Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 44: Si/Ge
HL 44.2: Vortrag
Donnerstag, 30. März 2006, 12:30–12:45, BEY 118
Phase segregation in laser-crystallized polycrystalline SiGe thin films — •Moshe Weizman1, Norbert Nickel1, Ina Sieber1, and Baojie Yan2 — 1Hahn-Meitner-Institut Berlin, Kekuléstr. 5, 12489 Berlin, Germany — 2United Solar Systems Corp. 1100 West Maple Road Troy, MI 48084, USA
Polycrystalline silicon-germanium (poly- SiGe) thin films on glass substrate are considered to be attractive for thin film electronic devices and for solar cells applications. The SiGe thin films investigated in this work were fabricated on glass and stainless steel substrates by the following steps. At first, amorphous silicon-germanium films (a-Si1-xGex:H) with 0.19<x<0.84 were deposited by glow-discharge decomposition of a mixture of disilane, germane, and hydrogen to a thickness of 100 to 255 nm. Secondly, the amorphous samples were crystallized employing a XeCl excimer laser. Phase segregation in the poly SiGe films was studied mainly by energy dispersive X-ray (EDX) and Raman backscattering measurements. The results show that laser crystallization of poly-Si1-xGex thin films on glass with 0.33<x<0.7 can reveal significant segregation into Ge rich and poor areas, which deviate by up to 40% from the homogeneous composition of the amorphous starting material. The Ge rich and poor areas are self assembled with a well defined periodicity length. Surprisingly, laser-crystallized SiGe thin films on stainless steel substrate under similar crystallization conditions show no detectable segregation and no self organization. These results are explained on the base of the Mullins-Sekerka instability growth model calculated for the case of SiGe alloys.