Definition, Furmula | Semiconductor
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
The net current flows across a semiconductor has two components: (i) Drift current (ii) Diffusion current.
electron and hole
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
The types of drift of electrons and of holes are different, the mobility of an electron at any temperature is different from (greater than) that of the hole.
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
In absence of an electrical field, the free electrons (electron gas) move in all directions in a random manner. They collide with other free electrons and positive ion core during the motion. This collision is known as elastic collision
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
In extrinsic semiconductor, the resistivity decreases linearly with increase in temperature. This variation is considered under three different regions.
Derivation
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
In p-type semiconductor, acceptor energy level is just above valence band
Energy band, Crystal Structure, Diagram
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
When a small amount of trivalent impurity is doped pure semiconductor, it becomes p-type semi-conductor.
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
The energy band diagram of n-type semiconductor is shown in figure 3.8. In n-type semiconductor, the donor level is just below conduction band
Covalent bond, Energy band, Crystal Structure, Diagram
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
When a small amount of pentavalent impurity (group V element) is doped to a pure semiconductor, it becomes n-type semiconductor.
Doping, Advantages, Types
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
In a semiconducting material, if the charge carriers originate from impurity atoms which are doped to the original material, then this type of semiconductor is known as extrinsic or impure semiconductor.
Derivation, Limitations
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
In an intrinsic semiconductor, the number of electrons in conduction band is equal to the number of holes in valence band.
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
We know that if an electron is transferred from valence band to conduction band, a hole is created in valence band
Density of Electrons in Conduction Band (Derivation)
Subject and UNIT: Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
The number of electrons in conduction band per unit volume of the material is called as electron concentration (n). In general, the number of charge carriers per unit volume of the material is called carrier concentration. It is also known as density of charge carriers.