Technical LED Glossary

The field of LED and optoelectronic technology is rapidly evolving, bringing with it a growing set of specialized terms that can be difficult to navigate. Tech-LED.com specializes in advanced LED solutions for applications such as medical diagnostics, industrial sensing, security, machine vision, and scientific research. Our products include infrared (IR), near-infrared (NIR), short-wave infrared (SWIR), ultraviolet (UV), and visible spectrum LEDs, photodiodes, and chip-on-board (COB) LED technology.

Whether you're an engineer, product developer, or researcher, this glossary serves as a comprehensive reference to help you better understand LED and photonics-related terminology. With a focus on clarity and accuracy, this guide provides concise definitions, industry insights, and direct links to relevant LED products.

Explore the terms below and expand your knowledge of specialized LED and optoelectronic technology!

A

**AC (Alternating Current)**An electric current that periodically reverses direction, commonly used in household power supplies.

Accent LightingLighting used to highlight specific areas or objects, often for decorative or architectural purposes.

**Active Layer
**A thin semiconductor layer at the p-n junction of an LED, where electron-hole recombination occurs to emit light.

**Aluminum Gallium Nitride (AlGaN)
**A semiconductor material used as a barrier layer to confine electrons in the active layer of blue LEDs.

Ambient LightingGeneral illumination that provides overall brightness to a space, ensuring visibility and comfort.

**Amperage (Amps)**The strength of an electric current measured in amperes (A), representing the flow of electricity.

**Annealing
**A process of heating a material to change its properties. Used in LED manufacturing to activate p-type doping.

AnodeThe positively charged electrode in an LED where current enters the device.

B

**Band Gap
**The energy difference between the valence band and conduction band in a semiconductor. The size of the band gap determines the color of light emitted in an LED.

Beam AngleThe angle at which light is emitted from a source, determining how widely the light spreads.

BinningThe process of sorting LEDs based on brightness, color, and other performance characteristics to ensure consistency.

Bi-Color LEDAn LED that contains two different semiconductor chips in a single package, allowing for two distinct colors. Learn more.

**Buffer Layer
**An intermediate layer used in semiconductor growth to reduce defects and improve crystal quality. E.g., Aluminum Nitride (AlN) was used to improve gallium nitride crystal growth.

C

**Candela (cd)**A unit of luminous intensity, measuring the power emitted by a light source in a specific direction.

CathodeThe negatively charged electrode in an LED where current exits the device.

Chip MaterialThe semiconductor material used in LED chips, such as AlInGaN or GaAs, affecting performance and wavelength.

Chip-on-Board (COB) LEDAn LED package where multiple LED chips are mounted on a single board for higher power and efficiency. Learn more.

**Color Rendering Index (CRI)**A measure of how accurately a light source displays colors compared to natural light, rated from 0 to 100.

Color TemperatureThe hue of light emitted by a source, measured in Kelvin (K). Warmer tones have lower Kelvin values, while cooler tones have higher values.

**Conduction Band
**The higher energy band in a semiconductor where electrons can move freely, allowing electrical conductivity.

ControllerA device that manages LED functions such as dimming, color changing, and sequencing.

**Crystal Lattice
**The orderly structure of atoms in a semiconductor crystal. High-quality crystal lattices are crucial for efficient LEDs.

D

**DC (Direct Current)**An electric current that flows in one direction, commonly used in LED applications.

Depletion Region – The region around the p-n junction where mobile charge carriers are depleted, creating an electric field that controls the flow of electrons and holes.

**Diode
**A component with two electrodes that allows current to flow in only one direction.

Dimmable LEDAn LED designed to support adjustable brightness levels when used with compatible dimmers.

Doping – The process of adding impurities to a semiconductor to change its electrical properties. It enables the creation of n-type and p-type semiconductors.

DriverAn electronic device that regulates power to an LED, ensuring stable performance and longevity.

E

EDC LEDA high-power LED designed for compact high-intensity lighting. Learn more.

EDCC LEDA high-power LED series providing a wide range of wavelengths, often used for specialized applications. Learn more.

EfficacyA measure of how efficiently a light source converts electricity into visible light, expressed in lumens per watt (lm/W).

ElectroluminescenceThe phenomenon where materials emit light when an electric current or strong electric field is applied, fundamental to LED operation.

**Electron Beam Irradiation
**A technique used to modify semiconductor properties, such as converting magnesium-doped gallium nitride into p-type.

**Electron Mobility
**A measure of how quickly electrons can move through a semiconductor material, affecting LED efficiency.

**External Quantum Efficiency (EQE)**The ratio of the number of photons emitted from an LED to the number of electrons passing through it, expressed as a percentage.

F

**Foot-candle (fc)**A unit measuring illuminance, indicating how much light falls on a surface from one foot away.

Forward CurrentThe amount of current required for an LED to operate efficiently, typically measured in milliamps (mA) or amps (A).

**Forward Voltage (Vf)**The voltage drop across an LED when it is forward-biased, critical for determining the proper operating voltage and power supply design.

G

**Gallium Arsenide (GaAs)
**A semiconductor material used as a substrate for growing other semiconductor layers.

**Gallium Nitride (GaN)
**A semiconductor material with a large band gap, critical for producing blue LEDs.

GlareExcessive brightness that causes discomfort or impairs visibility.

H

Half WidthA specification that describes the spectral width of an LED at half its peak intensity, often used to determine color purity.

Heat SinkA component that dissipates heat from LEDs, ensuring optimal performance and longevity.

High-Power Illuminator LEDA high-output LED array designed for industrial applications. Learn more.

**Hydrogen Passivation
**A phenomenon where hydrogen atoms bond with dopants like magnesium in gallium nitride, preventing p-type behavior until annealing removes the hydrogen.

