JP2009016684A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device capable of providing a laser beam of wavelength longer than peak wavelength of a spontaneous emission spectrum. <P>SOLUTION: The peak wavelength λ<SB>0</SB>of the spontaneous emission spectrum in a laser beam emitting part has the following relation, with respect to a peak wavelength λ<SB>1</SB>at which reflectance R1(λ) for light of wavelength λ in an outgoing side mirror is maximum and peak wavelength λ<SB>2</SB>in which reflectance R2(λ) for light of wavelength λ in a reflection side mirror is maximum: λ<SB>1</SB>>λ<SB>0</SB>and/or λ<SB>2</SB>>λ<SB>0</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser element that oscillates a laser beam having a desired wavelength band.

  Semiconductor laser elements are used in various applications depending on the wavelength of emitted laser light. For example, a GaN-based nitride semiconductor laser element is used as a laser light source for reading / writing information on an optical disk at high density. Among these, short-wavelength laser elements having a light emission wavelength of 380 nm to 420 nm including blue-violet are used as pickup light sources for optical disks with high density and high recording capacity. Laser elements in the UV band with an emission wavelength of 380 nm or less are used for exposure light sources, inspection light sources, and the like. On the other hand, long-wavelength laser elements with emission wavelengths of 420 nm to 550 nm including blue and green are expected to be used for display light sources for displaying images, medical light sources, bio or printing light sources, optical module light sources, and the like. ing.

A semiconductor laser element generally exhibits a spontaneous emission spectrum having a broad peak in a specific wavelength band according to the composition of each semiconductor layer constituting a double heterojunction structure. The spontaneous emission spectrum and the gain spectrum almost coincide with each other, and the oscillation gain of the laser is usually the highest near the peak of the spontaneous emission spectrum. However, the longer the wavelength band, the smaller the difference in refractive index between the cladding layer and the active layer, making it difficult to obtain a sufficient optical confinement factor. In such a case, a sufficient light confinement coefficient cannot be obtained near the wavelength peak of the spontaneous emission spectrum, and the gain on the short wavelength side of the wavelength peak of the spontaneous emission spectrum becomes high. For this reason, it has an oscillation peak considerably shorter than the wavelength peak of the spontaneous emission spectrum. For this reason, it becomes difficult to oscillate the laser in the long wavelength band. In particular, in a long wavelength laser whose oscillation wavelength exceeds 450 nm, the width of the spontaneous emission spectrum becomes wide, and this phenomenon becomes remarkable. For example, in a GaN-based nitride semiconductor laser element, it was very difficult to oscillate laser light having a wavelength of 450 nm or more, which is called a long wavelength band. In the past, in order to obtain a long emission wavelength in a GaN-based nitride semiconductor laser element, a configuration in which highly mixed crystal In is introduced into an active layer has been studied (Patent Document 1).
JP 2001-148546 A

  However, when the mixed crystal of In in the semiconductor layer is increased, the lattice mismatch increases and it becomes difficult to obtain a good crystal, so that the light emission efficiency is lowered. In addition, due to the generation of a piezoelectric field, the half-value width of the spontaneous emission spectrum becomes very large at 30 nm or more. Further, as described above, the longer the wavelength, the smaller the difference in refractive index between the clad layer and the active layer, so that it is difficult to obtain a sufficient optical confinement factor. As a result, oscillation occurs at a wavelength much shorter than the spontaneous emission wavelength.

  Among the nitride semiconductor laser elements, in particular, in a long wavelength laser element having an oscillation wavelength of 450 nm or more, the spontaneous emission spectrum becomes wide, so that there is little difference in gain in a wide wavelength range, that is, uniform gain in a wide wavelength range. Will have. In addition, since the refractive index difference at the interface between the clad layer and the active layer that performs optical confinement in the stacked semiconductor layers becomes larger on the short wavelength side, the wavelength in the long wavelength laser device having an oscillation wavelength of 450 nm or more is shown in FIG. And the optical confinement factor), the confinement factor on the short wavelength side increases. In other words, the confinement factor decreases as the wavelength increases.

  On the other hand, in the mirror configured on the resonator surface, the number of pairs of multilayer films for obtaining a desired reflectivity can be reduced by increasing the refractive index difference between the dielectric multilayer films constituting the mirror. it can. The reflectivity of the mirror is determined by the refractive index difference of the dielectric multilayer film, its film thickness, and the number of pairs. A conventional mirror manufactured by a combination of dielectric multilayer films having a large difference in refractive index exhibits substantially the same reflectance in a wavelength region of about 100 nm. That is, there is no difference in gain necessary to oscillate laser light in this wavelength region. Therefore, in the conventional laser, the reflectance peak of the mirror is manufactured around the spontaneous emission wavelength peak region having the highest gain or coincident with the wavelength to be oscillated. That is, there is little change in the reflectance of the mirror around the spontaneous emission wavelength peak region or around the wavelength region where laser light is desired to oscillate.

  For this reason, in the GaN-based nitride semiconductor laser element, the distribution of the confinement coefficient of the cladding layer and the active layer with respect to the wavelength greatly affects the oscillation wavelength. Therefore, laser oscillation is performed at a wavelength shorter than the spontaneous emission wavelength peak, making it difficult to perform laser oscillation at the longer wavelength.

  Accordingly, an object of the present invention is to adjust the reflectivity of the reflection side mirror and the emission side mirror constituting the resonator in a light emitting device having a wide spontaneous emission spectrum width by introducing highly mixed crystal In or the like. Accordingly, it is an object of the present invention to provide a semiconductor laser device capable of laser oscillation even in a long wavelength band in which it is difficult to obtain a sufficient light confinement coefficient.

In order to solve the above-described problem, the invention according to claim 1 is provided on a laminated semiconductor, an emission-side mirror provided on a laser emission-side end face of the laminated semiconductor, and an end face opposite to the laser emission-side end face. A reflection-side mirror, and a peak wavelength λ _{1 at} which the reflectance R 1 (λ) with respect to light of wavelength λ in the emission-side mirror is maximum, and light of wavelength λ in the reflection-side mirror. The peak wavelength λ ₀ of the spontaneous emission spectrum of the stacked semiconductor has a relationship such that λ ₁ > λ ₀ and / or λ ₂ > λ ₀ with respect to the peak wavelength λ _{2 at} which the reflectance R2 (λ) is maximum. It is characterized by that.

In this semiconductor laser device, and the peak wavelength lambda ₁ in the output mirror, with respect to the peak wavelength lambda ₂ in the reflection-side mirror, the peak wavelength lambda ₀ of the spontaneous emission spectrum of the laser light emitting portion of the stacked semiconductor λ _1> λ ₀ And / or λ ₂ > λ ₀ makes it possible to oscillate the laser on the longer wavelength side than the conventional laser. The reason is considered as follows. By shifting the reflectance peak of the mirror to the long wavelength side of the peak wavelength of the spontaneous emission spectrum, the mirror reflectance on the short wavelength side where the optical confinement factor is large is lowered, and the gain necessary for oscillation on the short wavelength side is increased. Increase. That is, the gain necessary for oscillation is smaller on the long wavelength side than on the short wavelength side. Thereby, it is possible to suppress the oscillation wavelength from being shortened due to the wavelength dependence of the optical confinement coefficient, and to realize laser oscillation in a long wavelength band.

