JP4731167B2 - Surface emitting laser element - Google Patents

Description

The present invention relates to a surface emitting laser element.

FIGS. 1A and 1B are diagrams showing a configuration example of a general vertical cavity surface emitting semiconductor laser element (surface emitting laser element (VCSEL)). 1A is a perspective view, and FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. 1A. Referring to FIGS. 1A and 1B, the surface emitting laser element (VCSEL) includes a lower reflecting mirror, a second cladding layer, an active layer, and a semiconductor substrate (in this example, a GaAs substrate). The first cladding layer and the upper reflecting mirror are laminated, and the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are made of a semiconductor material and processed as a mesa structure. An ohmic electrode is formed on the substrate. A first ohmic electrode is formed on the upper reflecting mirror, and a second ohmic electrode is provided below the GaAs substrate (not shown in FIG. 1B).

  In the VCSEL having such a configuration, by applying a bias voltage between the first ohmic electrode and the second ohmic electrode, a current flows through the active layer of the mesa structure, and from an opening provided in the upper part of the mesa structure. Laser light is emitted.

Examples of the material constituting the upper reflecting mirror include a material in which two kinds of materials having low absorption with respect to a desired wavelength and different refractive indexes are laminated, for example, GaAs / AlGaAs or GaAs / AlAs. Further, the thickness of each layer constituting the upper reflecting mirror must have a thickness corresponding to the material and wavelength, and the number of laminated layers should have a reflectance of 99% or more with respect to a desired wavelength. Must be determined. In the configuration of FIG. 1, it is necessary to use a semiconductor material as a material constituting the upper reflecting mirror, but the first ohmic electrode is electrically connected to the first cladding layer without passing through the upper reflecting mirror. In this case, a dielectric material can be used as the material of the upper reflecting mirror. Specific examples of the material in this case include SiO ₂ / TiO ₂ .

  Various combinations of the clad layer and the active layer are conceivable. In any case, a semiconductor material is used.

  In general, a semiconductor material is weak in strength, and is easily damaged by an external force. Moreover, in the VCSEL, the upper reflecting mirror and the resonator (cladding layer and active layer) are processed in a mesa shape, so that the VCSEL is more susceptible to damage. In particular, as described above, the reflecting mirror is precisely designed, and there is a high possibility that the oscillation of the laser light stops even if a part of the reflecting mirror is slightly lost.

Conventionally, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 have proposed various forms of VCSELs and manufacturing methods thereof. Means for protecting a mesa structure including a reflector and a resonator. Was not taken at all. Therefore, these VCSELs have a high possibility of damage to the mesa structure during the manufacturing process, incorporation into an optical communication module / optical pickup module using the VCSEL, or other handling. The reliability of various applications that had been greatly reduced.
JP-A-9-298337 Japanese Patent Laid-Open No. 10-65268 JP-A-11-243257 JP 2000-269586 A

  As described above, in the surface emitting laser element (VCSEL), the upper reflecting mirror and the resonator structure are precisely designed, and are easily affected by oscillation stoppage or the like even by slight physical damage. In the VCSEL, the upper reflecting mirror and the resonator have a mesa shape and are more easily damaged. In order to facilitate the handling of the VCSEL or improve the reliability of the VCSEL. It is necessary to provide a means for protecting them.

The present invention, the surface-emission laser device having a mesa structure on a semiconductor substrate (VCSEL), that protects the mesa structure or the like, provides a possible surface-emitting laser element of improving the overall reliability VCSEL It is aimed.

In order to achieve the above object, according to the first aspect of the present invention, a lower reflector, a second cladding layer, an active layer, a first cladding layer, and an upper reflector are laminated on a semiconductor substrate, The second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are made of a semiconductor material, processed as a mesa structure, and a surface emitting laser element (VCSEL) in which an ohmic electrode is formed on the upper reflecting mirror. In the above, a protective member is provided around the mesa structure, and the protective member is a laminated structure made of the same semiconductor material as the second cladding layer, the active layer, the first cladding layer, and the upper reflector of the mesa structure. A protective layer made of an organic material is formed thereon, and the height of the protective member is higher than that of the ohmic electrode formed on the upper reflecting mirror by forming the protective layer. Is also expensive It is characterized that it is as.

