JP2002353134A - Nitride based semiconductor element and method for forming nitride based semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a nitride based semiconductor in which dislocation can be reduced in both longitudinal and lateral directions. SOLUTION: The method for forming a nitride based semiconductor comprises a step for forming a facet of second GaN layer 5 on the upper surface of a first GaN layer 3 by growing the second GaN layer 5 selectively in the lateral direction, a step for forming a superlattice layer 6 having a periodic structure, where two layers having different lattice constant are laid alternately, on the surface of the facet, and a step for growing a third GaN layer 7 selectively in the lateral direction on the superlattice layer 6 formed on the surface of the facet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-based semiconductor device and a method for forming a nitride-based semiconductor, and more particularly to a nitride including a nitride-based semiconductor layer formed using selective lateral growth. The present invention relates to a method for forming a nitride semiconductor device and a nitride semiconductor.

[0002]

2. Description of the Related Art In recent years, as a semiconductor element used for a semiconductor light emitting element such as a light emitting diode element and an electronic element such as a transistor, a semiconductor element using a GaN-based compound semiconductor has been actively developed. Such GaN
Since it is difficult to manufacture a substrate made of GaN when manufacturing a system-based semiconductor element, a GaN-based semiconductor layer is epitaxially grown on a substrate made of sapphire, SiC, Si, GaAs, or the like.

In this case, a substrate such as sapphire and GaN
Since GaN-based semiconductor layers grown on a substrate such as sapphire have threading dislocations (lattice defects) extending vertically from the substrate, since the lattice constants of the GaN-based semiconductor layers are different. Such dislocations in the GaN-based semiconductor layer cause deterioration of device characteristics and reliability of the semiconductor device.

Therefore, as a method of reducing dislocations in the GaN-based semiconductor layer as described above, conventionally, selective lateral growth (ELO: Epitaxial Lateral) has been proposed.
Overgrowth) has been proposed.

As an example of a conventional method of forming a GaN-based semiconductor layer using selective lateral growth, for example, a GaN-based semiconductor layer having a thickness of about 20 nm on a sapphire substrate at a growth temperature of about 500 ° C. to about 600 ° C. Al _x Ga _1-x N (0 ≦ x ≦ 1)
After growing the buffer layer consisting of GaN, the substrate temperature is raised to about 1000 ° C., and a base of GaN having a thickness of about 1 μm to about 2 μm is grown on the buffer layer. The dislocation density of this underlayer is about 1.0 × 10 ⁹ cm ⁻² . Then, on the base, SiO ₂ or SiN
A GaN layer is selectively laterally grown from the exposed portion of the base at a growth temperature of about 1000 ° C. by providing a stripe-shaped mask for selective growth made of, for example,. As a result, the dislocations are bent in the lateral direction, and the dislocation density is 6.0 × 1 as a whole.
A GaN layer reduced to about 0 ⁷ cm ^-2 is formed.

[0006]

In the above-described conventional method for forming a nitride semiconductor using selective lateral growth, the density of threading dislocations reaching the surface of the GaN layer is obtained by bending the vertical dislocations in the horizontal direction. Was reduced. However, when the GaN layer is grown to a required thickness as a GaN substrate, dislocations bent in the horizontal direction are propagated in the vertical direction again, and vertical dislocations that are not bent in the horizontal direction remain. Thus, in the conventional method of forming a nitride-based semiconductor using selective lateral growth, the dislocation density is reduced to 1%.
It was difficult to make it smaller than × 10 ⁶ cm ⁻³ .

In the above-described conventional method of forming a nitride-based semiconductor using selective lateral growth, only vertical dislocations are bent in the horizontal direction, and the horizontal dislocations remain. And holes will move across the lateral dislocations. Therefore, the electrons and holes are scattered from the dislocations when crossing the dislocations, so that the vertical mobilities of the electrons and holes are reduced. This causes a disadvantage that the resistivity in the vertical direction increases.
As described above, when the resistivity in the vertical direction increases, there is a problem in that the light emission characteristics of the light emitting element are deteriorated due to heat generated by the current flowing in the vertical direction.

[0008] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide:
An object of the present invention is to provide a method for forming a nitride-based semiconductor capable of reducing dislocations in both the vertical and horizontal directions.

Another object of the present invention is to provide a nitride semiconductor device having good device characteristics including a nitride semiconductor layer in which dislocations in both the vertical and horizontal directions are reduced.

[0010]

According to one aspect of the present invention, there is provided a method of forming a nitride-based semiconductor, comprising the steps of:
Forming a facet made of the first nitride-based semiconductor layer by selectively laterally growing the nitride-based semiconductor layer; and forming a facet having a different lattice constant on the surface of the facet.
Forming a superlattice layer having a periodic structure in which two layers are alternately stacked; and selectively growing a second nitride-based semiconductor layer in the lateral direction on the superlattice layer formed on the facet surface. It has.

In the method for forming a nitride-based semiconductor according to this aspect, a superstructure having a periodic structure in which two layers having different lattice constants are alternately stacked on a facet which is a slip surface through which dislocations easily propagate is provided. By forming the lattice layer, the dislocations bent laterally by the facets are more easily bent in a direction parallel to the direction in which the superlattice layer extends, due to the interface stress generated by the lattice mismatch of the superlattice layer. Accordingly, dislocations bent in a direction parallel to the direction in which the superlattice layer extends collide with each other, so that the dislocations are likely to be coupled or eliminated, so that lateral dislocations can be reduced. For this reason, the mobility of electrons and holes in the vertical direction can be improved, and the resistivity in the vertical direction can be reduced. As a result, heat generation due to vertical energization can be suppressed, so that the light emission characteristics of the light emitting element can be prevented from deteriorating. In addition, by selectively laterally growing the second nitride-based semiconductor layer on the superlattice layer in which lateral dislocations have been reduced, longitudinal dislocations can be further reduced. As a result, a nitride-based semiconductor layer in which dislocations in both the vertical direction and the horizontal direction are reduced can be formed.

In the method for forming a nitride-based semiconductor according to the one aspect, preferably, the first nitride-based semiconductor layer comprises:
GaN, _{and, Al a B b In c Tl} d Ga 1-abcd N
(0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, 0 ≦ d <1,
comprise any of a + b + c + d < 1), the second nitride semiconductor layer, GaN, _{and, Al e B f In g Tl} h Ga
_1-efgh N (0 ≦ e <1, 0 ≦ f <1, 0 ≦ g <1,
0 ≦ h <1, e + f + g + h <1),
Superlattice layer is periodic of _{In x Ga 1-x N /} Al y Ga 1-y N
(0 ≦ x <1, 0 ≦ y ≦ 1), periodic In _x Ga _1-x N
/ Al _y Ga _{1- y} N (0 ≦ x ≦ 1, 0 <y ≦ 1) and periodic In _u Al _v Ga _1-uv N / In _x Al _y Ga
_1-xy N (0 ≦ u <1,0 ≦ v <1,0 ≦ x <1,0 ≦
y <1; In _u Al _v lattice constant of the Ga _1-uv N is, an In _x A
including one selected from the group consisting of less) than the lattice constant of the l _y Ga _1-xy N. With this configuration, it is possible to easily cause lattice mismatch in the superlattice layer.

