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Publication numberUS3630693 A
Publication typeGrant
Publication dateDec 28, 1971
Filing dateApr 6, 1970
Priority dateJun 5, 1968
Publication numberUS 3630693 A, US 3630693A, US-A-3630693, US3630693 A, US3630693A
InventorsMoody Jerry W, Reid Francis J
Original AssigneeAvco Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Infrared detecting materials
US 3630693 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent [72] Inventors Jerry W. Moody 3,351,502 11/1967 Rediker 148/ 177 Worthington, Ohio; 3,462,323 8/1969 Groves 148/175 [2]] A l N J. Reid, Syosset, N.Y. 3,463,680 8/1969 Melngailis et a1 148/172 o. [22] 6, 1970 Prirnary Examiner-L. Dewayne Rutledge [45] Patented Be 28 1971 Assistant Exammer-E. L. Wetse [73] Assign Avco corponuon Attorneys-Charles M. Hogan, [mm P. Garfinkle and Jerome Cincinnati, Ohio Original application June 5, 1968, Ser. No. 734,715, now Patent No. 3,558,373, dated Jan. 26, 1971. Divided and this application Apr. 6, 1970, Ser'. No. 31,063

ABSTRACT: Infrared detector material is formed by the epitaxial growth of a single crystal alloy of the two Ill-V com- [54] gf z g f zg MATERIALS pounds lnAs and lnSb on an lnAs substrate. In the method of g such growth, a liquid solution is prepared with excess indium 29/194, solvent, lnSb, and sufficient InAs to saturate the indium at 148/ 1.6 500 C. The lnAs substrate, oriented in the 111 direction is imllll- B3211 15/00 mersed in the solution, and the substrate and the solution are [50] Field of Search 29/ l 94; brought to equilibrium at approximately 500 C. Slowly lower- 148/ 1.6, 171; 75/134 T ing the solution temperature causes a single crystal to be epitaxially grown on the substrate as a solid homogeneous [56] Rehnnm cited lnAs-lnSb solution. Composition of the crystal is a function of UNITED STATES PATENTS solution composition and may be controlled by dissolving 3,312,570 4/]967 Ruehrwein selected quantities of InSb in the solution.


vgivuvvu AYYYAYAVAVAVA INDIUM WWW/ JERRY w MOODY BY E J. REID M ATTORNEY 1 INFRAREU verse-nus MATERIALS This is a division of application Ser. No. 734,715 filed June 5, l968hw US. Pat. No. 3,558,373, dated Jan. 26, I971.

BACKGROUND Our invention relates to' infrared "detector materials involving semiconductor crystals; anthrnore particularly relates to epitaxially grownsingle" crystal alloys of III-V compounds: In this connection, it may be' 'pointed out that by'groupll l elements'we mean aluminum gallium and indium; and by group V elements, we mean phosphorous, arsenic, and antimony. Various compounds of group lll'and group V elements have been found to have properties which, for some applications, aresupe'rior to those of the-groupIV semiconductor materials. They offera wider range of energy gaps; Several methods have become known for the preparation of various single III-V compound crystals; Homogeneous alloys by chemical vapor deposition have been made of certain gallium, aluminum, indium, phosphides-and arsenides, but attempts to make'other pseudobinai'y III-V alloys (e.g'., lnAs and InSb alloys) by chemical vapor deposition haveno't met withsucce'ss;

After the investigation of lIl'-V compounds was begun, it was suggested-that alloysof 'these compounds could be made, thereby extending-the range of'pr'operties' of the Ill-V compounds. Of particular interest to us'were' alloys of' indium arsenic and indium antim'onid'e. These have been found to' have an energy gap ranging from'ab out 0.1 ev. or less-to 0.45 ev., depending"oncomposition" and temperature, making them especially well suited forinfrared detection.

At least three methods have been used to make alloys of lnAs and InSb. These have usually resulted in polycrystalline alloys, or at bes'tin nonhom'ogeneoussingle crystal alloys; The properties of lnAs-lnSb alloys" have been deterrnin'ed from such polycrystalline or nonhomogeneous single crystal alloys; Although the art'has forseveral yearsappreciated 'the desirability of single crystalhoniog'eneous solidsolutions of Ill-V compounds; and althoog'hseveral attempts h'ave been made to producesuch crystals; to our knowledge none of 'the attempts madep'riorto our'in'ventioh have been successful.

