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Why indirect band gap material is used for manufacturing LED's?
Wiki User
∙ 11y ago
Optical sources like LEDs use direct band gap so that conduction band electorn can recombine directly with a hole in valence band .
Wiki User
∙ 11y ago
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What is the principle of light-emitting diode?
A light-emitting diode (LED) is a two-lead semiconductor light source. It is a basic pn-junction diode, which emits light when activated. When a fitting voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electro luminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor. An LED is often small in area (less than 1 mm2) and integrated optical components may be used to shape its radiation pattern. Appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-control circuits, such as those in remote controls for a wide variety of consumer electronics. The first visible-light LEDs were also of low intensity, and limited to red. Modern LEDs are available across the visible, ultraviolet, and infra-red wavelengths, with very high brightness.
Why does the Fermi energy level lie closer to the conduction band than the valence band?
Fermi energy levels can be anywhere. Anywhere. But can an electron actually be in a given energy level? There are specific Fermi energy levels associated with each atom where electrons might "hang out" or orbit. Certainly each electron in the atom occupies a given Fermi energy level. There are other Fermi energy levels where the electrons will go if they are given energy to go there. And there are yet other Fermi energy levels where the electron simply cannot be made to go because of quantum mechanical principles. That's in a single atom. There are other Fermi levels that electrons might occupy associated with collections of atoms that did not exist with just a single atom. Said another way, collections of atoms that make up a material cause other Fermi levels that didn't exist before (in the case of a single atom) to become possible places for electrons to be in the collection of atoms that is the material itself. In materials, the valence band is "here" and the conduction band is "here" and they either overlap (in conductive materials) or they don't. In insulators, the conduction band is above the valence band of the atoms and other bands that might be possible because of the macroatomic structure of the material. If the two bands do not overlap, then there is a band gap. The band gap is a "forbidden region" for electrons. They cannot exist there because the quantum mechanical properties of the electrons and the atoms of the material won't sustain their presence in that group of Fermi energy levels that make up the band gap. The question asks why the Fermi energy level lies closer to the conduction band than the valence band. Hopefully the information provided illuminates the situation and shows that Fermi energy levels don't lie closer to the conduction band than the valence band because Fermi energy levels can be anywhere. There is also the question of whether an electron can actually be allowed to be in a given Fermi energy level. Lastly, it's also a question of whether or not the conduction band is "low enough" that it overlaps the valence band where the valence electrons are hanging out.
How would the shape of an electron shell affect the ability of the material to conduct electricity?
Basically, the Electron shells in an insulator are complete, they are not prone to accepting external electrons or donating any of theirs. As such they aren't waystations for electrons looking to move (conduct). There is a need to slip away from what's going on with individual atoms when looking at conductivity (which can be used to sort out insulators from conductors). When a whole bunch of atoms or molecules are put together, a number of other opportunities or places for electrons to exist are created. The valence band of a given atom is subordinated and another type of "valence band" is set up. This new valence band (we are assigning a new definition) does not have a given energy level (like it would for a given atom) but, rather, has a range of allowable energy levels. This is because the many different atoms and molecules when combined to make up whatever it is we are making provide other places (energy levels) in which electrons can hang out. (Let's give Fermi, Schrödinger, Bloch and Brillouin the day off to keep from running off the page.) We have our newly defined valence band as a range of energy levels which an electron can occupy. (These were not available in a single atom of the material.) In a conductor, the band of energies in which an electron must be to support current flow actually are so low that they overlap part of the valence band. That means electrons in the material can support conduction and play musical electrons. In an insulator, there is a gap between the valence band (that group of energy levels allowed by the material as a whole) and the conduction band. Electrons cannot support conduction because they cannot reach the higher energy bands necessary to support it.
What is importance of band gap in semiconductors?
bandgap has an importance role for conduction.if bandgap is max,the conduction of electron is min. and vice-versa.hence we can say that the bandgap desides the conductivity of any material(may be metal or nonmetal)
Is South Africa quad band or tri band?
Tri-band
Why is silicon not used in fabrication of LED?
Silicon is an indirect band gap semiconductor
What are the Characteristics of Direct and indirect band gap semiconductors?
Direct band semconductors are mostly for LEDs. Indirect band semiconductors like Si and Ge are conventional diodes.
What are the indirect bandgap materials?
GaP in an indirect band gap material
Titanium dioxide is direct band gap or indirect band gap material?
Yes it is. Most Sn (tin) materials as semiconductors are direct band gap materials. Silicon on the other hand is an indirect band gap material.
Is ZnSe is direct or indirect band gap?
It is direct band gap material.
Is silicon a direct band gap material?
Silicon is by all means an indirect band gap material.
What are the difference between direct and indirect band gap materials?
In a direct band gap the electron only needs energy to jump to the conduction band. In an indirect band an electron needs energy and momentum to jump to the conduction band
Why is LED not made of silicon or germanium?
Silicon and Germanium are not used to make LEDs.They are opaque to visible lightThey have the wrong type of band gap (direct instead of indirect).LEDs are made with binary semiconductors, like:Indium Gallium NitrideSilicon CarbideIndium PhosphideGallium Indium Arsenide NitrideIndium Gallium Aluminum Phosphideetc.
How do you solder fly leads to LEDs?
Use a heat sink. Many LEDs are heat sensitive. I make a heat sink by putting a rubber band round the handles of a small pair of snipe nosed pliers.
Why silicon is not used for led?
bcz silicon has direct band gap.in intermediatestage its not required any external energy between conduction band and valence band..due to that radiation willbe less..more external energy more more energy radiate...
Why do we mostly use indirect semiconductors?
The indirect band gap semiconductors like silicon and germanium are mostly used because they are elemental, plentiful, and easier to process than the direct band gap semiconductors which are alloys or compounds.
What are applications of direct and indirect band gap?
direct band gap means in e-k diagram valance bands are exactly below covalance band,in this band electron falls from the conduction band to valance band directly without going to metastable state and in indirect band gap the band electron falls from the conduction band to valance band by first going through the metastable state
