JP2004103829A - Semiconductor laser device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a kink level by distributing the electric current symmetrically by forming a configuration of a ridge for a semiconductor laser device, on which a stripe shape ridge is formed so as to be left-and-right symmetrical configuration in order to restrain hole burning. <P>SOLUTION: In the manufacturing method of a semiconductor laser device, a first conductivity first clad layer 13, an active layer 14, the lower layer 15, upper layer 17 as well as intermediate layer 18 of a second conductivity second clad layer, and a cap layer 19 consisting of gallium arsenide are formed on a substrate 11 sequentially. Thereafter, wet etching is applied from the cap layer 19 to the half way of the second clad layer (upper side of the upper layer 17 of the second clad layer) to form the stripe ridges from the cap layer 19 to the upper layer 17 of the second clad layer. The wet etching of the cap layer 19 is effected by isotropic etching employing an etching solution consisting of the blended solution of phosphoric acid, containing the phosphoric acid more than hydrogen peroxide water, hydrogen peroxide water and water. <P>COPYRIGHT: (C)2004,JPO

Description

【００３７】
表１に示すように、ＧａＡｓ層からなるキャップ層のエッチング（エッチング１）では、｜Δｃ｜が従来のエッチングでは０．０８１であったのが本発明の製造方法によるエッチングでは０．００５に改善できた。すなわち、リッジを構成するキャップ層の部分はほぼ等脚台形状の断面に形成することができた。またＧａＩｎＰ層からなる中間層のエッチング（エッチング２）では、｜Δｃ｜が従来のエッチングでは０．１８７であったのが本発明の製造方法では０．０２９に改善できた。さらにＡｌＧａＩｎＰクラッド層のエッチング（エッチング３）では、｜Δｃ｜が従来のエッチングでは０．１７３であったのが本発明の製造方法では０．０８７に改善できた。このように、過酸化水素水よりもリン酸を多く含むリン酸と過酸化水素水と水との混合液からなるエッチング液を用いてキャップ層をエッチングすることにより、その後の中間層、第２クラッド層の上層のエッチングにおいても、｜Δｃ｜が改善された。これは、キャップ層がほぼ等脚台形状の断面に形成されたことに起因する。なお、上記｜Δｃ｜は、従来の技術で説明した定義による。
【００３８】
このように、本発明の半導体レーザ装置の製造方法を採用することにより、左右対称となる断面等脚台形のストライプ状のリッジを容易に形成することができるとともに、安全、安価に実現することが可能となる。また、ストライプ状のリッジの左右対称性が増すことによってレーザ動作時の電流分布も対称性が増し、結果としてホールバーニングが抑制されてキンクレベルが上昇する。
【００３９】
次に、半導体レーザ装置の微分効率と│ΔＣ│との関係を調べた。その結果を、図５の微分効率と│ΔＣ│との関係図により説明する。図５の縦軸の微分効率とはレーザ出力が９ｍＷ〜１１ｍＷ時の発光効率であり、横軸の│ΔＣ│は前記従来の技術で説明して通り、リッジの台形断面形状における上底の中心線と下底の中心線とのずれ量である。
【００４０】
図５に示すように、従来の技術で製造した半導体レーザ装置は領域Ｂに示す範囲に分布し、本発明の製造方法で製造した半導体レーザ装置は領域Ａに示す範囲に分布した。上記領域Ａ，領域Ｂの平均値を求めると、従来の製造方法で製造した半導体レーザ装置では、│ΔＣ│の平均値が０．２１２μｍであり、微分効率が０．８６Ｗ／Ａであった。本発明の製造方法で製造した半導体レーザ装置では、│ΔＣ│の平均値が０．１３７μｍであり、微分効率が０．９２Ｗ／Ａであった。よって、本発明の製造方法で製造した半導体レーザ装置は微分効率が向上されたものとなったことがわかる。
【００４１】
次に、半導体レーザ装置のスロープ効率を、図６の光出力と動作電流との関係図により説明する。図６では、（１）に従来の製造方法により製造された半導体レーザ装置を示し、（２）に本発明の製造方法により製造された半導体レーザ装置を示す。また各図の縦軸に半導体レーザ装置の光出力を表し、横軸に動作電流を表す。
