JP2002270967A - Semiconductor laser device - Google Patents

Abstract

(57) [Problem] To provide a semiconductor laser device capable of obtaining good FFP. SOLUTION: A stripe-shaped waveguide region is formed in a laminated structure in which a first conductivity type layer, an active layer, and a second conductivity type layer having a conductivity type different from the first conductivity type layer are sequentially stacked. Has,
In a semiconductor laser device in which electrodes are provided on the first conductivity type layer and the second conductivity type layer, respectively, the laminated structure is configured to absorb light in the vicinity of or in contact with the stripe-shaped waveguide region. Layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser device having a stripe-shaped waveguide region, and more particularly to a semiconductor laser device having a good far-field pattern.
Further, as a semiconductor used for the semiconductor laser device,
In particular, GaN, AlN, or InN, or which is a mixed crystal of r III-V nitride semiconductor _(In x _Al y Ga
_1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1).

[0002]

2. Description of the Related Art In recent years, semiconductor laser devices have become smaller, lighter,
High reliability and high output have been advanced, and electronic devices such as personal computers and DVDs, medical devices, processing devices, and light sources for optical fiber communication have been used. Of these nitride semiconductor _{(In x Al y Ga 1 -x} -y N, 0 ≦ x, 0
.Ltoreq.y, x + y.ltoreq.1) has attracted attention as a semiconductor laser device capable of emitting red light from a relatively short wavelength ultraviolet region.

[0003] Such a semiconductor laser device has a buffer layer, an n-type contact layer, a crack prevention layer, an n-type cladding layer, an n-type light guide layer, an active layer, a p-type light guide layer, and a p-type cap on a sapphire substrate. A layer, a p-type cladding layer, and a p-type contact layer are sequentially formed. Further, a striped light emitting layer is formed by etching or the like, and then a p-side electrode and an n-side electrode are formed. Further, after forming a cleaved surface with a predetermined resonator length, a mirror surface on the light reflection side is formed so that oscillation light can be efficiently extracted from the mirror surface on the light emission side.

[0004]

However, such a structure has a problem that irregularities (ripples) are generated in the far field pattern (FFP), resulting in a non-Gaussian distribution. In a semiconductor laser device in which the FFP has a non-Gaussian distribution, a large error occurs in the shape calculation of the FFP, and the FFP cannot be efficiently coupled to the optical system.

Accordingly, an object of the present invention is to provide a semiconductor laser device which has no ripple and can obtain a good FFP close to a Gaussian distribution at the time of high output operation.

[0006]

In order to solve the above problems, the present invention provides a first conductive type layer, an active layer, and a second conductive type layer having a conductive type different from that of the first conductive type layer. And a semiconductor laser device having a stripe-shaped waveguide region in a laminated structure in which the first and second conductive layers are provided with electrodes, respectively. ,
A light absorbing layer is provided near or in contact with the stripe-shaped waveguide region. With such a configuration, it is possible to prevent light (stray light) seeping out of the waveguide region from overlapping with the main beam emitted from the waveguide region, and to obtain an excellent FFP.

The light absorbing layer of the semiconductor laser device of the present invention is formed in contact with the laminated structure. Thus, stray light seeping out of the waveguide region can be efficiently absorbed.

It is preferable that the light absorbing layer of the semiconductor laser device of the present invention is provided at least near the light emitting surface of the cavity surface. Thereby, stray light can be efficiently absorbed even by a light absorbing layer in a small range.

The light absorbing layer of the semiconductor laser device of the present invention is formed apart from the electrodes when using a conductor or a semiconductor. Thereby, it is possible to efficiently supply a current to the laminated structure and to absorb stray light.

The light absorbing layer of the semiconductor laser device of the present invention can be formed on an insulating film provided on the surface of the multilayer structure. Thus, even a material made of a material having poor adhesion to the laminated structure can be used as the light absorbing layer.

Further, the light absorbing layer of the semiconductor laser device of the present invention can be made of any one of a conductor, a semiconductor and an insulator. Thereby, it is possible to cope with a laminated structure of various materials.

The light absorption layer of the semiconductor laser device of the present invention is made of Ni, Cr, Ti, Cu, Fe, Zr, Hf, N
b, W, Rh, Ru, Mg, Si, Al, Sc, Y, M
o, Ta, Co, Pd, Ag, Au, Pt simple substance, alloy, multilayer film, and any one selected from any one of these compounds such as oxides and nitrides Can be used. Further, a semiconductor having a shorter band gap than the active layer can be used. Thereby, various materials can be selected according to the material of the laminated structure, and stray light can be more effectively absorbed.

Further, the semiconductor laser device of the present invention has a first
A nitride semiconductor is used for the conductive type layer, the active layer, and the second conductive type layer. With this configuration,
A semiconductor laser device having excellent durability and safety and having a wide range of wavelengths from an ultraviolet region to a visible region can be obtained.

