SEMICONDUCTOR DIODES - Vocabulary Flashcards (Video Notes)

Vocabulary flashcards covering key terms and definitions from the Semiconductor Diodes notes (sections 13.1–13.19).

Intrinsic semiconductor

A semiconductor in its extremely pure form with impurity content below about 1 part in 100 million; at room temperature electrons are thermally excited across the energy gap creating electron–hole pairs.

Extrinsic semiconductor

Doped semiconductor whose conductivity is greatly increased by a small amount of impurity added during crystal growth.

Doping

Addition of impurity atoms to an intrinsic semiconductor to modify its electrical properties.

Donor impurity

Pentavalent impurity used to produce N-type semiconductors by donating extra electrons to the conduction band.

Donor energy level

A discrete energy level introduced just below the conduction band by donor impurities, e.g., about 0.05 eV (Si) or 0.01 eV (Ge), enabling easy promotion of electrons to the conduction band.

Acceptor impurity

Trivalent impurity used to produce P-type semiconductors by creating holes in the valence band.

Acceptor energy level

A discrete energy level just above the valence band created by acceptor impurities, requiring small energy to create holes (e.g., ~0.08 eV for Si, ~0.01 eV for Ge).

N-type semiconductor

Extrinsic semiconductor in which electrons are the majority carriers due to donor impurities; material is electrically neutral overall.

P-type semiconductor

Extrinsic semiconductor in which holes are the majority carriers due to acceptor impurities; the material is electrically neutral overall.

Depletion region

The zone around a PN junction where mobile charge carriers are depleted, leaving fixed ions and creating the space-charge region.

Barrier potential (built-in potential)

The contact potential that forms at a PN junction due to diffusion of carriers; typically about 0.3 V for Ge and 0.7 V for Si; depends on doping and temperature.

Knee voltage (cut-in voltage)

Forward voltage at which the PN junction current starts to rise rapidly; about 0.3 V (Ge) or 0.7 V (Si).

Forward bias

Connection of the P-type region to the positive terminal and the N-type region to the negative terminal, reducing the barrier and allowing current to flow.

Reverse bias

Connection of the P-type region to the negative terminal and the N-type region to the positive terminal, widening the depletion region and greatly reducing current.

Reverse saturation current

Very small current that flows in reverse due to minority carriers crossing the junction; increases with temperature.

Breakdown voltage

The reverse voltage at which a PN junction diode conducts a large reverse current due to breakdown mechanisms.

Zener breakdown

Breakdown in heavily doped junctions at relatively low reverse voltages, where a strong electric field causes bond breakage; temperature coefficient is typically negative.

Avalanche breakdown

Breakdown in lightly doped junctions due to impact ionization; current rises sharply under reverse voltage; temperature coefficient is positive.

Junction diode

A diode formed by a PN junction with two terminals; the basic unidirectional device used for rectification and switching.

Ideal diode

A hypothetical diode that conducts with zero forward drop and blocks all reverse current; infinitely abrupt on/off behavior.

Real diode

A practical diode modeled as an ideal diode in series with a barrier potential (Vo) and a forward resistance (r′); no perfect conductance or insulation.

Forward resistance (r′)

The small-signal or dynamic resistance of a diode when it is in forward conduction.

Mobility (μ)

Proportionality between drift velocity and applied electric field: v = μE; mobility measures how quickly charge carriers respond to an electric field.

Drift current

Current caused by the movement of charge carriers in response to an applied electric field.

Diffusion current

Current caused by the movement of carriers due to concentration gradients, from regions of high to low concentration.

Holes

Positive charge carriers created when an electron leaves a covalent bond; move opposite to electrons and contribute to current in the valence band.

Electrons

Negative charge carriers that populate the conduction band and drive current in the N-type region; mobility typically higher than holes.

Majority carriers

The most abundant type of charge carrier in a material (electrons in N-type, holes in P-type).

Minority carriers

The less abundant type of charge carrier in a material (holes in N-type, electrons in P-type).

Recombination

The process by which a free electron recombines with a hole, releasing energy and returning to a bound state.

Valence band

The energy band containing the outer-shell electrons that participate in bonding; holes are created as electrons leave this band.

Conduction band

The energy band in which electrons are free to move and contribute to electrical conduction.

Energy gap (for solids)

The forbidden energy gap between the valence band and the conduction band; wider in insulators, narrower in semiconductors, negligible in metals.

Energy level diagram

A schematic showing energy levels (in eV) and bands, illustrating allowed and forbidden regions for electrons in a material.

Forbidden energy gap

The energy range between valence and conduction bands where no electron states exist; electrons cannot occupy these energies under normal conditions.

Energy bands in solids

Bands of closely spaced energy levels that electrons can occupy in a solid; includes valence and conduction bands separated by the energy gap.

Conduction in solids

The mechanism by which electrical current flows in solids, via drift of electrons and/or diffusion of holes (and electron-hole pairs).

Bonding types (metallic, covalent, ionic)

Types of atomic bonds explained in solids: metallic (electron cloud), covalent (sharing electrons), and ionic (transfer of electrons).