DE2148433A1 - Process for growing single crystals of gallium phosphide - Google Patents

Description

DR. INO. SL HOFFMANK - BIPt. ING. W. BTTLB * DR. HER. NAT. K. HOFFMANN PATBIfTAIfWJLl ₁ TJB D-HWMDNCHENn - AIiABEIlASTIlASSE 4 · TELEPHONE (Mil)? LWi7

Semiconductor Research Foundation, City of Sendai, Japan

Method for growing single crystals of gallium phosphide

The invention relates to a method for growing single crystals of gallium phosphide from the melt.

So far, for growing single crystals of gallium phosphide (GaP) from the melt, a melt has generally been produced which comprised gallium (Ga) as a so-called solvent and in which the desired amount of polycrystalline! Gallium phosphide was melted into it to saturation solubility at the temperature at which growth began. Then the melt, which contained a seed crystal or seed crystals of gallium phosphide, was in the region of 110O ⁰ C to tree temperature with a cooling

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speed of about 1OO ° G per hour cooled to the To grow seed crystals or the seed crystal around a single crystal or single crystals. With this approach but the pulled or grown or grown single crystals came only from the polycrystalline gallium phosphide which was originally melted into the melt, while the gallium only served as a solvent and did not show any part of the resulting crystals *

It is therefore an object of the invention to provide an improved method for growing single crystals of gallium phosphide from a low-cost melt, in which the kenge of the raw materials that do not contribute directly to the formation of the single crystals, is reduced to a minimum value.

According to the invention this is achieved by a method for growing single crystals from a solid solution of the general Formula In Ga, P, where χ is 0 to 0.01, from one Melt dissolved in a manner known per se, which is characterized in that the melt uses indium as a solvent, k Contains phosphorus in a preselected amount and gallium in an amount sufficient to fully absorb to convert the phosphorus to form gallium phosphide.

The invention is explained in more detail with reference to the accompanying drawings explained. Show it:

1 is a diagram showing the principles of this invention;

Fig. 2 is a cross section of a culture vessel charged with the raw materials according to the prior art was, and

Fig. 3 is a similar figure to Figure 2, the inventive Procedure illustrated.

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2U8433

In the figure 1 gives for a solid solution of indium gallium phosphide ί ¹¹¹ · «- ⁰ ^ ..-» ^) »where χ varies from 0 to 1, the ordinate the amount of gallium (Ga) in atomic ratio against the Nenere des Gallium to indium (In) plus gallium in the abscissa (solid line) and against the amount of gallium relative to phosphorus (P) in the abscissa (dashed line), the atomic ratio of phosphorus to indium being kept at a value of 0.13.

It can be seen from FIG. 1 that in the melt of the indium-gallium-phosphorus system, the phosphorus reacts more easily with the gallium than with the indium. If, for example, a single crystal is drawn from a system from a melt, the greater part of which is formed by indium, that is to say, for example, which contains gallium in an atomic ratio of about 0.1 relative to indium, then the resulting drawn crystal comprises a composition which essentially can be printed out by (In _{n oGra n O} P) and which comes close to (GaP). It will also be seen that if the amount of gallium relative to indium plus gallium is 0.3 atomic ratio, then the resulting crystal will comprise 2% or less indium relative to gallium. FIG. 1 also shows that in the presence of gallium at an atomic ratio of 30 to kQ% siGh a solid solution is formed which consists of gallium and phosphorus, but which does not contain indium without the formation of a solid solution of indium and Phosphorus takes place.

