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Previous Year Exam Questions of Semiconductor Devices of BPUT - PSD by Verified Writer

  • Semiconductor Devices - PSD
  • 2017
  • PYQ
  • Biju Patnaik University of Technology Rourkela Odisha - BPUT
  • Electrical and Electronics Engineering
  • B.Tech
  • 38 Offline Downloads
  • Uploaded 2 years ago
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Registration No: Total Number of Pages: 02 B.Tech BSCP1207 3rd Semester Back Examination 2017-18 Physics of Semiconductor Devices BRANCH : AEIE, BIOTECH, CSE, ECE, EEE, EIE, ELECTRICAL, ETC, IEE, IT Time : 3 Hours Max Marks : 70 Q.Code : B878 Answer question No.1 which is compulsory and any five from the rest. The figures in the right hand margin indicate marks. Q1 a) b) c) d) e) f) g) h) i) j) Q2 a) b) Answer the following questions: How is density of states related to energy in 3-dimensional metal? What is the difference between direct band gap semiconductor and indirect band gap semiconductor? Give examples of two materials for each case: (a) indirect band gap semiconductor and (b) direct band gap semiconductor. What are the ways to make Ohmic contacts? Define common-emitter current gain and common-base current gain. Explain effective Richardson constant. Why is Schottky junction diode preferred over pn junction diode for highfrequency device application? Define Flat-Band voltage and Threshold voltage for MOS capacitor. What do you mean by compensated semiconductors and compound semiconductor? How is reverse saturation current of a pn junction diode related to temperature? (2×10) Show that in long pn junction diode, minority carrier concentration exponentially decreases with distance from edge of depletion region if low injection rate is assumed. Derive current-voltage relationship for ideal pn junction diode. (5) (5) Q3 a) b) Derive ambipolar transport equation. Show that, at low injection rate, ambipolar transport equation could be written by using minority carrier parameters. (5) (5) Q4 a) Explain Schottky effect. Show that actual Schottky barrier height proportionately related to position of maximum barrier height due to Schottky effect. Show that the Schottkey barrier lowering is around 0.03 V and the position of maximum barrier height is around 2 nm away from junction if it is assumed that E =6.8 × 104 V/cm, inside the semiconductor. (5) Explain thermoionic emission theory proposed by Bethe . Derive formula for current density due to flow of electron from n-type semiconductor to metal in a Schottky junction. (3) (7) b) Q5 a) b) (5)

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Q6 a) b) Q7 a) b) Q8 a) b) Derive formula for concentration of electron in conduction band for an intrinsic semiconductor at temperature T. Show that for intrinsic semiconductor, Fermi level lies around middle of band gap at room temperature. (5) Show that conductivity of an intrinsic semiconductor exponentially decreases with band gap at constant temperature. Explain the mechanisms mainly responsible for pn junction breakdown. (5) Explain about the formation of accumulation, depletion and inversion layer at Silicon Oxide/n-type Silicon interface with diagram. Draw the energy band diagram of metal – oxide- semiconductor (p-type) structure before contact and after contact at thermal equilibrium. (5) (5) (5) (5)

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