such an optical transmission module or such an optical transmission / reception module.

  By including the semiconductor laser element according to the first to fourth embodiments, both the optical transmission module, the optical transmission / reception module, and the optical transceiver can achieve both improved reliability and suppression of saturable absorption characteristics. ing.

  The semiconductor laser element, the optical transmission module (optical transmission / reception module), and the optical transceiver according to the embodiment have been described above. The present invention is not limited to these, and it goes without saying that the present invention can be widely applied to ridge waveguide type semiconductor laser elements including an InGaAlAs quantum well layer as an active layer.

  1 n-type InP substrate, 2 n-type InGaAlAs light guide layer, 3 active layer, 4 p-type InGaAlAs light guide layer, 5 p-type InAlAs first cladding layer, 6 p-type InGaAlAs etching stop layer, 7 p-type InP second cladding Layer, 8 p-type InGaAs contact layer, 9 ridge portion, 10: insulating film, 11 p-type electrode film, 12 n-type electrode film, 13, 14 reflective end face, 15 bonding pad portion, 16 electrode lead-out line portion, 17, 20 , 30, 40 Semiconductor laser device, 18 submount, 21: p-type first electrode film, 22: p-type second electrode film, 31, 32 width, 41 organic insulating layer

Claims (16)

A semiconductor comprising an active layer including a quantum well layer made of an InGaAlAs-based material, an etching stop layer, and an upper mesa portion extending along the optical waveguide region of the active layer and disposed above the etching stop layer With multiple layers,
An insulating film formed on an upper surface of the semiconductor multilayer;
An electrode film that covers the semiconductor multilayer and the insulating film and is in contact with the upper surface of the upper mesa portion;
With
A semiconductor laser device, wherein the upper mesa portion and a portion of the insulating film formed in contact with the upper mesa portion become a ridge portion,
Each side surface of the ridge portion has an exposed region that is exposed without the electrode film being formed,
The exposed regions on both side surfaces of the ridge portion extend from one end surface of the ridge portion to the inside from the tip where the electrode film extends from the top surface of the ridge portion to the one end surface,
A semiconductor laser device characterized by the above. The exposed area of each of the both side surfaces includes a portion extending from the lower end of the side surface to the upper end of the side surface.
The semiconductor laser device according to claim 1, wherein: In each of the exposed regions on both side surfaces, a portion extending from the lower end of the side surface to the upper end of the side surface extends from the one end surface to a distance of 5 μm or more and 20 μm or less.
The semiconductor laser device according to claim 2, wherein The exposed regions on the both side surfaces each include a portion extending from the lower end of the side surface to 2/3 or more of the height of the ridge.
The semiconductor laser device according to claim 1, wherein: In each of the exposed regions on both side surfaces, a portion extending from the lower end of the side surface to 2/3 or more of the height of the ridge extends over a distance of 5 μm or more and 20 μm or less from the one end surface.
The semiconductor laser device according to claim 4, wherein: The electrode film extends from the upper surface of the ridge portion to the both side surfaces and extends to the one end surface, and extends to the exposed region.
6. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is characterized in that:   The semiconductor laser device according to claim 6, wherein the electrode film has a tensile stress. Both side surfaces of the ridge portion are filled with an organic insulating layer except at least the exposed region, and the organic insulating layer extends to the exposed region.
6. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is characterized in that:   9. The semiconductor laser device according to claim 8, wherein the organic insulating layer has a tensile stress. Both side surfaces of the ridge portion are filled with an organic insulating layer except at least the exposed region, and the electrode film extends over the organic insulating layer,
8. The semiconductor laser device according to claim 6, wherein the semiconductor laser device is characterized in that: The electrode film has an upper surface exposed region that is exposed without forming the electrode film on each of both sides of a tip that extends the ridge portion upper surface to the one end surface;
The upper surface exposed areas on both sides of the tip extend to the exposed areas on both side surfaces of the ridge portion, respectively.
Each of the upper surface exposed regions on both sides of the tip has a portion that increases in width as it advances to the one end surface.
11. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is characterized in that: The tip that extends the upper surface of the ridge portion of the electrode film to the one end surface extends to the one end surface,
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is characterized in that The ridge portion has a portion that extends to the one end face and gradually increases in width.
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is characterized in that: Each of both side surfaces of the ridge portion further has another exposed region exposed without forming the electrode film,
The other exposed regions on both side surfaces of the ridge portion extend from the other end surface of both ends of the ridge portion to the inside from the tip where the electrode film extends the upper surface of the ridge portion to the other end surface. Yes,
14. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is characterized in that:   An optical transmission module comprising the semiconductor laser device according to claim 1.   An optical transceiver comprising the optical transmission module according to claim 15.

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