SEMI -CONDUCTOR DEVICES

The expected energy of the electrons at absolute zero is called

• (a) Fermi energy

• (b) Emission energy

• (c) Work function

• (d) Potential energ

When a semiconductor is heated, its resistance

• (a) Decreases

• (b) Increases

• (c) Remains unchanged

• (d) Nothing is definite

In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of

• (a) 1MeV

• (b) 0.1MeV

• (c) 1eV

• (d) 5 eV

The forbidden energy band gap in conductors, semiconductors and insulators are 1 2 EG , EG and EG3 respectively. The relation among them is

• (a) EG1 = EG2 = EG3

• (b) EG1 <EG2 <EG3

• (c) EG1 > EG2 > EG3

• (d) EG1 > EG2 < EG3

Wires P and Q have the same resistance at ordinary (room) temperature. When heated, resistance of P increases and that of Q decreases. We conclude tha

• (a) P and Q are conductors of different materials

• (b) P is N-type semiconductor and Q is P-type semiconductor

• (c) P is semiconductor and Q is conductor

• (d) P is conductor and Q is semiconductor

. In intrinsic semiconductor at room temperature, number of electrons and holes are

• (a) Equal

• (b) Zero

• (c) Unequal

• (d) Infinite

. Fermi level of energy of an intrinsic semiconductor lies

• (a) In the middle of forbidden gap

• (b) Below the middle of forbidden gap

• (c) Above the middle of forbidden gap

• (d) Outside the forbidden gap

At room temperature, a P-type semiconductor has

• (a)Large number of holes and few electrons

• (b) Large number of free electrons and few holes

• (c) Equal number of free electrons and holes

• (d) No electrons or holes

Which impurity is doped in Si to form N-type semi-conductor?

• (a) Al

• (b) B

• (c) As

• (d) None of these

. When p-n junction diode is forward biased, then

• (a) the depletion region is reduced and barrier height is increased

• (b) the depletion region is widened and barrier height is reduced

• (c) both the depletion region and barrier height are reduced

• (d) both the depletion region and barrier height are increased.