JP3456938B2 - Semiconductor laser device, optical disk device, and optical integrated 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 for outputting a blue laser light used as a laser light source of an optical information recording device such as an optical disc, and more particularly to a semiconductor laser device for preventing spontaneous emission light from being emitted to the outside. The present invention relates to a device, an optical disk device and an optical integrated device using the device.

[0002]

2. Description of the Related Art A nitride semiconductor laser device made of a group III nitride semiconductor containing a group III element, particularly aluminum (Al), gallium (Ga) or indium (In), has a mixed layer of InGaN as an active layer. By using a crystal, blue laser light having a wavelength of about 400 nm to 500 nm can be oscillated. When this blue semiconductor laser device is put to practical use, at present, the recording capacity of a DVD using a red semiconductor laser device that oscillates red light with a wavelength of 650 nm is 3
More than double, that is, it is possible to increase up to 15 gigabytes or more on one side of a disk having a diameter of 12 cm. This recording capacity of 15 gigabytes has a high recording quality (H) when the MPEG2 system which is an international standard of moving image information compression technology is used.
D) Since a video signal can be reproduced for 2 hours or more, it is strongly expected to realize a blue semiconductor laser device. At present, a nitride semiconductor laser device that has been successfully oscillated uses an InGaN mixed crystal as an active layer and an AlGaN mixed crystal as a cladding layer, and its oscillation wavelength is about 4
00 nm to 450 nm.

Usually, an active layer made of InGaN and Al
The clad layer made of GaN is formed by crystal growth of these layers on the substrate. Therefore, in order to obtain a growth film without crystal defects, it is optimal to use a substrate made of GaN having the same crystal structure as InGaN and AlGaN and having almost the same lattice constant. However, at present, a substrate made of GaN having a side of 10 mm or more that can be used as a substrate has not been obtained. Therefore, a substrate made of sapphire (single crystal Al ₂ O ₃ ) is generally used. Although sapphire has a lattice constant different from GaN by about 14%, sapphire has the same crystal structure as GaN and is stable even at a high temperature of 1000 ° C. or higher, and thus is suitable for growth of a nitride semiconductor crystal.

When a current exceeding the threshold current is injected into not only the nitride semiconductor laser device but also the p-side electrode and the n-side electrode of the semiconductor laser device, the electrons and holes generated from the injected current are regenerated. The emitted light due to the coupling is strongly confined in the active layer, amplified and oscillated, and emitted as laser light from the emission end face of the active layer.

As described above, an InGaN mixed crystal is used for the active layer of the nitride semiconductor laser device, and the In composition ratio is 15
%, Blue-violet laser light having an oscillation wavelength of 410 nm can be obtained. The energy gap between the active layer and the substrate side and the side opposite to the substrate is 0.4 eV or more,
Moreover, a clad layer having a refractive index smaller than that of the active layer is required. This clad layer contains AlG with an Al composition ratio of 7%.
An aN mixed crystal is used.

[0006]

However, in principle, the blue laser light emitted from the above-mentioned conventional nitride semiconductor laser device is more difficult to detect than the red laser light, and S / of a light receiving element such as a photodetector is difficult to detect. There is no choice but to reduce the N ratio. Therefore, in the short wavelength type nitride semiconductor laser device, the necessity of reducing the noise generated by the laser device becomes extremely high as compared with the red semiconductor laser device.

SUMMARY OF THE INVENTION It is an object of the present invention to reliably reduce the noise generated by the short wavelength type nitride semiconductor laser device, particularly optical noise.

[0008]

The inventors of the present application have studied various noise sources from a blue light laser device in order to put a short-wavelength laser into practical use. Is locating

That is, when a current is applied to the semiconductor laser device, spontaneous emission light is generated in the light emitting region of the active layer, and when the applied current exceeds a predetermined value, the spontaneous emission light in the longitudinal direction of the resonator is amplified. Laser light that oscillates and has a uniform phase is emitted from the emission end face of the active layer. This predetermined current value is called an oscillation threshold current, and only spontaneous emission light continues to increase until the applied current reaches the threshold current and laser oscillation occurs.

Since the spontaneous emission light is not a laser light whose phase is aligned, it has various adverse effects when mixed with the laser light. For example, when the laser device is used as an optical pickup for an optical disk, the spontaneous emission light component becomes noise of the laser light, which lowers the SN ratio during the information reading operation. Further, the spontaneous emission light emitted from other than the laser emission end face of the laser chip becomes bias light for the photodetector in the optoelectronic integrated device in which the laser chip is integrated with the photodetector or an electronic circuit, and adversely affects the detection operation. Will have an effect.

In order to achieve the above-mentioned object, the present invention has a structure in which a spontaneous emission light absorbing layer for absorbing spontaneous emission light is provided inside the chip or on the surface of the chip so as to prevent the spontaneous emission light leaking from the laser chip. And Further, a spontaneous emission light prevention film having a high reflectance for the spontaneous emission light is provided on the upper surface or the side surface of the chip so as to prevent the spontaneous emission light from leaking to the outside. Further, a light shielding unit for shielding the spontaneous emission light is provided between the laser chip and the monitor photodetector so that the spontaneous emission light does not mix with the monitor light for automatic output control of the laser chip.

The means for solving the present invention will be specifically listed below.

A first semiconductor laser device according to the present invention is
A first clad layer made of a nitride semiconductor of the first conductivity type formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. A second clad layer made of a second conductive type nitride semiconductor, and a natural clad layer made of the first conductive type nitride semiconductor between the substrate and the first clad layer and released from the active layer. A spontaneous emission light absorption layer that absorbs emitted light is formed.

According to the first semiconductor laser device, the spontaneous emission light emitted from the active layer is formed between the substrate and the first cladding layer, and is made of a nitride semiconductor of the same conductivity type as that of the first cladding layer. Since the spontaneous emission light absorbing layer that absorbs light is formed, the spontaneous emission light absorbing layer absorbs the spontaneous emission light emitted from the active layer to the substrate side.

In the first semiconductor laser device, it is preferable that the spontaneous emission light absorption layer contains indium and is formed so as to be in contact with the first cladding layer. By doing so, since the spontaneous emission light absorption layer contains indium, the energy gap of the spontaneous emission light absorption layer can be made smaller than the energy of the spontaneous emission light emitted from the nitride semiconductor. Can be reliably absorbed.

In the first semiconductor laser device, it is preferable that the spontaneous emission light absorption layer contains indium and is formed so as to be in contact with the substrate. By doing so, since the spontaneous emission light absorption layer contains indium, the energy gap of the spontaneous emission light absorption layer can be made smaller than the energy of the spontaneous emission light emitted from the nitride semiconductor. Can be reliably absorbed. Furthermore, when forming a buffer layer on the upper surface of the substrate for enhancing the crystallinity of the nitride semiconductor layer grown on the substrate, the spontaneous emission light absorption layer can also serve as the buffer layer.

A second semiconductor laser device according to the present invention is
A first clad layer made of a nitride semiconductor of the first conductivity type formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. A second clad layer made of a second conductivity type nitride semiconductor, and an electrode formed on the second clad layer. The second conductive layer is provided between the second clad layer and the electrode. Type nitride semiconductor, and a spontaneous emission light absorbing layer that absorbs spontaneous emission light emitted from the active layer is formed.

According to the second semiconductor laser device, the spontaneous emission light emitted from the active layer is formed between the second cladding layer and the electrode, and is made of a nitride semiconductor of the same conductivity type as the second cladding layer. Since the spontaneous emission light absorbing layer that absorbs is absorbed, the spontaneous emission light absorbing layer absorbs the spontaneous emission light emitted from the active layer to the electrode side provided on the second cladding layer.

In the second semiconductor laser device, it is preferable that the spontaneous emission light absorption layer contains indium and is formed so as to be in contact with the second cladding layer.

In the second semiconductor laser device, it is preferable that the spontaneous emission light absorption layer contains indium and is formed so as to be in contact with the electrode. This way,
When forming a contact layer in ohmic contact with the electrode above the second cladding layer, the spontaneous emission light absorption layer can also serve as the contact layer.

A third semiconductor laser device according to the present invention is
A first clad layer made of a nitride semiconductor of the first conductivity type formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. And a second cladding layer made of a second conductivity type nitride semiconductor, and a spontaneous emission light-preventing film for absorbing or reflecting spontaneous emission light emitted from the active layer on the surface of the substrate opposite to the active layer. Are formed.

