JP4940600B2 - Electro-optic element, optical transmission module, electronic device - Google Patents

Description

  The present invention relates to an electro-optical element and an optical transmission module. The present invention also relates to an electro-optical element and a light transmission module having a function of monitoring the light output of a light emitting element part by a light receiving element part.

  One of the electro-optic elements is a surface emitting laser (VCSEL). In the surface emitting laser, the light output varies depending on the ambient temperature. For this reason, some optical modules using a surface emitting laser have a function of monitoring a light output value and automatically controlling output by detecting a part of light emitted from the surface emitting laser. In the case of a surface emitting laser, it is possible to develop an integrated element that can stack a surface emitting laser and a light receiving element (photodiode, etc.) and monitor a part of the emitted light of the surface emitting laser within the same element.

  For example, an electro-optic element having a three-terminal structure in which a photo diode is stacked on the surface emitting laser and a common electrode is used for the anode electrode of the surface emitting laser and the anode electrode of the photo diode (see, for example, Patent Document 1). ).

  In addition, an electro-optic element having a four-terminal structure in which a photodiode is stacked on the surface emitting laser and an insulating film is disposed between the surface emitting laser and the photodiode is considered (for example, see Patent Document 2). .

Further, an electro-optical element is conceivable in which a surface emitting laser and a photodiode are arranged adjacent to each other on the upper surface of one substrate, and a dielectric mirror is arranged so as to cover the surface emitting laser and the photodiode. In this electro-optic element, most of the emitted light from the surface emitting laser penetrates the dielectric mirror to become signal light, etc., and a part of the emitted light propagates through the dielectric mirror and enters the photo diode, and the output can be monitored. It has a configuration.
Japanese Patent Laid-Open No. 10-135568 JP 2000-183444 A

  However, although the electro-optic element described in Patent Document 1 is relatively easy to manufacture, the surface emitting laser has a common electrode for the anode electrode of the surface emitting laser and the anode electrode of the monitoring photodiode. There is a restriction that a modulation signal to the laser can be input only from the cathode electrode. For this reason, when an array structure is provided in which a large number of surface emitting lasers are arranged close to each other, there arises a disadvantage that the surface emitting lasers cannot be independently modulated.

  In addition, in the electro-optical element described in Patent Document 2, the insulating film disposed between the surface emitting laser and the photodiode generates a parasitic capacitance, which deteriorates the high frequency characteristics of the surface emitting laser. There is. In addition, in the structure in which the photodiode is disposed on the upper layer of the insulating film, it is difficult to obtain a structure in which the film thickness of the insulating film is ensured so as to obtain good photodiode characteristics. For example, when the insulating film is formed by oxidation of AlAs or the like, the insulating film becomes fragile and it is difficult to form a thick insulating film.

  In addition, in an electro-optic element in which a dielectric mirror is disposed so as to cover the surface emitting laser and the photodiode, a part of the light emitted from the surface emitting laser must propagate through the dielectric mirror and enter the light receiving element. For this reason, it is necessary to set the reflectance of the dielectric mirror to a predetermined value or more, and there is a problem that the radiation angle becomes large up to the signal light in the emitted light of the surface emitting laser.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electro-optic element and an optical transmission module that have a photodetection section and good high-frequency characteristics.
It is another object of the present invention to provide an electro-optical element and an optical transmission module that can modulate each light-emitting element part independently even in the case of an array structure, have a light detection part, and have good high-frequency characteristics.
In addition, the present invention can modulate each light emitting element part independently even in the case of an array structure, has a light detection part and good high frequency characteristics, and further emits signal light emitted from the light emitting element part. It is an object of the present invention to provide an electro-optic element and an optical transmission module that can avoid an increase in size.

In order to achieve the above object, an electro-optical element of the present invention is formed on a light emitting element portion formed on a substrate, and on a side surface of the substrate on which the light emitting element portion is formed, and outside the region where the light emitting element portion is formed. A light-detecting part that is formed, a transparent layer made of a transparent member formed from the light-emitting element part to the light-detecting part, and at least an upper surface of the transparent layer other than the vicinity of the light-emitting axis of the light-emitting element part. And a reflective layer.
According to the present invention, a part (for example, most) of the emitted light from the light emitting element portion can travel near the light emitting axis and pass through the transparent layer to become signal light, and the other part of the emitted light can be the light emitting axis. It is possible to proceed from a position away from the vicinity of, and be reflected by the reflective layer and enter the light detection unit. Therefore, the light detection unit can detect the light output of the light emitting element unit. Therefore, since the electro-optic element of the present invention is not configured to provide a thin insulating film between the light emitting element part and the upper light detection part as described in Patent Document 2, it has good high frequency characteristics. Can have.
In addition, since the electro-optic element of the present invention has the light-emitting element part and the light detection part formed on the same plane of the substrate, it is easy to have a configuration in which each light-emitting element part can be independently modulated even in an array structure. Can be. Furthermore, the electro-optic element of the present invention avoids an increase in the emission angle of the signal light emitted from the light emitting element part because only the transparent layer is arranged in the vicinity of the light emitting axis above the light emitting element part. can do.
A substrate; a light-emitting element portion formed on the substrate; a light-detecting portion formed on a side surface of the light-emitting element portion on the substrate other than a region where the light-emitting element portion is formed; An insulating layer formed so as to fill a space between the element portion and the light detection portion, a transparent layer made of a transparent member formed so as to cover the light detection element portion and the light detection portion, and the transparent A reflective layer formed at least on the upper surface of the light emitting element portion other than the vicinity of the light emitting axis, and a lower reflective layer disposed between the transparent layer and the insulating layer. .

