JP2003023216A - Semiconductor element and method for forming semiconductor layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a semiconductor layer capable of easily hetero-growing the semiconductor layer having a low dislocation in a thin film thickness on a substrate. SOLUTION: A semiconductor element comprises a plurality of mask layers 2 formed at a predetermined interval to be brought into contact with an upper surface of a sapphire substrate 1 as a substrate, and to partly expose the substrate 1, a low-temperature buffer layer 3 formed on the upper surface of the substrate 1 exposed between the layers 2, and an undoped GaN layer 4 formed on the layer 3 and the layer 2 and made of a material different from that of the substrate 1. In this case, a thickness of the layer 3 formed near the layer 2 on the upper surface of the exposed substrate 1 is smaller than that of the layer 3 formed at a central part on the upper surface of the exposed substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element and a method for forming a semiconductor layer, and more particularly to a semiconductor element and a method for forming a semiconductor layer, in which a semiconductor layer made of a material different from that of the underlayer is formed on the underlayer by hetero growth. Regarding

[0002]

2. Description of the Related Art Conventionally, there has been known a technique for hetero-growing a semiconductor made of a material different from that of the underlayer on the underlayer. For example, in crystal growth of GaN, which is one of nitride-based semiconductors, since few substrates are lattice-matched, hetero growth is performed on a heterogeneous substrate such as a sapphire substrate. In this case, in order to grow GaN with few crystal defects and good crystallinity, a technique of inserting a buffer layer by low temperature growth between the substrate and the GaN layer is conventionally known.

However, even when the above low temperature buffer layer is used, there is a limit to the density of defects that can be reduced, and it is difficult to further reduce dislocations. Therefore, conventionally, when GaN is grown, selective lateral overgrowth (Epitaxial Lateral Overgr) is performed.
A technique using an underlayer in which dislocations have been reduced by the owth: ELOG) method has been proposed. Regarding the selective lateral growth, for example, Vol. 4 (1)
998) p. 53-58 and p. 210-2.
It is disclosed on page 15 and the like.

23 to 26 are sectional views for explaining an example of a conventional method for forming a nitride-based semiconductor layer using selective lateral overgrowth. Next, with reference to FIGS. 23 to 26, an example of a conventional method for forming a nitride-based semiconductor layer using selective lateral overgrowth will be described.

First, as shown in FIG. 23, after forming a low temperature buffer layer 202 on a sapphire substrate 201, a GaN layer 203 as a base is formed on the low temperature buffer layer 202.
Grow.

Next, as shown in FIG. 24, the GaN layer 20
A stripe-shaped (elongated) mask layer 204 made of SiO ₂ or the like is formed in a predetermined region on 3. Mask layer 20
When GaN layer 203 is regrown using 4 as a selective growth mask, a GaN layer 205 having a facet structure with a triangular cross section is first formed in the exposed portion of GaN layer 203.

Further, as the growth progresses, the GaN layer 205 having the facet structure is bonded as shown in FIG. 25, and the lateral growth becomes dominant. Therefore, c-axis direction (vertical direction)
The dislocations that had been extended to B are bent at the facet joints and do not reach the upper part. However, dislocations remain on the facet joints.

When the growth further proceeds, as shown in FIG. 26, the GaN layers 205 having the facet structure are united to form a continuous film. Thereby, the GaN layer 2 having a flat upper surface
05 is formed. The dislocations reaching the surface of the flattened GaN layer 205 are significantly reduced as compared with the underlayer.

[0009]

In the conventional method for forming a nitride-based semiconductor layer shown in FIGS. 23 to 26, when the GaN layer 205 is formed by selective lateral growth, dislocations are mask layers to which facets are coupled. Concentrate on the top of 204. Therefore, in order to reduce dislocations, the mask layer 2
The width of 04 is preferably small. However, if the width of the mask layer 204 is reduced in order to reduce dislocations, the width of the exposed portion of the GaN layer 203 serving as the base becomes wider, so that G
The facet made of GaN formed on the exposed portion of the aN layer 203 also becomes large (high). Therefore, it was necessary to form the GaN layer 205 thick in order to bond and flatten the large facets. As described above, conventionally, it was difficult to obtain the GaN layer 205 having a small film thickness and few dislocations.

Also, conventionally, there has been proposed a method of forming a mask layer directly on a substrate and growing a GaN layer by selective lateral growth. FIG. 27 is a sectional view for explaining the conventional method of forming a nitride-based semiconductor layer proposed in the related art. Referring to FIG. 27, in this conventional method proposed, a mask layer 212 made of SiO ₂ is directly formed on a sapphire substrate 211, and then a low temperature buffer layer 213 made of GaN and a GaN layer grown at high temperature are formed thereon. 214
Are formed to form the GaN layer 214 in which dislocations are reduced by one growth. In this conventional proposed method, since the mask layer 212 is formed directly on the sapphire substrate 211, the entire film thickness becomes thin because there is no underlying layer.

However, in the conventional proposed method shown in FIG. 27, the same problem as in the conventional example shown in FIGS. 23 to 26 occurs. That is, even when the mask layer 212 is directly formed on the sapphire substrate 211 and the selective lateral growth is performed, in order to reduce dislocations, the mask layer 212 is required.
It is necessary to reduce the width of. However, the mask layer 212
When the width of the low temperature buffer layer 21 is increased, the exposed area of the sapphire substrate 211 is increased.
The facets made of GaN formed on 3 are large (high). Therefore, in order to bond the large facets to flatten the GaN layer 214, it was necessary to form the GaN layer 214 with a large thickness of about 5 μm or more. As a result, it was difficult to obtain a GaN layer 214 with a small film thickness and few dislocations even by the conventionally proposed method shown in FIG.

Further, conventionally, AlGaN, InN, I
nGaN, BGaN, BAlGaN, BInGaN, A
When a mixed crystal such as 1GaInN is grown thick, it is more difficult to find a substrate that is lattice-matched. For example, when InGaN is directly grown on a sapphire substrate, it is difficult to grow the InGaN layer thick because the difference in lattice constant is large. Therefore, conventionally, as shown in FIG. 28, the GaN layer 223 is first grown on the sapphire substrate 221 via the buffer layer 222.
Then, after forming a mask layer 224 on the GaN layer 223, the mask layer 224 is used as a selective growth mask to perform selective lateral growth, whereby the low-dislocation GaN layer 2 is formed.
25 is formed. Then, the low dislocation GaN layer 225
An InGaN layer 226 was grown on top. As described above, by growing the InGaN layer 226 on the low-dislocation GaN layer 225 formed by using the selective lateral growth, the low-dislocation InGaN layer 226 can be grown to a certain thickness.

In the conventional method for forming a nitride-based semiconductor layer made of a mixed crystal shown in FIG. 28, as described above, in order to obtain the InGaN layer 226 with few dislocations, selective lateral overgrowth is used as an underlayer. It is necessary to form the low dislocation GaN layer 225. For this reason, in the conventional example shown in FIG. 28, the total thickness becomes large, and as a result, it was difficult to obtain an InGaN layer 226 having a thin film thickness and few dislocations as a whole. Further, in the conventional method for forming a nitride-based semiconductor layer made of a mixed crystal shown in FIG. 28, the GaN layer 225 formed by selective lateral growth is used as an underlayer, and InGa is further added.
Since the N layer 226 is grown, there is a problem that the process becomes complicated.

The present invention has been made to solve the above problems, and one object of the present invention is to easily hetero-grow a low dislocation semiconductor layer with a small film thickness on an underlayer. A method of forming a semiconductor layer is provided.

Another object of the present invention is to
It is an object of the present invention to provide a semiconductor element having a structure capable of forming a semiconductor layer having a small film thickness and low dislocation by hetero growth.

[0016]

In order to achieve the above object, the semiconductor element according to the first aspect of the present invention has a predetermined interval so as to contact the upper surface of the base and expose a part of the base. A plurality of mask layers formed by separating the
A buffer layer formed on the upper surface of the base exposed between the mask layers, and formed on the buffer layer and the mask layer,
The thickness of the buffer layer formed in the vicinity of the mask layer on the upper surface of the exposed base is equal to that of the buffer layer formed in the central portion on the upper surface of the exposed base. Less than layer thickness.

In the semiconductor device according to the first aspect, as described above, the thickness of the buffer layer formed in the vicinity of the mask layer on the upper surface of the exposed underlayer is equal to the central portion on the upper surface of the exposed underlayer. When the semiconductor layer is grown on the buffer layer by being formed so as to have a thickness smaller than that of the buffer layer formed in, the growth of the semiconductor layer becomes faster in the central part where the thickness of the buffer layer is large. In the vicinity of the mask layer where the thickness of the buffer layer is small, the growth of the semiconductor layer becomes slow. As a result, the semiconductor layer easily grows into a trapezoidal shape from the initial stage of growth, and the side surfaces of the trapezoidal semiconductor layer gradually grow in the lateral direction. This promotes lateral growth from the initial stage of growth of the semiconductor layer, so that dislocations are bent laterally from the initial stage of growth of the semiconductor layer. As a result, it is possible to reduce dislocations propagating in the vertical direction from the initial stage of growth of the semiconductor layer, so that a semiconductor layer having a low dislocation can be hetero-grown with a small film thickness on the underlayer.

A semiconductor element according to a second aspect of the present invention includes a plurality of mask layers formed at a predetermined interval so as to contact an upper surface of a base and expose a part of the base, and a mask interlayer. A buffer layer formed on the upper surface of the exposed underlayer, and a semiconductor layer formed on the exposed underlayer, the buffer layer and the mask layer and made of a material different from that of the underlayer. It is formed with substantially the same thickness in the central portion on the upper surface of the underlayer exposed between the mask layers, and is not formed in the vicinity of the mask layer on the exposed upper surface of the underlayer.

