JP2006019705A - Semiconductor laser device, method of manufacturing same, electrode structure of same, optical disk device and optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device capable of suppressing a diffusion of Au, without making the flatness of the interface between a semiconductor layer and an electrode and capable of acting a low electric power consumption with a high oscillation efficiency, by reducing an internal light scattering and an absorption loss, and to provide a method of manufacturing the semiconductor laser device. <P>SOLUTION: On an n-GaAs substrate 101, there are provided n-AlGaAs first, second bottom cladding layers 103, 104; a multiplex distorted quantum well active layer 106; p-AlGaAs first, second top cladding layers 109, 111; a p-GaAs contact layer 112; and a p<SP>+</SP>-GaAs contact layer 113. There is provided a p side electrode 115 conducting to the contact layer 113. At an interface between the contact layer 113 and the p side electrode 115, there is formed an alloy layer 120, consisting of elements which constitute Ni, Au, Zn and the contact layer 113. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser device, a method of manufacturing a semiconductor laser device, and an electrode structure of the semiconductor device. Typically, the present invention relates to a semiconductor laser element suitably used for an optical transmission device, an optical transmission module portion of an optical transmission system, a manufacturing method thereof, and an electrode structure of the semiconductor element.

  The present invention also relates to an optical disc apparatus and an optical transmission system provided with such a semiconductor laser element.

  Semiconductor laser elements are widely used in optical disk devices and optical transmission systems. Among them, the ridge waveguide type semiconductor laser element is known as a structure capable of manufacturing a semiconductor laser element simply and with good controllability (for example, Patent Document 1 (Japanese Patent Laid-Open No. 11-121856, particularly page 4, FIG. 2 (c)).

12 (a) to 12 (c) and FIGS. 13 (a) to 13 (c) show cross-sectional structures of the semiconductor laser device described in Patent Document 1. FIG. This semiconductor laser device is manufactured as follows. First, as shown in FIG. 12A, an n-Al _0.3 Ga _0.7 As clad layer 502 having a thickness of 1.5 μm is formed on an n-GaAs substrate 501 by MOCVD (metal organic chemical vapor deposition) or the like. An undoped GaAs active layer 503 having a thickness of 0.1 μm, a p-Al _0.3 Ga _0.7 As cladding layer 504 having a thickness of 1.5 μm, and a p-GaAs contact layer 505 having a thickness of 0.2 μm are sequentially formed.

  Here, “n−” and “p−” indicate that n-type and p-type are doped, respectively.

Next, as shown in FIG. 12B, a photoresist pattern 506 having a stripe-shaped opening having a width of 5 μm is formed by photolithography. The cross-sectional shape of the edge of this photoresist pattern is reversely tapered. Then, p-ohmic electrodes 507 and 508 are deposited by electron beam vapor deposition, and then SiO ₂ films 509 and 510 are deposited by electron beam vapor deposition. Here, the configuration of the p-ohmic electrodes 507 and 508 is a laminated structure of an AuZn alloy having a thickness of 100 nm and Au having a thickness of 100 nm from the bottom. The thicknesses of the SiO ₂ films 509 and 510 are 400 nm.

Next, as shown in FIG. 12C, by removing the photoresist pattern 506 with a solvent, the p-ohmic electrode 508 and the SiO ₂ film 510 deposited outside the photoresist opening are lifted off and remain. Using the SiO ₂ film 509 as an etching mask, the p-GaAs contact layer 505 and the p-Al _0.3 Ga _0.7 As cladding layer 504 are etched halfway by dry etching such as RIE (reactive ion etching) using Cl _2. Thus, a ridge portion is formed. Here, since dry etching is used, side etching does not occur. The thickness of the p-Al _0.3 Ga _0.7 As cladding layer 504 is set to 0.4 μm.

Next, after the SiO ₂ film 509 is removed with hydrofluoric acid, a 3000 N thick SiN film 511 is deposited by CVD (chemical vapor deposition) as shown in FIG.

Next, as shown in FIG. 13B, by photolithography, a photoresist pattern 512 having a stripe-shaped opening having a width of 3 μm is formed on the upper surface of the ridge, and this is used as an etching mask to perform RIE using CF ₄ or the like. Thus, the SiN film 511 on the p-ohmic electrode 507 is removed.

  Next, after removing the photoresist pattern 512 with a solvent, as shown in FIG. 13C, a bonding electrode 513 is deposited by electron beam evaporation. Further, an n-ohmic electrode 514 is formed on the lower surface of the n-GaAs substrate 501. To deposit. The n-ohmic electrode 514 has a laminated structure of an AuGeNi layer having a thickness of 100 nm and an Au layer having a thickness of 300 nm from the substrate side.

  Although not shown here, an optical resonator reflection surface is then formed by cleavage to obtain a ridge waveguide semiconductor laser element.

As described above, according to the method of manufacturing the semiconductor laser device, the striped p-ohmic electrode and the striped SiO ₂ film serving as an etching mask for ridge formation are formed by lift-off using the same photoresist pattern. As a result, the positions and widths of the two are exactly matched in a self-aligning manner.

  Further, since the ridge portion is formed by dry etching, side etching does not occur, so that the width of the ridge portion can be precisely controlled, and a uniform p-ohmic electrode is formed on the entire top surface of the ridge portion. Contacts can be formed.

  With respect to the p-ohmic electrode, another conventional ridge waveguide semiconductor laser element uses a non-alloy electrode that does not require heat treatment in which Ti, Pt, and Au are laminated, whereas the semiconductor laser element of Patent Document 1 Then, an AuZn alloy that requires heat treatment is used. This AuZn alloy has an advantage that an ohmic electrode having a lower resistance than that of a non-alloy electrode using Ti can be obtained by performing a heat treatment (alloy treatment).

  However, it has been found that the conventional semiconductor laser element disclosed in Patent Document 1 described above has the following problems.

That is, when an AuZn alloy is used as the material of the electrode provided on the ridge portion in a structure in which the distance from the active layer to the p-ohmic electrode is close as in the ridge waveguide semiconductor laser element, the p− produced by the alloy process is used. Increase in light scattering at the interface due to deterioration of the flatness of the interface between the contact layer and the p-ohmic electrode, and Au atoms in the AuZn alloy diffuse deeply into the semiconductor layer constituting the ridge portion. It has been found that there is a problem that the oscillation efficiency decreases due to light scattering inside the semiconductor and an increase in absorption loss.
Japanese Patent Laid-Open No. 11-121856

  Therefore, the problem of the present invention is that the flatness of the interface between the semiconductor layer and the electrode is not deteriorated, the diffusion of Au can be suppressed, the internal light scattering and the absorption loss are reduced, and the low oscillation operation with high oscillation efficiency is achieved. An object of the present invention is to provide a semiconductor laser device and a manufacturing method thereof. In particular, it is an object to provide a semiconductor laser device having high oscillation efficiency even when a p-ohmic electrode is formed using an AuZn alloy in a region close to an active layer, and a method for manufacturing the same.

  Another object of the present invention is to provide an electrode structure of a semiconductor element used for an electrode of a semiconductor laser element or the like.

  Another object of the present invention is to provide an optical disc apparatus and an optical transmission system using the semiconductor laser element.

  In order to solve the above problems, a semiconductor laser device according to the present invention includes at least an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer on an n-type substrate, and is electrically connected to the p-type contact layer. In the semiconductor laser device in which the electrode is formed, the p-type contact layer contains at least Ga and As, and the p-type contact layer side of the electrode contains at least Au, and the p-type contact layer An alloy layer made of Ni and at least one of the elements constituting the electrode and the elements constituting the p-type contact layer is formed at the interface between the electrode and the electrode.

