Main Page | See live article | Alphabetical index 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 cannot. 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. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.