JPH0778762A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a low-cost semiconductor device capable of significantly reducing a leak current, excellent in current controllability, and a manufacturing method thereof. [Structure] A GaAs layer 11 and an Inx Ga1-x As layer are provided between a GaAs substrate 1 and a non-doped GaAs buffer layer 2.
The strained superlattice layer 7 was formed by alternately laminating a plurality of layers 12, and the plurality of Inx Ga1-x As layers 12 were formed such that the In composition ratio x was smaller as it was farther from the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a compound semiconductor device used for high frequency communication and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 7 is a cross-sectional view showing the structure of a conventional semiconductor device. In the figure, 101 has a thickness of 100-2.
A semi-insulating GaAs substrate having a thickness of 00 μm, 102 is an undoped GaAs buffer layer having a thickness of about 1 μm, which is epitaxially grown on the semi-insulating GaAs substrate 101, and a non-doped GaAs buffer layer having a thickness of 103.
Epitaxially grown on, thickness is 0.2-0.5
n-type GaAs operating layer of μm, 104 is this n-type Ga
Formed on the As operating layer 103, the thickness is about 0.3 μm.
Is the source electrode, and 105 is the n-type GaAs operating layer 1
A drain electrode 106 having a thickness of about 0.3 μm formed on the gate electrode 03 and a gate electrode 106 having a thickness of about 0.5 μm formed on the n-type GaAs operating layer 103.

Next, a manufacturing process of this semiconductor device will be described. Molecular beam epitaxy (MB
E) method, metal organic chemical vapor deposition (MOCVD) method, liquid phase epitaxial (LPE) method, etc.
As buffer layer 102 and n-type GaAs operating layer 104
Are sequentially epitaxially grown, a source electrode 104 and a drain electrode 105 are formed on the surface, and a gate electrode 106 is further formed.

Next, the operation of this semiconductor device will be described. By applying a voltage to the gate 106, an n-type G
The carrier depletion layer in the aAs operation layer 103 is controlled, and the current flowing between the source 104 and the drain 105 is controlled.

Usually, the surface of the semi-insulating GaAs substrate 101, which is inexpensive as a semiconductor material, has a surface area of 10 ⁴ to 10 ⁵ cm.
^{There are 2} dislocations and other defects, most of which are GaAs buffer layers 10 epitaxially grown on the substrate 1.
2, and n-type GaAs operating layer 103. Therefore, the GaAs buffer layer 102 and the n-type GaA
In the s-operation layer 103, a defect caused by a defect on the surface of the substrate 1 occurs.

[0006]

Since the conventional semiconductor device is configured as described above, the level due to defects is formed in the non-doped GaAs buffer layer 102, which deteriorates the insulating property. Therefore, there is a problem that current leakage occurs.

Further, in the n-type GaAs operating layer 102, a level caused by a defect is formed, which makes it difficult to control the current flowing between the source and the drain of the semiconductor device. .

The present invention has been made to solve the above problems, and is an inexpensive semiconductor device capable of preventing a leak current and preventing deterioration of current controllability, and a method of manufacturing the same. The purpose is to provide.

[0009]

A semiconductor device according to the present invention comprises, between a semiconductor substrate and a buffer layer, a first semiconductor layer having the same crystal structure and lattice constant as those of the semiconductor substrate, and a crystal layer. A strained superlattice layer having the same structure as that of the semiconductor substrate and alternately laminating a plurality of second semiconductor layers having a lattice constant larger than that of the semiconductor substrate is provided, and the strained superlattice layer is configured. A plurality of second semiconductor layers,
The farther from the semiconductor substrate, the closer the lattice constant is to the lattice constant of the buffer layer.

In the semiconductor device according to the present invention, between the strained superlattice layer and the buffer layer, a third semiconductor layer having the same crystal structure and lattice constant as that of the semiconductor substrate, and a crystal structure are provided. And a superlattice layer in which a plurality of fourth semiconductor layers having the same lattice constant as that of the semiconductor substrate and a forbidden band width larger than that of the semiconductor substrate are alternately laminated.

According to the present invention, in the above semiconductor device, the semiconductor substrate, the buffer layer, and the first conductivity type operation layer are each formed of GaAs, and the first semiconductor layer forming the strained superlattice layer, and The second semiconductor layers are composed of GaAs and Inx Ga1-x As, respectively, and the In composition ratio x is smaller as the plurality of Inx Ga1-x As layers that are the second semiconductor layers are farther from the semiconductor substrate. It is formed so as to have.

