i)P-N junction diode: It is a semiconductor device in which half of its region is P-type and other half is N-type.
ii) Depletion layer: The region where free electrons and free holes are absent is called depletion layer.
iii) Forward bias: If the positive terminal of external battery is connected to p – side and negative terminal is connected to n-side of p-n junction diode, it is said to be forward bias.
iv) Reverse bias of P-N junction diode: If the positive terminal of external battery is connected to n – side and negative terminal is connected to p-side of p-n junction diode, it is said to be reverse bias.