JPH0357076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention provides a crystal growth method in which the composition of a melt, and thus the composition of a grown crystal, can be controlled externally when growing a multi-component compound semiconductor crystal. Regarding.

Prior Art and Problems FIG. 1 is a diagram showing the compositional relationship in an InGaAsP quaternary compound.

In the figure, the InGaAsP quaternary compound has a composition (a) that lattice-matches to the InP substrate and a composition that lattice-matches to the GaAs substrate.
(b) is shown.

In general, InGaAsP quaternary compounds have only two substrates, InP and GaAs, even though the entire composition range can physically exist, as shown in the figure, so the compositions that can actually be used are are only those existing on the characteristic lines a and b shown in the figure.

Therefore, if InGaAs, InAsP, InGaP,
Ternary bulk crystals such as GaAsP can be freely obtained,
If this can be used as a substrate, it becomes possible to use the InGaAsP quaternary compound in all the composition ranges shown in the figure, and from the perspective of devices, there is freedom in designing, creating, and using it. The degree should be extremely large. These problems are not limited to InGaAsP quaternary compounds, but are common to all - group multi-component compounds or - group multi-component compounds.

As mentioned above, although there has been a demand for multi-component compound semiconductor crystals, that is, bulk crystals or epitaxial crystals, the main reason why this has not been realized is as follows. explained.

Figure 2 is a phase diagram of the AC-BC quasi-binary system, and AC
is for example GaAs, BC is for example InAs, AC
Assuming that BC is a compound with a higher melting point than BC, if a certain growth temperature T _G is applied, its melt composition X ^l
Since the crystal composition X ^s that grows from the melt is different, if a finite volume of the melt is used, element A in the melt will gradually become insufficient and the melt composition will move in the direction of arrow 1. Along with this, the crystal composition also changes as shown by arrow 2. Therefore, if a finite volume of melt is used, a crystal with a uniform composition cannot be grown, and the result is always a bulk crystal or epitaxial crystal with a change in composition.

Therefore, in order to obtain a multi-component compound semiconductor crystal, it is important to prepare a saturated multi-component melt (or solution).
The objective is to replenish component elements with a high melting point, such as the above-mentioned compound AC, with good controllability.

However, such technology does not currently exist. That is, in the conventional technology, once crystal growth starts using a finite volume of melt or liquid, the only means to take is to allow the composition to change according to the phase diagram, and this cannot be controlled. It was completely impossible.

Purpose of the Invention The present invention provides a method for supplying a compound containing one or more of the constituent components of a multi-component compound semiconductor crystal to a melt (or solution) for growing a multi-component compound semiconductor crystal as described above with good controllability. Therefore, it is an object of the present invention to provide a technique for always maintaining the melt composition of the multi-compound semiconductor crystal growth melt (or solution) in a desired state.

Structure of the Invention The principle of the present invention is that a compound serving as a source is immersed in a melt (or solution) for growing a multi-compound semiconductor crystal. A current is passed toward the multi-component compound semiconductor crystal growth melt (or solution) and the compound is heated by the Peltier effect generated at the interface with the compound and Joule heat is generated in the compound to transform the compound into the multi-component compound semiconductor. It consists in melting it into a crystal growth melt (or solution).

