JP3891219B2 - Semiconductor laser device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a semiconductor laser device and a manufacturing method thereof, and more particularly to a one-chip multi-wavelength semiconductor laser device having an end window structure capable of high output operation.

  In recent years, an infrared semiconductor laser device using an AlGaAs mixed crystal or a red semiconductor using an AlGaInP mixed crystal as a light source for information processing equipment such as an optical disk such as a CD (compact disk) and a DVD (digital video disk). Laser devices have been put into practical use. In any case, a rewritable optical disc requires an optical output of 30 mW or more, and in order to realize a higher speed and a smaller size in the future, a higher optical output of about 50 mW to 200 mW is desired. Increasing the output of the semiconductor laser device is limited by characteristic deterioration due to crystal breakage at the laser end face, which is a serious problem particularly in a semiconductor laser device using an AlGaInP-based mixed crystal. As means for realizing high output, an end face window structure in which a material transparent to laser light is formed on the end face of the laser resonator is effective. In particular, in a double heterostructure having a quantum well structure as an active layer, an end face window structure utilizing a phenomenon in which atoms forming the quantum well structure are solid-phase diffused and disordered when impurities are diffused is, for example, Suzuki et al. (Electronics Letters, Vol. 20, Item 383, 1984).

  Recently, there is a strong demand for integrating semiconductor laser devices having different wavelengths on the same substrate. For example, DVD players and DVD-ROM devices require two types of lasers with an oscillation wavelength of 780 nm and an oscillation wavelength of 650 nm so that information from CDs and DVD disks can be extracted, and the configuration of the optical system is complicated. Here, if lasers of two types of wavelengths can be integrated on the same substrate, a great advantage can be obtained, such as miniaturization of the pickup. Even in such a multi-wavelength integrated laser on the same substrate, development for higher output is considered.

FIG. 5 is a structural view of an AlGaInP-based 650 nm band red semiconductor laser device having a conventional end face window structure manufactured based on the above disordering phenomenon. In FIG. 5, 501 is an n-type GaAs substrate, 502 is an n-type AlGaInP cladding layer, 503 is an active layer having a quantum well structure composed of a GaInP well layer and an AlGaInP barrier layer, 504 is a p-type AlGaInP first cladding layer, 505 is a p-type GaInP etching stop layer, 506 is a p-type AlGaInP second cladding layer, 507 is a p-type GaInP band discontinuous relaxation layer, 508 is a p-type GaAs cap layer, 509 is an n-type AlInP current confinement layer, 510 is p Type GaAs contact layer. Reference numeral 511 denotes an impurity diffusion region provided by solid phase diffusion of Zn in order to form an end face window structure on the laser end face. Reference numerals 512 and 513 denote n-side and p-side electrodes, respectively.
FIG. 6 is a structural diagram of an AlGaAs-based 780 nm band infrared semiconductor laser device having a conventional end window structure. In FIG. 6, 601 is an n-type GaAs substrate, 602 is an n-type AlGaAs cladding layer, 603 is an active layer having a quantum well structure composed of a GaAs well layer and an AlGaAs barrier layer, 604 is a p-type AlGaAs first cladding layer, 605 is a p-type GaAs etching stop layer, 606 is a p-type AlGaAs second cladding layer, 607 is a p-type GaAs cap layer, 608 is an n-type AlGaAs current confinement layer, and 609 is a p-type GaAs contact layer. Reference numeral 610 denotes an impurity diffusion region provided by solid phase diffusion of Zn in order to form an end face window structure on the laser end face. Reference numerals 611 and 612 denote n-side and p-side electrodes, respectively.

  Next, a method for manufacturing a semiconductor laser device having a conventional end face window structure will be described. FIGS. 7A to 7F show the manufacturing method of the semiconductor laser device shown in FIG. 7, the same parts as those in FIG. 5 are denoted by the same reference numerals. First, as shown in FIG. 7A, a quantum composed of an n-type AlGaInP cladding layer 502, a GaInP well layer, and an AlGaInP barrier layer on an n-type GaAs substrate 501 by MOVPE (metal organic chemical vapor deposition). The well-structured active layer 503, the p-type AlGaInP first cladding layer 504, the p-type GaInP etching stop layer 505, the p-type AlGaInP second cladding layer 506, the p-type GaInP band discontinuous relaxation layers 507 and 508 are p-type GaAs cap layers. Are sequentially formed to produce a laminate having a double heterostructure.

Next, a SiO ₂ film 514 is deposited on the upper surface of the double heterostructure, and patterned by wet etching, and stripe openings having a width of several tens of μm are formed at intervals of several hundreds of μm in a direction perpendicular to the laser resonator direction. Form. Thereafter, a ZnO film 515 is deposited on the entire surface by sputtering, and the ZnO film 515 other than the stripe openings is removed by wet etching (FIG. 7B).

Next, as shown in FIG. 7C, after depositing the SiO ₂ film 516 on the entire upper surface of the SiO ₂ film 514 and the ZnO film 515, annealing is performed by heat treatment in a nitrogen atmosphere, and ZnO in the stripe opening is formed. Using the film 515 as a diffusion source, Zn is solid phase diffused so as to reach the n-type AlGaInP cladding layer 502 from the upper surface of the p-type GaAs cap layer 508. As a result, an impurity diffusion region 511 is formed, in which the active layer 503 having a quantum well structure composed of a GaInP well layer and an AlGaInP barrier layer is disordered. The disordered quantum well in the impurity diffusion region has a band gap larger than the band gap of the quantum well in the non-disordered region, and functions as an end face window structure.

