WO2006090990A1 - Laser diode improved in heat-dissipating structure and fabricating method therefor - Google Patents

Laser diode improved in heat-dissipating structure and fabricating method therefor Download PDF

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Publication number
WO2006090990A1
WO2006090990A1 PCT/KR2006/000506 KR2006000506W WO2006090990A1 WO 2006090990 A1 WO2006090990 A1 WO 2006090990A1 KR 2006000506 W KR2006000506 W KR 2006000506W WO 2006090990 A1 WO2006090990 A1 WO 2006090990A1
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Prior art keywords
laser diode
mask
electrode
uneven structure
type electrode
Prior art date
Application number
PCT/KR2006/000506
Other languages
French (fr)
Inventor
Kwang-Soo Huh
Han-Gwon Ryu
Bon-Jo Koo
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Ls Cable Ltd.
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Publication date
Application filed by Ls Cable Ltd. filed Critical Ls Cable Ltd.
Priority to JP2007556968A priority Critical patent/JP2008532279A/en
Publication of WO2006090990A1 publication Critical patent/WO2006090990A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
    • H01S5/227—Buried mesa structure ; Striped active layer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V17/00—Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages
    • F21V17/10—Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages characterised by specific fastening means or way of fastening
    • F21V17/107—Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages characterised by specific fastening means or way of fastening using hinge joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V17/00—Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages
    • F21V17/10—Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages characterised by specific fastening means or way of fastening
    • F21V17/12—Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages characterised by specific fastening means or way of fastening by screwing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/0206—Substrates, e.g. growth, shape, material, removal or bonding
    • H01S5/0207—Substrates having a special shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/0201—Separation of the wafer into individual elements, e.g. by dicing, cleaving, etching or directly during growth
    • H01S5/0202—Cleaving
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/02235—Getter material for absorbing contamination
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/024—Arrangements for thermal management
    • H01S5/02461—Structure or details of the laser chip to manipulate the heat flow, e.g. passive layers in the chip with a low heat conductivity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/024—Arrangements for thermal management
    • H01S5/02469—Passive cooling, e.g. where heat is removed by the housing as a whole or by a heat pipe without any active cooling element like a TEC
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0425—Electrodes, e.g. characterised by the structure
    • H01S5/04254—Electrodes, e.g. characterised by the structure characterised by the shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser

Definitions

  • the present invention relates a laser diode and its fabricating method, and more particularly to a laser diode having an electrode structure capable of increasing a contact area with a heat sink and its fabricating method.
  • a laser diode is fabricated in a PBH (Planar Buried Heterostructure) type having a buried active layer and a flat surface.
  • PBH Planar Buried Heterostructure
  • a laser diode is generally configured so that an active layer 12, a current cut-off layer 13, 14, a clad layer 15, an Ohmic contact layer 16, an insulation layer 17 and a p-type electrode 18 are laminated on a n-type substrate 11, a n-type electrode 10 is formed on a lower surface of the n-type substrate 11, and a reflective film 19 is formed on the rear side of the chip.
  • the insulation layer 17 partially formed around the p-type electrode 18 is not illustrated in the side view of the laser diode for better understanding.
  • the active layer 12 generally having a MQW (Multiple Quantum Well) structure is formed in a mesa shape between optical waveguide structures.
  • the current cut-off layer 13, 14 for preventing an injected current from being leaked out of the active layer 12 is configured so that a p-InP current cut-off layer 13 and a n-InP current cut-off layer 14 are subsequently grown around the active layer 12.
  • the current cut-off layer 14 may be etched into a U shape so as to decrease parasitic electrostatic capacitance.
  • the laser diode is sensitive to temperature like other semiconductor elements, so a heat sink is attached to its one side by means of a predetermined submount. Thus, the heat generated during operation of the laser diode is transferred to the heat sink via the submount, and then dissipated out of a packaging frame.
  • the present invention is designed in consideration of the above problems, and therefore it is an object of the invention to provide a laser diode including an electrode with a three-dimensional surface structure so as to increase a contact area with a heat sink, and its fabricating method.
  • Another object of the invention is to provide a laser diode having an electrode structure capable of giving convenience to a chip bar breaking process and also giving a good heat dissipating function, and its fabricating method.
  • the present invention provides a laser diode including an active layer for converting an injected current into a light, and a p-type electrode and a n-type electrode for injecting a current to the active layer, wherein an uneven structure is repeatedly formed in the p-type electrode or the n-type electrode to which a heat sink is attached during a packaging process.
  • the uneven structure includes grooves having a stripe pattern with a V- shaped section.
  • the active layer has a mesa structure, and the grooves are formed perpendicular to a length direction of the mesa structure.
  • a method for fabricating a laser diode which includes an active layer for converting an injected current into a light, and a p-type electrode and a n-type electrode for injecting a current to the active layer
  • the p-type or n-type electrode forming process includes: (a) depositing a mask layer on a substrate on which the p-type or n-type electrode is to be formed; (b) forming a mask by eliminating a deposition film of the mask layer in a predetermined pattern by using a photolithography process and a BOE (Buffered Oxide Etch) etching process; (c) forming an uneven structure on a surface of the substrate by etching an exposed portion through the mask; (d) removing the mask; and (e) depositing an electrode material on the uneven structure so that an electrode has an uneven structure.
  • the active layer has a mesa structure, and, in the step (b), a mask having a window of a stripe pattern perpendicular to a length direction of the mesa structure is formed.
  • step (c) an uneven structure having grooves formed in a stripe pattern and having a V-shaped section may be formed.
  • FlG. 1 is a perspective view showing a general laser diode
  • FIG. 2 is a side view of FIG. 1 ;
  • FIG. 3 is a perspective view showing a laser diode according to a preferred embodiment of the present invention.
  • FIG. 4 is a side view of HG. 3 ;
  • FIG. 5 is a side view illustrating a chip bar breaking process executed in a laser diode fabricating method according to a preferred embodiment of the present invention
  • FIG. 6 shows a packaging configuration of a laser diode according to a preferred embodiment of the present invention
  • FIGs. 7 to 11 are side views illustrating a laser diode fabricating method according to a preferred embodiment of the present invention. Best Mode for Carrying Out the Invention