In the semiconductor device according to the present invention, the third semiconductor layer and the fourth semiconductor layer forming the superlattice layer are made of GaAs and Aly Ga1-y As, respectively.
And a plurality of Aly G which are the fourth semiconductor layers.
The a1-y As layer is formed so as to have a constant Al composition ratio y within the range of 0.2 or more and 0.3 or less.

In the semiconductor device according to the present invention, the semiconductor substrate, the buffer layer, and the first-conductivity-type operating layer are each formed of GaAs, and the first semiconductor layer forming the strained superlattice layer is formed. The second semiconductor layers are composed of Aly Ga1-y As and Inx Ga1-x As, respectively, and a plurality of Aly Ga1-x that are the first semiconductor layers are formed.
The Al composition ratio x of the y As layer is set to a constant value within the range of 0.2 or more and 0.3 or less, and the plurality of Inx Ga1-x As layers that are the second semiconductor layers are located far from the semiconductor substrate. The In composition ratio x is as small as possible.

In the semiconductor device according to the present invention, a GaAs layer is formed between the first semiconductor layer made of Aly Ga1-y As and the second semiconductor layer made of Inx Ga1-x As. It is a thing.

Further, in the method for manufacturing a semiconductor device according to the present invention, a first semiconductor layer having a crystal structure and a lattice constant identical to those of the semiconductor substrate and a crystal structure of the semiconductor substrate are provided on the semiconductor substrate. Second semiconductor layers which are the same as those of the first semiconductor layer and have a smaller lattice constant as the growth temperature increases, and are grown while increasing the temperature of the semiconductor substrate to form a strained superlattice layer. A buffer layer made of the same material as the semiconductor substrate and a first conductivity type operation layer made of the same material as the semiconductor substrate are sequentially formed on the strained superlattice layer.

According to the present invention, in the method for manufacturing a semiconductor device, after forming the strained superlattice layer, a third semiconductor layer made of the same material as the semiconductor substrate and a crystal structure are formed on the strained superlattice layer. And a fourth semiconductor layer having the same lattice constant as that of the semiconductor substrate and a forbidden band width larger than that of the semiconductor substrate, are alternately grown to form a superlattice layer, and then the superlattice layer is formed. It includes a step of forming the buffer layer on the lattice layer.

According to the present invention, in the method of manufacturing a semiconductor device, a GaAs layer is used as the first semiconductor layer and an Inx Ga1-x is used as the second semiconductor layer on a GaAs substrate.
An As layer is grown to form a strained superlattice layer, and a GaAs buffer layer and a first conductivity type GaAs operating layer are formed on the strained superlattice layer.

According to the present invention, in the method of manufacturing a semiconductor device described above, a GaAs layer is used as a third semiconductor layer, a fourth semiconductor layer is 0.2 or more, 0.
Aly G having a constant Al composition ratio y within the range of 3 or less
The a1-y As layer is grown to form a superlattice layer.

Further, according to the present invention, in the method of manufacturing a semiconductor device, Aly having a constant Al composition ratio y within the range of 0.2 or more and 0.3 or less as the first semiconductor layer on the GaAs substrate. A Ga1-y As layer and an Inx Ga1-x As layer as a second semiconductor layer are grown to form a strained superlattice layer, and a GaAs buffer layer and a first conductivity type GaAs operating layer are sequentially formed on the strained superlattice layer. To form.

Further, according to the present invention, in the method of manufacturing a semiconductor device described above, Aly Ga1-y forming the strained superlattice layer is formed.
This includes a step of forming a GaAs layer between the As layer and the Inx Ga1-x As layer.

[0021]

According to the present invention, a strained superlattice layer having a plurality of first semiconductor layers and second semiconductor layers alternately laminated is provided between the semiconductor substrate and the buffer layer. Since the plurality of second semiconductor layers forming the structure have a lattice constant closer to the lattice constant of the buffer layer as the distance from the semiconductor substrate increases, defects such as dislocations on the surface of the semiconductor substrate cause defects in the buffer layer and the buffer layer. It is possible to prevent the current from being passed on to the operating layer, which makes it possible to prevent leakage current and prevent deterioration of current controllability.

