JP2007189158A - Optical element and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element capable of enhancing reliability while uniformly injecting current, and a method therefor. <P>SOLUTION: The optical element comprises a pillar 130 having a top surface from or into which light emits or enters, a first electrode 122 formed on the top surface of the pillar, and a secondary electrode 124 formed above the first electrode. The first elctrode is formed annularly on the top surface of the pillar, and the second electrode is formed annularly having an opening 125 that opens externally from the center on the top surface of the pillar. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical element and a method for manufacturing the same.

In the structure of an optical element such as a surface emitting semiconductor laser, the electrodes are often formed in a ring shape in which the central portion of the upper surface of the columnar portion is closed in order to make current injection uniform. For example, Patent Document 1 discloses a surface emitting semiconductor laser including a contact metal layer formed so as to have a circular opening.
Japanese Patent Laid-Open No. 10-242560

  An object of the present invention is to provide an optical element capable of improving reliability while achieving uniform current injection and a method for manufacturing the same.

The optical element according to the present invention is
A columnar portion having an upper surface from which light is emitted or incident;
A first electrode formed on an upper surface of the columnar part;
A second electrode formed above the first electrode,
The first electrode is formed in a ring shape on the upper surface of the columnar part,
The second electrode is formed in an open ring shape having an opening that opens outward from the central portion on the upper surface of the columnar portion.

  In the present invention, the B layer is provided above the specific A layer means that the B layer is provided directly on the A layer and the B layer is provided on the A layer via another layer. And the case where The same applies to the following inventions.

  Further, in the present invention, the “ring shape” may be a shape having a through hole in the central portion, and is not limited to a shape having a circular inner edge and outer edge. The same applies to the “open ring shape”.

In the optical element according to the present invention,
The edge of the second electrode may have a curved shape from the opening to the outside or the inside of the open ring shape.

In the optical element according to the present invention,
The edge of the said 2nd electrode is an optical element which has a curve shape from the said opening part to the outer side of an open ring shape.

In the optical element according to the present invention,
The second electrode may be thicker than the first electrode.

In the optical element according to the present invention,
The second electrode may be formed such that at least a part of edges facing each other across the opening are formed in parallel.

In the optical element according to the present invention,
The first electrode may have a film thickness D1 that satisfies the following formula (1).

(4i + 1) λ / 8n ≦ D1 ≦ (4i + 3) λ / 8n (1)
(In Formula (1), i is an integer, λ is the oscillation wavelength, and n is the refractive index of the electrode material.)
In the optical element according to the present invention,
The second electrode may have a thickness of 0.2 μm or more.

In the optical element according to the present invention,
The inner end portion of the first electrode may be formed on the inner surface of the upper surface of the columnar portion from the end portion of the second electrode.

In the optical element according to the present invention,
The second electrode may have a film thickness D2 that satisfies the following formula (2).

A ≧ D2 × tan (θ / 2) (2)
(In Formula (2), A represents the difference between the diameter of the exit surface and the inner diameter of the second electrode, and θ represents the radiation angle.)
In the optical element according to the present invention,
The second electrode may have a wiring part extending outward from the columnar part.

In the optical element according to the present invention,
The opening can be opened in an outward direction different from a direction in which the wiring portion extends.

In the optical element according to the present invention,
A fourth electrode formed above the second electrode;
The fourth electrode may be formed in an open ring shape having an opening that opens in an outward direction different from the opening of the second electrode.

In the method for manufacturing an optical element according to the present invention,
Forming a columnar portion having an upper surface from which light is emitted or incident;
Forming a first electrode on the upper surface of the columnar part;
Forming a second electrode above the first electrode;
Including
The first electrode is formed in a ring shape on the upper surface of the columnar part,
The second electrode is formed in an open ring shape having an opening that opens outward from the central portion on the upper surface of the columnar portion.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, a surface-emitting semiconductor laser is described as an example of an optical element.

1. Surface Emitting Semiconductor Laser First, the structure of the surface emitting semiconductor laser according to the present embodiment will be described. FIG. 1 is a plan view of a surface emitting semiconductor laser to which the present invention is applied. FIG. 2 is a cross-sectional view of the surface emitting semiconductor laser according to the present embodiment, and is a cross-sectional view taken along the line II of FIG.

