POINT-CONTACT TRANSISTOR SURFACE EFFECTS 769 



expended towards the analysis and understanding of the physical mecha- 

 nisms of the point-contact transistor since its announcement in 1948, a 

 complete design theory for these transistors is not available. This lack 

 probably I'esults partially from a more general interest in the readily 

 designable junction transistor types, and partially from the relative 

 complexity of the device itself. Actual!}^ the physical mechanisms which 

 account for the operation of this device have their counterparts in at 

 least three basically unique devices: the point diode, the junction tran- 

 sistor, and the filamentary transistor. 



Thus, although the empirical knowledge of point-contact transistor 

 design and operation is large enough to allow a reasonable degree of 

 designability, and manufacture of these transistors in large quantities is 

 possible, there are, from time to time, manufacturing problems which 

 are often difficult to solve without sound theoretical understanding of 

 the physical mechanisms which make the device work. 



This article is concerned with describing the results of a general study 

 of the physical properties of a few specific kinds of point contacts. The 

 kinds of contact studied have been those of specific interest to those 

 concerned with manufacture and processing of point-contact transis- 

 tors. This investigation was conducted in parallel with the final develop- 

 ment for manufacture of the hermetically sealed point-contact transis- 

 tor. The study of these properties has led to practical solutions of several 

 problems encountered during manufacture of point-contact transistors, 

 and has provided experimental data which is of interest in consideration 

 of the basic physical mechanisms involved in the operation of the point- 

 contact transistor. 



The work to be described, primarily experimental in nature, follows 

 in Sections 2, 3 and 4. In section 2, the properties of formed, or electri- 

 cally pulsed point contacts, and their relation to the source of output 

 characteristic anomalies often responsible for lowering forming yields 

 in point-contact transistor production is discussed. The properties of 

 point contacts which have received no electrical forming in the conven- 

 tional sense are considered in section 3. The electrical properties of these 

 contacts, used as diodes or transistor collectors, are shown to be de- 

 I pendent on chemical history of the etched germanium surface. Thus 

 I "chemical forming" of point contacts is possible. Section 4 deals with 

 application of these results to forming problems which arise during 

 manufacture of point-contact transistors. The important relation be- 

 tween the chemical history of the surface and the forming on that sur- 

 face is considered. 



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