trapniveaus

Trapniveaus, or trap levels, are localized energy states located within the band gap of a solid, created by defects, impurities, or interfaces. These states can capture and release charge carriers such as electrons or holes, thereby influencing electrical conductivity, recombination, and charge storage in materials.

They arise from lattice defects (such as vacancies, interstitials, and antisites), dopant atoms, complex defect clusters, or structural interfaces. External factors like irradiation, processing, or aging can introduce or modify trap levels. The energy depth of a trap is described relative to the nearby conduction or valence band; shallow traps lie close to a band edge and can release carriers readily, while deep traps reside further from the band edges and retain carriers for longer periods.

The behavior of traplevels is governed by capture and emission processes, often described by Shockley-Read-Hall kinetics. The occupancy of traps depends on temperature, the Fermi level, and carrier concentration. Trap levels can act as recombination centers or as reservoirs that delay carrier transport, leading to phenomena such as persistent photoconductivity and nonradiative losses in optoelectronic devices.

Measurement and analysis of trap levels employ techniques such as deep-level transient spectroscopy (DLTS), admittance spectroscopy, and transient photocurrent or photocistance methods. These tools help determine the energy position, capture cross sections, and density of traps, informing material quality and device design.

Trap levels are important in semiconductors, solar cells, light-emitting devices, and detectors. Reducing trap density through material purification and passivation improves performance and stability, while controlled trap engineering can be used to tailor defect-assisted processes in certain applications.