JP4556591B2 - Semiconductor laser device - Google Patents

Description

  The present invention relates to a semiconductor laser device that increases light output by bringing light emitting points of a plurality of semiconductor laser elements close to each other. The present invention relates to a semiconductor laser device used as a light source for an optical communication, optical measurement, optical disc, and other exposure devices.

  As a semiconductor laser element, a gallium arsenide (GaAs) semiconductor laser element in which a compound semiconductor such as AlGaAs, InGaAlP, or InGaAsP is stacked on a GaAs substrate has been used. In addition, development of gallium nitride (GaN) semiconductor laser elements and the like having shorter oscillation wavelengths is steadily progressing and is approaching mass production. For example, an AlGaAs-based 780 nm laser element is used for a CD standard, an InGaAlP-based 650 nm laser element is used for a DVD standard, and an InGaAlN 400 nm laser element is used for a large capacity recording apparatus.

An exposure apparatus that exposes a photosensitive material using a semiconductor laser element is used in various applications such as a laser printer. The laser printer is equipped with R, G, and B laser light sources, and irradiates the photographic paper, which is a silver salt photosensitive material, with a laser beam modulated in accordance with the recording image data input from the image processing unit, thereby scanning exposure. To record an image (latent image) on the photographic paper. In order to improve the exposure image quality, it is effective to shorten the laser light wavelength itself to make the laser light spot diameter as small as possible. A specific example of the exposure apparatus is an image exposure apparatus that exposes a photosensitive material.
JP 2002-118331 A

  Patent Document 1 describes a configuration that enables two-wavelength integration using two semiconductor laser elements made of different semiconductors. However, the integrated semiconductor laser device described in Patent Document 1 has a structure in which LD1 and LD2 face each other, but each contact layer exists above the cap layer that is the uppermost layer of the ridge. The contact layers are joined together. Therefore, the distance between the light emitting points of LD1 and LD2 is large.

  There is also a problem of stability when LD1 and LD2 are joined. The reason is that the semiconductor layer at the junction surface of LD1 and LD2 uses GaN for the contact layer of LD1 and GaAs for the contact layer of LD2, resulting in a difference in thermal expansion coefficient and lattice constant. Since the contact area between the contact layers is on the entire surface, the semiconductor laser element is warped or cracked. In this case, the distance between the light emitting points of LD1 and LD2 is different for each semiconductor laser device. If the distance between the light emitting points of LD1 and LD2 is long or there is no light emitting point of LD2 above the light emitting point of LD1, it is difficult to collect light with one lens.

The present invention has been made in view of such a point, and an object thereof is to provide a semiconductor laser device having the same wavelength, high output, and high reliability.
It is another object of the present invention to provide a semiconductor laser device with an easy and reliable apparatus configuration when using a plurality of laser beams having different wavelengths.

  The semiconductor laser device of the present invention is a semiconductor laser device in which the upper surfaces of the ridge stripe portions of the first semiconductor laser element and the second semiconductor laser element on the first semiconductor laser element face each other. The first semiconductor laser element has a current confinement layer on both sides of the ridge stripe portion, and the current confinement layer includes a first region having a height that varies in order as the distance from the ridge stripe portion increases. And the second region is higher than the upper surface of the ridge stripe portion.

As shown in the above configuration, since the second region of the current confinement layer in the first semiconductor laser element is higher than the upper surface of the ridge portion, the first semiconductor laser element and the second semiconductor laser element are joined at the time of bonding. The two regions are direct contact interfaces or nearest neighbors. With this configuration, since damage to the semiconductor laser element, particularly the ridge stripe portion, generated at the time of bonding can be released to the second region side, the light emitting points of the two semiconductor laser elements can be set without causing unnecessary damage to the ridge stripe portion. You can get closer.
In addition, since the first semiconductor laser element has a current confinement layer, the uppermost surface of the semiconductor layer is bonded to the entire surface even when the first semiconductor laser element is bonded directly or via a eutectic material to the second semiconductor laser element. Absent. Therefore, even when the semiconductor layer materials of the first semiconductor laser element and the second semiconductor laser element are different, the light emitting points of the two semiconductor laser elements are set at a certain distance without being affected by the difference in the lattice constants. Can be kept in.

