JP2002329932A - Nitride iii-v compound semiconductor laser element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride III-V compound semiconductor laser element and a manufacturing method therefor which has a flatter resonator end face than a conventional one and a low threshold current. SOLUTION: The GaN type semiconductor laser element 40 has the same constitution as the conventional one, except the constitution of a seed crystal layer 42 which is a stripe type seed crystal layer of AlXGa1- XN (0<X<=1, e.g. X=0.08) in the form of a stripe ridge structure making an angle of 30 deg. to cracks grown in the AlGaN layer forming a seed crystal layer. The semiconductor laser element has a resonator end face formed perpendicularly to the laser stripe direction, the stripe direction of the crystal layer 42. This layer 42 is formed in an accurate orientation relative to a reference line. Hence, the resonator end face is smoother and flatter cleavage plane than the conventional GaN type semiconductor laser element 10, and the threshold current is also low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a nitride-based III-V
More specifically, the present invention relates to a nitride-based III-V compound semiconductor laser device having a flat cavity facet and a low threshold current, and a method of making the cavity facet uniform in-plane. And a method for manufacturing a nitride-based III-V compound semiconductor laser device.

[0002]

2. Description of the Related Art A nitride-based III-V compound semiconductor laser device (hereinafter simply referred to as a nitride-based semiconductor laser device) is generally used because it is difficult to obtain an economical GaN substrate. , Sapphire substrate, SiC, S
i, spinel, etc. Conventionally, when forming a nitride-based semiconductor laser device on a sapphire substrate, a laterally grown stripe-shaped seed crystal layer is formed with reference to the orientation flat of the sapphire substrate, and then a stripe-shaped seed crystal layer is formed. A laser stripe is formed in parallel. Next, cleavage is performed perpendicularly to the laser stripe to form an end face of the resonator, thereby manufacturing a nitride-based semiconductor laser device.

Here, an example of a typical structure of a nitride-based semiconductor laser device will be described with reference to FIG. 6, and a main part of a manufacturing method thereof will be described with reference to FIGS. 7 and 8. . FIG. 6 is a sectional view showing a typical configuration of a GaN-based semiconductor laser device. 7 (a) to 7 (d) and FIG. 8 are cross-sectional views for respective steps when fabricating a GaN-based semiconductor laser device according to a conventional method. The nitride-based semiconductor laser device 10 is a GaN-based semiconductor laser device, as shown in FIG. 6, on a c-plane of a sapphire substrate 12, or via a low-temperature-grown GaN buffer layer.
GaN seed crystal layer 14, n-type GaN contact layer 16, n-type AlGaN cladding layer 18, n-type Ga
N light guide layer 20, active layer 22, p-type GaN light guide layer 24, p-type AlGaN cladding layer 26, and p-type GaN
It has a laminated structure in which the contact layers 28 are sequentially laminated.

The upper layer of the p-type AlGaN cladding layer 26 and the p-type GaN contact layer 28 are formed as ridge stripes extending in one direction in the form of a ridge stripe. Further, an upper layer portion of the n-type GaN contact layer 16, n
-Type AlGaN cladding layer 18, n-type GaN optical guide layer 2
The lower layers of the active layer 22, the p-type GaN light guide layer 24, and the p-type AlGaN cladding layer 26 are formed as mesa portions extending in the same direction as the ridge stripe portion. Further, the GaN seed crystal layer 14 is formed as an uneven structure extending in the same direction as the extending direction of the ridge stripe portion and the mesa portion, and the ridge stripe portion is provided between two convex portions of the uneven structure.

[0005] The ridge stripe portion, the mesa portion, and the n-type GaN contact layer 16 beside the mesa portion, except for the openings 30a and 30b provided on the upper surface of the ridge stripe portion and a partial region of the n-type GaN contact layer 16, respectively. And Si
It is covered with a protective film 30 made of an O ₂ film. p-type Ga
Pd is formed on the N contact layer 28 through the opening 30a.
A p-side electrode 32 of a multilayer metal film such as a / Pt / Au electrode is provided as an ohmic junction electrode.
Ti / Ti is formed on the contact layer 16 through the opening 30b.
N-side electrode 3 of a multilayer metal film such as an Al / Pt / Au electrode
4 is provided as an ohmic junction electrode.

