A single crystal layer of either cadmium sulfide or an alloy of cadmium sulfide and indium phosphide is epitaxially deposited on a substrate of cadmium sulfide by liquid phase epitaxy using indium as the solvent

Hawrylo, Frank Z.

NASA Technical Reports Server

States Patent [191 
[54] METHOD OF EPITAXIALLY DEPOSITING 
CADMIUM SULFIDE 
[75] Inventor: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
Frank Z. Hawrylo, Trenton, N.J. 
RCA Corporation, New York, N.Y. 
965,239 
Nov. 30,1978 
[51] In(. c1.2 ........................................... HOlL 21/208 
[52] US. c1. .................................... 148/171; 148/172; 
148A.5; 427/87; 29/572; 136/89 CD 
[58] Field of Search ........................ 148/171, 172, 1.5; 
427/87; 29/572; 136/89 CD 
1561 References Cited 
U.S. PATENT DOCUMENTS 
2,820,841 1/1958 Carlson et al. ................. 136/89 C D  
2,844,640 7/1958 Reynolds ........................ 136/89 CD 
3,051,839 8/1962 Carlson et al. ................. 136/89 CD 
3,565,702 2/1971 Nelson ................................. 148/171 
3,578,507 
3,585,071 
3,600,236 
3,687,743 
3,913,212 
3,922,553 
3,988,172 
4,074,305 
4,113,531 
4,143,235 
5/1971 
6/1971 
8/1971 
8/1972 
10/1975 
11/1975 
10/1976 
2/1978 
9/1978 
3/1979 
Chiang et al. ......................... 148/1.5 
Koelmans .......................... 29/589 X 
Marley, Jr. ........................... 148/1.5 
LeDuc ................................. 148/171 
Bachmann et al. .............. 148/171 X 
Bachmann et al. .............. 148/171 X 
Bachrnann et al. ................... 148A.5 
Johnston et al. ....................... 357/67 
Zanio et al. .......................... 148/174 
Duisrnan ......................... 136/89 CD 
Primary Examiner-G. Ozaki 
Attorney, Agent, or Firm-H. Christoffersen; D. S .  
Cohen 
[571 ABSTRACT 
A single crystal layer of either cadmium sulfide or an 
alloy of cadmium sulfide and indium phosphide is epi- 
taxially deposited on a substrate of cadmium sulfide by 
liquid phase epitaxy using indium as the solvent. 
10 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=20080006906 2019-08-30T03:10:39+00:00Z
4,203,785 a 1 
METHOD OF EPITAXIALLY DEPOSITING 
CADMIUM SULFIDE 
The Government has rights in this invention pursuant 
to Contract Number NAS1-14349 awarded by NASA, 
the National Aeronautics and Space Administration. 
BACKGROUND OF THE INVENTION 
The present invention relates to a method of epitaxi- 
ally depositing a layer which includes cadmium sulfide, 
and particularly to such a method which uses liquid 
phase epitaxy. 
Cadmium sulfide, either alone or alloyed with certain 
other materials, is a semiconductor material which has 
been used for making piezoelectric devices, solar cells, 
radiation detectors and the like. Cadmium sulfide is also 
a direct bandgap material having a bandgap of 2.4 Ev 
and therefore has possibilities for use in light emitting 
semiconductor diodes. However, cadmium sulfide has a 
melting point of about 1750" C. and its elements are 
highly volatile. Therefore, fabrication of this material 
requires highly sophisticated equipment and skills. To 
permit greater ease of making devices which include 
cadmium sulfide, it would be desirable to be able to 
simply and easily deposit layers of this material on a 
substrate. 
SUMMARY OF THE INVENTION 
A single crystal layer which includes cadmium sul- 
fide is epitaxially deposited on a substrate by placing the 
surface of the substrate into contact with a solution 
which includes cadmium sulfide dissolved in indium 
and cooling the solution to precipitate out the cadmium 
sulfide which deposits as a layer on the substrate. 
DETAILED DESCRIPTION OF THE 
INVENTION 
The method of the present invention includes placing 
in a furnace boat a mixture of cadmium sulfide and 
indium. If the layer to be deposited is an ailoy of cad- 
mium sulfide and indium phosphide, indium phosphide 
is also included in the furnace boat. 
The furnace boat may be of any well known structure 
used for liquid phase epitaxy, such as a tilt boat of the 
structure shown in the article of H. Nelson, "EPITAX- 
IAL GROWTH FROM THE LIQUID STATE AND 
ITS APPLICATION TO THE FABRICATION OF 
