Method For Growing Germanium Epitaxial Films

Abstract

A method for growing germanium epitaxial films is disclosed. Initially, a silicon substrate is preconditioned with hydrogen gas. The temperature of the preconditioned silicon substrate is then decreased, and germane gas is flowed over the preconditioned silicon substrate to form an intrinsic germanium seed layer. Next, a mixture of germane and phosphine gases can be flowed over the intrinsic germanium seed layer to produce an n-doped germanium seed layer. Otherwise, a mixture of diborane and germane gases can be flowed over the intrinsic germanium seed laser to produce a p-doped germanium seed layer. At this point, a bulk germanium layer can be grown on top of the doped germanium seed layer.

What is claimed is: 
     
         1 . A method for growing germanium epitaxial films, said method comprising:
 preconditioning a silicon substrate with hydrogen gas at a first temperature;   decreasing said first temperature of said preconditioned silicon substrate to a second temperature;   flowing germane gas over said preconditioned silicon substrate to form an intrinsic germanium seed layer on said silicon substrate;   increasing said second temperature of said preconditioned silicon substrate to a third temperature;   flowing a mixture of diborane gas and germane gas over said intrinsic germanium seed layer to produce on p-doped germanium layer; and   growing a bulk germanium film layer on top of said p-doped germanium layer.   
     
     
         2 . The method of  claim 1 , wherein said preconditioning further includes preconditioning said silicon substrate with hydrogen gas at approximately 3E 31 4  mBar for approximately 60 minutes at approximately 750° C. 
     
     
         3 . The method of  claim 1 , wherein said decreasing further includes decreasing said first temperature from approximately 750° C. to approximately 350° C. at approximately 2° C. per minute. 
     
     
         4 . The method of  claim 1 , wherein said flowing germane gas further includes flowing germane gas over said preconditioned silicon substrate at approximately 1.5E −3  mBar for approximately 120 minutes. 
     
     
         5 . The method of  claim 1 , wherein said increasing further includes increasing said second temperature of said preconditioned silicon substrate from approximately 350° C. to approximately 600° C. at approximately 2° C. per minute. 
     
     
         6 . The method of  claim 1 , wherein said gas mixture includes an approximately 1:1 mixture of diborane and germane gases. 
     
     
         7 . The method of  claim 1 , wherein said gas mixture is flowed over said germanium seed layer at approximately 6E −4  mBar for approximately 30 minutes. 
     
     
         8 . The method of  claim 1 , wherein said bulk germanium film layer is intrinsic germanium film. 
     
     
         9 . The method of  claim 1 , wherein said bulk germanium film layer is doped germanium film. 
     
     
         10 . The method of  claim 1 , wherein said growing further includes flowing germane gas over said preconditioned germanium layer at approximately 1.5E −3  mBar for approximately 480 minutes.