CA1214381A - Method of growing gallium arsenide crystals using boron oxide encapsulant - Google Patents
Method of growing gallium arsenide crystals using boron oxide encapsulantInfo
- Publication number
- CA1214381A CA1214381A CA000432839A CA432839A CA1214381A CA 1214381 A CA1214381 A CA 1214381A CA 000432839 A CA000432839 A CA 000432839A CA 432839 A CA432839 A CA 432839A CA 1214381 A CA1214381 A CA 1214381A
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- Prior art keywords
- gaas
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- resistivity
- wafers
- heat treatment
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B27/00—Single-crystal growth under a protective fluid
- C30B27/02—Single-crystal growth under a protective fluid by pulling from a melt
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
- C30B29/42—Gallium arsenide
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- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Gallium arsenide single crystals are grown under an encapsulant of boron oxide which contains a predetermined amount of water in the range of 200 to 1000 ppm. The GaAs crystals so produced are stable in that the resistivity of the GaAs upon heat treatment remains substantially constant. The GaAs single crystals as produced may be subjected to a bulk anneal to further improve the stability.
Gallium arsenide single crystals are grown under an encapsulant of boron oxide which contains a predetermined amount of water in the range of 200 to 1000 ppm. The GaAs crystals so produced are stable in that the resistivity of the GaAs upon heat treatment remains substantially constant. The GaAs single crystals as produced may be subjected to a bulk anneal to further improve the stability.
Description
:
~$~L~
BACKGROUND OF THE INVENTION
This invention relates to a method for growing single crystals of gallium arsenide and, more particularly, to a method for growing semi-insulating single crystal gallium arsenide with improved physical characteristics using boron oxide encapsulant.
Gallium arsenide (GaAs) single crystals can be grown by any of a number of methods. Many of these methods use a liquid encapsulant, usually boron oxide (B203), to improve the quality of the single crystal GaAs. When grown under a layer of molten B203, the evaporation of the more volatile component of GaAs is better controlled, stoichiometry oE the single crystal is improved and the impurity content of the GaAs is lowered.
It is generally acknowledged in the industry, as witnessed by the published literature, that it is essential that the B203 must be substantially anhydrous in order to provide the above recited improvements. For instance, it has been stated that "it is essential to remove traces of water ` ~
~4;;1~i1 from the boron oxide" (J. Phys~. and Chem. Solidsm 26, 4, 782 (1965). Similar statements have been made during the 1966 Symposium on GaAs (Chemical Abstracts 69, 46579 y), in the J.
Crystal Growth, 3, 4, 281 (1968), in the Mat. Resources Bull., 6, 1297 (1971) and in the J. Electr. Matl., 4, 2, 389 (1975).
The water content of B2O3 is generally lowered by subjecting the B2O3 to vacuum baking for a period of time at temperatures as high as 1100C. In spite of the special treatment of B2O3 to reduce its water content, the water content of B2O3 used in crystal growth is not entirely eliminated and may range from substantially anhydrous, i.e.
less than 100 ppm, to as high as 1000 ppm. This residual water content of B2O3 has a distinct effect on the physical properties of GaAs.
It is desirable that semi-insulating GaAs crystal material has physical properties which do not cause instability. It is particularly desirable that such GaAs has a resistivity which does not decrease when the material, in the form of wafers, is subjected to a heat treatment to obtain suitable characteristics for electronic devices on the GaAs.
Some GaAs material shows a decrease in resistivity upon heat treatment, while other GaAs material shows an increase in resistivity or possesses a constant resistivity, the latter material being the preferred material.
SUMMARY OF THE INVENTION
It has now been found that the resistivity of semi-insulating GaAs single crystal material is related to the water content of the B2O3 encapsulant. More particularly, it has been surprisingly found that, contrary to prior art teachings, the use of B2O3 with a very low water content in the growth of semi-insulating single crystal GaAs yields GaAs unsuitable for application in electronic devices. More specifically, such very low water content yields GaAs which has a resistivity which decreases when such GaAs is submitted to a heat treatment. It has also been found that the use of B2O3 with a slightly higher, predetermined water content yields GaAs which has a resistivity which does not decrease when GaAs is subjected to a heat treatment. It has furthermore 3.
been found that, when semi-insulating GaAs single crystals grown under B2O3 having slightly higher, predetermined water contents are subjected to a bulk annealing operation of the crystals as grown, the GaAs becomes homogenized in that its resistivity has obtained the desired values even when subjected, in the form of wafers, to a second heat treatment.
