DE2411603A1 - METHOD FOR PRODUCING AN EPITACTIC LAYER AND EPITACTIC LAYER PRODUCED BY THIS PROCESS - Google Patents

Description

Method for producing an epitaxial layer and epitaxial layer produced by this method

The invention relates to a method for growing an epitaxial layer of a compound of elements of groups IHa and Va of the periodic table according to Mendelejeff in the vapor phase using an alkyl compound of an element of group IHa as a supplier for the element of group HIa. In particular, the invention relates to a method _s wherein a Naeh certain Synthe "seeerfahren produced Triätfaylaluminium whose SiIieiumgehalt _f determined according to the detail later described Analysenmetnode, most 4 ppm for growing an epitaxial Sent from a compound of elements of groups IIIa and Va on a surface of a substrate in the vapor phase, As a supplier of elements of group IHa with a gallium and / © <ä © r Xndiumhalcganid converted to triethylgallium and / or triethylindium, the resulting triethylgallium and / or triethylindium, optionally mixed with an alkylaluminum bond in the dam pfphase with an element of group Va, a hydride this

-2-

Element or an alkyl compound of this element mixed will.

Semiconductors in the form of compounds of elements of groups IHa and Va, for example GaP, GaAs, GaAs ₁ ^ _x P _x , Ga ^ _x Al _x As, InP and the like are particularly useful as materials for Gunn diodes, super high frequency devices and electroluminescent devices , which is why the demand for such semiconductors is increasing.

For vapor phase growth of an epitaxial layer of semiconductors in the form of compounds of elements of the Groups IHa and Va are currently aware of the following procedures:

1. Thermal decomposition processϊ This process exists in a thermal decomposition - an alkyl compound of a group III element and an element group Va or a volatile compound thereof;

2. Halogen Transport Process This process consists in the conversion of a chloride of an element of the group IHe and an element of group Va or a volatile one Connection of this.

At present, (only) halogen transport processes are carried out on an industrial scale. The reason is that how out "Journal of Electrochemical Society", Vol. 116, No. 12, Page 1729 {1969} shows the electron concentration an epi- made from trimethylgallium and arsine

tactical layer at room temperature at most 1 χ 10 / cnr and whose mobility is (only) 5000 cm / v-see. Both Parameters are not sufficient for Gunn diodes, for example

-3-409839 / 0932

imperative requirements, namely an electron concentration less than 1 χ 10 / cnr and a mobility of more than 6000 cm / v-sec. However, an epitaxial layer is obtained after the halogen transport process an electron concentration of about 1 χ 10 / cnr at room temperature and a mobility of more than 6000 cm / v-sec. Regardless of this, however, the production of epitaxial layers is based on the halogen transport method afflicted with various difficulties. This is how it is, for example, to successfully carry out the halogen transport process required to provide a reaction zone and a deposition zone and such conditions to maintain that there is a low temperature gradient of 7 ° to 12 ° C / cm near the substrate. Polly so the area suitable for growth is limited to an extremely small area. Furthermore, in usually only produce a few to about 30 pieces at a time, so that the productivity of such Halogen transport process is low. Finally, it is difficult to get mixed crystals of two or more Elements such as (Ga, Al) As, (Ga, In) P and the like.

On the other hand, when a thermal decomposition process is carried out, the growth of the epitaxial Achieve the layer by heating the substrate alone. In this way, the area of the growth zone and the productivity of the process can be chosen at will raise. Finally, as by thermal decomposition of an alkyl compound of an element of the group IHa compounds of elements of groups IHa and Va are deposited without further mixed crystals, such as (Ga, Al) P, (Ga, In) P and the like. On the-

-4 -40 9 839/093 2

In this way, the disadvantages inherent in the halogen transport process can be avoided. So far could however, epitaxial layers with an electron concentration which can be used practically for electronic devices and mobility cannot be established by thermal decomposition processes, hence these processes have not yet been used on a large scale. When trying to make epitaxial layers with a practically exploitable To be able to produce electron concentration and mobility according to a thermal decomposition process, was found that by reacting a) a Grignard reagent with a gallium halide, b) a dialkyl mercury compound with metallic gallium, and c) a dialkyl zinc compound with a gallium halide, i.e. towards the Preparation of alkyl compounds of group IHa elements, well known processes, prepared alkylgallium compounds inevitably contained Mg- * Hg and Zn impurities even after cleaning. if alkylgallium compounds as starting materials (for Production of epitaxial layers) are used, the grown crystals contain as background impurities the mentioned elements of group II in amounts similar to those in the starting materials were included. In this way it is not possible to determine the electron concentration of the crystals at space

16 ¹ ^

to lower the temperature to a value below 1 χ 10 / cnr. Practically usable epitaxial layers cannot be obtained even if after another Production process for alkyl compounds of elements of group IHa, namely from alkyl aluminum compounds and a gallium halide, produced and sufficiently purified by distillation alkylgallium

-5-ÜOS839 / 0932

connections are used * The same applies to Alkylindium compounds.

