JP5074863B2 - Nitride semiconductor light-emitting device, epi-wafer and method of manufacturing the same - Google Patents

Description

  The present invention mainly relates to a nitride semiconductor light emitting device having a long light emission lifetime and reduced generation of cracks, and an improvement in the manufacturing method thereof.

  In order to improve the light emission characteristics of the nitride semiconductor light emitting device, a groove is formed in the GaN layer stacked on the sapphire substrate, and the groove is again covered with a GaN film, and the semiconductor laser device is formed on the coating layer. Has been reported in Patent Document 1.

Patent Document 2 reports that a semiconductor laser element is formed on a window region of a SiO ₂ mask formed in a stripe shape by using a selective crystal growth technique.
JP 2000-124500 A JP-A-9-36473

  The nitride semiconductor light emitting device manufactured by the prior art as described above also has a problem that its light emission lifetime is not sufficient. Accordingly, the main object of the present invention is to provide a nitride semiconductor light emitting device having a long light emission lifetime and to suppress the occurrence of cracks in the device.

The present invention relates to a substrate in which a nitride semiconductor layer is grown on a heterogeneous substrate other than a nitride semiconductor, and then the nitride semiconductor layer is processed to form a concave portion and a convex portion made of a single material. A nitride semiconductor multilayer film structure having a crystal grown on the substrate, wherein the nitride semiconductor multilayer film structure has a light emitting portion above the convex portion and has a depression on the surface above the concave portion. The formed nitride semiconductor light emitting device, wherein the recess includes a bottom and a side wall, and the recess is formed by being not completely filled during crystal growth, and the width of the recess is the recess It is a nitride semiconductor light emitting device characterized by being narrower than the width of.

  In the nitride semiconductor light emitting device according to the present invention, the nitride semiconductor multilayer structure preferably includes a structure for injecting a current into the light emitting part above the convex part.

The present invention relates to a substrate in which a nitride semiconductor layer is grown on a heterogeneous substrate other than a nitride semiconductor, and then the nitride semiconductor layer is processed to form a concave portion and a convex portion made of a single material. An epitaxial wafer having a nitride semiconductor underlayer crystal-grown on the substrate and a recess and a flattened portion formed on the surface of the nitride semiconductor underlayer, wherein the recess has a bottom and a side wall The recess is formed by being not completely buried above the recess during crystal growth, and the recess is narrower than the recess and is flattened. Is an epi-wafer characterized by being wider than the width of the projection.
The present invention relates to a substrate in which a nitride semiconductor layer is grown on a heterogeneous substrate other than a nitride semiconductor, and then the nitride semiconductor layer is processed to form a concave portion and a convex portion made of a single material. An epitaxial wafer having a nitride semiconductor multilayer structure grown on the substrate and a recess and a flattened portion formed on the surface of the nitride semiconductor multilayer structure, the nitride semiconductor multilayer The film structure has a nitride semiconductor underlayer and a light emitting layer, the recess has a bottom and a side wall, and the recess is formed by not being completely buried above the recess during crystal growth. In addition, the width of the recess is narrower than the width of the concave portion, and the width of the flattened portion is wider than the width of the convex portion.
In the epitaxial wafer according to the present invention, it is preferable that the nitride semiconductor multilayer structure has a light emitting portion above the convex portion.

Nitride semiconductor light emitting device according to the present invention, in the epitaxial wafer has a structure for injecting current prior SL-emitting portion above the projecting portion, the epitaxial wafer is is preferably divided into individual chips.

Nitride semiconductor light emitting device according to the present invention, the light emitting portion is preferably formed in a region away to the right or left 1μm or more from the center in the width direction of the convex portion is preferable.

  In the nitride semiconductor light emitting device according to the present invention, the width of the recess is preferably in the range of 1 to 100 μm.

  In the nitride semiconductor light emitting device according to the present invention, the depth of the recess is preferably 1 μm or more, and the remaining thickness between the bottom of the recess and the back surface of the substrate is preferably 100 μm or more.

The nitride semiconductor light emitting device according to the present invention is a nitride semiconductor light emitting device including the plurality of recesses and having the relatively wide recesses, and is recessed only above the relatively wide recesses. It is preferable to have.

According to the present invention, after a step of growing a nitride semiconductor layer on a heterogeneous substrate other than a nitride semiconductor and a step of growing the nitride semiconductor layer, the surface of the nitride semiconductor layer is made of a single material by processing. A nitride semiconductor light emitting device comprising: a step of forming a concave portion and a convex portion; and a step of crystal-growing a nitride semiconductor multilayer structure having a light emitting portion above the convex portion and having a depression on the surface In the manufacturing method, the recess includes a bottom and a side wall, the recess is formed by being not completely buried above the recess during crystal growth, and the width of the recess is the width of the recess. It is a manufacturing method of the nitride semiconductor light emitting element characterized by being narrower than this.

  ADVANTAGE OF THE INVENTION According to this invention, the light emission lifetime and light emission intensity can be improved in the nitride semiconductor light-emitting device. Moreover, according to the present invention, in the nitride semiconductor light emitting device, it is possible to prevent the occurrence of cracks, electrode peeling, and wire bond peeling.

  In the following, the meanings of some terms will be clarified in advance in describing various embodiments according to the present invention.

  First, “groove” means a concave portion processed into a stripe shape on the processed substrate surface as shown in FIGS. 2A and 2B, for example, and “hill” is processed into a stripe shape similarly. Means a raised convex portion. The cross-sectional shape of the groove and the hill does not necessarily have to be a rectangular shape as shown in FIG. Moreover, although the groove | channel and hill shown by FIG. 2 are the stripe arrangement | sequences processed along one direction, the grid | lattice arrangement | sequence (refer FIG. 5) in which the groove | channel or the hill crossed mutually may be sufficient. In the drawings of the present application, dimensional relationships such as length, width, thickness, and depth are appropriately changed for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships.

  “Nitride semiconductor substrate” means a substrate made of AlxGayInzN (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1; x + y + z = 1). However, about 10% or less of the nitrogen element of the nitride semiconductor substrate may be replaced with an element of As, P, or Sb (provided that the hexagonal system of the substrate is maintained). Moreover, Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be may be doped in the nitride semiconductor substrate. Among these doping materials, Si, O, and Cl are particularly preferable as the n-type nitride semiconductor. The principal plane orientation of the nitride semiconductor substrate is preferably C plane {0001}, A plane {11-20}, R plane {1-102}, M plane {1-100}, or {1-101} plane. Can be used. Further, if the substrate main surface has an off angle within 2 ° from these crystal plane orientations, the surface morphology can be good.

  “Different substrate” means a substrate other than a nitride semiconductor. As a specific heterogeneous substrate, a sapphire substrate, a SiC substrate, a Si substrate, a GaAs substrate, or the like can be used.

  The “processed substrate” means a substrate in which grooves and hills are formed on the surface of a nitride semiconductor substrate or on the surface of a nitride semiconductor layer grown on a different substrate. The width of the groove and the width of the hill may have a certain period or may have different widths. In addition, regarding the depth of the grooves, all the grooves may have a certain depth or may have different depths.

  The “nitride semiconductor underlayer” is a layer grown on the uneven surface of the processed substrate, and is made of AlxGayInzN (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1; x + y + z = 1). ing. However, this nitride semiconductor underlayer may be doped with at least one of the impurity groups of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, and Be.

  The “light-emitting layer” means a layer that can include one or more quantum well layers or a plurality of barrier layers alternately stacked with the quantum well layers and can generate a light-emitting action. However, the light emitting layer having a single quantum well structure is composed of only one well layer, or is composed of a stack of barrier layer / well layer / barrier layer.

  The “light emitting element structure” means a structure further including an n-type layer and a p-type layer sandwiching the light emitting layer in addition to the light emitting layer.

  “Nitride semiconductor multilayer structure” means a structure including a nitride semiconductor underlayer and a light emitting device structure.

  “Dimple” means that when a nitride semiconductor underlayer or nitride semiconductor multilayer structure is grown and coated on the uneven surface of a processed substrate, the nitride semiconductor underlayer or nitride semiconductor multilayer structure is filled flat. This means a portion that is not formed (see FIG. 3 as an example in which the depression is on the surface of the nitride semiconductor underlayer). In particular, the recess in the present invention must be present on the surface of the nitride semiconductor multilayer structure. However, even if the depression is formed by etching after the nitride semiconductor multilayer film structure is flatly coated on the processed substrate, the effect of the present invention cannot be obtained. Whether or not the recess is formed by processing after crystal growth becomes clear by observing a cross section of the nitride semiconductor multilayer structure. This is because if the depression is formed by processing after the crystal growth is finished, the lateral continuity in the stack in the light emitting device structure is cut off by the depression, but if the depression is formed along with the crystal growth, the light emitting device This is because the continuity in the lateral direction in the stack in the structure is not cut off by the depression, and is continuous along the side wall surface of the depression.

  The “substrate with depressions” means an entire substrate including a depression on the nitride semiconductor underlayer coated on the processed substrate (see FIG. 3).

  “Coating film thickness” means the film thickness from the bottom of the groove of the processed substrate to the surface of the nitride semiconductor layer excluding the recess when the nitride semiconductor layer is grown on the processed substrate.

  [Embodiment 1] As a result of the study by the present inventors, the effect of extending the lifetime of the nitride semiconductor light-emitting device obtained by the present invention is that the strain in the nitride semiconductor multilayer structure crystal contained in the device is alleviated. It may be caused by 2 shows the form of the processed substrate used in the present invention and the names of the respective parts, FIG. 4 (a) shows the form of crystal growth in the present invention, and FIG. 4 (b) shows the conventional processed substrate as a nitride semiconductor. FIG. 4 (c) shows a crystal growth mode by a selective crystal growth method using a conventional crystal growth suppression film. FIG. When the present inventors arrived at the present invention, first, the conventional crystal growth mode was examined.

  (Conventional Crystal Growth Form) In FIG. 4B, when a processed substrate is completely and flatly covered with a nitride semiconductor multilayer film structure as taught in, for example, Japanese Patent Laid-Open No. 2000-124500, a processed substrate is used. Crystal growth starts in the horizontal direction (hereinafter referred to as lateral growth) from the side wall of the groove formed in (1). If such lateral growth occurs, a crystal reflecting the crystal lattice of the lower substrate is difficult to grow, and crystal distortion from below is relaxed. However, the crystals grown from the groove sidewalls on both sides collide with each other at the groove center in FIG. 4B, and therefore crystal distortion concentrates at the groove center. The crystals that collide with the center of the groove are then grown in the normal crystal growth direction (perpendicular to the main surface of the substrate), and the grooves not yet covered are completely and flatly buried. The reverse lateral growth from the center toward the center of the hill is promoted. Crystal collision similar to that at the center of the groove described above also occurs at the center of the hill, and as a result, concentration of crystal distortion occurs due to the crystal collision at the center of the hill. Then, if the center of the hill is buried or if the center of the hill is completely buried, the crystal growth changes in the normal crystal growth direction.