Next, the top surface of the layered body after the SiO ₂ film 514, ZnO film 515 and the SiO ₂ film 516 is removed by wet etching to form the SiO ₂ film 517 again, and patterned by wet etching, the number μm width The stripe is formed in a direction that becomes a laser resonator. Using the stripe made of the SiO ₂ film 517 as a mask, the p-type GaInP band discontinuous relaxation layer 507 is removed in a ridge shape by wet etching. Subsequently, the p-type AlGaInP second clad layer 506 is etched using a wet etchant that can selectively remove the p-type AlGaInP second clad layer 506, for example, sulfuric acid, which is an etchant having a significantly different etching rate between AlGaInP and GaInP. A ridge stripe 506 is formed and a p-type GaInP etching stop layer 505 is exposed at the stripe interval (FIG. 7D).

Next, as shown in FIG. 7E, an n-type AlInP current confinement layer 509 is buried and grown on the side surface of the ridge by the MOVPE method using the striped SiO ₂ film 516 as a selective growth mask. Thereafter, the SiO ₂ film 516 is removed by wet etching, and a p-type GaAs contact layer 510 is again formed on the entire top surface of the stack by MOVPE. Finally, electrodes are formed on the n-side and the p-side, and the stacked body is cleaved in a direction perpendicular to the ridge stripe in the impurity diffusion region 511, thereby forming a laser resonator having a pair of resonator end faces. (FIG. 7 (f)).

An AlGaAs-based 780 nm band infrared semiconductor laser device can also be manufactured by the same manufacturing method.
Suzuki et al., Electronics Letters, Vol. 20, Item 383, 1984

  Here, in the semiconductor laser device having the conventional end face window structure, the annealing time for solid phase diffusion of Zn until reaching the n-type cladding layer is 20 minutes at the annealing temperature of 600 ° C., for example. The latter was 110 minutes. This difference is due to the difference in the diffusion rate of Zn in the AlGaInP and AlGaAs mixed crystals. The diffusion rate of Zn is 10 times faster with AlGaInP than with AlGaAs. Even in the latter case, the annealing time can be shortened by about 20 minutes at an annealing temperature of 700.degree. However, annealing for a long time or annealing at a high temperature induces dopant diffusion and generation of point defects even in portions other than the end face window structure region, which adversely affects the increase in operating current and lifetime characteristics. Therefore, it was necessary to anneal at as low a temperature as possible and in a short time.

  Further, when a plurality of semiconductor laser device chips having different wavelengths are integrated on the same substrate and an end face window structure is applied to each, for example, the AlGaInP-based 650 nm band red semiconductor laser device and the AlGaAs-based 780 nm band infrared semiconductor are used. When laser devices are integrated, the layer structure and materials of the double hetero structure are different, so the Zn diffusion conditions for forming the end face window structure are different. It becomes impossible to function as an end face window structure and to obtain good characteristics. Therefore, even if Zn diffusion is performed at the same time, it is necessary to make it possible to perform the same degree of Zn diffusion in both lasers.

  The present invention has been made to solve the above-described problems, and is good even when a plurality of semiconductor laser device chips having different wavelengths are integrated on the same substrate and an end face window structure is applied to each. An object of the present invention is to provide a method for forming an end face window structure capable of obtaining excellent characteristics, and to ensure manufacturing yield and reliability.

In order to solve the above problems, a semiconductor laser device according to the present invention includes a plurality of double heterostructures formed on a semiconductor substrate and the double heterostructure formed on each of the plurality of double heterostructures. A diffusion control film for controlling the amount of impurities diffused in the active layer therein, each of the plurality of double heterostructures comprising a first conductivity type cladding layer, a well layer and a barrier formed sequentially on the semiconductor substrate. and the active layer of a quantum well structure including a layer, and a second-conductivity-type cladding layer a including the semiconductor laser device, said at least a portion of the second-conductivity-type cladding layer Alf1Ga1-f1-g1Ing1P (0 ≦ f1 ≦ 1, 0 ≦ g1 ≦ 1), and Alf2Ga1-f2-g2Ing2P (0 ≦ f2 ≦ 1, 0 ≦ g2 ≦ 1) is formed on at least a part of the second second conductivity type cladding layer. The plurality of doubles One of the heterostructures has an active layer of a quantum well structure having a well layer made of Aly1Ga1-y1-z1Inz1P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1), and another one has an AltGa1-tAs (0 ≦ has an active layer of a quantum well structure having a t ≦ 1) well layer made of a plurality of diffusion controlling membrane Ri name from each AlxGa1-xAs (0 ≦ x ≦ 1), consisting of the Alf1Ga1-f1-g1Ing1P the At least a portion of the second conductivity type cladding layer and at least a portion of the second conductivity type cladding layer made of the Alf2Ga1-f2-g2Ing2P are ridge-shaped stripes, which reduce the absorption of laser light at the cavity end face portion. Impurity diffusion regions to be end face window structures to be provided are provided .

