JP4144257B2 - Semiconductor laser and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser having a plurality of laser element portions having different emission wavelengths in one chip and a method for manufacturing the same, and more particularly to a semiconductor laser that oscillates by utilizing a pulsation phenomenon and a method for manufacturing the same.
[0002]
[Prior art]
In the field of semiconductor lasers, semiconductor lasers (LDs; laser diodes) (hereinafter referred to as multi-wavelength lasers) having a plurality of light emitting portions having different emission wavelengths on the same substrate are being actively developed. Such a multi-wavelength laser, for example, a two-wavelength laser, is used as a laser light source of an optical disc apparatus.
[0003]
At present, in an optical disc apparatus, a laser beam of 700 nm band (for example, 780 nm) is generally used for reproducing a CD (Compact Disk), and also a CD-R (CD recordable), CD-RW (CD Rewritable) or MD (Mini Disk). It is used for recording and reproduction of recordable optical discs. Further, laser light of 600 nm band (for example, 650 nm) is used for recording / reproduction of DVD (Digital Versatile Disk).
[0004]
As an example of such a two-wavelength laser, for example, two laser chips each having an emission wavelength of 780 nm and 650 nm are mounted in parallel on an arrangement substrate (so-called hybrid two-wavelength). Laser) has been proposed. This hybrid type two-wavelength laser is not particularly limited in the manufacturing process of the laser chip, and each laser chip can be manufactured using an optimum process, so that the degree of freedom of the manufacturing process is high. However, in the hybrid type laser, the accuracy of the beam interval and the beam emission direction is determined by the accuracy of the laser assembly. For example, it is difficult to adjust the interval of the laser chips, so that the accuracy of the beam is ensured. I can't. For this reason, in an optical disc apparatus equipped with a hybrid type two-wavelength laser, many optical components are required to ensure beam accuracy, and as a result, the cost of the entire optical disc apparatus increases.
[0005]
In view of this, there has been proposed a so-called monolithic two-wavelength laser including two laser element portions having emission wavelengths of 780 nm and 650 nm, respectively, in one chip. This monolithic two-wavelength laser has a laser element portion having an active layer made of an AlGaAs-based semiconductor material having an emission wavelength of 780 nm and an emission wavelength having an active layer made of a GaInP-based semiconductor material is 650 nm. The laser element portion is arranged in parallel on one surface side of a substrate made of GaAs (gallium arsenide) through a separation groove.
[0006]
As such a monolithic two-wavelength laser, for example, as shown in FIG. 6, a laser element unit 100A having an emission wavelength of 780 nm and a laser element unit having an emission wavelength of 650 nm on a substrate 111. There is a gain guide type semiconductor laser 100 having 100B (see Japanese Patent Laid-Open No. 2001-57462). In the laser element portion 100A, an n-type cladding layer 121 made of n-type AlGaInP, an active layer 122 made of AlGaAs, and a p-type cladding layer 123 made of p-type AlGaInP are sequentially formed on a substrate 111. In the laser element portion 100B, an n-type cladding layer 131 made of n-type AlGaInP, an active layer 132 made of GaInP, and a p-type cladding layer 133 made of p-type AlGaInP are sequentially formed on a substrate 111.
[0007]
Further, as the gain guide type semiconductor laser, as shown in FIG. 7, a laser element portion 200A having an emission wavelength of 780 nm and a laser element portion 200B having an emission wavelength of 650 nm are formed on a substrate 211. There is a laser 200 (see JP 2000-244060 A). In the semiconductor laser 200, unlike the semiconductor laser 100 described above, all semiconductor layers of the laser element portion 200A are formed of an AlGaAs-based semiconductor material. That is, in the laser element portion 200A, an n-type cladding layer 221 made of n-type AlGaAs, an active layer 222 made of AlGaAs, and a p-type cladding layer 223 made of p-type AlGaAs are sequentially formed on a substrate 211. The laser element portion 200B has the same configuration as the laser element portion 100B (FIG. 6) of the semiconductor laser 100.
[0008]
[Problems to be solved by the invention]
By the way, in recent years, a pulsation type semiconductor laser that oscillates by self-excited oscillation (repetition of output fluctuation) at a frequency of about several hundred MHz to several GHz is attracting attention as a low noise light source for an optical disc apparatus. ing. In this pulsation type laser element portion, as shown in FIG. 8, an n-side cladding layer 521, an active layer 522, and a p-type cladding layer 523 are sequentially formed. The upper portion of the p-type cladding layer 523 is formed in a thin strip shape so as to confine current, and current blocking regions 524 are provided on both sides of the p-type cladding layer 523.
