JP4566253B2 - Nitride semiconductor laser device - Google Patents

Description

  The present invention relates to a nitride semiconductor laser device, and more particularly to a nitride semiconductor laser device using a group III-V nitride semiconductor (hereinafter simply referred to as “nitride semiconductor”).

  Nitride semiconductors are attracting attention as materials for nitride semiconductor light emitting devices such as nitride semiconductor laser devices and nitride semiconductor light emitting diode devices that emit blue-violet, blue or green light. In recent years, nitride semiconductors have been used. Development of nitride semiconductor light emitting devices that emit blue-violet, blue, or green light has been actively conducted.

  Nitride semiconductor light emitting diode elements that emit blue or green light have already been put into practical use, and in order to improve the recording density of an optical recording medium such as an optical disk, the nitride semiconductor laser element also has an emission wavelength of around 400 nm. Nitride semiconductor laser elements that emit blue-violet light have been put into practical use.

  On the other hand, nitride semiconductor laser elements that emit pure blue or green light having an emission wavelength longer than 400 nm are expected to be applied to light sources for display devices, phosphor excitation light sources for illumination applications, and medical devices. The development is underway.

  Here, a nitride semiconductor laser element that emits blue-violet light having an emission wavelength of around 400 nm is a nitride semiconductor (such as AlGaN) that includes Al in addition to an n-type nitride semiconductor cladding layer and a p-type nitride semiconductor cladding layer. ).

  As described above, nitride semiconductor laser elements emitting blue-violet light have already been put into practical use, but nitride semiconductors containing Al that generate crystal defects such as dislocations in the nitride semiconductor cladding layer (AlGaN, etc.) ) Is a potential issue.

  Further, in nitride semiconductors containing Al (such as AlGaN), the acceptor ionization energy of magnesium (Mg) used as a p-type impurity increases in proportion to the Al composition ratio, so that a high hole concentration can be realized. This is one of the causes of the high resistance of the nitride semiconductor laser device. That is, it can be said that there is still room for reducing the resistance of the nitride semiconductor laser element.

  On the other hand, the nitride semiconductor laser element emitting blue or green light has the following problems. That is, when the emission wavelength is around 400 nm, the refractive index between the nitride semiconductor containing Al (AlGaN, etc.) used as the material of the nitride semiconductor cladding layer and GaN is large, but the emission wavelength is longer than 400 nm. In the region of blue light (light having a wavelength of 430 nm or more and 480 nm or less) or green light (light having a wavelength of greater than 480 nm and less than or equal to 580 nm), this refractive index difference is small.

  That is, assuming that only the emission wavelength is increased in the structure of the nitride semiconductor laser element having an emission wavelength of around 400 nm, light confinement in the nitride semiconductor active layer becomes insufficient. There is a concern that the light emission efficiency (ratio of the number of photons taken out of the nitride semiconductor laser element to the number of electrons injected into the nitride semiconductor laser element) is reduced.

  In order to realize a high-performance nitride semiconductor laser device for light in a long wavelength band such as pure blue, it is necessary to design the structure of the nitride semiconductor laser device in consideration of a reduction in the refractive index difference. . For example, as a method of suppressing a decrease in light confinement in the nitride semiconductor active layer, the Al composition ratio of a nitride semiconductor clad layer composed of a nitride semiconductor (such as AlGaN) containing Al is increased. The difference in refractive index can be increased.

  However, when the Al composition ratio of the p-type nitride semiconductor cladding layer is increased, as described above, the acceptor ionization energy of magnesium (Mg) used as the p-type impurity increases in proportion to the Al composition, so that it is high. There is a concern that it becomes difficult to realize the hole concentration, the resistance of the nitride semiconductor laser element increases, and the drive voltage increases.

  For example, in Japanese Patent Laid-Open No. 2000-236142, a nitride semiconductor laser element with few crystal defects is realized by forming a p-type nitride semiconductor cladding layer with a GaN layer that does not use Al. However, in the configuration of the nitride semiconductor laser element described in Japanese Patent Application Laid-Open No. 2000-236142, light confinement is insufficient with pure blue or green light, and a reduction in the light emission efficiency of the nitride semiconductor laser element can be avoided. Absent.

  Further, in Japanese Patent Application Laid-Open No. 2004-289157, a nitriding structure in which a transparent conductive film is provided on a waveguide layer instead of a p-type nitride semiconductor cladding layer, and a p-electrode is provided on the transparent conductive film. A semiconductor laser device is disclosed. In the configuration of the nitride semiconductor laser element described in Japanese Patent Application Laid-Open No. 2004-289157, the optical confinement coefficient can be maintained and a significant absorption loss in the p electrode can be avoided. Further, it is possible to avoid the use of a p-type nitride semiconductor clad layer made of a nitride semiconductor containing Al (AlGaN or the like), and a transparent conductive film is provided instead of the p-type nitride semiconductor clad layer. As a result, the resistance of the nitride semiconductor laser device can be reduced, and an increase in driving voltage can be suppressed.

  However, when the laser beam having a wavelength of 420 nm shown in the embodiment is emitted, the above-described effect can be expected, but when emitting a laser beam in a longer wavelength region such as 430 nm or more and 580 nm or less, it is particularly In the configuration disclosed in Japanese Unexamined Patent Application Publication No. 2004-289157, the effect of absorption loss is unavoidable if the p-electrode is provided on the transparent conductive film, so that the configuration of the nitride semiconductor laser device is insufficient.

Therefore, the present invention can be applied to the case of emitting laser light in a wider wavelength range, and the amount of p-type nitride semiconductor containing Al, which causes high resistance, is reduced as much as possible and the optical confinement is sufficiently satisfied. A nitride semiconductor laser element has been demanded.
JP 2000-236142 A JP 2004-289157 A

  In view of the above circumstances, an object of the present invention is to provide a nitride semiconductor laser element that can realize a low resistance of a nitride semiconductor laser element and that has a wide wavelength range of the laser light to be adapted. is there.

The present invention relates to an n-type nitride semiconductor layer, a nitride semiconductor active layer formed on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the nitride semiconductor active layer, and a p-type An upper transparent conductive film formed on the nitride semiconductor layer, the nitride semiconductor active layer having a nitride semiconductor well layer containing indium and a nitride semiconductor barrier layer, and from the nitride semiconductor active layer in the region of the upper transparent conductive film located above the region of the nitride semiconductor active layer corresponding to the width of the emitted laser beam, and contact with the air body surface of the upper transparent conductive film, released from the nitride semiconductor active layer In the region of the upper transparent conductive film located in a region different from the region above the region of the nitride semiconductor active layer corresponding to the width of the laser light to be applied , the surface of the upper transparent conductive film is in contact with the electrode made of metal This is a nitride semiconductor laser element.

The present invention also provides an n-type nitride semiconductor layer, a nitride semiconductor active layer formed on the n-type nitride semiconductor layer, a p-type nitride semiconductor layer formed on the nitride semiconductor active layer, an upper transparent conductive film formed on the p-type nitride semiconductor layer, and the nitride semiconductor active layer includes a nitride semiconductor well layer containing indium and a nitride semiconductor barrier layer, and the nitride semiconductor active layer In the region of the upper transparent conductive film located above the region of the nitride semiconductor active layer corresponding to the width of the laser light emitted from the layer, the surface of the upper transparent conductive film is in contact with the gas or the transparent dielectric film, and the nitride In the region of the upper transparent conductive film located in a region different from the region above the region of the nitride semiconductor active layer corresponding to the width of the laser light emitted from the semiconductor active layer, the surface of the upper transparent conductive film is made of metal In contact with the electrode, p-type At least a portion of the compound semiconductor layer is a nitride semiconductor laser device constituting the ridge stripe portion.

In the nitride semiconductor laser device of the present invention, preferably Rukoto electric field distribution of the laser beam is not exude above the upper transparent conductive film.

In the nitride semiconductor laser device of the present invention, the p-type nitride semiconductor layer has a p-type nitride semiconductor contact layer in contact with the upper transparent conductive film, and the p-type nitride semiconductor contact layer is p-type GaN or p-type. The p-type nitride semiconductor contact layer is preferably 1 μm or less in thickness.

  The nitride semiconductor laser device of the present invention further includes a nitride semiconductor lower light guide layer between the n-type nitride semiconductor layer and the nitride semiconductor active layer, and the nitride semiconductor lower light guide layer contains indium. The indium composition ratio of the nitride semiconductor lower optical guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer.

  The nitride semiconductor laser device of the present invention further includes a nitride semiconductor upper light guide layer between the nitride semiconductor active layer and the upper transparent conductive film, and the nitride semiconductor upper light guide layer is nitrided containing indium. The indium composition ratio of the nitride semiconductor upper light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer.

  The nitride semiconductor laser device of the present invention further includes a lower transparent conductive film on the side of the n-type nitride semiconductor layer opposite to the side where the nitride semiconductor active layer is installed, and the n-type nitride of the lower transparent conductive film It is preferable that at least a part of the surface on the opposite side of the semiconductor layer is in contact with the gas or the transparent dielectric film.

