JP2006100517A - Semiconductor laser device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device having high reliability by using the window-structure forming processes of each semiconductor laser element in common in a high-power monolithic two-wavelength semiconductor laser. <P>SOLUTION: In the semiconductor laser device, an infrared laser element 110 and a red laser element 120 are formed on the same n-type substrate 101. The infrared laser element 110 and the red laser element 120 have ridge-shaped waveguides respectively, and window structures 131 in which Zn is diffused are formed to the end faces of each resonator. A p-type contact layer 109 is contained in the ridge-shaped waveguide for the infrared laser element 110, and a p-type contact layer 119 in the ridge-shaped waveguide for the red laser element 120, respectively. The film thickness of the p-type contact layer 109 is set at a value thinner than that of the p-type contact layer 119. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser device and a manufacturing method thereof, and more particularly to a two-wavelength type semiconductor laser device having a monolithic structure including two semiconductor lasers having different oscillation wavelengths and a manufacturing method thereof.

  In recent years, DVD drives for recording and reproducing optical information characterized by a large storage capacity are rapidly spreading in various fields including video players. In addition, there is a strong demand for reading of CDs, CD-Rs, and CD-RWs that have been conventionally used with the same device. For this reason, an infrared semiconductor laser for 780 nm band for CD is used together with a red semiconductor laser for 650 nm band for DVD as a light source of an optical pickup used for recording / reproducing of DVD and CD.

  A recording / reproducing apparatus such as a DVD needs to be reduced in size and thickness as information processing equipment such as a personal computer is downsized. In order to realize this, it is essential to reduce the size and thickness of the optical pickup. In order to reduce the size and thickness of an optical pickup, it is effective to simplify the apparatus by reducing the number of optical components, and one of them is to integrate a red semiconductor laser and an infrared semiconductor laser.

  As a conventional example, a monolithic semiconductor laser in which a red semiconductor laser and an infrared semiconductor laser are integrated on the same semiconductor substrate is proposed in, for example, Patent Document 1 and the like. As a result, not only the semiconductor laser itself can be integrated into a single component, but also optical components such as collimator lenses and beam splitters can be shared by the red and infrared semiconductor lasers, which is effective in reducing the size and thickness of the device. is there.

  On the other hand, in this monolithic semiconductor laser, further improvement in light output is required, and in order to ensure stable operation and reliability during high output operation, an actual refractive index waveguide structure is used, and is emitted at the laser end face. An end face window structure having a larger band gap than laser light is being performed.

  As the laser output increases, the amount of injected current increases, but on the other hand, heat is likely to be generated in the vicinity of the end face due to non-radiative recombination that occurs at the interface state between the end face coat film and the laser end face.

  However, since the end face window structure as described above can suppress the laser deterioration due to heat generation, in the semiconductor laser element operated at a high output, the end face window structure is formed by infrared laser, red Both lasers are essential. The manufacturing method of the end face window structure is proposed in Patent Document 2, Patent Document 3, and the like.

  Among these, the manufacturing method of the end surface window structure of the red laser apparatus in the prior art described in patent document 2 is shown in FIG.

  As shown in FIG. 7A, an n-type cladding layer 402 made of GaAs and an n-type cladding layer made of AlGaInP are formed on an n-type substrate 401 made of GaAs by metal organic vapor phase epitaxial growth (hereinafter referred to as MOVPE method). Layer 403, active layer (multiple quantum well structure with oscillation wavelength of 660 nm) 404, p-type first cladding layer 405 made of AlGaInP, etching stop layer 406 made of GaInP, p-type second cladding layer 407 made of AlGaInP, and GaInP A p-type intermediate layer 408 and a p-type contact layer 409 made of GaAs are sequentially stacked.

  Next, a ZnO film 410 is deposited on the entire surface of the wafer using a film forming apparatus such as a sputtering apparatus (not shown), and patterning is performed by using a photoresist so that the ZnO film 410a remains only in the vicinity of the region serving as the laser end face. .

  Next, an insulating film 411 is deposited on the entire surface of the wafer, and heat treatment is performed at an appropriate temperature and time so that Zn is diffused and reached in the semiconductor layer laminated from the ZnO film 410a, particularly in the active layer (FIG. 7). (B)).

  In the region where Zn is diffused by this treatment, disordering of the active layer 404 occurs, and a window structure 412 having a band gap larger than that of the active layer 404 is formed. Finally, the ZnO film 410a is removed (FIG. 7C).