[0009]
In the pulsation type semiconductor laser having such a configuration, a saturable absorbing region (SAR) 522b having a light gain smaller than that of the light emitting region 522a is formed around the light emitting region 522a in the active layer 522. Yes. The saturable absorption region 522b changes the refractive index of the current blocking region 524, changes the width of the upper portion of the p-type cladding layer 523 for current confinement, and changes the thickness of the p-type cladding layer 523. Alternatively, it is formed by changing the volume of the active layer 522 and has a function of promoting interaction between electrons injected into the active layer 522 and light generated in the active layer 522. By such an action of the supersaturated absorption region 522b, the pulsation type semiconductor laser oscillates without relaxing the self-excited vibration.
[0010]
As such a pulsation type semiconductor laser, in order to realize a two-wavelength semiconductor laser in which each of a laser element portion having an emission wavelength of 780 nm and a laser element portion having an emission wavelength of 650 nm is a pulsation type In the laser element portion having an emission wavelength of 780 nm, the n-type cladding layer 521 and the p-type cladding layer 523 sandwiching the active layer 522 made of an AlGaAs semiconductor material must be made of the same AlGaAs semiconductor material as the active layer 522. I must. That is, like the conventional semiconductor laser 200, the laser element portion 200A having an emission wavelength of 780 nm is formed of an AlGaAs semiconductor material, and the laser element portion 200B having an emission wavelength of 650 nm is formed of a GaInP semiconductor material. As described above, each of the laser element portions 200A and 200B must be formed of different materials. For this reason, when these laser element portions are manufactured, it is difficult to perform the process at the same time, and as a result, the manufacturing process is restricted.
[0011]
Therefore, in order to eliminate such a limitation in the manufacturing process, the same applicant as the present applicant, as shown in FIG. 9, in the semiconductor laser 300, the laser element 300A having an emission wavelength of 780 nm is used. It is considered that a part of the p-type cladding layer and the p-type cladding layer of the laser element unit 300B are formed of the same GaInP-based semiconductor material. Specifically, the laser element unit 300A includes an n-type cladding layer 321 made of n-type AlGaAs, an active layer 324 made of AlGaAs, a first p-type cladding layer 325 made of p-type AlGaAs, and a p-type substrate on a substrate 311. A second p-type cladding layer 326 made of type AlGaInP is sequentially formed. The second p-type cladding layer 326 is formed in a thin band shape, and current blocking regions 342A are provided on both sides of the second p-type cladding layer 326. On the other hand, an n-type cladding layer 331 made of AlGaInP, an active layer 332 made of GaInP, and a p-type cladding layer 333 made of AlGaInP are sequentially formed on a substrate 311 in the laser element portion 300B having an emission wavelength of 650 nm. Yes. Current blocking regions 342B are provided on both sides of the p-type cladding layer 333.
[0012]
In the semiconductor laser 300 having such a configuration, since the second p-type cladding layer 326 is formed of AlGaInP in the 780 nm laser element portion 300A, the semiconductor laser 300 includes the first p-type cladding layer 325 and the second p-type cladding layer 326. The refractive index of the p-type cladding layer is smaller than the refractive index of the n-type cladding layer 321.
[0013]
However, it is difficult to make the refractive index of the p-type cladding layer the same as the refractive index of the n-type cladding layer 321 due to restrictions on the manufacturing process. Specifically, in order to make the refractive index of the p-type cladding layer composed of the first p-type cladding layer 325 and the second p-type cladding layer 326 the same as the refractive index of the n-type cladding layer 321, a laser element portion of 780 nm In 300A, if the Al composition of the second p-type cladding layer 326 is reduced, a large difference occurs in the Al composition between the second p-type cladding layer 326 of the laser element section 300A and the p-type cladding layer 333 of the laser element section 300B. As a result, when etching is performed using the same etching solution, the etching rate is greatly different, and therefore etching cannot be performed using the same etching solution.
[0014]
As a result, in the laser element portion 300A of the semiconductor laser 300, the refractive index of the p-type cladding layer composed of the first p-type cladding layer 325 and the second p-type cladding layer 326 is smaller than the refractive index of the n-type cladding layer 321. Furthermore, as shown in FIG. 10A, the light distribution of the light emitting region 324a in the active layer 324 is biased toward the n-side cladding layer 321 and becomes asymmetric.
