JP5079613B2 - Nitride-based semiconductor laser device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a nitride-based semiconductor laser device and a method for manufacturing the same.

  Nitride-based semiconductor laser elements are expected to be applied not only to optical disk light sources but also to various uses such as display light sources. In order to realize such an application, it is necessary to further improve the reliability of the nitride-based semiconductor laser device and to further increase the output.

  On the other hand, in order to increase the output of a semiconductor laser element, it is indispensable to suppress COD (Catalytic Optical Damage). Here, COD is known to occur as follows. That is, non-radiative recombination occurs at the light emitting end face where surface states exist at high density, and part of the laser light is absorbed by the light emitting end face and converted to heat. Due to this heat generation, the band gap of the active layer at the light emitting end face is reduced, so that the light absorption is further increased. This further increases heat generation. Such a cycle raises the temperature of the light emitting end face, so that the crystals constituting the semiconductor laser element are dissolved, and as a result, the light emitting end face is destroyed.

  As a method for suppressing such COD, there has been conventionally known a method in which a semiconductor laser element is provided with a window structure configured so that laser light is not absorbed by the end face by devising a light emitting end face (resonator end face). (For example, see Patent Document 1).

  Patent Document 1 discloses an AlGaAs-based structure in which the quantum well structure in the region near the light emitting end face (resonator end face) of the active layer is disordered by diffusing impurities in the region near the light emitting end face (resonator end face). A semiconductor laser device is disclosed. In this semiconductor laser element, the band gap in the vicinity of the light emitting end face (resonator end face) of the active layer becomes wider than other regions due to the disorder of the quantum well structure due to impurity diffusion, so that the light emitting end face (resonator end face) The light absorption at is reduced. That is, a window structure is formed in the vicinity of the light emitting end face (resonator end face). Thereby, since the temperature rise of the light emission end face (resonator end face) is suppressed, COD is suppressed.

  However, unlike nitride-based semiconductor laser elements (for example, AlGaAs-based AlGaAs-based semiconductor laser elements described in Patent Document 1), nitride semiconductor laser elements are difficult to diffuse impurities, so that a window structure is formed by impurity diffusion. Is inconvenient.

  Therefore, conventionally, there has been proposed a technique for increasing the output of the nitride-based semiconductor laser device while improving the reliability by suppressing the COD of the light emitting end face using a technique other than impurity diffusion (for example, , See Patent Document 2).

  Patent Document 2 discloses a method for realizing a window structure by inclining an active layer in a light emitting end face portion with respect to an active layer in other portions in a nitride-based semiconductor laser device. . Note that the technique disclosed in Patent Document 2 described above is that when the tilt angle of the active layer is 0.3 ° or more with respect to the (0001) plane of the GaN substrate, the emission wavelength is shortened as the tilt angle increases. That is, based on the knowledge that the band gap is increased.

  In the conventional method described above, a groove is formed in a predetermined region of the GaN substrate, and then a GaN layer is formed on the GaN substrate, whereby a V-shaped groove is formed in a region corresponding to the groove in the GaN layer. . Then, by sequentially growing the semiconductor layer on the GaN layer, a part of the active layer is inclined by the inclined surface of the V-shaped groove. Thereafter, the GaN substrate is cleaved at the central portion of the V-shaped groove, whereby a nitride-based semiconductor laser device in which the active layer in the light emitting end face portion is inclined is obtained.

JP-A-5-218593 JP 2008-10446 A

  However, in the technique disclosed in Patent Document 2, the window structure can be realized by inclining the active layer in the light emitting end face portion. However, in order to achieve higher output, the window effect is achieved. Is considered insufficient. For this reason, when the nitride semiconductor laser element is driven at a high output, there arises a disadvantage that it becomes difficult to suppress the generation of COD. This makes it difficult to drive the nitride-based semiconductor laser device at a high output and to suppress a decrease in reliability.

  In the method disclosed in Patent Document 2, as described above, after forming the groove portion in the GaN substrate, the GaN layer is formed on the GaN substrate to form the V-shaped groove in the GaN layer. For this reason, on the groove portion of the GaN substrate, the growth proceeds from various directions and defects occur at the growth meeting portion, so that the crystallinity of the V-shaped groove slope is lowered. Thereby, the crystallinity of the active layer formed on the V-shaped groove slope is also affected by the influence of the V-shaped groove slope. As a result, since the crystallinity of the active layer at the light emitting end face portion is lowered, light absorption occurs at the light emitting end face portion, and there is a problem that the device characteristics are lowered, for example, the operating current is increased.

  In addition, there is also a disadvantage that the COD level tends to be lowered due to a decrease in crystallinity of the active layer at the light emitting end face portion. Thereby, since it becomes more difficult to suppress generation | occurrence | production of COD, it becomes more difficult to suppress the fall of reliability.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to achieve high output and to suppress deterioration of element characteristics. And providing a highly reliable nitride-based semiconductor laser device and a method for manufacturing the same.

  To achieve the above object, a nitride semiconductor laser device according to a first aspect of the present invention includes a substrate made of a nitride semiconductor, a first semiconductor layer formed on the substrate, and a first semiconductor layer. And an active layer for generating laser light and a light emitting end face from which the laser light generated in the active layer is emitted. The first semiconductor layer is made of a semiconductor material having a band gap larger than that of the active layer, and at least in the first semiconductor layer, the light emission end face portion is raised. Due to the rise of the light emitting end face part, the height of the light emitting end face side of the active layer with respect to the substrate surface is higher than the height of the central part of the active layer. The light is emitted through the semiconductor layer.

  In the nitride-based semiconductor laser device according to the first aspect, as described above, the first semiconductor layer is activated by being configured such that the laser light is emitted through the first semiconductor layer at the light emitting end face portion. Since the band gap is larger than that of the layer, it is possible to suppress the laser light from being absorbed by the light emitting end face portion. That is, by configuring as described above, a window structure (window region) can be formed in the light emitting end face portion of the nitride-based semiconductor laser device. As a result, the COD level of the nitride-based semiconductor laser device can be improved, so that the generation of COD can be suppressed even when driven at a high output. Further, by suppressing the generation of COD, it is possible to suppress a decrease in reliability due to COD. As a result, in the nitride semiconductor laser element, high output can be achieved and high reliability can be obtained.

  In the nitride-based semiconductor laser device according to the first aspect, the raised portion can be formed at least in the first semiconductor layer as follows. That is, after a groove is formed in a predetermined region on the upper surface (main surface) of a semiconductor wafer to be a substrate, a first semiconductor layer is grown on the upper surface (main surface) of the semiconductor wafer by using a vapor phase growth method. At this time, by forming the size of the groove portion to a predetermined size or more, unlike the technique disclosed in Patent Document 2, the raised portion can be formed in the region near the groove portion of the first semiconductor layer. A nitride-based semiconductor laser device having a first semiconductor layer in which the light-emitting end surface portion is raised by forming a groove in the semiconductor wafer so that the raised portion is located at the light-emitting end surface portion of the nitride-based semiconductor laser device Can be obtained.

  Further, when the raised portion is formed in the first semiconductor layer as described above, when the semiconductor layer is grown, the growth on the groove portion of the semiconductor wafer proceeds from various directions, and the growth meeting portion is defective. On the other hand, the growth proceeds regularly on the region other than the groove, and the growth association accompanied by defects is suppressed. For this reason, since the generation of new defects is suppressed in the region near the groove, a crystal with few defects can be obtained. Thereby, since the crystallinity of the light emission end face portion can be improved, the crystallinity of the window region can be improved. Therefore, since light absorption at the light emitting end face portion can be suppressed, an increase in operating current can be suppressed. As a result, deterioration of element characteristics can be suppressed.

  In the nitride-based semiconductor laser device according to the first aspect, as described above, the crystallinity of the window region can be improved, so that the change in COD level with time can be reduced and the COD level can be reduced. It can be improved further. Thereby, the reliability of the nitride-based semiconductor laser device can be further improved.

  The nitride-based semiconductor laser device according to the first aspect preferably further includes a light reflecting end face opposed to the light emitting end face, and at least in the first semiconductor layer, the light reflecting end face portion is raised, and the light reflecting end face Due to the rise of the portion, the height of the light reflection end face side of the active layer with respect to the substrate surface is higher than the height of the central portion of the active layer. If comprised in this way, the light absorption not only in a light-projection end surface but the light reflection end surface can also be reduced.

  In the nitride semiconductor laser element according to the first aspect, the first semiconductor layer is preferably made of an n-type semiconductor. With this configuration, light absorption by the dopant is reduced compared to the case where the first semiconductor layer is formed from a p-type semiconductor doped with a dopant such as Mg (magnesium) that causes light absorption. Light absorption in the region can be effectively suppressed.

  In the nitride semiconductor laser element according to the first aspect, the second semiconductor layer is formed on the active layer, extends in a direction intersecting with the light emitting end face, and includes a convex ridge portion functioning as a current passage portion. Furthermore, it is preferable to provide.

  In this case, the groove is preferably formed in a region on the upper surface of the substrate that does not intersect with the ridge portion in plan view. With this configuration, when the nitride semiconductor laser element is formed using the semiconductor wafer, the raised portion can be formed in the first semiconductor layer of the adjacent nitride semiconductor laser element by the groove. . This makes it possible to form a nitride-based semiconductor laser element without removing the portion of the semiconductor wafer where the groove is formed, so that the semiconductor wafer can be used without waste (efficiently). As a result, the number of nitride-based semiconductor laser elements obtained from a single semiconductor wafer can be increased, so that the manufacturing yield can be improved and nitride corresponding to high output can be achieved. -Based semiconductor laser elements can be manufactured at low cost.

  In the configuration including the light emitting end face and the light reflecting end face, the groove can be formed in at least one of the vicinity of the light emitting end face and the vicinity of the light reflecting end face.

  In the configuration including the groove portion, preferably, the depth of the groove portion is 1 μm or more. If comprised in this way, when forming a nitride semiconductor laser element using a semiconductor wafer, a raised part can be easily formed in the first semiconductor layer of the adjacent nitride semiconductor laser element. Thereby, a window structure (window region) can be easily formed at least on the light emitting end face portion of the nitride-based semiconductor laser device.

  In the configuration including the groove portion, preferably, the width of the groove portion is 1 μm or more. Even in such a configuration, when a nitride semiconductor laser element is formed using a semiconductor wafer, a raised portion can be easily formed in the first semiconductor layer of the adjacent nitride semiconductor laser element. . If each of the depth of the groove and the width of the groove is configured to be 1 μm or more, the raised portion can be more easily formed in the first semiconductor layer of the adjacent nitride semiconductor laser element. Thereby, the window structure (window region) can be more easily formed at least on the light emitting end face portion of the nitride-based semiconductor laser device.

  In the configuration in which the second semiconductor layer is formed on the active layer, the second semiconductor layer further includes a dummy ridge portion that does not function as a current passage portion, and the dummy ridge portion is formed to extend along the ridge portion. The groove portion is preferably formed so as to intersect with the dummy ridge portion in plan view.

  In the nitride semiconductor laser device according to the first aspect, an n-type GaN buffer layer, an n-type AlGaN cladding layer, an active layer, a p-type AlGaN cladding layer, and a p-type GaN contact layer are formed on the substrate from the substrate side. And the first semiconductor layer can be composed of an n-type AlGaN cladding layer.

  In this case, the second semiconductor layer can be configured to include a p-type AlGaN cladding layer and a p-type GaN contact layer.

  In this case, each of the ridge portion and the dummy ridge portion can be composed of a p-type AlGaN cladding layer and a p-type GaN contact layer.

