HOLE IXJECTIOX l\ GEKMAMLWf 



353 



In Fig. 4 we show some plots of this sort. The ordinate is /p /, which 

 should approach y as the value of /(, becomes larger. The theory indicates 

 that a logarithmic plot should be used and that the abscissa should be made 

 jjroportioiial to transit time so that the case of no decay or zero transit time 



0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 



TRANSIT TIME,7-t, IN MICROSECONDS 



Fig. 4 — E.xlrapohiticii of measured hole and electron curreiUs to zero transit linic in 



order to determine 7. 



comes at the left edge.t The conclusion reached from this i)lot is that for the 

 case of the //-type sample, the value of 7 is substantially unity, — all the 



t It the lifetime of a hole is t, then the hole current at the points is I„ = ylt exp ( — //V) 

 where / is the transit lime to a point midway between the points, say a distance L from 

 the emitter. If the electric field is E = Al'/AA, then the transit time / = /,A/.,7i,,Ar. 

 Hence if In /,„ as determined from the ratio of conductivities is plotted afi;ainst / = LM. 

 fi„AV a straight line with intercej)! In 7/, and sloi)e - 1 r should he ohiained. 