[0015]
When the light is biased toward the n-side cladding layer 321 in this way, light absorption in the supersaturated absorption region 324b is reduced, and the pulsation margin is very narrow. As shown in FIG. There is a problem in that the FFP (Far Field Pattern) shape of the light emitted from 324a becomes extremely wide in the vertical direction. As a result, there is a problem that the directivity of the laser beam is deteriorated and the laser performance is deteriorated. Such a problem appears remarkably in a pulsation type semiconductor laser.
[0016]
The present invention has been made in view of such problems, and an object of the present invention is to improve the directivity of laser light, and to improve the performance of a laser, particularly a pulsation type laser, and its semiconductor laser. It is to provide a manufacturing method.
[0017]
[Means for Solving the Problems]
A semiconductor laser according to the present invention includes a first laser element portion and a second laser element portion having different emission wavelengths on a substrate, wherein the first laser element portion is a first semiconductor material. A first n-type cladding layer and a second n-type cladding layer. N Formed on the n-type cladding layer, the active layer made of the first semiconductor material, and formed on the active layer. As , A first p-type cladding layer made of a first semiconductor material And the same material as the second semiconductor laser element Second p-type cladding layer made of a second semiconductor material When Consists of P Formed between the n-type clad layer, the first n-type clad layer and the second n-type clad layer, and the difference in refractive index between the n-type clad layer and the p-type clad layer is determined. While reducing A light control layer made of a first semiconductor material; The first semiconductor laser element portion and the second semiconductor laser element portion are arranged in parallel along a direction orthogonal to the resonator direction. Is.
[0018]
A method of manufacturing a semiconductor laser according to the present invention includes a first laser element unit and a second laser element unit having different emission wavelengths on a substrate. Forming the first and second laser element portions in parallel along a direction perpendicular to the resonator direction; The step of forming the first laser element portion includes a first n-type cladding made of a first semiconductor material. Layer And a second n-type cladding layer N Forming a first clad layer, forming an active layer made of a first semiconductor material on the n-type clad layer, and first p-type made of a first semiconductor material on the active layer Cladding layer And the same material as the second semiconductor laser element portion Second p-type cladding layer made of a second semiconductor material When Consists of P Forming a mold cladding layer; and In the step of forming the n-type cladding layer, a light control layer that reduces a difference in refractive index between the n-type cladding layer and the p-type cladding layer is formed between the first and second n-type cladding layers. Is.
[0019]
In the semiconductor laser and the manufacturing method thereof according to the present invention, the light control layer made of the first semiconductor material is formed between the first n-type cladding layer and the second n-type cladding layer of the first laser element portion. The difference between the refractive index of the n-type cladding layer and the refractive index of the p-type cladding layer is caused by this light control layer. Reduction As a result, the center of the light distribution in the active layer coincides with the active layer and the vicinity thereof, and as a result, the light absorption in the supersaturated absorption region increases, thereby increasing the pulsation margin. In addition, the FFP shape of the light emitted from the active layer is prevented from widening in the vertical direction.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 shows a schematic cross-sectional structure of a two-wavelength semiconductor laser 10 according to an embodiment of the present invention. The semiconductor laser 10 includes, for example, a substrate 11 made of n-type GaAs having a thickness of about 100 μm and silicon (Si) added as an n-type impurity. On the substrate 11, for example, a pulsation type laser element unit 10A that emits light in a 700 nm band (for example, 780 nm) and a pulsation type laser element unit 10B that emits light in a 600 nm band (for example, 650 nm), Are formed respectively. The laser element unit 10A and the laser element unit 10B are arranged so as to be spaced apart by about 200 μm or less, for example. Specifically, an interval between a light emitting region described later of the laser element portion 10A and a light emitting region described later of the laser element portion 10B is about 120 μm.
[0022]
In the laser element portion 10A, on the substrate 11, for example, a first n-type cladding layer 21, a light control layer 22, a second n-type cladding layer 23, an active layer 24, a first p-type cladding layer 25, and a second p-type cladding layer. 26, a p-type intermediate layer (not shown) and a p-type cap layer 41A are sequentially formed.