  In addition, the nitride semiconductor laser element of the present invention preferably includes a heat dissipating member on at least a part of the surface different from the cavity end face of the nitride semiconductor laser element.

In the present invention, as the n-type nitride semiconductor layer, for example, Al _x1 Ga _y1 In _z1 N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1, 0 ≦ z1 ≦ 1, n-type conductivity type, A single layer or a plurality of layers made of a nitride semiconductor crystal represented by a formula of x1 + y1 + z1 ≠ 0) can be used. When the n-type nitride semiconductor layer is composed of a plurality of layers, at least one of the layers may be a layer having a composition different from that of the other layers.

In the present invention, the nitride semiconductor active layer is represented by, for example, the formula of Al _x2 Ga _y2 In _z2 N (0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1, 0 ≦ z2 ≦ 1, x2 + y2 + z2 ≠ 0). A single layer or a plurality of layers made of nitride semiconductor crystals can be used. The nitride semiconductor active layer may be undoped or may have an n-type or p-type conductivity type. When the nitride semiconductor active layer is composed of a plurality of layers, at least one of the layers may be a layer having a composition different from that of the other layers.

In the present invention, as the p-type nitride semiconductor contact layer, for example, Al _x3 Ga _y3 In _z3 N (0 ≦ x3 ≦ 1, 0 ≦ y3 ≦ 1, 0 ≦ z3 ≦ 1 having a p-type conductivity type is used. , X3 + y3 + z3 ≠ 0), a single layer or a plurality of layers made of a nitride semiconductor crystal can be used, but p3 GaN with x3 = z3 = 0 or p-type AlGaN with z3 = 0 is used. Is preferred. When the p-type nitride semiconductor contact layer is composed of a plurality of layers, at least one of the layers may be a layer having a composition different from that of the other layers.

  In the present invention, the p electrode is not particularly limited as long as it is a transparent conductive film that functions as an electrode in contact with the p-type nitride semiconductor contact layer, and particularly absorbs light having a wavelength of 390 nm or more and 580 nm or less. It is preferable to use a transparent conductive film that reduces the thickness.

In the present invention, the nitride semiconductor lower light guide layer is, for example, an Al _x4 Ga _y4 In _z4 N (0 ≦ x4 ≦ 1, 0 ≦ y4 ≦ 1, 0 ≦ z4 ≦ 1, x4 + y4 + z4 ≠ 0) formula. A single layer or a plurality of layers made of a nitride semiconductor crystal represented by the following formula can be used. When the nitride semiconductor lower light guide layer is composed of a plurality of layers, at least one of the layers may be a layer having a composition different from that of the other layers.

In the present invention, as the nitride semiconductor upper light guide layer, for example, Al _x5 Ga _y5 In _z5 N (0 ≦ x5 ≦ 1, 0 ≦ y5 ≦ 1, 0 ≦ z5 ≦ 1, x5 + y5 + z5 ≠ 0) A single layer or a plurality of layers made of a nitride semiconductor crystal represented by the following formula can be used. When the nitride semiconductor upper light guide layer is composed of a plurality of layers, at least one of the layers may be a layer having a composition different from that of the other layers.

  In the present invention, the indium composition ratio means the ratio of the number of indium atoms to the total number of atoms of indium, aluminum, and gallium.

  According to the present invention, a low resistance of a nitride semiconductor laser device can be realized, and a nitride semiconductor laser device having a wide wavelength range of the laser light to be adapted can be provided.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

(Embodiment 1)
FIG. 1 shows a schematic cross-sectional view of an example of the nitride semiconductor laser device of the present invention. Here, the nitride semiconductor laser element includes an n-type semiconductor substrate 100 made of, for example, n-type GaN, and an n-type nitride semiconductor doped with an n-type impurity formed on one main surface of the n-type semiconductor substrate 100. An n-type cladding layer 101 as a layer, an n-side light guide layer 102 formed on the n-type cladding layer 101, a lower adjacent layer 103 formed on the n-side light guide layer 102, and a lower adjacent layer 103 The nitride semiconductor active layer 104 formed on the upper surface, the upper adjacent layer 105 formed on the nitride semiconductor active layer 104, the p-side light guide layer 106 formed on the upper adjacent layer 105, and the p-side light guide P-type AlGaN layer 107 formed on layer 106, p-type nitride semiconductor contact layer 108 formed on p-type AlGaN layer 107, and p-type nitride semiconductor contact layer 108. And an upper transparent conductive film 109.

Here, as the p-type AlGaN layer 107, for example, Al _x Ga _1-x N (0.05 ≦ x ≦ 0.5) doped with a p-type impurity is preferably used. 107 may not be formed.

  As the p-type nitride semiconductor contact layer 108, for example, p-type GaN or p-type AlGaN is preferably used, but p-type InGaN, p-type AlInGaN, or the like can also be used.

  Further, at least a part of the surface of the upper transparent conductive film 109 opposite to the side on which the nitride semiconductor active layer 104 is disposed is in contact with a gas such as air or a transparent dielectric film. Therefore, as an example of the nitride semiconductor laser device of the present invention, for example, at least a part of the surface of the upper transparent conductive film 109 opposite to the side where the nitride semiconductor active layer 104 is disposed is exposed to the outside, and the upper transparent conductive film 109 A structure in which at least part of the surface of the conductive film 109 is in contact with a gas such as air can be given. Examples of the gas include a gas sealed when the nitride semiconductor laser element of the present invention is can packaged.

Here, as the upper transparent conductive film 109, for example, an oxide film such as indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), CuAlO _2, or SrCu ₂ O ₂ can be used.

  The thickness of the upper transparent conductive film 109 is preferably 0.05 μm or more and 0.5 μm or less, and more preferably 0.05 μm or more and 0.2 μm or less. When the thickness of the upper transparent conductive film 109 is 0.05 μm or more and 0.5 μm or less, particularly when it is 0.05 μm or more and 0.2 μm or less, the amount of laser light absorbed by the upper transparent conductive film 109 is reduced. Therefore, a nitride semiconductor laser element that can further improve the light emission efficiency can be obtained.

  FIG. 2 is a schematic enlarged sectional view in the vicinity of the nitride semiconductor active layer 104 shown in FIG. In this example, the nitride semiconductor active layer 104 can be configured to oscillate laser light having a wavelength of, for example, 390 nm to 580 nm.

  Here, as the nitride semiconductor well layer 131, for example, undoped InGaN or undoped InAlGaN, which is a nitride semiconductor containing indium, can be used. As the nitride semiconductor barrier layer 132, for example, undoped InGaN, undoped InAlGaN, undoped AlGaN, or undoped GaN can be used. The nitride semiconductor barrier layer 132 is not limited to a single layer configuration, and may have a two or more layer configuration.

  In this example, the nitride semiconductor active layer 104 employs a multiple quantum well structure including a plurality of nitride semiconductor well layers 131, but has a single quantum well structure including only one nitride semiconductor well layer 131. You may adopt.

  In addition, as the n-type semiconductor substrate 100, it is most preferable to use an n-type GaN substrate from the viewpoint of suppressing lattice mismatch with respect to the nitride semiconductor layer that is crystal-grown on the surface. A type AlGaN substrate or the like may be used. Further, when an n-type GaN substrate or an n-type AlGaN substrate is used as the n-type semiconductor substrate 100, a C-plane, M-plane, A-plane or {11-22} plane is used as the surface on which the nitride semiconductor layer is grown. It is also possible to use nonpolar surfaces such as

  The nitride semiconductor laser device shown in FIG. 1 can be manufactured using a known crystal growth method such as metal organic chemical vapor deposition (MOCVD method).

  FIG. 3A shows a schematic cross section along the cavity length direction of the nitride semiconductor laser element described in Japanese Patent Application Laid-Open No. 2004-289157, and FIG. 3B shows the nitriding of the present invention shown in FIG. 1 shows a schematic cross section along a cavity length direction of a semiconductor laser device.

  Here, as shown in FIG. 3A, the nitride semiconductor laser element described in JP-A-2004-289157 includes an upper transparent conductive film 109 as a cladding layer and a metal electrode 111 on the surface thereof. Therefore, for example, as shown in FIG. 4A, when the laser light emitted from the nitride semiconductor active layer 104 oozes upward, at least a part thereof is absorbed by the metal electrode 111. Therefore, in the conventional nitride semiconductor laser element, the amount of laser light that can be extracted to the outside is reduced, and sufficient light emission efficiency cannot be obtained. This problem becomes a problem when laser light in a long wavelength region where the refractive index difference between the nitride semiconductor active layer and the cladding layer is small is emitted.

