Semiconductors and PN Junctions - Vocabulary Flashcards

Vocabulary flashcards covering key terms from the semiconductor notes and PN junction concepts.

Conductor

A material that allows electric charges to flow easily due to many free electrons.

Insulator

A material that blocks or greatly reduces charge flow because it has very few free electrons.

Semiconductor

Material whose conductivity is between conductors and insulators and can be controlled by temperature and doping.

Switch

The basic unit of a computer that turns on and off; modern switches are solid-state with no moving parts.

Bound electron

An electron tightly held by the nucleus and not free to conduct.

Conduction electron

A free electron that can move and carry electric current.

Free electron

An electron not bound to an atom and able to move freely; often used interchangeably with conduction electron.

Pauli Exclusion Principle

No two electrons can have identical quantum states; governs how electrons fill energy levels.

Molecular orbital

Orbital formed by combining atomic orbitals when atoms form a solid; supports energy levels.

Energy band

A continuous range of allowed energies in a solid formed from overlapping atomic/molecular orbitals.

Valence band

Highest energy band that is filled with electrons at 0 K.

Conduction band

Next higher energy band; electrons must occupy it to conduct electricity.

Band gap

Energy difference between valence and conduction bands that controls conductivity.

Zero Kelvin (0 K)

Lowest possible energy state; absolute zero temperature.

Intrinsic semiconductor

Pure semiconductor with equal numbers of electrons and holes, generated thermally.

Intrinsic carrier concentration (ni)

Number of free electrons equals number of holes in an intrinsic semiconductor.

Donor impurity

Group 15 element added to silicon to donate extra electrons (n-type).

Donor level

Energy level near the bottom of the conduction band introduced by a donor impurity.

N-type semiconductor

Doped to have electrons as majority carriers; donors raise electron concentration.

Phosphorus (P) as donor

Group 15 element used to create n-type silicon by donating electrons.

Donor level proximity

Donor level lies close to the bottom of the conduction band for easy electron excitation.

Acceptor impurity

Group 13 element added to silicon to create holes (p-type).

Acceptor level

Energy level introduced by an acceptor impurity near the valence band.

P-type semiconductor

Doped to have holes as majority carriers; acceptor impurities create holes.

Boron (B) as acceptor

Group 13 element used to create p-type silicon by creating holes.

Holes

Mobile, positively charged absence of an electron in the valence band; carry current.

Neutrality

Overall electrical neutrality; donors and acceptors balance charges.

Doping

Process of adding impurities to a semiconductor to change its electrical properties.

Extrinsic semiconductor

Semiconductor whose properties are altered by intentional dopants (n- or p-type).

Doping concentration

Very low concentration of dopants to preserve the host band structure.

PN Junction

Interface formed by joining a p-type and an n-type semiconductor.

Depletion region

Region near the PN junction depleted of mobile charge carriers; contains fixed ions.

Barrier potential

Electric potential across the depletion region that opposes carrier diffusion (≈0.7 V in Si).

Diffusion current

Current due to diffusion of majority carriers across the PN junction.

Drift current

Current due to motion of minority carriers driven by the electric field in the depletion region.

Forward bias

Applying a voltage with + to P and - to N; lowers the barrier and increases diffusion current.

Reverse bias

Applying a voltage with - to P and + to N; widens depletion region and reduces current.

Forward-biased PN junction

Conducts heavily; diffusion current dominates as barrier drops near 0.7 V.

Reverse-biased PN junction

Acts as an insulator; very small current, mainly due to minority carriers.

Majority carrier

The most abundant charge carrier in a region (electrons in n-type, holes in p-type).

Minority carrier

The less abundant charge carrier (holes in n-type, electrons in p-type).

Generation

Process by which electrons are thermally excited to the conduction band, creating electron-hole pairs.

Recombination

Process where free electrons recombine with holes, annihilating the pair.

Thermal equilibrium

State where generation rate equals recombination rate, keeping carrier numbers constant.