JP3348024B2 - 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 semiconductor laser device, and more particularly to a semiconductor laser device having a structure in which a nitride-based compound semiconductor laser element can be securely mounted.

[0002]

2. Description of the Related Art A nitride-based compound semiconductor laser device uses a mixed crystal of InGaN for an active layer and an A layer for a cladding layer.
By using a mixed crystal of lGaN, the wavelength
Since blue-violet laser light of 0 nm to 430 nm can be oscillated, its practical use as a light source for high-density optical disks is expected.

Recently, Nakamura et al. Have succeeded in continuous operation for over 1000 hours at room temperature using a semiconductor laser device fabricated on a sapphire substrate by metal organic vapor phase epitaxy (MOVPE) (Appl. Phys. Let.).
t. , Vol. 72, no. 2, pp. 211-21
3, 1998).

In the case of a semiconductor laser device having a pn junction in which an n-type semiconductor and a p-type semiconductor are laminated on an insulating substrate made of sapphire, a p-side electrode for supplying a current to the p-type semiconductor and a current for the n-type semiconductor are provided. Must be formed on the same surface side of the substrate, that is, on the epitaxial layer side.

A conventional nitride semiconductor laser device disclosed in Japanese Patent Application Laid-Open No. 9-321381 will be described below with reference to the drawings.

FIG. 6 schematically shows a cross-sectional structure of a conventional nitride semiconductor laser device in a direction perpendicular to a laser light emitting direction. As shown in FIG. 6, an n-type semiconductor layer 102 and an active layer 1 are formed on a substrate 101 made of sapphire.
03 and a p-type semiconductor layer 104 are sequentially formed. p
A ridge 104a having a convex cross section and extending in the emission direction of the laser beam is formed on the upper portion of the mold semiconductor layer 104, and a p-side electrode 105 is formed on the upper surface of the ridge 104a. Further, the n-type semiconductor layer 102 is exposed on both sides of the ridge 104a, and the n-side electrode 106 is formed in the exposed region.

Thus, the n-side electrode 106 is connected to the p-side electrode 1
The contact area between the n-side electrode 106 and the n-type semiconductor layer 102 is increased by forming the n-side electrode 105 on both sides. For this reason, the contact resistance of the n-side electrode 106 is reduced, the operating voltage is reduced, and the current is applied to both sides of the p-side electrode 105, so that the bias of the current injected into the active layer 103 is eliminated. The characteristics are improved.

As shown in FIG. 6, the current flowing from the p-side electrode 105 flows through the n-type semiconductor layer 102 in parallel to the substrate surface. However, since the thickness of the n-type semiconductor layer 102 is as small as 2 μm to 3 μm, the resistance (Sheet resistance) increases the voltage.
Therefore, the end of the n-side electrode 106 on the p-side electrode 105 side is
It is desirable that the distance d1 between the side electrode 105 and the end on the n-side electrode 106 side is as small as possible.
μm or less.

Generally, a semiconductor laser device generates heat in a region where the resistance value is large, such as an active layer and an electrode. Therefore, it is important to efficiently radiate generated heat in order to extend the life of the laser device. Therefore, the element forming surface side (pn junction side)
By performing so-called junction-down bonding, in which the substrate is bonded to a holder (mount) having a high thermal conductivity, the efficiency of heat radiation is improved. Here, the junction-down bonding refers to an insulating and large thermal conductivity on a main surface of a holder made of silicon carbide (SiC), diamond (C), boron nitride (BN), aluminum nitride (AlN), or the like. To the laser element p
This method refers to a method in which electrodes facing the side electrode and the n-side electrode are provided, respectively, and the electrode of the laser element and the electrode of the support are joined using a solder material or a silver paste material having excellent electric and thermal conductivity.

[0010]

However, in the conventional nitride semiconductor laser device, the substrate 101 having a low thermal conductivity is bonded to the holder without performing junction-down bonding. The temperature rise of the device is remarkable, and the characteristics and reliability of the laser device decrease.

For this reason, a laser device in which the distance between the p-side electrode 105 and the n-side electrode 106 is made extremely small to reduce the resistance as in the above-mentioned conventional nitride-based semiconductor laser device is used to improve heat dissipation. When the junction down bonding is performed, the first problem arises in that the alignment with the holder becomes difficult.

That is, as shown in FIG.
When the distance d1 between the electrode 05 and the n-side electrode 106 becomes 100 μm or less, the distance d2 between the n-side electrodes 106 becomes 10 μm in width.
It becomes 210 μm or less in total with the p-side electrode of m or less. Since the resonator length of the semiconductor laser element is about 0.5 mm to 1 mm, the width of the electrode on the main surface of the holding member facing the p-side electrode sandwiched between the n-side electrodes of the laser element is the same as the length dimension. If the laser element and the holder are not precisely aligned, the p-side electrode of the laser element is connected to the n-side electrode of the holder, and the n-side electrode of the laser element is connected to the holder. It is easy to short-circuit with the p-side electrode.

In the semiconductor laser, the crystal plane functions as a resonator mirror, and the resonator mirror is formed by appropriately cleaving a substrate made of sapphire. The nitride semiconductor has a hexagonal crystal structure, and has a weaker cleavage property than cubic gallium arsenide (GaAs) or indium phosphide (InP). Have difficulty.

