JP2010056583A - Semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser element, which has a high efficiency of light emission, and which obtains the shape of a laser beam near a true circle shape as compared with that in the prior art. <P>SOLUTION: The semiconductor laser element includes an active layer 3 formed on an n-type side clad layer 2, and a p-type side clad layer 4 formed on the active layer 3 and having a protrusion and flat parts 4a and 4b except the protrusion. Moreover, the flat parts 4a and 4b of the p-type side clad layer 4 include the flat part 4a located on a region A1 near the resonator end face 10a of a light-emitting side and a flat part 4b located on a region B1 including the central region of the element except the region A1. The thickness tA1 of the flat part 4a is smaller than the thickness tB1 of the flat part 4b. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device including an active layer.

  Conventionally, there has been known a semiconductor laser element including a semiconductor layer having a convex portion (ridge portion) and a flat portion other than the convex portion on an active layer.

  FIG. 27 is a perspective view showing the structure of a conventional semiconductor laser device. FIGS. 28 and 29 are a side view and a top view, respectively, for explaining the vertical and horizontal spread angles of the laser light of the conventional semiconductor laser device shown in FIG. First, referring to FIG. 27, in the conventional semiconductor laser element, an n-side cladding layer 102 made of an n-type semiconductor is formed on an n-type semiconductor substrate 101. An active layer 103 is formed on the n-side cladding layer 102. A p-side cladding layer 104 made of a p-type semiconductor having a convex portion and a flat portion other than the convex portion is formed on the active layer 103. A contact layer 105 made of a p-type semiconductor is formed on the convex portion of the p-side cladding layer 104. The contact layer 105 and the convex portion of the p-side cladding layer 104 constitute a striped (elongated) ridge portion 106 extending in the resonator direction. A p-side ohmic electrode 107 is formed on the contact layer 105 constituting the ridge portion 106. Further, by removing a predetermined region from the upper surface of the flat portion of the p-side cladding layer 104 to an intermediate depth of the n-type semiconductor substrate 101, a part of the n-type semiconductor substrate 101 is exposed. An n-side ohmic electrode 108 is formed in a predetermined region on the exposed surface of the n-type semiconductor substrate 101. On the surface other than the p-side ohmic electrode 107 and the n-side ohmic electrode 108, a current blocking layer 109 made of an insulating film is formed.

  In the conventional semiconductor laser device shown in FIG. 27, the light generated by the active layer 103 is reflected by the resonator end faces 100a and 100b, thereby causing laser oscillation. The spot shape (light intensity distribution) of the laser light emitted from the light emitting side resonator end face 100a is controlled by light confinement from the vertical direction and the horizontal direction. Specifically, vertical light confinement is performed by the p-side cladding layer 104 and the n-side cladding layer 102 located above and below the active layer 103, respectively. Further, the optical confinement in the horizontal direction is performed by a portion where the convex portion and the flat portion of the p-side cladding layer 104 intersect (the lower end portion of the convex portion). In the conventional semiconductor laser device shown in FIG. 27, as shown in FIG. 28, the vertical spread angle θ1 of the emitted laser light is about 18 °. As shown in FIG. 29, the horizontal spread angle θ2 of the emitted laser light is about 6 °. That is, in the conventional semiconductor laser device shown in FIG. 27, θ1 (vertical spread angle) / θ2 (horizontal spread angle) = about 3.

  In the conventional semiconductor laser element shown in FIG. 27, as described above, the horizontal spread angle θ2 (about 6 °) is smaller than the vertical spread angle θ1 (about 18 °) of the laser beam. It was difficult to bring the shape of light close to a perfect circle (θ1 / θ2 = 1). For this reason, there is an inconvenience that it is difficult to obtain a semiconductor laser device having a good light intensity distribution close to a perfect circle shape.

  Therefore, conventionally, only in the region near the resonator end face on the light emission side, the optical confinement in the horizontal direction is made stronger, thereby suppressing the shape of the light emission spot (light intensity distribution) of the laser light from spreading in the horizontal direction. Has proposed a method of further increasing the horizontal spread angle θ2 of the laser light (see, for example, Patent Document 1). Note that the smaller the horizontal spread of the shape of the light emission spot (light intensity distribution), the larger the horizontal spread angle θ2.

  In Patent Document 1, an n-side cladding layer, an active layer, and a p-side cladding layer are sequentially formed on a substrate, and the p-side cladding layer has a convex portion and a flat portion other than the convex portion. In the device, only the region near the resonator end face on the light emitting side is etched from the upper surface of the flat portion of the p-side cladding layer to a depth in the middle of the active layer and the n-side cladding layer. In Patent Document 1, since the width of the active layer is reduced by etching the active layer, it becomes possible to further strengthen the optical confinement in the horizontal direction.

JP 2002-374035 A

  However, in Patent Document 1, since the active layer is etched in a region near the resonator end face on the light emitting side, there is a disadvantage that etching damage applied to the active layer becomes large. As a result, crystal defects in the active layer caused by etching damage increase, and there is a disadvantage that light absorption by the crystal defect portion of the active layer increases. As a result, there is a problem that the light emission efficiency is lowered. In addition, there is a problem in that crystal defects grow due to current flowing in the crystal defect portion of the active layer.

  Further, as another method for further strengthening the optical confinement in the horizontal direction, there is a method of reducing the width of the convex portion of the p-side cladding layer. In this case, since the interval between the edge portions having the light confinement function in the horizontal direction is reduced, the width of light confinement in the horizontal direction can be reduced.

  However, in the method of reducing the width of the convex portion of the p-side clad layer, the contact area with the electrode layer formed on the convex portion of the p-side clad layer is reduced, resulting in a disadvantage that the contact resistance increases. As a result, since the operating voltage of the element becomes high, the power consumption of the element increases.

  The present invention has been made in order to solve the above-described problems, and one object of the present invention is to have a high luminous efficiency and a shape of a laser beam that is closer to a perfect circle than in the past. It is an object of the present invention to provide a semiconductor laser device capable of obtaining the above.

  In order to achieve the above object, a semiconductor laser device according to one aspect of the present invention includes an active layer formed on a first semiconductor layer, a convex portion formed on the active layer, and a flat portion other than the convex portion. A second semiconductor layer. The flat portion of the second semiconductor layer is located in a second region including at least the first flat portion located in the first region near the resonator end face on the light emitting side and the central region of the element other than the first region. And the thickness of the first flat portion of the second semiconductor layer is smaller than the thickness of the second flat portion of the second semiconductor layer.

  In the semiconductor laser device according to the one aspect, as described above, the flat portion other than the convex portion of the second semiconductor layer formed on the active layer is positioned at least in the first region near the resonator end face on the light emitting side. And the second flat portion located in the second region including the central region of the element other than the first region, and the thickness of the first flat portion is set to be equal to that of the second flat portion. By making the thickness smaller than the thickness, the lower end of the convex portion of the second semiconductor layer located in the first region in the vicinity of the resonator end face on the light emitting side is located in the second region including the central region of the element. Since the lower end of the convex portion of the layer can be closer to the active layer, the lower end portion of the convex portion of the first region formed so as to be closer to the active layer can confine horizontal light confinement in the first region. Can be strong. As a result, the horizontal spread of the laser light emission spot can be reduced, so that the horizontal spread angle of the laser light can be increased. As a result, the shape of the laser beam can be made close to a perfect circle (vertical spread angle / horizontal spread angle = 1). In this case, when the convex portion (ridge portion) of the second semiconductor layer is formed by etching, the thickness of the second flat portion located in the second region of the second semiconductor layer is the first flat portion located in the first region. Therefore, the etching damage applied to the second flat portion of the second region can be made smaller than the etching damage applied to the first flat portion of the first region. Thereby, in the second region, it is possible to reduce the amount of crystal defects in the active layer under the second flat portion caused by etching damage. Also, even in the active layer located under the first flat portion of the first region, the active layer is not etched, so that it is caused by etching damage compared to the case where the ridge portion is formed by etching the portion including the active layer. Thus, the amount of crystal defects generated in the active layer can be reduced. As a result, it is possible to suppress an increase in leakage current that does not contribute to light emission flowing through the crystal defect portion of the active layer. In addition, the smaller the number of crystal defects in the active layer, the more the growth of crystal defects caused by current flow can be suppressed. As a result, it is possible to obtain a semiconductor laser element having a long lifetime and high emission efficiency. As described above, the semiconductor laser element according to one aspect can provide a semiconductor laser element that has a long lifetime and high light emission efficiency and can obtain a laser beam shape close to a perfect circle shape.