  Here, by utilizing the fact that a GaAs material has a smaller Zn diffusion coefficient compared to an AlGaInP material, the GaAs contact layer 409 functions as a Zn diffusion control layer in the Zn diffusion process, so that the end face portion can be obtained. The window structure can be stably formed. Further, by suppressing excessive diffusion of Zn in the window structure 412, in the subsequent process of processing the p-type second cladding layer 407 into a stripe pattern, the lower GaInP etching stop layer 406 is prevented from being scraped and gained. It is possible to make a stripe shape equivalent to the part.

  On the other hand, in a two-wavelength laser in which laser elements that emit infrared laser light and red laser light are formed monolithically on the same substrate, the following problems are mainly cited when forming a window structure.

  First, as described above, since the diffusion coefficient of Zn is small in a GaAs-based material, an infrared laser whose active layer is made of a GaAs-based material is more difficult to form a window structure than a red laser whose active layer is made of an AlGaInP-based material. It is.

  Further, for the above reasons, the window structure formation in the infrared laser and red laser portions having different active layer structures must be performed under different conditions.

  However, if the heat treatment for Zn diffusion is performed separately in this manner, excessive heat treatment is added to the laser in which the window structure has been previously formed, and as a result, the generation of defects in the semiconductor is induced. Due to the excessive diffusion of Zn, there is a concern that the reliability of the active layer in the laser gain portion is lowered.

  On the other hand, countermeasures are taken for these problems in Patent Documents 3 and 4, respectively.

  In Patent Document 3, the diffusion of Zn is facilitated by using AlGaAs instead of GaAs for the p-type contact layer. As a result, it has been reported that an infrared laser using a GaAs-based material can form a window structure with good controllability and high reproducibility.

Patent Document 4 reports that the window structure can be formed by diffusing Zn under the same heat treatment conditions by optimizing the thickness of the active layer of the infrared laser and the active layer of the red laser. Has been.
Japanese Patent Laid-Open No. 11-186651 JP 2001-210907 A JP 2002-26447 A JP 2001-345514 A

  However, in the above monolithic two-wavelength semiconductor laser device, even if the methods disclosed in Patent Documents 3 and 4 are used, it is still difficult to simultaneously form a window structure by solid phase diffusion of Zn.

  In order to make Zn diffusion equivalent to an AlGaInP-based material by the method disclosed in Patent Document 3, it is necessary to increase the Al composition ratio in AlGaAs serving as a contact layer.

  However, if the Al composition ratio in AlGaAs is increased, the resistivity also increases accordingly, which increases the device resistance of the infrared laser device, which is disadvantageous for increasing the output.

  On the other hand, as shown in Patent Document 4, in the method of optimizing the active layer film thickness with respect to Zn diffusion in each laser element, it is difficult to simultaneously optimize the performance of each laser element.

  Moreover, in manufacturing a monolithic two-wavelength laser element, in order to reduce the man-hour, the clad layer material is the same for both the red laser and the infrared laser, and an AlGaInP-based material is often used as the material. In order to optimize the performance of the laser element, the composition of the cladding layer may be changed between red and infrared.

  However, in that case, a difference in Zn diffusion coefficient in the clad layer occurs, and the diffusion of Zn cannot be controlled only by the thickness of the active layer.

  Therefore, in order to solve the above-described conventional problems, the present invention is capable of disordering the active layers of the infrared laser element and the red laser element by thermal diffusion of Zn at the same time with a simple configuration and is highly reliable. It is an object to provide a monolithic monochromatic two-wavelength semiconductor laser device and a method for manufacturing the same.

  In order to solve the above problems, a semiconductor laser device according to the present invention includes a substrate in which a first semiconductor laser element that emits light of a first wavelength and a second semiconductor laser element that emits light of a second wavelength are the same substrate. A monolithic type semiconductor laser device formed thereon, wherein each of the first semiconductor laser element and the second semiconductor laser element includes at least a first conductivity type cladding layer, an active layer, and a second conductivity type cladding. A ridge-shaped waveguide including a double heterostructure formed by laminating layers in this order, at least the second conductivity type cladding layer, and a contact layer provided thereon; Each of the semiconductor laser device and the second semiconductor laser device has a window structure region into which a high-concentration impurity is introduced at the cavity end face. Thickness respectively and the contact layer serial contact layer and in the second semiconductor laser element are different from each other.

  The active layer in the first semiconductor laser element is made of a material having a smaller diffusion coefficient for the impurities than the active layer in the second semiconductor laser element, and the contact layer in the first semiconductor laser element is The film thickness is preferably thinner than the contact layer in the second semiconductor laser element.

  In the first semiconductor laser element and the second semiconductor laser element, it is preferable that a current blocking layer is formed so as to cover a side surface of the ridge.

  The difference in film thickness between the contact layer of the first semiconductor laser element and the contact layer of the second semiconductor laser element is preferably 0.01 μm or more.