【００４２】
図６の（１）に示すように、従来の製造方法により製造された半導体レーザ装置では、光出力が１１．５ｍＷ〜１３ｍＷ付近にスロープ効率と呼ばれる電流／光出力変換効率に変化が見られる。これは、キンクが発生していることを表している。一方、図６の（２）に示すように、本発明の製造方法により製造された半導体レーザ装置では、光出力が１５ｍＷまでスロープ効率と呼ばれる電流／光出力変換効率は、電流の増加とともに光出力の一様に増加し、図６の（１）に示すような電流／光出力変換効率の変化は起こらない。これは、│ΔＣ│の改善によって、キンクの原因となるホールバーニングが抑制されたためと考えられる。
【００４３】
よって、従来の技術で製造された半導体レーザ装置ではキンクレベルが８〜１１ｍＷ程度であったのに対して、本発明の製造方法で製造された半導体レーザ装置は１１ｍＷ以上のキンクレベルが実現可能となった。
【００４４】
【発明の効果】
以上、説明したように本発明の半導体レーザ装置の製造方法によれば、キャップ層のウエットエッチングは、過酸化水素水よりもリン酸を多く含むリン酸と過酸化水素水と水との混合液からなるエッチング液を用いて等方性エッチングするので、電流供給領域となるストライプ状のリッジは、その断面がほぼ等脚台形に形成できるようになる。このため、リッジの非対称性に起因して発生していた半導体レーザ装置の動作時における電流分布の非対称性が改善され、キンクレベルの低下要因であるホールバーニングを抑制することができる。
【００４５】
本発明の半導体レーザ装置によれば、過酸化水素水よりもリン酸を多く含むリン酸と過酸化水素水と水との混合液からなるエッチング液を用いてガリウムヒ素層を等方性エッチングしたものからなるので、電流供給領域となるストライプ状のリッジは、その断面がほぼ等脚台形に形成されている。このため、リッジの非対称性に起因して発生していた半導体レーザ装置の動作時における電流分布の非対称性が改善され、キンクレベルの低下要因であるホールバーニングを抑制することができる。
【図面の簡単な説明】
【図１】本発明の半導体レーザ装置の製造方法に係る一実施の形態を示す概略構成断面図である。
【図２】｜Δｃ｜とエッチング液の温度との関係図である。
【図３】エッチング速度をパラメータとした水の成分比とエッチング液の温度との関係図である。
【図４】本発明の半導体レーザ装置に係る一実施の形態を示す概略構成断面図である。
【図５】半導体レーザ装置の微分効率と│ΔＣ│との関係図である。
【図６】半導体レーザ装置のスロープ効率を示す光出力と動作電流との関係図である。
【図７】｜Δｃ｜の定義の説明図である。
【符号の説明】
１１…基板、１３…第１クラッド層、１４…活性層、１５…第２クラッド層の下層、１７…第２クラッド層の上層、１８…中間層、１９…キャップ層、２１…リッジ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor laser device and a semiconductor laser device, and more particularly, to a method for manufacturing a semiconductor laser device in which a stripe ridge is formed and a semiconductor laser device.
[0002]
[Prior art]
A striped ridge of a semiconductor red laser formed using a gallium indium phosphide (AlGaInP) semiconductor layer and a glass indium phosphide (GaInP) semiconductor layer as main constituent materials on a gallium indium phosphide (GaInP) substrate having an OFF angle. For this reason, due to the influence of the inclination (OFF angle) of the crystal orientation of the GaInP substrate, the cross-sectional shape of the ridge formed by the ordinary etchant becomes asymmetrical in the left-right direction. In this case, as a process for forming a stripe-shaped ridge, for example, the following etchant is generally used. Etching (etching 1) of the GaAs cap layer uses a sulfuric acid (H ₂ SO ₄ ) -based etchant, and etching (etching 2) of the intermediate layer uses a hydrochloric acid (HCl) -based etchant to etch the AlGaInP clad layer (etching). In 3), a sulfuric acid (H ₂ SO ₄ ) -based etchant is used.