[0023]
Here, each of the first n-type cladding layer 21, the light control layer 22, the second n-type cladding layer 23, the active layer 24, the first p-type cladding layer 25, and the p-type cap layer 41A is, for example, in the short period periodic table. It is comprised from the III-V group compound semiconductor material which contains at least gallium (Ga) of 3B group elements and at least arsenic (As) of 5B group elements in a short period type periodic table. In addition, the second p-type cladding layer 26 and the p-type intermediate layer include, for example, at least indium (In) of the 3B group elements in the short period periodic table and at least phosphorus (P) of the 5B group elements in the short period periodic table. And a group III-V compound semiconductor material.
[0024]
Specifically, the first n-type cladding layer 21 is, for example, n-type Al having a thickness of 0.7 μm and silicon added as an n-type impurity. _x Ga _1-x It is formed of an As mixed crystal. The light control layer 22 is, for example, Al having a thickness of 0.2 μm and silicon added as an n-type impurity. _y Ga _1-y It is formed of an As mixed crystal. As will be described later in detail, the light control layer 22 compensates for the difference between the refractive index of the n-type cladding layer and the refractive index of the p-type cladding layer described later. The second n-type cladding layer 23 is, for example, n-type Al having a thickness of 0.3 μm and silicon added as an n-type impurity. _x Ga _1-x It is formed of an As mixed crystal.
[0025]
Here, the Al composition x in each of the first n-type cladding layer 21 and the second n-type cladding layer 23 is, for example, a value of 0.6 or more and less than 0.7. The Al composition y in the light control layer 22 is larger than the Al composition x of each of the first n-type cladding layer 21 and the second n-type cladding layer 23, for example, 0.7 or more. Thus, since the Al composition y of the light control layer 22 is larger than the Al composition x of each of the first n-type cladding layer 21 and the second n-type cladding layer 23, the refractive index of the light control layer 22 is The refractive index of each of the 1n-type cladding layer 21 and the second n-type cladding layer 23 is smaller.
[0026]
The active layer 24 has, for example, a thickness of 60 nm and different Al composition. _z Ga _1-z It has a multiple quantum well structure of a well layer and a barrier layer each formed by a mixed crystal of As (however, z ≧ 0). In addition, this active layer 24 functions as a light emission area | region, The light emission wavelength is 780 nm, for example.
[0027]
For example, the first p-type cladding layer 25 has a thickness of 0.4 μm and is formed of a p-type AlGaAs mixed crystal to which zinc is added as a p-type impurity. For example, the second p-type cladding layer 26 has a thickness of 0.7 μm and is formed of a p-type AlGaInP mixed crystal to which zinc is added as a p-type impurity. The p-type intermediate layer is formed of p-type GaInP to which zinc is added as a p-type impurity. For example, the p-type cap layer 41A has a thickness of 0.3 μm and is formed of p-type GaAs to which zinc is added as a p-type impurity.
[0028]
Here, when the second p-type cladding layer 26 is formed of AlGaInP mixed crystal, a part of the p-type cladding layer composed of the first p-type cladding layer 25 and the second p-type cladding layer 26 is formed of AlGaInP mixed crystal. Therefore, the refractive index of the p-type cladding layer is smaller than the refractive index of the n-type cladding layer in which both the first n-type cladding layer 21 and the second n-type cladding layer 23 are made of AlGaAs mixed crystal. The difference between the refractive index of the n-type cladding layer and the refractive index of the p-type cladding layer is compensated by the light control layer 22 formed between the first n-type cladding layer 21 and the second n-type cladding layer 23. Yes.
[0029]
Further, the second p-type cladding layer 26, the p-type intermediate layer, and the p-type cap layer 41A are in the form of a thin band extending in the direction of the resonator so as to confine current. On both sides of the belt-like portion, current block regions 42A made of n-type GaAs are provided. Incidentally, the region of the active layer 24 corresponding to the p-type cap layer 41A is a light emitting region.
[0030]
A p-side electrode 51A is formed on the p-type cap layer 41A. For example, the p-side electrode 51A is formed by sequentially laminating titanium, platinum, and gold from the p-type cap layer 41A side and alloying them by heat treatment, and is electrically connected to the p-type cap layer 41A. .
[0031]
In the laser element portion 10B, for example, an n-type cladding layer 31, an active layer 32, a p-type cladding layer 33, a p-type intermediate layer (not shown), and a p-type cap layer 41B are sequentially formed on the substrate 11. ing. Each of these layers includes, for example, a group III-V compound containing at least indium (In) among the group 3B elements in the short period type periodic table and at least phosphorus (P) among the group 5B elements in the short period type periodic table. It is composed of a semiconductor material.
