JP3300657B2 - Compound semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor laser device, and more particularly, to a III-V compound such as GaN,
The present invention relates to a gallium nitride-based semiconductor laser device basically made of a material represented by the following composition formula, such as AlGaN, InGaN, and InAlGaN. In _x Al _y Ga _z N, wherein x + y + z = 1,0 ≦
x, y, z ≦ 1

[0002]

2. Description of the Related Art Short-wavelength semiconductor laser devices have been developed for application to high-density optical disk systems and the like. In this type of laser device, it is required to shorten the oscillation wavelength in order to increase the recording density. As a short-wavelength semiconductor laser device, 60 of InGaAlP material is used.
The 0 nm band light source has already been put to practical use with its characteristics improved to a level at which both reading and writing of a disk are possible.

In order to further improve the recording density, blue semiconductor laser devices have been actively developed in recent years. G
The aN-based semiconductor laser device can be shortened to a wavelength of 350 nm or less, and the reliability of the LED has been confirmed to be 10,000 hours or more. Laser beam oscillation due to current injection at room temperature has also been confirmed. As described above, the nitride-based material is an excellent material that satisfies the conditions necessary for the light source of the next-generation optical disk system.

[0004] In order to be applicable to an optical disk system or the like, the oscillation characteristics of a laser beam are important. For example, in the light emitting section, it is essential to form a transverse mode control structure in a direction parallel to the bonding plane, and to obtain a semiconductor laser device having a low threshold current value and sufficiently low thermal resistance in order to obtain high reliability. Is important. As a candidate that satisfies these conditions in a short-wavelength semiconductor laser device applied to an optical disk system, a ridge structure in which an upper clad layer is formed by drilling is mentioned.

[0005]

However, in the conventional ridge structure, considering the mode control, the ridge width is relatively narrow, and the mode tends to be unstable in the direction perpendicular to the junction surface. There is a problem that the electrode loses a large amount of light and raises the threshold value. Also, the yield is extremely poor, the thermal resistance of the element becomes large, and continuous laser oscillation itself becomes difficult,
Even if oscillation occurs, the reliability of the device is significantly impaired. In the process, since the conventional ridge structure has an opening of the dielectric film on the ridge, difficult alignment is required at the time of the optical lithography process.

As described above, the conventional semiconductor laser device having the ridge structure has a problem that the thermal resistance is high, the mode is unstable, and the process becomes very difficult. The present invention has been made in view of the problems of the related art, and has excellent characteristics such as excellent process reproducibility, easy manufacturing steps, and operation at a low threshold. It is an object of the present invention to provide a transverse mode control type compound semiconductor laser device having a short wavelength band.

[0007]

SUMMARY OF THE INVENTION A first aspect of the present invention is as follows.
In the compound semiconductor laser device, a first cladding layer made of a compound semiconductor of a first conductivity type containing Al;
An active layer composed of a compound semiconductor disposed on the cladding layer, a second cladding layer composed of a second conductivity type compound semiconductor containing Al disposed on the active layer, and an interlayer between the first and second cladding layers. The active layer is sandwiched between the second cladding layer and the second cladding layer, the ridge projecting from the second cladding layer to the opposite side to the active layer and forming a part of a ridge structure extending along the laser beam oscillation direction. And a coating layer made of a dielectric covering each side surface of the ridge portion so as to be in contact with the second cladding layer, having a portion extending laterally on both sides of the ridge portion, A first electrode connected to the first cladding layer, and a first electrode connected to the second cladding layer via an upper surface of the ridge structure and forming a non-ohmic contact with the second cladding layer in the extension. Two electrodes , Characterized by including the.

According to a second aspect of the present invention, in the compound semiconductor laser device according to the first aspect, the active layer and the first
And the second cladding layer is made of a III-V compound semiconductor.