In order to achieve the above object, an electro-optical element of the present invention is formed on a light emitting element portion formed on a substrate, and on a side surface of the substrate on which the light emitting element portion is formed, and outside the region where the light emitting element portion is formed. And an optical waveguide layer formed so as to guide a part of the light emitted from the light emitting element portion to the light receiving element portion from the light emitting element portion to the light detecting portion. The optical waveguide layer is not formed near the light emitting axis of the light emitting element portion.
According to the present invention, a part (for example, most) of the emitted light from the light emitting element portion can travel near the light emitting axis to become signal light, and the other part of the emitted light is incident on the optical waveguide layer. Thus, it can propagate through the optical waveguide layer and enter the light detection section. Therefore, the light detection unit can detect the light output of the light emitting element unit. Therefore, since the electro-optic element of the present invention is not configured to provide a thin insulating film between the light emitting element part and the upper light detection part as described in Patent Document 2, it has good high frequency characteristics. Can have.
In addition, since the electro-optic element of the present invention has the light-emitting element part and the light detection part formed on the same plane of the substrate, it is easy to have a configuration in which each light-emitting element part can be independently modulated even in an array structure. Can be. Furthermore, since the electro-optic element of the present invention has no optical waveguide layer formed in the vicinity of the light emitting axis above the light emitting element part, it is possible to avoid an increase in the radiation angle of the signal light emitted from the light emitting element part. can do.

In the electro-optic element of the invention, the light emitting element portion is a surface emitting laser, and the reflective layer has an opening at a position coaxial with the light emitting axis of the light emitting element portion. The size is the same as or larger than the inner diameter of the current confinement layer of the surface emitting laser, and the same as or larger than the inner diameter of the electrode (second electrode) formed in the opening of the surface emitting laser. Small is preferable.
According to the present invention, since the size of the opening of the reflective layer is set as described above, the radiation angle of the signal light emitted from the light emitting element can be made narrower.

In the electro-optical element according to the aspect of the invention, it is preferable that the reflective layer is formed so as to cover almost all of the exposed surface of the transparent layer other than the vicinity of the light emitting axis.
According to the present invention, it is possible to prevent the light emitted from the light emitting element portion from going outside except the desired direction (light emitting axis direction) by the reflective layer, and it is possible to configure a safe electro-optical element. . In addition, in the side surface of a transparent layer, etc., the part where the wiring for the light emitting element part or the light detection part passes can be dealt with by providing an opening in the corresponding part in the reflective layer.

In the electro-optical element of the present invention, the transparent layer transmits light emitted from the light-emitting element part, and is formed of polyimide, epoxy resin, SiO ₂ , SiO, or SiN. Preferably it is.
According to the present invention, the transparent layer not only functions as a propagation path for the monitor light, but can also function as a moisture-proof layer for the light emitting element portion and the light detection portion.

In the electro-optical element of the present invention, it is preferable that the transparent layer functions as a moisture-proof layer.
According to the electro-optic element of the present invention, high-performance functions can be stably maintained over a long period of time.

In the electro-optical element according to the aspect of the invention, the reflective layer reflects a part of the light emitted from the light emitting element unit, and the light detection unit receives at least the light reflected by the reflective layer. It is preferable that they are arranged.
According to the present invention, the output of the light emitting element unit can be monitored by the light detection unit. Therefore, the output of the light emitting element unit can be feedback-controlled using the output of the light detection unit.

In the electro-optic element of the present invention, it is preferable that the optical waveguide layer is formed of a dielectric multilayer reflective layer.
According to the present invention, a part of the light emitted from the light emitting element part can be guided to the light detection part satisfactorily by the dielectric multilayer reflective layer.

The electro-optic element of the present invention is a lower reflection layer disposed on at least one of the upper surface of the light emitting element unit, the upper surface of the light detection unit, and the upper surface of the insulating film, which is a lower layer of the transparent layer. It is preferable to have a layer.
According to the present invention, a portion of the light emitted from the light emitting element portion can be favorably guided to the light detection portion by the reflective layer and the lower reflective layer.

In order to achieve the above object, an optical transmission module according to the present invention includes the electro-optical element.
According to the present invention, it is possible to provide an optical transmission module that has good high-frequency characteristics, can be made compact, and operates stably over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing referred to below, the scale of each component is appropriately changed and displayed for easy understanding of the drawing.

