DE2729889B2 - Process for the epitaxial growth of doped boron phosphide on a substrate - Google Patents

Description

R '

where M = Zn, Cd, Hg, R = radical of a hydrocarbon and R '= R or halogen, in an amount of 0.05 to 50 MoI per mole of the boron compound, or hydrogen sulfide, hydrogen selenide, hydrogen telluride in an amount of 10 ~ ⁴ to 10 moles per mole of the boron compound can be added.

2. The method according to claim 1, characterized in that that the reaction gas 0.5 to 50 moles of the compounds

R '

are added per mole of the boron compound.

3. The method according to claim I, characterized in that R is an alkyl group with 1 to 4 Carbon atoms and R 'is an alkyl group with 1 to 4 carbon atoms or chlorine or bromine mean.

4. The method according to claim 1, characterized in that one is a carrier gas or nitrogen a noble gas which contains less than 90 vol .-% hydrogen, or a mixture thereof, and Phosphorus trichloride and diborane in a ratio between 20 and 200 at a substrate temperature between 880 and 1100 ° C.

5. The method according to claim 4, characterized in that the concentration of the diborane in the reaction gas flowing through the reaction vessel per minute is between 2x10 ~ ⁶ and 5x10 ~ ³ mol.

difficult to one in a doping process by the Hb group impurity element of the PSE Acceptor content or a donor content through the foreign atom element of group VIb of the PSE produce.

The present invention is therefore based on the object of a method for epitaxial growth of doped boron phosphide on a substrate to which a high quality epitaxial boron phosphide layer of the p- or n-conductivity type is drawn from the gas phase.

This object is achieved by the method characterized in the main claim

The doped boron phosphide layer grown by the method according to the invention has an excellent quality Crystal structure, the Kikuchi band observed in the case of reflective electron diffraction will. A charge carrier mobility of up to 50 cmW is obtained. see, from which it follows that the after boron phosphide layer produced by the process according to the invention has excellent electrical properties Has.

In the claimed process, diborane is used as the boron compound and phosphine or phosphorus chloride, bromide or iodide in a PH ₃ / B ₂ H ₆ or PX ₃ (X = halogen) / B2H _e ratio of 10 to 400 is preferred.

Boron chloride, bromide and iodide are also advantageously used together with phosphorus chloride, bromide and iodide (in a ratio of PX ₃ ^ (BX ₃ ) (where X = halogen) of 10 to 400). A temperature between 950 and 1100 ⁰ C worked.
Another preferred embodiment of the process according to the invention consists in adding 0.5 to 50 mol of the compounds to the reaction gas

The invention relates to a method for the epitaxial growth of doped boron phosphide on a substrate, boron hydrides or halides with phosphorus hydrides or halides at a temperature of 850-1100 ⁰ C implemented.

Such a method is known from J. of Applied Physics 42 (Jan. 1971), pages 420-424.

It is difficult to produce a high quality boron phosphide crystal because of its crystal growth is more difficult than with other elements of group III, VI and V of the periodic table of the chemical elements (PSE) such as GaAs, GaP and the like. As a result, it is extraordinary

R '

are added per mole of the boron compound.

Another advantageous embodiment of the method according to the invention is that in the general formula R is an alkyl group with 1 to 4 carbon atoms and R 'is an alkyl group with 1 to 4 Mean carbon atoms or chlorine or bromine.

The carrier gas used can be nitrogen or a noble gas containing less than 90% by volume of hydrogen, or a mixture thereof, and phosphorus trichloride and diborane in a ratio between 20 and 200 at a substrate temperature between 880 and 1100 ° C. It is preferred that the noble gas used is selected from the group consisting of helium, xenon and argon. The concentration of diborane in the per minute flowing through the reaction vessel reaction gas can be between 2 χ 10 ^-6 and about 5 χ 10 ^-3

bo MoI.

An advantageous embodiment of the method according to the invention is that a substrate Silicon, germanium, silicon carbide, sapphire or spinel, single crystal or a composite semiconductor substrate

tr> strat is used, which is made up of a single crystal layer Boron phosphide is made on the surface of a silicon, germanium, silicon carbide, sapphire or Spinel single crystal has been applied.

