JP2006310766A - Gallium nitride compound semiconductor laser element and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing gallium nitride compound semiconductor laser elements that ensure large slope efficiency and lower drive voltage even when gallium nitride substrates with large off angles are used, maintain high yields, reduce variations, and emit high-power violaceous lights and compound semiconductor laser elements produced using this method. <P>SOLUTION: This method for manufacturing gallium nitride compound semiconductor laser elements is featured by using either an inclined plane with an absolute value of degree from 0.16 to 5.0 towards a <1-100> direction on a (0001) Ga surface or a surface where a square root of the value (A<SP>2</SP>+B<SP>2</SP>) is greater than or equal to 0.17 but less than or equal to 7.0, when assuming a (0001) Ga surface off angle towards <1-100> direction to be "A" and a (0001) Ga surface off angle towards <11-20> direction to be "B" as a crystal growth surface on a gallium nitride compound substrate, and growing an active layer at a rate faster than or equal to 0.5 Å/second but less than or equal to 5.0 Å/second. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a compound semiconductor laser device and a compound semiconductor laser device manufactured by the manufacturing method, and in particular, a gallium nitride-based compound semiconductor laser device having high slope efficiency and capable of emitting blue-violet light having a short wavelength. And a gallium nitride-based compound semiconductor laser device manufactured by this manufacturing method.

  In recent years, nitride-based semiconductors are mainly used for blue LEDs and blue-violet semiconductor lasers. This nitride-based semiconductor is usually formed on a nitride semiconductor substrate such as a sapphire substrate, SiC substrate or GaN by MOCVD (Metal Organic Chemical Vapor Deposition) method, MBE (Molecular Beam Epitaxy) molecule. The epitaxial growth is performed using a crystal growth method such as a line epitaxial growth method or a HVPE (Hydride Vapor Phase Epitaxy) method. Of these, the MOCVD method is most often used as the crystal growth method.

  A specific example of a conventional nitride-based semiconductor laser device is shown in FIG. FIG. 4 is a schematic cross-sectional view of a conventional nitride semiconductor device 50. The nitride-based semiconductor laser device 50 includes a buffer layer 52, an undoped GaN layer 53, an n-GaN contact layer 54, an n-AlGaN cladding layer 55, an n-GaN light guide layer 56, an active layer 57 on a sapphire substrate 51. A p-GaN light guide layer 58 is sequentially formed. A p-AlGaN cladding layer 59 is formed in a ridge shape on a region having a predetermined width of the p-GaN light guide layer 58, and a current confinement layer 60 is formed on the side surface of the ridge-shaped p-AlGaN cladding layer 59. Yes. Further, a p-GaN contact layer 61 is formed on the upper surface of the p-AlGaN cladding layer 59 and the current confinement layer 60. A partial region from the p-GaN contact layer 61 to the n-GaN contact layer 54 is removed, and the n-GaN contact layer 54 is exposed to form a mesa shape. An n electrode 62 is formed on a predetermined region of the exposed n-GaN contact layer 54, and a p electrode 63 is formed on the predetermined region of the p-GaN contact layer 61.

  By the way, in such a nitride semiconductor device in which a gallium nitride based semiconductor layer is formed on a sapphire substrate, the difference in lattice constant between the sapphire substrate and the gallium nitride based semiconductor layer is large. For this reason, the gallium nitride based semiconductor layer formed on the sapphire substrate contains many dislocations and has deteriorated crystallinity. Therefore, it is difficult to realize good device characteristics in a nitride semiconductor device using a sapphire substrate.

Therefore, in Patent Document 1 below, nitriding is performed using a SiC substrate having a plane (off-plane) inclined within a range of 0.02 to 0.6 degrees with respect to the (0001) Si plane of the SiC crystal as the substrate. It has been shown that when a physical semiconductor layer is formed, good crystallinity can be obtained, and it is suggested that similar results can be obtained even when a gallium nitride substrate is used. Further, the following Patent Document 2 discloses an invention of a nitride-based semiconductor light-emitting element using a gallium nitride substrate having a tilt angle from the C plane of 0.03 degrees or more and 10 degrees or less. If a gallium nitride substrate having an inclined surface of 1 degree to 20 degrees in a predetermined direction from the (0001) plane is used, a nitride-based semiconductor layer with good crystallinity can be obtained. 4 shows that a nitride semiconductor layer having good crystallinity can be obtained even in an InGaN system when a gallium nitride substrate having an inclined surface of 15 degrees or more and 60 degrees or less from the (0001) C plane is used. Has been.
JP-A-11-233391 JP 2000-223743 A JP 2002-16000 A JP 2002-344089 A

  However, in a gallium nitride-based compound semiconductor laser element formed using a gallium nitride substrate having a predetermined inclined surface from the (0001) plane as described above, a nitride-based semiconductor layer with good crystallinity is Even if it is obtained, the obtained gallium nitride compound semiconductor laser device has a low slope efficiency, has a problem in device characteristics, and may not be suitable for high light output use.