In the above-described method for forming a nitride-based semiconductor, preferably, the step of forming a facet including the substrate and the first nitride-based semiconductor layer includes forming a facet on the upper surface of the substrate. Forming a mask layer so that a portion thereof is exposed, and forming a facet by selectively laterally growing a first nitride-based semiconductor layer on the exposed upper surface of the substrate using the mask layer. The step of selectively growing the second nitride-based semiconductor layer in the lateral direction comprises forming a superlattice layer on the surface of the facet,
Forming a second nitride-based semiconductor layer having a substantially flat surface by selectively growing the nitride-based semiconductor layer in a lateral direction. According to this structure, the first nitride-based semiconductor layer and the second nitride-based semiconductor layer can be formed directly on the substrate without forming an underlayer on the substrate. The total thickness of the layers can be reduced. After forming the superlattice layer on the surface of the facet, the second nitride-based semiconductor layer is selectively grown in the lateral direction, so that the dislocations in the horizontal and vertical directions can be easily reduced.

In the above-described method for forming a nitride-based semiconductor, preferably, the step of forming a facet including the third nitride-based semiconductor layer formed on the substrate and forming the facet made of the first nitride-based semiconductor layer is preferably performed. Forming a mask layer on the surface of the third nitride-based semiconductor layer such that a part of the upper surface of the third nitride-based semiconductor layer is exposed; Forming a facet on the surface of the nitride-based semiconductor layer by selectively growing the first nitride-based semiconductor layer in the lateral direction, and selectively growing the second nitride-based semiconductor layer in the lateral direction. Forming a superlattice layer on the surface of the facet and then selectively laterally growing the second nitride-based semiconductor layer to form a second nitride-based semiconductor layer having a substantially flat surface. Including. With this configuration, the dislocations in the horizontal and vertical directions can be easily reduced.

In this case, preferably, a step of forming a facet by selectively laterally growing the first nitride-based semiconductor layer on the exposed surface of the third nitride-based semiconductor layer using a mask layer. Further exposing a side surface of the third nitride-based semiconductor layer by etching the third nitride-based semiconductor layer using the mask layer as a mask; and exposing the exposed side surface of the third nitride-based semiconductor layer. Forming a facet by selectively growing the first nitride-based semiconductor layer in the lateral direction as the growth interface. According to this structure, the dislocations in the vertical direction of the third nitride-based semiconductor layer are not propagated to the first nitride-based semiconductor layer, so that the dislocations of the first nitride-based semiconductor layer can be further reduced.

In the above-described method for forming a nitride-based semiconductor, preferably, the underlayer includes a substrate having an uneven shape, and the step of forming a facet made of the first nitride-based semiconductor layer is preferably performed on the substrate having the uneven shape. And forming a facet by selectively growing the first nitride-based semiconductor layer in the lateral direction. The step of selectively growing the second nitride-based semiconductor layer in the lateral direction comprises forming a superlattice layer on the surface of the facet. After the formation, the second nitride-based semiconductor layer is selectively laterally grown to form a second nitride semiconductor layer having a substantially flat surface.
Forming a nitride-based semiconductor layer. By using a substrate having such an uneven shape, selective lateral growth of the first nitride-based semiconductor layer can be easily performed without forming a mask layer. After forming the superlattice layer on the surface of the facet, the second nitride-based semiconductor layer is selectively grown in the lateral direction, so that the dislocations in the horizontal and vertical directions can be easily reduced.

In the above-described method of forming a nitride-based semiconductor, preferably, the facet includes a first facet and a second facet, and the superlattice layer includes a first superlattice layer and a second superlattice layer. Forming the lattice layer and selectively growing the second nitride-based semiconductor layer in the lateral direction;
Forming a first superlattice layer on the surface of the first facet, forming the first superlattice layer, and then forming a second facet by further selectively growing the first nitride-based semiconductor layer in the lateral direction; And on the surface of the second facet,
Forming a second superlattice layer, and, after forming the second superlattice layer, selectively growing the second nitride-based semiconductor layer in a lateral direction to form a second nitride-based semiconductor layer having a substantially flat surface. Forming a semiconductor layer. As described above, by forming the first superlattice layer and the second superlattice layer, lateral dislocations can be further reduced as compared with a case where the superlattice layer is formed only once.

A nitride-based semiconductor device according to another aspect of the present invention has a facet formed of a first nitride-based semiconductor layer formed on an upper surface of a base and formed on a surface of the facet, causing lattice mismatch. A superlattice layer having a periodic structure in which two layers are alternately stacked, a second nitride-based semiconductor layer formed so as to cover the superlattice layer and having a substantially flat surface, and a second nitride-based semiconductor layer. A nitride-based semiconductor device layer formed on the semiconductor layer and having a device region.

In the nitride-based semiconductor device according to another aspect, a superlattice having a periodic structure in which two layers having different lattice constants are alternately stacked on a facet which is a slip surface through which dislocations easily propagate. By forming a layer,
Dislocations bent laterally by the facets are more likely to be bent in a direction parallel to the direction in which the superlattice layer extends, due to the interfacial stress generated by the lattice mismatch of the superlattice layer. As a result, dislocations coupled by dislocations bent in a direction parallel to the direction in which the superlattice layer extends collide with each other.
Since extinction is likely to occur, lateral dislocations can be reduced. For this reason, the mobility of electrons and holes in the vertical direction can be improved, and the resistivity in the vertical direction can be reduced. As a result, heat generation due to vertical energization can be suppressed, so that the light emission characteristics of the light emitting element can be prevented from deteriorating. In addition, by selectively laterally growing the second nitride-based semiconductor layer on the superlattice layer in which lateral dislocations have been reduced, longitudinal dislocations can be further reduced. As a result, a nitride-based semiconductor layer in which dislocations in both the vertical and horizontal directions are reduced can be obtained. Then, by growing a nitride-based semiconductor element layer having an element region on such a nitride-based semiconductor layer in which dislocations in both the vertical direction and the horizontal direction are reduced, a nitride having good element characteristics can be obtained. A system semiconductor element can be formed.

In the method for forming a nitride semiconductor according to the one aspect, preferably, the first nitride semiconductor layer comprises:
GaN, _{and, Al a B b In c Tl} d Ga 1-abcd N
(0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, 0 ≦ d <1,
comprise any of a + b + c + d < 1), the second nitride semiconductor layer, GaN, _{and, Al e B f In g Tl} h Ga
_1-efgh N (0 ≦ e <1, 0 ≦ f <1, 0 ≦ g <1,
0 ≦ h <1, e + f + g + h <1),
Superlattice layer is periodic of _{In x Ga 1-x N /} Al y Ga 1-y N
(0 ≦ x <1, 0 ≦ y ≦ 1), periodic In _x Ga _1-x N
/ Al _y Ga _{1- y} N (0 ≦ x ≦ 1, 0 <y ≦ 1) and periodic In _u Al _v Ga _1-uv N / In _x Al _y Ga
_1-xy N (0 ≦ u <1,0 ≦ v <1,0 ≦ x <1,0 ≦
y <1; In _u Al _v lattice constant of the Ga _1-uv N is, an In _x A
including one selected from the group consisting of less) than the lattice constant of the l _y Ga _1-xy N. With this configuration, it is possible to easily cause lattice mismatch in the superlattice layer.

