JP2006222342A - Optical element and its fabrication process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element performing exact photodetection, and to provide its fabrication process. <P>SOLUTION: The optical element 100 comprises a surface emission semiconductor laser 130, an MSM (Metal Semiconductor Metal) detection element 210 for detecting a part of laser light emitted from the surface emission semiconductor laser, and a light receiving element 230 for receiving laser light externally. The MSM detection element comprises a first light absorption layer 201, a first electrode 202 and a second electrode 203, the light receiving element 230 comprises a second light absorption layer 221, a third electrode 222 and a fourth electrode 223, and the distance between the first and second electrodes in the MSM detection element is longer than the distance between the third and fourth electrodes in the light receiving element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element and a method for manufacturing the same, and more particularly to a surface-emitting semiconductor laser, a detection element that detects a part of laser light emitted from the surface-emitting semiconductor laser, and a laser beam received from the outside. The present invention relates to an optical element including a light receiving element that performs the same and a manufacturing method thereof.

  The surface emitting semiconductor laser has a characteristic that the light output varies depending on conditions such as environmental temperature. For this reason, an optical element using a surface emitting semiconductor laser is provided with a light detecting element for detecting a part of the laser light emitted from the surface emitting semiconductor laser and monitoring the light output value. There is a case. For example, Japanese Patent Laid-Open No. 10-135568 discloses an optical element having a three-terminal structure in which a surface emitting laser and a detection element have a common electrode.

In an optical element having a detection element, the detection element may receive not only light for monitoring but also light transmitted from the outside, and accurate light detection may not be performed.
Japanese Patent Laid-Open No. 10-135568

  An object of the present invention is to provide an optical element capable of performing accurate light detection and a method for manufacturing the same.

The optical element of the present invention is
A surface emitting semiconductor laser;
An MSM (Metal Semiconductor Metal) detection element for detecting a part of the laser light emitted from the surface emitting semiconductor laser;
A light receiving element for receiving laser light from the outside;
Including
The MSM detection element includes a first light absorption layer, a first electrode, and a second electrode,
The light receiving element has a second light absorption layer, a third electrode, and a fourth electrode,
A distance between the first electrode and the second electrode in the MSM detection element is larger than a distance between the third electrode and the fourth electrode in the light receiving element.

  According to the optical element of the present invention, the distance between the electrodes of the MSM detection element and the light receiving element can be set to a distance corresponding to the function of the response speed of the MSM detection element and the response speed of the light receiving element. it can. In addition, since the optical element integrates the surface emitting semiconductor laser, the MSM detection element, and the light receiving element in a monolithic manner, the element area can be reduced.

  In the present invention, other specific objects (hereinafter referred to as “B”) formed above a specific object (hereinafter referred to as “A”) are defined as B directly formed on A and A And B formed via the others on A. Further, in the present invention, forming B above A includes a case where B is formed directly on A and a case where B is formed on A via another on A.

In the optical element according to the present invention,
The surface emitting semiconductor laser is:
A first mirror formed above the substrate;
An active layer formed above the first mirror;
A second mirror formed above the active layer,
In the MSM detection element,
The first light absorption layer is formed above the second mirror,
The first electrode and the second electrode may be formed above the first light absorption layer.

In the optical element according to the present invention,
The light receiving element may be formed above the second mirror of the surface emitting semiconductor laser.

In the optical element according to the present invention,
The first light absorption layer and the second light absorption layer may include layers formed in the same process.

In the optical element according to the present invention,
The light receiving element may have an MSM (Metal Semiconductor Metal) type structure.

In the optical element according to the present invention,
The third electrode and the fourth electrode have a comb shape, and include a main shaft portion extending in a first direction and a comb tooth portion extending in a second direction perpendicular to the first direction. And the comb teeth are provided so as to mesh with each other,
The distance between the main shaft portion of the third electrode and the comb tooth portion of the fourth electrode, and the distance between the main shaft portion of the fourth electrode and the comb tooth portion of the third electrode are: The distance between the first electrode and the second electrode may be greater than the distance.

In the optical element according to the present invention,
The MSM detection element may be formed in the same process as the light receiving element.

In the optical element according to the present invention,
The light receiving element may have a pin type structure.

In the optical element according to the present invention,
The surface emitting semiconductor laser is:
A first mirror formed above the substrate;
An active layer formed above the first mirror;
A second mirror formed above the active layer,
The MSM detection element is formed above the substrate and around the surface-emitting semiconductor laser, and the active layer extends in a direction substantially perpendicular to a main laser beam emission direction emitted from the surface-emitting semiconductor laser. At least a part of the leaked light emitted from the light is received.