According to a second aspect of the present invention, a lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and an upper reflecting mirror are laminated on a semiconductor substrate, and the second cladding layer and the active layer are activated. In the surface emitting laser element (VCSEL) in which the layer, the first cladding layer, and the upper reflector are made of a semiconductor material and processed as a mesa structure, and an ohmic electrode is formed on the upper reflector, the mesa structure A protective member is provided in the periphery, and the protective member includes a protective layer made of a semiconductor material on a laminated structure made of the same semiconductor material as the second cladding layer, the active layer, and the first cladding layer of the mesa structure. be constituted by forming the height of the protective member, characterized in that by the protective layer is formed, has a higher than the upper surface of the ohmic electrodes formed on the upper reflector age There.

According to a third aspect of the present invention, a lower reflector, a second cladding layer, an active layer, a first cladding layer, and a contact layer containing a high-concentration impurity are stacked on a semiconductor substrate, The second cladding layer, the active layer, the first cladding layer, and the contact layer are made of a semiconductor material and are processed as a mesa structure, and a semiconductor material or dielectric material that does not contain impurities on the contact layer of the mesa structure In the surface emitting laser device in which an upper reflecting mirror is formed and an ohmic electrode is formed on the contact layer, a protective member is provided around the mesa structure, and the protective member is the mesa. second cladding layer of the structure, the active layer, first cladding layer, on the laminated structure composed of the same semiconductor material as the contact layer, the protective layer is formed of a semiconductor material or a dielectric material Made, the height of the protective member, by the protective layer is formed, the upper surface of the upper reflector, and is characterized in that has a higher than the upper surface of the ohmic electrode.

According to the first aspect of the present invention, the lower reflecting mirror, the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are laminated on the semiconductor substrate, and the second cladding layer and the active layer are activated. In the surface emitting laser element (VCSEL) in which the layer, the first cladding layer, and the upper reflector are made of a semiconductor material and processed as a mesa structure, and an ohmic electrode is formed on the upper reflector, the mesa structure A protective member is provided in the periphery, and the protective member is made of an organic material on a laminated structure made of the same semiconductor material as the second cladding layer, the active layer, the first cladding layer, and the upper reflector of the mesa structure . A protective layer is formed, and the height of the protective member is higher than the upper surface of the ohmic electrode formed on the upper reflecting mirror by forming the protective layer. Because Cavity (cladding layer, the active layer), it is possible to effectively protect the mesa structure and the ohmic electrode comprising a top mirror.

According to the second aspect of the present invention, the lower reflecting mirror, the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are laminated on the semiconductor substrate, and the second cladding layer The active layer, the first cladding layer, and the upper reflecting mirror are made of a semiconductor material and processed as a mesa structure, and in the surface emitting laser element (VCSEL) in which an ohmic electrode is formed on the upper reflecting mirror, the mesa A protective member is provided in the periphery of the structure, and the protective member is a protective member made of a semiconductor material on a laminated structure made of the same semiconductor material as the second cladding layer, the active layer, and the first cladding layer of the mesa structure. Since the protective member is formed , the height of the protective member is higher than the upper surface of the ohmic electrode formed on the upper reflecting mirror. ,Both Vessel (cladding layer, the active layer), it is possible to effectively protect the mesa structure and the ohmic electrode comprising a top mirror.

According to a third aspect of the present invention, the lower reflector, the second cladding layer, the active layer, the first cladding layer, and the contact layer containing a high concentration of impurities are stacked on the semiconductor substrate. The second clad layer, the active layer, the first clad layer, and the contact layer are made of a semiconductor material and processed as a mesa structure, and the mesa structure contact layer does not contain an impurity-containing semiconductor material or dielectric. In a surface emitting laser element in which an upper reflecting mirror made of a body material is formed and an ohmic electrode is formed in the contact layer, a protective member is provided around the mesa structure, the second cladding layer, the active layer of the mesa structure, the first cladding layer, on the laminated structure composed of the same semiconductor material as the contact layer, a protective layer made of a semiconductor material or a dielectric material formed Is configured, the height of the protective member, by the protective layer is formed, the upper surface of the upper reflector, and since has become higher than the upper surface of the ohmic electrode, the resonator ( The mesa structure including the cladding layer, the active layer) and the contact layer, the ohmic electrode, and the upper reflecting mirror can be effectively protected.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

(First form)
FIGS. 2A and 2B are diagrams showing a configuration example of the surface emitting laser element (VCSEL) according to the first embodiment of the present invention. 2A is a plan view, and FIG. 2B is a cross-sectional view taken along the line BB ′ in FIG. 2A.