[0032]
Specifically, the n-type cladding layer 31 has a thickness of 1.1 μm, for example, and is formed of an n-type AlGaInP mixed crystal to which silicon is added as an n-type impurity. The active layer 32 has, for example, a thickness of 70 nm and Al having a different composition. _x Ga _y In _1-xy It has a multiple quantum well structure of a well layer and a barrier layer each formed by a mixed crystal of P (where x ≧ 0 and y ≧ 0). In addition, this active layer 32 functions as a light emission area | region, The light emission wavelength is 650 nm, for example. For example, the p-type cladding layer 33 has a thickness of 0.4 μm and is formed of a p-type AlGaInP mixed crystal to which zinc is added as a p-type impurity. The p-type intermediate layer is formed of p-type GaInP to which zinc is added as a p-type impurity. For example, the p-type cap layer 41B has a thickness of 0.7 μm and is formed of p-type GaAs to which zinc is added as a p-type impurity.
[0033]
Note that a part of the p-type cladding layer 33, the p-type intermediate layer, and the p-type cap layer 41B are formed in a thin strip shape extending in the resonator direction so as to confine current. On both sides of the belt-like portion, current block regions 42B made of n-type GaAs are provided. Incidentally, the region of the active layer 32 corresponding to the p-type cap layer 41B is a light emitting region.
[0034]
A p-side electrode 51B is provided on the p-type cap layer 41B. The p-side electrode 51B has the same configuration as the p-side electrode 51A of the laser element portion 10A. For example, titanium, platinum and gold are sequentially laminated from the p-type cap layer 41B side and alloyed by heat treatment. And is electrically connected to the p-type cap layer 41B.
[0035]
Further, an n-side electrode 52 common to the laser element portions 10A and 10B is formed on the back surface of the substrate 11. For example, the n-side electrode 52 is formed by sequentially laminating an alloy of gold and germanium (Ge), nickel and gold from the substrate 11 side and alloying them by heat treatment.
[0036]
Next, a method for manufacturing the semiconductor laser 10 will be described with reference to FIGS.
[0037]
First, as shown in FIG. 2A, a substrate 11 made of n-type GaAs is prepared, and n-type Al is formed on the substrate 11 by MOCVD. _x Ga _1-x First n-type cladding layer 21 made of an As mixed crystal, Al _y Ga _1-y Light control layer 22 made of As mixed crystal, second n-type cladding layer 23, Al _Z Ga _1-Z An active layer 24 made of an As (where z ≧ 0) mixed crystal, a first p-type cladding layer 25 made of a p-type AlGaAs mixed crystal, a second p-type cladding layer 26 made of a p-type AlGaInP mixed crystal, and a p made of p-type GaInP. A mold intermediate layer (not shown) and a p-type cap layer 41A made of p-type GaAs are sequentially grown.
[0038]
Here, the Al composition x in the first n-type cladding layer 21 and the second n-type cladding layer 23 is set to a value of, for example, 0.6 or more and less than 0.7. The Al composition y of the light control layer 22 is larger than the Al composition x of each of the first n-type cladding layer 21 and the second n-type cladding layer 23, for example, 0.7 or more.
[0039]
Next, as shown in FIG. 2B, a resist film 61 is formed on the p-type cap layer 41A so as to correspond to the region where the laser element portion 10A is to be formed. Next, using the resist film 61 as a mask, the p-type cap layer 41A, the p-type intermediate layer, and the second p-type cladding layer 26 are selectively removed using, for example, a hydrochloric acid-based etching solution, and hydrofluoric acid-based etching is performed. The portions of the first p-type cladding layer 25, the active layer 24, the second n-type cladding layer 23, the light control layer 22, and the first n-type cladding layer 21 that are not covered with the resist film 61 are selectively removed using a solution. .
[0040]
After removing the resist film 61, as shown in FIG. 3A, the n-type cladding layer 31 made of an n-type AlGaInP mixed crystal, Al, for example, by MOCVD. _x Ga _y In _1-xy Active layer 32 made of P (where x ≧ 0 and y ≧ 0) mixed crystal, p-type cladding layer 33 made of p-type AlGaInP mixed crystal, p-type intermediate layer (not shown) made of p-type GaInP, p A p-type cap layer 41B made of type GaAs is sequentially grown.