TUNNEL AND LASER DIODES', RCA Review, 
No. 24, page 603, 1963, or a slide boat of the structure 
shown in U.S. Pat. No. 3,565,702 of H. Nelson entitled, 
CONDUCTIVE LAYERS FROM THE LIQUID 
PHASE" issued Feb. 23, 1971. The furnace boat is 
generally of a refractory material such as graphite. 
A substrate of cadmium sulfide is also placed in the 
furnace boat. In a tilt boat the substrate is placed in the 
same well as the mixture but spaced from the mixture. 
In a slide boat the substrate is placed in a recess in the 
slide with the mixture being in a well in the boat. The 
cadmium sulfide substrate is of N type conductivity and 
has its basal plane oriented perpendicularly to the C- 
axis. The surface of the cadmium sulfide substrate on 
which the epitaxial layer is to be deposited and which is 
positioned in the furnace boat so as to be exposed, is the 
sulphur rich surface, designated B surface. 
The furnace boat and its contents are placed in a 
furnace tube. While maintaining a flow of either a re- 
"DEPOSITING SUCCESSIVE EPITAXIAL SEMI- 
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L 
ducing gas, such as hydrogen, or an inert gas, such as 
argon through the furnace tube, the furnace tube is 
heated to a temperature at which the indium melts and 
the cadmium sulfide and indium phosphide, is used, 
dissolve in the indium. This is about 600° C. to 650" C. 
The furnace tube is held at this temperature long 
enough, 10 minutes to one hour, to insure complete 
melting and homogenization of the solution. 
The furnace is then cooled at a rate of 3" to 6" C./mi- 
nute and after the solution is cooled about 10-20 de- 
grees, the substrate is then brought into conatct with the 
molten solution. With a tilt boat, the furnace boat is 
heated while maintained in a tilted position with the 
mixture being at the lower end of the boat and the sub- 
strate being held at the upper end. After the solution is 
formed the boat is then tilted in the reverse direction to 
flood the exposed surface of the substrate with the mol- 
ten solution. With a slide boat, the substrate is brought 
into contact with the solution by moving the slide until 
the substrate enters the well containing the solution so 
that the exposed surface of the substrate is brought into 
contact with the solution. The furnace boat and its 
contents are then further cooled. Cooling the solution 
causes some of the cadmium sulfide or the alloy of 
cadmium sulfide and indium phosphide to precipitate 
out of the solution and deposit as an epitaxial layer on 
the surface of the substrate. 
After an epitaxial layer of the desired thickness is 
deposited, the substrate is removed from the solution. 
With a tilt boat this is achieved by tilting the boat back 
to its original position. With a slide boat, the slide is 
moved to remove the substrate from the well which 
contains the solution. The substrate with the epitaxial 
layer thereon, can then be removed from the furnace 
boat. 
EXAMPLE 1 
Using a slide furnace boat of the structure shown in 
U.S. Pat. No. 3,565,702, a mixture of 3 grams of indium 
and 60 mgs of cadmium sulfide was placed in a well of 
the furnace boat. A cadmium sulfide substrate, oriented 
with the [OOOl] basal plane perpendicular to the C axis, 
was placed in the recess in the slide of the furnace boat 
with the sulfur rich surface of the substrate facing up- 
wardly. The furnace boat and its contents were placed 
in a furnace tube and heated to a temperature of about 
650" C. After the mixture in the furnace boat became 
molten, the temperature was reduced to 630" C. and the 
slide was moved to carry the substrate into the well 
containing the molten solution. The furnace was then 
further cooled at a rate of about 5' C./minute causing 
some of the cadmium sulfide in the solution to precipi- 
tate out and deposit on the surface of the substrate. The 
slide was then moved to carry the substrate with the 
cadmium sulfide layer thereon out of the well contain- 
ing the solution. The substrate was removed from the 
furnace boat and residual indium left on the surface of 
the cadmium sulfide layer was removed by etching in 