According to the third semiconductor laser device, since the spontaneous emission light preventing film which absorbs or reflects the spontaneous emission light emitted from the active layer is formed on the surface of the substrate opposite to the active layer, the spontaneous emission light preventing film is formed. The emitted light prevention film prevents the spontaneous emission light emitted from the active layer to the substrate side from leaking to the outside.

A fourth semiconductor laser device according to the present invention is
A first clad layer made of a nitride semiconductor of the first conductivity type formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. A laser element body having a second clad layer made of a second conductivity type nitride semiconductor, and an emitting end surface of the active layer in the laser element body excluding a laser light emitting portion and a reflecting end surface opposite to the emitting end surface. In addition, a spontaneous emission light preventing film that absorbs or reflects the spontaneous emission light emitted from the active layer is formed.

According to the fourth semiconductor laser device, the spontaneous emission light emitted from the active layer is emitted to the emitting end face of the active layer of the laser element body excluding the laser beam emitting part and the reflecting end face opposite to the emitting end face. Since the spontaneous emission light blocking film that absorbs or reflects is formed, the spontaneous emission light blocking film leaks out the spontaneous emission light emitted from the active layer to the electrode side provided on the second cladding layer. Prevent. In the present specification, the laser element (chip) body refers to a plurality of semiconductor layer portions including a resonator structure formed on a substrate.

A fifth semiconductor laser device according to the present invention is
A first clad layer made of a first conductivity type nitride semiconductor formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. And a second cladding layer made of a second conductivity type nitride semiconductor, and a spontaneous emission light emitted from the active layer is provided on a side surface of the laser element main body parallel to the emission direction of the laser light. A spontaneous emission light blocking film that absorbs or reflects is formed.

According to the fifth semiconductor laser device, on the side surface parallel to the emitting direction of the laser beam in the laser element body,
Since the spontaneous emission light prevention film that absorbs or reflects the spontaneous emission light emitted from the active layer is formed, the spontaneous emission light prevention film prevents the spontaneous emission light emitted from the active layer in the lateral direction of the laser device main body. To prevent leakage.

In the third to fifth semiconductor laser devices,
It is preferable that the spontaneous emission light preventing film is made of metal containing gold or silicon. In this case, the energy gap of silicon is smaller than the energy of the spontaneous emission light emitted from the nitride semiconductor, so that the spontaneous emission light can be reliably absorbed. Further, gold is stable in material and reflects spontaneous emission light emitted from the nitride semiconductor with high reflectance. Furthermore, gold and silicon are very compatible with semiconductor manufacturing processes.

A sixth semiconductor laser device according to the present invention is
A first clad layer made of a nitride semiconductor of the first conductivity type formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. A second clad layer made of a second conductivity type nitride semiconductor, and an electrode formed on the second clad layer for injecting a current in a stripe shape to the active layer. A groove is formed on the side of the current injection region along the current injection region, and the groove is filled with a spontaneous emission light absorbing material that absorbs spontaneous emission light emitted from the active layer.

According to the sixth semiconductor laser device, a groove portion is provided on the side of the current injection region along the current injection region, and the groove portion naturally absorbs spontaneous emission light emitted from the active layer. Since the emitted light absorbing material is filled, the spontaneous emission light absorbing material prevents the spontaneous emission light emitted from the active layer in the lateral direction of the laser element body from leaking to the outside.

In the sixth semiconductor laser device, the spontaneous emission light absorbing material is preferably made of a metal containing silicon or gold.

A seventh semiconductor laser device according to the present invention is
A first clad layer made of a nitride semiconductor of the first conductivity type formed on the substrate; an active layer made of a nitride semiconductor formed on the first clad layer; and an active layer formed on the active layer. And a second clad layer made of a second conductivity type nitride semiconductor, and formed at a distance from at least one of the surface of the substrate opposite to the active layer and the side surface of the laser element body. And a spontaneous emission light prevention member that absorbs or reflects the spontaneous emission light emitted from the active layer.

According to the seventh semiconductor laser device, the spontaneous emission light emitted from the active layer is formed at a distance from at least one of the surface of the substrate opposite to the active layer and the side surface of the laser element body. Since the spontaneous emission light preventing member that absorbs or reflects is provided, the spontaneous emission light preventing member prevents the spontaneous emission light emitted from the active layer toward the substrate side or the side surface of the laser element body from leaking to the outside. .

In the seventh semiconductor laser device, the substrate is preferably made of sapphire, silicon carbide or gallium nitride.

An eighth semiconductor laser device according to the present invention is
A semiconductor laser chip, a photoelectric conversion element that receives a laser beam emitted from the semiconductor laser chip and detects an optical output value of the semiconductor laser chip, and a laser beam emitting section of the semiconductor laser chip and a light receiving section of the photoelectric conversion element. And a light-shielding unit that is provided between the semiconductor laser chips and shields at least a part of the spontaneous emission light.

According to the eighth semiconductor laser device, at least a part of the spontaneous emission light emitted from the semiconductor laser chip, which is provided between the laser light emitting portion of the semiconductor laser chip and the light receiving portion of the photoelectric conversion element, is shielded. Since the light shielding means is provided, the amount of spontaneous emission light mixed in the photoelectric conversion element for monitoring the light output value of the semiconductor laser chip is reduced, so that automatic output control can be reliably performed.

In the eighth semiconductor laser device, in the light shielding means, the attenuation amount of the spontaneous emission light when the spontaneous emission light passes through the light shielding means is smaller than the attenuation amount of the laser light when the laser light passes through the light shielding means. It is preferable that the number is increased.

In the eighth semiconductor laser device, it is preferable that the light shielding means is a light shielding plate having an opening on the optical axis of the laser light.

In the eighth semiconductor laser device, it is preferable that the semiconductor laser chip has a substrate made of a material that transmits laser light.

In this case, it is preferable that the semiconductor laser chip is made of a nitride semiconductor and the substrate is made of sapphire, silicon carbide or gallium nitride.

An optical disk device according to the present invention includes any one of the first to eighth semiconductor laser devices of the present invention and a laser beam emitted from the semiconductor laser device on a recording medium on which data is recorded. A condensing optical system device for condensing,
And a photodetector for detecting the laser light reflected by the recording medium.

In the optical integrated device according to the present invention, any one of the first to eighth semiconductor laser devices of the present invention and a laser beam emitted from the semiconductor laser device are provided on a semiconductor substrate. And a photodetector for detecting reflected light.

[0042]

(First Embodiment) First Embodiment of the Present Invention
Embodiments will be described with reference to the drawings.

FIG. 1 shows a cross-sectional structure of a nitride semiconductor laser device according to the first embodiment of the present invention. As shown in FIG. 1, the nitride semiconductor laser device 1 according to the present embodiment
A is mounted so that its element forming surface faces the main surface of the submount 2 made of silicon carbide (SiC) or diamond having an insulating property. Here, the nitride semiconductor laser device, a semiconductor having a composition constituting the laser Al _x Ga _y In _z N (where, x, y and z are, 0 ≦
x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, and x + y + z = 1).

In the nitride semiconductor laser device 1A, the main surface (element formation surface) of the substrate 11 made of sapphire on the submount 2 side relaxes the mismatch of the lattice constants of sapphire and the GaN-based crystal and crystal defects. Buffer layer 12 made of GaN or AlN for obtaining a semiconductor layer having a small amount
And an n-type contact layer 13 made of n-type GaN with Si as a dopant are sequentially formed. The lower surface of the n-type contact layer 13 has an element forming region for forming a laser structure formed of a double hetero (DH) pn junction and an n-side electrode forming region for forming an n-side electrode. In the region, for example, an n-side electrode 14 made of a laminated body of Ti / Al or Mo / Pt / Au is formed.

