7/29/2019 Engineering Physics2 UNIT-2

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Part-A

1. What is meant by semiconductor? Mention few properties of few conductors?

2. Distinguish between elemental and compound semiconductor?

3. Distinguish between intrinsic and extrinsic semiconductor.4. What are P type and N type semiconductor?

5. Explain the concept of hole in semiconductors.6. What are acceptor and donor impurities?

7. Sketch the Fermi level in energy band diagram of n type extrinsic semiconductor.

8. Mention the position of Fermi level in intrinsic and extrinsic semiconductors at 0K.

9. Define Fermi level in case of semiconductors. Mention its position in intrinsic and

extrinsic semiconductor at 0 K.

10. With increase of temperature the conductivity of semiconductor increases while thatof metals decreases. Give reasons.

11. Why do we prefer silicon for transistors and GaAs for laser diodes?

12. Mention some applications of Hall Effect.

13. The intrinsic carrier density at room temperature in Ge is 2.37 X 10-19

m-3

. If the

electron and hole mobility are 0.38 and 0.18 m2V

-1S

-1respectively, calculate the

resistivity.

14. The sample of silicon is doped with 1016phosphor atoms/m3. Find the hall voltage

in a sample with thickness 500 mm, area of cross section 2.25 X 10

-3

m

2

, current 1Aand magnetic field 10 X 104 Wb/m2.

15. Differentiate semiconductor from that of conductor and insulator with band diagram

and other properties.

Part-B

1. What is Hall effect? Derive an expression of Hall Coefficient for n typesemiconductor. Describe the experimental determination of Hall coefficient.

2. (i) Derive an expression for carrier concentration in intrinsic semiconductor.

(ii) Discuss the variation of Fermi level with temperature in the case of an intrinsic

semiconductor.3. Derive the expression for the number of electrons per unit volume in the conduction

band of N-type extrinsic semiconductor. Also discuss about the variation of Fermilevel with respect to temperature and impurity.

4. Obtain the expression of density of holes in the valence band of a P-type extrinsic

semiconductor and discuss the variation of Fermi level with respect to temperature

and concentration of hole.

Unit -2 Semiconducting Materials