According to a third aspect of the present invention, in a compound semiconductor laser device, a first cladding layer made of a first conductivity type group III nitride semiconductor containing Al and a first cladding layer are provided on the first cladding layer. An active layer made of a group III nitride semiconductor, a second cladding layer made of a second conductivity type group III nitride semiconductor containing Al disposed on the active layer, and a first cladding layer between the first and second cladding layers. That the active layer is sandwiched,
A second ridge portion protruding from the second clad layer on a side opposite to the active layer and forming a part of a ridge structure extending along a laser beam oscillation direction; Having an extending portion extending to
A coating layer made of a semiconductor having a low-resistance top covering the upper surface and both side surfaces of the ridge structure so as to be in contact with the second cladding layer; a first electrode connected to the first cladding layer; And a second electrode connected to the second clad layer via the coating layer.

According to a fourth aspect of the present invention, in the compound semiconductor laser device according to the third aspect, the covering layer forms a non-ohmic contact with the second cladding layer in the extending portion.

According to a fifth aspect of the present invention, in the compound semiconductor laser device according to any one of the first to fourth aspects, the second electrode is made of a metal. According to a sixth aspect of the present invention, in the compound semiconductor laser device according to any one of the first to fifth aspects, the active layer and the second cladding layer are supported on the substrate via the first cladding layer. Features.

According to a seventh aspect of the present invention, in the compound semiconductor laser device according to any one of the first to sixth aspects, the second conductivity type is a p-type. According to an eighth aspect of the present invention, in the compound semiconductor laser device according to any one of the first to seventh aspects, a heat sink layer made of a metal having a thickness of 0.5 μm or more contacts the upper surface and both side surfaces of the ridge structure. It is characterized by doing.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A compound semiconductor laser device according to an embodiment of the present invention will be described in detail. In the following description, components having substantially the same functions and configurations are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a sectional view showing a schematic configuration near a ridge structure of a blue semiconductor laser device according to a first embodiment of the present invention. FIG. 2 is a perspective view showing the laser device according to the first embodiment, with the upper electrode removed. The first embodiment relates to a laser device using a material represented by the following composition formula as a group III-V compound semiconductor forming a laser resonator.

In _x Al _y G _az N, where x + y + z
= 1, 0 ≦ x, y, z ≦ 1 As shown in FIG. 1, in this laser device, an n-GaN buffer layer 2 (Si-doped 1
× 10 ¹⁸ cm ⁻³ , thickness 3 μm) to form n-Al _0.15
Ga _0.85 N cladding layer 11 (Si doped 1 × 10 ¹⁸ cm
^-3 , thickness 0.32 μm), active layer 12, and p-Al
_0.15 Ga _0.85 N cladding layer 13 (Mg doped 5 × 10 ¹⁹
cm ^-3 and a thickness of 0.35 μm). The active layer 12 includes a pair of upper and lower GaN optical guide layers each having a thickness of 0.1 μm, and a multiple quantum well structure (M
QW). The multiple quantum well structure (MQW) has five sets of In _0.20 Ga _0.80 N well layers and I
The barrier layer is composed of n _0.02 Ga _0.98 N, and the thickness of each well layer is set to 3 nm, and the thickness of each barrier layer is set to 6 nm.

On the p-cladding layer 13, p-GaN
A contact layer 14 (Mg-doped 8 × 10 ¹⁹ cm ⁻³ , 0.4 μm thickness); a p-GaN contact layer 15 (Mg-doped 2 × 10
²⁰ cm ^-3 , thickness 0.1 μm), Pt / Ti / Pt / Au
A p-side electrode 16 made of such a metal is sequentially arranged. The p-side electrode 16, the p-contact layers 15 and 14, and the p-cladding layer 13 protrude on the opposite side to the active layer 12 and have a trapezoidal cross-sectional ridge structure 1 extending along the laser beam oscillation direction.
0 is formed.