In the semiconductor element according to the second aspect, as described above, the buffer layer is formed with substantially the same thickness in the central portion on the upper surface of the underlayer exposed between the mask layers, and the exposed underlayer is formed. By not forming in the vicinity of the mask layer on the upper surface of the buffer layer, when the semiconductor layer is grown on the buffer layer, the growth of the semiconductor layer becomes faster in the central portion where the thickness of the buffer layer is large, and In the vicinity of the mask layer having no thickness, the growth of the semiconductor layer becomes slow. As a result, the semiconductor layer easily grows into a trapezoidal shape from the initial stage of growth, and the side surfaces of the trapezoidal semiconductor layer gradually grow in the lateral direction. This promotes lateral growth from the initial stage of growth of the semiconductor layer, so that dislocations are bent laterally from the initial stage of growth of the semiconductor layer.
As a result, it is possible to reduce dislocations propagating in the vertical direction from the initial stage of growth of the semiconductor layer, so that a semiconductor layer having a low dislocation can be hetero-grown with a small film thickness on the underlayer.

In the above semiconductor device, preferably
The shortest distance between the adjacent mask layers is smaller than the width of the exposed portion of the base located between the adjacent mask layers. According to this structure, when the buffer layer is formed on the underlayer using the mask layer as a mask, the raw material is less likely to reach the exposed portion of the underlayer where the mask layer is formed above. As a result, in the portion of the exposed underlying portion where the mask layer is formed, the buffer layer having a smaller thickness than the buffer layer formed in the exposed portion of the underlying portion where the mask layer is not formed above. Or the buffer layer is not formed. When the semiconductor layer is formed using such a buffer layer, the semiconductor layer easily grows into a trapezoidal shape from the initial stage of growth. Thereby, the trapezoidal semiconductor layer can be easily formed from the initial stage of growth.

In this case, preferably, the mask layer has an overhang portion protruding above the exposed portion of the base.
According to this structure, the raw material is less likely to reach the upper surface of the underlayer located under the overhang portion, and thus the buffer layer is less likely to be formed on the upper surface of the underlayer located under the overhang portion. Thereby, it is possible to easily reduce the thickness of the buffer layer formed on the upper surface of the underlayer located under the overhang portion to be smaller than that of other portions, and prevent the buffer layer from being formed on the upper surface of the underlayer located under the overhang portion. can do.

In the above structure having the overhang portion, the thickness of the buffer layer located under the overhang portion of the mask layer may be smaller than the thickness of the buffer layer located under the shortest distance portion between the adjacent mask layers. Further, in this case, preferably, the thickness of the buffer layer located below the overhang portion of the mask layer decreases substantially at the same ratio as the distance from the shortest distance portion between the adjacent mask layers increases.

Further, in the above structure having the overhang portion, the buffer layer is formed with substantially the same thickness on the central portion of the upper surface of the base exposed between the mask layers, and the buffer layer is formed under the overhang portion. Need not be formed on the upper surface of the underlying layer.

In the above structure having the overhang portion, at least a part of the mask layer preferably has an inverted trapezoidal shape.

In the above method of forming a semiconductor layer, preferably, the underlayer includes a substrate, and the mask layer is formed so as to contact the upper surface of the substrate. According to this structure, it is possible to hetero-grow a thin dislocation semiconductor layer directly on the base with a small film thickness. In this case, the substrate is
Preferably, it includes one substrate selected from the group consisting of a group 3-5 semiconductor substrate containing no nitrogen, a group 4 semiconductor substrate, a sapphire substrate, a spinel substrate, a SiC substrate and a quartz substrate. By using such a substrate, it is possible to easily hetero-grow a semiconductor layer directly on the substrate.

In the above semiconductor element, preferably, the dislocation density of the semiconductor layer near the upper surface of the mask layer is smaller than the dislocation density of the semiconductor layer near the upper surface of the underlayer. According to this structure, since the dislocation density is already small near the upper surface of the mask layer, the dislocation can be easily reduced from the initial stage of growth of the semiconductor layer. In this case, the dislocation density of the semiconductor layer near the upper surface of the mask layer is 1 of the dislocation density of the semiconductor layer near the upper surface of the underlayer.
It is preferably / 2 or less.

In the above semiconductor device, the semiconductor layer may include a nitride semiconductor layer. According to this structure, lateral growth is promoted from the initial stage of growth of the nitride-based semiconductor layer, so that the nitride-based semiconductor layer with low dislocation can be hetero-grown with a small film thickness on the underlayer.

In the above semiconductor element, preferably, the buffer layer is formed at a growth temperature lower than the growth temperature of the semiconductor layer. According to this structure, the raw material is less likely to reach the upper surface of the underlayer located under the overhang portion, and thus the semiconductor layer is less likely to be formed on the upper surface of the underlayer located under the overhang portion. Accordingly, it is possible to easily form the buffer layer in which the thickness of the portion formed on the upper surface of the underlayer located under the overhang portion is smaller than that of the other portions.

The above semiconductor layer device preferably further includes a semiconductor device layer formed on the semiconductor layer and having a device region. According to this structure, the semiconductor element layer having the element region can be grown on the low-dislocation semiconductor layer formed on the base with a small film thickness.
A semiconductor element layer having good element characteristics can be easily formed. As a result, it is possible to form a semiconductor element which is thin and has good element characteristics.

In the method for forming a semiconductor layer according to the third aspect of the present invention, a step of forming a plurality of mask layers at a predetermined interval so as to contact the upper surface of the base and expose a part of the base. And a step of forming a buffer layer on the upper surface of the base, and a step of forming a semiconductor layer made of a material different from that of the base on the buffer layer and the mask layer,
The thickness of the buffer layer formed in the vicinity of the mask layer on the upper surface of the underlayer is smaller than the thickness of the buffer layer formed in the central portion on the upper surface of the underlayer.

In the method for forming a semiconductor layer according to the third aspect, as described above, the thickness of the buffer layer formed in the vicinity of the mask layer on the upper surface of the exposed underlayer is equal to that on the exposed upper surface of the underlayer. The thickness of the buffer layer formed in the central portion of the buffer layer is smaller than that of the buffer layer. It becomes faster and near the mask layer where the buffer layer thickness is small,
The growth of the semiconductor layer slows down. This makes it easier for the semiconductor layer to grow into a trapezoidal shape from the initial growth stage, and
The side surface of the trapezoidal semiconductor layer gradually grows in the lateral direction. This promotes lateral growth from the initial stage of growth of the semiconductor layer, so that dislocations are bent laterally from the initial stage of growth of the semiconductor layer. As a result, it is possible to reduce dislocations propagating in the vertical direction from the initial stage of growth of the semiconductor layer, so that a semiconductor layer having a low dislocation can be hetero-grown with a small film thickness on the underlayer.

In the method for forming a semiconductor layer according to the fourth aspect of the present invention, a step of forming a plurality of mask layers at a predetermined interval so as to contact the upper surface of the base and expose a part of the base. And a step of forming a buffer layer on the upper surface of the base, and a step of forming a semiconductor layer made of a material different from that of the base on the buffer layer and the mask layer,
The buffer layer is formed in the central portion on the upper surface of the underlayer with substantially the same thickness, and is not formed in the vicinity of the mask layer on the upper surface of the underlayer.

In the method for forming a semiconductor layer according to the fourth aspect, as described above, the buffer layer is formed in the central portion on the upper surface of the underlayer exposed between the mask layers to have substantially the same thickness, and is exposed. By not forming in the vicinity of the mask layer on the upper surface of the underlying layer, when the semiconductor layer is grown on the buffer layer, the growth of the semiconductor layer becomes faster in the central portion where the thickness of the buffer layer is large, In the vicinity of the mask layer, where the buffer layer is not thick, the growth of the semiconductor layer is slow. As a result, the semiconductor layer easily grows into a trapezoidal shape from the initial stage of growth, and the side surfaces of the trapezoidal semiconductor layer gradually grow in the lateral direction. This allows
Since the lateral growth is promoted from the initial growth stage of the semiconductor layer, dislocations are bent laterally from the initial growth stage of the semiconductor layer. As a result, it is possible to reduce dislocations propagating in the vertical direction from the initial stage of growth of the semiconductor layer, so that a semiconductor layer having a low dislocation can be hetero-grown with a small film thickness on the underlayer.

In the above method of forming a semiconductor layer, preferably, the shortest distance between the adjacent mask layers is smaller than the width of the exposed portion of the base located between the adjacent mask layers. According to this structure, when the buffer layer is formed on the underlayer using the mask layer as a mask, the raw material is less likely to reach the exposed portion of the underlayer where the mask layer is formed above. As a result, in the portion of the exposed underlying portion where the mask layer is formed, the buffer layer having a smaller thickness than the buffer layer formed in the exposed portion of the underlying portion where the mask layer is not formed above. Is formed,
Alternatively, the buffer layer is not formed. When the semiconductor layer is formed using such a buffer layer, the semiconductor layer easily grows into a trapezoidal shape from the initial stage of growth. Thereby, the trapezoidal semiconductor layer can be easily formed from the initial stage of growth.

In this case, preferably, the mask layer has an overhang portion protruding above the exposed portion of the base.
According to this structure, the raw material is less likely to reach the upper surface of the underlayer located under the overhang portion, and thus the buffer layer is less likely to be formed on the upper surface of the underlayer located under the overhang portion. Thereby, it is possible to easily reduce the thickness of the buffer layer formed on the upper surface of the underlayer located under the overhang portion to be smaller than that of other portions, and prevent the buffer layer from being formed on the upper surface of the underlayer located under the overhang portion. can do.

The above-mentioned method for forming a semiconductor layer preferably further includes a step of growing a semiconductor element layer having an element region on the semiconductor layer. According to this structure, the semiconductor element layer having the element region can be grown on the low-dislocation semiconductor layer formed with a small film thickness on the base, so that the semiconductor element layer having good element characteristics can be obtained. It can be easily formed. As a result, it is possible to form a semiconductor element which is thin and has good element characteristics.

[0037]

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

(First Embodiment) FIG. 1 is a sectional view for explaining a method for forming a nitride-based semiconductor layer according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer of the first embodiment shown in FIG.

First, with reference to FIG. 1, a method for forming a nitride semiconductor layer according to the first embodiment will be described. This first
In the embodiment, first, the mask layer 2 made of SiN is formed directly on the upper surface of the sapphire substrate 1 as a base.
The mask layer 2 is formed in an inverted mesa shape (inverted trapezoidal shape) having an overhang portion 2a. In this mask layer 2, the shortest distance between the adjacent mask layers 2 is smaller than the width of the exposed portion of the sapphire substrate 1 located between the adjacent mask layers 2.