  In the semiconductor laser device according to the aforementioned aspect, the current density of the current flowing through the first region is preferably configured to be smaller than the current density of the current flowing through the second region. If comprised in this way, the electric current injected into the active layer located in the first region in the vicinity of the resonator end face on the light emitting side is made to flow more than the current flowing in the active layer located in the second region including the central region of the element. Since the thickness of the first flat portion of the second semiconductor layer in the first region is smaller than the thickness of the second flat portion of the second semiconductor layer in the second region, the first region can be reduced. Even if the number of crystal defects in the active layer located in the region is larger than the number of crystal defects in the active layer located in the second region, the current flowing through the crystal defect portion of the active layer located in the first region can be reduced. it can. Accordingly, it is possible to suppress an increase in crystal defects due to a large amount of current flowing through the crystal defect portion of the active layer, and thus the lifetime of the element can be extended.

  In this case, preferably, the first electrode layer is formed on the second semiconductor layer and has a sheet resistance value of 1Ω / □ or more, and is formed on the first electrode layer. And a second electrode layer disposed at a predetermined interval from the side facet of the resonator. If comprised in this way, an electric current can be inject | poured from a 2nd electrode layer only to the area | region spaced apart from the resonator end surface by the side of the light emission of a 1st electrode layer. In addition, when the end of the light emission side of the first electrode layer reaches the end face of the resonator, the sheet resistance value of the first electrode layer is set to a large sheet resistance value of 1 Ω / □ or more, so that the second When current is injected from the electrode layer, it becomes difficult for the current to flow in the resonator direction (horizontal direction) in the first electrode layer, so that the current of the current flowing easily through the first region near the resonator end surface on the light emitting side is easily The density can be made smaller than the current density of the current flowing through the second region including the central region of the element other than the first region.

  In this case, it is preferable that the end of the second electrode layer on the light emission side is disposed on the second region side with respect to the boundary between the first region and the second region. With this configuration, as described above, in the configuration in which current does not easily flow in the direction of the resonator in the first electrode layer, a predetermined interval is provided between the light emitting side end of the second electrode layer and the first region. Since the interval is provided, current is less likely to be injected into the first region from the second electrode layer via the first electrode layer. Thereby, the current density of the current flowing through the first region in the vicinity of the resonator end face on the light emitting side is more easily made smaller than the current density of the current flowing through the second region including the central region of the element other than the first region. can do.

  In the semiconductor laser device according to the aforementioned aspect, the upper surface of the first flat portion and the upper surface of the second flat portion are preferably connected between the first flat portion and the second flat portion of the second semiconductor layer. As described above, an inclined portion is provided. If comprised in this way, since the boundary surface between a 1st flat part and a 2nd flat part inclines, the 1st flat part and 2nd flat part from which thickness differs are connected by the perpendicular | vertical boundary surface. Compared to the case, light is less likely to be reflected in the direction of the resonator end face opposite to the light exit side at the boundary surface. Thereby, generation | occurrence | production of the unnecessary laser oscillation mode between the boundary surface between a 1st flat part and a 2nd flat part and the resonator end surface on the opposite side to a light-projection side can be suppressed. As a result, the laser oscillation mode (laser oscillation mode between the resonator end surface on the light emitting side and the resonator end surface opposite to the light emitting side) having high light emission efficiency can be maintained up to the high output region. Therefore, the luminous efficiency can be further improved. Further, by providing an inclined portion so as to connect the upper surface of the first flat portion and the upper surface of the second flat portion between the first flat portion and the second flat portion of the second semiconductor layer, the thickness is increased. Compared with the case where different first flat portions and second flat portions are connected by a vertical boundary surface, the lower end portion (edge portion) of the boundary surface between the first flat portion and the second flat portion is smooth. Therefore, the light confinement by the edge portion can be weakened. Thereby, since the optical loss in the edge part of the interface between the 1st flat part and the 2nd flat part can be controlled, luminous efficiency can be improved more by this.

  In the semiconductor laser device according to the aforementioned aspect, preferably, the flat portion of the second semiconductor layer is located in the third region near the resonator end surface on the side opposite to the light emitting side, and from the thickness of the second flat portion. A third flat portion having a small thickness. With this configuration, even when the resonator end surface opposite to the light emitting side is used as the light emitting surface, the shape of the laser beam is a perfect circle (vertical spread angle / horizontal spread angle = 1). Can be approached. As a result, the shape of the laser beam can be made close to a perfect circle regardless of which one of the two resonator end faces is used as the light exit surface. Thereby, when assembling the element, a semiconductor laser element capable of obtaining a laser beam shape close to a perfect circle can be produced regardless of which resonator end face is set as the light emitting surface.

  In the semiconductor laser device according to the above aspect, the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction is preferably 3 μm or more and 50 μm or less. If comprised in this way, by making the length of the 1st flat part of the 2nd semiconductor layer located in a 1st area | region into the resonator direction 3 micrometers or more, in the 1st area | region near the resonator end surface by the side of light emission, It can be suppressed that the optical confinement in the horizontal direction in the first region becomes insufficient due to the length of the first flat portion located in the resonator direction being too small. Furthermore, when the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction is set to 3 μm or more, when the element is separated into each chip using the cleavage method, the first region It is possible to prevent the element from being separated in the second region including the central region of the element due to the length in the resonator direction of the first flat portion located in the region being too small. Further, by setting the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction to 50 μm or less, the first flat located in the first region where etching damage is larger than that in the second region. It is possible to suppress an increase in the number of crystal defects introduced into the active layer due to the excessive length of the portion in the resonator direction.

  In the semiconductor laser device according to the aforementioned aspect, the thickness of the second flat portion of the second semiconductor layer located in the second region is preferably 100 nm or more and 250 nm or less. If comprised in this way, the thickness of the 2nd flat part located in the 2nd area | region including the center area | region of an element is made by making the thickness of the 2nd flat part of the 2nd semiconductor layer located in a 2nd area | region into 100 nm or more. Since the etching damage applied to the second flat portion can be suppressed due to excessively reducing the thickness of the second flat portion, the amount of crystal defects generated in the active layer located under the second flat portion can be reduced. Can do. Thereby, since the increase in the light absorption by the crystal defect part of an active layer can be suppressed more, luminous efficiency can be improved more. In addition, since the growth of crystal defects can be suppressed, the device life can be further improved. Further, by making the thickness of the second flat portion of the second semiconductor layer located in the second region 250 nm or less, the thickness of the second flat portion located in the second region is excessively increased. Since increase in threshold current can be suppressed, increase in power consumption can be suppressed.

1 is a perspective view showing a structure of a nitride-based semiconductor laser device according to a first embodiment of the present invention. It is sectional drawing along the 100-100 line of FIG. It is sectional drawing along the 200-200 line | wire of FIG. It is the graph which showed the divergence angle of the horizontal direction of the laser beam at the time of changing the length of the resonator direction of the area | region near the resonator end surface by the side of light emission. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. FIG. 6 is a perspective view for explaining a manufacturing process for the nitride-based semiconductor laser device according to the first embodiment shown in FIG. 1. It is the perspective view which showed the structure of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing along the 300-300 line | wire of FIG. It is sectional drawing along the 400-400 line of FIG. It is the perspective view which showed the structure of the nitride type semiconductor laser element by 3rd Embodiment of this invention. It is sectional drawing along the 500-500 line | wire of FIG. It is sectional drawing along the 600-600 line of FIG. FIG. 16 is a perspective view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the third embodiment shown in FIG. 15. FIG. 16 is a perspective view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the third embodiment shown in FIG. 15. FIG. 16 is a perspective view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the third embodiment shown in FIG. 15. It is the perspective view which showed the structure of the nitride type semiconductor laser element by 4th Embodiment of this invention. FIG. 22 is a cross-sectional view taken along line 700-700 and 900-900 in FIG. It is sectional drawing along the 800-800 line | wire of FIG. FIG. 22 is a perspective view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21. FIG. 22 is a perspective view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21. FIG. 22 is a perspective view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21. It is the perspective view which showed the structure of the conventional semiconductor laser element. It is a side view for demonstrating the spreading angle of the perpendicular direction of the laser beam of the conventional semiconductor laser element shown in FIG. FIG. 28 is a top view for explaining a horizontal spread angle of laser light of the conventional semiconductor laser device shown in FIG. 27.

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

(First embodiment)
FIG. 1 is a perspective view showing the structure of a nitride-based semiconductor laser device according to the first embodiment of the present invention. 2 and 3 are cross-sectional views taken along lines 100-100 and 200-200 in FIG. 1, respectively. First, the structure of the nitride-based semiconductor laser device according to the first embodiment will be described with reference to FIGS. The nitride semiconductor laser element according to the first embodiment has a width W of about 300 μm and a resonator length L of about 600 μm.