  Therefore, in the conventional crystal growth mode shown in FIG. 4B, if the processed substrate is completely covered with a nitride semiconductor multilayer structure, crystal strains are concentrated at the center of the groove and the center of the hill. . Moreover, in other areas except the center of the groove and the center of the hill, even if the crystal strain from below is alleviated by lateral growth, residual strain occurs due to the influence of the crystal strain concentration at the center of the groove and the hill. End up. It is considered that the light emitting lifetime of the semiconductor light emitting element is shortened due to the crystal distortion as described above.

On the other hand, in FIG. 4C, as taught in, for example, Japanese Patent Laid-Open No. 9-36473, selective crystal growth (corresponding to lateral growth) using a growth suppressing film such as a SiO ₂ mask is performed. In some cases, a recess that is not completely covered with the nitride semiconductor film can be formed on the growth suppression film, similar to the crystal growth mode of the present invention (see FIG. 4A). However, the selective crystal growth using the growth suppressing film is different from the crystal growth form using the processed substrate in the present invention described below. This is because when a growth suppression film is used, crystal growth of the nitride semiconductor film starts from the window region of the GaN layer not covered with the growth suppression film, as shown in FIG. The nitride semiconductor film grown in this window region grows along the normal crystal growth direction (perpendicular to the substrate main surface). Therefore, the crystal grown above the window region (the hatched portion in FIG. 4C) receives crystal distortion (including distortion due to the difference in thermal expansion coefficient) from the lower GaN layer and sapphire substrate. As a result of detailed studies by the present inventors, the portion where the crystal distortion was relaxed was only the region above the crystal growth suppression film shown in FIG.

  However, even when a nitride semiconductor light emitting device is fabricated in the region above the crystal growth suppression film, the light emission lifetime is shorter than that of the light emitting device according to the present invention described later. This is probably due to the distortion caused by the difference in thermal expansion coefficient between the nitride semiconductor film and the growth suppression film, and also because the impurities contained in the growth suppression film are doped into the light emitting device structure through the recessed portions. .

For example, if the growth suppression film expands or contracts due to a temperature change, the growth suppression film may have a distortion in a direction perpendicular to the main surface of the substrate or a distortion at a portion where the growth suppression film and the crystal in the region above the window are in contact with each other. It is considered to propagate to the upper region. In addition, the volume expansion or contraction of the growth suppression film causes the upper region of the growth suppression film to rise, or a gap is generated between the upper region of the growth suppression film and the growth suppression film, and the upper region of the growth suppression film is curved. There is. Such a phenomenon not only causes crystal distortion in the region above the growth suppression film, but also reduces the crystal orientation. Furthermore, when the growth suppression film is SiO ₂ , it is considered that the Si or O is excessively doped into the light emitting device structure through the depression. It is considered that, due to these factors overlapping, the laser emission lifetime was short even when the semiconductor light emitting device was fabricated in the region above the growth suppression film.

  (Crystal Growth Form in the Present Invention) In the crystal growth form in the present invention shown in FIG. 4 (a), as in the conventional example shown in FIG. 4 (b), the side wall of the groove formed in the processed substrate. Then, lateral growth starts, and the crystals grown from the side walls of the grooves are joined together at the center of the groove in FIG. 4A, and then the growth proceeds in the normal crystal growth direction. However, in the crystal growth mode according to the present invention, since the nitride semiconductor multilayer structure is not completely buried above the hill, horizontal crystal distortion parallel to the main surface of the substrate is caused to pass through the recess. Can be relaxed. That is, the depression can reduce the crystal strain concentrated in the center of the groove in the conventional crystal growth mode shown in FIG. 4B, and can reduce the crystal strain of the entire nitride semiconductor multilayer structure. In addition, the crystal growth mode according to the present invention does not use the growth suppression film shown in FIG. 4C, and therefore is affected by the above-described difference in thermal expansion coefficient and impurity doping caused by the crystal growth film. Absent.

  In the crystal growth mode according to the present invention, it is more preferable that a depression is formed not only in the center of the hill but also in the center of the groove (see Embodiment 3). By utilizing such a crystal growth form, there is no portion where the crystal strain is concentrated, so that it is possible to form a nitride semiconductor multilayer structure in which crystal strain is almost alleviated.

  (Effects in the Present Invention) As described above, in the present invention, a nitride semiconductor multilayer film is formed by forming a recess that is not completely filled with a nitride semiconductor multilayer film structure on a processed substrate. The crystal distortion of the structure can be relaxed.

  When the nitride semiconductor laser element is formed on the processed substrate in the present invention using the nitride semiconductor substrate (for example, GaN substrate) shown in FIG. 2A, the laser output is 30 mW and the ambient temperature is 60 ° C. The oscillation lifetime of the nitride semiconductor laser element was about 18000 hours. This is much longer than the laser oscillation lifetime of about 700 hours when a conventional nitride semiconductor substrate is used.

  On the other hand, when a nitride semiconductor laser device is fabricated on the processed substrate in the present invention using the heterogeneous substrate (for example, sapphire substrate) shown in FIG. 2B, the laser output is 30 mW and the ambient temperature is 60 ° C. The oscillation lifetime of the nitride semiconductor laser element was about 1000 hours. This is sufficiently longer than the laser oscillation lifetime of about 200 hours when a conventional different substrate is used.

  The inventors have also found that the use of the processed substrate in the present invention can suppress the occurrence of cracks in the light-emitting element. This improved the yield in the productivity of the light emitting device.

For example, when the nitride semiconductor laser element is formed on the processed substrate in the present invention using the nitride semiconductor substrate (GaN substrate) shown in FIG. 2A, the crack density is 0 to 3 / cm ² . there were. On the other hand, when a light emitting device structure made of a nitride semiconductor was formed on a conventional GaN substrate, it was thought that almost no cracks occurred, but in the epiwafer surface after the light emitting device structure was actually grown, Many cracks occurred. This is considered to be caused by distortion due to the light emitting element structure being composed of a laminated structure of various layers (for example, the AlGaN layer has a smaller lattice constant than the GaN layer, and the InGaN layer has a smaller lattice constant than the GaN layer). Large lattice constant). Further, it is considered that residual strain is latent in the GaN substrate obtained by the current technology. Actually, when a nitride semiconductor laser element was formed on a conventional GaN substrate, the crack density was about 5 to 8 / cm ² . From this, it was found that the crack density can be reduced by using the nitride semiconductor processed substrate in the present invention.

On the other hand, when the nitride semiconductor laser element was formed on the processed substrate in the present invention using the heterogeneous substrate shown in FIG. 2B, the crack density was about 3 to 5 / cm ² . On the other hand, when a nitride semiconductor laser device was fabricated on a conventional processed substrate using a different substrate, the crack density was about 10 to 20 / cm ² . From this, it was found that the crack density can be reduced by using the processed substrate in the present invention even in the case of a processed substrate including a different substrate.

  The effect of suppressing cracks by the above-described depression was stronger as the depth of the depression was deeper, and stronger as the density of the depression was higher. In order to deepen the dent, it is effective to deepen the groove, widen the groove width, or widen the hill width when forming the processed substrate. On the other hand, in order to increase the density of the depressions, it is effective to narrow the groove width or the hill width when forming the processed substrate. Specific numerical values such as the groove width, groove depth, and hill width will be described in detail later.

  Furthermore, it turned out that the crack suppression effect of the hollow in this invention has the following characteristics. By including two or more depressions in one nitride semiconductor light emitting device divided into chips, the crack generation rate was reduced by about 30% compared to an element having one depression. Moreover, when a ridge stripe portion is provided between the recess 1 and the recess 2 as in the nitride semiconductor light emitting element (laser element) having the ridge stripe structure shown in FIG. 1, for example, the yield of the light emitting element is particularly high. Improved. As a result of examining this in detail, it was found that cracks crossing the longitudinal direction of the ridge stripe were reduced. This is presumably because the cracks were prevented from entering the ridge stripe portion of the nitride semiconductor light emitting device by having the depressions on both sides of the ridge stripe portion.

In addition, it has been found that the depression in the present invention has the following effects in the electrode of one nitride semiconductor light emitting device divided into chips. By including two or more depressions in the present invention in one nitride semiconductor light emitting device, the element defect rate due to electrode peeling was reduced by about 20% compared to an element having one depression. Moreover, when a ridge stripe portion is provided between the recess 1 and the recess 2 as in the nitride semiconductor light emitting device (laser element) having the ridge stripe structure shown in FIG. 1, for example, in the ridge stripe portion. Peeling of the p-electrode 112 (including the pad electrode) was prevented, and the yield of the light-emitting element was improved. From this, it is preferable that the electrode is formed on a region including two or more depressions, and more preferably, a ridge stripe portion is provided between the depressions, and the electrode is formed on the region including these depressions. Has been found to be preferred. The effect of preventing electrode peeling at the ridge stripe portion was the same as that for peeling of the dielectric film. For example, the same applies to the SiO ₂ dielectric film 113 shown in FIG. Instead of the SiO ₂ dielectric film 113, another dielectric film such as SiNx may be used.

  Furthermore, it has been found that the depression in the present invention has the following effects in wire bonding of one nitride semiconductor element divided into chips. By including one or more depressions in the present invention in the bonding region between the wire bond and the nitride semiconductor light emitting device, peeling of the wire bond itself or peeling of the electrode including the wire bond was reduced by about 20%. . From this, it was found that the junction region between the wire bond and the nitride semiconductor light emitting device preferably includes one or more depressions in the present invention.

  (Regarding Processed Substrate) The processed substrate in the present invention is configured using a nitride semiconductor substrate or a heterogeneous substrate. In particular, when a nitride semiconductor substrate is used as the processed substrate, it is preferable in the following points. That is, since the nitride semiconductor substrate has a small difference in thermal expansion coefficient from the nitride semiconductor underlying layer formed thereon, the warpage of the substrate is much smaller than when a different substrate is used. Therefore, the grooves and hills formed in the nitride semiconductor substrate can be formed with higher accuracy than those formed in the nitride semiconductor layer on the different substrate. Further, as will be described in more detail in the item described later (about the formation position of the light emitting portion), since the warpage of the substrate is very small, a region in which an element failure such as shortening of the light emission life is likely to occur (region III described later). IV) can be avoided and the light emitting element structure can be manufactured with high accuracy. Furthermore, the small warpage of the substrate itself acts to prevent the occurrence of new distortions and cracks, and also has the effect of extending the life of the semiconductor laser element and reducing other characteristic defects.