  Referring to FIGS. 2A and 2B, the VCSEL according to the first embodiment includes a lower reflector, a second cladding layer, an active layer, a first layer on a semiconductor substrate (in this example, a GaAs substrate). The first cladding layer and the upper reflecting mirror are laminated, and the second cladding layer, the active layer, the first cladding layer and the upper reflecting mirror are made of a semiconductor material and processed as a mesa structure, and are ohmic on the upper reflecting mirror. An electrode (first ohmic electrode) is formed. Although not shown in FIG. 2B, a second ohmic electrode is provided below the GaAs substrate.

  In the VCSEL having such a configuration, by applying a bias voltage between the first ohmic electrode and the second ohmic electrode, a current flows through the active layer of the mesa structure, and from an opening provided in the upper part of the mesa structure. Laser light is emitted. The upper reflecting mirror and the lower reflecting mirror in FIG. 2B are actually composed of multilayer films, but are not shown here.

  When the upper and lower reflectors are formed of p-type and n-type semiconductors, respectively, an n-type GaAs substrate is used as the GaAs substrate, and the upper and lower reflectors are respectively n-type semiconductor and When a p-type semiconductor is used, a p-type GaAs substrate must be used as the GaAs substrate, and the polarity of the VCSEL in the present invention may be any of these.

  Further, in the VCSEL of the first embodiment, a protective member is provided around the mesa structure, and the protective member is a protective layer made of an organic material on a structure made of a semiconductor material similar to the mesa structure. And the height of the protective member is higher than the upper surface of the ohmic electrode (first ohmic electrode) formed on the upper reflecting mirror.

  Here, the region where the protective member is formed may be any region other than the region where the first ohmic electrode is formed as shown in FIG. Also, the shape is not limited to a concentric shape as shown in FIG. 2A, and for example, any shape such as a prismatic shape, a cylindrical shape, or a block shape can be used.

  Moreover, as a semiconductor material which comprises a protection member, the thing similar to the semiconductor material which comprises a mesa structure can be used. Moreover, as an organic material which forms the protective layer of a protection member, materials, such as an acrylic resin, a styrene resin, a polyimide resin, can be used.

  In the VCSEL of the first form, the upper part of the mesa structure is protected by the surrounding protective member, so that the possibility that the mesa is physically damaged is low. In addition, since the ohmic electrode (first ohmic electrode) is formed at a position lower than the protective member, the possibility of breakage is similarly low, and physical damage to the mesa structure and the ohmic electrode can be effectively prevented. .

  That is, according to the first embodiment, the lower reflecting mirror, the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are stacked on the semiconductor substrate, and the second cladding layer and the active layer are activated. In the surface emitting laser element (VCSEL) in which the layer, the first cladding layer, and the upper reflector are made of a semiconductor material and processed as a mesa structure, and an ohmic electrode is formed on the upper reflector, the mesa structure A protective member is provided in the periphery, and the protective member is formed by forming a protective layer made of an organic material on a structure made of a semiconductor material similar to the mesa structure, and the height of the protective member is Since it is higher than the upper surface of the ohmic electrode formed on the upper reflecting mirror, the resonator (cladding layer, active layer), the mesa structure including the upper reflecting mirror and the ohmic electrode are effectively protected. thing It can be.

(Second form)
FIG. 3 is a diagram showing a configuration example of a surface emitting laser element (VCSEL) according to the second embodiment of the present invention.

  Referring to FIG. 3, the second mode is that a lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and an upper reflecting mirror are formed on a semiconductor substrate (in this example, a GaAs substrate). The second cladding layer, the active layer, the first cladding layer, and the upper reflector are made of a semiconductor material and processed as a mesa structure, and an ohmic electrode (first ohmic electrode) is formed on the upper reflector. In the surface emitting laser element (VCSEL), a protective member is provided around the mesa structure, and the protective member is made of a semiconductor material and has a configuration different from the configuration of the mesa structure. The height of the protective member is higher than the upper surface of the ohmic electrode (first ohmic electrode) formed on the upper reflecting mirror. Although not shown in FIG. 3, a second ohmic electrode is provided below the GaAs substrate.

  More specifically, in the example of FIG. 3, the protective member has the same structure as the second cladding layer, the active layer, and the first cladding layer of the mesa structure, but corresponds to the upper reflecting mirror of the mesa structure. The protective layer made of a semiconductor material is provided directly on the structure corresponding to the first cladding layer.