  In the nitride-based semiconductor laser device according to the first embodiment, as shown in FIG. 1, an n-type AlGaN (Al composition ratio: 7%) having a thickness of about 1.5 μm is formed on an n-type GaN substrate 1. A side cladding layer 2 is formed. The n-side cladding layer 2 is an example of the “first semiconductor layer” in the present invention. An active layer (light emitting layer) 3 is formed on the n-side cladding layer 2. The active layer 3 is composed of three well layers made of undoped InGaN (In composition ratio: 15%) having a thickness of about 3 nm and undoped InGaN (In composition ratio: 2%) having a thickness of about 20 nm. It has a multiple quantum well (MQW) structure in which three barrier layers are alternately stacked. A p-side cladding layer 4 is formed on the active layer 3. The p-side cladding layer 4 is composed of a light guide layer (not shown), a cap layer (not shown), and a p-type AlGaN layer (not shown) in this order from the active layer 3 side. The light guide layer constituting the p-side cladding layer 4 is made of undoped InGaN (In composition ratio: 1%) having a thickness of about 75 nm, and the cap layer is made of undoped AlGaN (Al composition having a thickness of about 20 nm). Ratio: 20%). The p-type AlGaN layer is doped with Mg and has an Al composition ratio of 7%. The p-side cladding layer 4 has a width of about 1.5 μm and has stripe-shaped (elongated) convex portions extending in the resonator direction. The p-side cladding layer 4 is an example of the “second semiconductor layer” in the present invention.

  Here, in the first embodiment, the flat portions 4a and 4b other than the convex portion of the p-side cladding layer 4 include the region A1 in the vicinity of the resonator end surface 10a on the light emitting side and the central region of the element other than the region A1. The region B1 has a different thickness. Specifically, in the region A1, as shown in FIG. 2, the thickness tA1 of the flat portion 4a from the upper surface of the active layer 3 to the p-side cladding layer 4 is about 100 nm, and the upper surface of the convex flat portion 4a. The height from is about 400 nm. Further, in the region B1, as shown in FIG. 3, the thickness tB1 of the flat portion 4b of the p-side cladding layer 4 is about 150 nm, and the height from the upper surface of the flat portion 4b of the convex portion is about 350 nm. . That is, the thickness tA1 of the flat portion 4a in the region A1 is smaller than the thickness tB1 of the flat portion 4b in the region B1. The regions A1 and B1 are examples of the “first region” and the “second region” in the present invention, respectively, and the flat portions 4a and 4b are respectively the “first flat portion” and the “first region” in the present invention. It is an example of “two flat portions”. The length of the region A1 in the resonator direction is about 10 μm, and the length of the region B1 in the resonator direction is about 590 μm.

As shown in FIG. 1, a contact layer 5 made of undoped InGaN (In composition ratio: 7%) having a thickness of about 3 nm is formed on the convex portion of the p-side cladding layer 4. The contact layer 5 is an example of the “second semiconductor layer” in the present invention. The contact layer 5 and the convex portion of the p-side cladding layer 4 form a stripe-shaped (elongated) ridge portion 6 having a width of about 1.5 μm and extending in the resonator direction. A current blocking layer 7 made of a SiO ₂ film having a thickness of about 200 nm is formed on the upper surfaces of the flat portions 4 a and 4 b of the p-side cladding layer 4 and on the side surfaces of the ridge portion 6. A p-side ohmic electrode 8 is formed on the contact layer 5 constituting the ridge portion 6. The p-side ohmic electrode 8 includes, in order from the contact layer 5 side, a Pt layer (not shown) having a thickness of about 1 nm, a Pd layer (not shown) having a thickness of about 100 nm, and an Au having a thickness of about 100 nm. It is comprised by the layer (not shown).

  An n-side ohmic electrode 9 is formed in a predetermined region on the back surface of the n-type GaN substrate 1. The n-side ohmic electrode 9 has an Al layer (not shown) having a thickness of about 6 nm, a Pd layer (not shown) having a thickness of about 10 nm, and a thickness of about 300 nm in this order from the n-type GaN substrate 1 side. It has an Au layer (not shown).

  In the nitride-based semiconductor laser device according to the first embodiment, the laser generated by the light generated by the active layer 3 is reflected by the resonator end faces 10a and 10b.

  FIG. 4 shows the horizontal direction of laser light when the length in the cavity direction of the region near the cavity facet on the light emitting side is changed in five steps (0 μm, about 3 μm, about 10 μm, about 50 μm and about 200 μm). It is the graph which showed the spreading angle of. Next, referring to FIG. 4, in the configuration of the nitride-based semiconductor laser device of the first embodiment, the length of the region A1 (region near the resonator end face on the light emitting side) in the resonator direction is changed. The result of measuring the horizontal spread angle θ2 of the laser light will be described.

  As shown in FIG. 4, when the length of the region A1 in the resonator direction is about 3 μm or more, the horizontal spread angle θ2 of the laser light is found to be as large as about 8 ° or more. Specifically, when the length of the region A1 in the resonator direction is about 3 μm, about 10 μm, about 50 μm, and about 200 μm, the horizontal spread angle θ2 of the laser light is about 8 °, about 10 °, respectively. They were about 11.3 ° and about 11.5 °. On the other hand, when the length of the region A1 in the resonator direction is 0 μm, the horizontal spread angle θ2 of the laser light is found to be as small as about 6 °. When the length of the region A1 in the resonator direction is 0 μm, the horizontal spread angle θ2 of the laser beam is reduced because the length of the flat portion 4a located in the region A1 in the resonator direction is zero. This is considered to be due to insufficient light confinement in the horizontal direction in the region A1. Therefore, in order to increase the horizontal spread angle θ2 of the laser light to about 8 ° or more, it is considered preferable to set the length of the region A1 in the resonator direction to about 3 μm or more. When the length of the flat portion 4a located in the region A1 in the resonator direction is small, the element is separated from the region B1 including the central region of the element when the element is separated into each chip using the cleavage method. In this respect, it is considered that the length of the region A1 in the resonator direction is preferably set to about 3 μm or more.

  Further, it has been found that the spread angle θ2 in the horizontal direction of the laser light hardly changes when the length of the region A1 in the resonator direction is about 50 μm and about 200 μm. Here, if the length of the region A1 in the resonator direction is excessively increased, the length in the resonator direction of the flat portion 4a of the region A1 having a smaller thickness than the flat portion 4b of the region B1 is increased. In this case, when the convex portion of the p-side cladding layer 4 is formed by etching, the etching amount in the p-side cladding layer 4 increases. As a result, the etching damage applied to the p-side cladding layer 4 increases, and the amount of crystal defects generated in the active layer 3 located under the p-side cladding layer 4 increases. Therefore, it is considered that the length of the region A1 in the resonator direction is preferably set to about 50 μm or less. From these results, the length of the region A1 in the resonator direction is preferably set to about 3 μm or more and about 50 μm or less.

  Here, in the first embodiment, since the length of the region A1 in the resonator direction is set to about 10 μm, it is possible to prevent the etching damage applied to the p-side clad layer 4 from increasing and the horizontal direction of the laser light. It is considered that the direction spread angle θ2 can be increased.

  Next, in the configuration of the nitride-based semiconductor laser device of the first embodiment, the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is set to five levels (about 70 nm, about 100 nm, about 150 nm, about 250 nm). Table 1 below shows the results of the measurement of the luminous efficiency and the threshold current with the change to about 300 nm.

上記表１を参照して、ｐ側クラッド層４の領域Ｂ１に位置する平坦部４ｂの厚みｔＢ１が約１００ｎｍ以上約２５０ｎｍ以下の場合には、発光効率が約１．３Ｗ／Ａ以上と高く、かつ、しきい値電流が約５３ｍＡ以下と低くなることが判明した。具体的には、ｐ側クラッド層４の領域Ｂ１に位置する平坦部４ｂの厚みｔＢ１が約１００ｎｍ、約１５０ｎｍおよび約２５０ｎｍの場合の発光効率は、それぞれ、約１．３Ｗ／Ａ、約１．５Ｗ／Ａおよび約１．４Ｗ／Ａであり、しきい値電流は、それぞれ、約３２ｍＡ、約３０ｍＡおよび約５３ｍＡであった。

Referring to Table 1, when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is about 100 nm or more and about 250 nm or less, the luminous efficiency is as high as about 1.3 W / A or more, In addition, the threshold current was found to be as low as about 53 mA or less. Specifically, the luminous efficiencies when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is about 100 nm, about 150 nm, and about 250 nm are about 1.3 W / A, about 1. The threshold currents were about 32 mA, about 30 mA, and about 53 mA, respectively, 5 W / A and about 1.4 W / A.

