semi-conductor

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a primary feature that distinguishes intrinsic semiconductors from conductors?

Intrinsic semiconductors contain four valence electrons. (correct)

Intrinsic semiconductors are made from metals.

Intrinsic semiconductors allow current to flow freely.

Intrinsic semiconductors have high resistance.

Which type of semiconductor is formed by adding elements with fewer valence electrons than the semiconductor material?

Intrinsic semiconductor

N-type semiconductor

P-type semiconductor (correct)

Superconductors

What effect do impurities have on semiconductor materials?

They prevent the formation of a crystal lattice structure.

They make the semiconductor transparent to electrons.

They can change the conductivity of the semiconductor. (correct)

They always increase the resistance of the semiconductor.

Which of the following is a common doping technique for creating N-type semiconductors?

Doping with phosphorus Signup and view all the answers

What primarily determines the conduction mechanism in semiconductors?

The number of valence electrons in the atoms Signup and view all the answers

What characteristic of a semiconductor allows it to be conditioned to behave like a conductor or an insulator?

Valence electron configuration Signup and view all the answers

How does doping affect the electron flow in semiconductors?

It introduces additional charge carriers. Signup and view all the answers

Which element is considered the best and most widely used semiconductor material?

Silicon Signup and view all the answers

What is the primary effect of doping semiconductors with donor dopants?

They provide extra electrons to improve conductivity. Signup and view all the answers

Which element is commonly used as a donor dopant in silicon?

Arsenic Signup and view all the answers

What type of semiconductor is formed when silicon is doped with boron?

P-type semiconductor Signup and view all the answers

In terms of conductivity, how does an increase in the number of donor dopants affect a semiconductor?

It lowers resistance and allows current to flow more freely. Signup and view all the answers

What charge does boron assume after acting as an acceptor dopant?

Negative ion Signup and view all the answers

What is a hole in the context of semiconductor materials?

A location where an electron is missing. Signup and view all the answers

Which of the following statements about N-type semiconductors is true?

They have more free electrons than holes. Signup and view all the answers

What is the relationship between the amount of doping and the resistance of a semiconductor?

More doping generally decreases resistance. Signup and view all the answers

What is the defining characteristic of an intrinsic semiconductor?

Has a filled valence band and an empty conduction band Signup and view all the answers

Which statement correctly describes doping in semiconductors?

It introduces impurities to enhance conductivity Signup and view all the answers

Which type of semiconductor is primarily characterized by the presence of excess holes?

P-type semiconductor Signup and view all the answers

What is the role of an impurity element like arsenic in a semiconductor?

To provide additional electrons for conduction Signup and view all the answers

What type of crystal structure does a monocrystal semiconductor possess?

A uniform three-dimensional structure Signup and view all the answers

What is the effect of tightly bound valence electrons in intrinsic semiconductors?

Prevents current flow by not allowing electrons to dislodge Signup and view all the answers

In the context of semiconductor theory, what is meant by electron-hole pairs?

The pairs formed due to covalent bonding in silicon Signup and view all the answers

What occurs when a semiconductor crystal is doped primarily with elements that have fewer valence electrons than silicon?

It primarily gains holes Signup and view all the answers

Study Notes

Introduction to Semiconductors

Electronic materials aim to generate and control electrical current flow.
Types of electronic materials include:
- Conductors: low resistance, allow current flow easily
- Insulators: high resistance, suppress current flow
- Semiconductors: can either allow or suppress current flow, depending on conditions

Conductors

Good conductors have low resistance, allowing easy electron flow.
Best elemental conductors include copper, silver, gold, aluminum, and nickel.
Alloys like brass and steel are also good conductors.
Some conductors can be liquid, such as salt water.

Conductor Atomic Structure

Good conductors' atomic structure usually has only one electron in their outer shell.
This outer electron, called a valence electron, is easily stripped from the atom, facilitating current flow.

Insulators

Insulators have high resistance, preventing current flow.
Common insulators include glass, ceramics, plastics, and wood.
Most insulators are compounds of multiple elements.
Atoms are tightly bound in insulators, making it hard to strip electrons for current flow.

Semiconductors

Semiconductors can be controlled to act as either good conductors or good insulators.
Common semiconductor elements include carbon, silicon, and germanium.
Silicon is the most widely used semiconductor.

Periodic Table of Elements

The provided periodic table highlights semiconductor materials.

Semiconductor Valence Orbit

The defining characteristic of a semiconductor element is its four valence electrons in the outer orbit. (Silicon is shown as an example.)

Crystal Lattice Structure

Semiconductors have a unique capability to link atoms together to form a physical structure called a crystal lattice.
Atoms link together by sharing outer electrons forming covalent bonds.
This creates a 2D and 3D crystal lattice structure.

Semiconductor Structure

Semiconductors can have a crystalline or polycrystalline structure.

Semiconductors Can Be Insulators

Pure semiconductors, like silicon, resist current flow due to tightly bound atoms in their crystal lattice.
These pure, intrinsic semiconductors are good insulators.

Intrinsic Material

A perfect semiconductor crystal without impurities or lattice defects is called an intrinsic semiconductor.

Doping

Doping is the addition of impurities to semiconductors to alter their electrical properties.
Impurities are different elements to those already present.
Doping allows semiconductors to either conduct electricity more easily (n-type) or resist electricity more easily (p-type)

Semiconductors Can Be Conductors

Impurity atoms, such as arsenic, with five valence electrons can be added to silicon to create an abundance of free electrons, becoming n-type semiconductors.
By adding these impurities, an abundance of 'free' electrons can move around to conduct current.

Improving Conduction by Doping

Adding impurities, also called dopants, can change the conductivity of semiconductors.
Elements with 5 outer electrons (donor dopants) contribute extra electrons, increasing conductivity (n-type).
Elements with 3 outer electrons (acceptor dopants) accept an electron from the silicon, creating holes for increased conductivity (p-type).

Doping - Phosphorus and Arsenic

Phosphorus and arsenic, added as impurities (dopants), introduce extra electrons, resulting in n-type.
The extra electron is free to move around and contribute to electric current.
The phosphorus becomes a positive ion after giving up an electron.

Doping - Boron

Boron, with three valence electrons, creates holes in the silicon crystal lattice, producing p-type.
The space left is identified as a hole, behaving like a positive charge and attracting electrons.
Boron becomes a negative ion after accepting an electron.

Resistance Effects of Doping

Higher doping concentration generally leads to lower resistance and greater conductivity in semiconductors.
Doping amount controls semiconductor resistance.

Another Way to Dope

Impurities with fewer than 4 valence electrons create a hole.
Creating holes gives them the capability to attract and conduct current.

Types of Semiconductor Materials

Silicon doped with extra electrons forms N-type semiconductors (N for negative due to the electron charge).
Silicon with electron-missing "holes" forms P-type semiconductors (P for positive due to the positive charge of the hole).

Current Flow in Semiconductors

A DC voltage source with a positive terminal attracts free electrons in a semiconductor, creating a positive charge.
Electrons flow from the negative terminal to the positive in conventional current flow.
In the semiconductor, 'hole' movement is an important conductor.

In Summary

Pure semiconductors are insulators.
Doping changes conductivity, creating N-type (extra electrons) and P-type (missing electrons/holes).
Increased doping increases conductivity.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.