[First Embodiment]
(Structure of electro-optic element)
FIG. 1 is a schematic cross-sectional view showing an example of an electro-optic element according to the first embodiment of the present invention. First, the structure of the electro-optical element 10 will be described.
The electro-optic element 10 includes a light emitting element portion 30 and a light receiving element portion (light detecting portion) 40 on the same semiconductor substrate (GaAs substrate 11). In FIG. 1, the light emitting element part 30 is shown on the left side, and the light receiving element part 40 is shown on the right side. The light emitting element portion 30 and the light receiving element portion 40 are formed on the same surface of the GaAs substrate 11. In the present embodiment, the light emitting element unit 30 is a surface emitting light emitting element or a surface emitting laser, while the light receiving element unit 40 is a photodiode.

A GaAs substrate 11 is used as a semiconductor substrate, and a first mirror layer 12 is formed on the GaAs substrate 11. The first mirror layer 12 is formed as a distributed multilayer film of about 40 pairs in which n-type Al _0.9 Ga _0.1 As layers and n-type Al _0.15 Ga _0.85 As layers are alternately stacked. Yes. A first electrode 20 is formed on the entire surface of the GaAs substrate 11 on the back surface side where the first mirror layer 12 is not formed. The first electrode 20 is an n-type electrode and is formed of a laminate of an alloy of Au and Ge and Au.

  An active layer 13 is formed on the first mirror layer 12. The active layer 13 is formed in a quantum well structure having three well layers. A light emitting element portion 30 and a light receiving element portion 40 are formed on the active layer 13, and an insulating layer 19 is formed in the element isolation region.

In the light emitting element portion 30, the second mirror layer 14 is formed on the active layer 13. The second mirror layer 14 is formed as a plurality of pairs of distributed multilayer films in which p-type Al _0.9 Ga _0.1 As layers and p-type Al _0.15 Ga _0.85 As layers are alternately stacked. Yes. Here, the second mirror layer 14 is formed much thinner than the first mirror layer 12. A first contact layer 15 is formed on the second mirror layer 14. The first contact layer 15 is formed of a p-type GaAs layer. A second electrode 21 is formed on part of the first contact layer 15 and the insulating layer 19. The second electrode 21 is a p-type electrode and is formed of a laminate of an alloy of Au and Zn and Au. The opening of the first contact layer 15 formed by the second electrode 21 serves as the light emitting surface 21a. A current confinement layer 18 is formed on a part of the second mirror layer 14 in contact with the active layer 13.
The current confinement layer 18 is formed by oxidizing a part of the second mirror layer 14 from the side surface of the element isolation region. Note that the current density of the active layer 13 and the like can be controlled by controlling the formation region of the current confinement layer 18.

  As described above, the light emitting element unit 30 includes the first electrode 20, the GaAs substrate 11, the first mirror layer 12, the active layer 13, the second mirror layer 14, the first contact layer 15, and the current confinement layer 18. In the present embodiment, the plurality of layers are referred to as a light emitting layer 25.

  On the other hand, in the light receiving element portion 40, the light absorption layer 16 having an area smaller than that of the first contact layer 15 is formed on the light emitting layer 25, that is, on the first contact layer 15. The light absorption layer 16 is formed of a GaAs layer into which no impurity is introduced. A second contact layer 17 is formed on the light absorption layer 16. The second contact layer 17 is formed of an n-type GaAs layer. A third electrode 22 is formed on part of the first contact layer 15 and the insulating layer 19 where the light absorption layer 16 is not formed. The third electrode 22 is a p-type electrode and is formed of a laminate of an alloy of Au and Zn and Au. A fourth electrode 23 is formed on the second contact layer 17. The fourth electrode 23 is an n-type electrode and is formed of a laminate of an alloy of Au and Ge and Au. The opening of the second contact layer 17 formed by the fourth electrode 23 becomes the light receiving surface 23a. Here, the light absorption layer 16 and the second contact layer 17 included in the light receiving element unit 40 are referred to as a light detection unit 26.

Further, the electro-optical element 10 of the present embodiment has a transparent layer 51 made of a transparent member formed from the light emitting element part 30 to the light receiving element part 40. That is, the transparent layer 51 is formed so as to cover the light emitting element unit 30 and the light receiving element unit 40. The transparent layer 51 can be formed of a member that transmits light emitted from the light emitting element unit 30. For example, the transparent layer 51 is preferably made of polyimide, epoxy resin, SiO ₂ , SiO, SiN, or the like. When the transparent layer 51 is configured with such a member, the transparent layer 51 can also function as a moisture-proof material for the light emitting element portion 30 and the light receiving element portion 40.

  A reflective layer 52 is formed on the upper surface and side surfaces of the transparent layer 51, that is, on the entire exposed surface of the transparent layer 51. However, the reflective layer 52 is not formed in the vicinity of the light emitting axis of the light emitting element unit 30 on the upper surface of the transparent layer 51, and the opening 53 is formed. The opening 53 of the reflective layer 52 is preferably formed so as to be coaxial with the light emitting axis of the light emitting element 30. The size of the opening 53 is the same as or larger than the inner diameter of the current confinement layer 18 of the light emitting element section 30 and is formed on the light emitting surface 21 a of the light emitting element section 30. The inner diameter of the electrode 21 is preferably the same as or smaller than the inner diameter of the second electrode 21. The reflective layer 52 can be made of a metal having high reflectivity, and for example, gold, chrome, titanium, copper, or the like can be applied.

