Properties of Ionic Bombarded Silicon 



BY RUSSELL S. OHL 



(Manuscript received August 23, 1951) 



This paper deals with a new and very interesting technique by which the 

 properties oi silicon surfaces are altered very materially by bombardment 

 with ions of such gases as hydrogen, helium, nitrogen and argon. The change 

 in rectifying properties has been of special interest but there have been con- 

 sidered also changes in the structural features of the material itself. The 

 effects of bombardment on the rectifying properties are illustrated by a series 

 of characteristic curves systematically arranged to bring out the effects of 

 the several variables of experiment such, for example, as ion velocity, in- 

 tensity of bombarding current, length of time of bombardment, kind of gas, 

 and the temperature of the specimen during bombardment. The effect of 

 bombardment on materials contaminated with impurities is also illustrated. 

 It is of particular practical importance that silicon contaminated with boron 

 to the point where it shows relatively little rectification can be modified by 

 bombardment to make it even better than most unbombarded materials. 



Some years ago, the writer discovered that the electrical properties of 

 silicon surfaces could be greatly modified by bombardment with positive 

 ions. The ions in fjuestion were generated in a low pressure discharge in 

 some gas, like hydrogen, helium or nitrogen, and after passing through a 

 perforated cathode were accelerated to a suitable velocity before imping- 

 ing on the surface to be treated. This scheme may be contrasted with 

 other methods subseciuently reported for treating germanium^ in which 

 high-velocity ions were derived from radioactive sources. Preliminary 

 results of the present research were described in a paper entitled Silicon 

 Transistors, by W. J. Pietenpol and the writer, presented at an Elec- 

 tronics Conference held at the University of Michigan, June 22, 1950. 

 Since that time exploration has continued with a \'iew both to learning 

 about basic principles and about possible practical applications. 



Editorial Note — Since the resurgence of interest in point-contact rectifiers, 

 considerable research has been carried on into the characteristics of silicon and 

 germanium. The author of this paper was a pioneer in this new field of study, as 

 evidenced, for example, by Patent No. 2,378,944, applied for on July 26, 1939, and 

 Patent No. 2,402,839, applied for on March 27, 1941. More recent work has been 

 descrilied in a large numl)or of text books and technical papers such as Electrons 

 and Holes in Semi-Condnclors l)y William Shockley, D. \'an Xostrand, 1950, and 

 numerous papers by Lark-Horowitz published mostly in Physical Review. The 

 work described in the accompanying paper is a continuation of this long research. 



1 Brattain and Pearson, Phys. Rev., 80, Dec. 1950. 



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