Bandedge

Bandedge, also written as band edge or band-edge, is a term used in several technical fields to denote a boundary within a defined frequency or energy band. Depending on context, it marks where a domain of allowed propagation or occupancy ends and a different regime begins.

In solid-state physics, the bandedge refers to the extreme energies that bound an electronic band. The valence-band maximum and conduction-band minimum define the bandedge of a semiconductor; the energy difference between them is called the band gap. The positions of bandedges influence optical absorption and emission, electrical conductivity, and charge-carrier dynamics. In heterostructures and quantum wells, the relative alignment of bandedges between materials determines carrier confinement and device behavior, such as type-I or type-II band alignments. Bandedge positions can be modulated by composition, strain, temperature, and quantum confinement in nanoscale structures. Bandedge energies are inferred through experiments such as photoemission spectroscopy, inverse photoemission, and optical absorption or photoluminescence measurements.

In the context of electronics and communications, the bandedge refers to the boundary frequencies of a defined spectral band. The lower and upper bandedge frequencies determine the passband of a filter, transmitter, or receiver. Signals with frequencies near the bandedges are affected by roll-off and out-of-band attenuation, which designs often compensate for with transition bands and higher filter orders. In optical communications, the term may describe the spectral edges of a channel, the cut-off of a waveguide, or the limits of a spectrally defined band where a system maintains specified performance.

Because bandedge has different meanings across disciplines, its precise interpretation should be stated in context.