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Term Paper

ELECTRONICS DEVICE AND CIRCUIT

Submitted by:

JAGBEER YADAV

Roll No. : A05

Section : D6905

Regd. No. : 10906497

Submitted to:

MISS NIDHI MADAM

(ELECTRONICS DEPT.)

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TOPIC:-

LIGHT EMITTING DIODE

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Light-emitting diode

Blue, green, and red LEDs; these can be combined to produce most perceptible colors,

including white.

Infrared and ultraviolet (UVA) LEDs are also available.

A light-emitting-diode (LED) is a semiconductor diode that emits light when an electric

current is applied in the forward direction of the device, as in the simple LED circuit. The

effect is a form of electroluminescence where incoherent and narrow-spectrum light is

emitted from thep-n junction.

LEDs are widely used as indicator lights on electronic devices and increasingly in higherpower applications such as flashlights and area lighting. An LED is usually a small area (less

than 1 mm2) light source, often with optics added to the chip to shape its radiation pattern and

assist in reflection. The colorof the emitted light depends on the composition and condition

of the semiconducting material used, and can be infrared, visible, or ultraviolet. Besides

lighting, interesting applications include using UV-LEDs for sterilization of water and

disinfection of devices,[4] and as agrow light to enhancephotosynthesis in plants.

http://en.wikipedia.org/wiki/Semiconductor_diodehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/LED_circuithttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Colorhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/UVhttp://en.wikipedia.org/wiki/LED#cite_note-water-3http://en.wikipedia.org/wiki/Grow_lighthttp://en.wikipedia.org/wiki/Grow_lighthttp://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/wiki/Image:LED_symbol.svghttp://en.wikipedia.org/wiki/Image:RBG-LED.jpghttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/LED_circuithttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Coherence_(physics)http://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Colorhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/UVhttp://en.wikipedia.org/wiki/LED#cite_note-water-3http://en.wikipedia.org/wiki/Grow_lighthttp://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/wiki/Semiconductor_diode

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HistoryDiscovery and development

The first known report of a light-emitting solid-state diode was made in 1907 by the British

experimenter H. J. Round of Marconi Labs. Russian Oleg Vladimirovich Losev

independently created the first LED in the mid 1920s; his research, though distributed in

Russian, German and British scientific journals, was ignored, and no practical use was made

of the discovery for several decades. Rubin Braunstein of the Radio Corporation of America

reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys

in 1955. Braunstein observed infrared emission generated by simple diode structures using

GaSb, GaAs, InP, and Ge-Si alloys at room temperature and at 77 K. In 1961, experimenters

Bob Biard and Gary Pittman working at Texas Instruments, found that gallium arsenide gave

off infrared radiation when electric current was applied. Biard and Pittman were able to

establish the priority of their work and received the patent for the infrared light-emitting

diode.

The first practical visible-spectrum (red) LED was developed in 1962 byNick Holonyak Jr.,

while working at General Electric Company. He later moved to the University of Illinois at

Urbana-Champaign. Holonyak is seen as the "father of the light-emitting diode". M. George

Craford, a former graduate student of Holonyak's, invented the first yellow LED and 10x

brighter red and red-orange LEDs in 1972.

Shuji Nakamura ofNichia Corporation of Japan demonstrated the first high-brightness blue

LED based on InGaN borrowing on critical developments in GaN nucleation on sapphire

substrates and the demonstration of p-type doping of GaN which were developed by I.

Akasaki and H. Amano in Nagoya. In 1995, Alberto Barbieri at the Cardiff University

Laboratory (GB) investigated the efficiency and reliability of high-brightness LEDs

demonstrating very high result by using a transparent contact made of indium tin oxide (ITO)

on (AlGaInP/GaAs) LED. The existence of blue LEDs and high efficiency LEDs quickly led

to the development of the first white LED, which employed a Y 3Al5O12:Ce, or "YAG",

phosphor coating to mix yellow (down-converted) light with blue to produce light that

appears white. Nakamura was awarded the 2006 Millennium Technology Prize for hisinvention.