  On the other hand, as shown in FIG. 3B, in the nitride semiconductor laser device of the present invention, no metal electrode is provided above the upper transparent conductive film 109, and the surface of the upper transparent conductive film 109 is exposed to the outside. For example, the exposed surface of the upper transparent conductive film 109 may be in contact with the air 112. Therefore, for example, as shown in FIG. 4B, even when the laser light of the nitride semiconductor active layer 104 oozes upward, the laser light is not absorbed by the metal electrode as in the conventional case, and the laser light is not absorbed by the nitride semiconductor. Since it can be taken out of the laser element, it can be applied when emitting laser light in a wide wavelength range. Further, unlike the nitride semiconductor laser element described in Japanese Patent Application Laid-Open No. 2004-289157, there is no absorption loss of laser light by the metal electrode 111, so that the light emission efficiency can be improved.

  In the nitride semiconductor laser element described in Japanese Patent Application Laid-Open No. 2004-289157, the upper transparent conductive film 109 is formed thick to prevent the leaked laser light from being absorbed by the metal electrode 111. It was necessary to increase the confinement factor.

  On the other hand, in the nitride semiconductor laser device of the present invention, it is not necessary to consider that the exuded laser beam is absorbed by the metal electrode, and the upper transparent conductive film 109 is made as thin as possible to the extent that it can function as a p-electrode. Therefore, the refractive index difference between the air 112 and the nitride semiconductor active layer 104 can be increased to maximize the light confinement effect. Can be made larger). Therefore, in the nitride semiconductor laser element of the present invention, the light confinement factor can be increased as compared with the conventional nitride semiconductor laser element, and thus the light emission efficiency can be improved also from this viewpoint.

  Here, in the above description, the case where at least a part of the surface of the upper transparent conductive film 109 is in contact with the air 112 has been mainly described, but the same applies to the case where it is in contact with a gas other than air or a transparent dielectric film instead of the air 112. It is.

  Here, as a gas other than air, for example, a mixed gas of nitrogen and oxygen (dry air), an inert gas such as nitrogen or argon, or a mixed gas thereof can be used.

  As the transparent dielectric film, for example, an oxide such as silicon oxide, titanium oxide, or zirconium oxide, or a nitride such as silicon nitride or aluminum nitride can be used.

  Further, the upper transparent conductive film 109 of the nitride semiconductor laser element shown in FIG. 1 is preferably made to function as a p-electrode. When the upper transparent conductive film 109 is made to function as a p-electrode, the upper transparent conductive film 109 can be used efficiently, so that an effect of improving light confinement can be expected.

  In addition, the thickness of the p-type nitride semiconductor contact layer 108 of the nitride semiconductor laser element shown in FIG. 1 is preferably 1 μm or less, and more preferably 0.5 μm or less. When the thickness of the p-type nitride semiconductor contact layer 108 is 1 μm or less, particularly when the thickness is 0.5 μm or less, the electric field distribution of light is efficiently collected in the nitride semiconductor active layer 104 and the drive voltage is reduced. Since there is a tendency to suppress the increase, a nitride semiconductor laser element having a low driving voltage and high emission efficiency tends to be obtained.

  The p-type nitride semiconductor contact layer 108 is generally formed at a growth temperature higher than the growth temperature of the nitride semiconductor active layer 104 from the viewpoint of obtaining superior crystal quality and conductivity. In this case, when the wavelength of the laser beam emitted from the nitride semiconductor laser element is in a long wavelength region such as a pure blue or green region, the nitride semiconductor active layer 104 has a large strain. There is concern about thermal damage due to high temperature growth. Therefore, the thinner the p-type nitride semiconductor contact layer 108 is, the shorter the growth time is, and it tends to be possible to reduce the influence of thermal damage to the nitride semiconductor active layer 104.

  In the nitride semiconductor laser device shown in FIG. 1, the n-side light guide layer 102 as the nitride semiconductor lower light guide layer may be made of, for example, GaN or AlGaN. 102 is made of a nitride semiconductor containing indium, and the indium composition ratio of the n-side light guide layer 102 as the nitride semiconductor lower light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer 131. In this case, since the electric field distribution of light can be efficiently collected in the nitride semiconductor active layer 104, a nitride semiconductor laser element with high emission efficiency tends to be obtained.

  In the nitride semiconductor laser element shown in FIG. 1, the p-side light guide layer 106 as the nitride semiconductor upper light guide layer may be made of, for example, GaN or AlGaN. 106 is made of a nitride semiconductor containing indium, and the indium composition ratio of the p-side light guide layer 106 as the nitride semiconductor upper light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer 131. Also in this case, since the electric field distribution of light can be efficiently collected in the nitride semiconductor active layer 104, there is a tendency that a nitride semiconductor laser device with high emission efficiency can be obtained.

  Note that each of the n-side light guide layer 102 and the p-side light guide layer 106 may have a superlattice structure of a nitride semiconductor layer containing In and a nitride semiconductor layer not containing In.

(Embodiment 2)
FIGS. 5A and 5B are schematic cross-sectional views of other preferable examples of the nitride semiconductor laser device of the present invention. Here, each of the nitride semiconductor laser elements shown in FIGS. 5A and 5B includes the current confinement layer 113 above or below the nitride semiconductor active layer 104 and the upper transparent conductive film 109. A metal electrode 111 as a p-electrode is provided on the surface of the nitride semiconductor active layer 104, and the metal electrode 111 is located above the region R of the nitride semiconductor active layer 104 corresponding to the width of the laser light 121 emitted from the nitride semiconductor active layer 104. It is characterized by not being arranged in. Note that the width of the region R can be substantially equal to the width between the current confinement layers 113. In addition, the current confinement layer 113 can be formed both above and below the nitride semiconductor active layer 104.

  Even with such a configuration, the absorption of the laser light that has exuded above the nitride semiconductor active layer 104 by the metal electrode 111 can be suppressed, so that the light emission efficiency of the nitride semiconductor laser device can be improved. It tends to be possible.

The description other than the above is the same as that of the first embodiment.
(Embodiment 3)
FIG. 6 is a schematic cross-sectional view of another example of the nitride semiconductor laser element of the present invention. Here, in the nitride semiconductor laser device shown in FIG. 6, a ridge stripe portion is formed by removing a part of the p-type AlGaN layer 107 and a part of the p-type nitride semiconductor contact layer 108, thereby forming a ridge stripe. A structure in which an upper transparent conductive film 109 is provided on the p-type nitride semiconductor contact layer 108 and the insulating layer 401 constituting the upper surface of the ridge stripe portion after the periphery of the portion is embedded with an insulating layer 401 such as SiO ₂ It is characterized by being said. Here, an example in which a part of the p-type AlGaN layer 107 is removed is shown, but the upper transparent conductive film 109, the middle of the p-type nitride semiconductor contact layer 108, or the p-type nitride semiconductor contact layer 108 are shown. As described above, the depth of the removed portion is not particularly limited.

  The nitride semiconductor laser device having such a structure is formed after the ridge stripe portion is formed by removing a part of the p-type AlGaN layer 107 and a part of the p-type nitride semiconductor contact layer 108 by, for example, an etching process. The periphery of the ridge stripe portion is filled with an insulating layer 401, and the upper transparent conductive film 109 is formed thereon.

  FIG. 7 is a schematic enlarged sectional view in the vicinity of the nitride semiconductor semiconductor active layer 104 of the nitride semiconductor laser device shown in FIG. In this example, the nitride semiconductor active layer 104 has three nitride semiconductor well layers 131 containing indium and two nitride semiconductor barrier layers 132. The nitride semiconductor well layers 131 and the nitride semiconductor barrier layers 132 are alternately stacked.

Descriptions other than those described above are the same as those in the first and second embodiments.
(Embodiment 4)
FIG. 8 is a schematic cross-sectional view of another example of the nitride semiconductor laser device of the present invention. Here, the nitride semiconductor laser element includes, for example, an n-type semiconductor substrate 200 made of n-type GaN having a cavity 210 provided therein, and an n-type impurity formed on one main surface of the n-type semiconductor substrate 200. An n-type cladding layer 201 as a doped n-type nitride semiconductor layer, an n-side light guide layer 202 formed on the n-type cladding layer 201, and a lower adjacent layer formed on the n-side light guide layer 202 203, the nitride semiconductor active layer 204 formed on the lower adjacent layer 203, the upper adjacent layer 205 formed on the nitride semiconductor active layer 204, and the p-side light guide formed on the upper adjacent layer 205 A p-type AlGaN layer 207 made of, for example, p-type Al _x Ga _1-x N (0.05 ≦ x ≦ 0.5), and a p-type AlGaN layer 207 formed on the p-side light guide layer 206. Formed on And a p-type nitride semiconductor contact layer 208 made of p-type GaN or p-type AlGaN, and an upper transparent conductive film 209 formed on the p-type nitride semiconductor contact layer 208.

  Further, at least a part of the surface of the upper transparent conductive film 209 opposite to the side on which the nitride semiconductor active layer 204 is installed is in contact with a gas such as air or a transparent dielectric film. Therefore, as an example of the nitride semiconductor laser device of the present invention, for example, at least a part of the surface of the upper transparent conductive film 209 opposite to the side on which the nitride semiconductor active layer 204 is installed is exposed to the outside, so that the upper transparent A structure in which at least part of the surface of the conductive film 209 is in contact with a gas such as air can be given. Examples of the gas include a gas sealed when the nitride semiconductor laser element of the present invention is can packaged.