  Here, when the electro-optic element 10 of the present embodiment is captured with a functional structure, the light emitting element portion 30 is formed only from the light emitting layer 25, while the light receiving element portion 40 is formed on the light emitting layer 25. In this structure, the light detection unit 26 is formed. Further, a transparent layer 51 is formed from the light emitting element portion 30 to the light receiving element portion 40, and a reflection layer 52 is formed on the transparent layer 51.

  FIG. 2 is a schematic plan view of the electro-optic element 10 as viewed from above the surface on which the light emitting element portion 30 and the light receiving element portion 40 are formed. The light emitting element portion 30 and the light receiving element portion 40 are formed adjacent to each other and are formed in a circular shape. An insulating layer 19 is formed between the light emitting element unit 30 and the light receiving element unit 40. 1, a transparent layer 51 is formed so as to cover the light emitting element portion 30 and the light receiving element portion 40, and a reflective layer 52 is formed above the transparent layer 51. The opening 53 of the reflective layer 52 is formed in a circular shape and is positioned coaxially with the light emitting surface 21 a of the light emitting element unit 30.

(Operation of electro-optic element)
Next, the operation of the electro-optical element 10 will be described. By applying a voltage between the first electrode 20 and the second electrode 21, holes and electrons are combined in the active layer 13 to emit light. This light is reflected by the first mirror layer 12 and the second mirror layer 14 to be emitted as laser light L1 from the light emitting surface 21a. Most of the laser light L1 penetrates through the transparent layer 51 and exits from the electro-optical element 10 through the opening 53 to become signal light or the like.

  As shown in FIG. 1, the light L <b> 2 that is a part of the laser light L <b> 1 emitted from the light emitting surface 21 a is incident on the transparent layer 51, is reflected by the reflective layer 52, and then enters the light receiving surface 23 a of the light receiving element unit 40. . Here, the light L2 is reflected by the reflective layer 52, then reflected by the fourth electrode (lower reflective layer) 23, further reflected by the reflective layer 52, and incident on the light receiving surface 23a of the light receiving element portion 40. There is also.

  By applying a voltage between the third electrode 22 and the fourth electrode 23 included in the light receiving element portion 40, the light L2 incident from the light receiving surface 23a is converted into electrons and holes inside the light absorption layer 16. And is moved to the third electrode 22 and the fourth electrode 23 to generate a current. By measuring this photocurrent generated in the light receiving element section 40, the characteristics (intensity, etc.) of the light emitted from the light emitting element section 30 can be grasped.

  According to the electro-optical element 10 of the present embodiment, the electrodes for starting the light emitting element unit 30 are the first electrode 20 and the second electrode 21, while the electrode for starting the light receiving element unit 40 is the third electrode. Since it is the electrode 22 and the fourth electrode 23, the light emitting element part 30 and the light receiving element part 40 can be controlled independently. That is, since the modulation signal can be transmitted only to either the light emitting element unit 30 or the light receiving element unit 40, there is an advantage that the degree of freedom of the driving method of the electro-optical element 10 is increased. Further, since the light emitting element unit 30 and the light receiving element unit 40 that detects the light emitted from the light emitting element unit 30 are not stacked, no parasitic capacitance is generated. Therefore, when the electro-optical element 10 is driven at a high frequency, it is possible to reduce the deterioration of the high frequency characteristics. Further, by forming the light emitting element portion 30 and the light receiving element portion 40 adjacent to each other, there is an advantage that it is easy to dispose electric wiring that electrically connects a power source that supplies a voltage or the like to the electrode.

  Furthermore, according to the electro-optical element 10 of the present embodiment, since only the transparent layer is disposed in the vicinity of the light emitting axis above the light emitting element portion, for example, a dielectric multilayer reflective layer is laminated above the light emitting element portion. The emission angle of the laser light L1 emitted from the light emitting surface 21a of the light emitting element portion can be made smaller than in the case where the above is performed. Further, in the electro-optic element 10, the fourth electrode 23 of the light receiving element portion 40 functions as a lower reflective layer for the light L2 that is the monitor light, so that the light L2 can be efficiently guided to the light receiving surface 23a. it can.

  Further, the portion of the opening 53 in the transparent layer 51 of the electro-optical element 10 may have a lens shape. In this way, the radiation angle of the laser beam L1 can be further reduced, and the focal point of the laser beam L1 can be adjusted.

  Next, the radiation angle θ of the light L2, the distance (d1) from the light emitting surface 21a to the lower surface of the reflecting film 52, the distance (d2) from the light receiving surface 23a to the lower surface of the reflecting film 52, the center of the light emitting surface 21a and the light receiving surface The relationship between the distance (d3) from the center of 23a will be described.

