JP2007059897A - Semiconductor laser device, optical pick-up device using same and optical device for reproducing information - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device having a film for protecting an end surface that is compatible with a trend toward a higher output or a shorter wavelength. <P>SOLUTION: The semiconductor laser device has, on at least one of the end surfaces of an optical resonator, a dielectric film, which comprises a first dielectric film and a second dielectric film composed of identical chemical elements and formed in order from the end surface side of the semiconductor, the first dielectric film including a film made of a single crystal and the second dielectric film including a film made of an amorphous material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device, and more particularly to a high-power semiconductor laser device having an oscillation wavelength of 600 nm or less.

  Currently, there is a demand for a high-power semiconductor laser device for writing on optical disks and magneto-optical disks. These semiconductor laser elements are required to operate stably in the basic mode for a long time.

  In addition, a semiconductor laser element using a nitride semiconductor has been studied in order to realize a short wavelength necessary for increasing the density of an optical disk. A laser element using a nitride semiconductor can be used for an exposure light source, a printing light source, a medical light source, an optical communication system light source, a measurement, and the like in addition to an optical disk light source. In addition, a laser element made of a nitride semiconductor can be used in an ultraviolet region having an oscillation wavelength of 400 nm or less, and thus is expected as a bio-related excitation light source.

Patent Document 1 discloses a structure in which an Al ₂ O ₃ film having a thickness of λ / 2 is formed on a reflecting mirror surface of a semiconductor laser element, an Al ₂ O ₃ film having a thickness of λ / 4, and amorphous silicon having a thickness of λ / 4. A configuration is shown in which films are alternately formed. Patent Document 2 discloses the use of Al ₂ O ₃ for the dielectric film and the formation conditions.

JP-A-9-162497 JP 2002-335053 A

However, when an Al ₂ O ₃ film having a thickness of λ / 2n is formed as a single layer, an amorphous Al ₂ O ₃ film reacts with a semiconductor element at the time of high output driving with an output of 30 mW or more, thereby causing end face deterioration. End up. Further, the heat generation during stress greatly driven by an Al ₂ O ₃ film of the single crystal, the the Al ₂ O ₃ film has a problem such as a peeled off from the semiconductor device.
In addition, in a semiconductor laser device using a nitride semiconductor, when operated at a high output, for example, 30 mW or more, end face breakdown is likely to occur when a dielectric film is formed as a single film on the end face on the light emission side. There was a problem that the service life was reduced. Further, when operating at a high output, there is a problem that the drive current increases if the slope efficiency is low.
When the current flowing through the semiconductor laser is increased, laser oscillation starts at a certain current. Thereafter, the light output increases in proportion to the current. The ratio (ΔP / ΔI) of the current increase (ΔI) to the light output increase (ΔP) is called (oscillation) slope efficiency. In a semiconductor laser having a large slope efficiency, a large increase in optical output can be obtained with a small increase in current, so that it is possible to reduce the drive current during high output operation. When the drive current increases, heat is generated in the semiconductor laser. When such heat is generated, the deterioration of the crystal is promoted and the crystal is destroyed. As countermeasures, it is conceivable to lower the reflectance of the outgoing (front) end face and to increase the slope efficiency. If the slope efficiency is increased, an increase in drive current can be suppressed. The reflectance and slope efficiency of the outgoing (front) end face can be controlled by the refractive index and thickness of the dielectric film.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor laser device having an end face protective film capable of responding to higher output or shorter wavelength.

  The semiconductor laser device of the present invention is a semiconductor laser device having a dielectric film on at least one of the end faces of the optical resonator, wherein the dielectric film includes a first dielectric film made of the same element and a second dielectric film. The first dielectric film contains a film made of a single crystal, and the second dielectric film is made of an amorphous film. It is characterized by containing. Further, the first dielectric film and the second dielectric film have substantially the same composition ratio.

  With the above structure, since the first dielectric film that is in direct contact with the resonator end face of the semiconductor laser element contains a single crystal film, it is possible to suppress the decomposition of the semiconductor layer on the end face. Preferably, the first dielectric film is a single crystal film. Thereby, decomposition suppression power improves. Furthermore, the adhesive force between the semiconductor layer and the dielectric film can be maintained by providing the second dielectric film containing the amorphous film on the first dielectric film. Preferably, the second dielectric film is made of an amorphous film.

  The semiconductor laser device of the present invention is a semiconductor laser device having a dielectric film on at least one of the end faces of the optical resonator, wherein the dielectric film includes a first dielectric film made of the same element and a second dielectric film. The first dielectric film is a reaction preventing film between the semiconductor and the dielectric film, and the second dielectric film is a laser. It is a light reflecting film.

  With the above structure, the first dielectric film in direct contact with the resonator end face of the semiconductor laser element can suppress the decomposition of the end face of the semiconductor layer by reacting with the dielectric film, and By having the second dielectric film made of a laser light reflecting film on the first dielectric film, the light confinement can be easily adjusted with good reproducibility. In particular, in a nitride semiconductor containing In in the active layer, such a configuration is effective because the active layer on the end face of the resonator is easily decomposed.

  In the semiconductor laser element, the first dielectric film contains a film made of single crystal, and the second dielectric film contains a film made of amorphous. The first dielectric film may contain microcrystals or polycrystals.

  In the semiconductor laser element, the first dielectric film has a refractive index lower than that of the second dielectric film. This is because the second dielectric film contains a film made of amorphous or is a film made of amorphous, and it is considered that oxygen vacancies are generated in the second dielectric film. Thereby, the adhesion of the dielectric film can be ensured.

  In the semiconductor laser device, it is preferable that the second dielectric film has a thickness larger than that of the first dielectric film. This is because the second dielectric film becomes an oxygen blocking layer that suppresses oxygen entry from the outside.

  In the semiconductor laser element, the dielectric film has a reflectance of 25% or less. A high output laser can be realized by setting the reflectance of the dielectric film formed on the end face of the optical resonator of the semiconductor laser element on the light emitting (front) side to 25% or less.

  In the semiconductor laser element, the reflectance of the dielectric film is 20% or less when the oscillation wavelength of the semiconductor laser element is approximately 400 nm. As a result, a high-power laser can be realized also in the nitride semiconductor laser element.

  In the semiconductor laser element, the first dielectric film and the second dielectric film have Al and O as constituent elements. With such a structure, a single crystal film and an amorphous film can be formed continuously. In addition, a pair structure in which single crystal films and amorphous films are alternately stacked can be easily performed.

  In the semiconductor laser element, the first dielectric film and the second dielectric film have substantially the same thermal expansion coefficient. Since the first dielectric film and the second dielectric film are made of the same material and have the same thermal expansion coefficient, the occurrence of cracks in the dielectric film can be suppressed.

