JP2007059672A - Vertical cavity surface-emitting semiconductor laser array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical cavity surface-emitting semiconductor laser which can control the transversal mode of a laser beam while realizing compatibility among a reduced spread angle, a high output, and a low resistance. <P>SOLUTION: A VCSEL (vertical cavity surface emitting laser) 100 has a semiconductor substrate 102 made of n-type lower DBR (distributed bragg reflector) layers 106, an active region 108, and p-type upper DBR layers 110, which are sequentially laminated to form a resonator together therewith; an upper electrode 118 provided on the upper DBR layers 110 and having an opening 120 forming an exit region of a laser beam generated in the active region 108; a current-path narrowing layer 114 having an oxidation region 114a formed at a peripheral edge of a current path provided between the upper electrode 118 and the lower DBR layers 106; and a semi-transparent electrode 122 electrically connected to the upper electrode 118, and having an opening 124 more inside than the opening 120. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface emitting semiconductor laser (Vertical-Cavity Surface-Emitting Laser diode, hereinafter referred to as a VCSEL), and more particularly to laser beam transverse mode control.

  A VCSEL is a laser diode that emits light from the surface of a semiconductor substrate, has a lower drive current than a surface emitting laser diode, can be inspected at the wafer level, and can be easily formed into a two-dimensional array. It has the feature of being. For this reason, it is used as a light source for optical information processing and optical communication, or as a light source for a data storage device that uses light.

  The basic configuration of the VCSEL is, for example, as shown in FIG. 17, a p-type upper multilayer reflector that forms a resonator together with the n-type lower multilayer reflector 12, the active region 14, and the lower multilayer reflector 12. N-type semiconductor substrate 10 in which 16 are sequentially stacked, and an upper electrode provided on the upper multilayer reflector 16 and having an opening 18 for forming an emission region of the laser light generated in the active region 14 20, a current confinement region 22 provided between the upper electrode 20 and the lower multilayer-film reflective mirror 12 and formed by insulating the peripheral portion of the current path, and a lower electrode 24 formed on the back surface of the substrate. Contains. A mesa is formed on the substrate from the upper multilayer reflector 16 to a part of the lower multilayer reflector 12, and a part of the bottom, side, and top of the mesa is covered with an interlayer insulating film 26. At the top of the mesa, a contact hole is formed in the interlayer insulating film 26, and the annular upper electrode 20 is connected to the uppermost contact layer of the upper multilayer reflector 16 through the contact hole. The current confinement portion 22 is made of a material such as p-type AlAs, and an oxide region 22a, which is an insulating region, is formed on the outer edge thereof.

  The fundamental transverse mode oscillation in the VCSEL occurs at the center of the optical waveguide (close to the optical axis), and the high-order transverse mode oscillation occurs at a position vertically separated from the optical axis. Therefore, in order to use the VCSEL as a light source for an optical transmission system or the like, it is necessary to control the oscillation transverse mode. That is, it is desirable to reduce the width and divergence angle (FFP) of the oscillation spectrum wavelength by controlling the oscillation transverse mode.

  In the VCSEL shown in FIG. 17 described above, the transverse mode can be controlled by making the diameter D1 of the circular opening of the conductive region surrounded by the oxidized region of the current confinement portion 22 smaller. When the diameter D1 is smaller than the diameter D2 of the opening of the upper electrode 20 (D2> D1), there is a problem that the resistance of the current path increases and the light output decreases.

  Several proposals have been made to avoid such problems. Patent Document 2 discloses an optical loss of a resonator in a higher-order transverse mode of laser light and an optical loss of the resonator in a fundamental transverse mode of laser light based on the reflectance of the resonator in a region corresponding to the p-side electrode of the VCSEL. The diameter of the opening and the diameter of the opening of the current constriction are determined so that the difference between the current and the current confinement becomes larger. Preferably, as shown in FIG. 18, the diameter D2 of the opening 18 of the upper electrode 20 is made smaller than the diameter D1 of the opening of the conductive region of the current constriction 22 (D2 <D1), Generation | occurrence | production is suppressed and the resistance of a current path is reduced simultaneously.

