|MLA Citation:||Bloomfield, Louis A. "Question 1207"|
How Everything Works 25 May 2018. 25 May 2018 <http://howeverythingworks.org/print1.php?QNum=1207>.
The energy in a particle of light (a photon) is related the color of that light—with blue photons having more energy than red photons. Here is where the difficulty in making blue LED's comes in: to produce a blue photon, the electron in an LED must give up lots of energy as it fills the hole in the anode. This need for a large energy release places a severe demand on the semiconductors from which the blue LED is made. These semiconductors need an unusually large band gap—the energy spacing between two types of paths that electrons can follow in the semiconductor. It wasn't until recently that good quality semiconductors with the appropriate electrical characteristics were available for this task.