DC FIELD IN A SWEPT INTRINSIC" SEMICONDUCTOR 691 



Upon substituting (34) and (36) into (63) and setting f = U (12), 

 we obtain 



Ae'"" + 2AB = A In j^ , (65) 



or, because both terms on the left are negligible under the assumptions 

 (40)*, 



A ^ Ae'^^'K (66) 



Similarly, substitution of (35) and (36) into (63) and setting of ^ = 

 — V yields 



Ae'"" + 2AB = A"' In ^T+i , (67) 



or, by virtue of (40), 



A^A'^e'^^'K (68) 



Combining (66) and (68) we obtain 



F ^ C7 - 2 hi A. (69) 



This formula gives the normalized potential magnitude at the 2>-intrinsic 

 interface in terms of that (U) at the n-intrinsic interface and the asym- 

 metry parameter A. 



Now the condition ^ = U ior y = requires (from 38a and 39a) that 



for -1 < B < 1, 

 or 



(mf^Kl^y'' «in^>tanh^] = A-C (70b) 

 forB > 1. 

 In addition, the condition \j/ = —V ior y = L requires 



4(^r]-4(4-T •-■~'a= "■•' 



A''\C - I) 



for -1 <B < 1, 



* It will be shown later that (40) implies AB « 1. 