sulfuric acid at room temperature. The composition and 
single crystal structure of the epitaxial layer was veri- 
fied by x-ray diffractometry. 
EXAMPLE 2 
Using a slide furnace boat, a mixture of 2 grams of 
indium, 1 gram of cadmium, 4 mgs of cadmium sulfide, 
1 mg of zinc and 3 mgs of indium phosphide were 
placed in a well of the furnace boat. A cadmium sulfide 
substrate of the same type as used in Example 1 was 
4,203,7145 
3 4 
placed in the recess in the slide. The furnace boat and its indium and the layer deposited consists essentially ol 
contents were placed in a furnace which was heated to cadmium sulfide. 
about 650" C .  The furnace boat was maintained at this 5. A method in accordance with claim 2 in which the 
temperature sufficiently to assure that the cadmium solution comprises cadmium sulfide and indium phos- 
sulfide, zinc and indium phosphide completely dis- 5 phide dissolved in indium and the layer deposited com- 
solved in the indium. The temperature was then re- prises an alloy Of cadmium sulfide and indium phos- 
duced at a rate of about 5" G./minute and at 610" G., the phide. 
slide was moved to carry the substrate into the solution. 65- A method of epitaxially depositing a layer which 
me cooling of the furnace was continued at a rate of 50 includes cadmium sulfide on a substrate which method 
C./min. A layer of an alloy of cadmium sulfide and Io 
indium phosphide (CdSInp) was deposited on the sur- placing in a furnace boat the substrate and a mixture 
face of the substrate. The slide was then moved to carry 
the layer thereon was removed from the furnace boat. 
The deposited layer had a red tint or luster to it. The 
composition and single crystal structure of the epitaxial 
layer was determined by x-ray diffractometry. 
the Of: 
including cadmium sulfide and indium, 
the indium becomes molten and the cadmium sul- 
fide dissolves in the molten indium, 
placing a surface of the substrate into contact with 
the molten solution, and 
cooling said furnace boat to precipitate out at least 
some of the cadmium sulfide which deposits on the 
substrate. 
in accordance with claimn in which the 
substrate is of cadmium sulfide. 
with claim 7 in which the 
layer is deposited on a sulfur rich sudace of the sub- 
9. p, method in accordance with claim 7 in which &lie 
mixture placed in the furnace boat consists essentially of 
cadmium sulfide and indium and the layer deposited 
consists essentially of cadmium snlfide. 
10. A method in accordance with claim 4 in which 
the mixture placed in the furnace boat comprises cad- 
mium sulfide, indium phosphide, and indium and the 
layer deposited comprises an alloy of cadmium sulfide 
and indium phosphide. 
the substrate out of the SoIution and the substrate with Ileati% said boat to a temperature at which 
15 
I claim: 
1. A method of epitaxially depositing a layer which 2o 
includes cadmium sulfide on a substrate which method 
comprises the steps of: 
placing a surface of the substrate into contact with a 
solution which includes cadmium sulfide dissolved 
in indium, and 25 strate. 
cooling said solution to precipitate out at least some 
of the cadmium sulfide which deposits on the Sub- 
strate. 
2. A method in accordance with claim 1 in which the 
substrate is of cadmium sulfide. 
3. A method in accordance with claim 2 in which the 
layer is deposited on a sulfur rich surface of the sub- 
strate. 
4. A method in accordance with claim 2 in which the 
solution consists essentially of cadmium sulfide and 35 
7. A 
8. A method in 
30 
lil ,!a * >tu 
45 
50 
55 
65 
' UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION 
PATENTNO. : 4,203,785 
DATED May 20,  1980 
INVENTOR(S) : Frank Zygmunt Hawrylo 
is hereby corrected as shown b l o w :  
It is certified that error appears in the above-identified patent and that said Letters Patent 
Column 1, l i n e  62: "basal plane" should be - - [ O O O l ]  b a sa l  
plane--. 
column 2 ,  l i n e  4:  should be --if--. 
Signed and Sealed this 
Fi/h  Day o f  August1980 
ISEALJ 
Attest: 
SIDNEY A. DIAMOND 
Commissioner of Patents and Trademarks 


Method of epitaxially depositing cadmium sulfide

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