Semiconductors Flashcards
Electronic Device
Any device which is based on the controlled flow of electrons through it.
Energy bands
The range of energies possessed by an electron in its orbit is called energy band.
Valence band
The range of energies possessed by valence electrons is called valence band.
Conduction band
The range of energies possessed by conduction electron is called conduction band
Define semi-conductors
A semi-conductor is a substance with almost filled valence band and nearly empty conduction band with small energy gap of about 1 eV separating the two.
What is energy gap?
The gap between the top of valence band and the bottom of conduction band is called the energy band gap
What are holes?
Due to external energy , when electrons from the valence band jump into the conduction band, vacancy of free electrons is created in the valence with an effective positive charge. These electron vacancies are called holes.
What is an intrinsic semiconductor?
A semiconductor in an extremely pure form is known as intrinsic semi-conductor. The current conductivity of intrinsic semi-conductor is very low.
What is doping?
The deliberate addition of desirable impurity to a pure semi-conductor so as to increase the current conductivity of the semi-conductor is called doping.
What is an extrinsic semi-conductor?
A semi-conductor doped with some suitable impurity atoms so as to increase its current conductivity is called an extrinsic semi-conductor.
What is n type semiconductor?
When a small amount of pentavalent impurity atom is added to a semi-conductor, the semiconductor is known as n-type semiconductor. The addition of pentavalent atoms provides a large number of free electrons in the semi-conductor crystal, hence is known as donor type semi-conductor.
What is p type semiconductor
When a trivalent impurity atom is added to a pure semiconductor, the semiconductor is known as p type semiconductor. The addition of trivalent impurity atoms provides a large number of holes in the semi-conductor crystal, hence known as acceptor type semi conductor.
What is a p-n junction?
When a p type semi-conductor is placed in contact with an n-type semiconductor, it is known as p-n junction.
What is depletion region?
The thin region around p-n junction having immobile positive and negative charges is known as depletion region.
What is barrier potential or junction barrier?
The potential difference due to the negative immobile ions on the side of the p-type and the positive immobile ions on the side of the n-type in a p-n junction is called barrier potential.
