Electronic Devices and Circuits
Engineering Sciences 154

Diode i-v Characteristics

Some preliminaries

Diffusion currents components

Jn = Dn dn/dx  and Jp = -Dp dp/dx

Drift currents components

Jn = q n mn E   and  Jp = q p mp E

Einstein relation

Dn/mn = Dp/mp VT

"Mass Action Law"

pn0 nn0 = pp0 np0 = pi ni = ni2= B T3 exp(-EG/VT)

Shockley equation for the diode i-v characteristic
I(VA) = A q ni2 {Dp/Lp Nd + Dn/Ln Na}[ exp(VA/VT) - 1]
I(VA) = Isat [ exp(VA/VT) - 1]


Working model of real silicon diode


 
 


 

 


 

Semilog version of the "Shockley" ("ideal") current-voltage characteristic

 


 

See supplimentary discussion of reverse bias diode breakdown

 
 

Current-voltage characteristic of a "real" silicon diode. 
(a) Generation-recombination region.  (b) "Ideal" or Shockley diffusion current region. (c) High-injection current region. (d) Series resistance effect.  (f) Reverse leakage current due to generation-recombination and surface effects. (After S. M. Sze, Physics of Semiconductor Devices)
See supplimentary discussion of reverse bias diode breakdown