  In Patent Document 3, as shown in FIG. 19, a transparent layer 30 made of a dielectric is formed inside the opening 18 of the upper electrode 20 on the mesa. An opening is formed in the transparent layer 30, and the diameter D3 of the opening is smaller than the diameter D2 of the opening of the upper electrode 20. By making the diameter of the opening D3 <D1 <D2, the oscillation transverse mode of the laser beam can be controlled.

JP 2001-210908 A JP 2002-208755 A JP 2001-156395 A

  In the VCSEL shown in FIG. 18 described above, an opaque electrode ring is used, and the diameter D2 of the opening is made smaller than the diameter D1 of the opening of the current confinement portion 22. As a result, the mode can be lowered and the spread angle can be suppressed, but on the other hand, because of the relationship D2 <D1, the laser light generated in the active layer is reflected at the interface with the upper electrode 20, There is a problem that the light output decreases.

  Further, the VCSEL shown in FIG. 19 has the transparent layer 30 made of a dielectric disposed inside the opening of the upper electrode 20, so that the laser light generated in the active layer is output through the transparent layer 30, thereby Therefore, it is possible to achieve both suppression of the divergence angle and high output by lowering the mode. However, since the upper electrode 20 is located outside the opening (oxidation aperture) of the current confinement part 22 (in the direction perpendicular to the optical axis), there is a problem that the resistance of the current path increases. This is because the lateral resistance of the multilayer reflector (DBR) of the resonator is high. Therefore, the conventional VCSEL still has the problems of reducing the spread angle (lowering the mode), achieving higher output and lowering the resistance.

  An object of the present invention is to provide a surface-emitting type semiconductor laser capable of performing transverse mode control of laser light while achieving all of reduction in divergence angle, high output, and low resistance, and a method for manufacturing the same.

  The surface emitting semiconductor laser according to the present invention includes a first conductive type lower multilayer reflector, an active region, and a second conductive type upper multilayer reflector that constitutes a resonator together with the lower multilayer reflector in order. A semiconductor substrate, a first upper electrode provided on the upper multilayer reflector and having a first opening for emitting laser light generated in the active region; and a first upper electrode; A current confinement region provided between the lower multilayer reflector and insulating the peripheral portion of the current path, and electrically connected to the first upper electrode, inside the first opening And a second upper electrode that covers a part of the upper multilayer-film reflective mirror, and the second upper electrode is made of a conductive and light-transmissive material.

  Preferably, a second opening having a smaller diameter than the first opening is formed in the second upper electrode, and a part of the upper multilayer-film reflective mirror is exposed by the second opening. The second upper electrode is preferably in ohmic contact with the contact layer that is the uppermost layer of the upper multilayer-film reflective mirror.

  The second upper electrode may be a translucent electrode. For example, the translucent electrode has a light attenuation factor of at least 50% or a light transmittance of at least 50%. The second upper electrode can be composed of a thin film metal. As the thin film metal, a multilayer structure of Cr / Au or ITO can be used.

  Preferably, the diameter of the third opening defining the current path of the current constriction is larger than the diameter of the second opening. Thereby, generation | occurrence | production of a higher mode can be suppressed. Further, the diameter of the third opening is approximately equal to the diameter of the first opening.

  According to the present invention, the second upper electrode electrically connected to the first upper electrode covers a part of the portion exposed by the first opening, and the second upper electrode Is made of a material having electrical conductivity and light transmission, higher order modes are suppressed, and the spread angle is reduced by lowering the mode. At the same time, since the second upper electrode is light transmissive, a part of the laser light is transmitted through the second upper electrode, so that a reduction in output is suppressed, and the second upper electrode has conductivity. Therefore, the resistance of the current path can be reduced.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

  FIG. 1A is a schematic plan view of a VCSEL according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along line XX. In the VCSEL 100, an n-type lower DBR (Distributed Bragg Reflector) layer 106, an active region 108, and a p-type upper DBR layer are formed on an n-type GaAs semiconductor substrate 104 having an n-side lower electrode 102 formed on the back surface. Semiconductor thin films are deposited in the order of 110. The uppermost layer of the upper DBR layer 110 is a p-type GaAs contact layer 112, and the lowermost layer is a current confinement layer 114 made of p-type AlAs.

