JP2016025171A - Surface-emitting laser device and method of manufacturing surface-emitting laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-emitting laser device which can be more simply driven at a low current.SOLUTION: Provided is a surface-emitting laser device including: an insulating heat sink in which a metal film pattern is formed on the surface; a surface-emitting laser array which is joined to the metal film pattern via a bond; a groove which is formed so as to reach the heat sink from the surface opposite to a composition plane with the metal film pattern in the surface-emitting laser array and separates the surface-emitting laser array to at least two surface-emitting laser arrays electrically insulated; and a wire which electrically serially-connects the at least two surface-emitting laser arrays separated by the groove.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface emitting laser device and a method for manufacturing the surface emitting laser device.

  Conventionally, a surface emitting laser array in which a plurality of surface emitting laser elements are two-dimensionally arranged is used as a light source for a high-power laser.

  This surface-emitting laser array is often configured to electrically connect a plurality of surface-emitting laser elements in parallel because the manufacturing method is simple. For this reason, as the output of the surface emitting laser array is increased, the driving current of the surface emitting laser array is increased, the amount of heat generation is increased, and the reliability and life characteristics of the surface emitting laser element may be deteriorated.

  Therefore, conventionally, a plurality of series connection elements in which a plurality of surface emitting laser elements are connected in series are provided, and the driving current of the surface emitting laser array is reduced by electrically connecting the plurality of series connection elements in parallel. (For example, refer to Patent Document 1).

  However, the conventional technique described above has a problem that the manufacturing process is complicated because the p-side electrode and the n-side electrode are formed on the surface side of the substrate.

  Accordingly, an object of the present invention is to provide a surface emitting laser device that can be driven more easily at a low current.

  In one proposal, an insulating heat sink having a metal film pattern formed on a surface thereof, a surface-emitting laser array bonded to the metal film pattern via a bonding agent, and the metal film pattern in the surface-emitting laser array And a groove that separates the surface-emitting laser array into at least two surface-emitting laser arrays that are electrically insulated from each other, and is separated by the groove. There is also provided a surface emitting laser device having a wire for electrically connecting at least two surface emitting laser arrays in series.

  According to one aspect, it is possible to provide a surface-emitting laser device that can be driven with a low current more easily.

The figure which illustrates schematic structure of the surface emitting laser apparatus which concerns on 1st Embodiment. XX sectional drawing of FIG. 1 is a cross-sectional view illustrating a schematic configuration of a surface emitting laser element according to a first embodiment. The figure for demonstrating the effect | action and effect of the surface emitting laser apparatus which concerns on 1st Embodiment. The figure which illustrates other schematic structures of the surface emitting laser apparatus which concerns on 1st Embodiment. The figure which illustrates schematic structure of the surface emitting laser apparatus which concerns on 2nd Embodiment. XX sectional drawing of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[First Embodiment]
(Configuration of surface emitting laser device)
First, an example of a schematic configuration of the surface emitting laser device according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram illustrating a schematic configuration of the surface emitting laser device according to the first embodiment. 2 is a cross-sectional view taken along line XX of FIG.

  As shown in FIG. 1, the surface-emitting laser device 100 includes a heat-radiating plate 101 made of an insulating material having a metal film pattern 102 for flowing a current on the surface, and a surface-emitting laser including a plurality of surface-emitting laser elements 200. And a laser array 103. As shown in FIG. 2, the metal film pattern 102 formed on the heat radiating plate 101 and the surface emitting laser array 103 are bonded together by a bonding agent 104.

  The surface emitting laser device 100 is formed so as to reach the heat radiating plate 101 from the surface opposite to the joint surface with the metal film pattern 102 in the surface emitting laser array 103, and the surface emitting laser array 103 is electrically insulated. Further, it has a groove A that separates into at least two surface emitting laser arrays 103a and 103b, and wires 105a and 105b that electrically connect the two surface emitting laser arrays 103a and 103b in series.

  More specifically, the metal film pattern 102 connected to the lower electrode 212 of the surface emitting laser array 103a and the metal film pattern 102 connected to the upper electrode 211 of the surface emitting laser array 103b and the wire 105b are connected to the wire 105a. Connected by. That is, the surface emitting laser array 103a and the surface emitting laser array 103b are connected in series. The lower electrode 212 and the upper electrode 211 will be described later.

  Further, the common p-side electrode terminal 106 is connected to the metal film pattern 102 connected to the upper electrode 211 of the surface emitting laser array 103a by the wire 105c. A common n-side electrode terminal 107 is connected to the metal film pattern 102 connected to the lower electrode 212 of the surface emitting laser array 103b.