First, a case where the reflection on the reflection film 52 is performed once, that is, a case where the light L2 emitted from the light emitting surface 21a is reflected on the reflection film 52 and then enters the light receiving surface 23a will be described. In this case, the following formula (1) is established.
d3 = (tan θ × d1) + (tan θ × d2) (1)

Next, when the reflection at the reflection film 52 and the lower reflection layer (fourth electrode 23) is three times, that is, the light L2 emitted from the light emitting surface 21a is reflected by the reflection film 52 and then reflected by the fourth electrode 23. Then, a case where the light is incident on the light receiving surface 23a after being reflected by the reflective film 52 will be described. In this case, the following formula (2) is established. Here, the distance from the upper surface of the fourth electrode 23 to the lower surface of the reflective film 52 is d4.
d3 = (tan θ × d1) + (2 tan θ × d4) + (tan θ × d2) (2)

  In the above equations (1) and (2), d1, d2, d3, and d4 are constant values, that is, the light emitting surface 21a, the reflective film 52, the fourth electrode 23, and the light receiving surface 23a are mutually connected. Is assumed to be parallel to

(Modification)
FIG. 3 is a schematic plan view of the electro-optic element according to the modification of the present embodiment as viewed from above the surface on which the light emitting element part and the light receiving element part are formed. 3, components having the same functions as those of the electro-optic elements in FIGS. 1 and 2 are denoted by the same reference numerals. This electro-optic element is different from the electro-optic element 10 of FIG. 1 in that the light-emitting element portion 30 and the light-receiving element portion 40 are arranged concentrically. That is, the light receiving element portion 40 is arranged on the outer periphery of the light emitting element portion 30. Others are the same as the electro-optical element 10 of FIG. Also in this modification, the same operation and effect as the electro-optic element shown in FIGS. 1 and 2 can be exhibited.

(Method for manufacturing electro-optical element)
Next, a method for manufacturing the electro-optical element 10 will be described with reference to FIGS.

  FIG. 4 shows a crystal growth process. In the crystal growth step, first, the first mirror layer 12, the active layer 13, the second mirror layer 14, the first contact layer 15, the light absorption layer 16 and the second contact layer 17 are formed on the surface of the n-type GaAs substrate 11. Then, the layers are formed using MOCVD (Metal Organic Chemical Deposition) method or MBE (Molecular Beam Epitaxy) method in order. The structure of each of these layers is as described in FIG.

  FIG. 5 shows an etching process for forming the light receiving element portion 40. First, the second contact layer 17 and the light absorption layer 16 are removed by dry etching using the photoresist as a mask. Thereafter, the photoresist is peeled off. Thereby, the light detection part 26 is formed. Although the dry etching method is used here, the above-described layer may be removed by using a wet etching method.

  FIG. 6 shows an etching process (element isolation region forming process) for forming the light emitting element portion 30. First, the first contact layer 15 and the second mirror layer 14 are removed by dry etching using the photoresist as a mask. The removed portion becomes an element isolation region, in which a region of the light emitting element unit 30 and a region of the light receiving element unit 40 having the light detection unit 26 are formed. Although the dry etching method is used here, the above-described layer may be removed by using a wet etching method.

  FIG. 7 shows a current confinement layer forming step. By exposing the GaAs substrate 11 on which the element isolation region is formed to water vapor at around 400 ° C., a part of the second mirror layer 14 on the active layer 13 is oxidized from the side surface of the element isolation region, thereby forming a current confinement layer. 18 is formed. The current confinement layer 18 is an insulating layer mainly composed of aluminum oxide. The second mirror layer 14 is a crystal growth step, and the layer in the vicinity of the active layer 13 forms GaAlAs crystals having a high aluminum content.

  FIG. 8 shows an insulating layer forming step. As the insulating layer 19, polyimide or the like is used. A liquid polyimide or the like is applied to the surface of the GaAs substrate 11 and the polyimide 19 is embedded in the element isolation region. Thereafter, excess polyimide is removed.

  FIG. 9 shows an electrode forming process. The first electrode 20 is formed on the back surface of the GaAs substrate 11 using a vacuum deposition method, a sputtering method, a plating method, or the like. Since the GaAs substrate is n-type, the first electrode 20 forms a metal layer that can form an n-type ohmic junction. Here, as described with reference to FIG. 1, a stack of Au and Ge alloy and Au is formed. When the first electrode 20 is formed, a heat treatment at about 400 ° C. is performed to form an ohmic junction with the GaAs substrate 11.

  The second electrode 21 and the third electrode 22 form a metal layer capable of forming a p-type ohmic junction. Since the electrodes have the same p-type conductivity, the second electrode 21 and the third electrode 22 can be formed in the same process. A laminated structure of Pt and Au can be applied as an electrode having p-type conductivity. The lift-off method or the dry etching method is used for pattern formation of the second electrode 21 and the third electrode 22.

  In the case of using the lift-off method, first, a photoresist (not shown) is patterned by using a photolithography method. The photoresist has a pattern in which portions where the second electrode 21 and the third electrode 22 are formed are opened. Next, similarly to the first electrode forming step, a metal layer capable of forming a p-type ohmic junction is formed by using a sputtering method or a vacuum evaporation method. Here, as described with reference to FIG. 1A, an alloy of Au and Zn and a laminate of Au are formed. After the metal layer is formed, the photoresist is removed together with the metal layer, so that the metal layer, that is, the second electrode 21 and the third electrode 22 remain only in a portion where the photoresist is not formed. Thereafter, similarly to the first electrode forming step, heat treatment is performed at about 400 ° C. to form an ohmic junction with the first contact layer 15.