  (Regarding the coating thickness of the nitride semiconductor underlayer covering the processed substrate) In the present invention, in order to form a recess in which the processed substrate is not covered with the nitride semiconductor multilayer structure, for example, the nitride semiconductor underlayer is thinned. It only has to grow. However, apart from the case where a depression is formed also in the upper region of the groove, it is difficult to form a light emitting element in the upper region of the groove unless the groove formed in the processed substrate is buried flat. Therefore, the coating thickness of the nitride semiconductor underlayer is preferably about 2 μm or more and 20 μm or less. If the coating film thickness is thinner than 2 μm, it will become difficult to completely and evenly bury the groove with the nitride semiconductor underlayer, depending on the width and depth of the groove formed on the processed substrate. . On the other hand, when the coating film thickness is greater than 20 μm, the processed substrate and the nitride semiconductor underlayer (or nitrided layer) are more effective than the effect of mitigating crystal distortion caused by the depression and the effect of suppressing cracks, particularly when the processed substrate includes a different type of substrate. The stress strain due to the difference in thermal expansion coefficient between the physical semiconductor multilayer film structure) is too strong, and the possibility that the effect of the present invention is not sufficiently exhibited becomes high.

  (Regarding Groove Width) A groove formed in the nitride semiconductor substrate is easily buried in the nitride semiconductor underlayer if the groove width is relatively narrow, and is difficult to be buried if it is wide. According to the examination results of the present inventors, the groove width G1 for completely and flatly covering the groove formed in the processed substrate with the nitride semiconductor underlayer is preferably 4 μm or more and 30 μm or less. Above, it was more preferable that it is 25 μm or less. On the other hand, the groove width G2 for forming the depression without completely covering the groove formed on the processed substrate with the nitride semiconductor underlayer is preferably 7 μm or more and 75 μm or less, but about 7 μm or more and about It could be 100 μm or less. However, whether or not a recess is formed above the groove of the processed substrate strongly depends on the coating thickness of the nitride semiconductor underlayer, so that a recess is formed when covering the groove completely and flatly or in the region above the groove. In this case, it is necessary to adjust the coating thickness of the nitride semiconductor underlayer together with the groove widths G1 and G2.

  The lower limit value and the upper limit value of the groove width G1 were estimated from the following viewpoints. The lower limit value of the groove width G1 of the groove 1 in which no depression is formed above the groove depends on the size of the light emitting part in the light emitting element. The formation position of the light emitting part in the light emitting element will be described in more detail with reference to FIG. 6 in the item described later (about the formation position of the light emitting part). For example, when a nitride semiconductor laser element is formed in a groove-covered upper region of a substrate with depressions, the light emitting portion below the ridge stripe portion of the nitride semiconductor laser element is shown in FIG. It is preferable to belong to the area | region I in (a). Therefore, at least the lower limit value of the groove width G1 needs to be wider than twice the ridge stripe width. Since the ridge stripe width is formed with a width of about 1 μm to 3 μm, the groove width G1 must be 4 μm or more including the width 2 μm of the region III in FIG. 7A and the stripe width (1 μm) × 2. It is estimated.

  On the other hand, the upper limit of the groove width G1 is that if the groove width G1 exceeds 25 μm, the nitride semiconductor base layer is laminated with a coating thickness of 10 μm or less and the groove 1 having the groove width G1 is completely buried. It is because it becomes difficult. Similarly, if the groove width G1 exceeds 30 μm, it is difficult to completely bury the groove 1 even if the nitride semiconductor underlayer is laminated with a coating thickness of 20 μm or more.

  The lower limit value and the upper limit value of the groove width G2 were estimated from the following viewpoints. Similarly to the lower limit value of the groove width G1, the lower limit value of the groove width G2 of the groove 2 where the depression is formed above the groove also depends on the size of the light emitting portion in the light emitting element. For example, when a nitride semiconductor laser device is fabricated in the upper region of the groove 2 where a recess is formed in the groove width G2, the light emitting portion below the ridge stripe portion of the laser device is shown in FIG. It is preferable to belong to the area | region II in (b). Since the ridge stripe width is approximately 1 μm to 3 μm and the minimum recess width can be estimated as 1 μm, the lower limit of the groove width G2 is the width of the region IV including the recess = the recess width (1 μm) +2 μm × 2 (FIG. 7 ( b) and a stripe width (1 μm) × 2 are required to be 7 μm or more. However, this is not the case when the nitride semiconductor laser element is not formed so that the ridge stripe portion is completely included in the region above the groove where the recess is formed, and the groove width G2 in that case is the recess width (1 μm). What is necessary is just above, and more preferably, it should be more than the width (5 μm) of the region IV including the depression. The meaning of the region IV will be described later with reference to FIG.

  On the other hand, the upper limit value of the groove width G2 of the groove 2 where the depression is formed above the groove is not particularly limited from the viewpoint of the laser oscillation lifetime. However, if G2 is too wide, the dent density per unit area of the wafer decreases, and the crystal strain relaxation effect and crack suppression effect are reduced. Along with this, the light emitting element chip yield per wafer is also reduced. Therefore, from the above viewpoint, the upper limit value of the groove width G2 is 100 μm or less, more preferably 75 μm or less.

  In the above description, the processed substrate in which only the groove width is changed has been described. Needless to say, the processed substrate may be formed by changing not only the groove width but also the groove depth and / or the hill width.

  (Regarding Groove Depth) The groove formed in the nitride semiconductor substrate is easily buried in the nitride semiconductor underlayer if the depth is relatively shallow, and is difficult to be buried if it is deep. The formation of the recess by adjusting the groove depth is preferable because the yield of light emitting element chips per wafer does not decrease as compared with the case where the recess is formed by adjusting the groove width.

  According to the examination results of the present inventors, the groove depth H1 for completely and flatly covering the groove formed in the processed substrate with the nitride semiconductor underlayer is preferably 1 μm or more and 9 μm or less, It was more preferable that it is 2 μm or more and 6 μm or less. On the other hand, the groove depth H2 for forming a recess without completely covering the groove on which the processed substrate is formed with the nitride semiconductor underlayer is preferably 1 μm or more, and more preferably 2 μm or more. I liked it. The upper limit value of the groove depth H2 is not particularly limited, and the remaining thickness h as shown in FIG. 2 (a) may be 100 μm or more. However, whether or not the recess is formed above the groove of the processed substrate strongly depends on the coating thickness of the nitride semiconductor underlayer, so that the recess is formed when the groove is completely and evenly covered. At this time, it is necessary to adjust the coating thickness of the nitride semiconductor underlayer together with the groove depths H1 and H2.

  The lower limit value and the upper limit value of the groove depth H1 were estimated from the following viewpoints. The lower limit value of the groove depth H1 of the groove 1 where no depression is formed above the groove is preferably 1 μm or more, and more preferably 2 μm or more. This is because if the groove depth H1 is shallower than 1 μm, the growth in the direction perpendicular to the main surface of the substrate takes precedence over the lateral growth in the crystal growth mode, and the effect of reducing crystal distortion due to the lateral growth. This is because there is a possibility that it will not be fully demonstrated. Then, if the lower limit value of the groove depth H1 is 2 μm or more, the effect of reducing crystal distortion due to lateral growth can be sufficiently exerted.

  On the other hand, the upper limit value of the groove depth H1 is preferably 9 μm or less, and more preferably 6 μm or less. This is because if the groove depth H1 exceeds 6 μm, it becomes difficult to completely bury the groove 1 having the groove depth H1 in a nitride semiconductor underlayer having a coating thickness of 10 μm or less. . Similarly, if the groove depth H1 exceeds 9 μm, it becomes difficult to completely bury the groove 1 even if the nitride semiconductor underlayer is laminated to a coating thickness of 20 μm or more.

  The lower limit value and the upper limit value of the groove depth H2 were estimated from the following viewpoints. The lower limit value of the groove depth H2 of the groove 2 in which the depression is formed above the groove is preferably 1 μm or more, and more preferably 2 μm or more, like the groove depth H1. This is because, as described with respect to the groove depth H1, if the effect of reducing crystal distortion due to lateral growth is not sufficiently obtained, the characteristics of the light emitting element formed in the upper region of the groove 2 (for example, laser oscillation lifetime). This is because it may decrease. Whether or not a recess is formed in the upper region of the groove by the nitride semiconductor film or is completely buried while the lower limit values of the groove depths H2 and H1 are the same, it is determined whether the nitride semiconductor underlayer is covered. Depends on film thickness. On the other hand, the upper limit value of the groove depth H2 is not particularly limited, and the formation of the recess becomes easier as the groove depth H2 is deeper. However, if the groove 2 is made too deep, the processed substrate is liable to be cracked, so the remaining thickness h between the bottom of the groove and the back surface of the substrate must be 100 μm or more (see FIG. 2A). .

  In the above description, the processed substrate in which only the groove depth is changed has been described. Needless to say, the processed substrate may be formed by changing not only the groove depth but also the groove width and / or the hill width.

  (Regarding Hill Width) Hills formed on the processed substrate are likely to be buried in the nitride semiconductor underlayer if the hill width is relatively narrow, and less likely to be buried if it is wide. According to the examination results of the present inventors, the hill width L1 for completely and flatly covering the hill formed on the processed substrate with the nitride semiconductor underlayer is preferably 4 μm or more and 30 μm or less. More preferably, it was 25 μm or less. On the other hand, the hill width L2 for forming the depression without completely covering the hill formed on the processed substrate with the nitride semiconductor underlayer is preferably 7 μm or more and 75 μm or less, and 7 μm or more and 100 μm or less. It was good to be there. However, whether or not a depression is formed above the hill of the processed substrate strongly depends on the coating thickness of the nitride semiconductor underlayer, so that when the hill is completely and evenly covered, a depression is formed in the upper area of the hill. When forming, it is necessary to adjust the coating thickness of the nitride semiconductor underlayer together with the hill widths L1 and L2.

  The lower limit value and the upper limit value of the hill width L1 were estimated from the following viewpoints. The lower limit value of the hill width L1 of the hill 1 where no depression is formed above the hill depends on the size of the light emitting portion in the light emitting element, as with the lower limit value of the groove width G1 described above. For example, when a nitride semiconductor laser device is formed in a region covered flat above a hill among substrates with depressions, from the viewpoint of laser oscillation lifetime, the light emitting portion below the ridge stripe portion of the laser element has a depression. It preferably belongs to a region I (see FIG. 7B) that is not formed. The ridge stripe width is formed with a width of about 1 μm to 3 μm, and the width of the region III when the depression is not formed above the hill can be estimated to be 2 μm. Therefore, the lower limit value of the hill width L1 is the stripe width (1 μm) × 2 And the width of the region III needs to be 4 μm or more including the width of 2 μm. On the other hand, the upper limit value of the hill width L1 can be estimated in the same manner as the upper limit value of the width of the groove 1 described above.

