JPS589797B2 - Method for doping strongly reducing impurities into Group 3-5 compound semiconductor single crystals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes strongly reducing materials such as silicon to produce a ■-■ group compound semiconductor single crystal by the liquid capsule drawing method (LEC method) using a boron oxide (B2O3) melt as a capsule agent. This invention relates to an improved method for effectively doping impurities.

In the LEC method, G, which is a type of ■-■ group compound semiconductor,
Silicon (Si), a type of strongly reducing impurity, is added to aAs.
Regarding the method of doping, first, S. J. Bas
s and P.S. E. Oliver: “Prope
rtiesof Gallium Arsenide
Crystals Produced by Liqui
d Encapsulation Pulling,”
1966 Symposium on GaAs (1
967), P41.

A 90 g crystal was grown using the so-called RF heating type LEC method.

However, it is stated that GaAs crystal doped with silicon at a high concentration became polycrystalline with small crystal grains in all experiments.

Next, Hiroshi Kojima and Motoyoshi Kishida: “■−■ Using the liquid capsule method
"About GaAs as a Main Process for the Production of Group Compounds", Semiconductor Research 9 (1973), p. 181 also describes the RF heating type L.
The carrier concentration of silicon is 1×1017 by EC method.
A method of doping by ˜2×10 18 cm −3 is described.

In other words, the raw material charge is approximately 2.5 x 101 of silicon.
GaAs polycrystal doped by 8cm-3 and 1.3×1
It is described as consisting of a mixture of only 0.019 to 7.7×10 19 cm −3 of silicon, with most of the silicon being converted to boron.

It is also stated that the dislocation density in GaAs obtained by this RF heating type LEC method is about 1 to 5 x 104 cm-2, which is inferior to that of the horizontal Bridgman method (HB method), which is less than 1 x 104 cm-2. There is.

Also, in this report, the raw material charge is placed all at once on top of B2O3.

There has been no report on a method of doping GaP, InP, or InAs, which are one of the typical ■-■ group compound semiconductors along with GaAs, with strongly reducing impurities by the LEC method.

(Japanese Unexamined Patent Publication No. 51-18471) On the other hand, in the invention of Japanese Patent Application No. 49-90991,
The silicon concentration is 5 x 1017 to 5 x 1018 cm-3, the cross-sectional area of the single crystal is 5 cm2 or more, and the dislocation density is 2
A method for manufacturing silicon-doped GaAs single crystals with a size of 103 cm-2 or less is proposed.

Furthermore, the invention of Japanese Patent Application No. 138395/1983
62200), the silicon concentration was 1.5×
1018~5.5x1018cm-3, cross-sectional area 5c
A silicon-heavily doped, low dislocation density GaAs single crystal with a dislocation density of m2 or more and a dislocation density of 100 cm-2 or less is proposed.

Furthermore, the present inventors have proposed a low dislocation density GaP single crystal doped with strongly reducing impurities such as boron, silicon, aluminum, magnesium, etc. , that is, the diameter is 30 mm or more and the dislocation density is 5 x 104c.
We have proposed a low dislocation density GaP single crystal with a diameter of 35 to 55 mm and a dislocation density of 2 x 104 cm-2 or less.

However, when strongly reducing impurities such as silicon, which has a stronger reducing property than boron, are used in the LEC method, the dislocation density is low, about one-tenth or less of the dislocation density in an undoped single crystal grown under the same manufacturing conditions. There has been no known method for doping a compound in a sufficient amount efficiently and with good reproducibility in order to obtain a semiconductor crystal of a -2 group compound.

The present invention provides a new and improved method that can effectively dope impurities with a stronger reducibility than boron by suppressing or controlling the conversion reaction to boron.

