JP2018104278A - Compound semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound semiconductor substrate including an AlInSb layer excellent in crystallinity and surface flatness.SOLUTION: A compound semiconductor substrate comprises a substrate 1, a first compound semiconductor layer 11 formed on the substrate and including In and Sb without including Al, and a second compound semiconductor layer 21 formed on the first compound semiconductor layer and including Al, In and Sb. Hydrogen atoms included in the second compound semiconductor layer is 1×10cmor more and 5×10cmor less; carbon atoms included in the second compound semiconductor layer is 1×10cmor more and 5×10cmor less; nitrogen atoms included in the second compound semiconductor layer is 1x10cmor more and 5x10cmor less; and the mean square roughness Rrms of the surface of the second compound semiconductor layer is 0.1 nm or more and 10 nm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compound semiconductor substrate.

A compound semiconductor containing InSb is a material having high mobility and a small band gap, and is used as a device such as a magnetic sensor, a high-speed device, and an IR sensor by taking advantage of this feature. In realizing a device using a compound semiconductor containing InSb, it is desired to use AlInSb as an electron barrier layer.
Conventionally, for producing an AlInSb thin film using metal organic vapor phase epitaxy, tritertiary butylaluminum (TTBAl) is used as an Al material, trimethylindium (TMIn) is used as an In material, and triethylantimony (TESb) is used as an Sb material. (See Patent Document 1).

US Pat. No. 6,071,109

Journal of Crystal Growth, Vol. 209 (2000) “Growth of InSb on GaAs using InAlSb buffer layer” M.M. Biefeld et. al.

However, in conventional AlInSb thin films using conventional TTBAl, TMIn, and TESb represented by Patent Document 1 (hereinafter referred to as conventional AlInSb thin films), a large amount of carbon impurities are mixed, and the function as an electronic barrier layer is reduced. In other words, the decrease in surface flatness was inevitable. Further, the conventional AlInSb thin film has not been sufficiently crystalline. Therefore, the conventional AlInSb thin film is not suitable for application to the above-described device.
On the other hand, as a means for suppressing the carbon impurity concentration, a method using trisdimethylaminoantimony (TDMASb) instead of TESb as the Sb raw material is conceivable. However, it has been reported that in the combination of TTBAl and TDMASb, a gas phase reaction occurs, and TTBAl and TDMASb react before reaching the substrate, so that only an AlInSb layer that is cloudy, that is, has poor surface flatness can be obtained (non-patent document). Reference 1).
This invention is made | formed in view of such a situation, Comprising: It aims at providing the compound semiconductor substrate containing the AlInSb layer which has favorable crystallinity and is excellent in surface flatness.

Further, as a result of intensive studies to solve the above problems, the present inventors have found that the substrate, the first compound semiconductor layer containing In and Sb formed on the substrate, and not containing Al, and A second compound semiconductor layer containing Al, In, and Sb formed on the first compound semiconductor layer, wherein hydrogen atoms contained in the second compound semiconductor layer are 1 × 10 ¹⁵ cm ^−3. 5 × 10 ¹⁹ cm ⁻³ or less, and carbon atoms contained in the second compound semiconductor layer are 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less, and the second compound semiconductor The nitrogen atoms contained in the layer are 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less, and the mean square roughness Rrms of the surface of the second compound semiconductor layer is 0.1 nm or more and 10 nm or less. It has been found that the above problem can be solved by a certain compound semiconductor substrate.

  According to one embodiment of the present invention, a compound semiconductor substrate including an AlInSb layer having favorable crystallinity and excellent surface flatness can be realized.

It is a cross-sectional schematic diagram which shows the manufacturing method of the compound semiconductor substrate which concerns on this embodiment in process order. It is a schematic diagram which shows the structural example of the MOCVD apparatus used by this embodiment. It is a figure which shows typically the change of the supply amount of the Al raw material in this embodiment.