  Furthermore, the lower limit value and the upper limit value of the hill width L2 were estimated as follows. The lower limit value of the hill width L2 of the hill 2 where no depression is formed on the hill depends on the size of the light emitting portion in the light emitting element, as with the lower limit value of the groove width G2. For example, when a nitride semiconductor laser device is formed in the upper region of the hill 2 having the hill width L2 including the depression, the light emitting portion below the ridge stripe portion of the laser device is shown in FIG. It preferably belongs to the middle region II. The ridge stripe portion is formed with a width of about 1 to 3 μm, and the minimum recess width can be estimated as 1 μm. Therefore, the lower limit value of the hill width L2 is the width of the region IV including the recess = the recess width (1 μm) +2 μm × 2 And the stripe width (1 μm) × 2 must be 7 μm or more. However, this is not the case when the nitride semiconductor laser element is not formed so that the ridge stripe portion is completely included in the region above the hill 2 where the depression is formed, and the hill width L2 in this case is the depression width (1 μm). What is necessary is just above, and more preferably, it should be more than the width (5 μm) of the region IV including the depression. On the other hand, the upper limit value of the hill width L2 of the hill 2 where the depression is formed above the hill is not particularly limited from the viewpoint of the laser oscillation lifetime. However, for the same reason as the upper limit value of the groove width G2 of the groove 2, the upper limit value of the hill width L2 is 100 μm or less, more preferably 75 μm or less.

  In the above description, the processed substrate in which only the hill width is changed has been described. Needless to say, the processed substrate may be formed by changing not only the hill width but also the groove width and / or the groove depth.

  (Regarding the longitudinal direction of the groove) The longitudinal direction of the groove formed in the nitride semiconductor substrate having a {0001} C plane as a principal surface or a nitride semiconductor layer on a different substrate is parallel to the <1-100> direction. Most preferably, it was next preferred to be parallel to the <11-20> direction. Even if the longitudinal direction of the groove with respect to these specific directions has an opening angle of about ± 5 ° in the {0001} C plane, no substantial effect was produced.

  The advantage of forming the groove along the <1-100> direction of the nitride semiconductor crystal is that the depression is difficult to fill and the effect of suppressing crystal distortion and crack generation is very high. When a nitride semiconductor underlayer grows in a groove formed along this direction, a {11-20} plane is likely to be formed mainly as a sidewall surface of the depression. Since the {11-20} side wall surface is perpendicular to the main surface of the substrate as shown in FIG. 8A, the recess tends to have a substantially rectangular cross section. When the cross section of the depression is close to a rectangular shape, the raw materials constituting the nitride semiconductor are not easily supplied to the depth of the depression, and the groove is less likely to be filled with the nitride semiconductor underlayer. For this reason, even if the processed substrate is covered with the nitride semiconductor underlayer relatively thickly, there is no fear that the recess is buried. Further, since the cross section of the recess is rectangular and difficult to fill, it becomes very deeper than a recess having a {1-101} side wall described below (mainly maintains the depth of the groove formed on the processed substrate). The crystal distortion of the nitride semiconductor underlayer grown on the processed substrate is alleviated by the deep depression, and the generation of cracks can be effectively suppressed.

  On the other hand, the advantage that the groove is formed along the <11-20> direction of the nitride semiconductor crystal is that the shape of the dent is steep and the fluctuation of the position of the dent is reduced. When a nitride semiconductor underlayer grows in a groove formed along this direction, a {1-101} plane is likely to be mainly formed on the side wall surface of the recess. Since the {1-101} side wall surface is very flat and the edge portion (see FIG. 3) is steep and difficult to meander, the depression along the <11-20> direction is also straight and difficult to meander. Accordingly, the regions I and II for forming a light emitting element having a long light emission lifetime, which will be described later, can be widened (improvement in the yield of the light emitting element), and the decrease in the element yield due to the misalignment of the laser element formation position can be prevented. can do.

  The above-mentioned grooves or hills are all striped, but the striped shape is preferable in the following points. That is, the portion contributing to the oscillation of the nitride semiconductor laser element (below the ridge stripe portion) is in a stripe shape, and if the preferred ridge stripe portion formation regions I and II are also in the stripe shape, the portion contributing to the oscillation is It is easy to build in the preferred region I or II. It is preferable that the grooves or hills have a grid shape in that the crystal distortion can be alleviated evenly in the substrate surface and the effect of suppressing the occurrence of cracks is high. For example, as shown in FIG. 5, the grooves may be formed in a grid shape.

  FIG. 5A shows a top view of a processed substrate having a concave portion and a convex portion when two different types of groove directions are formed to be orthogonal to each other. FIG. 5B shows a top view of a processed substrate having a concave portion and a convex portion when two different types of groove directions are formed so as to form an angle of 60 degrees with each other. FIG. 5C shows a top view of a processed substrate having a concave portion and a convex portion when three different types of groove directions are formed so as to form an angle of 60 degrees with each other.

  (Nitride Semiconductor Underlayer) As the underlayer made of a nitride semiconductor film covering the processed substrate, for example, a GaN film, an AlGaN film, or an InGaN film can be used. In addition, at least one impurity among the impurity groups of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, and Be can be added to the nitride semiconductor underlayer.

If the nitride semiconductor underlayer is a GaN film, it is preferable in the following points. That is, since the GaN film is a binary mixed crystal, the controllability of crystal growth is good. Also, since the surface migration length of the GaN film is longer than that of the AlGaN film and shorter than that of the InGaN film, the portion to be filled and flattened is covered with the GaN film appropriately, and the portion where the recess is to be formed is made of the GaN film. The coating is moderately limited. The impurity concentration of the GaN film used as the nitride semiconductor underlayer is preferably 1 × 10 ¹⁷ / cm ³ or more and 5 × 10 ¹⁸ / cm ³ or less. If impurities are added in such a concentration range, the surface morphology of the nitride semiconductor underlayer is improved, and as a result, the layer thickness of the light emitting layer is made uniform, and the device characteristics can be improved.

If the nitride semiconductor underlayer is an AlGaN film, it is preferable in the following points. Since the AlGaN film contains Al, the surface migration length is shorter than that of the GaN film or InGaN film. The short surface migration length maintains a steep cross-sectional shape of the recess (for example, the edge portion in FIG. 3 does not drift), and the nitride semiconductor does not easily flow into the bottom of the recess (the recess is difficult to fill). ) Means. In addition, the nitride semiconductor is difficult to flow into the bottom of the groove when the groove is covered, and crystal growth from the side wall of the groove is promoted, so that lateral growth becomes remarkable and crystal distortion is further alleviated. Is possible. The Al composition ratio x of the AlxGa1-xN film is preferably 0.01 or more and 0.15 or less, more preferably 0.01 or more and 0.07 or less. If the Al composition ratio x is smaller than 0.01, the above-described surface migration length may become long. On the other hand, if the Al composition ratio x is larger than 0.15, the surface migration length becomes too short, and it may be difficult to flatly fill up the region to be filled and flattened. In addition, not only the AlGaN film but also the same effect as this film can be obtained if the nitride semiconductor underlayer contains Al. The impurity concentration of the AlGaN film used as the nitride semiconductor underlayer is preferably 3 × 10 ¹⁷ / cm ³ or more and 5 × 10 ¹⁸ / cm ³ or less. If impurities are added simultaneously with Al in such a concentration range, the surface migration length of the nitride semiconductor underlayer is preferably shortened. This makes it possible to further relax the crystal distortion.

If the nitride semiconductor underlayer is an InGaN film, it is preferable in the following points. Since the InGaN film contains In, it is more elastic than the GaN film or AlGaN film. Therefore, the InGaN film has a function of burying in the groove of the processed substrate, diffusing crystal strain from the substrate to the entire nitride semiconductor multilayer film structure, and effectively relieving the crystal strain. The In composition ratio x of the InxGa1-xN film is preferably 0.01 or more and 0.15 or less, and more preferably 0.01 or more and 0.1 or less. If the In composition ratio x is smaller than 0.01, it may be difficult to obtain the effect of elasticity due to inclusion of In. Further, if the In composition ratio x is larger than 0.15, the crystallinity of the InGaN film may be lowered. In addition to the InGaN film, the same effect as this film can be obtained if the nitride semiconductor underlayer contains In. The impurity concentration of the InGaN film used as the nitride semiconductor underlayer is preferably 1 × 10 ¹⁷ / cm 3 or more and 4 × 10 ¹⁸ / cm ³ or less. It is preferable to add impurities simultaneously with In in such a concentration range because the nitride semiconductor underlayer has a good surface morphology and can retain elasticity.

  (Regarding the formation position of the light emitting portion) As a result of detailed investigations by the present inventors, depending on where the light emitting portion of the nitride semiconductor laser element (below the ridge stripe portion) is formed on the recessed substrate It has been found that the lasing lifetime varies. Here, the light emitting portion is a portion of the light emitting layer that substantially contributes to light emission when current is injected into the light emitting element. For example, in the case of a nitride semiconductor laser device having a ridge stripe structure, it is a light emitting layer portion below a ridge stripe portion into which current is constricted and injected.

  In FIG. 6, the horizontal axis of the graph represents the distance from the groove center c of the substrate with depressions to the ridge stripe end a in the width direction, and the vertical axis represents the laser oscillation lifetime under conditions of a laser output of 30 mW and an ambient temperature of 60 ° C. Represents. Here, the distance from the groove center c to the ridge stripe end a (hereinafter referred to as “ca distance”) is displayed as positive on the right side and negative on the left side in the width direction from the groove center c. The structure and the manufacturing method of the nitride semiconductor laser element measured in FIG. 6 are the same as those in Embodiment 8 described later, a GaN processed substrate is used, the ridge stripe width is 2 μm, and the groove width is 18 μm. The hill width was 15 μm and the depression width above the hill was 3 μm.

  As can be seen from FIG. 6, the lasing lifetime of the nitride semiconductor laser element in which the ridge stripe portion was formed above the groove tended to be longer than that in which the ridge stripe portion was formed above the hill. When the ridge stripe portion is formed in a region where the ca distance is larger than −3 μm and smaller than 1 μm even in the region above the groove, the laser oscillation lifetime is dramatically improved. It turned out to decrease. Here, considering that the width of the ridge stripe portion is 2 μm, the ca distance−3 μm is converted into the distance from the groove center c to the ridge stripe end b (hereinafter referred to as the cb distance). In this case, the cb distance is −1 μm. That is, when at least a part of the ridge stripe portion of the nitride semiconductor laser element is formed so as to be included within a range of less than 1 μm in the width direction from the groove center c, the laser oscillation lifetime is dramatically reduced. I understood it.

  Such a region where the laser oscillation lifetime is drastically reduced (a region less than 1 μm in the width direction from the groove center c) is referred to as a region III. Therefore, it is preferable that the ridge stripe portion of the nitride semiconductor laser element is formed so that the entire region (ab width) is included in the range excluding region III. Here, in the groove width range, a range of 1 μm or more in the width direction from the groove center c is referred to as a region I. This region I is a region where a nitride semiconductor laser element having a long laser oscillation lifetime can be formed as compared with the region II described below, and is the most preferable region among the substrates with depressions.