In view of the problems described, extensive investigations have been carried out on why alkylgallium or alkylindium compounds produced using alkylaluminum compounds as alkylating agents cannot be used for the production of epitaxial layers which can be used in practice. It was found that the epitaxial layers produced from such starting materials contain silicon. The silicon content of such epitaxial layers is probably due to the alkyl-aluminum compounds used to produce the alkylgallium or alkylindium compounds. first a suitable method had to be developed for the determination of (very small) amounts of silicon in aluminum aluric compounds. In the relevant experiments, it was found that the aluminum used as the starting material for the production of the alkyl aluminum binders can be traced back to silicon in the form of the most varied of organosilicium compounds nst @ u SMpunktsn exist and that some of these silicon compounds are only with great difficulty on the destllative ¥ eg © of the alkylgallium © of the alkylia can be separated diisünrerbindungen that "However, di © © silicon compounds hne further be separated by distillation from the Alkylaluaiiniuiaverbindungen Jcönn * ii, ®nn ¥ ^ © @ d O _f using an alkyl gallium-ÄlkyIindiTimverbindung produced using an

from which the silicon or the

-6-409839 / 0932

Silicon compounds have been separated, and a gallium and / or indium halide an epitaxial Layer is to be produced, it has been shown that in the event that the alkyl radicals consist of methyl radicals, a large amount of carbides are introduced into the epitaxial layer, thereby increasing the crystallinity the respective compound from the elements of groups IHa and Va is lowered. In the case that the alkyl radicals consist of propyl radicals or higher alkyl radicals, the vapor pressure is low, in which case such alkylgallium and / or Alkylindium compounds are not suitable for growing epitaxial layers. Furthermore the chlorides are also not suitable as volatile compounds of elements of group Va.

The invention was based on the object of a method for the production of high-purity epitaxial layers, e.g. of GaAs ^ layers, with a practically usable Electron concentration and mobility, in particular

16 "^ one? Electron concentration less than 1 χ 10 / cur at room temperature and a mobility of more than 6000 cm / v-see, by vapor growth using of alkyl compounds of elements of group IHa. The invention is thus a Process for the production of an epitaxial layer of a compound from elements of groups IHa and Va of the periodic table on a substrate surface, in which one is an alkyl compound of an element of the group IHa reacts with an element of group Va or a volatile compound thereof in the vapor phase and bringing the reaction product obtained into contact with the substrate, which is characterized in that triethylaluminum containing no more than 4 ppm silicon with a gallium or indium halide to form tri-

-7-409839 / 0932

äthylgallium or -indium converts and that you get the Triethyl gallium or indium, a mixture thereof or an aluminum alkyl compound containing Mixture thereof with an element of group Va or a hydride or an alkyl compound thereof in contact brings.

That in the context of the method according to the invention as a starting material triethylaluminum used and containing a silicon content of 4 ppm or less is firstly by converting triethylaluminum and / or diethylaluminum hydride, Aluminum, hydrogen and ethylene, secondly by reacting an alkyl aluminum compound with aluminum and hydrogen and optionally an olefin to form an alkyl aluminum compound, which are then subjected to an alkylene exchange with ethylene or, thirdly, by reducing one obtained by reacting aluminum with an ethyl halide Ethyl aluminum sesquihalide. Implementations 1 and 2 can be carried out according to the Japanese Patent applications 5710/57 and 927/58 as well as in the US-PS 2,835,689 described processes are carried out « Reaction 3 can be carried out under known reaction conditions.

As alkyl aluminum compounds, for example, trialkyl aluminum or dialkylaluminum hydride compounds whose alkyl radicals contain 3 to 20 carbon atoms, e.g. tripropyl aluminum, triisobutyl aluminum, tri-2-ethylhexyl aluminum, Trioctyl aluminum or their hydrides can be used.

