Suppression of nucleation during the aluminum-induced layer exchange process
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A2.2.1
Suppression of nucleation during the aluminum-induced layer exchange process Jens Schneider*, Juliane Klein, Andrey Sarikov1, Martin Muske, Stefan Gall and Walther Fuhs Hahn-Meitner-Institut Berlin, Dept. Silizium Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany * corresponding author: phone: 0049 30 8062 1395, fax: 0049 30 8062 1333, e-mail: [email protected] ABSTRACT Formation of polycrystalline silicon (poly-Si) thin films on inexpensive glass substrates is of great interest for large area electronic devices. Large grain sizes are desirable to reduce grain boundary effects. In the aluminum-induced layer exchange process Al/a-Si bi-layers exchange their positions with a concurrent crystallization of the amorphous Si (a-Si) in a simple annealing step. The process is characterized by the self regulated suppression of nucleation by existing grains resulting in large grain sizes above 10 µm. This paper elucidates the process within the Al Si phase diagram. The change in Si concentration within the Al is shown to cause the nucleation suppression. INTRODUCTION Polycrystalline silicon (poly-Si) thin films on inexpensive foreign substrates like glass are of great interest for large area electronic devices such as displays, sensors and solar cells. The use of glass substrates limits process temperatures to below 600°C. Fabrication of large grained silicon films at these low temperatures remains a big challenge. Solid phase crystallization (SPC) of amorphous silicon (a-Si) layers is one of the options for obtaining poly-Si films at low temperatures, but it suffers from two major problems. Crystallization takes a long time and the grain sizes obtained are small (
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