When manufacturing the above-mentioned GaN-based semiconductor laser device 10, first, as shown in FIG. 7A, a metalorganic chemical vapor deposition (MO) is performed on a c-plane sapphire substrate 12.
The GaN seed crystal layer 14 is grown by a CVD method. G
GaN on sapphire substrate 12 via aN buffer layer
When growing the seed crystal layer 14, the sapphire substrate 12
A GaN buffer layer is grown at a low temperature by MOCVD, and a GaN seed crystal layer 14 is subsequently formed on the GaN buffer layer. Here, the substrate is once taken out from the MOCVD apparatus, and a predetermined stripe-shaped protection mask 15 extending in a direction orthogonal to the orientation flat of the wafer is placed on the GaN seed crystal layer 14 as shown in FIG. Formed.

Subsequently, as shown in FIG. 7C, the GaN seed crystal layer 14 is etched by reactive ion etching (RIE) using the protective mask 15, and after the etching, the mask is removed. Thereby, as shown in FIG. 7D, the GaN seed crystal layer 1 is formed on the sapphire substrate 12.
4 are formed.

[0008] The substrate is returned to the MOCVD apparatus again, and under the growth conditions of a high lateral growth rate, an n-type GaN contact layer 16 is formed on the GaN seed crystal layer 14 having the projections and depressions as shown in FIG. A n-type AlGaN cladding layer 18, an n-type GaN light guide layer 20, an active layer 22,
The p-type GaN optical guide layer 24, the p-type AlGaN cladding layer 26, and the p-type GaN contact layer 28 are sequentially laminated to form a laminated structure. Subsequently, the laminated structure is etched to form a stripe-shaped ridge portion and a mesa structure,
A protective film 30 is formed, and a p-side electrode 32 and an n-side electrode 34 are formed. Next, the wafer is divided into bars by cleavage along a plane orthogonal to the stripe-shaped ridge portion, and further divided in parallel to the stripe-shaped ridge portion, whereby the GaN-based semiconductor laser device 10 shown in FIG. 6 can be manufactured. .

[0009]

However, since the sapphire substrate has poor cleavage properties, it is difficult to cleave the sapphire substrate so as to form a smooth and flat cleavage plane. Often face. If the cavity facets are not smooth, the threshold current tends to increase as a result of reduced facet reflectivity. In addition, in the above-described conventional method for manufacturing a nitride-based semiconductor laser device, the cleavage plane serving as the cavity end face has a stripe-shaped ridge in a direction orthogonal to the orientation flat with respect to the orientation flat having low angular accuracy. Since it is formed and cleaved, the flatness of the cavity end face often varies from wafer to wafer and further within the plane. As a result, there is a problem that the threshold current varies and increases. For example, the accuracy of the orientation flat is at most about ± 2 ° with respect to the surface A of the sapphire substrate. In this case, it is difficult to obtain a flat cleaved surface without dispersing the uniformity in the plane or even between the wafers.

SUMMARY OF THE INVENTION An object of the present invention is to provide a nitride III-V compound having a flat resonator facet and a lower threshold current than conventional ones without depending on the angular accuracy of the orientation flat of the sapphire substrate. An object of the present invention is to provide a semiconductor laser device and a manufacturing method thereof.

[0011]

Means for Solving the Problems In the course of research for solving the above problems, the present inventor has made AlGaN on a sapphire substrate.
Layer or AlN layer is grown epitaxially,
It was noted that cracks were generated in the direction perpendicular to the sapphire substrate along the crystal plane of the aN layer or AlN layer. Al
Since the crystal planes of the GaN layer and the AlN layer are formed in a certain direction with respect to the plane direction of the sapphire substrate, they can be very strict reference lines. Moreover, cracks grow to the surface of the AlGaN layer and the Al layer and appear on the surface as crack lines, so that it is easy to confirm. Therefore, for example, AlGa
When growing the N layer, a stripe-shaped seed crystal layer is formed based on cracks generated in the AlGaN layer, and a laser stripe is formed along the stripe-shaped seed crystal layer.
The idea was to cleave perpendicularly to the laser stripe to form the cavity end face uniformly without changing for each wafer. Then, based on the idea, the inventor repeated experiments and came to invent the present invention.

