JP6517956B2 - Compound semiconductor substrate - Google Patents

Description

  The present invention relates to a compound semiconductor substrate.

A compound semiconductor containing InSb is a material having a high mobility and a small band gap, and it is used as a device such as a magnetic sensor, a high-speed device, an IR sensor, etc. by taking advantage of this feature. In order to realize a device to which a compound semiconductor containing InSb is applied, it is desirable to use AlInSb as the electron barrier layer.
Conventionally, tributyl aluminum (TTBAl) as an Al source, trimethylindium (TMIn) as an In source, and triethylantimony (TESb) as an Sb source have been used for AlInSb thin film formation using metalorganic vapor phase epitaxy. (See Patent Document 1).

US Patent No. 6071109

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

However, in conventional AlInSb thin films (hereinafter referred to as conventional AlInSb thin films) using conventional TTBAl, TMIn, and TESb represented by Patent Document 1, a large amount of carbon impurities are mixed, and the function as an electron barrier layer is lowered alone. In addition, the decrease in surface flatness was inevitable. In addition, the conventional AlInSb thin film is not sufficiently crystalline. Therefore, the conventional AlInSb thin film is not suitable for the application to the above-mentioned device.
On the other hand, as a means for suppressing the carbon impurity concentration, it is conceivable to use trisdimethylaminoantimony (TDDMAb) instead of TESb as the Sb material. However, it has been reported that a combination of TTBAl and TDMASb causes a gas phase reaction, and TTBAl and TDMAb react before reaching the substrate, resulting in only an AlInSb layer which is clouded, that is, has poor surface flatness (non-patented) Reference 1).
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a compound semiconductor substrate including an AlInSb layer which is excellent in crystallinity and excellent in surface flatness.

Moreover, as a result of intensive studies to solve the above problems, the present inventors have found that there is a substrate, and a first compound semiconductor layer formed on the substrate and containing In and Sb but not containing Al. And a second compound semiconductor layer containing Al, In, and Sb formed on the first compound semiconductor layer, wherein a hydrogen atom contained in the second compound semiconductor layer is 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 atom content in the layer is 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 problems can be solved by a compound semiconductor substrate

  According to one aspect of the present invention, it is possible to realize a compound semiconductor substrate including an AlInSb layer which is excellent in crystallinity and excellent in surface flatness.

It is a cross-sectional schematic diagram which shows the manufacturing method of the compound semiconductor substrate which concerns on this embodiment to 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 Al raw material in this embodiment.

Hereinafter, modes (this embodiment) for carrying out the present invention will be described.
<Method of manufacturing compound semiconductor substrate>
In the method of manufacturing a compound semiconductor substrate according to the present embodiment, the In raw material and the Sb raw material are supplied onto the substrate using metal organic chemical vapor deposition (MOCVD: Metal Organic Chemical Vapor Deposition), and the first material is deposited on the substrate. In the step of growing the compound semiconductor layer (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 the supply amount is increased continuously and / or stepwise, and after the supplied amount of the Al raw material is increased, the respective supplied amounts of the In raw material, Sb raw material and Al raw material 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 of continuous, stepwise, continuous and stepwise. .

By providing each of these steps (the first compound semiconductor layer growth step, the second compound semiconductor layer growth step), the clouding of the obtained AlInSb layer is suppressed, and the AlInSb layer has good crystallinity and high mobility. It is possible to obtain a compound semiconductor substrate comprising
In the method of supplying the In raw material and the Sb raw material and growing the first compound semiconductor layer, the AlInSb layer is clouded by the method of supplying the In raw material, the Sb raw material and the Al raw material at a predetermined fixed ratio. Mobility will also be low. On the other hand, the white turbidity of the obtained AlInSb layer is suppressed by supplying the Al source while continuously and / or stepwise increasing the supply amount in addition to the In source and the Sb source as in this embodiment. And an AlInSb layer having good crystallinity.
Although the details of this mechanism are not clear, by supplying a large amount of Al at the beginning, the reaction with TDMAb in the gas phase tends to occur, and the particles are deposited on the substrate. It is guessed that it is by shifting to Volmer-Weber mode.