The invention is explained in more detail below with reference to the drawings

F i g. 1 is a graph showing the relationship between the temperature of liquid diethyl zinc and the carrier concentration of the grown boron phosphide layer, and

F i g. 2 is a schematic representation of an example for a device for waxing a porphosphide Semiconductor.

The reaction gas used for the growth of the boron phosphide in the gas phase comprises combinations of boron and phosphorus hydrides, boron and phosphorus halides, borohydride and a phosphorus halide and a boron halide and a phosphorus hydride. Typical boron hydrides include those of the formula B _n H _{11 + 4} , such as. B. diborane (B ₂ H ₆ ), B ₅ H ₉ and BioHh, and those of the formula B _n H "+6, such as. B. Teiraboran (B4H10) and BsHu. Phosphorus hydrides include phosphine (PH3) and diphosphire. (P2H4). Typical halides include boron trichloride (BCI3). Boron tribromide (BBr ₃ ), boron triiodide (BJ ₃ ), phosphorus trichloride (PCI3), phosphorus tribromide (PBr ₃ ), phosphorus triiodide (Pb). Phosphorus pentachloride (PCI5), phosphorus pentabromide (PBr ₅ ), phosphorus _{pentajodide (PJ 5} ).

The organic compound as a pollution source is kept in the liquid state and the amount of Impurity to be added to the reaction gas is varied by changing the vapor pressure The fluid compound is controlled by changing the temperature, and by changing the flow rate of the carrier gas for the uptake of the organic compound controls

Examples of compounds of the formula

R '

Dimethyl zinc, diethyl zinc, di-n-propyl zinc, diisopropyl zinc, Di-n-butyl zinc, di-sec-butyl zinc, dioctyl zinc, didecyl zinc, didodecyl zinc, distearyl zinc, dipropenyl zinc, Diphenylzinc, dimethylcadmium, diethylcadmium, di-n-propylcadmium, di-n-butylcadmium, dioctylcadmium, Didodecylcadmium, Dipropenylcadmium, Diphenylcadmium, Dimethylmercury, Diethylmercury, Di-n-propyl mercury, diisopropyl mercury, di-n-butyl mercury, Dioctyl mercury, didodecyl mercury, diphenyl mercury, methyl mercury chloride, Methyl mercury bromide, methyl mercury iodide, ethyl mercury chloride, ethyl mercury bromide,

n-propyl mercury chloride, isopropyl mercury superchloride, n-butyl mercury chloride. For doping can a mixture containing 2 or more impurity elements can be used.

In manufacturing a p-type boron phosphide semiconductor by epitaxially growing a Boron phosphide semiconductors using phosphorus trichloride and diborane become particularly advantageous Results obtained using crystal growth using nitrogen or a Noble gas containing less than 90 vol .-% hydrogen, or a mixture thereof as a carrier gas with a composition ratio of phosphorus trichloride to diborane of 20 to 200 and at one Substrate temperature between 880 and 1100 ° C.

The p-type boron phosphide semiconductor layer thus prepared forms a specular surface and has an excellent crystal structure, and Kikuchi bands are observed in the reflective electron diffraction. A mobility of up to 50 cm ² / V ■ sea (with a thickness of 1 micron) is obtained. Since diborane is the speed-determining stage in the growth of the boron phosphide semiconductor layer, the film thickness can be precisely controlled by merely controlling the amount of diborane.

Although each of the area indices (100), (110) and

(111) can be used for the semiconductor substrate, the best crystallinity is obtained with the semiconductor layer made of boron phosphide formed on a (100) face, in particular, a BP / Si composite semiconductor substrate made of a silicon substrate with boron phosphide formed thereon consists provides excellent crystallinity within a wide range under the growth conditions according to the invention.