With this configuration, since each of the plurality of diffusion control films is made of Al _x Ga _1-x As (0 ≦ x ≦ 1), the amount of impurities diffused into the active layer can be controlled, and defects in the active layer are controlled. The number of the active layers made up of the quantum well structures of the plurality of double heterostructures can be well balanced, and one of the plurality of double heterostructures is Al _y1 Ga _{1. -y1-z1} In _z1 P ( _{0≤y1≤1, 0≤z1≤1} ) having a quantum well structure active layer, and another one is Al _t Ga _1-t As (0≤ By having an active layer having a quantum well structure having a well layer of t ≦ 1), disordering of the active layer having the quantum well structure of the plurality of double heterostructures can be performed in a more balanced manner.

The semiconductor laser device according to the present invention has a quantum well structure on an active layer having a well layer made of Al _y1 Ga _{1 -y1-z1} In _z1 P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1). Of a quantum well structure having a diffusion control film made of Al _x1 Ga _1-x1 As (0 ≦ x1 ≦ 1) and a well layer made of Al _t Ga _1-t As (0 ≦ t ≦ 1) And a diffusion control film made of Al _x2 Ga _1-x2 As (0 ≦ x2 ≦ 1) formed on the layer, and the Al composition is x1 ≦ x2, whereby Al _x1 Ga _1-x1 As A well layer made of Al _y1 Ga _{1 -y1-z1} In _z1 P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1) is suppressed by suppressing diffusion of impurities from the diffusion control film made of (0 ≦ x1 ≦ 1). The amount of impurities diffusing into the active layer having the quantum well structure can be controlled.

According to the method of manufacturing a semiconductor laser device of the present invention, a first first-conductivity-type cladding layer and a well layer made of Aly1Ga1-y1-z1Inz1P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1) are formed on a semiconductor substrate. A first active layer having a quantum well structure, and a first second-conductivity-type cladding layer having a layer made of Alf1Ga1-f1-g1Ing1P (0 ≦ f1 ≦ 1, 0 ≦ g1 ≦ 1) at least partially . Forming a first multilayer structure by sequentially laminating a first diffusion control film for controlling the amount of impurities diffused in the first active layer made of Alz1Ga1-z1As (0 ≦ z1 ≦ 1); Removing a portion of the first multilayer structure to at least the first active layer; and a second first over the portion of the first multilayer structure removed to at least the first active layer. Conductive cladding layer and well made of AltGa1-tAs (0≤t≤1) A second active layer having a quantum well structure having a layer, and a second second-conductivity-type cladding layer having at least a layer made of Alf2Ga1-f2-g2Ing2P (0≤f2≤1, 0≤g2≤1) And a second diffusion control film for sequentially controlling the amount of impurities diffused in the second active layer made of Alz2Ga1-z2As (0 ≦ z2 ≦ 1) to form a second multilayer structure. Forming a material film serving as an impurity diffusion source in a predetermined region on the first and second diffusion control films and serving as a resonator end face; and heating the semiconductor substrate. a step of forming the first and the second diffusion control film by diffusing the impurity into said first and said second multi-layer structure via the by facet window structure from the material layer Te, the first At least a portion of the second conductivity type cladding layer and the second second conductivity type cladding layer. And at least a portion of the head layer are those simultaneously having the step of processing the stripe ridge.

With this configuration, disordering of the active layer having a quantum well structure included in a plurality of multilayer structures can be performed in a more balanced manner.

In the above embodiment, it is described that the p- type AlGaAs diffusion control film exists up to the final process in the manufacturing process, but it may be removed by etching in the process of completing the Zn diffusion.

According to the method of manufacturing a semiconductor laser device of the present invention, Al _y1 Ga _{1 -y1 -z1} In _z1 P (0 ≦ y1 ≦) in either one of the first multilayer structure and the second multilayer structure is used. 1. A first active layer having a quantum well structure having a well layer made of 0 ≦ z1 ≦ 1), and having a well layer made of Al _t Ga _1-t As (0 ≦ t ≦ 1) on the other side. By having a second active layer with a quantum well structure and the Al composition being z1 ≦ z2, the diffusion of impurities from the diffusion control film made of Al _x1 Ga _1-x1 As (0 ≦ x1 ≦ 1) is prevented. The amount of impurities diffused into the active layer of the quantum well structure having a well layer made of Al _y1 Ga _{1 -y1 -z1} In _z1 P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1) can be controlled. .

  The manufacturing method of the semiconductor laser device of the present invention can improve the crystallinity of the disordered active layer by forming a material film containing Zn or Mg as the material film for such a configuration.

  As described above, according to the present invention, it is possible to control Zn diffusion for forming an end face window structure by using an AlGaAs diffusion control film and using an AlGaInP mixed crystal in a cladding layer or a part of the cladding layer. Thus, even when a plurality of semiconductor laser device chips having different wavelengths are integrated on the same substrate and the end face window structure is applied to each of them, a method for forming the end face window structure capable of obtaining good characteristics becomes possible. It was.

  In particular, even when multiple semiconductor laser device chips with different wavelengths are integrated on the same substrate, it has been shown to be extremely useful for reducing threshold currents and operating currents, improving yields, and thus improving reliability. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, some parts are hatched for convenience.