The invention is based on these considerations. According to the Basics of this invention, a melt is produced, the indium as solvent and phosphorus in a predetermined Mens-e contains. Then it is in the melt in a sufficient ΐ · -βίΐ, νβ gallium given that all of the phosphorus on the rezo.-renen or grown or cultivated gallium converts to form gallium phosphide. After in the on

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2U8433

this partially formed melt has one or more seed crystals Seed crystals have been introduced, is cooled in a known liieise to room temperature, whereby a effective growth of the gallium phosphide single crystal. The elements indium, gallium and phosphorus can be deformed into a melt, so that the melt at the temperature at which growth begins, is saturated with gallium and phosphorus. Alternatively, a mixture of Indium and gallium phosphide can be added to the gallium in an appropriate amount. In the latter pail should be the resulting Melt at the temperature at which growth begins, saturated with both gallium and phosphorus be.

FIG. 2 shows a melting system according to the prior art. The melting system indicated by the reference number 1 consists of gallium and gallium phosphide, which can be polycrystalline and which are contained in a quartz tube 2. Then a single crystal or single crystals of gallium phosphide (not shown) is grown in a manner known per se. It will it can be seen that in a melting system of Figure 2, the Gät lium in the form of an element added to the system does not Forms part of the grown crystal, resulting in the need to use large amounts of gallium.

FIG. 3 shows, in which the corresponding reference numerals relate to the corresponding components as in FIG a melting system made in accordance with the principles of this invention has been prepared. The melting system as shown in Figure 3 is advantageous because it is compared to that of Figure 2 contains a very small amount of gallium. The resulting crystals contain indium as from the consideration of the diagram of FIG. 1 is readily apparent. To the extent that gallium is in abundance increases, the proportion of the contained in the crystals decreases

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Indiums from. It has been found that for an atomic ratio which is equal to one atom of gallium to one atom of indium, which corresponds, for example, to the amounts of indium, gallium and phosphorus of 3 g, 1.82 g and 0.100 g, the χ of the formula ^ - yß ^ i ^^ t which represents the resulting crystal, practically has the value 0.

The invention is illustrated in the examples. '

example 1

A mixture of 10 g indium, k _t b6 g gallium and 0.16 g phosphorus with an atomic ratio of 0.42 gallium to indium plus gallium and an atomic ratio of 10.9 gallium to phosphorus was placed in a quartz tube having an inside diameter of 15 mm and a length of 10 cm. After sealing of the quartz tube in vacuo one hour, the temperature was increased to HOO ⁰ C and held for one hour at this fourth over. Thereafter, the drilling was cooled to room temperature at a cooling rate of 10O ⁰ C to 5 ° G per hour. The resulting crystals were typically in the form of square plates 0.5 mm thick and 7 mm long or wide.

Example 2

The above procedure was repeated except that the quartz tube was moved downward at a speed of 1 mm per hour inside a longitudinal furnace was moved in order to bring about a cooling.

Example 3

The same melt as in Example 1 was prepared and the usual Nelson method was used to prepare on a Substrate to epitaxially form a layer of gallium phosphide.

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- 6 - 2K8433

Specifically, it has been the melt and the substrate of a quartz boat within a furnace disposed at both ends and heated in a .iasserstoffstrom or in a vacuum at 1000 G ^0. The furnace was then tilted to pour the melt onto the substrate, after which the system was cooled to room temperature at a rate of 1 ° C to 10 ° C per hour to effect the epitaxial growth.

From the foregoing it can be seen that the gallium used completely forms part of the resulting single crystals formed. The invention is therefore particularly advantageous because the raw material cost compared to the prior art Technology can be reduced by a factor of about seven «

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Claims (3)

7 _ 2U8433 claims 1. A method for growing single crystals of a solid solution of the formula In Ga ₁ P, in which χ extends from 0 "to 0.01, in a manner known per se from a melt, characterized in that the melt is indium as solvent, phosphorus in a predetermined length and gallium in a sufficient length that all of the phosphorus is deposited on the gallium with the formation of gallium phosphide. 2. The method according to claim 1, characterized in that the melt of indium, gallium and forms phosphorus in the form of the elements. 3. The method according to claim 1, characterized in that the melt of indium and gallium phosphide forms with added gallium. 2098 15/1531