It has been found that η-type electric wire is obtained when using only Hydrogen as a carrier gas forms a semiconductor layer made of boron phosphide, whereas an electrical one P-type conduction is obtained when the hydrogen is more than 10 vol.% Nitrogen or noble gases such as xenon. Contains argon, helium

The invention is illustrated in more detail by the following examples, without, however, being restricted thereto.

example 1

A Si substrate having a (100), (HO) or (111) face which had been subjected to mirror polishing was placed on a SiC-coated C carrier and by means of a radio frequency induction heating device connected to a quartz reaction tube , whereby an epitaxial growth at a B2H6 concentration of 2xlO ~ ⁵ mol / min, and at a PH3 / B2H6 molar ratio of 1 heated to a growth temperature of 93O ⁰ C was 50 causes. The temperature of the liquid Diäthylzinks contained in a stainless steel bubbler was maintained at the desired point within the range from -20 to 50 ⁰ C, in order to control the vapor pressure of Diäthylzinks during epitaxial growth. Hydrogen (H2) was used as the uptake gas at the desired rate between 5 and 100 cmVmin. fed by means of a stainless steel tube, which was maintained for the introduction of the reaction gas at about 90 ⁰ C is passed into the quartz reaction tube and then mixed with the reaction gas. The amount of diethyl zinc (DEZ) fed in was controlled so that a DEZ / B ₂ H ₆ molar ratio of 5.0 was obtained.

The gas phase grown BP layer doped with Zn had a film thickness of 2 microns. After the growth, the Si substrate was _{removed by etching using HF-HNO 3} and the carrier density became

bo measured by the Van der Pauw method. The layer doped with Zn had a p-type conduction. The BP layer grown in the gas phase, which had not been doped with zinc, had η conductivity and the carrier density was less than 5 × 10 ¹⁶ cm ^-3 .

b5 The F i g. 1 of the accompanying drawings shows the Relationship between the temperature of the liquid diethyl zinc and the carrier concentration in the grown BP layer. As shown in FIG. 1 to

As can be seen, no p-layer was obtained at a temperature of the liquid below 0 ° C. At a temperature above 10 ° C, the carrier density increased as the temperature of the liquid increased. In the case of the reflective electron diffraction, no significant deterioration of the BP layer grown in the gas phase by the addition of the diethyl zinc was observed. No satisfactory ZN doping could be achieved under conditions other than the above-specified temperature range for crystal growth and the range for the DEZ / B ₂ H6 molar ratio. The Zn content in the grown BP layer, as measured by an X-ray microanalyzer, was such that it substantially corresponded to the electrically measured carrier concentration.

Example 2

Under the same procedure as in Example 1 was doped with elemental cadmium from Diäthylcadmium (decd), wherein the epitaxial growth on the (lOO) face χ of a Si substrate at a B ₂ H ₆ concentration of 2 10 ^-5 mol / Min., A growth temperature of 930 ⁰ C and a PH3 / B ₂ H ₆ molar ratio of 1:50 was worked. The DECd / B2H6 molar ratio was 1: 5. The grown BP layer obtained thereby had a p-type and the carrier density therein was 2 × 10 "cm ^-3 . With an X-ray microanalyzer, about 10 ^Ι9 χ ΙΟ ^-3 cadmium was detected in the BP film undoped BP films was always less than 5 × ^{10 16 cm -3} .

As long as the amount of DECd was kept unchanged (DECd / B ₂ H ₆ = 1: 5) the carrier density showed no significant change and remained within a growth temperature range of 850 to 1000 ^° C. at about 2 × 10 ¹⁹ cm ^-3 .

Example 3

Using B ₂ Ho-PCI3-H ₂ as the reaction gas and adding DEZ to the reaction gas, BP was doped with Zn in the same manner as in Example 1. An Si substrate having a P-doped (lOO) face was placed on a SiC coated C-support and heated by radio frequency induction heating to a set to 1000 ⁰ C growth temperature and in a quartz reaction tube was added together with H ₂ as a carrier gas B ₂ He in a concentration of 2x10 " ⁵ mol / min, introduced. By introducing H ₂ as a carrier gas, phosphorus trichloride (PCI3) was blown in, while the vapor pressure of the PCI3 was controlled by changing the liquid temperature and then mixed with the carrier gas. The molar ratio PCI3 / B ₂ H ₆ was 25. Simultaneously, diethyl zinc (DEZ) was introduced into the reaction gas in the same manner as in Example 1 at a DEZ / B ₂ H ₆ molar ratio of 5 to carry out the introduction of the Zn impurity a p-type BP epitaxial layer 2 microns thick was obtained, the carrier density was 2 × ^{10 19 cm -3, and} a grown BP layer having no Zn doping had a conductive η-type and a carrier density of less than 5 χ 10 ¹⁷ cm ^-3 . The growth temperature was varied in the Zn dopant and the electrical properties of the grown BP layers were measured, wherein found 'that, while within the temperature range 950-1100 ⁰ C and at a dec / B ₂ H ₆ molar ratio between 0 , 05 and 50 satisfactory Zn-doped layers could be obtained, but that the properties of the doped layers outside the