In the optical element according to the present invention,
The MSM detection element may further include an optical unit for guiding the leaked light to the MSM detection element above the first light absorption layer.

The manufacturing method of the optical element according to the present invention is as follows:
An optical element including a surface emitting semiconductor laser, an MSM (Metal Semiconductor Metal) detecting element for detecting a part of laser light emitted from the surface emitting semiconductor laser, and a light receiving element for receiving an external laser beam A manufacturing method of
Forming a first conductive type first semiconductor layer above the substrate; forming an active layer above the first semiconductor layer; and a second conductive type second semiconductor layer above the active layer. Forming a semiconductor multilayer film including: forming a third semiconductor layer above the second semiconductor layer; and
Patterning the third semiconductor layer to form a first light absorption layer of the MSM detection element and a second light absorption layer of the light receiving element;
Patterning the active layer and the second semiconductor layer;
Forming a first electrode and a second electrode for driving the MSM detection element, and a third electrode and a fourth electrode for driving the light receiving element,
A distance between the first electrode and the second electrode is formed larger than a distance between the third electrode and the fourth electrode.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1. Structure of Optical Element FIG. 1 is a cross-sectional view schematically showing an optical element 100 according to the present embodiment. FIG. 2 is a plan view schematically showing the optical element 100 according to the present embodiment. Moreover, FIG. 1 is a figure which shows the cross section in the AA of FIG.

  As shown in FIGS. 1 and 2, the optical element 100 according to the present embodiment includes a surface emitting semiconductor laser 130, an MSM detection element 210, and a light receiving element 230. The MSM detection element 210 detects a part of the laser light emitted from the surface emitting semiconductor laser 130. The light receiving element 230 receives laser light from the outside via an optical fiber or the like.

  First, the configurations of the surface emitting semiconductor laser 130, the MSM detection element 210, and the light receiving element 230 will be described in detail.

1.1. Surface Emitting Semiconductor Laser The surface emitting semiconductor laser 130 includes a first mirror 102, an active layer 103, a second mirror 104, a current confinement layer 105, a fifth electrode 106, and a sixth electrode 107.

The first mirror 102 is formed on the substrate 101. For example, 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. Distributed Bragg reflection type (DBR) mirror.

  First, a vertical resonator composed of the first mirror 102, the active layer 103, and the second mirror 104 will be described.

The active layer 103 is formed on the first mirror 102. For example, a multiple quantum well structure in which three quantum well structures each composed of a GaAs well layer and an Al _0.3 Ga _0.7 As barrier layer are stacked. (MQW).

The second mirror 104 is formed on the active layer 103, for example, 25 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. It consists of a pair of distributed Bragg reflector mirrors. Note that the uppermost layer of the second mirror 104 is configured to be a layer having a smaller Al composition, that is, a p-type Al _0.15 Ga _0.85 As layer. The composition and the number of layers constituting each of the first mirror 102, the active layer 103, and the second mirror 104 are not limited to this. Note that the Al composition of the uppermost layer of the second mirror 104 is preferably less than 0.3. By making the Al composition of the uppermost layer of the second mirror 104 less than 0.3, an ohmic contact between the uppermost layer of the second mirror 104 and the sixth electrode 107 can be obtained better.

  The second mirror 104 is made p-type by doping carbon (C), for example, and the first mirror 102 is made n-type by doping silicon (Si), for example. Therefore, a pin diode is formed by the p-type second mirror 104, the active layer 103 not doped with impurities, and the n-type first mirror 102.

  Further, a portion of the surface emitting semiconductor laser 130 from the second mirror 104 to the middle of the first mirror 102 is etched into a circular shape in plan view as shown in FIG. In the present embodiment, the planar shape of the columnar portion 132 is circular, but this shape can be any shape.

  Further, a current confinement layer 105 obtained by oxidizing the AlGaAs layer from the side surface is formed in a region close to the active layer 103 among the layers constituting the second mirror 104. The current confinement layer 105 is formed in a ring shape along the periphery of the columnar portion 132. The current confinement layer 105 can be made of, for example, aluminum oxide.

  Next, the fifth electrode 106 and the sixth electrode 107 used for driving the surface emitting semiconductor laser 130 will be described.

  The fifth electrode 106 is formed on the back surface of the substrate 101. The fifth electrode 106 is made of, for example, a laminated film of an alloy of gold (Au) and germanium (Ge) and gold (Au).