  As shown in FIGS. 1 and 2, the surface emitting semiconductor laser 100 of the present embodiment includes a semiconductor substrate (GaAs substrate in the present embodiment) 110 and a vertical resonator (on the semiconductor substrate 110). (Hereinafter referred to as “resonator”) 140, first electrode 122, second electrode 123, and third electrode 124. The resonator 140 includes a first mirror 142, an active layer 144, and a second mirror 146.

  Next, each component of the surface emitting semiconductor laser 100 will be described.

First, the resonator 140 will be described. As described above, the resonator 140 includes the first mirror 142, the active layer 144, and the second mirror 146. As the first mirror 142, for example, 40 pairs of distributed Bragg reflection type mirrors (DBRs) 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 can be used. The active layer 144 is composed of a GaAs well layer and an Al _0.3 Ga _0.7 As barrier layer, and a layer including a quantum well structure having three well layers can be applied. As the second mirror 146, a distributed Bragg reflection mirror (DBR) comprising 25 pairs of semiconductor 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 is used. it can. Note that the composition and the number of layers of each of the first mirror 142, the active layer 144, and the second mirror 146 are not limited thereto.

  The second mirror 146 is made p-type by doping C, Zn, Mg, or the like, for example, and the first mirror 142 is made n-type by doping Si, Se, or the like, for example. Yes. Therefore, a pin diode is formed by the second mirror 146, the active layer 144 not doped with impurities, and the first mirror 142.

  The second mirror 146, the active layer 144, and a part of the first mirror 142 constitute a columnar semiconductor deposited body (hereinafter also referred to as “columnar portion”) 130. The side surface of the columnar part 130 is covered with a buried insulating layer 120.

  An insulating layer 132 that functions as a current confinement layer may be formed in a region close to the active layer 144 in the layers constituting the columnar section 130. The insulating layer 132 may have a ring shape along the periphery of the columnar part 130. The current confinement insulating layer 132 is made of, for example, aluminum oxide.

  The columnar section 130 according to the present embodiment includes a structure that is not completely columnar in shape, and may be a part of a rectangular parallelepiped resonator 140, for example. In this case, for example, in the case of a surface emitting semiconductor laser, the upper surface of the columnar portion 130 is a region overlapping in a plan view with a current confinement layer (insulating layer 132) that regulates a current path and a region surrounded by the current confinement layer. It can be.

  In the surface emitting semiconductor laser 100 according to the present embodiment, the buried insulating layer 120 is formed so as to cover the side surface of the columnar portion 130. The insulator constituting the embedded insulating layer 120 is various glass, metal oxides or resins, and as the resin, for example, polyimide resin, fluorine resin, acrylic resin, epoxy resin, or the like can be used. From the viewpoint of ease of processing and insulation, a polyimide resin or a fluorine-based resin is desirable.

  A first electrode 122 is formed on the columnar part 130 and the buried insulating layer 120. The first electrode 122 can be made of a single layer or a laminated film of two or more layers selected from Au, Pt, Ti, Zn, Cr, and alloys thereof. For example, the first electrode 122 is made of a laminated film of Cr, Ti, Pt, and Au. Become. The first electrode 122 has a ring shape on the upper surface of the columnar section 130.

  A second electrode 123 is formed on the first electrode 122. The second electrode 123 is made of a single layer or a laminated film containing Au at least on the outermost surface, and can be made of a laminated film of Cr and Au, for example. The second electrode 123 has an open ring shape having an opening 125 that opens outward from the central portion on the upper surface of the central portion.

  Further, as shown in FIG. 3, the edge of the second electrode 123 has a curved shape from the opening 125 to the outside or the inside of the open ring shape. FIG. 3 is an enlarged view of region II in FIG. Thereby, when forming the 2nd electrode 123, it can prevent that a burr | flash generate | occur | produces, for example at the time of lift-off. In addition, since the end portion of the second electrode 123 has a round shape with no corners in this way, electric field concentration on the end portion is suppressed, and deterioration of characteristics and reliability of the surface emitting semiconductor laser 100 are prevented. can do.