  More preferably, the film thickness difference is 0.05 μm or more.

  The first wavelength is preferably infrared light in the 780 nm band, and the second wavelength is preferably red light in the 660 nm band.

Both the contact layer in the first semiconductor laser element and the contact layer in the second semiconductor laser element are preferably made of Al _x Ga _1-x As (0 ≦ x ≦ 0.4).

The contact layer in the first semiconductor laser element and the contact layer in the second semiconductor laser element preferably each have a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ or more.

  The current blocking layer preferably covers at least the upper surface of the region where the window structure is formed in the ridge-shaped waveguide.

  It is preferable that an isolation groove is provided between the first semiconductor laser element and the second semiconductor laser element, and an insulating film is formed in the isolation groove.

  According to a method of manufacturing a semiconductor laser device of the present invention, a first first-conductivity-type cladding layer, a first active layer, a first second-conductivity-type cladding layer, and a first second layer are formed on a semiconductor substrate. Forming a first laminated semiconductor structure including a conductive contact layer in order from the substrate side; removing the first laminated semiconductor structure on a predetermined region of the semiconductor substrate; and A second first conductivity type cladding layer, a second active layer, a second second conductivity type cladding layer, a first second conductivity type contact layer, and a film are formed on the entire surface of the semiconductor substrate including the region. Forming a second laminated semiconductor structure including second conductive contact layers having different thicknesses in order from the substrate side; and the second laminated semiconductor formed in a region other than the predetermined region Removing the structure; and a surface and a surface of the first laminated semiconductor structure. A step of providing an impurity diffusion source in a predetermined region on the surface of the second stacked semiconductor structure; and heat-treating the semiconductor substrate so that the inside of the first stacked semiconductor structure and the first stack are formed from the impurity diffusion source. A step of diffusing the impurity inside the semiconductor structure to form a window structure; the first second conductivity type cladding layer; the first second conductivity type contact layer; and the second second conductivity type. A step of patterning the cladding layer and the second second conductivity type contact layer to form two ridge-shaped waveguides, and a current to cover the side surfaces of the two ridge-shaped waveguides A step of forming a block layer, and a step of forming two semiconductor laser elements by forming electrodes on the upper surface of the two ridge-shaped waveguides and on the rear surface of the substrate, respectively.

  Zn or Si is preferably used as the impurity.

  Preferably, the method further comprises a step of removing the first second conductivity type contact layer and the second second conductivity type contact layer in the vicinity of each resonator end face in the two semiconductor laser elements.

  In the step of removing the first second conductivity type contact layer and the second second conductivity type contact layer, the first first conductivity type is formed over a length of at least 5 μm from the cavity end face toward the laser gain portion. It is preferable to remove the two-conductivity type contact layer and the second second-conductivity type contact layer.

  In the step of forming a current blocking layer so as to cover the side surfaces of the two ridge-shaped waveguides, a region where the window structure is formed on the upper surface of the two ridge-shaped waveguides is defined as the current blocking layer. It is preferable to form so as to cover.

  According to the present invention, in a monolithic two-wavelength semiconductor laser, by forming a contact layer of a semiconductor laser that uses a material system in which impurities are difficult to diffuse, the two lasers can improve impurity diffusion and thus disorder during window structure formation. Since the window structure forming process can be performed at a time, the number of processes can be reduced, and thus the manufacturing cost can be reduced.

  Moreover, since unnecessary heat treatment steps can be reduced, excessive diffusion of impurities into the active layer can be prevented, and the reliability of each semiconductor laser can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
(Structure of two-wavelength semiconductor laser)
1A and 1B are schematic views showing the structure of the semiconductor laser device according to the first embodiment of the present invention. FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view.

  The monolithic two-wavelength semiconductor laser of the present embodiment includes an infrared laser element 110 and a red laser element 120 on an n-type GaAs substrate 101, and the configuration of each element is as follows.

The infrared laser element 110 includes an n-type GaAs buffer layer 102, an n-type (Al _x Ga _{1 -x} ) _y In _{1 -y} P cladding layer 103, and a GaAs / AlGaAs-based active layer 104 on an n-type GaAs substrate 101. , p-type _{(Al x Ga 1-x)} y in 1-y P first cladding layer 105, p-type GaInP etching stop layer 106, a ridge shape is formed in p-type _{(Al x Ga 1-x)} y in 1 _-y P second cladding layer 107, p-type GaInP intermediate layer 108, and p-type GaAs contact layer 109.