  Here, materials such as GaAs, AlGaAs, AlAs, GaInAs, and GaInP can be used as the semiconductor material constituting the protective layer of the protective member.

  Also in the second embodiment, the region where the protection member is formed and the shape of the protection member can be the same as those described in the first embodiment.

  In the VCSEL of the second form, since the upper part of the mesa structure is protected by the surrounding protective member, the possibility that the mesa is physically damaged is low. In addition, since the ohmic electrode (first ohmic electrode) is formed at a position lower than the protective member, the possibility of breakage is similarly low, and physical damage to the mesa structure and the ohmic electrode can be effectively prevented. .

  That is, according to the second embodiment, the lower reflecting mirror, the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are laminated on the semiconductor substrate, and the second cladding layer and the active layer are activated. In the surface emitting laser element (VCSEL) in which the layer, the first cladding layer, and the upper reflector are made of a semiconductor material and processed as a mesa structure, and an ohmic electrode is formed on the upper reflector, the mesa structure A protective member is provided in the periphery, and the protective member is made of a semiconductor material and has a configuration different from the configuration of the mesa structure. The height of the protective member is above the upper reflecting mirror. Since the height is higher than the upper surface of the formed ohmic electrode, the mesa structure including the resonator (cladding layer and active layer) and the upper reflecting mirror and the ohmic electrode can be effectively protected.

(Third form)
FIG. 4 is a diagram showing a configuration example of a surface emitting laser element (VCSEL) according to a third embodiment of the present invention.

  Referring to FIG. 4, the VCSEL of the third form includes a lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, a high reflection layer on a semiconductor substrate (in this example, a GaAs substrate). A contact layer containing impurities of a concentration, and the second cladding layer, the active layer, the first cladding layer, and the contact layer are made of a semiconductor material and processed as a mesa structure, on the contact layer of the mesa structure An upper reflecting mirror made of a semiconductor material or a dielectric material not containing impurities is formed, and an ohmic electrode (first ohmic electrode) is formed on the contact layer. Although not shown in FIG. 4, a second ohmic electrode is provided below the GaAs substrate.

  2 and 3, it is known that the laser light generated in the active layer is absorbed by the carriers (impurities) contained in the upper reflecting mirror, causing a decrease in light output. On the other hand, if the impurity concentration of the upper reflector is reduced in order to reduce the absorption by the carriers, the VCSEL has a high resistance and an increase in heat generation, thereby causing adverse effects such as a decrease in optical output and a shortened device life.

  On the other hand, by using the configuration shown in FIG. 4, these problems can be solved at the same time and the light output can be increased. That is, since the upper reflecting mirror does not contain carriers, the optical output of the VCSEL can be increased.

  Further, in the VCSEL of the third embodiment, a protective member is provided around the mesa structure, and the protective member is formed on a structure made of a semiconductor material similar to the mesa structure. A protective layer made of is formed, and the height of the protective member is higher than the upper surface of the upper reflecting mirror.

  In the VCSEL of the third form, since the upper part of the mesa structure is protected by the surrounding protective member, the possibility that the mesa is physically damaged is low. In addition, since the ohmic electrode (first ohmic electrode) is formed at a position lower than the protective member, the possibility of breakage is similarly low, and physical damage to the mesa structure and the ohmic electrode can be effectively prevented. . In particular, the position of the first ohmic electrode is lower than the configurations of the first and second embodiments shown in FIGS. 2 and 3, and the probability that the first ohmic electrode is damaged can be further reduced.

  The material constituting the upper reflecting mirror may be a semiconductor material or a dielectric material.

  Thus, according to the third embodiment, the lower reflecting mirror, the second cladding layer, the active layer, the first cladding layer, and the contact layer containing a high concentration impurity are stacked on the semiconductor substrate. The second clad layer, the active layer, the first clad layer, and the contact layer are made of a semiconductor material and processed as a mesa structure, and the mesa structure contact layer does not contain an impurity-containing semiconductor material or dielectric. In a surface emitting laser element in which an upper reflecting mirror made of a body material is formed and an ohmic electrode is formed in the contact layer, a protective member is provided around the mesa structure, A protective layer made of a semiconductor material or a dielectric material is formed on a structure made of a semiconductor material similar to the mesa structure, and the height of the protective member is higher than the upper surface of the upper reflecting mirror. Since a high resonator (cladding layer, the active layer), it is possible to effectively protect the mesa structure and the ohmic electrode and the top mirror including the contact layer.