In the crystal growth method of the present invention, a part of the compound containing at least one of the elements constituting the multi-component compound semiconductor crystal to be grown is immersed in a melt (or solution) for growing the multi-component compound semiconductor crystal; The basic method is to flow a direct current with a controlled current value in the direction of the multi-component compound semiconductor crystal to melt the compound and maintain the composition of the melt (or solution) for growing the multi-component compound semiconductor crystal at a desired value. and immersing a portion of each of multiple types of compounds containing at least one of the elements constituting the multi-compound semiconductor crystal to be grown in a melt (or solution) for growing the multi-compound semiconductor crystal,
A DC current whose current value is independently controlled is passed from the multi-compound semiconductor crystal growth melt (or solution) in the direction of each of the compounds to melt the compound, thereby forming the multi-component compound semiconductor crystal growth melt ( or solution) at a desired value;
Further, the tip of a rod-shaped compound containing at least one of the elements constituting the multi-component compound semiconductor crystal to be grown is brought into contact with the surface of the melt (or solution) for growing the multi-component compound semiconductor crystal, and the multi-compound semiconductor crystal is grown. A direct current with a controlled current value is passed in the direction of the rod-shaped compound from the semiconductor crystal growth melt (or solution) to melt the tip of the rod-shaped compound and the multi-component semiconductor crystal growth melt (or solution)
In addition, each tip of a plurality of rod-shaped compounds containing at least one of the elements constituting the multi-compound semiconductor crystal to be grown is contacting the surface of the liquid (or solution), and flowing a direct current whose current value is independently controlled from the multi-compound semiconductor crystal growth melt (or solution) in the direction of each of the rod-shaped compounds to form each of the rod-shaped compounds. Melting the tip of the compound to maintain the composition of the multi-compound semiconductor crystal growth melt (or solution) at a desired value, and in each of the above cases,
A characteristic feature of the method is that the multi-component compound semiconductor crystal to be grown is a bulk crystal or an epitaxial crystal.

With this, the composition of the melt (or solution) for multi-component compound semiconductor crystal growth can be freely controlled from the outside, and the finite volume melt (or solution) can be transformed into a virtually infinite volume melt. (or solution), and is used continuously until the source compound is completely used up to form an arbitrary compound, not only in bulk crystals made of multi-component compound semiconductors, but also in epitaxial crystals made of multi-component compound semiconductors. It can be easily grown with controlled composition.

Incidentally, there is a conventional technique called liquid-phase electro-epitaxial growth method, which involves passing an electric current through the substrate to lower the temperature at the interface between the substrate and the growth solution, and to prevent electro-migration. The method improves the crystal growth rate by moving atoms in the growth solution, and
Although this technique has been used to accurately monitor the thickness of the crystal by measuring the resistance value in the substrate, it should be noted that this technique is unrelated to the present invention. Must.

Embodiment of the Invention FIG. 3 is an explanatory diagram of essential parts showing an example of an apparatus for carrying out the present invention.

In the figure, 1 is a crucible, 2 is a melt for multi-component compound semiconductor crystal growth, 3 is a positive carbon electrode, and 4
is a positive stainless steel electrode, 5 is a source compound, 6 is a negative carbon electrode, 7 is a negative stainless steel electrode, 8
9 indicates a seed, and 9 indicates a seed holder, respectively.

As can be seen from the figure, the tip of the positive carbon electrode 3 attached to the positive stainless steel electrode 4 is immersed in the melt 2.

The source compound 5 is attached to the negative stainless steel electrode 7 via the negative carbon electrode 6, and its tip is brought into contact with the surface of the melt 2.

A direct current is passed between the positive carbon electrode 3 and the source compound 5 so that the source compound 5 is always on the negative side.

The melt 2 is a saturated melt of crystals that are about to grow via the seeds 8.

Now, when a direct current is passed between the positive carbon electrode 3 and the source compound 5, the melt 2 and the source compound 5
Heat is generated at the interface with and inside the compound, and the source compound 5 melts into the melt 2 according to the amount of DC current,
The composition of the melt 2 changes.

Therefore, by appropriately adjusting the amount of current according to the crystal growth process, the composition of the melt 2 can be freely controlled, and as a result, the composition of the crystal growing on the seed 8 can be maintained uniformly. Is possible. still,
By rotating the seed 8, the melt 2 is sufficiently stirred, so that the composition of the melt 2 tends to be uniform.

In the illustrated example, only one type of source compound 5 is used, but a plurality of types may be used and they may be brought into contact with the melt 2 at the same time. In this case, a DC current that is adjusted independently is caused to flow through each source compound 5, and the amount of melting thereof is controlled separately, thereby making it possible to grow compound semiconductor crystals with a greater number of elements.

The present invention combines the crystal growth method described above with a source current controlled method (SCC method).
method).

FIG. 4 is an explanatory diagram of essential parts for explaining an example of an apparatus for performing liquid phase epitaxial growth by applying the SCC method.