In the present invention, a third semiconductor layer is provided between the strained superlattice layer and the buffer layer, and a fourth semiconductor layer having a forbidden band width larger than that of the third semiconductor layer. Since a plurality of superlattice layers are alternately laminated, the leak current between the buffer layer and the substrate can be greatly reduced.

Further, in the present invention, since the semiconductor substrate, the buffer layer, the first-conductivity-type operation layer, and the first semiconductor layer of the strained superlattice layer are made of GaAs, which is an inexpensive material, leakage current is reduced. A semiconductor device which is small and has good current controllability can be obtained at low cost.

Further, in the present invention, the semiconductor substrate, the buffer layer, and the first conductivity type operation layer are made of GaAs, and the first semiconductor layer constituting the strained superlattice layer is
Since it is made of AlyGa1-yAs having a band gap larger than that of GaAs, the leak current between the buffer layer and the substrate can be further reduced.

In the present invention, the above Aly G
a1-y As first semiconductor layer and Inx Ga1-x
Since the GaAs layer is interposed between the second semiconductor layer made of As, the second semiconductor layer made of Inx Ga1-x As is formed on the GaAs layer having good crystallinity. The crystallinity can be improved.

Further, in the present invention, the first semiconductor layer and the second semiconductor layer having a smaller lattice constant as the growth temperature becomes higher are alternately arranged on the semiconductor substrate, and the temperature of the semiconductor substrate is raised. Since the strained superlattice layer is grown while being grown, the strained superlattice layer can be easily obtained only by controlling the temperature of the substrate, and further, the first semiconductor layer of the strained superlattice layer is It can be formed so that the closer to the buffer layer, the better the crystallinity.
A semiconductor device capable of reducing the leak current and improving the current controllability can be obtained with high yield.

[0027]

【Example】

Example 1. FIG. 1 is a schematic sectional view showing the structure of a semiconductor device according to a first embodiment of the present invention. In FIG. 1, 1 is a semi-insulating GaAs substrate having a thickness of 100 to 200 μm, and 7 is a GaAs substrate 1. The strained superlattice layer is formed on the GaAs layer 11 having a thickness of 50 to 100 angstroms and the Inx Ga1-x As layer 12 having a thickness of 100 to 200 angstroms alternately by epitaxial growth. Is formed. In the strained superlattice layer 7, the Inx Ga1-x As layer 12 and the GaAs layer 11 are repeatedly arranged for 5 cycles, and the strained superlattice layer 7
The In composition ratio x of the Inx Ga1-x As layer 12 is 0.2, 0.16, 0.12, 0.08, 0.
It is configured to be 04. Inx Ga1-x
The strained superlattice layer 7 composed of the As layer 12 and the GaAs layer 11 has a period of about 5 to 20 cycles, and the Inx Ga1-x As
The In composition ratio x of the layer 12 may be formed so that the In composition ratio x gradually decreases from the substrate side toward the upper side within a range of about 0.2 or less. Further, in order to surely prevent the inheritance of defects, it is preferable that the difference in the In composition ratio x between the upper and lower Inx Ga1-x As layers 12 is as uniform as possible. At this time, the substrate 1 and the buffer layer 2
The layer in contact with may be either the GaAs layer 11 or the Inx Ga1-x As layer 12. 2 is a non-doped GaA having a thickness of 0.3 to 0.5 μm formed on the strained superlattice layer 7.
The s buffer layer 3 is grown on the buffer layer 2 and has a thickness of 0.2 to 0.5 μm and an impurity concentration of 1 to 5 × 10 ^17.
It is an n-type GaAs operating layer of cm ^-3 .

Next, the operation will be described. When a voltage is applied to the gate portion, the carrier depletion layer in the n-type GaAs operating layer 3 changes, which controls the current flowing between the source and the drain.

Next, the operation will be described. In the present embodiment, in the strained superlattice layer 7 composed of the GaAs layer 11 and the Inx Ga1-x As layer 12, each layer is laminated so as to have no defect, so that a new defect is generated in each layer. It does not occur, and the strained superlattice at the interface of each layer prevents the inheritance of defects, whereby defects such as dislocations on the surface of the substrate 1 are relaxed in the strained superlattice layer 7. Then, this can be prevented from being inherited by the buffer layer 2. Also, the Inx Ga1-x As layer 1
Since the In composition ratio x of 2 is decreased from the substrate 1 side in the growth direction, that is, in the upward direction, Inx Ga1-x As
The lattice constant of the layer 12 becomes Ga as the distance from the substrate 1 increases.
The value is closer to the lattice constant of the As buffer layer 2, and when the buffer layer 2 is formed on the strained superlattice layer 7, no new defect is generated between the strained superlattice layer 7 and the buffer layer 2. . Therefore, by providing this strained superlattice layer 7, as described above, defects such as dislocations, which are often found on the surface of the GaAs substrate 1, are formed on the buffer layer 2,
And the operation layer 3 can be prevented from being inherited, the crystallinity of the buffer layer 2 and the operation layer 3 can be improved, and the generation of leak current in the buffer layer 2 and the current in the operation layer 3 can be prevented. It is possible to suppress deterioration of controllability.