Moreover, since the nitride semiconductor epitaxially grown on sapphire is shifted by 30 degrees from the crystal plane of sapphire, the plane where sapphire is easily cleaved does not coincide with the plane where nitride semiconductor crystal is easily cleaved. This makes it more difficult to form the mirror by cleavage.

To obtain a mirror surface from a nitride semiconductor layer, A
Although a plane (= (1-100) plane) is easy to obtain, sapphire at this time becomes an M plane shifted by 30 degrees from the A plane, and the substrate is not cleaved well. Therefore, if the substrate is not cleaved satisfactorily, cracks are likely to occur in the epitaxial layer, and in particular, there is a second problem that the ridge 104a shown in FIG. In the present application, the index following the negative sign “−” among the indexes of the plane orientation is an inverted index.

In Japanese Patent Application Laid-Open No. 9-321381, the cavity surface after cleavage is polished. At this time,
If the chipped portion of the ridge portion 104a is large, the damaged portion must be polished to remove all the damaged portion. This causes new problems such as contamination and heat generation during polishing. Therefore, it is important to minimize damage to the periphery of the ridge 104a during cleavage.

According to the present invention, there is provided a semiconductor laser device which solves the above-mentioned conventional problems and achieves a reduction in resistance.
A first object is to enable easy and reliable bonding, and a second object is to protect a ridge portion at the time of cleavage of a substrate.

[0018]

A semiconductor laser device according to the present invention achieves the first object and has a first semiconductor layer of a first conductivity type formed sequentially on a main surface of an insulating substrate. A laminate comprising an active layer and a second semiconductor layer of a second conductivity type, wherein the first semiconductor layer has an exposed portion on the second semiconductor layer side;
A semiconductor laser device having a first laser electrode provided on an exposed portion of a first semiconductor layer and a second laser electrode provided on a surface of the second semiconductor layer opposite to the first semiconductor layer A first holder electrode at a position facing the first laser electrode on the main surface, and a second holder electrode at a position facing the second laser electrode on the main surface. A semiconductor laser element that faces the main surface of the insulating substrate and that connects the first laser electrode and the first holder electrode and connects the second laser electrode and the second holder electrode; A region on the second laser electrode side of the first laser electrode is covered with an insulating film, and the first holding electrode is an insulating film of the first laser electrode. Connected to areas not covered by

According to the semiconductor laser device of the present invention, the first
The region on the side of the second laser electrode in the laser electrode is covered with an insulating film, and the first holder electrode is connected to the region of the first laser electrode that is not covered with the insulating film. The first laser electrode and the second
Even in a semiconductor laser device in which the distance between the first and second laser electrodes is small, the operating current flows within a short distance inside the semiconductor laser device, while the outer side facing the holder has the first laser electrode and the second laser electrode. Since the substantial distance from the laser electrode is increased, the margin of the mounting position is increased.

A first semiconductor laser device according to the present invention comprises:
To achieve the second object, a first conductive type first semiconductor layer, an active layer, and a second conductive layer are sequentially formed on a main surface of an insulating substrate.
A laser comprising: a stacked body including a conductive second semiconductor layer; and a convex portion formed to include a first semiconductor layer, an active layer, and a second semiconductor layer on an upper portion of the stacked body. A resonator forming portion for regulating the light emission direction, a first laser electrode provided on the first semiconductor layer beside the resonator forming portion, and a substantially central portion of the upper portion of the resonator forming portion. A ridge portion is provided between a pair of grooves formed at intervals and extending in the emission direction, and a second laser electrode provided on an upper surface of the ridge portion.

According to the first semiconductor laser device, a pair of grooves formed at a distance from each other and extending in the direction of emitting laser light are formed substantially at the center of the upper portion of the resonator forming portion formed of the convex portion. Is provided on the outer side of the ridge portion above the resonator forming portion, a region for protecting both ends of the ridge portion is formed. In the present application, this area is called a dummy post.

A second semiconductor laser device according to the present invention comprises:
A first conductive type first semiconductor layer, an active layer, and a second conductive type second semiconductor layer formed sequentially on a main surface of an insulating substrate to achieve the first and second objects; A first semiconductor layer formed on an upper portion of the stacked body so as to reach the first semiconductor layer, the first semiconductor layer being formed on a side of the groove in the stacked body; A resonator forming portion including an active layer and a second semiconductor layer, and a region formed on a region of the stacked body opposite to the resonator forming portion with respect to the groove, and having a height from a substrate surface of the resonator forming portion. A dummy post substantially equal to the height from the surface, a first laser electrode provided on the first semiconductor layer inside the groove, and a laser post provided on the second semiconductor layer in the cavity forming portion. A second laser electrode extending in a stripe shape in a light emitting direction; Electrodes, and a wiring electrode formed to extend over the side surfaces and upper surfaces of the dummy posts.

According to the second semiconductor laser device, the dummy posts whose height from the substrate surface is substantially equal to the height from the substrate surface of the resonator forming portion are provided on the side of the groove in the laminate. At the time of cleavage, damage of the second laser electrode forming portion of the second semiconductor layer can be prevented. Also, since the dummy post is formed so that the height from the substrate surface is substantially equal to the height from the substrate surface of the resonator forming portion, the dummy post is formed on the holder when performing the junction down bonding. Since the contact between the first laser electrode and the second laser electrode and the opposing holding electrodes is performed almost simultaneously, the stress applied to the resonator forming portion can be reduced.

