Difference Between Conductor, Insulator and Semiconductor

Depending on the ability to conduct the electric current, materials are categorized into three types they are conductors, insulators, and semiconductors. All these three materials show different electrical behavior according to their atomic structure. In this article, let us learn what is a conductor, insulator, and semiconductor with examples, also the differences between conductors, insulators, and semiconductors.

Conductor :

Conductors are materials that allow electricity to flow through them. Materials with a large number of free electrons are called conductors. Conductors have many free electrons in their outermost shell of atoms which can move freely throughout the whole material structure.

When a potential difference or voltage is applied across the conductor material, free electrons readily move through the conductor, thus constituting the electric current. Silver, copper, gold, and aluminum are good conductors of electricity. In general, all metals are good conductors of electricity.

Difference Between Conductor, Insulator and Semiconductor

Characteristics of Conductors :

Conductors have high conductance and low resistance.
They have a positive temperature coefficient of resistance.
They have large free electrons available in their conduction band.
They do not have a forbidden gap between the valence band and the conduction band resulting in the overlapping of both bands.
Conductors are formed by metallic bonds.

Semiconductor :

A material whose conductivity value lies between conductor and insulator is regarded as the Semiconductor. Semiconductors will neither completely allow the flow of electric current nor oppose the flow of electric current.

Semiconductors usually have four electrons in the outermost orbit of their atoms. They act as insulators at lower temperatures and as conductors at high temperatures. Some examples of semiconductors are silicon, germanium, gallium arsenide, cadmium selenide, etc.

Characteristics of Semiconductors :

The resistivity of a semiconductor lies between the insulator and the conductor.
Semiconductors have a negative temperature coefficient of resistance.
In semiconductors at room temperature, the forbidden energy gap is smaller.
By adding impurities into the semiconductor we can change its electrical properties.

Insulator :

A material that does not conduct electricity easily through them is said to be known as Insulator. In insulator materials, the outermost shell of the atoms is completely filled i.e., the electrons are tightly bound and cannot move freely throughout the material structure.

Most of the non-metals don't allow electric current through them and thus are good insulators. Some examples of insulators are plastic, wood, rubber, air, glass, etc. Insulators are used where there is a requirement to prevent the flow of electric charges.

Characteristics of Insulators :

Insulators have low conductance and high resistance.
They have a negative temperature coefficient of resistance.
They have large dielectric strength.
They have a large forbidden gap between the valence band and the conduction band.
Insulators have a high air permeability.

Difference Between Conductor, Semiconductor, and Insulator :