  In the configuration in which the n-type AlGaN cladding layer is formed on the substrate, the n-type dopant of the n-type AlGaN cladding layer is Si. If comprised in this way, the light absorption in a window area | region can be suppressed more effectively.

  A method for manufacturing a nitride-based semiconductor laser device according to a second aspect of the present invention includes a step of forming a groove extending in a predetermined direction on a main surface of a substrate, and a vapor phase growth method on the main surface of the substrate. And a step of growing a plurality of nitride-based semiconductor layers including a first semiconductor layer and an active layer, and a step of separating a region near the groove portion of the substrate along the groove portion. The step of growing the nitride-based semiconductor layer includes a step of growing the first semiconductor layer using a semiconductor material having a band gap larger than that of the active layer, and a step of arranging the active layer on the first semiconductor layer. Including.

  In the method for manufacturing a nitride semiconductor laser device according to the second aspect, as described above, a groove extending in a predetermined direction is formed on the main surface of the substrate (semiconductor wafer), and the main surface of the substrate (semiconductor wafer). By growing a nitride-based semiconductor layer including the first semiconductor layer on the top using a vapor phase growth method, a raised portion can be formed in a region near the groove of the nitride-based semiconductor layer. Then, by separating the vicinity of the groove portion of the substrate along the groove portion, the raised portion of the nitride-based semiconductor layer (first semiconductor layer) can be disposed on the separation surface portion. In addition, the active layer is disposed on the first semiconductor layer, and the separation surface is configured to be a light emitting end surface, whereby the height of the light emitting end surface side of the active layer with respect to the substrate surface is higher than the height of the central portion. Can be configured to be higher. As a result, a nitride-based semiconductor laser element in which laser light is emitted through the first semiconductor layer at the light emitting end face portion can be formed. In addition, since the first semiconductor layer is formed using a semiconductor material having a band gap larger than that of the active layer, it is possible to suppress the laser light from being absorbed by the light emitting end face. A nitride-based semiconductor laser device in which a window structure (window region) is formed can be manufactured. Accordingly, the COD level can be improved by the window structure (window region) formed in the light emitting end face portion, so that high output can be achieved and a highly reliable nitride semiconductor laser device is manufactured. can do.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, a nitride-based semiconductor layer is grown on a substrate (semiconductor wafer) on which a groove is formed by using a vapor phase growth method. On the other side of the groove, growth proceeds from various directions to cause defects at the growth meeting portion, while growth progresses regularly on regions other than the groove portion, and growth association with defects is suppressed. For this reason, since the generation of new defects is suppressed in the region near the groove, a crystal with few defects can be obtained. Thereby, since the crystallinity of the light emission end face portion can be improved, the crystallinity of the window region can be improved. Therefore, since light absorption at the light emitting end face portion can be suppressed, an increase in operating current can be suppressed. As a result, deterioration of element characteristics can be suppressed.

  Further, in the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, since a window region with good crystallinity can be formed, the change in COD level with time can be reduced, and the COD level can be further increased. Can be improved. Thereby, a highly reliable nitride-based semiconductor laser device can be easily manufactured.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, preferably, the vapor phase growth method is a metal organic vapor phase growth method. With this configuration, in the metal organic chemical vapor deposition method (MOCVD method), the migration of molecules on the substrate surface (main surface) occurs more strongly than in other vapor phase growth methods. In addition, the control range of the swell in the region near the groove can be widened, and the swell can be formed with high accuracy. As a result, since the window structure (window region) can be easily formed, it is possible to achieve high output, and it is possible to suppress deterioration of element characteristics and high reliability. A nitride-based semiconductor laser device can be manufactured with high yield.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, preferably, the step of growing the nitride-based semiconductor layer includes the step of forming the first semiconductor layer into an n-type using an n-type dopant. Including. With this configuration, light absorption by the dopant is reduced compared to the case where the first semiconductor layer is formed from a p-type semiconductor doped with a dopant such as Mg (magnesium) that causes light absorption. Light absorption in the region can be effectively suppressed.

  In this case, preferably the n-type dopant is Si. If comprised in this way, the light absorption in a window area | region can be suppressed more effectively.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, preferably, the step of forming the groove includes a step of configuring the depth of the groove to be 1 μm or more. If comprised in this way, the rising part which can form a window structure (window area | region) can be easily formed in the groove part vicinity area | region of a nitride-type semiconductor layer (1st semiconductor layer).

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, preferably, the step of forming the groove includes a step of configuring the width of the groove to be 1 μm or more. Even in such a configuration, a raised portion capable of forming a window structure (window region) can be easily formed in a region near the groove of the nitride-based semiconductor layer (first semiconductor layer). In addition, if each of the depth of the groove and the width of the groove is 1 μm or more, a window structure (window region) can be easily formed in the region near the groove of the nitride-based semiconductor layer (first semiconductor layer). Can be formed.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, preferably, the step of forming the groove portion includes a step of forming a plurality of groove portions extending continuously in the same direction at a predetermined distance from each other. Including. If comprised in this way, the nitride type semiconductor laser element by the said 1st aspect can be manufactured, without introduce | transducing a complicated process without significantly increasing an existing process.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, preferably, in the step of forming the groove portion, a plurality of groove portions are formed at predetermined positions on the main surface of the substrate by intermittently forming the groove portion. Including the step of arranging. Even in such a configuration, the nitride-based semiconductor laser device according to the first aspect can be manufactured without greatly increasing the number of existing processes and without introducing complicated processes. Further, if configured in this manner, a raised portion can be formed in the nitride-based semiconductor layer (first semiconductor layer) of the adjacent nitride-based semiconductor laser device, so that a groove portion of the substrate (semiconductor wafer) can be formed. It is possible to manufacture a nitride-based semiconductor laser device without removing the portion where the is formed. As a result, the substrate (semiconductor wafer) can be used without waste (efficiently), and therefore the number of nitride-based semiconductor laser elements (number of available) obtained from one substrate (semiconductor wafer) can be increased. it can. As a result, the manufacturing yield can be improved and the manufacturing cost of the nitride-based semiconductor laser device can be reduced.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, the nitride-based semiconductor layer further includes a second semiconductor layer formed on the active layer, and the second semiconductor layer has a direction in which the groove extends. A step of forming a convex ridge portion that extends in the intersecting direction and functions as a current passage portion may be further provided.

  In this case, preferably, the step of forming the ridge portion includes a step of forming a ridge portion that functions as a current path portion, and a step of forming a dummy ridge portion that does not function as a current path portion. With this configuration, it is possible to easily increase the number of nitride-based semiconductor laser elements obtained from a single substrate (semiconductor wafer) (the number that can be obtained), thereby easily improving the manufacturing yield. In addition, the manufacturing cost of the nitride-based semiconductor laser device can be easily reduced.

  In the method for manufacturing a nitride-based semiconductor laser device according to the second aspect, the first semiconductor layer is an n-type AlGaN cladding layer, and the step of growing the nitride-based semiconductor layer includes an n-type GaN buffer from the substrate side. Forming a layer, an n-type AlGaN cladding layer, an active layer, a p-type AlGaN cladding layer, and a p-type GaN contact layer.

  In this case, the second semiconductor layer includes a p-type AlGaN cladding layer and a p-type GaN contact layer, and the step of forming the ridge portion is a step of forming the ridge portion in the p-type AlGaN cladding layer and the p-type GaN contact layer. Is preferably included.

  As described above, according to the present invention, it is possible to achieve high output, and it is possible to suppress deterioration of element characteristics, and a highly reliable nitride semiconductor laser element and its A manufacturing method can be obtained easily.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. In the following description, the thickness of each layer is the thickness of the flat portion (other than the raised portion).

(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. FIG. 2 is a plan view of the nitride-based semiconductor laser device according to the first embodiment of the present invention. 3 is a cross-sectional view taken along line A1-A1 in FIG. 2, and FIG. 4 is a cross-sectional view taken along line B1-B1 in FIG. FIG. 5 is a sectional view showing the structure of the light emitting layer of the nitride-based semiconductor laser device according to the first embodiment of the present invention. First, the structure of the nitride-based semiconductor laser device 100 according to the first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the nitride-based semiconductor laser device 100 according to the first embodiment has a pair of resonator end faces 20 formed by cleavage and facing each other. The pair of resonator end faces 20 includes a light emitting end face 20a from which laser light is emitted and a light reflecting end face 20b opposite to the light emitting end face 20a. Further, the nitride-based semiconductor laser device 100 according to the first embodiment has a length L (resonator length L) of about 600 μm to about 1500 in a direction ([1-100] direction) orthogonal to the resonator end face 20. And a width W (resonator width W) of about 80 μm to about 300 μm in the direction along the resonator end face 20 ([11-20] direction).

Further, the nitride-based semiconductor laser device 100 according to the first embodiment is formed on the (0001) plane (upper surface (main surface)) of the n-type GaN substrate 1 as shown in FIGS. An n-type buffer layer 2 made of n-type GaN having a thickness of about 0.1 μm to about 10 μm (for example, about 4 μm) is formed. An n-type cladding layer 3 made of n-type Al _0.05 Ga _0.95 N having a thickness of about 0.5 μm to about 3.0 μm (for example, about 2 μm) is formed on the n-type buffer layer 2. The n-type GaN substrate 1 is an example of the “substrate” in the present invention, and the n-type buffer layer 2 is an example of the “n-type GaN buffer layer” in the present invention. The n-type cladding layer 3 is an example of the “first semiconductor layer” and the “n-type AlGaN cladding layer” in the present invention.

A light emitting layer 4 is formed on the n-type cladding layer 3. As shown in FIG. 5, the light emitting layer 4 includes three quantum well layers 4a made of In _x1 Ga _1-x1 N and four barrier layers 4b made of In _x2 Ga _1-x2 N (where x1> x2). And an active layer 4c having a multiple quantum well (MQW) structure in which are alternately stacked. The quantum well layer 4a is made of, for example, In _x1 Ga _{1 -x1} N (x1 = 0.05 to 0.1) having a thickness of about 4 nm, and the barrier layer 4b is made of, for example, about 8 nm. It is made of In _x2 Ga _1-x2 N (x2 = 0 to 0.05) having a thickness. Further, an evaporation preventing layer 4d made of p-type Al _0.3 Ga _0.7 N having a thickness of 0 to about 0.02 μm (for example, about 0.01 μm) is formed on the active layer 4c. Further, a lower guide layer 4e made of n-type GaN having a thickness of 0 to about 0.2 μm (for example, about 0.1 μm) and 0 to about 0.2 μm so as to sandwich the active layer 4c and the evaporation preventing layer 4d. An upper guide layer 4f made of p-type GaN (for example, about 0.01 μm) is provided. The active layer 4c, the evaporation preventing layer 4d, the lower guide layer 4e, and the upper guide layer 4f constitute the light emitting layer 4.

Further, as shown in FIG. 4, a p-type cladding layer 5 made of p-type Al _0.05 Ga _0.95 N having a convex portion and a flat portion other than the convex portion is formed on the light emitting layer 4. A p-type contact layer 6 made of p-type GaN having a thickness of about 0.01 μm to about 1.0 μm (for example, about 0.05 μm) is formed on the convex portion of the p-type cladding layer 5. The p-type contact layer 6 and the convex portion of the p-type cladding layer 5 form a striped (elongated) ridge portion 7 having a width of about 1 μm to about 3 μm (for example, about 1.5 μm). As shown in FIG. 2, the ridge portion 7 is formed to extend in a direction ([1-100] direction) orthogonal to the resonator end face 20. The ridge portion 7 functions as a current path portion to the light emitting layer 4 (active layer 4c). The p-type cladding layer 5 is an example of the “second semiconductor layer” and the “p-type AlGaN cladding layer” in the present invention, and the p-type contact layer 6 is the “second semiconductor layer” and “p” in the present invention. It is an example of a “type GaN contact layer”.