As ethyl halides, ethyl chloride, ethyl bromide and Ethyl iodide can be used.

-8-409839 / 0932

Those involved in making epitaxial layers from compounds of elements of Groups IHa and Va using alkylaluminum compound pose a problem Silicon compounds come from the low silicon content of the raw material used in production of triethylaluminum used «The silicon contained in the aluminum is during the Production of triethylaluminum is extracted as an organosilicon compound and is converted into triethylaluminum in this form a. Commercially available triethylaluminum, determined by the analytical method carried out according to the invention, generally contains more than 10 ppm (expressed as a silicon) silicon compound. The form of the silicon compound contained in the alkyl aluminum compound is not known, in any case it is difficult to get out of using the silicon-containing one Remove triethylgallium and / or triethylindium produced from triethylaluminum. Consequently, the silicon content must of the triethylaluminum used as the starting material for the production of triethylgallium and / or triethylindium before the reaction with the gallium and / or indium halide are reduced to a maximum of 4 ppm, A triethylaluminum, the silicon content of which is at most 4 ppm, is obtained by cleaning the after Process 1 obtained triethylaluminum, the alkylaluminum compound obtained by process 2 or des triethylaluminum obtained by process 2 or the ethylaluminum sesquihalide obtained by process 3 or triethylaluminum by customary known purification processes, e.g. by rectification, recrystallization and the same. It is preferred to filter and the like before cleaning to remove the ballast to degrade when cleaning.

-9-409839 / 0932

According to the invention it is of essential importance that the for the production of triethylgallium and / or triethylindium The alkylaluminum compound used consists of triethylaluminum. The reasons for this are as follows explained in more detail.

In the context of the. The method according to the invention according to the specified manufacturing process produced high-purity triethylaluminum, its silicon content at most 4 ppm was lowered, in the usual known manner with a gallium halide and / or indium halide converted to triethyl gallium and / or triethylindium. Gallium chloride, gallium bromide can be used as gallium halides. mid or gallium iodide, as indium halides indium chloride, Indium bromide or indium iodide can be used. The used Gallium and / or Indiunsnalogenide can consist of commercially available high-purity compounds or before their use can be purified by sublimation. You can land / or by blowing a halogen into a gallium Ladiumschmelze and subsequent purification of the halides formed have been produced by sublimation be.

The reaction between triethylaluminum and the gallium and / or indium halide proceeds according to the following equation Section

:, + 3A1 (C "H _K U - -> M (C ₅ H ₅ -), + 3 (C ₉ Hc) ₉ AlX

■ J <- OJ £ 3 C \ j C

where M stands for gallium and / or indium and X stands for Halogen atom means »

In the manufacture of triethyl gallium or triethylindium, gallium halide or indium halide are used per 1 hol

-10- 409839/0932

at least 3 moles, usually 3 to 4 moles, of triethylaluminum used.

The reaction can be generally carried out at temperatures from 0 ° to 150 ⁰ C under normal pressure or, if appropriate, elevated or reduced pressure are carried out "Optionally, a solvent having a boiling point of 30 ° during the reaction to 100 ⁰ C, for example petroleum ether, pentane, hexane and the like, be present.

The Triäthylgallium formed and / or Triäthylindium is (are) subjected to vacuum distillation or by addition of potassium chloride and / or sodium fluoride before or minutes after the vacuum distillation for the complex binding of the Diäthylaluminiumhalogenids about 10 byproduct to 2 hours at a temperature of 0 ° to 150 ⁰ C. held and finally rectified to obtain purified triethyl gallium or triethylindium.

As already mentioned, the alkyl radicals of the alkylgalaims and / or Alkylindiums consist of ethyl radicals. If the alkyl radicals consisted of methyl radicals, go into the epitaxial layer formed contains larger amounts of carbides, which increases the crystallinity of the compound Elements of groups IXIa and Va is lowered. If the alkyl radicals consisted of propyl or higher alkyl radicals, the vapor pressure is low, which is why such alkylgallium and / or alkylindium compounds are not considered to be Starting materials are suitable for growing crystals «As already mentioned, there are numerous other processes for the production of triethyl gallium and / or triethylindium, however, they are not suitable according to the invention because in the implementation of these known processes in the triethylgallium and / or triethylindium inevitable

-11- 409839/0932

Elements from group II of the periodic table (as impurities) enter, so that from such a triethyl gallium and / or triethylindium no practical usable products can be produced.

