DIFFUSED p-n JUNCTION SILICON RECTIFIERS 



665 



in this paper were fabricated by using phosphorus as the donor impurity. 

 In order to make the extremely low resistance contact to the tt side of 

 the junction that is desirable in rectifiers, acceptor nnpurities are dif- 

 fused into the opposite side of the x silicon slice. Boron was selected 

 from the several possible acceptor type impurities to use for the fabri- 

 cation of these devices. A configuration of the diffused slice is shown in 

 Figure 2. 



2.3 It will be shown in Section 3 that there are limits to the thick- 

 nesses of the three regions, N-{-, x, P+, due to the nature of the opera- 

 tion of these rectifiers With present techniques, it is necessary to keep 



^LOW-RESISTANCE CONTACTSn 

 / . . _ -\ 



ACTIVE p-n 



JUNCTION 



Fig. 2 — Diffused silicon rectifier configuration. 



the thickness of the t region to the order of two or three mils (thou- 

 sandths of^an inch). 



2,4 In the diffusion process of introducing impurities in silicon for 

 the purpose of creating junctions or ohmic contacts, the diffusant is 

 deposited on the silicon and serves as an infinite source. The resulting 

 concentration of the diffusant is given by 



9 rx/\/iDt , 



c = Cc 1 - 4- / ^ dy 



V TT ''0 



(1) 



= Co erf c y 



where C = concentration at distance x below surface 

 Co = concentration at surface 



D = diffusion constant for impurity at temperature of dif- 

 fusion 