The semiconductor laser device of the invention according to claim 2 has a reflectance R2 (λ ₂ ) at the peak wavelength λ ₂ of the reflection side mirror and a wavelength λ _{3 that} is 1.00 times the reflectance R2 (λ ₂ ). The reflectance R2 (λ ₃ ), the reflectance R 2 (λ ₄ ) at a wavelength λ _{4 that} is 0.30 times the reflectance R 2 (λ ₂ ), and the oscillation wavelength λ p are expressed by the following equations (1), ( 2) and a relationship represented by the formula (3).
R2 (λ ₃ ) = R2 (λ ₂ ) × 1.00 (1)
R2 (λ ₄ ) = R2 (λ ₂ ) × 0.30 (2)
λ ₃ >λp> λ ₄ (3)

In this semiconductor laser device, laser oscillation on a longer wavelength side can be realized by making the reflectance R2 (λ) of the reflection side mirror satisfy the above formulas (1), (2), and (3). . In particular, by setting the reflectance of the reflection-side mirror to 0.3 times R2 (λ ₂ ), it is possible to sufficiently suppress the shortening of the oscillation wavelength caused by the wavelength dependence of the optical confinement factor, and to increase the length. Laser oscillation on the wavelength side can be realized.

According to a third aspect of the present invention, there is provided a semiconductor laser device having a reflectance R1 (λ ₁ ) at a peak wavelength λ ₁ of the emission side mirror and a wavelength λ _{5 that} is 1.00 times the reflectance R1 (λ ₁ ). The reflectance R1 (λ ₅ ), the reflectance R1 (λ ₆ ) at a wavelength λ _{6 that} is 0.30 times the reflectance R1 (λ ₁ ), and the oscillation wavelength λp are expressed by the following equations (4), ( 5) and a relationship represented by the formula (6).
R1 (λ ₅ ) = R1 (λ ₁ ) × 1.00 (4)
R1 (λ ₆ ) = R1 (λ ₁ ) × 0.30 (5)
λ ₅ >λp> λ ₆ (6)

In this semiconductor laser device, laser oscillation on a longer wavelength side can be realized by making the emission side mirror satisfy the relations of the above expressions (4), (5) and (6). In particular, by setting the reflectance of the exit side mirror to 0.3 times R1 (λ ₁ ), it is possible to sufficiently suppress the shortening of the oscillation wavelength caused by the wavelength dependence of the optical confinement coefficient.

The semiconductor laser device according to a fifth aspect of the invention is characterized in that the stacked semiconductor is a III-V group compound semiconductor.
This semiconductor laser device is suitable when the laminated semiconductor is composed of a III-V group compound semiconductor.

The semiconductor laser device of the invention according to claim 5 is characterized in that the wavelength of the laser beam emitted from the emission side mirror is 450 nm or more.
In this semiconductor laser element, the wavelength of the laser beam emitted from the emission side mirror can be set to 450 nm or more.

The semiconductor laser device of the invention according to claim 6 is characterized in that the emission side mirror and / or the reflection side mirror have an oxide film or a nitride film.
In this semiconductor laser device, it is preferable that the emission side mirror and / or the reflection side mirror have an oxide film or a nitride film.

  The semiconductor laser device of the present invention can oscillate laser light having a long wavelength band of 450 nm or more.

Hereinafter, a semiconductor laser device according to the present invention will be described in detail with reference to FIGS.
FIG. 1 is a schematic cross-sectional view showing the main configuration of the semiconductor laser device 1 of the present invention, and FIG. 2 is a diagram showing a spontaneous emission spectrum at a peak wavelength λ ₀ of the semiconductor laser device 1 of the present invention.
A semiconductor laser device 1 shown in FIG. 1 includes a laminated semiconductor 7 formed by laminating a first conductive semiconductor layer 6, an active layer 4, and a second conductive semiconductor 5 in this order, and laser light emitted from the active layer 4. The output side mirror 2 and the reflection side mirror 3 are provided at both ends of the laminated semiconductor 7 along the waveguide.
The configuration of the semiconductor laser device 1 shown in FIG. 1 is a conceptual diagram for explaining the present invention. An electrode for injecting electrons and holes into the active layer 4 of the semiconductor laser device 1 and other The substrate, the protective layer, etc. are not shown in the figure. Therefore, the semiconductor laser device according to the present invention is not limited to such a configuration.

In the laminated semiconductor 7, the first conductivity type semiconductor layer 6 and the second conductivity type semiconductor layer 5 formed on the first conductivity type semiconductor layer 6 via the active layer 4 are layers made of a semiconductor material. An n-type or p-type semiconductor layer is formed by doping with a dopant. Specific examples of the semiconductor material constituting the first conductive semiconductor layer, the active layer 4 and the second conductive semiconductor layer include III-V group compound semiconductors. Among them, it is preferable to employ a nitride semiconductor (In _α Al _β Ga _1-α-β N, 0 ≦ α, 0 ≦ β, α + β ≦ 1) that is GaN, AlN, InN, or a mixed crystal thereof. . Further, a part or all of B as a group III element or a part of N as a group V element is substituted with P, As, Sb or the like, a mixed crystal such as AlGaAs or InGaAs, AlGaInP or the like. Other III-V group compound semiconductors such as InP-based materials and InGaAsP which is a mixed crystal thereof can also be employed. In addition, dopants doped into semiconductor materials include n-type dopants such as Si, Ge, Sn, S, O, Ti, and Zr group IV or VI elements, and p-type dopants such as Be, Zn, and Mn. , Cr, Mg, Ca and the like.

  The first conductive semiconductor layer 6 and the second conductive semiconductor layer 5 may each be formed in a multilayer structure. For example, the first conductivity type semiconductor layer 6 may have a multilayer structure in which a light guide layer and a cladding layer (light confinement layer) are laminated in this order from the active layer 4 side. The second conductivity type semiconductor layer 5 may have a multilayer structure in which a light guide layer, a cladding layer (light confinement layer), and a contact layer are laminated in this order from the active layer 4 side. Further, a buffer layer (buffer layer) may be formed between the substrate (not shown) and the first conductivity type semiconductor layer 6 and between the second conductivity type semiconductor layer 5 and the upper layer thereon. Furthermore, when the first conductive semiconductor layer 6 and the second conductive semiconductor layer 5 have a multilayer structure, an undoped or non-doped semiconductor layer may be included in a part of the multilayer structure. Furthermore, the structure containing the layer which laminated | stacked the undoped or non-doped semiconductor layer and the semiconductor layer doped with the impurity alternately may be sufficient.

  The active layer 4 is energy generated by recombination of holes and electrons injected from the first conductivity type semiconductor layer 6 and the second conductivity type semiconductor layer 5 which are n-type or p-type semiconductor layers. Is emitted as light.

  The active layer 4 preferably has a quantum well structure including a well layer and a barrier layer. The semiconductor material constituting the active layer 4 may be any of non-doped, n-type impurity doped, and p-type impurity doped. Especially, it is preferable to form with a semiconductor material of non-doped or n-type impurity doping. Furthermore, for example, the well layer may be undoped and the barrier layer may be n-type impurity doped.

The output-side mirror 2 and the reflection-side mirror 3 have a reflectance R1 (with respect to light having a wavelength λ in the output-side mirror 2 with respect to the peak wavelength λ ₀ of the spontaneous emission spectrum generated by recombination of electrons and holes in the active layer 4. The peak wavelength λ ₁ that maximizes λ) and the peak wavelength λ ₂ that maximizes the reflectance R 2 (λ) with respect to light of wavelength λ in the reflection-side mirror 3 are λ ₁ > λ ₀ and / or λ ₂ > When λ ₀ is reached, laser light having a wavelength longer than the oscillation wavelength obtained by the conventional laser manufacturing method in which λ ₁ = λ ₂ = λ ₀ is emitted from the resonator end face in the active layer 4 of the laminated semiconductor. Can do.