Accordingly, there is provided in the method of producing semi-insulating single crystal GaAs by growth from a melt covered with a layer of boron oxide as encapsulant, the improvement which comprises covering the melt with boron oxide which contains water in an amount in the range of about 200 to 1000 ppm, and recovering semi-insulating single crystal GaAs, which single crystal GaAs has a resistivity in the range of about 5x105 to 2xlO~ ohm cm.
According to a second embodiment, there is provided in the method of producing semi-insulating GaAs single crystals by growth from a melt covered with a layer of boron oxide as encapsulant, the improvement which comprises covering the melt with boron oxide which contains water in an amount in the range 20 of about 200 to 1000 ppm and bulk annealing the GaAs single crystals so produced at a temperature in the range of about 750 to 900C for a period of time in the range of about 30 to 120 minutes whereby the bulk annealed GaAs single crystals so produced are stable and have a resistivity in the range of 25 about 5x105 to 2X108 ohm cm.
Preferably, the boron oxide contains water in an amount in the range of about 250 to 600 ppm.
The GaAs crystals produced according to the first and second embodiments may be cut into wafers and the wafers subjected to a heat treatment at a temperature in the range of about 750 to 900C for a period of time in the range of about 30 to 120 minutes in a hydrogen atmosphere~ whereby the ratio between the resistivity of the GaAs wafers before said heat treatment and the resistivity after the heat treatment is in 35 the range of about 0.8:1.0 to 1.2:1Ø Preferably, the ratio is about unity and the resistivity of the GaAs crystals produced according to the first and second embodiments is in the range of about lx106 to 7x107 ohm cm.
~31~
It is a principal object o~ the present invention to produce GaAs single crystal material with improved physical characteristics.
Another object of the invention is to provide a method of growing GaAs single crystal material which retains its resistivity value upon heat treatment.
It is a further object of the invention to grow GaAs single crystals under a boron oxide encapsulant containing a predetermined amount of water.
It is yet a further object of the invention to subject GaAs single crystals as grown to a bulk-annealing operation to make stable, more homogeneous GaAs material.
These and other objects of the invention and the manner in which they can be attained will become apparent from the following detailed description.
DETAILED DESCRIPTION
The method of the present invention is suitable or the growth of semi-insulating single crystal GaAs using an encapsulant and, particularly, for the yrowth of single crystal GaAs using the Liquid-Encapsulated Czochralski (LEC) method employing B2O3 as the encapsulant. Although the invention is specifically described with reference to GaAs grown by the LEC method, it is to be understood that the method according to the invention is equally applicable to the manufacture of other semi-conductor compounds single crystals such GaP, InP, CoTe, CdS, ZnSe and ZnS, and to other methods used for preparing GaAs and other semi-conductor compound single crystal material using B2O3 encapsulant.
In the LEC method, a GaAs seed crystal is dipped into a melt of gallium and arsenic in the desired amounts and preferably contained in a boron nitride crucible, and the seed crystal is slowly raised to form a GaAs single crystal which is raised along with the seed crystal. The method can be carried out, for example, in a Melbourn Crystal Puller (Trade Mark) sold by Cambridge Instruments Ltd., U.K. The melt is covered with a layer of molten B2O3~ The single crystal of GaAs as grown is subsequently sliced into wafers which are then heat ~L~
5.
treated to provide the desired electrical characteristics required for application in electronic devices.
The electrical characteristics of the material are critical to device operation, particularly in relation to stability, reproducibility and uniformity. A measure of the electrical characteristics of the semi-insulating GaAs is the resistivity. It is noted that a large change in resistivity observed in the heat treatment of GaAs wafers is a surface effect rather than a bulk effect. The resistivity should preferably have the same value before and after or an increased value after the heat treatment step. "Undoped" GaAs single crystal material with a resistivity below about 2X108 ohm cm and especially below about 7x107 ohm cm remains stable or shows an increase in resistivity after a heat treatment of wafers at temperatures in the range of about 750 to 900c for a time period in the range of about 30 to 120 minutes in a hydrogen atmosphere. It is to be understood that other heat treatment procedures, such as those at higher temperatures and for shorter periods of time, e.g. flash annealing, are equally suitable, provided that such procedures provide adequate protection of the surface of the GaAs to prevent contamination, or loss of stoichiometry. In contrast, material with a resistivity above about 2xlO ohm cm is unstable and shows a decrease in resistivity when heat treated as described. For example, undoped GaAs single crystal material with a resistivity of 3X108 ohm cm had a resistivity of only lx105 ohm cm after heat treatment. This material was unsuitable for application in electronic devices.
