JP2000058966A - Semiconductor laser and semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser and a semiconductor laser device of GaN-based compound, which is capable of performing face down mounting and operation at the large output or at the high temperature. SOLUTION: This semiconductor laser comprises a GaN-based compound semiconductor laminated structure, wherein ohmic electrodes 75 and 76 on the p-side and the n-side are formed on the same surface. The p-side electrode 75 is formed at the uppermost layer of the GaN-based compound semiconductor layered structure constituting the semiconductor laser. The n-side electrode 76 is formed at the same height as that of the p-side electrode 75.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor laser and a semiconductor laser device.

[0002]

2. Description of the Related Art Conventionally, blue LEDs have low brightness compared to red and green, and have been difficult to put into practical use. However, recently, in a GaN-based compound semiconductor represented by the general formula InAlGaN, a low-temperature AlN buffer layer or Improvement of crystal growth technology by using low-temperature GaN buffer layer and M
Since a low-resistance p-type semiconductor layer doped with g was obtained, a high-intensity blue LED was put to practical use, and a semiconductor laser which did not reach practical use but continuously oscillated at room temperature was realized. Further, the development of a semiconductor laser forming technique on a low-defect substrate by combining selective growth and lateral growth has extended the lifetime of the semiconductor laser at room temperature continuous oscillation to about 1000 hours.

FIG. 4 is a cross-sectional view of a conventional edge-emitting laser diode manufactured by using a semiconductor laser forming technique on a low defect substrate by combining selective growth and lateral growth (Applied Physics Letters Vol. 72). (1998) p.21
1). The semiconductor laser shown in FIG. 4 is made of 100 to 300 μm of sapphire (Al ₂ O ₃ single crystal) having a (0001) plane as a main surface.
A low-temperature buffer layer 142 made of n-type GaN, a high-temperature buffer layer 143 made of n-type GaN, and a selective growth mask 144 made of SiO ₂ are formed on an m-type substrate 141. An n-In _0.1 Ga _0.9 N crack preventing layer 145 and an n-Al _0.14 Ga _0.86 N / GaN MD- are formed on a substrate composed of an n-type GaN layer formed by selective growth and lateral growth on the mask surface. S
LS (Modulation Doped Strain Superlattice) Cladding Layer 1
46, the n-GaN optical guide layer 147, and In _0.15 Ga
_0.85 N / In _0.02 Ga _0.98 N MQW active layer 148,
a p-Al _0.2 Ga _0.8 N dislocation propagation preventing layer 149;
aN layer light guide layer 150 and p-Al _0.14 Ga _0.86 N /
GaN MD-SLS cladding layer 151 and p-type GaN
The layer cap layer 152 is sequentially laminated by the MOCVD method.

An optical waveguide and an end face of an optical resonator are formed by dry-etching the stacked semiconductor layers in a ridge shape, and the n-G exposed by etching is further formed.
The n-side electrode 155 and the p-side electrode 155 are provided on the cap layer 152, which is the surface layer of the stacked semiconductor layers, respectively.
By providing the side electrode 153, a semiconductor laser is formed.

FIG. 5 is a sectional view of a conventional edge emitting laser diode disclosed in Japanese Patent Application Laid-Open No. 9-223846. In the apparatus shown in FIG. 5, a semiconductor laser chip is mounted face-down on a mounting substrate. ing. That is, in FIG. 5, the mounting substrate includes a support 1 having electrical conductivity such as a metal, an insulating film 20 formed on the support 1, and a lead electrode 30. Is composed of a substrate 10 such as sapphire, a nitride semiconductor layer 11 that oscillates a laser, a negative electrode 12 on the n-layer side, and a positive electrode 13 on the p-layer side. The semiconductor laser chip is supported on the electrode surface side. It is die-bonded via a conductive adhesive 40 such as solder or silver paste in a face-down state facing the body surface side.

More specifically, the nitride semiconductor layer 11 basically has a double hetero structure in which an n-type contact layer, an n-type optical confinement layer, an active layer, a p-type optical confinement layer, and a p-type contact layer are stacked. And a p-type contact layer, a p-type optical confinement layer,
The active layer and a part of the n-type light confinement layer are removed by etching to expose the n-type contact layer. The positive electrode 13 is provided on the uppermost p-type contact layer, and the negative electrode 12 is provided on the surface of the n-type contact layer exposed by etching. The insulating film 20 is adjusted to have a thickness of several hundreds to several tens of μm so that the semiconductor laser chip is horizontal with respect to the support 1. In FIG. 5, the negative electrode 12 side is wire-bonded with a gold wire 50.