In the semiconductor laser device, the outermost layer of the dielectric film is a nitride. With such a structure, it is possible to prevent oxygen in the outside air from entering the first dielectric film, the second dielectric film, and the semiconductor. In addition, when the dielectric film other than the outermost layer contains oxygen, oxygen desorption from these layers can be prevented. This makes it possible to maintain the light reflectance of the dielectric film when the semiconductor laser device is continuously driven.

  The semiconductor laser device of the present invention is a semiconductor laser device having a dielectric film on at least one of the end faces of the optical resonator, and the dielectric film includes a first dielectric film, a second dielectric film, and a first dielectric film. 3 dielectric films are formed in order from the semiconductor end face side, the first dielectric film and the second dielectric film are made of the same element, and the third dielectric film is The first dielectric film and the second dielectric film have different elements, and the first dielectric film is a reaction preventing film between a semiconductor and a dielectric film, and the second dielectric film The dielectric film is a stress relaxation film of a first dielectric film and a third dielectric film. In the present invention, the third dielectric film may be referred to as a reflection mirror.

With the above structure, the first dielectric film in direct contact with the resonator end face of the semiconductor laser element can suppress the decomposition of the end face of the semiconductor layer by reacting with the dielectric film, and the first By having the second dielectric film, it is possible to easily form the third dielectric film as a desired dielectric film on the outside thereof, so that it is possible to adjust the intensity of light confinement.

  In the semiconductor laser element, the first dielectric film and the second dielectric film contain oxygen.

  In the semiconductor laser device, the oxygen content of the first dielectric film is larger than the oxygen content of the second dielectric film.

  In the semiconductor laser device, the outermost layer of the dielectric film is a nitride.

In the present invention, the composition ratio is substantially the same, it is not necessary for the composition ratios to completely coincide with each other, and the content of contained substances common to the first dielectric film and the second dielectric film is within a range of ± 7%. It is preferable that

In the present invention, when the first dielectric film includes a single crystal film, the content of the single crystal film is 75% or more. Preferably it is 80% or more.

In the present invention, when the second dielectric film contains an amorphous film, the content of the amorphous film is 75% or more. However, in the light emitting region, the content of the amorphous film may be 60% or more.

  An optical pickup device of the present invention is an optical pickup device including the semiconductor laser element described above.

The optical information reproducing apparatus of the present invention reproduces information recorded on the optical information recording board by condensing and irradiating the optical information recording board with laser light and detecting the reflected light. An optical information reproducing apparatus using the semiconductor laser element described above as a light source.

  As described above, according to the present invention, a high-power semiconductor laser device can be provided by suppressing deterioration and optical damage (COD) of the end face of the optical resonator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are cross-sectional views schematically showing the structure of a semiconductor laser device using a nitride semiconductor according to this embodiment.

  As shown in FIG. 1, the semiconductor laser device of this embodiment includes an n-type nitride semiconductor layer 200 as a nitride semiconductor layer on a first main surface of a substrate 100 having a first main surface 100a and a second main surface 100b. An active layer 205 and a p-type nitride semiconductor layer 210 are laminated in order, and the cleaved end faces of the substrate 100 and the nitride semiconductor layer are substantially matched, The end face has a dielectric film 110 as shown in FIG. The dielectric film 110 is preferably formed on the nitride semiconductor layer and the cleaved end face of the substrate.

  FIG. 5 is a schematic perspective view of the dielectric film. The end face of the optical resonator has a light exit (front) side end face and a light reflection (rear) side end face. In this embodiment, the light emitting side end face has the dielectric film 110. Further, those having a dielectric film are preferable. The dielectric film 110 includes a first dielectric film 111 and a second dielectric film 112 made of the same element in order from the end face side of the nitride semiconductor layer. The first dielectric film 111 is preferably made of a single crystal film, and the second dielectric film 112 is preferably made of an amorphous film.

  The p-type nitride semiconductor layer 210 has a striped ridge portion and a p-electrode 230 thereon, and a counter electrode structure having an n-electrode 232 on the second main surface 100b of the substrate 100. It is a semiconductor laser element.

The dielectric film 110 contains at least one selected from the group consisting of Al, Si, Nb, Ti, Zr, Hf, Ta, Zn, Y, Ga, and Mg. Preferably, the oxides of these elements are Al _x O _y (1 <x, 1 <y), SiO _x (1 <x), Nb _x O _y (1 <x, 1 <y), TiO _x (1 <x), ZrO _x (1 <x), and the like. Examples include Al ₂ O ₃ , SiO ₂ , Nb ₂ O ₅ , TiO ₂ , ZrO _{2 and the} like.

  The dielectric film is referred to as an amorphous film when the result of measuring an electron beam diffraction image by an ultra-thin film evaluation apparatus (Hitachi: HD-2000) is a single spot. Further, as a result of measuring the crystallinity of the dielectric film by the above apparatus, a film having two or more spots in the diffraction pattern is called a single crystal film. Measurement is performed by applying a spot to the exposed dielectric film by cutting perpendicularly to the end surface of the semiconductor laser element where the dielectric film is formed.

The first dielectric film is preferably a reaction preventing film between the semiconductor and the dielectric film. In particular, in a nitride semiconductor laser element, an active layer is provided with a layer containing In, and the active layer In on the end face of the optical resonator may react with the dielectric film or decompose. However, such a problem is suppressed by providing the reaction preventing film.
Furthermore, the second dielectric film is preferably a laser light reflecting film. Thereby, the optical confinement in the optical resonator can be adjusted. By forming the first dielectric film which is a reaction preventing film, the second dielectric film can be used as a reflection film.

  The film thickness of the first dielectric film is 30 to 500 mm. Preferably they are 50 to 300 inches. By setting the film thickness of the first dielectric film within the above range, it can have a reaction preventing function without causing film peeling.

  The thickness of the second dielectric film is not less than 500 mm and not more than 2000 mm. Preferably they are 700 to 1750 mm. More preferably, the total thickness of the first dielectric film and the second dielectric film is not less than 1200 mm and not more than 1800 mm. By setting the thickness of the second dielectric film within the above range, the desired reflectance can be easily controlled.

  When the oscillation wavelength λ is approximately 400 nm, the first dielectric film has a refractive index of 1.65 or less, and the second dielectric film has a refractive index higher than 1.65. As a result, the COD level can be improved. In addition, in this specification, about 400 nm shall be 390 nm-415 nm.

  For forming the dielectric film, a film forming method such as a vacuum evaporation method or a sputtering method is used. As the sputtering film forming apparatus, for example, an ECR sputtering apparatus, a magnetron sputtering apparatus, or a high frequency sputtering apparatus is used.

