CONDUCTIVITY-MODULATED SILICON RECTIFIER 



983 



with increasing distance into the tt region. At sufficiently high reverse 

 bias the field may sweep into the P^ region. 

 Breakdown in silicon^ is a multiplicative process described by 



1 r 



(3-1) 



where M is the multiplication factor, W is the space-charge width, and 

 ai is the rate of ionization which is a strong function of the field in the 

 junction. For a PIN structure, the field is constant, at breakdowTi 

 M approaches x , and 



aiW = 1. 



(3-2) 



The ionization rate at breakdown is then a simple function of the wddth 

 of the intrinsic region. McKay and Wolf^^ have considered a^ as a func- 



Na-No 



p 



(C) 



E 



(d) 



Fig. 3 — Impurit}^ charge and field distribution in PIN and PttN junctions. 