  The surface emitting laser device 100 operates by applying a voltage between the common p-side electrode terminal 106 and the common n-side electrode terminal 107.

  Next, the surface emitting laser element 200 constituting the surface emitting laser array 103 will be described with reference to FIG. FIG. 3 is a cross-sectional view illustrating a schematic configuration of the surface emitting laser element according to the first embodiment. In the surface-emitting laser array 103 according to the first embodiment, a plurality of surface-emitting laser elements 200 are formed in an array as shown in FIG. 1, but in FIG. For easy understanding of the configuration, a cross-sectional view of one element is shown. In this specification, the laser light emission direction is the upper direction in FIG.

  The surface emitting laser element 200 has an oscillation wavelength of 808 nm band, and includes a substrate 201, a buffer layer 202, a lower semiconductor DBR 203, a lower spacer layer 204, an active layer 205, an upper spacer layer 206, an upper semiconductor DBR 207, and a selectively oxidized layer 208 ( An oxidized region 208a, a non-oxidized region 208b), a contact layer 209, a protective layer 210, an upper electrode 211, a lower electrode 212, and the like.

  The lower spacer layer 204, the active layer 205, the upper spacer layer 206, the upper semiconductor DBR 207, the selectively oxidized layer 208, and the contact layer 209 in the surface emitting laser element 200 form a mesa.

  The substrate 201 is made of n-GaAs.

  The buffer layer 202 is laminated on the upper surface of the substrate 201 and is a layer made of n-GaAs.

The lower semiconductor DBR 203 is stacked on the upper surface of the buffer layer 202, and includes a low refractive index layer made of n-Al _0.9 Ga _0.1 As and n-Al _0.3 Ga _0.7 As. A pair of high refractive index layers starts with n-Al _0.9 Ga _0.1 As, and 40.5 pairs are stacked.

  Between each refractive index layer, in order to reduce an electrical resistance, a composition gradient layer having a thickness of 20 nm in which the composition is gradually changed from one composition to the other composition is provided. Each refractive index layer is designed to include half of the thickness of the adjacent composition gradient layer and to have an optical thickness of λ / 4 with respect to the oscillation wavelength λ. When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n (where n is the refractive index of the medium of the layer).

The lower spacer layer 204 is laminated in the upper direction of the lower semiconductor DBR 203 and is a layer made of non-doped Al _0.6 Ga _0.4 As.

The active layer 205 is stacked in the upper direction of the lower spacer layer 204 and is an active layer having a triple quantum well structure made of Al _0.05 Ga _0.95 As / Al _0.3 Ga _0.7 As.

The upper spacer layer 206 is laminated in the upper direction of the active layer 205 and is a layer made of non-doped Al _0.6 Ga _0.4 As, and the oscillation wavelength is designed to be 808 nm.

  A portion composed of the lower spacer layer 204, the active layer 205, and the upper spacer layer 206 is also called a resonator structure, and the thickness thereof is set to be an optical thickness of one wavelength. The active layer 205 is provided at the center of the resonator structure, which is a position corresponding to the antinode in the standing wave distribution of the electric field, so that a high stimulated emission probability can be obtained.

The upper semiconductor DBR 207 is laminated in the upper direction of the upper spacer layer 206, and has a low refractive index layer made of p-Al _0.9 Ga _0.1 As and a high refractive index made of p-Al _0.3 Ga _0.7 As. It has 25 pairs of layers. A composition gradient layer is provided between the refractive index layers. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the thickness of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 207, a selective oxidation layer 208 made of AlAs is inserted with a thickness of 30 nm.

  The contact layer 209 is laminated in the upper direction of the upper semiconductor DBR 207 and is a layer made of p-GaAs.

  Note that a structure in which a plurality of semiconductor layers are stacked on the substrate 201 in this manner is also referred to as a “stacked body” for convenience in the following.

The protective layer 210 is a layer made of SiN, SiON, or SiO ₂ that is laminated in a region excluding the laser light emitting portion, that is, a part in the upper direction of the contact layer 209, the side surface of the mesa, and the upper direction of the lower semiconductor DBR 203. It is.

  The upper electrode 211 is a p-side electrode and is a multilayer film (metal film) formed of Ti / Pt / Au formed in the upper direction of the contact layer 209 and the upper direction of the protective layer 210.

  The lower electrode 212 is an n-side electrode and is a multilayer film (metal film) made of AuGe / Ni / Au formed on the lower surface of the substrate 201.

(Method for manufacturing surface-emitting laser device)
Next, a method for manufacturing the surface emitting laser device according to the first embodiment will be described.