[0003]
The sectional shape (asymmetry) of the stripe-shaped ridge formed by the above-described process is quantitatively quantified as follows.
[0004]
In the stripe-shaped ridge formed by the above-described etching method, as shown in FIG. 7, the cross-section of the ridge 21 does not become an isosceles trapezoid, and the center line Lu of the upper base Wu and the center Ld of the lower base Wd are trapezoidal. Are shifted by | Δc |. For example, when the ridge 21 is formed so that the height H becomes 0.6 μm by etching the GaAs cap layer, the GaInP intermediate layer, and the AlGaInP clad layer under the above conditions, | Δc | = 0.173 μm. Was formed in an asymmetric shape.
[0005]
Further, Japanese Patent Application Laid-Open No. Hei 10-270786 discloses a technique for forming a stripe-shaped ridge using a mixed solution containing hydrobromic acid and aqueous hydrogen peroxide. It should be noted that paragraph 0012 of the specification in JP-A-10-270786 states that "the p-type GaAs protective layer 83 is formed into a stripe shape by etching with a phosphoric acid-based etchant." Further, in the paragraph 0025 of the specification described in JP-A-10-270786, "a mixed solution containing hydrobromic acid and aqueous hydrogen peroxide is ... (omitted) ... phosphoric acid, hydrochloric acid, phosphoric acid It is also possible to control the etching rate, control the cross-sectional shape of the etching, or provide etching selectivity by mixing the etching gas with hydrochloric acid or water. "
[0006]
[Problems to be solved by the invention]
However, the left-right asymmetric shape of the stripe-shaped ridge causes the current distribution during the operation of the semiconductor laser device to be asymmetric, and consequently induces hole burning which causes a reduction in the kink level. As a result, the maximum usable oscillation output of the semiconductor laser device is reduced, which hinders high output and high reliability. Further, as a method of forming the stripe-shaped ridge in a symmetrical shape, for example, dry etching such as reactive ion etching (RIE) can be given. However, a dry etching apparatus is disadvantageous in that it is expensive and uses a toxic etching gas and thus lacks safety. Therefore, there is a demand for a manufacturing method for forming a striped ridge of a semiconductor laser device by wet etching which is cheaper and more secure than dry etching.
[0007]
Further, in the technology described in JP-A-10-270786, in which a stripe-shaped ridge is formed using a mixed solution containing hydrobromic acid and aqueous hydrogen peroxide, phosphoric acid, hydrochloric acid, phosphorus By mixing acid and hydrochloric acid, or water, it is possible to control the etching cross-sectional shape, but whether the ridge cross-sectional shape intended for the present invention can be formed into a symmetric trapezoidal shape or not. It is unknown because there is no description.
[0008]
[Means for Solving the Problems]
The present invention provides a method for manufacturing a semiconductor laser device and a semiconductor laser device which have been made to solve the above-mentioned problems.
[0009]
In the method of manufacturing a semiconductor laser device according to the present invention, a first cladding layer of a first conductivity type, an active layer, a second cladding layer of a second conductivity type, an intermediate layer, and a cap layer made of gallium arsenide are formed on a substrate in this order. After forming, the method of manufacturing a semiconductor laser device in which a stripe-shaped ridge is formed from the cap layer to an upper layer of the second clad layer by wet etching from the cap layer to the middle of the second clad layer. The wet etching of the cap layer is isotropically etching using an etching solution composed of a mixture of phosphoric acid, hydrogen peroxide and water containing more phosphoric acid than hydrogen peroxide.