The earliest attempt toproduce homogeneous ingots was the annealing of finecompressed powders of lnAs and InSb. Although this method did produce'ingots'with homogeneous regions, the ingot itself was not homogeneous. This methodtakes anywherefrom several weeks to several months and results in polycrystalline ingots.-

Zone recrystallization, similar to zone refining, has also been used. However, this method, while producing ingots with homogeneous regions; producespolycrystalline ingots;

Directional freezinghas' also been used, but it too produces polycrystallineingots.

There is needfor an infrared detector material utilizing a single crystal homogenous alloy of Ill-V compounds.

There is a need for a rr'iethod'w'hich can be used 'to produce single crystal homogenousalloys of III-V compounds.

There is a needfor a composition which can be used to produce single crystal homogenous alloys of III-V compounds.

It is therefore an object of our invention to provide infrared detector material utilizing a single crystal homogenous alloy of III-V compounds.-

It is a further object" of our invention to provideepitaxially' grown homogeneous alloysof Ill-V compounds on a suitable substrate.

A further more specific object-of our invention is to'provide a method and a composition fertile-epitaxial'growthof a solid homogeneous solution of lnA's and InSb on' a substrate of either lnAs or InSb;

Further objects and features of our invention will be apparent from the following specification and'claims when considered in connection with the accompanying drawings illustrating several embodiments of our invention;

SUMMARY OF THE INVENTION The invention involves, in one aspect, a n'ew'infi'ared'detector structure; In anotheraspect; it involves a methodfor producingasingle crystal alloy of two lII-V- compounds; such" as for example lnAsand InSb, the'm'ethod'comprising; (a) melting the two Ill- V compounds and'a'su'itable solvent, such as excess indium, in a crucible; (b eff ctirig the saturation of thesolvent with one of thecomp'ounds, such as for example lnAs; (c) immersinga suitable prepared 'substratein the solution, the substrate comprising a crystal having-a lattice structure and spacing similar to that of the III V compounds'dis solved in the solvent, such asfor example an' lnAs substrate; (d) effecting growth of an alloycrystal on the substrate-by lowering/the temperature of the solution; (e) 'andremoving the substrate andthe'grown alloy crystal from the solution; wherein said compounds crystallize onthe substrate to form a single crystal with improved homogeneity.

The invention also involves a composition which is a'solution for use inthe epitaxial growth of 'crystalscomprisin'g: (a) a solvent such as, for example, indium; (b) 'a'firstlll-V' com-- pound, such as for example lnAs; dissolved in the solvent; and

(c) a second lll-V compound, such as for exam'plelriSb, dis solved in the solvent. The solution is particularly useful when an excess indium solvent is saturated in either th m; or the InSb.

DESCRIPTIONOF THE VIEWS FIG. 1'- is a view in front elevation'of anapparatususeful' with our invention to produce crystals, the apparatus being shown with a segment removed to expose, in vertical section, the inside of the-apparatus;

FIG. 2 is a triangular coordinate diagram illustratingrthe DETAILED DESCRIPTION Apparatus used by us is similar to a Czochralslti crystal pulling apparatus and is illustrated in-FIG. 1. Generally, it comprises a suitable cylindricalcasing l0'witha sealable top 12. The casing has a pedestal 14 to supporta-graphite crucible 16.

A substrate holder 18, which-can be amodified'Czochralslti pulling rod, extends through the top 12- and'is longitudinally (i.e., vertically) movable. The rod, however, should not be a good heat conductor since we do not want'heat'loss through the rod. An RF or resistance heating coil 20 surrounds the casing 10 for heating the crucibleand its'con'tents'.

Suitable ternperature-sensing devices, such as thermocouple transducers, may be contained bytwo thermocouple tubes such as 2211 and 22b. One such thermocouple tube 2 2:; positioned within the substrate holder 18 isconnected by awire 24 to a temperature-indicating device (not shown) and senses-the temperature of the crucible contents;

In general, out method begins by obtaininga=soliition oftwo selected Ill-V compounds preferably having acommon group III element. This" is done by dissolving the compounds in a suitable solvent which we prefer to be an excess of the common group III element. We prefer to dissolve a sutficient quantity of one of the III-V compoundssothatwe can saturate the solution in that compound" at a'selected-equilibrium temperature. The quantity of the other lll -V compound is selected inorder to result in a desired crystalcomposition.

