Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 19: Silicon and Germanium

HL 19.11: Talk

Monday, March 14, 2011, 17:15–17:30, POT 251

Thermally stimulated current in solid phase crystallized poly-Si thin films — •Markus Moser, Lars-Peter Scheller, and Norbert Nickel — Helmholtz-Zentrum Berlin für Materialien und Energie, Kekuléstr. 5, 12489 Berlin, Germany

Polycrystalline silicon (poly-Si) is an attractive material for many thin film electronic devices due to its improved carrier mobility and long term stability compared to amorphous silicon (a-Si). Furthermore it can be deposited on large areas of cheap substrates such as glass or plastic. However, the use of such low cost substrates limits process temperatures to values below 600°C which strongly influences the electrical and structural properties of the material. In particular, the performance of electronic devices containing poly-Si is affected by grain boundaries, impurities and lattice defects that cause localized states in the band gap. These defect states can trap charge carriers and can act as efficient recombination centers limiting the performance of thin-film transistors and solar cells. Thermally stimulated current measurements (TSC) are a helpful tool to detect these states. In this work, TSC is applied to poly-Si films on Corning glass which are produced by electron beam evaporation and subsequent solid phase crystallization. The measurements reveal a superposition of contributions from different gap states. A thermal cleaning procedure is used to resolve the individual components. Six states with activation energies ranging from 116 meV to 543 meV are obtained. The results are discussed in terms of possible intrinsic and extrinsic defects.