[0010]
In the method of manufacturing a semiconductor laser device described above, the wet etching of the cap layer is isotropically performed using an etching solution containing a mixed solution of phosphoric acid, hydrogen peroxide, and water, which contains more phosphoric acid than hydrogen peroxide. Since the etching is performed, the cross section of the stripe-shaped ridge serving as the current supply region is formed to have a substantially equal leg trapezoidal shape. For this reason, the asymmetry of the current distribution during the operation of the semiconductor laser device, which has been caused due to the asymmetry of the ridge, is improved, and it is possible to suppress hole burning, which is a factor of lowering the kink level.
[0011]
A semiconductor laser device according to the present invention includes a first cladding layer of a first conductivity type formed on a substrate, an active layer formed on the first cladding layer, and an upper layer portion formed in a striped ridge shape. A semiconductor laser device comprising: a second cladding layer of a second conductivity type formed on the active layer; and a cap layer formed on the second cladding layer. The gallium arsenide layer is obtained by isotropically etching the gallium arsenide layer using an etching solution composed of a mixture of phosphoric acid, hydrogen peroxide and water containing more phosphoric acid than hydrogen water.
[0012]
In the above-described semiconductor laser device, the cap layer isotropically etches the gallium arsenide layer using an etching solution containing a mixture of phosphoric acid, hydrogen peroxide solution, and water, which contains more phosphoric acid than hydrogen peroxide solution. Therefore, the cross-section of the stripe-shaped ridge serving as the current supply region is formed in a substantially isosceles trapezoidal shape. For this reason, the asymmetry of the current distribution during the operation of the semiconductor laser device, which has been caused due to the asymmetry of the ridge, is improved, and it is possible to suppress hole burning, which is a factor of lowering the kink level.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of a method of manufacturing a semiconductor laser device according to the present invention will be described with reference to the schematic cross-sectional view of FIG. FIG. 1 shows a method of manufacturing a red-emitting semiconductor laser device as an example.
[0014]
As shown in FIG. 1A, for example, an n-type substrate is deposited on a substrate 11 of a first conductivity type (hereinafter, the first conductivity type is n-type) by an epitaxial growth method such as a metalorganic vapor phase epitaxial growth method. An n-type first cladding layer 13, an active layer 14 including a barrier layer and a guide layer 14, a second conductivity type (hereinafter, the second conductivity type is referred to as a p-type) via a buffer layer 12. A lower layer 15 of the cladding layer, an etching stopper layer 16, an upper layer 17 of the p-type second cladding layer, an intermediate layer 18, and a p-type cap layer 19 are sequentially formed.
[0015]
The substrate 11 is, for example, an n-type gallium arsenide (GaAs) substrate, the buffer layer 12 is formed of, for example, an n-type gallium indium phosphide (GaInP) layer, and the first cladding layer is, for example, an n-type aluminum gallium. It is formed of an indium phosphide (AlGaInP) layer. The active layer 14 is formed of, for example, a multiple quantum well layer structure having an oscillation wavelength of 650 nm, a layer including a barrier layer and a light guide layer.
[0016]
The lower layer 15 of the p-type second cladding layer is formed of, for example, a p-type aluminum gallium indium phosphide (AlGaInP) layer. The etching stopper layer 16 is formed of, for example, a gallium indium phosphide (GaInP) layer with a thickness of 15 nm, and the upper layer 17 of the second cladding layer is formed of, for example, a p-type aluminum gallium indium phosphide (AlGaInP) layer with a thickness of 250 nm. Formed. Further, the intermediate layer 18 is formed of, for example, a gallium indium phosphide (GaInP) layer with a thickness of 30 nm, and the cap layer 19 is formed of, for example, a p-type gallium arsenide (GaAs) layer with a thickness of 350 nm.
[0017]
Next, a mask layer 31 for forming a ridge on the contact layer 19 is formed of, for example, a resist using a normal lithography technique.
[0018]
Next, as shown in FIG. 1B, wet etching is performed using the mask layer 31 as a mask, leaving the upper layer 17 of the second cladding layer from the cap layer 19 under the mask layer 31. Except for the current injection stripe region 21, the portion from the cap layer 19 to the upper layer 17 of the second clad layer is removed.