In the above-described nitride-based semiconductor device, preferably, the base includes a substrate, and further includes a mask layer formed on the upper surface of the substrate so as to expose a part of the upper surface of the substrate. , Formed on the upper surface of the exposed substrate. According to this structure, the first nitride-based semiconductor layer and the second nitride-based semiconductor layer can be formed directly on the substrate without forming an underlayer on the substrate. The total thickness of the layers can be reduced.

In the above-mentioned nitride-based semiconductor device, the underlayer preferably includes a third nitride-based semiconductor layer formed on the substrate, and the third nitride-based semiconductor layer is formed on the upper surface of the third nitride-based semiconductor layer. The semiconductor device further includes a mask layer formed so that a part of the upper surface of the semiconductor layer is exposed, and the facet includes an exposed third surface.
It is formed on the surface of the nitride-based semiconductor layer. With this configuration, a facet made of the first nitride-based semiconductor layer can be easily formed using the mask layer.

In this case, preferably, the underlayer includes a third nitride-based semiconductor layer whose side surface is exposed, and the facet includes:
It is formed so as to contact at least the side surface of the third nitride-based semiconductor layer. With this configuration, selective lateral growth of the first nitride-based semiconductor layer can be easily performed using the side surface of the third nitride-based semiconductor layer as a growth interface.

In the above-described nitride semiconductor device, preferably, the base includes a substrate having an uneven shape, and the facets are formed on the bottom surface of the concave portion of the substrate and on the upper surface of the convex portion of the substrate. The use of the substrate having such a concavo-convex shape facilitates the selective lateral growth of the first nitride-based semiconductor layer without forming a mask layer.

In the above-described nitride-based semiconductor device, preferably, the facet includes a first facet and a second facet, and the superlattice layer includes a first superlattice layer and a second superlattice layer. The lattice layer is formed on the surface of the first facet, the second facet is formed to cover the first superlattice layer, and the second superlattice layer is formed on the surface of the second facet Have been. Thus, the first
By forming a superlattice layer and a second superlattice layer,
Dislocations in the lateral direction can be further reduced as compared with the case where the superlattice layer is formed only once.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 to 6 are sectional views for explaining a method of forming a nitride semiconductor according to a first embodiment of the present invention. The method for forming the nitride-based semiconductor according to the first embodiment will be described with reference to FIGS.

First, as shown in FIG. 1, a MOCVD method (Metal Organic C) is formed on a sapphire substrate 1.
chemical Vapor Deposition;
Metalorganic vapor phase epitaxy) or HVPE (Hydrid)
e Vapor Phase Epitaxy (halide vapor phase epitaxy), etc.
Al _x Ga _1-x having a thickness of about 20 nm at a growth temperature of
A low-temperature buffer layer 2 made of N (0 ≦ x ≦ 1) is formed. Then, the first GaN layer 3 having a thickness of about 1 μm to about 2 μm is formed on the low-temperature buffer layer 2 at a growth temperature of about 1050 ° C. by using the MOCVD method or the HVPE method.
Grow. The sapphire substrate 1 is an example of the “substrate” of the present invention, and the first GaN layer 3 is an example of the “base (third nitride-based semiconductor layer)” of the present invention.

Next, as shown in FIG. 2, the first GaN layer 3
A mask layer 4 made of a SiO ₂ film is formed on the entire upper surface of the substrate. The mask layer 4 is wet-etched to form a stripe-shaped mask layer 4 as shown in FIG.

After that, as shown in FIG. 4, the substrate temperature is raised again to about 1050 ° C., and the second GaN layer 5 is formed on the first GaN layer 3. In this case, it is difficult for the GaN layer to grow on the mask layer 4 made of SiO ₂ . Therefore, the second GaN layer 5 in the initial stage of growth selectively grows upward on the first GaN layer 3 exposed between the mask layers 4 made of SiO ₂ . As a result, a second GaN layer 5 having a facet structure with a triangular cross section as shown in FIG. 4 is formed only on the first GaN layer 3 exposed between the mask layers 4 made of SiO ₂ . The second Ga
The N layer 5 is an example of the “first nitride-based semiconductor layer” of the present invention.

After that, in the first embodiment, after the substrate temperature is lowered to about 800 ° C., a triangular facet made of the second GaN layer 5 composed only of the facet surface and having no c-plane appears. On the surface, as shown in FIG. 5, two layers having different lattice constants (In _0.05 Ga _0.95 N
(Thickness: about 4 nm) / Al _0.3 Ga _0.7 N (Thickness: about 4 n
The superlattice layer 6 is formed by laminating the laminated film composed of m)) eight times.

In this case, the surface (facet plane) of the facet composed of the second GaN layer 5 is formed by the growing crystal (second face).
This is the slip surface of the GaN layer 5). Dislocations have the property of easily propagating along this slip plane. In the superlattice layer 6 having a periodic structure in which two layers having different lattice constants are alternately stacked, dislocations are bent in a direction parallel to the direction in which the superlattice layer 6 extends due to interface stress generated by lattice mismatch. Cheap. Thereby, the lateral dislocation of the facet is easily bent along the superlattice layer 6 formed on the surface of the slip surface (facet surface) of the facet. Thereby, in the superlattice layer 6, since dislocations bent in the horizontal direction collide with each other, the dislocations are likely to be coupled and annihilated, so that the dislocations in the horizontal direction are reduced.

Then, as shown in FIG. 6, the substrate temperature is raised again to about 1050 ° C., and the third GaN layer 7 is formed on the superlattice layer 6 and the mask layer 4 by selective lateral growth.
Grow. This third GaN layer 7 is first grown on the superlattice layer 6 on the facet surface. In addition, the third
The GaN layer 7 grows in the lateral direction. The third GaN layer 7 is also formed on the mask layer 4 by the lateral growth.
Finally, the third GaN layers 7 are united to form the third GaN layer 7 made of a continuous film having a flat upper surface. The third GaN layer 7 is an example of the “second nitride-based semiconductor layer” of the present invention.

In the first embodiment, as described above, the second G
Two layers (In _0.05 Ga _0.95 N / Al _0.3 Ga) having different lattice constants are formed on the surface of the facet composed of the aN layer 5.
By forming the superlattice layer 6 having a periodic structure in which _0.7 N) are stacked on each other, lateral dislocations can be reduced, so that the vertical mobility of electrons and holes can be improved. . Accordingly, the resistivity in the vertical direction can be reduced, so that heat generation due to the current flowing in the vertical direction can be suppressed, and as a result, the emission characteristics of the light emitting element can be prevented from deteriorating.

In the first embodiment, as described above,
On the superlattice layer 6 with reduced lateral dislocations, a third GaN
By selectively growing the layer 7 in the lateral direction, the longitudinal dislocations can be further reduced. As a result, a nitride-based semiconductor layer (third GaN layer 7) in which dislocations in both the vertical direction and the horizontal direction are reduced can be formed.

In the first embodiment, as described above,
When the third GaN layer 7 grown on the superlattice layer 6 is flattened, a nitride-based semiconductor layer in which dislocations in both the vertical and horizontal directions are reduced is formed. Thereby, the thickness of the nitride-based semiconductor layer (third GaN layer 7) can be reduced, so that the occurrence of warpage or cracks due to the difference in thermal expansion coefficient between the sapphire substrate 1 and the nitride-based semiconductor layer can be prevented. Can be reduced.

Therefore, in the first embodiment, it is possible to form a nitride-based semiconductor in which dislocations in both the vertical and horizontal directions are reduced.