The ridge structure 10 is formed by forming a metal layer for the p-side electrode 16 and then removing both sides of the striped portion corresponding to the ridge structure 10 from above by etching to the middle of the p-cladding layer 13. Is done. For this reason, the p-cladding layer 13 has a ridge portion 13a which is a part of the ridge structure 10, and an extending portion 13b extending laterally on both sides of the ridge portion 13a.

On each side surface of the ridge structure 10, a coating layer 19 made of SiO _{2 as} a dielectric is provided. The covering layer 19 substantially corresponds to the ridge portion 13a of the p-cladding layer 13.
Is arranged to contact and completely cover both sides of the. An insulating layer 17 made of SiO _{2 is provided} on each extension 13 b of the p-cladding layer 13 at a distance from the lower end of each coating layer 19. The exposed surface of the extension 13b of the p-cladding layer 13 is left along the ridge structure 10 between the covering layer 19 and the insulating layer 17.

The ridge structure 10 is formed on one of the insulating layers 17.
So that it covers the entire length of
An electrode layer 18 made of a metal such as Cr / Au is provided.
The electrode layer 18 is connected to the p-side electrode 16 and forms a non-ohmic contact with the exposed surface of the extension 13b between the covering layer 19 and the insulating layer 17. An exposed surface of the n-buffer layer 2 is formed at a position off the ridge structure 10, and an n-side electrode 3 made of a metal such as Al / Ti / Au is provided thereon.

The ridge structure 10 and the coating layer 19 of the laser device according to the first embodiment, which were used in the experiments described below, were formed by the following method. First, gallium nitride layers 2 and 11 to 15 were all formed on a sapphire substrate 1 by MOCVD (metal organic chemical vapor deposition). Regarding growth conditions,
The pressure is normal pressure, and GaN and AlGaN other than the buffer layer 2 are used.
For the layer, a temperature in the range of 1000 ° C. to 1100 ° C. is basically used in an atmosphere in which nitrogen, hydrogen and ammonia are mixed, and for the active layer 12, a temperature in the range of 700 ° C. to 850 ° C. is used in the atmosphere of nitrogen and ammonia did.

The gallium nitride layers 2 and 11 to 15 are crystal-grown, and a Pt / Ti / Pt / Au for the p-side electrode 16 is grown.
After forming the metal layer, the ridge structure 10 was formed by removing both sides of the stripe-shaped portion corresponding to the ridge structure 10 from above by etching to the middle of the p-cladding layer 13. Here, a photolithography technique using a photosensitive resist and a dry etching technique using reactive chlorine ions are used. Thus, a ridge structure 10 having a trapezoidal cross section and a bottom surface width of 2 μm, protruding on the opposite side to the active layer 12 and extending along the oscillation direction of the laser beam, was formed.

Next, a dielectric (SiO ₂ ) film as a material of the covering layer 19 and the insulating layer 17 was formed with a thickness of 600 nm over the entire surface of the substrate by a thermal CVD method. Next, the coating layer 19
Extending portion 13b of p-cladding layer 13 between insulating layer 17 and insulating layer 17
A photoresist pattern having an opening width of 8 μm was formed on the dielectric film corresponding to the opening for exposing the surface of the substrate. Next, 300 n by reactive ions using CF ₄
The coating layer 19 made of SiO ₂ was formed on both sides of the ridge structure 10 in an average thickness of 200 nm in a self-aligned manner, aiming at an etching amount of m.

The self-alignment formation of the coating layer 19 on both side surfaces of the ridge structure 10 could be performed with good reproducibility. This is because the dielectric film becomes thicker on both sides of the ridge structure 10 when the SiO ₂ dielectric film is formed, reflecting the shape of the ridge structure 10, and the vapor phase etching by reactive ions is performed by ion implantation. It is thought that the fact that the supply is limited by the supply of seeds has an effect.