In order to achieve the above object, based on the above findings, a nitride III-V compound semiconductor laser device according to the present invention (hereinafter referred to as a first invention) is formed on a substrate. In the nitride-based III-V compound semiconductor laser device, Al _X Ga _{1 -X} N (0 <X ≦) formed on the substrate or formed on the substrate via a buffer layer.
1, hereinafter referred to as AlGaN), or a stripe-shaped seed crystal layer having an AlGaN layer as an uppermost layer, and a nitride-based seed crystal layer formed on the seed crystal layer and constituting a resonator structure. A stacked structure of a group III-V compound semiconductor layer, a laser stripe formed along the seed crystal layer, and a resonator end face composed of a cleavage plane cleaved perpendicular to the laser stripe, wherein the seed crystal layer has It is characterized in that it is formed as a stripe-shaped ridge structure at a predetermined angle with respect to cracks generated in the AlGaN layer constituting the seed crystal layer.

In the first invention, the seed crystal layer is made of AlGaN
It may be a multilayer film having an AlGaN layer as the uppermost layer, for example, a two-layer film of a GaN layer and an AlGaN layer. AlGa as a two-layer film of a GaN layer and an AlGaN layer
By reducing the thickness of the N layer, the number of cracks in the seed crystal layer can be suppressed. Here, AlGaN
The layer is an Al _x Ga ₁ -xN (0 <X ≦ 1) layer,
= 1 when the AlN layer is included.

Another nitride-based III-V compound semiconductor laser device according to the present invention (hereinafter, referred to as a second invention) is a nitride-based III-V compound semiconductor laser device formed on a substrate. A GaN layer having a superlattice structure formed on a substrate or formed on a substrate via a buffer layer, and an Al _x Ga _1-x film formed on the GaN layer, respectively.
A N-type (0 <X ≦ 1, hereinafter referred to as AlGaN) layered superlattice laminated film in which a two-layer film is laminated in a large number of periods; a stripe-shaped seed crystal layer; and a resonator formed on the seed crystal layer. The laminated structure of the nitride III-V compound semiconductor layers constituting the structure, the laser stripe formed along the seed crystal layer, and the cavity end face composed of a cleavage plane cleaved orthogonal to the laser stripe are formed. And wherein the seed crystal layer is formed as a stripe-shaped ridge structure that forms a predetermined angle with a crack generated in the AlGaN layer that forms the seed crystal layer.

In the second invention, since the seed crystal layer is formed of a superlattice laminated film having a large number of periods, each layer of the laminated structure formed on the seed crystal layer is flattened, and the surface of each layer has undulations ( Or a wavefront), so that the laser characteristics are improved.
Further, since the seed crystal layer is formed in a superlattice structure, crystal defects such as dislocations in the seed crystal layer are small, and even if dislocations are present, it is difficult to propagate to the upper part of the seed crystal layer. The effect on the laminated structure on the layer is small.

The method for fabricating a nitride III-V compound semiconductor laser device according to the present invention (hereinafter referred to as the first invention method) comprises fabricating a nitride III-V compound semiconductor laser device on a substrate. In this method, Al _x Ga ₁ -xN (0 <X ≦ N) is formed on the substrate or on the substrate via a buffer layer.
1, hereinafter referred to as AlGaN) layer or AlGaN
A growth step of epitaxially growing a laminated film having a layer as an uppermost layer, and patterning the AlGaN layer so as to form a stripe-shaped ridge structure forming a predetermined angle with respect to cracks generated in the AlGaN layer. Forming a seed crystal layer or a seed crystal layer composed of a laminated film having an AlGaN layer as an uppermost layer, and laminating a nitride III-V compound semiconductor layer constituting a resonator structure on the seed crystal layer The method is characterized by including a step of forming a structure, a step of forming a laser stripe along the seed crystal layer, and a step of cleaving perpendicular to the laser stripe to form a cavity end face.

