M.Sc. (Semester III) (CBCS) Examination Oct/Nov-2017
Materials Science
SEMICONDUCTOR DEVICES
Day Date: Thursday, 16-11-2017 Max. Marks: 70
Time: 02.30 PM to 05.00 PM
Instructions: Q.1 and Q.2 are compulsory.
Attempt any three questions from Q. 3 to 7.
Figures to the right indicate full marks.
Use of scientific calculator is allowed.
Q.1 Choose the correct alternative: 14
In the saturation mode, the base to collector junction of a transistor is

Reverse biased Forward biased
Both a b Required no bias
Power MOSFETs are controlled devices.
Power Voltage
Current Both a b
The dv/dt can be limited by connecting a
Resistance in series with the device
Capacitance in series with the device
A series combination of a resistance and a capacitance in series
with the devise
A series combination of a resistance and a capacitance in shunt
with the devise.
For a MIS diode system, the capacitance due to is voltage
independent.
Semiconductor Insulator
Metal p-n junction
Tunnel diode exhibits controlled NDR.
Current Voltage
Power None of the above
Thyristor exhibits controlled NDR.
Current Voltage
Power None of the above
In a CCD, charge transfer efficiencies larger than 99.99% can be
obtained in the presence of
Fringing field Density of interface states
Self-Induced drift Thermal diffusion
The maximum sensitivity of the eye is at
0.500 0.555
0.520 0.700
The dominating operating process for LED is
Spontaneous emission Absorption
Stimulated emission Reflection
Page 2 of 2
SLR-MR-526
10) in GaAs make it feasible for ultra-high speed CCD's.
Low electron mobility High hole mobility
High electron mobility High electron concentration
11) The major limitation of surface channel CCD's is
Interface trap effect Fringing field effect
Bias voltage effect None of these
12) Buried channel CD has a transfer inefficiency of
10-1 10-2 10-2 10-3
10-3 10-4 10-4 10-5
13) D-MOSFET means MOSFET.
Depleted Double dimensional
Double diffused Single dimensional
14) In TFT, the channel layer is
Polycrystalline silicon Polycrystalline GaAs
Monocrystalline silicon Monocrystalline GaAs
Q.2 Attempt the following. (any three) 14
Discuss the reverse recovery characteristics of Power diode.
What is the effect of gate signal on SCR performance?
Write a note on Organic LED's.
Discuss the construction and working principles of PIN Diode.
Q.3 With the help of a suitable circuit diagram, explain how an active device
can be protected from hazards of di/dt and dv/dt effects.
10
Discuss in brief the two transistor analogy of an SCR. 04
Q.4 Discuss the ideal MIS diode curve referred to energy band diagram and
charge, electric field and surface potential distribution.
10
Modern Si-MOSFET's are fabricated on oriented Si-Comment. 04
Q.5 Sketch and explain a basic 3-phase CCD and discuss how a charge
packet is transferred along the surface of a continuous substrate.
10
Write a note on TED. 04
Q.6 Discuss and compare transferred electron effect in GaAs and InP. 10
Sketch and explain velocity field characteristics for GaAs. 04
Q.7 Write a note on. (Any two)
Triac
IGBT
Solar Cells