In the laser device according to the first embodiment manufactured using such a method, the ridge structure 10
The Cr / Au electrode layer 18 is
-Contact with Al _0.15 Ga _0.85 N cladding layer 13. Since this contact is a contact between the p-AlGaN layer 13 having a low carrier concentration and the metal layer 18, an electrical barrier therebetween becomes large. On the other hand, at the top of the ridge structure 10, the p-GaN contact layer 15 doped with Mg at a high concentration and the Pt
The contact with the p-side electrode 16 made of / Ti / Pt / Au results in low contact resistance.

According to the experiment, the p-contact layer 15 and the p-side
Although a current of 150 mA or more could flow through the contact with No. 6, the current flowing through the contact between the electrode layer 18 and the p-cladding layer 13 was 1 mA or less. That is, the first
It has been found that the current confinement effect of the laser device according to the third embodiment is not as bright as that of the conventional structure having no electrode contact outside the ridge structure.

Further, in the laser device according to the first embodiment, since the metal electrode layer 18 having good heat conduction can be brought close to the active layer 12 which is a light emitting portion, the heat radiation is remarkably improved. Can be done. Further, the fundamental mode light is applied to the S layer corresponding to the low refractive index layer on the side surface of the ridge structure 10.
The higher-order mode is controlled by the iO ₂ coating layer 19 and has a structure in which the higher-order mode is further cut off by the metal electrode layer 18 outside the higher-order mode, so that the higher-order mode can be stably suppressed.
According to the experiment, the occurrence of a mode unstable element such as a kink could be suppressed to 10% or less.

In the laser device according to the first embodiment, even when the width of the ridge structure 10 is set to 2 μm or less, the threshold current value rises slowly, and the threshold value itself can be greatly reduced. . According to the experiment of the oscillation characteristics, the present laser device was able to continuously oscillate at room temperature at a threshold value of 15 mA. The oscillation wavelength was 405 nm, and the operating voltage was 5.5V. The beam characteristics were unimodal, and the astigmatic difference was a sufficiently small value of 5 μm. The maximum light output was obtained up to 10 mW by continuous oscillation, the maximum continuous oscillation temperature was 80 ° C., and the device stably operated at room temperature for 1000 hours or more in terms of reliability. These characteristics were obtained by a structure in which the substrate 1 was thinned to 50 μm by polishing, and the substrate 1 was bonded to a heat sink.

FIG. 6 is a sectional view showing the structure of the comparative example.
This is because the S formed over the entire surface including the side surfaces of the ridge structure 10
The electrode layer 18 does not contact the p-cladding layer 13 on the extension 13b outside the ridge structure 10 having the iO ₂ insulating layer 17. In the case of this comparative example, the vertical mode is confined downward, which is disadvantageous for lateral confinement around the ridge structure 10, so that the lateral mode cannot be stably controlled. Conversely, if the insulating layer 17 and the covering layer 19 are not provided, and the electrode layer 18 contacts the side surface of the ridge structure 10, light loss due to the electrode becomes larger than in the fundamental mode, and the threshold value increases. In this case, therefore, the width of the ridge structure 10 is 3
It cannot be reduced to less than μm.

An experiment on the oscillation characteristics of the structure of the comparative example shown in FIG. 6 was performed under the same conditions as those of the laser device according to the first embodiment. As a result, the threshold current value was as high as 80 mA, and the maximum continuous oscillation temperature was 30 ° C. Was low. In addition, a single-peak beam was obtained at a yield of less than half.

FIG. 3 is a sectional view showing a schematic configuration of a blue semiconductor laser device according to a second embodiment of the present invention. The second embodiment is the same as the first embodiment except that the electrode layer 18 made of a metal such as Cr / Au is as thick as 3 μm.

