JP2014072495A - Semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element capable of reducing an increase in current in high-temperature operation.SOLUTION: A semiconductor laser element comprises: a substrate (101); an active layer (105) formed on the substrate (101); a ridge (151) formed on the active layer (105); terrace parts (152, 153) formed on the lateral side of the ridge (151); and a metal (113) formed on the terrace parts (152, 153). Recesses (152a, 153a) are formed on upper surfaces of the terrace parts (152, 153), respectively.

Description

  The present invention relates to a semiconductor laser, for example, a semiconductor laser operating at high temperature or high output.

  Conventionally, as a semiconductor laser element used as a light source for reading or writing information on a DVD (digital universal disk), there is one described in Japanese Patent Laid-Open No. 2002-9382 (Patent Document 1).

  Hereinafter, a semiconductor laser device presented for convenience in order to clarify the problem of the present invention will be described with reference to FIGS. 5 (a) and 5 (b).

FIG. 5A is a diagram schematically showing a cross section of the semiconductor laser element taken along a plane perpendicular to the cavity length direction. FIG. 5B is a diagram schematically showing the upper surface of the semiconductor laser element. However, in FIG. 5B, the SiO ₂ film 1010 and the TiAu / Au plating electrode 1011 are not shown. In addition, a dotted line is inserted between FIG. 5 (a) and FIG. 5 (b) so that it can be seen where in FIG. 5 (b) the portion schematically showing the cross section of FIG. Pulling.

  The semiconductor laser element includes an n-type GaAs buffer layer 1002 formed on an n-type GaAs substrate 1001, an n-type AlGaInP lower cladding layer 1003, an undoped AlGaInP lower guide layer 1004, an undoped GaInP / AlGaInP multiple quantum well active layer 1005, an undoped. An AlGaInP upper guide layer 1006, a p-type AlGaInP upper cladding layer 1007, a p-type GaInP intermediate layer 1008, and a p-type GaAs cap layer 1009 are provided.

  The p-type AlGaInP upper cladding layer 1007 and the p-type GaAs cap layer 1009 are formed with a ridge portion 1051 and terrace portions 1052 and 1053. The upper surfaces of the terrace portions 1052 and 1053 are flat surfaces.

Further, the SiO ₂ film 1010 covers the side surface of the ridge portion 1051 and the upper surface and side surfaces of the terrace portions 1052 and 1053.

  In the semiconductor laser element, the Ti / Au plating electrode 1011 is formed as an upper electrode, and the AuGeNi electrode 1012 is formed as a lower electrode. The Ti / Au plated electrode 1011 is connected to the upper surface of the ridge portion 1051.

When manufacturing the semiconductor laser device, first, an n-type GaAs buffer layer 1002, an n-type AlGaInP lower cladding layer 1003, an undoped AlGaInP lower guide layer 1004, an undoped GaInP / AlGaInP multiple quantum well active layer on an n-type GaAs substrate 1001. 1005, an undoped AlGaInP upper guide layer 1006, a p-type AlGaInP upper cladding layer, a p-type GaInP intermediate layer, and a p-type GaAs cap layer are sequentially grown by, for example, metal organic vapor phase epitaxy.

  Next, a part of the p-type AlGaInP upper cladding layer and the p-type GaAs cap layer are removed by a photolithography process, and a ridge portion 1151 extending in the resonator length direction is formed. At this time, terrace portions 1152 and 1153 are also formed.

Next, the upper surface of the p-type GaAs cap layer 1009 of the terrace portions 1152 and 1153 and the surface exposed by the photolithography process in the p-type AlGaInP upper cladding layer 1007, the p-type GaInP intermediate layer 1008, and the p-type GaAs cap layer 1009. After covering with the SiO ₂ film 1010, the plating electrode 1011 and the electrode 1012 are formed. At this time, the plating electrode 1011 is obtained by forming an Au plating electrode with a thickness of, for example, 2.0 μm for heat dissipation after forming an ohmic electrode such as TiAu.

  Finally, a plurality of semiconductor laser elements are obtained by the element dividing step.

  The semiconductor laser device manufactured in this way is fixed to a submount (not shown), which is a heat dissipation component, via a solder layer (not shown) such as AuSn. At this time, the semiconductor laser element is fixed so that the p-type GaAs cap layer 1009 side close to the active layer 1005 which is a heat source is close to the submount.

  The semiconductor laser element has a property that the operating current increases as the temperature rises, and heat dissipation to the submount reduces the increase in operating current due to this temperature rise.

  Further, when a current is passed through the ridge portion 1051, light is confined under the ridge portion 1051, and laser light is generated around the active layer 1005 under the ridge portion 1051.

  If the terrace portions 1052 and 1053 are not formed, a large stress is applied to the ridge portion 1051 at the time of fixing to the submount, and problems such as deterioration of the reliability of the semiconductor laser element occur.

  In order to prevent the occurrence of this problem, the terrace portion 1052 is formed on one side of the ridge portion 1051 through a groove having a width of 5 μm, for example, and the terrace portion is formed on the other side of the ridge portion 1051 through a groove having a width of 5 μm, for example. 1053 is formed. Thereby, when the semiconductor laser element is fixed to the submount, the terraces 1052 and 1053 can be supported to prevent a large stress from being applied to the ridge 1051.

JP 2002-9382 A

  By the way, in the semiconductor laser device of the above reference example, the heat generated in the active layer 1005 under the ridge 1051 or the heat generated in the ridge 1051 which is a current path is released from the Ti / Au plated electrode 1011 to the submount. However, there is a problem that such heat dissipation is not sufficient.

