Laser Diode

• Triple layer structure: a p-type Al_xGa_1-xAs layer next to a p-type GaAs layer, followed by an n-type GaAs layer.

• The Al_xGa_1-xAs layer has a larger band gap energy than the GaAs layer.

• The presence of the larger band gap layer forces the electrons to stay within the GaAs region.

• Under high forward bias in an appropriately shaped cavity, there are a large number of holes in the valence band that combine with a large number of electrons, yielding lasing.