Advanced Semiconductor Laboratory
Developing cutting-edge technologies based on III-nitride semiconductors

Blog Posts

Knowledge you should know about LED


By
Renad AlJefri

December 29, 2016 - Posted in Discussion
Light emitting diodes are lighting our lives and are ten times more efficient than the century-old great light bulb. Both are made and optimized with the knowledge of electromagnetics. It is true that Edison did not need to solve Gausss law to build an incandescent light, but to understand the colors of light you need to understand Planck's law of black-body radiation which is derived from energy distribution of photons gas in thermal equilibrium. To understand laser diodes that transmit data through our internet and phone data in optic fiber, we need the wave equation to design and build lasers and fiber optics systems.

N-type materials have a tremendous number of electrons that are not able to get into the P-type material because of the built-in potential barrier. When we reduce the barrier, electrons from N-type diffuse across the depletion region. Only tiny voltages change is needed to make the current flow across the junction.

11.png 
 Figure 6: Light emitting diode (LED) junction and the f low of electrons and holes. 
Light emitting diodes are mad e from direct band gap materials. Such materials are highly crystalline---they need to have few defects so that they do not trap charged carriers. We inject electrons and holes into the materials and they recombine in quantum wells. 

Quantum mechanics and electromagnetics dictate electrons and holes behavior and their dipole transition. To understand the principle of LEDs, you also need to have knowledge of Maxwell’s equations, charge neutrality, current continuity, diffusion and drift current equation, Fermi distribution for carrier concentration in both equilibrium and non-equilibrium. 

Leave a Comment
* Comment:

1 Comment
Anonymous
December 29, 2016 at 11:29 AM
Nice. I should get back to my physics book ASAP.