In the element formation region on the lower surface of the n-type contact layer 13, n-type In _x Ga having an energy gap that absorbs spontaneous emission light emitted from the active layer described later.
A spontaneous emission light absorption layer 15A made of _1-x N (where x is 0 <x <1) and for confining generated light generated in the active layer in the active layer and electrons in the active layer. n-type clad layer 16 made of n-type AlGaN
And In _y Ga _1-y N (where y is 0 <y <1 to recombine the confined electrons and holes to generate recombination light).
Is. ), A p-type clad layer 18 made of p-type AlGaN for confining generated light generated in the active layer 17 in the active layer 17 and holes in the active layer 17, and a p-side described later. P-type contact layer 19 made of p-type GaN in ohmic contact with the electrode
And an insulating film 20 made of a silicon oxide film having a stripe-shaped opening are sequentially formed. Here, the relationship between the In composition x and y in the spontaneous emission light absorption layer 15A and the active layer 17 is x ≧ y.

Assuming that the In mixed crystal ratio y of the well layer in the active layer 17 is 15%, the wavelength of the lasing laser beam is 410.
nm. Therefore, if the In mixed crystal ratio x of the spontaneous emission light absorbing layer 15A is set to 15% or more, the spontaneous emission light absorbing layer 15 will be
Since A is not transparent to the spontaneous emission light emitted from the active layer 17, the spontaneous emission light that does not contribute to laser oscillation can be reliably absorbed. Here, the thickness of the well layer is about 5 nm.
It is as follows.

The lower surface of the insulating film 20 is filled with, for example, Ni / Au or Ni / P so as to fill the opening of the insulating film 20.
A p-side electrode 21 formed of a t / Au laminated body is formed.

The p-side electrode 2 is formed on the main surface of the submount 2.
The p-side terminal electrode 23 is formed in a region facing 1 and the n-side terminal electrode 25 is formed in a region facing the n-side electrode 14. The p-side electrode 21 and the p-side terminal electrode 23, and the n-side electrode 14 and the n-side terminal electrode 25 are made of lead (Pb) and tin (S).
n) or gold (Au), and are electrically connected to each other via solder materials 22 and 24.

As described above, when a current is injected into the p-side electrode 21 and the n-side electrode 14 of the nitride semiconductor laser device 1A, a current exceeding the threshold current is injected from the active layer 17. Even in this case, spontaneous emission light that does not contribute to laser oscillation continues to be emitted to the surroundings. Further, the emitted light having an oscillation wavelength of about 410 nm is applied to the substrate 11 made of sapphire, the n-type and p-type clad layers 16 and 18 made of AlGaN, and the n-type and p-type contact layers 13 and 19 made of GaN. Being transparent, it is emitted in all directions around the active layer 17.

However, according to this embodiment, the In mixed crystal ratio is larger than that of the active layer 17 between the n-type cladding layer 16 and the n-type contact layer 13, that is, the energy gap is larger than that of the active layer 17. Since the small spontaneous emission light absorbing layer 15A is provided, this spontaneous emission light absorbing layer 15A is provided.
A is not transparent to the spontaneous emission light from the active layer 17, and as a result, this spontaneous emission light is absorbed by the spontaneous emission light absorption layer 15
It will be absorbed by A.

As described above, according to this embodiment, when the nitride semiconductor laser device 1A is mounted on the submount 2, it is possible to prevent the spontaneous emission light emitted to the substrate 11 side of the active layer 17 from leaking out. , Optical noise with respect to the optical element arranged on the substrate 11 side can be removed.

Further, since the spontaneous emission light absorption layer 15A is provided adjacent to the n-type cladding layer 16, the spontaneous emission light absorption layer 15A is located closest to the active layer 17, which is a light source, and the spontaneous emission light absorption efficiency is high. .

In this embodiment, InGaN having a smaller energy gap than the active layer 17 is used for the spontaneous emission light absorption layer 15A, but the present invention is not limited to this.
Any semiconductor material can be used as long as it can grow the system semiconductor crystal.

A method of manufacturing the nitride semiconductor laser device 1A having the above structure will be described below.

Here, as a method for growing a nitride semiconductor,
Trimethylaluminium was used as a group III source in a high temperature reactor.
(TMA), Trimethylgallium (TMG) and Tri
Organometallic compound raw materials such as methyl indium (TMI)
Along with the introduction, ammonia (NH₃ ) Gas
Introduced, each organometallic compound raw material and NH in the reaction furnace ₃ 
A nitride semiconductor is grown on the substrate by thermally decomposing
Metalorganic vapor phase epitaxy (MOVPE) method
It

First, after setting the substrate temperature to about 600 ° C., while introducing TMG and NH ₃ onto the main surface of the substrate 11 held in the reaction furnace, a buffer made of GaN is formed on the main surface of the substrate 11. Grow layer 12. Thus, GaN
It is known that by providing a so-called low-temperature buffer layer that is grown on sapphire having a lattice constant different from that of the system semiconductor, defects such as cracks are less likely to occur.
When the buffer layer 12 made of AlN is grown on the substrate 11, TMA is used instead of TMG.

Next, after raising the substrate temperature to about 1000 ° C., while introducing TMG and NH ₃ , the upper surface of the buffer layer 12 was doped with Si as an n-type impurity.
The n-type contact layer 13 made of n-type GaN is grown.

Next, after the substrate temperature is lowered to about 800 ° C., TMI is added to the group III source to cause spontaneous emission of n-type In _x Ga _{1 -x} N on the upper surface of the n-type contact layer 13. The absorption layer 15A is grown.

Next, after raising the substrate temperature to about 1000 ° C., TMG and TMA as a group III source are added to the substrate 11
Introduced on top, the n-type A is formed on the upper surface of the spontaneous emission light absorption layer 15A.
An n-type clad layer 16 made of lGaN is grown.

Next, after lowering the substrate temperature to about 800 ° C., the introduction of TMA as a group III source is stopped and the TMI is replaced.
Is added to the upper surface of the n-type cladding layer 16 so that In _y Ga
_An active layer 17 made of _1-yN is grown. Here, as the active layer 17, for example, each having a film thickness of 5 nm or less,
The threshold current of laser oscillation can be reduced by forming a multiple quantum well structure in which well layers made of InGaN and barrier layers made of AlGaN are alternately laminated.

Next, after raising the substrate temperature to about 1000 ° C., TMG and TMA as a group III source are added to the substrate 11
By introducing the above, the p-type clad layer 18 made of p-type AlGaN doped with Mg as a p-type impurity on the upper surface of the active layer 17, and the introduction of TMA to stop the p-type clad layer 18 on the upper surface. The p-type contact layer 19 made of p-type GaN is sequentially grown.

Next, the substrate (epitaxial substrate) on which each nitride semiconductor layer is formed is taken out from the reaction furnace, and an insulating film 20 such as a silicon oxide film is formed on the upper surface of the p-type contact layer 19.
To form. Then, the insulating film 20 is selectively etched to form stripe-shaped openings in the insulating film 20.

Next, the p-side electrode 21 made of a laminated film of Ni / Au or the like is formed on the entire surface of the insulating film 20 including the opening by using a vapor deposition method or the like.

Next, the element formation region of the p-side electrode 21 is masked and the epitaxial layer is etched to expose the n-type contact layer 13 to form an n-side electrode formation region. On the n-side electrode formation region, the n-side electrode 14 made of a Ti / Al laminated film is formed by using, for example, an evaporation method.

Next, the epitaxial substrate is cleaved so that a resonator can be obtained from the epitaxial substrate. Subsequently, a predetermined end face coating is applied to the end face of the resonator, the element formation face side of the substrate 11 in the nitride semiconductor laser device 1A is made to face the main face of the submount 2, and the p-side electrodes 21 and n.
The p-side terminal electrode 23 and the n-side terminal electrode 25, which are respectively connected to the side electrodes 14, are aligned, and then the electrodes are fixed to each other by the solder materials 22 and 24, whereby the nitride shown in FIG. The semiconductor laser device 1A is obtained.

The substrate 11 side of the active layer 17 and the substrate 1
1 is formed on the side opposite to 1 so as to be in contact with the active layer 17,
When the n-type light guide layer made of n-type GaN and the p-type light guide layer made of p-type GaN are provided to improve the light confinement ratio in the active layer 17, the light confinement effect in the active layer 17 is improved. The threshold current can be further reduced.

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

FIG. 2 shows a cross sectional structure of a nitride semiconductor laser device according to a first modification of this embodiment. In FIG. 2, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 2, the nitride semiconductor laser device 1B according to the present modification has an n-type In having a smaller energy gap than the active layer 17.
The spontaneous emission light absorption layer 15B made of GaN is formed between the buffer layer 12 and the n-type contact layer 13.