(First embodiment)
A 780 nm band infrared semiconductor laser device having an end face window structure according to the first embodiment of the present invention and a method for manufacturing the same will be described.

  1 and 2 are perspective views showing a 780 nm band infrared semiconductor laser device having an end face window structure according to the first embodiment of the present invention and its manufacturing process.

In FIG. 1, 101 is an n-type GaAs substrate, 102 is an n-type AlGaInP cladding layer, 103 is an active layer having a quantum well structure composed of a GaAs well layer and an AlGaAs barrier layer, 104 is a p-type AlGaInP first cladding layer, 105 Is a p-type GaInP etching stop layer, 106 is a p-type AlGaInP second cladding layer, 107 is a p-type GaInP band discontinuous relaxation layer, 108 is a p-type AlGaAs diffusion control film, 109 is an n-type AlInP current confinement layer, and 110 is p Type GaAs contact layer. In order to realize the transverse mode control of the laser, the p-type AlGaInP second cladding layer 106 is formed as a ridge-shaped stripe. Reference numeral 111 denotes an impurity diffusion region (a region hatched differently from the n-type GaAs substrate 101 in the drawing) provided by solid phase diffusion of Zn in order to form an end face window structure on the laser end face. Reference numerals 112 and 113 denote n-side and p-side electrodes, respectively. Here, the main surface of the n-type GaAs substrate 101 is a substrate inclined by 8 ° in the [011] direction from the (100) plane. The p-type AlGaAs diffusion control film 108 has a carrier concentration of 10 ¹³ cm ⁻² or more and 10 ¹⁵ cm ⁻² or less at the p-type GaAs contact layer side interface (ie, boundary surface). Here, AlGaAs represents Al _x Ga _1-x As (0 ≦ x ≦ 1), and AlGaInP represents Al _y Ga _1-yz In _y P (0 ≦ y ≦ 1, 0 ≦ z ≦ 1). And x, y, and z have values determined for the respective layers. The same applies to the following embodiments.

  In this structure, an impurity diffusion region 111 in which Zn is solid-phase diffused in a direction (vertical direction) perpendicular to the ridge-shaped stripe is formed on the end face of the resonator. In the active layer 103 in this region, the quantum well active layer is disordered, and the well layer and the barrier layer are averaged, so that the band gap is expanded as compared with the impurity non-diffusion region. For example, the photoluminescence wavelength from the quantum well structure in the above structure is shifted to 740 nm and 80 meV in the diffusion region by a short wavelength with respect to 780 nm in the non-diffusion region. Therefore, the laser light emitted from the impurity non-diffusion region is transparent in the impurity diffusion region 111, light absorption at the end face is remarkably suppressed, and stable high output operation is achieved.

With the above configuration, since the AlGaAs diffusion control film 108 is provided, the amount of impurities diffusing into the active layer 103 and the diffusion time of impurities into the active layer can be controlled, and the number of defects in the active layer 103 is remarkably increased. In addition, the p-type AlGaAs diffusion control film 108 has p-type AlGaAs diffusion control because the surface concentration of carriers at the interface opposite to the active layer is 10 ¹³ cm ⁻² or more and 10 ¹⁵ cm ⁻² or less. The resistivity of the film 108 itself can be remarkably reduced, and the p-type AlGaAs diffusion control film 108 with good conductivity can be obtained, and reduction of the threshold current density and the like of the semiconductor laser device can be realized.

  Next, a method for manufacturing the semiconductor laser device according to the first embodiment of the present invention will be described.

  First, as shown in FIG. 2A, a strain quantum comprising an n-type AlGaInP clad layer 102, a GaAs well layer and an AlGaAs barrier layer on an n-type GaAs substrate 101 by MOVPE (metal organic vapor phase epitaxy). Well-structure active layer 103, p-type AlGaInP first clad layer 104, p-type GaInP etching stop layer 105, p-type AlGaInP second clad layer 106, p-type GaInP band discontinuous relaxation layer 107, p-type AlGaAs diffusion control film 108 Are sequentially formed to produce a laminate having a double heterostructure.

Next, as shown in FIG. 2B, a SiO ₂ film 114 is deposited and patterned by wet etching. For example, stripe openings with a width of 50 μm are formed at intervals of 700 μm in a direction perpendicular to the direction of the laser resonator. It is formed (in the direction perpendicular to the stripe). Thereafter, a ZnO film 115 (a material film serving as an impurity diffusion source in the present invention) is deposited on the entire surface by sputtering, and the ZnO film 115 other than the stripe openings is removed by wet etching.

Next, as shown in FIG. 2C, after depositing the SiO ₂ film 116 on the entire upper surface of the SiO ₂ film 114 and the ZnO film 115, annealing is performed by heat treatment in a nitrogen atmosphere, and the ZnO in the stripe opening is formed. Using the film 115 as a diffusion source, Zn is solid-phase diffused so as to reach the n-type AlGaInP cladding layer 102 from the upper surface of the p-type AlGaAs diffusion control film 108. As a result, an impurity diffusion region 111 is formed, and the active layer of the quantum well structure is disordered in this region. The disordered quantum well in the impurity diffusion region 111 has a band gap larger than the band gap of the quantum well in the non-disordered region, and functions as an end face window structure.