  In the semiconductor laser device of the present invention, it is preferable that the first region of the current confinement layer in the first semiconductor laser element is substantially the same height as the upper surface of the ridge stripe portion. As a result, the stress on the ridge stripe portion of the first semiconductor laser element is absorbed by the current confinement layer having substantially the same height. Therefore, it is possible to suppress the stress applied to the ridge portion and form a semiconductor laser device with good lifetime characteristics. Also, the width of the ridge portion is limited depending on the application of the semiconductor laser device. For optical disc use, the width of the ridge portion is 1.0 μm to 5.0 μm. When such a semiconductor laser element having a narrow ridge width is used as the first semiconductor laser element, the above configuration is effective for suppressing chipping and cracking of the ridge.

  In the semiconductor laser device of the present invention, the width of the ridge stripe of the second semiconductor laser element is preferably wider than the width of the ridge stripe in the first semiconductor laser element. With such a configuration, even if a eutectic material such as solder is interposed at the interface between the first semiconductor laser element and the second semiconductor laser element, the stress from the second semiconductor laser element is the first. Damage at the time of bonding can be absorbed by the current confinement layers at both ends of the ridge portion, not at the top surface of the ridge of the semiconductor laser device. Further, when the second semiconductor laser element has a wide stripe and the first semiconductor laser element and the second semiconductor laser element have the same oscillation wavelength as shown in the above configuration, a collimating lens is used. A high-power semiconductor laser device can be obtained by condensing the laser beam.

  In the semiconductor laser device of the present invention, the resonator of the first semiconductor laser element is preferably longer than the resonator of the second semiconductor laser element. In particular, since a semiconductor laser element made of an InGaAlN-based material has better temperature characteristics than other materials, it is preferable to make the resonator length longer than that of other semiconductor laser elements. Therefore, a semiconductor laser element made of an InGaAlN-based material is used as a first semiconductor laser element, and a semiconductor laser element made of another material is used as a second semiconductor laser element.

  In the semiconductor laser device, the distance between the light emitting point of the first semiconductor laser element and the light emitting point of the second semiconductor laser element is preferably 10 μm or less, more preferably 5 μm or less. Since the semiconductor laser device of the present invention has no extra configuration other than the solder that is a eutectic material between the ridges, the distance between the light emitting points can be in the above range. As a result, if the oscillation wavelengths of the two semiconductor laser elements are the same, it is easy to condense with the lens. Even if the two semiconductor laser elements have different wavelengths, the pickup can be downsized.

  In the semiconductor laser device, it is preferable that the first semiconductor laser element and the second semiconductor laser element are bonded via a eutectic material. For example, wire bonding can be performed on this through a eutectic material. Specific examples of the eutectic material include Au, Ag, and Sn. The eutectic material exhibits a ripple suppressing effect by using a material having a light absorption effect.

  In the semiconductor laser device, the first semiconductor laser element has a semiconductor layer on a substrate. Since the first semiconductor laser element is located at the lower portion, the structure including the support substrate absorbs damage that occurs during bonding with the second semiconductor laser element. The substrate is made of GaN, Cu-based alloy, or W-based alloy having excellent heat dissipation.

When the semiconductor layer is formed of a nitride semiconductor layer, the general formula is In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). The active layer is sandwiched between the n-side nitride semiconductor layer and the p-side nitride semiconductor layer, and has at least In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and has a single quantum well structure or a multiple quantum well structure. The n-side nitride semiconductor layer has an n-type nitride semiconductor layer containing at least an n-type impurity. The n-type impurity is any one of Si, Ge, O, and the like. The p-side nitride semiconductor layer has a p-type nitride semiconductor layer containing at least a p-type impurity. Examples of the p-type impurity include Mg and Zn.

