Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 30: Si/Ge
HL 30.7: Vortrag
Mittwoch, 25. März 2009, 11:00–11:15, POT 51
Electrical transport in undoped laser-crystallized polycrystalline silicon-germanium thin films — •Lars-Peter Scheller1, Moshe Weizman1, N. H. Nickel1, and Baojie Yan2 — 1Helmholtz-Zentrum Berlin für Materialien und Energie, Kekuléstr. 5, 12489 Berlin, Germany — 2United Solar Ovonic Corporation, 1100 West Maple Road Troy, MI 48084, USA
Due to its enhanced optical absorption in the IR and visible spectral range polycrystalline silicon-germanium (poly-SiGe) is a promising absorber material for future thin film and tandem solar cells.
In this study we report on the electrical transport properties of intentionally undoped laser-crystallized poly-Si1−xGex thin films (0 ≤ x ≤ 1) on quartz. Temperature dependent Hall and conductivity measurements reveal a strong dependence of the main transport mechanism on both, the alloy composition and the crystallization procedure. At low temperatures most of the intentionally undoped films show an unexpected high p-type conductivity with a characteristic temperature dependence of either variable range hopping (VRH) or metallic like transport. Moreover, a post hydrogen treatment of the laser-crystallized samples causes a strong decrease of the conductivity. In some cases this reduction is accompanied by a change in the dominating low temperature transport mechanism from either metallic to hopping or hopping to activated behavior. This effect will be explained with an intrinsic transport path along grain boundaries caused by Ge dangling bonds.