Parameter	Conductor	Semiconductor	Insulator
Definition	A material that allows the flow of electric charge or electricity through it easily is called a Conductor.	A material whose properties lie between conductor and insulator is called a semiconductor.	A material that blocks the flow of electric charge or electricity through it is called an Insulator.
Current Flow	Conductors conduct electric current very easily because of their free electrons.	In semiconductors electric current conducts due to both electrons and holes.	Insulators oppose electric current and hence there is no conduction.
Conductivity	High	Moderate	Very low
Resistivity	Low	Moderate	Very High
Band Gap or Energy Gap	Conductors have no band gap (i.e., the energy gap is zero) between their valence and conduction bands	Semiconductors have a small band gap (in the range of 1 to 2 eV).	Insulators have a large band gap in the order of 10 eV.
Valence Electrons	Conductors have one, two, or three valence electrons in their atoms.	Semiconductors usually have four valence electrons in their atoms.	Insulators have more than four valance electrons in their atoms.
Number of Charge Carriers	Conductors have high charge carriers	Semiconductors have fewer charge carriers when compared to conductors.	Insulators don't have any free charge carriers making them non-conductive.
Conductivity Value	The electrical conductivity of conductors lies in the range of 10⁴ to 10⁷ ohm^-1 metre^-1.	The electrical conductivity of semiconductors lies in the range of 10⁻⁶ to 10⁴ ohm^-1 metre^-1.	The electrical conductivity of insulators lies in the range of 10^-20 to 10^-10 ohm^-1 metre^-1.
Resistivity Value	The electrical resistivity of conductors (for metal and alloys) lies in the range of 10^–8 ohm-meter to 10^–6 ohm-meter.	The electrical resistivity of semiconductors lies in the range of 10^–5 ohm-meter to 10⁶ ohm-meter.	The electrical resistivity of insulators lies in the range of 10¹² ohm-meter to 10²⁰ ohm-meter.
Temperature Coefficient of Resistivity	Conductors have a positive temperature coefficient of resistance.	Semiconductors typically have a negative temperature coefficient of resistance.	Insulators have a negative temperature coefficient of resistance.
Effect of Temperature on Resistance	Resistance of conductors increases with temperature.	Resistance of semiconductors decreases with an increase in temperature and vice-versa.	Resistance of insulators decreases with an increase in temperature.
Behavior at Absolute Zero	Some conductors behave as a superconductor at absolute zero, while others have a minimum resistance.	At absolute zero temperature, semiconductors behave like an insulator.	At absolute zero resistance of the insulator increases i.e., behaves like insulator only.
Bonding Type	Conductors are formed by metallic bonds.	Semiconductors are formed by covalent bonding.	Insulators are formed by ionic and covalent bonds.
Examples	Examples of conductors are copper, aluminum, gold, mercury, silver, etc.	Examples of semiconductors are silicon, germanium, selenium, antimony, boron, gallium arsenide, etc.	Examples of insulators are wood, paper, air, mica, glass, plastic, ceramic, rubber, etc.
Applications	Metals like copper and aluminum are used to build wires and cables to carry electric current, Mercury is used in thermometers, etc.	Semiconductors are mostly used in electronic devices mobile phones, amplifiers, converters, laptops, switches, etc.	Insulators are used to separate electrical conductors, to provide insulation in electrical and electronic devices, in circuit boards and high-voltage systems, etc.

Key Differences Between Conductor, Semiconductor, and Insulator :

A material that allows electricity to flow through them easily is said to be known as a conductor. A material that doesn't allow electricity to flow through them is said to be known as Insulator. The conductivity of semiconductors lies between the conductor and the insulator.

In conductors, the continuous flow of electrons constitutes the electric current, while in semiconductors current is carried by both electrons and holes. Insulators do not carry electric current because they do not have free-charge carriers.

Conductors have high conductivity ranges between 10⁴ to 10⁷ ohm^-1 metre^-1, whereas semiconductors have an intermediate range of conductivity from 10⁻⁶ to 10⁴ ohm^-1 metre^-1. The insulator, on the other hand, has a very low conductivity of 10^-20 to 10^-10 ohm^-1 metre^-1.

Conductors have low resistivity ranging from 10^–8 to 10^–6 ohm-meter due to a high number of free electrons available to move through the material. The resistivity of a semiconductor lies in between conductor and insulator i.e., 10^–5 to 10⁶ ohm-meter. Insulators will resist the flow of current they have high resistivity from 10¹² to 10²⁰ ohm-meter.

The energy gap in a conductor is zero because the outermost electrons are loosely bound making them move easily in between the atoms. Semiconductors have a moderate energy gap in the order of 1eV. Insulators have a large energy gap because of tightly bound electrons making them difficult to conduct electricity.

Conductors have positive temperature coefficients whose resistance increases when their temperature is raised, whereas semiconductors and insulators have negative temperature coefficients whose resistance decreases when their temperature is raised.

Some common conductors are copper, aluminum, mercury gold, silver, etc. Some examples of semiconductors are silicon, germanium, gallium arsenide, etc. Some common insulators are glass, air, plastic, paper, rubber, wood, etc.

Since conductors allow current to flow through them easily, they are used for making electric cables, power transmission lines, electronics circuitry, etc. Whereas insulators restrict the flow of electric current they are used to provide insulation in the cables, overhead lines, circuit boards, wires, etc. The property of semiconductors neither being a good insulator nor a good conductor makes them used for controlling the current in the circuit, in electronic circuit fabrication, etc.