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WorksheetsSemiconductor and Electrostatics MCQs
Total questions: 39
Worksheet time: 20mins
What is luminescence?
Emission of light from a body only when it is heated to high temperature.
Absorption of light by a material without any emission.
Emission of light by a material due to non-thermal processes such as electronic transitions, chemical reactions or electrical excitation.
Reflection of incident light from a polished surface.
In MOSFET fabrication, ion implantation is primarily used to:
Grow the gate oxide layer on the silicon surface.
Introduce dopant atoms into selected regions of the semiconductor with precise control of dose and depth.
Etch unwanted parts of the photoresist pattern.
Deposit a metal layer for making interconnections.
In which application is a P–N junction used mainly to convert light energy directly into electrical energy?
Zener diode voltage regulator.
Bipolar junction transistor.
Solar cell / photodiode.
LED used for display.
In non-equilibrium conditions in a semiconductor, the quasi-Fermi levels for electrons and holes:
Remain equal to the equilibrium Fermi level.
Split into two distinct levels, one for electrons and one for holes.
Move together rigidly while always staying equal to each other.
Disappear because the concept of Fermi level is no longer valid.
A Schottky barrier is formed at a metal–n-type semiconductor interface typically when:
The work function of the metal is smaller than that of the n-type semiconductor.
The work function of the metal is larger than that of the n-type semiconductor.
The metal work function is smaller than that of a p-type semiconductor.
The metal and semiconductor have exactly the same work function.
What happens to the barrier potential of a P–N junction when a forward bias is applied?
The barrier potential increases and the depletion width widens.
The barrier potential decreases and the depletion width narrows.
The barrier potential remains unchanged.
The barrier potential becomes negative.
Which of the following statements about the conduction band and valence band in a semiconductor is NOT correct?
Electrons in the conduction band are relatively free to move under an electric field.
Holes are associated with missing electrons in the valence band.
At absolute zero temperature, an intrinsic semiconductor has many free electrons in the conduction band.
The valence band lies at a lower energy than the conduction band.
Two point charges, q1=3.0×10−6 C and q2=5.0×10−6 C , are separated by a distance of 0.12 m in vacuum. What is the magnitude of the electrostatic force between them? ( k=9.0×109 N⋅m2/C2 )
2.5 N
4.7 N
9.4 N
18.0 N
In which of the following semiconductor devices is a P–N junction commonly used as the basic building block?
Metal–oxide varistor.
Bipolar junction transistor (BJT).
Operational amplifier.
Electrolytic capacitor.
If the resistance of a resistor is doubled while the applied voltage remains constant, what happens to the current through the resistor?
The current doubles.
The current is halved.
The current becomes zero.
The current remains unchanged.
Kirchhoff's Voltage Law (KVL) states that:
The algebraic sum of all currents entering a node is zero.
The algebraic sum of all voltages around any closed loop in a circuit is zero.
The product of current and voltage in a loop is constant.
The total power supplied equals the total power stored.
Which of the following factors directly contributes to the decrease in mobility of charge carriers as temperature increases in a semiconductor?
Increased ionized impurity scattering only.
Increased lattice (phonon) vibrations causing more frequent scattering of carriers.
Decrease in the intrinsic carrier concentration.
Increase in the crystal grain size.
Which CMOS logic gate is implemented using one PMOS transistor and one NMOS transistor in a complementary configuration?
NAND gate.
NOR gate.
Inverter (NOT gate).
XOR gate.
How many basic structure types are commonly used to describe solids in semiconductor physics and materials science?
One – only crystalline solids.
Two – crystalline and amorphous solids.
Three – single crystal, polycrystalline and amorphous.
Four – single crystal, polycrystalline, amorphous and liquid.
In the saturation region of a MOSFET, the drain current (I_D):
Is approximately independent of the drain–source voltage and mainly controlled by the gate–source voltage.
Increases linearly with the drain–source voltage.
Is zero for all values of gate–source voltage.
Decreases as the gate–source voltage increases.
A spherical Gaussian surface encloses a net charge q. If the radius of the Gaussian surface is doubled, how does the total electric flux through the surface change?
It becomes four times larger.
It becomes half as large.
It becomes one-fourth as large.
It remains the same.
What is the primary function of photoresist in the CMOS fabrication process?
To act as a permanent insulating layer on the wafer.
To serve as a temporary radiation-sensitive mask that defines regions for etching or implantation.
To increase the mechanical strength of the silicon wafer.
To provide electrical contact between metal layers.
In which operating mode of a BJT does the transistor function as a small-signal amplifier?
Cut-off mode.
Saturation mode.
Active (forward-active) mode.
