The resistance of a p-n junction is low, when forward biased and is high, when reverse is biased. Explain.

Explanation

When a p-n junction is formed, a small potential difference (factitious battery) is set up across the depletion layer. When the junction diode is reverse biased, the polarity of the applied d.c., source aids the fictitious battery. Due to this, potential drop across the junction increases and diffusion of holes and electrons across the junction decreases. It make the width of the depletion layer larger. As a result, diffusion of charge carriers across the junction decreases and we can say that resistance of p-n junction increases. When p-n junction is forward biased, the polarity of applied d.c., source opposes the fictitious battery. As a result diffusion of charge carriers across the junction increases and hence resistance of p-n junction and width of depletion layer decreases.