  Here, in the first embodiment, as shown in FIGS. 1 and 3, at least the resonator end surface portion of the n-type buffer layer 2 formed on the n-type GaN substrate 1 and the n-type buffer layer 2. Resonator end face portions of the n-type cladding layer 3 formed on each are raised. Specifically, in the n-type buffer layer 2 and the n-type cladding layer 3, raised portions 25 are formed on the light emitting end face portion 21 and the light reflecting end face portion 22, respectively. As shown in FIGS. 2 and 3, the light emitting end face portion 21 is composed of the light emitting end face 20a and its vicinity area (area from the light emitting end face 20a to a distance a1 (for example, about 3 μm to about 150 μm)). The light reflection end face portion 22 is a portion composed of the light reflection end face 20b and its vicinity area (area from the light reflection end face 20b to a distance a1 (for example, about 3 μm to about 150 μm)).

  Further, as shown in FIG. 2, the raised portions 25 of the n-type buffer layer 2 and the n-type cladding layer 3 have the resonator end face 20 along the resonator end face 20 (light emitting end face 20a, light reflecting end face 20b). From one end of the resonator to the other end of the resonator end surface 20. For this reason, a part of the raised portion 25 is located below the ridge portion 7. That is, when viewed in a plan view, the raised portion 25 is arranged so as to intersect (orthogonal) the ridge portion 7.

  Further, as shown in FIG. 3, the raised portions 25 of the n-type cladding layer 3 are raised with a size equal to or greater than the thickness of the light emitting layer 4 (for example, about 0.16 μm). Specifically, the raised portion 25 of the n-type cladding layer 3 is configured such that the upper surface thereof is positioned 0.3 μm or more above the upper surface of the portion other than the raised portion 25. As a result, the light emitting layer 4 (active layer 4c) is formed on the n-type cladding layer 3, so that the height on the resonator end face 20 side with respect to the (0001) face of the n-type GaN substrate 1 (on the light emitting end face 20a side). Of the light reflection end face 20b side) is higher than the height of the central portion of the light emitting layer 4 (active layer 4c). Therefore, the active layer 4c (see FIG. 5) is originally provided on the light emitting end surface portion of the light emitting layer 4 (active layer 4c) and the light reflecting end surface portion of the light emitting layer 4 (active layer 4c). An n-type cladding layer 3 having a larger band gap is formed. That is, in the nitride-based semiconductor laser device 100 according to the first embodiment, the end face region of the waveguide is the n-type cladding layer 3 having a band gap larger than that of the active layer 4c.

  In the first embodiment, as described above, the end face region of the waveguide is the n-type cladding layer 3 having a band gap larger than that of the active layer 4c, so that the laser amplified in the active layer 4c. Light is emitted through the n-type cladding layer 3 at the light emission end face portion 21. Thereby, absorption of the laser beam in the light emission end surface part 21 (light emission end surface 20a) is suppressed. Therefore, with the above configuration, a window structure (window region 30; hatched portion in FIG. 2) is formed in the light emitting end surface portion 21 (light emitting end surface 20a) and the light reflecting end surface portion 22 (light reflecting end surface 20b).

  In the nitride semiconductor laser device 100 according to the first embodiment, Si (silicon) is used as the n-type dopant, and Mg (magnesium) is used as the p-type dopant.

  Also, as shown in FIG. 4, on the p-type contact layer 6 constituting the ridge portion 7, a p-side ohmic electrode 8 having a thickness t is formed in a stripe shape (elongated shape). The p-side ohmic electrode 8 is formed so as to be in direct contact with the p-type contact layer 6. Nitride-based semiconductors have the disadvantage that it is difficult to achieve ohmic contact because the resistivity of p-type semiconductors is large and p-type carriers are not easily generated. Therefore, the p-side ohmic electrode 8 is made of Pd, which is a metal material having a large work function, in order to make ohmic contact with the p-type contact layer 6. The thickness t of the p-side ohmic electrode 8 is set to a thickness of 5 nm to 100 nm (for example, about 15 nm).

On both sides of the ridge portion 7, a buried layer 9 for current confinement is formed. Specifically, the thickness is about 0.1 μm to about 0.3 μm (for example, about 0.15 μm) on the p-type cladding layer 5, the side surface of the p-type contact layer 6, and the side surface of the p-side ohmic electrode 8. And a buried layer 9 mainly composed of SiO ₂ is formed. With such a configuration, it becomes possible to perform optical confinement in the horizontal and vertical transverse modes. In addition, since the buried layer 9 may cause a waveguide loss due to light absorption when the thickness is less than 50 nm, the thickness is set to 50 nm or more unless the property (light absorption) is actively used. It is preferable.

  On the upper surface of the buried layer 9, a p-side pad electrode 10 having a larger area than the p-side ohmic electrode 8 is formed so as to cover a part of the p-side ohmic electrode 8. As shown in FIGS. 1 to 4, the p-side pad electrode 10 is in direct contact with the p-side ohmic electrode 8 in a portion covering a part of the p-side ohmic electrode 8. The p-side pad electrode 10 has a multilayer structure in which a Ti layer (not shown), a Mo layer (not shown), and an Au layer (not shown) are sequentially stacked from the buried layer 9 side. Further, since the p-side pad electrode 10 supplies current to the p-side ohmic electrode 8 from the outside, the p-side pad electrode 10 is configured to have a low electrical resistance (film resistance). Specifically, the p-side pad electrode 10 is configured to have a thickness larger than the thickness t of the p-side ohmic electrode 8 described above. More specifically, the p-side pad electrode 10 is set to a total thickness of about 0.2 μm. Thereby, current can be injected substantially uniformly into the p-side ohmic electrode 8 without causing a voltage drop.

  Further, as shown in FIG. 2, the p-side pad electrode 10 is formed in a substantially rectangular shape in plan view. The p-side pad electrode 10 is disposed in a region separated from the resonator end face 20 (light emitting end face 20a, light reflecting end face 20b) by a predetermined distance.

  Further, as shown in FIGS. 1, 3 and 4, on the back surface of the n-type GaN substrate 1, an Hf layer (not shown) and an Al layer (not shown) are sequentially formed from the back surface side of the n-type GaN substrate 1. The n-side electrode 11 having a multi-layered structure is formed. Further, the n-side electrode 11 has a multilayer structure in which an Mo layer (not shown), a Pt layer (not shown), and an Au layer (not shown) are sequentially stacked from the n-side electrode 11 side. An n-side pad electrode 12 is formed. The n-side pad electrode 12 is formed to facilitate mounting on a submount (not shown) or the like.

  As shown in FIGS. 2 and 3, for example, an aluminum nitride layer (not shown) and an aluminum oxide layer (not shown) are laminated on the light emitting end face 20a from the light emitting end face 20a side. An AR (Anti-Reflection) coating layer 40 composed of layers is formed. On the other hand, on the light reflection end face 20b, for example, an HR (High-Reflection) coating layer 50 in which a total of nine silicon oxide layers (not shown) and titanium oxide layers (not shown) are alternately laminated is formed. ing.

  In the nitride-based semiconductor laser device 100 according to the first embodiment, as described above, the laser light is emitted from the light emitting end face portion 21 through the n-type cladding layer 3, thereby forming the n-type cladding layer. 3 has a band gap larger than that of the active layer 4c, so that the laser light can be prevented from being absorbed by the light emitting end face portion 21 (light emitting end face 20a). That is, by configuring as described above, the window structure (window region 30) can be formed in the light emitting end face portion 21 of the nitride-based semiconductor laser device 100. Thereby, since the COD level of the nitride-based semiconductor laser device 100 can be improved, the generation of COD can be suppressed even when driven at a high output. Further, by suppressing the generation of COD, it is possible to suppress a decrease in reliability due to COD. As a result, in the nitride-based semiconductor laser device 100, high output can be achieved and high reliability can be obtained.

  In the first embodiment, in the light emitting layer 4 (active layer 4c) formed on the n-type cladding layer 3, the height of the light reflection end face 20b side with respect to the (0001) plane of the n-type GaN substrate 1 is light emission. By configuring the layer 4 (active layer 4c) so as to be higher than the height of the central portion, not only the light emission end face 20a but also the light absorption at the light reflection end face 20b can be reduced. That is, when the laser light is amplified, the light reflection end face portion 22 reaches the light reflection end face 20b via the n-type cladding layer 3 having a band gap larger than that of the active layer 4c, and the laser reflection light is reflected by the light reflection end face 20b. Therefore, light absorption at the light reflecting end face 20b is reduced.

  In the first embodiment, the laser light is emitted through the n-type cladding layer 3 so that the laser light is emitted through the p-type cladding layer 5. As compared with, light absorption in the window region 30 can be effectively suppressed. That is, when the laser beam is configured to be emitted through the p-type cladding layer 5, Mg that causes light absorption as the p-type dopant is doped, so that light absorption in the window region 30 is effectively performed. There is an inconvenience that it becomes difficult to suppress. On the other hand, when the laser light is configured to be emitted through the n-type cladding layer 3, the above inconvenience can be solved.

  6 to 20 are views for explaining a method of manufacturing the nitride-based semiconductor laser device according to the first embodiment of the present invention. A method for manufacturing the nitride-based semiconductor laser device 100 according to the first embodiment of the present invention is now described with reference to FIGS.

First, an SiO ₂ layer (not shown) having a thickness of about 1 μm is formed on the entire upper surface of the n-type GaN substrate (semiconductor wafer) 1 by using a sputtering method or the like. Next, stripe-like openings (not shown) as resist patterns are formed on the SiO ₂ layer at a pitch of about 650 μm to about 1550 μm (resonator length L + 50 μm) by using a photolithography technique. Next, by removing a predetermined region of the SiO ₂ layer by dry etching, a stripe-shaped opening is formed in the SiO ₂ layer. Thereafter, the resist pattern is removed. Then, using a dry etching technique such as RIE (Reactive Ion Etching), the n-type GaN substrate 1 is etched using the SiO ₂ layer as a mask, thereby removing a predetermined region of the n-type GaN substrate 1. Thereafter, using an etchant such as HF (hydrofluoric acid), the SiO ₂ layer is removed and impurities on the surface are removed by pretreatment.

  As a result, as shown in FIG. 6, a plurality of grooves 1 a that are spaced from each other by a predetermined distance and extend in the same direction are formed on the upper surface of the n-type GaN substrate 1. The groove portion 1a continuously extends in the [11-20] direction and is formed in a stripe shape at a distance (pitch) a2 of about 650 μm to about 1550 μm (resonator length L + 50 μm) in the [1-100] direction. As shown in FIG. 7, the plurality of groove portions 1a are formed so that at least one of the depth d1 and the width w in the thickness direction of the n-type GaN substrate 1 is 1 μm or more. Specifically, for example, when a 2-inch substrate is used as the n-type GaN substrate (semiconductor wafer) 1, the groove portion 1a has a depth d in the thickness direction of the n-type GaN substrate 1 of about 1 mm due to its in-plane distribution. It is formed so as to be 1.5 μm to about 2 μm, and is formed so that the width w is about 2 μm to about 2.5 μm.

