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Posted Date: 30 Jun 2012      Posted By:: Vishnu.s    Member Level: Gold    Points: 5 (Rs. 4)

2009 Kerala University B.Tech Electrical and Electronics Engineering Third Semester B.Tech. Degree Examination, November 2009 Question paper



Course: B.Tech Electrical and Electronics Engineering   University/board: Kerala University

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 p-n 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 n-p-n. BJT in terms of its
dimensions, doping etc. State the approximations used.
15. a) Plot the input and output characteristics of a p-n-p 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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