Thus the two Ill-V compounds are first melted together with the solvent to obtain the desired solution, and the solution is homogenized. A substrate is then immersed in the solution and equilibrated with it at an equilibrium temperature. The substrate should be a material which has the same lattice structure as each of the III-V compounds and as nearly as practical the same lattice spacing. We prefer to use a substrate of one of the two III-V compounds of the solution, and in particular of the III-V compound in which the solution is saturated.

Such a substrate when immersed in and equilibrated with the solution provides a favorable site for precipitation. As the solution then is cooled, a single crystal alloy is epitaxially grown on the substrate. The composition of the epitaxial layer is a function of the solution composition. After growth, the substrate is withdrawn, treated, and tested in ways familiar to those skilled in the art.

We have found it desirable to soak the substrate in the solution at equilibrium prior to initiating growth. This is especially helpful when we plan to cool at a fast rate such as approximately 200 C. per hour. In such case, we have "soaked" the substrate for 2 hours before, and the substrate and grown crystal 2 hours after, growth.

To grow lnAs-lnSb alloy crystals according to the preferred embodiment of our invention, we first obtain a solution of InAs and lnSb dissolved in indium. The solution is obtained by melting together suitable amounts of lnAs, lnSb and excess indium in the crucible 16. Heat is supplied from the heater 20. Of course, prior to melting, the substrate holder 18 is maintained out of the crucible 16 so that a suitably prepared substrate can be positioned in a lateral slot in the holder 18 at the raised position of 30a.

After the indium, lnAs, and lnSb are melted and the solution 32 in the crucible 16 is homogenized, the substrate holder 18 is lowered, and the substrate is immersed in the solution 32 at the lowered position of 30b. The substrate and the solution are equilibrated at a temperature which is between the melting point of indium (155 C.) and the melting point of the substrate which in the case of lnAs is 942 C. and in the case of lnSb is 525 C. We have at times used an equilibrium temperature of about 500 C. If the solution is saturated in lnAs, we prefer to use an lnAs substrate. As we cool the solution 32, a single crystal alloy of lnAs and InSb is obtained on the substrate by epitaxial growth.

FIG. 2 and FIG. 3 illustrate the compositions of some of the specific examples we have performed and the crystals we have obtained. The coordinates are for mole percentages of indium, arsenic, and antimony. The lines 50 and 51 represent a range of liquid solution compositions, and the lines 52 and 53 represent the range of crystal compositions. In the examples illustrated in FIG. 2, the solutions were equilibrated at approximately 500 C. before cooling and crystal growth was begun. In the examples illustrated in FIG. 3, 400 C. was the approximate equilibrium temperature.

In performing the examples, the indium, indium arsenide, and indium antimonide used were substantially pure so that the compounds, substrate and alloy consisted essentially of the elements in the proportions and ranges specified. However, it is obvious that other proportions may be used and that additional impurities could be either unintentionally or intentionally introduced.

The following examples illustrate the process and the composition of the invention using particular materials, steps and conditions. It is to be understood that these examples are furnished by way of illustration and are not intended to be by way of limitation.

EXAMPLE I Indium, lnSb, and sufficient lnAs to saturate about 20 grams of indium at 500 C. were melted together to obtain a solution, illustrated by the point 54 in FIG. 2, comprising in mole percentages-1,10 percent arsenic (1.36 percent lnAs), 18.12 percent antimony (22.44 percent lnSb), and 80.78 percent indium (72.20 percent excess indium). This solution was equilibrated with an immersed lnAs substrate oriented in the [III] direction, at 500 C., and was then cooled 20 C. at the natural cooling rate of the furnace of 197 C. per hour.

A single crystal epitaxial layer was grown 42 microns thick and comprising 10 percent lnSb and percent lnAs as illustrated at point 56 in FIG. 2.

EXAMPLE II Indium, lnSb and sufficient lnAs to saturate about 20 grams of indium at 500 C. were melted together to obtain a solution comprising, in mole percentages 78.08 percent indium, 21.18 percent antimony, and 0.74 percent arsenic, as illustrated at point 58 in FIG. 2. The solution was equilibrated with an immersed lnAs substrate, oriented in the [III] direction at 500 C., and was cooled 18 C. at a rate of 5 C. per hour.

A single crystal epitaxial layer was grown comprising 24.0 percent InSb and 76.0 percent lnAs, as illustrated at point 60 in FIG. 2.

