Introduction to Semiconductors 283

all-electrical

A circuit or device without any moving mechanical parts. All-electrical devices like semiconductor devices are smaller, faster, and more reliable than mechanical devices.

amorphous solid

A type of solid matter that does not have a regular, ordered pattern to its atomic structure. Amorphous solid semiconductors mainly include glassy materials.

amplification

The process of increasing the size or strength of a signal. Amplification processes often use semiconductors to increase electrical signals or optical signals like light tens of thousands of times.

anode

An electrode with a positive charge. In forward-bias diodes, current moves from the cathode to the anode.

antimony

Sb. A silvery-white, brittle metal. Antimony is a common dopant in N-type semiconductors.

arsenic

As. A silvery metalloid. Arsenic is a common dopant in N-type semiconductors.

atom

The smallest distinguishable unit of a material that maintains that material's characteristics. Atoms include protons, neutrons, and electrons.

atomic structure

The organization of atoms in a substance. Atomic structure determines the properties of a material.

automated

Controlled by machines or computers with little human interaction. Automated semiconductor fabrication uses robots to reduce the risk of contamination and to improve precision.

avalanche region

The area of a characteristic curve that begins after a forward-bias semiconductor reaches its peak inverse voltage and begins to pass an unlimited amount of reverse current. Entering the avalanche region destroys forward-bias semiconductors.

bandgap

The range of energy levels between the valence and conductive states, or bands, of an electron. The size of a bandgap determines how much energy is required to excite electrons from the valence to the conductive state in order to conduct current.

bias

The direction in which a voltage is applied to a diode. Most typical diodes pass voltage applied from cathode to anode, or in forward-bias, and block voltage applied from anode to cathode, or in reverse-bias.

bismuth

Bi. A white, brittle metal with a pinkish tinge. Bismuth is a common dopant in N-type semiconductors.

boron

B. A gray metalloid that has three valence electrons. Boron is commonly used as a dopant to create holes in silicon semiconductors.

cadmium telluride

CdTe. A compound of cadmium and tellurium. Cadmium telluride is a less common semiconductor material that is often used in solar cells.

cathode

An electrode with a negative charge. In forward-bias diodes, current moves from the cathode to the anode.

characteristic curves

A graphical representation of the relationship between current and voltage in a semiconductor. Characteristic curves, or IV curves, are often included in semiconductor datasheets.

charge carriers

A particle with a corresponding positive or negative electric charge. Holes are considered positive charge carriers, while electrons are considered negative charge carriers.

chips

A complete, miniaturized electronic circuit that contains a variety of components on a single piece of a semiconductor wafer. Chips, also known as microchips or integrated circuits (ICs), include components like transistors, resistors, capacitors, and diodes.

circuits

A completely enclosed path along which electrical current flows. Circuits often contain semiconductor devices.

clean rooms

An enclosed environment that has a low level of environmental contaminants such as dust, airborne microbes, aerosol particles, and chemical vapors. In a clean room, the temperature, humidity, and air pressure are also precisely controlled.

compounds

A substance consisting of the atoms of two or more different elements in fixed proportions. Compounds used as semiconductors include organic materials like doped polyacetylene and inorganic materials like gallium arsenide and cadmium telluride.

conductivity

A material's ability to act as a medium for conveying electricity. A material's level of electrical conductivity depends on its atomic structure.

conductor

A material or element that allows the free movement of electrons and, therefore, easily transmits electricity. Most conductors are metals.

covalent bonds

A chemical bond that occurs when two atoms share electrons. The covalent bonds that form between the atoms of intrinsic semiconductors create a crystalline structure that does not allow much electrical conduction.

crystalline solids

A non-flowing form of a substance with atoms that are arranged in a rigid order with a repeating pattern. Most semiconductors, including silicon, are crystalline solids.

current

The flow of electricity. Current strength is called amperage and is measured in amperes (A).

depletion region

A small band across the junction of a diode where recombination occurs. The depletion region fills with ions that generate an electric field.

diode

A semiconductor device that allows electrical current to flow in one direction and blocks current from flowing in the opposite direction. P-N junctions are the simplest type of diode.

dopants

A trace amount of an element that is added to an intrinsic semiconductor to increase its conductivity. Dopants must have a different number of valence electrons than the intrinsic semiconductor and are generally present in semiconductors at levels of parts per billion or smaller.

doping

Enriching an intrinsic semiconductor with trace amounts of other elements to increase its conductivity. Doping adds holes or free electrons to a semiconductor's atomic structure.

electric field

A region around a charged particle that exerts a force on other charged particles. Electric fields form around ions in diodes and prevent electrons from flowing freely unless sufficient external voltage is applied.

electron acceptors

A semiconductor that has holes that can accommodate free electrons. P-type semiconductors are considered electron acceptors.

electron donors

A semiconductor that has free electrons moving through it. N-type semiconductors are considered electron donors.

electron theory

The belief that electricity flows out from a negative source to seek a positive conclusion. Electron theory is currently accepted.

elements

A basic substance consisting only of atoms that share the same number of protons. Elements include carbon, hydrogen, and oxygen.