  In particular, in a red semiconductor laser device composed of an AlGaInP-based semiconductor crystal, the energy barrier between the active layer and the barrier layer becomes lower as the oscillation wavelength is set shorter, and the rate at which carriers in the active layer escape to the barrier layer at higher temperatures. Will increase. As a result, the operating current is remarkably increased at high temperatures, which hinders high temperature operation.

  Accordingly, an object of the present invention is to provide a semiconductor laser device capable of reducing an increase in current in a high temperature operation.

In order to solve the above problems, the semiconductor laser device of the present invention is
A substrate,
An active layer formed on the substrate;
A ridge formed on the active layer;
A terrace formed on the side of the ridge,
A metal formed on the terrace part,
A concave portion is formed on the upper surface of the terrace portion.

  According to the above configuration, since the concave portion is formed on the upper surface of the terrace portion, the bonding area between the terrace portion and the metal becomes larger than when the upper surface of the terrace portion is a flat surface. Thereby, the heat generated in the active layer under the ridge portion or the heat generated in the ridge portion can be efficiently transmitted to the metal through the terrace portion. Therefore, when the metal is fixed to, for example, the submount, the metal has good thermal conductivity, so that heat can be efficiently released from the metal to the submount. As a result, the effective temperature of the active layer can be kept low, so that an increase in current during high-temperature operation can be reduced.

  Note that the bonding area between the terrace portion and the metal means an area of a portion where the terrace portion is directly or indirectly bonded to the metal.

In the semiconductor laser device of one embodiment,
The recess extends in a direction parallel to the resonator length direction.

  According to the above embodiment, when the metal is fixed to, for example, a submount, the concave portion extends in a direction parallel to the resonator length direction, so that the stress generated in the terrace portion is dispersed and applied to the ridge portion. Stress is reduced. As a result, it is possible to reduce deterioration of the polarization characteristics of the semiconductor laser element or disturbance of the radiation pattern of the semiconductor laser element.

  On the other hand, when the semiconductor laser device of the above reference example is fixed to the submount, the thermal expansion coefficient of the substrate is different from the thermal expansion coefficient of the submount. Works in the ridge. As a result, the polarization characteristics of the semiconductor laser device of the reference example are deteriorated, or the shape of the radiation pattern of the semiconductor laser device of the reference example is disturbed.

In the semiconductor laser device of one embodiment,
The concave portion extends in a direction perpendicular to the resonator length direction.

  According to the above embodiment, when the metal is fixed to, for example, a submount, the concave portion extends in a direction perpendicular to the resonator length direction, so that stress due to the fixing is reduced. Therefore, it is possible to prevent a decrease in reliability due to warpage of the semiconductor laser element in the resonator direction or a crack of the semiconductor laser element.

  On the other hand, when the semiconductor laser element of the above reference example is fixed to the submount, the thermal expansion coefficient of the substrate is different from the thermal expansion coefficient of the submount. work. As a result, the semiconductor laser element of the above reference example is warped in the cavity direction and the reliability is lowered, or the semiconductor laser element of the above reference example is cracked.

In the semiconductor laser device of one embodiment,
The concave portion is formed only in a portion within 30.0 μm from the end of the terrace portion on the ridge portion side in a direction away from the ridge portion.

  According to the embodiment, since the recess is formed only in the portion within 30.0 μm from the end of the terrace portion on the ridge portion side in the direction away from the ridge portion, the heat of the active layer below the ridge portion, The heat of the portion can be effectively released to the metal, and the occurrence of overhang due to the strength reduction of the terrace portion can be prevented.

The semiconductor laser device of one embodiment
It is perpendicular to the resonator length direction and includes an emission end face that emits laser light.
The concave portion is formed only in a portion within 300.0 μm in the direction away from the emission end face from the emission end face of the terrace portion.

  According to the above embodiment, in order to increase the extraction efficiency of the laser beam, when the reflectance on the emission end face side is reduced and the reflectance on the side opposite to the emission end face is increased, the inside of the element is in the resonator length direction. The light intensity increases as the light distribution becomes asymmetric and the closer to the exit end face. At this time, even if the temperature in the vicinity of the emission end face rises, the recess is formed only in a portion within 300.0 μm from the emission end face of the terrace portion in the direction away from the emission end face. (Optical damage) can be prevented, and occurrence of overhang due to a decrease in strength of the terrace portion can be prevented.

In the semiconductor laser device of one embodiment,
The metal contains Au and has a thickness of 1.0 μm or more and 4.0 μm or less.

  According to the above embodiment, the metal contains Au and has a thickness of 1.0 μm or more and 4.0 μm or less, so that the heat dissipation effect of the metal can be increased and the polarization characteristics due to the stress generated inside the element can be increased. Deterioration can be prevented.

  If the metal contains Au and the thickness is less than 1.0 μm, the heat dissipation effect of the metal is reduced. On the other hand, if the metal contains Au and the thickness exceeds 4.0 μm, the state of the metal As a result, stress is easily generated, and polarization characteristics are deteriorated.

In the semiconductor laser device of one embodiment,
The recess is formed such that the bottom of the recess is located above the upper surface of the active layer.

  According to the embodiment, since the recess is formed so that the bottom of the recess is located above the upper surface of the active layer, the recess can be formed simultaneously with the ridge in the ridge formation process. . Therefore, it is not necessary to add a process only for forming the recess.

In the semiconductor laser device of one embodiment,
A plurality of the concave portions are formed on the upper surface of the terrace portion,
The width of each recess is 0.5 μm or more and 2.0 μm or less,
The interval between the adjacent recesses is not less than the depth of the recess and not more than 2.0 μm.

  According to the above embodiment, since the width of each recess is 0.5 μm or more, the effect of enlarging each recess in the etching process and expanding the heat radiation area can be increased.