It has been discovered that undoped GaAs possessing high resistivities, i.e. above about 2X108 ohm cm, is obtained when the GaAs single crystal is pulled from a melt by the LEC method when the B2O3 encapsulant contains less than about 200 ppm water.
The resistivity of such GaAs decreases upon heat treatment as described and the GaAs is consequently considered to be unstable. ~hen the GaAs crystal is grown under B2O3 containing about 200 to 250 ppm water, the resistivity of the ~2~9~31 3~
GaAs upon heat treatment as described decreases only slightly and in some cases remains constant. When the GaAs crystal is grown under B2O3 containing water in the range of about ~50 to 1000 ppm, preferably about 250 to 600 ppm, the GaAs is stable and has a resistivit~ which remains constant or increases upon heat treatment as described. The desirable values for the resistivity of gaAs single crystal material are in the range of about 5x105 to 2X108 ohm cm, preferably about lx106 to 7x107 ohm cm.
The resistivity values of undoped as-grown GaAs single crystals by the LEC method under B2O3, which has a water content of more than 200 ppm and less than about 1000 ppm, varies with the water content, and are less than 2X108 ohm cm and usually in the range of about lx105 to 2x]08 ohm cm.
It has been found that when the undoped as-grown GaAs crystals grown under B2O3 having water contents in the preferred range are subjected to a bulk anneal, the GaAs having bulk resistivity values prior to the anneal in the lower en~ of the range of lx105 to 2X108 ohm cm will show increased 20 values for the bulk resistivity and the annealed GaAs is stable, more homogeneous and possesses bulk resistivities in the desired range of about lx106 to 7x107 ohm cm.
The bulk anneal is carried out by heating the undoped as-grown GaAs single crystal in a furnace to a temperature in the range of about 750 to 900C for a period of time in the range of about 30 to 120 minutes and cooling the annealed crystal. If desired, the bulk-annealed GaAs crystals may be cut into wafers and the wafers subjected to a heat treatment as described. The GaAs material which has been bulk annealed and 30 heat treated has a ratio between the resistivity of the GaAs wafer before the heat treatment and the resistivity of the GaAs wafer after the heat treatment in the range of about 0.8:1 to 1.2:1. The resistivity ratio is preferably about unity. As noted before, the changes in resistivity observed in heat treatment of "unstable" GaAs wafers are a surface rather than a bulk effect. Therefore, the resistivity of the heat treated wafers may show a small increase or decrease compared to the value of the bulk resistivity of the as-grown GaAs. The heat treatment of the wafers of bulk-annealed GaAs yields resistivity values in the desired range of about lx106 to 7x107 ohm cm, which values are substantially the same as the bulk resistivity values of the bulk-annealed GaAs single crystal.
The use of B2O3 with a predetermined water content in the range of about 200 to lO00 ppm in combination with a bulk anneal of the undoped as-grown GaAs single crystals is an excellent means to produce more homogeneous GaAs single crystals, to control the physical characteristics of GaAs single crystal material and to yield a GaAs material which is eminently suitable for use in electronic devices.
The invention will now be illustrated by the following non-limitative examples.
Example l Using a Melbourn Crystal Puller (Trade ~ark), a number of single crystals of GaAs were grown from a melt consisting of 69 grade Ga and 69 grade As. In each growth test, the melt was covered with a layer of molten B2Q3 containing a different amount of water. The undoped single crystal obtained from each test was cut into wafers and a wafer from the top section of the crystal and one from the bottom section were heat treated at 850C for 30 minutes ln a hydrogen atmosphere. The resistivity of the wafers was measured by the van der Pauw technique before and after the heat treatment. The water contents of the B2O3 and the measured resistivities are given in Table I.