According to the semiconductor laser device having the above structure, at the interface between the p-type contact layer containing at least Ga and As and the electrode, at least one of the element constituting the electrode and the element constituting the p-type contact layer and Ni Since the alloy layer made of is formed, Au atoms contained in the electrode can be prevented from abnormally diffusing in a spike shape, and the flatness of the interface between the electrode and the p-type contact layer can be maintained. Become. Further, since the refractive index of the electrode containing Au is very small compared to the refractive index of the semiconductor layer, the effect of confining the oscillated laser light in the semiconductor layer is increased. In general, a metal has a light absorption coefficient that is 10 ⁴ to 10 ⁵ times larger than that of a semiconductor layer, and if the oscillated laser light leaks to an electrode made of metal, the oscillation efficiency is significantly reduced. However, according to the above configuration, the effect of confining such oscillated laser light in the semiconductor layer is great, internal scattering at the interface between the contact layer and the electrode, and Au atoms diffused deep inside the semiconductor layer. By suppressing internal light scattering and absorption loss, it is possible to provide a semiconductor laser device capable of operating with low oscillation power with high oscillation efficiency.

  In addition, it is preferable that another electrode that forms an ohmic junction with this surface is provided on the surface of the n-type substrate opposite to the surface on which the above layers are stacked. As a result, energization is easily performed between the two electrodes through the active layer, and laser oscillation is realized.

  In one embodiment, the p-type contact layer is preferably GaAs and the electrode is preferably AuZn.

  According to the semiconductor laser device of the above embodiment, by using an electrode made of AuZn for the p-type GaAs contact layer, it is possible to achieve both low contact resistance and high power consumption while having high oscillation efficiency. A semiconductor laser element can be provided.

  In one embodiment, the dopant of the p-type contact layer made of GaAs is Zn.

  According to the semiconductor laser device of the above embodiment, by using the same material as Zn contained in the electrode as the dopant, Zn diffuses from the electrode to the p-type contact layer in the heat treatment for forming the ohmic junction, and the electrode And the contact resistance between the p-type contact layer can be further reduced.

  In one embodiment, the thickness of the p-type contact layer made of GaAs is 0.2 μm or more, and the alloy layer is made of Ni, at least one of Ga, As, Au, and Zn. It is preferable.

  According to the semiconductor laser device of the above embodiment, the p-type contact layer made of GaAs is formed to have a thickness of 0.2 μm or more, and at least one of Ga, As, Au, and Zn and Ni By providing the alloy layer made of at the interface between the p-type contact layer and the electrode, it is possible to prevent the Au atoms contained in the electrode from diffusing beyond the p-type contact layer.

  In one embodiment of the present invention, the alloy layer includes a first alloy layer made of Ga, As, Zn and Ni formed on the p-type contact layer side, and an Au formed on the electrode side. And Zn and a second alloy layer made of Ga and Ni, and the electrode preferably has an AuZn layer formed on the second alloy layer.

  According to the semiconductor laser device of the above embodiment, the alloy layer has the second alloy layer containing Au in order from the electrode side and the first alloy layer not containing Au, and the first alloy layer, The two alloy layers contain Ga, Zn, and Ni in common, and the electrode has an AuZn layer on the second alloy layer, so that the Au contained in the electrode exceeds the p-type contact layer by p. It is possible to prevent abnormal diffusion to the mold clad layer side, maintain interface flatness between the electrode and the contact layer, and reduce contact resistance between the electrode and the p-type contact layer. Furthermore, since the refractive index of the electrode layer made of AuZn is as small as half or less of the refractive index of a semiconductor layer such as GaAs, the force for confining the oscillated laser light in the semiconductor layer material is very large. As a result, it is possible to provide a semiconductor laser device with good characteristics having low device resistance and high oscillation efficiency by suppressing light scattering and absorption loss at the interface and inside the semiconductor layer, and further suppressing absorption loss at the electrode. Is possible.

  In one embodiment, the p-type contact layer is InGaAs and the electrode is AuZn.

  According to the semiconductor laser device of the above embodiment, by using an electrode made of AuZn for the p-type InGaAs contact layer, it is possible to achieve both low contact resistance and operation with low power consumption while having high oscillation efficiency. A semiconductor laser device can be provided.

  In one embodiment, the p-type cladding layer is made of AlGaAs, and the Al mixed crystal ratio in the group III element in the AlGaAs is larger than 0.6 and not larger than 0.7. The layer thickness of the p-type cladding layer in the lower region of the p-type contact layer is preferably 0.5 μm or more.

  According to the semiconductor laser device of the above embodiment, when the p-type cladding layer is made of AlGaAs and the Al mixed crystal ratio in the group III element in the AlGaAs is larger than 0.6 and not larger than 0.7, By setting the layer thickness of the p-type contact layer (AlGaAs) in the lower region of the p-type contact layer (for example, the lower region of the ridge in a semiconductor laser element having a ridge structure) to 0.5 μm or more, It is possible to prevent the light distribution of the oscillation laser light in the direction perpendicular to the substrate from leaking to the p-type contact layer side. Since the electrode configuration described above is used, Au constituting the electrode does not diffuse to the p-type cladding layer. Therefore, it is possible to avoid the influence of internal scattering and absorption loss caused by the electrode material, and to provide a semiconductor laser element having high oscillation efficiency.

  Here, the ridge structure is a structure having at least a clad layer, a contact layer, and an electrode provided on the active layer, and serves as a path for injecting a current for operating the semiconductor laser element, and the substrate. It is provided to bear the confinement of the oscillation laser light in the direction parallel to the.

  In one embodiment, the p-type cladding layer is made of AlGaAs, and the Al mixed crystal ratio in the group III element in the AlGaAs is 0.4 or more and 0.6 or less. The p-type cladding layer in the lower region of the contact layer preferably has a thickness of 1 μm or more.

  According to the semiconductor laser device of the above embodiment, when the Al mixed crystal ratio in the group III element in the AlGaAs is 0.4 or more and 0.6 or less, the lower region of the p-type contact layer (for example, a ridge structure) In the semiconductor laser device having a thickness of 1 μm or more in the p-type contact layer (AlGaAs) in the lower region of the ridge portion, the light distribution of the oscillation laser light in the direction perpendicular to the substrate can be increased. Almost no leakage to the contact layer side can be achieved. Since the above-described electrode configuration is used also in the above embodiment, Au constituting the electrode does not diffuse to the p-type cladding layer. Therefore, it is possible to avoid the influence of internal scattering and absorption loss caused by the electrode material, and to provide a semiconductor laser element having high oscillation efficiency.

  According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor laser device, comprising: sequentially forming at least an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer on a n-type substrate by crystal growth; After depositing one of Ni or AuZn on the contact layer and then depositing the other of Ni or AuZn, and depositing Ni and AuZn, heat treatment is performed on the p-type contact layer. forming an alloy layer made of Ni and at least one of Au and Zn and an element constituting the p-type contact layer, and forming an electrode electrically connected to the p-type contact layer through the alloy layer. It is characterized by that.

  According to the method for manufacturing a semiconductor laser device, when AuZn is deposited after Ni is deposited, an alloy layer is formed by heat treatment, and then a part of the deposited AuZn is separated from the p-type contact layer. It remains as an electrode that conducts through the alloy layer. On the other hand, when Ni is deposited after AuZn is deposited, an alloy layer is formed by heat treatment, and then a part of the deposited AuZn is electrically connected to the p-type contact layer through the alloy layer. Remain. The thus formed Ni-containing alloy layer eliminates the abnormal diffusion of Au contained in the electrode, so that the flatness of the interface between the p-type contact layer and the electrode is maintained, and internal scattering and increase in absorption loss can be prevented. In addition, a method for manufacturing a semiconductor laser device having a low device resistance is obtained. As a result, it is possible to provide a method of manufacturing a semiconductor laser device capable of achieving both high oscillation efficiency and low power consumption operation.