As a method of forming such a mask layer 2, first, a SiN layer (not shown) is formed on the entire surface of the sapphire substrate 1, and then a resist (not shown) is formed in a predetermined region on the SiN layer. To form. Then, the SiN layer is wet-etched using the resist as a mask, whereby the inverted trapezoidal mask layer 2 having the overhang portion 2a can be easily formed. The mask layer 2 is formed in a stripe shape (slender shape) having a period of about 7 μm and a thickness of about 10 nm to about 1000 nm. The openings of the mask 2 may be formed, for example, in the [11-20] direction of sapphire or [1-1 of sapphire.
[00] direction is preferable.

After that, about 500 sapphire substrate 1 was formed.
About 10 nm to about 50 n under temperature conditions of ℃ to about 700 ℃
A low temperature buffer layer 3 made of AlGaN or GaN having a thickness of m is grown. The low temperature buffer layer 3 is an example of the "buffer layer" in the present invention. And
MOCVD method (Metal Organic Chem
Ionic Vapor Deposition; metal-organic vapor phase epitaxy) or HVPE (Hydride V)
Aper Phase Epitaxy (halide vapor deposition method) is used to form the undoped GaN layer 4 on the low-temperature buffer layer 3 using the mask layer 2 as a selective growth mask. The undoped GaN layer 4 is formed to have a thickness of about 2 μm under a temperature condition of about 950 ° C. to about 1200 ° C. The undoped GaN layer 4 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

When the low temperature buffer layer 3 is grown,
Since the mask layer 2 has the overhang portion 2a, it becomes difficult for the raw material to reach under the overhang portion 2a. Therefore, the thickness of the low temperature buffer layer 3 below the overhang portion 2a is smaller than the thickness of the portion (central portion) other than below the overhang portion 2a. Thereby, the low temperature buffer layer 3
When the undoped GaN layer 4 is grown on the upper portion of the low temperature buffer layer 3, the low temperature buffer layer 3 has an undoped Ga at the central portion where the thickness is large.
The growth of the N layer 4 becomes faster, and the growth of the undoped GaN layer 4 becomes slower under the overhang portion 2a where the low temperature buffer layer 3 has a smaller thickness. Therefore, the trapezoidal undoped GaN layer 4a (see FIG. 1) is likely to be formed from the initial stage of growth, and the side surfaces of the trapezoidal undoped GaN layer 4a gradually grow in the lateral direction. Lateral growth is promoted from the initial growth stage of No. 4. As a result, dislocations are bent laterally from the initial stage of growth of the undoped GaN layer 4, so that dislocations propagating in the vertical direction from the initial stage of growth of the undoped GaN layer 4 can be reduced. As a result, the low-dislocation undoped GaN layer 4 can be hetero-grown on the sapphire substrate 1 with a small film thickness.

Next, with reference to FIG. 2, the structure of the semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer of the first embodiment will be described.

In the semiconductor laser device of the first embodiment, as shown in FIG. 2, on the undoped GaN layer 4 shown in FIG. 1, a first conductivity type contact layer 105 made of n-type GaN having a thickness of about 4 μm. Are formed. On the first conductivity type contact layer 105, the first conductivity type cladding layer 10 made of n-type AlGaN having a film thickness of about 0.45 μm.
6 is formed. A multiple quantum well (MQW) light emitting layer 107 made of InGaN is formed on the first conductivity type cladding layer 106. On the MQW light emitting layer 107,
A second conductivity type cladding layer 108 made of p-type AlGaN having a thickness of about 0.45 μm is formed. A second conductivity type contact layer 109 made of p-type GaN having a film thickness of about 0.15 μm is formed on the second conductivity type clad layer 108. An n-type first conductivity type electrode 110 is formed on the exposed upper surface of the first conductivity type contact layer 105. In addition, on the upper surface of the second conductivity type contact layer 109, a p-type second conductivity type electrode 111 is formed.
Are formed.

The first-conductivity-type contact layer 105, the first-conductivity-type clad layer 106, the MQW light-emitting layer 107, and the second
The conductivity type cladding layer 108 and the second conductivity type contact layer 109 are examples of the “semiconductor element layer” in the present invention.

In the semiconductor laser device of the first embodiment described above, the layers 105 to 109 are formed on the undoped GaN layer 4 having a thin thickness and reduced dislocations formed by using the forming method shown in FIG. Therefore, good crystallinity can be realized in each of the layers 105 to 109. Therefore, in the first embodiment, it is possible to obtain a semiconductor laser device having a small thickness and good device characteristics.

(Second Embodiment) FIG. 3 is a sectional view for explaining a method for forming a nitride semiconductor layer according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer of the second embodiment shown in FIG.

First, referring to FIG. 3, this second embodiment
The method of forming the nitride-based semiconductor layer of is described. this
In the second embodiment, the n-type SiC substrate 11 as a base is
A mask layer 12 is formed on the surface. This mask layer 12
Is the SiN layer 12a and SiO₂Layer 12b and SiN layer
It has a three-layer structure consisting of 12c and about 10n
It has a thickness of m to about 1000 nm. Also, the mask layer 1
2 is SiO of the intermediate layer ₂Layer 12b protruding to both sides
Shape (overhang shape). This mask layer 12
Then, the shortest distance between the adjacent mask layers 12 is
Exposed part of the n-type SiC substrate 11 located between the mask layers 12
Less than the width of.

As a method of forming such a mask layer 12, a SiN layer 12a and SiO 2 are formed on an n-type SiC substrate 11.
After sequentially forming the _two layers 12b and the SiN layer 12c, S
A resist (not shown) is formed in a predetermined region on the iN layer 12c. Then, using the resist as a mask, wet etching is performed using a hydrofluoric acid-based etching solution, and thereby the SiO ₂ layer 12b and the SiN layers 12a and 1 are formed.
The mask layer 12 having the overhang shape as shown in FIG. 3 is formed by utilizing the difference in etching rate from 2c.

Then, about 50 is formed on the n-type SiC substrate 11.
Under a temperature condition of 0 ° C. to about 700 ° C., about 10 nm to about 50 nm
A low temperature buffer layer 13 made of AlGaN or GaN having a thickness of nm is formed. The low temperature buffer layer 13 is an example of the “buffer layer” in the present invention. Then, using the MOCVD method or the HVPE method, the n-type GaN layer 14 is grown on the low temperature buffer layer 13 using the mask layer 12 as a selective growth mask. The n-type GaN layer 14 has a temperature of about 950 ° C. to about 1200 ° C.
It is formed with a thickness of μm. The n-type GaN layer 14
Is the “semiconductor layer” and the “nitride-based semiconductor layer” of the present invention.
Is an example.

When the low temperature buffer layer 13 is grown, since the mask layer 12 has an overhang shape,
It becomes difficult for the raw material to reach under the overhang portion (SiO ₂ layer 12b). Therefore, the overhang portion (Si
The thickness of the low temperature buffer layer 13 below the O ₂ layer 12b) is smaller than the thickness of the portion (central portion) other than below the overhang portion (SiO ₂ layer 12b). As a result, when the n-type GaN layer 14 is grown on the low-temperature buffer layer 13, the n-type GaN layer 14 is n
The growth of the n-type GaN layer 14 becomes faster, and the growth of the n-type GaN layer 14 becomes slower under the overhang portion where the thickness of the low temperature buffer layer 13 is small. Therefore, as in the first embodiment shown in FIG. 1, n-type GaN is grown from the initial growth stage.
The layer 14 is easily formed into a trapezoidal shape, and the side surface of the trapezoidal n-type GaN layer 14 gradually grows in the lateral direction, so that the lateral growth is promoted from the initial growth stage of the n-type GaN layer 14. . As a result, the dislocations are laterally bent from the initial growth stage of the n-type GaN layer 14, so that n-type Ga
It is possible to reduce dislocations propagating in the vertical direction from the initial stage of growth of the N layer 14. As a result, the n-type GaN layer 14 having a thin film thickness and reduced dislocations can be hetero-grown on the n-type SiC substrate 11.

Next, referring to FIG. 4, the second portion shown in FIG.
The structure of the semiconductor laser device manufactured using the forming method of the embodiment will be described.

In the semiconductor laser device of the second embodiment, as shown in FIG. 4, on the n-type GaN layer 14 shown in FIG.
A first conductivity type layer 115 made of n-type GaN having a film thickness of about 4 μm is formed. A first conductivity type clad layer 116 made of n-type AlGaN having a film thickness of about 0.45 μm is formed on the first conductivity type layer 115. A multiple quantum well (MQW) light emitting layer 117 made of InGaN is formed on the first conductivity type cladding layer 116. A second conductivity type cladding layer 118 made of p-type AlGaN having a film thickness of about 0.45 μm is formed on the MQW light emitting layer 117. The second conductivity type cladding layer 1
P-type GaN having a film thickness of about 0.15 μm
The second conductive type contact layer 119 is formed. On the back surface of the n-type SiC substrate 11, the n-type first
The conductivity type electrode 120 is formed. A p-type second conductivity type electrode 121 is formed on the upper surface of the second conductivity type contact layer 119.

The first conductive type layer 115, the first conductive type cladding layer 116, the MQW light emitting layer 117, the second conductive type cladding layer 118, and the second conductive type contact layer 119 are
It is an example of the "semiconductor element layer" of the present invention.

In the semiconductor laser device according to the second embodiment, after the n-type GaN layer 14 having a small thickness and reduced dislocations is formed, the layers 115 to 1 are formed on the n-type GaN layer 14.
Since 19 is formed, good crystallinity can be realized in each of the layers 115 to 119. As a result, in the second embodiment, it is possible to obtain a semiconductor laser device having a small thickness and good device characteristics.

In the second embodiment, as shown in FIG. 3, the difference in etching rate between the SiO ₂ layer 12b as the intermediate layer and the lower SiN layer 12a and the upper SiN layer 12c is utilized. Although the mask layer 12 having a different overhang shape is formed, other combinations are possible as long as the upper layer and the lower layer are more easily etched than the intermediate layer. For example, the upper layer or the lower layer is made of a metal such as tungsten, and the intermediate layer is made of SiO ₂ , SiN, or T.
It may be composed of iO ₂ , TiN or the like.

(Third Embodiment) FIG. 5 is a sectional view illustrating a method for forming a nitride-based semiconductor layer according to a third embodiment of the present invention. 6 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer shown in FIG.