In the first invention method, the seed crystal layer is made of AlG
An aN layer alone may be used, or a multilayer film having an AlGaN layer as the uppermost layer, for example, a two-layer film of a GaN layer and an AlGaN layer may be used. Furthermore, if the layer on the AlGaN layer is transparent,
The GaN layer need not necessarily be on the top layer. Here, the AlGaN layer is made of Al _x Ga ₁ -xN (0 <X ≦ 1).
This is a concept including an AlN layer when X = 1. In the first invention method, since the stripe-shaped seed crystal layer is formed on the basis of a crack line having a constant orientation, the cavity end face has the same plane orientation in the wafer plane and further over the entire target wafer. Since the cleavage plane is uniform, the threshold current does not vary. Further, since the cavity end face is formed by a smooth and flat cleavage plane, the threshold current can be reduced.

The striped seed crystal layer may be formed as a seed crystal layer having a super lattice structure. In that case, in the step of epitaxially growing the AlGaN layer, a superlattice laminated film is formed by laminating a two-layer film of a GaN layer and an AlGaN layer each having a superlattice structure in a large number of cycles, and a seed crystal layer is formed. In the step, the superlattice laminated film is patterned so as to form a stripe-shaped ridge structure at a predetermined angle with respect to a crack generated in the AlGaN layer, thereby forming a seed crystal layer made of the superlattice laminated film. By forming the seed crystal layer into a superlattice laminated film, each layer of the laminated structure formed on the seed crystal layer can be flattened, and the surface of each layer can be made free from undulation (or wavefront). Is improved. Further, by forming the seed crystal layer as a superlattice structure, the occurrence of crystal defects such as dislocations in the seed crystal layer is suppressed,
Even if it occurs, propagation to the upper portion of the seed crystal layer can be suppressed.

Further, another nitride III-V according to the present invention
A method for manufacturing a group III compound semiconductor laser (hereinafter, referred to as a second invention method) is a method for manufacturing a nitride III-V compound semiconductor laser element on a substrate, the method comprising: forming a substrate on a substrate or via a buffer layer; On top, a GaN layer, then Al _{X
Ga 1- X N (0 <X} ≦ 1, hereinafter referred to as AlGaN) and epitaxially growing a layer, AlGaN
The GaN layer and the Al are formed so as to form a stripe-shaped ridge structure at a predetermined angle with respect to cracks generated in the layer.
The GaN layer and A
forming a seed crystal layer composed of an lGaN layer, etching the AlGaN layer from the seed crystal layer, and removing;
Forming a stacked structure of a nitride III-V compound semiconductor layer constituting a resonator structure on the seed crystal layer, forming a laser stripe along the seed crystal layer, and orthogonally intersecting the laser stripe. Cleaving and forming a resonator end face.

In the second invention method, since the seed crystal layer is formed only of the GaN layer, the number of cracks in the seed crystal layer is significantly reduced, stable operation can be performed for a long time, and excellent laser characteristics are obtained. A nitride-based III-V compound semiconductor laser device can be manufactured. In the second invention method, as in the first invention method, since the stripe-shaped seed crystal layer is formed with reference to the crack line having a constant orientation, the cavity end face is further formed within the wafer plane. Since a uniform cleavage plane having the same plane orientation is obtained over the entire target wafer, the threshold current does not vary. Further, since the cavity end face is formed by a smooth and flat cleavage plane, the threshold current can be reduced.

In the first and second inventions and the invention method, Al
The cracks in the GaN layer grow in a certain direction depending on the plane orientation of the substrate surface of the sapphire substrate. For example, when an AlGaN layer is formed on the C-plane of the sapphire substrate, the cracks are less than <1-- 100> occurs in the azimuth. When the orientation flat of the sapphire substrate is provided along the A-plane, the AlGa
When the N layer is formed, cracks grow at an angle of about 60 ° with respect to the orientation flat. Therefore, when the stripe-shaped seed crystal layer is formed at an angle of 30 ° with respect to the crack, the direction becomes orthogonal to the orientation flat, which is convenient in manufacturing.

