What are semiconductors?

A semiconductor is a material that has electrical conductivity between that of a conductor and an insulator. Semiconductors can be compounds such as gallium arsenide or pure elements, such as germanium or silicon. Physics explains the theories, properties, and mathematical approaches governing semiconductors.

type of semiconductor

The use of semiconductors in place of mechanical switches is what makes a circuit “electronic,” because they enable electrical signals to be switched at extremely high speeds, which is not possible with mechanical circuits. There are many different semi-conductor.

What is an Intrinsic Semiconductor?

An intrinsic semiconductor is a pure form of semiconducting material, such as silicon or germanium, that does not contain any impurities or dopants. It has a limited number of free electrons, which are responsible for its electrical conductivity. The electrical conductivity of intrinsic semiconductors is much lower than that of conductors and higher than that of insulators.

Intrinsic semiconductors are not commonly used in electronic devices because their electrical conductivity is too low. However, they play an important role in the fabrication of extrinsic semiconductors, which are formed by adding impurities, or dopants, to the intrinsic semiconductor to increase the number of free electrons and holes.

The electrical properties of intrinsic semiconductors can be manipulated through various processes such as heating, which can increase the number of free electrons and holes by releasing them from their bound states. This is the basic principle behind the operation of thermoelectric devices, which convert thermal energy into electrical energy and vice versa.

What is an Extrinsic Semiconductor

An extrinsic semiconductor is a type of semiconducting material that has impurities or dopants, added to it to increase the number of free electrons and holes, making it more conductive. The conductivity of an extrinsic semiconductor can be controlled by adjusting the amount and type of dopants added.

There are two main types of extrinsic semiconductors:

p-type
n-type.

P-type semiconductors are created by adding impurities such as boron, which have one less electron than the semiconductor atoms. This creates a shortage of electrons, or “holes,” which can carry electrical current.

N-type semiconductors are created by adding impurities such as phosphorus, which have one extra electron. This creates an excess of electrons, which can also carry electrical current.

Properties of P-type semiconductors

It mainly occurs due to holes.
Completely neutral.
I = Ih and nh >> ne
Majority – holes, and minority – Electrons.

Whenever a pure semiconductor is doped with the trivalent impurity (B, Ge, Al, In), then three valence electrons of the impurity bonds make a bond with the four valence electrons of the semiconductor.

In this case, the electron will be absent from the impurity. These impurity atoms, now ready to accept bonded electrons, are known as acceptors. With the increase of impurity, the hole will also increase; hence it is called the P-type semiconductor.

DIODE:

Like a one-way valve for electrical current, this device enables only electrical current to pass through it in one direction–extremely useful by itself, but also the basis for all solid-state electronics.

LIGHT EMITTING DIODE (LED):

This type of diode emits a small amount of light when an electrical current passes through it.

LIGHT DEPENDENT RESISTOR (LDR):

This type of semiconductor has a changing resistance, depending on the amount of light present.

BIPOLAR JUNCTION TRANSISTOR (BJT):

This is a current-driven electronic switch used for its fast-switching properties.

METAL-OXIDE SEMICONDUCTOR FIELD-EFFECT TRANSISTOR (MOSFET):

This is a voltage-driven electronic switch used for its fast switching properties, low resistance, and capability to be operated in a parallel circuit. These are the basis for most power amplifier circuits.

These devices all have multiple layers of positively and negatively charged silicon attached to a chip with conductive metal leads exposed for soldering into the circuit. Some transistors and MOSFETs have built-in diodes to protect them from reverse voltages and Back-EMF.