  On the other hand, in the region above the hill, similar to the region above the groove, if the light emitting portion of the nitride semiconductor laser element is formed in a region where the ca distance is larger than 11 μm and smaller than 20 μm, the laser oscillation lifetime is obtained. Can be seen to decrease dramatically. Here, if the state of the ca distance of 11 μm is expressed by the distance from the recessed end d to the ridge stripe end b, it is 2 μm. Similarly, the state of the ca distance of 20 μm is from the recessed end e to the ridge stripe end a. If it displays by distance, it will be 2 micrometers. That is, it can be seen that the laser oscillation lifetime is drastically reduced when at least a part of the light emitting portion below the ridge stripe portion is included in the range of 2 μm from the end of the recess to both sides thereof. This region where the laser oscillation lifetime is dramatically reduced will be referred to as IV. Therefore, in the region above the hill, the entire ridge stripe portion (ab) is included in a range that is 2 μm or more on the left side in the width direction from the hollow end d excluding the region IV or 2 μm or more on the right side from the hollow end e. It is preferable to be manufactured. Here, in the region above the hill, a region having a range of 2 μm or more to the left in the width direction from the depression end d and 2 μm or more to the right from the depression end e is referred to as a region II. In this region II, although the laser oscillation lifetime is shorter than in the above-described region I, a nitride semiconductor laser element having a lifetime of several thousand hours can be formed.

  In FIG. 7, the above-mentioned regions I to IV are shown in a schematic cross-sectional view of a substrate with depressions. That is, it is preferable that the light emitting portion of the nitride semiconductor laser device manufactured on the substrate with the depression is formed at a position avoiding at least the regions III and IV, among which the region I is the most preferable and the region II is the same. It was then preferred (see Figure 6).

  FIG. 7A shows a case where a depression is formed only in the region above the hill. For example, as in Embodiments 5 to 7 described later, the region above the hill is a nitride semiconductor underlayer. As shown in FIG. 7 (b), the range of the area I when completely and flatly covered with is in the upper area of the hill and is 1 μm or more away from the center of the hill to the right or left side in the width direction. It was an area. This is because if the light emitting portion is included in the range of 1 μm from the center of the hill to the left and right (region III when no depression is formed above the hill), the laser oscillation lifetime will be drastically reduced. It is.

  Similarly, in FIG. 7A, no depression is formed above the groove, but for example, a region II where a depression is also formed above the groove as in Embodiments 3, 6, and 7 described later. The range was the region above the groove and 2 μm or more away from both ends of the recess in the width direction (see FIG. 7B). This is because if the light emitting portion is included in the range of 2 μm from the both ends of the recess to the left and right (region IV in the case of having the recess above the groove), the laser oscillation lifetime is dramatically reduced. Because.

  Even when the groove width, hill width, and ridge stripe width were variously changed, the same tendency as in FIG. 6 was exhibited. Further, even when the processed substrate was changed from a GaN substrate to one containing a different substrate, the laser oscillation lifetime was shorter than that of the GaN substrate, but the same tendency as in FIG. 6 was shown. Therefore, even in these cases, it is considered that the light emitting portion forming region of the light emitting element to be formed on the substrate with the depression has a relationship shown in FIG. Similarly, for the light emitting diode (LED) element, the effect of the present invention can be obtained if any of the regions I or II shown in FIG. 7 exists below the light emitting portion into which current is injected. It is.

  6 has a ridge stripe structure, the same tendency as in FIG. 6 can be obtained even with a nitride semiconductor laser element having a current blocking structure. In the case of the current blocking structure, the ridge stripe portion in FIG. 6 corresponds to the current confined portion, and the ridge stripe width corresponds to the current confined width). That is, in the nitride semiconductor laser element, it is sufficient that current is constricted and injected into the light emitting layer, and any one of the regions I or II shown in FIG. 7 exists below the light emitting portion contributing to laser oscillation.

  However, in the case of a nitride semiconductor laser element having a current blocking structure, the laser oscillation lifetime is about 20-30% lower than that of the element having the ridge stripe structure described above. In addition, the nitride semiconductor laser element having a current blocking structure has a large decrease in yield due to the occurrence of cracks, compared with the element having a ridge stripe structure. Although these causes are not clear, it is probably a process of forming a current confinement portion in the current blocking layer and a step of growing a nitride semiconductor layer again on the current blocking layer in which the current confinement portion is formed. There may be a problem. For example, in the step of forming the current confinement portion in the current blocking layer, a mask material such as a resist material is used, and these mask materials are attached in the recess of the nitride semiconductor light emitting device according to the present invention. It is thought that the regrowth as it was had an adverse effect on the characteristics of the light emitting device. In addition, for example, the step of crystal-growing a nitride semiconductor again on the current blocking layer in which the current confinement portion has been formed is a crystal growth once during the fabrication of the light emitting device structure in order to form the current confinement portion in the current blocking layer. It is taken out from the apparatus (at room temperature) and loaded again into the crystal growth apparatus, and the remaining light emitting device structure is crystal grown (about 1000 ° C.). In this way, if a thermal history with a rapid temperature difference is given during the fabrication of the light emitting device structure, even if the nitride semiconductor light emitting device according to the present invention has a recess, the crystal in the light emitting device structure is formed by the recess. It is considered that cracks are generated because the strain is not sufficiently relaxed.

  [Embodiment 2] As Embodiment 2, a method for manufacturing a substrate with a recess according to the present invention will be described with reference to FIGS. Note that matters not particularly mentioned in the present embodiment are the same as those in the first embodiment. FIG. 3 shows names of the respective parts of the substrate with depressions, FIG. 8A shows the substrate with depressions when the cross-sectional shape of the depressions is a rectangular shape, and FIG. 8B shows the cross-sectional shape of the depressions. It represents a substrate with a depression in the case of an inverted trapezoidal shape (when the crystal growth further proceeds, it becomes a V shape).

The processed substrate in FIG. 8 can be manufactured as follows. First, a dielectric film such as SiO ₂ or SiNx was vapor-deposited on the surface of an n-type GaN substrate whose principal plane orientation is (0001) plane. Then, a resist material was applied to the dielectric film using a normal lithography technique, and the resist material was formed into a striped mask pattern. Along the mask pattern, a groove was formed by etching a part of the surface of the dielectric film and the GaN substrate using a dry etching method. Thereafter, the resist material and the dielectric film were removed. The grooves and hills thus formed were along the <1-100> direction of the n-type GaN substrate, and had a groove width of 18 μm, a groove depth of 3 μm, and a hill width of 7 μm. Similarly, a low-temperature GaN buffer layer is formed on a sapphire substrate whose principal plane orientation is the (0001) plane at a relatively low temperature of about 500 to 600 ° C., and then an n-type GaN layer is formed on the low-temperature GaN buffer layer. Then, a processed substrate may be manufactured using the same method as described above (see FIG. 2B).

The fabricated processed substrate was sufficiently organically cleaned and then carried into an MOCVD (metal organic vapor phase epitaxy) apparatus, and a nitride semiconductor underlayer composed of an n-type GaN film having a coating thickness of 6 μm was laminated. In the formation of the n-type GaN underlayer, NH ₃ (ammonia) as a group V element raw material and TMGa (trimethyl gallium) or TEGa (triethyl gallium) as a group III element raw material are formed on a processed substrate set in an MOCVD apparatus. ) And SiH ₄ (Si impurity concentration 1 × 10 ¹⁸ / cm ³ ) was added to these raw materials at a crystal growth temperature of 1050 ° C.

  FIG. 8A shows a schematic cross-sectional view of a substrate with depressions produced by the above-described method. As can be seen from this figure, under the growth conditions described above, a depression was formed only in the upper region of the hill, and the groove was flatly buried by the n-type GaN underlayer. The depression was formed so that the central position of the hill width and the central position of the depression width substantially coincided. Furthermore, the cross-sectional shape of the recess when the groove was formed along the <1-100> direction of the GaN crystal was almost a rectangular shape.

  The nitride semiconductor light emitting device according to the present invention is formed on the substrate with the recess thus manufactured.

  In addition to the groove forming method in the present embodiment described above, an ordinary resist material may be applied directly to the surface of the nitride semiconductor substrate to produce a processed substrate. However, as described above, it is preferable to form the groove via the dielectric film because the shape of the groove is steep.

  Note that when a processed substrate including a heterogeneous substrate (for example, a sapphire substrate) is used as shown in FIG. 2B, the low-temperature GaN buffer layer may be a low-temperature AlN buffer layer. Here, the low temperature buffer layer means a buffer layer formed at a growth temperature of about 500 to 600 ° C. as described above. The buffer layer formed in such a relatively low growth temperature range was amorphous or polycrystalline. However, when SiC or Si is used as the heterogeneous substrate, a nitride grown on the buffer layer is used unless a high-temperature nitride semiconductor buffer layer containing at least Al (a relatively high growth temperature of 700 to 1000 ° C.) is used. This is not preferable because the crystallinity of the semiconductor layer is lowered.

  In the present embodiment, the n-type GaN layer (nitride semiconductor underlayer) grown on the low-temperature GaN buffer layer is not limited to this, and AlxGayInzN (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1; x + y + z = 1) layer may be used, and Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be may be doped.

  In this embodiment, the groove forming method by the dry etching method is exemplified, but it goes without saying that other groove forming methods may be used. For example, a wet etching method, a scribing method, a wire saw process, an electric discharge process, a sputtering process, a laser process, a sand blast process, or a focus ion beam process can be used.

  In the present embodiment, the grooves are formed along the <1-100> direction of the GaN crystal, but the grooves may be formed along the <11-20> direction. When the groove was formed along the <11-20> direction of the GaN crystal, the cross-sectional shape of the recess was close to an inverted trapezoidal shape as shown in FIG. However, if the bottom of the depression is filled, the cross-sectional shape becomes close to a V shape.

  In this embodiment, a GaN substrate or a sapphire heterogeneous substrate having a (0001) plane as the main surface is used, but other plane orientations or other heterogeneous substrates may be used. The numerical values of the groove width, hill width, and groove depth formed on the processed substrate described in this embodiment, and the numerical value of the coating thickness of the nitride semiconductor underlayer are the same as those in the first embodiment. Other numerical values may be adopted as long as the numerical range conditions described are satisfied. This is the same in other embodiments.

  [Embodiment 3] In Embodiment 3, a method for manufacturing a substrate with a depression having depressions not only above a hill but also above a groove will be described with reference to FIG. Note that matters not specifically mentioned in the present embodiment are the same as those in the first and second embodiments.

  That is, the processed substrate and the nitride semiconductor underlayer in FIG. 9 (GaN underlayer in this embodiment) are manufactured in the same manner as in the second embodiment. However, the coating thickness of the GaN underlayer was relatively thin and was 3 μm.

  Since the substrate with depressions has depressions not only above the hills but also above the grooves, as described in the previous item (the crystal growth mode in the present invention), the crystals collided by the lateral growth. There is no concentrated portion of crystal strain due to GaN, and it can be covered with a GaN underlayer whose crystal strain is almost alleviated.

  The nitride semiconductor light emitting device according to the present invention is manufactured on the substrate with the recess thus manufactured.

  In addition, the substrate with a depression in the third embodiment can be easily obtained mainly by adjusting the coating thickness of the GaN foundation layer covering the processed substrate to be thin.

