Dangling-Bond Levels and Structure Relaxation in Hydrogenated Amorphous Silicon.
Author: Biswas, R.; Li, Q.; Yoon, Y.; Branz, H. M.
Source: Physical Review. B, Condensed Matter. Vol. 56(15) 15 October 1997-I
Pages/Volumes: pp. 9197-9200
Publication Year: 1997
Document Type: Journal Article
Subject Code Description: Silicon Materials and Devices; Solar Energy - Photovoltaics; Amorphous Silicon
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 of the 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.
Accession Number: 24435
Library Notes: NPL-9803 REV
Report Numbers: 24435
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