338 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1956 



7 



> 4 



LU 



o 

 > 



I 



0,5 1.0 1 



CURRENT F 



5 2.0 2.5 3.0 3.5 4.0 



LOW IN MILLIAMPERES PER CM^ 



4.5 



Fig. 4. — Anodic voltage -current curves for various resistivities of germanium. 



SCRATCHES AND PITTING 



The voltage- current curve of an electrolyte-germanium barrier is 

 very sensitive to scratches. The curves given in the illustrations were : 

 obtained on material previously etched smooth in CP-4, a chemical I 

 etch.* '' 



If, instead, one starts with a lapped piece of n-type germanium, the 

 electrolyte-germanium barrier is essentially "ohmic;" that is, the voltage 

 drop is small and proportional to the current. A considerable reverse 

 voltage can be attained if lapped n-type germanium is electrolytically 

 etched long enough to remove most of the damaged germanium. How- 

 ever, a pitted surface results and the breakdown voltage achieved is 

 not as high as for a smooth chemically-etched surface. 



The depth of damage introduced by typical abrasive sawing and 

 lapping was investigated by noting the voltage-current curve of the 



Br2 



Five parts HNO3 , 3 parts 48 per cent HF, 3 parts glacial acetic acid, ^0 P^-^t 