The first invention of the present invention is to produce a ■-■ group compound semiconductor single crystal by the liquid capsule drawing method (LEC method) using a boron oxide (B2O3) melt as a capsule. At least one strongly reducing impurity having a strong reducing property is arranged so as not to come into direct contact with the B203 melt during heating and temperature raising of the single crystal raw material charge, and then added to the single crystal raw material melt. The strongly reducing impurities are effectively dissolved in the above-mentioned melt to form a low dislocation density ■-■ group compound semiconductor monomer having a dislocation density of about one-tenth or less of the dislocation density in an undoped single crystal grown from the above melt under the same manufacturing conditions. Provided is a method for doping a strongly reducing impurity into a ■-■ group compound semiconductor single crystal, which is characterized by growing a low dislocation density ■-■ group compound semiconductor single crystal doped in a sufficient amount to obtain a crystal. It is something.

Here, using the resistance heating LEC method,
When an undoped single crystal of a group compound semiconductor is grown, it is generally about 2 x 105 to 5 x 105 cm-2 for GaP.
About 1 x 103 to 5 x 103 cm-2 for GaAs, In
Recognizing that it is about 1 x 103 to 5 x 103 cm-2 for P and about 1 x 103 to 3 x 103 cm-2 for InAs, in the present invention, a low dislocation density single crystal with a diameter of 30 mm or more refers to GaP 2 x 104 ~ 5 x 104 cm-
2 or less, 1 x 102 to 5 x 102 cm in Ga As
Needless to say, it means a single crystal of -2 or less, 1 x 102 to 5 x 102 cm-2 or less for InP, and 1 x 102 to 3 x 102 cm-2 or less for InAs.

Furthermore, the doping amount of strongly reducing impurities necessary for lowering the dislocation density is disclosed in Japanese Patent Application No. 49-90991 (Japanese Unexamined Patent Publication No. 51-18).
471 Publication), Japanese Patent Application No. 138395/1983 (
Japanese Patent Application Laid-Open No. 52-62200), Japanese Patent Application No. 51-524
It is understood from the specification of No. 85 (Japanese Unexamined Patent Publication No. 52-134898).

In this invention, the ■-■ group compound semiconductor is Ga
It may be selected from P, GaAs, InP, and InAs.

Further, it is preferable that the strong reducing impurity is at least one of silicon (Si), aluminum (Al), and magnesium (Mg).

In this invention, silicon is a strongly reducing impurity.
×1016 cm−3 or more doped into GaP, GaP
The diameter of the single crystal is 30 mm or more, and the dislocation density is 5 × 1
It is also possible to grow a GaP single crystal with a low dislocation density of 0.04 cm -2 or less.

In this invention, the raw material charge is GaP polycrystal, G
aP polycrystalline mixture, and this GaP
The polycrystal may be doped with silicon in an amount of 1×10 17 cm −3 or more in advance.

In addition, 1×1017 cm of silicon is contained in this GaP polycrystal.
3 or more and 2×10 18 cm −3 or more of poron may be doped in advance.

Of course, silicon may be added quickly through the B2O3 melt after the raw charge has completely melted.

Also, silicon is covered with gallium in the raw material charge and B2O
There may be no direct contact with 3.

The third aspect of the present invention (described in claim 6) is as follows:
In the first invention, silicon is used as a strongly reducing impurity at a concentration of 3 x 1017 to 5 x 1018 cm-3.
Doped into aP, the diameter of GaP single crystal is 35~55
It is characterized by growing a low dislocation density GaP single crystal with a diameter of 1.5 mm and a dislocation density of 2×10 4 cm −2 or less.

Furthermore, a mixture of GaP polycrystal and gallium in which silicon has been dissolved in advance may be used for the raw material charge,
GaP polycrystal and silicon are dissolved in advance in an amount necessary for the silicon concentration in the GaP grown crystal to be 3 x 1017 cm-3 or more, and the boron concentration in the GaP grown crystal to be 5 x 1018 cm-3 or more. A mixture with as much boron as necessary may also be used.

