Formation of high-Sn content polycrystalline GeSn films by pulsed laser annealing on co-sputtered amorphous GeSn on Ge substrate

摘要

Polycrystalline Ge1-xSnx (poly-Ge1-xSnx) alloy thin films with high Sn content (＞ 10％) were fabricated by cosputtering amorphous GeSn (a-GeSn) on Ge (100) wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm2 to 550 mJ/cm2.High quality poly-crystal Ge0.90Sn0.10 and Ge0.82Sn0.18 films with average grain sizes of 94 nm and 54 nm were obtained,respectively.Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn.The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers.The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution,strain,and disorder.The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum (FWHM) is well quantified by a linear relationship,which provides an effective method to evaluate the quality of poly-Ge1-x Snx by Raman spectra.