DIFFUSED EMITTER AND BASE SILICON TRANSISTORS 



11 



DONORS 



ACCEPTORS 



DISTANCE 



(a) 



DISTANCE *• 



(b) 



Fig. 8 — Diagrammatic representation of (a) donor and acceptor distributions 

 and (b) uncompensated impuritj- distribution in a double diffused n-p-n tran- 

 sistor. 



plot of Nd — Na which would result from the distribution in Fig. 8(a). 

 Kromer has shown that a nonuniform distribution of impurities in a 

 semiconductor will produce electric fields which can influence the flow 

 of electrons and holes. For example, in the base region the fields between 

 the emitter junction, Xe , and the minimum in the Nd — Na curve, x', 

 will retard the flow of electrons toward the collector while the fields 

 between this minimum and the collector jvmction, Xc , will accelerate the 

 flow of electrons toward the collector. These base laj^er fields will affect 

 the transit time of minority carriers across the base and thus contribute 



* H. Kromer, On Diffusion and Drift Transistor Theory I, II, III, Archiv. der 

 Electr. Ubertragung, 8, pp. 223-228, pp. 363-369, pp. 499-504, 1954. 