  In the surface-emitting type semiconductor laser 100 according to the present embodiment, the edge of the second electrode 123 has a curved shape from the opening 125 to both the outside and the inside of the open ring shape, but only one of them has a curved shape. It may be a curved shape. For example, as in the surface emitting semiconductor laser 100 according to the present embodiment, the inner end of the opening 125 is provided on the upper surface of the first electrode 122, but the outer end of the opening 125 is the first end. When not formed on the upper surface of the first electrode 122, the second electrode 123 may have a curved shape only from the opening 125 to the outside of the open ring shape.

  The second electrode 123 is formed such that at least a part of the edges facing each other across the opening 125 are parallel. In other words, the line m1 and the line m2 along the opposite edges across the opening 125 are parallel. Thereby, when forming the 2nd electrode 123 by lift-off etc., it can form with sufficient precision. Further, the contact area between the first electrode 122 and the second electrode 123 can be maximized, and the resistance can be lowered.

The second electrode 123 is formed thicker than the first electrode 122. By forming the second electrode 123 thick, more stable bonding strength can be maintained. Further, since the second electrode 123 is formed thick, the wiring resistance can be reduced and the heat dissipation can be improved.
Further, since the first electrode 122 is formed thin, disconnection of the second electrode 123 can be prevented. It is preferable that the 1st electrode 122 has the film thickness D of the range of following formula (1).

(4i + 1) λ / 8n ≦ D ≦ (4i + 3) λ / 8n (1)
(In formula (1), i is an integer, λ is the oscillation wavelength, n is the refractive index of the electrode material, and n is the refractive index of air in FIG. 5).
Here, the advantage of having the film thickness in the above range will be described with reference to FIG. 5A and 5B, the horizontal axis indicates the film thickness of the electrode, and the vertical axis indicates the radiation angle of the laser beam. FIG. 5A is a diagram showing the relationship between the electrode film thickness and the laser beam radiation angle, and FIG. 5B shows the electrode film thickness D in the range of 0 <D ≦ λ / 2n. It is a figure which shows the relationship between the film thickness of an electrode, and the radiation angle of a laser beam. Note that the results of FIGS. 5A and 5B are the results of obtaining the radiation angle by the time domain difference method (FDTD method). As shown in FIG. 5A, the inventor of the present application has found that the radiation angle of the laser beam varies with a substantially constant period with respect to the film thickness of the electrode. Specifically, the radiation angle varies with a period of λ / 2n. Furthermore, it has been found that the film thickness of the electrode having the minimum radiation angle varies within a certain range with (λ (oscillation wavelength) / 4n) as the center. Then, it was examined in which range the minimum value of the radiation angle fluctuated when the electrode film thickness D was in the range of 0 <D ≦ λ / 2n. The result is shown in FIG. As can be seen from FIG. 5 (B), it was found that the position where the radiation angle is minimum fluctuates within the range of λ / 8n ≦ D ≦ 3λ / 8n. From the result of the above simulation, the radiation angle of the laser beam can be reduced by designing the film thickness of the first electrode 122 to be within the range of the above formula (1). As a result, it is possible to provide a surface emitting semiconductor laser with good characteristics.

  The outer end of the first electrode 122 is covered with the second electrode 123 as indicated by a dotted line in FIG. Further, the inner end portion of the first electrode 122 is formed on the inner surface of the inner end portion of the second electrode 123 on the upper surface of the columnar portion 130. That is, as shown in FIGS. 1 and 2, the inner diameter of the first electrode 122 is smaller than the inner diameter of the second electrode 123, and the emission surface 126 of the surface emitting semiconductor laser 100 is formed by the first electrode 122. . In other words, the first electrode 122 has an exposed portion 127 that is not covered by the second electrode 123 around the emission surface 126. Furthermore, the film thickness of the second electrode 123 is preferably a film thickness D2 that satisfies the following formula (2).