Heat generated in the active layer and the contact region is dissipated to the heat sink. Therefore, when the substrate is fused to the heat sink, the escape of heat from the side opposite to the substrate is the key to improving the characteristics. In the second embodiment, since the electrode layer 18 is not only close to both sides of the ridge structure 10 but also the electrode layer 18 is thick, the heat radiation effect is further enhanced. The thickness of the electrode layer 18 is determined in consideration of the thermal parameters of each part in design. According to the experiment, the heat radiation effect became remarkable by setting the thickness of the electrode layer 18 to 0.5 μm or more, preferably 1 μm or more. When an oscillation characteristic experiment was performed on the second embodiment under the same conditions as those of the laser device according to the first embodiment, the maximum continuous oscillation temperature exceeded 90 ° C., and the reliability test was performed at 50 ° C. for 3000 hours. It was confirmed that the operation was stable.

FIG. 4 is a sectional view showing a schematic configuration near a ridge structure of a red semiconductor laser device according to a third embodiment of the present invention. The third embodiment relates to a laser device using a material represented by the following composition formula as a III-V compound semiconductor forming a laser resonator.

[0033] In _x Ga _y Al _z P, where x + y + z
= 1, 0 ≦ x, y, z ≦ 1 As shown in FIG. 4, in this laser device, an n-InAlP cladding layer 21, an active layer 22, and a p-InAlP cladding layer are formed on a substrate (not shown). 23 are sequentially arranged. The active layer 22 has a pair of upper and lower light guide layers and an InGaAlP multiple quantum well structure (MQW) sandwiched between the two light guide layers.

On the p-cladding layer 23, p-InG
An aP contact layer 24 and a p-GaAs contact layer 25 doped with impurities at a high concentration (low resistance) are sequentially provided. The p-contact layers 25 and 24 and the p-cladding layer 23 project on the opposite side to the active layer 22 and have a trapezoidal ridge structure 20 having a trapezoidal cross section and extending along the laser beam oscillation direction.
To form The p-cladding layer 23 has a ridge portion 23a which is a part of the ridge structure 20, and an extending portion 23b extending laterally on both sides of the ridge portion 23a.

On each side surface of the ridge structure 20, a covering layer 29 made of SiO _{2 as} a dielectric is provided. The coating layer 29 substantially corresponds to the ridge portion 23a of the p-cladding layer 23.
Is arranged to contact and completely cover both sides of the. An insulating layer 27 made of SiO _{2 is provided} on each extension 23 b of the p-cladding layer 23 at a distance from the lower end of each coating layer 29. The exposed surface of the extension 23b of the p-clad layer 23 is left along the ridge structure 20 between the covering layer 29 and the insulating layer 27.

The ridge structure 20 is formed on one of the insulating layers 27.
So as to cover the entire length of
An electrode layer 28 made of a metal such as AuZn / Au is provided. The electrode layer 28 is connected to the p-contact layer 25 and forms a non-ohmic contact with the exposed surface of the extension 23b between the covering layer 29 and the insulating layer 27.

According to the experiment of the oscillation characteristics, each semiconductor layer is
In the laser device according to the third embodiment, which was manufactured by growth by OCVD, continuous oscillation at room temperature was possible at a threshold value of 8 mA. The oscillation wavelength was 650 nm, and the operating voltage was 2.3 V. Beam characteristics are unimodal,
Astigmatic difference was a sufficiently small value of 5 μm.
The maximum light output can be obtained up to 10 mW by continuous oscillation, the maximum continuous oscillation temperature is 90 ° C, and the reliability is 500
It worked stably for more than an hour. These characteristics were obtained with a structure in which the substrate side was bonded to a heat sink.

FIG. 5 is a sectional view showing a schematic configuration near a ridge structure of a blue semiconductor laser device according to a fourth embodiment of the present invention. The fourth embodiment is the same as the first embodiment except for a point relating to the coating layer 31 made of a semiconductor.