  Further, since the width of each of the concave portions is 2.0 μm or less, it is possible to prevent the effect of supporting the terrace portion from being reduced. Therefore, an increase in stress on the ridge portion can be prevented.

  Moreover, since the space | interval of the said adjacent recessed parts is more than the depth of a recessed part, the intensity | strength of the part between recessed parts becomes high, and it can prevent that part applying.

  Moreover, since the space | interval of the said adjacent recessed part is 2.0 micrometers or less, the area | region in which the recessed part is not formed reduces, and the effect which expands a thermal radiation area can be enlarged.

In the semiconductor laser device of one embodiment,
The distance between the ridge portion and the terrace portion is 4.0 μm or more and 10.0 μm or less.

  According to the above embodiment, since the distance between the ridge portion and the terrace portion is 4.0 μm or more, the terrace portion is unlikely to adversely affect the distribution of the laser beam, and the radiation angle of the laser beam deviates from a predetermined angle. Can be prevented.

  In addition, since the distance between the ridge portion and the terrace portion is 10.0 μm or less, the heat of the active layer under the ridge portion and the heat of the ridge portion can be effectively released to the metal.

The semiconductor laser device of one embodiment
A dielectric film is formed to confine current flowing toward the active layer, and covers a side surface of the ridge portion and a bottom surface and a side surface of the recess.
In the dielectric film, the thickness of the portion covering the side surface of the ridge portion is not less than 100 nm and not more than 200 nm.

  According to the embodiment, since the thickness of the portion covering the side surface of the ridge portion in the dielectric film is 100 nm or more, the laser beam does not spread to the metal formed on the dielectric film, and the metal absorption Current increase due to loss can be prevented.

  Further, in the dielectric film, since the thickness of the portion covering the side surface of the ridge portion is 200 nm or less, it is possible to prevent heat dissipation from deteriorating due to the thermal resistance of the dielectric film.

In the semiconductor laser device of one embodiment,
In the dielectric film, the thickness of the portion covering the bottom and side surfaces of the recess is 100 nm or less.

  According to the embodiment, since the thickness of the portion covering the bottom surface and the side surface of the recess is 100 nm or less in the dielectric film, heat can be effectively radiated to the metal through the portion.

In the semiconductor laser device of one embodiment,
The metal is directly joined to the terrace part,
Direct bonding between the metal and the terrace portion is a Schottky junction.

  According to the embodiment, since the metal is directly joined to the terrace portion, the heat dissipation efficiency from the terrace portion to the metal can be extremely increased.

  Further, since the direct bonding between the metal and the terrace portion is a Schottky junction, a Schottky barrier is formed, and no current flows between the metal and the terrace portion. Therefore, the current flowing toward the active layer can be reliably narrowed.

  The semiconductor laser device of the present invention includes a substrate, an active layer formed on the substrate, a ridge formed on the active layer, a terrace formed on the side of the ridge, and the terrace. The surface area of the terrace portion and the metal is larger than when the top surface of the terrace portion is a flat surface. Therefore, the heat generated in the active layer under the ridge portion or the heat generated in the ridge portion can be efficiently transmitted to the metal through the terrace portion. Therefore, heat can be efficiently released from the metal to the outside, and the effective temperature of the active layer can be kept low. As a result, an increase in current during high-temperature operation can be reduced.

FIG. 1A is a schematic cross-sectional view of the main part of the semiconductor laser device of Example 1 of the present invention, and FIG. 1B is a schematic top view of the semiconductor laser device. FIG. 2A is a schematic cross-sectional view of the main part of the semiconductor laser device according to the second embodiment of the present invention, and FIG. 2B is a schematic top view of the semiconductor laser device. FIG. 3A is a schematic cross-sectional view of the main part of the semiconductor laser device according to the third embodiment of the present invention, and FIG. 3B is a schematic top view of the semiconductor laser device. FIG. 4A is a schematic cross-sectional view of the main part of the semiconductor laser device of Example 4 of the present invention, and FIG. 4B is a schematic top view of the semiconductor laser device. FIG. 5A is a schematic cross-sectional view of the main part of the semiconductor laser device of the reference example, and FIG. 5B is a schematic top view of the semiconductor laser device.

  The semiconductor laser device of the present invention will be described in detail below with reference to the illustrated embodiments.

[Example 1]
FIG. 1A is a diagram schematically showing a cross section of the semiconductor laser device according to Example 1 of the present invention taken along a plane perpendicular to the cavity length direction. FIG. 1B is a diagram schematically showing the upper surface of the semiconductor laser element. However, in FIG. 1B, the SiO ₂ film 112 and the TiAu / Au plating electrode 113 are not shown. A dotted line is shown between FIG. 1 (a) and FIG. 1 (b) so that it can be seen where in FIG. 1 (b) the portion schematically showing the cross section of FIG. 1 (a) corresponds. Pulling.

  As shown in FIGS. 1A and 1B, the semiconductor laser element includes an n-type GaAs substrate 101 and an n-type GaInP (thickness 0) formed on the substrate 101 by metal organic vapor phase epitaxy. .25 μm) buffer layer 102, n-type AlGaInP (Al composition ratio 0.7, thickness 3.0 μm) lower cladding layer 103, undoped AlGaInP (Al composition ratio 0.55, thickness 20 nm) lower guide layer 104, undoped GaInP (thickness) 4 nm) / AlGaInP (Al composition ratio 0.55, thickness 6 nm) multiple quantum well active layer 105, undoped AlGaInP (Al composition ratio 0.55, thickness 20 nm) upper guide layer 106, p-type AlGaInP (Al composition ratio 0.7) , Thickness 0.15 μm) first upper cladding layer 107, p-type GaInP (thickness 13 nm) etching stop layer 108, p-type AlGaInP (Al group) Ratio 0.7, and a thickness 1.0 .mu.m) second upper cladding layer 109, p-type GaInP (thickness 35 nm) intermediate layer 110 and the p-type GaAs (thickness 0.3 [mu] m) cap layer 111. The substrate 101 is an example of a substrate, and the multiple quantum well active layer 105 is an example of an active layer.