A ≧ D2 × tan (θ / 2) (2)
(In Formula (2), A represents the difference between the diameter of the exit surface and the inner diameter of the second electrode, and θ represents the radiation angle.)
Equation (2) will be described with reference to FIG. FIG. 4 is an enlarged view of region II in FIG. Assuming that the radiation angle of the laser beam is θ, if the difference A between the diameter of the exit surface, which is the size of the exposed portion 127, and the inner diameter of the second electrode is equal to or greater than D2 × tan (θ / 2), it is theoretical. In addition, the laser beam is not applied to the second electrode 123. Therefore, when the difference A between the diameter of the emission surface and the inner diameter of the second electrode is D2 × tan (θ / 2) or more in this way, the influence of the electromagnetic field of the second electrode 123 on the radiation pattern of the laser beam. Can be reduced.

  Further, the film thickness of the second electrode 123 is preferably 0.2 μm or more. This is because if the thickness of the second electrode 123 is less than 0.2 μm, wire bonding may not be possible. The film thickness of the second electrode 123 is more preferably 1.0 μm or more. This is because by setting the film thickness of the second electrode 123 to 1.0 μm or more, sufficient bonding strength can be obtained during mounting.

  Further, the second electrode 123 has a wiring part 128 that extends outward from the columnar part 130. The wiring part 128 extends in an outward direction different from the opening 125 provided in the region II, and preferably extends in a direction facing the opening 125, for example.

  Further, as shown in FIG. 1, the second electrode 123 has an electrode pad portion 129 connected to the wiring portion 128. Since the second electrode 123 has a thick film as described above, disconnection from the upper surface of the columnar portion 130 to the electrode pad portion 129 can be prevented, and the reliability of the surface emitting semiconductor laser 100 can be improved.

  Further, a third electrode 124 is formed on the back surface of the semiconductor substrate 110. The third electrode 124 can be composed of a single layer or a laminated film of two or more layers selected from Au, Ge, Ni, In, W, Cr and alloys thereof. For example, the third electrode 124 can be made of Cr, AuGe, Ni, or Au. It consists of a laminated film. That is, in the surface emitting semiconductor laser 100 shown in FIGS. 1 and 2, the first electrode 122 and the second electrode 123 are joined to the second mirror 146 on the columnar portion 130, and the third electrode 124 is the semiconductor substrate 110. It is joined with. Current is injected into the active layer 144 by the first electrode 122, the second electrode 123, and the third electrode 124.

  According to the surface-emitting type semiconductor laser 100 according to the present embodiment, the emission angle of the laser beam can be reduced by controlling the film thickness of the first electrode 122 so as to satisfy the above-described formula (1). . As a result, it is possible to provide a surface emitting semiconductor laser with good characteristics.

  However, generally, when an electrode is formed, the film thickness varies, and as a result, the film thickness of the first electrode 122 may not be controlled so as to satisfy Equation (1). Specifically, in the above-described formula (1), for example, if i = 7, n = 3, and λ = 850 nm, a suitable range of film thickness D is 1027 nm ≦ D ≦ 1097 nm. When the center value 1062 nm in the range of the film thickness D is formed, assuming that the variation in the film thickness to be considered is ± 5%, the thickness is 1062 ± 53 nm. The film thickness of the electrode 122 cannot be controlled, and the first electrode 122 having a film thickness outside the range of the suitable film thickness D may be formed.

  On the other hand, in the formula (1), for example, if i = 0, n = 3, and λ = 850 nm, a suitable range of the film thickness D is 35 nm ≦ D ≦ 106 nm. When the central value of 70 nm in the range of the film thickness D is formed, assuming that the variation in the film thickness to be considered is ± 5%, the thickness is 70 ± 3.5 nm. The film thickness of the first electrode 122 can be controlled.

  That is, since the variation tends to increase as the film thickness increases, the film thickness is preferably small in order to control the film thickness of the first electrode 122 so as to satisfy the formula (1). However, if the film thickness of the first electrode 122 is small, there is a problem that the wire bonding strength is lowered. Therefore, the thickness of the first electrode 122 is controlled to satisfy the formula (1) by forming the second electrode 123 having a thickness capable of obtaining sufficient wire bonding strength on the first electrode 122. be able to.

2. Device Operation A general operation of the surface emitting semiconductor laser 100 according to the present embodiment will be described below. The following driving method of the surface emitting semiconductor laser 100 is an example, and various modifications can be made without departing from the gist of the present invention.

