Method for producing a single crystal of In{hd x{b Ga{hd 1{118 x{b P
United States Patent 1191 Nishizawa et al.  
 1 1 Apr. 29, 1975 1 METHOD FOR PRODUCING A SINGLE CRYSTAL OF IN GA P [75] Inventors: Jun-ichi Nishizawa; Ken Suto;  
 Yasuo ()kuno, all of Sendai, Japan [73] Assignce: Zaidan Hojiri Handotai Kenkyu Shinkokai, Sendai-shi, Japan 221 Filed: Dec. 27, 1972 211 Appl. No.: 318,884  
 [52] US. Cl. 156/624; 148/171; 148/172;  
  75/134 &#39;1; 252/623 GA [51] Int. Cl. H011 7/38 158| Field of Search 148/16, 171l73;  
 75/134 T; 252/623 GA [56] References Cited UNITED STATES PATENTS 3,278,342 10/1966 John et a1. 148/].6 3,414,441 12/1968 (iershenzon et al. 252/623 GA 3,614,549 111/1971 Lorenz et al 148/171 X 3,628,998 12/1971 Blum et al. 148/171 OTHER PUBLICATIONS Scifres et al., Physical Review B, Vol. 5, No. 6, Mar. 15, 1972. PP. 2206-2215.  
 Logan et al., Journal of Applied P/rvsias, Vol. 42, No. 6, May 1971, pp. 2328-2335.  
 Hakki et al., Journal of Applied Physics, Vol. 41, No. 13, Dec. 1971), pp. 529l5296.  
 Primary kIrumim&#39;rG. Ozaki Attorney, Agent, or Firm-Craig &amp; Antonelli [57] ABSTRACT A single crystal of ln ,Ga ,P(O l.\&#39; (l.9) having the desired l-.\&#39; value is produced when an In melt including P whose mole ratio to In is less than about 0.2 and Ga whose mole ratio to P is between (1.\&#39;)M,.  
 and 2(1-.\&#39;)M, wherein M,. is mole ratio of P to 1n in the ln melt is heated at a temperature higher than a solidus temperature which ranges from 800C. to 1 150C. ofa single crystal of ln ,.Ga, .,.P to he obtained for 1() hours to 21) hours, and cooled to a room temperature or some practical temperature higher than the room temperature at a cooling rate of about 2C/hour to about 50C/hour.  
 10 Claims. 2 Drawing Figures METHOD FOR PRODUCING A SINGLE CRYSTAL OF IN GA P The present invention relates to a method for producing a single crystal of In Ga P, more particularly to a method for producing In Ga -P by utilizing a liquid phase epitaxial method.  
  Single crystals of In Ga P have recently attracted much interest since they are useful for light-emitting diodes which emit efficient radiation up to the green portion of the visible spectrum.  
  Generally, single crystals of In,Ga, ,P are grown by a liquid phase epitaxial method in which In is used as a melt.  
  It is, however, difficult to obtain single crystals of In, Ga, ,P having a desired value of x.  
  For controlling the value of in the single crystals of In,Ga, ,P in the paper of Elaboration et proprietes optiques dalliages Ga In P by H. Rodot et al., in Comples Rendus De L&#39;Academie Des Sciences, Vol. 269 B, (September 1969) pp. 381-384, P is diffused into a ln-Ga melt, and in the paper of Electroluminescent Properties of lnGaP grown by LPE on GaAs by B.W. Hakki, in 137 National Meeting of Electrochemical Society, Los Angeles (1970), Abstract No. 74, pp. 204-206. the molar ratios of InP and GaP which are provided as the source of P and Ga are controlled.  
  An object of the present invention is to provide a novel method for producing a single crystal of In, Ga, ,P wherein O l.\&#39; 0.9, i.e., x is greater than 0.1 and less than 1.0, by utilizing the liquid phase epitaxial method.  
  Another object of the present invention is to provide a method for producing a single crystal of In,Ga, ,P l.\&#39; 0.9) having the desired .r value (0.1 1).  
  A further object of the present invention is to provide a method for producing a single crystal of In,Ga, ,P (0 l.\ 0.9) wherein the .r value is easily controlled.  
  For obtaining the above-mentioned objects, in the present invention, the mole ratio M of Ga to P in the In melt is controlled between /2( l.\&#39;)M, and 2( I.\&#39; )M, in the In melt, wherein Mp is the mole ratio of P to the In in the In melt, for obtaining In,Ga, ,P, and wherein 0 M,, 0.2.  
  These and other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following specification and claims, taken in conjunction with the accompanying drawings in which:  
  FIG. 1 shows a sectional view of an apparatus wherein In,Ga ,P according to the present invention is obtained; and  
  FIG. 2 is a diagram showing a relationship between the 1-.\ value of In,Ga,-,P obtained by the present invention and the mole ratio of Ga to P in the In melt.  
  A crystal, In,Ga, P, having desired value of l-x is obtained, when a quartz ampoule I, wherein In melt 2, a certain amount of phosphorous 3 whose mole ratio to In(M,.) is less than about 0.2. and a certain amount of Ga4 whose mole ratio M to P in the In melt is controlled between (when the mole ratio of P in the In melt is Mp), /2(I )Mp and 2(1-.\&#39;)M, are introduced is dis posed in a quartz tube 5 disposed in a furnace 6, and the quartz ampoule 1 is heated at a temperature higher than a solidus temperature which ranges from 800C. to 1150C. of a single crystal of In Ga P to be ob tained by the furnace 6 for from about 10 hours to about 20 hours, and is cooled to a room temperature at a cooling rate of from about 2C/hour to about 50C/hour. It will be understood that the single crystal may be cooled from a temperature between about 200C. from the solidus temperature to room temperature, i.e., about 25C.  