  In the dry etching method, a metal layer is formed first, and then a photoresist is formed in a region where the second electrode 21 and the third electrode 22 are formed. Next, the metal layer is dry etched to remove the metal layer other than the second electrode 21 and the third electrode 22. Thereafter, the photoresist is peeled off.

  In the present embodiment, the second electrode 21 and the third electrode 22 are formed in the same process. For example, when the second electrode 21 and the third electrode 22 are formed as electrodes having different conductivity, These are formed in separate steps.

  The fourth electrode 23 can be formed in the same manner as the formation process of the second electrode 21 and the third electrode 22. However, since the fourth electrode 23 is n-type, it is formed of a metal layer that is substantially the same as the first electrode 20.

FIG. 10 shows a process for forming the transparent layer 51. For the transparent layer 51, for example, a transparent material such as polyimide, epoxy resin, SiO ₂ , SiO, or SiN is used. In addition, even if it is a material with a color, what is necessary is just the material which the light radiate | emitted from the light emitting element part 30 permeate | transmits. As a film forming method for forming the transparent layer 51, a spin coating method, an ink jet method, or the like can be applied. Further, as a patterning method for forming the transparent layer 51, a developing method, an inkjet method, a dispenser method, a lift-off method, or the like can be applied. For example, in the case of the lift-off method, the resist is patterned by photolithography (so that the resist does not remain in the portion where the transparent layer 51 is formed), and SiO ₂ is formed by sputtering or the like. After the film formation, lift-off is performed in an organic solution (IPA, acetone, etc.).

  FIG. 11 shows a process for forming the reflective layer 52. First, a metal layer is formed on the exposed surface of the transparent layer 51 by vapor deposition, sputtering, or the like. Next, the reflective layer 52 having the opening 53 is formed by patterning the metal layer by a lift-off method or the like. As a result, the electro-optical element 10 as shown in FIGS. 1 and 2 is completed.

  FIG. 12 is a schematic plan view showing a modification of the electro-optical element 10 manufactured as described above. In FIG. 12, the surface on which the light emitting element portion 30 and the light receiving element portion 40 are formed is viewed from above. This modification is similar to the configuration shown in FIG. 2, and the light emitting element unit 30 and the light receiving element unit 40 are adjacent to each other. However, in this modification, the planar shapes of the second electrode 21, the third electrode 22, and the fourth electrode 23 are different from those in FIG.

  FIGS. 13 and 14 are diagrams showing another modification of the electro-optical element 10 manufactured as described above. FIG. 13 is a schematic cross-sectional view. FIG. 14 is a schematic plan view of the configuration of FIG. 13 as viewed from above the surface on which the light emitting element portion 30 and the light receiving element portion 40 are formed. This modification is similar to the modification shown in FIG. 3, and has a configuration in which the light emitting element section 30 and the light receiving element section 40 are arranged concentrically. However, in this modification, the planar shapes of the second electrode 21, the third electrode 22, and the fourth electrode 23 are different from those in FIG.

[Second Embodiment]
FIG. 15 is a schematic cross-sectional view showing an example of an electro-optic element 10A according to the second embodiment of the present invention. In FIG. 15, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals. The difference between the electro-optical element 10A of the present embodiment and the electro-optical element 10 of the first embodiment is that the electro-optical element 10A has a dielectric mirror (optical waveguide layer) 61.

  The dielectric mirror 61 corresponds to the transparent layer 51 and the reflective layer 52 in the electro-optical element 10 of the first embodiment. The dielectric mirror 61 is formed from the light emitting element unit 30 to the light receiving element unit 40. The dielectric mirror 61 is formed so as to guide a part of the light (light L2) emitted from the light emitting element unit 30 to the light receiving surface 23a of the light receiving element unit 40, and functions as an optical waveguide layer. Further, the dielectric mirror 61 is not formed in the vicinity of the light emitting axis of the light emitting element portion 30 and has an opening 63.

  According to the electro-optical element 10A of the present embodiment, a part (for example, most) of the emitted light (laser light L1) from the light emitting element unit 30 can travel near the light emitting axis and become signal light. Further, another part of the emitted light (light L <b> 2) can enter the dielectric mirror 61, propagate through the dielectric mirror 61, and enter the light receiving surface 23 a of the light receiving element unit 40. Therefore, the light receiving element unit 40 can detect the light output of the light emitting element unit 30.

  Therefore, the electro-optical element 10A does not have a structure in which a thin insulating film is provided between the light-emitting element part and the upper light-detecting part as described in Patent Document 2, and therefore has good high-frequency characteristics. Can do.

  Further, since the light-emitting element unit 30 and the light-receiving element unit 40 are formed on the same plane of the substrate, the electro-optical element 10A has a configuration in which each light-emitting element unit 40 can be independently modulated even in an array structure. Can be easily. Furthermore, since the dielectric mirror (optical waveguide layer) 61 is not formed in the vicinity of the light emitting axis above the light emitting element unit 30 in the electro-optical element 10A, the radiation angle of the signal light emitted from the light emitting element unit 30 is Can be avoided.