  On the other hand, the present inventors have conducted various experiments in order to examine the cause for producing the gallium nitride compound semiconductor laser element having a low slope efficiency. As a result, the gallium nitride compound semiconductor laser element having a low slope efficiency is Occurs when the inclination angle of the (0001) Ga surface, which is the crystal growth surface of the gallium nitride substrate, is out of the predetermined numerical range, whether it is inclined in one direction or in two directions. As a result, a patent application has already been filed as Japanese Patent Application No. 2005-023322 (hereinafter referred to as “prior application”) regarding a gallium nitride-based compound semiconductor laser device having a large slope efficiency with a limited inclination angle.

  That is, in the specification and drawings of the prior application, the off angle of the gallium nitride substrate surface that can be used for the manufacture of the gallium nitride compound semiconductor laser device having a large slope efficiency is limited, and the off angle outside the range is large. It has been pointed out that slope efficiency decreases when a gallium nitride-based compound semiconductor laser device is fabricated on a substrate.

  On the other hand, it has been found that when a gallium nitride compound semiconductor laser device is formed on the surface of a gallium nitride substrate in a region with a large off angle, there is another advantage that the device resistance is reduced and the driving voltage can be reduced. However, since an element satisfying such slope efficiency cannot be obtained, a substrate having a large off angle has not been used for manufacturing a gallium nitride-based compound semiconductor laser element.

  The present inventors have conducted various experiments in order to investigate the cause of producing a gallium nitride compound semiconductor laser device having a low slope efficiency when using a gallium nitride substrate having a large off angle as described above. It has been found that the slope efficiency is limited by the growth rate of the active layer of the gallium nitride compound semiconductor laser device formed on the gallium nitride substrate in the region with a large off angle, and the present invention has been completed.

  That is, the present invention is intended to solve the problem of the prior art that a gallium nitride compound semiconductor laser device having a low slope efficiency can be obtained when a gallium nitride compound semiconductor laser device is fabricated on a gallium nitride substrate having a large off angle. Even when a gallium nitride substrate with a large off angle is used, the slope efficiency is large, the device resistance is small, the drive voltage can be reduced, and the manufacturing yield is high, variation is small, and the output is blue-violet. An object of the present invention is to provide a method for manufacturing a gallium nitride-based compound semiconductor laser device capable of emitting the above light and a gallium nitride-based compound semiconductor laser device manufactured by this manufacturing method.

  The above object of the present invention can be achieved by the following configurations. That is, the invention of the method for manufacturing a gallium nitride-based compound semiconductor laser device according to claim 1 is a method for producing a gallium nitride-based compound semiconductor laser device on a gallium nitride substrate, and the crystal growth surface of the gallium nitride substrate. As a surface inclined in the <1-100> direction of the (0001) Ga plane with an absolute value of 0.16 degrees or more and 5.0 degrees or less, and the active layer is 0.5 Å / second or more and 5.0 Å / second or less. It is characterized by growing at a growth rate.

  In this case, when the inclination of the crystal growth surface of the gallium nitride substrate is 0.16 degrees or more in absolute value in the <1-100> direction of the (0001) Ga surface, the growth rate of the active layer is less than 0.5 Å / sec. In some cases, the slope efficiency of the uncoated gallium nitride compound semiconductor laser element does not reach 0.3 W / A. However, when the growth rate of the active layer is 0.5 Å / second or more, the slope efficiency is 0.6 W / A. That's it. However, even if the growth rate of the active layer is too high, the crystal quality of the MQW active layer is deteriorated and the reliability of the device is lowered. Therefore, the upper limit of the growth rate of the active layer should be limited to 5.0 kg / sec. . In addition, if the upper limit of the tilt angle exceeds 5 degrees, In atoms cannot sufficiently enter the MQW active layer, and the oscillation wavelength becomes 395 nm or less, which is not preferable.

