JP2010016261A - Nitride semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor laser element which can drive in lower output, higher in luminous efficiency, and emits light of long wavelength of about 440-550 nm. <P>SOLUTION: The nitride semiconductor laser element is characterized by including at least a first n-type nitride semiconductor layer, a p-type nitride semiconductor layer, an active layer, and a second n-type nitride semiconductor layer on a substrate from the side of the substrate in this order. The nitride semiconductor laser element is constructed in such a manner that the substrate or the first n-type nitride semiconductor layer contacts with a first electrode, the second n-type nitride semiconductor layer contacts with a second electrode, the first electrode is an anode electrode, and the second electrode is a cathode electrode. It is preferable to provide a conductive oxide layer to the second n-type nitride semiconductor layer on the opposite side to the active layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor laser device used for optical storage media, illumination, and displays.

  In recent years, a light-emitting element using a nitride-based semiconductor that emits blue or violet light as a light-emitting layer has been studied as a light-emitting element used in a semiconductor laser or a light emitting diode (LED).

  Of these, nitride semiconductor laser elements used in semiconductor lasers are considered to have improved from both the manufacturing process and the element structure, and problems in the manufacturing process have been substantially solved through improvements in yield and the like. However, the device structure is still under improvement, and development of a light emitting device that can be driven at a lower output and that exhibits high light emission efficiency is underway.

  A conventional nitride semiconductor laser device includes an n-type GaN buffer layer, an n-type AlGaN cladding layer, an n-type GaN guide layer, an InGaN multiple quantum well active layer, a p-type AlGaN current blocking layer, and a p-type GaN on an n-type GaN substrate. A guide layer, a p-type AlGaN clad layer, and a p-type GaN contact layer are formed in this order from the n-type GaN substrate side, and an n-type AlGaN clad layer and a p-type AlGaN clad layer are arranged vertically above and below the InGaN multiple quantum well active layer. By providing, the light emitted from the InGaN multiple quantum well active layer was confined in the device without leaking outside the device, and an optical waveguide was formed in the device.

  However, since the refractive index of the p-type AlGaN cladding layer is not sufficiently lower than the refractive index of the p-type GaN contact layer, part of the light emitted from the InGaN multiple quantum well active layer leaks to the p-type GaN contact layer side. As a result, there is a problem in that light emission efficiency (current-light conversion efficiency: SE Slope Efficiency) is lowered without being sufficiently guided in the light emitting element.

  Therefore, in order to solve the above problem, Patent Document 1 discloses light emission that uses Mg as a dopant of the p-type AlGaN cladding layer to lower the refractive index of the p-type AlGaN cladding layer, thereby preventing light leakage. Devices have been proposed.

As shown in FIG. 13, the layer structure of the nitride semiconductor laser element 910 described in Patent Document 1 has a thickness of 2. on an n-type GaN substrate 911 having a thickness of 400 μm in order from the n-type GaN substrate side. 5 μm n-type Al _0.05 Ga _0.95 N cladding layer 913, 0.2 μm thick n-type GaN guide layer 914, 0.152 μm thick InGaN multiple quantum well active layer 923, and 0.012 μm thick p layer Type Al _0.15 Ga _0.85 N carrier block layer 922, p-type GaN guide layer 921 having a thickness of 0.2 μm, p-type Al _0.05 Ga _0.95 N clad layer 924 having a thickness of 0.6 μm, and 0.2 μm in thickness A p-type GaN contact layer 924a and a p-electrode 940 are included in this order, and the surface of the p-type Al _0.05 Ga _0.95 N clad layer 924 is inductively coupled plasma (ICP) etched. The p-type Al _0.05 Ga _0.95 N clad layer 924 is etched to a part, and an SiO ₂ film 925 comprising a 200 nm thick SiO ₂ layer and a 50 nm thick TiO ₂ layer is formed in the etched portion. A p-electrode 940 is formed, and an n-electrode 941 is formed on the lower surface of the n-type GaN substrate 911. The p-type nitride semiconductor layer 920 includes the p-type Al _0.15 Ga _0.85 N carrier block layer 922, the p-type GaN guide layer 921, the p-type Al _0.05 Ga _0.95 N clad layer 924, and the p-type GaN contact layer 924a. That's it.
JP 2002-124737 A

According to the invention described in Patent Document 1, the conventional p-type AlGaN cladding layer was excellent in that the refractive index could be lowered and light leakage could be effectively prevented. The element using the doped p-type Al _0.05 Ga _0.95 N clad layer 924 has the following two problems in terms of obtaining high luminous efficiency.

  The first problem of this element is that light emitted from the InGaN multiple quantum well active layer 923 is strongly absorbed by Mg contained in the dopant of the p-type nitride semiconductor layer 920, and the emission efficiency of the semiconductor laser is reduced. It is a problem.

In the case of an element normally used for a light emitting diode, it is not necessary to confine light in the element, and therefore, the p-type Al _0.05 Ga _0.95 N cladding layer is not included and the p-type nitride semiconductor layer is also thin. Even when Mg was contained in the layer, the thickness of the light-absorbing layer itself was small, and it was not a problem. However, since an element used in a semiconductor laser resonates light through a waveguide in the element, light absorption of Mg contained in the p-type nitride semiconductor layer becomes a very big problem.

  Furthermore, another problem is that when the p-type nitride semiconductor layer 920 is formed at a relatively low temperature of about 600 to 800 ° C., the resistance of the p-type nitride semiconductor layer 920 becomes high and the driving voltage becomes high. This is a problem that the light emission efficiency of the semiconductor laser is lowered.

  That is, if the p-type nitride semiconductor layer 920 is formed at a high temperature of 1000 ° C. or higher, it tends to be difficult to increase the resistance, but if heated to a high temperature of 1000 ° C. or higher, it is included in the InGaN multiple quantum well active layer 923. Since crystals deteriorate due to heat damage, it was necessary to form a film at about 600 to 800 ° C. For this reason, the problem that the p-type nitride semiconductor layer 920 is increased in resistance cannot be avoided.

  This is because when the laser is oscillated at a relatively long wavelength of about 440 to 550 nm, the In composition x of the well layer included in the InGaN multiple quantum well active layer 923 is relatively large, from 0.15 to 0.3. However, in the case of the above In composition x, heat at the time of manufacturing the p-type nitride semiconductor layer 920 is greatly affected, and is easily damaged by heat. For this reason, when trying to oscillate a laser with a relatively long wavelength of about 440 to 550 nm, this thermal damage is a serious problem.

  Therefore, the present invention has been made in view of the above situation, and is a nitride semiconductor that can be driven at a lower output, has higher luminous efficiency, and emits light having a long wavelength of about 440 to 550 nm. The object is to provide a laser element.

  As a result of various studies to solve the above-mentioned problems, the present inventor considers that the replacement of the p-type nitride semiconductor layer with the second n-type nitride semiconductor layer is most effective for the above purpose. Based on this finding, the present invention was finally completed by further intensive studies.

  According to the present invention, it is possible to provide a nitride semiconductor laser device that can be driven at a lower output, has higher luminous efficiency, and emits light having a long wavelength of about 440 to 550 nm.

  That is, the nitride semiconductor laser device of the present invention includes at least the first n-type nitride semiconductor layer, the p-type nitride semiconductor layer, the active layer, and the second n-type nitride semiconductor layer on the substrate from the substrate side. It is characterized by including in order.

  The substrate or the first n-type nitride semiconductor layer is in contact with the first electrode, the second n-type nitride semiconductor layer is in contact with the second electrode, the first electrode is an anode electrode, and the second electrode Is preferably a cathode electrode.

Moreover, it is preferable to provide a conductive oxide layer on the opposite side of the second n-type nitride semiconductor layer from the active layer. The substrate or the first n-type nitride semiconductor layer is in contact with the first electrode, the conductive oxide layer is in contact with the second electrode, the first electrode is an anode electrode, and the second electrode is A cathode electrode is preferable. The active layer includes a well layer made of In _x Ga _1-x N (0 ≦ x ≦ 1), and the In composition x of the well layer is preferably 0.15 or more and 0.30 or less. .

FIG. 1 is a schematic cross-sectional view of a typical nitride semiconductor laser device 10 of the present invention. As shown in FIG. 1, the nitride semiconductor laser device 10 of the present invention includes a first n-type nitride semiconductor layer 12 comprising a first cladding layer 13 and a first n-type guide layer 14 on a substrate 11, Al _y Ga _1-y N intermediate layer 30, p-type nitride semiconductor layer 20 composed of p-type guide layer 21 and p-type carrier block layer 22, active layer 23, second n-type guide layer 16 and second cladding layer 17 And the n-type contact layer 18, the second n-type nitride semiconductor layer 15, the current confinement insulating film 25, and the second electrode 40, and the first electrode 41 is provided on the substrate surface opposite to these layers. It has a structure. Each layer included in this structure will be described below.

<First n-type nitride semiconductor layer>
The first n-type nitride semiconductor layer 12 included in the nitride semiconductor laser element 10 of the present invention is a layer on the substrate 11 and is in contact with the substrate, or a buffer layer or a thin undoped layer (on the substrate). An n-type semiconductor layer formed with a thickness of 0.5 μm or less. For example, the first cladding layer 13 and the first n-type guide layer 14. The material used for the first n-type nitride semiconductor layer 12 is Al _x Ga _y In _z N using Si as a dopant (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z <1; x + y + z = 1). Further, the first n-type nitride semiconductor layer 12 can be formed at a relatively low temperature of about 600 to 800 ° C., and a layer having a lower resistance than the p-type nitride semiconductor layer 20 can be formed. This is characterized in that a nitride semiconductor having higher crystallinity than the p-type nitride semiconductor layer 20 can be easily formed.