  The sixth electrode 107 is formed on the second mirror 104. As shown in FIG. 2, the sixth electrode 107 has a ring shape in plan view, and is formed so as to surround the MSM detection element 210 and the light receiving element 230. The sixth electrode 107 is made of, for example, a laminated film of platinum (Pt), titanium (Ti), and gold (Au). A current is injected into the active layer 103 by the fifth electrode 106 and the sixth electrode 107. Note that the material for forming the fifth electrode 106 and the sixth electrode 107 is not limited to the above-described material, and for example, an alloy of gold (Au) and zinc (Zn) can be used.

1.2. Separation Layer The separation layer 240 is formed between the surface emitting semiconductor laser 130, the MSM detection element 210, and the light receiving element 230, specifically on the second mirror 104. The isolation layer 240 is formed, for example, by stacking a semi-insulating high Al composition AlGaAs layer not doped with impurities on the second mirror 104 by epitaxial growth. Here, the AlGaAs layer having a high Al composition is, for example, an Al _0.9 Ga _0.1 As layer.

  In the optical element 300, by providing the separation layer 240, the film between the first electrode 202, the second electrode 203, the third electrode 222, the fourth electrode 223, and the sixth electrode 107 can be thickened. . Therefore, parasitic capacitance generated between the first electrode 202, the second electrode 203, the third electrode 222, the fourth electrode 223, and the sixth electrode 107 can be reduced.

1.3. MSM Detection Element The MSM detection element 210 is formed above the surface emitting semiconductor laser 130, specifically on the separation layer 240. The MSM detection element 210 includes a first light absorption layer 201, a first electrode 202, and a second electrode 203.

  The first light absorption layer 201 is formed on the separation layer 240. The first light absorption layer 201 has a rectangular planar shape as shown in FIG. 2, and is made of a GaAs layer not doped with impurities.

  The first electrode 202 and the second electrode 203 are used to drive the MSM detection element 210 by applying a voltage to the MSM detection element 210. As shown in FIG. 2, the first electrode 202 and the second electrode 203 have a rectangular planar shape.

  For the first electrode 202 and the second electrode 203, a material that is in Schottky contact with the first light absorption layer 201 can be used. The first electrode 202 and the second electrode 203 are, for example, a laminated film of titanium (Ti), platinum (Pt), and gold (Au), or a laminated film of titanium and gold, aluminum (Al), titanium And a laminated film of palladium (Pd) and gold. A voltage is applied to the first light absorption layer 201 by the first electrode 202 and the second electrode 203. Note that materials for forming the first electrode 202 and the second electrode 203 are not limited to those described above.

1.4. Light Receiving Element The light receiving element 230 is formed above the surface emitting semiconductor laser 130, specifically, formed on the separation layer 240. The light receiving element 230 includes a second light absorption layer 221, a third electrode 222, and a fourth electrode 223.

  The second light absorption layer 221 is formed on the separation layer 240. The second light absorption layer 221 has a rectangular planar shape as shown in FIG. 2 and can be made of the same material as the first light absorption layer 201 described above. For example, GaAs not doped with impurities. Can consist of layers.

  The third electrode 222 and the fourth electrode 223 are used to drive the light receiving element 230 by applying a voltage to the light receiving element 230. As shown in FIG. 2, the third electrode 222 and the fourth electrode 223 each have a comb shape in plan view, and are provided so that the comb teeth are engaged with each other at a predetermined interval.

  Specifically, the third electrode 222 includes a main shaft portion 222a extending in a first direction (X direction in the example of FIG. 2) and a second direction (in the example of FIG. 2) orthogonal to the first direction. And a comb tooth portion 222b extending in the Y direction). Similar to the third electrode 222, the fourth electrode 223 includes a main shaft portion 223a extending in the first direction and a comb tooth portion 223b extending in a second direction orthogonal to the first direction.

  In addition, the 3rd electrode 222 and the 4th electrode 223 are not limited to having a comb shape, For example, you may have shapes, such as a rectangular shape and a spiral shape.

  For the third electrode 222 and the fourth electrode 223, a material that is in Schottky contact with the second light absorption layer 221 can be used. The third electrode 222 and the fourth electrode 223 can be made of the same material as the first electrode 202 and the second electrode 203 described above. That is, the third electrode 222 and the fourth electrode 223 are, for example, a laminated film of titanium (Ti), platinum (Pt), and gold (Au), or a laminated film of titanium and gold, aluminum (Al). Further, it can be made of a laminated film of titanium, palladium (Pd), and gold. A voltage is applied to the second light absorption layer 221 by the third electrode 222 and the fourth electrode 223. Note that the materials for forming the third electrode 222 and the fourth electrode 223 are not limited to those described above.

