Semiconductor laser element and semiconductor laser Number:6,738,403 from the United States Patent and Trademark Office (PTO) owispatent

Title: Semiconductor laser element and semiconductor laser

Abstract: In a semiconductor laser element having a plurality of semiconductor layers formed on a substrate, a groove-form concave portion is formed on the surface of the substrate opposite to the surface having the semiconductor layers. The concave portion is filled with metal having a higher heat conductivity higher than the substrate. The semiconductor laser element achieves improved heat dissipation characteristics and high reliability even under high-output operation.

Patent Number: 6,738,403 Issued on 05/18/2004 to Kuniyasu,   et al.

---

Inventors:	Kuniyasu; Toshiaki (Kaisei-machi, JP), Hayakawa; Toshiro (Kaisei-machi, JP), Fukunaga; Toshiaki (Kaisei-machi, JP)
Assignee:	Fuji Photo Film Co., Ltd. (Kanagawa-ken, JP)
Appl. No.:	09/826,851
Filed:	April 6, 2001

---

Foreign Application Priority Data

---

Apr 06, 2000 [JP]			2000-104902
Apr 17, 2000 [JP]			2000-114614
Sep 11, 2000 [JP]			2000-274774

Current U.S. Class:	372/43.01 ; 372/34; 372/36
Current International Class:	H01S 5/00 (20060101); H01S 5/024 (20060101); H01S 5/02 (20060101); H01S 3/04 (20060101); H01S 3/0941 (20060101)
Field of Search:	372/43.46,36,34

---

References Cited [Referenced By]

---

U.S. Patent Documents

	5608749		March 1997		Kizuki
	6108361		August 2000		Fujihara et al.
	6239033		May 2001		Kawai
	6281524		August 2001		Yamamoto et al.
	6597716		July 2003		Takatani
	2001/0048114		December 2001		Morita et al.

Other References

Appl. Phys. Lett. 72 (1), Jan. 5, 1998, ":6.1 W continuous wave front-facet power from Al-free active-region (.lambda.=805 nm) diode lasers", J.K. Wade, et al. . Jpn. J. Appl. Phys. vol. 34 (1995) pp. L1175-L1177 Part 2, No. 9B, Sep. 15, 1995, "Highly Reliable Oper ation of High-Power InGaAsP/InGaP/AlGaAs 0.8 .mu.m Separate Confinement Heterostructure Lasers", Toshiaki Fukunaga, et al. . IEEE Journal of Quantum Electronics, vol. 28., No. 4, Apr. 1992, "Modular Microchannel Cooled Heatsinks for High Average Power Laser Diode Arrays", Ray Beach, et al. . Jpn. J. Appl. Phys. vol. 37 (1998) pp. L1020-L1022 Part. 2, No. 9A/B, Sep. 15, 1998, "InGaN/GaN/AlGaN-Based Laser Diodes Grown on GaN Substrates with a Fundamental Transverse Mode", Shuji Nakamura, et al..

Primary Examiner: Ip; Paul
Assistant Examiner: Menefee; James
Attorney, Agent or Firm: Sughrue Mion, PLLC

---

Claims

---

What is claimed is:

1. A semiconductor laser element comprising a substrate, a plurality of semiconductor layers, including at least an active layer, formed on the substrate, and a first concave portion formed on one surface of the substrate, said one surface being opposite to the other surface having the semiconductor layers formed thereon, wherein the first concave portion is filled with a metal having a heat conductivity higher than the substrate, and wherein the depth of the first concave portion is at least equal to the thickness of the substrate.

2. A semiconductor laser element comprising a substrate, a plurality of semiconductor layers formed on the substrate, and a first concave portion formed on at least a part of one surface of the semiconductor layer, said one surface being the surface further from the substrate, wherein the first concave portion is filled with a metal having a heat conductivity higher than the semiconductor layer.

3. The semiconductor laser element according to claim 2, wherein a second concave portion is formed on one surface of the substrate, said one surface being opposite to the other surface having the semiconductors layers formed thereon, and wherein said second concave portion is filled with a metal having a heat conductivity higher than the substrate.

4. The semiconductor laser element according to any of claims 1 to 3, wherein the first concave portion has a reverse mesa form in a direction vertical to a light-emitting face.

5. The semiconductor laser element according to any of claims 1 to 3, wherein a heatsink is connected to the metal filled in the concave portion.

6. The semiconductor laser element according to any of claims 1 to 3, wherein a plurality of light-emitting portions are formed on the semiconductor layer to form a semiconductor laser array.

7. The semiconductor laser element according to any of claims 1 to 3, wherein said semiconductor laser element is a light source for exciting a solid laser.

8. A semiconductor laser element comprising: a GaN substrate equipped with one of a pair of electrodes, a semiconductor layer made of a GaN-base semiconductor including at least an active layer, said semiconductor layer disposed on the GaN substrate, and the other one of the pair of electrodes disposed on the semiconductor layer, and an electric current injection region formed on the semiconductor layer, wherein a groove is formed on one surface of the GaN substrate at a region thereon corresponding to the electric current injecting region, said one surface being the surface further from the semiconductor layer, said groove reaching to the depth of the semiconductor layer, and wherein said one of the pair of electrodes is formed on the surface of the groove, wherein a contact layer is formed on the GaN substrate side of the semiconductor layer, wherein the contact layer is ohmic-connected to the electrode formed on the surface of the groove, wherein the groove is filled with a metal having a heat conductivity higher than the GaN substrate, wherein the surface having the groove is flattened, and wherein, a heatsink is connected to the flattened surface.

9. The semiconductor laser element according to claim 8 wherein the metal is Au.

10. A semiconductor laser element comprising a substrate, a plurality of semiconductor layers, including at least an active layer, formed on the substrate, and a groove formed on one surface of the substrate, said one surface being opposite to the other surface having the semiconductor layers formed thereon, wherein the groove extends to the depth of the substrate, and wherein the groove is filled with a metal having a heat conductivity higher than the substrate.

---

Description

---

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor laser element and a semiconductor laser, and more specifically to a semiconductor laser element and a semiconductor laser having an improved heat dissipation characteristic. The present invention also relates to a semiconductor laser element comprising a GaN-base semiconductor and to a semiconductor laser provided with such a semiconductor laser element.