  First, when a forward voltage is applied to the pin diode at the first electrode 122, the second electrode 123, and the third electrode 124, recombination of electrons and holes occurs in the active layer 144, and the recombination is caused by the recombination. Luminescence occurs. Stimulated emission occurs when the generated light reciprocates between the second mirror 146 and the first mirror 142, and the intensity of the light is amplified. When the optical gain exceeds the optical loss, laser oscillation occurs, and laser light is emitted in a direction perpendicular to the semiconductor substrate 110 from the emission surface 126 on the upper surface of the columnar portion 130.

3. Manufacturing Method of Surface Emitting Laser Next, an example of a manufacturing method of the surface emitting semiconductor laser 100 shown in FIGS. 1 and 2 will be described with reference to FIGS. 6 to 9 are cross-sectional views schematically showing manufacturing steps of the surface-emitting type semiconductor laser 100 of the present embodiment shown in FIGS. 1 and 2, each corresponding to the cross section shown in FIG. FIG. 10 is a plan view schematically showing the manufacturing process of the surface emitting semiconductor laser 100, and corresponds to FIG.

(1) First, a semiconductor multilayer film 150 is formed on the surface of a semiconductor substrate 110 made of n-type GaAs by epitaxial growth while modulating the composition, as shown in FIG. Here, the semiconductor multilayer film 150 includes, for example, 40 pairs of first mirrors 142 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, a GaAs well layer, and Al _0.3 Ga _0.7. 25 pairs in which an active layer 144 including a quantum well structure composed of an As barrier layer and including three well layers, and p-type Al _0.9 Ga _0.1 As layers and p-type Al _0.15 Ga _0.85 As layers alternately stacked Second mirror 146. The semiconductor multilayer film 150 is formed by sequentially stacking these layers on the semiconductor substrate 110.

Here, the uppermost layer of the second mirror 146 is preferably composed of a p-type Al _0.9 Ga _0.1 As layer having a lower refractive index. In the second mirror 146, an AlAs layer may be used instead of the p-type Al _0.9 Ga _0.1 As layer.

  When the second mirror 146 is grown, at least one layer in the vicinity of the active layer 144 can be formed on an AlAs layer or an AlGaAs layer that is oxidized later and becomes the insulating layer 132 for current confinement. The AlGaAs layer serving as the insulating layer 132 has an Al composition of 0.95 or more. Further, it is desirable that the outermost layer of the second mirror 146 has a high carrier density and facilitates ohmic contact with the electrode (first electrode 122).

  The temperature at which the epitaxial growth is performed is appropriately determined depending on the growth method and the raw material, the type of the semiconductor substrate 110, or the type, thickness, and carrier density of the semiconductor multilayer film 150 to be formed. Preferably there is. Further, the time required for performing the epitaxial growth is also appropriately determined in the same manner as the temperature. In addition, as a method of epitaxial growth, a metal-organic vapor phase epitaxy (MOVPE) method, an MBE (Molecular Beam Epitaxy) method, an LPE (Liquid Phase Epitaxy) method, or the like can be used.

  Next, after applying a resist on the semiconductor multilayer film 150, the resist is patterned by a lithography method to form a resist layer R having a predetermined pattern as shown in FIG. The resist layer R is formed above a region where the columnar portion 130 (see FIGS. 1 and 2) is to be formed.

  (2) Next, using this resist layer R as a mask, a part of the second mirror 146, the active layer 144, and the first mirror 142 is etched by, for example, a dry etching method, and as shown in FIG. The semiconductor deposited body (columnar portion) 130 is formed. Thereafter, the resist layer R is removed.

  (3) Next, as shown in FIG. 8, by introducing the semiconductor substrate 110 on which the columnar portion 130 is formed by the above process into a water vapor atmosphere of about 400 ° C., for example, A layer having a high Al composition (a layer having an Al composition of 0.95 or more) is oxidized from the side surface to form an insulating layer 132 for current confinement. 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.

  (4) Next, as shown in FIG. 8, the buried insulating layer 120 surrounding the columnar portion 130, that is, a part of the first mirror 142, the active layer 144, and the second mirror 146 is formed.