That from a triethylaluminum, its silicon content had been lowered to a maximum of 4 ppm in the manner described, triethylgallium and / or triethylindium formed is, optionally in a mixture with an alkyl aluminum compound, more common in the vapor phase to form an epitaxial layer on a substrate surface known manner mixed with an element of group Va or a hydride or an alkyl compound thereof.

As an element of group Va, arsenic or phosphorus are suitable. The hydrides or alkyl compounds of these elements of group Va can, for example, from phosphine, alkylphosphines, such as triethylphosphine, diethylphosphine, monoethylphosphine, tripropylphosphine and the like, arsine, alkylarsines, such as triethylarsine, diethylarsine, monoethylarsine, monopropylarsine and the like exist. It can ammonia can also be used here. As compounds of elements of group Va, for example, phosphorus trichloride and arsenic trichloride not preferred, since in this case crystal growth is difficult "

In a mixture with the triethyl gallium and / or triethylindium, for example triethyl aluminum, Diethyl aluminum hydride, tripropyl aluminum, dipropyl aluminum hydride, dibutyl aluminum hydride and the like can be used. The silicon content of these compounds should preferably be per aluminum atom be less than 1 ppm,

-12-

409839/0932

The crystals can be cultivated or grown by customary known methods and in customary known devices. Here, for example, the alkyl compound of the HIa group element is introduced in gaseous form into the crystal growth zone at a rate of (0.05 to 10) χ 10 mol / min. The Group Va element or its hydride or alkyl compound is fed into the crystal growth zone at a rate of (0.05 to 50) χ 10 mol / min. Of course, hydrogen and / or argon can be introduced into the crystal growth zone as a carrier together with the alkyl compound of the element from group HIa and the element from group Va or its hydride or alkyl compound. As known, "The crystal growth is generally carried out at a temperature of 500 ° to 1300 ⁰ C. as substrates the same crystals constituting the growing layer, silicon, sapphire, spinel and the like

To carry out the method according to the invention, one of conventional refractory materials is suitable, such as Quartz, porcelain, carborundum, graphite and the like existing reactor. The gaseous reactants are fed into the reactor individually or as a mixture. The substrate is heated in the reactor usually by induction heating, so that the compound of elements of groups IHa and Va only is deposited on the substrate surface.

The method according to the invention has so far only been explained on the basis of the production of high-purity crystals. Of course you can during the growing layer

-13-

409839/0932

of the crystal growth, donors or acceptors can also be incorporated in the customary known manner.

Semiconductors with an epitaxial layer produced according to the invention are excellent for production of Gunn diodes, super high frequency devices and electroluminescent devices use.

As already explained in detail, the process according to the invention can be used to produce epitaxial layers with practically usable electrical properties from alkyl compounds of elements of group IHa, from which epitaxial layers with practically usable electrical properties could not be produced by conventional methods. The industrial importance of this process is therefore extremely great. The productivity of the process according to the invention is more than twice as great as the productivity of the conventional halogen transport process. Using the usual halogen transport process, mixed crystals, for example ^Ga _x ^In >) _ _x ^p »Ga ^ Al ^ Is and the like, and epitaxial layers different from the substrate can only be produced with great difficulty. According to the invention, on the other hand, it is readily possible to produce mixed crystals as well as epitaxial layers different from the substrate.

The quantitative determination of the silicon content of the triethylaluminum used as the starting material was carried out as follows:

A 300 ml quartz flask was charged with 120 ml of water and 50 ml of hexane and then gradually added dropwise 10 g of triethylaluminum were added. Here