The second semiconductor laser element is made of an insulator having a higher thermal conductivity than the insulating substrate, has a first holding electrode at a position on the main surface opposite to the first laser electrode, and has a first holding electrode. A second holder electrode at a position facing the second laser electrode, the main surface of the second holder electrode faces the main surface of the insulating substrate, and the first laser electrode and the first holder electrode are connected to each other. It further includes a holder holding the semiconductor laser element so as to be connected via the conductive bonding material and to connect the second laser electrode and the second holder electrode via the conductive bonding material. Is preferred.

In the second semiconductor laser device, the second
When the semiconductor laser device is bonded to the holder, it is preferable that the groove is filled with a filler made of aluminum oxide, silicon nitride, aluminum nitride, or diamond.

A third semiconductor laser device according to the present invention comprises:
A second semiconductor of a first conductivity type, an active layer, and a second semiconductor of a second conductivity type are sequentially formed on a main surface of a conductive substrate having a first conductivity type to achieve the second object. A first laser electrode provided on the lower surface of the conductive substrate, and a pair of grooves formed at an interval above the multilayer body and extending in the laser light emission direction. And a second ridge provided on the upper surface of the ridge.
Laser electrodes.

According to the third semiconductor laser device, even when a conductive substrate is used, a gap is formed between a pair of grooves formed in the upper portion of the laminate at an interval from each other and extending in the laser light emission direction. Since the second semiconductor layer of the stacked body is spread in the region of the stacked body opposite to the ridge portion with respect to each groove, the second semiconductor layer is spread when the substrate is cleaved. Damage to the electrode forming portion of the layer can be prevented.

In the third semiconductor laser device, it is preferable that an insulating film is formed over the entire surface including the groove in a region other than the upper surface of the ridge on the stacked body. In this case, if the wiring electrode is provided on the insulating film provided in the region except for the upper surface of the ridge portion of the laminate, the region of the wiring electrode except for the groove is the region where the laminate is not etched. For this reason, the height of the wiring electrode from the substrate surface of the ridge portion is substantially equal to the height of the other region from the substrate surface.

[0029]

(First Embodiment) A first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross-sectional structure in a direction perpendicular to a laser light emitting direction in a nitride-based semiconductor laser device according to a first embodiment of the present invention. In FIG. 1, 10
Denotes a semiconductor laser device, and 20 denotes a semiconductor laser device.
0, for example, S which is an insulator and has excellent heat conduction
It is a holder made of iC. As shown in FIG. 1, the semiconductor laser device 10 is joined by junction-down bonding in which the device forming surface of the semiconductor laser device 10 faces the main surface of the holder 20.

The semiconductor laser device 10 has a C-plane (= (00
(01) plane) on a main surface of a substrate 11 made of sapphire having n-type GaN and n-type AlGaN.
Semiconductor layer 12, active layer 13 having a multiple quantum well structure containing InGaN, p-type GaN and p-type AlGaN
And a p-type semiconductor layer 14 formed by laminating the layers in this order.

At the center of the epitaxial layer of the substrate 11 is formed a convex portion including an n-type semiconductor layer 12, an active layer 13 and a p-type semiconductor layer 14, and a resonator forming portion for regulating the emission direction of laser light. Further, a ridge portion 14a whose central portion protrudes in a stripe shape is formed on the p-type semiconductor layer 14 in the resonator forming portion. Nickel (Ni) / gold (A) is formed on the ridge portion 14a.
A p-side electrode 15 as a second laser electrode made of u) or magnesium (Mg) / gold (Au) is formed.

A first laser electrode made of titanium (Ti) / aluminum (Al) or titanium (Ti) / molybdenum (Mo) is provided on both sides of the cavity forming portion and on the exposed portion of the n-type semiconductor layer 12. N-side electrodes 16 are formed. The p-side electrode 15 is in contact with p-type GaN, and the n-side electrode 16 is in contact with n-type GaN, which is more effective in reducing the contact resistance.

As a feature of the present embodiment, the region on the p-side electrode 15 side of the n-side electrode 16 and the top and side surfaces of the resonator forming portion excluding the p-side electrode 15 are formed of silicon nitride (S
iN), silicon oxide (SiO ₂ ) or aluminum oxide (Al ₂ O ₃ ).

The p-side electrode 15 of the resonator forming portion and the insulating film 1
A p-side wiring electrode 18 is formed on the upper surface including the wiring 7.
Here, titanium (Ti) / gold (Au), chromium (Cr) / gold (Au) or titanium (T
i) / platinum (Pt) / gold (Au).

On the main surface of the holder 20, a p-side holder electrode 21 as a second holder electrode and a p-side holder electrode 21 as a second holder electrode are located at positions facing the p-side wiring electrode 18 and the n-side electrode 16 of the semiconductor laser device 10, respectively. N-side holding electrode 2 as holding electrode 1
2 are formed, and the main surface of the holder 20 and the main surface of the semiconductor laser device 10 are opposed to each other to hold the semiconductor laser device 10. The p-side wiring electrode 18 and the p-side holding electrode 21 facing each other, and the n-side electrode 16 and the n-side holding electrode 22 are respectively a lead-tin solder, a gold-tin solder or a silver paste excellent in electric conduction and heat conduction. Are joined by a conductive joining material 23 made of.