  • FIG. 3 is a perspective view showing a laser diode according to a preferred embodiment of the present invention
  • FIG. 4 is a side view of FIG. 3.
  • the laser diode of this embodiment is configured so that an active layer 102, a current cut-off layer 103, 104, a clad layer 105, an Ohmic contact layer 106, an insulation layer 107 and a p-type electrode 108 are laminated on a n-type substrate 101, a n-type electrode 100 having an uneven structure is provided to a lower surface of the n-type substrate 101, and a reflective film 109 is formed on the rear side of the chip.
  • the active layer 102 converts a current injected through the p-type electrode 109 and the n-type electrode 100 into a light, and it is composed of a MQW (Multiple Quantum Well) structure having a mesa shape with a width of about 1 to 1.5 D.
  • the active layer 102 preferably has a buried heterostructure, and it is preferably interposed between ridged optical waveguide structures.
  • the active layer 102 has a single-mode or multi-mode spectrum, and it is configured to be capable of emitting light of a specific wavelength within a wavelength range from a visible ray to an infrared ray.
  • the n-type electrode 100 prepared to the lower surface of the n-type substrate 101 is configured so that an uneven structure is repeatedly formed therein.
  • the present invention may be modified so that an uneven structure is formed in the p-type electrode 108.
  • the uneven structure may be formed only in an exposed surface of the n-type electrode 100.
  • the uneven structure is formed to have grooves 110 in a stripe pattern with a V-shaped section.
  • the portions of the grooves 110 may be cut during the chip bar breaking process, which facilitates easier chip bar breaking.
  • FlG. 6 shows a packaging configuration of the laser diode according to a preferred embodiment of the present invention.
  • a heat sink 202 is attached to a surface of a n-type electrode of the laser diode 200 of this embodiment by means of an adhering member 201 corresponding to, for example, a metallic bonding.
  • the heat sink 202 may be indirectly attached to the adhering member 201 by means of a predetermined submount.
  • the heat generated in the laser diode 200 is transferred to the adhering member 201 and then dissipated toward the heat sink 202. At this time, since the uneven structure is repeatedly formed on the surface of the n-type electrode of the laser diode 200, the heat may be dissipated via a wide contact area.
  • FlGs. 7 to 14 subsequently illustrate a process for forming the n-type electrode 100 in the laser diode fabricating method according to a preferred embodiment of the present invention.
  • other processes for fabricating a laser diode may be executed using a common laser diode fabricating technique.
  • a lower surface of the wafer corresponding to a surface of the above n-type substrate 101 is grinded, and then a mask layer 90 is deposited thereto (see FlG. 7).
  • the mask layer 90 is made of a silicon nitride (SiNx) film, but any material that can become an etching mask of the n-type substrate 101, described later, may be used.
  • Oxide Etch Oxide Etch
  • the mask 91 is preferably configured so that windows 92 extended in a
  • a surface of the n-type substrate 101 exposed through the windows 92 of the mask 91 is etched using a hydrochloric acid solution so as to form grooves 101 with a V-shaped section in the surface of the substrate (see FIG. 9).
  • the mask 91 is removed using the BOE etching process, and then a pattern in which an uneven structure is repeatedly formed in the surface of the n-type substrate 101 is obtained as shown in FIG. 10.
  • the divided laser diode chip is packaged together with a heat sink by using a common TOCAN (Transistor Outline CAN) or the like.
  • the heat sink is preferably made of material having excellent thermal conductivity and thermal expansion coefficient similar to a semiconductor material such as silicon carbide (SiC), boron nitride (BN), aluminum nitride (AlN) and so on, and the heat sink and the laser diode chip are preferably adhered by means of the eutectic bonding using an alloy of gold (Au) and tin (Sn).
  • a contact area of the electrode and the heat sink of the laser diode is broadened due to the uneven structure, so a heat dissipating char- acteristic is improved and thus the laser diode may be operated in a safer way.
  • the chip bar breaking process may be executed just by cutting the grooves of the uneven structure, thereby improving workability.