(4th form)
According to a fourth aspect of the present invention, a lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and an upper reflecting mirror are sequentially formed on a semiconductor substrate, and the upper reflecting mirror is formed on the upper reflecting mirror. After forming the protective layer made of an organic material, dry etching and / or wet etching are used to form a mesa structure including the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror, and the mesa structure A method of manufacturing a surface emitting laser element, comprising: a protective member having a height higher than the height of the mesa structure by an amount including the protective layer.

  FIGS. 5A, 5 </ b> B, 6 </ b> A, and 6 </ b> B are diagrams illustrating a manufacturing process example of the fourth embodiment (a process example of manufacturing the VCSEL of the first embodiment).

  5 and 6, first, a lower reflector, an etch stop layer, a second cladding layer, an active layer, a first cladding layer, and an upper reflector are formed on a semiconductor substrate (in this example, a GaAs substrate). Crystals grow sequentially (FIG. 5A).

  Next, after applying a polyimide resin on this, the inside of the broken line (protective member pattern) in FIG. 5B is removed by using a photolithography method or the like, and the polyimide resin is completely removed to form a protective layer. To do.

  Next, after a photoresist is uniformly applied on a substrate patterned with a polyimide resin, a mesa pattern is formed (FIG. 6A).

  Next, after etching the patterned substrate up to the etch stop layer, the previously formed photoresist is completely removed (FIG. 6B).

  Through the steps so far, the mesa structure and the protective member are formed, but the height of the protective member is higher than the mesa structure by the amount of the protective layer. As an etching method, RIE or the like can be used for dry etching. In the case of wet etching, as an etchant to be used, an upper reflecting mirror / resonator is made of a GaAs-based semiconductor material, and an etch stop layer is GaInP In the case where it is constituted, a sulfuric acid-based etchant can be mentioned.

  After these steps, the first form of VCSEL as shown in FIG. 2 can be manufactured by sequentially performing oxidation constriction, insulating film formation, and electrode formation.

  Thus, according to the fourth embodiment, the lower reflecting mirror, the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are sequentially formed on the semiconductor substrate, A mesa structure comprising a second cladding layer, an active layer, a first cladding layer, and an upper reflecting mirror using a dry etching and / or wet etching after forming a protective layer made of an organic material on the reflecting mirror; Since a protective member higher than the height of the mesa structure is formed around the mesa structure so as to include the protective layer, the mesa structure including the resonator (cladding layer, active layer) and the upper reflector and the ohmic electrode It is possible to manufacture a surface emitting laser element (VCSEL) having means for effectively protecting the above.

(5th form)
According to a fifth aspect of the present invention, a lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and a protective layer made of a semiconductor material are sequentially formed on a semiconductor substrate, and a mesa structure is formed. After removing the protective layer in the portion to be formed, a mesa structure composed of the second cladding layer, the active layer, and the first cladding layer and a protective member are formed, and the top surface of the mesa structure has a high height of the protective member. A surface-emitting laser element manufacturing method is characterized in that an upper reflecting mirror having a height equal to or lower than that is formed.

  FIGS. 7A, 7B, 8A, and 8B are diagrams showing an example of a manufacturing process of the fifth embodiment (an example of a process for manufacturing the VCSEL of the second embodiment).

  7 and 8, first, a lower reflecting mirror, an etch stop layer, a second cladding layer, an active layer, a first cladding layer, and a protective layer are sequentially formed on a semiconductor substrate (in this example, a GaAs substrate). Crystal growth occurs (FIG. 7A).

  Next, after a photoresist is uniformly applied to the substrate surface to form a protective member pattern, the protective layer is removed by dry etching or wet etching (FIG. 7B), and then the photoresist is completely removed. . As an etching method, RIE or the like can be used for dry etching. In the case of wet etching, as an etchant to be used, a resonator is made of a GaAs-based semiconductor material, and a protective layer is made of GaInP. In this case, a hydrochloric acid-based etchant can be used.

  Next, a photoresist is uniformly applied to the surface, the protective member and the mesa pattern are removed, and the photoresist is completely removed, and then the first cladding layer, the active layer, and the second cladding layer are dry etched or wet etched. The etch stop layer is removed (FIG. 8A), and then the photoresist is completely removed. As an etching method, RIE or the like can be used for dry etching. In the case of wet etching, as an etchant to be used, a resonator is made of a GaAs-based semiconductor material, and an etch stop layer is made of GaInP. If present, a sulfuric acid-based etchant can be used.