  On the opposite side of the semiconductor laser element from the substrate 101 side, a ridge portion 151 and terrace portions 152 and 153 sandwiching the ridge portion 151 from the lateral direction are formed by a photolithography process. Each of the ridge 151 and the terraces 152 and 153 includes a part of the second upper cladding layer 109, the intermediate layer 110, and the cap layer 111, respectively.

  A plurality of groove-shaped recesses 152a extending in a direction parallel to the resonator length direction are formed over the entire top surface of the terrace portion 152. In addition, a plurality of groove-like recesses 153a extending in a direction parallel to the resonator length direction are formed over the entire top surface of the terrace portion 153.

  In Example 1, a p-type AlGaInP layer, a p-type GaInP layer, and a p-type GaAs layer are stacked in this order, and then dry etching is performed above the etching stop layer 108, and then the etching stops at the etching stop layer 108. The ridge 151 and the terraces 152 and 153 are formed by performing wet etching until this is done.

In addition, the side surface of the ridge 151 and the top and side surfaces of the terraces 152 and 153 are covered with the SiO ₂ film 112. In this SiO ₂ film 112, the thickness of the portion covering the side surface of the ridge 151 is 100 nm. In the SiO ₂ film 112, the thickness of the portion covering the side surface of the ridge 151 is also 100 nm. The SiO ₂ film 112 is an example of a dielectric film.

A TiAu / Au plating electrode 113 is formed on the SiO ₂ film 112 and the ridge portion 151. On the other hand, an AuGeNi electrode 114 is formed under the substrate 101. The TiAu / Au plating electrode 113 is an example of a metal.

  The width of the ridge 151 (the length in the resonator length direction and the direction perpendicular to the layer thickness direction) is 1.7 μm, and the distance between the ridge 151 and the terraces 152 and 153 is 5.0 μm. The resonator length is 1500 μm and the chip width is 110 μm. The oscillation wavelength of the laser light is 640 nm. The chip width means the length in the direction perpendicular to the cavity length direction and the layer thickness direction of the semiconductor laser element.

  In the photolithography process for forming the ridge portion 151, a plurality of recesses 152a and 153a are formed simultaneously with the ridge portion 151. The widths of the recesses 152a and 153a are 2.0 μm. Moreover, the space | interval of adjacent recessed parts 152a and the space | interval of adjacent recessed parts 153a are 2.0 micrometers. The depths of the recesses 152a and the recesses 153a are 1.3 μm, which is the same as the height of the ridge 151.

In addition, after the formation of the recesses 152a and 153a, a part of the plating electrode 113 is embedded in the recesses 152a and 153a through the SiO ₂ film 112 by an electrode forming process. The thickness of the thickest part of the plating electrode 113 is 2.5 μm.

  In FIG. 1B, reference numeral 161 denotes a front end face as an example of an emission end face, and 162 denotes a rear end face.

  According to the semiconductor laser device having the above configuration, since the concave portions 152a and 153a are formed on the upper surfaces of the terrace portions 152 and 153, the terrace portions 152 and 153 are formed more than when the upper surfaces of the terrace portions 152 and 153 are flat surfaces. And the bonding area of the plating electrode 113 becomes large. Accordingly, heat generated in the multiple quantum well active layer 105 under the ridge 151 or heat generated in the ridge 151 can be efficiently transmitted to the metal via the terraces 152 and 153. Therefore, when the plating electrode 113 is fixed to, for example, a submount, the plating electrode 113 has a good thermal conductivity, so that heat can be efficiently released from the plating electrode 113 to the submount. As a result, since the effective temperature of the multiple quantum well active layer 105 can be kept low, an increase in current during high-temperature operation can be reduced.

  In addition, the semiconductor laser device can be operated at a temperature of 10 ° C. and can be operated at 70 ° C. by continuous oscillation driving of 100 mW, for example, as compared with a conventional semiconductor laser device having no recess in the terrace portion.

  Further, when the plated electrode 113 is fixed to, for example, a submount, the recesses 152a and 153a extend in a direction parallel to the resonator length direction, so that the stress generated in the terrace portions 152 and 153 is dispersed, and the ridge The stress applied to the portion 151 decreases. As a result, it is possible to reduce deterioration of the polarization characteristics of the semiconductor laser element or disturbance of the radiation pattern of the semiconductor laser element.

  Further, since the plating electrode 113 contains Au and the thickness of the thickest portion is 2.5 μm, the heat dissipation effect of the plating electrode 113 can be increased, and the polarization characteristics are deteriorated due to the stress generated inside the element. Can be prevented.

  Further, since the width of each of the recesses 152a and 153a is 2.0 μm, the effect of enlarging the heat dissipation area by deepening the recesses 152a and 153a in the etching process can be increased.

  In addition, since the width of each of the concave portions 152a and 153a is 2.0 μm, it is possible to prevent the effect of supporting the terrace portions 152 and 153 from being reduced. Therefore, an increase in stress on the ridge 151 can be prevented.

  Moreover, since the space | interval of the said adjacent recessed parts 152a is 2.0 micrometers beyond the depth of the recessed part 152a, the intensity | strength of the part between recessed parts 152a becomes high, and it can prevent that the part applies.