Further, the semiconductor laser device of the present invention has a first
Wherein the conductive type layer has an n-type nitride semiconductor, and the second conductive type layer has a p-type nitride semiconductor.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings, but the semiconductor laser device of the present invention is not limited to the device structure and electrode configuration shown in the embodiment.

The present embodiment relates to a semiconductor laser device using a nitride semiconductor. FIG. 1 is a schematic perspective view showing a structure of a nitride semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along a line AB, and FIG.
FIG. 4 is a sectional view taken along line D-D, and FIG. As shown in these figures, this semiconductor laser device has a laminated structure composed of a first conductivity type layer 1, an active layer 3, and a second conductivity type layer 2 having a conductivity type different from the first conductivity type. Provided on the element,
A stripe-shaped projection 8 is formed in the second conductivity type layer at a depth that does not reach the active layer. Both end surfaces formed so as to be perpendicular to the stripe are resonator surfaces, and a waveguide region having the stripe direction as the resonator direction is formed. One of the resonator surfaces is a light emission surface side resonator (light emission surface) mainly having a function of emitting light to the outside,
The other is a light-reflecting-surface-side resonator (monitor surface) mainly having a function of reflecting light into the waveguide region. In addition, a protective film (first insulating film 10) is formed on the side surface of the stripe-shaped protrusion and on the surface of the laminated structure continuous with the side surface. Further, a stripe-shaped ohmic electrode 5 that is in ohmic contact with the second conductive type layer on the upper surface of the convex portion of the second conductive type layer via the first insulating film is provided. Also,
An ohmic electrode 7 in ohmic contact with the first conductivity type layer is formed in a stripe shape on the exposed first conductivity type layer by removing from the second conductivity type layer to a part of the first conductivity type layer. Have been. Both electrodes are provided to be substantially parallel. A second insulating film 11 having an opening is further formed on these electrodes, and pad electrodes 4 and 6 are formed so as to be in contact with the ohmic electrodes via the second insulating film.

Here, in the semiconductor laser device of the present invention,
The light absorbing layer 9 is provided near the stripe-shaped waveguide region. In particular, in the present embodiment,
The laminated structure has a waveguide region composed of stripe-shaped convex portions, and a light absorbing layer is provided near the waveguide region. Specifically, the light absorption layer 9 is formed so as to be in contact with the surface of the stripe-shaped convex portion and the exposed surface of the multilayer structure. Since the light absorbing layer is in direct contact with the laminated structure, stray light seeping out of the waveguide region can be efficiently absorbed, and a good FFP can be obtained. (Waveguide region) In the semiconductor laser device of the present invention, the stripe-shaped waveguide region is formed mainly in the plane of the active layer sandwiched between the first conductivity type layer and the second conductivity type layer. At this time, the stripe direction and the resonator direction are almost the same. Here, the term “in-plane of the active layer” refers to a plane parallel to a bonding surface between the active layer, the first conductivity type layer, and the second conductivity type layer, and refers to the inside of the active layer. Also,
The stripe-shaped waveguide region may be provided not only in the above-described active layer, but also in an optical waveguide (waveguide layer) provided inside the multilayer structure. For example, a region up to a guide layer sandwiching the active layer described later is provided. May be an optical waveguide layer, which may be a waveguide region.

In order to make the stripe direction the resonator direction, the pair of resonator surfaces provided on the end faces are flat surfaces formed by cleavage or etching, etc., so that the emission wavelength of the active layer can be efficiently controlled. For good reflection, a reflection film composed of a single film or a multilayer film may be formed. One of the resonator surfaces is composed of a relatively high reflectivity surface and serves as a light reflection side resonator that mainly reflects light into the waveguide region, and the other is composed of a relatively low reflectivity surface and emits light mainly to the outside. It functions as a light emitting side resonator.

The light absorbing layer of the present invention is preferably provided near the side surface of the striped waveguide region so as not to block the main beam emitted from the light emitting side resonance surface. At this time, it may be provided over the entire waveguide region or may be provided only partially. When the light absorbing layer is provided in a part near the waveguide region, it is preferable to provide the light absorbing layer at least near the light emitting side. The stray light is seeping out from an arbitrary place in the stripe-shaped waveguide region, but it is sufficient if the stray light can be absorbed before the light is actually emitted from the end face. The light absorption effect can be obtained only by providing the light-emitting element in the first position.

In the present embodiment, when the light absorbing layer is made of a conductor or a semiconductor, the light absorbing layer is provided so as not to be in direct contact with the electrode. When the light absorbing layer having such a property is in contact with the electrode, the flow of current in the laminated structure is hindered,
It is not preferable because the element characteristics are impaired. In the case of an insulator, there is no problem even if it is in contact with the electrode.

