Question
Explain, with the help of a circuit diagram, how the thickness of depletion layer in a p-n junction diode changes when it is forward biased. In the following circuits which one of the two diodes is forward biased and which is reverse biased?
(i)
Solution
When applied voltage is such that n-side of the diode is connected to the negative terminal of the battery and p-side is connected to positive terminal of the battery, the applied voltage is opposite to the barrier potential. The direction of applied potential is opposite to that of the built-in potential.
Hence, the effective barrier potential becomes VB - V, and the energy barrier across the junction decreases. Thus, the junction width decreases. 
In the figure given,
(i) p-n junction is forward biased.
(ii) p-n junction is reverse biased.