-14-409839 / 0932

the triethylaluminum was hydrolyzed. The aluminum hydroxide formed was dried for 10 hours in vacuo at a temperature of 90 ^° C., whereupon 3 g of the dried aluminum hydroxide were transferred to a 50 ml platinum crucible and 6 g sodium carbonate and 2 g boric acid were added. The mixture in the platinum crucible was thoroughly stirred, after which the platinum crucible was covered with a platinum lid. Now, the covered platinum crucible was preheated to a sand bath for 40 minutes and then placed for 20 minutes in an electric heating furnace to a temperature of 1000 ⁰ C. After the platinum crucible and its contents had cooled down, water was added, whereupon the whole thing was heated to dissolve the crucible contents in the water. The resulting solution was transferred to a 200 ml polyethylene beaker. The platinum crucible was washed with heating with 1 ml of 8N nitric acid, whereupon the washing solution was also transferred to the polyethylene beaker. A further 20 ml of 8N nitric acid were then poured into the beaker, whereupon the beaker was covered with a polyethylene watch glass. The beaker was then heated to completely dissolve the precipitate that had formed. After the precipitate had dissolved, the solution obtained was cooled, transferred to a polyethylene volumetric flask and brought to a certain volume there. The solution obtained served as a sample solution. 30 ml of the sample solution were removed from the volumetric flask and transferred to a 100 ml polyethylene beaker. The pH of the sample solution was adjusted to 0.8 using an aqueous ammonia solution (nitric acid may also have to be used), whereupon the whole thing was combined into one

-15- 409839/0932

50 ml polyethylene volumetric flask was transferred. so the sample solution was made with 2.5 ml of a by dissolving

/ ml prepared from 10 g ammonium molybdate in 100 / water Ammonium molybdate solution was added and the whole was stirred and left to stand for 5 minutes. Well was the sample solution further with 2.5 ml of 8N nitric acid and 2.5 ml of a reduced sulfonic acid solution (mixture of a solution A, which is obtained by dissolving 7 g of sodium sulfite and 1.5 g of 1-amino-2-naphthol-4-sulfonic acid in 100 ml of water and a solution B made by dissolving 90 g of sodium bisulfite in water was added) and made up to a certain volume with water. Part of the resulting solution was transferred to a cuvette of a spectrophotometer, whereupon the absorption of this solution against water at one wavelength of 825 mu was determined. One in the one described Well prepared solution, but no dried aluminum hydroxide is used in its production was used as a blank. The absorption of this blank sample was also measured at one wavelength from 825

Finally, a calibration curve was made as follows:

Of water glass with hydrochloric acid (1 + 1) Reverse precipitated silica gel and was washed with warm water Chlorine washed then dried at a temperature of 100 ° ± 5 ⁰ C "A part of the silica obtained was dissolved in a Polyäthylengefäß in an aqueous sodium hydroxide and with an appropriate amount Was water diluted to make a silica standard solution. A portion of the standard solution obtained was transferred to a cuvette of the spectrophotometer, whereupon

-16 - '+ 09839 / Ö932

the absorption of the resulting solution against water a wavelength of 825 mu was measured.

The amount of silicon obtained in the silica standard solution was determined gravimetrically by adding to the Standard solution of sulfuric acid was added and the whole thing was then evaporated with heating to complete To obtain insoluble silicon dioxide »The calibration curve was drawn up in the manner described.

The amount of silicon was calculated from the calibration curve obtained from the absorption values. The silicon content of the Triethylaluminum was calculated according to the following equation:

Silicon content of the _ AB "Triäthylaluminiums (ppm) _{T. r} .. c

W X

where mean:

A silicon content of the sample solution (»g) j

B silicon content of the blank sample (iig);

C amount of sample solution used (ml);

W amount of aluminum hydroxide (g);

F Conversion factor from triethylaluminum to getrock netes aluminum hydroxide (in the present case is the value F 0.6).

The following reagents were used in the analytical procedures described:

Water: The water used was purified by distilling an ion exchanger in water

-17-

409839/0932

cleaned a quartz distillation apparatus and had one specific resistance, determined at a temperature of 30 ° C, of 150000OiI. cm;

Hexane: The hexane used was obtained by treating an analytically pure hexane with sulfuric acid and then treating it Distillation made.

Anhydrous sodium carbonate, boric acid, aqueous ammonia solution (in a polyethylene bottle) and nitric acid (in a polyethylene bottle): These reagents were commercially available high purity reagents Reagents.

Ammonium molybdate, sodium sulfite, and 1-sulfonic acid: these reagents were reagent grade reagents,

For the crystal growth of a compound composed of elements of groups IHa and Va using an alkyl compound of an element of group IHa in the context of the process according to the invention is naturally the purity of the element of group Va or of the hydride or the alkyl compound thereof is also of great importance. In the following examples, commercially available materials for manufacturing semiconductors were used as raw materials used.