  An example of a method for forming the dielectric film 110 will be described below. A wafer having a semiconductor layer laminated on a substrate is changed from a wafer shape to a bar shape, and a semiconductor having an end face of an optical resonator formed thereon is set on a film forming jig, and then a dielectric film is formed by a film forming apparatus. Here, a dielectric film is formed by an ECR film forming apparatus. As a raw material, a rare gas (Ar, He, Xe, etc.), an oxygen gas, and a metal target are used. For this metal target, Al, Zr, Si, Nb, Hf, Ti or the like having a purity of 3N (99.9%) or higher is used. In the case of Al, it is preferable to form the dielectric film using a material having a purity of 5N (99.999%) or higher.

The first dielectric film is formed by increasing the amount of oxygen compared to the case of forming the second dielectric film. The first dielectric film is formed by microwaves of 300 to 800 W or less, Rf of 300 to 800 W or less, a rare gas flow rate of 10 to 50 sccm (standard cubic centimeter per minute) or less, and an oxygen gas flow rate of 5 to 5. 20 sccm. By forming the film under these conditions, the first dielectric film becomes a single crystal.
The second dielectric film is formed by microwaves of 300 to 800 W or less, Rf of 300 to 800 W or less, a rare gas flow rate of 10 to 50 sccm or less, an oxygen gas flow rate of 2 to 10 sccm, It is assumed that the flow rate of oxygen gas is smaller than that for forming one dielectric film. By forming the film under these conditions, the second dielectric film can contain an amorphous film. Further, the second dielectric film can be an amorphous film by setting the flow rate of oxygen gas to less than 5 sccm. The second dielectric film has the same or less oxygen content for the same metal than the first dielectric film.
As other film forming conditions, the pressure of the film forming atmosphere is set to 0.01 Pa or more and 1 Pa or less. Further, the deposition rate of the first dielectric film is set to 1 nm / min or more. The deposition rate of the second dielectric film is 5 nm / min or more. Thereby, a film made of a single crystal and a film made of amorphous can be formed.
The dielectric film may be formed simultaneously on the light emitting (front) side end surface and the light reflecting (rear) side end surface, or may be formed under different conditions.

  The nitride semiconductor layer in this embodiment is formed in the order of the n-type nitride semiconductor layer 200, the active layer 205, and the p-type nitride semiconductor layer 210 from the substrate 100 side, but the present invention is not limited to this. The p-type nitride semiconductor layer, the active layer, and the n-type nitride semiconductor layer may be formed in this order from the substrate side. The active layer 205 has a multiple quantum well structure or a single quantum well structure. The nitride semiconductor layer preferably has an SCH (Separate Confinement Heterostructure) structure, which is an isolated light confinement structure in which an active layer is sandwiched between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer. This comprises an optical waveguide by providing light guide layers having a band gap larger than that of the active layer above and below the active layer.

The nitride semiconductor layer has a general formula of In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). In addition to this, it is possible to partially include B as a group III element. Further, a part of N as a group V element can be substituted with P or As. The n-type nitride semiconductor layer contains at least one of group IV elements such as Si, Ge, Sn, S, O, Ti, Zr, and Cd, or group VI elements as n-type impurities. . The p-type nitride semiconductor layer contains Mg, Zn, Be, Mn, Ca, Sr, etc. as p-type impurities. The impurity concentration is preferably 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ²¹ / cm ³ or less.

  The growth method of the nitride semiconductor layer is not particularly limited, but MOVPE (metal organic chemical vapor deposition), MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor deposition), MBE (molecular beam). Any method known as a method for growing a nitride semiconductor, such as an epitaxy method, can be suitably used. In particular, MOCVD is preferable because it can be grown with good crystallinity. The nitride semiconductor is preferably grown by appropriately selecting various nitride semiconductor growth methods depending on the purpose of use.

  Hereinafter, a nitride semiconductor will be described as a method for manufacturing the semiconductor laser device of the present embodiment, but the present invention is not limited to the following configuration. FIG. 11 shows a schematic cross-sectional view of a nitride semiconductor laser device formed under the following conditions.

(First step)
First, the substrate 100 having the first main surface 100a and the second main surface 100b is prepared. This substrate 100, a substrate 100 having a first major surface, and / or 0.05 ⁰ to 1.0 ⁰ off angle of the second main surface. The thickness of the substrate 100 is 50 μm to 1 mm, preferably 100 μm to 500 μm. The nitride semiconductor substrate 100 is preferably used as a nitride semiconductor growth substrate. The manufacturing method of the nitride semiconductor substrate 100 includes vapor phase growth methods such as MOCVD method, HVPE method, MBE method, hydrothermal synthesis method for crystal growth in a supercritical fluid, high pressure method, flux method, melting method and the like. .

The first main surface of the nitride semiconductor substrate 100 is preferably a C (0001) plane, an M (1-100) plane, or an A (11-20) plane. If the first main surface of the nitride semiconductor substrate 100 is a C (0001) plane, the second main surface is a (000-1) plane. The number of dislocations per unit area in the nitride semiconductor substrate 100 is 5 × 10 ⁶ / cm ² or less by CL observation or TEM observation. The nitride semiconductor substrate 100 has a (0002) diffraction X-ray rocking curve full width at half maximum of 2 minutes or less, preferably 1 minute or less by a biaxial crystal method. The radius of curvature of the nitride semiconductor substrate 100 is 1 m or more.
First major surface, and / or polishing or grinding a second main surface of said nitride semiconductor substrate, the laser irradiation by 0.05 ^{from 0} to 1.0 ^0, preferably ^0.1 0 to 0.7 ⁰ Form an off angle. If the off-angle is formed within this range, the element characteristics can be stabilized in the range where the oscillation wavelength of the laser element extends from the ultraviolet region of 365 nm or less to the long wavelength region of 500 nm or more. Specifically, the composition distribution of the active layer in the chip can be made uniform. In the present specification, a bar (-) in parentheses representing an area index represents a bar to be added on the back number.

(Second step)
Next, a nitride semiconductor layer is grown on the first main surface 100a of the nitride semiconductor substrate having an off angle. The following layers are grown under conditions of reduced pressure to atmospheric pressure by MOCVD. The nitride semiconductor layer is laminated on the first main surface of the nitride semiconductor substrate 100 in the order of an n-type nitride semiconductor layer 200, then an active layer 205, and then a p-type nitride semiconductor layer 210. N-type nitride semiconductor layer 200 stacked on first main surface 100a of nitride semiconductor substrate 100 is a multilayer film. The first n-type nitride semiconductor layer 201 is Al _x Ga _1-x N (0 <x ≦ 0.5), preferably Al _x Ga _1-x N (0 <x ≦ 0.3). As specific growth conditions, the growth temperature in the reactor is set to 1000 ° C. or higher and the pressure is set to 600 Torr or lower. The first n-type nitride semiconductor layer 201 can also function as a cladding layer. The film thickness is 0.5-5 μm. Next, a second n-type nitride semiconductor layer 202 is formed. The second n-side nitride semiconductor layer is Al _x Ga _1-x N (0 ≦ x ≦ 0.3) that functions as a light guide layer. The film thickness is 0.5-5 μm.
The n-type nitride semiconductor layer includes an intermediate layer composed of In _x Al _y Ga _1-xy N (0 <x ≦ 1, 0 ≦ y <1, 0 <x + y ≦ 1). You can also The intermediate layer has a single-layer structure or a multi-layer structure.