Table I
Resistivities in ohm cm Test B2O3 Top Sample Bottom Sample No.H20 in ppm Before After Before After 1 16~ 5.7x108 ~.6x103 Ç.4x107 l.9x104
~$~L~
BACKGROUND OF THE INVENTION
This invention relates to a method for growing single crystals of gallium arsenide and, more particularly, to a method for growing semi-insulating single crystal gallium arsenide with improved physical characteristics using boron oxide encapsulant.
Gallium arsenide (GaAs) single crystals can be grown by any of a number of methods. Many of these methods use a liquid encapsulant, usually boron oxide (B203), to improve the quality of the single crystal GaAs. When grown under a layer of molten B203, the evaporation of the more volatile component of GaAs is better controlled, stoichiometry oE the single crystal is improved and the impurity content of the GaAs is lowered.
It is generally acknowledged in the industry, as witnessed by the published literature, that it is essential that the B203 must be substantially anhydrous in order to provide the above recited improvements. For instance, it has been stated that "it is essential to remove traces of water ` ~
~4;;1~i1 from the boron oxide" (J. Phys~. and Chem. Solidsm 26, 4, 782 (1965). Similar statements have been made during the 1966 Symposium on GaAs (Chemical Abstracts 69, 46579 y), in the J.
Crystal Growth, 3, 4, 281 (1968), in the Mat. Resources Bull., 6, 1297 (1971) and in the J. Electr. Matl., 4, 2, 389 (1975).
The water content of B2O3 is generally lowered by subjecting the B2O3 to vacuum baking for a period of time at temperatures as high as 1100C. In spite of the special treatment of B2O3 to reduce its water content, the water content of B2O3 used in crystal growth is not entirely eliminated and may range from substantially anhydrous, i.e.
less than 100 ppm, to as high as 1000 ppm. This residual water content of B2O3 has a distinct effect on the physical properties of GaAs.
It is desirable that semi-insulating GaAs crystal material has physical properties which do not cause instability. It is particularly desirable that such GaAs has a resistivity which does not decrease when the material, in the form of wafers, is subjected to a heat treatment to obtain suitable characteristics for electronic devices on the GaAs.
Some GaAs material shows a decrease in resistivity upon heat treatment, while other GaAs material shows an increase in resistivity or possesses a constant resistivity, the latter material being the preferred material.
SUMMARY OF THE INVENTION
It has now been found that the resistivity of semi-insulating GaAs single crystal material is related to the water content of the B2O3 encapsulant. More particularly, it has been surprisingly found that, contrary to prior art teachings, the use of B2O3 with a very low water content in the growth of semi-insulating single crystal GaAs yields GaAs unsuitable for application in electronic devices. More specifically, such very low water content yields GaAs which has a resistivity which decreases when such GaAs is submitted to a heat treatment. It has also been found that the use of B2O3 with a slightly higher, predetermined water content yields GaAs which has a resistivity which does not decrease when GaAs is subjected to a heat treatment. It has furthermore 3.
been found that, when semi-insulating GaAs single crystals grown under B2O3 having slightly higher, predetermined water contents are subjected to a bulk annealing operation of the crystals as grown, the GaAs becomes homogenized in that its resistivity has obtained the desired values even when subjected, in the form of wafers, to a second heat treatment.
Accordingly, there is provided in the method of producing semi-insulating single crystal GaAs by growth from a melt covered with a layer of boron oxide as encapsulant, the improvement which comprises covering the melt with boron oxide which contains water in an amount in the range of about 200 to 1000 ppm, and recovering semi-insulating single crystal GaAs, which single crystal GaAs has a resistivity in the range of about 5x105 to 2xlO~ ohm cm.
According to a second embodiment, there is provided in the method of producing semi-insulating GaAs single crystals by growth from a melt covered with a layer of boron oxide as encapsulant, the improvement which comprises covering the melt with boron oxide which contains water in an amount in the range 20 of about 200 to 1000 ppm and bulk annealing the GaAs single crystals so produced at a temperature in the range of about 750 to 900C for a period of time in the range of about 30 to 120 minutes whereby the bulk annealed GaAs single crystals so produced are stable and have a resistivity in the range of 25 about 5x105 to 2X108 ohm cm.
Preferably, the boron oxide contains water in an amount in the range of about 250 to 600 ppm.