[0007] By performing such face-down mounting, the heat radiation from the electrode portion is enhanced, and the operation is stabilized.
Improves reliability.

[0008]

As described above, the technique of forming a GaN-based compound semiconductor on a heterogeneous substrate such as sapphire is achieved by the technique of a low-temperature buffer layer and the technique of forming a GaN thick film by a combination of selective growth and lateral growth. Crystal growth became possible, a high-brightness LED was realized, and continuous oscillation at room temperature of a semiconductor laser was also realized.

However, since the GaN-based compound semiconductor generally cannot increase the carrier concentration of the p-type layer, the resistance of the p-type layer is high, and the contact resistivity of the ohmic electrode is as high as 10 ^-2 Ωcm ^-2 . Therefore, the operating voltage is high and heat is easily generated, so that the life is extremely short in a high-output operation or a high-temperature operation.

Further, a conventional GaN as shown in FIG.
The compound semiconductor laser is formed on a sapphire substrate 141 and has a selective growth mask 1 made of SiO _2.
Since 44 was inserted between the substrate and the semiconductor laser laminated structure, the heat radiation characteristics were extremely poor.

In the conventional semiconductor laser as shown in FIG. 5, heat radiation is improved by face-down mounting. However, the height of the n-side electrode and the height of the p-side electrode of the semiconductor laser chip are different. In order to prevent the chip from being tilted and mounted to deteriorate the beam shape, the insulating film 20 formed on the mounting substrate to make the chip horizontal with respect to the support 1.
Height adjustment was required. This height adjustment requires a high-precision adjustment of several hundred angstroms to several tens of microns, and it is difficult to easily produce the height.

An object of the present invention is to provide a semiconductor laser and a semiconductor laser device of a GaN-based compound semiconductor which can be easily mounted face down and can operate at a high output or at a high temperature.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a semiconductor comprising a GaN-based compound semiconductor laminated structure in which p-side and n-side ohmic electrodes are formed on the same surface. A laser, wherein the p-side electrode is formed on the uppermost layer of the GaN-based compound semiconductor laminated structure forming the semiconductor laser, and the n-side electrode is formed at the same height as the p-side electrode. .

According to a second aspect of the present invention, there is provided the semiconductor laser according to the first aspect, wherein the GaN-based semiconductor laser has the same structure as the semiconductor laser, and is formed through the groove with the semiconductor laser. A ridge portion made of a compound semiconductor multilayer structure, a p-side electrode is formed on the upper surface of the semiconductor laser portion, and an n-type layer at the bottom of the groove is formed on the side surface and the upper surface of the ridge portion by an ohmic contact. It is characterized in that the n-side electrode in contact is extended.

According to a third aspect of the present invention, in the semiconductor laser according to the first or second aspect, the substrate is optically transparent.

A fourth aspect of the present invention is characterized in that the semiconductor laser according to any one of the first to third aspects is face-down mounted.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a semiconductor laser according to the present invention. FIG. 1 is a cross-sectional view in which the light emission direction of the semiconductor laser is perpendicular to the paper surface. Referring to FIG. 1, this semiconductor laser is made of sapphire (0001)
On a C-plane substrate 61, a GaN low-temperature buffer layer 62, n-G
aN layer 63, p-G in which a stripe-shaped opening is formed
aN layer 64, n-GaN layer 6 laminated on n-GaN layer 63 exposed on this opening and on p-GaN layer 64
5. Crack preventing layer 6 made of n-In _0.1 Ga _0.9 N
6, n-Al _0.14 Ga _0.86 N / GaN cladding layer 67 made of MD-SLS (modulation-doped-strain superlattice), light guide layer 68 made of n-GaN layer, In
_An active layer 69 made of _0.15 Ga _0.85 N / In _0.02 Ga _0.98 N MQW, a dislocation propagation preventing layer 70 made of a p-Al _0.2 Ga _0.8 N layer, an optical guide layer 71 made of a p-GaN layer, p
A cladding layer 72 made of Al _0.14 Ga _0.86 N / GaN MD-SLS, and a cap layer 73 made of a p-type GaN layer
Are sequentially laminated to form a laminated structure of the semiconductor laser.

