JPS6065799A - Process for crystal growth - Google Patents

Abstract

PURPOSE:To enable the growth of a uniform crystal having desired composition, by immersing a source compound in a molten liquid for the growth of a multi- component compound semiconductor crystal, and passing controlled DC current from the molten liquid to the source compound. CONSTITUTION:The molten liquid 2 for the growth of a multi-component compound semiconductor crystal is put into the crucible 1, the carbon anode 3 is dipped in the molten liquid 2, and the source compound 5 attached to the carbon cathode 6 is brought into contact with the surface of the molten liquid 2. A controlled DC current is passed between the carbon anode 3 and the source compound 5 from the electrode to the compound to effect the heat generation at the interface of the molten liquid 2 and the source compound 5 and at the inner part of the source compound 5 to effect the melting of the source compound 5 in the molten liquid according to the intensity of the DC current. The composition of the molten liquid can be maintained at a definite level, and accordingly, the composition of the crystal grown on the seed 8 can be kept to a uniform state.

Description

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

Prior Art and Problems Figure 1 shows the compositional relationship in an InGaAsP quaternary compound.

In the figure, I in the I n Ga A s P quaternary compound
n+) Composition (a) lattice-matched to the substrate and Ga A
The composition (b) is lattice matched to the S substrate.

In general, in the case of InGaAsP quaternary compounds, as shown in the figure, even though the entire composition range can physically exist,
Since there are only two boards, n p and QaAs,
The composition that can be used for length is the characteristic line (a) shown in the diagram.
and (b) line "-".

Therefore, if 1nGaAs, 1nAsP, InGa
If ternary bulk crystals such as P and GaAsP can be freely obtained and used as substrates,
InGaAs in all compositional regions shown
It is possible to use P quaternary compounds (i), and from the perspective of devices, the degree of freedom in designing, creating, and using them should be extremely large.
Not limited to nGaAsPd base compounds, all III-V
This is a common problem with group multi-component compounds or H-Vl 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 an AC-BC quasi-binary system phase diagram, where AC is GaAs, BC is InAs, and AC is B
Assuming that the compound has a higher melting point than C, now a certain growth temperature T. If a finite volume of melt is used, element A in the melt will gradually become insufficient and the melt will be The liquid composition changes in the direction shown by arrow (1), and the crystal composition changes accordingly, 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 add a saturated multi-component melt (or solution) with good controllability.
It is to replenish component elements having a melting point of 1:11, such as the above-mentioned compound AC.

However, such technology does not currently exist. That is, in the prior art, a finite volume of liquid or solution is used, and once crystal formation begins, the composition changes according to the phase diagram within 1! There is no other option but to
It was completely impossible to control this.

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. The above-mentioned multi-compound semiconductor crystal growth melt (
The present invention aims to provide a technique for maintaining the melt composition of (or solution) in a desired state.

Structure of the Invention The principle of the present invention is that a multi-component compound semiconductor crystal growth melt (
A current is passed from the multi-compound semiconductor crystal growth melt (or solution) to the compound as a source immersed in the multi-component semiconductor crystal growth melt (or solution). The compound is converted into the multi-component compound semiconductor crystal growth melt (
or a 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 L
7. In addition, a portion of each of multiple types of compounds containing a small number of elements constituting the multi-compound semiconductor crystal to be grown is added to the melt (or solution) for growing the multi-compound semiconductor crystal. immersion, and flowing a direct current with independently controlled current values in the direction of each compound from the multi-component compound semiconductor crystal growth melt (or solution) to melt each compound and grow the multi-component compound semiconductor crystal. It is necessary to maintain the composition of the melt/& (or solution) at a desired value, and to maintain the composition of the multi-component compound semiconductor crystal to be grown at a desired value. Compound semiconductor crystal growth melt: contacting the surface of the liquid (or solution), and flowing a direct current with a controlled current value from the multi-component compound semiconductor crystal growth melt (or solution) in the direction of the rod-shaped compound. Melting the tip of the rod-shaped compound to maintain the composition of the multi-compound semiconductor crystal growth melt (or 18 liquid) at a desired value;
Each tip of a rod-shaped compound containing a small number of elements (including one) of a multi-element compound semiconductor crystal to be grown and having a force of 1 is added to a melt for growing a multi-element compound semiconductor crystal (
or a solution), and a direct current with an independently controlled current value is passed from the multi-compound semiconductor crystal growth melt (or /8 solution) in the direction of each of the rod-shaped compounds to form each of the rod-shaped compounds. The tip of the compound is melted 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, the multi-component compound semiconductor crystal to be grown is It is characterized by being a bulk crystal or epitaxial crystal.