In the figure, 11 is a carbon boat, 12 is a positive stainless steel electrode, 13 is a carbon slider, 14 is a boron nitride (BN) plate, 15 is a carbon source and electrode holder, and 16 is a negative stainless steel electrode. electrode, 17 is a source compound, 18 is a carbon
The substrate held on the boat 11, 19 is a carbon
The multi-component compound semiconductor crystal growth solution held on the slider 13 is shown.

The characteristic configuration of the illustrated device is that carbon
The positive stainless steel electrode 12 is attached to the boat 11, and the carbon slider 13 is
A carbon source/electrode holder 15 is attached in an insulated state with a BN plate 14 interposed therebetween, a source compound 17 is attached to the tip of the carbon source/electrode holder 15, and a negative side is attached to the rear end of the carbon source/electrode holder 15. The stainless steel electrode 16 is attached.

To perform epitaxial growth using this apparatus, a growth solution 19 saturated at the growth temperature is brought onto the substrate 18, the source compound 17 is immersed in the growth solution 19, and the source compound 17 is removed from the growth solution 19. When a direct current is passed in the direction of the source compound 17, heat is generated at the interface between the source compound 17 and the growth solution 19 and in the compound, and the source compound 17 is dissolved.
Therefore, by controlling the amount of the direct current, the amount of the source compound 17 dissolved can be freely controlled. This makes it possible to arbitrarily change the solution composition of the growth solution 19, so that a desired crystal composition for epitaxial growth can be obtained.

In this case as well, if a plurality of types of source compounds 17 are used and the direct current applied to them is independently controlled, the degree of freedom in selecting the solution composition is improved, and the controllability of the crystal composition is also improved.

By the way, when a source compound is immersed in a growth melt (or solution) and a direct current is applied, a phenomenon as shown in FIG. 5 occurs.

In FIG. 5, 21 is a growth melt (or solution), 21A is a raised part due to surface tension in the growth melt (or solution) 21, 22 is a source compound, and 22A is a The part of the source compound 22 that is most easily melted (or dissolved), the arrow i indicates the direct current, and the arrow S indicates the direction in which the source compound is fed.

As you can see from the figure, the growth melt (or solution)
When the source compound 22 is immersed in the growth melt (or solution) 21, a raised portion 21A is generated in the growth melt (or solution) 21 due to surface tension. Since the heat generated in this raised portion 21A propagates through the growth melt (or solution) 21 and has a low rate of dissipation, the source compound 22 in that portion is deep in the growth melt (or solution) 21. It becomes hotter than the part inside it. Therefore, the portion 22A of the source compound 22 that is in contact with the raised portion 21A of the growth melt (or solution) 21 melts (or dissolves) the fastest.

If this state continues, the tip of the source compound 22 will eventually break off.

Therefore, if the source compound 22 is shaped into a rod and only its tip is brought into contact with the growth melt (or solution) 21, only the tip will melt (or dissolve). When the direct current stops flowing due to its melting (or dissolution), the rod-shaped source compound 2
2 in the direction of arrow S to bring the tip into contact with the growth melt (or solution) 21. By performing such operations continuously, the source compound 22 is not cut off during crystal growth.
All can be effectively melted (dissolved) and used.

As can be understood from the above,
Whether or not bulk crystals or epitaxial crystals of multi-component compound semiconductors can be grown by the SCC method depends on whether the crystal composition can be controlled by the SCC method.

The present inventor has conducted sufficient experiments regarding this point, which will be explained next.

The experiment was carried out using the apparatus described in connection with Fig. 4.
In _1-x Ga _x As on InP substrate with plane index (111)A
This study was carried out for the case of growing a crystal layer.

In this case, the source compounds include InAs and
GaAs was used, and an InGaAs solution saturated at 790 [°C] was used as the growth solution.

The composition of the InGaAs solution and its weighed value are as follows.

X ^l _Ga = 0.040 X ^l _As = 0.170 X ^l _Io = 0.790. Here, X ^l _i (i: here Ga, As, or In) represents the atomic fraction of component i in the ternary solution.