  When the amount of In, P and Ga are 4.000 gr., 0.140 gr., and 0.200 gr., respectively, single crystals of In,Ga, ,P having a value of 0.660, 0.665, 0.655 a..u 0.699 for l-x are obtained. And also, when the amount of In, P and Ga are 4.000 gr., 0.140 gr. and 0.315 gr., respectively, single crystal of In Ga P having 0.76 as a value of 1.\&#39; is obtained.  
  Numerous experiments were conducted by the pres ent inventors and the results of the experiments are shown in FIG. 2.  
  In FIG. 2, a vertical direction shows the 1-x value of In Ga P, and a horizontal direction shows mole M of Ga to P in the In melt.  
  As apparent from FIG. 2, when mole M of Ga to P in the In melt is controlled between /2(I.\&#39;)M, and 2(1.\&#39;)M,,, wherein Mp is mole ratio of P to In in the In melt, a single crystal of ln Ga P having desired value of I.\&#39; can be obtained. And also, it is apparent that, for obtaining single crystals of ln Ga, ,P having desired value of l-x, a preferable range of mole ratio M of Ga is between I.\&#39;)M, and (3/2) (1-.\&#39;)M and especially between I.\)MP and (5/4) I.\&#39;)M,,.  
  However, when l-x value of In Ga P is over 0.9, that is, is less than 0.1, the above-mentioned relationship between mole ratio M of Ga to P in the In melt and mole ratio M, of P to In is not suitable. Therefore, the present invention is suitable for a method for producing single crystals of In Ga, P wherein the range of l-x value is more than 0 but less than 0.9.  
  In the above-mentioned embodiment, though the single crystal of In,Ga, ,P is obtained in a closed tube,  
 that is, in the quartz ampoule, it is understood that the present invention is applicable to another type of liquid phase epitaxial method, such that, a method wherein In melt including Ga and P is contacted with a seed material, such as GaAs and GaP, heated at a temperature lower than that of the In melt. It will be appreciated that the temperature of the In melt should be kept at a temperature higher than a temperature ranging from 800C. to 1 C. (the solidus temperature of the desired crystal) which temperature of the melt is dependent on the single crystal to be obtained. The difference in temperature may be several degrees, e.g., 5 to 50C.  
  While the invention has been explained in detail, it is to be understood that the technical scope of the present invention is not limited to that of the foregoing embodi ment but applicable to all liquid phase epitaxial methods as stated in the claims.  
 What is claimed is:  
  l. A method for producing a single crystal of In Ga P wherein 0 1.\&#39; 0.9, comprising the steps of:  
 preparing an In melt; introducing P so that its mole ratio to In in the melt is less than about 0.2 into the In melt;  
 introducing. Ga whose mole ratio to P in the In melt is between V2(1.\&#39;)M and 2( l-x)M wherein Mp is mole ratio of P to In in the In melt, into the In melt;  
 heating the In melt including P and Ga at a temperature higher than a solidus temperature of a single crystal of ln ,Ga .,P to be obtained. for a period of from about 10 hours to about 20 hours; and  
 cooling the resultant ln melt to room temperature at a cooling rate of about 2(/hour to about 5()C/hour.  
  2. A method for producing a single crystal of In, Ga, ,P according to claim I, wherein the mole ratio of Ga to P in the ln melt is between &#34;/4( )M,- and (3/2) l.\&#39;)M,  
  3. A method for producing a single crystal of In Ga ,P according to Claim 1, wherein the mole ratio of Ga to P in the ln melt is between /-l( l.\&#39;)M, and (5/4)( l.\&#39;)M,  
  4. A method for producing a single crystal according to claim I, which further comprises the steps of introducing said In melt, P and Ga into an ampoule. and closing said ampoulc prior to heating the ln melt including P and Ga.  
  5. A method for producing a single crystal according to claim I, wherein the ln melt including P and Ga is heated in a closed container.  
  6. A method for producing a single crystal of ln,-. Ga ,.P wherein l.\&#39; comprising the steps of:  
 preparing an ln melt;  
 introducing P so that its mole ratio to In in the melt is less than about 0.1 into the ln melt; introducing Ga so that its mole ratio to P in the ln M,- is the mole ratio of P to In in the ln melt. into ln melt; disposing the ln melt including P and Ga in a furnace; disposing a seed material at a different portion in the furnace from the portion at which ln melt is disposed; heating the ln melt including Ga and P at a temperature higher than a solidus temperature of a single crystal of ln,Ga ,P to be obtained. for about 10 hours to about 20 hours: heating the seed material at a temperature lower than that of In melt; Contacting the ln melt with the seed material; and cooling the ln melt to a room temperature at a cooling rate of about 2C./hour to about 50C./hour. 7. A method for producing a single crystal of In,. Ga ,P according to claim 6, wherein the mole ratio of (la to P in the ln melt is between l.\)M,. and (3/2)( l-.\&#39;)M,..  
  8. A method for producing a single crystal of ln Ga P according to claim 6. wherein the mole ratio of Ga to P in the ln melt is between /s( l \&#39;)M, and  
  l )M 9. A method for producing a single crystal according to claim 6. wherein the seed material is GaAs or GaP.  
  10. A method for producing a single crystal according to claim 6. wherein the mole ratio Mp of P to&#39;ln in the ln melt is greater than 0.