  The semiconductor laser device of the present invention can be a device in which the pickup is downsized and reproducible. If the oscillation wavelengths of the two semiconductor laser elements are the same, higher output can be realized. In addition, even if the materials of the semiconductor layers are different, it is possible to provide a semiconductor laser device having excellent life characteristics and element characteristics of the respective semiconductor laser elements.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view schematically showing the structure of the semiconductor laser device 10 according to the first embodiment. In this semiconductor laser device, upper and lower semiconductor laser elements shown in FIG. 2 are joined via a eutectic material 30. The first semiconductor laser element 100 and the second semiconductor laser element 200 are made of a nitride semiconductor and are formed on the upper surface of the nitride semiconductor substrate.

  As shown in FIG. 2, the first semiconductor laser device 100 according to the present embodiment includes an n-side nitride semiconductor layer 120, an active layer 130 containing In, and a first main surface of a nitride semiconductor substrate 101. , A p-side nitride semiconductor layer 140, a striped ridge portion on the p-side nitride semiconductor layer, and a p-electrode 52 on the p-side nitride semiconductor layer. 2 is a nitride semiconductor laser element having a counter electrode structure having an n-electrode 51 on the main surface, and has a current confinement layer 150 on both sides of the ridge portion. Is provided with a heat sink via an n-electrode 51. Here, the first main surface and the second main surface of the nitride semiconductor substrate are main surfaces facing each other. The semiconductor laser element has an SCH (Separate Confinement Heterostructure) structure that is a separated light confinement structure in which an active layer containing In is sandwiched between an n-side semiconductor layer and a p-side semiconductor layer.

  The second semiconductor laser element 200 is formed on the first semiconductor laser element as shown in FIG. Similarly to the first semiconductor laser element, the n-side nitride semiconductor layer 220, the In-containing active layer 230, the p-side nitride semiconductor layer 240, and the p-side nitride semiconductor layer are striped on the substrate 201. And a p-electrode 53 on the p-side nitride semiconductor layer. The p-electrode of the second semiconductor laser element 200 is joined to the first semiconductor laser element via the eutectic material 30. A wire is bonded to the second main surface of the substrate 201 through an n-electrode 54.

  A wire 130 is bonded to the eutectic material 30. The eutectic material may be an alloyed single layer or a multilayer structure made of a conductive material. Here, the wire 130 is electrically joined to the p-electrode 52 of the first semiconductor laser element 100 and the p-electrode 53 of the second semiconductor laser element 200. The first semiconductor laser element and the second semiconductor laser element can be driven independently. Further, the two semiconductor laser elements in the present embodiment are laser elements having the same oscillation wavelength.

Hereinafter, although the manufacturing method of a 1st semiconductor laser element is demonstrated, this invention is not necessarily limited to the following.
(First step)
First, the nitride semiconductor substrate 101 is formed. This may have a single substrate made of a nitride semiconductor, or a support substrate made of sapphire, SiC, GaAs, or the like, which is a different material from the nitride semiconductor. The main surface of the substrate is, for example, a (0001) plane, a (11-20) plane, or a (1-100) plane. In the present specification, a bar (-) in parentheses representing an area index represents a bar to be added on the back number.

A buffer layer made of Al _x Ga _1-x N (0 ≦ x ≦ 1) is grown on the main surface of the substrate using a vapor phase growth method (the buffer layer is not shown). The growth temperature of the buffer layer is set to 900 ° C. or lower. The buffer layer can be omitted. The thickness of the substrate is from 50 μm to 10 mm, preferably from 100 μm to 1000 μm. The nitride semiconductor substrate 101 may be a substrate having an off angle. The manufacturing method of the nitride semiconductor substrate 101 includes MOCVD method using ELO method or selective growth method, vapor phase growth method such as HVPE method, MBE method, etc., hydrothermal synthesis method for crystal growth in supercritical fluid, There are high pressure method, flux method, melting method and so on.