By this, the composition of the melt (or solution) for multi-component compound semiconductor crystal growth can be freely controlled from the outside, and the limited volume of the melt (or solution) can be virtually infinite. It is made into a volumetric melt (or solution) and used continuously as long as the source compound is not completely used to produce not only bulk crystals made of multi-compound semiconductors, but also epitaxial crystals made of multi-compound semiconductors. It can be easily grown to any desired composition.

Incidentally, there is a technology called liquid-phase electro-epitaxial growth method, which involves passing an electric current through the substrate.
This technology improves the crystal growth rate by lowering the temperature at the interface between the substrate and the growth solution and moving atoms in the growth solution through electromigration. The thickness of the crystal is monitored with high accuracy by measuring the resistance value in the substrate, but it must be noted that such technology is unrelated to the present invention. .

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

In the figure, l is a crucible, 2 is a melt for multi-compound semiconductor crystal growth, 3 is a positive carbon Li electrode, 4 is a positive stainless steel electrode, 5 is a source compound, 6 is a negative carbon electrode, 7 8 indicates the negative stainless steel electrode, 8 indicates the seed, and 9 indicates the 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 side carbon salt 4!43 and the source compound 5 so that the source compound 5 is always on the negative side.

It is assumed that the melt 2 is a saturated melt of a crystal that is about to grow via the seed 8.

Now, when a direct current is passed between the positive carbon electrode 3 and the source compound 5, heat is generated at the interface between the melt 2 and the source compound 5 and inside the compound, and the source compound 5 is turned into the melt according to the amount of direct current. 2, and 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. Incidentally, 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 fffi types may be used and they may be brought into contact with the melt 2 at the same time. In this case, an independently adjusted direct current is passed through each source compound 5, and the amount of melting thereof is controlled separately.
Compound semiconductor crystals with more elements can be grown.

The present inventor has developed the crystal growth method described above using a source current control method (SCC method: 5 source current control method).
On L r o I e d m e th
It is called od).

FIG. 4 is a diagram illustrating the main parts of an example of an apparatus for performing liquid phase epitaxial growth using the SCC method.

In the figure, 11 is a carbon boat, 12 is a positive side stainless steel electrode, 13 is a carbon slider, 14 is a boron nitride (BN) plate, 15 is a carbore source/electrode holder, and 16 is a negative side stainless steel electrode, 17 a source compound, 18 a substrate held in a carbon boat 11, 1
Reference numeral 9 indicates a multi-component compound semiconductor crystal growth solution held by the carbon slider 13, respectively.

The characteristic configuration of the illustrated device is the carbon boat 1
1, the positive stainless steel electrode 12 is removed, and the carbon source/electrode holder 15 is insulated from the carbon slider 13 with a BN plate 14 interposed.
is attached, and its carbon source/electrode holder 1
A source compound 17 is attached to the tip of 5, and a negative stainless steel electrode 16 is attached to the rear end.

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 is removed from the growth solution 19. When a direct current is passed in the direction 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 DC current,
The amount of dissolved source compound 17 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, by using a plurality of types of source compounds 17 and independently controlling the direct current flowing through them, 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 /8 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);
1A is a raised part due to surface tension in the growth melt (or solution) 21, 22 is a source compound, 22A
indicates the part of the source compound 22 that is most easily melted (or melted), arrow l indicates the direct current, and arrow S indicates the feeding direction of the source compound.

As can be seen from the figure, when the source compound 22 is immersed in the growth melt (or solution) 21, the growth melt (or solution) 2
1, a raised portion 21A is generated due to surface tension. Since the heat generated in these raised parts 2 J and A has a low rate of propagating through the growth melt (or solution) 21 and emitting +1&, the source compound 22 in those parts is absorbed by the growth melt (or solution). ) 21 The temperature will be higher than the part that is deeper inside. Therefore, the growth melt (or solution)
The portion 22A of the source compound 22 that is in contact with the raised portion 21A of the source compound 21 melts (or melts) the fastest.

If this situation continues, eventually source compound 2
The end of number 2 is torn off.