[0041]
Next, as shown in FIG. 3B, a resist film 62 is formed on the p-type cap layer 41B so as to correspond to the region where the laser element portion 10B is to be formed. Subsequently, using the resist film 62 as a mask, the p-type cap layer 41B, the p-type intermediate layer, the p-type cladding layer 33, the active layer 32, and the n-type cladding layer 31 are selectively used, for example, using a hydrochloric acid-based etching solution. To remove.
[0042]
After removing the resist film 62, as shown in FIG. 4A, for example, a thin strip is formed on the p-type cap layer 41A of the laser element unit 10A and the p-type cap layer 41B of the laser element unit 10B. The SiO2 films 63A and 63B are formed. Subsequently, using these SiO2 films 63A and 63B as masks, for example, a p-type cap layer 41A, a p-type intermediate layer, a second p-type cladding layer 26, a p-type cap layer 41B, and a p-type intermediate layer using a hydrochloric acid-based etching solution. Each of the layer and part of the p-type cladding layer 33 is selectively removed. At this time, for example, a hydrochloric acid etching solution having a ratio of hydrochloric acid to water of 2: 1 is used.
[0043]
Using the SiO2 films 63A and 63B as a selective growth mask, current block regions 42A and 42B made of n-type GaAs are formed as shown in FIG. 4B. Here, since the positions of the current injection regions are defined using the lithography technique, these positions can be accurately controlled.
[0044]
As described above, in the present embodiment, the second p-type cladding layer 26 of the laser element unit 10A and the p-type cladding layer 33 of the laser element unit 10B are formed of the same semiconductor material. At the same time, processes such as etching can be performed, and as a result, the manufacturing process is facilitated.
[0045]
After removing the SiO2 films 63A and 63B, for example, nickel, platinum and gold are sequentially deposited on the surfaces of the p-type cap layers 41A and 41B and in the vicinity thereof to form p-side electrodes 51A and 51B, respectively. For example, the back side of the substrate 11 is lapped and polished. Subsequently, for example, an alloy of gold and germanium, nickel, and gold are sequentially deposited on the back side of the substrate 11 to form an n-side electrode 52 that is common to the laser element portions 10A and 10B. After that, heat treatment is performed to alloy the p-side electrodes 51A and 51B and the n-side electrode 52. Further, although not shown here, the substrate 11 is cleaved with a predetermined width perpendicular to the length direction of the p-side electrodes 51A and 51B, for example, and a pair of reflecting mirror films is formed on the cleaved surfaces. Thereby, the semiconductor laser 10 shown in FIG. 1 is manufactured.
[0046]
In this semiconductor laser 10, when a predetermined voltage is applied between the p-side electrode 51 </ b> A and the n-side electrode 52 of the laser element portion 10 </ b> A, a current is injected into the active layer 24 and light is emitted by electron-hole recombination. Occurs, and light having a wavelength of 780 nm is emitted from the laser element portion 10A. Further, when a predetermined voltage is applied between the p-side electrode 51B and the n-side electrode 52 of the laser element portion 10B, a current is injected into the active layer 32, and light emission occurs due to electron-hole recombination, and the laser Light having a wavelength of 650 nm is emitted from the element portion 10B. Here, the light emitted from the laser element units 10A and 10B is emitted from the same side of the pair of reflecting mirrors.
[0047]
At this time, each of the laser element units 10A and 10B oscillates by utilizing the pulsation phenomenon. However, in the laser element unit 10A, as shown in FIG. A light emitting region 24a that emits light by recombination of electrons injected into the layer 24 with holes and a supersaturated absorption region 24b having a light gain smaller than that of the light emitting region 24a are formed. The saturable absorption region 24b changes the refractive index of the current blocking region 42A, changes the width of the second p-type cladding layer 26 for current confinement, and changes the thickness of the first p-type cladding layer 25. Alternatively, it is formed by changing the volume of the active layer 24 and has a function of promoting the interaction between the electrons injected into the active layer 24 and the light generated in the light emitting region 24a. By such an action of the supersaturated absorption region 24b, laser oscillation is performed without relaxing the self-excited vibration.