In the fourth embodiment, the aforementioned Si
Instead of the coating layer 19 made of O _{2, the} coating layer 3 made of Si
1 is provided. The coating layer 31 is doped (low-resistance) with a high concentration of impurities so as to function as an electrode or a wiring. The covering layer 31 is disposed so as to cover the entire length of the ridge structure 10 from one of the insulating layers 17 in a contact state, and further to reach the other insulating layer 17. The covering layer 31 forms an ohmic contact with the p-side electrode 16 and forms a non-ohmic contact with the exposed surface of the extension 13 b between the covering layer 19 and the insulating layer 17. Further, a Cr / Au electrode layer 18 is provided so as to cover the entire coating layer 31.

The coating layer 31 of the laser device according to the fourth embodiment, which was used for experiments described below, was formed by the following method. Gallium nitride layers 11 to 15 are crystal-grown, and the p-side electrode 1
After the formation of the Pt / Ti / Pt / Au metal layer for 6, the ridge structure 10 is removed by etching both sides of the striped portion corresponding to the ridge structure 10 from above to the middle of the p-cladding layer 13. Formed. next,
A dielectric (SiO ₂ ) film serving as a material of the insulating layer 17 is subjected to thermal CV.
Formed over the entire surface of the substrate by Method D. Next, an opening was provided near the ridge structure 10 by repeatedly using the photolithography technique and the chemical etching technique. Then, the Si coating film 31 and the electrode layer 18 were sequentially formed by the sputtering method. The width of the ridge structure 10 was 3 μm at the bottom, and the opening width of the SiO ₂ film (insulating layer 17) was 8 μm.

In the laser device according to the first embodiment manufactured using such a method, the ridge structure 10 is used.
Of the Si covering layer 31 is p-Al
It comes into contact with the _0.15 Ga _0.85 N cladding layer 13. This contact is made between the p-AlGaN layer 13 having a low carrier concentration and the low-resistance Si.
Since the contact is made with the coating layer 31, the contact becomes a non-ohmic contact. On the other hand, at the top of the ridge structure 10, the p-side electrode 16 comes into contact with the low-resistance Si coating layer 31, so that an ohmic contact is formed. Further, the low-resistance Si coating layer 31 and the electrode layer 18 outside the low-resistance Si coating layer 31 can substantially function as an integrated electrode.

That is, in the fourth embodiment, if the ridge structure 10 is covered by selecting the type of the semiconductor material of the covering layer 31, the same effect as in the first to third embodiments can be effectively obtained. It shows that it can be obtained. The Si coating layer 3
In 1, the resistance may be lowered by selectively doping impurities into a portion where a current is to flow, such as a contact portion with the electrode 16.

According to the experiment on the oscillation characteristics, in the laser device according to the fourth embodiment, the threshold current value at room temperature was 20 mA, and the maximum continuous oscillation temperature could be increased to 80 ° C. Also, a reliability test confirmed that the device operates stably at 50 ° C. for 100 hours or more.

The present invention is not limited to the above embodiment. For example, in the first embodiment and the like, a sapphire substrate is used.
Substrates can be used. In addition, other than SiO ₂ , Al ₂ O _{3 and the} like can be used as the dielectric and the insulator.

In the above-described embodiment, the general formula of the semiconductor forming the laser resonator is In _x Al _y G _az N, where x + y + z = 1, 0 ≦
x, y, z ≦ 1 In x Ga y Al z P, where x + y + z = 1,0 ≦
x, y, z ≦ 1, but each semiconductor layer is made of Ti, Si, C, Ni
And the like may be contained in an amount of an impurity that does not form a mixed crystal. Furthermore, as a semiconductor forming a laser cavity
The present invention can be applied to a case where a II-VI compound semiconductor, Si, or Ge is used.

The structure of the laser device can be variously modified as long as it does not adversely affect the threshold value of the laser. In addition, the present invention is also applicable to the field of optical devices such as a waveguide structure, a light receiving element, and a transistor.