An In _1-x Ga _x As crystal layer epitaxially grown on an InP substrate with a planar index of (111) A from a solution with the above composition has a planar index of (111) A as shown in FIG.
Almost lattice matched to InP substrate.

In this case, the actual weight value of the component is In=20.2327 [g] InAs=6.5857 [g] GaAs=1.5447 [g] And so.

The actual growth process goes through the following process.

Initially, the solution and the InP substrate were not in contact with each other. Then, with the source compound taken out of the solution, the temperature was maintained at 790 [°C] or higher for 30 [minutes] or more to homogenize the solution, and then the solution was heated at 1 [°C]/1 [minute].
Start cooling the furnace at a constant rate of . The temperature of the furnace
When the temperature reaches 790 [℃], slide the slider to bring the solution onto the InP substrate and start growth. Thereafter, the carbon source/electrode holder is moved to vertically immerse the plate-shaped source compound in the solution, so that a direct current is passed from the solution side to the compound side. Note that at this time, almost no current flows through the InP substrate.

Figure 7 shows the current [A/cm ² ] flowing through the source when the crystal is grown as described above.
FIG. 3 is a diagram showing the relationship with the thickness [μm] of an InGaAs crystal layer.

The temperature drop range during this growth is from 790 [℃]
The temperature was 760 [℃], that is, 30 [℃].

From Figure 7, when no current is passed through the source compound, the lamp cooling method is used.
In this case, an InGaAs crystal layer is epitaxially grown to a thickness of 32 [μm].

In addition, when similar growth is performed using an InAs source compound while flowing a current, the average value obtained by dividing the current value by the total area is i _IoAs = 1.7 [A/cm ² ] (However, if the dissolved part is If we consider that the current is concentrated, the current density will be about 10 times this value), and a crystal layer with a thickness of 85 [μm] can be obtained in 30 [minutes]. This difference of 85-32=53 [μm] is InAs
Dissolved in saturated InGaAs solution from source compound
This is due to the growth due to both the effect of InAs and the solute atom removal effect due to electromigration.

When a similar experiment is carried out using a GaAs source compound and a similar growth is performed while flowing a current, the average value obtained by dividing the current value by the total area is i _GaAs = 16 [A/cm ² ] (however, the dissolved part If we consider that the current was concentrated only in the layer, the current density would be about 10 times this value), and it grew to a thickness of 82 [μm] in 15 [minutes]. Compared to using an InAs source compound, the GaAs source compound has a higher melting point, so
It will be understood that melting will not occur unless a larger current is applied.

In the case of the GaAs source compound, a large current flows through it, so it is thought that the increase in thickness due to this current flow is due to electromigration and exceeds the amount due to dissolution of the GaAs source compound.

Figure 8 is a diagram showing the relationship between the thickness [μm] of the In _1-x Ga _x As crystal layer and the composition X of the Ga component in the crystal layer when the crystal is grown in the same manner as above. be.

This figure shows the composition change in the thickness direction of an epitaxially grown crystal layer using XMA in its cross section.
(X-ray micro analysis).

First, when the current i _S flowing through the source compound is 0, the composition in the crystal layer gradually changes from X = 0.45 to X = 0.35, and the composition of the Ga component in the In _1-x Ga _x As crystal layer changes. ,
It can be seen that the Ga content decreases due to depletion of the Ga component in the ternary InGaAs solution as explained in connection with FIG.

Also, the current flowing through the source compound i _IoAs = 1.7 [A/
cm ² ], excess InAs is dissolved in the InGaAs solution, so the crystal composition is X=0.28, and the Ga component is extremely reduced.

Furthermore, the current flowing through the source compound i _GaAs = 16
[A/cm ² ], GaAs dissolves a little in the InGaAs solution, so the Ga component increases _to It appears that it is slowing down.

The reason why there is less change when a current is applied to a GaAs source compound than when an electric current is applied to an InAs source compound is because the GaAs source compound has a high melting point and is difficult to dissolve.