energy band theory

The theory that describes the range of energy levels corresponding to different electron states as bands separated by bandgaps. According to energy band theory, materials with larger bandgaps require more energy to excite electrons from the valence state to the conductive state.

extrinsic semiconductors

A semiconductor material that has had a small amount of another element added to it. Extrinsic semiconductors, or doped semiconductors, contain dopants to increase their conductivity.

forward voltage

A voltage that is applied from the cathode to the anode of a forward-bias diode. Forward-bias diodes can pass an exponential amount of forward voltage.

forward-bias

A condition in which current flows from the cathode to the anode of a diode. Forward-bias diodes are more popular than reverse-bias diodes.

free electron

A valence electron that is not part of a covalent bond or otherwise permanently attached to an atom. Free electrons can move and carry current in a semiconductor.

gallium

Ga. A silvery-blue, crystalline metal that is relatively soft at room temperature. Gallium is a common dopant in P-type semiconductors.

gallium arsenide

GaAs. A compound of gallium and arsenic. Gallium arsenide is one of the most common intrinsic semiconductors.

germanium

Ge. A gray-white, crystalline metalloid that is hard and brittle. Germanium is one of the most common intrinsic semiconductors.

hole

An extra opening in a semiconductor material that free electrons can move into and form new bonds. Holes play an integral role in conducting current.

indium

In. A silvery-gray, soft and ductile metal. Indium is a common dopant in P-type semiconductors.

Institute of Electrical and Electronics Engineers

IEEE. An international professional organization for engineers who work with electricity and electronics. The Institute of Electrical and Electronics Engineers helps develop semiconductor standards in the U.S.

insulator

A material or element that has little electrical conductivity and high resistance to electrical charges. Most insulators are plastics and ceramics.

integrated circuits

ICs. A complete, miniaturized electronic circuit that contains a variety of components on a single piece of a semiconductor wafer. Integrated circuits, also known as microchips or chips, include components like transistors, resistors, capacitors, and diodes.

intrinsic semiconductors

A naturally occurring semiconductor material. Intrinsic semiconductors have a low level of electron movement and must be altered, or doped, to increase their conductivity to desirable levels.

ions

An atom or molecule with an electric charge caused by losing or gaining electrons. Positive ions develop in N-type semiconductors as they lose electrons, while negative ions develop in P-type semiconductors as they gain electrons.

IV curves

A graphical representation of the relationship between current and voltage in a semiconductor. IV curves, or characteristic curves, are often included in semiconductor datasheets.

Joint Electron Device Engineering Council

JEDEC. An independent semiconductor engineering trade organization. The Joint Electron Device Engineering Council helps develop semiconductor standards that are used in the U.S.

junction potential

The minimum amount of voltage that is required to pass electrons through the depletion region of a diode and turn it on. Junction potential varies based on the amount of energy required to excite the electrons from the valence state to the conductive state.

knee

The point on a characteristic curve at which a forward-bias diode reaches its junction potential. After surpassing the knee, diodes can pass a nearly unlimited amount of current.

leakage

A negligible amount of current. A small amount of leakage current passes through forward-bias diodes when reverse voltage is applied.

light sensors

A group of photovoltaic semiconductor devices that detects light, including photodiodes, photoresistors, phototransistors, and photovoltaic sensors. Light sensors can respond to changes in the amount of light received, measure illuminance, or convert light to electricity.

light-emitting diodes

LEDs. A semiconductor device that emits a narrow spectrum of light in a forward direction. Light-emitting diodes are replacing most standard incandescent lightbulbs.

localized

Confined to a specific region between two atoms. Localized electrons remain in a fixed position due to a covalent bond and generally do not allow much electrical conduction.

majority charge carrier

A type of charge carrier that is present in the largest quantities in a semiconductor and carries the electric current. The majority charge carriers in N-type semiconductors are electrons and the majority charge carriers in P-type semiconductors are holes.

metal

A naturally occurring material that is strong, hard, ductile, and thermally and electrically conductive. Common metals include iron, steel, aluminum, and copper.

microchips

A complete, miniaturized electronic circuit that contains a variety of components on a single piece of a semiconductor wafer. Microchips, also known as chips or integrated circuits (ICs), include components like transistors, resistors, capacitors, and diodes.

microelectronics

A miniaturized electronic device or circuit. Microelectronics, including microchips and microcircuits, rely on semiconductor devices.

motor controls

The use of various devices to start, stop, or change the speed or direction of a motor. Motor control applications can be made increasingly fast and accurate with the use of semiconductor devices.

negative

Having more electrons than protons. Negative charges move through N-type semiconductors, which have free electrons and no holes.

N-type

A semiconductor that causes current to flow by creating free electrons that are easily excited into movement. N-type semiconductors are considered electron donors and are commonly doped with arsenic, bismuth, phosphorus, and antimony.

peak inverse voltage

PIV. The maximum amount of reverse voltage a forward-bias diode can withstand before being destroyed. After exceeding peak inverse voltage, a forward-bias diode enters its avalanche region and can experience thermal runaway.

phosphorus

P. A waxy, nonmetallic element that has five valence electrons. Phosphorus is commonly used as a dopant to add free electrons to silicon semiconductors.

photons

A particle of light energy. Photons are released by some semiconductors when their electrons are excited.

photovoltaics

The conversion of light into electricity. Photovoltaics require semiconductor materials that convert light into electrical energy and are used in technology like solar charging and photosensors.