Here, as the upper transparent conductive film 209, for example, an oxide film such as indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), CuAlO _2, or SrCu ₂ O ₂ can be used.

  The thickness of the upper transparent conductive film 209 is preferably 0.05 μm or more and 0.5 μm or less, and more preferably 0.05 μm or more and 0.2 μm or less. When the thickness of the upper transparent conductive film 209 is 0.05 μm or more and 0.5 μm or less, particularly when it is 0.05 μm or more and 0.2 μm or less, the amount of laser light absorbed by the upper transparent conductive film 209 is reduced. Therefore, a nitride semiconductor laser element that can further improve the light emission efficiency can be obtained.

  The nitride semiconductor active layer 204 can be configured to oscillate light having a wavelength of, for example, 390 nm or more and 580 nm or less, and can include one or more nitride semiconductor well layers and nitride semiconductor barrier layers. Can do. Here, as the nitride semiconductor well layer, for example, undoped InGaN or undoped InAlGaN which is a nitride semiconductor containing indium can be used. As the nitride semiconductor barrier layer, for example, undoped InGaN, undoped InAlGaN, undoped AlGaN, or undoped GaN can be used.

  In addition, as the n-type semiconductor substrate 200, it is most preferable to use an n-type GaN substrate from the viewpoint of suppressing lattice mismatch with respect to the nitride semiconductor layer that is crystal-grown on the surface. A type AlGaN substrate or the like may be used. Further, when an n-type GaN substrate or an n-type AlGaN substrate is used as the n-type semiconductor substrate 200, the C-plane, M-plane, A-plane, or {11-22} plane is used as the surface on which the nitride semiconductor layer is grown. It is also possible to use nonpolar surfaces such as

  The nitride semiconductor laser element shown in FIG. 8 can be manufactured using a known crystal growth method such as metal organic chemical vapor deposition (MOCVD method).

  The cavity 210 in the n-type semiconductor substrate 200 is formed by laterally growing an n-type nitride semiconductor after forming a groove on the surface of the n-type semiconductor substrate 200 as described in, for example, Japanese Patent Laid-Open No. 2000-106455. Can be formed.

  Also in the nitride semiconductor laser device having the configuration shown in FIG. 8, no metal electrode is provided above the upper transparent conductive film 209, and the surface of the upper transparent conductive film 209 is exposed to the outside, so that the upper transparent conductive film The surface of 209 can be in contact with air. Therefore, even when the laser light of the nitride semiconductor active layer 204 oozes upward, the laser light is not absorbed by the metal electrode as in the conventional case, and the laser light can be taken out of the nitride semiconductor laser element. Therefore, the luminous efficiency can be further improved.

  Here, in the above description, the case where at least a part of the surface of the upper transparent conductive film 209 is in contact with air has been mainly described, but the same applies to the case where it is in contact with a gas other than air or a transparent dielectric film instead of air. .

  As described above, even in the nitride semiconductor laser element having the configuration shown in FIG. 8, it is not necessary to consider that the exuded laser light is absorbed by the metal electrode, and the upper transparent conductive film 209 can function as the p electrode. Therefore, the refractive index lower than that of the upper transparent conductive film 209 is utilized to the maximum as in the case of a gas such as air or the refractive index of the transparent dielectric film (that is, the nitride semiconductor active layer 204). It is possible to increase the optical confinement effect by increasing the difference in the refractive index between the two. Therefore, also in the nitride semiconductor laser device having the configuration shown in FIG. 8, the light confinement factor can be increased as compared with the conventional nitride semiconductor laser device, so that the light emission efficiency can be improved also from this viewpoint. Become.

  Here, as a gas other than air, for example, a mixed gas of nitrogen and oxygen (dry air), an inert gas such as nitrogen or argon, or a mixed gas thereof can be used.

  As the transparent dielectric film, for example, an oxide such as silicon oxide, titanium oxide, or zirconium oxide, or a nitride such as silicon nitride or aluminum nitride can be used.

  Further, in the nitride semiconductor laser device having the configuration shown in FIG. 8, since the cavity 210 is provided inside the n-type semiconductor substrate 200, the composition and thickness of the cladding layer are adjusted so that only the p-side is present. In addition, the light confinement effect can be expected from the n-side by using the low refractive index material.

  Further, the upper transparent conductive film 209 of the nitride semiconductor laser element shown in FIG. 8 is preferably functioned as a p-electrode. When the upper transparent conductive film 209 functions as a p-electrode, the upper transparent conductive film 209 can be used efficiently, so that an effect of improving light confinement can be expected.

  In addition, the thickness of the p-type nitride semiconductor contact layer 208 of the nitride semiconductor laser element shown in FIG. 8 is preferably 1 μm or less, and more preferably 0.5 μm or less. When the thickness of the p-type nitride semiconductor contact layer 208 is 1 μm or less, particularly when the thickness is 0.5 μm or less, the electric field distribution of light is efficiently collected in the nitride semiconductor active layer 204 and the driving voltage is reduced. Since there is a tendency to suppress the increase, a nitride semiconductor laser element having a low driving voltage and high emission efficiency tends to be obtained.

  The p-type nitride semiconductor contact layer 208 is generally formed at a growth temperature higher than the growth temperature of the nitride semiconductor active layer 204 from the viewpoint of obtaining superior crystal quality and conductivity. In this case, when the wavelength of the laser light emitted from the nitride semiconductor laser element is in a long wavelength region such as a pure blue or green region, the nitride semiconductor active layer 204 has a large strain, and thus the nitride semiconductor active layer 204 There is concern about thermal damage due to high temperature growth. Therefore, the thinner the thickness of the p-type nitride semiconductor contact layer 208, the shorter the growth time, and it tends to be possible to reduce the influence of thermal damage to the nitride semiconductor active layer 204.

  In the nitride semiconductor laser element shown in FIG. 8, the n-side light guide layer 202 as the nitride semiconductor lower light guide layer may be made of, for example, GaN or AlGaN. 202 is made of a nitride semiconductor containing indium, and the indium composition ratio of the n-side light guide layer 202 as the nitride semiconductor lower light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer. In this case, since the electric field distribution of light can be efficiently collected in the nitride semiconductor active layer 204, a nitride semiconductor laser element with high emission efficiency tends to be obtained.

  In the nitride semiconductor laser device shown in FIG. 8, the p-side light guide layer 206 as the nitride semiconductor upper light guide layer may be made of, for example, GaN or AlGaN. 206 is made of a nitride semiconductor containing indium, and the indium composition ratio of the p-side light guide layer 206 as the nitride semiconductor upper light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer. Also in this case, since the electric field distribution of light can be efficiently collected in the nitride semiconductor active layer 204, a nitride semiconductor laser element with high emission efficiency tends to be obtained.

  Each of the n-side light guide layer 202 and the p-side light guide layer 206 may have a superlattice structure of a nitride semiconductor layer containing In and a nitride semiconductor layer not containing In.

(Embodiment 5)
FIG. 9 shows a schematic cross-sectional view of another example of the nitride semiconductor laser device of the present invention. Here, in the nitride semiconductor laser device shown in FIG. 9, a ridge stripe portion is formed by removing a part of the p-type AlGaN layer 207 and a part of the p-type nitride semiconductor contact layer 208, respectively. A structure in which an upper transparent conductive film 209 is provided on the p-type nitride semiconductor contact layer 208 and the insulating layer 401 constituting the upper surface of the ridge stripe portion after the periphery of the portion is embedded with an insulating layer 401 such as SiO ₂ It is characterized by being said. Here, an example in which a part of the p-type AlGaN layer 207 is removed is shown, but the upper transparent conductive film 209, the middle of the p-type nitride semiconductor contact layer 208, or the p-type nitride semiconductor contact layer 208 are shown. As described above, the depth of the removed portion is not particularly limited.

  In the nitride semiconductor laser element shown in FIG. 9, an n-electrode 212 is provided on the back surface of the n-type semiconductor substrate 200. As the n-electrode 212, for example, a conventionally known metal can be used.

  The nitride semiconductor laser device having such a structure is formed after the ridge stripe portion is formed by removing a part of the p-type AlGaN layer 207 and a part of the p-type nitride semiconductor contact layer 208 by, for example, an etching process. The periphery of the ridge stripe portion is filled with an insulating layer 401, and the upper transparent conductive film 209 is formed on the upper portion thereof.

The description other than the above is the same as that of the fourth embodiment.
(Embodiment 6)
FIG. 10 shows a schematic cross-sectional view of another example of the nitride semiconductor laser device of the present invention. Here, in the nitride semiconductor laser element shown in FIG. 10, the first ridge stripe portion is formed by removing a part of p-type AlGaN layer 207 and a part of p-type nitride semiconductor contact layer 208, respectively. Further, the second ridge stripe part is formed by removing until a part of the surface of the lower adjacent layer 203 below the nitride semiconductor active layer 204 is exposed. The side walls and surfaces of the first ridge stripe portion and the second ridge stripe portion are covered with an insulating layer 501 having good heat dissipation, such as aluminum nitride, and an upper transparent conductive film 209 is provided on the upper surface of the first ridge stripe portion. Further, in the vicinity of the nitride semiconductor active layer 204, a heat radiating member 502 having good heat radiating property such as copper is provided adjacent to the insulating layer 501.