Al_XGa_1-XAl of N (0 <X ≦ 1) layer
The composition is preferably between 0.03 and 0.20. Also,
The nitride-based III-V compound semiconductor layer is widely referred to as Al_a
B_bGa_cIn _dN (a + b + c + d = 1, 0 ≦ a,
b, c, d ≦ 1) means a layer. First and second inventions
And the invention method comprises a sapphire substrate, a SiC substrate, a GaN-based
It can be applied when using a substrate such as a plate or a spinel substrate. Ma
Further, the first and second inventions and the invention method are characterized in that they have a stripe shape.
It has a feature in the direction of the seed crystal layer,
Of laminated structure, laser stripe, etc. on the seed crystal layer
Has no restrictions. Laser stripes are
Non-ridged internal switches
A tripe structure may be used. There are no restrictions on the waveguide structure.
Alternatively, a refractive index waveguide structure or a gain waveguide structure may be used. Ma
The lower structure of the stripe-shaped seed crystal layer is not limited.
That is, the AlG is formed on the sapphire substrate via the buffer layer.
When forming the aN seed crystal layer, the buffer layer
Of the sapphire substrate
To the lower part of the ridge structure.
A gap may be provided between the structure. In addition,
Even if the wafer layer is omitted, the seed crystal layer is etched and
When forming a tripe-shaped seed crystal layer, the surface of the sapphire substrate
Etch the layer to the bottom of the ridge structure and sapphire
A gap may be provided between the substrate and the laminated structure.
No.

[0023]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, the film type, film thickness,
The film forming method, other dimensions, and the like are examples for facilitating the understanding of the present invention, and the present invention is not limited to these examples. Embodiment 1 of the Nitride-Based Semiconductor Laser Device This embodiment is an embodiment of the nitride-based III-V compound semiconductor laser device according to the first invention (hereinafter referred to as a nitride-based semiconductor laser device). As an example, FIG. 1 is a cross-sectional view showing a configuration of a nitride-based semiconductor laser device of the present embodiment. In FIG. 1, the same components as those shown in FIGS. 6 to 8 are denoted by the same reference numerals. 2 to 5 below,
The same is true. The nitride-based semiconductor laser device 40 according to the present embodiment is a GaN-based semiconductor laser device, and as shown in FIG. It has the same configuration as.

The seed crystal layer 42 is formed of a 0.1 μm-thick Al _X
Ga _1−X N (0 <X ≦ 1, for example, X = 0.08, hereinafter,
(Referred to as AlGaN) layer, and a crack generated in the AlGaN layer constituting the seed crystal layer is defined as a reference line, and is 30 ° with respect to the reference line.
Is formed as a stripe-shaped ridge structure having an angle of.

In this embodiment, the cavity facet is formed perpendicular to the laser stripe, ie, the stripe direction of the seed crystal layer 42, and the seed crystal layer 42 is formed in an accurate direction with respect to the reference line. Therefore, the cavity end face becomes a smooth and flat cleavage plane as compared with the conventional GaN-based semiconductor laser device 10, and the threshold current is low.

Actual method of manufacturing a nitride-based semiconductor laser device
Embodiment 1 In this embodiment, a method for manufacturing a nitride-based semiconductor laser device according to the first invention method is described by using a GaN-based semiconductor laser device 40.
1 is an example of an embodiment applied to the manufacture of the present invention. FIGS. 2A to 2D respectively show G according to the method of the present embodiment.
FIG. 6 is a cross-sectional view of each step when manufacturing the aN-based semiconductor laser element 40. In the method of this embodiment, first, FIG.
As shown in (a), M is placed on the C surface of the sapphire substrate 12.
The Al _0.08 Ga _0.92 N layer (hereinafter referred to as Al
GaN layer) is epitaxially grown as a seed crystal layer. The thickness of the AlGaN layer 42 is, for example, 0.5
It may be from 2 μm to 2 μm. Next, an SiO ₂ film is formed on the AlGaN layer 42 grown as a seed crystal layer,
_{The two} films are patterned to form an etching mask 44 having a predetermined stripe pattern, as shown in FIG.

As shown in FIG. 3, the stripe direction of the etching mask 44 is such that a crack line formed by growing a crack generated in the AlGaN layer 42 is used as a reference line.
It forms an angle Φ of 30 ° with respect to the reference line. The crack line is the wafer orientation flat (OF)
Extends in a direction inclined at an angle θ of about 60 °, the etching mask 44 is arranged in a direction substantially orthogonal to the orientation flat.

Using the etching mask 44, the AlGaN layer 42 is etched by the RIE method, as shown in FIG.
As shown in FIG. 7, a stripe-shaped ridge is formed. After removing the etching mask 44, as shown in FIG. 2D, a GaN layer 16 'to be the n-type contact layer 16 is grown on the stripe-shaped ridge by a lateral growth method. FIG. 2D shows the progress of the lateral growth of the GaN layer 16 '.