  On the other hand, when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is about 70 nm, the threshold current is reduced to about 35 mA, while the luminous efficiency is as low as about 0.6 W / A. Turned out to be. This is presumably because the etching damage applied to the p-side cladding layer 4 has increased due to the thickness tB1 of the flat portion 4b of the p-side cladding layer 4 located in the region B1 being too small. As a result, the amount of crystal defects generated in the active layer 3 located under the p-side cladding layer 4 is increased, so that light absorption by the crystal defect portion of the active layer 3 is increased. It is done. Further, when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is about 300 nm, the light emission efficiency is about 1.3 W / A, while the threshold current is about 105 mA. It has been found.

  From these results, if the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is set to about 100 nm or more and about 250 nm or less, the light emission efficiency can be increased and the threshold current can be reduced. It is thought that it can be lowered.

  Here, in the first embodiment, since the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is set to about 150 nm, the light emission efficiency can be increased and the threshold value can be increased. It is considered that the current can be lowered.

  In the first embodiment, as described above, the thickness tA1 (about 100 nm) of the flat portion 4a located in the region A1 in the vicinity of the resonator end surface 10a on the light emitting side is set to the region B1 including the central region of the elements other than the region A1. By making the thickness smaller than the thickness tB1 (about 150 nm) of the flat portion 4b located in the region, the lower end portion of the convex portion of the p-side cladding layer 4 located in the region A1 in the vicinity of the resonator end surface 10a on the light emitting side is reduced. Since the lower end portion of the convex portion of the p-side cladding layer 4 located in the region B1 including the central region can be closer to the active layer 3, the convex portion of the region A1 formed so as to be closer to the active layer 3 The lower end portion can strengthen the light confinement in the horizontal direction in the region A1. As a result, the horizontal spread of the laser light emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, the shape of the laser beam can be made close to a perfect circle (vertical spread angle θ1 / horizontal spread angle θ2 = 1). In this case, when the convex portion (ridge portion 6) of the p-side cladding layer 4 is formed by etching, the thickness tB1 (about 150 nm) of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is located in the region A1. Since the etching is performed so as to be larger than the thickness tA1 (about 100 nm) of the flat portion 4a to be etched, the etching damage applied to the flat portion 4b in the region B1 can be made smaller than the etching damage applied to the flat portion 4a in the region A1. . Thereby, in the region B1, the amount of crystal defects in the active layer 3 below the flat portion 4b generated due to etching damage can be reduced. Also, even in the active layer 3 located under the flat portion 4a of the region A1, the active layer 3 is not etched, so that etching is performed as compared with the case where the ridge portion 6 is formed by etching the portion including the active layer 3. The amount of crystal defects generated in the active layer 3 due to damage can be reduced. As a result, an increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high emission efficiency can be obtained. In addition, since growth of crystal defects can be suppressed, a highly reliable element having a high lifetime can be obtained. Thus, in the first embodiment, a nitride-based semiconductor laser device that has high light emission efficiency and can obtain a laser beam shape close to a perfect circle shape can be obtained.

  Further, in the first embodiment, the flat portion located in the region A1 is set by setting the length in the resonator direction of the flat portion 4a located in the region A1 near the resonator end surface 10a on the light emitting side to about 10 μm. It can be suppressed that the light confinement in the horizontal direction in the region A1 becomes insufficient due to the fact that the length in the resonator direction of 4a becomes too small. Further, when the element is separated into each chip using the cleavage method, the element includes the central region of the element because the length of the flat portion 4a located in the region A1 in the resonator direction becomes too small. It is possible to suppress an element manufacturing defect separated in the region B1. Further, it is possible to suppress an increase in crystal defects introduced into the active layer 3 due to the length in the resonator direction of the flat portion 4a located in the region A1 where the etching damage is larger than that in the region B1. can do.

  In the first embodiment, the thickness tB1 of the flat portion 4b located in the region B1 of the p-side cladding layer 4 is set to about 150 nm, thereby making the thickness tB1 of the flat portion 4b located in the region B1 too small. As a result, it is possible to suppress an increase in etching damage applied to the flat portion 4b, thereby reducing the amount of crystal defects generated in the active layer 3 located under the flat portion 4b. Thereby, since the increase in light absorption by the crystal defect part of the active layer 3 can be reduced more, luminous efficiency can be improved more. In addition, since the threshold current can be prevented from increasing due to excessively increasing the thickness tB1 of the flat portion 4b located in the region B1, the increase in power consumption can be suppressed. it can.

  5 to 11 are perspective views for explaining a manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG. A manufacturing process for the nitride-based semiconductor laser device according to the first embodiment is now described with reference to FIGS.

  First, as shown in FIG. 5, an n-side cladding layer 2 made of n-type AlGaN having a thickness of about 1.5 μm and an active layer are formed on an n-type GaN substrate 1 by using a MOCVD (Metal Organic Chemical Deposition) method. Layer 3 is grown sequentially. When the active layer 3 is grown, first, three well layers (not shown) made of undoped InGaN having a thickness of about 3 nm and three barriers made of undoped InGaN having a thickness of about 20 nm. By alternately growing layers (not shown), a multilayer film having an MQW structure is formed. Thereby, the active layer 3 composed of a multilayer film having an MQW structure composed of three well layers and three barrier layers is formed. Next, on the active layer 3, a light guide layer (not shown) made of undoped InGaN having a thickness of about 75 nm, a cap layer (not shown) made of undoped AlGaN having a thickness of about 20 nm, and about 500 nm. A p-type AlGaN layer (not shown) doped with Mg having the following thickness is sequentially grown. As a result, the p-side cladding layer 4 composed of the light guide layer, the cap layer, and the p-type AlGaN layer is formed. Thereafter, a contact layer 5 made of undoped InGaN having a thickness of about 3 nm is grown on the p-side cladding layer 4.

  Thereafter, a Pt layer (not shown) having a thickness of about 1 nm, a Pd layer (not shown) having a thickness of about 100 nm, and a thickness of about 100 nm are formed on the contact layer 5 by using a vacuum deposition method or the like. An Au layer (not shown) is sequentially formed. Thereby, the p-side ohmic electrode 8 constituted by the Pt layer, the Pd layer, and the Au layer is formed.

  Next, as shown in FIG. 6, a resist 11 is formed in the formation region of the ridge portion 6 (see FIG. 1) on the p-side ohmic electrode 8.

Next, as shown in FIG. 7, a predetermined region of the p-side ohmic electrode 8 is removed using the resist 11 as a mask by using a reactive ion etching (RIE) method using CF ₄ gas. Subsequently, using the RIE method using Cl ₂ gas, using the resist 11 as a mask, a depth in the middle of the p-side cladding layer 4 from the upper surface of the contact layer 5 (a depth of about 350 nm from the upper surface of the p-side cladding layer 4). ) Is removed. Thereafter, the resist 11 is removed.

  Next, as shown in FIG. 8, a resist 12 is formed so as to cover only the p-side cladding layer 4, the contact layer 5 and the p-side ohmic electrode 8 located in the region B1 including the central region of the element.

Next, as shown in FIG. 9, from the upper surface of the flat portion 4 b of the p-side cladding layer 4 using the RIE method using Cl ₂ gas as a mask with the resist 12 and the p-side ohmic electrode 8 located in the region A 1 as a mask. A predetermined region up to a depth of about 50 nm is removed. Thereby, the flat portions 4a and 4b other than the convex portion of the p-side cladding layer 4 are regions including the region A1 in the vicinity of the light emitting side resonator end surface 10a (see FIG. 1) and the central region of the element other than the region A1. The thickness is different from B1. Specifically, in the region A1, the thickness tA1 of the flat portion 4a of the p-side cladding layer 4 is about 100 nm, and the height from the upper surface of the flat portion 4a of the convex portion is about 400 nm. On the other hand, in the region B1, the thickness tB1 of the flat portion 4b of the p-side cladding layer 4 is about 150 nm, and the height from the upper surface of the flat portion 4b of the convex portion is about 350 nm. As a result, a ridge portion 6 composed of the convex portion of the p-side cladding layer 4 and the contact layer 5 is formed. Thereafter, the resist 12 is removed to obtain the state shown in FIG.

Next, as shown in FIG. 11, an SiO ₂ film (not shown) having a thickness of about 200 nm is formed by plasma CVD so as to cover the entire surface, and then the upper surface of the p-side ohmic electrode 8 and By removing the SiO ₂ film located on the side surface, the current blocking layer 7 made of the SiO ₂ film is formed.