  A cylindrical mesa M is formed on the substrate from the upper DBR layer 110 to a part of the lower DBR layer 102. The current confinement layer 114 includes an oxidized region 114a that is oxidized from the side surface of the mesa toward the inside by a certain distance, and the oxidized region 114a defines an opening that is a circular conductive region that reflects the outer shape of the mesa. The The diameter D1 of this opening is about 12 μm.

  A part of the bottom, side, and top of the mesa M is covered with an interlayer insulating film 116. A contact hole for exposing the contact layer 112 is formed in the interlayer insulating film 116 at the top of the mesa, and an annular p-side upper electrode 118 that is electrically connected to the contact layer 112 through the contact hole is formed. ing. The upper electrode 118 is composed of, for example, a laminate of Ti and Au, and the film thicknesses thereof are 0.03 μm and 1.0 μm, respectively. A circular opening 120 is formed at the center of the upper electrode 118 so as to be aligned with the opening of the current confinement layer 114. The diameter D2 of the opening 120 is about 12 μm.

  Furthermore, in this embodiment, an annular translucent electrode 122 electrically connected to the upper electrode 118 is formed. The translucent electrode 122 is, for example, a thin film metal in which Cr having a film thickness of 5 nm and Au having a film thickness of 20 nm are stacked, and has conductivity and light transmission. Preferably, it transmits at least 50% of the laser light having a wavelength generated in the active region of the VCSEL 100, or has an attenuation factor of 50% or less of the laser light. A circular opening 124 is formed at the center of the semitransparent electrode 122 so as to be aligned with the opening of the current confinement layer 114. The diameter D3 of the opening 124 is about 10 μm. As a result, the translucent electrode 122 is formed on the upper electrode 118 so that the opening 124 is located inside the opening 120 and covers a part of the contact layer 112 exposed by the opening 120. The translucent electrode 122 is preferably ohmically connected to the contact layer 112 in a region inside the opening 120.

  When a forward voltage is applied between the lower electrode 102, the upper electrode 118, and the translucent electrode 122 and the drive current exceeds a threshold value, laser light is generated from the active region 108. Laser light is emitted in the direction perpendicular to the substrate from the openings 120 and 124 at the top of the mesa M along the optical axis (approximate to the center of the mesa in the axial direction). At this time, the fundamental transverse mode of the laser light is generated in the vicinity of the optical axis, and a higher-order mode is generated in a direction away from the optical axis. However, the higher-order mode light is suppressed by optical loss due to the translucent electrode 122. As a result, the mode is lowered and the spread angle is suppressed. Furthermore, the light transmittance of the translucent electrode 122 does not completely shield the laser light, but a part of the laser light is transmitted through the translucent electrode 122, so that a reduction in light output is suppressed. Furthermore, since the diameter D3 of the opening of the semitransparent electrode 122 has a relationship of D3 <D2 = D1, the semitransparent electrode 122 can function as an electrode facing the current confinement layer 114. Thereby, the resistance of the current path of the upper DBR layer 110 can be reduced.

  FIG. 2 is a graph comparing the IL characteristics of the VCSEL of this example with a conventional VCSEL. The horizontal axis represents the current I, and the vertical axis represents the light output L. A curve A shows the characteristics of the VCSEL shown in FIG. 1, and a curve B shows the characteristics of the VCSEL shown in FIG. As is apparent from the graph, in the VCSEL 100 of the present embodiment, the light output is increased as compared with the conventional VCSEL by adopting the translucent electrode 122.

  As described above, according to the present embodiment, by using the semitransparent electrode, the resistance of the current path is reduced while the suppression of the higher-order mode, the oscillation spectrum wavelength width, and the divergence angle is maintained, and the reduction of the light output is prevented. Can be realized.