2. Description of the Prior Art

Recently, the use of semiconductor lasers has been expanding remarkably In many of these uses, there has been a demand for a semiconductor laser with higher output. Accordingly, for realizing higher output of a semiconductor laser, various attempts have been made to improve the structure of the semiconductor laser element itself. For example, reported in Literature 1), J. K. Wada et al, "6.1 W continuous wave front-facet power from Al-free active-region (.lambda.=805 nm) diode lasers", Applied Physics Letters, Vol. 72, No. 1 (1998) pp. 4-6, is a semiconductor laser having an active layer made of InGaAsP containing no Al, an optical waveguide layer made of Ingap, and a clad layer made of InAlGap, and oscillating in a 805 nm band.

Suggested in Literature 1) as the structure for lowering the photodensity of the active layer to improve the high output characteristic is an LOC (Large Optical Cavity) structure with widened thickness of the optical waveguide layer. The increase of the maximum light output thereby is reported.

Also known as the semiconductor laser having an active layer with no Al and oscillating in a 0.8 .mu.m band is a semiconductor laser having, on an n-GaAs substrate, an n-AlGaAs clad layer, an i-InGaP optical waveguide layer, an InGaAsP quantum well active layer, an i-InGaP optical waveguide layer, a p-AlGaAs clad layer, and a p-GaAs cap layer, as shown in Literature 2); T Fukunaga et al. "Highly Reliable Operation of High-Power InGaAsP/InGaP/AlGaAs 0.8 .mu.m Separate Confinement Hetrostructure Lasers", Jpn. J. Appl. Phys. Vol. 34, (1995) pp. L1175-1177.

Also, to improve the heat dissipation effect of a semiconductor laser element, various structures of forcibly cooling the device with a cooling medium such as water have already been proposed. For example, proposed in Literature 3), Ray Beach et al., "Modular Michrochannel Cooled Heatsinks for High Average power Laser Diode", IEEE JOURNAL OF QUANTUM ELECTRONICS, Vol. 28. No. 4, April 1992, is a structure of a water-cooling mechanism for a semiconductor laser element using a microchannel.

On the other hand, about a semiconductor laser of a 400 nm band having a fine spot, required in the field of printing, etc., using an optical disk memory and a photosensitive material, is a beam having a high reliability and a high quality which oscillates in the optical density fundamental transverse mode with a Gauss distribution so as to fit for the increase of the image density and the increase of the image quality. For example, reported in Nakamura et al., Literature 4) InGaN/GaN/AlGaN-Based Laser Diodes Grown on GaN Substrates with a Fundamental Transverse Mode, described in "Jpn. J. Appl. Phys. Lett., Vol. 37, pp. L1020, is a semiconductor laser obtained by depositing an n-GaN buffer layer, an n-InGaN clack-preventing layer, an n-AlGaN/GaN-modulated dope supper lattice clad layer, an n-GaN optical waveguide layer, an m-InGaN/InGaN multiple quantum well active layer, a p-AlGaN carrier block layer, a p-AlGaN/GaN modulated dope super lattice clad layer, and a p-GaN contact layer on a GaN substrate, the Gan substrate being obtained by forming a GaN layer on a sapphire substrate utilizing the selective growth using SiO.sub.2 as a mask and by releasing the GaN layer and a part of the sapphire substrate as the Gan substrate.

However, the structure shown in Literature 1) may lead to a phenomenon of COMD (Catastrophic optical mirror damage) , where the end face of the device is damaged because of temperature increase of the end face triggered by an electric current generated by the light absorption at the end face, and because of smaller bandgap which increases light absorption at the end face. Therefore, the maximum light output is restrained to avoid the COMD. Since the light output which may trigger the COMD changes time-by-time, it sometimes happens that the operation of the semiconductor laser is suddenly stopped. As a result of such circumstances, it is difficult to obtain a high reliability at the time of a high output driving in the semiconductor laser proposed by Literature 1).

Also, in the semiconductor laser shown in Literature 2), the maximum light output is considerably low, in fact as low 1.8 W.

Furthermore, in the structure described in Literature 3) above, there is a problem that a large-scale cooling mechanism is required even in the case of cooling a single semiconductor device. Such a large scale cooling mechanism also requires a large place. Another problem is that it is difficult to obtain the sufficient cooling effect required for the recent high-output laser element because cooling is indirectly carried out from one surface connected to a module.

On the other hand, in the semiconductor device described in Literature 4), the reduction of the element resistance is attempted using a modulation dope super lattice clad layer but the reduction is not insufficient. Thus, the deterioration of the reliability due to the joule heat occurs during operation. Also, the resistance of the element is high in the semiconductor laser comprised of the semiconductor layers of the above-described system. Therefore, particularly in the laser of a single mode where the contact area with the contact layer is narrow, the influence of heat generation becomes a problem in practical use. The generation of the joule heat is coped with by cooling using a heatsink, etc. However, in the structure of the above-described semiconductor device, the heat dissipation is insufficient, because a heatsink is formed on the n-GaN layer exposed by etching the side surface of the semiconductor laser device making the form of the device complicated. That is, cooling from the p-electrode side near the active layer generating heat is difficult, and only cooling from the n-electrode side far from the active layer is possible. Also, because the p-electrode and the n-electrode are not disposed in a vertical direction but are disposed to the right and left, the stream of the electric current injected from the p-electrode is not straight but is liable to become inhomogeneous, whereby a uniform light emission where the optical density is a Gauss-type distribution cannot be obtained. For obtaining the light emission of a Gauss-type distribution, it is necessary to make the ridge width as narrow as possible. However, when the ridge width is narrowed, there is a problem that increase of the output is difficult.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-described circumstances and an object of the invention is to provide a semiconductor laser element having a high reliability even under high output.

Also, in view of the above-described circumstances, another object of the invention is to provide a semiconductor laser having a high reliability even under high output by improving the heat dissipation of a semiconductor laser element.

Furthermore, in view of the above-described circumstances, still another object of the invention is to provide a semiconductor laser element and a semiconductor laser, which realize a uniform and high-quality beam having the optical density of a Gauss-type distribution and thus have a high reliability under high output, by improving the heat dissipation and by making the injection of an electric current into the active layer uniform.

That is, the semiconductor laser element according to the first aspect of the invention is a semiconductor laser element having a plurality of semiconductor layers formed on a substrate, comprising a concaved portion formed on a surface of the substrate, said surface being opposite to the surface having the semiconductor layers formed thereon, wherein a metal having a higher heat conductivity than the substrate is filled in the concaved portion.

