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?
Depletion region width, d = 400 nm = 4 × 10−7 m
Electric field, E = 5 × 105 Vm−1
(a) Let the potential barrier be V.
The relation between the potential and the electric field is given by V = Ed
\[\Rightarrow\]V = E × d = 5 × d
Energy of any electron accelerated through a potential of V = eV
Also, the minimum energy of the electron should be equal to the band gap of the material.
∴ Potential barrier × e = 0.2 eV (e = Charge of the electron)