By doing so, the spontaneous emission light absorbing layer 15 is formed.
Since B can cover the entire main surface of the substrate 11, it is possible to further prevent leakage of spontaneous emission light emitted to the substrate 11 side.

Further, if the spontaneous emission light absorbing layer 15B is grown at a low temperature and used as the buffer layer 12, it will not be a burden on the manufacturing process.

(Second Modification of First Embodiment) A second modification of the first embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a sectional structure of a nitride semiconductor laser device according to a second modification of this embodiment. In FIG. 3, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 3, the nitride semiconductor laser device 1C according to the present modification is a p-type In having a smaller energy gap than the active layer 17.
The spontaneous emission light absorption layer 15C made of GaN is formed between the p-type cladding layer 18 and the p-type contact layer 19. Here, the spontaneous emission light absorption layer 15
C must be p-type, and Mg as a p-type dopant
Is used.

By doing so, the spontaneous emission light absorbing layer 15 is formed.
C can prevent the spontaneous emission light emitted from the active layer 17 to the p-side electrode 21 side from leaking out.

(Third Modification of First Embodiment) A third modification of the first embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows a cross-sectional structure of a nitride semiconductor laser device according to the third modification of this embodiment. 4, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 4, the nitride semiconductor laser device 1D according to the present modification is a p-type In having a smaller energy gap than the active layer 17.
The spontaneous emission light absorption layer 15D made of GaN is formed between the p-type contact layer 19 and the p-side electrode 21.

By doing so, the spontaneous emission light absorbing layer 15 is formed.
Since D has a smaller energy gap than the p-type contact layer 19 made of GaN, the contact resistance becomes smaller than that of the p-type contact layer 19, so that the threshold voltage can be reduced.

As described above, in the first embodiment and each modification thereof, any of the spontaneous emission light absorption layers 15A to 15D is provided in the epitaxial layer forming the laser structure. As the light absorption layer is closer to the active layer 17, the spontaneous emission light absorption layer absorbs a part of the laser light, and the loss during laser oscillation increases. Therefore, on the contrary, since the oscillation threshold current increases, it is necessary to design in consideration of the light distribution of the laser light.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 shows a cross-sectional structure of a nitride semiconductor laser device according to the second embodiment of the present invention. In FIG. 5, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the spontaneous emission light absorption layer is not provided in the epitaxial layer as in the first embodiment, but the spontaneous emission light prevention film is provided on the outer surface of the laser chip body.

As shown in FIG. 5, the nitride semiconductor laser device 1E according to this embodiment includes a substrate 1 made of sapphire.
A spontaneous emission light prevention film 31A that absorbs or reflects the spontaneous emission light from the active layer 17 is formed on the surface (rear surface) opposite to the element formation surface of No. 1.

Here, as the material that absorbs the spontaneous emission light emitted from the active layer 17 made of InGaN, crystalline silicon or amorphous silicon having an energy gap smaller than the energy of the spontaneous emission light is used.
This silicon (Si) film is formed by using, for example, a sputtering method or the like. Not limited to Si, any material may be used as long as it has an energy gap smaller than the energy of spontaneous emission light and is easily adapted to the process.

Further, as a material highly reflecting the spontaneous emission light emitted from the active layer 17, for example, an Au film or a laminated layer of Au and another metal such as Ti / Pt / A is used.
A laminated film made of u is preferable. An electron beam vapor deposition method, a resistance heating vapor deposition method, or the like is used for these metal films or laminated films.

In addition to Au, Ti, and Pt, Cr, Sn, Cu, and
A metal such as Fe, Ag, or In, or a laminated film or alloy thereof (for example, Au and Sn) is used.

Further, the absorption film and the high reflection film may be combined, and for example, it is more effective to stack the high reflection film made of Au on the absorption film made of Si.

As described above, according to the present embodiment, when the nitride semiconductor laser device 1E is mounted on the submount 2, it is possible to prevent the spontaneous emission light emitted to the substrate 11 side of the active layer 17 from leaking out. , Nitride semiconductor laser device 1
It is possible to remove optical noise with respect to the optical element arranged in the peripheral portion of the substrate E on the substrate 11 side.

(First Modification of Second Embodiment) A first modification of the second embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 shows the appearance of a nitride semiconductor laser device according to the first modification of this embodiment. 6, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 6, the nitride semiconductor laser device 1F according to the present modification has, on the emitting end face of the active layer of the laser chip body, excluding the laser light emitting part, and on the reflecting end face opposite to the emitting end face, A spontaneous emission light prevention film 31B that absorbs or reflects the spontaneous emission light emitted from the active layer is formed.

The spot size of the laser beam emitting portion is 5 μm
It is about a corner. In addition, for example, when the laser light for monitoring is not taken out from the reflection end face, it is preferable to form the spontaneous emission light prevention film 31B on the entire reflection end face.
By doing so, the oscillation threshold value can be further reduced.

As the absorbing film, a Si film is preferable as in the second embodiment. The high reflection film may be the above-mentioned metal film. However, when a conductive film of metal or the like is provided, an insulating film made of SiO ₂ or the like is previously formed to prevent electrical short circuit of each semiconductor layer. Must be formed as an underlayer.

Here, since the spontaneous emission light prevention film 31B according to the present modification is provided on the end face of the laser chip body in the direction perpendicular to the resonance direction of the laser light, the reflection film is used rather than the absorption film. Is preferred. This is because the spontaneous emission light reflected by the spontaneous emission light prevention film 31B can contribute to the laser oscillation.

The high reflection film is made of, for example, SiO ₂ / T.
A laminated film made of a dielectric material such as i0 ₂ may be used. In this case, by alternately laminating SiO ₂ films and TiO ₂ films each having a film thickness corresponding to ¼ of the wavelength of spontaneous emission light, a reflectance of up to 94% can be obtained in a 6-layer structure, for example. Obtainable.

Thus, according to this modification, the active layer 1
Since it is possible to prevent the spontaneous emission light emitted from the laser diode 7 from being emitted in a direction substantially parallel to the resonator, the nitride semiconductor laser device 1F is arranged in the emitting direction of the laser beam or in the peripheral portion in the opposite direction to the emitting direction. The optical noise with respect to the optical element can be removed.

(Second Modification of Second Embodiment) A second modification of the second embodiment of the present invention will be described below with reference to the drawings.

FIG. 7 shows a cross-sectional structure of a nitride semiconductor laser device according to a second modification of this embodiment. In FIG. 7, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 7, the nitride semiconductor laser device 1G according to the present modification absorbs or reflects the spontaneous emission light emitted from the active layer 17 on the side surface of the laser chip body parallel to the emission direction of the laser light. A spontaneous emission light prevention film 31C is formed.

Here, the absorption film is preferably a Si film as in the second embodiment. Further, as the high reflection film,
The above-mentioned metal film of Au or the like may be used, but when a conductive film of metal or the like is provided, an insulating film made of SiO ₂ or the like is previously formed as a base layer in order to prevent an electrical short circuit of each semiconductor layer. You need to do it.

Further, the absorption film and the high reflection film may be used in combination, and for example, Au may be formed on the absorption film made of Si.
You may use the laminated body which laminated | stacked the highly reflective film which consists of.

As described above, according to this modification, the active layer 1
Since it is possible to prevent the spontaneous emission light emitted from the optical fiber 7 from being emitted in a direction substantially perpendicular to the resonator, it is possible to eliminate optical noise with respect to the optical elements arranged in the peripheral portion in the direction perpendicular to the resonator. 1 embodiment and its modification, and 2nd
Although the embodiment and the modified example thereof have been described, the spontaneous emission light leaking from the laser chip body can be almost completely prevented by combining these embodiments and modified examples.

Considering that the manufacturing process becomes complicated, for example, the spontaneous emission light absorbing layer 15A according to the first embodiment shown in FIG. 1 or the first modification of the first embodiment shown in FIG. Example spontaneous emission light absorption layer 15B, and FIG.
It is preferable to provide the absorption layer and the prevention film made of the spontaneous emission light prevention film 31A according to the second embodiment shown in FIG.