  [Embodiment 4] Embodiment 4 is the same as Embodiments 1 and 2 described above, except that the width of the hill formed on the processed substrate is not a constant value but various different values.

  The schematic cross-sectional view of FIG. 10 shows the substrate with a recess in this embodiment, the groove width G1 is 12 μm, the groove depth H1 is 3 μm, and only the hill width is L1 = 8 μm and L2 = 14 μm. Had a numerical value. A nitride semiconductor underlayer made of an InGaN film with a coating thickness of 5 μm was laminated on such a processed substrate, and the substrate with a recess according to the fourth embodiment was manufactured.

  The nitride semiconductor light emitting device according to the present invention is formed on the substrate with the recess thus manufactured.

  As can be seen from FIG. 10, the depression 2 formed above the relatively wide hill 2 is changed to the depression formed above the narrow hill 1 by variously changing the hill width formed on the processed substrate. It tends to be larger than 1. A relatively large dent has a larger crystal strain mitigating effect and crack suppressing effect than a small dent. The board | substrate with a hollow containing the hollow from which a magnitude | size differs like this embodiment is preferable at the following points.

  That is, a relatively small dent in a substrate with dents is a region in which a light emitting element having a long laser oscillation lifetime can be formed although the effect of reducing crystal distortion and the effect of suppressing cracks are small compared to a large dent ( Regions I and II in FIG. 7 can be widened (the yield of the light emitting element chip is increased), which is preferable. On the other hand, a relatively large dent in the substrate with dents reduces the area in which a light-emitting element with a long laser oscillation lifetime can be formed, but does not generate residual crystal distortion or cracks that could not be suppressed with a small dent. This is preferable because it can be prevented (this increases the yield of the light emitting element chip). That is, it can be seen that the substrate with a recess according to the present embodiment is preferable from the viewpoints of productivity and yield.

  In the present embodiment, the processed substrates having two different hill widths are exemplified, but it goes without saying that processed substrates having two or more different hill widths may be used.

  [Fifth Embodiment] In the fifth embodiment, the hill width formed on the processed substrate is not a constant value, but is set to various different values, whereby the depression 1 shown in the above-described fourth embodiment (FIG. 10). Reference) is completely and flatly covered with the nitride semiconductor film, and is the same as the fourth embodiment. Further, matters not particularly mentioned in the present embodiment are the same as those in the first and second embodiments.

  The schematic cross-sectional view of FIG. 11 shows a substrate with a recess in this embodiment. The groove width G1 is 16 μm, the groove depth H1 is 2 μm, and only the hill width is L1 = 4 μm and L2 = 24 μm. Had a numerical value. An AlGaN film having a coating thickness of 4 μm was laminated on such a processed substrate, and the substrate with a recess according to the fifth embodiment was produced.

  The nitride semiconductor light emitting device according to the present invention is formed on the substrate with the recess thus manufactured.

  As can be seen from FIG. 11, by changing the hill width formed on the processed substrate in various ways, a depression 2 is formed above the relatively wide hill 2 and above the relatively narrow hill 1. Is completely and flatly buried with a nitride semiconductor underlayer made of an AlGaN film. Such a substrate with a recess in this embodiment is preferable in the following points.

  That is, since no depression is formed above the hill 1 in the substrate with depressions, there is a region where a light emitting element having a long laser oscillation lifetime can be formed, although the effect of reducing crystal distortion and the effect of suppressing cracks are small. It can be wider than that of the fourth embodiment (the yield of the light emitting element chip is increased). On the other hand, the recess 2 formed above the hill 2 in the substrate with recesses has a crystal strain relaxation effect and a crack suppression effect (the yield of the light emitting element chips is increased). Accordingly, a substrate with a recess in which a recess is not formed above some hills among the hills formed on the processed substrate and a recess is formed above other hills is an embodiment from the viewpoint of productivity. 4 is preferable.

  In the present embodiment, the processed substrates having two different hill widths are exemplified, but it goes without saying that processed substrates having two or more different hill widths may be used.

  [Embodiment 6] Embodiment 6 is the same as Embodiments 1 and 2 described above, except that the depth of the groove formed on the processed substrate is not a constant value but various different values.

  The schematic cross-sectional view of FIG. 12 shows a substrate with a recess according to this embodiment. The groove width G1 is 18 μm, the hill width L1 is 5 μm, and only the groove depth is H1 = 2.5 μm and H2 = 10 μm. Had street numbers. A nitride semiconductor underlayer made of a GaN film with a coating thickness of 6 μm was laminated on such a processed substrate, and the substrate with a recess according to the sixth embodiment was manufactured.

  The nitride semiconductor light emitting device according to the present invention is formed on the substrate with the recess thus manufactured.

  As can be seen from FIG. 12, the recess 2 is formed only above the relatively deep groove 2 by variously changing the depth of the groove formed in the processed substrate. The substrate with a recess in this embodiment is preferable in the following points.

  That is, since no depression is formed above the groove 2 other than the groove 2 in the substrate with the depression, a region where a light emitting element having a long laser oscillation lifetime can be formed although the effect of reducing the crystal distortion and the effect of suppressing the crack are small. (The yield of the light emitting element chip is increased). On the other hand, the recess 2 formed above the groove 2 in the substrate with recesses has an effect of reducing crystal distortion and an effect of suppressing cracks. Therefore, a substrate with a recess in which a recess is formed above some of the grooves formed on the processed substrate and no recess is formed on the other grooves, from the viewpoint of productivity of the light emitting element chip. preferable.

  In the present embodiment, a processed substrate having two different groove depths is illustrated, but it goes without saying that processed substrates having two or more different groove depths may be used. It goes without saying that the present embodiment may be combined with at least one of the above-described third to fifth embodiments.

  [Embodiment 7] Embodiment 7 is the same as Embodiments 1 and 2, except that the groove width formed on the processed substrate is not a constant value but various different values. .

  The schematic cross-sectional view of FIG. 13 shows a substrate with a recess in this embodiment. Hill width L1 is 5 μm, groove depth H1 is 4 μm, and only the groove width is G1 = 12 μm and G2 = 24 μm. Had a value. A nitride semiconductor underlayer made of a GaN film with a coating thickness of 6 μm was laminated on such a processed substrate, and the substrate with a recess according to the seventh embodiment was manufactured.

  And the nitride semiconductor light-emitting device based on this invention is formed on the board | substrate with a depression produced in this way.

  As can be seen from FIG. 13, the recess 2 is formed only above the relatively wide groove 2 by variously changing the width of the groove formed on the processed substrate. The substrate with a recess in the present embodiment has the same effects as those of the sixth embodiment.

  In the present embodiment, the processed substrate having two different groove widths is exemplified, but it goes without saying that processed substrates having two or more different groove widths may be used. Needless to say, this embodiment may be combined with at least one of the above-described third to sixth embodiments.

  [Eighth Embodiment] In an eighth embodiment, a nitride semiconductor laser device is fabricated on any of the substrates with depressions in the first to seventh embodiments.

(Crystal Growth) FIG. 1 shows a nitride semiconductor laser device after a nitride semiconductor laser wafer grown on a substrate with depressions is divided into chips. The nitride semiconductor laser device shown in FIG. 1 includes a substrate 100 with a recess made of a processed substrate (n-type GaN substrate) 101 and an n-type Al _0.05 Ga _0.95 N underlayer 102, an n-type In _0.07 Ga _0.93 N crack prevention layer. 103, n-type Al _0.1 Ga _0.9 N cladding layer 104, n-type GaN light guide layer 105, light emitting layer 106, p-type Al _0.2 Ga _0.8 N carrier block layer 107, p-type GaN light guide layer 108, p-type Al _0.1 Ga. _0.9 N-cladding layer 109, p-type GaN contact layer 110, n-electrode 111, p-electrode 112 and SiO ₂ dielectric film 113 are included.

  In manufacturing such a nitride semiconductor laser device, first, a substrate 100 with a recess according to any one of Embodiments 1 to 7 was formed. However, in the eighth embodiment, the groove direction is formed along the <1-100> direction of the GaN substrate.

Next, using the MOCVD apparatus, the group V element raw material NH ₃ (ammonia) and the group III element raw material TMGa (trimethyl gallium) or TEGa (triethyl gallium) TMIn (trimethylindium) as an elemental raw material and SiH ₄ (silane) as an impurity were added, and an n-type In _0.07 Ga _0.93 N crack prevention layer 103 was grown to a thickness of 40 nm at a crystal growth temperature of 800 ° C. Next, the substrate temperature is raised to 1050 ° C., and a group III element raw material TMAl (trimethylaluminum) or TEAl (triethylaluminum) is used to form an n-type Al _0.1 Ga _0.9 N cladding layer 104 having a thickness of 0.9 μm. (Si impurity concentration 1 × 10 ¹⁸ / cm ³ ) was grown, and then n-type GaN light guide layer 105 (Si impurity concentration 1 × 10 ¹⁸ / cm ³ ) was grown to a thickness of 0.1 μm.

Thereafter, the substrate temperature is lowered to 800 ° C., and a light emitting layer (multiple quantum well structure) 106 in which an In _0.01 Ga _0.99 N barrier layer having a thickness of 8 nm and an In _0.15 Ga _0.85 N well layer having a thickness of 4 nm are alternately stacked. Formed. In this embodiment, the light emitting layer 106 has a multiple quantum well structure that starts with a barrier layer and ends with a barrier layer, and includes three (three periods) quantum well layers. Further, Si impurity was added to both the barrier layer and the well layer at a concentration of 1 × 10 ¹⁸ / cm ³ . A crystal growth interruption period of 1 second or more and 180 seconds or less may be inserted between the barrier layer and the well layer or between the well layer and the barrier layer. This is preferable because the flatness of each layer is improved and the half width of the emission spectrum is reduced.

Using AsH ₃ or TBAs (tertiary butyl arsine) when As is added to the light-emitting layer 106, using a PH ₃ or TBP (tertiary butyl phosphine) when P is added, and Sb is added In this case, TMSb (trimethylantimony) or TESb (triethylantimony) may be used. Further, when the light emitting layer is formed, N ₂ H ₄ (dimethylhydrazine) may be used as the N raw material in addition to NH ₃ .

Next, the temperature of the substrate is raised again to 1050 ° C., and a p-type Al _0.2 Ga _0.8 N carrier blocking layer 107 having a thickness of 20 nm, a p-type GaN light guide layer having a thickness of 0.1 μm, and a 0.5 μm thickness is formed. A p-type Al _0.1 Ga _0.9 N clad layer 109 and a p-type GaN contact layer 110 having a thickness of 0.1 μm were sequentially grown. As the p-type impurity, Mg (EtCP ₂ Mg: bisethylcyclopentadienyl magnesium) was added at a concentration of 5 × 10 ¹⁹ / cm ³ to 2 × 10 ²⁰ / cm ³ . The p-type impurity concentration of the p-type GaN contact layer 110 is preferably increased as it approaches the interface with the p-electrode 112. By doing so, the contact resistance at the interface with the p-electrode is reduced. Further, in order to remove residual hydrogen in the p-type layer that hinders activation of Mg, which is a p-type impurity, a trace amount of oxygen may be mixed during the growth of the p-type layer.