  In one embodiment of the method for manufacturing a semiconductor laser device, in the step of depositing Ni and AuZn on the p-type contact layer, Ni is deposited to a thickness of 5 nm or more before AuZn, and then AuZn is deposited. Is preferably deposited.

  According to the method for manufacturing a semiconductor laser device of the above embodiment, first, Ni is deposited on the p-type contact layer so that its thickness is 5 nm or more, AuZn is deposited, and then heat treatment is performed. An alloy layer containing Ni is formed. This Ni-containing alloy layer can prevent abnormal diffusion of Au atoms contained in AuZn, and can maintain good flatness at the interface between the p-type contact layer and the electrode. Therefore, a method for manufacturing a semiconductor laser device capable of performing high-efficiency oscillation and low power consumption operation is provided.

  In one embodiment of the method for manufacturing a semiconductor laser device, it is preferable to perform heat treatment at a temperature of 350 ° C. or higher and 450 ° C. or lower in the step of forming the alloy layer and the electrode by the heat treatment.

  According to the method for manufacturing a semiconductor laser device of the above embodiment, an alloy layer containing Ni can be formed by performing heat treatment at a temperature of 350 ° C. or higher. On the other hand, if the temperature exceeds 450 ° C., the flatness of the interface between the p-type contact layer and the electrode deteriorates, and Au begins to diffuse abnormally beyond the alloy layer, which is not preferable.

  According to one embodiment of the present invention, there is provided a method for manufacturing a semiconductor laser device, comprising: forming at least the n-type cladding layer, the active layer, the p-type cladding layer, and the p-type contact layer; Forming a ridge portion by removing a part of the layer; and forming an inorganic insulating film in a region excluding the top portion of the p-type contact layer after the step of forming the ridge portion. preferable.

  According to the manufacturing method of the semiconductor laser device of the above embodiment, a method is provided in which a semiconductor laser device having both high oscillation efficiency and low power consumption operation can be manufactured without performing crystal regrowth for current confinement.

  The electrode structure of a semiconductor element according to the present invention is an electrode structure of a semiconductor element having a p-type contact layer and an electrode conducting to the p-type contact layer, wherein the p-type contact layer contains at least Ga and As. The p-type contact layer side of the electrode contains at least Au, and an element constituting the electrode and an element constituting the p-type contact layer are present at the interface between the p-type contact layer and the electrode. An alloy layer made of Ni and at least one of the above is formed.

  According to the electrode structure of the semiconductor element having the above configuration, Ni is formed at the interface between the p-type contact layer containing at least Ga and As and the electrode and at least one of the elements constituting the electrode and the p-type contact layer. Since the alloy layer is formed, the Au atoms contained in the electrode can be prevented from abnormally diffusing in a spike shape, and the flatness of the interface can be maintained, so that the contact resistance is good and the reliability is improved. High electrode structure can be obtained.

  The electrode structure of the semiconductor element according to one embodiment is such that the alloy layer includes a first alloy layer made of Ga, As, Zn, and Ni, and a second alloy layer made of Au, Zn, Ga, and Ni. And the electrode has an AuZn layer formed on the second alloy layer.

  The optical disk apparatus of the present invention uses any one of the above semiconductor laser elements.

  According to the above optical disk apparatus, it is possible to provide an optical disk apparatus that can be written at a lower cost and at a lower cost than the conventional optical disk apparatus, and is configured at a lower cost.

  The optical transmission system of the present invention is characterized by using any one of the above semiconductor laser elements.

  According to the optical transmission system, by using the semiconductor laser element, it is possible to provide an optical transmission module that is cheaper, lower power consumption, and capable of high-speed data communication than conventional ones. High performance can be achieved.

  As apparent from the above, according to the semiconductor laser device of the present invention, at the interface between the p-type contact layer and the electrode, at least one of the element constituting the electrode and the element constituting the p-type contact layer is formed from Ni. By forming the alloy layer, it is possible to prevent Au atoms contained in the electrode from being abnormally diffused in a spike shape, and to maintain the flatness of the interface between the p-type contact layer and the electrode. Therefore, internal scattering at the interface between the p-type contact layer and the electrode, internal light scattering due to Au atoms diffused deep inside the semiconductor layer, and absorption loss can be reduced. Furthermore, since the refractive index of the electrode containing Au is much smaller than the refractive index of the semiconductor layer, the effect of confining the oscillated laser light in the semiconductor layer is increased, and absorption loss due to the electrode made of metal can be suppressed. . Accordingly, it is possible to provide a semiconductor laser device capable of operating with low oscillation power with high oscillation efficiency.

  Further, according to the method for manufacturing a semiconductor laser device of the present invention, there is provided a method for manufacturing a semiconductor laser device capable of realizing a low contact resistance while preventing abnormal diffusion of Au. Thereby, a semiconductor laser device having high oscillation efficiency and capable of operating with low power consumption can be manufactured.

  According to the electrode of the semiconductor element of the present invention, an alloy layer made of Ni and at least one of the element constituting the electrode and the element constituting the p-type contact layer is formed at the interface between the p-type contact layer and the electrode. By forming it, Au contained in the electrode can be prevented from abnormally diffusing in a spike shape, and the flatness of the interface can be maintained, so that an electrode structure with good contact resistance and high reliability can be obtained.

  In addition, according to the optical disk apparatus of the present invention, by using the semiconductor laser element of the present invention, it is possible to write data at a high speed with low power consumption and at a lower cost than the conventional optical disk apparatus.

  In addition, according to the optical transmission system of the present invention, by using the semiconductor laser device of the present invention for the optical transmission module, an optical transmission module that is cheaper, lower power consumption, and capable of high-speed data communication can be obtained. Therefore, it is possible to reduce the price and improve the performance of the optical transmission system.

  The semiconductor laser device, the method for manufacturing the semiconductor laser device, the electrode structure of the semiconductor device, the optical disk device, and the optical transmission system according to the present invention will be described below in detail with reference to the illustrated embodiments.

[First Embodiment]
FIG. 1 shows the structure of the semiconductor laser device according to the first embodiment of the present invention. This semiconductor laser element oscillates at a wavelength of 890 nm and is used for infrared communication.

  Hereinafter, “n−” and “p−” indicate that n-type and p-type are doped, respectively.

This semiconductor laser device has an n-GaAs substrate layer 101, an n-GaAs buffer layer 102, an n-Al _0.5 Ga _0.5 As first lower cladding layer 103, an n-Al _0.422 Ga _0.578 As second lower cladding layer 104, Al. _0.25 Ga _0.75 As lower guide layer 105, multiple strain quantum well active layer 106, Al _0.25 Ga _0.75 As first upper guide layer 107, Al _0.4 Ga _0.6 As second upper guide layer 108, p-Al _0.456 Ga _0.544 As first An upper cladding layer 109 and a p-In _0.1568 Ga _0.8432 As _0.4 P _0.6 semiconductor layer 110 are sequentially stacked.

On this semiconductor layer 110, a p-Al _0.5 Ga _0.5 As second upper cladding layer 111, a p-GaAs contact layer 112, and a p ⁺ -GaAs contact layer 113 are sequentially formed so as to form a ridge portion 130 having a forward mesa stripe shape. Is provided.

