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THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 



age rate Pmax • (-Pmax is the staukonstante of Kromer.) The holes probably 

 achieve this rate when their energy is near the middle of the valence 

 band. Under these conditions the power input from the electric field 

 must be no greater than Fmax : 



From this it follows that 



qEu ^ Pr, 



u ^ PmaJqE, 



(5.1) 



(5.2) 



so that the drift velocity Avill decrease mth increasing field at sufficiently 

 high fields. 



Furthermore, if the \\idth of the valence band is less than the energy 

 gap, then a hole cannot acquire enough energy to produce hole electron 

 pairs. Thus in such a case, the negative resistance range should be reached 

 before breakdown effects occur. 



In Fig. 5.1 we illustrate the general trends of the u versus E curve, to 

 be expected if the staueffekt occurs. As is indicated, the maximum drift 

 velocity will be referred to as iim ■ It occurs at a field Em . Since we are 

 here concerned A\dth principles rather than details, no attempt has been 

 made to indicate the square root range in which u is proportional to E^^^. 

 This range has been observed by E. J. Ryder ' and shown by G. C. 

 Dacey^'^ to control hole flow in space charge limited hole currents in 

 germanium and has been treated theoretically. ' Dacey has also in- 

 vestigated the effect of the square root law upon the D(t) curves for the 

 p-n-p structure of Section 4 and reports that the effects are so unfavor- 

 able that no negative resistance is to be expected. 



The staueffekt opens the attractive possibility of making negative 

 resistance devices in which the current decreases with increased dc 

 voltage so that negative resistance will be exhibited over a wide fre- 

 quency range. Unfortunately, when the boundary conditions are taken 



Fig. 5.1 • — Qualitative representation of drift velocity versus field as affected 

 by "staueffekt." 