  In the above embodiment, a thin film metal is used for the translucent electrode. However, other materials having conductivity and optical transparency capable of obtaining ohmic contact with GaAs or the like can also be used. For example, indium-tin oxide (ITO) can be used. ITO has electrical conductivity and light transmittance, and it becomes possible to obtain good ohmic contact with GaAs by annealing ITO at a certain temperature or higher.

  FIG. 3 is a graph showing the relationship between the annealing temperature and contact resistance of ITO, which is disclosed in the following document (CL Chua. Et al, Indium Tin Oxide Transparent Electrodes for Broad-Area Top-Emitting Vertical-Cavity lasers Fabricated using a Single Lithography Step, IEEE PHOTONICS TECHNOLOGY LETTERS. VOL, .9, NO.5, MAY 1997, p551). When annealing is performed at about 600 degrees, good ohmic contact between ITO and GaAs can be obtained.

  In the above embodiment, the diameter D2 of the opening 120 of the upper electrode 118 is substantially equal to the diameter D1 of the opening of the current confinement layer 114, but the diameter D2 of the opening may be larger than the diameter D1. In this case, the diameter of the opening is D2> D1> D3.

Next, a manufacturing method of the VCSEL of this embodiment will be described with reference to FIGS. As shown in FIG. 4A, an n-type Al _0.8 Ga _0.2 As layer and an n-type Al _0.1 Ga layer are formed on the (100) plane of the n-type GaAs substrate 104 by metal organic chemical vapor deposition (MOCVD). _A lower DBR layer 106 made of a multi-layer stack of _0.9 As layers, a spacer layer made of an undoped Al _0.4 Ga _0.6 As layer, a barrier layer made of an undoped Al _0.2 Ga _0.8 As layer, and an undoped GaAs layer A multi-layer stack including an active region 108 formed of a stack with a quantum well layer, a p-type Al _0.8 Ga _0.2 As layer including a p-type AlAs layer and a GaAs contact layer, and a p-type Al _0.1 Ga _0.9 As layer The upper DBR layer 110 is sequentially stacked.

The lower DBR layer 106 is formed of a multi-layer stack of an n-type Al _0.8 Ga _0.2 As layer and an n-type Al _0.1 Ga _0.9 As layer, and the thickness of each layer is λ / 4nr (where λ is the oscillation wavelength) , Nr corresponds to the optical refractive index in the medium), and layers having different mixed crystal ratios are alternately laminated for 36.5 periods. The carrier concentration after doping silicon as an n-type impurity is 3 × 10 ¹⁸ cm ⁻³ . The active region 108 is formed by alternately stacking an 8 nm thick quantum well active layer made of an undoped GaAs layer and a 5 nm thick barrier layer made of an undoped Al _0.2 Ga _0.8 As layer (where the outer layer is a barrier layer). The stack is arranged in the center of the spacer layer made of an undoped Al _0.4 Ga _0.6 As layer, and the thickness of the spacer layer including the quantum well active layer and the barrier layer is designed to be an integral multiple of λ / 4nr. ing. Radiation light having a wavelength of 850 nm is obtained from the active region 108 having such a configuration.

The upper DBR layer 110 is a stacked layer composed of a plurality of semiconductor layers of a p-type Al _0.8 Ga _0.2 As layer and a p-type Al _0.1 Ga _0.9 As layer. The thickness of each layer is λ / 4 nr, similar to the lower multilayer reflective film 106, and layers having different mixed crystal ratios are alternately stacked in 22 cycles. This number of periods is the number of the AlAs layer 114 provided in the lower layer and the contact layer 112 provided in the upper layer. The carrier concentration after doping carbon as a p-type impurity is 3 × 10 ¹⁸ cm ⁻³ .

  An upper electrode 118 having a two-layer structure of Ti / Au is patterned on the upper DBR layer 110 by a lift-off process. A circular opening 120 is formed in the upper electrode 118 so as to expose the contact layer 112 that is the uppermost layer of the upper DBR layer 110. The diameter D2 of the opening 120 is about 12 μm. Next, as shown in FIG. 4B, a Cr film having a thickness of 5 nm, a 20 nm film thickness, and Au are stacked on the upper electrode 118, and an opening 124 is formed inside the opening 120. And Au are patterned to form a translucent electrode 122. The diameter D3 of the opening 124 is 10 μm. After these electrode patterns are formed, annealing is performed at a predetermined temperature.

