685 



that the normahzed voltage at the p-intrinsic interface is given by 



V = -^(L) ^U - 2\nA. (44) 



The average normahzed field intensity over the intrinsic region is then 

 given by 



For A = 1, of course 



L 

 Unless the degree of asymmetry is great, 



~U 



will be small compared to vinity and Sav will still be almost 



2U 

 L • 



In order to present a simple quantitiative picture of the penetration 

 of the field into the interior of the intrinsic region it is convenient to 

 introduce the field penetration parameter rj defined by 



_ minimum field intensity 

 average field intensity 



For fixed intrinsic region thickness and small applied voltages, t? <$C 1, 

 indicating localization of the regions of high field intensity. For large 

 applied voltage, i? — > 1, implying substantial uniformity of field through- 

 out the intrinsic region. Subject to the assumptions (40) relations will 

 now be derived among the apphed voltage, the intrinsic layer thickness, 

 the asymmetry parameter A, and the field penetration parameter r]. 



The minimum field intensity occurs where ^ = 0. Therefore, from 

 (36) and (45) 



^ l2AiB + 1)]"- 

 2L~\U -/nA) 



Ehminating A from (46) by the use of (41) and L by the use of (43) 

 leads to 



2"\B + iY'MB) 



V 



/^^ 



U - Ink 



