COMBINED MEASUREMENTS ON ETCHED GERMANIUM SURFACES 1029 



Table II • — 8.1 ohm cm ^-type Cycle 5. 

 Relative Light Intensity 0.25 



III and 1\'. Values of 8 were obtained from the photoconductivity signal, 

 as before, taking the actual ilhiminated length as the length of the 

 sample. In making use of the standard square-wave calibration for the 

 surface photo-voltage measurement (Section III), it is necessary to 

 allow for the fact that the measured capacity involves the whole length 

 of the sample, plus end and side fringing effects, whereas the surface 

 photo-voltage measurements im'ohcs only the illuminated length, plus 

 the fringe effect at the sides. 



The penultimate column in Tables III and 1\ shows the ratio of the 

 change in contact potential, measured in units of (kT/e), to the added- 

 carrier parameter 5, which was deduced from the photoconductivity. 

 This is not j^et, however, the true surface photo- voltage function 

 {dY/d8), since the observed change in contact potential includes also 

 the Dember potential AF/^"^ which occurs between the illuminated and 

 non-illuminated parts of the body of the semiconductor. The last column 

 in Tables III and lY shows the true values of (dY/d8), obtained by sub- 



