Introduction to Semiconductors Practice Flashcards

Vocabulary practice flashcards covering semiconductor materials, energy bands, diodes, rectification, and transistor operations based on the lecture transcript.

Conductor

A material or metal which allows the flow of electric current under the application of an electric field or voltage source of limited magnitude, such as copper or aluminum.

Insulator

A material which does not allow the flow of electric current under the application of an electric field, such as rubber or wood.

Semi-conductors

Substances that fall in an intermediate position between metals and insulators with resistivity higher than that of a good conductor; examples include silicon and germanium.

Tetravalent

A characteristic of silicon and germanium atoms where they have four electrons in their outermost shell, known as valence electrons.

Intrinsic semiconductor

A pure semiconductor in which both electrons and holes are solely responsible for current flow, and the number of free electrons is always equal to the number of holes.

Extrinsic semiconductor

Also called an impurity semiconductor, it is a pure semiconductor that has had its electrical conductivity increased by adding a small amount of impurity of the order of one atom per million atoms.

Doping

The process of adding impurities to semiconductors to increase their electrical conductivity.

Dopant

The specific impurity atom added during the doping process.

N-type semiconductor

A semiconductor formed when a small quantity of a pentavalent element, such as phosphorus, arsenic, or antimony, is added to a pure silicon crystal.

Donor

Pentavalent atoms that provide an extra electron to the conduction band of a crystal.

P-type semiconductor

An extrinsic semiconductor formed when a trivalent atom, such as boron or aluminum, is added to a pure crystal, creating a deficiency of one valence electron called a hole.

Hole

A deficiency of one valence electron that is free to move within the crystal, acting as a positively charged particle contributing to current flow.

Acceptors

Impurity atoms that contribute holes to a semiconductor by accepting electrons from germanium or silicon atoms.

Valence band

The energy band formed by valence electrons in the outermost shell, representing the highest occupied energy band.

Conduction band

The energy band containing free electrons that have left the valence band to conduct current; it is the band with the lowest occupied energy.

Forbidden energy gap

The gap between the valence band and the conduction band consisting of a series of energies which electrons cannot possess.

P-N Junction

A boundary of the order of $10^{-3}\,mm$ formed when a p-type material semiconductor is joined and melted/diffused with an n-type semiconductor.

Forward bias

An arrangement where the positive terminal of a battery is connected to the p-type and the negative terminal to the n-type, lowering the potential barrier and allowing high current flow.

Reverse bias

An arrangement where the positive terminal is connected to the n-type and the negative to the p-type, increasing the potential barrier and resulting in negligibly small current.

Avalanche breakdown

A process where electrons are released from atomic bonds and move across a junction, causing more electrons to break loose from other atoms.

Rectification

The process of using diodes to convert alternating current (AC) into direct current (DC).

Rectifier

A circuit that employs one or more diodes to convert AC voltage to DC voltage.

Ripple factor

The ratio of the RMS value of the AC component of the output voltage to the DC component of the output voltage.

Form factor

The ratio of the RMS value to the DC value, which is $1.57$ for a half-wave rectifier.

Rectifier efficiency ($\eta$)

The ratio of output DC power to the input AC power, which is $40.6\%$ for a half-wave rectifier.

Bridge rectifier

A full-wave rectifier circuit involving four diodes that does not require a center-tapped transformer.

Transistor

A semiconducting device invented in 1948 by William Shockley, John Bardeen, and Walter Brattain consisting of an emitter, base, and collector used to produce output signals in response to input signals.

Cut-off region

The operating region where a transistor is "Fully-OFF," characterized by zero base current ($I_B = 0$) and zero collector current ($I_C = 0$).

Saturation region

The operating region where a transistor is "Fully-ON," characterized by maximum base current and maximum collector current.

Active region

The region of the curve where a transistor acts as an amplifier, situated between the cut-off and saturation regions.

Input resistance

The resistance offered by the emitter-base junction to the flow of signal, defined as the ratio of change in emitter-base voltage to change in base current.

Current gain

The ratio of the change in the collector current to the change in the base current, typically ranging from $20$ to $500$.

Power gain

The ratio of the output signal power to the input signal power in a transistor amplifier.