The semiconductor device of this embodiment is manufactured by a molecular beam epitaxy method (hereinafter referred to as MBE method), a metal organic chemical vapor deposition method (MOCVD method), or the like.
The manufacturing method when the method E is used will be described. First, the strained superlattice layer 7 is formed by alternately epitaxially growing the GaAs layers 11 and the Inx Ga1-x As layers 12 on the semi-insulating GaAs substrate 1 in the MBE apparatus.
At this time, the Inx Ga1-x As layers 12 are formed from the substrate side while decreasing the In composition ratio x between 0.2 and 0.04 for each layer. Is controlled by changing the temperature of the In evaporation source cell,
This is performed by controlling the evaporation amount of n. Next, a GaAs buffer layer 2 and an operating layer 3 are sequentially epitaxially grown on the strained superlattice layer 7, a source electrode and a drain electrode (not shown) are further formed on the operating layer 3, and then a gate electrode is formed. (Not shown) is formed to obtain a semiconductor device.

As described above, in this embodiment, between the GaAs substrate 1 and the GaAs buffer 2 layer made of an inexpensive material, the GaAs layer 11 and the Inx Ga1 having a smaller In composition ratio x as the distance from the substrate 1 is smaller. Since the strained superlattice layers 7 in which a plurality of -x As layers 12 are alternately stacked are inserted, it is possible to prevent defects on the surface of the substrate 1 from being inherited to the buffer layer 2 and the operation layer 3, and It is possible to inexpensively obtain the semiconductor device having excellent characteristics capable of suppressing the generation of the leak current in the layer 2 and the deterioration of the controllability of the current in the operation layer 3.

Example 2. FIG. 3 is a schematic sectional view showing the steps of a method for manufacturing a semiconductor device according to the second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 designate the same or corresponding parts. In the second embodiment, instead of changing the evaporation amount of In in the MBE apparatus and controlling the In composition ratio x of the strained superlattice layer 7 as in the first embodiment, instead of controlling the In composition ratio x,
The temperature of the In evaporation source cell is controlled to be constant, the evaporation amount of In from the cell is controlled to be constant, and the substrate temperature during growth is changed, whereby the Inx Ga in the strained superlattice layer 7 is changed.
By controlling the In composition ratio x of the 1-xAs layer 12, a semiconductor device having a structure similar to that of the first embodiment shown in FIG. 1 can be obtained.

Next, the manufacturing method of the second embodiment will be described with reference to FIG. First, after preparing the GaAs substrate 1, the substrate temperature is changed from about 670 ° C. to 7 ° C. with a constant In evaporation amount.
Inx Ga1-x As layer 1 while increasing the temperature to about 50 ° C
The strained superlattice layer 7 is formed by alternately growing the 2 and GaAs layers 11. Here, FIG. 2 is a diagram showing the relationship between the temperature of the GaAs substrate during epitaxial growth and the sticking coefficient of In. From FIG. 2, when the substrate temperature is 670 ° C. or higher, the sticking coefficient of In to the substrate decreases. It turns out that it has the property of doing. Therefore, while controlling the substrate temperature by using this property, the Inx Ga1-x As layer 1
2 is grown so that the In composition ratio x decreases as the distance from the substrate 1 increases. Then, the strained superlattice layer 7
A GaAs buffer layer 2 and a GaAs operating layer 3 are sequentially grown thereon to obtain a semiconductor device.

In the manufacturing method of the second embodiment, the substrate 1
Inx G grown on the substrate 1 as the temperature of
Since the crystallinity of the a1-x As layer 12 and the GaAs layer 11 is improved, the crystallinity of the strained superlattice layer 7 is superior to that obtained by the manufacturing method of the above-described Example 1 as the distance from the substrate increases. Becomes Therefore, this strained superlattice layer 7
The crystallinity of the buffer layer 2 and the operation layer 3 formed above can be further improved.