In these more preferred embodiments, the oscillation wavelength λp is a reflectance R2 (λ ₂ ) at the peak wavelength λ ₂ of the reflection side mirror 3 and a reflection that is 1.00 times the reflectance R2 (λ ₂ ). a rate R2 (λ _3), the wavelength lambda ₃ in the reflectivity R2 (λ _3), the reflectance R2 (lambda ₂₎ 0.30 times to become reflectivity R2 and (λ _4), the reflectance R2 The relationship with the wavelength λ ₄ in (λ ₄ ) has a relationship represented by the following formulas (1), (2) and (3).
R2 (λ ₃ ) = R2 (λ ₂ ) × 1.00 (1)
R2 (λ ₄ ) = R2 (λ ₂ ) × 0.30 (2)
λ ₃ >λp> λ ₄ (3)

Further, in the exit side mirror 2, the reflectivity R1 (λ ₁ ) at the peak wavelength λ ₁ of the exit side mirror 2 and the reflectivity R1 at a wavelength λ _{5 that} is 1.00 times the reflectivity R1 (λ ₁ ). (Λ ₅ ), the reflectance R ₁ (λ ₆ ) at the wavelength λ _{6 that} is 0.30 times the reflectance R ₁ (λ ₁ ), and the oscillation wavelength λp are expressed by the following equations (4), (5), and It is preferable to have the relationship represented by Formula (6).
R1 (λ ₅ ) = R1 (λ ₁ ) × 1.00 (4)
R1 (λ ₆ ) = R1 (λ ₁ ) × 0.30 (5)
λ ₅ >λp> λ ₆ (6)

In the semiconductor laser device 1 of the present invention, the reflectances R2 (λ) and R1 (λ) with respect to light of wavelength λ in the reflection side mirror 3 and / or the emission side mirror 2 are expressed by the above formulas (1) to (6). The reason why the laser oscillation on the long wavelength side can be realized by using the relationship shown is considered as follows. In the reflection side mirror 3 and / or the emission side mirror 2, by making the rise of the reflectance with respect to the increase in wavelength steep, it is possible to cause a steep decrease in the gain necessary for oscillation. Therefore, by adjusting the mirror reflectivity of the semiconductor laser element so as to satisfy the above relational expression, it is possible to effectively suppress the shortening of the oscillation wavelength due to the wavelength distribution of the confinement coefficient, and to further reduce the laser oscillation in the long wavelength region. It can be easily realized. Furthermore, in order to increase the sharp rise of the reflectance more effectively, there is a method of increasing the number of dielectric film pairs constituting the mirror. As an example, FIG. 3 shows the reflectance when the number of mirror pairs made of SiO ₂ and ZrO ₂ is changed. The 3, 0.5 pairs of ZrO ₂ single film, a combination of SiO ₂ film and ZrO ₂ film _(SiO 2 / ZrO ₂₎ in a configuration that would count as a pair, in 0.5 pairs (Fig. 3, a ZrO ₂ single film), 2.5 pairs (indicated by b in FIG. 3), 4.5 pairs (indicated by c in FIG. 3), 6.5 pairs (indicated by d in FIG. 3) , 8.5 pairs (indicated by e in FIG. 3) and 10.5 pairs (indicated by f in FIG. 3). As shown in FIG. 3, the reflection-side mirror 3 and / or the emission-side mirror 2 can be sharply increased in reflectance near 500 nm by increasing the number of mirror pairs made of SiO ₂ and ZrO _2. it can. As a result, laser oscillation in the long wavelength region can be realized more effectively.

In the semiconductor laser device 1 of the present invention, the reflectance R (λ) of the emission side mirror 2 and / or the reflection side mirror 3 has the above relationship with the peak wavelength λ ₀ of the spontaneous emission spectrum of the laminated semiconductor 7. In addition, the film composition, film thickness, and configuration are adjusted. Usually, the reflection side mirror 2 and the emission side mirror 3 are formed of SiO ₂ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ , Nb ₂ O ₅ , AlN, AlGaN, SiN, TiN, or the like.

Here, an experiment was conducted on the reflectance R2 (λ) with respect to the wavelength of the light of the exit side mirror 3 in the semiconductor light emitting device having the spontaneous emission peak wavelength λ ₀ = 500 nm.
First, the reflection-side mirror 3 is formed with Al ₂ O ₃ having a thickness of 1674 nm from the semiconductor side, and further, eight layers of ZrO ₂ (613 nm) and Al ₂ O ₃ (837 nm) are alternately formed. Al ₂ O ₃ (837 nm) was formed in this order. About this reflection side mirror 3, reflectance R2 ((lambda)) was measured with the ellipsometer. As a result, a reflectance of 96% was obtained at a peak wavelength (λ ₂ ) of 530 nm. At this time, as shown in FIG. 4 which is a mirror reflectance distribution diagram with respect to the wavelength of the reflection side mirror, the wavelength λ of the peak reflectance × 0.3 is 475 nm, and the wavelength λ of the peak reflectance × 0.98 is 505 nm. became.

Further, the output side mirror 2 is formed by forming Al ₂ O ₃ with a thickness of 1674 nm from the semiconductor side, and further forming six layers of ZrO ₂ (613 nm) and Al ₂ O ₃ (837 nm) alternately, and finally, It was formed by al ₂ O ₃ (837nm). About this output side mirror 2, reflectance R1 ((lambda)) was measured with the ellipsometer. As a result, the reflectance peak wavelength (λ ₁ ) was 525 nm, and a reflectance of 83% was obtained. At this time, as shown in FIG. 5 which is a mirror reflectance distribution diagram with respect to the wavelength of the output side mirror, the wavelength λ of peak reflectance × 0.3 is 465 nm, and the wavelength λ of peak reflectance × 0.98 is 505 nm. became.
From the results of this experiment, it was found that the semiconductor laser device of the present invention can be realized by the reflection side mirror 3 and the emission side mirror 2 as described above.

Next, as an embodiment of the semiconductor laser device of the present invention, a nitride semiconductor laser device shown in FIGS. 6A and 6B will be described.
FIG. 6A is a schematic cross-sectional view showing the structure of the nitride semiconductor laser device 31 according to the embodiment of the present invention, and FIG. 6B is a perspective view showing the external structure of the nitride semiconductor laser device 31. . FIG. 6A shows a cross-sectional view when the nitride semiconductor laser element 31 is cut in a direction perpendicular to the resonance direction of the laser beam.

The nitride semiconductor laser element 31 has a basic structure in which an n-type semiconductor layer 33, an active layer 34, and a p-type semiconductor layer 35 are stacked in this order on a substrate 32, as shown in FIG. The n-type semiconductor layer 33, the active layer 34, and the p-type semiconductor layer 35 constitute the basic structure of the laminated semiconductor in the present invention.
As the substrate 32, an insulating substrate such as sapphire (Al ₂ O ₃ , A plane, C plane, R plane), spinel (MgAl ₂ O ₄ , 111 plane), and GaN, SiC, MgO, Si, ZnO A single crystal substrate or a conductive substrate is used.

  The n-type semiconductor layer 33 has a multilayer structure in which an n-type light confinement layer and an n-type light guide layer are stacked in this order from the substrate 32 side. Further, the n-type light guide layer can be omitted, and when the substrate 32 is used as the light confinement layer, the n-type light confinement layer can also be omitted.