Also, the semiconductor laser element according to the second aspect of the invention is a semiconductor laser element having a plurality of semiconductor layers formed on a substrate, comprising a concaved portion formed at least in a part of a surface of the semiconductor layer, said surface being opposite to the surface on the side of the substrate, wherein a metal having a higher heat conductivity than the semiconductor layer is filled in the concaved portion.

In addition, it is desirable that in the semiconductor laser element of the second aspect, as well as the semiconductor laser element of the first aspect, another concaved portion is formed on a surface of the substrate opposite to the surface having the semiconductor layers formed thereon, and that a metal having a higher heat conductivity than the substrate is filled in the concaved portion.

Also, in the semiconductor laser elements of the invention described above, it is desirable that the concaved portion formed the substrate on the semiconductor layer has a reverse mesa form with respect to the direction perpendicular to the light-emitting face.

Also, it is desirable that a heatsink is bonded to the metal filled in the concaved portion.

Furthermore, it is desirable that in the semiconductor laser elements of the invention described above, plural light-emitting portions are formed on the semiconductor layer to constitute a semiconductor laser array.

Moreover, it is desirable that the semiconductor laser elements of the invention described above are used as the light sources for exciting a solid laser.

In the semiconductor laser elements according to the first aspect of the invention described above, where a metal having a higher heat conductivity than the substrate is filled in the concaved portion formed on the substrate, the heat generated at the active layer and the vicinity thereof is dissipated through the metal more efficiently than through the substrate only. Thus, the temperature of the semiconductor laser element (more practically, the temperature in the vicinity of the active layer) is kept low, whereby a high reliability is insured even under a high output operation.

Also in the semiconductor laser element according to the second aspect of the invention, where a metal having a higher heat conductivity than the semiconductor layer is filled in the concaved portion formed on the semiconductor layer, the heat generated at the active layer and the vicinity thereof is dissipated through the metal more efficiently than through the semiconductor layer only. Thus, in the construction, the temperature of the semiconductor laser element (more practically, the temperature in the vicinity of the active layer) is kept low, whereby a high reliability is insured even under a high output operation.

Also, in the case where the semiconductor laser element of the second aspect has the concaved portion which is filled with a metal having a higher heat conductivity than the substrate and which is formed in the substrate as in the case of the semiconductor laser element of the first aspect, the heat dissipating effect from the substrate side is also improved. Thus, the temperature of the semiconductor laser element is kept lower, and still higher reliability is insured under a high output operation.

Also, in the case where the semiconductor laser elements of the invention described above have the concaved portions formed in reverse mesa forms on the substrate and the semiconductor layer, the above-described metal can be arranged up to the portion closer the light-emitting face of the semiconductor laser element. Thus, the light-emitting face, which is liable to become high temperature, can be effectively cooled.

Furthermore, in the semiconductor laser elements of the invention described above having a heatsink bonded to the metal filled in the concaved portion, the heat conducted through the metal can be efficiently dissipated via the heatsink in a three-dimensional manner, whereby a higher reliability can be obtained even under a high output operation.

On the other hand, the semiconductor laser device according to the third aspect of the invention is comprised of a semiconductor laser element, a heatsink disposed in contact with the semiconductor laser element, a cooling medium passageway formed between the heatsink and the semiconductor laser element using at least a part of each of them as a passageway wall, and means for transferring a cooling medium through the cooling medium passageway.

In addition, the term "a cooling medium passageway is formed between the heatsink and the semiconductor laser element" as described above does not always mean that the cooling medium passageway is formed separately from the heatsink but also includes the state where the cooling medium passageway is formed using a part of the heatsink and the cooling medium passageway covers the area from the rest portion of the heatsink to the semiconductor laser element.

In the above-described construction, it is desirable that the heat sink includes a first heatsink disposed in contact with the substrate of the semiconductor laser element and a second heatsink disposed in contact with the surface of the semiconductor laser element opposite to the substrate side, wherein passageways are respectively formed between each of the first and second heatsinks and the semiconductor laser element first and second cooling medium.

Also, it is preferred that at least a part of the cooling medium passageway is constituted of the groove formed in the substrate of the semiconductor laser element. Also, it is preferred that the groove formed in the substrate is formed in a reverse mesa form. Furthermore, at least a part of the cooling medium passageway may be constituted of a ridge groove formed on the surface of the semiconductor laser element opposite to the substrate.

Also, it is desirable that the wall portion of the groove formed on the semiconductor laser element as described above is coated with a dielectric film such as an SiO.sub.2 film, an SiN film, an Al.sub.2 O.sub.3 film, etc.

On the other hand, it is desirable that in the heatsink there are formed a supply passageway for supplying a cooling medium to the above-described cooling medium passageway by connecting thereto and/or a discharge passageway for discharging the cooling medium from the cooling medium passageway.

Also, it is desirable that the heatsink is bonded to the semiconductor laser element using a brazing material having a resistance to the cooling medium.

Furthermore, it is desirable that in the semiconductor laser described above, plural semiconductor laser elements are formed to construct a semiconductor laser array and, on the other hand, the cooling medium passageway connects each of the plural semiconductor laser elements and the heatsink.

Also, it is desirable that the semiconductor laser element(s) constituting the semiconductor laser of the invention are used as the light sources for exciting a solid laser.

Because, in the semiconductor laser of the invention described above, the cooling medium passageway is formed between the heatsink and the semiconductor laser element using at least a part of each of the heatsink and the semiconductor laser element as the wall of the passageway and the apparatus is constructed such that a cooling medium flows through the cooling medium passageway, the cooling medium flows while directly contacting with the semiconductor laser element and the heatsink. Thus, the heat dissipation from the semiconductor laser element to the heatsink is carried out sufficiently well via the cooling medium, the heat-dissipating characteristics of the semiconductor laser element (more practically, the vicinity of the active layer) are improved, and a high reliability is insured even under a high-output operation.

In addition, in the case where the semiconductor laser of the invention described above has the first and second heatsinks formed as described above, and where first and second cooling medium passageways are formed between the semiconductor laser element and the first and second heatsinks respectively, the heat dissipating characteristics are remarkably improved and the reliability under a high output operation is further increased.

Also, in the case where the semiconductor laser of the invention described above has at least a part of the cooling medium passageway constructed of the groove formed on the substrate of the semiconductor laser element, or of the ridge groove formed on the surface of the semiconductor laser element opposite to the substrate, the structured of the cooling medium passageway becomes simple and can be formed in a small size. Therefore, the structure of the semiconductor laser can be simplified and miniaturized.

