M.Sc. (Semester III) (CBCS) Examination Mar/Apr-2018
Physics (Materials Science)
SEMICONDUCTOR DEVICES
Time: 2½ Hours
Max. Marks: 70
Instructions: Q.1 and Q.2 are compulsory. Attempt any three questions from Q. 2 to 7. All questions carry equal marks. Use of scientific calculator is allowed.
Q.1
Choose the correct alternative:
14
The over drive factor for a BJT is given as
Ic Icsat
Ib Ib sat
Ic sat Ic
Ib sat Ib
In the linear region, power MOSFETs have I/P impedance in terms of
Ω
kΩ
mΩ

In the NDR devices, stability is achieved when
Semiconductor initially homogeneous becomes electrically heterogeneous
Semiconductor initially homogeneous becomes electrically homogeneous
Semiconductor initially heterogeneous becomes electrically homogeneous
Semiconductor initially heterogeneous becomes electrically heterogeneous
If the bottom of the conduction band is located at it is called




In a SiO2-Si MOS diode, the layer SiOx is stoichiometric when
x 0
x 1
x 2
x 3
The MIS interface charges are accurately reliably measured by
Capacitive method
Inductive method
Both a b
Conductance method
For SiO2- Si system, storage time τs is of the order of
10-3 to 10-2 s
10-5 to 10-3 s
10-3 to 10-2 ms
10-5 to 10-3 ms
The dominating operating process for Laser diode is
Stimulated emission
Absorption
Spontaneous emission
Reflection
For normal vision at the peak response of the eye, 1W of radiant energy is equivalent.
600
683
650
693
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SLR-UN-484
10) The NDR is due to a field induced transfer of conduction band electrons form to satellite valley.
Low energy high mobility valley to high energy low mobility valley
Low energy low mobility valley to high energy low mobility valley
High energy low mobility valley to low energy high mobility valley
Low energy low mobility valley to high energy high mobility valley
11) In the MOS diodes strong inversion occurs at
V VT
V VT
VT 0
V 0
12) The figure of merit of a tunnel diode is given by,
Ip
Io
Ip Iv
Iv Ip
13) The light modulation band width is the frequency at which the light output is
Reduced to 1/√2
Increased to 1/√2
Reduced to ½
Reduced to 2/√2
14) A simple p-n junction diode in which both p n sides are degenerate is
Tunnel diode
Schottky diode
Gunn diode
Zener diode
Q.2
Attempt the following. (Any three)
14

Explain static induction transistor.

Measurement of interface trapped charges.

Photoconductor.

What is flat-band shift?
Q.3

Explain how transfer efficiency can be improved with a buried channel CCD.
10

Write a note on frequency response of a CCD.
04
Q.4

Discuss with an energy band diagram and equivalent circuit, the p-n junction solar cell referred to open circuit voltage short circuit current maximum power output conversion efficiency
10

Calculate the modulation band width of a GaAs LED with a carrier life time of 100ps.
04
Q.5

Discuss in detail the MOS-Controlled Thyristor.
10

Mention its merits and demerits.
04
Q.6

Explain 4 quadrant operation of a Triac.
10

State which mode of operation is most sensitive and why?
04
Q.7

Give a brief account of CMOS device.
07

Discuss the volt-ampere characteristics of a tunnel diode.
07