JP2007258673A - Nitride semiconductor laser, and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an embedding nitride semiconductor laser having stable characteristics, and to provide a method of manufacturing the same. <P>SOLUTION: A nitride semiconductor laser 10 has a recessed structure including an active layer 12 interposed between an n-type clad layer 11 and a p-type clad layer 13, and a current constriction layer 14 having an opening for constricting current to the active layer 12. In this embedding configuration, a regrown layer 15 is formed on the current constriction layer 14 so as to cover the opening of the current constriction layer 14. The regrown layer 15 is made up of a nitride semiconductor layer (InGaN layer, AlInGaN layer) containing In to which a p-type impurity is added. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor laser device and a manufacturing method thereof, and more particularly to a nitride semiconductor laser device having an embedded current confinement structure and a manufacturing method thereof.

Currently, aluminum, which is a group III element represented by gallium nitride (GaN) and represented by the general formula In _x Ga _y Al _1-XY N (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, X + Y ≦ 1) A group III-V nitride compound semiconductor composed of (Al), gallium (Ga) and indium (In) and nitrogen (N) which is a group V element, a so-called nitride semiconductor (hereinafter referred to as a GaN semiconductor). It attracts attention. For example, with respect to optical devices, light emitting diodes (LEDs) using nitride semiconductors are used in large display devices and traffic lights. In addition, some white LEDs combining a nitride semiconductor LED and a phosphor have been commercialized, and it is expected to replace the current lighting device if the luminous efficiency is improved in the future.

  Also, blue-violet semiconductor laser devices using nitride semiconductors have been actively researched and developed. The blue-violet semiconductor laser device can reduce the spot diameter on the optical disc as compared with a semiconductor laser device that emits light in the red range or infrared range, which is used in conventional optical discs such as CDs and DVDs. Therefore, it is possible to improve the recording density of the optical disc.

  A blue-violet semiconductor laser device currently in practical use employs a ridge structure as shown in FIG. In this structure, the ridge 101 is formed by dry etching, and the transverse mode is controlled by adjusting the ridge width and the ridge depth.

  However, in this ridge structure, since the electrode 102 needs to be formed on the ridge 101, the electrode area width is limited. Further, since the ridge 101 is formed by dry etching, the ridge depth varies, and as a result, the transverse mode characteristics vary. Due to such structural and manufacturing problems, a reliable blue-violet semiconductor laser device having sufficient performance has not been obtained with a high yield.

  On the other hand, an embedded laser device as shown in FIG. 9 is used in a GaAs semiconductor laser device, but has not yet been adopted in a GaN semiconductor laser device. This is because it is difficult to stably etch a GaN-based semiconductor with low damage. A general method for processing a GaN-based material is dry etching. However, when the opening 104 is formed in the current confinement layer 103, if dry etching is used, damage is caused in the vicinity thereof, and device characteristics deteriorate. Moreover, although there is generally a wet etching technique as a low damage etching method, a wet etching technique with good reproducibility for a GaN-based material has not been established. In addition to such a processing technique for GaN-based semiconductors, GaN-based semiconductors are difficult to grow crystals, and after the opening 104 is formed in the current confinement layer 103, the cladding layer 106 having good crystallinity can be regrown. The difficulty is also one of the reasons for not hiring.

  However, the buried structure can accurately control the distance from the InGaN active layer to the current confinement layer 103 that affects the transverse mode characteristics, and can reduce the series resistance because a wide contact electrode area can be realized. Therefore, there are many advantages in terms of performance and reliability as compared with the ridge structure.

  Therefore, several techniques for solving the problems inherent in the GaN-based semiconductor in the above-described buried structure have been proposed.

  Patent Document 1 describes a technique for improving the etching reproducibility of the opening of the current confinement layer by increasing the etching selectivity of the GaN-based semiconductor. That is, after forming an amorphous current confinement layer on a crystalline cladding layer, a part of the current confinement layer is etched by wet etching using a phosphoric acid-containing liquid, and then a high temperature heat treatment is performed. Thus, the amorphous current confinement layer is crystallized.