An SiN film 114 is formed on the side surface of the ridge portion 130 and the upper surface of the semiconductor layer 110 except for the top of the ridge portion 130. Further, an Ni layer 115a, an AuZn layer 115b, and an Au layer 115c are stacked in this order. A multilayer metal thin film formed in this manner is provided as a p-side electrode 115 that is electrically connected to the p ⁺ -GaAs contact layer 113 at the top of the ridge portion 130. At this time, an alloy composed of Ni, Au, Zn, and an element constituting the p ⁺ -GaAs contact layer 113 is formed at the interface between the p ⁺ -GaAs contact layer 113 and the AuZn layer 115b in the top region of the ridge portion 130. A layer 120 is formed. Further, an unalloyed Ni layer 115a is formed at the interface between the SiN film 114 and the AuZn layer 115b.

  On the back surface of the substrate 101, an n-side electrode 116 made of a multilayer metal thin film of AuGe / Ni / Au is formed as another electrode.

  Next, a method for manufacturing the semiconductor laser device will be described with reference to FIGS. FIG. 6 shows an enlarged schematic view around the ridge structure of the semiconductor laser device.

First, as shown in FIG. 2, an n-GaAs buffer layer 102 (layer thickness: 0.5 μm, Si doping concentration: 7.2 × 10 ¹⁷ cm ⁻³ ) is formed on the (100) plane of the n-GaAs substrate 101. N-Al _0.5 Ga _0.5 As first lower cladding layer 103 (layer thickness: 2.0 μm, Si doping concentration: 5.4 × 10 ¹⁷ cm ⁻³ ), n-Al _0.422 Ga _0.578 As second lower cladding layer 104 (Layer thickness: 0.1 μm, Si doping concentration: 5.4 × 10 ¹⁷ cm ⁻³ ), Al _0.25 Ga _0.75 As lower guide layer 105 (layer thickness: 3.0 nm), multiple strain quantum well active layer 106, Al _0.25 Ga _0.75 As first upper guide layer 107 (layer thickness: 3.0 nm), Al _0.4 Ga _0.6 As second upper guide layer 108 (layer thickness: 0.1 μm), p-Al _0.456 Ga _0.544 As first upper cladding layer 109 (thickness: 0.2 [mu] m, Zn doping ^{concentration: 1 × 10 18 cm -3)} , In 0.1568 Ga 0.8432 As 0.4 P 0.6 semiconductor layer 110 (a layer : 15 nm, Zn doping ^{concentration: 2 × 10 18 cm -3)} , p-Al 0.5 Ga 0.5 As second upper cladding layer 111 (thickness: 1.28, Zn doping concentration ^{4 × 10 18 cm -3),} p -GaAs contact layer 112 (layer thickness: 0.2 μm, Zn doping concentration: 3 × 10 ¹⁸ cm ⁻³ ), p ⁺ -GaAs contact layer 113 (layer thickness: 0.3 μm, Zn doping concentration: 1 × 10 ²⁰ cm) ^-3 ) are successively grown by MOCVD (metal organic chemical vapor deposition).

The multiple strained quantum well active layer 106, In _0.1001 Ga _0.8999 As compressive strained quantum well layer (strain 0.7%, layer thickness: 4.6 nm, 2-layer) and In _0.238 Ga _0.762 As _0.5463 P _0.4537 tensile strain barrier layer (Strain 0.1%, band gap Eg≈1.60 eV, layer thickness from substrate side: 21.5 nm, 7.9 nm, 21.5 nm, and the layer closest to the substrate 101 is the n-side barrier layer , The farthest is the p-side barrier layer).

  Next, as shown in FIG. 2, a resist mask 117 (mask width 3.5 μm) is formed on the ridge portion formation region 117a (see FIG. 1) where the ridge portion 130 is to be formed by a photolithography process. The resist mask 117 is formed to extend in the <0-11> direction in a stripe shape corresponding to the direction in which the ridge portion 130 to be formed extends.

  Next, as shown in FIG. 3, using this resist mask 117 as a mask, out of the contact layer 113, the contact layer 112, and the second upper cladding layer 111, the ridge portion formation outside region corresponding to both sides of the resist mask 117. The 117b portion is removed by etching, and a ridge portion 130 in the form of a forward mesa stripe is formed immediately below the resist mask 117. This etching is performed up to just above the semiconductor layer 110 using a mixed aqueous solution of sulfuric acid and hydrogen peroxide. Subsequently, overhang portions of the GaAs contact layers 112 and 113 are taken with a mixed aqueous solution of ammonia and hydrogen peroxide. The depth of etching is 1.78 μm, and the bottom width of the ridge portion 130 is about 3.2 μm. After the etching is completed, the resist mask 117 is removed.

  Subsequently, as shown in FIG. 4, a 300 nm silicon nitride (SiNx) film 114 is formed on the top and side surfaces of the ridge 130 and the semiconductor layer 110 by using a plasma-CVD (chemical vapor deposition) method. Thereafter, a resist mask (not shown) having only the top of the ridge 130 is opened using a photolithography process, and the SiN film formed on the top of the ridge 130 is removed using hydrofluoric acid. Thereafter, the resist mask (not shown) is removed.

  Subsequently, as shown in FIG. 5, by using resistance heating vapor deposition, Ni layer 115a (layer thickness: 10 nm) and AuZn layer 115b (alloy of Au 95% and Zn 5%, layer thickness: 100 nm as p-side electrode 115. ) And an Au layer 115c (layer thickness: 300 nm) in this order.

  Thereafter, as shown in FIG. 1, the substrate 101 is ground from the back surface side to a desired thickness (here, about 100 μm) by a lapping method. Then, by using resistance heating vapor deposition from the back side, as the n-side electrode 116, an AuGe layer (alloy of Au 88% and Ge 12%, layer thickness: 100 nm), Ni layer (layer thickness: 15 nm), Au layer (layer thickness) : 300 nm).

Thereafter, an alloy process is performed by heating at 400 ° C. for 1 minute in an N ₂ atmosphere. As a result, as shown in FIG. 6, the Ni layer 115a completely disappears at the interface between the p-side electrode 115 and the p-type contact layer 113 in contact with the p-side electrode 115 except on the SiN film 114, An alloy layer 120 is formed by alloying Ni, the AuZn layer 115b, and the semiconductor layer material constituting the p-type contact layer 113.

  As shown in the enlarged view on the right side of FIG. 6, the alloy layer 120 is formed on the first alloy layer 120a made of Ga, As, Zn and Ni formed on the p-type contact layer 113 side, and on the electrode 115 side. And a second alloy layer 120b made of Ga and Ni.

  After dividing the substrate 101 into a plurality of bars having a desired resonator length (here, 500 μm), end coating is performed on the bars, and the bars are further divided into chips (500 μm × 250 μm). The chip after the division is fixed on a stem (not shown) using In glue. Then, an Au wire (not shown) for electrical connection with an external circuit is bonded on the p-side electrode 115. Thus, the semiconductor laser element is completed.

In the semiconductor laser device of the first embodiment, an alloy layer containing at least Ni and comprising Au, Zn, Ga, and As at the interface between the p ⁺ -GaAs contact layer 113 and the p-side electrode 115 (particularly the AuZn layer 115b). 120 is formed, the flatness of the interface between the p-type contact layer 113 and the p-side electrode 115 deteriorates despite the AuZn layer being formed at a relatively close distance from the active layer 106. In addition, the Au atoms did not diffuse abnormally until reaching the p-type cladding layer 111 beyond the p-type contact layers 113 and 112.

  This is because the alloy layer 120 containing Ni is formed at the interface between the p-type contact layer 113 made of GaAs and the p-side electrode 115 containing the AuZn layer.

  Here, the distance relatively close to the active layer refers to a distance within about 3 μm, and is distinguished from the case of a semiconductor laser device having a contact layer of several tens of μm.

