UHV-CVD growth of high quality GeSn using SnCl4: from material growth development to prototype devices

The persistent interest of the epitaxy of group IV alloy GeSn is mainly driven by the demand for an efficient light source that could be monolithically integrated on Si for mid-infrared Si photonics. For chemical vapor deposition of GeSn, the exploration of the growth window is difficult from the beginning due to the metastable nature of the material requiring non-equilibrium growth condition. In this work, we demonstrated an effective pathway to achieve high quality GeSn with high levels of Sn incorporation. The GeSn films were grown on Ge-buffered Si via ultra-high vacuum chemical vapor deposition using GeH4 and SnCl4 as the precursor. The influence of both SnCl4 flow fraction and growth temperature on the Sn incorporation and material quality were investigated. Different growth regimes were explored leading to an optimized regime at low temperature which suppressed the Sn precipitation allowing for increased Sn incorporation. The prototype GeSn photoconductors were fabricated with typical samples, which show the promising device applications.