The dielectric mirror 61 is preferably formed of a dielectric multilayer reflective layer. If it does in this way, a part of emitted light of light emitting element part 30 can be led to receiving surface 23a satisfactorily.

[Third Embodiment]
FIG. 16 shows an example of an optical transmission module using the electro-optic element of this embodiment. An OSA (Optical Sub-Assembly) 100 as an optical transmission module has the electro-optical element 10 (or electro-optical element 10A) described above mounted on a system 101. In addition, a lens 103 is disposed above the electro-optical element 10 and on the optical axis of the light-emitting element unit 30. Further, a cover 102 is formed from the base of the system 101 to a part of the optical fiber 104 to protect the electro-optical element 10 and the like from the external environment. An optical fiber 104 is disposed on the optical axis of the lens 103. In the present embodiment, the cover 102 is made of resin and is formed integrally with the lens 103.

  When a voltage is applied to the first electrode 20 to the fourth electrode 23 of the electro-optical element 10 via the pins of the system 101, the light emitting element unit 30 and the light receiving element unit 40 are driven. Light is emitted from the light emitting element section 30, and part of the light passes through the dielectric multilayer reflection calendar 24 and reaches the lens 103. The reached light is collected by the lens 103 and enters the optical fiber 104. In addition, a part of the light emitted from the light emitting element unit 30 is multiple-reflected inside the dielectric multilayer reflective layer 24 and enters the light detection unit 26 included in the light receiving element unit 40. The light incident on the light detection unit 26 generates a photocurrent in the light absorption layer 16. By measuring this photocurrent, the optical characteristics emitted from the light emitting element section 30 can be grasped. Since only one electro-optic element 10 has a light emitting function and can monitor the light emission state, a light receiving element or the like for monitoring the light emission state of the cover glass or the light emitting element is unnecessary as compared with the conventional OSA100. Therefore, there is an advantage in terms of cost or downsizing of the OSA 100.

(Light transmission device)
FIG. 17 is a diagram illustrating a light transmission device including the electro-optic element 10 (or the electro-optic element 10A) according to the embodiment of the invention. The light transmission device 200 connects electronic devices 202 such as a computer, a display, a storage device, and a printer to each other. The electronic device 202 may be an information communication device. The optical transmission device 200 may be one in which plugs 206 are provided at both ends of the cable 204. The cable 204 includes an optical fiber. The plug 206 contains the electro-optical element 10 (or electro-optical element 10A) shown in FIG. The plug 206 may be the OSA 100 including the electro-optic element 10 shown in FIG. The plug 206 may further incorporate a semiconductor chip.

  The plug 206 provided at one end of the cable 204 incorporates the electro-optic element 10 according to the above-described embodiment, and the plug 206 provided at the other end of the cable 204 may incorporate a light receiving element. Good. By using two sets of such cables 204 and plugs 206, bidirectional communication can be performed. That is, the electrical signal output from the electronic device 202 is converted into an optical signal at the plug 206 at one end of the cable 204. This optical signal passes through the cable 204 and is converted into an electrical signal at the plug 206 at the other end of the cable 204. This electric signal is taken into the electronic device 202 to which the plug 206 at the other end is connected. Thus, according to the optical transmission device 200 according to the present embodiment, information transmission can be performed between the electronic devices 202 using the optical signal.

(Usage of optical transmission device)
FIG. 18 is a diagram illustrating a usage pattern of the optical transmission device illustrated in FIG. 17. The light transmission device 212 corresponds to the light transmission device 200 of FIG. The optical transmission device 212 connects the electronic devices 210. As the electronic device 210, a liquid crystal display monitor or a digital CRT (may be used in the fields of finance, mail order, medical care, education), a liquid crystal projector, a plasma display panel (PDP), a digital TV, a retail store A cash register (for POS (Point of Sale Scanning)), a video, a tuner, a game device, a printer, and the like can be given.

  The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention, and the specific materials and layers mentioned in the embodiment can be added. The configuration is merely an example, and can be changed as appropriate.

  For example, in the above embodiment, even if the p-type and n-type in each semiconductor layer are interchanged, it does not depart from the spirit of the present invention. The electro-optic element according to the present invention can be widely applied to electronic devices using light. That is, as an application circuit or electronic device provided with the electro-optic element according to the present invention, an optical interconnection circuit, an optical fiber communication module, a laser printer, a laser beam projector, a laser beam scanner, a linear encoder, a rotary encoder, a displacement sensor , Pressure sensor, gas sensor, blood blood flow sensor, fingerprint sensor, high-speed electrical modulation circuit, wireless RF circuit, mobile phone, wireless LAN, and the like.