Next, as shown in FIGS. 8 to 10, a nitride-based semiconductor layer is grown on the n-type GaN substrate 1 using MOCVD. Specifically, an n-type buffer layer 2 made of n-type GaN having a thickness of about 0.1 μm to about 10 μm (for example, about 4 μm) is formed on the upper surface of the n-type GaN substrate 1 (on the (0001) plane). An n-type cladding layer 3 and a light-emitting layer 4 made of n-type Al _0.05 Ga _0.95 N having a thickness of 0.5 μm to about 3.0 μm (for example, about 2 μm) are sequentially grown.

When the light emitting layer 4 is grown, as shown in FIG. 5, first, n-type GaN having a thickness of 0 to about 0.2 μm (for example, about 0.1 μm) is formed on the n-type cladding layer 3. A lower guide layer 4e made of is grown. Next, on the lower guide layer 4e, four barrier layers 4b made of In _x2 Ga _1-x2 N (x2 = 0 to 0.05) having a thickness of about 8 nm, and In _x1 Ga having a thickness of about 4 nm are formed. Three quantum well layers 4a made of _1-x1 N (x1 = 0.05 to 0.1) are alternately grown. As a result, an active layer 4c having an MQW structure composed of three quantum well layers 4a and four barrier layers 4b is formed on the lower guide layer 4e. Then, on the active layer 4c, an evaporation preventing layer 4d made of p-type Al _0.3 Ga _0.7 N having a thickness of 0 to about 0.02 μm (for example, about 0.01 μm), 0 to about 0.2 μm (for example, about 0.00). The upper guide layer 4f made of p-type GaN having a thickness of 1 μm is sequentially grown. Thus, the light emitting layer 4 including the active layer 4c, the evaporation preventing layer 4d, the lower guide layer 4e, and the upper guide layer 4f is formed on the n-type cladding layer 3.

Subsequently, as shown in FIG. 9 and FIG. 10, p-type Al _0.05 Ga having a thickness of about 0.1 μm to about 1.0 μm (for example, about 0.5 μm) is formed on the light emitting layer 4 using the MOCVD method. _A p-type cladding layer 5 made of _0.95 N and a p-type contact layer 6 made of p-type GaN having a thickness of about 0.01 μm to about 1.0 μm (for example, about 0.05 μm) are successively grown. Further, Si is used as an n-type dopant when growing an n-type nitride-based semiconductor layer, and Mg is used as a p-type dopant when growing a p-type nitride-based semiconductor layer. The n-type buffer layer 2, the n-type cladding layer 3, the light emitting layer 4, the p-type cladding layer 5 and the p-type contact layer 6 are examples of the “nitride-based semiconductor layer” in the present invention.

  Here, in the first embodiment, the groove 1a is formed on the upper surface of the n-type GaN substrate 1, and the nitride-based semiconductor layer is formed on the upper surface of the n-type GaN substrate 1 on which the groove 1a is formed using the MOCVD method. As shown in FIGS. 8 and 10, the region near the groove of the nitride-based semiconductor layer can be raised. Specifically, in groove portion 1a, at least one of depth d and width w is 1 μm or more, so that raised portion 25 is formed in the vicinity of the groove portion of the nitride-based semiconductor layer.

  Further, as shown in FIG. 8, the groove portion 1 a is formed on the upper surface of the n-type GaN substrate 1 so that the raised portion 25 in the n-type cladding layer 3 is raised with a size larger than the thickness of the light emitting layer 4. . Specifically, the raised portion 25 of the n-type cladding layer 3 is set such that the difference a3 between the upper surface of the raised portion 25 of the n-type cladding layer 3 and the upper surface of the portion other than the raised portion 25 is 0.3 μm or more. Form. By setting at least one of the depth d and the width w of the groove 1a to 1 μm or more, the difference a3 between the upper surface of the raised portion 25 of the n-type cladding layer 3 and the upper surface of the portion other than the raised portion 25 is set to 0. It becomes possible to make it 3 μm or more.

  In the first embodiment, after forming the groove portion 1 a on the upper surface of the n-type GaN substrate 1, a nitride-based semiconductor layer is grown on the upper surface of the n-type GaN substrate 1 using the MOCVD method. On the groove portion 1a of the GaN substrate 1, growth proceeds from various directions to cause defects at the growth meeting portion, while growth proceeds regularly on regions other than the groove portion 1a, and growth association with defects is suppressed. . For this reason, since the generation of new defects is suppressed in the region near the groove, a crystal with few defects can be obtained.

Next, as shown in FIG. 11, a stripe shape (elongated shape) having a width of about 1 μm to about 3 μm (for example, about 1.5 μm) and extending in the [1-100] direction on the p-type contact layer 6. The SiO ₂ layer 60 is formed. Then, as shown in FIG. 12, the RIE (reactive ion etching) method using a chlorine-based gas such as SiCl ₄ or Cl ₂ or Ar gas is used to form the p-type cladding layer 5 using the SiO ₂ layer 60 as a mask. Etching is performed up to a halfway depth. Thus, a striped (elongated) ridge portion 7 extending in the [1-100] direction is formed along with the convex portion of the p-type cladding layer 5 and the p-type contact layer 6. Thereafter, the SiO ₂ layer 60 is removed.

Subsequently, as shown in FIG. 13, a SiO ₂ layer 9a having a thickness of about 0.1 μm to about 0.3 μm (for example, about 0.15 μm) is formed on the entire surface by sputtering or the like. Then, the upper surface portion of the ridge portion 7 of the SiO ₂ layer 9a is removed by using a photolithography technique and an etching technique. As a result, an opening 9b is formed in the SiO ₂ layer 9a, the upper surface (p-type contact layer 6) of the ridge portion 7 is exposed, and buried layers 9 made of SiO ₂ are formed on both sides of the ridge portion 7. Is done.

  Thereafter, a resist (not shown) is formed in a region other than the upper portion of the ridge portion 7, and a p-side ohmic electrode made of Pd is formed on the p-type contact layer 6 by using, for example, EB vapor deposition. At this time, the p-side ohmic electrode is formed so that its thickness t is 5 nm to 100 nm (for example, 15 nm). Then, the resist (not shown) is removed by lift-off. The p-side ohmic electrode 8 thus formed is shown in FIG.

  After forming the p-side ohmic electrode on the entire upper surface of the n-type GaN substrate 1, the portions other than the upper portion of the ridge portion 7 are removed by using a photolithography technique and an etching technique, so that the p-type contact layer 6 is p-type. The side ohmic electrode 8 may be formed.

  Next, a resist (not shown) is formed on the entire upper surface of the n-type GaN substrate 1 on which the buried layer 9 is formed, and a part of the ridge portion 7 (p-side ohmic electrode 8) is formed using photolithography technology. A plurality of openings are formed to expose a predetermined region including. Then, on the n-type GaN substrate 1 on which a resist (not shown) is formed, a Ti layer (not shown), an Mo layer (not shown), and an Au layer are used from the substrate side using a vacuum deposition method or the like. By sequentially forming (not shown), a p-side pad electrode having a multilayer structure is formed. Thereafter, the resist is removed by lift-off. Thereby, as shown in FIG. 15, the p-side pad electrode 10 is formed so as to cover a part of the p-side ohmic electrode 8 (in direct contact with a part of the upper surface of the p-side ohmic electrode 8). As shown in FIG. 2, the p-side pad electrode 10 is formed in a substantially rectangular shape when seen in a plan view.

  Subsequently, in order to facilitate separation of the substrate (semiconductor wafer), the back surface of the n-type GaN substrate 1 is ground or polished so that the n-type GaN substrate 1 has a thickness of about 80 μm to about 150 μm (for example, about 100 μm). make it thin. Then, the surface is adjusted by dry etching or the like on the ground or polished surface.

  Next, as shown in FIG. 16, an Hf layer (not shown) and an Al layer (not shown) are formed on the back surface of the n-type GaN substrate 1 from the back surface side of the n-type GaN substrate 1 using a vacuum deposition method or the like. ) Are sequentially formed to form the n-side electrode 11 having a multilayer structure. Then, an Mo layer (not shown), a Pt layer (not shown), and an Au layer (not shown) are sequentially formed on the n-side electrode 11 from the n-side electrode 11 side, so that n having a multilayer structure is formed. The side pad electrode 12 is formed. The n-side pad electrode 12 is formed so as to cover the n-side electrode 11. Note that before the n-side electrode 11 is formed, dry etching or wet etching may be performed for the purpose of adjusting the electrical characteristics of the n-side.

  Through the above steps, as shown in FIG. 17, a plurality of elements (nitride semiconductor laser elements) are formed on the substrate (semiconductor wafer). A window region 30 (shaded portion) is formed in the region near the groove 1a by raising the region near the groove of the nitride-based semiconductor layer grown on the n-type GaN substrate 1.

  Next, the substrate (semiconductor wafer) is separated by cleavage to form the resonator end face 20 (see FIGS. 1 and 2). As shown in FIGS. 17 and 18, the substrate (semiconductor wafer) is cleaved by a distance a4 (see FIG. 18) of about 5 μm from the groove 1a by using a scribing / breaking method or a laser scribing method. This is performed along the separation line (scheduled separation line) P1. Thereby, as shown in FIG. 19, the substrate (semiconductor wafer) is separated at the position of the separation line P1, and the resonator end face 20 along the [11-20] direction is formed. Further, by separating the substrate (semiconductor wafer), the resonator end surface 20 to be the light emitting end surface 20a of one element (chip) and the resonator end surface to be the light reflecting end surface 20b of the other adjacent element (chip). 20 are formed simultaneously. In addition, a window structure (window region 30) is formed in the resonator end face portion (light emitting end face portion 21, light reflecting end face portion 22). Note that a bar-like element 70 as shown in FIG. 19 is obtained by the above-described separation step. Further, the portion of the substrate (semiconductor wafer) where the groove 1a is formed is removed by the separation step.

  Then, as shown in FIG. 20, a coating is applied to the end face (resonator end face 20) of the bar-like element 70 by using a technique such as vapor deposition or sputtering. Specifically, the AR coating layer 40 composed of two layers in which, for example, an aluminum nitride layer (not shown) and an aluminum oxide layer (not shown) are laminated on the light emitting end face 20a from the light emitting end face 20a side. Form. Further, for example, an HR coating layer 50 in which nine layers of silicon oxide layers (not shown) and titanium oxide layers (not shown) are alternately stacked is formed on the light reflecting end face 20b.

  Finally, the bar-shaped element 70 is separated by a separation line P2 along the [1-100] direction, so that individual chips (elements) are separated. Thus, the nitride-based semiconductor laser device 100 according to the first embodiment of the present invention shown in FIG. 1 is manufactured.

  The nitride semiconductor laser device 100 according to the first embodiment is actually manufactured by the above manufacturing method, and the nitride semiconductor laser device 100 is mounted on a laser stem via a submount to measure characteristics. did. A nitride-based semiconductor laser device manufactured without forming a groove in an n-type GaN substrate was used as a comparative example. The nitride-based semiconductor laser device according to the comparative example was manufactured by the same method as the manufacturing method according to the first embodiment except that no groove was formed in the n-type GaN substrate.

  As a result, the nitride semiconductor laser device according to the comparative example had a COD level of 400 mW, whereas the nitride semiconductor laser device 100 according to the first embodiment had a COD level of 600 mW, and good results were obtained. It was. Further, during aging under conditions of 80 ° C. and 105 mW, the COD level after elapse of 500 hours was 200 mW in the nitride semiconductor laser device according to the comparative example, whereas the nitride system according to the first embodiment was used. In the semiconductor laser element 100, it was 400 mW or more. From this, it was confirmed that in the nitride-based semiconductor laser device 100 according to the first embodiment, the decrease in COD level (change over time) is reduced.