  In the case of a conventional electrode structure using an AuZn alloy and a p-type contact layer without an alloy layer containing Ni, Au is mainly used for a semiconductor layer mainly composed of GaAs or GaAs, such as InGaAs. When an AuZn alloy is deposited and an alloy (alloying) process is performed, a good contact resistance is obtained, but first, a reaction occurs in which Ga contained in the contact layer is sucked into the Au-based electrode. Thereafter, Au diffused deeply in the trace of Ga being lost, and an abnormal diffusion phenomenon of spike-like Au atoms generally called “alloy spike” occurred. Further, the AuZn alloy mainly composed of Au has not so good adhesion to the GaAs-based semiconductor layer, and the interface between the semiconductor layer and the electrode tends to be rough and flatness tends to be poor. The interface lacking in flatness is further deteriorated by performing a heat treatment thereafter.

  Such deterioration of the flatness of the interface and the abnormal diffusion phenomenon of Au atoms are problematic in the case of the semiconductor laser device having the above-mentioned thick contact layer because it occurs at a position sufficiently away from the active layer. However, when the electrode is provided at a position within 3 μm, which is a relatively close distance to the active layer, as in the first embodiment, the device characteristics deteriorate in the conventional configuration. Furthermore, when the distance from the active layer is 2 μm or less, the deterioration of static characteristics such as efficiency and threshold current value and the deterioration of reliability become very remarkable.

  However, as in the method of manufacturing the semiconductor laser device of the first embodiment, the Ni layer is first deposited before the AuZn layer is deposited, thereby greatly improving the flatness of the interface between the semiconductor layer and the electrode. We were able to. It has also been found that the flatness of the interface does not deteriorate even by heat treatment. Further, it was found that after the formation of the alloy layer containing Ni, Au does not diffuse abnormally beyond the alloy layer and further to the active layer side.

  At this time, the thickness of Ni to be deposited is preferably 5 nm or more. When the thickness of Ni is less than 5 nm, the amount of Ni is insufficient to form a sufficient alloy layer, and the effect of maintaining the flatness of the interface between the p-type contact layer and the electrode is small. On the other hand, when it is deposited over 25 nm, some Ni may remain unalloyed even after heat treatment, which may be undesirable. That is, when Ni remains as a single layer, the refractive index is higher than that of AuZn alloy or Au, and this may affect the distribution of oscillation laser light in the direction perpendicular to the substrate. In this first embodiment, 10 nm of Ni was deposited. As a result, the Ni layer reacted completely by heat treatment in the temperature range described later, and became the alloy layer 120 together with the elements constituting the electrode and the elements constituting the p-type contact layer.

  In addition, the Ni layer is formed before the AuZn layer is deposited, so that the effect on both the improvement of the flatness of the interface and the abnormal diffusion of Au atoms is enhanced. However, in some cases, the AuZn is deposited. Then, the order of depositing Ni may be used. In this case, the above effect is slightly reduced for both.

  When the alloy layer 120 was heat-treated at 350 ° C. or higher and 450 ° C. or lower as in the method of manufacturing the semiconductor laser device of the first embodiment, the thickness did not exceed 0.2 μm at the maximum. . Therefore, when the thickness of the p-type contact layer is set to 0.2 μm or more as in the first embodiment, the Au atoms of the metal thin film constituting the p-side electrode are abnormally diffused to the p-type cladding layer. It was possible to prevent internal scattering and increase in absorption loss. However, if the temperature of this heat treatment is less than 350 ° C., sufficient alloy reaction does not occur and low contact resistance cannot be obtained. On the other hand, if the temperature exceeds 450 ° C., the alloy layer containing Ni prevents abnormal diffusion of Au atoms. Can not.

  In the semiconductor laser device of the first embodiment, the dopant of the p-type contact layer made of GaAs is Zn. Thus, by using the same material as Zn contained in the p-side electrode as a dopant for the contact layer, Zn contained in the electrode diffuses to the contact layer side when heat treatment is performed to form an ohmic junction. In addition, the doping concentration of the contact layer can be increased after epi growth. Thereby, the contact resistance between the electrode and the p-type contact layer can be further reduced.

  In addition, since the p-side electrode 115 of the first embodiment is mainly composed of Au, the refractive index of the p-side electrode 115 is generally less than half that of the semiconductor layer. Therefore, for example, the effect of confining the oscillated laser light in the semiconductor layer can be greatly increased as compared with the case where a Ti-based electrode having a refractive index comparable to that of the semiconductor layer is used. In addition, by forming the alloy layer 120 containing Ni as described above, the flatness of the interface between the electrode and the semiconductor layer is good, and abnormal diffusion of Au atoms into the semiconductor layer can also be prevented. A semiconductor laser device having high oscillation efficiency without increasing internal scattering and absorption loss can be produced.

  Further, as in the semiconductor laser device of the first embodiment, when the p-side electrode 115 mainly composed of Au having the alloy layer 120 containing Ni is formed and the p-type cladding layer 111 is made of AlGaAs, III When the Al mixed crystal ratio in the group element is larger than 0.6 and equal to or smaller than 0.7, the thickness of the p-type cladding layer 111 is set to 0.5 μm or more so that the p-type cladding layer 111 is formed on the p-type cladding layer 111. It is possible to prevent the oscillation laser beam from leaking to the p-type contact layers 112 and 113 provided. Therefore, the prevention of abnormal diffusion of Au atoms into the p-type cladding layer 111 as described above and the fact that there is almost no leakage of the oscillation laser light prevent the increase in internal scattering and absorption loss. be able to. However, the larger the Al mixed crystal ratio, the higher the rate of oxygen incorporation, and the deep level resulting from it becomes a non-radiative recombination center, which may reduce efficiency or deteriorate reliability. Therefore, the upper limit of the Al mixed crystal ratio is better set to 0.7, and in the case of such a high mixed crystal AlGaAs, the thickness is preferably smaller than 1 μm from the viewpoint of reliability. .

  Further, when the Al mixed crystal ratio in the III group of the p-type cladding layers 109 and 111 made of AlGaAs is 0.4 or more and 0.6 or less, when the thickness is 1 μm or more, the p-type cladding layer 109, 111 It is possible to prevent the oscillation laser light from leaking to the p-type contact layers 112 and 113 provided on 111. In the first embodiment, the Al mixed crystal ratio in the group III element of the p-type cladding layers 109 and 111 made of AlGaAs is about 0.45 to 0.5, and the total layer thickness is 1.48 μm (= 0. 0.2 μm + 1.28 μm). From the viewpoint of light confinement, it is sufficient that the thickness of the p-type cladding layer is 2.0 μm when the Al mixed crystal ratio is 0.4 or more and 0.6 or less.

  Note that the thickness of the p-type cladding layer refers to the total thickness of the p-type cladding layer 111 of the ridge 130 and the p-type cladding layer 109 in the region below the p-type cladding layer 111.

  As described above, the present invention is highly effective when the contact layer is a semiconductor layer (eg, InGaAs) having GaAs or GaAs as the main component, and an alloy containing Au as the main component is used as the p-side electrode. It should be noted that Au has a certain thickness (typically, 100 nm or more) on an alloy containing Au as a main component in order to achieve good bonding with a metal wire provided for electrical conduction with the outside. It is better to provide additional layers. By providing the Au layer, it is possible to reduce the connection resistance of metal (Au or Al is used) wire and to improve the adhesion. In the first embodiment, an Au layer 115c having a thickness of 300 nm is formed on the AuZn layer 115b.