The substrate temperature of the first compound semiconductor layer is controlled to 420 ° C. or more and 525 ° C. or less in the step of supplying the Al raw material while continuously and / or stepwise increasing the supply amount in addition to the In raw material and the Sb raw material . If the surface temperature is higher than 525 ° C. or lower than 420 ° C., a highly flat compound semiconductor substrate can not be obtained. Also, in the case where the formed Al _x In _1-x Sb layer has x> 0.7 (that is, the case where the Al composition ratio 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 can not be obtained.

  The feed rates of the Al source when making the respective feed amounts of the In source, the Sb source and the Al source constant are the addition of the In source and the Sb source, and the Al source is continuously and / or gradually increased. It is not particularly limited as long as it is larger than the supply amount of the Al raw material at the time of supply. However, it is preferable that the supply amount of the Al source after the supply amount of the Al source is constant is 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 in supplying the Al raw material while continuously and / or stepwise increasing the supply amount is not particularly limited, the ratio of the Al raw material to 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 method of manufacturing a compound semiconductor substrate 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 In materials include trimethylindium (TMIn) and triethylindium (TEIn). Examples of the Sb source include trimethylantimony (TMSb), triethylantimony (TESb), trisdimethylaminoantimony (TDMASb), and triisopropylantimony (TIPSb). Examples of the Al source include trimethylamine alane (TMAAl), triisobutylaluminum (TIBAl), dimethylaluminum hydride (DMAH), dimethylethylamine alane (DMEAAl), and tributylaluminum (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 tributyl 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 tributylaluminum (TTBAl) and trisdimethylaminoantimony (TDMASb) caused opacification of the AlInSb layer, so that a good AlInSb layer could not be obtained. However, in the present embodiment, the combination of tributylaluminum (TTBAl) and trisdimethylaminoantimony (TDMASb) by providing the first compound semiconductor layer growth step and the second compound semiconductor layer growth step described above. However, it is preferable because clouding of the AlInSb layer is suppressed and carbon impurities in the AlInSb layer are also suppressed.

In the method of manufacturing a compound semiconductor substrate of the present 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 just before the 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. Do not mix the Al source, In source and Sb source until just before introduction into the growth chamber in which the substrate is placed, and supply each of In source, Sb source and Al source to the growth chamber in which the substrate is placed. By using independent supply lines, it is possible to suppress the reaction between the raw materials and the disappearance before the raw materials reach the substrate. The independent supply line means a pipe connected to the growth chamber, in which a supply line of one raw material is not directly connected to a supply line of another raw material.
Also, in order to control the conductivity type, dimethylzinc (DMZn), diethylzinc (DEZn), dimethyltellurium (DMTe), diethyltellurium (DETe), tetramethyltin (TMSe) tetraethyltin ( A dopant such as TESn) may be supplied.

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

(Example of manufacturing method, manufacturing apparatus)
1 (a) to 1 (c) are cross-sectional schematic views showing a method of manufacturing a compound semiconductor substrate according to the present embodiment in the order of steps. First, as shown in FIG. 1A, a substrate 1 is prepared. Next, as shown in FIG. 1 (b), the In raw material and the Sb raw material are supplied onto the substrate 1 by using the metal organic chemical vapor deposition method, and the first compound semiconductor layer 11 is formed on the substrate 1. Grow (first compound semiconductor layer growth step).
Next, while the substrate temperature of the first compound semiconductor layer 11 is maintained at 420 ° C. or more and 525 ° C. or less, the In raw material and the Sb raw material are added to the first compound semiconductor layer 11 to continuously supply amounts. Supply Al source while increasing stepwise. Then, after increasing the supply amount of the Al source continuously and / or stepwise, the supply amounts of the In source, the Sb source, and the Al source on the first compound semiconductor layer 11 are made constant. Thus, 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. (2nd compound semiconductor layer growth step).

  FIG. 2 is a schematic view 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 for exhausting the inside of the growth chamber 51 and an exhaust pump 54, and the growth chamber. And 51 a supply line 60 for supplying a source gas. The supply line 60 includes an In pipe 61 for supplying In material, an Sb pipe 62 for supplying Sb material, and an Al pipe 63 for supplying Al material, and the growth chamber 51 is provided. It is possible to supply each raw material without mixing until it reaches.