In the nitride semiconductor substrate 101, for example, the first region and the second region are periodically distributed in the plane. In the case where the first region and the second region are alternately stripe-formed using the ELO method, the effect of relieving the stress generated inside the nitride semiconductor works, so that the nitride semiconductor can be used as a substrate. The nitride semiconductor layer can be laminated with a thickness of 5 μm or more without forming a stress relaxation layer on the substrate. The stripe includes one formed in a broken line shape.
The number of dislocations per unit area of the nitride semiconductor substrate is 1 × 10 ⁷ / cm ² or less, preferably 1 × 10 ⁶ / cm ² or less. These dislocations are measured by CL observation, TEM observation, or the like.

Examples of the nitride semiconductor substrate include GaN and AlN that are compounds of group III elements B, Ga, Al, In, and the like and nitrogen, and AlGaN and InAlGaN that are ternary and quaternary mixed crystal compounds. The nitride semiconductor substrate preferably contains an n-type impurity or a p-type impurity. Examples of the n-type impurity include Si, Ge, Se, S, and O. The impurity concentration of the n-type impurity or the p-type impurity is 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ . The outer peripheral shape of the nitride semiconductor substrate is not particularly limited, and may be a wafer shape, a rectangular shape, or the like. In the case of a wafer shape, the size is 1 inch or more.

(Second step)
Next, the nitride semiconductor layer 10 is grown on the first main surface of the nitride semiconductor substrate having an off angle. In the present embodiment, the following layers are grown under conditions of reduced pressure to atmospheric pressure by MOCVD. The nitride semiconductor layer 10 is stacked on the first main surface of the nitride semiconductor substrate in the order of an n-side nitride semiconductor layer, an active layer, and a p-side nitride semiconductor layer. Note that the n-side nitride semiconductor layer and the p-side nitride semiconductor layer are multilayer films.
The n-side nitride semiconductor layer 120 is Al _x Ga _1-x N (0 <x ≦ 0.5), preferably Al _x Ga _1-x N (0 <x ≦ 0.3). The first n-side nitride semiconductor layer 11 containing Al is preferably formed by lateral growth. As specific conditions for the lateral growth, 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-side nitride semiconductor layer 11 can also function as a cladding layer. The film thickness is 0.5-5 μm. Next, the second n-side nitride semiconductor layer 12 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.

Next, the active layer 130 has a 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 film thickness of the well layer is 30 to 200 angstroms, and the film thickness of the barrier layer is 20 to 300 angstroms. It is preferable to repeat the pair of the well layer and the barrier layer 2 to 3 times to lower the threshold value and improve the life characteristics.

Next, the p-side nitride semiconductor layer 140 is stacked on the active layer. The first p-side nitride semiconductor layer 16 is p-type impurity doped Al _x Ga _1-x N (0 ≦ x ≦ 0.5). The first p-side nitride semiconductor layer 16 functions as a p-side electron confinement layer. Next, Al _x Ga _1-x N (0 ≦ x ≦ 0.3) is used as the second p-side nitride semiconductor layer 17, and p-type impurity doped Al _x Ga _{1− is used} as the third p-side nitride semiconductor layer 18. _xN (0 ≦ x ≦ 0.5) and p-type impurity-doped Al _x Ga _1-x N (0 ≦ x ≦ 1) are sequentially formed as the fourth p-side nitride semiconductor layer 19. Further, In may be mixed into these semiconductor layers. The first p-side nitride semiconductor layer 16 can be omitted. The film thickness of each layer is 30 to 5 μm. Each of the layers may have a single-layer structure, a two-layer structure, or a superlattice structure including two layers having different composition ratios.