  Also, a part of the surface of the first n-type nitride semiconductor layer 12 opposite to the surface in contact with the substrate 11 can be replaced with a p-type cladding layer. However, it is not preferable to make the p-type cladding layer thicker than 2 μm because the light absorption by Mg contained in the p-type cladding layer is increased, and from the viewpoint of light emission efficiency, the layer thickness to replace the p-type cladding layer is 2 μm or less. preferable. Hereinafter, the first cladding layer 13 and the first n-type guide layer 14 included in the first n-type nitride semiconductor layer 12 will be described.

(I) First Cladding Layer The first cladding layer 13 included in the first n-type nitride semiconductor layer 12 of the present invention extends in the direction perpendicular to the nitride semiconductor growth surface in the light emitted from the active layer 23. The layer plays a role of confining light inside the device around the active layer, and is a layer in which light guided in the nitride semiconductor layer is distributed. In order to effectively confine the light emitted from the active layer 23 inside the device, the refractive index of the first cladding layer 13 should be lower than that of the active layer 23 and the first n-type guide layer 14. Is desirable.

As a material used for the first cladding layer 13, an n-type nitride semiconductor made of Al _x Ga _y In _z N (0 ≦ x <1; 0 ≦ y <1; 0 ≦ z <1; x + y + z = 1) is used. In particular, Al _y Ga _1-y N (0 ≦ y ≦ 0.1) is preferably used from the viewpoint of lowering the refractive index of the first cladding layer 13. This is because, in general, a nitride semiconductor made of Al _x Ga _y In _z N tends to have a higher refractive index as it contains In, and lower as it contains Al. The layer thickness of the first cladding layer 13 can be 0.1 μm or more and 10 μm or less. The crystal structure of the first cladding layer may be a superlattice structure of AlGaN and GaN, or a superlattice structure of Al _p Ga _1-p N and Al _q Ga _1-q N having different compositions. There may be.

(II) First n-type Guide Layer Materials used for the first n-type guide layer 14 included in the first n-type nitride semiconductor layer 12 of the present invention include Al _y Ga _1-y N, Al _x Ga _y. In _z N, GaN, etc. can be mentioned. The layer thickness of the first n-type guide layer 14 can be set to 0.1 μm or more and 10 μm or less.

<P-type nitride semiconductor layer>
The p-type nitride semiconductor layer 20 included in the nitride semiconductor laser device 10 of the present invention is a layer including a p-type guide layer 21 and a p-type carrier block layer 22. A feature of the present invention is that a p-type nitride semiconductor layer is provided below the active layer 23 and has a pn junction with the first n-type nitride semiconductor layer. By providing the p-type nitride semiconductor layer 20 before forming the active layer 23, the temperature rise after the formation of the active layer 23 can be suppressed, and the thermal decomposition of the active layer 23 can be effectively prevented. it can. The p-type guide layer 21 preferably has a thickness of 0.01 to 1 μm, and the p-type carrier block layer 22 preferably has a thickness of 1 to 1000 nm.

  If the p-type nitride semiconductor layer 20 is formed before forming the active layer 23 as in the present invention, the p-type nitride semiconductor layer 20 is formed at the optimum growth temperature and film formation conditions without worrying about thermal damage of the active layer 23. The type nitride semiconductor layer 20 can be produced. A low-resistance p-type nitride semiconductor layer is required to have high quality crystallinity. However, a conventional general nitride semiconductor laser, and a long wavelength light emitting device having an active layer with a high In composition, are grown with an active layer. Since a p-type nitride semiconductor layer was formed later, it could not be formed at a very high temperature. However, in the present invention, since the p-type nitride semiconductor layer can be formed at a high temperature of about 1125 ° C., the p-type nitride semiconductor layer 20 having a high crystallinity and a very low resistance can be manufactured. The p-type nitride semiconductor layer 20 with high carrier density and low light absorption can be produced. In this way, holes can be efficiently injected into the active layer, and the reliability and light emission efficiency (slope efficiency) after laser oscillation are improved.

  Further, Mg used as the dopant of the p-type nitride semiconductor layer 20 forms a deep energy level, and thus the p-type nitride semiconductor layer 20 tends to have a high resistance, and in particular, the p-type nitride semiconductor layer containing Al. 20 tends to be particularly high resistance. For this reason, as the thickness of the p-type nitride semiconductor layer 20 is increased, the series resistance increases, so that the drive voltage increases and the light emission efficiency decreases. Therefore, the p-type nitride semiconductor layer 20 is preferably formed as thin as possible.

<Pn junction>
The nitride semiconductor laser device 10 of the present invention is characterized in that a pn junction is included between the substrate 11 and the active layer 23 in addition to a pn junction included in the active layer 23. For example, in FIG. 1, a pn junction is included between the first n-type guide layer 14 and the p-type guide layer 21. The direction of the pn junction is that when the forward bias is applied to the pn junction of the active layer, that is, when a positive bias is applied to the first electrode 41 and a negative bias is applied to the second electrode 40, the substrate 11 and the active layer 23 A pn junction is provided in the direction of biasing in the reverse direction to the pn junction between the two. Here, when laser oscillation is performed, a positive bias is applied to the first electrode 41 and a negative bias is applied to the second electrode 40.

  However, when a pn junction is provided so as to bias the pn junction between the substrate 11 and the active layer 23 in the reverse direction, the width of the depletion layer at the pn junction interface widens, so that a tunnel current hardly flows. . However, by adopting the methods shown in the following (I) and (II), the tunnel current can be easily passed.

(I) In the first method, as shown in FIG. 2, the Si doping amount is increased in the vicinity of the pn junction interface between the first n-type guide layer 14 and the p-type guide layer 21. This is a method of providing an n + doped layer 14a and a p + doped layer 21a with an increased Mg doping amount. Thus, by providing the n + doped layer 14a and the p + doped layer 21a in the vicinity of the interface of the pn junction, the width of the depletion layer between the first n-type guide layer 14 and the p-type guide layer 21 is reduced, and the tunnel current is reduced. Becomes easier to flow. When the n + doped layer 14a and the p + doped layer 21a are provided in this manner, the carrier concentration in the n + doped layer 14a and the carrier concentration in the p + doped layer 21a are preferably 5 × 10 ¹⁸ / cm ³ or more. The layer thickness of the n + doped layer 14a and the p + doped layer 21a may be about several atoms at the pn junction interface, or may be about 10 to 30 nm.

<Al _y Ga _1-y N intermediate layer>
(II) Another method is to provide an Al _y Ga _1-y N intermediate layer 30 between the first n-type guide layer 14 and the p-type guide layer 21 as shown in FIG. By providing the Al _y Ga _1-y N intermediate layer 30 at the interface of the pn junction in this way, lattice strain due to lattice mismatch occurs in the c-plane nitride semiconductor, and spontaneous polarization due to piezoelectric field is generated from this lattice strain. In addition, there is an effect of distorting the band energy of the conduction band and the band energy of the valence band. Due to this strain, the width of the depletion layer becomes narrow, and a tunnel current easily flows when biased in the reverse direction. Here, there are two types of lattice strain due to lattice mismatch, strain due to the direction of compressive stress and strain due to the direction of tensile stress. Of these two strains, the width of the depletion layer is narrow. Therefore, it is necessary to appropriately select the distortion to be distorted. In the present invention, for example, by using AlN, the width of the depletion layer can be narrowed from the lattice distortion due to lattice mismatch, and the tunnel current can be easily passed.

The layer thickness of the Al _y Ga _1-y N intermediate layer 30 can be set to 0.5 to 100 nm. Further, Al _y Ga _1-y N (0 ≦ y ≦ 1) can be suitably used for the Al _y Ga _1-y N intermediate layer 30, and it is particularly preferable to use AlN. In the present invention, the above-described Al _y Ga _1-y N intermediate layer may be formed in the pn junction, and nitride semiconductors such as AlN, InGaN, InN, and AlInGaN have a thickness of 0.5 to 100 nm. It may be formed. The Al _y Ga _1-y N intermediate layer may be doped with impurities so as to exhibit n-type conduction or p-type conduction, or may be undoped.

<Second n-type nitride semiconductor layer>
The second n-type nitride semiconductor layer 15 included in the nitride semiconductor laser device 10 of the present invention is characterized in being located on the side opposite to the substrate 11 when viewed from the active layer 23.

  The conventional nitride semiconductor laser device has a problem that when the p-type nitride semiconductor layer is formed at a high temperature exceeding 1000 ° C. after the active layer 23 is formed, the active layer containing In is decomposed. However, according to the present invention, without forming a p-type nitride semiconductor layer after forming an active layer containing In, the second n-type is formed at a relatively low temperature of about 600 to 800 ° C. where thermal decomposition of In hardly occurs. Since a nitride semiconductor layer can be formed, a nitride semiconductor laser element can be manufactured without causing thermal decomposition even if an active layer having an In composition x of about 0.15 to 0.4 is included.

