SEMICONDUCTOR - created from Mind Map

Page 1

Bohr’s Atomic Theory

Periodic Table

Material Classification

Semiconductor

Energy Band

•Central nucleus, surrounded by orbiting electrons.

The orbit paths of the electrons surrounding the nucleus are called shells.

The outer shell is called the valence shell and electrons at this layer are called valence electrons.

•Nucleus contains protons and neutrons.

•Electrons orbit the nucleus.

Each shell has a defined number of electrons it will hold (2n2).

n=1, 2, 3, …..

Example: Copper: 2.8.18.1 Electron valence: 1

Maximum number of valence electron is 8.

The material is more conductive if less electron valence orbiting the outer shell.

Conductor

Insulator

Semiconductor

Low resistance which allows electrical current flow

Charge flows freely

Copper, silver, gold, aluminum, nickel etc.

High resistance which suppresses electrical current flow

Almost no charge flows

Glass, ceramic, plastic, wood etc.

Can allow or suppress electrical current flow

Conductivity lies between conductor and insulator

Carbon, silicon, germanium etc.

Extrinsic

Intrinsic

Impuruties are added to improved semiconduvtivity

Dopping Process

N-type (Pentavalant)

P-type (Trivalant)

Pure form of semiconductir

Conductor

Semiconductor

Insulator

Valence band – filled with electrons.

Conduction band – empty.

Band gap – empty.

Electrons are unable to gain enough energy to jump from the valence band to the conduction band.

Enables some electrons with enough energy to jump from the valence band to the conduction band easily.

Temperature low – no free electron in the conduction band.

Temperature high - electric conductivity high.

When potential difference is connected, the holes and electrons move in opposite directions.

Large number of electrons being excited into the conduction band, leaving a large number of holes in the valence band.

Occupied by many conduction electrons, causing metal to become good electric conductor.