First, with reference to FIG. 5, a method of forming a nitride semiconductor layer of the third embodiment will be described. This third
In the embodiment, first, the sapphire substrate 21 as a base
A mask layer 22 having an overhang portion is formed directly thereon. The mask layer 22 is a lower SiN layer 22 formed by plasma CVD with an RF power of 150 W.
It has a two-layer structure consisting of a and an upper SiN layer 22b formed by a plasma CVD method with an RF power of 250 W, and has a thickness of about 50 nm to about 1000 nm. In this case, the upper SiN layer 22b formed as described above is less likely to be etched than the lower SiN layer 22a.

As a specific method of forming the mask layer 22, first, the lower layer Si is formed on the entire surface of the sapphire substrate 21.
After the N layer 22a and the upper SiN layer 22b are sequentially formed under the above conditions, a resist (not shown) is formed in a predetermined region on the upper SiN layer 22b. Then, using the resist as a mask and using buffered hydrofluoric acid,
By wet-etching the upper SiN layer 22b and the lower SiN layer 22a, a mask layer 22 having a two-layer structure having an overhang shape as shown in FIG.
To form. In this mask layer 22, the shortest distance between the adjacent mask layers 22 is smaller than the width of the exposed portion of the sapphire substrate 21 located between the adjacent mask layers 22.

After this, about 70
Under the temperature condition of 0 ° C. to about 900 ° C., a low temperature buffer layer made of AlGaN or GaN having a thickness of about 20 nm is grown. Further, under the temperature condition of about 400 ° C. to about 600 ° C., a low temperature buffer layer made of AlGaN or GaN having a thickness of about 30 nm is grown. In this case, if it is formed under a high temperature condition of about 700 ° C. to about 900 ° C., the overhang portion of the mask layer 22 (SiN layer 22
Since atoms are likely to diffuse on the surface of the sapphire substrate 21 up to the bottom of b), the overhang portion (Si
A low temperature buffer layer is formed up to the bottom of the N layer 22b).
On the other hand, when formed under a low temperature condition of about 400 ° C. to about 600 ° C., the overhang portion of the mask layer 22 (SiN layer 2
Since atoms do not easily diffuse on the sapphire substrate 21 to the lower part of 2b), the overhang portion (S
It is difficult to form a low temperature buffer layer under the iN layer 22b). By thus forming the two buffer layers at different temperatures, the low temperature buffer layer 23 having the shape shown in FIG. 5 is formed. The low temperature buffer layer 23 is an example of the "buffer layer" in the present invention.

After that, the undoped GaN layer 24 is grown on the low temperature buffer layer 23 by using the MOCVD method or the HVPE method with the mask layer 22 as a selective growth mask. The undoped GaN layer 24 has a temperature of about 950 ° C. to about 1 ° C.
It is formed with a thickness of about 2 μm under the temperature condition of 200 ° C. The undoped GaN layer 24 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

Also in the third embodiment, the thickness of the low temperature buffer layer 23 below the overhang portion (SiN layer 22b) is smaller than the thickness of the portion (central portion) other than below the overhang portion. Thereby, the low temperature buffer layer 2
3, when growing the undoped GaN layer 24, the undoped GaN layer 24 grows faster in the central portion where the low temperature buffer layer 23 has a large thickness, and below the overhang portion where the low temperature buffer layer 23 has a small thickness. The growth of the undoped GaN layer 24 becomes slow. For this reason,
Similarly to the first embodiment shown in FIG. 1, the undoped GaN layer 24 is likely to be formed into a trapezoidal shape from the initial growth stage, and the side surfaces of the trapezoidal undoped GaN layer 24 gradually grow in the lateral direction. Lateral growth is promoted from the initial growth stage of the GaN layer 24. As a result, dislocations are bent laterally from the initial stage of growth of the undoped GaN layer 24, so that dislocations propagating in the vertical direction from the initial stage of growth of the undoped GaN layer 24 can be reduced. As a result, the undoped GaN layer 24 having a small film thickness and reduced dislocations can be hetero-grown on the sapphire substrate 21.

Next, with reference to FIG. 6, a semiconductor laser device manufactured using the method for forming a nitride-based semiconductor layer of the third embodiment will be described. In the semiconductor laser device according to the third embodiment, as shown in FIG. 6, the first conductivity type contact layer 10 is provided on the undoped GaN layer 24 shown in FIG.
5, first conductivity type cladding layer 106, MQW light emitting layer 10
7, a second conductivity type cladding layer 108, a second conductivity type contact layer 109, an n-type first conductivity type electrode 110, and a p-type second conductivity type electrode 111 are formed. In addition, each layer 1
The compositions and film thicknesses of 05 to 109 are similar to those of the semiconductor laser device of the first embodiment shown in FIG.

In the third embodiment, each layer 105-109 is formed by forming each layer 105-109 on the low-dislocation undoped GaN layer 24 having such a thin film thickness.
In 109, good crystallinity can be realized. As a result, in the third embodiment, as in the first embodiment, it is possible to obtain a semiconductor laser device having a small thickness and good characteristics.

(Fourth Embodiment) FIG. 7 is a sectional view for explaining a method for forming a nitride-based semiconductor layer according to a fourth embodiment of the present invention. FIG. 8 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer of the fourth embodiment shown in FIG.

First, with reference to FIG. 7, a method for forming a nitride semiconductor layer according to the fourth embodiment will be described. This 4th
In the embodiment, on the n-type SiC substrate 31 as a base,
An inverted mesa shape (inverted trapezoidal shape) mask layer 32 having an overhang portion 32a made of tungsten (W) is formed. The mask layer 32 has a thickness of about 10 nm to about 1000 n.
It is formed in a stripe shape with a thickness of m and a period of about 5 μm. In this mask layer 32, the shortest distance between the adjacent mask layers 32 is the n-type S located between the adjacent mask layers 32.
It is smaller than the width of the exposed portion of the iC substrate 31.

As a method of forming the mask layer 32 having the overhang portion 32a made of W, first, n-type S
After a W layer (not shown) is formed on the entire surface of the iC substrate 31, a resist (not shown) is formed in a predetermined region on the W layer. Then, when the W layer is etched using the resist as a mask, the etching conditions are adjusted so that over-etching occurs. As a result, the mask layer 32 having the overhang portion 32a made of W is formed.

Thereafter, about 50 is formed on the n-type SiC substrate 31.
Under a temperature condition of 0 ° C. to about 700 ° C., about 10 nm to about 50 nm
A low temperature buffer layer 33 made of GaInN having a thickness of nm is formed. The low temperature buffer layer 33 is an example of the “buffer layer” in the present invention. And MOCV
By using the D method or the HVPE method with the mask layer 32 as a selective growth mask, n-type Al is formed on the low temperature buffer layer 33.
_{W B X Ga Y In Z Tl} 1- WXYZ N layer is grown. Al _W
The composition of B _X Ga _Y In _Z Tl _1-WXYZ N is a composition excluding Y = Z = 0, and Al _W B _X Ga _Y In _Z Tl _1-WXYZ
The lattice constant of N is larger than that of GaN. In the fourth embodiment, for example, the n-type InGaN layer 34 is
It is formed with a thickness of about 2 μm under a temperature condition of about 650 ° C. to about 900 ° C. The n-type InGaN layer 34 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

When the low temperature buffer layer 33 is grown, the mask layer 32 has the overhang portion 32a, so that the raw material is less likely to reach below the overhang portion 32a. For this reason, the thickness of the low temperature buffer layer 33 below the overhang portion 32a is smaller than the thickness of the portion (central portion) other than below the overhang portion 32a. This allows
When the n-type InGaN layer 34 is grown on the low-temperature buffer layer 33, the n-type InGaN layer 34 grows quickly and the low-temperature buffer layer 33 has a small thickness in the central portion where the low-temperature buffer layer 33 has a large thickness. Under the overhang portion 32a, the growth of the n-type InGaN layer 34 becomes slow. Therefore, similar to the first embodiment shown in FIG. 1, the trapezoidal n-type InGaN layer 34 is likely to be formed from the initial stage of growth, and the side surface of the trapezoidal n-type InGaN layer 34 is gradually flattened. N-type InG as it grows in the direction
Lateral growth is promoted from the initial growth stage of the aN layer 34. As a result, the n-type InGaN layer 34 with a low dislocation can be grown thick on the n-type SiC substrate 31 without providing a GaN layer as a base layer as in the conventional example shown in FIG. In this case, since it is not necessary to provide a GaN layer as a base layer, the entire thickness can be made smaller than that of the conventional example shown in FIG.

Next, with reference to FIG. 8, a structure of a semiconductor laser device formed by using the method for forming a nitride semiconductor layer according to the fourth embodiment will be described. In the semiconductor laser device of the fourth embodiment, the first conductivity type layer 115 made of n type InGaN, the first conductivity type cladding layer 116 made of n type GaN, and InGa are formed on the n type InGaN layer 34 shown in FIG.
An MQW light emitting layer 117 made of N, a second conductivity type cladding layer 118 made of p-type GaN, and a second conductivity type contact layer 119 made of p-type InGaN are formed. An n-type first conductivity type electrode 120 is formed on the back surface of the n-type SiC substrate 31. The p-type second conductivity type electrode 12 is formed on the upper surface of the second conductivity type contact layer 119.
1 is formed. In addition, each of the layers 115 to 11 described above
The film thickness of 9 is the same as that of the semiconductor laser device of the second embodiment shown in FIG.

In the semiconductor laser device according to the fourth embodiment, the layers 115 to 119 are formed on the low-dislocation n-type InGaN layer 34 formed by the forming method shown in FIG. 7, so that the layers 115 to 119 are formed. It is possible to realize good crystallinity. Further, in the method for forming a nitride-based semiconductor layer shown in FIG. 7, since the entire thickness is formed thin, when the layers 115 to 119 are formed thereon, the thickness of the semiconductor laser element becomes thin. This makes this fourth
In the embodiment, as in the second embodiment, it is possible to obtain a semiconductor laser device having a small thickness and good device characteristics.