Examples of the n-type impurity used in this embodiment include Si, Ge, Sn, S, O, Ti, Zr, and Cd. Examples of the p-type impurity include Be, Zn, Mn, Ca, Sr, etc. in addition to Mg. Is mentioned. The doping amount of the n-type impurity is preferably 1 × 10 ¹⁷ / cm ^{3 to} 5 × 10 ¹⁹ / cm ³ . When the n-type impurity is doped in this range, the resistivity can be lowered and the crystallinity is not impaired. The doping amount of the p-type impurity is preferably 1 × 10 ¹⁹ / cm ³ to 1 × 10 ²¹ / cm ³ . When the p-type impurity is doped in this range, the crystallinity is not impaired. When the impurity concentration is higher than 1 × 10 ²¹ / cm ³ , the crystallinity of the nitride semiconductor layer deteriorates, and the output tends to decrease. The same applies to modulation doping. The substrate and the nitride semiconductor layer are grown using vapor phase growth methods such as metal organic chemical vapor deposition (MOCVD), halide vapor phase epitaxy (HVPE), and molecular beam epitaxy (MBE).

(Third step)
The wafer in which the nitride semiconductor layer 10 is laminated on the nitride semiconductor substrate is taken out from the reaction vessel of the semiconductor growth apparatus. Next, the n-side nitride semiconductor layer is exposed by etching. Although the exposed surface of the n-side nitride semiconductor layer is not particularly limited, the first n-side nitride semiconductor layer is exposed in this embodiment. Although this has an effect of stress relaxation, this step can be omitted. Etching is performed by RIE method using Cl ₂ , CCl ₄ , BCl ₃ , SiCl ₄ gas, or the like.

Next, a striped ridge portion 20 is formed in the p-side nitride semiconductor layer. A mask made of SiO ₂ or the like is formed on the surface of the fourth p-side nitride semiconductor layer 19 that is the uppermost layer of the p-side semiconductor layer. The mask pattern has a pattern shape for forming a stripe-shaped ridge portion, and regions other than the stripe-shaped ridge portion are removed by etching. Etching is performed using a RIE method and a chlorine-based gas such as Cl ₂ , CCl ₄ , SiCl ₄ , or BCl ₃ . The width of the ridge portion, which is the waveguide region, is 1.0 μm to 30.0 μm. The length of the resonator is 300 μm to 1000 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-side nitride semiconductor layer 18 is exposed, and may be exposed up to the first p-side nitride semiconductor layer 16. When a large current is applied, the current rapidly spreads in the lateral direction below the ridge. Therefore, the etching depth for forming the ridge is preferably up to the second p-side nitride semiconductor layer 17.

(Fourth process)
Next, a current confinement layer 150 having a first region and a second region is formed on the side surface of the ridge portion. The current confinement layer 150 has a refractive index smaller than that of the semiconductor layer and is selected from insulating materials. Since the nitride semiconductor layer is used in this embodiment, specific examples of the current confinement layer include ZrO ₂ , SiO ₂ , oxides such as V, Nb, Hf, Ta, and Al, and AlN. A manufacturing process of the current confinement layer 150 will be described below.

  First, the side surface of the striped ridge portion 20 is protected by the first mask 21 (FIG. 5a). Here, the heights of the first mask 21 and the fourth p-side nitride semiconductor layer that is the uppermost surface of the p-side semiconductor layer are substantially equal. Next, a p-electrode layer 22 is formed on the surface of the ridge portion and the first mask (FIG. 5b). Since the p electrode layer functions as an etching stop layer in a later step, the p electrode preferably has a multilayer structure. For example, in the case of a two-layer structure composed of Ni and Au, Ni is first formed on the fourth p-side nitride semiconductor layer to a thickness of 50 to 200 mm, and then Au is formed to a thickness of 500 to 3000 mm. . More preferably, the p-electrode has a three-layer structure. Specifically, it is formed in the order of Ni / Au / Pt or Ni / Au / Pd. The final layer, Pt or Pd, is 500 to 5000 mm. After forming the p-electrode, ohmic annealing is performed. As detailed conditions, the annealing temperature is 300 ° C. or higher, preferably 500 ° C. or higher. Further, the atmosphere for annealing is set to a condition containing nitrogen and / or oxygen.