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

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

The 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.
The experiment was carried out for the case of growing an s-crystal layer.

In this case, the source compounds are [nAs and Ga
InGaAs/'a solution saturated at 790 [°C] was used as the growth solution.

The composition of InGaAs1'gtlk and its weight value are as follows.

X Qi - 0,040 X Qi - 0,170 X,, = 0.790. Here, X; (i: here Ga, As, or In) represents the atomic fraction of component i in the ternary seed liquid.

InP substrate with surface index (11'l) A was epitaxially grown from a solution having the above composition.
As shown in Figure 6, the xAs crystal layer has a plane index (111
) It is approximately lattice matched to the InP substrate of A.

The actual weight value of the components in this case is ln=20.
2327 (g) InAs=6.5857 (g) GaAs=1.5447 (g).

The actual growth process goes through the following process.

Initially, the solution and the InP substrate were not brought into 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 heated in a furnace at a constant speed of 1 ('C)/1 [minute]. When the temperature of the furnace reaches 790 ("C), 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. At this time, almost no current flows through the InP substrate.

Figure 7 shows the results when the crystal is grown as described above.
Current flowing through the source (A/cm2), 1! : l
FIG. 3 is a diagram showing the relationship with the thickness [μm] of an nGa AS crystal layer.

The temperature drop range during this growth is from 790 ('c) to 76
0 ('C), that is, 30 jiC].

From FIG. 7, when no current is passed through the source compound, an InGaAS crystal layer is epitaxially grown to a thickness of 32 μm using only the ramp cooling method.

Furthermore, 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 1iaAs= 1,7 (A/cm2) (however, f
If we consider that the current is concentrated only in the divided portion, 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=53Cμm] is In
Is the effect due to 1nAs dissolved in a saturated 1nGaAs solution from the As source compound and due to electromigration? This is due to the growth due to two factors: the evaporation effect of gt atoms.

When a similar experiment is carried out using a GaAs source compound and a similar growth is performed while applying a current, the average value obtained by dividing the current value by the total area is 'GaAs=1'6 (A/Cm2) (and, If we consider that the current was concentrated only in the part where the InAs source compound was fused, the current density would be about 10 times that of this value), and it grew to a thickness of 82 [μrn] in 15 (minutes). It will be appreciated that the GaAs source compound has a higher melting point and will not dissolve unless a larger current is applied.

In the case of a GaAs source compound, there is an incoming current flowing, so this current? The thickness increase due to li is 4J, electro
It is thought that the amount due to migration is ten times greater than the amount due to /8: of the GaAs source compound.

Figure 8 is a diagram showing the relationship between the thickness of the In1-xGa, As crystal layer, um:l, and the composition X of the Ga component in the crystal layer when the crystal is grown in the same manner as above. It is.

This figure shows the composition change in the thickness direction of an epitaxially grown crystal layer using XMA (X-ray) on its W1 plane.
+n1cro analysis).

First, when the current 1s flowing through the source compound is 0, the composition in the crystal layer is X='0. '45 to X = 0.35, and the G in the crystal layer
The composition of the l component is ternary I as explained in connection with FIG.
It can be seen that the amount decreases due to the depletion of the Ga component in the nGaAs 1g solution.

Also, the current flowing through the source compound is 1v, , A, -1, 7(
A/cm2), InGaAs/8 liquid contains In
Since excess As is dissolved, the crystal composition is X-0.28, with an extremely reduced Ga component.

Furthermore, the current IG flowing through the source compound, LAg= l
6 (A/Cl112), GaAs dissolves a little in the InGaAs solution, so the Ga component is X=O.

I understand that.

It becomes possible to grow crystals even at low temperatures.

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 an electric current is passed through it to make the growth solution supersaturated, 1. A crystal layer is epitaxially grown on the plate. Therefore, since the crystal JM is epitaxially grown in accordance with the time during which the current is applied, it is possible to control the layer jV of the crystal layer.

In addition, the growth solution (1) which is in a saturated state at a low temperature (in case of Since it can be grown, it is useful 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 multi-component Ifz compound semiconductor crystal growth-M solution (or a solution). ), and a controlled DC current (1 step) is passed from the multi-component compound semiconductor crystal growth melt (or υ91 solution) in the direction of the compound described in 0ii to transform the multi-component compound semiconductor crystal growth melt. The W principle is to maintain the composition of the solution (or solution) at a desired value.The effects obtained by this are listed below.

