Electrons that have energies in the next lower band are bound to their respective atoms more strongly and are unable to break free from the atoms. This lower energy band is called the valence band. Electrons with these low energies have large negative values because they require more energy to escape their respective atoms.
The space between the conduction band and valence band has no allowed electron energies. This region is called the energy gap.
Now let's look at how energy bands are related to the spectra of LEDs.
At the beginning of this activity, we used Gas Lamp Spectroscopy to get an idea about how the energy level diagram must look to explain the spectrum emitted by an LED. At that time we created a pseudo-band by putting several energy levels close together. Now, we will look specifically at the energy bands in LEDs.
In the Spectroscopy Lab Suite software package, select LEDs from the main menu.
For non Java Browsers: (Instructions)