  Next, as shown in FIG. 5A, a protective film 126 such as SiON is formed and patterned to protect the upper DBR layer exposed by the opening 124 of the translucent electrode 122. The protective film 126 protects the emission surface so that the surface of the upper DBR layer, that is, the GaAs contact layer 112 is not contaminated in subsequent processes. Laser light generated in the active region is output to the outside through this protective film 126.

  Next, as shown in FIG. 5B, a mask insulating film 128 is formed and patterned so as to cover the upper electrode 118 and the transparent electrode 122. The mask insulating film 128 defines the outer shape of the mesa formed thereafter. Here, in order to form a cylindrical mesa, the mask insulating film 128 is patterned into a circle. Next, dry etching is performed using the mask insulating film 128 as a mask to form a mesa M on the substrate. The mesa M is performed at least to a depth at which the current confinement layer 114 is exposed.

Next, as shown in FIG. 6A, the substrate on which the mesa M is formed is exposed to a 340 ° C. water vapor atmosphere using nitrogen-containing carrier gas (flow rate: 2 liters / minute) for 40 minutes to perform an oxidation treatment. Do. Since the AlAs layer constituting the current confinement layer 114 has a significantly faster oxidation rate than the Al _0.8 Ga _0.2 As layer and the Al _0.1 Ga _0.9 As layer of the upper DBR layer, it is directly above the active region 108 that is a part of the mesa M. An oxidized region 114a reflecting the post shape is formed in the portion. A non-oxidized region remaining without being oxidized becomes an opening of a current injection region or a conductive region. The diameter D1 of the opening of the current confinement layer 114 obtained in this oxidation step is 12 μm. Although the oxidized region 114a serves as a current confinement portion, it simultaneously functions as a light confinement region because the optical refractive index is about half that of the surrounding semiconductor layer.

  Next, as shown in FIG. 6B, an interlayer insulating film 130 such as SiOx is formed on the substrate, and a part of the interlayer insulating film 130 is etched so that the top of the mesa is exposed. As a result, a contact hole 132 in which a part of the upper electrode 118 and a part of the translucent electrode 122 are exposed by the interlayer insulating film 130 and the protective film 126 is formed.

  Next, as shown in FIG. 7A, the upper wiring 134 is formed and patterned. The upper wiring 134 is connected to the upper electrode 118 and the semitransparent electrode 122 exposed by the interlayer insulating film 130 and the protective film 126. The upper wiring 134 is connected to a bonding pad (not shown) here. Finally, as shown in FIG. 7B, the n-side lower electrode 102 is formed on the back surface of the substrate.

  The above manufacturing process is an example, and can be formed by other processes. For example, the upper electrode 118 and the translucent electrode 122 may be formed after the mesa M is formed. Further, when ITO is used as the semitransparent electrode, it is preferable to form the electrode before the current confinement layer oxidation step because annealing of about 600 degrees is required as shown in FIG.

  Furthermore, in the above embodiment, an example in which a single VCSEL element is formed on a substrate is shown. Of course, a so-called multi-spot type or multi-bit in which a plurality of VCSEL elements are formed in an array on a substrate. The present invention can also be applied to a type of VCSEL array.

  FIG. 8 is a schematic cross-sectional view showing an example of a package (module) of a semiconductor laser device on which a chip on which a single or a plurality of VCSEL elements are formed is mounted. As shown in the figure, the package 300 fixes a chip 310 on which a VCSEL array is formed on a disk-shaped metal stem 330 via a die attach on the mounter 320. The conductive leads 340 and 342 are inserted into through holes (not shown) of the stem 330, and one lead 340 is electrically connected to the lower electrode formed on the back surface of the chip 310, and the other lead 342. Are electrically connected to the upper electrode formed on the upper surface of the chip 310 via a bonding wire or the like.