  A gallium nitride-based compound semiconductor laser device having a slope efficiency of 0.6 W / A or more can be stably obtained by combining the tilt angle range of the crystal growth surface of the gallium nitride substrate and the growth rate of the active layer. The reason for this result is not clear at present, and it is necessary to wait for further research. The reason is as follows.

  Conventionally, when a substrate surface having a large off-angle is used, the reason why the slope efficiency of the laser element is lowered is estimated as follows. Generally, the slope efficiency is mainly determined by the magnitude of the luminous efficiency of the active layer, but in the case of an InGaN active layer, a localized phenomenon of In composition occurs in the growth layer when island-like growth occurs. An active layer with high luminous efficiency is obtained. However, if the growth rate of the active layer is reduced and grown on the substrate surface having a large off angle as in the conventional case, the step density of the crystal plane is significantly affected by the large off angle, and the crystal growth The morphology is step growth, and the island-like growth as seen on the substrate surface with a small off-angle is not obtained. Therefore, for these reasons, conventionally, only a nitride compound semiconductor laser element having a low slope efficiency has been obtained on a substrate surface having a large off angle.

  On the other hand, in the present invention, the above-mentioned problems can be improved by increasing the growth rate of the active layer to 0.5 Å / second or more and 5.0 Å / second or less. In other words, even on a substrate surface with a large absolute value of the off-angle, by increasing the growth rate, it becomes possible to obtain a crystal growth form of island-like growth instead of step growth. It is considered that an active layer having high emission efficiency can be obtained in the growth layer.

  The invention according to claim 2 is the method for manufacturing a gallium nitride-based compound semiconductor laser device according to claim 1, wherein the oscillation wavelength of the semiconductor laser device is 395 to 405 nm.

  According to a third aspect of the present invention, in the method of manufacturing a gallium nitride compound semiconductor laser device according to the first or second aspect, the resonator surface of the semiconductor laser device is a natural scratched surface of a crystal. To do.

  According to a fourth aspect of the present invention, in the method of manufacturing a gallium nitride-based compound semiconductor laser device according to any one of the first to third aspects, the reflectance of the emission surface of the resonator surface of the semiconductor laser device is It is adjusted to 10 to 30%, and an end face coat having a reflectance of 70% or more is formed on the rear surface of the resonator surface.

  According to a fifth aspect of the present invention, in the method for manufacturing a gallium nitride-based compound semiconductor laser device according to any one of the first to third aspects, a reflectance of 10 is applied to an emission surface of the resonator surface of the semiconductor laser device. % End face coat is formed, and 70% or more end face coat is formed on the rear face of the resonator surface.

Further, the invention of a method for manufacturing a gallium nitride compound semiconductor laser device according to claim 6 is a method for producing a gallium nitride compound semiconductor laser device on a gallium nitride substrate, wherein the crystal growth surface of the gallium nitride substrate (A ² + B ² ) where A is the off angle of the (0001) Ga plane in the <1-100> direction and B is the off angle of the (0001) Ga plane in the <11-20> direction. The surface having a square root of 0.17 or more and 7.0 or less is used, and the active layer is grown at a growth rate of 0.5 Å / second or more and 5.0 Å / second or less.

In this case, when the square root of (A ² + B ² ) is 0.17 or more and 7.0 or less, the slope efficiency of the uncoated gallium nitride-based compound semiconductor laser device when the growth rate of the active layer is less than 0.5 Å / sec. May not reach 0.3 W / A or more, but the slope efficiency becomes 0.6 W / A or more when the growth rate of the active layer is 0.5 Å / second or more. However, even if the growth rate of the active layer is too high, the crystal quality of the MQW active layer is deteriorated and the reliability of the device is lowered. Therefore, the upper limit of the growth rate of the active layer should be limited to 5.0 kg / sec. . Further, if the square root of (A ² + B ² ) exceeds 7.0, it is not preferable because In atoms cannot sufficiently enter the MQW active layer and the oscillation wavelength becomes 395 nm or less.

  The invention according to claim 7 is the method of manufacturing a gallium nitride-based compound semiconductor laser element according to claim 6, wherein the oscillation wavelength of the semiconductor laser element is 395 to 405 nm.

  The invention according to claim 8 is the method of manufacturing a gallium nitride-based compound semiconductor laser device according to claim 6 or 7, characterized in that the resonator surface of the semiconductor laser device is a natural scratch face of a crystal. To do.

  The invention according to claim 9 is the method for manufacturing a gallium nitride-based compound semiconductor laser device according to any one of claims 6 to 8, wherein the reflectance of the exit surface of the resonator surface of the semiconductor laser device is It is adjusted to 10 to 30%, and an end face coat having a reflectance of 70% or more is formed on the rear surface of the resonator surface.