  Next, after uniformly applying a photoresist on the surface of the substrate on which the protective member and the mesa structure are formed and completely removing the photoresist on the mesa structure, the upper reflector made of a semiconductor material is selectively only on the mesa structure. After crystal growth (FIG. 8B), the photoresist is completely removed.

  After these steps, the second embodiment of the VCSEL as shown in FIG. 3 can be manufactured by sequentially performing oxidation constriction, insulating film formation, and electrode formation.

  According to the fifth embodiment, a lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and a protective layer made of a semiconductor material are sequentially formed on a semiconductor substrate, thereby forming a mesa structure. After removing the protective layer in the portion to be formed, a mesa structure composed of the second cladding layer, the active layer, and the first cladding layer and a protective member are formed, and the top surface of the mesa structure has a high height of the protective member. A surface emitting laser device having means for effectively protecting the resonator (cladding layer, active layer), mesa structure including the upper reflector and ohmic electrode is formed. VCSEL) can be manufactured.

(Sixth form)
According to a sixth aspect of the present invention, a lower reflector, a second cladding layer, an active layer, a first cladding layer, and a contact layer are sequentially formed on a semiconductor substrate, and an organic layer is formed on the contact layer. After forming the protective layer made of the material, using dry etching and / or wet etching, a mesa structure including the second cladding layer, the active layer, the first cladding layer, and the contact layer, and around the mesa structure, A protective member that is higher than the height of the mesa structure by an amount including the protective layer is formed, and an upper reflection that does not contain impurities is formed on the mesa structure so that the upper surface is lower than the height of the protective member. A method of manufacturing a surface-emitting laser element characterized by forming a mirror.

  9 (a), 9 (b), 10 (a), 10 (b), and 11 are diagrams showing an example of a manufacturing process of the sixth embodiment (an example of a process for manufacturing a VCSEL of the third embodiment). .

  Referring to FIGS. 9, 10, and 11, first, on a semiconductor substrate (in this example, a GaAs substrate), a lower reflector, an etch stop layer, a second cladding layer, an active layer, a first cladding layer, and a contact. The layers are sequentially crystal-grown (FIG. 9A).

  Next, after a polyimide resin is applied thereon, a protective layer is formed as shown in FIG. 9B by using a photolithography method or the like.

  Next, after uniformly applying a photoresist on a substrate patterned with a polyimide resin, a mesa pattern is formed, a mesa is formed by dry etching or wet etching (FIG. 10A), and an oxidation constriction step is performed. carry out.

  Next, a semiconductor material or dielectric material that does not contain impurities is formed as an upper reflecting mirror material on the substrate on which the mesa structure and the protective member are formed (FIG. 10B).

  Next, an upper reflecting mirror pattern is formed, and the upper reflecting mirror material (ie, semiconductor material or dielectric material) is removed by dry etching or wet etching to form an upper reflecting mirror (FIG. 11). At this time, the semiconductor material or dielectric material on the contact layer must be completely removed in order to ensure electrical connection with the ohmic electrode, but other regions do not necessarily have to be removed.

  After these steps, the insulating film formation and the electrode formation are sequentially performed, whereby the VCSEL of the third form as shown in FIG. 4 can be manufactured.

  According to the sixth embodiment, the lower reflector, the second cladding layer, the active layer, the first cladding layer, and the contact layer are sequentially formed on the semiconductor substrate, and the organic layer is formed on the contact layer. After forming the protective layer made of the material, using dry etching and / or wet etching, a mesa structure including the second cladding layer, the active layer, the first cladding layer, and the contact layer, and around the mesa structure, A protective member that is higher than the height of the mesa structure by an amount including the protective layer is formed, and an upper reflection that does not contain impurities is formed on the mesa structure so that the upper surface is lower than the height of the protective member. Since a mirror is formed, a surface emitting laser device (VCSEL) having a mesa structure including a resonator (cladding layer, active layer), a contact layer, an ohmic electrode, and means for effectively protecting the upper reflecting mirror is manufactured. Rukoto can.

  In the present invention, the first ohmic electrode and the second ohmic electrode are composed of, for example, the same member, but are pads for connecting a contact member that is in direct contact with the VCSEL and an external circuit. The members may be composed of different members. However, in that case, both the contact member and the pad member must be at a height equal to or lower than the protective member.