  Moreover, since the space | interval of the said adjacent recessed parts 152a is 2.0 micrometers, the area | region in which the recessed part 152a is not formed reduces, and the effect which expands a thermal radiation area can be enlarged.

  Moreover, since the space | interval of the said adjacent recessed parts 153a is 2.0 micrometers beyond the depth of the recessed part 153a, the intensity | strength of the part between recessed parts 153a becomes high, and it can prevent that part applying.

  Moreover, since the space | interval of the said adjacent recessed parts 153a is 2.0 micrometers, the area | region in which the recessed part 153a is not formed reduces, and the effect which expands a thermal radiation area can be enlarged.

  In addition, since the distance between the ridge 151 and the terraces 152 and 153 is 5.0 μm, the terraces 152 and 153 are less likely to adversely affect the distribution of the laser beam, and the radiation angle of the laser beam deviates from a predetermined angle. Can be prevented.

  Further, since the interval between the ridge 151 and the terraces 152 and 153 is 10.0 μm or less, the heat of the multiple quantum well active layer 105 under the ridge 151 and the heat of the ridge 151 are transmitted to the plating electrode 113. Can be effectively missed.

In addition, since the thickness of the portion covering the side surface of the ridge 151 in the SiO ₂ film 112 is 100 nm, the laser beam does not spread to the plating electrode 113 formed on the SiO ₂ film 112, and An increase in current due to absorption loss can be prevented, and deterioration of heat dissipation due to the thermal resistance of the SiO ₂ film 112 can be prevented.

Further, in the SiO ₂ film 112, the thickness of the portions covering the bottom surfaces and the side surfaces of the recesses 152a and 153a is 100 nm, so that heat can be effectively radiated to the plating electrode 113 through the portions.

In the first embodiment, the SiO ₂ film 212 is used as an example of a dielectric film, but may be used as an example of an SiN or Al ₂ O ₃ dielectric film.

  In the first embodiment, the plurality of groove-shaped recesses 152a extending in the direction parallel to the resonator length direction are formed on the upper surface of the terrace portion 152, but are parallel to the resonator length direction. A single groove-like recess extending in the direction may be formed. Alternatively, a single or a plurality of cylindrical or quadrangular columnar concave portions may be formed on the upper surface of the terrace portion 152.

  In the first embodiment, the plurality of groove-like recesses 153a extending in the direction parallel to the resonator length direction are formed on the upper surface of the terrace portion 153, but are parallel to the resonator length direction. A single groove-like recess extending in the direction may be formed. Alternatively, a single or a plurality of cylindrical or quadrangular columnar concave portions may be formed on the upper surface of the terrace portion 153.

  In the first embodiment, the plurality of recesses 152a extending in the direction parallel to the resonator length direction are formed on the upper surface of the terrace portion 152 with the same width, but are parallel to the resonator length direction. A plurality of recesses extending in the direction may be formed with different widths.

  In the first embodiment, the plurality of concave portions 153a extending in the direction parallel to the resonator length direction are formed on the upper surface of the terrace portion 153 with the same width, but are parallel to the resonator length direction. A plurality of recesses extending in the direction may be formed with different widths.

  In the first embodiment, the plurality of recesses 152a extending in the direction parallel to the resonator length direction are formed on the upper surface of the terrace portion 152 at the same interval, but are parallel to the resonator length direction. A plurality of recesses extending in the direction may be formed at different intervals.

  In the first embodiment, the plurality of recesses 153a extending in the direction parallel to the resonator length direction are formed on the upper surface of the terrace portion 153 at the same interval, but are parallel to the resonator length direction. A plurality of recesses extending in the direction may be formed at different intervals.

  In the first embodiment, the interval between the ridge 151 and the terraces 152 and 153 is 5.0 μm, but may be other than 4.0 μm and 10.0 μm and other than 5.0 μm.

  In the first embodiment, the width of each recess 152a is 2.0 μm, but may be a width other than 0.5 μm and 2.0 μm and other than 2.0 μm.

  In the first embodiment, the width of each recess 153a is 2.0 μm, but may be a width other than 0.5 μm and 2.0 μm and other than 2.0 μm.

  In the first embodiment, the interval between the adjacent recesses 152a is 2.0 μm. However, the interval may be other than the depth of the recess 152a but not more than 2.0 μm and not more than 2.0 μm.

  In the first embodiment, the interval between the adjacent recesses 153a is 2.0 μm, but may be an interval other than the depth of the recess 153a and not more than 2.0 μm and not more than 2.0 μm.

  In the first embodiment, the thickness of the thickest part of the plating electrode 113 is 2.5 μm, but may be a thickness other than 1.0 μm and 4.0 μm and other than 2.5 μm.

  In the first embodiment, the plating electrode 113 is formed on the upper side of the semiconductor laser element. However, other than the plating electrode 113, a metal containing Au may be formed.

In the first embodiment, the thickness of the portion covering the side surface of the ridge 151 in the SiO ₂ film 112 is 100 nm. However, the thickness may be 100 nm or more and 200 nm or less and other than 100 nm.

In the first embodiment, the thickness of the portion covering the bottom surface and the side surface of the recess 152a in the SiO ₂ film 112 is 100 nm. However, the thickness may be less than 100 nm.