In addition, in the semiconductor laser device according to the fourth embodiment, the MQW light emitting layer 11 is formed on the low-dislocation n-type InGaN layer 34 thickly formed by the forming method shown in FIG.
7 is formed, even if the In composition of the MQW light emitting layer is increased to increase the lattice constant of the MQW light emitting layer 117,
Good crystallinity can be realized. Therefore, a semiconductor laser having a long wavelength such as green can be realized as compared with the conventional nitride semiconductor laser.

(Fifth Embodiment) FIG. 9 is a sectional view for explaining a method for forming a nitride-based semiconductor layer according to a fifth embodiment of the present invention. FIG. 10 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer shown in FIG. First, with reference to FIG. 9, a method for forming a nitride-based semiconductor layer according to the fifth embodiment will be described.

First, in the fifth embodiment, a mask layer 42 made of SiN having a thickness of about 10 nm to about 1000 nm is formed on the surface of an n-type GaAs substrate 41 as a base.
It is formed with a period of μm. Then, the n-type GaAs substrate 41 is etched using the mask layer 42 as a mask.
At this time, over-etching is performed to form the inverted mesa-shaped convex portion 41a on the n-type GaAs substrate 41. The etching of the n-type GaAs substrate 41 is
H ₂ SO ₄ + H ₂ O ₂ + H ₂ O (4: 1: 1) or H ₃ PO
Performed using ₄ + H ₂ O ₂ + H ₂ O (3: 1: 1).

Then, a low temperature buffer layer 43 made of AlGaN or GaN having a thickness of about 10 nm to about 50 nm is formed on the exposed surface of the n-type GaAs substrate 41 under a temperature condition of about 500 ° C. to about 700 ° C. Form. In addition,
The low temperature buffer layer 43 is an example of the "buffer layer" in the present invention. Then, the MOCVD method or the HVPE method is used to selectively laterally grow the n-type GaN layer 44 on the low-temperature buffer layer 43 using the mask layer 42 as a selective growth mask. The n-type GaN layer 44 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

In this case, since the convex portion 41a under the mask layer 42 has an inverted mesa shape, both end portions of the mask layer 42 have an overhang shape protruding above the exposed portion of the n-type GaAs substrate 41. It will have a structure. That is, in this mask layer 42, the shortest distance W1 between the adjacent mask layers 42 is the n-type GaA located between the adjacent mask layers 42.
It is smaller than the width W2 of the exposed portion of the substrate 41. Thereby, when the low temperature buffer layer 43 is grown, the convex portion 41a is formed.
It becomes difficult for the ingredients to reach the bottom. Therefore, the thickness of the low temperature buffer layer 43 below the convex portion 41a is smaller than the thickness of the portion (central portion) other than below the convex portion 41a. This allows
When the n-type GaN layer 44 is grown on the low-temperature buffer layer 43, the n-type GaN layer 44 grows faster and the low-temperature buffer layer 43 has a smaller thickness in the central portion where the low-temperature buffer layer 43 has a large thickness. Under the convex portion 41a, the growth of the n-type GaN layer 44 becomes slow. Therefore, as in the first embodiment shown in FIG. 1, the trapezoidal n
Since the type GaN layer 44 is easily formed and the side surface of the trapezoidal n-type GaN layer 44 gradually grows in the lateral direction, the lateral growth is promoted from the initial growth stage of the n-type GaN layer 44. As a result, dislocations are laterally bent from the initial growth stage of the n-type GaN layer 44, so that n-type Ga
It is possible to reduce dislocations propagating in the vertical direction from the initial growth stage of the N layer 44. As a result, the n-type GaAs substrate 41
The low-dislocation n-type GaN layer 44 can be hetero-grown thereon with a small film thickness.

Next, with reference to FIG. 10, a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer of the fifth embodiment shown in FIG. 9 will be described. In the semiconductor laser device of the fifth embodiment, the n-type GaN shown in FIG. 9 is used.
A first conductivity type layer 115, a first conductivity type clad layer 116, an MQW light emitting layer 117, a second conductivity type clad layer 118, and a second conductivity type contact layer 119 are formed on the layer 44. Further, an n-type first conductivity type electrode 120 is formed on the back surface of the n-type GaAs substrate 41. Also, the second
A p-type second conductivity type electrode 121 is formed on the upper surface of the conductivity type contact layer 119. The composition and film thickness of each of the layers 115 to 119 described above are the same as those of the second layer shown in FIG.
This is similar to the semiconductor laser device of the embodiment.

In the semiconductor laser device according to the fifth embodiment, the layers 115 to 119 are formed on the low-dislocation low-dislocation n-type GaN layer 44 formed by the forming method shown in FIG.
Therefore, good crystallinity can be realized in each of the layers 115 to 119. Thus, in the fifth embodiment, as in the second and fourth embodiments, it is possible to obtain a semiconductor laser device having a small thickness and good device characteristics.

(Sixth Embodiment) FIG. 11 shows a sixth embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating the method for forming the nitride-based semiconductor layer according to the embodiment. FIG. 12 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer of the sixth embodiment shown in FIG.

First, with reference to FIG. 11, a method for forming a nitride semiconductor layer according to the sixth embodiment will be described. In the sixth embodiment, a tungsten (W) layer is formed on the surface of the n-type Si substrate 51 as a base in a thickness of about 10 nm to about 1000 n.
After being formed with a film thickness of m, patterning is performed using a photolithography technique to form a mask layer 52 made of W in a stripe shape with a period of about 10 μm. Then, using the mask layer 52 as a mask, HF: HNO ₃ : C
N-type Si substrate 5 using H ₃ COOH (1: 5: 1)
1 is etched to form a shape in which the region of the n-type Si substrate 51 located under both ends of the mask layer 52 is scooped as shown in FIG. That is, both end portions of the mask layer 52 have an overhang shape protruding above the end portion of the exposed portion of the n-type Si substrate 51. In this mask layer 52, the shortest distance W1 between the adjacent mask layers 52 is
Is an n-type Si substrate 5 located between the adjacent mask layers 52.
1 is smaller than the width W2 of the exposed portion.

After that, about 1 is formed on the exposed surface of the n-type Si substrate 51 by MOCVD or HVPE.
About 10 nm to about 50 n under the temperature condition of 100 ° C. (high temperature)
A buffer layer 53 made of AlGaN having a thickness of m is formed. Then, using the mask layer 52 as a selective growth mask, the n-type GaN layer 54 is selectively laterally grown on the buffer layer 53. The n-type GaN layer 54 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

In this case, since the region of the n-type Si substrate 51 located below both ends of the mask layer 52 has a sculpted shape, both ends of the mask layer 52 have n-type Si substrate 51.
The structure has an overhang shape protruding above the exposed portion of the. That is, in this mask layer 52, the shortest distance W1 between the adjacent mask layers 52 is smaller than the width W2 of the exposed portion of the n-type Si substrate 51 located between the adjacent mask layers 52. This makes it difficult for the raw material to reach under the mask layer 52 having an overhang shape when the buffer layer 53 is grown. As a result, n is formed on the buffer layer 53.
When the n-type GaN layer 54 is grown, the n-type GaN layer 54 grows faster on the buffer layer 53, and the n-type GaN layer is formed below the overhang-shaped mask layer 52 where the buffer layer 53 is not formed. 54 grows slower. Therefore, similar to the first embodiment shown in FIG. 1, the trapezoidal n-type GaN layer 54 is likely to be formed from the initial growth stage, and the side surface of the trapezoidal n-type GaN layer 54 is gradually flattened. Since the n-type GaN layer 54 is grown in the direction, lateral growth is promoted from the initial growth stage of the n-type GaN layer 54. As a result, the dislocations are bent laterally from the initial growth stage of the n-type GaN layer 54, so that the dislocations propagating in the vertical direction from the initial growth stage of the n-type GaN layer 54 can be reduced. As a result, the low-dislocation n-type GaN layer 5 is formed on the n-type Si substrate 51.
4 can be hetero-grown with a thin film thickness.

Next, with reference to FIG. 12, the structure of the semiconductor laser device formed by using the method for forming the nitride-based semiconductor layer of the sixth embodiment shown in FIG. 11 will be described. In the semiconductor laser device of the sixth embodiment, the first conductivity type layer 115, the first conductivity type clad layer 116, the MQW light emitting layer 117, and the second conductivity type clad layer are formed on the n-type GaN layer 54 shown in FIG. 118 and second conductivity type contact layer 119
Are formed. An n-type first conductivity type electrode 120 is formed on the back surface of the n-type Si substrate 51. A p-type second conductivity type electrode 121 is formed on the upper surface of the second conductivity type contact layer 119. The compositions and film thicknesses of the layers 115 to 119 described above are similar to those of the semiconductor laser device according to the second embodiment shown in FIG.

In the semiconductor laser device according to the sixth embodiment, each of the layers 115 to 11 is formed on the low-dislocation low-dislocation n-type GaN layer 54 formed by the forming method shown in FIG.
9 is formed, good crystallinity can be realized in each of the layers 115 to 119. This makes this sixth
In the embodiment, similar to the second, fourth and fifth embodiments,
It is possible to obtain a semiconductor laser device having a thin thickness and good device characteristics.

In the first to sixth embodiments described above, the substrate is a sapphire substrate, a Si substrate, or a SiC substrate.
Although the substrate and the GaAs substrate are used, in addition to these substrates, a spinel substrate, a GaP substrate, an InP substrate, a quartz substrate, or the like may be used. In particular, when using a substrate other than these nitride-based semiconductors, dislocation The reduction effect is great.

(Seventh Embodiment) FIG. 13 shows a seventh embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating the method for forming the nitride-based semiconductor layer according to the embodiment. FIG. 14 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer of the seventh embodiment shown in FIG.

First, with reference to FIG. 13, a method for forming a nitride-based semiconductor layer according to the seventh embodiment will be described. In the seventh embodiment, an inverted mesa-shaped Si having an overhang portion 62a is formed on an n-type GaN substrate 61 as a base.
A mask layer 62 made of N is formed. The mask layer 62 made of SiN has a film thickness of about 10 nm to about 1000 nm and is formed in a stripe shape at a cycle of about 10 μm. As a method of forming the mask layer 62, first, a SiN layer (not shown) is formed on the entire surface of the n-type GaN substrate 61, and then a resist (not shown) is formed in a predetermined region on the SiN layer. . Then, when the SiN layer is etched using the resist as a mask, overetching is performed. Thereby, the overhang portion 62a
Forming an inverted mesa-shaped mask layer 62 having In this mask layer 62, the shortest distance between the adjacent mask layers 62 is smaller than the width of the exposed portion of the n-type GaN substrate 61 located between the adjacent mask layers 62.