In addition, when the groove wall portions of the groove formed in the semiconductor laser element are coated with the dielectric, it prevents problems such as short-circuiting, etc., which may be caused by the direct contact of the cooling medium with the portion conducting an electric current of the semiconductor laser element.

Furthermore, in the case where the semiconductor laser of the invention described above has the supply passageway for supplying the cooling medium to the cooling medium passageway by connecting thereto and/or the discharge passageway for discharging the cooling medium from the cooling medium passageway is formed in the heatsink, the structures of the supply passageway and the discharge passageway for the cooling medium can be simplified. Therefore, the structure of the semiconductor laser can be simplified and miniaturized.

In addition, when the heatsink is bonded to the semiconductor laser element using a brazing material having a resistance to the cooling medium, the occurrence of the problem that the brazing material is deteriorated by the cooling medium to weaken the bonding between the heatsink and the semiconductor laser element can be prevented.

Further, in the case where the semiconductor laser of the invention described above has a plurality of semiconductor laser elements constituting a semiconductor laser array and where the cooling medium passageway connects each of the semiconductor laser elements and the heatsink, each of the semiconductor laser elements can be efficiently cooled and the reliability of the semiconductor laser array under high-output operation can be increased.

Also, the semiconductor laser element according to another aspect of the invention is a semiconductor laser element comprising a GaN substrate provided with one of a pair of electrodes, a semiconductor layer which is made of a GaN-base semiconductor containing at least an active layer and which is disposed on the GaN substrate, the other of the pair of electrodes disposed on the semiconductor layer, and an electric current injection region for injecting an electric current onto the semiconductor layer, wherein a groove is formed on a region of the GaN substrate corresponding to the electric current injection region to a depth reaching the semiconductor layer from the surface of the substrate opposite to the side of the semiconductor layer, and wherein one of the electrodes is formed on the surface of the groove.

In this case, it is desirable that a contact layer is formed on the GaN substrate side of the semiconductor layer, and the contact layer is ohmic-connected to one of the electrodes formed on the surface of the groove.

Also, it is desired that the surface of the groove filled with a metal having a higher heat conductivity than GaN is flattened and a heatsink is bonded to the flattened surface. It is preferred that the metal is Au.

Also, the semiconductor laser device according to another aspect of the invention comprises the semiconductor laser element of the present invention according to the above-described construction, a heatsink which is connected to the GaN substrate side of the semiconductor laser element and which has a supply passageway for supplying a cooling medium to a groove and a discharge passageway for discharging the cooling medium from the groove, and means for transferring a cooling medium through the groove via both the passageways.

In addition, the groove may be formed along an entire length from one end face vertical to the resonance direction of light to the other end face, or may be a part between one end face and the other end face.

Also, the above-described one of the electrodes may be formed so as to not only the inside surface of the groove but also the area between the inside of the groove and the surface opposite to the surface laminated with the semiconductor layer of the GaN substrate.

In addition, the above-described GaN-base semiconductor a semiconductor including Ga and N as the constituent features, for example, GaN, InGaN or AlGaN.

According to the semiconductor laser element of the invention described above, where a groove is formed at the region of the GaN substrate corresponding to the electric current injection region to a depth reaching the semiconductor layer and where one of the electrodes is formed on the surface of the groove, the construction thereof includes a pair of electrodes formed at both end faces in of the laminated layer direction making the passage for the electric current straight. Thus, the electric current is uniformly injected onto the active layer, whereby a uniform oscillation mode with the optical density of a Gauss-type distribution can be obtained. Therefore, unlike in the prior art, the output can be increased without narrowing the ridge width for making the optical density uniform. Thus, it is possible to increase the output and to obtain the oscillation beam having a high quality and a high reliability.

In addition, because the side surface of the semiconductor laser element was etched to the n-GaN layer and an n-electrode was formed thereon in the semiconductor laser element using the GaN substrate of prior art, the form of the semiconductor laser element was complicated. Thus, the p-electrode side near the active layer could not connect (p-down bonding) to the heatsink, and cooling was carried out from the n-electrode side. However, according to the semiconductor laser element of the invention, it becomes possible to connect the p-electrode side near the active layer to the heatsink, the cooling effect is increased, and the oscillation mode of a high quality can be obtained even under high output operation. Alternatively, it becomes possible to connect the n-electrode side to the heatsink (n-down bonding). Furthermore, it is possible to connect both the electrodes to the heatsink, whereby the cooling effect is further increased and the oscillation mode of a high quality can be obtained even under high output operation.

Also, as the contact layer is formed on the GaN substrate side of the semiconductor layer and as the contact layer and one of the electrodes formed on the surface of the groove forms an ohmic-connection, the resistance of the semiconductor laser element can be reduced. Thus, the influence of the heat generation is restrained and the beam of a high quality can be obtained.

Also, because the groove is filled with a metal having a higher heat conductivity than GaN, the surface of the side having the groove is flattened, and the heatsink is connected to the flattened surface, the semiconductor laser element is uniformly connected to the heatsink. Therefore, the heat dissipating characteristics are improved to restrain the influence of the heat generation. Also, good heat dissipation can be obtained because the metal filled in the groove is Au.

Furthermore, the heat can be more efficiently dissipated and the oscillation mode of a high quality can be obtained even under high output operation, according to the semiconductor laser of the invention described above comprising the semiconductor laser element of the invention having the above-described construction, the heatsink connected to the substrate side of the semiconductor laser element, and a supply passageway for supplying a cooling medium to the groove, a discharge passageway for discharging the cooling medium from the groove, and means for causing the cooling medium to flow to the groove through both the passageways.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the semiconductor laser element according to the first embodiment of the invention in use,

FIG. 2 is a view showing the light-emitting face of the semiconductor laser element of FIG. 1,

FIG. 3 is a cross-sectional view of the semiconductor laser element of FIG. 2,

FIG. 4 is a graph showing the driving electric current to light output characteristics of the semiconductor laser element of FIG. 1, and the corresponding characteristics of the device of the prior art,

FIG. 5 is a perspective view of the semiconductor laser element of the second embodiment of the invention,

FIG. 6 is a view showing the light-emitting face of the semiconductor laser array of FIG. 5,

FIG. 7 is a cross-sectional view of the semiconductor laser array of FIG. 5,

FIG. 8 is a view showing the light-emitting face of the semiconductor laser element of the third embodiment of the invention,

FIG. 9 is a cross-sectional view of the semiconductor laser element of FIG. 8,

FIG. 10 is a view showing the fourth embodiment of the invention during operation thereof,

