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Which type of material has low resistance and allows electrical current to flow?
Which type of material has low resistance and allows electrical current to flow?
Semiconductors can only allow electrical current to flow and never suppress it.
Semiconductors can only allow electrical current to flow and never suppress it.
False
What are the negatively charged particles orbiting the nucleus called?
What are the negatively charged particles orbiting the nucleus called?
Electrons
The process of losing a valence electron results in a ______ ion.
The process of losing a valence electron results in a ______ ion.
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What is the maximum number of electrons that can occupy the outermost shell of an atom?
What is the maximum number of electrons that can occupy the outermost shell of an atom?
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Match the following materials with their classification:
Match the following materials with their classification:
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Define ionization in the context of an atom.
Define ionization in the context of an atom.
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Valence electrons are tightly bound to the nucleus of an atom compared to inner electrons.
Valence electrons are tightly bound to the nucleus of an atom compared to inner electrons.
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Which of the following materials is an example of an insulator?
Which of the following materials is an example of an insulator?
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Semiconductors have a low level of conductivity in their pure state.
Semiconductors have a low level of conductivity in their pure state.
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What is the main characteristic of conductors concerning electron behavior?
What is the main characteristic of conductors concerning electron behavior?
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A semiconductor in its intrinsic state behaves like an __________.
A semiconductor in its intrinsic state behaves like an __________.
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Match the following materials with their classification:
Match the following materials with their classification:
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What is the main property of insulators related to their resistance?
What is the main property of insulators related to their resistance?
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Silicon, germanium, and carbon are the most common single-element semiconductors.
Silicon, germanium, and carbon are the most common single-element semiconductors.
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What kind of bonding is primarily found in silicon atoms?
What kind of bonding is primarily found in silicon atoms?
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What is the role of boron in a p-type semiconductor?
What is the role of boron in a p-type semiconductor?
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In a p-type semiconductor, the majority charge carriers are electrons.
In a p-type semiconductor, the majority charge carriers are electrons.
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What happens to the conductivity of silicon when it is doped with boron?
What happens to the conductivity of silicon when it is doped with boron?
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The positive holes in p-type silicon move towards the ______ terminal.
The positive holes in p-type silicon move towards the ______ terminal.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What is the role of the phosphorus atom in n-type semiconductors?
What is the role of the phosphorus atom in n-type semiconductors?
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N-type silicon is characterized by the majority charge carriers being holes.
N-type silicon is characterized by the majority charge carriers being holes.
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What term is used to describe the trivalent impurity atoms that increase holes in silicon?
What term is used to describe the trivalent impurity atoms that increase holes in silicon?
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In n-type silicon, the process of adding phosphorus is known as __________.
In n-type silicon, the process of adding phosphorus is known as __________.
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Match the following atoms with their categories in semiconductors:
Match the following atoms with their categories in semiconductors:
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Which of the following best describes holes in a semiconductor?
Which of the following best describes holes in a semiconductor?
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Removing a silicon atom and replacing it with a phosphorus atom increases the number of conduction electrons.
Removing a silicon atom and replacing it with a phosphorus atom increases the number of conduction electrons.
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What happens to the electrons when a potential difference is applied across n-type silicon?
What happens to the electrons when a potential difference is applied across n-type silicon?
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What happens to valence electrons in silicon when heat is applied?
What happens to valence electrons in silicon when heat is applied?
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Free electrons and holes are essential for conduction in silicon.
Free electrons and holes are essential for conduction in silicon.
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What is formed when heat is applied to silicon?
What is formed when heat is applied to silicon?
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In silicon, the absence of an electron in a covalent bond is called a _____
In silicon, the absence of an electron in a covalent bond is called a _____
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What effect does applying more heat to silicon have?
What effect does applying more heat to silicon have?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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An intrinsic silicon crystal as a semiconductor has a high level of resistance at room temperature.
An intrinsic silicon crystal as a semiconductor has a high level of resistance at room temperature.
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Describe the movement of electrons in an electric field applied to silicon.
Describe the movement of electrons in an electric field applied to silicon.
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Which of the following statements about n-type semiconductors is true?
Which of the following statements about n-type semiconductors is true?
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For p-type semiconductors, p is approximately equal to the acceptor concentration NA.
For p-type semiconductors, p is approximately equal to the acceptor concentration NA.
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What is the equation that relates the positive and negative charge density in a semiconductor?
What is the equation that relates the positive and negative charge density in a semiconductor?
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In intrinsic silicon at 300K, the resistivity can be calculated using the formula ρ = 1 / qn₁(μη + μp), where ρ represents ______.
In intrinsic silicon at 300K, the resistivity can be calculated using the formula ρ = 1 / qn₁(μη + μp), where ρ represents ______.
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Match the following properties with their respective semiconductor types:
Match the following properties with their respective semiconductor types:
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What does the drift current density equation for semiconductors primarily account for?
What does the drift current density equation for semiconductors primarily account for?
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The current in a semiconductor is solely dependent on the movement of free electrons.
The current in a semiconductor is solely dependent on the movement of free electrons.