Hereinafter, a mode for carrying out the present invention (this embodiment) will be described.
<Method for producing compound semiconductor substrate>
The manufacturing method of the compound semiconductor substrate of this embodiment supplies an In raw material and an Sb raw material on a substrate using metal organic chemical vapor deposition (MOCVD), and a first material is formed on the substrate. In the state where the compound semiconductor layer is grown (first compound semiconductor layer growth step) and the substrate temperature of the first compound semiconductor layer is maintained at 420 ° C. or more and 525 ° C. or less, on the first compound semiconductor layer, In addition to the In raw material and the Sb raw material, the Al raw material is supplied while increasing the supply amount continuously and / or stepwise, and the supply amount of the In raw material, the Sb raw material, and the Al raw material is increased after the supply amount of the Al raw material is increased. by constant, the first compound Al _X in _1-X Sb layer on the semiconductor layer (0 <x ≦ 0.7) forming a (second compound semiconductor layer Comprises a long step), the. Here, “continuous and / or stepwise” means “at least one of continuous and stepwise” and means any one of continuous, stepwise, continuous and stepwise. .

By providing each of these steps (first compound semiconductor layer growth step, second compound semiconductor layer growth step), the AlInSb layer obtained is suppressed in white turbidity and has good crystallinity and high mobility. It becomes possible to obtain a compound semiconductor substrate comprising:
In the method of supplying the In material, the Sb material, and the Al material at a predetermined fixed ratio after the step of supplying the In material and the Sb material and growing the first compound semiconductor layer, the AlInSb layer becomes clouded. Mobility will also be low. On the other hand, in addition to the In raw material and the Sb raw material as in this embodiment, the whitening of the resulting AlInSb layer is suppressed by supplying the Al raw material while increasing the supply amount continuously and / or stepwise. And an AlInSb layer with good crystallinity.
The details of this mechanism are not clear, but by supplying a large amount of Al in the initial stage, the reaction with TDMASb in the gas phase is likely to occur, and particles are deposited on the substrate. It is assumed that this is due to the transition to the Volmer-Weber mode.

The substrate temperature of the first compound semiconductor layer is controlled to be 420 ° C. or higher and 525 ° C. or lower in the step of supplying the Al raw material while increasing the supply amount continuously and / or stepwise in addition to the In raw material and the Sb raw material. . When the surface temperature is higher than 525 ° C. or lower than 420 ° C., a compound semiconductor substrate with high flatness cannot be obtained. Further, when the formed Al _x In _1-X Sb layer is x> 0.7 (that is, when the Al composition ratio with respect to the total amount of group III elements in the Al _x In _1-X Sb layer exceeds 70%), A compound semiconductor substrate with high flatness cannot be obtained.

  The supply amount of the Al raw material when the supply amounts of the In raw material, the Sb raw material, and the Al raw material are made constant is the same as that of the In raw material and the Sb raw material, while the supply amount is increased continuously and / or stepwise. If it is more than the supply amount of the Al raw material at the time of supply, it will not restrict | limit. However, the supply amount of the Al raw material after making the supply amount of the Al raw material constant is preferably a desired supply amount that determines the ratio of each element of the AlInSb layer. Although the specific supply amount of the Al raw material when supplying the Al raw material while increasing the supply amount continuously and / or stepwise is not particularly limited, the proportion of the Al raw material in the group III raw material is preferably 0.10 or more It can be in the range of 0.75 or less, more preferably 0.10 or more and 0.65 or less.

(material)
In the compound semiconductor substrate manufacturing method of the present embodiment, the In raw material, the Sb raw material, and the Al raw material are not particularly limited as long as they can form an InSb layer and an AlInSb layer. Examples of the In raw material include trimethylindium (TMIn) and triethylindium (TEIn). Examples of the Sb raw material include trimethylantimony (TMSb), triethylantimony (TESb), trisdimethylaminoantimony (TDMASb), and triisopropylantimony (TIPSb). Examples of the Al raw material include trimethylamine allane (TMAAl), triisobutylaluminum (TIBAl), dimethylaluminum hydride (DMAH), dimethylethylaminealane (DMEAAl), and tritertiary butylaluminum (TTBAl).