The optical resonator end face of the semiconductor laser is formed by dry-etching this laminated structure down to the GaN layer 63. Also, the exposed GaN layer 63
An SiO ₂ insulating film 7 is provided on the surface and the laminated structure surface and side surfaces.
4 have been deposited. Then, the SiO ₂ insulating film 74
Has p-type GaN, which is the surface layer of the stacked structure of the semiconductor laser
Openings whose surfaces are exposed are formed in the portion of the cap layer 73 and the portion of the n-GaN layer 63, respectively, where the p-side electrode 75 and the n-side electrode 76 are formed. ing. Further, the n-side electrode 76 climbs up on the insulating film 74 on the side surface of the stacked structure and is formed up to the same height as the upper surface of the stacked structure, that is, the p-side electrode 75.

FIG. 6 is a diagram showing another configuration example of the semiconductor laser according to the present invention. FIG. 6 is a cross-sectional view in which the light emission direction of the semiconductor laser is perpendicular to the paper surface. Referring to FIG. 6, this semiconductor laser includes a GaN low-temperature buffer layer 112, an n-GaN layer 113, and n-In _0.1 Ga _0.9 N on a sapphire (0001) C-plane substrate 111.
Anti-cracking layer 114 of n-Al _0.14 Ga _0.86
Cladding layer 115 made of N / GaN MD-SLS (modulation doping-strain superlattice), optical guide layer 116 made of n-GaN layer, In _0.15 Ga _0.85 N / In
Active layer 117 of _0.02 Ga _0.98 N MQW, p-A
The dislocation propagation preventing layer 118 made of an l _0.2 Ga _0.8 N layer, p-
Light guide layer 119 composed of a GaN layer, p-Al _0.14 Ga
Cladding layer 12 composed of _0.86 N / GaN MD-SLS
A cap layer 121 composed of 0, p-type GaN layers is sequentially laminated to form a laminated structure of a semiconductor laser.

The laminated structure is dry-etched to the GaN layer 113 to form an optical resonator end face of the semiconductor laser. In addition, the exposed GaN layer 1
An SiO ₂ insulating film 122 is deposited on the surface 13 and the surface and side surfaces of the laminated structure. The SiO ₂ insulating film 122 has a p layer which is a surface layer of a laminated structure of the semiconductor laser.
Layer 121 comprising n-type GaN layer and n-GaN layer 1
13 are formed with openings whose surfaces are exposed. The p-side electrode 123 and the n-side electrode
Are formed respectively. Here, the opening formed in the SiO ₂ insulating film 122 on the cap layer 121 made of the p-type GaN layer has a stripe shape. Also,
The n-side electrode 124 climbs over the insulating film 122 on the side surface of the stacked structure and is formed at the same height as the top surface of the stacked structure, that is, the p-side electrode 123.

As described above, the semiconductor laser shown in FIG. 1 or 6 has the p-side and n-side ohmic electrodes 75 or 12.
Ga on which 3, 76 or 124 are formed on the same surface
In a semiconductor laser having an N-based compound semiconductor multilayer structure, a p-side ohmic electrode 75 or 123 is formed on the uppermost layer of a GaN-based compound semiconductor multilayer structure forming a semiconductor laser, and an n-side ohmic electrode 76 or 124 is formed.
Are formed at the same height as the p-side ohmic electrode 75 or 123.

Conventionally, as shown in FIGS. 4 and 5, the n-side electrode is formed on the exposed surface of the n-side layer by removing the p-side layer of the laminated structure by dry etching. Therefore, the n-side electrode is formed at a position lower than the p-side electrode. However, the semiconductor laser shown in FIG. 1 or FIG. A contact is made, and wiring is formed on the insulating film 74 or 122 from the contact to the uppermost layer of the GaN-based compound semiconductor laminated structure constituting the semiconductor laser.

As described above, in the semiconductor laser shown in FIG. 1 or 6, the n-side electrode 76 or 124 is replaced by the p-side electrode 75.
Alternatively, since it is formed at the same height as 123, there is no need to consider the difference in electrode height, and face-down mounting can be easily performed. That is, the semiconductor laser shown in FIG. 1 or FIG. 6 can be easily face-down mounted on a mounting substrate, has better heat dissipation than mounting the substrate side on a heat sink material, and can perform a large output operation and a high temperature operation.

