Dangling-Bond Levels and Structure Relaxation in Hydrogenated Amorphous Silicon

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Abstract

Tight-binding molecular-dynamics calculations are utilized to study the spatial extent and time scales of the structure relaxation, following a change of the charge state of dangling bonds in hydrogenated amorphous silicon. Structural relaxation is found to be local, primarily involving large displacements (>0.1 ..ANG..) of the nearest neighbors of the dangling bond and of a few nearby H atoms.Calculated optical transition levels have the D- level below both D0 levels and the D+ level above the D0 levels. A smooth energy surface is found for transitions between the neutral and charged dangling-bond configurations. Molecular-dynamics simulations show that electron levels relax in tens of picoseconds following electron capture or emission by a dangling bond, but large oscillations ofthe gap levels may be present as a result of the strong coupling between the charge and local structure. The results do not appear to support either the slow relaxation model of Cohen, Leen, and Rasmussen, or the D structural memory model of Branz and Fedders.
Original languageAmerican English
Pages (from-to)9197-9200
Number of pages4
JournalPhysical Review B
Volume56
Issue number15
DOIs
StatePublished - 1997

NREL Publication Number

  • NREL/JA-520-24435

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