  According to this technique, when etching a current confinement layer that is amorphous, the etching layer is used to remove the cladding layer having the underlying crystallinity by utilizing the large etching ratio between the amorphous layer and the crystalline layer. Thereby, the etching process of the current confinement layer can be performed with good control.

  However, even after forming an opening in an amorphous current confinement layer, the amorphous layer is crystallized by performing a high-temperature heat treatment, as described above, it is difficult to grow a crystal of a GaN-based semiconductor. The recrystallized layer obtained by the heat treatment is not necessarily good quality. Even if a regrown layer is further formed on such a current confinement layer with low crystallinity, it is difficult to obtain a regrown layer with good crystallinity.

Patent Document 2 discloses a technique for forming an opening in a current confinement layer without etching a base clad layer by forming a reevaporation layer serving as an etching stop layer between the clad layer and the current confinement layer. Is described. Here, the re-evaporated layer exposed in the opening portion of the current confinement layer is made of a material that is selectively removed by forming an opening portion in the current confinement layer and then evaporating it by heat treatment. Since the step of evaporating the re-evaporated layer can be performed in the MOCVD apparatus, the re-grown layer is maintained following the evaporation step while maintaining a clean surface without exposing the exposed underlying cladding layer to the atmosphere. Therefore, a regrowth layer with good crystallinity can be obtained.
JP 2003-78215 A JP-A-10-93199

  By using the technique described in Patent Document 2, the workability of the current confinement layer and the crystallinity of the regrowth layer can be improved, but a GaN-based semiconductor laser having high performance and reliability can be obtained. At present, a buried GaN-based semiconductor laser has not yet been put into practical use.

  By the way, the inventor of the present application has been studying a method capable of forming the opening of the current confinement layer with good control, paying attention to the essential performance advantage of the buried structure, and has found the following method, A patent application (Japanese Patent Application No. 2005-253824) has been filed for this method.

  In this method, an active layer sandwiched between clad layers is formed on a GaN substrate, a current confinement layer is formed on the clad layer, and an opening is formed in the current confinement layer. The surface of the current confinement layer (Group III surface) is wet-etched by a method called photoelectrochemical (PEC) etching while protecting the Group V surface from the etching solution.

  Here, PEC etching is performed by immersing a GaN substrate in an electrolytic solution and irradiating an object to be etched (in this case, a current confinement layer) with ultraviolet light, and is generated on the surface of the current confinement layer by ultraviolet irradiation. Etching proceeds due to the dissolution reaction of the current confinement layer caused by the holes.

  The inventor of the present application has a property that holes generated by irradiating ultraviolet rays move to the group V surface of the GaN-based semiconductor, and therefore, the etching of the group III surface does not proceed. The current confinement layer (Group III surface) etching is not stable because of this phenomenon, and the current confinement layer is etched with the back surface (Group V surface) of the GaN substrate protected from the etching solution. As a result, stable etching can be performed.

  By applying this etching method, the present inventor can stably obtain a buried GaN-based semiconductor laser device, and as a result, evaluate the characteristics of the semiconductor laser device with good reproducibility. Became possible.

  Under such circumstances, the characteristics of the buried GaN-based semiconductor laser device were evaluated, and it was found that there was a sample whose laser oscillation threshold current greatly deviated from the design value despite the same structure. .

  Usually, in order to confirm the finished structure of the prepared sample, it is often performed to observe the cross section of the sample with an electron microscope. FIG. 1A shows a cross-sectional photograph of a sample with a threshold current greatly deviating from a design value by an electron microscope, and FIG. 1B schematically shows it.

  As shown in FIG. 1B, an n-type AlGaN current confinement layer 2 having an opening 4 is formed on a p-type GaN guide layer 1, and a p-type GaN guide layer 3 is formed thereon. (Note: This sample has a structure in which a guide layer is provided between the cladding layer and the active layer).

  By the way, in order to observe such a cross-sectional structure with an electron microscope, it is performed by detecting reflected electrons and looking at the contrast due to the difference in crystal composition, but by detecting secondary electrons, Differences in conductivity can also be seen in contrast.