After the p-type GaN contact layer 110 is grown in this way, the entire gas in the reactor of the MOCVD apparatus is changed to nitrogen carrier gas and NH ₃ , and the substrate temperature is cooled at a cooling rate of 60 ° C./min. It was. When the substrate temperature was cooled to 800 ° C., the supply of NH ₃ was stopped, and the substrate temperature was maintained for 5 minutes and then cooled to room temperature. The holding temperature of the substrate is preferably between 650 ° C. and 900 ° C., and the holding time is preferably 3 minutes or more and 10 minutes or less. Moreover, it is preferable that the cooling rate to room temperature is 30 degree-C / min or more. The crystal growth film thus formed was evaluated by Raman measurement. As a result, even if the conventional p-type annealing was not performed, the growth film had already exhibited p-type characteristics (that is, Mg was active). ). Further, the contact resistance when the p-electrode 112 is formed is also reduced. In addition to this, if the conventional p-type annealing was combined, the Mg activation rate was further improved, which was preferable.

  In the crystal growth process according to the present embodiment, the crystal may be continuously grown from the processed substrate to the nitride semiconductor laser element, or the nitride is formed after the growth process from the processed substrate to the substrate with the depression is performed in advance. Re-growth for growing the semiconductor laser element may be performed.

The In _0.07 Ga _0.93 N crack prevention layer 103 in this embodiment may have an In composition ratio other than 0.07, or the InGaN crack prevention layer may be omitted. However, when the lattice mismatch between the cladding layer and the GaN substrate becomes large, it is preferable to insert an InGaN crack prevention layer.

  The light emitting layer 106 of this embodiment has a configuration starting with a barrier layer and ending with a barrier layer, but may have a configuration starting with a well layer and ending with a well layer. Further, the number of well layers in the light emitting layer is not limited to the above-described three layers, and if it is 10 layers or less, the threshold current value becomes low and room temperature continuous oscillation is possible. In particular, when the number of well layers was 2 or more and 6 or less, the threshold current value was low, which was preferable.

In the light emitting layer 106 of this embodiment, Si is added to both the well layer and the barrier layer at a concentration of 1 × 10 ¹⁸ / cm ³ , but Si may not be added. However, the emission intensity was stronger when Si was added to the light emitting layer. The impurity added to the light emitting layer is not limited to Si, and at least one of O, C, Ge, Zn, and Mg may be added. The total amount of impurities added was preferably about 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ . Furthermore, the layer to which the impurity is added is not limited to both the well layer and the barrier layer, and the impurity may be added to only one of these layers.

The p-type Al _0.2 Ga _0.8 N carrier block layer 107 of this embodiment may have an Al composition ratio other than 0.2, or the carrier block layer may be omitted. However, the threshold current value was lower when the carrier block layer was provided. This is because the carrier block layer 107 has a function of confining carriers in the light emitting layer 106. Increasing the Al composition ratio of the carrier block layer is preferable because this increases carrier confinement. Conversely, it is preferable to reduce the Al composition ratio within a range in which carrier confinement is maintained, because the carrier mobility in the carrier block layer increases and the electrical resistance decreases.

In this embodiment, Al _0.1 Ga _0.9 N crystals are used as the p-type cladding layer 109 and the n-type cladding layer 104, but the Al composition ratio may be other than 0.1. If the mixed crystal ratio of Al increases, the energy gap difference and the refractive index difference with the light emitting layer 106 increase, and carriers and light are efficiently confined in the light emitting layer, and the laser oscillation threshold current value can be reduced. become. On the other hand, if the Al composition ratio is reduced within the range in which the confinement of carriers and light is maintained, the carrier mobility in the cladding layer increases and the operating voltage of the device can be lowered.

  The thickness of the AlGaN cladding layer is preferably in the range of 0.7 μm to 1.5 μm. This improves the single peak of the vertical transverse mode and increases the optical confinement efficiency, and improves the optical characteristics of the laser and the laser threshold. The value current value can be reduced.

  The cladding layer is not limited to an AlGaN ternary mixed crystal, and may be a quaternary mixed crystal such as AlInGaN, AlGaNP, or AlGaNAs. The p-type cladding layer has a superlattice structure including a p-type AlGaN layer and a p-type GaN layer or a superlattice structure including a p-type AlGaN layer and a p-type InGaN layer in order to reduce electrical resistance. May be.

  In the present embodiment, the crystal growth method using the MOCVD apparatus is exemplified, but a molecular beam epitaxy method (MBE), a hydride vapor phase epitaxy method (HVPE), or the like may be used.

  (Chip forming step) An epi-wafer formed by the above-described crystal growth (a wafer in which a nitride semiconductor multilayer structure is epitaxially grown on a processing substrate) is taken out from the MOCVD apparatus and processed into a laser element. Here, the surface of the epi-wafer on which the nitride semiconductor multilayer film structure was formed had a depression and was not completely and completely buried.

  Since the processed substrate 101 is an n-type conductive nitride semiconductor, an n-electrode 111 is formed on the back side thereof in the order of stacking of Hf / Al (see FIG. 1). As the n-electrode, a laminate of Ti / Al, Ti / Mo, Hf / Au, or the like can also be used. It is preferable to use Hf for the n-electrode because the contact resistance is lowered.

The p-electrode portion was etched in a stripe shape along the groove direction of the processed substrate 101, whereby a ridge stripe portion (see FIG. 1) was formed. When the grooves of the processed substrate are grid-shaped, either the <1-100> direction or the <11-20> direction of the nitride semiconductor may be selected as the longitudinal direction of the grooves. The ridge stripe portion has a stripe width W = 2.0 μm and is formed so as to be included in the region I described above (see FIG. 1). Thereafter, a SiO ₂ dielectric film 113 is deposited, and the upper surface of the p-type GaN contact layer 110 is exposed from the dielectric film, and a p-electrode 112 is deposited thereon as a Pd / Mo / Au stack. It was. As the p-electrode, a laminate of Pd / Pt / Au, Pd / Au, Ni / Au, or the like may be used. Further, a pad electrode made of Au may be interposed between the p electrode 112 and the wire bond.

  Finally, the epi-wafer was cleaved at a plane perpendicular to the longitudinal direction of the ridge stripe to produce a Fabry-Perot resonator having a resonator length of 500 μm. In general, the resonator length is preferably in the range of 300 μm to 1000 μm. The mirror end face of the resonator length in which the groove is formed along the <1-100> direction has the M face {1-100} of the nitride semiconductor crystal as the end face. The cleavage for forming the mirror end face and the division of the laser element were performed from the back side of the processed substrate 101 using a scriber. However, the cleavage is not performed by scribing the scriber across the entire back surface of the wafer, but by cleaving the scriber on only a part of the wafer, for example, both ends of the wafer. . As a result, steepness of the end face of the element and shavings due to scribing do not adhere to the epi surface, thereby improving the element yield. On the surface of the nitride semiconductor light emitting element (laser element) divided into chips, there are two or more depressions across the ridge stripe portion of the nitride semiconductor light emitting element. The p-electrode 112 was formed on a region including two or more dents, and the wire bond was formed on a region including one or more dents.

  As a feedback method of the laser resonator, generally known DFB (distributed feedback), DBR (distributed Bragg reflection), or the like can be used.

After the mirror end face of the Fabry-Perot resonator was formed, SiO ₂ and TiO ₂ dielectric films were alternately deposited on the mirror end face to form a dielectric multilayer reflective film having a reflectivity of 70%. . As this dielectric multilayer reflective film, a multilayer film such as SiO ₂ / Al ₂ O ₃ can also be used.

Although the n-electrode 111 is formed on the back surface of the processed substrate 101, a part of the n-type Al _0.05 Ga _0.95 N film 102 is exposed from the front side of the epi-wafer using the dry etching method, and the n-electrode 111 is formed on the exposed region. An n-electrode may be formed.

  (Package Mounting) The obtained semiconductor laser element is mounted on a package. When a nitride semiconductor laser device with high output (30 mW or more) is used, attention must be paid to heat dissipation measures. The high-power nitride semiconductor laser device can be connected to the package body using an In solder material with the semiconductor junction either up or down, but it is preferable from the viewpoint of heat dissipation to connect the semiconductor junction down. . The high-power nitride semiconductor laser element can usually be directly attached to the package body or the heat sink, but a submount such as Si, AlN, diamond, Mo, CuW, BN, Fe, SiC, Cu, or Au is used. It may be connected via.

  As described above, the nitride semiconductor laser device according to the present embodiment was fabricated. In this embodiment, the GaN processed substrate 101 is used. However, other nitride semiconductor processed substrates may be used. For example, in the case of a nitride semiconductor laser, a layer having a lower refractive index than the cladding layer needs to be in contact with the outside of the cladding layer in order to make the vertical transverse mode unimodal, and an AlGaN substrate can be preferably used. .

  In this embodiment, the nitride semiconductor laser element is formed on the substrate with the depression, so that the crystal distortion is alleviated and the generation of cracks is suppressed, and the laser output is 30 mW under the condition of the atmospheric temperature of 60 ° C. A laser oscillation life of about 18000 hours was obtained, and an improvement in device yield due to a crack suppression effect was achieved.

  [Embodiment 9] In Embodiment 9, a nitride semiconductor light emitting diode (LED) element is formed on any of the substrates with depressions in Embodiments 1-7. At this time, the nitride semiconductor LED element layer was formed by a method similar to the conventional method.

  In the nitride semiconductor LED device according to the present embodiment, the color unevenness is reduced and the emission intensity is improved as compared with the conventional one. In particular, LED elements having a light emission wavelength of a short wavelength (450 nm or less) or a long wavelength (600 nm or more), such as a white nitride semiconductor LED element or an amber nitride semiconductor LED element using a nitride semiconductor as a raw material, are described in the embodiments. By being formed on the substrate with depressions 1 to 7, it was possible to have a light emission intensity of about twice or more compared with the conventional one.

[Embodiment 10] Embodiment 10 is the same as Embodiments 8 and 9, except that the light-emitting layer contains at least one substitution element of As, P, and Sb to be substituted for part of N. Met. More specifically, a substitution element of at least one of As, P, and Sb was included in the light emitting layer of the nitride semiconductor light emitting device by substituting at least a part of N of the well layer. At this time, when the composition ratio of the sum of As, P and / or Sb contained in the well layer is x and the composition ratio of N is y, x is smaller than y and x / (x + y) is 0. .3 (30%) or less, preferably 0.2 (20%) or less. Further, the lower limit value of the preferred concentration of the sum of As, P, and / or Sb was 1 × 10 ¹⁸ / cm ³ or more.