From the viewpoint of the raw material decomposition temperature, the In raw material is preferably trimethylindium (TMIn), triethylindium (TEIn), or a combination thereof. From the viewpoint of the long-term stability of the raw material, the Al raw material is preferably tritertiary butyl aluminum (TTBAl). From the viewpoint of suppressing carbon impurities, the Sb raw material is preferably trisdimethylaminoantimony (TDMASb).
As reported in Non-Patent Document 1, the combination of tritertiary butylaluminum (TTBAl) and trisdimethylaminoantimony (TDMASb) causes white turbidity of the AlInSb layer, and thus a good AlInSb layer cannot be obtained. However, in the present embodiment, a combination of tritertiary butyl aluminum (TTBAl) and trisdimethylaminoantimony (TDMASb) is provided by including the first compound semiconductor layer growth step and the second compound semiconductor layer growth step described above. However, it is preferable because white turbidity of the AlInSb layer is suppressed and carbon impurities in the AlInSb layer are also suppressed.

In the manufacturing method of the compound semiconductor substrate of this embodiment, the TTBAl raw material has high reactivity with other raw materials. Therefore, it is preferable not to mix the Al raw material, the In raw material, and the Sb raw material until just before introduction into the growth chamber, and it is more preferable to supply the In raw material, the Sb raw material, and the Al raw material through independent supply lines. Until the introduction to the growth chamber where the substrate is arranged, Al raw material, In raw material and Sb raw material are not mixed, and each supply of In raw material, Sb raw material and Al raw material to the growth chamber where the substrate is arranged, By using an independent supply line, there is an effect of suppressing the reaction and disappearance of raw materials before reaching the substrate. An independent supply line means a pipe connected to a growth chamber, in which a supply line of one raw material is not directly connected to a supply line of another raw material.
In order to control the conductivity type, in addition to the above-mentioned raw materials, dimethyl zinc (DMZn), diethyl zinc (DEZn), dimethyl tellurium (DMTe), diethyl tellurium (DETe), tetramethyltin (TMSn) tetraethyltin ( A dopant such as TESn) may be supplied.

(substrate)
In the compound semiconductor substrate manufacturing method of the present embodiment, the substrate is not particularly limited as long as it can grow an InSb layer and an AlInSb layer using metal organic vapor phase epitaxy. It is preferable to have the same crystal symmetry as InSb, and further, for example, GaAs and InSb are preferable materials because a cheap and large-sized substrate is easily available. From the viewpoint of manufacturing an electronic device, the substrate is more preferably GaAs having an electrical resistivity of 1 × 10 ⁵ Ωcm or more.

(Example of manufacturing method and manufacturing equipment)
FIG. 1A to FIG. 1C are schematic cross-sectional views showing a method of manufacturing a compound semiconductor substrate according to this embodiment in the order of steps. As shown in FIG. 1A, first, a substrate 1 is prepared. Next, as shown in FIG. 1B, an In raw material and an Sb raw material are supplied onto the substrate 1 by metal organic vapor phase epitaxy, and the first compound semiconductor layer 11 is formed on the substrate 1. Growing (first compound semiconductor layer growth step).
Next, in the state where the substrate temperature of the first compound semiconductor layer 11 is maintained at 420 ° C. or more and 525 ° C. or less, the supply amount is continuously added on the first compound semiconductor layer 11 in addition to the In material and the Sb material. And / or supply Al raw material while increasing in steps. Then, after the supply amount of the Al raw material is increased continuously and / or stepwise, the supply amounts of the In raw material, the Sb raw material, and the Al raw material on the first compound semiconductor layer 11 are made constant. As a result, as shown in FIG. 1C, an Al _x In _1-x Sb layer (0 <x ≦ 0.7) is formed as the second compound semiconductor layer 21 on the first compound semiconductor layer 11. (Second compound semiconductor layer growth step).

  FIG. 2 is a schematic diagram showing a configuration example of the MOCVD apparatus used in the present embodiment. As shown in FIG. 2, the MOCVD apparatus includes a growth chamber 51, a heatable stage 52 disposed in the growth chamber 51, an exhaust pipe 53 and an exhaust pump 54 for exhausting the growth chamber 51, and a growth chamber. 51 is provided with a supply line 60 for supplying a raw material gas. The supply line 60 includes an In pipe 61 for supplying an In raw material, an Sb pipe 62 for supplying an Sb raw material, and an Al pipe 63 for supplying an Al raw material. It is possible to supply each raw material without mixing until it reaches.