  When the inventor of the present application detected secondary electrons in the same region as in FIG. 1A, a secondary electron image as shown in FIG. 1C was observed. FIG. 1D is a diagram schematically showing this.

  When FIGS. 1A and 1B are compared with FIGS. 1C and 1D, there is a difference between the boundary due to the difference in composition (arrow A) and the boundary due to the difference in conductivity (arrow B). I understood that. This is because, in the GaN guide layer 3 that should be p-type conductive, the region in contact with the side surface of the opening 4 of the current confinement layer 2 is changed to an n-type conductive or high-resistance layer with a certain width. Means that.

  Although the cause of the occurrence of the n-type phenomenon is not clear, when the p-type GaN guide layer 3 is regrown, the growth layer from the side surface of the opening 4 easily takes in the n-type impurity or acts as a donor. It is considered that a defect is likely to occur.

  In order to further verify this, the growth temperature of the p-type GaN guide layer 3 is changed for a sample having a different width of a region changing to n-type conductivity (hereinafter referred to as an n-type region), When the laser oscillation threshold current of the obtained sample was measured, results as shown in the graph of FIG. 2 were obtained. The horizontal axis indicates the growth temperature of the p-type GaN guide layer 3, and the vertical axis indicates the magnitude of the laser oscillation threshold current. As can be seen from the graph of FIG. 2, it can be seen that the threshold current starts to increase when the growth temperature exceeds 1100 ° C.

  For the sample formed at each growth temperature, the result of measuring the width of the n-type region by observing the reflected electron image and the secondary electron image with an electron microscope is plotted on the horizontal axis (upper side) of the graph of FIG. As a result, it was found that the increase in the threshold current is related to the width of the n-type region. That is, a tendency for the threshold current to increase was clearly seen when the width of the n-type region exceeded 0.15 μm.

  This phenomenon can be understood as follows. That is, as shown in FIG. 3, the current from the p-type AlGaN cladding layer 5 is confined to the p-type GaN guide layer 3 in which n-type conversion has not occurred, and is applied to an active layer (not shown) located therebelow. By flowing, the active layer emits light and a large gain is obtained. On the other hand, since almost no current flows from the n-type region 6 to the active layer located below the n-type AlGaN current confinement layer 2, the active layer functions as an absorption layer. Since the optical confinement in the lateral direction is performed by the difference in refractive index between the n-type AlGaN current confinement layer 2 and the p-type GaN guide layer 3, light is distributed at a high rate in the region where absorption occurs. Therefore, it is considered that the laser oscillation threshold current has increased.

  In addition, if the width of the n-type region is widened and the substantial current guide width is narrowed, the resistance component in the region becomes large, which may cause the electrical characteristics to deteriorate.

  Such unexpected n-type conversion is considered to be a phenomenon caused by various factors. Therefore, if the structure design or process design of the semiconductor laser is performed without recognizing the n-type conversion phenomenon, the current threshold value is obtained. There is a risk of unexpected variations or fluctuations in electrical characteristics.

  The present invention has been made based on such knowledge, and an object thereof is to provide an embedded nitride semiconductor laser device having stable characteristics and a method for manufacturing the same.

  A nitride semiconductor laser device according to the present invention is a nitride semiconductor laser device including an active layer sandwiched between clad layers and a current confinement layer having an opening for confining current to the active layer. A regrowth layer is formed on the current confinement layer so as to cover the opening of the current confinement layer, and the regrowth layer is made of a nitride semiconductor layer containing In to which a p-type impurity is added. And

  According to the above configuration, the regrowth layer covering the opening of the current confinement layer is a nitride semiconductor layer containing In to which a p-type impurity is added, so that the region in contact with the side surface of the opening becomes n-type. Can be suppressed. Thereby, it is possible to provide an embedded nitride semiconductor laser device having stable characteristics.

  Here, the nitride semiconductor layer containing In is preferably made of InGaN or AlInGaN. Since InGaN can take in high-concentration p-type impurities, it is possible to suppress the formation of n-type during the formation of the regrowth layer. In addition, since AlInGaN has a larger band gap than InGaN, it is possible to suppress n-type conversion, suppress laser light absorption, and prevent deterioration of laser characteristics.