  In the first embodiment, as a p-side electrode, a low-resistance layer made of Au is provided on an AuZn layer, and then an alloy process is performed on them. In some cases, a material layer for improving the adhesion of the Au layer or a material layer for preventing the Au layer from diffusing through the AuZn layer is provided between the AuZn layer and the Au layer. May be. For these purposes, it is preferable to use Ti or Mo, or a platinum group element or a platinum group element compound. When Ti or Mo is provided at the interface between the AuZn layer and the Au layer, after vapor deposition up to the (Ni layer) and the AuZn layer, the alloying process is performed once, and then the Ti and Mo layer deposition steps are performed again. It is good also as a process of vapor-depositing an Au layer.

  Here, the platinum group element is a general term for ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). A compound containing at least one of Ru, Rh, Pd, Os, Ir and Pt.

  In the first embodiment, AuZn is used as an electrode material containing Au as a main component, but other applicable materials include AuMn and AuCr. Even when these materials are used, the alloy layer containing Ni has an effect of preventing abnormal diffusion of Au atoms, and can achieve both low contact resistance and suppression of scattering / absorption loss. However, for example, AuCr material is not suitable in view of the environmental impact because it contains Cr. Further, AuZn is easier to realize a lower contact resistance for the p-type contact layer than AuMn.

In the semiconductor laser device of the first embodiment, after the crystal growth to the p ⁺ -GaAs contact layer 113, the ridge portion 130 is formed, and the top portion of the ridge portion 130 is removed, and SiN (silicon nitride) is used. The contact layer / electrode configuration described above is applied to the one in which the current confinement layer is formed.

  As a result, it is possible to obtain a method of manufacturing a semiconductor laser device capable of obtaining high oscillation efficiency and low device resistance and capable of operating with low power consumption while being a simple manufacturing method. Here, as the current confinement layer, a silicon oxide film can be used in addition to the silicon nitride film used in the first embodiment. Further, an organic insulating film such as polyimide having heat resistance may be used.

  In the first embodiment, an SCH (Separate Confinement Heterostructure) structure having a guide layer between the active layer and the clad layer is used. However, the present invention is not limited to this. For example, each layer thickness, material change, and the like can be added without departing from the spirit of the present invention, such as adding an intermediate layer for smooth crystal growth.

  In the first embodiment, the semiconductor laser device having the ridge structure has been described. However, the present invention may be applied to a semiconductor laser device having no ridge structure.

  In the first embodiment, the electrode structure of the semiconductor laser element has been described. However, the semiconductor laser element is not limited to the semiconductor laser element, and all semiconductor elements having a p-type contact layer and an electrode that is electrically connected to the p-type contact layer (for example, The present invention can be applied to light emitting diodes, heterojunction bipolar transistors, and the like.

[Second Embodiment]
FIG. 7 shows the structure of the semiconductor laser device according to the second embodiment of the present invention. This semiconductor laser element is used as a light source for a DVD (digital video disk) that oscillates at a wavelength of 650 nm.

As shown in FIG. 7, an n- (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P lower clad layer 202 (layer thickness: 1.5 μm, Si doping concentration: 5 × 10 ¹⁷ cm ⁻³ ) on an n-GaAs substrate 201. ), GaInP active layer 203, p- (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P upper cladding layer 204 (layer thickness: 1.5 μm, Be doping concentration: 5 × 10 ¹⁷ cm ⁻³ ), p-GaInP intermediate layer 205 , P-GaAs contact layer 206 (layer thickness: 0.3 μm, Be doping concentration: 1 × 10 ¹⁹ cm ⁻³ ) is epitaxially grown sequentially by MBE (molecular beam epitaxy) method. A striped ridge portion 207 is formed by etching on a part of the upper side. The layer thickness of the upper cladding layer 204 outside the ridge portion 207 region is 0.3 μm.

  An insulating film 208 made of an SiN film is formed on the upper surface of the upper cladding layer 204 and the side surfaces of the ridge portion 207 except for the upper surface of the ridge portion 207 that becomes the current injection region. On the insulating film 208 and the contact layer 206 exposed from the insulating film 208, an AuZn layer (alloy of Au95% and Zn5%, layer thickness: 100 nm) and an Au layer (layer thickness: 300 nm) are formed as the p-side electrode 209. Further, an alloy layer containing Ni is formed at the interface between the contact layer and the AuZn layer.

  In this second embodiment, an Ni layer having a film thickness of 15 nm is deposited in advance, and then the above AuZn layer and Au layer are formed and heat treatment is performed, whereby an alloy containing Ni at the interface between the contact layer and the AuZn layer is formed. A layer was formed. Further, a Ni layer (layer thickness: 15 nm, not shown) that has not been alloyed remains at the interface between the insulating film 208 and the AuZn layer. Furthermore, a multilayer metal thin film of, for example, AuGe / Ni / Au is formed on the back surface of the GaAs substrate 201 as the n-side electrode 210.

  Since the red semiconductor laser element for DVD as shown in the second embodiment described above meets the demand for further shortening the recording time, measures to further increase the output are being actively studied.

For that purpose, the following three points are considered as important measures.
One is to narrow the bottom of the ridge in order to stabilize the transverse oscillation mode at high output.
Secondly, when a large current is injected to obtain a high output, the resistance of the ridge side electrode can be suppressed and improved as much as possible by reducing the width of the bottom of the ridge.
Third, to eliminate as much as possible the influence of the contact layer serving as the light absorbing material on the ridge portion side.

  However, for example, if the first countermeasure is executed, the width of the ridge portion side electrode is also narrowed, resulting in a demerit that the element resistance increases. Moreover, as shown in the second example, in order to obtain a higher output, it is necessary to inject a larger current than before. As a result, the electrical loss at the ridge side electrode further increases, resulting in power consumption. And the disadvantage of deteriorating reliability.

  On the other hand, since the GaAs material used as the contact layer has a refractive index larger than that of the cladding layer, the oscillated laser beam is attracted and the light distribution is biased toward the contact layer. In order to prevent this, by increasing the thickness of the upper cladding layer constituting the ridge portion so far, the distance from the active layer to the contact layer is increased as much as possible, and the influence of the contact layer on the oscillated laser beam is reduced. It was like that. As a result, the height of the ridge portion is further increased and the width of the electrode is further reduced, resulting in a vicious circle.

  On the other hand, according to the semiconductor laser device of the second embodiment of the present invention, by forming an alloy layer containing Ni at the interface between the contact layer and the electrode, and using AuZn as the ridge portion side electrode material, Also for the contact layer formed on the ridge portion width narrowed for the above-described purpose, an electrode having a lower resistance than the conventional Ti-based electrode can be realized. Furthermore, since the alloy layer containing Ni prevents the diffusion of Au atoms to the active layer side, there is no decrease in reliability.

  In addition, since an electrode mainly composed of Au having a very small refractive index with respect to the semiconductor material is formed on the contact layer, the force for confining the oscillated laser light to the active layer side is increased and the contact layer is formed. Light leakage can be suppressed. Therefore, it is not necessary to increase the thickness of the cladding layer, and unnecessary reduction in electrode width is eliminated. At this time, since the Ni alloy layer is formed, the flatness of the interface between the electrode and the contact layer is maintained and the diffusion of Au atoms is suppressed, so that the internal scattering caused by the interface and Au atoms is caused. There is no loss.

  Since light does not leak to the contact layer, naturally light leakage to the electrode material itself can be prevented, and a semiconductor laser device having high oscillation efficiency with extremely little absorption loss and scattering loss can be realized. .

  As a result, it is possible to reduce power consumption when realizing high output oscillation. As a result, since the same light output can be obtained with a smaller current, there is a merit that the reliability is further improved as a synergistic effect.

  The etching process of the ridge portion in the second embodiment may be either a wet method or a dry method. By using dry etching, the verticality of the side surface of the ridge can be easily improved, so that the width of the contact layer can be secured while the width of the bottom of the ridge is reduced, and as a result, the contact resistance of the electrode is reduced. There is an effect that can be done. However, if the structure of the second embodiment is used, the conventional Ti-based electrode can be formed even when the ridge is formed using the wet etching method and the width of the contact layer is narrowed because the ridge portion is forward tapered. The advantage that a lower resistance electrode can be realized occurs.