The following examples are intended to illustrate the invention in more detail.

example 1

Preparation of an alkyl compound of an element of the group pe IHa:

409839/0932 -18-

1. 320 parts of triethyl aluminum and 120 parts of aluminum were charged into an autoclave and by alternately blowing of 110 ° to 115 ⁰ C hot hydrogen (hydrogen pressure: 150 to 160 atm) and 70 ° to 75 ° Qheißem ethylene (ethylene pressure: 20 to 30 atm ) allowed to react to triethylaluminum. The triethylaluminum obtained was filtered off, distilled and finally rectified in a packed column with 70 theoretical plates, a triethylaluminum containing 0.5 ppm of silicon being obtained.

On the other hand, metallic gallium was introduced into a transparent quartz reactor and melted therein. Chlorine was blown into the resulting molten gallium to produce gallium chloride. The gallium chloride thus formed was purified by sublimation.

450 parts of the triethylaluminum prepared in the manner described were placed in a borosilicate glass reactor filled in and, while stirring, dropwise within 1 hour with a dissolving of 207 Parts of the gallium chloride prepared in the manner described in 650 parts of petroleum ether Solution of gallium chloride in petroleum ether was added. After the end of the dropping, the reaction was between the triethylaluminum and the gallium chloride allowed to run off for a further 1 hour. Thereupon became the petroleum ether under normal pressure and then the triethyl gallium from the diethyl aluminum chloride and triethyl aluminum distilled off by fractional distillation under reduced pressure. The separated üäthylgallium was mixed with 20 parts of potassium chloride and 18 parts of sodium fluoride and the complex binding of the

-19-

409839/0932

stirred in a small amount existing Triäthylaluminiums and diethylaluminum chloride for 1 hr at a temperature of 100 ⁰ C. The whole was then rectified in a borosilicate glass column having a diameter of 15 mm and a length of 1 m, which was packed with borosilicate glass spiral rings, whereby 162 parts of high-purity triethylgallium were obtained.

2. 800 parts of triisobutyl aluminum, 250 parts of aluminum and 1,800 parts of isobutylene were placed in an autoclave filled, whereupon hydrogen was blown into this until the pressure rose to 200 atm was. The autoclave was then heated to a temperature of 110 ° to form triisobutylaluminum Heated to 120 ° C. The obtained triisobutylaluminum became now brought into contact with ethylene at a temperature of 100 ° C. in order to achieve an alkyla exchange reaction Manufacture triethylaluminum. The triethylaluminum thus formed was filtered off, distilled and finally rectified in a packed column with 70 theoretical plates, with a triethylaluminum with 2.4 ppm silicon was obtained. Then, as described under 1., using the in the Triethylaluminum triethylgallium produced in the manner described.

3 · 43 parts of aluminum and 2 parts Äthylaluminiurasesquibromid was dissolved in methylcyclohexane, whereupon the resulting solution for reaction at a temperature of 50 ° to 100 ⁰ C was added dropwise 250 parts of ethyl bromide was added. Then, 80 parts of a K-Na (2: 1) was added alloy and heated to a temperature of 100 ° to 180 ⁰ C, with triethyl aluminum

-20-

409839/0932

was formed. The obtained triethylaluminum was filtered off, distilled and finally rectified in a packed column with 70 theoretical plates, a triethylaluminum containing 1.5 ppm silicon became. Using the triethylaluminum prepared in the manner described, in the manufactured under 1. described way triethylgallium.

4, metal indium was packed into a transparent quartz reactor, followed by blown into them for the manufacture of indium chloride at a temperature of 160 ° to 200 ⁰ C chlorine. The indium chloride thus formed was purified by sublimation.

Using the triethylaluminum prepared according to 1. and containing 0.5 ppm of silicon and according to 4. The indium chloride produced was described under 1. for the production of triethylgallium Wise made triethylindium.

5. The triethylaluminum produced under 1. was simply distilled, with a triethylaluminum having 10 ppm silicon was obtained. This was then triethylaluminum in the manner described under 1 Triethyl gallium produced.

Example 2

This example illustrates the epitaxial growth of GaAs using triethyl gallium and arsine as starting materials,

-21-

409839/0932

(a) As a substrate, a halMsolierender GaAs crystal (100), which had been doped with Cr, heated to a temperature of 650 ⁰ C. The triethyl gallium and arsine prepared according to 1. of Example 1 were allowed to flow over the substrate at a rate of 0.5 × 10 mol / min and 1.5 × 10 mol / min, and further hydrogen at a rate of 2.5 l Passed through the system / min, epitaxial growth took place at a growth rate of GaAs of 20 µ / h. The electrical properties of the grown layer, measured by the Hall measurement method, were as follows:

Electron concentration at room temperature: 1 χ 10 / cur Mobility: 9000 cm ² / v-sec.