On the other hand, the red laser element 120 includes an n-type GaAs buffer layer 112, an n-type (Al _x Ga _{1 -x} ) _y In _{1 -y} P cladding layer 113, and a GaInP / AlGaInP-based active layer on an n-type GaAs substrate 101. 114, p-type _{(Al x Ga 1-x)} y in 1-y P first cladding layer 115, p-type GaInP etching stop layer 116, a ridge shape is formed in p-type _{(Al x Ga 1-x)} y in _1-y P second cladding layer 117, p-type GaInP intermediate layer 118, and p-type GaAs contact layer 119.

  A current blocking layer 132 is formed over the side surface of the ridge formed of the second cladding layers 107 and 117 and the upper surface of the etching stop layers 106 and 116, and Zn is diffused in the vicinity of the end face of each laser element. A window structure 131 is formed.

  At this time, the GaAs contact layers 109 and 119 on the window structure region 131 are removed by etching.

  The infrared laser element 110 and the red laser element 120 are electrically insulated by a separation groove 130 formed by etching up to the n-type substrate 101, and an insulating film is formed in the separation groove 130. Each layer in the infrared laser element 110 and the red laser element 120 is formed by the MOCVD method.

  The feature of this embodiment is that the p-type GaAs contact layer 109 in the infrared laser element 110 is formed to be thinner than the p-type GaAs contact layer 119 in the red laser element 120. In the present embodiment, the p-type GaAs contact layer 109 on the infrared laser side has a thickness of 0.1 μm, and the p-type GaAs contact layer 119 on the red laser side has a thickness of 0.2 μm. Further, the GaAs contact layers 109 and 119 on the window structure 131 are removed by etching. The effect of providing a film thickness difference between these contact layers, the effect of removing the contact layer on the window structure, and the like will be described in the following description of the manufacturing method.

(Manufacturing method of two-wavelength semiconductor laser)
Next, a method for manufacturing the semiconductor laser device having the above structure will be described with reference to FIGS. 2, 3, and 4 are cross-sectional views showing each step of the manufacturing method in the present embodiment.

First, as shown in FIG. 2 (a), on the n-type GaAs substrate 201, n-type GaAs buffer layer 202, n-type _{(Al x Ga 1-x)} y In 1-y P cladding layer 203, GaAs / AlGaAs An active layer 204 of a system material, a p-type (Al _x Ga _{1 -x} ) _y In _{1 -y} P first cladding layer 205, a p-type GaInP etching stop layer 206, and a p-type (Al _x Ga _{1 -x} ) _y In _{The 1-y} P second cladding layer 207, the p-type GaInP intermediate layer 208, and the p-type GaAs contact layer 209 are sequentially formed using the MOCVD method.

In the present embodiment, the composition of (Al _x Ga _1-x ) _y In _1-y P in each cladding layer is x = 0.7 and y = 0.5.

  Next, as shown in FIG. 2B, in the region where the red laser element is formed, the above-mentioned laminated semiconductor layer is removed by using a photolithography technique and a wet etching technique to form an infrared laser element region 210. .

  Here, a hydrochloric acid-based etchant is used for etching the semiconductor layer containing P, and a sulfuric acid-based etchant is used for etching the semiconductor layer containing As, so that the etching selectivity is improved and the n-type GaAs buffer is used. Etching was performed to leave layer 202.

Next, as shown in FIG. 2C, an n-type GaAs buffer layer 212 and an n-type (Al _x Ga _1-x ) are formed on an n-type substrate 201 including a region where the surface of the n-type GaAs buffer layer 202 is exposed. _{a y} In _{1 -y} P cladding layer 213, a GaInP / AlGaInP-based active layer 214, a p-type (Al _x Ga _{1 -x} ) _y In _{1 -y} P first cladding layer 215, a p-type GaInP etching stop layer 216, and A p-type (Al _x Ga _{1 -x} ) _y In _{1 -y} P second cladding layer 217, a p-type GaInP intermediate layer 218, and a p-type GaAs contact layer 219 are sequentially formed using the MOCVD method.

In the present embodiment, the composition of (Al _x Ga _1-x ) _y In _1-y P in each cladding layer is x = 0.7 and y = 0.5.

  Next, as shown in FIG. 2 (d), each of the layers constituting the red laser element formed on the infrared laser element region 210 is removed (the formation of the red laser region 220), and at the same time, the infrared laser In order to separate the element from the red laser element, a separation groove 230 is formed by photolithography and wet etching.

  Here, since each layer constituting the red laser element is a semiconductor layer containing P, a hydrochloric acid-based etchant was used as the etchant.