In this embodiment, it is preferable that the light absorption layer is formed so as to be in direct contact with the laminated structure. When the wafer is divided into chips and the surface of the laminated structure is exposed without providing a protective film on the surface near the division surface (end surface) in consideration of the ease of division and the like. There are many. In this embodiment, by forming the light absorbing layer directly on the exposed surface of the stacked structure near the end face, the light absorbing layer can be easily provided directly on the stacked structure near the light emitting surface. In addition, even if the electrodes are formed first, the positions can be adjusted so that they do not come into contact with the electrodes, and the flow of current is not hindered.

The light absorbing layer may be formed inside the laminated structure. For example, as described above, after forming the light absorbing layer on the surface of the laminated structure, further layer growth can be performed. Accordingly, exposure of the light absorbing layer can be reduced, which is suitable when a material that easily deteriorates is used. (Stripe-shaped convex portion) In the semiconductor laser device of the present invention,
The stripe-shaped waveguide region can be easily formed by providing a projection on the laminated structure. Specifically, a striped waveguide is formed by removing a part of the laminated structure having the first conductivity type layer, the active layer, and the second conductivity type layer by means such as etching to form a projection. Regions can be formed. The convex portion is not limited to the forward mesa shape, may be an inverted mesa shape, or may be a stripe having a side surface perpendicular to the lamination surface, and the stripe-shaped waveguide is
The widths need not be approximately the same. Further, a buried type laser element in which a crystal is regrown on the surface of the convex portion after forming such a convex portion may be used. The protrusion may be formed by removing a part of the second conductivity type layer, or may be formed by removing the first conductivity type layer.
Of the conductive type layer, the active layer and the first conductive type layer. In the former, the active layer is not exposed, so that it is possible to obtain a semiconductor laser element which is hardly deteriorated,
The latter has a waveguide region in the projection, so that a semiconductor laser device excellent in controlling the transverse mode can be obtained. By providing the light absorbing layer on the upper surface and the side surface of the convex portion, and further on the exposure of the laminated structure continuous from the side surface, a light absorbing layer capable of efficiently absorbing stray light can be easily obtained. As described above, it is preferable that the light absorbing layer is formed at least in the vicinity of and in contact with the waveguide region on at least the side surfaces of the projections or the exposed surface of the laminated structure.

When an insulating film is formed on the surface of the laminated structure exposed by forming the stripe-shaped projections, a light absorbing layer may be provided thereon. This makes it possible to cope with a case where a material having poor adhesion to the material of the laminated structure is used as the light absorbing layer. However, in order to exhibit the light absorbing effect, the thickness of the insulating film between the laminated structure and the light absorbing layer is preferably 0.2 μm or less. 0.2
If it exceeds μm, the light absorption effect is undesirably reduced. In addition, by providing a light absorbing layer over an insulating film, contact with an electrode can be avoided.

As the light absorbing layer of the semiconductor laser device of the present invention, any of a conductor, a semiconductor and an insulator can be used. However, when a conductor is used, it is necessary to prevent short-circuit and to prevent direct contact with the electrode so as not to obstruct the flow of current in the element structure. Also,
When a semiconductor is used, it is preferable to use a semiconductor having a narrower band gap than the active layer. If the band gap is wider than that of the active layer, it is difficult to obtain a light absorbing effect, which is not preferable. In the case where an insulator is used, the insulator may be in contact with the electrode and thus is easy to handle, but the light absorption effect is slightly inferior. The most preferable of these materials can be selected according to the structure of the element, the manufacturing process, the manufacturing method, and the like.

When a nitride semiconductor is used as the laminated structure, specific materials used for the light absorbing layer include Ni, Cr, Ti, Cu, Fe, and Z as conductive materials.
r, Hf, Nb, W, Rh, Ru, Mg, Al, Sc,
Y, Mo, Ta, Co, Pd, Ag, Au, Pt, a simple substance, an alloy, a multilayer film, and further any one selected from compounds such as oxides and nitrides thereof Can be used. These may be used alone or in combination of two or more. Preferred materials include Ni, Cr, Ti, Cu, Fe, Zr,
A material using Hf, Nb, W, Rh, Ru, and Mg, and more preferably a material using Ni, Cr, and Ti. Further, as a semiconductor material, Si, InGaN, Ga
As, InP, or the like can be used. TiO ₂ , CrO _2, or the like can be used as the insulator material. Various methods such as vapor deposition and sputtering can be used to form the film at the desired position. (Laminated Structure) As a semiconductor used as a laminated structure of the semiconductor laser device of the present invention, a nitride semiconductor such as GaN, AlN, or InN, or a III-V group nitride semiconductor (In _{x Al y Ga 1-x-} y
N, 0 ≦ x, 0 ≦ y, x + y ≦ 1) are preferable. Less than,
The semiconductor laser device of the present invention will be specifically described using a nitride semiconductor. Here, the laser device using a nitride semiconductor means that a nitride semiconductor is used for any one of the layers of a stacked structure in which a first conductivity type layer, an active layer, and a second conductivity type layer are sequentially stacked. And a semiconductor laser device using a nitride semiconductor for all layers. Specifically, the first conductivity type layer and the second conductivity type layer are provided with a cladding layer having a nitride semiconductor to form a waveguide, and more specifically, The first conductivity type layer is composed of an n-type nitride semiconductor layer, the second conductivity type layer is composed of a p-type nitride semiconductor layer, and the active layer is composed of a layer containing a nitride semiconductor layer containing In. . (Nitride semiconductor) As a material used for the semiconductor laser device of the present invention, a material having a nitride semiconductor layer containing In is preferable. This makes it possible to obtain a laser beam having a wavelength from blue to red in the ultraviolet and visible regions. Further, when a nitride semiconductor layer containing In is used, if the active layer is exposed to the air, extremely serious device deterioration may occur when the laser device is driven. This is because, since the melting point of In is low, decomposition and evaporation are likely to occur, and damage is caused by etching at the time of forming the convex portion, and it becomes difficult to maintain the crystallinity in processing after exposure of the active layer. Is preferably formed to a depth that does not reach the active layer. The active layer may have a quantum well structure, in which case, it may be either a single quantum well or a multiple quantum well.