FIG. 11 is a view showing the light-emitting face side of the semiconductor laser element of FIG. 10,

FIG. 12 is a cross-sectional view of the semiconductor laser element of FIG. 10,

FIG. 13 is a schematic side view of a solid laser apparatus using the semiconductor laser element of the invention,

FIG. 14 is a cross-sectional view of the semiconductor laser of the fifth embodiment of the invention,

FIG. 15 is a view showing the light-emitting face of the semiconductor laser element constituting the semiconductor laser of FIG. 14,

FIG. 16 is a cross-sectional view of the semiconductor laser of FIG. 15,

FIG. 17 is a graph showing the driving electric current to light output characteristics of the semiconductor laser of FIG. 14, and the corresponding characteristics of the apparatus of prior art,

FIG. 18 is an exploded perspective view of the semiconductor laser of the sixth embodiment of the invention,

FIG. 19 is a perspective view showing a semiconductor laser array constituting the semiconductor laser of FIG. 18,

FIG. 20 is a view showing the light-emitting face of the semiconductor laser array of FIG. 19,

FIG. 21 is a cross-sectional view of the semiconductor laser array of FIG. 19,

FIG. 22 is a cross-sectional view of a modified embodiment of the semiconductor laser array of FIG. 21,

FIG. 23 is a cross-sectional view of the semiconductor laser of the seventh embodiment of the invention,

FIG. 24 is a view showing the light-emitting face of the semiconductor laser element constituting the semiconductor laser of FIG. 23,

FIG. 25 is a cross-sectional view of the semiconductor laser element of FIG. 24,

FIG. 26 is a schematic side view of a solid laser apparatus using the semiconductor laser of the invention,

FIGS. 27A and 27B are cross-sectional views showing the preparation process of a GaN substrate,

FIG. 28 is a cross-sectional view taken vertical to an outgoing light, showing the semiconductor laser element of the eighth embodiment of the invention,

FIG. 29 is a side view showing the semiconductor laser element of the eighth embodiment of the invention,

FIG. 30 is a cross-sectional view taken vertical to an outgoing light, showing the semiconductor laser element of the ninth aspect of the invention,

FIG. 31 is a side view showing the semiconductor laser element of the ninth embodiment of the invention, and

FIG. 32 is a cross-sectional view taken vertical to an outgoing light, showing the semiconductor laser element of the tenth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention will be described in detail by referring to the accompanying drawings. FIG. 1 shows a cross-sectional view of the semiconductor laser element according to the first embodiment of the invention. Also, FIG. 2 shows the light-emitting face of the semiconductor laser element 25, which is the form of the end face becoming a resonator face, and FIG. 3 shows the cross-sectional form (state during the preparation) taken along the line A--A of FIG. 2.

First, by referring to FIG. 2 and FIG. 3, the construction of the semiconductor laser element 25 is explained together with the preparation method thereof. Successively grown using an organometallic vapor-phase growing method on a (100) n-GaAs substrate 1 are an n-GaAs buffer layer 2, an n-In.sub.0.49 Ga.sub.0.51 P etching preventing layer 3, an n-GaAs contact layer 4, an n-Ga.sub.1-z1 Al.sub.z1 As lower clad layer 5 (0.55.ltoreq.z1.ltoreq.0.8), an n- or i-In.sub.0.49 Ga.sub.0.51 P lower optical waveguide layer 6, an In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer 7 (0.ltoreq.x3.ltoreq.0.3, 0.ltoreq.y3.ltoreq.0.6), a p- or i-In.sub.0.49 Ga.sub.0.51 P upper optical waveguide layer 8, a p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9, and a p-GaAs contact layer 10. Then, an insulating film 11 is formed thereon, with a stripe direction being parallel to the orientation flat direction

The insulating film 11 is removed in a stripe form having a width of about 200 .mu.m by an ordinary lithographic method. Then, a p-side electrode 12 is formed thereon.

Then, the n-GaAs substrate 1 is abraded to be made thin. Formed on the back surface thereof is an insulating film (not shown). Then, an SiO.sub.2 pattern (not shown) having a stripe-form opening is formed by a lithographic method using the insulating film as a mask, with the lengthwise direction of the groove defined parallel to the (100) plane. Using the SiO.sub.2 pattern as a mask, the substrate 1 is etched with a sulfuric acid-base or ammonia-base etchant to form a reverse mesa-form groove (concaved portion) 1a. In this case, the etching is automatically stopped at the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3 and GaAs is etched down to the etching-preventing layer 3.

Then, the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3 is removed with a hydrochloric acid-base etching solution. Also, after removing the above-described insulating film, an n-side electrode 14 is formed. After a solvent containing an Au material is deposited thereon by a spin coating method, annealing is carried out at about 400.degree. C. for 30 minutes to form an Au layer 61 in the form of flatly filling the groove 1a. In addition, as the coating method of the solvent containing the Au material described above, the method shown, for example, in Japanese Unexamined Patent Publn. No. 10(1998)-22574 can be suitably used.

Thereafter, the semiconductor laser element 25 shown in FIG. 1 is obtained when the n-side electrode 14 and the Au layer 61 of a sample cleavage region are removed by a photolitho-etching method to form a high-reflectance coat 15 and a low-reflectance coat 16 on the resonator faces the faces formed by cleaving the sample at the designated positions for both faces.

The semiconductor laser element 25 is constituted of the n-GaAs substrate 1, the n-GaAs buffer layer 2, the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3, the n-GaAs contact layer 4, the n-Ga.sub.1-z1 Al.sub.z1 As lower clad layer 5 (0.55.ltoreq.z1.ltoreq.0.8), the n- or i-In.sub.0.49 Ga.sub.0.51 P lower optical waveguide layer 6, the In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer 7 (0.ltoreq.x3.ltoreq.0.3, 0.ltoreq.y3.ltoreq.0.6), the p- or i-In.sub.0.49 Ga.sub.0.51 P upper optical waveguide layer 8, the p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9, the p-GaAs contact layer 10, the insulating film 11, the p-side electrode 12, the n-side electrode 14, the Au layer 61, the high-reflectance coat 15, and the low-reflectance coat 16.

The semiconductor laser element 25 is used in the state having the p-side bonded to a copper-made heatsink 17 with an In brazing material 18. Laser light L emitted from the end face applied with the above-described low-reflectance coat 16. In addition, the active layer may be any type of a compression set, a lattice matching, and a tensile strain quantum well.