Further, a buffer layer may be formed as a single layer or a multilayer between the substrate 32 and the n-type semiconductor layer 33. In the case of forming the buffer layer as a single layer, the buffer layer may be composed of a nitride semiconductor having a composition represented by In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1). it can. Further, when the buffer layer is formed of two or more multilayers, Al _x Ga _1-X N (0 ≦ X ≦ 1) is used as the first buffer layer from the substrate side, and In _Y Ga _{1-Y is used} as the second buffer layer. It can be set as the structure laminated | stacked in order of N (0 <= Y <= 1). When this buffer layer is formed as a single layer, a configuration containing an n-type impurity is preferable regardless of whether it is formed as a multilayer. Thereby, the n-type semiconductor layer 33 having a sufficient carrier concentration exhibiting n-type is obtained. In addition, when the n-side electrode 37 is formed on the surface of the laminated semiconductor, having such an n-type semiconductor layer 33 in the configuration can provide a preferable ohmic contact, so that the threshold value of the nitride semiconductor laser element 1 is obtained. Effective for lowering current. Nitride semiconductors, not limited to GaN, have n-type properties due to nitrogen vacancies that can be formed inside the crystal even in non-doped (undoped state), but crystal growth of donor impurities such as Si, Ge, O, Sn, etc. By doping in, a nitride semiconductor having a high carrier concentration and a preferable n-type characteristic can be obtained.

  In addition, when the buffer layer is formed in multiple layers, the second buffer layer can be a nitride semiconductor layer containing In, thereby suppressing cracks generated in the laminated semiconductor.

The n-type optical confinement layer can be made of, for example, an n-type nitride semiconductor containing Al or GaN. This n-type optical confinement layer is made of ternary mixed crystal Al _Y Ga _1-Y N (0 ≦ Y ≦ 1), so that a good crystallinity can be obtained, and the refractive index difference from the active layer can be reduced. It becomes large and is effective as a light confinement layer. This n-type optical confinement layer is usually preferably grown to a thickness of 0.1 μm to 4 μm. If it is thinner than 0.1 μm, it does not easily function as a light confinement layer. The n-type optical confinement layer also functions as an n-type cladding layer that supplies carriers by containing an n-type impurity.

The n-type light guide layer has an n-type nitride semiconductor containing In or n-type GaN, and a multilayer structure including a layer made of these n-type nitride semiconductors and a layer made of n-type GaN. Also good. This n-type light guide layer is preferably made of ternary mixed crystal or binary mixed crystal In _x Ga _1-X N (0 ≦ X <1). This n-type light guide layer is usually desirably grown to a thickness of 100 to 1 μm, and is preferably formed of InGaN from the viewpoint of optical confinement. Further, there is an advantage that it can be grown with good crystallinity by using a superlattice structure of GaN or GaN or a multilayer structure.

The active layer 34 has a structure containing a nitride semiconductor layer containing In. Specifically, the active layer 34 has a single quantum well structure or a multiple quantum well structure, and ternary mixed crystal In _x Ga _1-x N (0 <X <1) is formed in the well layer. It is what you have. It is assumed that the barrier layer has In _{X ′} Ga _{1-X ′} N (0 ≦ X ′ <1, X ′ <X). Since the ternary mixed crystal InGaN has better crystallinity than the quaternary mixed crystal, the light emission output is improved. In particular, an active layer having a multiple quantum well structure (MQW: Multi-quantum-well) in which a well layer made of In _x Ga _1-x N and a barrier layer made of a nitride semiconductor having a larger band gap than the well layer are stacked. Is preferred. As an example of forming the multi-quantum well structure, the multi-quantum well structure is stacked so as to be barrier + well + barrier + well +... + Barrier + well layer + barrier. Further, an intermediate layer having a smaller thickness than the well layer and the barrier layer may be provided between the barrier layer and the well layer or between the well layer and the barrier layer.

  The total thickness of the active layer 34 is preferably adjusted to 100 mm or more. When the thickness is less than 100 mm, light confinement is weak and laser oscillation tends to be difficult. If the thickness of the active layer 34 is too thick, the output tends to decrease, and it is desirable to adjust the thickness to 1 μm or less, preferably 0.5 μm or less, more preferably 0.2 μm or less. When the film thickness is larger than 1 μm, the crystallinity of the active layer is deteriorated, or emitted light spreads in the active layer, and the threshold current tends to increase.

  The p-type semiconductor layer 35 has a multilayer structure in which a p-type optical confinement layer and a p-type contact layer are laminated in this order from the active layer 34 side. In this case, the p-type optical confinement layer also functions as a carrier confinement layer, and the active layer 34 also functions as a guide layer. Therefore, these functions may be separated by forming a structure via the p-type carrier confinement layer and the p-type light guide layer between the active layer 34 and the p-type light confinement layer. In this case, only the p-type light guide layer may be omitted, or only the p-type carrier confinement layer may be omitted. Specifically, when the p-type optical confinement layer also functions as a carrier confinement layer, the p-type carrier confinement layer can be omitted.

  The p-type nitride semiconductor is obtained by doping an acceptor impurity such as Zn, Mg, Be, Cd, and Ca during crystal growth, and among them, Mg exhibits the most preferable p-type characteristics. Further, after crystal growth, the p-type semiconductor layer 35 with lower resistance can be obtained by annealing at 400 ° C. or higher in an inert gas atmosphere.

The p-type carrier confinement layer is made of, for example, a nitride semiconductor containing Al or GaN, and is made of ternary mixed crystal Al _Y Ga _1-Y N (0 <Y ≦ 1). This carrier confinement layer is usually desirably 10 to 500 mm thick, and is particularly preferably AlGaN because it can effectively suppress the overflow of electrons from the active layer. This carrier confinement layer may be composed of a multilayer film.

The p-type light guide layer is made of, for example, a nitride semiconductor containing In or GaN, and preferably made of binary mixed crystal or ternary mixed crystal In _Y Ga _1-Y N (0 ≦ Y <1). The This light guide layer is usually desirably a film thickness of 100 to 1 μm, and particularly preferably formed of InGaN from the viewpoint of light confinement. Further, there is an advantage that it can be grown with good crystallinity by using a superlattice structure of GaN or GaN or a multilayer structure.

The p-type optical confinement layer can be composed of a p-type nitride semiconductor containing Al or GaN. This p-type optical confinement layer is preferably made of a binary mixed crystal or a ternary mixed crystal Al _Y Ga _1-Y N (0 ≦ Y ≦ 1), so that a layer with good crystallinity can be obtained. The p-type optical confinement layer 35b is preferably 0.1 μm to 1 μm in thickness, and a p-type nitride semiconductor containing Al such as AlGaN increases the refractive index difference from the active layer. Functions as a light confinement layer.

p-type contact layer _may be composed of _{In X Al Y Ga 1-X} -Y N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1). In particular, when p-type GaN doped with InGaN, GaN, and Mg among them, a p-type semiconductor layer with the highest carrier concentration is obtained, a good ohmic contact with the p-side electrode 30 is obtained, and the threshold current is lowered. Can be made.

  In this nitride semiconductor laser element 31, a ridge stripe structure is formed in the resonance direction of the laser beam. This ridge stripe structure is formed by etching the p-type semiconductor layer 35. The etching depth is not particularly limited. For example, the etching depth is formed by etching a p-type contact layer, a p-type light confinement layer, and a p-type light guide layer, and the stripe width is preferably 0.1 to 70 μm. Is formed with a thickness of 1 to 15 μm. The etching means is preferably dry etching. For example, reactive ion etching, ion milling, ECR etching, focused ion beam etching, ion beam assist etching, ICP etching, or the like can be used.