In the semiconductor laser shown in FIG. 1 or 6, current is injected from the p-side electrode 75 or 123 and the n-side electrode 76 or 124 formed on the ridge. This electrode 75 or 123, 76 or 124
By applying a forward voltage to and injecting a current, carriers recombine in the active layer 69 or 117 to emit light, which is emitted from the end face of the optical resonator as stimulated emission light.

The laminated structure of the semiconductor laser is not particularly limited, and may have any structure such as a double hetero structure, a single hetero structure, and a quantum well structure. If the substrate 61 or 111 is a substrate on which a GaN-based compound semiconductor crystal grows, its material,
The electrical characteristics and the like are not particularly limited.

FIG. 2 is a view showing another configuration example of the semiconductor laser according to the present invention. Referring to FIG. 2, this semiconductor laser is formed by dry etching a GaN-based compound semiconductor laminated structure laminated on a sapphire substrate 81, and is provided with a ridge 201 serving as a semiconductor laser part and an n-type ridge 201.
And ridges 202 for forming side electrodes.

In other words, the semiconductor laser of FIG.
Groove 203 reaching N-side layer in N-type compound semiconductor laminated structure
The active layer is divided into two ridges 201 and 202. One ridge 201 functions as a semiconductor laser unit, and a p-side ohmic electrode 95 is formed on the surface of an upper p-type layer. On the other ridge 202, an insulating film 94 is deposited on the surface, and the n-side electrode 96 having ohmic contact with the exposed n-side surface at the bottom of the groove 203 is formed on the side surface of the ridge 202 and the upper surface of the ridge 202. Has also been extended.

More specifically, the semiconductor laser shown in FIG. 2 has a GaN low-temperature buffer layer 82, an n-GaN layer 83, a p-GaN layer 84, an n-type GaN layer 84 on a sapphire (0001) C-plane substrate 81.
-GaN layer 85, crack prevention layer 86 made of n-In _0.1 Ga _0.9 N, n-Al _0.14 Ga _0.86 N / GaN MD
A cladding layer 87 made of SLS (modulation doping-strain superlattice), and a light guide layer 8 made of n-GaN layer
8, In _0.15 Ga _0.85 N / In _0.02 Ga _0.98 N MQW
Active layer 89 made of, a dislocation propagation preventing layer 90 made of a p-Al _0.2 Ga _0.8 N layer, an optical guide layer 91 made of a p-GaN layer, p-Al _0.14 Ga _0.86 N / GaN MD-SLS
, And a cap layer 93 made of a p-type GaN layer are sequentially laminated. Here, the p-GaN layer 8 having a laminated structure constituting the semiconductor laser 8
4, a stripe-shaped opening is formed to form a current confinement structure.

By dry-etching this laminated structure, an optical resonator end face of the semiconductor laser is formed, and a groove 203 is formed. The surface of the GaN layer 83 exposed by the groove 203 and the surface of the laminated structure are
An O ₂ insulating film 94 is deposited. And this SiO ₂
The insulating film 94 includes a portion of a cap layer 93 made of a p-type GaN layer, which is a surface layer of the stacked structure of the semiconductor laser, and n-Ga
Openings whose surfaces are exposed are formed in the portion of the N layer 83, and a p-side electrode 95 and an n-side electrode 96 are formed in those portions. Then, the n-side electrode 9
6 is formed to extend over a ridge 202 having substantially the same height as the semiconductor laser unit 201 adjacent to the semiconductor laser unit 201.

As described above, in the semiconductor laser shown in FIG. 2, the ridge 202 formed of the GaN-based compound semiconductor laminated structure having the same structure as the semiconductor laser unit 201 is formed on the semiconductor laser unit 201 via the groove 203. , Groove 20
N-side electrode 9 in ohmic contact with the n-type layer at the bottom of 3
6, the p-side electrode 95 and the n-side electrode 96 can be positioned at substantially the same height, and it is necessary to consider differences in electrode height. And face down mounting can be easily performed. Further, the ohmic contact position of the n-side electrode 96 can be made closer to the semiconductor laser unit 201, so that the series resistance is reduced, the operating voltage is reduced accordingly, and the calorific value is also reduced.