  The regrowth layer is preferably composed of a multilayer film in which a thin film made of GaN or AlGaN is formed under a nitride semiconductor layer containing In. By forming a thin film made of GaN having excellent crystallinity at the initial stage of forming a nitride semiconductor layer containing In, forming a regrown layer having excellent crystallinity by suppressing n-type formation. Can do. Further, at the initial stage of forming the nitride semiconductor layer containing In, a thin film made of AlGaN with little lateral growth can be formed to further improve the suppression of n-type.

  Further, the current confinement layer is preferably made of GaN or AlGaN doped with an N-type impurity. By forming a PN junction between the N-type current confinement layer and the P-type regrowth layer, the current confinement effect can be further exhibited.

  The refractive index of the current confinement layer is preferably smaller than the refractive index of the regrowth layer. Further, the regrowth layer may constitute a part of the cladding layer.

  Of the regrowth layer embedded in the opening portion of the current confinement layer, the region adjacent to the side surface of the opening portion is made n-type, and the width of the n-type region is embedded in the regrowth layer embedded in the opening portion. Of these, the width is preferably 10% or less of the width of the non-n-type region. Thus, an embedded nitride semiconductor laser device having stable characteristics can be provided.

  A nitride semiconductor laser device according to the present invention is a nitride semiconductor laser device including an active layer sandwiched between clad layers and a current confinement layer having an opening for confining current to the active layer. Then, a regrowth layer made of a nitride semiconductor to which a p-type impurity is added is formed on the current confinement layer so as to cover the opening of the current confinement layer, and the regrowth layer embedded in the opening of the current confinement layer Among these, a region adjacent to the side surface of the opening is n-type, and the width of the n-type region is 0.15 μm or less.

  According to the above configuration, among the regrowth layers embedded in the opening portion of the current confinement layer, the width of the n-type region formed adjacent to the side surface of the opening portion is stabilized to 0.15 μm or less. An embedded nitride semiconductor laser device having characteristics can be provided.

  A method of manufacturing a nitride semiconductor laser device according to the present invention includes a nitride semiconductor laser including a current confinement layer having an active layer sandwiched between clad layers and an opening for confining current to the active layer. A method of manufacturing an apparatus, comprising: forming an active layer sandwiched between clad layers on a substrate; forming a current confinement layer on the clad layer; and etching a part of the current confinement layer, A step of forming an opening for confining a current to the active layer, and a step of forming a regrowth layer on the current confinement layer so as to cover the opening of the current confinement layer. It is characterized by comprising a nitride semiconductor layer containing In to which a p-type impurity is added.

  According to the above method, the regrowth layer covering the opening of the current confinement layer is made of a nitride semiconductor layer containing In to which a p-type impurity is added, so that the region in contact with the side surface of the opening becomes n-type. Can be suppressed. As a result, it is possible to provide an embedded nitride semiconductor laser device having stable characteristics.

  Here, the step of forming the regrowth layer includes a step of forming a thin film made of GaN or AlGaN on the current confinement layer so as to cover the opening of the current confinement layer, and a p-type impurity is added to the thin film. And a step of forming a nitride semiconductor layer containing In.

  The nitride semiconductor layer containing In is preferably made of InGaN or AlInGaN.

  A method of manufacturing a nitride semiconductor laser device according to the present invention includes a nitride semiconductor laser including an active layer sandwiched between clad layers and a current confinement layer having an opening for confining current to the active layer. A method for manufacturing an apparatus, comprising: forming an active layer sandwiched between clad layers on a substrate; forming a current confinement layer on the clad layer; and etching a part of the current confinement layer to activate the device A step of forming an opening for confining current to the layer, and a regrowth layer made of a nitride semiconductor layer to which a p-type impurity is added on the current confinement layer so as to cover the opening of the current confinement layer Forming the regrowth layer includes a first step of depositing at a first growth temperature at which the lateral growth of the nitride semiconductor layer is slow, and a growth of the nitride semiconductor layer is a crystal. Second step of performing deposition at a second growth temperature with good characteristics Characterized in that it comprises a.

