Q.No.222: - Describe the motion of electron and holes in a semiconductor.

Q.No.222: - Describe the motion of electron and holes in a semiconductor.

Ans: - In a semiconductor the current flows due to the motion of electrons and shifting of holes. The electrons occupy the place of holes and made a hole in their own place and the upcoming electron take the place of that hole and so on. So in semiconductors the current due to electrons flow in one direction and the current due to shifting of holes flow in other direction. 

Q.No.218: - Discuss the diffusion across a pn junction.

Q.No.218: - Discuss the diffusion across a pn junction.

Ans: - The free electrons in the n-region are attracted toward the p-region of diode they are attracted toward the p-region due to majority of positive charge and diffuse across the junction into the p-region where they combine with holes.

Q.No.217: - Describe a diode and how a pn junction is formed?

Q.No.217: - Describe a diode and how a pn junction is formed?

Ans: - If a piece of intrinsic semiconductor silicon is doped so that one part is n-type and the other is p-type, a pn junction forms at the boundary between the two regions and a diode is created. The p-region has many holes (majority carriers) from      the impurity atom and very small quantity of thermally generated free electrons (minority carriers). The n-region has electrons as majority charge carriers which come from impurity atoms and very small quantity of holes which are created due to break known of bonds.