  Further, when a nitride-based semiconductor laser device was fabricated using a vapor phase growth method other than the MOCVD method, the manufacturing yield was about 50%, whereas the MOCVD method was used for the vapor phase growth method. In the manufacturing method according to the first embodiment, the manufacturing yield was about 60%, and a good result was obtained.

  In the method of manufacturing the nitride-based semiconductor laser device 100 according to the first embodiment, as described above, the stripe-shaped groove portion continuously extending in the [11-20] direction on the upper surface of the n-type GaN substrate (semiconductor wafer) 1. 1a is formed, and the nitride semiconductor layers 2 to 6 are grown on the upper surface of the n-type GaN substrate (semiconductor wafer) 1 by using the MOCVD method, thereby rising to the region near the groove of the nitride semiconductor layer. The portion 25 can be formed. Then, by separating the region near the groove portion of the n-type GaN substrate 1 along the groove portion 1a by cleaving, the raised portion 25 of the nitride-based semiconductor layer can be disposed on the separation surface portion. In addition, the light emitting layer 4 (active layer 4c) is disposed on the n-type cladding layer 3, and the separation surface is configured to be the resonator end surface 20 (light emitting end surface 20a, light reflecting end surface 20b). The height of the light emitting layer 4 (active layer 4c) on the resonator end face 20 side (light emitting end face 20a side, light reflecting end face 20b side) with respect to the upper surface ((0001) face) of the n-type GaN substrate 1 is higher than the height of the central portion. Can be configured to be higher. As a result, it is possible to form the nitride-based semiconductor laser device 100 in which laser light is emitted from the light emitting end face portion 21 via the n-type cladding layer 3 having a band gap larger than that of the active layer 4c. Therefore, since it is possible to suppress the laser light from being absorbed by the light emitting end face 20a, the nitride semiconductor laser element 100 in which the window structure (window region 30) is formed on the light emitting end face portion 21 is manufactured. Can do. As a result, the window structure (window region 30) formed in the light emitting end face portion 21 can improve the COD level, so that it is possible to achieve high output and a highly reliable nitride semiconductor laser. The element 100 can be manufactured.

  In the first embodiment, each of the nitride-based semiconductor layers 2 to 6 is grown on the n-type GaN substrate (semiconductor wafer) 1 in which the groove 1a is formed by using the MOCVD method. On the groove portion 1a of the semiconductor wafer 1, growth proceeds from various directions and defects occur in the growth meeting portion, while growth progresses regularly on the region other than the groove portion 1a, thereby suppressing growth association with defects. It is done. For this reason, since the generation of new defects is suppressed in the region near the groove, a crystal with few defects can be obtained. Thereby, since the crystallinity of the light emission end surface portion 21 and the light reflection end surface portion 22 can be improved, the crystallinity of the window region 30 can be improved. Therefore, light absorption at the light emitting end face portion 21 and the light reflecting end face portion 22 can be suppressed, and an increase in operating current can be suppressed. As a result, deterioration of element characteristics can be suppressed.

  In the first embodiment, as described above, since the window region 30 with good crystallinity can be formed, the change in COD level with time can be reduced, and the COD level can be further improved. it can. Thereby, the nitride semiconductor laser element 100 with high reliability can be easily manufactured.

  In the first embodiment, the MOCVD method is used to grow the nitride-based semiconductor layers 2 to 6, and in the MOCVD method, molecules on the substrate surface (main surface) are compared to other vapor phase growth methods. Therefore, the control range of the swell in the region near the groove can be widened, and the swell portion 25 can be formed with high accuracy. As a result, the window structure (window region 30) can be easily formed, so that high output can be achieved, and deterioration of element characteristics can be suppressed, and reliability can be improved. High nitride semiconductor laser device 100 can be manufactured with high yield.

  In the first embodiment, the groove portion of the nitride-based semiconductor layer (n-type cladding layer 3) can be easily formed by configuring the depth d of the groove portion 1a to be 1 μm or more (for example, about 1.5 μm to about 2 μm). A raised portion 25 capable of forming a window structure (window region 30) can be formed in the vicinity region.

  Further, in the first embodiment, by configuring the width w of the groove 1a to be 1 μm or more (for example, about 2 μm to about 2.5 μm), the vicinity of the groove of the nitride-based semiconductor layer (n-type cladding layer 3) can be easily obtained. A raised portion 25 capable of forming a window structure (window region 30) can be formed in the region. If each of the depth d of the groove portion 1a and the width w of the groove portion 1a is configured to be 1 μm or more, a window structure (window) can be more easily formed in a region near the groove portion of the nitride-based semiconductor layer (n-type cladding layer 3). A raised portion 25 capable of forming the region 30) can be formed.

  In the first embodiment, by forming the plurality of groove portions 1a continuously extending in the same direction at a distance a2, it is possible to introduce a complicated process without greatly increasing the number of existing processes. In addition, the nitride-based semiconductor laser device 100 according to the first embodiment can be manufactured.

(Second Embodiment)
FIG. 21 is a plan view of a nitride-based semiconductor laser device according to the second embodiment of the present invention. 22 is a cross-sectional view taken along line B2-B2 in FIG. 21, and FIG. 23 is a cross-sectional view taken along line A2-A2 in FIG. Next, the structure of the nitride-based semiconductor laser device 200 according to the second embodiment of the present invention will be described with reference to FIGS. 5 and 21 to 23.

  The nitride semiconductor laser device 200 according to the second embodiment includes two ridge stripes 207 extending in parallel with each other, as shown in FIGS. The ridge stripe 207 includes a ridge portion 207 a that functions as a current path portion to the light emitting layer 4 and a dummy ridge portion 207 b that does not function as a current path portion to the light emitting layer 4.

  Specifically, as shown in FIG. 22, the p-type cladding layer 5 formed on the light emitting layer 4 is provided with two convex portions arranged at a predetermined distance from each other. A p-type contact layer 6 (6a and 6b) is formed on each convex portion. Then, a stripe (elongated) having a width of about 1 μm to about 3 μm (for example, about 1.5 μm) is formed by the convex portion of the p-type cladding layer 5 and the p-type contact layer 6 formed on the convex portion. A ridge portion 207a and a dummy ridge portion 207b are configured.

On the p-type contact layer 6a (6) constituting the ridge portion 207a, the p-side ohmic electrode 8 is formed in a stripe shape (elongated shape). Also, buried layers 9 for current confinement are formed on both sides of the ridge portion 207a. Specifically, the thickness is about 0.1 μm to about 0.3 μm (for example, about 0.15 μm) on the p-type cladding layer 5, the side surface of the p-type contact layer 6, and the side surface of the p-side ohmic electrode 8. And a buried layer 9 mainly composed of SiO ₂ is formed. On the upper surface of the buried layer 9, a p-side pad electrode 10 having a larger area than the p-side ohmic electrode 8 is formed so as to cover a part of the p-side ohmic electrode 8. The p-side pad electrode 10 is in direct contact with the p-side ohmic electrode 8 in a portion covering a part of the p-side ohmic electrode 8.

  On the other hand, unlike the ridge portion 207a, the dummy ridge portion 207b is configured such that the p-side ohmic electrode 8 is not formed on the p-type contact layer 6b (6) constituting the dummy ridge portion 207b. Further, the buried layer 9 covers the side surface and the upper surface of the dummy ridge portion 207b. The p-side pad electrode 10 is formed on the dummy ridge portion 207b via the buried layer 9. As a result, no current is supplied to the dummy ridge portion 207b.

  Therefore, with the above configuration, the ridge portion 207a functions as a current path portion to the light emitting layer 4 (active layer), while the dummy ridge portion 207b does not function as a current path portion to the light emitting layer 4 (active layer). .

  As shown in FIGS. 21 and 23, a window structure (window region 230; hatched portion) is formed on the light emitting end face portion 21 of the ridge portion 207a functioning as a current passage portion. Specifically, at least in the n-type buffer layer 2 and the n-type cladding layer 3, a raised portion 25 is formed on a part of the light emitting end face portion 21. The raised portion 25 is formed so as to intersect with the ridge portion 207a when viewed in plan. Then, by forming the light emitting layer 4 (active layer) on the n-type cladding layer 3, the height of the light emitting end face 20a side with respect to the (0001) plane of the n-type GaN substrate 1 is set to be the light emitting layer 4 (active layer). ) Is higher than the center height. Therefore, the n-type cladding layer 3 having a band gap larger than that of the active layer 4c (see FIG. 5) is originally formed on the light emitting end face portion of the light emitting layer 4 (active layer). Thereby, the laser light amplified in the active layer 4 c is emitted through the n-type cladding layer 3 at the light emitting end face portion 21.

  Further, as shown in FIG. 21, a groove 1 b is formed on the upper surface of the n-type GaN substrate 1. The groove portion 1b is formed on the light reflection end face 20b side of the dummy ridge portion 207b that does not function as a current passage portion. Further, the groove portion 1b is formed so as to intersect with the dummy ridge portion 207b in a plan view while not intersecting with the ridge portion 207a functioning as a current passage portion. In the manufacturing method described later, the groove 1b is formed by raising a part of the n-type buffer layer 2 and the n-type cladding layer 3 of the nitride semiconductor laser element adjacent in the [1-100] direction, thereby forming the adjacent nitride. This is provided to form the window region 230 in the semiconductor laser device. For this reason, the groove 1b is formed so that at least one of the depth and the width is 1 μm or more. Specifically, the groove 1b has a depth of about 1.5 μm to about 2 μm and a width (width in the [1-100] direction) of about 2 μm to about 2.5 μm. It is formed to become. The length of the groove 1b in the [11-20] direction is about 5 μm to about 7 μm. The groove portion 1b is formed in a region separated from the resonator end face 20 (light reflection end face 20b) by a distance a4 (about 5 μm).

  In addition, the nitride-based semiconductor laser device 200 according to the second embodiment has a length of about 600 μm to about 1500 in a direction ([1-100] direction) orthogonal to the resonator end face 20 as in the first embodiment. L (resonator length L) and a width W (resonator width W) of about 80 μm to about 300 μm in the direction along the resonator end face 20 ([11-20] direction).

  Other configurations of the second embodiment are the same as those of the first embodiment.

  24 to 35 are views for explaining a method of manufacturing a nitride-based semiconductor laser device according to the second embodiment of the present invention. Next, with reference to FIG. 21 and FIGS. 24-35, the manufacturing method of the nitride-type semiconductor laser element 200 by 2nd Embodiment of this invention is demonstrated.

First, an SiO ₂ layer (not shown) having a thickness of about 1 μm is formed on the entire upper surface of the n-type GaN substrate (semiconductor wafer) 1 by using a sputtering method or the like. Next, openings (not shown) as resist patterns are formed on the SiO ₂ layer at a pitch of about 600 μm to about 1500 μm (resonator length L) using a photolithography technique. Next, an opening is formed in the SiO ₂ layer by removing a predetermined region of the SiO ₂ layer by dry etching. Thereafter, the resist pattern is removed. Then, using a dry etching technique such as RIE (reactive ion etching), the n-type GaN substrate 1 is etched using the SiO ₂ layer as a mask, thereby removing a predetermined region of the n-type GaN substrate 1. Thereafter, using an etchant such as HF (hydrofluoric acid), the SiO ₂ layer is removed and impurities on the surface are removed by pretreatment.

