THE BELL SYSTEM 



TECHNICAL JOURNAL 



VOLUME XXXV JULY 1956 number 4 



Copyright 1956, American Telephone and Telegraph Company 



The Effect of Surface Treatments on 



Point-Contact Transistor 



Characteristics 



By J. H. FORSTER and L. E. MILLER 



(Manuscript received January 23, 1956) 



A description is given of the electrical properties of formed point con- 

 facts on germanium. A useful technique for observation of the equipotentials 

 surrounding such contacts is described. The contrasting properties of donor- 

 free and donor-doped, contacts, used as diodes or transistor collectors are 

 emphasized. 



It is shown that unformed point contacts {which have electrical properties 

 largely determined by a surface barrier layer) , may exhibit analogous dif- 

 ferences. Such changes are produced by chemical treatments calcidated to 

 influence properties of a soluble germanium oxide film on the surface. 



The above information is applied to a study of transistor forming as it 

 is done in present point-contact transistor processing. It is shown that high 

 yields from the forming process can be expected on oxidized surfaces, and 

 (hat chemical ivashes which remove soluble germanium oxide drastically 

 lower forming yields. These and, other effects are evaluated as sources of 

 variability in forming yield. 



Table of Contents 



I 



[l . Introduction 768 



2. Pro]ierties of Formed Point Contacts 770 



I 2.1 Effects of Electrical Forming on Point Contacts 770 



1 2.2 Donor-Free and Donor-Doped Contacts 774 



767 