3A to 3C are diagrams schematically showing changes in the supply amount of the Al raw material. 3A to 3C, the horizontal axis indicates time, and the vertical axis indicates the supply amount of Al raw material per unit time.
FIG. 3A shows a case where the supply amount of the Al raw material is continuously increased. When the supply amount of the Al raw material is continuously increased, the increase rate may be constant or not constant.
FIG.3 (b) has shown the case where the supply amount of Al raw material is increased in steps. When increasing the supply amount of the Al raw material stepwise, it may be increased in one step as shown in FIG. 3B, or may be increased in multiple steps.
FIG. 3 (c) shows a case where the supply amount of the Al raw material is increased continuously and stepwise.

<Compound semiconductor substrate>
The compound semiconductor substrate of this embodiment includes a substrate, a first compound semiconductor layer that includes In and Sb and does not include Al, and Al that is formed on the first compound semiconductor layer. A compound semiconductor substrate comprising a second compound semiconductor layer containing In and Sb, wherein hydrogen atoms contained in the second compound semiconductor layer are 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. The carbon atom contained in the second compound semiconductor layer is 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less, and the nitrogen atom contained in the second compound semiconductor layer is 1 × 10 ¹⁵ cm. ^{−3 to} 5 × 10 ¹⁸ cm ⁻³ .

Conventionally, mixing of carbon atoms is inevitable, and therefore, the technical significance of atoms contained in the second compound semiconductor layer containing Al, In, and Sb has not been noticed. On the other hand, in the compound semiconductor substrate of this embodiment, the hydrogen atoms contained in the second compound semiconductor layer are 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less, and the carbon atoms are 1 × 10 10. ^{It is 15} cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less, and the nitrogen atom is 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less. A mobile compound semiconductor substrate can be realized.

In the compound semiconductor substrate of the present embodiment, the mean square roughness Rrms of the surface of the second compound semiconductor layer is preferably 0.1 nm or more and 10 nm or less from the viewpoint of application suitability to an optical device.
In the compound semiconductor substrate of the present embodiment, the Al composition ratio with respect to the total amount of group III elements in the second compound semiconductor layer is 0.1% or more and 70% or less from the viewpoint of application suitability to an optical device.
The full width at half maximum FWHM calculated from the ω-scan rocking curve measurement by X-ray diffraction of the second compound semiconductor layer is preferably within a range calculated by the following formula (1).
a × Al composition ratio [%] + {− 90 × ln (t) +730} [arcsec]
≦ FWHM [arcsec] ≦ a × Al composition ratio [%] + {− 90 × ln (t) +830} [arcsec]
(A = 23.5 [arcsec /%], t = second compound semiconductor layer thickness (nm))

In the compound semiconductor substrate of this embodiment, the Al composition ratio with respect to the total amount of Group III elements in the second compound semiconductor layer is 20% or more and 70% or less from the viewpoint of application suitability to an optical device. It is also preferable that the half width FWHM calculated from the ω-scan rocking curve measurement by X-ray diffraction of the compound semiconductor layer satisfies the following formula (2).
FWHM [arcsec] ≦ a × Al composition ratio [%] + {− 90 × ln (t) +830} [arcsec]
(A = 23.5 [arcsec /%], t = second compound semiconductor layer thickness (nm))

In the compound semiconductor substrate of this embodiment, the first compound semiconductor layer is a layer formed on the substrate and containing In and Sb and not containing Al. Specifically, a layer made of a mixed crystal of InSb and InSb can be given. Moreover, in order to make it an n-type conductive layer, a desired dopant such as Te or Sn may be included, and in order to make a p-type conductive layer, a desired dopant such as Zn or Si may be included.
In the compound semiconductor substrate of this embodiment, the second compound semiconductor layer is a layer formed on the first compound semiconductor layer and containing Al, In, and Sb. Specifically, a layer made of AlInSb and a mixed crystal of AlInSb and Ga and As can be given. Moreover, in order to make it an n-type conductive layer, a desired dopant such as Te or Sn may be included, and in order to make a p-type conductive layer, a desired dopant such as Zn or Si may be included.
Hereinafter, the compound semiconductor substrate and the manufacturing method thereof according to the present embodiment will be described in detail with reference to specific examples.