  Here, a case where a polyimide resin is used as a material for forming the buried insulating layer 120 will be described. First, a precursor (polyimide precursor) is applied onto the semiconductor substrate 110 having the columnar portion 130 using, for example, a spin coating method to form a precursor layer. At this time, the precursor layer is formed to have a thickness greater than the height of the columnar section 130. As a method for forming the precursor layer, known techniques such as a dipping method, a spray coating method, and a droplet discharge method can be used in addition to the spin coating method described above.

  Next, the semiconductor substrate 110 is heated using, for example, a hot plate to remove the solvent from the precursor layer, and then semi-cured at about 200 ° C. Subsequently, as shown in FIG. 8, the upper surface 130a of the columnar portion 130 is exposed, and then placed in a furnace at about 350 ° C., and the precursor layer is imidized, whereby the buried insulating layer 120 that is almost completely cured is obtained. Form. As a method for exposing the upper surface 130a of the columnar section 130, a CMP method, a dry etching method, a wet etching method, or the like can be used. Alternatively, the buried insulating layer 120 can be formed using a photosensitive resin. The buried insulating layer 120 or the layers in each stage up to curing can be patterned by lithography or the like as necessary.

  (5) Next, a process of forming the first electrode 122 and the third electrode 124 for injecting current into the active layer 144 and the laser light emission surface 126 (see FIGS. 9 and 10) will be described.

  First, before forming the first electrode 122 and the third electrode 124, the exposed upper surfaces of the columnar part 130 and the semiconductor substrate 110 are cleaned using a plasma treatment method or the like as necessary. Thereby, an element having more stable characteristics can be formed. Subsequently, after forming a patterned resist layer and a laminated film of, for example, Cr, Ti, Pt, and Au on the upper surfaces of the buried insulating layer 120 and the columnar portion 130 by, for example, a vacuum deposition method, the columnar portion 130 is formed by a lift-off method. A portion where the laminated film is not formed is formed on the upper surface of the substrate. This portion becomes the emission surface 126.

  In general, when an electrode is formed in a ring shape, the electrode is often formed in a ring shape in order to make current injection uniform. When patterning such an electrode, for example, a lift-off method can be applied. According to this method, it is necessary to provide the resist in an isolated pattern at a position corresponding to the center portion of the ring shape. In this case, this isolated pattern resist is difficult to remove, or even if removed, the lifted-off conductive material may be reattached.

  In this embodiment mode, the first electrode 122 is formed thin. More specifically, the first electrode 122 may be formed thinner than the resist provided at the time of lift-off. This facilitates the removal of the resist having the isolated pattern described above, and improves the reliability of the surface emitting semiconductor laser 100.

  In the above process, a dry etching method or a wet etching method can be used instead of the lift-off method. At this time, the first electrode 122 is formed so that its film thickness falls within a desired range as described above.

  Further, a laminated film of, for example, Cr, AuGe, Ni, and Au is formed on the exposed surface of the semiconductor substrate 110 by, for example, a vacuum deposition method.

  (6) Next, the process of alloying the first electrode 122 and the third electrode 124 formed in (5) will be described. Alloying is performed by annealing. The annealing temperature depends on the electrode material. In the case of the electrode material used in the present embodiment, it is usually performed at around 400 ° C. Through the above steps, the first electrode 122 and the third electrode 124 are formed. Thereby, an ohmic contact can be obtained.

  (7) Next, the step of forming the second electrode 123 (see FIG. 2) will be described. The second electrode 123 is formed on the upper surface of the first electrode 122 by a lift-off method after forming a patterned resist layer and a laminated film of, for example, Au and Cr on the upper surface of the first electrode 122 by, for example, vacuum deposition. A portion where the laminated film is not formed is formed. This portion becomes the exposed portion 127. In the above process, a dry etching method or a wet etching method can be used instead of the lift-off method. At this time, the second electrode 123 is formed so that its film thickness falls within a desired range as described above.

  Here, the 2nd electrode 123 is formed in the open ring shape which has the opening part 125 opened to an outward direction from a center part in the upper surface of a center part. By using the open ring shape in this manner, for example, at the time of lift-off, the resist on the inner side and the outer side of the ring is continuously provided in the opening 125, so that an isolated pattern is not formed and the resist can be easily removed. In addition, the reliability of the surface emitting semiconductor laser 100 can be improved.

  Through the above steps, the surface emitting semiconductor laser 100 according to the present embodiment can be formed.