As described above, in the present embodiment, GaAs
GaAs layer 11 and Inx Ga1-x As layer 1 on the substrate 1
Since the strained superlattice layer 7 is formed by alternately growing 2 and increasing the temperature of the GaAs substrate 1, the strained superlattice layer 7 can be easily formed only by controlling the temperature of the substrate 1.
Further, the crystallinity of the buffer layer 2 and the operating layer 3 can be further improved, whereby a semiconductor device having more excellent characteristics can be easily obtained with high yield.

Example 3. FIG. 4A is a schematic view showing the structure of the semiconductor device according to the third embodiment of the present invention.
(b) is a diagram showing a bandgap energy distribution of a main part of the semiconductor device of the third embodiment. In the figure,
8 indicates GaA, and 8 indicates GaA.
It is a superlattice layer composed of an s layer 13 and an Aly Ga1-y As layer (y = 0.3) 14. The Al composition ratio y
Is a constant value of about 0.2 to 0.3 such that the forbidden band width of the Aly Ga1-y As layer 14 is larger than the forbidden band width of GaAs. The semiconductor device of the third embodiment is
The superlattice layer 8 is provided between the strained superlattice layer 7 and the buffer layer 2 of the semiconductor device of the first embodiment.

Next, the manufacturing method of the third embodiment will be described. First, the strained superlattice layer 7 is formed on the substrate 1 by the method shown in the first or second embodiment. Next, in the MBE apparatus, a GaAs layer 13 having a constant thickness in the range of 50 to 100 angstroms is formed on the strained superlattice layer 7 at a constant growth substrate temperature of about 650 to 750 ° C. and 1
A having a constant thickness of 00 to 200 angstroms
ly Ga1-y As layer (y = 0.3) 14 and 5-20
It is formed alternately so as to have a cycle. After that, after forming the buffer layer 2 and the operating layer 3 on the superlattice layer 8, the source, drain electrode and the gate electrode (not shown) are formed on the operating layer 2 to obtain a semiconductor device.

In this embodiment, as shown in FIG. 4 (b), the forbidden band width of the Aly Ga1-y As layer (y = 0.3) 14 is larger than that of GaAs. Since 8 acts as a current blocking layer, a leak current flowing from the buffer layer 2 to the substrate 1 can be blocked.

As described above, in the third embodiment, by providing the superlattice layer 8 on the strained superlattice layer 7, the leak current flowing from the buffer layer 2 can be greatly reduced,
A semiconductor device having excellent characteristics can be obtained.

Example 4. FIG. 5A is a diagram showing the structure of the semiconductor device according to the fourth embodiment of the present invention, and FIG.
FIG. 4 is a diagram showing a band gap energy distribution of a main part of this semiconductor device. In the figure, the same reference numerals as those in FIG. 4 denote the same or corresponding portions, and 9 denotes Inx Ga1-x As
It is a strained superlattice layer composed of a layer 12 and an Aly Ga1-y As layer 14. The fourth embodiment is based on the first or second
In the strained superlattice layer 7 of the embodiment, the strained superlattice layer is provided by replacing the GaAs layer 11 with an Aly Ga1-y As layer (y = 0.3) 14 having a thickness of 100 to 200 angstroms. 9 is formed, and is formed by the manufacturing process similar to that of the first or second embodiment. In addition,
The Al composition ratio y of the Aly Ga1-y As layer 14 is Aly G
It may be a constant value between 0.2 and 0.3 such that the forbidden band width of the a1-y As layer 14 is larger than the forbidden band width of GaAs. In general, Inx Ga1-x As has better crystallinity when it is not in direct contact with GaAs. Therefore, the layer in contact with GaAs substrate 1 and GaAs buffer layer 2 is Inx G1-x As.
The Aly Ga1-y As layer 14 is better than the a1-x As layer 12, and the strained superlattice layer 7, the GaAs substrate 1, and Ga are
The crystallinity of the growth interface with the As buffer layer 2 can be improved, the inheritance of defects on the substrate 1 can be eliminated more reliably, and the strained superlattice layer 7 and the GaAs
It is possible to prevent new defects from being generated between the substrate 1 and the GaAs buffer layer 2.

