794 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1956 



Table VI 



/c(0, -10). 

 a(5.0, -10) 

 Noisv 



Point 



Beryllium Copper Collector 



Phosphor Bronze Collector 



Occasion 



Before Forming 



-0.75 

 1.5 

 Yes 



After Four 

 Forming Pulses 



-0.50 

 



Yes 



Before Forming 



-0.80 

 1.5 



Yes 



After Four 

 Forming Pulses 



-2.5 

 2.0 

 No 





alpha invariably requires at least three and sometimes many more-, 

 ''shots", although it can be done. This type of formed unit does not 

 exhibit excessive noise in the a-I^ sweeping gear. However, pulsing of 

 the beryllium copper points on the latter kind of surface, in similar fash- 

 ion, invariably results in loss of alpha and never eliminates the exces- 

 sive noise. Initially, the pulsing decreases the Ico magnitude, but con- 

 tinued pulsing will eventually cause large increases in this case. These 

 results provide circumstantial evidence, at least, that the treated sur- 

 face and the point are operationally free of any donor element and that 

 the transistor collector barrier involved is at the germanium surface. 

 For example, in Table VI are given some typical data obtained during 

 pulsing of points on a superoxol-etched surface after treatment with 

 near boiling zinc chloride-ammonium chloride solder-flux. A tungsten 

 emitter was used.* 



3.4 Discussion of Experimental Results 



.3.4.1 Effects of the Chemical Treatment on the Superoxol-Etched Surfaces 



It might be presumed that an inversion layer and a relatively high 

 surface conductivity is responsible for the increase in negative floating 

 potential and reverse current observed on the superoxol-etched n-ger- 

 manium surface after the HF treatment. On the other hand, if it be 

 assumed that at the etched surface, in room air, an inversion layer ex- 

 ists which does not introduce excessive surface conductivity, one can 

 say that the effect of the HF treatment is merely to raise the surface 

 potential, (i.e., to reduce the barrier height for electrons). This might 



* Alpha values are usually lower in any given situation when the conventional 

 chisel-type beryllium copper emitter point is replaced by an etched tungsten 

 point. 