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

<Compound semiconductor substrate>
The compound semiconductor substrate of the present embodiment includes a substrate, a first compound semiconductor layer formed on the substrate and containing In and Sb and not containing Al, and Al formed on the first compound semiconductor layer. a compound semiconductor substrate and a second compound semiconductor layer containing in and Sb, hydrogen atoms contained in the second compound semiconductor layer is in least 1 × 10 ¹⁵ cm ^-3 5 × 10 ¹⁹ cm ^-3 or less And the number of carbon atoms 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 number of nitrogen atoms contained in the second compound semiconductor layer is 1 × 10 ¹⁵ cm 3. ^-3 or more and 5 × 10 ¹⁸ cm ^-3 or less.

Conventionally, mixing of carbon atoms is inevitable, and therefore, the technical significance of the atoms contained in the second compound semiconductor layer containing Al, In and Sb has not been focused on. On the other hand, in the compound semiconductor substrate of the present embodiment, the number of hydrogen atoms contained in the second compound semiconductor layer is 1 × 10 ¹⁵ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less, and the number of carbon atoms is 1 × 10 10 ^{It is 15} cm ^-3 or more and 5 x 10 ¹⁸ cm ^-3 or less, and the nitrogen atom is 1 x 10 ¹⁵ cm ^-3 or more and 5 x 10 ¹⁸ cm ^-3 or less, thereby suppressing the white turbidity of the substrate and increasing the height. A mobility compound semiconductor substrate can be realized.

In the compound semiconductor substrate of the present embodiment, the average 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.
The compound semiconductor substrate of the present embodiment has an Al composition ratio of 0.1% to 70%, based on the total amount of group III elements of the second compound semiconductor layer, from the viewpoint of application suitability to an optical device.
The half width FWHM calculated from the ω scan rocking curve measurement of the second compound semiconductor layer by X-ray diffraction is preferably in the 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))

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

In the compound semiconductor substrate of the present embodiment, the first compound semiconductor layer is a layer formed on the substrate and containing In and Sb but not containing Al. Specifically, layers made of mixed crystals of InSb and InSb can be mentioned. In addition, desired dopants such as Te and Sn may be included to form an n-type conductive layer, and desired dopants such as Zn and Si may be included to form a p-type conductive layer.
In the compound semiconductor substrate of the present embodiment, the second compound semiconductor layer is a layer formed on the first compound semiconductor layer and containing Al, In, and Sb. Specifically, layers made of AlInSb and mixed crystals of AlInSb, Ga and As can be mentioned. In addition, desired dopants such as Te and Sn may be included to form an n-type conductive layer, and desired dopants such as Zn and Si may be included to form a p-type conductive layer.
Hereinafter, in order to explain the compound semiconductor substrate of the present embodiment and the method of manufacturing the same in more detail, the present invention will be described with reference to specific examples.

Example 1
A semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. Trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) are supplied on this semi-insulating GaAs substrate as a source of InSb at a substrate temperature of 340 ° C., and the first compound semiconductor is produced under the condition of V / III ratio = 5.0. An InSb layer was formed as a layer. The V / III ratio is the 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 film thickness of this InSb layer was 700 nm.

  On this InSb layer, tributyl aluminum (TTBAl), trimethylindium (TMIn), trisdimethylaminoantimony (TDMASb) are supplied as a raw material of AlInSb at a substrate temperature of 500 ° C., and AlInSb as a second compound semiconductor layer A layer was formed. The MOCVD apparatus was used for formation of this AlInSb layer. When growing this AlInSb layer, the Al source was supplied together with the In source and the Sb source so that the source ratio of Al to In 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 for determining each element ratio of the AlInSb layer. At this time, film formation was performed under the condition of V / III ratio = 5.0. Usually, the raw materials are supplied to the growth chamber by group III and V materials by respective pipes to the growth chamber, but this time, only TTBAl alone was supplied to just before the growth chamber without passing through the block valve. That is, the Sb raw material was independently supplied to the growth chamber, and the Al raw material and the In raw material were supplied independently until immediately before the growth chamber. The film thickness of this AlInSb layer was 700 nm.