The GaAs crystals produced according to the first and second embodiments may be cut into wafers and the wafers subjected to a heat treatment at a temperature in the range of about 750 to 900C for a period of time in the range of about 30 to 120 minutes in a hydrogen atmosphere~ whereby the ratio between the resistivity of the GaAs wafers before said heat treatment and the resistivity after the heat treatment is in 35 the range of about 0.8:1.0 to 1.2:1Ø Preferably, the ratio is about unity and the resistivity of the GaAs crystals produced according to the first and second embodiments is in the range of about lx106 to 7x107 ohm cm.
~31~
It is a principal object o~ the present invention to produce GaAs single crystal material with improved physical characteristics.
Another object of the invention is to provide a method of growing GaAs single crystal material which retains its resistivity value upon heat treatment.
It is a further object of the invention to grow GaAs single crystals under a boron oxide encapsulant containing a predetermined amount of water.
It is yet a further object of the invention to subject GaAs single crystals as grown to a bulk-annealing operation to make stable, more homogeneous GaAs material.
These and other objects of the invention and the manner in which they can be attained will become apparent from the following detailed description.
DETAILED DESCRIPTION
The method of the present invention is suitable or the growth of semi-insulating single crystal GaAs using an encapsulant and, particularly, for the yrowth of single crystal GaAs using the Liquid-Encapsulated Czochralski (LEC) method employing B2O3 as the encapsulant. Although the invention is specifically described with reference to GaAs grown by the LEC method, it is to be understood that the method according to the invention is equally applicable to the manufacture of other semi-conductor compounds single crystals such GaP, InP, CoTe, CdS, ZnSe and ZnS, and to other methods used for preparing GaAs and other semi-conductor compound single crystal material using B2O3 encapsulant.
In the LEC method, a GaAs seed crystal is dipped into a melt of gallium and arsenic in the desired amounts and preferably contained in a boron nitride crucible, and the seed crystal is slowly raised to form a GaAs single crystal which is raised along with the seed crystal. The method can be carried out, for example, in a Melbourn Crystal Puller (Trade Mark) sold by Cambridge Instruments Ltd., U.K. The melt is covered with a layer of molten B2O3~ The single crystal of GaAs as grown is subsequently sliced into wafers which are then heat ~L~
5.
treated to provide the desired electrical characteristics required for application in electronic devices.
The electrical characteristics of the material are critical to device operation, particularly in relation to stability, reproducibility and uniformity. A measure of the electrical characteristics of the semi-insulating GaAs is the resistivity. It is noted that a large change in resistivity observed in the heat treatment of GaAs wafers is a surface effect rather than a bulk effect. The resistivity should preferably have the same value before and after or an increased value after the heat treatment step. "Undoped" GaAs single crystal material with a resistivity below about 2X108 ohm cm and especially below about 7x107 ohm cm remains stable or shows an increase in resistivity after a heat treatment of wafers at temperatures in the range of about 750 to 900c for a time period in the range of about 30 to 120 minutes in a hydrogen atmosphere. It is to be understood that other heat treatment procedures, such as those at higher temperatures and for shorter periods of time, e.g. flash annealing, are equally suitable, provided that such procedures provide adequate protection of the surface of the GaAs to prevent contamination, or loss of stoichiometry. In contrast, material with a resistivity above about 2xlO ohm cm is unstable and shows a decrease in resistivity when heat treated as described. For example, undoped GaAs single crystal material with a resistivity of 3X108 ohm cm had a resistivity of only lx105 ohm cm after heat treatment. This material was unsuitable for application in electronic devices.
It has been discovered that undoped GaAs possessing high resistivities, i.e. above about 2X108 ohm cm, is obtained when the GaAs single crystal is pulled from a melt by the LEC method when the B2O3 encapsulant contains less than about 200 ppm water.
The resistivity of such GaAs decreases upon heat treatment as described and the GaAs is consequently considered to be unstable. ~hen the GaAs crystal is grown under B2O3 containing about 200 to 250 ppm water, the resistivity of the ~2~9~31 3~
GaAs upon heat treatment as described decreases only slightly and in some cases remains constant. When the GaAs crystal is grown under B2O3 containing water in the range of about ~50 to 1000 ppm, preferably about 250 to 600 ppm, the GaAs is stable and has a resistivit~ which remains constant or increases upon heat treatment as described. The desirable values for the resistivity of gaAs single crystal material are in the range of about 5x105 to 2X108 ohm cm, preferably about lx106 to 7x107 ohm cm.