  In the method for manufacturing the surface emitting semiconductor laser according to the present embodiment, the alloying step of step (6) is performed before the formation of the second electrode 123. That is, since it is not necessary to perform an annealing process after the formation of the second electrode 123, diffusion of Cr into the outermost surface of Au by the annealing process is prevented, and the surface of the second electrode 123 is prevented from being oxidized. be able to.

4). Modifications The surface emitting laser according to the present embodiment is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist of the present invention. An example of the modification will be described below.

  FIG. 11 is a plan view schematically showing a surface emitting semiconductor laser according to a modification, and corresponds to the plan view shown in FIG. FIG. 12 is a cross-sectional view schematically showing a surface emitting semiconductor laser according to a modification, and corresponds to the cross-sectional view shown in FIG.

  The surface emitting semiconductor laser 200 according to the modification is different from the surface emitting semiconductor laser 100 according to the present embodiment in that it further includes a fourth electrode 224. The fourth electrode 224 is formed on the upper surface of the second electrode 223. Thereby, the whole electrode can be formed thickly, a disconnection can be prevented, and the heat dissipation of a device can be improved. The fourth electrode 224 is formed in an open ring shape having an opening 226 that opens in an outward direction different from the opening 225 of the second electrode 223. In the surface emitting semiconductor laser 200 according to the modification, for example, when the center of the first electrode 122 is a reference position and the extending direction of the wiring portion 128 is a 12 o'clock direction, the opening 225 of the second electrode 223 is In the 4 o'clock direction, the opening 226 of the fourth electrode 224 is provided in the 8 o'clock direction. Thus, by providing the opening 225 of the second electrode 223 and the opening 226 of the fourth electrode 224 at different positions, variations in film thickness can be suppressed.

  About the manufacturing method of the surface emitting semiconductor laser 100, the 4th electrode 224 is made into the same as the 2nd electrode 123 after the manufacturing process (1)-(7) of the surface emitting semiconductor laser 100 concerning this Embodiment mentioned above. The manufacturing process (7) may be used. Moreover, about the alloying process of a process (6), you may perform before formation of the 2nd electrode 223, and may perform it after formation.

  Since the other configuration and manufacturing method of the surface emitting semiconductor laser 200 are the same as those of the surface emitting semiconductor laser 100 described above, description thereof is omitted.

5). Experimental Example The following experiment was performed on the surface emitting semiconductor laser including the first electrode and the second electrode described above.

5.1. First Experimental Example FIGS. 13 and 14 are diagrams showing a surface emitting semiconductor laser according to a first experimental example, and FIG. 14 shows a region IV in FIG. The surface-emitting type semiconductor laser according to the first experimental example includes a first electrode, a second electrode formed on the upper surface of the first electrode, and a fourth electrode formed on the upper surface of the second electrode. The first electrode, the second electrode, and the fourth electrode all have openings. That is, the surface emitting semiconductor laser according to the first experimental example is different from the surface emitting semiconductor laser 100 having the ring-shaped first electrode in that the first electrode has an open ring shape.

  In the first experimental example, as shown in FIG. 14, the contact state is different from that of the current injection region other than the opening on the upper surface of the columnar portion near the opening of the first electrode. It is thought that it was destroyed.

5.2. Second Experimental Example FIG. 15 is a diagram showing the surface emitting semiconductor laser 100 according to the above-described embodiment. Since the first electrode has a ring shape, the electrode directly in contact with the columnar part can inject current uniformly, and there is no bias in the contact state, so there is no structural breakdown seen in the first experimental example, which is good It was a state.

  Therefore, according to the first experimental example and the second experimental example, the inner end portion of the first electrode is formed inside the end portion of the second electrode on the upper surface of the columnar portion, and the first electrode is It was confirmed that structural breakdown due to electric field concentration can be prevented by the ring shape having no opening.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  The optical element according to the present invention is not limited to the above-described surface emitting semiconductor laser, but may be another light emitting element (for example, a semiconductor light emitting diode or an organic LED) or a light receiving element (for example, a photodiode). There may be.