P-N junction diode

An electrical device that combines a P-type semiconductor and an N-type semiconductor to control the direction of current flow. The P-N junction diode allows the electricity to flow from the N-type semiconductor to the P-type semiconductor.

polarized devices

A component with two oppositely charged poles, one positive and one negative. Polarized devices block or allow the flow of current depending on their orientation in a circuit.

positive

Having fewer electrons than protons. Positive charges move through P-type semiconductors, which have more holes than electrons.

P-type

A semiconductor that causes current to flow by creating holes that enable the movement of valence electrons. P-type semiconductors are considered electron acceptors and are commonly doped with gallium, boron, and indium.

recombination

A rapid process during which holes from a P-type semiconductor and electrons from an N-type semiconductor move towards each other and combine. Recombination occurs in a small band of a diode called the depletion region.

rectification

The process of converting AC to DC power for use in an electrical circuit. In rectification processes, semiconductor diodes prevent the flow of current in more than one direction.

resistivity

A material's tendency to oppose the flow of current. The resistivity of semiconductors decreases as their temperature increases.

reverse voltage

A voltage that is applied from the anode to the cathode of a forward-bias diode. Reverse voltage will destroy most forward-bias devices.

reverse-bias

A condition in which current flows from the anode to the cathode of diode. Reverse-bias diodes, such as Zener diodes, are less common than forward-bias diodes.

robots

A machine that automatically performs complicated and repetitive tasks. Robots often perform work that is more precise and consistent than work performed by humans.

SEMI

An international organization for semiconductor development, trade, regulation, and supply chain research. SEMI partners with professional and governmental agencies to advance the semiconductor industry.

semiconductor devices

An all-electrical component made from semiconductor materials. Semiconductor devices such as diodes, transistors, and integrated circuits (ICs) are small, fast, reliable components.

semiconductors

A material or element with an electrical conductivity level between that of a conductor and an insulator. Semiconductors have four valence electrons and are most commonly crystalline solids.

signal processing

The analysis, synthesis, or altering of signals such as images, sound waves, and electrical current. Signal processing applications can be made increasingly fast and accurate with the use of semiconductor devices.

silicon

Si. A blue-gray, nonmetallic, crystalline material that is hard and brittle. Silicon is the most popular intrinsic semiconductor.

solar cells

A photovoltaic semiconductor device that converts light energy into electrical energy. Solar cells, or photovoltaic cells, can be used in solar panels and light sensors.

solar charging

A power generation process that uses solar energy to supply electricity to devices or batteries. Solar charging uses photovoltaic semiconductor devices.

solid state

A state of matter that exists in a non-flowing form at room temperature. Most semiconductors have a crystalline atomic structure in the solid state.

solid-state switches

A solid-state semiconductor device used to make, break, or change the route of current flow in a circuit. Solid-state switches like diodes have no moving parts, unlike electromechanical devices, such as pushbuttons and toggle switches.

terminal

A conductive component on an electrical device to which other components can be attached. Terminals have a negative or a positive charge.

thermal conductivity

A material's ability to act as a medium for conveying heat. Some semiconductors can be used for their properties of thermal conductivity to convert heat into electricity or transfer it.

thermal runaway

An uncontrollable chain reaction that occurs when increases in temperature cause a semiconductor to release increasing amounts of energy. Thermal runaway destroys semiconductors and can result in fires.

thermoelectric coolers

A semiconductor with low thermoelectric conductivity that transfers heat away from hot areas. Thermoelectric coolers have applications in refrigeration and temperature control.

thermoelectric generators

A semiconductor with low thermoelectric conductivity that converts heat directly into electricity. Thermoelectric generators do not require additional steps or machinery to convert heat, unlike mechanical turbines and generators.

thermoelectric properties

A material's tendency to produce electricity through a change in temperature. Thermoelectric properties of semiconductors include cooling, heating, and decreasing in resistivity with an increase in temperature.

tubes

An electromechanical device that uses two or more electrodes sealed in near-vacuum conditions in an airtight case to control the flow of electrons. Tubes are usually made of glass, bulky, and failure prone.

valence electrons

An electron located in the outermost, or valence, shell of an atom. Valence electrons are easily shared or transferred, and their availability and movement influence electrical conductivity.

voltage

A measure of electrical pressure or potential that causes current to flow in a circuit. Voltage is measured in volts (V).

volts

V. A unit used to measure the electrical pressure or potential that causes current to flow in a circuit. Volts are a unit of voltage.

wafer

A thin, round slice of semiconductive material, such as silicon, in which electrical circuitry is embedded. Semiconductor wafers must be perfectly flat.

Zener diodes

A special type of semiconductor device that is designed to work in reverse-bias. Zener diodes efficiently conduct current when a reverse voltage is applied, which most standard diodes block.