FIG. 8 shows a spontaneous emission light absorption layer 15 according to the present invention.
The light output characteristics of the nitride semiconductor laser device and the conventional nitride semiconductor laser device with respect to each injection current when A and the spontaneous emission light prevention film 31A are provided are shown.
In FIG. 8, the horizontal axis represents the current value (unit mA) injected into the laser device, and the vertical axis represents the output value of laser light (unit m).
W), curve 3 represents the laser device according to the invention and curve 4 represents the conventional laser device. As shown in FIG. 8, in the conventional semiconductor laser device shown by the curve 4, leakage of spontaneous emission light is observed until the oscillation threshold is reached, whereas in the semiconductor laser device according to the present invention shown by the curve 3, It can be seen that there is almost no output of spontaneous emission light near the oscillation threshold, and only laser light is emitted.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 9 shows a cross-sectional structure of a nitride semiconductor laser device according to the third embodiment of the present invention. In FIG. 9, the same components as those shown in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 9, the nitride semiconductor laser device 1H according to the present embodiment is
The active layer 17 is a region on the side of a current injection region (so-called stripe region) in which a current is injected from the p-side electrode 21 in the laser chip body, and reaches the n-type contact layer 13 from the p-type contact layer 19. Is divided in the longitudinal direction of the resonator, and a groove portion 26 extending substantially parallel to the current injection region is formed by etching.

Further, on the surface of the substrate 11 opposite to the element formation surface, a spontaneous emission light prevention film 31 made of, for example, silicon.
A is formed.

An insulating film 27 made of a silicon oxide film or the like is formed on the wall surface of the groove 26, and the groove 26 can absorb spontaneous emission light such as gold (Au) on the insulating film 27. The spontaneous emission light absorbing material 28 is filled by vapor deposition or the like.

The laser chip body laminated by the MOVPE method has a small total film thickness of about 5 μm, but since it is a laminated body, the spontaneous emission light emitted from each semiconductor layer in the in-plane direction of the substrate surface cannot be ignored. .

According to this embodiment, a spontaneous emission light absorption region that divides the active layer 17 by the groove portion 26 filled with the spontaneous emission light absorption material 28 is formed in a region on the side of the current injection region in the laser chip body. Therefore, the spontaneous emission light emitted in the in-plane direction of the substrate 11 can be absorbed.

Although Au was used as the spontaneous emission light absorbing material 28, it is not limited to this, and Ti, Cr, Sn, Cu, F may be used.
A metal such as e, Ag, Pt, or In, or a laminated film or alloy containing a plurality of metals (for example, Ti / Au) may be used. Alternatively, a semiconductor having a relatively small energy gap such as single crystal silicon or amorphous silicon may be used.

Further, in the present embodiment, the spontaneous emission light absorbing material 28 is provided only in the region opposite to the n-side electrode 14 with respect to the current injection region in the laser chip body. You may provide in the area | region by the side electrode 14 side.

As shown in FIG. 9, even when the groove 26 is not provided in the region on the n-side electrode side with respect to the current injection region, it is interposed between the n-side electrode 14 and the n-side terminal electrode 25. The solder material 24 can absorb spontaneous emission light. Further, instead of the solder material 22 containing Pb, Sn and the like, a material capable of absorbing spontaneous emission light, for example, a conductive adhesive material or a silver paste material may be used.

Further, the groove 26 only needs to suppress the spontaneous emission light emitted from the active layer 17 to portions other than the waveguide, and is not necessarily provided in parallel with the current injection region.

It has been observed that the light output characteristics with respect to the injection current in the nitride semiconductor laser device according to the present embodiment show characteristics substantially equivalent to the curve 3 shown in FIG.

As described above, according to this embodiment, the spontaneous emission light absorbing material 28 provided inside the laser chip body,
Also, since the spontaneous emission light prevention film 31A provided on the surface of the substrate 11 opposite to the element formation surface reduces spontaneous emission light emitted from the laser chip, coherent laser light can be reliably obtained. it can. Further, the influence of the spontaneous emission light on the photodiode for monitoring the light output can be reduced, so that the controllability of the light output of the laser light can be improved.

(Fourth Embodiment) A fourth embodiment of the present invention will be described below with reference to the drawings.

FIG. 10 shows a cross-sectional structure of a nitride semiconductor laser device according to the fourth embodiment of the present invention. Figure 10
In FIG. 5, the same components as those shown in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 10, the nitride semiconductor laser device 1 according to the present embodiment
I is provided on the submount 2 via the p-side terminal electrode 23 or the n-side terminal electrode 25 and at a side surface parallel to the emission direction of laser light in the laser chip body, and is emitted from the active layer 17. A spontaneous emission light prevention wall 32 that absorbs or reflects the spontaneous emission light is formed.

Furthermore, on the surface of the substrate 11 opposite to the element forming surface, for example, as described in the second embodiment,
A spontaneous emission light prevention film 31A made of Au, Si or the like is formed.

The spontaneous emission light prevention wall 32 may be made of the same material as the spontaneous emission light prevention film 31A, and is preferably a material that absorbs the spontaneous emission light emitted from the laser chip.

The method for forming the spontaneous emission light prevention wall 32 is as follows.
Formed as a bulk or sintered block material made of the above-mentioned metal, or a block material made of SiC,
The p-side terminal electrode 23 and the n-side terminal electrode 2 of the submount 2
The upper surface of the laser chip is fixed to the upper surface of the laser chip 5 by a solder material or the like with a space therebetween. Here, the p-side terminal electrode 23 or n
An insulating film may be interposed between the side terminal electrode 25 and the spontaneous emission light prevention wall 32.

As another forming method, a thin film made of the above-described metal is formed on the surface of a block material made of glass by vapor deposition, and the thin film is made of each terminal electrode 23 by using an adhesive or the like.
You may fix it on 25.

As described above, according to the present embodiment, the spontaneous emission light prevention wall 32 provided on the side surface of the laser chip main body in the direction parallel to the emission direction of the laser light at intervals.
Also, since the spontaneous emission light prevention film 31A provided on the surface of the substrate 11 opposite to the element formation surface reduces spontaneous emission light emitted from the laser chip, coherent laser light can be reliably obtained. it can.

Further, neither the spontaneous emission light prevention film 31A nor the spontaneous emission light prevention wall 32 in this embodiment has a risk of damaging each epitaxial layer of the laser chip.

The spontaneous emission light prevention wall 32 may be one of the side surfaces of the laser chip body parallel to the emitting direction of the laser light.

When a conductive substrate such as n-type GaN is used for the substrate 11 instead of insulating sapphire, the spontaneous emission light blocking film 31A may be used as the n-side electrode 14.

(Modification of Fourth Embodiment) A modification of the fourth embodiment of the present invention will be described below with reference to the drawings.

FIGS. 11A and 11B show a nitride semiconductor laser device according to a modification of the fourth embodiment of the present invention, where FIG. 11A shows a sectional structure and FIG. 11B. Shows the appearance. 11 (a) and 11 (b), FIG.
The same components as those shown in are denoted by the same reference numerals. As shown in FIGS. 11A and 11B, a nitride semiconductor laser device 1J according to this modification is made of a metal or the like containing Au, Ti, or Pt on the submount 2 and covers the laser chip body. It is characterized by having a lid-shaped light-shielding case 33 provided in such a manner. The light-shielding case 33 has a bottom surface spaced from the surface of the substrate 11 opposite to the element formation surface, an inner wall surface spaced from each side surface of the laser chip body, and the p-side terminal electrode 23 and the n-side terminal. The electrodes 25 and the electrodes 25 are fixed to each other with an insulating film 34 interposed therebetween.

As shown in FIG. 11B, the light shielding case 33 is provided with an opening 33a for outputting the laser light to the outside in a portion of the laser chip facing the laser light emitting portion. . Since the width of the current injection region of the active layer 17 is about 5 μm, the spot size on the emission end face of the laser light is about 5 μm square. Therefore, the opening diameter of the opening 33a may be 5 μm or slightly larger than 5 μm.

When it is necessary to monitor the output of the laser light, the opening 3 on the side surface of the light shielding case 33 is used.
Another opening (not shown) having the same shape as that of the opening 33a may be provided in a portion opposed to 3a.

Depending on the use of the nitride semiconductor laser device 1J, it is not always necessary to cover the four side surfaces of the laser chip body. For example, either side plate of the light shielding case 33 on the side intersecting the optical axis direction may be provided, or both side plates may not be provided.