Subsequently, in the same manner as in the conventional method of manufacturing a nitride-based semiconductor laser device, a contact layer, a clad layer, an optical guide layer, an active layer, and the like are sequentially formed to form a laminated structure constituting a resonator structure. I do. Next, the laminated structure is etched to form a laser stripe along the stripe-shaped seed crystal layer, and is cleaved in a direction perpendicular to the laser stripe to form a cavity end face. In the present embodiment, since the various crystal layers 42 are formed in an accurate orientation with respect to the reference line, the crystal layers are uniform in the plane, and do not vary from wafer to wafer.
The nitride-based semiconductor laser device according to the embodiment having a flat cavity end face and a low threshold current can be manufactured.

Embodiment 2 of the Nitride-Based Semiconductor Laser Device This embodiment is an example of an embodiment of the nitride-based semiconductor laser device according to the second invention, and FIG. FIG. 2 is a cross-sectional view illustrating a configuration of a nitride-based semiconductor laser device. The nitride-based semiconductor laser device 50 of the present embodiment is
A GaN-based semiconductor laser device, as shown in FIG.
It has the same configuration as that of the system semiconductor laser device 10.

The seed crystal layer 52 includes, for example, a 2.5-nm-thick GaN layer 52a and a 2.5-nm-thick Al _x Ga ₁ -xN
(0 <X ≦ 1, for example, X = 0.08, hereinafter, AlGaN
The two-layer film with the layer 52b is changed from 100 periods to 20 periods.
An AlGaN layer 5 that is a stripe-shaped seed crystal layer of a superlattice multilayer film stacked in zero cycle and that forms the seed crystal layer 52
It is formed as a stripe-shaped ridge structure forming an angle of 30 ° with the crack generated in 2b. The nitride-based semiconductor laser device 50 of the present embodiment is obtained by forming the above-described superlattice multilayer film instead of forming the AlGaN layer 42 by the method of manufacturing the nitride-based semiconductor laser device of the above-described first embodiment. By doing so, it can be manufactured.

In this embodiment, the cavity facets are formed perpendicular to the laser stripe, ie, the stripe direction of the seed crystal layer 52. Since the seed crystal layer 52 is formed in an accurate orientation with respect to the reference line, the cavity facet is a smooth and flat cleavage plane as compared with the conventional GaN-based semiconductor laser device 10, and the threshold current is reduced. Low. Further, since the seed crystal layer 52 is a superlattice laminated film, each compound semiconductor layer having a laminated structure formed on the seed crystal layer 52 is flattened,
Since there is no undulation (or wavefront) on the surface of each compound semiconductor layer, laser characteristics are improved.

The actual method of manufacturing a nitride-based semiconductor laser device
Embodiment 2 This embodiment is an embodiment in which the method of manufacturing a nitride-based semiconductor laser device according to the second invention method is applied to manufacture of a GaN-based semiconductor laser device having the same configuration as the conventional GaN-based semiconductor laser device 10. It is an example of a form. 5 (a) to 5 (e)
FIGS. 4A to 4C are cross-sectional views for respective steps when manufacturing a GaN-based semiconductor laser device having the same configuration as the GaN-based semiconductor laser device 10 according to the method of the present embodiment. In the method of this embodiment, first, as shown in FIG. 5A, a film having a thickness of 1 is formed on the C surface of the sapphire substrate 12 by MOCVD.
μm GaN layer 54 and then 1 μm thick Al _0.08 Ga
_{A 0.92} N layer (hereinafter referred to as an AlGaN layer) 56 is epitaxially grown as a seed crystal layer.

Next, an SiO ₂ film is formed on the AlGaN layer 56, and the SiO ₂ film is patterned, as shown in FIG.
As shown in FIG. 7, an etching mask 58 having a predetermined stripe pattern is formed. As shown in FIG. 3, the stripe direction of the etching mask 58 forms an angle Φ of 30 ° with respect to the reference line when a crack line formed by growing a crack generated in the AlGaN layer 56 is used as a reference line. . Since the crack line extends in a direction inclined at an angle θ of about 60 ° with respect to the orientation flat of the wafer, the etching mask 58 is arranged in a direction substantially orthogonal to the orientation flat. .