  Next, the nitride semiconductor laser element 31 on which the ridge stripe is formed may be further etched to expose the outer periphery where the laser element is chipped. The exposed surface is the n-type semiconductor layer 36 or the substrate 32, but the etching depth is not particularly limited.

  In addition, an insulating film 38 is formed on the side surface of the ridge stripe and the surface of the p-type semiconductor layer 35 exposed by etching. The insulating film 38 is made of at least one oxide or nitride selected from the group consisting of Zr, Si, Nb, Pb, Ti, Ce, Hf, Al, Bi, Cr, In, Nd, Sb, Ta, Y, and V. It is a thing. The thickness of this insulating film is 100 to 8000 mm. The insulating film may be a single layer or a multilayer. This insulating film can be formed by ECR plasma sputtering, plasma CVD, sputtering, ECR plasma sputtering, molecular beam evaporation, or the like.

Further, a p-type semiconductor layer (p-type carrier confinement layer, p-type light guide layer, p-type light confinement layer, p-type contact layer) 35, active layer 34, and n-type semiconductor layer exposed on the surface by etching. (N-type light confinement layer, n-type light guide layer) 33 and the upper surface and side surfaces of the substrate 32 may be made of SiO ₂ , SiN, TiN, TiO ₂ , AlN, Al ₂ O ₃ , ZrO _2, etc. A second insulating film 39 made of a high dielectric material may be formed. Moreover, these insulating films may be formed in a multilayer on the whole surface or partially. The second insulating film 39 can be formed by ECR plasma sputtering, plasma CVD, sputtering, magnetron sputtering, molecular beam evaporation, or the like.

Further, on the p-type semiconductor layer (p-type contact layer) 35, a multilayer film including a plurality of metals such as Ni, Pd, Ir, Rh, Pt, Mo, Ag, Au, or a layer made of these metals, or these A p-side electrode 36 made of the alloy is formed. A p-side pad electrode 40 is formed on the p-side electrode 36.
Further, the back surface of the substrate 32 is made of a multilayer film or an alloy composed of a metal such as V, Pt, Au, Al, Ti, W, Cu, Zn, Sn, In, or a plurality of layers made of these metals, or an alloy. A side electrode 37 is formed.

As shown in FIG. 6B, in this nitride semiconductor laser element 31, the output side mirror 39F and the reflection side mirror 39R are respectively provided with an n-type semiconductor layer 33, an active layer 34, a p-type semiconductor layer 35, and a substrate. 32 are provided on both end faces. The peak wavelength λ _{1 at} which the reflectance R 1 (λ) with respect to light of wavelength λ in the emission side mirror 39 F is maximum, and the peak wavelength λ at which the reflectance R 2 (λ) with respect to light of wavelength λ at the reflection side mirror 39 R is maximum. ₂ and the emission side mirror 39F and / or the reflection side so that the relationship between the peak wavelength λ ₀ of the spontaneous emission spectrum generated in the active layer 34 satisfies the relationship of λ ₁ > λ ₀ and / or λ ₂ > λ ₀ The film configuration, film composition, film thickness, etc. of the mirror 39R are adjusted.

As a mirror material for forming the emission side mirror 39F and the reflection side mirror 39R, for example, Zr, Si, Nb, Pb, Ti, Ce, Hf, Al, Bi, Cr, In, Nd, Sb, Ta, Y, V For example, AlF ₃ , BaF ₂ , CeF ₂ , CaF ₂ , MgF ₂ , NdF ₃ , PbF ₂ , SrF ₂ , ZnS, ZnSe, or the like can be used. Particularly preferably, an insulating film made of a high dielectric material such as SiO ₂ , SiN, AlN, Al ₂ O ₃ , ZrO ₂ , TiO ₂ , or Nb ₂ O ₅ is used. This insulating film can be formed by ECR plasma sputtering, plasma CVD, sputtering, magnetron sputtering, molecular beam evaporation, or the like.

More specifically, the reflection side mirror 39R has a single layer or a multilayer structure using two or more kinds of materials. For example, AlN single layer, AlN and SiO ₂ , AlN and SiO ₂ and ZrO ₂ , AlN and SiO ₂ and Al ₂ O ₃ , AlN and SiO ₂ , Al ₂ O ₃ and ZrO ₂ , Al ₂ O ₃ , Al ₂ O ₃ and ZrO ₂ , Al ₂ O ₃ and ZrO ₂ and SiO ₂ , ZrO ₂ and SiO ₂ , TiO ₂ and SiO ₂ , AlN, SiO ₂ and TiO ₂ , and Nb ₂ O ₅ . In particular, a laser element having a high COD level can be manufactured by using an Al ₂ O ₃ film or an AlN film as the first layer of the reflection side mirror 39R.

The exit mirror 39F has a single layer or a multilayer structure using two or more kinds of materials. For example, AlN single layer, AlN and SiO ₂ , AlN and SiO ₂ and ZrO ₂ , AlN and SiO ₂ and Al ₂ O ₃ , AlN and SiO ₂ , Al ₂ O ₃ and ZrO ₂ , Al ₂ O ₃ , Al ₂ O ₃ and ZrO ₂ , Al ₂ O ₃ and ZrO ₂ and SiO ₂ , ZrO ₂ and SiO ₂ , TiO ₂ and SiO ₂ , AlN, SiO ₂ and TiO ₂ , and Nb ₂ O ₅ . In particular, a laser element having a high COD level can be manufactured by using an Al ₂ O ₃ film or an AlN film as the first layer of the emission side mirror 39F.

  In this nitride semiconductor laser device 31, the film thickness is adjusted so that the wavelength of the reflectance peak of the reflection side mirror 39R and / or the emission side mirror 39F is on the long wavelength side, for example, 10 nm or more with respect to the peak of the spontaneous emission wavelength. By doing so, a long wavelength laser beam of 450 nm or more can be emitted from the emission side mirror 39F.

ここで、J_th：閾値電流密度、Γ：閉じ込め係数、d：井戸層総厚み、R1：出射側ミラーの反射率、R2：反射側ミラーの反射率、J₀：利得を発生させるに必要な電流密度、L：共振器長、α：損失、β：伝搬定数である。 These were calculated from the formula for obtaining the threshold current density shown below.

Here, J _th : threshold current density, Γ: confinement factor, d: total well layer thickness, R1: reflectance of output side mirror, R2: reflectance of reflection side mirror, J ₀ : necessary for generating gain Current density, L: resonator length, α: loss, β: propagation constant.