  A ball lens 360 is fixed in the exit window 352 of the cap 350. The optical axis of the ball lens 360 is positioned so as to substantially coincide with the center of the chip 310. In addition, the distance between the chip 310 and the ball lens 360 is adjusted so that the ball lens 360 is included within the radiation angle (expansion angle) θ of the laser light from the chip 310. When a forward voltage is applied between the leads 340 and 342, laser light is emitted from the chip 310 and output to the outside through the ball lens 360. Note that a light receiving element for monitoring the light emission state of the VCSEL may be included in the cap.

  FIG. 9 is a diagram showing the configuration of still another package, and is preferably used in a spatial transmission system described later. In the package 302 shown in the drawing, a flat glass 362 is fixed in an emission window 352 at the center of the cap 350 instead of using the ball lens 360. The center of the flat glass 362 is positioned so as to substantially coincide with the center of the chip 310. The distance between the chip 310 and the flat glass 362 is adjusted so that the opening diameter of the flat glass 362 is not less than the radiation angle θ of the laser beam from the chip 310.

  FIG. 10 is a cross-sectional view showing a configuration when the package or module shown in FIG. 8 is applied to an optical transmitter. The optical transmission device 400 includes a cylindrical housing 410 fixed to the stem 330, a sleeve 420 integrally formed on an end surface of the housing 410, a ferrule 430 held in the opening 422 of the sleeve 420, a ferrule And an optical fiber 440 held by 430.

  An end of the housing 410 is fixed to a flange 332 formed in the circumferential direction of the stem 330. The ferrule 430 is accurately positioned in the opening 422 of the sleeve 420 and the optical axis of the optical fiber 440 is aligned with the optical axis of the ball lens 360. The core wire of the optical fiber 440 is held in the through hole 432 of the ferrule 430.

  The laser light emitted from the surface of the chip 310 is collected by the ball lens 360, and the collected light is incident on the core wire of the optical fiber 440 and transmitted. Although the ball lens 360 is used in the above example, other lenses such as a biconvex lens and a plano-convex lens can be used. Further, the optical transmission device 400 may include a drive circuit for applying an electrical signal to the leads 340 and 342. Furthermore, the optical transmission device 400 may include a reception function for receiving an optical signal via the optical fiber 440.

  FIG. 11 is a diagram showing a configuration when the package shown in FIG. 9 is used in a spatial transmission system. The spatial transmission system 500 includes a package 300, a condenser lens 510, a diffusion plate 520, and a reflection mirror 530. In the spatial transmission system 500, instead of using the ball lens 360 used in the package 300, a condensing lens 510 is used. The light condensed by the condenser lens 510 is reflected by the diffusion plate 520 through the opening 532 of the reflection mirror 530, and the reflected light is reflected toward the reflection mirror 530. The reflection mirror 530 reflects the reflected light in a predetermined direction and performs optical transmission. In the case of a spatial transmission light source, a multi-spot type VCSEL may be used to obtain a high output.

  FIG. 12 is a diagram illustrating a configuration example of an optical transmission system using a VCSEL as a light source. The optical transmission system 600 receives a light source 610 including a chip 310 on which a VCSEL is formed, an optical system 620 that collects laser light emitted from the light source 610, and the laser light output from the optical system 620. A light receiving unit 630 and a control unit 640 that controls driving of the light source 610 are included. The control unit 640 supplies a drive pulse signal for driving the VCSEL to the light source 610. Light emitted from the light source 610 is transmitted to the light receiving unit 630 via an optical system 620 by an optical fiber, a reflection mirror for spatial transmission, or the like. The light receiving unit 630 detects the received light with a photodetector or the like. The light receiving unit 630 can control the operation of the control unit 640 (for example, the start timing of optical transmission) by the control signal 650.