  Finally, as shown in FIG. 1, an Al layer (not shown) having a thickness of about 6 nm and a thickness of about 10 nm are formed in a predetermined region on the back surface of the n-type GaN substrate 1 by using a vacuum deposition method or the like. A Pd layer (not shown) having a thickness of approximately 300 nm and an Au layer (not shown) having a thickness of about 300 nm are sequentially formed. Thereby, the n-side ohmic electrode 9 constituted by the Al layer, the Pd layer, and the Au layer is formed. Thus, the nitride semiconductor laser element according to the first embodiment is formed.

  Next, the results of examining the laser beam divergence angle and the light emission efficiency of the nitride-based semiconductor laser device according to the first embodiment actually manufactured according to the above manufacturing process will be described. In the first embodiment, it has been found that the spread angle θ1 in the vertical direction and the spread angle θ2 in the horizontal direction of the laser light are about 18 ° and about 10 °, respectively. That is, θ1 / θ2 = about 1.8, and it was confirmed that the shape of the laser beam was close to a perfect circle (θ1 / θ2 = 1). In addition, the luminous efficiency was about 1.5 W / A, and it was confirmed that high luminous efficiency could be obtained.

(Second Embodiment)
FIG. 12 is a perspective view showing the structure of a nitride-based semiconductor laser device according to the second embodiment of the present invention. 13 and 14 are sectional views taken along lines 300-300 and 400-400 in FIG. 12, respectively. 12 to 14, in the second embodiment, unlike the first embodiment, the center of the element other than the region in the vicinity of the resonator end face on the light emitting side so as to contact the p-side ohmic electrode. A case where the sheet resistance value of the p-side ohmic electrode is about 10Ω / □ by forming the p-side pad electrode in the region including the region and making the thickness of the p-side ohmic electrode smaller than that of the first embodiment. explain. The nitride-based semiconductor laser device according to the second embodiment has a width W of about 300 μm and a resonator length L of about 600 μm, as in the first embodiment.

  In the nitride-based semiconductor laser device according to the second embodiment, as shown in FIG. 12, an n-side cladding layer 2 and an active layer having the same composition and thickness as those of the first embodiment are formed on an n-type GaN substrate 1. 3 are sequentially formed. A p-side cladding layer 24 having the same composition as the p-side cladding layer 4 of the first embodiment is formed on the active layer 3. The p-side cladding layer 24 has a width of about 1.5 μm and has stripe-shaped (elongated) convex portions extending in the resonator direction. The p-side cladding layer 24 is an example of the “second semiconductor layer” in the present invention.

  Here, in the second embodiment, the flat portions 24a and 24b other than the convex portions of the p-side cladding layer 24 include the region A2 in the vicinity of the resonator end surface 20a on the light emitting side and the central region of the element other than the region A2. The region B2 has a different thickness. Specifically, in the region A2, as shown in FIG. 13, the thickness tA2 of the flat portion 24a of the p-side cladding layer 24 is about 60 nm, and the height from the upper surface of the flat portion 24a of the convex portion is about 440 nm. Further, in the region B2, as shown in FIG. 14, the thickness tB2 of the flat portion 24b of the p-side cladding layer 24 is about 150 nm, and the height from the upper surface of the flat portion 24b of the convex portion is about 350 nm. . That is, the thickness tA2 (about 60 nm) of the flat portion 24a in the region A2 is smaller than the thickness tB2 (about 150 nm) of the flat portion 24b in the region B2. The regions A2 and B2 are examples of the “first region” and the “second region” in the present invention, respectively, and the flat portions 24a and 24b are respectively the “first flat portion” and the “first region” in the present invention. It is an example of “two flat portions”. The length of the region A2 in the resonator direction is about 10 μm, and the length of the region B2 in the resonator direction is about 590 μm.

  As shown in FIG. 12, a contact layer 25 having the same composition and thickness as the contact layer 5 of the first embodiment is formed on the convex portion of the p-side cladding layer 24. The contact layer 25 is an example of the “second semiconductor layer” in the present invention. The contact layer 25 and the convex portion of the p-side cladding layer 24 form a striped (elongated) ridge portion 26 having a width of about 1.5 μm and extending in the resonator direction. A current blocking layer 27 having the same composition and thickness as the current blocking layer 7 of the first embodiment is formed on the upper surfaces of the flat portions 24a and 24b of the p-side cladding layer 24 and on the side surfaces of the ridge portion 26. Is formed.

  Here, in the second embodiment, the p-side ohmic electrode 28 having a thickness set so as to have a sheet resistance value of about 10Ω / □ is formed on the contact layer 25 constituting the ridge portion 26. The p-side ohmic electrode 28 is composed of a Pt layer (not shown) having a thickness of about 1 nm and a Pd layer having a thickness of about 10 nm in this order from the contact layer 25 side. The p-side ohmic electrode 28 is an example of the “first electrode layer” in the present invention. In the second embodiment, the p-side pad electrode 30 is formed in the region B2 including the central region of the element other than the region A2 in the vicinity of the light emitting side resonator end surface 20a so as to be in contact with the p-side ohmic electrode 28. ing. Specifically, the light emitting side end 30a of the p-side pad electrode 30 is disposed at a distance L2 of about 10 μm from the region A2 in the vicinity of the light emitting side resonator end surface 20a. The p-side pad electrode 30 has a Ti layer (not shown) having a thickness of about 100 nm, a Pd layer (not shown) having a thickness of about 200 nm, and a thickness of about 3 μm in this order from the p-side ohmic electrode 28 side. It is comprised by Au layer (not shown) which has. The p-side pad electrode 30 is an example of the “second electrode layer” in the present invention.

  Further, an n-side ohmic electrode 9 having the same composition and thickness as in the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1.

  In the nitride-based semiconductor laser device according to the second embodiment, the light generated by the active layer 3 is oscillated by being reflected by the resonator end faces 20a and 20b.

  Next, in the configuration of the nitride-based semiconductor laser device of the second embodiment, the sheet resistance value of the p-side ohmic electrode 28 is changed in three steps (about 10Ω / □, about 1Ω / □, and about 0.1Ω / □). Table 2 below shows the results of measuring MTTF (Mean Time To Failure).

上記表２を参照して、ｐ側オーミック電極２８のシート抵抗値が約１０Ω／□および約１Ω／□の場合では、それぞれ、ＭＴＴＦが約５０００時間および約４０００時間と長くなることが判明した。これは、ｐ側オーミック電極２８において共振器方向（水平方向）に電流が流れにくくなったために、素子の中心領域を含む領域Ｂ２よりも結晶欠陥の量が多い領域Ａ２に流れる電流を減少させることができたためであると考えられる。これにより、領域Ａ２に位置する活性層３の結晶欠陥部分に電流が流れることに起因する結晶欠陥の増大が抑制されたので、ＭＴＴＦが約４０００時間以上と長くなったと考えられる。その一方、ｐ側オーミック電極２８のシート抵抗値が約０．１Ω／□の場合では、ＭＴＴＦが約７００時間と短くなることが判明した。この結果から、ｐ側オーミック電極２８のシート抵抗値を約１Ω／□以上に設定すれば、ＭＴＴＦを約４０００時間以上に長くすることができると考えられる。

Referring to Table 2 above, it was found that when the sheet resistance value of the p-side ohmic electrode 28 was about 10Ω / □ and about 1Ω / □, the MTTF was increased to about 5000 hours and about 4000 hours, respectively. This is because current is less likely to flow in the resonator direction (horizontal direction) in the p-side ohmic electrode 28, so that the current flowing in the region A2 having more crystal defects than the region B2 including the central region of the element is reduced. This is probably because of As a result, an increase in crystal defects caused by current flowing in the crystal defect portion of the active layer 3 located in the region A2 is suppressed, and therefore it is considered that the MTTF is increased to about 4000 hours or more. On the other hand, when the sheet resistance value of the p-side ohmic electrode 28 is about 0.1Ω / □, the MTTF was found to be as short as about 700 hours. From this result, it is considered that the MTTF can be increased to about 4000 hours or more by setting the sheet resistance value of the p-side ohmic electrode 28 to about 1Ω / □ or more.