Next, by removing the mask on both sides of the ridge portion and the p-electrode layer thereon by lift-off, the p-electrode 52 is formed, leaving the p-electrode layer only on the fourth p-side nitride semiconductor layer. (FIG. 5c). The p-electrode is preferably formed by a self-alignment method that can simplify the number of steps.
Next, a current confinement layer 150 is formed so as to cover the exposed upper surface of the p-side semiconductor layer and the p-electrode (FIG. 5d). Next, a second mask 23 is formed on the current confinement layer 150 (FIG. 5e). The second mask 23 has a pattern shape having an opening. The current confinement layer is partially etched from this opening to make the current confinement layer have a desired shape, and then the second mask is removed (FIG. 5f). The current confinement layer has a first region a and a second region b in order from the ridge stripe portion, and a stepped portion c is formed between the first region a and the second region b. (FIG. 6). The first region a is adjusted by the width of the opening between the second masks 23. The first region a is 0.5 μm or more and 30 μm or less, preferably 1.0 μm or more and 10 μm or less. Thereby, even when the width of the ridge portion is narrow, deterioration of the ridge portion can be suppressed when the semiconductor laser elements are joined to each other. The second region b is 30 μm or more, preferably 50 μm or more. Thereby, it is possible to absorb an impact generated when the semiconductor laser elements are joined to each other.
Further, the step portion c, which is a step between the first region a and the second region b, is 0.5 μm or more and 30 μm or less, preferably 0.5 μm or more and 10 μm or less. Thereby, the current confinement layer 150 can absorb the impact generated when the semiconductor laser elements are joined to each other. If the stepped portion c is smaller than 0.5 μm, a considerable impact is given to the ridge portion. Further, if the stepped portion c is larger than the above range, the distance between the light emitting points of the semiconductor laser element is undesirably increased. The height d from the bottom surface of the ridge portion to the top surface of the current confinement layer is determined by the height of the stepped portion c and the ridge portion and the electrode 52, but may be 100 μm or less.

(Fifth step)
Thereafter, an n-electrode 51 is formed on the second main surface of the nitride semiconductor substrate 101. An n-electrode is formed on the second main surface of the nitride semiconductor substrate by CVD, sputtering, vapor deposition, or the like. The electrode has at least one selected from the group consisting of Ti, Ni, Au, Pt, Al, Pd, W, Rh, Ag, Mo, V, and Hf. Further, it is preferable that the uppermost layer of the multilayer structure of the electrode is Pt or Au because heat dissipation from the electrode can be improved. The film thickness of the n electrode is 10,000 mm or less, preferably 6000 mm or less. When the n-electrode has a multilayer structure, specifically, the first layer is made of V, Ti, Mo, W, Hf, or the like. Here, the thickness of the first layer is 500 mm or less. Further, if the first layer is W, it is preferable that the thickness is 300 mm or less because good ohmic characteristics can be obtained. If the first layer is V, the heat resistance is improved, which is preferable. Here, when the film thickness of V is 50 to 300 mm, preferably 70 to 200 mm, good ohmic characteristics can be obtained.

When the n electrode 51 is formed in the order of Ti / Al, the thickness of the n electrode is 10000 mm or less, for example, the film thickness is 100 mm / 5000 mm. Further, if the n electrode is laminated in the order of Ti / Pt / Au from the second main surface side of the nitride semiconductor substrate, the film thickness is 60 mm / 1000 mm / 3000 mm. Further, after forming the n-electrode, annealing may be performed at 300 ° C. or higher.
The n electrode is formed in a rectangular shape. The n-electrode is patterned on the second main surface side in a range excluding a region that becomes a scribe line in a scribe process for forming a nitride semiconductor substrate in a subsequent process. Further, when the metallized electrode (which can be omitted) is formed on the n electrode in the same pattern shape as the n electrode, scribing is facilitated and the cleavage property is improved. As metallized electrodes, 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 can be used.

(Sixth step)
After the n-electrode 51 is formed, the wafer is divided into bars in order to form the resonant surface of the semiconductor layer in the direction perpendicular to the striped p-electrode 52. Here, the resonance plane is an M plane (1-100) or an 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.