As described above, according to the present embodiment, the semiconductor laser device 10 has a structure in which the distance between the p-side electrode 15 and the n-side electrode 16 is shortened to reduce the resistance, and the p-side of the n-side electrode 16 is reduced.
Since a part of the region on the side electrode 15 side is covered with the insulating film 17, the margin of the connection position with each of the holder electrodes 21 and 22 when bonding to the holder 20 is substantially increased. Therefore, it is possible to prevent a short circuit between the electrodes at the time of junction down bonding. This allows
It is possible to achieve both low resistance and improved heat dissipation of the nitride-based semiconductor laser device 10.

It is to be noted that merely increasing the distance between the p-side holding electrode 21 and the n-side holding electrode 22 formed on the holding member 20 may cause the semiconductor laser device 10 to be bonded to the holding member 20 when bonding. If the semiconductor laser element 10 rotates and shifts with respect to the main surface of the semiconductor laser element, for example, the n-side electrode 16 and the p-side holder electrode 21 of the semiconductor laser element 10 may be short-circuited.

Hereinafter, an outline of a method of manufacturing the nitride-based semiconductor laser device configured as described above will be described.

First, for example, a group III source such as trimethylgallium (TMG) or trimethylaluminum (TMA)
N-type semiconductor layer 12, active layer 13 and p-type semiconductor layer while heating the substrate temperature to 1000 ° C. using MOVPE method using trimethylindium (TMI) and ammonia (NH ₃ ) as a nitrogen source as raw materials. 14 are sequentially epitaxially grown to form a stacked body made of a nitride semiconductor.

Here, the n-type semiconductor layer 12 is doped with silicon (Si) as an n-type dopant, and the p-type semiconductor layer 14 is doped with magnesium (Mg) as a p-type dopant. The insulating substrate 11 is not limited to sapphire, and may be a single crystal such as spinel (MgAl ₂ O ₄ ), magnesium oxide (MgO), or zinc oxide (ZnO).

Next, the substrate 11 on which the epitaxial layer is formed is taken out of the reaction furnace, and for example, Ni and Au are sequentially deposited on a predetermined region of the upper surface of the p-type semiconductor layer 14 to form the p-side electrode 15. Thereafter, the substrate 11 is put into an ion milling apparatus, and the p-type semiconductor layer 14 is etched using argon (Ar) ions with the p-side electrode 15 as a mask, thereby forming a p-type semiconductor layer 14 having a width of A ridge 14a of about 3 μm is formed.

Next, the cavity forming portion on the substrate 11 is masked, and etching is performed using an ion milling device or a reactive ion etching device until the n-type semiconductor layer 12 is exposed. A convex resonator forming portion including the active layer 13 and the p-type semiconductor layer 14 is formed.

Next, for example, Ti and Al are sequentially deposited on both sides of the resonator forming portion on the n-type semiconductor layer 12,
An n-side electrode 16 having a width of about 150 μm and a distance from the side of the p-side electrode 15 of about 20 μm is formed.

Next, an insulating film 17 made of, for example, SiN is deposited on the region of the n-side electrode 16 on the p-side electrode 15 side and on the upper surface and side surfaces of the resonator forming portion except for the p-side electrode 15.
Thereafter, a p-side wiring electrode 18 is formed on the upper surface including the p-side electrode 15 and the insulating film 17 of the resonator forming portion, and the ridge portion 14 is formed.
By substantially increasing the width of the p-side electrode 15 whose width on “a” is extremely small, current injection is facilitated.

Next, the thickness of the substrate 11 is set to 70
Then, the substrate 11 is cleaved using a diamond scriber to reduce the cavity length to about 70 μm.
The semiconductor laser device 10 of 0 μm is obtained.

Subsequently, the main surface of the holder 20 on which the holder electrodes 21 and 22 are formed and the element forming surface of the semiconductor laser element 10 are aligned so that the electrodes face each other.
Thereafter, the conductive bonding material 2 made of, for example, lead-tin solder
3, the holder 20 and the semiconductor laser element 10 are joined.

When a pulse current was applied to the semiconductor laser device thus obtained to oscillate laser light having a wavelength of about 400 nm, when the oscillation operation current was 100 mA, the light output was 5 mW and the operation voltage was It has been confirmed that the device exhibits excellent electrical and optical characteristics of 5 V.

In this embodiment, the active layer 13
Although the resonator forming portion including the above is formed to protrude above the substrate 11, the present invention is not limited to this, and a buried hetero (BH) type laser device in which the active layer 13 is buried in the epitaxial layer may be used.

Although the n-side electrodes 16 are provided on both sides of the resonator forming region, either one may be provided.

Although SiC is used for the holder 20,
Not limited to this, BN, A which is an insulator and has a large thermal conductivity
1N or diamond may be used.

(Second Embodiment) Hereinafter, a second embodiment according to the present invention will be described with reference to the drawings.

FIG. 2 shows a sectional structure of a nitride semiconductor laser device according to a second embodiment of the present invention in a direction perpendicular to a laser light emitting direction. As shown in FIG.
The semiconductor laser element 30A has n-type GaN and n-type AlGa on a main surface of a substrate 31 made of sapphire having a C-plane.
N-type semiconductor layer 32 in which N is stacked, active layer 33 having a multiple quantum well structure containing InGaN, p-type Ga
N-type and p-type AlGaN laminated p-type semiconductor layer 3
4 has an epitaxial layer as a laminated body formed sequentially.