Using the etching mask 58, the AlGaN layer 56 and the GaN layer 54 are etched by the RIE method to form a stripe-shaped ridge as shown in FIG. After removing the etching mask 58, FIG.
As shown in (d), the AlGaN layer 56 is formed by the RIE method.
Is removed to form a seed crystal layer consisting only of the GaN layer 54. Subsequently, as shown in FIG. 5E, a GaN layer 16 'serving as the n-type contact layer 16 is grown on the stripe-shaped ridge by a lateral growth method. In addition, FIG.
The middle part of the lateral growth of the aN layer 16 'is shown.

Thereafter, in the same manner as in the conventional method of manufacturing a nitride-based semiconductor laser device, a contact layer, a clad layer, an optical guide layer, an active layer and the like are sequentially formed to form a laminated structure constituting a resonator structure. I do. Next, the laminated structure is etched to form a laser stripe along the stripe-shaped seed crystal layer, and is cleaved in a direction perpendicular to the laser stripe to form a cavity end face.

In this embodiment, since the various crystal layers 52 are formed in an accurate orientation with respect to the reference line, the crystal layers 52 have a flat resonator end face that is uniform in the plane and does not vary from wafer to wafer. Thus, a nitride-based semiconductor laser device according to the embodiment having a low threshold current can be manufactured. Further, since the AlGaN layer 56 having the cracks has been removed, the number of cracks existing in the seed crystal layer is significantly smaller than that in the manufacturing method of the first embodiment.

[0038]

According to the present invention, according to the present invention, A
A seed crystal layer is formed as a stripe-shaped ridge structure at a predetermined angle with respect to cracks generated in the lGaN layer, and a cleavage plane cleaved at a plane orthogonal to a laser stripe formed along the seed crystal layer resonates. Nitride based material with a smooth cavity facet and low threshold current
A III-V compound semiconductor laser device is realized. The method of the present invention has a flat resonator end face according to the present invention,
A method for fabricating a nitride III-V compound semiconductor laser device having a low threshold current, which is uniform in a plane and does not vary from wafer to wafer, is realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a GaN-based semiconductor laser device according to a first embodiment.

2 (a) to 2 (d) are cross-sectional views for respective steps when fabricating a GaN-based semiconductor laser device according to the method of Embodiment 1;

FIG. 3 is a plan view of a wafer showing a positional relationship between a crack line and an etching mask.

FIG. 4 is a cross-sectional view illustrating a configuration of a GaN-based semiconductor laser device according to a second embodiment.

5 (a) to 5 (e) are cross-sectional views for respective steps when fabricating a GaN-based semiconductor laser device according to the method of Embodiment 2;

FIG. 6 is a sectional view showing a typical configuration of a GaN-based semiconductor laser device.

FIGS. 7A to 7D are cross-sectional views for respective steps when fabricating a GaN-based semiconductor laser device according to a conventional method.

FIG. 8 is a cross-sectional view of each step of manufacturing a GaN-based semiconductor laser device according to a conventional method, following FIG. 7 (d).

[Explanation of symbols]

10: GaN-based semiconductor laser device, 12: sapphire substrate, 14: GaN seed crystal layer, 16: n-type GaN
Contact layer, 18 n-type AlGaN cladding layer, 2
0 ... n-type GaN light guide layer, 22 ... active layer, 24 ...
... p-type GaN optical guide layer, 26 ... p-type AlGaN cladding layer, 28 ... p-type GaN contact layer, 30 ... S
iO ₂ protective film, 32... p-side electrode, 34.
40... The GaN-based semiconductor laser device of the first embodiment, 4
2 ... AlGaN seed crystal layer, 44 ... etching mask, 50 ... GaN-based semiconductor laser device of Embodiment 2, 52 ... superlattice formed by laminating a two-layer film of a GaN layer and an AlGaN layer in a large number of periods Laminated film, 54 GaN layer, 5
6 ... AlGaN layer, 58 ... Etching mask.