EXAMPLE III Indium, lnSb and sufficient InAs were melted together to obtain a solution comprising, in mole percentages, 75.04 percent indium, 24.30 percent antimony, and 0.66 percent arsenic. The solution was equilibrated with an immersed lnAs substrate at 500 C. and was cooled 19 C. at a rate of 1.6 C. per hour.

A single crystal epitaxial layer was grown comprising 50 percent lnSb and 50 percent lnAs.

EXAMPLES IV-VI Further similar examples are illustrated in FIG. 2. In all the examples I-VI, and lnAs substrate was equilibrated with a solution saturated in lnAs at 500 C.

EXAMPLE VII Indium, lnSb, and sufficient InAs to saturate about 20 grams of indium at 400 C. were melted together to obtain a solution comprising, in mole percentages, 91.32 percent indium, 8.6 percent antimony, and 0.08 percent arsenic, as illustrated at point 62 in FIG. 3. The solution was equilibrated with an immersed lnAs substrate oriented in the [111] direction at 400 C., and was cooled 40 C. at a rate of 5C. per hour.

A single crystal epitaxial layer was grown 70 microns thick and comprising 17.5 percent lnSb and 82.5 percent lnAs as illustrated at point 64 in FIG. 3.

EXAMPLES VIII and IX Further similar examples are illustrated in FIG. 3. In all the examples VII-IX, lnAs substrate was equilibrated with a solution saturated in lnAs at 400 C.

EXAMPLE X A solution of 20 grams of indium and 3 grams of lnSb was heated to 300 C., the 3 grams of lnSb saturating the solution in lnSb at 300 C. An ingot of lnAs was positioned in the solutlon overnight to attempt to saturate the solution in lnAs. An lnSb substrate was positioned in the solution and the solution temperature was lowered 23 C. at a rate of 6 C. per hour. An epitaxial was formed on the substrate.

We prefer, for making infrared detectors, to obtain an alloy of approximately 50 percent or 60 percent lnSb because the alloy exhibits an energy gap minimum of 0.1 ev. at approximately this composition.

It is to be understood that while the detailed drawings and specific examples given describe preferred embodiments of our invention, they are for the purposes of illustration only, that the apparatus of the invention is not limited to the precise details and conditions disclosed, and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims.

wherein the substrate consists essentially of indium antimonide.

4. An article of manufacture comprising a substrate consisting of a wafer composed of a compound selected from the group consisting of indium arsenide and indium antimonide having grown thereon a single crystal of a pseudobinary indium arsenide-indium antimonide allay.

t t i l Attesting Officer UNITED S'IATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3,630,693 Dated December- 28, 1971 Inventor-(s) Jerry W. Moody and Francis J. Reid It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Line 6 of Abstract, 'III" should read "[III]".

Column 1, lines 27 -28, "arsenic" should read "'arse'nide".

1, line 69, "a method and a composition for the epitaxial growth of a solid should read "an epitaxially grown solid".

Column 3, line "1,10 percent" should read "1.10 percent".

Column 4, line 36, "and" shouldread "an".

4, line 64, "epitaxial was" should read epitaxial layer was".

4, line 67, "ev." should read "eV".

Signed and sealed. this 27th day of February 1973..

(SEAL) Attest:


ROBERT GOTTSCHALK I Commissioner of Patents

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3312570 *May 29, 1961Apr 4, 1967Monsanto CoProduction of epitaxial films of semiconductor compound material
US3351502 *Oct 19, 1964Nov 7, 1967Massachusetts Inst TechnologyMethod of producing interface-alloy epitaxial heterojunctions
US3462323 *Dec 5, 1966Aug 19, 1969Monsanto CoProcess for the preparation of compound semiconductors
US3463680 *Nov 25, 1966Aug 26, 1969Massachusetts Inst TechnologySolution growth of epitaxial layers of semiconductor material
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4876210 *Mar 4, 1988Oct 24, 1989The University Of DelawareSolution growth of lattice mismatched and solubility mismatched heterostructures
US5011564 *Mar 17, 1989Apr 30, 1991Massachusetts Institute Of TechnologyEpitaxial growth
U.S. Classification148/33, 438/47, 117/60, 428/642, 117/939, 117/67, 428/620
International ClassificationC30B19/06, C30B19/00, G01J5/28, G01J5/10
Cooperative ClassificationG01J5/28, C30B19/062
European ClassificationC30B19/06F, G01J5/28
Legal Events
Sep 29, 1988ASAssignment
Effective date: 19870828
Jul 25, 1988ASAssignment
Effective date: 19880712