592 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1956 



have been performed in this field. A fairly large group of these exist, and 

 it remains to describe them in detail. We shall begin with the study of 

 the diffusion of lithium in p-type germanium. 



At the outset a matter having to do with the diffusion 'potential de- 

 mands attention. This is the potential which arises, for example, in 

 p-type material, because the mobility of a hole is so much greater than 

 the mobility of a lithium ion. In consequence, holes diffuse into regions 

 containing high concentrations of lithium more rapidly than lithium ions 

 can diffuse out to maintain space charge neutrality. As a result such re- 



o 



2 

 O 



o 



ai 

 in 



\ 



10'5 



N IN CM-3 



10' 



Fig. 20 — Relaxation time as a function of temperature and concentration com- 

 puted from equation (10.25) using the data of Figs. 18 and 19. 