This is because if the composition ratio x of the substitution element is higher than 20%, concentration separation with different composition ratio of the substitution element starts to occur in the well layer, and if the composition ratio x is higher than 30%, the concentration separation starts. This is because there is a high possibility that the crystallinity of the well layer is lowered by starting to shift to a crystal system separation in which a hexagonal system and a cubic system are mixed. On the other hand, if the total concentration of the substituting elements is less than 1 × 10 ¹⁸ / cm ³ , it is difficult to obtain the effect of including the substituting elements in the well layer.

  As an effect of the present embodiment, by including at least one of substitution elements of As, P, and Sb in the well layer, the effective mass of electrons and holes in the well layer is reduced and the mobility is increased. In the case of a semiconductor laser device, a small effective mass means that a carrier inversion distribution for laser oscillation can be obtained with a small amount of current injection, and a large mobility means that electrons and holes disappear in the light emitting layer due to light emission recombination. This also means that new electrons and holes can be injected at high speed by diffusion. That is, compared to an InGaN-based nitride semiconductor laser device that does not contain any of As, P, and Sb in the light emitting layer, the present embodiment has a low threshold current density and excellent self-oscillation characteristics (noise). It is possible to obtain a semiconductor laser having excellent characteristics.

  On the other hand, when this embodiment is applied to a nitride semiconductor LED, it is compared with a nitride semiconductor LED element including a conventional InGaN well layer by including substitution elements of As, P, and / or Sb in the well layer. Thus, the In composition ratio in the well layer can be reduced. This means that a decrease in crystallinity due to concentration separation of In can be suppressed. Therefore, the effect of the addition of the substitution element is synergistic with the effect related to the nitride semiconductor LED of the eighth embodiment, and further increases the emission intensity and reduces the color unevenness. In particular, a nitride semiconductor LED element having a short wavelength (450 nm or less) or a long wavelength (600 nm or more), such as a white nitride semiconductor LED element or an amber nitride semiconductor LED element using a nitride semiconductor as a raw material. In this case, since the well layer can be formed with low or no In composition ratio, the color unevenness is small compared to the conventional InGaN-based nitride semiconductor LED device, and strong light emission intensity is obtained.

  [Embodiment 11] In Embodiment 11, the nitride semiconductor laser element of Embodiment 8 or 10 is applied to an optical device. The blue-violet nitride semiconductor laser element (wavelength of 380 to 420 nm) according to Embodiment 8 or 10 can be preferably used in various optical devices. For example, it is preferable in the following points when used in an optical pickup device. That is, such a nitride semiconductor laser element operates stably at a high output (30 mW) in a high-temperature atmosphere (60 ° C.), has few element defects, and has a long laser oscillation life. It is most suitable for an optical disk device for density recording / reproduction (the shorter the light wavelength, the higher the density recording / reproduction is possible).

  In FIG. 14, as an example in which the nitride semiconductor laser element according to Embodiment 8 or 10 is used in an optical device, an optical disk device including an optical pickup such as a DVD device is shown in a schematic block diagram. In this optical information recording / reproducing apparatus, a laser beam 3 emitted from a light source 1 including a nitride semiconductor laser element is modulated by an optical modulator 4 in accordance with input information, and on a disk 7 via a scanning mirror 5 and a lens 6. To be recorded. The disk 7 is rotated by a motor 8. At the time of reproduction, the reflected laser light optically modulated by the bit arrangement on the disk 7 is detected by the detector 10 via the beam splitter 9, whereby a reproduction signal is obtained. The operation of each of these elements is controlled by the control circuit 11. The output of the laser element 1 is usually 30 mW during recording and about 5 mW during reproduction.

  The laser element according to the present invention can be used not only for the optical disk recording / reproducing apparatus as described above, but also for a laser printer, a barcode reader, a projector using three primary colors of light (blue, green, red) laser.

  [Embodiment 12] In Embodiment 12, the nitride semiconductor light-emitting diode element according to Embodiment 9 or 10 is used in a semiconductor light-emitting device. That is, the nitride semiconductor light-emitting diode element according to Embodiment 9 or 10 can be used in at least one of the three primary colors (red, green, and blue) of light, such as a display device (semiconductor light-emitting device). By using such a nitride semiconductor light emitting diode element, a display device with little color unevenness and high emission intensity can be manufactured.

  A nitride semiconductor light-emitting diode element capable of generating such three primary colors of light can also be used in a white light source device. On the other hand, the nitride semiconductor light-emitting diode device according to the present invention having an emission wavelength in the ultraviolet region to the violet region (about 380 to 420 nm) can also be used as a white light source device by applying a fluorescent paint.

  By using such a white light source, it becomes possible to realize a backlight with low power consumption and high brightness in place of the halogen light source used in the conventional liquid crystal display. This can also be used as a backlight for a liquid crystal display of a man-machine interface in a portable notebook computer or a mobile phone, and can provide a small and high-definition liquid crystal display.

It is typical sectional drawing which shows an example of the nitride semiconductor laser element formed on the board | substrate with a recess in this invention. (A) is typical sectional drawing which shows an example of the processed substrate of the nitride semiconductor which can be used in this invention, (b) has shown the processed substrate containing a dissimilar substrate. It is typical sectional drawing which shows an example of the board | substrate with a dent which may be used in this invention. (A) represents the crystal growth form on the processed substrate in the present invention, (b) represents the crystal growth form when the processed substrate is completely and flatly coated with the nitride semiconductor multilayer structure, and (c) Represents a crystal growth form in selective growth using a crystal growth inhibiting film. The form of the groove | channel (recessed part) and the hill (convex part) formed in the process board | substrate which can be used in this invention is shown, (a) shows the case where the groove | channel which has two types of directions is mutually orthogonal, (b ) Shows a case where grooves having two kinds of directions intersect with each other at an angle of 60 °, and (c) shows a case where grooves having three kinds of directions intersect with each other at an angle of 60 °. It is a figure which shows the relationship between the formation position of the ridge stripe part of the nitride semiconductor laser element formed on the board | substrate with a dent which can be used in this invention, and a laser oscillation lifetime. It is typical sectional drawing which shows the preferable formation area of the light emission part in the light emitting element structure formed on the board | substrate with a dent which may be used in this invention. It is typical sectional drawing which shows the other example of the board | substrate with a dent which may be used in this invention. It is typical sectional drawing which shows the other example of the board | substrate with a dent which may be used in this invention. It is typical sectional drawing which shows the other example of the board | substrate with a dent which may be used in this invention. It is typical sectional drawing which shows the other example of the board | substrate with a dent which may be used in this invention. It is typical sectional drawing which shows the other example of the board | substrate with a dent which may be used in this invention. It is typical sectional drawing which shows the other example of the board | substrate with a dent which may be used in this invention. It is a typical block diagram which shows an example of the optical apparatus containing the optical pick-up apparatus using the nitride semiconductor laser element by this invention.

Explanation of symbols

100 substrate with depression, 101 processed substrate, 102 n-type Al _0.05 Ga _0.95 N underlayer, 103 n-type In _0.07 Ga _0.93 N crack prevention layer, 104 n-type Al _0.1 Ga _0.9 N clad layer, 105 n-type GaN light guide layer , 106 light emitting layer, 107 p-type Al _0.2 Ga _0.8 N carrier blocking layer, 108 p-type GaN guide layer, 109 p-type Al _0.1 Ga _0.9 N cladding layer, 110 p-type GaN contact layer, 111 n electrode, 112 p electrode, 113 SiO ₂ dielectric film.

Claims (11)

A nitride semiconductor layer is grown on a heterogeneous substrate other than a nitride semiconductor, and then the nitride semiconductor layer is processed to form a concave portion and a convex portion made of a single material; and
A nitride semiconductor multilayer structure having a crystal grown on the substrate,
The nitride semiconductor multilayer film structure is a nitride semiconductor light emitting device having a light emitting portion above the convex portion and a recess formed on the surface above the concave portion,
The recess includes a bottom and a side wall,
The depression is formed by not being completely filled during crystal growth,
The nitride semiconductor light emitting device, wherein a width of the recess is narrower than a width of the recess.   2. The nitride semiconductor light emitting device according to claim 1, wherein the nitride semiconductor multilayer film structure includes a structure in which a current is injected into the light emitting portion above the convex portion. 3. A nitride semiconductor layer is grown on a heterogeneous substrate other than a nitride semiconductor, and then the nitride semiconductor layer is processed to form a concave portion and a convex portion made of a single material; and
A nitride semiconductor underlayer crystal-grown on the substrate;
An epitaxial wafer in which a depression and a flattened portion are formed on the surface of the nitride semiconductor underlayer,
The recess includes a bottom and a side wall,
The recess is formed by not being completely buried above the recess during crystal growth, and the width of the recess is narrower than the recess, and the width of the flattened portion Is an epi-wafer wider than the width of the projection. A nitride semiconductor layer is grown on a heterogeneous substrate other than a nitride semiconductor, and then the nitride semiconductor layer is processed to form a concave portion and a convex portion made of a single material; and
A nitride semiconductor multilayer structure having a crystal grown on the substrate;
An epitaxial wafer in which a depression and a flattened portion are formed on the surface of the nitride semiconductor multilayer structure,
The nitride semiconductor multilayer structure has a nitride semiconductor underlayer and a light emitting layer,
The recess includes a bottom and a side wall,
The recess is formed by not being completely buried above the recess during crystal growth, and the width of the recess is narrower than that of the recess, and the flattened portion An epi-wafer characterized in that the width is wider than the width of the convex portion.   The epi-wafer according to claim 4, wherein the nitride semiconductor multilayer structure has a light emitting portion above the convex portion.   6. The nitride semiconductor light emitting device according to claim 5, wherein said epitaxial wafer has a structure in which current is injected into said light emitting part above said convex part, and said epi wafer is divided into individual chips.   7. The nitride semiconductor according to claim 1, wherein the light emitting part is formed in a region separated by 1 μm or more from the center of the convex part to the right or left side in the width direction. 8. Light emitting element.   7. The nitride semiconductor light emitting device according to claim 1, wherein a width of the recess is in a range of 1 to 100 [mu] m.   The depth of the recess is 1 μm or more, and the remaining thickness between the bottom of the recess and the back surface of the substrate is 100 μm or more. The nitride semiconductor light emitting device described. It said recess is provided with a plurality,
A plurality of said recesses includes a narrow the recess relatively wide and relatively wide the recess,
The nitride semiconductor light emitting device according to claim 1, further comprising a recess only above the relatively wide recess. Growing a nitride semiconductor layer on a heterogeneous substrate other than the nitride semiconductor;
After the step of growing the nitride semiconductor layer, forming a concave portion and a convex portion made of a single material by processing on the surface of the nitride semiconductor layer;
A method of manufacturing a nitride semiconductor light-emitting device, comprising: a step of crystal-growing a nitride semiconductor multilayer film structure having a light-emitting portion above the convex portion and having a depression on the surface,
The recess includes a bottom and a side wall,
The method of manufacturing a nitride semiconductor light emitting device, wherein the recess is formed by not being completely buried above the recess during crystal growth, and the width of the recess is narrower than the recess .