The localization of electrons in amorphous semiconductors: A twenty-first century perspective

Critical discussion of models proposed to explain photo‐induced anisotropies in chalcogenide glasses

“…The electron-phonon interaction is so strong that a local change of charge of an atom tends to promote, within a time of the inverse of a phonon frequency, a change in local bonding, if allowed by the open structure of the material. Such lattice relaxation overcomes the Coulomb repulsion and allows the placement of two electrons on one defect [8]. The result is a negative effective correlation energy −U with unusual consequences for the defect chemistry of chalcogenides glasses: there are no singly occupied natural defects detectable by ESR [9].…”

“…These are not as effective for pinning E f as dispersed members of VAPs because interconverting a positive defect into a negative one in intimate vicinity of a negative defect is energetically not so favorable. Taylor pointed out that the effective correlation energy U does not remain negative for all alloy concentrations containing chalcogenides [8]. U tends to become positive below certain chalcogen concentrations in the alloy.…”

“…U tends to become positive below certain chalcogen concentrations in the alloy. He suggests to detect the change of sign of U by measuring the mid-gap absorption if an ESR system is not available [8]. The mid-gap absorption is quite high for +U materials.…”

Recombination and transport through localized states in hydrogenated amorphous and microcrystalline silicon

“…This figure also demonstrates that these residual carriers can be freed by excitation with IR light which, switched on after a dark period t D , causes a rapid decrease of the residual LESR signal and the generation of transient photoconductivity and photoluminescence. Taylor demonstrated in his Mott Lecture at ICANS 21 that such long-time decays of band-tail carriers are a quite universal feature observable in many disordered materials [28].…”

Relation of defects and grain boundaries to transport and photo-transport: Solved and unsolved problems in microcrystalline silicon

“…Surprisingly, the transport (trapping and recombination) in a-Si:H and μc-Si:H is better understood at low temperatures [8,9], while room-temperature operation is of interest for real-life devices.…”