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Influence of post-hydrogenation upon electrical, optical and structural properties of hydrogen-less sputter-deposited amorphous silicon

Gerke, S. and Becker, H.-W. and Rogalla, D. and Singer, F. and Brinkmann, N. and Fritz, S. and Hammud, A. and Keller, P. and Skorka, D. and Sommer, D. and Weiß, C. and Flege, S. and Hahn, G. and Job, R. and Terheiden, B. :
Influence of post-hydrogenation upon electrical, optical and structural properties of hydrogen-less sputter-deposited amorphous silicon.
[Online-Edition: http://dx.doi.org/10.1016/j.tsf.2015.11.063]
In: Thin Solid Films, 598 pp. 161-169. ISSN 0040-6090
[Article] , (2016)

Official URL: http://dx.doi.org/10.1016/j.tsf.2015.11.063

Abstract

Amorphous silicon (a-Si) is common in the production of technical devices and can be deposited by several techniques. In this study intrinsic and doped, hydrogen-less amorphous silicon films are RF magnetron sputter deposited and post-hydrogenated in a remote hydrogen plasma reactor at a temperature of 370 degrees C. Secondary ion mass spectrometry of a boron doped (p) a-Si layer shows that the concentration of dopants in the sputtered layer becomes the same as present in the sputter-target. Improved surface passivation of phosphorous doped 5 Omega cm, FZ, (n) c-Si can be achieved by post-hydrogenation yielding a minority carrier lifetime of similar to 360 mu s finding an optimum for similar to 40 nm thin films, deposited at 325 degrees C. This relatively low minority carrier lifetime indicates high disorder of the hydrogen-less sputter deposited amorphous network. Post-hydrogenation leads to a decrease of the number of localized states within the band gap. Optical band gaps (Taucs gab as well as E-04) can be determined to similar to 1.88 eV after post-hydrogenation. High resolution transmission electron microscopy and optical Raman investigations show that the sputtered layers are amorphous and stay like this during post-hydrogenation. As a consequence of the missing hydrogen during deposition, sputtered a-Si forms a rough surface compared to CVD a-Si. Atomic force microscopy points out that the roughness decreases by up to 25% during post-hydrogenation. Nuclear resonant reaction analysis permits the investigation of hydrogen depth profiles and allows determining the diffusion coefficients of several post-hydrogenated samples from of a model developed within this work. A dependency of diffusion coefficients on the duration of post-hydrogenation indicates trapping diffusion as the main diffusion mechanism. Additional Fourier transform infrared spectroscopy measurements show that hardly any interstitial hydrogen exists in the post-hydrogenated a-Si layers. The results of this study open the way for further hydrogen diffusion experiments which require an initially unhydrogenated drain layer. (C) 2015 Elsevier B.V. All rights reserved.

Item Type: Article
Erschienen: 2016
Creators: Gerke, S. and Becker, H.-W. and Rogalla, D. and Singer, F. and Brinkmann, N. and Fritz, S. and Hammud, A. and Keller, P. and Skorka, D. and Sommer, D. and Weiß, C. and Flege, S. and Hahn, G. and Job, R. and Terheiden, B.
Title: Influence of post-hydrogenation upon electrical, optical and structural properties of hydrogen-less sputter-deposited amorphous silicon
Language: English
Abstract:

Amorphous silicon (a-Si) is common in the production of technical devices and can be deposited by several techniques. In this study intrinsic and doped, hydrogen-less amorphous silicon films are RF magnetron sputter deposited and post-hydrogenated in a remote hydrogen plasma reactor at a temperature of 370 degrees C. Secondary ion mass spectrometry of a boron doped (p) a-Si layer shows that the concentration of dopants in the sputtered layer becomes the same as present in the sputter-target. Improved surface passivation of phosphorous doped 5 Omega cm, FZ, (n) c-Si can be achieved by post-hydrogenation yielding a minority carrier lifetime of similar to 360 mu s finding an optimum for similar to 40 nm thin films, deposited at 325 degrees C. This relatively low minority carrier lifetime indicates high disorder of the hydrogen-less sputter deposited amorphous network. Post-hydrogenation leads to a decrease of the number of localized states within the band gap. Optical band gaps (Taucs gab as well as E-04) can be determined to similar to 1.88 eV after post-hydrogenation. High resolution transmission electron microscopy and optical Raman investigations show that the sputtered layers are amorphous and stay like this during post-hydrogenation. As a consequence of the missing hydrogen during deposition, sputtered a-Si forms a rough surface compared to CVD a-Si. Atomic force microscopy points out that the roughness decreases by up to 25% during post-hydrogenation. Nuclear resonant reaction analysis permits the investigation of hydrogen depth profiles and allows determining the diffusion coefficients of several post-hydrogenated samples from of a model developed within this work. A dependency of diffusion coefficients on the duration of post-hydrogenation indicates trapping diffusion as the main diffusion mechanism. Additional Fourier transform infrared spectroscopy measurements show that hardly any interstitial hydrogen exists in the post-hydrogenated a-Si layers. The results of this study open the way for further hydrogen diffusion experiments which require an initially unhydrogenated drain layer. (C) 2015 Elsevier B.V. All rights reserved.

Journal or Publication Title: Thin Solid Films
Volume: 598
Uncontrolled Keywords: AFM, Amorphous silicon, Hydrogen depth profiling, NRRA, Post-hydrogenation, Raman, RF sputter-deposition
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Material Analytics
Zentrale Einrichtungen
Date Deposited: 06 Jun 2016 11:34
Official URL: http://dx.doi.org/10.1016/j.tsf.2015.11.063
Identification Number: doi:10.1016/j.tsf.2015.11.063
Funders: Part of this work was supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (FKZ 0325581).
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