In semiconductor physics
, a direct bandgap
means that the conduction band
lies directly above the valence band
, in momentum
space (see E-k plots). A semiconductor with a direct bandgap can be used to emit light. Indirect bandgap semiconductors such as crystalline silicon
The prime example of a direct bandgap semiconductor is gallium arsenide - a material commonly used in laser diodes.
See indirect bandgap for an explanation of the connection between bandgap offset and light emission.