The central portion of the epitaxial layer of the substrate 31 is composed of a convex portion formed so as to include the n-type semiconductor layer 32, the active layer 33 and the p-type semiconductor layer 34, and regulates the emission direction of the laser beam. A resonator forming section 1 is formed. Further, the p-type semiconductor layer 34 in the resonator forming section 1
A ridge portion 34a having a width of about 3 μm is formed between a pair of grooves which are spaced from each other and extend in the emission direction. On both sides of the ridge portion 34a in the upper part of the resonator forming portion 1, each of the ridge portions 34a is separated from the ridge portion 34a by a pair of grooves and has a width of about 3.
A pair of dummy posts 34b of 0 μm are formed.

On the upper surface of the ridge portion 34a, for example, Ni /
A p-side electrode 35 as a second laser electrode made of Au is formed, and the resonator forming portion 1 on the n-type semiconductor layer 32 is formed.
Are made of, for example, Ti / Al and have a width of about 150
An n-side electrode 36 as a first laser electrode of μm is formed.

The region of the n-side electrode 36 on the side of the resonator forming portion 1 and the top and side surfaces of the resonator forming portion 1 excluding the p-side electrode 35 are covered with insulating films 37A and 37B made of SiN, respectively. A p-side wiring electrode 38 made of, for example, Ti / Au is formed on almost the entire top surface of the container forming section 1 including the p-side electrode 35 and the insulating film 37B.

Further, an n-side wiring electrode 39 made of, for example, Ti / Au is provided on the n-type semiconductor layer 32 in a region on the opposite side of the resonator forming portion 1 with respect to each of the n-type electrodes 36.
The width of the overlapping portion with the mold electrode 36 is formed to be about 50 μm.

As described above, according to the present embodiment, the semiconductor laser device 30A has a pair of dummy posts 34b in which both sides of the ridge portion 34a for injecting a current into the active layer 33 are separated by grooves. Therefore, it is possible to prevent the ridge portion 34a from being chipped when the resonator mirror is formed, and it is easy to obtain a cleavage plane having a flat surface.
If a good cleavage plane is obtained, the laser resonator mirror is completed. However, if unevenness remains on the cleavage plane, finishing by polishing is required. Even in this case, the ridge portion 34a is not easily chipped during cleavage, so that the polishing time can be shortened and the throughput is improved. Incidentally, in the first embodiment, the yield at the time of forming the mirror is 60%, but in the second embodiment, it is improved to 90%.

Further, while the distance between the p-side electrode 35 and the n-side electrode 36 is reduced to reduce the resistance, the p-side electrode 36
Since the side electrode 35 side is covered with the insulating film 37A,
When bonding to a holder (not shown), the margin of the bonding position with each holder electrode is substantially increased. Therefore, it is possible to prevent a short circuit between the electrodes at the time of junction down bonding. This makes it possible to achieve both low resistance and improved heat dissipation of the nitride-based semiconductor laser element 30A, and to improve the yield when the ridge portion 34a is formed.

Hereinafter, only the differences between the method of manufacturing the semiconductor laser device 30A configured as described above and the semiconductor laser device 10 of the first embodiment will be described.

First, after an epitaxial layer is grown on the substrate 31, an opening is formed in the ridge forming region and the dummy post forming region on the resonator forming portion 1 for forming a p-type electrode and in the groove forming region. A metal film is formed, and the p-type semiconductor layer 34 is etched by ion milling using the metal film as a mask. Next, the metal film on the dummy post is removed, and etching is performed until the n-type semiconductor layer 32 is reached by using the mask of the resonator forming portion 1 to form the resonator forming portion 1 having a convex cross section.

When a pulse current was applied to the semiconductor laser device 30A thus obtained to oscillate laser light having a wavelength of about 400 nm, the oscillation operation current was 100 m
In the case of A, it was confirmed that the optical output was 5 mW, and the operating voltage was 5.5 V, indicating electrical and optical characteristics. It is considered that the reason why the operating voltage was increased as compared with the first embodiment was that the distance between the p-side electrode 35 and the n-side electrode 36 was increased to 50 μm.

(Third Embodiment) Hereinafter, a third embodiment according to the present invention will be described with reference to the drawings.

FIG. 3 shows a cross-sectional configuration in a direction perpendicular to a laser light emission direction in a nitride-based semiconductor laser device according to a third embodiment of the present invention. In FIG. 3, FIG.
The description of the same components as shown in FIG.

The difference from the second embodiment is that only a ridge portion 34 a made of a p-type semiconductor layer 34 and having a convex portion is formed above the resonator forming portion 1, and the dummy post 3 is formed.
4b is formed at both ends with the groove 2 forming the resonator forming portion 1 interposed therebetween. Furthermore, each of the n-side wiring electrodes 39 has a portion of the upper surface of the n-side electrode 36 provided at the bottom of the groove 2 with the insulating film 37C interposed therebetween,
This is a point formed so as to straddle the side surface and the upper surface of 4b.

In this case, the height of the ridge portion 34a from the substrate surface and the height of the dummy post 34b from the substrate surface are substantially the same because both the ridge portion 34a and the dummy post 34b are not etched. I have. Therefore, the p-side electrode 35 and the n-side electrode 36 of the semiconductor laser device 30B have substantially the same height, and when the down-bonding to the holder is performed, the p-side electrode 35 and the n-side electrode
Since both the side electrodes 36 are almost simultaneously bonded to the respective electrodes on the holder, the stress applied to the ridge portion 34a, that is, the active layer 33 can be reduced. As a result, it is possible to prevent an adverse effect on the laser characteristics due to the distortion, for example, an adverse effect such as a deviation of the polarization plane, so that the reliability of the semiconductor laser element 30B is improved.