FIG. 7 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the first embodiment. Next, the structure of a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the first embodiment will be described with reference to FIG. The “semiconductor laser device” is an example of the “nitride-based semiconductor device” of the present invention.

The structure of the semiconductor laser device of the first embodiment is such that an n-type contact layer 8 of n-type GaN is formed on the third GaN layer 7 of the first embodiment shown in FIG. 6 as shown in FIG. , An n-type cladding layer 9 and a light-emitting layer 10 made of n-type AlGaN. On the light emitting layer 10, a p-type cladding layer 11 made of p-type AlGaN is formed so as to have a convex portion. A p-type contact layer 12 made of p-type GaN is formed so as to be in contact with the entire upper surface of the projection of the p-type cladding layer 11. Also, p
On the exposed upper surface of the mold contact layer 12, a p-side electrode 13 is formed. Further, a part of the region from the p-type cladding layer 12 to the n-type contact layer 8 is removed.
An n-side electrode 14 is formed on the exposed surface of the n-type contact layer 8.

The n-type contact layer 8, the n-type cladding layer 9, the light-emitting layer 10, the p-type cladding layer 11, and the p-type contact layer 12 correspond to the “nitride-based semiconductor element layer having an element region” of the present invention. This is an example.

In the above-described semiconductor laser device of the first embodiment, both the vertical and horizontal dislocations formed by using the nitride-based semiconductor forming method of the first embodiment shown in FIGS. By forming each of the layers 8 to 12 on the third GaN layer 7 in which is reduced, as a base layer, good crystallinity can be realized in each of the layers 8 to 12. Thus, in the first embodiment, a semiconductor laser device having good device characteristics can be obtained.

(Second Embodiment) FIGS. 8 to 11 are sectional views for explaining a method of forming a nitride-based semiconductor according to a second embodiment of the present invention. In the second embodiment, unlike the first embodiment, an example is shown in which facets and superlattice layers are formed a plurality of times (three times in the present embodiment). Hereinafter, the method for forming the nitride-based semiconductor according to the second embodiment will be described in detail with reference to FIGS.

First, using a process similar to that shown in FIGS. 1 to 5 of the first embodiment, as shown in FIG. 8, an Al _x Ga ₁ -xN (0 ≦ x
≦ 1) low-temperature buffer layer 22 made of a GaN second 1GaN layer 23 made of, and the mask layer 2 made of SiO ₂
4 are sequentially formed. Then, the GaN is exposed on the first GaN layer 23 exposed between the mask layers 24 by the selective lateral growth.
Forms a first facet 25 having a triangular cross section. Then, two layers (In _0.05 Ga _0.95 N) having different lattice constants are formed on the surface of the triangular first facet 25.
(Thickness: about 4 nm) / Al _0.3 Ga _0.7 N (Thickness: about 4 n
The first superlattice layer 26 is formed by laminating the laminated film composed of m)) eight times.

The sapphire substrate 21 is an example of the “substrate” of the present invention, and the first GaN layer 23 is an example of the “base (third nitride-based semiconductor layer)” of the present invention. The first facet 25 is an example of the “first nitride-based semiconductor layer” of the present invention.

Thereafter, in the second embodiment, as shown in FIG. 9, the second facet 2 made of GaN and having a triangular cross section is formed on the first superlattice layer 26 by using selective lateral growth.
7 is formed. Then, the triangular second facet 27
A second superlattice layer 28 having the same configuration as the first superlattice layer 26 is formed on the surface of the first superlattice layer 26.

Further, as shown in FIG.
On the surface of the triangular third facet 29, the first superlattice layer 26 is formed on the surface of the triangular third facet 29 by using selective lateral growth.
Then, a third superlattice layer 30 having a configuration similar to that of the second superlattice layer 28 is formed.

After the process of forming the superlattice layer on the surface of the facet is repeated three times, the substrate temperature is increased again to about 1050 ° C. as shown in FIG. By the growth, the second GaN layer 31 made of GaN is grown on the third superlattice layer 30 and the mask layer 24. This second GaN layer 31 is
After being grown thereon, it grows laterally on the mask layer 24. Finally, the second GaN layers 31 are combined to form the second GaN layer 31 formed of a continuous film having a flat upper surface. The second GaN layer 31 is an example of the “second nitride-based semiconductor layer” of the present invention.

In the second embodiment, as described above, the first superlattice layer 26, the second superlattice layer 28, and the third superlattice layer 30
By forming, the dislocation in the lateral direction can be further reduced as compared with the case where the superlattice layer 6 of the first embodiment is formed only once.

In the second embodiment, as described above,
The second superlattice layer 30 having reduced lateral dislocations has a second
By selectively growing the GaN layer 31 in the lateral direction, dislocations in the vertical direction can be further reduced. As a result, a nitride-based semiconductor layer (second GaN layer 31) in which dislocations in both the vertical direction and the horizontal direction are further reduced can be formed.

FIG. 12 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the second embodiment. Next, referring to FIG.
A structure of a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the embodiment will be described.

The structure of the semiconductor laser device according to the second embodiment is similar to that of the second GaN according to the second embodiment shown in FIG.
On the layer 31, as in the first embodiment, the n-type contact layer 8, the n-type cladding layer 9, the light emitting layer 10, the p-type cladding layer 1
1 and a p-type contact layer 12 are formed. The composition of each of the layers 8 to 12 is the same as in the first embodiment.

On the upper surface of the p-type contact layer 12, a p-side electrode 13 is formed.
A side electrode 14 is formed.

In the above-described semiconductor laser device of the second embodiment, both the vertical and horizontal dislocations formed by using the method of forming the nitride-based semiconductor of the second embodiment shown in FIGS. By forming each of the layers 8 to 12 on the second GaN layer 31 in which is reduced as a base layer,
Good crystallinity can be realized in each of the layers 8 to 12. Thus, in the second embodiment, a semiconductor laser device having good device characteristics can be obtained.

(Third Embodiment) FIGS. 13 to 17 are sectional views for explaining a method of forming a nitride-based semiconductor according to a third embodiment of the present invention. In the third embodiment, after forming a mask layer 42 directly on a sapphire substrate 41,
An example is shown in which a facet made of a first GaN layer 44 and a superlattice layer 45 are formed on a sapphire substrate 41 exposed between mask layers 42. Hereinafter, the method for forming the nitride-based semiconductor according to the third embodiment will be described in detail with reference to FIGS.

First, as shown in FIG. 13, a mask layer 4 made of a SiN film is formed on the entire upper surface of the sapphire substrate 41.
Form 2 The mask layer 42 is wet-etched to form a stripe-shaped mask layer 42 as shown in FIG. The sapphire substrate 4
1 is an example of the “substrate” of the present invention.

Next, as shown in FIG.
On the sapphire substrate 41 exposed in between, at a growth temperature of about 500 ° C. to about 600 ° C., an Al film having a film thickness of about 20 nm
_{x Ga 1-x N (0} ≦ x ≦ 1) made of low-temperature buffer layer 43
To form Then, the substrate temperature is raised to about 1050 ° C., and a first facet structure having a triangular cross section is formed on the low-temperature buffer layer 43 by selective lateral growth.
A GaN layer 44 is formed. Note that the first GaN layer 44 is
It is an example of the "first nitride-based semiconductor layer" of the present invention.