In the nitride semiconductor laser device according to the present embodiment and its modification, it has been observed that the light output characteristic with respect to the injection current is substantially the same as the curve 3 shown in FIG.

The nitride semiconductor laser device 1A described above
1J, the p-type contact layer 19 was covered with the insulating film 20 having a stripe-shaped opening to form a stripe-shaped current injection region in the active layer 17, but the lateral mode controllability of laser light was further improved. In order to increase the height, the p-type contact layer 19 and the p-type cladding layer 18 may be formed in a ridge shape.

Not only the nitride semiconductor laser device having the active layer 17 made of InGaN but also a nitride semiconductor laser device using the substrate 11 having an energy gap larger than that of the active layer 17.

In each of the embodiments, the nitride semiconductor crystal is formed by the MOVPE method. However, the present invention is not limited to this, and the molecular beam epitaxy (MBE) method or the halide VPE method is used.
You may form using (H-VPE) etc.

(Fifth Embodiment) Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 12 schematically shows the structure of an optical disk device according to the fifth embodiment of the present invention. The optical disk device according to the present embodiment uses the nitride semiconductor laser device of the present invention in the light emitting section of the optical disk device. 12
As shown in FIG. 5, the optical disc device is provided so that the emission end face of the semiconductor laser device 41 and the data holding face of the optical disc 50 which is a recording medium on which desired data is recorded face each other. Between the optical disc 50 and the optical disc 50, a condensing optical unit 4 as a condensing optical system device.
0 is provided.

The condensing optical section 40 comprises a semiconductor laser device 41.
A collimator lens 42, which is provided in order from the side, collimates emitted light 51 emitted from the semiconductor laser device 41 into parallel light.
, A diffraction grating 43 that splits parallel light into three beams (not shown), and a half prism 44 that transmits the emitted light 51 and changes the optical path of the reflected light 52 from the optical disk 50.
And a condenser lens 45 for condensing the three beams on the optical disc 50. Here, laser light having a wavelength of about 410 nm is used as the emitted light 51.

The three beams focused on the optical disk 50 each have a spot shape with a diameter of about 0.4 μm. A drive system circuit 46 is provided to correct the radial displacement of the optical disc 50 detected by the positions of these three spots by appropriately moving the condenser lens 45.

On the optical path of the reflected light 52 from the half prism 44, a light-receiving lens 47 that narrows the reflected light 52, a cylindrical lens 48 that detects a positional shift of the focal point, and the condensed reflected light 52 is converted into an electric signal. And a photodiode element 49 as a photodetector.

As described above, the optical disk device provided with the condensing optical section 40 for guiding the emitted light 51 from the semiconductor laser device 41 to the optical disk 50 and the photodiode element 49 for receiving the reflected light 52 reflected by the optical disk 50. Since the semiconductor laser device 41 that suppresses or prevents the leakage of spontaneous emission light is used as the light emitting unit, even if the optical disc 50 is a high-density optical disc having a high data recording density, reading (reproduction) of data from the optical disc 50 is performed. S of time
Since the / N ratio is improved, a low distortion read (reproduction) operation can be realized.

In order to record data on the optical disc 50, it is necessary to accurately control the output value of the laser light output during recording from a low output of about 5 mW to a high output of about 30 mW. This is because it is necessary to look for an address at a low output before writing at the output of 30 mW.

According to the optical disk device of the present embodiment, since the spontaneous emission light which is a noise source is prevented from leaking from the semiconductor laser device 41, a photodiode (not shown) for detecting (monitoring) the optical output of the semiconductor laser device 41 is shown. No)
Will be able to more accurately convert the output laser light into a current. Specifically, the semiconductor laser device 4
In No. 1, since the monitor current changes linearly when the light output is changed, the output operation of the semiconductor laser device 41 can be reliably controlled. As a result, the operation during reproduction or recording of the optical disk device is improved.

(Sixth Embodiment) A sixth embodiment of the present invention will be described below with reference to the drawings.

FIG. 13 schematically shows the structure of an optical integrated device according to the sixth embodiment of the present invention. As shown in FIG. 13, the optical integrated device according to the present embodiment is formed on one substrate 61 made of Si. A concave portion 61a is provided on the main surface of the base 61, and the semiconductor laser device 62 of the present invention is fixed to the bottom surface of the concave portion 61a with a solder material or the like. Semiconductor laser device 6 in recess 61a
The side wall on the side of the emission end face of 2 is 4 with respect to the main surface of the base 61.
A micro mirror 63 having an angle of 5 ° is provided. As a result, the emitted light 51 emitted from the laser chip 62 is reflected by the micro mirror 63 and is reflected by the base 6
It proceeds almost perpendicular to the main surface of No. 1. Here, it is preferable to use the (111) plane having the plane orientation of Si as the micromirror 63.

On the wall surface of the concave portion 61a of the base 61 facing the micro mirror 63, an output monitor photo for monitoring the output value of the laser chip from the laser light slightly emitted from the reflection end surface of the semiconductor laser device 62 is provided. The diode element 64 is formed. The surface of the micromirror 63 may be silicon as it is, or a metal thin film such as Au, Ag, or Al may be vapor-deposited.

Micromirror 6 on top of substrate 61
3 in the direction parallel to the reflecting surface of the micro mirror 63
In a region sandwiching the two, a first photodiode element 65A and a second photodiode element 65B as a photodetector for receiving the reflected light 52 of the emitted light 51 from an optical disc (not shown) are directly attached to the base 61. Has been formed.

As described above, the light emitting portion and the light receiving portion are provided on one substrate, and the emission of spontaneous emission light is suppressed to a low level in the light emitting portion of the optical integrated device for downsizing and thinning. Since the semiconductor laser device 62 is used, the S /
The N ratio can be reliably improved.

(Seventh Embodiment) The seventh embodiment of the present invention will be described below.

The present embodiment will explain a configuration capable of reliably executing automatic output control (APC) in a semiconductor laser device.

In general, the optical output value of the semiconductor laser device changes depending on the value of the current passed through the laser chip. Therefore, when the semiconductor laser device is used in an optical information processing device such as an optical disk or optical communication, the current passed through the semiconductor laser device is increased. A predetermined light output is obtained by adjusting the value. Hereinafter, this situation will be described with a graph.

FIG. 16A shows the relationship between the operating current value and the optical output value of the semiconductor laser device (hereinafter referred to as the IL characteristic curve), and FIG. 16B shows the IL characteristic curve. It represents the temperature change. The change (ΔL) in light output with respect to the change (ΔI) in operating current shown in FIG. 16A is generally called slope efficiency.

FIG. 16B shows that if a predetermined light output value L0 is obtained at the first operating current value I1 at the first temperature T1, the light output value L0 is A second temperature T2 higher than the first temperature T1, and a second temperature T
At a third temperature T3 higher than 2, the first
A second operating current value I2 larger than the operating current value I1 of
And that it is necessary to provide a third operating current value I3 that is larger than the second operating current value I2.

The slope efficiency varies sensitively with temperature because there is a large difference between individual laser elements. Specifically, as shown in FIG. 16B, the threshold current tends to increase and the slope efficiency tends to decrease as the temperature rises. Therefore, as described above, it is necessary to increase the operating current for obtaining a predetermined light output value as the temperature rises.

When a semiconductor laser device having such temperature dependency is applied to a product, the operating current value is adjusted with respect to the temperature of the laser element in order to maintain a predetermined light output value L0. Alternatively, temperature control is required to keep the temperature of the laser element at a predetermined value.

As a method for maintaining the optical output value regardless of the temperature, generally, an automatic output for detecting a part of the laser light by a photoelectric conversion element to monitor the optical output and adjusting the operating current value of the semiconductor laser device. A control method is adopted. In order to monitor the optical output value required for automatic output control, it is necessary to receive the emitted light from the semiconductor laser device by a photoelectric conversion element such as a photodiode. The semiconductor laser device is
Usually, since laser light is emitted from both end faces of the resonator mirror, one emitted light (hereinafter, referred to as front light) is taken out from the package of the element and the other emitted light (hereinafter, referred to as rear light). ) Is received by the photodiode in the package.

