*Most Important Questions for Exam - Semiconductor Physics*

__Unit-1__

*Short Questions (2-Marks)*

- What are the limitations of the classical free electron theory?
- Draw the dependence of density of states on energy in 1D, 2D, and 3D.
- State Bloch's theorem and Bloch function.
- What do you mean by E-K diagram ?
- What is the range of energy bandgap in conductor, semiconductor, and insulator?
- What are direct and indirect bandgaps?
- What do you mean by effective mass?
- Define forbidden energy gap.
- Numericals on Occupation probability and Fermi energy, velocity.

*Long Answer Questions (8-marks)*- Derive an expression for the fermi energy of a free electron gas (Sommerfield theory).
- Obtain expression for density of states for a free electron gas in 3 dimension. show the variation of density of state with energy.
- Discuss the Kronig-Penney model and show that how it explain the forbidden gap.
- Distinguish between metals, semiconductors and insulators on the basis of band theory of solids.

__Unit-2__*Short Questions (2-Marks)*

- What do you mean by valence band, conduction band and forbidden gap?
- What are extrinsic semiconductors.
- What do you mean by carrier generation and recombination?
- What is diffusion current.
- Give examples of materials used for optoelectronic devices.

*Long Answer Questions (8-marks)*- 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.
- Discuss the variation of the fermi level with temperature for an n-type semiconductor.
- Derive an expression for drift current.
- Explain Schottky and Ohmic metal-semiconductor junction in detail.

__Unit-3__*Short Questions (2-Marks)*

- Explain spontaneous and stimulated emission.
- What do you mean by population inversion.
- Write applications of semiconductor laser.
- Discuss Fermi's golden rule.
- What is Photovoltaic effect?
- What do you mean by exciton.

*Long Answer Questions (8-marks)*- What are Einstein coefficients. Draw expression for it.
- Obtain expression for Joint density of states.
- Discuss Drude model in detail.

__Unit-4__*Short Questions (2-Marks)*

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

*Long Answer Questions (8-marks)*- How you can measure divergence and wavelength of semiconductor laser.
- Explain the determination of resistivity of material by using Four point probe method.
- Explain the determination of resistivity of material by using Van der Pauw method.
- Discuss Hot point probe method in detail.

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