By substituting the confinement factor (Γ), the reflectivity (R2) of the reflection side mirror, and the reflectivity (R1) of the output side mirror into this equation for each wavelength, the threshold currents of the conventional laser and the semiconductor laser device of the present invention are obtained. FIG. 7 shows the result of plotting the relationship between the wavelength and the wavelength. FIG. 7 shows the relationship between the threshold current density and the oscillation wavelength in one embodiment of the present invention and a conventional semiconductor laser device. At this time, d = 6 nm, α = 20 cm ⁻¹ , L = 600 μm, respectively, and J ₀ = 0 for simplicity. In the conventional example, the threshold current density increases as the wavelength shifts to a longer wavelength. On the other hand, in the semiconductor laser device according to the embodiment of the present invention, when the wavelength shifts to the long wavelength side, the threshold current density decreases sharply in the vicinity of 480 to 490 nm. This also indicates that the semiconductor laser device of the present invention can easily oscillate on the long wavelength side. In this example, the wavelength region where the threshold current sharply decreases is 480 to 490 nm. However, by adjusting the reflectance (R2) of the reflection side mirror and the reflectance (R1) of the emission side mirror, this wavelength region can be reduced. It is possible to shift to the longer wavelength side, and it is possible to easily increase the laser oscillation wavelength. Further, the semiconductor laser device manufactured in this manner oscillated at 491 nm as described later in Example 1.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on the Example of this invention, the following Examples do not limit this invention.
Example 1
First, on the n-type GaN substrate wafer, a first conductivity type nitride semiconductor layer, an active layer, and a second conductivity type nitride semiconductor layer are sequentially laminated to produce a nitride semiconductor laser device having the structure shown in FIG. did.
Here, the first conductivity type nitride semiconductor layer is an n-layer structure in which a first buffer layer (n-side AlGaN), a second buffer layer (n-side InGaN), an n-side cladding layer, and an n-side guide layer are stacked in order. A side nitride semiconductor layer was formed.

As the first buffer layer, a layer containing Si of about 10 ¹⁸ / cm ^{3 and having} a composition formula of Al _0.02 Ga _0.98 N and a film thickness of 0.5 μm was formed. This layer also serves as a regrowth buffer layer with the substrate.

Next, as the second buffer layer, the composition formula containing about 10 ¹⁸ / cm ^{3 of} Si on the first buffer layer is In _0.04 Ga _0.96 N, and the film thickness is 0.15 μm. A layer was formed. This second buffer layer has a role of suppressing the occurrence of cracks and the like.
Further, on the second buffer layer, as an n-side cladding layer, a composition formula containing about 10 ¹⁸ / cm ^{3 of} Si is Al _0.04 Ga _0.96 N, and the film thickness is 1.2 μm. A layer was formed.

Next, a composition formula containing about 10 ¹⁸ / cm ^{3 of} Si as an n-side guide layer on the n-side cladding layer is In _0.04 Ga _0.96 N, and the film thickness is 20 mm. A superlattice structure of one layer and a second layer having a composition formula of GaN and a film thickness of 40 mm was formed with a total film thickness of 0.06 μm. These layers exhibit n-type conductivity without Si doping.

Next, an active layer is formed on the n-side nitride semiconductor layer having the multilayer structure.
First, a first barrier layer having a composition formula containing Si of about 10 ¹⁸ / cm ^{3 and} In _0.04 Ga _0.96 N and a thickness of 900 形成 was formed. Next, a GaN layer containing about 10 ¹⁸ to 10 ¹⁹ / cm ³ of Si having a thickness of 150 Å was formed on the first barrier layer.
Next, a first well layer having a composition formula of In _0.20 Ga _0.80 N and a thickness of 30 mm was formed on the first barrier layer.

Further, on the first well layer, a layer having a composition formula of GaN and a thickness of 100 mm was formed as the second barrier layer.
On the second barrier layer, a layer having a composition formula of In _0.20 Ga _0.80 N and a thickness of 30 mm was formed as the second well layer.

Further, on the second well layer, a layer having a composition formula of GaN and a thickness of 100 mm was formed as a third barrier layer.
On the third barrier layer, a layer having a composition formula of In _0.20 Ga _0.80 N and a thickness of 30 mm was formed as a third well layer.
Finally, a layer having a composition formula of GaN and a film thickness of 200 mm was formed as a fourth barrier layer on the third well layer.

  Next, a second conductivity type nitride semiconductor layer is stacked on the active layer. This second-conductivity-type nitride semiconductor layer includes a p-side nitridation having a multilayer structure in which a first carrier confinement layer, a second carrier confinement layer, a p-side guide layer, a p-side cladding layer, and a p-side contact layer are stacked in this order. A physical semiconductor layer was formed.

First, as a first carrier confinement layer, a layer containing about 10 ¹⁸ / cm ³ of Mg and having a composition formula of Al _0.15 Ga _0.85 N and a thickness of 30 mm was formed.
Then, the composition formula containing about 10 ¹⁹ / cm ³ of Mg as the second carrier confinement layer on the first carrier confinement layer is Al _0.25 Ga _0.75 N, and the film thickness is 100 mm. A layer was formed.

Next, an undoped In _0.04 Ga _0.96 N layer having a thickness of 700 mm was formed as a p-side guide layer on the second carrier confinement layer. Next, an undoped GaN layer having a thickness of 400 mm was formed on the In _0.04 Ga _0.96 N layer. These layers may not be doped with Mg but may be doped with Mg.

Next, on the p-side guide layer, as a p-side cladding layer, a first layer having a composition formula of Al _0.12 Ga _0.88 N and a film thickness of 25 mm, and Mg of about 10 ¹⁸ / cm ³ a GaN containing, thickness to form a layer of the super lattice structure of total thickness 0.45μm comprising the second layer is 25 Å.

Finally, on the p-side cladding layer, a layer containing GaN having a composition formula containing about 10 ²⁰ / cm ^{3 of} Mg and having a thickness of 150 mm was formed as a p-side contact layer.

  A laminated semiconductor of a semiconductor laser element was formed with the above laminated structure. The spontaneous emission spectrum of this laminated semiconductor has a peak wavelength of 490 nm and a half-value width of the emission wavelength of 50 nm.

Next, a ridge was formed in the upper region from the middle of the p-side cladding layer, the interface between the p-side cladding layer and the p-side guide layer, the middle of the p-side guide layer, and the like. An insulating film was formed on both sides of the ridge, and a p-electrode was formed on the surface of the p-side contact layer, which is the upper surface of the ridge. Furthermore, a pad electrode electrically connected to the p electrode was formed. An n electrode was formed on the back surface of the n-type GaN substrate.
Thereafter, the wafer was cleaved into a bar shape with the cleaved surface as the resonance surface.

Next, a mirror was formed on the resonance surface.
Then, a reflection-side mirror was formed on the nitride semiconductor on one end of the resonance surface, and an emission-side mirror was formed on the resonance surface on the other end, and then formed into a chip to obtain a nitride-based semiconductor laser device.

The reflection-side mirror is formed by first forming an Al ₂ O ₃ film with a thickness of 1647 on the resonant surface of the laminated semiconductor including the substrate, and then forming a ZrO ₂ film with a thickness of 613 mm and an Al ₂ O with a thickness of 837 mm. Eight pairs of _three films were alternately formed, and finally an Al ₂ O ₃ film having a thickness of 837 mm was formed. The total film thickness of this reflection side mirror was 14111 mm.
The reflectivity R2 (λ) of the reflection side mirror is such that the mirror reflectivity peak is 96% at a wavelength of 530 nm, and the reflectivity 29% (96 × 0.3) wavelength (from the mirror reflectivity peak). The wavelength on the short wavelength side) was 475 nm.

The exit-side mirror first forms an Al ₂ O ₃ film with a thickness of 1647 on the resonance surface at the other end from the reflection-side end face, and then forms a ZrO ₂ film with a thickness of 613 mm and a thickness of 837 mm. Five pairs of Al ₂ O ₃ films were alternately formed, and finally an Al ₂ O ₃ film having a thickness of 837 mm was formed. The total film thickness of the exit side mirror was 9761 mm.
The reflectivity R1 (λ) of the output side mirror has a reflectivity peak of 83% at a wavelength of 525 nm and a reflectivity of 25% (83 × 0.3) wavelength (shorter than the reflectivity peak of the mirror). Side wavelength) was 465 nm.