Next, the SiO ₂ film 114, ZnO film 115 and the SiO ₂ film 116 on the top surface of the stack after removal by wet etching, depositing a SiO ₂ film 117 again, and patterned by wet etching, for example, 3 [mu] m width Are formed in the direction of the laser resonator. Using the stripe made of the SiO ₂ film 117 as a mask, the p-type AlGaAs diffusion control film 108 and the p-type GaInP band discontinuous relaxation layer 107 are removed in a ridge shape by wet etching. Next, a wet etching solution capable of selectively removing the p-type AlGaInP second clad layer 106, for example, sulfuric acid is used to form a ridge stripe of the p-type AlGaInP second clad layer 106, and at the stripe interval, p The type GaInP etching stop layer 105 is exposed (FIG. 2D).

Next, as shown in FIG. 2E, an n-type AlInP current confinement layer 109 is buried and grown on the side surface of the ridge by the MOVPE method using the striped SiO ₂ film 117 as a selective growth mask. Thereafter, the SiO ₂ film 117 is removed by wet etching, and the p-type GaAs contact layer 110 is again formed on the entire top surface of the multilayer body by the MOVPE method (FIG. 2F). Finally, electrodes are formed on the n-side and the p-side, and the laminate is cleaved in the impurity diffusion region 111 in a direction perpendicular to the ridge stripe, thereby forming a laser resonator having a pair of resonator end faces. To do.

  By using the AlGaInP layer having a high annealing rate in place of AlGaAs as the cladding layer or a part of the cladding as described above, the annealing time is 20 minutes at an annealing temperature of 600 ° C., and the conventional example shown in FIG. Compared to this, the time can be significantly shortened. As a result, in the 780 nm band infrared semiconductor laser device having the end face window structure, the introduction of defects due to heat treatment can be suppressed and the operating current can be reduced by 5 mA.

  In the above embodiment, an AlGaAs well layer having a composition different from that of the barrier layer may be used for the active layer 103 instead of the GaAs well layer.

  Note that Mg may be used as the solid phase diffusion source instead of Zn as the solid phase diffusion source.

(Second Embodiment)
Next, a two-wavelength integrated semiconductor laser device of 650 nm band and 780 nm band having an end face window structure according to a second embodiment of the present invention and a method for manufacturing the same will be described.

  3 and 4 are perspective views showing a semiconductor laser device and its manufacturing process according to the second embodiment of the present invention.

  In FIG. 3, reference numeral 301 denotes an n-type GaAs substrate. In the A region (650 nm band red semiconductor laser device), 302a is an n-type AlGaInP cladding layer, 303a is an active layer having a quantum well structure composed of a GaInP well layer and an AlGaInP barrier layer, 304a is a p-type AlGaInP first cladding layer, and 305a. Is a p-type GaInP etching stop layer, 306a is a p-type AlGaInP second cladding layer, 307a is a p-type GaInP band discontinuous relaxation layer, 308a is a p-type AlGaAs diffusion control film, 309a is an n-type AlInP current confinement layer, and 310a is p Type GaAs contact layer. In order to realize the transverse mode control of the laser, the p-type AlGaInP second clad layer 306a is formed as a ridge-shaped stripe. Reference numeral 311a denotes an impurity diffusion region (a region hatched differently from the n-type GaAs substrate 301 in the drawing) provided by solid phase diffusion of Zn in order to form an end face window structure on the laser end face. Reference numerals 312 and 313a denote n-side and p-side electrodes, respectively. In the B region (780 nm band infrared semiconductor laser device), 302b is an n-type AlGaInP cladding layer, 303b is an active layer having a quantum well structure composed of a GaAs well layer and an AlGaAs barrier layer, and 304b is a p-type AlGaInP first layer. Cladding layer, 305b is a p-type GaInP etching stop layer, 306b is a p-type AlGaInP second cladding layer, 307b is a p-type GaInP band discontinuous relaxation layer, 308b is a p-type AlGaAs diffusion control film, and 309b is an n-type AlInP current confinement layer 310b are p-type GaAs contact layers. In order to realize the transverse mode control of the laser, the p-type AlGaInP second cladding layer 306b is formed as a ridge-shaped stripe. Reference numeral 311b denotes an impurity diffusion region (a region hatched differently from the n-type GaAs substrate 301 in the figure) provided by solid phase diffusion of Zn in order to form an end face window structure on the laser end face. Reference numerals 312 and 313b denote n-side and p-side electrodes, respectively. Here, the main surface of the n-type GaAs substrate 301 is a substrate inclined by 8 ° in the [011] direction from the (100) plane.

  With this configuration, since the p-type AlGaAs diffusion control films 308a and 308b are used, the amount of impurities diffused into the respective active layers 303a and 303b can be controlled, and the number of defects in the active layers 303a and 303b can be remarkably increased. It is possible to reduce the number of active layers, and to disorder the active layers made of the quantum well structures of the respective laser structures.

  Next, a method for manufacturing a semiconductor laser device according to the second embodiment of the present invention will be described.