In the semiconductor laser element 25, the heat dissipation is made as usual via the heatsink 17. In addition to that, because the groove la formed in the n-GaAs substrate 1 is filled with the Au layer 61 having a higher heat conductivity than the substrate 1, the heat generated at the quantum well active layer 7 and the vicinity thereof is more efficiently dissipated though the Au layer than through the substrate 1 only. Thus, the temperature of the semiconductor laser element 25 (more practically, the temperature in the vicinity of the quantum well active layer 7) is kept low, and a high reliability is insured even under high-output operation. Herein, the heat conductivity of the n-GaAs substrate 1 is about 50 W/(m.circle-solid.K), while the heat conductivity of the Au layer 61 is about 3000 W(m.circle-solid.K).

FIG. 4 shows the electric current to light output characteristics of the semiconductor laser element 25 of the embodiment, together with the corresponding characteristics of a semiconductor laser element of the prior art. The semiconductor laser element of the prior art has almost the same layer construction as that of the semiconductor laser element 25 of the embodiment of the invention, except that it is not equipped with the above-described Au layer 61. The p-side thereof is connected to the copper-made heatsink same as that in FIG. 1 by an In brazing material. Also, in both the semiconductor laser elements, the heatsink bonded to the p-side is further connected to an electronic cooling element and the temperature of the heatsink is fixed at 25.degree. C.

As shown in FIG. 4, in the semiconductor laser element 25 of the invention, the slope efficiency is improved in the high-driving electric current side (that is, a high light output side), and the maximum light output is improved by about 1.5 W compared to the semiconductor laser element of prior art. Also, the semiconductor laser element of the invention has the effect of restraining the generation of a kink even in the range of a high light output.

In addition, although the present invention is applied to a gain waveguide stripe laser having an insulating film stripe in the above-described embodiment of the invention, the invention is not limited to this embodiment but can be similarly applied to a semiconductor laser equipped with a refractive index waveguide mechanism, a semiconductor laser equipped with a diffraction grating, and a light integrated circuit having a semiconductor laser element.

Also, the clad layer may be an InGaAlP-system or an InGsAlAsP-system lattice-matching to the GaAs substrate 1. Also, although the n-type conductive substrate is used as the GaAs substrate 1 in the above-described embodiment, a p-type conductive substrate may instead be used. In this case, all the conductivity types in the above description will be reversed.

Furthermore, although the groove 1a formed in the substrate 1 is formed in an almost rectangular parallelepiped form if the slanting form of the sidewalls is disregarded in the above-described embodiment, other groove forms may be employed as far as similar effects can be obtained. Also, because the groove 1a formed by etching with a sulfuric acid-base etching solution is in a reverse mesa form when viewed from the end face of the semiconductor laser element and extends beyond the etching mask to the light-emitting facet side, the groove 1a works effectively in cooling the light-emitting face by locating the Au layer 61 closer the light-emitting face.

The second embodiment of the invention will now be explained. FIG. 5 shows the perspective view of the semiconductor laser element 30 according to the second embodiment of the invention, FIG. 6 shows the form of the light-emission side face (the end face working as a resonator face) of one light-emitting portion of the semiconductor laser array 30. FIG. 7 shows the form of the cross-section taken along the line B--B of FIG. 6. In addition, in FIG. 5 and the figures thereafter, elements that are identical to elements in FIGS. 1 to 4 have the identical numbers and, if unnecessary, the explanations of them are omitted.

First, by referring to FIG. 6 and FIG. 7, the construction of the semiconductor laser array 30 and the preparation method thereof are explained. On a (100) n-GaAs substrate 1 there are successively grown an n-GaAs-buffer layer 2, an n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3, an n-GaAs contact layer 4, an n-In.sub.0.5 (Ga.sub.1-z2 Al.sub.z2).sub.0.5 P lower clad layer (0.2.ltoreq.z2.ltoreq.1) 42, an n- or i-In.sub.0.49 Ga.sub.0.51 P lower optical waveguide layer 43, an In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer 44 (0.ltoreq.x3.ltoreq.0.3, 0.ltoreq.y3.ltoreq.0.6), a p- or i-In.sub.0.49 Ga.sub.0.51 P upper optical waveguide layer 45, a p-In.sub.0.5 (Ga.sub.1-z2 Al.sub.z2).sub.0.5 P upper clad layer 46, a p-In.sub.x4 Ga.sub.1-x4 As.sub.1-y4 P.sub.y4 etching-preventing layer (0.ltoreq.x4.ltoreq.0.3, 0.ltoreq.y4.ltoreq.0.6) 47, an n-In.sub.0.5 (Ga.sub.1-z3 Al.sub.z3).sub.0.5 P current constricting layer (0.1.ltoreq.z3.ltoreq.z2) 48, and an n-GaAs cap layer (not shown) by an organometallic vapor phase growing method.

Thereafter, after applying a resist (not shown) onto the above-described GaAs cap layer, the stripe-form resist region having a width of about 3 .mu.m in the vertical direction to the cleaved face of the laser is removed in a direction parallel to the substrate orientation flat direction

by an ordinary lithographic method. Thus, using the resist having the stripe-form opening as a mask form together with a tartaric acid etchant, the above-described GaAs cap layer is removed in a stripe.

Then, after peeling off the resist, using the GaAs cap layer as a mask, the n-In.sub.0.5 (Ga.sub.1-z3 Al.sub.z3).sub.0.5 P current constricting layer 48 is etched with a hydrochloric acid-base etchant. Further, the p-In.sub.x4 Ga.sub.1-x4 As.sub.1-y4 P.sub.y4 etching-preventing layer 47 and the above-described n-GaAs cap layer are removed with a sulfuric acid-base etchant.

A p-In.sub.0.5 (Ga.sub.1-z1 Al.sub.z1).sub.0.5 P upper clad layer 53 and a p-GaAs contact layer 54 are also grown thereon. The thickness of the upper clad layer 53 is such a thickness that the refractive index waveguide by a single fundamental mode can be maintained up to high output in a waveguide passageway in the groove of the center portion of the resonator. Then, a p-side electrode 55 is formed and thereafter, the substrate 1 is abraded and an insulating film (not shown) having plural stripe-form openings is formed on the substrate side. Also, using the insulating film as a mask, the GaAs substrate 1 is etched in stripe forms by an ECR dry etching using a Cl.sub.2 gas to form plural grooves 1a. In this case, the etching is automatically stopped at the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3.

