Growth of Direct Bandgap Ge1−xSnx Alloys by Modified Magnetron Sputtering

We report the growth of direct bandgap single-crystalline Ge
_1-x
Sn
_x
thin films on unheated substrates by a modified magnetron sputtering system. The Ge
_1-x
Sn
_x
thin films were deposited on Si, Ge, and GaAs substrates at room temperature. They were characterized by X-ray diffraction and X-ray photoelectron spectroscopy that revealed the existence of Ge
_1-x
Sn
_x
(004) peak and Ge-Sn bonds. Transmission and photoluminescence (PL) measurements confirm the direct bandgap dominated transition, and the bandgap values obtained are in agreement with the results calculated by 8-band k.p method. This article provides a simple and cost-effect way for fabrication direct bandgap GeSn films.