  In the present embodiment, the thickness of the p-type GaAs contact layer 219 of the red laser element is 0.2 μm, and the thickness of the p-type GaAs contact layer 209 of the infrared laser element is 0.1 μm, which is thinner than that. It was made to become. Further, since the oxide film on the surface of the contact layer is removed before the electrode is formed or the contact layer is etched in other steps, the thickness of each contact layer is preferably 0.1 μm or more at the time of formation.

  Next, as shown in FIG. 3E, the end face window structure 231 is formed by the following method.

ZnO (not shown) is deposited on the entire surface of the n-type substrate 201 by sputtering, and patterning is performed so that ZnO remains only in a region of about 20 μm from the laser cleavage portion. Further, a SiO ₂ film (not shown) is deposited as a cap film on the entire surface of the n-type substrate 201 containing ZnO.

  Thereafter, heat treatment is performed, and Zn is thermally diffused from the ZnO to the semiconductor layer immediately therebelow, and the active layer is disordered to form the window structure 231.

  In the present embodiment, since the film thickness of the p-type GaAs contact layer 209 and the film thickness of the p-type GaAs contact layer 219 are different, heat treatment under the same conditions is performed from the same diffusion source as described above to thermally diffuse Zn. The diffusion profile is originally different.

  However, in this embodiment, the active layer of the infrared laser element is a semiconductor layer containing As, the active layer of the infrared laser element is a semiconductor layer containing P, and the thermal diffusion coefficient of Zn in the former semiconductor layer is Smaller than that of the latter.

  Therefore, by setting the contact layer thickness in the infrared laser element to be thinner than the contact layer thickness in the red laser element as in the present embodiment, the respective active conditions can be obtained under the same heat treatment condition. Similarly, the layers can be disordered and have an average composition.

Next, as shown in FIG. 3 (f), SiO ₂ films (not shown) are formed in the infrared laser region and the infrared laser region, respectively, and stripes are formed using photolithography technology and dry etching technology. The mask pattern is processed into a shape (not shown). Using this stripe pattern as a mask, the second cladding layer 207 of the infrared laser element and the second cladding layer 217 of the red laser element are etched to reach the GaInP etching stop layers 206 and 216, respectively, thereby forming a ridge.

  This etching was performed by using both dry etching and wet etching using inductively coupled plasma or reactive ion plasma.

  Thereafter, the mask pattern is removed with a hydrofluoric acid-based etchant, and further, the p-type GaAs contact layers 209 and 219 are formed on the infrared laser region and the window structure 231 region in the red laser element by using a photolithography technique and a wet etching technique. To the gain part was removed up to the area inside 25 μm (not shown).

  Here, a sulfuric acid-based etching solution was used as an etchant for etching the contact layer.

  Next, as shown in FIG. 4G, a dielectric film to be the current blocking layer 232 is deposited on the entire surface of the wafer, and the current blocking layer 232 above the ridge is removed using photolithography and etching techniques. At this time, the patterning was performed so as to leave the block layer on the contact layer etched from the Zn diffusion region to the inside.

  4H is a cross-sectional view taken along line AA ′ shown in FIG. 4G. FIG. 4I is a cross-sectional view of the laser gain section, and FIG. 4I is a cross-sectional view taken along line B- shown in FIG. It is sectional drawing in B ', and hits the cross section of a window area | region.

  As shown in FIG. 4I, the contact layer is removed on the window structure 231 region, and the current blocking layer 232 is covered with the current blocking layer 232 by injecting current into the window forming region 221 at the end face of the resonator. This is to prevent heat generation from occurring, causing deterioration and reducing reliability.

  In order to prevent current injection into the window structure 231, it is necessary to remove at least 5 μm or more of the contact layer on the inner side of the gain structure than the window structure 231 and further cover with a current blocking layer.

  However, if the contact layer is removed too much, there is a risk of characteristic fluctuations such as the threshold value of the current-light output characteristic of the laser due to an increase in resistance or the like. In order to suppress such fluctuations, it is desirable to keep the removal width within 80 μm.

  Finally, a p-side electrode (not shown) is formed on the surface of the n-type substrate 201 including each layer, and an n-side electrode (not shown) is formed on the back surface of the substrate 201.

  As described above, according to the present embodiment, when forming the end face window structure by Zn diffusion, the thickness of the GaAs contact layer in each laser element is varied to control the Zn diffusion, thereby performing the same annealing. Even under the conditions, the active layer of each laser element can be disordered and average composition can be achieved, and the number of processes can be reduced.

  In addition, if a window structure is formed separately for each laser element, excessive thermal history is likely to be applied to one element, and it is difficult to optimize the average composition and the like while preventing a decrease in reliability in each laser element. However, according to the present embodiment, the window structure can be formed without adding an extra thermal history, so that the yield and reliability of the laser device can be improved.