Furthermore, using one of GaP polycrystals and a mixture of GaP polycrystals and gallium as a raw material charge, this GaP
The polycrystal may be doped with 3×1017 cm or more of silicon in advance, or 3×1017 cm of silicon may be doped in advance.
In addition to m −3 or more, boron of 5×10 18 cm −3 or more may be doped in advance.

Hereinafter, the present invention will be explained in detail with reference to Examples.

First, the results of doping silicon into GaP using a conventional common doping method will be described.

That is, 150 g of GaP polycrystal and 3.2 x 1 silicon
019cm-3 equivalent (90mg) and sulfur (S) 1
．． GaP single crystal doped with silicon and sulfur was grown in the <111> direction by the resistance heating LEC method using 5 x 1017 cm-3 equivalent (4.0 mg) as a raw material charge and a nitrogen gas pressure of about 50 atm. Ta.

The growth rate is approximately 10 mm/hour, but the details are in the patent application filed in 1972.
Please refer to specification No. 52485 (Japanese Unexamined Patent Publication No. 52-134898).

The dislocation density in the thus obtained GaP single crystal with a diameter of about 30 mm is about 1 x 105 cm-2, and the silicon concentration is about 9.
x 1015 cm-3 and the carrier concentration at 300°K was approximately 1.6 x 1017 cm-3.

That is, it can be seen that only about 9×10 15 cm −3 of silicon was doped out of the silicon addition amount equivalent to 3.2×10 19 cm −3 .

Figure 1 shows raw material melt 1 and B2O3 in a pressurized chamber (not shown).
The arrangement of melt 2, quartz crucible 3, and carbon crucible 4 in a steady state is shown.

The B2O3 melt 2 thinly enters between the raw material melt 1 and the quartz crucible 3.

In the temperature range 1410℃~1613℃, 3Si (liquid)
+2B2O3 (liquid) = 4B (solid) + SiO2 (β
-quartz) (1) reaction is considered, but Si and B are GaP
It will be mixed into the melt or B2O3.

It was found that there is a relationship approximately n(2~3)×1022n81 between the boron concentration (nB) and silicon concentration (n81) in a GaP single crystal that is effectively and appropriately doped with Si. However, as mentioned above, silicon may not be effectively doped using conventional doping methods.

It was found that the reason for this can be explained by considering another reaction in the temperature range of 564°C to 1410°C: 3Si (solid) + 2B2O3 (liquid) = 4B (solid) + 38iO2 (β-quartz) (2).

In other words, silicon in the raw material charge becomes B during heating and temperature rise.
When it comes into contact with the 2O3 melt, most of it is converted to boron by the reaction (2).

The generated boron is distributed into B2O3 and the raw material melt.

Moreover, since silicon is no longer supplied after the steady state shown in FIG. 1, the reaction (1) also stops.

It has also been found that due to differences in the history during heating and temperature rise, the final doping ratio of added silicon also varies greatly.

Therefore, the concentration of boron that is finally doped also shows variations.

Example 1 In this example, as shown in FIG.
00g and 1128m of silicon covered with 5g of gallium.
g (equivalent to 15 x 1020 cm-3) and dehydrated B2O3
The disk 6 was arranged as shown to prevent the silicon 8 from coming into direct contact with the B2O3 that melts during heating.

After heating and increasing the temperature to obtain a steady state as shown in FIG. 1, a GaP single crystal was pulled according to the method described above.

The dislocation density in the obtained single crystal was about 1 x 104 cm-2, the silicon concentration was 4.8 x 1018 cm-3, and the diameter of the single crystal was about 38 mm.

It can be seen that silicon was doped more effectively than in the conventional method described above.

Example 2 In this example, silicon was used as the raw material charge in an amount of approximately 6×1
A mixture of 310 g of GaP polycrystal containing about 1×10 20 cm −3 and boron and 5 g of gallium was used.

Other conditions were the same as in Example 1.