  According to a tenth aspect of the present invention, in the gallium nitride-based compound semiconductor laser device according to any one of the sixth to eighth aspects, a reflectance of 10% or less is applied to an emission surface of the resonator surface of the semiconductor laser device. An end face coat is formed, and an end face coat having a reflectance of 70% or more is formed on the rear face of the resonator face.

  Furthermore, the invention of a gallium nitride compound semiconductor laser device according to claim 11 is a gallium nitride compound semiconductor laser device formed on a gallium nitride substrate, wherein the crystal growth surface of the gallium nitride substrate is (0001). It has a surface inclined in the <1-100> direction of the Ga surface with an absolute value of 0.16 degrees or more and 5.0 degrees or less, and the active layer has a growth rate of 0.5 Å / second to 5.0 Å / second. It is characterized by being grown.

The invention of a gallium nitride compound semiconductor laser device according to claim 12 is a gallium nitride compound semiconductor laser device formed on a gallium nitride substrate, wherein the crystal growth surface of the gallium nitride substrate is (0001). ) The square root of (A ² + B ² ) is 0 when the off angle of the Ga surface in the <1-100> direction is A and the off angle of the (0001) Ga surface in the <11-20> direction is B. It has a surface of .17 or more and 7.0 or less, and the active layer is grown at a growth rate of 0.5 Å / sec or more and 5.0 Å / sec or less.

  By providing the above configuration, the present invention has the following excellent effects. That is, according to the gallium nitride compound semiconductor laser device manufacturing method according to claim 1 and claim 6, a gallium nitride compound semiconductor having a slope efficiency of 0.6 W / A or more stably even if variation is taken into account. Laser elements can be manufactured.

  Moreover, according to the invention which concerns on Claim 2 and Claim 7, when the oscillation wavelength is the violet range of 395-405 nm, the effect of this invention appears more notably.

  In addition, according to the inventions according to claims 3 and 8, the manufacturing yield of the gallium nitride-based compound laser device is greatly improved by making the resonator surface a natural scratched surface of the crystal. The effect of can be utilized more remarkably.

  Further, according to the inventions according to claims 4 and 9, the exit surface of the resonator surface is adjusted to have a reflectance of 10 to 30%, and the rear surface of the resonator surface is an end surface coat having a reflectance of 70% or more. By applying the present invention to the semiconductor laser element on which the optical characteristics are formed, the noise characteristics can be improved when applied to an optical pickup, so that the effects of the present invention can be used more remarkably.

  According to the inventions according to claim 5 and claim 10, the exit surface of the resonator surface is formed with an end surface coat having a reflectance of 10% or less, and the rear surface of the resonator surface is an end surface having a reflectance of 70% or more. By applying the present invention to a semiconductor laser element on which a coat is formed, the present invention can be adapted to an application requiring a higher light output, and thus the effects of the present invention can be used more remarkably.

  Furthermore, according to the eleventh and twelfth aspects of the present invention, a gallium nitride-based compound semiconductor laser device having a slope efficiency of 6 W / A or more can be obtained stably even when variations are taken into account.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples and drawings. The examples described below are gallium nitride compound semiconductors for embodying the technical idea of the present invention. The method of manufacturing a laser device and a gallium nitride-based compound semiconductor laser device manufactured by this manufacturing method are exemplified, and the present invention is not intended to be limited to this embodiment. The present invention can be equally applied to various modifications without departing from the technical idea shown in the above-mentioned range.
[Experimental Example 1] (Examples 1 to 3 and Comparative Examples 1 to 3)
As the crystal growth surface of the GaN substrate, a (0001) Ga surface with an off angle in the <1-100> direction of 0.30 degrees is used, and each semiconductor layer is stacked on the substrate as follows. As a result, the growth rate of the active layer was 0.20 Å / second (Comparative Example 1), 0.30 Å / second (Comparative Example 2), 0.40 Å / second (Comparative Example 3), 0.50 Å / second ( By producing six types of gallium nitride-based compound semiconductor laser elements of Example 1), 0.70 Å / sec (Example 2), and 1.00 Å / sec (Example 3), the growth rate of the active layer The relationship with slope efficiency was investigated.

First, as shown in FIG. 1, a growth temperature of 1100 ° C. is used on a GaN substrate (1) by MOCVD (metal organic chemical vapor deposition), and NH ₃ , trimethylgallium, trimethylaluminum, and GeH ₄ are used as raw materials. The n-type AlGaN cladding layer (2) was grown at 1.0 μm at a growth rate of 3.0 Å / sec.