  With respect to the nitride-based semiconductor laser device fabricated as described above, the reflectivity of the reflection side mirror is as shown in FIG. 4, the reflectivity of the exit side mirror is as shown in FIG. 5, and the obtained oscillation spectrum is as shown in FIG. Had an oscillation peak at 491 nm.

Example 2
A semiconductor laser device having the same structure as the semiconductor laser device of Example 1 was manufactured except that the first buffer layer and the second buffer layer were omitted. In the semiconductor laser device having such a structure, stable optical confinement can be realized. This semiconductor laser element has an oscillation peak at 490 nm.

Example 3
A semiconductor laser device having the same structure as the semiconductor laser device of Example 1 was manufactured except that the structure of the n-side guide layer and the active layer was changed to the following structure.
Specifically, the n-side guide layer formed on the n-side cladding layer was an undoped In _0.04 Ga _0.96 N layer having a thickness of 0.10 μm. These layers may be doped with Si.

Next, the first barrier layer of the active layer formed on the n-side guide layer was a GaN layer having a thickness of 150 mm and containing Si of about 10 ¹⁸ / cm ³ . The structure of other active layers was the same as that in Example 1.
With respect to the nitride semiconductor laser element manufactured as described above, the obtained oscillation spectrum is a semiconductor laser element having an oscillation peak at 490 nm.

Example 4
A semiconductor laser element having the same structure as that of the semiconductor laser element of Example 1 was manufactured except that the laminated semiconductor was formed under the following conditions.
The first conductivity type nitride semiconductor layer formed on the GaN substrate includes an n-side nitride semiconductor layer having a multilayer structure in which a first buffer layer, a second buffer layer, an n-side cladding layer, and an n-side guide layer are sequentially stacked. did.

As the first buffer layer, a layer containing Si of about 10 ¹⁸ / cm ^{3 and having} a composition formula of Al _0.02 Ga _0.98 N and a film thickness of 2 μm was formed.
Next, as the second buffer layer, the composition formula containing about 10 ¹⁸ / cm ^{3 of} Si on the first buffer layer is In _0.06 Ga _0.94 N, and the film thickness is 0.15 μm. A layer was formed.
Further, the composition formula containing about 10 ¹⁸ / cm ^{3 of} Si as the n-side cladding layer on the second buffer layer is Al _0.03 Ga _0.97 N, and the film thickness is 1.2 μm. A layer was formed.

Next, a composition formula containing about 10 ¹⁸ / cm ^{3 of} Si as an n-side guide layer on the n-side cladding layer is In _0.04 Ga _0.96 N, and the film thickness is 10 mm. A superlattice structure of one layer and a second layer having a composition formula of GaN and a film thickness of 20 mm was formed with a total film thickness of 0.24 μm.

Next, an active layer was formed on the n-side nitride semiconductor layer having the multilayer structure.
First, a first barrier layer having a composition formula containing Si of about 10 ¹⁸ / cm ³ was In _0.04 Ga _0.96 N and a thickness of 700 mm was formed. Next, a GaN layer having a thickness of 10 mm was formed on the first barrier layer.
A first well layer having a composition formula of In _0.20 Ga _0.80 N and a thickness of 30 mm was formed on the first barrier layer.

Furthermore, a layer having a composition formula of GaN and a film thickness of 140 mm was formed as a second barrier layer on the first well layer.
On the second barrier layer, a layer having a composition formula of In _0.20 Ga _0.80 N and a thickness of 30 mm was formed as the second well layer.
Finally, a layer having a composition formula of In _0.04 Ga _0.96 N and a thickness of 700 mm was formed as a third barrier layer on the second well layer.

  Next, a p-side nitride having a multilayer structure in which a first carrier confinement layer, a second carrier confinement layer, a p-side guide layer, a p-side cladding layer, and a p-side contact layer are stacked in this order on the active layer. A semiconductor layer was formed.

First, as a first carrier confinement layer, a layer containing about 10 ¹⁸ / cm ³ of Mg and having a composition formula of Al _0.15 Ga _0.85 N and a thickness of 30 mm was formed.
The composition formula containing about 10 ¹⁹ / cm ³ of Mg as the second carrier confinement layer on the first carrier confinement layer is Al _0.25 Ga _0.75 N, and the film thickness is 70 mm. A layer was formed.

Next, on the second carrier confinement layer, as a p-side guide layer, a first layer having a composition formula of IN _0.04 Ga _0.96 N and a film thickness of 10 mm, and Mg of about 10 A superlattice structure layer having a total film thickness of 0.24 μm, which is composed of a second layer having a composition formula of ¹⁷ / cm ³ containing GaN and a film thickness of 20 mm, was formed.

Next, on the p-side guide layer, as a p-side cladding layer, a first layer having a composition formula of Al _0.12 Ga _0.88 N and a film thickness of 25 mm, and Mg of about 10 ¹⁸ / cm ³ a GaN containing, thickness to form a layer of the super lattice structure of total thickness 0.45μm comprising the second layer is a 25 Å.

Finally, on the p-side cladding layer, a layer containing GaN having a composition formula containing about 10 ²⁰ / cm ^{3 of} Mg and having a thickness of 150 mm was formed as a p-side contact layer.

  The laminated semiconductor formed by the above laminated structure constitutes a laser emission unit. This semiconductor laser element is a semiconductor laser element having a spontaneous emission spectrum peak wavelength of 510 nm and an oscillation peak at 490 nm.

Example 5
In the semiconductor laser device of this example, in Example 1, the In mixed crystal of the well layer constituting the active layer is adjusted so that the peak wavelength of the spontaneous emission spectrum is 530 nm, and the wavelength of the reflectance peak of the mirror is set. 570 nm. The reflectance distribution diagram of the output side mirror in this semiconductor laser element is as shown in FIG. 9, and the reflectance distribution diagram of the reflection side mirror is as shown in FIG.

The output side mirror first forms an Al ₂ O ₃ film with a thickness of 1734 、, and then forms five pairs of 635 Ｚ ZrO ₂ films and an 867 膜厚 Al ₂ O ₃ film alternately. Finally, an Al ₂ O ₃ film having a thickness of 867 mm was formed. The total film thickness of the exit side mirror was 10111 mm.

  The reflectance R1 (λ) of the output side mirror is such that the reflectance peak is 85% at a wavelength of 570 nm, 83% (85 × 0.98) at a wavelength of 540 nm, and 26% (85 × 0. The reflectance of 3) is shown.

For the reflection side mirror, first, an Al ₂ O ₃ film having a thickness of 1734 mm was formed on a nitride semiconductor. Next, eight pairs of 635 mm thick ZrO ₂ films and 867 mm thick Al ₂ O ₃ films were alternately formed, and finally 867 mm thick Al ₂ O ₃ films were formed. The total film thickness of this reflection side mirror was 14617 mm.
The reflectivity R2 (λ) of the reflection side mirror has a reflectivity peak of 97% at a wavelength of 570 nm, a reflectivity of 95% (97 × 0.98) at a wavelength of 530 nm, and 29% (97 × at a wavelength of 500 nm). 0.3) reflectivity.

  The semiconductor laser device manufactured as described above has an oscillation peak at 510 nm.

Example 6
The semiconductor laser device of this example has a multilayer film structure including ZrO ₂ and SiO ₂ in which the reflection side mirror is formed under the following conditions in Example 5. The reflectance distribution diagram of the mirror with respect to the wavelength of the reflection side mirror in this semiconductor laser device is as shown in FIG. The other conditions are the same as in Example 5.

