p-n JUNCTIONS IN SEMICONDUCTORS 



445 



upon 5(^ for various types of transition regions and to express the result as 

 a capacity. 



The justitkation for this pseudo-equilibrium treatment is as follows: 

 Under actual a-c. conditions the potential drop in the p- and n-regions them- 

 selves are small because of their high conductivity so that most of the po- 



FOR BOTH CASES-, 



._i r. 



-140 -120 -100 -80 -60 -40 -20 



20 40 60 80 100 120 140 160 

 DISTANCE, X, IN UNITS OF '-a=-^ 



Fig. 4 — Electrostatic potential and densities for p-n junctions. 



tential drop occurs across the transition region. On the />-side of the transi- 

 tion region a large supply of holes is available to modify the potential and 

 the fact that a current is flowing across the junction disturbs their concen- 

 tration negligibly; the electrons on the «-side are similarly situated. Hence 

 the distribution of holes and electrons in the transition region will be much 

 the same as for the pseudo-equilibrium case. The question of how the hole 



