Semiconductor Electronics Quiz

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Questions and Answers

What is an insulator?

An insulator is a material that has a very high resistance to the flow of electricity. This means that very little electric current can flow through an insulator. Examples of insulators include rubber, wood, glass, and air.

Which of the following is NOT a property of a semiconductor?

Conductivity increases with increasing temperature

Conductivity is intermediate to that of conductors and insulators

Conductivity is always high (correct)

Conductivity can be increased by adding impurities

In an intrinsic semiconductor, what is the relationship between the number of free electrons and the number of holes?

The number of free electrons is much less than the number of holes

The number of free electrons is not related to the number of holes

The number of free electrons is much greater than the number of holes

The number of free electrons is equal to the number of holes (correct)

What is doping?

Doping is the process of intentionally adding impurities to a semiconductor material. This is done to control the semiconductor's electrical conductivity and to make it more useful for specific applications. Signup and view all the answers

In an n-type semiconductor, which type of charge carrier is the majority carrier?

Electrons Signup and view all the answers

What is a p-n junction?

A p-n junction is a boundary formed between a p-type semiconductor and an n-type semiconductor. It forms the basis for many semiconductor devices, like diodes and transistors. Signup and view all the answers

What is the depletion region in a p-n junction?

The depletion region is a thin layer that forms at the junction between a p-type semiconductor and an n-type semiconductor. It's created by the diffusion of charge carriers across the junction, and it is characterized by a lack of free charge carriers. Signup and view all the answers

What is the barrier potential in a p-n junction?

The barrier potential is a potential difference that builds up across the depletion region in a p-n junction. It is created by the fixed positive and negative charges within the depletion region. Signup and view all the answers

What happens to the width of the depletion region in a p-n junction when it is forward biased?

The width of the depletion region decreases Signup and view all the answers

What happens to the width of the depletion region in a p-n junction when it is reverse biased?

The width of the depletion region increases Signup and view all the answers

What is a diode?

A diode is a semiconductor device that allows current to flow easily in one direction (forward bias) but strongly resists current flow in the opposite direction (reverse bias). Signup and view all the answers

What is the difference between a diode and a transistor?

While both transistors and diodes are built from semiconductors, diodes are two-terminal devices that act as a gate for current flow, while transistors are three-terminal devices that can amplify or switch a signal. Signup and view all the answers

What is rectification?

Rectification is the process of converting alternating current (AC) into direct current (DC). This involves limiting the flow of current in one direction while allowing current to pass freely in the opposite direction. Signup and view all the answers

What is a half-wave rectifier?

A half-wave rectifier is a circuit that uses a diode to allow only one half-cycle of an AC waveform to pass through, resulting in a pulsating DC output. Signup and view all the answers

What is the dynamic resistance of a diode?

The dynamic resistance of a diode is a measure of its resistance to changes in current at a particular voltage point. It varies depending on the operating point of the diode. Signup and view all the answers

The forward bias dynamic resistance of a diode is much lower than the reverse bias dynamic resistance.

True Signup and view all the answers

How is an n-type semiconductor formed?

An n-type semiconductor is made by adding a small amount of pentavalent dopant element, such as phosphorus or arsenic, to a pure semiconductor material like silicon or germanium. Signup and view all the answers

Study Notes

Semiconductor Electronics: Materials, Devices and Simple Circuits

Learning Objectives: After studying this unit, learners will understand the classification of solids based on conductivity, energy band theory, intrinsic and extrinsic semiconductors, p-n junction diodes, and their characteristics.

Introduction

Vacuum Tubes vs. Semiconductor Devices: Semiconductor devices replaced vacuum tubes because they are less bulky, consume less power, and are more reliable.

Classification of Solids

Conductors: Solids with high conductivity (low resistivity). Conductivity ranges from 10² to 10⁸ S m⁻¹. Examples include aluminum, copper, silver, and gold.
Insulators: Solids with low conductivity (high resistivity). Conductivity ranges from 10⁻¹¹ to 10⁻¹⁹ S m⁻¹. Examples include rubber, plastic, mica, and glass.
Semiconductors: Solids with conductivity intermediate to metals and insulators. Conductivity ranges from 10⁻¹ to 10⁶ S m⁻¹ and resistivity ranges from 10⁵ to 10⁹ Ωm. Examples include silicon and germanium.

Band Theory of Solids

Energy Bands: Closely spaced energy levels in solids form energy bands.
Valence Band: Energy levels occupied by valence electrons.
Conduction Band: Energy levels above the valence band, occupied by conduction electrons.
Energy Gap (Eg): The separation in energy between the valence and conduction bands. A larger energy gap implies an insulator, a smaller energy gap a semiconductor, a gap of zero implies a conductor.

Intrinsic Semiconductor

Definition: A pure semiconductor with no impurities. Its conductivity is low at absolute zero temperature, but increases progressively with increasing temperature.
Electron-Hole Pair Generation: Thermal energy enables electrons to jump from the valence band to the conduction band, creating electron-hole pairs (free electrons and holes).

Extrinsic Semiconductor

Definition: An impure semiconductor with added impurities to increase conductivity.
Doping: The process of adding impurities to an intrinsic semiconductor.
N-type Semiconductor: Pentavalent impurities (e.g., phosphorus, arsenic, antimony) are added. The extra valence electrons from the impurity atoms become conduction electrons. Electrons are majority carriers.
P-type Semiconductor: Trivalent impurities (e.g., boron, aluminum, gallium) are added. The missing valence electrons create 'holes' that behave as positive charge carriers. Holes are majority carriers.

p-n Junction Diode

Formation: A p-n junction is formed when a p-type and an n-type semiconductor are joined together.
Depletion Region: A region near the junction where majority charge carriers are depleted, creating an electric field that opposes further diffusion of charge carriers.
Forward Bias: Applying positive voltage to the p-side and negative voltage to the n-side reduces the barrier potential, allowing current flow.
Reverse Bias: Applying negative voltage to the p-side and positive voltage to the n-side increases the barrier potential, decreasing current flow.
Characteristics: The I-V (current-voltage) characteristics of a diode exhibit different behaviors under forward and reverse bias.

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Description

Test your knowledge on semiconductor electronics including the classification of solids, energy band theory, and p-n junction diodes. This quiz will cover fundamental concepts and characteristics of conductors, insulators, and semiconductors.