In the semiconductor laser shown in FIG.
The p-side electrode 95 formed above the ridges 201 and 202,
This is performed from the n-side electrode 96. By applying a forward voltage to the electrodes 95 and 96 and injecting a current, the active layer 89 is formed.
Then, recombination of carriers occurs, and light is emitted, and emitted to the outside from the end face of the optical resonator as stimulated emission light. The laminated structure of the semiconductor laser is not particularly limited,
Any structure such as a double hetero structure, a single hetero structure, and a quantum well structure may be employed. Further, as long as the substrate 81 is a substrate on which a GaN-based compound semiconductor crystal grows, its material, electric characteristics, and the like are not particularly limited.

In the semiconductor laser shown in FIGS. 1, 2, and 6, optically transparent substrates can be used as the substrates 61, 81, and 111. Here, the substrate is optically transparent means that the substrate is optically transparent in terms of material properties, particularly transparent in the visible light range, and the back surface of the substrate has been subjected to mirror polishing or a process similar thereto. This means that the electrodes of the semiconductor laser formed on the front surface can be easily observed from the back surface of the substrate with an optical microscope or the like. As such a substrate, for example, sapphire, MgAl ₂ O ₄ , GaN, Z
A mirror-polished back surface such as nO can be used.

Thus, for example, sapphire (0001)
Not only are the C-plane substrates 61 and 81 optically transparent in terms of material properties, but also the rear surfaces of the substrates 61, 81 and 111 are mirror-polished or processed according to the same, so that they are formed on the substrate surfaces. The electrode of the semiconductor laser can be easily observed from the back surface of the substrate. In particular, for example, at the time of alignment at the time of mounting, the positions of the electrodes of the semiconductor laser and the electrodes of the mounting substrate can be observed from the back surface of the substrate, so that face-down mounting can be easily performed.

FIG. 3 is a diagram showing a configuration example of a semiconductor laser device according to the present invention. Referring to FIG. 3, the semiconductor laser device is configured such that the electrode surface of the semiconductor laser of FIG.
Face-down mounted on the mounting board.

Here, the mounting substrate is formed on a support substrate 102 made of insulating ceramic, and a positive electrode 100 and a negative electrode 101 made of a metal material having good heat dissipation and also serving as a heat sink.
Are formed, and on each of them, a metal electrode pad 98,
99 are formed.

Then, the p-side electrode 95 of the semiconductor laser is adhered to the electrode pad 98 of the mounting substrate with the conductive adhesive 97, and the n-side electrode of the semiconductor laser is mounted on the electrode pad 99 of the mounting substrate.
The side electrode 96 is adhered, and the semiconductor laser of FIG. 2 is mounted face down on a mounting substrate.

In the semiconductor laser device of FIG. 3, the sapphire (0001) C-plane substrate 81 of the semiconductor laser is
A mirror-polished back surface can be used. In this case, the electrodes 95 and 96 formed on the semiconductor laser on the front surface of the substrate can be observed from the back surface of the substrate, and the positioning at the time of face-down mounting becomes easy, so that the face-down mounting can be easily performed.

Further, in the semiconductor laser device of FIG. 3, the p-side electrode 95 and the n-side electrode 96 of the semiconductor laser can be positioned at substantially the same height, and it is not necessary to consider the difference in electrode height. In addition, a special structure such as a height adjusting mechanism is not required on the mounting substrate, and face-down mounting can be easily performed as compared with the related art.

Further, since the semiconductor laser is face-down mounted, the heat radiation of the semiconductor laser is improved as compared with the case where the substrate is mounted on a heat sink material, so that a large output operation and a high temperature operation can be performed.

In the semiconductor laser device shown in FIG.
When a current is injected with the electrode 101 as a positive electrode and the electrode 101 as a negative electrode, laser oscillation occurs.

[0042]

As described above, according to the first aspect of the present invention, there is provided a semiconductor laser having a GaN-based compound semiconductor multilayer structure in which p-side and n-side ohmic electrodes are formed on the same surface. Therefore, the p-side electrode is formed on the uppermost layer of the GaN-based compound semiconductor stacked structure forming the semiconductor laser, and the n-side electrode is formed at the same height as the p-side electrode. There is no need to consider it, and face-down mounting can be easily performed.