  In the second embodiment, as described above, the thickness tA2 (about 60 nm) of the flat portion 24a located in the region A2 near the resonator end surface 20a on the light emitting side is set to the region B2 including the central region of the elements other than the region A2. By making the thickness smaller than the thickness tB2 (about 150 nm) of the flat portion 24b located at the same position as in the first embodiment, the optical confinement in the horizontal direction in the region A2 in the vicinity of the resonator end face 20a on the light emitting side is strengthened. Can do. As a result, the horizontal spread of the laser light emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, similar to the first embodiment, the shape of the laser light can be made close to a perfect circle. In this case, when the convex portion (ridge portion 26) of the p-side cladding layer 24 is formed by etching, the thickness tB2 (about 150 nm) of the flat portion 24b located in the region B2 of the p-side cladding layer 24 is located in the region A2. Etching is performed so as to be larger than the thickness tA2 (about 60 nm) of the flat portion 24a to be formed, and the portion including the active layer 3 is not etched, so that the amount of crystal defects in the active layer 3 is reduced as in the first embodiment. Can be made. As a result, as in the first embodiment, an increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high emission efficiency can be obtained. As described above, in the second embodiment, as in the first embodiment, a nitride-based semiconductor laser element having high light emission efficiency and capable of obtaining a laser beam shape close to a perfect circle shape is obtained. be able to.

  In the second embodiment, the p-side pad electrode 30 is formed in the region B2 including the central region of the element other than the region A2 in the vicinity of the light emitting-side resonator end surface 20a so as to contact the p-side ohmic electrode 28. As a result, current can be injected from the p-side pad electrode 30 only into the region A2 in the vicinity of the resonator end face 20a on the light emitting side of the p-side ohmic electrode 28. Further, by setting the sheet resistance value of the p-side ohmic electrode 28 to about 10 Ω / □, when current is injected from the p-side pad electrode 30, the current in the resonator direction (horizontal direction) in the p-side ohmic electrode 28. Therefore, the current density of the current flowing in the region A2 near the resonator end face 20a on the light emitting side is made smaller than the current density of the current flowing in the region B2 including the central region of the element other than the region A2. it can. Thereby, even if the number of crystal defects in the active layer 3 located in the region A2 becomes larger than the crystal defect in the active layer 3 located in the region B2, the current flowing in the crystal defect portion of the active layer 3 located in the region A2 Can be reduced. As a result, it is possible to suppress an increase in crystal defects due to a large amount of current flowing through the crystal defect portion of the active layer 3, thereby extending the life of the element. Further, by arranging the light emitting side end 30a of the p-side pad electrode 30 at a distance L2 of about 10 μm from the region A2 in the vicinity of the light emitting side resonator end surface 20a, the light emitting side end 30a can be easily arranged. The current density of the current flowing through the region A2 in the vicinity of the resonator end face 20a can be made smaller than the current density of the current flowing through the region B2 including the central region of the element other than the region A2. Specifically, the resistance value of the p-side ohmic electrode 28 having a length of about 10 μm is about 70Ω, which is larger than the series resistance value (about 15Ω) of the element. Therefore, in the p-side ohmic electrode 28 located between the end 30a of the p-side pad electrode 30 and the region A2, it is possible to make it difficult for current to flow from the end 30a of the p-side pad electrode 30 toward the region A. it can.

  Further, in the region A2 in the vicinity of the resonator emitting face 20a on the light emitting side in the second embodiment, the p-side cladding layer 24 is entirely etched with the p-type AlGaN layer, and the light guide layer is etched to an intermediate depth. Has been. Even if the etching depth is increased in this way, the above-described effects can be obtained if the etching depth does not reach the active layer 3.

  The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

  Next, referring to FIG. 12, as the manufacturing process of the second embodiment, first, the current blocking layer 27 is formed using the same process as that of the first embodiment shown in FIGS. . However, when the p-side ohmic electrode 28 is formed, a Pt layer (not shown) having a thickness of about 1 nm and a Pd layer having a thickness of about 10 nm are sequentially formed in this order from the contact layer 25 side. Thereafter, the p-side pad electrode 30 is formed in the region B2 including the central region of the element so as to be in contact with the p-side ohmic electrode 28 using a vacuum deposition method or the like. Specifically, the p-side pad electrode 30 is arranged such that the end 30a on the light emission side of the p-side pad electrode 30 is disposed at a distance L2 of about 10 μm from the region A2 in the vicinity of the resonator end surface 20a on the light emission side. The electrode 30 is formed. When the p-side pad electrode 30 is formed, a Ti layer (not shown) having a thickness of about 100 nm and a Pd layer (not shown) having a thickness of about 200 nm are sequentially formed from the p-side ohmic electrode 28 side. Then, an Au layer (not shown) having a thickness of about 3 μm is sequentially formed.

  Finally, an n-side ohmic electrode 9 having the same composition and thickness as in the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1 using a vacuum deposition method or the like. Thus, the nitride semiconductor laser element according to the second embodiment is formed.

  Next, the results of examining the laser beam divergence angle and the light emission efficiency of the nitride-based semiconductor laser device according to the second embodiment actually manufactured according to the above manufacturing process will be described. In the second embodiment, it has been found that the vertical spread angle θ1 and the horizontal spread angle θ2 of the laser light are about 18 ° and about 13 °, respectively. That is, θ1 / θ2 = about 1.4, and it was confirmed that the shape of the laser beam was closer to a perfect circle (θ1 / θ2 = 1) than in the first embodiment. In addition, the luminous efficiency was about 1.5 W / A, and it was confirmed that high luminous efficiency was obtained as in the first embodiment.

(Third embodiment)
FIG. 15 is a perspective view showing the structure of a nitride-based semiconductor laser device according to the third embodiment of the present invention. 16 and 17 are cross-sectional views taken along lines 500-500 and 600-600 in FIG. 15, respectively. Referring to FIGS. 15 to 17, in the third embodiment, unlike the first and second embodiments, the inclined portions are connected so as to connect the upper surfaces of the flat portions of the p-side cladding layer having different thicknesses. The case of providing the will be described. The nitride-based semiconductor laser device according to the third embodiment has a width W of about 300 μm and a resonator length L of about 600 μm, as in the first embodiment.

  In the nitride-based semiconductor laser device according to the third embodiment, as shown in FIG. 15, an n-side cladding layer 2 and an active layer having the same composition and thickness as those of the first embodiment are formed on an n-type GaN substrate 1. 3 are sequentially formed. A p-side cladding layer 44 having the same composition as that of the p-side cladding layer 4 of the first embodiment is formed on the active layer 3. The p-side cladding layer 44 has a width of about 1.5 μm and has stripe-shaped (elongated) convex portions extending in the resonator direction. The p-side cladding layer 44 is an example of the “second semiconductor layer” in the present invention.

  Here, in the third embodiment, the flat portions 44a and 44b other than the convex portion of the p-side cladding layer 44 include the region A3 in the vicinity of the resonator end surface 40a on the light emitting side and the central region of the element other than the region A3. The region B3 has a different thickness. Specifically, in the region A3, as shown in FIG. 16, the thickness tA3 of the flat portion 44a of the p-side cladding layer 44 is about 100 nm, and the height from the upper surface of the flat portion 44a of the convex portion is about 400 nm. In the region B3, as shown in FIG. 17, the thickness tB3 of the flat portion 44b of the p-side cladding layer 44 is about 150 nm, and the height from the upper surface of the flat portion 44b of the convex portion is about 350 nm. . The regions A3 and B3 are examples of the “first region” and the “second region” in the present invention, respectively, and the flat portions 44a and 44b are respectively the “first flat portion” and the “first region” in the present invention. It is an example of “two flat portions”. The length of the region A3 in the resonator direction is about 10 μm, and the length of the region B3 in the resonator direction is about 590 μm. In the third embodiment, as shown in FIG. 15, the upper surface of the flat portion 44 a and the upper surface of the flat portion 44 b are connected between the flat portion 44 a and the flat portion 44 b of the p-side cladding layer 44. An inclined portion 44c having an inclination angle of about 60 ° is provided.

  A contact layer 45 having the same composition and thickness as the contact layer 5 of the first embodiment is formed on the convex portion of the p-side cladding layer 44. The contact layer 45 is an example of the “second semiconductor layer” in the present invention. The contact layer 45 and the convex portion of the p-side cladding layer 44 form a striped (elongated) ridge 46 having a width of about 1.5 μm and extending in the resonator direction. A current blocking layer 47 having the same composition and thickness as the current blocking layer 7 of the first embodiment is formed on the upper surfaces of the flat portions 44 a and 44 b of the p-side cladding layer 44 and on the side surfaces of the ridge portion 46. Is formed. A p-side ohmic electrode 48 having the same composition and thickness as in the first embodiment is formed on the contact layer 45 constituting the ridge portion 46.

  Further, an n-side ohmic electrode 9 having the same composition and thickness as in the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1.

  In the nitride-based semiconductor laser device according to the third embodiment, the laser generated by the light generated by the active layer 3 is reflected by the resonator end faces 40a and 40b.