Then, the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3 is removed with a hydrochloric acid-base etching solution. After removing the above-described insulating film, an n-side electrode 14 is formed thereon. When a solvent containing an Au material is applied thereon by a spin coating method and annealing is carried out at about 400.degree. C. for 30 minutes, an Au layer 61 is formed in the form of flatly filling the groove 1a.

Thereafter, the n-side electrode 14 and the Au layer 61 at the cleavage region of the sample are removed by a photolithographic etching method. Manufacturing process of the semiconductor laser array 30 is ended by forming a high-reflectance coat 57 and a low-reflectance coat 58 at the surfaces of the resonator of the laser array bar formed by cleaving the sample at the designated positions for both the end faces.

As shown in FIG. 7, the semiconductor laser array 30 is constituted of the n-GaAs substrate 1, the n-GaAs-buffer layer 2, the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3, the n-GaAs contact layer 4, the n-In.sub.0.5 (Ga.sub.1-z2 Al.sub.z2).sub.0.5 P lower clad layer (0.2.ltoreq.z2.ltoreq.1) 42, then- or i-In.sub.0.49 Ga.sub.0.51 P lower optical waveguide layer 43, the In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer 44 (0.ltoreq.x3.ltoreq.0.3, 0.ltoreq.y3.ltoreq.0.6), the p- or i-In.sub.0.49 Ga.sub.0.51 P upper optical waveguide layer 45, the p-In.sub.0.5 (Ga.sub.1-z2 Al.sub.z2).sub.0.5 P upper clad layer 46, the p-In.sub.x4 Ga.sub.1-x4 As.sub.1-y4 P.sub.y4 etching-preventing layer (0.ltoreq.x4.ltoreq.0.3, 0.ltoreq.y4.ltoreq.0.6) 47, the n-In.sub.0.5 (Ga.sub.1-z3 Al.sub.z3).sub.0.5 P current constricting layer (0.1.ltoreq.z3.ltoreq.z2) 48, the p-In.sub.0.5 (Ga.sub.1-z1 Al.sub.z1).sub.0.5 P upper clad layer 53, the p-GaAs contact layer 54, the p-side electrode 55, the n-side electrode 14, the Au layer 61, the high-reflectance coat 57, and the low-reflectance coat 58.

As shown in FIG. 5, the semiconductor laser array 30 has a plurality of light-emitting portions arranged in the lengthwise direction of the array with a predetermined interval between each other. Laser light L is emitted by each light-emitting portion. In addition, although omitted in FIG. 5, the semiconductor laser array 30 may be used by connecting each of the p-side and the n-side to a heatsink having a size corresponding to the array bar size using a brazing material to improve the heat dissipation effect.

In the semiconductor laser array 30, the Au layer 61 having a higher heat conductivity than the n-GaAs substrate 1 is filled in the groove 1a formed in the substrate 1. Thus, the heat generated at the quantum well active layer 44 and the vicinity thereof is more efficiently dissipated through the Au layer 61 than in the case of being dissipated only though the substrate 1.

Thus, temperature rising of the semiconductor laser array 30 (more practically, the vicinity of the quantum well active layer 44) is restrained to insure high reliability even under high output operation while keeping the single transverse mode. In addition, though the same effect is obtained whether or not the above-described heatsink is connected to the Au layer 61, it is preferred that the heatsink is connected for obtaining a better heat dissipation effect.

Although the invention is applied to the fundamental transverse mode oscillating semiconductor laser in the above-described embodiment, the invention can instead be applied to the semiconductor laser having a wide stripe of at least 3 .mu.m. Also, although the GaAs substrate 1 is an n-type substrate in the above-described embodiment, a p-type conductive substrate may instead be used. In the latter case, all the conductivity types described above may be reversed. Also, the oscillating wavelength band can be controlled within the range of from 700 nm to 1200 nm by the composition of the In.sub.x Ga.sub.1-x As.sub.1-y P.sub.y quantum well active layer. Also, by using an InGaAlP-base clad layer and an InGaAlP-base optical waveguide layer in which the band gap is smaller than the clad layer, the oscillation within the range of 600 nm to 700 nm becomes possible.

Furthermore, the crystal growing method may be a molecular beam epitaxial growing method using a solid or a gas as the raw material.

Also, the form of the groove formed in the semiconductor laser array is not limited to a rectangle or a comb shape, and other forms may be employed as far as the similar effects are obtained.

The third embodiment of the invention will now be explained. FIG. 8 shows the form of the light-emitting face (the end face becoming a resonator face) of the semiconductor laser element 60 according to the third embodiment of the invention. FIG. 9 shows the shape of the cross-section taken along the line D--D of FIG. 8.

The semiconductor laser element 60 of the third embodiment is formed as a single element, but the layer structure is the same as the semiconductor laser array 30 of the second embodiment of the invention described above. Therefore, layers, etc. in FIGS. 8 and 9 are identified with the same numbers (or numerals) as those of FIGS. 6 and 7, and explanations for them are omitted.

The semiconductor laser element 60 uses a mounting method known as connected surface up, wherein the n-side, that is a substrate 1 side, is connected to a heatsink 17 using an In brazing material 18. In addition, in this case, an Au layer 61 is directly connected to the heatsink 17 via the In brazing material 18. In the construction, because a groove 1a formed in the n-GaAs substrate 1 is filled with the Au layer 61 having a higher heat conductivity than that of the substrate 1, the heat generated at a quantum well active layer 44 and the vicinity thereof is more efficiently conducted to the heatsink 17 through the Au layer 61 than in the case of being conducted through the substrate 1 only. Accordingly, the heat dissipation effect is improved.

Thus, the temperature rising of the semiconductor laser element 60 (more practically, the temperature in the vicinity of the quantum well active layer 44) is restrained, a high reliability is insured even under a high output operation while keeping the single transverse mode.

In addition, in the case of using a ridge-type semiconductor laser element, the ridge groove can be utilized as the cooling medium passageway similar to the groove of the substrate side as described above. In such a case, it becomes possible to effectively cool both the p and n surfaces of the semiconductor laser element. The fourth embodiment of the invention constructed as described above will now be explained.

FIG. 10 shows the semiconductor laser element 70 according to the fourth embodiment of the invention during operation thereof. Also, FIG. 11 shows the form of the light-emitting face of the semiconductor laser element 70, that is, the end face becoming the resonator face. FIG. 12 shows the cross-sectional shape (the state during the preparation) taken along the line C--C of FIG. 12.