1.5. Overall Configuration The light output of the surface emitting semiconductor laser 130 is determined mainly by the bias voltage applied to the surface emitting semiconductor laser 130. In particular, the optical output of the surface emitting semiconductor laser 130 varies greatly depending on the ambient temperature of the surface emitting semiconductor laser 130 and the lifetime of the surface emitting semiconductor laser 130. For this reason, it is necessary to maintain a predetermined light output in the surface emitting semiconductor laser 130.

  Therefore, in the optical element 100 according to the present embodiment, the light output of the surface emitting semiconductor laser 130 is monitored, and the voltage value applied to the surface emitting semiconductor laser 130 based on the value of the current generated in the MSM detection element 210. Adjust. Thereby, the value of the current flowing through the surface emitting semiconductor laser 130 can be adjusted, and the surface emitting semiconductor laser 130 can maintain a predetermined light output. Control for feeding back the optical output of the surface emitting semiconductor laser 130 to the voltage value applied to the surface emitting semiconductor laser 130 can be performed using an external electronic circuit (drive circuit; not shown).

  The MSM detection element 210 and the light receiving element 230 are formed on the surface emitting semiconductor laser 130. The first light absorption layer 201 of the MSM detection element 210 and the second light absorption layer 221 of the light receiving element 230 can be formed by the same process.

  As shown in FIG. 2, the first electrode 202 of the MSM detection element 210 is formed at a position a1 away from the second electrode 203 in the X direction.

  The comb tooth portion 222b of the third electrode 222 is formed at a position separated from the comb tooth portion 223b of the fourth electrode 223 by a distance b1 in the X direction. Further, the comb tooth portion 223b in the fourth electrode 223 is formed at a position away from the main shaft portion 222a of the third electrode 222 by a distance b2 in the Y direction. Similarly, the comb-tooth portion 222b of the third electrode 222 is formed at a position separated from the main shaft portion 223a of the fourth electrode 223 by a distance b2.

  The distance a1 between the first electrode 202 and the second electrode 203 of the MSM detection element 210 is larger than the distances b1 and b2 between the third electrode 222 and the fourth electrode 223 in the light receiving element 230.

  The third electrode 222 and the fourth electrode 223 have a comb-shaped planar shape, whereas the first electrode 202 and the second electrode 203 have a rectangular planar shape. With such a configuration, the distance between the first electrode 202 and the second electrode 203 of the MSM detection element 210 should be much larger than the distance between the third electrode 222 and the fourth electrode 223 of the light receiving element 230. Can do. Thus, by increasing the electrode interval of the MSM detection element 210, the response speed of the MSM detection element 210 can be made slower than the response speed of the light receiving element 230.

  Even if the response speed of the MSM detection element 210 is slowed down, the MSM detection element 210 only needs to be able to monitor the average value of the amount of light from the surface-emitting type semiconductor laser 130, and therefore can fulfill its function. . On the other hand, since the light receiving element 230 is required to have an electrode interval that can correspond to the drive frequency of the received signal, the electrode interval cannot be increased like the MSM detection element 210.

2. Next, an example of a method for manufacturing the optical element 100 according to the embodiment to which the present invention is applied will be described with reference to FIGS. 3 to 6 and FIGS. 8 to 10 are cross-sectional views schematically showing one manufacturing process of the optical element 100 shown in FIGS. 1 and 2, and each correspond to the cross-sectional view shown in FIG. FIG. 7 is a plan view schematically showing one manufacturing process of the optical element 100 shown in FIGS. 1 and 2, and corresponds to the plan view shown in FIG.

  (1) First, as shown in FIG. 3, epitaxial growth is performed on the upper surface of the substrate 101 made of an n-type GaAs layer while modulating the composition, so that the first conductivity type first semiconductor layer 10, the active layer 20, A two-conductivity type second semiconductor layer 30, a separation layer 40, and a third semiconductor layer 50 are formed.

  The optical thicknesses of the third semiconductor layer 50 and the separation layer 40 for the first light absorption layer 201 and the second light absorption layer 221 are set so that the set wavelength of the surface emitting semiconductor laser 130 is λ. In this case, it can be an odd multiple of λ / 4. As a result, the first light absorption layer 201, the second light absorption layer 221, and the separation layer 240 can function as a mirror. Therefore, the MSM detection element 210 can function as a part of the distributed Bragg reflection type mirror without adversely affecting the characteristics of the surface emitting semiconductor laser 130.

  In addition, when the sixth electrode 107 is formed in a later step, at least a portion of the second semiconductor layer 30 that is in contact with the sixth electrode 107 is connected to the sixth electrode 107 by increasing the carrier density. It is desirable to make ohmic contact easy.