  First, as shown in FIG. 4A, a strain quantum comprising an n-type AlGaInP cladding layer 302a, a GaInP well layer, and an AlGaInP barrier layer on an n-type GaAs substrate 301 by MOVPE (metal organic chemical vapor deposition). Well-structure active layer 303a, p-type AlGaInP first cladding layer 304a, p-type GaInP etching stop layer 305a, p-type AlGaInP second cladding layer 306a, p-type GaInP band discontinuous relaxation layer 307a, p-type AlGaAs diffusion control film 308a Are sequentially formed to produce a laminate having a double heterostructure.

Next, an SiO ₂ film is deposited on the double heterostructure and patterned by wet etching to form, for example, 300 μm wide stripe openings at 300 μm intervals. Thereafter, the double heterostructure of the stripe opening is removed by wet etching until it reaches the substrate to form an A region.

Next, as shown in FIG. 4B, a strain composed of an n-type AlGaInP cladding layer 302b, a GaAs well layer, and an AlGaAs barrier layer on an n-type GaAs substrate 301 by MOVPE (metal organic chemical vapor deposition). Quantum well structure active layer 303b, p-type AlGaInP first cladding layer 304b, p-type GaInP etching stop layer 305b, p-type AlGaInP second cladding layer 306b, p-type GaInP band discontinuous relaxation layer 307b, p-type AlGaAs diffusion control film 308b is sequentially formed to produce a stacked body having a double heterostructure. Thereafter, the deposits and the SiO ₂ film on the SiO ₂ film is removed by wet etching.

Next, as shown in FIG. 4C, a SiO ₂ film 314 is deposited again and patterned by wet etching. For example, stripe openings with a width of 50 μm are spaced at intervals of 700 μm in a direction perpendicular to the laser resonator direction. (In the direction orthogonal to the stripes). Thereafter, a ZnO film 315 (a material film serving as an impurity diffusion source in the present invention) is deposited on the entire surface by sputtering, and the ZnO film other than the stripe openings is removed by wet etching.

Next, as shown in FIG. 4D, an SiO ₂ film 316 (dielectric film in the present invention) is deposited on the entire upper surface of the SiO ₂ film 314 and the ZnO film 315, and then annealed by heat treatment in a nitrogen atmosphere. Then, Zn is diffused in a solid phase so as to reach the n-type AlGaInP cladding layers 302a and 302b from the upper surfaces of the p-type AlGaAs diffusion control films 308a and 308b using the ZnO film 315 in the stripe opening as a diffusion source. As a result, impurity diffusion regions 311a and 311b are formed, and the active layer of the quantum well structure is disordered inside. The disordered quantum well in the impurity diffusion region has a band gap larger than the band gap of the quantum well in the non-disordered region, and functions as an end face window structure.

Next, as shown in FIG. 4E, a SiO ₂ film 317 is again deposited on the upper surface of the laminate after the SiO ₂ film 314, the ZnO film 315 and the SiO ₂ film 316 are removed by wet etching, Patterning is performed by etching, and, for example, stripes 317a and 317b having a width of 3 μm in the A region and a width of 2 μm in the B region are formed in the direction of the laser resonator. Using the stripe made of the SiO ₂ film 317 as a mask, the p-type AlGaAs diffusion control films 308a and 308b and the p-type GaInP band discontinuous relaxation layers 307a and 307b are removed in a ridge shape by wet etching. Next, etching is performed using a wet etchant that can selectively remove the p-type AlGaInP second clad layers 306a and 306b, for example, sulfuric acid to form ridge stripes of the p-type AlGaInP second clad layers 306a and 306b. The p-type GaInP etching stop layers 305a and 305b are exposed at the stripe interval.

Next, as shown in FIG. 4F, n-type AlInP current confinement layers 309a and 309b are embedded and grown on the side surfaces of the ridge by the MOVPE method using the striped SiO ₂ film 317 as a selective growth mask. Thereafter, the SiO ₂ film 317 is removed by wet etching, and p-type GaAs contact layers 310a and 310b are again formed on the entire top surface of the stack by MOVPE. Further, in order to electrically separate the A region and the B region, a separation groove reaching the n-type GaAs substrate is formed. Finally, electrodes are formed on the n side and the p side, and the laminate is cleaved in the direction perpendicular to the ridge stripe in the impurity diffusion regions 311a and 311b, thereby forming a laser resonator having a pair of resonator end faces. A two-wavelength laser chip in which two types of lasers composed of the region and the region B are formed on the same substrate is used (FIG. 4G).

  According to the manufacturing method, disordering of the active layers 303a and 303b made of the quantum well structure of the plurality of laser structures can be performed in a more balanced manner. In particular, since the p-type AlGaInP second cladding layers 306a and 306b are of the same material system, the p-type AlGaInP second cladding layers 306a and 306b can be formed by a single crystal growth, thereby simplifying the crystal growth process. And the yield rate of the semiconductor laser device can be improved.

Here, Zn as an impurity is solid-phase diffused in the active layer of the quantum well structure, and the quantum well structure in the diffusion region is induced to be disordered and functions as an end face window structure. However, if Zn is excessively present, free carrier absorption is increased, resulting in an increase in operating current and a decrease in reliability. Therefore, there should be no variation in the Zn diffusion concentration in the A and B regions. As an appropriate Zn diffusion concentration, the carrier concentration of the p-type AlGaAs diffusion control films 308a and 308b on the p-type GaAs contact layers 310a and 310b side surface is 10 ¹³ cm ⁻² or more and 10 ¹⁵ cm ⁻² or less. What is necessary is just to have the surface density of the carrier on the order of 10 ¹³ cm ⁻² .