  According to the above method, in the initial stage of growing the regrowth layer, the deposition is performed at the first growth temperature where the lateral growth is slow, and then the deposition is performed at the second growth temperature where the crystallinity is good. By performing the formation, it is possible to suppress the region in contact with the side surface of the opening from becoming n-type.

  Note that the first growth temperature is preferably lower than the second growth temperature. Of the regrowth layer embedded in the opening portion of the current confinement layer, the region adjacent to the side surface of the opening portion is made n-type, and the width of the n-type region is embedded in the regrowth layer embedded in the opening portion. Of these, the width is preferably 10% or less of the width of the non-n-type region.

  According to the nitride semiconductor laser device and the manufacturing method thereof according to the present invention, the regrowth layer covering the opening of the current confinement layer is formed into a nitride semiconductor layer containing In to which a p-type impurity is added. It can suppress that the area | region which contact | connects the side surface of a part becomes n-type. As a result, it is possible to provide an embedded nitride semiconductor laser device having stable characteristics.

  Further, by forming the regrowth layer as a multilayer film in which a thin film made of GaN having good crystallinity is formed under the nitride semiconductor layer containing In, n-type conversion is suppressed, and crystallinity is excellent. A regrowth layer can be formed.

  Further, the regrowth layer is composed of a multilayer film in which a thin film made of AlGaN with little lateral growth is formed under the nitride semiconductor layer containing In, thereby further improving the suppression of n-type growth. Can do.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of simplicity. In addition, this invention is not limited to the following embodiment.

(First embodiment)
FIG. 4 is a cross-sectional view schematically showing a basic configuration of the nitride semiconductor laser device according to the first embodiment of the present invention.

  The nitride semiconductor laser device 10 includes an active layer 12 sandwiched between an n-type cladding layer 11 and a p-type cladding layer 13 and a current confinement layer 14 having an opening for confining current to the active layer 12. It has an embedded structure. In this buried structure, a regrowth layer 15 made of a nitride semiconductor layer containing In doped with a p-type impurity is formed on the current confinement layer 14 so as to cover the opening of the current confinement layer 14. .

  Here, the regrowth layer 15 generally constitutes a part of the p-type cladding layer, but the regrowth layer 15 is not limited to this and has various functions (for example, a guide layer) depending on the characteristics of the semiconductor laser device 10. Can also be provided.

  In the present invention, the reason why the nitride semiconductor containing In is selected as the material of the regrowth layer 15 is that the nitride containing In as compared with the material of GaN or AlGaN conventionally used as the cladding layer or the guide layer. This is because the semiconductor can take in a high concentration of p-type impurities. In other words, by adding a high-concentration impurity to the nitride semiconductor layer containing In so as not to cause n-type inversion, the regrowth layer 15 can be effectively made n-type when the regrowth layer 15 is formed. It becomes possible to suppress.

  Here, InGaN, AlInGaN, or the like can be used as the nitrogen compound containing In. Since InGaN has a smaller band gap than GaN, AlINGaN having a large band gap may be used when there is a concern that InGaN will deteriorate the laser characteristics by absorbing laser light.

  The n-type phenomenon is considered to occur at the initial stage of forming the regrowth layer 15, that is, at the stage where lateral growth from the side surface of the opening portion of the current confinement layer 14 occurs. Therefore, in the initial stage of forming the regrowth layer 15, a thin film made of AlGaN with little lateral growth is first formed, and a nitride semiconductor layer containing In that suppresses n-type formation is formed thereon. You may do it. By forming the regrowth layer 15 with such a multilayer film, the n-type can be further suppressed.

  Further, the regrowth layer 15 must have good crystallinity in order to exhibit its original function (clad layer, guide layer, etc.). Therefore, in the initial stage of forming a nitride semiconductor layer containing In, a thin film made of GaN having excellent crystallinity is first formed, and a nitride semiconductor layer containing In that suppresses n-type formation is formed thereon. You may make it form. By forming the regrowth layer 15 with such a multilayer film, it is possible to form the regrowth layer 15 with suppressed n-type growth and excellent crystallinity.

