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2009 Kerala University B.Tech Electrical and Electronics Engineering Third Semester B.Tech. Degree Examination, November 2009 Question paper
This is a question paper of Third Semester B.Tech. Degree Examination, November 2009. This question paper is from Kerala University. The name of this paper is SOLID STATE DEVICES. This exam is held for all department students. I am sure that this question paper will helpful to students who are going to appear this exam. I am sure that this question paper will helpful for engineering students of all university. There is a chance in examination that the questions are may repeat in question paper. So to get good marks in examination students can utilize this question paper. And also it can give them so many confidence to the students.
Third Semester B.Tech. Degree Examination, November 2009 (2008 Scheme) 08.302 : SOLID STATE DEVICES (TA) Time : 3 Hours Max. Marks : 100 PART – A Answer all questions. Each question carries 4 marks. 1. Draw three crystal planes equivalent to (100). 2. Derive an expression for the effective mass of a free electron in a semiconductor. 3. How do the electron concentration in an n type semiconductor vary with temperature ? 4. Two ideal and identical pn junction diodes with reverse saturation current of 10nA are connected in series across a 1.2 V battery such that both of them are forward biased. What will be the current through the diodes at 300 K ? 5. A P+n silicon diode requires a breakdown voltage of 150 V at 300 K. If the critical field strength for avalanche breakdown is 3×105 V/cm, determine the doping on the n side of the diode. 6. Draw the energy band diagram of a hetero junction diode under thermal equilibrium condition. 7. Define injection efficiency and transport factor of a BJT. What are the factors on which these parameters depend ? 8. Plot the CV diagram of an ideal MOS capacitor and explain. 9. Explain hot electron effect in MOSFETs. 10. For a MOS structure with silicon substrate of doping 1016 Arsenic atoms/cm3, what is the surface potential at the onset of strong inversion, at 300 K. PART – B Answer any two questions from each Module. Each Module carries 20 marks. Module – I 11. a) Derive an expression for the electron diffusion current in a semiconductor. b) The conductivity of intrinsic silicon at 300 K is 4.4×10–4(O cm)–1. Determine the conductivity at 310 K, if Eg (300 K)=1.11 e V. 12. Derive the ideal diode equation stating the approximations used. Assume that the length of the neutral regions towards the n and p sides are Wn and Wp respectively. 13.a) Derive an expression for the depletion layer capacitance of an abrupt pn junction. b) A silicon sample doped with 1018 cm–3 arsenic atoms is optically excited such that gop=1021 EHP/cm3/s . Defermine sample resistivity before and after illumination. Assume n 3 p 1200 cm / V.s µ = µ = 2 . Module – II 14. Derive expressions for the terminal currents of an npn. BJT in terms of its dimensions, doping etc. State the approximations used. 15. a) Plot the input and output characteristics of a pnp BJT in common emitter configuration and explain. What are the effects of base width modulation on the characteristics. b) A Schottky barrier diode with n type silicon has ND=2×1015 cm–3 of the electron affinity of silicon is 4.15 eV and the work function of the metal is 4.9 eV, determine : i) The built in voltage ii) The width of depletion layer. 16. a) Draw the energy band diagram of a metal n type semiconductor ohmic contact under thermal equilibrium. b) A silicon bipolar junction transistor has base doping of ND = 8×1015cm–3 and the collector is heavily doped. The metallurgical width of the base is 2 µm and the critical field strength for avalanche breakdown is 3×105 V/cm. Determine the breakdown voltage of the collector base junction (avalanche breakdown) and the punch through voltage. Module – III 17. Derive expression for the drain current of a JFET. 18. a) Explain the principle of operation of an IGBT. b) Determine the low frequency and high frequency capacitance of a MOS capacitor with oxide of thickness 100A°, relative permittivity 3.9 and substrate doping of NA = 1015cm–3. 19. a) Explain the principle of operation of a UJT. b) A silicon n channel JFET has ND = 1015cm –3, NA = 1018 cm–3 and a = 2 µm . Determine the built in voltage and pinch off voltage. __________________________
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