In the first embodiment, the thickness of the portion covering the bottom surface and the side surface of the recess 153a in the SiO ₂ film 112 is 100 nm. However, the thickness may be less than 100 nm.
FIG. 2A is a diagram schematically showing a cross section of the semiconductor laser element according to Example 2 of the present invention, taken along a plane parallel to the cavity length direction and the layer thickness direction. FIG. 2B is a diagram schematically showing the upper surface of the semiconductor laser element. However, in FIG. 2B, the SiO ₂ film 212 and the TiAu / Au plating electrode 213 are not shown. Note that a dotted line is inserted between FIG. 2 (a) and FIG. 2 (b) so that the portion schematically showing the cross section of FIG. 2 (a) corresponds to which part of FIG. Pulling. 2 (a) and 2 (b), the same components as those of the first embodiment shown in FIGS. 1 (a) and 1 (b) are designated by the reference numerals of the components of the first embodiment. The same reference numbers are attached.

  2A and 2B, the semiconductor laser element includes an n-type GaAs substrate 101 and an n-type GaInP (thickness 0) formed on the substrate 101 by metal organic vapor phase epitaxy. .25 μm) buffer layer 102, n-type AlGaInP (Al composition ratio 0.7, thickness 3.0 μm) lower cladding layer 103, undoped AlGaInP (Al composition ratio 0.55, thickness 20 nm) lower guide layer 104, undoped GaInP (thickness) 4 nm) / AlGaInP (Al composition ratio 0.55, thickness 6 nm) multiple quantum well active layer 105, undoped AlGaInP (Al composition ratio 0.55, thickness 20 nm) upper guide layer 106, p-type AlGaInP (Al composition ratio 0.7) , Thickness 1.5 μm) upper cladding layer 207, p-type GaInP (thickness 35 nm) intermediate layer 110, and p-type GaAs (thickness 0.3 μm) cap layer 11 It is equipped with a.

  Further, a ridge portion 251 and terrace portions 252 and 253 sandwiching the ridge portion 251 from the lateral direction are formed on the side opposite to the substrate 101 side of the semiconductor laser element by a photolithography process. The ridge portion 251 and the terrace portions 252 and 253 are composed of a part of the upper cladding layer 207, the intermediate layer 110, and the cap layer 111, respectively.

  A plurality of recesses 252a extending in a direction perpendicular to the resonator length direction is formed over the entire top surface of the terrace portion 252. A plurality of recesses 253a extending in the direction perpendicular to the resonator length direction are also formed on the entire top surface of the terrace portion 253.

Further, the side surfaces of the ridge portion 251 and the upper surfaces and side surfaces of the terrace portions 252 and 253 are covered with a SiO ₂ (thickness 100 nm) film 212. The SiO ₂ film 212 is an example of a dielectric film.

A TiAu / Au plating electrode 213 is formed on the SiO ₂ film 212 and the ridge portion 251. On the other hand, an AuGeNi electrode 114 is formed under the substrate 101. The TiAu / Au plating electrode 213 is an example of a metal.

  The width of the ridge portion 251 (the length in the resonator length direction and the direction perpendicular to the layer thickness direction) is 1.7 μm, and the distance between the ridge portion 251 and the terrace portions 252 and 253 is 5.0 μm. The resonator length is 1500 μm and the chip width is 110 μm. The oscillation wavelength of the laser light is 640 nm.

  In the photolithography process for forming the ridge portion 251, a plurality of recesses 252 a and 253 a are formed simultaneously with the ridge portion 251. The widths of the recesses 252a and 253a are 2.0 μm. Moreover, the space | interval of adjacent recessed parts 252a and the space | interval of adjacent recessed parts 253a are 2.0 micrometers. The depths of the recess 252a and the recess 253a are 1.3 μm, which is the same as the height of the ridge 251.

In addition, after the formation of the recesses 252a and 253a, a part of the plating electrode 213 is embedded in the recesses 252a and 253a through the SiO ₂ film 212 by an electrode forming process. The thickness of the thickest part of the plating electrode 213 is 2.0 μm.

  In FIG. 2B, reference numeral 261 denotes a front end face as an example of an emission end face, and 262 denotes a rear end face.

  According to the semiconductor laser device having the above configuration, since the concave portions 252a and 253a are formed on the upper surfaces of the terrace portions 252 and 253, the terrace portions 252 and 253 are formed rather than when the upper surfaces of the terrace portions 252 and 253 are flat surfaces. And the bonding area of the plating electrode 213 becomes large. Thereby, the heat generated in the multiple quantum well active layer 105 under the ridge 251 or the heat generated in the ridge 251 can be efficiently transmitted to the metal through the terraces 252 and 253. Therefore, when the plated electrode 213 is fixed to, for example, a submount, the plated electrode 213 has good thermal conductivity, so that heat can be efficiently released from the plated electrode 213 to the submount. As a result, since the effective temperature of the multiple quantum well active layer 105 can be kept low, an increase in current during high-temperature operation can be reduced.

  In addition, the semiconductor laser device can be operated at a temperature of 10 ° C. and can be operated at 70 ° C. by continuous oscillation driving of 100 mW, for example, as compared with a conventional semiconductor laser device having no recess in the terrace portion.

  Further, when the plating electrode 213 is fixed to, for example, a submount, the recesses 252a and 253a extend in a direction perpendicular to the resonator length direction, so that the stress due to the fixing decreases. Therefore, it is possible to prevent a decrease in reliability due to warpage of the semiconductor laser element in the resonator direction or a crack of the semiconductor laser element.

Example 3
FIG. 3A is a diagram schematically showing a cross section of the semiconductor laser device according to Example 3 of the present invention taken along a plane perpendicular to the cavity length direction. FIG. 3B is a diagram schematically showing the upper surface of the semiconductor laser element. However, in FIG. 3B, the SiO ₂ film 312 and the TiAu / Au plating electrode 313 are not shown. Note that a dotted line is inserted between FIG. 3 (a) and FIG. 2 (b) so that the portion schematically showing the cross section of FIG. 3 (a) corresponds to which portion of FIG. 3 (b) corresponds. Pulling. 3 (a) and 3 (b), the same components as those of the first embodiment shown in FIGS. 1 (a) and 1 (b) are designated by the reference numerals of the components of the first embodiment. The same reference numbers are attached.