At this time, before reaching the oscillation threshold of the laser light, nondirectional spontaneous emission light is emitted from the active region of the semiconductor laser device to the periphery of the laser device. Of these, the component emitted in the direction of the cavity mirror of the semiconductor laser device appears as an optical output before the applied current reaches the threshold current value on the IL characteristic curve shown in FIG.

Hereinafter, the IL characteristics due to the difference in the material of the semiconductor laser device, that is, the oscillation wavelength will be compared.

FIG. 17 is an IL characteristic curve of semiconductor laser devices having different oscillation wavelengths. Curve 5 is InGa having an oscillation wavelength of about 650 nm formed on a substrate made of GaAs.
A curve 6 shows the IL characteristics of the AlP semiconductor laser device.
Is formed on a substrate made of sapphire and has an oscillation wavelength of about 4
I-L of 00 nm InGaAlN semiconductor laser device
It shows the characteristics. As can be seen from FIG. 17, as compared with the InGaAlP-based semiconductor laser device shown in the curve 5, the InGaAlN-based semiconductor laser device shown in the curve 6 has more than five times the spontaneous emission amount at the threshold value. This is Ga
Since the As substrate absorbs light with a wavelength of 870 nm or less,
The wavelength of the InGaAlP semiconductor laser device is 650 nm.
While the spontaneous emission light is absorbed, the sapphire substrate has an InGaAlN semiconductor laser device having a wavelength of 400 nm.
This is because the spontaneous emission light of cannot be absorbed.

As described above, if there is a large amount of spontaneous emission light before reaching the oscillation threshold value, the light is input to the monitoring photodiode as bias light, which makes it difficult to perform accurate optical output control by automatic output control. .

A semiconductor laser package according to the seventh embodiment of the present invention will be described below with reference to the drawings.

FIG. 14 is a perspective view in which a part of the semiconductor laser package 70 according to the present embodiment is cut away. 14
As shown in FIG. 2, the semiconductor laser package 70 according to the present embodiment has a disc-shaped base 71 made of metal or the like having excellent heat dissipation and a quadrangular pyramid trapezoidal shape made of metal or the like having excellent heat dissipation. The mount 7 whose side surface is fixed to the upper surface of the base 71 so that the upper bottom surface is parallel to the axial direction of the base 71.
2, and a semiconductor laser chip 7 fixed on the upper bottom surface of the mount 72 with a submount 73 interposed therebetween so that the axial direction of the base 71 and the optical axis of the laser light are substantially aligned with each other.
4 and.

The semiconductor laser chip 7 is mounted on the base 71.
A photodiode element 75 as a photoelectric conversion element for detecting the backward light Lb from the semiconductor laser chip 74 is fixed to a region facing the base 71 in FIG.

A light-shielding plate 76, which is provided between the semiconductor laser chip 74 on the upper bottom surface of the mount 72 and the photodiode element 75 and has an opening 76a on the optical axis of the backward light Lb, is provided. There is. The light shielding plate 76 may be made of any material that does not allow laser light to pass therethrough, and a metal material, a plastic material, a glass material, or the like is used. Further, the facing surface of the light shield plate 76 facing the semiconductor laser chip 74 has a rear light L.
It is preferable that at least the opposing surface is matte (matte) so that the reflected light b is not mixed with the front light Lf. Further, a material for the light shielding plate 76 to absorb the laser light,
Alternatively, it is preferable that at least the opposing surface is coated with a coating material or the like that absorbs laser light.

A cap that covers the mount 72 and the light shielding plate 76 is airtightly fixed to the upper surface of the base 71. A window portion for transmitting the front light Lf is provided on the optical axis of the front light Lf in the cap 77, and a window glass 78 is airtightly provided inside the window portion. Further, an external lead 79 for electrically connecting the semiconductor laser chip 74 and the photodiode 75 to the outside is provided on the lower surface of the base.

Laser light has a strong directivity and is emitted along the optical axis with a certain spread angle. On the other hand, the spontaneous emission light is emitted from the semiconductor laser chip 74 to the entire periphery of the chip 74. It is difficult to separate the component of the spontaneous emission light emitted in the optical axis direction of the laser light from the laser light. However, as in this embodiment, the light shielding plate 7 having the opening 76a at a position along the optical axis of the laser light is used.
6, a semiconductor laser chip 74 and a photodiode 75
It is possible to prevent the component different from the direction of the optical axis of the spontaneous emission light from being detected by the photodiode 75 by disposing the component between and.

As described above, the semiconductor laser chip 74
In an InGaAlN-based laser device using sapphire, SiC, or GaN for the substrate having an oscillation wavelength of about 400 nm, the substrate does not absorb the spontaneous emission light, so the spontaneous emission light leaking from the semiconductor laser chip 74 has an oscillation wavelength of 650 nm. Much more than in the case of a red laser device.
Therefore, as in this embodiment, the semiconductor laser chip 74
And the photodiode 75 for light output monitoring are provided such that the amount of attenuation of the spontaneous emission light after passing through the light shielding plate 76 is larger than the amount of attenuation of the backward light Lb after passing through the light shielding plate 76. The configuration including the light shielding plate 76 is extremely effective.

The larger the aperture diameter of the opening 76a, the smaller the attenuation amount of the backward light Lb and the spontaneous emission light. Therefore, the attenuation amount of the backward light Lb is small and the attenuation amount of the spontaneous emission light is large. Therefore, it is preferable to select an appropriate diameter. Further, it is preferable to set the attenuation amount of the backward light Lb to be zero.

The opening shape of the opening 76a of the light shielding plate 76 may be circular or square. More preferably, since the beam shape of the laser light emitted from the semiconductor laser chip is generally an elliptical shape, the elliptical shape corresponding to the beam shape is used. However, depending on the mounting state of the semiconductor laser chip,
The beam shape of the backward light may be disturbed, and the oval shape is not always the optimum shape.

FIG. 15 schematically shows how the semiconductor laser package according to this embodiment is automatically controlled for output. 15, the same components as those shown in FIG. 14 are designated by the same reference numerals. As shown in FIG. 15, the backward light L emitted from the semiconductor laser chip 74
b is photoelectrically converted by the photodiode 75 and is AP
It is output to the C circuit 80 as a monitor signal. The APC circuit 80 that receives the monitor signal is a semiconductor laser chip 74.
The current amount of the operating current of the semiconductor laser chip 74 is adjusted so that the optical output value of 1 can maintain a predetermined value.

According to this embodiment, the components of the spontaneous emission light emitted from the semiconductor laser chip 74 excluding the components emitted in the same direction as the backward light Lb of the laser light are the semiconductor laser chip 74 and the photodiode 75. Since the light is blocked by the light shielding plate 76 provided between and, the light does not enter the photodiode 75. As a result, the detection amount of spontaneous emission light can be reduced to about 1/10 of that in the case where the light shielding plate 76 is not provided. As a result, even in a low light output state near the threshold value of the operating current, the influence of spontaneous emission light can be reduced, and automatic output control can be performed with high accuracy.

In the past, the photodiode 75 has been designed so that the rear light L
Even the spontaneously emitted light that is relatively mixed in b is backward light Lb.
Since photoelectric conversion is performed as the detection light of, the actual output value of the laser light is highly evaluated. As a result, AP
The C circuit 80 sets an operating current lower than a predetermined light output value.

In this embodiment, the light shielding means is the light shielding plate 76 having the opening 76a.
6a is not always necessary. For example, a thin film in which the amount of spontaneous emission light attenuation is larger than the amount of laser light attenuation may be used.

Besides the plate-like member, for example, a cylindrical member extending so as to include the optical axis of the backward light Lb may be used.

The light shielding means is the semiconductor laser chip 7
It is not limited to the member provided between the photodiode 4 and the photodiode 75. For example, a gas or a resin material that is filled in the cap 77 shown in FIG. 14 and in which the attenuation amount of spontaneous emission light is larger than the attenuation amount of laser light may be used.

Although the effect is weakened, it is needless to say that the long-wavelength oscillation type InGaAlP laser device can be provided with the same light shielding plate 76 as in the present embodiment to reduce the spontaneous emission light.

[0172]

According to the semiconductor laser device of the present invention, since spontaneous emission light accompanying laser oscillation is not emitted to the outside of the device, optical noise with respect to optical elements arranged in the peripheral portion of the device is removed. it can. Therefore, the S / N ratio during the reading operation of the optical disc or the like is improved, so that the automatic output control can be more surely performed and the application to the optical integrated device becomes possible.