  Next, the configuration of an optical transmission device used in the optical transmission system will be described. FIG. 13 is a diagram illustrating an external configuration of the optical transmission apparatus, and FIG. 14 is a diagram schematically illustrating an internal configuration thereof. The optical transmission device 700 includes a case 710, an optical signal transmission / reception connector joint 720, a light emitting / receiving element 730, an electric signal cable joint 740, a power input unit 750, an LED 760 indicating that an operation is in progress, an LED 770 indicating occurrence of an abnormality, and a DVI. A connector 780 and a transmission circuit board / reception circuit board 790 are provided.

  A video transmission system using the optical transmission apparatus 700 is shown in FIGS. In these drawings, the video transmission system 800 uses the optical transmission device shown in FIG. 10 to transmit the video signal generated by the video signal generation device 810 to the image display device 820 such as a liquid crystal display. That is, the video transmission system 800 includes a video signal generation device 810, an image display device 820, a DVI electric cable 830, a transmission module 840, a reception module 850, a video signal transmission optical signal connector 860, an optical fiber 870, and a video signal transmission. An electric cable connector 880, a power adapter 890, and an electric cable 900 for DVI are included.

  In the video transmission system described above, electrical signals are transmitted between the video signal generation device 810 and the transmission module 840, and between the reception module 850 and the image display device 820 using the electrical cables 830 and 900. Transmission between these signals is an optical signal. It is also possible to do this. For example, a signal transmission cable including an electrical / optical conversion circuit and an optical / electrical conversion circuit in a connector may be used instead of the electrical cables 830 and 900.

  Since the surface emitting semiconductor laser according to the present invention has a small divergence angle and a high light output, it can be used as a very useful light source in the above-described modules, optical transmission devices, optical transmission devices, spatial transmission systems, and the like. .

  The surface emitting semiconductor laser according to the present invention can be used for a light source of an image recording apparatus or an optical communication apparatus, a light source of an image forming apparatus such as a printer or a copying apparatus, and the like.

FIG. 1A is a schematic plan view of a VCSEL according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along line XX. It is the graph which compared the IL characteristic of VCSEL by a present Example, and conventional VCSEL. It is a graph which shows the relationship between the annealing temperature of ITO and the contact resistance with GaAs. It is process sectional drawing which shows the schematic manufacturing process of VCSEL which concerns on the Example of this invention. It is process sectional drawing which shows the schematic manufacturing process of VCSEL which concerns on the Example of this invention. It is process sectional drawing which shows the schematic manufacturing process of VCSEL which concerns on the Example of this invention. It is process sectional drawing which shows the schematic manufacturing process of VCSEL which concerns on the Example of this invention. It is a schematic sectional drawing which shows the structure of the package which mounted the semiconductor chip in which VCSEL was formed. It is a schematic sectional drawing which shows the structure of another package. It is sectional drawing which shows the structure of the optical transmission device using the package shown in FIG. It is a figure which shows a structure when the package shown in FIG. 9 is used for a spatial transmission system. It is a block diagram which shows the structure of an optical transmission system. It is a figure which shows the external appearance structure of an optical transmission apparatus. 14A shows the internal structure of the optical transmission device, FIG. 14A shows the internal structure when the top surface is cut off, and FIG. 14B shows the internal structure when the side surface is cut off. It is a figure which shows the video transmission system using the optical transmission apparatus of FIG. It is the figure which showed the video transmission system of FIG. 15 from the back side. It is sectional drawing which shows the structure of the conventional VCSEL. It is sectional drawing which shows the structure of the conventional VCSEL. It is sectional drawing which shows the structure of the conventional VCSEL.

Explanation of symbols

100: VCSEL 102: Lower electrode 104: Substrate 106: Lower DBR layer 108: Active region 110: Upper DBR layer 112: Contact layer 114: Current confinement layer 114a: Oxidized region 116: Interlayer insulating film 118: Upper electrode 120: Opening 122: Translucent electrode 124: Opening

Claims (24)