Thereafter, as shown in FIG. 16, after the substrate temperature is lowered to about 800 ° C., a lattice is formed on the surface of the triangular facet which is constituted only by the facet surface and has no c-plane. Two layers with different constants (In _0.05 G
The superlattice layer 45 is formed by laminating a laminated film composed of a _0.95 N (film thickness: about 4 nm) / Al _0.3 Ga _0.7 N (film thickness: about 4 nm) eight times.

Next, as shown in FIG. 17, the substrate temperature is again raised to about 1050 ° C., and the second GaN is formed on the superlattice layer 45 and the mask layer 42 by selective lateral growth.
The layer 46 is grown. The second GaN layer 46 is grown on the superlattice layer 45 and then on the mask layer 42 in the lateral direction. Then, finally, the second GaN layers 46 are united to form the second GaN layer 46 formed of a continuous film having a flat upper surface.
Is formed. The second GaN layer 46 is an example of the “second nitride-based semiconductor layer” of the present invention.

In the third embodiment, as described above, after forming the mask layer 42 directly on the sapphire substrate 41 without forming the underlayer on the sapphire substrate 41, the sapphire substrate exposed between the mask layers 42 is formed. By forming a facet made of the first GaN layer 44, a superlattice layer 45, and a second GaN layer 46 on the low-temperature buffer layer 43 via the low-temperature buffer layer 43, the total film of the layers formed on the sapphire substrate 41 is formed. The thickness can be reduced.

In the third embodiment, as described above,
On the surface of the facet composed of the first GaN layer 44, two layers (In _0.05 Ga _0.95 N / Al _0.3
By Ga _{0 .7} N) to form a super lattice layer 45 having stacked periodic structure to each other, dislocations bent laterally by the facets, the interfacial stress generated by the lattice mismatch of the superlattice layer 45 , Can be more easily bent in a direction parallel to the direction in which the superlattice layer 45 extends. Thereby, dislocations bent in a direction parallel to the direction in which the superlattice layer 45 extends collide with each other, so that the dislocations are likely to be coupled or eliminated, so that lateral dislocations can be reduced. For this reason, the mobility of electrons and holes in the vertical direction can be improved, and the resistivity in the vertical direction can be reduced. As a result, heat generation due to vertical energization can be suppressed, so that the light emission characteristics of the light emitting element can be prevented from deteriorating.

In the third embodiment, as described above,
The second Ga is formed on the superlattice layer 45 in which the lateral dislocations are reduced.
By selectively growing the N layer 46 in the lateral direction, dislocations in the vertical direction can be further reduced. As a result, a nitride-based semiconductor layer (second GaN layer 46) in which dislocations in both the vertical direction and the horizontal direction are reduced can be formed.

Therefore, in the third embodiment, it is possible to form a nitride-based semiconductor with reduced dislocations in both the vertical and horizontal directions.

FIG. 18 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the third embodiment. Next, referring to FIG.
A structure of a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the embodiment will be described.

The structure of the semiconductor laser device according to the third embodiment is similar to that of the second GaN device according to the third embodiment shown in FIG.
On the layer 46, as in the first embodiment, the n-type contact layer 8, the n-type cladding layer 9, the light emitting layer 10, the p-type cladding layer 1
1 and a p-type contact layer 12 are formed. The composition of each of the layers 8 to 12 is the same as in the first embodiment.

On the upper surface of the p-type contact layer 12, a p-side electrode 13 is formed. On the surface of the n-type contact layer 8 which is partially removed and exposed,
A side electrode 14 is formed.

In the semiconductor laser device of the third embodiment described above, both the vertical and horizontal dislocations formed by using the method of forming the nitride-based semiconductor of the third embodiment shown in FIGS. By forming each of the layers 8 to 12 on the second GaN layer 46 in which is reduced as a base layer, good crystallinity can be realized in each of the layers 8 to 12. Thus, in the third embodiment, a semiconductor laser device having good device characteristics can be obtained.

(Fourth Embodiment) FIGS. 19 to 23 are sectional views for explaining a method of forming a nitride-based semiconductor according to a fourth embodiment of the present invention. In the fourth embodiment, an example is shown in which after forming a facet composed of the second GaN layer 55 with the side surface of the first GaN layer 53 exposed by etching as a growth interface, a superlattice layer 56 is formed on the surface of the facet. ing. The side of the first GaN layer 53 exposed by etching is used as a growth interface, and the second Ga
A method of forming a facet composed of the N layer 55 is called pendeo growth. Phys
s. Lett. Vol. 75, no. 2,12 Jul
y 1999. Hereinafter, FIGS. 19 to 23
The method for forming the nitride-based semiconductor according to the fourth embodiment will be described in detail with reference to FIG.

First, using a process similar to that shown in FIGS. 1 to 5 of the first embodiment, as shown in FIG. 19, an Al _x Ga ₁ -xN (0 ≦ x
A low temperature buffer layer 52 of ≦ 1) and a first GaN layer 53 of GaN are sequentially formed. The first Ga
A mask layer 54 made of a SiO ₂ film is formed on the entire upper surface of the N layer 53. The sapphire substrate 51 is an example of the “substrate” of the present invention, and the first GaN layer 53 is an example of the “base (third nitride-based semiconductor layer)” of the present invention.

Thereafter, in the fourth embodiment, the mask layer 54 and the first GaN layer 53 are etched in a stripe shape by using plasma etching. As a result, FIG.
The patterned mask layer 54 and the first GaN layer 53 are formed as shown in FIG.

Next, the temperature of the substrate is raised to about 1050 ° C., and the side surfaces of the first GaN layer 53 exposed as described above are used as growth interfaces to perform the first lateral growth by selective lateral growth.
On the low-temperature buffer layer 52 exposed between the aN layers 53, a second GaN layer 55 having a facet structure with a triangular cross section is provided.
To form The second GaN layer 55 is an example of the “first nitride-based semiconductor layer” of the present invention.

Then, as shown in FIG. 22, after the substrate temperature is lowered to about 800 ° C., a lattice constant is formed on the surface of the triangular facet which is constituted only by the facet surface and has no c-plane. Two layers (In _0.05 G
The superlattice layer 56 is formed by laminating a laminated film composed of a _0.95 N (film thickness: about 4 nm) / Al _0.3 Ga _0.7 N (film thickness: about 4 nm) eight times.

Next, as shown in FIG. 23, the substrate temperature is raised again to about 1050 ° C., and the third GaN layer is formed on the superlattice layer 56 and the mask layer 54 by selective lateral growth.
The layer 57 is grown. The third GaN layer 57 is grown on the superlattice layer 56 and then laterally on the mask layer 54. Finally, the third GaN layers 57 are united, and the third GaN layer 57 is formed of a continuous film having a flat upper surface.
Is formed. The third GaN layer 57 is an example of the “second nitride semiconductor layer” of the present invention.

In the fourth embodiment, as described above, a facet made of the second GaN layer 55 is formed with the side surface of the first GaN layer 53 exposed by etching as a growth interface, so that the vertical direction of the first GaN layer 53 is Are not propagated to the second GaN layer 55, so that the second GaN layer 5
5 can be further reduced.