  The semiconductor laser device of Example 3 is obtained by the same manufacturing process as that of Example 1. As shown in FIGS. 3A and 3B, this semiconductor laser device has the same epi structure as that of the first embodiment, but the formation of the recesses 352a and 353a of the terrace portions 352 and 353. The range is different from the formation range of the concave portions 152a and 153a of the terrace portions 152 and 153 of the first embodiment.

  More specifically, the concave portions 352a and 353a are formed only in a portion within 30.0 μm from the end of the terrace portions 352 and 353 on the ridge portion 151 side in the direction away from the ridge portion 151.

Further, the side surface of the ridge portion 151 and the upper surfaces and side surfaces of the terrace portions 352 and 353 are covered with the SiO ₂ film 312. The SiO ₂ film 312 is an example of a dielectric film.

In the SiO ₂ film 312, the thickness between the ridge 151 and the terraces 352 and 353 is 200 nm, but covers the top surfaces of the terraces 352 and 353 and the bottom and side surfaces of the recesses 352a and 353a. The thickness of is set to 50 nm. Such an SiO ₂ film 312 can be obtained by forming the SiO ₂ film 112 of Example 1 and then covering the ridge 151 and part of both sides thereof with a resist, followed by etching.

  In FIG. 3B, reference numeral 361 denotes a front end face as an example of an emission end face, and 362 denotes a rear end face.

  According to the semiconductor laser device having the above configuration, the concave portions 352a and 353a are formed only in the portion within 30.0 μm from the end on the ridge portion 151 side of the terrace portions 352 and 353 toward the direction away from the ridge portion 151. Therefore, the heat of the multi-quantum well active layer 105 under the ridge 151 and the heat of the ridge 151 can be effectively released to the plating electrode 313, and the occurrence of overhang due to the strength reduction of the terraces 352 and 353 can be prevented. be able to.

In addition, since the thickness of the portion covering the bottom and side surfaces of the recesses 352a and 353a in the SiO ₂ film 312 is 50 nm, heat can be radiated from the recesses 352a and 353a more effectively than in the first embodiment.

Example 4
FIG. 4A is a diagram schematically showing a cross section of the semiconductor laser element according to Example 4 of the present invention cut along a plane parallel to the cavity length direction and the layer thickness direction. FIG. 4B is a diagram schematically showing the upper surface of the semiconductor laser element. However, in FIG. 4B, the SiO ₂ film and the TiAu / Au plating electrode 413 are not shown. Note that a dotted line is inserted between FIG. 4 (a) and FIG. 4 (b) so that the portion schematically showing the cross section of FIG. 4 (a) corresponds to which portion of FIG. 4 (b) corresponds. Pulling. 4 (a) and 4 (b), the same components as those of the second embodiment shown in FIGS. 2 (a) and 2 (b) are designated by the reference numerals of the components of the second embodiment. The same reference numbers are attached. In the following description, the same components as those in the second embodiment shown in FIGS. 2A and 2B are denoted by the same reference numerals as those in the second embodiment. ing.

  The semiconductor laser device of Example 4 is obtained by the same manufacturing process as that of Example 2. As shown in FIGS. 4A and 4B, this semiconductor laser device has the same epi structure as that of the second embodiment, but formation of recesses 452a and 453a in the terraces 452 and 453. The range is different from the formation range of the concave portions 252a and 253a of the terrace portions 252 and 253 of the second embodiment.

  More specifically, the recesses 452a and 453a are formed only in a portion within 300.0 μm in the direction away from the front end surface 461 from the front end surface 461 of the terrace portions 452 and 453. The front end surface 461 is an example of an emission end surface.

An SiO ₂ film (thickness 200 nm) is formed between the terrace portions 452 and 453 and the ridge portion 251, but no SiO ₂ film is formed on the terrace portions 452 and 453. That is, the side surfaces of the ridge portion 251 are covered with the SiO ₂ film, but the upper surfaces of the terrace portions 452 and 453 and the bottom surfaces and side surfaces of the recesses 452a and 453a are not covered with the SiO ₂ film.

  Each of the terrace portions 452 and 453 includes a part of the upper cladding layer 207. The terrace portions 452 and 453 do not include the intermediate layer 110 and the cap layer 111.

More specifically, after the SiO ₂ film 112 is formed by the manufacturing process of the first embodiment, the ridge 251 and part of both sides thereof are covered with a resist, and the SiO ₂ film 112 and the cap layer 111 that are not covered with the resist are covered. Further, the terrace portions 452 and 453 are formed by removing the intermediate layer 110 by etching.

  Thereafter, a TiAu / Au plating electrode 413 is formed on the ridge portion 251 and the terrace portions 452 and 453. Since TiAu forming the lower part of the plating electrode 413 is in ohmic contact with GaAs forming the upper part of the ridge 251, a current flows to the ridge 251 with a bias voltage of about 2V, for example. On the other hand, since TiAu makes a Schottky junction with AlGaInP forming the upper portions of the terrace portions 452 and 453, no current flows. As a result, a current constriction can be obtained in which current flows through the ridge portion 251 but current does not flow through the terrace portions 452 and 453.

  In FIG. 4B, reference numeral 462 denotes a rear end surface.

  According to the semiconductor laser device having the above configuration, even if the temperature in the vicinity of the front end surface 461 rises, the concave portions 452a and 453a are formed only in the portion within 300.0 μm from the front end surface 461 of the terrace portion in the direction away from the front end surface 461. Therefore, the COD of the front end surface 461 can be prevented, and the occurrence of overhang due to the strength reduction of the terrace portions 452 and 453 can be prevented.