Reverse-active mode.
In an n-type extrinsic semiconductor, the majority charge carriers are:
Holes.
Electrons.
Both holes and electrons equally.
Positive ions.
Which statement correctly describes drift and diffusion of charge carriers in a semiconductor?
Drift motion is due to concentration gradients, while diffusion is due to an electric field.
Both drift and diffusion require an external electric field.
Drift is motion of carriers under an electric field, while diffusion is motion from high- to low-concentration regions.
Diffusion only occurs at absolute zero temperature.
Which of the following is a major disadvantage of Integrated Circuits (ICs) related to component failure?
ICs consume very high power.
Individual faulty components inside an IC usually cannot be repaired or replaced.
ICs cannot operate at high frequencies.
ICs occupy a very large volume.
What is the electric potential at a point in an electric field?
The force experienced by a unit positive charge placed at that point.
The work done per unit positive charge in moving it from infinity to that point.
The power delivered to a charge at that point.
The kinetic energy of a unit charge at that point.
According to the right-hand rule for the magnetic field around a straight current-carrying conductor:
If the thumb points in the direction of the magnetic field, the fingers curl in the direction of current.
If the thumb points in the direction of current, the curled fingers indicate the direction of the magnetic field lines.
If the fingers point towards the conductor, the thumb points towards the north pole.
The rule applies only to electrostatic fields, not magnetic fields.
Electroluminescence refers to:
Emission of light from a material when it is heated to high temperature.
Emission of light from a material when it is subjected to an electric field or current.
Light emission only due to chemical reactions in a material.
Light emission due to radioactive decay.
Which of the following best describes the relationship between conductivity (σ) and resistivity (ρ) of a material?
σ = ρ.
σ = 1 / ρ.
σ = ρ².
σ = √ρ.
When two electric charges of equal magnitude but opposite sign are placed near each other, they will:
Repel each other.
Attract each other.
Experience no force.
First repel then attract.
A bulb requires a current of 2 A when connected to a 12 V battery. What are the resistance of the bulb and the power it consumes?
R = 4 Ω, P = 8 W.
R = 6 Ω, P = 12 W.
R = 6 Ω, P = 24 W.
R = 12 Ω, P = 24 W.
In the active mode of a BJT, the base–emitter junction is:
Reverse biased.
Forward biased.
Open-circuited.
Short-circuited.
In the cut-off region of a MOSFET, the gate–source voltage (V_GS) is:
Greater than the threshold voltage (V_th).
Equal to the threshold voltage (V_th).
Equal to zero for all devices.
Less than the threshold voltage (V_th), so the channel is off.
What is the anti-bonding orbital of the composite two-electron wavefunctions?
The even combination of the individual atomic orbitals.
The even and symmetric combination of the individual atomic orbitals.
The symmetric combination of the individual atomic orbitals.
The odd or antisymmetric combination of the individual atomic orbitals.
What is the magnetic force on a straight current-carrying conductor placed in a uniform magnetic field when the conductor is exactly parallel to the field lines?
Maximum.
Zero.
Half of its maximum value.
Cannot be determined.
Which of the following best describes the Pauli Exclusion Principle?
Electrons in an atom can occupy any energy level without restriction.
No two electrons in an atom can have the same set of four quantum numbers.
Electrons always fill the highest energy orbitals first.
Electrons in the same orbital must have the same spin.
What is the primary characteristic of a semiconductor material?
It is a perfect insulator with zero conductivity.
Its electrical conductivity lies between that of a conductor and an insulator.
It has the same conductivity as a good metal.
It cannot conduct electricity under any conditions.
The inductance of a coil is 4H . If the current through the coil changes at the rate of 2A/s , what is the magnitude of the induced emf in the coil?
2V
4V
8V
16V
In a MOSFET fabrication process, which of the following steps is typically performed last to complete the device?
Gate oxidation.
Gate electrode deposition.
Source and drain implantation.
Contact metallization.
Which of the following is true for a metal–semiconductor junction that forms an Ohmic contact?
There is no significant potential barrier to current flow in either direction.
The contact is strongly rectifying and allows current in only one direction.
The contact always has a very high forward voltage drop.
The metal forms a large Schottky barrier with the semiconductor.
In a semiconductor, a hole is considered to have what kind of effective charge?
Negative charge.
Positive charge.
Neutral charge.
It has no charge associated with it.
The speed of electromagnetic waves in vacuum is approximately:
3×106m/s
3×108m/s
3×1010m/s
3×104m/s
In an n-type extrinsic semiconductor, the minority charge carriers are:
Holes.
Electrons.
Both holes and electrons in equal numbers.
Positive ions.