I

IlluminanceThe amount of light falling onto a surface area, measured in lux or foot-candles.

**Indium Gallium Nitride (InGaN)
**A compound semiconductor used as an active layer in blue LEDs to enhance light emission and improve efficiency.

Ingress Protection (IP) RatingA classification indicating a light fixture’s resistance to dust and water.

Infrared (IR) LEDAn LED that emits infrared light, often used in night vision, security, and remote sensing applications. Learn more.

J

**Junction Temperature (Tj)**The operating temperature at the LED's semiconductor junction. Maintaining a low junction temperature is crucial for optimizing performance, efficiency, and longevity.

K

**Kelvin (K)**A unit measuring color temperature, describing whether light appears warm or cool.

KGD (Known-Good-Die) LEDA semiconductor die that has passed full electrical and optical testing before packaging. Learn more.

L

**Lattice Mismatch
**The difference in atomic spacing between a substrate and a semiconductor layer grown on top of it. High lattice mismatch leads to defects that reduce LED efficiency.

Lead Frame DieThe metallic structure that supports the LED chip and provides electrical connectivity.

**LED (Light-Emitting Diode)**A semiconductor device that emits light when an electric current flows through it. The color of the emitted light depends on the band gap of the semiconductor material used.

LED ChipsSemiconductor chips that form the core of an LED, determining color and brightness. Learn more.

LensAn optical component placed over an LED to control the direction and spread of emitted light.

**Lumen (lm)**A measure of the total amount of visible light emitted by a source.

Luminous EfficacyThe ratio of lumens produced per watt of electricity consumed, indicating the efficiency of a light source.

Luminous FluxThe total visible light emitted by a source, measured in lumens.

**Lux (lx)**A unit of illuminance measuring how much light is received on a surface area.

**Luminance (cd/m²)**A measure of the brightness of a surface, defined as the amount of light emitted in a given direction per unit area.

M

MacAdam EllipseA region on a chromaticity diagram representing colors that appear indistinguishable to the human eye.

**Metal-Organic Chemical Vapor Deposition (MOCVD)
**A technique for growing high-purity semiconductor crystals by injecting metal-organic vapor molecules into a heated chamber where they react and deposit layers onto a substrate.

**Micro LEDs
**Extremely small LEDs (as small as 5 microns) used for high-resolution displays, AR/VR applications, and next-generation lighting.

Micro UV-LED ChipA small ultraviolet LED chip used in specialized applications. Learn more.

N

Narrow Beam Angle LEDLEDs designed with a focused light output (e.g., +/-10° lenses) for high-intensity applications.

**Nanometer (nm)**A unit of measurement equal to one billionth of a meter, commonly used to define wavelengths of light.

Near UV LEDAn LED that emits ultraviolet light in the 400-420nm range, used in forensic analysis and material sensing. Learn more.

**N-type Semiconductor
**A semiconductor doped with elements (e.g., phosphorus) that provide extra electrons, making negative charge carriers (electrons) the majority.

O

OptoelectronicsThe study and application of electronic devices that source, detect, and control light, including LEDs, photodiodes, and laser diodes.

P

Phosphor ConversionThe process used in white LEDs where a blue or ultraviolet LED excites a phosphor material that then emits light across a broader spectrum.

**Phosphor Coating
**A layer of material applied to LEDs (e.g., a yellow phosphor over a blue LED) to modify the light spectrum and produce white light.

PhotodiodeA semiconductor device that converts light into an electrical current. Learn more.

**P-N Junction
**The boundary between p-type and n-type semiconductor materials in an LED, where electrons recombine with holes to emit light.

**P-type Semiconductor
**A semiconductor doped with elements (e.g., boron) that create "holes" (absence of electrons), making positive charge carriers (holes) the majority.

**Pulse Width Modulation (PWM)**A control method that dims or adjusts LED brightness by rapidly switching it on and off. The duty cycle determines the perceived brightness.

R

Radiant IntensityA measure of the power emitted by an LED in a particular direction per unit solid angle, usually measured in milliwatts per steradian (mW/sr).

S

SMBB LEDA high-power surface-mount LED designed for industrial applications. Learn more.

SMD (Surface Mount Device) LEDA compact LED mounted directly onto a circuit board, commonly used in high-density lighting applications. Learn more.

**Semiconductor
**A material that has electrical conductivity between that of a conductor and an insulator. Used in LEDs to emit light efficiently.

**Spectral Power Distribution (SPD)**A profile showing the power emitted by a light source at each wavelength, used to evaluate the color characteristics and quality of the LED’s output.

STEM LEDA type of LED with a stem-based package for enhanced durability and optical performance. Learn more.

**Substrate
**The base material on which semiconductor layers are grown. In LED production, materials like sapphire are used as substrates.

SWIR LEDA short-wave infrared LED emitting light in the 1050-1900nm range, used in food sorting and medical imaging. Learn more.

T

Through-Hole LEDA traditional LED with wire leads designed for mounting through circuit board holes. Learn more.

U

UV LEDAn LED that emits ultraviolet light in the 180-400nm spectrum, commonly used for sterilization, curing, and fluorescence applications. Learn more.

V

**Valence Band
**The energy band in a semiconductor where electrons are normally present. In an LED, electrons move from the conduction band to the valence band to emit light.

Visible LEDLEDs emitting light within the human-visible spectrum (400-800nm), available in multiple colors. Learn more.

W

Wide Beam Angle LEDAn LED designed to disperse light over a broad area, suitable for general illumination.

Z

**Zinc Selenide (ZnSe)
**Another semiconductor material considered for blue LEDs, but ultimately less successful due to difficulties in producing p-type material.