  Here, an example is shown in which up to a part of the p-type AlGaN layer 207 and up to a part of the lower adjacent layer 203 are removed, but the depth of the removed part is not particularly limited. It is important that a material with good heat dissipation is placed in the vicinity of the nitride semiconductor active layer 204. Further, it is more effective to use a conventional method of loading a material with good heat dissipation on the n side.

In the present invention, the width W ₂ of the second ridge stripe portion is larger than the width W ₁ of the first ridge stripe portion, and is particularly preferably 100 μm or less, and more preferably 50 μm or less. .

  In the nitride semiconductor laser device having such a configuration, the first ridge stripe portion is formed by removing a part of the p-type AlGaN layer 207 and a part of the p-type nitride semiconductor contact layer 208 by an etching process, for example. After that, a layer below the nitride semiconductor active layer 204 such as the lower adjacent layer 203 is further removed to form a second ridge stripe portion. An insulating layer 501 having good heat dissipation, such as aluminum nitride, is formed on the side wall and the surface of the first ridge stripe portion and the second ridge stripe portion by, for example, sputtering, and is formed on the upper surface of the first ridge stripe portion. An upper transparent conductive film 209 is formed. Further, on the insulating layer 501 in the vicinity of the nitride semiconductor active layer 204, for example, a heat radiating member 502 having excellent heat radiating properties such as copper can be formed by, for example, vapor deposition or sputtering.

  With such a configuration, more heat generated in the nitride semiconductor laser element can be released from the heat radiating member 502 to the outside as compared with the fifth embodiment. The tendency to be able to deter further increases.

Descriptions other than those described above are the same as those in the fourth and fifth embodiments.
(Embodiment 7)
FIG. 11 is a schematic cross-sectional view of another example of the nitride semiconductor laser element of the present invention. Here, the nitride semiconductor laser element is formed of an n-type semiconductor substrate 300 made of, for example, n-type GaN, and a nitride containing, for example, GaN or Al provided in contact with one main surface of the n-type semiconductor substrate 300. An n-type cladding layer 301 as an n-type nitride semiconductor layer doped with an n-type impurity, an n-side light guide layer 302 formed on the n-type cladding layer 301, and an n-side light guide layer 302 are formed. The lower adjacent layer 303, the nitride semiconductor active layer 304 formed on the lower adjacent layer 303, the upper adjacent layer 305 formed on the nitride semiconductor active layer 304, and the upper adjacent layer 305 a p-type light guide layer 306; a p _- type AlGaN layer 307 made of, for example, p-type Al _x Ga _1-x N (0.05 ≦ x ≦ 0.5) formed on the p-side light guide layer 306; Type Al a p-type nitride semiconductor contact layer 308 made of p-type GaN or p-type AlGaN formed on the aN layer 307; and an upper transparent conductive film 309 formed on the p-type nitride semiconductor contact layer 308. Yes.

  In the nitride semiconductor laser element shown in FIG. 11, the lower transparent conductive film 312 is formed on the back surface of the n-type cladding layer 301 exposed by removing a part of the n-type semiconductor substrate 300 and on the n-type semiconductor substrate 300. It has a formed configuration.

  Here, n-type semiconductor substrate 300 can be removed by dry etching or the like after being thinned by polishing or the like. In this example, the lower transparent conductive film 312 is formed on the back surface of the n-type cladding layer 301, but the lower transparent conductive film 312 may be formed on the back surface of the n-side light guide layer 302. .

  In addition, at least a part of the surface of the upper transparent conductive film 309 opposite to the side where the nitride semiconductor active layer 304 is installed and at least one of the surface of the lower transparent conductive film 312 opposite to the side where the n-type cladding layer 301 is installed. The portion is in contact with a gas such as air or a transparent dielectric film.

Here, as the upper transparent conductive film 309 and the lower transparent conductive film 312, for example, an oxide film such as indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), CuAlO _2, or SrCu ₂ O ₂ is used. Can be used.

  Here, the thickness of the upper transparent conductive film 309 is preferably 0.05 μm or more and 0.5 μm or less, and more preferably 0.05 μm or more and 0.2 μm or less. When the thickness of the upper transparent conductive film 309 is 0.05 μm or more and 0.5 μm or less, particularly when it is 0.05 μm or more and 0.2 μm or less, the amount of laser light absorbed by the upper transparent conductive film 309 is reduced. Therefore, a nitride semiconductor laser element that can further improve the light emission efficiency can be obtained.

  The nitride semiconductor active layer 304 can be configured to oscillate light having a wavelength of, for example, 390 nm or more and 580 nm or less, and can include one or more nitride semiconductor well layers and nitride semiconductor barrier layers. Can do. Here, as the nitride semiconductor well layer, for example, undoped InGaN or undoped InAlGaN which is a nitride semiconductor containing indium can be used. As the nitride semiconductor barrier layer, for example, undoped InGaN, undoped InAlGaN, undoped AlGaN, or undoped GaN can be used.

  In addition, as the n-type semiconductor substrate 300, it is most preferable to use an n-type GaN substrate from the viewpoint of suppressing lattice mismatch with respect to the nitride semiconductor layer crystal-grown on the surface. A type AlGaN substrate or the like may be used. Further, when an n-type GaN substrate or an n-type AlGaN substrate is used as the n-type semiconductor substrate 300, the C-plane, M-plane, A-plane or {11-22} plane is used as the surface on which the nitride semiconductor layer is grown. It is also possible to use nonpolar surfaces such as

  In the nitride semiconductor laser device having the configuration shown in FIG. 11, not only the surface of the upper transparent conductive film 309 but also the surface of the lower transparent conductive film 312 is exposed to the outside, and the nitride semiconductor active layer 304 of the upper transparent conductive film 309 is exposed. At least a part of the surface on the opposite side to the installation side of the lower transparent conductive film 312 and at least a part of the surface on the opposite side to the installation side of the n-type cladding layer 301 of the lower transparent conductive film 312 may be in contact with air. Therefore, even when the laser light of the nitride semiconductor active layer 304 leaks upward and downward, the laser light is not absorbed by the p electrode and the n electrode, and more laser light can be taken out of the nitride semiconductor laser element. Therefore, the luminous efficiency can be further improved.

  Here, in the above description, the case where at least a part of the surface of the upper transparent conductive film 309 and at least a part of the surface of the lower transparent conductive film 312 are in contact with air has been mainly described. The same applies to contact with gas or a transparent dielectric film.

  As described above, in the nitride semiconductor laser element having the configuration shown in FIG. 11, it is not necessary to consider that the leaked laser light is absorbed by the p electrode and the n electrode, and the upper transparent conductive film 309 and the lower transparent conductive element Since the film 312 can be made extremely thin as long as it can function as a p-electrode and an n-electrode, respectively, the upper transparent conductive film 309 and the lower transparent conductive film 312 can be made like a gas such as air or the refractive index of the transparent dielectric film. Furthermore, it is possible to make the best use of the low refractive index (that is, to increase the refractive index difference between the nitride semiconductor active layer 304 and the light confinement effect). Therefore, also in the nitride semiconductor laser element having the configuration shown in FIG. 11, the light confinement factor can be increased as compared with the conventional nitride semiconductor laser element, so that it is possible to improve the light emission efficiency also from this viewpoint. Become.

  Here, as a gas other than air, for example, a mixed gas of nitrogen and oxygen (dry air), an inert gas such as nitrogen or argon, or a mixed gas thereof can be used.

  As the transparent dielectric film, for example, an oxide such as silicon oxide, titanium oxide, or zirconium oxide, or a nitride such as silicon nitride or aluminum nitride can be used.

  The nitride semiconductor laser element shown in FIG. 11 can be manufactured using a known crystal growth method such as metal organic chemical vapor deposition (MOCVD method).

  Further, the upper transparent conductive film 309 of the nitride semiconductor laser element shown in FIG. 11 is preferably made to function as a p-electrode. When the upper transparent conductive film 309 functions as a p-electrode, the upper transparent conductive film 309 can be used efficiently, so that an effect of improving light confinement can be expected.

  In addition, the thickness of the p-type nitride semiconductor contact layer 308 of the nitride semiconductor laser element shown in FIG. 11 is preferably 1 μm or less, and more preferably 0.5 μm or less. When the thickness of the p-type nitride semiconductor contact layer 308 is 1 μm or less, particularly when it is 0.5 μm or less, the electric field distribution of light is efficiently collected in the nitride semiconductor active layer 304, and the driving voltage is reduced. Since there is a tendency to suppress the increase, a nitride semiconductor laser element having a low driving voltage and high emission efficiency tends to be obtained.