Further, the semiconductor laser device of the present invention
N-type nitride in the first conductivity type layer
Having a semiconductor, a p-type nitride semiconductor in the second conductivity type layer
It is preferable to use
An n-type cladding layer and a p-type cladding layer are provided on the electric layer,
It constitutes a waveguide region. At this time, each clad
Guide layer, electron confinement layer, etc. between the layer and the active layer
May be provided. (Clad layer) A semiconductor laser using the nitride semiconductor of the present invention.
A p-type nitride semiconductor layer and an n-type nitride
The semiconductor layer has a p-type cladding layer and an n-type cladding layer, respectively.
It is preferable to provide a metal layer. Used for cladding layer
As a nitride semiconductor, a refractive index sufficient to confine light
It is sufficient that a difference is provided, and the nitride semiconductor layer containing Al
Is preferably used. This layer may be single or
It may be a multilayer film, in which AlGaN and GaN are alternately formed.
A stacked superlattice structure may be used. In addition, this layer
Impurities may be doped or undoped.
In the case of a multilayer film, at least one of the
One layer may be doped. Note that the oscillation wave
A semiconductor laser device having a long wavelength of 430 to 550 nm.
Means that the cladding layer has a p-type impurity in a p-type layer and an n-type layer
Is preferably GaN doped with an n-type impurity. Also, membrane
The thickness is not particularly limited, but is not more than 100 mm.
It is preferable that the thickness be 2 μm or less, more preferably
Is sufficient to be formed in the range of 500 ° to 1 μm.
It has an effective light confinement effect. Also, the active layer and the p-type and n-type
An electron confinement layer and a light guide layer between the mold cladding layer
Provided to sandwich the active layer and the light guide layer.
Is preferred. (P-type cap layer) is provided between the p-type clad layer and the active layer.
As the p-type cap layer to be formed, AlGaN or the like is preferable.
This allows the carrier to be transferred to the active layer.
A layer having a confinement effect, and a threshold current
And easier oscillation can be obtained. AlGaN is
Even if it is doped with p-type impurities,
There may be. The thickness is preferably 500 ° or less.
Good. (Guide Layer) In the present invention, a guide layer sandwiching the active layer
Forming an optical waveguide inside the cladding layer
To form an excellent waveguide in nitride semiconductor
Can be. At this time, the waveguide (the active layer and both
The thickness of the guide layer is preferably 6000 mm or less.
The rapid increase of the oscillation threshold current can be suppressed.
You. More preferably, it is set to 4500 ° or less,
Low oscillation threshold current, basic mode, long life
Continuous oscillation becomes possible. Also, both guide layers are almost the same film
It is preferably formed in a thickness of not less than 100 ° and not more than 1 μm.
It is preferably 500 ° or more and 2000 ° or less. Guy
The nitride semiconductor used for the
Compared to a cladding layer that can be
As long as it has a bending ratio, either a single film or a multilayer film
May be. Specifically, the oscillation wavelength is 370 nm to 47
At 0 nm, undoped GaN is preferred and relatively long wave
In the long region (450 nm or more), InGaN / GaN
It is preferable to use the multilayer film structure of the above. (Electrode) In the semiconductor laser device of the present invention,
The electrode formed on the convex part is not particularly limited.
Good ohmic contact with nitride semiconductor
The obtained material can be preferably used. Waveguide area
To be formed corresponding to the stripe-shaped projections that will be the regions
Thus, carrier injection can be performed efficiently.
In addition, a nitride semiconductor is in contact with an insulating film described later.
It can also be provided. Also, in contact with the semiconductor
Ohmic electrode provided and material suitable for bonding
A pad electrode made of a material may be provided. This embodiment
In, after the first insulating film is formed, an opening is provided to open the first insulating film.
A second electrode having an opening thereon.
Structure with a pad electrode formed on it.
It is made. (Insulating film) The semiconductor laser device of the present invention has the above-described laminated structure.
Resonance by removing a part of the body to form a stripe-shaped protrusion
If it is a container, the side and its side of the stripe-shaped convex part
A protective film is formed on an exposed surface (flat surface) continuous with the surface. Convex
Insulation is not a problem if it is formed only on the part that protects the part.
However, the use of an insulating protective film can reduce
Function as an insulating film to prevent heat and protect exposed layers
Film that functions as a protective film
You. Specifically, SiO₂, TiO₂, ZrO ₂Such as
A single film or a multilayer film can be preferably used. Ma
In addition, as described above, a multilayer film is formed via an electrode.
You may.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a first structure constituting a laminated structure is described.
The device structure of the conductive type layer, the active layer, and the second conductive type layer is not particularly limited, and various layer structures can be used. As a specific structure of the device, for example, a device structure described in an embodiment described later is cited.
The electrodes, insulating films (protective films), and the like are not particularly limited, and various types can be used. In the case of a semiconductor laser device using a nitride semiconductor, GaN, AlN, or I
nitride semiconductors such as nN, and III-V
Nitride semiconductor _{(In x Al y Ga 1-} x-y N, 0 ≦
x, 0 ≦ y, x + y ≦ 1) can be used. MOVPE, MOCVD (metal organic chemical vapor deposition), HVPE (halide vapor phase epitaxy),
All known methods for growing nitride semiconductors, such as MBE (Molecular Beam Epitaxy), can be applied.