In the present embodiment, as shown in FIG. 5B, the band gap energy difference between the Inx Ga1-x As layer 12 and the Aly Ga1-y As layer 14 is the same as that in the third embodiment. Aly Ga1-y As layer of superlattice layer 8 (y =
0.3) 14 and the GaAs layer 133 have a larger bandgap energy difference, the strained superlattice layer 9 of the fourth embodiment has better current blocking performance than the superlattice layer 8 described above. You can see that

Also in the fourth embodiment as described above, by providing the strained superlattice layer 9, the crystallinity of the buffer layer 2 and the operation layer 3 can be improved, and the leak current flowing from the buffer layer 2 can be improved. Can be prevented as compared with the third embodiment, so that a higher performance semiconductor device can be obtained.

Example 5. FIG. 6A is a diagram showing a structure of a semiconductor device according to a fifth embodiment of the present invention, and FIG.
FIG. 4 is a diagram showing a band gap energy distribution of a main part of this semiconductor device. In the figure, 10 is a strained superlattice layer composed of a GaAs layer 17, an Inx Ga1-x As layer (x≤0.2) 12, and an Aly Ga1-y As layer (y = 0.3) 14. In addition, the Aly Ga1-y As layer 1
The Al composition ratio y of 4 is 0. so that the forbidden band width of the Aly Ga1-y As layer 14 is larger than the forbidden band width of GaAs.
It may be a constant value between 2 and 0.3.

The strained superlattice layer 10 of the fifth embodiment is the same as the Aly Ga1-y As layer (y = 0. 0) constituting the strained superlattice layer 9 in the semiconductor device having the structure shown in the fourth embodiment. 3)
14 and Inx Ga1-x As layer 12 each having a thickness of 50 to 100 angstroms.
7 is manufactured by the same manufacturing method as in the fourth embodiment. Here, in general, GaA
When s and Aly Ga1-y As are compared, GaAs is superior in crystallinity, and therefore, as in the fifth embodiment,
It is better to grow the Inx Ga1-x As layer 12 on the GaAs layer 17 to form the Inx Ga1-x As layer 12 on the Aly Ga1-y As layer 12 like the strained superlattice layer 9 shown in the fourth embodiment.
The crystallinity of the Inx Ga1-x As layer 12 can be improved more than that on the s layer 14. This makes I
In the nx Ga1-x As layer 12, inheritance of defects can be more reliably prevented, and a semiconductor device having excellent characteristics can be obtained.

In each of the above embodiments, a GaAs substrate is used as a substrate, and Inx Ga1-x As is formed on the substrate.
The case where a strained superlattice layer composed of a layer and an Aly Ga1-y As layer or a GaAs layer has been described, but the present invention uses a substrate made of a material other than GaAs instead of the GaAs substrate, The above Inx Ga1-x As
Instead of the layer, using a layer made of a material having the same crystal structure as the substrate and having a larger lattice constant than the substrate,
Instead of the GaAs layer, a layer made of a material having the same crystal structure and lattice constant as the substrate is used.
The present invention can be applied to the case where a layer made of a material having the same crystal structure and lattice constant as that of the above-mentioned substrate and a band gap larger than that of the above-mentioned substrate is used instead of the y Ga1-y As layer. The same effect can be achieved.

[0046]

As described above, according to the present invention, a strained superlattice layer formed by alternately laminating a plurality of first semiconductor layers and second semiconductor layers is provided between a semiconductor substrate and a buffer layer. Prepare,
Since the plurality of second semiconductor layers forming the strained superlattice layer have a structure having a lattice constant closer to the lattice constant of the buffer layer as the distance from the semiconductor substrate increases, defects such as dislocations on the surface of the semiconductor substrate are generated. The semiconductor device can be prevented from being inherited to the buffer layer and the operation layer, which can prevent a leak current and can prevent deterioration of current controllability.

Further, according to the present invention, a third semiconductor layer is provided between the strained superlattice layer and the buffer layer, and a fourth semiconductor layer having a forbidden band width larger than that of the third semiconductor layer. Since a superlattice layer formed by alternately stacking a plurality of and is provided, there is an effect that a high-performance semiconductor device capable of greatly reducing the leak current between the buffer layer and the substrate can be obtained.

Further, according to the present invention, since the semiconductor substrate, the buffer layer, the first conductivity type operation layer, and the first semiconductor layer of the strained superlattice layer are made of GaAs which is an inexpensive material, the leakage current Is small, and a high-performance semiconductor device with good current controllability can be obtained at low cost.