  As a result, as shown in FIG. 24, a plurality of grooves 1 b are formed on the upper surface of the n-type GaN substrate 1. The groove 1b is intermittently formed in the [11-20] direction at a distance (pitch) b1 of about 80 μm to about 300 μm (resonator width W). Further, the groove portion 1b is formed in the [1-100] direction with a distance b2 of about 600 μm to about 1500 μm (resonator length L) as a linear distance. The plurality of grooves 1b are formed so that the length in the [11-20] direction is about 5 μm to about 7 μm, and at least one of the depth and the width is 1 μm or more. Specifically, the groove 1b is formed so that the depth is about 1.5 μm to about 2 μm, and the width in the [1-100] direction is about 2 μm to about 2.5 μm. To do.

  Further, as shown in FIG. 25, the groove 1b is formed in a region separated from the separation line (scheduled separation line) P11 by a distance a4 (about 5 μm), and as shown in FIG. 24, one of the plurality of grooves 1b is formed. The portions (groove portions 1b belonging to odd rows or groove portions 1b belonging to even rows) are formed shifted in the [11-20] direction. As shown in FIG. 24, one groove portion 1b is disposed in the element region surrounded by the separation line P11 (separation line P11 adjacent to each other) and the separation line P2 (separation line P2 adjacent to each other). As a result, a plurality of groove portions 1b are formed.

  Next, using the same method as in the first embodiment, each nitride-based semiconductor layer is sequentially grown on the n-type GaN substrate 1. Specifically, as shown in FIG. 26, an n-type buffer layer 2, an n-type cladding layer 3, a light-emitting layer 4, a p-type cladding layer 5 and a p-type layer are formed on an n-type GaN substrate 1 using MOCVD. The contact layer 6 is grown sequentially.

Then, a striped (elongated) SiO ₂ layer 260 having a width of about 1 μm to about 3 μm (for example, about 1.5 μm) and extending in the [1-100] direction is formed on the p-type contact layer 6. .

Here, in the second embodiment, two SiO ₂ layers 260 are formed on a single element at a predetermined distance from each other.

Thereafter, etching is performed to a depth in the middle of the p-type cladding layer 5 using the SiO ₂ layer 260 as a mask by using a RIE (reactive ion etching) method using a chlorine-based gas such as SiCl ₄ or Cl ₂ or Ar gas. . As a result, the ridge stripe 207 formed by the convex portion of the p-type cladding layer 5 and the p-type contact layer 6 and extending in the [1-100] direction is surrounded by the separation line P11 and the separation line P2. Two are formed in the region. Then, the SiO ₂ layer 260 is removed. The ridge stripe 207 thus formed is shown in FIG.

  Further, as shown in FIG. 28, the ridge stripe 207 formed as described above is configured such that any one of the ridge stripes 207 and the groove portion 1b intersect each other in plan view in one element region. The As a result, the window region 230 (shaded portion) is formed in the element adjacent in the [1-100] direction.

Subsequently, as shown in FIG. 29, a SiO ₂ layer 9a having a thickness of about 0.1 μm to about 0.3 μm (for example, about 0.15 μm) is formed on the entire surface by sputtering or the like.

Next, as shown in FIG. 30, on the SiO ₂ layer 9a, after forming a resist 270 having an opening 270a, by etching the SiO ₂ layer 9a the resist 270 as a mask, the SiO ₂ layer 9a Ridge The upper surface portion of the stripe 207 is removed. At this time, as shown in FIG. 31, in the element region surrounded by the separation line P11 and the separation line P2, do not remove the upper surface portion of the ridge stripe 207 that intersects the groove 1b in plan view. To do. Thus, as shown in FIGS. 30 and 31, the SiO ₂ layer 9a is removed to form an opening 9c, and the upper surface (p-type contact layer 6) of one of the ridge stripes 207 is formed in the element region. ) Is exposed.

Further, buried layers 9 (hatched portions in FIG. 31) made of SiO ₂ are formed on both sides of the ridge stripe 207 whose upper surface is exposed. In the element region, the ridge stripe 207 with the upper surface exposed is a ridge portion 207a that functions as a current path portion, and the ridge stripe 207 with the upper surface not exposed is a dummy ridge portion 207b that does not function as a current path portion. Become. In other words, the plurality of ridge stripes 207 are respectively formed into a ridge portion 207a and a dummy ridge portion 207b. As shown in FIG. 31, in the second embodiment, the opening 9c of the SiO ₂ layer 9a is formed from one separation line P11 to the other separation line P11 in the separation lines P11 adjacent to each other.

  Then, as shown in FIG. 32, the p-side ohmic electrode 8 made of Pd is formed on the p-type contact layer 6a (6) of the ridge 207a by using the same method as in the first embodiment.

  Thereafter, as shown in FIG. 33, using the same method as in the first embodiment, a part of the p-side ohmic electrode 8 is covered (directly in contact with a part of the upper surface of the p-side ohmic electrode 8). The p-side pad electrode 10 is formed.

  Subsequently, as shown in FIG. 34, the back surface of the n-type GaN substrate 1 is ground or polished in the same manner as in the first embodiment, so that the n-type GaN substrate 1 is about 80 μm to about 150 μm (for example, about 100 μm). ) To the thickness of Then, the surface is adjusted by dry etching or the like on the ground or polished surface. Next, the n-side electrode 11 and the n-side pad electrode 12 are sequentially formed from the n-type GaN substrate 1 side on the back surface of the n-type GaN substrate 1 using the same method as in the first embodiment.

  Through the above steps, as shown in FIG. 35, a plurality of elements (nitride semiconductor laser elements) are formed on the substrate (semiconductor wafer). In each of the plurality of elements (nitride semiconductor laser elements), a window region 230 (shaded portion) is formed by the groove 1b.

  Thereafter, using the same method as in the first embodiment, the substrate (semiconductor wafer) is cleaved at the separation line P11 separated from the groove 1b by a distance a4 (about 5 μm; see FIG. 25), and then the resonance formed by cleavage. An AR coating layer (not shown) and an HR coating layer (not shown) are formed on the end face of the vessel.

  Finally, the chip is separated into individual chips (elements) by cleaving (separating) along the [1-100] direction along the separation line P2. In this manner, the nitride-based semiconductor laser device 200 according to the second embodiment of the present invention shown in FIG. 21 is manufactured.

  The nitride semiconductor laser device 200 according to the second embodiment is actually manufactured by the above manufacturing method, and the nitride semiconductor laser device 200 is mounted on a laser stem via a submount to measure characteristics. did.

  As a result, the COD level of the nitride-based semiconductor laser device 200 according to the second embodiment was 600 mW, and good results were obtained as in the first embodiment. Further, during aging under conditions of 80 ° C. and 105 mW, the COD level after 500 hours is also 400 mW or more, and the nitride-based semiconductor laser device 200 according to the second embodiment is similar to the first embodiment. It was confirmed that the decrease (change with time) of the COD level was reduced.

  In the second embodiment, as described above, the grooves 1b are intermittently formed, thereby disposing the plurality of grooves 1b at predetermined positions on the upper surface (main surface) of the n-type GaN substrate 1 in this case. However, the nitride-based semiconductor laser device 200 can be manufactured without greatly increasing the number of existing processes and without introducing complicated processes.

  In the second embodiment, the raised portions 25 are formed in the nitride-based semiconductor layer (n-type cladding layer 3) of the adjacent nitride-based semiconductor laser device by disposing the plurality of grooves 1b at predetermined positions. Therefore, unlike the first embodiment, the nitride-based semiconductor laser device 200 can be manufactured without removing the portion of the substrate (semiconductor wafer) where the groove 1b is formed. Thereby, since the substrate (semiconductor wafer) can be used without waste (efficiently), the number of nitride-based semiconductor laser elements 200 obtained from one substrate (semiconductor wafer) is increased. Can do. As a result, the manufacturing yield can be improved, and the manufacturing cost of the nitride semiconductor laser element 200 can be reduced. Actually, when the nitride-based semiconductor laser device 200 was manufactured using the method according to the second embodiment, the cost could be reduced by about 20% compared to the first embodiment.

  In the second embodiment, by forming the ridge portion 207a functioning as a current path portion and the dummy ridge portion 207b not functioning as a current path portion, it can be easily obtained from one substrate (semiconductor wafer). Since the number of nitride-based semiconductor laser elements 200 (the number that can be obtained) can be increased, the manufacturing yield can be easily improved, and the manufacturing cost of the nitride-based semiconductor laser elements 200 can be easily reduced. can do.

  In the nitride-based semiconductor laser device 200 according to the second embodiment, the window region 230 is formed only on the light emitting end face 20a side, but COD usually occurs on the light emitting end face 20a side. As described above, even when the window region 230 is formed only on the light emitting end face 20a side, generation of COD can be suppressed.

  Other effects of the second embodiment are the same as those of the first embodiment.

(Third embodiment)
FIG. 36 is a plan view of a nitride-based semiconductor laser device according to the third embodiment of the invention. Next, the structure of the nitride-based semiconductor laser device 300 according to the third embodiment of the present invention will be described with reference to FIG.

  Similar to the second embodiment, the nitride-based semiconductor laser device 300 according to the third embodiment includes a ridge portion 207a that functions as a current path portion and a dummy ridge portion 207b that does not function as a current path portion. In the third embodiment, a window structure (window region 230; hatched portion) is formed on both the light emitting end face portion 21 and the light reflecting end face portion 22 of the ridge portion 207a. Further, a groove portion 1 c is formed on the upper surface of the n-type GaN substrate 1. Unlike the second embodiment, the groove 1c is formed on both the light emitting end face 20a side and the light reflecting end face 20b side of the dummy ridge part 207b that does not function as a current path part. Each of the groove portions 1c is configured so as to intersect with the dummy ridge portion 207b in plan view, but not to intersect with the ridge portion 207a functioning as a current passage portion.

  In addition, the said groove part 1c has the same shape as the groove part 1b of 2nd Embodiment. Further, the groove 1c on the light emitting end face 20a side is formed in a region separated from the light emitting end face 20a by about 5 μm, and the groove 1c on the light reflecting end surface 20b side is formed in a region separated from the light reflecting end face 20b by about 5 μm. Is formed.

  Other configurations of the third embodiment are the same as those of the second embodiment.

  37 to 39 are plan views for explaining the method for manufacturing the nitride-based semiconductor laser device according to the third embodiment of the invention. Next, with reference to FIGS. 29, 30, and 36 to 39, a method of manufacturing the nitride-based semiconductor laser device 300 according to the third embodiment of the invention will be described.

  First, a plurality of grooves 1c are formed on the upper surface of an n-type GaN substrate (semiconductor wafer) 1 using the same method as in the second embodiment. At this time, in the third embodiment, the plurality of groove portions 1c are formed as shown in FIG. That is, in the third embodiment, the plurality of groove portions 1c are formed such that two groove portions 1c are arranged in the element region surrounded by the separation lines P11 and P2. Thereby, when the resonator end face is formed by the subsequent separation step, the groove 1c is arranged on both the light emitting end face side and the light reflecting end face side. The plurality of grooves 1c are formed so as to be separated from the separation line P11 by a distance of about 5 μm. Each of the plurality of grooves 1c is formed in the same shape (width, depth, length) as in the second embodiment.

  Next, the nitride-based semiconductor layers 2 to 6 are sequentially grown on the n-type GaN substrate 1 using the same method as in the first and second embodiments. Then, using the same method as in the second embodiment, a ridge stripe 207 extending in the [1-100] direction is formed as shown in FIG. Thus, any one of the ridge stripes 207 and the groove 1c intersect each other in plan view in one element region. Since the groove 1c can bulge the region near the groove of the nitride-based semiconductor layer (n-type clad layer 3), the light emitting end face portion 21 and the light reflection in the element adjacent in the [1-100] direction. A window region 230 (shaded portion) can be formed on both end face portions 22.

