In a p-n junction, the depletion region is 400 nm wide and an electric field of 5 × 105 V m–1 exists in it.

(a) Find the height of the potential barrier.


(b) What should be the minimum kinetic energy of a conduction electron which can diffuse from the n-side to the p-side.


Width of depletion region, d= 400 nm= 4×10-7 m

Electric Field, E= 5×105 Vm-1


(a) Let the height of potential barrier be V Volts.


We know that,


• E=V/d


• V=Ed


• V=5×105×4×10-7


• V=0.2 Volts


(b) The minimum kinetic energy required for diffusion of an electron from n-side to p-side


K.Emin= Potential barrier × Charge on an electron


= 0.2 V × 1.6 × 10-19 C


= 0.2 eV


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