(b) The process described under (a) was repeated, but for the epitaxial crystal growth the triethyl gallium described under 2. of Example 1 was used. The epitaxial layer thus obtained possessed the following electrical properties:

15 / "5 electron concentration at room temperature: 3 x 10 / cm mobility: 8000 cm ² / v-sec.

(c) The process described under (a) was repeated, but for the epitaxial crystal growth the triethyl gallium prepared under 3. of Example 1 was used. The epitaxial layer thus obtained possessed the following electrical properties:

Electron concentration at room temperature: 6 χ 10 / car Mobility: 8500 cm ² / v-sec.

('d) The procedure described under (a) was repeated, however, instead of the arsine, triethylarsine is used

409839/0 93 2 -22-

was turned. The electrical properties of the epitaxial layer obtained in this way were practically the same the epitaxial layer produced according to (a).

(e) For comparison purposes, the procedure described under (a) was repeated, with that under 5. of Example 1 produced triethylgallium was used. The epitaxial layer thus obtained had the following electrical properties Characteristics:

17 / ^ 5 electron concentration at room temperature: 1.3 x 10 / cnr

Mobility: 4100 cm ² / v-sec.

The results obtained clearly show that the desired success will only be achieved if the The silicon content of the triethylaluminum used to produce the triethylgallium is at most 4 ppm.

Example 3

This example illustrates the epitaxial growth of GaP using triethyl gallium and phosphine or phosphorus.

(a) As the substrate for crystal growth, a semi-insulating GaP crystal (Achsenrichtungj 100), which was doped with chromium in a high concentration, heated to a temperature of 810 ⁰ C. The triethylgallium and phosphine prepared according to 1. of Example 1 was allowed to flow over the substrate at a rate of 0.5 × 10 mol / min or »2 × 10 mol / min and hydrogen was passed through at a rate of 2.5 l / min the system, the speed of the epi-

-23-

409839/0932

tactical growth of GaP 20 p. /hours. The electrical properties of the grown layer were determined in the manner described in Example 2.

"1 Ix ~ * \ electron concentration at room temperature: 3 χ 10 / cm

Mobility: 180 cm ² / v-sec _e

(b) The procedure outlined under (a) was repeated with yellow phosphorus instead of phosphine. The yellow one Phosphorus was heated and supplied to the reaction system at a rate of 3 × 10 10 mol / min. Here could the GaP crystal grow «The electrical properties of the epitaxial layer obtained were as follows:

15/5 electron concentration: 1.3 x 10 / cm

Mobility: 165 cm ² / v-sec.
Example 4

This example illustrates the epitaxial growth of GaAlAs and its use as a light emitting Diode.

The substrate used was a (100) GaAs crystal, which had been doped with Te, and an electron concentration of 1 χ 10 / CNP had heated to a temperature of 800 ⁰ C. HpTe diluted to 100 ppm was supplied to the system in such a way that the electron concentration of the growing layer was 1 10 '/ ^cm . At the same time were for the epitaxial growth of GaAs yon on the GaAs substrate 30 min the Triäthylgallium under 1 _o prepared in Example 1, arsine and H "at speeds of 5 x 10 ^-5 mol / min, 2 χ 10" * mol / min or 2.5 l / min through

-24-409839 / 0932

let the system flow. Thereupon the according to 1 Triethylaluminum prepared from Example 1 and containing 0.5 ppm silicon was gradually introduced into the system. After 1 hour, the flow rate of the triethylaluminum fed to the system was reduced to 2 χ 1O ~ ^ mol / min, and the crystal growth was allowed to proceed for a further hour at this concentration.

An epitaxial layer of Ga ^ T ₁ Al _x As with an aluminum concentration χ = 0.39 was obtained. In this crystal, a PN junction was formed by the Zn diffusion method. A sealed pipe was used here. Finally a diode was made. The luminescence of the red emission at 20 mA was 200 fL. This value corresponds practically to the luminescence of a commercially available GaAsP light-emitting diode. If no H ₀ Te was added to the system as an impurity, the electron concentration of the epitaxial layer was 3 × 10 / cm, a sufficiently "highly pure" crystal being obtained according to the method described.