Thereafter, the temperature is lowered, and an InGaN well layer of the three-period structure MQW active layer (3) is grown at a growth temperature of 800 ° C. using NH ₃ , trimethyl gallium, and trimethyl indium as raw materials, and then grown to 0.003 μm. Of the active layer (3), a GaN barrier layer was grown by 0.02 μm using NH ₃ and trimethyl gallium as raw materials. The growth rate of the MQW active layer described above corresponds to the growth rate of the active layer referred to in the present invention, and here, the growth rate was controlled so as to correspond to Comparative Examples 1 to 3 and Examples 1 to 3, respectively. Further, NH ₃ , trimethyl gallium, and trimethyl indium were used as raw materials at a growth temperature of 800 ° C., and an InGaN optical guide layer (4) was grown to 0.1 μm.

Thereafter, the growth temperature of 800 ° C., NH ₃ as a raw material, using trimethyl gallium, trimethyl aluminum, AlGaN cap layer (5) is 0.02μm growing, then the temperature is increased, the growth temperature of 1100 ° C., NH ₃ as a raw material , Trimethylgallium, trimethylaluminum, and cyclopentadenylmagnesium were used to grow a p-type AlGaN cladding layer (6) by 0.5 μm at a growth rate of 3.0 Å / sec. Finally, a p-type GaN contact layer (7) was grown to 0.005 μm using a growth temperature of 1100 ° C. and NH ₃ , trimethyl gallium, and cyclopentadienyl magnesium as raw materials.

Next, the electrode process was performed according to the following procedure. First, a P-type electrode (8) made of Pt / Pd is formed, and then ridges (7, 8) as current confinement portions are formed by dry etching, and then SiO is formed on both sides of the ridge using a CVD apparatus. _Two films (10) were formed. Next, a pad electrode (9) made of Ti / Pd / Au is formed, the back side of the substrate is polished to a thickness of about 110 μm, and finally an n-type electrode (11) made of Al / Pt / Au. To complete the wafer. Subsequently, the device was separated using a scribing process, and the gallium nitride compound semiconductor laser device shown in FIG. 1 was completed.

  About the completed six types of gallium nitride-based compound semiconductor laser elements, 10 pieces of each were evaluated in an uncoated state at room temperature, and the average value was obtained. The relationship between the growth rate of the active layer and the slope efficiency (W / A) of the uncoated laser element is shown in FIG. 2, and the oscillation wavelengths are shown in Table 1.

図２に示した結果によると、（０００１）Ｇａ面の＜１−１００＞方向に傾斜した角度の絶対値が０．３０度の基板を用いた場合、活性層の成長速度が０．５Å／秒以上であればスロープ効率が０．７５Ｗ／Ａ以上となっていることが分かる。この活性層の成長速度が０．７Å／秒以上であるとスロープ効率が０．８Ｗ／Ａ以上を期待できる。活性層の成長速度が速すぎてもＭＱＷ活性層の結晶品質が悪くなるために素子の信頼性が低下するので、活性層の成長速度の上限は５．０Å／秒に止めるべきである。また、傾斜角度の上限が５度を超えるとＭＱＷ活性層内にＩｎ原子が十分に入らなくなり、発振波長が３９５ｎｍ以下となってしまうので好ましくない。
［実験例２］（実施例４〜６及び比較例４〜６）
次に、ＧａＮ基板の結晶成長面として、（０００１）Ｇａ面の＜１−１００＞方向へのオフ角度をＡとし、（０００１）Ｇａ面の＜１１−２０＞方向へのオフ角度をＢとした場合、（Ａ^２＋Ｂ^２）の平方根が０．３０のものを使用し、この基板上にそれぞれ実験例１の場合と同様にして各半導体層を積層することにより、活性層の成長速度が、０．２０Å／秒（比較例４）、０．３０Å／秒（比較例５）、０．４０Å／秒（比較例６）、０．５０Å／秒（実施例４）、０．７０Å／秒（実施例５）、１．００Å／秒（実施例６）である６種類の窒化ガリウム系化合物半導体レーザ素子を作製した。