The Al composition of the sample (AlInSb layer) thus formed was examined using XRD measurement to find that the Al composition was 18% and the half width calculated from the ω scan rocking curve was 620 arcsec. SIMS measurement was performed on this sample (AlInSb layer) to find that 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 to In at the time of AlInSb formation was set to Al / (Al + In) = 0.63. The film thickness of this AlInSb layer was 700 nm. The Al composition of the thus-formed sample (AlInSb layer) was examined using XRD measurement to find that the Al composition was 1% and the half width calculated from the ω scan rocking curve was 205 arcsec. SIMS measurement was performed on this sample (AlInSb layer) to find that hydrogen atoms were 3 × 10 ¹⁶ cm ⁻³ , carbon atoms 1 × 10 ¹⁵ cm ⁻³ , and nitrogen atoms 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 to In at the time of AlInSb formation was set to Al / (Al + In) = 0.75. The film thickness of this AlInSb layer was 700 nm. The Al composition of the sample (AlInSb layer) thus formed was examined using XRD measurement to find that the Al composition was 40% and the half width calculated from the ω scan rocking curve was 1120 arcsec. SIMS measurement was performed on this sample (AlInSb layer) to find that hydrogen atoms were 2 × 10 ¹⁸ cm ⁻³ , carbon atoms 4 × 10 ¹⁷ cm ⁻³ , and nitrogen atoms 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 to In was Al / (Al + In) = 0.90 when AlInSb was formed. The film thickness of this AlInSb layer was 700 nm. The Al composition of the sample (AlInSb layer) thus formed was examined using XRD measurement to find that the Al composition was 70% and the half width calculated from the ω scan rocking curve was 1800 arcsec. SIMS measurement of this sample (AlInSb layer) showed that 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 at the formation of AlInSb was 420 ° C. The film thickness of this AlInSb layer was 700 nm. The Al composition of the sample thus formed (AlInSb layer) was examined using XRD measurement, and the Al composition was 3%, and the half width calculated from the ω scan rocking curve was 230 arcsec. SIMS measurement was performed on this sample (AlInSb layer) to find that hydrogen atoms were 2 × 10 ¹⁷ cm ⁻³ , carbon atoms 5 × 10 ¹⁶ cm ⁻³ , and nitrogen atoms 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 was 525 ° C. when AlInSb was formed. The film thickness of this AlInSb layer was 700 nm. The Al composition of the sample (AlInSb layer) thus formed was examined using XRD measurement, and the Al composition was 25%, and the half width calculated from the ω scan rocking curve was 720 arcsec. SIMS measurement was performed on this sample (AlInSb layer) to find that 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 semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, trimethylindium (TMIn) and trisdimethylaminoantimony (TDMACb) were supplied as a source of InSb 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, tributyl aluminum (TTBAl), trimethylindium (TMIn), trimethylantimony (TMSb) are supplied as a raw material of AlInSb at a substrate temperature of 500 ° C. to form an AlInSb layer as a second compound semiconductor layer. Formed. The MOCVD apparatus was used for formation of this AlInSb layer. When the AlInSb layer was grown, an Al source was supplied together with the In source and the Sb source such that the source ratio of Al to In was Al / (Al + In) = 0.50. After the growth for 1 minute, the supply amount was increased to Al / (Al + In) = 0.70, which is a desired supply amount for determining each element ratio of the AlInSb layer.

Usually, the raw materials are supplied to the growth chamber by group III and V materials by respective pipes to the growth chamber, but this time, only TTBAl alone was supplied to just before the growth chamber without passing through the block valve. The film thickness of this AlInSb layer was 700 nm.
The Al composition of the thus-formed sample (AlInSb layer) was examined using XRD measurement to find that the Al composition was 10% and the half width calculated from the ω scan rocking curve was 400 arcsec. SIMS measurement of this sample (AlInSb layer) showed that 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 semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) were supplied as a source of InSb 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, tributyl aluminum (TTBAl), trimethylindium (TMIn), trisdimethylaminoantimony (TDMASb) were supplied as a source of AlInSb at a substrate temperature of 500 ° C. to form an AlInSb layer. The MOCVD apparatus was used for formation of this AlInSb layer. An AlInSb layer was formed at a raw material ratio of Al and In such that Al / (Al + In) = 0.70.