  The temperature at which the epitaxial growth is performed is appropriately determined depending on the growth method, the raw material, the type of the substrate 101, or the type, thickness, and carrier density of the semiconductor multilayer film to be formed. Is preferred. Further, the time required for performing the epitaxial growth is also appropriately determined in the same manner as the temperature. As a method for epitaxial growth, a metal-organic vapor phase epitaxy (MOVPE) method, an MBE method (Molecular Beam Epitaxy) method, or an LPE method (Liquid Phase Epitaxy) can be used.

  (2) Next, the third semiconductor layer 50 is patterned into a predetermined shape to form the first light absorption layer 201 and the second light absorption layer 221 (see FIG. 5).

  First, after applying a resist (not shown) on the third semiconductor layer 50, the resist is patterned by a lithography method to form a resist layer R1 having a predetermined shape as shown in FIG.

  Next, the third semiconductor layer 50 is etched by, eg, dry etching using the resist layer R1 as a mask (see FIG. 5). Thereafter, the resist layer R1 is removed (see FIG. 5). The first light absorption layer 201 and the second light absorption layer 221 are formed separately as shown in FIG.

  (3) Next, the separation layer 40 is patterned into a predetermined shape (see FIG. 6).

  First, after applying a resist (not shown) on the third semiconductor layer 50 and the separation layer 40, the resist is patterned by a lithography method to form a resist layer (not shown). For example, dry etching is performed. By this method, the separation layer 40 is etched and the resist layer is removed (see FIG. 6). 6 is a view showing a cross section taken along the line DD of FIG. As shown in FIG. 7, the separation layer 240 is formed under the first light absorption layer 201 and the second light absorption layer 221 so as to have, for example, a rectangular planar shape.

  (4) Next, the surface emitting semiconductor laser 130 including the columnar portion 132 is formed by patterning (see FIG. 9). Specifically, first, a resist (not shown) is applied on the second mirror 104, the first light absorption layer 201, the second light absorption layer 221, and the separation layer 240, and then the resist is applied by a lithography method. By patterning, a resist layer R2 having a predetermined pattern is formed (see FIG. 8). Next, using the resist layer R2 as a mask, the second semiconductor layer 30, the active layer 20, and a part of the first semiconductor layer 10 are etched by, for example, a dry etching method. As a result, as shown in FIG. 7, a columnar section 132 having the second mirror 104, the active layer 103, and the first mirror 102 is formed.

  Through the above steps, the vertical resonator (surface emitting semiconductor laser 130) including the columnar portion 132 is formed on the substrate 101. Thereafter, the resist layer R2 is removed.

  (5) Next, by introducing the substrate 101 on which the columnar portion 132 is formed by the above process in a steam atmosphere of about 400 ° C., for example, the layer having a high Al composition in the second mirror 104 is seen from the side surface. Oxidation forms a current confinement layer 105 (see FIG. 10).

  The oxidation rate depends on the furnace temperature, the amount of steam supplied, the Al composition of the layer to be oxidized and the film thickness. In a surface emitting laser having a current confinement layer formed by oxidation, current flows only in a portion where the current confinement layer is not formed (a portion not oxidized) during driving. Therefore, in the step of forming the current confinement layer by oxidation, the current density can be controlled by controlling the range of the current confinement layer 105 to be formed.

  (6) Next, the sixth electrode 107 is formed on the upper surface of the second mirror 104, the fifth electrode 106 is formed on the lower surface of the substrate 101, and the first electrode 202 and the first electrode are formed on the upper surface of the first light absorption layer 201. The two electrodes 203 are formed, and the third electrode 222 and the fourth electrode 223 are formed on the upper surface of the second light absorption layer 221 (see FIGS. 1 and 2).

  First, as necessary, the upper surface of the second mirror 104, the upper surface of the first light absorption layer 201, the upper surface of the second light absorption layer 221 and the lower surface of the substrate 101 are cleaned using a plasma treatment method or the like. . Thereby, an element having more stable characteristics can be formed.

  Next, the first electrode 202 and the second electrode 203 are formed. The first electrode 202 and the second electrode 203 can be formed of the same material. For example, platinum (Pt), titanium (Ti), and gold (on the upper surface of the first light absorption layer 201 are formed by vacuum evaporation. A stacked film (not shown) of Au) is formed. Next, the first electrode 202 and the second electrode 203 are formed by removing the laminated film other than the predetermined position by a lift-off method. The third electrode 222 and the fourth electrode 223 are formed by similar processes and materials.

  As materials for the first electrode 202, the second electrode 203, the third electrode 222, and the fourth electrode 223, materials for forming a Schottky barrier with the first light absorption layer 201 and the second light absorption layer 221, respectively. If it is, it will not specifically limit, The laminated film of titanium (Ti), platinum (Pt), and gold (Au), or the laminated film of titanium and gold, aluminum (Al), titanium, and palladium (Pd) A laminated film of gold and gold may be used.