First, the above laminate is formed by crystal growth by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxial growth (MBE). Here, an example using the MOCVD method is shown. Further, here, trimethylaluminum (TMA) and trimethylgallium (TMG) are used as Group III materials, and arsine (AsH ₃ ) is used as Group V materials. Further, carbon tetrabromide (CBr ₄ ) is used as a p-type dopant material, and hydrogen selenide (H ₂ Se) is used as an n-type dopant material.

  Subsequently, a square resist pattern having a side of 25 μm corresponding to a desired mesa shape is formed in an array on the surface of the laminate by lithography.

  Subsequently, a square pillar mesa is formed by ICP dry etching using the resist pattern as a photomask, and the resist pattern is removed.

  Subsequently, an oxidation process is performed using the stacked body on which the mesa is formed as an object to be oxidized. Here, as shown in FIG. 3, aluminum (Al) in the selective oxidation layer 208 is selectively oxidized from the outer peripheral portion of the mesa. Then, the non-oxidized region 208b surrounded by the Al oxidized region 208a is left in the center of the mesa. As a result, an oxidized constriction structure is formed that restricts the drive current path of the light emitting part to only the central part of the mesa. The non-oxidized region 208b is a current passage region (current injection region).

  Subsequently, a resist pattern is formed by lithography so as to expose the outer peripheral groove forming portion and a region for electrically separating the array in a later step, and ICP dry etching is performed on the laminated body that has been oxidized. Groove A is formed using a method, and the resist pattern is removed.

  Subsequently, the laminate is placed in a heating chamber and held in a nitrogen atmosphere at a temperature of 380 to 400 ° C. for 3 minutes. As a result, a natural oxide film formed by oxygen or water adhering to the surface in the atmosphere or a small amount of oxygen or water in the heat treatment chamber becomes a stable passive film by heat treatment in a nitrogen atmosphere.

Subsequently, a protective layer 210 made of SiN, SiON, or SiO ₂ is formed by using a chemical vapor deposition method (CVD method).

  Subsequently, a window for the p-side electrode contact is opened on the mesa. Here, after masking with a photoresist, the opening at the top of the mesa was exposed to remove the photoresist at that portion, and the protective layer 210 was etched and opened with BHF. At the same time, the protective layer in the scribe region on the bottom surface of the groove A is also removed.

  Subsequently, a square resist pattern having a side of 10 μm and a resist pattern for connecting the electrode pad and the light emitting portion are formed in a region to be a laser beam emitting portion on the mesa, and a p-side electrode material is deposited. As the electrode material on the p side, a multilayer film made of Ti / Pt / Au is used.

  Subsequently, the electrode material of the laser beam emitting portion is lifted off to form the p-side electrode (upper electrode 211).

  Subsequently, after polishing the back side of the substrate 201 to a predetermined thickness (for example, about 100 μm), an n-side electrode (lower electrode 212) is formed. Here, a multilayer film made of AuGe / Ni / Au is used as the n-side electrode material.

  Subsequently, ohmic conduction is established between the upper electrode 211 and the lower electrode 212 by annealing. Thereby, the mesa becomes a light emitting part.

  Subsequently, it is divided into surface emitting laser array chips by scribing and braking.

  Subsequently, the radiator plate 101 made of an aluminum nitride (AlN) material and the surface emitting laser array chip are bonded to each other on a hot plate heated to 300 to 350 ° C. by a bonding agent 104 containing gold tin (AuSn). Here, the heat sink 101 made of an AlN material has an Au pattern with a thickness of 1 μm for flowing current on the surface, and AuSn is formed on the surface to form a 3 μm film in a region where the chip is bonded. . Bonding is performed while applying an appropriate load in order to obtain good bonding on the entire surface of the chip. When bonded by a material containing AuSn, flux is not required and there is an effect of reducing electric resistance.

  Subsequently, the region in which the groove portion A is formed is separated so as to reach the heat radiating plate 101 by dicing.

  Subsequently, wires 105a, 105b, and 105c are formed so as to be connected in series.

  By the above method, the surface emitting laser device 100 shown in FIGS. 1 and 2 can be manufactured.

(Action / Effect)
Next, operations and effects of the surface emitting laser device and the method of manufacturing the surface emitting laser device according to the first embodiment will be described.

  In the surface-emitting laser device according to the first embodiment, a surface-emitting laser array in which a plurality of surface-emitting laser elements are connected in parallel is separated into at least two surface-emitting laser arrays by a groove, and the separated surface-emitting laser array is It has the structure electrically connected in series by the wire. For this reason, it is possible to drive at a lower current compared to a surface emitting laser device in which a plurality of conventional surface emitting laser elements are connected in parallel.