The development of LED technology has caused their efficiency and light output to increase

exponentially, with a doubling occurring about every 36 months since the 1960s, in a similar

way to Moore's law. The advances are generally attributed to the parallel development of

other semiconductor technologies and advances in optics and material science. This trend is

normally called Haitz's Law after Dr. Roland Haitz.

http://en.wikipedia.org/wiki/H._J._Roundhttp://en.wikipedia.org/wiki/Marconi_Labshttp://en.wikipedia.org/wiki/Oleg_Vladimirovich_Losevhttp://en.wikipedia.org/w/index.php?title=Rubin_Braunstein&action=edit&redlink=1http://en.wikipedia.org/wiki/Radio_Corporation_of_Americahttp://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Gallium_antimonidehttp://en.wikipedia.org/wiki/GaAshttp://en.wikipedia.org/wiki/Indium_phosphidehttp://en.wikipedia.org/wiki/Texas_Instrumentshttp://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Nick_Holonyakhttp://en.wikipedia.org/wiki/General_Electric_Companyhttp://en.wikipedia.org/wiki/General_Electric_Companyhttp://en.wikipedia.org/wiki/University_of_Illinois_at_Urbana-Champaignhttp://en.wikipedia.org/wiki/University_of_Illinois_at_Urbana-Champaignhttp://en.wikipedia.org/wiki/Shuji_Nakamurahttp://en.wikipedia.org/wiki/Nichia_Corporationhttp://en.wikipedia.org/wiki/Indium_gallium_nitridehttp://en.wikipedia.org/wiki/Gallium_nitridehttp://en.wikipedia.org/wiki/Nagoyahttp://en.wikipedia.org/w/index.php?title=Alberto_Barbieri&action=edit&redlink=1http://en.wikipedia.org/wiki/Cardiff_Universityhttp://en.wikipedia.org/wiki/Indium_tin_oxidehttp://en.wikipedia.org/wiki/YAGhttp://en.wikipedia.org/wiki/Millennium_Technology_Prizehttp://en.wikipedia.org/wiki/Exponentiallyhttp://en.wikipedia.org/wiki/Exponentiallyhttp://en.wikipedia.org/wiki/Moore's_lawhttp://en.wikipedia.org/wiki/Haitz's_Lawhttp://en.wikipedia.org/wiki/H._J._Roundhttp://en.wikipedia.org/wiki/Marconi_Labshttp://en.wikipedia.org/wiki/Oleg_Vladimirovich_Losevhttp://en.wikipedia.org/w/index.php?title=Rubin_Braunstein&action=edit&redlink=1http://en.wikipedia.org/wiki/Radio_Corporation_of_Americahttp://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Gallium_antimonidehttp://en.wikipedia.org/wiki/GaAshttp://en.wikipedia.org/wiki/Indium_phosphidehttp://en.wikipedia.org/wiki/Texas_Instrumentshttp://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Nick_Holonyakhttp://en.wikipedia.org/wiki/General_Electric_Companyhttp://en.wikipedia.org/wiki/University_of_Illinois_at_Urbana-Champaignhttp://en.wikipedia.org/wiki/University_of_Illinois_at_Urbana-Champaignhttp://en.wikipedia.org/wiki/Shuji_Nakamurahttp://en.wikipedia.org/wiki/Nichia_Corporationhttp://en.wikipedia.org/wiki/Indium_gallium_nitridehttp://en.wikipedia.org/wiki/Gallium_nitridehttp://en.wikipedia.org/wiki/Nagoyahttp://en.wikipedia.org/w/index.php?title=Alberto_Barbieri&action=edit&redlink=1http://en.wikipedia.org/wiki/Cardiff_Universityhttp://en.wikipedia.org/wiki/Indium_tin_oxidehttp://en.wikipedia.org/wiki/YAGhttp://en.wikipedia.org/wiki/Millennium_Technology_Prizehttp://en.wikipedia.org/wiki/Exponentiallyhttp://en.wikipedia.org/wiki/Moore's_lawhttp://en.wikipedia.org/wiki/Haitz's_Law

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Practical use

The first commercial LEDs were commonly used as replacements for incandescent

indicators, and in seven-segment displays, first in expensive equipment such as laboratory

and electronics test equipment, then later in such appliances as TVs, radios, telephones,

calculators, and even watches (see list of signal applications). These red LEDs were brightenough only for use as indicators, as the light output was not enough to illuminate an area.