The resistivity values of undoped as-grown GaAs single crystals by the LEC method under B2O3, which has a water content of more than 200 ppm and less than about 1000 ppm, varies with the water content, and are less than 2X108 ohm cm and usually in the range of about lx105 to 2x]08 ohm cm.
It has been found that when the undoped as-grown GaAs crystals grown under B2O3 having water contents in the preferred range are subjected to a bulk anneal, the GaAs having bulk resistivity values prior to the anneal in the lower en~ of the range of lx105 to 2X108 ohm cm will show increased 20 values for the bulk resistivity and the annealed GaAs is stable, more homogeneous and possesses bulk resistivities in the desired range of about lx106 to 7x107 ohm cm.
The bulk anneal is carried out by heating the undoped as-grown GaAs single crystal in a furnace to a temperature in the range of about 750 to 900C for a period of time in the range of about 30 to 120 minutes and cooling the annealed crystal. If desired, the bulk-annealed GaAs crystals may be cut into wafers and the wafers subjected to a heat treatment as described. The GaAs material which has been bulk annealed and 30 heat treated has a ratio between the resistivity of the GaAs wafer before the heat treatment and the resistivity of the GaAs wafer after the heat treatment in the range of about 0.8:1 to 1.2:1. The resistivity ratio is preferably about unity. As noted before, the changes in resistivity observed in heat treatment of "unstable" GaAs wafers are a surface rather than a bulk effect. Therefore, the resistivity of the heat treated wafers may show a small increase or decrease compared to the value of the bulk resistivity of the as-grown GaAs. The heat treatment of the wafers of bulk-annealed GaAs yields resistivity values in the desired range of about lx106 to 7x107 ohm cm, which values are substantially the same as the bulk resistivity values of the bulk-annealed GaAs single crystal.
The use of B2O3 with a predetermined water content in the range of about 200 to lO00 ppm in combination with a bulk anneal of the undoped as-grown GaAs single crystals is an excellent means to produce more homogeneous GaAs single crystals, to control the physical characteristics of GaAs single crystal material and to yield a GaAs material which is eminently suitable for use in electronic devices.
The invention will now be illustrated by the following non-limitative examples.
Example l Using a Melbourn Crystal Puller (Trade ~ark), a number of single crystals of GaAs were grown from a melt consisting of 69 grade Ga and 69 grade As. In each growth test, the melt was covered with a layer of molten B2Q3 containing a different amount of water. The undoped single crystal obtained from each test was cut into wafers and a wafer from the top section of the crystal and one from the bottom section were heat treated at 850C for 30 minutes ln a hydrogen atmosphere. The resistivity of the wafers was measured by the van der Pauw technique before and after the heat treatment. The water contents of the B2O3 and the measured resistivities are given in Table I.
Table I
Resistivities in ohm cm Test B2O3 Top Sample Bottom Sample No.H20 in ppm Before After Before After 1 16~ 5.7x108 ~.6x103 Ç.4x107 l.9x104
2 164 4.8x108 7~5x104 7~0x107 1.3x106
3 192 1.4x108 l.Ox104 4.1x107 l.Ox106
4 460 6.5x106 l.9x107 9.7x106 2.6x107 460 6.0x106 3.8x107 2.3x106 1.2x107 10 6 460 5.5~106 2.1x107 7.8x106 1.3x107 7 460 4,2x106 2.2x107 3.6x106 2.0x107 8 1000 1.2x107 8.7xlo6 - _ The tabulated test results show that a water content of the B2O3 below 200 ppm gives resistivities which 15 decrease at least an order of magnitude upon heat treatment of wafers cut from the single crystal and that a water content of B2O3 between 200 and 1000 ppm gives resistivities which remain substantially constant or which increase somewhat upon heat treatment of wafers. The resistivities of the material 20 grown under B O3 with 200-1000 ppm water are in the desired range of lxlO~ to 7x107.
Example 2 Using a Melbourn Crystal Puller (Trade Mark), a single crystal of GaAs was grown from a melt consisting of 69 grade Ga 25 and 69 grade As. The melt was covered with molten B2O3 containing an amount of water in the preferred range. The undoped as-grown single crystal was subjected to a bulk anneal by placing the crystal in a furnace, heating the furnace to 850C, maintaing the temperature at 850C for one hour and 30 cooling the crystal to room ~emperature. The top and bottom portions of the crystal were sampled before and after bulk annealing of the crystal and the resistivity determined using the van der Pauw technique. The water content of the B2O3 and the measured resistivities are given in Table II.