  Usually, the raw materials are supplied to the growth chamber by group III and V materials by respective pipes to the growth chamber, but this time, only TTBAl alone was supplied to just before the growth chamber without passing through the block valve. The appearance of the sample (AlInSb layer) formed in this manner was cloudy, 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. In addition, since the surface of this sample (AlInSb layer) has large irregularities, it has been 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 semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. An InSb layer was formed on this semi-insulating GaAs substrate at a substrate temperature of 340 ° C. using trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) as a source of InSb. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tributyl aluminum (TTBAl), trimethylindium (TMIn), trisdimethylaminoantimony (TDMASb) were supplied as a raw material of AlInSb at a substrate temperature of 535 ° C. to form an AlInSb layer. The MOCVD apparatus was used for formation of this AlInSb layer. When the AlInSb layer was grown, an Al source was supplied together with the In source and the Sb source such that Al / (Al + In) = 0.50. After 1 minute growth, the Al feed was increased to the desired feed ratio Al / (Al + In) = 0.70. At this time, film formation was performed under the condition of V / III ratio = 5.0.

Usually, the raw materials are supplied to the growth chamber by group III and V materials by respective pipes to the growth chamber, but this time, only TTBAl alone was supplied to just before the growth chamber without passing through the block valve.
The appearance of the sample (AlInSb layer) formed in this manner was cloudy, 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. In addition, since the surface of this sample (AlInSb layer) has large irregularities, it has been 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 semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. An InSb layer was formed on this semi-insulating GaAs substrate at a substrate temperature of 340 ° C. using trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) as a source of InSb. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tributyl aluminum (TTBAl), trimethylindium (TMIn), trisdimethylaminoantimony (TDMASb) were supplied as a raw material of AlInSb at a substrate temperature of 400 ° C. to form an AlInSb layer. The MOCVD apparatus was used for formation of this AlInSb layer. When the AlInSb layer was grown, an Al source was supplied together with the In source and the Sb source such that Al / (Al + In) = 0.50. After 1 minute growth, the feed rate is increased to the desired feed ratio, Al / (Al + In) = 0.70. At this time, film formation was performed under the condition of V / III ratio = 5.0.

Usually, the raw materials are supplied to the growth chamber by group III and V materials by respective pipes to the growth chamber, but this time, only TTBAl alone was supplied to just before the growth chamber without passing through the block valve.
The appearance of the sample (AlInSb layer) formed in this manner was cloudy, 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. In addition, since the surface of this sample (AlInSb layer) has large irregularities, it has been 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 semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. An InSb layer was formed on this semi-insulating GaAs substrate at a substrate temperature of 340 ° C. using trimethylindium (TMIn) and trisdimethylaminoantimony (TDMASb) as a source of InSb. An MOCVD apparatus was used to form this InSb layer.
On this InSb layer, tributyl aluminum (TTBAl), trimethylindium (TMIn), trisdimethylaminoantimony (TDMASb) were supplied as a source of AlInSb at a substrate temperature of 500 ° C. to form an AlInSb layer.
The MOCVD apparatus was used for formation of this AlInSb layer. When the AlInSb layer was grown, an Al source was supplied together with the In source and the Sb source such that Al / (Al + In) = 0.50. After 1 minute growth, the feed of Al source is increased to the desired source ratio Al / (Al + In) = 0.92. At this time, film formation was performed under the condition of V / III ratio = 5.0.