Further, the dummy post 34 b is connected to the n-side electrode 36.
Is provided on the side opposite to the p-side electrode 35, the distance between the p-side electrode 35 and the n-side electrode 36 can be reduced, so that the ridge portion 34a is not damaged at the time of cleavage without causing an increase in operating voltage. Can be prevented.

Hereinafter, only the differences between the method of manufacturing the semiconductor laser device 30B configured as described above and the semiconductor laser device 10 of the first embodiment will be described.

First, after an epitaxial layer is grown on the substrate 31, a metal film for forming a p-type electrode is formed on the resonator forming portion 1, and the p-type semiconductor layer 34 is formed using the metal film as a mask.
Is etched by ion milling.
The ridge portion 34a is formed. Next, by masking the resonator forming portion 1 and the dummy post forming region, the n-type semiconductor layer 32 is formed.
, Dry etching using chlorine (Cl) ions is performed to form a pair of grooves 2 for separating the cavity forming portion 1 and the dummy post 34b.

FIG. 4 shows a cross-sectional configuration in a state where the semiconductor laser device according to the present embodiment is bonded to a holder. 4, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.
As shown in FIG. 4, the semiconductor laser element 30 </ b> B is bonded to the holder 40 with the resonator forming portion side facing the main surface of the holder 40 made of, for example, SiC or BN.

On the main surface of the holder 40, a p-side holder electrode 41 as a second holder electrode and a p-side holder electrode 41 as a second holder electrode are provided at positions facing the p-side wiring electrode 38 and the n-side wiring electrode 39 of the semiconductor laser element 30 B, respectively. An n-side holding electrode 42 as a first holding electrode is formed. Further, the p-side wiring electrode 38 and the p-side holder electrode 41 facing each other and n
The side wiring electrode 39 and the n-side holding electrode 42 are joined by a conductive joining material 43 made of a lead-tin-based solder or the like which has excellent electric and thermal conductivity.

Further, the groove 2 of the semiconductor laser element 30B
Are insulators having excellent thermal conductivity, such as alumina (Al
_A filler 44 made of ₂ O ₃ ) is filled.

As a result, the main surface of the holder 40 and the semiconductor laser element 30B are in close contact with each other, even though the grooves 2 having a relatively large volume are formed on both sides of the resonator forming section 1. Heat generated from the layer 33 can be efficiently transmitted to the holder 40 side.

The semiconductor laser device thus obtained can continuously oscillate short-wavelength laser light having a wavelength of about 400 nm, and can continuously oscillate even when the ambient temperature is 100 ° C. It is.

In this embodiment, alumina is used as the filler 44 for filling the groove 2 of the semiconductor laser element 30B, but SiN, AlN or diamond may be used.

By providing a pair of grooves 2,
Although a pair of dummy posts 34b are provided, one of them may be provided.

(Fourth Embodiment) Hereinafter, a fourth embodiment according to the present invention will be described with reference to the drawings.

FIG. 5 shows a sectional structure of a nitride semiconductor laser device according to a fourth embodiment of the present invention in a direction perpendicular to a laser light emitting direction. As shown in FIG.
The semiconductor laser element 50 has conductivity, for example, S
an n-type semiconductor layer 52 in which n-type GaN and n-type AlGaN are stacked on a main surface of a substrate 51 made of iC, GaN, GaAs or Si; an active layer 53 having a multiple quantum well structure including InGaN; p-type GaN and p-type AlG
A p-type semiconductor layer 54 formed by laminating aN has an epitaxial layer as a layered body in which layers are sequentially formed.

On the p-type semiconductor layer 54, a ridge 54 is formed between a pair of grooves 2 which are formed substantially parallel to each other at intervals so as to regulate the emission direction of laser light.
a is provided, and the ridge portion 54 a forms the resonator forming portion 1. On the other side of the ridge portion 54a with respect to each groove portion 2, a vast dummy post 54b is formed.

The p-type semiconductor layer 5 is formed on the upper surface of the ridge portion 54a.
A p-side electrode 55 as a second laser electrode made of, for example, Ni / Au is formed in contact with the substrate 4, and an n-side electrode 56 as a first laser electrode made of, for example, Ti / Al is formed on the lower surface of the substrate 51. Are formed over the entire surface.

Ridge 54a in p-type semiconductor layer 54
An insulating film 57 made of, for example, SiO ₂ or SiN is formed in a region excluding the upper surface of the substrate, that is, in a region excluding the p-side electrode 55, and over the entire surface of the insulating film 57 including the p-side electrode 55 on the substrate 51, A p-side wiring electrode 58 made of Ti / Au is formed.

As described above, according to the present embodiment, since the insulating substrate 51 is used as the substrate, the n-side electrode 56 can be formed on the lower surface of the substrate 51. Thereby, the electrode forming process can be simplified.

Further, the groove 2 in the p-side wiring electrode 58
Are formed on the region where the p-type semiconductor layer 54 is not etched, so that the height of the p-side wiring electrode 58 from the substrate surface between the resonator forming portion 1 and the other region is substantially equal. Become. Therefore, a current can be injected into the active layer 53 from the p-side electrode 55 on the ridge portion 54a in a stripe shape, and almost the entire surface of the p-type semiconductor layer 54 is covered with the p-side wiring electrode 58.
Bonding also becomes easy.

