LED Physics and LED Science Explained Briefly by Article
As per LED Chemistry, Silicon Germanium bandgap semiconductor materials are not suitable for LED because the very higher percentage of electrical energy is to be converted into thermal energy hence emission of light is negligible.In silicon germanium semiconductor diodes electrons and holes recombined non-radiative radiation.Since no optical emission could be obtained.It could be an indirect bandgap semiconductor definition materials.Gallium Phosphide (GaP) and Gallium Arsenide Phosphide (GaAsP) materials are compatible with LED production. As the main reason, as per transduction property, the full amount of electrical energy is to be converted into light energy.Most materials used for Light Emitting Diode production have very high refractive indices.In LED physics, electrons and holes make recombined radiative radiation.Hence, optical emission could be obtained.It is to be said direct band gap materials. Gallium Phosphide (GaP) and Gallium Arsenide Phosphide (GaAsP) materials are direct bandgap material examples.
Light Emitting Diode is a part of the Fundamentals of Electronics
Since above image explanation of the physics of led lights (LED physics & LED chemistry) and p-n junction diode, by applying reverse bias no current flow across the Light Emitting Diode circuit.At the state of reverse bias condition, majority charge carriers electrons and minority charge carriers, holes do not recombine by making pairs mutually.As a reason, both charge carriers, holes & electrons are going towards negative and positive terminals of applied battery electrical power supply source respectively.Hence, the width of the depletion region becomes very thick, electrons & holes make the long distance between each other.Charge carrier could not make recombination between each other. Hence, no current flow as well as not emits light in applied reverse bias state., the positive terminal of applied battery power source is connected with the p-type semiconductor material Light Emitting Diode and the negative terminal of battery power source is connected with the n-type semiconductor material Light Emitting Diode.In case of applied forward bias, the positive terminal of battery repel positive charge carrier holes and attract negative charge carrier electrons mutually each other.Similarly, the negative terminal of battery repel electrons and attract holes.Charge carriers electrons and holes move towards the p-n junction.Hence, this phenomenon, width of the depletion layer region become very narrow. Current flow direction from positive battery end to negative battery end.Charge carrier electrons and holes are recombined pairs between each other. The difference of energy between conduction band & valence band is known as Band Gap Energy which is to be converted into light energy.Radiation of light energy is occurred due to each and every recombination of electron and hole.This phenomenon effect is called “Electroluminescence Principle“. The brightness of the radiated light is directly proportional to the forward bias current.Light Emitting Diodes always work in forwarding bias, also known as the Photo Diode.
v-i characteristics of LED physics & LED chemistry as well as LEDs Engineering:-
This video shows hole current vs electron current in Light Emitting Diode.