  In Example 1, the surface emitting laser element (VCSEL) shown in FIGS. 2 (a) and 2 (b) was fabricated by the steps of FIGS. 5 (a), (b), FIGS. 6 (a), and (b).

That is, in Example 1, n-GaAs is used as a substrate, n-AlAs / GaAs is laminated as 35 periods as a lower reflector, GaInP is used as an etch stop layer, and In is used as a second cladding layer. _0.15 Ga _0.85 As _0.6 P _0.4 is used, In _0.2 Ga _0.8 As is used as the active layer, and In _0.15 Ga _0.85 As _0.6 is used as the first cladding layer. P _0.4 was used, and an upper reflecting mirror in which 26 periods of p-Al _0.9 Ga _0.1 As / GaAs were stacked as one period was used. Note that an AlAs layer (not shown) is formed in the first cladding layer.

  A manufacturing method of the VCSEL of Example 1 having such a configuration will be described below. First, an n-GaAs substrate is prepared by cleaning the substrate surface and removing the oxide film. A lower reflector, an etch stop layer, a second cladding layer, an active layer, a first cladding layer, and an upper reflector are sequentially grown on the substrate (FIG. 5A). As a specific method for crystal growth, any method such as a molecular beam epitaxy (MBE) method or a metal organic chemical vapor deposition (MOCVD) method may be used.

  Next, a photosensitive polyimide precursor is applied to the crystal growth surface, and everything is removed except inside the broken line shown in FIG. Thereafter, a photoresist is applied to the surface, the mesa pattern is removed, and the photoresist is completely removed (FIG. 6A), and then etching is performed to the etch stop layer using a sulfuric acid-based etchant to obtain a mesa structure and a protective member. Form.

  Thereafter, the photoresist is eroded and a material that does not erode polyimide is used, and only the photoresist is completely removed (FIG. 6B). As a result, the protective member becomes higher than the mesa structure by the thickness of the polyimide (protective layer).

Next, a part of an AlAs layer (not shown) included in the first cladding layer is oxidized in a water vapor atmosphere to provide a current confinement structure, and then SiO ₂ is deposited on the entire VCSEL surface. The other SiO ₂ is masked, and only SiO _{2 on the} upper surface of the mesa structure is removed using BHF or the like as an etchant.

  Thereafter, a first ohmic electrode is formed on the crystal growth surface by vapor deposition or sputtering. As a specific material of the first ohmic electrode, a material that is not deformed or deteriorated by heat generated from the active layer or the like at the time of driving the VCSEL, such as Au, Pt, Zn, Al, or an alloy thereof is desirable. As the patterning method, any method such as a lift-off method can be used.

  A second ohmic electrode is formed on the back surface of the substrate. The means and materials used at this time include all of those shown at the time of forming the first ohmic electrode.

  Through the above steps, the VCSEL shown in FIG. 2B can be manufactured.

  In Example 2, the surface emitting laser element (VCSEL) shown in FIG. 4 was fabricated by the steps of FIGS. 9A, 9B, 10A, 10B, and 11. FIG.

That is, in Example 2, n-GaAs is used as a substrate, n-AlAs / GaAs is laminated as 35 periods as a lower reflector, GaInP is used as an etch stop layer, and In is used as a second cladding layer. _0.15 Ga _0.85 As _0.6 P _0.4 is used, In _0.2 Ga _0.8 As is used as the active layer, and In _0.15 Ga _0.85 As _0.6 is used as the first cladding layer. P _0.4 was used as the contact layer, p-GaAs was used as the contact layer, TiO ₂ / SiO ₂ was laminated as one period for 12 periods, and GaInP was used as the protective layer. Note that an AlAs layer (not shown) is formed in the first cladding layer.

  A method of manufacturing the VCSEL of Example 2 having such a configuration will be described below. First, an n-GaAs substrate is prepared by cleaning the substrate surface and removing the oxide film. A lower reflecting mirror, an etch stop layer, a second cladding layer, an active layer, a first cladding layer, a contact layer, and a protective layer are sequentially grown on the substrate (FIG. 9A). Specific methods for crystal growth include all the methods shown in Example 1.

  Next, after applying a photoresist on the crystal growth surface and completely removing the photoresist in a region other than the protective member region, the protective layer is etched using a hydrochloric acid-based etchant (FIG. 9B). Remove completely.