  In the nitride semiconductor laser element shown in FIG. 11, the n-side light guide layer 302 as the nitride semiconductor lower light guide layer may be made of, for example, GaN or AlGaN. 302 is made of a nitride semiconductor containing indium, and the indium composition ratio of the n-side light guide layer 302 as the nitride semiconductor lower light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer. In this case, since the electric field distribution of light can be efficiently collected in the nitride semiconductor active layer 304, a nitride semiconductor laser element with high emission efficiency tends to be obtained.

  In the nitride semiconductor laser device shown in FIG. 11, the p-side light guide layer 306 as the nitride semiconductor upper light guide layer may be made of, for example, GaN or AlGaN. 206 is made of a nitride semiconductor containing indium, and the indium composition ratio of the p-side light guide layer 306 as the nitride semiconductor upper light guide layer is preferably smaller than the indium composition ratio of the nitride semiconductor well layer. Also in this case, since the electric field distribution of light can be efficiently collected in the nitride semiconductor active layer 304, a nitride semiconductor laser element with high emission efficiency tends to be obtained.

  Each of the n-side light guide layer 302 and the p-side light guide layer 306 may have a superlattice structure of a nitride semiconductor layer containing In and a nitride semiconductor layer not containing In.

(Embodiment 8)
FIG. 12 is a schematic cross-sectional view of another example of the nitride semiconductor laser element of the present invention. Here, in the nitride semiconductor laser element shown in FIG. 12, a ridge stripe portion is formed by removing a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308, thereby forming a ridge stripe. peripheral parts for example on embedded in the insulating layer 401, such as SiO _2, structure in which a upper transparent conductive film 309 on the p-type nitride semiconductor contact layer 308 and the insulating layer 401 constituting the upper surface of the ridge stripe portion It is characterized by being said. Here, an example in which a part of the p-type AlGaN layer 307 is removed is shown, but the upper transparent conductive film 309, the middle of the p-type nitride semiconductor contact layer 308, or the p-type nitride semiconductor contact layer 308 are shown. As described above, the depth of the removed portion is not particularly limited.

  In the nitride semiconductor laser device shown in FIG. 12, lower transparent conductive films 312 are respectively formed on the back surface of n-type cladding layer 301 exposed from the removed portion of n-type semiconductor substrate 300 and on the surface of n-type semiconductor substrate 300. It is also characterized by the provision.

  The nitride semiconductor laser device having such a structure is formed after the ridge stripe portion is formed by removing a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308 by, for example, an etching process. The periphery of the ridge stripe portion is filled with an insulating layer 401, an upper transparent conductive film 309 is formed thereon, and then a part of the n-type semiconductor substrate 300 is removed, and then on the back surface of the n-type cladding layer 301 and It can be manufactured by providing the lower transparent conductive film 312 on the surface of the n-type semiconductor substrate 300.

The description other than the above is the same as that of the seventh embodiment.
(Embodiment 9)
FIG. 13 is a schematic cross-sectional view of another example of the nitride semiconductor laser element of the present invention. Here, in the nitride semiconductor laser element shown in FIG. 13, a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308 are removed to form the first ridge stripe portion. Further, the second ridge stripe portion is formed by removing until a part of the surface of the lower adjacent layer 303 below the nitride semiconductor active layer 304 is exposed. The side walls and surfaces of the first ridge stripe portion and the second ridge stripe portion are covered with an insulating layer 501 having good heat dissipation, such as aluminum nitride, and an upper transparent conductive film 309 is provided on the upper surface of the first ridge stripe portion. Further, in the vicinity of the nitride semiconductor active layer 304, a heat radiating member 502 having good heat radiating property such as copper is provided adjacent to the insulating layer 501.

  Here, an example is shown in which up to a part of the p-type AlGaN layer 307 and a part of the lower adjacent layer 303 are removed, but the depth of the removed part is not particularly limited. It is important to place a material with good heat dissipation near the nitride semiconductor active layer 304. Further, it is more effective to use a conventional method of loading a material with good heat dissipation on the n side.

In the present invention, the width W ₂ of the second ridge stripe portion is larger than the width W ₁ of the first ridge stripe portion, and is particularly preferably 100 μm or less, and more preferably 50 μm or less. .

  In the nitride semiconductor laser device having such a configuration, the first ridge stripe portion is formed by removing a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308 by, for example, an etching process. After that, a layer below the nitride semiconductor active layer 304 such as the lower adjacent layer 303 is further removed to form a second ridge stripe portion. An insulating layer 501 with good heat dissipation, such as aluminum nitride, is formed on the side wall and the surface of the first ridge stripe portion and the second ridge stripe portion by, for example, sputtering, and is formed on the upper surface of the first ridge stripe portion. An upper transparent conductive film 309 is formed. Furthermore, it can be produced by forming, for example, a heat radiating member 502 having excellent heat radiating property such as copper on the insulating layer 501 in the vicinity of the nitride semiconductor active layer 304 by, for example, vapor deposition or sputtering.

  With such a configuration, more heat generated in the nitride semiconductor laser element can be released from the heat dissipation member 502 to the outside as compared with the eighth embodiment. The tendency to be able to deter further increases.

The description other than the above is the same as in the seventh and eighth embodiments.
(Embodiment 10)
FIG. 14 is a schematic cross-sectional view of another example of the nitride semiconductor laser element of the present invention. Here, in the nitride semiconductor laser element shown in FIG. 14, a ridge stripe portion is formed by removing a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308, respectively. A structure in which an upper transparent conductive film 309 is provided on the p-type nitride semiconductor contact layer 308 and the insulating layer 401 constituting the upper surface of the ridge stripe portion after the periphery of the portion is embedded with an insulating layer 401 such as SiO ₂ It is characterized by being said. Here, an example in which a part of the p-type AlGaN layer 307 is removed is shown, but the upper transparent conductive film 309, the middle of the p-type nitride semiconductor contact layer 308, or the p-type nitride semiconductor contact layer 308 are shown. As described above, the depth of the removed portion is not particularly limited.

  The nitride semiconductor laser element shown in FIG. 14 is also characterized in that a lower transparent conductive film 312 is provided on the back surface of the n-type cladding layer 301 exposed by removing all of the n-type semiconductor substrate.

  The nitride semiconductor laser device having such a structure is formed after the ridge stripe portion is formed by removing a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308 by, for example, an etching process. The periphery of the ridge stripe portion is filled with an insulating layer 401, an upper transparent conductive film 309 is formed on the insulating layer 401, and after removing all the n-type semiconductor substrate 300, the lower transparent on the back surface of the n-type cladding layer 301 It can be manufactured by providing the conductive film 312.

The description other than the above is the same as in the seventh to ninth embodiments.
(Embodiment 11)
FIG. 15 is a schematic cross-sectional view of another example of the nitride semiconductor laser element of the present invention. Here, in the nitride semiconductor laser element shown in FIG. 15, a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308 are removed to form the first ridge stripe portion. Further, the second ridge stripe portion is formed by removing until a part of the surface of the lower adjacent layer 303 below the nitride semiconductor active layer 304 is exposed. The side walls and surfaces of the first ridge stripe portion and the second ridge stripe portion are covered with an insulating layer 501 having good heat dissipation, such as aluminum nitride, and an upper transparent conductive film 309 is provided on the upper surface of the first ridge stripe portion. Further, in the vicinity of the nitride semiconductor active layer 304, a heat radiating member 502 having a good heat radiating property such as copper is provided so as to be adjacent to the insulating layer 501.

  Here, an example is shown in which up to a part of the p-type AlGaN layer 307 and a part of the lower adjacent layer 303 are removed, but the depth of the removed part is not particularly limited. It is important to place a material with good heat dissipation near the nitride semiconductor active layer 304. Further, it is more effective to use a conventional method of loading a material with good heat dissipation on the n side.

In the present invention, the width W ₂ of the second ridge stripe portion is larger than the width W ₁ of the first ridge stripe portion, and is particularly preferably 100 μm or less, and more preferably 50 μm or less. . However, the width W ₂ of the second ridge stripe portion is preferably larger than the width W of the laser beam 321 emitted from the nitride semiconductor active layer 304. By adopting such a configuration, the laser beam 321 tends not to be lost by the heat radiating member 502.

  In the nitride semiconductor laser device having such a configuration, the first ridge stripe portion is formed by removing a part of the p-type AlGaN layer 307 and a part of the p-type nitride semiconductor contact layer 308 by, for example, an etching process. After that, a layer below the nitride semiconductor active layer 304 such as the lower adjacent layer 303 is further removed to form a second ridge stripe portion. An insulating layer 501 having good heat dissipation, such as aluminum nitride, is formed on the side wall and the surface of the first ridge stripe portion and the second ridge stripe portion by, for example, sputtering, and is formed on the upper surface of the first ridge stripe portion. Forms an upper transparent conductive film 309. Further, on the insulating layer 501 in the vicinity of the nitride semiconductor active layer 304, for example, a heat radiating member 502 having excellent heat radiating properties such as copper can be formed by, for example, vapor deposition or sputtering.