  In the present invention, the material of the current confinement layer 14 is not particularly limited, but the current confinement layer 14 is composed of a GaN layer or an AlGaN layer doped with an N-type impurity in order to exhibit the current confinement effect more. It is preferable. This is because the effect of current confinement can be enhanced by forming a PN junction between the N-type current confinement layer and the P-type regrowth layer.

  In order to enhance the light confinement effect, it is preferable that the refractive index of the current confinement layer 14 is smaller than the refractive index of the regrowth layer 15.

  Next, an example of a specific configuration of the nitride semiconductor laser device 20 according to the present invention will be described with reference to FIG.

On the 2-inch GaN substrate 21, an n-GaN layer 22, an n-Al _0.06 Ga _0.94 N cladding layer 23, an n-GaN guide layer 24, an InGaN MQW active layer 25, a p-Al _0.15 Ga _0.85 N overflow suppression layer 26, A p-GaN guide layer 27 and an n-Al _0.15 Ga _0.85 N current confinement layer 28 are sequentially formed.

The n-Al _0.15 Ga _0.85 N current blocking layer 28 opening is formed, on the p-GaN guide layer 27 exposed at the opening, and on the n-Al _0.15 Ga _0.85 N current blocking layer 28, p-InGaN The guide layer 29, the p-AlGaN cladding layer 30, and the p-GaN contact layer 31 are regrown. A p-type electrode 32 is formed on the p-GaN contact layer 31, and an n-type electrode 33 is formed on the surface where the growth layer of the GaN substrate 21 is not formed.

Here, current flows through the p-InGaN guide layer 29, and light having a wavelength of 405 nm is emitted from the MQW active layer 25. Further, the optical confinement in the direction parallel to the active layer 25 is performed by the refractive index difference between the n-Al _0.15 Ga _0.85 N current confinement layer 28 and the p-InGaN guide layer 29.

  In this embodiment, the nitride semiconductor layer containing In is used as the regrowth layer. However, even when a nitride semiconductor layer not containing In (for example, a GaN layer or an AlGaN layer) is used, FIG. As shown in FIG. 5, among the regrowth layers embedded in the opening portion of the current confinement layer, the width of the n-type region formed adjacent to the side surface of the opening portion is reduced to 0.15 μm or less so that stable characteristics are obtained. An embedded nitride semiconductor laser device having the following can be provided. For example, when forming a GaN layer as a regrowth layer, as shown in FIG. 2, by forming the GaN layer at a temperature (1050 ° C. to 1080 ° C.) lower than the normal growth temperature (1100 ° C. to 1130 ° C.). The width of the n-type region can be suppressed to 0.15 μm or less.

  FIG. 6 shows an n-type region 6 corresponding to the width (W) of the non-n-type region of the regrowth layer 3 embedded in the opening of the current confinement layer 2 in the structure shown in FIG. 5 is a graph showing the result of calculating the magnitude of the laser oscillation threshold current by simulation when the ratio (L / W) of the width (L) of the laser is changed. In both cases of W = 1.2 μm and 1.5 μm, it can be seen that the magnitude of the laser oscillation threshold current increases when L / W exceeds 10%. Therefore, in order to obtain a nitride semiconductor laser device having stable characteristics, L / W is preferably 10% or less.

(Second Embodiment)
7A to 7D are process cross-sectional views schematically showing a method for manufacturing a nitride semiconductor laser device according to the second embodiment of the present invention.

First, as shown in FIG. 7A, on a 2-inch GaN substrate 21, an n-GaN layer 22, an n-Al _0.06 Ga _0.94 N cladding layer 23, an n-GaN guide layer 24, an InGaN MQW active layer 25, A p-Al _0.15 Ga _0.85 N overflow suppression layer 26, a p-GaN guide layer 27, and an n-Al _0.15 Ga _0.85 N current confinement layer 28 are formed in this order.

