PTU B.Tech ECE 1st Semester May 2019 75363 SEMI CONDUCTOR AND OPTOELECTRONICS PHYSICS Question Papers

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Roll No.

Total No. of Pages : 02

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Total No. of Questions : 09

B.Tech. (ECE) (2018 Batch) (Sem.-1,2)

SEMI-CONDUCTOR AND OPTOELECTRONICS PHYSICS

Subject Code : BTPH-105-18

M.Code: 75363

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Time: 3 Hrs.

Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION - B & C have FOUR questions each.

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3. Attempt any FIVE questions from SECTION B & C carrying EIGHT marks each.
4. Select atleast TWO questions from SECTION - B & C.

SECTION-A [2×10=20]

1. Write briefly :
   1. What are the limitations of free electron theory
   2. Discuss the physical significance of the wave function ?.

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   3. What are Brillouin zones?
   4. How n-type and p-type semiconductors are produced?
   5. What is the character difference between metals and semiconductors from the consideration of temperature coefficient of resistivity?
   6. The threshold wavelength of a photo diode is 750 nm. Calculate the energy gap in the photo diode in electron volts.
   7. Explain the term absorption and spontaneous emission of radiation.

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   8. Why four probes are required for the measurement of resistivity of semiconductor in four probe method.
   9. What do you mean by effective mass of electron?
   10. What physical parameters can be known from I-V characteristics of diode?

SECTION-B

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2. What are density of energy states in metals? Derive an expression for density of energy states of a metal. [8]
3. Discuss the Kronig-Penny model for the motion of an electron in a periodic potential. [8]
4. Derive an expression for the densities of electrons and holes in the conduction and valence bands respectively of an intrinsic semiconductor [8]
5. 1. What do you mean by carrier generation and recombination process? [4]
   2. Differentiate metals, semiconductors and insulators on the basis of band theory. [4]

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SECTION-C

6. What do you mean by laser and its working principle? Obtain a relation between transition probabilities of spontaneous and stimulated emission. [3+5=8]
7. Discuss structure and working of PIN and Avalanche photodiodes. [8]
8. Discuss in detail the working and characteristics of light emitting diodes. [8]

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9. Illustrate with proper diagram about the measurement of carrier density, resistivity and hall mobility by van der Pauw method. [8]

NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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