By the way, according to the present invention, it is possible not only to control the crystal composition as seen in the above embodiments, but also to control the layer thickness of the crystal layer and to grow crystals even at low temperatures where the amount of dissolved components is small. It becomes possible.

For example, when performing liquid phase epitaxial crystal growth, if a source compound is immersed in a growth solution that is saturated at a predetermined temperature and a current is applied to it to supersaturate the growth solution, a crystal layer can be grown epitaxially on the substrate. will be grown. Therefore, since the crystal layer is epitaxially grown in accordance with the time during which the current is applied, it is possible to control the thickness of the crystal layer.

In addition, if the growth solution is saturated at a low temperature, by passing a current through the source compound, the growth solution, which is saturated at a low temperature, can be brought into a supersaturated state and crystals can be grown. It is effective for obtaining crystal layers that require growth at low temperatures.

Effects of the Invention In the crystal growth method of the present invention, a part of the compound containing at least one of the elements constituting the multi-compound semiconductor crystal to be grown is added to a melt (or solution) for growing the multi-compound semiconductor crystal. Immersion, for multi-component compound semiconductor crystal growth (or solution)
Basically, the composition of the multi-component compound semiconductor crystal growth melt (or solution) is maintained at a desired value by flowing a direct current with a controlled current value in the direction of the compound. The effects obtained by this are listed as follows.

(1) The source compound can be melted (or dissolved) even in a saturated melt (or solution) by applying an electric current to the source compound.

(2) The composition of the melt (or solution) can be freely changed depending on the current applied to the source compound, and therefore the composition of the crystal layer can also be controlled, making it possible to reproduce a crystal layer with a uniform composition. It can be grown well.

(3) The thickness of the crystal layer can be controlled by the current flowing through the source compound, and by increasing the amount of the source compound sufficiently, the thickness of the crystal layer can be controlled compared to the case using conventional technology. It can be grown to an almost infinitely thick layer, and is effective for obtaining bulk crystal layers of multi-compound semiconductors.

(4) Since the source compound can be immersed in a solution that is saturated at a low temperature and brought to a supersaturated state by passing an electric current through it, it is suitable for forming crystals that are preferably grown at a low temperature.
InP or GaSb can be grown at temperatures below 500 [°C].

(5) A superlattice structure of a heterojunction can be realized by using multiple types of solutions, energizing the source compounds in these solutions to bring them into a supersaturated state, and using them alternately.

(6) InGaAs or
Direct growth of InP on InGaAsP crystals can be realized.

(7) By applying current to source compounds in multiple InP solutions with different carrier concentrations, it is possible to create two InP layers with different carrier concentrations, which was considered difficult in the past.
It is possible to easily form more than one layer.

(8) AlGaSb, GaSb heterojunction or
Heterojunctions of AlGaAs and GaAs can also be realized.

(9) Since no current is applied to the parts where the crystal is grown, i.e. the substrate and the seed crystal, there is no temperature rise on the surface of the parts, and therefore there is no risk of melting. , thick film crystals can be easily grown.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the compositional relationship in the InGaAsP quaternary compound, Fig. 2 is a phase diagram of the AC-BC quasi-binary system, and Fig. 3 is an explanatory diagram of the main parts showing an example of a device implementing the present invention. , Fig. 4 is an explanatory diagram of the main part to explain an example of an apparatus for performing liquid phase epitaxial growth applying the SCC method, and Fig. 5 is an explanatory diagram of the main part showing the state of melting (or dissolution) of the source compound. Figure, 6th
The figure is a diagram for explaining the state of lattice matching of a crystal layer epitaxially grown by applying the present invention.
The figure is a diagram for explaining the relationship between the current flowing through the source compound and the thickness of the crystal layer, and FIG. 8 is a diagram for explaining the relationship between the thickness of the crystal layer and the composition X of the components. In the figure, 1 is a crucible, 2 is a melt for multi-component compound semiconductor crystal growth, 3 is a positive carbon electrode, and 4
is a positive stainless steel electrode, 5 is a source compound, 6 is a negative carbon electrode, 7 is a negative stainless steel electrode, 8
is a seed, 9 is a seed holder, 11 is a carbon
Boat, 12 is a positive stainless steel electrode, 13 is a carbon slider, 14 is a boron nitride plate, 15
16 is a carbon source and electrode holder, 16 is a negative stainless steel electrode, 17 is a plate-shaped source compound, 18 is a substrate held on a carbon boat 11, and 19 is a multi-compound semiconductor crystal held on a carbon slider 13. Growth melt, 21 is the growth melt (or solution), 21A is the raised part, 22 is the source compound, 22A is the most melted (or dissolved)
i is the direct current, and S is the feeding direction of the source compound.