Example 1
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) are supplied as InSb raw materials at a substrate temperature of 340 ° C., and the first compound semiconductor is used under the condition of V / III ratio = 5.0. An InSb layer was formed as a layer. The V / III ratio is a ratio of the supply amount of the group V element to the supply amount of the group III element. An MOCVD apparatus was used to form this InSb layer. The thickness of this InSb layer was 700 nm.

  On this InSb layer, tritertiary butylaluminum (TTBAl), trimethylindium (TMIn), and trisdimethylaminoantimony (TDMASb) are supplied as AlInSb raw materials at a substrate temperature of 500 ° C., and AlInSb is used as the second compound semiconductor layer. A layer was formed. An MOCVD apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, the Al material was supplied together with the In material and the Sb material so that the Al / In material ratio was Al / (Al + In) = 0.50.

  After the growth for 1 minute, the supply amount of the Al raw material is increased to Al / (Al + In) = 0.70, which is a desired supply amount that determines the ratio of each element of the AlInSb layer. At this time, the film was formed under the condition of V / III ratio = 5.0. Normally, the raw materials of Group III and Group V are supplied to the growth chamber by the respective pipes for each group, but this time, only TTBAl was supplied alone until immediately before the growth chamber without passing through the block valve. That is, the Sb raw material was supplied alone to the growth chamber, and the Al raw material and the In raw material were supplied separately until just before the growth chamber. The thickness of this AlInSb layer was 700 nm.

For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 18%, and the half width calculated from the ω-scan rocking curve was 620 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 3 × 10 ¹⁸ cm ⁻³ , carbon atoms were 9 × 10 ¹⁶ cm ⁻³ , and nitrogen atoms were 5 × 10 ¹⁷ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 0.3 nm. The compound semiconductor substrate obtained in Example 1 satisfied the formulas (1) and (2).

(Example 2)
A compound semiconductor substrate was manufactured in the same manner as in Example 1 except that the raw material ratio of Al and In at the time of AlInSb formation was Al / (Al + In) = 0.63. The thickness of this AlInSb layer was 700 nm. For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 1%, and the half width calculated from the ω-scan rocking curve was 205 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 3 × 10 ¹⁶ cm ⁻³ , carbon atoms were 1 × 10 ¹⁵ cm ⁻³ , and nitrogen atoms were 1 × 10 ¹⁷ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 0.1 nm. The compound semiconductor substrate obtained in Example 2 satisfied the formula (1).

(Example 3)
A compound semiconductor substrate was manufactured in the same manner as in Example 1 except that the raw material ratio of Al and In at the time of AlInSb formation was Al / (Al + In) = 0.75. The thickness of this AlInSb layer was 700 nm. For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 40% and the half width calculated from the ω-scan rocking curve was 1120 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 2 × 10 ¹⁸ cm ⁻³ , carbon atoms were 4 × 10 ¹⁷ cm ⁻³ , and nitrogen atoms were 3 × 10 ¹⁷ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 1.5 nm. The compound semiconductor substrate obtained in Example 3 satisfied the formulas (1) and (2).

Example 4
A compound semiconductor substrate was manufactured in the same manner as in Example 1 except that the raw material ratio of Al and In at the time of AlInSb formation was Al / (Al + In) = 0.90. The thickness of this AlInSb layer was 700 nm. For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 70%, and the half width calculated from the ω-scan rocking curve was 1800 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 2 × 10 ¹⁹ cm ⁻³ , carbon atoms were 5 × 10 ¹⁸ cm ⁻³ , and nitrogen atoms were 3 × 10 ¹⁸ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 3.0 nm. The compound semiconductor substrate obtained in Example 4 satisfied the formulas (1) and (2).

(Example 5)
A compound semiconductor substrate was manufactured in the same manner as in Example 1 except that the substrate temperature during the formation of AlInSb was 420 ° C. The thickness of this AlInSb layer was 700 nm. For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 3%, and the half width calculated from the ω-scan rocking curve was 230 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 2 × 10 ¹⁷ cm ⁻³ , carbon atoms were 5 × 10 ¹⁶ cm ⁻³ , and nitrogen atoms were 2 × 10 ¹⁷ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 0.2 nm. The compound semiconductor substrate obtained in Example 5 satisfied the formula (1).

