POINT-CONTACT TRANSISTOR SURFACE EFFECTS 



787 



4.5 

 4.0 



3.5 

 3.0 



< 2.5 



I 

 Q. 



< 2.0 

 1.5 

 1.0 

 0.5 



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 



CURRENT, Ig, IN MILLIAMPERES 



4.5 



5.0 



Fig. 10 

 collectors. 



Comparison of alpha-emitter-current characteristics for unformed 



Curve II, Fig. 3, indicates that the «(/£), obtained after the HF treat- 

 ment, is comparable to that of a phosphor bronze collector formed con- 

 ventionally on the same etched surface before treatment. (It turns out 

 that conventional electrical forming on the etched surface after the HF 

 treatment is more difficult, and in cases as referred to above, where the 

 a is not initially high, requires an excessive number of pulses to bring 

 the a to a normal value.) 



In Table III are listed the maximum and minimum values of some 

 transistor parameters found on the same superoxol-etched surface be- 

 fore and after the HF treatment (point spacing about 2 mils). 



It is seen that the effect of the subsequent HF treatment after the 

 superoxol etch is at least in some locations on the treated surface to in- 

 crease the /c(0, —10) and the average a, in some cases to values ap- 

 proaching those encountered in conventionally formed point-contact 

 transistors. There is also a lowering of the forward current of the un- 

 formed collector point after the HF treatment. It is not to be implied 

 from this table that the Ico is always found to be low on fresh superoxol- 

 etched surfaces. Actually high values of 7c(0, —10) have been occa- 

 sionally found on surfaces freshly etched in superoxol. However, these 

 collectors seldom have high values of average a, and it is suspected that 

 here the higher reverse current is associated with excessive surface 

 conductivity. Treatment of such a surface with HF always serves to 

 increase the average a, and decrease the forward emitter current, with 