After dividing the wafer into bars, a reflection mirror can be formed on the resonance surface formed by cleavage. Reflecting mirrors is a dielectric multilayer film made of SiO ₂ or _{ZrO 2, TiO 2, Al 2} O 3, Nb 2 O 5 or the like. The reflection mirror is formed on the light reflection side of the resonance surface and / or the light emission surface. Thereafter, the nitride semiconductor substrate in a bar shape is divided in parallel with the stripe direction of the electrode to form a nitride semiconductor laser device as a chip. The shape of the semiconductor laser device after chip formation is rectangular, and the resonator length of the rectangular shape is 1000 μm or less. Thus, the first semiconductor laser element is formed.

Next, a method for manufacturing the second semiconductor laser element will be described. The second semiconductor laser element in the present embodiment is formed by the same manufacturing method as the first semiconductor laser element except for the following conditions.
The width of the ridge portion of the second semiconductor laser element is 1.0 μm to 30.0 μm, and is preferably wider than the width of the ridge portion of the first semiconductor laser element. The current confinement layer 160 in the second semiconductor laser element 200 may be formed on the side surface of the ridge and the exposed surface of the nitride semiconductor layer (FIG. 2). It is assumed that the resonator length of the second semiconductor laser element is about 100 μm shorter than that of the first semiconductor laser element. For example, if the resonator length of the first semiconductor laser element is 700 μm, the resonator length of the second semiconductor laser element is 600 μm. This secures an area for wire bonding.

Next, a method for manufacturing a semiconductor laser device using the first semiconductor laser element and the second semiconductor laser element will be described in order.
(First step)
The first semiconductor laser element 100 and the second semiconductor laser element 200 are bonded via a eutectic material. As the eutectic material, an alloy of Au and Sn, an alloy of Ag and Sn, a bismuth alloy, or the like is used. The eutectic temperature is set to 500 ° C. or lower and bonding is performed by pressure bonding. The film thickness is 1 μm to 10 μm.

(Second step)
Next, it is placed on the heat sink member via a eutectic material by pressure bonding to the second main surface of the substrate of the first semiconductor laser element. A nitride such as GaN or AlN is used for the heat sink member, and SiC, Cu, Al or the like is used for the others. The eutectic material is an alloy of Au and Sn, an alloy of Ag and Sn, a bismuth-based alloy, or the like, and the mounting temperature is 500 ° C. or less.
Next, wire bonding is performed on the opening of the first semiconductor laser element. Wire bonding is also performed on the n-electrode side of the second semiconductor laser element (FIG. 7). Also, the substrate of the second semiconductor laser element can be provided with irregularities so as to have an air cooling function (FIG. 8).

  Further, the present invention is not limited to the configuration in which the semiconductor laser element is one chip, and the first semiconductor laser element and / or the second semiconductor laser element can also have an array structure. When a semiconductor device having a plurality of semiconductor laser elements having a ridge portion is formed in a bar shape, or a semiconductor element having a plurality of ridge portions is bonded in a bar shape, the top surfaces of the ridge stripe portions face each other. However, such a shock is absorbed by the current confinement layer of the present invention, and cracks that are likely to occur in each ridge portion can be suppressed. Here, the plural is not particularly limited as long as it is two or more.

Embodiment 2. FIG.
FIG. 3 is a sectional view schematically showing the structure of the semiconductor laser device according to the second embodiment. In this semiconductor laser device, upper and lower semiconductor laser elements shown in FIG. 4 are joined via a eutectic material 30. The first semiconductor laser element 300 and the second semiconductor laser element 400 are made of a nitride semiconductor, and are formed on the upper surface of the nitride semiconductor substrate.

  There is a first region a of the current confinement layer 150 at substantially the same height as the ridge portion of the first semiconductor laser element 300, and there is a second region b next to it. A p-electrode 52 is formed on the ridge portion and the first region a of the current confinement layer. In addition, the p-electrode 53 of the second semiconductor laser element may be formed only on the ridge or on the ridge and the current confinement layer. Other configurations are the same as those of the first embodiment.

