New approaches for micro-controlling of oxygen dopant contents in silicon-based thin films with application to multi-band gap solar cells

Abstract

Using the neutral-beam-assisted chemical vapor deposition (NBaCVD) system [5-12], an alternative technique that can control the oxygen doping in a silicon-based thin film has been developed. This brand-new technique has the ability to controlling of optical band gaps by micro-control the oxygen dopant concentrates in the nc-Si thin films. This control of the oxygen doping results in self-biasing on the internal antenna of an inductively coupled plasma (ICP) source; it also results in the hydrogen neutral beam (NB) energy being adjusted by the reflector bias. The oxygen atoms are supplied from the sputtering of an internal ICP antenna covered by a quartz tube and are eliminated by the energetic hydrogen NB in the NBaCVD system, rather than by a mass-flow-controller (MFC) used in conventional CVD. These results are observed via Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, Secondary Ion Mass Spectroscopy and UV-visible data. The result of this experiment allows the fabrication of multi-junction solar cells with gradually varying optical band gaps. (c) 2012 Elsevier B.V. All rights reserved.