  In the third embodiment, as described above, the thickness tA3 (about 100 nm) of the flat portion 44a located in the region A3 in the vicinity of the resonator end surface 40a on the light emitting side is set to the region B3 including the central region of the elements other than the region A3. By making the thickness smaller than the thickness tB3 (about 150 nm) of the flat portion 44b located at the same position as in the first embodiment, the optical confinement in the horizontal direction in the region A3 in the vicinity of the resonator end surface 40a on the light emitting side is strengthened. Can do. As a result, the horizontal spread of the laser light emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, similar to the first embodiment, the shape of the laser light can be made close to a perfect circle. In this case, when the convex portion (ridge portion 46) of the p-side cladding layer 44 is formed by etching, the thickness tB3 (about 150 nm) of the flat portion 44b located in the region B3 of the p-side cladding layer 44 is located in the region A3. Etching is performed so as to be larger than the thickness tA3 (about 100 nm) of the flat portion 44a to be performed, and the portion including the active layer 3 is not etched, so that the amount of crystal defects in the active layer 3 is reduced as in the first embodiment. Can be made. As a result, as in the first embodiment, an increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high emission efficiency can be obtained. As described above, in the third embodiment, a nitride-based semiconductor laser element that has high light emission efficiency and can obtain a laser beam shape close to a perfect circle shape is obtained as in the first embodiment. be able to.

  In the third embodiment, an inclination angle of about 60 ° is provided so that the upper surface of the flat portion 44a and the upper surface of the flat portion 44b are connected between the flat portion 44a and the flat portion 44b of the p-side cladding layer 44. Since the boundary surface between the flat portion 44a and the flat portion 44b is inclined by providing the inclined portion 44c having a thickness, the flat portion 44a and the flat portion 44b having different thicknesses are connected by a vertical boundary surface Compared to the above, light is less likely to be reflected in the direction of the resonator end surface 40b opposite to the light emitting side at the boundary surface. Thereby, generation | occurrence | production of the unnecessary laser oscillation mode between the boundary surface between the flat part 44a and the flat part 44b and the resonator end surface 40a on the opposite side to the light emission side can be suppressed. This maintains a laser oscillation mode (laser oscillation mode between the resonator end surface 40a on the light emitting side and the resonator end surface 40b on the opposite side to the light emitting side) having a high luminous efficiency up to the high output region. Therefore, luminous efficiency can be further improved. Further, the lower end portion (edge portion) of the boundary surface between the flat portion 44a and the flat portion 44b is smoother than in the case where the flat portion 44a and the flat portion 44b having different thicknesses are connected by a vertical boundary surface. become. Thereby, since the optical loss in the edge part of the boundary surface between the flat part 44a and the flat part 44b can be suppressed, luminous efficiency can be improved more by this.

  The remaining effects of the third embodiment are similar to those of the aforementioned first embodiment.

  18 to 20 are perspective views for explaining a manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG. A manufacturing process for the nitride-based semiconductor laser device according to the third embodiment is now described with reference to FIGS. 15 and 18 to 20.

  First, as shown in FIG. 18, predetermined regions of the p-side ohmic electrode 48, the contact layer 45, and the p-side cladding layer 44 are etched using a process similar to that of the first embodiment shown in FIGS. Thus, the protrusions of the p-side cladding layer 44 are formed. Thereafter, a resist 51 is formed so as to cover only the p-side cladding layer 44, the contact layer 45, and the p-side ohmic electrode 48 located in the region B3 including the central region of the element. At this time, the surface 51a of the resist 51 located at the boundary between the region A3 in the vicinity of the light emitting side resonator end surface 40a (see FIG. 15) and the region B3 including the central region of the element is controlled by controlling exposure conditions and the like. However, the resist 51 is formed so that the inclination angle after etching is about 60 °.

Next, as shown in FIG. 19, by using the RIE method using Cl ₂ gas, the p-side ohmic electrode 48 located in the region A3 is used as a mask, and the flat portion 44a located in the region A3 of the p-side cladding layer 44 is formed. The resist 51 and the p-side cladding layer 44 are etched simultaneously until the thickness tA3 becomes about 100 nm. As a result, the flat portions 44a and 44b other than the convex portions of the p-side cladding layer 44 include a region A3 in the vicinity of the light emitting side resonator end surface 40a (see FIG. 15) and a central region of the element other than the region A3. The thickness is different from B3. Specifically, in the region A3, the thickness tA3 of the flat portion 44a of the p-side cladding layer 44 is about 100 nm, and the height from the upper surface of the flat portion 44a of the convex portion is about 400 nm. On the other hand, in the region B3, the thickness tB3 of the flat portion 44b of the p-side cladding layer 44 is about 150 nm, and the height from the upper surface of the flat portion 44b of the convex portion is about 350 nm. Further, between the flat portion 44a and the flat portion 44b of the p-side cladding layer 44, an inclined portion 44c having an inclination angle of about 60 ° is connected so as to connect the upper surface of the flat portion 44a and the upper surface of the flat portion 44b. Is provided. As a result, a ridge portion 46 constituted by the convex portion of the p-side cladding layer 44 and the contact layer 45 is formed. Thereafter, the resist 51 is removed to obtain the state shown in FIG.

  Next, as shown in FIG. 15, using the same process as in the first embodiment shown in FIG. 11, the upper surfaces of the flat portions 44a and 44b of the p-side cladding layer 44, the side surfaces of the ridge portion 46, Then, a current blocking layer 47 having the same composition and thickness as the current blocking layer 7 of the first embodiment is formed.

  Finally, an n-side ohmic electrode 9 having the same composition and thickness as in the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1 using a vacuum deposition method or the like. Thus, the nitride semiconductor laser element according to the third embodiment is formed.

(Fourth embodiment)
FIG. 21 is a perspective view showing the structure of a nitride-based semiconductor laser device according to the fourth embodiment of the present invention. 22 is a cross-sectional view taken along line 700-700 and 900-900 in FIG. 21, and FIG. 23 is a cross-sectional view taken along line 800-800 in FIG. Referring to FIGS. 21 to 23, in the fourth embodiment, unlike the first to third embodiments, the p-side cladding layer also has a region near the resonator end face on the side opposite to the light emitting side. The case where a flat portion having a thickness smaller than the thickness of the flat portion located in the region including the central region of the element is provided will be described. The nitride-based semiconductor laser device according to the fourth embodiment has a width W of about 300 μm and a resonator length L of about 600 μm, as in the first embodiment.

  In the nitride-based semiconductor laser device according to the fourth embodiment, as shown in FIG. 21, an n-side cladding layer 2 and an active layer having the same composition and thickness as those of the first embodiment are formed on an n-type GaN substrate 1. 3 are sequentially formed. On the active layer 3, a p-side cladding layer 64 having the same composition as the p-side cladding layer 4 of the first embodiment is formed. The p-side cladding layer 64 has a width of about 1.5 μm and has stripe-shaped (elongated) convex portions extending in the resonator direction. The p-side cladding layer 64 is an example of the “second semiconductor layer” in the present invention.

  Here, in the fourth embodiment, the flat portions 64a, 64b, and 64c other than the convex portion of the p-side cladding layer 64 are the resonance on the region A4 in the vicinity of the resonator end surface 60a on the light emitting side and on the side opposite to the light emitting side. The region C4 in the vicinity of the vessel end surface 60b and the region B4 including the central region of the elements other than the regions A4 and C4 have different thicknesses. Specifically, in the regions A4 and C4, as shown in FIG. 22, the thickness tA4 of the flat portions 64a and 64c of the p-side cladding layer 64 is about 100 nm, and from the upper surfaces of the flat portions 64a and 64c of the convex portions. The height of is about 400 nm. In the region B4, as shown in FIG. 23, the thickness tB4 of the flat portion 64b of the p-side cladding layer 64 is about 150 nm, and the height from the upper surface of the flat portion 64b of the convex portion is about 350 nm. . That is, the thickness tA4 (about 100 nm) of the flat portions 64a and 64c of the regions A4 and C4 is smaller than the thickness tB4 (about 150 nm) of the flat portion 64b of the region B4. The regions A4, B4, and C4 are examples of the “first region”, “second region”, and “third region” of the present invention, respectively, and the flat portions 64a, 64b, and 64c are respectively the present invention. Are "first flat part", "second flat part" and "third flat part". The length of the regions A4 and C4 in the resonator direction is about 10 μm, and the length of the region B4 in the resonator direction is about 580 μm.

