Polycrystalline silicon thin films on glass deposited from chlorosilane at intermediate temperatures

¹ Instituto de Desarrollo Tecnológico para la Industria Química (INTEC), CONICET-UNL, Güemes 3450, S3000GLN Santa Fe, Argentina
² Facultad de Ingeniería Química, UNL, Santiago del Estero 2829, S3000AOM Santa Fe, Argentina

^a e-mail: jschmidt@intec.unl.edu.ar

Received: 5 August 2011
Revised: 29 March 2012
Accepted: 30 March 2012
Published online: 9 May 2012

Abstract

We show that commercial float glass can be used as a substrate to deposit polycrystalline silicon (poly-Si) by chemical vapor deposition from trichlorosilane at temperatures between 740 and 870 °C. By using scanning electron microscopy an average grain size lower than 0.4 μm was observed, with a columnar structure suitable for the electrical conduction in photovoltaic cells. X-ray diffraction reveals a strong (2 2 0) preferential orientation of the films, which is indicative of a low density of intra-grain defects. Atomic force microscope images reveal a conical structure, with a root mean square roughness of ~65 nm for samples of around 3 μm in thickness. This natural texture is a positive characteristic from the point of view of light trapping. By using boron tribromide as a doping agent, degrees of doping ranging from intrinsic to clearly p-doped were obtained, as shown by dark conductivity measurements as a function of temperature. The process, the reactants and the substrate used are of low cost and proved to be adequate for direct poly-Si deposition.