In the fourth embodiment, a dielectric film (for example, the front end face 461 is made of Al ₂ O ₃ and the rear end face is formed on the end face so that the reflectivity of the front end face 461 is 5% and the reflectivity of the rear end face 462 is 95%. 462 is a multilayer film of Al ₂ O ₃ and TiO). In this case, inside the laser, the light intensity is higher on the front end face 461 side than on the rear end face 462 side, and this region is formed by forming the recesses 452a and 453a in the terrace portions 452 and 453 where the light intensity is higher. It is possible to effectively suppress the COD reduction due to the heat generation.

  Further, since the plating electrode 413 is directly joined to the terrace portions 452 and 453, the heat radiation efficiency from the terrace portions 452 and 453 to the plating electrode 413 can be made extremely high.

  In addition, since direct bonding between the plating electrode 413 and the terrace portions 452 and 453 is Schottky bonding, no current flows between the plating electrode 413 and the terrace portions 452 and 453. Therefore, the current toward the multiple quantum well active layer 105 can be reliably narrowed.

  In the first to third embodiments, an example in which the present invention is applied to a red semiconductor laser element using an AlGaInP-based semiconductor crystal has been described. However, the semiconductor laser element using another crystal system such as an AlGaAs-based or AlGaInAs-based semiconductor laser element has been described. The present invention may also be applied.

  Moreover, what combined suitably the said Examples 1-3 and its modification is good also as one Example of this invention.

That is, the semiconductor laser element of the present invention is
A substrate,
An active layer formed on the substrate;
A ridge formed on the active layer;
A terrace formed on the side of the ridge,
A metal formed on the terrace part,
A concave portion is formed on the upper surface of the terrace portion.

In the semiconductor laser device of one embodiment,
The recess extends in a direction parallel to the resonator length direction.

In the semiconductor laser device of one embodiment,
The concave portion extends in a direction perpendicular to the resonator length direction.

In the semiconductor laser device of one embodiment,
The concave portion is formed only in a portion within 30.0 μm from the end of the terrace portion on the ridge portion side in a direction away from the ridge portion.

The semiconductor laser device of one embodiment
It is perpendicular to the resonator length direction and includes an emission end face that emits laser light.
The concave portion is formed only in a portion within 300.0 μm in the direction away from the emission end face from the emission end face of the terrace portion.

In the semiconductor laser device of one embodiment,
The metal contains Au and has a thickness of 1.0 μm or more and 4.0 μm or less.

In the semiconductor laser device of one embodiment,
The recess is formed such that the bottom of the recess is located above the upper surface of the active layer.

In the semiconductor laser device of one embodiment,
A plurality of the concave portions are formed on the upper surface of the terrace portion,
The width of each recess is 0.5 μm or more and 2.0 μm or less,
The interval between the adjacent recesses is not less than the depth of the recess and not more than 2.0 μm.

In the semiconductor laser device of one embodiment,
The distance between the ridge portion and the terrace portion is 4.0 μm or more and 10.0 μm or less.

The semiconductor laser device of one embodiment
A dielectric film is formed to confine current flowing toward the active layer, and covers a side surface of the ridge portion and a bottom surface and a side surface of the recess.
In the dielectric film, the thickness of the portion covering the side surface of the ridge portion is not less than 100 nm and not more than 200 nm.

In the semiconductor laser device of one embodiment,
In the dielectric film, the thickness of the portion covering the bottom and side surfaces of the recess is 100 nm or less.

The semiconductor laser device of one embodiment
The metal is directly joined to the terrace part,
Direct bonding between the metal and the terrace portion is a Schottky junction.

101 n-type GaAs substrate 102 n-type GaInP buffer layer 103 n-type AlGaInP lower cladding layer 104 undoped AlGaInP lower guide layer 105 undoped GaInP / AlGaInP multiple quantum well active layer 106 undoped AlGaInP upper guide layer 107 p-type AlGaInP first upper cladding layer 108 p-type GaInP etching stop layer 109 p-type AlGaInP second upper cladding layer 110 p-type GaInP intermediate layer 111 p-type GaAs cap layer 112,212,312 SiO ₂ film 113,213,313,413 TiAu / Au plated electrode 114 AuGeNi electrode 151,251 Ridge part 152,153,252,253,352,353,452,453 Terrace part 152a, 153a, 252a, 253a, 352a, 353a, 452a, 453a Recess 207 Cladding layer on p-type AlGaInP

Claims (5)

A substrate,
An active layer formed on the substrate;
A ridge formed on the active layer;
A terrace formed on the side of the ridge,
A metal formed on the terrace part,
A semiconductor laser device, wherein a concave portion is formed on an upper surface of the terrace portion. The semiconductor laser device according to claim 1,
A semiconductor laser element, wherein the recess extends in a direction parallel to the cavity length direction. The semiconductor laser device according to claim 1,
A semiconductor laser element, wherein the recess extends in a direction perpendicular to the cavity length direction. In the semiconductor laser device according to any one of claims 1 to 3,
The semiconductor laser device, wherein the concave portion is formed only in a portion within 30.0 μm from the end of the terrace portion on the ridge portion side in a direction away from the ridge portion. In the semiconductor laser device according to any one of claims 1 to 4,
It is perpendicular to the resonator length direction and includes an emission end face that emits laser light.
2. The semiconductor laser device according to claim 1, wherein the concave portion is formed only in a portion within 300.0 [mu] m in a direction away from the emission end face from the emission end face of the terrace portion.

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