1040 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



suits. Wc hope to discuss this at a future date, (iii) The accuracy of the 

 measurements is not high. Some of the more directly-derivable quanti- 

 ties, such as s, should be known to 5 per cent, but a quantity 

 like (d'2s/d8)/(dZs/dY), which is only obtained after a long and elabo- 

 rate calculation involving a number of corrections, is perhaps uncertain 

 to 30 per cent. ^ 



VII. CONCLUSIONS 



This paper has presented results of combined measurements of field 

 effect, photoconductivity, change of photoconductivity with field, fila- 

 ment lifetime and surface photo-voltage, on slices of germanium. From 

 the measurements, the surface potential Y has been found at each point, 

 and the variations of the quantities (dZs/dV), s and {dI,,/d8)/(dI,s/dY) 

 with Y determined. 



It is a pleasure to record our thanks to W. L. Brown, for comments 

 on field effect techniques and many stimulating discussions, to H. R. 

 Moore, mIio constructed the high-voltage power supply, and to A. A. 

 Studna, who assisted in the experiments. We are also grateful to C\ 

 Herring for comments on the text. 



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