  By adopting such a configuration, more heat generated in the nitride semiconductor laser element can be released from the heat dissipation member 502 to the outside as compared with the tenth embodiment. The tendency to be able to deter further increases.

  The description other than the above is the same as in the seventh to tenth embodiments.

Example 1
As the nitride semiconductor laser element of Example 1, a nitride semiconductor laser element having the configuration shown in FIG. Here, the wavelength of the laser beam emitted from the nitride semiconductor laser element of Example 1 was about 440 nm to 450 nm.

Specifically, the nitride semiconductor laser element of Example 1 has a thickness made of Al _0.06 Ga _0.94 N doped with silicon (Si) on one surface of an n-type semiconductor substrate 100 made of n-type GaN. an n-type cladding layer 101 of 2.2 .mu.m, the n-side optical guide layer 102 having a thickness of 0.1μm made of undoped in _0.03 Ga _0.97 n, a lower adjacent layer 103 having a thickness of 20nm made of undoped in _0.03 Ga _0.97 n , a nitride semiconductor active layer 104, an upper adjacent layer 105 having a thickness of 20nm made of undoped in _0.03 Ga _0.97 N, a p-side optical guide layer 106 having a thickness of 50nm made of undoped in _0.03 Ga _0.97 N, magnesium (Mg p,) of the p-type AlGaN layer 107 having a thickness of 20nm of doped Al _0.3 Ga _0.7 N, made of GaN magnesium (Mg) doped A nitride semiconductor contact layer 108, and the upper transparent conductive film 109 having a thickness of 0.1μm made of indium tin oxide (ITO) are laminated in this order. The nitride semiconductor laser device of Example 1 having such a configuration was formed by metal organic chemical vapor deposition. The upper transparent conductive film 109 was formed by a conventionally known vapor deposition method.

For comparison, a nitride semiconductor laser element of Comparative Example 1 having the configuration shown in FIG. 16 was also produced. The nitride semiconductor laser device of Comparative Example 1 has an Al _0.06 Ga _0.94 N doped with magnesium (Mg) on a 20 nm thick p-type AlGaN layer 107 made of Al _0.3 Ga _0.7 N doped with magnesium (Mg). A p-type cladding layer 110 having a thickness of 0.55 μm is formed, and a p-type nitride semiconductor contact layer 108 having a thickness of 0.1 μm made of GaN doped with magnesium (Mg) is formed on the p-type cladding layer 110. The structure is the same as that of the nitride semiconductor laser device of Example 1 except that the metal electrode 111 made of Au is provided on the p-type nitride semiconductor contact layer 108.

The nitride semiconductor active layer 104 of each nitride semiconductor laser element of Example 1 and Comparative Example 1 has a triple quantum well structure as shown in FIG. 7, and has a thickness of In _0.13 Ga _0.87 N. A nitride semiconductor well layer 131 having a thickness of 3 nm and a nitride semiconductor barrier layer 132 having a three-layer structure of In _0.03 Ga _0.97 N having a thickness of 6 nm / GaN having a thickness of 4 nm / In _0.03 Ga _0.97 N having a thickness of 6 nm. is doing.

  FIG. 17 shows the relationship between the thickness of the p-type nitride semiconductor contact layer 108 and the absorption coefficient when the thickness of the p-type nitride semiconductor contact layer 108 of the nitride semiconductor laser element having the configuration of the first embodiment is changed. FIG. 18 shows the relationship between the thickness of the p-type nitride semiconductor contact layer 108 and the optical confinement factor. The relationship shown in FIGS. 17 and 18 is calculated as a relative value with respect to the nitride semiconductor laser element having the configuration of the comparative example. The relationship shown in FIGS. 17 and 18 is calculated using the values shown in Table 1 below.

  As shown in FIGS. 17 and 18, in the nitride semiconductor laser element having the configuration of the above-described embodiment 1, optical confinement is obtained when the thickness of the p-type nitride semiconductor contact layer 108 is set to about 0.2 μm. The coefficient can be increased and the absorption loss can be reduced. Here, the absorption loss here takes into consideration only the relative value to the absorption loss in the metal electrode made of Au on the p-type nitride semiconductor contact layer 108 of the nitride semiconductor laser element of Comparative Example 1 (that is, the metal electrode). The absorption loss due to the other parts is not taken into account in the calculation of the relative value of the nitride semiconductor laser device of Example 1.)

  By adopting the configuration as in Example 1 described above, a p-type cladding layer made of p-type AlGaN can be eliminated, so that a significant reduction in driving voltage can be expected.

(Example 2)
The configuration of the nitride semiconductor laser element of Example 2 was the same as the configuration of the nitride semiconductor laser element of Example 1 described above. On the other hand, as a comparison, a metal electrode made of Au is formed on the entire surface of the upper transparent conductive film 109 of the nitride semiconductor laser element of Example 1 opposite to the side on which the nitride semiconductor active layer 104 is installed to form an upper transparent conductive film. A nitride semiconductor laser device of Comparative Example 2 was prepared in which the surface of 109 was not exposed to the outside.

  Then, when the absorption loss of the nitride semiconductor laser element of Example 2 and the nitride semiconductor laser element of Comparative Example 2 were compared, it was possible to suppress the absorption loss to about 1/3.

  That is, as in the nitride semiconductor laser element of Example 2, the light emitting efficiency is improved by adopting a structure in which the surface of the upper transparent conductive film 109 opposite to the side where the nitride semiconductor active layer 104 is disposed is in contact with air. It was confirmed that

(Example 3)
As the nitride semiconductor laser element of Example 3, a nitride semiconductor laser element having the configuration shown in FIG. 8 was produced. Here, the wavelength of the laser light emitted from the nitride semiconductor laser element of Example 3 was about 440 nm to 450 nm.

In the nitride semiconductor laser device of Example 3, a cavity 210 is formed by laterally growing n-type GaN after forming grooves on the surface of the n-type GaN substrate as described in JP-A-2000-106455. On one surface of the n-type semiconductor substrate 200, an n-type cladding layer 201 made of Al _0.10 Ga _0.90 N doped with silicon (Si) and having a thickness of 0.1 μm, and a thickness made of undoped In _0.03 Ga _0.97 N An n-side light guide layer 202 having a thickness of 0.1 μm, a lower adjacent layer 203 having a thickness of 20 nm made of undoped In _0.03 Ga _0.97 N, a nitride semiconductor active layer 204, and a thickness of 20 nm made of undoped In _0.03 Ga _0.97 N. Upper adjacent layer 205, p-side light guide layer 206 made of undoped In _0.03 Ga _0.97 N and having a thickness of 50 nm, and doped with magnesium (Mg) 20 nm thick p-type AlGaN layer 207 made of Al _0.3 Ga _0.7 N, 0.05 μm thick p-type nitride semiconductor contact layer 208 made of GaN doped with magnesium (Mg), and indium tin oxide The upper transparent conductive film 209 made of (ITO) and having a thickness of 0.1 μm is laminated in this order. The nitride semiconductor laser element of Example 3 having such a configuration was formed by metal organic chemical vapor deposition. The upper transparent conductive film 209 was formed by a conventionally known vapor deposition method.

Note that the nitride semiconductor active layer 204 of the nitride semiconductor laser device of Example 3 has a triple quantum well structure, a nitride semiconductor well layer made of In _0.13 Ga _0.87 N with a thickness of 3 nm, and a thickness. A nitride semiconductor barrier layer having a three-layer structure of 6 nm In _0.03 Ga _0.97 N / 4 nm thick GaN / 6 nm thick In _0.03 Ga _0.97 N is stacked alternately.

  The nitride semiconductor laser element of Example 3 configured as described above can improve the optical confinement factor by about 1.5 times compared to the nitride semiconductor laser element of Comparative Example 1 described above. Further, the nitride semiconductor laser element of Example 3 does not have a p-type cladding layer unlike the nitride semiconductor laser element of Comparative Example 1, and therefore can be a nitride semiconductor laser element with a low driving voltage. .

Example 4
As shown in FIG. 10, a two-stage ridge stripe portion is provided, and the side wall and surface of the ridge stripe portion are covered with an insulating layer 501 made of aluminum nitride, and a heat dissipation member made of copper in the vicinity of the nitride semiconductor active layer 204 A nitride semiconductor laser device of Example 4 having the same configuration as that of Example 3 except that 502 was provided was manufactured.

  In the nitride semiconductor laser device of Example 4 having the above-described configuration, an improvement during high-temperature operation can be expected as compared with the nitride semiconductor laser device of Example 3.

(Example 5)
As the nitride semiconductor laser element of Example 5, a nitride semiconductor laser element having the configuration shown in FIG. 11 was produced. Here, the wavelength of the laser beam emitted from the nitride semiconductor laser element of Example 5 was about 440 nm to 450 nm.