  For the GaAs contact layer 209 of the infrared laser element 210, it is desirable to wet-clean the surface of the p-type GaAs contact layer in order to reduce the contact resistance and suppress the interface state with the electrode. Considering this, the thickness of the GaAs contact layer 209 needs to be 0.05 μm or more.

  Further, the film thickness difference between the GaAs contact layers 209 and 219 of the infrared laser element 210 and the red laser element 220 is determined by the difference in the Zn diffusion rate into the active layer. This speed depends on the carrier concentration of the GaAs contact layer and the carrier concentration of the p-type cladding layer of each element. However, considering the difference in diffusion coefficient in each element, the difference in film thickness is 0.01 μm or more. It is necessary to attach a difference of 0.05 μm or more.

  Furthermore, the carrier concentration setting of the contact layer is also important for reducing the contact resistance.

In order to simply lower the contact resistivity between the contact layer and the electrode to about 10 ⁻⁵ Ω · cm ² , the carrier concentration of the contact layer needs to be 1 × 10 ¹⁸ cm ⁻³ or more.

However, since the resistance of the laser element is also determined by the ridge width, for example, when the element resistance is to be suppressed within 5Ω, at least the carrier concentration is required to be 5 × 10 ¹⁷ cm ⁻³ or more.

In this embodiment, the carrier concentration is set to 1 × 10 ¹⁹ cm ⁻³ for both the p-type GaAs contact layers 209 and 219.

  As for the upper limit of the carrier concentration, high-concentration doping is possible up to a level that can be doped by crystal growth and a level that does not affect the Zn diffusion into the active layer.

  In addition, as described above, by providing a carrier concentration difference between the p-type GaAs contact layer 209 of the infrared laser and the p-type GaAs contact layer 219 of the red laser, the disordering of the active layer due to Zn diffusion is controlled. It is possible to some extent.

  Thus, in addition to providing a difference in film thickness between p-type GaAs contact layers, even if a difference in carrier concentration is provided, even if the film thickness and composition of the active layer structure and the cladding layer change, the film thickness of each contact layer The difference can be reduced, and when this monolithic semiconductor laser element is mounted on a submount, each light emitting point can be made parallel to the mounting reference plane, limiting the design of the optical system using this laser element. There is an advantage that it is not necessary.

For example, by increasing the carrier concentration of the p-type GaAs contact layer 209 on the infrared laser side from about 1 × 10 ¹⁹ cm ⁻³ to about 3 × 10 ¹⁹ cm ⁻³ , the film thickness can be increased by 30% or more. The film thickness difference from the contact layer 219 can be reduced.

In this embodiment, GaAs is used as the p-type contact layer of the infrared laser and the p-type contact layer of the red laser, but Al _x Ga _1-x As (0 <x ≦ 0.4) is used. Also good.

  By including Al in the contact layer, it becomes easy to diffuse Zn into the active layer, particularly on the infrared laser side. However, the inclusion of Al facilitates the formation of an oxide on the surface of the contact layer and causes an increase in contact resistance due to the interface state. Therefore, the Al content x is preferably 0.4 or less.

  In this embodiment, the composition of the cladding layer is the same for both the infrared laser and the red laser, but the composition ratio of Al, Ga, and In in the cladding layer is different for the infrared laser and the red laser. Also good. In that case, it is necessary to adjust the film thickness difference or carrier concentration difference of the contact layer.

  In this embodiment, the cladding layer is made of an AlGaInP material, but may be made of a GaAs material. For example, a semiconductor layer such as AlInP may be used as the current blocking layer.

  In this embodiment, Zn is diffused to form the window structure, but other impurities such as Si may be used.

(Embodiment 2)
Next, a second method of manufacturing the semiconductor laser having the above structure will be described with reference to the process cross-sectional view of FIG.

  Similarly to the first embodiment, ridge stripes to be waveguides are formed through the steps shown in FIGS. 2A to 3F.

Next, as shown in FIG. 5A, the SiO ₂ film (not shown) and the contact layers 309 and 319 on the window structure 331 are etched using photolithography.

Next, as shown in FIG. 5B, the AlInP current blocking layer 332 is formed by selective growth while leaving the mask pattern made of SiO ₂ on the gain contact layers 309 and 319 used at the time of ridge formation. As a result, current injection into the window structure on the end face can be prevented.

  Next, the AlInP current blocking layer 332 grown on the element isolation portion 330 is removed using photolithography and etching techniques. In etching the AlInP current blocking layer 332, a hydrochloric acid-based etchant was used to selectively remove the GaAs substrate 301 and the AlGaInP cladding layers 307 and 317 (not shown).