In the fourth embodiment, the second GaN layer 5
5 having different lattice constants on the surface of
By forming the superlattice layer 56 having a periodic structure in which two layers (In _0.05 Ga _0.95 N / Al _0.3 Ga _0.7 N) are stacked on each other, the dislocations bent in the lateral direction by the facets cause the dislocations of the super lattice layer 56. The interface stress generated by the lattice mismatch makes it easier to bend in a direction parallel to the direction in which the superlattice layer 56 extends. Thereby, the superlattice layer 5
Since dislocations bent in a direction parallel to the direction in which the dislocations 6 collide with each other are likely to be coupled and eliminated due to collision with each other, lateral dislocations can be reduced. For this reason, the mobility of electrons and holes in the vertical direction can be improved, and the resistivity in the vertical direction can be reduced. As a result, heat generation due to vertical energization can be suppressed, so that the light emission characteristics of the light emitting element can be prevented from deteriorating.

In the fourth embodiment, as described above,
The third Ga is formed on the superlattice layer 56 in which the lateral dislocations are reduced.
By selectively growing the N layer 57 in the lateral direction, the dislocation in the vertical direction can be further reduced. As a result, a nitride-based semiconductor layer (third GaN layer 57) in which dislocations in both the vertical and horizontal directions are reduced can be formed.

Therefore, in the fourth embodiment, it is possible to form a nitride-based semiconductor with reduced dislocations in both the vertical and horizontal directions.

FIG. 24 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the fourth embodiment. Next, referring to FIG.
A structure of a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the embodiment will be described.

The structure of the semiconductor laser device of the fourth embodiment is similar to that of the third GaN device according to the fourth embodiment shown in FIG.
On the layer 57, as in the first embodiment, the n-type contact layer 8, the n-type cladding layer 9, the light emitting layer 10, the p-type cladding layer 1
1 and a p-type contact layer 12 are formed. The composition of each of the layers 8 to 12 is the same as in the first embodiment.

On the upper surface of the p-type contact layer 12, a p-side electrode 13 is formed. On the surface of the n-type contact layer 8 which is partially removed and exposed,
A side electrode 14 is formed.

In the semiconductor laser device of the fourth embodiment described above, both the vertical and horizontal dislocations formed by using the method of forming the nitride-based semiconductor of the fourth embodiment shown in FIGS. By forming each of the layers 8 to 12 on the third GaN layer 57 in which is reduced, as a base layer, good crystallinity can be realized in each of the layers 8 to 12. Thus, in the fourth embodiment, a semiconductor laser device having good device characteristics can be obtained.

(Fifth Embodiment) FIGS. 25 to 28 are sectional views for explaining a method of forming a nitride-based semiconductor according to a fifth embodiment of the present invention. In the fifth embodiment, an example is shown in which a facet composed of a first GaN layer 63 is formed on a sapphire substrate 61 having an uneven shape, and then a superlattice layer 64 is formed on the surface of the facet. Less than,
The method for forming the nitride-based semiconductor according to the fifth embodiment will be described in detail with reference to FIGS.

First, as shown in FIG. 25, a sapphire substrate 61 is formed so as to have a striped unevenness by plasma etching or the like. And FIG.
As shown in the figure, an Al _x Ga ₁ -xN (0) film having a thickness of about 20 nm is formed on the upper surface of the convex portion and the bottom surface of the convex portion of the sapphire substrate 61 at a growth temperature of about 500 ° C. to about 600 ° C. ≤x
A low temperature buffer layer 62 of ≦ 1) is grown. The sapphire substrate 61 is an example of the “substrate” of the present invention.

Thereafter, as shown in FIG. 27, the substrate temperature is raised to about 1050 ° C., and by selective lateral growth,
On the low-temperature buffer layer 62, a first GaN layer 63 having a facet structure having a triangular cross section is grown. And
After the substrate temperature is lowered to about 800 ° C., two layers (In _{0.05) having} different lattice constants are formed on the surface of a triangular facet which is composed only of facets and does not have a c-plane.
The superlattice layer 64 is formed by laminating a multilayer film of Ga _0.95 N (thickness: about 4 nm) / Al _0.3 Ga _0.7 N (thickness: about 4 nm) eight times. The first GaN layer 63 is an example of the “first nitride-based semiconductor layer” of the present invention.

Next, as shown in FIG. 28, the substrate temperature is raised again to about 1050 ° C., and by lateral growth,
On the superlattice layer 64, a second GaN layer 65 made of GaN is grown. The second GaN layer 65 also grows in the lateral direction after being grown on the superlattice layer 64. Then, finally, the second GaN layers 65 are united to form the second GaN layer 65 made of a continuous film having a flat upper surface. The second GaN layer 65 is an example of the “second nitride-based semiconductor layer” of the present invention.

In the fifth embodiment, as described above, the sapphire substrate 61 is formed in an uneven shape, and the sapphire substrate 61 is formed on the upper surface of the convex portion and the lower surface of the convex portion via the low-temperature buffer layer 62. By forming the first GaN layer 63, the first GaN layer 63 can be formed without forming a mask layer.
Facets consisting of layer 63 can be formed by selective lateral growth.

In the fifth embodiment, as described above,
Two layers having different lattice constants (In _0.05 Ga _0.95 N / Al _0.3 G) are formed on the surface of the facet composed of the first GaN layer 63 formed on the sapphire substrate 61 having the uneven shape.
a _0.7 N) to form a superlattice layer 64 having a periodic structure stacked on each other, the dislocations bent in the lateral direction by the facets cause superlattice stress generated by lattice mismatch of the superlattice layer 64 to cause superlattice stress. It becomes easier to bend in a direction parallel to the direction in which the lattice layer 64 extends. Thereby, the dislocations bent in the direction parallel to the direction in which the superlattice layer 64 extends collide with each other, so that the dislocations are likely to be combined and eliminated, so that the lateral dislocations can be reduced. For this reason, the mobility of electrons and holes in the vertical direction can be improved, and the resistivity in the vertical direction can be reduced. As a result, heat generation due to vertical energization can be suppressed, so that the light emission characteristics of the light emitting element can be prevented from deteriorating.

In the fifth embodiment, as described above,
The second Ga is formed on the superlattice layer 64 in which the lateral dislocations are reduced.
By selectively growing the N layer 65 in the horizontal direction, the dislocation in the vertical direction can be further reduced. As a result, a nitride-based semiconductor layer (second GaN layer 65) in which dislocations in both the vertical and horizontal directions are reduced can be formed.

Therefore, in the fifth embodiment, it is possible to form a nitride-based semiconductor with reduced dislocations in both the vertical and horizontal directions.

FIG. 29 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the fifth embodiment. Next, referring to FIG.
A structure of a semiconductor laser device manufactured by using the method for forming a nitride semiconductor according to the embodiment will be described.

The structure of the semiconductor laser device of the fifth embodiment is similar to that of the second GaN device according to the fifth embodiment shown in FIG.
On the layer 65, as in the first embodiment, the n-type contact layer 8, the n-type cladding layer 9, the light-emitting layer 10, the p-type cladding layer 1
1 and a p-type contact layer 12 are formed. The composition of each of the layers 8 to 12 is the same as in the first embodiment.

On the upper surface of the p-type contact layer 12, a p-side electrode 13 is formed. On the surface of the n-type contact layer 8 which is partially removed and exposed,
A side electrode 14 is formed.

In the semiconductor laser device of the fifth embodiment described above, both the vertical and horizontal dislocations formed by using the nitride semiconductor forming method of the fifth embodiment shown in FIGS. By forming each of the layers 8 to 12 on the second GaN layer 65 in which is reduced as a base layer, good crystallinity can be realized in each of the layers 8 to 12. Thus, in the fifth embodiment, a semiconductor laser device having good device characteristics can be obtained.