[0019]
The cap layer 19 made of gallium arsenide is etched by isotropic wet etching using an etching solution containing a mixed solution of phosphoric acid, hydrogen peroxide solution, and water containing more phosphoric acid than hydrogen peroxide solution. You.
[0020]
Here, the etching solution will be described in detail. The etchant has a component ratio of, for example, phosphoric acid (H ₃ PO ₄ ): hydrogen peroxide (H ₂ O ₂ ): water (H ₂ O) = 3: 1: 30 to 50.
[0021]
When the ratio of water is set to 30 to 50 in the case of phosphoric acid: hydrogen peroxide solution = 3: 1 when the ratio of water is smaller than 30, the etching rate increases and the etching time increases. This is because control becomes difficult, and when the proportion of water is more than 50, the etching rate is conversely reduced, and the variation in the amount of etching in the wafer surface with the prolonged etching time is increased. Therefore, the ratio of water was set to 30 to 50.
[0022]
If the temperature of the etching solution composed of a mixture of phosphoric acid containing a larger amount of phosphoric acid than the aqueous hydrogen peroxide, hydrogen peroxide and water is lower than 20 ° C., the etching of the gallium arsenide layer is aligned with the crystal orientation. Since a large number of components become anisotropic etching, isotropic etching becomes difficult. Furthermore, as shown in the relationship diagram between | Δc | and the temperature of the etchant in FIG. 2, | Δc | decreases as the temperature of the etchant increases. Since | Δc | is the difference between the center line Lu of the trapezoid in the cross-sectional shape of the ridge 21 and the center Ld of the lower base, the higher the temperature of the etching solution, the more the cross-sectional shape of the ridge 21 becomes an equilateral trapezoid. It turns out that it becomes close. This is not limited to the etching solution of phosphoric acid (H ₃ PO ₄ ): hydrogen peroxide solution (H ₂ O ₂ ): water (H ₂ O) = 3: 1: 50. This can be said for an etching solution composed of a mixture of phosphoric acid containing a large amount of phosphoric acid, hydrogen peroxide water and water. It is preferable that | Δc | be as small as possible, but it is desired to be at most 0.15 μm, preferably at most 0.1 μm. Therefore, the temperature of the etching solution needs to be 20 ° C. or more and 35 ° C. or less. Further, it is preferable that the variation in the temperature of the etching solution whose temperature is set be set to ± 1.0 ° C.
[0023]
Further, it is required that the etching rate be 100 nm / min to 130 nm / min from the viewpoint of workability of the process. For example, when phosphoric acid: hydrogen peroxide solution = 3: 1, the etching rate is preferably set to 100 nm / min to 130 nm / min.
[0024]
Here, each of the above conditions is shown in the relationship diagram between the component ratio of water and the temperature of the etching solution using the etching rate as a parameter in FIG. Therefore, as shown in FIG. 3, the area shown by the hatched area surrounded by the solid line is a range that satisfies the above-mentioned temperature of the etching solution and the component ratio of water. Therefore, as an example, it is preferable that the etching liquid is phosphoric acid: hydrogen peroxide solution: water = 3: 1: 30 to 50 and the liquid temperature is set to 30.0 ± 1.0 ° C. By using such an etchant, the etching of the cap layer 19 made of gallium arsenide proceeds isotropically with respect to the crystal orientation of the cap layer 19.
[0025]
Next, the intermediate layer 18 is etched using an acetic acid-based etchant (for example, a mixed solution of acetic acid, a hydrogen peroxide solution, and hydrochloric acid). Further, the upper layer 17 of the second clad layer is etched using a sulfuric acid-based etchant (for example, a mixed solution of sulfuric acid and water). In this etching, the etching is temporarily stopped by the etching stopper layer 16. Thus, the stripe-shaped ridge 21 is formed.