  As shown in FIG. 6C, an insulating film is deposited, and patterning is performed so that the insulating film 333 remains on the element isolation portion 330 by photolithography and etching.

  Etching of the AlInP current blocking layer 332 in the element isolation part exposes the surface of the GaAs substrate 301 in the isolation part. When the semiconductor laser device is assembled in this state, a chip adhesive material such as solder enters the groove part and the red part is exposed. The outer laser 310 and the red laser 320 are short-circuited. As shown in this embodiment mode, if the insulating film 333 is provided in the separation groove 330, the above-described short circuit can be suppressed.

  Finally, a p-side electrode (not shown) is formed on the surface of the n-type substrate 301 including each layer, and an n-side electrode (not shown) is formed on the back surface of the substrate 301.

According to the present embodiment, in addition to the same effects as those shown in the first embodiment, a short circuit between the laser elements during assembly can be prevented as described above. In addition, by using AlInP, which is a semiconductor layer that does not absorb the light emitted from each laser element, as the current blocking layer, high output can be achieved, and heat dissipation can be improved because it has higher thermal conductivity than a dielectric film such as SiO _2. Excellent and advantageous for high output. In addition, it is advantageous for high output in that the difference in refractive index from the semiconductor layer constituting each laser element can be set smaller than that of a dielectric film such as SiO ₂ .

  Although the AlInP current blocking layer is used in the present embodiment, AlGaInP having a high Al content may be used in that it does not absorb the light emitted from each laser element.

  The semiconductor laser device according to the present invention enables the active layer to be disordered by the same heat treatment when both the infrared laser and the red laser are monolithically formed and the end face window structure is formed. Therefore, not only simplification of the process but also excessive heat treatment is not required, so that a high-output and high-reliability element can be obtained, which is particularly useful when applied to a recording optical disk device or the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic diagram which showed the structure of the semiconductor laser apparatus in Embodiment 1 of this invention, (a) is a perspective view, (b) is sectional drawing. Manufacturing process explanatory drawing of the semiconductor laser apparatus in Embodiment 1 of this invention Manufacturing process explanatory drawing of the semiconductor laser apparatus in Embodiment 1 of this invention Manufacturing process explanatory drawing of the semiconductor laser apparatus in Embodiment 1 of this invention Manufacturing process explanatory drawing of the semiconductor laser apparatus in Embodiment 2 of this invention Manufacturing process explanatory drawing of the semiconductor laser apparatus in Embodiment 2 of this invention Explanatory drawing of the manufacturing process of the end face window structure of the red laser device in the prior art

Explanation of symbols

101, 201, 301 n-type GaAs substrate 102, 202, 302 n-type GaAs buffer layer 103, 203, 303 n-type (Al _x Ga _1-x ) _y In _1-y P clad layer 104, 204, 304 GaAs / AlGaAs Active layer 105, 205, 305 p _- type (Al _x Ga _{1 -x} ) _y In _{1 -y} P first cladding layer 106, 206, 306 p-type GaInP etching stop layer 107, 207, 307 p-type (Al _x Ga _1-x ) _y In _1-y P second cladding layer 108, 208, 308 p-type GaInP intermediate layer 109, 209, 309 p-type GaAs contact layer 110, 210, 310 Infrared laser device 112, 212, 312 n -type GaAs buffer layer 113, 213, 313 n-type _{(Al x Ga 1-x)} y In 1-y P cladding layer 114, 214, 314 AINP / AlGaInP-based active layer 115,215,315 p-type _{(Al x Ga 1-x)} y In 1-y P first cladding layer 116,216,316 p-type GaInP etching stop layer 117,217,317 p-type _{(Al x Ga 1-x)} y In 1-y P second cladding layer 118, 218, 318 p-type GaInP intermediate layer 119,219,319 p-type GaAs contact layer 120, 220, 320 red laser diode 130, 230, 330 Separation groove 131 231 331 Window structure 132 232 Dielectric current blocking layer 332 AlInP current blocking layer 333 Insulating film 401 n-type GaAs substrate 402 n-type GaAs buffer layer 403 n-type AlGaInP cladding layer 404 Multiplex with oscillation wavelength of 660 nm Quantum well structure active layer 405 p-type AlGaInP second Cladding layer 406 GaInP etching stop layer 407 p-type AlGaInP second cladding layer 408 p-type GaInP intermediate layer 409 p-type GaAs contact layer 410,410A ZnO film 411 insulating film 412 window structure

Claims (15)