Usually, the raw materials are supplied to the growth chamber by group III and V materials by respective pipes to the growth chamber, but this time, only TTBAl alone was supplied to just before the growth chamber without passing through the block valve.
The appearance of the sample (AlInSb layer) formed in this way is cloudy, and it was difficult to separate the peak of AlInSb from the XRD measurement and to calculate the half width from the ω scan rocking curve, which is based on XRF When the Al composition was measured, it was calculated that the Al composition was 75%. In addition, since the surface of this sample (AlInSb layer) has large irregularities, it has been 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 semi-insulated GaAs substrate of zinc blende type was prepared. The electrical resistivity of this semi-insulating GaAs substrate is 8 × 10 ⁷ Ωcm. On this semi-insulating GaAs substrate, an InSb layer was formed as a first compound semiconductor layer under the condition of V / III ratio = 4.0 at a substrate temperature of 350.degree. An MBE apparatus was used to form this InSb layer. The film thickness of this InSb layer was 700 nm. An AlInSb layer was formed on the InSb layer at a substrate temperature of 350.degree.
An MBE apparatus was used to form this AlInSb layer. When the AlInSb layer was grown, an Al source was supplied together with the In source and the Sb source such that Al / (Al + In) = 0.08. At this time, film formation was performed under the condition of V / III ratio = 4.0. The film thickness of this AlInSb layer was 700 nm.

The Al composition of the sample (AlInSb layer) thus formed was examined using XRD measurement to find that 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 hydrogen atoms, carbon atoms, and nitrogen atoms were each 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 Formula (1).

(Comparative example 6)
When growing the AlInSb layer, a compound semiconductor substrate was manufactured in the same manner as in Comparative Example 5 except that the amount of Al raw material was changed to Al / (Al + In) = 0.25. The Al composition of the sample (AlInSb layer) thus formed was examined using XRD measurement to find that 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 hydrogen atoms, carbon atoms, and nitrogen atoms were each 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)
The conditions of the manufacturing methods of Examples 1 to 7 and Comparative Examples 1 to 6 and the measurement results of the obtained compound semiconductor substrates are shown in Table 1.

From the example and comparative example described above and Table 1, the following can be understood, for example.
(1) In Examples 1 to 7, in addition to the In raw material and the Sb raw material at a surface temperature of 420 ° C. or more and 525 ° C. or less, the Al raw material is supplied while continuously and / or stepwise increasing the supply amount. After increasing the supply amount of Al, the AlInSb layer was formed by making the supply amounts of the In raw material, the Sb raw material and the Al raw material constant. According to Examples 1 to 7, good crystals are obtained as compared with Comparative Example 1 in which the Al raw material is always supplied constantly, Comparative Example 2 in which the surface temperature is 535 ° C., and Comparative Example 3 in which the surface temperature is 400 ° C. 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 (especially Examples 3, 4 and 6) using MOCVD, the Al composition ratio which is difficult to maintain good crystallinity by MBE of the conventional method is 20% or more. In comparison with the AlInSb layer of Comparative Example 6 (Comparative Example 6), a compound semiconductor substrate including an AlInSb layer of good crystallinity was obtained.

  INDUSTRIAL APPLICABILITY The present invention is suitable as a compound semiconductor substrate manufacturing method and compound semiconductor substrate applied to devices such as magnetic sensors, high-speed devices, IR sensors, and the like.

Reference Signs List 1 substrate 11 first compound semiconductor layer 21 second compound semiconductor layer 51 growth chamber 52 stage 53 exhaust piping 54 exhaust pump 60 supply line 61 piping for In 62 piping for Sb piping 63 for aluminum

Claims (3)

A substrate,
A first compound semiconductor layer formed on the substrate and containing In and Sb and not containing Al;
And a second compound semiconductor layer formed on the first compound semiconductor layer, the second compound semiconductor layer containing Al, In, and Sb,
The hydrogen atom contained in the second compound semiconductor layer is 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,
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,
The compound semiconductor substrate whose mean square roughness Rrms of the surface of a said 2nd compound semiconductor layer is 0.1 nm or more and 10 nm or less. The Al composition ratio is 0.1% or more and 70% or less with respect to the total amount of group III elements of the second compound semiconductor layer,
The compound semiconductor substrate according to claim 1, wherein the half width FWHM calculated from the ω scan rocking curve measurement of the second compound semiconductor layer by X-ray diffraction 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)) The Al composition ratio is 20% or more and 70% or less with respect to the total amount of group III elements in the second compound semiconductor layer.
The compound semiconductor substrate according to claim 1, wherein a half width FWHM calculated from measurement of ω scan rocking curve 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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