Claims (7)

[Claims] 1. A nitride III-V compound semiconductor laser device formed on a substrate, comprising: Al _X Ga _{1 -X} formed on the substrate or formed on the substrate via a buffer layer. N (0 <X ≦ 1, hereinafter, A
and a stripe-shaped seed crystal layer having an AlGaN layer as an uppermost layer; and a nitride-based layer formed on the seed crystal layer and constituting a resonator structure.
A stacked structure of III-V compound semiconductor layers, a laser stripe formed along the seed crystal layer, and a cavity end face formed by a cleavage plane cleaved perpendicular to the laser stripe; A nitride-based III-V compound semiconductor laser device having a stripe-shaped ridge structure formed at a predetermined angle with respect to a crack generated in an AlGaN layer constituting a seed crystal layer. 2. A nitride-based III-V compound semiconductor laser device formed on a substrate, wherein each of the nitride-based III-V compound semiconductor laser devices has a superlattice structure formed on the substrate or formed on the substrate via a buffer layer. GaN layer and G
Al _x Ga ₁ -xN formed on the aN layer (0 <X ≦ 1,
(Hereinafter abbreviated as AlGaN)), a stripe-shaped seed crystal layer composed of a superlattice laminated film obtained by laminating a two-layer film with a large number of periods, and a nitride-based layer formed on the seed crystal layer and constituting a resonator structure.
A stacked structure of III-V compound semiconductor layers, a laser stripe formed along the seed crystal layer, and a cavity end face formed by a cleavage plane cleaved perpendicular to the laser stripe; A nitride-based III-V compound semiconductor laser device having a stripe-shaped ridge structure formed at a predetermined angle with respect to a crack generated in an AlGaN layer constituting a seed crystal layer. 3. The nitride-based II according to claim 1, wherein the predetermined angle is 30 ° or 90 °.
Group IV compound semiconductor laser device. 4. A method of fabricating a nitride III-V compound semiconductor laser device on a substrate, comprising the steps of: forming an Al _X G on a substrate or on a substrate via a buffer layer;
a _1-X N (0 <X ≦ 1, hereinafter referred to as AlGaN)
A step of epitaxially growing a layer or a laminated film having an AlGaN layer as an uppermost layer; and forming an AlG layer so as to form a stripe-shaped ridge structure at a predetermined angle with respect to cracks generated in the AlGaN layer.
patterning the aN layer to form a seed crystal layer made of an AlGaN layer or a seed crystal layer made of a laminated film having an AlGaN layer as an uppermost layer; and a nitride forming a resonator structure on the seed crystal layer System III-V
Forming a stacked structure of group compound semiconductor layers, forming a laser stripe along the seed crystal layer, and cleaving perpendicular to the laser stripe to form a cavity facet. Of producing a nitride III-V compound semiconductor laser device. 5. In the growing step, a superlattice laminated film is formed by laminating a two-layer film of a GaN layer and an AlGaN layer each having a superlattice structure in a large number of cycles, and in the step of forming a seed crystal layer, Patterning the superlattice laminated film so as to form a stripe-shaped ridge structure at a predetermined angle with respect to cracks generated in the layer, thereby forming a seed crystal layer composed of the superlattice laminated film. A method for manufacturing a nitride III-V compound semiconductor laser device according to claim 4. 6. A method of fabricating a nitride III-V compound semiconductor laser device on a substrate, comprising: forming a GaN film on the substrate or on the substrate via a buffer layer.
Layer, followed by _{Al X Ga 1- X N (0} <X ≦ 1, or less, Al
A step of epitaxially growing a layer (denoted as GaN); and forming a GaN layer into a stripe-shaped ridge structure at a predetermined angle with respect to cracks generated in the AlGaN layer.
Patterning the layered film of the AlGaN layer and the AlGaN layer to obtain Ga
Forming a seed crystal layer composed of an N layer and an AlGaN layer; etching and removing the AlGaN layer from the seed crystal layer; and a nitride III-V compound forming a resonator structure on the seed crystal layer Forming a stacked structure of semiconductor layers, forming a laser stripe along the seed crystal layer, and cleaving perpendicular to the laser stripe to form a cavity facet. A method for manufacturing a nitride III-V compound semiconductor laser device. 7. The method for manufacturing a nitride III-V compound semiconductor laser device according to claim 4, wherein said predetermined angle is 30 ° or 90 °.