According to the results shown in FIG. 2, when a substrate having an absolute value of an angle inclined in the <1-100> direction of the (0001) Ga plane is 0.30 degrees, the growth rate of the active layer is 0.5 Å / It can be seen that the slope efficiency is 0.75 W / A or more if it is 2 seconds or more. When the growth rate of this active layer is 0.7 K / sec or more, a slope efficiency of 0.8 W / A or more can be expected. Even if the growth rate of the active layer is too high, the crystal quality of the MQW active layer is deteriorated and the reliability of the device is lowered. Therefore, the upper limit of the growth rate of the active layer should be limited to 5.0 kg / sec. In addition, if the upper limit of the tilt angle exceeds 5 degrees, In atoms cannot sufficiently enter the MQW active layer, and the oscillation wavelength becomes 395 nm or less, which is not preferable.
[Experimental Example 2] (Examples 4 to 6 and Comparative Examples 4 to 6)
Next, as the crystal growth surface of the GaN substrate, the off angle of the (0001) Ga plane in the <1-100> direction is A, and the off angle of the (0001) Ga plane in the <11-20> direction is B. In this case, when the square root of (A ² + B ² ) is 0.30 and each semiconductor layer is stacked on this substrate in the same manner as in Experimental Example 1, the growth rate of the active layer is increased. 0.20 K / sec (Comparative Example 4), 0.30 K / sec (Comparative Example 5), 0.40 K / sec (Comparative Example 6), 0.50 K / sec (Example 4), 0.70 K / sec (Example 5) Six types of gallium nitride-based compound semiconductor laser elements of 1.00 K / sec (Example 6) were fabricated.

About the completed six types of gallium nitride-based compound semiconductor laser elements, 10 pieces of each were evaluated in an uncoated state at room temperature, and the average value was obtained. When the crystal growth surface of the GaN substrate has an off angle in the <1-100> direction of the (0001) Ga plane as A, and an off angle in the <11-20> direction of the (0001) Ga plane as B. The relationship between the square root of (A ² + B ² ) and the slope efficiency (W / A) of the uncoated laser element is shown in FIG. 3, and the respective oscillation wavelengths are shown in Table 2.

図３に示した結果によると、前記（Ａ^２＋Ｂ^２）の平方根が０．３０の基板を用いた場合は、活性層の成長速度が０．５Å／秒以上であればスロープ効率が０．７０Ｗ／Ａ以上となっていることが分かる。この活性層の成長速度が０．５〜０．９０Å／秒であるとスロープ効率が０．７５Ｗ／Ａ以上を期待できる。しかしながら、図３においてはバラツキの範囲内で５．０Å／秒まで同程度のスロープ効率が得られている。活性層の成長速度が速すぎてもＭＱＷ活性層の結晶品質が悪くなるために素子の信頼性が低下するので、活性層の成長速度の上限は５．０Å／秒に止めるべきである。
［実施例７及び比較例７］
実施例７及び比較例７として、ＧａＮ基板の結晶成長面が（０００１）Ｇａ面の＜１−１００＞方向のへの傾斜角度が０．３０度のものを用い、この基板上に活性層の成長速度を１．０Å（実施例７）及び０．４Å／秒（比較例７）となるように、それぞれ実験例１の場合と同様にして各半導体層を積層することにより２種類の窒化ガリウム系化合物半導体レーザ素子を作製した。それぞれのスロープ効率及び発振波長は、１０素子の平均値として、実施例７の窒化ガリウム系化合物半導体レーザ素子の場合は０．８Ｗ／Ａ及び４０７ｎｍとなり、比較例７の場合は０．２Ｗ／Ａ及び３９８ｎｍとなった。なお、実施例７及び比較例７の窒化ガリウム系化合物半導体レーザ素子の発振波長については、他の例との比較のために、表１にまとめて示した。
［実施例８及び比較例８］
実施例８及び比較例８として、ＧａＮ基板の結晶成長面が（０００１）Ｇａ面の＜１−１００＞方向へのオフ角度をＡとし、（０００１）Ｇａ面の＜１１−２０＞方向へのオフ角度をＢとした場合、Ａ＝０．２５及びＢ＝０．１７であり、（Ａ^２＋Ｂ^２）の平方根が０．３０である基板を用い、この基板上に活性層の成長速度を１．０Å／秒（実施例８）及び０．４Å／秒（比較例８）となるように、それぞれ実験例１の場合と同様にして各半導体層を積層することにより２種類の窒化ガリウム系化合物半導体レーザ素子を作製した。それぞれのスロープ効率及び発振波長は、１０素子の平均値として、実施例８の窒化ガリウム系化合物半導体レーザ素子の場合は０．７Ｗ／Ａ及び４０９ｎｍとなり、比較例８の場合は０．３Ｗ／Ａ及び３９９ｎｍとなった。なお、実施例８及び比較例８の窒化ガリウム系化合物半導体レーザ素子の発振波長については、他の例との比較のために、表２にまとめて示した。