Since the groove 2 has a relatively small cross-sectional shape, the effect of preventing the ridge 54a from being damaged during cleavage is extremely large. In the case of this embodiment, the yield at the time of forming the mirror is as high as 95%.

Since the n-side electrode 56 is provided on the entire lower surface of the substrate 51, carriers can be injected through the entire lower surface of the substrate 51, so that the operating voltage can be reduced.

Since the p-side electrode 55 and the n-side electrode 56 can be formed on both surfaces of the substrate 51, both the p-side electrode and the n-side electrode are provided on the main surface of the holder (not shown). No need. Therefore, a conductive support such as Si or Cu can be used. When SiC is used for the substrate 51, since the substrate itself has good thermal conductivity, the substrate made of sapphire can be used even when so-called junction-up bonding is performed in which the pn junction surface (the ridge portion 54a is formed) is not opposed to the holder. It has better heat dissipation characteristics than junction-down bonding when used.

When SiC or GaN is used for the substrate 51, the cleavage direction of the epitaxial growth layer matches the cleavage direction of the substrate 51, so that a very good resonator mirror surface can be formed by cleavage.

A semiconductor laser device 50 was formed on a substrate 51 made of n-type SiC, and the semiconductor laser device bonded to the holder by junction-up bonding was measured. As a result, when the operating current was 100 mA, the operating voltage was 4 mA. It has been confirmed that continuous oscillation can be performed at 0.7 V until the ambient temperature reaches 120 ° C.

The semiconductor laser device according to the present invention is not limited to a nitride-based compound semiconductor laser device, but can be applied to a semiconductor laser device for reducing resistance and improving heat radiation characteristics.

Further, not only the semiconductor laser element but also a part of a predetermined electrode that makes contact with the semiconductor layer (element formation surface) is covered with an insulating film, or a wiring electrode is connected to the predetermined electrode. The configuration that improves the heat radiation characteristics by bonding the semiconductor layer side with a large amount of heat to the holder with the semiconductor layer side facing the holder is also effective for light emitting elements such as light emitting diodes and electronic devices such as bipolar transistors or field effect transistors. It is.

[0091]

According to the semiconductor laser device of the present invention, even if the distance between the first laser electrode and the second laser electrode is reduced in order to reduce the resistance, the inside of the semiconductor laser device is reduced. In the case of, the operating current flows through a short distance, and the substantial distance between the first laser electrode and the second laser electrode on the external side facing the holder increases, so that the margin of the mounting position increases. As a result, junction down bonding can be reliably performed, so that a reduction in operating voltage and an improvement in heat radiation characteristics can be achieved at the same time. When a nitride-based semiconductor is used, the performance of a blue-violet semiconductor laser with a wavelength of 400 nm is improved. The reliability can be improved and it greatly contributes to practical use.

According to the first semiconductor laser device of the present invention, regions (dummy posts) for protecting both ends of the ridge are formed on both sides of the ridge, so that the cavity mirror is formed by cleavage. Since the ridge portion can be prevented from being damaged, the production yield can be increased.

According to the second semiconductor laser device of the present invention, since the height of the dummy post is substantially the same as the height of the cavity formation portion from the substrate surface, the second semiconductor laser device is formed when the substrate is cleaved.
Since the damage of the portion where the second laser electrode is formed in the semiconductor layer can be prevented, the yield at the time of forming the resonator mirror can be improved. Further, since the dummy post has substantially the same height as the resonator forming portion, when performing the junction down bonding, the first and second laser electrodes formed on the holder are not connected to the dummy post. Since the contact with the opposing holder electrodes can be made almost simultaneously, the stress applied to the resonator forming portion can be reduced. As a result, it is possible to prevent the laser characteristics from being adversely affected by the distortion, such as a shift in the polarization plane, thereby improving the reliability of the device.

The second semiconductor laser element is made of an insulator having a higher thermal conductivity than the insulating substrate, has a first holding electrode at a position on the main surface opposite to the first laser electrode, and has a first holding electrode. A second holder electrode at a position facing the second laser electrode, the main surface of the second holder electrode faces the main surface of the insulating substrate, and the first laser electrode and the first holder electrode are connected to each other. It further includes a holder holding the semiconductor laser element so as to be connected via the conductive bonding material and to connect the second laser electrode and the second holder electrode via the conductive bonding material. And junction down bonding can be performed reliably.

In the second semiconductor laser device, the second
When the semiconductor laser device is bonded to the holder and the groove is filled with a filler made of aluminum oxide, silicon nitride, aluminum nitride or diamond, the main surface of the holder and the semiconductor laser device Since the element formation surface is in close contact, the heat generated from the active layer can be efficiently transmitted to the holder. As a result, the long-term reliability of the device can be further improved.

According to the third semiconductor laser device of the present invention, even when a conductive substrate is used, the second semiconductor layers of the laminate are respectively formed in the regions outside the grooves formed in the laminate. Since it is wide, only the ridge portion does not protrude. For this reason, it is possible to prevent damage to the electrode formation portion of the second semiconductor layer at the time of cleaving the substrate, thereby improving the yield when forming the resonator mirror.

In the third semiconductor laser device, if an insulating film is formed over the entire surface including the groove in the region excluding the ridge portion in the stacked body, if the wiring electrode is provided on the insulating film, the active layer In addition, a current can be injected in a stripe form from an electrode on the ridge portion, almost the entire surface of the second semiconductor layer of the laminate is covered by the wiring electrode, and the ridge portion of the wiring electrode and another region are not covered by the wiring electrode. Since the heights from the substrate surface are substantially equal, junction down bonding is facilitated.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view showing a nitride-based semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a nitride-based semiconductor laser device according to a second embodiment of the present invention.