Claims (1)

[Claims] 1. A part of a compound containing at least one of the elements constituting a multi-compound semiconductor crystal to be grown on a substrate is immersed in a melt (or solution) for growing a multi-compound semiconductor crystal. , melting the compound by flowing a direct current with a controlled current value in the direction of the multi-compound semiconductor crystal growth melt (or solution) and the compound from a region other than the substrate without passing through the substrate; A crystal growth method comprising the step of maintaining the composition of the multi-compound semiconductor crystal growth melt (or solution) at a desired value. 2. The crystal growth method according to claim 1, wherein the substrate is a seed and the multi-compound semiconductor crystal to be grown is a bulk crystal. 3. The crystal growth method according to claim 1, wherein the base body is a substrate and the multi-compound semiconductor crystal to be grown is an epitaxial crystal. 4. Immerse a portion of each of multiple types of compounds containing at least one of the elements constituting the multi-compound semiconductor crystal to be grown on the substrate in a melt (or solution) for growing the multi-compound semiconductor crystal, A DC current whose current value is independently controlled is passed in the direction of the multi-compound semiconductor crystal growth melt (or solution) and each of the compounds from a region other than the base without passing through the base. 1. A crystal growth method comprising the step of melting a compound and maintaining the composition of the multi-compound semiconductor crystal growth melt (or solution) at a desired value. 5. The crystal growth method according to claim 4, wherein the substrate is a seed and the multi-compound semiconductor crystal to be grown is a bulk crystal. 6. The crystal growth method according to claim 4, wherein the base body is a substrate and the multi-compound semiconductor crystal to be grown is an epitaxial crystal. 7. Bringing the tip of a rod-shaped compound containing at least one of the elements constituting the multi-compound semiconductor crystal to be grown on the substrate into contact with the surface of the melt (or solution) for growing the multi-compound semiconductor crystal, and The melt (or solution) for multi-compound semiconductor crystal growth can be obtained from other areas without passing through the substrate.
and flowing a direct current with a controlled current value in the direction of the rod-shaped compound to melt the tip of the rod-shaped compound and maintain the composition of the multi-component compound semiconductor crystal growth melt (or solution) at a desired value. A crystal growth method characterized by comprising a step of: 8. The crystal growth method according to claim 7, wherein the substrate is a seed and the multi-compound semiconductor crystal to be grown is a bulk crystal. 9. The crystal growth method according to claim 7, wherein the base body is a substrate and the multi-compound semiconductor crystal to be grown is an epitaxial crystal. 10 Contact the tips of multiple types of rod-shaped compounds containing at least one of the elements constituting the multi-component compound semiconductor crystal to be grown on the substrate with the surface of the melt (or solution) for growing the multi-component compound semiconductor crystal. and flowing a direct current whose current value is independently controlled in the direction of the multi-compound semiconductor crystal growth melt (or solution) and each of the rod-shaped compounds from a region other than the base body without passing through the base body. A crystal growth method comprising the step of melting the tip of each of the rod-shaped compounds to maintain the composition of the multi-component compound semiconductor crystal growth melt (or solution) at a desired value. 11. The crystal growth method according to claim 10, wherein the substrate is a seed and the multi-compound semiconductor crystal to be grown is a bulk crystal. 12. Claim 1, wherein the base body is a substrate, and the multi-component compound semiconductor crystal to be grown is an epitaxial crystal.
The crystal growth method described in item 0.