DocumentCode :
1873798
Title :
The relation between the band gap and the anisotropic nature of hydrogenated amorphous silicon
Author :
Smets, A.H.M. ; Wank, M.A. ; Vet, B. ; Fischer, M. ; van Swaaij, R.A.C.M.M. ; Zeman, M. ; Bobela, D.C. ; Wronski, C.R. ; van de Sanden, M.C.M.
Author_Institution :
Delft Univ. of Technol., Delft, Netherlands
fYear :
2011
fDate :
19-24 June 2011
Abstract :
The network and nature of hydrogenated amorphous silicon (a-Si:H) are conventionally interpreted in terms of a continuous random network (CRN) of Si-Si bonds, weak Si-Si, Si-H bond and dangling bonds. A CRN requires that the smallest anisotropic features like dangling bonds and bonded hydrogen are randomly distributed and reside as isolated configurations in the network. However, in recent years more and more theoretical and experimental evidence have been found that both the isolated dangling bond and the isolated hydrogen are not present in the a-Si:H network. To the contrary, all studies come to the conclusion that the real nature of the a-Si:H is to contain more local structural order than expected from a CRN. These insights offer new opportunities to revisit the origin of several properties of a-Si:H, which are up to now explained within the framework of the CRN model. In this contribution we will discuss that many diagnostics like nuclear magnetic resonance, positron annihilation, small angle x-ray spectroscopy, density analysis and infrared spectroscopy on a-Si:H consistently demonstrate that a-Si:H exhibits an anisotropic network. In dense disordered networks the hydrogen predominantly resides in hydrogenated divacancies, whereas for less dense networks the hydrogen predominantly resides in poly-vacancies up to nanosized voids. We will discuss that hydrogenated divacancies in a disordered network contribute to the amorphous nature of a-Si:H and its electronic structure like the band gap, gap tails and the defect gap states.
Keywords :
X-ray spectra; amorphous semiconductors; dangling bonds; elemental semiconductors; energy gap; hydrogen; infrared spectra; nuclear magnetic resonance; positron annihilation; silicon; Si:H; anisotropic nature; anisotropic network; band gap; bonded hydrogen; continuous random network; defect gap states; dense disordered networks; density analysis; electronic structure; gap tails; hydrogenated amorphous silicon; hydrogenated divacancies; infrared spectroscopy; isolated dangling bond; local structural order; nanosized voids; nuclear magnetic resonance; poly-vacancies; positron annihilation; small angle x-ray spectroscopy; Amorphous silicon; Educational institutions; IEEE Xplore; Photonic band gap; Positrons; Solar power generation; Spectroscopy;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Photovoltaic Specialists Conference (PVSC), 2011 37th IEEE
Conference_Location :
Seattle, WA
ISSN :
0160-8371
Print_ISBN :
978-1-4244-9966-3
Type :
conf
DOI :
10.1109/PVSC.2011.6186662
Filename :
6186662
Link To Document :
بازگشت