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Photoelectron spectroscopic investigations of very thin a-Si:H layers

Published online by Cambridge University Press:  01 February 2011

M. Schmidt ,
A. Schoepke ,
O. Milch ,
Th. Lussky  and
W. Fuhs
M. Schmidt
Affiliation:
Hahn Meitner Institut Berlin, Abteilung Silizium-Photovoltaik, Kekuléstr. 5, D-12489Berlin, Germany
A. Schoepke
Affiliation:
Hahn Meitner Institut Berlin, Abteilung Silizium-Photovoltaik, Kekuléstr. 5, D-12489Berlin, Germany
O. Milch
Affiliation:
Hahn Meitner Institut Berlin, Abteilung Silizium-Photovoltaik, Kekuléstr. 5, D-12489Berlin, Germany
Th. Lussky
Affiliation:
Hahn Meitner Institut Berlin, Abteilung Silizium-Photovoltaik, Kekuléstr. 5, D-12489Berlin, Germany
W. Fuhs
Affiliation:
Hahn Meitner Institut Berlin, Abteilung Silizium-Photovoltaik, Kekuléstr. 5, D-12489Berlin, Germany
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Abstract

We report on a detailed study on gap-state distribution in thin amorphous silicon layers (a-Si:H) with film thicknesses between 5 nm and 20 nm on c-Si wafers performed by UV excited photoelectron spectroscopy (UV-PES). We measured how the work function, the gap state density, the position of the Fermi-level and the Urbach-energy depend on the layer thickness and the doping level of the ultra thin a-Si:H(n) layers. It was found, that for phosphorous doping the position of the Fermi level saturates at EF–EV=1.47 eV. This is achieved at a gas phase concentration of 10000 ppm PH3 in the SiH4/H2 mixture which was used for the PECVD deposition process. The variation of the doping level from 0 to 20000 ppm PH3 addition results in an increase of the Urbach energy from 65 meV to 101 meV and in an increase of the gap state density at midgap (EV-Ei= 0.86eV) from 3·1018 to 2·1019 cm-3eV-1.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 762: Symposium A – Amorphous and Nanocrystalline Silicon-Based Films – 2003 , 2003 , A19.11
Copyright
Copyright © Materials Research Society 2003

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