Direct and indirect bandgap semiconductors The difference between the photon-emitting semiconductor laser and a conventional phonon-emitting (non-light-emitting) semiconductor junction diode lies in the type of semiconductor used, one whose physical and atomic structure confers the possibility for photon emission. These photon-emitting semiconductors are the so-called "direct bandgap" semiconductors. The properties of silicon and germanium, which are single-element semiconductors, have bandgaps that do not align in the way needed to allow photon emission and are not considered direct. Other materials, the so-called compound semiconductors, have virtually identical crystalline structures as silicon or germanium but use alternating arrangements of two different atomic species in a checkerboard-like pattern to break the symmetry. The transition between the materials in the alternating pattern creates the critical direct bandgap property. Gallium arsenide, indium phosphide, gallium antimonide, and gallium nitride are all examples of compound semiconductor materials that can be used to create junction diodes that emit light.
Direct and indirect bandgap semiconductors The difference between the photon-emitting semiconductor laser and a conventional phonon-emitting (non-light-emitting) semiconductor junction diode lies in the type of semiconductor used one whose physical and atomic structure confers the possibility for photon emission These photon-emitting semiconductors are the so-called "direct bandgap" semiconductors The properties of silicon and germanium which are single-element semiconductors have bandgaps that do not align in the way needed to allow photon emission and are not considered direct Other materials the so-called compound semiconductors have virtually identical crystalline structures as silicon or germanium but use alternating arrangements of two different atomic species in a checkerboard-like pattern to break the symmetry The transition between the materials in the alternating pattern creates the critical direct bandgap property Gallium arsenide indium phosphide gallium antimonide and gallium nitride are all examples of compound semiconductor materials that can be used to create junction diodes that emit light