As a condition for forming a good end face window structure by using the AlGaInP layer having a high annealing rate instead of AlGaAs for the cladding layer or part of the cladding in both the A and B regions, the annealing time is as follows. Both regions were 20 minutes at an annealing temperature of 600 ° C. For example, the photoluminescence wavelength from the quantum well structure is shifted by a short wavelength of 610 nm and 740 nm in the diffusion region with respect to 650 nm and 780 nm in the non-diffusion region in the A region and B region, respectively. Therefore, it is transparent in the impurity non-diffusion region, light absorption at the end face is remarkably suppressed, and stable high output operation is achieved. In this way, even if annealing is performed at the same time, the introduction of defects due to heat treatment in both regions can be suppressed, the original characteristics can be maintained, and good characteristics can be obtained with good reproducibility within the wafer plane. It was.

Note that an AlGaAs diffusion control film 308a formed on an active layer 303a having a strained quantum well structure composed of a GaInP well layer and an AlGaInP barrier layer, and a strained quantum well composed of a GaAs well layer and an AlGaAs barrier layer. For the AlGaAs diffusion control film 308b formed on the active layer 303b having the structure, the Al composition of the AlGaAs diffusion control film 308a is preferably smaller than the Al composition of the AlGaAs diffusion control film 308b. This is because the active layer 303a composed of the GaInP well layer and the AlGaInP barrier layer diffuses impurities more easily than the active layer 303b composed of the GaAs well layer and the AlGaAs barrier layer, and the AlGaAs diffusion control film. This is because by making the Al composition of 308a smaller than the Al composition of the AlGaAs diffusion control film 308b, it is possible to control the amount of impurities diffused into the active layer 303a while suppressing the diffusion of impurities from the AlGaAs diffusion control film 308a. .

  In the above embodiment, instead of using AlGaInP for the second cladding layer formed on the active layer 303b composed of the GaAs well layer and the AlGaAs barrier layer, or the first cladding layer under the active layer 303b. Alternatively, AlGaAs may be used. In that case, for example, the Al composition of the AlGaAs diffusion control film 308b is made larger than the Al composition of the second cladding layer formed on the active layer 303b, or much larger than the Al composition of the AlGaAs diffusion control film 308a. If this is done (for example, Al composition is increased 10 times or more), the Zn diffusion method in the two laser structures, that is, the red laser structure and the infrared laser structure can be made similar, and the time for Zn diffusion can be shortened. be able to.

  In the above embodiment, an AlGaInP well layer having a composition different from that of the barrier layer may be used instead of the GaInP well layer for the active layer 303a, and an AlGaAs having a composition different from that of the barrier layer may be used instead of the GaAs well layer for the active layer 303b. A well layer may be used.

  In the above embodiment, it is described that the n-type AlGaAs diffusion control film exists up to the final step in the manufacturing process, but it may be removed by etching in the process of completing the Zn diffusion.

1 is a perspective view showing a semiconductor laser device according to a first embodiment of the present invention. The perspective view which shows each process of the manufacturing method of the semiconductor laser apparatus concerning the 1st Embodiment of this invention The perspective view which shows the semiconductor laser apparatus based on the 2nd Embodiment of this invention The perspective view which shows each process of the manufacturing method of the semiconductor laser apparatus concerning the 2nd Embodiment of this invention. A perspective view of an AlGaInP-based 650 nm band red semiconductor laser device having a conventional end face window structure A perspective view of an AlGaAs 780 nm band infrared semiconductor laser device having a conventional end face window structure The perspective view which shows each process of the manufacturing method of the AlGaInP type 650 nm band red semiconductor laser device which has the conventional end surface window structure

Explanation of symbols

101 n-type GaAs substrate 102 n-type AlGaInP cladding layer 103 active layer having quantum well structure 104 p-type AlGaInP first cladding layer 105 p-type GaInP etching stop layer 106 p-type AlGaInP second cladding layer 107 p-type GaInP band discontinuous relaxation layer 108 p-type AlGaAs diffusion control film 109 n-type AlInP current confinement layer 110 p-type GaAs contact layer 111 impurity diffusion region 112 n-side electrode 113 p-side electrode 301 n-type GaAs substrate 302 n-type AlGaInP cladding layer 303 active layer 304 p-type AlGaInP First cladding layer 305 p-type GaInP etching stop layer 306 p-type AlGaInP second cladding layer 307 p-type GaInP band discontinuous relaxation layer 308 p-type AlGaAs diffusion control film 309 n-type AlI nP current confinement layer 310 p-type GaAs contact layer 311 impurity diffusion region 312 n-side electrode 313 p-side electrode

Claims (10)

