Intrinsic and Extrinsic semiconductors the concept of effective

Intrinsic and Extrinsic semiconductors- the concept of effective mass
Intrinsic semiconductors are pure semiconductors, meaning they are made up of only one type of element, such as silicon (Si) or germanium (Ge). At absolute zero temperature (-273.15°C or 0 Kelvin), intrinsic semiconductors behave like insulators because all of the electrons are tightly bound to their atoms.
However, as the temperature increases, some electrons gain enough energy to break free from their atoms and move into the conduction band, where they can conduct electricity. These electrons leave behind holes in the valence band, which can also act as charge carriers.
The number of electrons in the conduction band and the number of holes in the valence band are always equal in an intrinsic semiconductor.
Extrinsic semiconductors are semiconductors that have been doped with impurities. Doping is the process of adding a small amount of a different element to a semiconductor.
The type of impurity that is added determines whether the semiconductor becomes an n-type semiconductor or a p-type semiconductor.
N-type semiconductors are created by doping an intrinsic semiconductor with a donor impurity, which is an element that has more valence electrons than the host semiconductor.
This creates an excess of electrons in the conduction band, making the semiconductor more conductive.
P-type semiconductors are created by doping an intrinsic semiconductor with an acceptor impurity, which is an element that has fewer valence electrons than the host semiconductor.
This creates an excess of holes in the valence band, making the semiconductor more conductive.
Effective mass is a concept used to describe the behavior of charge carriers in semiconductors. In a free-electron model, electrons are considered to be point particles with a mass equal to the rest mass of an electron.
However, in a semiconductor, electrons are not free to move as they please; they are instead confined to the crystal lattice. This confinement affects the way that electrons interact with the crystal lattice, which in turn affects their effective mass.
The effective mass of an electron in a semiconductor can be larger or smaller than the rest mass of an electron, depending on the direction of motion and the band structure of the semiconductor.
The concept of effective mass is important for understanding the transport properties of semiconductors, such as electrical conductivity and mobility.
Effective mass also plays a role in other semiconductor phenomena, such as optical absorption and recombination.