Next, the active layer 205 has the general formula In _x Al _y Ga _1-xy N (0 <x ≦ 1, 0 ≦ y <1, 0 <x + y ≦ 1) containing at least In. Increasing the Al content enables emission in the ultraviolet region. Further, light emission on the long wavelength side is also possible, and light emission from 360 nm to 580 nm is possible. Further, when the active layer is formed with a quantum well structure, the light emission efficiency is improved. Here, the composition of the well layer is such that the mixed crystal of In is 0 <x ≦ 0.5. The thickness of the well layer is 30 to 200 angstroms, preferably 30 to 100 angstroms. The thickness of the barrier layer is 20 to 300 angstroms, preferably 70 to 200 angstroms. The multi-quantum well structure of the active layer may start with a barrier layer and end with a well layer, start with a barrier layer, end with a barrier layer, start with a well layer and end with a barrier layer, and start with a well layer. It may end with

Next, the p-type nitride semiconductor layer 210 is stacked on the active layer. The first p-type nitride semiconductor layer 211 is Al _x Ga _1-x N (0 ≦ x ≦ 0.5) containing a p-type impurity. The first p-type nitride semiconductor layer functions as a p-side electron confinement layer. Then _Al x _{Ga 1-x} N as the second p-type nitride semiconductor layer 212 (0 ≦ x ≦ 0.3) , Al x Ga containing a p-type impurity as a third p-type nitride semiconductor layer 213 _1-xN (0 <x ≦ 0.5). The third p-type nitride semiconductor layer preferably has a superlattice structure and functions as a cladding layer. Specifically, it is composed of an Al _x Ga _1-x N (0 ≦ x <1) layer and an Al _y Ga _1-y N (0 <y ≦ 1, x <y) layer. Al _x Ga _1-x N (0 ≦ x ≦ 1) containing a p-type impurity is sequentially formed as the fourth p-type nitride semiconductor layer 214. Further, In may be mixed into these semiconductor layers. The first p-type nitride semiconductor layer 211 can be omitted. The film thickness of each layer is 30 to 5 μm.

After the completion of the reaction, the wafer is annealed in a nitrogen atmosphere at a temperature of 700 ° C. or higher in the reaction vessel to reduce the resistance of the p-type nitride semiconductor layer.
The n-type nitride semiconductor layer and the p-type nitride semiconductor layer may have a superlattice structure composed of two layers having different composition ratios.

(Third step)
The wafer in which the nitride semiconductor layer is laminated on the nitride semiconductor substrate 100 is taken out from the reaction container. Next, the n-type nitride semiconductor layer 200 is exposed by etching. By this etching, the resonator length is 200 μm to 1500 μm, and the chip width is 150 μm to 500 μm. Although the exposed surface of the n-type nitride semiconductor layer is not particularly limited, the first n-type nitride semiconductor layer 201 is exposed in this embodiment. Thereby, there is an effect of stress relaxation between the nitride semiconductor substrate and the nitride semiconductor layer formed thereon. This step can be omitted. Simultaneously with this etching, the W-shaped groove 120 may be formed in the vicinity of the light emitting side end face. This W-shaped groove prevents stray light from being emitted from the end face. Simultaneously with the etching, cleavage assist grooves may be formed at the four corners of the element. This cleavage assisting groove facilitates the formation of a bar from the wafer and further the formation of a chip. Etching is performed by RIE method using Cl ₂ , CCl ₄ , BCl ₃ , SiCl ₄ gas or the like.

  Next, a striped ridge portion is formed in the p-type nitride semiconductor layer. The width of the ridge portion, which is the waveguide region, is 1.0 μm to 30.0 μm. When the single mode laser beam is used, the width of the ridge is preferably 1.0 μm to 3.0 μm. The height of the ridge portion (etching depth) may be at least within a range in which the third p-type nitride semiconductor layer 213 is exposed, and may be exposed up to the first p-type nitride semiconductor layer 211.

  Thereafter, a first insulating film 220 is formed on the exposed surface of the p-type nitride semiconductor layer. The first insulating film 220 is preferably formed on the side surface of the ridge. The first insulating film 220 has a refractive index smaller than that of the nitride semiconductor layer and is selected from insulating materials. Specific examples include oxides or nitrides such as Zr, Si, V, Nb, Hf, Ta, and Al.

Thereafter, a p-electrode 230 is formed on the surface of the fourth p-type nitride semiconductor layer 214. Preferably, the p-electrode 230 is formed only on the fourth p-type nitride semiconductor layer 214. The p electrode has a multilayer structure. For example, in the case of a two-layer structure made of Ni and Au, Ni is first formed on the fourth p-type nitride semiconductor layer to a thickness of 50 to 200 mm, and then Au is formed to a thickness of 500 to 3000 mm. . When the p-electrode has a three-layer structure, it is formed in the order of Ni / Au / Pt or Ni / Au / Pd. When the p-electrode has a three-layer structure, Ni and Au have the same film thickness as the two-layer structure, and Pt and Pd serving as the final layer are 500 to 5000 mm. Further, after the p-electrode 230 is formed, ohmic annealing may be performed. As annealing conditions, the annealing temperature is set to 300 ° C. or higher, preferably 500 ° C. or higher. Further, the atmosphere for annealing is set to a condition containing nitrogen and / or oxygen.
The end face of the p electrode 230 is preferably substantially coincident with the light emitting side end face of the semiconductor layer, but the end face of the p electrode 230 may be separated from the light emitting side end face by about 10 μm as shown in FIG.

Next, a second insulating film 240 is formed on the side surface of the n-type nitride semiconductor layer exposed in the previous step. This second insulating film is made of ZrO ₂ , SiO ₂ , and other oxides such as V, Nb, Hf, Ta, and Al.

  Next, the pad electrode 250 is formed on the p-electrode 230 (FIG. 3). In the plan view of the nitride semiconductor laser device shown in FIG. 3, the first insulating film 220 and the second insulating film 240 are omitted. The pad electrode is preferably a laminate made of a metal such as Ni, Ti, Au, Pt, Pd, or W. For example, the pad electrode is formed in the order of W / Pd / Au, Pt / Ti / Au, or Ni / Ti / Au from the p-electrode side. The film thickness of the pad electrode is not particularly limited, but the film thickness of Au in the final layer is 1000 mm or more.