[0026]
Thereafter, the etching stopper layer 16 is etched under the condition that only the etching stopper layer 16 is selectively etched, and the etching stopper layer on the upper layer 15 of the second cladding layer excluding the current injection region 21 into which the current is injected from the ridge 21. 16 is removed. As a result, as shown in FIG. 1C, the surface of the lower layer 15 of the second clad layer excluding the area under the ridge 21 is exposed. Note that, without providing the etching stopper layer 16, the lower layer 15 of the second clad layer and the upper layer 17 of the second clad layer may be formed of one layer, for example, a p-type AlGaInP layer. In this case, by stopping the etching of the p-type AlGaInP layer halfway, the p-type AlGaInP layer is formed in a ridge shape on the current injection stripe region 21 and the p-type AlGaInP layer is formed on the active layer 14. It may be left on the whole surface.
[0027]
After that, the mask layer 31 is removed. Subsequent steps depend on the existing process. For example, although not shown, an n-side electrode and a p-side electrode are formed. Thus, the semiconductor laser device 1 is manufactured. It is also possible to form a current confinement layer on the lower layer 15 of the second cladding layer on both sides of the ridge 21.
[0028]
In the method of manufacturing the semiconductor laser device, the wet etching of the cap layer 19 is isotropically performed using an etching solution containing a mixed solution of phosphoric acid, hydrogen peroxide solution, and water containing more phosphoric acid than hydrogen peroxide solution. Due to the characteristic etching, the cross section of the stripe-shaped ridge 21 serving as the current supply region is formed substantially in the shape of a trapezoid. For this reason, the asymmetry of the current distribution during the operation of the semiconductor laser device 1 which has been caused due to the asymmetry of the ridge 21 is improved, and it is possible to suppress hole burning which is a cause of a decrease in the kink level. .
[0029]
Next, one embodiment of the semiconductor laser device of the present invention will be described below with reference to FIG.
[0030]
As shown in FIG. 4, an n-type first cladding layer 13 is formed on a substrate 11 of a first conductivity type (hereinafter, the first conductivity type is described as n-type) via a buffer layer 12. The substrate 11 is made of, for example, an n-type GaAs substrate, and the buffer layer 12 is made of an n-type gallium indium phosphide (GaInP) layer. The first cladding layer is made of an n-type aluminum gallium indium phosphide (AlGaInP) layer.
[0031]
On the first cladding layer 13, an active layer 14 including a multiple quantum well layer structure having an oscillation wavelength of 650 nm, a barrier layer, and a light guide layer is formed. On the active layer 14, a lower layer 15 of a second cladding layer of a second conductivity type (hereinafter, the second conductivity type is described as p-type) is formed. The lower layer 15 of the second cladding layer is made of, for example, a p-type aluminum gallium indium phosphide (AlGaInP) layer.
[0032]
In the current injection region 21 on the lower layer 15 of the second clad layer, an upper layer 17 of a second conductive type second clad layer is formed in a stripe shape via an etching stopper layer 16. A cap layer 19 is formed on the upper layer 17 with an intermediate layer 18 interposed. That is, a stripe-shaped ridge 21 is formed by a laminated body from the etching stopper layer 16 to the cap layer 19.
[0033]
The etching stopper layer 16 is made of, for example, a gallium indium phosphide (GaInP) layer. The upper layer 17 of the second cladding layer is made of, for example, a p-type aluminum gallium indium phosphide (AlGaInP) layer. The intermediate layer 18 is, for example, a gallium indium phosphide (GaInP) layer. The cap layer 19 is made of a p-type gallium arsenide (GaAs) layer isotropically using an etching solution composed of a mixture of phosphoric acid, hydrogen peroxide and water containing more phosphoric acid than hydrogen peroxide. It consists of etched ones. Note that, without providing the etching stopper layer 16, the lower layer 15 of the second cladding layer and the upper layer 17 of the second cladding layer may be formed of one layer, for example, a p-type aluminum gallium indium phosphide (AlGaInP) layer. It is.