(Example 6)
A compound semiconductor substrate was manufactured in the same manner as in Example 1 except that the substrate temperature during the formation of AlInSb was 525 ° C. The thickness of this AlInSb layer was 700 nm. For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 25%, and the half width calculated from the ω-scan rocking curve was 720 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 3 × 10 ¹⁸ cm ⁻³ , carbon atoms were 9 × 10 ¹⁶ cm ⁻³ , and nitrogen atoms were 8 × 10 ¹⁷ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 0.4 nm. The compound semiconductor substrate obtained in Example 6 satisfied the formulas (1) and (2).

(Example 7)
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) were supplied as InSb raw materials at a substrate temperature of 340 ° C. to form an InSb layer as a first compound semiconductor layer. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tritertiary butylaluminum (TTBAl), trimethylindium (TMIn), and trimethylantimony (TMSb) are supplied as AlInSb raw materials at a substrate temperature of 500 ° C., and the AlInSb layer is used as the second compound semiconductor layer. Formed. An MOCVD apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, an Al raw material with an Al / In raw material ratio of Al / (Al + In) = 0.50 was supplied together with the In raw material and the Sb raw material. After the growth for 1 minute, the supply amount was increased to Al / (Al + In) = 0.70, which is a desired supply amount that determines the ratio of each element in the AlInSb layer.

Normally, the raw materials of Group III and Group V are supplied to the growth chamber by the respective pipes for each group, but this time, only TTBAl was supplied alone until immediately before the growth chamber without passing through the block valve. The thickness of this AlInSb layer was 700 nm.
For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 10%, and the half width calculated from the ω-scan rocking curve was 400 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), hydrogen atoms were 1 × 10 ¹⁹ cm ⁻³ , carbon atoms were 3 × 10 ¹⁸ cm ⁻³ , and nitrogen atoms were 1 × 10 ¹⁵ cm ⁻³ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 0.3 nm. The compound semiconductor substrate obtained in Example 7 satisfied the formula (1).

(Comparative Example 1)
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) were supplied as InSb raw materials at a substrate temperature of 340 ° C. to form an InSb layer. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tritertiary butylaluminum (TTBAl), trimethylindium (TMIn), and trisdimethylaminoantimony (TDMASb) were supplied as AlInSb raw materials at a substrate temperature of 500 ° C. to form an AlInSb layer. An MOCVD apparatus was used to form this AlInSb layer. An AlInSb layer was formed at a raw material ratio of Al and In such that Al / (Al + In) = 0.70.

  Normally, the raw materials of Group III and Group V are supplied to the growth chamber by the respective pipes for each group, but this time, only TTBAl was supplied alone until immediately before the growth chamber without passing through the block valve. The sample thus formed (AlInSb layer) was cloudy in appearance, and it was difficult to separate the AlInSb peak from the XRD measurement and to calculate the half width from the ω scan rocking curve. Further, since the surface of this sample (AlInSb layer) has large irregularities, it is difficult to perform accurate film thickness and SIMS measurement. When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 15.0 nm.

(Comparative Example 2)
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, an InSb layer was formed at a substrate temperature of 340 ° C. using trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) as InSb raw materials. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tritertiary butylaluminum (TTBAl), trimethylindium (TMIn), and trisdimethylaminoantimony (TDMASb) were supplied as AlInSb raw materials at a substrate temperature of 535 ° C. to form an AlInSb layer. An MOCVD apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, an Al raw material such that Al / (Al + In) = 0.50 was supplied together with the In raw material and the Sb raw material. After the growth for 1 minute, the supply amount of Al was increased to Al / (Al + In) = 0.70 which is a desired raw material ratio. At this time, the film was formed under the condition of V / III ratio = 5.0.