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What is the relationship expressed in the mass action law for p-type semiconductors?
What is the relationship expressed in the mass action law for p-type semiconductors?
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Study Notes
Introduction to Semiconductors
- Electronics is the science and technology of charge motion in gases, vacuum, or semiconductors.
- There are three types of materials: conductors, insulators, and semiconductors.
- Conductors have low resistance and allow current flow.
- Insulators have high resistance and suppress current flow.
- Semiconductors can either allow or suppress current flow, depending on conditions.
Materials
- Conductivity (and resistivity) of semiconductors falls between conductors and insulators.
- Resistivity is measured in Ω-m.
The Atom (Bohr Model)
- Atoms have a nucleus (protons and neutrons), and orbiting electrons.
- Electrons orbit the nucleus in specific energy levels (shells).
- Electrons near the nucleus have lower energy than those farther out.
Electrons and Shells
- Electrons orbit at discrete distances from the nucleus, corresponding to specific energy levels called shells.
- Each shell has a maximum number of electrons it can hold.
- Valence electrons are those in the outermost shell, and are especially important for chemical bonding and material properties.
Valence Electrons
- Valence electrons farther from the nucleus have higher energy and are less tightly bound to the atom.
- The force of attraction between the nucleus and valence electrons decreases with distance.
- Electrons in the outermost shell are called valence electrons.
Ionization
- When an atom absorbs energy, its electrons can jump to higher energy levels.
- Losing a valence electron is called ionization.
- An atom that loses an electron becomes a positive ion.
- An atom that gains an electron becomes a negative ion.
Insulators
- Insulators have tightly bound electrons in their outer shells.
- Large amounts of energy are needed to free the electrons for conduction.
- Insulators do not conduct electricity under normal conditions.
Conductors
- Conductors have loosely bound valence electrons in their outer shells.
- Low energy is needed to free the electrons from their orbits.
- Electrons can move freely from atom to atom, facilitating current flow.
Current in Conductors
- Current (I) is the rate of charge flow (Q) over time (T).
- Drift velocity (vd) is the average velocity of charge carriers in a conductor.
- Electron mobility (µ) is a measure of how easily electrons move in a material.
- Electric field (ε) is the force per unit charge.
- Electrical field can cause drift velocity and current.
- Current density (J) is the current per unit area (A).
- Ohm's law defines the relationship between current, voltage, and resistance (V = IR).
- Conductivity (σ) is the inverse of resistivity (ρ) , σ = 1/ρ;
- Current (I) = current density J x Area (A)
- Electrical field (ε) = Voltage(V)/Length (L)
Intrinsic Semiconductors
- Pure semiconductors, like silicon and germanium, are neither good conductors nor good insulators at moderate temperatures.
- At very low temperature (0K) intrinsic semiconductors act as insulators.
- At room temperature, thermal energy causes some valence electrons to jump to the conduction band, becoming free electrons.
- The absence of an electron in the valence band is called a hole.
- Electron-hole pairs are created in intrinsic semiconductors due to thermal energy.
Electron Movement in Silicon
- Free electrons move through the lattice structure.
- Holes represent the empty spaces where electrons have moved.
- Heat provides energy for the creation of electron-hole pairs.
- This electron movement allows current flow.
Intrinsic Conduction
- Applying a potential difference sets up an electric field across the material.
- Electrons and holes are accelerated in the electric field, and current flows.
- Applying more heat creates more electron-hole pairs, increasing the conductivity of the semiconductor.
- The silicon crystal behaves like a thermistor , its resistance decreases with increasing temperature.
Extrinsic Semiconductors
- Doping is adding impurity atoms to an intrinsic semiconductor to modify its electrical properties.
- N-type semiconductors have extra electrons (donor atoms), making them electron-rich.
- P-type semiconductors have missing electrons (acceptor atoms), making them hole-rich.
- The number of electrons in n-type or holes in p-type can be controlled during doping.
The Mass-Action Law
- Under thermal equilibrium, the product of the electron and hole concentrations is a constant (independent of dopant concentration).
- np = ni2
- ni is the intrinsic carrier concentration, determined by temperature.
Charge Densities in a Semiconductor
- For n-type material, the electron concentration is approximately equal to the donor atom concentration.
- For p-type material, the hole concentration is approximately equal to the acceptor atom concentration.
The Thermistor
- A thermistor is a heat-sensitive resistor.
- Its resistance decreases as temperature increases .
- Used in temperature measurement and control applications.
- A thermistor exhibits negative temperature coefficient when the temperature increase causes the resistance to decrease and vice versa.
The Light Dependent Resistor (LDR)
- An LDR resistance changes based on light (light energy instead of heat energy).
- Its resistance decreases when exposed to light, and increases in darkness.
- Used in automatic lighting systems and light meters.
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Description
Test your knowledge on the basics of semiconductors and their properties. This quiz covers the differences between conductors, insulators, and semiconductors, as well as foundational concepts in atomic structure related to electronics. Explore key concepts such as conductivity, resistivity, and electron shells.