[0034]
Although not shown, an n-side electrode connected to the cap layer 19 and a p-side electrode connected to the first cladding layer 13 are formed. It is also possible to form a current confinement layer on the lower layer 15 of the second cladding layer on both sides of the ridge 21.
[0035]
Next, the cross-sectional shape of the stripe-shaped ridge 21 of the semiconductor laser device formed by the above-described manufacturing method is quantified, and the cross-sectional shape of the stripe-shaped ridge of the semiconductor laser device formed by the manufacturing method described in the background art is described. And the results are shown in Table 1.
[0036]
[Table 1]

[0037]
As shown in Table 1, in the etching of the cap layer made of a GaAs layer (etching 1), | Δc | was 0.081 in the conventional etching, but was improved to 0.005 in the etching by the manufacturing method of the present invention. did it. That is, the portion of the cap layer constituting the ridge could be formed in a substantially equilateral trapezoidal cross section. In the etching of the intermediate layer made of the GaInP layer (etching 2), | Δc | was 0.187 in the conventional etching, but could be improved to 0.029 in the manufacturing method of the present invention. Further, in the etching of the AlGaInP cladding layer (etching 3), | Δc | was 0.173 in the conventional etching, but could be improved to 0.087 in the manufacturing method of the present invention. As described above, by etching the cap layer using the etching solution composed of a mixture of phosphoric acid, hydrogen peroxide and water containing more phosphoric acid than the hydrogen peroxide, the intermediate layer and the second Also in etching the upper layer of the cladding layer, | Δc | was improved. This is due to the fact that the cap layer was formed in an approximately isosceles trapezoidal cross section. Note that | Δc | is based on the definition described in the related art.
[0038]
As described above, by adopting the method of manufacturing a semiconductor laser device of the present invention, it is possible to easily form a symmetrical cross-sectional trapezoidal stripe-shaped ridge having a bilaterally symmetric shape, and to realize safe and inexpensive. It becomes possible. In addition, by increasing the left-right symmetry of the stripe-shaped ridge, the current distribution during the laser operation also increases, and as a result, hole burning is suppressed and the kink level increases.
[0039]
Next, the relationship between the differential efficiency of the semiconductor laser device and | ΔC | was examined. The result will be described with reference to FIG. 5 showing the relationship between the differential efficiency and | ΔC |. The differential efficiency on the vertical axis in FIG. 5 is the luminous efficiency when the laser output is 9 mW to 11 mW, and | ΔC | on the horizontal axis is the center of the upper base in the trapezoidal cross-sectional shape of the ridge as described in the related art. This is the amount of deviation between the line and the center line at the bottom.
[0040]
As shown in FIG. 5, the semiconductor laser device manufactured by the conventional technique is distributed in a range shown in a region B, and the semiconductor laser device manufactured by the manufacturing method of the present invention is distributed in a range shown in a region A. When the average value of the regions A and B was obtained, the average value of | ΔC | was 0.212 μm and the differential efficiency was 0.86 W / A in the semiconductor laser device manufactured by the conventional manufacturing method. In the semiconductor laser device manufactured by the manufacturing method of the present invention, the average value of | ΔC | was 0.137 μm, and the differential efficiency was 0.92 W / A. Therefore, it can be seen that the semiconductor laser device manufactured by the manufacturing method of the present invention has improved differential efficiency.
[0041]
Next, the slope efficiency of the semiconductor laser device will be described with reference to the relationship between the optical output and the operating current in FIG. In FIG. 6, (1) shows a semiconductor laser device manufactured by the conventional manufacturing method, and (2) shows a semiconductor laser device manufactured by the manufacturing method of the present invention. In each figure, the vertical axis represents the optical output of the semiconductor laser device, and the horizontal axis represents the operating current.