  Further, as shown in FIG. 21, a contact layer 65 having the same composition and thickness as the contact layer 5 of the first embodiment is formed on the convex portion of the p-side cladding layer 64. The contact layer 65 is an example of the “second semiconductor layer” in the present invention. The contact layer 65 and the convex portion of the p-side cladding layer 64 form a striped (elongated) ridge 66 having a width of about 1.5 μm and extending in the resonator direction. A current blocking layer having the same composition and thickness as the current blocking layer 7 of the first embodiment is formed on the upper surfaces of the flat portions 64a, 64b and 64c of the p-side cladding layer 64 and on the side surfaces of the ridge portion 66. 67 is formed. A p-side ohmic electrode 68 having the same composition and thickness as in the first embodiment is formed on the contact layer 65 constituting the ridge portion 66.

  Further, an n-side ohmic electrode 9 having the same composition and thickness as in the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1.

  In the nitride-based semiconductor laser device according to the fourth embodiment, the light generated by the active layer 3 is oscillated by being reflected by the resonator end faces 60a and 60b.

  In the fourth embodiment, as described above, the thickness tA4 (about 100 nm) of the flat portion 64a located in the region A4 in the vicinity of the resonator end surface 60a on the light emitting side is set to the region B4 including the central region of the elements other than the region A4. By making the thickness smaller than the thickness tB4 (about 150 nm) of the flat portion 64b located at the same position as in the first embodiment, the optical confinement in the horizontal direction in the region A4 in the vicinity of the resonator end surface 60a on the light emitting side is strengthened. Can do. As a result, the horizontal spread of the laser light emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, similar to the first embodiment, the shape of the laser light can be made close to a perfect circle. In this case, when the convex portion (ridge portion 66) of the p-side cladding layer 64 is formed by etching, the thickness tB4 (about 150 nm) of the flat portion 64b located in the region B4 of the p-side cladding layer 64 is located in the region A4. Etching is performed so as to be larger than the thickness tA4 (about 100 nm) of the flat portion 64a to be formed, and the portion including the active layer 3 is not etched, so that the amount of crystal defects in the active layer 3 is reduced as in the first embodiment. Can be made. As a result, as in the first embodiment, an increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high emission efficiency can be obtained. Thus, in the fourth embodiment, as in the first embodiment, a nitride-based semiconductor laser element that has a high light emission efficiency and can obtain a laser beam shape close to a perfect circle shape is obtained. be able to.

  In the fourth embodiment, the flat portion having a thickness tA4 (about 100 nm) smaller than the thickness tB4 (about 150 nm) of the flat portion 64b also in the region C4 in the vicinity of the resonator end surface 60b opposite to the light emitting side. By providing 64c, even if the resonator end surface 60b opposite to the light emitting side is used as the light emitting surface, the shape of the laser light can be made close to a perfect circle. As a result, the shape of the laser beam can be made close to a perfect circle, regardless of which of the two resonator end surfaces 60a and 60b is used as the light exit surface. Thus, when assembling the element, a semiconductor laser element capable of obtaining a laser beam shape close to a perfect circle shape can be produced regardless of which resonator end face 60a and 60b is set as the light emission surface. it can.

  24 to 26 are perspective views for explaining a manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. A manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment is now described with reference to FIGS.

  First, as shown in FIG. 24, predetermined regions of the p-side ohmic electrode 68, the contact layer 65, and the p-side cladding layer 64 are etched using a process similar to that of the first embodiment shown in FIGS. 5 to 7. Thus, the protrusions of the p-side cladding layer 64 are formed. Thereafter, a resist 71 is formed so as to cover only the p-side cladding layer 64, the contact layer 65, and the p-side ohmic electrode 68 located in the region B4 including the central region of the element.

Next, as shown in FIG. 25, the flat portion of the p-side cladding layer 64 is masked using the resist 71 and the p-side ohmic electrode 68 located in the regions A4 and C4 by using the RIE method using Cl ₂ gas. A predetermined region from the upper surface of 64b to a depth of about 50 nm is removed. As a result, the flat portions 64a, 64b and 64c other than the convex portions of the p-side cladding layer 64 are formed in the region A4 in the vicinity of the light emitting side resonator end surface 60a (see FIG. 21) and the resonator on the side opposite to the light emitting side. The region C4 in the vicinity of the end surface 60b (see FIG. 21) and the region B4 including the central region of the element other than the regions A4 and C4 have different thicknesses. Specifically, in the regions A4 and C4, the thickness tA4 of the flat portions 64a and 64c of the p-side cladding layer 64 is about 100 nm, and the height from the upper surface of the flat portions 64a and 64c of the convex portion is about 400 nm. On the other hand, in the region B4, the thickness tB4 of the flat portion 64b other than the convex portion of the p-side cladding layer 64 is about 150 nm, and the height from the upper surface of the flat portion 64b of the convex portion is about 350 nm. As a result, a ridge portion 66 composed of the convex portion of the p-side cladding layer 64 and the contact layer 65 is formed. Thereafter, the resist 71 is removed to obtain the state shown in FIG.

  Next, as shown in FIG. 21, using the same process as in the first embodiment shown in FIG. 11, the upper surfaces of the flat portions 64a, 64b and 64c of the p-side cladding layer 64 and the side surfaces of the ridge portion 66 On top, a current blocking layer 67 having the same composition and thickness as the current blocking layer 7 of the first embodiment is formed.

  Finally, an n-side ohmic electrode 9 having the same composition and thickness as in the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1 using a vacuum deposition method or the like. Thus, the nitride semiconductor laser element according to the fourth embodiment is formed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to fourth embodiments, the case where the present invention is applied to a semiconductor laser element made of a nitride-based semiconductor has been described. However, the present invention is not limited to this, and is made of a semiconductor other than a nitride-based semiconductor. The present invention can also be applied to a semiconductor laser element.

  In the first to fourth embodiments, the length in the resonator direction of the region near the resonator end face on the light emitting side is set to about 10 μm. However, the present invention is not limited to this, and the length on the light emitting side is not limited thereto. The length in the resonator direction of the region in the vicinity of the resonator end surface may be in the range of about 3 μm to 50 μm.

  In the first, third, and fourth embodiments, the thickness of the flat portion located in the region including the central region of the element of the p-side cladding layer is set to about 150 nm. However, the present invention is not limited to this. If the thickness of the flat portion located in the region including the central region of the element of the p-side cladding layer is set to about 100 nm or more and about 250 nm or less, the luminous efficiency can be increased and the threshold current can be lowered. can do.

  Further, in the second embodiment, the light emitting side end 30a of the p-side pad electrode 30 is arranged with an interval L2 of about 10 μm from the region A2 in the vicinity of the light emitting side resonator end surface 20a. The invention is not limited to this, and if the end of the p-side pad electrode on the light exit side does not reach the resonator end surface, the end of the p-side pad electrode on the light exit side is located near the resonator end surface on the light exit side. You may arrange in an area.

  In the second embodiment, the sheet resistance value of the p-side ohmic electrode is set to about 10 Ω / □. However, the present invention is not limited to this, and the sheet resistance value of the p-side ohmic electrode is set to about 1 Ω / □. If set above, the MTTF (mean failure time) can be increased. Thereby, the lifetime of an element can be lengthened.

  Moreover, in the said 3rd Embodiment, although the inclination part which has an inclination angle of about 60 degrees was provided so that each upper surface of the flat part of the p side cladding layer from which thickness differs may be provided, this invention is not limited to this. Alternatively, the upper surfaces of the flat portions of the p-side cladding layers having different thicknesses may be connected by an inclined portion having an inclination angle other than about 60 °.

2 n-side cladding layer (first semiconductor layer)
3 active layer 4, 24, 44, 64 p-side cladding layer (second semiconductor layer)
4a, 24a, 44a, 64a Flat part (first flat part)
4b, 24b, 44b, 64b Flat part (second flat part)
5, 25, 45 Contact layer 28 p-side ohmic electrode (first electrode layer)
30 p-side pad electrode (second electrode layer)
64c flat part (third flat part)
A1, A2, A3, A4 area (first area)
B1, B2, B3, B4 area (second area)
C4 area (third area)

Claims (2)

An active layer formed on the first semiconductor layer;
A second semiconductor layer formed on the active layer and having a convex portion and a flat portion other than the convex portion;
A current blocking layer formed on the second semiconductor layer up to an end of the resonator end face;
A first electrode layer formed on the convex portion;
A second electrode layer formed on the first electrode layer and the current blocking layer,
The first electrode layer is formed to extend to a region near the resonator end face,
The semiconductor laser device, wherein an end of the second electrode layer on the resonator end face side is disposed at a predetermined interval from a region near the resonator end face.   2. The semiconductor laser device according to claim 1, wherein a concave portion is formed in a region of the flat portion in the vicinity of the resonator end face and in the vicinity of the convex portion.

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