The obtained single crystal has a diameter of about 50 mm and a dislocation density of 5×
103~2x104cm-2, carrier concentration at 300°K is 1.2x1018cm-3, silicon concentration is 2~
3 x 1018 cm-3, boron concentration 1.5 to 3 x 10
It was 19 cm-3.

It can be clearly seen that silicon was doped extremely efficiently.

Example 3 In this example, GaP polycrystal 40 was simply used as the raw material charge.
0 g, about 240 g of silicon 8 as shown in Figure 3.
G with <111> direction attached to the pulling shaft 10
It was placed on an aP single crystal seed, and after reaching a steady state, silicon was quickly added to the melt 1 through B2O32.

Other conditions were the same as in Example 1.

The obtained GaP single crystal has a diameter of about 40 mm, a dislocation density of about 1.5 x 104 cm-2, a carrier concentration at 300°K of 5 x 1017 cm-3, and a silicon concentration of 6 x 1.
It was 017 cm-3.

Again, it can be seen that silicon was doped quite effectively.

In the first embodiment, it is more effective to dissolve silicon into the gallium in the raw material charge in advance.

Further, it is more effective to add gallium in which silicon is dissolved in an amount equivalent to 3 x 1017 cm-3 and boron in an amount equivalent to 5 x 1018 cm-3 or more to the raw material charge.

In addition, in Example 2, it is not necessary to dope boron into the raw material GaP polycrystal, and silicon is doped at 1×10
Doping over 17cm-3 can reduce the dislocation density by 5cm-3 or more.
It is possible to dope silicon in an amount as large as possible to reduce the amount of silicon to less than 1.times.10@4 cm@-2, that is, approximately 1.times.10@16 cm@-3 or more.

Of course, boron is added in the GaP polycrystal at 2×1018cm-
If 3 or more doping is performed, doping control of silicon will be easier.

Also, silicon may be doped into both of the gallium in the GaP polycrystal.

The diameter is 35 to 55 mm, and the dislocation density is 2 x 104 cm.
In order to obtain a low dislocation density GaP of −2 or less, it is preferable to use a GaP polycrystal doped with 3×10 17 cm −3 or more of silicon and 5×10 18 cm −3 or more of boron in Example 2.

Of course, boron is not always necessary.

Further, although the quartz crucible 3 is used in these embodiments, a crucible made of pyrolytic boron nitride (PBN) or the like may be used instead.

Furthermore, silicon and boron may be added in the form of a compound such as SiP or BP, rather than as a single substance, so that the silicon compound does not come into direct contact with the B2O3 melt during heating and temperature raising of the raw material charge.

Furthermore, the methods of Examples 1 to 3 were applied to the silicon doping method for GaAs and InP, and the silicon concentration was approximately 1.
．． 5 x 1018 cm-3 or more, especially 2 x 1018 cm-3
A doped single crystal with a cross-sectional area of 5 cm or more, with a dislocation density of 5 x 102 cm or less, sometimes 1 x 102 cm
It was possible to reduce it to -2 or less.

In addition, strong reducing impurities other than silicon include aluminum and magnesium, but although these are difficult to enter into the growing crystal, they have the effect of removing "weak points" in the crystal such as oxygen and oxides, and they also contribute to low dislocation density. The effect of the doping method of the present invention was observed.

Of course, along with these strongly reducing impurities, there are n-type impurities S, Se, Te, Sn, P-type impurities Zn, Cd, impurities Cr and Fe that create deep levels, or isoelectronic impurities N.
, Bi, etc. may be doped singly or in the form of a compound.

However, if the concentration of S, Se, Te, etc. is too high, i.e. 1~
If it is doped in an amount of 2×10 18 cm −3 or more, it may form a “weak point” by itself, just like oxygen, so it should be doped only in an appropriate amount.

Some of these "weak points" can cause extremely small dislocation loops, and even if the single crystal has a low dislocation density according to X-rays, when an epitaxial layer is grown using this as a substrate, the epitaxial This may increase the dislocation density in the layer.