It should be noted that the embodiment disclosed this time is an example in all respects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

For example, in the first to fifth embodiments,
Although a sapphire substrate was used as the substrate, the present invention is not limited to this, and Si, SiC, Al _m Ga _1-m N (0 ≦ m ≦ 1)
Alternatively, a similar effect can be obtained by using a substrate made of another material such as GaAs.

In the second embodiment, the facet and the superlattice layer are formed three times. However, the present invention is not limited to this. The facet and the superlattice layer may be formed twice, or four or more times. It may be formed.

In the third to fifth embodiments, the facet and the superlattice layer are formed once. However, the present invention is not limited to this, and the facet and the superlattice layer may be formed two or more times. By doing so, the lateral dislocation can be further reduced.

In the first to fifth embodiments, In
_0.05 Ga _0.95 N / Al _0.3 has formed the Ga superlattice layer consisting of _0.7 N, this invention is not limited thereto and may be a super lattice layer two different layers on the lattice mismatching occurs lattice constants. For example, In _x Ga _1-x N / In having different In compositions
_y Ga _1-y N (x ≠ y) superlattice layer, InGaN / GaN
Super lattice layer or Al _x Ga _1-x N /
Al _y Ga _1-y N (x ≠ y) superlattice layer, GaN / AlG
Even when an aN superlattice layer is used, lateral dislocations can be reduced.

In the first to fourth embodiments, the mask layer is formed in a stripe shape. However, the present invention is not limited to this, and the mask layer may be formed in a circular, hexagonal or triangular shape. Or a dot pattern such as a circle, a hexagon or a triangle. Further, the first GaN layer 53 and the sapphire substrate 61 formed in the stripe shape by the etching of the fourth and fifth embodiments may be formed in a circular, hexagonal or triangular shape,
It may be formed in a dot pattern such as a circle, a hexagon or a triangle. When formed in a dot pattern, the shape of a facet made of GaN obtained by crystal growth is mainly a hexagonal pyramid.

In the first to fifth embodiments, selective lateral growth and pendeo growth are used as lateral growth techniques. However, the present invention is not limited to this, and other lateral growth techniques may be used. Is also good.

[0100]

As described above, according to the present invention, it is possible to provide a method of forming a nitride-based semiconductor capable of reducing both vertical and horizontal dislocations.

Further, the present invention provides a nitride-based semiconductor device including a nitride-based semiconductor device layer having good device characteristics formed on a nitride-based semiconductor layer in which dislocations in both the vertical and horizontal directions are reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method for forming a nitride-based semiconductor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a method of forming a nitride-based semiconductor according to a first embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the first embodiment of the present invention.

FIG. 6 is a sectional view illustrating the method for forming the nitride-based semiconductor according to the first embodiment of the present invention.

FIG. 7 is a sectional view showing a semiconductor laser device formed by using the method for forming a nitride-based semiconductor according to the first embodiment shown in FIGS. 1 to 6;

FIG. 8 is a cross-sectional view for explaining a method for forming a nitride-based semiconductor according to a second embodiment of the present invention.

FIG. 9 is a cross-sectional view for explaining a method for forming a nitride-based semiconductor according to a second embodiment of the present invention.

FIG. 10 is a sectional view illustrating the method for forming the nitride-based semiconductor according to the second embodiment of the present invention.

FIG. 11 is a cross-sectional view for explaining a method for forming a nitride-based semiconductor according to a second embodiment of the present invention.

FIG. 12 is a cross-sectional view showing a semiconductor laser device formed by using the nitride-based semiconductor forming method of the second embodiment shown in FIGS.

FIG. 13 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the third embodiment of the present invention.

FIG. 14 is a cross-sectional view for explaining a method for forming a nitride-based semiconductor according to a third embodiment of the present invention.

FIG. 15 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the third embodiment of the present invention.

FIG. 16 is a sectional view for explaining the method for forming the nitride-based semiconductor according to the third embodiment of the present invention.

FIG. 17 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the third embodiment of the present invention.

FIG. 18 is a cross-sectional view showing a semiconductor laser device formed by using the method for forming a nitride-based semiconductor according to the third embodiment shown in FIGS.

FIG. 19 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fourth embodiment of the present invention.

FIG. 20 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fourth embodiment of the present invention.

FIG. 21 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fourth embodiment of the present invention.

FIG. 22 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fourth embodiment of the present invention.

FIG. 23 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fourth embodiment of the present invention.

FIG. 24 is a cross-sectional view showing a semiconductor laser device formed by using the method for forming a nitride-based semiconductor according to the fourth embodiment shown in FIGS. 19 to 23;

FIG. 25 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fifth embodiment of the present invention.

FIG. 26 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fifth embodiment of the present invention.

FIG. 27 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fifth embodiment of the present invention.

FIG. 28 is a cross-sectional view for explaining the method for forming the nitride-based semiconductor according to the fifth embodiment of the present invention.

FIG. 29 is a sectional view showing a semiconductor laser device formed by using the nitride-based semiconductor forming method of the fifth embodiment shown in FIGS. 25 to 28;

[Explanation of symbols]

1, 21, 41, 51, 61 Sapphire substrate (substrate) 3, 23, 53 First GaN layer (underlying; third nitride-based semiconductor layer) 4, 24, 42, 54 Mask layer 5, 55 Second GaN layer (first 1 Nitride-based semiconductor layer) 6, 45, 56, 64 Superlattice layer 7, 57 Third GaN layer (second nitride-based semiconductor layer) 8 n-type contact layer (nitride-based semiconductor element layer) 9 n-type clad layer (Nitride-based semiconductor device layer) 10 Light-emitting layer (nitride-based semiconductor device layer) 11 p-type clad layer (nitride-based semiconductor device layer) 12 p-type contact layer (nitride-based semiconductor device layer) 25 First facet ( (First nitride-based semiconductor layer) 26 First superlattice layer 27 Second facet 28 Second superlattice layer 29 Third facet 30 Third superlattice layer 31, 46, 65 Second GaN layer (Second nitride-based semiconductor layer) ) 44, 63 1st GaN layer (first nitride-based semiconductor layer)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayuki Hata 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Tatsuya Kunisato 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5-5 Sanyo Electric Co., Ltd. (72) Inventor Hiroki Oho 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5F041 AA31 CA05 CA40 CA46 CA65 5F045 AA04 AB14 AB17 AB18 AB19 AD09 AD12 AD14 AF02 AF03 AF09 BB12 BB16 CA12 DA53 DA54 DB02 DB06 5F052 KA01 KA03

Claims (14)

