M.Sc. (Semester III) (CBCS) Examination Nov/Dec-2018
Materials Science
SEMICONDUCTOR DEVICES
Time: 2½ Hours Max. Marks: 70
Instructions: Use of Non-programmable calculator is allowed.
All questions carry equal marks.
Q.1 Select the most corrective alternative 08
A Schottky diode is a
vacuum device
metal semiconductor device
intrinsic semiconductor device
a MOS device
The basic advantage of the CMOS technology is
it is easily implemented
considerable reduction in size
low power consumption
better switching capabilities
The VGS of an n-channel E-MOSFET is,
Less than the threshold voltage
Equal to the gate source cut off voltage
Greater than VDS
Greater than VGS
The output V-I characteristics of an enhancement type MOSFET has only
An Ohmic region
Saturation region
An Ohmic region at low voltage value followed by saturation region at
higher voltages
An Ohmic region at higher voltage values preceded by the saturation
region at lower voltages
A MOS capacitor made using P type substrate in the accumulation mode.
The dominant charge is due to the presence of
Holes Electrons
Positively charged ions Negatively charged ions
An SCR is a
four layer, four junction device
four layer, three junction device
four layer, two junction device
three layer, single junction device
In case of an ideal power diode, the leakage current flows from
anode to cathode
cathode to anode
in both the directions
leakage current does not flow
Page 2 of 3
SLR-VN-385
The peak inverse current IP for a power diode is given by the expression,
IP t di/dt IP t ∗ log I
IP t ∗ di/dt IP t ∗ t∗i dt
When the electric field applied to GaAs specimen is less than the threshold
electric field, the current in the material:
increases linearly decreases linearly
increases exponentially decreases exponentially
10) The fundamental element of every CCD is
the metal oxide semiconductor capacitor
the metal oxide semiconductor inductor
the metal oxide semiconductor diode
None of the above
11) photo voltaic devices in the form of thin films.
Cadmium Telluride Cadmium oxide
Cadmium sulphide Cadmium sulphate
12) is less than or unity for photo detectors.
Absorption coefficient Band gap energy
Responsivity Quantum efficiency
13) When either a voltage or current is applied to the terminals of bulk solid
state compound GaAs, a differential is developed in that bulk device.
negative resistance positive resistance
negative voltage none of the mentioned
14) A photo diode is used in the reverse bias because
Majority of the electron hole pairs swept are reversed across the
junction
Only one side is illuminated
Reverse current is small compared to photocurrent
Reverse current is large compared to photocurrent
Q.2 Answer the following (any four) 08
What is a Schottky diode? How it differs from − junction diode.
List the advantages of enhance type MOSFETS.
Sketch the two transistor analogy of SCR.
Give the applications of CCD.
List the Materials for semiconductor LASER.
Write notes on (any two) 06
Current flow mechanisms in MS and MIS junction.
Gate Turn Off thryrister
Transferred Electron Effect
Q.3 Answer the following (any two) 08
Discuss the construction and working of N-channel enhancement
MOSFET.
Explain the working principle of IGBT.
With a neat diagram, discuss the working of basic three phase CCD.
Write notes (any one) 06
and characteristics
Significance of Negative coefficient of resistance with relevant example.
Page 3 of 3
SLR-VN-385
Q.4 Answer the following (any two) 10
With the help of neat schematic, describe the construction, working and
characteristics of SCR.
Draw the structure of PUT explain briefly its operation.
With a neat schematic, discuss the Quantum well hetero structures.
Answer the following (any one) 04
Discuss briefly on the construction and working of DIAC.
Explain the basic requisites for the efficient performance of IR LEDs and
give their applications.
Q.5 Answer the following (any two) 14
With a neat diagram, discuss the construction and working of TRIAC.
A double heterojunction InGaAsP LED emitting at a peak wavelength of
1310 nm has radiative and non radiative recombination times of 30 and
100 ns respectively. The drive current is 40 mA, then find
Bulk recombination lifetime
ii) Internal quantum efficiency
iii) Internal power
With a neat schematic discuss the construction and working of LASER.