title: Micro-spectroscopy on silicon wafers and solar cells.
abstract: Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the doping density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the doping density and the carrier lifetime in selective emitters, laser fired doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.
authors.affiliation: Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr, 2, 79110 Freiburg, Germany. paul.gundel@ise.fraunhofer.de.
authors.forename: Paul
authors.initials: P
authors.lastname: Gundel
authors.forename: Martin C
authors.initials: MC
authors.lastname: Schubert
authors.forename: Friedemann D
authors.initials: FD
authors.lastname: Heinz
authors.forename: Robert
authors.initials: R
authors.lastname: Woehl
authors.forename: Jan
authors.initials: J
authors.lastname: Benick
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Giesecke
authors.forename: Dominik
authors.initials: D
authors.lastname: Suwito
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Warta