(Fourth process)
Thereafter, the above-described n-electrode 232 is formed on the second main surface 100b of the nitride semiconductor substrate. Polishing from the second main surface side of the substrate reduces the thickness of the substrate to 100 μm or less. Next, an n-electrode is formed in multiple layers by sputtering or the like. The n electrode 232 is at least one selected from the group consisting of V, Mo, Ti, Cr, W, Al, Zr, Au, Pd, Rh, Nb, Hf, Ta, Re, Mn, Zn, Pt, and Ru. Alloys or layer structures containing can be used. Preferably, V / Pt / Au, Ti / Pt / Au /, Mo / Pt / Au, W / Pt / Au, Ti / Pd / Al, Ti / Al, Cr / Au, W / Al, Rh / Al It is a two-layer structure or a three-layer structure. Further, Ti, Mo, Si, W, Pt, Ni, Rh, or an oxide or nitride thereof may be laminated on the surface of the n electrode for the purpose of barrier. The mounting strength of the chip can be increased.
The thickness of the n electrode is, for example, 100 V using V for the first layer. The second layer is formed with a thickness of 2000 mm using Pt, and the third layer is formed with a film thickness of 3000 mm using Au. In addition to sputtering, it may be formed by CVD or vapor deposition. Further, after forming the n-electrode, annealing may be performed at 500 ° C. or higher.

  After the n-electrode 232 is formed, a metallized electrode can be further formed. The metallized electrodes include Ti—Pt—Au— (Au / Sn), Ti—Pt—Au— (Au / Si), Ti—Pt—Au— (Au / Ge), Ti—Pt—Au—In, Au / Sn, In, Au / Si, Au / Ge, or the like is used.

  After the n-electrode 232 is formed, the wafer is divided into bars so as to form a resonator end face of the nitride semiconductor layer in a direction perpendicular to the striped p-electrode 230. Here, the resonator end faces are the M plane (1-100) and the A plane (11-20). As a method of dividing the wafer into bars, there is a blade break, a roller break, or a press break.

  Further, the wafer dividing process may be performed in two stages. By this method, the resonator end face can be formed with high yield. First, a cleavage assist groove is formed in advance by etching or the like from the first main surface side or the second main surface side of the substrate. The cleavage assist grooves are formed at the four corners of the element to be chipped. Thereby, bending of the cleavage direction can be suppressed. Next, the wafer is divided into bars by a breaker.

(Fifth step)
Next, the dielectric film 110 described above is formed on the end face of the resonator. FIG. 4 is a plan view of a nitride semiconductor laser element in which a dielectric film 110 is formed on the light emitting side end face. The dielectric film 110 may be configured such that a first dielectric film 111 and a second dielectric film 112 are sequentially formed on the light emitting side end face, and then a dielectric film 110 ′ is also formed on the light reflecting side end face. FIG. 6 shows a perspective view of a nitride semiconductor laser device in which a dielectric film 110 is formed on the light emitting side end face. In other cases, as shown in FIG. 7, the dielectric film 110 also wraps around the side surface of the nitride semiconductor laser element. With such a configuration, it is possible to prevent deterioration of not only the end face of the nitride semiconductor but also the side face. Further, as shown in FIG. 8, there is a dielectric film that wraps around to cover the electrode. With such a configuration, it is possible to effectively prevent side surface deterioration.

  After the dielectric film 110 composed of the first dielectric film 111 and the second dielectric film 112 is formed on the light emitting side end face of the semiconductor 300, the reflection mirror 310 is formed on the light reflecting side end face (FIG. 5a). The reflection mirror 310 has a reflectance of 85% or more, and has a pair structure of a low refractive index layer and a high refractive index layer. The reflectance of the reflection side end face is preferably 90% or more, more preferably 95% or more.

  As another configuration, a reflection mirror 310 is formed after forming a dielectric film 110 ′ including a first dielectric film 111 ′ and a second dielectric film 112 ′ in order from the light reflection side end face of the semiconductor 300. is there. Such a configuration improves the life characteristics (FIG. 5b).

Further, as another configuration, after the dielectric film 110 is formed on the light emitting side end face of the semiconductor 300, the reflection mirror 310 may be formed on the surface (FIG. 5c). The reflection mirror has a pair configuration of a low refractive index layer and a high refractive index layer, for example, a pair configuration of SiO ₂ and ZrO ₂ . The number of pairs is 2 to 10, preferably 3 to 8, and more preferably 6. As other materials, compounds such as oxides, nitrides, and fluorides of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, and B can be used.

(Sixth step)
After forming a dielectric film on the end face of the resonator of the bar-shaped semiconductor, the nitride semiconductor laser element is formed by converting the bar shape into a chip. The nitride semiconductor laser element has a rectangular shape after being formed into chips, and the rectangular resonator length is 650 μm or less. From the above, the nitride semiconductor laser element obtained has a COD level of 1 W or higher and a Kink power of 500 mW. Moreover, as a result of conducting a life test (Tc = 70 ° C., CW output of 100 mW), a result of 5000 hours or more could be obtained.
Furthermore, in the present invention, the nitride semiconductor laser device has a counter electrode structure with reduced contact resistance, and the contact resistivity is 1.0E ⁻³ Ωcm ² or less.

  Hereinafter, a semiconductor laser device using a nitride semiconductor will be described as an example. However, the present invention is not limited to the following example, and various modifications based on the technical idea of the present invention are possible. Needless to say.

[Example 1]
As the substrate, a wafer-like GaN substrate 100 having a C surface as a main surface is used. The substrate is not particularly limited to this, and a GaN substrate having the R plane and the A plane as main surfaces is used as necessary.

(N-type cladding layer 201) Next, the GaN substrate is transferred to an MOCVD apparatus. An atmosphere temperature in the furnace is set to 1050 ° C., and TMA (trimethylaluminum), TMG and ammonia are used as source gases, and an n-type cladding layer made of undoped Al _0.04 Ga _0.96 N is formed to a thickness of 2.0 μm. Grow.

(N-type light guide layer 202) Next, TMG and ammonia are used as source gases at substantially the same temperature as the n-type cladding layer, and an n-type light guide layer made of undoped GaN is grown to a thickness of 0.19 μm. This layer may be doped with n-type impurities.

(Active layer 205) Next, the temperature is set to 800 ° C., TMI (trimethylindium), TMG and ammonia are used as raw materials, silane gas is used as impurity gas, and Si-doped In _0.02 Ga _0.98 N is formed. The barrier layer is grown to a thickness of 140 mm. Subsequently, the silane gas is stopped and a well layer made of undoped In _0.1 Ga _0.9 N is grown to a thickness of 80 mm. This operation is repeated twice. Finally, a barrier layer made of Si-doped In _0.02 Ga _0.98 N is grown to a film thickness of 140 mm, and an active layer having a total quantum film structure (MQW) of 580 mm is formed. Grow.