According to the results shown in FIG. 3, when a substrate having a square root of (A ² + B ² ) of 0.30 is used, the slope efficiency is 0. It turns out that it is 70 W / A or more. A slope efficiency of 0.75 W / A or more can be expected when the growth rate of the active layer is 0.5 to 0.90 Å / sec. However, in FIG. 3, the same slope efficiency is obtained up to 5.0 Å / sec within the range of variation. Even if the growth rate of the active layer is too high, the crystal quality of the MQW active layer is deteriorated and the reliability of the device is lowered. Therefore, the upper limit of the growth rate of the active layer should be limited to 5.0 kg / sec.
[Example 7 and Comparative Example 7]
As Example 7 and Comparative Example 7, the crystal growth surface of the GaN substrate has an inclination angle of 0.30 degree to the <1-100> direction of the (0001) Ga surface, and the active layer is formed on this substrate. Two types of gallium nitride are formed by laminating each semiconductor layer in the same manner as in Experimental Example 1 so that the growth rate is 1.0 Å (Example 7) and 0.4 Å / sec (Comparative Example 7). A compound semiconductor laser device was produced. The slope efficiency and oscillation wavelength of the respective elements were 0.8 W / A and 407 nm in the case of the gallium nitride compound semiconductor laser element of Example 7, and 0.2 W / A in the case of Comparative Example 7, as an average value of 10 elements. And 398 nm. The oscillation wavelengths of the gallium nitride compound semiconductor laser elements of Example 7 and Comparative Example 7 are collectively shown in Table 1 for comparison with other examples.
[Example 8 and Comparative Example 8]
As Example 8 and Comparative Example 8, the crystal growth surface of the GaN substrate has an off angle in the <1-100> direction of the (0001) Ga surface as A, and the (0001) Ga surface in the <11-20> direction. When the off angle is B, a substrate in which A = 0.25 and B = 0.17 and the square root of (A ² + B ² ) is 0.30 is used. Two types of gallium nitride systems are obtained by laminating each semiconductor layer in the same manner as in Experimental Example 1 so as to be 1.0 Å / sec (Example 8) and 0.4 Å / sec (Comparative Example 8). A compound semiconductor laser device was fabricated. Each slope efficiency and oscillation wavelength are 0.7 W / A and 409 nm in the case of the gallium nitride-based compound semiconductor laser device of Example 8 as an average value of 10 devices, and 0.3 W / A in the case of Comparative Example 8. And 399 nm. The oscillation wavelengths of the gallium nitride compound semiconductor laser elements of Example 8 and Comparative Example 8 are collectively shown in Table 2 for comparison with other examples.

  The gallium nitride-based compound semiconductor laser device of the present invention can change the oscillation wavelength by changing the In composition of the well layer of the MQW active layer, but the effect is more effective when the oscillation wavelength is 395 to 405 nm. Become prominent.

  In addition, by making the resonator surface a natural rough surface of the crystal, a resonator surface with good specularity can be obtained, so that the element yield is greatly improved, so that the effect of the present invention can be used more remarkably industrially. it can.

  Further, when the present invention is applied to a semiconductor laser device in which the reflectance of the emission surface of the resonator surface is adjusted to 10 to 30% and an end surface coat having a reflectance of 70% or more is formed on the rear surface of the resonator surface, Since the return light noise that enters through the exit surface can be reduced, the noise characteristics can be improved when applied to an optical pickup, and the effects of the present invention can be utilized more remarkably.

  Further, when the present invention is applied to a semiconductor laser device in which the exit surface of the resonator surface forms an end surface coat with a reflectance of 10% or less and the rear surface of the resonator surface has an end surface coat with a reflectance of 70% or more, Since the reflectance of the exit surface is low, the proportion of light exiting to the outside increases and a higher output can be obtained, so that the effects of the present invention can be used more remarkably.