Normally, the raw materials of Group III and Group V are supplied to the growth chamber by the respective pipes for each group, but this time, only TTBAl was supplied alone until immediately before the growth chamber without passing through the block valve.
The sample thus formed (AlInSb layer) was cloudy in appearance, and it was difficult to separate the AlInSb peak from the XRD measurement and to calculate the half width from the ω scan rocking curve. Further, since the surface of this sample (AlInSb layer) has large irregularities, it is difficult to perform accurate film thickness and SIMS measurement. When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 13.5 nm.

(Comparative Example 3)
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, an InSb layer was formed at a substrate temperature of 340 ° C. using trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) as InSb raw materials. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tritertiary butylaluminum (TTBAl), trimethylindium (TMIn), and trisdimethylaminoantimony (TDMASb) were supplied as AlInSb raw materials at a substrate temperature of 400 ° C. to form an AlInSb layer. An MOCVD apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, an Al raw material such that Al / (Al + In) = 0.50 was supplied together with the In raw material and the Sb raw material. After the growth for 1 minute, the supply amount is increased to Al / (Al + In) = 0.70 which is a desired raw material ratio. At this time, the film was formed under the condition of V / III ratio = 5.0.

Normally, the raw materials of Group III and Group V are supplied to the growth chamber by the respective pipes for each group, but this time, only TTBAl was supplied alone until immediately before the growth chamber without passing through the block valve.
The sample thus formed (AlInSb layer) was cloudy in appearance, and it was difficult to separate the AlInSb peak from the XRD measurement and to calculate the half width from the ω scan rocking curve. Further, since the surface of this sample (AlInSb layer) has large irregularities, it is difficult to perform accurate film thickness and SIMS measurement. When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 10.5 nm.

(Comparative Example 4)
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, an InSb layer was formed at a substrate temperature of 340 ° C. using trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) as InSb raw materials. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tritertiary butylaluminum (TTBAl), trimethylindium (TMIn), and trisdimethylaminoantimony (TDMASb) were supplied as AlInSb raw materials at a substrate temperature of 500 ° C. to form an AlInSb layer.
An MOCVD apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, an Al raw material such that Al / (Al + In) = 0.50 was supplied together with the In raw material and the Sb raw material. After the growth for 1 minute, the supply amount of the Al raw material is increased to Al / (Al + In) = 0.92 which is a desired raw material ratio. At this time, the film was formed under the condition of V / III ratio = 5.0.

Normally, the raw materials of Group III and Group V are supplied to the growth chamber by the respective pipes for each group, but this time, only TTBAl was supplied alone until immediately before the growth chamber without passing through the block valve.
The sample thus formed (AlInSb layer) was cloudy in appearance, and it was difficult to separate the AlInSb peak from the XRD measurement and to calculate the full width at half maximum from the ω scan rocking curve. When the Al composition was measured, it was calculated that the Al composition was 75%. Further, since the surface of this sample (AlInSb layer) has large irregularities, it is difficult to perform accurate film thickness and SIMS measurement. When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 12.5 nm.

(Comparative Example 5)
A zinc-blende semi-insulating GaAs substrate was prepared. The semi-insulating GaAs substrate has an electric resistivity of 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, an InSb layer was formed as a first compound semiconductor layer at a substrate temperature of 350 ° C. under the condition of V / III ratio = 4.0. An MBE apparatus was used to form this InSb layer. The thickness of this InSb layer was 700 nm. An AlInSb layer was formed on the InSb layer at a substrate temperature of 350 ° C.
An MBE apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, an Al material such that Al / (Al + In) = 0.08 was supplied together with the In material and the Sb material. At this time, the film was formed under the condition of V / III ratio = 4.0. The thickness of this AlInSb layer was 700 nm.

For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 8%, and the half width calculated from the ω-scan rocking curve was 475 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), it was confirmed that each of hydrogen atoms, carbon atoms, and nitrogen atoms was less than 1 × 10 ¹⁵ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 0.1 nm. The compound semiconductor substrate obtained in Comparative Example 5 did not satisfy the formula (1).