Abstract

A laser diode has an electrode structure increasing a contact area with a heat sink, and includes an active layer for converting an injected current into light, and p-type and n-type electrodes for injecting current to the active layer. An uneven structure is repeatedly formed in the p-type or n-type electrode to which a heat sink is attached during a packaging process. In a laser diode fabricating method, the electrode forming process includes depositing a mask layer on a substrate on which the p-type or n-type electrode is formed; forming a mask by eliminating a deposition film of the mask layer in a pattern by using photolithography and BOE etching processes; forming an uneven structure on a substrate surface by etching an exposed portion through the mask; removing the mask; and depositing electrode material on the uneven structure to form an electrode having an uneven structure.

Description

Description
LASER DIODE IMPROVED IN HEAT-DISSIPATING STRUCTURE AND FABRICATING METHOD THEREFOR
Technical Field
[1] The present invention relates a laser diode and its fabricating method, and more particularly to a laser diode having an electrode structure capable of increasing a contact area with a heat sink and its fabricating method. Background Art
[2] Recently, a laser diode is fabricated in a PBH (Planar Buried Heterostructure) type having a buried active layer and a flat surface.
[3] Referring to FlGs. 1 and 2, a laser diode is generally configured so that an active layer 12, a current cut-off layer 13, 14, a clad layer 15, an Ohmic contact layer 16, an insulation layer 17 and a p-type electrode 18 are laminated on a n-type substrate 11, a n-type electrode 10 is formed on a lower surface of the n-type substrate 11, and a reflective film 19 is formed on the rear side of the chip. Hereinafter, the insulation layer 17 partially formed around the p-type electrode 18 is not illustrated in the side view of the laser diode for better understanding.
[4] The active layer 12 generally having a MQW (Multiple Quantum Well) structure is formed in a mesa shape between optical waveguide structures. The current cut-off layer 13, 14 for preventing an injected current from being leaked out of the active layer 12 is configured so that a p-InP current cut-off layer 13 and a n-InP current cut-off layer 14 are subsequently grown around the active layer 12. At this time, the current cut-off layer 14 may be etched into a U shape so as to decrease parasitic electrostatic capacitance.
[5] The laser diode is sensitive to temperature like other semiconductor elements, so a heat sink is attached to its one side by means of a predetermined submount. Thus, the heat generated during operation of the laser diode is transferred to the heat sink via the submount, and then dissipated out of a packaging frame.
[6] In order to enhance a heat transferring efficiency for the heat generated in the laser diode, it is required to increase a contact area between the laser diode and the heat sink and configure the heat sink with a material having excellent thermal conductivity.
[7] Here, in case the heat sink is made of metal material, a thermal expansion coefficient is so increased to cause stress. Thus, there are many limitations in selecting a material, and for example ceramic having a thermal expansion coefficient similar to a semiconductor is used.
[8] In particular, considering that heat dissipation is highest at an electrode portion in a laser diode, it is important to increase a contact area between the electrode and the heat sink so as to enhance a heat transferring efficiency. However, in the conventional laser diode, the p-type electrode 18 and the n-type electrode 10 are configured in a simple flat plate structure, so there is a limit in increasing the contact area. Disclosure of Invention Technical Problem
[9] The present invention is designed in consideration of the above problems, and therefore it is an object of the invention to provide a laser diode including an electrode with a three-dimensional surface structure so as to increase a contact area with a heat sink, and its fabricating method.
[10] Another object of the invention is to provide a laser diode having an electrode structure capable of giving convenience to a chip bar breaking process and also giving a good heat dissipating function, and its fabricating method.
Technical Solution
[11] In order to accomplish the above object, the present invention provides a laser diode including an active layer for converting an injected current into a light, and a p-type electrode and a n-type electrode for injecting a current to the active layer, wherein an uneven structure is repeatedly formed in the p-type electrode or the n-type electrode to which a heat sink is attached during a packaging process.
[12] Preferably, the uneven structure includes grooves having a stripe pattern with a V- shaped section.
[13] Preferably, the active layer has a mesa structure, and the grooves are formed perpendicular to a length direction of the mesa structure.
[14] In another aspect of the invention, there is also provided a method for fabricating a laser diode, which includes an active layer for converting an injected current into a light, and a p-type electrode and a n-type electrode for injecting a current to the active layer, wherein the p-type or n-type electrode forming process includes: (a) depositing a mask layer on a substrate on which the p-type or n-type electrode is to be formed; (b) forming a mask by eliminating a deposition film of the mask layer in a predetermined pattern by using a photolithography process and a BOE (Buffered Oxide Etch) etching process; (c) forming an uneven structure on a surface of the substrate by etching an exposed portion through the mask; (d) removing the mask; and (e) depositing an electrode material on the uneven structure so that an electrode has an uneven structure.
[15] Preferably, the active layer has a mesa structure, and, in the step (b), a mask having a window of a stripe pattern perpendicular to a length direction of the mesa structure is formed.
[16] In the step (c), an uneven structure having grooves formed in a stripe pattern and having a V-shaped section may be formed. Brief Description of the Drawings
[17] These and other features, aspects, and advantages of preferred embodiments of the present invention will be more fully described in the following detailed description, taken accompanying drawings. In the drawings:
[18] FlG. 1 is a perspective view showing a general laser diode;
[19] FIG. 2 is a side view of FIG. 1 ;
[20] FIG. 3 is a perspective view showing a laser diode according to a preferred embodiment of the present invention;
[21] FIG. 4 is a side view of HG. 3 ;