  Thereafter, a photoresist is uniformly applied on the surface, and the photoresist in the region other than the mesa pattern is completely removed. Next, a mesa structure and a protective member are formed using a sulfuric acid-based etchant (FIG. 10A), and an oxidation constriction step is performed. At this time, GaInP is exposed on the protective member, and the material is not eroded by the sulfuric acid-based etchant. Therefore, it is not necessary to form a pattern again on the protective member.

Thereafter, 12 periods of TiO ₂ / SiO ₂ are laminated on the surface as an upper reflecting mirror material (FIG. 10B). Examples of the method of laminating TiO ₂ / SiO ₂ include sputtering and vapor deposition. After laminating the upper reflector material, an upper reflector pattern is formed, and the upper reflector is formed by dry etching (FIG. 11). At this time, at least the upper reflector material on the contact layer must be completely removed.

Thereafter, the VCSEL shown in FIG. 4 can be manufactured by performing the first and second ohmic electrode forming steps in the same manner as in the first embodiment.

It is a figure which shows the structural example of a general vertical cavity surface emitting semiconductor laser element (surface emitting laser element (VCSEL)). It is a figure which shows the structural example of the surface emitting laser element (VCSEL) of the 1st form of this invention. It is a figure which shows the structural example of the surface emitting laser element (VCSEL) of the 2nd form of this invention. It is a figure which shows the structural example of the surface emitting laser element (VCSEL) of the 3rd form of this invention. It is a figure which shows the example of a manufacturing process of 4th form (process example of manufacturing VCSEL of 1st form). It is a figure which shows the example of a manufacturing process of 4th form (process example of manufacturing VCSEL of 1st form). It is a figure which shows the example of a manufacturing process of 5th form (process example of manufacturing VCSEL of a 2nd form). It is a figure which shows the example of a manufacturing process of 5th form (process example of manufacturing VCSEL of a 2nd form). It is a figure which shows the example of a manufacturing process of 6th form (process example of manufacturing VCSEL of 3rd form). It is a figure which shows the example of a manufacturing process of 6th form (process example of manufacturing VCSEL of 3rd form). It is a figure which shows the example of a manufacturing process of 6th form (process example of manufacturing VCSEL of 3rd form).

Claims (3)

A lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and an upper reflecting mirror are stacked on a semiconductor substrate, and the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are stacked. Is made of a semiconductor material, processed as a mesa structure, and in a surface emitting laser element (VCSEL) in which an ohmic electrode is formed on an upper reflecting mirror, a protective member is provided around the mesa structure, The protective member is formed by forming a protective layer made of an organic material on a laminated structure made of the same semiconductor material as the second clad layer, active layer, first clad layer, and upper reflector of the mesa structure, the height of the protective member, by the protective layer is formed, a surface-emitting laser element, characterized in that has a higher than the upper surface of the ohmic electrodes formed on the upper reflector . A lower reflecting mirror, a second cladding layer, an active layer, a first cladding layer, and an upper reflecting mirror are stacked on a semiconductor substrate, and the second cladding layer, the active layer, the first cladding layer, and the upper reflecting mirror are stacked. Is made of a semiconductor material, processed as a mesa structure, and in a surface emitting laser element (VCSEL) in which an ohmic electrode is formed on an upper reflecting mirror, a protective member is provided around the mesa structure, The protective member is formed by forming a protective layer made of a semiconductor material on a laminated structure made of the same semiconductor material as the second clad layer, the active layer, and the first clad layer of the mesa structure. The surface-emitting laser element, wherein the height is higher than an upper surface of an ohmic electrode formed on the upper reflecting mirror by forming the protective layer . A lower reflector, a second cladding layer, an active layer, a first cladding layer, and a contact layer containing a high concentration of impurities are stacked on the semiconductor substrate, and the second cladding layer, the active layer, and the first layer are stacked. The cladding layer and the contact layer are made of a semiconductor material and processed as a mesa structure. On the contact layer of the mesa structure, an upper reflecting mirror made of a semiconductor material or a dielectric material not containing impurities is formed, and In the surface emitting laser element in which an ohmic electrode is formed in the contact layer, a protective member is provided around the mesa structure, and the protective member includes a second cladding layer, an active layer, and the mesa structure . the first cladding layer, on the laminated structure composed of the same semiconductor material as the contact layer, a protective layer made of a semiconductor material or a dielectric material is formed is formed, the height of the protective member Wherein by a protective layer is formed, the upper surface of the upper reflector, and a surface-emitting laser element characterized by being a higher than the upper surface of the ohmic electrode.

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