(Comparative Example 6)
A compound semiconductor substrate was manufactured in the same manner as in Comparative Example 5 except that the Al raw material amount was changed to Al / (Al + In) = 0.25 when the AlInSb layer was grown. For the sample thus formed (AlInSb layer), the Al composition was examined using XRD measurement. As a result, the Al composition was 25%, and the half width calculated from the ω-scan rocking curve was 1400 arcsec. When SIMS measurement was performed on this sample (AlInSb layer), it was confirmed that each of hydrogen atoms, carbon atoms, and nitrogen atoms was less than 1 × 10 ¹⁵ . When AFM measurement was performed on the surface of this sample (AlInSb layer), the mean square roughness was 1.0 nm. The compound semiconductor substrate obtained in Comparative Example 6 did not satisfy the formulas (1) and (2).

(result)
Table 1 shows the conditions of the production methods of Examples 1 to 7 and Comparative Examples 1 to 6 and the measurement results of the obtained compound semiconductor substrates.

From the above-mentioned Examples and Comparative Examples and Table 1, for example, the following can be understood.
(1) In Examples 1 to 7, in the surface temperature of 420 ° C. or more and 525 ° C. or less, in addition to the In raw material and the Sb raw material, the Al raw material is supplied while increasing the supply amount continuously and / or stepwise. After increasing the supply amount of Al, the AlInSb layer was formed by keeping the supply amounts of the In raw material, the Sb raw material, and the Al raw material constant. According to Examples 1-7, compared with Comparative Example 1 in which the Al raw material was constantly supplied constantly, Comparative Example 2 with a surface temperature of 535 ° C., and Comparative Example 3 with a surface temperature of 400 ° C., a good crystal Thus, a compound semiconductor substrate including an AlInSb layer exhibiting excellent properties and excellent surface flatness was obtained.
(2) According to Examples 1 to 7 (particularly Examples 3, 4 and 6) using MOCVD, the Al composition ratio, which was difficult to maintain good crystallinity with the conventional MBE, was 20% or more. Compared with the AlInSb layer (Comparative Example 6), a compound semiconductor substrate including an AlInSb layer having good crystallinity was obtained.

  The present invention is suitable as a compound semiconductor substrate manufacturing method and a compound semiconductor substrate applied to devices such as a magnetic sensor, a high-speed device, and an IR sensor.

DESCRIPTION OF SYMBOLS 1 Substrate 11 1st compound semiconductor layer 21 2nd compound semiconductor layer 51 Growth chamber 52 Stage 53 Exhaust piping 54 Exhaust pump 60 Supply line 61 In piping 62 Sb piping 63 Al piping

Claims (3)

A substrate,
A first compound semiconductor layer containing In and Sb and not containing Al, formed on the substrate;
A second compound semiconductor layer containing Al, In, and Sb formed on the first compound semiconductor layer;
Hydrogen atoms contained in the second compound semiconductor layer are 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less,
The carbon atoms contained in the second compound semiconductor layer are 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less,
The nitrogen atom contained in the second compound semiconductor layer is 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less,
A compound semiconductor substrate in which a mean square roughness Rrms of a surface of the second compound semiconductor layer is 0.1 nm or more and 10 nm or less. The Al composition ratio with respect to the total amount of Group III elements in the second compound semiconductor layer is 0.1% or more and 70% or less;
2. The compound semiconductor substrate according to claim 1, wherein a half-value width FWHM calculated from ω scan rocking curve measurement by X-ray diffraction of the second compound semiconductor layer is a range calculated by the following formula (1).
a × Al composition ratio [%] + {− 90 × ln (t) +730} [arcsec]
≦ FWHM [arcsec] ≦ a × Al composition ratio [%] + {− 90 × ln (t) +830} [arcsec] (1)
(A = 23.5 [arcsec /%], t = second compound semiconductor layer thickness (nm)) Al composition ratio with respect to the total amount of Group III elements of the second compound semiconductor layer is 20% or more and 70% or less,
2. The compound semiconductor substrate according to claim 1, wherein a full width at half maximum FWHM calculated from ω scan rocking curve measurement by X-ray diffraction of the second compound semiconductor layer satisfies the following formula (2).
FWHM [arcsec] ≦ a × Al composition ratio [%] + {− 90 × ln (t) +830} [arcsec] (2)
(A = 23.5 [arcsec /%], t = second compound semiconductor layer thickness (nm))

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