[Third Embodiment]
FIG. 8 shows an example of the structure of the optical disc apparatus 300 according to the present invention. This is for writing data on the optical disc 301 and reproducing the written data. As a light emitting element used at that time, a wavelength band of 780 nm using the configuration of the first embodiment described above. The semiconductor laser element 302 that oscillates at λ is provided.

  This optical disk device will be described in more detail. At the time of writing, the signal light emitted from the semiconductor laser element 302 is converted into parallel light by the collimator lens 303, passes through the beam splitter 304, the polarization state is adjusted by the λ / 4 polarizing plate 305, and then the objective lens 306. Is condensed and irradiated onto the optical disc 301. At the time of reading, the optical disc 301 is irradiated with a laser beam carrying no data signal along the same path as at the time of writing. This laser beam is reflected on the surface of the optical disc 301 on which data is recorded, passes through the laser beam irradiation objective lens 306 and the λ / 4 polarizing plate 305, and then is reflected by the beam splitter 304 to change the angle by 90 °. The light is condensed by the light receiving element objective lens 307 and is incident on the signal detecting light receiving element 308. The recorded data signal is converted into an electric signal by the intensity of the laser light incident in the signal detecting light receiving element 308 and is reproduced by the signal light reproducing circuit 309 to the original signal.

  In the optical disk device according to the third embodiment, since the semiconductor laser element 302 that operates with higher oscillation efficiency and has a lower element resistance than the conventional one is used, power consumption can be greatly reduced. Accordingly, it is possible to provide an optical disc apparatus with less environmental load at a low cost.

  Here, an example in which the semiconductor laser element 302 using the configuration of the first embodiment is applied to a recording / reproducing optical disc apparatus has been described. However, an optical disc recording apparatus, an optical disc reproducing apparatus using the same wavelength 780 nm band, other Needless to say, the present invention is also applicable to an optical disc apparatus using a semiconductor laser element in a wavelength band (for example, the 650 nm band shown in the second embodiment).

[Fourth Embodiment]
FIG. 9 is a cross-sectional view showing an optical transmission module 400 used in the optical transmission system of the fourth embodiment of the present invention. FIG. 10 is a perspective view showing a light source portion, and FIG. 11 is a schematic diagram of an optical transmission system. In the fourth embodiment, the InGaAs semiconductor laser element (laser chip) 401 having the oscillation wavelength of 890 nm described in the first embodiment is used as a light source, and a silicon (Si) pin photodiode is used as the light receiving element 402. As will be described in detail later, by providing the same optical transmission module 400 on both sides (for example, a terminal and a server) that perform communication, an optical transmission system that transmits and receives optical signals between both optical transmission modules 400 is configured. The

  In FIG. 9, a pattern of both positive and negative electrodes for driving a semiconductor laser is formed on a circuit board 406. As shown in the drawing, a recess 406a having a depth of 300 μm is provided in a portion where the laser chip 401 is mounted. A laser mount (mounting material) 410 on which the laser chip 401 is mounted is fixed to the recess 406a with solder. A flat portion 413 (shown in FIG. 10) of the positive electrode 412 of the laser mount 410 is electrically connected to a laser driving positive electrode portion (not shown) on the circuit board 406 by a wire 407a. The recess 406a has a depth that does not hinder the emission of laser light, and the roughness of the surface does not affect the emission angle.

  The light receiving element 402 is also mounted on the circuit board 406, and an electrical signal is taken out by the wire 407b. In addition, an IC circuit 408 for laser driving / reception signal processing is mounted on the circuit board 406.

  Next, an appropriate amount of a liquid silicon resin 409 is dropped on a portion where the laser mount 410 fixed to the concave portion 406a is mounted with solder. A filler that diffuses light is mixed in the silicon resin 409. The silicon resin 409 stays in the recess due to the surface tension, covers the laser mount 410 and fixes it to the recess 406a. In the fourth embodiment, the recess 406a is provided on the circuit board 406 and the laser mount 410 is mounted. However, as described above, the silicon resin 409 remains on the laser chip surface and its vicinity due to surface tension. 406a is not necessarily provided.

  Thereafter, it is heated at 80 ° C. for about 5 minutes to be cured until it forms a jelly. Next, it is covered with a transparent epoxy resin mold 403. Above the laser chip 401, a lens portion 404 for controlling the radiation angle is formed, and above the light receiving element 402, a lens portion 405 for condensing the signal light is integrally formed as a molded lens. .

  Next, the laser mount 410 will be described with reference to FIG. As shown in FIG. 10, a laser chip 401 is die-bonded to an L-shaped heat sink 411 using In glue. The laser chip 401 is the InGaAs-based semiconductor laser element described in the first embodiment, and the chip lower surface 401b is coated with a high reflection film, while the laser chip upper surface 401a is coated with a low reflection film. ing. These reflective films also serve as protection for the end face of the laser chip.

  A positive electrode 412 is fixed to the base portion 411 b of the heat sink 411 with an insulator so as not to conduct with the heat sink 411. The positive electrode 412 and the electrode region 401c on the surface of the laser chip 401 are connected by a gold wire 407c. As described above, this laser mount 410 is soldered to the negative electrode (not shown) of the circuit board 406 in FIG. 9, and the flat part 413 on the upper side of the positive electrode 412 and the positive electrode part (see FIG. (Not shown) with a wire 407a. By forming such wiring, as shown in FIG. 10, an optical transmission module 400 that can obtain a laser beam 414 by oscillation is completed.

  Since the optical transmission module 400 according to the fourth embodiment uses the above-described high-efficiency, low-resistance semiconductor laser element, the power consumption of the module can be significantly reduced as compared with the prior art. Since the optical transmission system using the optical transmission module 400 operates with low power consumption, the load on the environment can be reduced. Further, when this optical transmission system is mounted on a portable device, the battery driving time can be made longer than before, and the portable device can be used more comfortably.

  As described above, by providing the same optical transmission module 400 on both sides that perform communication, an optical transmission system that transmits and receives optical signals between both optical transmission modules 400 is configured. FIG. 11 shows a configuration example of an optical transmission system using the optical transmission module 400. In this optical transmission system, the base station 415 installed on the ceiling of the room includes the optical transmission module 400, and the personal computer 416 includes the same optical transmission module as described above (denoted by reference numeral 400 ′ for distinction). ing. The optical signal emitted from the light source of the optical transmission module 400 ′ on the personal computer 416 side is received by the light receiving element of the optical transmission module 400 on the base station 415 side. An optical signal emitted from the light source of the optical transmission module 400 on the base station 415 side is received by the light receiving element of the optical transmission module 400 ′ on the personal computer 416 side. In this way, data communication using light (infrared rays) can be realized.

  Note that the semiconductor laser device, the optical disk device, and the optical transmission system of the present invention are not limited to the above illustrated examples. For example, various changes can be made without departing from the gist of the present invention, such as the layer thickness and the number of layers of the well layers and barrier layers.