A monolithic type semiconductor laser device in which a first semiconductor laser element that emits light of a first wavelength and a second semiconductor laser element that emits light of a second wavelength are formed on the same substrate. ,
Each of the first semiconductor laser element and the second semiconductor laser element has a double hetero structure formed by laminating at least a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer in this order;
A ridge-shaped waveguide including at least the second conductivity type cladding layer and a contact layer provided thereon;
In each of the first semiconductor laser element and the second semiconductor laser element, a window structure region in which a high-concentration impurity is introduced is formed on each cavity end face,
A semiconductor laser device, wherein the contact layer in the first semiconductor laser element and the contact layer in the second semiconductor laser element have different film thicknesses. The active layer in the first semiconductor laser element is made of a material having a smaller diffusion coefficient for the impurities than the active layer in the second semiconductor laser element,
2. The semiconductor laser device according to claim 1, wherein the contact layer in the first semiconductor laser element is thinner than the contact layer in the second semiconductor laser element. In the first semiconductor laser element and the second semiconductor laser element,
3. The semiconductor laser device according to claim 1, wherein a current blocking layer is formed so as to cover a side surface of the ridge. 3. The semiconductor laser according to claim 1, wherein a difference in film thickness between the contact layer of the first semiconductor laser element and the contact layer of the second semiconductor laser element is 0.01 μm or more. apparatus. 5. The semiconductor laser device according to claim 4, wherein a difference in film thickness between the contact layer of the first semiconductor laser element and the contact layer of the second semiconductor laser element is 0.05 [mu] m or more. 6. The semiconductor laser device according to claim 1, wherein the first wavelength is infrared light in a 780 nm band, and the second wavelength is red light in a 660 nm band. The contact layer in the first semiconductor laser element and the contact layer in the second semiconductor laser element are both made of Al _x Ga _1-x As (0 ≦ x ≦ 0.4). The semiconductor laser device according to claim 1. 8. The contact layer of the first semiconductor laser element and the contact layer of the second semiconductor laser element each have a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ or more, respectively. The semiconductor laser device according to any one of the above. The semiconductor laser device according to claim 1, wherein the current blocking layer covers at least an upper surface of a region where the window structure is formed in the ridge-shaped waveguide. 10. A separation groove is provided between the first semiconductor laser element and the second semiconductor laser element, and an insulating film is formed in the separation groove. The semiconductor laser device according to any one of the above. A first first conductivity type cladding layer, a first active layer, a first second conductivity type cladding layer, and a first second conductivity type contact layer are formed on the semiconductor substrate from the substrate side. Forming a first laminated semiconductor structure comprising in sequence;
Removing the first laminated semiconductor structure on a predetermined region of the semiconductor substrate;
A second first conductivity type cladding layer, a second active layer, a second second conductivity type cladding layer, and the first second conductivity type contact are formed on the entire surface of the semiconductor substrate including the predetermined region. Forming a second stacked semiconductor structure including, in order from the substrate side, a second second conductivity type contact layer having a thickness different from that of the layer;
Removing the second stacked semiconductor structure formed in a region other than the predetermined region;
Providing an impurity diffusion source in a predetermined region on the surface of the first laminated semiconductor structure and the surface of the second laminated semiconductor structure;
Heat-treating the semiconductor substrate to diffuse the impurities from the impurity diffusion source into the first laminated semiconductor structure and into the first laminated semiconductor structure to form a window structure;
The first second conductivity type cladding layer and the first second conductivity type contact layer, and the second second conductivity type cladding layer and the second second conductivity type contact layer are patterned respectively. Forming two ridge-shaped waveguides;
Forming a current blocking layer so as to cover the side surfaces of the two ridge-shaped waveguides;
Forming a semiconductor laser device by forming electrodes on the upper surface of the two ridge-shaped waveguides and on the rear surface of the substrate, respectively. 12. The method of manufacturing a semiconductor laser device according to claim 11, wherein Zn or Si is used as the impurity. The method further comprises the step of removing the first second conductivity type contact layer and the second second conductivity type contact layer in the vicinity of each resonator end face of the two semiconductor laser elements. Item 13. A method for manufacturing a semiconductor laser device according to Item 11 or 12. In the step of removing the first second conductivity type contact layer and the second second conductivity type contact layer, the first first conductivity type is formed over a length of at least 5 μm from the cavity end surface toward the laser gain portion. 14. The method of manufacturing a semiconductor laser device according to claim 13, wherein the two-conductivity type contact layer and the second second-conductivity type contact layer are removed. In the step of forming a current blocking layer so as to cover the side surfaces of the two ridge-shaped waveguides, a region where the window structure is formed on the upper surface of the two ridge-shaped waveguides is defined as the current blocking layer. The method of manufacturing a semiconductor laser device according to claim 11, wherein the semiconductor laser device is formed so as to cover.

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