Semiconductor Electronic Material Devices and Simple Circuits

Physics

NCERT

1   In an n-type silicon, which of the following statements is true:$\\$

Solution :

The correct statement is (c).$\\$ In an n-type silicon, the electrons are the majority carriers, while the holes are the minority carries. An n-type semiconductor is obtained when pentavalent atoms, such as phosphorus, are doped in silicon atoms.

2   Which of the statements given in Exercise 14.1 is true for p-type semiconductor.

Solution :

The correct statement is (d).$\\$ In a p-type semiconductor, the holes are the majority carriers, while the holes are the minority carries. A p-type semiconductor is obtained when trivalent atoms, such aluminium, are doped in silicon atoms.

3   Carbon, silicon and germanium have four valence electrons each. These are characterized by valence and conduction bands separated by energy band gap respectively equal to $(E_g)_c,(E_g)_{Si}$ and $(E_g)_{Ge}$. Which of the following statements is true?

Solution :

The correct answer is (c).$\\$ Of the three given elements, the energy band gap of carbon is the maximum and that germanium is the least.$\\$ The energy bang gap of the these elements are related as :$\\$ $(E_g)_C > (E_g)_{Si} > (E_g)_{Ge}$

4   In an unbiased p-n junction, holes diffuse from the p-region to n-region because

Solution :

The correct statement is (c).$\\$ The diffusion of charge carriers across a junction takes place from the region of higher concentration to the region of lower concentration. In this case, the p-region has greater concentration of holes than the n-region. Hence, in an unbiased p-n junction, holes diffuse from the p-region to the n-region.

5   When a forward bias is applied to a p-n junction, it

Solution :

The correct statement is (c).$\\$ When forward bias is applied to a p-n junction, it lower the values of potential barrier. In the case of forward bias, the potential barrier is opposed by the applied voltage. Hence, the potential barrier across the junction gets reduced.