  In addition, since the p-type nitride semiconductor layer 920 used in the conventional nitride semiconductor laser element 910 is essentially less likely to have a low resistance, the series resistance is increased and the driving voltage of the nitride semiconductor laser element is likely to increase. There was also. However, if the second n-type nitride semiconductor layer 15 having a low resistance is used on the active layer 23 as in the present invention, the nitride semiconductor laser element can be obtained due to the high conductivity of the second n-type nitride semiconductor layer 15. The driving voltage of 10 can also be lowered. Even when a conductive oxide layer, which will be described later, is further provided on the second n-type nitride semiconductor layer 15, the electrical resistance does not increase so much, so that the drive voltage of the nitride semiconductor laser element 10 is set to the conductive oxide layer. It is almost the same as the case where no is provided.

  Further, since the conventional nitride semiconductor laser element 910 has the p-electrode 940 formed on the p-type nitride semiconductor layer 920, the p-type 940 and the n-electrode 941 are provided at both ends of one nitride semiconductor laser element. Was. However, according to the present invention, it is not necessary to produce the p-electrode 940, both ends of the nitride semiconductor laser element can be produced only by the n-electrode, and the two n-electrodes can be formed from the same material. Productivity during electrode deposition can be improved and costs can be reduced. The materials used for the two n-electrodes are not limited to the same material, and different materials may be used.

The second n-type nitride semiconductor layer 15 used in the nitride semiconductor laser device 10 of the present invention is any one of the second n-type guide layer 16, the second cladding layer 17, and the n-type contact layer 18. _{Examples of the} material used for the second n-type nitride semiconductor layer 15 include Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1) using Si as a dopant. 1; 0 ≦ z ≦ 1; x + y + z = 1), that is, an n-type nitride semiconductor.

The second n-type nitride semiconductor layer 15 can also be formed by laser ablation (PLD: Pulsed Laser Deposition). The PLD method is a growth method that uses sublimation of raw materials by a high-energy ultraviolet laser. Nitrogen gas dissociates and reacts due to a strong local non-equilibrium field created by the sublimated material. Can be grown in an atmosphere. In the PLD method, a target (Ga, Al, In, AlN, GaN, InN, etc.) as a raw material is irradiated with a KrF excimer laser at an energy density of 3 J / cm ² and a repetition frequency of 10 to 15 Hz. The target material is instantly sublimated by this laser irradiation, becomes a kind of plasma called plume, and repeatedly collides with atmospheric gas molecules (nitrogen gas, oxygen gas, etc.), then reaches the substrate and forms a thin film. Form. Nitrogen gas is introduced as a nitrogen source at a pressure of 10 ⁻⁵ to 10 ⁻¹ Torr. According to this method, a high-quality nitride semiconductor can be produced at room temperature, and damage to the active layer due to heat can be significantly reduced.

  The second n-type nitride semiconductor layer 15 can also be formed by pulse sputtering (PSD: Pulsed Sputter Deposition). After the active layer is formed, the second n-type nitride semiconductor layer 15 can be formed at a lower temperature by forming the second n-type nitride semiconductor layer by the PSD method. The heat damage to 23 can be remarkably reduced. All the second n-type nitride semiconductor layers may be formed by the PSD method, or only a part thereof may be formed.

(I) Second n-type Guide Layer The second n-type guide layer 16 included in the second n-type nitride semiconductor layer 15 of the present invention is a layer in contact with the second cladding layer 17. _{Examples of the} material used for the second n-type guide layer 16 include Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1; x + y + z = 1). . The layer thickness of the second n-type guide layer 16 can be 0.01 μm or more and 1 μm or less, but a part of the second n-type guide layer 16 is removed by etching or the like when forming a ridge stripe portion 70 described later. As shown, the layer thickness of the portion removed by etching of the second n-type guide layer is d.

(II) Second Cladding Layer The second cladding layer 17 included in the second n-type nitride semiconductor layer 15 of the present invention spreads in the direction perpendicular to the nitride semiconductor growth surface in the light emitted from the active layer 23. This layer serves to confine light inside the semiconductor near the active layer 23. The second cladding layer 17 preferably has a refractive index lower than that of the active layer 23 and the second n-type guide layer 16. In the present invention, since the optical confinement is performed in the second cladding layer 17 without using the p-type AlGaN cladding layer known for its high resistance, the driving voltage can be reduced as compared with the conventional nitride semiconductor laser element. Here, as a material used for the second cladding layer 17, Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z <1; x + y + z = 1), Al _y Ga _{1 -y} N (0 ≦ y ≦ 0.1), GaN, and the like can be mentioned. From the viewpoint of lowering the refractive index of the second cladding layer 17, Al _y Ga _1-y N (0 ≦ y ≦ More preferably, 0.1) is used. Further, when a GaN material is used for the second cladding layer 17, there is a concern that the refractive index difference with the active layer 23 is not sufficient and the optical confinement effect is weakened. A conductive oxide layer can also be used, and a conductive oxide layer can be further included on the second cladding layer 17.

The crystal structure of the second cladding layer 17 may be a superlattice structure of AlGaN and GaN, or a superlattice structure of Al _p Ga _1-p N and Al _q Ga _1-q N having different compositions. It may be. The layer thickness of the second cladding layer 17 is preferably 0.01 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 8 μm or less.

(III) n-type Contact Layer The n-type contact layer 18 included in the second n-type nitride semiconductor layer 15 of the present invention is a layer located between the second cladding layer 17 and the second electrode 40. The layer thickness of the n-type contact layer 18 can be 0.01 μm or more and 1 μm or less.

<Board>
As a material used for the substrate 11 of the nitride semiconductor laser device of the present invention, a material having a crystal structure with a hexagonal crystal structure can be particularly preferably used. Examples of such a material include a nitride semiconductor substrate and sapphire. A substrate, a SiC substrate, etc. can be mentioned. Further, from the viewpoint of enhancing lattice matching between the substrate 11 and the nitride semiconductor layer formed on the substrate 11, a nitride semiconductor substrate is preferably used as the substrate 11, and an n-type nitride semiconductor substrate is particularly preferable. It is preferable to use it.

Further, when a nitride semiconductor substrate is used, the composition of the nitride semiconductor substrate is Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z <1; x + y + z = 1). In particular, GaN, AlGaN, AlN, InGaN, or the like can be used. If the hexagonal crystal shape of the nitride semiconductor substrate is maintained, at least one element selected from the group consisting of As, P, or Sb may be used as a part of the N element contained in the nitride semiconductor substrate. Can also be substituted. Here, “a part of the N element” means 10% or less of N in N contained in the nitride semiconductor substrate Al _x Ga _y In _z N.

  The layer thickness of such a substrate is preferably 10 μm or more and 1000 μm or less, more preferably 100 μm or more and 800 μm or less, and ideally 200 μm or more and 600 μm or less.

<Active layer>
The active layer 23 used in the nitride semiconductor laser device 10 of the present invention has a laminated body in which barrier layers and well layers are alternately laminated, and further has a structure in which this laminated body is sandwiched by buffer layers from both sides. It is a multiple quantum well active layer structure, and it is preferable to form a film at a temperature of 600 to 800 ° C. In _x Ga _1-x N is used for the barrier layer, and In _x Ga _1-x N having a higher In composition than the barrier layer is used for the well layer. The layer thickness of the active layer 23 can be represented by the total thickness of the barrier layer and the well layer described above, and is preferably 0.01 μm or more and 1 μm or less.

Further, between the active layer and the p-type nitride semiconductor layer of the present invention and between the active layer and the second n-type nitride semiconductor layer, Al _x Ga _y In _z N (0 ≦ x <1; 0 ≦ It is preferable to provide a buffer layer of y ≦ 1; 0 ≦ z <1; x + y + z = 1). The composition of the buffer layer is preferably In _x Ga _1-x N (In composition x: 0 ≦ x ≦ 0.1). Further, when the buffer layer is formed when forming the active layer 23 having a large In composition (In composition 0.15 or more and 0.3 or less), the crystallinity of the well layer can be improved. This is presumably because a large strain caused by lattice mismatch applied to the well layer can be reduced by the buffer layer.

  Here, the thickness of the buffer layer is preferably 1 nm or more and 0.4 μm or less. The buffer layer provided between the active layer and the p-type nitride semiconductor layer is preferably non-doped or p-type doped, and the buffer layer provided between the active layer and the second n-type nitride semiconductor layer. Is preferably non-doped or n-type doped. However, the same effects as those of the present invention can be obtained without providing a buffer layer.

The material used for the active layer 23 is preferably a compound of at least one group 3 element selected from the group consisting of aluminum, indium, and gallium and nitrogen, which is a group 5 element, represented by a composition formula. And Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1; x + y + z = 1). That is, although only the active layer using In _x Ga _1-x N is described in the examples described later, the present invention is not limited to this, and a mixed crystal containing Al in the active layer can also be used. .

Further, the barrier layer and the well layer included in the active layer 23 are both layers made of non-doped In _x Ga _1-x N (0 <x ≦ 1). The thickness of the barrier layer is preferably 1 nm or more and 100 nm or less, and particularly preferably 1 nm or more and 40 nm or less. If it is thinner than 1 nm, it is not preferable because the effect as a barrier layer of carriers cannot be obtained. If it is thicker than 40 nm, the distance between well layers is too far, and carriers may be injected unevenly into the well layer. It is not preferable.