[0048]
Here, when the second p-type cladding layer 26 is formed of AlGaInP mixed crystal, a part of the p-type cladding layer composed of the first p-type cladding layer 25 and the second p-type cladding layer 26 is formed of AlGaInP mixed crystal. Therefore, the refractive index of the p-type cladding layer is smaller than the refractive index of the n-type cladding layer in which both the first n-type cladding layer 21 and the second n-type cladding layer 23 are made of AlGaAs mixed crystal. In this embodiment, the light control layer 22 is formed between the first n-type cladding layer 21 and the second n-type cladding layer 23, and the light control layer 22 allows the refractive index of the n-type cladding layer and the p-type cladding layer. The difference from the refractive index is compensated.
[0049]
Thus, the light control layer 22 compensates for the difference between the refractive index of the n-type cladding layer and the refractive index of the p-type cladding layer, so that the light distribution of the light emitting region 24a in the active layer 24 is the active layer 24. And the region in the vicinity thereof, and is symmetric with respect to the active layer 24. Therefore, the light absorption in the supersaturated absorption region 24b increases and the pulsation margin increases. In addition, as shown in FIG. 5B, the FFP shape of the light emitted from the active layer 24 is prevented from widening in the vertical direction. As a result, the directivity of the laser beam can be increased, and the performance of the pulsation type laser can be improved.
[0050]
Thus, in the semiconductor laser 10 according to the present embodiment, the light control layer 22 is formed between the first n-type cladding layer 21 and the second n-type cladding layer 23 of the laser element portion 10A, and this light control layer is formed. 22 compensates for the difference between the refractive index of the n-type cladding layer and the refractive index of the p-type cladding layer, so that the light distribution of the light-emitting region 24a in the active layer 24 is the same as that of the active layer 24 and its neighboring regions. These can be made symmetrical with respect to the active layer 24. Therefore, by increasing the light absorption in the saturable absorption region 24b, the pulsation margin can be widened, and the FFP shape of the light emitted from the active layer 24 is prevented from widening in the vertical direction. Can do. As a result, the directivity of the laser beam can be increased, and the performance of the laser, particularly the pulsation type laser can be improved.
[0051]
While the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the present invention is applied to the two-wavelength laser including the laser element unit 10A and the laser element unit 10B. However, the present invention is applicable to a laser having three or more wavelengths composed of three or more laser element units. You may apply.
[0052]
In the above embodiment, the present invention is applied to the pulsation type semiconductor laser 10. However, the present invention is applied to other semiconductor lasers such as a gain guide type semiconductor laser and an index guide type semiconductor laser. Also good.
[0053]
【The invention's effect】
As described above, according to the semiconductor laser and the manufacturing method thereof of the present invention, the light control layer is formed between the first n-type cladding layer and the second n-type cladding layer of the first laser element portion. This optical control layer can be used to determine the difference between the refractive index of the n-type cladding layer and that of the p-type cladding layer. Reduce Thus, the light distribution of the light emitting region in the active layer can be made symmetric with respect to the active layer so as to coincide with the active layer and the region in the vicinity thereof. Therefore, by increasing light absorption in the saturable absorption region in the active layer, the pulsation margin can be widened, and the FFP shape of the light emitted from the active layer is prevented from widening in the vertical direction. can do. As a result, the directivity of laser light can be increased, and the performance of a laser, particularly a pulsation type laser, can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a configuration of a semiconductor laser according to an embodiment of the present invention.
2 is a cross-sectional view showing a manufacturing process of the semiconductor laser shown in FIG. 1. FIG.
3 is a cross-sectional view showing a manufacturing step that follows FIG. 2; FIG.
4 is a cross-sectional view showing a manufacturing step that follows FIG. 3; FIG.
FIG. 5 is a schematic configuration diagram for explaining the characteristics of a laser element portion having an emission wavelength of 780 nm in the semiconductor laser shown in FIG. 1;
FIG. 6 is a schematic configuration diagram showing a configuration of a conventional semiconductor laser.
FIG. 7 is a schematic configuration diagram showing a configuration of a conventional semiconductor laser.
FIG. 8 is a schematic configuration diagram of a laser element portion of a conventional pulsation type semiconductor laser.
FIG. 9 is a schematic configuration diagram showing a configuration of a pulsation type semiconductor laser.
