A HIGH-FREQUENCY DIFFUSED BASE GERMANIUM TRANSISTOR 33 



30 46 60 75 90 



TIME IN MILLIMICROSECONDS 



>" 



-15 



15 



30 45 60 75 90 



TIME IN MILLIMICROSECONDS 



105 



120 



136 



Fig. 5 — Transmission of a 50 millimicrosecond pulse at emitter currents up 

 to 18 ma by a typical unit. (Courtesy of F. K. Bowers). 



region is of the order of 



and this is to be compared with injected hole density at the base region 

 iside of the emitter junction. The relation between the injected hole 

 density and the current density may be approximated by^ 



J. 



w 



where pi = hole density at emitter side of base region 



w = width of base region 



jA short calculation indicates that the emitter efficiency should remain 

 'high at a current density of an order of magnitude higher than 1,800 

 |amp/cm'. The measurements were not carried to higher current densities 

 jbecause the voltage drop across the spreading resistance in the collector 

 was producing saturation of the collector junction. 



CONCLUSIONS 



Impurity diffusion is an extremely powerful tool for the fabrication 

 of high frequency transistors. Moreover, of the 50-odd transistors which 