  Further, for example, a stacked film of, for example, an alloy of gold (Au) and zinc (Zn) and gold (Au) is formed on the upper surface of the columnar portion 132 by a vacuum deposition method, and then the sixth electrode 107 is formed by a lift-off method. To do.

  Further, a laminated film of, for example, an alloy of gold (Au) and germanium (Ge) and gold (Au) is formed on the exposed surface of the substrate 101 by, for example, a vacuum deposition method, and the fifth electrode 106 is formed. .

  Note that in the above process, a dry etching method or a wet etching method can be used instead of the lift-off method. In the above process, a sputtering method can be used instead of the vacuum evaporation method.

  (7) Next, annealing is performed. The annealing temperature depends on the electrode material. In the case of the electrode material used in this embodiment, it is normally performed at around 400 ° C. Through the above steps, the first electrode 202, the second electrode 203, the third electrode 222, the fourth electrode 223, the fifth electrode 106, and the sixth electrode 107 are formed.

  Through the above steps, as shown in FIGS. 1 and 2, the optical element 100 of the present embodiment is obtained.

3. Modification 3.1. First Modified Example Next, an optical element 300 according to a first modified example will be described. FIG. 11 is a cross-sectional view schematically showing the optical element 300. FIG. 12 is a plan view schematically showing the optical element 300. 11 is a diagram showing a cross section taken along line BB in FIG. The optical element 300 differs from the optical element 100 shown in FIGS. 1 and 2 in that the light receiving element 232 is provided not around the columnar part 132 of the surface emitting semiconductor laser 130 but around the columnar part 132.

  Specifically, only the MSM detection element 212 is formed on the separation layer 240. The MSM detection element 212 includes a first light absorption layer 204, a first electrode 205, and a second electrode 206. The first light absorption layer 204 is separated in a planar shape as shown in FIG. It can have the same shape as layer 240. Although a plurality of light receiving elements 232 are provided around the columnar portion 132, a single light receiving element 232 may be provided. The light receiving element 232 includes a second light absorption layer 224, a third electrode 225, and a fourth electrode 226. The second light absorption layer 224 has a rectangular planar shape, and the third electrode 225. The fourth electrode 226 has the same shape as the third electrode 222 and the fourth electrode 223 in FIGS. 1 and 2, but is not limited thereto. For example, the second light absorption layer 224 includes the columnar portion 132. The third electrode 225 and the fourth electrode 226 may be formed in a spiral shape, for example, so as to surround the periphery.

  In the optical element 100 shown in FIGS. 1 and 2, the light receiving element 230 is formed on the emission surface, which is the opening of the current confinement layer 105, and blocks the laser light emitted from the surface emitting semiconductor laser 130. . On the other hand, since the optical element 300 is not formed on the emission surface of the surface-emitting type semiconductor laser 130 because the light-receiving element 232 is formed around the columnar portion 132, the optical element 300 is emitted from the surface-emitting type semiconductor laser 130. It does not block the laser beam. On the other hand, the MSM detection element 212 is formed on the emission surface of the surface emitting semiconductor laser 130, but the first electrode 205 and the second electrode 206 have a rectangular planar shape, and the comb-shaped electrode. Compared with the light receiving element 232 having the above, the amount of blocking the laser beam is much smaller. Therefore, the optical element 300 can prevent the emission power from decreasing more than the optical element 100. Furthermore, it is preferable to form the first electrode 205 and the second electrode 206 of the optical element 300 only above the current confinement layer 105. As a result, the first electrode 205 and the second electrode 206 are not formed on the emission surface, which is the opening of the current confinement layer 105, so that the laser beam is not blocked and the emission power can be more reliably prevented from decreasing. .

  In addition, since the other structure of the optical element 300 concerning a 1st modification is the same as that of the optical element 100 mentioned above, description is abbreviate | omitted.

3.2. Second Modification Example Next, an optical element 400 according to a second modification example will be described. FIG. 13 is a cross-sectional view schematically showing the optical element 400, and corresponds to the cross section of FIG. FIG. 14 is a plan view schematically showing the optical element 400. 13 is a view showing a cross section taken along the line CC of FIG. The optical element 400 is different from the optical element 100 shown in FIGS. 1 and 2 in that the light receiving element 430 has a pin-type structure and that the light receiving element 430 is provided around the columnar portion 132.