[22] FIG. 5 is a side view illustrating a chip bar breaking process executed in a laser diode fabricating method according to a preferred embodiment of the present invention;
[23] FIG. 6 shows a packaging configuration of a laser diode according to a preferred embodiment of the present invention;
[24] FIGs. 7 to 11 are side views illustrating a laser diode fabricating method according to a preferred embodiment of the present invention. Best Mode for Carrying Out the Invention
[25] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.
[26] FIG. 3 is a perspective view showing a laser diode according to a preferred embodiment of the present invention, and FIG. 4 is a side view of FIG. 3.
[27] Referring to FIGs. 3 and 4, the laser diode of this embodiment is configured so that an active layer 102, a current cut-off layer 103, 104, a clad layer 105, an Ohmic contact layer 106, an insulation layer 107 and a p-type electrode 108 are laminated on a n-type substrate 101, a n-type electrode 100 having an uneven structure is provided to a lower surface of the n-type substrate 101, and a reflective film 109 is formed on the rear side of the chip.
[28] The active layer 102 converts a current injected through the p-type electrode 109 and the n-type electrode 100 into a light, and it is composed of a MQW (Multiple Quantum Well) structure having a mesa shape with a width of about 1 to 1.5 D. Here, the active layer 102 preferably has a buried heterostructure, and it is preferably interposed between ridged optical waveguide structures.
[29] In addition, the active layer 102 has a single-mode or multi-mode spectrum, and it is configured to be capable of emitting light of a specific wavelength within a wavelength range from a visible ray to an infrared ray.
[30] In particular, the n-type electrode 100 prepared to the lower surface of the n-type substrate 101 is configured so that an uneven structure is repeatedly formed therein. Here, the present invention may be modified so that an uneven structure is formed in the p-type electrode 108. In addition, though it is shown that an uneven structure is formed in both surfaces of the n-type electrode 100, the uneven structure may be formed only in an exposed surface of the n-type electrode 100.
[31] Preferably, the uneven structure is formed to have grooves 110 in a stripe pattern with a V-shaped section. At this time, if the uneven structure is formed so that the grooves 110 are extended perpendicular to a length direction of the mesa structure of the active layer 102, the portions of the grooves 110 (see a cut indicator 150 of FlG. 5) may be cut during the chip bar breaking process, which facilitates easier chip bar breaking.
[32] FlG. 6 shows a packaging configuration of the laser diode according to a preferred embodiment of the present invention. As shown in FlG. 6, during the packaging process, a heat sink 202 is attached to a surface of a n-type electrode of the laser diode 200 of this embodiment by means of an adhering member 201 corresponding to, for example, a metallic bonding. As an alternative, the heat sink 202 may be indirectly attached to the adhering member 201 by means of a predetermined submount.
[33] The heat generated in the laser diode 200 is transferred to the adhering member 201 and then dissipated toward the heat sink 202. At this time, since the uneven structure is repeatedly formed on the surface of the n-type electrode of the laser diode 200, the heat may be dissipated via a wide contact area.
[34] FlGs. 7 to 14 subsequently illustrate a process for forming the n-type electrode 100 in the laser diode fabricating method according to a preferred embodiment of the present invention. Here, other processes for fabricating a laser diode may be executed using a common laser diode fabricating technique.
[35] First, after the p-type electrode 108 is completely formed on the upper surface of a wafer, a lower surface of the wafer corresponding to a surface of the above n-type substrate 101 is grinded, and then a mask layer 90 is deposited thereto (see FlG. 7). The mask layer 90 is made of a silicon nitride (SiNx) film, but any material that can become an etching mask of the n-type substrate 101, described later, may be used. [36] After the depositing process, a photolithography process and a BOE (Buffered
Oxide Etch) etching process are executed to remove the mask layer 90 in a predetermined pattern so that a mask 91 is formed (see FIG. 8). Considering that the length direction of the mesa structure is commonly a
<l Tθ> direction of the wafer (see FIG. 3), the mask 91 is preferably configured so that windows 92 extended in a
<1 10> direction perpendicular thereto (see FIG. 3) with a stripe shape are repeatedly formed.
[37] After the mask 91 is formed, a surface of the n-type substrate 101 exposed through the windows 92 of the mask 91 is etched using a hydrochloric acid solution so as to form grooves 101 with a V-shaped section in the surface of the substrate (see FIG. 9).
[38] Subsequently, the mask 91 is removed using the BOE etching process, and then a pattern in which an uneven structure is repeatedly formed in the surface of the n-type substrate 101 is obtained as shown in FIG. 10.
[39] Finally, an electrode material is deposited on the uneven structure to keep a curve corresponding to the uneven structure as shown in FIG. 11, and then a n-type electrode 100 having the uneven structure is formed on the surface of the n-type substrate 101, as shown in FIG. 11.
[40] As described above, after the n-type electrode 100 is completely formed, a chip bar breaking process is executed along the grooves 110 of the uneven structure, and then an optical coating process is executed for chip bar sections.
[41] Subsequently, the divided laser diode chip is packaged together with a heat sink by using a common TOCAN (Transistor Outline CAN) or the like. At this time, the heat sink is preferably made of material having excellent thermal conductivity and thermal expansion coefficient similar to a semiconductor material such as silicon carbide (SiC), boron nitride (BN), aluminum nitride (AlN) and so on, and the heat sink and the laser diode chip are preferably adhered by means of the eutectic bonding using an alloy of gold (Au) and tin (Sn).
[42] The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Industrial Applicability
[43] According to the present invention, a contact area of the electrode and the heat sink of the laser diode is broadened due to the uneven structure, so a heat dissipating char- acteristic is improved and thus the laser diode may be operated in a safer way. [44] In addition, in the laser diode fabricating method, the chip bar breaking process may be executed just by cutting the grooves of the uneven structure, thereby improving workability.