Specifically, the nitride semiconductor laser element of Example 5 has a thickness of 0.02 μm made of GaN doped with silicon (Si) on one surface of an n-type semiconductor substrate 300 made of n-type GaN. an n-type cladding layer 301, an n-side optical guide layer 302 having a thickness of 0.1μm made of undoped in _0.03 Ga _0.97 n, a lower adjacent layer 303 having a thickness of 20nm made of undoped in _0.03 Ga _0.97 n, the nitride semiconductor an active layer 304, an upper adjacent layer 305 having a thickness of 20nm made of undoped in _0.03 Ga _0.97 N, a p-side optical guide layer 306 having a thickness of 50nm made of undoped in _0.03 Ga _0.97 N, magnesium (Mg) is doped A p-type AlGaN layer 307 made of Al _0.3 Ga _0.7 N and having a thickness of 0.05 μm made of GaN doped with magnesium (Mg). The p-type nitride semiconductor contact layer 308 of m and the upper transparent conductive film 309 made of indium tin oxide (ITO) and having a thickness of 0.1 μm are stacked in this order. Further, a lower transparent conductive film 312 having a thickness of 0.1 μm is formed on the back surface of the n-type cladding layer 301 exposed by removing a part of the n-type semiconductor substrate 300 and on the n-type semiconductor substrate 300. Yes.

  The nitride semiconductor laser element of Example 5 having such a configuration was formed by metal organic chemical vapor deposition. The upper transparent conductive film 309 and the lower transparent conductive film 312 were each formed by a conventionally known vapor deposition method. The n-type semiconductor substrate 300 was thinned by polishing to a thickness of 150 μm.

In addition, the nitride semiconductor active layer 304 of the nitride semiconductor laser device of Example 5 has a triple quantum well structure, a nitride semiconductor well layer made of In _0.13 Ga _0.87 N and having a thickness of 3 nm, A nitride semiconductor barrier layer having a three-layer structure of 6 nm In _0.03 Ga _0.97 N / 4 nm thick GaN / 6 nm thick In _0.03 Ga _0.97 N is stacked alternately.

  The nitride semiconductor laser element of Example 5 configured as described above can improve the optical confinement factor by about 1.8 times compared to the nitride semiconductor laser element of Comparative Example 1 described above.

(Example 6)
As shown in FIG. 13, a two-stage ridge stripe portion is provided, and the side wall and surface of the ridge stripe portion are covered with an insulating layer 501 made of aluminum nitride, and a heat dissipation member made of copper in the vicinity of the nitride semiconductor active layer 304 A nitride semiconductor laser element of Example 6 having the same configuration as that of Example 5 except that 502 was provided was manufactured.

  In the nitride semiconductor laser element of Example 6 having the above-described configuration, improvement in characteristics at high temperature operation can be expected as compared with the nitride semiconductor laser element of Example 5.

(Example 7)
As shown in FIG. 15, a two-step ridge stripe portion is provided, and the side wall and surface of the ridge stripe portion are covered with an insulating layer 501 made of aluminum nitride, and a heat dissipation member made of copper in the vicinity of the nitride semiconductor active layer 304 A nitride semiconductor laser element of Example 7 having the same configuration as that of Example 5 except that 502 was provided was manufactured.

  In the nitride semiconductor laser device of Example 7 having the above-described configuration, further improvement in characteristics during high-temperature operation can be expected as compared with the nitride semiconductor laser device of Example 6.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, a low resistance of a nitride semiconductor laser device can be realized, and a nitride semiconductor laser device having a wide wavelength range of the laser light to be adapted can be provided.

It is typical sectional drawing of an example of the nitride semiconductor laser element of this invention. FIG. 2 is a schematic enlarged sectional view in the vicinity of the nitride semiconductor active layer shown in FIG. 1. (A) is typical sectional drawing along the resonator length direction of the conventional nitride semiconductor laser element, (b) is along the resonator length direction of the nitride semiconductor laser element of this invention shown in FIG. It is a typical sectional view. (A) is typical sectional drawing illustrating the case where the laser beam emitted from the conventional nitride semiconductor laser element oozes upwards, (b) is the nitride semiconductor laser of this invention shown in FIG. It is typical sectional drawing illustrating the case where the laser beam emitted from an element oozes out upwards. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. FIG. 7 is a schematic enlarged sectional view in the vicinity of the nitride semiconductor active layer shown in FIG. 6. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor laser element of this invention. 6 is a schematic cross-sectional view showing a configuration of a nitride semiconductor laser element of Comparative Example 1. FIG. FIG. 6 is a diagram showing the relationship between the thickness of the p-type nitride semiconductor contact layer and the absorption coefficient when the thickness of the p-type nitride semiconductor contact layer of the nitride semiconductor laser element of Example 1 is changed. FIG. 6 is a diagram showing the relationship between the thickness of the p-type nitride semiconductor contact layer and the optical confinement factor when the thickness of the p-type nitride semiconductor contact layer of the nitride semiconductor laser element of Example 1 is changed.

Explanation of symbols

  100, 200, 300 n-type semiconductor substrate, 101, 201, 301 n-type cladding layer, 102, 202, 302 n-side light guide layer, 103, 203, 303 lower adjacent layer, 104, 204, 304 nitride semiconductor active layer 105, 205, 305 Upper adjacent layer, 106, 206, 306 p-side light guide layer, 107, 207, 307 p-type AlGaN layer, 108, 208, 308 p-type nitride semiconductor contact layer, 109, 209, 309 upper Transparent conductive film, 111 metal electrode, 112 air, 113 current confinement layer, 121,321 laser light, 131 nitride semiconductor well layer, 132 nitride semiconductor barrier layer, 210 cavity, 212 n electrode, 312 lower transparent conductive film, 401 501 Insulating layer 502 Heat dissipation member.

Claims (8)

an n-type nitride semiconductor layer;
A nitride semiconductor active layer formed on the n-type nitride semiconductor layer;
A p-type nitride semiconductor layer formed on the nitride semiconductor active layer;
An upper transparent conductive film formed on the p-type nitride semiconductor layer,
The nitride semiconductor active layer has a nitride semiconductor well layer containing indium and a nitride semiconductor barrier layer,
In the region of the upper transparent conductive film located above the region of the nitride semiconductor active layer corresponding to the width of the laser light emitted from the nitride semiconductor active layer, the surface of the upper transparent conductive film is in contact with the gas. ,
In the region of the upper transparent conductive film located in a region different from above the region of the nitride semiconductor active layer corresponding to the width of the laser light emitted from the nitride semiconductor active layer, the surface of the upper transparent conductive film Is in contact with an electrode made of metal, a nitride semiconductor laser device. an n-type nitride semiconductor layer;
A nitride semiconductor active layer formed on the n-type nitride semiconductor layer;
A p-type nitride semiconductor layer formed on the nitride semiconductor active layer;
An upper transparent conductive film formed on the p-type nitride semiconductor layer,
The nitride semiconductor active layer has a nitride semiconductor well layer containing indium and a nitride semiconductor barrier layer,
In the region of the upper transparent conductive film located above the region of the nitride semiconductor active layer corresponding to the width of the laser light emitted from the nitride semiconductor active layer, the surface of the upper transparent conductive film is gas or transparent In contact with the dielectric film,
In the region of the upper transparent conductive film located in a region different from above the region of the nitride semiconductor active layer corresponding to the width of the laser light emitted from the nitride semiconductor active layer, the surface of the upper transparent conductive film Is in contact with an electrode made of metal,
A nitride semiconductor laser device, wherein at least a part of the p-type nitride semiconductor layer forms a ridge stripe portion.   3. The nitride semiconductor laser element according to claim 1, wherein an electric field distribution of the laser light leaks out above the upper transparent conductive film. The p-type nitride semiconductor layer has a p-type nitride semiconductor contact layer in contact with the upper transparent conductive film,
The p-type nitride semiconductor contact layer is made of p-type GaN or p-type AlGaN,
4. The nitride semiconductor laser element according to claim 1, wherein the p-type nitride semiconductor contact layer has a thickness of 1 μm or less. 5. A nitride semiconductor lower light guide layer is provided between the n-type nitride semiconductor layer and the nitride semiconductor active layer;
The nitride semiconductor lower light guide layer is made of a nitride semiconductor containing indium,
5. The nitride semiconductor laser device according to claim 1, wherein an indium composition ratio of the nitride semiconductor lower light guide layer is smaller than an indium composition ratio of the nitride semiconductor well layer. 6. A nitride semiconductor upper light guide layer is provided between the nitride semiconductor active layer and the upper transparent conductive film,
The nitride semiconductor upper light guide layer is made of a nitride semiconductor containing indium,
6. The nitride semiconductor laser device according to claim 1, wherein an indium composition ratio of the nitride semiconductor upper light guide layer is smaller than an indium composition ratio of the nitride semiconductor well layer. A lower transparent conductive film is provided on the side of the n-type nitride semiconductor layer opposite to the side where the nitride semiconductor active layer is installed;
7. At least a part of the surface of the lower transparent conductive film opposite to the side where the n-type nitride semiconductor layer is installed is in contact with a gas or a transparent dielectric film. A nitride semiconductor laser device according to claim 1.   8. The nitride semiconductor laser element according to claim 1, further comprising a heat dissipating member on at least a part of a surface different from the resonator end face of the nitride semiconductor laser element.

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