[0047]

According to the present invention, an excellent transverse mode semiconductor laser device having a sufficiently low thermal resistance and a simple manufacturing method can be realized. In particular, since the characteristics can be lowered in threshold value, the beam characteristics are good, and the reliability is greatly improved, the usefulness of the semiconductor laser device according to the present invention is high.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration near a ridge structure of a blue semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing the laser device according to the first embodiment, with an upper electrode removed;

FIG. 3 is a sectional view showing a schematic configuration of a blue semiconductor laser device according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a schematic configuration near a ridge structure of a red semiconductor laser device according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a schematic configuration near a ridge structure of a blue semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a schematic configuration of a laser device of a comparative example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sapphire substrate 2 n-GaN buffer layer 3 n-side electrode 10 ridge structure 11 n-AlGaN cladding layer 12 active layer 13 p-AlGaN cladding layer 14 and 15 p-GaN contact layer 16 p Side electrode 17 Dielectric coating layer 18 Electrode layer 19 Insulating layer 20 Ridge structure 21 n-InAlP cladding layer 22 Active layer 23 p-InAlP cladding layer 24, 25 p-contact layer 27 dielectric Covering layer 28 ... Electrode layer 29 ... Insulating layer 31 ... Semiconductor covering layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-260772 (JP, A) JP-A-3-101286 (JP, A) JP-A-10-223970 (JP, A) JP-A-10- 303502 (JP, A) JP-A-4-111375 (JP, A) JP-A-62-281384 (JP, A) JP-A-57-53990 (JP, A) JP-A-7-202344 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 JICST file (JOIS)

Claims (8)

(57) [Claims] A first cladding layer made of a compound semiconductor of a first conductivity type containing Al; an active layer made of a compound semiconductor provided on the first cladding layer; and an active layer provided on the active layer. a second cladding layer made of a compound of the second conductivity type semiconductor containing al, and said active layer is sandwiched between the first and second cladding layers, said second cladding layer, said from said second cladding layer A ridge portion protruding on the opposite side to the active layer and forming a part of a ridge structure extending along the oscillation direction of the laser beam;
An extension portion extending laterally on both sides of the ridge portion; a coating layer made of a dielectric covering each side surface of the ridge portion so as to contact the second cladding layer; A first electrode connected to the cladding layer, a second electrode connected to the second cladding layer via an upper surface of the ridge structure, and forming a non-ohmic contact with the second cladding layer in the extension. A compound semiconductor laser device comprising: 2. The compound semiconductor laser device according to claim 1, wherein said active layer and said first and second cladding layers are made of a group III-V compound semiconductor. 3. A first cladding layer made of a first conductivity type group III nitride semiconductor containing Al, an active layer made of a group III nitride semiconductor disposed on the first cladding layer, and the active layer. A second cladding layer made of a second conductivity type group III nitride semiconductor containing Al disposed thereon, the active layer being sandwiched between the first and second cladding layers, the second cladding layer A ridge part of a ridge structure protruding from the second cladding layer on the opposite side to the active layer and extending along the laser beam oscillation direction, and extending laterally on both sides of the ridge part An extension portion; a coating layer made of a semiconductor having a top portion having a reduced resistance and covering an upper surface and both side surfaces of the ridge structure so as to be in contact with the second cladding layer; and the first cladding layer. A first electrode connected to the And a second electrode connected to the second cladding layer via a cover layer. 4. The semiconductor device according to claim 1, wherein said coating layer is formed on said extending portion.
4. The compound semiconductor laser device according to claim 3, wherein a non-ohmic contact is formed with the cladding layer. 5. The compound semiconductor laser device according to claim 1, wherein said second electrode is made of a metal. 6. The method according to claim 1, wherein said active layer and said second cladding layer are formed of said first layer.
6. The compound semiconductor laser device according to claim 1, wherein the compound semiconductor laser device is supported on a substrate via a cladding layer. 7. The compound semiconductor laser device according to claim 1, wherein said second conductivity type is p-type. 8. The compound semiconductor laser device according to claim 1, wherein a heat sink layer made of a metal having a thickness of 0.5 μm or more is in contact with an upper surface and both side surfaces of said ridge structure. .