  Moreover, according to the surface emitting laser device according to the first embodiment, the n-side electrode is formed by forming a metal film on the back side of the substrate and performing annealing. For this reason, the step of exposing the contact layer by etching or the like, which is necessary when an n-side electrode is formed on the surface side of the substrate and a plurality of surface-emitting laser elements are connected in series, is unnecessary. As a result, the surface emitting laser device can be more easily manufactured.

  Further, according to the surface emitting laser device according to the first embodiment, the surface emitting laser array is separated by dicing or the like after the surface emitting laser array is joined to the heat sink. For this reason, a plurality of surface emitting laser arrays can be accurately arranged at desired positions.

  Next, for comparison with the surface-emitting laser device according to the first embodiment, a surface-emitting laser device in which a plurality of surface-emitting laser arrays separated in advance are separately joined to a heat sink will be described with reference to FIG. explain. FIG. 4 is a diagram for explaining the operation and effect of the surface emitting laser device according to the first embodiment.

  As shown in FIG. 4, the surface emitting laser device 400 includes a heat radiating plate 401, a metal film pattern 402, and a surface emitting laser array 403. In the surface emitting laser device 400 shown in FIG. 4, the surface emitting laser arrays 403a and 403b separated into two in advance are separately joined to the heat radiating plate 401, so that the upper and lower surfaces of the two surface emitting laser arrays 403a and 403b are It is difficult to improve the accuracy of left and right positions and parallelism.

  As described above, according to the surface emitting laser device and the method for manufacturing the surface emitting laser device according to the first embodiment, it is possible to provide a surface emitting laser device that can be driven with a low current more easily.

  In the first embodiment, the surface-emitting laser device having the surface-emitting laser array in which a plurality of surface-emitting laser elements are arranged in a quadrangular shape has been described. However, the present invention is not limited in this respect.

  For example, as shown in FIG. 5, a surface emitting laser device having a surface emitting laser array 103A in which a plurality of surface emitting laser elements are arranged in a circle and separated into two surface emitting laser arrays 103a and 103b by a groove A. 100A may be sufficient. The surface emitting laser array 103 </ b> A is bonded to the metal film pattern 102 formed on the heat radiating plate 101 via a bonding agent 104. When the surface emitting laser array 103A in which a plurality of surface emitting laser elements are arranged in a circle is used, the laser can be efficiently incident on the circular condenser lens, so that the laser beam is collected without wasting the output. be able to.

  Moreover, although 1st Embodiment demonstrated the form which joins the metal film pattern and surface emitting laser array which were formed in the heat sink using the bonding agent which consists of material containing AuSn, this invention is in this point. It is not limited. As the bonding agent, for example, paste solder can be used. When paste solder is used as a bonding agent, there is an advantage that handling is easy.

  Moreover, although 1st Embodiment demonstrated the form using the heat sink which consists of AlN material, this invention is not limited in this point. As the heat sink, for example, a heat sink made of a diamond material can be used. When a diamond material is used as the heat radiating plate, the thermal conductivity is particularly good, and the heat radiating effect is greatly improved as compared with the case where an AlN material is used.

  However, since the thermal expansion coefficient difference between the diamond material and GaAs is large, if the heat sink and the surface emitting laser array are bonded using a bonding agent having a small stress relaxation effect such as AuSn, the stress between them is reduced. And the surface emitting laser array may be damaged. For this reason, when using a diamond material as a heat sink, it is preferable to use a material containing a soft metal such as indium (In) as a bonding agent.

  When a material containing In is used as the bonding agent, since In is a soft metal, stress between the heat sink after the bonding and the surface emitting laser array can be absorbed. That is, it becomes possible to join materials having a large difference in thermal expansion coefficient.

When using In as a bonding agent, first, for example, a heat sink made of a diamond material having a pattern formed of Au with a 5 μm-thick In thin film formed on the surface and a surface emitting laser array are combined with H ₂ and N ₂ to 150-200 ° C. in a mixed atmosphere. Subsequently, an appropriate load is applied to the surface emitting laser array to join the Au pattern formed on the heat sink and the surface emitting laser array.

  In the first embodiment, the mode using a surface emitting laser element having an oscillation wavelength of 808 nm has been described. However, the present invention is not limited in this respect, and the wavelength band absorbed by the solid-state laser, etc. May be changed.

  In the first embodiment, the surface-emitting laser device has been described as having one groove portion that separates the surface-emitting laser array into two electrically insulated surface-emitting laser arrays. It is not limited. The surface emitting laser device may have a form having a groove for separating the surface emitting laser array into at least two or more surface emitting laser arrays. Further, the shape and quantity of the groove are not limited.