Table II
Bulk Resistivities in ohm cm TestB2O3 Top Sample Bottom Sample NoH2O in ppm Before After Before After 9 340 8.9x105 5.9x107 2.4x107 6.4x107 The results sho~ that bulk annealing of as-grown GaAs single crystals increases the resistivity and produces a more homogeneous crystal. The results also show that bulk annealing results in resistivities in the desired range of lx106 to 19 7x107 ohm cm.
Example 3 A wafer was cut from the top portion of the bulk-annealed crystal obtained in test No. 9 and the wafer was subjected to a heat treatment of 850C for 30 minutes in a hydrogen atmosphere. I'he resistivity of the heat-treated wafer was measured at 7.3x107 ohm cm. The ratio between resistivities measured before and after the heat treatment was 1.2. The results show that the resistivity of heat treated wafers cut from a bulk-annealed GaAs single crystal has a substantially constant value within the desired range of about lx106 to 7x107 ohm cm.
It should be understood that the invention is capable of further modifications and variations without departing from the scope and purview of the attached claims~
Example 2 Using a Melbourn Crystal Puller (Trade Mark), a single crystal of GaAs was grown from a melt consisting of 69 grade Ga 25 and 69 grade As. The melt was covered with molten B2O3 containing an amount of water in the preferred range. The undoped as-grown single crystal was subjected to a bulk anneal by placing the crystal in a furnace, heating the furnace to 850C, maintaing the temperature at 850C for one hour and 30 cooling the crystal to room ~emperature. The top and bottom portions of the crystal were sampled before and after bulk annealing of the crystal and the resistivity determined using the van der Pauw technique. The water content of the B2O3 and the measured resistivities are given in Table II.
Table II
Bulk Resistivities in ohm cm TestB2O3 Top Sample Bottom Sample NoH2O in ppm Before After Before After 9 340 8.9x105 5.9x107 2.4x107 6.4x107 The results sho~ that bulk annealing of as-grown GaAs single crystals increases the resistivity and produces a more homogeneous crystal. The results also show that bulk annealing results in resistivities in the desired range of lx106 to 19 7x107 ohm cm.
Example 3 A wafer was cut from the top portion of the bulk-annealed crystal obtained in test No. 9 and the wafer was subjected to a heat treatment of 850C for 30 minutes in a hydrogen atmosphere. I'he resistivity of the heat-treated wafer was measured at 7.3x107 ohm cm. The ratio between resistivities measured before and after the heat treatment was 1.2. The results show that the resistivity of heat treated wafers cut from a bulk-annealed GaAs single crystal has a substantially constant value within the desired range of about lx106 to 7x107 ohm cm.
It should be understood that the invention is capable of further modifications and variations without departing from the scope and purview of the attached claims~
Claims (8)
1. In the method of producing semi-insulating single crystal GaAs by growth from a melt covered with a layer of boron oxide as encapsulant, the improvement which comprises covering the melt with boron oxide which contains water in an amount in the range of about 200 to 1000 ppm, and recovering semi-insulating single crystal GaAs, which single crystal GaAs has a resistivity in the range of about 5x105 to 2X108 ohm cm.
2. In the method of producing semi-insulating GaAs single crystals by growth from a melt covered with a layer of boron oxide as encapsulant, the improvement which comprises covering the melt with boron oxide which contains water in an amount in the range of about 200 to 1000 ppm and bulk annealing the GaAs single crystals so produced at a temperature in the range of about 750 to 900°C for a period of time in the range of about 30 to 120 minutes whereby the bulk annealed GaAs single crystals so produced are stable and have a resistivity in the range of about 5x105 to 2x108 ohm cm.
3. The improvement as claimed in claim 1, wherein the semi-insulating GaAs crystals so produced are cut into wafers and said wafers are subjected to a heat treatment at a temperature in the range of about 750 to 900°C for a period of time in the range of about 30 to 120 minutes in a hydrogen atmosphere, whereby the ratio between the resistivity of the GaAs wafers before said heat treatment and the resistivity of the GaAs wafers after the heat treatment is in the range of about 0.8:1.0 to 1.2:1Ø
4. The improvement as claimed in claim 2, wherein the semi-insulating bulk-annealed GaAs crystals so produced are cut into wafers and said wafers are subjected to a heat treatment at a temperature in the range of about 750 to 900°C for a period of time in the range of about 30 to 120 minutes in a hydrogen atmosphere, whereby the ratio between the resistivity of the GaAs wafers before said heat treatment and the resistivity of the GaAs wafers after the heat treatment is in the range of about 0.8:1.0 to 1.2:1Ø
5. The improvement as claimed in claim 1 or 2, wherein the GaAs crystals so produced have a resistivity in the range of about 1x106 to 7x107 ohm cm.