Subsequently, the upper surface (p-type contact layer) of any ridge stripe 207 in the element region is exposed using the same method as that of the second embodiment shown in FIGS. 29 and 30. As a result, the buried layer 9 made of SiO ₂ is formed on both sides of the ridge stripe 207 with the upper surface exposed. At this time, as shown in FIG. 39, in the element region surrounded by the separation line P11 and the separation line P2, the upper surface portion of the ridge stripe 207 that intersects the groove 1c in plan view is not removed. To do.

  Thereafter, using the same method as in the first and second embodiments, the process is performed up to the step of dividing into individual chips (elements). Thereby, the nitride-based semiconductor laser device 300 according to the third embodiment of the present invention shown in FIG. 36 is manufactured.

  In the third embodiment, as described above, by forming the window region 230 in both the light emitting end surface portion 21 and the light reflecting end surface portion 22 of the ridge portion 207a functioning as a current passage portion, only the light emitting end surface 20a is formed. In addition, since light absorption at the light reflecting end face 20b can be reduced, higher reliability can be obtained. Further, by reducing light absorption not only at the light emitting end face 20a but also at the light reflecting end face 20b, it is possible to further suppress an increase in operating current, thereby further suppressing deterioration in element characteristics.

  Other effects of the third embodiment are the same as those of the first and second embodiments.

  FIG. 40 is a plan view for explaining a nitride-based semiconductor laser device according to a modification of the third embodiment. In the modification of the third embodiment, the portion on the resonator end face side (the portion on the separation line P11 side) of the ridge portion 207a functioning as the current path portion is covered with the buried layer 309 (hatched portion in FIG. 40). For this reason, unnecessary current injection into the resonator end face portion (light emitting end face portion, light reflecting end face portion) is suppressed, so that the COD level can be further improved.

  In the modification of the third embodiment, the upper surface of the ridge stripe 207 is exposed by adopting a configuration in which the portion on the resonator end face side (the portion on the separation line P11 side) of the ridge portion 207a is covered with the buried layer 309. At this time, in the adjacent element region, the upper surface of the ridge stripe 207 that becomes the dummy ridge portion 207b that does not function as the current passage portion can be easily exposed. As a result, it is possible to easily suppress the inconvenience that two light emitting points are formed on the light emitting end surface due to the exposure of a part of the upper surface of the dummy ridge 207b.

  When two light emitting points are produced, when using a nitride-based semiconductor laser element as a light source such as an optical pickup, the alignment is performed with emitted light (EL (Electro-Luminescence) light). Inconvenience occurs.

  The above-described configuration can be obtained by changing the patterning of the opening that exposes the upper surface of the ridge stripe 207. That is, by forming the opening 9d so that the length in the [1-100] direction is equal to or shorter than the length between the adjacent separation lines P11 (resonator length (about 600 μm to about 1500)). The above configuration can be obtained.

  The thickness and composition of the buried layer 309 according to the modification of the third embodiment are the same as those of the buried layer 9 of the first to third embodiments. Other configurations and effects of the modification of the third embodiment are the same as those of the third embodiment.

(Fourth embodiment)
FIG. 41 is a plan view of a nitride semiconductor laser element according to the fourth embodiment of the present invention. 42 is a cross-sectional view taken along line B3-B3 of FIG. Subsequently, the structure of the nitride-based semiconductor laser device 400 according to the fourth embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 41, the nitride-based semiconductor laser device 400 according to the fourth embodiment has a configuration in which a part of the dummy ridge portion 207b is removed from the configuration of the third embodiment shown in FIG. Yes. Specifically, as shown in FIGS. 41 and 42, a dummy ridge portion 407b is formed by removing a portion under the p-side pad electrode 10. Thereby, current supply to the dummy ridge portion 407b can be reliably suppressed.

  The remaining configuration of the dummy ridge portion 407b is the same as that of the third embodiment. The other configurations and effects of the fourth embodiment are also the same as those of the third embodiment.

  43 and 44 are plan views for explaining the method for manufacturing the nitride-based semiconductor laser device according to the fourth embodiment of the present invention. Next, with reference to FIGS. 29, 30, 37, and 41 to 44, a method of manufacturing the nitride-based semiconductor laser device 400 according to the fourth embodiment of the present invention will be described.

  In the method of manufacturing the nitride-based semiconductor laser device 400 according to the fourth embodiment, first, using the same method as that of the third embodiment, the groove 1c similar to that of the third embodiment shown in FIG. (Semiconductor wafer) 1 is formed on the upper surface. Next, the nitride-based semiconductor layers 2 to 6 (see FIG. 42) are sequentially grown on the n-type GaN substrate 1 in which the groove 1c is formed, using the same method as in the first to third embodiments. .

  Next, a ridge stripe 407 as shown in FIG. 43 is formed using the same method as in the second and third embodiments.

  Here, in the fourth embodiment, unlike the second and third embodiments, the ridge stripe 407 is intermittently formed in the [1-100] direction. Thus, the dummy ridge portion 407b (see FIG. 41) is not located in the formation region of the p-side pad electrode 10 (see FIG. 41) in the element region surrounded by the separation line P11 and the separation line P2. can do.

  In the fourth embodiment, the ridge stripe 407 is formed so as to intersect with the groove 1c in plan view at the end thereof. The intermittently formed ridge stripe 407 can be obtained by changing the mask pattern.

Subsequently, the upper surface (p-type contact layer) of the ridge stripe 407 in the element region is exposed using a method similar to that of the second embodiment shown in FIGS. As a result, the buried layer 9 made of SiO ₂ is formed on both sides of the ridge stripe 407 with the upper surface exposed. At this time, as shown in FIG. 44, in the element region surrounded by the separation line P11 and the separation line P2, the upper surface portion of the ridge stripe 407 that intersects the groove portion 1c in plan view is not removed. To do. Thus, in the element region, the ridge stripe 407 with the upper surface exposed becomes a ridge portion 207a that functions as a current path portion, and the ridge stripe 407 without the upper surface exposed has a dummy ridge portion 407b that does not function as a current path portion. It becomes. In other words, the plurality of ridge stripes 407 are configured in a ridge portion 207a and a dummy ridge portion 407b, respectively.

  Thereafter, using the same method as in the first to third embodiments, the process up to the step of dividing into individual chips (elements) is performed. As a result, the nitride-based semiconductor laser device 400 according to the fourth embodiment of the present invention shown in FIG. 41 is manufactured.

  The effect of the manufacturing method of 4th Embodiment is the same as that of the said 1st-3rd embodiment.

  FIG. 45 is a plan view for explaining a nitride-based semiconductor laser device according to a modification of the fourth embodiment. In the modified example of the fourth embodiment, as in the modified example of the third embodiment, the portion on the resonator end face side (the portion on the separation line P11 side) of the ridge portion 207a that functions as the current path portion is embedded in the buried layer 409 ( The hatched portion in FIG. 45 is covered. For this reason, unnecessary current injection into the resonator end face portion (light emitting end face portion, light reflecting end face portion) is suppressed, so that the COD level can be further improved.

  In the modification of the fourth embodiment, the upper surface of the ridge stripe 407 is exposed by adopting a configuration in which the resonator end face side portion (the separation line P11 side portion) of the ridge portion 207a is covered with the buried layer 409. At this time, in the adjacent element region, the upper surface of the ridge stripe 407 that becomes the dummy ridge portion 407b that does not function as a current passage portion can be easily exposed. As a result, it is possible to easily suppress the inconvenience that two light emitting points are formed on the light emitting end surface due to the exposure of a part of the upper surface of the dummy ridge 407b.

  The thickness and composition of the buried layer 409 according to the modification of the fourth embodiment are the same as those of the buried layer 9 of the first to fourth embodiments. Other configurations and effects of the modification of the fourth embodiment are the same as those of the fourth embodiment.

(Fifth embodiment)
FIG. 46 is a plan view of a nitride semiconductor laser element according to the fifth embodiment of the present invention. Next, with reference to FIGS. 36 and 46, the structure of the nitride-based semiconductor laser device 500 according to the fifth embodiment of the invention will be described.

  The nitride-based semiconductor laser device 500 according to the fifth embodiment has a configuration in which the dummy ridge portion 207b is removed from the configuration of the third embodiment shown in FIG. That is, the nitride-based semiconductor laser device 500 according to the fifth embodiment includes only the ridge portion 207a that functions as a current path portion. The remaining configuration of the fifth embodiment is similar to that of the aforementioned third embodiment.

  The effects of the nitride-based semiconductor laser device 500 according to the fifth embodiment are the same as those of the first to fourth embodiments.

  47 and 48 are plan views illustrating the method for manufacturing the nitride-based semiconductor laser device according to the fifth embodiment of the invention. A method for manufacturing the nitride-based semiconductor laser device 500 according to the fifth embodiment of the present invention is now described with reference to FIGS.

  In the method of manufacturing the nitride-based semiconductor laser device 500 according to the fifth embodiment, the ridge stripe is formed so as not to intersect the groove 1c when viewed in plan in the manufacturing method of the fourth embodiment. Specifically, as shown in FIG. 47, the ridge stripe 507 is intermittently formed in the [1-100] direction so that the ridge stripe 507 does not intersect with the groove 1c in plan view. .

  Subsequently, similarly to the fourth embodiment, the upper surface (p-type contact layer) of the ridge stripe 507 is exposed in the element region surrounded by the separation lines P11 and P2. As a result, the ridge stripe 507 whose upper surface is exposed becomes a ridge portion 207a that functions as a current path portion, and therefore only the ridge portion 207a is formed in the element region.

  Thereafter, using the same method as in the first to fourth embodiments, the process up to the step of dividing into individual chips (elements) is performed. Thereby, the nitride-based semiconductor laser device 500 according to the fifth embodiment of the present invention shown in FIG. 46 is manufactured.

  The effect of the manufacturing method of 5th Embodiment is the same as that of the said 1st-4th embodiment.

  FIG. 49 is a plan view for explaining a nitride-based semiconductor laser device according to a modification of the fifth embodiment. In the modification of the fifth embodiment, as in the modifications of the third and fourth embodiments, the portion on the resonator end face side (the portion on the separation line P11 side) of the ridge portion 207a that functions as the current passage portion is embedded. It is covered with a layer 509 (hatched portion in FIG. 49). For this reason, unnecessary current injection into the resonator end face portion (light emitting end face portion, light reflecting end face portion) is suppressed, so that the COD level can be further improved.

  The thickness and composition of the buried layer 509 according to the modification of the fifth embodiment are the same as those of the buried layer 9 of the first to fourth embodiments. Other configurations and effects of the modified example of the fifth embodiment are the same as those of the fifth embodiment.

  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 fifth embodiments, the example in which the laser beam is emitted through the n-type cladding layer is shown. However, the present invention is not limited to this, and the band gap is larger than that of the active layer. If the nitride-based semiconductor layer is large, the laser light may be emitted through a layer other than the n-type cladding layer.

  In the first to fifth embodiments, an example in which a nitride semiconductor laser element is formed using an n-type substrate has been described. However, the present invention is not limited thereto, and nitridation is performed using a p-type substrate. A physical semiconductor laser element may be formed. That is, each conductivity type may be a conductivity type opposite to that of the nitride semiconductor laser element according to the above embodiment.

