THE BELL SYSTEM 



TECHNICAL JOURNAL 



VOLUME XXXV JANUARY 1956 number 1 



Copyright 1956, American Telephone and Telegraph Company 



Diffused Emitter and Base Silicon 



Transistors* 



By M. TANENBAUM and D. E. THOMAS 



(Manuscript received October 21, 1955) 



Silicon n-p-n transistors have been made in which the base and emitter 

 regions were produced by diffusing impurities from the vapor phase. Tran- 

 sistors with base layers 3.8 X 10~ -cm thick have been made. The diffusion 

 techniques and the processes for making electrical contact to the structures 

 are described. 



The electrical characteristics of a transistor with a maximum alpha of 

 0.97 and an alpha-cutoff of 120 mc/sec are presented. The manner in which 

 some of the electrical parameters are determined by the distribution of the 

 doping impurities is discussed. Design data for the diffused emitter, dif- 

 fused base structure is calcidated and compared with the rneasured char- 

 acteristics. 



INTRODUCTION 



The necessity of thin base layers for high-frequency operation of tran- 

 sistors has long been apparent. One of the most appealing techniques for 

 controlling the distribution of impurities in a semiconductor is the dif- 

 fusion of the impurity into the solid semiconductor. The diffusion co- 

 efficients of Group III acceptors and Group V donors into germanium 

 and silicon are sufficiently low at judiciously selected temperatures so 



* A portion of the material of this paper was presented at the Semiconductor 

 Device Conference of the Institute of Radio Engineers, Philadelphia, Pa., June, 

 1955. 