  Further, the thickness of the well layer is preferably 0.5 nm or more and 10 nm or less. If it is thinner than 0.5 nm, the well layer is not formed uniformly, and it is not preferable. If it is thicker than 10 nm, it is not preferable because In aggregation is likely to occur due to strain due to lattice mismatch. Furthermore, it is preferable to form about 1 to 3 well layers. Further, the wavelength of the laser light oscillated from the nitride semiconductor laser element of the present invention can be appropriately adjusted within a range of 440 nm to 550 nm, for example, depending on the mixed crystal ratio of the well layer of the active layer 23. Further, the In composition x of the well layer included in the active layer 23 is preferably 0.15 to 0.3. When the In composition x of the active layer is 0.15, the laser oscillation wavelength is about 440 nm. When the In composition x is 0.3, the laser oscillation wavelength is about 550 nm. As the In composition increases, the oscillation wavelength also increases linearly.

  In the nitride semiconductor laser device of the present invention, it is preferable to provide a carrier block layer (not shown) between the active layer 23 and the second n-type guide layer 16. If the second n-type guide layer 16 is formed at a low temperature after forming the active layer 23, the crystallinity of the second n-type guide layer 16 becomes poor, so that the active layer 23 (especially a well layer having a large In composition) is formed. In some cases, it cannot be adequately protected. However, by providing a carrier block layer between the active layer 23 and the second n-type guide layer 16, it is possible to carry out carrier block of electrons overflowing from the active layer 23, and to further protect the active layer 23. You can also. The thickness of the carrier block layer can be set to 10 nm, for example.

As a material used for this carrier block layer, for example, Al _x Ga _y In _z N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1; 0 ≦ z <1; x + y + z = 1), Al _p Ga _1-p N (0 <p ≦ 1) or the like can be used. Here, when Al _p Ga _1-p N is used for the carrier block layer, the Al composition p is preferably larger than 0. However, if the Al composition p is too large, cracks due to lattice mismatching are not preferable. Such an Al composition p can be set to about 0.18, for example. The carrier block layer is preferably n-type doped, but may be non-doped.

Further, from the viewpoint of alleviating cracks caused by lattice mismatch and from the viewpoint of being able to form a film at a lower temperature, the material used for the carrier block layer may be Al _x Ga _y In _z N (0 <x <1). 0 <y <1; 0 <z <1; x + y + z = 1) is preferably used. In this case, it is preferable that the In composition z is larger than 0 and smaller than 0.3, and if it exceeds 0.3, there is a problem that layer separation occurs and a problem that re-evaporation of the carrier block layer occurs. . The Al composition x is preferably larger than 0, and can be about 0.18, for example.

  Further, in order to manufacture a nitride semiconductor laser device that emits light in a long wavelength region in visible light such as green light and red light, the In composition x of the active layer is as high as 0.15 to 0.3. An active layer with an In content is required. However, an active layer having a high In composition with an In composition x of about 0.15 to 0.3 has a considerably low thermal decomposition temperature of the active layer emitting red or green light. When the p-type nitride semiconductor layer is formed at a high temperature of 1000 ° C. or higher after the film is formed, the active layer causes crystal degradation due to heat damage. Therefore, the nitride semiconductor laser element that emits green light or red light is used. Manufacturing was difficult. As an example showing the low thermal decomposition temperature of a nitride semiconductor crystal containing In, for example, the thermal decomposition temperature of an active layer containing In is so low that InN undergoes thermal decomposition at 600 to 700 ° C.

  However, the nitride semiconductor laser device 10 manufactured according to the present invention is formed at a relatively low temperature of about 600 to 900 ° C. without forming the p-type nitride semiconductor layer after forming the active layer 23. Since the n-type nitride semiconductor layer 15 is formed and the temperature is not raised to a temperature exceeding 900 ° C. in the subsequent manufacturing process, an active layer containing 0.15 or more of the In composition x may be used. A nitride semiconductor laser device can be manufactured without thermal decomposition, and a nitride semiconductor laser device can also be manufactured without thermal decomposition even if the In composition x is an active layer containing 0.2 or more. it can.

<Main surface of substrate>
The principal surface of the substrate 11 used in the present invention includes c-plane {0001}, A-plane {11-20}, R-plane {1-102}, M-plane {1-100}, {1-101} plane, and At least one surface selected from the {11-22} surfaces can be used. From the viewpoint of reducing the resistance of the p-type nitride semiconductor layer formed on this substrate, it is preferable to use a substrate having a c-plane as a main surface.

  In addition, when expressing a crystal plane, it should be expressed by adding a bar on a required number. However, because there are restrictions on expression means, in this specification, the required number Instead of the expression with a bar, the symbol “-” is added in front of the required number.

  Moreover, if the off angle with respect to the main surface of the substrate is 0.1 to 2 °, the surface morphology is good, so that the in-plane layer thickness distribution can be reduced. Therefore, for example, when the main surface of the substrate is the M plane {1-100}, if the off-angle in the c-axis direction in the M plane is inclined by 0.1 to 2 °, the surface morphology is good and the in-plane The layer thickness distribution can be reduced.

  Here, if the off angle with respect to the main surface of the substrate is less than 0.1 °, the in-plane layer thickness distribution may increase, which is not preferable. Further, when the off angle with respect to the main surface of the substrate is larger than 2 °, the step shape of the surface becomes remarkable, and the in-plane layer thickness distribution may be increased, which is not preferable.

<Conductive oxide layer>
The conductive oxide layer used in the nitride semiconductor laser device of the present invention is a layer formed on the nitride semiconductor layer and made of a material having a high refractive index. In addition, as a material used for the conductive oxide layer, tin-doped indium oxide (ITO), aluminum-doped zinc oxide (ZnO: Al), gallium-doped zinc oxide (ZnO: Ga) fluorine-doped tin oxide ( SnO ₂ : F), titanium dioxide doped with niobium (Nb), conductive oxide such as β-Ga ₂ O ₃ or molecular beam epitaxy (MBE) method or metal organic chemical vapor deposition (MOCVD) An n-type zinc oxide (ZnO) produced by the Metal Organic Chemical Vapor Deposition method can be mentioned.

  The conductive oxide layer can be formed by EB vapor deposition, sputter deposition, MBE, MOCVD, etc., and these methods can be used to conduct conductive oxidation at a relatively low temperature of 300 ° C. or lower. A physical layer can be formed. Therefore, there is an advantage that the conductive oxide layer can be formed while avoiding thermal decomposition of the active layer 23.

  Moreover, since the refractive index of the second cladding layer 17 using GaN is higher than that of the second cladding layer using AlGaN, the light confinement effect of the second cladding layer 17 is weakened. In such a case, if a conductive oxide layer is further provided on the second cladding layer 17, the refractive index difference between the second cladding layer 17 and the conductive oxide layer becomes larger, and the second cladding layer It is thought that the light confinement effect of 17 can be improved. Further, a conductive oxide layer can be used instead of the second cladding layer 17.

<Current confinement insulating film>
The current confinement insulating film 25 used in the nitride semiconductor laser device of the present invention is a film provided so as to be in contact with the second n-type guide layer 16 and the second cladding layer 17 and having an insulating property. is there.

  Examples of the material used for the current confinement insulating film 25 include silicon oxide, aluminum oxide, zirconia oxide, titanium oxide, tantalum oxide, silicon oxynitride, and aluminum oxynitride. , Zirconia oxynitride, titanium oxynitride, tantalum oxynitride, silicon nitride, aluminum nitride, non-doped AlN, non-doped AlGaN, non-doped InAlN, p-type AlN, p-type AlGaN, p-type InAlN And at least one selected from materials such as However, when p-type AlN, p-type AlGaN, or p-type InAlN is used, Mg contained therein absorbs light, so that the smaller the amount of Mg doped, the more preferably non-doped.

  The current confinement insulating film 25 can be formed by a conventionally known method, and can be formed by, for example, an EB vapor deposition method, a sputtering method, an MOCVD method, an MBE method, or the like. The current confinement insulating film 25 is not limited to a single layer structure, and may have a multilayer structure.

  The layer thickness of the current confinement insulating film 25 is preferably 6 to 1000 nm, and more preferably 6 to 500 nm. If the layer thickness is less than 6 nm, it is difficult to form a uniform film in the surface, which is not preferable because current leaks and may not serve as the current confinement insulating film 25, and the layer thickness is less than 1000 nm. When the thickness is increased, the second n-type guide layer 2016, the second cladding layer 2017, and the n-type contact layer 2018 formed after the current confinement insulating film 2025 in the configuration of the nitride semiconductor laser element 2010 according to the second embodiment to be described later are used. This is not preferable because there is a problem that the stripe portion of the current confinement insulating film 2025 is not completely filled when it is regrown.

<First electrode>
The first electrode 41 used in the nitride semiconductor laser device of the present invention is a layer provided in contact with the substrate 11 and is an anode electrode for external connection. As the material used for the first electrode 41, conventionally known materials can be used, and for example, Ti, Al, Mo, Pt, Au, Hf, and the like can be used. The first electrode 41 is not limited to a single layer structure, and may have a multilayer structure.

<Second electrode>
The second electrode 40 used in the nitride semiconductor laser element 10 of the present invention is provided on the surface opposite to the first electrode 41 among the end faces of the nitride semiconductor laser element, and is used for external connection. It is a cathode electrode. As the material used for the second electrode 40, conventionally known materials can be used, and for example, Ti, Al, Mo, Pt, Au, Hf, and the like can be used. The second electrode 40 is not limited to a single layer structure, and may have a multilayer structure.