  In the first to fifth embodiments, the example in which the nitride semiconductor layers are crystal-grown using the MOCVD method has been shown. However, the present invention is not limited to this, and the vapor phase growth method other than the MOCVD method is used. May be used for crystal growth of each nitride-based semiconductor layer. For example, the nitride semiconductor layers may be crystal-grown by a method such as a molecular beam crystal growth method or a chemical beam growth method using an organic metal. Even when configured in this manner, the same effects as those of the first to fifth embodiments can be obtained.

  In the first to fifth embodiments, the thickness, composition, and the like of the nitride-based semiconductor layers that are crystal-grown on the substrate are appropriately combined or changed to those that meet desired characteristics. It is possible. For example, the semiconductor layers may be added or deleted, or the order of the semiconductor layers may be partially changed. Further, the conductivity type may be changed for some semiconductor layers. That is, it can be freely changed as long as the basic characteristics as a nitride semiconductor laser element are obtained.

In the first to fifth embodiments, the example in which the buried layer is made of SiO ₂ is shown. However, the present invention is not limited to this, and the buried layer may be made of an insulating material other than SiO _2. . For example, the buried layer may be made of SiN, Al ₂ O ₃ , ZrO ₂ or the like.

  Moreover, in the said 1st-5th embodiment, although the example which comprised the p side ohmic electrode from Pd was shown, this invention is not restricted to this, If it is a material with a big work function, it will p side by materials other than Pd An ohmic electrode may be configured. For example, the p-side ohmic electrode may be made of Ni, Pt, Au, or the like.

  Moreover, in the said 1st-5th embodiment, although the example which comprised the p side pad electrode to the thickness of about 0.2 micrometer was shown, this invention is comprised not only in this but in the thickness larger than 0.2 micrometer. May be. Further, the p-side pad electrode may be formed as a thick film on the order of microns.

  In the first to fifth embodiments, the p-side pad electrode is formed by sequentially laminating the Ti layer, the Mo layer, and the Au layer from the buried layer side. For example, the p-side pad electrode may be formed by sequentially laminating a Mo layer and an Au layer from the buried layer side.

  In the first to fifth embodiments, the n-side electrode is formed by sequentially stacking the Hf layer and the Al layer from the back side of the n-type GaN substrate. However, the present invention is not limited to this. Alternatively, the n-side electrode may be formed by sequentially laminating a Ti layer and an Al layer, for example, from the back side of the n-type GaN substrate.

  Moreover, although the example which formed the resonator end surface by cleavage was shown in the said 1st-5th embodiment, this invention is not restricted to this, Using methods other than cleavage, a resonator end surface (light emission end surface, A light reflection end face) may be formed. For example, the resonator end face may be formed using a technique such as dry etching.

  In the first to fifth embodiments, an example in which the present invention is applied to a ridge type laser structure has been described. However, the present invention is not limited to this, and a BH (Buried Heterostructure) type other than the ridge type, RiS ( The present invention can also be applied to a laser structure such as a Ridge by Selective re-growth type.

  In the first to fifth embodiments, the case where the ridge portion is formed to extend in the [1-100] direction and the resonator end face is formed in the direction along the [11-20] direction has been described. However, the present invention is not limited to this, and it is sufficient that these directions are crystallographically equivalent directions. That is, the ridge portion may be formed so as to extend in the direction represented by <1-100>, and the resonator end surface may be formed along the direction represented by <11-20>.

  In addition to the nitride-based semiconductor laser element used as the light source of the optical pickup, the present invention requires a high light output, such as a broad area semiconductor laser element used for illumination or a communication laser element, and operates. The present invention can also be applied to elements in which voltage or the like is important.

1 is a perspective view showing a structure of a nitride-based semiconductor laser device according to a first embodiment of the present invention. 1 is a plan view of a nitride-based semiconductor laser device according to a first embodiment of the present invention. FIG. 3 is a sectional view taken along line A1-A1 of FIG. It is sectional drawing along the B1-B1 line | wire of FIG. 1 is a cross-sectional view showing a structure of a light emitting layer of a nitride semiconductor laser element according to a first embodiment of the present invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 1st Embodiment of this invention. It is a top view of the nitride semiconductor laser element by 2nd Embodiment of this invention. FIG. 22 is a cross-sectional view taken along line B2-B2 of FIG. It is sectional drawing along the A2-A2 line of FIG. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 2nd Embodiment of this invention. It is a top view of the nitride semiconductor laser element by 3rd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 3rd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 3rd Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 3rd Embodiment of this invention. It is a top view for demonstrating the nitride type semiconductor laser element by the modification of 3rd Embodiment. It is a top view of the nitride type semiconductor laser element by 4th Embodiment of this invention. It is sectional drawing along the B3-B3 line | wire of FIG. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 4th Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 4th Embodiment of this invention. It is a top view for demonstrating the nitride type semiconductor laser element by the modification of 4th Embodiment. It is a top view of the nitride semiconductor laser element by 5th Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 5th Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the nitride type semiconductor laser element by 5th Embodiment of this invention. It is a top view for demonstrating the nitride type semiconductor laser element by the modification of 5th Embodiment.

Explanation of symbols

1 n-type GaN substrate (substrate)
1a, 1b, 1c groove 2 n-type buffer layer (n-type GaN buffer layer,
Nitride semiconductor layer)
3 n-type cladding layer (first semiconductor layer,
n-type AlGaN cladding layer, nitride semiconductor layer)
4 Light emitting layer (nitride semiconductor layer)
4c active layer 4e lower guide layer 4f upper guide layer 5 p-type cladding layer (second semiconductor layer,
p-type AlGaN cladding layer, nitride semiconductor layer)
6 p-type contact layer (second semiconductor layer,
p-type GaN contact layer, nitride semiconductor layer)
7, 207a Ridge part 207b, 407b Dummy ridge part 8 P-side ohmic electrode 9, 309, 409 Buried layer 10 P-side pad electrode 11 n-side electrode 12 n-side pad electrode 20 Resonator end face 20a Light emitting end face 20b Light reflecting end face 21 Light exit end face portion 22 Light reflection end face portion 25 Swelling portion 30, 230 Window region 40 AR coating layer 50 HR coating layer 100, 200, 300, 400, 500 Nitride-based semiconductor laser device

Claims (21)

A substrate made of a nitride semiconductor;
A first semiconductor layer formed on the substrate;
An active layer formed on the first semiconductor layer and generating laser light;
A light emitting end face from which the laser light generated in the active layer is emitted ;
A second semiconductor layer formed on the active layer, extending in a direction intersecting with the light emitting end face, and including a convex ridge portion functioning as a current passage portion;
A groove portion is formed in a region of the upper surface of the substrate that does not intersect with the ridge portion in plan view,
The first semiconductor layer is made of a semiconductor material having a band gap larger than that of the active layer, and at least the first semiconductor layer has the light emitting end face portion raised,
Due to the rise of the light emitting end face portion, the height of the light emitting end face side of the active layer with respect to the substrate surface is higher than the height of the central portion of the active layer, whereby laser light is emitted from the light emitting end face. A nitride-based semiconductor laser device, wherein a portion of the nitride-based semiconductor laser device is configured to emit light through the first semiconductor layer. A light reflecting end face facing the light emitting end face;
At least in the first semiconductor layer, the light reflection end face portion is raised, and the height of the light reflection end face side of the active layer with respect to the substrate surface is raised in the center of the active layer due to the rise of the light reflection end face portion. The nitride-based semiconductor laser device according to claim 1, wherein the nitride-based semiconductor laser device is higher than a height of the portion.   The nitride semiconductor laser element according to claim 1, wherein the first semiconductor layer is made of an n-type semiconductor. 4. The nitride-based semiconductor laser device according to claim 1, wherein the groove is formed in at least one of the vicinity of the light emitting end face and the vicinity of the light reflecting end face . 5. The nitride-based semiconductor laser device according to claim 1, wherein a depth of the groove is 1 μm or more . The nitride semiconductor laser element according to claim 1, wherein a width of the groove is 1 μm or more . The second semiconductor layer further includes a dummy ridge portion that does not function as a current passage portion,
The dummy ridge portion is formed to extend along the ridge portion,
The nitride-based semiconductor laser device according to claim 1, wherein the groove is formed so as to intersect with the dummy ridge when viewed in a plan view . An n-type GaN buffer layer, an n-type AlGaN cladding layer, the active layer, a p-type AlGaN cladding layer, and a p-type GaN contact layer are formed on the substrate from the substrate side,
The nitride semiconductor laser element according to claim 1, wherein the first semiconductor layer is composed of the n-type AlGaN cladding layer . The nitride-based semiconductor laser device according to claim 8 , wherein the second semiconductor layer includes the p-type AlGaN cladding layer and a p-type GaN contact layer . 8. The nitride-based semiconductor laser device according to claim 7 , wherein each of the ridge portion and the dummy ridge portion includes a p-type AlGaN cladding layer and a p-type GaN contact layer . The nitride semiconductor laser element according to claim 8 or 9 , wherein the n-type dopant of the n-type AlGaN cladding layer is Si . Forming a groove extending in a predetermined direction on the main surface of the substrate;
Growing a plurality of nitride-based semiconductor layers including a first semiconductor layer and an active layer on the main surface of the substrate using a vapor phase growth method;
Separating the vicinity of the groove portion of the substrate along the groove portion,
The step of growing the nitride-based semiconductor layer includes the step of growing the first semiconductor layer using a semiconductor material having a band gap larger than that of the active layer, and disposing the active layer on the first semiconductor layer. Process,
The step of forming the groove portion includes a step of disposing the plurality of groove portions at predetermined positions on the main surface of the substrate by intermittently forming the groove portions. Manufacturing method . 13. The method for manufacturing a nitride-based semiconductor laser device according to claim 12, wherein the vapor phase growth method is a metal organic vapor phase growth method . The nitride system according to claim 12 or 13, wherein the step of growing the nitride semiconductor layer includes a step of forming the first semiconductor layer into an n-type by using an n-type dopant. Manufacturing method of semiconductor laser device. The method of manufacturing a nitride-based semiconductor laser device according to claim 14, wherein the n-type dopant is Si . 16. The method of manufacturing a nitride semiconductor laser element according to claim 12, wherein the step of forming the groove includes a step of configuring the depth of the groove to be 1 [mu] m or more. . The method for manufacturing a nitride-based semiconductor laser device according to claim 12, wherein the step of forming the groove includes a step of configuring the width of the groove to be 1 μm or more . The nitride-based semiconductor layer further includes a second semiconductor layer formed on the active layer,
18. The method according to claim 12, further comprising a step of forming a convex ridge portion extending in a direction intersecting with a direction in which the groove portion extends in the second semiconductor layer and functioning as a current passage portion. A method for manufacturing a nitride-based semiconductor laser device according to any one of the preceding claims. The step of forming the ridge portion includes
Forming the ridge portion functioning as a current path portion;
19. The method of manufacturing a nitride-based semiconductor laser device according to claim 18, further comprising a step of forming a dummy ridge portion that does not function as a current passage portion . The first semiconductor layer is an n-type AlGaN cladding layer;
The step of growing the nitride-based semiconductor layer includes forming an n-type GaN buffer layer, the n-type AlGaN cladding layer, the active layer, a p-type AlGaN cladding layer, and a p-type GaN contact layer from the substrate side. The method for manufacturing a nitride-based semiconductor laser device according to claim 12, further comprising a step . The second semiconductor layer includes a p-type AlGaN cladding layer and a p-type GaN contact layer,
The nitride-based semiconductor laser according to claim 18 or 19, wherein the step of forming the ridge portion includes a step of forming the ridge portion in the p-type AlGaN cladding layer and the p-type GaN contact layer. Device manufacturing method.

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