An icosahedral quasicrystalline model for amorphous semiconductors

Schmitz, J.

doi:10.1007/s002570050096

Cited by 1 publication

(3 citation statements)

References 4 publications

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“…This result agrees with the investigations of other authors. 18,20,42,14 It also agrees with other experimental investigations. 67 The DOS shows an asymmetry in the band edges in the gap region, i.e., for a given energy above and below the Fermi level the DOS is higher in the VB than in the CB.…”

Section: A Structural Aspectssupporting

confidence: 93%

“…The numerical value of the mobility gap has been computed by Holender and Morgan 42 and Schmitz and co-workers. 14 Holender and Morgan have studied the localization behavior of the electronic states for a-Si and a-Si:H using the inverse participation ratio ͑IPR͒ and find a mobility gap of 1.2 eV for a-Si and 1.8 eV for a-Si:H. Schmitz and co-workers have calculated the localization behavior of different structural models containing only silicon atoms utilizing two different criteria ͑the participation ratio and the localization length͒. They find mobility gaps that lie between 1.33 and 2.0 eV.…”

Section: Introductionmentioning

confidence: 97%

“…Holender and Morgan have constructed large systems ͑up to 13 824 atoms͒ by assembling small simulation cells, followed by a relaxation procedure using a classical interaction potential. Schmitz, Peters, and Trebin 14 have investigated the suitability of a tetrahedral quasicrystal to describe both the structural and the electronic properties of amorphous silicon. Their models contain up to 20.000 atoms and a fraction of 0.0156 atoms with Zϭ3, which is close to the experimental value.…”

Section: Introductionmentioning

confidence: 99%

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Defects ina−Sianda−Si:H: A numerical study

1998

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We present a numerical study of the electronic properties of various structural models of amorphous silicon and hydrogenated amorphous silicon. Starting from an ideal random network, dangling bonds, floating bonds, double bonds, microvoids, hydrogenated dangling bonds, and hydrogenated floating bonds are introduced. The concentrations of these defects can be varied independently, the amount of disorder introduced to the system is therefore strictly controllable. Two continuous random networks, the vacancy model of Duffy, Boudreaux, and Polk and the bond switching model of Wooten, Winer, and Weaire ͑WWW model͒ are investigated. For the relaxation of the structures the potentials of Keating and of Stillinger and Weber are employed. The electronic structure is described by a tight-binding Hamiltonian; the localized or extended character of the eigenstates is investigated via a scaling approach. The vacancy model shows a band gap for small defect concentrations but this fills up with increasing disorder. Similar behavior is found for the case of the other models. In general defects introduce states into the gap region of a-Si, where the dangling bonds lead to the largest density of states in the gap region for a given defect concentration. This model turns out to be unique. For small system sizes an impurity band results that dramatically changes its character for large systems above 4000 atoms to a nearly uniform density of states as observed experimentally. In a-Si:H the dangling and floating bonds are removed and a mobility gap results with a width in good agreement with experiment. The experimentally observed tailing of the band into the gap region ͑first linear, then exponential͒ is well described only for the a-Si:H model derived from the vacancy model and for very large system sizes above 4000 atoms. The WWW model does not lead to this tail behavior. Localized states are found at all band edges but states at the bottom of the conduction band are more strongly localized than those at the top of the valence band.

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