First, by referring to FIGS. 11 and 12, the structure of the semiconductor laser element 70 is explained together with the preparation method thereof. On a (100) n-GaAs substrate 1 there are successively grown an n-GaAs buffer layer 2, an n-In.sub.0.49 Ga.sub.0.51 P etching preventing layer 3, an n-GaAs contact layer 4, an n-Ga.sub.1-z1 Al.sub.z1 As lower clad layer 5 (0.55.ltoreq.z1.ltoreq.0.8), an n- or i-In.sub.0.49 Ga.sub.0.51 P lower optical waveguide layer 6, an In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer 7 (0.ltoreq.x3.ltoreq.0.3, 0.ltoreq.y3.ltoreq.0.6), a p- or i-In.sub.0.49 Ga.sub.0.51 P upper optical waveguide layer 8, a p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9, and a p-GaAs contact layer 10, by an organometallic vapor-phase growing method.

Thereafter, two ridge grooves 21 extending in the lengthwise direction of the resonator are formed on the p-GaAs contact layer 10 and the upper clad layer 9 by a photolithographic method. These ridge grooves 21 are parallel to the substrate orientation flat direction

For example, the width thereof may be 10 .mu.m, and the interval between them may be 50 .mu.m.

After forming an insulating film 11 thereon, the insulating film 11 is removed in a stripe form having a width of about 45 .mu.m between the two ridge grooves. Then, a p-side electrode 12 is formed thereon. By applying thereon a solvent containing an Au material using a spin coating method and annealing it at about 400.degree. C. for 30 minutes, an Au layer 62 is formed in the form of flatly filling the ridge grooves 21.

Thereafter, parts of the p-side electrode and the Au layer 62 within the sample cleavage region are removed by a photolithographic etching method. The n-GaAs substrate 1 is abraded to be thinned to form an insulating layer (not shown) on the back surface thereof. Then, while keeping, a part of the above-described insulating film between the designated positions of both end faces is removed by a lithographic method the lengthwise direction of the grooves parallel to the above-described orientation flat. Then, using the insulating film as a mask, an SiO.sub.2 pattern (not shown) having a stripe-form opening is formed. Using the SiO.sub.2 as a mask, the substrate 1 is etched with a sulfuric acid-base or ammonia-base etchant to form a reverse mesa-form groove 1a. In this case, the etching is automatically stopped at the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3 and GaAs is etched up to the etching-preventing layer 3.

Then, the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3 is removed with a hydrochloric acid-base etching solution. Also, after removing the above-described insulating film, an n-side electrode 14 is formed. Then, when a solvent containing an Au material is applied thereon using a spin coating method and annealing is carried out at about 400.degree. C. for 30 minutes, an Au layer 61 is formed by flatly filling the groove 1a.

Thereafter, the n-side electrode 14 and the Au layer 61 of a sample cleavage region are removed by a photolithographic etching method. Then, the manufacturing process of the semiconductor laser element 70 shown in FIG. 10 is finished by forming a high-reflectance coat 15 and a low-reflectance coat 16 on the resonator surface formed by cleaving the sample at the positions of establishing both end faces to form a chip.

The semiconductor laser element 70 is constituted of the n-GaAs substrate 1, the n-GaAs buffer layer 2, the n-In.sub.0.49 Ga.sub.0.51 P etching-preventing layer 3, the n-GaAs contact layer 4, the n-Ga.sub.1-z1 Al.sub.z1 As lower clad layer 5 (0.55.ltoreq.z1.ltoreq.0.8), the n- or i-In.sub.0.49 Ga.sub.0.51 P lower optical waveguide layer 6, the In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer 7 (0.ltoreq.x3.ltoreq.0.3, 0.ltoreq.y3.ltoreq.0.6), the p- or i-In.sub.0.49 Ga.sub.0.51 P upper optical waveguide layer 8, the p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9, the p-GaAs contact layer 10, the insulating film 11, the p-side electrode 12, the n-side electrode 14, the Au layer 61, the Au layer 62, the high-reflectance coat 15 and the low-reflectance coat 16.

As shown in Table 10, the semiconductor laser element 70 is used in the state where the Au layer 62 of the p-side is connected to the copper-made heatsink 22 via an AuZn brazing material 20 and the Au layer 61 of the n-side is similarly also connected to the copper-made heatsink 19 via the AuZn brazing material 20, and where a laser light L is emitted from the end face having the above-described low-reflectance coat 16. In addition, the active layer may be any of a compression set type, a lattice matching type, and a tensile strain quantum swell type.

Because in the groove 1a formed in the n-GaAs substrate 1 is filled with the Au layer 61 having a higher heat conductivity than that of the substrate 1 in the present embodiment, the heat generated at a quantum well active layer 7 and the vicinity thereof is more efficiently conducted to the heatsink 19 through the Au layer 61 than in the case of being conducted through the substrate 1. Accordingly, the heat dissipation effect is improved.

Furthermore, because the ridge grooves 21, each formed on the p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9 and the p-GaAs contact layer 10, are filled with the Au layer 62 having a higher heat conductivity than those of these layers 9 and 10, the heat generated at a quantum well active layer 7 and the vicinity thereof is still more efficiently conducted to the heatsink 20 through the Au layer 10 than in the case of being conducted through the p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9 and the p-GaAs contact layer 10. Accordingly, the heat dissipating effect is improved. In addition, each of the heat conductivities of the p-Ga.sub.1-z1 Al.sub.z1 As upper clad layer 9 and the p-GaAs contact layer 10 is about 50 W/(m.circle-solid.K) while the heat conductivity of the Au layer 62 is about 3000 W/(m.circle-solid.K).

Thus, temperature rising of the semiconductor laser element 70 (more practically, the temperature rising in the vicinity of the quantum well active layer 7) is restrained, and a high reliability is insured even under a high-output operation while keeping the single transverse mode.

In addition, the shape each of the heatsinks 19 and 20 is not limited to the rectangular parallelepiped block shape, but other shapes equipped with a feather-like or projection form heat dissipation fan, etc., can be suitably used. This is the same as the heatsinks used in the first embodiment and the third embodiment.

Also, the metal filled in the concaved portions formed on the substrate and the semiconductor layer is not limited to Au used in the embodiments described above, but other metals such as Ag, Al, Cu, etc., having a relatively high heat conductivity on Au added with impurities can be suitably used.

Referring to FIG. 13, an application example of the semiconductor laser element of the invention will now be explained. The semiconductor laser element 70 used in this case is, for example, the semiconductor laser el