Next, as shown in FIG. 7B, a part of the n-Al _0.15 Ga _0.85 N current confinement layer 28 is removed by etching. Here, by applying the PEC etching described above, stable etching can be performed without removing the underlying p-GaN guide layer 27. At this time, a protective film (not shown) such as an oxide film is formed on the bottom surface of the GaN substrate 21.

Next, as shown in FIG. 7C, the p-InGaN guide layer 29, the p-AlGaN cladding layer 30, and the p-GaN contact layer 31 are regrown on the n-Al _0.15 Ga _0.85 N current confinement layer 28. Let

  Finally, as shown in FIG. 7D, activation annealing is performed in a nitrogen atmosphere at 780 ° C. for 20 minutes to lower the resistance of the p-type layer. Thereafter, a p-type electrode 32 is formed on the p-type contact layer 31. As the p-type electrode 32, a multilayer film containing Ni or Pd is preferable. Subsequently, the V group surface side of the GaN substrate 21 is polished to reduce the thickness of the GaN substrate 21, and then the n-type electrode 33 is formed on the polished surface. As the n-type electrode 33, a multilayer film containing Ti or V is preferable.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course, various modifications are possible. For example, in the second embodiment, the nitride semiconductor layer containing In is used as the regrowth layer. However, even when a GaN layer or an AlGaN layer not containing In is used, the regrowth layer has a two-stage growth temperature. It is also possible to effectively suppress the n-type formation. That is, as shown in FIG. 2, in the initial stage of forming the regrowth layer, the first stage growth is performed at a temperature lower than the normal growth temperature (temperature at which the lateral growth is slow), and then the normal growth temperature. By performing the growth at the second stage at (temperature at which crystallinity is good), it is possible to form a regrowth layer that suppresses n-type growth and has good crystallinity.

  According to the present invention, it is possible to provide an embedded nitride semiconductor laser device having stable characteristics and a method for manufacturing the same.

(A)-(d) is the microscope picture explaining the subject of the nitride semiconductor laser apparatus concerning this invention, and its schematic diagram. It is a graph of the laser oscillation threshold current concerning the subject of this invention. It is a schematic diagram explaining the n-type-ization phenomenon concerning the subject of this invention. 1 is a cross-sectional view schematically showing a configuration of a nitride semiconductor laser device according to a first embodiment of the present invention. 1 is a cross-sectional view showing a specific configuration of a nitride semiconductor laser device according to a first embodiment of the present invention. It is a graph of the laser oscillation threshold current of the nitride semiconductor laser device in the present invention. (A)-(d) is process sectional drawing which showed typically the manufacturing method of the nitride semiconductor laser apparatus in the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the nitride semiconductor laser apparatus which has the conventional ridge structure. It is sectional drawing which shows the structure of the nitride semiconductor laser apparatus which has the conventional embedding structure.

Explanation of symbols

1 p-type GaN guide layer 2 n-type AlGaN current confinement layer 3 p-type GaN guide layer 4 opening 5 p-type AlGaN clad layer 6 n-type region 10 nitride semiconductor laser device 11 n-type clad layer 12 active layer 13 p-type Cladding layer 14 Current confinement layer 15 Regrown layer 20 Nitride semiconductor laser device 21 GaN substrate 22 n-GaN layer 23 n-Al _0.06 Ga _0.94 N cladding layer 24 n-GaN guide layer 25 InGaN MQW active layer 26 p-Al _0.15 Ga _0.85 N overflow suppression layer 27 p-GaN guide layer 28 n-Al _0.15 Ga _0.85 N current confinement layer 29 p-InGaN guide layer 30 p-AlGaN cladding layer 31 p-GaN contact layer 32 p-type electrode 33 n-type electrode 101 Ridge 102 Electrode 103 Current confinement layer 104 Opening 105, 106 p AlGaN cladding layer

Claims (14)