Diffusion control for controlling a plurality of double heterostructures formed on a semiconductor substrate and an amount of impurities diffusing into an active layer in the double heterostructures formed on each of the plurality of double heterostructures And having a membrane
Each of the plurality of double heterostructures includes a first conductivity type cladding layer sequentially formed on the semiconductor substrate, an active layer having a quantum well structure including a well layer and a barrier layer, and a second conductivity type cladding layer. a including a semiconductor laser device,
At least a part of the second conductivity type cladding layer has a layer made of Alf1Ga1-f1-g1Ing1P (0 ≦ f1 ≦ 1, 0 ≦ g1 ≦ 1), and at least a part of the second conductivity type cladding layer. And a layer made of Alf2Ga1-f2-g2Ing2P (0 ≦ f2 ≦ 1, 0 ≦ g2 ≦ 1),
One of the plurality of double heterostructures has an active layer of a quantum well structure having a well layer made of Aly1Ga1-y1-z1Inz1P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1), and another one is an AltGa1- an active layer having a quantum well structure having a well layer made of tAs (0 ≦ t ≦ 1);
The plurality of diffusion controlling membrane Ri name from each AlxGa1-xAs (0 ≦ x ≦ 1),
At least part of the second conductivity type cladding layer made of Alf1Ga1-f1-g1Ing1P and at least part of the second conductivity type cladding layer made of Alf2Ga1-f2-g2Ing2P are ridge-shaped stripes,
A semiconductor laser device in which an impurity diffusion region serving as an end face window structure portion for reducing absorption of laser light is provided at an end face portion of a resonator . Diffusion made of Alx1Ga1-x1As (0≤x1≤1) formed on an active layer of a quantum well structure having a well layer made of Aly1Ga1-y1-z1Inz1P (0≤y1≤1, 0≤z1≤1). A control film and a diffusion control film made of Alx2Ga1-x2As (0≤x2≤1) formed on an active layer having a quantum well structure having a well layer made of AltGa1-tAs (0≤t≤1). Have
2. The semiconductor laser device according to claim 1, wherein the Al composition is x1 ≦ x2. The semiconductor laser device according to claim 1, wherein an AlInP current confinement layer is formed on a side surface of the ridge. The photoluminescence wavelength of the active layer of the quantum well structure having a well layer made of Aly1Ga1-y1-z1Inz1P (0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1) included in the impurity diffusion region is 610 nm, and the impurity diffusion 4. The semiconductor laser device according to claim 1, wherein a photoluminescence wavelength of an active layer having a quantum well structure having a well layer made of AltGa1-tAs (0 ≦ t ≦ 1) contained in a region is 740 nm or less. . 5. The semiconductor laser device according to claim 1, wherein the active layer having a quantum well structure having a well layer made of AltGa1-tAs (0 ≦ t ≦ 1) further includes an AlGaAs barrier layer. 6. The double hetero structure having an active layer of a quantum well structure having a well layer made of AltGa1-tAs (0 ≦ t ≦ 1), wherein the first conductivity type cladding layer is made of AlGaAs. A semiconductor laser device according to claim 1. A first active type clad layer on a semiconductor substrate; a first active layer having a quantum well structure having a well layer made of Aly1Ga1-y1-z1Inz1P (0≤y1≤1 , 0≤z1≤1) ; A first second-conductivity-type cladding layer having at least a layer made of Alf1Ga1-f1-g1Ing1P (0 ≦ f1 ≦ 1, 0 ≦ g1 ≦ 1) , and Alz1Ga1-z1As (0 ≦ z1 ≦ 1) Forming a first multilayer structure by sequentially laminating a first diffusion control film for controlling the amount of impurities diffused in the first active layer,
Removing a portion of the first multilayer structure to at least the first active layer;
Quantum having a second first-conductivity-type cladding layer and a well layer made of AltGa1-tAs (0 ≦ t ≦ 1) on a portion of the first multilayer structure removed to at least the first active layer A second active layer having a well structure, a second second-conductivity-type clad layer having at least a layer made of Alf2Ga1-f2-g2Ing2P (0≤f2≤1, 0≤g2≤1) , and Alz2Ga1- forming a second multilayer structure by sequentially laminating a second diffusion control film for controlling the amount of impurities diffused in the second active layer made of z2As (0 ≦ z2 ≦ 1);
Forming a material film serving as a diffusion source of impurities in a predetermined region on the first and second diffusion control films and serving as a cavity end face ;
The semiconductor substrate is heated to diffuse the impurities from the material film through the first and second diffusion control films into the first and second multilayer structures to form an end face window structure. Process,
A method of manufacturing a semiconductor laser device, comprising: simultaneously processing at least a part of the first second conductivity type cladding layer and at least a part of the second second conductivity type cladding layer into a ridge-shaped stripe . In the first diffusion control film made of Alz1Ga1-z1As (0 ≦ z1 ≦ 1) and the second diffusion control film made of Alz2Ga1-z2As (0 ≦ z2 ≦ 1), each Al composition is z1 ≦ z2. The method of manufacturing a semiconductor laser device according to claim 7 . The method further comprises the step of simultaneously and selectively forming an AlInP current confinement layer on the side surface of the ridge in the first second conductivity type cladding layer and the side surface of the ridge in the second second conductivity type cladding layer. 9. A method for manufacturing a semiconductor laser device according to 7 or 8. The semiconductor laser device manufacturing method according to claim 7, further comprising a step of removing the first diffusion control film and the second diffusion control film after the step of forming the end face window structure. Method.

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