Further, according to the present invention, the semiconductor substrate, the buffer layer, and the first conductivity type operation layer are made of GaAs, and the first semiconductor layer forming the strained superlattice layer is formed by:
Since it is composed of AlyGa1-yAs having a larger forbidden band width than GaAs, it has an effect of further reducing the leak current between the buffer layer and the substrate.

Further, according to the present invention, the above Aly Ga is
A first semiconductor layer of 1-y As and Inx Ga1-x A
Since the GaAs layer is interposed between the second semiconductor layer made of s, the second semiconductor layer made of Inx Ga1-x As is formed on the GaAs layer having good crystallinity, There is an effect that the crystallinity can be improved.

According to the present invention, the first semiconductor layer and the second semiconductor layer having a smaller lattice constant as the growth temperature increases are alternately provided on the semiconductor substrate, and the temperature of the semiconductor substrate is controlled. Since the strained superlattice layer is grown by raising the strained superlattice layer, the strained superlattice layer can be easily obtained only by controlling the temperature of the substrate. It can be formed so that the closer it is to the buffer layer, the better the crystallinity.
There is an effect that a high-performance semiconductor device capable of reducing the leak current and improving the current controllability can be obtained with high yield.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between a growth substrate temperature and an In attachment coefficient in a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a manufacturing process of a semiconductor device according to a second embodiment of the invention.

FIG. 4 is a sectional view showing the structure of a semiconductor device according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a semiconductor device according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing the structure of a semiconductor device according to a fifth embodiment of the present invention.

FIG. 7 is a sectional structural view showing a structure of a conventional semiconductor device.

[Explanation of symbols]

1 GaAs substrate 2 Non-doped GaAs buffer layer 3 n-type GaAs operating layer 7 Inx Ga1-x As / GaAs strained superlattice layer 8 Aly Ga1-y As / GaAs superlattice layer 9 Inx Ga1-x As / Aly Ga1-y As strained Superlattice layer 10 GaAs / Inx Ga1-x As / Aly Ga1-y
As strained superlattice layer 11 GaAs layer 12 Inx Ga1-x As layer 13 GaAs layer 14 Aly Ga1-y As layer 17 GaAs layer 101 GaAs substrate 102 non-doped GaAs buffer layer 103 n-type GaAs operating layer 104 source electrode 105 drain electrode 106 gate electrode

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[Procedure amendment]

[Submission date] October 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 7

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

As described above, in this embodiment, the quality is low.
Between cheap GaAs substrate 1 and GaAs buffer 2 layers,
The farther from the GaAs layer 11 and the substrate 1, the smaller In
Since the strained superlattice layer 7 in which a plurality of Inx Ga1-x As layers 12 having the composition ratio x are alternately laminated is inserted, defects on the surface of the substrate 1 are inherited to the buffer layer 2 and the operation layer 3. It is possible to obtain a semiconductor device having excellent characteristics that can prevent the occurrence of leakage current and suppress the generation of leak current in the buffer layer 2 and the deterioration of current controllability in the operation layer 3 at low cost.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

Further, according to the present invention, since the semiconductor substrate, the buffer layer, the first-conductivity-type operation layer, and the first semiconductor layer of the strained superlattice layer are made of a low-quality and inexpensive GaAs substrate , leakage is prevented. There is an effect that a high-performance semiconductor device having a small current and good current controllability can be obtained at low cost.

Claims (12)

