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i Learn
1. Fermi level of metal semiconductor junction ranges
0.20–0.70 eV 0.35–0.95 eV 0.30–0.90 eV 0.25–0.75 eV
Ans: 3
2. A junction of metal and lightly doped silicon is called as
Tunnel diode PN Junction diode Zener diode Schottky diode
Ans: 4
3. Types of metal semiconductor contacts (MCA)
PN junction contact Ohmic contact Avananche contact Zener contact
Rectifying contact
Ans: 2 5
4. Which of the below mentioned statements is false regarding Schottky diodes?
Schottky diodes have a Al-Silicon junction There is no storage of charges in a
Schottky diode The majority charge carriers in a Schottky diode are holes
Schottky diodes can be switched off faster than a p-n junction diode of the
same rating
View Answer
Answer: c
5. To make a good ohmic contact to a semiconductor, what should be done?
Choose a metal with a high Schottky barrier height. Use a lightly doped
semiconductor. Introduce defects into the semiconductor to lower its lifetime.
Dope the semiconductor very heavily. Reduce the contact area.
Ans: d
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i Explore
1. What are the consequences of Fermi level pinning?
The Schottky barrier height will be insensitive to the type of metal. The SB will
behave like a PN junction. The SB will be ohmic – not rectifying. The
thermionic emission theory will have to be replaced by drift-‐diffusion theory.
The ideality factor of the SB will decrease.
Ans: a
2. In order to reduce the reverse recovery time of the diodes, _______________ is
carried out.
antimony doping adding ans extra silicon layer platinum & gold dopping
shortening of the length of the device
Ans:3
3. Select the junction layers of Schottky diode
Aluminum Platinum Germanium Arsenide Solicon
Ans: 1 5
4. The materials having a nonlinear voltage-current relationship are
ohmic non-ohmic batteries capacitors
Ans:2
5. Over a large range of applied voltages, ohmic conductor have a
linear voltage current relationship vibratory voltage current relationship
circular voltage current relationship random voltage current relationship
Ans: A
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i Analyse
1. Assume an arbitary metal forms a Schottky contact with an n-type semiconductor.
How does the Schottky barrier height vary if the doping in the semiconductor
decreases?
remains unchange increases decreases becomes zero
Ans: 1
2. An arbitrary metal is deposited on a lightly doped n-type semiconductor. Work-
function of the metal is much higher than the work-function of the semiconductor.
Q1 Identify the type of junction
PN Junction PIN Junction Metal-Semoconductor Junction PN+ Junction
Ans: 1
Q2 Which of the following steps will make the metal-semiconductor junction into an
ohmic contact?
Doping the semiconductor heavily with a p-type impurity far away from the contact
Doping the semiconductor lightly with a p-type impurity near the contact to
make the semiconductor an intrinsic Doping the semiconductor heavily with an n-type
impurity near the contact region No further processing is required, as it is
already an ohmic contact
Ans: 3
Q3 Which of the following steps will make the metal-semiconductor junction into
rectifying contact?
Doping the semiconductor heavily with a p-type impurity far away from the contact
Doping the semiconductor lightly with a p-type impurity near the contact to
make the semiconductor an intrinsic No further processing is required, as it is
already an ohmic contact Doping the semiconductor heavily with an n-type
impurity near the contact region
Ans: 4
3. Which of the following is not correct regarding an M-S junction?
Thermionic emission depends on the shape of the band bending inside the
semiconductor near the junction. Tunneling current through a triangular barrier
at the junction increases with the doping concentration in the semiconductor.
Diffusion transport through a junction is negligible in case of reverse bias.
Thermionic emission transport enhances with the increase in temperature.
Ans: 1
4. The threshold voltage cannot be determined using
concentration density channel thickness implanted impurity channel depth
View Answer
Answer: d
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i Design
1. Dinesh has not read the MESFET basics and help him to ans the below questions
Q1 Which MOSFET contains Schottky diode?
GaAs Ga Si SiO2
View Answer
Answer: a
Q2. Which is ON device?
e type MESFET d type MESFET depletion enhancement
View Answer
Answer: b
Q3 In MESFET for gate _____ junction is used.
pnp junction npn junction schottky junction n junction
View Answer
Answer: c
2. Ragul wants to learn the MESFET basics, help him to answering the below question
for better understanding
Q1 Which region is heavily doped?
Drain Gate Source Substrate
Ans: Drain
Q2 Threshold voltage cannot be determined using
concentration density channel thickness implanted impurity channel depth
Ans : channel depth
Q3 Schottky barrier is created due to the difference in
voltage thickness work function density
Ans: workfunction
Q4 In MESFET gate type of the junction is
PNP junction NPN junction Schottky junction N Junction P Junction
Ans: Schottky junction
3. Answer the below questions for the MESFET
Q1 Which id ON device normally?
Depletion mode Enhancement mode E type MESFET D type MESFET
Ans: D type MESFET
Q2 MESFET is constructed in (MCA)
Ans: SiC InP GaAs
Q3 Doping level of the drain is
Normaly doped Slightly doped Heavily doped No doping
Ans : Heavy
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i Assess
1. Concentrate the on the construction of a electronic device answer the following
questions
Q1 Identify the device
JFET MOSFET MESFET PINFET
Q2 Identify the Layer
P Type N Type Metal P+ Type N+ Type
Q3 Identify the type of junction
PN Junction P+N Junction PN+ Junction Metal-Semiconductor junction
Q4 In the above device if doping level is increases the value of threshold voltage
is
larger negative larger positive smaller negative smaller positive
Ans: larger negative
2. Georg wants to analyse the MESFET construction, fabrication and its working help
him to analyse
Q1 Schottky barrier is created due to the difference in
Voltages Thickness Work function Density
View Answer
Answer: c
Q2 4. As the separation between metal-semiconductor surface is reduced, induction
charge
Increases Decreases Remains constant Is not affected
View Answer
Answer: a
Q3 Method used for fabrication of GaAs MESFET is
Disposition Ion implantation Diffusion Conduction
Ans:B
Q4 How many masking stages does fabrication GaAs FET require?
8
4
10
6
Ans: 8
Q5 In MESFET, if gap between metal-semiconductor surface is reduced what happen to
the induction charge
increases decreases remains constant not changed
Ans: Increses
3. Symbol Identification