Example 5

This example illustrates the growth of an InGaP crystal and the properties of a light-emitting diode made with this crystal.

A (100) GaP crystal, ^{which had been doped with 1 × 10 18} / cm ³ Te, was heated to a temperature of 830 ^{° C. as the substrate.} While phosphine was flowing through the system at a flow rate of 3 × 10 10 mol / min, 100 ppm H ₂ Te was simultaneously passed through the system so that the electron concentration of the grown layer became 7 × 10 4 / cm ³ . so

-25-409839 / 0932

using hydrogen as a carrier for the growth of the GaP crystal, the triethylgallium prepared under 1. of Example 1 was fed in at a flow rate of 3 × 10 mol / min for 30 minutes. The total amount of hydrogen flowing through the system at this point was 2 L / min. The triethylindium produced under 4. of Example 1 was then introduced gradually into the system in such a way that the flow rate of the triethylindium reached a value of 1 10 mol / min after 1 hour. The crystal growth was allowed to proceed for an additional hour under these conditions. The growth was then interrupted. The crystal obtained contained the gallium corresponding to In ,, Ga P in a concentration of χ = 0.7. A diode produced by Zn diffusion using a closed tube showed a yellowish-green emission of luminescence of 130 fL at 50 mA. In the event that no H ₂ Te was used as an impurity, the electron concentration of the grown layer was 8 χ 10 ¹⁴ / cm ³ .

-26-409839 / 0932

Claims (1)

Claims 1. Process for producing an epitaxial layer a compound of elements from groups IHa and Va of the periodic table on a substrate surface, in which an alkyl compound of an element from group IHa with an element from group Va or a volatile compound thereof reacts in the vapor phase and the reaction product obtained with the substrate brings into contact, characterized in that triethylaluminum containing at most 4 ppm of silicon is used with a gallium or indium halide to form triethylgallium or indium and that the obtained Triethylgallium or triethyl indium is a mixture thereof or containing an aluminum alkyl compound Mixture of the same with an element of group Va or a hydride or an alkyl compound thereof brings in touch. 2. The method according to claim 1, characterized in that a triethylaluminum is used which is obtained by reacting triethylaluminum and / or diethylaluminum hydride, Aluminum, hydrogen and ethylene was produced, 3. The method according to claim 1, characterized in that a triethylaluminum is used, which is obtained by reacting an alkylaluminum compound, aluminum and Hydrogen or an alkyl aluminum compound, aluminum, hydrogen and an olefin, and then Alkyl exchange reaction between the obtained alkyl aluminum and ethylene was established. 409839/0932 - 27 - 4 _β method according to claim 1, characterized in that one uses a triethylaluminum, which was prepared by reduction of a by reaction of aluminum with a Äthylhalogenid Äthylaluminiumsesquihalogenids formed. Process according to Claim 1, characterized in that the gallium halide used is gallium chloride, gallium bromide or gallium iodide is used. Method according to claim 1, characterized in that the indium compound used is indium chloride, indium bromide or indium iodide. 7ο method of claim 3 _t characterized in that one or indium uses at least 3 moles of triethylaluminum in implementing the Triäthylaluminiums with the gallium halide and indium halide per 1 mole of gallium, 8. The method according to claim 1, characterized in that the reaction between triethylaluminum and the gallium or indium _o performs under normal pressure at temperatures of from 0 ° to 15O ⁰ C. 9. The method according to claim 1, characterized in that there is arsenic and / or phosphorus as the element of group Va used. 10c method according to claim 1, characterized in that one as hydride or alkyl compound of an element of group Va phosphine, triethylphosphine, diethylphosphine, Monoethylphosphine, tripropylphosphine, arsine, triethyl- 409839/0932 - 28 - arsine, diethylarsine, monoethylarsine, monopropylarsine or ammonia is used. 11. The method according to claim 1, characterized in that as with triethylgallium and / or triethylindium mixed alkylaluminum compound triethylaluminum, Diethyl aluminum hydride, tripropyl aluminum, dipropyl. aluminum hydride and / or dibutyl aluminum hydride used 12. The method according to claim 1, characterized in that the crystal growth is carried out at a temperature of 500 ° to 1300 ⁰ C » Epitaxial layer with an electrical concentration at room temperature of less than 1 χ 10 ^ produced according to one or more of the preceding claims. ; 09839/0932