[Brief description of drawings]

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

FIG. 2 is a structural cross-sectional view showing a nitride semiconductor laser device according to a first modification of the first embodiment of the present invention.

FIG. 3 is a structural cross-sectional view showing a nitride semiconductor laser device according to a second modification of the first embodiment of the present invention.

FIG. 4 is a structural cross-sectional view showing a nitride semiconductor laser device according to a third modification of the first embodiment of the present invention.

FIG. 5 is a structural cross-sectional view showing a nitride semiconductor laser device according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a nitride semiconductor laser device according to a first modification of the second embodiment of the present invention.

FIG. 7 is a structural cross-sectional view showing a nitride semiconductor laser device according to a second modification of the second embodiment of the present invention.

FIG. 8 is a graph showing respective light output characteristics with respect to respective injection currents of the nitride semiconductor laser device according to the present invention and the conventional nitride semiconductor laser device.

FIG. 9 is a structural cross-sectional view showing a nitride semiconductor laser device according to a third embodiment of the present invention.

FIG. 10 is a structural cross-sectional view showing a nitride semiconductor laser device according to a fourth embodiment of the present invention.

11A and 11B show a nitride semiconductor laser device according to a modification of the fourth embodiment of the present invention,
(A) is a sectional view of the configuration, and (b) is a perspective view.

FIG. 12 is a schematic configuration diagram showing an optical disk device according to a fifth embodiment of the present invention.

FIG. 13 is a schematic perspective view showing an optical integrated device according to a sixth embodiment of the present invention.

FIG. 14 is a partially cutaway sectional perspective view showing a semiconductor laser device according to a seventh embodiment of the present invention.

FIG. 15 is a schematic configuration diagram showing an automatic output control method in a semiconductor laser device according to a seventh embodiment of the present invention.

FIG. 16A is a graph showing a relationship (IL characteristic curve) between an operating current value and an optical output value in a normal semiconductor laser device. (B) is a graph showing the temperature dependence of the IL characteristic curve.

FIG. 17 is a graph comparing the IL characteristic curves of a conventional short wavelength oscillation type semiconductor laser device and a conventional long wavelength oscillation type semiconductor laser device.

[Explanation of symbols]

1A Nitride semiconductor laser device 1B Nitride semiconductor laser device 1C nitride semiconductor laser device 1D nitride semiconductor laser device 1E Nitride semiconductor laser device 1F Nitride semiconductor laser device 1G nitride semiconductor laser device 1H nitride semiconductor laser device 1I Nitride semiconductor laser device 1J Nitride semiconductor laser device 2 submount 11 board 12 buffer layers 13 n-type contact layer 14 n-side electrode 15A spontaneous emission light absorption layer 15B Spontaneous emission light absorption layer 15C spontaneous emission light absorption layer 15D spontaneous emission light absorption layer 16 n-type clad layer (first clad layer) 17 Active layer 18 p-type clad layer (second clad layer) 19 p-type contact layer 20 insulating film 21 p-side electrode 22 Solder material 23 p-side terminal electrode 24 Solder material 25 n side terminal electrode 26 Groove 27 Insulating film 28 Natural emission light absorber 31A Spontaneous emission light prevention film 31B Spontaneous emission light prevention film 31C Spontaneous emission light prevention film 32 Natural emission light prevention wall 33 Shading case 34 Insulating film 40 Condensing optical unit (condensing optical system device) 41 Semiconductor laser device 42 Collimator lens 43 diffraction grating 44 Half prism 45 condensing lens 46 Drive system circuit 47 Light receiving lens 48 Cylindrical lens 49 Photodiode element (photodetector) 50 optical disks 51 emitted light 52 reflected light 61 base 61a recess 62 Semiconductor laser device 63 micro mirror Photodiode element for 64 output monitor 65A First photodiode element (photodetector) 65B Second photodiode element (photodetector) 70 Semiconductor laser package 71 base 72 mount 73 submount 74 Semiconductor laser chip 75 Photodiode element (photoelectric conversion element) 76 Light-shielding plate (light-shielding means) 76a opening 77 cap 78 windshield 79 External lead Lb back light Lf forward light

Front page continuation (72) Inventor Ryoko Miyanaga 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masakatsu Suzuki, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56 ) Reference JP-A-9-232685 (JP, A) JP-A-6-152046 (JP, A) JP-A-7-335969 (JP, A) JP-A-62-282474 (JP, A) JP-A 49-104590 (JP, A) JP-A-11-251685 (JP, A) JP-A-11-68256 (JP, A) JP-A-2-214182 (JP, A) JP-A-63-198390 (JP, A) JP-A 63-34991 (JP, A) JP-A 60-16489 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 H01L 33 / 00

Claims (7)

(57) [Claims] 1. A first cladding layer made of a nitride semiconductor of a first conductivity type formed on a substrate, an active layer made of a nitride semiconductor formed on the first cladding layer, A second clad layer made of a second conductive type nitride semiconductor formed on the active layer, and a first conductive type first contact between the substrate and the first clad layer. A layer is sandwiched between the substrate and the first contact layer of the first conductivity type.
And a buffer layer is sandwiched between the buffer layer and the first contact layer.
A spontaneous emission light absorption layer that is made of a first conductivity type nitride semiconductor containing n and that absorbs spontaneous emission light emitted from the active layer is formed, and the spontaneous emission light absorption layer includes a buffer layer and To touch
And the active layer contains In and is included in the first-conductivity-type nitride semiconductor layer containing In.
The amount of In is the same as the amount of In contained in the active layer, or
The energy of the first-conductivity-type nitride semiconductor layer containing In that is more than that
-Gap is larger than the energy gap of the active layer
A small semiconductor laser device. 2. A first clad layer made of a first conductivity type nitride semiconductor formed on a substrate, an active layer made of a nitride semiconductor formed on the first clad layer, A second clad layer made of a nitride semiconductor of a second conductivity type formed on the active layer, the first conductivity type being provided between the substrate and the first clad layer.
And a first electrode is connected to the first contact layer.
A second conductive layer sandwiching the second cladding layer between the second conductive layer and the active layer.
Has a second contact layer made of an electric nitride semiconductor
Between the second contact layer and the second cladding layer.
An insulating film with a striped opening
If the insulating film is sandwiched between the insulating film and the second contact layer,
Has a second electrode filling the opening , and In is provided between the insulating film and the second contact layer.
Including consists second conductivity type nitride semiconductor layer, the which spontaneous emission light absorbing layer that absorbs the spontaneous emission light emitted is formed from the active layer, the spontaneous emission light absorbing layer is in contact with the second electrode The active layer contains In and is included in the second-conductivity-type nitride semiconductor layer containing In.
The amount of In is the same as the amount of In contained in the active layer, or
The energy of the second-conductivity-type nitride semiconductor layer containing In that is more than that
-Gap is larger than the energy gap of the active layer
A small semiconductor laser device. 3. The contract, wherein the insulating film is made of silicon oxide.
The semiconductor laser device according to claim 2. 4. A semiconductor laser device, a condensing optical system device for condensing laser light emitted from the semiconductor laser device onto a recording medium on which data is recorded, and laser light reflected by the recording medium. A semiconductor laser device according to claim 1 , further comprising a photodetector for detecting the semiconductor laser device.
Optical disk apparatus which is a laser device. 5. A semiconductor laser device, a condensing optical system device for condensing laser light emitted from the semiconductor laser device onto a recording medium on which data is recorded, and laser light reflected by the recording medium. The semiconductor laser device according to claim 2 , further comprising: a photodetector for detecting.
Optical disk apparatus which is a laser device. 6. A semiconductor laser device provided on a base body made of a semiconductor, and a photodetector formed on the base body for detecting reflected light of laser light emitted from the semiconductor laser device. The semiconductor laser device is a semiconductor laser device according to claim 1.
Optical integrated device which is a laser device. 7. A semiconductor laser device provided on a base body made of a semiconductor, and a photodetector formed on the base body for detecting reflected light of laser light emitted from the semiconductor laser device, The semiconductor laser device is a semiconductor laser device according to claim 2.
Optical integrated device which is a laser device.