1 is an enlarged longitudinal sectional view of a gallium nitride compound semiconductor laser device of the present invention. Relationship between growth rate of active layer and slope efficiency in gallium nitride-based compound semiconductor laser device when crystal growth surface of GaN substrate is tilted to <1-100> direction of (0001) Ga surface at 0.30 degree FIG. When the crystal growth surface of the GaN substrate has an off-angle in the <1-100> direction of the (0001) Ga plane as A and an off-angle in the <11-20> direction of the (0001) Ga plane as B, if the square root of a 2 ^{+ B 2)} is 0.30, which is a diagram showing the relationship of the active layer growth rate and the slope efficiency of the semiconductor laser element gallium nitride-based compound. It is an enlarged vertical sectional view of a conventional gallium nitride-based compound semiconductor laser device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 GaN substrate 2 n-type AlGaN clad layer 3 MQV active layer 4 InGaN optical guide layer 5 AlGaN cap layer 6 p-type AlGaN clad layer 7 p-type GaN contact layer 8 p-type electrode 9 pad electrode 10 SiO ₂ film 11 n-type electrode

Claims (12)

  A method for fabricating a gallium nitride-based compound semiconductor laser device on a gallium nitride substrate, wherein the absolute value of the crystal growth surface of the gallium nitride substrate is 0.16 degrees in the <1-100> direction of the (0001) Ga plane. A method for producing a gallium nitride-based compound semiconductor laser device, characterized by using a surface inclined at 5.0 ° or less and growing an active layer at a growth rate of 0.5 Å / second to 5.0 Å / second.   2. The method of manufacturing a gallium nitride-based compound semiconductor laser device according to claim 1, wherein an oscillation wavelength of the semiconductor laser device is 395 to 405 nm.   3. The method of manufacturing a gallium nitride-based compound semiconductor laser device according to claim 1, wherein the resonator surface of the semiconductor laser device is a natural scratched surface of a crystal.   The exit surface of the resonator surface of the semiconductor laser element is adjusted to have a reflectivity of 10 to 30%, and an end face coat having a reflectivity of 70% or more is formed on the rear surface of the resonator surface. 4. The method for producing a gallium nitride-based compound semiconductor laser device according to claim 3.   2. An end face coat having a reflectivity of 10% or less is formed on the exit surface of the resonator surface of the semiconductor laser element, and an end face coat having a reflectivity of 70% or more is formed on the rear face of the resonator face. The manufacturing method of the gallium nitride type compound semiconductor laser element of any one of -3. A method for fabricating a gallium nitride-based compound semiconductor laser device on a gallium nitride substrate, wherein the off-angle in the <1-100> direction of the (0001) Ga plane is defined as A as the crystal growth surface of the gallium nitride substrate. , A surface having a square root of (A ² + B ² ) of 0.17 or more and 7.0 or less when the off-angle in the <11-20> direction of the (0001) Ga surface is B, and the active layer is A method for producing a gallium nitride-based compound semiconductor laser device, comprising growing at a growth rate of 0.5 Å / second to 5.0 Å / second.   7. The method for manufacturing a gallium nitride-based compound semiconductor laser device according to claim 6, wherein an oscillation wavelength of the semiconductor laser device is 395 to 405 nm.   8. The method of manufacturing a gallium nitride-based compound semiconductor laser device according to claim 6, wherein the resonator surface of the semiconductor laser device is a natural scratched surface of a crystal.   7. The emission surface of the resonator surface of the semiconductor laser element is adjusted to have a reflectance of 10 to 30%, and an end face coat having a reflectance of 70% or more is formed on the rear surface of the resonator surface. 9. A method for producing a gallium nitride compound semiconductor laser device according to any one of items 8 to 9.   7. An end face coat having a reflectance of 10% or less is formed on the exit surface of the resonator surface of the semiconductor laser element, and an end face coat having a reflectivity of 70% or more is formed on the rear face of the resonator surface. The manufacturing method of the gallium nitride type compound semiconductor laser element of any one of -8.   A gallium nitride-based compound semiconductor laser device formed on a gallium nitride substrate, wherein a crystal growth surface of the gallium nitride substrate has an absolute value of 0.16 degrees or more in the <1-100> direction of the (0001) Ga plane. A gallium nitride-based compound semiconductor laser device having a surface inclined by less than or equal to 0 degrees and having an active layer grown at a growth rate of 5 to 5.0 K / s. A gallium nitride-based compound semiconductor laser device formed on a gallium nitride substrate, wherein the crystal growth surface of the gallium nitride substrate has an off angle of the (0001) Ga surface in the <1-100> direction as A, 0001) Ga surface has a surface where the square root of (A ² + B ² ) is 0.17 or more and 7.0 or less when the off-angle in the <11-20> direction is B, and the active layer is 0 Gallium nitride-based compound semiconductor laser device grown at a growth rate of 5 Å / sec or more and 5.0 Å / sec or less

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