A semiconductor substrate in which a first conductive type lower multilayer reflector, an active region, and a lower multilayer reflector reflecting the second conductive type upper multilayer reflector constituting the resonator are sequentially stacked;
A first upper electrode provided on the upper multilayer reflector and formed with a first opening for emitting laser light generated in the active region;
A current confinement region provided between the first upper electrode and the lower multilayer-film reflective mirror and formed by insulating the peripheral portion of the current path;
A second upper electrode that is electrically connected to the first upper electrode and covers a part of the upper multilayer film reflector inside the first opening,
The second upper electrode is a surface emitting semiconductor laser composed of a material having conductivity and light transmission. The surface emitting semiconductor laser according to claim 1, wherein a second opening having a diameter smaller than that of the first opening is formed in the second upper electrode. 3. The surface emitting semiconductor laser according to claim 1, wherein the second upper electrode is ohmically connected to a contact layer which is an uppermost layer of the upper multilayer-film reflective mirror. The surface emitting semiconductor laser according to any one of claims 1 to 3, wherein the second upper electrode is a translucent electrode. The surface emitting semiconductor laser according to claim 1, wherein the second upper electrode is made of a thin film metal. The surface emitting semiconductor laser according to claim 7, wherein the thin film metal has a multilayer structure. The surface emitting semiconductor laser according to claim 5 or 6, wherein the thin film metal includes at least one of Cr and Au. The surface emitting semiconductor laser according to claim 1, wherein the second upper electrode includes ITO. 9. The surface emitting semiconductor laser according to claim 1, wherein the contact layer of the upper multilayer mirror is a GaAs layer of a second conductivity type. 10. The surface-emitting type semiconductor laser according to claim 1, wherein a diameter of the third opening defining the current path of the current constriction is larger than a diameter of the second opening. The surface emitting semiconductor laser according to claim 1, wherein a diameter of the third opening is substantially equal to a diameter of the first opening. The current confinement portion includes an AlAs layer of a second conductivity type, an oxidized region selectively oxidized is formed at a peripheral portion of the AlAs layer, and a third opening is defined by the oxidized region. Thru | or any one of 11 surface emitting semiconductor lasers. 13. The surface emitting semiconductor laser according to claim 12, wherein a mesa from the upper multilayer reflector to the current confinement portion is formed on the substrate, and an oxidation region of the current confinement portion is oxidized from the side surface of the mesa. The surface emitting semiconductor laser according to any one of claims 1 to 13, wherein multimode light is generated from the active region of the mesa, and a higher-order mode is suppressed by the second upper electrode. A module on which the surface emitting semiconductor laser according to claim 1 is mounted. An optical transmission device comprising: the module according to claim 15; and a transmission unit configured to transmit a laser beam emitted from the module via an optical medium. An optical space transmission apparatus comprising: the module according to claim 15; and a transmission unit that spatially transmits light emitted from the module. An optical transmission system comprising: the module according to claim 15; and a transmission unit that transmits a laser beam emitted from the module. An optical space transmission system comprising the module according to claim 15 and a transmission means for spatially transmitting light emitted from the module. A method of manufacturing a surface emitting semiconductor laser,
Laminating a semiconductor layer including a lower multilayer reflector, an active region, a current constriction, and an upper multilayer reflector on a substrate;
Forming a first upper electrode in which a first opening is formed on the upper multilayer-film reflective mirror;
Forming a second upper electrode such that the second opening is positioned inside the first opening;
Forming a protective film covering the upper multilayer mirror exposed by the second opening;
Forming a mesa on the substrate from the upper multilayer reflector to at least the current confinement portion;
Oxidizing a portion of the current constriction;
Forming a wiring connected to at least one of the first or second upper electrode,
The second upper electrode is a method for manufacturing a surface emitting semiconductor laser, wherein the second upper electrode is made of a material having conductivity and light transmittance. 21. The manufacturing method according to claim 20, wherein the diameter of the third opening of the current path defined by the oxidizing step is larger than the diameter of the second opening of the second upper electrode. The manufacturing method according to claim 20, wherein the diameter of the third opening is substantially equal to the diameter of the first opening of the first upper electrode. The manufacturing method according to claim 20, further comprising a step of annealing at a constant temperature after forming the first and second upper electrodes. The manufacturing method according to claim 23, wherein the second upper electrode is in ohmic contact with a part of the upper multilayer-film reflective mirror.

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