For the reflection-side mirror, first, a ZrO ₂ film having a thickness of 646 mm was formed on the resonance surface of the laminated semiconductor. Next, 6 pairs of 972 Å thick SiO ₂ films and 646 Ｚ ZrO ₂ films were formed alternately. The total film thickness of this reflection side mirror was 10354 mm.
The reflectance R2 (λ) of this reflection side mirror is such that the reflectance peak is 98% at a wavelength of 580 nm, a reflectance of 96% (98 × 0.98) at a wavelength of 530 nm, and 29% (96 × 0. The reflectance of 3) is shown.

  The semiconductor laser device manufactured as described above is a semiconductor laser device having an oscillation peak at 510 nm.

Example 7
The semiconductor laser device of this example has a multilayer film structure including ZrO ₂ and SiO ₂ in which the reflection side mirror is formed under the following conditions in Example 5. The reflectance distribution diagram of the mirror with respect to the wavelength of the reflection side mirror in this semiconductor laser device is as shown in FIG. The other conditions are the same as in Example 5.

In the reflection side mirror, first, a ZrO ₂ film having a thickness of 668 mm is formed on the resonance surface of the laminated semiconductor. Next, six pairs of SiO ₂ films having a thickness of 1006 と and ZrO ₂ films having a thickness of 668 交互 are alternately formed. The total film thickness of this reflection side mirror was 10712 mm.
The reflectivity R2 (λ) of the reflection side mirror shows a reflectivity peak of 98% at a wavelength of 600 nm, a reflectivity of 96% (98 × 0.98) at a wavelength of 550 nm, and 29% at a wavelength of 510 nm ( 98 × 0.3) reflectivity.

  The semiconductor laser device fabricated as described above has an oscillation peak at 530 nm.

Example 8
In the semiconductor laser device of this example, the In mixed crystal of the well layer is adjusted so that the peak wavelength of the spontaneous emission spectrum is 540 nm in Example 5, and the reflection side mirror is made of a multilayer of ZrO ₂ and SiO ₂ . It is a film structure. The reflectance distribution diagram of the mirror with respect to the wavelength of the reflection-side mirror in this semiconductor laser element is as shown in FIG. The other conditions are the same as in Example 5.

Specifically, the first well layer was formed with a composition formula of In _0.25 Ga _0.80 N and a film thickness of 30 mm. The second well layer was formed with a composition formula of In _0.25 Ga _0.80 N and a thickness of 30 mm. Further, the third well layer was formed with a composition formula of In _0.25 Ga _0.80 N and a film thickness of 30 mm.

For the reflection side mirror, first, a ZrO ₂ film having a thickness of 691 mm was formed on the resonance surface of the laminated semiconductor. Next, 6 pairs of SiO ₂ films having a thickness of 1039 mm and ZrO ₂ films having a thickness of 691 mm were alternately formed. The total film thickness of this reflection side mirror was 11071 mm.
The reflectivity R2 (λ) of the reflection-side mirror has a mirror reflectivity peak of 98% at a wavelength of 620 nm, a reflectivity of 96% (98 × 0.98) at a wavelength of 565 nm, and 29% at a wavelength of 526 nm ( 98 × 0.3) reflectivity.
The manufactured semiconductor laser element has an oscillation peak at 550 nm.

It is a conceptual diagram explaining the main structures of the semiconductor laser element of this invention. It is a figure which shows the spontaneous emission spectrum of peak wavelength (lambda) ₀ of the semiconductor laser element 1 of this invention. It shows the reflectance in the case where is changing the number of pairs mirror of SiO ₂ and ZrO ₂ Metropolitan. It is a mirror reflectance distribution map with respect to the wavelength of the reflection side mirror based on embodiment of this invention. It is a mirror reflectance distribution map with respect to the wavelength of the output side mirror based on embodiment of this invention. (A) is a schematic cross-sectional view showing the structure of a semiconductor laser device according to an embodiment of the present invention, and (B) is a perspective view showing the semiconductor laser device. It is a threshold current density distribution figure with respect to the wavelength calculated | required by calculation about the semiconductor laser element which concerns on embodiment of this invention. It is an oscillation spectrum figure of the semiconductor laser element of this invention. It is a mirror reflectance distribution map with respect to the wavelength of the output side mirror based on embodiment of this invention. It is a mirror reflectance distribution map with respect to the wavelength of the reflection side mirror based on embodiment of this invention. It is a mirror reflectance distribution map with respect to the wavelength of the reflection side mirror based on embodiment of this invention. It is a mirror reflectance distribution map with respect to the wavelength of the reflection side mirror based on embodiment of this invention. It is a mirror reflectance distribution map with respect to the wavelength of the reflection side mirror based on embodiment of this invention. It is a figure which shows the relationship between the wavelength and optical confinement coefficient in a long wavelength laser element whose oscillation wavelength is 450 nm or more.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser element 2 Output side mirror 3 Reflection side mirror 4 Active layer 5 2nd conductivity type semiconductor layer 6 1st conductivity type semiconductor layer 7 Multilayer semiconductor

Claims (6)

A semiconductor laser device comprising: a laminated semiconductor; an emission side mirror disposed on a laser emission side end face of the laminated semiconductor; and a reflection side mirror provided on an end face opposite to the laser emission side end face,
The peak wavelength λ _{1 at} which the reflectance R 1 (λ) with respect to light of wavelength λ in the emission side mirror becomes maximum, and the peak wavelength λ _{2 at which the} reflectance R 2 (λ) with respect to light of wavelength λ in the reflection side mirror becomes maximum. Wherein the peak wavelength λ ₀ of the spontaneous emission spectrum of the stacked semiconductor has a relationship of λ ₁ > λ ₀ and / or λ ₂ > λ ₀ . The reflectance R2 (λ ₂ ) at the peak wavelength λ ₂ of the reflection side mirror, the reflectance R 2 (λ ₃ ) at the wavelength λ _{3 which} is 1.00 times the reflectance R 2 (λ ₂ ), and the reflectance The relationship represented by the following expressions (1), (2), and (3) is the reflectance R2 (λ ₄ ) at a wavelength λ _{4 that} is 0.30 times R2 (λ ₂ ) and the oscillation wavelength λp. The semiconductor laser device according to claim 1, comprising:
R2 (λ ₃ ) = R2 (λ ₂ ) × 1.00 (1)
R2 (λ ₄ ) = R2 (λ ₂ ) × 0.30 (2)
λ ₃ >λp> λ ₄ (3) The reflectance R1 (λ ₁ ) at the peak wavelength λ ₁ of the output side mirror, the reflectance R ₁ (λ ₅ ) at the wavelength λ _{5 that} is 1.00 times the reflectance R ₁ (λ ₁ ), and the reflectance The relationship represented by the following equations (4), (5), and (6) is the reflectance R1 (λ ₆ ) at a wavelength λ _{6 that} is 0.30 times R1 (λ ₁ ) and the oscillation wavelength λp. The semiconductor laser device according to claim 1, wherein:
R1 (λ ₅ ) = R1 (λ ₁ ) × 1.00 (4)
R1 (λ ₆ ) = R1 (λ ₁ ) × 0.30 (5)
λ ₅ >λp> λ ₆ (6)   4. The semiconductor laser device according to claim 1, wherein the stacked semiconductor is a III-V group compound semiconductor. 5.   The semiconductor laser device according to claim 4, wherein the wavelength of the laser beam emitted from the emission side mirror is 450 nm or more.   6. The semiconductor laser device according to claim 1, wherein the output side mirror and / or the reflection side mirror includes an oxide film or a nitride film.

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