FIG. 1 is a schematic sectional view of a semiconductor laser device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the manufacturing process of the semiconductor laser device, and shows a state in which a photomask for forming a ridge portion is provided after crystal growth. FIG. 3 is a schematic diagram for explaining a manufacturing process of the semiconductor laser device, and shows a state after an etching process for forming a ridge portion. FIG. 4 is a schematic diagram for explaining the manufacturing process of the semiconductor laser device, and shows a state after the SiN film forming process for current confinement. FIG. 5 is a schematic diagram for explaining the manufacturing process of the semiconductor laser device, and shows a state after the deposition process of the p-side electrode. FIG. 6 is an enlarged schematic view around the ridge structure of the semiconductor laser device. FIG. 7 is a schematic sectional view of a semiconductor laser device according to the second embodiment of the present invention. FIG. 8 is a schematic diagram of an optical disc apparatus according to a third embodiment of the present invention. FIG. 9 is a schematic view of an optical transmission module used in the optical transmission system according to the fourth embodiment of the present invention. FIG. 10 is a perspective view of a light source according to the optical transmission system. FIG. 11 is a perspective view showing a configuration example of the optical transmission system. FIG. 12 is a schematic cross-sectional view for explaining a conventional semiconductor laser device and a manufacturing method thereof. FIG. 13 is a schematic cross-sectional view for explaining the method for manufacturing the semiconductor laser element following FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... n-GaAs substrate 102 ... n-GaAs buffer layer 103 ... n-AlGaAs first lower cladding layer 104 ... n-AlGaAs second lower cladding layer 105 ... AlGaAs lower guide layer 106 ... Multiple strain quantum well active layer 107 ... AlGaAs First upper guide layer 108... P-AlGaAs second upper guide layer 109... P-AlGaAs first upper cladding layer 110... P-InGaAsP semiconductor layer 111... P-AlGaAs second upper cladding layer 112. ... p ⁺ -GaAs contact layer 114 ... SiN film 115 ... p-side electrode 115a ... Ni layer 115b ... AuZn layer 115c ... Au layer 116 ... n-side electrode 117 ... resist mask 117a ... ridge portion forming region 117b ... ridge portion forming outside region DESCRIPTION OF SYMBOLS 120 ... Alloy layer 120a ... 1st alloy layer 120b ... 2nd alloy layer 130 ... Ridge part 201 ... n GaAs substrate 202 ... n-AlGaInP lower cladding layer 203 ... GaInP active layer 204 ... p-AlGaInP upper cladding layer 205 ... GaInP intermediate layer 206 ... p-GaAs contact layer 207 ... Ridge part 208 ... Insulating film 209 ... p-side electrode 210 ... n-side electrode 300 ... optical disk device 301 ... optical disk 302 ... semiconductor laser element 303 ... collimating lens 304 ... beam splitter 305 ... λ / 4 polarizing plate 306 ... objective lens 307 ... objective lens for light receiving element 308 ... light receiving element for signal detection 309 ... Signal light regeneration circuit 400, 400 '... Optical transmission module 401 ... Semiconductor laser element (laser chip)
401a ... Low reflection film 401b ... High reflection film 401c ... Schottky bonded electrode region 402 ... Light receiving element 403 ... Epoxy resin mold 404,405 ... Lens portion 406 ... Circuit substrate 406a ... Recess 407a, 407b, c407 ... Wire 408 ... IC circuit 409 ... Silicon resin 410 ... Laser mount 411 ... Heat sink 411b ... Base 412 ... Positive electrode 413 ... Flat part 414 ... Laser beam 415 ... Base station 416 ... Personal computer 501 ... n-GaAs substrate 502 ... n-AlGaAs cladding layer 503 ... undoped GaAs active layer 504 ... p-AlGaAs cladding layer 505 ... p-GaAs contact layer 506 and 512 ... photoresist pattern 507 and 508 ... p-ohmic electrode 509, 510 ... SiO ₂ film 511 ... SiN film 513 ... Bindings electrodes 514 ... n-ohmic electrode

Claims (16)

In a semiconductor laser device comprising an n-type substrate, at least an n-type clad layer, an active layer, a p-type clad layer, and a p-type contact layer, wherein an electrode that is electrically connected to the p-type contact layer is formed.
The p-type contact layer contains at least Ga and As,
The p-type contact layer side of the electrode contains at least Au,
An alloy layer made of Ni and at least one of the elements constituting the electrode and the elements constituting the p-type contact layer is formed at the interface between the p-type contact layer and the electrode. Semiconductor laser element. The semiconductor laser device according to claim 1,
A semiconductor laser element, wherein the p-type contact layer is GaAs and the electrode is AuZn. The semiconductor laser device according to claim 2,
A semiconductor laser element, wherein the dopant of the p-type contact layer made of GaAs is Zn. The semiconductor laser device according to claim 2,
The thickness of the p-type contact layer made of GaAs is 0.2 μm or more,
A semiconductor laser element, wherein the alloy layer is made of Ni, at least one of Ga, As, Au, and Zn. The semiconductor laser device according to claim 4,
The alloy layer includes a first alloy layer made of Ga, As, Zn and Ni formed on the p-type contact layer side, and a second alloy layer made of Au, Zn, Ga and Ni formed on the electrode side. An alloy layer,
The semiconductor laser device, wherein the electrode has an AuZn layer formed on the second alloy layer. The semiconductor laser device according to claim 1,
A semiconductor laser element, wherein the p-type contact layer is InGaAs and the electrode is AuZn. The semiconductor laser device according to claim 1,
The p-type cladding layer is made of AlGaAs, and the Al mixed crystal ratio in the group III element in the AlGaAs is larger than 0.6 and not larger than 0.7, and the p-type cladding layer has a lower p region. A semiconductor laser device, wherein the thickness of the mold cladding layer is 0.5 μm or more. The semiconductor laser device according to claim 1,
The p-type cladding layer is made of AlGaAs, and the Al mixed crystal ratio in the group III element in the AlGaAs is 0.4 or more and 0.6 or less, and the p-type cladding in the lower region of the p-type contact layer A semiconductor laser device, wherein the layer thickness is 1 μm or more. forming at least an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer on a n-type substrate in order by crystal growth;
Depositing one of Ni or AuZn and then depositing the other of Ni or AuZn on the p-type contact layer;
After the step of depositing Ni and AuZn, an alloy layer comprising Ni, at least one of Au and Zn, and Ni is formed on the p-type contact layer by heat treatment. And a step of forming an electrode that is electrically connected to the p-type contact layer through the alloy layer. In the manufacturing method of the semiconductor laser device according to claim 9,
In the step of depositing Ni and AuZn on the p-type contact layer, the AuZn is deposited after depositing Ni to a thickness of 5 nm or more prior to AuZn. . The method of manufacturing a semiconductor laser device according to claim 9, wherein in the step of forming the alloy layer and the electrode by the heat treatment, heat treatment is performed at a temperature of 350 ° C or higher and 450 ° C or lower. Production method. In the manufacturing method of the semiconductor laser device according to claim 9,
After the step of forming at least the n-type cladding layer, the active layer, the p-type cladding layer, and the p-type contact layer, the ridge portion is formed by removing the p-type contact layer and a part of the p-type cladding layer. Process,
And a step of forming an inorganic insulating film in a region excluding the top portion of the p-type contact layer after the step of forming the ridge portion. In an electrode structure of a semiconductor element having a p-type contact layer and an electrode conducting to the p-type contact layer,
The p-type contact layer contains at least Ga and As,
The p-type contact layer side of the electrode contains at least Au,
An alloy layer made of Ni and at least one of the elements constituting the electrode and the elements constituting the p-type contact layer is formed at the interface between the p-type contact layer and the electrode. Electrode structure of semiconductor element. The electrode structure of the semiconductor element according to claim 13,
The alloy layer includes a first alloy layer made of Ga, As, Zn, and Ni, and a second alloy layer made of Au, Zn, Ga, and Ni.
The electrode structure of a semiconductor element, wherein the electrode has an AuZn layer formed on the second alloy layer.   9. An optical disc apparatus using the semiconductor laser element according to claim 1. An optical transmission system using the semiconductor laser element according to claim 1.

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