  The light receiving element 430 includes an n-type contact layer 421, a second light absorption layer 422, a p-type contact layer 433, a third electrode 434, and a fourth electrode 435. The n-type contact layer 421 is formed on the separation layer 240, the second light absorption layer 422 is formed on the n-type contact layer 421, and the p-type contact layer 433 is formed on the second light absorption layer 422. It is formed. The n-type contact layer 421, the second light absorption layer 422, the p-type contact layer 433, the third electrode 434, and the fourth electrode 435 are all formed in a ring shape around the columnar portion 132 of the surface emitting semiconductor laser 130. Has been.

  The n-type contact layer 421 is made of, for example, an n-type GaAs layer, the second light absorption layer 422 is made of, for example, a GaAs layer into which no impurity is introduced, and the p-type contact layer 433 is made of, for example, a p-type GaAs layer. it can. Specifically, the n-type contact layer 421 is made n-type by doping silicon (Si), for example, and the p-type contact layer 433 is made p-type by doping carbon (C), for example. ing. Accordingly, the p-type contact layer 433, the second light absorption layer 422 not doped with impurities, and the n-type contact layer 421 form a pin diode.

  The third electrode 434 and the fourth electrode 435 are formed by a known material and process. The fourth electrode 435 is formed on the n-type contact layer 421 and can be formed of, for example, a stacked film of platinum (Pt), titanium (Ti), and gold (Au). The third electrode 434 is formed on the p-type contact layer 433, and can be made of, for example, a laminated film of gold (Au) and germanium (Ge) alloy and gold.

  The MSM detection element 410 includes a first light absorption layer 401, an impurity-containing layer 402, a first electrode 403, and a second electrode 404. The functions of the first light absorption layer 401, the first electrode 403, and the second electrode 404 are the functions of the first light absorption layer 201, the first electrode 202, and the second electrode 203 described above with reference to FIGS. The planar shape is the same as that of the MSM detection element 212 of the optical element 300 according to the first modified example, but is different in that it further includes an impurity-containing layer 402. The impurity-containing layer 402 can function as a light absorption layer.

  Since the optical element 400 includes the light receiving element 430 having a pin structure, the distance between the electrodes can be controlled by the thickness of a film formed between the electrodes. Compared with the light receiving element of the MSM structure, the electrode interval can be narrowed, and the response speed can be increased. Therefore, the light receiving element 430 can cope with a received signal having a higher driving frequency.

  In addition, about the other structure of the optical element 400 concerning a 1st modification, since it is the same as that of the optical element 100 mentioned above, description is abbreviate | omitted.

3.3. Third Modification Next, an optical element 500 according to a third modification will be described. FIG. 15 is a cross-sectional view schematically showing the optical element 500, and corresponds to the cross section of FIG. In the optical element 500, the MSM detection element 510 and the light receiving element 530 are formed around the surface emitting semiconductor laser 130, and the MSM detecting element 210 and the light receiving element 230 are formed on the surface emitting semiconductor laser 130. Different from the optical element 100.

  The MSM detecting element 510 and the light receiving element 530 can have, for example, a rectangular or ring-shaped planar shape surrounding the periphery of the surface emitting semiconductor laser 130. The MSM detection element 510 includes a first light absorption layer 501, a first electrode 502, a second electrode 503, and an optical unit 504. The light receiving element 530 includes a second light absorption layer 521, a third electrode 522, and a fourth electrode 523. The first light absorption layer 501, the second light absorption layer 521, and the semiconductor layer 550 are made of the same material as that of the first light absorption layer 201 of the optical element 100. The first electrode 502, the second electrode 503, the third electrode 522, and the fourth electrode 523 are made of the same material as the first electrode 202 of the optical element 100.

  The optical unit 504 of the MSM detection element 510 has a convex lens structure and has a function of guiding leakage light emitted from the side surface of the surface emitting semiconductor laser 130 to the incident surface of the first light absorption layer 501. For example, as shown in FIG. 15, leakage light emitted from the side surface of the surface emitting semiconductor laser 130 is emitted in the direction of the arrow C1, refracted in the directions of the arrows C2 and C3 by the optical unit 504, and the first light. The light enters the absorption layer 501. In this way, the MSM detection element 510 can detect the light emitted from the surface emitting semiconductor laser 130. The optical unit 504 is formed by curing a curable liquid material by applying energy such as heat or light. Specifically, the optical unit 504 is formed by discharging and curing a droplet made of a liquid material. For example, an ultraviolet curable resin or a thermosetting resin can be used as the liquid material. Examples of the ultraviolet curable resin include acrylic resin and epoxy resin. An example of the thermosetting resin is a polyimide resin.

  Since the MSM detection element 510 and the light receiving element 530 are formed around the surface emitting semiconductor laser 130 in this way, the laser light emitted from the surface emitting semiconductor laser 130 is not blocked, and thus the emission power is more reliably determined. Can be prevented.

