Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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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. - Physics

Short Note

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?

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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

\[\Rightarrow\] V = 5 × 105 × 4 × 10−7 = 0.2 V
(b) To find: Kinetic energy required
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) 
Concept: p-n Junction
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HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 23 Semiconductors and Semiconductor Devices
Q 16 | Page 419
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