1046 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



z 



>- 



w 



>- 

 in 



3.0 



2.5 



2.0 



1.5 



1.0 



0.5 



-0.5 



-1.0 



-1.5 



-5 



-2 



-1 



Y-Ln\ 



Fig. 1 — The fit between Equations (13) and (14) and the experimental data. 

 The circles and dots give the experimental data for the n and jo-type samples 

 respectively and the solid straight lines represent Equations (13) and (14). 



But it is also possible, once A^(j'), x and (cr^o-p)^'^ are known, to calculate 

 the expected behavior of the surface photo-voltage and surface recombi- 

 nation rate at high light intensities, and compare the answer with the 

 experimental findings. We hope to discuss this matter in a later paper. 



III. ANALYSIS OF THE EXPERIMENTAL DATA BY USE OF THE DELTA- 

 FUNCTION APPROXIMATION 



Let US first consider the interpretation of our field effect measure- 

 ments by means of (11). We start by finding empirical expressions that 

 describe the observed dependence of (d'Zs/dY) on Y (Fig. 6 of the pre- 

 ceding paper^). Except at values of (F —(n X) close to the extremes 

 reached one may fit quite well by a hyperbolic cosine function. Fig. 1 

 shows the function whose hyperbolic cosine is {d'2s/dY)/(d'Es/dY)min 

 plotted against Y — tn X. From this figure we find: 



22.6 ohm-cm n-type: 



^" ) = 4.5c/i[0.36(y - (n X) - 0.8] 



(13) 



(for (F - (n X) > -4 