After that, the MOCVD method or the HVPE method is used.
On the n-type GaN substrate 61, about 700 ° C. to about 90 ° C.
Under the temperature condition of 0 ° C, a thickness of about 10 nm to about 50 nm is obtained.
Low temperature buffer layer made of AlGaN or GaN
63 is formed. The low temperature buffer layer 63 is
It is an example of the "buffer layer" of the invention. And the mask layer
62 on the low temperature buffer layer 63 as a selective growth mask
To n-type Al_WB_XGa _YIn_ZTl_1-WXYZForm N layers
Make it longer. Al_WB_XGa_YIn_ZTl_1-WXYZComposition of N
Is a composition excluding X = Y = 0, and Al_WB_XGa_YI
n_ZTl_1-WXYZThe lattice constant of N is the same as that of GaN.
Small For example, Al_WGa_1-WN (0 <W ≦ 1)
Or B_XGa_1-XN (0 <X ≦ 1) and the like. This 7th
In the embodiment, for example, B_0.05Ga_0.95N consisting of N
Type BGaN layer 64 at a temperature of about 850 ° C. to about 1400 ° C.
It is formed with a thickness of about 2 μm under the conditions. In addition, this n-type B
The GaN layer 64 is the “semiconductor layer” and “nitride” of the present invention.
It is an example of a "semiconductor layer".

When the low temperature buffer layer 63 is grown, the mask layer 62 has the overhang portion 62a, so that the raw material is hard to reach under the overhang portion 62a. Therefore, the low temperature buffer layer 63 below the overhang portion 62a is thin. However, in the seventh embodiment, since the low temperature buffer layer 63 is formed at a relatively high temperature (about 700 ° C. to about 900 ° C.), the overhang portion 62a is formed.
Raw materials reach the bottom to some extent. Therefore, the low temperature buffer layer 63 is formed up to the position where it contacts the side surface of the mask layer 62. Thereby, the n-type BGa is formed on the low temperature buffer layer 63.
When the N layer 64 is grown, the n-type BGaN layer 64 grows faster in the central portion where the low-temperature buffer layer 63 has a large thickness, while the n-type BGaN layer 64 grows below the n-type BGaN layer 64 where the thickness is low. The BGaN layer 64 grows slowly. Therefore, similar to the first embodiment shown in FIG. 1, the trapezoidal n-type BGaN layer 64 is easily formed from the initial growth stage, and the trapezoidal n-type BGa layer 64 is formed.
Since the side surface of the N layer 64 gradually grows in the lateral direction, n-type B
Lateral growth is promoted from the initial growth stage of the GaN layer 64. As a result, the n-type BGaN layer 64 with a low dislocation can be grown thick on the n-type GaN substrate 61 without providing a GaN layer as an underlayer as in the conventional example shown in FIG. In this case, since it is not necessary to provide a GaN layer as a base layer, the entire thickness can be made smaller than that of the conventional example shown in FIG.

Next, with reference to FIG. 14, a semiconductor laser device formed by using the method for forming a nitride-based semiconductor layer according to the seventh embodiment will be described. In the semiconductor laser device of the seventh embodiment, the first conductivity type layer 115 made of n-type BGaN and the n-type BGaN are formed on the n-type BGaN layer 64 shown in FIG.
First conductivity type cladding layer 116 made of GaN, AlGa
An MQW light emitting layer 117 made of N, a second conductivity type cladding layer 118 made of p-type BGaN, and a second conductivity type contact layer 119 made of p-type GaN are formed. Further, an n-type first conductivity type electrode 120 is formed on the back surface of the n-type GaN substrate 61. The p-type second conductivity type electrode 12 is formed on the upper surface of the second conductivity type contact layer 119.
1 is formed. In addition, each of the layers 115 to 11 described above
The film thickness of 9 is the same as that of the semiconductor laser device of the second embodiment shown in FIG.

In the semiconductor laser device according to the seventh embodiment, each of the layers 115 to 1 is formed on the low dislocation n-type BGaN layer 64.
Since 19 is formed, good crystallinity can be realized in each of the layers 115 to 119. Further, in the forming method of FIG. 13, since the entire thickness is formed thin, when each of the layers 115 to 119 is formed thereon, the thickness of the semiconductor laser element becomes thin. As a result, also in the seventh embodiment, a semiconductor laser device having a small thickness and good device characteristics can be obtained as in the second and fourth to sixth embodiments.

Further, in the semiconductor laser device according to the seventh embodiment, since the MQW light emitting layer 117 is formed on the thickly formed low-dislocation n-type BGaN layer 64, the MQW light emitting layer 117 has a small lattice constant. MQW light emitting layer 11
Even if the Al composition of 7 is increased, good crystallinity can be realized. Therefore, it is possible to realize a semiconductor laser having a shorter wavelength than the conventional nitride semiconductor laser.

In the seventh embodiment, the n-type GaN substrate 61 is used as the substrate, but the n-type GaN substrate 6 is used.
1 instead of sapphire substrate, Si substrate, SiC substrate,
A GaAs substrate, a spinel substrate, a GaP substrate, an InP substrate, a quartz substrate or the like may be used.

(Eighth Embodiment) FIG. 15 shows an eighth embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating the method for forming the nitride-based semiconductor layer according to the embodiment. FIG. 16 is a sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer according to the eighth embodiment shown in FIG.

First, with reference to FIG. 15, a method for forming a nitride semiconductor layer according to the eighth embodiment will be described. In the eighth embodiment, the temperature is about 500 ° C. on the sapphire substrate 71.
~ About 700nm under temperature conditions of about 700nm
Forming a low temperature buffer layer 72 made of AlGaN or GaN having a thickness of On the low-temperature buffer layer 72, an underlying GaN layer 73 is formed with a thickness of about 2 μm by MOCVD or HVPE. That Ga
A mask layer 74 made of SiN having an inverted mesa shape having an overhang portion 74a is formed on the N layer 73. In this mask layer 74, the shortest distance between the adjacent mask layers 74 is smaller than the width of the exposed portion of the GaN layer 73 located between the adjacent mask layers 74.

Then, on the GaN layer 73, a temperature of about 400.degree.
Under the temperature condition of about 500 ° C., the low temperature buffer layer 75 made of GaInN having a thickness of about 10 nm to about 50 nm is formed. The low temperature buffer layer 75 is an example of the “buffer layer” in the present invention. Then, using the MOCVD method or the HVPE method, with the mask layer 74 as a selective growth mask, Al _{1 -WXYZ} B _{W is formed} on the low temperature buffer layer 75.
A Ga _x In _Y Tl _Z N layer is grown. Al _1-WXYZ B _W
The composition of Ga _X In _Y Tl _Z N is a composition excluding Y = Z = 0, and the lattice constant of Al _1-WXYZ B _W Ga _X In _Y Tl _Z N is larger than that of GaN. For example, Ga
_1-Y In _Y N (0 <Y ≦ 1) or Ga _1-Z Tl _Z N (0 <
Z ≦ 1) and the like. In the eighth embodiment, for example, the AlGaInN layer 76 is formed at about 600 ° C. to about 1200 ° C.
It is formed with a thickness of about 1 μm under a temperature condition of ° C. The AlGaInN layer 76 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

When the low temperature buffer layer 75 is grown, since the mask layer 74 has the overhang portion 74a, it becomes difficult for the raw material to reach under the overhang portion 74a. In the eighth embodiment, a relatively low temperature (about 400 ° C to
Since the low temperature buffer layer 75 is formed at about 500 ° C., the low temperature buffer layer 75 is not formed under the overhang portion 74a. As a result, on the low temperature buffer layer 75, A
When the lGaInN layer 76 is grown, the AlGaInN layer 76 is formed in the central portion where the low temperature buffer layer 75 has a large thickness.
Of the AlGaIn layer under the overhang portion 74a where the low temperature buffer layer 75 has a small thickness.
The growth of the N layer 76 slows down. Therefore, the trapezoidal AlGaInN layer 76a (see FIG. 15) is easily formed from the initial stage of growth, and the trapezoidal AlGaI layer 76a is formed.
Since the side surface of the nN layer 76a gradually grows in the lateral direction,
Lateral growth is promoted from the initial growth stage of the 1GaInN layer 76. Therefore, since the dislocations are laterally bent from the initial growth stage of the AlGaInN layer 76, AlGaIn
It is possible to reduce dislocations propagating in the vertical direction from the initial growth stage of the N layer 76. As a result, the low-dislocation AlGaInN layer 76 can be hetero-grown on the GaN layer 73 with a small film thickness.

Next, with reference to FIG. 16, a structure of a semiconductor laser device formed by using the method for forming a nitride semiconductor layer shown in FIG. 15 will be described. In the semiconductor laser device of the eighth embodiment, the AlGaInN shown in FIG.
On the layer 76, as shown in FIG. 16, a first conductivity type contact layer 105, a first conductivity type clad layer 106, an MQW light emitting layer 107, a second conductivity type clad layer 108, a second conductivity type contact layer 109, n. Type first conductivity type electrode 110 and p type second conductivity type electrode 111 are formed. In addition,
The composition and film thickness of each of the layers 105 to 109 are similar to those of the semiconductor laser device of the first embodiment shown in FIG.

In the eighth embodiment, each layer 1 is formed on the low-dislocation AlGaInN layer 76 having such a thin film thickness.
05-109 to form each layer 105-1
In 09, good crystallinity can be realized.
As a result, in the eighth embodiment, it is possible to obtain a semiconductor laser device having a small thickness and good characteristics.

(Ninth Embodiment) FIGS. 17 to 19 are sectional views for explaining a method for forming a nitride-based semiconductor layer according to a ninth embodiment of the present invention. FIG. 20 shows FIGS.
FIG. 10 A sectional view showing a semiconductor laser device manufactured by the method for forming the nitride-based semiconductor layer according to the ninth embodiment shown in FIG. 9. A method for forming a nitride-based semiconductor layer according to the ninth embodiment will be described with reference to FIGS.