(P-type electron confinement layer 211) A p-type electron confinement layer made of Mg-doped Al _0.25 Ga _0.75 N is grown to a thickness of 30 mm in a N ₂ atmosphere at the same temperature. Next, a p-type electron confinement layer made of Mg-doped Al _0.25 Ga _0.75 N is grown to a thickness of 70 mm in an H ₂ atmosphere.

(P-type light guide layer 212) Next, the temperature is set to 1050 ° C., TMG and ammonia are used as source gases, and a p-type light guide layer made of undoped GaN is grown to a thickness of 0.13 μm.

(P-type cladding layer) Subsequently, an A layer made of undoped Al _0.08 Ga _0.92 N is grown to a thickness of 80 mm, and a B layer made of Mg-doped GaN is grown to a thickness of 80 mm. Grow. This is repeated 28 times, and the A layer and the B layer are alternately laminated to grow a p-type cladding layer made of a multilayer film (superlattice structure) having a total film thickness of 0.45 μm.

(P-type contact layer 213) Finally, a p-type contact layer made of Mg-doped GaN is grown on the p-type cladding layer at 1050 ° C. to a thickness of 150 mm. The p-type contact layer can be composed of p-type In _x Al _y Ga _1-xy N (x ≦ 0, y ≦ 0, x + y ≦ 1). The most favorable ohmic contact with the electrode is obtained. After the completion of the reaction, the wafer is annealed at 700 ° C. in a nitrogen atmosphere in the reaction vessel to further reduce the resistance of the p-type layer.

After the nitride semiconductor is grown on the GaN substrate to form a laminated structure as described above, the wafer is taken out of the reaction vessel, and a protective film made of SiO ₂ is formed on the surface of the uppermost p-type contact layer. Etching with Cl ₂ gas using RIE (reactive ion etching) to expose the surface of the n-type cladding layer. At this time, the W-shaped groove is formed in the vicinity of the light emitting side end face.

Next, in order to form a striped waveguide region, a protective film made of Si oxide (mainly SiO ₂ ) is formed to a thickness of 0.5 μm on almost the entire surface of the uppermost p-type contact layer by a CVD apparatus. After the formation, a mask having a predetermined shape is formed on the protective film by a photolithography technique, and a protective film made of striped Si oxide is formed by etching using CHF ₃ gas by an RIE apparatus. Using this Si oxide protective film as a mask, the semiconductor layer is etched using Cl ₂ gas and SiCl ₄ gas to form a ridge stripe above the active layer. At this time, the width of the ridge is set to 1.4 μm.

With the SiO ₂ mask formed, a first insulating film made of ZrO ₂ is formed on the surface of the p-type semiconductor layer with a film thickness of about 1000 mm. After forming the first insulating film, the wafer is heat-treated at 600 ° C. As described above, when a material other than SiO ₂ is formed as the first insulating film, the insulating film material is heat-treated at 300 ° C. or higher, preferably 400 ° C. or higher and 1200 ° C. or lower after the first insulating film is formed. Stabilize things. After the heat treatment, the substrate is immersed in a buffered solution to dissolve and remove SiO ₂ formed on the upper surface of the ridge stripe, and ZrO ₂ on the p-type contact layer is removed together with SiO ₂ by a lift-off method. Thereby, the upper surface of the ridge is exposed and the side surface of the ridge is covered with ZrO ₂ .

Next, a p-electrode 230 made of Ni—Au is formed on the p-type contact layer. The film thickness of Ni is 100 mm, and the film thickness of Au is 1500 mm. Thereafter, heat treatment is performed at 600 ° C. (can be omitted). Next, SiO ₂ is formed on the side surface of the laser element as a second insulating film. Further, Ni—Ti—Au is formed in this order as a p pad electrode on the p electrode. Next, after adjusting the GaN substrate to have a film thickness of about 85 μm, an n-electrode having a thickness of 100 mm, 2000 mm, and 3000 mm is formed on the back surface of the substrate in the order of V-Pt-Au.

  Next, braking is performed from the nitride semiconductor layer side, and the bar shape is obtained by cleaving. The cleavage plane of the nitride semiconductor layer is the M plane (11-00 plane) of the nitride semiconductor, and this plane is the resonator plane.

(Dielectric film 110)
A dielectric film is provided on the light emitting side end face of the bar-shaped nitride semiconductor formed as described above. The light emitting side end face is cleaned with a plasma of an active gas such as oxygen using an ECR sputtering apparatus, and then the first end face such as ZrO ₂ , Nb ₂ O ₅ , Al ₂ O ₃ , TiO ₂ is used. A dielectric film and a second dielectric film are formed. In this embodiment, the dielectric film 110 is made of Al _x O _y . The first dielectric film 111 is formed to a thickness of 20 nm under the conditions of microwave power 600 W and RF 600 W, using 5N Al for the metal target, Ar flow rate of 15 sccm, O ₂ flow rate of 10 sccm. Next, the second dielectric film 112 is formed to a thickness of 130 nm under the conditions of an Ar flow rate of 10 sccm, an O ₂ flow rate of 3 sccm, a microwave power of 450 W, and an RF of 450 W. Here, the refractive index of the first dielectric film is 1.63 and the refractive index of the second dielectric film is 1.67 with respect to 405 nm light.

(Dielectric film 110 ′)
Next, a dielectric film 110 ′ made of Al _x O _y is formed on the light reflection side end face, and then a reflection mirror 310 made of SiO ₂ and ZrO ₂ is formed.
After the reflection side end face is cleaned using plasma of an active gas such as oxygen using an ECR sputtering apparatus, a dielectric film 110 ′ is formed under the following conditions. As the Al source, metal target Al is used. First, after depositing a first dielectric film 111 ′ to a thickness of 20 nm under the conditions of an Ar flow rate of 15 sccm, an O ₂ flow rate of 10 sccm, a microwave power of 600 W and an RF 600 W, an Ar flow rate of 10 sccm and an O ₂ flow rate of 3 sccm. Then, a second dielectric film 112 ′ is formed to a thickness of 40 nm under the conditions of microwave power 450 W and RF 450 W, and a protective film made of Al ₂ O ₃ is formed. Here, the refractive index of the first dielectric film is 1.63 and the refractive index of the second dielectric film is 1.67 with respect to 405 nm light.