[0042]
As shown in FIG. 6A, in the semiconductor laser device manufactured by the conventional manufacturing method, a change in current / light output conversion efficiency called slope efficiency is observed around 11.5 mW to 13 mW in optical output. This indicates that kink has occurred. On the other hand, as shown in FIG. 6B, in the semiconductor laser device manufactured by the manufacturing method of the present invention, the current / light output conversion efficiency called the slope efficiency until the light output becomes 15 mW increases as the current increases. And the current / light output conversion efficiency does not change as shown in FIG. This is considered to be because hole burning that causes kink was suppressed by improving | ΔC |.
[0043]
Therefore, while the kink level of the semiconductor laser device manufactured by the conventional technique is about 8 to 11 mW, the kink level of 11 mW or more can be realized by the semiconductor laser device manufactured by the manufacturing method of the present invention. became.
[0044]
【The invention's effect】
As described above, according to the method for manufacturing a semiconductor laser device of the present invention, the wet etching of the cap layer is performed by using a mixed solution of phosphoric acid, hydrogen peroxide, and water containing more phosphoric acid than hydrogen peroxide. Since the isotropic etching is performed using an etching solution composed of, the cross section of the stripe-shaped ridge serving as the current supply region can be formed in a substantially isosceles trapezoidal shape. For this reason, the asymmetry of the current distribution during the operation of the semiconductor laser device, which has occurred due to the asymmetry of the ridge, is improved, and hole burning, which is a cause of a decrease in the kink level, can be suppressed.
[0045]
According to the semiconductor laser device of the present invention, the gallium arsenide layer is isotropically etched using an etching solution composed of a mixture of phosphoric acid, hydrogen peroxide and water containing more phosphoric acid than hydrogen peroxide. Therefore, the cross-section of the stripe-shaped ridge serving as the current supply region is formed in a substantially isosceles trapezoidal shape. For this reason, the asymmetry of the current distribution during the operation of the semiconductor laser device, which has occurred due to the asymmetry of the ridge, is improved, and hole burning, which is a cause of a decrease in the kink level, can be suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing one embodiment of a method for manufacturing a semiconductor laser device of the present invention.
FIG. 2 is a relationship diagram between | Δc | and the temperature of an etching solution.
FIG. 3 is a diagram illustrating a relationship between a water component ratio and a temperature of an etchant using an etching rate as a parameter.
FIG. 4 is a schematic sectional view showing one embodiment of a semiconductor laser device of the present invention.
FIG. 5 is a relationship diagram between the differential efficiency of the semiconductor laser device and | ΔC |.
FIG. 6 is a diagram illustrating a relationship between an optical output indicating a slope efficiency of the semiconductor laser device and an operating current.
FIG. 7 is an explanatory diagram of the definition of | Δc |.
[Explanation of symbols]
11: substrate, 13: first clad layer, 14: active layer, 15: lower layer of second clad layer, 17: upper layer of second clad layer, 18: intermediate layer, 19: cap layer, 21: ridge

Claims (2)

After forming a first cladding layer of the first conductivity type, an active layer, a second cladding layer of the second conductivity type, an intermediate layer, and a cap layer made of gallium arsenide on the substrate in order from the lower layer, the second layer is formed from the cap layer. In a method for manufacturing a semiconductor laser device, a wet etching is performed halfway through a cladding layer to form a stripe-shaped ridge from the cap layer to an upper layer of the second cladding layer.
A semiconductor, wherein the wet etching of the cap layer is isotropically etched using an etching solution composed of a mixture of phosphoric acid, hydrogen peroxide and water containing more phosphoric acid than hydrogen peroxide. A method for manufacturing a laser device. A first conductive type first cladding layer formed on the substrate;
An active layer formed on the first cladding layer;
An upper layer portion formed in a stripe-shaped ridge shape, and a second cladding layer of a second conductivity type formed on the active layer;
A semiconductor laser device comprising: a cap layer formed on the second cladding layer;
The cap layer is formed by isotropically etching the gallium arsenide layer using an etching solution including a mixed solution of phosphoric acid, hydrogen peroxide solution, and water containing more phosphoric acid than hydrogen peroxide solution. Characteristic semiconductor laser device.

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