  Further, when the optical unit 504 is formed, a bank for forming the optical unit 504 may be further included. The bank can be made of, for example, silicon nitride.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments and can take various forms. For example, in the above embodiment, even if the laser light of the surface emitting semiconductor laser is emitted from the back side of the substrate, it does not depart from the spirit of the present invention.

Sectional drawing which shows typically the optical element concerning this Embodiment. The top view which shows typically the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. The figure which shows typically the manufacturing process of the optical element concerning this Embodiment. Sectional drawing which shows typically the optical element concerning a 1st modification. The top view which shows typically the optical element concerning a 1st modification. Sectional drawing which shows typically the optical element concerning a 2nd modification. The top view which shows typically the optical element concerning a 2nd modification. Sectional drawing which shows typically the optical element concerning a 3rd modification.

Explanation of symbols

100 optical element, 101 substrate, 102 first mirror, 103 active layer, 104 second mirror, 105 current confinement layer, 106 fifth electrode, 107 sixth electrode, 130 surface emitting laser, 132 columnar portion, 201 first light Absorption layer, 202 1st electrode, 203 2nd electrode, 210 MSM detection element, 221 2nd light absorption layer, 222 3rd electrode, 223 4th electrode, 230 Light receiving element, 240 Separation layer

Claims (11)

A surface emitting semiconductor laser;
An MSM (Metal Semiconductor Metal) detection element for detecting a part of light emitted from the surface emitting semiconductor laser;
A light receiving element for receiving laser light from the outside;
Including
The MSM detection element includes a first light absorption layer, a first electrode, and a second electrode,
The light receiving element has a second light absorption layer, a third electrode, and a fourth electrode,
The optical element, wherein a distance between the first electrode and the second electrode in the MSM detection element is larger than a distance between the third electrode and the fourth electrode in the light receiving element. In claim 1,
The surface emitting semiconductor laser is:
A first mirror formed above the substrate;
An active layer formed above the first mirror;
A second mirror formed above the active layer,
In the MSM detection element,
The first light absorption layer is formed above the second mirror,
The optical element, wherein the first electrode and the second electrode are formed above the first light absorption layer. In claim 2,
The light receiving element is an optical element formed above the second mirror of the surface emitting semiconductor laser. In any one of Claims 1 thru | or 3,
The first light absorption layer and the second light absorption layer are optical elements having layers formed in the same process. In any of claims 1 to 4,
The light receiving element is an optical element having an MSM (Metal Semiconductor Metal) type structure. In claim 5,
The third electrode and the fourth electrode have a comb shape, and include a main shaft portion extending in a first direction and a comb tooth portion extending in a second direction perpendicular to the first direction. And the comb teeth are provided so as to mesh with each other,
The distance between the main shaft portion of the third electrode and the comb tooth portion of the fourth electrode, and the distance between the main shaft portion of the fourth electrode and the comb tooth portion of the third electrode are: An optical element that is larger than the distance between the first electrode and the second electrode. In claim 5 or 6,
The MSM detection element is an optical element formed in the same process as the light receiving element. In any of claims 1 to 4,
The light receiving element is an optical element having a pin type structure. In claim 1,
The surface emitting semiconductor laser is:
A first mirror formed above the substrate;
An active layer formed above the first mirror;
A second mirror formed above the active layer,
The MSM detection element is formed above the substrate and around the surface-emitting semiconductor laser, and the active layer extends in a direction substantially perpendicular to a main laser beam emission direction emitted from the surface-emitting semiconductor laser. An optical element that receives at least part of leaked light emitted from the optical element. In claim 9,
The MSM detection element further includes an optical unit for guiding the leakage light to the MSM detection element above the first light absorption layer. An optical element including a surface emitting semiconductor laser, an MSM (Metal Semiconductor Metal) detecting element for detecting a part of laser light emitted from the surface emitting semiconductor laser, and a light receiving element for receiving an external laser beam A manufacturing method of
Forming a first conductive type first semiconductor layer above the substrate; forming an active layer above the first semiconductor layer; and a second conductive type second semiconductor layer above the active layer. Forming a semiconductor multilayer film including: forming a third semiconductor layer above the second semiconductor layer; and
Patterning the third semiconductor layer to form a first light absorption layer of the MSM detection element and a second light absorption layer of the light receiving element;
Patterning the active layer and the second semiconductor layer;
Forming a first electrode and a second electrode for driving the MSM detection element, and a third electrode and a fourth electrode for driving the light receiving element,
A method for manufacturing an optical element, wherein a distance between the first electrode and the second electrode is formed larger than a distance between the third electrode and the fourth electrode.

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