Light emission diode
Light emission diode (English: light-emitting diode; LED) is a semiconductor that emits
incoherent monochromatic light when given a forward voltage.
These symptoms include elektroluminesensi form. The resulting color depends on the
semiconducting material used, and can be near ultraviolet or near infrared.
An LED is a special type of semiconductor diode. Like a normal diode, LED consists of a chip of
semiconductor material that is fully charged, or in-dop, with impurities to create a structure
called a pn junction. Charge-carriers - electrons and holes flow into the junction from electrodes
with different voltage. When an electron meets a hole, he fell into a lower energy level, and
release energy in the form of photons.
Wavelength of light emitted, and therefore its color, depending on the difference in the energy
band of material forming a pn junction. A normal diode, typically made of silicon or germanium,
emits visible light near infrared, but the material used for an LED have a difference between the
energy band near-infrared light, visible, and near ultraviolet.
LED lighting in the application as a ceiling light
Unlike incandescent and fluorescent lamps, LEDs have a tendency of polarization. LED chip has
a positive pole and negative (pn) and will only light up when given forward current. This is
because LEDs are made from semiconductor materials that will only allow electric current to
flow in one direction and not in the other direction. When given current LED reverse, there
would be little current through the LED chip. This causes the LED chip will not emit light.
LED chips generally have a relatively low voltage damage. When given voltage a few volts
reverse direction, usually the nature of unidirectional isolator LED will burst causing a current to
flow in the opposite direction.
Characteristics of the LED chip is generally equal to the characteristics of a diode which only
requires a certain voltage to operate. But when given a voltage that is too large, the LED will be
damaged even though the applied voltage is the forward voltage.
Voltage required to operate a diode is forward voltage (Vf).
LED circuits can be designed by arranging the LEDs in series or parallel position. When
arranged in series, then that needs to be considered is the amount of voltage required around the
LED in the series before. However, if the LED is placed in parallel circumstances, it is worth
noting that the amount of current required to be all LEDs in this circuit.
Develop LEDs in series would be more difficult if the LED color is different, because each has a
different color LED forward voltage (Vf) is different. This difference will cause when the
amount of voltage supplied by power source is insufficient to LED chips, then some of the LED
will not light up. Conversely, when the voltage is too large will result in damage to the LED
which has a relatively low forward voltage.
In general, LEDs are arranged in series should have a forward voltage of the same or at least not
much different to the LED circuit can work properly. If the LED is used for the indicator is
higher than the operating voltage coupled with a series resistor to adjust the flow so as not to
exceed the maximum LED current, the maximum current that the LED goes bad too.
LED development began with infrared and red devices made with gallium arsenide.
Perkembagan in materials science have enabled the production of devices with shorter
wavelengths, producing light with varying colors.
Conventional LEDs are made from a variety of inorganic minerals, resulting in the following
aluminum gallium arsenide (AlGaAs) - red and infrared
gallium aluminum phosphide - green
gallium arsenide / phosphide (GaAsP) - red, orange-red, orange, and yellow
gallium nitride (GaN) - green, pure green (or emerald green), and blue
gallium phosphide (GaP) - red, yellow, and green
zinc selenide (ZnSe) - blue
indium gallium nitride (InGaN) - bluish green and blue
aluminum gallium indium phosphide - orange-red, orange, yellow, and green
silicon carbide (SiC) - blue
diamond (C) - ultraviolet
silicon (Si) - Blue (in development)
sapphire (Al2O3) - blue
Blue and white LEDs
A GaN LED ultraviolet
The first blue LEDs that can be achieved using the commercial description of the gallium nitride
substrate is found by Shuji Nakamura in 1993 as a career at Nichia Corporation in Japan. LED
was then popular in the late 90's. Blue LEDs can be combined into the red and green LED that
has gone before to create white light.
With white LED light right now the majority are made by coating a substrate of gallium nitride
(GaN) with yellow phosphorus. Because the receiver stimulate yellow red and green in the
human eye, the combination of yellow and blue phosphors of the substrate will give the
impression of a white color for the human eye.
White LEDs can also be made by coating the phosphor blue, red and green in the substrate near
ultraviolet is more or less similar to the way fluorescent lamps work.
New method for creating white light from LEDs is by not using phosphorus at all but instead use
zinc selenide substrate that can emit blue light from the active area and the light yellow of the