3 areas indicated above were greatly deteriorated. Satisfactory Zn doping of BP for the BCb-PCb-HrSystem was also observed within practically the same ranges for the growth temperature and the DEZ / B _{2 H6 molar ratio.}

There were no differences with regard to the doping effects of BP compared to the area indices (111) and (110) in Examples 1 and 2.

Example! 4th

! 5 A Si substrate with (100), (110) and (lil) faces, which had been subjected to mirror polishing, was placed on a C carrier coated with SiC and kept at a growth temperature of 930 ^° C. by radio frequency induction heating, Furthermore, a B ₂ H6 concentration of 2 10 " ⁵ mol / min and a PH ₃ / B ₂ H6 molar ratio of 50 were set. At the same time, H, S, H ₂ Se, H ₁ Te, were diluted with H ₂ , mixed with the reaction gas and introduced into a quartz reaction tube while the amount supplied was controlled with a flow meter. The doped BP layer had a film thickness of about 2 microns. After the growth was completed, the silicon substrate was etched with HF - HNO3 removed and the carrier density was measured by the Van der Pauw method. The doped BP layer had an η conduction. An undoped layer had an n conduction and a carrier density of less than 5 × 10 ¹⁶ cm ^-3 Gas flow rate iten at 100ccm / min., 500ccm / min. and lOOOccm / min ..

which indicate the carrier density for the BP layer grown in the gas phase and which consisted of varying the amount of the doping gas supplied, consisting of H ₂ S, H ₂ Se and H ₂ Te diluted with H ₂ up to 300 ppm, are in Table I below and these flow rates correspond to the molar ratio between the H ₂ S, H ₂ Se, H ₂ Te and B ₂ H ₆ of 0.067, 033 and 0.67. As can be seen from the following Table 1, the carrier concentration increased with the increase in the amount of H ₂ S, H ₂ Se, H ₂ Te supplied.

Table I.

Relationship between the flow rate of H ₂ S, H ₂ Se, H ₂ Te and the carrier density

Carrier density

Flow rate (cm ³ / min.) Of H ₂ S, H ₂ Se, H ₂ Tc based on 300 ppm H ₂

100 500 1000

H ₂ S
H ₂ Se
H ₂ Te

8X10 ¹⁷ 1.5 XlO ¹⁸ 2X10 ¹⁸

5XlO ¹⁸ 8X10 ¹⁸ IXlO ¹⁹

9X10 ¹⁸

1.5XlO ¹⁹

1.5XlO ¹⁹

Example 5 There was a doping of BP with S, Se, Te on the

same way as in example 4 carried out under_

Use of B ₂ H ₆ - PCl ₃ - H ₂ as reaction gas. A' BP substrate with a (100) face for growth