<Ridge stripe part>
In the ridge stripe portion 70 formed in the nitride semiconductor laser device 10 of the present invention, a part of the second n-type guide layer 16 and the second cladding layer 17 is removed by etching, and the striped ridge stripe portion 70 is formed. It is formed to extend in the resonator length direction. The width of the stripe in the ridge stripe portion cannot be clearly defined because it varies depending on the application. For example, when used in a broad area used for illumination, the stripe width can be about 2 to 100 μm. When used as a nitride semiconductor laser element, the stripe width is preferably in the range of 1.2 to 2.4 μm. The resonator length is preferably in the range of 300 μm to 1.8 mm.

  Since the ridge stripe portion of the conventional nitride semiconductor laser element is formed of the p-type nitride semiconductor layer, there is a problem that the resistance tends to be high and the drive voltage increases. However, since the ridge stripe portion 70 of the present invention forms a current confinement portion with an n-type nitride semiconductor layer, the resistance can be further reduced and the drive voltage can be lowered. Further, by adopting this structure, the contact resistance between the second n-type nitride semiconductor layer and the second electrode can be made lower than the contact resistance between the p-type nitride semiconductor layer and the p-type electrode. Therefore, the drive voltage can be further reduced.

  By adopting this structure, there is no contact between the p-electrode and the p-type nitride semiconductor layer as in the prior art, and a structure that can reduce the proportion of the p-type nitride semiconductor layer in the entire nitride semiconductor laser device is easy. There is an advantage that it can be manufactured.

  A preferred embodiment 1 of the present invention will be described below with reference to FIG. 3, and a second embodiment will be described with reference to FIG. 4. The present invention is a nitride semiconductor laser device shown in the first and second embodiments. It is not limited to the structure.

<Embodiment 1>
FIG. 3 shows a schematic cross-sectional view of a preferred example of the nitride semiconductor laser device of the present invention. A nitride semiconductor laser device 1010 according to the present invention includes a first cladding layer 1013 made of n _- type Al _y Ga _1-y N, a first n-type guide layer 1014 made of n-type GaN, p on a nitride semiconductor substrate 1011. p-type carrier blocking layer 1022 made of p-type guide layer 1021, p-type Al _y Ga _1-y N formed of the mold _{GaN, Al p In q Ga r} N (0 ≦ p ≦ 1,0 ≦ q <1,0 ≦ An active layer 1023 made of r <1), a second n-type guide layer 1016 made of n-type GaN, and a second cladding layer 1017 made of n-type Al _y Ga _1-y N were used in this order using the MOCVD film forming apparatus. After that, in order to form the ridge stripe portion 1070, the portion where the mask is not formed is removed by etching to the middle of the second n-type guide layer 1016 by a photolithography process or the like. To form a di-stripe portion 1070. Then, the current confinement insulating film 1025 is formed by the EB vapor deposition method, and the stripe-shaped mask and the current confinement insulating film 1025 on the mask are removed by the lift-off method, whereby the second electrode 1040 and the first electrode 1041 are formed.

The nitride semiconductor substrate 1011 of the nitride semiconductor wafer obtained as described above was ground and polished to a thickness of about 100 μm, scribed with a diamond needle, and cleaved into a bar shape. Further, an end face coat film made of AlO _x N _1-x (0 ≦ x ≦ 1) having a thickness of, for example, about 30 nm is formed on the end face formed by cleaving. This is to suppress optical destruction of the end face during high output operation. Further, on this end face coat film, silicon oxide, aluminum oxide, zirconium oxide, tantalum oxide, titanium oxide, niobium oxide, silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride A layer made of at least one selected from the above is formed for adjusting the reflectance. Thus, the nitride semiconductor laser device of the first embodiment is an end face light emission type nitride semiconductor laser.

  The layer thickness d of the second n-type guide layer 1016 left by the etching is preferably larger than 0 and not larger than 0.5 μm. If the layer thickness d of the second n-type guide layer 1016 is larger than 0.5 μm, the current spreads outside the ridge stripe, which is not preferable.

<Embodiment 2>
FIG. 4 shows a schematic cross-sectional view of a preferred example of the nitride semiconductor laser device of the present invention. The nitride semiconductor laser element 2010 has a layer structure in which a first cladding layer 2013, a first n-type guide layer 2014, a p-type guide layer 2021, a p-type carrier block layer 2022, and an active layer 2023 are formed on a nitride semiconductor substrate 2011. Then, the nitride semiconductor wafer is taken out of the MOCVD apparatus, and a current confinement insulating film 2025 is formed by a sputtering apparatus.

  Thereafter, a resist is applied on the current confinement insulating film 2025 by a photolithographic process, the resist is processed into a stripe shape having a width of about 1 to 3 μm, and gas phase etching is performed by inductively coupled plasma (ICP) to provide current confinement insulation. After removing the film 2025 in the form of stripes, the resist is removed, and the film is again introduced into the MOCVD apparatus, and the second n-type guide layer 2016, the second cladding layer 2017, and the n-type contact layer 2018 are formed from the nitride semiconductor substrate 2011 side. A film is formed in this order by the MOCVD method, and further, a first electrode 2041 and a second electrode 2040 are formed.

  The nitride semiconductor laser element 2010 according to the second embodiment is different from the first embodiment in that the current confinement insulating layer is provided in a buried form, and this is a feature. Since the second n-type guide layer 2016, the second cladding layer 2017, and the n-type contact layer 2018 formed above the active layer have low resistance, carriers easily diffuse in the parallel direction to the surface of the nitride semiconductor layer. It is easy and current confinement is difficult. For this reason, since the current confinement insulating film 2025 is formed immediately above the active layer 2023, carriers can be effectively confined, which is a very preferable structure. The distance between the current confinement insulating film 2025 and the last well layer formed in the active layer 2023 is preferably 3 nm or more and 0.5 μm or less. If the distance is less than 3 nm, the well layer of the active layer 2023 cannot be protected at the stage of performing the process of forming the current confinement insulating film 2025, and the active layer is damaged, which is not preferable. Further, if this distance is larger than 0.5 μm, it is not preferable because current confinement cannot be effectively performed.

Thus, by forming the current confinement insulating film 2025 in a buried form, there is an advantage that a current confinement insulating structure can be easily manufactured. The current confinement insulating film 2025 may be formed on the active layer, or the current confinement insulating film 2025 is formed on the carrier block layer made of Al _γ Ga _1-γ N formed on the active layer. Also good.

  In the first embodiment, in order to prevent the electrons injected from the ridge stripe portion 1070 from diffusing in the second n-type guide layer 1016, the etching amount of the second n-type guide layer 1016 is adjusted, and the second n-type guide layer 1016 is adjusted. The layer thickness of the mold guide layer 1016 needs to be accurately controlled. However, in the second embodiment, since the current confinement insulating film 2025 is provided immediately above the active layer 2023, such a layer thickness control is not necessary, and this point has the merit of the present embodiment. is there.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to this.

Example 1
FIG. 5 shows a schematic cross-sectional view of a preferred example of the nitride semiconductor laser element 110 of the first embodiment. The nitride semiconductor laser device 110 according to the first embodiment is a first semiconductor layer made of n-type Al _0.05 Ga _0.95 N with a thickness of 2.5 μm on a nitride semiconductor substrate 111 made of n-type GaN with a thickness of 400 μm and 2 inches. One cladding layer 113, a first n-type guide layer 114 made of n-type GaN having a thickness of 0.1 μm, a p-type guide layer 121 made of p-type GaN having a thickness of 0.2 μm, and a p-type Al having a thickness of 0.01 μm _0.1 Ga _0.9 p-type carrier block layer 122 composed of N, having a thickness of _{0.152μm Al p in q Ga r N} (0 ≦ p ≦ 1,0 ≦ q ≦ 1,0 ≦ r ≦ 1) composed of the active layer 123 Then, a second n-type guide layer 116 made of n-type GaN having a thickness of 0.2 μm and a second clad layer 117 made of n-type Al _0.05 Ga _0.95 N having a thickness of 0.6 μm are formed by using a MOCVD film forming apparatus. Formed in order. Here, the second n-type guide layer 116 and the second cladding layer 117 are collectively referred to as a second n-type nitride semiconductor layer 115. The first cladding layer 113 to the non-doped GaN layer closer to the nitride semiconductor substrate 111 of the active layer 123 were formed at 1125 ° C., and the remaining layers were formed at 850 ° C.

Thereafter, in order to form the ridge stripe portion 170, a striped mask is formed on the second cladding layer 117 by a photolithography process, and the mask is formed by using an inductively coupled plasma (ICP) etching method. The part which is not formed is removed by etching to the middle of the second n-type guide layer 116 to form a ridge stripe part 170 having a width of 1.6 μm. Then, the current confinement insulating film 125 made of SiO ₂ and a thickness of 50 nm TiO ₂ Metropolitan of thickness 200nm was formed by EB vapor deposition method, a current constriction insulating film 125 on the stripe-shaped mask and the mask is removed by lift-off Then, a fifth layer consisting of a hafnium layer having a thickness of 30 nm, an aluminum layer having a thickness of 200 nm, a molybdenum layer having a thickness of 30 nm, platinum having a thickness of 50 nm, and gold having a thickness of 200 nm is in contact with the nitride semiconductor substrate 111. One electrode 141 was formed. Furthermore, the second electrode 140 was formed by EB vapor deposition.

