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LEDs are p-n junction devices constructed of gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), or gallium phosphide (GaP). Silicon and germanium are not suitable because those junctions produce heat and no appreciable IR or visible light. An exposed semiconductor surface can then emit light.
Why Cannot we use silicon and germanium in fabrication of LED?
Answer: We cannot use Silicon or germanium in the fabrication of LED’s because they produce energy in the form of heat, and not in the form of Visible light of IR.
Why do silicon and germanium diodes not emit light?
Light-emitting diodes are as cheap as chips, but they aren’t made from silicon. In silicon, electrons have to emit a photon and a sound vibration (a phonon) at the same time to reach the valence band. Instead, the electron typically finds a way to lose the energy without emitting a photon, so no light comes out.
Do LEDs contain silicon?
But lasers and LEDs are made of exotic substances called III-V semiconductors—from their columns on the periodic table of the elements. These materials, which include gallium arsenide and indium phosphide, cost anywhere from 30 to 200 times as much as silicon.
Why is gallium used in LEDs?
For several decades, light emitting diodes have used materials such as gallium arsenide(GaAs), gallium arsenide phosphide(GaAsP), or gallium phosphide(GaP), which make PN junctions more efficient at producing light. This enables the production of the more common LED colours of red, orange, yellow and green.
Why is silicon not used for LED?
LEDs are p-n junction devices constructed of gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), or gallium phosphide (GaP). Silicon and germanium are not suitable because those junctions produce heat and no appreciable IR or visible light. An exposed semiconductor surface can then emit light.
Why silicon is not used in fabrication of LED?
Since Silicon is an Indirect Band Gap semiconductor so electron cannot fall directly to the valence band but must undergo a momentum change as well as a change in energy. So, energy is released as heat along with the light. Hence, silicon is not suitable for the fabrication of LEDs.
What should be the biasing of LED?
Since LED or light emitting diode is a p-n junction diode, we can say that LED operates under forward bias. Hence the correct answer is option A. Note: The p-n junction diode allows the flow of current only in one direction and also does not allow the current flow in reverse direction.
What is the LEDs of SI?
A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons.
Why band gap of silicon is more than germanium?
The electrons in the silicon atoms are more tightly bound to the nucleus than the electrons of the germanium atom due to its small size. This is the reason why the band gap of silicon is more than that of germanium.
Why silicon is not used in lasers?
Silicon, the material par excellence for electronics, is not used for light sources because of the lack of efficient light emitters and lasers.
Who invented LED strips?
In 1962, a scientist name Nick Holonyak, Jr. working for GE created the first light emitting diode (LED), or at least the first practical, visible model similar to the ones we use today.
Who invented LED Malayali?
M A Johnson, an unschooled 49-year-old man, from Peruvannamuzhi, a sleepy hilly hamlet in Kozhikode district, is known to be a pioneer in the manufacture of LED (Light Emitting Diodes) bulbs in the country.
Is gallium used in LED?
Gallium The first and primary element used in the manufacture of almost all semiconductor LED devices is gallium.
Why is gallium arsenide better than silicon?
Gallium arsenide is one such material and it has certain technical advantages over silicon – electrons race through its crystalline structure faster than they can move through silicon. But silicon has a crushing commercial advantage. It is roughly a thousand times cheaper to make.
Which metal is used in LED light?
Metals such as arsenic, gallium, indium, and the rare-earth elements (REEs) cerium, europium, gadolinium, lanthanum, terbium, and yttrium are important mineral materials used in LED semiconductor technology.
Which material is used for LED?
The material used most often in LEDs is gallium arsenide, though there are many variations on this basic compound, such as aluminum gallium arsenide or aluminum gallium indium phosphide.
What are the advantages of LED bulbs?
Here are some advantages of LED lights: Long Lifespan. Energy Efficiency. Improved Environmental Performance. The Ability to Operate in Cold Conditions. No Heat or UV Emissions. Design Flexibility. Instant Lighting and the Ability to Withstand Frequent Switching. Low Voltage Operation.
What is the difference between a diode and an LED?
Normal diodes are designed to affect electrical current, while LEDs are created to make light. This makes a lot of difference when it comes to placement and production. Normal diodes are hidden away in circuits where they can do their job, while LEDs are displayed so their light can be easily seen.
What is the most commonly used semiconductor material?
The most used semiconductor materials are silicon, germanium, and gallium arsenide. Of the three, germanium was one of the earliest semiconductor materials used. Germanium has four valence electrons, which are electrons located on the outer shell of the atom.
Which one of the following is not LED material?
The most basic material for the fabrication of an LED is GaAs (Gallium Arsenide). SiO2 is not an LED material, as it is an insulator, used as an oxide layer in MOSFET.
On what factors Colour of LED depends?
The colour of the light emitted by the LED depends on the wavelength of the light which in turn depends on the semiconductor material used in the diode while manufacturing LED. No other factor is responsible for the colour of light.
Is zener a diode?
A Zener diode is a silicon semiconductor device that permits current to flow in either a forward or reverse direction. The diode consists of a special, heavily doped p-n junction, designed to conduct in the reverse direction when a certain specified voltage is reached.
What happens when LED gets reverse biased?
When light emitting diode is reverse biased, the free electrons (majority carriers) from n-side and holes (majority carriers) from p-side moves away from the junction. As a result, the width of depletion region increases and no recombination of charge carriers occur. Thus, no light is produced.
Why do LEDs only work in one direction?
A diode is a device that allows current to flow in only one direction. When a so-called forward bias (a voltage in the “forward” direction) is applied, current flows freely through the device. When the voltage is applied in the opposite direction (called a reverse bias), no current flows.