[Claims] 1. A semiconductor device comprising a buffer layer made of the same material as that of the semiconductor substrate and a first-conductivity-type operating layer, which are sequentially formed on the semiconductor substrate, and are provided between the semiconductor substrate and the buffer layer. A first semiconductor layer having a crystal structure and a lattice constant identical to those of the semiconductor substrate, and a second semiconductor layer having a crystal structure identical to that of the semiconductor substrate and a lattice constant larger than that of the semiconductor substrate. And the plurality of second semiconductor layers constituting the strained superlattice layer, the lattice constants of which are closer to the lattice constant of the buffer layer, the farther from the semiconductor substrate. A semiconductor device characterized by being formed so as to be close to each other. 2. The semiconductor device according to claim 1, further comprising a third semiconductor layer which is provided between the strained superlattice layer and the buffer layer and has the same crystal structure and lattice constant as those of the semiconductor substrate. A superlattice layer having the same crystal structure and the same lattice constant as that of the semiconductor substrate, and a plurality of fourth semiconductor layers having a forbidden band width larger than that of the semiconductor substrate are alternately laminated. A semiconductor device characterized by: 3. The semiconductor device according to claim 1, wherein the semiconductor substrate, the buffer layer, and the first conductivity type operation layer are each made of GaAs, and the first semiconductor forming the strained superlattice layer. The layer and the second semiconductor layer are GaAs and Inx Ga1-x A, respectively.
and a plurality of Inx Ga1-x As layers, which are the second semiconductor layers, have a smaller In composition ratio x with increasing distance from the semiconductor substrate. 4. The semiconductor device according to claim 3, wherein the third semiconductor layer and the fourth semiconductor layer forming the superlattice layer are made of GaAs and Aly Ga1-y As, respectively. A plurality of AlyGa1-yAs layers, which are layers, have a constant Al composition ratio y within a range of 0.2 or more and 0.3 or less. 5. The semiconductor device according to claim 1, wherein the semiconductor substrate, the buffer layer, and the first conductivity type operation layer are each made of GaAs, and the first semiconductor forming the strained superlattice layer. The layer and the second semiconductor layer are Aly Ga1-y As and Inx, respectively.
The plurality of Aly Ga1-y As layers, which are Ga1-x As and are the first semiconductor layers, have a constant Al composition ratio y within the range of 0.2 or more and 0.3 or less, A plurality of Inx Ga1-x As layers, which are the second semiconductor layers, have a smaller In composition ratio x as they are farther from the semiconductor substrate. 6. The semiconductor device according to claim 5, wherein the first semiconductor layer made of Aly Ga1-y As and I
Between the second semiconductor layer made of nx Ga1-x As,
A semiconductor device having a GaAs layer formed thereon. 7. A first semiconductor layer having a crystal structure and a lattice constant identical to those of the semiconductor substrate on a semiconductor substrate, and a crystal structure identical to that of the semiconductor substrate, and a higher growth temperature Forming a strained superlattice layer by alternately growing second semiconductor layers having a smaller lattice constant and increasing the temperature of the semiconductor substrate, and forming the strained superlattice layer on the strained superlattice layer with the semiconductor substrate. A method of manufacturing a semiconductor device, comprising: a step of forming a buffer layer made of a material; and a step of forming a first conductivity type operation layer made of the same material as the semiconductor substrate on the buffer layer. 8. The method of manufacturing a semiconductor device according to claim 7, wherein after forming the strained superlattice layer, a third semiconductor layer made of the same material as the semiconductor substrate and a crystal are formed on the strained superlattice layer. A plurality of fourth semiconductor layers having the same structure and lattice constant as those of the semiconductor substrate and having a forbidden band width larger than that of the semiconductor substrate are alternately grown to form a superlattice layer. A method of manufacturing a semiconductor device, comprising forming the buffer layer on a superlattice layer. 9. The method for manufacturing a semiconductor device according to claim 7, wherein GaAs is formed as the first semiconductor layer on a GaAs substrate.
Layer, a Inx Ga1-x As layer is grown as a second semiconductor layer to form a strained superlattice layer, and a GaAs buffer layer and a first conductivity type G are formed on the strained superlattice layer.
A method of manufacturing a semiconductor device, comprising forming an aAs operating layer. 10. The method for manufacturing a semiconductor device according to claim 8, wherein GaAs is formed as a third semiconductor layer on the strained superlattice layer.
Aly Ga1-y As having a constant Al composition ratio y within the range of 0.2 or more and 0.3 or less as the fourth semiconductor layer
A method for manufacturing a semiconductor device, which comprises growing a layer to form a superlattice layer. 11. The method for manufacturing a semiconductor device according to claim 7, wherein the first semiconductor layer has a constant Al composition ratio y within a range of 0.2 or more and 0.3 or less on the GaAs substrate. Aly Ga1-y As layer, Inx G as second semiconductor layer
An a1-x As layer is grown to form a strained superlattice layer, and a GaAs buffer layer and a first conductivity type G are formed on the strained superlattice layer.
A method of manufacturing a semiconductor device, which comprises sequentially forming an aAs operation layer. 12. The method of manufacturing a semiconductor device according to claim 11, wherein the strained superlattice layer comprises an AlyGa1-yAs layer and an IyGa1-yAs layer.
A method of manufacturing a semiconductor device, comprising a step of forming a GaAs layer between nx Ga1-x As layers.