Here, the active layer 123 used in this example includes a non-doped GaN layer having a thickness of 60 nm, a barrier layer made of non-doped In _0.04 Ga _0.96 N having a thickness of 10 nm, and a well made of non-doped In _0.25 Ga _0.75 N having a thickness of 4 nm. AlGaInN including a 10 nm thick non-doped In _0.04 Ga _0.96 N barrier layer, a 4 nm thick non-doped In _0.25 Ga _0.75 N well layer, and a 60 nm thick non-doped GaN layer in this order from the nitride semiconductor substrate side It was produced in a multi-well active layer structure.

The nitride semiconductor substrate 111 of the nitride semiconductor wafer obtained as described above is ground and polished to a thickness of about 100 μm, scribed with a diamond needle, cleaved into a bar shape, and formed by cleavage. An end face coat film made of AlO _x N _1-x (0 ≦ x ≦ 1) having a thickness of about 30 nm was formed on the end face, and an aluminum oxide film was further formed on the end face coat film for reflectance adjustment. The reflectance of the end surface on the light emitting side of such a nitride semiconductor laser element was 10%, and the reflectance on the light reflecting side was 95%. Thus, the laser of Example 1 is an end face light emission type nitride semiconductor laser.

  When the oscillation threshold value of the nitride semiconductor laser device thus fabricated and the average emission efficiency (slope efficiency) after oscillation were determined, the average oscillation threshold value of the 20 nitride semiconductor laser devices of Example 1 was 30 mA. The average luminous efficiency was 1.65 W / A. Here, the oscillation threshold is a value representing the low driving current of the nitride semiconductor laser device, and the smaller the value is, the light emitting device having a smaller driving current. The luminous efficiency is a value that represents the ratio of photons that can be extracted outside the element with respect to the current injection amount of the nitride semiconductor laser element, and the larger the value, the better the light emitting element.

  For comparison, the nitride semiconductor laser element disclosed in Patent Document 1 was manufactured by the same method, and the average oscillation threshold and the average light emission efficiency were determined by the same method as described above. The average oscillation threshold of the 20 semiconductor laser elements was 38 mA, and the average light emission efficiency was 1.35 W / A. From the above, the nitride semiconductor laser device fabricated in Example 1 was able to greatly improve the characteristics of the average oscillation threshold and the average light emission efficiency as compared with the nitride semiconductor laser device of Patent Document 1. This is considered to be because in Example 1, the p-type AlGaN cladding doped with Mg disappeared, the light absorption was suppressed, and the internal loss (αi) was reduced.

(Example 2)
FIG. 6 is a schematic perspective view of the nitride semiconductor laser element 210 manufactured in Example 2 of the present invention. The nitride semiconductor laser element 210 of this example has a structure similar to that of Example 1, and a part of the first cladding layer 113 and the first n-type guide layer 114 in the nitride semiconductor laser element 110 of Example 1 are used. In that the p-type cladding layer 213a is replaced with the n-type contact layer 218 between the second cladding layer 217 and the second electrode 240. It is characterized by. Further, the structure of the active layer 223 of the nitride semiconductor laser element 210 of Example 2 is the same as that of Example 1, but the In composition of the well layer is 0.15 and the oscillation wavelength is 450 nm. It is different in point.

The nitride semiconductor laser element 210 of Example 2 is formed on an n-type Al _0.05 .mu.m thickness of 2.3 .mu.m on a nitride semiconductor substrate 211 made of an n-type GaN substrate of 400 .mu.m thickness by the same MOCVD apparatus as in Example 1. FIG. First clad layer 213 made of Ga _0.95 N, p-type Al _{0.03 having} a thickness of 0.2 μm, p-type clad layer 213 a made of Ga _0.97 N, p-type guide layer 221 having a thickness of 0.2 μm, and having a thickness of 0.01 μm p-type carrier blocking layer 222, active layer 223 having a thickness of 0.152 μm, second n-type guide layer 216 having a thickness of 0.2 μm, and a second cladding layer made of n-type Al _0.05 Ga _0.95 N having a thickness of 0.6 μm. 217 and an n-type contact layer 218 made of GaN having a thickness of 0.2 μm are formed in this order. 240 was formed.

  As in Example 2, the average oscillation threshold and the average luminous efficiency are good by replacing part of the first cladding layer 213 and the entire first n-type guide layer with the p-type cladding layer 213a. The same effect as in Example 1 was obtained.

(Example 3)
FIG. 7 is a schematic perspective view of the nitride semiconductor laser element 310 manufactured in Example 3 of the present invention. The nitride semiconductor laser device 310 of this example includes a current confinement insulating layer in a buried form like the nitride semiconductor laser device shown in the second embodiment. Further, the structure of the active layer 323 of the nitride semiconductor laser device 310 of the third embodiment is the same as that of the first embodiment, but is different in that the In composition of the well layer is 0.20.

As shown in FIG. 7, the layer structure of the nitride semiconductor laser device 310 of Example 3 is formed on an n-type Al _0.05 having a thickness of 2.5 μm on a nitride semiconductor substrate 311 made of n-type GaN having a thickness of 400 μm. First cladding layer 313 made of Ga _0.95 N, first n-type guide layer 314 made of n-type GaN having a thickness of 0.1 μm, p-type guide layer 321 made of GaN having a thickness of 0.2 μm, thickness of 0.01 μm A p-type carrier block layer 322 made of Al _0.1 Ga _0.9 N and an active layer 323 made of Al _x Ga _1-x InN having a thickness of 0.152 μm were formed by MOCVD, and this nitride semiconductor wafer was taken out from the MOCVD apparatus A current confinement insulating film 325 made of SiO _{2 having} a thickness of 500 nm was formed by a sputtering apparatus.

After that, a resist is applied onto SiO ₂ by a photolithographic process, the resist is processed into a stripe shape having a width of about 2 μm, and gas phase etching by inductively coupled plasma (ICP) is performed to remove SiO ₂ in a stripe shape. Then, the resist is removed and introduced into the MOCVD apparatus again, the second n-type guide layer 316 made of GaN having a thickness of 0.2 μm, and the second cladding layer made of n-type Al _0.05 Ga _0.95 N having a thickness of 0.6 μm. An n-type contact layer 318 made of n-type GaN having a thickness of 317 and a thickness of 0.2 μm was formed by MOCVD in this order from the nitride semiconductor substrate 311 side, and a first electrode 341 and a second electrode 340 were further formed.

  For the same reason as described in the first embodiment, the nitride semiconductor laser device 310 manufactured in the third embodiment has a p-type nitride semiconductor layer formed at a high temperature of 1000 ° C. or higher after the active layer 323 is formed. Since it is not necessary to form a film, it is possible to manufacture a nitride semiconductor laser element having an active layer that requires a high composition in which the In composition x of the well layer of the active layer 323 is about 0.15 or more. The nitride semiconductor laser element fabricated in this Example 3 also had a better average oscillation threshold and average emission efficiency than the conventional example, and the same effects as in Example 1 were obtained.

Example 4
The layer structure of the nitride semiconductor laser device 410 of the fourth embodiment is similar to that of the third embodiment, but indium instead of the second cladding layer and the n-type contact layer in the nitride semiconductor laser device of the third embodiment. It is different in that a conductive oxide layer 424 made of tin oxide (ITO: Indium Tin Oxide) is used. The structure of the active layer of the nitride semiconductor laser device of Example 4 is the same as that of Example 1, except that the In composition of the well layer is 0.27 and the oscillation wavelength is 520 nm. Is different.

As shown in FIG. 8, the layer structure of the nitride semiconductor laser device 410 of Example 4 is a n-type Al _0.05 layer having a thickness of 2.5 μm on a nitride semiconductor substrate 411 made of n-type GaN having a thickness of 400 μm. A first cladding layer 413 made of Ga _0.95 N, a first n-type guide layer 414 made of n-type GaN having a thickness of 0.1 μm, a p-type guide layer 421 made of GaN having a thickness of 0.2 μm, and a thickness of 0.01 μm After forming the p-type carrier block layer 422 made of Al _0.1 Ga _0.9 N and the active layer 423 made of Al _x Ga _1-x InN having a thickness of 0.152 μm by the MOCVD method, the nitride semiconductor wafer is formed into an MOCVD apparatus. The current confinement insulating film 425 made of SiO _{2 having} a thickness of 500 nm was formed by a sputtering apparatus.

Thereafter, a current confinement insulating film 425 made of SiO ₂ is formed by the same method as in Example 3, and then introduced again into the MOCVD apparatus, and the second n-type guide layer 416 made of GaN having a thickness of 0.2 μm is formed by the MOCVD method. A conductive oxide layer 424 made of indium tin oxide having a thickness of 0.3 μm was formed by a sputtering film formation method, and finally a first electrode 441 and a second electrode 440 were formed.

  As described above, by using the conductive oxide layer 424 instead of the second cladding layer and the n-type contact layer, it is not necessary to form the second cladding layer on the active layer 423, and thus the resistance can be further reduced. It became. The nitride semiconductor laser device fabricated in Example 4 also had a better average oscillation threshold and average emission efficiency than the conventional example, and the same effects as in Example 1 were obtained.

(Example 5)
In this example, the nitride semiconductor substrate shown in Example 1 was fabricated on a sapphire substrate having no electrical conductivity. In the nitride semiconductor laser element 510 of this embodiment, the first electrode 541 and the second electrode 540 are formed in the same direction as viewed from the sapphire substrate, and the first electrode 541 is formed on the first n-type nitride semiconductor layer. It is characterized by providing.