6. The improvement as claimed in claim 1 or 2, wherein the boron oxide contains water in an amount in the range of about 250 to 600 ppm.
7. The improvement as claimed in claims 3 or 4, wherein the said ratio is about unity.
8. The improvement as claimed in claim 3 or 4, wherein the boron oxide contains water in an amount in the range of about 250 to 600 ppm, the ratio is about unity and the resistivity of the GaAs wafers is in the range of about 1x106 to 7x107 ohm cm.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000432839A CA1214381A (en) | 1983-07-20 | 1983-07-20 | Method of growing gallium arsenide crystals using boron oxide encapsulant |
| GB08418095A GB2143745B (en) | 1983-07-20 | 1984-07-16 | Growing semi conductor crystals |
| DE19843426250 DE3426250A1 (en) | 1983-07-20 | 1984-07-17 | METHOD FOR PRODUCING SEMI-INSULATING SINGLE CRYSTAL GAS |
| JP59148690A JPS6071600A (en) | 1983-07-20 | 1984-07-19 | Growth of gallium arsenide crystal using boron oxide sealing agent |
| FR8411593A FR2549500A1 (en) | 1983-07-20 | 1984-07-20 | PROCESS FOR THE PREPARATION OF SEMI-INSULATING MONOCRYSTALS OF GAAS |
| HK183/88A HK18388A (en) | 1983-07-20 | 1988-03-10 | Method of growing gallium arsenide crystals using boron oxide encapsulant |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000432839A CA1214381A (en) | 1983-07-20 | 1983-07-20 | Method of growing gallium arsenide crystals using boron oxide encapsulant |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1214381A true CA1214381A (en) | 1986-11-25 |
Family
ID=4125719
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000432839A Expired CA1214381A (en) | 1983-07-20 | 1983-07-20 | Method of growing gallium arsenide crystals using boron oxide encapsulant |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS6071600A (en) |
| CA (1) | CA1214381A (en) |
| DE (1) | DE3426250A1 (en) |
| FR (1) | FR2549500A1 (en) |
| GB (1) | GB2143745B (en) |
| HK (1) | HK18388A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61178497A (en) * | 1985-02-04 | 1986-08-11 | Mitsubishi Monsanto Chem Co | Method for growing gallium arsenide single with low dislocation density |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3551116A (en) * | 1968-06-04 | 1970-12-29 | Ibm | Process for preparing low resistivity high purity gallium arsenide |
| JPS5815095A (en) * | 1981-07-16 | 1983-01-28 | Toshiba Corp | Production of single crystal |
| JPS5914440B2 (en) * | 1981-09-18 | 1984-04-04 | 住友電気工業株式会社 | Method for doping boron into CaAs single crystal |
| JPS58181799A (en) * | 1982-04-16 | 1983-10-24 | Nippon Telegr & Teleph Corp <Ntt> | Manufacture of gaas single crystal containing boron |
-
1983
- 1983-07-20 CA CA000432839A patent/CA1214381A/en not_active Expired
-
1984
- 1984-07-16 GB GB08418095A patent/GB2143745B/en not_active Expired
- 1984-07-17 DE DE19843426250 patent/DE3426250A1/en not_active Ceased
- 1984-07-19 JP JP59148690A patent/JPS6071600A/en active Pending
- 1984-07-20 FR FR8411593A patent/FR2549500A1/en not_active Withdrawn
-
1988
- 1988-03-10 HK HK183/88A patent/HK18388A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6071600A (en) | 1985-04-23 |
| GB8418095D0 (en) | 1984-08-22 |
| DE3426250A1 (en) | 1985-01-31 |
| HK18388A (en) | 1988-03-18 |
| GB2143745B (en) | 1987-01-21 |
| GB2143745A (en) | 1985-02-20 |
| FR2549500A1 (en) | 1985-01-25 |
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