[Second Embodiment]
(Configuration of surface emitting laser device)
Next, a surface emitting laser apparatus according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a diagram illustrating a schematic configuration of the surface emitting laser device array according to the second embodiment. 7 is a cross-sectional view taken along line XX of FIG.

  The surface-emitting laser device according to the second embodiment includes one microlens array optically corresponding to the surface-emitting laser array in the upper direction of the two surface-emitting laser arrays described in the first embodiment. This is different from the surface emitting laser device according to the first embodiment.

  The surface emitting laser apparatus according to the second embodiment has the same configuration as the surface emitting laser apparatus according to the first embodiment except for the above differences. For this reason, in the following description, it demonstrates focusing on the point which is different from 1st Embodiment.

  As shown in FIG. 6, the surface emitting laser device 100B includes one surface emitting laser array 103a, 103b optically corresponding to the upper direction of the surface emitting laser arrays 103a, 103b separated into two by the groove A. A microlens array 108 is included.

  Since other configurations are the same as those in the first embodiment, description thereof is omitted.

(Method for manufacturing surface-emitting laser device)
Next, a method for manufacturing the surface emitting laser device according to the second embodiment will be described.

  First, from the formation of the laminated body to the formation of the wires 105a, 105b, and 105c by the same method as in the first embodiment.

  Subsequently, the position of the microlens array 108 is adjusted so as to match the position of the surface emitting laser element 200, and attached using an ultraviolet curable resin.

  By the above method, the surface emitting laser device 100B shown in FIGS. 6 and 7 can be manufactured.

(Action / Effect)
Next, operations and effects of the surface emitting laser device and the surface emitting laser device manufacturing method according to the second embodiment will be described.

  Since the surface emitting laser device according to the second embodiment includes the same configuration as the surface emitting laser device according to the first embodiment, the same operations and effects as the surface emitting laser device according to the first embodiment are exhibited.

  In addition, according to the surface emitting laser device according to the second embodiment, since a plurality of surface emitting laser arrays can be accurately arranged at desired positions, it is not necessary to provide a microlens array for each surface emitting laser array. . That is, alignment (positioning) of a plurality of surface emitting laser arrays is possible with one microlens array. For this reason, the frequency | count of performing the alignment operation | work of a micro lens array can be reduced. As a result, the manufacturing process can be simplified, the manufacturing cost can be reduced, and the like.

  As described above, according to the surface emitting laser device and the method for manufacturing the surface emitting laser device according to the second embodiment, it is possible to provide a surface emitting laser device that can be driven with low current more easily.

  The surface emitting laser device and the method for manufacturing the surface emitting laser device have been described above by the embodiments. However, the present invention is not limited to the above embodiments, and various modifications and improvements can be made within the scope of the present invention. is there.

100, 100A, 100B Surface emitting laser device 101 Heat sink 102 Metal film pattern 103 Surface emitting laser array 104 Bonding agent 105a, 105b, 105c Wire 108 Micro lens array A Groove

JP 2012-028412 A

Claims (7)

An insulating heat sink with a metal film pattern formed on the surface;
A surface emitting laser array bonded to the metal film pattern via a bonding agent;
The surface-emitting laser array is formed so as to reach the heat radiating plate from the surface opposite to the joint surface with the metal film pattern, and the surface-emitting laser array is electrically insulated from at least two surface-emitting laser arrays. A groove to be separated;
A wire electrically connecting in series at least two surface emitting laser arrays separated by the groove,
Surface emitting laser device. The heat sink is made of aluminum nitride.
The surface emitting laser device according to claim 1. The bonding agent is made of a material containing gold tin,
The surface emitting laser device according to claim 1. The heat sink is made of a diamond material.
The surface emitting laser device according to claim 1. The bonding agent is made of a material containing indium,
The surface emitting laser device according to claim 4. A microlens array disposed at a position optically corresponding to the surface emitting laser array separated into at least two by the groove portion;
The surface-emitting laser device according to claim 1. Bonding the surface emitting laser array to the metal film pattern formed on the surface of the heat sink using a bonding agent;
The heat-radiating plate is reached from the surface opposite to the bonding surface of the surface-emitting laser array bonded to the metal film pattern, and the surface-emitting laser array is separated into at least two surface-emitting laser arrays that are electrically insulated. Forming a groove,
Electrically connecting in series at least two surface emitting laser arrays separated by the groove with a wire,
Manufacturing method of surface emitting laser device.

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