of the crystal was coated on one with SiC

C-carrier set and maintained by radio frequency induction heating at a growth temperature of 1000 ⁰ C and B2H6 was introduced together with H ₂ carrier gas in a concentration of 2x10 ^-5 mol / min, in a quartz reaction tube. H ₂ as a carrier gas was introduced into phosphorus trichloride (PCI3), the PCl3 vapor pressure being controlled by changing the liquid temperature. The ratio between phosphorus trichloride and diborane (molar ratio PCI3 / B ₂ H ₆ ) was 2.5. H ₂ S, H ₂ Se or H ₂ Te was simultaneously introduced into the reaction gas in the same manner as in Example 4. As a result, a BP epitaxial layer having an η-line was obtained in a thickness of 2 microns. The carrier concentration for the BP layer grown in the gas phase obtained using H ₂ S, H ₂ Se and H ₂ Te, diluted with H ₂ to 300 ppm, as impurity doping gas at a molar ratio of H ₂ S / B ₂ H ₆ of 0.067, H ₂ Se / B ₂ H ₆ of 0.067, and H ₂ Te / B ₂ H ₆ of 0.067 was 1.5 10 ¹⁹ cm ^-3 , 1.7 10 ¹⁹ cm ^-3, and 2.0 x 10 ¹⁹ CiIi- ^J. The carrier density in the undoped grown BP layer was less than 5 × 10 ¹⁷ cm ⁻³ and the layer had an η conductivity. It has been found that within the temperature range. Ches between 950 and 1100 ⁰ C and the molar ratio range between H ₂ S, H ₂ Se, H ₂ Te and B ₂ H ₆ from ΙΟ " ⁴ to 10 a satisfactory layer doped with S, Se, Te was obtained, but that the Properties of the layer outside the ranges mentioned deteriorated significantly.

Example 6

JO

The F i g. 2 shows a schematic representation of a device for the method according to the invention. A J5 η-type silicon substrate 16 doped with phosphorus (P) and having a specific resistance of 10 Ohm χ cm and an area index (100) was placed on a C-carrier 15 coated with SiC. then helium carrier gas was introduced by opening a tap 6 on a helium bomb 1 to a reaction tube 14th

A radio frequency power source was applied to the water-cooled cooling coils 13, to bring the SiC-coated carbon carrier inductively to the temperature of the substrate 16 of 950 ⁰ C. Then a cock 8 was opened and diborane (B ₂ H ₆ ), diluted with H ₂ , was introduced from a bomb 3 into the reaction tube. The diborane concentration was 2 χ 10 ^-5 mol / min. On the other hand, by operating a three-way cock 12 and a cock 11 on a bomb 4, hydrogen was introduced into a vessel 10 into which liquid phosphorus trichloride (PCI3) 5 had been filled. The bubbling gas was introduced into the reaction tube 14 through a tap 9. The molar ratio between the phosphorus trichloride and diborane (PCbZB ₂ He) was 25. The phosphorus trichloride concentration was controlled by changing the flow rate of the hydrogen bubbling through and by varying the liquid temperature and thus the vapor pressure of the liquid phosphorus trichloride. The boron phosphide grown semiconductor device had a film thickness of 2 microns.

The surface of the grown layer was spike-shaped and flat, and it had satisfactory crystallinity when tested under reflective microelectron diffraction. The layer had a p-conduction and a Hall measurement showed a carrier concentration of 1 χ 10 ¹⁹ cm ^-3 and a mobility of 5 cm / 5 sec.

Example 7

A BP / Si composite semiconductor has been used as the single crystal semiconductor substrate used. The substrate consisted of a boron phosphide single crystal layer on top of a (100) face of an η-type silicon substrate. The single crystal layer used had a thickness between 500 and 10,000 Å. The single crystal layer with a mirror-shaped and flat surface showed stripes and Kikuchi bands when viewed under reflective electron diffraction, the show that it had excellent crystallinity.

On the above substrate of the BP / Si composite semiconductor, using the same procedures as in Example 6, a boron phosphide semiconductor layer was grown to a thickness of 5 microns by introducing a mixture of hydrogen and helium (He / H ₂ = 1) as a carrier gas from a helium bomb 1 and a hydrogen bomb 2 by operating the taps 6 and 7 at a growth temperature of 1000 ⁰ C, a diborane concentration of IxIO- ⁴ mol / min, and a PCI ₃ ZB ₂ H ₆ ratio of 20. The surface of the grown Layer was mirror-like and flat and had satisfactory crystallinity when tested under reflective electron diffraction. The surface had a p-conduction and the Hall measurement showed a carrier density of 5 10 ¹⁷ cm ^-3 and a mobility of 50 cm / V χ sec.

For this purpose 2 sheets of drawings

Claims (1)

Patent claims: 1. A method for the epitaxial growth of doped boron phosphide on a substrate, wherein boron hydrides or halides are reacted with phosphorus hydrides or halides at a temperature between 850 and 1100 ⁰ C, characterized in that the reaction mixture compounds of the general formula