The top view which shows typically the surface emitting semiconductor laser concerning this Embodiment. 1 is a cross-sectional view schematically showing a surface emitting semiconductor laser according to an embodiment. The enlarged view which shows the area | region II of FIG. 1 in detail. The enlarged view which shows the area | region III of FIG. 2 in detail. FIG. 5A is a diagram showing the relationship between the electrode film thickness and the laser beam radiation angle, and FIG. 5B shows the electrode film thickness D in the range of 0 <D ≦ λ / 2n. It is a figure which shows the relationship between the film thickness of an electrode, and the radiation angle of a laser beam. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser concerning this Embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser concerning this Embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser concerning this Embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser concerning this Embodiment. The top view which shows typically the manufacturing process of the surface emitting semiconductor laser concerning this Embodiment. The top view which shows typically the surface emitting semiconductor laser concerning a modification. Sectional drawing which shows typically the surface emitting semiconductor laser concerning a modification. The figure which shows the surface emitting semiconductor laser concerning a 1st experiment example. The enlarged view which shows the surface emitting semiconductor laser concerning a 1st experiment example. The figure which shows the surface emitting semiconductor laser concerning the 2nd experiment example.

Explanation of symbols

100 surface emitting semiconductor laser, 110 semiconductor substrate, 120 buried insulating layer, 122 first electrode, 123 second electrode, 124 third electrode, 125 opening, 126 emitting surface, 127 exposed portion, 128 wiring portion, 129 electrode pad Part, 130 columnar part, 132 insulating layer, 140 resonator, 142 first mirror, 144 active layer, 146 second mirror, 200 surface emitting semiconductor laser, 223 second electrode, 224 fourth electrode, 225, 226 opening

Claims (13)

A columnar portion having an upper surface from which light is emitted or incident;
A first electrode formed on an upper surface of the columnar part;
A second electrode formed above the first electrode,
The first electrode is formed in a ring shape on the upper surface of the columnar part,
The said 2nd electrode is an optical element formed in the open ring shape which has an opening part opened to the outward from the center part in the upper surface of the said columnar part. In claim 1,
The edge of the said 2nd electrode is an optical element which has a curved shape from the said opening part to the outer side or inner side of an open ring shape. In claim 2,
The edge of the said 2nd electrode is an optical element which has a curve shape from the said opening part to the outer side of an open ring shape. In any of claims 1 to 3,
The optical element, wherein the second electrode is formed thicker than the first electrode. In any of claims 1 to 4,
The second electrode is an optical element in which at least a part of edges facing each other across the opening is formed in parallel. In any of claims 1 to 5,
The first electrode is an optical element having a film thickness D1 that satisfies the following formula (1).
(4i + 1) λ / 8n ≦ D1 ≦ (4i + 3) λ / 8n (1)
(In Formula (1), i is an integer, λ is the oscillation wavelength, and n is the refractive index of the electrode material.) In any one of Claims 1 thru | or 6.
The second electrode is an optical element having a thickness of 0.2 μm or more. In any one of Claims 1 thru | or 7,
An optical element, wherein an inner end portion of the first electrode is formed inside an end portion of the second electrode on an upper surface of the columnar portion. In any of claims 1 to 8,
The second electrode is an optical element having a film thickness D2 that satisfies the following formula (2).
A ≧ D2 × tan (θ / 2) (2)
(In Formula (2), A represents the difference between the diameter of the exit surface and the inner diameter of the second electrode, and θ represents the radiation angle.) In any one of Claim 1 thru | or 9,
The second electrode is an optical element having a wiring portion extending outward from the columnar portion. In claim 10,
The said opening part is an optical element opened to the outward direction different from the direction where the said wiring part extends. In any one of Claims 1 thru | or 11,
A fourth electrode formed above the second electrode;
The optical element, wherein the fourth electrode is formed in an open ring shape having an opening that opens in an outward direction different from the opening of the second electrode. Forming a columnar portion having an upper surface from which light is emitted or incident;
Forming a first electrode on the upper surface of the columnar part;
Forming a second electrode above the first electrode;
Including
The first electrode is formed in a ring shape on the upper surface of the columnar part,
The method of manufacturing an optical element, wherein the second electrode is formed in an open ring shape having an opening that opens outward from a central portion on an upper surface of the columnar portion.