# Most Important Questions for Exam - Engineering Physics

Most Important Questions for Exam - Semiconductor Physics

Unit-1

Short Questions (2-Marks)

1. What are the limitations of the classical free electron theory?
2. Draw the dependence of density of states on energy in 1D, 2D, and 3D.
3. State Bloch's theorem and Bloch function.
4. What do you mean by E-K diagram ?
5. What is the range of energy bandgap in conductor, semiconductor, and insulator?
6. What are direct and indirect bandgaps?
7. What do you mean by effective mass?
8. Define forbidden energy gap.
9. Numericals on Occupation probability and Fermi energy, velocity.
1. Derive an expression for the fermi energy of a free electron gas (Sommerfield theory).
2. Obtain expression for density of states for a free electron gas in 3 dimension. show the variation of density of state with energy.
3. Discuss the Kronig-Penney model and show that how it explain the forbidden gap.
4. Distinguish between metals, semiconductors and insulators on the basis of band theory of solids.
Unit-2

Short Questions (2-Marks)

1. What do you mean by valence band, conduction band and forbidden gap?
2. What are extrinsic semiconductors.
3. What do you mean by carrier generation and recombination?
4. What is diffusion current.
5. Give examples of materials used for optoelectronic devices.
1. Show mathematically that, for an intrinsic semiconductor the fermi level lies exactly halfway between the top of the valence band and bottom of the conduction band.
2. Discuss the variation of the fermi level with temperature for an n-type semiconductor.
3. Derive an expression for drift current.
4. Explain Schottky and Ohmic metal-semiconductor junction in detail.

Unit-3

Short Questions (2-Marks)

1. Explain spontaneous and stimulated emission.
2. What do you mean by population inversion.
3. Write applications of semiconductor laser.
4. Discuss Fermi's golden rule.
5. What is Photovoltaic effect?
6. What do you mean by exciton.
1. What are Einstein coefficients. Draw expression for it.
2. Obtain expression for Joint density of states.
3. Discuss Drude model in detail.
Unit-4

Short Questions (2-Marks)

1. What is Hall effect.
2. Draw schematic diagram of four point probe method.
3. Draw schematic diagram of Hot point probe method.
4. List various parameters which can be extracted from I-V curve for a diode.