Depending on the current applied to the source compound, the source compound can be melted (or melted) even in a saturated melt (or solution).
can be done.

(2) The composition of the melt (or solution) can be freely changed depending on the current flowing through the source compound, and therefore the composition of the crystal layer can also be controlled, making it possible to reproducibly create 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 so thick that it can be said to be infinite.
This method 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 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 low temperatures, such as InP. Or 500 Garb
('C) Can be grown at or below.

(5) A superlattice structure of a Peter junction is realized by using multiple types of solutions, applying electricity to the source compound in one of them to bring it into a supersaturated state, and using them alternately. I can do it.

(0) 1nGaAs or GjI, which was considered difficult in the past
Direct growth of I n P onto nGaAsP crystals can be realized.

(7) Multiple l n P with different carrier concentrations? 3
Conventionally, by passing an electric current through the source compound in the liquid,! +46
: 1nPI with different carrier concentration seen in IC:
It is possible to easily form two or more layers of 4t.

f8) A 12 G a S b , G a S
It is also possible to realize a heterojunction of b or a heterojunction of ΔβGaAs or GaAs.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the compositional relationship in the InGaAsPd base compound, and Fig. 2 is a diagram showing the relationship between the compositions of the InG a As P d base compound.
Figure 3 is a main part 1 diagram showing an example of a shim arrangement for carrying out the present invention, Figure 4 is an example of an apparatus for performing liquid phase epitaxy medium growth using the SCC method. Figure 5 is an explanatory diagram of the main parts showing the state of melting (or melting) of the source compound. Fig. 6 is a diagram for explaining the lattice matching state of a crystal layer grown evixically by applying the present invention, and Fig. 7 is a diagram for explaining the relationship between the current flowing through the source compound and the thickness of the crystal layer. 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, 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 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, 19 is a multi-compound semiconductor crystal solution held on a carbon slider 13, and 21 is a Growth melt (or solution), 21Δ is the raised part, 22 is the source compound, 22Δ is the part that is most easily melted (or dissolved), i is DC? h flow, S is the feeding direction of the source compound. Patent applicant: Fujitsu Ltd./Company Attorney Ben I! I! TL - Shoji Aitani Patent attorney Hiroshi Watanabe -- Figure 1 Figure 2

Claims (1)

[Scope of Claims] Fi A direct current with a controlled current value is passed in the direction of the compound from the melt (or solution) for growing multi-compound semiconductor crystals to melt the compound, and the composition of the melt (or solution) for growing multi-component compound semiconductor crystals is determined. A crystal growth method characterized in that it includes a step of maintaining at a desired value. (2) 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 in the melt (or solution) for growing the multi-compound semiconductor crystal, and A DC current whose current value is independently controlled is passed from the multi-component compound semiconductor crystal growth melt (or solution) in the direction of each of the compounds to melt each of the compounds, thereby forming the multi-component compound semiconductor crystal growth melt ( 4. A crystal growth method characterized by comprising step 4-1 of maintaining the composition of (or solution) at a desired value.・(3
) The tip of the rod-shaped material containing at least one of the elements constituting the multi-compound semiconductor crystal to be grown is brought into contact with the surface of the melt (or solution) for growing the multi-component semiconductor crystal, and A v1 current with a controlled current value is passed in the direction of the rod-shaped compound from the melt (or solution) for growing the compound semiconductor crystal to melt the tip of the rod-shaped compound and form the multi-compound semiconductor crystal growth surface P & (or A crystal growth method characterized by including the step of adjusting the composition of the IB solution to a desired value. (4) At least one of the elements constituting the multi-compound semiconductor crystal to be grown Each tip of a rod-shaped compound of multiple types 1J1 containing 1J1 is brought into contact with the surface of the multi-compound semiconductor crystal growth melt (or solution), and the A DC current whose current value is independently controlled is passed in the direction of each rod-like compound to melt the tip of each rod-like compound and adjust the composition of the multi-component compound semiconductor crystal growth melt (or solution) to a desired value. (5) The multi-compound semiconductor crystal to be grown is a bulk crystal. The crystal growth method according to claim 1 or 3 or 4. (6) The method according to claim 1 or 2 or 4, wherein the multi-compound semiconductor crystal to be grown is an epitaxial crystal. The crystal growth method according to item 3 or 4.