[Claims] 1. A step of forming a facet made of the first nitride-based semiconductor layer by selectively growing a first nitride-based semiconductor layer in a lateral direction on an upper surface of a base; Forming a superlattice layer having a periodic structure in which two layers having different lattice constants are alternately laminated; and forming a second nitride-based semiconductor layer on the superlattice layer formed on the surface of the facet. Selectively growing in the lateral direction. 2. The method according to claim 1, wherein the first nitride-based semiconductor layer includes GaN,
_{And, Al a B b In c Tl} d Ga 1-abcd N (0 ≦ a
<1,0 ≦ b <1,0 ≦ c <1,0 ≦ d <1, a + b +
c + d <1), wherein the second nitride-based semiconductor layer includes GaN and Al _{e
B f In g Tl h Ga 1} -e- fgh N (0 ≦ e <1,0 ≦ f <
Comprise either 1,0 ≦ g <1,0 ≦ h < 1, e + f + g + h <1), the superlattice layers are periodic in _{In x Ga 1-x N /} Al y Ga
_1-y N (0 ≦ x <1, 0 ≦ y ≦ 1), periodic In _x Ga
_{1-x N / Al y Ga} 1-y N (0 ≦ x ≦ 1,0 <y ≦ 1),
And, periodic of _{In u Al v Ga 1-uv} N / In x Al y
Ga _1-xy N (0 ≦ u <1, 0 ≦ v <1, 0 ≦ x <1,
0 ≦ y <1; the lattice constant of In _u Al _v Ga _1-uv N is I
n _x Al _y Ga _1-xy includes N one selected from the group consisting of less) than the lattice constant of the nitride-based semiconductor method of forming according to claim 1. 3. The method according to claim 1, wherein the base includes a substrate, and the step of forming a facet made of the first nitride-based semiconductor layer includes: exposing a part of the upper surface of the substrate on the upper surface of the substrate; Forming a facet by selectively laterally growing the first nitride-based semiconductor layer on the exposed upper surface of the substrate using the mask layer; The step of selectively growing the second nitride-based semiconductor layer in the lateral direction comprises: after forming the superlattice layer on the surface of the facet,
3. The nitride according to claim 1, further comprising a step of forming the second nitride-based semiconductor layer having a substantially flat surface by selectively laterally growing the second nitride-based semiconductor layer. 4. Method of forming a system semiconductor. 4. The method according to claim 1, wherein the underlayer includes a third nitride-based semiconductor layer formed on a substrate, and the step of forming a facet made of the first nitride-based semiconductor layer includes: Forming a mask layer on the upper surface such that a part of the upper surface of the third nitride-based semiconductor layer is exposed; and forming the exposed third nitride-based semiconductor layer using the mask layer. Forming a facet by selectively growing the first nitride-based semiconductor layer in a lateral direction on a surface; and selectively growing the second nitride-based semiconductor layer in a lateral direction on the surface; After forming the superlattice layer thereon,
The second nitride-based semiconductor layer is further selectively laterally grown, so that the second nitride semiconductor layer has a substantially flat surface.
The method for forming a nitride-based semiconductor according to claim 1 or 2, further comprising a step of forming a nitride-based semiconductor layer. 5. The step of forming a facet by selectively laterally growing the first nitride-based semiconductor layer on the exposed surface of the third nitride-based semiconductor layer using the mask layer. Further exposing a side surface of the third nitride-based semiconductor layer by etching the third nitride-based semiconductor layer using the mask layer as a mask; and exposing the third nitride-based semiconductor layer. Forming a facet by selectively laterally growing the first nitride-based semiconductor layer using the side surface as a growth interface.
A method for forming a nitride-based semiconductor according to claim 4. 6. The method according to claim 6, wherein the base includes a substrate having an uneven shape, and the step of forming a facet made of the first nitride semiconductor layer includes: forming the first nitride semiconductor on the substrate having the uneven shape. Forming a facet by selectively growing a layer in a lateral direction; and forming the second nitride-based semiconductor layer in a lateral direction by forming the superlattice layer on a surface of the facet.
3. The nitride according to claim 1, further comprising a step of forming the second nitride-based semiconductor layer having a substantially flat surface by selectively laterally growing the second nitride-based semiconductor layer. 4. Method of forming a system semiconductor. 7. The facet includes a first facet and a second facet, the superlattice layer includes a first superlattice layer and a second superlattice layer, a step of forming the superlattice layer, and The step of selectively laterally growing the 2-nitride-based semiconductor layer includes: forming the first superlattice layer on the surface of the first facet; and forming the first superlattice layer on the first facet. Forming the second facet by further selectively laterally growing a nitride-based semiconductor layer; forming the second superlattice layer on a surface of the second facet; Forming a second nitride-based semiconductor layer having a substantially flat surface by selectively laterally growing the second nitride-based semiconductor layer after forming the layer. In any one of ~ 6 A method for forming a nitride-based semiconductor according to the above. 8. A periodic structure in which a facet formed of a first nitride-based semiconductor layer formed on an upper surface of a base and two layers having different lattice constants formed on the surface of the facet are alternately stacked. A superlattice layer, a second nitride-based semiconductor layer formed so as to cover the superlattice layer, and having a substantially flat surface; and a second nitride-based semiconductor layer formed on the second nitride-based semiconductor layer. And a nitride-based semiconductor device layer having the same. 9. The method according to claim 1, wherein the first nitride-based semiconductor layer comprises GaN,
_{And, Al a B b In c Tl} d Ga 1-abcd N (0 ≦ a
<1,0 ≦ b <1,0 ≦ c <1,0 ≦ d <1, a + b +
c + d <1), wherein the second nitride-based semiconductor layer includes GaN and Al _{e
B f In g Tl h Ga 1} -e- fgh N (0 ≦ e <1,0 ≦ f <
Comprise either 1,0 ≦ g <1,0 ≦ h < 1, e + f + g + h <1), the superlattice layers are periodic in _{In x Ga 1-x N /} Al y Ga
_1-y N (0 ≦ x <1, 0 ≦ y ≦ 1), periodic In _x Ga
_{1-x N / Al y Ga} 1-y N (0 ≦ x ≦ 1,0 <y ≦ 1),
And, periodic of _{In u Al v Ga 1-uv} N / In x Al y
Ga _1-xy N (0 ≦ u <1, 0 ≦ v <1, 0 ≦ x <1,
0 ≦ y <1; the lattice constant of In _u Al _v Ga _1-uv N is I
n _x Al _y Ga lattice constant of _1-xy N including one selected from the group consisting of lower) than, nitride-based semiconductor device according to claim 8. 10. The substrate further includes a mask layer formed on the upper surface of the substrate so that a part of the upper surface of the substrate is exposed, wherein the facet includes the substrate. The nitride-based semiconductor device according to claim 8, wherein the nitride-based semiconductor device is formed on an upper surface of the device. 11. The underlayer includes a third nitride-based semiconductor layer formed on a substrate, and a part of an upper surface of the third nitride-based semiconductor layer on an upper surface of the third nitride-based semiconductor layer. 10. The nitride-based semiconductor according to claim 8, further comprising a mask layer formed so that the third nitride-based semiconductor layer is exposed, and wherein the facet is formed on a surface of the exposed third nitride-based semiconductor layer. 11. element. 12. The underlayer includes the third nitride-based semiconductor layer having a side surface exposed, and the facet is formed so as to contact at least a side surface of the third nitride-based semiconductor layer. Claim 11
3. The nitride-based semiconductor device according to item 1. 13. The substrate according to claim 8, wherein the base includes a substrate having an uneven shape, and the facet is formed on a bottom surface of a concave portion of the substrate and on a top surface of a convex portion of the substrate.
3. The nitride-based semiconductor device according to item 1. 14. The facet includes a first facet and a second facet, the superlattice layer includes a first superlattice layer and a second superlattice layer, and the first superlattice layer includes the first superlattice layer. The second facet is formed on a surface of a facet, and the second facet is formed to cover the first superlattice layer. The second superlattice layer is formed on a surface of the second facet. The nitride-based semiconductor device according to any one of claims 8 to 13.