Thereafter, SiO ₂ is formed with a film thickness of 67 nm using a Si target under the conditions of an Ar flow rate of 20 sccm, an O ₂ flow rate of 7 sccm, a microwave power of 500 W, and an RF power of 500 W. Next, using a ZrO ₂ as a Zr target, an Ar flow rate of 20 sccm, an O ₂ flow rate of 27.5 sccm, a microwave power of 500 W, and an RF power of 500 W are formed to a thickness of 44 nm. Under the above conditions, six pairs of SiO ₂ and ZrO ₂ are alternately stacked to form the reflection mirror 310.

Thereafter, the bar-shaped semiconductor is chipped to form a rectangular nitride semiconductor laser element. The resonator length is 600 μm and the chip width is 200 μm. From the above, the obtained nitride semiconductor laser device has a COD level of 800 mW or more as shown in FIG. As a comparative example, FIG. 10 shows the COD level of the nitride semiconductor laser device having no dielectric film of this example. The horizontal axis indicates the drive current, and the vertical axis indicates the Kink power. In this embodiment, the Kink power is 400 mW. As a result of a life test (Tc = 70 ° C., CW output of 100 mW), a result of 5000 hours or more could be obtained. In addition, the nitride semiconductor laser element in this example can continuously oscillate at a threshold current density of 3.5 kA / cm ² at room temperature and a high output of 150 mW when driven at CW and an oscillation wavelength of 405 nm.

[Example 2]
In Example 1, a nitride semiconductor laser device is formed in the same manner except that the dielectric film 110 on the light emitting side end face has the following configuration. An ECR sputtering apparatus is used. After cleaning the light emitting side end face using plasma of an active gas such as oxygen, a first dielectric film and a second dielectric film made of Al _x O _y are formed. First, 5N Al is used as a metal target, and the first dielectric film is formed to a thickness of 20 nm under the conditions of an Ar flow rate of 15 sccm, an O ₂ flow rate of 10 sccm, a microwave power of 600 W, and an RF power of 600 W. Thereafter, 5N Al is used for the metal target, and the second dielectric film is formed to a thickness of 100 nm under the conditions of an Ar flow rate of 10 sccm, an O ₂ flow rate of 3 sccm, a microwave power of 450 W, and an RF of 450 W. Here, the refractive index of the first dielectric film is 1.63 and the refractive index of the second dielectric film is 1.67 with respect to 405 nm light. The nitride semiconductor laser device obtained as described above exhibits substantially the same characteristics as in Example 1.

[Example 3]
In Example 1, a nitride semiconductor laser device is formed in the same manner except that the dielectric film has the following configuration.
The end surface of the light exit side is cleaned with an active gas plasma such as oxygen using an ECR sputtering apparatus, and then 5N Al is used for the metal target, the flow rate of Ar is 15 sccm, and the flow rate of O 2 is set. After the first dielectric film 111 is formed to a thickness of 20 nm under the conditions of 10 sccm, microwave power 600 W, and RF 600 W, 5N Al is used for the metal target, the flow rate of Ar is 10 sccm, the flow rate of O ₂ is 3 sccm, and the microwave power The dielectric film 110 is formed by forming a second dielectric film with a thickness of 40 nm under the conditions of 450 W and RF 450 W. Here, the refractive index of the first dielectric film is 1.63 and the refractive index of the second dielectric film is 1.67 with respect to 405 nm light.

Next, Al ₂ O ₃ is used as a metal target, Al is formed at a film thickness of 60 nm under the conditions of an Ar flow rate of 10 sccm, an O ₂ flow rate of 3 sccm, microwave power of 450 W, and RF 450 W. Thereafter, ZrO ₂ is formed with a thickness of 44 nm using a target made of Zr under the conditions of an Ar flow rate of 20 sccm, an O ₂ flow rate of 27.5 sccm, a microwave power of 500 W, and an RF power of 500 W. Under the above conditions, two pairs of Al ₂ O ₃ and ZrO ₂ are alternately laminated to form the reflection mirror 310.

Next, the end surface of the light reflection side is cleaned with an active gas plasma such as oxygen using an ECR sputtering apparatus, and then the Al is used for the metal target, the flow rate of Ar is 15 sccm, and the flow rate of O ₂ is set. After the first dielectric film 111 ′ is formed to a thickness of 20 nm under the conditions of 10 sccm, microwave power 600 W, and RF 600 W, Al is used as the metal target, the flow rate of Ar is 10 sccm, the flow rate of O ₂ is 3 sccm, and the microwave power is 450 W. The second dielectric film 112 ′ is formed to a thickness of 40 nm under the condition of RF450W, thereby forming the dielectric film 110 ′ made of Al ₂ O ₃ .

Next, Al is used as the metal target, and a low refractive index film having a thickness of 60 nm is formed under the conditions of an Ar flow rate of 10 sccm, an O ₂ flow rate of 3 sccm, a microwave power of 450 W, and an RF power of 450 W. Thereafter, Zr is used as a metal target, and a high refractive index film having a film thickness of 44 nm is formed under the conditions of an Ar flow rate of 20 sccm, an O ₂ flow rate of 27.5 sccm, a microwave power of 500 W, and an RF power of 500 W. Under the above conditions, six pairs of Al ₂ O ₃ and ZrO ₂ are alternately stacked to form the reflection mirror 310.
Thereafter, the bar-shaped semiconductor is chipped to form a rectangular nitride semiconductor laser element having a resonator length of 300 μm and a chip width of 200 μm. From the above, the nitride semiconductor laser element obtained has a COD level of 350 mW or higher and a Kink power of 100 mW. Moreover, as a result of conducting a life test (Tc = 70 ° C., CW output 20 mW), a result of 20000 hours or more can be obtained. In addition, the nitride semiconductor laser device in this example is capable of continuous oscillation at a threshold current density of 4.2 kA / cm ² at room temperature and a continuous output with an oscillation wavelength of 405 nm at a high output of 50 mW when driven by CW.

[Example 4]
In Example 1, a nitride semiconductor laser device is formed in the same manner except that the dielectric film on the light reflection side end face has the following configuration.
The light reflection side end face is cleaned using an active gas plasma such as oxygen using an ECR sputtering apparatus, and then the Al ₂ O ₃ flow rate of Ar is 15 sccm, the flow rate of O 2 is 10 sccm, microwave After the first dielectric film is formed to a thickness of 20 nm under the conditions of power 600 W and RF 600 W, the second dielectric film is 40 nm under the conditions of Ar flow rate of 10 sccm, O ₂ flow rate of 3 sccm, microwave power of 450 W and RF 450 W. A dielectric film made of Al ₂ O ₃ is formed. Here, the refractive index of the first dielectric film is approximately 1.63 for light of 405 nm, and the refractive index of the second dielectric film is approximately 1.67.