Claims

Claims
[1] A laser diode including an active layer for converting an injected current into a light, and a p-type electrode and a n-type electrode for injecting a current to the active layer, wherein an uneven structure is repeatedly formed in the p-type electrode or the n- type electrode to which a heat sink is attached during a packaging process.
[2] The laser diode according to claim 1, wherein the uneven structure includes grooves having a stripe pattern with a V- shaped section.
[3] The laser diode according to claim 2, wherein the active layer has a mesa structure, and wherein the grooves are formed perpendicular to a length direction of the mesa structure.
[4] A method for fabricating a laser diode, which includes an active layer for converting an injected current into a light, and a p-type electrode and a n-type electrode for injecting a current to the active layer, wherein the p-type or n-type electrode forming process includes:
(a) depositing a mask layer on a substrate on which the p-type or n-type electrode is to be formed;
(b) forming a mask by eliminating a deposition film of the mask layer in a predetermined pattern by using a photolithography process and a BOE (Buffered Oxide Etch) etching process;
(c) forming an uneven structure on a surface of the substrate by etching an exposed portion through the mask;
(d) removing the mask; and
(e) depositing an electrode material on the uneven structure so that an electrode has an uneven structure.
[5] The method for fabricating a laser diode according to claim 4, wherein the active layer has a mesa structure, and wherein, in the step (b), a mask having a window of a stripe pattern perpendicular to a length direction of the mesa structure is formed.
[6] The method for fabricating a laser diode according to claim 5, wherein, in the step (c), an uneven structure having grooves formed in a stripe pattern and having a V-shaped section is formed.
PCT/KR2006/000506 2005-02-25 2006-02-13 Laser diode improved in heat-dissipating structure and fabricating method therefor WO2006090990A1 (en)

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