Hereinafter, a semiconductor laser device using a nitride semiconductor will be described as an example. However, the semiconductor laser device of the present invention is not limited to this, and the technical idea of the present invention can be applied to various semiconductors. Needless to say.

[Embodiment 1] In Embodiment 1, a different kind of substrate different from a nitride semiconductor is used as a substrate, but a substrate made of a nitride semiconductor such as a GaN substrate may be used. Here, as the heterogeneous substrate, for example, C-plane, R-plane, and A-plane
Sapphire, spinel, Zn
A substrate material capable of growing a nitride semiconductor, such as an oxide substrate lattice-matched with S, ZnO, GaAs, Si, SiC, and a nitride semiconductor, can be used. Preferable substrates of different types include sapphire and spinel. Also, the heterogeneous substrate may be off-angle,
In this case, it is preferable to use a step-shaped off-angle because the underlayer made of gallium nitride can be grown with good crystallinity. Further, when a heterogeneous substrate is used, a nitride semiconductor serving as a base layer before forming an element structure is grown on the heterogeneous substrate, and then the heterogeneous substrate is removed by a method such as polishing to form a single substrate of the nitride semiconductor. Alternatively, the element structure may be formed, or after the element structure is formed, a method of removing a heterogeneous substrate may be used. When a heterogeneous substrate is used, the growth of the nitride semiconductor can be improved by forming the element through the buffer layer and the underlayer. (Buffer Layer) A heterogeneous substrate made of sapphire having a 2-inch φ and C-plane as a main surface is set in a MOVPE reaction vessel, the temperature is set to 500 ° C., and trimethylgallium (TM)
G), a buffer layer made of GaN is grown to a thickness of 200 ° using ammonia (NH ₃ ). (Underlayer) After forming the buffer layer, the temperature is set to 1050 ° C., and a nitride semiconductor layer made of undoped GaN is grown to a thickness of 4 μm using TMG and ammonia. This layer functions as an underlayer (growth substrate) in the growth of each layer forming the element structure. In addition to this,
LOG (Epitaxially Laterally)
When a nitride semiconductor grown by Overgrowth is used, a growth substrate having good crystallinity can be obtained. As a specific example of the ELOG growth layer, a mask region formed by growing a nitride semiconductor layer on a heterogeneous substrate and providing a protective film on the surface of which a nitride semiconductor is difficult to grow, and a nitride semiconductor layer may be used. A non-mask region to be grown is provided in a stripe shape,
By growing the nitride semiconductor from the non-mask region, in addition to the growth in the film thickness direction, the growth in the lateral direction was performed, so that the nitride semiconductor was also grown and deposited in the mask region. And a film formed by forming an opening in a nitride semiconductor layer grown on a heterogeneous substrate and growing laterally from the side surface of the opening.

Next, on the underlayer made of a nitride semiconductor,
Next, each layer constituting the laminated structure is formed. (N-type contact layer) on underlying layer (nitride semiconductor substrate)
Uses silane gas as TMG, ammonia and impurity gas
1 × 10 at 1050 ° C¹⁸/ Cm³Doped
4.5-μm film with n-type contact layer made of GaN
Grow in thickness. (Crack prevention layer) Next, TMG, TMI (trimethyl
Using indium) and ammonia, raise the temperature to 800 ° C
In_0.06Ga_0.94Crack prevention layer made of N
Is grown to a thickness of 0.15 μm. Note that this crack
The anti-blocking layer can be omitted. (N-type cladding layer) Next, the temperature was raised to 1050 ° C.
TMA (trimethylaluminum), TMG and
Made of undoped AlGaN using water and ammonia
Grow layer A to a thickness of 25 °, then stop TMA,
Using silane gas as impurity gas, Si
¹⁸/ Cm³B layer of doped GaN
It grows with the film thickness. And repeat this operation 160 times
The layer A and the layer B are alternately laminated so that the total film thickness is 8000.
Ｎ An n-type clad layer consisting of a multilayer film (superlattice structure)
Lengthen. At this time, Al mixed crystal of undoped AiGaN
If the ratio is in the range of 0.05 or more and 0.3 or less,
Provide a sufficient refractive index difference to function as a cladding layer
Can be. (N-type light guide layer) Next, TM was added to the source gas at the same temperature.
Made of undoped GaN using G and ammonia
An n-type light guide layer is grown to a thickness of 0.1 μm. this
The layer may be doped with n-type impurities. (Active Layer) Next, the temperature was raised to 800 ° C.
(Trimethylindium), TMG and ammonia
Silane gas is used as impurity gas, and Si
0 ¹⁸/ Cm³Doped In_0.05Ga_0.95N
A barrier layer made of 100 .ANG. Is grown. continue
Stop silane gas and undoped In_0.1Ga_{0 . 9}
A well layer of N is grown to a thickness of 50 °. This operation
The operation is repeated three times, and finally a barrier layer is laminated to form a total film thickness of 5
Growing an active layer of 50 Å multiple quantum well structure (MQW)
Let (P-type cap layer) Next, at the same temperature, T
Using MA, TMG and ammonia as impurity gas
Cp₂For Mg (cyclopentadienyl magnesium)
And Mg is 1 × 10¹⁹/ Cm³Doped AlGaN
A p-type electron confinement layer consisting of
Let (P-type light guide layer) Next, the temperature was raised to 1050 ° C.
Undoped G using TMG and ammonia as source gas
A p-type light guide layer made of aN is grown to a thickness of 750 °.
Let This p-type light guide layer is grown as undoped.
However, Mg may be doped. (P-type cladding layer) Subsequently, at 1050 ° C., undoped A
l_0.16Ga_0.84N layer with a thickness of 25 °
Growing, then stopping TMG, Cp₂M using Mg
growing a layer of g-doped GaN to a thickness of 25 °,
A p-type cladding layer composed of a superlattice layer having a total film thickness of 0.6 μm
Let it grow. At least one of the p-type cladding layers is made of Al.
Including the bandgap energy
Manufactured with a superlattice of stacked nitride semiconductor layers with different energy
In this case, doping is heavily doped in one layer.
Therefore, the crystallinity tends to improve when so-called modulation doping is performed.
However, both may be doped in the same manner. (P-type contact layer) Finally, p-type cladding at 1050 ° C
1 × 10 Mg on the layer²⁰/ Cm³Doped p-type G
Growth of a-type p-type contact layer with a thickness of 150 °
Let it. The p-type contact layer is p-type In_xAl_yGa
_1-xyN (x ≦ 0, y ≦ 0, x + y ≦ 1)
And preferably GaN doped with Mg.
Then, the most preferable ohmic contact with the p-electrode can be obtained.
After the reaction is completed, the wafer is placed in a nitrogen atmosphere in the reaction vessel.
Annealing at 700 ° C to further reduce the resistance of the p-type layer
I do. (Exposure of n-type layer and formation of stripe-shaped protrusions)
To form a laminated structure by growing a nitride semiconductor
Then, the wafer is taken out of the reaction vessel, and the uppermost p-type
SiO on the surface of the tact layer₂Forming a protective film of
SiCl using IE (Reactive Ion Etching)₄gas
Contact to form an n-electrode by etching
The surface of the layer is exposed.

Next, in order to form a stripe-shaped waveguide region, CV is formed on almost the entire surface of the uppermost p-type contact layer.
After a protective film made of Si oxide (mainly SiO ₂ ) is formed to a thickness of 0.5 μm by the D apparatus, a mask of a predetermined shape is put on the protective film, and CF ₄ is applied by the RIE apparatus.
A stripe-shaped protective film is formed by photolithography using a gas, and a stripe-shaped projection is formed above the active layer. (First Insulating Film) A first insulating film made of ZrO ₂ is formed on the surface of the p-type layer while keeping the SiO ₂ mask. This first insulating film may be provided over the entire surface of the semiconductor layer by masking the surface on which the n-side ohmic electrode is formed. Further, a portion where an insulating film is not formed is provided so as to be easily divided later. This portion has a stripe shape of 10 μm and is provided so as to be orthogonal to the convex portion. After the first insulating film formed is immersed in a buffered solution, the SiO ₂ formed on the upper surface of the stripe-shaped convex portions dissolve and remove, with SiO ₂ by lift-off, p-type contact layer (and the n-type contact Z on the layer)
to remove the rO _2. Thereby, the upper surface of the stripe-shaped protrusion is exposed, and the side surface of the protrusion is covered with ZrO ₂ . (Ohmic electrode) Next, a p-side ohmic electrode is formed on the first insulating film on the outermost surface of the projection on the p-type contact layer. This p-side ohmic electrode is made of Au-Ni.
An n-side ohmic electrode in the form of a stripe is also formed on the surface of the n-type contact layer exposed by the etching. The n-side ohmic electrode is made of Ti-Al. After these are formed, each is annealed at 600 ° C. in an atmosphere of oxygen: nitrogen at a ratio of 80:20, whereby p
Alloying the ohmic electrodes on both sides to obtain good ohmic characteristics (light absorbing layer) After forming the p-side ohmic electrode and the n-side ohmic electrode as described above, the direction orthogonal to the stripe-shaped convex portion The light absorption layer is provided in the vicinity of the dividing plane (near the resonator plane). This light absorbing layer is made of Ni, and is formed with a width of 5 μm on the surface of a 10 μm wide nitride semiconductor on which electrodes and insulating films are not formed. At this time, it is formed so as not to be in contact with the electrode. In addition, the protrusions are formed in a stripe shape from the upper surface to the side surface, and further from the side surface to the surface of the p-type layer. At this time, it is not necessary to form on the upper surface of the stripe-shaped convex portion. It can be arbitrarily selected depending on the height of the convex portion or the positional relationship of the active layer. (Second insulating film) Then, Si oxide (mainly SiO 2)
₂ ) A second insulating film made of ₂ ) is formed on the entire surface excluding the dividing position, a resist is applied to a part of the p-side ohmic electrode and a part of the n-side ohmic electrode on the stripe-shaped convex portion, and dry etching is performed. The ohmic electrode and a part of the n-side ohmic electrode are exposed. Note that the division position is a position where the division is made so as to be orthogonal to the stripe-shaped protrusions.
Further, no second insulating film or electrode is formed. (Pad electrode) Next, a p-side pad electrode and an n-side pad electrode are formed so as to cover the insulating film. The electrodes are made of Ni-Ti-Au. This pad electrode
It is in contact with the exposed ohmic electrode in a stripe shape. (Cavity surface) After forming the light absorption layer as described above,
After polishing the sapphire substrate of the wafer to 70 μm,
Cleavage was performed in a bar shape from the substrate side in a direction perpendicular to the stripe-shaped electrodes, and a cavity surface was formed on the cleaved surface (11-00 surface, a surface corresponding to the side surface of hexagonal columnar crystal = M surface). . This resonator surface may be formed by etching. (Formation of Mirror) A dielectric multilayer film made of SiO ₂ and ZrO ₂ is formed as a mirror on the resonator surface formed as described above. On the resonator surface on the light reflection side, a protective film made of ZrO ₂ is formed using a sputtering device, and then a SiO ₂ film is formed.
And ZrO ₂ were alternately laminated in three pairs to form a high reflection film. Here, the thicknesses of the protective film, the SiO ₂ film and the ZrO ₂ film constituting the high reflection film can be set to preferable thicknesses according to the wavelength of light emitted from the active layer. Also,
No resonator surface on the light emission side may be provided, and a first low-reflection film made of ZrO ₂ and S
A _second low-reflection film made of iO ₂ may be formed. Next, finally, the bar is cut in a direction parallel to the stripe-shaped convex portions to obtain the semiconductor laser device of the present invention.

The semiconductor laser device obtained as described above has a threshold of 2.0 kA / cm ² and 30 mW at room temperature.
At a high output, continuous oscillation with an oscillation wavelength of 405 nm was confirmed, and in FFP, a good beam without ripple was obtained.

[Embodiment 2] In the embodiment 1, before forming the second insulating film made of Si oxide (mainly SiO ₂ ), the vicinity of the division plane in the direction perpendicular to the stripe-shaped projections (resonator plane) (Near) the light absorbing layer. This light absorption layer is made of W, and is formed with a width of 5 μm on the surface of a 10 μm wide nitride semiconductor on which the electrodes and the first insulating film are not formed. At this time, it is formed so as not to be in contact with the electrode. In addition, the protrusions are formed in a stripe shape from the upper surface to the side surface, and further from the side surface to the surface of the p-type layer. At this time, it is not necessary to form on the upper surface of the stripe-shaped convex portion. It can be arbitrarily selected depending on the height of the convex portion or the positional relationship of the active layer.

After forming the light absorbing layer as described above, a second insulating film is formed on the entire surface including the dividing position, and a part of the p-side ohmic electrode and a part of the n-side ohmic electrode on the stripe-shaped convex portion are removed. A resist is applied to the entire surface and dry etching is performed to expose a part of the p-side ohmic electrode and a part of the n-side ohmic electrode. Next, by providing a pad electrode in the same manner as in Example 1, a second insulating film was formed on the light absorbing layer as shown in FIGS. 5 and 6, and a p-side pad electrode was formed thereon. The semiconductor laser device of the present invention is obtained. Example 1
In the example, the second insulating film and the pad electrode are not formed up to the position reaching the end face of the element, but in the second embodiment, they are formed reaching the end face. However, since the light absorption layer and the pad electrode are interposed through the insulating film, no short circuit occurs. With such a structure, the light absorption layer can be easily formed without using a mask at a division position when the second insulating film and the pad electrode are formed.

The semiconductor laser device obtained as described above has a threshold of 2.0 kA / cm ² and 30 mW at room temperature.
At a high output, continuous oscillation with an oscillation wavelength of 405 nm was confirmed, and in FFP, a good beam without ripple was obtained.

Example 3 In Example 1, after the formation of the stripe-shaped protrusions, a light absorption layer is formed on the exposed semiconductor layer along the side surfaces of the stripe-shaped protrusions as shown in FIG. This light absorbing layer is made of InGaN and has a width of 30.
It has a thickness of 0.2 μm from one resonator surface to the other resonator surface. Next, a first insulating film is formed in the same manner as in Example 1, an ohmic electrode, a second insulating film, and a pad electrode are formed. A mirror is formed after opening the cleft to obtain a semiconductor laser device of the present invention.

The semiconductor laser device obtained as described above has a threshold of 2.0 kA / cm ² and 30 mW at room temperature.
At a high output, continuous oscillation with an oscillation wavelength of 405 nm was confirmed, and in FFP, a good beam without ripple was obtained.

[0038]

The semiconductor laser device of the present invention has a light absorbing layer in the vicinity of the waveguide region, so that stray light seeping from the waveguide can be absorbed and only the main beam can be emitted. FFP can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating a semiconductor laser device of the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line AA′-BB ′ in FIG. 1;

FIG. 3 is a schematic cross-sectional view taken along the line CC′-DD ′ in FIG. 1;

FIG. 4 is a schematic cross-sectional view taken along the line EE′-FF ′ of FIG. 1;

FIG. 5 is a schematic sectional view illustrating an embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view taken along the line G-G ′ of FIG. 5;

FIG. 7 is a schematic perspective view illustrating an embodiment of the present invention.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 ... 1st conductivity type layer 2 ... 2nd conductivity type layer 3 ... Active layer 4 ... p-side pad electrode 5 ... p-side ohmic electrode 6 ... n-side pad electrode 7 n-side ohmic electrode 8 stripe-shaped protrusions 9, 109, 209 light absorbing layer 10 first insulating film 11 second insulating film 12 substrate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F073 AA45 AA74 AA83 AA84 BA02 BA09 CA17 CB05 DA05 DA25 DA32 DA33 EA19 EA23

Claims (10)

[Claims] 1. A striped waveguide in a laminated structure in which a first conductivity type layer, an active layer, and a second conductivity type layer having a conductivity type different from the first conductivity type layer are sequentially stacked. Has an area,
In the semiconductor laser device in which electrodes are provided on the first conductivity type layer and the second conductivity type layer, respectively, the laminated structure is configured to absorb light in the vicinity of or in contact with the stripe-shaped waveguide region. A semiconductor laser device having a layer. 2. The semiconductor laser device according to claim 1, wherein said light absorbing layer is formed in contact with said laminated structure. 3. The semiconductor laser device according to claim 1, wherein the light absorbing layer is provided at least near a light emitting surface of the resonator surface. 4. The semiconductor laser device according to claim 1, wherein said light absorption layer is formed apart from said electrode. 5. The semiconductor laser device according to claim 1, wherein at least a part of the light absorption layer is formed on an insulating film provided on a surface of the multilayer structure. 6. The semiconductor laser device according to claim 1, wherein the light absorption layer is made of any one of a conductor, a semiconductor, and an insulator. 7. The light absorbing layer is made of Ni, Cr, Ti, C
u, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg,
Si, Al, Sc, Y, Mo, Ta, Co, Pd, A
7. The semiconductor laser device according to claim 6, comprising at least one element selected from the group consisting of g, Au, and Pt, an alloy, a multilayer film, and a compound such as an oxide or a nitride thereof. 8. The semiconductor laser device according to claim 6, wherein said light absorbing layer is a semiconductor having a narrower band gap than said active layer. 9. The semiconductor laser device according to claim 1, wherein a nitride semiconductor is used for the first conductivity type layer, the active layer, and the second conductivity type layer. 10. The semiconductor laser device according to claim 9, wherein the first conductivity type layer has an n-type nitride semiconductor, and the second conductivity type layer has a p-type nitride semiconductor.