Later, other colors became widely available and also appeared in appliances and equipment.

As the LED materials technology became more advanced, the light output was increased,

while maintaining the efficiency and the reliability to an acceptable level, causing LEDs to

become bright enough to be used for illumination, in various applications such as lamps and

other lighting fixtures.

Most LEDs were made in the very common 5 mm T1 and 3 mm T1 packages, but withhigher power, it has become increasingly necessary to shed excess heat in order to maintain

reliability, so more complex packages adapted for efficient heat dissipation are becoming

common. Packages for state-of-the-art high power LEDs bear little resemblance to early

LEDs.

LED technology

Physical principles

The inner workings of an LED

http://en.wikipedia.org/wiki/Incandescencehttp://en.wikipedia.org/wiki/Seven-segment_displayhttp://en.wikipedia.org/wiki/Led#Indicators_and_signshttp://en.wikipedia.org/wiki/Led#Lightinghttp://en.wikipedia.org/wiki/Led#High_power_LEDshttp://en.wikipedia.org/wiki/Image:Rectifier_vi_curve.GIFhttp://en.wikipedia.org/wiki/Image:PnJunction-LED-E.PNGhttp://en.wikipedia.org/wiki/Incandescencehttp://en.wikipedia.org/wiki/Seven-segment_displayhttp://en.wikipedia.org/wiki/Led#Indicators_and_signshttp://en.wikipedia.org/wiki/Led#Lightinghttp://en.wikipedia.org/wiki/Led#High_power_LEDs

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Like a normal diode, the LED consists of a chip of semiconducting material impregnated, or

doped, with impurities to create a p-n junction. As in other diodes, current flows easily from

the p-side, oranode, to the n-side, orcathode, but not in the reverse direction. Charge-carriers

electrons and holesflow into the junction from electrodes with different voltages. Whenan electron meets a hole, it falls into a lowerenergy level, and releases energy in the form of

aphoton.

The wavelength of the light emitted, and therefore its color, depends on the band gap energy

of the materials forming the p-n junction. In silicon orgermanium diodes, the electrons and

holes recombine by a non-radiative transition which produces no optical emission, because

these are indirect band gap materials. The materials used for the LED have a direct band gap

with energies corresponding to near-infrared, visible or near-ultraviolet light.

LED development began with infrared and red devices made with gallium arsenide.

Advances in materials science have made possible the production of devices with ever-

shorterwavelengths, producing light in a variety of colors.

LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer

deposited on its surface. P-type substrates, while less common, occur as well. Many

commercial LEDs, especially GaN/InGaN, also usesapphiresubstrate.

Colors and Materials

Conventional LEDs are made from a variety of inorganic semiconductor materials, the

following table shows the available colors with wavelength range, voltage drop and material:

ColorWavelength

(nm)Voltage (V) Semi-conductor Material

Infrared > 760 V < 1.9Gallium arsenide (GaAs)

Aluminium gallium arsenide (AlGaAs)

Red 610 < < 1.63 < VAluminium gallium arsenide (AlGaAs)

http://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Indirect_band_gaphttp://en.wikipedia.org/wiki/Direct_band_gaphttp://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Sapphirehttp://en.wikipedia.org/wiki/Sapphirehttp://en.wikipedia.org/wiki/Sapphirehttp://en.wikipedia.org/wiki/Semiconductor_materialshttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Delta_(letter)http://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Aluminium_gallium_arsenidehttp://en.wikipedia.org/wiki/Redhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Aluminium_gallium_arsenidehttp://en.wikipedia.org/wiki/Diodehttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Energy_levelhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Indirect_band_gaphttp://en.wikipedia.org/wiki/Direct_band_gaphttp://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Sapphirehttp://en.wikipedia.org/wiki/Semiconductor_materialshttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Delta_(letter)http://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Aluminium_gallium_arsenidehttp://en.wikipedia.org/wiki/Redhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Aluminium_gallium_arsenide

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760 < 2.03

Gallium arsenide phosphide (GaAsP)

Aluminium gallium indium phosphide

(AlGaInP)

Gallium(III) phosphide (GaP)

Orange590