First, as shown in FIG. 17, the MOVPE method is used on the C-plane of the sapphire substrate 81 to be the base.
While maintaining the substrate temperature at about 600 ° C., a buffer layer made of undoped AlGaN having a thickness of about 15 μm is formed. A predetermined region of the buffer layer is formed by photolithography and RIE (Reactive Ion).
Etching) or the like is used to perform patterning to form the stripe-shaped buffer layer 82. The buffer layer 82 is the sapphire substrate 81.
And a nitride-based semiconductor layer (undoped GaN layer 84) formed on the buffer layer 82 in a later step are provided to reduce the difference in lattice constant. When the width of the buffer layer 82 is W3 and the width of the opening between the buffer layers 82 is b3, the stripe shape of the buffer layer 82 is the buffer layer 82.
And the width b3 of the opening between the buffer layer 82 and
It is preferably formed so as to satisfy the following formulas (1), (2) and (3).

B3 [μm] + W3 [μm] ≦ 40 [μm] (1) b3 [μm] ≧ 3 [μm] (2) W3 [μm] ≧ 1 [μm] ( 3) The above formula (1) is the sum of the width W3 of the buffer layer 82 and the width b3 of the opening between the buffer layers 82 (the buffer layer 82).
The period) is 40 μm or less.

Next, the buffer layer 82 and the buffer layer 8
On the upper surface of the sapphire substrate 81 exposed between the two, about 1
SiN or SiO ₂ having a film thickness of 00 nm to several μm
After a mask layer (not shown) made of is formed, the mask layer on the buffer layer 82 is removed by wet etching or the like to expose a part of the upper surface of the sapphire substrate 81 between the buffer layers 82. Then, a mask layer 83 is formed as shown in FIG. In this case, at least about 1 is provided between the buffer layer 82 and the mask layer 83.
The sapphire substrate 81 of about μm is exposed.

Thereafter, as shown in FIG. 19, MOCVD is performed.
Method or HVPE method, using the mask layer 83 as a selective growth mask, the undoped GaN is formed on the buffer layer 82.
Form layer 84. The undoped GaN layer 84 is formed to have a thickness of about 2 μm under a temperature condition of about 950 ° C. to about 1200 ° C. In addition, this undoped Ga
The N layer 84 is an example of the “semiconductor layer” or the “nitride-based semiconductor layer” in the present invention.

Here, undoped G is formed on the buffer layer 82.
When growing the aN layer 84, since the buffer layer 82 is not formed on the upper surface of the sapphire substrate 81 exposed between the buffer layer 82 and the mask layer 83, the undoped GaN layer 84 is hard to grow. . Therefore, the trapezoidal undoped GaN layer 84a (FIG.
(Refer to FIG. 3) is easily formed, and the side surface of the trapezoidal undoped GaN layer 84a gradually grows in the lateral direction, so that the lateral growth is promoted from the initial growth stage of the undoped GaN layer 84. Therefore, since the dislocations are bent laterally from the initial growth stage of the undoped GaN layer 84, the dislocations propagating in the vertical direction from the initial growth stage of the undoped GaN layer 84 can be reduced. As a result, the low-dislocation undoped GaN layer 8 is formed on the sapphire substrate 81.
4 can be hetero-grown with a thin film thickness.

Next, with reference to FIG. 20, a structure of a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer of the ninth embodiment will be described. In the semiconductor laser device of the ninth embodiment, the undoped Ga shown in FIG.
On the N layer 84, as shown in FIG. 20, a first conductivity type contact layer 105, a first conductivity type clad layer 106, an MQW light emitting layer 107, a second conductivity type clad layer 108, a second conductivity type contact layer 109, An n-type first conductivity type electrode 110 and a p-type second conductivity type electrode 111 are formed. The compositions and film thicknesses of the layers 105 to 109 are the same as those of the semiconductor laser device according to the first embodiment shown in FIG.

In the ninth embodiment, the layers 105 to 109 are formed on the low-dislocation undoped GaN layer 84 having such a small film thickness, so that the layers 105 to 105 are formed.
In 109, good crystallinity can be realized. As a result, in the ninth embodiment, as in the first and third embodiments, a semiconductor laser device having a small thickness and good characteristics can be obtained.

(Tenth Embodiment) FIG. 21 is a sectional view for explaining a method for forming a semiconductor layer according to a tenth embodiment of the present invention. 22 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a semiconductor layer of the tenth embodiment shown in FIG. In the tenth embodiment, unlike the first to ninth embodiments, a method of forming a semiconductor layer (ZnO layer (zinc oxide layer)) other than the nitride semiconductor layer will be described.

First, a method of forming a semiconductor layer according to the tenth embodiment will be described with reference to FIG. In the tenth embodiment, first, the mask layer 92 made of SiN is formed directly on the upper surface of the sapphire substrate 91 as a base. The mask layer 92 is formed in an inverted mesa shape (inverted trapezoidal shape) having an overhang portion 92a. In this mask layer 92, the shortest distance between the adjacent mask layers 92 is smaller than the width of the exposed portion of the sapphire substrate 91 located between the adjacent mask layers 92.

As a method of forming such a mask layer 92, first, a SiN layer (not shown) is formed on the entire surface of the sapphire substrate 91, and then a resist (not shown) is formed in a predetermined region on the SiN layer. To form. Then, the resist layer is used as a mask to wet-etch the SiN layer to easily form the inverted trapezoidal mask layer 92 having the overhang portion 92a. The mask layer 92 is formed in a stripe shape (elongated shape) having a period of about 7 μm and a thickness of about 10 nm to about 1000 nm. Further, it is preferable that the opening of the mask layer 92 is formed, for example, in the [11-20] direction of sapphire or the [1-100] direction of sapphire.

After that, the MOC is formed on the sapphire substrate 91.
Using the VD method or MBE (molecular beam epitaxy) method, a growth rate of about 0.08 μm / sec and a temperature of about 150 ° C.
A ZnO thin film 93 having a thickness of about 2 nm to about 10 nm is grown at a growth temperature of about 200 ° C. In addition, this Zn
The O thin film 93 is an example of the “buffer layer” in the present invention.
Then, using the mask layer 92 as a selective growth mask, ZnO
A ZnO layer 94 is formed on the thin film 93. The ZnO layer 94 has a growth rate of about 1 μm / sec and a temperature of about 400 ° C.
At a growth temperature of about 2 μm. The ZnO layer 94 is the “semiconductor layer” of the present invention.
Is an example.

When the ZnO thin film 93 is grown, since the mask layer 92 has the overhang portion 92a, it becomes difficult for the raw material to reach under the overhang portion 92a. Therefore, the thickness of the ZnO thin film 93 below the overhang portion 92a is smaller than the thickness of the portion (central portion) other than below the overhang portion 92a. Accordingly, when the ZnO layer 94 is grown on the ZnO thin film 93, the ZnO layer 94 grows faster in the central portion where the ZnO thin film 93 has a larger thickness, and the overhang portion 92a where the ZnO thin film 93 has a smaller thickness. Below, the growth of the ZnO layer 94 slows down. Therefore, similar to the first embodiment shown in FIG. 1, the ZnO layer 94 is likely to be formed into a trapezoidal shape from the initial stage of growth, and the side surface of the trapezoidal ZnO layer 94 gradually grows in the lateral direction. Therefore, lateral growth is promoted from the initial stage of growth of the ZnO layer 94. Therefore, the ZnO layer 9
Since the dislocations are laterally bent from the initial growth stage of 4,
It is possible to reduce dislocations propagating in the vertical direction from the initial growth stage of the ZnO layer 94. As a result, the sapphire substrate 9
A low-dislocation ZnO layer 94 can be hetero-grown on the first layer with a small film thickness.

Next, with reference to FIG. 22, a structure of a semiconductor laser device manufactured by using the method for forming a semiconductor layer of the tenth embodiment will be described.

In the semiconductor laser device of the tenth embodiment,
As shown in FIG. 22, a first conductivity type contact layer 105a made of Ga-doped n-type ZnO having a thickness of about 4 μm is formed on the ZnO layer 94 shown in FIG. About 0.4 is formed on the first conductivity type contact layer 105a.
Ga-doped n-type Mg _0.15 Zn _0.85 having a film thickness of 5 μm
A first conductivity type cladding layer 106a made of O is formed. On the first conductivity type cladding layer 106a, ZnO /
A multiple quantum well (MQW) light emitting layer 107a made of Cd _0.1 Zn _0.9 O is formed. Nitrogen-doped p-type M having a thickness of about 0.45 μm is formed on the MQW light emitting layer 107a.
Second conductivity type cladding layer 108 made of g _0.15 Zn _0.85 O
a is formed. The second conductivity type cladding layer 108
On a, nitrogen-doped p having a film thickness of about 0.15 μm
A second conductivity type contact layer 109a made of ZnO is formed. In addition, the first conductivity type contact layer 105a
An n-type first conductivity type electrode 110a made of Al, Ti, or the like is formed on the exposed upper surface. Further, N is formed on the upper surface of the second conductivity type contact layer 109a.
A p-type second conductivity type electrode 111a made of i, Pd, Pt, or the like is formed.

The first conductivity type contact layer 105a,
First conductivity type cladding layer 106a, MQW light emitting layer 107
The second conductive type clad layer 108a and the second conductive type contact layer 109a are examples of the "semiconductor element layer" in the present invention.

In the semiconductor laser device of the first embodiment described above, each layer 105 is formed on the ZnO layer 94 which is formed by using the forming method shown in FIG. 21 and has a reduced dislocation and reduced dislocations.
a to 109a are formed, each layer 105a to 109a is formed.
In, good crystallinity can be realized. Therefore, in the tenth embodiment, it is possible to obtain a semiconductor laser device having a small thickness and good device characteristics.

It should be understood that the embodiments disclosed this time are exemplifications in all respects and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and includes meaning equivalent to the scope of claims for patent and all modifications within the scope.

For example, although the mask layers having various overhang shapes are shown in the above-described embodiments, the present invention is not limited to this, and the exposed portion of the underlying layer in which the distance between the adjacent mask layers is located between the adjacent mask layers. A structure other than the above-described embodiments may be used as long as the shape is smaller than the width of the above.