A nitride semiconductor laser device comprising an active layer sandwiched between clad layers and a current confinement layer having an opening for confining current to the active layer,
A regrowth layer is formed on the current confinement layer so as to cover the opening of the current confinement layer,
The nitride semiconductor laser device, wherein the regrowth layer is made of a nitride semiconductor layer containing In to which a p-type impurity is added.   The nitride semiconductor laser device according to claim 1, wherein the nitride semiconductor layer containing In is made of InGaN or AlInGaN.   2. The nitride semiconductor according to claim 1, wherein the regrowth layer includes a multilayer film in which a thin film made of GaN or AlGaN is formed under the nitride semiconductor layer containing In. Laser device.   2. The nitride semiconductor laser device according to claim 1, wherein the current confinement layer is made of GaN or AlGaN doped with an N-type impurity. 3.   2. The nitride semiconductor laser device according to claim 1, wherein a refractive index of the current confinement layer is smaller than a refractive index of the regrowth layer.   The nitride semiconductor laser device according to claim 1, wherein the regrowth layer constitutes a part of the cladding layer.   Of the regrowth layer embedded in the opening portion of the current confinement layer, a region adjacent to the side surface of the opening portion is n-type, and the width of the n-type region is embedded in the opening portion. 2. The nitride semiconductor laser device according to claim 1, wherein the nitride semiconductor laser device is 10% or less of a width of a region of the regrowth layer that is not n-type. A nitride semiconductor laser device comprising: an active layer sandwiched between clad layers; and a current confinement layer having an opening for confining current to the active layer,
A regrowth layer made of a nitride semiconductor to which a p-type impurity is added is formed on the current confinement layer so as to cover the opening of the current confinement layer,
Of the regrowth layer embedded in the opening portion of the current confinement layer, a region adjacent to the side surface of the opening portion is n-type, and the width of the n-type region is 0.15 μm or less. A nitride semiconductor laser device that is characterized. A method for manufacturing a nitride semiconductor laser device comprising: an active layer sandwiched between clad layers; and a current confinement layer having an opening for confining current to the active layer,
Forming an active layer sandwiched between clad layers on a substrate;
Forming a current confinement layer on the cladding layer;
Etching a part of the current confinement layer to form an opening for confining the current to the active layer;
Forming a regrowth layer on the current confinement layer so as to cover the opening of the current confinement layer,
The method of manufacturing a nitride semiconductor laser device, wherein the regrowth layer includes a nitride semiconductor layer containing In to which a p-type impurity is added. The step of forming the regrowth layer includes:
A first step of forming a thin film made of GaN or AlGaN on the current confinement layer so as to cover the opening of the current confinement layer;
A method for manufacturing a nitride semiconductor laser device according to claim 9, further comprising a second step of forming a nitride semiconductor layer containing In doped with a p-type impurity on the thin film. The method for manufacturing a nitride semiconductor laser device according to claim 9, wherein the nitride semiconductor layer containing In is made of InGaN or AlInGaN. A method of manufacturing a nitride semiconductor laser device comprising: an active layer sandwiched between clad layers; and a current confinement layer having an opening for confining current to the active layer,
Forming an active layer sandwiched between clad layers on a substrate;
Forming a current confinement layer on the cladding layer;
Etching a part of the current confinement layer to form an opening for confining the current to the active layer;
Forming a regrowth layer made of a nitride semiconductor layer doped with a p-type impurity on the current confinement layer so as to cover the opening of the current confinement layer,
The step of forming the regrowth layer includes:
A first step of depositing at a first growth temperature at which the lateral growth of the nitride semiconductor layer is slow;
A method of manufacturing a nitride semiconductor laser device, characterized in that the growth of the nitride semiconductor layer includes a second step of depositing at a second growth temperature with good crystallinity.   13. The method for manufacturing a nitride semiconductor laser device according to claim 12, wherein the first growth temperature is lower than the second growth temperature.   Of the regrowth layer embedded in the opening portion of the current confinement layer, a region adjacent to the side surface of the opening portion is n-type, and the width of the n-type region is embedded in the opening portion. 13. The method for manufacturing a nitride semiconductor laser device according to claim 9, wherein the width is 10% or less of a width of the regrowth layer that is not n-type.