As shown in FIG. 9, the nitride semiconductor laser element 510 of the present embodiment has a buffer layer 502 made of GaN having a thickness of 5 μm formed on a sapphire substrate 501, and n-type Al _y Ga on the buffer layer 502. _A first cladding layer 513 made of _{1-yN, a} first n-type guide layer 514 made of n-type GaN, a p-type guide layer 521 made of p-type GaN, and a p _- type carrier made of p _- type Al _y Ga _1-y N blocking layer _{522, Al p In q Ga r} n (0 ≦ p <1,0 ≦ q <1,0 ≦ r <1) composed of the active layer 523, n-type GaN consisting second n-type guide layer 516 and the n A second cladding layer 517 made of type Al _y Ga _1-y N is formed in this order using a MOCVD film forming apparatus, and then a mask is formed by a photolithography process or the like to form a ridge stripe portion. Absent Minute up to the middle of the second n-type guide layer 516 is removed by etching to form a ridge stripe portion.

  Then, the current confinement insulating film 525 was formed by the EB vapor deposition method, the stripe-shaped mask and the current confinement insulating film 525 on the mask were removed by the lift-off method, and the second electrode 540 was formed. Further, the first electrode 541 was formed on the first clad layer 513 that was removed by etching through the photolithography process described above until the middle of the first clad layer 513 and was further exposed by the etching. Thus, also by providing the first electrode 541 on the first n-type nitride semiconductor layer, the average oscillation threshold and the average light emission efficiency are good as compared with the conventional example, and the same effect as in Example 1 is obtained. It was. In this embodiment, a sapphire substrate is used as the substrate, but the same effect can be obtained even if a substrate of SiC, GaN, ZnO, Si or the like is used.

(Example 6)
FIG. 10 is a schematic perspective view of the nitride semiconductor laser device manufactured in Example 6 of the present invention. The nitride semiconductor laser device of Example 6 has a similar structure to the nitride semiconductor laser device of Example 1, and Examples 1 to 5 are materials for the first n-type guide layer and the second n-type guide layer. GaN was used for the first clad layer and the second clad layer. In Example 6, InGaN was used for the first n-type guide layer and the second n-type guide layer. GaN is used as the material of the first cladding layer and the second cladding layer. Thus, the same effect as in Example 1 can be obtained by using InGaN for the first n-type guide layer and the second n-type guide layer and using GaN for the first cladding layer and the second cladding layer. it can. The structure of the active layer of the nitride semiconductor laser device of Example 6 is the same as that of Example 1, but the In composition of the well layer was set to 0.30.

As shown in FIG. 10, the layer structure of the nitride semiconductor laser element 610 of Example 6 is formed on a nitride semiconductor substrate 611 made of an n-type GaN substrate having a thickness of 400 μm by the same MOCVD apparatus as that of Example 1. A first cladding layer 613 made of n-type GaN having a thickness of 4.5 μm, a first n-type guide layer 614 made of n-type InGaN having a thickness of 0.1 μm, and a p-type made of p-type InGaN having a thickness of 0.2 μm. guide layer 621, p-type carrier block layer 622 made of thick 0.01 [mu] m p-type Al _0.1 Ga _0.9 N, a thickness of _{0.152μm Al p in q Ga r N} (0 ≦ p ≦ 1,0 ≦ q ≦ 1, 0 ≦ r ≦ 1), a second n-type guide layer 616 made of n-type InGaN having a thickness of 0.2 μm, a second cladding layer 617 made of n-type GaN having a thickness of 1 μm, and a thickness 0.2 μm n-type G An n-type contact layer 618 made of aN was formed in this order, and then a current confinement insulating film 625, a first electrode 641, and a second electrode 640 were formed by the same method as in Example 1.

  Thus, a nitride semiconductor laser device using GaN as the material of the first cladding layer 613 and the second cladding layer 617 and InGaN as the material of the first n-type guide layer 614 and the second n-type guide layer 616, However, compared with the conventional example, the average oscillation threshold and the average luminous efficiency were good, and the same effect as in Example 1 was obtained.

(Example 7)
The nitride semiconductor laser elements manufactured in Examples 1-6 used the c-plane {0001} as the main surface of the n-type GaN substrate, but the nitride semiconductor laser elements manufactured in Example 7 were n-type GaN. A feature is that a M-plane {1-100} substrate is used as the main surface of the substrate. Further, the structure of the active layer of the nitride semiconductor laser device of Example 7 is the same as that of Example 1, but the In composition of the well layer was set to 0.30. In this example, when the substrate was fabricated with an off angle of 0.2 ° with respect to the main surface, the in-plane film thickness variation was about 50 nm, and the average oscillation threshold and the average luminous efficiency were higher than in the conventional example. It was good and the same effect as Example 1 was acquired. In addition, when the off angle with respect to the main surface of the substrate is in the range of greater than 0 ° and less than or equal to 2 °, the in-plane film thickness variation was good at about 50 nm.

(Example 8)
FIG. 11 is a schematic perspective view of the nitride semiconductor laser device manufactured in Example 8 of the present invention. The structure of the nitride semiconductor laser device 810 of this example is similar to the structure of the nitride semiconductor laser device of Example 3, but an M-plane {1-100} is used for the main surface of the n-type GaN substrate. This is different from the third embodiment in that an n-type carrier block layer 816a made of n-type Al _0.12 Ga _0.88 N is formed on the active layer 823, and this is a feature of this embodiment. The structure of the active layer 823 of the nitride semiconductor laser element 810 of Example 8 is the same as that of Example 1, except that the In composition of the well layer is 0.22.

  By forming the n-type carrier block layer 816a on the active layer 823 in this way, overflow due to carrier heat can be reduced, temperature characteristics can be improved, and in-plane flatness on the active layer 823 can be improved. There is an advantage that crystallinity is improved when film formation is performed at a relatively low temperature of about 800 ° C.

As shown in FIG. 11, the layer structure of the nitride semiconductor laser element 810 of Example 8 is a n-type Al _0.05 layer having a thickness of 2.5 μm on a nitride semiconductor substrate 811 made of n-type GaN having a thickness of 400 μm. First cladding layer 813 made of Ga _0.95 N, first n-type guide layer 814 made of n-type GaN having a thickness of 0.1 μm, p-type guide layer 821 made of p-type GaN having a thickness of 0.2 μm, thickness 0 After the p-type carrier block layer 822 made of .01 μm p-type Al _0.1 Ga _0.9 N and the active layer 823 made of Al _x Ga _1-x InN having a thickness of 0.152 μm are formed by MOCVD, this wafer is MOCVDed The current confinement insulating film 825 made of SiO _{2 having} a thickness of 500 nm was formed by a sputtering apparatus. Thereafter, SiO ₂ was striped in the same manner as in Example 3. Further, the resist is removed, and the resist is again introduced into the MOCVD apparatus, and an n-type carrier block layer 816a made of n-type Al _0.12 Ga _0.88 N having a thickness of 0.2 μm and a second n-type made of GaN having a thickness of 0.2 μm. A guide layer 816, a second cladding layer 817 made of n-type Al _0.05 Ga _0.95 N having a thickness of 0.6 μm, and an n-type contact layer 818 made of n-type GaN having a thickness of 0.2 μm are formed from the nitride semiconductor substrate 811 side. A film was formed in order by MOCVD, and a first electrode 840 and a second electrode 841 were further formed.

  The nitride semiconductor laser device fabricated in Example 8 also had a better average oscillation threshold and average emission efficiency than the conventional example, and the same effects as in Example 1 were obtained.

Example 9
Example 9 is characterized in that a conductive oxide layer made of tin-doped indium oxide is used in place of the n-type contact layer in the nitride semiconductor laser element of Example 6. Note that the same active layer as in Example 6 is used.

  That is, the second clad layer was formed by the same method as in Example 6, and then a conductive oxide layer made of tin-doped indium oxide having a thickness of 0.2 μm was formed at a relatively low temperature of about 300 ° C. A nitride semiconductor light emitting device of Example 9 was fabricated by forming a conductive oxide layer. The nitride semiconductor laser element fabricated in Example 9 also had a better average oscillation threshold and average emission efficiency than the conventional example, and the same effects as in Example 1 were obtained.

(Example 10)
The layered structure of the nitride semiconductor laser device of Example 10 is similar to that of Example 8, except that a p + GaN layer and an n + GaN layer are provided between the first n-type guide layer and the p-type guide layer. It is different in point and is characterized by this point.

  Thus, by providing the p + GaN layer and the n + GaN layer between the first n-type guide layer and the p-type guide layer, the depletion layer between the first n-type guide layer and the p-type guide layer becomes narrower, Therefore, there is an advantage that the resistance value of the pn junction is reduced and the tunnel current easily flows. Thus, the nitride semiconductor laser device fabricated in Example 10 also had a better average oscillation threshold and average emission efficiency than the conventional example, and the same effects as in Example 1 were obtained.

(Example 11)
The layer structure of the nitride semiconductor laser device of Example 11 is similar to that of Example 8, but the Al _y Ga _1-y N intermediate layer is interposed between the first n-type guide layer and the p-type guide layer. It is different in that it is provided with this feature.

Thus, by providing the Al _y Ga _1-y N intermediate layer between the first n-type guide layer and the p-type guide layer, there is an advantage that the width of the depletion layer is reduced and the tunnel current can easily flow. .