Further, in the above-mentioned first to tenth embodiments, the example in which the stripe-shaped mask layer is formed is shown, but the present invention is not limited to this, and for example, a hexagonal mask layer, a triangular mask layer, A mask layer having hexagonal openings, a mask layer having triangular openings, or the like may be used.

Further, the material of the mask layer in the above first to tenth embodiments is not limited to the above embodiment, and other materials may be used. For example, SiO _x ,
TiO _x , ZrO _x, refractory metal, etc. are considered.

Further, in the above-mentioned first to tenth embodiments, the case where the semiconductor laser device is manufactured has been described, but the present invention is not limited to this, and other devices such as a light emitting diode, a field effect transistor, a photodiode or a solar cell are used. The present invention can also be applied to the case of manufacturing the semiconductor element.

[0122]

As described above, according to the present invention, it is possible to easily hetero-grow a low dislocation semiconductor layer with a small film thickness on a base.

[Brief description of drawings]

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

2 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the first embodiment shown in FIG.

FIG. 3 is a cross-sectional view illustrating a method of forming a nitride-based semiconductor layer according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the second embodiment shown in FIG.

FIG. 5 is a sectional view illustrating a method for forming a nitride-based semiconductor layer according to a third embodiment of the present invention.

6 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the third embodiment shown in FIG.

FIG. 7 is a cross-sectional view illustrating a method for forming a nitride-based semiconductor layer according to a fourth embodiment of the present invention.

8 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the fourth embodiment shown in FIG.

FIG. 9 is a sectional view illustrating a method of forming a nitride-based semiconductor layer according to a fifth embodiment of the present invention.

10 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the fifth embodiment shown in FIG.

FIG. 11 is a sectional view illustrating a method of forming a nitride-based semiconductor layer according to a sixth embodiment of the present invention.

12 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the sixth embodiment shown in FIG.

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

14 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the seventh embodiment shown in FIG.

FIG. 15 is a sectional view illustrating the method for forming the nitride-based semiconductor layer according to the eighth embodiment of the present invention.

16 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a nitride-based semiconductor layer according to the eighth embodiment shown in FIG.

FIG. 17 is a sectional view illustrating the method for forming the nitride-based semiconductor layer according to the ninth embodiment of the present invention.

FIG. 18 is a sectional view illustrating the method for forming the nitride-based semiconductor layer according to the ninth embodiment of the present invention.

FIG. 19 is a sectional view illustrating the method for forming the nitride-based semiconductor layer according to the ninth embodiment of the present invention.

FIG. 20 is a cross-sectional view showing a semiconductor laser device manufactured by using the method for forming the nitride-based semiconductor layer according to the ninth embodiment shown in FIGS. 17 to 19.

FIG. 21 is a sectional view illustrating a method of forming a semiconductor layer according to a tenth embodiment of the present invention.

22 is a sectional view showing a semiconductor laser device manufactured by using the method for forming a semiconductor layer according to the tenth embodiment shown in FIG. 21. FIG.

FIG. 23 is a cross-sectional view for explaining an example of a conventional method for forming a nitride-based semiconductor layer using selective lateral growth.

FIG. 24 is a cross-sectional view for explaining an example of a conventional method for forming a nitride-based semiconductor layer using selective lateral overgrowth.

FIG. 25 is a cross-sectional view for explaining an example of a conventional method for forming a nitride-based semiconductor layer using selective lateral growth.

FIG. 26 is a cross-sectional view for explaining an example of a conventional method for forming a nitride-based semiconductor layer using selective lateral growth.

FIG. 27 is a cross-sectional view illustrating a conventional method for directly forming a nitride-based semiconductor layer on a substrate by using selective lateral growth.

FIG. 28 is a cross-sectional view for explaining a conventional method for forming a nitride-based semiconductor layer made of a mixed crystal.

[Explanation of symbols]

1, 21, 81, 91 Sapphire substrate (base) 2, 12, 22, 32, 42, 52, 62, 74, 8
3,92 Mask layers 2a, 32a, 62a, 74a, 92a Overhang part 3, 13, 23, 33, 43, 63, 75 Low temperature buffer layer (buffer layer) 4, 24, 84 Undoped GaN layer (semiconductor layer) 11 , 31 n-type SiC substrate (base) 14, 44, 54 n-type GaN layer (semiconductor layer) 12a, 12c, 22a, 22b SiN layer 12b SiO ₂ layer 34 n-type InGaN layer (semiconductor layer) 41 n-type GaAs substrate ( Base layer 51 n-type Si substrate (base layer) 53, 82 Buffer layer 61 n-type GaN substrate (base layer) 64 n-type BGaN layer (semiconductor layer) 73 GaN layer (base layer) 76 AlGaInN layer (semiconductor layer) 93 ZnO thin film (buffer) Layer) 94 ZnO layer (semiconductor layer) 105, 105a first conductivity type contact layer (semiconductor element layer) 115 first conductivity type layer (half) Body element layer) 106, 106a, 116 First conductivity type cladding layer (semiconductor element layer) 107, 107a, 117 MQW light emitting layer (semiconductor element layer) 108, 108a, 118 Second conductivity type cladding layer (semiconductor element layer) 109 , 109a, 119 Second conductivity type contact layer (semiconductor element layer)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroki Ohbo             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Takashi Kano             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Nobuhiko Hayashi             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F-term (reference) 5F041 AA41 AA43 AA44 CA03 CA34                       CA65                 5F045 AA02 AA04 AA05 AB14 AB17                       AB18 AB22 AB23 AD09 AD10                       AD11 AF02 AF04 AF09 BB12                       CA12 DA53 DA55 DA63 DA64                       DB01                 5F073 AA74 CA07 CB02 CB04 CB05                       DA05 DA22 DA35 EA28

Claims (20)

[Claims] 1. A plurality of mask layers formed at a predetermined interval so as to contact the upper surface of a base and expose a part of the base, and an upper surface of the base exposed between the mask layers. A buffer layer formed on the buffer layer, and a semiconductor layer formed on the buffer layer and the mask layer, the semiconductor layer being made of a material different from that of the base, and in the vicinity of the mask layer on the upper surface of the exposed base. The thickness of the formed buffer layer is smaller than the thickness of the buffer layer formed in the central part on the upper surface of the exposed underlayer. 2. A plurality of mask layers formed at a predetermined interval so as to contact the upper surface of the base and expose a part of the base, and the upper surface of the base exposed between the mask layers. A buffer layer formed on the exposed underlayer, the buffer layer and the mask layer, and a semiconductor layer made of a material different from that of the underlayer, wherein the buffer layer is the mask layer. A semiconductor element, which is formed in a central portion on the upper surface of the exposed underlayer with substantially the same thickness and is not formed in the vicinity of the mask layer on the exposed upper surface of the underlayer. 3. The shortest distance between the adjacent mask layers is
The semiconductor element according to claim 1, wherein the width is smaller than the width of the exposed portion of the base located between the adjacent mask layers. 4. The semiconductor device according to claim 3, wherein the mask layer has an overhang portion protruding above the exposed portion of the base. 5. The semiconductor according to claim 4, wherein the thickness of the buffer layer located under the overhang portion of the mask layer is smaller than the thickness of the buffer layer located under the shortest distance portion between the adjacent mask layers. element. 6. The thickness of the buffer layer located under the overhang portion of the mask layer decreases substantially at the same rate as the distance from the shortest distance portion between the adjacent mask layers decreases. The semiconductor device described. 7. The buffer layer is formed on the central portion of the upper surface of the underlayer exposed between the mask layers to have substantially the same thickness, and the upper surface of the underlayer located below the overhang portion of the mask layer. The semiconductor device according to claim 4, which is not formed on the semiconductor device. 8. The semiconductor device according to claim 4, wherein at least a part of the mask layer has an inverted trapezoidal shape. 9. The underlayer includes a substrate, and the mask layer is formed so as to be in contact with an upper surface of the substrate.
The semiconductor device according to claim 1. 10. The substrate includes one substrate selected from the group consisting of a nitrogen-free Group 3-5 semiconductor substrate, a Group 4 semiconductor substrate, a sapphire substrate, a spinel substrate, a SiC substrate, and a quartz substrate. Item 9. The semiconductor device according to item 9. 11. The semiconductor according to claim 1, wherein a dislocation density of the semiconductor layer near an upper surface of the mask layer is smaller than a dislocation density of the semiconductor layer near an upper surface of the base. element. 12. The dislocation density of the semiconductor layer near the upper surface of the mask layer is ½ or less of the dislocation density of the semiconductor layer near the upper surface of the base.
The semiconductor device according to 1. 13. The semiconductor device according to claim 1, wherein the semiconductor layer includes a nitride semiconductor layer. 14. The buffer layer is formed at a growth temperature lower than a growth temperature of the semiconductor layer.
The semiconductor device according to any one of 1 to 13. 15. The semiconductor device layer further comprising a semiconductor device layer formed on the semiconductor layer and having a device region.
The semiconductor element according to any one of 1. 16. A step of forming a plurality of mask layers at a predetermined interval so as to contact the upper surface of the base and expose a part of the base, and a buffer layer is formed on the upper surface of the base. And a step of forming a semiconductor layer made of a material different from that of the base on the buffer layer and the mask layer, wherein the buffer formed near the mask layer on the upper surface of the base. The method for forming a semiconductor layer, wherein the thickness of the layer is smaller than the thickness of the buffer layer formed in the central portion on the upper surface of the base. 17. A step of forming a plurality of mask layers at a predetermined interval so as to contact the upper surface of the underlayer and expose a part of the underlayer, and forming a buffer layer on the upper surface of the underlayer. And a step of forming, on the buffer layer and the mask layer, a semiconductor layer made of a material different from that of the base, the buffer layer being substantially at a central portion on an upper surface of the base. A method of forming a semiconductor layer, which has the same thickness and is not formed in the vicinity of the mask layer on the upper surface of the base. 18. The method for forming a semiconductor layer according to claim 16, wherein the shortest distance between the adjacent mask layers is smaller than the width of the exposed portion of the base located between the adjacent mask layers. 19. The mask layer has an overhang portion protruding above the exposed portion of the base.
A method for forming a semiconductor layer according to item 1. 20. The method for forming a semiconductor layer according to claim 16, further comprising growing a semiconductor device layer having a device region on the semiconductor layer.