As detailed above, the present invention provides a novel doping method for manufacturing a low dislocation density ■-■ group compound semiconductor single crystal by effectively doping strongly reducing impurities such as silicon using a liquid capsule method. Even under the same manufacturing conditions, a low dislocation density ■-■ group single crystal, especially a large low dislocation density GaP single crystal, which is approximately one-tenth of the dislocation density in an undoped single crystal, can be obtained, resulting in highly efficient green or orange-red light emission. This greatly contributes to the industrial manufacturing of devices.

[Brief Description of the Drawings] Figure 1 is a diagram showing the state of the crucible and melt in a steady state in the liquid capsule pulling method, Figure 2 is the arrangement of the raw material charge in one embodiment of the present invention, and Figure 3 is the diagram showing the state of the crucible and melt in a steady state. FIG. 7 is a diagram showing a method of adding silicon to a GaP melt in another example of the present invention. In the figure, 1 is GaP melt, 2 is B2O3 melt, 3 is quartz crucible, 4 is carbon crucible, 5 is GaP polycrystal, 6
is B2O3 disk, 7 is gallium, 8 is silicon, 9
is a GaP seed, and 10 is a pulling axis.

Claims (1)

[Claims] 1. In producing a ■-■ group compound semiconductor single crystal by a liquid capsule pulling method using a boron oxide melt as a capsule, at least one type of strong reducing agent having a stronger reducing ability than boron. The impurities are placed so that they do not come into direct contact with the boron oxide melt during heating of the single crystal raw material charge, and are then effectively dissolved into the single crystal raw material melt, and the impurities are then effectively dissolved into the raw material melt of the single crystal, and then Doping with a sufficient amount of sexual impurities to obtain a low dislocation density ■-■ group compound semiconductor single crystal having a low dislocation density of approximately one-tenth or less of the dislocation density in an undoped single crystal grown from the above melt under the same manufacturing conditions. 1. A method for doping a strongly reducing impurity into a ■-■ group compound semiconductor single crystal, the method comprising growing a low dislocation density ■-■ group compound semiconductor single crystal. 2 ■-■ group compound semiconductors are GaP, GaAs, InP
, InAs, and the strong reducing impurity is at least one of silicon, aluminum, and magnesium, and the strong reducing impurity is a strongly reducing impurity to the ■-■ group compound semiconductor single crystal according to claim 1. doping method. 3 ■-■ Group compound semiconductor single crystal has a diameter of 35 to 55 mm
and a low dislocation density GaP single crystal with a dislocation density of 2 x 104 cm-2 or less, and the strongly reducing impurity is silicon and the concentration in the GaP single crystal is 3 x 1017 to 5 x 1018.
3. A method for doping a GaP single crystal with a strongly reducing impurity according to claim 2, wherein the GaP single crystal is 4. The method of doping strongly reducing impurities into a GaP single crystal according to claim 3, wherein the raw material charge is a mixture of GaP polycrystal and gallium in which silicon has been dissolved in advance. 5. The method of doping strongly reducing impurities into a GaP single crystal according to claim 3, wherein the raw material charge is a mixture of GaP polycrystal and gallium and poron into which silicon has been dissolved in advance. 6 The raw material charge is a type of GaP polycrystal or a mixture of GaP polycrystal and gallium, and the concentration of silicon pre-doped in the GaP polycrystal is at least 3×1.
017 cm-3 or more. 7 The raw material charge is a type of GaP polycrystal or a mixture of GaP polycrystal and gallium, and the concentration of silicon pre-doped in the GaP polycrystal is at least 3×10
17 cm-3 or more, and the concentration of boron pre-doped in the GaP polycrystal is at least 5 x 10 cm-3.
3 or more, the method for doping a GaP single crystal with a strongly reducing impurity according to claim 3.