According to the second aspect of the present invention, the semiconductor laser portion and the ridge having the same structure as the semiconductor laser portion and a GaN-based compound semiconductor laminated structure formed via the groove with the semiconductor laser portion. And a p-side electrode is formed on the upper surface of the semiconductor laser portion, and an n-side electrode having ohmic contact with an n-type layer at the bottom of the groove is formed on a side surface and an upper surface of the ridge portion. Is formed so that the ohmic contact position of the n-side electrode can be made closer to the semiconductor laser, the series resistance is reduced, the operating voltage is reduced accordingly, and the heat generation is also reduced. Further, the p-side electrode is formed on the uppermost layer of the GaN-based compound semiconductor laminated structure constituting the semiconductor laser, and the n-side electrode is formed at the same height as the p-side electrode. There is no need to consider it, and face-down mounting can be easily performed.

According to the third aspect of the present invention, not only is the substrate optically transparent in terms of material properties, but also the back surface of the substrate is subjected to mirror polishing or a process similar thereto, and Since the formed semiconductor laser electrodes can be easily observed from the backside of the substrate, the positions of the electrodes of the semiconductor laser and the electrodes of the mounting board can be observed from the backside of the board during alignment at the time of mounting. Face-down mounting can be performed.

According to the fourth aspect of the present invention, since the semiconductor laser according to any one of the first to third aspects is mounted face-down, the height is adjusted on the mounting substrate. It is possible to provide a semiconductor laser device that is mounted face down more easily than in the past without requiring a special structure such as a mechanism. In the semiconductor laser device mounted face-down in this way, the heat radiation of the semiconductor laser is improved as compared with the semiconductor laser device mounted on the heat sink material on the substrate side, and a large output operation and a high temperature operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a semiconductor laser according to the present invention.

FIG. 2 is a diagram showing another configuration example of the semiconductor laser according to the present invention.

FIG. 3 is a diagram showing a configuration example of a semiconductor laser device according to the present invention.

FIG. 4 is a diagram showing a conventional semiconductor laser.

FIG. 5 is a diagram showing a conventional semiconductor laser.

FIG. 6 is a diagram showing another configuration example of the semiconductor laser according to the present invention.

[Explanation of symbols]

61, 81, 111 Sapphire (0001) C-plane substrate 62, 82, 112 GaN low-temperature buffer layer 63, 83, 113 n-GaN layer 64, 84 p-GaN layer 65, 85 n-GaN layer 66, 86, 114 n -In _0.1 Ga _0.9 N crack prevention layer 67, 87, 115 n-Al _0.14 Ga _0.86 N / Ga
N MD-SLS - optical guide layer _{69,89,117 In 0.15 Ga 0.85 N / In} 0.02 constituted by the cladding layer 68,88,116 n-GaN layer made of (modulation doped strained superlattice)
Ga _0.98 N light guide layer 72,92 p-Al _0.14 Ga _0.86 composed of the active layer 70,90,118 p-Al _0.2 Ga _0.8 N consisting layer dislocation propagation preventing layer 71,91,119 p-GaN layer made of MQW N / Ga
NMD-SLS cladding layer 73,93,121 Cap layer 74,94,122 SiO ₂ insulating film 75,95,123 p-type GaN layer p-side electrode 76,96,124 n-side electrode 100 positive electrode 101 Negative electrode 102 Support substrate 98, 99 Metallic electrode pad 97 Conductive adhesive

Claims (4)

[Claims] 1. A semiconductor laser having a GaN-based compound semiconductor multilayer structure in which p-side and n-side ohmic electrodes are formed on the same surface, wherein the p-side electrode is a GaN-based compound semiconductor multilayer constituting the semiconductor laser. A semiconductor laser formed on the uppermost layer of the structure, wherein the n-side electrode is formed at the same height as the p-side electrode. 2. The semiconductor laser unit, comprising: a semiconductor laser unit; and a ridge having the same structure as the semiconductor laser unit and having a GaN-based compound semiconductor laminated structure formed through a groove. A p-side electrode is formed on the upper surface of the ridge portion, and an n-side electrode having ohmic contact with an n-type layer at the bottom of the groove is formed on the side surface and the upper surface of the ridge portion. A semiconductor laser characterized by the above-mentioned. 3. The semiconductor laser according to claim 1, wherein the substrate is optically transparent. 4. A semiconductor laser device comprising the semiconductor laser according to claim 1 mounted face down.