  A manufacturing process of the first semiconductor laser device in this embodiment will be described below. A stripe-shaped ridge portion is formed in the semiconductor layer. Next, a current confinement layer is formed up to the height of the ridge, and the uppermost layer is flattened. Next, the p electrode 52 is patterned on the ridge portion and the first region a. Thereafter, the current confinement layer is regrown to form a second region b higher than the p-electrode. Since the p-electrode 52 of the first semiconductor laser element also functions as a stress absorbing layer at the time of element bonding, it is preferable for improving the life characteristics of the semiconductor laser device.

Embodiment 3. FIG.
This embodiment is a two-wavelength integrated semiconductor laser device having different oscillation wavelengths. The first semiconductor laser element is an InAlGaN 400 nm band semiconductor laser. The second semiconductor laser element is an InGaAlP-based 650 nm band semiconductor laser. The semiconductor laser elements can be driven independently.
The second semiconductor laser element in this embodiment is formed as follows. First, an n-side InGaAlP cladding layer, an InGaAlP light guide layer, an InGaAlP active layer, an InGaAlP light guide layer, a p-side InGaAlP cladding layer, and a p-side InGaP contact layer are sequentially stacked on a GaAs substrate. Other configurations and conditions are the same as those in the first embodiment. Since a GaN-based semiconductor is excellent in thermal conductivity, even if an InGaAlP-based 650 nm band semiconductor laser is formed on the first semiconductor laser element, it can operate satisfactorily without any problem of heat generation.

  The semiconductor laser device of the present invention can be used for optical disc applications, optical communication systems, printers, bio-related excitation light sources, optical communication systems, exposure applications, measurements, and the like. A bio-related photogen for excitation that can detect the presence or location of a substance by irradiating a substance having sensitivity to a specific wavelength with light obtained from a nitride semiconductor laser.

1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention. It is sectional drawing which shows one manufacturing process of the semiconductor laser element which concerns on embodiment of this invention. It is sectional drawing of the semiconductor laser element which concerns on embodiment of this invention. 1 is a schematic side view of a semiconductor laser device according to an embodiment of the present invention. 1 is a schematic side view of a semiconductor laser device according to an embodiment of the present invention.

Explanation of symbols

30 ... eutectic material, 51 ... n electrode, 52 ... p electrode, 53 ... p electrode, 54 ... n electrode, 100 ... first semiconductor laser element, 101 ... substrate, 120 ... n-side semiconductor layer, 130 ... active layer 140 ... p-side semiconductor layer, 150 ... current confinement layer, 160 ... current confinement layer, 201 ... substrate, 220 ... n-side semiconductor layer, 230 ... active layer, 240 ... p-side semiconductor layer

Claims (7)

A semiconductor laser device in which upper surfaces of ridge stripe portions of a first semiconductor laser element and a second semiconductor laser element on the first semiconductor laser element face each other,
The first semiconductor laser element has current confinement layers on both sides of the ridge stripe portion,
The current confinement layer includes a first region and a second region, the heights of which differ sequentially from the ridge stripe portion, and the second region is higher than the upper surface of the ridge stripe portion. apparatus. 2. The semiconductor laser device according to claim 1, wherein the first region of the current confinement layer in the first semiconductor laser element is substantially the same height as an upper surface of the ridge stripe portion. 2. The semiconductor laser device according to claim 1, wherein the width of the ridge stripe portion in the second semiconductor laser element is wider than the width of the ridge stripe portion in the first semiconductor laser element. The semiconductor laser device according to claim 1, wherein a resonator of the first semiconductor laser element is longer than a resonator of the second semiconductor laser element. 2. The semiconductor laser device according to claim 1, wherein a distance between a light emitting point of the first semiconductor laser element and a light emitting point of the second semiconductor laser element is 10 μm or less. The semiconductor laser device according to claim 1, wherein the first semiconductor laser element and the second semiconductor laser element are bonded to each other through a eutectic material. The semiconductor laser device according to claim 1, wherein the first semiconductor laser element has a semiconductor layer on a substrate.

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