1028 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 195G 



Table I — 22,6 ohm cm n-TYPE Cycle 12. 

 Relative Light Intensity 0.082 



AF2 by use of the formula: 8 = wtpiAVn/Kmpo', where p, is the intrinsic 

 resistivity and fm the length of the illuminated part of the slice. The 

 fourth column shows the apparent effective mobility in the presence of 

 light,* obtained from the field effect signal voltage AF3 in the presence 

 of light, using the same formula as that giving iJen . The last column 

 shows the surface recombination velocity, which is proportional to 8" 

 for fixed light intensity, the constant of proportionality being deter- 

 mined by comparison with measurements of the fundamental mode 

 lifetime. 



The results of typical surface photo-voltago nms are sho\\n in Tables 



* One must be careful to avoid thinking of Mtif* as a true field clfect mobilit.y, 

 since it is really a sum of two cjuite different components: the true held effect 

 mobility Meff , and a term, proportional to thickness of the slice, arising from the 

 jjhotoconductivity. 



?! 



