question

(a) why is an intrinsic semiconductor deliberately converted into an extrinsic semiconductor by adding impurity atoms ?

(b) explain briefly the two processes that occur in p-n junction region to create a potential barrier.

 

 

 

 

 

 

a) to increase the number density of charge carriers the intrinsic semiconductor deliberately converted into an extrinsic semiconductor

b)diffusion: during the formation of the p-n junction, due to the concentration gradient across the p and n sides, the motion of majority charge carriers give rise to the diffusion current.
drift: due to the electric field developed at the junction, the motion of the minority charge carriers due to the electric field is called drift.

at some point of time, the diffusion current equals drift current and p-n junction under equilibrium is formed and there is no net current.