SURFACE PROPERTIES OF GERMANIUM 



29 



[G'-?)— ]. 



equation 21, and as Vb — Vbo becomes small and negative, c.p. decreases 

 and 8Vl goes through zero and approaches the positive maximum 



+ 



[(?'»?)+-■]■ 



For p-type germanium Ui/n is greater than pi/p so that the negative 

 maximum for 8Vl is greater than the positive maximum. Just the 

 opposite is true for n-type germanium. 



In this comparison of theory and experiment a tacit assumption has 

 been made that the germanium surface is uniform in its properties. It 

 might well be that this is not the case. The surface might be "patchy." 

 To estimate what effect patches or non-uniformities might have the 



10 



-0.15 -0.10 -0.05 0.05 0.10 0.15 0.20 0.25 0.30 0.35 

 C.P. -(c.p. Jo IN VOLTS 



Fig. 15 — Change of contact potential with illumination, SVl , versus c.p.; 

 experiment and theory sample D, p-type. 