Next, a low refractive index film having a thickness of 67 nm is formed using a magnetron sputtering apparatus under the conditions of SiO ₂ with an Ar flow rate of 50 sccm, O ₂ flow rate of 5 sccm, and RF 500 W. Thereafter, the ZrO ₂ 50 sccm flow rate of Ar, the flow rate of _{O 2} 10 sccm, to form a high refractive index film having a film thickness of 46nm under conditions of RF500W. Under the above conditions, six pairs of SiO ₂ and ZrO ₂ are alternately stacked to form the reflection mirror 310. The nitride semiconductor laser device obtained as described above exhibits substantially the same characteristics as in Example 1.

[Example 5]
In Example 1, a nitride semiconductor laser device is formed in the same manner except that the dielectric film on the light reflection side end face has the following configuration.
The first dielectric film is formed with a thickness of 200 mm, the second dielectric film is formed with a thickness of 1000 mm, ZrO2 is formed with a thickness of 440 mm, and then (Al2O3 is 600 mm and ZrO2 is 440 mm). 7 pairs are formed. Finally, Al2O3 is formed with a thickness of 1200 mm. The nitride semiconductor laser device obtained as described above has excellent lifetime characteristics.

[Example 6]
In Example 1, a nitride semiconductor laser device is formed in the same manner except that the dielectric film on the light reflection side end face has the following configuration.
The first dielectric film is formed with a thickness of 200 mm, the second dielectric film is formed with a thickness of 1000 mm, ZrO2 is formed with a thickness of 440 mm, and then (Al2O3 is 600 mm and ZrO2 is 440 mm). 7 pairs are formed. Finally, Al 2 O 3 is formed with a thickness of 1000 mm and AlN with a thickness of 200 mm. The nitride semiconductor laser device obtained as described above has excellent lifetime characteristics.

[Example 7]
In Example 1, a nitride semiconductor laser device is formed in the same manner except that the dielectric film on the light reflection side end face has the following configuration.
The first dielectric film is formed on the front end face with a thickness of 200 mm, the second dielectric film is formed with a thickness of 800 mm, and the film thickness is 200 mm under the same formation conditions as the first dielectric film. Dielectric films are sequentially formed. The nitride semiconductor laser device obtained as described above has excellent lifetime characteristics.

  The semiconductor laser device of the present invention can be used for optical disc applications, optical communication systems, printing presses, exposure applications, measurements, and the like. Moreover, it can also be used as a bio-related excitation light source that can detect the presence or absence or position of a substance by irradiating a substance sensitive to a specific wavelength with light obtained from a semiconductor laser. In addition, it can also be used as a medical light source or a display light source.

1 is a schematic cross-sectional view of a nitride semiconductor laser element according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a nitride semiconductor laser element according to an embodiment of the present invention. 1 is a schematic plan view of a nitride semiconductor laser element according to an embodiment of the present invention. 1 is a schematic plan view of a nitride semiconductor laser element according to an embodiment of the present invention. It is a typical sectional view of a dielectric film concerning an embodiment of the present invention. 1 is a schematic perspective view of a nitride semiconductor laser device according to an embodiment of the present invention. 1 is a schematic perspective view of a nitride semiconductor laser device according to an embodiment of the present invention. 1 is a schematic perspective view of a nitride semiconductor laser device according to an embodiment of the present invention. It is a figure which shows the COD level of the nitride semiconductor laser element concerning this invention. It is a figure which shows the COD level of the conventional nitride semiconductor laser element. 1 is a schematic cross-sectional view of a nitride semiconductor laser element according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Substrate, 110 ... Dielectric film, 200 ... N-type nitride semiconductor layer, 205 ... Active layer, 210 ... P-type nitride semiconductor layer, 220 ... First insulating film, 230 ... P electrode, 232 ... N electrode 240 ... second insulating film, 250 ... pad electrode

Claims (16)

A semiconductor laser element having a dielectric film on at least one of the end faces of the optical resonator,
The dielectric film is formed by sequentially forming a first dielectric film and a second dielectric film made of the same element from the end face side of the semiconductor,
The first dielectric film includes a film made of a single crystal;
The second dielectric film includes an amorphous film;
A semiconductor laser device, wherein the first dielectric film and the second dielectric film have substantially the same composition ratio. A semiconductor laser element having a dielectric film on at least one of the end faces of the optical resonator,
The dielectric film is formed by sequentially forming a first dielectric film and a second dielectric film made of the same element from the end face side of the semiconductor,
The semiconductor laser device according to claim 1, wherein the first dielectric film is a reaction preventing film between the semiconductor and the dielectric film, and the second dielectric film is a reflection film for laser light. 3. The semiconductor laser device according to claim 2, wherein the first dielectric film contains a film made of a single crystal, and the second dielectric film contains a film made of amorphous. 4. The semiconductor laser device according to claim 1, wherein the first dielectric film has a lower refractive index than the second dielectric film. 5. 5. The semiconductor laser device according to claim 1, wherein the second dielectric film is thicker than the first dielectric film. 6. The semiconductor laser device according to claim 1, wherein the dielectric film has a reflectance of 25% or less. 7. The semiconductor laser device according to claim 1, wherein the reflectance of the dielectric film is 20% or less when the oscillation wavelength of the semiconductor laser device is approximately 400 nm. The semiconductor laser device according to claim 1, wherein the first dielectric film and the second dielectric film have Al and O as constituent elements. 9. The semiconductor laser device according to claim 1, wherein the first dielectric film and the second dielectric film have substantially the same thermal expansion coefficient. The semiconductor laser device according to claim 1, wherein the outermost layer of the dielectric film is a nitride. A semiconductor laser element having a dielectric film on at least one of the end faces of the optical resonator,
The dielectric film is formed by sequentially forming a first dielectric film, a second dielectric film, and a third dielectric film from the end face side of the semiconductor,
The first dielectric film and the second dielectric film are made of the same element,
The third dielectric film has a different element from the first dielectric film and the second dielectric film,
The first dielectric film is a reaction preventing film between a semiconductor and a dielectric film,
2. The semiconductor laser device according to claim 1, wherein the second dielectric film is a stress relaxation film composed of a first dielectric film and a third dielectric film. The semiconductor laser device according to claim 11, wherein the first dielectric film and the second dielectric film contain oxygen. 13. The semiconductor laser device according to claim 12, wherein the oxygen content of the first dielectric film is higher than the oxygen content of the second dielectric film. The semiconductor laser device according to claim 11, wherein the outermost layer of the dielectric film is a nitride. An optical pickup device comprising the semiconductor laser element according to claim 1. An optical information reproducing apparatus for reproducing information recorded on the optical information recording board by condensing and irradiating laser light on the optical information recording board and detecting reflected light thereof,
15. An optical information reproducing apparatus using the semiconductor laser element according to claim 1 as a light source.

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