Worksheets2nd yr week 1 edc
Total questions: 35
Worksheet time: 18mins
What is the value of the electronic charge used in the calculations?
1.6 × 10⁻¹⁹ C
1.6 × 10⁻¹⁸ C
1.6 × 10⁻²⁰ C
1.6 × 10⁻¹⁷ C
What is the typical value of the diffusion constant (Dn) for electrons in silicon at 300 K?
35 cm²/s
25 cm²/s
15 cm²/s
45 cm²/s
What is the typical value of the carrier mobility for electrons in silicon at 300 K?
0.13 m²/V-s
0.03 m²/V-s
1.3 m²/V-s
0.013 m²/V-s
What is the intrinsic carrier density of silicon at 300 K?
1.5 × 10¹⁰/cm³
2.25 × 10¹⁵/cm³
1.5 × 10¹⁵/cm³
1.0 × 10⁵/cm³
What is the bandgap of silicon at room temperature?
1.1 eV
0.7 eV
1.3 eV
1.4 eV
What is the unit of resistivity?
Ω-cm
Ω-m
Ω
Ω/cm
What is the typical value of the diffusion constant (Dn) in the base of a bipolar transistor?
25 cm²/s
35 cm²/s
15 cm²/s
45 cm²/s
What is the longest wavelength that can be absorbed by silicon with a bandgap of 1.12 eV?
1.1 μm
0.87 μm
1.5 μm
0.5 μm
What is the typical value of the donor impurity concentration (N_D) in a uniformly doped n-type silicon sample?
2.5 × 10¹⁵/cm³
2 × 10¹⁶/cm³
1 × 10¹⁶/cm³
2 × 10¹⁵/cm³
What is the primary reason for the widespread use of Silicon in semiconductor device technology?
Abundance of Silicon on the surface of the Earth
Larger bandgap of Silicon in comparison to Germanium
Favorable properties of Silicon-dioxide (SiO₂)
Lower melting point
A Silicon sample A is doped with 10¹⁸ atoms/cm³ of Boron. Another sample B of identical dimensions is doped with 10¹⁸ atoms/cm³ of Phosphorus. The ratio of electron to hole mobility is 3. The ratio of conductivity of the sample A to B is
3
1/3
2/3
3/2
The concentration of minority carriers in an extrinsic semiconductor under equilibrium is
Directly proportional to the doping concentration
Inversely proportional to the doping concentration
Directly proportional to the intrinsic concentration
Inversely proportional to the intrinsic concentration
The majority carriers in an n-type semiconductor have an average drift velocity v in a direction perpendicular to a uniform magnetic field B. The electric field E induced due to Hall effect acts in the direction
v × B
B × v
Along v
Opposite to v
A heavily doped n-type semiconductor has a hole-electron mobility ratio of 0.4, doping concentration of 4.2 × 10¹⁸ atoms/m³, and intrinsic concentration of 1.5 × 10⁴ atoms/m³. The ratio of conductance of the n-type semiconductor to that of the intrinsic semiconductor of same material and at the same temperature is
0.00005
2,000
10,000
20,000
The electron and hole concentrations in an intrinsic semiconductor are nᵢ per cm³ at 300 K. If acceptor impurities are introduced with a concentration of N_A per cm³ (where N_A >> nᵢ), the electron concentration per cm³ at 300 K will be
nᵢ
nᵢ + N_A
N_A - nᵢ
nᵢ² / N_A
Which of the following is true?
A silicon wafer heavily doped with boron is a p⁺ substrate
A silicon wafer lightly doped with boron is a p⁺ substrate
A silicon wafer heavily doped with arsenic is a p⁺ substrate
A silicon wafer lightly doped with arsenic is a p⁺ substrate
The ratio of the mobility to the diffusion coefficient in a semiconductor has the unit
V⁻¹
cm·V⁻¹
V·cm⁻¹
V·s
Which type of current dominates for minority carriers under low level injection in an extrinsic semiconductor?
Drift current
Diffusion current
Recombination current
Induced current
If the ratio of electron to hole mobility is 3, and the conductivity ratio of sample A to B is 2/3, which sample is doped with boron?
Sample A
Sample B
Both
Neither
Which of the following is a property of Silicon-dioxide (SiO₂) that makes it favorable for semiconductor technology?
High melting point
Good insulator
High conductivity
Magnetic property
If a silicon wafer is heavily doped with boron, what type of substrate is formed?
n-type
p-type
p⁺ substrate
n⁺ substrate
What happens to the Fermi level of silicon when doped with boron compared to undoped silicon?
It goes up
It goes down
It remains unchanged
It becomes zero
What is the effect of acceptor impurities on the electron concentration in an intrinsic semiconductor?
Increases it
Decreases it
No effect
Makes it zero
If the doping concentration is much greater than the intrinsic carrier concentration, the minority carrier concentration is approximately
Equal to the doping concentration
Equal to the intrinsic concentration squared divided by the doping concentration
Zero
Double the intrinsic concentration
What is the typical value of kT/q at 300 K?
13 mV
25 mV
50 mV
100 mV
What is the effect on the Fermi level when silicon is doped with boron?
It moves closer to the conduction band
It moves closer to the valence band
It remains at the intrinsic level
It becomes undefined
A silicon sample with unit cross-sectional area is shown in thermal equilibrium. The following information is given: T = 300 K, electronic charge = 1.6 × 10⁻¹⁹ C, thermal voltage = 26 mV, and electron mobility = 1350 cm²/V·s. What is the value of the donor concentration N_D in the sample?
10¹⁶/cm³
10¹⁷/cm³
10¹⁸/cm³
10¹⁹/cm³
The magnitude of the electric field at x = 0.5 μm is
1 kV/cm
5 kV/cm
10 kV/cm
26 kV/cm
The magnitude of the electron drift current density at x = 0.5 μm is
2.16 × 10⁴ A/cm²
1.08 × 10⁴ A/cm²
4.32 × 10³ A/cm²
6.48 × 10² A/cm²
A silicon bar is doped with donor impurities N_D = 2.25 × 10¹⁵ atoms/cm³. Given the intrinsic carrier concentration of silicon at T = 300 K is nᵢ = 1.5 × 10¹⁰ cm⁻³. Assuming complete impurity ionization, the equilibrium electron and hole concentrations are
n₀ = 1.5 × 10¹⁶ cm⁻³, p₀ = 1.5 × 10⁵ cm⁻³
n₀ = 1.5 × 10¹⁰ cm⁻³, p₀ = 1.5 × 10¹⁵ cm⁻³
n₀ = 2.25 × 10¹⁵ cm⁻³, p₀ = 1.5 × 10⁵ cm⁻³
n₀ = 2.25 × 10¹⁵ cm⁻³, p₀ = 10⁵ cm⁻³
What is the effect of increasing temperature on the intrinsic carrier concentration in silicon?
It decreases
No effect
It increases
It becomes zero
In a p-type semiconductor, what is the majority carrier type?
Holes
Both
Neither
Electrons
What happens to the conductivity of silicon when it is doped with a higher concentration of donor impurities?
It increases
It decreases
It remains the same
It becomes zero
In a p-type semiconductor, what happens to the Fermi level as the temperature increases?
It becomes undefined
It remains constant
It moves closer to the valence band
It moves closer to the conduction band
What is the effect of increasing doping concentration on the mobility of charge carriers in a semiconductor?
It increases
It decreases
It becomes zero
No effect