1 is a schematic cross-sectional view illustrating an example of an electro-optic element according to a first embodiment of the present invention. It is a schematic plan view of the same electro-optic element. It is a schematic plan view which shows the modification of an electro-optical element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic cross section which shows the manufacturing process of the electro-optic element same as the above. It is a schematic plan view of the electro-optical element manufactured by the manufacturing process same as above. It is a schematic cross section which shows the modification of an electro-optical element same as the above. It is a schematic plan view of the modification same as the above. FIG. 6 is a schematic cross-sectional view illustrating an example of an electro-optic element according to a second embodiment of the invention. It is a schematic cross section which shows an example of the optical transmission module which concerns on embodiment of this invention. It is a figure which shows the optical transmission apparatus which concerns on embodiment of this invention. It is a figure which shows the usage condition of an optical transmission apparatus same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electro-optic element, 11 ... GaAs substrate, 12 ... 1st mirror layer, 13 ... Active layer, 14 ... 2nd mirror layer, 15 ... 1st contact layer, 16 ... Light absorption layer, 17 ... 2nd contact layer, DESCRIPTION OF SYMBOLS 18 ... Current confinement layer, 19 ... Insulating layer, 20 ... 1st electrode, 21 ... 2nd electrode, 22 ... 3rd electrode, 23 ... 4th electrode, 25 ... Light emitting layer, 26 ... Light detection part, 30 ... Light emitting element 40, a light receiving element portion (light detecting portion), 51 ... a transparent layer, 52 ... a reflective layer, 53 ... an opening, 61 ... a dielectric mirror (optical waveguide layer), 63 ... an opening, 100 ... an optical transmission module, DESCRIPTION OF SYMBOLS 101 ... System, 102 ... Cover, 103 ... Lens, 104 ... Optical fiber

Claims (13)

A substrate,
A light emitting element portion formed on the substrate;
A light detection portion formed on a side surface of the light emitting element portion on the substrate and formed outside the light emitting element portion;
An insulating layer formed so as to fill between the light emitting element portion and the light detection portion;
A transparent layer made of a transparent member formed to cover the light-emitting element unit and the light detection unit and the insulating layer ;
A reflective layer formed at a position other than the vicinity of the light emitting axis of the light emitting element portion on at least the upper surface of the transparent layer;
An electro-optic element comprising a lower reflective layer disposed between the transparent layer and the insulating layer . A substrate,
A light emitting element portion formed on the substrate;
A light detection portion formed on a side surface of the light emitting element portion on the substrate and formed outside the light emitting element portion;
An insulating layer formed so as to fill between the light emitting element portion and the light detection portion;
An optical waveguide layer formed so as to guide a part of the light emitted by the light emitting element part to the light receiving element part from the light emitting element part to the light detection part;
A lower reflective layer disposed between the optical waveguide layer and the insulating layer ;
The electro-optic element, wherein the optical waveguide layer is not formed in the vicinity of a light emitting axis of the light emitting element portion. The light emitting element portion is a surface emitting laser,
The reflective layer has an opening at a position coaxial with the light emitting axis of the light emitting element portion,
The size of the opening is the same as or larger than the inner diameter of the current confinement layer of the surface emitting laser, and the same as or larger than the inner diameter of the electrode formed in the opening of the surface emitting laser. The electro-optic element according to claim 1, wherein the electro-optic element is small.   The electro-optical element according to claim 1, wherein the reflective layer is formed so as to cover almost all of the exposed surface of the transparent layer other than the vicinity of the light emitting axis. 2. The transparent layer transmits light emitted from the light emitting element portion, and is formed of any one of polyimide, epoxy resin, SiO ₂ , SiO, and SiN. The electro-optical element according to any one of 3, 4 and 4.   The electro-optical element according to claim 1, wherein the transparent layer functions as a moisture-proof layer. The reflective layer reflects a part of the light emitted from the light emitting element part,
The electro-optical element according to claim 1, wherein the light detection unit is arranged to receive at least light reflected by the reflective layer.   The electro-optical element according to claim 2, wherein the optical waveguide layer is formed of a dielectric multilayer reflective layer. The downside reflecting layer, said transparent layer, between at least one of the upper or the photo detecting portion upper surface of the light emitting element portion, that from claim 1, characterized in that is further arranged 8 The electro-optic element according to any one of the above. With substrate
A light emitting device provided on the substrate ;
A light receiving element provided outside the region where the light emitting element is formed on the substrate ;
An insulating layer formed so as to fill between the light emitting element portion and the light detection portion;
A translucent member formed to cover the light emitting element , the light receiving element and the insulating layer ;
A light reflecting member disposed on the surface of the light transmissive member and having an opening so that light from the light emitting element passes through;
A lower reflective member disposed between the translucent member and the insulating layer;
An electro-optic element comprising: A substrate,
A light emitting device provided on the substrate ;
A light receiving element provided outside the region where the light emitting element is formed on the substrate ;
An insulating layer formed so as to fill between the light emitting element portion and the light detection portion;
An optical waveguide formed to cover the light receiving element and the insulating layer , and having an opening so that light from the light emitting element passes through;
A lower reflective member disposed between the optical waveguide and the insulating layer;
An electro-optic element comprising:   An optical transmission module comprising the electro-optic element according to any one of claims 1 to 11.   An electronic apparatus comprising the electro-optic element according to claim 1.

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