FIG. 3 is a configuration sectional view showing a nitride-based semiconductor laser device according to a third embodiment of the present invention.

FIG. 4 is a configuration sectional view showing a nitride semiconductor laser device according to a third embodiment of the present invention, which is in a state of being bonded to a holder.

FIG. 5 is a sectional view showing a configuration of a nitride-based semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 6 is a configuration sectional view showing a conventional nitride-based semiconductor laser device.

[Explanation of symbols]

 Reference Signs List 1 resonator forming portion 2 groove portion 10 semiconductor laser element 11 substrate 12 n-type semiconductor layer (first semiconductor layer) 13 active layer 14 p-type semiconductor layer (second semiconductor layer) 14a ridge portion 15 p-side electrode (second 16 n-side electrode (first laser electrode) 17 insulating film 18 p-side wiring electrode 20 holder 21 p-side holder electrode (second holder electrode) 22 n-side holder electrode (first Holder electrode) 23 Conductive bonding material 30A Semiconductor laser device 30B Semiconductor laser device 31 Substrate 32 N-type semiconductor layer (first semiconductor layer) 33 Active layer 34 P-type semiconductor layer (second semiconductor layer) 34a Ridge portion 34b Dummy post 35 p-side electrode (second laser electrode) 36 n-side electrode (first laser electrode) 37A insulating film 37B insulating film 37C insulating film 38 p-side wiring electrode (second holding body electrode) ) 39 n-side wiring electrode (first holder electrode) 40 holder 41 p-side holder electrode 42 n-side holder electrode 43 conductive bonding material 44 filler 50 semiconductor laser element 51 substrate 52 n-type semiconductor layer (first electrode) Active layer 54 p-type semiconductor layer (second semiconductor layer) 54a ridge 54b dummy post 55 p-side electrode (second laser electrode) 56 n-side electrode (first laser electrode) 57 insulation Film 58 p-side wiring electrode

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Ueyama 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Ayu Tsujimura 1006 Odaka Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Akihiko Ishibashi 1006 Kazuma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshiaki Hasegawa 1006, Oji Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Ryoko Miyanaga 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-11-145562 (JP, A) JP-A 10-200213 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (4)

(57) [Claims] A first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type sequentially formed on a main surface of an insulating substrate, wherein the first semiconductor layer is Is the second
A laminate having an exposed portion on the semiconductor layer side of the first semiconductor layer, a first laser electrode provided on the exposed portion of the first semiconductor layer, and a second semiconductor layer on the opposite side of the first semiconductor layer. A semiconductor laser element having a second laser electrode provided on a surface, and a wiring electrode provided on a surface of the second laser electrode opposite to the second semiconductor layer; A first holder electrode at a position facing the first laser electrode and a second holder electrode at a position facing the second laser electrode; And the first laser electrode and the first holder electrode are electrically connected to each other, and the second laser electrode and the second holder electrode are electrically connected to each other. A holder holding the semiconductor laser element so that A region of the first laser electrode on the side of the second laser electrode is covered with an insulating film, the wiring electrode covers the insulating film and the second laser electrode, and the first holding A semiconductor laser device, wherein the body electrode is connected to a region of the first laser electrode that is not covered by the insulating film. 2. A laminate comprising a first conductive type first semiconductor layer, an active layer, and a second conductive type second semiconductor layer sequentially formed on a main surface of an insulating substrate; A groove formed on an upper part of the body so as to reach the first semiconductor layer, the groove configured to regulate an emission direction of laser light; and a groove formed in a side of the groove in the laminate, the first semiconductor layer and the active layer. And a resonator forming portion including a second semiconductor layer, formed in a region of the laminated body opposite to the resonator forming portion with respect to the groove, and having a height from a substrate surface of the resonator forming portion. A dummy post having a height substantially equal to a height from a substrate surface; a first laser electrode provided on the first semiconductor layer inside the groove; and a second semiconductor layer on the resonator forming portion. And extends in a stripe shape in the laser light emission direction. A second laser electrode, a first laser electrode, and a wiring electrode formed so as to straddle a side surface and an upper surface of the dummy post, and an upper surface of the resonator forming portion excluding the second laser electrode. And a side surface, a region on the first laser electrode on the side of the second laser electrode, and the dummy post are covered with an insulating film, and the wiring electrode in contact with the first laser electrode is A semiconductor laser device provided on the dummy post via an insulating film. 3. A semiconductor device comprising: an insulator having a thermal conductivity higher than that of the insulating substrate; a first holding electrode provided at a position on the main surface opposite to the first laser electrode; A second holder electrode is provided at a position facing the electrode, and a main surface of the second holder electrode faces the main surface of the insulating substrate, and the first laser electrode and the first holder electrode are connected to each other. A holding member that holds the semiconductor laser element so as to be connected via a conductive bonding material and to connect the second laser electrode and the second holding member electrode via a conductive bonding material; The semiconductor laser device according to claim 2 , wherein the semiconductor laser device is provided. 4. The groove is filled with a filler made of aluminum oxide, silicon nitride, aluminum nitride or diamond, and the filler fills a space formed by the groove and the holder. 4. The semiconductor laser device according to claim 3 , wherein: