JP2003008145A - Semiconductor laser and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To provide a semiconductor laser capable of reducing a driving voltage and a method of manufacturing the same. A first semiconductor layer is provided on one surface of a substrate.
0, an active layer 30, and a second semiconductor layer 40 are sequentially stacked. The first semiconductor layer 20 has an n-type contact layer 21, an n-type cladding layer 22, and an n-type guide layer 23 in this order from the substrate 10. n-type contact layer 21 and n
A current confinement layer 24 for limiting a current injection region of the active layer 30 is provided between the mold guide layer 23. Therefore,
The area of the p-type contact layer 43 can be increased,
The contact area between the mold contact layer 43 and the p-side electrode 70 can be increased. Therefore, the contact resistance can be reduced, and the drive voltage can be reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a first semiconductor layer, an active layer and a second layer each made of a nitride semiconductor on a substrate.
And a method for manufacturing the same, in which the semiconductor layers are sequentially stacked.

[0002]

2. Description of the Related Art In recent years, in the technical fields of optical disk devices, magneto-optical disk devices, etc., there is an increasing demand for higher density recording / reproducing and higher resolution. BACKGROUND ART Research and development of semiconductor lasers (laser diodes; LDs) capable of emitting light in the short wavelength region of the ultraviolet region have been actively conducted. As a material constituting such a semiconductor laser capable of emitting light in a short wavelength region, Ga is
Nitride semiconductors typified by N, AlGaN mixed crystals or GaInN mixed crystals are receiving attention.

FIG. 15 shows a configuration example of a conventional semiconductor laser using a nitride semiconductor. In this semiconductor laser, an n-type contact layer 121, an n-type clad layer 122, an n-type guide layer 123, an active layer 130, p are formed on a substrate 110.
The type guide layer 141, the p-type cladding layer 142, and the p-type contact layer 143 are sequentially stacked to form the p-type contact layer 1.
43 and a part of the p-type cladding layer 142 are strip-shaped protrusions. A p-side electrode 170 is electrically connected to the p-type contact layer 143 via an insulating film 150 having an opening.

When such a semiconductor laser is used in, for example, a writable optical disk, it is required to have a low driving current at a high output, a low driving voltage, stability of horizontal radiation angle, and long life.

[0005]

However, the conventional semiconductor laser has the following three problems, for example. The first problem is that since the p-type contact layer 143 has a strip shape, the contact area between the p-side electrode 170 and the p-type contact layer 143 is narrow and the driving voltage becomes high. In addition, the p-side electrode 170 is the insulating film 150.
Since it is in contact with the p-type contact layer 143 via
The contact area between the p-side electrode 170 and the semiconductor layer is also small, and the effect of dissipating the heat generated in the active layer 130 cannot be sufficiently obtained, which causes deterioration of the active layer 130.

The second problem is that the n-type cladding layer 122 is made of AlGaN mixed crystal and the n-type contact layer 12 is
When n is composed of GaN, the n-type clad layer 122 and the n-type contact layer 121 have different compositions, so that the n-type clad layer 122 is likely to be cracked due to the difference in lattice constant or thermal expansion coefficient, resulting in a long life. It is limited. As a method for reducing the stress acting on the n-type cladding layer 122 and reducing the cracks, n
Although it is conceivable to reduce the thickness of the mold cladding layer 122 or reduce the composition of aluminum, these are not preferable because they weaken the light confinement effect in the vertical direction.

The third problem is that the horizontal emission angle of the laser light is determined by the p-type contact layer 143 and the p-type cladding layer 14.
2 has a strong dependence on the depth of the protrusions, in other words, the thickness of the p-type cladding layer 142 other than the protrusions. Therefore, high dimensional accuracy is required when forming the p-type cladding layer 142, the yield is low, and it is difficult to increase the stability of the horizontal radiation angle.

The present invention has been made in view of the above problems, and a first object thereof is to provide a semiconductor laser capable of lowering a driving voltage and a manufacturing method thereof.

A second object of the present invention is to provide a semiconductor laser and a method for manufacturing the same which can prolong the life by improving heat dissipation or reducing cracks.

A third object of the present invention is to provide a semiconductor laser capable of easily obtaining a stable horizontal radiation angle and a method of manufacturing the same.

[0011]

A semiconductor laser according to the present invention comprises a substrate, on which a first semiconductor layer, an active layer, and a second semiconductor layer, each of which is made of a nitride semiconductor, are sequentially stacked. The first semiconductor layer has a current confinement layer that limits the current injection region of the active layer.

The method of manufacturing a semiconductor laser according to the present invention is
A method for manufacturing a semiconductor laser in which a first semiconductor layer, an active layer, and a second semiconductor layer each made of a nitride semiconductor are sequentially laminated on a substrate, wherein the first semiconductor layer comprises:
It includes a step of forming a current confinement layer that limits a current injection region of the active layer.

In the semiconductor laser according to the present invention, the current injection region of the active layer is limited by the current confinement layer provided in the first semiconductor layer. Therefore, the area for electrically connecting the external power supply to the second semiconductor layer can be increased, the contact resistance with respect to the second semiconductor layer is reduced, and the driving voltage is lowered. In addition, heat dissipation is improved, and deterioration of the active layer is prevented.

In the method of manufacturing a semiconductor laser according to the present invention, the current confinement layer is formed in the first semiconductor layer. Therefore, the semiconductor laser of the present invention is easily manufactured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows a structure of a semiconductor laser according to a first embodiment of the present invention. This semiconductor laser is provided with a first
Semiconductor layer 20, active layer 30, and second semiconductor layer 40
Has a structure in which layers are sequentially stacked. The substrate 10 is made of, for example, sapphire (α-Al ₂ O ₃ ) having a thickness in the stacking direction (hereinafter, simply referred to as “thickness”) of about 80 μm, and the c-plane of the first semiconductor layer 20 and the active layer 30. And the second semiconductor layer 40 is formed.

The first semiconductor layer 20, the active layer 30, and the second semiconductor layer 40 are each composed of a nitride semiconductor. The nitride semiconductor means at least one of the elements of Group 3B in the short periodic table,
A compound semiconductor containing at least nitrogen (N) among Group 5B elements in the short periodic table.

The first semiconductor layer 20 is, for example, the substrate 10
It has an n-type contact layer 21, an n-type clad layer 22, and an n-type guide layer 23 which are sequentially stacked from the side. In addition, in the present embodiment, “n-type” is changed to “first conductivity type”.
The "p-type" corresponds to the "second conductivity type", and the "n-type guide layer" corresponds to the "first guide layer". The n-type contact layer 21 has, for example, a thickness of 4 μm, and is made of n-type GaN doped with silicon (Si) as an n-type impurity.

The n-type cladding layer 22 has, for example, a thickness of 1
μm, n-type A doped with silicon as an n-type impurity
It is composed of an lGaN mixed crystal. The n-type clad layer 22 is provided corresponding to a current injection region of the active layer 30 into which a current is injected, and has a thin strip shape extending in the resonator direction (direction perpendicular to the paper surface in FIG. 1). It is said that. The width of the n-type clad layer 22 in the I direction shown in FIG.
It is narrower than the width of the mold guide layer 23 and the like. As a result, in this semiconductor laser, the stress acting on the n-type cladding layer 22 can be reduced, and the occurrence of cracks in the n-type cladding layer 22 can be prevented. Note that FIG.
The I direction shown in is a direction perpendicular to the stacking direction and the resonator direction.

The n-type guide layer 23 has, for example, a thickness of 0.
It is 1 μm and is made of n-type GaN to which silicon is added as an n-type impurity.

The first semiconductor layer 20 also has, between the n-type contact layer 21 and the n-type guide layer 23, a current confinement layer 24 that limits the current injection region of the active layer 30.
The current confinement layer 24 has an opening 24A extending in the cavity direction corresponding to the current injection region of the active layer 30, and the n-type cladding layer 22 is provided so as to fill the opening 24A. ing. The openings 24A have the same width in the resonator direction, for example. Current constriction layer 24
Is a material having a higher resistance than the n-type cladding layer 22 or p
It is made of a semiconductor, and the current is constricted thereby.

As a material for forming the current constriction layer 24,
For example, a semiconductor having the same composition as the n-type guide layer 23 is preferable. If the upper surface and the side surface of the n-type cladding layer 22 in FIG. 1 are covered with the semiconductor of the same composition, the difference in effective refractive index in the lateral direction is caused by the difference in effective refractive index between the n-type cladding layer 22 and the current confinement layer 24. Since it is determined, it is possible to obtain a stable horizontal radiation angle that is not affected by the dimensional accuracy and has little variation. For example, the n-type guide layer 23
Is composed of n-type GaN, the current confinement layer 2
4 is high resistance undope-GaN with no added impurities
It is preferable that

The active layer 30 has, for example, a thickness of 30 nm, and has an undope-type having a different composition without adding impurities.
It has a multiple quantum well structure in which Ga _x In _1-x N (however, 1 ≧ x ≧ 0) mixed crystal layers are stacked. This active layer 30 is
A current injection region into which a current is injected is provided corresponding to the opening 24A of the current confinement layer 24, that is, the n-type cladding layer 22. The current injection region functions as a light emitting region.

The second semiconductor layer 40 is, for example, the active layer 3
The second conductivity type p-type guide layer 41, the p-type clad layer 42, and the p-type contact layer 4 which are sequentially stacked from the 0 side.
Have three. The p-type guide layer 41 has, for example, a thickness of 0.1 μm, and magnesium (M
g) is added to form p-type GaN. The p-type cladding layer 42 has, for example, a thickness of 0.5 μm,
It is composed of an AlGaN mixed crystal to which magnesium is added as a p-type impurity. The p-type contact layer 43 has, for example, a thickness of 0.1 μm, and is made of GaN to which magnesium is added as a p-type impurity. In the present embodiment, since the current confinement layer 24 is provided in the first semiconductor layer 20, the width of the second semiconductor layer 40 is the same as the width of the active layer 30. 24
Is wider than the width of the opening 24A, that is, the width of the n-type cladding layer 22.

In this semiconductor laser, the width of the n-type contact layer 21 is another n-type cladding layer 22, n-type guide layer 23, current confinement layer 24, active layer 30, p-type guide layer 4.
1, the width is wider than the widths of the p-type clad layer 42 and the p-type contact layer 43, and the n-type clad layer 22, the n-type guide layer 23, the current confinement layer 24, the active layer are formed in a part of the n-type contact layer 21. 30, p-type guide layer 41, p-type clad layer 42 and p-type contact layer 43 are laminated.

An insulating film 50 made of, for example, silicon dioxide (SiO ₂ ) is formed on the surfaces of the n-type contact layer 21 to the p-type contact layer 43. The insulating film 50 includes
Openings are provided respectively corresponding to the n-type contact layer 21 and the p-type contact layer 43, and an n-side electrode 60 is formed on the n-type contact layer 21 through the opening.
A p-side electrode 70 is formed on the p-type contact layer 43 so as to correspond to the opening.

The n-side electrode 60 is made of, for example, titanium (Ti),
It has a structure in which aluminum (Al) and gold (Au) are sequentially laminated and alloyed by heat treatment, and is electrically connected to the n-type contact layer 21. p-side electrode 70
Has a structure in which, for example, palladium (Pd), platinum (Pt), and gold are sequentially stacked, and is electrically connected to the p-type contact layer 43. In the present embodiment, since the current confinement layer 24 is provided in the first semiconductor layer 20 as described above, the p-type contact layer 43 and the p-side electrode 7 are provided.
The contact area with 0 can be widened, and the contact area is preferably as wide as possible. This is because the contact resistance can be lowered, the driving voltage can be lowered, the dissipation of the heat generated in the active layer 30 can be improved, and the deterioration of the active layer 30 can be prevented.

Further, in this semiconductor laser, a pair of side faces facing each other in the cavity direction are cavity end faces, and a pair of reflecting mirror films (not shown) are respectively formed on the cavity end faces. The reflectance is adjusted so that one of the pair of reflecting mirror films has a low reflectance and the other has a high reflectance. As a result, the light generated in the active layer 30 is amplified by traveling back and forth between the pair of reflecting mirror films, and is emitted as a laser beam from the reflecting film on the low reflectance side.

A semiconductor laser having such a structure is
It can be manufactured as follows.

2 and 3 show a method of manufacturing a semiconductor laser according to this embodiment in the order of steps. First,
As shown in FIG. 2A, for example, a substrate 10 made of sapphire having a thickness of 400 μm is prepared, and MOCVD (Metal Organic Chemic) is formed on one surface (c-plane) of the substrate 10.
al Vapor Deposition; metal-organic chemical vapor deposition) method for forming the n-type contact layer 21 and u made of n-type GaN.
A current confinement layer 24 made of ndope-GaN is sequentially grown. At this time, as described above, it is preferable that the current confinement layer 24 is formed of the same material as the n-type guide layer 23 to be grown later. By doing so, the effective refractive index difference in the lateral direction is not affected by the dimensional accuracy, so strict dimensional accuracy becomes unnecessary, and the manufacturing yield can be improved.

Next, as shown in FIG. 2B, for example, a mask layer 81 made of silicon dioxide is formed on the current confinement layer 24, and this mask layer 81 is used to perform RIE.
The current confinement layer 24 is selectively removed by (Reactive Ion Etching), and an opening 24A is formed corresponding to the formation position of the n-type cladding layer 22.

Subsequently, as shown in FIG. 3A, for example, the n-type contact layer 2 exposed by the opening 24A.
1 on the basis of the n-type contact layer 21
N-type Al is formed by the VD method so as to fill the opening 24A.
An n-type clad layer 22 made of a GaN mixed crystal is grown.
Here, since the region where the n-type clad layer 22 made of n-type AlGaN mixed crystal is grown is narrow, the n-type clad layer 22 is
The stress applied to the surface is small and the occurrence of cracks is small.
After growing the n-type cladding layer 22, the mask layer 81 is removed.

After removing the mask layer 81, FIG.
, The n-type GaN is formed on the n-type clad layer 22 and the current confinement layer 24 by the MOCVD method.
N-type guide layer 23 made of und with no added impurities
active layer 30, p made of ope-Ga _x In _1-x N mixed crystal
A p-type guide layer 41 made of p-type GaN, a p-type cladding layer 42 made of a p-type AlGaN mixed crystal, and a p-type contact layer 43 made of p-type GaN are sequentially grown.

When MOCVD is performed, the source gas of gallium is, for example, trimethylgallium ((CH ₃ )
₃ Ga), aluminum source gas is, for example, trimethyl aluminum ((CH ₃ ) ₃ Al), and indium source gas is, for example, trimethyl indium ((C
As the source gas for H ₃ ) ₃ In) and nitrogen, for example, ammonia (NH ₃ ) is used. Also, for example, monosilane (SiH ₄ ) is used as the silicon source gas, and bis = cyclopentadienyl magnesium ((C ₅ H ₅ ) ₂ Mg) is used as the magnesium source gas.

After growing the p-type contact layer 43,
Part of the p-type contact layer 43, p-type cladding layer 42, p-type guide layer 41, active layer 30, n-type guide layer 23, current confinement layer 24 and n-type contact layer 21 is selectively removed by, for example, etching. A part of the n-type contact layer 21 is exposed on the surface corresponding to the formation position of the n-side electrode 60. After that, the insulating film 50 made of silicon dioxide is formed on the entire surface of the substrate 10 by, for example, a vapor deposition method.

After forming the insulating film 50, a resist film (not shown) is formed by coating on the insulating film 50, and the insulating film 50 is selectively removed by using the resist film (not shown) as a mask to form the n-side electrode 60. An opening is formed corresponding to the formation position. After that, titanium, aluminum, and gold are sequentially laminated on the entire surface of the substrate 10 by, for example, a vacuum evaporation method, and a resist film (not shown) is removed together with the metal laminated thereon (lift-off) and alloyed to form an n-side electrode. Form 60.

After forming the n-side electrode 60, similarly, a resist film (not shown) is formed on the entire surface of the substrate 10 by coating, and the insulating film 50 is selectively removed using the resist film (not shown) as a mask. An opening is formed corresponding to the formation position of the side electrode 70. After that, on the entire upper surface of the substrate 10,
For example, palladium, platinum, and gold are sequentially laminated by a vacuum vapor deposition method, and a resist film (not shown) is removed together with the metal formed thereon (lift-off) to form the p-side electrode 70.

After forming the n-side electrode 60 and the p-side electrode 70, the substrate 10 is ground to have a thickness of, for example, 80 μm. After that, arrange the substrate 10 into a predetermined size,
A reflecting mirror film (not shown) is formed on a pair of resonator end faces facing each other in the resonator length direction. As a result, the semiconductor laser shown in FIG. 1 is completed.

This semiconductor laser operates as follows.

In this semiconductor laser, the n-side electrode 60 and p
When a predetermined voltage is applied between the side electrode 70 and the side electrode 70, a current is injected into the current injection region of the active layer 30 corresponding to the n-type cladding layer 22, and light is emitted by electron-hole recombination. This light is reflected by a pair of reflecting mirror films (not shown), reciprocates between them to generate laser oscillation, and is emitted to the outside as a laser beam. Here, the current confinement layer 24 is provided on the first semiconductor layer 20, and the p-type contact layer 4 is provided.
Since the contact area between 3 and the p-side electrode 70 is wide,
It has low contact resistance and operates at low operating voltage. Further, the heat generated in the active layer 30 is positively dissipated through the p-side electrode 70, and the deterioration of the active layer 30 is prevented. Further, since the current confinement layer 24 and the n-type guide layer 23 are each made of, for example, a semiconductor having the same composition, there is little variation in the effective refractive index difference in the lateral direction, and the horizontal radiation angle is stable.

As described above, according to the semiconductor laser of the present embodiment, the first semiconductor layer 20 has the current confinement layer 24. Therefore, the contact area between the p-type contact layer 43 and the p-side electrode 70. Can be widened. Therefore, the contact resistance can be reduced and the drive voltage can be reduced. Further, the heat dissipation property can be improved, and the heat generated in the active layer 30 can be actively dissipated. Therefore, deterioration of the active layer 30 can be prevented,
The life can be extended.

In particular, the opening 24A of the current confinement layer 24 is formed in the n-type cladding layer 22 corresponding to the current injection region of the active layer 30.
Since the width of the n-type clad layer 22 is narrowed, the n-type clad layer 22 has a lattice constant or a thermal expansion coefficient different from that of the n-type clad layer 22.
It is possible to reduce the stress acting on and to prevent the occurrence of cracks. Therefore, the life can be extended.

Further, the current confinement layer 24 is replaced with the n-type guide layer 23.
If it is made of a semiconductor having the same composition as that of the n-type clad layer 22 and the current confinement layer 2 in the lateral effective refractive index difference,
It is determined by the difference between the effective refractive index of 4 and the effective refractive index of 4 and can be made not to be influenced by the dimensional accuracy. Therefore, it is possible to obtain a stable horizontal radiation angle with little variation, and it is not necessary to have strict dimensional accuracy, so that the manufacturing yield can be improved.

Further, according to the method of manufacturing the semiconductor laser of this embodiment, after growing the current confinement layer 24,
An opening 24A is formed in the current confinement layer 24, and the opening 2A is formed.
Since the n-type cladding layer 22 is grown on 4A, the semiconductor laser according to the present embodiment can be easily manufactured. Moreover, since the region where the n-type cladding layer 22 is grown is narrow, the stress applied to the n-type cladding layer 22 can be reduced, and the n-type cladding layer 22 with few cracks can be formed. Therefore, the life can be extended.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
2 shows a cross-sectional structure of the semiconductor laser according to the embodiment. This semiconductor laser includes a dielectric layer 90 between the n-type contact layer 21 and the current confinement layer 24, and
The first semiconductor layer 20, the active layer 30, and the second semiconductor layer 40 have the same configuration, action, and effect as those of the first embodiment except that the laminated form is different. Therefore,
Here, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description of the same portions will be omitted.

The dielectric layer 90 has, for example, a thickness of 0.3 μm.
m, and silicon dioxide or silicon nitride (Si ₃ N
₄ ) and other dielectric materials. Like the current confinement layer 24, the dielectric layer 90 is provided with an opening 91 corresponding to the current injection region of the active layer 30,
The n-type cladding layer 22 is provided so as to fill the opening 91 and the opening 24A of the current confinement layer 24.

The side surface of the current confinement layer 24 located in the I direction is inclined, for example, so that the width becomes wider toward the substrate 10. The cross-sectional shape of the current confinement layer 24 perpendicular to the cavity direction is trapezoidal. The n-type guide layer 23, the active layer 30, the p-type guide layer 41, the p-type clad layer 42, and the p-type contact layer 43, which are stacked on the current confinement layer 24, cover the upper surface and side surfaces of the current confinement layer 24. Is formed.

The semiconductor laser having such a structure is
It can be manufactured as follows.

5 and 6 show a method of manufacturing a semiconductor laser according to this embodiment in the order of steps. First,
As shown in FIG. 5A, for example, the n-type contact layer 21 is grown on the substrate 10 in the same manner as in the first embodiment. Then, on the n-type contact layer 21, a dielectric layer 90 made of, for example, silicon dioxide is formed by a vapor deposition method.
Then, the dielectric layer 90 is selectively removed by, for example, lithography to form an opening 91 corresponding to the formation position of the n-type cladding layer 22.

Subsequently, as shown in FIG. 5B, for example, the n-type contact layer 21 exposed by the opening 91.
On top of the n-type contact layer 21 as a basis for MOCV
An n-type clad layer 22 made of an n-type AlGaN mixed crystal is grown by the D method. At that time, the dielectric layer 90 functions as a mask layer for selectively growing the n-type cladding layer 22.

After the n-type clad layer 22 is grown, as shown in FIG. 6A, the current confinement layer 24 made of undope-GaN is laterally formed on the side surface of the n-type clad layer 22. Selectively grow. At that time, the side surface of the current confinement layer 24 grows in a state in which the substrate 10 side is widely inclined depending on the crystal orientation, for example. This current constriction layer 2
The step of growing No. 4 is finished when the width of the current constriction layer 24 reaches a predetermined value.

After forming the current confinement layer 24, FIG.
As shown in (B), n is formed on the n-type cladding layer 22 and the current confinement layer 24 in the same manner as in the first embodiment.
The type guide layer 23, the active layer 30, the p type guide layer 41, the p type clad layer 42, and the p type contact layer 43 are sequentially grown. At this time, the n-type guide layer 23 and the like are formed so as to cover the upper surface and the side surface of the current constriction layer 24, for example.

As described above, in this embodiment, the current confinement layer 24, the n-type guide layer 23, the active layer 30, the p-type guide layer 41, the p-type cladding layer 42 and the p-type contact layer 43.
Are selectively formed on a part of the n-type contact layer 21. Therefore, unlike the first embodiment, it is not necessary to etch each of these semiconductor layers to expose a part of the n-type contact layer 21.

After the p-type contact layer 43 is formed, the insulating film 50 is formed on the entire surface of the substrate 10 in the same manner as in the first embodiment, and then the n-side electrode 60 and the p-type electrode are formed.
The side electrodes 70 are formed respectively. After that, for example, as in the case of the first embodiment, the substrate 10 is adjusted to a predetermined size, and then a reflecting mirror film (not shown) is formed on the pair of resonator end faces. As a result, the semiconductor laser shown in FIG. 4 is completed.

As described above, according to the present embodiment, the n-type cladding layer 22 is grown on the n-type contact layer 21 through the dielectric layer 90 having the opening 91, and then n
Since the current confinement layer 24 is grown laterally based on the side surface of the n-type clad layer 22, the n-type contact layer 2
The current confinement layer 24, the n-type guide layer 23, the active layer 30, the p-type guide layer 41, the p-type clad layer 42, and the p-type contact layer 43 can be selectively formed in a part of 1. Therefore, the step of exposing a part of the n-type contact layer 21 becomes unnecessary, and the productivity can be improved.

[Third Embodiment] FIG. 7 shows a third embodiment of the present invention.
2 shows a cross-sectional structure of the semiconductor laser according to the embodiment. This semiconductor laser has the same configuration, action, and effect as those of the first embodiment, except that the first semiconductor layer 20, the active layer 30, and the second semiconductor layer 40 are different in stacking form. . Therefore, here, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description of the same portions will be omitted.

In this semiconductor laser, the thickness of the current confinement layer 24 on the side in contact with the n-type cladding layer 22 is large, and the thickness on the side away from the n-type cladding layer 22 is small.
Therefore, the n-type guide layer 23, the active layer 30, the p-type guide layer 41, the p-type clad layer 42, and the p-type contact layer 43, which are stacked on the current confinement layer 24, are the current confinement layer 2
It is curved corresponding to 4.

The semiconductor laser having such a structure is
It can be manufactured as follows.

FIG. 8 shows a method of manufacturing the semiconductor laser according to this embodiment in the order of steps. First, FIG. 8 (A)
As shown in, the n-type contact layer 21 is grown on the substrate 10 in the same manner as in the first embodiment, for example. Then, on the n-type contact layer 21, for example, n
A mask layer 82 made of silicon dioxide having an opening corresponding to the formation position of the mold cladding layer 22 is formed. continue,
For example, on the n-type contact layer 21 exposed from the opening, based on the n-type contact layer 21, MOCVD is performed.
N-type clad layer 2 made of n-type AlGaN mixed crystal by method
Grow two.

After growing the n-type cladding layer 22, as shown in FIG. 8B, for example, the mask layer 82 is removed and the side surface of the n-type cladding layer 22 is used as a base for undo.
The current confinement layer 24 made of pe-GaN is selectively grown in the lateral direction. At this time, the current confinement layer 24 grows laterally from the side surface of the n-type cladding layer 22, but also slightly grows from the upper surface of the n-type contact layer 21. Therefore, the thickness of the current confinement layer 24 is thicker on the side in contact with the n-type cladding layer 22 and thinner on the side away from the n-type cladding layer 22.

After growing the current confinement layer 24, FIG.
As shown in (C), on the n-type cladding layer 22 and the current confinement layer 24, n is formed in the same manner as in the first embodiment.
The type guide layer 23, the active layer 30, the p type guide layer 41, the p type clad layer 42, and the p type contact layer 43 are sequentially grown. At that time, the n-type guide layer 23 and the like are formed to be curved corresponding to the current confinement layer 24, for example.

After growing the p-type contact layer 43,
For example, as in the first embodiment, the p-type contact layer 43, the p-type cladding layer 42, the p-type guide layer 41, the active layer 30, the n-type guide layer 23, and the current confinement layer 24 are selectively removed. Then, a part of the n-type contact layer 21 is exposed. At this time, in the present embodiment, the thickness of the current confinement layer 24 on the side away from the n-type cladding layer 22 is thin, so that the n-type contact layer 21 is different from that of the first embodiment.
It takes less time to expose. After that, for example, the first
In the same manner as in the above embodiment, the insulating film 50 and the n-side electrode 60
Then, the p-side electrode 70 is formed and adjusted to a predetermined size to form a reflecting mirror film. As a result, the semiconductor laser shown in FIG. 7 is completed.

This semiconductor laser can also be manufactured as follows.

FIG. 9 shows another method of manufacturing the semiconductor laser according to the present embodiment in the order of steps. First, FIG.
As shown in (A), the n-type contact layers 21 and n are formed on the substrate 10 in the same manner as in the first embodiment, for example.
The mold cladding layer 22 is sequentially grown.

Next, as shown in FIG. 9B, for example, a mask layer 83 made of silicon dioxide is formed on the n-type clad layer 22 corresponding to the position where the n-type clad layer 22 is formed.
To form. Then, using this mask layer 83, RI
The n-type clad layer 22 is selectively removed by E to form the n-type clad layer 22 into a strip shape corresponding to the current injection region of the active layer 30. After that, the mask layer 83 is removed, and thereafter, a semiconductor laser is manufactured in the same manner as the above manufacturing method.

As described above, according to the present embodiment, the current confinement layer 24 is laterally grown on the basis of the side surface of the n-type clad layer 22, so that the thickness of the current confinement layer 24 is n-type. The side in contact with the layer 22 is thick, and the side away from the n-type cladding layer 22 is thin. Therefore, the time required to expose the n-type contact layer 21 can be shortened,
Productivity can be improved.

[Fourth Embodiment] FIG. 10 shows a sectional structure of a semiconductor laser according to a fourth embodiment of the present invention. This semiconductor laser has the same configuration, operation and effect as the first embodiment except that the substrate 10 is made of a conductive material and the n-side electrode 60 is formed on the back surface of the substrate 10. ing. Further, it can be manufactured in the same manner as in the first embodiment. So here,
The same components as those in the first embodiment are designated by the same reference numerals, and detailed description of the same components will be omitted.

The substrate 10 is made of, for example, an n-type GaN single crystal doped with silicon as an n-type impurity. In this semiconductor laser, it is not necessary to expose a part of the n-type contact layer 21 and electrically connect the n-side electrode 60. Therefore, the width of the n-type contact layer 21 is the width of the n-type guide layer 23 and the active layer 30. , P-type guide layer 41, p-type cladding layer 42, and p-type contact layer 43 have the same width.

As described above, according to this embodiment, the substrate 1
Since n is made of a conductive material, the n-side electrode 6
0 can be provided on the back surface side of the substrate 10, that is, on the side opposite to the p-side electrode 70. Therefore, wiring for the semiconductor laser can be facilitated.

Although not described in detail here, this embodiment can be similarly applied to the second and third embodiments.

[Fifth Embodiment] FIGS. 11 and 12
Shows a cross-sectional structure of the semiconductor laser according to the fifth embodiment of the present invention, and shows a surface including the n-type cladding layer 22 perpendicular to the stacking direction. This semiconductor laser has the same configuration as that of the first embodiment, except that the width of the opening 24A of the current confinement layer 24 is wider or narrower on the resonator end face side than the central portion in the resonator direction. Has an action and an effect. Further, it can be manufactured in the same manner as in the first embodiment. Therefore, here, the first
The same components as those of the embodiment are given the same reference numerals,
Detailed description of the same parts will be omitted.

The width of the opening 24A of the current confinement layer 24 is adjusted according to the intended characteristics of the semiconductor laser. For example, in the case of a high-power semiconductor laser, as shown in FIG. 11, the width of the opening 24A is preferably wider on the resonator end face side than on the central portion. The current injection region of the active layer 30 corresponds to the opening 24A of the current confinement layer 24. By increasing the width of the current injection region on the cavity end face side, optical damage (Catastroph) on the cavity end face and its vicinity is formed.
This is because ic optical damage (COD) can be prevented. Further, in the case of a low-power semiconductor laser, as shown in FIG. 12, it is preferable that the width of the opening 24A is narrower on the resonator end face side than on the central portion. Compared to the case of high output, the optical damage on the resonator end face and its vicinity is small, and by narrowing the width of the current injection region on the resonator end face side, the half-width (θ _{/ This is because /} ) can be increased and it becomes easier to use.

The n-type cladding layer 22 is the current confinement layer 2
The width of the n-type cladding layer 22 is wider or narrower on the resonator end face side than on the central portion in the resonator direction, like the width of the opening 24A.

As described above, in the present embodiment, the current injection region of the active layer 30 is controlled by the current confinement layer 24, so that the current injection region is different from the conventional semiconductor laser in which the p-type contact layer is projected. The width can be easily changed, and even if the width of the current injection region is easily changed, the connection state of the p-side electrode 70 does not change and stable characteristics can be obtained.

As described above, according to the present embodiment, the current confinement layer 24 is provided in the first semiconductor layer 20. Therefore, by changing the shape of the opening 24A of the current confinement layer 24, the current can be easily generated. The width of the implant area can be adjusted. Even if the shape of the opening 24A is changed, the p-side electrode 7
The connection state of 0 does not change, and stable characteristics can be obtained. Therefore, the current confinement layer 2 can be formed according to the desired characteristics.
If the width of the opening 24A of No. 4 is made wider or narrower on the resonator end face side than the central portion in the resonator direction, the characteristics can be easily and stably improved.

Although not described in detail here, this embodiment can be similarly applied to the second to fourth embodiments.

[Sixth Embodiment] FIG. 13 shows a sectional structure of a semiconductor laser according to a sixth embodiment of the present invention. This semiconductor laser has a plurality of (three in FIG. 13) openings 24A in the current confinement layer 24, and
Except that a plurality of n-type cladding layers 22 are provided correspondingly, it has the same configuration, operation, and effect as the first embodiment. Further, it can be manufactured in the same manner as in the first embodiment. Therefore, here, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description of the same portions will be omitted.

The plurality of openings 24A of the current confinement layer 24 are provided in parallel with each other. Corresponding to this, the active layer 3
0 also has a plurality of current injection regions located in parallel.
The plurality of current injection regions are not separated from each other, and
The side electrode 60 and the p-side electrode 70 are common to them. That is, this semiconductor laser is adapted to emit a plurality of parallel laser beams.

As described above, the present invention can be applied to the semiconductor laser according to the present embodiment, that is, the semiconductor laser emitting a plurality of laser beams. In addition,
This embodiment is not limited to the first embodiment, but can be similarly applied to the second embodiment as shown in FIG. Further, the same can be applied to the third to fifth embodiments.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above-described embodiment, the n-type cladding layer 22 is formed in the opening 24 of the current confinement layer 24.
Although it is formed into a strip shape corresponding to the current injection region of the active layer 30, a part of the n-type cladding layer, more preferably a part of the active layer side is provided in the opening of the current constriction layer, A band may be formed corresponding to the current injection region of the active layer. Also in this case, the same effect as that of the above embodiment can be obtained.

In addition to the n-type cladding layer or n
Instead of the type cladding layer, at least part of the n-type contact layer or at least part of the n-type guide layer may be provided in the opening of the current confinement layer.

Further, in the above-mentioned embodiment, the structure of the semiconductor laser has been described by giving a concrete example, but the present invention can be applied to the semiconductor lasers having other structures in the same manner. For example, the n-type guide layer and the p-type guide layer may not be provided, and the deterioration prevention layer may be provided between the active layer and the p-type guide layer. Further, in the above-described embodiment, the first semiconductor layer 20 has the n-type contact layer 21, the n-type cladding layer 22 and the n-type guide layer 23, and the second semiconductor layer 40 is the p-type guide layers 41, p. Although the case where the first clad layer 42 and the p-type contact layer 43 are provided has been described, the first semiconductor layer has a p-type contact layer, a p-type clad layer, a p-type guide layer, and the like, and the second semiconductor layer has an n-type. Type guide layer, n-type cladding layer and n
The same can be applied to the case where the mold contact layer is provided. In this case, “p-type” corresponds to “first conductivity type”, “n-type” corresponds to “second conductivity type”,
The “p-type guide layer” corresponds to the “first guide layer”.

In addition, in the above embodiment, the substrate 10 is
Use sapphire or gallium nitride
However, silicon carbide (SiC) or spinel (MgAl
₂O _Four) And other materials
Yes.

Furthermore, in the above-described embodiment, the first semiconductor layer 20, the active layer 30, and the second semiconductor layer 40 are M.
Although the case of forming by the OCVD method has been described, M
It may be formed by another vapor phase growth method such as a BE (Molecular Beam Epitaxy) method, a hydride vapor phase growth method, or a halide vapor phase growth method. Note that the hydride vapor phase epitaxy method is a vapor phase epitaxy method in which hydride (hydride) contributes to a reaction or transportation of a source gas. Further, the halide vapor phase growth method is a vapor phase growth method in which a halide (halide) contributes to a reaction or transportation of a source gas.

In addition, although the semiconductor laser using the nitride semiconductor has been described in the above embodiment, the present invention is not limited to the other III-V group compound semiconductor or II-V.
It can also be applied to a semiconductor laser using another semiconductor such as a group I compound semiconductor.

[0086]

As described above, according to the semiconductor laser of any one of claims 1 to 9, since the first semiconductor layer has the current confinement layer, The area for electrically connecting the external power supply to the semiconductor layer can be increased. Therefore, the contact resistance with respect to the second semiconductor layer can be reduced and the driving voltage can be reduced. Further, the heat dissipation property can be improved, and the heat generated in the active layer can be actively dissipated. Therefore, deterioration of the active layer can be prevented and the life can be extended.

Particularly, according to the semiconductor laser of any one of claims 2 to 6, at least a part of the first-conductivity-type cladding layer is formed into a strip shape corresponding to the current injection region. The stress acting on the first conductivity type cladding layer can be reduced, and the occurrence of cracks can be prevented. Therefore, the life can be extended.

According to the sixth aspect of the semiconductor laser, since the current confinement layer and the first guide layer are made of semiconductors having the same composition, the lateral effective refractive index difference is the first. It is determined by the difference in effective refractive index between the conductivity type cladding layer and the current constriction layer, and can be prevented from being affected by the dimensional accuracy. Therefore, it is possible to obtain a stable horizontal radiation angle with little variation, and it is not necessary to have strict dimensional accuracy, so that the manufacturing yield can be improved.

Further, according to the semiconductor laser of the ninth aspect, the width of the opening of the current confinement layer is made wider or narrower on the resonator end face side than on the central portion in the resonator direction. Therefore, the characteristics can be easily and stably improved.

In addition, according to the method of manufacturing a semiconductor laser of any one of claims 10 to 20,
Since the step of forming the current confinement layer in the first semiconductor layer is included, the semiconductor laser of the present invention can be easily realized.

Furthermore, according to the method of manufacturing a semiconductor laser of claim 12, claim 14 or claim 15,
After forming an opening in the current confinement layer, the first portion is formed in this opening.
Since the conductive type clad layer is grown, or after the dielectric layer or the mask layer having the opening is formed, the first conductive type clad layer is grown in the opening. The stress applied to the clad layer can be reduced, and the first conductivity type clad layer with few cracks can be formed. Therefore, the life can be extended.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a manufacturing process of the semiconductor laser shown in FIG.

FIG. 3 is a cross-sectional view showing a manufacturing process following FIG.

FIG. 4 is a sectional view showing a configuration of a semiconductor laser according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing process of the semiconductor laser shown in FIG.

FIG. 6 is a cross-sectional view showing a manufacturing process that follows FIG.

FIG. 7 is a sectional view showing a configuration of a semiconductor laser according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a manufacturing process of the semiconductor laser shown in FIG.

9 is a cross-sectional view showing another manufacturing process of the semiconductor laser shown in FIG.

FIG. 10 is a sectional view showing a configuration of a semiconductor laser according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view showing a configuration of a semiconductor laser according to a fifth embodiment of the present invention.

FIG. 12 is a sectional view showing the configuration of another semiconductor laser according to the fifth embodiment of the invention.

FIG. 13 is a sectional view showing a configuration of a semiconductor laser according to a sixth embodiment of the present invention.

FIG. 14 is a sectional view showing a configuration of a semiconductor laser according to a modification of the sixth embodiment of the present invention.

FIG. 15 is a sectional view showing a configuration of a conventional semiconductor laser.

[Explanation of symbols]

10 ... Substrate, 20 ... First semiconductor layer, 21, 121 ... N
-Type contact layer, 22, 122 ... N-type cladding layer, 2
3, 123 ... N-type guide layer, 24 ... Current constriction layer, 24
A, 91 ... Opening part, 30, 130 ... Active layer, 40 ... Second
Semiconductor layers, 41, 141 ... P-type guide layers, 42, 14
2 ... P-type cladding layer, 43, 143 ... P-type contact layer, 50, 150 ... Insulating film, 60 ... N-side electrode, 70, 1
70 ... P-side electrode, 81.82, 83 ... Mask layer, 90 ...
Dielectric layer

Continued front page    (72) Inventor Shiro Uchida             3-53-2, Shiratori, Shiroishi, Miyagi Prefecture Sony             Shiraishi Semiconductor Co., Ltd. F-term (reference) 5F073 AA21 AA45 AA74 AA83 BA06                       CA07 CB22 DA05 DA25 EA28                       EA29

Claims (20)

[Claims] 1. A semiconductor laser in which a first semiconductor layer, an active layer, and a second semiconductor layer each made of a nitride semiconductor are sequentially stacked on a substrate, wherein the first semiconductor layer has the active layer. A semiconductor laser having a current confinement layer that limits the current injection region of the semiconductor laser. 2. The first semiconductor layer has a first conductivity type clad layer, the second semiconductor layer has a second conductivity type clad layer, and at least a part of the first conductivity type clad layer. 2. The semiconductor laser according to claim 1, wherein the semiconductor laser has a strip shape corresponding to the current injection region. 3. The current confinement layer has an opening corresponding to the current injection region, and at least a part of the first conductivity type cladding layer is provided in the opening. The semiconductor laser according to claim 2. 4. The first conductivity type clad layer is AlGaN
The semiconductor laser according to claim 2, wherein the semiconductor laser is made of a mixed crystal. 5. The semiconductor laser according to claim 2, wherein the first conductivity type cladding layer is n-type. 6. The first semiconductor layer has a first guide layer on the side of the active layer of the first conductivity type cladding layer, and the first guide layer and the current confinement layer are different from each other. 3. The semiconductor laser according to claim 2, wherein the semiconductor lasers are made of semiconductors having the same composition. 7. The semiconductor laser according to claim 1, wherein the current confinement layer is made of GaN. 8. The semiconductor laser according to claim 1, wherein the current confinement layer is made of a semiconductor to which impurities are not added. 9. A pair of resonator end faces facing each other in the resonator direction are provided, and the current confinement layer has an opening extending in the resonator direction corresponding to the current injection region. 2. The semiconductor laser according to claim 1, wherein the width of the portion is wider or narrower on the cavity facet side than on the central portion in the cavity direction. 10. A method of manufacturing a semiconductor laser in which a first semiconductor layer, an active layer, and a second semiconductor layer each made of a nitride semiconductor are sequentially stacked on a substrate, wherein the first semiconductor layer has an active layer. A method of manufacturing a semiconductor laser, comprising the step of forming a current confinement layer that limits a current injection region of the layer. 11. A first semiconductor layer, at least a part of which has a band shape corresponding to the current injection region of the active layer.
11. The method of manufacturing a semiconductor laser according to claim 10, further comprising the step of forming a conductive clad layer. 12. A current confinement layer is grown, an opening is formed in the current confinement layer corresponding to the current injection region of the active layer, and then a first conductivity type cladding layer is grown in the opening. The method for manufacturing a semiconductor laser according to claim 11. 13. The method of manufacturing a semiconductor laser according to claim 11, wherein the current confinement layer is grown at least on the basis of the first conductivity type cladding layer. 14. The step of forming the first-conductivity-type cladding layer includes the step of forming a dielectric layer having an opening corresponding to the current injection region of the active layer, and the step of forming a dielectric layer in the opening of the dielectric layer. 14. The method of manufacturing a semiconductor laser according to claim 13, further comprising the step of growing a one conductivity type cladding layer. 15. The step of forming the first-conductivity-type cladding layer comprises the step of forming a mask layer having an opening corresponding to the current injection region of the active layer, and the step of forming the first conductive layer in the opening of the mask layer. 14. The method of manufacturing a semiconductor laser according to claim 13, further comprising: a step of growing the type clad layer; and a step of growing the first conductivity type clad layer and then removing the mask layer. 16. The step of forming the first-conductivity-type clad layer corresponds to the step of growing the first-conductivity-type clad layer, and at least a part of the first-conductivity-type clad layer corresponds to the current injection region of the active layer. 14. The method of manufacturing a semiconductor laser according to claim 13, further comprising a step of forming a strip shape. 17. The method of manufacturing a semiconductor laser according to claim 11, wherein the first conductivity type cladding layer is formed of an AlGaN mixed crystal. 18. The method of manufacturing a semiconductor laser according to claim 11, wherein the first conductivity type cladding layer is formed of an n-type semiconductor. 19. The method of manufacturing a semiconductor laser according to claim 10, wherein the current confinement layer is made of GaN. 20. The method of manufacturing a semiconductor laser according to claim 10, wherein the current confinement layer is formed of a semiconductor to which impurities are not added.