FIG. 10 is a schematic configuration diagram for explaining the characteristics of a laser element portion having an emission wavelength of 780 nm in a pulsation type semiconductor laser.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Semiconductor laser, 10A, 10B ... Laser element part, 11 ... Substrate, 21 ... 1st n-type cladding layer, 22 ... Light control layer, 23 ... 2nd n-type cladding layer, 24, 32 ... active layer, 24a ... light emitting region, 24b ... supersaturated absorption region, 25 ... first p-type cladding layer, 26 ... second p-type cladding layer, 31 ... n-type cladding layer, 33 ... p-type cladding layer, 41A, 41B ... p-type cap layer, 42A, 42B ... current blocking region, 51A, 51B ... p-side electrode, 52 ... n-side electrode, 61, 62 ... Resist film, 63A, 63B ... SiO ₂ film

Claims (12)

A semiconductor laser comprising a first laser element portion and a second laser element portion having different emission wavelengths on a substrate,
The first laser element unit is:
And n-type cladding layer composed of a first n-type cladding layer and a second n-type clad layer of a first semiconductor material,
An active layer formed on the n-type cladding layer and made of a first semiconductor material;
Formed on the active layer Rutotomoni, a first p-type cladding layer of a first semiconductor material, a second p-type of a second semiconductor material of the second laser element part and the same material and p-type cladding layer composed of a clad layer,
A first semiconductor layer formed between the first n-type cladding layer and the second n-type cladding layer to reduce a difference in refractive index between the n-type cladding layer and the p-type cladding layer; A light control layer made of a material ,
Wherein the first and the second laser element part and the laser element portion, a semi-conductor laser having a are arranged in parallel along a direction perpendicular to the resonator direction. The first semiconductor material includes at least gallium among group 3B elements and at least arsenic among group 5B elements.
The semiconductor laser of 請 Motomeko 1, wherein the. The second semiconductor material includes at least indium of group 3B elements and at least phosphorus of group 5B elements.
The semiconductor laser of 請 Motomeko 1, wherein the. Each of the first n-type cladding layer, the second n-type cladding layer, and the light control layer includes aluminum,
The composition of aluminum contained in the light control layer is larger than the composition of aluminum contained in each of the first n-type cladding layer and the second n-type cladding layer.
The semiconductor laser of 請 Motomeko 2 described. The second laser element portion includes a p-type cladding layer made of the same second semiconductor material as the second p-type cladding layer of the first laser element portion.
The semiconductor laser of 請 Motomeko 1, wherein the. The emission wavelength of the first laser element unit is in the 700 nm band, and the emission wavelength of the second laser element unit is in the 600 nm band.
The semiconductor laser of 請 Motomeko 1, wherein the. A method of manufacturing a semiconductor laser comprising a first laser element portion and a second laser element portion having different emission wavelengths on a substrate,
Forming the first and second laser element portions in parallel along a direction orthogonal to the resonator direction;
The step of forming the first laser element portion includes:
Forming a first n-type cladding layer contact and the n-type cladding layer composed of a second n-type clad layer of a first semiconductor material,
Forming an active layer made of a first semiconductor material on the n-type cladding layer;
On the active layer, from the first p-type cladding layer of a first semiconductor material, and the second of the second p-type cladding layer made of a semiconductor material of the second laser element part and the same material and forming a p-type cladding layer made of,
In the step of forming the n-type cladding layer,
A light control layer that reduces a difference in refractive index between the n-type cladding layer and the p-type cladding layer is formed between the first and second n-type cladding layers.
Method of manufacturing a semi-conductor laser. The first semiconductor material includes at least gallium among group 3B elements and at least arsenic among group 5B elements.
請 Motomeko 7 A method of manufacturing a semiconductor laser according. The second semiconductor material includes at least indium of group 3B elements and at least phosphorus of group 5B elements.
請 Motomeko 7 A method of manufacturing a semiconductor laser according. Each of the first n-type cladding layer, the second n-type cladding layer, and the light control layer includes aluminum,
The composition of aluminum contained in the light control layer is made larger than the composition of aluminum contained in each of the first n-type cladding layer and the second n-type cladding layer.
請 Motomeko 8 semiconductor laser manufacturing method according. The step of forming the second laser element portion includes the step of forming a p-type cladding layer made of the same second semiconductor material as the p-type cladding layer of the first laser element portion.
請 Motomeko 7 A method of manufacturing a semiconductor laser according. The emission wavelength of the first laser element unit is set to 700 nm band, and the emission wavelength of the second laser element unit is set to 600 nm band.
請 Motomeko 7 A method of manufacturing a semiconductor laser according.

Images