SURFACE PROPERTIES OF GERMANIUM 



31 



mately linear fashion throughout most of the experimental range. The 

 change in Vb is approximately one-fifth the change in contact potential. 

 {Vb — Vo) is positive for the p-type sample and negative for the n-type 

 sample throughout most of the range. If the trap distribution on the 

 surface were symmetrical about the intrinsic position of the Fermi 

 level, then pbo would be equal to Uao and Vo would be zero. In this case 

 the space charge layers on n- and p-type germanium would be about 

 equally developed. All the experimental evidence on germanium indi- 

 cates that this is not the case but rather that — Vbti is much larger than 

 Vbp . This then means that Fo is negative and that the trap distribution 

 is unsymmetrical either in number or energy or both in such a way that 

 riao > PbO . 



In Table II values are given for the differences {Vb — Vbo), etc., 



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

 C.R-(C.R)o IN VOLTS 



Fig. 17 — Same as Fig. 15 for sample B, n-type. 



