Photoelectric Properties 

 of lonically Bombarded Silicon 



By EDWIN F. KINGSBURY and RUSSELL S. OHL 



(Manuscript received March 25, 1952) 



In the course of investigation of the rectifying 'properties of silicon very 

 interesting photoelectric properties were found. The first photo-cells were cut 

 from bulk silicon in which a natural potential barrier tvas found. A typical 

 spectral characteristic of such a cell is shown. This early work was followed 

 by the discovery of the ionic bombardment method of producing photo active 

 silicon surfaces. The effects of the temperature of the target and of the energy 

 of the bombarding particles in the photoelectric properties is illustrated by 

 characteristic curves. Relative equi-energy spectral response characteristics as 

 a function of wavelength are illustrated. The photon efficiency as a function 

 of wavelength of a typical cell is shown. 



INTEODUCTION 



Because of the importance that barriers have come to assume in the 

 general field of semiconductors the authors have been urged to publish 

 results of their early experiments in this field. These experiments were 

 undertaken in the course of a search for semiconductive material suitable 

 for use as point contact rectifiers. 



Before March 1941 one of the writers discovered a well-defined bar- 

 rier having a high degree of photovoltaic response. The barrier was found 

 only in melts of some lots of commercially available high-purity silicon. 

 This barrier showed a high photovoltaic sensitivity to radiation from 

 incandescent lamps. 



The existence of this natural barrier was first observed in rods cut 

 from melts for resistivity measurements. These rods showed a high de- 

 gree of photovoltaic response, were found to have a high thermoelectric 

 coefficient, and had good rectifying properties. The fact that one end 

 of the rod developed a negative potential when ilhmiinated or heated 

 and that when supplied with a negative potential showed low resistance 

 to current flow across the barrier led to the terminology of n-type 



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