FIG. 12 shows a band energy diagram near the pn junction of this example. In FIG. 12, the horizontal axis represents the distance from the PN junction, and the position 500 on the horizontal axis is the interface between the Al _y Ga _1-y N intermediate layer and the p-type guide layer, and the 2.5 nm Al _The case where the yGa1 _-yN intermediate layer is formed is shown. The unit of the horizontal axis is nm. The left vertical axis represents energy (eV), and the right vertical axis represents the carrier concentration (/ cm ³ ) distribution. Further, from the curve representing the distribution of the p-type carrier density 51 from the p-type guide layer to the pn junction and the curve representing the distribution of the n-type carrier density 52 from the first n-type guide layer to the pn junction, the nitride semiconductor The width 60 of the depletion layer of the laser element can be obtained, and the tunnel current hardly flows as the width 60 of the depletion layer increases.

Further, in the band energy diagram in the vicinity of the pn junction of the nitride semiconductor laser device of this example, the transition of the conduction band energy 53 and the transition of the valence band energy 54 are expressed as shown in FIG. An equilibrium state in which the energy 55 coincides is shown. The width of the depletion layer of the nitride semiconductor laser element of Example 11 is 2.5 nm, which is about one tenth of the width of the depletion layer of the nitride semiconductor laser element of Example 10. I understood it. From the above, by providing the Al _y Ga _1-y N intermediate layer between the first n-type guide layer and the p-type guide layer, the width of the depletion layer is greatly reduced, and the resistance of the device is reduced. As a result, it was found that the tunnel current easily flows.

  Thus, the nitride semiconductor laser device fabricated in Example 11 also had better average oscillation threshold and average emission efficiency than the conventional example, and the same effects as in Example 1 were obtained.

Example 12
The nitride semiconductor laser device of the present embodiment has the same structure as that of the nitride semiconductor laser of Embodiment 1, but is a GaAs semiconductor laser using a GaAs substrate as a substrate. That is, an n-type GaAs buffer layer having a thickness of 0.5 μm on a GaAs substrate, a first clad layer made of In _0.49 (Ga _0.3 Al _0.7 ) _0.51 P having a thickness of 2.0 μm, and (Al _0.50 Ga _{0.50 having} a thickness of 50 nm). ) Active layer consisting of a p-type guide layer made of InP, a well layer made of GaInP (4 layers, thickness 6 nm) and a barrier layer (3 layers, thickness 5 nm) made of (Al _0.50 Ga _0.50 ) InP, thickness An n-type guide layer made of 50 nm (Al _0.50 Ga _0.50 ) InP, a second clad layer made of n-type In _0.49 (Ga _0.3 Al _0.7 ) _0.51 P, and an n-type GaAs contact layer having a thickness of 0.4 μm were formed. .

  Thereafter, the n-type guide layer made of InGaAlP was removed by etching using a general process as described above, and a ridge-stripe edge-emitting GaAs red semiconductor laser was fabricated. A current confinement insulating film is formed on both sides of the ridge stripe portion. Mg, Zn, or Be is used as the p-type dopant material. Thus, it can be suitably used also in a GaAs semiconductor laser. A semiconductor laser using n-type ZnO, p-type ZnO, or a combination of GaN and ZnO may be used.

(Example 13)
The structure of the nitride semiconductor laser device of this example is the same as that of the nitride semiconductor laser device of Example 4 up to the active layer, and after forming the active layer, a carrier block layer is formed on the active layer. It is characterized by that. A method for manufacturing the nitride semiconductor laser element of Example 13 will be described below.

After forming up to the active layer by the same method as in Example 4, a carrier block layer made of n-type Al _0.12 Ga _0.88 N having a thickness of 20 nm is formed. Thereafter, the nitride semiconductor wafer is taken out from the MOCVD apparatus, and the thickness is increased. A current confinement insulating film made of SiO _{2 having a} thickness of 500 nm was formed by a sputtering apparatus. Thereafter, a current confinement insulating film made of SiO ₂ is formed by the same method as in Example 4, and then introduced again into the MOCVD apparatus, and the second n-type made of n-type ZnO having a thickness of 0.2 μm is formed on the carrier block layer. A guide layer was formed. Thereafter, a conductive oxide layer made of indium tin oxide having a thickness of 0.3 μm was formed by sputtering, and finally a first electrode and a second electrode were formed.

  Even if n-type ZnO is formed on the nitride semiconductor layer by sputtering, MBE, MOCVD, PLD, etc. as in this embodiment, the average oscillation threshold and the average luminous efficiency are better than the conventional examples. Thus, the same effect as in Example 1 was obtained.

(Comparative Example 1)
The nitride semiconductor laser element of Comparative Example 1 is the same as that of the nitride semiconductor laser element manufactured in Example 7, except that the main surface of the n-type GaN substrate is an M-plane {1-100} substrate. When the off-angle was manufactured at 0 °, the nitride semiconductor laser element of Example 7 had an in-plane film thickness variation of about 50 nm, but the nitride semiconductor laser element of Comparative Example 1 had an in-plane thickness variation of about 50 nm. The film thickness variation was about 200 to 300 nm, and the same effect as in Example 1 was not obtained.

  In addition, although expressed as a nitride semiconductor laser element in this specification, this nitride semiconductor laser element is not limited to an element used for a semiconductor laser, but also includes a nitride semiconductor light emitting diode element used for a light emitting diode. It is.

  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, it is possible to provide a nitride semiconductor laser device that can be driven at a lower output, has higher luminous efficiency, and emits light having a long wavelength of about 440 to 550 nm.

It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is an expanded typical sectional view showing the pn junction part of the nitride semiconductor laser element of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is a typical sectional view showing an example of the nitride semiconductor laser device of the present invention. It is an energy band diagram when an AlN intermediate layer is formed in a pn junction different from the pn junction of the active layer of the nitride semiconductor laser device of the present invention. FIG. 6 is a schematic cross-sectional view showing a conventional nitride semiconductor laser element.

Explanation of symbols

10, 110, 210, 310, 410, 510, 610, 810, 910, 1010, 2010 Nitride semiconductor laser element, 11 substrate, 501 sapphire substrate, 502 buffer layer, 111, 211, 311, 411, 611, 811 1011, 1011 nitride semiconductor substrate, 12 first n-type nitride semiconductor layer, 13, 113, 213, 313, 413, 513, 613, 813, 1013, 2013 first cladding layer, 14, 114, 314, 414 514, 614, 814, 1014, 2014 1st n-type guide layer, 14a n + doped layer, 15, 115 2nd n-type nitride semiconductor layer, 16, 116, 216, 316, 416, 516, 616, 816, 1016 , 2016 second n-type guide layer, 17, 117, 217, 317, 517, 617 817, 1017, 2017 Second clad layer, 18, 218, 318, 618, 818, 2018 n-type contact layer, 20 p-type nitride semiconductor layer, 21, 121, 221, 321, 421, 521, 621, 821, 1021, 2021 p-type guide layer, 21a p + doped layer, 22, 122, 222, 322, 422, 522, 622, 822, 1022, 2022 p-type carrier block layer, 23, 123, 223, 323, 423, 523 623,823,1023,2023 active layer, 424 a conductive oxide layer, 25,125,225,325,425,525,625,825,1025,2025 current narrowing insulating _{film, 30 Al y Ga 1-y} N intermediate Layer, 40, 140, 240, 340, 440, 540, 640, 840, 1040, 204 0 second electrode, 41, 141, 241, 341, 441, 541, 641, 841, 1041, 2041 first electrode, 51 p-type carrier density, 52 n-type carrier density, 53 conduction band energy, 54 valence band Band energy, 55 Fermi energy, 60 depletion layer width, 70, 170, 1070 ridge stripe, 213a p-type cladding layer, 816a n-type carrier block layer, 911 n-type GaN substrate, 913 n-type Al _0.05 Ga _0.95 N cladding Layer, 914 n-type GaN guide layer, 920 p-type nitride semiconductor layer, 921 p-type GaN guide layer, 922 p-type Al _0.15 Ga _0.85 N carrier block layer, 923 InGaN multiple quantum well active layer, 924 p-type Al _0.05 Ga _0.95 N clad layer, 924a p-type GaN contact layer, 925 SiO ₂ , 940 p electrode, 941 n electrode.

Claims (5)

  A nitride semiconductor laser device comprising, on a substrate, at least a first n-type nitride semiconductor layer, a p-type nitride semiconductor layer, an active layer, and a second n-type nitride semiconductor layer in this order from the substrate side. The substrate or the first n-type nitride semiconductor layer is in contact with the first electrode;
The second n-type nitride semiconductor layer is in contact with the second electrode;
The first electrode is an anode electrode;
The nitride semiconductor laser element according to claim 1, wherein the second electrode is a cathode electrode.   The nitride semiconductor laser element according to claim 1, further comprising a conductive oxide layer on a side opposite to the active layer with respect to the second n-type nitride semiconductor layer. The substrate or the first n-type nitride semiconductor layer is in contact with the first electrode;
The conductive oxide layer is in contact with the second electrode;
The first electrode is an anode electrode;
The nitride semiconductor laser element according to claim 3, wherein the second electrode is a cathode electrode. The active layer includes a well layer made of In _x Ga _1-x N;
The nitride semiconductor laser element according to claim 1, wherein an In composition x of the well layer is 0.15 or more and 0.30 or less.

Images